Electron tunneling transport in ultrathin, highly doped silicon pn junctions is likely dominated by quasi-one-dimensional conduction paths. As devices are miniaturized, and doping concentrations are increased, deviations from the three-dimensional model of transport may occur in the form of current inflections, representing local band-to-band tunneling (BTBT) transport. This work proposes a method to interpret such current inflections, emerging particularly in the excess-current region of nanoscale silicon pn diodes, correlated with the formation of quasi-one-dimensional BTBT paths. By experimental and numerical study on ultrathin, highly doped silicon pn junctions, inflections in the excess-current region can be attributed to the presence of deep-potential multiple-dopant clusters. The findings described here can encourage the development of a new approach to detect the presence of dopant clusters with specific characteristics, confined in quasi-one-dimensional paths in ultrathin pn junctions. © 2026 Wiley-VCH GmbH.