Physical mechanism of fin-gate AlGaN/GaN MIS-HEMT: Vth model

Abstract

The physical mechanism of fin-shaped tri-gate AlGaN/GaN Metal Insulator Semiconductor High Electron Mobility Transistors (Fin-MISHEMT) with Al2O3 gate oxide is studied with theoretical model derived and TCAD simulation verified. The relationship between its threshold voltage and fin-width is obtained. The theoretical model of the depletion effect of side gates is based on a two-dimensional Poisson equation of potential, by which to determine the condition when the conduction band is lifted up to the Fermi level. The influences of the thickness and dielectric permittivity of the gate oxide are included in the model. It can be concluded that a narrower fin-width together with a thinner gate oxide is advantageous to a positive shift of threshold voltage. To the best of our knowledge, this is the first time such a physical model is derived which provides design guidelines for normally-off fin-gate AlGaN/GaN MIS-HEMTs.