High-purity single and entangled photon emission from droplet-epitaxy quantum dots on GaAs(111)A platform

We report on the realization of single-photon emission from droplet-epitaxy quantum dots on GaAs(111)A platform. GaAs/AlGaAs QDs emitting at 780–795 nm show very narrow linewidth of about 9 μeV, high purity SPE with second-order correlation function g⁽²⁾(0) = 0.03, and low fine structure splitting (FSS) below 4 μeV due to high symmetry of QD shape and high growth temperature. To realize emission in the second telecom window (O-band, 1.3 μm), InAs QDs were integrated into GaAs-based photonic structure on vicinal GaAs(111)A. By employing an InAlAs metamorphic buffer layer to engineer strain, we achieve telecom emission over a broad range of 1170–1360 nm. Embedded in a planar GaAs/AlGaAs DBR microcavity, these QDs exhibit high-purity SPE with g⁽²⁾(0) = 0.012 under CW excitation and g⁽²⁾(0) = 0.069 under pulsed excitation. Time-resolved photoluminescence measurements yield a short average lifetime of about 0.98 ns, and the cavity design improves the extraction efficiency up to 5.8-fold, with a value of approximately 3.9% to the first lens. These results highlight the potential of DE QD for scalable quantum photonic technologies and pave the way for practical quantum communication.