Dresden 2009 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 34: Spin controlled transport II
HL 34.6: Talk
Wednesday, March 25, 2009, 15:30–15:45, BEY 118
Resonant circular photogalvanic effect in GaN/AlGaN heterojunctions — •B. Wittmann1, L. Golub2, S. Danilov1, J. Karch1, C. Reitmaier1, D. Kvon3, N. Vinh4, A. van der Meer4, B. Murdin5, and S. Ganichev1 — 1Terahertz Center, University of Regensburg, Germany — 2A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia — 3Institute of Semiconductor Physics, Novosibirsk, Russia — 4FOM Institute for Plasma Physics “Rijnhuizen”, Nieuwegein, The Netherlands — 5University of Surrey, Guildford, UK
The resonant circular photogalvanic effect is observed in wurtzite (0001)-oriented GaN/AlGaN heterojunction excited by infrared radiation. The current is induced by angular momentum transfer of photons to the photoexcited electrons at resonant intersubband optical transitions. The signal reverses upon the reversal of the radiation helicity or, at fixed helicity, when the propagation direction of the photons is reversed. Making use of the tunability of the free-electron laser FELIX, we measured the spectral behaviour of the photocurrent in the vicinity of the inter-subband resonance. We observed that the variation of the photon energy results in the change of sign of the photocurrent[1]. This proves that the dominant contribution to the total current is from the asymmetry in momentum distribution of carriers excited in optical transitions. We analyze spin-dependent as well as spin-independent mechanisms giving rise to a resonant photocurrent and demonstrate that, in spite of the weak spin-orbit interaction, the resonant CPGE in GaN is mostly caused by the spin-dependent mechanism.
[1] B. Wittmann, S.D. Ganichev et al., PRB 78, 205435 (2008)