Modeling of the Gate Bias-Dependent Velocity–Field Relationship and Physics-Based Current-Voltage Characteristics in AlGaN/GaN HFETs

In this paper, a gate bias-dependent velocity-field relationship model and a physics-based analytical model of current-voltage characteristics in AlGaN/GaN HFETs are developed. Based on Monte Carlo simulations, the experimental phenomenon that the channel electron velocity varies with the gate voltage is successfully reproduced. A modified gate bias-dependent velocity-field relationship model is established to obtain the velocity-field relationship of our fabricated AlGaN/GaN HFETs considering Polarization Coulomb Field (PCF) Scattering. This new velocity-field model can accurately describe the experimental phenomenon of velocity modulation by various gate biases and effectively reduce the fitting parameters. The parameters of the velocity-field model are incorporated into the compact model. The method cleverly maintains the direct relation between the velocity-field model parameters and AlGaN/GaN HFETs. All parameters have a specific physical meaning in our compact model and parasitic resistance factors and channel modulation effects are also incorporated. We validate the model with experimental data for AlGaN/GaN HFETs with gate lengths of $0.2~\mu \text{m}$ and $0.35~\mu \text{m}$ , respectively, and obtain good agreement.