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Crystal GrowthLaboratoryYour Competent Partnerin Crystal Growth andSolidification Processes
Annual Report 2002
- Equipment and Process Development -- Optical and Electrical Characterization -
- Numerical Modeling -
Content
1. Structure
2. Overview
3. Silicium Crystals with a Weight of More than 200kg
4. Low Defect GaAs Substrates for High Power LaserDiodes
5. Low Defect InP Substrates for Optical FiberCommunication
6. Fundamentals of Bulk Growth of GaN
7. Growth of High Quality CaF2 Crystal for NextGeneration Lithography
8. Chalcopyrite Semiconductors for Thin Film Solar Cells
9. Trends in the Modeling of Crystal Growth Processes
10. Thermal Modeling of Microgravity Experiments
11. Staff
12. Publications
13. Projects
14. Equipment
15. Contact
16. Travel Information
Structure
Crystal Growth LaboratoryBulk Crystal Growth of“classical” Semiconductors
• Silicon for Microelectronics• Low Defect GaAs and InP for
High Power Laser Diodes andHigh Speed Electronics
Bulk Crystal Growth of OpticalMaterials
• CaF2 Crystals for Lenses in DUVMicrolithography
• Oxides for High Speed Communi-cation and Medical Applications
Materials for Solar Cells
• Low Cost Silicon• CIS Thin Films
Software Development
• Process and Defect Models• 3D Simulation• Advanced Mathematical or
Numerical Methods• Graphical User Interface
Thermal Modeling
• Crystal Growth and AlloySolidification
• Licensing of SimulationTools
Bulk Crystal Growth of WideBand Gap Semiconductors
• Bulk Growth of Group III-Nitrides from Solutions
Overview
Crystal growth processesprovide basic materials formany applications and arefor example one key tech-nology in the chain of allmanufacturing processes for(opto-)electronic devices.The research and develop-ment of crystal growth proc-esses is driven by the de-mands which come from thespecific applications; but incommon there is a need foran increase of crystal di-mensions, improved uni-formity of the relevant crystalproperties in the micro- andmacroscale and materialswith new properties.
Therefore, the focal area ofresearch of the CrystalGrowth Laboratory (CGL),which is a world-wide ac-knowledged center of com-petence, is to develop – inclose collaboration with in-dustry - equipment and pro-cesses for the production ofbulk crystals and thin films in
order to meet the increasingrequirements on crystalquality and cost reduction.
The strategy of CGL is tooptimize the crystal growthprocessing by a combineduse of experimental processanalysis and computer mod-eling. This activities arebased on a suitable experi-mental infrastructure and onhighly efficient user friendlysimulation programs namedCrysVUn, STHAMAS andSTHAMAS3D. These com-puter codes, which are con-tinuously further developed,are used for and by the in-dustrial partners to developcrystal growth equipmentand processes.
CGL was founded at theDepartment of MaterialsScience of the University ofErlangen - Nuremberg byProf. Dr. Georg Mueller in1979. Since 1996 the CrystalGrowth Laboratory has
established the workinggroup "crystal growth" at theFraunhofer Institute forIntegrated Systems andDevice Technology (IISB) inErlangen. This workinggroup became theDepartment crystal growth inautumn 1999.
Since the foundation of CGLmore than 200 papers inscientific journals andconference proceedingshave been published.Furthermore, CGL haseducated a lot of experts inthis field. 115 "Study"theses, 80 diploma thesesand 33 PhD. theses mayserve as a reference for this.
More than 90% of funding ofCGL results from researchcontracts directly withindustrial partners and withthe German Ministry forResearch and Development,the Bavarian ResearchFoundation, the Bavarian
Fig. 1: Round table discussion during the Nitride Days of Erlangen (Person from left to right: Dr. Härle, Osram,Dr. Blanck, UMS, Dr. Duchemin, Thales, Prof. Müller, CGL, Dr. Brandes, Atmi, Prof. Gibart, Lumilog)
Overview
Government, the GermanResearch Foundation(DFG). Since 1996 almost11 Mio Euro have beenacquired from the differentsources indicated above.
Today, CGL consists ofmore than 30 highlymotivated coworkers. Theyare experts in differentfields, e.g. systemsengineering, metrology,computer simulation,physics, material science,mathematics.
The R&D activities of CGL in2002 can be brieflysummarized as follows:
In its traditional fields of CGLall industrial co-operationswere continued nearly on thesame level despite of theeconomic contractions of theglobal market.
The confidence of the in-dustrial partner in CGL andits excellent scientific posi-tion in the field of crystalgrowth is evident from thefact that more than 130crystal growers from all overthe world came together inErlangen at the beginning of2002. The reason was a sci-entific symposium on occa-sion of the 60. birthday ofthe head of CGL Prof. Dr.Georg Müller, in which theR&D activities which are on-going since more than twodecades in Erlangen wereillustrated
Furthermore, CGL hasspread its activities to newresearch areas in 2002.CGL started in the frame of
a "bmb+f" project as the onlyR&D institution in Germanyto develop methods for thegrowth of gallium nitride bulkcrystals. Gallium nitride is astrategic important materialfor the opto-electronic aswell as for the RF powerelectronic. This was con-firmed also during the "Er-langen's Nitride Days" whichwere organized by CGL inOctober 2002 and to whichmore than 130 experts cametogether from all over theworld.
Furthermore, CGL started in2002 to extend its activitiesin the field of optical crystals.For example a project wasinitiated on the developmentand optimization of thegrowth of oxide crystalswhich are used as scintilla-tors in so called positron -emission-tomographs in themedical technology.
In addition, the CGL hasextended its position as re-search institution in the fieldof material science undermicrogravity conditions. An
order from the Europeanspace agency ESA was ac-quired, in which CGLwill de-velop software programs.This will create the basis,that in the future experi-ments related to materialscience on the internationalspace station will be plannedand optimized by using thesoftware tools developed atthe CGL.
The international outstand-ing position of CGL wasconfirmed during a strategyaudit which was held in Oc-tober 2002 at the FraunhoferIISB. Nine experts from in-dustry and research ana-lyzed the current businessunits and core competencesas well as the strategies forthe future of the FraunhoferIISB during a two-day audit.Thereby, the auditors as-sessed the activities of CGLextremely positive.
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Fig. 2: Annual development of the acquired funding of CGL
Silicium Crystals with a Weight of Morethan 200kg
With every new generationof integrated circuits, thechip size has been in -creasing, because theproceeding miniaturization ofdevices is not sufficient tocompensate the steadilyincreasing number ofdevices per chip. Thispushes the semiconductorindustry, including the crystalsupplier Wacker SiltronicAG, to provide wafers with adiameter up to 300mm inproduction and currently400mm or 450mm forresearch, which are requiredfor today `s, as well as forfuture generations ofadvanced large scaleintegrated circuits.
