Vertical GaN-on-GaN PIN diodes fabricated on free-standing GaN wafer using an ammonothermal method

Abstract

We report vertical GaN-on-GaN PIN diodes with a record high figure-of-merit (VBR2/Ron) of 29.7 GW/cm2 on free-standing GaN wafer using a complementary metal-oxide-semiconductor (CMOS) compatible contact materials. Due to the low substrate resistivity, low contact resistance, and high quality of GaN drift layer, a low on-state resistance Ron of 0.31 mΩ cm2 is obtained. With integrating of the metal filed plate structure in the vertical device, the peak electrical field along the GaN mesa edge can be significantly reduced, thus leading to a high breakdown voltage VBR of 3.04 kV. The vertical GaN-on-GaN PIN diodes in this work show turn-on voltage Von of ∼3.4 V, on/off current ratio of ∼1.3 × 107, and ideal factor n of ∼2.2. According to the reverse switching measurement, the reverse recovery time Trr (reverse recovery charge Qrr) is 22.8 ns (4.8 nC) and 24.0 ns (5.4 nC), respectively, under a testing temperature of 300 K and 500 K.