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

Photoluminescence studies from 5 to 296 K have been performed on a series of iodine-doped CdTe epilayers grown by molecular beam epitaxy. The samples exhibit excess electron concentrations in the range from 8X10(16) to 3X10(18) cm(-3). Bright edge emission is observed at 296 K from 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 of growth parameters with photoluminescence data fits a model of the deep-level band being predominantly donor-acceptor pair recombination involving the shallow iodine donor (I-Te) and the iodine A-center acceptor complex (V-Cd-I-Te). Zero-phonon emission related to this pair recombination occurs at 1.470 eV at 5 K. Thermal quenching of the integrated intensity of this donor-acceptor band is described by activation energies of 15 and 125 meV corresponding to thermalization of electrons from shallow I-Te donors to the conduction band and complete thermalization from the valence band to iodine A centers, respectively. (C) 1995 American Institute of Physics.