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May 2011

Volume 29, Issue 3, Articles (03xxxx)

Issue Cover Spotlight Figure

J. Vac. Sci. Technol. B 29, 03C124 (2011); http://dx.doi.org/10.1116/1.3567419 (5 pages)

Liang He, Brian A. Collins, Frank Tsui, and Yong S. Chu
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Dry etching of GaAs in asymmetric bipolar pulsed dc BCl3 plasmas

K. H. Choi, S. H. Lee, J. H. Park, K. Y. Sohn, J. W. Lee, and S. J. Pearton

J. Vac. Sci. Technol. B 29, 030601 (2011); http://dx.doi.org/10.1116/1.3574369 (4 pages) | Cited 1 time

Online Publication Date: 5 April 2011

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Dry etching of GaAs in asymmetric bipolar pulsed dc BCl3 plasmas using only mechanical pumping is reported. The mean pulsed dc voltage on the cathode was used as a process variable in the experiment. When the mean pulsed dc voltage changed from −350 to −550 V at the cathode electrode, the dependent mean current and power were increased from 0.22 to 0.33 A and from 100 to 220 W, respectively. The etch rate of GaAs increased from 0.01 to 0.55 μm/min, and etch selectivity over photoresist was also strongly increased from 0.2:1 to 2.2:1 with this voltage change. The threshold mean voltage for plasma ignition pulsed dc plasma was −350 V. Scanning electron microscopy micrographs showed that dry etching at −500 V provided excellent surface smoothness (rms roughness of ∼ 1 nm) and sidewall passivation. At a lower mean voltage of −400 V, there was a rough surface and some undercutting of GaAs after etching at −400 V. Degradation of the photoresist surface was negligible in both cases.
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81.65.Cf Surface cleaning, etching, patterning
68.35.bg Semiconductors
81.05.Ea III-V semiconductors
52.77.Bn Etching and cleaning

Transfer of carbon nanosheet films to nongrowth, zero thermal budget substrates

Ronald A. Quinlan, Artjay Javier, Edward E. Foos, Leonard Buckley, Mingyao Zhu, Kun Hou, Erika Widenkvist, Martin Drees, Ulf Jansson, and Brian C. Holloway

J. Vac. Sci. Technol. B 29, 030602 (2011); http://dx.doi.org/10.1116/1.3574524 (6 pages)

Online Publication Date: 7 April 2011

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Carbon-based nanostructures and materials have become a popular subject of research due to their unique thermal, mechanical, electrical, and optical properties. For example, the strong C–C bonds of graphene-based systems allow for excellent thermal conduction at room temperature and the conjugation of the sp2 lattice enables extremely high electron mobility. However, the use of carbon nanostructures as a component in polymer composites, sensors, mirco-electro-mechanical systems, and both rigid and flexible electronics has been limited by several factors, including the incompatibility with standard photolithography techniques, the high temperatures required for the nanostructure growth, and the presence of—or complication—of removing noncarbon species. Here, the authors report on a novel method for the transfer of carbon nanosheets to a low or zero thermal budget substrate while maintaining their original morphology and electrical properties. Four-point probe measurements’ post-transfer shows the retention of in-plane conductivity and scanning electron microscopy reveals the preservation of the original vertical morphology. Raman spectroscopy measurements confirm the retention of the graphitic structure of the post-transfer nanosheet film. This new transfer technique builds on the ability to conformally coat nanosheets while maintaining the original ultrahigh surface area morphology and the ability to fully incorporate nanosheets into several polymers while maintaining the original nanostructure separation. For a demonstration of the usefulness of polymer filling, carbon nanosheets were used as an ultrahigh surface area electrode for the photoactive polymer poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] in proof of principle experiments of a nanosheet-based organic photovoltaic device.
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81.05.uf Graphite
81.07.-b Nanoscale materials and structures: fabrication and characterization
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
78.30.Na Fullerenes and related materials
73.63.-b Electronic transport in nanoscale materials and structures
68.35.bp Fullerenes

Growth and optical properties of InP nanowires formed by Au-assisted metalorganic chemical vapor deposition: Effect of growth temperature

Jingwei Guo, Hui Huang, Xiaomin Ren, Xin Yan, Shiwei Cai, Wei Wang, Qi Wang, Yongqing Huang, and Xia Zhang

J. Vac. Sci. Technol. B 29, 030603 (2011); http://dx.doi.org/10.1116/1.3573985 (4 pages)

Online Publication Date: 7 April 2011

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Vertical indium phosphide nanowires (NWs) were grown at different temperatures by metalorganic chemical vapor deposition via a gold (Au)-assisted vapor-liquid-solid mechanism. At a low growth temperature (420 °C), the lengths of the NWs were diameter independent, which indicated that the NWs were grown with significant contributions from the direct impingement of the precursors onto the alloy droplets. In this process, the droplet acts as a catalyst rather than an adatom collector. However, at a high growth temperature (480 °C), the lengths of the NWs were inversely diameter dependent. The wurtzite percentage of NWs increases with the growth temperature. Room temperature photoluminescence properties of NWs grown under different temperatures were investigated.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
78.67.Lt Quantum wires
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
78.55.Cr III-V semiconductors
78.67.Uh Nanowires

Surface stiffness modification by e-beam irradiation for stem cell growth control

Bing-Rui Lu, Mathieu Lanniel, Morgan Alexandar, Ran Liu, Yifang Chen, and Ejaz Huq

J. Vac. Sci. Technol. B 29, 030604 (2011); http://dx.doi.org/10.1116/1.3580587 (4 pages) | Cited 1 time

Online Publication Date: 25 April 2011

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This article reports a novel method to effectively modify the surface stiffness for the differentiation of stem cell growth. To achieve large range of surface hardness, focused electron beam is first employed to radiate hydrogen silsesquioxane (HSQ) film. With different degrees of curing caused by certain e-beam exposure, the HSQ demonstrates various Young’s modulus from 0.5 to 2 GPa, measured by an atomic force microscope. Fourier transform infrared spectra were used to investigate the origin of the stiffness change, which is due to the e-beam irradiation induced network formation inside HSQ. The novel technique possesses a number of advantages such as precision control of stiffness in a broad matrix with high spatial resolution. It also offers a good opportunity to define the geometry shape with a constant stiffness in nanometer scale.
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61.80.Fe Electron and positron radiation effects
68.35.Gy Mechanical properties; surface strains
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Jj Elasticity and anelasticity, stress-strain relations
87.17.-d Cell processes
78.30.-j Infrared and Raman spectra

Nucleation and growth characteristics of electroplated Cu on plasma enhanced atomic layer deposition-grown RuTaN direct plate barriers

Tonmoy Chakraborty, Daniel Greenslit, and Eric T. Eisenbraun

J. Vac. Sci. Technol. B 29, 030605 (2011); http://dx.doi.org/10.1116/1.3585664 (8 pages) | Cited 1 time

Online Publication Date: 18 May 2011

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A study has been carried out to understand the mechanism that enables plasma enhanced atomic layer deposition (PEALD)-grown RuTaN barriers to support direct (seedless) copper electroplating. In particular, the effects of changing the liner surface chemistry on the subsequent plated copper nucleation behavior have been evaluated. Amperometric measurements and short pulse plating experiments were carried out directly on PEALD-grown RuTaN barriers. To enhance copper nucleation, a liner surface cleaning protocol was developed and evaluated. In order to understand the effect of intrinsic liner composition and conductivity on the film microstructure and subsequent plated copper nucleation, a study of copper nucleation density as it relates to the Ru:Ta ratio in the liner was carried out. The thickness extendibility of these direct plate liners was also explored. These liners were also tested for potential use in sub-45-nm copper metallization applications.
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68.55.A- Nucleation and growth
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
64.60.Q- Nucleation
81.15.Pq Electrodeposition, electroplating
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
81.65.Cf Surface cleaning, etching, patterning
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Improvement in the performance of ZnO thin film transistors by using ultralow-pressure sputtering

Myung Soo Huh, Seok-Jun Won, Bong Seob Yang, Seungha Oh, Myeong Sook Oh, Jae Kyeong Jeong, and Hyeong Joon Kim

J. Vac. Sci. Technol. B 29, 031201 (2011); http://dx.doi.org/10.1116/1.3571760 (5 pages)

Online Publication Date: 29 March 2011

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Thin film transistors (TFTs) were fabricated with a zinc oxide (ZnO) channel deposited by ultralow-pressure sputtering (ULPS) at a pressure less than 1.3×10−3 Pa. The field-effect mobility (μFE) and the subthreshold gate swing (SS) of the ULPS-ZnO TFTs were dramatically improved up to 8.5 cm2/V s and 0.31 V/decade, respectively, compared to 1.6 cm2/V s and 1.31 V/decade for the ZnO TFTs fabricated by a conventional sputtering pressure (CSP) of 6.7×10−1 Pa. The improved characteristics of the ULPS-ZnO TFTs compared to the CSP-ZnO one can be attributed to the greater densification of the ZnO semiconductor film at the lower deposition pressure.
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85.30.Tv Field effect devices
81.15.Cd Deposition by sputtering
85.40.Sz Deposition technology
68.55.ag Semiconductors

Novel postetch process to realize high quality photonic crystals in InP

N. Shahid, S. Naureen, M. Y. Li, M. Swillo, and S. Anand

J. Vac. Sci. Technol. B 29, 031202 (2011); http://dx.doi.org/10.1116/1.3574760 (4 pages) | Cited 1 time

Online Publication Date: 7 April 2011

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Thermally driven reflow of material during annealing was positively used to obtain near-vertical sidewall profiles for high-aspect-ratio nanostructures in InP fabricated by dry etching. This is very promising for achieving high optical quality in photonic crystal (PhC) components. Nearly cylindrical profiles were obtained for high-aspect-ratio PhC holes with diameters as small as 200–350 nm. Mini stop bands (MSBs) in line-defect PhC waveguides were experimentally investigated for both as-etched and reshaped hole geometries, and their spectral characteristics were used to assess the quality of PhC fabrication. The spectral characteristics of the MSB in PhC waveguides with reshaped holes showed significant improvement in performance with a transmission dip as deep as 35 dB with sharp edges dropping in intensity more than 30 dB for ∼ 4 nm of wavelength change. These results show potential for using high extinction drop-filters in InP-based monolithic photonic integrated circuit applications. Finally, it is proposed that other nanostructure geometries may also benefit from this reshaping process.
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81.05.Ea III-V semiconductors
81.40.Gh Other heat and thermomechanical treatments
81.16.-c Methods of micro- and nanofabrication and processing
81.65.Cf Surface cleaning, etching, patterning

Studies on Al/ZrO2/GaAs metal-oxide-semiconductor capacitors and determination of its electrical parameters in the frequency range of 10 kHz–1 MHz

Souvik Kundu, Sandipta Roy, P. Banerji, Supratic Chakraborty, and T. Shripathi

J. Vac. Sci. Technol. B 29, 031203 (2011); http://dx.doi.org/10.1116/1.3585608 (7 pages) | Cited 1 time

Online Publication Date: 29 April 2011

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Aluminum (Al)/zirconium oxide (ZrO2)/GaAs metal-oxide-semiconductor (MOS) capacitors were fabricated on p-GaAs. The carrier concentration of n-GaAs was varied by metal organic chemical vapor deposition. The ZrO2 gate dielectrics were prepared by the sol-gel process and then spin-coated onto GaAs substrates. Three different thicknesses of the ZrO2 layer, viz., 25, 40 and 50 nm, were used to study the effect of oxide thickness on different MOS parameters. Sulfur (S) passivation of the GaAs surface was done to control the interface state densities before ZrO2 deposition. It was found that S passivation resulted in both low hysteresis and high accumulation capacitance of the device. Frequency dependent studies on the dielectric characterizations were made in the frequency range of 10 kHz–1 MHz. It was found that within this frequency range dispersion of the oxide capacitance was 2%/decade. It was observed that interface trap densities (Dit) increased with an increase in the carrier concentration of n-GaAs from a value of 1.5×1012 cm−2 eV−1 at 1×1014 cm−3 to a value of 3.8×1012 cm−2 eV−1 at 3×1016 cm−3 doping concentration of the semiconductor. It was also found that Dit increased with an increase in the oxide thickness from a value of 0.75×1012 cm−2 eV−1 at 25 nm to a value of 2.4×1012 cm−2 eV−1 at 50 nm thickness of the oxide layer. Studies on temperature dependent current densities indicated that the leakage current decreased by three orders of magnitude with the change in temperature from 290 to 80 K. Leakage current was also found to decrease with an increase in the thickness of the dielectric layer due to a decrease in the transmission probability. Loss tangent was found to decrease with frequency, whereas the ac conductivity showed an opposite trend. Considering different MOS parameters investigated in the present study, it was observed that ZrO2 could be a potential candidate for GaAs based MOS devices.
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84.32.Tt Capacitors
85.30.Tv Field effect devices
82.45.Un Dielectric materials in electrochemistry

