8. Appendix C - User`s Manual Version 1.4.2
Contents
1. i character denotes that an integer follows the given keyword The n character denotes a floating point numerical value The s denotes a string of characters The string of characters can not contain spaces The f character denotes a user function A list of variables for the function will also follow the f character As an example length i Nd n material s conc f x T 124 The first example means that an integer must follow length The second example means that a floating point number or an integer must follow Nd The third example means a string of characters must follow material The fourth example means that a function of the variables x and T must follow conc This manual assumes that the reader has a working knowledge of Microsoft Windows and are familiar with terms such as pull down menus dialog boxes click and drag and etc In addition the reader should have an understanding of the basic file and directory structure of standard MSDOS Windows based computers 8 2 Getting Started To start SimWindows just double click on the SimWindows icon from the Program Manager This starts the simwinl6 exe file simwin32 exe for SimWindows32 Two auxiliary files must be in the same directory as SimWindows One of those files is the bwecc dll bwcc32 dll for SimWindows32 Borland International supplies this file with their compiler The second file that must be present is materi2. TDialogElectricalModels simdial cpp TDialogThermalModels simdial cpp TDialogLaser simdial cpp TDialogWriteBand simdial cpp TDialogDataWrite All simdial cpp Figure 48 Dialog box classes 157 TParse parclass cpp l parclass cpp TParseMaterialParam TMacroStorage macclass cpp y TMacro macclass cpp TParseDevice parclass cpp TParseMaterial parclass cpp TVoltageMacro macclass cpp TFlag supclass cpp TValueFlag supclass cpp TEffectFlag supclass cpp l TValueFlagWithObject supclass cpp i TFilterValidator he anaa ENEP md TPreferences supclass cpp TErrorHandler supclass cpp TMustEnterValidator simvalid cpp TScientificUpperValidator simvalid cpp TScientificRangeValidator simvalid cpp TScientificLowerValidator simvalid cpp Figure 49 Support and text validator classes TMaterialStorage matclass cpp TMaterial matclass cpp TAlloy matclass cpp TMaterialParamModel matclass cpp TPieceWiseFunction TDeviceFileInput infclass cpp funclass cpp TUserFunction funclass cpp TPolynomial funclass cpp TModelMobility funclass cpp TConstant funclass cpp Y TModelBandGap funclass cpp TFunction funclas
3. TElectricalServices TThermalElement elcclass cpp eleclass cpp threlass cpp TBulkElectricalElement TQWElectricalElement TBulkThermalElement TQWThermalElement elcclass cpp elcclass cpp threlass cpp threlass cpp TOhmicBoundaryElement TBoundaryThermalElement elcclass cpp threlass cpp Figure 52 Element classes
4. operators and functions that SimWindows understands To use pi and rnd in a function you have to include the parentheses after the function f d 0 5 cos 2 pi d 0 5 invalid function no parentheses f d 0 5 cos 2 pi d 0 5 valid parentheses included 135 Table 9 Operators and functions understood by SimWindows Subtract atan2 x y sqrt x Cosine x in radians 8 3 2 Material Parameters Files Material parameters files supply SimWindows with parameters associated with different material systems These files use a default extension of PRM A default material parameters file materialprm comes with SimWindows and contains parameters for Si and Al Ga _ As SimWindows loads this file at the beginning and will display an error message if this file is not present Choose EnvironmentIPreferences to set which material parameters file SimWindows loads at startup Until it loads a material parameters file SimWindows can not generate a device SimWindows will also accept new materials in either a modified material prm file or a new material parameters file It is advisable to use a new material parameters 136 file instead of modifying material prm New versions of SimWindows will overwrite the existing material prm and erase the changes Keep in mind that the material prm is expanding as SimWindows uses new parameters custom material parameters files will often need updating for new versions of SimWindows To load a custo
5. the comalgpn dev file SimWindows will create a window which contains the text in the device file The window itself is called the device window and is one of three kinds of windows that SimWindows uses The first part of the window caption is DEVICE FILE which indicates that this window creates and edits device files Device files are just ASCII files that contain a description of the device They contain parameters such as the material dimensions and doping SimWindows can edit many device files simultaneously and the options under the Edit menu can cut and paste selections from one device file to another When SimWindows opens a file it 127 determines what type of file it is There is only one kind of file called a state file that only SimWindows can read This tutorial and section 8 3 4 will discuss more about state files If the file is not a state file then SimWindows will assume it is a text file and load it into a device window Therefore SimWindows can edit any kind of text file With a device file loaded into SimWindows the DevicelGenerate menu option becomes enabled To start simulating the comalgpn device choose DevicelGenerate If several device files are open select the window containing the comalgpn device then choose DevicelGenerate When SimWindows generates a device a number of things happen First SimWindows saves the device file to disk If the file is a new file and untitled SimWindows will ask for a new
6. the donor level is below the conduction band and the acceptor level is above the valence band If the statement omits either of the parameters then SimWindows uses a default value of 0 As with the grid and structure statements the total length of the doping regions must equal the total length of the device Note that for every doping statement d starts at 0 Do not consider in the function f d where in the device the structure actually starts 149 8 3 3 1 4 Region region bulk length n region qw length n The region statement denotes regions as bulk regions or quantum well regions Device files do not require region statements In this case the entire device will consist of bulk materials If a device contains quantum wells then the device file must contain region statements for both the quantum well and bulk regions 8 3 3 1 5 Cavity cavity surface area n length n In conjunction with mirror statements see the next section the cavity statement defines a laser cavity within your device The only type of cavity that SimWindows supports is for surface emitting lasers This implies that the light emission is parallel to the current flow The cavity statement requires the area perpendicular to the light output and the effective cavity length Only one cavity statement may be in the device file The length of the cavity determines the distributed mirror loss and the output power of the mirrors 8 3 3 1 6 Mirror mir
