Ultraclean Single Photon Emission from a GaN Quantum Dot

Wide bandgap III-nitride quantum dots (QDs) are promising materials for the realization of solid-state single-photon sources, especially operating at room temperature. However, so far a large degree of inhomogeneous broadening induced by spectral diffusion has compromised their use. Here, we demonstrate the ultraclean emission from single GaN QDs formed at macrostep edges in a GaN/AlGaN quantum well. As a likely consequence of the high growth temperature and hence a reduced defect density, spectral diffusion is heavily suppressed to levels at least 1 order of magnitude lower than conventional GaN QDs. A record narrow line width of as small as 87 μeV is obtained, while the low inhomogeneous broadening enables us to assess an upper limit of homogeneous broadening in the QDs (27 μeV). Furthermore, the uncontaminated emission facilitates the generation of ultraviolet single-photons with unprecedented purity (g⁽²⁾(0) = 0.02). The realization of high-quality GaN QDs will enable exploration of optoelectronic properties of III-nitrides, opening up the possibility of realizing single-photon quantum information systems operating at room temperature.