Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 33: Poster I: Transport, including Magnetic-Field Effects
HL 33.5: Poster
Dienstag, 23. März 2010, 18:30–20:30, Poster D1
Pure orbital photocurrents in (111) Si-MOSFETs — •J. Kamann1, J. Karch1, P. Olbrich1, S.A. Tarasenko2, E.L. Ivchenko2, T. Schönberger1, Z.D. Kvon3, and S.D. Ganichev1 — 1THz Center, University of Regensburg, Regensburg, Germany — 2Ioffe Institute, St. Petersburg, Russia — 3Institute of Semiconductor Physics, Russian Academy of Sciences, Novosibirsk, Russia
We report on pure orbital photocurrents in (111) grown Si-MOSFET structures. Photocurrents are generated by illumination with a pulsed high power THz laser of several wavelengths. We obtain photon-helicity dependant currents, changing sign when we switch the circular polarization of the incident pulse from left- to righthanded. Furthermore we were able to measure currents that vary with the orientation of linear polarized radiation. In addition to the spin, free carriers in solid states can be characterized by other internal properties, e.g., a valley index in manyvalley semiconductors. In this case, one can consider pure orbit-valley currents, where partial electron fluxes in valleys are nonzero but the net electric current ∑Iν vanishes. Here, the role of spin-up and spin-down states is replaced by the valley index: there is no net charge current, but the electrons in different valleys travel in different directions. Si-MOSFETs grown in (111) direction belong to the symmetry group C3v, denying currents that are sensitive to unpolarized or circular polarized radiation under normal incidence. However, a net electric current induced by linearly polarized light is allowed. In this case, the partial fluxes become nonequal and do not compensate each other. This is demonstrated in our experimental results.