EFFECTS OF BUFFER LAYERS IN GAAS-IN0.2AL0.8 AS STRAINED-LAYER SUPERLATTICES

Raman spectroscopy has been used to study strains in GaAs-In//0//. //2Al//0//. //8As strained-layer superlattices with a fixed layer thickness (100-100 A) and various In//xAl//1// minus //xAs buffer layers left bracket x equals 0 (GaAs in place of AlAs), 0. 1, and 0. 2 right bracket . 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 equals 0) the mismatch between the superlattice and the buffer layer is accommodated by dislocations near the interface region, while for the In//0//. //2Al//0//. //8As buffer layer the mismatch is accommodated by the tensile strain in the GaAs layers.