In this letter, we apply an oxidation technique for p-GaN to a normally-off p-GaN/AlGaN/GaN HEMT to improve the threshold voltage and gate reliability. Oxygen-plasma and low-temperature Oxygen post-annealing treatment (OPAT) of p-GaN before the deposition of gate metal has introduced a 5 nm oxidation interlayer, resulting in a significant improvement in gate breakdown voltage, from 10.4 V to 20.6 V. Thanks to this interlayer, the threshold voltage of p-GaN gate HEMTs is increased from 1.9 V to 4.6 V, while an almost same on-state resistance and a higher drain breakdown voltage are obtained. Time-dependent gate breakdown measurement shows OPAT-HEMTs have a maximum on-state gate drive voltage of 9.2 V for a 10-year lifetime with a 63 % gate failure rate. In addition, a more stable threshold voltage under gate stress indicates the promising application of this technology in GaN power devices.

In this work, we present the fabrication of a fully vertical β-Ga2O3 Schottky barrier diode with junction termination extension (JTE-SBD) utilizing a p-GaN layer produced by sputtering, offering a solution to the absence of p-Ga2O3 materials. The p-GaN/n-Ga2O3 JTE-SBD demonstrates a turn-on voltage (Von) of 0.8 V, a specific on-resistance (Ron,sp) of 6.15 mΩ·cm2, an ideality factor (n) of 1.24, a breakdown voltage of 3 kV, and a Baliga's Figure of Merit of 1.46 GW/cm2. The current–voltage–temperature (I–V–T) testing has confirmed a transition in the dominant leakage mechanisms from the Poole–Frenkel mechanism to variable-range hopping.

In this paper, we report a high-performance enhancement-mode GaN HEMT fabricated on high-quality ultrathin buffer, which achieved by a two-step-graded (TSG) transition structure on high-resistivity (HR) silicon substrate. Owing to rapid dislocation annihilation of TSG transition structure, the ultrathin buffer exhibits a low total dislocation density (TDD) of 1.7×10 ⁹ cm ^-2 , which could make a contribution to the improvement of current and RF power performance. As a result, an E-mode GaN HEMT fabricated on this structure presents a maximum drain current of 620 mA/mm, a threshold voltage ( V _th ) of 0.7 V, and a transconductance of 360 mS/mm. Furthermore, load-pull measurements yield a maximum output power density ( P _out ) of 5.32 W/mm at 3.6 GHz and V _DS = 35V in pulse mode, which represents the top level for E-mode GaN-on-Si devices reported to date. The high-quality GaN epitaxy and splendid E-mode HEMT shown in this work reveal great potential for GaN-on-Si RF applications.

To improve the threshold voltage and gate reliability of conventional enhancement-mode p-GaN-gated AlGaN/GaN high electron mobility transistors while maintaining a low on-resistance, an improved design solution for p-GaN HEMTs with P-I-N junction gate (PIN-HEMTs) has been proposed. Simulation results show that energy band modulation is achieved by adjusting the doping concentration and thickness of each layer of the PIN junction, and high-performance p-GaN gate HEMTs with adjustable threshold voltages ranging from 0.56 V to 4.75 V and gate breakdown voltages ranging from 19.8 V to 30.3 V would be prepared. The PIN-HEMT has a quasi-self-alignment property, which means that good gate control is independent of gate metal alignment. This not only improves the production efficiency but also solves the problems of weak gate control and electric field aggregation at the gate edge caused by the gate misalignment in conventional p-GaN gate HEMTs, thus realizing lower on-resistance and higher gate breakdown voltage, which demonstrates this proposed structure has excellent potentials for realizing effective and reliable high-power transistors.

In this paper, AlN films grown by magnetron sputtering method have been proposed as the gate insulator layer of AlGaN/GaN high electron mobility transistors (HEMTs) to decrease gate leakage current and suppress the interface trap. The effect of the temperature of substrate on the quality of AlN films have been investigated. By inserting the thin AlN film (35 nm) as a gate insulator layer, the on-state resistance of AlGaN/GaN HEMTs decrease from 11.1 Ω mm to 10.3 Ω mm @V _g = 0 V, the current collapse decreases from 16.6% to 3.2%, the gate leakage can be reduced from 1.2 × 10⁻¹A mm⁻¹ to 4.4 × 10⁻⁶A mm⁻¹ @V _g = 2 V by five orders of magnitude, and the fast interface states disappear and the normal trap density decreases from 0.96–1.3 × 10¹³ cm⁻²eV⁻¹ to 1.3–3.4 × 10¹² cm⁻² eV⁻¹, proving that magnetron-sputtered AlN is an effective way to improve the performance of GaN HEMTs.