Epitaxial Growth and Photoresponse Properties of BaSi 2 Layers toward Si-Based High-Efficiency Solar Cells

We have grown BaSi 2 epitaxial films and polycrystalline films by molecular-beam epitaxy on Si(111) and on (111)-oriented 100-nm-thick polycrystalline Si layers fabricated by an aluminum-induced crystallization method on SiO 2 , respectively. Electron backscatter diffraction analysis was performed on the 200-nm-thick BaSi 2 epitaxial film and the grain size of the film was found to be approximately 3–10 µm. Photocurrents were clearly observed for the BaSi 2 (900 nm)/Si and BaSi 2 (300 nm)/SiO 2 samples for photons with energies greater than 1.25 eV at room temperature when bias voltage was applied between the 1.5-mm-spacing striped electrodes formed on the surface. The photoresponsivity of the samples increased sharply with increasing photon energy and attained its maximum at approximately 1.60 eV. From the temperature dependence of the photoresponsivity, the activation energies of the BaSi 2 epitaxial films and polycrystalline films were estimated to be approximately 6 and 52 meV, respectively.