We present wearout reliability assessment of GaN HEMTs fabricated on SiC. Based on 3 temperature 48V dc stress tests and using a failure criterion of 10% reduction in I dss , the 60% confidence interval on estimate of E a was [2.00,2.94] eV and the predicted 60% confidence interval on estimate of MTTF at Tj=200 °C was [1.0 x 10 6 , 3.0 x 10 7 ] hours. To compare the impact of dc and RF stress, additional experiments were conducted on a smaller sample set and the results indicate that the impact of dc and RF stress is not significantly different.