Regensburg 2016 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Silicon-based Semiconductors II

HL 39.4: Vortrag

Dienstag, 8. März 2016, 15:30–15:45, H14

Disentangling Surface from Bulk Conductivity by Distance-dependent Four-Probe Transport Measurements Combined with an Analytical Conductance Model — •Sven Just¹, Helmut Soltner², Stefan Korte¹, Vasily Cherepanov¹, and Bert Voigtländer¹ — ¹Peter Grünberg Institut (PGI-3) and JARA-FIT, Forschungszentrum Jülich — ²Central Institute for Engineering, Electronics and Analytics (ZEA-1), Forschungszentrum Jülich

Distance-dependent four-probe measurements performed with a multi-tip scanning tunneling microscope (STM) allow to distinguish between 2D and 3D charge transport channels. In combination with a conductance model for mixed 2D-3D geometries, a disentanglement of surface transport from bulk contributions and a determination of the surface conductivity is possible. Often a very simple parallel circuit model of surface and bulk is used, but it has a very limited applicability due to the rough approximation of only two layers. So, an analytical model for charge transport in N layers is derived from the solution of Poisson’s equation, which e.g. can be used for semiconductors in combination with a calculation of the near-surface band-bending to model very precisely the measured four-point resistance on the surface. By applying this model to published data on Ge(001), Si(100) and Si(111) with different doping concentrations, the surface conductivity of these materials can be determined without any further needs of special sample preparation. Furthermore, this generic approach for determining surface conductivity can be easily applied to other material systems, e.g. to topological insulators.