Cl2/BCl3/Ar plasma etching and in situ oxygen plasma treatment for leakage current suppression in AlGaN/GaN high-electron mobility transistors

Hyeongnam Kim, Michael L. Schuette, and Wu Lu

J. Vac. Sci. Technol. B 29, 031204 (2011); http://dx.doi.org/10.1116/1.3581090 (5 pages)

Online Publication Date: 2 May 2011

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An effective mesa-isolation process using Cl-based gas chemistry and oxygen plasma post-treatment is investigated to minimize the effect of plasma-induced damage on AlGaN/GaN high-electron mobility transistor (HEMT) performance. Plasma-induced dc bias of the dry etching of AlGaN/GaN heterostructures is optimized using Cl2/BCl3/Ar gases by monitoring leakage current between adjacent mesas and etch profiles near mesa edges. A dc bias of ∼ 100 V leads to a smoother etched surface and mesa surface near mesa edge and a lower leakage current than dc bias of 260 V. AlGaN/GaN HEMTs fabricated under a dc bias of 100 V show a reasonable pinch-off performance but still high drain leakage current level (tens of microamperes). Oxygen plasma treatment after dry etching is introduced for further reduction in the leakage current. In situ oxygen plasma treatment more effectively improves the leakage current/breakdown performance than ex situ oxygen plasma treatment after the HEMTs are exposed to air. Combination of low-bias Cl-based dry etching and in situ plasma treatment leads to a breakdown voltage higher than 90 V and a drain leakage current of a few nanoamperes at (VDS,VGS) = (5 V,<VT). It is suggested that in situ oxygen treatment, together with low-bias dry etching, passivates the plasma-induced surface damage and results in good pinch-off/breakdown characteristics in AlGaN/GaN HEMTs.
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85.30.Tv Field effect devices
81.65.Cf Surface cleaning, etching, patterning

Fabrication of InAlAs/InGaAsSb/InGaAs double heterojunction bipolar transistors

C. F. Lo, F. Ren, C. Y. Chang, S. J. Pearton, S.-H. Chen, C.-M. Chang, S.-Y. Wang, J.-I. Chyi, and I. I. Kravchenko

J. Vac. Sci. Technol. B 29, 031205 (2011); http://dx.doi.org/10.1116/1.3589808 (5 pages)

Online Publication Date: 16 May 2011

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A trilevel resist system was employed to fabricate self-aligned, submicron emitter finger In0.52Al0.48As/In0.42Ga0.58As0.77Sb0.23/In0.53Ga0.47As double heterojunction bipolar transistors (DHBTs). Selective wet-etchants were used to define the emitter fingers and to form an InGaAs guard-ring around the emitter fingers. Due to the low energy bandgap of the InGaAsSb base layer and type II base-collector junction, a low turn-on voltage of 0.38 V at 1 A/cm2 and a high dc current gain of 123.8 for a DHBT with a 0.65×8.65 μm2 emitter area were obtained. A unity gain cutoff frequency (fT) of 260 GHz and a maximum oscillation frequency (fmax) of 485 GHz at JC = 302 kA/cm2 were achieved.
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85.30.Pq Bipolar transistors

Fabrication of high-aspect-ratio lightpipes

Winnie N. Ye, Peter Duane, Munib Wober, and Kenneth B. Crozier

J. Vac. Sci. Technol. B 29, 031206 (2011); http://dx.doi.org/10.1116/1.3589809 (5 pages) | Cited 1 time

Online Publication Date: 16 May 2011

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The authors report the development of two fabrication processes for creating high-aspect-ratio lightpipes in a 10 μm thick SiO2 layer, with smooth, uniform, and straight vertical sidewalls. Both processes require only standard optical lithography, without the need for advanced electron beam or deep-UV lithography. One process employs a dielectric etch mask and the other uses a negative photoresist as the etch mask. The experiments show that the CF4-based reaction gases are best for deep etching with high selectivity and etch rate. Trenches with diameters or width of 1.5 μm are demonstrated, with an aspect ratio of 7.2:1 and a sidewall angle of 87.4°. The authors also achieve cylindrical lightpipes with an aspect ratio of 3.8:1 and a sidewall angle of 89.5°. They anticipate that these high-aspect-ratio lightpipe structures would be useful for complementary metal-oxide semiconductor image sensors, where they would increase the efficiency of light collection, and reduce interpixel cross-talk.
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81.20.-n Methods of materials synthesis and materials processing
77.55.-g Dielectric thin films
68.55.aj Insulators

Comprehensive comparison of electrical and reliability characteristics of various copper barrier films

Yi-Lung Cheng, Jiung Wu, Tai-Jung Chiu, Shiuan-An Chen, and Ying-Lang Wang

J. Vac. Sci. Technol. B 29, 031207 (2011); http://dx.doi.org/10.1116/1.3591340 (7 pages) | Cited 3 times

Online Publication Date: 18 May 2011

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The physical, electrical, and reliability characteristics of various Copper (Cu) barrier films, including SiC, SiCN, SiCO, SiCNO, and SiN, were investigated. The experimental results indicate that the SiN film is the best barrier film against Cu diffusion, adheres strongly to Cu film, and exhibits reliable electromigration (EM) performance, but its dielectric constant is too high. Nitrogen-doped or oxygen-doped silicon carbide films (SiCN or SiCO) have a lower dielectric constant, but at the cost of reduced reliability. SiCNO film that is doped with both nitrogen and oxygen exhibits more reliable EM and stress-migration with a comparable physical and electrical performance to that of the SiN film.
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77.55.Bh Low-permittivity dielectric films
77.22.Ch Permittivity (dielectric function)
66.30.Qa Electromigration
68.35.Np Adhesion

Antireflection properties and solar cell application of silicon nanostructures

Huihui Yue, Rui Jia, Chen Chen, Wuchang Ding, Yanlong Meng, Deqi Wu, Dawei Wu, Wei Chen, Xinyu Liu, Zhi Jin, Wenwu Wang, and Tianchun Ye

J. Vac. Sci. Technol. B 29, 031208 (2011); http://dx.doi.org/10.1116/1.3591344 (5 pages)

Online Publication Date: 19 May 2011

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Silicon nanowire (Si NW) arrays were fabricated on polished and pyramids textured mono-crystalline Si (mc-Si) using an aqueous chemical etching method. The Si NWs and a hybrid texture of NWs and pyramids both show strong anti-reflectance properties in the wavelength region of 300–1000 nm, with the minimum average reflectance of 2.52% and 8%, respectively. The above two nanostructures were fabricated on mc-Si solar cells with the area of 125×125 mm2. Then the influences of Si NWs and hybrid textures on the performances of mc-Si solar cells created using different fabrication processes were analyzed by internal quantum efficiency measurement and by systematical comparisons of efficiency, filling factor, open circuit voltage and short-circuit current. Passivation is found to be essential for the hybrid textured solar cells, and the average open circuit voltage can be improved by 7% after a passivation layer was deposited. The short circuit current could be increased when Si NWs were fabricated on a substrate with an initial PN junction.
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81.05.Cy Elemental semiconductors
81.07.Gf Nanowires
81.65.Cf Surface cleaning, etching, patterning
81.65.Rv Passivation
88.40.hj Efficiency and performance of solar cells
88.40.jj Silicon solar cells

Analysis of charging effects on highly resistive materials under electron irradiation by using transient-absorbed-current method

Natsuki Tsuno, Yusuke Ominami, Hiroya Ohta, Hiroyuki Shinada, Hiroshi Makino, and Yoshinobu Kimura

J. Vac. Sci. Technol. B 29, 031209 (2011); http://dx.doi.org/10.1116/1.3592188 (6 pages)

Online Publication Date: 24 May 2011

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Accumulation and relaxation properties of charge in highly resistive materials under electron irradiation were investigated by using an absorption current stimulated by sequential two-pulse electron beams. The amount of absorbed charge corresponding to induced surface charge was obtained from the time integration of the absorption component of the substrate current. The absorbed charge of both highly resistive poly-Si (109–1010 Ω cm) and SiO2 substrates increases to 35 nC/cm2 with increasing injected charge and saturates; in contrast, there is a significant difference in absorbed charges for the two substrates at low injected charge (i.e., less than 1 μC/cm2). The time constant of absorbed-charge relaxation is obtained from the analysis of sequential absorbed current, namely, 0.4 ms for poly-Si and 12.5 ms for SiO2. A distinct voltage-contrast image of poly-Si plugs buried in a SiO2 film was successfully obtained by scanning electron microscopy with charging control in accordance with the difference in the charging characteristics of poly-Si and SiO2.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
61.80.Fe Electron and positron radiation effects
61.82.Fk Semiconductors
73.61.Cw Elemental semiconductors

Growth and transport studies of BaMn2As2 thin films

Dang Duc Dung, Wuwei Feng, and Sunglae Cho

J. Vac. Sci. Technol. B 29, 031210 (2011); http://dx.doi.org/10.1116/1.3592991 (5 pages)

Online Publication Date: 25 May 2011

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Epitaxial BaMn2As2 thin films were grown on GaAs(001) using molecular beam epitaxy. The samples exhibited temperature-dependent resistivity, a behavior typical of semiconductors. Activation energies for samples grown at 350, 450, and 550 °C were 24.1, 24.3, and 51.9 meV, respectively. Holes are the dominant carrier for the samples grown at 450 and 550 °C, while electrons are the dominant carrier for the sample grown at 350 °C. Negative magnetoresistance was obtained at low temperature and became positive at high temperature, which was attributed to MnAs nanoclusters.
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68.55.ag Semiconductors
73.61.Le Other inorganic semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Effects of silicon nitride passivation on isolation-blocking voltage in algan/gan high electron mobility transistors

Chien-Fong Lo, T. S. Kang, L. Liu, F. Ren, S. J. Pearton, Jinhyung Kim, S. Jang, O. Laboutin, Y. Cao, and J. W. Johnson

J. Vac. Sci. Technol. B 29, 031211 (2011); http://dx.doi.org/10.1116/1.3593002 (5 pages) | Cited 3 times

Online Publication Date: 25 May 2011

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The effects of plasma enhanced vapor deposited silicon nitride (SiNx) passivation layer thickness and the spacing between the contact windows openings in the SiNx layer on the isolation-blocking voltage of nitrogen ion implanted AlGaN/GaN high electron mobility transistors were studied. The isolation-blocking voltage was proportional to the thickness of the SiNx passivation layer. Early breakdown was observed for the samples without thick enough SiNx due to surface breakdown. The device was permanently damaged after the occurrence of this early breakdown. The dependence of the isolation-blocking voltage on the SiNx thickness was also modeled and the general trends of the simulated results were in good agreement with the experiment data. The effect of rf power used for depositing the SiNx layer on the isolation-blocking voltage was also studied. Ion bombardments during the SiNx deposition could cause the reduction of breakdown voltage. By employing optimized SiNx passivation conditions, a saturation drain current and a drain breakdown voltage of 300 mA/mm and 1000 V, respectively, for HEMTs with gate dimension of 1×200 μm2 and gate to drain distance of 37.5 μm were achieved.
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85.30.Tv Field effect devices
81.65.Rv Passivation

Ultranarrow bandpass filter with wide nontransmission region composed of randomly distributed layer thicknesses

Guibin Chen and Haichun Yu

J. Vac. Sci. Technol. B 29, 031212 (2011); http://dx.doi.org/10.1116/1.3592989 (3 pages)

Online Publication Date: 26 May 2011

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By introducing disorder into a periodic Fabry–Pérot type of ultranarrow bandpass (UNBP) filter, the nontransmission region of the filter can be remarkably enlarged while maintaining the UNBP. The filter that was used was fabricated by using electronic beam evaporation. The introduction of disorder into the periodic structure ensures that the nontransmission region is significantly extended by 14%, with a very narrow bandpass of full width at half maximum <1.9 nm and intensity = 80%.
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84.30.Vn Filters

Ultrahigh luminescence extraction via the monolithic integration of a light emitting active region with a semiconductor hemisphere

