Study on Avalanche Uniformity in 1.2KV GaN Vertical PIN Diode with Bevel Edge-Termination

GaN vertical PIN diodes with different bevel edge termination angles were fabricated on three wafers with varying p-layer doping concentrations, respectively. The breakdown behavior in terms of the breakdown voltage and the electroluminescence were studied as functions of these variables. The repeatable avalanche breakdown and highest breakdown voltage were measured with the lowest p doping of
$3\times 10^{17}\ \text{cm}^{-3}$
and with the lowest bevel angle, indicating the efficacy of the bevel edge termination under these specific circumstances. As p-layer doping increases and the bevel angle becomes steeper, the devices exhibit lower breakdown voltages and less robust breakdown characteristic, often destructive. From this study, we also conclude that at very high p-layer doping of
$2\times 10^{19}\ \text{cm}^{-3}$
, the bevel etch alone cannot provide an effective edge termination.