Methods for spin injection managing in InGaAs/GaAs/Al$_{2}$O$_{3}$/CoPt spin light-emitting diodes

Spin injection in CoPt/Al$_{2}$O$_{3}$/(Al)GaAs spin light-emitting diodes (SLEDs) was studied. The oscillations of the degree of circular polarization upon variation of a distance between the active region of the SLED and a CoPt ferromagnetic injector were observed. The oscillations depend neither on a SLED material (GaAs or AlGaAs), nor on the type of injected spin-polarized carriers (electrons and holes) and are related to the action of a perpendicular magnetic field on the injected spin-polarized carriers that causes their precession. During the transfer to the active region through a distance of 50–100 nm from the injector, a $z$–component of a spin changes a phase that is detected experimentally as the change in sign of the degree of circular polarization of luminescence. Conceivably, a source of the internal magnetic field leading to spin precession is the magnetic field of the nonuniformly magnetized CoPt contact.