Growth and optical properties of GaSb/GaAs type-II quantum dots with and without wetting layer

Abstract

We investigated the effect of a wetting layer (WL) on the optical properties of GaSb type-II quantum dots (QDs) in GaAs. GaSb QDs were grown by droplet epitaxy, where Ga droplets are first formed on GaAs and then exposed to Sb flux, followed by an annealing step. By adjusting the annealing temperature, we fabricated GaSb QDs with and without a well-defined WL-like structure. Photoluminescence (PL) measurements showed that the high-temperature-annealed samples exhibit a strong PL of the WL, whereas the WL luminescence is quite weak for the samples annealed at low temperatures. As the measurement temperature T increases, the PL energy decreases for the GaSb QDs without the WL. In contrast, the PL energy of the GaSb QDs with the WL has little dependence on T. These PL energy shifts are explained by considering the effects of the hole population and energy-dependent absorption.