PHOTODISSOCIATION DYNAMICS OF TRIMETHYLGALLLIUM ON GAAS

The UV photodissociation of Ga(CH3)(3) on GaAs(100) has been investigated as a model system for the understanding of laser nonthermal deposition of group III metals from organometallic precursors. When irradiated by UV laser Light, CH3 radicals desorb from surface Ga(CH3)(x) (x = 1-3) species. The initial excitation is a direct single photon process, as evidenced by the dependence of photodesorption yield and velocity distribution on laser pulse energy and wavelength. The translational energy distributions of CH3 from both adsorbed and solid Ga(CH3)(3) are similar, pointing to a common dynamic process, although the cross section for the adsorbate is more than two orders lower than that for the solid. The remarkably low translational energy, as compared to the photon energy or the excess bond energy, suggests the presence of shallow bound potentials in the dynamic process in both adsorbed and condensed states. A similar mechanism might also apply to the photodesorption of CH3 from surface GaCH3, which exhibits a substrate temperature dependent bimodal velocity distribution.