DESIGN OF SIGE HBTS
As semiconductor technology continues to evolve, numerical modelling of the electrical behaviour of advanced devices has become vital. Numerical device modelling based on the self-consistent solution of the fundamental semiconductor equations dates back to the famous work of Gummel in 1964 . In Gummel’s one-dimensional (1D) discretization, the Poisson equation and the current continuity equations are decoupled and solved sequentially until convergence. Gummel’s approach was later extended by de Mari  and applied to transient simulations of a 1D p-n junction. A very important breakthrough in the discretization of the current transport equations was reported by Scharfetter and Gummel in 1969 . The Scharfetter-Gummel (SG) discretization scheme has since been used by all important device simulation programs.