NiO/Ga2O3 Vertical Rectifiers of 7 kV and 1 mm2 with 5.5 A Forward Conduction Current

Abstract

In this study, we present the fabrication and characterization of vertically oriented NiO/β polymorph n-Ga2O3/n+ Ga2O3 heterojunction rectifiers featuring a substantial area of 1 mm2. A dual-layer SiNX/SiO2 dielectric field plate edge termination was employed to increase the breakdown voltage (VB). These heterojunction rectifiers exhibit remarkable simultaneous achievement of high breakdown voltage and substantial conducting currents. In particular, the devices manifest VB of 7 kV when employing a 15 µm thick drift layer doping concentration of 8.8 × 1015 cm−3, concurrently demonstrating a forward current of 5.5 A. The thick drift layer is crucial in obtaining high VB since similar devices fabricated on 10 µm thick epilayers had breakdown voltages in the range of 3.6–4.0 kV. Reference devices fabricated on the 15 µm drift layers had VB of 5 kV. The breakdown is still due to leakage current from tunneling and thermionic emission and not from avalanche breakdown. An evaluation of the power figure-of-merit, represented by VB2/RON, reveals a value of 9.2 GW·cm−2, where RON denotes the on-state resistance, measuring 5.4 mΩ·cm2. The Coff was 4 nF/cm2, leading to an RON × Coff of 34 ps and FCO of 29 GHz. The turn-on voltage for these rectifiers was ~2 V. This exceptional performance surpasses the theoretical unipolar one-dimensional (1D) limit of both SiC and GaN, underscoring the potential of β-Ga2O3 for forthcoming generations of high-power rectification devices.

A Review of β-Ga2O3 Power Diodes

“…The performance of HJDs can be further enhanced through the introduction of additional terminal structures. Li et al [228] prepared a large-area (1 × 1 mm 2 ) NiO/β-Ga 2 O 3 HJD on β-Ga 2 O 3 with a 15 µm drift layer, simultaneously introducing a SiO 2 /SiN x bilayer field plate structure, as portrayed in Figure 11a. Compared to the device without the field plate structure, the BV increased from 5 kV to 7 kV, and the PFOM improved from 5.7 to 9.2 GW•cm −2 .…”

Three-step field-plated β-Ga2O3 Schottky barrier diodes and heterojunction diodes with sub-1 V turn-on and kilovolt-class breakdown

“…9,10) Among two-terminal devices, p-NiO/β-Ga 2 O 3 heterojunction devices showcase the best reported performance, enabling the demonstration of ampere-class devices. 11) To enhance the breakdown voltage characteristics of β-Ga 2 O 3 vertical devices, field termination structures are critical for reducing electric-field crowding at the edge of the device. Several field termination structures have been demonstrated in β-Ga 2 O 3 , including field plates, ion-implanted termination, mesa etch termination, guard rings (p-NiO), and junction termination extensions.…”