Low temperature air-annealing of Cu(InGa)Se2 single crystals

CuInSe2 and CuIn0.95Ga0.05Se2 single crystals, grown by vertical Bridgman, were annealed in air at temperatures from 100 to 160 °C. Both CuInSe2 and CuIn0.95Ga0.05Se2 samples were studied using photoluminescence (PL). The CuInSe2 samples were also studied using Rutherford Backscattering Channeling (RBS/C) and nuclear reaction analysis (NRA). Before annealing the samples showed low dechanneling parameters suggesting high quality lattice structure. The PL spectra of both CuInSe2 and CuIn0.95Ga0.05Se2 revealed bands associated with band-tail recombination mechanism. Annealing at 120 °C and higher temperatures considerably modified the RBS/C and PL spectra. NRA indicated a gradual increase in the oxygen content. PL analysis suggested that annealing increases both the mean-square amplitude of potential fluctuations and the level of compensation. Changes in the RBS/C spectra demonstrated that annealing at up to 160 °C does not result in the growth of In2O3 surface layer but modifies primarily the Se- and Cu-related RBS/C yield. These modifications are consistent with an increase in the concentration of defect complexes.