Electrical spin injection into InGaAs/GaAs quantum wells: A comparison between MgO tunnel barriers grown by sputtering and molecular beam epitaxy methods

Abstract

Équipe 101 : Nanomagnétisme et électronique de spinInternational audienceAn efficient electrical spin injection into an InGaAs/GaAs quantum well light emitting diode is demonstrated thanks to a CoFeB/MgO spin injector. The textured MgO tunnel barrier is fabricated by two different techniques: sputtering and molecular beam epitaxy. The maximal spin injection efficiency is comparable for both methods. Additionally, the effect of annealing is also investigated for the two types of samples. Both samples show the same trend: an increase of the electroluminescence circular polarization (P-c) with the increase of annealing temperature, followed by a saturation of P-c beyond 350 degrees C annealing. Since the increase of P-c starts well below the crystallization temperature of the full CoFeB bulk layer, this trend could be mainly due to an improvement of chemical structure at the top CoFeB/MgO interface. This study reveals that the control of CoFeB/MgO interface is essential for an optimal spin injection into semiconductor

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“…The full range survey spectra (Figure A) clearly displays three featured peaks ascribed to O 1s, Zn 2p, and Mg 1s, respectively. Concerning Mg 1s spectra (Figure B), an intensive peak centered at around 1304.5 eV corresponds to the MgO overlayers . Focusing on Zn 2p data (Figure C), the positions of two resolved peaks observed in the spectra of 4‐cycle MgO@ZnO NRA closely resemble to those appearing in the pristine ZnO NRA.…”

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