  Thin Ge layers deposited on Si(105) form a stable single-domain film
structure with large terraces and rebonded-step surface termination, thus
realizing an extended and ordered Ge/Si planar hetero-junction. At the coverage
of four Ge monolayers angle-resolved photoemission spectroscopy reveals the
presence of two-dimensional surface and film bands displaying energy-momentum
dispersion compatible with the 5x4 periodicity of the system. The good
agreement between experiment and first-principles electronic structure
calculations confirms the validity of the rebonded-step structural model. The
direct observation of surface features within 1 eV below the valence band
maximum corroborates previously reported analysis of the electronic and optical
behavior of the Ge/Si hetero-interface.
