SiLENSe—software tool for light emitting diode (LED) bandgap engineering

The software tool SiLENSe is offered for simulation of band diagrams and spectra of light emitting and laser diodes (LEDs and LDs) based on Group-III nitrides and other wurtzite materials as well as hybrid structures. Carrier transport model implemented in the software allows simulation of polar, semipolar, and nonpolar structures and accounts for specific features of nitride heterostructures including polarization effects, high density of threading dislocations and Auger recombination. The last one is responsible for the droop of internal quantum efficiency observed in nitride LEDs at moderate and high current densities. SiLENSe provides distribution of critical parameters over the LED heterostructure, including partial (electron and hole) currents, electric field and potential, rate of carrier recombination, and carrier concentrations. The program is capable of calculations for graded-composition heterostructures.

The code provides the following properties of an LED heterostructure:

  • Band diagram of a nitride LED at various biases;
  • Distribution of electron and hole concentrations in the device structure;
  • Electric field distribution;
  • Radiative and non-radiative recombination rates;
  • Current-voltage (I-V) characteristic;
  • Internal light emission efficiency as a function of current density;
  • Wave functions of electrons and holes in a quantum-well active region;
  • Emission and gain spectra of individual quantum wells and the whole diode;
  • Waveguide TE and TM modes*;
  • Threshold and power-current characteristics*.

* these options are available in Laser Edition only

The above information forms a good basis for the LED structure optimization and for development of new light emitting devices.

Supported materials

Band diagram variation with bias for an MQW LED

Figure 1. Band diagram variation with bias for an MQW LED

The SiLENSe package includes a special module for easy specification of materials properties. The default database contains properties of AlInGaN and ZnMgO alloys. The user can edit this database and even add new materials. Recently, the software was successfully applied to analysis of 808 nm AlInGaAs laser.

 

Examples of simulations

To illustrate SiLENSe capabilities we suggest for you attention the following simulation examples:

Example 1 Blue SQW and MQW LED heterostructures

Example 2 UV Laser Diode on sapphire substrate

Example 3 Hybrid II-O/III-N LED (ZnO-based LED)

Example 4 Polar/Semipolar/Nonpolar Heterostructures

Some of these example are accompanied by project files that allow license holders to reproduce the computations.

Interface

The SiLENSe software has a friendly graphical user interface (GUI) designed to minimize user efforts needed to start simulations. Interactive visualization of the calculation results provides an excellent representation of the LED operation. The results can also be stored in a number of output files allowing a post-processing analysis using either commercial Tecplot graphical package (Tecplot, Inc.) or other software operating with plain-text data files.

 

Layer-by-layer LED structure specification and input data visalization.

Figure 2. Layer-by-layer LED structure specification and input data visalization.

Band diagram and carrier wave functions.

Figure 3. Band diagram and carrier wave functions.

Key Publications

GaN-based devices

ZnO-based devices and hybrid II-O/III-N devices

Conventional III-V compounds