Semiconductor-metal phase transition of iron disilicide by laser annealing and its application to form device electrodes

Phase transition of semiconducting beta-FeSi2 to metallic beta-FeSi2 has been realized by laser annealing (Nd:YAG laser,), lambda=1.064 mum) in order to form ohmic electrodes for beta-FeSi2 devices. The starting samples were 200-nm-thick beta-FeSi2 films formed on Si substrates by reactive deposition epitaxy method. XRD and micro-Raman spectroscopy measurements confirmed the successful phase transition. The electrical resistivity of the alpha-FeSi2 film was 2.0 x 10(-4) Omega.cm, three orders lower than that of the original beta-FeSi2 film (1.4x10(-1) Omega.cm). Cross-sectional TEM images and electron diffraction patterns indicated that the upper similar to100 nm of the annealed film was changed to alpha-FeSi2 while the lower part remained to be beta-FeSi2. alpha-FCSi2 layer had good ohmic contact with beta-FeSi2. A testing p-beta-FeSi2/n-Si diode with laser-annealed alpha-FeSi2 as the electrode on beta-FeSi2 Showed the same rectifying characteristic as that using Al-evaporated electrode. (C) 2004 Elsevier B.V. All rights reserved.