High-voltage AlGaN/GaN Schottky barrier diodes on silicon using a post-process O2 treatment

Abstract

High-voltage AlGaN/GaN Schottky barrier diodes (SBDs) were fabricated using on a silicon (111) substrate, and a post-process O2 treatment was carried out to reduce the leakage current and increase the breakdown voltage. Time-of-flight secondary ion mass spectroscopy revealed that, following the post-process O2 treatment, oxygen diffused into an AlGaN barrier and AlO was generated. A significant suppression of the leakage current (of approximately 6 orders of magnitude) occurred in the buffer isolation structures following the O2 treatment. Our method also resulted in suppression of the surface leakage current through the mesa-etched surface. A virgin GaN SBD exhibited a leakage current of 1.76×10−2A/cm2, whereas the equivalent O2-treated device had a leakage current of 1.75×10−4A/cm2 (the anode–cathode distance was LAC=10μm, and the applied bias was −100V). This reduction in the leakage current was caused by surface passivation at the anode and cathode. The post-process O2 treatment also increased the breakdown voltage from Vb=808V to Vb=1590V for a device with LAC=10μm. GaN SBDs with and without the post-process O2 treatment exhibited low specific on-resistance of Ron,sp=2.51mΩcm2 and Ron,sp=2.48mΩcm2, respectively, with LAC=10μm. Devices with the post-process O2 treatment exhibited a figure of merit of Vb2/Ron,sp=1006MW/cm2, whereas devices without the O2 treatment exhibited a figure of merit of Vb2/Ron,sp=263MW/cm2. These high-voltage GaN SBDs employing the post-process O2 treatment are suitable for applications including DC–DC converters, inverters, and power factor correction circuits, where high voltage operation is required with low leakage currents.