Formation and characterization of NixInAs/InAs nanowire heterostructures by solid source reaction.

The formation of crystalline NixInAs and NixInAs/InAs/NixInAs heterostructure nanowires by the solid source reaction of InAs nanowires with Ni is reported for the first time. The fundamental kinetics of the Ni/InAs alloying reaction is explored, with the Ni diffusion reported as the rate determining step. The diffusivity of Ni is independent of the nanowire diameter, with an extracted diffusion activation energy of approximately 1 eV/atom. The metallic NixInAs exhibits a modest resistivity of approximately 167 micro omega x cm for diameters >30 nm, with the resistivity increasing as the nanowire diameter is further reduced due to the enhanced surface scattering. The alloying reaction readily enables the fabrication of NixInAs/InAs/NixInAs heterostructure nanowire transistors for which the length of the InAs segment (i.e., channel length) is controllably reduced through subsequent thermal annealing steps, therefore enabling a systematic study of electrical properties as a function of channel length. From the electrical transport studies, an electron mean free path on the order of a few hundred nm is observed for InAs NWs with a unit length normalized, ON-state resistance of approximately 7.5 k omega/microm. This approach presents a route toward the fabrication for high performance InAs nanowire transistors with ohmic nanoscale contacts and low parasitic capacitances and resistances.