WO2020238646A1 - 锗单晶片、其制法、晶棒的制法及单晶片的用途 - Google Patents

锗单晶片、其制法、晶棒的制法及单晶片的用途 Download PDF

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WO2020238646A1
WO2020238646A1 PCT/CN2020/090402 CN2020090402W WO2020238646A1 WO 2020238646 A1 WO2020238646 A1 WO 2020238646A1 CN 2020090402 W CN2020090402 W CN 2020090402W WO 2020238646 A1 WO2020238646 A1 WO 2020238646A1
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atoms
germanium
atom concentration
germanium single
wafer
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PCT/CN2020/090402
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English (en)
French (fr)
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拉贾拉姆 谢蒂
王元立
刘卫国
周雯婉
朱颂义
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北京通美晶体技术有限公司
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Priority to US17/615,484 priority Critical patent/US20220238746A1/en
Priority to EP20814220.8A priority patent/EP3978657A4/en
Publication of WO2020238646A1 publication Critical patent/WO2020238646A1/zh

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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 Table
    • 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 Table including only Ge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
    • B24B9/00—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor
    • B24B9/02—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground
    • B24B9/06—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain
    • B24B9/065—Machines or devices designed for grinding edges or bevels on work or for removing burrs; Accessories therefor characterised by a special design with respect to properties of materials specific to articles to be ground of non-metallic inorganic material, e.g. stone, ceramics, porcelain of thin, brittle parts, e.g. semiconductors, wafers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28D—WORKING STONE OR STONE-LIKE MATERIALS
    • B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/002—Crucibles or containers for supporting the melt
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
    • C30B11/02—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method without using solvents
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/08—Germanium
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H—ELECTRICITY
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    • 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 potential barriers
    • H01L31/068—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 potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H01L31/0687—Multiple junction or tandem solar cells
    • H—ELECTRICITY
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    • 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 potential barriers
    • H01L31/075—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 potential barriers the potential barriers being only of the PIN type, e.g. amorphous silicon PIN solar cells
    • H01L31/077—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 potential barriers the potential barriers being only of the PIN type, e.g. amorphous silicon PIN solar cells the devices comprising monocrystalline or polycrystalline materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
    • H01L29/16—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only elements of Group IV of the Periodic Table

Definitions

  • the invention relates to a germanium (Ge) single wafer, a method for preparing a germanium single wafer, a method for preparing a crystal rod for preparing a germanium single wafer, and the use of the germanium single wafer obtained by the invention.
  • Germanium monolithic wafer is an ideal substrate material for this high-efficiency and high-power multi-cell solar cell.
  • germanium single crystal materials all obtain P-type germanium single crystal substrates by doping gallium, in which the carriers are positive electrons, also known as holes. Since the segregation coefficient of gallium atoms in germanium materials is only 0.087, gallium atoms are gradually enriched in the liquid phase during the growth of germanium single crystals, and the concentration of gallium atoms in the grown single crystals of germanium gradually increases from beginning to end.
  • the so-called impurity segregation coefficient can be understood as follows: for the solid-liquid interface, because the solubility of impurities in different phases is different, the concentration of impurities in the materials on both sides of the interface is different, which is the so-called impurity segregation phenomenon.
  • the impurity segregation phenomenon leads to poor resistivity between the head and tail of the crystal rod. If the difference between the head and tail resistivity of the crystal rod exceeds six times, it will adversely affect the consistency of its performance in the preparation of multi-cell solar cells.
  • the present invention is proposed. Through co-doping of gallium atoms and boron atoms, the difference in segregation coefficient of gallium atoms and boron atoms in the germanium material is used to obtain uniform carrier concentration and resistivity distribution.
  • the purpose of the present invention is achieved by adjusting the amount of co-doped elements silicon, boron and gallium in the germanium single wafer, the ratio of co-doped elements gallium, boron and silicon, and the temperature gradient and rate of germanium single crystal growth.
  • the present invention relates to the following technical solutions.
  • the present invention provides a single germanium wafer, wherein the germanium single wafer contains dopant elements silicon, boron and gallium, the silicon atom concentration is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 8:1 to 1:240.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 5:1 to 1:170.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 3:1 to 1:100.
  • the ratio of the silicon atom concentration to the gallium atom concentration of the germanium single wafer is 4:1-100.
  • the ratio of the silicon atom concentration to the gallium atom concentration of the germanium single wafer is 3:1-80.
  • the ratio of the silicon atom concentration to the gallium atom concentration of the germanium single wafer is 2:1-50.
  • the thickness of the germanium single wafer is 100-700 ⁇ m, preferably 100-500 ⁇ m, more preferably 100-200 ⁇ m, even more preferably 120-140 ⁇ m.
  • the sum A of the concentration of silicon atoms, boron atoms and gallium atoms of the germanium single wafer is in the range of 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on the amount of germanium meter.
  • the present invention also provides a method for preparing a single germanium wafer, the method comprising:
  • a germanium single crystal initial wafer is cut from a germanium single crystal rod containing the elements silicon and gallium, wherein the silicon atom concentration in the cut germanium single crystal initial wafer is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/ cc, the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the thickness of the initial wafer is 200- 800 ⁇ m;
  • step 4 Perform rough polishing on the germanium single crystal initial wafer after surface treatment in step 3), and then perform fine polishing to obtain a germanium single wafer product, wherein the thickness of the obtained germanium single crystal wafer is 100-700 ⁇ m.
  • the silicon atom concentration is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 8:1 to 1:240.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 5:1 to 1:170.
  • the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 3:1 to 1:100.
  • the ratio of silicon atom concentration to gallium atom concentration is 4:1-100.
  • the ratio of the silicon atom concentration to the gallium atom concentration is 3:1-80.
  • the ratio of silicon atom concentration to gallium atom concentration is 2:1-50.
  • the thickness of the germanium single wafer is 100-700 ⁇ m, preferably 100-500 ⁇ m, more preferably 100-200 ⁇ m, even more preferably 120-140 ⁇ m.
  • the sum A of the silicon atom, boron atom and gallium atom concentration of the germanium single wafer is in the range of 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on Germanium gauge.
  • a method for preparing a germanium single crystal rod according to the present invention includes:
  • step 3 Place the crucible described in step 1) and the loading container described in step 2) in a quartz tube, and seal the quartz tube under vacuum;
  • step 6 Cooling the melt in the crucible obtained in step 5), while controlling the temperature gradient and cooling rate of the melt, so that the germanium single crystal rods are crystallized and grown when the melt is in contact with the seed crystal;
  • the amount of dopant elements silicon and gallium added in step 1) is such that the silicon atom concentration of the germanium single crystal rod is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc in the effective length.
  • the concentration of boron atoms is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc
  • the concentration of gallium atoms is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration within the effective length of the germanium single crystal rod is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration within the effective length of the germanium single crystal rod is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc, and the boron atom concentration It is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc, and the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the range of the sum A of the silicon atom, boron atom and gallium atom concentration within the effective length of the germanium single crystal rod is 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on germanium meter.
  • the ratio of the boron atom concentration and the gallium atom concentration in the head of the crystal rod is 8-5:1, preferably 7-4:1, more preferably 5- 3:1
  • the ratio of the boron atom concentration and the gallium atom concentration at the tail of the crystal rod is 1:100-240, preferably 1:130-210, more preferably 1:160-180.
  • the ratio of silicon atom concentration to gallium atom concentration is 4:1-100.
  • the ratio of silicon atom concentration to gallium atom concentration is 3:1-80.
  • the ratio of silicon atom concentration to gallium atom concentration is 2:1-50.
