GaAs and InAs Nanowires for Ballistic Transport

Tailoring of GaAs and InAs nanowires (NWs) to be suited for measurements of ballistic transport is discussed in this paper. Methods used to avoid imperfections most harmful for the transport properties are described. We consider the imperfections, which frequently occur in III-V NWs: occasional stacking faults, unintentional impurities (like gold atoms originating from the catalyst in the vapor-liquid-solid growth method) and imperfections associated with the NW side facets. Foremost important is obtaining GaAs and InAs NWs, in which either a pure wurtzite or pure zinc-blende structure is enforced, i.e., overcoming the inherent tendency of the two structures to intermix in III-V NWs. Next follows elimination, or at least minimization of the number of incorporated impurities. In InAs NWs, this has been achieved by using low-growth temperature combined with a low-growth rate. Finally, embedding the NWs in an in situ grown shell has provided a robust way for passivation of the surface states and keeping the electrons away from any impurities adhered to the surface.