Abstract: A series of slow drain current recovery transients at different gate biases after a short-term stress are observed in an AlGaN/GaN HEMT.As the variation of the time constants of the transients is small,the working trap is determined to be electronic.A numerical simulation verifies this conclusion and reproduces the measured transients.The electron traps at different spatial positions in the device-on the ungated surface of the AlGaN layer,in the AlGaN barrier,and in the GaN layer are considered;corresponding behaviors in the stress and the transients are discussed;and for the simulated transients,agreement with and deviation from the measured transients are explained.Based on this discussion,we suggest that the measured transients are caused by the combined effects of a deep surface trap and a bulk trap in the GaN layer.

Key words: AlGaN/GaN HEMT, slow transients, virtual gate, surface trap, bulk trap