Access-Region Defect Spectroscopy of DC-Stressed N-Polar GaN MIS-HEMTs

Distinct trap levels in the drain access regions of an N-polar GaN MIS-HEMT are investigated before and after semi-on dc stressing by thermal and optical trap spectroscopies. The most prominent dc stress effect was an increase in concentration of a pre-existing electron trap with an activation energy of 0.54 eV, accompanied by a decrease in concentration of an electron trap with a 0.65-eV activation energy. These distinct states had similar concentrations before stressing, with the 0.54-eV trap concentration dominating (by 6×) after stress. Deeper states revealed via optical measurements showed a mild ~20% increase in total concentration after stressing.