  We have shown that electron spin density can be generated by a dc current
flowing across a $pn$ junction with an embedded asymmetric quantum well. Spin
polarization is created in the quantum well by radiative electron-hole
recombination when the conduction electron momentum distribution is shifted
with respect to the momentum distribution of holes in the spin split valence
subbands. Spin current appears when the spin polarization is injected from the
quantum well into the $n$-doped region of the $pn$ junction. The accompanied
emission of circularly polarized light from the quantum well can serve as a
spin polarization detector.
