On-state breakdown in power HEMTs: measurements and modeling

A new definition of and measurement technique for on-state breakdown in high electron mobility transistors (HEMTs) is presented. The new gate current extraction technique is unambiguous, simple, and non-destructive. Using this technique in conjunction with sidegate and temperature-dependent measurements, we illuminate the different roles that thermionic field emission and impact ionization play in HEMT breakdown. This physical understanding allows the creation of a phenomenological model for breakdown, and demonstrates that depending on device design, either on-state or off-state breakdown can limit maximum power.