Cl-doping in highly mismatched ZnTe1−xOx alloys for intermediate band solar cells

Abstract

We report the effect of Cl-doping in highly mismatched ZnTeO alloys grown on ZnTe substrate by molecular beam epitaxy using ZnCl2 as a dopant source in order to introduce electrons into the intermediate band of ZnTeO that is required to be half-filled with electrons for the efficient operation of an intermediate band solar cell. The ZnCl2 cell temperature was varied between 70 and 250 °C. In order to characterize the photoluminescence (PL) properties exactly, the temperature dependence of band gap energies for E+ and E- bands of ZnTeO was first determined by photoreflectance measurements. Changes in band gap energies were found to be in accordance with those expected by the band anticrossing model. In the low temperature PL spectra, a donor-acceptor pair emission was found, indicating the formation of Cl-related donors.