A Physics-Based Compact Model for Kink Effects in GaN HEMTs

An accurate model of the kink effect is critical for understanding device operation mechanisms, ensuring reliability, and enabling robust circuit design. However, accurate modeling of the kink effect-arising from both trapping effects and impact ionization-remains a significant challenge. Conventional empirical models often lack physical insight, particularly regarding the interplay between impact ionization and the electric field. In this work, a physics-based compact model that incorporates both impact ionization and trapping effects is proposed. First, a well-calibrated technology computer-aided design model is developed to investigate the physical origins of the kink effect. By analyzing the variations in physical parameters-such as the electric field and trap ionization density-before and after the onset of the kink, it is shown that both impact ionization and buffer/substrate-related trapping effects jointly contribute to its occurrence. Subsequently, a compact model is derived based on a zone-division approach, capturing the underlying physical mechanisms. This model is then integrated into the drain-source current formulation for validation. Simulation results confirm that the proposed model accurately reproduces the electric field distribution and I-V characteristics. Thus, the model is well-suited for circuits simulations and device performance optimization.