Luminescence of CuGaS2

Abstract

The luminescence of single crystals of CuGaS2 grown by iodine-vapor transport was studied. As-grown crystals and crystals annealed in S, Ga, or in a vacuum were used. The crystals annealed in S showed a very intensive green luminescence, which was ascribed to donor-acceptor pair transitions interacting with lattice phonons. Studies in terms of excitation intensity, temperature, and time allow us to extract two impurity levels:ED∼50 meV and EA∼130 meV. The acceptor may be due to cation vacancies. The crystals annealed in Ga (or vacuum) showed a red luminescence which was attributed to S vacancies associated with another impurity.