RF Degradation of GaN HEMTs and its Correlation with DC Stress and I-DLTS Measurements

The reliability of GaN HEMTs under RF stress has been evaluated and correlated with DC stress and current DLTS measurements techniques. During RF operation a degradation of output power, PAE and an increase in reverse gate current has been observed. A similar degradation has been observed by applying reverse biases to the gate terminal under DC operation, resulting in an increase in drain current-collapse as well as in the gate reverse current. DLTS measurements showed that the physical mechanisms involved in the RF- and DC- degradation are the same and that can be related to a defect which is thermally activated with an energy of 0.5 eV. The strong correlation between RF- and DC-stress results suggests that the RF degradation is related to the formation of localized defects at the gate contact. These defects degrade device performances by increasing both drain current collapse and reverse gate current.