Ion Implanted GaAs MESFET Fabrication and Vt Test : Ion Implanted GaAs MESFET Fabrication and Vt Test

Requires: SSuprem 4/DevEdit/Blaze
Minimum Versions: Atlas 5.24.1.R

This example demonstrates fabrication and electrical analysis of a MESFET structure using the FLASH module of Athena and the Blaze capability of Atlas. The example uses DEVEDIT at various points in the process to optimize the grid. The example shows:

  • MESFET fabrication using FLASH
  • Re-meshing of structure in DEVEDIT
  • Setting of device parameters for electrical simulation
  • Electrical simulation of an Id/Vgs curve

This example starts by interfacing Athena and DEVEDIT to provide a GaAs MESFET structure using silicon and beryllium implants. Details of using FLASH can be found in the ATHENA_FLASH examples section.

It is necessary to set contact workfunctions for every Schottky contact in each Atlas input file. The command contact name=gate work=4.87 is used to set the gate workfunction. Source and drain contacts are assumed to be ohmic. Users should note that this contact statement is necessary even though the material Titanium was used in the Athena simulation. Atlas does not recognize different metals, and the properties of different metal regions are not transferred from Athena to Atlas. Atlas calculates the barrier height of a Schottky barrier in the following mannor:

barrier height = (metal work function - semiconductor electron affinity).

Care should be taken to ensure the appropriate barrier height is chosen.

Low lifetimes typical of GaAs are set in the material statement. The models statement is used to specify appropriate models within the simulation. The fldmob parameter turns on the electric field dependent mobility. conmob specifies the concentration dependent mobility. These values are taken from a look-up table and exist only for room temperature.

The solution sequence for MESFET threshold voltage is first to obtain the initial solution at zero bias on all contacts. Then the drain is set to 0.1V. A log file is opened by the log statement to store all terminal characteristics. The final solve statement ramps the gate from zero to -3V. Note that Atlas requires the zero bias solution to be solved first in all cases. Thus the gate voltage should be swept from zero to the value required. If a range of both negative and positive gate voltages is required two sweeps can be done by saving and loading the zero bias solution.

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.