Annealed Ge/Pd/n-GaAs samples utilizing substrates with superlattice marker layers have been analyzed using high resolution backside secondary ion mass spectrometry and cross-sectional transmission electron microscopy. Interfacial compositional and microstructural changes have been correlated with changes in contact resistivity. The onset of good ohmic behavior is correlated with the decomposition of an intermediate epitaxial Pd4(GaAs,Ge2) phase and solid-phase regrowth of Ge-incorporated GaAs followed by growth of a thin Ge epitaxial layer.

Au-Zn is one of several metal systems applied to p-GaAs to form ohmic contacts. Although it exhibits a fair degree of reliability, the thrust toward higher power and adverse environments raises concern. Observations indicate that the electrical and mechanical properties as well as the stability of AuZn/GaAs vary with Zn thickness. In this study devices with thin and thick layers were tested visually, mechanically and using SEM and X-ray diffraction techniques. Results revealed significantly different reactivity and product chemistry that could significantly affect overall device performance.

The phases which result from the oxidation of III-V compound semiconductors can be predicted from a knowledge of the condensed phase portion of their equilibrium phase diagrams. Examples will be shown for arsenides, antimonides, and phosphides. Use of these diagrams explicitly presumes equilibrium growth conditions, and that assumption often fails. In such cases kinetic rather than thermodynamic factors dominate the determination of the observed phases. Examples of this phenomenon for anodic oxidation will be presented. Recent interest in high pressure oxidation conditions as a means of alleviating kinetic limitations will be discussed for InP. The phase diagrams can also be used to predict interfacial reactions under certain conditions and data for GaAs will serve to illustrate this point.

We have used molecular beam epitaxy to grow CaxSr1−xF2 films of various thicknesses on GaAs substrates with different orientations, i.e. (100), (111)A, (511)A, (511)B, (711)A and (711)B. On all orientations, the same crystallographic direction is normal to the surface in both the substrate and fluoride film. For all orientations except (111), the fluoride surface is reconstructed with (111) facets. Without annealing, the best crystallinity is obtained for the (100), (111) and (511)B orientations.

We have studied the effect of different annealing conditions on the crystallinity and morphology of 1000Å epitaxial CaF2 films on Si(100). The crystallinity of the films is improved by the anneals, with the highest anneal temperatures giving the greatest improvement. The results are consistent with the model previously proposed to explain the success of rapid thermal annealing in improving thicker epitaxial CaF2 films.

Studies of chemical trends may provide additional insights in complicated reactions between adsorbates and substrates. Here, the interaction of gallium with InP, InAs and InSb cleaved surfaces was investigated by using photoemission spectroscopy (UPS).

Ga was evaporated from a Knudsen-type cell which was placed at a distance of approximately 15 cm in front of the surfaces cleaved in situ. After the evaporation rate, which was monitored by using a quartz oscillator, had stabilized the amount of Ga deposited was determined from the exposure time. The film thicknesses given in A are nominal values since Ga was found to exhibit island growth. The energy distribution curves (EDC-s) of the photoemitted electrons, which were excited by HeI and HeII radiation provided by a home-built discharge lamp, were recorded by using a single or a double-pass cylindrical mirror analyzer.

In this paper, the fundamental mechanisms of procedures improving the structural quality of GaAs grown on Si are discussed. Patterned growth, strained layer superlattices and proper thermal cycling are promising approaches to achieve a high quality of GaAs layers grown on Si substrates.

Since the discovery in 1973 that GaAs/GaAsP superlattices can be grown with low dislocation densities, considerable interest has developed in utilizing superlattices as dislocation filters in multilayer semiconductor device structures. Many attempts to implement this process have been described, with varying degrees of success being achieved. Some investigators have reported favorable results; some have observed no effect; and in some cases the situation was actually made worse. This paper analyzes these reports and attempts to clarify the confusion that has arisen. Suggestions are made for improved effectiveness. Factors considered include the strain between layers, the layer thickness, the concept of critical thickness, the dislocation geometry, and the influence of buffer layers and growth conditions.

