Published in Phys. Rev. B 69, 081309 (2004).

Transport limitations in tunneling spectroscopy of Ge(111)c(2x8) surfaces

R. M. Feenstra (a), G. Meyer (b), and K. H. Rieder (c)
(a)Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b)Paul Drude Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany
(c)Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin, Germany


Scanning tunneling spectroscopy is used to study p-type Ge(111)c(2x8) surfaces at temperatures between 7 and 61 K and over a wide range of tunnel currents. The spectral feature arising from Ge rest-atoms is found to shift in voltage with increasing tunnel current. Comparison of the current dependence of the results with electrostatic computations of tip-induced band bending yields poor agreement. A model is discussed in which the observed shift in the rest-atom state arises from an accumulation of nonequilibrium carriers at the surface.

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