  • the germanium single crystal rod is a crystal rod with a circular transverse cross section, and the diameter of the circular cross section does not exceed 10 inches.
  • step 6 when the melt is brought into contact with the seed crystal, the crystal grows into a germanium single crystal rod.
  • a temperature gradient of 0.5-3.5° C./cm is established in the growth zone of the crystal rod.
  • a temperature gradient of 1.0-3.0° C./cm is established in the growth zone of the crystal rod.
  • step 6 when the melt is brought into contact with the seed crystal, the crystal grows into a germanium single crystal rod. 1.5°C/cm temperature gradient.
  • a temperature gradient of 0.2-1.0° C./cm is established at the end of the seed crystal.
  • a temperature gradient of 0.2-0.5° C./cm is established at the end of the seed crystal.
  • step 6 the furnace temperature is cooled at a rate of 0.2° C./h to 0.6° C./h.
  • step 6 the furnace temperature is cooled at a rate of 0.3° C./h to 0.5° C./h.
  • the average dislocation density of the head wafer of the germanium single crystal rod is less than 80 cm 2
  • the average dislocation density of the tail wafer is less than 75 cm 2 .
  • the present invention also provides the germanium single crystal wafer of the present invention, the germanium single wafer prepared by the method for preparing germanium single crystal rod of the present invention, and the germanium single crystal rod obtained by cutting the germanium single crystal rod prepared by the method for preparing germanium single crystal rod of the present invention
  • the wafer is used to increase the open circuit voltage of multiple solar cells.
  • the invention prepares germanium single crystal rods with uniform electrical properties through the co-doping of gallium, boron and silicon of germanium single crystals, which can increase the open circuit voltage of germanium (Ge) single crystal multi-cell solar cells and simultaneously prepare germanium single crystals.
  • the carrier concentration and electrical properties are more evenly distributed in the entire germanium single crystal rod range, so that a multi-cell solar cell based on germanium single crystal with more uniform performance can be obtained.
  • the germanium single wafer obtained in the present invention has improved electrical properties, especially a smaller difference in resistivity and carrier concentration. Specifically, the difference in resistivity of the germanium single wafer of the present invention is not more than 2 times.
  • the germanium single wafer obtained by the present invention can also increase the open circuit voltage of the solar cell, thereby improving the photoelectric conversion efficiency and power output of the solar cell.
  • the invention increases the open circuit voltage Voc of the solar cell device by controlling, reducing and eliminating the recombination position of photo-generated carriers.
  • the invention increases the open circuit voltage of the multi-cell solar cell by adding a certain amount of trace co-dopant element to the germanium single crystal rod, that is, the single crystal substrate.
  • the reason for the increase in open circuit voltage is the reduction and elimination of the antiphase domain boundary on the bottom cell interface of the multi-cell solar cell epitaxially grown on the germanium substrate, thereby reducing the non-radiative recombination of photogenerated carriers on the bottom cell interface.
  • Figure 1 shows the resistivity (Res) distribution from the beginning to the end of the gallium-doped germanium single crystal rod in the prior art.
  • the abscissa in the figure represents the length from the beginning to the end of the crystal rod from left to right, and the ordinate corresponds to the position Resistivity; Among them, the head resistivity 1.5E-02Ohm.cm is 5.9 times the tail resistivity 2.54E-03Ohm.cm.
  • Figure 2 shows the resistivity distribution from the beginning to the end of the prior art boron-doped germanium single crystal rod.
  • the abscissa in the figure represents the length from the beginning to the end of the crystal rod from left to right, and the ordinate is the resistivity corresponding to the position; ,
  • the tail resistivity 2.98E-02Ohm.cm is 4.7 times that of the head resistivity 6.3E-03Ohm.cm.
  • Figure 3 shows the resistivity of the silicon, boron, and gallium-doped crystal rod head of the present invention is 3.34E-2Ohm.cm, and the resistivity of the crystal rod tail is 3.07E-2Ohm.cm; the abscissa of the figure is from Left to right represent the length of the crystal rod from head to tail, and the ordinate is the resistivity corresponding to the position; among them, the maximum resistivity in the crystal rod is 4.94E-2Ohm.cm, and the value of the maximum resistivity is the value of the minimum resistivity. 1.6 times.
  • Figure 4 shows the resistivity of the silicon, boron, and gallium doped crystal rod head of the present invention is 5.84E-3Ohm.cm, and the resistivity of the crystal rod tail is 3.87E-3Ohm.cm; the abscissa of the figure is from Left to right represents the length of the crystal rod from head to tail, and the ordinate is the resistivity corresponding to the position; among them, the maximum resistivity in the crystal rod is 7.40E-3Ohm.cm, and the value of the maximum resistivity is the value of the minimum resistivity. 1.9 times.
  • Fig. 5 is a schematic diagram of antiphase domains formed by epitaxial growth of III-V group on germanium (100) single crystal substrate.
  • Fig. 6 is a front view of a sealed container for germanium single crystal growth.
  • Fig. 7 is a cross-sectional view of a crystal growth apparatus including a sealed container.
  • Fig. 8 is a flow chart of the entire process of growing a germanium single crystal rod starting from the germanium raw material by using the sealed container and single crystal growth equipment shown in Fig. 6.
  • Figure 9 is a schematic diagram of a three-section solar cell on a germanium substrate.
  • Fig. 10 is a schematic diagram of the crystal rod fixing device of the wafer preparation method of the present invention half surrounding graphite.
  • Fig. 11 is a schematic diagram of wafer chamfering in the wafer preparation method of the present invention, wherein the chamfer in Fig. 11-1a is arc-shaped, and the chamfer in Fig. 11-1b is slope-shaped.
  • Fig. 12 is an example of equipment used to implement the grinding and polishing steps of the wafer preparation method of the present invention.
  • the diameter of the wafer should be understood as follows: when the wafer is round, it refers to the diameter of the circle; when the wafer is in other shapes (such as irregular circles, squares, rectangles, etc.), it refers to the diameter of the wafer
  • the center of the circle is the center of the circle, so that the circle includes the diameter of the circle formed by all parts of the wafer.
  • the term "effective length" means the actual length of the ingot that can be used for cutting into wafers.
  • the co-dopant element means an element other than the element germanium, especially the elements silicon (Si), boron (B), and gallium (Ga).
  • the resistivity is carried out using the method described in GB/T 26074-2010 "Measurement Method of Germanium Single Crystal Resistivity Direct Current Four-Probe".
  • the present invention provides a single germanium wafer, wherein the germanium single wafer contains dopant elements silicon, boron and gallium, the silicon atom concentration is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is preferably 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc, more preferably 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc; boron
  • the atom concentration is preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc, more preferably 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc; and the gallium atom concentration is preferably 2 ⁇ 10 16 atoms /cc to 9 ⁇ 10 19 atoms/cc, more preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the unit "atoms/cc" means “atoms/cc”.
  • the silicon atom concentration is 0.5-25 ppm based on germanium
  • the boron atom concentration is 0.1-200 ppm based on germanium
  • the gallium atom concentration is based on germanium. 1-100ppm.
  • the concentration of silicon atoms is preferably 2-20 ppm based on the amount of germanium, more preferably 3-15 ppm based on the amount of germanium; and the concentration of boron atoms is 5 ppm based on the amount of germanium. -180 ppm, more preferably 10-160 ppm based on the amount of germanium; and the gallium atom concentration is preferably 10-80 ppm based on the amount of germanium, more preferably 20-60 ppm based on the amount of germanium.
  • the range of the sum A of the concentration of silicon atoms, boron atoms and gallium atoms is 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on the amount of germanium.
