3D Diode using lifetime killing

diodeex08.in : 3D Diode using lifetime killing

Requires: DevEdit 3D/Device 3D/Giga 3D
Minimum Versions: Atlas 5.28.1.R

A common practice in high power electronics is to vary carrier lifetime across a device by bombarding the region of silicon with particles or introducing gold impurities. This example demonstrates how such an analysis may be performed using device simulation. This example shows:

  • The formation of a 3D diode structure in DEVEDIT3D
  • Device simulation driving the diode into forward bias
  • How to create a 3D plot showing the current crowding effect

The structure is first created by running DEVEDIT3D in batch mode using the command go devedit. DEVEDIT3D performs three functions: creation of the diode topology with the region statement, addition of impurities with the impurity statement and finally creates the mesh for the device simulation by setting various Meshing Parameters options. Further information on these statements may be found in the VWF Interactive Tools User's Manual: Volume 1 .

Only the top left quarter of the complete cell will be simulated as the three quarters are identical. The structure created by DEVEDIT3D contains two different silicon regions which will exhibit different carrier lifetimes during the device simulation.

The completed structure is then piped into the device simulator which is started with the go atlas command. The Atlas syntax is then used to modify the material parameters in the different regions. The material statement is used to specify the electron and hole lifetime in each silicon region. In this example we have made the carrier lifetime 20 times smaller in the region which has undergone a lifetime killing process- region number 1. It is also highly important that the necessary physical models are switched on if the simulation is to be accurate. The model statement is used to switch on the appropriate models for the simulation. In this case the example uses analytic and conmob: the doping and temperature dependent low field mobility model, fldmob: the lateral electric field-dependent mobility model, srh: Shockley-Read-Hall recombination, auger: recombination accounting for high level injection effects, and bgn: band gap narrowing.

In addition, if thermal self heating effects are required in the simulation, an additional parameter lat.temp will be required to cause the simulator to solve the lattice heat flow equation. If this is the case a thermal boundary condition must also be specified using the thermcontact statement. This example uses the cathode electrode, number 2, as the thermal boundary condition and specifies a fixed temperature there of 300 K.

As the solution proceeds all terminal characteristics are saved into a file, with the command log outf=<filename> , which can then be plotted at the end of the simulation. Two simulations are performed in this example, with and without the lattice heating model switched on, both driving the diode into forward bias. TonyPlot is then used to display both of the I-V results on the same plot as well as the change in lattice temperature. When the lattice heating model is turned on the increase in lattice temperature causes a decrease in carrier mobility and thereby a roll-off in current under forward bias.

Note that the user can use TonyPlot3d to plot the 3D mesh and solution files. By displaying the total current density in an isosurface contour plot, the current crowding effect can be seen.

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.