In this letter, gate leakage mechanisms in different gate contact normally off p-GaN/AlGaN/GaN high electron mobility transistors (HEMTs) have been studied by the temperature-dependent current-voltage (I_G-V_G) measurement. It is found that two-dimensional variable range hopping is responsible for gate leakage current at the reverse gate bias and low forward gate bias in both high-leakage and low-leakage Schottky gate contact devices. At high forward gate bias, in the case of high-leakage Schottky contact, the dominant current conduction mechanism is found to be thermionic field emission while it is Poole–Frenkle emission (PFE) for the case of low-leakage Schottky contact and the activation energy of trap states for PFE current is derived as 0.6 eV. Besides, related models are also proposed to describe the gate leakage current in p-GaN gate HEMTs and they match well with the experimental gate leakage current within a wide range of temperatures and gate biases.

We characterized an ionic liquid (1-butyl-3-methylimidazolium nitrate, C₈H₁₅N₃O₃) as a photo-electrochemical etchant for fabricating normally-off AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). Using the ionic liquid, we achieved an etching rate of ∼2.9 nm/min, which is sufficiently low to facilitate good etching control. The normally-off AlGaN/GaN MIS-HEMT was fabricated with an etching time of 6 min, with the 20 nm low-pressure chemical vapor deposition (LPCVD) silicon nitride (Si₃N₄) gate dielectric exhibiting a threshold voltage shift from −10 to 1.2 V, a maximum drain current of more than 426 mA/mm, and a breakdown voltage of 582 V.

A method of fluorine ion thermal diffusion has been proposed to realize enhancement-mode (E-mode) AlGaN/GaN HEMTs. By AlF3 solid diffusion source, fluorine ion has successfully diffused in the gate region of AlGaN layer at 800 °C 2 h with a diffusion depth about 20 nm demonstrated by secondary ion mass spectrometry. The fabricated device exhibits a positive threshold voltage of 1.8 V, a drain current density of 95 mA/mm at Vg = 4 V, a peak transconductance of 50 mS/mm, a breakdown voltage of 700 V. Besides, the device is also demonstrated with good Vth stability under different stress conditions.

A simplified packaging process was successfully developed for a wafer-level light emitting diode (WL-LED) chip aiming at very-high power solid-state lighting (SSL) applications. Compared with the traditional chip-on-board (COB) technology, WL-LED chip not only greatly simplifies the packaging process but also enables the lighting source more compact. The fabricated blue WL-LED SSL source with a record-high light output power of 305 W exhibits ~30% wall plug efficiency at an input electrical power of 1026 W.

A high-performance temperature sensor based on a p-GaN/AlGaN/GaN hybrid anode diode (HPT-HAD) fabricated by hydrogen plasma treatment is demonstrated. The sensor exhibits accurate and stable temperature responses from 73 to 573 K. The forward anode voltage is linearly proportional to the temperature over the measured temperature range at a fixed current. At a forward current density of 10⁻⁷ mA/mm, the device achieves a maximum sensitivity of 1.93 mV/K. The long-time anode current stress measurement reveals that the HPT-HAD shows almost no degradation even at 573 K for 1 h at a current of 100 μA, and the anode voltage shifts only 120 mV at 573 K for 1000 s at 1 nA. This work shows that the HPT-HAD temperature sensor can be reliably operated over a wide temperature range from cryogenic to high temperatures, so can be used in a variety of extreme environments.

InGaN quantum dots (QDs) are promising candidates for GaN-based all-visible optoelectronic devices such as micro light-emitting diode and laser. In this study, self-assembled InGaN/GaN multi-quantum dots (MQDs) have been grown by plasma-assisted molecular beam epitaxy on c-plane GaN-on-sapphire template. A high density of over 3.8 × 10¹⁰ cm⁻² is achieved and InGaN QDs exhibit a relatively uniform size distribution and good dispersity. Strong localization effect in as-grown InGaN QDs has been evidenced by temperature-dependent photoluminescence (PL). The variation of peak energy is as small as 35 meV with increasing temperature from 10 K to 300 K, implying excellent temperature stability of emission wavelength for InGaN MQDs. Moreover, the radiative and nonradiative recombination times were calculated by time-resolved PL (TRPL) measurements, and the temperature dependence of PL decay times reveal that radiative recombination dominates the recombination process due to the low dislocation density of QDs structure.