A high responsivity and controllable recovery ultraviolet (UV) photodetector based on a tungsten oxide (WO₃) gate AlGaN/GaN heterostructure with an integrated micro-heater is reported for the first time.

We report a multiple laser stealth dicing (multi-LSD) method to improve the light extraction efficiency (LEE) of InGaN-based light-emitting diodes (LEDs) using a picosecond (Ps) laser. Compared with conventional LEDs scribed by a nanosecond (Ns) laser and single stealth-diced LEDs, the light output power (LOP) of the LEDs using multi-LSD method can be improved by 26.5% and 11.2%, respectively. The enhanced LOP is due to the increased side emission from the large-area roughened sidewalls of the sapphire substrates fabricated in the multi-LSD process. Numerical simulation results show that the multi-LSD process has little thermal damages to the multiple quantum wells (MQWs) of the LEDs.

This Letter proposes a circularly polarized (CP) light GaN micro-LED which is integrated with functional metasurfaces. The one-dimensional metallic nanograting can achieve a high transverse electric (TE) reflectivity ( R T E ) and extinction ratio (ER) of TE and transverse magnetic (TM) waves, which is highly polarized output for micro-LEDs. Besides, the nanograting, which is integrated on the bottom of the GaN layer, can also support a resonant cavity, together with the top distributed Bragg reflector, which can shape the radiation pattern. By optimizing the structure parameters of nanograting, the R T E achieves over 80%, and the ER reaches higher than 38 dB at 450 nm for the GaN micro-LED. Additionally, the metasurface, which acts as a quarter-wave plate, was investigated to control the phase delay between the polarization state of the electric wave in two orthogonal components. Finally, the circular shape of the transmitted pattern denotes the high performance of the metasurface which is integrated in the micro-LED for CP light emission. The work reported in this Letter might provide potential application in a 3D polarized light display.

The optical and electrical properties of nitride materials are closely related to their crystallographic orientation. Here, we report our effort on crystallographic orientation manipulation of GaN NWs using vapour–liquid–solid hydride vapour phase epitaxy (VLS-HVPE). The growth orientations of the GaN NWs are tuned from the polar c-axis to the non-polar m-axis by simply varying the supply of III precursors on various substrates, including c-, r, m-plane sapphire, (111) silicon and (0001) GaN. By varying the size of the Ni/Au catalyst, we found that the catalyst size has a negligible influence on the growth orientation of GaN NWs. All these demonstrate that the growth orientation of the GaN NWs is dominated by the flow rate of the precursor, regardless of the catalyst size and the substrate adopted. Moreover, the optical properties of GaN NWs were characterized using micro-photoluminescence, revealing that the observed red luminescence band (near 660 nm) is related to the lateral growth of the GaN NWs. The work presented here will advance the understanding of the VLS process of GaN NWs and represents a step forward towards controllable GaN NW growth.

Electrical characteristics of p-, n-GaN/graphene junctions before and after nitric acid doping have been investigated. Acid treatment can significantly improve the junction conductance in both cases, which is advantageous for the light emitting diode (LED) to reduce the operating voltage. GaN-based vertical LEDs incorporating graphene as transparent electrodes are further assembled and tested, showing significant improvement in forward electrical characteristics and light output power upon acid modification.