Effect of Sb composition on the band alignment of InAs/GaAsSb quantum dots*

Aiming to achieve InAs quantum dots (QDs) with a long carrier lifetime, the effects of Sb component in cap layers on the band alignment of the InAs/GaAsSb QDs have been studied. InAs QDs with high density and uniformity have been grown by molecular beam epitaxy. With increasing Sb composition, the InAs/GaAsSb QDs exhibit a significant red-shift and broadening photoluminescence (PL). With a high Sb component of 22%, the longest wavelength emission of the InAs/GaAs 0.78 Sb 0.22 QDs occurs at 1.5 μm at room temperature. The power-dependence PL measurements indicate that with a low Sb component of 14%, the InAs/GaAs 0.86 Sb 0.14 QDs have a type-I and a type-II carrier recombination processes, respectively. With a high Sb component of 22%, the InAs/GaAs 0.78 Sb 0.22 QDs have a pure type-II band alignment, with three type-II carrier recombination processes. Extracted from time-resolved PL decay traces, the carrier lifetime of the InAs/GaAs 0.78 Sb 0.22 QDs reaches 16.86 ns, which is much longer than that of the InAs/GaAs 0.86 Sb 0.14 QDs (2.07 ns). These results obtained here are meaningful to realize high conversion efficiency intermediate-band QD solar cells and other opto-electronic device.