Effects of DC and AC stress on the VT shift of AlGaN/GaN MIS-HEMTs

AlGaN/GaN MIS-HEMTs with adjusted V-T were fabricated using a recess gate to investigate the effect on actual operation when the polarity of the gate voltage is opposite in the on-and off-state. The direction and time ex-ponents of V-T shift depend on the polarity of the gate bias stress. Electrons detrapping from the Al2O3/AlGaN interface trap site to AlGaN under negative gate bias stress has to overcome the energy barrier, resulting in a higher temperature dependence. In addition, the unaffected gm and SS show that the degradation occurred primarily at the Al2O3/AlGaN interface rather than channel or mobility degradation. For unipolar and bipolar AC stresses, the time exponent of the V-T shift during stress time has two values, and a relatively low value during relaxation after bipolar AC stress. These results may be due to the further degradation by V-min at the broader energy levels of the Al2O3/AlGaN interface.

Automated summary

AlGaN/GaN MIS-HEMTs fabricated with a recess gate exhibit sensitivity to changes in the polarity of the gate voltage. Under negative gate bias stress, electron detrapping requires overcoming an energy barrier, leading to increased temperature dependence. Degradation occurs primarily at the Al2O3/AlGaN interface rather than in the channel or mobility. During relaxation, the time exponent of V-T shift is relatively low, which may be attributed to further degradation at the broader energy levels of the Al2O3/AlGaN interface.