NiO junction termination extension for high-voltage (>3 kV) Ga2O3 devices

Abstract

Edge termination is the enabling building block of power devices to exploit the high breakdown field of wide bandgap (WBG) and ultra-wide bandgap (UWBG) semiconductors. This work presents a heterogeneous junction termination extension (JTE) based on p-type nickel oxide (NiO) for gallium oxide (Ga2O3) devices. Distinct from prior JTEs usually made by implantation or etch, this NiO JTE is deposited on the surface of Ga2O3 by magnetron sputtering. The JTE consists of multiple NiO layers with various lengths to allow for a graded decrease in effective charge density away from the device active region. Moreover, this surface JTE has broad design window and process latitude, and its efficiency is drift-layer agnostic. The physics of this NiO JTE is validated by experimental applications into NiO/Ga2O3 p–n diodes fabricated on two Ga2O3 wafers with different doping concentrations. The JTE enables a breakdown voltage over 3.2 kV and a consistent parallel-plate junction field of 4.2 MV/cm in both devices, rendering a power figure of merit of 2.5–2.7 GW/cm2. These results show the great promise of the deposited JTE as a flexible, near ideal edge termination for WBG and UWBG devices, particularly those lacking high-quality homojunctions.

The Optimization of NiO Doping, Thickness, and Extension in kV-Class NiO/Ga2O3 Vertical Rectifiers

“…The ultra-wide-bandgap semiconductor, Ga 2 O 3 , has advantages over Si electronics in terms of the ability to achieve higher breakdown voltage and lower on-state resistance [1][2][3][4][5][6][7][8][9]. Recent demonstrations of the ability of NiO/β-Ga 2 O 3 vertical geometry rectifiers to achieve excellent performance [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] and breakdown voltages in excess of 8 kV [7,[25][26][27] has revitalized interest in the heterojunction approach to overcome the lack of a practical p-type doping capability for β-Ga 2 O 3 . Several groups have now demonstrated devices with breakdown voltage and on-state resistance beyond the 1D limit of both GaN and SiC, showing the increasing maturity of Ga 2 O 3 power device technology [7,25].…”

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

“…Figure 5(b) shows the benchmark comparison of R on eff -V br obtained in this work with prior reports of p-NiO/Ga 2 O 3 HJDs. 9,15,16,20,21,29,31,32) Due to the lower turnon voltage, we obtain one of the lowest effective onresistances reported for a p-NiO/Ga 2 O 3 HJD using a standard 10-μm-thick epilayer from NCT.…”

β-Ga2O3-Based Heterostructures and Heterojunctions for Power Electronics: A Review of the Recent Advances

“…Xiao et al [62] demonstrated a ~3.5 kV NiO x /β-Ga 2 O 3 p-n diode with multiple JTEs of NiO x layers with different lengths (Figure 4a). This mechanism allows a gradual decrease in the effective charge carriers away from the device's active region to smoothen the electric field crowding at the anode edge, as in Figure 4b.…”

“…This facilitates charge balance at the heterojunction, reducing electric field crowding and enhancing the device's high-voltage-handling capabilities. NiOx-based JTEs [56,62,68], guard rings [69], and reduced surface field structures (RESURFs) [70,71] have In addition to p-n junctions, NiO x can serve as a material for edge termination in β-Ga 2 O 3 devices. This facilitates charge balance at the heterojunction, reducing electric field crowding and enhancing the device's high-voltage-handling capabilities.…”

“…This facilitates charge balance at the heterojunction, reducing electric field crowding and enhancing the device's high-voltage-handling capabilities. NiO x -based JTEs [56,62,68], guard rings [69], and reduced surface field structures (RESURFs) [70,71] have been reported as edge terminations for β-Ga 2 O 3 devices. Yan et al [56] demonstrated a β-Ga 2 O 3 SBD with NiO x heterojunction edge termination and a SiO 2 FP structure (Figure 5a).…”