Optical characterization of the type-II hybrid nanostructure with the GaSb/GaAs quantum dots coupled to an...

A hybrid nanostructure is constructed with self-assembled GaSb/GaAs quantum dots (QDs) coupling to an In_0.125Ga₀.₈₇₅As/GaAs quantum well (QW) through a 4.5 nm GaAs thin spacer. This quantum dot-well (QDW) hybrid structure retains the characteristics of a type II band alignment while enabling flexibility in engineering the hybrid energy levels by independently controlling the configuration of the QDs, the QW, and the spacer layer. Photoluminescence measurements prove that this structure has several advantages in comparison with a structure containing QDs only. These advantages include a reduction in the effective band gap and an enhancement of the carrier generation as well as collection efficiency due to carrier injection from the QW. Thus, it holds promise for photovoltaic and photodetector applications. However, there is also carrier localization and emission in the wetting layer (WL) of the QDs, which competes for carriers with the dots. Thus, the QDW system should be carefully optimized to reduce the carrier localization impact while it is applied to improve the ultimate performance of photovoltaic and photodetector devices.