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.

Fig. 1. Band diagram variation with bias for a MQW LED.

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^*.

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

Supported materials

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 LED heterostructure

Example 2 Blue MQW LED heterostructure

Example 3 UV Laser Diode on sapphire substrate

Example 4 Hybrid II-O/III-N LED (ZnO-based LED)

Example 5 Polar/Semipolar/Nonpolar Heterostructures

Interface

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

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.

System requirements

Fig. 3. Band diagram and carrier wave functions.

• Operating System—Windows XP/Vista/7

Key Publications

GaN-based devices

• K. A. Bulashevich, O. V. Khokhlev, I. Yu. Evstratov, and S. Yu. Karpov
  Simulation of light-emitting diodes for new physics understanding and device design
  “Light-Emitting Diodes: Materials, Devices and Applications for Solid- State Lighting XVI”, Proc. of SPIE, vol. 8278 (2012)
• Sergey Yu. Karpov
  Modeling of III-nitride Light-Emitting Diodes: Progress, Problems, and Perspectives
  Proc. of SPIE, vol. 7939 (2011) 79391C / DOI 10.1117/12.872842
• Sergey Yu. Karpov
  Effect of localized states on internal quantum efficiency of III-nitride LEDs
  Phys. Status Solidi RRL 4, No.11, 320–322 (2010) / DOI 10.1002/pssr.201004325
• K.A. Bulashevich, M.S. Ramm, and S.Yu. Karpov
  Effects of electron and optical confinement on performance of UV laser diodes
  phys. stat. solidi (c) 6, No 2, 603–606 (2009)
• M.V. Bogdanov, K.A. Bulashevich, I.Yu. Evstratov, S.Yu. Karpov
  Current spreading, heat transfer, and light extraction in multipixel LED array
  phys. stat. solidi (c) 5, No. 6, 2070–2072 (2008)
• K.A. Bulashevich and S.Yu. Karpov
  Is Auger recombination responsible for the efficiency rollover in III-nitride light-emitting diodes?
  phys. stat. solidi (c) 5, No. 6, 2066–2069 (2008)
• K.A. Bulashevich, M.S. Ramm, and S.Yu. Karpov
  Assessment of various LED structure designs for high-current operation
  phys. stat. solidi (c) 6, No. S2, S804-S806 (2009).
• V.F. Mymrin, K.A. Bulashevich, N.I. Podolskaya, I.A. Zhmakin, S.Yu. Karpov, and Yu.N. Makarov
  Modelling study of MQW LED operation
  phys. stat. sol. (c) 2, 2928-2931 (2005).

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

• J.W. Mares, M. Falanga, A.V. Thompson, A. Osinsky, J.Q. Xie, B. Hertog, A. Dabiran, P.P. Chow, S. Karpov, and W.V. Schoenfeld
  Hybrid CdZnO/GaN quantum-well light emitting diodes
  J. Appl. Phys. 104, 093107 (2008).
• K.A. Bulashevich, I.Yu. Evstratov, and S.Yu. Karpov
  Hybrid ZnO/III-nitride light-emitting diodes: modelling analysis of operation
  phys. stat. solidi (a) 204, No. 1, 241–245 (2007).
• K.A. Bulashevich, I.Yu. Evstratov, V.N. Nabokov, S.Yu. Karpov
  Simulation of hybrid ZnO/AlGaN single-heterostructure light-emitting diode
  Appl. Phys. Lett 87, No. 24, 243502 (2005).

Conventional III-V compounds

• K.A. Bulashevich, V.F. Mymrin, S.Yu. Karpov
  Effect of Free-Carrier Absorption on Performance of 808 nm AlGaAs-Based High-Power Laser Diodes
  Semcond. Sci. Technol. 22, No 5, 502-510 (2007).