A simple and meaningful expression of heterojunction built-in voltage between p-type SiGe and n-type Si

In this work, the heterojunction built-in voltage between n-type Si and strained p-type SiGe is derived from their energy band diagrams, a simple and meaningful quantitative expression is presented. For unstrained SiGe, it reduces to a more simple expression, say, it can be simply determined by the built-in voltage of Si homojunction and the bandgap narrowing of SiGe. The expression is convenient in calculation.