The electron holography shows increased mean phase with higher doping. This indicates that the MIP in the Si:P+/Si:B-stack increases with increased doping. To understand this, we start by analyzing the effective carriers generated across epitaxial Si(P+)/Si(B-) substrate interface. The Fermi level is closer to the conduction band inside the epitaxially grown Si:P film and vice versa in the substrate. The presence of trap states, at an interface, can create isolated states inside the band gap. These trap states can contribute to changes in the static charge across the interface, leading to changes in MIP .