Whereas the motivation forthe changeover from smallto large wafer-diameters hasbeen originally driven bytechnical reasons, theincreasing size of siliconcrystals and the correspon –ding size of the meltvolumes is mainly caused bythe aim of cost reduction.
Semiconductor industry isexpecting essentialeconomical advantages dueto the changeover fromgrowth processes fromcrucibles with a smalldiameter to larger meltvolumes. In modernindustrial growth facilitiessilicon crystals with a weightup to 450kg can be grownby the Czochralski method incrucibles with a diameter upto one meter. Large chargeweights are essential toimprove the ratio of polycrystalline charge weightand useable single crystalsweight. In the past big
efforts have been made torealize reproducible growthprocesses of heavy crystalsfrom large melt volumes asfor instance the develop-ment of supporting systems,low power hot zones and themanufacturing of largediameter and high qualitysilica crucibles.
However, large ingotscauses the melt flow, whichis driven by buoyancyforces, to be threedimensional, time dependantand turbulent what meanshigher temperaturefluctuations inside the meltresulting in more unstablegrowth conditions. In mostcases this has a detrimentaleffect on heat- and mass-
transfer and thereby on thecrystal quality. Additionally,an unstable melt flow variesthe contact area betweenliquid silicon and silicacrucible during a growth run,whereas it became difficultto adjust a homogenousoxygen concentration alongthe whole crystal length inthe required level. Moreover,long runtimes and highpower levels necessary forlarge melt volumes enlargecrucible corrosions anddeformation what leads to adecreased yield.
Therefore it has becomenecessary for thesemiconductor industry todevelop new types ofprocess parameters like the
Fig. 1: 300mm Silicium Cz crystal with a mass of 250kg, grownform a 32” crucible (source Wacker Siltronic AG)
Silicium Crystals with a Weight of Morethan 200kg
application of static andalternating magnetic fieldswhich give a suitablepossibility to adjust theoxygen concentration in arequired range by controllingthe melt flow. However, arealistic numerical simulationof the melt flow in such largemelt volumes is at abeginning stage and onlypartly possible at themoment. For that reason,the heat – and mass-transferin such melts still has to beinvestigated experimentallyusing appropriate sensorequipment.
In order to achieve furtherimprovement of the Si-Czochralski process, theIISB has developed appro-priate measurement equip-ment to carry out a preciseanalysis of the temperaturefield in large scale crystalgrowth facilities. Tempera-ture distributions within allparts of the silicium melt in-cluding the crucible wall aswell as temperature fluctua-tions can be detected duringa crystal growth run usingspecial thermocouple ar-rangements and fiber -
optical temperature sensorsmade from a sapphire orsilica. The experimentaldata, obtained for differentgrowth parameters, are pri-marily used for an optimiza-tion of the crystal growthprocess.
Furthermore, the data canbe useful for verification anddevelopment of numericalmodels, what is a part of thework of the IISB as well.
Recent PublicationsD. Vizman, O. Graebner, G.Mueller, Journal of CrystalGrowth 236(4) (2002) pp.545-550
D. Vizman, J. Friedrich, G.Mueller, Proc. of the 5th Int.lPamir Conf., Fundamentaland Applied MHD, 16-20September, 2002,Ramatuelle, France, 19-24
O. Graebner; G. Mueller; J.Virbulis; E. Tomzig; W. v.Ammon, Microelectronic-Engineering 56 2001, 83-88
A. Muehe; G. Mueller,Microelectronic-Engineering56, 2001, 147-152
D. Vizman, J. Friedrich, G.Müller, Journal of Crystal-Growth, 230, 2001, 73-80
D. Vizman, O. Graebner, G.Mueller, Journal of CrystalGrowth, 233, 2001, 687-698
S. Enger; O. Grabner; G.Muller; M. Breuer; F. Durst,Journal of Crystal Growt,230, 2001, 135-142
Fig. 2: Measured temperature distribution in a silicon meltwith 14” diameter for different types of magnetic fields
Low Defect GaAs Substrates for HighPower Laser Diodes
Nowadays there is a greatdemand for III/V-semiconductors due to thegrowing markets of highfrequency electronics (formobile telephones) andoptoelectronic devices. Thelatter includes highbrightness light emittingdiodes and diode lasers. Forexample, today conventionallamps are partially replacedin some fields by lightemitting diodes, due to theirlower consumption ofenergy. The same appliesfor lasers: There are plans topartially replace solid statelasers for applications likewelding and cutting bysemiconductor lasers, or atleast to use diode lasers foroptical pumping of solidstate lasers. Because of the high currentand power densities in theactive zones of thesedevices crystal defects in thesubstrates e.g. dislocationslead to a rapid devicedegradation. Thereforesingle crystals with a lowdefect density and a highhomogeneity are required. Inthe case of Gallium Arsenide(GaAs) a typical upper bondfor the dislocation density,which is measured in termsof the etch pit density (EPD),is 500 cm-2. Additionally acharge carrier density (n) of0.8⋅1018 - 3.0⋅1018 cm-3 isnecessary to enable thesubstrate to carry currentdensities in the order ofsome kA/cm-2. As the standard growthtechnique for III/V-materials,the liquid encapsulatedCzochralski (LEC)
technique, is not able toprovide crystals which fulfillthe requirements mentionedabove, a new growthtechnique (Vertical GradientFreeze, VGF) wasdeveloped within the lastdecade. Today the VGFtechnique is already in theproduction stage in industryand is gaining considerablemarket shares. In the VGF-technique thepolycrystalline material ismolten in a crucible. Afterthe melting process thematerial is directionallysolidified from a single-crystalline seed at thebottom of the crucible. Thisis achieved by lowering thetemperature whilemaintaining a positivetemperature gradient in themelt. As the crystal growth isusually performed in multi-zone furnaces there aremany degrees of freedom.Numerical modeling isapplied for the optimization
of the furnaces and thegrowth processes. In the past there wereextensive studies in order tooptimize the geometrical set-up as well as the thermalprocessing for the growthfurnaces available at theCrystal Growth Laboratory.As a result the EPD of Sidoped GaAs crystals with 3inch diameter decreased tovalues below 100 cm-2 in thewhole crystal. This EPD isfar below the values whichwas specified as the projectgoal. It was also possible togrow reproducibly 4 inchsingle crystals with weightsof 7kg or even more. In the last year the origin ofdislocations in the Si-dopedmaterial was studied in moredetail by using x-raytopography (in collaborationwith the ESRF in Grenoble).The Burgers vector ofdifferent types ofdislocations were
Fig.1: X-Ray topogram of a longitudinal cut of Si doped GaAs crystal.
