Study of β-Ga2O3-Based Thin-Channel MODFET Devices Using a Coupled Drift-Diffusion/Multisubband BTE Solver

Gallium-oxide-based modulation-doped field-effect transistors (MODFETs) are theoretically investigated. In order to properly consider the electrical characteristics of the two-dimensional electron gases (2DEGs) in thin-channel devices, a coupled drift-diffusion (DD)/multisubband Boltzmann transport equation (MS-BTE) solver is implemented. Parameters adopted in the simulation are determined by referring to the experimental results of existing long-channel devices. The impact of the channel length, the channel thickness, the ungated region length, and contact resistance on the cutoff frequency is rigorously calculated. It is found that the cutoff frequency can have about 90 GHz with a contact resistance of
$0.4~\Omega ~\cdot $
mm and a channel whose length and thickness are 30 and 5 nm, respectively.