Dependence of Energy Gap on x in CuAlxGa1-xS2 Mixed Crystal System

Abstract
The transmission and reflectance spectra for various x in CuAl x Ga1-x S2 single crystals have been measured with polarized light. The photon energies of excitons associated with the uppermost valence bands are determined by analyzing the exciton absorption spectra and the reflectance anomaly spectra at room temperature and at about 80 K. The exciton energies have an approximately quadratic dependence of x. The valence band splitting is predominantly due to the crystal field splitting. The splitting energy varies almost linearly with x.