Low Defect GaAs Substrates for HighPower Laser Diodes
determined (see fig.1). Theknowledge of the Burgersvector allowed to establish amodel which explainsdislocation walls in the wafercenter by glidepolygonization of grown-indislocations. In addition alternativedopants were studied.Tellurium is a promisingdonor as it is onlyincorporated on the As-sitein the GaAs-lattice. This isdifferent to the amphotericbehavior of Silicon, whichsubstitutes both As- and Ga-atoms. Therefore, higherdensities of conductionelectron and mobilities canbe expected. Apart from theelectrical also the structuralproperties (EPD) should beinfluenced by this dopant.Unfortunately it turned outthat the EPD in Te-dopedGaAs is similar in distribution
and number to that ofundoped GaAs. Fig. 2 givesa comparison of the EPD-distribution on a Si- and aTe-doped wafer, which weregrown using identical growthprocesses. Recent PublicationsB. Birkmann, R.Weingaertner, P. Wellmann,B. Wiedemann, G. Mueller,Journal of Crystal Growth237-239 (2002) 345-349
I. R. Grant, U. Sahr, G.Mueller, Conf. Proc., 14thInternational Conference onIndium Phosphide andRelated Materials (2002)413-415
M. Hainke, J. Friedrich, G.Mueller, Proc. of 5th Int.Pamir Conf. (2002) V-1
G. Mueller, B. Birkmann,Journal of Crystal Growth,237-239 (2002) 1745-1751
G. Mueller, Journal ofCrystal Growth 237-239(2002)1628-1637
M. Metzger, Journal ofCrystal Growth, Volume 230,Issues 1-2, August 2001,Pages 210-216
G. Mueller, B. Fischer,Advances in Crystal GrowthResearch, eds. K. Sato, Y.Furukawa, K. Nakajima,Elsevier, Amsterdam, (2001)167-190
M. Rasp, B. Birkmann, G.Mueller, Journal of CrystalGrowth 222, (2001) 88
Fig.2: EPD Mapping of 3" GaAs crystals doped with Si (left) and Tellurium (right).
Low Defect InP Substrates for OpticalFiber Communication
Indium phosphide is a III-Vcompound semiconductorcrystallizing in the sphaleritestructure, which has afortuitous lattice match toalloys with bandgapscoinciding with the 1.3 and1.55 µm windows in opticalfiber. The revolution inoptical fiber communicationshas swept InP into adominant position inoptoelectronics. For lattice-matched growth of ternaryalloys InGaAs and InAlAsand quarternary InGaAsPand AlInGaAs, InP is thesubstrate of choice.Heterostructure devicesbased on these alloys, byvirtue of their band-gaps,provide a strong drivingforce for bulk InP crystalgrowth development.
During the past twenty-fiveyears, as the growth of InPsingle crystals has gonefrom a laboratory curiosity toa commercial process, manynew applications for InPsubstrates have emerged.The mainstay of demandcontinues to be in the field oftelecommunications, butother uses for InP materialinvolving high speedelectronic and photoniccircuits have arrived. Inaddition to high frequencywireless communications,broadband gigahertz radarhas been achieved using InPphotoconducting antennas.
The state of the art today forInP crystal growth is dividedbetween three competingtechnologies; the Liquid-Encapsulated-Czochralski-Technique (LEC) and the
Vapour-Pressure-Controlled-Czochralski-Technique
(VCZ) with top seeding andvertical growth in a container(VGF, VB) with bottomseeding. The pulling methodhas generally been the mostcost effective, but itsdisadvantage is the highdislocation density causedby high levels of strainduring growth. On the otherhand, vertical containergrowth offers a very lowdislocation density becauseof its low-stressenvironment. But it isplagued by yield problemsdue to twinning and interfacebreakdown in heavily dopedcrystals.
InP crystals were grown bythe VGF-technique in<100>-direction. The seedsused, up to now, were grownby the LEC-method. Theetch-pit-density (EPD) variedbetween 3·104 cm-2 and5·104 cm-2. In figure 1 the
EPD of several VGF-crystalsis shown.
Sulfur was used as dopantand the carrier concentrationwas investigated by Hallmeasurements.Case 1 describes the axialdistribution of dislocations ina crystal grown with adoping concentration in therange 3 – 8·1017 cm-3. Dueto dislocation annihilationand conditions of lowthermal stress alreadyduring the seeding processthe dislocation densitydecreases rapidly. Up to asulfur concentration of 4·1017
cm-3 the EPD decreasesfurther.
Above a sulfur concentrationof 4·1017 cm-3 the EPDincreases because newdislocations are generatedby thermal stress. For thetotal crystal length the EPDis below 2000 cm-2.For case 2 the dopingconcentration is in the range1 – 3·1018 cm-3. The EPD
Fig. 1: EPD of 2” VGF-InP crystals in dependence of the Sulfurconcentration
Low Defect InP Substrates for OpticalFiber Communication
decreases continuously. Dueto the hardening effect ofSulfur the dislocation densitydrops down to 480 cm-2.Further at the end of thecrystal growth processtwinning occurred. To avoidtwinning, the main problemduring the growth of InP, aso called flat-bottom crucibleis used. However thestacking fault energy for theformation of a rotational twinis very small (18 mJ/m2) andconsequently twinningoccurs sometimes.Case 3 shows the EPD for acrystal grown in theconcentration range 3 –9·1018 cm-3. A LEC-seed witha dislocation density below500 cm-2 was used. Howeverdue to thermal stress theEPD near the seed end (seeFig. 2) is higher than 500cm-2. Then the EPDdecreases continuouslysimilar to case 2. An EPD of490 cm-2 was reached. Thelast data point represents atwinned substrate with anEPD of 180 cm-2.
Fig. 2 shows the lateraldistribution of dislocations onthe substrate. On the leftside the EPD-mapping for awafer near the seed end isshown. The EPD is 5500 cm-
2. An accumulation in thecenter and at the <100>-poles is clearly visible. Thiscan be explained by thecrystallographic data. Thefigure on the right siderepresents the tail end of thecrystal. The samedistribution can berecognized, but thedislocation density is lower(EPDmean = 490 cm-2).
