Abstract:
Research in semiconductor spintronics has revealed new physical effects and led to microelectronic device concepts both in homogeneously polarized semi-conductors and in more complex non-uniform structures. In uniformly polar- ized semiconductors, the anomalous Hall effect (AHE) and the photo-galvanic effect are important examples of transverse and longitudinal transport phenomena probing the coupled spin-charge dynamics in the system. In non-uniform structures the research has focused on developing schemes to detect spin-polarization of electrons transported away from the area in which the polarization is generated. Although detection by optical means or by utilizing ferromagnet/semiconductor hybrid structures has been demonstrated, no direct electrical probe of the polarization of the current along the non-magnetic semiconductor channel has been discovered prior to this work. Here we report the observation of spatially-dependent Hall voltages in a co-planar two-dimensional electron-hole photovoltaic cell. The Hall signals are detected non-locally, away from the spin-generation area. They measure simultaneously spin-dependent transverse deflection and spin-rotation of injected electrons along the channel without disturbing the spin-polarized current. This spin-injection Hall effect (SIHE) extends the physics related to the AHE to the non-uniform systems which has broad implications. The effect yields a transverse-resistance variant of the Datta-Das transistor concept.16 The co-planar p-n junction we designed to observe the SIHE represents also an experimental realization of a non-magnetic spin-photovoltaic polarimeter, again utilizing the transverse electrical signal. The observation of the SIHE in the archetypal two-dimensional electron gas system allows us to develop a semiquantitative microscopic theory of the phenomenon.