Interface and contact structures for nanoelectronic devices using assemblies of metallic nanoclusters,conjugated organic molecules and chemically stable semiconductor layers

Self-assembly (‘building’) approaches can provide well-controlled structures and assemblies at the nanometer scale, but typically do not provide the specific structures or functionalities required for robust nanoelectronic circuits. One approach to realize high-density nanoelectronic circuits is to combine self-assembly techniques with more conventional semiconductor device and circuit approaches (‘chiseling`) in order to provide suitable functionality and arbitrary circuit functions. An interesting challenge is to find approaches where these techniques can be combined to realize suitable device structures. This paper describes recent work which combines self-assembly techniques involving metal nanoclusters and conjugated organic molecules with semiconductor interface and device structures to form structures of interest for nanoelectronics. One key requirement for this approach is the availability of a chemically stable semiconductor surface layer, which can provide a low-resistance interface between the metallic nanostructure and the semiconductor device layers following room-temperature, ex situ processing. As an illustration of the structures which can be realized, we describe a nanometer-scale ohmic contact to n-type GaAs which utilizes low-temperature-grown GaAs as the chemically stable interface layer. Contact structures have been realized using both isolated (sparse) clusters and using close-packed arrays of clusters on the surface. The low-resistance contacts between the nanoclusters and the semiconductor device layers indicates that relatively low surface barriers and high doping densities have been achieved in these ex situ structures. The general conduction model for this contact structure is described in terms of the interface electrical properties and the contributions from the various components are discussed.