Photoluminescences and Excitation Spectra of Some I-III-VI2Compounds

Photoluminescences and their excitation spectra of undoped CuGaS 2 , CuAlS 2 , CuAlSe 2 and CuAlS 2 x Se 2(1- x ) are investigated at 110 K both under the polarized and unpolarized excitations. Each sulfide shows a broad polarization-independent luminescence peak, while its excitation spectra split into a couple of polarization-dependent peaks. CuAlSe 2 , however, shows two polarization-independent luminescence peaks, each of which has its own excitation spectrum with little polarization dependence. In every compound the peak energies and the separation of the excitation spectra are found to correlate with those of the valence bands determined by reflection measurement. Assuming a deep lying donor level, tentative explanations of these luminescence and excitation processes are attempted.