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Jul 1984

Volume 2, Issue 3, pp. 301-603


Negative resist profiles in x‐ray lithography

Yoshiki Suzuki, Nobuyuki Yoshioka, and Teruhiko Yamazaki

J. Vac. Sci. Technol. B 2, 301 (1984); http://dx.doi.org/10.1116/1.582813 (5 pages) | Cited 1 time

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The processing characteristics of a negative resist (CPMS) exposed with a x‐ray exposure system are studied by a comparison between developed profiles and calculated results of absorbed energy in the resist. In fine lines, reduction in volume is caused by vertical and horizontal shrinkage. In patterns which cover large areas, where the resist is fixed to the substrate by the adhesion between the resist and the substrate, the reduction in volume is mainly caused by the vertical shrinkage, while the horizontal shrinkage causes deformation of the profile at the pattern edge. This fact means that the normalized thickness for the large patterns agrees with the volume reduction ratio for the fine lines. These results are applied to a simulation program to estimate the profiles of the negative resist exposed with a x‐ray exposure system. The program is based on the sensitivity curve of the resist. The theoretical results calculated with the program agree well with the experimental results in the case where penumbral shadows due to mask to wafer gap exist.
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81.65.-b Surface treatments
75.20.Ck Nonmetals

A low‐energy, ultrahigh vacuum, solid‐metal ion source for accelerated‐ion doping during molecular beam epitaxy

A. Rockett, S. A. Barnett, and J. E. Greene

J. Vac. Sci. Technol. B 2, 306 (1984); http://dx.doi.org/10.1116/1.582814 (8 pages) | Cited 9 times

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The design and operation of a compact single‐grid, ultrahigh‐vacuum‐compatible, low‐energy ion gun capable of utilizing gaseous, liquid, or solid source material are described. The gun can provide >100 μA/cm2 at ion energies ranging from 20 to 500 eV, and grid and filament lifetimes of several hundred hours have been obtained while operating with Zn and As. Current–voltage characteristics of the source as well as resulting ion beam profiles are reported. With appropriate grid design, uniform ion beam intensities were obtained over 4 cm diam wafers at a distance of 20 cm from a 1 cm diam ion source. In initial experiments using the ion source for accelerated‐ion doping of (100)Si and (100)GaAs, several orders of magnitude increases in elemental As and Zn incorporation probabilities were observed.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
41.75.Ak Positive-ion beams
41.75.Cn Negative-ion beams
61.72.U- Doping and impurity implantation

Interface properties of Al–SiO2–In0.53Ga0.47As MIS devices

C. C. Shen and K. P. Pande

J. Vac. Sci. Technol. B 2, 314 (1984); http://dx.doi.org/10.1116/1.582815 (2 pages) | Cited 2 times

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n‐In0.53Ga0.47As MIS capacitors with SiO2 dielectric films have been investigated. The SiO2 films, which were deposited by a novel low temperature process, exhibit stoichiometric composition. The MIS devices show a sharp interface and a minimum interface state density of 7×1011 cm−2 eV−1. The devices also show small hysteresis effects.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
77.55.-g Dielectric thin films
84.32.-y Passive circuit components

Thermal nitridation of silicon: An XPS and LEED investigation

C. Maillot, H. Roulet, and G. Dufour

J. Vac. Sci. Technol. B 2, 316 (1984); http://dx.doi.org/10.1116/1.582816 (4 pages) | Cited 24 times

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Two thermal, low pressure nitridation processes are achieved on silicon(111), using two different nitridant gases, and studied in situ by x‐ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED). The results show two different growth rates but the same evolution of the electronic and surface crystallographic stucture. A correlation is established between XPS and LEED measurements, associating the characteristic ‘‘quadruplet’’ patterns with the presence of intermediate nitrides. On the contrary, such compounds are absent when the LEED displays ‘‘8×8’’ patterns. Complementary results by reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM), permit us to conclude that our thickest films, up to 40 Å, are stoichiometric Si3N4, poorly crystallized in the β phase, presenting no surface rugosity.
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68.55.-a Thin film structure and morphology
81.65.-b Surface treatments
73.61.Ng Insulators
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Vacuum evaporation system for depositing thick polycrystalline silicon

Yusuke Ota and Raymond A. Clapper

J. Vac. Sci. Technol. B 2, 320 (1984); http://dx.doi.org/10.1116/1.582817 (7 pages) | Cited 1 time

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Thick polysilicon (>1 mm) deposition on heated SiO2‐coated silicon substrates at high deposition rate (≥4 μm/min) at temperatures to 1100 °C was achieved by vacuum evaporation of silicon using two high power e guns. The deposition system was able to accommodate ten 75 mm diam substrates or eight 100 mm diam substrates. The system was designed as an alternative to the CVD process for depositing polysilicon material for dielectrically isolated integrated circuit substrates. This paper describes the system design and its capabilities.
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81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Xx Hybrid microelectronics; thick films

Displacements parallel to the surface of reconstructed GaAs(110)

C. B. Duke and A. Paton

J. Vac. Sci. Technol. B 2, 327 (1984); http://dx.doi.org/10.1116/1.582818 (5 pages) | Cited 2 times

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Analysis of measured elastic low energy electron diffraction (ELEED) intensities from GaAs(110) reveals that the relaxations parallel to the surface associated with a ω1=29° bond‐length‐conserving rotated surface structure can be reduced by 75% without substantially affecting the quality of the model description of these intensities. Optimizing the surface geometry while constraining the atomic displacements parallel to the surface to be zero, however, leads to a significantly inferior description of these data. A model embodying greatly reduced but nonzero parallel displacements is compatible both with the ELEED intensities and with recent ion channeling data.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.66.Fn Inorganic compounds
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

A method of mounting small samples for surface analysis

Paul L. Gutshall

J. Vac. Sci. Technol. B 2, 332 (1984); http://dx.doi.org/10.1116/1.582819 (1 page)

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Abstract Unavailable
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06.60.Ei Sample preparation (including design of sample holders)

Investigation of the surface structure of GaAs(110) by high energy ion channeling

H.‐J. Gossmann and W. M. Gibson

J. Vac. Sci. Technol. B 2, 343 (1984); http://dx.doi.org/10.1116/1.582820 (3 pages) | Cited 1 time

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The first application of high energy ion channeling for the structure determination of the atomically clean GaAs(110) surface is reported. It is found that the surface Ga and As atoms have small lateral displacements (≤0.1 Å) from ideal bulklike sites, whereas a normal component of the first layer shear vector as large as 0.7 Å is compatible with the experimental data. The implications of these results with respect to current LEED models are discussed.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
61.85.+p Channeling phenomena (blocking, energy loss, etc.)