Recent PublicationsU. Sahr, G. Mueller, Conf.Proc., 12th Semiconductingand Insulating MaterialsConference (2002)
U. Sahr, I. Grant, G. Mueller,Conf. Proc., 13thInternational and RelatedMaterials (2001) 533-536
I. R. Grant, U. Sahr, Conf.Proc., 14th InternationalConference on IndiumPhosphide and RelatedMaterials (2002) 413-415
U. Sahr, M. Baeumler, I.Grant, W. Jantz, G. Müller,Conf. Proc., 14thInternational Conference onIndium Phosphide andRelated Materials (2002)405-408G. Mueller, Journal ofCrystal Growth 237-239(2002)1628-1637
M. Metzger, Journal ofCrystal Growth, Volume 230,Issues 1-2, August 2001,Pages 210-216
G. Mueller, B. Fischer,Advances in Crystal GrowthResearch, eds. K. Sato, Y.Furukawa, K. Nakajima,Elsevier, Amsterdam, (2001)167-190
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Fig. 2: EPD-mappings of 2” VGF-substrates, at the seed end (left side) the EPD is 5500 cm-2, at the tailend (right side) the EPD is 490 cm-2.
Fundamentals of Bulk Growth of GaN
Since the realization of theblue light emitting diode andthe blue semiconductor laseron the basis of GaN, there isgrowing interest in the groupof III/V-nitrides. The reasonfor this are the applications,which will become possible ifblue light is available. Due tothe high saturation velocitiesand the high breakdownfields the III/V-nitrides arealso of great interest for highpower and high frequencydevices.
So far the activities in thearea of the III/V-nitrides inGermany are restricted tothe fabrication of devices byepitaxial methods. Incontrast to othersemiconductors nosubstrates of the samematerial are available, thusepitaxy is done onheterosubstrates, usuallysapphire or SiC. Because oftypical problems like poorwetting of the substrate, alarge lattice mismatch anddifferent thermal expansioncoefficients, the epitaxiallayers are very defective(high dislocation densities,mosaic structure, cracks).
In order to cope with theseproblems big technologicalefforts are necessary:At low temperatures anucleation layer is depositedwhich enhances the wettingof the substrate and therebysuppresses the occurrenceof growth islands. For laserdevices the dislocationdensity is additionallyreduced by socalled “Epitaxial LateralOvergrowth” (ELO).
The necessary technologicalefforts will be significantlyreduced by performinghomoepitaxy on GaN-substrates. Simultaneouslythe quality of epitaxial layersand therefore theperformance of the deviceswill improve noticeably.Hence there are world wideattempts to develop amethod which allows thefabrication of GaNsubstrates.
Despite of the big efforts nomethod for the growth of realbulk GaN was developed upto now.
Among the examined growthtechniques the so called“Hydride Vapor PhaseEpitaxy” (HVPE) is the bestdeveloped method so far.The HVPE allows forexample the growth of singlesubstrates.
The growth under very highpressures and hightemperatures (15kbar,1500°C) is well establishedand studied, but has only ledto platelet like crystals withlateral dimensions ofapproximately 1 cm up tonow.
One year ago research atthe Crystal growthLaboratory on the solutiongrowth of GaN-bulk crystalswas started, which is fundedby the German Ministry forResearch (FKz. 01BM158).The aim of the project is todevelop a solution growthprocess, which allows thegrowth of crystals withindustrially relevantdiameters under moderatepressures and temperatures.
Due to the very low solubilityof GaN in Ga-melts it isnecessary to find a solventin which the solubility is
Fig.1: GaN-crystal grown from a Ga containing solution at lowpressures
Fundamentals of Bulk Growth of GaN
enhanced compared to pureGa. Therefore examinationsusing thermogravimetry (TG)and differentialthermoanalysis (DTA) areplanned. Finally a suitablegrowth facility for thesolution growth of GaN willbe built.
During the last year theexperimental infrastructurewas installed, especially thesupply and the disposal ofthe necessary processgases. Several smallerexperimental growthfurnaces were set up, inwhich basic examinations onsuitable solvents are done.The TG/DTA-device ismeanwhile delivered and theprototype of the GaN-growthfacility is being built.
As a result of theexaminations there arepromising candidates forsolvents, which will befurther examined in the nextyear.
The results of the work doneso far are crystallites (fig.1)exhibiting an average size ofup to 1000 µm. They wereconfirmed to be GaN bymeans of X-ray diffraction(fig.2).
At the same time it waspossible to deposit GaN onSiC-substrates orientedly.
With these results the basisfor continuing the crystalgrowth has been laid. Theknowledge gained so far hasnow to be transferred to thegrowth set-up which is underconstruction.
Recent PublicationsJ. Friedrich, ErlangerNitridtage: Erlangen imZeichen des blauen Lasersund UMTSDGKK Mitteilungsblatt76/Dezember 2002
[email protected] .2: identification of the crystallites by X-ray diffraction
Growth of High Quality CaF2 Crystal forNext Generation Lithography
Optical photolithographyuses shorter wavelengths toproduce more denselypacked electronic circuits onthe silicon chips. To achievethis performance F2 laserswith a wavelength of 157 nmwill be used in the so-calledwafer steppers. At thiswavelength high purity singlecrystalline calcium fluoride(CaF2) has excellenttransmission characteristics.It is therefore selected asthe main optical material forthe next generation oflithography apparatus.
For this optical applicationthe material requirementsare extremely high. CaF2single crystals with therequired properties andlarge dimensions can beonly grown by anoptimization of the crystalgrowth process by the aid ofnumerical simulation. It isvery important to evaluatethe numerical model byaccurate measurements ofthe temperature distributionin CaF2 during the crystalgrowth process. Themeasurements turn out to bequite difficult due to thehighly corrosive properties ofCaF2 at highertemperatures.
In order to obtainexperimental data inside themelt as well as inside thesolid phase, we developed anew measurementtechnique. Themeasurements were carriedout in a special Bridgman-type R&D growth facility atthe Crystal GrowthLaboratory. Theexperimental set-up used for
the novel temperaturemeasurements isschematically shown infigure 1.
A protection tube with aclosed bottom side wasinstalled inside the crucibleand thereby arranged alongthe symmetry axis. This tubewas embedded in the rawCaF2 powder before startingthe melting process. Aftermelting of the raw materialthe growth process wasstarted. The protection tuberemained fixed during thewhole crystal growth andenabled in-situ detection oftemperatures in liquid aswell as in solid regions bymoving a thermocoupleinside the tube. Further onthe thermocouple equipmentwas protected by the tubeagainst the highly corrosiveenvironment. Thismeasurement techniqueyields temperature data at a
lot of reading pointsthroughout the whole growthprocess by using only onesingle temperature sensor.
