  We report on experiments in which a spin-polarized current is injected from a
$GaMnAs$ ferromagnetic electrode into a $GaAs$ quantum well through an AlAs
barrier. The resulting spin polarization in the GaAs well is detected by
measuring how the current, tunneling to a second $GaMnAs$ ferromagnetic
electrode, depends on the orientation of its magnetization. Our results can be
accounted for the non-relaxed spin splitting of the chemical potential, that is
spin accumulation, in the $GaAs$ well. We discuss the conditions on the hole
spin relaxation time in GaAs that are required to obtain the large effects we
observe.
