Solar Energy, Vol.199, 183-191, 2020
Engineering of carrier localization in BGaAs SQW for novel intermediate band solar cells: Thermal annealing effect
In this study, the effects of thermal annealing on the morphological, structural and optical properties of BGaAs/GaAs Quantum Wells (QWs) are investigated for the first time. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) show that boron islands nucleate on the surface and their rugosity increases after annealing due to boron segregation phenomenon. The segregation is further validated through high-resolution X-ray diffraction (HR-XRD) measurements, which also confirms a good crystalline quality of the system. After annealing at 710 degrees C for 10 min a significant compositional increment of boron is also observed. Nevertheless, a negligible enhancement of photoluminescence (PL) intensity and minor shift in PL peak energy are found, which is attributed to the defect density and the spatial reduction of localization effects. Time-resolved photoluminescence (TRPL) results exhibit an initial decay time in the microsecond regime from localization emission, followed by an even slower decay from deep levels states. Our results can be the first step towards the engineering of carriers localization in BGaAs/GaAs SQWs by thermal annealing and can orient the material system to be an active layer in intermediate band solar cells.