Electrical transport properties of Ge-doped GaN nanowires

• Published in: Nanotechnology 2015-03, Vol.26 (13), p.135704-135704
• Main Authors: Schäfer, M, Günther, M, Länger, C, Müßener, J, Feneberg, M, Uredat, P, Elm, M T, Hille, P, Schörmann, J, Teubert, J, Henning, T, Klar, P J, Eickhoff, M
• Format: Article
• Language: English
• Subjects: Carrier density; charge carrier concentration; Density; Electrical resistivity; electrical transport properties; Emission analysis; gallium nitride; Gallium nitrides; GaN nanowires; micro photoluminescence; molecular beam epitaxy; Nanotechnology; Nanowires; Resistivity; Seebeck coefficient; Temperature dependence
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/26/13/135704

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 × 1018 to 5.5 × 1019 cm−3, well above the Mott density of 1.6 × 1018 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 × 1019 cm−3. The latter was attributed to the simultaneous influence of band filling, band gap renormalization, and strain.