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10 kV, 39 mΩ·cm2 Multi-Channel AlGaN/GaN Schottky Barrier Diodes

device structure
Fig. 1. Schematics of the multi-channel AlGaN/GaN SBD with (a) p-GaN edge termination and (b) p-GaN RESURF. (c) Cross-sectional SEM images of the p-GaN/multi-channel re-gion. (d) SEM image of the p-GaN edge termination region. (e) Top-view SEM image of p-GaN RESURF SBD.
  High voltage (HV, >1.7 kV) power rectifiers are needed in various power electronics applications, e.g., renewable-energy generation, industrial motor drives, electricity grid, and transportations. Bipolar Si diodes are commercially available up to 6.5 kV, but they suffer from slow switching speed. Unipolar SiC junction barrier Schottky (JBS) diodes up to 10 kV have been recently pre-commercialized by Cree. However, commercial 3.3-kV+ SiC diodes are barely available due to high cost; their market penetration is still slow. This work demonstrates multi-channel AlGaN/GaN Schottky barrier diodes (SBDs) with a breakdown voltage (BV) over 10 kV, the highest BV reported in GaN devices to date.

  The epitaxial structure consists of a p-GaN cap layer and five AlGaN/GaN channels continuously grown on a low-cost 4-inch sapphire substrate. Fig 1(a) shows a reference sample with the p-GaN termination. A novel device design is proposed for electric field management, i.e., the p-GaN reduced surface field (RESURF) structure, which balances the net charges in the multi-channel at reverse biases (Fig. 1(b)). Fig. 2 benchmarks the RON,SP v.s. BV of our GaN SBDs with the state-of-the-art HV (BV > 2 kV) GaN SBDs, SiC JBS/SBDs, and Ga2O3 SBDs. The SBD with a 98-µm anode-to-cathode length (LAC) shows a BV of 9.15 kV and a specific on resistance (RON) of 29.5 mΩ·cm2, rendering a Baliga's figure of merit (FOM) of 2.84 GW/cm2. The SBD with a 123-µm LAC shows a BV over 10 kV and a RON of 39 mΩ·cm2, which is 2.5-fold lower than the RON of the state-of-the-art 10-kV SiC junction barrier Schottky diodes. The Baliga's FOMs of our 4.6-10 kV GaN SBDs well exceed the SiC unipolar limit. These results show the great promise of GaN for medium- and high-voltage power electronics.
Fig. 2. The differential RON,RP v.s. BV benchmark for our SBDs and the state-of-the-art GaN, SiC, and Ga2O3 HV SBDs. The Si, SiC, GaN bulk

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