SB–PE drift-diffusion algorithm for FET devices global modeling

We present an efficient numerical global modeling approach for the RF and microwave physic-based analysis of active devices that combines frequency-domain Fourier series expansion (Spectral Balance, SB) and space-domain polynomial expansion (PE) of the physical quantities inside the semiconductor. The proposed method (SB–PE), suited for the simulation of high-frequency Si, GaAs, and GaN FET devices, is based on the solution of the drift-diffusion transport equations, for the horizontal transport phenomena along the channel, coupled with a vertical self-consistent Schrödinger–Poisson solution for the vertical charge control. The frequency- and space-domain expansions drastically reduce the number of time and space sampling points where the equations are computed, greatly reducing the computational burden with respect to classical finite-difference approaches. Also the inclusion of frequency-dependent parameters of the semiconductor, important at very high frequencies (e.g. dielectric constant), and the coupling with an EM numerical solver, for a global modeling simulation, becomes straightforward, due to the frequency-domain approach, and to the reduced interconnection nodes between the physical simulator and the passive embedding network. A demonstrator for PC implementing a quasi-2D model with a drift-diffusion formulation has been implemented, and its results are compared with a standard finite-difference time-domain approach and with a standard Harmonic Balance formulation.