LATTICE STRAIN IN AGGAS2 EPITAXIAL LAYERS GROWN ON GAAS (100) BY MULTISOURCE EVAPORATION

Lattice strain in ApGaS(2) epitaxial layers of different thicknesses, which are grown on GaAs (100) by the multisource evaporation method, i s described. Biaxial compressive mismatch strain in thin layers relaxe s with increasing layer thickness, and biaxial tensile thermal strain becomes dominant in thick layers. The thin AgGaS2 epitaxial layers are completely oriented toward the c-axis, but the thick layers contain 1 80 degrees-rotated {112} twin crystals. The generation of twin crystal s is considered to cause partial relaxation of the thermal strain. The observed variation in the A(1)-mode frequency with thickness is fully explained by considering the layer thickness dependence of the lattic e strain. Full width at half-maximum of the A(1)-mode Raman scattering line is affected by the spatial inhomogeneity of the strain magnitude in the depth direction. Raman scattering measurement of the A(1) mode can be used as a sensitive technique to evaluate the lattice strain i n AgGaS2.