Very Fast Dynamics of Threshold Voltage Drifts in GaN-Based MIS-HEMTs

The very fast dynamics of threshold voltage drift (ΔV
_th
) of GaN-based metal-insulator-semiconductor-HEMTs induced by forward gate bias stress is investigated with a simple oscilloscope based setup. We show that the logarithmic recovery time dependence of ΔV
_th
, previously found for recovery times ranging from 10 ms up to 1 ms, extend even to the μs regime. Further, we observed an accumulation of ΔV
_th
because of repetitive stress pulses of 100 ns. Consequences for device operation and reliability are discussed.