Deep defect levels in CuInSe2 single crystals using DLTS, MCTS and photoacoustic spectroscopy

Abstract

In this paper, we investigate the presence of deep defect levels in as-grown p-conducting CuInSe2 single crystals using deep level transient spectroscopy, minority carrier transient spectroscopy and photoacoustic spectroscopy. The samples were cut from the middle of ingots grown by employing a vertical displaced Bridgman furnace. This material is attracting increasing interest in solar cells fabrication as the absorber layer. Aluminum Schottky contacts were deposited on the as-grown and etched material in an evaporation system pumped down to less than 10−6 mbar. Three majority carrier traps were observed using deep level transient spectroscopy, and one minority carrier trap was detected by minority carrier transient spectroscopy. The concentrations of the traps have been estimated. The results hence obtained are compared to deep defect levels observed in the measured spectral dependence of the samples prior to junction’s fabrication by using the technique of photoacoustic spectroscopy in the photon energy range 0.6 to 1.3 eV. The study shows a good agreement between the results of DLTS/MCTS to those of photoacoustic and to published data.