Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 49: Poster: Nanostructures on Surfaces I

O 49.21: Poster

Dienstag, 13. März 2018, 18:15–20:30, Poster A

Controlling telegraph noise in a few donor system by laser illumination — •Ole Bunjes, Philipp Kloth, Judith von der Haar, and Martin Wenderoth — IV. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

Extending a low-temperature Scanning Tunneling Microscope with optical excitation, we have investigated the effect of laser-induced minority charge carriers on temporal charge fluctuations within the tip-induced space charge region (SCR) on the (110) surface of n-doped GaAs. Discrete charging events in GaAs cause the tunneling current to switch abruptly between well-defined values [1], a signature referred to as telegraph signal. We investigated the temporal characteristic of the underlying single-electron charging events with a spatial resolution on the atomic scale by recording a time series of the tunneling current at every tip position. We studied the variation of the telegraph signal in the presence of laser-induced free charge carriers in the SCR. Reduction of the current*s noise originating in the telegraph signal is found for small but non-vanishing hole concentrations, using the tunneling current as control parameter [2]. We attribute the reduction of the telegraphic step height to the photo-generated low-density hole gas that homogenizes the potential landscape at the sample surface. We acknowledge the financial support by the SFB1073 C04. [1] K. Teichmann et al., Nano Lett. 11, 3538-3542 (2011) [2] P. Kloth et al., Nat. Commun. 7, 10108 (2016)