Study of the Degradation in p-GaN Gate HEMTs Under Gate Pulse Stress by Transient Current Analysis

This work investigates the trap-induced degradation in p-GaN gate HEMTs under gate pulse stress via transient current analysis. Electrical measurements demonstrate a positive threshold voltage shift and a reduction in drain current with prolonged bipolar pulse stress. Using the transient current method combined with Bayesian deconvolution, three distinct trap levels designated DP1 to DP3 are identified, whose amplitudes grow consistently with stress time. To clarify the underlying mechanism, bipolar and unipolar pulse stresses are compared at varying frequencies. The threshold voltage shift increases with frequency under bipolar stress but decreases under unipolar stress, confirming that bipolar stress enhances trap density rather than causes transient trap filling. Furthermore, DP1 and DP3 exhibit the significant enhancement in amplitudes, indicating their location near the gate interface where they are vulnerable to pulse-induced carrier injection. Temperature-dependent measurements further confirm that the degradation stems from the density increase of pre-existing traps, with no new trap levels generated. These findings provide critical insight into trap-induced degradation in p-GaN HEMTs, supporting reliability optimization in switching applications.