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 (Tmax) 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 Teqt in the device instead of Tmax to model the temperature dependence of device electrical parameters. In this paper, we demonstrate the importance of Teqt in compact modeling of devices using well-calibrated TCAD simulation. We compute the thermal resistance from Teqt data for a device which is termed as equivalent thermal resistance (Rth,eqt) and demonstrate its bias independence. Furthermore, we propose the use of Rth,eqt in self-heating compact model for GaN-HEMT by incorporating the Rth,eqt based thermal sub-circuit in an existing drain current compact model. An excellent match was seen between the Rth,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.