Electrical Spin Injection from Ferromagnetic Nanocontacts into Nondegenerated Silicon at Low Temperatures

We present results on the magnetoresistance of the system Ni/Al 2 O 3 /Si/Al 2 O 3 /Ni fabricated in lateral nanostructures. The substrate n-type Si is a nondegenerated semiconductor with a doping level of 10 15 cm −3 . The results are presented between 11 and 30 K, where the electrical resistivity of the semiconductor varies about 4 orders of magnitude. The reduction of magnetoresistance at 30 K is consistent with the standard theory for spin injection between a metal and a semiconductor. By fitting the data with , the diffusion condition, as a function of the channel length t N , where the magnetoresistance takes place, we deduced the values of spin diffusion length L SD and spin lifetime τ s .