Accuracy Improvement of the Large-Signal Model of a High-Power GaN HEMT using Power-Dependent Constant and Tapered Thermal Resistance Methods

This study improved the accuracy of the large-signal model of a high-power gallium nitride (GaN) high electron mobility transistor (HEMT) by using power-dependent constant and tapered thermal resistance methods. The findings indicate that the channel temperature of a GaN HEMT is affected by the number of gate fingers and the thickness of the package substrate as well as the structure of the transistor. Furthermore, the rise in the channel temperature in the transistor was considered by including thermal resistance in the large-signal model. To account for thermal effects, power-dependent constant thermal resistance and power-dependent tapered thermal resistance were included in the large-signal model of the high-power transistor, and their effectiveness was validated for a 140-W GaN HEMT with 80 gate fingers. The proposed power-dependent thermal resistance approaches predicted optimum load impedance and power performance better than the conventional power-independent constant thermal resistance approach. Furthermore, the simulated results for these approaches were in good agreement with the measured load pull results.