A new route toward semiconductor nanospintronics: highly Mn-doped GaAs nanowires realized by ion-implantation under dynamic annealing conditions.

Institute for Solid State Physics, Jena University, Max-Wien-Platz 1, 07743 Jena, Germany.
Nano Letters (Impact Factor: 13.59). 08/2011; 11(9):3935-40. DOI: 10.1021/nl2021653
Source: PubMed

ABSTRACT We report on highly Mn-doped GaAs nanowires (NWs) of high crystalline quality fabricated by ion beam implantation, a technique that allows doping concentrations beyond the equilibrium solubility limit. We studied two approaches for the preparation of Mn-doped GaAs NWs: First, ion implantation at room temperature with subsequent annealing resulted in polycrystalline NWs and phase segregation of MnAs and GaAs. The second approach was ion implantation at elevated temperatures. In this case, the single-crystallinity of the GaAs NWs was maintained, and crystalline, highly Mn-doped GaAs NWs were obtained. The electrical resistance of such NWs dropped with increasing temperature (activation energy about 70 meV). Corresponding magnetoresistance measurements showed a decrease at low temperatures, indicating paramagnetism. Our findings suggest possibilities for future applications where dense arrays of GaMnAs nanowires may be used as a new kind of magnetic material system.

Download full-text


Available from: Sandeep Kumar, Aug 16, 2015
1 Follower
  • Source
    • "In this work, we concentrate on the higher doped wires. The NW growth and implantation techniques were discussed in detail previously [13]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Nanowires with magnetic doping centers are an exciting candidate for the study of spin physics and proof-of-principle spintronics devices. The required heavy doping can be expected to have a significant impact on the nanowires' electron transport properties. Here, we use thermopower and conductance measurements for transport characterization of Ga0.95Mn0.05As nanowires over a broad temperature range. We determine the carrier type (holes) and concentration and find a sharp increase of the thermopower below temperatures of 120 K that can be qualitatively described by a hopping conduction model. However, the unusually large thermopower suggests that additional mechanisms must be considered as well.
    Journal of Nanotechnology 01/2012; 2012. DOI:10.1155/2012/480813
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We report on temperature-dependent charge transport in heavily doped Mn(+)-implanted GaAs nanowires. The results clearly demonstrate that the transport is governed by temperature-dependent hopping processes, with a crossover between nearest neighbor hopping and Mott variable range hopping at about 180 K. From detailed analysis, we have extracted characteristic hopping energies and corresponding hopping lengths. At low temperatures, a strongly nonlinear conductivity is observed which reflects a modified hopping process driven by the high electric field at large bias.
    Nano Letters 08/2012; 12(9):4838-42. DOI:10.1021/nl302318f · 13.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on the structural and electrical characterizations of MnAs/GaAs hybrid nanowires fabricated by combining selective-area metal--organic vapor phase epitaxy of undoped GaAs nanowires and endotaxial nanoclustering of MnAs. As a result of endotaxy, MnAs nanoclusters are typically embedded in the six ridges of hexagonal GaAs nanowires. However, the MnAs nanoclusters are formed not only at the six ridges, but on the surfaces of six {0\bar{1}1} facets of hexagonal GaAs nanowires, when we decrease the growth temperature from 600 to 400 °C. From the cross-sectional characterizations by transmission electron microscopy, the size and density of the MnAs nanoclusters formed at the top part of the GaAs nanowires are much larger than those formed at the bottom part of the nanowires. Current and voltage characteristics of MnAs/GaAs hybrid nanowires are investigated using two-terminal device structures of free-standing hybrid nanowires. The hybrid nanowires formed on Zn-doped p-type GaAs (111)B substrates show ohmic characteristics, while those formed on Si-doped n-type GaAs (111)B substrates show clear rectifying characteristics. The hybrid nanowires show p-type conductivity possibly owing to the formation of p-type GaAs layers near the nanowire surfaces caused by the thermal diffusion of Mn atoms into GaAs nanowires during the endotaxial nanoclustering of MnAs.
    Japanese Journal of Applied Physics 11/2012; 51(11). DOI:10.1143/JJAP.51.11PE01 · 1.06 Impact Factor
Show more