Fabrication of heterostructure p-β-Fe 0.95Mn 0.0 5Si 2/n-Si diodes by Fe + and Mn + co-implantation in Si(100) substrates

Abstract

We report on the structural and electrical properties of iron silicides in the transformation process from ε-FeSi to β-FeSi 2 and show the electrical characteristics of heterostructure p-β-Fe 0.95Mn 0.05Si 2/n-Si diodes formed by high-dose Fe + and Mn + co-implantation in Si (100). A mixture of polycrystalline ε-FeSi and β-FeSi 2 with a thickness of 75 nm and the resistivity of ρ=4.9×10 −4 Ω·cm was in-situ formed during Fe +-implantation in Si (100) at 350°C. These samples were annealed at Ta=400–1100°C and characterized by Rutherford backscattering spectrometry, van der Pauw and X-ray diffraction. Single β-FeSi 2 layers with ρ=0.31 Ω·cm were formed after annealing at Ta =600°C. Although the samples with Ta<600°C exhibited p-type conductivity (hole concentrations of p=5.3–11×10 20 cm −3 and hole mobilities of μ h=8.7–32 cm 2/V/s), the samples with Ta≧600°C presented n-type conductivity ( n=4.2–14×10 16 cm −3 and μ e=220–520 cm 2/V/s). The origin of p-type conductivity may be due to contribution of Fe-rich β-FeSi 2, while that of the electron carrier could be related to the formation of stoichiometric β-FeSi 2, in which the predominant impurity phosphorous atoms remaining in the n-Si substrates could be electrically activated as donors in β-FeSi 2 by high-temperature annealing. The I–V and C–V characteristics of the p-β-Fe 0.95Mn 0.05Si 2/n-Si(100) diodes indicated that the impurity distribution of the pn junction is linearly graded, which leads to a high ideality factor of η=4.4.