High resolution measurement of the step distribution at the Si/SiO2 interface

M. Henzler and P. Marienhoff

J. Vac. Sci. Technol. B 2, 346 (1984); http://dx.doi.org/10.1116/1.582821 (3 pages) | Cited 2 times

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With a recently developed high resolution LEED instrument spot profiles of the 00–beam of Si/SiO2 interfaces have been taken after the removal of the oxide. It is demonstrated, that beyond the half‐width the full profile down to a hundredth of peak intensity gives valuable information. The distribution of terraces up to more than 50 nm contribute essentially to a sharp central spike, which is only visible with a high resolution system. Whereas with usual LEED optics only terraces up to about 20 nm are evaluated from spot profile, the present data for the first time allow an evaluation in an extended range of terrace widths besides step atom density. Model calculations show the influence of instrument response and of details of the terrace width distribution on the spot profile.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Summary Abstract: Direct observation of band mixing in GaAs–(AlxGa1−x)As quantum heterostructures

R. Sooryakumar, D. S. Chemla, A. Pinczuk, A. Gossard, W. Weigmann, and L. J. Sham

J. Vac. Sci. Technol. B 2, 349 (1984); http://dx.doi.org/10.1116/1.582822 (2 pages) | Cited 5 times

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Abstract Unavailable
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.40.Fy Semiconductors
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

The oxidation of GaAs(110): A reevaluation

G. Landgren, R. Ludeke, Y. Jugnet, J. F. Morar, and F. J. Himpsel

J. Vac. Sci. Technol. B 2, 351 (1984); http://dx.doi.org/10.1116/1.582823 (8 pages) | Cited 43 times

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Photoemission spectra of 3d core levels excited with synchrotron radiation reveal a multicomponent substructure which increases in complexity with oxygen exposures over the range 106–1014L (langmuir). Spectral changes are already evident for Ga at 104 L, and for As near 106 L. Two oxide components shifted by 0.45 and 1 eV relative to the bulk Ga‐3d core level are evident throughout the exposure range, but shift to 0.8 and 1.4 eV for 1014 L. With increasing exposure the As‐3d core level develops a sequential set of shifted components at 0.8, 2.3, 3.2, and 4.2 eV relative to the bulk position in GaAs, which are attributed to single through fourfold coordinated bond formation to oxygen. Both surface and bulk‐sensitive core spectra reveal a nearly equally intense oxide substructure, which indicates that contrary to previous notions subsurface oxidation is the dominant mechanism throughout the exposure range. The core spectra furthermore indicate preferential Ga oxidation—which suggests that separate Ga and As oxide phases form. Thus the oxidation of GaAs(110) is both spatially and chemically inhomogeneous. Changes in the position of the Fermi energy at the surface correlate well with the initial oxidation of surface sites and the onset of subsurface oxidation near 106 L. A final pinning position of the Fermi energy was not observed.
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81.65.-b Surface treatments

Adsorption of H, O, and H2O at Si(100) and Si(111) surfaces in the monolayer range: A combined EELS, LEED, and XPS study

J. A. Schaefer, F. Stucki, D. J. Frankel, W. Göpel, and G. J. Lapeyre

J. Vac. Sci. Technol. B 2, 359 (1984); http://dx.doi.org/10.1116/1.582824 (7 pages) | Cited 20 times

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This paper is a summary of a series of experiments studying the exposure of hydrogen, oxygen, and water, on the (2×1) surfaces of Si(100) and Si(111). While the primary focus has been on high resolution electron energy loss (EELS) results, low energy electron diffraction (LEED) and x‐ray photoelectron spectroscopy (XPS) are also used in the studies. Both the (100) and cleavage (111) surfaces form a monohydride and a dihydride exhibiting a (2×1) and a (1×1) LEED pattern, respectively. These systems exhibit saturation, which is consistent with the model of hydrogen saturation of the dangling bonds. Upon water adsorption the Si–H and Si–OH vibronic modes are observed, indicating that water is decomposed. On the cleavage surface only, there is evidence of a very weak scissor mode, allowing for the possibility of a few percent of molecular water adsorption. Oxygen adsorption is complex. For samples formed at high temperatures (∼1000 K) the observed vibronic features are similar to those known for the Si–O–Si complexes in vitreous glasses. For thin oxide layers (0.5<θ<1.3 monolayers) a linear relationship is observed between oxygen coverage and asymmetric mode frequency. These data are fit with models developed for glasses which, for the monolayer regime, yield an average bond angle of about 130° and a bond distance of 1.65 Å. The results support the model in which the oxygens are envisioned as being inserted into the Si–Si back bonds.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

The ZnSe(110) puzzle: Comparison with GaAs(110)

C. B. Duke, A. Paton, A. Kahn, and D‐W Tu

J. Vac. Sci. Technol. B 2, 366 (1984); http://dx.doi.org/10.1116/1.582825 (5 pages) | Cited 3 times

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New low‐temperature (T∼200 K) elastic low‐energy electron diffraction (ELEED) intensity data obtained for ZnSe films grown epitaxially on GaAs(110) are analyzed using an R‐factor methodology. The differences between the measured ELEED intensities for ZnSe(110) and those for GaAs(110) reveal the possibility that these two surfaces may not exhibit comparable atomic geometries. A bond‐length‐conserving top‐layer rotation of the Se species outward and the Zn inward corresponding to ω1=4° provides a description of the measured intensities (Rx =0.22, RI =0.21) comparable to that afforded by the ZnSe(110) analog of the GaAs(110) structure (a relaxed version of an ω1=29° structure, Rx =0.24, RI =0.16). Since GaAs and ZnSe exhibit essentially identical bulk lattice constants, the possibility that their (110) surfaces exhibit different atomic geometries poses a puzzle within the framework of current understanding of this topic.
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68.55.-a Thin film structure and morphology
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

New approach to the k⋅ p theory of semiconductor superlattices

C. Mailhiot, T. C. McGill, and D. L. Smith

J. Vac. Sci. Technol. B 2, 371 (1984); http://dx.doi.org/10.1116/1.582826 (5 pages) | Cited 8 times

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Along with the growing interest in semiconductor superlattices, various theoretical schemes have been proposed to study the nature of the electronic states within these structures. The work presented here highlights a new method to investigate the electronic and optical properties of semiconductor superlattices. The backbone of the theory rests on a realistic description of the complex‐k band structure of the constituent semiconductors coupled with a suitable set of boundary conditions for the superlattice wave function. The bulk Bloch solutions, propagating and evanescent, in each semiconductor are described within a full‐zone k ⋅ p Hamiltonian that provides an accurate description of the solutions up to the first Brillouin zone edge. An attractive feature of the present treatment is that the complex‐k bulk Bloch solutions of each constituent semiconductor are expanded on the same set of zone‐center basis functions. A new technique for constructing the k ⋅ p Hamiltonian of each constituent semiconductor is presented. The superlattice wave function is described by a linear combination of propagating and evanescent bulk Bloch solutions. The expansion amplitudes are determined by imposing a set of boundary conditions on the superlattice wave function across the superlattice interfaces. These boundary conditions are used to formulate an eigenvalue problem whose solution yields directly the corresponding superlattice states associated with real or complex superlattice wave vector q. This method provides an accurate technique to treat superlattices where one of the constituent semiconductors has an indirect energy band gap. An exposition of the formalism is presented, and the physical origin of the superlattice states is studied. The test case of the GaAs–AlAs (100) superlattice is presented. Pertinent applications are also discussed.
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71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.10.-w Theories and models of many-electron systems
78.20.Bh Theory, models, and numerical simulation

