SimWindows16 and SimWindows32 Version 1.4.2 User`s Manual
Contents
1. the device file can also contain overrides of any of the material parameters This means that any device file can use a 34 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 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 lengthzn value f x T d 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 particula2. SimWindows There are many subtleties about the user interface that 15 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 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 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 3 2 through 3 5 describe each file in detail Section 3 1 describes how to use general purpose functions in SimWindows 3 1 User Functions User functions greatly increase the flexibility of SimWindows by allowing it to accept general functions in material parameters files and devic
3. 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 3 2 1 3 3 1 Band Gap Model name Band gap 2 2 function f x D a bx cx 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 3 2 1 3 3 2 Thermal Conduciivity 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 26 the alloy percentage and the lattice temperature The derivative of this relation with respect to the temperature yields another relation of the same form 3 2 1 3 3 3 Mobility Model name Mobility function f x T C N A a bx ex XS f gx hx UE MN 1 Ne Material Parameter ELECTRON MOBILITY HOLE MOBILITY This model applies to the electron and hole mobilities to control their variation with respect to the alloy concentration x the lattice temperature T the carri
4. energy level is in the band gap 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 32 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 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 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 mirror
5. 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 e2g4 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 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 85 0 14 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 1e 8 Hole shr lifetime Value 1e 8 Rad recomb const Value 1 5e 10 Electron energy lifetime Value 1 e 12 28 29 Hole energy lifetime Value 1 e 12 Qw rad recomb const Value 1 54e
6. 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 11 displays information during device simulations Simulations are now ready to begin The iconified device window serves no purpose from here on 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 store all of the simulation results to let the
7. 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 employ a built in 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 Table 4 SimWindows material parameters 21 Symbol Meaning Unit Variables Band_Gap Band gap eV x T Electron_Affinity Electron affinity eV x T Static_Permitivity Electrostatic permitivity none X Refractive Index Refractive index none x T E G H Absorption Optical absorption cm x T E G H Thermal_Conductivity Thermal conductivity W K cm x T Deriv Thermal Conduct Thermal conductivity W K cm x T derivative wrt temperature Electron Mobility Electron mobility cm V s x T C N A Hole_Mobility Hole mobility cm V s x T
8. 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 12 as other parameters are set using EnvironmentlPreferences 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 various parameters are available by choosing DevicelDevice Information To plot any position dependent parameter select any of the options under the Plot menu The next section gives more informatio
9. 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 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 24 x for which the value function is valid Since the band gap is a function of T as well use a start t and an end t 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 t 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 same as line 2 except that it uses a different fun
10. 4 Electron collision factor Value 0 5 Hole collision factor Value 0 5 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 t
11. C N A Felectron Dos Mass Electron density of states none X mass Hole Dos Mass Hole density of states none x mass Electron Cond Mass Electron conductivity none X mass Hole Cond Mass Hole conductivity mass none X Electron Shr Lifetime Electron SHR lifetime S X Hole_Shr_Lifetime Hole SHR lifetime S X Rad_Recomb_Const Radiative recombination cm s X constant Electron Energy Lifetime Electron energy relaxation S X lifetime Hole Energy Lifetime Hole energy relaxation S X lifetime Qw Rad Recomb Const Radiative recombination cm s X constant when used in a QW Electron Collision Factor Electron scattering none X coefficient 1 2 0 1 2 3 2 Hole Collision Factor Hole scattering coefficient none x 1 2 0 1 2 3 2 22 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 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 alloy then use Alloy default E
12. D EXCLUSIVELY TO PRODUCT REPLACEMENT Table of Contents 2 1 THE SIMWINDOWS DESKTOP seiniin hrir ri e er a i ir eS 8 OE ONDINE DEVICE AEE E E EE EN A E E OEA EEE EE E 9 2 3 PERFORMING SIMULATIONS recon T NTE S TES 11 ZA GENERATING OUTPUT Arten isea t eea EUR a stun dulce ea a dee chee Ee EE a 12 2 5 SUMMARY iia ia E a 14 3 SIMWINDOWS FILE TYPES eee eese eee ene en nennen esos seen seen seen se enses sesnseenseenseenseenses LO IE USER FUNCTIONS ie atre bete tec tem tee aie C O Ute vete eet eat te eee at 15 A AA AS 17 EA A oe eee but ettet da para DL outer 17 3 1 3 General FUNCION p NI IBID T TB MB NINE RE 17 3 2 MATERIAL PARAMETERS FILES e 3 2 1 Format inen RIG RR HIT HN RONDE 20 3 22 Bx mple Material SECHON iza ome pere tet ie tee e tete Enab adia da adotado pags 27 3 3 DEVICE FILES ci e aia said 29 333 1 Key Words 5 Gee teet teste ette te teme tete tent itte Certe rode bet te e 30 3 3 2 Overriding Material Parameters eene nennen nnne 33 3 3 3 Example Device Files Lony cemere eee dete e etie ete Ere ere 34 34 STATE FILES EE 35 3 5 DATA FILES 2t ette ett en da ts e Det cts ER e t er e aa ET ex it edu be 35 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 resul
13. SimWindows16 and SimWindows32 Version 1 4 2 User s Manual by David W Winston O 1995 David W Winston All rights reserved Microsoft MS and MS DOS are registered trademarks and Windows is a trademark of Microsoft Corporation in the United States and other countries Borland is a registered trademark of Borland International Inc License Agreement You are hereby licensed to use the freeware version of the software for an unlimited period of time make as many copies of the freeware version of this software and documentation as you wish give exact copies of the original freeware version to anyone and distribute the freeware version of the software and documentation in its unmodified form via electronic means There are no restrictions on distribution as long as the contents of the original version and all supporting files and copyright notices are unchanged Disclaimer of Warranty THIS SOFTWARE AND THE ACCOMPANYING FILES ARE AVAILABLE AS IS AND WITHOUT WARRANTIES AS TO PERFORMANCE OF MERCHANTABILITY OR ANY OTHER WARRANTIES WHETHER EXPRESSED OR IMPLIED Because of the various hardware and software environments into which SimWindows may be put NO WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE IS OFFERED Good data processing procedure dictates that any program be thoroughly tested with non critical data before relying on it The user must assume the entire risk of using the program ANY LIABILITY OF THE AUTHOR WILL BE LIMITE
14. TMaterialStorage o TMaterial ire TAlloy Do TMaterialParamModel matclass cpp E matclass cpp matclass cpp matclass cpp A TDeviceFileInput i infclass cpp THEN T TENE E n Y TPolynomial TPieceWiseFunction funclass cpp Y TUserFunction funclass cpp TConstant funclass cpp TFunction funclass cpp TTermsFunction funclass cpp TModelM obility funclass cpp TModelBandGap funclass cpp TModelThermalConductivity funclass cpp funclass cpp TModelAlGaAsPermitivity funclass cpp TModelPowerAbsorption funclass cpp TModelPowerAbsorptionBandGap funclass cpp TModelAlGaAsRefractiveIndex funclass cpp TModelExpAbsorption funclass cpp TModelAIGaAsAbsorption funclass cpp TModelExpAbsorptionBandGap funclass cpp Figure 5 Material and function classes 41 TEnvironment envclass cpp T TDeviceFileInput i TCavity p TMirror infclass cpp ES v cavclass cpp mirclass cpp TDevice Ap a S TContact TMode conclass cpp X devclass cpp EON modclass cpp TSolution y 7 i gt E al TSurface solclass cpp Sa surclass cpp 1 x i i DN i SS i a Us Node Structure A i TNode lt q TGrid Bc dclass dclass ES nodcl
15. ach 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 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 4 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 4 also lists those variables Keeping in mind that each material parameter is a function of particular 23 variables there are two ways to specify the value of a material parameter The first is 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 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 value for the band gap that is valid for all
16. am more efficient manageable faster etc SimWindows improves in all of these area 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 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 I character separates nested menu options For example MENUlIIOptionllOption2 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 Optionl Option2 Option3 This means to perform Optionl and Option2 but Option3 is optional The third convention is used with keywords in the SimWindows input files The 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 exa
17. amming classes 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 E Name Abstract pere bo ree E Name OWL 2 5 Class E B Bisafriend class of A A gt B Bisa derived class from A A esses B Bis pointed to by A not all pointers are shown Figure 1 Symbols used in class diagrams The following six figures comprise the class structures for SimWindows Figure 2 shows the main classes that create the various windows in the user interface Figure 3 presents the classes that create all of the dialog boxes Figure 4 shows various support classes The validator classes in this figure are used to verify the input to edit controls Figure 5 shows the material storage material and alloy classes This figure also shows various function and physical models classes Figure 6 presents the device and grid related classes Figure 7 shows the corresponding solution and element classes simplot cpp TPrintEditFile simedit cpp TSimWindowsEditFile simedit cpp TSimWindowsMacroPlot simplot cpp TSimWindowsEnvironPlot simplot cpp TSimWindowsDeviceStatus simedit cpp Figure 2 Main Windows interface classes TDialogSelectOneParameter simcdial cpp TDialogO pticalInput simdial c
18. and are very 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 Obarley colorado edu Bug type 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 38 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 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 39 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 progr
