Regensburg 2010 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 37: Quantum Dots and Wires: Optical Properties III
HL 37.5: Talk
Wednesday, March 24, 2010, 10:30–10:45, H15
Intraband resonances of GaAs/InAs quantum dots detected via photo induced current changes — •Boris Eichenberg1, Heiko Wunderlich1, Sabine Dobmann1, Alois Seilmeier1, Vadim Yu. Panevin2, Leonid E. Vorobjev2, Dmitry A. Firsov2, and Alexander A. Tonkikh3 — 1Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth, Deutschland — 2St. Petersburg State Polytechnic University, St. Petersburg 195251, Russia — 3Ioffe Physico-Technical Institute, St. Petersburg 194021, Russia
The investigation of intraband (IB) transitions in semiconductor quantum dots (QD) via fourier transform infrared (FTIR) spectroscopy often suffers from very low absorption signals due to moderate absorption cross sections and a low dot sheet density. In this contribution we discuss a photocurrent method, which provides clear signals at the frequency positions of IB absorption lines. The QD sample is laterally contacted at the processed surface and biased by several 10V. Current changes due to excitation by intense picosecond mid infrared laser pulses monitor the IB transitions. Enhanced current signals are observed at frequencies of both bound to bound and bound to continuum IB transitions. Data taken at 77K and at 300K on highly doped GaAs/InAs QD samples, in which up to five QD levels are occupied, are presented. This technique provides interlevel spectra of QDs in the mid infrared with a considerably improved signal to noise ratio compared to FTIR measurements. The experimentally observed IB transition frequencies nicely agree with those from calculated QD levels.