Binding energies of acceptors in GaAs–AlxGa1−xAs quantum wells

W. T. Masselink, Yia‐Chung Chang, and H. Morkoç

J. Vac. Sci. Technol. B 2, 376 (1984); http://dx.doi.org/10.1116/1.582827 (7 pages) | Cited 7 times

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We have used the variational method to calculate the acceptor binding energies in GaAs–AlxGa1−xAs quantum wells. The calculation includes the coupling of the top four valence bands of both materials in the multiband effective mass approximation. To ensure the convergence of the calculation, a large number of basis functions which are made up of the s‐like or d‐like spatial states multiplied by j=3/2 spinors are used for the expansion of the acceptor wave function. Because the quantum well potential reduces the symmetry from Td to D2d, the bulk Γ8 acceptor ground state splits into Γ6 and Γ7 states. The Γ6 state is predominantly derived from the heavy‐hole subband and the Γ7 state is predominantly derived from the light‐hole subband. We have calculated the binding energies of the Γ6 state (measured from the top of the heavy‐hole subband) and the Γ7 state (measured from the top of the light‐hole subband) for both center doped and edged doped quantum wells for various barrier heights as functions of well width. Except for well widths smaller than ≊40 Å, the Γ7 binding energy is greater than the Γ6 binding energy. In recent studies, the photoluminescence resulting from the acceptor levels to conduction band transition in MBE grown GaAs–AlGaAs superlattices has been measured. Our theoretical results are in excellent agreement with these experimental data.
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73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.40.Fy Semiconductors
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Summary Abstract: (110) surface geometry of GaAs

D. J. Chadi

J. Vac. Sci. Technol. B 2, 383 (1984); http://dx.doi.org/10.1116/1.582828 (1 page)

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Abstract Unavailable
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

High resolution electron energy loss studies of Fermi level states of clean and metallized Si(111) surfaces

J. E. Demuth and B. N. J. Persson

J. Vac. Sci. Technol. B 2, 384 (1984); http://dx.doi.org/10.1116/1.582829 (6 pages) | Cited 2 times

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High resolution electron energy loss spectroscopy has been performed as a function of temperature (15–300 K) to determine the electronic transitions of clean and metallized Si(111) surfaces. A quantitative analysis of these EELS results is used to delineate and identify the localized and delocalized states at the Fermi level. Si(111)‐7×7 is found to have a 100 meV surface state band gap in which lies a narrow, half occupied state that determines the Fermi level. Hydrogen titration studies suggest densities of these states at ∼1.6×1013/cm2. In contrast, metal impurity stabilized Si(111)‐1×1 surfaces are not found to have these narrow states at EF. Au overlayers on Si(111)‐1×1 produce a metallic overlayer for coverages above ∼1.6×1015 Au/cm2. Pd reaction with Si(111)‐1×1 forms a semimetal or semiconducting compound at coverages ≲1×1015 atoms/cm2 and appears to generate narrow partially occupied Si states at the interface. At higher Pd coverages a metallic silicide forms which uniformly covers the surface.
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73.20.-r Electron states at surfaces and interfaces
73.20.Hb Impurity and defect levels; energy states of adsorbed species
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
81.65.-b Surface treatments

Electronic states of the (100) (2×1) reconstructed Ge surface

David V. Froelich, Marshall A. Bowen, and John D. Dow

J. Vac. Sci. Technol. B 2, 390 (1984); http://dx.doi.org/10.1116/1.582830 (3 pages)

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We present calculations of the surface electronic state dispersion curves E(math) of the (100) (2×1) reconstructed surface of Ge, and compare them with recent angle‐resolved photoelectron measurements by Nelson et al. We assumed Chadi’s asymmetric dimer model of the surface reconstruction and performed our calculations using the analytic Green’s function technique, with an empirical tight‐binding Hamiltonian.
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73.20.-r Electron states at surfaces and interfaces
81.65.-b Surface treatments

The geometric structures of the GaAs(111) and (110) surfaces

S. Y. Tong, W. N. Mei, and G. Xu

J. Vac. Sci. Technol. B 2, 393 (1984); http://dx.doi.org/10.1116/1.582831 (6 pages) | Cited 13 times

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We present results of a reconstruction model proposed for the (2×2) GaAs(111) surface, together with a reexamination of the (1×1) GaAs(110) surface structure. Our model indicates that the reconstruction mechanisms on the (111) and (110) surfaces are similar to one another. In both cases, surface electronic energies are lowered via orbital rehybridization between nearest neighbor Ga and As atoms with dangling bonds. Reexamination of the GaAs(110) surface structure confirms our previous result of a tilt angle of ω=27°±2° and rejects a recently proposed value of ω=7°.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.20.-r Electron states at surfaces and interfaces

Summary Abstract: Total‐energy study of the vacancy model for the GaAs(111) surface

D. J. Chadi

J. Vac. Sci. Technol. B 2, 399 (1984); http://dx.doi.org/10.1116/1.582832 (1 page)

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Abstract Unavailable
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73.20.Hb Impurity and defect levels; energy states of adsorbed species

Morphological and chemical considerations for the epitaxy of metals on semiconductors

R. Ludeke

J. Vac. Sci. Technol. B 2, 400 (1984); http://dx.doi.org/10.1116/1.582833 (7 pages) | Cited 2 times

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The generally strong chemical interactions between semiconductors and metals introduce additional complexities in the experimental characterization and modelling of epitaxial growth. This article reviews the relevant epitaxial parameters and growth modes in relation to what is known to occur on semiconductors. A salient property of some metals and semimetals is their tendency to form covalent bonds, whose directionality strongly influences the epitaxial relationship between substrate and overgrowth. Both the substrate orientation and, for the binary semiconductors, the stoichiometry of the substrate, strongly influence the epitaxial relationships. Representative examples of the different growth modes are discussed in relation to interfacial bonding, with emphasis on the growth differences between Al, a reactive metal, and Ag, a nonreactive metal on GaAs. The latter part of the article discusses some of the outstanding issues of the epitaxy of metals on semiconductors and possible approaches to their solution.
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68.55.-a Thin film structure and morphology

Summary Abstract: Ge deposition on Si(111)‐7×7 and Si(100)‐2×1: Effects on Si surface structure

H.‐J. Gossmann, L. C. Feldman, and W. M. Gibson

J. Vac. Sci. Technol. B 2, 407 (1984); http://dx.doi.org/10.1116/1.582834 (2 pages)

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Abstract Unavailable
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68.55.-a Thin film structure and morphology
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Heats of solution and substitution in semiconductors

Edgar A. Kraut and Walter A. Harrison

J. Vac. Sci. Technol. B 2, 409 (1984); http://dx.doi.org/10.1116/1.582835 (6 pages) | Cited 9 times

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The heats of solution and substitution for one semiconductor in another are important quantities for an understanding of heterojunction formation. Harrison’s universal‐parameter tight‐binding method (1983) is used to obtain predictions for these quantities and for cohesive energies, defect formation energies, and solid‐state core shifts as well. The cohesive energies and solid‐state core‐shifts are compared with experiment and antistructure defect energies are compared with earlier calculations by Van Vechten. Cohesive energies are accurate to about one‐half an electron volt per bond. Agreement between experimental and theoretical cohesive energy differences is better. Predicted heats of solution and substitution depend on cohesive energy differences and therefore are likely to be realiable and are in accord with experiment in the few cases where experimental values are available. Antistructure defect formation energies agree well with Van Vechten’s earlier work. Predicted solid‐state core shifts are only accurate to a few electron volts.
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65.20.-w Thermal properties of liquids
65.40.gd Entropy
82.60.Cx Enthalpies of combustion, reaction, and formation
05.70.-a Thermodynamics

