Epitaxial Cu-poor CuInSe2 films have been synthesized on GaAs(111)B [As-terminated], (111)A[Ga-terminated] and (001) substrates by co-sputtering Cu/In and evaporating Se method. Scanning electron micrograph results show that surface morphologies of the epitaxial Cu-poor CuInSe2(112)B[Se-terminated], (112)A[metal-terminated] and (001)-oriented films are substantially different. The surface morphology results clarify that the (112)B facets are the lowest energy, being the only surfaces which are stable against roughening. The characteristic stacking fault, twin, dislocation and anti-phase domain boundary structures in the epitaxial films, and the faceted second phase and Kirkendall void structures in the GaAs substrates have been observed by the cross-sectional transmission electron microscope and secondary ion mass spectrometry examinations. The resistivities of the grain boundary-free epitaxial Cu-poor films are two orders lower than those of the compositionally corresponding polycrystalline films. It implies that there exists a resistive Cu-poor point-defect and/or ordered vacancy compound in the grain boundaries of the polycrystalline Cu-poor films. (c) 2006 Elsevier B.V. All rights reserved.