Recent advances in NiO/Ga₂O₃ heterojunctions for power electronics

Abstract

Beta gallium oxide (β-Ga2O3) has attracted significant attention for applications in power electronics due to its ultra-wide bandgap of ~ 4.8 eV and the large critical electric field of 8 MV/cm. These properties yield a high Baliga’s figures of merit (BFOM) of more than 3000. Though β-Ga2O3 possesses superior material properties, the lack of p-type doping is the main obstacle that hinders the development of β-Ga2O3-based power devices for commercial use. Constructing heterojunctions by employing other p-type materials has been proven to be a feasible solution to this issue. Nickel oxide (NiO) is the most promising candidate due to its wide band gap of 3.6–4.0 eV. So far, remarkable progress has been made in NiO/β-Ga2O3 heterojunction power devices. This review aims to summarize recent advances in the construction, characterization, and device performance of the NiO/β-Ga2O3 heterojunction power devices. The crystallinity, band structure, and carrier transport property of the sputtered NiO/β-Ga2O3 heterojunctions are discussed. Various device architectures, including the NiO/β-Ga2O3 heterojunction pn diodes (HJDs), junction barrier Schottky (JBS) diodes, and junction field effect transistors (JFET), as well as the edge terminations and super-junctions based on the NiO/β-Ga2O3 heterojunction, are described.

Superior high temperature performance of 8 kV NiO/Ga2O3vertical heterojunction rectifiers

“…The various polytypes of Ga 2 O 3 are attracting attention for their potential application in power switching, solar-blind UV detectors and lateral transistors with enhanced two-dimensional electron gas densities. [1][2][3][4][5][6][7][8] It is relatively easy to grow bulk crystals of the stable monoclinic b-polymorph from the melt, which enables large-diameter, high-quality substrates for homoepitaxy at potentially low cost. 2 This is attractive for lower manufacturing costs since the material comprises a significant component of the cost of manufacture.…”

“…Ga 2 O 3 has a high critical electric field strength, which allows for higher operating voltages and lower switching losses in power electronics. [1][2][3][4][5][6] Its ultrawide bandgap also makes it promising for high temperatures and radiation environment applications. As a result of these advantages, Ga 2 O 3 is being considered for several power electronics applications, including inverters, motor drives, and power supplies.…”

“…A figure of merit for power electronic devices is defined as (V B ) 2 /R ON , where V B is the reverse breakdown voltage and R ON-is the on-state resistance. 1,3,4 To achieve a high-power figure of merit, a rectifier must have a low drift layer concentration, with high electron mobility, as well as low R ON , and optimized edge termination to prevent current crowding. 1,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The breakdown voltage is larger for thicker drift layers, but this degrades the on-resistance.…”

“…In addition, vertical geometry devices are desirable, because of their higher power conversion efficiency and absolute currents compared to lateral devices. 1,[3][4][5] Power rectifiers are also building blocks for many advanced power handling systems.…”

15 MeV proton damage in NiO/β-Ga2O3vertical rectifiers

“…β-Ga 2 O 3 is attracting significant recent attention for power switching devices [1][2][3] and solar-blind UV photodetectors [4]. In particular, significant advancements have been achieved in the development of NiO/β-Ga 2 O 3 power rectifiers, surpassing the performance limitations observed in GaN structures, particularly in one-dimensional configurations [5][6][7][8].…”