Low-Density InGaAs/AlGaAs Quantum Dots in Droplet-Etched Nanoholes

Over the past two decades, epitaxial semiconductor quantum dots (QDs) have demonstrated very promising properties as sources of single and entangled photons on-demand. Among different growth methods, droplet etching epitaxy has allowed the growth of almost strain-free QDs, with low and controllable surface densities, small excitonic fine structure splitting (FSS), and fast radiative decays. Here, we extend the technique to In(Ga)As QDs in AlGaAs, thereby increasing the achievable emission wavelength range beyond that accessible to GaAs/AlGaAs QDs while preserving some of the key advantages of this growth method. We observe QD densities of ∼0.25 μm^-2, FSS values as small as 3 μeV, and short radiative lifetimes of ∼300 ps, while extending the achievable emission wavelength to ∼900 nm at cryogenic temperatures. We envision these QDs to be particularly suitable for integrated quantum photonics applications.