Browse - Journal of Vacuum Science & Technology Archives 1964-1982

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Ion–surface interactions during vapor phase crystal growth by sputtering, MBE, and plasma‐enhanced CVD: Applications to semiconductors

J. E. Greene and S. A. Barnett

J. Vac. Sci. Technol. 21, 285 (1982); http://dx.doi.org/10.1116/1.571767 (18 pages) | Cited 33 times

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The effects of low‐energy particle bombardment of growing films during vapor phase epitaxy are considered in some detail. Ion bombardment plays an important and sometimes dominant role in controlling the growth kinetics and physical properties of films deposited by glow discharge and ion beam sputter deposition, molecular beam epitaxy using accelerated dopants, and plasma‐ assisted chemical vapor deposition. Ion–surface interaction effects, including trapping, sputtering, preferential sputtering, and collisional mixing, are used to interpret and model experimental results concerning the effects of low‐energy particle bombardment on nucleation, film growth, enhanced diffusion at interfaces, and elemental incorporation probabilities. Finally, recent results on the growth of unique single‐crystal metastable semiconducting alloys are discussed.

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68.55.-a	Thin film structure and morphology
79.20.Rf	Atomic, molecular, and ion beam impact and interactions with surfaces
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Measurement of semiconductor–insulator interface states by constant‐capacitance deep‐level transient spectroscopy

N. M. Johnson

J. Vac. Sci. Technol. 21, 303 (1982); http://dx.doi.org/10.1116/1.571768 (12 pages) | Cited 46 times

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Localized electronic states at the semiconductor–insulator interface adversely affect the operation of insulated‐gate, field‐effect devices. Characterization of interface states provides essential information for minimizing their effect through process optimization, for predicting device performance, and ultimately for microscopic identification of interface defects. This paper reviews the application of deep‐level transient spectroscopy (DLTS) for characterizing interface states on metal–insulator–semiconductor capacitors, with emphasis on the constant‐capacitance (CC) mode of measurement. The DLTS measurement yields both the energy distribution of interface states and their cross section for capturing free carriers. In addition, it has the versatility of being applicable to both interface and bulk defect characterization. The CC‐DLTS technique offers the combined features of high sensitivity (<1×10⁹ eV⁻¹ cm⁻²), minimum signal distortion at high defect densities, high energy resolution, and the determination of dynamic properties. After a description of the measurement system and experimental procedures, the theoretical basis is developed for data reduction of majority‐carrier‐dominated transients for the following cases: (1) under saturating‐pulse conditions and (2) with Fermi‐level controlled trap occupancy. Under the first topic is included a summary of transient‐current spectroscopy, and the second is illustrated with the energy‐resolved DLTS technique. The presentation includes an analysis of the effect of surface generation on the DLTS measurement of interface states near the semiconductor midgap and an analysis of the limits of applicability of the transient‐capaci tance mode for DLTS measurement of interface states. The techniques are illustrated with measurements of electronic defect levels at the Si–SiO₂ interface.

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73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
71.55.-i	Impurity and defect levels

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Laser‐induced order–disorder transition of the (100)InP surface

J. M. Moison and M. Bensoussan

J. Vac. Sci. Technol. 21, 315 (1982); http://dx.doi.org/10.1116/1.571769 (4 pages) | Cited 9 times

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The first investigation of laser‐processed (100)InP surfaces is reported. Under irradiation by a pulsed (3 ns) green laser, above a threshold fluence of 0.2 J/cm², both stoichiometry and structure of the surface are altered: Matter departure from the surface takes place, together with a transition towards a (1×1) LEED pattern which is attributed to a surface formed by (1×1) terraces and a random array of steps. At higher fluences, desorption increases and a fully disordered surface is obtained. A comparison with the results obtained on other semiconductors and implications for future studies are outlined.

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68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics
64.70.K-	Solid-solid transitions

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Theory of the electronic and atomic structure of Si(111): Surface spin‐polarization effects

D. J. Chadi and R. Del Sole

J. Vac. Sci. Technol. 21, 319 (1982); http://dx.doi.org/10.1116/1.571770 (8 pages) | Cited 2 times

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The electronic structure 1×1 and 2×1 reconstructed Si(111) surfaces are examined using a simple theoretical model which incorporates intra‐atomic correlation effects. Electron spin polarization is shown to lead to a low‐energy nonmetallic ground state for the nonbuckled Si(111) surface which is energetically more favorable than the metallic, half‐filled band state. Spin‐ polarization and spin‐ordering effects are shown to be important for the buckled surface. The incorporation of electronic correlations and spin in the calculations yields results consistent with photoemission, optical, and low energy electron diffraction data. The calculated oscillator strength for optical transitions between dangling‐bond bands and its anisotropy are found to be in satisfactory agreement with experimental data. The buckling is estimated to be 0.3 Å.

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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
68.35.Gy	Mechanical properties; surface strains
68.35.Iv	Acoustical properties

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Summary Abstract: The (1×1) structure of Si(111) and C(111): Strong correlations in surface‐state bands?

C. B. Duke and W. K. Ford

J. Vac. Sci. Technol. 21, 327 (1982); http://dx.doi.org/10.1116/1.571771 (1 page)

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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
75.10.Lp	Band and itinerant models

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Summary Abstract: Mott insulator model of the Si(111)‐(2×1) surface

Antonio Redondo, William A. Goddard, and T. C. McGill

J. Vac. Sci. Technol. 21, 328 (1982); http://dx.doi.org/10.1116/1.571772 (2 pages)

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73.20.-r

Electron states at surfaces and interfaces

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Estimation of surface charge densities for low‐energy atom diffraction

D. Haneman and Roger Haydock

J. Vac. Sci. Technol. 21, 330 (1982); http://dx.doi.org/10.1116/1.571773 (3 pages) | Cited 6 times

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For purposes of comparing models of surface atomic structure with atom diffraction data, it is proposed that the surface of critical charge density for atom scattering be obtained from the superposition of atomic charge densities. The results of this method, which has the advantage of permitting fast calculation for many structures, including complex ones, are compared with the self‐consistent calculations of Hamann for GaAs(110) and Ni(110). The method is then applied to the Si(111) surface and used to illustrate the effects of atom shifts on corrugations of the surface of critical charge density.

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68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics
68.37.-d	Microscopy of surfaces, interfaces, and thin films

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Electronic structure of the π‐bonded chain model and the nonbuckled antiferromagnetic insulator model for the Si(111) surface

John E. Northrup and Marvin L. Cohen

J. Vac. Sci. Technol. 21, 333 (1982); http://dx.doi.org/10.1116/1.571774 (4 pages) | Cited 5 times

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The electronic structure of the Si(111) surface is investigated with the pseudopotential method and the local density functional formalism. The π‐bonded chain model proposed by Pandey is found to be more stable than the nonbuckled antiferromagnetic insulating surface by 0.15 eV/ (surface atom).

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73.20.-r

Electron states at surfaces and interfaces

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Summary Abstract: (1×1) surface unit cell on Ge cleaved at liquid helium temperatures

D. Haneman and R. Z. Bachrach

J. Vac. Sci. Technol. 21, 337 (1982); http://dx.doi.org/10.1116/1.571775 (1 page)

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68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics
61.05.jh	Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)

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Summary Abstract: SEXAFS studies of surface chemistry on Si and Ge

J. E. Rowe and P. H. Citrin

J. Vac. Sci. Technol. 21, 338 (1982); http://dx.doi.org/10.1116/1.571776 (2 pages)

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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
78.70.Dm	X-ray absorption spectra

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First‐principles determination of the structure of the Al/GaAs(110) surface

J. Ihm and J. D. Joannopoulos

J. Vac. Sci. Technol. 21, 340 (1982); http://dx.doi.org/10.1116/1.571777 (4 pages) | Cited 3 times

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The structure of Al atoms deposited on the GaAs (110) surface has been studied using a first‐ principles pseudopotential energy minimization calculation. The lowest energy configurations are determined by minimizing the total energy of the system with respect to its structural degrees of freedom. The most stable configuration is such that Al atoms replace the second (or deeper) layer Ga atoms. At temperatures where this reaction cannot be activated, two important processes are found to exist. In the low coverage limit, atoms favor twofold sites connecting an As atom and a Ga atom (in the next zigzag chain) on the surface, forming strong chemical bonds with the substrate. At higher coverages, on the other hand, Al atoms tend to cluster and make new bonds among themselves. The chemisorption energy map over the surface has been obtained and the possible path of the migration of Al atoms for clustering is investigated.

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73.40.Ns	Metal-nonmetal contacts
68.43.-h	Chemisorption/physisorption: adsorbates on surfaces
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

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Electronic correlation and the Si(100) surface: Buckling versus nonbuckling

Antonio Redondo and William A. Goddard

J. Vac. Sci. Technol. 21, 344 (1982); http://dx.doi.org/10.1116/1.571778 (7 pages) | Cited 38 times

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Theoretical cluster calculations for the Si(100) surface show that the use of doubly occupied orbital wavefunctions, such as the closed‐shell Hartree–Fock (HF), lead to an asymmetric dimer description of the surface. The inclusion of electron correlation produces a symmetric dimer description with a ground state ∠1.0 eV below the minimum of the HF buckled dimer. There are two low‐lying states of the symmetric dimer (a singlet and a triplet) with very different geometries. Energy minimization calculations indicate that a (2×1) structure is favored over a c(2×2) structure. We also report ionization potentials for surface and Si(2p) core electrons that are consistent with current experimental data.

