Geometric frustration of 2D dopants in silicon: Surpassing electrical saturation

A novel application of scanning transmission electron microscopy, combined with data from x-ray absorption spectroscopy, establishes that high concent rations of n-type Sb dopants distributed within a two-dimensional (2D) laye r in Si can contribute up to an order of magnitude higher free-carrier dens ity than similar dopant concentrations distributed over a three-dimensional region. This difference is explained using a simple model in which formati on of electrically deactivating centers is inhibited by solely geometric co nstraints. It should be possible to extend these ideas for obtaining even h igher free-carrier densities in Si from 2D layers of Sb and other group V d onors.