Temperature measurementsalong the symmetry axiswere performed at differentgrowth stages i.e. atdifferent positions of solid-liquid interface. Theobtained temperatureprofiles, shown in figure 2a,represent the entire growthprocess. The firsttemperature profile wasmeasured at the beginningof growth. It shows mainlythe temperature distributionin a large melt region. Thesecond one, obtained in themiddle of the growth run,gives the temperaturedistribution in the liquid aswell as in solid region. Thethird temperature profile,performed after entirecrystallization, shows thetemperature distribution in
crucible
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fixedprotection tube
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Fig. 1: Set-up for temperature measurements in CaF2 melt and crystalduring growth
Growth of High Quality CaF2 Crystal forNext Generation Lithography
the crystal. As can be seenfrom figure 2a, all measuredtemperature profiles insideCaF2 show a lineardependence. The axialtemperature gradient isequal for all temperatureprofiles, measured atdifferent growth stages. Thisindicates that the axialtemperature gradient inCaF2 does not depend onthe position of the solid-liquid interface. It isremarkable that thetemperature gradient in themelt and in the crystal areidentical.
The precise calculation ofheat transport andtemperature distribution in
solid and liquid CaF2 duringcrystal growth requires theapplication of a suitablequantitative numericalmodel. The radiative heattransfer in semitransparentmedia is often described bythe so-called “diffusion-approximation”. This modeltakes internal radiation intoaccount by adding onefurther term to the heatconductivity. In order toimprove the accuracy of thenumerical results wedeveloped an advancedmodel where the radiativepart of the heat transport inCaF2 is directly calculatedinstead of the approximationused in the standarddiffusion model. Numerical
results of the temperaturedistribution in the CaF2region are shown in figure2b. The advanced modelgives a better agreementwith experimental dataconcerning temperature fieldin the CaF2 region and theposition of the solid-liquidinterface. The deviations ofthe absolute temperaturesare less than 1%.
Recent PublicationsA. Molchanov, O. Graebner,G. Wehrhan, J. Friedrich, G.Mueller, Journal of theKorean Crystal Growth andTechnology 13 (2003) 15-18
A. Molchanov, U. Hilburger,J. Friedrich, M. Finkbeiner,G. Wehrhan, G. Mueller,Cryst. Res. Technol. 37(2002), 77-82
G. Mueller, J. Friedrich,Schott Info 100 (2002) 12-14
axial position Z
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Fig. 2: Measured (a) and calculated (b) temperature profiles inCaF2 along the symmetry axis
Chalcopyrite Semiconductors for ThinFilm Solar Cells
Chalcopyrite semi-conductors are promisingabsorber materials for thinfilm solar cell applicationsdue to their high absorptioncoefficient. The mostimportant compound isCu(In,Ga)Se2 (CIS). InGermany the state of the artin CIS solar celldevelopment is theinstallation of two pilotmanufacturing facilities forthe production of moduleswith monolithically integratedcells.
CGL is working in co-operation with Shell Solarwith the financial support ofthe Bavarian ResearchFoundation on theoptimisation andcharacterisation of the thinfilm deposition and theabsorber formation process.To achieve further insight inthe involved chemicalreactions in-situ methodsare applied like Thin FilmCalorimetry (TFC), in-situresistivity measurementsand X-ray- diffraction(cooperation with theInstitute of Crystallographyand Structural Physics, FAUErlangen- Nürnberg) duringsemiconductor formation.
Although produced in anindustrial scale, some CISsolar cell absorber proper-ties are not yet fullyunderstood. One topic is theincorporation of the Galliumin the absorber during itsindustrial (so-called ‘stackedelemental layer’) formation,where the elementalcomponents of the absorberare deposited sequentially(in the order Cu � In � Se),
and afterwards a RapidThermal Process (RTP) isapplied to synthesise thechalcopyrite.
Initially intended as a meansof widening the band gap ofCuInSe2 for a betteradaptation to the sunspectrum, galliumnevertheless fails tohomogenise in the absorberlayer. Instead, itaccumulates at the backcontact of the solar cell, andforms a back surface fieldwhich increases the cellefficiency but does not fullyexploit the efficiency-increasing potential ofhomogeneously distributedgallium. Below, our recentwork in this area isdescribed as an example ofour analysis andoptimisation strategy.
According to our latestinvestigations, theinhomogeneous Ga-distribution can be explainedby the different reactionkinetics of the metallicabsorber components Cu, In
and Ga during chalcopyriteformation, together with adirectional growth of thechalcopyrite layer.Latter can be seen in anSEM image (Fig. 1) of thecross-section of a CISsample (here Ga-free) afterpartial thermal processing to400 °C. Two layers of astacked structure can bedistinguished. In the toplayer the metallic absorbercomponents were attackedby the selenium and havereacted to binary selenidesand CIS, whereas at thebottom layer an intermetallicphase Cu16In9 is stable for alarge fraction of the thermalprocess.
Kinetic models derived fromextensive in-situ analysis ofthe selenization processsteps show that gallium ismuch more inert to theselenium attack than e.g.indium: the sequence of thedifferent phases whichprogressively incorporateselenium during the thermalprocess is delayed by about
Fig. 1: SEM image of a cross-section of a CIS-absorber during theStacked Elemental Layer process.
Cu16In9
Chalcopyrite Semiconductors for ThinFilm Solar Cells
50 K when comparing Gawith In.
As a result the metallicindium is already completelyconsumed under theseprocess parameters whileGa is just beginning to react.So gallium is notincorporated in the top layerselenides but isaccumulating at the bottomof the solar cell near theback contact where it finallyforms a Ga- rich chalcopyritelayer.
This important insight in themechanism of absorberformation should allow foroptimisationstrategies – either byaltering the depositionprocess or the thermaltreatment of the absorber –resulting in a morehomogeneous Ga-depthprofile and subsequentlyhigher efficiencies of theindustrial solar cells.
Recent PublicationsP. Berwian, A. Weimar, G.Mueller, Thin Solid Films431-432 (2003) 41-45
Ch. Hack, D. Seng, P.Wellmann, G. Mueller, E-MRS Spring Meeting 2002,Strasbourg
J. Auer, Ch. Hack, P.Berwian, G. Mueller, E-MRSSpring Meeting 2002,Strasbourg
P. Berwian, J. Hirmke, A.Brummer, G. Mueller, 13th
International Conference onTernary and MultinaryCompounds, Paris, 2002
Ch. Hack, J. Auer, S. Hussy,G. Mueller, 13th InternationalConference on Ternary andMultinary Compounds, Paris,2002
0%
25%
50%
75%
100%
200 250 300 350 400 450Temperatur [°C]
Konz
entra
tion
In+SeIn4Se3InSeIn2Se3Ga+SeGaSe
Fig. 2: Modelled phase content of In-Se and Ga-Se thin films during rapid thermal processing.
Trends in the Modeling of CrystalGrowth Processes
Due to the diversity ofmaterials and differentprocesses, the modeling ofcrystal growth processesrequires very differentphysical phenomena and theapplication of as differentnumerical methods. It wouldgo beyond the scope of thisarticle to list all of thesehere. Nevertheless, anattempt will be made todepict shortly ongoing andcoming developments andfields of activities in thecompass of modeling ofcrystal growth processes.
