We show that, in scanning electron microscopy, it is possible to use the secondary electrons produced by the backscattered electrons to obtain chemical information on the dopant distribution in Sb-implanted silicon. Theoretical investigations and experimental data concur to point out that the resolution of the method is defined by the probe size—values of 1 nm or even lower are possible in the present instruments—while the contrast depends on the electron range and on the boundary conditions. A proper choice of beam energy and boundaries of the doped layer may allow a sensitivity below 1%, suitable to characterize the high-dose near-surface region of the ultrashallow junctions in cross-sectioned bulk specimens.