Quantifying the relationship between interface chemistry and metal electronegativity of metal–semiconductor interfaces

Abstract

To reveal the role of interface chemistry in Schottky barrier formation for metals on a given semiconductor, we re-examine the reported empirical models that correlate Schottky barrier heights or metal work functions to some bulk properties like eutectic temperatures or heats of formation of metal–semiconductor compounds. We find much improved linear relations between the bulk properties (e.g. heat of formation ΔH) and metal electronegativity X by plotting ΔH/X²versus X, which suggests that ΔH is a non-linear function of X. To explore the physical basis of these relations, we first study the interface space-charge density Q_sc as a function of Schottky barrier height ϕ_B, and found that Q_sc can be approximated by a non-linear function of X, similar to the relation of ΔH/X² and X. We further look into the possible structures in the metal–semiconductor interface to host the Q_sc by the standard quasi-chemical model. Our study shows that the empirical relation of ΔH/X² and X is well explained from the calculated tendency of forming new chemical bonds in the interface based on the quasi-chemical model. The developed nonlinear dependence of interface chemistry on X provides an opportunity for investigating the formation mechanism of a Schottky barrier. We also predicted the interfacial energies for all metals on HfO₂.