Berlin 2008 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 33: III-V semiconductors II
HL 33.14: Talk
Wednesday, February 27, 2008, 18:00–18:15, EW 201
Manipulation of charge on a single donor atom by Scanning Tunneling Microscopy — •K. Teichmann1, M. Wenderoth1, S. Loth1, R.G. Ulbrich1, J.K. Garlef2, A.P. Wijnheijmer2, and P.M. Koenraad2 — 1IV. Phys. Inst. Georg-August-Universität Göttingen — 2PSN, Eindhoven University of Technology, the Netherlands
We investigated Silicon donors in highly doped GaAs by spatially resolved Scanning Tunneling Spectroscopy at 6 K. Recently it was shown by Feenstra [1], that the shape of the tip has a strong influence of the extension of the tip induced bend bending (TIBB) in the semiconductor. Sharp tips produce a lateral extension of TIBB in the semiconductor within the range of nanometers. The charge of an individual impurity can be manipulated by the TIBB in the following way: Donors, away from the tip, will be neutral, as the thermal energy at 6K is much smaller than the ionisation energy of the donor. The bands and the donor energy levels are lifted for positive sample voltage. At a certain amout of TIBB the donor ground state is lifted above the onset of the conduction band and the donor will be ionised. In the measurement the ionisation of the donor is seen as a peak in the dI/dV signal. In spatially resolved dI/dV maps the signal has a ring like structure. For higher applied voltages the diameter of the ring increases. By comparing the calculated TIBB and the voltage dependence of the lateral displacement of the measured peak a value of about 150 meV for the donor level can be extracted. This work was supported by DFG SFB 602 and DFG SPP 1285.
[1] R. M. Feenstra, J. Vac. Sci. Technol. B21(5) 2080 (2003)