We have investigated the lattice location of Sn atoms in Sn‐doped GaAs thin films grown by molecular beam epitaxy using ion channeling techniques. Accumulation of ≊2×1014atoms/cm2of Sn on the GaAs surface was detected. These surface Sn atoms were determined to be randomly distributed within ≊20 A˚ of the surface of the GaAs. Angular scans of the Ga K&agr;, As K&bgr;, and Sn Lx rays across the ⟨100⟩, ⟨110⟩, and ⟨111⟩ axial channels indicated that the Sn atoms in the GaAs layer are mostly substitutional. No displacement of the Sn atoms larger than 0.14 A˚ from the substitutional sites was detected.