Ballistic transport in semiconductor

nanostructures: From quasi-classical oscillations

to novel THz-emitters

G H DÖHLER^1,2, M ECKARDT², A SCHWANHÄUßER², F RENNER²,

S MALZER^1,2, S TRUMM³, M BETZ³, F SOTIER^3,4, A LEITENSTORFER^3,4,

G LOATA⁵, T LÖFFLER⁵, H ROSKOS⁵, T MÜLLER⁶, K UNTERRAINER⁶,

D DRISCOLL⁷, M HANSON⁷ and A C GOSSARD⁷

¹Max-Planck-Research Group of Optics, Information and Photonics,

Günther-Scharowski-Strasse 1, Bau 24, University of Erlangen, 91058 Erlangen, Germany

²Institute of Technical Physics I, Erwin-Rommel-Strasse 1, University of Erlangen,

91058 Erlangen, Germany

³Physik-Department E 11, Technische Universität München, 85748 Garching,

Germany

⁴Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany

⁵Institute of Physics, Johann Wolfgang Goethe University, Max-von-Laue-Str. 1,

60438 Frankfurt, Germany

⁶Institut für Festkörperelektronik, Technische Universität Wien, Vienna, Austria

⁷Materials Department, University of California, Santa Barbara, CA 93106, USA

E-mail: dohler@physik.uni-erlangen.de

Abstract. By suitable design it is possible to achieve quasi-ballistic transport in

semiconductor nanostructures over times up to the ps-range. Monte-Carlo

simulations reveal that under these conditions phase-coherent real-space

oscillations of an electron ensemble, generated by fs-pulses become possible in

wide potential wells. Using a two-color pump-and-probe technique we have been

able to observe this new phenomenon in excellent agreement with the theoretical

predictions. Apart from its fundamental significance, ballistic transport in

nanostructures can also be used for high-efficiency coherent THz-sources. The

concept of these THz-emitters and its experimental confirmation will also be

presented.

Keywords. Ultrashort laser pulses; semiconductor nanostructures;

ballistic transport.

PACS Nos 42.65.Re; 73.23.Ad; 73.50.Fq; 73.50.Gr; 42.65.Re