G. P. Schwartz

Analysis of native oxide films and oxide-substrate reactions on III–V semiconductors using thermochemical phase diagrams

Abstract In this paper a review is presented of the known ternary phase diagrams for group III–group V-oxygen systems and the manner in which these diagrams can be applied to an analysis of native oxide films and the existence of oxide-substrate reactions on III–V semiconductors. Aspects which are relevant to device processing or film degradation are summarized at the conclusion of the paper.

Raman scattering from anodic oxide‐GaAs interfaces

The nature of the interface between anodically grown oxide films and gallium arsenide substrates was studied using Raman backscattering. Room‐temperature spectra of GaAs covered with as‐grown anodic films as well as anodized samples dried under nitrogen at 250°C showed only the first‐order longitudinal (LO) and transverse (TO) optical modes and the less‐intense two‐phonon features of the GaAs substrate. Heating the films at 450°C and above results in the appearance of intense LO (257 cm−1) and TO (198 cm−1) bands due to crystalline arsenic and the structureless Raman scattering near 200–250 cm−1 due to amorphous arsenic. Polarized Raman spectra indicate that elemental arsenic is not an intrinsic oxidation product of the room‐temperature anodization. We suggest that the thermally induced solid‐state interfacial reaction, As2O3+2GaAs→Ga2O3+4As, is responsible for the presence of arsenic at the oxide‐semiconductor interface following annealing.

Raman scattering study of the thermal oxidation of InP

Reflection Raman scattering has been used to study thermally grown air‐oxidized films on InP. Elemental red phosphorus is detected in films grown between 350 and 550 °C. At oxidation temperatures exceeding 550 °C, InPO4 is observed with some In2O3 also present as a minor film constituent.

X‐ray and Raman characterization of AlSb/GaSb strained layer superlattices and quasiperiodic Fibonacci lattices

Double‐crystal rocking curves of samples grown on (001)‐oriented GaSb substrates by molecular‐beam epitaxy have been analyzed by fitting computer simulations to data for the symmetric (004) and (002) reflections and for asymmetric (115) reflections. Rocking curves revealed a multiplicity of superlattice diffraction peaks. Dynamical diffraction theory using Abeles matrix method [D. W. Berreman, Phys. Rev. B 14, 4313 (1976)] was applied for the symmetrical reflections. We compare our results to standard kinematical simulations, and we find that there are significant differences. For the asymmetric reflections a new dynamical computer simulation code [D. W. Berreman and A. T. Macrander, Phys. Rev. B 37, 6030 (1988)] involving an 8×8 matrix solution of Maxwell’s equations was used. Lattice incoherency was determined from measurements of the in‐plane mismatch. Dramatic diffraction peak broadening was observed for incoherent superlattices, and this broadening was attributed to a mosaic structure formed by misfi...

Thermal oxidation and native oxide-substrate reactions on InAs and InxGa1−xAs

The condensed phase portion of the In-As-O phase diagram has been used in conjuction with Raman scattering and photoemission studies to examine certain compositional aspects of native oxide-substrate reactions and thermal oxidation patterns on InAs and InxGa1−xAs. Elemental arsenic is found to be an intrinsic interfacial phase in native oxides grown under conditions close to thermodynamic equilibrium. Thermally driven oxide-substrate reactions yielding elemental arsenic can also be induced in anodic films which initially contained no elemental arsenic.

Comment on ’’Thermal oxidation of InP and properties of oxide film’’

In a recent paper, Yamaguchi and Ando [J. Appl. Phys. 51, 5007 (1980)] discussed the composition of thermally grown oxide films on InP. Reanalysis of their infrared absorption data in conjunction with Raman data shows that their assignments of oxide products are in error. The dominant product at T≳620 °C is indium orthophosphate.

Manifestations of melt‐carry‐over in InP and InGaAsP layers grown by liquid phase epitaxy

Macroscopic evidence for the occurrence of melt‐carry‐over (MCO) in InP and InGaAsP layers, grown by liquid phase epitaxy, is presented. It is shown that MCO can manifest itself in the form of dissolution pits and holes in epilayers. Further, this carry‐over can occur in any stage of epi growth and can propagate through subsequent epitaxial layers. Thus, holes transcending all four layers constituting a device wafer can form if wipe‐off after an In‐melt back is incomplete, and these holes have deleterious effects on device yield.

Arsenic incorporation in native oxides of GaAs grown thermally under arsenic trioxide vapor

The presence of crystalline and amorphous elemental arsenic in films grown by the thermal oxidation of GaAs under arsenic trioxide vapor was observed using Raman backscattering. Arsenic was detected for all oxidation temperatures (350–500 °C) and resulting film thicknesses (∼80–1000 A). Chemical etching demonstrated that the arsenic is retained in the interfacial region during growth and does not result from physical adsorption of gas‐phase species during cooling.

Elemental arsenic in native oxide films on AlxGa1−xAs

Surface reflection Raman scattering has been used to detect the presence of elemental arsenic in native oxide films grown on epitaxial (100) AlxGa1−xAs layers. Oxide films formed either by direct thermal oxidation in air at 450 °C or by electrochemical anodization followed by thermal aging (450 °C, in vacuo) were both found to contain elemental arsenic. Anodic films which were not subjected to a heat treatment showed no evidence for elemental arsenic inclusions within the detection limits of the technique. These observations are consistent with the occurrence of a thermally induced interfacial reaction involving As2O3 in the anodic film and the substrate.

Condensed phase diagram for the In-As-O system

An estimate of the condensed phase portion of the equilibrium In-As-O ternary diagram has been constructed from thermodynamic calculations and checked against binary mixture reaction experiments. Utilization of the diagram to explain the phase composition of thin films associated with thermal oxidation and native oxide-substrate reaction processes on InAs and InxGa1-xAs are presented in a companion paper.