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 HEMTs under a normal device operation: self-heating and charge trapping. A unique approach that investigates charge trapping using both source (I_S) and drain (I_D) 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 I_S and I_D, a bulk charge trapping time constant is found to be independent of both drain (V_DS) and gate (V_GS) biases. Surface charge trapping is found to have a much greater impact on a slow degradation when compared to bulk trapping and self-heating. At a short timescale (1 ms), the dynamic ON resistance degradation is predominantly limited by surface charge trapping