Diffraction Studies of the Growth of Strained Epitaxial Layers

Abstract

AbstractThe molecular beam epitaxial growth of strained InGaAs films grown on GaAs(100) substrates has been studied using in situ reflection high-energy electron diffraction (RHEED). Both the intensity, shape and position of the diffracted beams were monitored during growth. Growth was found to be layer-by-layer up to a strain dependent thickness, at which point three-dimensional clusters were formed. These clusters exhibited (114) facets and were elongated in the [011] direction. The onset of 3D cluster formation was simultaneous with measurable lattice relaxation. The relaxation was determined using electromagnetic deflection of the RHEED pattern across two detectors. With this arrangement, the lattice constant could be measured to within 0.003Å. The onset could be delayed by lowering the growth temperature. For misfit strain greater than about 2%, the onset occurs at thicknesses less than the Matthews-Blakeslee critical thickness. For smaller strains, the onset occurs at larger thicknesses.