Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 63: Ultrakurzzeitph
änomene
HL 63.3: Vortrag
Mittwoch, 9. März 2005, 11:15–11:30, TU P-N201
Observation of THz collective oscillations of ballistic electrons in wide heterostructure potential wells — •M. Betz1, M. Eckardt2, A. Schwanhäußer2, S. Trumm1, F. Sotier1,3, L. Robledo2, S. Malzer2, T. Müller4, K. Unterrainer4, A. Leitenstorfer1,3 und G. H. Döhler2 — 1Physik-Department E11, TU München — 2Institut für technische Physik, Universität Erlangen — 3Fachbereich Physik, Universität Konstanz — 4Institut für Festkörperelektronik, Universität Wien
Parabolic shaped potential wells of a width between 120 nm and 250 nm are defined in a band gap engineered p+-n-p+ heterostructure. After femtosecond photoinjection of carriers near the boundary of the well, electrons are found to coherently oscillate across the well with the classical harmonic oscillator frequency of a few THz instead of performing the intuitively expected unidirectional relaxation towards the bottom of the well. Most strikingly, the coherence of this periodic electron motion is maintained despite multiple phonon scattering events. This novel transport is predicted by detailed Monte Carlo simulations and verified analyzing the femtosecond transmission of the heterostructure as well as by directly detecting the THz radiation emitted by the oscillating electron-hole dipole. Decreasing the well width, this semi-classical ballistic transport regime is expected to converge towards a quantum-beat regime.