Reliability issues of AlGaN/GaN heterostructures field-effect transistors

Reliability of the AlGaN/GaN HFETs was investigated by applying a short-time (70 min) off-state stress: the drain voltage was 50 V and the channel was pinched off. Significant decrease of the drain current at the stressing conditions was observed. Simultaneously, a decrease of the gate currents wasfound. On the other hand, the transconductance and threshold voltage did not changed with the stressing time. A modification of the Schottky barier during the stress is considered to explain this behaviour. Near-surface defects, created during the AlGaN surface preparation before the gate deposition, were suppressed as a result of performed high-electric-field stress.