Optimization of Abrupt Profile of Germanium in Si/SiGe Heterojunction Bipolar Transistor Specified for Radio Frequency Range Systems

In this paper, we present modeling of Heterojunction Bipolar Transistors (HBT)based on Si / SiGeC very high performance for telecommunications applications dedicated to radio frequency RF. The major objective of our work will be devoted to the influence of the germanium profile on the static and dynamic characteristics of the latter. The optimization of the profile of germanium in the base is a major element in the study of electrical characteristics of the HBT. This optimisation improves the static gain (beta) of the transistor, while increasing the germanium profile in the base of 10% to 30%. However, the transition frequency (f(T)), and the maximum oscillation frequency (f(max)) decrease when the profile of germanium is greater than 20%. A numerical modelling approach is investigated using our 2D simulator "SIBIDIF", which is based on the Drift-Diffusion Model (DDM). This method solves the continuity equations for electrons and holes and is coupled with the Poisson's equation based on the concept of the finite difference mesh.