Thermal Studies of Operating AlGaN/GaN/SiC Based High Electron Mobility Transistors

AlGaN/GaN structures grown on SiC substrates can be used to create high power, high electron mobility transistors by exploiting the peizo-electric effect. These materials are highly desirable for their high thermal conductivity, high bandgap, and slow degradation. We have performed Raman and AFM- based thermal measurements on operating and non-operating devices in order to study thermal defects. In addition to measuring temperatures at a sub-micron scale, we find that even structures with excellent electronic and optical properties display sub-micron sized thermal defects, resulting in lowered thermal conductivity for the structures. Finite element analysis was used to better understand the thermal flows and experimental results.