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 g(2)(0)$g^{(2)}(0)$ = 0.012−0.012+0.051$0.012^{+0.051}_{-0.012}$ under continuous‐wave excitation and g(2)(0)$g^{(2)}(0)$ = 0.069±0.032$0.069 \pm 0.032$ 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 %$\%$ 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.