  • the invention uses the co-doping of gallium atoms and boron atoms, and uses the difference in segregation coefficients of gallium atoms and boron atoms in germanium materials to obtain uniform carrier concentration and resistivity between germanium single crystal wafers and in germanium single crystal rods. distributed. This is because boron atoms of the same family as gallium can also be used as P-type dopants for germanium single crystals, and the segregation coefficient of boron atoms in germanium single crystals is 18. During the growth of germanium single crystals, boron atoms Enriched in the solid phase, the concentration of boron atoms in the remaining liquid phase decreases, and the resistivity becomes larger.
  • the ratio of the boron atom concentration to the gallium atom concentration is 8:1 to 1:240, preferably 5:1 to 1:170, more preferably 3:1 to 1:100.
  • the ratio of silicon atom concentration to gallium atom concentration is 4:1-100, preferably 3:1-80, and more preferably 2:1-50.
  • the thickness of the germanium single wafer of the present invention is 100-700 ⁇ m, preferably 100-500 ⁇ m, more preferably 100-200 ⁇ m, even more preferably 120-140 ⁇ m.
  • the germanium single crystal wafer of the present invention is made by cutting a germanium single crystal rod.
  • the germanium single crystal rod is a crystal rod with a circular transverse cross section (circular crystal rod for short).
  • the cross section in the longitudinal direction is rectangular or square, and the cross section of the germanium single crystal rod is circular.
  • the diameter of is usually no more than 10 inches, preferably 1-8 inches, preferably 2-6 inches, and even more preferably 2-4 inches.
  • the germanium single crystal rod can also be a crystal rod with a transverse cross section of other shapes, such as a germanium single crystal rod with a square (square or rectangular) cross section obtained by processing a round crystal rod.
  • the wafer is a non-circular germanium single wafer.
  • the germanium single wafer of the present invention is preferably cut from an ingot obtained by the method for preparing an ingot as described below.
  • the elemental silicon and germanium matrix are infinitely miscible.
  • the present invention found that the co-doping effect produced by adding silicon and gallium to the germanium raw material can significantly improve the electrical properties of germanium single crystals. .
  • the difference in resistivity between the co-doped germanium single wafers of the present invention is smaller, and when used to prepare multi-level solar cells, the open circuit voltage of the solar cells can be significantly increased.
  • the present invention also provides a method for preparing a single germanium wafer, the method comprising:
  • a germanium single crystal initial wafer is cut from a germanium single crystal rod containing the elements silicon and gallium, wherein the silicon atom concentration in the cut germanium single crystal initial wafer is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/ cc, the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the thickness of the initial wafer is 200- 800 ⁇ m;
  • step 4 Perform rough polishing on the germanium single crystal initial wafer after the surface treatment in step 3), and then perform fine polishing to obtain a germanium single wafer product, wherein the thickness of the obtained germanium single crystal wafer is 100-700 ⁇ m.
  • the germanium single crystal rod used in the method for preparing a germanium single wafer of the present invention is preferably prepared by the method for preparing the crystal rod described below.
  • the cutting in step 1) is performed by a cutting machine.
  • the cutting machine is usually performed using an external circular cutting machine, an internal circular cutting machine or a multi-wire cutting machine known in the art. Since the multi-wire cutting machine has good production efficiency and sheet yield, the multi-wire cutting machine is preferred.
  • the multi-wire cutting machine usable in the present invention is, for example, the multi-wire cutting machine MWM442DM purchased from Komatsu NTC of Japan.
  • the mud can be prepared from powdered substances and cutting oil.
  • the powdered substance is known in the art and commercially available, and may be, for example, diamond powder, boron carbide, and silicon carbide.
  • the particle size of the powdery substance can be selected. In principle, powdery substances with a particle size of 5-15 microns for preparing the slurry for semiconductor ingot cutting can be used.
  • the particle size of the powdered substance is preferably 6-13 microns, more preferably 8-12 microns.
  • the cutting oil is also known in the art and commercially available, and may be vegetable oil (such as olive oil and soybean oil), mineral oil.
  • the powdery substance is preferably silicon carbide, and the cutting oil is preferably mineral oil.
  • the particle size can be measured by a commercially known particle size analyzer, such as Malvern's Laser diffraction particle size analyzer measurement.
  • the germanium single crystal rod in order to reduce the shaking of the germanium single crystal rod and improve the surface quality, the germanium single crystal rod can be fixed.
  • the fixing method is not particularly limited, as long as it can effectively prevent the germanium single crystal rod from shaking during the cutting process.
  • a fixing device with a semi-enclosed structure is used to fix the germanium single crystal rod so as to conveniently separate it from the wafer in subsequent steps.
  • the material for preparing the semi-enclosed structure fixing device is not particularly limited, as long as the material can not be deformed or adversely affect the cut wafer during the cutting process, it can be used, for example, graphite.
  • the preferred semi-enclosed structure fixing device of the present invention is semi-enclosed graphite (as shown in Fig. 10).
  • the edging process is performed on the germanium single crystal initial wafer, that is, the edge chamfering process is performed on the germanium single crystal initial wafer (as shown in Figure 11-1a and Figure 11-1b).
  • the edge chamfering process is performed on the germanium single crystal initial wafer (as shown in Figure 11-1a and Figure 11-1b).
  • Figures 11-1a and 11-1b are cross-sectional illustrations of the wafer before and after chamfering.
  • the cross-section of the edge of the germanium single wafer has an arc-shaped edge (FIG.
  • the chamfering process is usually performed using a chamfering machine, and any prior art chamfering machine can be used in this step.
  • chamfering with a chamfering machine it is preferable to set the feed amount of the chamfering machine within 0.4 mm, preferably within 0.3 mm.
  • the edged germanium single crystal initial wafer is subjected to surface treatment, and the surface treatment can use a grinder to grind the edged germanium single crystal initial wafer. If it is necessary to grind both sides of the edged germanium single crystal initial wafer, you can grind one side and then grind the other side.
  • the grinding process is to eliminate the saw pattern damage on the surface of the germanium single crystal initial wafer during the slicing process, and to obtain sufficient wafer flatness to prepare for the subsequent polishing process.
  • the grinding can be carried out by any method known in the art, for example, can be carried out in a known grinding equipment (for example, an equipment similar to FIG.
  • the germanium single crystal initial wafer is placed in a supporting pad, and the upper and lower sides are pads There is a polishing pad (usually a polyester polishing pad), and the polishing process uses a polishing liquid (a known polishing liquid can be used).
  • a polishing liquid a known polishing liquid can be used.
  • the upper disk rotation speed is 2-12 rpm, preferably 3-10 rpm; the lower disk rotation speed is 5-20 rpm, preferably 8-15 rpm.
  • the amount of grinding fluid is 60-120ml/m 2 grinding disc area/min (calculated on one side of the equipment disc).
  • the grinding time is 20-50 minutes, preferably 25-40 minutes.
  • the surface treatment can also be performed by a chemical method.
  • the germanium single crystal initial wafer may be immersed in an etching solution, or the germanium single crystal initial wafer may be rinsed with the etching solution.
  • the etching solution may be a conventional etching solution used in the art for surface treatment of germanium single crystal initial wafers.
  • a grinder and a chemical surface treatment method can be used in combination, for example, the grinder is used first, and then the chemical surface treatment is performed.
  • the temperature is above room temperature, preferably above 30°C, more preferably above 35°C; the treatment time is 5-20 seconds, preferably 8-18 seconds, more preferably 10-15 seconds.
  • the etching solution is an aqueous solution containing NH 3 and hydrogen peroxide.
  • NH 3 is 0.1-5 mol%; hydrogen peroxide is 5-15 mol%; the balance is water.
  • the method further includes rough polishing the surface-treated germanium single wafer, and then performing fine polishing.
