SURFACE CHEMICAL PROCESSES IN METAL ORGANIC MOLECULAR-BEAM EPITAXY - GA DEPOSITION FROM TRIETHYLGALLIUM ON GAAS(100)

The adsorption of triethylgallium on the GaAs (100) (4×1) surface has been studied using the techniques of low energy electron diffraction, x-ray photoelectron and Auger spectroscopies, high resolution electron energy loss spectroscopy and temperature-programmed desorption. Condensed multilayers of the organometallic compound formed following adsorption at 150 K desorb from the surface at ∼170 K to leave a chemisorbed molecular monolayer of triethylgallium. Upon further heating this layer partially desorbs and partially decomposes to form diethylgallium in two competing processes. The diethylgallium so formed can also desorb or otherwise decompose ultimately to adsorbed Ga atoms in a reaction which results in the formation of hydrogen, ethene, and ethane. The temperature-programmed desorption characteristics of these latter species are found to be similar to those observed for a dissociated layer of ethyl bromide. A reaction scheme is proposed to account for the observations and kinetic parameters are obtained from computer modeling of the temperature-programmed desorption results. The reaction scheme is also used to evaluate the temperature-dependent growth rate expected in metal organic molecular beam epitaxial growth of GaAs. Comparison with experimental results is made and the work is discussed in the light of the previous model which has been proposed for the epitaxial growth of GaAs by metal organic molecular-beam epitaxy.