Native defects in undoped semi-insulating CdSe studied by photoluminescence and absorption.

Abstract

Recombination of carriers in semi-insulating undoped CdSe was studied using infrared absorption and both the polarization and excitation power dependence of the photoluminescence spectra. The photoluminescence measurements showed that a deep donor and a shallow-acceptor state dominate the recombination process, which is slightly modified by a conduction-band tail. Polarization studies showed that the shallow-acceptor level is spin split by \ensuremath{\sim}1.7 meV, and that the band-tail states do not have the same symmetry as the maximum allowed symmetry of the crystal. The absorption spectra showed indirect absorption from energy levels of the shallow-acceptor defect, including a possible deep level at \ensuremath{\sim}1.3 eV. Deep-donor levels of the shallow-acceptor defect may be responsible for high-resistivity undoped CdSe and the self-compensation of p-CdSe.