J.C. Grenet

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.

Oriented overgrowths in MOVPE-grown GaAs

Abstract The crystallographic structure of crater-containing oriented overgrowths on GaAs epitaxial layers grown by metalorganic vapor phase epitaxy (MOVPE) has been studied by transmission electron microscopy and diffraction. The craters are the visible outward sign of polycrystalline constructions of 6 grains or more having low order twin relations with the matrix. Anisotropic development of the facets of the grains is proposed to be the growth mechanism of the hillock. Stacking fault pyramids are present but their correlation with craters and overgrowths is not systematic.

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.

Efficient GaAs tunnel diode as an inter-cell ohmic contact in the tandem Al/sub x/Ga/sub 1-x/As/GaAs

The authors report the growth of GaAs tunnel diodes by atmospheric pressure OMVPE, using diethyl tellurium and carbon tetrachloride as n and p-type dopants respectively, for use as the inter-cell ohmic contact in the monolithic tandem Al/sub x/Ga/sub 1-x/As/GaAs. After annealing under conditions which simulate the growth of the complete tandem structure, the diodes retained a peak current of typically 15.4 A/cm/sup 2/ at 120/spl deg/C, which should enable satisfactory operation of this system for space applications under a concentration of up to 500 suns.<<ETX>>

New results in hetero-epitaxy of GaAs/Ge/Si for high efficiency III-V solar cells on low cost substrates

The chemical vapor deposition (CVD) heteroepitaxy of germanium on silicon has been carefully controlled for the improvement of the epitaxial layer crystalline quality. Double-crystal X-ray diffraction rocking curves exhibit FMWH values as low as 65 arcsec on 2.8 mu m thick, mirrorlike germanium layers are obtained. Structural, optical, and electronic properties of GaAs grown on these Ge/Si substrates by metalorganic vapor phase epitaxy (MOVPE) are presented and discussed. A minority carrier lifetime of 3 ns shows that these GaAs/(Ge/Si) structures are applicable to photovoltaic applications.<<ETX>>

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.