ELIMINATION OF SURFACE SITE BLOCKAGE DUE TO ETHYL SPECIES IN MOMBE OF ZNSE

The metalorganic molecular beam epitaxial growth of ZnSe using diethylzinc and/or diethylselenium gas sources results in an abnormally low growth rate of several hundred angstroms per hour. Experiments with dimethylzinc or elemental zinc with elemental selenium confirm that adsorbed ethyl-based radicals contribute to the low growth rate. Surface sites for incorporation of the metal atom are saturated by the chemisorbed ethyl radicals or by an ethyl molecule that is postulated to cause the growth rate limitation. It is observed that laser and electron beam irradiation overcome the site blockage phenomenon under appropriate growth conditions. For beam-assisted growth, significant increases over the unilluminated growth rate are measured. Experiments designed to investigate the wavelength dependence of the photon-enhanced growth rate provide evidence that photo-generated electron/hole pairs are necessary to assist in releasing the ethyl radical from the unpyrolyzed DEZn molecule that is adsorbed to the surface.