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 structure s and assemblies at the nanometer scale, but typically do not provide the s pecific structures or functionalities required for robust nanoelectronic ci rcuits. One approach to realize high-density nanoelectronic circuits is to combine self-assembly techniques with more conventional semiconductor devic e and circuit approaches ('chiseling') in order to provide suitable functio nality and arbitrary circuit functions. An interesting challenge is to find approaches where these techniques can be combined to realize suitable devi ce structures. This paper describes recent work which combines self-assembl y techniques involving metal nanoclusters and conjugated organic molecules with semiconductor interface and device structures to form structures of in terest for nanoelectronics. One key requirement for this approach is the av ailability of a chemically stable semiconductor surface layer, which can pr ovide 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-temperatur e-grown GaAs as the chemically stable interface layer. Contact structures h ave been realized using both isolated (sparse) clusters and using close-pac ked arrays of clusters on the surface. The low-resistance contacts between the nanoclusters and the semiconductor device layers indicates that relativ ely low surface barriers and high doping densities have been achieved in th ese ex situ structures. The general conduction model for this contact struc ture is described in terms of the interface electrical properties and the c ontributions from the various components are discussed. (C) 2000 Academic P ress.