Quantum dots (QDs) based on III-nitride semiconductors are promising for single photon emission at non-cryogenic temperatures due to their large exciton binding energies. Here, we demonstrate GaN QD single photon emitters operating at 300 K with g (2) (0) = 0.17±0.08 under continuous wave excitation. At this temperature, single photon emission rates up to 6 × 10 6 s −1 are reached while g (2) (0) ≤ 0.5 is maintained. Our results are achieved for GaN QDs embedded in a planar AlN layer grown on silicon, representing a promising pathway for future interlinkage with optical waveguides and cavities. These samples allow exploring the limiting factors to key performance metrics for single photon sources, such as brightness and single photon purity. While high brightness is assured by large exciton binding energies, the single photon purity is mainly affected by the spectral overlap with the biexcitonic emission. Thus, the performance of a GaN QD as a single photon emitter depends on the balance between the emission linewidth and the biexciton binding energy. We identify small GaN QDs with an emission energy in excess of 4.2 eV as promising candidates for future room temperature applications, since the biexciton binding energy becomes comparable to the average emission linewidth of around 55 meV.Quantum dots (QDs) based on III-V semiconductors have attracted a lot of attention for their use as nonclassical light sources, with the single photon source being the simplest and most elemental representative. Such a source of single photons should be as bright as possible, while retaining a high single photon purity [1, 2]. However, key metrics for such QD-based single photon sources are usually achieved at cryogenic temperatures with the seminal In(Ga)As/(Al)GaAs system [3][4][5]. Identifying a material platform that can enable sufficiently performant single photon sources up to room temperature remains a challenging quest. In this respect, the main contenders are point defects in wide-bandgap semiconductors (2D materials [6] and bulk semiconductors [7, 8]), nitrogen and silicon vacancies in diamond [9], as well as semiconductor QDs [10][11][12]. It would be advantageous to employ a material system with high integrability into a suitable photonic environment that offers epitaxial control. In this regard, III-nitrides offer a unique possibility as bipolar doping can be achieved, foreign and homoepitaxial substrates are available, and growth and processing techniques are well established, leading to their widespread implementation at an industrial scale for solid state lighting.III-nitrides have shown promising advances in terms of single photon emission (SPE) by employing GaN/AlN [13,14], GaN/AlGaN [15,16] and InGaN/GaN QDs [17][18][19][20][21]. Furthermore, SPE at temperatures as high as 350 K [22] and two-photon emission up to 50 K [23] have been demonstrated. The progress towards room temperature operation is directly linked to the exciton-phonon coupling. With rising temperature the phonon bath becomes * sebastian.tamariz...

AlGaN films were grown on face-to-face annealed sputter-deposited AlN/sapphire (FFA Sp-AlN) templates via metalorganic vapor phase epitaxy (MOVPE), and the growth behavior of the AlGaN films was investigated. The sapphire substrates with small off-cut exhibited poor surface flatness of AlGaN grown on the FFA Sp-AlN templates owing to the formation of large hillock structures. To understand the origin of these hillock structures, the crystallinity and surface morphology of conventional fully MOVPE-grown AlN/sapphire (MOVPE-AlN) templates and the FFA Sp-AlN template were comprehensively studied. The screw- and mixed-type threading dislocation density of the FFA Sp-AlN template was estimated to be approximately 1.8 × 106 cm−2, which was two orders of magnitude lower than that of the MOVPE-AlN template. Consequently, the uniquely observed growth of the hillock structures in the FFA Sp-AlN templates was attributed to their low density of screw- and mixed-type threading dislocations. The large surface off-cut sapphire substrates suppressed the hillock structures on the FFA Sp-AlN templates. The improvement in surface flatness resulted in better optical properties of multiple quantum wells grown on the AlGaN layer. These results demonstrate a promising method for achieving highly efficient and cost effective AlGaN based deep ultraviolet light-emitting diodes.

Combination of sputter deposition and high-temperature annealing is a promising technique for preparing AlN templates with a low threading dislocation density (TDD) at a lower film thickness compared to those prepared by the conventional metalorganic vapor phase epitaxy. However, cracking of AlN films during annealing is a critical issue. In this study, we controlled the residual stress of the sputter-deposited AlN films by modifying the sputtering conditions. Consequently, the occurrence of cracking was effectively suppressed. By optimizing the fabricating conditions, a TDD of 2.07 × 108 cm−2 was achieved for the AlN template with a thickness of 480 nm.

N-polar (−c-plane) InGaN light-emitting diodes with emission wavelengths ranging from blue to green to red were fabricated on a c-plane sapphire substrate by metalorganic vapor phase epitaxy. The optimization of growth conditions for −c-plane InGaN/GaN multiple quantum wells was performed. As a result, the extension of the emission wavelength from 444 to 633 nm under a constant current of 20 mA was achieved by changing the growth temperature of quantum wells from 880 to 790 °C.

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