Localization effects and band gap of GaAsBi alloys

The structural and optical properties of GaAs1-xBix alloys for x up to 0.108 have been investigated by high resolution X-ray diffraction and photoluminescence (PL). At room temperature (RT), the PL intensity of the GaAs0.97Bi0.03 sample was found to be similar to 300 times higher than a GaAs control sample grown at the same temperature (400 degrees C). PL measurements carried out at 10K show that when excitation power, P-ex was increased from 0.11 to 1140Wcm(-2), the PL peak energy blue-shifts by 80 meV while the full-width-at-half-maximum reduces from 115 to 63 meV. However, the PL peak emission energy becomes independent of the excitation power at RT. The results indicate the presence of localized energy states in the GaAs0.97Bi0.03 sample, which trap carriers at low temperatures and that the majority of the carriers become delocalized at RT. Furthermore, the temperature dependent PL also shows an S-shape behavior, which is a signature of localization effects. A theoretical model, which was derived by solving a rate equation was employed. The model successfully reproduces the observed S-shape behavior and the theory fits well with the experimental data. The RT band gap of GaAs1-xBix for x up to 0.108 has been plotted and compared with the literature. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim