EP1228539A2 - Hocheffiziente uv-emitter auf nitridhalbleiterbasis - Google Patents
Hocheffiziente uv-emitter auf nitridhalbleiterbasisInfo
- Publication number
- EP1228539A2 EP1228539A2 EP00993057A EP00993057A EP1228539A2 EP 1228539 A2 EP1228539 A2 EP 1228539A2 EP 00993057 A EP00993057 A EP 00993057A EP 00993057 A EP00993057 A EP 00993057A EP 1228539 A2 EP1228539 A2 EP 1228539A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- layer
- substrate
- light
- semiconductor
- phase
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000004065 semiconductor Substances 0.000 title claims abstract description 61
- 150000004767 nitrides Chemical class 0.000 title description 13
- 239000000758 substrate Substances 0.000 claims abstract description 67
- 239000013078 crystal Substances 0.000 claims abstract description 29
- -1 nitride compounds Chemical class 0.000 claims abstract description 13
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/16—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
- H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/32—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures
- H01S5/3202—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures grown on specifically orientated substrates, or using orientation dependent growth
- H01S5/32025—Structure or shape of the active region; Materials used for the active region comprising PN junctions, e.g. hetero- or double- heterostructures grown on specifically orientated substrates, or using orientation dependent growth non-polar orientation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/34333—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
Definitions
- the invention relates generally to a layer structure with a substrate and at least one semiconductor layer based on a nitride semiconductor compound, a layered semiconductor crystal based on at least one nitride compound, light-emitting semiconductor components which contain at least one such layer structure or such a semiconductor crystal, and methods for producing the Layer structure, the semiconductor crystal or the components.
- nitride semiconductors e.g. molecular beam epitaxy (MBE) or metal organic chemical vapor deposition (MOCVD).
- MBE molecular beam epitaxy
- MOCVD metal organic chemical vapor deposition
- multilayer systems are constructed from hexagonal nitrides (GaN, AIN and InN) as multiple quantum wells (MQWs).
- MQWs multiple quantum wells
- the band gap varies from 1.8 eV (InN) to 3.4 eV (GaN) to 6.2 eV (AIN).
- the entire visible spectrum and the near UV can thus be covered with hexagonal nitride compounds.
- the two types of white LEDs mentioned above can be implemented.
- the unitary cell of hexagonal GaN has a hexagonal GaN (0001) plane (C plane, basal plane) and six rectangular GaN (1-100) planes (M planes, prism planes).
- the c-axis runs perpendicular to the C-surface, while the equivalent a-axes point from the center of the hexagon to its corners (see Fig. 2).
- Analogous names apply to nitride compounds (Al, In, Ga) N.
- a special feature of the hexagonal nitride semiconductors are the enormous electrical polarization fields (in the range of 0.1 C / m 2 ) along the c-axis.
- the polarization fields exist both in untensioned and in tensioned layers as spontaneous or piezo-polarization.
- At the interfaces between different nitride compounds there is a discontinuity in the electrical polarization, which can lead to the formation of huge electrical fields. This effect is particularly pronounced with quantum wells, whose layer thickness d is in the range of a few nm, and leads to field strengths F in the range of several MV / cm, see FIG. 1 (b).
- the object of the invention is to provide an improved semiconductor layer structure based on nitrides, which has a high wavelength stability and an emission in the UV region with a high quantum efficiency.
- the semiconductor layer structure should, in particular, enable an increased radiation transition rate in light-emitting MQW structures.
- the object of the invention is also to provide a light-emitting semiconductor component which contains such a layer structure and is distinguished by an increased luminous efficiency with high wavelength stability in the UV range. In particular, a white light-emitting diode with a constant color impression and particularly high and reproducible intensity should be created.
- the object of the invention is also to provide methods for producing such a layer structure or such a light-emitting semiconductor component.
- the basic idea of the invention consists in the production of a semiconductor layer structure, a layered semiconductor crystal or a light-emitting semiconductor component (LED or laser diode), in which one or more semiconductor layers based on group III nitride compounds with a hexagonal structure also have such an orientation is provided that the c-axes of the hexagonal structure parallel to the respective Substrate surface or layer level run.
- At least one semiconductor layer made of a group III-N ⁇ tr ⁇ dverbmdung with a hexagonal structure on a flat, crystalline substrate is provided, which forms a monocrystalline epitaxial layer, the entire semiconductor layer being oriented so that the c-axis of the hexagonal structure parallel to the substrate surface proceeds.
- the group III nitride compound eg GaN
- the semiconductor layer is deposited epitaxially from the pure Group III nitride compound free of mixed phases.
- a particularly advantageous feature of the invention is that the semiconductor layer has no internal spontaneous polarization.
- the layer structure according to the invention thus differs fundamentally from conventional mixed phase systems, which in particular contain C-plane phases.
- FIG. 1 (a) shows the situation in a semiconductor layer structure according to the invention, which is given without polarizations or electrical fields perpendicular to the MQW structure.
- the valence and conduction bands are not inclined.
- the spatial separation of the electron and hole states is avoided. This increases the overlap between the wave functions and the radiating recombination rate.
- a concept for a UV diode is provided which contains a hexagonal nitride semiconductor, but has no electric fields parallel to the growth direction (perpendicular to the layer direction).
- the avoidance of electrical polarization is realized by a special crystal orientation, the field freedom of which has been recognized by the inventors.
- An M area is chosen as the growth area.
- the M surface is non-polar (J.
- the invention also relates to a method for growing crystalline group III nitride semiconductor layers on a substrate, in which the layer growth takes place during a first nucleation phase at a lower substrate temperature than during a later growth phase.
- the drawing of M-level growth in the sequence of nucleation and growth phases according to the invention is a surprising result. After the previous growth attempts with GaN, for example on LAO, the growth could be done with the better lattice adaptation (M-level growth) at a high substrate temperature expected in the nucleation phase. At a high temperature, more energy was available to take up a layer structure with optimal lattice adaptation. hen. However, the inventors have found that a lower substrate temperature during the nucleation phase is important for the M-plane growth.
- the invention has the following advantages.
- the electrical fields in the layer growth direction are excluded in layer structures according to the invention.
- the luminous efficiency of appropriately constructed light emitters increases considerably.
- the M-level growth is not only isolated or dominant, but takes place over the whole area on wafer sizes, as are of interest for the construction of light-emitting components.
- the M-plane growth also occurs with larger layer thicknesses above 1 ⁇ m.
- known deposition methods e.g. MBE or MOCVD can be used.
- an LED or laser diode which simultaneously fulfills requirements with regard to the high luminous efficiency and a stable emission (in particular a stable wavelength that is independent of the pump power) in the UV range.
- Layer-shaped semiconductor crystals according to the invention are extremely easy to handle. A large number of layer-shaped semiconductor crystals can be used to construct so-called solid-state light sources, which are distinguished by a considerably improved use of energy due to the increased quantum efficiency.
- FIG. 2 shows a schematic illustration of the orientation of hexagonal nitride compounds in a (a) and conventional (b) layer structure according to the invention
- FIG. 3 shows a schematic illustration of the growth of M-plane GaN on an LAO substrate
- FIG 8 shows schematic illustrations of layer structures or light-emitting components according to the invention.
- the inventors have succeeded in producing hexagonal M-surface GaN on ⁇ -L ⁇ A10 2 (100) substrates of particularly good crystalline and morphological quality. They use the LiAlO 2 (100) surface mentioned above, but are by no means restricted to this material.
- the substrate of a layer structure according to the invention The structure consists of ⁇ -L ⁇ A10 2 (LAO) and is oriented with its surface (100).
- FIG. 2 The differences in the structure structure of the inventive layer structures in comparison with conventional GaN layers are illustrated schematically in FIG. 2.
- a semiconductor layer 1 with a hexagonal crystal structure is arranged on a substrate 2 such that the c-axes lie in reference planes that run parallel to the substrate surface 3.
- the three a-axes are arranged parallel or inclined relative to the substrate surface 3.
- the semiconductor layer 1 consists of GaN, AIN or InN or a mixed composition (Ga, AI, In) N.
- the substrate 2 is an LAO substrate (for details see FIG. 3), the substrate surface 3 being aligned parallel to the (100) surface of the LAO stall.
- the (100) area of LAO is illustrated schematically in FIG. 3.
- the GaN c-axis is oriented parallel to the LAO (010) direction. Two examples of M surfaces are shown in FIG. 3. However, other substrate materials such as ZnO or special areas of sapphire or SiC could also be suitable.
- the substrate wafer is manufactured as follows. LAO crystals with a diameter of 35 mm are grown in a manner known per se using a fully automated Czochralski method with RF induction heating. The temperature gradients are set with an active post-heater and a floor heater, which is connected to additional turns of the RF coil. The growth rate is 2 mm / h at a rotation frequency of 40 Hz. The growth takes place in a nitrogen atmosphere. The wafers with a size of 10 ⁇ 10 mm 2 are cut and polished from the grown crystal, as is known per se from semiconductor technology, for example from the processing of Si wafers. The wafers are characterized by a high structural and morphological quality.
- X-ray diffraction measurements result in symmetrical XRC signals (so-called rockmg curves) with characteristic latitudes below 25 arc seconds.
- a scanning force microscopic examination reveals a roughness (“mountain-valley roughness”) of less than 10 nm over an area of 10 ⁇ 10 ⁇ m 2 .
- the LAO wafers are then immediately subjected to the further process or stored in a dry atmosphere.
- the wafer is then cleaned. It has been found that careful substrate cleaning is of great importance for achieving the desired crystal orientation in layered structures according to the invention.
- the cleaning is preferably carried out in an anhydrous solvent with simultaneous ultrasound treatment. For example, 100% pure acetone is used as the solvent.
- the GaN layer on the wafer is grown using a commercially available MBE apparatus, e.g. with a standard Riber system equipped with conventional effusion cells and an EPI-RF plasma cell for the release of active nitrogen.
- the MBE apparatus is also equipped with a RHEED device to observe the layer growth.
- the substrate temperature is monitored pyro etrically.
- the layers are deposited in two phases.
- a lower substrate temperature in the range of around 550 ° C to 600 ° C
- the temperatures are preferably 570 ° C in the first phase and 700 ° C in the second phase.
- GaN is nucleated on the LAO wafer until a layer thickness of approx. 20 to 30 n is achieved.
- the first phase (nucleation phase) at the lower substrate temperature lasts with a growth rate of approximately 0.3 ⁇ m / h. 3 minutes.
- the temperature is then increased to the higher value.
- the approx. 3 min phase of the temperature transition the layer Growth continued.
- the increased substrate temperature is then increased.
- the layer growth takes place at a speed in the range from 0.3 ⁇ m / h to 1 ⁇ m / h.
- the crystal orientation of the M-plane GaN and the phase purity of the layers produced according to the invention is determined by the methods described below with reference to FIGS. 4 to 6 characterized.
- phase purity of the layer and its orientation relative to the substrate are examined using X-ray and Raman measurements.
- 6 shows a high-resolution X-ray examination, a symmetrical three-crystal ⁇ / 2 ⁇ profile.
- the signal at 16.15 ° corresponds exactly to the Ga (1-100) planes
- the substrate is represented by the LAO (200) peak at 17.32 °.
- Possible portions of C-GaN were characterized by a signal at 17.28 °, the GaN (0002) reflex.
- the production of phase-pure M-GaN is thus proven within the measuring accuracy.
- "x-ray rocking curves" hm no tilting of the M-GaN area relative to the
- LAO (200) faces can be found.
- the surface morphology of the M-surface oriented GaN layers is also characterized by a low roughness.
- Atomic force microscopic investigations showed a "mountain valley roughness" of approximately 1 n to 5 x 5 ⁇ m 2 .
- an MQW structure 10 according to FIG. 8 (a) continues the growth phase described above with successively different layer compositions Fig. 9 (b) formed.
- the MQW structure 10 comprises a sequence of thin InGaN layers 11 (thickness approximately 2 to 3 nm) and thicker GaN layers 12 (thickness approximately 10 mm).
