Origin of Soft Breakdown in Thin-Barrier AlGaN/GaN SBD With C-Doped GaN Buffer

In this work, we investigate the soft breakdown (BD) behavior in thin-barrier (TB) AlGaN/GaN Schottky barrier diode (SBD) with carbon-doped GaN buffer. The soft BD behavior is the result of the coupling of multiple mechanisms. In the off-state, the ionized carbon (C) acceptors make the electric field (E-field) crowd at the cathode and cause the impact ionization. Then, the holes generated by impact ionization compensate with the ionized C acceptors, thus suppressing E-field crowding and preventing the further avalanche BD. The residual holes flow to and accumulate under the anode, which leads to a continuous increase in the Schottky E-field and Schottky leakage, eventually causing the soft BD. Due to the tunneling effect, Schottky leakage is highly sensitive to the Schottky E-field in TB structure, so the leakage rise rate during soft BD is abnormally high.