Design and Simulation of GaN-Based Trench Gate MISFET with AlxGa1-xN as the Vertical Channel Barrier Layer

Abstract

GaN-based devices are setting off a technological revolution, which is expected to replace silicon transistors to develop high efficiency power converters. GaN-based vertical power field-effect transistors (FETs) are very promising in various power switching applications because of their high current density and small chip size. In this letter, a novel GaN-based trench gate metal-insulator-semiconductor field-effect transistor (MISFET) featuring an $\mathrm{Al}_{0.3} \mathrm{Ga}_{0.7} \mathrm{~N} / \mathrm{GaN} / \mathrm{Al}_{\mathrm{x}} \mathrm{Ga}_{1-\mathrm{x}} \mathrm{N} / \mathrm{n}-$GaN double heterostructure (DH) is proposed and modeled. Instead of using the traditional unstable Mg-doped p-GaN as the vertical channel barrier layer $\mathbf{A l}_{x} \mathbf{G a}_{1-x} \mathbf{N}$ is adopted and proved to be able to form a potential barrier height larger than 3 eV by the negative polarization charges at the $\mathrm{GaN} / \mathrm{Al}_{\mathrm{x}} \mathrm{Ga}_{1-\mathrm{x}} \mathbf{N}$ interface. The proposed device exhibits a high drain current density, a low on-resistance, and an adjustable threshold voltage from 3.4 to $8.9 V$ only by changing the Al content and thickness of the $Al_{x}Ga_{1-x}N$ VCBL.