Ultrafast Green Single Photon Emission from an InGaN Quantum Dot-in-a-GaN Nanowire at Room Temperature

Single photon emitters, preferably working at room temperature, are crucial components of a diverse set of quantum technologies. Nanowire-supported quantum dots (NWQDs) of InGaN have emerged in the recent past as promising candidates of single photon emission (SPE) at visible wavelengths, though their efficient operation so far has been restricted to cryogenic temperatures. Here, we report the demonstration of visible-wavelength (λ=561 nm) SPE at room temperature, from specially designed InGaN NWQDs, wherein the second-order correlation function at zero-delay is measured to be the lowest reported so far (g2 (0) = 0.11), for this system. Using a single-step molecular-beam-epitaxy-based fabrication technique, we realized InGaN NWQDs with both lateral and vertical dimensions scaled down to the Bohr-radius limit. This achievement is responsible not only for the efficient single photon emission at room temperature but also for the reduction of carrier lifetimes to the order of several hundreds of picoseconds. The latter has been made possible by the suppression of the built-in polarization field, which is attributed to the strong radial confinement obtained in the NWQDs fabricated by our method. These InGaN NWQDs are thus extremely promising for the development of visible-wavelength single photon sources, operating at room temperature and GHz repetition rates.