Strongly Coherent Single-Photon Emission from Site-Controlled InGaN Quantum Dots Embedded in GaN Nanopyramids

Group III-nitride materials have drawn a great deal of renewed interest due to their versatile characteristics as quantum emitters including room-temperature operation, widely tunable wavelengths from ultraviolet to infrared, and a high degree of linear polarization. However, most reported results for III-nitride-based quantum emitters show large inhomogeneous line width broadening in comparison to their lifetime-limited values, which is detrimental to achieving indistinguishability with high visibility. To overcome this, we propose an unprecedented InGaN quantum dot formation technique at the apex of GaN nanopyramid structures, which significantly suppresses inhomogeneous line width broadening. Using high-resolution transmission electron microscopy, a site-controlled InGaN quantum dot with small height (<2 nm) was estimated. No measurable screening effect or frequency jitter of the single-photon emission was observed, which leads to the narrow homogeneous emission line width (64 ± 8 μeV) beyond the spectral resolution limit via Fourier-transform spectroscopy. The emitted photons exhibited superb antibunching characteristics with a near-unity degree of linear polarization, which is highly relevant for polarized nonclassical light sources for applications in quantum information processing

Optical and Facet-Dependent Carrier Recombination Properties of Hendecafacet InGaN/GaN Microsized Light Emitters

A hendecafacet (HF) microsized light emitter based on an InGaN/GaN multiple quantum well (MQW) is grown via selective area metal–organic chemical vapor deposition. The HF microsized light emitter is found to possess four crystallographic facets, (0001), {11̅01}, {112̅2}, and {11–20}. Distinct facet-dependent emission properties, investigated by confocal scanning photoluminescence (PL) and cathodoluminescence (CL) measurements, are found to originate from differences in indium composition and InGaN quantum well thickness of the MQW. Facet-dependent recombination properties, examined by temperature-dependent micro-PL and PL streak images, suggest that the localization energy and nonradiative recombination of carriers at MQW on each facet are varied with the polarization fields and threading dislocations. Besides, scanning time-resolved PL measurements reveal that the recombination lifetime around the edge where different facets meet is shorter than that in the facet regions, implying such nonradiative recombination can be a significant obstacle for achieving high quantum efficiency microstructured light-emitting diodes