High-Purity Single-Photon Emission in the Telecom O-Band from Droplet-Epitaxy InAs Quantum Dots Integrated into a GaAs/AlGaAs Planar Microcavity on Vicinal GaAs(111)A Platform

Efficient single-photon emitters operating at telecom wavelengths are pivotal for implementing long-distance quantum communication through existing fiber-optic networks. Here, the realization of single-photon emission is reported in the second telecom window from droplet-epitaxy InAs quantum dots (QDs) integrated into a GaAs-based photonic structure. By employing an InAlAs metamorphic buffer layer to engineer strain, telecom-wavelength emission is achieved over a broad range of 1170–1360 nm, while maintaining compatibility with mature GaAs device platforms. Embedded in a planar GaAs/AlGaAs distributed Bragg reflector microcavity, these QDs exhibit high-purity single-photon emission, as indicated by a second-order correlation function (Formula presented.) = (Formula presented.) under continuous-wave excitation and (Formula presented.) = (Formula presented.) under pulsed above-band 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 (Formula presented.) to the first lens. These results highlight the potential of droplet-epitaxy InAs QDs for scalable, fiber-compatible quantum photonic technologies and pave the way for practical long-distance quantum communication.