In this letter, we propose to implement a microwave lateral GaN Schottky barrier diode (SBD) in a designed 5.8-GHz rectifier circuit for future high-power and high-efficiency wireless power transfer. The low-pressure chemical vapor deposition SiN-passivated lateral GaN SBD demonstrates a low turn- on voltage of 0.38 V, a low on -resistance of 4.5 Ω, a low junction capacitance of 0.32 pF at 0-V bias, and a high breakdown voltage of 164 V, which are essentials for a high-efficiency and high-power rectifying application. By incorporating this lateral GaN SBD in a well-designed 5.8-GHz rectifier circuit, an unprecedented combination of high efficiency and high power is achieved simultaneously. The rectifier circuit demonstrates a high RF/dc conversion efficiency ( η _RF/DC ) of 71 ± 4.5% with an input power ( P _in ) of 2.5 W and η _RF/DC = 50 ± 4.5% with P _in = 6.4 W per single diode, showing the great promise of embracing lateral GaN SBD for future wireless high-power transfer application.

(Al)GaN recess-free normally OFF technology is developed for fabrication of high-yield lateral GaN-based power devices. The recess-free process is achieved by an ultrathin-barrier (UTB) AlGaN/GaN heterostructure that features a natural pinched-off 2-D electron gas channel. The top-down manufacturing technique overcomes the challenges in etching of AlGaN barrier with well-controlled depth and uniformity, which is especially attractive for fabrication of normally OFF GaN-based high-electron-mobility transistors (HEMTs) and metal-insulator-semiconductor HEMTs (MIS-HEMTs) on large-size Si substrate. With SiNx passivation grown by low-pressure chemical-vapor deposition, on-resistance of the UTB-AlGaN/GaN-based power devices can be significantly reduced. High-uniformity low-hysteresis normally OFF HEMTs and Al₂O₃/AlGaN/GaN MIS-HEMTs are successfully demonstrated on the UTB AlGaN/GaN-on-Si platform. It is also a compelling technology platform for manufacturing high-performance GaN-based lateral power diodes, and normally OFF p-(Al)GaN heterojunction field-effect transistors.

In this work, the deep-level transient spectroscopy (DLTS) is conducted to investigate the gate stack of the p-GaN gate HEMT with Schottky gate contact. A metal/p-GaN/AlGaN/GaN heterojunction capacitor is prepared for the study. The DLTS characterization captures the transient capacitance change in the stack, from which the capacitance of the metal/p-GaN Schottky junction can be extracted. By proper selection of the rate window, the impacts of the hole insufficiency effect are avoided during trap states evaluation. Thus, the information of deep energy levels in the p-GaN layer is revealed, which consists of an electron trap state with activation energy of 0.85 eV and a hole trap state with activation energy of 0.49 eV. The identification of these trap states in the p-GaN layer provides a physical foundation for understanding the threshold voltage instability in Schottky-type p-GaN gate power HEMTs.

Ultra-thin-barrier (UTB) AlGaN/GaN heterostructure is utilized for fabrication of normally-OFF GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). The sheet resistance of 2-D electron gas in the UTB Al _0.22 Ga _0.78 N(5-nm)/GaN heterostructure is effectively reduced by SiN _x passivation grown by low-pressure chemical vapor deposition, from 2570 to $334~\Omega $ /□. The fabricated Al ₂ O ₃ /AlGaN/GaN MIS-HEMTs exhibit normally-OFF behavior with good $V_{\mathrm {TH}}$ uniformity and low $V_{\mathrm {TH}}$ -hysteresis. 20 mm-gate-width power devices featuring a low $R_{\sc {\mathrm{ on}}}$ of $0.75~\Omega $ ( $\text{I}_{\mathrm {D,MAX}} =6.5$ A) are also demonstrated on the platform.

In this letter, an enhancement-mode (E-mode) GaN p-channel field-effect transistors (p-FETs) with current density of −5.6 mA/mm and ${I} _{{\mathrm {ON}}}/{I} _{{\mathrm {OFF}}}$ ratio of 10 ⁶ was demonstrated on a p-GaN/AlN/AlGaN/GaN heterostructure on Si substrate. A decent ohmic contact resistivity of $9.25 \times 10^{-5} \Omega \cdot {\mathrm {cm}}^{2}$ is achieved by capping the heterostructure with a 10-nm heavily Mg-doped p ⁺⁺ -GaN epilayer. A two-step gate trench etching process, is implemented to overcome the decreased OFF-state blocking voltage associated with the surface p ⁺⁺ -GaN layer. The proposed structure is compelling for monolithic integration of GaN-based logic and power devices.

We report on the electrical and microstructural characterization of Au-free Ti/Al/Ti/TiN contacts for AlGaN/GaN heterostructures. Ultra-low Au-free ohmic contact has been obtained with contact resistance and specific contact resistivity as low as 0.21 Ω · mm and 1.16 x 10 ^-6 Ω · cm ² , respectively. The ohmic alloy temperature is reduced as low as 550 °C by pre-ohmic recess of the AlGaN barrier and optimization of the thickness of bottom Ti layer. We found that interfacial layer formation of AlN between the ohmic metal and AlGaN surface is crucial to realize a low contact resistance with reduced low annealing temperature by a combination of electrical I-V characterization and high-resolution transmission electron microscopy analysis. Furthermore, we suggest a hypothesis that the bottom Ti layer plays a catalytic role for the Al-N reaction with optimized thickness.