Donor-acceptor pair luminescence involving the iodine <i>A</i> center in CdTe

Abstract

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 8×1016 to 3×1018 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&amp;lt;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 (ITe) and the iodine A-center acceptor complex (VCd-ITe). 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 ITe donors to the conduction band and complete thermalization from the valence band to iodine A centers, respectively.