Different Gate Current Degradation Mechanisms in AlGaN/GaN High Electron Mobility Transistors

Negative gate voltage bias step-stress experiments were implemented to research the degradation mechanisms in AlGaN/GaN HEMTs. Although the stress gate current increases sharply above a "critical voltage" for the devices with large gate-to-source distance, no such voltage could be found when the gate-to-source distance is small. It is postulated that surface leakage current becomes prominent when the gate and source of the device come near, thus the degradation of gate leakage caused by the inverse piezoelectric effect is shield.