High electron mobility transistors (HEMTs) based on AlGaN/GaN hetero-structures are promising for both commercial and military applications that require high power, high voltage, and high temperature operation. Reliability and radiation effects of AlGaN-GaN HEMTs need to be thoroughly studied before they are successfully deployed in potential satellite systems. A few AlGaN HEMT manufacturers have recently reported encouraging reliability, but long-term reliability of these devices under high electric field operation and extreme space environments still remains a major concern. A large number of traps and defects are present in the bulk as well as at the surface, leading to undesirable characteristics including current collapse. The present study is part of our investigation to study traps and defects in the AlGaN HEMT devices using micro-analytical techniques before and after they are life-tested.