Excitonic luminescence and edge emission in AgGaS sub(2) crystals

The low temperature cathodoluminescence spectra of AgGaS sub(2) are investigated in this work. In the purest single crystals (sample A sub(1)) at 4.2 K, the luminescence spectra are dominated by free excitons, by exciton bound to impurities, and by an edge emission peaked at 2.590 eV. The authors' study shows the presence of an acceptor level at 110 meV which should be responsible of the bound exciton at 2.689 eV as well as of the edge emission. In other samples, they only observe the free exciton at 2.700 eV and a green broad emission band at 2.470 eV.