Trap-Assisted and Stress Induced Safe Operating Area Limits of AlGaN/GaN HEMTs

This experimental study reports a systematic investigation of Safe Operating Area (SOA) limits in AlGaN/GaN HEMT using sub-μs pulse characterization. During stress, on-the fly Raman and CV characterization is done to probe mechanical strain evolution and the resultant defect/ trap generation across HEMT. Role of carrier trapping induced electric field shift and associated piezoelectric strain in SOA degradation is investigated. SOA is reported to recovery under sub-bandgap UV exposure. Impact of gate recess depth on SOA boundary is discovered and its related physics is unveiled. Post failure analysis done using cross-sectional SEM, EDX and HR-TEM corroborates well with the failure physics proposed in this work.