(a) and (b) SEM micrographs of contacted n-GaAs nanowires with the two different contact systems annealed at various temperatures. (c) SEM image and EDS mapping including the elements Ga, As, Au, and Ge of a thinned GaAs nanowire with Ge/Ni/Ge/Au contacts after annealing at 360 °C. All scale bars are 1 μm.
Correlation coefficients R 2 of a linear best-fit to the I-V plots vs the slope of this best-fit line (resistance) for Pd/Ge/Au contacts annealed at 280 °C (triangles) and Ge/Ni/Ge/Au contacts annealed at 320 °C (squares). The inset shows the low-resistance regime in a more adequate scale.
(Color online) (a) I-V characteristics of the Pd/Ge/Au contacts to n-GaAs nanowires for different contact spacing l1-2, l2-3, l3-4 after contact annealing at 280 °C. The determined contact spacings were 1.2, 2.5, and 4 μm, respectively. The inset shows an optical micrograph of the TLM structure. Scale bar is 20 μm. (b) Total resistance R T derived from (a) as a function of the contact spacing l. The inset shows a SEM micrograph of the investigated nanowire TLM device with a scale bar of 2 μm.
Histograms of the contact resistance R c (a) and specific contact resistance ρ c (b) for the two investigated contact systems Pd/Ge/Au (black columns) and Ge/Ni/Ge/Au (gray columns). In total, TLM data of 12 Pd-based and 4 Ni-based devices was analyzed.
Parameters extracted from the measurements of the TLM and two point structures with Ge/Ni/Ge/Au and Pd/Ge/Au contacts to n-GaAs nanowires.
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