Thermionic Field Emission in the Lifetime Estimation of p-GaN Gate HEMTs

The current transport mechanism at metal gate/p-GaN interface in p-GaN HETMs has been investigated. Space Charge Limited Current (SCLC) well describes the behaviour of current density (JG) at lower applied bias (VG < 6 V), while Thermionic Field Emission (TFE) represents the dominant current mechanism at higher VG. Then, p-GaN gate reliability was investigated by time-to-failure (TTF) analysis carried out at constant positive VG. In particular, the devices' lifetime as function of the applied VG was described considering the JG-VG dependence according the TFE model. In this way, a maximum VG for 10-year lifetime (V10 years Gmax ) of 8.5 V has been estimated, significantly higher than that extracted by conventional E-model (7 V).