Study of thermal annealing on gallium oxide heteroepitaxial layers grown on SiC for vertical Schottky barrier diodes applications

This study successfully grew ꞵ-Ga₂O₃ epitaxial films on silicon carbide substrates by metalorganic chemical vapor deposition and fabricated vertical Schottky barrier diodes (SBDs), which were annealed in a high temperature furnace. The high surface roughness and oxygen vacancies of the unannealed device caused a large leakage current, thus three different annealing durations were used to repair the surface oxygen vacancies in an O₂:N₂=1:4 gas environment. The results showed that a 5-minute thermal annealing process was the most effective in repairing surface oxygen vacancies. According to the X-ray photoelectron spectroscopy spectra of the O 1 s core levels in Ga₂O₃ epilayers, the proportion of oxygen vacancies decreased from 56.56 % to 49.71 %. Additionally, the leakage current density was decreased from 10⁻³ to 10⁻⁵ A/cm² and the surface roughness decreases to 32.6 nm due to stress release. Furthermore, the barrier heights (φ_b) of the SBDs without annealing, and after annealed for 5, 20, and 40 min were measured at 0.911, 1.229, 1.090, and 1.115 eV, respectively. It was observed that the SBD fabricated on the epilayer annealed for 5 min exhibited the lowest leakage current (approximately 2 × 10⁻⁵ A/cm²) and the highest breakdown voltage, measuring around 132 V.