Electron and Phonon Tunneling Spectroscopy in Metal-Germanium Contacts

Measurements of the tunneling characteristics of metal electrodes on vacuum-cleaved Sb-doped Ge reveal greatly improved agreement with the one-electron model relative to chemically fabricated units. Strong phonon-assisted tunneling in both Sb- and As-doped Ge is observed, and is interpreted in terms of a twostep process via an evanescent state at Γ₂^'. The tunneling characteristics at eV±ωLO in Ga-doped Ge are interpreted in terms of the alternation of the electronic dispersion relation due to deformation-potential coupling between the holes and the LO phonons.