Breakthrough Short Circuit Robustness Demonstrated in Vertical GaN Fin JFET

Insufficient short-circuit (SC) robustness of currently commercial GaN power devices, i.e., the high electron mobility transistors (HEMTs), is a key roadblock for their applications in automotive powertrains. At a 400 V bus voltage (
V
_BUS
), the SC withstanding time (
t
_SC
) of commercial GaN HEMTs is typically below 1 μs, far below the usual system requirement (>10 μs). This letter presents breakthrough short-circuit capability in a vertical GaN fin-channel junction-gate field-effect transistor (Fin-JFET). The Fin-JFET is normally
off
with a 0.7 mΩ·cm
²
specific
on
-resistance and 800 V avalanche breakdown voltage (BV
_AVA
) at the room temperature. The gate driver in the short-circuit test was designed to be identical to that in device switching applications. The
t
_SC
of GaN Fin-JFETs was measured to be 30.5 μs at a
V
_BUS
of 400 V, 17.0 μs at 600 V, and 11.6 μs at 800 V, all among the longest reported for 600–700 V normally
off
transistors. In addition, GaN Fin-JFETs failed open in these tests and retained BV
_AVA
after failure, which is highly desirable for system applications. In the repetitive 10
μ
s, 400 V short-circuit tests, GaN Fin-JFETs showed no degradation after 30 000 cycles. Furthermore, to the best of our knowledge, this is the first report of a power transistor with good short-circuit ruggedness at a bus voltage close to its BV
_AVA
. The underlying mechanism is the unique avalanche-through-fin in the Fin-JFET, which is validated by mixed-mode TCAD simulations and unclamped inductive switching tests. These results reveal the inherent ruggedness of GaN Fin-JFETs in the concurrent presence of short-circuit and overvoltage in power electronics systems.