Energy levels from lattice defects in AgGaS2

The luminescence of single crystals of AgGaS₂ from shallow centers is studied. As-grown crystals and crystals annealed in S, Ga, or in vacuum, were used. We show that the S vacancy causes a donor level at 50 meV (probably due to a charge state of V_S) and that the cation vacancy (perhaps Ag) introduces an acceptor level at 110 meV. Two other levels are found: a donor level at 30 meV and an acceptor level at 200 meV. Their origin is unknown.