MgO thickness dependence of spin injection efficiency in spin-light emitting diodes

We have studied the electron spin injection efficiency from a CoFeB/MgO spin injector into AlGaAs/GaAs semiconductor light emitting diodes. The circular polarization of the electroluminescence signal reaches a value as large as 32% at 100K under a 0.8T magnetic field. We show that the spin injection efficiency increases with the increase in the MgO barrier thickness from 1.4to4.3nm. Moreover, a higher spin injection efficiency is obtained for MgO barriers grown at 300°C compared to the ones grown at room temperature. This effect is attributed to the MgO texturing occurring at high temperatures.

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