7. type of function to specify a function f 8 3 1 1 Constant A constant is the simplest type of a user function but it is useful to think of a constant as the following f x y z 5 is equivalent to 5 0x 0y 0z When SimWindows requires a function a constant value will always suffice 8 3 1 2 Polynomial A polynomial represents an arbitrary order polynomial The syntax is the following 134 f x y z 1 2 3 is equivalent to 1 2x 3x 0y 0z SimWindows can accept as many terms as necessary separated by commas The more terms the higher the order of the polynomial When using polynomials there is a difference between f x y z and f y x z Here s why f x y z 1 2 3 is equivalent to 1 2x 3x 0y 0z but f y x z 1 2 3 is equivalent to 1 2y 3y 0x 0z When using polynomials keep in mind which variable the polynomial actually uses The first variable in the list of variables for the function will be the variable for the polynomial If this is difficult to remember just use a general function next section to input the polynomial The reason for having this polynomial as well as a general function is that SimWindows evaluates polynomials much faster than a general function 8 3 1 3 General Function Many times both a constant and a polynomial are not sufficient for specifying a function but SimWindows can interpret and evaluate any algebraic function For example f x y Z x y z y 24 2 x is a valid function Table 9 lists the
8. 8 Appendix C User s Manual Version 1 4 2 8 1 Introduction SimWindows is a semiconductor device simulation program under development at the Optoelectronics Computing Systems Center at the University of Colorado Boulder It handles a variety of optoelectronic devices by solving the semiconductor equations in one dimension As a result SimWindows assumes that all variables such as current field and potential etc vary parallel to the flow of current but are uniform in the direction perpendicular to the current Depending on the nature of the device a one dimensional simulation may or may not be sufficient To receive announcements concerning new versions of SimWindows send e mail to winston barley colorado edu Announcements will be sent only when the version number changes by 0 1 or higher A change of 0 0 1 in the version number represents bug fixes and interface changes while changes in physics will receive a version change of 0 1 or higher SimWindows is freely available over the Internet through the World Wide Web A web browser such as Netscape or Mosaic can access the home page for SimWindows at http ucsu colorado edu winston simwin html Anonymous ftp can also access the program files at hopper colorado edu 128 138 248 150 in the pub modeling SimWindows directory Check periodically to see when a new version is available SimWindows is a Microsoft Windows application and is available in two varieties SimWindows16 and SimWindow
9. FilelSave menu option and SimWindows will save the state file to the old filename To restore a state file use the FilelOpen menu option and select the state file to open If a device already exists SimWindows will prompt to save the results of that device If SimWindows opens the state file successfully the message Device successfully created will appear in the state window The device will be in exactly the same state as when SimWindows saved it 8 3 5 Data Files SimWindows can also generate data files that contain the numerical values of any desired data Plots can generate data files directly by selecting a plot on the screen and choosing the FilelSave As option After entering a file name SimWindows will output the data to the file Also use the menu items under the Data pull down menu to output non position dependent data or to create custom sets of data Data files are always ASCII files that any standard word processor or spreadsheet can read The data is comma delimited which makes it difficult to read on the screen However it is easy to load the data into a spreadsheet program that accepts 153 comma delimited text The resulting spreadsheet will be easy to read and manipulate 154 8 4 Bug Report In an effort to increase the stability and usefulness of SimWindows the following bug report can be used to report any problems that you encounter Many problems result from the configuration of your system and are very
10. The file consists of three sections physics user interface and user transparent The physics section consists of enhancements to equations as well as numerical techniques The user interface section corresponds to the mechanism in which the user manipulates the physics The user transparent section is the code that helps make the entire program more efficient manageable faster etc SimWindows improves in all of these area 123 simultaneously There are also release notes that explain the latest features of each version of SimWindows Double clicking on the icon label Latest Features will access the file latest wri that describes the latest features associated with the version of SimWindows This file also contains the release notes for all versions of SimWindows are stored in the file latest wri Scroll through this file to see the evolution of SimWindows 8 1 1 Conventions for this manual There are a few typographical conventions that are of particular importance The first is the method to describe menu options The character separates nested menu options For example MENU 1lOption1 Option2 This means to go to MENUI select Option which will display another menu and select Option2 The second convention is to denote optional items using For example Option Option2 Option3 This means to perform Option and Option2 but Option3 is optional The third convention is used with keywords in the SimWindows input files The