Application of „soft-computing“ approachesThe term „soft-computing“embraces algorithms whichdo not necessary result inexact solutions, buteventually yieldapproximations in a simpleand efficient way. Furtherapplications are problemswhich due to their inherentcomplexity have no analyticdescription. Examples forsoft-computing approachesare fuzzy logics, neuralnetworks and evolutionaryalgorithms.
Currently, the CGL isdeveloping and usinggenetic algorithms for theoptimization of processparameters (see fig. 1). Thisis aiming at the developmentof a universally applicableoptimization software
Improvements to themodeling of thermalradiationDue to the generally hightemperatures in crystalgrowth processes, heattransport by radiation plays a
dominant role. It can bemodeled satisfactorily usingthe view-factor method ifthere are only materialswhich can be consideredeither as completely opaqueor as completelytransparent. An additionalnecessary assumption isdiffuse reflection, which isnot justified e.g. at metallicsurfaces.
Especially, the increasingimportance of opticallyparticipating media (e.g.optical crystals for lasers,scintillators, ..) requires thedevelopment and use ofmore capable models. Hereis a trend towards the furtherdevelopment and use ofmethods which have alreadybeen developed in the areaof computer graphics. Ray-tracing based algorithmsseem to be promising, asthey allow inclusion of allrelevant physicalphenomena relatively easily.Such an approach iscurrently being realized inthe department for crystalgrowth in the developmentof a new 3D simulationprogram.
Multi scale modelingWith increasingcomputational power themodeling of multi-scaleproblems is becomingpossible. This means, thatprocesses taking place onvery different spatial or timescales have to be taken intoaccount within one model.An example for diverse timescales is the modeling ofdefect formation in agrowing crystal, which has tobe modeled on a much
smaller time scale than e.g.the variations of the thermalfield. On the other hand verydiverse spatial scales haveto be considered whentaking into account detailedgrowth models (formation ofdendrites, grains, facets, ...)within a global thermalsimulation of a furnace.
In this field, CGL is active inthe modeling of defect anddislocation formation insilicon and the modeling ofthe microstructure of metallicalloys.
Fig.1: Principle of genetic algorithm
Trends in the Modeling of CrystalGrowth Processes
Coupling of 2D and 3DcodesEspecially, considering thegrowth of silicon by theCzochralski process it iscompletely sufficient andefficient to perform theglobal modeling oftemperature within thefurnace using anaxisymmetric model. On theother hand it has becomeobvious that this is notcorrect for the convectiveprocesses within the melt,which have a significantinfluence on the growth ofthe crystal. This suggeststhe coupling of a globalaxisymmetric temperaturemodel with a detailed three-dimensional model of themelt, which is currently workin progress in CGL (see fig.2).
ParallelisationThe actual list of the top 500computers in the world(www.top500.org, Dec.2002) lists already 93clusters, with increasingtendency, among them 14which are titled as „self-
made“. Concerning softwaredevelopment, this leads tothe requirement that newprojects should be designedfrom the very beginning insuch way that computationscan be performed effectivelyand easily on such relativelycheap self-made clusters aswell as on heterogeneousnetworks as they aregenerally available ininstitutes and companies.
CGL has providedprerequisites for parallelcomputing by parallelisingthe 3D flow simulatorSTHAMAS3D and thecomputation of viewfactorsin the 2D code CrysVUn.
Recent PublicationsJ. Derby, P. Daoutidis, Y.Kwon, A. Pandy, P. Sonda,B. Vartak, A. Yeckel, M.Hainke, G. Mueller, in HighPerformance Scientific andEngineering Computing(eds. M. Breuer, F. Durst, C.Zenger in Lecture Notes inComputational Science andEngineering), Springer,Heidelberg (2002) 185-201
M. Hainke, T. Jung, J.Friedrich, B. Fischer, M.Metzger, G. Mueller,Progress in IndustrialMathematics (Eds. Anile,A.M.; Capasso, V.; Greco,A.), Springer (2002), 218-222
G. Mueller, Journal ofCrystal Growth 237-239(2002)1628-1637
O. Paetzold, B. Fischer, A.Croell, Cryst. Res. Technol.37 (2002) 1058-1065
Y. Stry, M. Hainke, T. Jung,Int. Journal of NumericalMethods for Heat&FluidFlow, Vol. 12(8) (2002)1009-1031
2D axisymmetric partial 3Dglobal 3DFig.2: Coupling of global axisymmetric models with partial full three-dimesnional models
Thermal Modeling of MicrogravityExperiments
Materials research undermicrogravity conditions hasalready a more than twentyyears old tradition inErlangen. The specificconditions of microgravityallow a systematicinvestigation of certainphysical effects duringsolidification ofsemiconductor and metals,which is not possible in thisway under terrestrialconditions.
An impressive example isthe growth of the largestGaAs-crystal by the so-called Floating-Zone methodduring the German D2mission by Prof. Dr. G.Müller.Research activitiesunder microgravityconditions developed to awell established branchwithin the field of materialscience during the lastyears. Thereby, the build-upof the international spacestation ISS offerspossibilities for systematicexperimental investigations,which were not possiblebefore. CGL is actuallyinvolved in the field of basicresearch, as well as actingas a service center which issupporting other researchgroups. In any case, themain part of the activities isthe development andapplication of suitablenumerical tools foroptimizing the experimentsto be carried onboard thespace station.
Within the European projectMICAST, fundamentalaspects of the solidificationof alloys are investigated.The research activities are
focused on a systematicanalysis of the influence ofconvective heat- andspecies transport on themicrostructure development(fig. 1). The basis for theexperimental as well as thenumerical investigations aretechnical Al alloys.
The task of CGL is thedevelopment and applicationof suitable simulation tools.For this purpose, thesoftware package CrysVUnwas extended with propermodels for the treatment ofthe complex coupledphenomena duringsolidification, that areappearing on different lengthscales. By the use of thesimulation tool, theexperimental investigationswithin the MICAST projectare supported to define theprocess conditions, e.g. themagnetic field strength.
Furthermore, numericalmodeling gives a deeperunderstanding of the
complex phenomena,appearing duringsolidification.
As the ISS is not availablefor material science relatedexperiments in the nearfuture, the first experimentsunder microgravityconditions within theMICAST project are carriedout with so-called soundrocket missions. The firstexperiment is scheduled onspring 2004. The furnacemodel of the ARTEX facilityof the DLR which will thenbe launched onboard therocket is actually developedat CGL (fig. 2).
