SCANNING FORCE MICROSCOPY MEASUREMENT OF EDGE GROWTH-RATE ENHANCEMENT IN SELECTIVE AREA EPITAXY

Using scanning force microscopy we have studied the growth rate enhancement at the edge of InP and lattice matched InGaAs layers grown into openings on SiO2-masked InP- substrates by selective area epitaxy. The growth method was metalorganic molecular beam epitaxy. The growth rates were measured at the center and at the edge of the openings using a scanning force microscope. We have found that the growth rate enhancement can be minimized by using lower metalorganic and hydride flows, and that diffusion is the dominant process at work in the formation of the edge. The migration length of the species depends on the arrival rate of the precursor molecules to the substrate, determined by the absolute group III and V flows, and not on the nominal V/III ratio used for the growth.