Chapter 6 - Semiconductor Atomic Superlattice (SAS)

Abstract

Superlattices and quantum wells were introduced as man-made quantum structures to engineer the quantum states for electrical and optical applications. The concept of the semiconductor atomic superlattice (SAS) materializes in stages. Initially it was thought that if oxide was made thin enough, it might form a strained-layer super-lattice. This chapter discusses the SAS stages by using polycrystalline silicon on polycrystalline silicon dioxide. The epitaxial growth is very aggressive; however, what counts is how low the defect density is. It takes a while to learn how to grow epitaxial silicon on saturated adsorbed oxygen. The chapter also provides theoretical study of hand-built models, calculating the strain and energy states and comparing with density functional calculation (DFC). DFC calculations basically agree with simple calculations, that the strain is surprisingly low. The chapter gives a good example of how an idea was developed and metamorphosed into an all epitaxially formed structure. The process is fundamentally different from atomic layered epitaxy (ALE), because in SAS, for Si–O superlattice, silicon dictates what sites oxygen can occupy consistent with the surface reconstruction, whereas in ALE, no one constituent dictates, resulting in a random alloy.