Very-low-energy electron microscopy of doped semiconductors

Imaging of As- and B-doped silicon regions has been performed in a scanning electron microscope operated in the cathode lens mode, with incident elect ron energies (E-P) as low as 15 eV. The doped regions of n(+) (As, 2.5x10(2 0) cm(-3)) and p(+) (B, 8x10(19) cm(-3)) on n-type silicon (similar to 10(1 5) cm(-3)) show distinct contrast with electron energies of about 3 keV. Th e brightest region is n(+) followed by p(+), then the n-type substrate. The highest contrast for the p(+) and n(+) type regions is reached at about E- P=300 and 15 eV, respectively. The contrast mechanisms are explained in ter ms of metal-semiconductor contact assuming an adventitious carbon film at t he surface. (C) 2001 American Institute of Physics.