  Although the electrical injection, transport and detection of spins in
silicon have been achieved, the induced spin accumulation was much smaller than
expected and desired, limiting the potential impact of Si-based spintronic
devices. Here, using non-local spin-transport devices with an n-type Si channel
and Fe/MgO magnetic tunnel contacts, we demonstrate that it is possible to
create a giant spin accumulation in Si, with the spin splitting reaching 13 meV
at 10 K and 3.5 meV at room temperature. The non-local spin signals are in good
agreement with a numerical evaluation of spin injection and diffusion that
explicitly takes the size of the injector contact into account. The giant spin
accumulation originates from the large tunnel spin polarization of the Fe/MgO
contacts (53 % at 10 K and 18 % at 300 K), and the spin density enhancement
achieved by using a spin injector with a size comparable to the spin-diffusion
length of the Si. The ability to induce a giant spin accumulation enables the
development of Si spintronic devices with a large magnetic response.
