In this work, we report on demonstrating the firstvertical ${\rm{\beta}-Ga_{2}O_{3}}$ junction barrier Schottky (JBS) diode with theimplementation of thermally oxidized p-type NiO to compensatethe dilemma of the forfeit of the p-type ${\rm{\beta}-Ga_{2}O_{3}}$ . With this widebandgap p-type NiOx, ${\rm{\beta}-Ga_{2}O_{3}}$ JBS diodes with an area of 100×100 ${\mu m^{2}}$ achieves a breakdown voltage (BV) and specific onresistance(Ron,sp) of 1715 V and 3.45 ${m\Omega\cdot cm^{2}}$ , respectively,yielding a Baliga'figure of merit (FOM) of ${BV^{2}/R_{on,sp}= 0.85 \rm{GW/cm^{2}}}$ , which is the highest direct-current (DC) FOM valueamong all ${\rm{\beta}-Ga_{2}O_{3}}$ diodes. Meanwhile, a large size JBS diodewith area of 1×1 ${mm^{2}}$ shows a forward current (IF) and BV of 5A/700 V, which is also the best IF and BV combinations (FOM =64 MW/ ${cm^{2}}$ ) among all published results about large area Ga2O3diodes. Dynamic switching characteristics reveal that the diodesuffers from negligible current collapse phenomenon even at a -600 V and 103 s stress, showing the great promise ofimplementing p-NiO in the future ${\rm{\beta}-Ga_{2}O_{3}}$ power electronicdevices.

In this letter, high-performance p-NiO/ β -Ga ₂ O ₃ heterojunction diodes (HJDs) with composite terminal structures, a p-NiO junction termination extension (JTE), and a small-angle beveled field plate (BFP) are demonstrated. By implementing a p-NiO JTE structure, the optimal breakdown voltage ( V _br ) of β -Ga ₂ O ₃ HJD increases from 955 to 1945 V, and the integration of the small-angle BFP further boosts the breakdown voltage up to 2410 V. An 80-nm thin p-NiO layer is adopted in the heterojunction to reduce the specific on -resistance ( R _on,sp ), while the composite terminal structures have little effect on R _on,sp , due to the super-large lateral spread resistance. The β -Ga ₂ O ₃ HJD with composite terminal structures achieves a low R _on,sp of 1.12 mΩ·cm ² , yielding the highest direct-current Baliga's figure-of-merit (FOM = V _br ² / R _on,sp ) among all reported β-Ga ₂ O ₃ diodes with a value of 5.18 GW/cm ² _, which is about 15% of the theoretical value. These results suggest that the electrical field engineering with a composite terminal structure is a viable and effective technological strategy to enable the realization of β -Ga ₂ O ₃ bipolar power rectifiers.

Diamond field-effect transistor (FET) has great application potential for high frequency and high power electronic devices. In this work, diamond FETs were fabricated on (0 0 1) single crystal diamond with homoepitaxial layer. The nitrogen impurity content in the homoepitaxial layer is greatly decreased as measured by the Raman and photoluminescence spectra. The diamond field effect transistor with 100 nm Al₂O₃ as gate dielectric shows ohomic contact resistance of 35 Ω . mm, maximum drain saturation current density of 500 mA/mm, and maximum transconductance of 20.1 mS/mm. Due to the high quality of Al₂O₃ gate dielectric and single crystal diamond substrate, the drain work voltage of −58 V is achieved for the diamond FETs. A continuous wave output power density of 4.2 W/mm at 2 GHz is obtained. The output power densities at 4 and 10 GHz are also improved and achieve 3.1 and 1.7 W/mm, respectively. This work shows the application potential of single crystal diamond for high frequency and high power electronic devices.

In this letter, the ultrafast reverse recovery β -Ga ₂ O ₃ Schottky barrier diode (SBD) with improved breakdown voltage is proposed and investigated experimentally. It features the compound termination, consisting of air space field plate and thermal oxidation terminal. The compound termination not only reduces high-density interface states at the dielectric/Ga ₂ O ₃ interface and the electron concentration in the oxidation terminal, but also modulates the electric-field distribution and suppresses the peak electric-field at the bottom of anode. Therefore, the reverse leakage current is suppressed as well as the reverse recovery and breakdown characteristics are improved effectively. The Ga ₂ O ₃ SBDs with the diameter of 1000 μm obtain ultrashort reverse recovery time of 7.5 ns and ultralow reverse recovery charge of 1.0 nC at di / dt = 50 A/μs with its breakdown voltage up to 400 V, maintaining good rectification characteristics. The temperature-dependences of both forward conduction and reverse recovery characteristics are discussed in temperature range from 300 to 500 K. The results prove that the superior electronics performance of the β -Ga ₂ O ₃ SBDs with good electronics thermal tolerance can overcome the low thermal conductivity of β -Ga ₂ O ₃ to a certain extent. The fabricated β -Ga ₂ O ₃ SBDs have great potential for high power and high-frequency applications.