  In a recent publication, we demonstrated electrical spin injection and
detection in n-type silicon at temperatures up to 500K using ferromagnetic
metal / SiO2 tunnel barrier contacts in a three-terminal geometry (Nature
Commun. 2:245 doi:10.1038/ncomms125 (2011)). In comparing our measured
spin-voltage signal with the value predicted by theory, we followed the
analysis of Tran et al, (Phys. Rev. Lett. 102, 036601 (2009)), and
inadvertently propagated an error found therein. As they note in a recent
erratum (arXiv:0810.4770v2), the correct expression for the spin resistance
area product from the theory for a sample with a spin diffusion length LSD much
less than the contact width or channel thickness (our experimental situation)
is given by the product {gamma}^2 {rho} LSD, where {gamma} is the tunneling
spin polarization, and {rho} is the resistivity of the semiconductor transport
channel. With this correction, our measured spin voltages are much larger than
those predicted by theory, rather than in good agreement as we stated. We
emphasize that the basic conclusions of our paper are the same - the systematic
decrease in electron spin lifetime with increasing electron density
demonstrates spin accumulation in the Si channel rather than in interface
states. We further show that the measured spin lifetimes are essentially
independent of the tunnel barrier material (SiO2, Al2O3, MgO) or the magnetic
metal used (Fe, CoFe, NiFe), demonstrating clear correlation of the measured
spin lifetime with the character of the Si, and little correlation with the
tunnel barrier / interface or magnetic metal.
