A. Freundlich

Heteroepitaxy of GaAs on Si: The effect of in situ thermal annealing under AsH3

This letter shows that an in situ thermal annealing step in AsH3/H2 during the metalorganic vapor phase epitaxy of GaAs on Si(001) improves the crystalline quality. The dislocation density is reduced (below 107 cm−2) without affecting the Si diffusion across the heterointerface or the strain level in the epilayer. The nature of the various near‐band‐gap recombinations present in the unannealed and annealed samples is discussed in light of selective photoluminescence experiments.

Defect‐related Si diffusion in GaAs on Si

Preferential diffusion channels of silicon are evidenced in GaAs grown by metalorganic vapor phase epitaxy on Si(100). The density of these diffusion channels is found to be consistent with the measured dislocation density. In addition, combining scanning electron microscopy and x‐ray fluorescence it is shown that a large amount of Si emerges at the surface inside small 〈011〉 overgrowth oriented defects (≊1 μm) present at the GaAs/Si surface.

Evidence by Raman spectroscopy and x‐ray diffraction of a strong influence of H2O traces on the metalorganic vapor phase epitaxy of GaAs on Si

The metalorganic vapor phase epitaxy of GaAs on Si is shown to be strongly sensitive to the residual water vapor content in the growth reactor atmosphere. This finding is evidenced both by Raman spectroscopy and double‐crystal x‐ray diffraction. For the growth of good crystalline quality GaAs on Si, the upper hygrometric level limit is found around 0.5 ppm by volume.

INFLUENCE OF MOVPE GROWTH-PARAMETERS ON THE STRUCTURAL AND OPTICAL-PROPERTIES OF GAAS ON SI(100)

Abstract The influence of various parameters such as the initial low temperature buffer layer and layer thickness on the overall MOVPE-grown GaAs on Si crystal properties has been investigated. An accurate control of the initial buffer layer, nucleating as a three-dimensional island on Si (TEM results), induces a substantial defect reduction in GaAs on Si epilayers. Further defect reduction is achieved by in-situ high temperature annealing (850°C) under AsH 3 /H 2 flow during growth. No change of the silicon cross diffusion profile (SIMS) or residual stress magnitude was observed, in contrast with post-growth annealing processes which are shown also to affect detrimentally the optical properties. Moreover, the modification of the main residual acceptor species and the (100) coplanar tensile stress in GaAs on Si is discussed in the light of photoluminescence spectroscopy.

Photoluminescence and Raman studies of residual stresses in GaAs directly grown on InP

We report first‐order Raman spectroscopy and low‐temperature photoluminescence (PL) studies of GaAs layers grown by metalorganic vapor phase epitaxy (MOVPE) on InP (100) substrates. From both the shift of the longitudinal‐optical phonons in the Raman spectra and the splitting and shift of band‐edge exciton lines in PL, the epilayers are found to be under (100) coplanar tensile stress, which is consistent with the difference between the thermoelastic properties of the two materials. The PL analysis shows that carbon is the main residual acceptor impurity in MOVPE‐grown GaAs/InP.

Stress‐free GaAs grown on Si using a stress balance approach

A novel technique, based on a stress balance principle, is proposed to control residual stress magnitude in GaAs layers grown on Si substrates. It is demonstrated that, using a suitable GaAs1−xPx buffer layer, room (300 K) or low (2 K) temperature stress‐free GaAs can be grown on Si (100).

Strained GaAs layers grown on GaAs substrates with an intermediate GaAs1−xPx buffer layer

The possibility of growing strained GaAs layers on GaAs (100) substrates using a nonpseudomorphic GaAs1−xPx buffer layers is examined. It is demonstrated that by varying the phosphorus content in a thick buffer (significantly thicker than the critical thickness for strain relaxation), uniform biaxial stress magnitude can be monitored in GaAs, e.g., 8 kbar biaxial compression can be achieved by a P composition of 0.16 in the alloy. After an x‐ray diffraction study of strain relaxation in the buffers, low temperature photoluminescence measurements are used to evaluate the effect of such a stress upon monitoring the near band gap properties of GaAs layers.

Acceptor excited states in gallium arsenide on silicon

Abstract Excited and ground states of carbon, silicon and germanium acceptor impurities in GaAs on Si are studied using selective donor-acceptor pair luminescence (SPL) and photoluminescence excitation. Acceptor spectroscopy in such a biaxially strained material is shown to be possible and a good agreement between the experimental observation and a theoretical approach based on effective mass calculations is obtained for the ground state. Ground-to-excited-state 1S 3 2 -2S 3 2 transitions of C, Si and Ge were observed for the first time. A noticeable binding energy reduction of these excited states is evidenced.

Metal Organic Vapor Phase Epitaxy of GaAs on Si Using II/sub a/-Floride Buffer Layers

Metalorganic vapor phase epitaxy has been used for the first time to grow epitaxial GaAs layers on (111) and (100) oriented Si either using CaF2 or stacked (Ca,Sr)F2/CaF2 as a buffer. The GaAs layers show sharp and well resolved electron channeling patterns. The Rutherford backscattering (RBS) ion channeling minimum yield is 5% for (111) orientation and 6% for (100) orientation. The GaAs(111) layers are untwinned. The strain in the GaAs layer has been measured with RBS and X-ray diffraction and it is found that the thermal mismatch-induced strain in the GaAs layer is considerably lower than in similar GaAs films grown without flouride buffer.

GaAs on Si Solar Cells: Photovoltaic Characterization of GaAs Grown Directly on Si and with Intermediate Buffer

An investigation of GaAs films grown on Si substrates for solar cells is presented. Two types of layered structures are examined. One is GaAs grown on Ge (2–3 µm) coated Si substrate; GaAs/Ge/Si structure. The other is a direct growth of GaAs on Si using an original AlAs nucleating layer (10nm). Both type materials exhibit good structural and electrical characteristics. The solar cell fabricated using the AlAs nucleating layer showed 12.2% (AMO) conversion efficiency.