Fermi level pinning for zinc-blende semiconductors explained with interface bonds

Schottky barrier heights (SBHs) measured at polycrystalline metal-semiconductor (MS) interfaces have displayed an insensitivity to the work function (WF) of the metal, known as the "Fermi level pinning" (FLP) phenomenon. The obstacle presented by FLP in thwarting technological efforts to tune the SBH has been difficult to overcome because of a lack of understanding of the origin of the FLP effect. Presently, SBH explanation still largely relies on empirical models, and FLP remains a mystery. Here, the phenomenon of FLP for zinc-blende/diamond (ZBD) semiconductors is explicitly demonstrated to originate from interface metal-cation bonds, which are metallic in nature. Based on the analysis of two representative and electrically distinct types of interface, it is shown that screening by metallic bonds weakens the dependence of SBH on the metal and results in a SBH close to that found between the semiconductor and its own cation in elemental metal form. The latter SBH is shown to agree well with experimentally measured SBH from polycrystalline interface, i.e., the apparent pinning levels. A fundamental, self-consistent explanation of the FLP phenomenon thus emerges, and with it, strategies to avoid FLP for technological applications may also be suggested.