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Modeling of Crystal Growth and Devices

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WHAT'S NEW

SiLENSe Version 5.4 & Version 5.4 Laser Edition have been released.

1. Module for handling material properties is re-designed and the following new options are available:
- Using functions in material properties with temperature, wavelength, and alloy composition dependence.
- Editing material properties just from SiLENSe interface by "Material Properties->Edit" menu item.
- Properties Editor module has been renewed with a lot of useful features like opening file from command line argument (enabling file association), list of recent files in File menu, rename and moving alloys, and so on. Also, when a new material or alloy is added, all the necessary properties are added automatically.

Updated material properties for wurtzite and zinc-blende materials are included into distributive ("wurtzite.matprop" and "zinc_blende.matprop"). All the example files are based on these material properties. Potentially, new system allows more handy treatment of zinc-blende materials by using composition-dependent functions instead of making different materials for direct and indirect semiconductors. In "zinc_blende_new.matprop" database, the above approach is implemented for AlGaAs alloy.

2. Simulation of PL experiment is added (with some strong assumptions on the excitation). Please note that to use PL for projects converted from older versions one needs specify the absorption coefficient material property (by default, zero absorption is added after conversion).

SiLENSe Version 5.2 & Version 5.2 Laser Edition have been released.

Improvements in physical model as compared to version 5.0 include:

- Support of custom inclination angle by choosing "Custom Inclination Angle" option in the "Orientation" drop-down list in "Heterostructure" tab.

- Two errors in computation of the piezoelectric polarization for semi-polar orientation are fixed. The error was in paper by Romanov et. al from where equations were borrowed. Now we have completely re-derived these equations and resolved all the errors appeared in the paper. Please note that computations for polar orientations contained no error and were not changed. So, this update does not affect results for polar orientations.

- A new model for effect of the composition fluctuations on the emission spectrum is implemented. The model includes new parameter Usp, which is specified for the QW layer. If a QW consists of several layers, the maximum value of Usp is used for the whole QW. The model is used only if the checkbox for using composition fluctuation model is checked. Roughly, Usp is the typical energy of deviation of the energy gap of the QW from the value computed from the layer composition. Such a deviation changes the shape of the emission spectrum to a more realistic view. As the model broadens the spectrum, a lower value of uniform spectrum broadening should be used in "Global Parameters" tab (see Eq. (8.14)). The model is used in updated SQW, SQW-relaxed, and MQW examples. The default values are Usp = 25 meV and gamma_uniform = 5 meV. Since the impact of the fluctuations strongly depends on the growth conditions, users are welcome to change the above parameters to fit their experimental spectrum shape.

- The model for composition fluctuations effect on the IQE is slightly changed compared to version 5.0 . Now, fluctuations do not affect the recombination on defects other than dislocations (i.e. do not change the lifetimes directly specified by the user). So, some difference in the results compared to version 5.0 is possible.

- User can change the power law for dependence of the radiative and Auger recombination constants (B, Cn, Cp). Default settings exactly reproduce version 5.0.

Improvements in user interface as compared to version 5.0 include:

- An error in opening project files of versions 4.2 and older is fixed. Version 5.2 can open files of all previous versions.

- Four new columns are added to "List of Results" table: the J_SRH and J_Auger represent the current density converted into the SRH and Auger recombination, respectively, the non-ideality factor "m" is calculated according to Eq. (7.4) of Physics Summary, and the peak wavelength of the emission spectrum "Peak WL". Since spectrum computations are required to compute the wavelength, the user needs to use "Run -> Update Peak Wavelength" menu item (or the respective button from the toolbar) to see the wavelength. It may look inconvenient, but we decided to go this way to avoid situation when visualization of the table is delayed because of the automatic computation of the spectra (the computational time for spectra may be considerable). As the peak wavelength is calculated for some bias, it is stored and close\open of the table will not clear the peak wavelength.

- Export of all results in a single file (List of Results window, "Export -> All Results in Single File" menu item or the respective button) is introduced.

SiLENSe Version 5.0 & Version 5.0 Laser Edition have been released.

Quantum potential model is developed to account for quantum effects: tunneling current and quantum confinement of the carriers inside the quantum wells. Use of the quantum potential model allows more realistic prediction of the current-voltage characteristics of the p-n junction. Also, the carrier concentration in the quantum wells is predicted more accurately. One can switch on/off use of the quantum potential model in "Global parameters" tab.

SiLENSe Version 4.4 & Version 4.4 Laser Edition has been released.

New options include:

Multiple periodic structures are supported. Periodic structures are specified exactly as in the previous versions.

Automatic generation of data for SpeCLED. The user need once set a list of biases and a list of temperatures, and the program will automatically run simulations and store a set of *.sct files for input into SpeCLED. Optionally, intermediate SiLENSe project files with results are also stored.

SiLENSe Version 4.2 & Version 4.2 Laser Edition has been released.

New options include:

Material properties of zinc blende III-V compounds were updated. Particularly, AlGaInP and GaInAsP alloys lattice matched to GaAs are added, as well as respective simulation examples.

After computation of the emission spectrum, detailed information about contribution of each subband of the valence band is available, as well as contribution of each particular transition. Use ‘Window->Detailed Spectrum’ menu item and enjoy complete information about the emission spectrum!

Carrier non-radiative lifetimes related to dislocations and point defects are available both in the internal visualization and in export ASCII files.

SiLENSe Version 4.1 & Version 4.1 Laser Editionhas been released.

New options include:

Material properties of InAlGaAs alloy and simulation example for AlGaAs laser diode are added.

Material properties of CdMgZnO alloy and simulation examples for hybrid II-O/III-N heterostructures are updated.

