Magnetically controlled spin light-emitting diode

The fundamental physical principles underlying the operation of basic elements of spintronics are considered, including the giant magnetoresistance effect, injection of spin-polarized charge carriers from a magnetized ferromagnetic contact, and radiative recombination in semiconductors involving spin-polarized carriers. An integrated GaAs-based structure implementing all of the above phenomena, a magnetoresistive spin light-emitting diode, has been fabricated and investigated. As an electrical circuit, the device under consideration is a magnetoresistive element and a metal/tunnel-thin dielectric/semiconductor light-emitting diode connected in series. It is shown that a magnetic field directed in the plane of the layers changes the state of the magnetoresistive element (high or low resistance) and thus allows controlling the intensity of electroluminescence. A magnetic field directed perpendicular to the plane of the layers ensures magnetization of the magnetic contact of the light-emitting diode and spin injection, accompanied by the emission of circularly polarized light. The resulting device can find itself in four stable magnetic states (high-low intensity, ‘positive’–‘negative’ circular polarization). Such a structure can serve as a basis for magnetic recording and information transmission elements, in which four stable states form quaternary instead of binary logic.