Electronic properties of semiconducting FeSi2 films

Abstract

Polycrystalline iron disilicide thin films are prepared by furnace annealing of electron-beam deposited iron layers. As substrates we use single-crystal silicon wafers, epitaxial silicon thin films on sapphire substrates, and low-pressure chemical vapor deposited polycrystalline silicon thin films on oxidized silicon wafers. X-ray diffraction indicates that orthorhombic β-FeSi2 is obtained for growth temperatures in the range 800-900 °C. Photothermal deflection spectroscopy reveals a direct band-gap of 0.85 eV. Optical transitions at energies above 1.4 eV are investigated by spectroscopic ellipsometry. Measurements of the subgap defect absorption, photoluminescence, conductivity, and of the Hall mobility suggest that lower growth temperatures yield material of better quality.