Advanced physical modeling approaches for high-precision TCAD simulation of GaN HEMT power devices: a review

High-electron-mobility transistors (HEMTs) based on wide bandgap (WBG) materials like gallium nitride (GaN) are vital for next-generation power electronics and high-frequency applications, offering high breakdown voltage, electron mobility, and power density. The global shift toward electrification and sustainability is driving demand for GaN and silicon carbide (SiC) power devices. However, challenges such as current collapse and increased channel resistance under high-power conditions hinder performance. To address these limitations, numerous solutions have been explored, with simulation emerging as an indispensable starting point. Technology Computer-Aided Design (TCAD) simulations play a critical role by enabling accurate modeling, performance optimization, and reduced experimental effort. This paper reviews key and advanced physical models in TCAD simulations of GaN HEMTs, covering mechanisms such as carrier transport, thermal effects, and impact ionization. Mobility models-FLDMOB, Albrecht, Gansat, Yamaguchi, Brooks-Herring, and Conwell-Weisskopf-are analyzed for capturing velocity saturation and nonlocal transport. Recombination models like Shockley-Read-Hall and Auger are discussed in relation to carrier lifetime, while impact ionization models, including van-Overstraeten-de-Man, Selberherr, and Okuto-Crowell, are evaluated for breakdown prediction. Emphasis is placed on choosing models suited to specific structures and conditions to ensure simulation accuracy. Advanced modeling enhances TCAD's predictive power, supporting innovation in GaN-based power electronics.