Semiconductor Nanowires: from Nanoelectronics to Macroelectronics
Medford, MA 02155 USA
This is an abstract
for a presentation given at the
Foresight Conference on Molecular Nanotechnology
Transistors are the fundamental building blocks for modern electronics. The advancement of electronics has been moving towards two extremes in terms of physical scale. Rapid miniaturization of microelectronics according to Moore's law has led to remarkable increases in computing power while at the same time enabling reductions in cost. In parallel, extraordinary progress has also been made in macroelectronics, where electronic devices are distributed yet integrated over large area substrates with sizes measured in square meters. Current macroelectronis are primarily based on amorphous or polycrystalline silicon thin film transistor (TFT) on glass technology. Plastics macroelectronics have attracted considerable interest for macroelectronic substrate due to their light weight, flexibility, shock resistance and low cost. However, it is rather challenging to fabricate high performance transistors on plastic because of low process temperature required. Emerging organic semiconductor TFT technology is intrinsically compatible with plastics but limited by low carrier mobility. Alternative semiconductor materials leading to TFTs with performance comparable to or better than single crystal silicon, along with the ability to process the "active" materials at low temperatures over large area plastic substrates, will not only improve the existing technologies, but also enable new opportunities.
One-dimensional nanostructures represent the smallest dimension for efficient transport and route information carriers, and thus are ideal building blocks for assembly of functional electronic systems. In this regard, semiconductor nanowires represent a particular interesting material system since they can be produced with precisely controlled chemical composition, physical dimension and electronic properties, and can function as both the interconnect and critical device elements. It has recently been demonstrated that individual nanowires can be used to fabricate nanoscale field effect transistors (FETs) with electronic performance comparable to or exceeding that of the highest-quality single-crystal materials. Further more, functional logic gates and computational circuits have also been assembled. These nanocircuits promise to push the Moore's law to the ultimate limit (molecular level) with unprecedented performance. They are, however, currently very difficult to implement for production-scale nanoelectronics due to the complicated and limited scalability of the device fabrication processes used.
In this talk, followed by a brief introduction of nanowire-based nanoelectronics, we present a paradigm shift in nanomaterial-enabled electronics, exploiting nanomaterials not for next generation of nanoelectronics, but for high performance large area macroelectronics on flexible substrate. A new concept of high performance TFTs has been demonstrated on various substrates including plastics. These TFTs have a conducting channel consisting of multiple single crystal nanowires in parallel, or a single crystal nanoribbon, spanning the full distance from source to drain, thus ensuring high carrier mobility. Both p- and n-channel TFTs have been demonstrated with, carrier mobility approaching that of single crystal materials, on-off ratios greater than 107 and subthreshold swing as small as 70 mV per decade. These TFTs have been combined to produce a complementary inverter with a voltage gain of 27. Notably, this TFT fabrication approach dissociates the high temperature processes required to produce high quality semiconductor materials from device substrates: the active semiconductor materials are synthesized separately and subsequently applied to substrates via a solution assembly process, and thus enables a general platform for preparation of high performance semiconductor devices on various substrates over large area. With this technology, low-cost low-temperature processes such as ink-jet printing may be employed to produce flat-panel displays, image sensor arrays as well as a whole new range of flexible, wearable, and disposable computing, storage and communication electronics.
Advanced Research Center, Nanosys Inc.
200 Boston Ave.
Medford, MA 02155 USA
Phone: 617-448-0983 Fax: 781-391-3803