ATLAS常见问题解答.docx

ATLAS常见问题解答.docx

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ATLAS常见问题解答

ATLAS常见问题解答

Q1

TheATLASUser’smanual,Vol.IIsaidthattheconversionfromresistivitytocarrierconcentrationisbaseontable,whichisderivedfromAroramobilitymodel.Couldyouinformmeinmoredetailaboutthosetablesandtheconversiontool（ifthereisone）?

A1

TheconversionofresistivitytocarrierconcentrationinsiliconusingtheRESISTIparameterintheDOPINGstatementisbaseonthefollowingequation:

CarrierConcentration=1/（R*q*u）（incm-3）

whereRistheresistivity（inohm-cm）;qisthecharge;anduisthemobility（incm^2/.

InATLAS,Aroramobilityisusedforcomputingthecarrierconcentration.ThecomputationoftheresistivitytocarrierconcentrationinSiliconforbothN-typeandp-typecarrierareasshowninthefigurebelow.

Q2

PartI:

HowcanIsimulatetheshortcircuitcurrent,Iscandopenvoltage,VocofaSolarCellinATLAS?

A2

Theshortcircuitcurrent,IsccanbeextractedfromtheIVcurvewhenthevoltageis0whiletheopencircuitvoltagecanbeextractedfromtheIVcurvewhenthecurrent0.ThefigurebelowshowsthelocationoftheIscandVocvalues.Thecommandsusedtoextractbothvaluesareasfollows:

extractinitinf=""

#ExtractShortCircuitCurrentextractname="short_circuit_current"fromcurve（v."cathode",i."cathode"）where=0

#ExtractOpenCircuitVoltageextractname="open_circuit_voltage"fromcurve（v."cathode",i."cathode"）where=0

Q3

PartII:

HowcanIincludeavariableloadresistance（externalload）intothesimulationprogramandsimulatetheIVcharacteristicsofaSolarCell?

A3

Thereare2methodsofaddinganexternalresistancetoadevice:

i.Thefirstmethodistoaddalumpelement;and

ii.Thesecondmethodistoaddadistributedcontactresistance.

Thefirstmethodistospecifythevalueoftheresistanceinthe"RESISTANCE"optionoftheCONTACTstatement.However,thismethodisonlyapplicableforplanarmetal-semiconductorsurface.

Thesecondmethodistoaddadistributedcontactresistance,fornon-uniformmetal-semiconductorsurface.Forthismethod,theoptionwasusedinsteadintheCONTACTstatement.Belowgiveanexampleofhowtocomputethevalue.

Assuminganexternalloadof50ohmattheCathodecontact,the（inohm-cm^2）iscalculatedasfollow:

=50xCathode_lengthxcathode_width=50x140umx1um=7e-5ohm-cm^2

Then,youneedtospecifytheCONTACTstatementasbelow:

CONTACTNAME=CATHODE=7E-5

BelowshowsthesimulatedIVcharacteristicsofaSolarCellwithandwithouta50ohmexternalload.

Toextractthechannellength,usethefollowingEXTRACTstatementasfollows:

extractname="junc_source"xjsilicon=1==1extractname="junc_drain"xjsilicon=1==2extractname="ChannelLength"$"junc_drain"-$"junc_source" 

Q4

HowtoextractIoffinSILVACOTCADtools?

A4

FirstlyyoushouldknowthedefinitionofIdsatandIoff.WhenIoffisdefinedasthedraincurrentatgatevoltageequalsto0v,youcanusefollowingstatement:

Extractname=”Ioff”fromcurve（v.”gate”,i.”drain”）where=0

Afterrunthisstatement,youwillgetaresultwhichisstoredinfile"".

Q5

IhavefinishedthesimulationofBJTandgettheIVcurve,butIcouldfindhowtodisplaythecurvebetavs.basevoltage.Isthatpossibletodisplaysuchcurve?

A5

Yes,itcan.FirstlylaunchTonyPlotandopenthelogfilewhichincludeIVcurve.Then,click“tools”->“display”inthemenu,select“Function1”inthe“YQuantities”

Afterthat,clickbutton“Functions…”whichisintheleft-bottom.Awindowwillpopuplikefollowing:

Inthiswindow,typein“CollectorCurrent/BaseCurrent”whichisalsoshowedinabovepicture（becausebetaisdefinedasbeta=Ic/Ib）

Thenclick“Ok”tofinish.Thenyouwillgetacurvewhichxaxisisbasevoltage,andyaxisisbeta.Seefollows:

Q6

HowtoobtaintheCapacitance-Voltage（CV）curveofaMOScapacitoratlowfrequency?

A6

InthesimulationofCVcurve,SRHmodelneedstobeaddedtotheinputdeckfile.ThisisbecausewhenreversebiasingtheMOScapacitor,GENERATIONinthedepletionregionactuallydominateoverRECOMBINATION,asthecarrierconcentrationsarelessthantheirthermalequilibriumvalues;.pn

Thegeneratedcarriersinthedepletionregioncancontributetotheflowofanexternalcurrent,I.ThisI=IntegralofCV.Therefore,whenthegeneratedcarriersincreases->Iincreases->Cincreases.

Thegenerationrateinthedepletionregion,G=ni/2T,whereTisthelifetimeoftheeffectivelifetime,.T=（Tn+Tp）/2.Therefore,GisinverselyproportionaltoT=>TheshorterthelifetimeT,thegreaterthegenerationrateG=>greaterI=>greaterC.

