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Medium-Voltage Multi-Channel AlGaN/GaN Power Schottky Barrier Diodes

SBD structure and equivalent circuit
Fig. 1. (a) Junction-Fin-anode (JFA) SBD structure and (b) equivalent circuit model.
  This work demonstrates multi-kilovolt AlGaN/GaN Schottky barrier diodes (SBDs) on a 4-inch, 5-channel, low-cost GaN-on-sapphire wafer. Our device highlights a new 3-D anode architecture, in which the p-n junction wraps around the multi-2DEG-channel fins. Fig. 1 (a) and (b) show the device structure diagram and equivalent circuit model of this Junction-Fin-anode (JFA) SBD, respectively. This junction-fin structure differs from all existing tri-anode and tri-gate structures, which employ a Schottky or a metal-insulator-semiconductor (MIS) stack at the fin sidewalls. Our junction-fin structure is realized with regrown p-GaN on the top of the fin and p-type NiOx at the fin sidewalls. Thanks to the strong charge depletion, this structure allows an over 10-fold reduction in device leakage current. The top p-GaN further extends towards the cathode, which shields the fin-anode region from the high electric field. Our SBDs show a breakdown voltage (BV) from 300 V to 5.2 kV with a leakage current of 1.4 µA/mm at 90% BV, as well as super-low on-resistance (Ron), rending a Baliga's figure of merit (FOM) exceeding the SiC 1-D unipolar limit and among the highest in all kilovolts power SBDs. The projected VFQC (forward voltage times reverse charges) metrics is also superior over commercial SiC devices at multi-kilovolt levels. Large-area, multi-channel AlGaN/GaN SBDs are demonstrated for the first time, with a 1.5 A current, a 4.8 kV BV with ~µA leakage current, and a 13 nC total charge. Fig. 2 benchmarks the specific differential Ron vs. BV of our multi-channel AlGaN/GaN JFA-SBDs, compared to the state-of-the-art lateral GaN, vertical GaN, SiC, and Ga2O3 SBDs. As our device is the first large-area multi-kilovolts AlGaN/GaN SBD. These results show the great potential of AlGaN/GaN multi-channel devices for medium-voltage power applications.
Specific RON vs. BV
Fig. 2. Specific RON vs. BV of our multi-channel AlGaN/GaN JFA-SBDs.

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