Spin transport driven by giant ambipolar diffusion

We report on the dynamics of photoinduced spin-polarized carriers in p–i–n–i–p doped structures. The lateral diffusion process along the doping layers in such structures is strongly enhanced due to the spatial separation of electrons and holes (giant ambipolar diffusion). We show that this fast diffusion process can be utilized to transport spin polarization within the short relaxation time over distances large compared to bulk semiconductors. Besides the fast diffusion process, the spin diffusion length is also strongly enhanced due to the fact that both internal recombination and spin relaxation due to electron–hole interaction (Bir–Aronov–Pikus mechanism) are negligible because of the spatial separation of electrons and holes.