In this letter, the underlying physics of threshold voltage (Vth)
instability and the eventual device failure mechanism of 100V Schottky
p-GaN gate high electron mobility transistors (HEMTs) under repetitive
short-circuit (SC) stress with varied drain voltage (VDD= 40-70V) and SC
pulse duration (TSC=10 μs & 20 μs) is studied. In the lenient SC stress
with lower SC energy (e.g. SC stress @ VGS=6 V, VDD=40-70 V, TSC=10 μs),
the devices exhibit significantly positive Vth shift while the Vth
instability shows positive dependence with the stressed drain voltage
and the repetitive SC pulses. For device stressed at VDD=70 V with 150
SC pulses, a substantial ΔVth as high as +0.68 V is observed. Such a
prominent Vth instability is induced by the electron trapping in the
p-GaN gate region during the SC events, which also results in the
suppressed gate and drain leakage current after SC stress. In the more
stringent SC stress (VGS=6 V, VDD=70 V, TSC=20 μs) with much higher
corresponding SC energy, the device failed due to the drain electrode
burned out initiated by the significantly high SC energy during the SC
events.
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