  We demonstrate the epitaxial growth of optical-quality electrically-gated
III-V ferromagnetic quantum structures. Photoluminescence spectroscopy reveals
that initially unpolarized photoexcited holes in a GaAs quantum well become
spin-polarized opposite to the magnetization of an adjacent digital
ferromagnetic layer in the AlGaAs barrier. A vertical bias is used to tune the
spin polarization from -0.4 to 6.3 percent at T = 5 K and B = 1 kG during which
the luminescence becomes quenched, indicating that the polarization is mediated
by wave function overlap between heavy holes in the quantum well and Mn-ions in
the barrier. Polarization is observed under negligible current flow and is
insensitive to the initial spin orientation of the carriers, differentiating
the effect from both electrical and optical spin injection.
