3.4.1.3 Quantity Definition

All quantity types are described by a single structure. An instance of this structure describes a single quantity and includes:

• The quantity and class identifier (see Section 3.4.1.1).
• The scope of the quantity.
• A pointer to the corresponding device structure as well as the number of the segment or boundary in case of a segment or boundary quantity, respectively.
• A description and a name for output and debugging purposes.
• A pointer to the corresponding properties structure (see Section 3.4.1.1).
• Some additional information to communicate with the PIF-Libraries.
• The grid the quantity is defined on. It is used only in case of segment or boundary quantities.
• The values (see Section 3.4.1.2).
• Maximum and minimum values define the range of reasonable values for the quantity. This information is used during the Newton iteration to ensure that, for instance, the temperature stays positive.
• For unit handling a lot of information is needed. This information is, however, not stored within the quantity structure. During the initialization phase when quantities are read from the input libraries they are scaled to the internal unit associated with the unit class of the actual quantity type (see Section 3.4.1.1). The scaling factor is implicitly given by the internal unit associated to the unit class of the quantity type.
• Information is stored which depends on the quantity type, e.g., the charge state of carrier quantities or the impurity number and the doping material for impurity quantities.
• Each quantity allows to store so called old values. Old values are written after each successful iteration. In case of a unsuccessful iteration, the old values which are the result of the previous iteration can be loaded. Additionally, update values and the residuum values can be stored to monitor the progress of the Newton iteration process.

Fig. 3.5 shows the quantity structure and the important cross references to the quantity type and the quantity values.

Figure 3.5: The quantity structure.