We fabricated self-aligned quasi-vertical trench p-NiO/GaN merged p-n Schottky diodes with p-NiO guard-rings and investigated the effects of trench depth (dt) and n-region width (Wn) on the electrical characteristics. The MPS diode with Wn of 2 μm and dt of 1 μm exhibited a high forward current density of 1 kA cm−2 and a low differential Ron,sp of 1.4 mΩ·cm2. Guard-rings edge termination was introduced to improve the breakdown voltage from 330 V to 430 V. The average breakdown electric field was calculated to be 1.1 MV cm−1 for the MPS diode on a sapphire substrate.

Enhancement-mode (E-mode) p-channel field-effect transistors (p-FETs) remain challenging for GaN complementary logic (CL) technology due to their unstable threshold voltage (Vth), low current density, and large on-resistance (RON) at 6 V CL-compatible operation. In this work, we demonstrate a high-performance E-mode GaN p-FET with a p-NiO/p-GaN heterojunction gate. Notably, the suppressed Vth shift and improved channel conductivity were simultaneously achieved in the E-mode channel. The improvement is primarily due to the type-II band alignment at the p-NiO/p-GaN interface. This structure reduces band overlap, resulting in a low interface trap density (DT) of 3.29–5.71 × 1010 cm−2 eV−1 as measured by the sub-bandgap photo-assisted capacitance–voltage method. The fabricated device with LG/LGS/LGD = 1.5/3/3 μm exhibits a Vth of −0.6 V with a minimal hysteresis of 0.02 V and maximum shift of 0.04 V under stress, a ID of 5.5 mA/mm, a RON of 0.47 k Ω mm, and a transconductance (gm) of 1.8 mS/mm for 6 V CL-compatible operation.

In this paper, we reported the mechanism of a bimodal Weibull distribution for TDDB of gate dielectric in GaN MISHEMT. It is shown that the properties of traps in the dielectric layer would have a great influence on the long time reliability and life time prediction process. 

In this study, the physical properties of F ion-implanted GaN were thoroughly studied, and the related electric-field modulation mechanisms in ion-implanted edge termination were revealed. Transmission electron microscopy results indicate that the ion-implanted region maintains a single-crystal structure even with the implantation of high-energy F ions, indicating that the high resistivity of the edge termination region is not induced by amorphization. Alternately, ion implantation-induced deep levels could compensate the electrons and lead to a highly resistive layer. In addition to the bulk effect, the direct bombardment of high-energy F ions resulted in a rough and nitrogen-deficient surface, which was confirmed via atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. The implanted surface with a large density of nitrogen vacancies can accommodate electrons, and it is more conductive than the bulk in the implanted region, which is validated via spreading resistance profiling and conductive AFM measurements. Under reverse bias, the implanted surface can spread the potential in the lateral direction, whereas the acceptor traps capture electrons acting as space charges, shifting the peak electric field into the bulk region in the vertical direction. As a result, the Schottky barrier diode terminated with high-energy F ion-implanted regions exhibits a breakdown voltage of over 1.2 kV.

A ridge-channel AlGaN/GaN high-electron mobility transistor (HEMT) utilizing selective-area growth and epitaxial lateral overgrowth (ELO) technique is proposed in this work to achieve high-performance normally-off devices. It has a c-plane platform for the source and the drain contacts, and sidewalls of lattice plane for the gate contact. The sidewalls have characteristics of weak polarization and thin barrier, which are advantageous for realizing normally-off operation. Two ridge HEMTs with triangular and trapezoid channel are designed. Theoretical simulation demonstrates a threshold voltage of 0.03 V for the sidewall channel with reduced polarization and barrier thickness, and a threshold voltage of 1.1–1.3 V for the ridge HEMTs assuming no polarization charge in sidewall channel. The ridge-channel device also exhibits high saturation drain current. The ELO-based ridge-channel opens a new way to achieve normally-off AlGaN/GaN HEMT.