Injection and detection of a spin-polarized current in a light-emitting diode

Abstract

The field of magnetoelectronics has been growing in practical importance in recent years¹. For example, devices that harness electronic spin—such as giant-magnetoresistive sensors and magnetoresistive memory cells—are now appearing on the market². In contrast, magnetoelectronic devices based on spin-polarized transport in semiconductors are at a much earlier stage of development, largely because of the lack of an efficient means of injecting spin-polarized charge. Much work has focused on the use of ferromagnetic metallic contacts^3,4, but it has proved exceedingly difficult to demonstrate polarized spin injection. More recently, two groups^5,6 have reported successful spin injection from an NiFe contact, but the observed effects of the spin-polarized transport were quite small (resistance changes of less than 1%). Here we describe a different approach, in which the magnetic semiconductor Be_xMn_yZn_1-x-ySe is used as a spin aligner. We achieve injection efficiencies of 90% spin-polarized current into a non-magnetic semiconductor device. The device used in this case is a GaAs/AlGaAs light-emitting diode, and spin polarization is confirmed by the circular polarization state of the emitted light.