Oxygen Vacancy Control Engineering in Ga2O3/4H-SiC Schottky Rectifiers

This work investigates oxygen vacancy (VO) engineering in Ga2O3/4H-SiC heterojunction Schottky barrier diodes (HJ-SBDs) through post-deposition O2 annealing to enhance breakdown performance. Aerosol-deposited Ga2O3 films (~900 nm) on n-type 4H-SiC substrates were annealed in O2 ambient at 800 ℃, 900 ℃, and 1000 ℃. The oxygen deficiency ratio was found to decrease substantially from 48.5% to 23.4% as the annealing temperature increased to 900 ℃, accompanied by a nine-fold reduction in deep trap density from 7.3×1013 cm-3 to 8.1×1012 cm-3. The as-deposited devices exhibit dual conduction mechanisms of Schottky emission (SE) and Poole-Frenkel emission (PFE), with breakdown voltage limited to 960 V due to high VO concentration. The reverse leakage current in O2-annealed devices was found to be governed by variable-range hopping conduction under high electric fields. At optimal annealing conditions of 900 ℃, the breakdown voltage increases remarkably from 960 V to {greater than or equal to}3000 V. The enhanced breakdown results from the significant reduction of VO-related traps that dominate the leakage mechanisms in as-deposited Ga2O3 films. Our VO-engineered Ga2O3/4H-SiC HJ-SBDs demonstrate superior breakdown and thermal stability, showing the great potential of defect engineering for high-voltage power applications.