> Please find below a brief description of the new options.
>
> 1. Physical model is similar to that implemented in PVcell. There are three options for tunnel junction: parametric, function, and
> simulation. Compared to PVcell, calculation option was excluded.
>
> 2. Create/delete tunnel junctions. Tunnel junction regions are highlighted in the table with heterostructure layers by grey color
> and index of the tunnel junction (starting from 1). Tunnel junction regions can not overlap with periodic structures or other
> tunnel junctions.
>
> To create new tunnel junction region one needs select several adjacent layers in the table (similarly it is done for creating a
> periodic structure) and use "Heterostructure -> Create/Delete Tunnel Junction" menu item. If the selected range of layers overlaps
> with another tunnel junction or periodic structure, a dialog window will appear where you will be able to choose between three
> options:
> (i) Delete old periodic structures and tunnel junctions and create a new tunnel junction in the selected range of layers.
> (ii) Delete old periodic structures and tunnel junctions (this option if to enable deleting tunnel junctions).
> (iii) Cancel (quite dialog with no changes).
>
> To delete tunnel junction one needs select a layer within the tunnel junction, use "Heterostructure -> Create/Delete Tunnel
> Junction" menu item, and choose "Delete old periodic structures and tunnel junctions" in the dialog.
>
> 3. To edit tunnel junction parameters, one needs select a layer within the tunnel junction and use "Heterostructure -> Edit Tunnel
> Junction" menu item. Then a window appears where one can set the parameters. The button "Update Plot" plots the j-V curve of the
> tunnel junction. If "Simulation" type is chosen, it will cause simulation of the tunnel junction. J-V curve will be plotted in the
> same window. Simultaneously, the band diagram, carrier concentrations, etc will be saved in "Results -> Tunnel Junctions -> TJ#i"
> window.
>
> 4. There are other new menu items in the user interface related to the tunnel junctions.
> (i) "Run -> Run Tunnel Junction -> TJ#i" runs simulation of the j-V curve of the tunnel junction #i. The effect is very similar to
> selecting a layer of the tunnel junction, using "Heterostructure -> Edit Tunnel Junction" menu item, and updating the plot. At the
> moment, this option works only for "simulation" type of the tunnel junction (it was intended for).
> (ii)  "Window -> Tunnel Junction Results -> TJ#i" opens table with simulation results for the tunnel junction #i. It resembles
> "LED Results" and similar windows, but with a reduced information. The key idea is one can double-click result for a certain bias
> and see the band diagram, carrier concentration, etc, very similarly to LED results. Some tabs which are not applicable for TJ
> results are not shown.
>
> 5. LED/PL/Laser computations for structures including tunnel junctions works like in previous versions. If a structure includes
> tunnel junction(s), there will be additional columns in the table for the bias at a certain tunnel junction and tunnel current at
> this tunnel junction. Also, in "Current" tab, the tunnel current is indicated, and the total current is added, too.
>
> 6. Now SiLENSe can simulate structures such a described below:
>
> - n-region
> - MQW LED/LD active region
> - p-region
> - tunnel junction
> - n-region
>
> In this case, things like IQE, injection efficiency, electron/hole leakage to be reconsidered. In this version, we have
> implemented the following definitions:
> - IQE has the same definition (ratio of the radiative recombination inside QWs to the total current).
> - Injection efficiency has the same definition (ratio of the total recombination inside QWs to the total current) and now can be
> higher than 100% in case of multi-cascade structures.
> - We do not say "leakage current" and just report electron and hole fluxes at the left and right external boundaries of the structure.
>
> In the above structure, we can interchange MQW active region and tunnel junction. In this case, the direction of the current
> necessary to produce light will be inverted. In the current version, we avoid any complicated automatic analysis of the whole
> structure to determine where is the p-n junction direction, and provide users an option explicitly specify the target direction of
> the current (see last item in the list of global physical parameters which includes temperature and quantum potential settings).
> The default value is "negative", as in all previous versions of SiLENSe (electrons go forward along z-axis, while holes go
> backwards, and total current is directed in the direction opposite to direction of z-axis).
>
> 7. Examples of III-N based tunnel junctions are included in distributive in "Examples III-N TJ" folder. Two structures, "A - Top
> TJ.sls" and "B - Bottom TJ.sls", are borrowed from the attached paper (please note that current direction is different for these
> structures). The third structure, "MQW-3AR-2TJ.sls", demonstrates simulation of structure with three active regions connected by
> two tunnel junctions of different design. It is not based on any practical example, it just serves to illustrate simulation with
> two different tunnel junctions.
>
> 8. Generally, tunnel junctions can be used in all kinds of structures: LEDs, LDs, solar cells (PL simulations with zero or
> positive bias) and photodetectors (PL simulations with reverse bias). We have mainly tested LED structure.
>
> 9. Known issues:
> - Physics summary is not updated yet.
>
> 10. We have also fixed some considerable drawback in simplified laser model. Equation (11.20), of SiLENSe Physics Summary includes
> injection efficiency (i.e. ratio of the recombination in QWs to the total current), and it is correct from physical point of view.
> However, we have found that in the code it was used the difference between unity and the ratio of the leakage current to the total
> current. In other words, we used injection efficiency, bu calculated for the whole structure (not only to QWs). It is fixed now.
> The problem is important in case when both below conditions are met:
> (i) there is a considerable carrier leakage
> (ii) there is a considerable recombination outside QWs.
> For instance, the laser output power in simplified laser model in "LaserDiode_UV.sls" example is decreased about 1.5 times
> compared to previous versions. Please note that the problem does not affect results for self-consistent laser model.
>
> 11. We have tried several variations of the algorithms for determination of the tunnel junction boundaries in the simulation of
> the whole structure. The last  item in the list of global physical parameters includes name of the selected variant. In the
> version in the distributive, the value is shown in read-only mode and choice is "old" (the model used in PVcell). We show this
> parameter in the user interface in order allow STR team to change it manually in the project file, if necessary.
>
> 12. Three examples of III-nitride structures with tunnel junctions are added into distributive.