Photoluminescence from localized states in GaAsBi epilayers

The structural and optical properties of GaAs_1-xBi_x samples with x = 0.048 and 0.06 were investigated by high resolution X-ray diffraction (HR-XRD) and photoluminescence (PL). The HR-XRD results show that both samples have a smooth and coherent GaAs_1-xBi_x/GaAs interface. The PL peak energy shows an S-shape behavior with temperature (10 K to room temperature) which is an evidence of carrier localizations. An Arrhenius analysis reveals that the thermal quenching activation energy is 30 and 19 meV for the GaAs_0.952Bi_0.048 and GaAs_0.94Bi_0.06 sample, respectively. It was found that the activation energy is not necessarily originated from alloy fluctuations but may also due to CuPt ordering-induced band gap fluctuations. The power dependent PL indicates that the localized energy states are continuously present and located up to 40-47 meV from the valence band.