- FIG. 8 (c) A light-emitting component that is constructed with an MQW structure according to FIG. 8 (b) is illustrated schematically in FIG. 8 (c).
- a first electrical contact 21 m in connection with the lowermost sublayer and a second electrical contact 22 in connection with the uppermost sublayer are illustrated.
- 8 (c) is only a schematic illustration. Basically, a light-emitting component is constructed in terms of the dimensions, the introduction of dopings to form pn junctions and the attachment of the electrical contacts, as is known from conventional light emitters ,
- a key point of the invention is a UV diode with a stable emission wavelength, which is achieved by field freedom within the MQW.
- the inventors have grown GaN / (Al, Ga) N MQW structures on the conventional C surface and the novel M surface. 7 shows photoluminescence spectra of these samples at room temperature.
- C-area-oriented MQWs have a lower transition energy (due to the internal field F) and a reduced quantum efficiency.
- the luminescence of the M-area oriented MQWs corresponds exactly to that which is determined by means of self-consistent Schrodmger-Poisson calculations for such a layer sequence in the absence of any internal fields.
- the theoretically predicted field freedom has also been shown experimentally. In addition to the improvement of the internal
- the inventors also presented quantum efficiency as a concept for improving the coupling-out efficiency.
- External quantum efficiency is the product of internal quantum efficiency and decoupling efficiency.
- the former denotes the fraction of the internally radiant recombining electron-hole pairs, the latter the fraction of the photons internally generated by radiative recombination, which leave the material.
- the goal must therefore be to maximize the fraction of the internally generated photons that can leave the material after the first internal emission act. This goal can be achieved by the concept of the integrated thin film LED, which was developed in 1993 by Schnitzer et al. ("Appl. Phys. Lett.”, Vol.
- the substrate is removed and the epitaxial layer bonded to a reflector. This measure prevents the absorption of the light in the substrate or the lateral decoupling of the light with a transparent substrate and thus the need for an external reflector.
- the surface is statistically textured. This texturing reduces the internal reflection and therefore means that a much larger part of the light can be coupled out than with the usual planar design.
- the external quantum efficiency of (AI, Ga) As LEDs is more than tripled.
- structured texturing is carried out using a sacrificial mask. Compared to the conventional dome design of an LED can be based on this
- SMD surface mounted devices
- the substrate material LAO was not considered as substrate material of interest before the invention, because it is chemically highly reactive. This property is advantageously used in the production of layered crystals according to the invention.
- the self-supporting layer 30, which can also be a multi-layer according to FIG. 8 (b), can then be used to construct an on-chip LED, which is shown schematically in plan view in FIG. 8 (e).
- An on-chip LED comprises a plurality of MQW structures 10, which are arranged as lighting elements on a common carrier 20.
- the individual MQWs 10 have a size of 200 x 200 ⁇ m 2 , for example. They can be extremely dense with mutual distances of less than 50 ⁇ m are arranged. In the distances between the MQWs
- the carrier 20 can be formed by any suitable flat or curved substrate material.
- the carrier 20 is preferably a foreign substrate which is adapted to the application of the light-emitting component, that is to say preferably serves as a reflector.
- the size of the individual lighting elements is essentially given by possible thermal stresses between the MQW structure and the carrier substrate and can be brought into the range of square centimeters by a suitable choice. This represents an essential advantage of the invention. Such large lighting elements cannot be produced with conventional semiconductor components.
- the MQW structures 10 are arranged on the carrier 20 as follows. First, according to FIG. 8 (d), MQW structures are produced as self-supporting layers. When dissolving the original LAO substrate z. B. in water, the crystal layers 30 float on the water surface. For the transfer to the target substrate 20, the crystal layers 30 are fished out from the water surface and arranged accordingly on the carrier 20 as MQW structures 10. An additional fastening is not necessary since a physical bond (van der Waals bond) is formed between the MWQ structures 10 and the carrier 20.
- the light emitting device shown in Fig. 8 (e) is with
- the carrier 20 itself is formed by a reflector.
