Significance of Equivalent Channel Temperature in Compact Modeling of GaN HEMTs

Significant self-heating affects both the performance and reliability of devices. The estimation of maximum temperature (T max ) and the location of hot-spot in the device is important from the reliability point of view. But it is to be noted that the thermal sub-circuit in any compact model of the device needs to find an equivalent temperature denoted as T eqt in the device instead of T max to model the temperature dependence of device electrical parameters. In this paper, we demonstrate the importance of T eqt in compact modeling of devices using well-calibrated TCAD simulation. We compute the thermal resistance from T eqt data for a device which is termed as equivalent thermal resistance (R th,eqt ) and demonstrate its bias independence. Furthermore, we propose the use of R th,eqt in self-heating compact model for GaN-HEMT by incorporating the R th,eqt based thermal sub-circuit in an existing drain current compact model. An excellent match was seen between the R th,eqt based compact model and the measurements whereas maximum temperature based model gives higher device temperature and hence larger drop in current at higher voltages.