  • the rough polishing solution used in addition to water, also includes dichloroisocyanurate, sulfonate, pyrophosphate, bicarbonate and silica sol.
  • the components other than water in the rough polishing solution are calculated by their weight percentages (based on the total amount of components other than water), including dichloroisocyanurate 8.0 -22.0%, sulfonate 0.01-0.30%, pyrophosphate 4.5-19.0%, bicarbonate 3.0-13.0% and silica sol 55.0-72.0%, the total content of each component is 100%.
  • the total weight percentage of the above-mentioned components dissolved in water is limited to not adversely affecting the wafer, and may be any concentration, but is preferably not higher than 6.0%.
  • the wafer is subjected to a pressure of 0.04-0.15 kg/cm2, preferably 0.05-0.12 kg/cm2 during the polishing process.
  • the upper disk rotation speed is 10-45 rpm, preferably 12-35 rpm; the lower disk rotation speed is 5-40 rpm, preferably 8-30 rpm.
  • the polishing liquid flow rate is 60-120 liters/cm 2 wafer area/hour.
  • the polishing time is 20-70 minutes, preferably 25-60 minutes.
  • the fine polishing solution used in addition to water, includes dichloroisocyanurate, sulfonate, acid pyrophosphate, bicarbonate, and carbonate.
  • the polishing solution in addition to water, by weight percentage (based on the total amount of ingredients other than water), includes dichloroisocyanurate 29.00-40.00%, Sulfonate 0.20-0.45%, acid pyrophosphate 18.00-35.00%, bicarbonate 17.00-24.00% and carbonate 15.00-23.00%, the total content of each component is 100%.
  • the total weight percentage of the above components after dissolving in water is limited to not having an adverse effect on the wafer, and can be any concentration, but is preferably not higher than 3.0%.
  • the pressure on the wafer during the polishing process is 0.05-0.15 kg/cm2, preferably 0.06-0.12 kg/cm2.
  • the upper disk rotation speed is 20-60 rpm, preferably 25-50 rpm; the lower disk rotation speed is 10-35 rpm, preferably 12-25 rpm.
  • the polishing liquid flow rate is 0.5-1.0ml/cm 2 wafer area/min.
  • the polishing time is 3-20 minutes, preferably 5-15 minutes.
  • dichloroisocyanurate, (acid) pyrophosphate, bicarbonate, and carbonate may use one of their respective water-soluble salts.
  • dichloroisocyanurate, (acid) pyrophosphate, bicarbonate and carbonate are one of the respective water-soluble alkali metal salts or ammonium salts, particularly preferably the respective sodium Salt or ammonium salt.
  • silica sol a conventional silica sol, such as a commercially available silica sol, or a silica sol prepared by a prior art method can be used.
  • a water-soluble sulfonate can be used, preferably one of the water-soluble alkali metal salts or an ammonium salt, particularly preferably a sodium salt or an ammonium salt.
  • the sulfonate is, for example, a monosulfonate or disulfonate of a C 6-16 aryl group (ie, an aryl group containing 6-16 carbon atoms, including substituted aryl groups) (e.g., C 4-10 Alkyl-benzene sulfonate, benzene sulfonate, naphthalene sulfonate, anthracene sulfonate, C 4-10 alkyl-phenyl disulfonate, phenyl disulfonate, naphthyl disulfonate Acid di-salt or anthracene disulfonic acid di-salt, such as 1,2-benzene disulfonic acid di-salt,
  • the surface roughness of the germanium single wafer is not higher than 0.5 nanometers, and the flatness is 3-7 microns, preferably 3-5 microns.
  • the surface roughness and wafer flatness of the germanium single wafer can meet the requirements of this field.
  • the method for preparing a germanium single wafer of the present invention further includes: performing surface cleaning treatment on the germanium single wafer after fine polishing.
  • the surface wet cleaning treatment is carried out in a clean room not lower than class 1000.
  • the definition of the clean room class refers to the US Federal Standard 209D clean room specifications (see Table 1 below).
  • a thousand-level clean room generally refers to the number of particles ⁇ 0.5 microns ⁇ 1000 particles per cubic foot; the number of particles ⁇ 5.0 microns ⁇ 10 particles.
  • the wafer surface is free of particles and white fog by visual inspection under light.
  • the residual metal Zn and Cu on the surface of the wafer are ⁇ 10 ⁇ 10 10 atoms/cm 2 respectively .
  • the germanium single wafer of the method of the present invention does not need to undergo any pre-epitaxial processing, and can reach the level of being used out of the box. Since the cleaning can use the method of the prior art, it will not be further described here.
  • the present invention also provides a method for preparing a germanium single crystal rod, the method comprising:
  • step 3 Place the crucible described in step 1) and the loading container described in step 2) in a quartz tube, and seal the quartz tube under vacuum;
  • step 6 Cool down the melt in the crucible obtained in step 5), and control the temperature gradient and cooling rate of the melt at the same time, so that the germanium single crystal rod is crystallized and grown when the melt is in contact with the seed crystal;
  • the amount of dopant elements silicon and gallium added in step 1) is such that the silicon atom concentration of the germanium single crystal rod is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc in the effective length.
  • the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc
  • the thickness of the initial wafer is 200-800 ⁇ m.
  • the silicon atom concentration is preferably 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc, more preferably 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc; boron
  • the atom concentration is preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc, more preferably 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc; and the gallium atom concentration is preferably 2 ⁇ 10 16 atoms /cc to 9 ⁇ 10 19 atoms/cc, more preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is 0.5-25 ppm based on germanium
  • the boron atom concentration is 0.1-200 ppm based on germanium
  • the gallium atom concentration is based on germanium. 1-100ppm.
  • the concentration of silicon atoms is preferably 2-20 ppm based on the amount of germanium, more preferably 3-15 ppm based on the amount of germanium; and the concentration of boron atoms is 5 ppm based on the amount of germanium. -180 ppm, more preferably 10-160 ppm based on the amount of germanium; and the gallium atom concentration is preferably 10-80 ppm based on the amount of germanium, more preferably 20-60 ppm based on the amount of germanium.
  • the ratio of the boron atom concentration to the gallium atom concentration at the head of the crystal rod is 8-5:1, preferably 7-4:1, It is more preferably 5-3:1, and the ratio of the boron atom concentration and the gallium atom concentration at the tail of the crystal rod is 1:100-240, preferably 1:130-210, and more preferably 1:160-180.
  • the ratio of silicon atom concentration to gallium atom concentration within the effective length of the germanium single crystal rod is 4:1-100, preferably 3:1-80, more preferably 2: 1-50.
  • the range of the sum A of the silicon atom, boron atom and gallium atom concentration within the effective length of the germanium single crystal rod is 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on Germanium gauge.
  • the germanium raw material used in the method for preparing crystal rods of the present invention is a high-purity germanium raw material.
  • high purity germanium means germanium with a resistivity of up to 4000 ⁇ m and a purity of 99.999% or more.
  • the high-purity germanium raw material with ultra-low dopant content ensures the repeated controllability of the desired characteristics and performance of the germanium wafer, thereby ensuring the stability of the germanium substrate for preparing solar cell devices.
  • High-purity germanium raw materials are commercially available, and commercially available high-purity germanium raw materials are usually in block or powder form.
  • the present invention preferably uses bulk high-purity germanium raw materials, for example, bulk high-purity germanium purchased from Zhongnuo New Materials (Beijing) Technology Co., Ltd.
  • the container for the growth of germanium single crystal rods can be prepared with suitable crucible materials, such as pyrolytic boron nitride (PBN) crucibles.
