Type-I to type-II band alignment switching for (In,Ga)(As,Sb)/GaAs/GaP quantum dots overgrown by a thin GaSb capping layer

Abstract

We study the optical and theoretical properties of (In,Ga)(As,Sb)/GaAs quantum dots (QDs) embedded in a GaP (100) matrix, which are overgrown by a thin GaSb capping layer with variable thickness. QD samples are studied by temperature-dependent photoluminescence, and the results analyzed with the help of theoretical simulations by eight-band~\textbf{k$\cdot$p}, with multiparticle corrections using the configuration interaction. We reveal a type-I to type-II band alignment switching when QDs are overgrown by a GaSb layer with a thickness larger than one monolayer. Moreover, we observe a temperature driven blueshift of the quantum dot luminescence, which is explained by decomposing the spectra into sum of Gaussians. Our analysis reveals that the GaSb overlayer causes switching of the intensity between $\Gamma$- and L-transitions, making the ${\bf k}$-indirect electron-hole transition in type-II regime to be optically more radiant than the $\Gamma$-direct one. Finally, we provide theoretical expectations for the storage time for (In,Ga)(As,Sb)/GaAs/GaP QDs overgrown by the GaSb layer with an AlP barrier underneath, to be embedded in a nanomemory device. We find that by increasing the thickness of the GaSb layer from 0 to 1.5~monolayers (MLs) leads to an increase in the storage time of four orders of magnitude, from 1 hour to up almost a year, rendering such QDs very promising candidates as storage units for nanomemory devices