The concept of a “buffer” layer in the epitaxial growth of compound semiconductors on (001) silicon substrate is discussed on the basis of homogeneous and heterogeneous surface nucleation. Experimental results on the nucleation of β-SiC on (001) Si by Chemical Vapor Deposition (CVD) are presented and they are discussed in terms of the model for the growth of the buffer layer.

Effects of growth temperature on crystallinity and surface morphology of MOCVD-grown GaAs-on-Si were studied. The FWHM of the (400) x-ray peak in the rocking curve of GaAs-on-Si reduces from 340 to 230 arcs with increasing growth temperature from 650 to 700°C, but further increase of growth temperature does not significantly decrease the FWHM. The surface morphology of GaAs-on-Si grown at higher temperature is scaly and rough. Lower growth temperature is desirable to obtain GaAs-on-Si with good surface morphology. In order to eliminate the trade-off between crystallinity and surface morphology, the three-step growth process is proposed.

Transmission electron microscopy of GaAs grown on Si for metal-semiconductor-metal photodetectors is presented in this paper. Two kinds of samples are compared: GaAs grown on a 15 Å Si epilayer grown on GaAs, and GaAs grown at low temperature (300°C) on Si substrates. It is shown that the GaAs epitaxial layer grown on thin Si layer has reverse polarity to the substrate (antiphase relation). Higher defect density is observed for GaAs grown on Si substrate. This higher defect density correlates with an increased device speed, but with reduced sensitivity.

We have studied heteroepitaxial growth of GaAs on Si using an AlxGa1−xP intermediate layer in an atmospheric-pressure metal organic chemical vapor deposition (NOCVD) reactor. The crystallinity of the GaAs layer depends on AlP composition(x) of the intermediate layer. The bett crystal quality of GaAs layer is obtained when the AlP composition(x) of the intermediate layer is close to 0.5. The X-ray FWHX of 180 arcs and the etch pit density (EPD) of 2.5 × 107cm−2 were obtained in this GaAs/AlGaP/Si structure.

Heteroepitaxial growth of GaAs on Silicon substrates is being actively pursued, since this technology offers numerous potential benefits in terms of optoelectronic and high speed devices. However a complete understanding of the fundamental causes for film properties such as surface morphology and crystal quality is still lacking at the present time. We present here the results of a study of GaAs grown on Silicon substrates using AlxGa1−xP intermediate layers. This system offers the advantage of studying the effects of surface properties and bulk properties of heteroepitaxial films separately. Surface and interface properties are shown to be the dominant factors in the growth of AlxGa1−xP on Si, where the lattice match between the two materials is very good. For low Al mole fractions the layers tend to form islands indicative of 3D growth, whereas for x>0.4, the layers are planar indicative of 2D growth. Bulk properties such as the lattice constant mismatch are presumed to play a key role in the growth of GaAs on AlxGa1−xP intermediate layers, where it is shown that the GaAs still has an island type nucleation phase, even though surface and interface factors such as contamination and polar-on-nonpolar growth are avoided. In addition the nucleation of the GaAs on the AlxGa1−xP intermediate layers appears to be modified by the nature of the AlxGa1−xP layer i.e. whether the intermediate layer is in the form of islands or a planar layer. The final surface morphology and the crystalline quality of 3gtm GaAs films grown on AlxGa1−xP intermediate layers can be correlated to the initial nucleation.

It is shown that antiphase boundary (APB) is annihilated during the growth, by monitoring the surface with reflection high energy electron diffraction (RHEED). The RHEED observation indicates that double domain GaAs changes to single domain within a thickness of 100 nm, while the transition region is estimated to exist within 200 nm from GaAs-Si interface by scanning electron microscope (SEM) observation of etch pits on vicinally polished surface. The self-annihilation mechanism of APB is discussed from these results.

