  We identify a universality in the Fermi level change of Van der Waals
interacting semiconductor interfaces-based Schottky junctions. We show that the
disappearing of quasi-Fermi level pinning at a certain thickness of
semiconductor films for both intrinsic (undoped) and extrinsic (doped)
semiconductors, over a wide range of bulk systems including inorganic, organic,
and even organic-inorganic hybridized semiconductors. The Fermi level (EF)
position located in the energy bandgap was dominated by not only the substrate
work function, but also the thickness of semiconductor films, in which the
final EF shall be located at the position reflecting the thermal equilibrium of
semiconductors themselves. Such universalities originate from the charge
transfer between the substrate and semiconductor films after solving
one-dimensional Poisson's equation. Our calculation resolves some of the
conflicting results from experimental results determined by using ultraviolet
photoelectron spectroscopy (UPS) and unifies the general rule on extracting EF
positions in energy bandgaps from (i) inorganic semiconductors to organic
semiconductors and (ii) intrinsic (undoped) to extrinsic (doped)
semiconductors. Our findings shall provide a simple analytical scaling for
obtaining the quantitative energy diagram regarding thickness in the real
devices, thus paving the way for a fundamental understanding of interface
physics and designing functional devices.
