Optical properties of multi-stacked InAs/GaNAs strain-compensated quantum dots

Abstract

Abstract Structural and optical properties of multi-stacked self-assembled InAs quantum dots (QDs) on GaAs (0 0 1) substrates have been investigated, for which dilute nitride GaN x As 1− x layers were used as strain-compensation layers (SCLs). The growth was achieved by atomic hydrogen-assisted radio frequency (RF)-molecular beam epitaxy. The high-quality QD structures were maintained without generation of coalesced islands and dislocations even after 20 layers of stacking. The photoluminescence (PL) peak showed an increasing redshift up to 1.2 μm at room temperature with increasing N composition up to 1.0% in GaNAs as a result of the lowering of quantum confinement energy. Furthermore, the PL showed a bimodal size distribution-like feature. The temperature dependence of PL characteristics showed a minimum linewidth at an intermediate temperature range of ∼100 K, and existence of the two components obeying the Varshni law. Such behavior can be explained by the dynamics of thermally activated carriers that migrate or tunnel from the smaller-sized QDs to larger QDs via wetting layers. The main reason for the anomalous PL characteristics measured for InAs QDs embedded in GaNAs SCLs is possibly the fluctuations of potential energy in GaNAs layers.