Abstract
Low temperature (∼5 K) photoluminescence spectroscopy was performed on undoped CdTe epilayers grown by molecular beam epitaxy on (211)B oriented bulk GaAs substrates at substrate temperatures ranging from 230 to 275 °C. The emission spectra from all samples studied contained evidence of the diffusion of gallium and arsenic atoms from the substrate. A broad, low amplitude emission band observed at 1.594 eV was related to the GaCd donor level in CdTe. Donor-acceptor pair recombination observed at 1.51 eV was due to the substitutional GaCd donor and AsTe acceptor. The level of compensation in the CdTe layers was determined from the energy shift of the donor-acceptor emission peak with excitation power, with the lowest degree of compensation observed in a sample grown at 230 °C. In addition, a bright emission peak was observed at 1.47 eV. This peak, which had been observed previously in homoepitaxial and heteroepitaxial growth of CdTe, was related to electron-hole recombination of a structural defect in the CdTe/GaAs epilayers with an electronic binding energy of ∼130 meV.
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