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Jeudi 17 février 2010, 16h00
Amphi Boreau, Esc C, 2ème etage
Quasi one-dimensional transport in GaAs/AlGaAs core-shell nanowires
D. Lucot
Laboratoire de Photonique et de Nanostructures – CNRS, Route de Nozay, 91460 Marcoussis, France
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Radial core-shell nanowires (NWs) attract increasing interest for their use in potential applications as well as for studying one dimensional (1D) physics. With its well-established properties in 2D heterostructures and intrinsically high electron mobility, GaAs/AlGaAs system is of particular interest to realize core-shell NW. Here, we discuss the controlled growth and electrical measurements of single vertical GaAs/AlGaAs core/shell nanowires with a radial modulation doping.
At low temperature (1K<T<50K) transport measurements show a nonohmic behavior of the conductance at zero bias, with temperature and voltage dc-bias dependences consistent with power laws, as expected for a quasi-1D system. Moreover, a negative magneto-resistance indicative of weak localization (WL) was observed and the temperature dependence of the extracted phase coherence length is consistent with a decoherence mechanism governed by electron-electron interaction. At lower temperature (T<1K), we observe an unexpected strong increase of the resistance whose amplitude is not compatible with standard interference effect (i.e. WL). Furthermore, a magnetic field as small as 100mT is strong enough to suppress the resistance increase and bring back the system to the intermediate temperature state. At the same time the differential conductance shows a strong zero bias features indicating the presence of a gap in the career excitation. Magnetic field anisotropy is also presented.