DONOR-ACCEPTOR PAIR LUMINESCENCE INVOLVING THE IODINE-A CENTER IN CDTE

Photoluminescence studies from 5 to 296 K have been performed on a ser ies of iodine-doped CdTe epilayers grown by molecular beam epitaxy. Th e samples exhibit excess electron concentrations in the range from 8X1 0(16) to 3X10(18) cm(-3). Bright edge emission is observed at 296 K fr om all samples. A deep-level band centered near 1.45 eV is observed at T<210 K and increases in intensity with doping level. A correlation o f growth parameters with photoluminescence data fits a model of the de ep-level band being predominantly donor-acceptor pair recombination in volving the shallow iodine donor (I-Te) and the iodine A-center accept or complex (V-Cd-I-Te). Zero-phonon emission related to this pair reco mbination occurs at 1.470 eV at 5 K. Thermal quenching of the integrat ed intensity of this donor-acceptor band is described by activation en ergies of 15 and 125 meV corresponding to thermalization of electrons from shallow I-Te donors to the conduction band and complete thermaliz ation from the valence band to iodine A centers, respectively. (C) 199 5 American Institute of Physics.