Si–InAs heterojunction p-n diodes were fabricated by growing InAs nanowires in oxide mask openings on silicon substrates. At substrate doping concentrations of 1×1016 and 1×1019 cm−3, conventional diode characteristics were obtained, from which a valence band offset between Si and InAs of 130 meV was extracted. For a substrate doping of 4×1019 cm−3, heterojunction tunnel diode characteristics were obtained showing current densities in the range of 50 kA/cm2 at 0.5 V reverse bias. In addition, in situ doping of the InAs wires was performed using disilane to further boost the tunnel currents up to 100 kA/cm2 at 0.5 V reverse bias for the highest doping ratios.

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We report on in situ doping of InAs nanowires grown by metal-organic vapor-phase epitaxy without any catalyst particles. The effects of various dopant precursors (Si(2)H(6), H(2)S, DETe, CBr(4)) on the nanowire morphology and the axial and radial growth rates are investigated to select dopants that enable control of the conductivity in a broad range and that concomitantly lead to favorable nanowire growth. In addition, the resistivity of individual wires was measured for different gas-phase concentrations of the dopants selected, and the doping density and mobility were extracted. We find that by using Si(2)H(6) axially and radially uniform doping densities up to 7 × 10(19) cm(-3) can be obtained without affecting the morphology or growth rates. For sulfur-doped InAs nanowires, we find that the distribution coefficient depends on the growth conditions, making S doping more difficult to control than Si doping. Moreover, above a critical sulfur gas-phase concentration, compensation takes place, limiting the maximum doping level to 2 × 10(19) cm(-3). Finally, we extract the specific contact resistivity as a function of doping concentration for Ti and Ni contacts.

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