laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Séminaire 27 septembre 2010

Joseph DUFOULEUR - Walter Schottky Institut (Allemagne)
Transport Measurements in MBE-grown p-doped GaAs Nanowires

Semiconductor nanowires are filamentary crystals with a large aspect ratio and the diameter in the order of the nanometer range. Their study is a rapidly expanding field, due to the expectations that nanoscale object and their associated phenomena offer to basic and applied science. Recently, we have been able to synthesize III-V nanowires without the use of an external catalyst by MBE [1]. The optical properties of the nanowires have shown to be excellent, due to the good crystal quality and purity. By adding Si atoms during the growth, we are able to p-doped those nanowires. The hole-hole interaction being more pronounced than in the case of electron and due to the suppression of hyperfine interaction between the hole and the nuclei of the host material, giving rise to a very long expected spin coherence time, p-doped GaAs NW are a particularly interesting material for the study of carrier-carrier interactions or for the study of quantum dot in spin blockade regime.

Nevertheless, for studies of the electronic transport phenomena in nanowires, controlled doping is an important issue. We will present our latest results in the investigation of doping of catalyst-free MBE grown GaAs nanowires. The doping concentration along a wire is shown to be non-homogeneous. This experiment has enabled us to understand the path by which the dopants incorporate in the nanowire. Taking into account these results, we will present low temperature measurements down to 300 mK. At low temperature, some steps appears in the resistance what we have interpret as a signature of the phase coherence of holes. An estimation of the phase coherence length will be determined and the transport mechanisms will be discussed. This work opens the route for the use of semiconductor GaAs nanowires as quantum nanodevices.


[1A. Fontcuberta i Morral et al., Appl. Phys. Lett. 92, 063112-3 (2008), C. Colombo et al. Phys. Rev. B, 77, 155326 (2008), A. Fontcuberta i Morral et al., Small 4, 899 (2008)

[2J. Dufouleur et al., Nano Lett. 10, 1734–1740 (2010)