Two-Dimensional Localization Effect with Spin-Orbit Scattering in Arsenic Doped Polycrystalline Silicon Films

We have investigated the 3D-2D crossover of the localization effect in a system of heavily arsenic doped polycrystalline silicon films with thickness 40 to 1350 Å. The films with d ≦220 Å show a log T dependence of the conductance. For a 220 Å film, ∼60% of the quantum correction to the conductivity is attributed to the electron-electron interaction effect, and the rest to the localization effect. Analyses of the magnetoconductance behavior have indicated that a weak spin-orbit scattering should be taken into account in the localization effect; a feature not observed in n-type bulk Si. The diffusion length of the spin-orbit scattering is estimated to be 0.28µm. The inelastic scattering time τ in for the 220 Å film varies as T -0.95 , indicating that the electron-electron scattering is the dominant phase breaking process in the present dirty 2D systems.