• TCAD Examples

ledex04.in : Retangular Domain vs. Cylindrical Domain of LED

Requires: Blaze/LED Minimum Versions: Atlas 5.28.1.R

This example demonstrate how the radiative recombination models of LED in 2 dimensional Atlas can be used to analyze the electro-luminescence in rectangular vs. cylindrical domains.

The objective of this example is to obtain and compare the basical LED characteristics such as the I-V-L curve depenenced on the simulation domain. The cylindrical domain characteristics are obtained in the same manner as in the rectangular except the CYLINDRICAL parameter should be set on the MESH statement.

Also for cylindrical analysis only the right half of the X-Y plane should be defined.

There are 7 sections to define the structure, material models, biasing conditions and data extraction of the operational characteristics.

In this example there are two input decks. The first deck specifies the 2D experiment.

Mesh Generation

In the first section of the input file, the unit of the rectangular domain is chosen as [A] with WIDTH parameter of MESH statement. Device size is 3.14*4^2 um2 as 8um diameter, so 12.566 [um] to make the exact Anode Area on top view, set on WIDTH parameter.

Region and Electrode Specification

This section defines a 5 layer GaAs/AlGaAs diode with compositional grading in layers numbered 2 and 5. In region 2 the composition fraction of Al increases from 0.0 at the top to 0.35 at the bottom of the layer. This grading is specified using the X.COMP and GRAD.12 parameters of the REGION statement. Similar definitions are used in the REGION statement for region number 5 .

The ANODE and CATHODE contacts are defined on the top and bottom of the device.

Doping Profiles

Layers 1 and 2 have a P-type doping of 1e18 cm-3. Layer 3 is P-type doped at 1e15 cm-3. Layers 4 and 5 are doped at 2e18 cm-3 N-type. All doping profiles have a uniform distribution within the region.

Material and Models

The MATERIAL statements in this section define parameters for the radiative recombination rate constant, COPT , the low field mobilities, MUN , the satruation velocity, VSAT and the conduction band alignment, ALIGN .

The MODELS statement in this section selects models for Fermi-Dirac statistics, FERM , Auger recombination, AUGER , radiative recombination, OPTR , and Shockley-Read-Hall recombination, SRH .


Many parameters are output to any generated structure files by default. The OUTPUT statement can be specified to include quantities that are not output by default. In this case the conduction band edge energy, CON.BAND , the valence band edge energy, VAL.BAND , various band parameters (e.g. Eg, Nc, Nv etc.), BAND.PARAM , various recombination rates, RECOMB, U.SRH, U.AUG, U.RAD , and the current flowlines, FLOWLINES .

Initial Solution and Bias Ramp

In these sections the bias conditions of the diode are set on various SOLVE statements. Structure files showing the internal conditions of the device are saved at various biases using SAVE statements. The LOG statment is used to capture terminal conditions as well as the integrated radiative and total recombination rates using the PROBE statements.

The second deck performs the cylindrical device analysis. It is instructive to compare the two decks. The second deck is identical to the first one except that the device is defined as a cylindrical device using the CYLINDRICAL parameter of the MESH statement.

Plotting Curves

The I-V curve compared and I-L curve calculated using the EXTRACT statement.

The current flowlines dependency on the device domain and bais point is also shown.

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.

Additional Info:

Input Files
Output Results
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