A Comprehensive Investigation on Temperature-Dependent Small-Signal Characterization and Modeling of GaN HEMT on Si Substrate

Thermal effects represent a major challenge for all semiconductor devices, particularly high-power transistors such as GaN High Electron Mobility Transistors (HEMTs). The combined internal and external temperatures have a significant impact on the small and large signal characteristics of the device, degrading its performance. In this paper, a 10 x 200-mu m GaN on Si substrate HEMT is characterized using small-signal S-parameter measurement setups at different ambient temperatures. The measurements are used to analyze the impact of temperature on the capacitances, inductances, and resistances of the transistor, as well as the gain and input/output reflection coefficients. Direct characterization of the gain shows a 3 dB reduction when the temperature increased by 100 degrees C. The results of the characterization are used to build a temperature-dependent model for the investigated device. The model's accuracy is validated through S-parameter simulation at different bias conditions and ambient temperatures. Additionally, the model's scalability has been demonstrated by modeling other GaN-on-Si HEMTs of different sizes. Excellent results and very good agreement between the simulations and measurements are achieved. The results of this investigation highlight the importance of thermal effects and the crucial need for efficient electrothermal modeling in designing reliable application circuits.