Degradation in AlGaN/GaN HEMT under high temperature reverse bias stress

In this work, we investigate the time evolution of electrical degradation in AlGaN/GaN high electron mobility transistors after high temperature reverse bias(HTRB) stress. The threshold voltage shows a positive shift after stress, and then turns to negative shift. Comparing with the stressed and fresh devices, the fresh devices have more trap effect than the stressed which have stressed over 1000hours at high temperature. However, both devices have the same permanent degradation after stress. In fact, it is the inverse piezoelectric effect in which a defect formation could happen, due to the mechanical strain produced by electric field. Therefore, the trapping behaviors chiefly caused by negative charging in the state of surface. A lower potential of drain was applied after stressed, which in order to avoid a permanent degradation.