Photodissociation of trimethylindium and trimethylgallium on GaAs at 193 nm studied by angle-resolved photoelectron spectroscopy

The chemisorption and photodecomposition of trimethylindium (TMIn) and trimethylgallium (TMGa) on a GaAs(100) surface have been studied by means of angle-resolved X-ray and ultraviolet photoelectron spectroscopy. Increase in the substrate temperature from 150 to 300 K causes the In-C bond cleavage of the adsorbed TMIn to generate methyl radicals that react with Ga species in the substrate to form Ga-C bonds. The 193 nm irradiation of TMIn adsorbed on GaAs at 150 K induces the In-C bond cleavage. The carbon species desorb from the substrate. Irradiation at 351 nm causes no change in the X-ray photoelectron spectra of the adsorbed species. These results imply that photodissociation is not due to photoabsorption of the GaAs substrate but that of the adsorbed species on the substrate. Photoirradiation of 488 nm on TMIn adsorbed on GaAs at 150 K induces pyrolytic cleavage of the In-C bond.