The nature of molecular beam epitaxial growth examined via computer simulations

Abstract Man-made synthetic structures involving epitaxially grown thin films of one or more compound semiconductors have been finding an increasingly important role in semiconductor device technology.1 Remarkable advances have been made over the past decade in the realization of a variety of such structures involving III-V, II-VI. and IV-VI compound semiconductors, as well as combinations of semiconductors with dielectrics and metals.' The major part of this progress has come about primarily due to the advent of, and refinements in, two vapor phase growth techniques — molecular beam epitaxy (MBE)' and metal-organic chemical vapor deposition (MO-CVD).3 The underlying motivation has been the remarkably altered and potentially useful electronic and optical properties of electrons, holes, and light arising from their confinement in a quasi-two-dimensional environment in the ultrathin films (thickness less than the particle deBroglie wavelength).4 However, confinement of the par- ticles in such ultrathin layers (typically 10 to 200 Å) places stringent requirements on the atomic level structural and chemical perfection of the films and their interfaces involved. At the same time, spatial control of the abruptness (in the growth direction) and uniformity (in the planes normal to the growth direction) of dopant distribution becomes equally sig- nificant in realizing the potential electrical and optical properties of camers and light in such structures. Both MBE and MO-CVD have been shown to meet these stringent requirements for the growth of III-V compound semiconductors, although differences between materials and structures produced by these techniques also remain. The purpose of this article is to review the progress made in understanding the process of MBE growth with particular focus on computer simulations of the growth proess.1–15 These simulations have provided con- siderable insight into the role played by the atomistic surface kinetic processes in controlling the morphology of the growing surfaces and consequently the resulting nature of the interfaces formed upon deposition of another material on such surfaces.