Normally-off HEMTs have been fabricated with regrown p-GaN gate and SiN _x passivation by Low-pressure chemical vapor deposition (LPCVD) using an AlN pre-layer, featuring a high-temperature passivation-first technique with no incompatibility issues. Through careful surface treatments, high-quality interfaces (regrown p-GaN/AlGaN and SiN _x /AlGaN), as well as a stable p-GaN contact, can be achieved, enabling a robust gate operation and improved dynamic performance. The as-fabricated device exhibits a low reverse gate leakage of 2 nA/mm @ V _GD = −200 V, a stable forward gate current of $10~\mu \text{A}$ /mm @ V _GS = 5 V, a positive threshold voltage of +1.7 V @ ${I}_{\text {DS}} = {10}\,\,\mu \text{A}$ /mm with a high saturation current of 435 mA/mm, a high I _on /I _off ratio of ${5}\times {10}^{10}$ , and a low R _on,d /R _on,s ratio of 1.5. The as-developed technique with the LPCVD SiN _x passivation and p-GaN gate regrowth may provide a way to enhance the performance of p-GaN E-HEMTs.

This Letter studies the reverse leakage and breakdown mechanisms of vertical GaN-on-Si Schottky barrier diodes (SBDs) with and without argon-implanted termination (ArIT). The electrical leakage characteristics in the vertical GaN-on-Si SBD without edge termination sequentially go through the thermionic field emission, variable range hopping (VRH), and trap-assisted tunneling conduction mechanisms as the reverse bias increases gradually. Its leakage and breakdown mechanisms are limited by the edge electric field crowding effect. While for the vertical GaN-on-Si SBD with ArIT (ArIT-SBD), the electrons conduction at a low reverse bias, following the space-charge-limited conduction (SCLC) model, is limited by the damage-induced traps in the implanted GaN. As the reverse bias increases up to the occurrence of breakdown, the VRH and SCLC dominate the leakage mechanism of the ArIT-SBD, which stem from intrinsic traps in GaN grown on Si. A rapidly growing leakage under a low reverse bias and enhanced breakdown voltage performance in the ArIT-SBD is attributed to the charging of the damage-induced traps in implanted GaN. This Letter not only gives in-depth insights of vertical GaN-on-Si SBDs but also provides a useful design guidance of implanted termination for high-voltage power devices.

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.

A high-performance quasi-vertical GaN Schottky barrier diode (SBD) was successfully fabricated by using a high-quality n ^- -GaN drift layer with a precisely-controlled n-type doping. A high current on/off ratio of 10 ¹⁰ , an ideality factor of 1.03, a low specific on-resistance of 1.41 mΩ·cm ² , and a relatively high breakdown voltage (BV) of 250 V have been achieved for the SBD without edge termination. Furthermore, with an Argon-implanted termination, the as-fabricated GaN-on-Si SBD shows a record high BV of 405 V, yielding a critical electric field of ~ 2 MV/cm, while the forward conduction characteristics are well maintained.

This work demonstrates a novel Nitrogen-implanted (N-implanted) guard ring (GR) technology for the 600-V quasi-vertical GaN-on-Si Schottky barrier diode (SBD). The GR parameters are designed and studied in detail by the TCAD simulation. With a 4.4- $\mu \text{m}$ -thick GaN drift layer, seven GRs with a precise design greatly enhance the breakdown voltage of GaN SBDs from ~290 to ~600 V, and barely degrade the ON-state characteristics, including a high ${I}_{ {\scriptscriptstyle { \mathrm {ON}}}}/{I}_{ {\scriptscriptstyle { \mathrm {OFF}}}}$ of 10 ¹¹ , a low ideality factor of 1.06, a low turn-on voltage of 0.64 V (at 1 A/cm ² ), and a low-specific ON-resistance ( ${R}_{ {\scriptscriptstyle { \mathrm {ON}}},{\mathrm {sp}}}$ ) of 1.40 $\text{m}\Omega ~\cdot ~{\mathrm {cm}}^{2}$ , leading to a record Baliga’s figure of merit (BFOM) of 0.26 GW/cm ² among all the reported vertical GaN-on-Si SBDs. At 175 °C, the SBD with seven GRs shows a slightly increased ${R}_{ {\scriptscriptstyle { \mathrm {ON}}},{\mathrm {sp}}}$ of 1.86 $\text{m}\Omega ~\cdot ~{\mathrm {cm}}^{2}$ and an excellent electrical characteristic even under a reverse bias of 380 V, implying a high-temperature operation capability of N-implanted GRs.

This letter reports the influence of material quality and device processing on the performance of AlGaN-based Schottky barrier deep ultraviolet photodetectors grown on Si substrates. The thermal annealing can significantly improve Schottky barrier height and wet chemical etching can effectively remove etching damage. Meanwhile, the decrease of threading dislocation density and the pit size, especially the later, can substantially suppress reverse leakage. As a result, the reverse leakage current density of the as-fabricated deep UV photodetector was reduced down to 3×10⁻⁸ A/cm². Furthermore, the responsivity of the deep UV photodetectors was greatly improved by reducing the point defect concentration.