- a fluorescent layer is applied over the MQW structures 10, as is known from discharge fluorescent tubes. The UV emission of the MQW structures 10 excites the phosphor to emit visible light.
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Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19953839 | 1999-11-09 | ||
DE19953839A DE19953839A1 (de) | 1999-11-09 | 1999-11-09 | Hocheffiziente UV-Emitter auf Nitridhalbleiterbasis |
PCT/EP2000/011044 WO2001035447A2 (de) | 1999-11-09 | 2000-11-08 | Hocheffiziente uv-emitter auf nitridhalbleiterbasis |
Publications (1)
Publication Number | Publication Date |
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EP1228539A2 true EP1228539A2 (de) | 2002-08-07 |
Family
ID=7928406
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP00993057A Withdrawn EP1228539A2 (de) | 1999-11-09 | 2000-11-08 | Hocheffiziente uv-emitter auf nitridhalbleiterbasis |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP1228539A2 (de) |
DE (1) | DE19953839A1 (de) |
WO (1) | WO2001035447A2 (de) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6648966B2 (en) | 2001-08-01 | 2003-11-18 | Crystal Photonics, Incorporated | Wafer produced thereby, and associated methods and devices using the wafer |
US7169227B2 (en) | 2001-08-01 | 2007-01-30 | Crystal Photonics, Incorporated | Method for making free-standing AIGaN wafer, wafer produced thereby, and associated methods and devices using the wafer |
DE10228311B4 (de) * | 2002-06-25 | 2012-02-02 | Paul-Drude-Institut für Festkörperelektronik im Forschungsverbund Berlin e.V. | Polarisationsempfindliches Photodetektorbauelement und Verfahren zum Detektieren der Polarisation |
US7033858B2 (en) | 2003-03-18 | 2006-04-25 | Crystal Photonics, Incorporated | Method for making Group III nitride devices and devices produced thereby |
DE102015217330A1 (de) | 2015-09-10 | 2017-03-16 | Technische Universität Berlin | Halbleitervorrichtung mit gegen interne Felder abgeschirmtem aktiven Gebiet |
EP3373343B1 (de) | 2017-03-09 | 2021-09-15 | Technische Universität Berlin | Halbleiterbauelement mit einer aktiven, von einem internen feld abgeschirmten region |
Family Cites Families (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19506323A1 (de) * | 1995-02-23 | 1996-08-29 | Siemens Ag | Halbleitervorrichtung mit aufgerauhter Halbleiteroberfläche |
US5625202A (en) * | 1995-06-08 | 1997-04-29 | University Of Central Florida | Modified wurtzite structure oxide compounds as substrates for III-V nitride compound semiconductor epitaxial thin film growth |
US6072197A (en) * | 1996-02-23 | 2000-06-06 | Fujitsu Limited | Semiconductor light emitting device with an active layer made of semiconductor having uniaxial anisotropy |
JP3816176B2 (ja) * | 1996-02-23 | 2006-08-30 | 富士通株式会社 | 半導体発光素子及び光半導体装置 |
JP3644191B2 (ja) * | 1996-06-25 | 2005-04-27 | 住友電気工業株式会社 | 半導体素子 |
JPH1051029A (ja) * | 1996-07-31 | 1998-02-20 | Sharp Corp | 半導体発光素子及びその製造方法 |
JP3955367B2 (ja) * | 1997-09-30 | 2007-08-08 | フィリップス ルミレッズ ライティング カンパニー リミテッド ライアビリティ カンパニー | 光半導体素子およびその製造方法 |
-
1999
- 1999-11-09 DE DE19953839A patent/DE19953839A1/de not_active Withdrawn
-
2000
- 2000-11-08 EP EP00993057A patent/EP1228539A2/de not_active Withdrawn
- 2000-11-08 WO PCT/EP2000/011044 patent/WO2001035447A2/de not_active Application Discontinuation
Non-Patent Citations (1)
Title |
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See references of WO0135447A2 * |
Also Published As
Publication number | Publication date |
---|---|
WO2001035447A3 (de) | 2001-10-18 |
DE19953839A1 (de) | 2001-05-10 |
WO2001035447A2 (de) | 2001-05-17 |
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