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73.20.-r	Electron states at surfaces and interfaces
68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics

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Ideal and relaxed surfaces of SiC

D. H. Lee and J. D. Joannopoulos

J. Vac. Sci. Technol. 21, 351 (1982); http://dx.doi.org/10.1116/1.571779 (7 pages) | Cited 9 times

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During the past few years there has been considerable interest in the relaxation of GaAs(110) and Si(100)‐(2×1) surfaces. The surfaces of SiC, however, provide an intermediate system between these heteropolar and homopolar structures. It is interesting therefore to investigate the kinds of relaxation that might occur at the zincblende and wurtzite surfaces of SiC. We perform calculations using Chadi’s energy minimization scheme, with the coefficients of linear, quadratic, and cubic energy correction terms fitted to the bulk lattice constant, bulk modulus, and thermal expansion coefficient. To check the validity of this model, we calculate six experimentally known phonon frequencies. The agreement between theory and measured values is quite good. With this model, we investigate the relaxation at the SiC(110) surface in the zincblende structure and SiC(101̄0) and (112̄0) surfaces in the wurtzite structure. The results show a combination of downward movement and buckling for all three surfaces. The reduction in total energy is about 0.21 eV/atom for the (110) surface, and 0.24 eV/atom, 0.18 eV/atom for (101̄0) and (112̄0), respectively. Further results include the determination of ideal and relaxed electronic structure and optimum relaxed geometries. Finally, a new theory which extends Chadi’s scheme to do first principles phonon calculations is presented and discussed.

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73.20.-r

Electron states at surfaces and interfaces

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Vacancies and hydrogen adsorption at GaAs(110): Theoretical model studies of the electronic structure

J. Beyer, P. Krüger, A. Mazur, J. Pollmann, and M. Schmeits

J. Vac. Sci. Technol. 21, 358 (1982); http://dx.doi.org/10.1116/1.571780 (6 pages) | Cited 2 times

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We have carried out model calculations for the electronic properties of point perturbations at the relaxed GaAs(110) surface. The calculations are based on the tight‐binding scattering theoretical method for semi‐infinite solids. Ga and As vacancies at or near the surface and in the bulk crystal are discussed in terms of vacancy‐induced changes in the local density of states. Comparison with the results of other vacancy calculations is made. H adsorption was investigated by studying a model system consisting of an atomic s level coupled to the GaAs(110) substrate. We discuss our results in terms of local densities of states at the adsorbate and at the nearest‐neighbor substrate atom. Substrate‐mediated interactions between different vacancies or between different adsorbed atoms are discussed, as well.

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73.20.Hb	Impurity and defect levels; energy states of adsorbed species
68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics
61.72.jd	Vacancies
61.72.jj	Interstitials

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Photoemission and photon‐stimulated ion desorption studies of diamond(111): Hydrogen

B. B. Pate, M. H. Hecht, C. Binns, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. 21, 364 (1982); http://dx.doi.org/10.1116/1.571781 (4 pages) | Cited 19 times

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The interaction of hydrogen with the diamond (111) surface is examined using our new results in photoemission spectroscopy (PES) and photon‐stimulated ion desorption (PSID) yield at photon energies near the carbon K edge. Also discussed in the light of our new results are previous studies using PES and low energy electron diffraction (LEED). PSID verifies that the mechanically polished 1×1 surface is hydrogen terminated and finds that the reconstructed surface is hydrogen free. Atomic hydrogen is found to be reactive with the reconstructed surface, while molecular hydrogen is relatively inert. Exposure of the reconstructed surface to atomic hydrogen results in chemisorption of hydrogen and removal of the intrinsic surface state emission in and near the band gap region.

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68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics
81.65.-b	Surface treatments

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Direct verification of hydrogen termination of the semiconducting diamond(111) surface

B. J. Waclawski, D. T. Pierce, N. Swanson, and R. J. Celotta

J. Vac. Sci. Technol. 21, 368 (1982); http://dx.doi.org/10.1116/1.571782 (3 pages) | Cited 21 times

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Low‐energy, high‐resolution electron energy loss spectroscopy has been used to identify the vibrational modes of hydrogen on the semiconducting diamond surface providing the first direct evidence that the (111) 1×1 surface is terminated by hydrogen. The vibrational loss spectrum from the ’’as‐polished’’ surface shows two major losses near 160 meV (CH₃ deformation), a major loss at 360 meV (CH₃ stretch), and two minor losses at 520 and 720 meV (combinations and overtones). All of these losses disappear from the spectrum after heating the sample to ∠1000 °C (which has been established by other experiments to be sufficient to reconstruct the surface to 2×2/2×1). The loss spectrum for the reconstructed surface is indicative of a two‐dimensional metallic state of the dangling‐bond surface states for clean diamond. Exposure of this reconstructed surface to atomic hydrogen results in a loss spectrum which is essentially identical to that for the as‐polished surface. Further verification that the loss spectrum results from hydrogen is provided by the shift of the structure to lower loss energies when deuterium is absorbed.

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73.20.Hb	Impurity and defect levels; energy states of adsorbed species
81.40.Ef	Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization

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Theoretical investigation of hydrogen chemisorption on Ga‐containing III–V compounds

F. Manghi, C. M. Bertoni, C. Calandra, and E. Molinari

J. Vac. Sci. Technol. 21, 371 (1982); http://dx.doi.org/10.1116/1.571783 (4 pages) | Cited 11 times

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A fully self‐consistent pseudopotential calculation of the electronic properties of atomic hydrogen chemisorbed on GaAs and GaP(110) surfaces is reported. Different chemisorption geometries and substrate coverages are considered. The results are compared with the experimental information to select a structural model.

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68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics

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Interface electronic structure of Pb on GaAs(001)

J. F. van der Veen, L. Smit, P. K. Larsen, J. H. Neave, and B. A. Joyce

J. Vac. Sci. Technol. 21, 375 (1982); http://dx.doi.org/10.1116/1.571784 (5 pages) | Cited 3 times

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The electronic structure of two‐dimensional, ordered Pb overlayers in submonolayer coverages on MBE grown GaAs(001) surfaces has been studied by angle‐resolved photoemission using synchrotron radiation. A Pb(6s) derived interface state of Δ₁ symmetry has been identified in the heteropolar gap of GaAs at an energy of −8.3 eV below the valence‐band maximum. Two surface resonances of dangling bond character and of inplane character ( p_x−p_y) are located near the top of the valence bands, at −0.4 eV and −2.0 eV, respectively. High resolution studies of Ga(3d), As(3d), and Pb(5d) core levels show that there is no significant chemical interaction between the overlayer and the substrate.

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73.40.Ns	Metal-nonmetal contacts
79.60.Bm	Clean metal, semiconductor, and insulator surfaces
81.65.-b	Surface treatments

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Comparative LEED studies of Al_xGa_1−xAs(110) and GaAs(110)–Al(ϑ)

A. Kahn, J. Carelli, D. L. Miller, and S. P. Kowalczyk

J. Vac. Sci. Technol. 21, 380 (1982); http://dx.doi.org/10.1116/1.571785 (4 pages) | Cited 6 times

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LEED intensity profiles recorded from Al_xGa_1−xAs(110) MBE surfaces are compared with data obtained from GaAs(110)‐Al(ϑ) annealed interfaces. This comparison confirms the hypothesis of a heat induced Al–Ga replacement reaction and the formation of AlGaAs when Al is annealed on GaAs(110). AlAs(110) produces I–V profiles very different from those of GaAs(110) and preliminary modeling computations indicate small surface atomic reconstructions. The effect of the elemental As layer used to protect Al_xGa_1−xAs(110) surfaces during ambient transfer is also investigated.

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61.05.jh	Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
79.20.Fv	Electron impact: Auger emission
79.20.Kz	Other electron-impact emission phenomena
73.40.Ns	Metal-nonmetal contacts

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Planar channeling of ions in compound semiconductor superlattices

John H. Barrett

J. Vac. Sci. Technol. 21, 384 (1982); http://dx.doi.org/10.1116/1.571786 (2 pages)

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Computer simulations have been done to show how planar channeling of high‐energy ions in compound semiconductor superlattices offers a further means of studying structure at the interfaces in these materials. Such a technique will supplement earlier work with axial channeling concerning offsets at the interfaces in rows of atoms inclined to the surface normal. The method involves having the interface at a depth of 10–20 nm and adjusting the ion energy so that the ions travel about one quarter wavelength in reaching the interface. The tilt angle of the beam relative to the planar channel can be varied to sweep the beam across the channel and make a precise determination of the offset position. This procedure can provide a confirmation of the offset and a more accurate determination of its size.

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61.85.+p

Channeling phenomena (blocking, energy loss, etc.)

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Channeling measurements of lattice disorder at the GaAs–InAs(100) heterojunction

R. Stanley Williams, B. M. Paine, W. J. Schaffer, and S. P. Kowalczyk

J. Vac. Sci. Technol. 21, 386 (1982); http://dx.doi.org/10.1116/1.571787 (3 pages) | Cited 5 times

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Rutherford backscattering spectrometry (RBS) combined with channeling techniques has been used to analyze the lattice disorder present in InAs thin films less than 1 μm thick grown on GaAs(100) substrates by molecular beam epitaxy (MBE). The axial channeling yields along [100], [110], and [111] reveal that roughly one quarter of the atoms in the thin films are out of registry with the InAs lattice at the heterojunction interface. The amount of lattice disorder decreases rapidly to undetectable (<1%) amounts at film thicknesses greater than 0.5 μm. The interface disorder arises as a result of the ≳7% lattice mismatch between GaAs and InAs.

