WO2011056090A1 - Substrate for cascade solar cells - Google Patents

Substrate for cascade solar cells Download PDF

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Publication number
WO2011056090A1
WO2011056090A1 PCT/RU2010/000533 RU2010000533W WO2011056090A1 WO 2011056090 A1 WO2011056090 A1 WO 2011056090A1 RU 2010000533 W RU2010000533 W RU 2010000533W WO 2011056090 A1 WO2011056090 A1 WO 2011056090A1
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substrate
germanium
stripes
film
width
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PCT/RU2010/000533
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French (fr)
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Evgeny Invievich Givargizov
Mikhail Evgenievich Givargizov
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Evgeny Invievich Givargizov
Mikhail Evgenievich Givargizov
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Publication of WO2011056090A1 publication Critical patent/WO2011056090A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
    • H01L31/1808—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System including only Ge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0392—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0725—Multiple junction or tandem solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0735—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising only AIIIBV compound semiconductors, e.g. GaAs/AlGaAs or InP/GaInAs solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • H01L31/1852—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP comprising a growth substrate not being an AIIIBV compound
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/544—Solar cells from Group III-V materials

Definitions

  • the invention relates to materials science, preferentially to electronic materials, in particular to solar energetic.
  • the most simple version of the PSC is the p-n junction in silicon.
  • the silicon solar cells (SSC) have the efficiency -15%, and the value can not be larger because SSC are based on the only p-n junction.
  • a 3 B 5 compounds e.g., gallium arsenide and related ones
  • a B compounds e.g., ZnSe and related ones
  • the entrant, in respect to the solar light, semiconductor layer must have the largest forbidden energy gap.
  • a remarkable feature of the families of the semiconductor compounds consists in the fact that the compounds have various energy gaps, the compounds overlap almost all the solar spectrum, whereas the crystal lattices of the compounds in the families differ insignificantly so that it is possible to realize their rather perfect epitaxial growth.
  • the Ge substrate represents a crucial factor because Ge is a rare chemical element in the Earth crust. On this reason, it is rather expensive. However, the high price is not the only problem. The situation becomes far more complicated when a mass solar energetic is developed that takes place currently. The resource limit is considered as a threatening circumstance.
  • the US germanium reservoir is estimated to last for 25 years at the current consumption. An anxiety on this is expressed in (S.Kurtz, "Opportunities and Challenges for Development of a Mature Concentrating Photovoltaic Power Industry", Technical Report NRLE, Sept. 2008, 19pp).
  • the price of Ge substrate in the international market is l$/cm 2 .
  • the Ge wafer was thinned down to 200 ⁇ from the initial circa 500-1000 ⁇ (the solar cells were intended for using in cosmos, e.g., in feeding the cosmic station: there the weight of the PSC is decreased maximally).
  • the initial Ge wafer should be more thick, e.g., 500 ⁇ in any case: when it must be thinned (for using in cosmos) or it is necessary for terrestrial applications when the weight problem is absent.
  • the layer can be formed by chemical vapor deposition at decomposition of Ge compound that can be obtained by a treatment of germanium raw material:
  • the Ge film 5 ⁇ in thickness was deposited on wafers of polycrystalline alumina, fused quartz, or polycrystalline Si from vapor phase and then underwent to annealing during 10-30 min at high temperatures, 800-950°C (in order to anneal the Ge film above 940°C, the melting point of Ge; the Ge film was coated by a layer of refractory material, such as tungsten or Si0 2 ).
  • refractory material such as tungsten or Si0 2
  • the design of Ge film that has not such failures is proposed.
  • the substrate proposed for PSC allows to decrease significantly its price.
  • the design proposed can be created by techniques known in modern microelectronics.
  • the substrate for cascade solar cells is formed as single crystalline germanium film with thickness no more than 5 ⁇ on a basic insulator wafer.
  • the Ge film has a striated form where uncoated substrate areas (clearances) take less than 5% of general substrate area, the width of the clearances being less than 5 ⁇ .
  • the germanium stripes have the form of rectangulars; perpendicularly to them rectangular electrocontact platforms with width equal to the width of the germanium stripes are deposited, the distances between the platforms at least ten times exceeding the width of the stripes.
  • the electrocontact platforms are passed either on lower surface of the stripes (between the germanium film and the initial basic insulator wafer), or on upper surface of the stripes.
  • the single crystalline germanium film is created by deposition on the basic wafers and subsequent recrystallization.
  • Fig. 1 A scheme of cascade PSC with triple p-n junction on basis of germanium substrate according to M.Yamaguchi, "Multi-junction solar cells and novel structures for solar cell applications” Physica E14 (2002) 84-90.
  • Fig. 2 A scheme of cascade PSC with triple p-n junction on basis of germanium substrate according to Zh.I.Alferov, V.M.Andreev, V.D.Rumyantsev, "Trends and perspectives for developments of solar energetics", Physics and Technique of Semiconductors, 38 (2004) 937-947.
  • Fig. 3. A scheme of stripe germanium film according to the given invention (view from above);
  • Fig. 5 Structure of germanium stripes in gross-section. Flat p-n junctions are parallel to the initial silicon wafer. Electrical contact platforms are parallel to p-n junctions.
  • the germanium film less than 5 micrometers in thickness is deposited on a cheap substrate, e.g. silicon wafer with the crystallographic orientation (100) or (1 11) (or on a polycrystalline silicon wafer) 0.3-0.5 mm in thickness.
  • the silicon wafer is preliminary thermally coated by Si0 2 film 0.3-0.5 in thickness.
  • the deposition of the germanium film can be done by various techniques, e.g., by chemical vapor deposition (CVD), by evaporation I vacuum, by magnetron sputtering, etc.
  • the germanium film is underwent to directional recrystallization that resulted in formation of well-oriented single-crystalline film.
  • a central part of the rectangular stripes represents an ideally perfect single crystal.
  • FIG. 3 view from above
  • Fig.4 cross-section of the stripe germanium film
  • an epitaxial layer of the semiconductor compound A B or a relative compound of the same family is deposited on the germanium film.
  • the material must have more broad forbidden gap than germanium.
  • one more layer of a semiconductor A 3 B 5 compound with more broad forbidden gap than the previous layer is deposited, again epitaxially.
  • epitaxial layer of semiconductor compound A 2 B 6 e.g., zinc selenide ZnSe that is isoelectronic to gallium arsenide is deposited on all the previous layers.
  • This material has a broad forbidden gap, about 3.2 eV.
  • a layer of ZnO is deposited as the A 2 B 6 compound, also above the ZnSe layer. The material has forbidden gap 3.37 eV so that it is able to absorb sun light of near ultraviolet spectrum.
  • the multilayered epitaxial formed on the basis of the germanium substrate is able to absorb almost all the sun light that fall on the Earth.
  • the layers of the semiconductor compounds A3B5 and A2B6 can be deposited by any known techniques: molecular-beam epitaxy (MBE), chemical vapor deposition (CVD), from mixtures of metal-organic compounds (MOCVD), liquid epitaxy, by magnetron sputtering etc.
  • MBE molecular-beam epitaxy
  • CVD chemical vapor deposition
  • MOCVD metal-organic compounds
  • liquid epitaxy by magnetron sputtering etc.
  • the electric contact with the germanium is created as a thin film of refractory metal, e.g., molybdenum or tungsten.
  • refractory metal e.g., molybdenum or tungsten.
  • zinc selenide or zinc oxide
  • the generated voltage can be taken also by the contacts attached to several semiconductor layers. In such a way more efficient taking the voltages appeared on various areas of PSC can be realized.
  • FIG. 5 A total cross-section of the formed PSC, including the initial silicon wafer, electrical structure of the grown epitaxial structures and contact areas are shown in Fig. 5.

Abstract

Germanium substrate for epitaxial deposition of semiconductor A3B5 and A2B6 compounds for multijunction solar cells is prepared as single-crystalline film with thickness not more than 5 micrometers. The film has a form of rectangles where non-coated substrate areas (clearances) take no more than 5% of total surface of the substrate, the width of the clearances being smaller than 5 micrometers. The film is implemented by deposition and subsequent recrystallization.

