Lateral nanofabrication has already reached the 20-30 nm range, allowing the demonstration of new physical effects such as ballistic transport, quantum interference phenomena, resonant tunneling through quantum dots and single electronics. This has been studied in LATMIC (3043). The aim in LATMIC II is to push the fabrication of sophisticated structures down to 10 nm, to fabricate and study transport in nanostructures integrating some of the above-mentioned effects, and to study the temperature limits which can be reached in single electronics in III-V semiconductors.
Research is being carried out in order to push the nanofabrication in III-V semiconductors down to 10 nm and below. This ultrasmall fabrication will be used to study fundamental transport properties in low dimensionality structures, including the integration of ballistic and quantum interference effects, and single electron electronics and it competition with 0-dimension resonant tunnelling.
50 nm nanolithography has been demonstrated, using either organic polymethyl methacrylate (PMMA) resists or inorganic fluorides. Among the fluorides, epitaxial calcium strontium fluoride has been obtained and optimized for lithography. The dry etching capability at a small scale has now reached dimensions as small as 20 nm. Alloy mixing using surface induced diffusion has been shown to be strongly strain dependent, and this will be used for sub-10 nm structures. Results on transport properties of these nanostructures cover the different areas of resonant tunnelling through quantum dots, single electron transport and Coulomb blockade, both from the theoretical and experimental sides.
Further results involve:
a transport mechanism study in single electron effect transistors;
demonstration of quantum Hall effect in 3-dimensional in a superlattice;
an experimental investigation of a parallel split gate device;
the observation of persistent currents in a single loop.
APPROACH AND METHODS
The nanofabrication will use new approaches in ultrahigh resolution electron-beam lithography, and associated etching, metal deposition or alloy mixing techniques. X-ray nanolithography, with a potential application to a quick reproduction of small features, will be developed in order to explore its resolution limit.
Optimisation of nanometre-scale structures will include a reduction of the size fluctuations, the introduction of independent control of all dimensions for fundamental studies, and the use of composition-induced high confinement energies allowing single electron effects at temperatures higher than that of liquid helium. Optical characterisation (extremely sensitive to fluctuation and confinement) will be used, as well as transport characterisation.
This ultra-small fabrication capability will then be used to study fundamental transport properties in low dimensionality structures at low temperatures, including new approaches such as an independent size and carrier concentration control, and the integration of ballistic injection and quantum interference effects. Single electron electronics will also be studied, as well as its temperature limits and competition with zero-dimensional quantum resonant tunelling effects on the basis of coupled experimental and theoretical studies.
These objectives will be reached through already established interactions of laboratories with state-of-the-art fabrication technologies and established competences in the physics of nanostructures.
The high-resolution lithography and etching technology developed will be used throughout the European community for the application to ultra-small devices and high integration. The new physics developped can be the basis of further developments of microelectronics.
CB2 3RF Cambridge
EX4 4QJ Exeter