Demonstration of 4.7 kV breakdown voltage in NiO/ β -Ga2O3 vertical rectifiers

Abstract

Vertical heterojunction NiO/β n-Ga2O/n+ Ga2O3 rectifiers employing NiO layer extension beyond the rectifying contact for edge termination exhibit breakdown voltages (VB) up to 4.7 kV with a power figure-of-merits, VB2/RON of 2 GW·cm−2, where RON is the on-state resistance (11.3 mΩ cm2). Conventional rectifiers fabricated on the same wafers without NiO showed VB values of 840 V and a power figure-of-merit of 0.11 GW cm−2. Optimization of the design of the two-layer NiO doping and thickness and also the extension beyond the rectifying contact by TCAD showed that the peak electric field at the edge of the rectifying contact could be significantly reduced. The leakage current density before breakdown was 144 mA/cm2, the forward current density was 0.8 kA/cm2 at 12 V, and the turn-on voltage was in the range of 2.2–2.4 V compared to 0.8 V without NiO. Transmission electron microscopy showed sharp interfaces between NiO and epitaxial Ga2O3 and a small amount of disorder from the sputtering process.

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

“…The front surface was cleaned by UV/Ozone exposure for 15 mins to remove contamination. 17 The 10/10 nm NiO bilayer was deposited after the Ohmic contacts by rf (13.56 MHz) magnetron sputtering at a working pressure of 3 mTorr. The hole concentration in these films was adjusted using the Ar/O 2 ratio.…”

“…The bilayer NiO thickness of 10/10 nm and the length of the NiO extension beyond the top contact (12 mm) to form the field plate-like overhang were held constant. 17 The drift region thickness was 10 mm and these layers were grown by halide vapor phase epitaxy (HVPE) on a (001) Sn-doped (10 19 cm À3 ) b-Ga 2 O 3 single crystal substrate. The samples were purchased from Novel Crystal Technology, Japan.…”

“…The device design for NiO thickness and extension was guided by TCAD simulations. 17 The current density-voltage ( J-V) characteristics were measured on Tektronix 370-A and 371-B curve tracers and an Agilent 4156C parameter analyser. For the reverse voltages 42 kV, a Glassman power supply was employed and all the measurements were performed in a Fluorinert atmosphere to avoid breakdown of the air at these high voltages.…”

“…The forward current transport mechanism in such junctions is typically recombination at low biases and trap-assisted tunneling at higher bias. 10,21–26 Promising rectifier performance has been reported with this approach, 14–36 including V B of 8.32 kV, with figure of merit 13.2 GW cm −2 . 15…”

“…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.…”