The nature and behavior of anti-phase-boundaries in GaAs/Si heterostructures using GaP, GaP/GaAsP and GaAsP/GaAs strained layer superlattices as intermediate buffer layers, have been investigated by transmission electron microscopy. It has been found that anti-phasedomains are very complicated three dimensional polygons consisting of several sub-boundaries in different orientations. Self-annihilation of anti-phase-domains during crystal growth of GaAs on (001)just or (001)2°off Si substrates is directly observed for the first time through planview and cross-sectional observations. Based on these findings, a mechanism of annihilation of these domains is proposed.

We have studied the crystallinity and Schottky diode characteristics of GaAs/Si grown by MOCVD. In comparison with two-step growth and GaP/strained layer superlattice techniques, the crystallinity and the Schottky diode characteristics are superior for the GaAs/Si with Al0.5Ga0.5P as an intermediate layer. The GaAs/Si grown with the Al0.5Ga0.5 intermediate layer shows mirror—like surface morphology and an X-ray FMHM of 188 arcs. The ideality factor of the Schottky diode fabricated on the GaAs/Si grown with the Al0.5Ga0.5P intermediate layer is 1.06, but its forward current-voltage characteristic shows a significant leakage current at small forward bias. It is also found that the composition of Al affects strongly the crystallinity and the Schottky characteristics of GaAs/Si.

Results are reported for XPS and LEED evaluations of Si(100) wafers cleaned, etched, andhydrogen terminated by various low — temperature, wet — chemical techniques. We have obtained especially promising results with the JPL spin — etch technique. Under quite practical tolerances for the spin etch, our XPS measurements indicate about lx10-2 monolayer (ML) of total residue. The LEED showed sharp spots in a (1x1) pattern. We review our experimental results and suggest an interpretation in termsof both the chemistry of silicon surfaces in contact with HF in a polar solvent, and thehydrodynamics of liquids on spinning surfaces.

Photoemission spectra (XPS and UPS) of As-covered Si (001) surfaces prepared at high (>600ºC) and low (<450ºC) temperatures and GaAs epilayers subsequently grown on them were measured without exposing to air. It was found that the surface electronic structures of As/Si prepared at the low temperature are different from those of the high temperature sample, the spectra of which can be interpreted as a symmetric dimer model. Differences were also observed between the GaAs epilayers on the As—covered Si surfaces prepared at the high and low temperatures. The temperature dependence of the surface and interface structures are discussed.

Thin films of the platinum-gallium (Pt-Ga) family have been grown on gallium arsenide (GaAs) and silicon (Si) by molecular beam epitaxy (MBE). A partial list of potential uses for these and similar structures is high temperature stable photodetectors, Schottky andOhmic contacts, epitaxial buried contacts, and field effect transistors. In this work the electrical properties of Pt2Ga, PtGa, and PtGa2 on both GaAs andSi will be presented. The resistivity of these thin films has been found to depend on the crystal quality and phase of the material.

We report the growth and characterizations of 31μm thick GaAs films grown on (100) InP substrates by MBE employing different buffer layer structures during the initial deposition. The buffer layer structures under study are: 1) GaAs layer grown at low temperature; 2) GaAs layer grown at low temperature plus two sets of In0.08Ga0.92As/GaAs strained layer superlattices (SLS) and 3) a transitional compositionally graded InxGal-xAs layer between the InP substrate and the GaAs film. After the buffer layer deposition, the growth was continued by conventionalMBE to a total thickness of 3μm for all samples. From the 77K photoluminescence (PL) measurement, it was found that the sample with SLS layers has the highest PL intensity and the narrowest PL linewidth. Cross-sectional transmission electron microscopy (TEM) studies showed that the SLS is effective in reducing the propagation of threading dislocations and explains the observed superior optical quality from the PL measurement.