11. accept general functions in material parameters files and device files This section describes what general functions are and how to input them Section 8 3 2 will describe how to use general functions in material parameters files and section 8 3 3 will describe how to use general functions in device files There a three types of user functions constant polynomial and general They are all interchangeable in that each type of function when can be used when necessary In order to use any of the types of functions it is important to know the variables of the function This manual denotes functions as f x y z where x y and z are the variables of the function f Table 8 lists the nine different variables that SimWindows 133 USES Table 8 Variables used in general functions da Position x Alloy percentage 0 1 TT Lattice Temperature G Carrier Temperature O 9 BE PhotonEnergy N Donor Concentration AJ Acceptor Concentration le Z A A function denoted by f x G means a function of the alloy percentage and the band gap Also the case of the variables is irrelevant The function f x t is equivalent to f x T Note that the function f x t is not the same as the function f t x This difference is only important when using a polynomial to specify the function f See section 8 3 1 2 to see why f x t is not the same as f t x The following sections describe how to use each
12. al prm This file is the default material parameters file for Si and AlGaAs which SimWindows loads when it starts See section 8 3 2 for more information on material parameters files SimWindows will generate error messages if neither of these files is present Both of these files should be present if the installation was successful SimWindows will now display an introductory screen followed by the desktop window The following sections comprise a simple tutorial for SimWindows It begins by outlining the basic interface of SimWindows It will then explain how to load a 125 device file perform simulations and generate output 8 2 1 The SimWindows Desktop The SimWindows desktop is the main window that will open files perform simulations and examine results There are four major components to the desktop the menu tool bar window area and status bar This section only describes these components in general and gives a brief tutorial on SinWindows Table 7 List of SimWindows menu items le Fie operation commands Plot Produce and output plots With the desktop running there are three items to observe First most of the menu items are disabled since no devices are loaded Once a device is loaded SimWindows will enable most of the menu items The menu is updated dynamically meaning that depending on which window is active or which options are selected only valid menu options will be enabled However the File Environmen
13. ale for the x and y axes either double click on the plot or choose the PlotlScale menu option This will activate the Scale dialog box for the selected plot This dialog box accepts input for the minimum and maximum x and y values and gives options for either a linear or logarithmic y axis Three operations are also available for the y axis The operations are either none negative or absolute value These operations help to view values that can vary by many orders of magnitude but can also be positive and negative The best example of this is the recombination rate It is often desirable to view the recombination on a log plot but this is problematic since the recombination rate can be both positive a negative By default plots do not display zero and negative values on a log plot but selecting either y or abs y in the scale dialog box will display these values An easier way to set the scale is to use the zoom feature Click and hold the left mouse button on a plot then drag a rectangle over the plot The plot will zoom to the portion within the rectangle and display it in the entire plot area To return to the automatic scale choose the PlotlAuto Scale menu item or press the ESC key The plot window can also yield actual numerical data in two ways The first method is the trace window Select a plot and then choose the PlotiShow Trace Window option This will display a dialog box associated with the selected plot When the mouse pointer moves ac
14. an also contain overrides of any of the material parameters This means that any device file can use a new value for a material parameter and not use the default value that is in the material parameters file To do this use exactly the same syntax that appears in the material parameters file with the following additions 1 On the first line for the material parameter include a length n option where n is the length for which the override will apply Use multiple lines to override the material parameter differently for different parts of the device but override the 151 material parameter over the entire device 2 In addition to the regular variables for the material parameter a general function can also use the variable d position for the material parameter This provides a position dependent material parameter For example the material parameters file specifies the band gap according to BAND GAP Value f x T In the device file the statement would be BAND GAP length n value f x T d 8 3 3 3 Example Device Files The following is an example device file that comes with SimWindows It is a simple AlGaAs p n diode It uses a number of grid statements to adjust the grid spacing through the device It has two structure statements to vary the Al composition of the device and it specifies a position dependent doping concentration The grid lines are used to specify the number of grid points in a particular region Instead of us
15. asses can be derived from other classes This means that the derived classes inherit the data and functionality of the parent classes while adding some data and functionality of its own The following figure shows the legend of symbols used by the class diagrams ERE Name Abstract PR f oe ERE Name OWL 2 5 Class re B is a friend class of A A B Bisa derived class from A Dy a gt B Bis pointed to by A not all pointers are shown Figure 46 Symbols used in class diagrams The following six figures comprise the class structures for SimWindows Figure 47 shows the main classes that create the various windows in the user interface Figure 48 presents the classes that create all of the dialog boxes Figure 49 shows various support classes The validator classes in this figure are used to verify the input to edit controls Figure 50 shows the material storage material and alloy classes This figure also shows various function and physical models classes Figure 51 presents the device and grid related classes Figure 52 shows the corresponding solution and element classes TPrintEditFile medit cpp TSimWindowsEditFile TSimWindowsDeviceStatus simedit cpp simedit cpp TSimWindowsEnvironPlot TSimWindowsMacroPlot simplot cpp simplot cpp Figure 47 Main Windows interface classes TDialogOpticalInput simdial cpp TDialogDeviceContacts simdial cpp TDialogDeviceSurface simdial cpp
