Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 53: Nanostructures at Surfaces: Other Aspects

O 53.4: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1C

Controlling charge dynamics in a space charge region under optical excitation — •Judith von der Haar, Philipp Kloth, Ole Bunjes, and Martin Wenderoth — IV. Physikalisches Institut, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany

By combining laser excitation and Scanning Tunneling Microscopy we have investigated the charge dynamics of a few donor system at the n-doped GaAs(110) surface. When a STM-tip is positioned close to the GaAs a SCR is induced inside the sample. In equilibrium it is screened by ionized donors at the surface. We force the system out of equilibrium by illuminating the sample and generating free charge carriers. The photo-generated holes can be addressed by tunneling electrons, leading to an additional transport channel. Using the tunnel current as a control parameter we are able to actively change the hole concentration at the surface [1]. The temporal evolution of the photo-generated holes was studied for different laser intensities, tunnel currents and bias voltages using pulsed optical excitation with nanosecond time resolution [2]. This gives access to the screening dynamics of the tip-induced potential. Furthermore, we have measured the charging and discharging processes of single donors. Atomically resolved data proof that the relaxation time depends on the relative depth of the donors to the surface. This work was supported by the DFG via the SFB1073 C04. [1] P. Kloth et al., Nat. Commun. 7, 10108 (2016) [2] P. Kloth et al. A versatile implementation of pulsed optical excitation in Scanning Tunneling Mircroscopy. Rev. Sci. Instr. (acc. 2016)