HenceitisnecessarytoaddtheSRHmodelandalsoreducetheeffectivelifetimeofthecarriersinthebulkforsimulatingtheCVcurve.Thiscanbedonebyaddingthefollowingstatements:

materialtaun0=1e-11taup0=1e-11modelsrh

BelowshowsthesimulatedCapacitance-Voltage（CV）curveofaMOScapacitorathighandlowfrequency.

Q7

TheMOScapacitorbeingatwoterminaldevice,thetwocapacitancesshouldbeidenticalinmagnitude.Simulationhowevershowsthemtobeafewordersofmagnitudedifferent.OurtheoreticalestimationtellusthatCsubstrate-gatebetween8e-16toFaradiscorrect.Cgate-substrateisbetweenandFisconfusingtous.

A7

AtlasperformsasmallsignalacanalysisasdescribedinthepaperbyLauxRef.74ofAtlasvolIIBibliography.

Accordingtoref.46,theadmittancematrixisdefinedas:

Y（ij）=I（i）/V（j）

whereI（i）andV（j）arethephasorterminalcurrentandvoltagerespectively.TherealpartandimaginarypartoftheadmittancematrixdeterminetheconductancematrixGandthecapacitancematrixCrespectively.

InAtlas,itistheseconductanceandcapacitancethatarebeingoutput.Forinstance,thecapacitancematrixCiscalculatedasfollows:

ImagY21=-1*（2**frequency*Cgate>substrate）[inputport=Gate,outputport=Substrate]

ImagY12=-1*（2**frequency*Csubstrate>gate）[inputport=Substrate,outputport=Gate]

Therefore,thevalueofCgate>substratedoesnotequaltoCsubstrate>gate.

Q8

Ingeneral,howtosolveconvergenceproblem?

A8

Tosolveconvergenceproblem,

1）TrytherefineyourmeshespeciallyatareaswherecarriersactivityaremostprominentsuchasareasnearandatthejunctionortheSchottkycontact,

2）Useasmallerstepsize.vstep=orevenvstep=ratherthanalargeonesuchas2V.

3）Bydefault,onlyNewtonmethodisused.TrytouseboththeGummelandNewtonMethodsintheMethodstatement.ThiswillcausethesolvertostartwithGummeliterationsandthenswitchtoNewton,ifconvergenceisnotachieved.Thisisaveryrobust,althoughmoretimeconsumingwayofobtainingsolutionsforanydevice.

4）RefertoATLASUser'sManualon"ChoosingNumericalMethod"pp.2-27todecideonthemostappropriatemethodstobeusedforyourdevice.

Q9

CanyoutellmehowtoretrievethedefaultparametersofSiCintheATLAS?

A9

ThedefaultvalueofallmaterialcanbefoundinATLASUser'smanualvol.IIAppendixB（YoushouldhaveapdfformatofATLASmanualinyoursilvacodirectory:

/doc）.Youmayalsoviewitbyaddingthe"print"optionintheModelstatement.

Q10

InoticeinAppendixB,Page21,therelistssomeopticalpropertiesofseveralsemiconductorssuchasSi,AlAs,GaAs...Howaboutternarycompoundsemiconductorandquaternarysemiconductors,suchasInGaAsorInGaAsP?

A10

AllthedefaultcomplexindexofrefractionforSi,AlAs,etcarelistedinB-21.Forthosematerialswhicharelackofcomplexindexofrefraction,youneedtospecifytheindexindicatedinpp.8-11ofATLASUser'sManualVol.1.

i.TosetsinglevaluesofRefractiveIndexregardlessofwavelength,youmayusetheandparametersoftheMATERIALstatementtosettherealandimaginaryindicesoftheternaryandquaternarymaterial,regionorregions;

ii.TosetaWavelengthDependentRefractiveIndexformultispectralsimulations,youneedtospecifyindexversuswavelength:

a.InafileknownastheINDEXfile.Notethatifyouusethismethod,onlylinearinterpolationfromthetableintheINDEXfilewillbeused.

b.UsetheC-INTERPRETERfunctioninwhichitcanreturnswavelengthdependentrealandimaginaryindices.

AlsonotethatyoucanaddtheparametertoanySOLVEstatementtoprintouttherefractiveindicesbeingusedforthatbiasstep.

Q11

HowtodefineanewmaterialsuchasInGaNbyusingtheC-Interpreter?

A11

Itispossibletosimulatetheuser-definedmaterialsuchasInGaNbyusingtheC-Interpreter.ThetemplatefilefortheC-Interpreterisasattached.Pleasesavethisfileinyourworkingdirectory.C:

\SILVACO\work.Theprocedureinvolvesinspecifying.thebandcomposition,foruser-definedmaterial.InGaNusingtheC-Interpreterarelistedbelow:

1.InyourMATERIALstatement,youneedtodefine:

materialmaterial=InGaN=""

wherespecifiesthenameofafile（inthiscaseiscontainingaC-INTERPRETERfunctionforthespecificationoftemperatureandcompositiondependentbandparametermodels.

2.Next,openthetemplatefile.C_template,usingWORDPADApplication.Gotothefunctionandyouwillseesomethingasshownbelow:

/*

*Temperatureandcompositiondependentbandparameters

*Statement:

MATERIAL

*Parameter:

*Note:

ThisfunctioncanonlybeusedwithBLAZE.

*Arguments:

*xcompcompositionfraction"X"

*ycompcompositionfraction"Y"

*temptemperature（K）

**egreturn:

bandgap（eV）

**chireturn:

affinity（eV）

**nc