• Nagarajan, Soundarya
• Trommer, Jens
• König, Dirk
• Ratschinski, Ingmar
• Smith, Sean C.
• Hiller, Daniel
• Mikolajick, Thomas

Abstract

<p>Doping silicon on the nanoscale by the intentional introduction of impurities into the intrinsic semiconductor suffers from effects such as dopant deactivation, random dopant fluctuations, out-diffusion, and mobility degradation. This paper presents the first experimental proof that doping of silicon nanowires can also be achieved via the purposeful addition of aluminium-induced acceptor states to the SiO₂ shell around a silicon nanowire channel. It is shown that modulation doping lowers the overall resistance of silicon nanowires with nickel silicide Schottky contacts by up to six orders of magnitude. The effect is consistently observed for various channel geometries and systematically studied as a function of Al₂O₃ content during fabrication. The transfer length method is used to separate the effects on the channel conductivity from that on the barriers. A silicon resistivity is achieved as low as 0.04–0.06 Ω ·cm in the nominal undoped material. In addition, the specific contact resistivity is also strongly influenced by the modulation doping and reduced down to 3.5E-7 Ω · cm², which relates to lowering the effective Schottky barrier to 0.09 eV. This alternative doping method has the potential to overcome the issues associated with doping and contact formation on the nanoscale.</p>

Topics

• impedance spectroscopy
• nickel
• resistivity
• mobility
• aluminium
• Silicon
• random
• silicide
• intrinsic semiconductor