Chemical Bonding and Fermi Level Pinning at Metal-Semiconductor Interfaces

The insensitivity of experimentally observed Schottky barrier heights (SBH) to the metal work function is known as Fermi level pinning. Since the time of Bardeen, this phenomenon has traditionally been attributed to interface gap states, even though many basic assumptions of the gap state models have been shown to disagree with experimental and theoretical results. 

In this letter, it is shown that chemical bonding at metal-semiconductor interfaces can lead to apparent Fermi level pinning effect. A conventional method in molecular physics has been used to estimate the strength of the electric dipole due to chemical bonding at metal seminconductor interfaces. Good agreement with various systematics polycrytalline Schottky barrier height experiments has been found. These findings suggest that chemical bonding is the primary reason for Fermi level pinning.