Critical Aluminum Etch Material Amount for Local Droplet-Etched Nanohole-Based GaAs Quantum Dots

Local droplet-etched-based GaAs quantum dots are promising candidates for high-quality single and entangled photon sources. They have excellent optical and spin properties thanks to their size, shape and nearly strain-free matrix integration. In this study, we investigate the onset of aluminum nanodroplet formation for the local droplet etching process. Using molecular beam epitaxy, we grew several local droplet-etched quantum dot samples with different arsenic beam equivalent pressures. In each sample, we varied the etch material amount using a gradient technique and filled the nanoholes with GaAs to form optically active quantum dots after overgrowth. We repeated the local droplet etching process without the filling process, enabling us to characterize surface nanoholes with atomic force microscopy and compare them with photoluminescence from the buried quantum dots. We found a linear dependency on the arsenic beam-equivalent pressures for a critical aluminum amount necessary for nanohole formation and analyzed shape, density and optical properties close to this transition.