Intrinsic and extrinsic photoluminescence spectra of ZnTe films on GaAs deposited by molecular-beam and organo-metallic vapor-phase epitaxy

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Abstract
We present low-temperature photoluminescence spectra of molecular-beam epitaxy (MBE) and organo-metallic vapor-phase epitaxy (OMVPE) ZnTe layers deposited on GaAs substrates under different growth conditions. Strong bands associated with Zn vacancies are observed in the MBE materials, while the OMVPE spectra are dominated by sharp impurity-related lines. A number of instrinsic and extrinsic emission lines are identified. No significant shift of these lines is observed relative to their positions in bulk ZnTe, implying stress levels less than 0.1 kbar for both the MBE and OMVPE layers. A study of the effects of the Zn:Te ratio in the MBE growth chamber reveals that for a growth temperature of 325 °C, an optimal value of ∼2.2 produces the highest photoluminescence efficiencies and the strongest intrinsic features. The relative intensity of the vacancy-related emission decreases as the Zn:Te ratio is increased.