CRYSTAL-GROWTH KINETICS IN (GAAS)N-(ALAS)M SUPER-LATTICES DEPOSITED BY MOLECULAR-BEAM EPITAXY .1. GROWTH ON SINGULAR (100)GAAS SUBSTRATES

A new technique for the study of crystal growth processes on an atomic scale is presented. The technique comprises epitaxial growth of layered crystals by alternate molecular beam depositions of monolayer quantities of GaAs and AlAs, followed by examination of cross section of the crystals by transmission electron microscopy. Epitaxial films of (GaAs)n-(AlAs)m consisting of n monolayers of GaAs deposited alternately with m monolayers of AlAs (monolayers thickness ≊2.83 Å) have been studied by this technique. Effects of both chemical composition (0.9 ≤ n ≤ 4 and 0.98 ≤ m ≤5) and growth temperature TS (510 ≤ TS ≤ 630°C are reported. Both imaging and diffraction modes of cross sections of films are examined and are used to study the process of crystal growth. Critical temperatures, Tc, above which surface roughening effects prevent the formation of an ordered layered structure are found with Tc ≊ 610°C at n=m=1, Tc being a function of n and m. © 1978.