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 redshift and broadening photoluminescence(PL).With a high Sb component of 22%,the longest wavelength emission of the InAs/GaAs0.78Sb0.22QDs occurs at 1.5 μm at room temperature.The power-dependence PL measurements indicate that with a low Sb component of 14%,the InAs/GaAs0.86Sb0.14QDs have a type-Ⅰ and a type-Ⅱ carrier recombination processes,respectively.With a high Sb component of 22%,the InAs/GaAs0.78Sb0.22QDs 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/GaAs0.78Sb0.22QDs reaches 16.86 ns,which is much longer than that of the InAs/GaAs0.86Sb0.14QDs(2.07 ns).These results obtained here are meaningful to realize high conversion efficiency intermediate-band QD solar cells and other opto-electronic device.