The effect of residual strain on photoreflectance (PR) signals near the heteroepitaxial interface in gallium arsenide (GaAs) grown directly on a silicon substrate has been systematically investigated. With use of data on the stress-induced splitting and the shift of the ${\mathit{E}}_0$ (${\Gamma }_{8v}$-${\Gamma }_{6c}$) fundamental transition, the distribution of residual strain in the vicinity of the heteroepitaxial interface in the GaAs layer has been evaluated. It has been found that compressive strain caused by the lattice mismatch between the materials is not completely compensated and is about 0.4% near the heterointerface in the GaAs layer grown at relatively low growth temperature. This compressive strain gradually relaxes with increasing thickness and then transforms to tensile strain around thicknesses greater than 2 μm. The residual tensile strain at the surface of a 3.6-μm-thick GaAs layer is about 0.2%. In the thickness range from 0.5 to 2 μm, the observed PR spectra demonstrate the presence of two regions with different strain in the epitaxial layer. For thicknesses less than 0.5 μm, crystal quality is degraded by defects associated with misfit compensation during the initial stage of growth.

• Received 19 June 1989

DOI:https://doi.org/10.1103/PhysRevB.41.2936