The effects of Cl ion implantation on the properties of CulnSC(2) epitaxial thin films have been investigated. Using five kinds of accelerating energies, the doped layer with a constant profile of Cl concentration along the depth direction was fabricated. From the results of reflection of high-energy electron diffraction, the damages due to implantation were removed by annealing at 400degreesC in N-2. The conductivity type in all implanted films was n-type, and the carrier concentration was increased with increasing Cl concentration in the thin films. Consequently, it is considered that Cl acts as a donor in CuInSe2. (C) 2002 Elsevier Science B.V. All rights reserved.