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

• High-voltage AlGaN/GaN SBDs on a Si substrate fabricated using a post O2 treatment.
• TOF-SIMS reveals that the oxygen diffused into an AlGaN and AlO was generated.
• Performance of decreasing leakage current and increasing breakdown voltage.
• Improvement in FOM (Vb2/Ron,sp) of GaN SBD from 263 to 1006 MW/cm2.

High-voltage AlGaN/GaN Schottky barrier diodes (SBDs) were fabricated using on a silicon (1 1 1) 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 × 10−2 A/cm2, whereas the equivalent O2-treated device had a leakage current of 1.75 × 10−4 A/cm2 (the anode–cathode distance was LAC = 10 μm, and the applied bias was −100 V). 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 = 808 V to Vb = 1590 V for a device with LAC = 10 μm. GaN SBDs with and without the post-process O2 treatment exhibited low specific on-resistance of Ron,sp = 2.51 mΩ cm2 and Ron,sp = 2.48 mΩ cm2, respectively, with LAC = 10 μm. Devices with the post-process O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 1006 MW/cm2, whereas devices without the O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 263 MW/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.

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