S.-N. Wu, S.-Q. Yu, D. Ding, S. R. Johnson, and Y.-H. Zhang

J. Vac. Sci. Technol. B 29, 031213 (2011); http://dx.doi.org/10.1116/1.3592190 (6 pages)

Online Publication Date: 31 May 2011

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A light emitting active region with three InGaAs quantum wells is monolithically integrated with a GaAs hemisphere as a means to increase the extraction efficiency of light emitting diodes. For a device with a small active region and large hemisphere and optimal antireflection, theoretical calculations show that the extracted fraction of spontaneous emission incident on the hemisphere is greater than 99.9% and the overall extraction efficiency of the integrated device is as high as 90%. The hemisphere is fabricated with a consistent aspect ratio (height versus width) using photoresist reflow and inductive coupled plasma etching. Detailed numerical simulations are performed to predict the reflow and dry etch processes as an aid to device fabrication. The fabrication results show that near perfect GaAs hemispheres can be successfully integrated with light emitting active regions and that the resulting light emitting diodes have the potential for mass production.
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85.60.Jb Light-emitting devices
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Cryogenic thermal simulator for testing low temperature thermophotovoltaic cells

Dante F. DeMeo and Thomas E. Vandervelde

J. Vac. Sci. Technol. B 29, 031401 (2011); http://dx.doi.org/10.1116/1.3581095 (6 pages)

Online Publication Date: 15 April 2011

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Thermophotovoltaic (TPV) devices convert infrared electromagnetic radiation into electricity. The authors’ research involves the use of strained-layer superlattices to enable TPV devices to operate at longer wavelengths than the current state of the art designs. To determine the performance of these devices, a novel test apparatus was designed and constructed. Here, the authors present a custom-built, cryogenic vacuum chamber for the testing and characterization of TPV samples. As TPV cells become sensitive to longer wavelength photons (lower source temperatures) in the infrared, the need to control the sample’s ambient temperature becomes critical for accurate testing; thus, the tester includes two copper heat shields cooled via conduction with two liquid nitrogen reservoirs. A calibrated blackbody source is used to illuminate a temperature controlled sample in high vacuum ( ∼ 10−6 Torr). The chamber temperature is extensively monitored and is designed to generate current-voltage (I-V) curves for TPV samples at different temperatures and input radiation in order to determine cell conversion efficiency. The system is evaluated based on the performance of its component systems.
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88.40.hj Efficiency and performance of solar cells
84.60.Jt Photoelectric conversion
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
88.40.ff Performance testing
85.30.De Semiconductor-device characterization, design, and modeling
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Nanostructure and magnetic properties of c-axis oriented L10-FePt nanoparticles and nanocrystalline films on polycrystalline TiN underlayers

Yoshiko Tsuji, Suguru Noda, and Shinichi Nakamura

J. Vac. Sci. Technol. B 29, 031801 (2011); http://dx.doi.org/10.1116/1.3575155 (10 pages) | Cited 2 times

Online Publication Date: 7 April 2011

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We performed a systematic study of the nanostructure and magnetic properties of FePt on templates of either (200)-oriented polycrystalline TiN underlayers with in-plane grain sizes from 5.8 to 10 nm (poly-TiN) or highly (200)-textured TiN underlayers epitaxially grown on single-crystalline MgO (100) substrates (epi-TiN). For small nominal FePt thicknesses (0.7–8.0 nm), FePt forms particulate films with the magnetic easy axis perpendicular to the film plane on every template TiN underlayer. In addition, the coercivity of nominally 1.4-nm-thick FePt at 300 K in the out-of-plane direction increases from 5.3 kOe for 5.8-nm-sized poly-TiN to 12.9 kOe for 10-nm-sized poly-TiN and reaches 16.3 kOe for epi-TiN, which shows that the coercivity strongly depends on the degree of the c-axis orientation. For larger FePt nominal thicknesses (16–64 nm), FePt particles percolate and form continuous films, and the direction of the easy magnetic easy axis becomes random. The coercivity of nominally 64-nm-thick FePt at 300 K in the out-of-plane direction is still as large as 8.8 kOe for 10-nm-sized poly-TiN, but it drastically decreases to 0.5 kOe for epi-TiN. The absence of in-plane texture in the FePt layer on the poly-TiN suppresses the decrease in coercivity, which prevents domain-wall displacement.
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81.05.Bx Metals, semimetals, and alloys
81.07.Bc Nanocrystalline materials
75.75.Fk Domain structures in nanoparticles
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Tt Fine-particle systems; nanocrystalline materials
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Electric potential of a metallic nanowall between cathode and anode planes

Xizhou Qin, Weiliang Wang, and Zhibing Li

J. Vac. Sci. Technol. B 29, 031802 (2011); http://dx.doi.org/10.1116/1.3574391 (4 pages)

Online Publication Date: 18 April 2011

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The electric field around a nanowall that is vertically mounted on a planar cathode is studied. The system is designed as a cold field electron emitter or an electron tunneling line scanner. Exact expressions for the electric potential and the edge field enhancement factor are obtained for arbitrary cathode-anode distances. It is found that the finite distance correction is significant for the cathode-anode distances less than twice the height of the nanowall. The angle-dependent transmission probability implies that the forward emission is dominant.
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41.20.Cv Electrostatics; Poisson and Laplace equations, boundary-value problems
61.46.-w Structure of nanoscale materials
82.45.Fk Electrodes

Effects of segregation strength and an external field on the thermal line edge and line width roughness spectra of a diblock copolymer resist

August W. Bosse

J. Vac. Sci. Technol. B 29, 031803 (2011); http://dx.doi.org/10.1116/1.3581107 (7 pages) | Cited 1 time

Online Publication Date: 22 April 2011

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The author uses computer simulations to measure the spectra of thermal line edge roughness (LER) and line width roughness (LWR) in a two-dimensional, symmetric, lamellar diblock copolymer melt over a range of segregation strengths. These measurements demonstrate that increased segregation strength results in a significant suppression of periodic LER and LWR with a wavelength of order of the pattern pitch. The author also examines the effects of a chemically selective external field on the LER and LWR spectra and finds that not only does the external field suppress long-wavelength and periodic LER and LWR but also it acts to decouple interface-interface fluctuations, as measured by the interface-interface covariance. These results will prove useful for block copolymer (BCP) resist design as they highlight the ability to tune the LER and LWR spectra via manipulating BCP segregation strength and the properties of a chemically selective external field. Furthermore, these simulations will function as an important baseline model for planned diffraction experiments aimed at measuring the BCP thermal LER and LWR spectra.
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64.75.Va Phase separation and segregation in polymer blends/polymeric solutions

Polarity controlled InAs{111} films grown on Si(111)

Akihiro Ohtake and Kazutaka Mitsuishi

J. Vac. Sci. Technol. B 29, 031804 (2011); http://dx.doi.org/10.1116/1.3589807 (4 pages) | Cited 2 times

Online Publication Date: 13 May 2011

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InAs heteroepitaxy on Si(111) has been studied using scanning tunneling microscopy and high-angle annular dark-field scanning transmission electron microscopy. The growth mode and polarity of the InAs{111} films drastically change, depending on the pregrowth treatment of Si(111) surfaces. High-quality (111)A-oriented InAs films are two-dimensionally grown on the In-terminated Si(111)-(4×1) surface, while large three-dimensional InAs islands were formed on the Si(111)-(7×7) and Si(111)-(1×1)–As surfaces. Two-dimensional InAs(111)B islands were obtained by supplying an As molecular beam on the In crystals formed on the As-terminated Si(111)-(1×1) surface. The authors also performed growth experiments of GaAs and In0.5Ga0.5As on In-terminated Si(111) and found that the two-dimensional growth is more promoted as the In content (i.e., lattice mismatch) is increased.
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68.55.ag Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Fabrication of ordered Au nanodot arrays utilizing anodic aluminum oxide templates formed on Si substrate

Namyong Kwon, Namkyu Kim, Jekwan Yeon, Geunyoung Yeom, and Ilsub Chung

J. Vac. Sci. Technol. B 29, 031805 (2011); http://dx.doi.org/10.1116/1.3592431 (7 pages)

Online Publication Date: 25 May 2011

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The authors have fabricated Au nanodot arrays using anodic aluminum oxide (AAO). Two types of AAO, namely, hexagonal and matrix pores, were used as a template for Au deposition. Au nanodots with a controlled size between 20 and 80 nm were obtained by changing the pore size in the AAO template. AAO templates of 200 nm thick were fabricated using two-step anodization. Al films of 150 nm thick grown on Si (100) substrates were indented using the nanoimprint method prior to the anodization for the matrix array of AAO. In addition, for smaller size pores, neutral beam etching was used to remove the barrier layer. The pore size was extracted from the image analysis to the images obtained by field emission secondary electron microscopy.
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81.16.Nd Micro- and nanolithography
61.46.-w Structure of nanoscale materials
81.65.-b Surface treatments
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Rapid serial prototyping of magnet-tipped attonewton-sensitivity cantilevers by focused ion beam manipulation

Jonilyn G. Longenecker, Eric W. Moore, and John A. Marohn

J. Vac. Sci. Technol. B 29, 032001 (2011); http://dx.doi.org/10.1116/1.3581102 (8 pages) | Cited 2 times

Online Publication Date: 10 May 2011

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The authors report a method for rapidly prototyping attonewton-sensitivity cantilevers with custom-fabricated tips and illustrate the method by preparing tips consisting of a magnetic nanorod overhanging the leading edge of the cantilevers. Micron-long nickel nanorods with widths of 120–220 nm were fabricated on silicon chips by electron beam lithography, deposition, and lift-off. Each silicon chip, with its integral nanomagnet, was attached serially to a custom-fabricated attonewton-sensitivity cantilever using focused ion beam manipulation. The magnetic nanorod tips were prepared with and without an alumina capping layer, and the minimum detectable force and tip magnetic moment of the resulting cantilevers was characterized by cantilever magnetometry. The results indicate that this serial but high-yield approach is an effective way to rapidly prepare and characterize magnetic tips for the proposed single-electron-spin and single-proton magnetic resonance imaging experiments. The approach also represents a versatile route for affixing essentially any vacuum-compatible sample to the leading edge of an attonewton-sensitivity cantilever.
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81.05.Bx Metals, semimetals, and alloys
81.07.Bc Nanocrystalline materials
81.16.Nd Micro- and nanolithography
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Cr Saturation moments and magnetic susceptibilities
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Effect of UV wavelength on the hardening process of porogen-containing and porogen-free ultralow-k plasma-enhanced chemical vapor deposition dielectrics

Adam M. Urbanowicz, Kris Vanstreels, Patrick Verdonck, Els Van Besien, Trompoukis Christos, Denis Shamiryan, Stefan De Gendt, and Mikhail R. Baklanov

J. Vac. Sci. Technol. B 29, 032201 (2011); http://dx.doi.org/10.1116/1.3572063 (9 pages)

Online Publication Date: 29 March 2011

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The effect of narrow-band 172 nm and broad-band >200 nm UV sources in the new curing scheme of the plasma-enhanced chemical vapor deposition (PECVD) dielectrics is studied. The new curing scheme is based on porogen removal (organic sacrificial phase introduced to generate open porosity) from PECVD dielectric before its final UV curing. The results are compared with the PECVD films fabricated in the conventional scheme in which porogen is still present during the UV curing. The same curing time of porogen-containing conventional PECVD films with 172 nm and >200 nm UV sources results in only 10% difference in their Young’s modulus (YM): 5.84 and 5.32 GPa, respectively. However, the porogen-free films cured with 172 nm UV source show a YM of 6.64 GPa (k100 kHz ∼ 2.2, 44% open porosity), approximately twice as large as those cured with >200 nm UV having a YM of 3.38 GPa (k100 kHz ∼ 2.0, 48% open porosity). The mechanical properties, optical properties in the range of 150–800 nm, dielectric constants at 100 kHz and 4 GHz, porosities, pore size distributions, and bonding structure are evaluated. The impact of porogen on optical characteristics and, therefore, on the photochemical UV-hardening mechanism is discussed. The achieved mechanical properties are explained on a basis of the percolation of rigidity theory and random network concepts.
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77.55.Bh Low-permittivity dielectric films
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition
77.22.Ch Permittivity (dielectric function)
68.60.Bs Mechanical and acoustical properties
78.66.Qn Polymers; organic compounds

Epitaxial growth of (100)-oriented ceria film on c-plane GaN/Al2O3 using YSZ/TiO2 buffer layers by pulse laser molecular beam epitaxy