19. ariation of the alloy concentration through the 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 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 O Do not consider in the function f d where in the device the structure actually starts 3 3 1 3 Doping doping length n Nd f d Na f d Nd deg 1 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
20. ass cpp as e gri Ud Vous sa TElectron THole TSS TQuantumWell carclass cpp carclass cpp qwclass cpp TFreeElectron TBoundElectron TFreeHole TBoundHole a pe T2DHole T2DElectron frcclass cpp bdcclass cpp frcclass cpp bdcclass cpp 2dcclass cpp 2dcclass cpp Figure 6 Device and node classes Element Structure TSolution solclass cpp Ze X TDevice devclass cpp All classes except TElement TElement eleclass cpp ES are friends of TNode TElectricalElement elcclass cpp TElectricalServices eleclass cpp TThermalElement thrclass cpp TBulkElectricalElement elcclass cpp TQWElectricalElement elcclass cpp TBulkThermalElement TQWThermalElement thrclass cpp thrclass cpp TOhmicBoundaryElement elcclass cpp TBoundary ThermalElement thrclass cpp Figure 7 Element classes 42
21. ays 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 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 PlotlFreeze 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 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 bug report if nothing seems to help 2 Play with
22. ction for 0 45 x 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 O 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 0 5 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 25 models apply to certain material parameters and SimWindows will display a message 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 that Sim Windows uses in the model Each model uses a
23. e files This section 16 describes what general functions are and how to input them Section 3 2 will describe how to use general functions in material parameters files and section 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 2 lists the nine different variables that SimWindows uses Table 2 Variables used in general functions Symbol Definition d Position Alloy percentage 0 1 Lattice Temperature Carrier Temperature X T C E Photon Energy G Band Gap H N A Band Gap at 300K Donor Concentration Acceptor Concentration 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 3 1 2 to see why f x t is not the same as f t x The following sections describe 17 how to use each type of fu
24. er 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 3 2 1 3 3 4 Absorption Model name Power absorption function f x T E G at bx cx XE dy Material Parameter ABSORPTION Model name Exp absorption function f x T E G 2 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 a bx cx XE G d Material Parameter ABSORPTION 27 Model name Exp band gap absorption function f x T E G aexp b E G c Material Parameter ABSORPTION 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 3 2 1 3 3 5 Refractive Index Model name Oscillator_refractive_index function Internal no coefficients required Material Parameter REFRACTIVE INDEX This is a s
25. 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 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 custom 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 3 2 1 Section 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 20 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 3 2 1 Format The
26. he length for a particular statement SimWindows applies them in the order that they appear in the device file 30 For example grid length 0 5 points 100 grid length 0 3 points 200 This order of grid statements means that from O 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 O to 0 3 microns SimWindows should use 200 grid points From 0 3 to 0 8 microns it will use 100 grid points 3 3 1 Keywords 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 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 31 function to describe the v
27. mple length i Nd n material s conc f x T 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 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 bwcc dll bwcc32 dll for SimWindows32 Borland International supplies this file with their compiler The second file that must be present is material prm This file is the default material parameters file for Si and AlGaAs which SimWindows loads when it starts See section 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 a
28. n introductory screen followed by the desktop window The following sections comprise a simple tutorial for SimWindows It begins 8 by outlining the basic interface of SimWindows It will then explain how to load a device file perform simulations and generate output 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 SimWindows Table 1 List of SimWindows menu items Pull down menu Purpose File File operation commands Edit Edit and search commands for device files Environment Modify environment parameters Device Modify device and simulation parameters Plot Produce and output plots Data Input and output misc data Window Control layout of windows Help Display general information about SimWindows 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 Environment and Help menu op
29. n 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 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 13 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 PlotlBand Diagram to see a band diagram of the comalgpn device To change the scale for the x and y axes either double click o