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68.55.-a	Thin film structure and morphology
68.60.-p	Physical properties of thin films, nonelectronic
61.85.+p	Channeling phenomena (blocking, energy loss, etc.)
73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

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Localized and delocalized charge transfer during adsorption on semiconductors: Experiments and cluster calculations on the prototype surface ZnO(101̄0)

W. Göpel and G. Rocker

J. Vac. Sci. Technol. 21, 389 (1982); http://dx.doi.org/10.1116/1.571788 (9 pages) | Cited 3 times

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We present a combined experimental and theoretical study on chemisorption effects at an ionic semiconductor surface which exhibits negligible concentration of intrinsic surface states in the band gap. Chemisorption may be characterized by localized electronic charge redistribution in the valence‐band range and by delocalized charge transfer between the adsorption complex and free electrons in the conduction‐band range. Geometries, electronic structures, and total energies of adsorption complexes are discussed on the basis of results from sindo1 cluster calculations.

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73.20.-r	Electron states at surfaces and interfaces
73.25.+i	Surface conductivity and carrier phenomena
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces

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Giant replicate cell approach to the electronic structure calculation of graded interface regions

W. Y. Ching

J. Vac. Sci. Technol. 21, 398 (1982); http://dx.doi.org/10.1116/1.571789 (4 pages)

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The usual approach to the theory of interfacial electron states is to assume that the interfaces join abruptly. A multilayer slab geometry is then elected for the calculation of electronic states using methods of varying degree of sophistication. In many cases, the interfaces between semiconductors or dielectric insulators may involve a transition region of several atomic layers. The electron states at one side of the transition region may be quite different from those of the other side. The artificial abrupt connection of the two faces in this case will result in a great strain of bonds at the interface and could lead to the identification of unrealistic interfacial states. An alternate approach to this problem is proposed. We construct a series of giant periodic cells with atomic coordination commensurate with the bonding configurations of the interfacial region. A microscopic first‐principles electronic structure calculation is then applied to each giant cell which replicates the bulk interfacial region. Information such as density of states, partial density of states, gap states, and electron localization can be obtained and correlated to the atomic structures. Results for density of states are presented for SiO_x with x = 1.5, 1.0, and 0.5 as would be appropriate for the Si–SiO₂ interfacial region. States at the upper region of the valence band are found to consist of mainly Si orbitals and their degree of localization is proportional to x. Application of this method to other compound semiconductor interfaces is also discussed.

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73.40.-c	Electronic transport in interface structures
71.20.-b	Electron density of states and band structure of crystalline solids
71.15.-m	Methods of electronic structure calculations

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An investigation of the interface electronics structure of Si–SiO₂ junctions

S. Ciraci, Ş. Ellialtioğlu, and Ş. Erkoç

J. Vac. Sci. Technol. 21, 402 (1982); http://dx.doi.org/10.1116/1.571664 (3 pages) | Cited 1 time

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To understand the physical origin of the interface states in the Si band gap, we have performed empirical tight‐binding calculations for various model structures. We have shown that oxygen atoms breaking the bonds of a Si tetrahedron and forming Si–O–Si or Si–O bonds induce empty states localized at the backbonds. Energy location of these states is seen to depend on the depletion of charge from the backbonds. The role of Si and O vacancies in the vicinity of the interface is also discussed.

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73.20.Hb	Impurity and defect levels; energy states of adsorbed species
73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

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Effect of low‐intensity laser radiation during oxidation of the GaAs(110) surface

W. G. Petro, I. Hino, S. Eglash, I. Lindau, C. Y. Su, and W. E. Spicer

J. Vac. Sci. Technol. 21, 405 (1982); http://dx.doi.org/10.1116/1.571665 (4 pages) | Cited 14 times

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Considerable interest in the use of laser irradiation as a means of processing (annealing, cleaning, alloying, etc.) semiconductor materials, as well as the importance of the oxygen surface chemistry on III‐V semiconductors, has led us to study the effect of low‐intensity (?3 W/cm²) laser radiation on the oxidation behavior of (110) surfaces of GaAs cleaved in UHV (<10⁻¹⁰ Torr). The oxygen sticking probability in the submonolayer coverage range has been increased by a factor of 10³ (from a probability of ∠10⁻⁹ to ∠10⁻⁶) by uniform irradiation of the GaAs surface with a continuous wave Ar⁺ laser (λ = 5145 Å) during the oxygen exposure. We find the data cannot be explained in terms of either heating of the surface or excitation of the oxygen by the laser radiation; it appears that the most likely explanation of the phenomena is an increase in the density of electrons and/or holes at the surface. A limiting step in the oxygen uptake process is the breakup of the oxygen molecule; this dissociation would be increased by increasing the number of electrons at or near the surface. In chemical terms, the reconstructed GaAs surface has no orbitals suitable for binding oxygen—such orbitals can be provided by changing the charge state of a surface atom via optical excitation.

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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
79.20.Ds	Laser-beam impact phenomena

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Interaction of oxygen with silicon d‐metal interfaces: A photoemission investigation

I. Abbati, G. Rossi, L. Calliari, L. Braicovich, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. 21, 409 (1982); http://dx.doi.org/10.1116/1.571666 (4 pages) | Cited 15 times

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We have carried out synchrotron radiation measurements both from valence states and core levels from Si(111)–Cu, Si(111)–Ag, Si(111)–Au, Si(111)–Pd interfaces before and after exposure at room temperature to 30×10⁶ L of oxygen and we compare the results with those for the oxidation of Si(111). In all cases the oxygen interacts with Si and not with the metal, and the Si reaction rate is strongly increased with respect to that of Si(111). The strongest oxidation enhancement is obtained with Cu and Pd. In the noble metal case the interaction with oxygen produces the overgrowth of a SiO₂‐like phase having a Si 2 p chemical shift of ∠3.8 eV as opposite to Si(111) which cannot be oxidized to SiO₂ in these conditions. Moreover, in the Si–Pd case the oxidation number is lower and the chemical shift is ∠2.3 eV. We discuss the relevance of the results both in terms of the structure of the interface and of the nature of the chemical interaction between Si and d metals.

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73.40.Ns	Metal-nonmetal contacts
81.05.Bx	Metals, semimetals, and alloys
79.60.Jv	Interfaces; heterostructures; nanostructures

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Peroxide etch chemistry on 〈100〉In_0.53Ga_0.47As

D. E. Aspnes and H. J. Stocker

J. Vac. Sci. Technol. 21, 413 (1982); http://dx.doi.org/10.1116/1.571667 (4 pages) | Cited 14 times

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We investigate reactions of peroxide etches on 〈100〉 surfaces of In_0.53Ga_0.47As by measuring the pseudodielectric function 〈ϵ〉 with spectroscopic ellipsometry. By comparing these data to calculations in the Bruggeman effective medium approximation, we find that residual 10–80 Å layers of low density oxide, amorphous arsenic, or mixed oxide–arsenic compositions are formed depending primarily on solution pH. The chemical identity of these overlayers is in accord with their known solubility dependence on pH. Etch compositions previously shown to reduce reverse‐ leakage currents in In_0.53Ga_0.47As photodiodes correspond to those for which arsenic precipitates at the surface.

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81.65.-b	Surface treatments
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
78.20.Ci	Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.40.Tv	Optical and dielectric properties related to treatment conditions

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Initial stages of anodic oxidation of GaAs

W. H. Makky, F. Cabrera, K. M. Geib, and C. W. Wilmsen

J. Vac. Sci. Technol. 21, 417 (1982); http://dx.doi.org/10.1116/1.571668 (5 pages) | Cited 3 times

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The island stage of the anodic oxidation of GaAs was investigated with transmission electron microscopy (TEM). Many island details are seen in the high‐resolution photomicrographs of platinum–carbon secondary replicas of the GaAs surface. The nucleation and coalescence processes are seen to take place continuously during the passivation time. The islands are normally circular in shape except when altered by coalescence. The height of the islands increase with island size up to an area of ≊0.1 μ² after which the island height increases only slowly or not at all.

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81.65.-b	Surface treatments
07.79.Cz	Scanning tunneling microscopes
61.05.-a	Techniques for structure determination

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Wavelength dependence of laser‐enhanced oxidation of silicon

S. A. Schafer and S. A. Lyon

J. Vac. Sci. Technol. 21, 422 (1982); http://dx.doi.org/10.1116/1.571669 (4 pages) | Cited 22 times

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The thermal oxidation rate of Si in dry oxygen is increased by illumination with low‐power visible and ultraviolet laser light and is found to be a function of the wavelength of the laser radiation. Visible laser radiation increases the thermal oxidation rate of Si by approximately 40%, and ultraviolet radiation at 350 nm by 60%, over the temperature range of 770–900 °C. A laser‐ induced rate increase of 40% is also observed in wet (H₂O+O₂) thermal oxidation. However, no significant wavelength dependence is seen in this case. It may be concluded from these data that ultraviolet laser light affects some component of the dry oxygen reaction that is not present (or not important) in wet thermal oxidation. There appears to be a threshold energy of 3.0 to 3.5 eV for this observed optical effect. Possible mechanisms for the optical interaction are discussed.

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81.65.-b	Surface treatments
82.30.Nr	Association, addition, insertion, cluster formation

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Orientation dependence of oxygen adsorption on a cylindrical GaAs crystal

W. Ranke, Y. R. Xing, and G. D. Shen

J. Vac. Sci. Technol. 21, 426 (1982); http://dx.doi.org/10.1116/1.571670 (3 pages) | Cited 3 times

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The orientation dependence of oxygen adsorption was studied by AES using a cylindrically shaped GaAs single crystal prepared by ion bombardment and annealing. The cylinder axis was [11̄0] so that the cylinder surface exposed all the main low index surfaces and all transitions between them. The adsorption behavior in the range (001)–(111)Ga–(110)–(111̄)As can basically be understood in terms of enhanced adsorption on edge adjacent sites. A thorough analysis in the range (111)Ga–(110) reveals a transition from steps one (110) layer high near (110) to steps two (110) layers high at (331) between the two low index faces.

