GaN-based single-photon sources have received immense attention for applications in quantum technologies. An isolated semiconductor quantum dot (QD) is an attractive and proven choice. Most experimental demonstrations involve epitaxial growth or etching of the QD embedded in a vertical nanopillar/nanowire structure. Here, we demonstrate room-temperature single-photon emission from an InGaN QD embedded in a GaN nanoneedle. The nanoneedle is tapered at the bottom and is formed by a succession of inductively coupled plasma reactive ion etching and crystallographic direction-dependent wet etching techniques. The nanofabrication process steps yield reproducible and uniform-sized QDs in the needle structures. Cross-sectional SEM images show needles are centered at the center of a hexagonal base, which confirms a good crystalline property of the QD. Micro-photoluminescence measurements on a single QD manifest a short time constant for radiative decay channels without any prominent non-radiative decay path. Second-order correlation measurements confirm the antibunching of the emitted photons. Higher spectral purity and smaller value of the second-order correlation are maintained up to a good excitation power, indicating the usefulness of the methodology for quantum technologies.

No abstract

No abstract

This work demonstrates the improvement in DC and RF characteristics and a reduction in the gate leakage current for thermally grown Nb2O5 as a gate dielectric in AlGaN/GaN metal–oxide–semiconductor high electron-mobility transistors (MOS-HEMTs). The MOS-HEMTs with an amorphous 10 nm thick Nb2O5 as the gate dielectric show a reduced gate leakage current of 10-9 A/mm. Nb2O5 thin film creates a tensile strain in the AlGaN layer, enhancing the density of two-dimension electron gas (2-DEG). The performance of the device also improves in terms of saturation drain current, peak transconductance, subthreshold swing, and unity current gain frequency. An increase in the source-to-drain ON/OFF current ratio to 108 and a significant reduction in the subthreshold leakage current by at least two orders of magnitude are measured compared to the control HEMTs.

No abstract