Laser-induced decomposition of triethylgallium and trimethylgallium adsorbed on GaAs(100).

We report X-ray photoelectron spectroscopy (XPS) studies of excimer laser stimulated decomposition of triethylgallium (TEGa) and trimethylgallium (TMGa) adsorbed on GaAs(100) surfaces in ultrahigh vacuum. TMGa and TEGa dissociatively chemisorb on GaAs at room temperature, whereupon irradiation by a pulsed ArF excimer laser at 193 nm leads to further dissociation and desorption of carbon-containing species. The carbon removal rate (per laser pulse) decreases as carbon is removed, suggesting multiple reaction sites or second-order reactions. Based on the dependence on laser wavelength and fluence, we conclude that at low fluence, a two-photon process involving direct electronic excitation of the adsorbate occurs, while at high fluence, thermal decomposition due to transient laser-induced heating is the predominant mechanism.