Electronic structure of metal/semiconductor interfaces from cathodoluminescence and soft X-ray photoemission spectroscopies

Abstract

The dependence of Schottky barrier formation on surface and interface preparation offers several broad avenues for understanding electronic structure and charge transfer at metal/semiconductor junctions. Interface cathodo- and photoluminescence measurements reveal that electrically active deep levels form at III-V and II-VI compound semiconductor surfaces and metal interfaces which depend on temperature-dependent surface stoichiometry and reconstruction, chemical interaction, as well as surface misorientation and bulk crystal quality. These interface states are discrete and occur at multiple gap energies which can account for observed band bending. Characteristic trends in such deep level emission with interface processing provide guides for optimizing interface electronic behavior. Correspondingly, photoemission and internal photoemission spectroscopy measurements indicate self-consistent changes in barrier heights which may be heterogeneous and attributable to interface chemical reactions observed on a monolayer scale. These results highlight the multiple roles of atomic-scale in forming macroscopic electronic properties of compound semiconductor/metal junctions.