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Threshold voltage shift and interface/border trapping mechanism in Al2O3/AlGaN/GaN MOS-HEMTs

Threshold voltage instability (Vth) is a critical issue to the device reliability of GaN-based metal-oxide-semiconductor high-electron-mobility transistors (MOS-HEMTs). As well as the transient voltage shift caused by interface trapping effect, retentive voltage shift in Al2O3/AlGaN/GaN MOS-HEMTs was also demonstrated in this paper, which was attributed to border trapping effects. Interface trapping is found dominant at low gate voltage, and then the transient voltage shift tends to be saturated (∼1.2 V) with gate voltage above 5 V. After the interface traps (∼3×1012cm−2) are fully filled, border trapping with long emission time constant become remarkable, resulting in retentive positive voltage shift over 8 V. In addition to the low-field emission, border de-trapping mechanism of high-field electron tunneling is proposed, which is proved by the Vth recovery after off-state high-voltage sweep.