  • PBN pyrolytic boron nitride
  • This kind of crucible has relatively good stability and will not pollute the germanium raw materials, and will not be ) React with germanium melt under the above conditions of 100°C.
  • the container or crucible for single crystal growth includes a body part that can be cylindrical, the diameter of the cylindrical body is slightly larger than the diameter of the germanium single crystal rod to be prepared (provided that the germanium single crystal rod can be completely contained and the germanium single crystal rod does not touch the cylindrical shape
  • the wall of the main body), the bottom is a small-diameter seed tank, and there is a conical transition zone between the bottom seed tank and the cylindrical body (as shown in Figure 6).
  • the seed tank is used to place cylindrical seed crystals prepared from high-purity germanium single crystals.
  • the crystal orientation of the upper end surface of the seed crystal is the desired surface crystal orientation of the germanium single crystal substrate, such as (100) or a surface crystal orientation that is deflected to a certain angle from the adjacent crystal orientation axis relative to the (100) crystal orientation.
  • the germanium polycrystalline block of suitable shape is loaded into the growth crucible above the seed cavity.
  • liquid sealing agent such as boron trioxide and germanium raw materials into the crucible located at the lower part (also called "growth crucible", as shown in Figure 6 and Figure 7).
  • the liquid sealing agent can separate the inner wall of the crucible from the surface of the germanium melt or the solid germanium crystal rod during the growth of single crystal, reduce the adhesion between the surface of the germanium crystal rod and the inner wall of the crucible, and it is easier to obtain complete germanium Single crystal rod.
  • the amount of the liquid sealing agent is a conventional amount in the field.
  • a loading container containing the same germanium raw material is placed above the growth crucible.
  • the bottom of the loading container is provided with a hole, and the germanium raw material is melted and dropped into the growth crucible.
  • the growth crucible is filled with molten germanium raw material, as shown in Figure 6.
  • the loading container can be a crucible. In this case, the loading container is also called a feeding crucible.
  • the germanium single crystal rod is grown by the vertical gradient condensation method melt growth technology.
  • the germanium single crystal production device used to implement the germanium single crystal rod preparation method of the present invention is described in US Pat. No. 8,506,706B2, and the full text of the document is hereby incorporated into this specification by reference.
  • Fig. 7 shows a cross-sectional view of an example of a germanium crystal growth apparatus.
  • This device is a furnace commonly used in the vertical gradient condensation growth method. It can include a quartz tube support 11 located in the furnace 1.
  • the heater 2 is composed of multiple zones, and each zone is controlled by a computer controlled by a control system. control.
  • a temperature gradient of 0.2-0.5°C/cm is preferred.
  • the quartz tube holder 11 provides physical support and thermal gradient control of the quartz tube 3 containing the crucible 12 (growth crucible).
  • the crucible 12 in the quartz tube has a seed tank 18 for storing seed crystals.
  • the quartz tube support 11 can axially move up and down during the crystal growth process.
  • the crucible 12 may contain a seed crystal 17, and the crystal grows a single crystal along the top of the seed crystal.
  • the crucible 12 can be a pyrolytic boron nitride structure with a cylindrical crystal growth portion 13, a seed tank cylinder 18 with a smaller diameter, and a tapered transition portion 7.
  • the crystal growth part 13 is open at the top of the crucible 12, and its diameter is equal to the diameter of the desired crystal product.
  • the seed tank cylinder 18 at the bottom of the crucible 12 may have a closed bottom and a diameter slightly larger than the high-quality seed crystal 17, for example, about 6-25 mm, and a length of about 30-100 mm.
  • the cylindrical crystal growth part 13 and the seed tank cylinder 18 may have straight walls, or the cone may gradually expand outward by about 1-30 degrees to facilitate removal of the crystals in the crucible 12.
  • the tapered transition portion 7 between the growth portion 13 and the seed tank cylinder 18 has an inclined side wall with an angle of, for example, about 45-60 degrees, and its larger diameter is equal to the diameter of the growth zone and connects the walls of the growth zone. , The smaller diameter is equal to the diameter of the seed tank and connects to the wall of the seed tank.
  • the angled sidewall may also have other angles that are steeper or less steep than 45-60 degrees.
  • the quartz tube 3 has a shape similar to the crucible 12.
  • the quartz tube 3 is cylindrical in the seed growth region 19-the cylinder has a narrow diameter in the seed tank region 19 of the quartz tube 3, and there is a tapered transition region 8 between the two regions.
  • the crucible 12 fits inside the quartz tube 3 and has a narrow gap between them.
  • the quartz base 6 is encapsulated in the middle part of the quartz tube 3.
  • the feeding crucible 4 is made of PBN.
  • germanium raw material 5 for example, 60-80% by weight, preferably 60-70% by weight based on the germanium raw material in the growth crucible and the feed crucible.
  • the germanium raw material melts and drips into the crucible 12 from the bottom hole of the feed crucible 4.
  • the quartz tube 3 is closed at the bottom of its seed tank area 19, and sealed at the top after being loaded into the crucible and raw materials.
  • the quartz tube holder 11 is required to fit the funnel shape and keep the quartz tube 12 stable and standing inside the furnace.
  • the quartz tube-crucible assembly can maintain different shapes, and the basic structure of the quartz tube holder 11 will be changed according to different shapes.
  • the stability and support strength of the quartz tube and its contents are provided by the strong thin-walled cylinder 16 of the quartz tube support 11.
  • the strong thin-walled cylinder 16 accommodates the funnel-shaped bottom of the quartz tube structure 3.
  • the crucible support cylinder 16 is composed of a thermally conductive material, preferably quartz.
  • silicon carbide or ceramics may also be used to form the crucible support cylinder 16.
  • the cylinder 16 is in circumferential contact with the quartz tube 3, wherein the upper edge of the cylinder 16 contacts the shoulder of the tapered area 8 of the quartz tube.
  • the configuration results in the minimization of solid-to-solid contact, which ensures that little or no undesirable, relatively uncontrollable heat conduction occurs. Therefore, other more controllable methods can be used for heating.
  • a low-density insulating material for example, ceramic fiber
  • a hollow shaft 20 at approximately the center of the insulating material remains empty (not filled with any insulating material)
  • the low-density insulating material may also include alumina fibers (melting point 1,800°C), alumina-silica fibers (melting point 1,426°C), and/or zirconia fibers (melting point 2,200°C). Place the insulating material carefully in the quartz tube holder 11. The weight of the quartz tube 3-when it is placed on the top of the cylinder 16-pushes the insulating material down and forms an inclined edge 9 of insulating material. Filling most of the cylinder with low-density insulators reduces air flow, which ensures that little or no unwanted, relatively uncontrollable convection occurs. Similar to conduction, convection is an uncontrollable heat transfer process that is detrimental to VGF and other crystal growth methods.
  • the hollow core 20 with a diameter approximately equal to the quartz tube seed tank 19 extends downward to a short distance below the bottom of the quartz tube seed tank 19.
  • the hollow core 20 extends from the bottom of the seed tank through the crucible support to the bottom of the furnace device 1.
  • the hollow core 20 provides a way to cool from the center of the crystal. This approach helps to cool the seed tank and the center of the crystal being grown. With this configuration, thermal energy can escape downward through the center of the solid crystal and seed crystal, and downward through the hollow core 20 in the insulating material in the crystal support 11. Without the hollow core 20, the temperature at the center of the cooled ingot will of course be higher than the crystalline material near the outer surface.
  • the center of any horizontal cross section of the ingot will crystallize later after the periphery of the ingot has solidified. It is impossible to prepare crystals with uniform electrical properties under such conditions.
