1 kV Self-Aligned Vertical GaN Superjunction Diode

This work demonstrates vertical GaN superjunction (SJ) diodes fabricated via a novel self aligned 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 (R-ON) of 0.4 m Omegacm(2), and a SJ drift-region resistance (R-dr) of 0.13 m Omegacm(2). The device also exhibits good thermal stability with BV retained over 1 kV and RON dropped to 0.3 m Omegacm(2) at 125 C-o. 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.