A new decoupled algorithm for nonstationary, transient simulations of GaAs MESFETs

Simulation of devices for which nonlocal, hot carrier transport cannot be ignored requires solution of the Poisson equation and at least the first three moments of the Boltzmann transport equation or the use of Monte Carlo techniques. These equations form nonlinear, coupled, time-dependent partial differential equations. In conventional decoupled solvers, decoupling of the equations puts a limit on the maximum allowable time step Δt, which should be kept smaller than the dielectric relaxation time τ_d of the material. This constraint makes these solvers very inefficient, especially for obtaining steady-state solutions. A highly efficient decoupled numerical algorithm which allows Δt as large as 20-50 times τ _d is presented. Results of simulations of GaAs MESFETs using both a conventional and the new decoupled solver and CPU time taken on a CRAY Y-MP by the two solvers are discussed