Physical Modeling and Thermal Characterization of Multi-Finger GaN HEMTs

The electrical performance and reliability of gallium nitride (GaN) high electron mobility transistors (HEMTs) are significantly affected by the self-heating effect, whose severity is quantified by thermal resistance $(R_{th})$. This paper combines a 2D TCAD electrothermal physical model and a 3D finite element thermal model, considering the bias correlation of the heat source model. An iterative algorithm for multi-finger electrothermal coupling is proposed to improve the accuracy of the $R_{th}$ extraction. The results reveal that the difference between optimized model and the conventional thermal model is 14.3%, and the optimized thermal model is verified by infrared (IR) thermography within 5% of error. Furthermore, a third-order RC thermal sub-network model is developed and validated to characterize the transient thermal response of the device based on the transient pulse current response, and the prediction error of the model is within 5mA/mm under different bias conditions. The full-flow thermal characterization method of the device proposed in this paper is an important reference for thermal evaluation, thermal optimization, and thermal design of GaN HEMTs.