TABLE OF CONTENTS Understanding the performance of SiGe HBTs is to a great extent determined by ones knowledge of the strained-Si 1- xGe x layer properties. The incorporation of Ge significantly changes the properties of the base region and the base-emitter and base-collector junctions in a Si/Si 1- xGe x/Si heterostructure. Various material properties essential for device simulation and their dependence on the composition for coherently strained-Si 1- xGe x alloy on Si (100) substrate must be known. Commercially available simulation software such as Silvaco-ATLAS, MEDICI and university software such as PISCES-2ET [48, 51, 52] have been used for the simulation of SiGe HBTs [25].
Most of the available simulators handle strained-SiGe materials with a very conservative approach, especially in the carrier mobility models. Also, the reported models for SiGe material parameters are scattered over a vast body of literature. It has been reported that for adequate modelling, a proper selection of model options are also needed [53, 54]. More accurate strained layer mobility models for majority and minority carrier are required to take into account the different mobilities along parallel (in plane) and perpendicular (out-of-plane) to the growth plane of the strained-SiGe layer. A MC model for mobility in SiGe has been developed and validated with the available transport data [55].
In this section, focus is placed on developing accurate SiGe material parameter models for robust numerical simulation for SiGe HBTs that fit into the TCAD software framework currently used for the design...