16. at SimWindows uses in the model Each model uses a different numbers of coefficients and SimWindows will display a message if there is an incorrect number of coefficients for the model Each of the following sections describes the various built in models 8 3 2 1 3 3 1 Band Gap Model name Band_gap 2 2 function FonT a4brber td T 300 e T e 300 Material Parameter BAND GAP ELECTRON AFFINITY This model simply allows for the variation in the band gap with respect to temperature At T 300K the model reduces to a second order polynomial relationship between the alloy percentage and the band gap This model is valid for the electron affinity in order to control how the band gap narrowing is divided between the conduction and valence bands 8 3 2 1 3 3 2 Thermal Conductivity Model name Thermal conduct a b cx dx Material Parameter THERMAL CONDUCTIVITY DERIV THERMAL CONDUCT function f x T This model allows for the variation of the thermal conductivity with respect to the alloy percentage and the lattice temperature The derivative of this relation with respect to the temperature yields another relation of the same form 143 8 3 2 1 3 3 3 Mobility Model name Mobility o C k 1 NE Material Parameter ELECTRON MOBILITY HOLE MOBILITY function f x T C N A a bx cx 5 f gxt hx This model applies to the electron and hole mobilities to control their variation with respect to the alloy concent
17. ctron collision factor Value 0 5 Hole collision factor Value 0 5 Alloy Al Band gap Segments 2 Start x 0 00 end x 0 45 Model Band gap terms 1 424 1 247 0 5 405e 4 204 Start x 0 45 end x 1 00 Model Band gap terms 1 9 0 125 0 143 5 405e 4 204 Electron affinity Segments 2 Start x 0 0 end x 0 45 Model Band gap terms 4 07 0 7482 0 2 702e 4 204 Start x 0 45 end x 1 0 Model Band gap terms 3 594 0 3738 0 143 2 702e 4 204 Static permitivity Value 13 18 3 12 REFRACTIVE INDEX Model oscillator refractive index Absorption Segments 2 start e 0 end e g 0 00087 model exp band gap absorption terms 1 71 0 104 start e g 0 00087 end e 100 model power band gap absorption terms 3 5e4 0 0 0 0 5 Thermal conductivity Model Thermal Conduct terms 549 356 1 12 7 13 22 1 25 Deriv thermal conduct Model Thermal Conduct terms 686 695 1 12 7 13 22 2 25 Electron mobility Segments 2 Start x 0 0 end x 0 45 Value 8000 22000 10000 Start x 0 45 end x 1 0 Value 255 1160 720 Hole mobility Value 370 970 740 Electron dos mass Value 0 067 0 083 Hole dos mass Value 0 62 0 14 Electron cond mass Segments 2 Start x 0 0 end x 0 45 Value 0 067 0 083 Start x 0 45 end x 1 0 Value 0 32 0 06 Hole cond mass Value 0 62 0 14 Electron shr lifetime Value le 8 Hole shr lifetime Value 1e 8 Rad recomb const Value 1 5e 10 Electron energy lifetime Value 1 e 12 Hole energy lifetime Value 1 e 12 Qw rad recomb const Value 1 54e 4 Electron collision factor Value 0 5 Hole c
18. difficult for me to test Therefore I strongly encourage you to fill out a bug report You may send it by U S mail fax or e mail to the following address David W Winston Dept of Computer and Electrical Engr Campus Box 425 University of Colorado Boulder CO 80309 0425 Fax 303 492 3674 e mail winston barley colorado edu Bug type L System Crash SimWindows caused Windows to crash or required reboot L SimWindows Crash SimWindows crashed but did not affect Windows programs L Program Error You noticed a bug in SimWindows Description Describe in as much detail as possible what happens 155 Error Messages If there were any error messages what exactly did it say include descriptions of dialog box captions and buttons that were available Misc Questions Can you repeat the problem L Yes L No If so what procedure will reproduce the problem What Version of SimWindows do you use use HelplAbout When was it last modified use HelplLast Updated Which version of Windows do you use Which processor do you have Clock speed List other programs if any that were running when you executed SimWindows 156 8 5 Class Diagrams The following class diagrams depict the class structure for SimWindows version 1 4 2 Classes are essentially modules that combine data and functionality In object oriented programming cl
19. e all of the simulation results to let the user examine them later without performing the simulations over again To open a state file choose the FilelOpen option and choose the name of the state file The initial state of the comalgpn device is charge neutral This is a non physical state that SimWindows uses as the initial state for performing device simulations To return to the initial state select the DevicelReset option The first physical state that SimWindows calculates is thermal equilibrium Choose DevicelStart Simulation and SimWindows will begin iterating The state window shows the present operating conditions and then the iteration number as well as the corresponding numerical error for the iteration Since solving for equilibrium requires only one variable potential the state window displays only one error value By default the numerical error must be less than 10 before the iterations stop The iterations will also stop if the iteration number reaches the default value of 15 The error maximum iteration number as well as other parameters are set using EnvironmentIPreferences When the iterations stop the state window will display the result of the iteration converged or not converged the present device state and the elapsed time When the calculation is completed 129 various parameters are available by choosing DevicelDevice Information To plot any position dependent parameter select any of the options under the Plot me
