Overview

Epitaxy was defined by Royer1 as the oriented growth of one substance on the crystal surface of another substance. At this writing this definition belongs to what is called heteroepitaxy. The oriented growth of a substance on the crystal surface of the same substance is now called homoepitaxy. In the previous chapter we called the process of extending the grain structure by deposition, without the formation of grain boundaries between the deposit and the substrate, granular epitaxy. The latter is a form of homoepitaxial deposition.

The defects contained in epitaxial monocrystalline films are the main subject matter of epitaxial structure. These defects are produced in the deposition process. Also, there are unique epitaxial structures, such as superlattices involving alternate sets of atomic planes of different species, vertically integrated circuits and quantum wells, wires, and boxes. These unique geometric arrangements or epitaxial units also have their associated defects, which are mainly of interfacial origin.

An exploration of the factors controlling the different modes of epitaxial deposition is carried out in Section 1. Section 2 considers defects and their origins in homoepitaxial films grown layer-by-layer.

Heteroepitaxial films may involve small or large misfits between the lattice parameters of the unit cells of film and substrate. In the former case, as the film thickens during deposition the first few monatomic layers tend to grow pseudomorphically, adjusting the unit cell dimensions of the film to that of the substrate in their common coherent interface. There are a variety of pseudomorphic films. The crystal...