Description

SUBSTRATE FOR CASCADE SOLAR CELLS
Technical Field
The invention relates to materials science, preferentially to electronic materials, in particular to solar energetic.
Background Art
Solar energetic - an ecologically clean and practically inexhaustible source of energy. Therefore, large programs in this direction are accepted in all the developed countries (USA, Europe, Japan).
The most natural and widespread approach - the use of the energy that is generated by the sun in the semiconductor p-n junction. A totality of various devices on the transformation of the solar energy by semiconductor p-n junctions is titled as photovoltaic solar cells (PSC).
The most simple version of the PSC is the p-n junction in silicon. Currently, the silicon solar cells (SSC) have the efficiency -15%, and the value can not be larger because SSC are based on the only p-n junction.
However, in order to use maximally the solar energy a cascade of at least 3-4 flat mutually parallel junctions among semiconductor A3B5 compounds (e.g., gallium arsenide and related ones) and/or A B compounds (e.g., ZnSe and related ones) are necessary. The entrant, in respect to the solar light, semiconductor layer must have the largest forbidden energy gap.
A remarkable feature of the families of the semiconductor compounds consists in the fact that the compounds have various energy gaps, the compounds overlap almost all the solar spectrum, whereas the crystal lattices of the compounds in the families differ insignificantly so that it is possible to realize their rather perfect epitaxial growth.
Further, it is important that the crystal lattice of GaAs (as well as of ZnSe) coincides practically with the crystal lattice of germanium Ge (a difference is only in the second cipher after comma). Therefore, epitaxial layers of GaAs on Ge have been successfully grown, including for solar energetic (M.Yamaguchi, A.Luque, "High Efficiency and High Concentration in Photovoltaics", IEEE Trans. Electron Devices, ED46 (1999) 2139-2144).
According to recent data, in the cascade PSC based on Ge substrate, a record efficiency value more than 40% has been reached (R.R.King, D.C.Law, K.M.Edmonson, C.M.Fetzer, G.S.Kinsey, H.Yoon, R.A.Sherif, and N.H.Karam, "40% efficient metamorphic GalnP/GalnAs/Ge multij unction solar cells", Appl. Phys. Lett., 90 (2007) 183516), and the value can be increased in future.
Schemes of the cascade PSC based on Ge are given in Fig. 1 of M. Yamaguchi, "Multi- junction solar cells and novel structures for solar cell applications" Physica E14 (2002) 84-90 and Fig. 2 of Zh.I.Alferov, V.M.Andreev, V.D.Rumyantsev, "Trends and perspectives for developments of solar energetics", Physics and Technique of Semiconductors, 38 (2004) 937- 947.
Usually, the thickness of Ge substrate for PSC is 400 μηι (=0.4 mm); more thin substrates are technologically unsuitable because they can be destroyed during numerous procedures of growing the multiple epitaxial structures.
The Ge substrate represents a crucial factor because Ge is a rare chemical element in the Earth crust. On this reason, it is rather expensive. However, the high price is not the only problem. The situation becomes far more complicated when a mass solar energetic is developed that takes place currently. The resource limit is considered as a threatening circumstance. For example, in the review (M.Bosi and C.Pelosi, "The Potential of III-V Semiconductors as Terrestrial Photovoltaic Devices", Prog. Photovolt: Res Appl. 15 (2007) 51-68) the US germanium reservoir is estimated to last for 25 years at the current consumption. An anxiety on this is expressed in (S.Kurtz, "Opportunities and Challenges for Development of a Mature Concentrating Photovoltaic Power Industry", Technical Report NRLE, Sept. 2008, 19pp).
The price of Ge substrate in the international market is l$/cm2. When the Ge substrate was used for growth of A3B5 semiconductor compounds for PSC, the Ge wafer was thinned down to 200 μπι from the initial circa 500-1000 μηι (the solar cells were intended for using in cosmos, e.g., in feeding the cosmic station: there the weight of the PSC is decreased maximally). Using more thin Ge wafers is unsuitable, as it was indicated above. This means that the initial Ge wafer should be more thick, e.g., 500 μιη in any case: when it must be thinned (for using in cosmos) or it is necessary for terrestrial applications when the weight problem is absent.
Our proposal - to create a Ge layer with the thickness less than 5 μπι - has a significance because this allows to economize at least 95% of the deficit material.
It is also important that the layer can be formed by chemical vapor deposition at decomposition of Ge compound that can be obtained by a treatment of germanium raw material:
this is very important for saving the rare diffused element. Earlier, attempts to replace the Ge wafer for Ge film have been undertaken. Most nearly to this were authors of M.G.Mauk, J.R.Balett, B.W.Feyock, "Large-grain (>l-mm), recrystallized germanium films on alumina, fused silica, oxide-coated silicon substrates for III- V solar cell applications", J. Crystal Growth 250 (2003) 5056. There, the Ge film 5 μπι in thickness was deposited on wafers of polycrystalline alumina, fused quartz, or polycrystalline Si from vapor phase and then underwent to annealing during 10-30 min at high temperatures, 800-950°C (in order to anneal the Ge film above 940°C, the melting point of Ge; the Ge film was coated by a layer of refractory material, such as tungsten or Si02). However, the authors of [7] failed in their attempts: Ge films were cracked, small voids (about 10 μιη in diameter) were formed in them.
