Effect of stress voltage on reliablity of GaN HEMTs

Reliability tests are performed on MOVPE grown AIGaN/GaN HEMTs on SiC from two different wafers, which only differ in an additional cap layer on top of the AIGaN barrier. The tests were conducted at different drain-source voltages and at elevated temperature, but at same power dissipation P_Diss. Performance of devices from both wafers are compared; those from the wafer with cap have lower gate leakage current. Yet no difference was observed in degradation. Devices stressed at higher drain source voltage degrade much faster than those at lower voltage do. In addition a measurement procedure during DC stress tests has been suggested.