Jun Zhu, Jing Jing, Wenbo Luo, Yin Zhang, and Yanrong Li

J. Vac. Sci. Technol. B 29, 032202 (2011); http://dx.doi.org/10.1116/1.3574523 (6 pages)

Online Publication Date: 5 April 2011

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Ceria (CeO2) films with fluorite structures were grown on c-axial-oriented GaN/Al2O3 substrates with and without YSZ/TiO2 double-bridge layer using pulse laser molecular beam epitaxy, respectively. The growth behavior was in situ monitored by reflection high-energy electron diffraction (RHEED). The epitaxial orientation relationship was confirmed by the x-ray diffraction (XRD) technique. With the introduction of the YSZ/TiO2 double-buffer layer, high-quality a-axial-oriented CeO2 films were successfully grown on GaN substrate. The epitaxial relation-ships of this heterostructure were CeO2(200)∥YSZ(200)∥TiO2(200)∥GaN(0002) and CeO2[010]∥YSZ[010]//TiO2[001]//GaN[11math0]. XRD and RHEED analyses reveal in-plane tensile strain in CeO2 film, which is mainly caused by lattice mismatch. The in-plane alignment of CeO2 film on YSZ/TiO2 bridge layer is attributed to the interface stress between the film and substrate. Furthermore, without the YSZ/TiO2 buffer layer, CeO2 film directly grown on GaN was oriented along the [111] direction. The different out-of-plane orientations of CeO2 films on GaN substrate could be explained by the different in-plane crystallographic symmetries of templates.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
68.55.aj Insulators

Technology computer-aided design simulation study for a strained InGaAs channel n-type metal-oxide-semiconductor field-effect transistor with a high-k dielectric oxide layer and a metal gate electrode

Shu-Tong Chang, Chang-Chun Lee, and P.-H. Sun

J. Vac. Sci. Technol. B 29, 032203 (2011); http://dx.doi.org/10.1116/1.3578466 (5 pages)

Online Publication Date: 12 April 2011

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The stress distributions in the InGaAs channel regions of strained InGaAs metal-oxide-semiconductor (MOS) field-effect transistors with high-k dielectric layer, metal gate, and InGaAs alloy souce/drain (S/D) stressors were studied with three-dimensional process simulations. It was shown that the geometric effects, such as channel width and length, could impact the achievable transistor performance gains. In this work, high-performance III-V MOS devices were achieved by stressors, such as S/D stressors, with the InGaAs alloy material. The resulting mobility improvement was analyzed by the Monte Carlo simulations. Tensile stress along the transport direction was found to dominate mobility gain while narrower devices (<1 μm), and a decrease of tensile stress along the channel direction contributed to a decrease in mobility gain owing to the decreasing width. This work helps the future III-V-based MOS device design and demonstrates that strain engineering is important for future nanoscale device technology.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling

Effect of source field plate on the characteristics of off-state, step-stressed AlGaN/GaN high electron mobility transistors

Lu Liu, Tsung Sheng Kang, David A. Cullen, Lin Zhou, Jinhyung Kim, Chih-Yang Chang, Erica A. Douglas, Soohwan Jang, David. J. Smith, S. J. Pearton, Wayne J. Johnson, and Fan Ren

J. Vac. Sci. Technol. B 29, 032204 (2011); http://dx.doi.org/10.1116/1.3581078 (5 pages) | Cited 2 times

Online Publication Date: 18 April 2011

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The effects of source field plates on AlGaN/GaN high electron mobility transistor reliability under off-state stress conditions were investigated using step-stress cycling. The source field plate enhanced the drain breakdown voltage from 55 to 155 V and the critical voltage for off-state gate stress from 40 to 65 V, relative to devices without the field plate. Transmission electron microscopy was used to examine the degradation of the gate contacts. The presence of pits that appeared on both source and drain sides of the gate edges was attributed to the inverse piezoelectric effect. In addition, a thin oxide layer was observed between the Ni gate contact and the AlGaN layer, and both Ni and oxygen had diffused into the AlGaN layer. After step-stress cycling, additional threading dislocations were observed.
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85.30.Tv Field effect devices

Integration of thin film transistors and vertical thin film field emitter arrays using ion-induced bending

Tomoya Yoshida, Takashi Nishi, Masayoshi Nagao, Takashi Shimizu, and Seigo Kanemaru

J. Vac. Sci. Technol. B 29, 032205 (2011); http://dx.doi.org/10.1116/1.3581881 (4 pages)

Online Publication Date: 22 April 2011

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A vertical thin film field emitter array (VTF-FEA) was integrated with a thin film transistor (TFT) through a simple fabrication process that is compatible with the existing TFT manufacturing process. Specifically, the authors integrated a poly-Si TFT and a previously reported VTF-FEA. The VTF-FEA was fabricated using the ion-induced bending (IIB) technique. The IIB is a technique that can bend a cantilever by ion-beam irradiation and can be used with a wide range of materials. The emission from the TFT-VTF-FEA was controlled from subnanoampere to microampere levels using the built-in TFT. This work demonstrated that VTF-FEAs can be integrated with poly-Si TFTs and other electronic devices, such as metal-oxide semiconductor field effect transistors.
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81.05.Cy Elemental semiconductors
85.30.Tv Field effect devices
85.45.Db Field emitters and arrays, cold electron emitters
61.80.Jh Ion radiation effects

Increasing the speed of solid-state nanopores

Philip S. Waggoner, Aaron T. Kuan, Stas Polonsky, Hongbo Peng, and Stephen M. Rossnagel

J. Vac. Sci. Technol. B 29, 032206 (2011); http://dx.doi.org/10.1116/1.3585536 (5 pages) | Cited 1 time

Online Publication Date: 2 May 2011

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In this work, the authors studied the time response of solid-state nanopores to the applied potentials and the corresponding capacitances. They primarily examined the effect of the doping of the silicon substrates as well as the addition of dielectrics above and below the device membrane. For simple silicon nitride membranes on a moderately doped Si, the measured RC time constants in 1M KCl are on the order of hundreds of microseconds or larger. The authors found that the silicon substrate’s doping level has a significant effect on the equivalent circuit of the device and the use of a more lightly doped Si significantly speeds up the device response. They attributed this effect to the reduction of depletion layer capacitance at the Si-electrolyte interfaces. In the best device structure tested, time constants of ∼ 425 ns were observed in 1M KCl, which is much faster than most DNA translocation times and on the same order of magnitude as the transit time of each base through typical nanopores.
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87.14.gk DNA
87.16.D- Membranes, bilayers, and vesicles
85.40.Ry Impurity doping, diffusion and ion implantation technology
82.45.Gj Electrolytes
81.05.Cy Elemental semiconductors
81.07.Bc Nanocrystalline materials

Phase change random access memory featuring silicide metal contact and high-κ interlayer for operation power reduction

Lina Wei-Wei Fang, Rong Zhao, Kian-Guan Lim, Hongxin Yang, Luping Shi, Tow-Chong Chong, and Yee-Chia Yeo

J. Vac. Sci. Technol. B 29, 032207 (2011); http://dx.doi.org/10.1116/1.3584823 (6 pages)

Online Publication Date: 6 May 2011

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A phase change memory device integrated with a nickel monosilicide (NiSi) bottom electrode and a dielectric (Ta2O5) interlayer was investigated. The presence of a low thermal conductivity thin film between the bottom electrode and phase change layer promotes heating efficiency in the device. Reset voltages down to 2.2 and 1.86 V could be achieved for memory device without and with the Ta2O5 interlayer, respectively. In addition, low reset current of 0.66 mA and SET current of 0.2 mA were obtained for devices with Ta2O5 interlayer having a contact dimension of ∼ 1 μm. Endurance of the devices was also studied.
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84.30.Sk Pulse and digital circuits

Quantitative depth profiling of ultrathin high-k stacks with full spectrum time of flight–secondary ion mass spectrometry

Matthieu Py, Jean-Paul Barnes, Rachid Boujamaa, Michael Gros-Jean, Kaoru Nakajima, Kenji Kimura, Charbel Roukoss, Bernard Pelissier, and Narciso Gambacorti

J. Vac. Sci. Technol. B 29, 032208 (2011); http://dx.doi.org/10.1116/1.3589806 (9 pages) | Cited 4 times

Online Publication Date: 16 May 2011

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Elemental concentration depth profiles of high-k material stacks for 32 nm node devices and below were acquired by high resolution backscattering spectrometry (HRBS), parallel angle resolved-x-ray photoelectron spectroscopy (pAR-XPS), and time of flight–secondary ion mass spectrometry (ToF-SIMS). ToF-SIMS data were analyzed using an original calibration method which the authors shall refer to as the full spectrum protocol. Three different samples were studied in this work, one ultrathin insulating layer (IL) alone and two nitridized high-k/IL samples with different nitridation conditions for the IL. Although HRBS and AR-XPS already proved their ability in this domain, SIMS or ToF-SIMS characterization of high-k material stacks is still hampered by various matrix effects. Comparison of the elemental profiles obtained by all three techniques allows the accuracy of the full spectrum ToF-SIMS protocol to be assessed, both in terms of chemical composition quantification and depth resolution. This study reveals the feasibility of quantitative and depth resolved ToF-SIMS profiling of ultrathin high-k material stacks.
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79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
77.55.-g Dielectric thin films

Self-aligned contact metallization technology for III-V metal-oxide-semiconductor field effect transistors

Xingui Zhang, Huaxin Guo, Hau-Yu Lin, Chao-Ching Cheng, Chih-Hsin Ko, Clement H. Wann, Guang-Li Luo, Chun-Yen Chang, Chao-Hsin Chien, Zong-You Han, Shih-Chiang Huang, Hock-Chun Chin, Xiao Gong, Shao-Ming Koh, Phyllis Shi Ya Lim, et al.

J. Vac. Sci. Technol. B 29, 032209 (2011); http://dx.doi.org/10.1116/1.3592211 (5 pages) | Cited 2 times

Online Publication Date: 26 May 2011

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The demonstration of a salicidelike self-aligned contact technology for III-V metal-oxide-semiconductor field-effect transistors (MOSFETs) is reported. A thin and continuous crystalline germanium-silicon (GeSi) layer was selectively formed on n+ doped gallium arsenide (GaAs) regions by epitaxy. A new self-aligned nickel germanosilicide (NiGeSi) Ohmic contact with good morphology was achieved using a two-step annealing process with precise conversion of the GeSi layer into NiGeSi. NiGeSi contact with the contact resistivity (ρc) of 1.57 Ω mm and sheet resistance (Rsh) of 2.8 Ω/◻ was achieved. The NiGeSi-based self-aligned contact technology is promising for future integration in high performance III-V MOSFETs.
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73.40.Ns Metal-nonmetal contacts
73.40.Cg Contact resistance, contact potential
68.55.ag Semiconductors
61.72.Cc Kinetics of defect formation and annealing

Characteristics of PMN-PZT ferroelectric electron emitters with three-dimensional emission sites formed by chemical etching

Tomohiko Sugiyama, Iwao Ohwada, Tsutomu Nanataki, Yukihisa Moriguchi, Osamu Eryu, Masaya Ichimura, and Manabu Gomi

J. Vac. Sci. Technol. B 29, 032210 (2011); http://dx.doi.org/10.1116/1.3592993 (4 pages)

Online Publication Date: 26 May 2011

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Pb(Mg1/3N2/3)O3-PbZrO3-PbTiO3 (PMN-PZT) ferroelectric electron emitters with a novel electrode structures were formed by photolithography and chemical etching to investigate their electron emission characteristics. For the electron emitter formed with the most suitable etching time, the electron emission density was 17 nC/cm2. An electric potential distribution was simulated to clarify the effects of the vacuum gap, and results confirmed that the vacuum gap produces an electric field that leads electrons from the ferroelectric surface to the surrounding space.
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79.70.+q Field emission, ionization, evaporation, and desorption
81.65.Cf Surface cleaning, etching, patterning
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity

High performance platinum-silicided p-type Schottky barrier metal-oxide-semiconductor field-effect transistors scaled down to 30 nm

Myungsim Jun, Youngsam Park, Younghoon Hyun, Taehyoung Zyung, Moongyu Jang, and Sung-Jin Choi

