Approximately 900- and 400-nm-thick BaSi2 epitaxial films were grown on Si(1 1 1) and Si(0 0 1) substrates, respectively, by molecular beam epitaxy, and their photoresponse properties were compared at room temperature. When the bias voltage V-bias applied between the 1.5-mm-spacing stripe-shaped electrodes on the BaSi2 surfaces increased, photocurrents were clearly observed for photon energies greater than the band gap for both samples. However, the photoresponsivity for BaSi2 on Si(0 0 1) was more than 8 times larger than that for BaSi2 on Si(1 1 1); reaching approximately 50 and 5 mA/W at 1.6 eV, respectively, when V-bias was 1.0 V. This is attributed to the difference in the grain size of BaSi2 films confirmed by plan-view transmission electron microscopy. (c) 2013 Elsevier B.V. All rights reserved.