Large photoresponsivity in semiconducting BaSi2 epitaxial films grown on Si(001) substrates by molecular beam epitaxy

Approximately 900- and 400-nm-thick BaSi2 epitaxial films were grown on Si(111) and Si(001) substrates, respectively, by molecular beam epitaxy, and their photoresponse properties were compared at room temperature. When the bias voltage Vbias 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(001) was more than 8 times larger than that for BaSi2 on Si(111); reaching approximately 50 and 5mA/W at 1.6eV, respectively, when Vbias was 1.0V. This is attributed to the difference in the grain size of BaSi2 films confirmed by plan-view transmission electron microscopy. ► BaSi2 films were epitaxially grown on Si(111) and Si(001). ► The grain size of BaSi2 on Si(001) was much larger than that on Si(111). ► The photoresponsivity for BaSi2 on Si(001) was more than 8 times larger.