Optoelectric spin injection in semiconductor heterostructures without a ferromagnet

We have shown that electron-spin density can be generated by a dc current flowing across a $\mathrm{pn}$ 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 $\mathrm{pn}$ junction. The accompanied emission of circularly polarized light from the quantum well can serve as a spin polarization detector.