Schottky contact formation by an insulator: Lithium fluoride on silicon

The low work function material lithium fluoride (LiF) facilitates electron-selective contacts to n-type silicon and is frequently used in dopant-free heterocontacts for silicon solar cells. Our photoelectron spectroscopy (PES) data show that LiF deposition on n-Si leads, indeed, to Fermi-level crossing of the conduction band minimum. Furthermore, PES reveals intrinsic surface band bending on hydrogen-terminated p-Si(100). LiF deposition on p-Si leads to a rigid shift of the Si core-levels and the vacuum-level pointing to ideal Schottky contact formation. This is further supported by the open-circuit voltage of Al/LiF/p-Si/Al solar cells, which corresponds to the photoelectron spectroscopy (PES)-measured band bending magnitude.