30. n 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 PlotlShow Trace Window option This will display a dialog box associated with the selected plot When 14 the mouse pointer moves across the plot the trace window displ
31. name just choose the 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 3 5 Data Files SimWindows can also generate data files that contain the numerical values of 36 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 comma delimited text The resulting spreadsheet will be easy to read and manipulate 37 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
32. nction to specify a function f 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 07 When SimWindows requires a function a constant value will always suffice 3 1 2 Polynomial A polynomial represents an arbitrary order polynomial The syntax is the following f x y z 1 2 3 is equivalent to 142x 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 142x 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 18 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 S x y z y 24 2 x is a valid function Table 3 lists the operators and functions
33. ndows 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 10 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 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 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 file name If the file already has a
34. pecial 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 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 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 Electron collision factor Value 0 5 Hole collision
35. pp TDialogSelectParameters simcdial cpp TDialogDeviceContacts simdial cpp TDialogPreferences simcdial cpp TDialogDeviceSurface simdial cpp TDialogSelectMacro simcdial cpp TDialogElectricalModels RR Saes simdial cpp TDialog TCenterDialog simcdial cpp Ls repa OO e e TDialogV oltageMacro simcdial cpp TDialogThermalModels simdial cpp TDialogDeviceInfo simcdial cpp TDialogLaser simdial cpp TDialogTrace simcdial cpp TDialogScale simcdial cpp TDialogW riteBand simdial cpp TDialogA bout simcdial cpp TDialogDataWriteA ll simdial cpp Figure 3 Dialog box classes 40 TParse parclass cpp l TParseMaterialParam parclass cpp TMacroStorage macclass cpp Y TMacro macclass cpp i TParseDevice parclass cpp TParseMaterial parclass cpp TVoltageMacro macclass cpp TFlag supclass cpp TValueFlag supclass cpp TEffectFlag supclass cpp l TValueFlagW ithObject supclass cpp ume un TPreferences supclass cpp TErrorHandler supclass cpp TMustEnterV alidator simvalid cpp TScientificUpperV alidator simvalid cpp TScientificRangeV alidator simvalid cpp TScientificLowerValidator simvalid cpp Figure 4 Support and text validator classes
36. r region Instead of using 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 35 The structure lines are used to specify the material alloy and alloy Hcomposition 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 1e 17 5e16 0 5 d doping length 500000 Nd 5e 16 5e16 0 5 d 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
37. r 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 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 progr
38. s 3 3 1 6 Mirror mirror metal position n ref n In conjunction with a cavity statement see previous section mirror 33 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 mirror statements for laser simulations SimWindows will compute the electromagnetic field profile only between the mirrors 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 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 3 3 2 Overriding Material Parameters In addition to specifying the device structure
39. t 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 winstonObarley 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 SimWindowsl6 and SimWindows32 The operation of the programs is identical and all files are compatible between the two versions The programs differ in that SimWindows32 is a 32 bit version that runs about twice as fast as 5 SimWindows16 This means that SimWindows32 executes instructions and accesses memory using 32 bits instead of 16 Every microprocesso
40. 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 20 5 cos 2 pi d 0 5 valid parentheses included Table 3 Operators and functions understood by SimWindows Operator Function Definition Add Subtract ii Multiply Divide Power exp x Exponential In x Natural Logarithm sin x Sine x in radians cos x Cosine x in radians tan x Tangent x in radians asin x arcsine result in radians acos x arcosine result in radians atan x arctangent result in radians atan2 x y arctangent of x y result in radians abs x absolute value sqrt x square root piO returns pi rnd random number between 1 and 1 19 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 material prm 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 EnvironmentlPreferences to set which material parameters file SimWindows loads at startup Until it loads a material parameters
41. tions are enabled because these do not depend on devices Table 1 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 9 SimWindows to display in the status bar at the bottom a hint associated with each 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 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 examplesicomments 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 examplesicomments subdirectory and open the comalgpn dev file SimWi
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