Preparation and electronic properties of abrupt Ge-GaAs(110) interfaces

Ge thin films are grown using molecular beam epitaxy on clean cleaved GaAs (110) substrate at a temperature of 160 degrees C which ensures the formation of a smooth and crystalline layer with an abrupt interface. The film and the interface are characterised using low-energy electron diffraction, Auger electron spectroscopy and photoemission yield spectroscopy. The latter, measured as a function of film thickness from 10 -3 monolayer (1 ML=8.8*10 14 atoms cm -2 ) to 50 ML, brings a direct measurement of the energy separation between the valence band edges of the two semiconductors at the interface, Delta E v =0.55 eV, and shows the existence of a filled band of interface states, the tail of which penetrates the lower part of the GaAs band gap. The escape depth of electrons in Ge at several energy values is also determined.