Analytical Model for Gate Capacitance and Threshold Voltage in Fin-Shaped GaN HEMTs

Fin-shaped tri-gate structure is an alternative way to achieve positive threshold voltage shift in gallium nitride (GaN)-based high electron mobility transistors (HEMTs). This results from the combined effect of top-gate and side-gate electric fields. In this work, side-gate capacitance of fin-shaped high electron mobility transistor (fin-HEMT) is estimated using conformal mapping technique. Subsequently, a model is developed to estimate the threshold voltage of the device by incorporating this side-gate capacitance in the existing threshold formulation. This model can be included in any existing compact model framework of HEMTs to predict the threshold voltage for fin-shaped devices. The proposed model, being completely physics-based and scalable, is useful to circuit engineers for optimal design.