20. e as line 2 except that it uses a different function for 0 45 lt x lt 1 00 An important feature of the start and end values is that they can also be functions not just numbers For example since the band gap is a function of x and T the start and end values for both x and T can be functions of x and T An example using the absorption of GaAs ABSORPTION Segments 2 start e 0 end e g value 0 start e g end e 100 value 3 5e4 e g 0 5 For a photon energy e between 0 and the band gap g the absorption coefficient will be 0 For a photon energy between the band gap and 100 the absorption will be 3 5e4 e g 40 5 8 3 2 1 3 3 Built in Models In addition to general functions several built in models for material parameters are available Built in models are just functions of a certain form for which the user specifies the coefficients Built in models are available for the electron affinity band gap mobility thermal conductivity derivative of the thermal conductivity with respect to temperature optical absorption and the index of refraction Only certain models apply to certain material parameters and SimWindows will display a message 142 when a model is not applicable to the material parameter The syntax for a built in model is MATERIAL PARAM Model model name terms a b c d e where MATERIAL PARAM is the name of the material parameter model name is the name of the model and a b c d e are the coefficients th
21. file name If the file already has a file name then it saves the file using the current file name Note that this will overwrite the previous file Second SimWindows reads the device file allocates memory and performs initial calculations If there is a syntax error in the device file SimWindows will display the line number of the error and the cause of the error Third SimWindows will iconify the device window and create a second window The new window is a state window and is the second of the three important kinds of windows that SimWindows uses The state window represents the state of the device Lastly SimWindows will enable most menu items If everything was successful the state window will display the message Device successfully created The state window displays information during device simulations Simulations are now ready to begin The iconified device window serves no purpose from here on 128 8 2 3 Performing Simulations An important item to remember is that SimWindows always completely stores the present state of the device Each new simulation begins from where the last simulation ended SimWindows can simulate only one device at a time It can also save the state of the device on disk This is done by clicking on the state window and then choosing the FilelSave As option If the state has not been previously saved then SimWindows will ask for a file name The default extension for state files is STA State files stor
22. g report if nothing seems to help 2 Play with SimWindows There are many subtleties about the user interface that will appear with experience Submit a bug report if there are suggestions on improving the interface 3 Be careful when saving Remember that there are three kinds of windows device state and plot The FilelSave and FilelSave As work differently for each one For a device window SimWindows saves the device file Likewise SimWindows saves the state file when the state window is active It will save 132 the plot data when a plot window is active 4 SimWindows always stores the present state of the device Any time it performs a simulation it starts from the end of the last simulation To start from the beginning choose the DevicelReset option 8 3 SimWindows File Types SimWindows uses a number of different kinds of files These files are the material parameters files device files state files and data files The default extension for each file is PRM DEV STA and DAT respectively but SimWindows will accept any extension Material parameters files device files and data files are all simple text files while the state file is a binary file that only SimWindows can read Sections 8 3 2 through 8 3 5 describe each file in detail Section 8 3 1 describes how to use general purpose functions in SinWindows 8 3 1 User Functions User functions greatly increase the flexibility of SimWindows by allowing it to
23. ing points you can also use size to specify the spacing between grid points grid length 450 points 25 grid length 049 points 40 grid length 002 points 40 grid length 049 points 40 grid length 450 points 25 The structure lines are used to specify the material alloy and alloy composition The names for material and alloy must correspond to names in the material parameters file It is not necessary to specify an alloy If no alloy is specified then the default material parameters specified material prm are used structure material gaas alloy al length 0 50 conc 0 40 structure material gaas alloy al length 0 50 conc 0 00 The doping lines are just used to specify the doping If no doping is specified then the region is intrinsic doping length 500000 Na le 17 5e16 0 5 d doping length 500000 Nd 5e 16 5e16 0 5 d 152 8 3 4 State Files Since device simulations can be a time consuming task state files can save results for later examination A state file contains all of the data that is in memory As a result state files can be quite large depending primarily on the number of grid points in the device State files are binary files that only SimWindows can interpret To save a state file click on the state window of your device and choose the FilelSave As menu option SimWindows will ask for a filename The default extension for state files is STA If the state file already has a file name just choose the
24. lloy then use Alloy default Each material section can have any number of alloys for that material The material parameters file can reuse the names of alloys if they are in different material sections 8 3 2 1 3 Material Parameters There are presently 21 material parameters that the material parameters file must specify for each material alloy combination Table 10 lists the keywords for each material parameter Each alloy in the material parameters file must use each keyword or an error message will result Each keyword must use a function constant polynomial or general function to specify the value of the material parameter Each function is function of certain variables and Table 10 also lists those variables Keeping in mind that each material parameter is a function of particular variables there are two ways to specify the value of a material parameter The first is 140 to specify one function that is valid for all values of the variables The second is to specify different functions that apply for different ranges of input variables The following sections describe each of the methods 8 3 2 1 3 1 Single Function If a single function is sufficient to specify a material parameter then use just one line for the material parameter Some examples using the band gap follow Remember that the band gap is a function of the alloy percentage x and the lattice temperature T BAND_GAP Value 1 424 This specifies a constant
