Theoretical study of the gallium chloride molecule and its interaction with arsenic dangling bonds

Ab initio molecular-orbital calculations have been carried out on the ground, excited, and ionized states of the gallium monochloride GaCl, which is used as a source molecule to generate Ga layers in GaAs epitaxial crystal growth. The calculated spectroscopic constants show good agreement with the experimental data. The calculated molecular properties of GaCl explain reasonably well the mechanism of its adsorption onto the As surface. The adsorption process is investigated by using a cluster model of GaCl-(${\mathrm{AsH}}_2$ ${)}_2$. The adsorption is found to occur as the result of covalent-bond formation with the As atoms through electronic-configuration mixing.