A Reseach Of High Performance GAN Power Rectifier

Recent years, GaN(Gallium Nitride) power devices develop very fast in power electronics for their high power, high frequency, high linearity and high efficiency. Rectifiers play an important role in power electronics, but conventional GaN heterojunction Schottky Barrier Diodes and PN Diodes(SBD and PN) have large turn-on voltage for the reason of Schottky Barrier Height and large leakage current for the contact of Schottky metal and semiconductor, which has a dramatic leakage in reverse voltage. Large turn-on voltage can cause large turn-on power dissipation, and to a certain extent device’s safe operation area depends on reverse leakage current and breakdown voltage. So we want to achieve rectifiers with low turn-on voltage, low reverse leakage current and high breakdown voltage in the practical application. This work is to propose a GaN power rectifier with low turn-on voltage, low reverse leakage current and high breakdown voltage. The main research contents include:(1) An AlGaN/GaN Power Rectifier with Edge-Terminated Hybrid Anode(ETH-Rectifier) is proposed. This ETH-Rectifier has two characteristics: 1、By means of etching a groove, optimize the AlGaN barrier layer thickness under Schottky gate for a 2 dimension electron gas density(2DEG) modulation, thus achieve the modulation of device’s turn-on voltage. Simulation results show that the turn-on voltage of ETH-Rectifier is 0.25 V, which is 1/6 of SBD. 2、The introduction of edge-termination(ET) in the Schottky groove near the cathode side significantly reduces the reverse leakage current of the rectifier and improve the breakdown voltage. ETH-Rectifier with an ET of 0.5 μm reduces the reverse leakage current(down to 2×10-7mA/mm at-100V) by more than five orders of magnitude lower than that of rectifier without ET and features up to 510 V breakdown voltage. Additionally, a field plate is added to the schottky gate to improve breakdown voltage(BV) of the proposed rectifier further from 510 V to 800 V at anode-to-cathode distance(Lac) of 5μm, with a 56.86% improvement. According to BFOM, the optimism of edge-termination and field-plate are 1.0μm and 2.0μm.(2) According to the reliability of ETH-Rectifier, An improvement AlGa N/GaN Power Rectifier with MIS-Gated Hybrid Anode(MG-HAR) is proposed. This MG-HAR has two characteristics:1、The test results show that MG-HAR achieves low turn-on voltage of 0.6V by thinning the AlGaN barrier layer under Schottky gate, and which of SBD is 0.9V. 2、The groove was deposited by the gate dielectric to decrease reverse leakage current and improve breakdown voltage. MG-HAR reduces the reverse leakage current by more than two orders of magnitude lower than that of SBD at-100 V. Define when reverse leakage current of MG-HAR is 10μA/mm, MG-HAR break down. Thus the breakdown voltage of MG-HAR is 438 V and 575 V at anode-to-cathode(Lac) of 5.0μm and 10.0μm; this is more than the breakdown voltage of SBD, which is 512V@1mA/mm at anode-to-cathode(Lac) of 20.0μm. At anode-to-cathode(Lac) of 20.0μm, the breakdown voltage of MG-HAR is up to 1100 V, and the reverse leakage current is less than 1μA/mm before 790 V.