Photoluminescence of ZnTe and ZnTe:Cr grown by molecular-beam epitaxy

Photoluminescence (PL) from undoped and chromium-doped ZnTe epilayers was studied in the spectral range from 0.3to2.4eV over the temperature range from 5K to room temperature. Films approximately 2μm thick were grown by molecular-beam epitaxy on GaAs substrates. For undoped ZnTe, spectra are dominated by a sharp acceptor-bound-exciton line related to arsenic, with only weak emission observed due to substitutional oxygen (OTe). An analysis of strain-induced shifts in excitonic energies was performed to clarify transition assignments for two PL bands near 2.375 and 2.379eV. For ZnTe:Cr epilayers, the infrared Cr2+ emission near 2.5μm (0.5–0.6eV) was found to be a function of both doping concentration and Zn∕Te beam-equivalent-pressure ratio. Direct excitation of the Cr2+ ions with 1.89‐μm light produced emission up to room temperature. Indirect excitation with 514.5‐nm light produced emission that could be detected up to 180K. Luminescence decay curves measured from a ZnTe:Cr film ([Cr]∼1×1018cm−3) using pu...