Spin control in semiconductors: Variations on a theme

The manipulation of electron spins in semiconductors is a core concept in semiconductor spintronics. We review recent experiments that show how optical, electrical and exchange fields allow the control of spin-dependent phenomena in semiconductor devices. The first example addresses the all-electrical generation of electron spin polarization in conventional semiconductors via the spin-orbit interaction. Our experiments show that current-induced spin polarization and the spin Hall effect can be observed even in wide band gap semiconductors such as ZnSe, despite a relatively weak spin-orbit coupling parameter. The next example shows how circularly polarized photons allow us to both pump and probe spin polarized states in semiconductor microcavity lasers, resulting in the surprising finding that the spin dephasing time is correlated with the Q-factor of the cavity and the onset of stimulated emission. Finally, we discuss how we exploit the exchange interaction between local moments and band electrons to manipulate electronic and local moment spin dynamics in magnetic semiconductor quantum structures.