Intrinsic and extrinsic photoluminescence spectra of ZnTe films on GaAs deposited by molecularhyphen;beam and organohyphen;metallic vaporhyphen;phase epitaxy

摘要

We present lowhyphen;temperature photoluminescence spectra of molecularhyphen;beam epitaxy (MBE) and organohyphen;metallic vaporhyphen;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 impurityhyphen;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 325thinsp;deg;C, an optimal value of sim;2.2 produces the highest photoluminescence efficiencies and the strongest intrinsic features. The relative intensity of the vacancyhyphen;related emission decreases as the Zn:Te ratio is increased.