Electrical spin accumulation with improved bias voltage dependence in a crystalline CoFe/MgO/Si system

We report the electrical spin accumulation with enhanced bias voltage dependence in n-type Si, employing a crystalline CoFe/MgO tunnel contact. A sizable spin signal of similar to 4.8 k Omega mu m(2), a spin lifetime of similar to 155 ps, and a spin diffusion length of similar to 220 nm were obtained at 300 K. The spin signal and lifetime obtained in this system show consistent behavior with the temperature variation irrespective of the bias voltage. Notably, the spin signal exhibits nearly symmetric dependence with respect to the bias polarity, which is ascribed to the improved bias dependence of tunnel spin polarization. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600787]