Fabrication of heterostructure p-β-Fe0.95Mn0.05Si2/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 e-FeSi to β-FeSi 2 and show the electrical characteristics of heterostructure p-β-Fe 0.95 Mn 0.05 Si 2 /n-Si diodes formed by high-dose Fe + and Mn + co-implantation in Si (100). A mixture of polycrystalline e-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 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 0.95 Mn 0.05 Si 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.