  • the thermal energy is conducted downward through the bottom of the quartz tube 3 and the hollow core 20, and thus radiated back and out of the radiation channel 10. It is important to reduce the thermal energy at the center of the growing crystal, so as to keep the isothermal layer straight across the crystal diameter. Maintaining a straight crystal-melt interface can produce crystals with uniform electrical and physical properties.
  • the low-density insulating material in the cylinder 11 prevents heat radiation from flowing from a set of furnace heating elements 2 to the seed tank area 19 in the quartz tube 3, so this method requires the formation of multiple horizontal radiation channels/openings/pipes 10 through the insulating material. .
  • the radiation channel 10 penetrates the insulating material to provide a heat radiation outlet to controllably transfer heat from the furnace heating element 2 to the quartz tube seed tank 19.
  • the number, shape, and diameter of the radiation channels 10 vary according to specific conditions.
  • the radiation channel can also be inclined, curved or wavy.
  • the radiation channels do not have to be continuous either, because they can only partially pass through the insulating material. This helps minimize convection.
  • the diameter of these channels is small, about the width of a pencil, so convective airflow is not significant. According to other embodiments of the present invention, large holes with a cross-sectional area of about 6.4516 cm 2 (1 square inch) or more may also be used.
  • the radiation channel 10 passing through the insulating material can also be combined with the hollow core 20 in the center of the insulating material to radiate heat from the center of the crystal and cool the crystal with a two-dimensional isothermal temperature gradient layer.
  • the radiation channel 10 can control the temperature and is directly related to the yield of crystal growth.
  • the furnace temperature is cooled at a rate of about 0.2° C./h to about 0.6° C./h to allow the single crystal germanium ingot to grow.
  • Figure 7 illustrates an exemplary method of melting and supplying germanium. From the initial state of explanation, the solid germanium is present in the loading container 4 and the crucible 12. As a new heating technology feature and method advancement, an intermediate state of germanium melt appears, a state where solid germanium has been melted into a liquid state in the crucible 12.
  • the temperature of the area in the furnace with the loading container is heated to a range of 940° C. to 955° C., and this process continues until all the raw materials in the loading container are injected into the crucible 12.
  • the furnace 1 shown in FIG. 7 is an example of a furnace that can be used for the vertical gradient condensation (VGF) crystal growth method.
  • VGF vertical gradient condensation
  • Other furnaces and configurations can also be used, such as the vertical Bridgman method.
  • VGF crystal growth method the crystallization temperature gradient of a fixed heat source is moved by an electrical control method, and the crystal is fixed.
  • the required temperature gradient distribution needs to be established in the furnace, and the power of the heating zone of the furnace is separately and individually controlled by a computer, which is programmed to heat and cool to suit the furnace crystallization temperature and Temperature gradient required.
  • the temperature fluctuation of the furnace may need to be controlled to ⁇ 0.1°C.
  • the germanium polycrystalline raw material is loaded into the quartz tube 3 as described.
  • the PBN loading container 4 having a hole in the tapered part is fixed in the quartz tube 3, and placed on a support 6 made of quartz on the crucible 12.
  • Loading container 4 causes crucible 12 to be loaded with more raw materials.
  • the germanium raw material 5 is a solid block or sheet, and therefore cannot be tightly filled into the crucible 12 for melting. Therefore, the loading container is used to store additional raw materials that can be melted, which are then discharged down into the crucible 12, which causes more germanium in the crucible 12 to be charged, thereby obtaining longer germanium crystals.
  • the loading container is used to store additional raw materials that can be melted, which are then discharged down into the crucible 12, which causes more germanium in the crucible 12 to be charged, thereby obtaining longer germanium crystals.
  • about 65% of the raw materials can be charged into the loading container 4, and 35% of the raw materials can be directly charged into the growth crucible 12.
  • silicon and gallium are used as dopants.
  • the raw materials and an appropriate amount of dopant are charged into the crucible, and the crucible and the loading container are placed in the quartz tube 3.
  • the sealed quartz tube is then loaded into the furnace, as shown in Figure 7. Turn on the heating furnace to heat the quartz tube and its contents.
  • the heating rate can be 5-40°C/min, preferably 10-30°C/min, more preferably 15-20°C/min, and the heating temperature is 1000 ⁇ 50 °C (the melting point of germanium is about 940 °C).
  • the temperature gradient of the crystal interface can be adjusted to 0.2-10°C/cm according to different positions of the crystal rod. Adjust the entire temperature distribution to give a crystallization rate of 1-2 mm/h. After the solidification is completed, the furnace is cooled at 20-40°C/h.
  • the germanium single crystal rod grown using the above exemplary growth process parameters has a low defect density in the entire length direction and a uniform defect distribution. Cut the head and tail wafer erosion dislocation density from the grown crystal.
  • the dislocation density of the head and tail wafers is very uniform, and the average dislocation density of the head wafer can be lower than 80cm 2 , or 78/cm 2 , or 75/cm 2 , or 70/cm 2 , or 65/ cm 2 , the average dislocation density of the tail wafer can be less than 75 cm 2 , or 70/cm 2 , or 65/cm 2 , or 66/cm 2 , or 10% of the amount measured or given here, 20% or 30% of other such numerical windows (numerical numbers). Therefore, with the process of the present invention, the defect density is reduced by about 15-20%. The reason for the decrease in defect density is the solid solution strengthening effect brought about by the co-doped dopant elements added during crystal growth.
  • the dislocation density is determined by the method described in GB/T5252-2006 "Measurement Method of Germanium Single Crystal Dislocation Corrosion Pit Density".
  • the device of the present invention is composed of a quartz tube into which a PBN loading container and a crucible can be embedded, and a support 6 for storing the PBN loading container.
  • the dimensions of the crucible are: the diameter of the growing crystal section is about 150 mm, the length of the growing crystal section is 160 mm, and the diameter of the seed crystal section is 7 mm.
  • a (100)-oriented germanium seed crystal is embedded in the seed well of a PBN crucible, and boron trioxide as a liquid sealant is added to the PBN crucible above the seed crystal.
  • the germanium polycrystalline material was put into the PBN growth crucible and the PBN feeding crucible respectively, and the PBN growth crucible and the PBN feeding crucible were both embedded in the quartz tube, and the quartz tube was heated at about 2.00 ⁇ 10 -4 Pascal (1.5 ⁇ 10 -6 Torr) and sealed with a quartz cover under reduced pressure. The sealed quartz tube is then loaded into the furnace and placed on the quartz tube support.
  • the above-mentioned quartz ampoule is heated at a rate of approximately 270°C/hour. When the temperature is about 30°C higher than the melting point of the crystalline material, the heating is maintained until all the polycrystalline material is melted.
  • the present invention needs to meet the following elements in the single crystal growth process:
  • the growth procedure used needs to maintain a suitable single crystal growth rate and temperature gradient to avoid the formation of polycrystals during the growth process due to the co-doping of dopant elements.
  • the atomic concentration of silicon, boron and gallium varies in the axial direction of the ingot, and the effective length of the ingot is 3 ⁇ 10 14 atoms/cc.
  • the concentration of boron atoms is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc
  • the concentration of gallium atoms is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc.
  • the silicon atom concentration is preferably 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc, and more preferably 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc.
  • the concentration of boron atoms is preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc, more preferably 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc.
  • the gallium atom concentration is preferably 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc, and more preferably 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • the designed growth program can obtain a suitable growth rate and a suitable temperature gradient near the solid-liquid interface from the end of the seed crystal to the end of the single crystal growth (or the entire melt solidifies and grows into a solid single crystal).
  • the growth process of germanium single crystal rods containing dopants requires a lower growth rate of single crystals, and the rate of solid-liquid interface movement is lower than normal without doping added.
