AlGaAs/GaAs HBT Gummel Plot Simulation : AlGaAs/GaAs HBT Gummel Plot Simulation

Requires: Blaze
Minimum Versions: Atlas 5.22.1.R

This example demonstrates the simulation of an AlGaAs/GaAs HBT to extract Ic and Ib versus Vbe and plots the bipolar gain. It shows:

  • Device formation using Atlas syntax
  • Specification of s graded AlGaAs composition fraction
  • Selection of models for AlGaAs and GaAs
  • DC simulation for Ic and Ib versus Vbe

As in the previous example the majority of this example is similar to the silicon bipolar Gummel plot example described in the BJT section. This description will focus on specific GaAs and AlGaAs syntax. More details on various types of bipolar simulation can be found in the BJT examples section.

The graded AlGaAs composition fraction is set in the region statement. The parameter x.comp defines the Al content inside the box defined by x.min, x.max, y.min and y.max. Outside the box the Al content falls linearly to zero in a distance grad.*. For more details on grad.* parameters see the Blaze chapter of the manual. Non-linear composition gradings can only be handled by DEVEDIT. Since devices constructed in Atlas syntax must be rectangular, a silicon dioxide region is used to fill the space to the left of the emitter.

The material statement sets the low-field mobilities for the AlGaAs region. Note that the concentration dependent mobility model 'conmob' can only be applied to GaAs so two model statements are used to define the models used in all regions and then just the GaAs regions.

The model statements are used to specify the following set of models: field dependent mobility, SRH and optical recombination. Optical recombination (also known as band to band recombination) is an important effect in III-V devices. The parameter 'optr' sets this model on.

The electrical simulation proceeds as in the silicon BJT example referenced above. Results can be seem in 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.