The Degradation Mechanism of GaN RF HEMTs Under High-Temperature Operation Stress: Effects of High Drain Current and High Drain Voltage

In this work, the effects of high drain current and high drain voltage on the electrical performance degradation and burnout mechanism of gallium nitride (GaN) RF high-electron mobility transistors (HEMTs) under high-temperature operation stress have been investigated in-depth. It was found that gate leakage increases with stress drain current, while the degradation of the saturation drain current and RF output power is influenced by stress drain voltage. The photon emission and scanning electron microscopy (SEM) analyses show that damage mainly occurs at the edges of central gate fingers under high current. The longitudinal electric field at the gate, caused by positive gate voltage, allows channel electrons to overcome the AlGaN/GaN barrier and pass through the AlGaN layer and Schottky junction. This leads to damage and leakage paths that degrade the Schottky contact and increase gate leakage. The results also show that catastrophic burnout occurs in the gate–drain access region, particularly near the drain electrode under high drain voltage. This is due to new defect formation and electron trapping caused by hot electrons near the drain, creating a strong longitudinal electric field. Once this field reaches a critical level, burnout occurs.