The geometric structures of Si_nAu⁺ (n = 2–11, 14, and 15) clusters are investigated using density functional theory computations in combination with infrared multiple-photon dissociation spectra measured on the corresponding cluster·argon and cluster·xenon complexes. The Si_nAu⁺ clusters adopt planar structures for the smallest sizes (n = 2–4) and have three-dimensional geometries for larger sizes (n ≥ 5). All of the investigated Si_nAu⁺ clusters have exohedral structures in which the Au dopant atom is adsorbed on a surface site of the bare Si_n⁺ cluster at a low-coordinated position. The growth mechanism of Si_nAu⁺ clusters is discussed and compared with those of Si_nCu⁺ and Si_nAg⁺. The present results indicate that the filled d shell and the atomic radii of the dopant atoms may play important roles in the cage formation of the transition-metal-doped Si clusters. Moreover, it is found that the localization of charge on the Au dopant atoms in Si_nAu⁺ determines the extent of complex formation with argon and xenon.