SPIN-FLIP SCATTERING TIMES IN SEMICONDUCTOR QUANTUM-WELLS

We report theoretical results bearing on the spin-flip relaxation time of electrons and holes in semiconductor quantum wells based either on nonmagnetic materials (like Ga(Al)As) or on diluted magnetic semiconductors (DMS). In nonmagnetic quantum wells we discuss the D'Yakonov-Perel mechanism for electrons and show that the size quantization along the growth axis leads to a drastic quenching of the hole spin-flip scattering. We show that the s-d exchange is a very efficient spin-flip scatterer or electrons in DMS-based quantum wells. Finally, we point out that the electronic spin-flip is accelerated by the electron-hole correlation in bound exciton state even though the hole is only a spectator in the scattering event.