J. Vac. Sci. Technol. B 29, 032211 (2011); http://dx.doi.org/10.1116/1.3592483 (4 pages)

Online Publication Date: 27 May 2011

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Platinum-silicided p-type Schottky barrier metal-oxide-semiconductor field-effect-transistors with sizes varying from 350 to 30 nm were fabricated on silicon-on-insulator substrates. Threshold voltage, subthreshold swing, drain-induced barrier lowering, and saturation current were investigated as a function of gate length and channel width. The device with a gate length of 30 nm showed excellent short channel characteristics with an on/off current ratio larger than 107, an off-leakage current less than 10 pA/μm, and a subthreshold swing of 110 mV/decades.
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85.30.Tv Field effect devices
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Gradual pressure release for reliable nanoimprint lithography

Jung-Sub Wi, Robert J. Wilson, Robert M. White, and Shan X. Wang

J. Vac. Sci. Technol. B 29, 033001 (2011); http://dx.doi.org/10.1116/1.3574390 (3 pages) | Cited 2 times

Online Publication Date: 5 April 2011

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Reliable generation of nanometer-scale features is one of the most critical subjects for the industrial use of nanoimprint lithography. In this brief report, the authors investigate the influence of imprinting pressure history on the fidelity of a molded pattern in thermal nanoimprint lithography. The authors demonstrate that the morphology of molded patterns can be drastically improved by altering the pressure applied during the cooling step. A gradual release of imprinting pressure is found to augment reliable pattern transfer of high-density nanodot arrays without any noticeable polymer reflow or delamination of the patterned layer.
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81.07.-b Nanoscale materials and structures: fabrication and characterization
81.16.Nd Micro- and nanolithography
81.16.Rf Micro- and nanoscale pattern formation
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Effect of interfacial formation on the properties of very long wavelength infrared InAs/GaSb superlattices

H. J. Haugan, G. J. Brown, and L. Grazulis

J. Vac. Sci. Technol. B 29, 03C101 (2011); http://dx.doi.org/10.1116/1.3525642 (5 pages) | Cited 2 times

Online Publication Date: 11 January 2011

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In InAs/GaSb superlattices (SLs) designed for infrared detection, the interfacial layers comprise approximately 10%–15% of the heterostructure. As interdiffusion into the InAs and GaSb layers is considered, this percentage is expected to be even higher. Although the primary goal for engineering these transient layers is to balance the SL strain to the GaSb substrate, the interfacial quality can impact the performance of the SL in other ways as well. Many believe that the majority of nonradiative defects that shorten carrier lifetime can be generated from the SL interfaces or regions near them due to the poor interface engineering. Because the degree of lattice mismatch tends to be higher in very long wavelength infrared InAs/GaSb designs, the approach tuning growth parameters to optimize the strain balancing process is different from that for midinfrared SLs. To investigate this optimization, a systematic approach was applied to achieve strain compensated 16 monolayers (MLs) InAs/7 MLs GaSb SLs aimed for a target onset wavelength of 15 μm. The authors systematically explored the effect of growth parameters, such as group V fluxes, growth rates, and shutter sequences, on the SL strain and interfacial quality. For this study, high-resolution x-ray diffraction and atomic force microscopy analysis were extensively used to monitor the effect of interfaces on material properties.
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78.30.Fs III-V and II-VI semiconductors
68.35.Fx Diffusion; interface formation
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials

II-VI heterostructures obtained by encapsulation of colloidal CdSe nanowires by molecular beam epitaxy deposition of ZnSe

Xinyu Liu, A. M. Mintairov, J. Herzog, F. Vietmeyer, R. E. Pimpinella, M. Kuno, J. L. Merz, T. H. Kosel, M. Dobrowolska, and J. K. Furdyna

J. Vac. Sci. Technol. B 29, 03C102 (2011); http://dx.doi.org/10.1116/1.3547715 (4 pages)

Online Publication Date: 24 January 2011

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In this work, 10 and 20 nm diameter colloidal CdSe nanowires (NWs) have been successfully incorporated into ZnSe layers grown by molecular beam epitaxy on GaAs substrates. Atomic force microscopy and scanning electron microscopy were carried out to study the surface morphology of the samples. Transmission electron microscopy and energy-dispersive x-ray analysis were also carried out to study the chemical composition and lattice structure around the embedded CdSe NWs. Finally, single NW photoluminescence (PL) spectroscopy and PL imaging were used to study the optical properties of ZnSe films containing CdSe NWs. The experimental results confirm the presence of embedded CdSe NWs in the ZnSe films and show that the embedded NWs remain optically active.
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81.07.Gf Nanowires
78.67.Uh Nanowires
82.70.Dd Colloids
68.55.ag Semiconductors
81.05.Dz II-VI semiconductors
78.55.Et II-VI semiconductors

Molecular beam epitaxy approach to the graphitization of GaAs(100) surfaces

Paul J. Simmonds, John Simon, Jerry M. Woodall, and Minjoo Larry Lee

J. Vac. Sci. Technol. B 29, 03C103 (2011); http://dx.doi.org/10.1116/1.3547716 (5 pages)

Online Publication Date: 25 January 2011

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The authors present a method for obtaining graphitized carbon on GaAs(100) surfaces. Carbon-doped GaAs is grown by molecular beam epitaxy before controlled thermal etching within the growth chamber. An AlAs layer beneath the carbon-doped GaAs acts as a thermal etch stop. As the GaAs is etched away, the carbon dopant atoms remain on the surface due to their low vapor pressure. The total number of carbon atoms available is precisely controllable by the doping density and thickness of the carbon-doped GaAs layer. Characteristic phonon modes in Raman spectra from the thermally etched surfaces show that the residual surface carbon atoms form sp2-bonded graphitic crystallites.
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81.65.Cf Surface cleaning, etching, patterning
78.68.+m Optical properties of surfaces
78.30.Fs III-V and II-VI semiconductors
68.35.Ja Surface and interface dynamics and vibrations
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Cross-sectional scanning tunneling microscopy and spectroscopy of semimetallic ErAs nanostructures embedded in GaAs

Jason K. Kawasaki, Rainer Timm, Trevor E. Buehl, Edvin Lundgren, Anders Mikkelsen, Arthur C. Gossard, and Chris J. Palmstrøm

J. Vac. Sci. Technol. B 29, 03C104 (2011); http://dx.doi.org/10.1116/1.3547713 (5 pages) | Cited 1 time

Online Publication Date: 26 January 2011

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The growth and atomic/electronic structure of molecular beam epitaxy-grown ErAs nanoparticles and nanorods embedded within a GaAs matrix are examined for the first time via cross-sectional scanning tunneling microscopy and spectroscopy. Cross sections enable the interrogation of the internal structure and are well suited for studying embedded nanostructures. The early stages of embedded ErAs nanostructure growth are examined via these techniques and compared with previous cross-sectional transmission electron microscopy work. Tunneling spectroscopy I(V) for both ErAs nanoparticles and nanorods was also performed, demonstrating that both nanostructures are semimetallic.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.07.Bc Nanocrystalline materials
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Localized dry-etch substrate thinning for dislocation reduction in heteroepitaxial CdTe/Si(211)

R. N. Jacobs, J. K. Markunas, C. Nozaki, M. Jaime-Vasquez, P. J. Smith, J. D. Benson, and J. Pellegrino

J. Vac. Sci. Technol. B 29, 03C105 (2011); http://dx.doi.org/10.1116/1.3547711 (6 pages)

Online Publication Date: 28 January 2011

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Threading dislocations are a significant problem for heteroepitaxial growth of thin films on large lattice-mismatched substrates. In the case of HgCdTe thin films on Si, Ge, or GaAs, the molecular beam epitaxy (MBE) of 10–15-μm-thick CdTe buffer layers has historically played a crucial role in reducing threading dislocation densities to current state-of-the-art levels. In this work, the authors investigate a localized substrate thinning approach and its overall effect on further reducing dislocation densities in the CdTe/Si heteroepitaxial system. In using substrates with regions thinned to thicknesses on the order of the CdTe buffer, the attempt is to reduce the dislocation image force acting from the interface toward the epilayer surface. The authors employ both wet- and dry-etching techniques to create locally back-thinned regions of Si(211) wafers. Localized rather than whole wafer thinning was necessary to maintain sufficient substrate thickness for handling. The opposite sides of the wafers were cleaned using standard techniques prior to CdTe MBE. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to measure epilayer and substrate thicknesses. Using CdTe defect-decoration techniques, a decrease in threading dislocation density by up to 60% has been observed in regions for which the underlying Si substrate was thinned to 2 μm. Results obtained for wet-etch and dry-etch back-thinning approaches suggest that the dislocation-reduction mechanism is not solely based on substrate-thickness induced image forces.
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81.65.Cf Surface cleaning, etching, patterning
78.30.Fs III-V and II-VI semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
78.66.Hf II-VI semiconductors
68.55.ag Semiconductors
81.05.Dz II-VI semiconductors

Molecular beam epitaxy growth of InGaN-GaN superlattices for optoelectronic devices

Chris Boney, David Starikov, Ivan Hernandez, Rajeev Pillai, and Abdelhak Bensaoula

J. Vac. Sci. Technol. B 29, 03C106 (2011); http://dx.doi.org/10.1116/1.3549887 (6 pages) | Cited 1 time

Online Publication Date: 31 January 2011

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In the absence of native substrates for InGaN films, the achievement of thick InGaN films of high structural quality remains a challenge. The investigation of InGaN-GaN superlattice (SL) structures is one potential way to increase optical absorption at energies below the GaN bandgap while reducing the formation of detrimental defects. In this article the authors evaluate the structural and optical properties of InGaN-GaN superlattices grown by plasma assisted molecular beam epitaxy with indium compositions of up to 38% and periods from 8 to 20 nm. Of primary concern was the degree of film relaxation as determined by x-ray diffraction (XRD) reciprocal space mapping as a function of indium content and thickness of the InGaN layers. Indium well fractions of up to 0.15 were found to exhibit little or no relaxation for the structures tested by x-ray diffraction. For indium well fractions near ∼ 0.2, relaxations of the superlattices were in the range of 35% depending on total layer thickness. The samples with indium fractions of 0.33 and 0.38 had relaxations near 30%. For all of the superlattice layers, the onset of absorption began at significantly lower energy if one compares the average indium fraction in the SL to a uniform InGaN film of the same fraction. p-n photodiode structures based on superlattice layers were fabricated and tested for I-V characteristics and spectral response. The high indium content superlattice devices exhibited a substantial spectral response extension down to ∼ 2.3 eV. However, the I-V behavior was leaky at both forward and reverse biases, which is in a good agreement with the XRD analysis showing that material relaxation and defect generation occur in the SL layers with higher indium content.
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68.55.ag Semiconductors
78.40.Fy Semiconductors
78.67.Pt Multilayers; superlattices; photonic structures; metamaterials
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors

AlGaN/GaN high electron mobility transistors on 100 mm silicon substrates by plasma molecular beam epitaxy

W. E. Hoke, T. D. Kennedy, J. J. Mosca, A. J. Kerr, A. Torabi, S. Davis-Hearns, and J. R. LaRoche

J. Vac. Sci. Technol. B 29, 03C107 (2011); http://dx.doi.org/10.1116/1.3549889 (5 pages) | Cited 2 times

Online Publication Date: 1 February 2011

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GaN high electron mobility transistor (HEMT) structures have been grown by plasma molecular beam epitaxy on 100 mm diameter 〈111〉 silicon substrates. Crack-free films with thicknesses of up to 1.7 μm were deposited without the use of strain-relaxing buffer layers. X-ray measurements indicate high structural uniformity and the Pendellosung oscillations are observed due to the abruptness of the AlGaN/GaN interface. Capacitance-voltage measurements display a sharp pinch-off with a depleted GaN buffer layer and no measurable charge accumulation at the substrate-epi interface. Transmission line measurements on the GaN HEMT buffer and substrate indicate a loss of less than 0.2 dB/mm up to 20 GHz. An average sheet resistance of 443 Ω/sq with a standard deviation of 0.8% and a mobility of 1600 cm2/V s were obtained for an Al0.25Ga0.75N/GaN HEMT. Transistors were fabricated with a current density of 1.2 A/mm and a transconductance of 290 mS/mm which is quite comparable to GaN HEMTs on SiC.
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85.30.Tv Field effect devices