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68.03.Fg	Evaporation and condensation of liquids
68.43.Mn	Adsorption kinetics

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Surface donors and acceptors on GaAs and InP exposed to oxygen

A. Nedoluha

J. Vac. Sci. Technol. 21, 429 (1982); http://dx.doi.org/10.1116/1.571671 (5 pages) | Cited 7 times

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A quantitative analysis of existing experimental data on the surface Fermi energies of vacuum‐ cleaved n‐ and p‐type GaAs and InP as a function of oxygen exposure has been performed. A systematic approach has been developed for a two‐level model with surface acceptor and donor energies E_a, E_d and densities N_a,N_d to determine the admissible regions in the E_a,E_d plane. Two admissible energy regions are found for GaAs, but just one very restricted region for InP. With some reservations, the conventional assignments for E_a,E_d in GaAs and InP may be considered as compatible with these admissible regions. The derived dependence of N_a,N_d on oxygen exposure, both for GaAs and InP, suggests the existence of two oxidation mechanisms, the first active at low surface exposures and saturating at 10⁴–10⁵ Langmuir, the second becoming dominant at 0.02– 0.05 monolayers of surface oxygen coverage and saturating at high‐exposure levels.

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73.20.Hb	Impurity and defect levels; energy states of adsorbed species
81.65.-b	Surface treatments

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Reduction of surface states on GaAs by the plasma growth of oxyfluorides

R. K. Ahrenkiel, L. L. Kazmerski, P. J. Ireland, O. Jamjoum, P. E. Russell, D. Dunlavy, R. S. Wagner, S. Pattillo, and T. Jervis

J. Vac. Sci. Technol. 21, 434 (1982); http://dx.doi.org/10.1116/1.571672 (4 pages) | Cited 3 times

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Bonding chemistry predicts that native oxides on GaAs produce intrinsic surface state. Native oxyfluoride dielectric are predicted to be stable and free of bonding defects. We have grown native oxides and oxyfluorides on GaAs by a glow discharge plasma process. Oxide MIS structures always have large densities of fast interface states. We have grown oxyfluoride structures in which surface state effects are reduced by about a factor of 50. ESCA and SIMS analysis of the oxyfluoride dielectric showed a uniform fluorine distribution in thermally annealed samples. X‐ ray photoemission spectroscopy (XPS) indicate that the molecular components of the glass are GaF₃ and AsOF₃.

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81.05.Kf	Glasses (including metallic glasses)
81.65.-b	Surface treatments

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Analysis of electrical and optical properties of insulating film–GaAs interfaces using MESFET‐type structures

M. Ozeki, K. Kodama, M. Takikawa, and A. Shibatomi

J. Vac. Sci. Technol. 21, 438 (1982); http://dx.doi.org/10.1116/1.571673 (4 pages) | Cited 14 times

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The electrical and optical measurements of low‐frequency characteristics for the GaAs MESFET structures with long gate width were found to be an effective tool for the studies of interface states between insulating films and GaAs. The surface leakage current through the interface layer plays an important role in the frequency dependence of the transconductance and the gate admittance. An equivalent circuit which quantitatively explains the experimental results is proposed. Using the MESFET structure overcoated with insulating films (SiO₂, Si₃N₄, and AlN), electrical and optical properties of the interface between these insulating films and GaAs were studied and it was found that these films have characteristic activation energies of 0.62, 0.44, and 0.27 eV, respectively.

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73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.61.Ng	Insulators
85.30.Tv	Field effect devices

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Hg_0.70Cd_0.30Te anodic oxidation

Bruce K. Janousek and Richard C. Carscallen

J. Vac. Sci. Technol. 21, 442 (1982); http://dx.doi.org/10.1116/1.571674 (4 pages) | Cited 13 times

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It has been determined that anodic oxidation of (Hg,Cd)Te proceeds via a dissolution– precipitation mechanism. The initial film formation can be understood in terms of electrochemical parameters and, therefore, can be controlled in a rational manner. For example, stirring the anodization solution during dissolution prohibits film formation at low current densities due to an increase in the rate of diffusion of ionic species away from the anode. Increasing the solution pH makes the anodic oxide more soluble and semiconductor dissolution can be sustained at a higher current density. MOS structures fabricated incorporating this electroetch in the passivation process show a lower oxide fixed charge likely owing to the removal of the TeO₂ film present on the semiconductor following a Br₂/methanol etch.

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82.45.-h	Electrochemistry and electrophoresis
81.05.Bx	Metals, semimetals, and alloys

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Summary Abstract: Photochemical oxidation of (Hg,Cd)Te

S. P. Buchner, G. D. Davis, and N. E. Byer

J. Vac. Sci. Technol. 21, 446 (1982); http://dx.doi.org/10.1116/1.571675 (2 pages) | Cited 5 times

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81.05.Bx	Metals, semimetals, and alloys
82.50.-m	Photochemistry

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Hg_1−xCd_xTe native oxide reduction by CVD SiO₂

David R. Rhiger and Robert E. Kvaas

J. Vac. Sci. Technol. 21, 448 (1982); http://dx.doi.org/10.1116/1.571676 (5 pages) | Cited 4 times

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An interfacial reaction is shown to occur between the native oxide on Hg_1−xCd_xTe and a CVD SiO₂ overlayer. Native oxides were grown by anodizing and coated with SiO₂ by the reaction of SiH₄ and O₂ at 100 °C. The structure was analyzed by sputter‐XPS profiling. The chemically split components of the Te(3d5/2) line indicate a much greater ratio of reduced to oxidized Te compared to the anodic oxide without SiO₂. The reduced material is equivalent to roughly 15 Å of anodic oxide. Calculations indicate that reactions in which oxide compounds of Hg, Cd, and Te are reduced by SiH₄, Si, and SiO are thermodynamically favored.

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68.35.Md	Surface thermodynamics, surface energies
82.30.Lp	Decomposition reactions (pyrolysis, dissociation, and fragmentation)
81.65.-b	Surface treatments

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Improvements in GaAs/plasma‐deposited silicon nitride interface quality by predeposition GaAs surface treatment and postdeposition annealing

Marion D. Clark and C. Lawrence Anderson

J. Vac. Sci. Technol. 21, 453 (1982); http://dx.doi.org/10.1116/1.571677 (4 pages) | Cited 7 times

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Substantial improvements in the electrical properties of interfaces between n‐type GaAs and Si₃N₄ formed by plasma‐enhanced CVD have been obtained by in situ substrate surface treatment with a hydrogen plasma and postdeposition annealing. For samples with surface treatment and deposition performed at 300 °C, annealing at 600° for 30 min in N₂ produced a dramatic reduction of capacitance frequency dispersion. Capacitance and conductance data indicate a major reduction of surface state density. Low‐frequency C–V on an illuminated sample show evidence of surface inversion. AES composition profiles are presented as evidence that the hydrogen plasma treatment reduces native oxide on the GaAs.

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73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.65.-b	Surface treatments
81.15.Gh	Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

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Photoionization and thermal activation of compound semiconductor MOS interfaces and origin of interface states

Hideki Hasegawa and Takayuki Sawada

J. Vac. Sci. Technol. 21, 457 (1982); http://dx.doi.org/10.1116/1.571678 (6 pages) | Cited 12 times

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Dynamic properties of GaAs and InP anodic MOS interfaces are studied, using photocapacitance transient spectroscopy (PCTS) and deep level transient spectroscopy (DLTS) techniques. Measured PCTS spectra possess a gate bias dependent portion corresponding to U‐shaped continuous distribution of interface states and a bias‐independent portion with a large photoionization rate. The photoionization cross section of a state continuum increases monotonically with photon energy, similarly to Si MOS, but very differently from bulk deep traps. Anomalously reduced DLTS activation energies of interface states are observed for electron emission in GaAs and for hole emission in InP, and they are correlated to a bias‐independent portion of PCTS spectra. Measured results are explained by coexistence of an energetically and spatially distributed localized state continuum region and a partially delocalized state region. Surface disorder is proposed to be the origin of such composite interface state structure rather than the surface‐vacancy based model.

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73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.20.Hb	Impurity and defect levels; energy states of adsorbed species

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Investigation of GaAs field‐effect transistor interfaces using pulsed electron beam excitation

L. D. Flesner, A. K. Nedoluha, and H. H. Wieder

J. Vac. Sci. Technol. 21, 463 (1982); http://dx.doi.org/10.1116/1.571679 (4 pages)

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Electron‐beam pulses applied to various regions of an operating GaAs field‐effect transistor (FET) produce both fast and slow changes in gate and drain currents. These effects provide information regarding transient phenomena occurring at the top and bottom interfaces which define the FET channel. In particular, large changes observed in the drain current reflect the kinetics of charge carrier trapping and recombination at the interfaces. Additional information is obtained from changes which result when the gate and drain bias are varied, and from comparison of different device structures, for example, devices with and without gates. Data are presented for a junction FET (JFET) and an analogous device without a gate. The gate bias dependence observed suggests that the trapping phenomena are occurring below the FET channel. A rapid transient response which is observed in the JFET that is absent in devices without a gate indicates enhanced recombination due to the p‐n junction.

