ENERGY LEVEL ALIGNMENT OF SOLID INTERFACES

This book, Energy Level Alignment of Solid Interfaces, focuses on the Schottky barrier height (SBH) of metal-semiconductor interfaces and the band offset (BO) of semiconductor heterojunction interfaces, which are crucial to the performance of advanced solid-state devices and have been extensively investigated for decades. These interface parameters are direct results of interface charge distribution and should be explained on that basis. For a long time, however, such a scientifically grounded approach was not possible, and the explanation of SBH and BO largely relied on empirical models.

Several breakthroughs in recent years have finally provided a scientific explanation of these band-alignment conditions through charge distribution. To achieve this, the long tradition of employing surface quantities to represent solid crystals-dating back to the time of Schottky and Mott and followed by researchers ever since-was abandoned. Instead, model solids without surface dipoles were adopted as the proper representatives of solid crystals.

This book discusses these recent developments, beginning with a semiclassical host-bath approach to analyse all energy-level-alignment problems. It also explains in detail how the nearsightedness principle is used to construct model solids through neutral polyhedra theory (NPT), and how SBH and BO can be quantitatively modelled using bulk crystal charge density. The wide success of this density-based approach in explaining and predicting BO at covalent, ionic, and polycrystalline heterojunction interfaces, as well as SBH at epitaxial and polycrystalline metal-semiconductor interfaces, is examined.

The phenomenon of Fermi-level pinning, which dominated the SBH and BO field and puzzled researchers for decades, is likewise shown to have a simple explanation based on charge distribution, once the important issues of the metallicity boundary and SBH inhomogeneity are properly recognised.