25. m material parameters file into SimWindows prior to simulating a device use the EnvironmentlLoad Material Parameters menu option While loading a material parameters file SimWindows will display an message if the file contains any errors Material parameters files are simple text files that SimWindows can edit They must conform to the format outlined in section 8 3 2 1 Section 8 3 2 2 shows the GaAs section of the material prm file as an example There are a few general rules that are important when modifying material parameters files 1 A at the beginning of the line comments out any statement 2 Everything is case insensitive GrId means the same as Grid 3 Never use any spaces before or after an or a 4 Every statement must begin in the first column The material prm file distributed with SimWindows include comments with additional information on the format of material parameters files 8 3 2 1 Format The material parameters file consists of an arbitrary number of material sections with one section for each material system Within each material section there is an arbitrary number of alloy sections Therefore Si and GaAs would be in different material sections However InGaAs and AlGaAs would be in the same material section but different alloy sections Each alloy section includes a list of values for each material parameter The values may either be a simple constant a general function or 137 employ a built i
26. mWindows applies them in the order that they appear in the device file For example grid length 0 5 points 100 grid length 0 3 points 200 147 This order of grid statements means that from 0 to 0 5 microns SimWindows should use 100 grid points From 0 5 to 0 8 microns it will use 200 grid points grid length 0 3 points 200 grid length 0 5 points 100 This order of grid statements means that from 0 to 0 3 microns SimWindows should use 200 grid points From 0 3 to 0 8 microns it will use 100 grid points 8 3 3 1 Keywords 8 3 3 1 1 Grid grid length f points i grid length f size f The grid key word specifies either the number 1st form or the spacing 2nd form of grid points within the specified length of the device Using more than one grid line in the device file will vary the grid spacing in different parts of the device Note that the sum of all lengths specified in the grid statements must equal the total length of the device 8 3 3 1 2 Structure structure material s length f alloy s conc f d The structure statement defines the material composition for a specified length of the device The material parameters file must contain the specified material name If the material has an associated alloy name then alloy specifies the name The option conc represents the percentage of the alloy in the material Conc can use a general function to describe the variation of the alloy concentration through the
27. n model for the parameter Adding new material or alloy sections can expand the material parameters file There are no limits as to the type of materials and therefore SimWindows can handle any material system The following sections describe the keywords and syntax for material parameters files 138 Table 10 SimWindows material parameters Deriv Thermal Conduct Thermal conductivity WK cm x T derivative wrt temperature Electron_Mobility Electron mobility x T C N A Hole_Mobility Hole mobility x T C N A mass mass mass Hole_Cond_Mass Hole conductivity mass Electron_Shr_Lifetime lectron SHR lifetime Pos x Hole_Shr_Lifetime Hole SHR lifetime s S Radiative recombination constant lifetime lifetime Qw_Rad_Recomb_Const Radiative recombination cm s x constant when used in a QW coefficient 1 2 0 1 2 3 2 1 2 0 1 2 3 2 139 8 3 2 1 1 Material Section Material s The material keyword starts a material section Device files will select the material by using the specified name of the material s The name can not contain spaces 8 3 2 1 2 Alloy Section Alloy default Alloy s To specify different alloys for a particular material use the alloy keyword Device files will select the alloy by using the specified name of the alloy s As with the material keyword the name of the alloy can not contain spaces If the material has default parameters that apply if the device file does not specify an a
28. nu The next section gives more information on obtaining output To control the operating conditions applied bias optical input etc there are a number of menu options to choose The simplest operating condition is an applied bias To apply a 0 5 V forward bias choose the DevicelContacts menu option Since this is a pn diode and not an np diode a positive voltage on the left contact will forward bias the device Enter 0 5 in the edit box label Applied Bias V and then press the OK button Simulate the device by choosing DevicelStart Simulation SimWindows will begin iterating but this time the state window will display three error values for the potential the electron quasi fermi level and the hole quasi fermi level One aspect of the fact that SimWindows always stores the present state of the device is that if it does not achieve convergence before it reaches the maximum number of iterations just start the simulation again SimWindows will continue from where it left off 8 2 4 Generating Output Plot windows are the third kind of window in SimWindows The plot menu lists the various options associated with plots Most of the options from this menu are only available when a device is loaded The exception to this is the External Optical Spectra plot which SimWindows enables when the environment includes external optical generation Choose PlotIBand Diagram to see a band diagram of the comalgpn device To 130 change the sc
29. ollision factor Value 0 5 146 8 3 3 Device Files Device files describe the physical characteristics of the device These characteristics include device dimensions materials and doping The device file is an ASCII file that SimWindows can create and edit By default device files use the DEV extension The same basic rules for material parameters files are applicable to device files They are 1 A at the beginning of the line comments out any statement 2 Everything is case insensitive GrId means the same as Grid 3 Never use any spaces before or after an or a 4 Every statement must begin in the first column To describe the device there are a number of keywords that SimWindows will interpret from the device file and each keyword has a number of available options The following section describes each keyword that SimWindows understands Many keywords have a number of variations that the same device file can mix with the other variations Most statements are optional in the device file but every device file must contain at least one grid statement one structure statement and one doping statement The total length for all of the grid statements structure statements and doping statements must be equal which represents the total length of the device The order of statements in the device file is very important for statements using the same keyword Since the length parameter describes the length for a particular statement Si
