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

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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 contacts3,4, but it has proved exceedingly difficult to demonstrate polarized spin injection. More recently, two groups5,6 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 BexMnyZn1-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.

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Figure 1: Conduction and valence band states of BexMnyZn1-x-ySe and GaAs in an external magnetic field, B.
Figure 2: Device geometry and electric band structure.
Figure 3: Degree of circular polarization of the electroluminescence.
Figure 4: Temperature dependence of the degree of circular polarization of the electroluminescence of the dSM = 300 nm diode.


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We acknowledge the financial support of the European Commission (Esprit project SPIDER) as well as the Bundesministerium für Bildung und Forschung (Verbundprojekt Elektronische Korrelationen und Magnetismus). We would also like to thank Th. Gruber, V. Hock, B. König, D.Yakovlev, G. Müller and G. E. W. Bauer for discussions and help.

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Correspondence to L. W. Molenkamp.

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Fiederling, R., Keim, M., Reuscher, G. et al. Injection and detection of a spin-polarized current in a light-emitting diode. Nature 402, 787–790 (1999) doi:10.1038/45502

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