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Characterization of InAs/GaAs core-shell nanowires grown on (111) InAs by molecular beam epitaxy


  Jung-Hyun Kang [1]  ,  Yonatan Cohen [1]  ,  Yuval Ronen [1]  ,  Moty Heiblum [1]  ,  Ronit Popovitz-Biro [1]  ,  Hadas Shtrikman [1]  ,  María de la Mata [2]  ,  Jordi Arbiol [3]  
 [1] Weizmann Institute of Science
[2] Institute of de Ciència de Materials de Barcelona
[3] Institució Catalana de Recerca I Estudis Avançats (ICREA)



The substantial interest in InAs nanowires (NWs), as promising objects for one-dimensional quantum transport experiments, is motivated by the combination of their electronic properties which makes them suitable for hosting the theoretically predicted and experimentally measured Majorana fermions.[1, 2] Since the transport in InAs NWs is believed to take place in close vicinity to the surface, controlling the quality of the NW surface is one of the main challenges for growth process optimization. The most efficient method of reducing the influence of the surface states, surface oxides and impurities adhered to the surface is likely to be passivation of the NWs surface by in-situ growth of a shell of different composition.

In this study, we have grown by gold-assisted VLS-MBE high quality, uniform morphology, InAs/GaAs core/shell NWs. This core/shell structure is intriguing in terms of understanding the strain relaxation in such highly mismatched cylindrical system on one hand and on the other hand likely to provide passivated InAs NWs for transport measurements with the possibility of exhibiting conductance steps. We present high resolution transmission electron microscope (HR-TEM) and high angle annular dark field (HAADF) data measured on InAs/GaAs core/shell NWs. The InAs core grown along the [000-1] axis and the surrounding GaAs shell both consisting of pure wurtzite structure, in full epitaxial relationship with each other: (0001)[1100]InAs||(0001)[1100]GaAs. These two crystalline structures have a lattice mismatch of 7.99% (cInAs = 7.00Å, cGaAs = 6.441Å) along the c-growth plane, which would suggest the formation of misfit dislocations in the shell as a relaxation mechanism. [3] We managed to determine the location of the dislocation origin with respect to the compositional interface between the InAs core and GaAs shell and found them to be located at the periphery within the InAs core.



[1] Lutchyn, R. M.; Sau, J. D.; Das Sarma, S. Phys. Rev. Lett., 105, 077001, (2010)

[2] Das, A.; Ronen, Y.; Most, Y.; Oreg, Y.; Heiblum, M. Nat. Phys., 8, 887, (2012)

[3] Popovitz-Biro, R.; Kretinin, A.; Huth P. V.; Shtrikman, H. Cryst. Growth Des, 11, 3858-3865, (2011)