  • the growth rate of the germanium single crystal rod of the agent element is 20% lower, and the temperature drop rate of different temperature zones is also reduced by about 20%.
  • single crystal growth was maintained throughout the length of the ingot.
  • a germanium single crystal rod with a diameter of 4 inches and a length of about 200 mm can be grown.
  • the grown crystal rod is cooled to room temperature under temperature control conditions, and the cooling rate is -20-40° C./h in the described embodiment.
  • the co-doping effect produced by the addition of silicon and gallium to the germanium raw material improves the electrical characteristics of the germanium single crystal.
  • it also makes the germanium crystal rod from the seed end To the tail end, the resistivity distribution along the whole germanium crystal rod is more uniform.
  • the value of the maximum resistivity of the germanium crystal rod is 1.0-3.0 times of the value of the minimum resistivity, preferably 1.2-2.5 times, more preferably 1.5-2.0 times.
  • the invention also relates to the use of the germanium single chip of the invention to increase the open circuit voltage of a multi-cell solar cell.
  • the open circuit voltage of the multi-cell solar cell using the germanium single wafer of the present invention is increased by 0.4-3.5% (equivalent to an increase of 10-95mV), preferably 1.2-3.0% (equivalent to an increase of 31-81mV), more preferably an increase of 1.5-2.5% (equivalent to an increase of 40-67mV).
  • the invention increases the open circuit voltage of the solar cell device by controlling, reducing and eliminating the recombination position of photo-generated carriers.
  • the present invention relates to the following solutions:
  • a single germanium wafer wherein the germanium single wafer contains dopant elements silicon, boron and gallium, the silicon atom concentration is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc;
  • the silicon atom concentration is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc;
  • the silicon atom concentration is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • germanium single wafer according to embodiment 1, wherein the ratio of the boron atom concentration to the gallium atom concentration of the germanium single wafer is 8:1 to 1:240, preferably 5:1 to 1:170, more preferably 3:1 to 1:100.
  • germanium single wafer according to any one of embodiments 1-2, wherein the ratio of silicon atom concentration to gallium atom concentration of the germanium single wafer is 4:1-100, preferably 3:1-80, more preferably 2:1-50.
  • germanium single wafer according to any one of embodiments 1-3, wherein the thickness of the germanium single wafer is 100-700 ⁇ m, preferably 100-500 ⁇ m, more preferably 100-200 ⁇ m, even more preferably 120-140 ⁇ m .
  • germanium single wafer according to any one of the embodiments 1-4, wherein the sum A of the silicon atom, boron atom and gallium atom concentration of the germanium single wafer is in the range of 2ppm ⁇ A ⁇ 120ppm, preferably 4ppm ⁇ A ⁇ 70ppm, based on germanium.
  • the present invention also provides a method for preparing a single germanium wafer, the method comprising:
  • a germanium single crystal initial wafer is cut from a germanium single crystal rod containing the elements silicon, boron and gallium, wherein the silicon atom concentration in the cut germanium single crystal initial wafer is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/cc, the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc, the thickness of the initial wafer is 200-800 ⁇ m,
  • the silicon atom concentration is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc;
  • the silicon atom concentration is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc
  • step 4 Perform rough polishing on the germanium single crystal initial wafer after the surface treatment in step 3), and then perform fine polishing to obtain a germanium single wafer product, wherein the thickness of the obtained germanium single crystal wafer is 100-700 ⁇ m.
  • a method for preparing a germanium single crystal rod comprising:
  • step 3 Place the crucible described in step 1) and the loading container described in step 2) in a quartz tube, and seal the quartz tube under vacuum;
  • step 6 Cooling the melt in the crucible obtained in step 5), while controlling the temperature gradient and cooling rate of the melt, so that the germanium single crystal rods are crystallized and grown when the melt is in contact with the seed crystal;
  • the amount of dopant elements silicon, boron and gallium added in step 1) is such that the silicon atom concentration in the effective length of the germanium single crystal rod is 3 ⁇ 10 14 atoms/cc to 10 ⁇ 10 18 atoms/ cc, and the boron atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 18 atoms/cc, and the gallium atom concentration is 1 ⁇ 10 16 atoms/cc to 10 ⁇ 10 19 atoms/cc;
  • the silicon atom concentration is 4 ⁇ 10 14 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 9 ⁇ 10 19 atoms/cc;
  • the silicon atom concentration is 5 ⁇ 10 14 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the boron atom concentration is 4 ⁇ 10 16 atoms/cc to 7 ⁇ 10 18 atoms/cc
  • the gallium atom concentration is 2 ⁇ 10 16 atoms/cc to 8 ⁇ 10 19 atoms/cc.
  • step 6 when the melt is brought into contact with the seed crystal, the crystal grows into a germanium single crystal rod.
  • 0.3-4.0°C/cm is established in the rod growth zone; preferably, a temperature gradient of 0.5-3.5°C/cm is established in the ingot growth zone; more preferably, a temperature gradient of 1.0-3.0°C/cm is established in the ingot growth zone.
  • germanium single wafer according to any one of the embodiments 1-5, the germanium single wafer produced by the method for preparing the germanium single wafer according to any one of the embodiments 6-10, and the preparation according to any one of the embodiments 11-15 The germanium single crystal rod obtained by the germanium single crystal rod method is used to increase the open circuit voltage of the multi-cell solar cell.
  • Polishing machine (upper and lower discs with a diameter of 1.0m), as shown in Figure 12, where R1 and R2 are rotating shafts, 11 is the slurry or polishing liquid pipe, 12 is the upper plate of the equipment, 13 is the lower plate of the equipment, and 14 is the wafer and support Pad, 16 is a polishing pad or polishing pad (the polishing pad is a polyester polishing pad purchased from Universal Optics Co. Ltd., the brand is LPS polishing pad; the rough polishing pad is a polyurethane polishing pad purchased from DOW, USA , Grade Suba-X Pad; the fine polishing pad is a polyurethane polishing pad purchased from DOW, USA, grade POLICEX Pad.
  • the polishing pad is a polyester polishing pad purchased from Universal Optics Co. Ltd., the brand is LPS polishing pad
  • the rough polishing pad is a polyurethane polishing pad purchased from DOW, USA , Grade Suba-X Pad
  • the fine polishing pad is a polyurethane polishing pad
  • the bottom plate also has a polishing pad and a polishing pad, which are the same as the upper plate, located under the wafer and support pad, not shown Out).
  • the supporting pad (the same supporting pad is used for grinding and polishing), the grinding pad and the polishing pad have a diameter of 1 meter; the 4 holes of the supporting pad for carrying the wafer are located in the middle of the radius direction and are evenly distributed along the circumferential direction.
  • the grinding fluid is a mixture of Japan Fujimi Corporation Fujimi 20T aluminum oxide grinding powder and water, with a weight ratio of 1:1, and the grinding fluid flow rate during the grinding process is 90 ml per minute/square meter equipment disk area (single-side meter) ).
  • Multi-wire cutting machine MWM442DM, purchased from Japan Komatsu NTC.
  • Silicon carbide with a particle size of 10 microns was purchased from Shanghai Shangmo Abrasives Co., Ltd.
  • Multifunctional digital four-probe tester ST2258A type, purchased from Suzhou Jingge Electronics Co., Ltd.
  • NanoSIMS 50L High resolution secondary ion mass spectrometer, NanoSIMS 50L, purchased from CAMECA, France.
  • the inspection conditions of the prepared germanium single crystal initial wafer are as follows: visual inspection of the wafer is complete and no cracks on the surface are qualified.
  • the electrical resistivity is tested using the method described in GB/T 26074-2010 "Method for Measuring the Resistivity of Germanium Single Crystal DC Four-Probe" using the above-mentioned multifunctional digital four-probe tester.
