A Parametric Technique for Trap Characterization in AlGaN/GaN HEMTs

A new parametric and cost-effective technique is developed to decouple the mechanisms behind current degradation in AlGaN/GaN high-electron mobility transistors (HEMTs) under a normal device operation: self-heating and charge trapping. Our unique approach investigates charge trapping using both source ( ${I}_{\text {S}}$ ) and drain ( ${I}_{\text {D}}$ ) transient currents for the first time. Two types of charge-trapping mechanisms are identified: 1) bulk charge trapping occurring on a timescale of less than 1 ms and 2) surface charge trapping with a time constant larger than a millisecond. Through monitoring the difference between ${I}_{\text {S}}$ and ${I}_{\text {D}}$ , a bulk charge-trapping time constant is found to be independent of both drain ( ${V}_{\text {DS}}$ ) and gate ( ${V}_{\text {GS}}$ ) biases. Surface charge trapping is found to have a much greater impact on slow degradation than bulk trapping and self-heating. At a short timescale ( 1 ms), the dynamic ON-resistance degradation is predominantly limited by surface charge trapping.