Summary Abstract: Ge–GaAs heterostructures: From chemisorption to heterojunction interface formation

P. Krüger and J. Pollmann

J. Vac. Sci. Technol. B 2, 415 (1984); http://dx.doi.org/10.1116/1.582885 (2 pages)

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Abstract Unavailable
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Summary Abstract: Growth of high quality (100)CdTe films on (100)GaAs substrates by molecular beam epitaxy

R. N. Bicknell, N. C. Giles‐Taylor, R. W. Yanka, J. F. Schetzina, T. J. Magee, C. Leung, H. Kawayoski, and G. R. Woolhouse

J. Vac. Sci. Technol. B 2, 417 (1984); http://dx.doi.org/10.1116/1.582886 (2 pages) | Cited 6 times

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Abstract Unavailable
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68.55.-a Thin film structure and morphology

RHEED oscillation studies of MBE growth kinetics and lattice mismatch strain‐induced effects during InGaAs growth on GaAs(100)

B. F. Lewis, T. C. Lee, F. J. Grunthaner, A. Madhukar, R. Fernandez, and J. Maserjian

J. Vac. Sci. Technol. B 2, 419 (1984); http://dx.doi.org/10.1116/1.582887 (6 pages) | Cited 38 times

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We present the first report of RHEED intensity changes and recovery as a function of monolayer and submonolayer MBE depositions of InxGa1−xAs (x≤0≤0.5) on GaAs(100) substrates. The influence of the lattice mismatch‐induced strain on the growth mechanisms and the incorporation behavior of In and Ga is suggested by new and In concentration dependent effects in the RHEED intensity waveform behavior during growth. The monolayer oscillation period is determined by the combined In and Ga fluxes. The initial growth of InGaAs on GaAs(100) is planar, but after an amount of deposition depending upon InAs content and growth conditions, a sudden change from a streaked reflection pattern to a spotty transmission pattern is observed indicating formation of 3D islands. The film thickness at which this transition occurs is strongly influenced by the step density of the GaAs surface when InGaAs growth is initiated. We have examined the recovery behavior of the specular spot intensity after the growth of 0.1 to 15 monolayers of GaAs on an annealed metal‐stabilized GaAs(100) surface. In this experiment, the RHEED intensity has dropped from its initial (no‐growth) value and, after termination of growth, it slowly recovers to its steady‐state value. We report RHEED intensity recovery rates as a function of the number of monolayers of GaAs deposited and compare them to recovery rates after steady‐state growth has been reached. The recovery rate is a strong function of the completeness of the surface when growth is stopped.
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68.55.-a Thin film structure and morphology
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

Summary Abstract: Thermodynamics of monolayer formation on an impure substrate

P. Gelband and S. Doniach

J. Vac. Sci. Technol. B 2, 425 (1984); http://dx.doi.org/10.1116/1.582888 (2 pages)

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Abstract Unavailable
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68.35.Md Surface thermodynamics, surface energies
68.55.-a Thin film structure and morphology
64.60.-i General studies of phase transitions
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

A theoretical study of the epitaxial growth of metal overlayers on semiconductor surfaces

Inder P. Batra and S. Ciraci

J. Vac. Sci. Technol. B 2, 427 (1984); http://dx.doi.org/10.1116/1.582889 (6 pages) | Cited 1 time

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We report on the energetics for the epitaxial growth of metals on semiconductors and obtain optimal interplanar distances using the self‐consistent pseudopotential method. A prototype system for which the lattice mismatch is not too severe has been considered so that the lattice can strain elastically to achieve coherency. An example of such a system is Al(001)–Ge(001) in an epitaxial relation (001)[100]Al∥(001)[110]Ge where the [100]Al axis has been rotated 45° with respect to the Ge [100] axis. We have investigated the pseudomorphic growth of Al from submonolayer to multilayers (in various registry patterns) on the rigid unreconstructed Ge(001) substrate. One significant result of our calculation is that the A1–Ge bond length relaxes as one goes from submonolayer to multilayer coverages of metal indicating a transition from directional covalent to more metallic type of bonding. Another important conclusion is that at monolayer coverages, aluminum at bridging positions in the first layer is more stable (∼1 eV) than at on top positions. This suggests that Frank–van der Merwe growth sequence is likely to initiate at the bridging sites. Furthermore, the energy lost due to an overall strain in pseudomorphically growing many layers is estimated to be well below the energy benefit due to interfacial bonding in bridging sites. We also report that the calculated interfacial bonding energy and the interplanar separation reaches limiting values at about one monolayer coverage, but other properties show slow convergence. The implications of these results for the electronic structure of interfaces and Fermi‐level pinning are briefly investigated.
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68.55.-a Thin film structure and morphology
73.20.-r Electron states at surfaces and interfaces
73.40.Ns Metal-nonmetal contacts

Barrier control and measurements: Abrupt semiconductor heterojunctions

Herbert Kroemer

J. Vac. Sci. Technol. B 2, 433 (1984); http://dx.doi.org/10.1116/1.582890 (7 pages) | Cited 10 times

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A brief critical review is given of diverse techniques used to measure heterojunction band lineups; they range from very reliable to worthless. Another problem pertains to the heterosystems themselves: Data on systems in which two semiconductors from a different pair of columns of the periodic table are combined, should be reviewed with suspicion, although some selected pairs are probably trustworthy—but none in which a compound semiconductor was grown on an elemental one. Technologies that do not lead to device‐quality interfaces also probably do not yield device‐quality lineup data. A list of the most trustworthy experimental data is given. The simplest possible theoretical framework for a theory of band lineups is a model of linear superpositon of atomiclike bulk potentials. Such a model automatically leads to a theory that is linear and transitive, in which the band lineups are orientation independent, and in which a technology dependence of the band lineups requires a technology‐dependent deviation of the atomic arrangement from the ideal one. The Harrison theory is both the simplest and the most successful theory of band lineups, although it still does not meet the needs of the device physicist. The set of most reliable data selected earlier agree very well with this theory, with a largest deviation of 0.18 eV and a standard deviation of 0.13 eV.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.30.+y Surface double layers, Schottky barriers, and work functions
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Band offsets, defects, and dipole layers in semiconductor heterojunctions

A. Zur and T. C. McGill

J. Vac. Sci. Technol. B 2, 440 (1984); http://dx.doi.org/10.1116/1.582891 (5 pages) | Cited 3 times

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The role of defects in heterojunctions was investigated. The density of such defects required to pin the Fermi level or to affect the band offset was estimated using simple electrostatic considerations. We conclude that it is very unlikely that defects play any role in determining the band offsets, but they might affect the Fermi‐level position at the interface.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
61.72.-y Defects and impurities in crystals; microstructure