In this invention, the design of Ge film that has not such failures is proposed. The substrate proposed for PSC allows to decrease significantly its price. The design proposed can be created by techniques known in modern microelectronics.
Disclosure of Invention
The substrate for cascade solar cells is formed as single crystalline germanium film with thickness no more than 5 μπι on a basic insulator wafer. The Ge film has a striated form where uncoated substrate areas (clearances) take less than 5% of general substrate area, the width of the clearances being less than 5 μιη. The germanium stripes have the form of rectangulars; perpendicularly to them rectangular electrocontact platforms with width equal to the width of the germanium stripes are deposited, the distances between the platforms at least ten times exceeding the width of the stripes.
The electrocontact platforms are passed either on lower surface of the stripes (between the germanium film and the initial basic insulator wafer), or on upper surface of the stripes.
The single crystalline germanium film is created by deposition on the basic wafers and subsequent recrystallization.
Brief Description of Drawings
Fig. 1. A scheme of cascade PSC with triple p-n junction on basis of germanium substrate according to M.Yamaguchi, "Multi-junction solar cells and novel structures for solar cell applications" Physica E14 (2002) 84-90.
Fig. 2. A scheme of cascade PSC with triple p-n junction on basis of germanium substrate according to Zh.I.Alferov, V.M.Andreev, V.D.Rumyantsev, "Trends and perspectives for developments of solar energetics", Physics and Technique of Semiconductors, 38 (2004) 937-947.
Fig. 3. - A scheme of stripe germanium film according to the given invention (view from above);
Fig. 4 - cross-section of PSC perpendicular to the stripes;
Fig. 5 - Structure of germanium stripes in gross-section. Flat p-n junctions are parallel to the initial silicon wafer. Electrical contact platforms are parallel to p-n junctions.
Best Mode for Carrying out the Invention
According to this invention, it is proposed to create a substrate that has a sufficiently low cost and, in the same time, allows, according to a multilayer epitaxy, to realize necessary cascade semiconductor PSC with a high structural perfection.
One of the versions of the realization of the PSC based on the design that is proposed in this invention consists in the following. The germanium film less than 5 micrometers in thickness is deposited on a cheap substrate, e.g. silicon wafer with the crystallographic orientation (100) or (1 11) (or on a polycrystalline silicon wafer) 0.3-0.5 mm in thickness. The silicon wafer is preliminary thermally coated by Si02 film 0.3-0.5 in thickness. The deposition of the germanium film can be done by various techniques, e.g., by chemical vapor deposition (CVD), by evaporation I vacuum, by magnetron sputtering, etc.
It is known from crystallography that it is rather difficult to ensure the single-crystalline growth of films on an extended front of a substrate. Therefore, we propose to create the single- crystalline germanium film as a relatively narrow rectangular stripes so that a summary area of clearances between the stripes is not more than 5% of total area of the film.
The germanium film is underwent to directional recrystallization that resulted in formation of well-oriented single-crystalline film. A central part of the rectangular stripes represents an ideally perfect single crystal.
A scheme of such a stripe germanium film is shown in Fig. 3 (view from above) and Fig.4 (cross-section of the stripe germanium film), where w- width of the stripes, several tens of micrometers s - clearance between the stripes, several μιη.
3 5
Then, an epitaxial layer of the semiconductor compound A B or a relative compound of the same family is deposited on the germanium film. The material must have more broad forbidden gap than germanium.
After that, one more layer of a semiconductor A3B5 compound with more broad forbidden gap than the previous layer is deposited, again epitaxially. Finally, epitaxial layer of semiconductor compound A2B6, e.g., zinc selenide ZnSe that is isoelectronic to gallium arsenide is deposited on all the previous layers. This material has a broad forbidden gap, about 3.2 eV. In another version, as the A2B6 compound, also above the ZnSe layer, a layer of ZnO is deposited. The material has forbidden gap 3.37 eV so that it is able to absorb sun light of near ultraviolet spectrum.
In all the semiconductor layers p-n junctions parallel to neighbor layers, i.e., parallel to the initial silicon wafer, are created.
In such a way, the multilayered epitaxial formed on the basis of the germanium substrate is able to absorb almost all the sun light that fall on the Earth.
The layers of the semiconductor compounds A3B5 and A2B6 can be deposited by any known techniques: molecular-beam epitaxy (MBE), chemical vapor deposition (CVD), from mixtures of metal-organic compounds (MOCVD), liquid epitaxy, by magnetron sputtering etc.
On the lower surface of germanium, that contacts with the initial wafer, the electric contact with the germanium is created as a thin film of refractory metal, e.g., molybdenum or tungsten. Similarly, on the upper surface of the layer of zinc selenide (or zinc oxide) one more electrical contact is created. In such a way, all the multilayered structure is held between two electrical contacts. The contacts take the voltage generated by the solar cell.
To this aim, the generated voltage can be taken also by the contacts attached to several semiconductor layers. In such a way more efficient taking the voltages appeared on various areas of PSC can be realized.
A total cross-section of the formed PSC, including the initial silicon wafer, electrical structure of the grown epitaxial structures and contact areas are shown in Fig. 5.

