Use the Geometric Doping Model to define a dopant distribution in terms of the distance from selected boundaries. This is convenient when specifying distributions which are not easily expressed in terms of the coordinate system. For example, if a profile is defined in terms of the distance from a surface then it may not need to have its expression modified if the geometry is altered. This feature also allows any user defined decay profile away from the selected boundaries, which is suitable for cases where none of the preset decay functions available in the Analytic Doping Model are appropriate.

A default Boundary Selection for Doping Profile is added where the boundaries from which the distance is calculated can be specified.

The configuration of doping is critical in semiconductor modeling. You can visualize doping profiles by clicking the preview buttons before solving the model. Two buttons named as Plot Doping Profile for Selected and Plot Net Doping Profile for All are available both in the toolbar and the context menu. The doping profile will be shown in a separate plot window named as Doping Profile Plot. Note that p-type and n-type domains are shown in red and blue color, respectively.

These settings are the same as for Analytic Doping Model.

Select an option from the Profile away from the boundary list — Gaussian (the default), Linear, Error function (erf), or User defined.

For Gaussian, Linear, or Error function (erf) profiles, select the Impurity type — Acceptor doping (the default) or Donor doping. Then specify the maximum doping concentration of the distribution; this is the concentration of the dopants at the selected boundaries.

For User defined profiles select the Dopant type — Acceptor doping (the default) or Donor doping. Then enter an expression for Define profile as a function of the distance, D, from the boundaries N(D) (SI unit 1/m3). The distance from the selected boundaries is available as variable semi.gdm#.D, which can be used in an expression to define the doping profile. The default expression gives an example of a Gaussian profile defined using this variable.

For the Gaussian, Linear, and Error function (erf) profiles it is necessary to specify the length scale of the profile decay. The Profile section allows the length scale of the profile to be controlled. As with the Analytic Doping Model, the length scale can be controlled either by entering a junction depth or via a profile-specific length scale parameter. See Analytic Doping Model, under Profile for the settings for more details.