Trap Location and Stress Degradation Analysis of GaN High Electron Mobility Transistors Based on the Transient Current Method

In this paper, the carrier trapping behavior and electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) under different bias conditions are studied based on the transient current. By considering the transient drain current of HEMTs at different temperatures, three trapping mechanisms are identified: (1) charge trapping in the AlGaN barrier layer, in the gate-drain region near the two-dimensional electron gas (2DEG) channel; (2) charge trapping in the GaN layer, in the gate-drain region near the gate; and (3) charge trapping on the surface of the AlGaN layer, in the gate-drain region near the gate. The influences of the source-gate and drain-gate voltages on trapping behavior are analyzed to further elucidate the trap locations. The experimental results show that charge capture is mainly affected by the drain-gate voltage. High electric field stress affects the local structure order inside the device, thus affecting the charge escape rate. The threshold voltage shift is mainly affected by the surface trap of the AlGaN layer near the gate.