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85.30.Tv

Field effect devices

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Summary Abstract: Cation bonds in Hg_1−xCd_xTe

J. A. Silberman, P. Morgen, I. Lindau, W. E. Spicer, A.‐B. Chen, A. Sher, and J. A. Wilson

J. Vac. Sci. Technol. 21, 467 (1982); http://dx.doi.org/10.1116/1.571680 (2 pages) | Cited 1 time

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73.20.-r	Electron states at surfaces and interfaces
79.60.Bm	Clean metal, semiconductor, and insulator surfaces

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Electronic structure of GaAs_xP_1−x/GaP strained‐layer superlattices with x<0.5

G. C. Osbourn

J. Vac. Sci. Technol. 21, 469 (1982); http://dx.doi.org/10.1116/1.571681 (4 pages) | Cited 17 times

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The electronic properties of GaAs_xP_1−x/GaP(100) strained‐layer superlattices with x<0.5 are studied using both a tight‐binding model and an effective‐mass model. By varying the alloy compositions and thicknesses of the layers, it is possible to independently vary the band gap and lattice constant of these structures. For the structures in which the bulk [100] minima are mapped into the strained‐layer superlattice Γ point, a direct band gap occurs in the superlattice even though the bulk materials have indirect gaps. The results illustrate that strained‐layer superlattices in general form a broad new class of semiconductor materials with tailorable electronic properties.

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71.20.Nr	Semiconductor compounds
71.20.Ps	Other inorganic compounds

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Growth and photoluminescence characterization of a GaAs_xP_1−x/GaP strained‐layer superlattice

P. L. Gourley and R. M. Biefeld

J. Vac. Sci. Technol. 21, 473 (1982); http://dx.doi.org/10.1116/1.571682 (3 pages) | Cited 10 times

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We have succeeded in growing a GaAs_xP_1−x/GaP strained‐layer superlattice (SLS). The structure was grown by alternate metal–organic chemical vapor deposition of thin (60 Å) layers (20 each) of GaAs_0.4P_0.6 and GaP. These layers were deposited onto a GaAs_xP_1−x layer which was graded in composition from x = 0 (composition of underlying GaP substrate) to x = 0.2 (average composition of SLS). Photoluminescence studies of the SLS were carried out to determine the optical band gap. At T = 78 K, the emission from the SLS exhibits a dominant peak at 2.03 eV, as well as weaker peaks at higher energies. We attribute these peaks to direct transitions between SLS conduction and valence band states. The measured energies for the fundamental gap and higher energy transitions are in good agreement with recent theoretical results.

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71.20.Nr	Semiconductor compounds
71.20.Ps	Other inorganic compounds
78.55.Hx	Other solid inorganic materials
81.10.Bk	Growth from vapor

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Observation of Ge‐induced electronic states at the Ge:GaAs(110) interface by means of polarization‐dependent UPS

P. Zurcher, G. J. Lapeyre, J. Anderson, and D. Frankel

J. Vac. Sci. Technol. 21, 476 (1982); http://dx.doi.org/10.1116/1.571683 (6 pages) | Cited 2 times

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Strong evidence for Ge‐induced valence band states for ∠0.5 monolayer (ML) Ge on cleaved GaAs(110) is presented. Normal emission energy distribution curves have been measured for two different polarization [A⊥ mirror plane (MP) and A∥MP] for photon energies from hν = 14–27 eV at the University of Wisconsin Synchrotron Radiation Center. Four different kinds of Ge‐induced features are observed: (i) attenuation of clean substrate transitions, (ii) energy shifts of substrate transitions, (iii) new transitions with hν dispersion, and (iv) new transition with no dispersion. The latter dispersionless transition observed for hν between 17 and 23 eV must originate from a two‐ dimensional structure, and we propose that it is due to a Ge:GaAs(110) interface state. With respect to the valence band maximum, its binding energy (E_B) is 6.8 eV which compares to E_B = 7.95 eV predicted for a coverage of 3 ML Ge by Mazur, Pollmann, and Schmeits for a Ge–Ga interface state. The observed interface state shows a relatively strong polarization dependence which implies that the initial state symmetry is odd. Strong Ge‐induced transitions are observed with binding energies between 1 and 3 eV which show large dispersion. This means that the initial states must have a three‐dimensional character. They are identified as GaAs(110) substrate transitions whose matrix elements are strongly enhanced by the chemisorption of Ge, making them observable in UPS.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
81.65.-b	Surface treatments
73.20.-r	Electron states at surfaces and interfaces

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Measurement of ZnSe–GaAs(110) and ZnSe–Ge(110) heterojunction band discontinuities by x‐ray photoelectron spectroscopy (XPS)

Steven P. Kowalczyk, E. A. Kraut, J. R. Waldrop, and R. W. Grant

J. Vac. Sci. Technol. 21, 482 (1982); http://dx.doi.org/10.1116/1.571684 (4 pages) | Cited 31 times

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X‐ray photoelectron spectroscopy was used to study the growth and energy‐band alignment of ZnSe–GaAs(110) and ZnSe–Ge(110) heterojunctions. The ZnSe–GaAs heterojunctions were formed by growing ZnSe on GaAs(110). Growth temperatures were varied to produce both epitaxial and nonepitaxial interfaces. For ZnSe grown at ∠300 °C on GaAs(110), the valence‐ band discontinuity ΔE_v was 0.96 eV; for ZnSe deposited at room temperature and crystallized at ∠300 °C, ΔE_v is 1.10 eV. The Ge–ZnSe(110) interfaces were formed by depositing Ge(ZnSe) on ZnSe(Ge)(110) at room temperature, followed by ∠300 °C crystallization. The corresponding ΔE_v’s were 1.52 and 1.29 eV, respectively. Our measured ΔE_v values for epitaxial heterojunctions are compared with the predictions of theoretical models. Our results demonstrate that substantial interface structure dependent contributions to ΔE_v can occur at Ge–ZnSe(110) and GaAs– ZnSe(110) heterojunctions.

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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
81.65.-b	Surface treatments

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Formation, growth, and stability of the CdS/CuInSe₂ interface

L. L. Kazmerski, O. Jamjoum, P. J. Ireland, R. A. Mickelsen, and W. S. Chen

J. Vac. Sci. Technol. 21, 486 (1982); http://dx.doi.org/10.1116/1.571744 (5 pages) | Cited 11 times

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The initial formation and subsequent development of the CdS/CuInSe₂ interface are studied. XPS depth‐compositional data are used to identify the composition of a interfacial reacted region between the CdS and Cu‐ternary layers. Angular‐resolved XPS confirm the existence of this transition layer which is a mixed Cu₂S–Cu₂S binary. Auger transitions in the XPS spectra are used to resolve those compounds. Differences in EELS spectra as a function of CdS growth are also ascribed to the existence of the interface region. The effects of annealing on the integrity of this interface and photovoltaic performance of the device are also presented. Three distinct regimes are identified: (1) T<150 °C. Device and interface properties are stable; (2) 200<T<300 °C. Se and S interdiffusion occurs, with 50%–75% degradation in cell performance; and (3) T≳350 °C. Rapid diffusion of the Cd into the Cu‐ternary takes place, destroying junction integrity and causing complete device failure.

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84.60.Jt	Photoelectric conversion
73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

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Surface processes controlling MBE heterojunction formation: GaAs(100)/Ge interfaces

Robert S. Bauer and J. C. Mikkelsen

J. Vac. Sci. Technol. 21, 491 (1982); http://dx.doi.org/10.1116/1.571745 (7 pages) | Cited 18 times

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In situ LEED and synchrotron radiation photoemission spectroscopy were performed on Ge interfaces grown by MBE on GaAs(100) surfaces ranging from the As‐rich c(4×4) to the Ga‐rich 4×6 ordered MBE surface phases. By comparison to MBE and bulk grown c‐GeAs, we find that when lattice‐matched heterojunctions are grown on GaAs surfaces, GeAs forms an ordered 3×1 phase at the free surface of Ge(110) and a two‐domain (2×1) phase at the free surface of Ge(100). The GeAs_x two‐domain (2×1) ordered Ge(100): As surface phase is obtained independent of the initial GaAs(100) surface As concentration. Further, As outdiffusion does not occur during the initial deposition of Ge; rather, we observe an As enrichment of the Ge surface at a Ge coverage corresponding to the initial surface As concentration. The As diffusion from the interface layer, while lowering the free energy of the Ge surface layers, also changes the band‐gap offset.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.-a	Thin film structure and morphology

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The electronic structure of Ge:GaAs(110) interfaces

W. Mönch, Robert S. Bauer, H. Gant, and R. Murschall

J. Vac. Sci. Technol. 21, 498 (1982); http://dx.doi.org/10.1116/1.571746 (9 pages) | Cited 16 times

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Ge:GaAs heterostructures were investigated by photoemission from core levels excited with soft x rays. Epitaxial and amorphous films were grown by condensing Ge on surfaces cleaved from n‐ GaAs held at 300 and 20 °C, respectively. On the GaAs side of the heterostructure, the Fermi level is pinned (0.75±0.1) eV above the valence band edge, regardless of whether the Ge overgrowth was crystalline or amorphous. This may be caused by chemisorption‐induced defects. The valence band discontinuity depends on the structure of the Ge film and amounts to 0.42 with epitaxial and to 0.65 eV with amorphous overgrowths. Half a monolayer of As (most probably bound as GeAs) and ∠0.03 monolayer of Ga were found to be segregated at the crystalline film surfaces.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
68.55.-a	Thin film structure and morphology
71.20.Nr	Semiconductor compounds
71.20.Ps	Other inorganic compounds
81.65.-b	Surface treatments

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Summary Abstract: The onset of intersubband scattering in a two‐dimensional electron system

H. L. Störmer, A. C. Gossard, and W. Wiegmann

J. Vac. Sci. Technol. 21, 507 (1982); http://dx.doi.org/10.1116/1.571747 (2 pages)

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Dp	General theory, scattering mechanisms

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Picosecond time‐resolved photoelectron spectroscopy of ZnTe

R. T. Williams, T. R. Royt, J. C. Rife, J. P. Long, and M. N. Kabler

J. Vac. Sci. Technol. 21, 509 (1982); http://dx.doi.org/10.1116/1.571748 (5 pages) | Cited 5 times

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We describe a new time‐resolved probe of excited electronic states near surfaces of semiconductors, as applied to cleaved crystals of ZnTe. Electrons photoexcited to the conduction band by a 5‐ps laser pulse are re‐excited by a second pulse to states above vacuum energy. Analysis of the photoelectrons resulting from this resonant two‐photon process yields data on energy distributions and relaxation times of electrons in the intermediate states. Preliminary evidence for persistent (∠150 ps) occupation of states up to 1.6 eV above the conduction band minimum in ZnTe is presented.

