Effects of buffer layers in GaAs-In0.2Al0.8As strained-layer superlattices

Abstract
Raman spectroscopy has been used to study strains in GaAs‐In0.2Al0.8As strained‐layer superlattices with a fixed layer thickness (100–100 Å) and various InxAl1−xAs buffer layers [x=0 (GaAs in place of AlAs), 0.1, and 0.2]. Strain‐induced frequency shifts of the longitudinal optic phonon modes depend on the alloy composition (lattice constant) of the buffer layer. For the GaAs buffer layer (x=0) the mismatch between the superlattice and the buffer layer is accommodated by dislocations near the interface region, while for the In0.2Al0.8As buffer layer the mismatch is accommodated by the tensile strain in the GaAs layers.