Sputtered epitaxial chalcopyrite CuInSe2 films grown on GaAs substrates

Epitaxial Cu-poor CuInSe2 films have been synthesized on GaAs(1 1 1)B [As-terminated], (1 1 1)A[Ga-terminated] and (0 0 1) substrates by co-sputtering Cu/In and evaporating Se method. Scanning electron micrograph results show that surface morphologies of the epitaxial Cu-poor CuInSe2(1 1 2)B[Se-terminated], (1 1 2)A[metal-terminated] and (0 0 1)-oriented films are substantially different. The surface morphology results clarify that the (1 1 2)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.