Nanowire-based high-performance electronics. Nanowires are single-crystals with diameters of a few nanometers and lengths of a few to hundreds of micrometers. Here we are interested in nanowires that are not fabricated from planar substrates through lithography and etching processes, but ones that are grown from a chemical synthesis process. These one-dimensional structures exhibit excellent electrical, optical and material properties due to the reduced dimensionality and the near-perfect crystal structure, and can lead to a number of device applications. In the past, we have shown that high-performance nanowire transistors can be fabricated on diverse substrates including glass and plastics (Dattoli EDL 2009, Dattoli Nano Lett. 2007, Wan Nano Lett. 2006). Our simulation and experimental results have also verified that nanowire density fluctuations among different devices can be controlled and may not be relevant in practical circuits. Such devices are potentially suitable for a number of applications including flexible and transparent electronics. Currently, we focus on high-performance, vertical nanowire transistors and tunneling devices that can be directly integrated on existing Si substrates to achieve very high function density.
Nanowire optoelectronic devices.
The nanowire system allows different materials to be heterogeneously integrated with very clean interfaces. For example, we demonstrated high-yield growth of Ge nanowires epitaxially on Si with undetectable intermixing and interface defects. Besides being used as electronic devices such as vertical transistors, the Ge nanowires show excellent response to IR (e.g. at 1.55um) with extremely low dark currents. This approach allows high-performance optical modulators to be directly integrated with high-performance electronic devices which allow efficient optical communication. Currently, we are studying scaling of the modulator performance and improving the modulation speed.