1.2 kV Vertical GaN Fin JFETs with Robust Avalanche and Fast Switching Capabilities

This work, for the first time, demonstrates a 1.2-kV-class, 4-A normally-off vertical GaN fin-channel JFET on GaN substrate, and characterizes its static and dynamic performance as well as avalanche robustness. The device shows an on/off current ratio of ~10
⁹
, a specific on-resistance (R
_ON
) of 0.82 mΩ·cm
²
, and a threshold voltage (V
_TH
) over 0.5 V extracted at a drain current of 1 mA. The on/off ratio and V
_TH
exhibit very little changes at high temperatures up to 125°C. A robust avalanche is observed under the unclamped inductive switching (UIS) conditions, showing an avalanche breakdown voltage (BV
_AVA
) of 1470 V and an avalanche current (I
_AVA
) over 1 A. The I
_AVA
is found to mainly flow through the p-GaN gate instead of the n-GaN fins. The JFET also shows small junction capacitances. Double-pulse tests at 600-V/4-A reveal a rise/fall time of 12.9 ns/10.3 ns and a total loss of 37 μJ. Almost no reverse recovery is observed on the body diode, due to the short lifetime of minority carriers. To the best of our knowledge, we report one of the highest Baliga's figure-of-merit (BV
²
/R
_ON
) and the first avalanche robustness in vertical GaN power transistors. Our results suggest the great potential of vertical GaN JFETs for medium-voltage high-frequency power applications.