Investigation of factors affecting electrical contacts on single germanium nanowires

Abstract

We report an experimental investigation of the quality of electrical contacts made on single Germanium nanowires (grown using Au catalyst from vapor) using Cr/Au contact pads. The nanowires are single crystalline and have a thin layer of oxide on them. We find that a low specific contact resistivity of 10−6 Ω cm2 can be obtained in nanowires with low resistance and the contact resistance enhances almost linearly with the nanowire resistivity. The metal semiconductor junction shows an ideality factor close to unity. A low barrier height of 0.15 eV can be obtained in nanowires of lower resistivities which increase to nearly 0.3 eV for nanowires of higher resistivity. The experiments were carried down to 10 K, and junction characteristics as a function of temperature were evaluated. The specific contact resistance increases on cooling but the barrier shows suppression as the nanowire is cooled, along with an enhancement of the ideality factor. We analyze the temperature dependence of these parameters using a model that assumes a Gaussian distribution of barrier heights in the contact region. The temperature dependence predicted by the model was observed, and the relevant parameters were obtained from the data.