Barrier Height Stability and Reverse Leakage Mechanisms in Ni/Ga2O3 (001) Schottky Barrier Diodes

Ga2O3 Schottky barrier diodes (SBDs) have shown promising performance as power rectifiers recently [1]–[3], showcasing the fast-improving material quality as well as the touted high electric field strength (6–8 MV/cm). In an SBD, the barrier height $(\mathrm{q}\phi_{\mathrm{B}})$ largely determines the turn-on voltage and the reverse leakage current. Previous studies on the barrier height of different metal contacts on Ga2O3 indicate a certain level of Fermi-level pinning [4], [5], likely due to interface-trap states. Under different temperature $(T)$ or biasing conditions, the filling of those trap states could be altered and thus the barrier height could be unstable, as evidenced in previous studies [6]. For Ga2O3 grown by halide vapor phase deposition (HVPE), a chemical-mechanical polishing (CMP) process is used to flatten the surface. In this work, we examine the barrier height stability of Ni/Ga2O3 SBDs fabricated on the CMP-ed surface via repeated and temperature-dependent $I-V$ measurements. We found that post metallization annealing (PMA) improves the barrier height stability. In addition, the reverse leakage mechanisms of the non-field-plated SBDs have been identified.