Defect specific luminescence dead layers in CdS and CdSe

CdS and CdSe are often used in optoelectronic devices whose effectiveness may be dictated by defects in the near surface region. Luminescence is one of the main tools for studying such defects. The energy dependence of the X-ray excited optical luminescence (XEOL) spectra of these materials enables the extraction of the depth dependence of the defect distribution. Normal and time-gated XEOL spectra were obtained from these materials in the energy range 600–1500 eV. We find that the results can best be understood in terms of a luminescence dead layer whose width depends on the position of the defect level in the band gap.