User Model Development with the C-Interpreter : User Model Development with the C-Interpreter

Requires: Blaze/C-Interpreter
Minimum Versions: Atlas 5.22.1.R

This example demonstrates the use of the C-Interpreter to develop user defined material parameters and models for AlGaAs/GaAs HEMT simulation. Here the interpreter is used to prototype a composition dependent electron mobility model for AlGaAs. The interpreted function in this case corresponds to the built-in model for AlGaAs. The two can be compared. The example consists of the following parts:

  • Construction of the device and the grid using Atlas syntax
  • Specification of material regions including a graded AlGaAs heterojunction
  • Definition of electrodes, doping, material and models parameters
  • Use of a C-Interpreter function for composition and doping dependent electron mobility
  • Simulation of Id-Vds characteristic
  • Display of the results in TonyPlot

In the first part of the input file the device is described using Atlas syntax including mesh, regions and electrodes locations, and doping distribution. The region statements are used to define AlGaAs and GaAs regions. The Al composition fraction (x.composition=0.3) and grading distance are defined here as well.

After the device description, the material statement is used to specify some of the material parameters different from the default values. These are electron and hole SRH lifetimes (capture times) which apply to both GaAs and AlGaAs material regions. In the same statement we indicate that the low field electron mobility as a function of composition and doping will be calculated using the C-Interpreter. The name of the function and the name of the corresponding file in which this function is described are specified as a parameter f.conmun=hemtex01_interp.lib in the material statement. Additionally, the alignment parameter is specified which defines the band offset between the conduction and valance bands. The value of 0.6 sets 60% of the step to the conduction band.

The model statement is used to specify the following set of models: band-gap narrowing, field dependent mobility, and Shockley-Read-Hall recombination. The two carrier transport model is specified here by the parameter carriers=2. The contact statement is used to set the workfunction at the Schottky gate electrode.

The solution procedure begins from the initial solution at zero bias or thermodynamic equilibrium. The structure of the device at zero bias is displayed using TonyPlot. For the subsequent simulation, the combined Gummel-Newton iteration method is specified in the method statement. The output statement is used to include additional parameters in the output structure file: conduction and valence band potentials, and electron and hole mobilities. The gate bias is then ramped to -0.6V. For this gate bias the Id-Vd characteristic is calculated by sweeping the drain voltage up to 5V. The results of simulation are saved in the log file and then displayed using TonyPlot.

To load and run this example, select the Load example button in DeckBuild. This will copy the input file and any support files to your current working directory. Select the run button to execute the example.