Physical degradation of GaN HEMT devices under high drain bias reliability testing

The AlGaN/GaN heterostructure HEMTs were epitaxially grown using MOCVD on semi-insulating SiC substrates. Standard III–V commercial production processing technology was used to fabricate the devices, which were then subjected to stress under accelerated DC life-tests with base-plate temperatures of 82, 112, and 142 C. Drain bias of 40 V and time-zero drain current of 250 mA/mm were applied. TEM samples were prepared via the lift-out technique using a focused ion beam (FIB). TEM analysis revealed that electrically degraded devices always contain a pit-like defect next to the drain in the top AlGaN layer. It has been found that the degree of the defect formation strongly correlates to drain current (IDmax) degradation.