Dresden 2014 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 49: Spintronics (organized by MA)

TT 49.4: Vortrag

Dienstag, 1. April 2014, 14:30–14:45, HSZ 401

Spin Solar Cell for Spin Injection into Semiconductors. — Bernhard Endres, Mariusz Ciorga, Maximilian Schmid, Martin Utz, Dominique Bougeard, Dieter Weiss, Christian Back, and •Günther Bayreuther — Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg

Optical spin pumping allows to create spin-polarized carriers in III-V semiconductors, but requires circularly polarized light of a well-defined wavelength. Here we describe a spin-generating solar cell without such limitations [1,2]. The device consists of a p-n junction with highly n-doped GaAs at the n-side and ferromagnetic (Ga,Mn)As at the p-side. Illuminating this junction creates a photo-voltage causing electrons to tunnel across the narrow barrier from the n-GaAs into the (Ga,Mn)As. Due to the spin-dependent tunneling probability a spin accumulation occurs in the n-GaAs. This spin solar cell effect is demonstrated with a laser beam generating electron-hole pairs and detecting the spin accumulation via the polar magneto-optic Kerr effect and by measuring non-local voltages. On applying a large negative bias the sign of the photo-induced spin polarization is reversed as expected due to the suppression of the tunneling current through a wider barrier. This mode of operation corresponds to a spin photodiode. The spin solar cell effect should equally work for metallic ferromagnets with a high Curie temperature and allow to convert unpolarized light into a spin current also in semiconductors without a direct band gap like Si and Ge.

[1] B. Endres et al., Nature Commun. 4, 2068 (2013).

[2] R. Jansen, Nature Mater. 12, 779 (2013)