There are several mechanisms that can contribute to failure during high temperature gate stress at high gate voltage. These included dielectric failure, gate sidewall rupture, and an increase in off-state drain leakage resulting from gate stress. The dominant gate failure mechanism for eGaN FETs is an increase in off-state drain leakage induced by extended operation at high gate voltage and is highly accelerated with gate voltage. To determine the voltage acceleration of HTGB failure, a matrix of tests was conducted at voltages between 6 V and 7 V, all at a temperature of 150°C. Note that this voltage range is outside of the safe operating range of less than 6 V for eGaN FETs. The data was analyzed using the same methods as described for the HTRB acceleration study, and the MTTF and FIT rate versus gate voltage was calculated. The results are shown in the graphs on this slide. At 6 V - the datasheet limit - the MTTF is well above 10 yrs at 150°C. Please note that eGaN FET’s should never be operated with gate bias above 6 V.