Polarization Charge Analysis

ganfetex18.in : Polarization Charge Analysis

Requires: Victory Device
Minimum Versions: Victory Device 1.14.1.R

This example demonstrates the interaction between polarization charges, surface states, cap layer thickness and Al composition in AlGaN/GaN HFETs.

By default Victory Device run on just one processor. To ensure better perfomance on your computer the following simulation condition simflags="-P all" could be specidied in the go line starting Victory Device. This means that all processors available will be used. If you want to use a smaller number of processors you can substitute "all" with a desired number, e.g. simflags="-P 4".

The input deck vdex06.in uses dbinternal to obtain the channel charge density (i.e 2DEG) for each of the saved structure files. It does this using the file vdex06_aux_0.in and vdex06_aux_1.in. The advantage of using dbinternal is that the data file containing the charge densities can be plotted using TonyPlot . These charge densities are plotted against the cap layer thickness and Al composition in AlGaN Cap layer.

The input deck containing the actual description of the devices is found in ganfetex01_aux_0.in and ganfetex01_aux_0.in.

Victory device is a 2D and 3D device simulator.In this example we demonstrate the use of Victory Device in 2D mode.

The Victorydevice input deck consists of the following parts:

  • Construction of the device and the grid using victorydevice syntax
  • Specification of material regions
  • models, interface charge and interface trap parameters
  • Extraction of the 2DEG.

In the first part of the input deck (ganfetex01_aux_0.in) the device is described using Victorydevice syntax, including mesh, regions and electrodes locations. The REGION statements are used to define AlGaN and GaN regions. The Al composition fraction (x.composition=0.27) is defined here as well. After the device description, the MODEL statement is used to specify the built-in polarization model set by specifying POLARIZATION for spontaneous polarization and CALC.STRAIN for piezoelectric polarization. PCH.INS and PCH.ELEC are set in order to allow charges at the interface between AlGaN and Oxide (pch.ins) and between GaN and conductor at the bottom of the structure (pch.elec).

Next the SOLVE statement is used to obtain a zero biased solution. The SAVE statement is used to save this solution for perform extraction of the 2DEG.

In the second part of the input deck we do the same simulation but instead of using the built-in polarization model that calculate the polarization charges as a function of composition, strain and lattice constant for the various materials, we set polarization charges directly using the INTERFACE CHARGE= statement.

2DEG simulation results using the built-in polarization model, manually added charges and measurement taken from the dissertation "High voltage GaN HEMTs with low on-resistance for switching applications" written by Naiqian Zhang UNIVERSITY of CALIFORNIA Santa Barbara September 2002 are compared and show good correlation.

The built-in polarization model being validated, it can be used to perform the same simulation but instead of making variation of cap layer thickness, Al composition is used instead (ganfetex18_aux_1.in). As expected 2DEG increases with Al composition.

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