30. ration x the lattice temperature T the carrier temperature C and the doping concentrations N donors A acceptors Note that this model does not explicitly use the lattice temperature but rather the carrier temperature Under most circumstances the carrier temperature is the same as the lattice temperature However the mobilities can depend on the lattice temperature and a user function that uses T as a variable is applicable 8 3 2 1 3 3 4 Absorption Model name Power_absorption function f x T E G a bx cx VE d Material Parameter ABSORPTION Model name Exp absorption function f x T E G aexp b E c Material Parameter ABSORPTION These two models are analytical expressions that relate the photon energy to the absorption coefficient There is no temperature dependence in these models but a user function can include the temperature Model name Power_band_gap_absorption function f x T E G at bx cx E G d Material Parameter ABSORPTION Model name Exp band gap absorption function f x T E G a exp b E G c Material Parameter ABSORPTION 144 These two models are the same as the first two except for the incorporation of the bulk band gap Since the band gap can vary as a function of temperature these absorption models will also vary with temperature 8 3 2 1 3 3 5 Refractive Index Model name Oscillator_refractive_index function Internal no coefficients required Material Parame
31. region If a structure line omits the alloy and conc options then SimWindows will use the default material parameters if any from the material parameters file Note that the 148 sum of all lengths specified in the structure statements must equal the total length of the device Note that for every structure statement d starts at 0 Do not consider in the function f d where in the device the structure actually starts 8 3 3 1 3 Doping doping length n Nd f d Na f d Nd deg i Na deg i Nd level f d Na level f d The doping statement defines different doping regions The length parameter specifies the length of the region The Nd and Na parameters specify the donor and acceptor concentration respectively These can use a general function f d to describe the variation of the doping density through the region If the statement omits both doping concentrations then it uses an intrinsic material The Nd_deg and Na_deg parameters specify the degeneracy factor for the dopant Incomplete ionization of dopants uses the degeneracy factor The value is usually 2 for donors and 4 for acceptors If the statement omits either of these parameters then SimWindows uses a default value of 0 meaning complete ionization of dopants The parameters Nd level and Na level specify the energy level of the dopant in eV A positive value for these parameters means that the energy level is in the band gap
32. ror metal position n ref n In conjunction with a cavity statement see previous section mirror statements define a laser cavity within your device The only type of cavity that SimWindows supports is for surface emitting lasers This implies that the light emission is parallel to the current flow The mirrors are placed at discrete points within the device usually at the ends of the device This statement only requires the position of the mirror and the power reflectivity of the mirror A device file must include two 150 mirror statements for laser simulations SimWindows will compute the electromagnetic field profile only between the mirrors 8 3 3 1 7 Radius radius n The radius statement defines the radius of your device SimWindows assumes that all devices are cylindrical The default radius is one micron if a device file omits the radius statement Only the lateral heat flow model in SimWindows uses the radius parameter It is only necessary when using this model in thermal simulations 8 3 3 1 8 Repeat repeat start repeat n The repeat statement allows a device file to specify periodic structures Use the repeat start statement before any group of statements and then use the repeat n after the group of statements SimWindows will repeat these statements for the specified number of times 8 3 3 2 Overriding Material Parameters In addition to specifying the device structure the device file c
33. ross the plot the trace window displays the x and y values for the closest data point Note that each plot has its own trace window If two plot windows are open there is a separate trace window for each plot The second way to obtain data from a plot is to select the plot and choose the FilelSave option SimWindows will ask for a file name and then write the x and y values to the file The 131 format of the file is comma delimited columns that any typical spreadsheet program can load for further analysis When plots are visible and SimWindows simulates a device it also updates the data in the plots automatically to reflect the new results To prevent this choose PlotIFreeze Plot The plot is now frozen with the current data This feature is useful for displaying two plots of the same quantity for different states of the device different voltages for example To update a frozen plot click on the plot window and choose PlotiMelt Plot 8 2 5 Summary This section has presented a basic look at the functionality of SimWindows There are a number of items to keep in mind while using SimWindows 1 Use SimWindows intelligently It is a software tool just like any other program If there are problems obtaining convergence then there may be a problem with the program The problem may also be related to the nature of the device For example using too few grid points can cause convergence problems Play around with your device and submit a bu
