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 Delta H) and metal electronegativity X by plotting Delta H/X-2 versus X, which suggests that Delta H 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 phi(B), and found that Q(sc) can be approximated by a non-linear function of X, similar to the relation of Delta H/X-2 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 Delta H/X-2 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.