Analysis of the buffer trap-induced kink effect in AlGaN/GaN HEMT on SiC substrate

In this study, the mechanism of the kink effect observed during the switching operation in AlGaN/GaN high-electron-mobility transistors is thoroughly analyzed. The I (D)-V (G) characteristics show a drop in I (D) and a positive shift in threshold voltage (V (T)) when the kink effect occurs. Then, using Silvaco software to simulate the trap position, the negative buffer trap induces the V (T) to shift positively, dominating the decrease in the I (D). By using a long-term DC stress test under bias conditions, where the kink phenomenon occurred, the V (T) will shift in the negative direction, which shows that the hole generated by impact ionization (II) plays a key role in the kink effect. Furthermore, the I (D)-V (G) after kink-effect stress does not respond to red, green or blue light illumination but does to UV light, which means that electron de-trapping cannot restore the V (T) shift caused by the kink effect. Finally, the complete mechanism of the kink effect is provided. The recombination of hot holes generated by II with the electron trapped in buffer defects is the main mechanism for the kink phenomenon.