  Electrical conductance through InAs nanowires is relevant for electronic
applications as well as for fundamental quantum experiments. Here we employ
nominally undoped, slightly tapered InAs nanowires to study the diameter
dependence of their conductance. Contacting multiple sections of each wire, we
can study the diameter dependence within individual wires without the need to
compare different nanowire batches. At room temperature we find a
diameter-independent conductivity for diameters larger than 40 nm, indicative
of three-dimensional diffusive transport. For smaller diameters, the resistance
increases considerably, in coincidence with a strong suppression of the
mobility. From an analysis of the effective charge carrier density, we find
indications for a surface accumulation layer.
