Properties of photoluminescence in type-II GaAsSb/GaAs multiple quantum wells

The optical properties of type-II GaAsSb/GaAs multiple quantum wells were investigated by photoluminescence. It was found that the peak position of photoluminescence (PL) spectra shows a giant blueshift under a moderate optical excitation level. As the pumping intensity increases further, the saturation of the peak position was observed. The giant blueshift can be interpreted in terms of the band-bending effect due to the spatially photoexcited carriers in a type-II alignment. The saturation effect was attributed to the creation of an energy barrier induced by photocarriers, which prevents the charge transfer. The change of integrated photoluminescence intensity with increasing excitation intensity is also consistent with the band-bending model. In addition, the temperature dependence of the PL spectra reveals that the thermal escape of electrons from the GaAs well into the GaAsSb barrier is responsible for the PL quenching.