Electron mobility influenced by optical phonons in AlGaN/GaN MISHEMTs with different gate dielectrics

Abstract

The electron mobility influenced by optical phonons in AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors with different gate dielectrics around room temperature is investigated theoretically. The electronic states are obtained by the finite difference method in consideration of built-in electric fields and the conduction band bending. The optical phonons are analyzed using the dielectric continuum model. Based on the theory of force balance equation, the electron mobility of two-dimensional electron gas is obtained for the structures with four different gate dielectrics of Al2O3, HfO2, SiO2 and Si3N4. Our results show that the electron mobility is the highest in HfO2 systems when Al composition in AlGaN is small, whereas the mobility is the highest in Al2O3 systems as Al composition increases to a certain value. The effects of the ternary mixed crystals, each layer’s size and the fixed charges on the sheet density and electron mobility are also discussed for different gate dielectric materials.