Electrical properties of ideal metal contacts to GaAs: Schottky‐barrier height

J. R. Waldrop

J. Vac. Sci. Technol. B 2, 445 (1984); http://dx.doi.org/10.1116/1.582892 (4 pages) | Cited 52 times

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The electrical properties, with emphasis on Schottky‐barrier height ϕB, of ideal (no interfacial oxide) contacts to GaAs have been measured for a diverse group of 14 metals by using current‐voltage and capacitance–voltage methods. The contact interfaces were formed under controlled ultrahigh vacuum conditions by metal evaporation onto clean (100) surfaces of both n‐type and p‐type GaAs. The range of ϕB for n‐type contacts is 0.96 to 0.62 eV in the decreasing order: Cu, Pd, Ag, Au, Al, Ti, Mn, Pb, Bi, Ni, Cr, Co, Fe, and Mg. For p‐type contacts, the ϕB range is 0.45 to 0.62 eV. No simple correlation is apparent between ϕB and contact metal work function nor between ϕB and the metal–GaAs interface chemistry.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Theory of surface‐defect states and Schottky barrier heights: Application to InAs

Roland E. Allen, Terry J. Humphreys, John D. Dow, and Otto F. Sankey

J. Vac. Sci. Technol. B 2, 449 (1984); http://dx.doi.org/10.1116/1.582893 (4 pages) | Cited 10 times

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Theoretical predictions of electronic energy levels associated with s‐ and p‐bonded substitutional point defects at (110) surfaces of InAs and other III–V semiconductors are presented and discussed. The specific defects considered for InAs are: anion and cation vacancies, the (native) antisite defects InAs and AsIn, and 26 impurities. The predicted surface‐defect deep levels are used to interpret Schottky barrier height data for (a) n‐ and p‐(InAs) and (b) the alloys AlxGa1−xAs, GaAs1−xPx, In1−xGaxP, and In1−xGaxAs. The rather complicated dependence of the Schottky barrier height ϕB on alloy composition x provides a nontrivial test of the theory (and competing theories). The following unified microscopic picture emerges from these and previous calculations: (1) For most III–V and group IV semiconductors, Fermi‐level pinning by native defects can explain the observed Schottky barrier heights. (2) For GaAs, InP, and other III–V semiconductors interfaced with nonreactive metals, the Fermi‐level pinning is normally due to antisite defects. (3) When InP is interfaced with a reactive metal, surface P vacancies are created which pin the Fermi level. (4) Impurities and defect complexes are sometimes implicated. (5) At Si/transition‐metal‐silicide interfaces, Si dangling bonds pin the Fermi level. (6) These defects at the semiconductor/metal interfaces are often ‘‘sheltered’’ or ‘‘encapsulated.’’ That is, the states responsible for Fermi‐level pinning are frequently ‘‘dangling‐bond’’ states that dangle into a neighboring vacancy, void, or disordered region. The defects are partially surrounded by atoms that are out of resonance with the semiconductor host, causing the defect levels to be deep‐level pinned and to have energies that are almost independent of the metal.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Systematics of interfacial chemical reactions on InP(110)

T. Kendelewicz, W. G. Petro, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. B 2, 453 (1984); http://dx.doi.org/10.1116/1.582894 (6 pages) | Cited 9 times

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The room temperature chemical reactions of noble metals (Ag, Au, Cu), some transitions metals (Ni, Pd), and Al with the InP(110) surface have been studied using surface sensitive core level photoemission spectroscopy and photon beam excited Auger spectroscopy. It is shown that chemical reactions on InP are largely similar to the reactions of these metals with GaAs and Si surfaces. Metals that react with Si to produce phosphides also produce phosphides with similar types of chemical bonding. Silver overlayers give rise to the most abrupt interface with InP as is also the case for the nonreactive Ag–Si system. The kinetic limitations of the room temperature reaction and the types of overlayer growth are also considered.
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82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
68.55.-a Thin film structure and morphology

Nonuniform surface potentials and their observation by surface sensitive techniques

J. Y.‐F. Tang and J. L. Freeouf

J. Vac. Sci. Technol. B 2, 459 (1984); http://dx.doi.org/10.1116/1.582895 (6 pages) | Cited 8 times

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Various models of Schottky barrier formation have been proposed in the last few years which involve metallurgical interactions at the metal–semiconductor interface. Most of these models involve nonuniform lateral variations in the surface potential. For metallic clusters and/or anion clusters, these variations involve a relatively large size scale (tens to hundreds of angstroms). For interface defect formation, the suggestion of cluster formation energy as the driving force for defect formation could also lead to a nonuniform distribution of pinning sites on a similar size scale. We have studied the effects of various spatial distributions of pinning sites (e.g., surface defects, clusters of anions and/or adsorbed metal atoms) and variations of their energy levels upon surface potentials and their depth distribution via a two‐dimensional finite difference program that integrates Poisson’s equation. Our results suggest that surface sensitive spectroscopies provide a less than exact measure of pinning levels in many such cases. For example, for 1018 n‐GaAs and pinning site separation of 100 Å, our calculations imply a Kelvin probe band‐bending result for the surface potential of ≊0.15 V less than the ‘‘pinning’’ value (for pinning values of 0.8 and 0.6). Furthermore, such nonuniform distributions alter the effect of probe depth. The surface potential determined via e.g., UPS, with a 20 Å mean free path, would differ from the ‘‘true’’ surface averaged value by ≊0.09 eV for a uniform 0.8 V surface; while this difference is ≊0.07 for 100 Å separations, and ≊0.05 for 400 Å separations, the ratio of this λ dependent term to the total measured band bending increases as the distance between pinning sites increases. Note that a pinning level 0.8 eV below the conduction band minimum leads (under the assumptions of 100 Å between sites, probe depth ≊20 Å, and 1018 cm−3 bulk doping) to a ‘‘measured’’ surface potential within 0.6 eV of the conduction band minimum. These results should impact the interpretation of surface dependent studies of Schottky barrier formation, especially for specific models of such formation.
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73.30.+y Surface double layers, Schottky barriers, and work functions

Schottky barrier heights of single crystal silicides on Si(111)

R. T. Tung

J. Vac. Sci. Technol. B 2, 465 (1984); http://dx.doi.org/10.1116/1.582896 (6 pages) | Cited 16 times

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Capacitance–voltage and current–voltage characteristics at single crystal silicide–silicon interfaces are studied. Schottky barrier heights are determined for epitaxial NiSi2 and CoSi2 layers grown under ultrahigh vacuum conditions on Si(111). These results demonstrate that there is an influence of interface structure on Schottky barrier height. This dependence suggests a reassessment of many previous interpretations or models of Schottky barriers. It also shows that experimentally measured barrier heights of metal–semiconductor systems with inhomogeneous interface structure are likely to be the averages from those associated with different regions of the interface. Homogeneous metal–semiconductor interfaces are therefore the simplest and most desirable systems for the study of Schottky barrier mechanisms. In particular, the present epitaxial silicide–silicon interfaces represent ideal candidates for detailed theoretical investigations based on experimentally obtained atomic structures.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts

Fermi level position and valence band discontinuity at GaAs/Ge interfaces

A. D. Katnani, P. Chiaradia, H. W. Sang, and R. S. Bauer

J. Vac. Sci. Technol. B 2, 471 (1984); http://dx.doi.org/10.1116/1.582897 (5 pages) | Cited 9 times

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We present a photoemission study of the valence band discontinuity ΔEv and the Fermi level EF at the abrupt n‐GaAs/Ge interface. We investigated these properties during the early stages of interface formation between different reconstructions of GaAs(100) and epitaxial Ge. While GaAs(100) As surface stoichiometry variations from 0.25 to 1.25±0.10 monolayers caused no change in ΔEv, the Fermi position indicated an increasingly n‐type interface of >0.3 eV with the presence of As. Intentional As4 annealing of the Ge or addition into the growth environment only produced a more n‐type barrier with no corresponding change in ΔEv. Variations in crystallographic orientations do not contribute to the band discontinuities by more than ±0.05 eV.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Metallic and atomic approximations at the Schottky barrier interfaces

W. E. Spicer, S. Pan, D. Mo, N. Newman, P. Mahowald, T. Kendelewicz, and S. Eglash

J. Vac. Sci. Technol. B 2, 476 (1984); http://dx.doi.org/10.1116/1.582898 (5 pages) | Cited 6 times

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Stimulated by the work of Zur, McGill, and Smith (ZMS), we have undertaken a broad examination of the ‘‘potential normalization’’ conditions at the metal–semiconductor interface. We have made calculations using a metallic approximation and the model of Bardeen. Strong overall agreement is found with the results of ZMS; however, the details depend on the specific parameters used in the calculations. In particular, parameters were identified which give different pinning positions on n‐ and p‐type semiconductor materials. Experimentally, Cs is found to be in strong disagreement with any ‘‘metallic’’ approximation at the interface; rather, it is shown that the experimental and theoretical understanding of Cs on solids indicates that an atomic model for the last atomic layer of Cs (with some fixed charge due to the induced Cs atomic dipole at the interface) is a more appropriate approximation than the metallic approximation used by ZMS and ourselves. Experimental results for thick noble metals (Au, Cu, and Ag) deposited in situ on clean GaAs(110) formed by cleaving in UHV are reported. These give a pinning position at the donor level as do properly analyzed PES measurements on thin (sub‐ to full‐monolayer) deposits of noble metals on GaAs. An atomic explanation based on the large electron affinity of the noble metals is suggested and this is related to the interfacial chemistry. In contrast, significant differences are found between the thin and thick pinning positions of Al on GaAs in general agreement with the metallic approximations of ZMS and ourselves.
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73.40.Jn Metal-to-metal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.-r Electron states at surfaces and interfaces

Aluminum Schottky barrier formation on arsenic capped and heat cleaned MBE GaAs(100)

Stephen J. Eglash, M. D. Williams, P. H. Mahowald, Nathan Newman, Ingolf Lindau, and W. E. Spicer

J. Vac. Sci. Technol. B 2, 481 (1984); http://dx.doi.org/10.1116/1.582899 (5 pages) | Cited 6 times

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The fabrication and characterization of an aluminum Schottky barrier on an arsenic capped and heat cleaned GaAs(100) surface is described. The GaAs surface was prepared by molecular beam epitaxy (MBE), and covered with an arsenic cap for protection during transfer through air. The arsenic cap was sublimed by heating, and its removal was monitored by photoemission spectroscopy utilizing synchrotron radiation. After the formation of an aluminum Schottky barrier on this surface, the interfacial position of the Fermi level was measured by photoemission spectroscopy, and the barrier height was measured by I–V and C–V techniques.
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73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.De Semiconductor-device characterization, design, and modeling
85.30.Hi Surface barrier, boundary, and point contact devices

Heterojunction band off‐sets: Variation with ionization potential compared to experiment

Edgar A. Kraut

J. Vac. Sci. Technol. B 2, 486 (1984); http://dx.doi.org/10.1116/1.582900 (5 pages) | Cited 4 times

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Semiconductor valence‐band edges are computed on absolute energy scales determined by Herman‐Skillman and Hartree–Fock neutral atom ionization energies, respectively. These calculations use Harrison’s (1977) elementary theory of heterojunctions. Differences are compared with experimental heterojunction band discontinuities. It is shown that calculations based on Herman–Skillman neutral atom energies and Harrison’s original solid‐state matrix elements agree somewhat better with experiment than later results (1981) based on Hartree–Fock neutral atom energies and modified solid‐state matrix elements. Although no simple theory for heterojunction core‐level discontinuities seems to exist, it is shown that the experimentally measured heterojunction core‐level discontinuities are roughly equal to the binding energy differences of fully relaxed neutral atom core levels such as those calculated by Huang and co‐workers.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds

Theory of Schottky barrier formation for transition metals on Si, Ge, diamond, and Six Ge1−x alloys

Otto F. Sankey, Roland E. Allen, and John D. Dow

J. Vac. Sci. Technol. B 2, 491 (1984); http://dx.doi.org/10.1116/1.582901 (5 pages) | Cited 5 times

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The heights of the Schottky barriers for various transition metals on Si, Ge, diamond, and Six Ge1−x alloys are calculated using a defect model, in which the Fermi energy is pinned by deep levels associated with interfacial dangling bonds.
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.20.Hb Impurity and defect levels; energy states of adsorbed species
73.40.Ns Metal-nonmetal contacts

Interfacial constraints on device performance

D. L. Lile

J. Vac. Sci. Technol. B 2, 496 (1984); http://dx.doi.org/10.1116/1.582806 (8 pages) | Cited 10 times

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Electronic devices can be significantly affected in their behavior by the properties of the surfaces and interfaces which delineate their structure. Unfortunately, such surface effects are often degrading, acting to reduce the performance of the device below that to be expected in the ideal case. This paper will attempt to review these processes and relate them to what is known about the properties and structures of surfaces. In particular those deficiencies which most severely impact device performance will be identified, and suggestions made as to where improvements in understanding of surface control might have the greatest impact on resulting device development.
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85.30.De Semiconductor-device characterization, design, and modeling
68.60.-p Physical properties of thin films, nonelectronic
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
73.40.-c Electronic transport in interface structures

The role of interfaces in ultrasmall semiconductor devices

D. K. Ferry

J. Vac. Sci. Technol. B 2, 504 (1984); http://dx.doi.org/10.1116/1.582807 (6 pages) | Cited 6 times

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As semiconductor devices become smaller, the temporal and spatial scales become sufficiently short and the electric field sufficiently large that new physical constraints are reached in treating the transport of carriers within the devices. These devices are now controlled by strong size‐related effects: coupling to the environment of contacts, interfaces/boundaries/surfaces, interconnects, and other devices. This is especially the case in MOSFET’s, where remote interface phonons and surface roughness scattering dominate the transport. In this talk, a general treatment of device–environment interaction will be discussed. Special cases for MOS transport and the specific role of interfaces will be treated.
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85.30.De Semiconductor-device characterization, design, and modeling
73.40.-c Electronic transport in interface structures

Summary Abstract: Surface treatment and interface properties: What really matters?

