Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots and wires: Optical properties I

HL 39.10: Vortrag

Donnerstag, 4. April 2019, 12:00–12:15, H34

Capacitance-Voltage spectroscopy on Quantum Dots as sensor for trap charge density — •Giang Nam Nguyen1, Alexander Rolf Korsch1, Carsten Ebler1, Marcel Schmidt1, Pia Lochner1,2, Fabian Brinks1,2, Andreas Dirk Wieck1, and Arne Ludwig11Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, Germany — 2Fakultät für Physik and CENIDE, Universität Duisburg-Essen, Germany

Self assembled quantum dots (QDs) act as major candidates for many future quantum devices for which much higher material quality are needed. While disadvantages of non-radiative recombination centers are obvious for optoelectronic devices, fluctuating charges in the environment of QDs lead to spectral wandering or blinking, as the electric field varies randomly and changes the emitter's energy levels by quantum confined Stark effect [1].

A trap charge density sensor using capacitance-voltage (C-V) spectroscopy on QDs embedded in a diode structure is demonstrated. After optically exciting our device at different biases and wavelengths, we find a strongly electric field and photon energy dependent persistent shift of the QDs' charging resonances. We propose a Franz-Keldysh or k-space indirect type of excitation of trap states within the diode. To quantify the according charge trap density, we model the band bending by 1D band structure simulation. For low trap densities we find an excellent agreement with a simple linear dependence, making our device an efficient charge trap density monitor.

[1] J. Houel et al, Phys. Rev. Lett. 108, 107401 (2012)

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