Rashba Spin-Splitting and Spin Currents in GaN Heterojunctions
- PDF / 258,563 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 25 Downloads / 179 Views
0999-K01-05
Rashba Spin-Splitting and Spin Currents in GaN Heterojunctions Wolfgang Weber1, Simon Seidl1, Leonid E. Golub2, Sergey N. Danilov1, Vasily V. Bel'kov2, Eugenious L. Ivchenko2, Wilhelm Prettl1, Zee Don Kvon3, Hyun-Ick Cho4, Jung-Hee Lee4, and Sergey D. Ganichev1 1 Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany 2 A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg, Russian Federation 3 Institut of semiconductor physics, Novosibirsk, Russian Federation 4 Kyungpook National University, Sankyuk-Dong, Korea, Republic of ABSTRACT The circular photogalvanic effect, spin-galvanic effect and magneto-gyrotropic effect have been observed in hexagonal (0001)-oriented GaN low-dimensional structures excited by infrared and terahertz radiation. Experimental and theoretical analysis exhibits that the observed photocurrents are related to the gyrotropy of the GaN based heterojunctions and give evidence for a substantial structural inversion asymmetry caused by the built-in electric fields at the AlGaN/GaN interface. INTRODUCTION Gallium nitride is a potentially interesting material system for spintronics since long spin relaxation times are detected in this material [1] and it is expected to become ferromagnetic with a Curie-temperature above room temperature if doped with manganese [2]. Recently we observed that in GaN heterojunctions also a substantial Rashba spin-splitting in the electron band structure is present, allowing spin manipulation by an electric field [3]. The Rashba spin-splitting due to structural inversion asymmetry, which is not expected in wide-band semiconductors, is caused in GaN heterostructures by a large piezoelectric effect which yields a strong electric field at the AlGaN/GaN interface and a strong polarization induced doping effect. In [4,5] it was shown by magneto-transport measurements that this splitting is comparable to that of GaAs heterostructures being of the order of 0.3 meV at the Fermi energy. Here we report on an investigation of the circular photogalvanic effect (CPGE) caused by the Rashba spin-splitting [6] and on the observation of the spin-galvanic effect (SGE) [6] and magneto-gyrotropic photogalvanic effect (MGPGE) [7-9] in this material. All these effects have been detected in (0001)-oriented GaN heterostructures in a wide range of temperatures from technologically important room temperature to 4.2 K. The CPGE results in a spin polarized electric current and is caused by selective photoexcitation of carriers in k-space with circularly polarized light due to optical selection rules. The microscopic origin of the spin-galvanic effect is the inherent asymmetry of spin-flip scattering of electrons in systems with removed k-space spin degeneracy of the band structure. The magneto-gyrotropic photogalvanic effect so far was demonstrated in GaAs, InAs, and SiGe QWs where its microscopic origin is a zero-bias spin separation [8,9]. Zero-bias spin separation is caused by spin-dependent scattering of electrons d
Data Loading...