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81.65.-b

Surface treatments

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Summary Abstract: n‐i‐p‐i superlattices: Theoretical predictions and experimental verification

G. H. Döhler

J. Vac. Sci. Technol. 21, 514 (1982); http://dx.doi.org/10.1116/1.571749 (2 pages)

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Abstract Unavailable

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73.40.Ty

Semiconductor-insulator-semiconductor structures

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Light scattering study of electrons confined at Ge/GaAs interfaces

R. Merlin, A. Pinczuk, W. T. Beard, and C. E. E. Wood

J. Vac. Sci. Technol. 21, 516 (1982); http://dx.doi.org/10.1116/1.571750 (3 pages) | Cited 4 times

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Resonant inelastic light scattering experiments in Ge/GaAs interfaces show a new spectral band associated with quasi‐two‐dimensional electron states in a Ge‐accumulation layer. A theoretical fit of the position and shape of this structure indicates that it is due to interband transitions between a quasi‐two‐dimensional band and the continuum.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
78.40.Ha	Other nonmetallic inorganics
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

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Energy spectra of donors in GaAs–Ga_1−xAl_xAs quantum well structures in the effective mass approximation

C. Mailhiot, Yia‐Chung Chang, and T. C. McGill

J. Vac. Sci. Technol. 21, 519 (1982); http://dx.doi.org/10.1116/1.571751 (5 pages) | Cited 2 times

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We present the results of a study of the energy spectrum of the ground state for shallow donors in quantum well structures, consisting of a single slab of GaAs sandwiched between two semi‐ infinite layers of Ga_1−xAl_xAs. The effect of the position of the impurity atom within the central GaAs slab is investigated for different slab thicknesses and alloy compositions. Two limiting cases are presented: One in which the impurity atom is located at the center of the quantum well (on‐ center impurity), the other in which the impurity atom is located at the edge of the quantum well (on‐edge impurity). Both the on‐center and the on‐edge donor ground state are bound for all values of GaAs slab thicknesses and alloy compositions. The alloy composition x is varied between 0.1 and 0.4. In this composition range, Ga_1−xAl_xAs is direct and the single‐valley effective mass theory is a valid technique for treating shallow donor states. Calculations are carried out in the case of finite potential barriers determined by realistic conduction band offsets.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.18.+y	Fermi surface: calculations and measurements; effective mass, g factor
71.55.Ht	Other nonmetals

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Band structure of impurity‐sheet‐doped superlattice alloys

Harold P. Hjalmarson

J. Vac. Sci. Technol. 21, 524 (1982); http://dx.doi.org/10.1116/1.571752 (4 pages) | Cited 11 times

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The band structure and density of states for large superlattices of (100) Ga‐site Ge and As‐site N impurity sheets in GaAs have been calculated by a semiempirical tight‐binding technique. Both of these two‐dimensional conduction‐band derived bands with a J‐point indirect minimum which is deep in energy (∠0.5 eV) relative to the bulk conduction band edge. The calculation, which was performed on a single impurity sheet, demonstrates that, in general, a planar defect localizes or binds one or more states. It is suggested that the large binding energies of these sheets will confine electric‐field‐accelerated carriers and thus such superlattices will be highly conductive parallel to the impurity sheets.

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73.20.Hb	Impurity and defect levels; energy states of adsorbed species
71.20.-b	Electron density of states and band structure of crystalline solids

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Electronic structure of GaP–AlP(100) superlattices

J. Y. Kim and A. Madhukar

J. Vac. Sci. Technol. 21, 528 (1982); http://dx.doi.org/10.1116/1.571753 (3 pages) | Cited 7 times

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The band structure of GaP–AlP(100) superlattices with unit‐cell thickness up to 32 atomic layers is reported. It is found that for the expected range of band‐edge discontinuity, the superlattices exhibit a direct‐gap behavior—an interesting result given the indirect nature of GaP and AlP. The wave functions associated with the top of the valence band show behavior characteristic of interface states, whereas the wave functions associated with the bottom of the conduction band are characteristic of two‐dimensionally confined states.

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71.20.Nr	Semiconductor compounds
71.20.Ps	Other inorganic compounds

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Self‐consistent calculations in InAs–GaSb heterojunctions

G. Bastard, E. E. Mendez, L. L. Chang, and L. Esaki

J. Vac. Sci. Technol. 21, 531 (1982); http://dx.doi.org/10.1116/1.571754 (3 pages) | Cited 7 times

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Self‐consistent calculations, in the electric quantum limit, of GaSb–InAs–GaSb heterostructures show the existence of a semiconductor‐to‐semimetal transition when the InAs thickness exceeds 100 Å, as a result of electron transfer from GaSb. Under the effect of an intense magnetic field a reverse electron transfer leads to a semimetal‐to‐semiconductor transition which occurs at a thickness‐dependent critical field.

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73.40.Lq

Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

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Polar‐on‐nonpolar epitaxy: Sublattice ordering in the nucleation and growth of GaP on Si(211) surfaces

Steven L. Wright, Masanori Inada, and Herbert Kroemer

J. Vac. Sci. Technol. 21, 534 (1982); http://dx.doi.org/10.1116/1.571755 (6 pages) | Cited 26 times

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When a binary compound with two different atoms per primitive cell is grown on a lattice‐ matched elementary substrate in which the two atoms are identical, there exists an inherent ambiguity in the nucleation of the compound, with two different possible atomic arrangements, distinguished by an interchange of the two sublattices of the compound. For defect‐free growth, one of the two possible nucleation modes must be suppressed. The problems involved in doing so depend very strongly on the crystallographic orientation of the substrate; for most orientations they are greatly complicated by the additional problem of electrical neutrality at the resulting polar/nonpolar interface. For zincblende‐on‐diamond growth, the (211) orientation is potentially one of the most promising orientations to overcome both classes of problems. The simplest possible atomic configuration for this orientation exhibits two different classes of bonding sites, some with one dangling bond, some with two, in the correct arrangement to create a strong preference for one of the two atomic configurations. We have grown GaP on Si (211) by MBE. Etching studies have indicated that (under the proper nucleation conditions) the growth is largely free of antiphase disorder, and that the sublattice ordering corresponds to P‐atoms bonded to those interface sites that have two back bonds to Si. The likely nucleation sequence is discussed.

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

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Theory of heterostructures: A reduced Hamiltonian method with evanescent states and transfer matrices

Yia‐Chung Chang and J. N. Schulman

J. Vac. Sci. Technol. 21, 540 (1982); http://dx.doi.org/10.1116/1.571756 (4 pages) | Cited 5 times

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A new theoretical technique for calculating the electronic properties of heterostructures is presented. This method is computationally more efficient than any current technique and has physically intuitive clarity. Furthermore, it can be applied to heterostructures with arbitrary perturbations varying in the direction perpendicular to the interface, such as smoothly varying electrostatic potentials caused by doping, compositional grading disruptions, and long range lattice relaxations. Using this method, we have studied several semiconductor surfaces, interfaces, and superlattices, including doping and relaxation effects in a realistic tight‐binding model. The results for the Si (111)–(2×1) surface and the GaAs/AlAs interface with doping are presented.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.20.-r	Electron states at surfaces and interfaces
71.15.-m	Methods of electronic structure calculations

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Effective‐mass theory for electrons in heterostructures

S. R. White, G. E. Margues, and L. J. Sham

J. Vac. Sci. Technol. 21, 544 (1982); http://dx.doi.org/10.1116/1.571757 (4 pages) | Cited 6 times

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We present an effective‐mass theory which can treat the potential due to the redistribution of electrons in heterostructures of III–V semiconductors, including MIS junctions and superlattices. A multiband representation deals with the interaction of the conduction and valence bands. Matching conditions for the components of the envelope function across an interface are deduced by two methods, one in terms of Kane’s k⋅p model, and the other in terms of a tight‐binding model. Consequences of these matching conditions are discussed briefly.

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71.20.Nr	Semiconductor compounds
71.20.Ps	Other inorganic compounds
73.40.Qv	Metal-insulator-semiconductor structures (including semiconductor-to-insulator)

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Bound and resonant surface states at the (110) surfaces of AlSb, AlAs, and AlP

Richard P. Beres, Roland E. Allen, Jean Pierre Buisson, Marshall A. Bowen, George F. Blackwell, Harold P. Hjalmarson, and John D. Dow

J. Vac. Sci. Technol. 21, 548 (1982); http://dx.doi.org/10.1116/1.571758 (3 pages) | Cited 1 time

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The dispersion curves E(?) have been calculated for bound and resonant (110) surface states of AlSb, AlAs, and AlP. AlSb is predicted to have no surface states within the bulk fundamental band gap, but AlAs and AlP are predicted to have surface state band minima which are very near the conduction band edge, and could lie either within the gap or immediately above the edge.