34. s cpp TTermsFunction funclass cpp TModelThermalConductivity funclass cpp TModelAlGaAsPermitivity funclass cpp TModelPowerAbsorption funclass cpp TModelPowerAbsorptionBandGap funclass cpp TModelAlGaAsRefractiveIndex funclass cpp TModelExpAbsorption funclass cpp TModelAlGaAsAbsorption TModelExpAbsorptionBandGap funclass cpp Figure 50 Material and function classes 158 159 TEnvironment envclass cpp TDeviceFileInput I TCavity TMirror infclass cpp cavclass cpp mirclass cpp y TDevice devclass cpp TContact conclass cpp TMode modclass cpp TSolution solclass cpp TSurface surclass cpp Node Structure y TNode a TGrid nodclass cpp m grdclass cpp Pa es TElectron THole TQuantumWell carclass cpp carclass cpp qwclass cpp TFreeElectron TBoundElectron TFreeHole TBoundHole T2DHole T2DElectron freclass cpp bdcclass cpp freclass cpp bdcclass cpp 2dcclass cpp 2dcclass cpp Figure 51 Device and node classes TSolution TDevice solclass cpp devclass cpp ZN p Element Structure i All classes except TElement I are friends of TNode TElement eleclass cpp TElectricalElement
35. s32 The operation of the programs is identical and all files are compatible between the two versions The programs differ in 122 that SimWindows32 is a 32 bit version that runs about twice as fast as SimWindows16 This means that SimWindows32 executes instructions and accesses memory using 32 bits instead of 16 Every microprocessor since the 80386 has had the capability of executing 32 bit programs However the development tools have only recently become available Since Microsoft Windows 3 1 and Windows for Workgroups 3 11 are 16 bit applications these operating systems require the Win32s library This library does not come with Windows but Microsoft distributes it to developers for their own 32 bit applications The Win32s library allows 32 bit applications to interface to 16 bit versions of Windows The library is available on the distribution disks for SimWindows32 and on the same Internet computer site as the SimWindows programs Windows NT and Windows 95 do not require the Win32s library since they already incorporate the Win32 functionality As of this writing SimWindows32 will run on Windows NT and Windows 95 but it has not been thoroughly tested As with any continuing software project there are many features that are not yet implemented in SimWindows The file update wri lists possible future enhancements Double clicking on the icon labeled Future Updates in the SimWindows group of the Program Manager will access this file
36. t and Help menu options are enabled because these do not depend on devices Table 7 describes the menu items and their basic function The second item to notice is that moving the mouse pointer over menu options with the left mouse button pressed will cause SimWindows to display in the status bar at the bottom a hint associated with each 126 menu item The status bar not only displays help hints but it also displays the current state of the Num Lock and Cap Lock keys on the keyboard While editing files the status bar also displays the line number of your cursor The last item to notice is the tool bar The tool bar contains buttons that will perform the same function as a particular menu item Just like the menu SimWindows updates the tool bar dynamically When a menu option is enabled its associated tool button if any will be enabled SimWindows also displays help hints when mouse pointer moves over the various tool buttons 8 2 2 Loading a Device The first step in using SimWindows is to either load or create a device file There are a number of example device files that come with SimWindows The device file for this tutorial is comalgpn dev which is a simple AlGaAs p n diode The examples comments subdirectory for SimWindows contains this file To load the device file choose FilelOpen This will display the Open File dialog box The default extension for device files is DEV Move to the examples comments subdirectory and open
37. ter REFRACTIVE INDEX This is a special model that requires no terms and is applicable to Al Ga As only It appears and was reported in J Appl Phys 70 1 1 July 1991 by Terry This is dependent on the aluminum percentage in the alloy It is also dependent on the temperature through the temperature dependence of the band gap 8 3 2 2 Example Material Section The following is the GaAs section of the material prm that comes with SimWindows It shows how to use the various keywords described in the previous sections Material GaAs Alloy Default Band_gap Model Band_gap terms 1 424 0 0 5 405e 4 204 Electron_affinity Model Band gap terms 4 07 0 0 2 702e 4 204 Static permitivity Value 13 18 Refractive index Model oscillator refractive index Absorption Segments 2 start e 0 end e g 0 00087 model exp band gap absorption terms 1 71 0 104 start e g 0 00087 end e 100 model power band gap absorption terms 3 5e4 0 0 0 0 5 Thermal conductivity Model Thermal Conduct terms 549 356 1 0 0 1 25 Deriv thermal conduct Model Thermal Conduct terms 686 695 1 0 0 2 25 Electron_mobility Value 8000 Hole_mobility Value 370 Electron_dos_mass Value 0 067 Hole_dos_mass Value 0 62 Electron_cond_mass Value 0 067 145 Hole cond mass Value 62 Electron shr lifetime Value 1e 8 Hole shr lifetime Value 1e 8 Rad recomb const Value 1 5e 10 Electron energy lifetime Value 1 e 12 Hole energy lifetime Value 1 e 12 Qw rad recomb const Value 1 54e 4 Ele
38. value for the band gap that is valid for all values of x and T BAND_GAP Value 1 424 1 247 This example specifies to use a polynomial for the value of the band gap This is equivalent to 1 424 1 247 x 0 T BAND GAP Value 1 4244 1 25 x 5 4e 4 T42 T 204 300 2 300 204 This is a general function for the band gap as a function of x and T 8 3 2 1 3 2 Piecewise Function A piecewise function can specify different functions that are valid over different ranges of the variables Some examples again using the band gap follow BAND_GAP Segments 2 Start_x 0 00 end_x 0 45 start_t 0 end_t 0 value 1 424 1 247 Start_x 0 45 end_x 1 00 start_t 0 end_t 0 value 1 9 0 125 0 143 On line 1 segments specifies the number of different functions that will follow On line 2 value specifies the actual function Start x and end x specify the range of x for which the value function is valid Since the band gap is a function of T as well 141 use a start t and an end 1 to specify the ranges of T In this case start t and end t are both zero meaning that the value function is valid over all T If the line does include a start and end value then SimWindows assumes that the function is valid over the entire range of the variable Therefore start t and end 1 statements in line 2 are not necessary In summary line 2 means to give the band gap a value of 1 424 1 247 x for 0 00 lt x lt 0 45 and for all T Line 3 is the sam
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