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The microstructure of green-emitting InGaN/GaN quantum well (QW) samples grown at different temperatures was studied using cross-section scanning transmission electron microscopy (STEM) and plan-view cathodoluminescence (CL). The sample with the lowest InGaN growth temperature exhibits microscale variations in the CL intensity across the sample surface. Using STEM analysis of such areas, the observed darker patches do not correspond to any observable extended defect. Instead, they are related to changes in the extent of gross-well width fluctuations in the QWs, with more brightly emitting regions exhibiting a high density of such fluctuations, whilst dimmer regions were seen to have InGaN QWs with a more uniform thickness.

Single-photon emitters with high degrees of purity are required for photonic-based quantum technologies. InGaN/GaN quantum dots are promising candidates for the development of single-photon emitters but have typically exhibited emission with insufficient purity. Here, pulsed single-photon emission with high purity is measured from an InGaN quantum dot. A raw g(2)(0) value of 0.043 ± 0.009 with no corrections whatsoever is achieved under quasi-resonant pulsed excitation. Such a low value is, in principle, sufficient for use in quantum key distribution systems.

This study focuses on the thermal characterization of porous gallium nitride (GaN) usingan extended 3ω method. Porous semiconductor materials provide a solution to the need for on-chipthermal insulation, a fundamental requirement for low-power, high-speed and high-accuracythermal sensors. Thermal insulation is especially important in GaN devices, due to the intrinsicallyhigh thermal conductivity of the material. The results show one order of magnitude reduction inthermal conductivity, from 130 W/mK to 10 W/mK, in line with theoretical predictions for porousmaterials. This achievement is encouraging in the quest for integrating sensors with opto-, powerandRF-electronics on a single GaN chip.

© 2017 Author(s). Nitride quantum dots are well suited for the deterministic generation of single photons at high temperatures. However, this material system faces the challenge of large in-built fields, decreasing the oscillator strength and possible emission rates considerably. One solution is to grow quantum dots on a non-polar plane; this gives the additional advantage of strongly polarized emission along one crystal direction. This is highly desirable for future device applications, as is electrical excitation. Here, we report on electroluminescence from non-polar InGaN quantum dots. The emission from one of these quantum dots is studied in detail and found to be highly polarized with a degree of polarization of 0.94. Single-photon emission is achieved under excitation with a constant current giving a g(2)(0) correlation value of 0.18. The quantum dot electroluminescence persists up to temperatures as high as 130 K.

In many InGaN/GaN single photon emitting structures, significant contamination of the single photon stream by background emission is observed. Here, utilizing InGaN/GaN quantum dots incorporated in mesoporous distributed Bragg reflectors (DBRs) within micropillars, we demonstrate methods for the reduction of this contamination. Using the resulting devices, autocorrelation measurements were performed using a Hanbury Brown and Twiss set-up, and thus, we report a working quantum dot device in the III-nitride system utilizing mesoporous DBRs. Uncorrected g(2)(0) autocorrelation values are shown to be significantly improved when excited with a laser at longer wavelengths and lower powers. Through this optimization, we report a g(2)(0) value from a blue-emitting InGaN/GaN quantum dot of 0.126 ± 0.003 without any form of background correction.

There is a consensus in the nanoecotoxicology community that better analytical tools i.e. faster and more accurate ones, are needed for the physicochemical characterisation of nanomaterials in environmentally/biologically relevant media. In this study, we introduce the concept of μTAS (Micro Total Analysis Systems), which was a term coined to encapsulate the integration of laboratory processes on a single microchip. Our focus here is on the use of a capillary electrophoresis (CE) with conductivity detection microchip and how this may be used for the measurement of dissolution of metal oxide nanomaterials. Our preliminary results clearly show promise in that the device is able to: a) measure ionic zinc in various ecotox media with high selectivity b) track the dynamic dissolution events of zinc oxide (ZnO) nanomaterial when dispersed in fish medium.

Atomic layer deposition (ALD) offers a low thermal budget method for producing α-Ga2O3 films on sapphire substrate. In this paper we review the recent progress on plasma-enhanced ALD growth of α-Ga2O3 and present the optical and photoconductive properties of the deposited films. We show that the deposited material exhibits an epitaxial relationship with the sapphire substrate, and with an atomically sharp film-substrate interface. The α-Ga2O3 films had an optical bandgap energy measured at 5.11 eV, and exhibited a broad luminescence spectrum dominated by ultraviolet, blue and green bands, in line with current literature. We finally demonstrate the suitability of the material for solar-blind photodetection.