J. M. Woodall and J. L. Freeouf

J. Vac. Sci. Technol. B 2, 510 (1984); http://dx.doi.org/10.1116/1.582808 (2 pages)

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Abstract Unavailable
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81.65.-b Surface treatments
73.40.-c Electronic transport in interface structures
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Surface properties of semi‐insulating indium phosphide

James W. Roach and H. H. Wieder

J. Vac. Sci. Technol. B 2, 512 (1984); http://dx.doi.org/10.1116/1.582809 (4 pages)

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Electrical measurements on two‐terminal structures and on A‐MISFET’s, with 20 and 30 μm long channels, fabricated on SiO2 or Al2O3 coated semi‐insulating InP, indicate that charge transport between their Au–Ge eutectic contacts takes place by a combination of electron transport in the accumulation layer and space charge limited current flow, both affected by deep level traps. Following application of a step voltage, the total time dependence current may be described qualitatively by I(t)=I0 exp (−t/τ2)+I1[1−exp (−t/τ1], where τ2≫τ1 and I0 is the accumulation current.
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73.61.Cw Elemental semiconductors
73.61.Ey III-V semiconductors
73.61.Ga II-VI semiconductors
73.61.Jc Amorphous semiconductors; glasses
73.61.Le Other inorganic semiconductors
73.30.+y Surface double layers, Schottky barriers, and work functions

Influence of interfacial structure on the electronic properties of SiO2/InP MISFET’s

K. M. Geib, S. M. Goodnick, D. Y. Lin, R. G. Gann, C. W. Wilmsen, and J. F. Wager

J. Vac. Sci. Technol. B 2, 516 (1984); http://dx.doi.org/10.1116/1.582810 (6 pages) | Cited 7 times

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In order to make a viable InP MISFET technology, two major problems remain to be solved: (1) instability in the channel current and (2) variations in the channel mobility with processing. These problems are strongly affected by the chemical and physical structure of the semiconductor/insulator interface. This paper presents results of an investigation of the deposited SiO2/InP interface using XPS, UPS, and ELS combined with transport measurements on special Hall geometry MISFET’s. Physical studies of the SiO2/InP interface using XPS show the presence of a 20–40 Å thick native oxide layer primarily composed of InPO4 next to the InP and In2O3 close to the SiO2. UPS and ELS data suggests that the In2O3 forms a trap level slightly above the conduction band. The variation of the channel mobility with surface field and temperature imply that for these devices, the channel mobility is completely dominated by scattering from interface charges and surface roughness, with only a small contribution arising from the bulk optical phonon.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.30.Tv Field effect devices

High mobility insulated gate transistors on InP

M. J. Taylor, D. L. Lile, and A. K. Nedoluha

J. Vac. Sci. Technol. B 2, 522 (1984); http://dx.doi.org/10.1116/1.582811 (5 pages) | Cited 9 times

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The surface charge carrier transport of electrons in accumulation mode insulated gate FET’s fabricated on [100] oriented samples of semi‐insulating InP has been investigated, both as a function of surface and dielectric preparation as well as of temperature over the range of 85 to 300 K. Results of these studies indicate that room temperature field‐effect mobilities as large as 4200 cm2/V s and effective mobilities of 3300 cm2/V s can be achieved in the linear region on material whose bulk Hall mobility does not exceed 3000 cm2/V s.
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85.30.Tv Field effect devices
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.Fr Low-field transport and mobility; piezoresistance

Structural dependent electrical characteristics of submicron gallium arsenide devices

H. L. Grubin and J. P. Kreskovsky

J. Vac. Sci. Technol. B 2, 527 (1984); http://dx.doi.org/10.1116/1.582812 (7 pages) | Cited 1 time

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Numerical studies of the transient and dc electrical behavior of submicron N+N−N+ gallium arsenide structures are discussed. It is shown that the transient results are dominated, during the first fraction of a picosecond, by displacement current contributions. Velocity overshoot is less important. Under dc conditions and high bias levels, submicron effects may be masked by transport within the N+ regions.
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85.30.De Semiconductor-device characterization, design, and modeling
72.80.Ey III-V and II-VI semiconductors

Computer simulations of surfaces, interfaces, and physisorbed films

Farid F. Abraham

J. Vac. Sci. Technol. B 2, 534 (1984); http://dx.doi.org/10.1116/1.582836 (16 pages) | Cited 9 times

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We survey selected computer simulations or ‘‘experiments’’ relating to the statistical physics of surface phenomena. An introduction to the Monte Carlo and molecular dynamics simulation techniques is presented, followed by chosen computer simulation applications which have been done mainly at the IBM Research Laboratory over the last several years. The examples are taken from studies of the structure and thermodynamics of microclusters, liquid–vapor and liquid–solid interfaces and quasi‐two‐dimensional physisorbed films. An up‐to‐date bibliography of the various topics is given at the conclusion.
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05.20.-y Classical statistical mechanics
68.08.-p Liquid-solid interfaces
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
02.70.-c Computational techniques; simulations
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)

Classical stochastic diffusion theory for thermal desorption from solid surfaces

Antonio Redondo, Yehuda Zeiri, and William A. Goddard

J. Vac. Sci. Technol. B 2, 550 (1984); http://dx.doi.org/10.1116/1.582837 (11 pages) | Cited 2 times

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As a first step in the microscopic study of dynamic processes on surfaces and at interfaces, we have considered the thermal desorption of adsorbed species on solid surfaces. We review recent developments based on a classical stochastic diffusion formulation. Using this theory, we obtained a simple rate expression, R=(Ω0/2π) f(T)exp(−De/kT), where Ω0 is the surface‐adsorbate vibrational frequency and De the dissociation energy. For atoms f(T)=1, whereas for molecules f(T) depends on the parameters for the frustrated rotations at the surface. The effect of coverage on the rate of desorption and the process of desorption into a fluid are also examined. Finally, we discuss the relationship between our theory and the expressions obtained from activated complex (transition‐state) theory.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces

Metal contacts on semiconductors: The adsorption of Sb, Sn, and Ga on InP(110) cleaved surfaces

R. H. Williams, A. McKinley, G. J. Hughes, T. P. Humphreys, and C. Maani

J. Vac. Sci. Technol. B 2, 561 (1984); http://dx.doi.org/10.1116/1.582838 (8 pages) | Cited 6 times

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We have studied the adsorption and growth of Ga (group III), Sn (group IV), and Sb (group V) on InP(110) clean cleaved surfaces, using a range of surface sensitive techniques. The adsorption processes differ for the three adsorbate elements ranging from cluster growth for Ga to layer upon layer growth for Sb. The systematics of the adsorption processes as well as the mechanisms driving the chemical reactions and interdiffusion are considered and strong indications of a close relationship between adlayer clustering and the movement of atoms across the interface is reported. The electrical barriers at these interfaces are also briefly discussed as well as some studies at liquid nitrogen temperatures for Sn and Al overlayers.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.43.-h Chemisorption/physisorption: adsorbates on surfaces
66.30.Ny Chemical interdiffusion; diffusion barriers
73.30.+y Surface double layers, Schottky barriers, and work functions

