First Demonstration of Vertical Superjunction Diode in GaN

We report the first experimental demonstration of a vertical superjunction device in GaN. P-type nickel oxide (NiO) is sputtered conformally in $6 \mu \mathrm{m}$ deep n-GaN trenches. Sputter recipe is tuned to enable $10 ^{17}$ cm $^{-3}$ level acceptor concentration in NiO, easing its charge balance with the $9 \times 10 ^{16}$ cm $^{-3}$ doped n-GaN. Vertical GaN superjunction p-n diodes (SJ-PNDs) are fabricated on both native GaN and low-cost sapphire substrates. GaN SJ-PNDs on GaN and sapphire both show a breakdown voltage $( BV)$ of 1100 V, being at least 900 V higher than their 1-D PND counterparts. The differential specific on-resistance $( R_{ON,SP})$ of the two SJ-PNDs are both $0.3 \mathrm{m}\Omega \cdot$ cm ² , with the drift region resistance $( R_{DR,SP})$ extracted to be $0.15 \mathrm{m}\Omega \cdot$ cm ² . The $R_{ON,SP} \sim BV$ trade-off is among the best in GaN-on-GaN diodes and sets a new record for vertical GaN devices on foreign substrates. The $R_{DR,SP} \sim BV$ trade-off exceeds the 1-D GaN limit, fulfilling the superjunction functionality in GaN.