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.