First Demonstration of Vertical Superjunction Diode in GaN
Ming Xiao, Yunwei Ma, Zhonghao Du, Yuan Qin, Kai Liu, Kai Cheng, Florin Udrea, Andy Xie, Edward Beam, Boyan Wang, Joseph Spencer, Marko J. Tadjer, Travis J. Anderson, Han Wang, Yuhao Zhang
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 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , with the drift region resistance $( R_{DR,SP})$ extracted to be $0.15 \mathrm{m}\Omega \cdot$ cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . 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.