Direct observation of potential distribution across Si/Si p-n junctions using off-axis electron holography

Off-axis electron holography was used to observe the potential distribution across a 2×1018/cm3 p- and n-doped Si/Si p-n junction. With digital image recording and processing, and a novel method for thickness determination, we have successfully extracted two-dimensional maps of the depletion region potential. For a defect-free region, we measured relatively abrupt changes in potential in the range 1.0–1.5 V across lateral distances of 20–30 nm. Although influenced by instrumental and sample limitations, these values are reasonably consistent with expected Si junction parameters and thus establish the promise of this technique for measuring potential distributions across device junctions and interfaces.