Embedded ErAs nanorods on GaAs (n11) substrates by molecular beam epitaxy

Trevor E. Buehl, Christopher J. Palmstrøm, and Arthur C. Gossard

J. Vac. Sci. Technol. B 29, 03C108 (2011); http://dx.doi.org/10.1116/1.3549888 (4 pages)

Online Publication Date: 2 February 2011

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This article investigates the codeposited growth of ErAs and GaAs at concentrations of 6% and 10% of Er on (111)A, (211)A, (311)A, and (511)A GaAs. On (111)A, (211)A, and (311)A GaAs, ErAs nanorods were observed. Those observed on the (111)A GaAs surface were found to align themselves normal to the substrate, along the [111] direction, whereas those on the (211)A and (311)A GaAs substrates were found to align along the [211] direction, as was previously observed on (411)A GaAs. All observed nanorods had a diameter of approximately 2 nm and a period of 5–6 nm. Codeposited growth on (511)A GaAs produced ErAs nanoparticles that were elliptical in shape and aligned along the (311) planes with their major axis pointing along the [311] direction. Growth of these nanorods and nanoparticles most likely occurs by a surface phase-separation mechanism.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Antimonide-based pN terahertz mixer diodes

R. Magno, J. G. Champlain, H. S. Newman, and D. Park

J. Vac. Sci. Technol. B 29, 03C109 (2011); http://dx.doi.org/10.1116/1.3549885 (5 pages)

Online Publication Date: 3 February 2011

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High frequency pN heterojunction diodes with cutoff frequencies over 1 THz have been fabricated using narrow bandgap high-mobility semiconductors. The pN heterojunction is composed of a 30 nm thick p-type In0.27Ga0.73Sb alloy and a 130 nm thick In0.69Al0.31As0.41Sb0.59 n-layer. A high-mobility n-type InAs0.66Sb0.34 contact layer is used to connect the mesa diode to a metal Ohmic contact. These alloys have a lattice constant a0 = 6.2 Å and are grown on semi-insulating GaAs, a0 = 5.65 Å, using a buffer consisting of 1 μm of In0.21Ga0.19Al0.6Sb with a0 = 6.2 Å and 0.5 μm of Ga0.35Al0.65Sb with a0 = 6.12 Å.
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85.30.Kk Junction diodes

Effect of strain and confinement on the effective mass of holes in InSb quantum wells

C. K. Gaspe, M. Edirisooriya, T. D. Mishima, P. A. R. Dilhani Jayathilaka, R. E. Doezema, S. Q. Murphy, M. B. Santos, L. C. Tung, and Y.-J. Wang

J. Vac. Sci. Technol. B 29, 03C110 (2011); http://dx.doi.org/10.1116/1.3553457 (4 pages)

Online Publication Date: 10 February 2011

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An experimental study of the hole effective mass was conducted in a series of five remotely doped InSb quantum wells under biaxial compressive strain. From cyclotron resonance measurements at 4.2 K, an increase in hole effective mass was observed with increasing hole density in otherwise similar structures from 0.045me at 2.1×1011 cm−2 to 0.083me at 5.1×1011 cm−2. The smallest effective mass (0.017me) was observed in the quantum well with the largest compressive strain (1.05%) and narrowest well width (7 nm). Our measurements are in qualitative agreement with theoretical expectations.
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73.63.Hs Quantum wells
76.40.+b Diamagnetic and cyclotron resonances
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
71.20.Nr Semiconductor compounds

Substrate wobble compensation for in situ spectroscopic ellipsometry measurements

Blaine Johs and Ping He

J. Vac. Sci. Technol. B 29, 03C111 (2011); http://dx.doi.org/10.1116/1.3555332 (5 pages)

Online Publication Date: 14 February 2011

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Spectroscopic ellipsometry (SE) is an optical characterization technique that has been implemented on molecular beam epitaxy chambers for in situ characterization and growth control. SE measurements require collecting light reflected obliquely from the substrate. As the substrate is usually rotating during growth (to promote uniformity), acquiring accurate in situ SE data typically requires a substrate manipulator with low wobble (preferably <0.1°). To overcome the low wobble manipulator requirement, the authors have designed and tested a return path SE configuration that compensates for the effects of substrate wobble. The prototype wobble compensation system demonstrated the near elimination of beam precession in the outgoing ellipsometer beam. The accuracy of the SE data acquired in the return path configuration during substrate rotation was also studied.
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07.60.Fs Polarimeters and ellipsometers

Study of molecular beam epitaxially grown InGaAsSbN/GaSb single quantum wells

Sudhakar Bharatan, Shanthi Iyer, Jia Li, Thomas A. Rawdanowicz, and Lewis Reynolds, Jr.

J. Vac. Sci. Technol. B 29, 03C112 (2011); http://dx.doi.org/10.1116/1.3555368 (6 pages) | Cited 1 time

Online Publication Date: 28 February 2011

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InGaAsSbN quantum wells (QWs) have been investigated for potential light-emitting devices in the midinfrared region. This paper presents the growth and properties of molecular beam epitaxially grown InGaAsSbN single QWs using a variety of characterization techniques. A 10 K photoluminescence emission at 2.27 μm, with a lowest full width at half maxima of 5 meV which shifted to 2.30 μm on in situ annealing, has been observed. The presence of well resolved Pendellosung fringes in high resolution x-ray diffraction and sharp abrupt interfaces in the corresponding transmission electron microscope (TEM) images are indications of the high quality of these QWs. Raman spectroscopy studies reveal the presence of well resolved Raman peaks with higher intensity, along with the presence of sharp second order modes of GaSb, further attesting to the high quality of the QW structures grown. Investigation of the annealed samples using Z-contrast scanning TEM images reveals atomic interdiffusion between the QW and surrounding GaSb layers, increasing the effective thickness of the QW, which explains the redshift upon annealing.
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81.07.St Quantum wells
68.55.A- Nucleation and growth
78.55.Cr III-V semiconductors
85.60.Jb Light-emitting devices
78.30.Fs III-V and II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

High power 1.25 μm InAs quantum dot vertical external-cavity surface-emitting laser

Alexander R. Albrecht, Christopher P. Hains, Thomas J. Rotter, Andreas Stintz, Kevin J. Malloy, Ganesh Balakrishnan, and Jerome V. Moloney

J. Vac. Sci. Technol. B 29, 03C113 (2011); http://dx.doi.org/10.1116/1.3555379 (4 pages)

Online Publication Date: 28 February 2011

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The authors demonstrate InAs quantum dot (QD)-based optically pumped vertical external-cavity surface-emitting lasers grown by molecular beam epitaxy. Active region designs utilizing two different resonant periodic gain (RPG) structures are compared. The first RPG structure is a more traditional design consisting of three QD layers per antinode of the E-field standing wave, repeated four times, for a total of 12 QD layers. The second RPG has a single-QD layer per antinode, repeated 12 times. The single-QD layer per antinode structure allows for both superior strain relief as well as more complete pump absorption and thus results in significantly improved device performance over the traditional multi-QD layer per antinode design. The authors were able to demonstrate over 3 W of output power at room temperature using a thermal grade polycrystalline chemical-vapor deposition diamond heat spreader mounted on the backside of a sample thinned by mechanical polishing.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Growth and characterization of TbAs:GaAs nanocomposites

Laura E. Cassels, Trevor E. Buehl, Peter G. Burke, Chris J. Palmstrøm, Art C. Gossard, Gilles Pernot, Ali Shakouri, Chelsea R. Haughn, Matthew F. Doty, and Joshua M. O. Zide

J. Vac. Sci. Technol. B 29, 03C114 (2011); http://dx.doi.org/10.1116/1.3555388 (5 pages) | Cited 2 times

Online Publication Date: 28 February 2011

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Recently, there has been interest in semimetallic rare earth monopnictide nanoparticles epitaxially embedded in III-V semiconductors due to the drastic changes brought about in these materials’ electrical and thermal properties. The properties of terbium codeposited with gallium arsenide by molecular beam epitaxy are discussed here. These new materials were characterized by x-ray diffraction, Rutherford backscattering spectrometry, resistivity measurements, photoluminescence, time-domain thermoreflectance thermal conductivity measurements, optical absorption spectroscopy, and plan-view high-angle annular dark-field scanning transmission electron microscopy. Results revealed successful formation of randomly distributed nanoparticles with an average diameter of ∼ 1.5 nm, reduction of thermal conductivity by a factor of about 5, and consistency with theoretical predictions of mid-band-gap Fermi level pinning and behavior of past similar materials. The success of these TbAs:GaAs materials will lead the way for growth of similar materials [TbAs:InGa(Al)As] which are expected to exhibit highly desirable thermoelectric properties.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.63.Bd Nanocrystalline materials
73.22.-f Electronic structure of nanoscale materials and related systems
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)

Low-misfit epilayer analyses using in situ wafer curvature measurements

Ryan France and Aaron J. Ptak

J. Vac. Sci. Technol. B 29, 03C115 (2011); http://dx.doi.org/10.1116/1.3556974 (6 pages)

Online Publication Date: 28 February 2011

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Several benefits of in situ wafer curvature monitoring on simple structures with low misfit are discussed. The misfit of lattice-mismatched layers is measured during pseudomorphic growth, allowing for experiments that test relationships between misfit and growth conditions. As an example, Bi incorporation in GaAs is quantified by varying the substrate temperature throughout growth while using curvature measurements to continuously calculate the composition. Results agree well with x-ray diffraction measurements on individual GaAsBi samples, demonstrating the utility of this technique for the study of incorporation in mismatched systems. Once relaxation begins, the strain and dislocation energetics of low-misfit epilayers are determined from changes in wafer curvature. The authors perform several analyses on GaInAs epilayers with different misfits using an anisotropic thin film approximation. Substantial information on dislocation formation and motion is derived from the wafer curvature. Potential applications of this technique include the study of devices that utilize coherently strained layers and structures that intentionally use dislocations to relieve strain. Wafer curvature is a powerful method for comparing strain evolution in mismatched materials.
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68.55.-a Thin film structure and morphology

Growth of epitaxial NiTi shape memory alloy films on GaAs(001) and evidence of martensitic transformation

J. Buschbeck, J. Kawasaki, T. E. Buehl, A. C. Gossard, and C. J. Palmstrøm

J. Vac. Sci. Technol. B 29, 03C116 (2011); http://dx.doi.org/10.1116/1.3556973 (5 pages)

Online Publication Date: 1 March 2011

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The molecular beam epitaxy growth of epitaxial NiTi shape memory alloy films on GaAs(001) semiconductor substrates is demonstrated. An ErAs interlayer was used as a template to promote the epitaxial growth and as a diffusion barrier to effectively suppress intermixing between NiTi film and GaAs substrate. Though the films are constrained by the substrate, temperature dependent x-ray diffraction and resistivity measurements reveal reversible martensitic transformations upon heating and cooling near room temperature.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.at Other materials
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder
64.70.kd Metals and alloys
81.30.Kf Martensitic transformations
81.40.Gh Other heat and thermomechanical treatments

Electrical properties of Er-doped In0.53Ga0.47As

Peter G. Burke, Hong Lu, Nicholas G. Rudawski, Susanne Stemmer, Arthur C. Gossard, Je-Hyeong Bahk, and John E. Bowers

J. Vac. Sci. Technol. B 29, 03C117 (2011); http://dx.doi.org/10.1116/1.3559480 (5 pages) | Cited 3 times

Online Publication Date: 3 March 2011

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The electrical properties of In0.53Ga0.47As thin films Er-doped to concentrations of 1.5×1017–7.2×1020 cm−3 grown by molecular beam epitaxy at 490 °C on (001) InP substrates were studied. Electrical conductivity, carrier density, and carrier mobility as a function of Er doping were measured by Hall effect at temperatures of 20–750 K. Additionally, high-angle annular dark-field scanning transmission electron microscopy and infrared absorption spectroscopy confirmed the presence of epitaxially embedded ErAs nanoparticles at Er concentrations ≥ 8×1019 cm−3. The observed electrical properties are discussed in terms of the dependence of ErAs nanoparticle formation with Er doping.
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73.61.Ey III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
78.66.Fd III-V semiconductors
61.72.uj III-V and II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
68.55.ag Semiconductors

Molecular beam epitaxy of metamorphic InyGa1−yP solar cells on mixed anion GaAsxP1−x/GaAs graded buffers

Stephanie Tomasulo, John Simon, Paul J. Simmonds, Jonathan Biagiotti, and Minjoo L. Lee

