Interpretation of phase images of delta-doped layers

An approach is presented that allows independent determination of the mean inner potential contribution to a phase image of a highly doped layer in a semiconductor measured using off-axis electron holography, in order to quantify the contribution to the recorded phase from the dopant potential alone. The method takes into account the possible presence of both substitutional and interstitial dopant atoms and is used here to analyse an experimental phase image of 12 delta-doped B layers in Si that are separated from each other by <6 nm.