A Parametric Technique for Traps Characterization in AlGaN/GaN HEMTs

A new parametric and cost-effective tech- nique is developed to decouple the mechanisms behind current degradation in AlGaN/GaN HEMTs under a nor- mal device operation: self-heating and charge trapping. A unique approach that investigates charge trapping using both source (IS) and drain (ID) transient currents for the first time. Two types of charge trapping mechanisms are identified: (i) bulk charge trapping occurring on a time scale of less than 1 ms, followed by (ii) surface charge trapping with a time constant larger than a millisecond. Through monitoring the difference between IS and ID, a bulk charge trapping time constant is found to be independent of both drain (VDS ) and gate (VGS ) biases. Surface charge trapping is found to have a much greater impact on a slow degrada- tion when compared to bulk trapping and self-heating. At a short timescale (< 1 ms), the RF performance is mainly restricted by both bulk charge trapping and self-heating effects. However, at a longer time (> 1 ms), the dynamic ON resistance degradation is predominantly limited by surface charge trapping.