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73.20.-r

Electron states at surfaces and interfaces

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On the interface connection rules for effective‐mass wave functions at an abrupt heterojunction between two semiconductors with different effective mass

Herbert Kroemer and Qi‐Gao Zhu

J. Vac. Sci. Technol. 21, 551 (1982); http://dx.doi.org/10.1116/1.571759 (3 pages) | Cited 15 times

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The problem of the connection rules for effective‐mass wave functions across an abrupt heterojunction is investigated by expressing the results of a one‐dimensional, tight‐binding approximation in terms of effective‐mass wave functions. It is shown that the widely used conventional connection rules of continuous wave function and slope break down if the effective masses on the two sides are different, except if a certain interface matrix element happens to equal the geometric mean of two analogous bulk matrix elements, a case referred to as χ normal. In this case the conventional connection rules yield correct energy eigenvalues, but the effective‐mass wave functions themselves differ from true probability amplitudes by a factor depending on the local effective mass, different on the two sides. Heterojunctions that deviate from χ normality may, to the first order, be described as if a δ‐function potential had been added at the interface.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
71.18.+y	Fermi surface: calculations and measurements; effective mass, g factor

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Summary Abstract: Thermodynamics of overlayer ordering and epitaxy

Max G. Lagally

J. Vac. Sci. Technol. 21, 554 (1982); http://dx.doi.org/10.1116/1.571760 (3 pages)

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68.55.-a

Thin film structure and morphology

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Summary Abstract: Ion‐enhanced gas‐surface chemistry

J. W. Coburn

J. Vac. Sci. Technol. 21, 557 (1982); http://dx.doi.org/10.1116/1.571761 (2 pages) | Cited 1 time

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81.65.-b	Surface treatments
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
52.40.Hf	Plasma-material interactions; boundary layer effects

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Chemical control of recombination at grain boundaries and liquid interfaces: Electrical power and hydrogen generating photoelectrochemical cells

A. Heller

J. Vac. Sci. Technol. 21, 559 (1982); http://dx.doi.org/10.1116/1.571762 (3 pages) | Cited 3 times

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Recombination of carriers at a surface or at a grain boundary of a semiconductor is associated with the presence of chemical bonds that are weaker than those in the bulk. Upon strengthening these bonds, by reacting the interface with a strongly bound impurity, the rate of recombination is drastically reduced. For example, a 10³‐fold increase in EBIC charge collection efficiency for the polycrystalline p–InP/Ti Schottky junction and a corresponding increase in the efficiency of the photoelectrochemical cell polycrystalline p–InP/VCl₃–VCl₂–HCl/C are observed when silver is chemisorbed on the semiconductor grain boundaries. Chemical control of carrier recombination at semiconductor solution interfaces and grain boundaries results in 12 % efficient monocrystalline and 8 % efficient thin film polycrystalline solar cells, that generate either electrical power or hydrogen.

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84.60.Jt	Photoelectric conversion
61.72.Mm	Grain and twin boundaries
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces

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Summary Abstract: Monte Carlo simulation of growth and nature of binary and pseudobinary model systems grown via molecular beam epitaxy

J. Singh and A. Madhukar

J. Vac. Sci. Technol. 21, 562 (1982); http://dx.doi.org/10.1116/1.571763 (2 pages)

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68.55.-a	Thin film structure and morphology
81.15.Cd	Deposition by sputtering

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Fermi‐level pinning and chemical structure of InP–metal interfaces

L. J. Brillson, C. F. Brucker, A. D. Katnani, N. G. Stoffel, R. Daniels, and G. Margaritondo

J. Vac. Sci. Technol. 21, 564 (1982); http://dx.doi.org/10.1116/1.571764 (6 pages) | Cited 19 times

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We have used soft x‐ray photoemission spectroscopy (SXPS) to investigate the dependence of Fermi‐level pinning on chemical structure at InP–metal interfaces. SXPS core level spectra of Al, Ti, Ni, Au, Pd, Ag, and Cu on UHV‐cleaved InP(110) surfaces reveal evidence for semiconductor outdiffusion, metal indiffusion, metal‐anion bonding and metal‐cation alloying. Corresponding Fermi‐level movements indicate a range of pinning positions at significantly different energies within the n‐type InP band gap. These results demonstrate that the Schottky barrier heights depend sensitively on changes in interface chemical bonding and diffusion, which strongly affect the type of electrically active sites and interfacial layers formed.

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73.40.Ns	Metal-nonmetal contacts
71.18.+y	Fermi surface: calculations and measurements; effective mass, g factor
79.60.Jv	Interfaces; heterostructures; nanostructures

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Size dependence of ’’effective’’ barrier heights of mixed‐phase contacts

J. L. Freeouf, T. N. Jackson, S. E. Laux, and J. M. Woodall

J. Vac. Sci. Technol. 21, 570 (1982); http://dx.doi.org/10.1116/1.571765 (4 pages) | Cited 31 times

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The literature currently abounds with experimental studies of Schottky barrier heights of various metals upon many semiconductors. Unfortunately, these studies present some puzzling aspects: (1) Commonly, barriers determined by C–V studies are larger than barriers determined by I–V studies, and (2) Results obtained by different workers under apparently identical conditions are not always similar. A possible explanation for such effects is simply that many/most contacts experimentally achieved are in fact multiphase; these different barrier‐height regions could result from variations in the metallurgical reactions assumed by many current models of Schottky barrier energetics. The different barrier heights measured by different techniques follow directly from the functional form of the relevant probes (e.g., I–V would more heavily weight a low‐barrier region). The lack of reproducibility would follow from kinetic aspects of the relevant metallurgical interactions. A recent publication discusses the functional form for I–V and C–V ’’effective’’ barrier heights from mixed‐phase contacts isolated from one another. These results apply directly to mixed‐phase contacts only if the linear dimensions of all contact regions are large compared to the Debye length of the substrate (≊0.1 μ for 10¹⁵ silicon). In this paper, we examine the effects of contact dimensions upon equilibrium potentials (e.g., band bending) as well as transport studies to infer ’’effective’’ barrier heights for truly mixed‐phase contacts of varying dimensions but fixed area ratios.

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73.30.+y

Surface double layers, Schottky barriers, and work functions

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Summary Abstract: Are they really Schottky barriers after all?

J. M. Woodall and J. L. Freeouf

J. Vac. Sci. Technol. 21, 574 (1982); http://dx.doi.org/10.1116/1.571766 (3 pages) | Cited 20 times

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Abstract Unavailable

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73.30.+y

Surface double layers, Schottky barriers, and work functions

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Structural model of III–V compound semiconductor Schottky barriers

B. W. Lee, D. C. Wang, R. K. Ni, G. Xu, and M. Rowe

J. Vac. Sci. Technol. 21, 577 (1982); http://dx.doi.org/10.1116/1.571790 (8 pages) | Cited 4 times

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Schottky barriers have been fabricated on n‐type GaP(111) crystals to study the structural characteristics of the diodes. The formation of Schottky barriers by evaporating a metal layer onto the III–V compound semiconductor surface generally created an amorphous film interlayer between the metal and the semiconductor. Current–voltage (I–V), capacitance–voltage (C–V) and Auger electron spectroscopy (AES) data were used to characterize the interface amorphous film. A model of a resistor in parallel with a capacitor and then in series with the metal and the semiconductor layers is used to describe the properties of a real Schottky barrier. The thickness of the amorphous film is in the range 50–500 Å, dependent on evaporation details. The dielectric constant and the resistivity of the amorphous film are experimentally estimated, and are found to be frequency dependent. A metal‐amorphous film–semiconductor (MAS) configuration is proposed to be the structural model for a real Schottky barrier. The structural model is combined with the defect model to explain the fundamental transition in interface electronic nature between covalent and ionic semiconductors as well as other properties of a real Schottky barrier.

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73.30.+y	Surface double layers, Schottky barriers, and work functions
73.40.Ns	Metal-nonmetal contacts

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High Schottky barriers on and thermally induced processes at the Au– GaAs(110) interface

W. G. Petro, I. A. Babalola, P. Skeath, C. Y. Su, I. Hino, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. 21, 585 (1982); http://dx.doi.org/10.1116/1.571791 (5 pages) | Cited 4 times

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New photoemission measurements show higher Schottky barrier heights (≳1.3 eV) on atomically clean GaAs(110) surfaces at a Au coverage of about 25 monolayers. It is suggested that this effect is due to the movement of Au into the semiconductor; at room temperature it creates acceptor states near the valence band maximum (VBM) that cause the Fermi level at the surface (E_fs ) to move close to the VBM. We found that heating of the GaAs(110) surface (above 100 °C) covered with a small amount of Au (0.2 monolayer) causes E_fs to move back to its original position (on the clean surface before Au deposition). The heating process is found to greatly inhibit the formation of large barrier heights due to the removal of defect states from the surface region.

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73.40.Ns	Metal-nonmetal contacts
73.30.+y	Surface double layers, Schottky barriers, and work functions
73.20.Hb	Impurity and defect levels; energy states of adsorbed species
81.40.Rs	Electrical and magnetic properties related to treatment conditions

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Schottky barrier modulation at metal contacts to CdS and CdSe

C. F. Brucker, L. J. Brillson, A. D. Katnani, N. G. Stoffel, and G. Margaritondo

J. Vac. Sci. Technol. 21, 590 (1982); http://dx.doi.org/10.1116/1.571792 (4 pages) | Cited 4 times

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Soft x‐ray photoemission spectroscopy measurements have been used to study the pinning position of the surface Fermi level as well as the nature of the electrostatic band bending for single and interlayer metal contacts to ultrahigh‐vacuum‐cleaved CdSe and CdS (101̄0) surfaces. Single metal (Al,Au) contacts are found to exhibit a one‐to‐one correspondence between the pinning position and the effective Schottky barrier height as measured by in situ C–V and I‐V analyses. However, a fundamentally different mechanism of barrier modulation is indicated for interlayer contacts, i.e., contacts formed by interspersing an ultrathin reactive metal interlayer (Al) between the semiconductor and a noble metal contact (Au). Core level broadenings as a function of photon energy are interpreted in terms of sharp band bending at the surface, leading to the possibility of quantum mechanical tunneling through the barrier. This barrier narrowing effect is attributed to an indirect doping effect as a consequence of metal–semiconductor interfacial reaction.