Besides the basic researchactivities within the MICASTproject, CGL hassuccessfully participated inan international call fortenders of the Europeanspace agency ESA. Thegoal of this project is todevelop proper furnacemodels of the foreseenfacilities on the ISS. These
Fig. 1: Dendritic morphology of a solidified Al alloy, obtained by adecanting technique (source: ACCESS e.V.).
Thermal Modeling of MicrogravityExperiments
models should help todecrease both costs anddevelopment time ofdifferent furnace cartridgesinserts. Furthermore,experimental runs can bebetter prepared by theconsequent application ofnumerical modeling. Hereby,CGL could establish itself asa User Support Center withinthe next years.
Recent PublicationsJ. Derby, P. Daoutidis, Y.Kwon, A. Pandy, P. Sonda,B. Vartak, A. Yeckel, M.Hainke, G. Mueller, in HighPerformance Scientific andEngineering Computing(eds. M. Breuer, F. Durst, C.
Zenger in Lecture Notes inComputational Science andEngineering), Springer,Heidelberg (2002) 185-201
J. Friedrich, R. Backofen, G.Mueller, Adv. Space Res.29/4 (2002) 549-552
M. Hainke, J. Friedrich, G.Mueller, Elgra News 23(2003) 103
M. Hainke, T. Jung, J.Friedrich, B. Fischer, M.Metzger, G. Mueller,Progress in IndustrialMathematics (Eds. Anile,A.M.; Capasso, V.; Greco,A.), Springer (2002), 218-222
O. Paetzold, B. Fischer, A.Croell, Cryst. Res. Technol.37 (2002) 1058-1065
Fig.2: The ARTEX facility of the DLR (left) and the furnace model developed with CrysVUn (right).
Staff
Name Tel. +49-9131- Email
Rainer Apelt
Gheorghe Ardelean
Noemi Banos
Patrick Berwian
Dr. Peter Binder
Dr. Bernhard Birkmann
Johannes Dagner
Dr. Jakob Fainberg
Dr. Jochen Friedrich
Tim Fühner
Oliver Gräbner
Christina Hack
Horst Hadler
Marc Hainke
Elisabeth Henneberger
Stephan Hussy
Jiri Janeba
Dr. Thomas Jung
Flaviu Jurma
Michael Kellner
Lothar Kowalski
Bernd Kreß
Ulrike Marten Jahn
Dr. Elke Meissner
Alexander Molchanov
Prof. Dr. Georg Müller
Michael Purwins
Uwe Sahr
Peter Schwesig
Carine Scordo
Guoli Sun
Dr. Daniel Vizman
761-252
761-265
761-229
852-7757
761-231
761-136
761-266
761-264
761-344
761-261
761-226
852-7757
761-273
761-233
852-7729
761-251
761-233
761-264
761-135
761-273
852-7720
85-27722
852-7757
761-136
761-225
852-7636
852-7757
852-7722
852-7722
761-311
761-135
761-229
Publications in 2002
M. Baeumler, E. Diwo, W. Jantz, U. Sahr, G. Mueller and I. GrantOptical evaluation of spatial carrier con-centration fluctuations in doped InP substratesConf. Proc., 29th International Symposium on Compound Semiconductors (2002)
B. Birkmann, R. Weingaertner, P. Wellmann, B. Wiedemann, G. MuellerAnalysis of silicon incorporation into VGF-grown GaAsJ. Crystal Growth 237-239 (2002) 345-349
J. Derby, P. Daoutidis, Y. Kwon, A. Pandy, P. Sonda, B. Vartak, A. Yeckel, M. Hainke, G.MuellerHigh performance computing, multi scale models for crystal growth systemsHigh Performance Scientific and Engineering Computing (eds. M. Breuer, F. Durst, C.Zenger in Lecture Notes in Computational Science and En-gineering), Springer, Heidelberg(2002) 185-201
J. Friedrich, R. Backofen, G. MuellerNumerical simulation of grain structure and global heat transport during solidification oftechnical alloys in MSL inserts under diffusive conditionsAdv. Space Res. 29/4 (2002) 549-552
J. FriedrichErlanger Nitridtage: Erlangen im Zeichen des blauen Lasers und UMTSDGKK Mitteilungsblatt 76/Dezember 2002
I. R. Grant, U. Sahr, G. MuellerGrowth of InP and GaAs Substrate Crystals by the Vertical Gradient Freeze MethodConf. Proc., 14th International Conference on Indium Phosphide and Related Materials(2002) 413-415
M. Hainke, T. Jung, J. Friedrich, B. Fischer, M. Metzger, G. MuellerEquipment and Process Modelling of Industrial Crystal Growth Using the Finite VolumeCodes CrysVUn and STHAMASProgress in Industrial Mathematics (Eds. Anile, A.M.; Capasso, V.; Greco, A.), SpringerVerlag, ISBN 3540425829 (2002), 218-222
M. Hainke, J. Friedrich, G. MuellerNumerical Study of the Effects of Rotating Magnetic Fields during VGF Growth of 3" GaAsCrystalsProc. of 5th Int. Pamir Conference (2002) V-1
A. Molchanov, U. Hilburger, J. Friedrich, M. Finkbeiner, G. Wehrhan, G. MuellerExperimental verification of the numerical model for a CaF2 crystal growth processCrystal Reseach and Technology 37 (2002), 77-82
G. Mueller, B. Birkmann,Optimization of VGF-growth of GaAs crystals by the aid of numerical modelling,J. Crystal Growth, 237-239 (2002) 1745-1751
G. Mueller, J. FriedrichJuwelen für InnovationSchott Info 100 (2002) 12-14
Publications in 2002
G. Mueller, J. FriedrichZüchtung von Einkristallen - eine Herausforderung für Wissenschaft und TechnikNachrichten des Fraunhofer-Verbunds Mikroelektronik 8 (2002) 2
G. MuellerExperimental analysis and modeling of melt growth processesJ. Crystal Growth 237-239 (2002)1628-1637
O. Paetzold, B. Fischer, A. CroellMelt flow and species transport in µg-gradient freeze growth of GermaniumCryst. Res. Technol. 37 (2002) 1058-1065
U. Sahr, M. Baeumler, I. Grant, W. Jantz, G. MuellerPhotoluminescence Topography of Sulfur doped 2” InP grown by the Vertical GradientFreeze TechniqueConf. Proc., 14th International Conference on Indium Phosphide and Related Materials(2002) 405-408
Y. Stry, M. Hainke, T. JungComaprison of linear and quadratic shape functions for a hybrid control-volume finiteelement methodInt. Journal of Numerical Methods for Heat&Fluid Flow, Vol. 12(8) (2002) 1009-1031
U. Sahr, G. MüllerGrowth of InP Substrate Crystals by the Vertical Gradient Freeze TechniqueConf. Proc., 12th Semiconducting and Insulating Materials Conference (2002)
D. Vizman, O. Graebner, G. Mueller3D numerical simulation and experimental investigations of melt flow in a Si Czochralski meltunder the influence of a cusp-magnetic fieldJournal of Crystal Growth 236(4) (2002) pp. 545-550
D. Vizman, J. Friedrich, G. MuellerHMCZ and EMCZ in the Industrial Czochralski Growth of 300mm Si CrystalsProceedings of the 5th International Pamir Conference, Fundamental and Applied MHD, 16-20 September, 2002, Ramatuelle, France, 19-24