Claims

Claim 1. A substrate for cascade solar cells containing thin basis part as insulating wafer wherein single-crystalline germanium film with thickness not more than 5 micrometers is formed, the film has in its plane a stripe form where non-coated substrate areas (clearances) take no more than 5% of total surface of the substrate, the width of the clearances being smaller than 5 micrometers.
Claim 2. The substrate of claim 1 wherein the germanium stripes have a form of rectangles, perpendicularly to the rectangles rectangular electrocontact platforms with width equal to the width of the germanium stripes are implemented, and the distances between the platforms exceed the width of the stripes more than in 10 times.
Claim 3. The substrate of claim 2 wherein the electrocontact platforms lie on lower surface of the stripes, between germanium and initial wafer.
Claim 4. The substrate of claim 2, wherein the electrocontact platforms lie on upper surface of The stripes.
Claim 5. The substrate of on any of the claims 1-4, wherein the single-crystalline germanium film is formed by deposition on the substrate and subsequent recrystallization.
PCT/RU2010/000533 2009-11-06 2010-09-27 Substrate for cascade solar cells WO2011056090A1 (en)

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US7456057B2 (en) * 2005-12-31 2008-11-25 Corning Incorporated Germanium on glass and glass-ceramic structures

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RU2340979C1 (en) * 2004-10-28 2008-12-10 Мимасу Семикондактор Индастри Ко., Лтд Method of semiconductor wafer manufacture, semiconductor wafer for solar plants, and etching solution
RU2368038C1 (en) * 2007-12-07 2009-09-20 Физико-технический институт им. А.Ф. Иоффе РАН Method for manufacturing of multilayer photoconverter chips

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Publication number Priority date Publication date Assignee Title
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