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.

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.

It is demonstrated that, using a suitable GaAs1-xPx buffer layer, stress free GaAs can be grown on Si (100) substrates. In fact the lattice mismatch between GaAs and GaAs1-xPx will introduce a (100) biaxial compressive stress component in the GaAs top layer. The magnitude of this lattice mismatch induced stress can be monitored from 1 to 7 Kbar by varying the P content of the buffer from x = 0.02 to x = 0.15. Results on GaAs/ GaAs1-xPx/ Si (100) ( but also on strained GaAs grown on GaAs1-xPx/GaAs(100)) are discussed in the light of photoluminescence and X-ray diffraction experiments. It is shown that, by adjusting the P composition in such buffer, the lattice mismatch induced stress can exactly compensate the thermoelastic stress, leading thus to an almost stress free GaAs at room (300K) or at low (2K) temperature.

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.< >