  We demonstrate a method which can hyperpolarize both the electron and nuclear
spins of 31P donors in Si at low field, where both would be essentially
unpolarized in equilibrium. It is based on the selective ionization of donors
in a specific hyperfine state by optically pumping donor bound exciton
hyperfine transitions, which can be spectrally resolved in 28Si. Electron and
nuclear polarizations of 90% and 76%, respectively, are obtained in less than a
second, providing an initialization mechanism for qubits based on these spins,
and enabling further ESR and NMR studies on dilute 31P in 28Si.