J. Vac. Sci. Technol. B 29, 03C118 (2011); http://dx.doi.org/10.1116/1.3559119 (6 pages) | Cited 1 time

Online Publication Date: 7 March 2011

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The authors have grown metamorphic InyGa1−yP on optimized GaAsxP1−x/GaAs graded buffers via solid source molecular beam epitaxy (MBE) for multijunction solar cell applications. In this work, the authors show that a previously developed kinetic growth model can be used to predict the composition of mixed anion GaAsxP1−x alloys on GaAs as a function of substrate temperature and group-V flux. The advantages of using a high growth temperature of 700 °C are then described, including the minimized dependence of composition on small temperature variations, a linear dependence of film composition on incident group-V flux ratio, and the ability to attain low threading dislocation densities of ≤ 106 cm−2. The authors then discuss the effect of faceted trenches, a morphological defect specific to tensile strain relaxation, on minority carrier properties, as well as strategies to eliminate them. Growth temperature effects, phase separation, and difficulties encountered in n-type doping of InAlP:Si are then described in the context of InyGa1−yP solar cell growth. The MBE growth techniques presented here have enabled the demonstration of 2.00 eV band gap metamorphic In0.39Ga0.61P solar cells, exhibiting open-circuit voltages as high as 1.42 V. These results indicate that metamorphic InyGa1−yP is a promising material for future multijunction solar cells.
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88.40.jp Multijunction solar cells
88.40.H- Solar cells (photovoltaics)

Optical measurements of single CdTe self-assembled quantum dots grown on ZnTe/GaSb

R. E. Pimpinella, A. M. Mintairov, X. Liu, T. H. Kosel, J. L. Merz, J. K. Furdyna, and M. Dobrowolska

J. Vac. Sci. Technol. B 29, 03C119 (2011); http://dx.doi.org/10.1116/1.3562182 (4 pages)

Online Publication Date: 9 March 2011

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The CdTe quantum dots (QDs) grown on a ZnTe epilayer deposited directly on a GaSb substrate are studied by transmission electron microscopy (TEM) and near-field scanning optical microscopy. High resolution TEM images show CdTe QD of planoconvex shape. Near-field photoluminescence (NPL) in an applied magnetic field is used to measure the Zeeman splitting and diamagnetic shift of single CdTe QDs. Finally, time resolved NPL measurements suggest that the higher energy lines in the CdTe QD NPL spectra correspond to exciton transitions occurring in larger CdTe QDs and have shorter exciton lifetimes.
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78.67.Hc Quantum dots
78.47.jd Time resolved luminescence
71.35.-y Excitons and related phenomena
73.21.La Quantum dots
78.20.Ls Magneto-optical effects
78.55.Et II-VI semiconductors

Two-dimensional III-V nucleation on Si for nonlinear optics

Angie C. Lin, James S. Harris, and M. M. Fejer

J. Vac. Sci. Technol. B 29, 03C120 (2011); http://dx.doi.org/10.1116/1.3562191 (5 pages)

Online Publication Date: 9 March 2011

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The nucleation of AlGaP and GaP on offcut (100) Si was studied by molecular beam epitaxy for the purpose of improving GaP films on Si. Atomic force microscopy and high-resolution transmission electron microscopy were used to characterize film quality. Significant reduction in surface rms roughness and antiphase domain annihilation within 30 nm of the III-V/Si interface was observed when using AlGaP as a nucleation layer. This technique was optimized for development of orientation-patterned GaP on Si for nonlinear optics but could also be applied to III-V integration on Si.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
68.35.bg Semiconductors
78.66.Fd III-V semiconductors
42.65.-k Nonlinear optics
68.55.ag Semiconductors

Atomic ordering and phase separation in MBE GaAs1−xBix

Andrew G. Norman, Ryan France, and Aaron J. Ptak

J. Vac. Sci. Technol. B 29, 03C121 (2011); http://dx.doi.org/10.1116/1.3562512 (5 pages) | Cited 3 times

Online Publication Date: 11 March 2011

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Transmission electron microscopy studies of GaAs1−xBix layers grown at low temperature by molecular beam epitaxy have revealed evidence of both atomic ordering and phase separation. In layers containing up to ∼ 10% Bi, the two variants of CuPtB-type atomic ordering on {111}B planes were observed and this is believed to be associated with the surface reconstruction present during growth. In a sample containing ∼ 13% Bi, no atomic ordering was observed but instead an anisotropic platelike structure was present that is believed to result from phase separation, possibly associated with the surface segregation of excess Bi during growth. Both of these effects are expected to have significant effects on the electrical and optical properties of the material.
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68.35.bg Semiconductors
68.55.ag Semiconductors

Self-aligned inversion-channel In0.2Ga0.8As metal-oxide-semiconductor field-effect transistor with molecular beam epitaxy Al2O3/Ga2O3(Gd2O3) as the gate dielectric

W. H. Chang, T. H. Chiang, Y. D. Wu, M. Hong, C. A. Lin, and J. Kwo

J. Vac. Sci. Technol. B 29, 03C122 (2011); http://dx.doi.org/10.1116/1.3565057 (4 pages) | Cited 1 time

Online Publication Date: 11 March 2011

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Self-aligned inversion-channel In0.2Ga0.8As metal-oxide-semiconductor field-effect transistors (MOSFETs) with in situ molecular beam epitaxy grown Al2O3/Ga2O3(Gd2O3) (GGO) as a gate dielectric and a TiN metal gate have been fabricated on GaAs (100) substrates. A 4 μm gate-length MOSFET using a gate dielectric of Al2O3 (3 nm thick)/GGO (8 nm thick) demonstrates a maximum drain current of 9.5 μA/μm and an extrinsic transconductance of 3.9 μS/μm. The device performances are compared favorably with those of other inversion-channel GaAs MOSFETs on GaAs (100) and also of the device on GaAs (111)A substrates using atomic layer deposited Al2O3 as a gate dielectric.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
85.30.Tv Field effect devices
77.55.dj For nonsilicon electronics (Ge, III-V, II-VI, organic electronics)

Enhanced normal incidence photocurrent in quantum dot infrared photodetectors

Jiayi Shao, Thomas E. Vandervelde, Ajit Barve, Woo-Yong Jang, Andreas Stintz, and Sanjay Krishna

J. Vac. Sci. Technol. B 29, 03C123 (2011); http://dx.doi.org/10.1116/1.3562186 (6 pages)

Online Publication Date: 18 March 2011

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The authors report an enhancement in the photocurrent caused by normal incidence (s-polarization) radiation in a quantum dot-in-a-well (DWELL) based infrared photodetector. The s-to-p polarization ratio was increased to 50%, compared to the 20% in conventional quantum dot (QD) detectors. This improvement was achieved through engineering the dot geometry and the quantum confinement via postgrowth capping materials of the QDs. The effect of the capping procedures was determined by examining the dot geometry using transmission electron microscopy (TEM) and s-to-p ratio of the polarized photocurrent in the DWELL infrared photodetector. The TEM image shows a quantum dot with a reduced base of 12 nm and an increased height of 8 nm. The infrared photodetector fabricated from this material shows peak photodetectivities of 1×109 cm Hz1/2/W at 77 K for a peak wavelength of 4.8 μm and 1×107 cm Hz1/2/W at 300 K for a peak wavelength of 3.2 μm. The dark current density is as low as 2×10−4 A/cm2 and the photoconductive gain is 100 at the optimal operating bias.
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85.60.Gz Photodetectors (including infrared and CCD detectors)

Epitaxial growth of CoxMnySiz (111) thin films in the compositional range around the Heusler alloy Co2MnSi

Liang He, Brian A. Collins, Frank Tsui, and Yong S. Chu

J. Vac. Sci. Technol. B 29, 03C124 (2011); http://dx.doi.org/10.1116/1.3567419 (5 pages)

Online Publication Date: 18 March 2011

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Epitaxial growth and structural properties of CoxMnySiz thin films on Ge (111) substrates, including the Heusler alloy Co2MnSi (111), have been studied using combinatorial molecular beam epitaxy (MBE) techniques. In situ reflection high energy electron diffraction and ex situ x-ray diffraction experiments show that high quality coherent MBE growth with fcc (111) stacking can be achieved over a relatively large composition space that includes Co2MnSi. The highest structural and chemical ordering is observed near the composition of Co0.63Mn0.14Si0.23 rather than that at the Heusler stoichiometry of Co2MnSi. The in-plane crystallographic axis of the fcc film exhibits a 60° rotation with respect to that of the Ge substrate. The rotation appears to be originated at the film-substrate interface, as a result of the symmetry and stacking of the Ge (111) surface reconstruction.
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81.05.Bx Metals, semimetals, and alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.bd Metals and alloys
68.55.at Other materials

In situ real time Auger analyses during oxides and alloy growth using a new spectrometer design

Philippe G. Staib

J. Vac. Sci. Technol. B 29, 03C125 (2011); http://dx.doi.org/10.1116/1.3562195 (6 pages)

Online Publication Date: 21 March 2011

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A new Auger electron spectrometer probe designed to monitor the surface composition during growth is presented. The device is able to operate without impairing the deposition process and is compatible with the environmental constraints of deposition chambers. Auger electron excitation can be generated by the electron beam used for reflection high energy electron diffraction studies, thus allowing simultaneous elemental and structural sample analyses. The Auger probe is mounted using one of the ports facing the sample, preferably at normal incidence angle. The distance between the sample surface and analyzer is large enough to clear the fluxes of material from multiple deposition sources commonly used in growth chambers. The probe has a variable energy resolution that can be electronically adjusted and can be set for higher sensitivity and shorter acquisition time or for better energy resolution. Examples of applications are shown to illustrate the capabilities of the instrument. In one example, the growth of zinc oxide (ZnO) layers is monitored during the deposition and in the other example, the stoichiometry of the lanthanide alloys (dysprosium and terbium) is deduced from the variation of the Auger MNN lines for pure elements and alloyed layers. In addition to AES, the probe provides reflection electron energy loss spectroscopy spectra of the distribution of characteristic energy losses.
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07.81.+a Electron and ion spectrometers
79.20.Uv Electron energy loss spectroscopy
68.55.ag Semiconductors
79.20.Fv Electron impact: Auger emission
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)

Metamorphic growth of III-V semiconductor bicrystals

C. J. K. Richardson, L. He, and S. Kanakaraju

J. Vac. Sci. Technol. B 29, 03C126 (2011); http://dx.doi.org/10.1116/1.3565436 (5 pages)

Online Publication Date: 21 March 2011

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The authors report on the structural properties of III-V semiconductor films that are not lattice matched to the GaAs substrates on which they are grown. Using molecular beam epitaxy, a uniform two-dimensional edge dislocation network is formed that abruptly relaxes the misfit strain at the film/substrate interface. The nucleation and initial growth of a GaSb film on GaAs are analyzed using reflection high-energy electron diffraction to show growth that becomes two dimensional in approximately five monolayers. Comparisons of the experimental reciprocal space map peak shapes and theoretical shapes show that some of these films are approaching the theoretical limit where all of the strain is completely relaxed at the interface.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
81.05.Ea III-V semiconductors
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
81.10.Aj Theory and models of crystal growth; physics and chemistry of crystal growth, crystal morphology, and orientation

Optical property improvement of InAs/GaAs quantum dots grown by hydrogen-plasma-assisted molecular beam epitaxy

A. V. Katkov, C. C. Wang, J. Y. Chi, C. Cheng, and A. K. Gutakovskii

J. Vac. Sci. Technol. B 29, 03C127 (2011); http://dx.doi.org/10.1116/1.3570870 (7 pages) | Cited 1 time

Online Publication Date: 28 March 2011

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An order-of-magnitude increase of photoluminescence (PL) efficiency at room temperature has been observed in the GaAs/InAs quantum dots (QDs)-in-a-well structure grown with in situ irradiation of atomic hydrogen supplied by a radio-frequency hydrogen-plasma source. The enhancement in PL intensity rapidly increases with the hydrogen flow rate and is stable with a variation of excitation power in the radio-frequency plasma source. Extensive thermal annealing of grown samples up to 634 °C did not show any significant degradation of photoluminescence intensity compared with the reference sample. The reduction of nonradiative recombination centers in the as-grown sample causes the greatly enhanced luminescence property. In addition to PL enhancement the authors observed that the H-assisted growth of InAs QDs has suppressed bimodal distribution of QD shape. In contrast to the hydrogen-plasma-assisted growth, irradiation by hydrogen in molecular form has a detrimental effect on the optical properties of similar structures. The high thermal stability of improved optical properties suggests that the formation of the defects which are responsible for nonradiative recombination channels is suppressed during H-assisted epitaxy although in situ defect passivation by atomic hydrogen cannot be completely ruled out.
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78.66.Fd III-V semiconductors
71.55.Eq III-V semiconductors
78.55.Cr III-V semiconductors
81.05.Ea III-V semiconductors
78.67.Hc Quantum dots
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Single-crystalline aluminum grown on MgAl2O4 spinel using molecular-beam epitaxy

