Band alignment at polycrystalline interfaces explained with bulk densities

Abstract

The band offset (BO) at semiconductor heterojunctions and the Schottky barrier height (SBH) at metal–semiconductor interfaces are important device parameters that are directly related to the charge distribution at the interface. Recently, an approach based on the neutral polyhedra theory (NPT) was developed that allowed interface charge density to be modeled and the BO/SBH at epitaxial interfaces to be quantitatively explained and predicted. The present work shows that the band alignment conditions for a large number of practical interfaces, the majority of which are polycrystalline, can also be explained by modeling the charge distribution at the interface with densities of bulk crystals. Two types of interfaces are distinguished: those between crystals with similar chemical bonds and those with dissimilar bonds. The majority of interfaces presently studied belong to the first category, with their experimentally measured BO/SBHs in good agreement with the structure-independent predictions from NPT. The similarity of bonds at the interface and in bulk crystals makes it unnecessary to make adjustments for the interface bonds and is argued to be the reason behind “bulk-like” behavior in band alignment conditions at such interfaces. The effect of interface bonds that cannot be ignored at some interfaces with perovskite oxides is successfully treated by model solids constructed with the atoms-in-molecules theory. The validity and the wide applicability of density-based theories in the explanation and prediction of band alignment at solid interfaces are demonstrated.