Variability of heterostructure type with thickness of barriers and temperature in the InAs/GaAsSb quantum dot system

We report photoluminescence studies of InAs quantum dots embedded in GaAsSb barrier layers of various thicknesses. Time resolved photoluminescence results suggest that the thicknesses of the GaAsSb barrier layers determines whether the quantum dot system acts as a type I (thicker) or type II (thinner) heterostructure due to strain induced changes in the band energies. Temperature dependent photoluminescence reveal that the transition type is also dependent on the temperature with one sample seeming to transform from type II to type I heterostructure as the temperature is increased. These results support previous assertions that it is possible to obtain a zero valence band offset in the InAs/GaAsSb quantum dot system, making it a system of interest for realization of a novel photovoltaic structure, the intermediate band solar cell. The results highlight some of the inherent issues in designing structures with specific band offsets. Some of the implications of these results on the design methodology for quantum dot based solar cells are briefly discussed.