Effect of lattice strain on exciton energy of AgGaS2 epitaxial layers on GaAs (100)

The lattice strain and its related change of exciton energy in AgGaS2 epita xial layers, which are grown on GaAs (100) by the multisource evaporation m ethod, are discussed. The lattice strain and the strain relaxation in AgGaS 2 layers an evaluated in terms of the temperature dependence of the A(1)-mo de Raman shift difference between the layer and bulk crystal. The observed change of lattice strain with temperature is explained by temperature depen dences of mismatch strain, thermal strain and their relaxation. The exciton energy related to the uppermost valence band in the AgGaS2 layers increase s with biaxial tensile strain, in contrast to the exciton energies of zincb lende compounds and Cu-III-VI2 epitaxial layers. The effect of the lattice strain on the exciton energy of the AgGaS2 layers is considered to be induc ed predominantly by the change in the Ag d-level contribution to uppermost p-like valence bands.