The ongoing miniaturization of semiconductor devices leads to an exponential increase in production cost. The computer simulation of the electrical and thermal characteristics proposes a fast and inexpensive way to check device designs and processes prior to fabrication. Simulation of semiconductor devices can be based on a semi-classical description such as the Boltzmann transport equation. Using the method of moments, sophisticated transport models can be derived.
For very small devices, however, quantum effects come into play and require the solution of the Schroedinger equation or the application of the non-equilibrium Green's function formalism. Alternatively, the Wigner equation can be used which provides a link between the classical and the quantum-mechanical description of carrier transport. These methods, however, are computationally demanding.
At the Institute for Microelectronics, research is undertaken in both directions: On the one hand, classical device simulators need sophisticated models and three-dimensional simulation capabilities to describe the wide range of materials and applications of semiconductor devices. On the other hand, quantum mechanical simulations are used to predict the behavior of advanced quantum devices and to find approximations which can be used for efficient device simulations.