Abstract:

Electrical spin-injection and detection is a conditio sine qua non for semiconductor spin-tronics. Here we demonstrate electrical injection and detection of spin-polarized electrons in a single wafer, all-semiconductor, GaAs-based lateral spintronic device, employing p+-(Ga,Mn)As/n+-GaAs ferromagnetic Esaki diodes as spin aligning contacts [1]. As (Ga,Mn)As is a hole conductor, electrical spin injection into a n-type GaAs transport channel involves conversion of spin polarized holes into spin-polarized electrons via Esaki tunneling which leaves its mark in a characteristic bias dependence of the spin-injection efficiency. The maximum spin-injection efficiency at low temperatures is so far 50%. Due to spin-orbit in-teraction the spin polarization is anisotropic with respect to different crystallographic di-rections [2]. We observe an in-plane anisotropy of 8% in case of spins oriented either along or [110] directions and 25% anisotropy between in-plane and perpendicular-to-plane orientation of spins [3]. Apart from transport experiments we also probed the spin-polarization employing spatially resolved magneto-optical Kerr measurements. By cleaving the sample the spin-polarization can also be mapped underneath a contact [4].
Work carried out in collaboration with Andreas Einwanger, Mariusz Ciorga, Roland Voelkl, Tobias Korn, Christian Schueller, Ursula Wurstbauer, Dieter Schuh, Werner Wegscheider, Bernhard Endres, Frank Hoffmann, Christian Back and Guenther Bayreuther,
[1] M. Ciorga, A. Einwanger, U. Wurstbauer, D. Schuh, W. Wegscheider, and D. Weiss, Phys. Rev. B 79, 165321 (2009).
[2] P. Sankowski, P. Kacman, J. A. Majewski, and T. Dietl, Phys. Rev. B 75, 045306 (2007).
[3] A. Einwanger, M. Ciorga, U. Wurstbauer, D. Schuh, W. Wegscheider and D. Weiss, Appl. Phys. Lett. 95, 152101 (2009)
[4] P. Kotissek, M. Bailleul, M. Sperl, A. Spitzer, D. Schuh, W. Wegscheider, C. H. Back and G. Bayreuther, Nature Physics 3, 872 (2007)

 
 
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