Y. Lin, A. G. Norman, W. E. McMahon, H. R. Moutinho, C.-S. Jiang, and A. J. Ptak

J. Vac. Sci. Technol. B 29, 03C128 (2011); http://dx.doi.org/10.1116/1.3570869 (4 pages)

Online Publication Date: 29 March 2011

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Al thin films were grown on MgAl2O4 spinel substrates using solid-source molecular-beam epitaxy. The structural properties of Al layers were systematically investigated as a function of substrate orientation and growth temperature. Scanning electron microscopy and atomic force microscopy show that low growth temperatures lead to smoother and more coalesced Al films. X-ray diffraction and electron backscatter diffraction (EBSD) measurements demonstrate that Al layers are single crystalline and coherently grown on both (100)- and (111)-oriented spinel substrates. EBSD data also clearly reveal a high density of twin domain structures in Al films grown on (111) spinel substrates, and all twin boundaries were determined to be Σ3 boundaries. High-resolution transmission electron microscopy was used to confirm the presence of twin structures. Al grown on (001) spinel roughens more easily than Al grown on (111) spinel at higher growth temperatures. It is suggested that Al surface energy and thermal expansion mismatch play a critical role in the evolution of surface morphology of Al thin films grown on MgAl2O4 spinel.
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81.05.Bx Metals, semimetals, and alloys
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.35.Md Surface thermodynamics, surface energies
68.35.bd Metals and alloys
65.40.De Thermal expansion; thermomechanical effects
61.72.Mm Grain and twin boundaries

Reflection high energy electron diffraction investigation and comparison of the initial stage during molecular beam epitaxy of AlN on Si(111) and Si(110) substrates

Vladimir Mansurov, Xiaoyan Xu, Mahesh Pandikunta, Rakib Uddin, and Sergey Nikishin

J. Vac. Sci. Technol. B 29, 03C129 (2011); http://dx.doi.org/10.1116/1.3570922 (4 pages) | Cited 1 time

Online Publication Date: 29 March 2011

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The onset of AlN nucleation on Si(111) and Si(110) surfaces during gas source molecular beam epitaxy with ammonia was carried out by reflection high energy electron diffraction. Exposing the clean Si surfaces to NH3 flux at 600 °C yields the formation of crystalline Si3N4 on both (111) and (110) surfaces. An 8×8 Si3N4 structure was observed for the Si(111) surface. On the Si(110) surface a 2.87 Å periodic structure was observed for electron beam directed along [001] azimuth and 2.46 Å periodic structure for the [math12] azimuth. Together, these periodic structures confirm the formation of Si3N4 (0001) plane on both Si(111) and Si(110) surfaces.
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68.55.ag Semiconductors
68.35.bg Semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors

Growth and thermal conductivity analysis of polycrystalline GaAs on chemical vapor deposition diamond for use in thermal management of high-power semiconductor lasers

S. P. R. Clark, P. Ahirwar, F. T. Jaeckel, C. P. Hains, A. R. Albrecht, T. J. Rotter, L. R. Dawson, G. Balakrishnan, P. E. Hopkins, L. M. Phinney, J. Hader, and J. V. Moloney

J. Vac. Sci. Technol. B 29, 03C130 (2011); http://dx.doi.org/10.1116/1.3565054 (4 pages)

Online Publication Date: 11 April 2011

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The authors demonstrate the growth of polycrystalline GaAs thin films on polycrystalline chemical vapor deposition (CVD) diamond by low-temperature molecular beam epitaxy. The low-temperature GaAs (LT-GaAs) layer is easily polished compared to the CVD diamond, and this process results in a reduction of rms surface roughness from >50 to <5 nm. This makes the LT-GaAs on diamond layer an ideal wafer-bonding interface for high-power semiconductor devices. The samples were grown at 0.2 μm/h with a substrate temperature of 250 °C and a 1:8 III/V beam equivalent pressure ratio. The samples were analyzed by x-ray powder diffraction, atomic force microscopy for surface roughness, and in situ reflective high-energy electron diffraction during molecular beam epitaxy growth. The authors also measure the thermal conductivity of the GaAs layer on CVD diamond using pump-probe time domain thermoreflectance.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
81.05.Ea III-V semiconductors
66.70.Df Metals, alloys, and semiconductors
68.55.ag Semiconductors

Formation of single-orientation epitaxial islands of TiSi2 on Si(001) using Sr passivation

A. Posadas, R. Dargis, M. R. Choi, A. Slepko, A. A. Demkov, J. J. Kim, and D. J. Smith

J. Vac. Sci. Technol. B 29, 03C131 (2011); http://dx.doi.org/10.1116/1.3579598 (6 pages) | Cited 1 time

Online Publication Date: 14 April 2011

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Epitaxial islands of C49-phase TiSi2 of up to 100 nm in size, and with a single crystallographic orientation, have been fabricated on Si(001) substrates. The growth process involves passivation of the Si surface using Sr, followed by deposition of Ti in the form of SrTiO3, which prevents the reaction between Ti and Si. Decomposition of SrTiO3 at temperatures above 800 °C drives off Sr and O completely, leaving epitaxial islands of TiSi2 dispersed on the Si surface. The TiSi2 islands have (010) orientation and an in-plane epitaxial relationship of Si[110]∥TiSi2[100]. Density functional calculations of the surface and interface energies show that the island sizes and contact angles are consistent with surface energy minimization.
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81.16.-c Methods of micro- and nanofabrication and processing
61.46.-w Structure of nanoscale materials
68.03.Cd Surface tension and related phenomena
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

High In content InxGa1−xN grown by energetic neutral atom beam lithography and epitaxy under slightly N-rich conditions

Todd L. Williamson, Joshua J. Williams, Jonathan C. D. Hubbard, and Mark A. Hoffbauer

J. Vac. Sci. Technol. B 29, 03C132 (2011); http://dx.doi.org/10.1116/1.3581870 (5 pages)

Online Publication Date: 19 April 2011

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Two series of In-rich InGaN films with compositions of ∼ 25% and ∼ 35% In, grown over a substrate temperature range from 490 to 620 °C, show how the film properties improve as the growth temperature is lowered below the InN decomposition temperature of ∼ 550 °C in vacuum. These InGaN films have been grown using a novel growth technique utilizing energetic N atoms as the active growth species. Under N-rich growth conditions, these InGaN films show how compositional uniformity, crystallinity, band edge photoluminescence, and surface morphology are improved as growth temperatures are reduced. The results emphasize the importance of energetic N atoms and lower substrate temperatures for overcoming difficulties associated with growing high-quality In-rich InxGa1−xN thin film materials. Utilizing energetic N atoms allows for the growth of high-quality, thick (>500 nm) InxGa1−xN films at temperatures below 500 °C.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
81.05.Ea III-V semiconductors
68.55.ag Semiconductors
78.55.Cr III-V semiconductors
68.35.bg Semiconductors

Atomic-scale modeling of InxGa1−xN quantum dot self-assembly

Zhenli Zhang, Alok Chatterjee, Christoph Grein, Anthony J. Ciani, and Peter W. Chung

J. Vac. Sci. Technol. B 29, 03C133 (2011); http://dx.doi.org/10.1116/1.3579462 (7 pages)

Online Publication Date: 26 April 2011

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The authors simulate in three dimensions the molecular beam epitaxial growth of InxGa1−xN with classical molecular dynamics. Atomic interactions are simulated with Stillinger–Weber potentials. Both homoepitaxial and heteroepitaxial growths are studied. The effects of substrate temperature and indium concentration on quantum dot morphology, concentration profiles, and the thickness of wetting layers qualitatively agree with experimental findings. The authors’ simulations support earlier suggestions that quantum dot formation in the InGaN/GaN system is governed by a stress-driven phase separation mechanism.
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81.07.Ta Quantum dots
81.05.Ea III-V semiconductors

Growth of AlGaN containing nanometer scale compositional inhomogeneities for ultraviolet light emitters

A. V. Sampath, G. A. Garrett, R. W. Enck, P. Rottella, Jr., H. Shen, and M. Wraback

J. Vac. Sci. Technol. B 29, 03C134 (2011); http://dx.doi.org/10.1116/1.3585660 (4 pages)

Online Publication Date: 16 May 2011

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The incorporation of nanometer scale compositional inhomogeneities in AlGaN has a great promise for improving the performance of UV light emitting diodes based on these materials by suppressing nonradiative recombination associated with dislocations. In this article, the authors report on the growth and characterization of AlGaN containing nanometer scale compositional inhomogeneity (NCI-AlGaN) alloys deposited by plasma-assisted molecular beam epitaxy. Growth under N-limited and nearly stoichiometric growth is observed to enhance the photoluminescence intensity in AlGaN alloys by promoting the spontaneous formation of these NCI regions. This is attributed to the lower adatom mobility of group III and N species on the AlGaN layer surface under these conditions as well as the formation of beneficial surface faceting.
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85.60.Jb Light-emitting devices

High quality m-plane GaN grown under nitrogen-rich conditions by plasma assisted molecular beam epitaxy

Marta Sawicka, Anna Feduniewicz-Żmuda, Henryk Turski, Marcin Siekacz, Szymon Grzanka, Marcin Kryśko, Igor Dzięcielewski, Izabella Grzegory, and Czesław Skierbiszewski

J. Vac. Sci. Technol. B 29, 03C135 (2011); http://dx.doi.org/10.1116/1.3589228 (5 pages) | Cited 2 times

Online Publication Date: 18 May 2011

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Homoepitaxial growth of m-plane GaN (1math00) as a function of substrate miscut and temperature was studied by plasma assisted molecular beam epitaxy (PAMBE). The authors demonstrate that it is possible to obtain high-quality GaN on the m-plane under nitrogen-rich conditions at 730 °C. This is in contrast to the c-plane where three-dimensional growth mode is observed under the same conditions. They find a strong growth anisotropy and describe GaN (1math00) surface morphology dependence on the sample miscut direction. The results indicate that by introducing a sample miscut toward 〈11mathmath〉 one may expect parallel atomic steps when growing under nitrogen-rich conditions at 730 °C by PAMBE.
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81.05.Ea III-V semiconductors
68.47.Fg Semiconductor surfaces
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.ag Semiconductors
52.77.Dq Plasma-based ion implantation and deposition
68.35.bg Semiconductors

Growth mechanism of InGaN by plasma assisted molecular beam epitaxy

H. Turski, M. Siekacz, M. Sawicka, G. Cywinski, M. Krysko, S. Grzanka, J. Smalc-Koziorowska, I. Grzegory, S. Porowski, Z. R. Wasilewski, and C. Skierbiszewski

J. Vac. Sci. Technol. B 29, 03C136 (2011); http://dx.doi.org/10.1116/1.3590932 (5 pages)

Online Publication Date: 20 May 2011

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In this article, the authors discuss the mechanism of InGaN growth by plasma assisted molecular beam epitaxy. They present the evidence of the influence of substrate miscut on indium incorporation for the growths with different gallium fluxes. They propose and discuss the phenomenological model which describes the incorporation of indium into InGaN layers grown under the indium-rich conditions that takes into account following parameters: gallium and nitrogen fluxes, miscut angle, and the growth temperature.
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81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth

Photoluminescence and secondary ion mass spectrometry study of layer-by-layer grown Zn1−xCdxSe quantum wells

I. Hernández-Calderón, M. García-Vázquez, L. M. Hernández-Ramírez, and M. A. Vidal

J. Vac. Sci. Technol. B 29, 03C137 (2011); http://dx.doi.org/10.1116/1.3590721 (3 pages)

Online Publication Date: 25 May 2011

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Quantum wells of Zn1−xCdxSe can be grown in a layer-by-layer mode by submonolayer pulsed beam epitaxy (SPBE). The authors present the results of the characterization of a sample containing three quantum wells with different Cd contents produced without interrupting the growth process or changing the effusion cell temperatures. The quantum wells exhibit intense and narrow excitonic emission. Information about their structure and composition was obtained by means of low temperature photoluminescence and secondary ion mass spectrometry. A very good agreement was observed between both techniques, demonstrating that SPBE offers a great control of quantum well thickness and composition.
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81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
73.21.Fg Quantum wells
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
71.35.-y Excitons and related phenomena
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