3.3 Implementation of Grids

Minimos-NT is capable of using any kind of grid for device simulation which fulfills the criteria described in Section 2.3. In Minimos-NT a grid is always defined for a complete device. Segment grids refer to the part of the device grid which lies within the volume of the segment. Therefore, boundaries between two adjacent segments describe the grid at the contact area of the segments.

As explained in Section 2.4 Minimos-NT requires only the unstructured neighborhood information for grid representation. Grid elements like faces or volumes as shown in Fig. 2.16 are not of interest to the simulator.

The grid module of the two-dimensional version of Minimos-NT has been designed closely related to the PIF-Libraries. Therefore, only two-dimensional grids like ortho-product and triangular grids could be supported. Grid refinement has only been implemented for these kind of grids. Furthermore, grid refinement is done before simulation during the initialization phase and no refinement during simulation is done. For three-dimensional simulations due to the complexity of tetrahedral grids no inherent grid module has been developed. Moreover, grid refinement of such grids is a complex task which requires adequate external tools [112].

Thus, to support multi-dimensional grids a gridder binding module has been developed. The two-dimensional PIF-support is encapsulated in a separate module which still can be used for two-dimensional simulations. This module is chosen automatically, if PIF-input files are provided. For multi-dimensional simulations a module supporting a native file format has been implemented. External gridder modules can be easily applied by implementing a module. External gridder tools have to offer an interface which allows to read in the unstructured neighborhood information so that the gridder module can set up the internal data structures.