Three programs have been developed for the simulation of semiconductor nanostructures in quasi-equilibrium conditions in one-, two-, and three-dimensional domains (NANOTCAD1D, NANOTCAD2D, NANOTCAD3D, respectively). All codes are based on the solution of the many-body Schrodinger equation with density functional theory, local density approximation, and allow subdivide the domain in several regions with different types of quantum confinement, providing a reasonable level of flexibility. In addition, NANOTCAD2D also allows simulating ballistic FET both in the III-V and in the Si-SiO2 material system.
During the project duration such codes have allowed to simulate several nanoelectronic devices fabricated within and outside the project, and to gain important insights into the transport mechanisms of such devices.
Particularly interesting results have been obtained in the simulation of quantum dot flash memories, both in the silicon-silicon oxide and in the AlGaAs-InGaAs material systems, of single electron transistors, of silicon-germanium quantum wires and of ballistic field effect transistors.
With respect to initial project objectives, several additional results have been obtained. Indeed, the simulation of nanoscale field effect transistors was not present among original objectives, but was included in the course of the project since after the first year it was very clear that the formalism and the tools developed for other ballistic devices such as quantum point contacts could be easily extended to include FETs. In addition, a model for mesoscopic transport in the presence of decoherence, that was not an original objective of the project, was developed in order to obtain a better agreement with experiments as far as the simulation of transport in coherent or quasi-coherent devices is concerned. On the other hand, the three-dimensional codes are not as fast as initially expected. This aspect actually limits the possibility of using them as a design tool, since it makes a detailed exploration of the design space unpractical.
Sinergy with other european and national projects has been very fruitful for access to experimental data, in particular with the EU project ADAMANT, aimed at the development of silicon nanocrystal memories, and mainly focused on large scale fabrication and reliability aspects, and with the Italian Ministry of Research project "Single Electron Devices".
If nanotechnology will acquire industrial and economic relevance, it will strongly depend for its development on reliable Computer Aided Design tools, in the same way as Microelectronics relies upon TCAD tools. In that case, a broad basis of expertise in the development of CAD tools for nanotechnology - firmly established in Europe - would represent a real competitive advantage, with significant impact in terms of economic development and employment. NANOTCAD codes are tools for research and prototyping, but we believe their development has helped creating the necessary expertise on which a possible industrially oriented successor of the NANOTCAD project could be based.