1 kV Self-Aligned Vertical GaN Superjunction Diode

This work demonstrates vertical GaN superjunction (SJ) diodes fabricated via a novel selfaligned process. The SJ comprises n-GaN pillars wrapped by the charge-balanced p-type nickel oxide (NiO). After the NiO sputtering around GaN pillars, the self-aligned process exposes the top pillar surfaces without the need for additional lithography or a patterned NiO etching which is usually difficult. The GaN SJ diode shows a breakdown voltage (BV) of 1100 V, a specific on-resistance (RON) of 0.4 mΩ·cm2, and a SJ drift-region resistance (Rdr) of 0.13 mΩ·cm2. The device also exhibits good thermal stability with BV retained over 1 kV and RON dropped to 0.3 mΩ·cm2 at 125 °C. The trade-off between BV and Rdr is superior to the 1D GaN limit. These results show the promise of vertical GaN SJ power devices. The self-aligned process is applicable for fabricating the heterogeneous SJ based on various wide- and ultra-wide bandgap semiconductors.