On the photophysics and room temperature quantum emission of various epitaxial p-type GaN

Quantum technologies have progressed rapidly in recent years, enabling new capabilities in computation, communication, and sensing. A major requirement is reliable room-temperature single-photon generation to carry quantum information, reducing the overhead of cryogenic cooling and improving scalability. GaN is a CMOS-compatible, technologically mature semiconductor that can host room-temperature single-photon emitters (SPEs) and can be grown at wafer scale by the two dominant epitaxial techniques, MOCVD and MBE. GaN color centers have shown room-temperature photon rates of 1–1.5 MHz, linewidths of ~2 nm, and single-photon purity above 95%, spanning emission from the ultraviolet to the telecom band. GaN can also be fabricated as sub-micrometer films on sapphire, enabling GaN-on-insulator (GANOI) photonic circuits that are not readily accessible with diamond or SiC. However, the atomic origin of the most stable near-infrared GaN color centers remains unclear, and the role of growth conditions, impurities, and doping in creating bright SPEs is not yet established. Here, we directly compare epitaxial p-type GaN films grown by MOCVD and plasma-assisted MBE (PAMBE) with the goal of correlating growth conditions with the defect/impurity configurations responsible for SPE behaviour. We observe a higher density of optically active defects in the MOCVD-grown sample and measure higher single-photon purity, with g2(0)=0.07. Importantly, we also report, for the first time, single-photon emission from the MBE-grown p-GaN sample, with g2(0)=0.16. Saturation measurements further show that the MOCVD emitter (SPE1) is brighter under our collection conditions, while the MBE emitter (SPE2) saturates at slightly lower power but reaches a lower maximum count rate. Photostability measurements indicate that MOCVD emitters remain highly stable over long durations, whereas MBE emitters exhibit blinking consistent with nearby trap activation. These results establish clear growth-dependent trends that guide engineering of bright, stable GaN SPEs for scalable quantum photonics.