Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots and wires: Optical properties I

HL 39.8: Vortrag

Donnerstag, 4. April 2019, 11:30–11:45, H34

Ultrasensitive, high spectral resolution photocurrent detection of QDs excitons — •Sebastian Krehs, Alex Widhalm, Björn Jonas, Nand Lal Sharma, Dirk Reuter, and Artur Zrenner — Physics Department, University of Paderborn, Warburger Str. 100, Paderborn

In optical experiments on single quantum dots the exciton ground state transition appears as a two-level system with a lifetime limited linewidth of a few µeV. In contrast to resonance fluorescence, photocurrent (PC) spectroscopy is a quantitative method to read out the occupancy of the QD. In the past PC detection was limited to a regime with high tunneling rates and elevated excitation powers, which results in PC in the pA-range. Therefore the linewidth of QD excitons, as observed in the PC measurements suffered from lifetime and power broadening. Refined PC detection enabled us to improve its sensitivity down to the fA-range. This allows us to investigate the linewidth of QDs at exceptionally low tunneling rates and at very low excitation powers.

For this work we have fabricated Schottky photodiodes with embedded high quality MBE grown QDs. We have been able to demonstrate exciton ground state linewidths as low as 1.62 µeV in the low tunneling regime. Our results are close to the Fourier transform limit of InAs/GaAs QD systems, as shown by Kuhlmann et al. using resonance fluorescence [1].

[1] A.V. Kuhlmann et al. Nature Physics 9, 570-575 (2013).