AlGaN/GaN high electron mobility transistors(HEMTs)are fabricated by employing SiN passivation,this paper investigates the degradation due to the high-electric-field stress.After the stress,a recoverable degradation has been found,consisting of the decrease of saturation drain current IDsat,maximal transconductance gm,and the positive shift of threshold voltage VTH at high drain-source voltage VDS.The high-electric-field stress degrades the electric characteristics of AlGaN/GaN HEMTs because the high field increases the electron trapping at the surface and in AlGaN barrier layer.The SiN passivation of AlGaN/GaN HEMTs decreases the surface trapping and 2DEG depletion a little during the high-electric-field stress.After the hot carrier stress with VDS=20 V and VGS=0 V applied to the device for 104 sec,the SiN passivation decreases the stress-induced degradation of IDsat from 36% to 30%.Both on-state and pulse-state stresses produce comparative decrease of IDsat,which shows that although the passivation is effective in suppressing electron trapping in surface states,it does not protect the device from high-electric-field degradation in nature.So passivation in conjunction with other technological solutions like cap layer,prepassivation surface treatments.or field-plate gate to weaken high-electric-field degradation should be adopted.