G. Mueller, O. Graebner, D. VizmanSimulation of crystal pulling and comparison to experimental analysis of the CZ-processin Semiconductor Silicon 2002 (eds. H.R. Hunt, L. Fabry, S. Kishino) ElectrochemicalSociety (2002) 489-504
Projects in 2002
Bulk Growth of GaAs, InP, Si and CaF2, and solarcell materials experimentalFundamentals of the crystal growth process of InP bythe Vertical Gradient-Freeze methodFunded by: (BMBF)
Crystal growth and processing of Si – wafer with 300mm diameterFunded by: Wacker Siltronic (BMBF)
Development and process optimization of CaF2 for the157 nm applicationFunded by: Schott Lithotec (BMBF)
Fundamentals of GaN bulk crystal growth andsubstrate developmentFunded by: BMBF
Processing of CIS: optimization and characterizationFunded by: Shell Solar, BayerischeForschungsstiftung
Numerical simulation of crystal growthDevelopment of software programs to be used for theconstruction of energy-saving furnaces in the field ofmaterials production and crystal growthFunded by: Crystal Growing Systems (BMWI)
Numerical simulation for the support of process andfurnace development for the growth of large diameterGaAs crystalsFunded by: Freiberger Compound Materials (BMVG)
Further development STHAMAS3D for the simulationof the convective heat and mass transport processesduring LEC growth of GaAsFunded by: Freiberger Compound Materials (BMVG)
Global thermal simulation of the Tri-Si Czochralskiprocess for the production of Si crystals for solar cellsFunded by: Shell Solar (BMBF)
Study of grain structure during solidification oftechnical alloys under diffusive and magneticallycontrolled convective conditions with the help ofmicrogravity experimentsFunded by: DLR
Microstructure formation in technical alloys underdiffusive and magnetically controlled convectiveconditionsFunded by: ESA
MSL Furnace Insert and Sample Cartridge AssemblyThermal ModelingFunded by: ESA
Numerical simulation of the growth of InP crystals bythe LEC techniqueFunded by: MACOM
Development and validation of a numerical model forthe growth of oxide crystalsFunded by: Photonicmaterials
Development and license of the computer codeCrysVUnFunded by: Freiberger Compound Materials, D
Development and license of the computer codeCrysVUnFunded by: Linn High Therm, D
Development and license of the computer codeCrysVUnFunded by: DLR, D
Development and license of the computer codeCrysVUnFunded by: University Freiberg, D
Development and license of the computer codeCrysVUnFunded by: CAESAR, D
Development and license of the computer codesCrysVUn and STHAMASFunded by: Institute of Crystal Growth Berlin, D
Development and license of the computer codeCrysVUnFunded by: Wafertechnology,UK
Development and license of the computer codeCrysVUnFunded by: MEMC, I
Development and license of the computer codeSTHAMAS and CrysVUnFunded by: Shinetsu, Japan
Development and license of the computer codeSTHAMASFunded by: Komatsu, Japan
Development and license of the computer codeSTHAMASFunded by: Sumco, Japan
Development and license of the computer codeSTHAMASFunded by: LG Siltron, Korea
Development and license of the computer codeCrysVUnFunded by: Hiqtech, Korea
Development and license of the computer codeCrysVUnFunded by: Umicore, Belgium
Development and license of the computer codeSTHAMASFunded by: University Taiwan, Taiwan
Development and license of the computer codeCrysVUnFunded by: University Minnesota, USA
Equipment
Laboratory space:200 m2 laboratory space in total at university and Fraunhofer IISB plus offices.
Crystal growth• several high-pressure furnaces (for 2" - 6" crystal diameter)• 1 multi zone furnace for vacuum (for up to 6" crystal diameter)• several multi zone furnaces for sample preparation and growth of small diameter crystals• 1 liquid phase epitaxy facility
Analysis and characterization of materials• Several optical/infrared microscopes• Access to high resolution microscopes• Mapping system for optical spectroscopy of semiconductor wafers• Interferometric profilometer for surface analysis of semiconductor wafers• X-ray Laue camera• Hall-measurement-system (temperature dependent 15K-650K)• Measurement system for characterization of deep and shallow levels by capacitance
techniques (CV, DLTS) and by conductance techniques (TSC, PICTS)• Photoluminescence system (14K and 300K), IR-absorption, both systems suitable for
mapping• Differential Thermal Analysis for determination of phase diagrams• Differential Scanning Calorimeter for thermodynamic and kinetic studies• Thermogravimetrie
Preparation and metallography• Facilities for preparative work related to wafer preparation (grinder, annular and wire
saws, lapping and polishing equipment)• Several evaporation systems• Sputtering systems (DC, 6" target diameter)
ContactCrystal Growth Laboratory Crystal Growth LaboratoryProf. Dr. Georg Müller Dr. Jochen FriedrichUniversity Erlangen-Nürnberg Fraunhofer IISBMartensstrasse 7 Schottkystrasse 1091058 Erlangen 91058 ErlangenPhone: +49-9131-852-7636 Phone: +49-9131-761-344Fax: + 49-9131-852-8495 Fax: + 49-9131-761-312http://www.kristallabor.de http://www.kristallabor.deEmail: [email protected] Email: [email protected]
Travel Information
By carUse Autobahn A3, exit Tennenlohe,follow signs for Erlangen, after 2 km takeexit for "Universität Südgelände", thenfollow signs for IISB: 1.6 km north onKurt-Schumacher-Straße, then turn lefttwice into Cauerstraße andSchottkystraße.
By planeFrom Nürnberg (Nuremberg) airport usetaxi (15 minutes) or bus 32 to Nürnberg-Thon and then bus 30/30E to Erlangen-Süd (30 minutes).
By trainFrom Erlangen station, use taxi (15minutes) or bus 287 to Stettiner Straße(30 minutes). Convenient train servicesfrom Nürnberg Hauptbahnhof (centralstation) to Erlangen station.
Tourist InformationVerkehrsverein Erlangen e.V.Rathausplatz 1, 91052 Erlangen,GermanyPhone: +49-9131 89-150Fax: +49-9131 89-5151WWW: www.erlangen.de