Advanced epitaxial growth techniques: atomic layer epitaxy and migration-enhanced epitaxy

New epitaxial growth techniques based on modulated source supplies such as atomic layer epitaxy (ALE) and migration-enhanced epitaxy (MEE) have been developed to grow atomically controlled surfaces and interfaces of compound semiconductors. ALE is based on repeated adsorption saturation of constituent atoms on the substrate surface which guarantees complete 1 ML coverage. To achieve an adsorption saturation, volatile compound sources are often used for low vapor-pressure elements. In contrast, the MEE process is simply composed of an alternate supply of pure constituent atoms. Because of this simplicity, MEE has been applied to both metalorganic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). In MEE, layer-by-layer growth takes place with the commensurate deposition of group III atoms. Even for an imcommensulate deposition, in principle, the roughness of the resulting surface is at most 1 ML. MEE has found a variety of applications in the growth of heterostructures with largely lattice-mismatched systems, wires and dots, selective area epitaxy of fine structures, and so on. (C) 1999 Elsevier Science B.V. All rights reserved.