Modeling and characterization of a strained Si/Si1-xGex transistor with delta-doped layers

A two-dimensional model of a strained Si/Si1-xGex transistor with delta-dop ed layers was developed. A semiclassical drift diffusion model is used to s tudy the effects of different conduction-band offsets and variation of the distance between the Si channel and an n-type delta-doped layer as well as the thickness of this delta-doped layer at room temperature. We found that a large conduction-band offset, or a large Ge concentration, confines elect rons more strongly to the Si channel. These factors raise the drain current when the doping level per unit area is constant. The area between the Si c hannel and the delta-doped layer and the delta-doped layer itself forms a b arrier to electrons donated by the donor atoms in the delta-doped layer. He nce, the smaller the distance between the Si channel and the delta-doped la yer and the thinner the delta-doped layer, the larger the number of electro ns in the Si channel. Through the present analysis, an optimum design conce pt is clarified for device applications of Si/Si1-xGex systems. (C) 1999 Am erican Institute of Physics. [S0021-8979(99)04615-0].