Characterization of Thermal and Trapping Time Constants in a GaN HEMT

A commercial pulsed-IV system is used to test a GaN HEMT with the purpose of extracting exponential time constants used for dynamic electro-thermal and charge-carrier trapping models. The time constants of these different physical phenomena can not only vary by many orders of magnitude, but also have regions of overlap. Self-heating and trapping are common phenomena affecting GaN HEMTs, thus characterization and understanding these dynamics is critical for developing accurate compact models. We investigated the approach of recording the drain current transient response under a careful selection of the bias conditions, to approximately separate the two phenomena to derive useful estimate of the different associated time constants. Modeling of these time constants is of concern for modulated signal processing, where they fall within typical bandwidths of modern communication systems.