Field Plating for Improved Ga2O3 Schottky Rectifier Performance

Abstract

Ga2O3­ rectifiers have the potential to surpass SiC and GaN diodes due to the ultrawide-bandgap of 4.9 eV. In this context to reach the maximum potential for Schottky rectifiers, electric field mitigation techniques must be used to optimize performance. In this study, the effects of various dielectric field plates (SiO2/SiN, Al2O3/SiN, HfO2/SiN) on device performance of circular Ga2O3 Schottky rectifiers was investigated. The rectifiers were fabricated on 10 µm, lightly doped (n = 2.8 × 1016 cm-3) β-Ga2O3 epitaxial layers grown by Hydride Vapor Phase Epitaxy on conducting substrate (n = 4.8 × 1018 cm-3) grown by Edge-Defined, Film-Fed growth. Temperature dependent forward current-voltage characteristics were used to extract the average Schottky barrier height of 1.14 eV ± 0.03 eV for Ni, average ideality factor of 1.02 ± 0.02, and the Richardson’s constant of 48.1 A/cm2K2. The reverse breakdown and leakage current were the two characteristics which were predominantly affected by the field plate dielectrics. The highest reverse breakdown reached was 730 V for Al2O3/SiN, which was significantly higher than SiO2/SiN and HfO2/SiN, 562 V and 401 V, respectively. Electric field modeling was used to determine the location of peak electric field and was found to occur at the edge of the field plate, which agreed with experimental observations of breakdown induced defects occurring on the edge of the device. The on-resistance ranged from 3.8-5.0 × 10-3 Ω-cm2 which was dependent on diode size, diameters from 50 to 200 µm. This led to a power figure-of-merit (VB 2/RON) of 1.4 × 108 W-cm2.