  We analyze BEEM experiments. At low temperatures and low voltages, near the
threshold value of the Schottky barrier, the BEEM current is dominated by the
elastic component. Elastic scattering by the lattice results in the formation
of focused beams and narrow lines in real space. To obtain the current injected
in the semiconductor, we compute the current distribution in reciprocal space
and, assuming energy and $k_{\parallel}$ conservation. Our results show an
important focalization of the injected electron beam and explain the similarity
between BEEM currents for Au/Si(111) and Au/Si(100).
