Multiscale-Multiphysics Simulation of Nanostructured Devices: the TiberCAD Project

Abstract

The TIBERCAD project [1] is aimed at the implementation of a device simulator which captures the most important physical concepts encountered in present and emerging electronic and optoelectronic devices. On the one hand the down-scaling of device dimensions requires the inclusion of more advanced quantum mechanical concepts which go beyond classical transport theories. On the other hand, functionality of new emerging devices is based both on electrons/holes, and other quasi-particles such as excitons, polaritons, etc. Usually the active part of a device which needs a more elaborate and careful treatment is small compared to the overall simulation domain. The computational cost of the more accurate model however forbids its application to the whole domain, especially when using atomistic approaches. TIBERCAD implements the following physical models: (a) A structural model that allows to calculate strain and shape deformation of lattice mismatched heterostructures based on linear elasticity theory of solids, assuming pseudomorphic interfaces between different materials [2]. External mechanical forces can be included in the simulation. (b) Quantum-mechanical models to calculate eigenstates of confined particles based on the envelope function approximation including single-band and multiband k . p approach. We solve a stationary Schrodinger equation and obtain energy spectrum, particle density and probabilities of optical transitions [3]. (c) Semi-classical transport models that consider electrons, holes and excitons. Transport is treated in the drift-diffusion approximation. The electrochemical potentials are used as dependent variables such that the particle flux is equal to the gradient of a driving potential multiplied by a particle conductivity: φ