Abnormal Threshold Voltage Degradation Under Semi-On State Stress in Si₃N₄/AlGaN/GaN-HEMT

In this study, the threshold voltage (VT) degradation mechanism for a hot electron stress (HES) under semi-ON state conditions in AlGaN/GaN high electron mobility transistors is analyzed. The drain current versus gate voltage (ID–VG) characteristic curves indicate that VTshifts in the positive direction after the stress. However, an abnormal phenomenon that VTcontinuously shifts in the positive direction even after recovery is observed. A result comparison of a negative bias stress (NBS) experiment indicates that a hole recombination in pre-existing buffer defects is crucial. Therefore, a complete model of VTdegradation mechanism is proposed. Moreover, the proposed model is confirmed through an illumination experiment and a Silvaco simulation.