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73.30.+y	Surface double layers, Schottky barriers, and work functions
73.40.Ns	Metal-nonmetal contacts
79.60.Bm	Clean metal, semiconductor, and insulator surfaces

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Metal–GaSe and metal–InP interfaces: Schottky barrier formation and interfacial reactions

R. H. Williams, A. McKinley, G. J. Hughes, V. Montgomery, and I. T. McGovern

J. Vac. Sci. Technol. 21, 594 (1982); http://dx.doi.org/10.1116/1.571793 (5 pages) | Cited 17 times

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We have studied the formation of the interface between a range of metals and the semiconductors GaSe and InP using photoelectron spectroscopy and a synchrotron source. We concentrate in particular on the reactive metal Ni and the relatively unreactive metals Au and Ag. It is shown that metals which interact only weakly with GaSe yield a Fermi‐level pinning behavior close to the Schottky limit but those metals which interact strongly lead to strong pinning of the Fermi level by interfacial defects. The complex interactions at Ni–InP and Au–InP interfaces are considered and the Fermi‐level pinning behavior is discussed in terms of the defect model.

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73.30.+y	Surface double layers, Schottky barriers, and work functions
82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
73.40.Vz	Semiconductor-metal-semiconductor structures
81.65.-b	Surface treatments

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Crystallographic relationships and interfacial properties of Ag on GaAs(100) surfaces

R. Ludeke, T.‐C. Chiang, and D. E. Eastman

J. Vac. Sci. Technol. 21, 599 (1982); http://dx.doi.org/10.1116/1.571794 (8 pages) | Cited 18 times

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The crystallographic relationships, growth morphology, chemical activity, and electronic properties of Ag deposited at room temperature on GaAs(100) c(2×8) and (4×6) surfaces were investigated. Ag(110) growth was observed independent of growth rates. The growth is three‐ dimensional (nucleated) and the interfaces are abrupt. Stabilization of the Fermi level occurs beyond Ag coverages of 10 Å, is uncorrelated with the appearance of the metallic Ag phase at ∠0.5 Å and appears to be dependent on the formation of atomiclike interfacial states near the bottom of the bandgap. Schottky barrier heights of 0.83 and 0.97 eV were determined for Ag on the c(2×8) and (4×6) surfaces, respectively. The results are at variance with current Schottky barrier models.

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73.40.Ns	Metal-nonmetal contacts
71.20.-b	Electron density of states and band structure of crystalline solids
73.30.+y	Surface double layers, Schottky barriers, and work functions

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Refractory metal contacts to GaAs: Interface chemistry and Schottky‐barrier formation

J. R. Waldrop, S. P. Kowalczyk, and R. W. Grant

J. Vac. Sci. Technol. 21, 607 (1982); http://dx.doi.org/10.1116/1.571795 (4 pages) | Cited 16 times

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A survey of the interface chemistry of the refractory metals W, Ta, Re, Ir, and Mo during room‐ temperature Schottky‐barrier contact formation to GaAs by using x‐ray photoemission spectroscopy (XPS) is reported. The metals were deposited onto clean n‐type GaAs (100) surfaces within the XPS system by two methods: Evaporation and plasma sputtering. For each metal a distinct interfacial reaction which produced GaAs dissociation and formation of a new metal arsenide is observed. Refractory metals are in general not chemically inert in contact to GaAs and nonabrupt interfaces ∠10 Å in width are formed. XPS was also used to correlate interface chemistry with measurement of Schottky‐barrier height during contact formation. XPS measured barrier heights ranged from 0.9–0.7 eV, in the order W, Ir, Mo, Ta, and Re.

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82.65.+r	Surface and interface chemistry; heterogeneous catalysis at surfaces
73.30.+y	Surface double layers, Schottky barriers, and work functions
73.40.Vz	Semiconductor-metal-semiconductor structures
81.65.-b	Surface treatments

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Structural characterization of the interfacial reactions between palladium and gallium arsenide

Xian‐Fu Zeng and D. D. L. Chung

J. Vac. Sci. Technol. 21, 611 (1982); http://dx.doi.org/10.1116/1.571796 (4 pages) | Cited 11 times

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X‐ray diffraction was performed in situ at temperatures from 25–550 °C to investigate the process of compound formation at the interface between evaporated Pd thin films (∠1000 Å thick) and GaAs single crystals. For heating in 1 atm argon, the interfacial reactions occurred at temperatures above ∠250 °C—isothermal heating at 250 °C resulted in the appearance of PdGa and a small amount of Pd₂Ga after 30–40 min; isothermal heating at 350 °C resulted in the appearance of Pd₂Ga, PdGa, and PdAs₂ after 15–20 min; isothermal heating at 500 °C resulted in the appearance of PdGa alone after ∠5 min. The PdAs₂ phase was found to be a surface layer which could be removed mechanically by ultrasonic cleaning or by the use of an adhesive tape. Removal of PdAs₂ was indicated by ex situ x‐ray diffraction results, which showed the disappearance of the PdAs₂ diffraction peaks and the enhancement of the PdGa peaks. For heating in vacuum (10⁻⁶ Torr), the interfacial reactions occurred at temperatures above ∠200 °C—the appearance of PdGa and a small amount of Pd₂Ga was observed after ∠15 min of heating at 200 °C; PdAs₂ was not observed at any temperature.

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73.40.Ns	Metal-nonmetal contacts
82.30.Hk	Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

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Summary Abstract: Schottky barrier formation at Pd/Si(111) and V/Si(111) interfaces

R. Purtell, J. G. Clabes, G. W. Rubloff, P. S. Ho, B. Reihl, and F. J. Himpsel

J. Vac. Sci. Technol. 21, 615 (1982); http://dx.doi.org/10.1116/1.571797 (2 pages) | Cited 1 time

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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

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Summary Abstract: The Si(111)/Mo interface as studied with synchrotron radiation photoemission and Auger electron spectroscopies

G. Rossi, I. Abbati, L. Braicovich, I. Lindau, and W. E. Spicer

J. Vac. Sci. Technol. 21, 617 (1982); http://dx.doi.org/10.1116/1.571798 (2 pages) | Cited 1 time

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Abstract Unavailable

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73.40.Ns	Metal-nonmetal contacts
81.15.Jj	Ion and electron beam-assisted deposition; ion plating

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Structural studies of Schottky barrier formation by means of surface EXAFS: Pd and Ag on Si(111) 7×7

J. Stöhr and R. Jaeger

J. Vac. Sci. Technol. 21, 619 (1982); http://dx.doi.org/10.1116/1.571799 (5 pages) | Cited 4 times

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The initial stages of Schottky barrier formation for Pd and Ag on Si(111) 7×7 have been investigated by means of surface extended x‐ray absorption fine structure (SEXAFS) measurements above the metal L₂ absorption edges. For Pd deposition at room temperature (RT) and 1.5 monolayer coverage the local structure around the Pd atoms is found to closely resemble that of a thick (∠300 Å) Pd₂Si layer grown on Si(111). The Ag/Si system exhibits a distinctly different interface formation. At RT and around 2.5 monolayers Ag coverage the SEXAFS spectrum is found to be identical to Ag metal. Upon heating to 500 °C a √3×√3 LEED pattern is observed and the polarization dependent SEXAFS signal reveals that the LEED pattern is due to Ag atoms in a threefold site on Si(111) with a Ag–Si distance of 2.45±0.05 Å. At higher Ag coverage the periodic √3×√3 Ag sites on the annealed (500 °C) surface are accompanied by large Ag clusters. The derived structural models are discussed in comparison with various models suggested previously.

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73.30.+y	Surface double layers, Schottky barriers, and work functions
73.40.Ns	Metal-nonmetal contacts
78.70.Dm	X-ray absorption spectra

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Chemical bonding at the Si–metal interface: Si–Ni and Si–Cr

A. Franciosi, J. H. Weaver, D. G. O’Neill, Y. Chabal, J. E. Rowe, J. M. Poate, O. Bisi, and C. Calandra

J. Vac. Sci. Technol. 21, 624 (1982); http://dx.doi.org/10.1116/1.571800 (4 pages) | Cited 11 times

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Chemical bonding at the interface of a near‐noble‐metal (Ni) and a transition metal (Cr) with Si is examined through synchrotron radiation photoelectron spectroscopy studies of in situ formed interfaces, of cleaved bulk silicides, and of disordered surfaces prepared by sputter etching of the silicides. Interpretation of these experimental results is guided by parallel linear combination of atomic orbitals (LCAO) (extended Huckel approximation) calculations of stoichiometric Ni and Cr silicides.

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73.40.Lq	Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
82.80.Pv	Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
81.65.-b	Surface treatments
68.35.-p	Solid surfaces and solid-solid interfaces: structure and energetics

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Valence band and core lines investigation on the Ge–Au system by photoelectron spectroscopy with synchrotron radiation

BROWSE VOLUMES

Jul 1982

Volume 21, Issue 2, pp. 285-709