Why does a p-doped area show a higher contrast in electron holography than a n-doped area of the same dopant concentration?
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Holographic measurement of semiconductor dopant profiles combined with focused ion beam (FIB) preparation has become increasingly important. Electron holography in a transmission electron microscope (TEM) delivers 2D-projected potential images of a 3D-object. However, for an exact quantitative evaluation it is necessary to understand the potential distribution in a FIB-specimen along the electron beam. Because the distribution is averaged in the 2D-projection, the structure along z is lost. It is shown that the averaging process has an unexpectedly different impact on the 2D-projections for complementarily doped structures. The result is a remarkably stronger signal and better contrast for p-doped structures in the phase image, compared to that of n-doped structures.
KeywordsPotential Distribution Potential Structure Electron Holography Scanning Electron Microscope Topview Profile Scan
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