We report on nanoelectronic device applications of a nonalloyed contact structure which utilizes a surface layer of low-temperature grown GaAs as a chemically stable surface. In contrast to typical ex situ ohmic contacts formed on n-type semiconductors such as GaAs, this approach can provide uniform contact interfaces which are essentially planar injectors, making them suitable as contacts to shallow devices with overall dimensions below 50 nm. Characterization of the native layers and surfaces coated with self-assembled monolayers of organic molecules provides a picture of the chemical and electronic stability of the layer structures. We have recently developed controlled nanostructures which incorporate metallic nanoclusters, a conjugated organic interface layer, and the chemically stable semiconductor surface layers. These studies indicate that stable nanocontacts (4 nmX4 nm) can be realized with specific contact resistances less than 1 X 10(-6) Ohm cm(2) and maximum current densities (1 X 10(6) A/cm(2)) comparable to those observed in high quality large area contacts. The ability to form stable, low resistance interfaces between metallic nanoclusters and semiconductor device layers using ex situ processing allows chemical self-assembly techniques to be utilized to form interesting nanoscale semiconductor devices. This article will describe the surface and nanocontact characterization results, and will discuss device applications and novel techniques for patterning close-packed arrays of nanocontacts and for imaging the resulting structures. (C) 1999 American Vacuum Society. [S0734-211X(99)05504-3].
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