CHARACTERIZATION OF BULK CU0.85IN1.05SE2 BY PHOTOLUMINESCENCE AND CATHODOLUMINESCENCE

Melt grown crystals in the Cu-In-Se system show the phenomenon of phas e segregation into a nearly stoichiometric CuInSe2 compound with chalc opyrite structure and a strongly copper deficient compound with an ord ered defect chalcopyrite (ODC) structure. The photoluminescence of suc h a two phase Bridgman-grown Cu-In-Se crystal with the selected compos ition Cu0.85In1.05Se2 has two broad emission bands: a transition A aro und 0.93 eV and a transition B around 1.10 eV, the latter being above the bandgap energy of CuInSe2. Both transitions A and B exhibit donor- acceptor pair type recombination behaviour. Spatially resolved cathodo luminescence shows that the two emission energies come from different regions of the crystal and have the form of micrometer-sized stripes. We conclude that the two transitions A and B originate from the two di fferent phases which penetrate the crystal in growth direction as micr ometer-sized lamellae [M. Hornung et al., J. Crystal Growth 154 (1995) 315]. From the emission energies, transition A at 0.93 eV can be attr ibuted to the CuInSe2 compound whereas transition B at 1.10 eV belongs to the ODC phase. (C) 1998 Elsevier Science B.V. All rights reserved.