Electrical transport properties of Ge-doped GaN nanowires

The conductivity and charge carrier concentration of single GaN nanowires (NWs) doped with different concentrations of Ge were determined by four-point resistivity and temperature-dependent Seebeck coefficient measurements. We observed high carrier concentrations ranging from 9.1???10 18 to 5.5???10 19 cm ?3 , well above the Mott density of 1.6???10 18 cm ?3 , and conductivities up to 625 S cm ?1 almost independent of the NW diameter. The weak temperature dependence of the conductivity between 2 and 10 K could be assigned to the formation of an impurity band. For the sample with the highest conductivity metallic behaviour was found, indicated by a positive temperature coefficient of the resistivity. The near band edge emission analyzed by micro-photoluminescence spectroscopy showed only a small increase of the peak width up to 70 meV and no spectral shift for carrier concentrations up to 5.5???10 19 cm ?3

M Sch?fer, M G?nther, C L?nger, J M??ener, M Feneberg, P Uredat, M T Elm, P Hille, J Sch?rmann, J Teubert, T Henning, P J Klar and M Eickhoff

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