Luminescence Due to Oxygen and Self-Activated Centers in Zinc Telluride

Abstract

Red emissions in ZnTe containing In and O are described. In addition to the isoelectronic oxygen emission, emission due to indium appears at a wavelength longer than 7500Å at low temperatures. The emission changes its peak position with indium content. The emission at high indium concentrations is thought to be the self-activated emission in ZnTe, since it shows characteristics of donor-acceptor pair emission and is accompanied by thermal glow. The self-activated emission at low temperatures is excited efficiently by the host absorption, in contrast to the oxygen emission. This difference seems to reflect large difference of capture cross sections of these two quite different centers for free carriers. Structures below the band gap energy in the excitation spectrum of the self-activated emission are apparently related to the levels of Zn vacancies and In impurities. In this spectrum, a dip is seen at an energy corresponding to the sum of energies of a free exciton and a LO phonon.