Effect of interfaces upon atomic diffusion: Si and Zn in GaAs

J. A. Van Vechten

J. Vac. Sci. Technol. B 2, 569 (1984); http://dx.doi.org/10.1116/1.582839 (4 pages) | Cited 10 times

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The activation energy for atomic diffusion often includes terms resulting from a change in ionization state of the diffusing species. It is argued that these terms ought to be affected by the electronic states of the material not only at the site of the diffusion but also within a range of order of the Debye screening length of it. Thus, atomic diffusion ought to be a nonlocal phenomenon with a scale comparable with modern device structures. Major increases in the rate of diffusion near interfaces, surfaces and dislocations are predicted and should be considered when modeling processes. GaAs–AlAs superlattices allow testing of these conclusions.
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66.30.Dn Theory of diffusion and ionic conduction in solids
66.30.J- Diffusion of impurities
78.40.Fy Semiconductors
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

Effective potentials for kinetic processes on semiconductor surfaces

S. C. Ying and T. L. Reinecke

J. Vac. Sci. Technol. B 2, 573 (1984); http://dx.doi.org/10.1116/1.582840 (3 pages) | Cited 1 time

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The effective potentials for atomic motion on semiconductor surfaces are given in terms of the displacement–displacement correlation functions of the substrate by a Langevin equation approach. The method is illustrated by detailed calculations of the surface dynamics of the unreconstructed Si(100) surface for which several interesting new features are obtained. It is shown that the total effective potential for atomic diffusion on the surface differs substantially from the adatom‐rigid substrate interaction as a result of coupling to the dynamic substrate vibrations.
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68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
66.30.Dn Theory of diffusion and ionic conduction in solids
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
68.35.Md Surface thermodynamics, surface energies

Theoretical investigations of the nature of the normal and inverted GaAs–AlGaAs structures grown by molecular beam epitaxy

Jasprit Singh and K. K. Bajaj

J. Vac. Sci. Technol. B 2, 576 (1984); http://dx.doi.org/10.1116/1.582841 (6 pages) | Cited 10 times

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We have developed an atomistic model for the growth of GaAs and AlGaAs and have simulated the MBE growth of both the normal (AlGaAs on GaAs) and the inverted (GaAs on AlGaAs) structures along (100) direction using Monte Carlo techniques. We assume the growth to occur under anion overpressure with As2 molecular species as the anion source and Ga and Al atoms as the cation sources. We find that some of the differences in the quality of the two interfaces can be explained on the basis of the surface kinetics operational for the two kinds of cations. In our model there is a considerable interlayer surface migration for the Ga atoms due to the relatively weak Ga–As bond compared to the Al–As bond. For comparable substrate temperatures the stronger Al–As bonds lower the interlayer diffusion for Al atoms. The role of this key kinetic step, namely, the interlayer surface migration on the quality of the growth front profiles of GaAs and AlGaAs as well as their interfaces is examined.
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68.55.-a Thin film structure and morphology
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
66.30.Fq Self-diffusion in metals, semimetals, and alloys

Summary Abstract: Unusual interfacial kinetics and Schottky barrier formation of thallium on the GaAs(110) surface

T. Kendelewicz, W. G. Petro, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. B 2, 582 (1984); http://dx.doi.org/10.1116/1.582842 (2 pages)

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Abstract Unavailable
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73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics

SiO2/InP interfaces with reduced interface state density

J. F. Wager, M. D. Clark, and R. A. Jullens

J. Vac. Sci. Technol. B 2, 584 (1984); http://dx.doi.org/10.1116/1.582843 (4 pages) | Cited 2 times

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By employing a new InP surface preparation procedure based upon KOH/methanol, the interface state density of plasma‐enhanced chemically vapor deposited SiO2/InP structures has been significantly reduced. Capacitance–voltage characteristics of these structures exhibit unusual nonequilibrium behavior which appears to be assoicated with the formation of a p‐type inversion layer and with the presence of interface traps with very slow response times. This surface preparation procedure yields an InP native oxide which has no detectable In2O3 and is contaminated with K.
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73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
06.60.Ei Sample preparation (including design of sample holders)

Summary Abstract: Two‐stage process for silicide formation at metal–silicon interfaces

R. J. Nemanich, B. L. Stafford, W. B. Jackson, M. J. Thompson, J. R. Abelson, and T. W. Sigmon

J. Vac. Sci. Technol. B 2, 588 (1984); http://dx.doi.org/10.1116/1.582848 (1 page) | Cited 2 times

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Abstract Unavailable
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
73.40.Ns Metal-nonmetal contacts
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

Summary Abstract: Activated oxygen uptake on HgTe, CdTe, and Hg0.69Cd0.31Te

J. A. Silberman, D. Laser, I. Lindau, W. E. Spicer, and J. A. Wilson

J. Vac. Sci. Technol. B 2, 589 (1984); http://dx.doi.org/10.1116/1.582849 (2 pages) | Cited 1 time

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81.65.-b Surface treatments

Control and characterization of metal–InP and GaAs interface structures formed by laser‐enhanced reactions

H. W. Richter, L. J. Brillson, M. K. Kelley, R. R. Daniels, and G. Margaritondo

J. Vac. Sci. Technol. B 2, 591 (1984); http://dx.doi.org/10.1116/1.582850 (5 pages) | Cited 1 time

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We have used pulsed laser annealing to produce highly localized chemical reactions at the Al–InP and Al–GaAs interfaces. At successive stages of these laser induced reactions, we have monitored atomic movement and chemical structure on a microscopic scale using soft x‐ray photoemission spectroscopy (SXPS) and Auger electron spectroscopy (AES). We have found a finite range of energy density such that a chemical reaction is promoted without disrupting the surface morphology. The reactions and atomic movements are explained by simultaneous melting of the Al overlayer and a thin layer of the semiconductor substrate.
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68.35.-p Solid surfaces and solid-solid interfaces: structure and energetics
68.55.-a Thin film structure and morphology
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces

Summary Abstract: Fractional quantum effect in transport along the GaAs–AlxGa1−xAs interface

D. C. Tsui

J. Vac. Sci. Technol. B 2, 596 (1984); http://dx.doi.org/10.1116/1.582844 (1 page)

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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Summary Abstract: Elastic and inelastic tunneling characteristics of AlAs/GaAs heterojunctions

R. T. Collins, J. Lambe, T. C. McGill, and R. D. Burnham

J. Vac. Sci. Technol. B 2, 597 (1984); http://dx.doi.org/10.1116/1.582845 (2 pages) | Cited 1 time

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73.40.Gk Tunneling
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Electrical characterization of the GaAs/AlxGa1−xAs interface by conductance DLTS

G. N. Maracas, W. D. Laidig, and H. R. Wittmann

J. Vac. Sci. Technol. B 2, 599 (1984); http://dx.doi.org/10.1116/1.582846 (5 pages) | Cited 3 times

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Experimental data taken from MBE‐grown GaAs/Al0.25 Ga0.75 As modulation doped structures are presented. Interface states are observed using backside modulated conductance deep level transient spectroscopy. This technique allows evaluation of states within the 2DEG as well as on either side of the interface. Energies of the subbands, Si donors in the AlGaAs, and the amount of band bending have been determined. The measurements agree closely with calculations of band energies in a triangular well with an interface electric field of ∼9×106 V/m.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.40.Fy Semiconductors
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
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