Computation of the band diagram, carrier energy levels and wave functions under reverse bias (see Sec. 11 of SiLENSe Physics Summary). NB! This option does not include prediction of the reverse current!

Computation of the internal quantum efficiency taking into account only emission from the active region, and computation of the injection efficiency (see end of Sec. 7 of SiLENSe Physics Summary).

SiLENSe Version 4.0 & Version 4.0 Laser Edition has been released.

New options as compared to version 3.60 Laser Edition are as follows:

Simulation of nonpolar and semipolar orientations. The user can choose the orientation in the respective combo box in the ‘Heterostructure’ tab. To calculate the piezoelectric fields in semipolar structures, new material ptoperties were introduced: lattice constant c, piezoelectric constant e15, and stiffness constants C11, C12, and C44.

NB! It is strongly recommended to add new material properties in the files created by earlier versions, use ‘Material Properties->Import’ menu item and choosing default database supplied with the current version of the software.

Substrate’ section is removed from the ‘Heterostructure’ tab. Instead, the user should indicate if the first heterostructure layer is strained1. If yes, one should specify its lattice constants a and c. The option of input of the substrate lattice constant by composition is removed. By default, all files newly created or converted from older versions are assumed to have relaxed first layer. If you see a warning about the lattice constant specification during opening old project file, please check the input data in the ‘Strain in the first layer’ section in the center of the ‘Heterostructure’ tab.

Changes in the user interface:

  • Export of plots to graphic files (*.bmp, *.wmf, and *.emf) is available by ‘Export->Save current chart’ menu item.
  • Visualization of the layer properties (doping, mobility, dislocation density, carrier lifetimes, etc) in the bottom chart of the ‘Heterostructure’ window.
  • Two solver parameters are made read-only: ‘Potential solver parameter’ and ‘Fermi level solver parameter’.

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1 First layer appearing in the heterostructure list is a thick n-type layer, usually made of GaN. Typically, it is not strained. The user need not input the nucleation and buffer layers in the heterostructure list.

 

SiLENSe 3.60 Laser Edition has been released on July 2-nd, 2008

New options as compared to version 3.42 Laser Edition are as follows:

  • Temperature dependence of the energy gap is described in terms of Varshni parameters a and b. However, SiLENSe project files (*.sls ) of older versions will be converted as having temperature-independent energy gap (a=0, b=1), to provide backward compatibility of the results. The user can update material properties by using "Materials Properties -> Import" menu item.
  • Model of Indium composition fluctuations on the IQE. SiLENSe project files (*.sls ) of older versions will be converted as having no fluctuations (Un=Up=0) to provide backward compatibility of the results.
  • Some improvements are made in the user interface. Particularly, we have added internal visualization of the following variables: unstrained and strained in-plane lattice constants, strain, spontaneous polarization, piezoelectric polarization, and total polarization.

 

SiLENSe 3.42 Laser Edition has been released on February 4-th, 2008

New options as compared to version 3.4 include:

  • Computation, visualization, and export of the far field distribution (available in Laser Edition only);
  • Support of network corporate/department HASP license;
  • No limitation on the maximum number of the points in the quantum well in computation of the carrier wave functions;
  • A number of improvements in the user interface.

 

SiLENSe 3.4 Laser Edition has been released on May 28-th, 2007

New options as compared to version 3.0 include:

  • Computation of the gain spectrum.
  • Visualization of the emission and gain spectra of individual quantum wells (the previous version shows the total spectrum only).
  • Listing of the overlap integrals between each pair of electron and hole wave functions in the active region.
  • A number of improvements in the user interface.

The following options are available in Laser Edition only:

  • Computation and visualization of the waveguide mode intensity distribution for both TE and TM polarizations with account for the birefringence in wurtzite crystals. Computation of the optical confinement factors.
  • Analysis of the laser diode operation for selected waveguide mode: optical gain, optical losses caused by the free carrier absorption, threshold current and differential quantum efficiency.
  • Updated database of materials properties to include optical characteristics of III-nitride materials.

NB: To run laser computations for the project files of version 3.0 and older one should previously update the materials properties to add optical properties! Use the Materials Properties I Import menu item and select an appropriate file with materials properties. The default database is provided with the package, and the user can modify it via the Properties Editor tool.

 

SiLENSe 3.0 has been released on September 8-th, 2006

This section describes new options in the SiLENSe™ 3.0 package compared to version 2.1:

  1. Non-radiative recombination through the point defects is calculated within the Shokley-Read-Hall model. The user can manually specify the electron and hole lifetimes in each layer of the heterostructure.
  2. Auger recombination. This option is included in order to enable the user to analyze conventional III-V heterostructures where Auger recombination is important channel of non-radiative recombination.
  3. Partial strain relaxation is included for accurate calculation of the piezoelectric charges at the boundaries of partially relaxed layers. The user can manually specify the degree of relaxation for each layer of the heterostructure.
  4. Export/import of material properties. The user can save the materials properties of the existing SiLENSe™ project (*.sls) in a separate material database file (*.mats) as well as load new material properties to the existing SiLENSe™ project from other database files or other SiLENSe™ projects.
  5. The project files of 2.1 version are converted as follows:
  6. The user can specify different threading dislocation density for different layers.
    • For each layer:
      • zero degree of relaxation:
      • no additional recombination via point defects
      • dislocation density taken from the old file
    • Zero Auger coefficients are added to material properties of all materials and alloys listed in the project file.
    • In the saved results all the total non-radiative recombination is suggested to come from the dislocations.
    Under these conditions re-running an old project file with version 3.0 will give the same result as for 2.1 version.

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