Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 13: Poster 1
HL 13.43: Poster
Monday, March 26, 2007, 15:00–17:30, Poster A
Temperature dependent photocurrent spectroscopy of a single InGaAs quantum dot — •Marc C. Hübner1, Stefan Stufler1, Patrick Ester1, Steffen Michaelis de Vasconcellos1, Artur Zrenner1, and Max Bichler2 — 1Universität Paderborn, Fakultät Naturwissenschaften, Department Physik, Warburger Straße 100, 33098 Paderborn, Germany — 2Walter Schottky Institut, TU München, Am Coulombwall, 85748 Garching, Germany
Semiconductor quantum dots (QDs) exhibit discrete energy levels which can be described as two-level systems if resonant excitation within spectrally narrow regions is applied. Here we present cw excitation-experiments, carried out in a variable temperature setup up to 70 K allowing for investigations of coupling mechanisms to acoustic phonons.
We have measured the photocurrent (PC) of a single InGaAs QD using a tuneable TiSa laser for resonant excitation. If a sufficiently high reverse bias voltage is applied, photogenerated carriers tunnel out of the QD. By tuning the excitation wavelength the spectral absorption of a single QD can be monitored via the PC. Within a limited range, a PC spectrum can be obtained by a sweep of the bias voltage at fixed laser wavelength. Tuning the applied voltage allows us to vary the linewidth, due to changing tunnelling probabilities. Increasing the temperature significantly shifts the transition energies of the QD to the red, extends the boundaries of the PC regime due to enhanced thermionic emission and also shows effect on the Rabi oscillations of the system.