Studies of heteroepitaxial growth of thin II–VI semiconductor layers by sequential ultrahigh vacuum dosing

An in situ molecular-level study of material growth using a binary reaction sequence of hydride and metalorganic precursors is presented. The study used a model material system of CdS/ZnSe(100) and focused on the material chemistry of heteroepitaxy growth. In the growth process, dimethylcadmium and H2S precursors were sequentially dosed onto a c(2×2) ZnSe(100) substrate under high-vacuum conditions. At temperatures of ∼300 K, saturated chemisorption of a Cd and a S monolayer occurred during each cycle of the binary reaction sequence. Characterization of the growth surface was accomplished in the growth chamber using Auger electron spectroscopy, x-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy for probing surface chemical composition and low-energy electron diffraction for determining surface order. These measurements showed layer-by-layer growth at a substrate temperature of ∼300 K, yielding an ordered stoichiometric CdS film. Strong variations in the composition of the grown surface layer were observed at different substrate temperatures; these variations were found to be related to the temperature dependence of the precursor reactions with the growth surfaces.