Reliability investigation of 0.25 /spl mu/m AlGaN/GaN HEMTs under elevated temperature lifetesting

Reliability investigation was performed on 0.25 pin AIGaN/GaN HEMTs grown by MOCVD on 2-inch SIC substrates. The devices were fabricated using Northrop Gruminan Space Technology’s (NGST) AlGaNlGaN HEMTs process technology. A temperature step stress (starting at 150°C with a step of 15°C; ending at 240°C; 48 hrs for each temperature cycle) was employed for the quick reliability evaluation of AIGaN/CiaN HEMTs. It was found that the degradation of AlGaN/GaN HEMTs was initiated at junction temperature of 345°C. The degradation characteristics consist of a decrease of drain current and transconductance? and an increase of channel-onresistance. However, there is no noticeable degradation of the gate diode (ideality factor, barrier height, and reverse gate leakage current). The FIB/STEM technique was used to examine the degraded devices. There is no detectable ohmic metal or gate metal interdiffusion into the epitaxial materials from STEM. Accordingly, the degradation inechanism of AIGaN/GaN HEMTs under elevated temperature lifctesting is different from the degradation mechanisms observed in GaAs PHEMTs and InP HEMTs. The reliability performance was also compared between two vendors of AIGaN/GaN epilayers. The results show that the reliability of AIGaN/GaN HEMTs could strongly depend on the material quality of AlGaN/GaN epitaxial layers on SIC substrates. been demonstrated at 10 GHz [I]. AIGaNIGaN