  We demonstrate spin polarized tunneling from Fe through a SiO2 tunnel barrier
into a Si n-i-p heterostructure. Transport measurements indicate that single
step tunneling is the dominant transport mechanism. The circular polarization,
Pcirc, of the electroluminescence (EL) shows that the tunneling spin
polarization reflects Fe majority spin. Pcirc tracks the Fe magnetization,
confirming that the spin-polarized electrons radiatively recombining in the Si
originate from the Fe. A rate equation analysis provides a lower bound of 30%
for the electron spin polarization in the Si at 5 K.
