First Demonstration of Vertical Superjunction Diode in GaN

Abstract

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.