  • the dislocation density is determined by the method described in GB/T5252-2006 "Measurement Method of Dislocation Corrosion Pit Density of Germanium Single Crystal".
  • the open circuit voltage is tested with a multimeter.
  • the atomic concentration of the dopant elements silicon, boron, and germanium was measured by the above-mentioned high-resolution secondary ion mass spectrometer.
  • the measurement conditions were as follows: when measuring the Si atomic concentration, a cesium ion (Cs+) beam was used as the incident ion beam, sputtering from the sample surface The average Si atom concentration is obtained within the thickness of 10 microns inside the sample; the oxygen ion (O2+) ion beam is used as the incident ion beam when testing the B atom concentration, and the average B atom concentration is obtained from the surface of the sample to the thickness of 10 microns inside the sample; When measuring the Ga atom concentration, an oxygen ion (O2+) beam is used as the incident ion beam, and the average Ga atom concentration is obtained by sputtering from the sample surface to the thickness of 10 microns inside the sample; the vacuum degree of the test chamber is 10 -7 Torr (torr) , The incident i
  • germanium single crystal rods with a diameter of 4 inches to increase the open circuit voltage of multi-cell solar cells.
  • germanium single crystal rods with other diameter sizes such as crystal rods with a diameter of 1 inch to 8 inches or more, can be used.
  • the method for preparing a germanium single crystal rod of the present invention is used for preparation.
  • step 3 Put the quartz tube sealed with the first growth crucible and the second feeding crucible obtained in step 3) into a crystal growth furnace with a movable quartz tube support, which is used to support the quartz tube;
  • step 6 Cool the melt obtained in step 5), and control the cooling rate of the melt, so that when the melt is in contact with the seed crystal, it crystallizes to form a germanium single crystal rod.
  • the temperature gradient of the germanium single crystal growth and the germanium single crystal from the seed crystal end The crystal cooling rate of crystal growth is shown in Table 2; and;
  • the germanium single crystal rod is cooled to room temperature, and the cooling rate is 30°C/h.
  • Figures 3 and 4 show the resistivity (Res) distribution from the beginning to the end of the gallium, boron and silicon doped germanium single crystal rods of the invention 1 and 2, respectively.
  • the maximum resistivity and the minimum resistivity are obtained according to the graph.
  • the invention 3- 4 Obtained in a similar manner.
  • germanium single crystal rods prepared in the above embodiments are cut into germanium single wafers according to the following steps.
  • the germanium single crystal rod is cut into a germanium single crystal initial wafer with a thickness of 240 ⁇ m with a multi-wire saw. During the cutting process, a semi-enclosed graphite is used to fix the round germanium single crystal rod. After the cutting is completed, the initial germanium single crystal wafer is manually taken out, and the operation is completed by the same person under the same conditions.
  • Chamfering Use a chamfering machine to chamfer the edges of each round wafer so that the edge section becomes an arc.
  • Fixing Place one side of the wafer on a flat ceramic plate with a diameter of 5.2 cm and a thickness of 250 microns (Ra ⁇ 0.5 microns), and gently apply pressure to ensure that there are no bubbles between the wafer and the ceramic plate.
  • the etching solution is composed of 1 mol% NH 3 , 10 mol% hydrogen peroxide, and the remainder is water.
  • Polishing Then place the ceramic plate with the wafer in the support pad cavity of the polishing machine (close to the ceramic plate), and fix it. First, apply the rough polishing solution shown in Table 4 to the polishing equipment, as shown in Table 4. Polished for 60 minutes under polishing conditions, cleaned with deionized water (resistivity greater than 17.5 Mohm ⁇ cm-at 25°C), dried, and then used the polishing solution shown in Table 5 on the polishing equipment. After polishing for 6 minutes under the fine polishing conditions shown in Table 5, the ceramic plate carrying the wafer was taken out and placed on the heating furnace to melt the glue, and the wafer was removed from the ceramic plate, washed with deionized water, and dried.
  • the thickness of the obtained germanium single wafer was 140 ⁇ m, and the performance test results of the obtained germanium single wafer are shown in Table 6 below.
  • the germanium single crystal obtained by using the germanium single crystal rod prepared in the above cutting embodiment is used to prepare a solar cell according to the following steps.
  • the gas and metal organic sources used in the epitaxy process include high-purity hydrogen and phosphorus Alkane (PH 3 ), arsine (AsH 3 ), trimethyl gallium (TM-Ga), trimethyl indium (TM-In), using phosphorus as n-type doping, forming a PN junction with the germanium substrate ;
  • anti-reflection layer The purpose of depositing anti-reflection layer is to reduce surface reflection and increase refractive index. Use PECVD to deposit SiN. Because PECVD deposits SiN, not only does SiN grow as anti-reflection film, but also a large number of atoms are generated Hydrogen, these hydrogen atoms can have the dual effect of surface passivation and bulk passivation on polycrystalline silicon wafers, which can be used for mass production;
  • Electrode formation Electron beam evaporation process is used to coat gold, germanium and nickel on the front and back of the solar cell to form positive and negative electrode leads;
  • an appropriate amount of silicon dopant is added during the process of loading germanium raw material into the crucible, and at the same time, using a suitable growth procedure, almost all the loaded raw materials grow into single crystal materials, and almost the entire ingot can be used for photovoltaic devices Preparation of substrate material for epitaxy. Silicon atoms were detected in these ingots, and the germanium single crystal substrate material prepared by using these ingots significantly increased the open circuit voltage of photovoltaic devices epitaxially grown on them.
  • germanium crystal substrate such as ingot, wafer, etc.
  • any product such as electronic equipment or optoelectronic equipment, etc.
  • containing such a germanium crystal substrate prepared by one of the methods of the present invention also conforms to the present invention.

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Abstract

一种锗单晶片，包含原子浓度为3×10 14atoms/cc至10×10 18atoms/cc的硅、原子浓度为1×10 16atoms/cc至10×10 18atoms/cc的硼以及原子浓度为1×10 16atoms/cc至10×10 19atoms/cc的镓。还提供了一种锗单晶片的制法、一种锗单晶棒的制法，以及一种锗单晶片用于增加太阳能电池开路电压的用途。锗单晶片具有改进的电学性能，具有更小的电阻率差和载流子浓度差。

Description

锗单晶片、其制法、晶棒的制法及单晶片的用途 技术领域
本发明涉及锗(Ge)单晶片、锗单晶片的制备方法、制备锗单晶片的晶棒的制备方法以及本发明获得的锗单晶片的用途。
背景技术
高效大功率太阳能电池在太空太阳能系统和大规模地面聚光太阳能系统中获得了广泛的应用。锗单单晶片是这种高效大功率多节太阳能电池的理想衬底材料。目前所用的锗单晶材料均通过掺杂镓获得P型锗单晶衬底，其中载流子是正电子(positive electron)，也称为空穴。由于镓原子在锗材料中的分凝系数仅为0.087，所以锗单晶生长过程中镓原子逐渐在液相中富集，生长的锗单晶从头到尾镓原子的浓度逐渐增加。所谓杂质分凝系数可作如下理解：对于固相-液相界面，由于杂质在不同相中的溶解度不一样，所以杂质在界面两边材料中分布浓度不同，即所谓的杂质分凝现象。这种杂质分凝作用的大小常常用分凝系数来描述：“分凝系数”＝(杂质在固相中的溶解度)/(杂质在液相中的溶解度)。杂质分凝现象导致晶棒头尾电阻率差，如果晶棒头尾电阻率差超过六倍以上，则在制备多节太阳能电池中对其性能的一致性产生不利影响。
发明内容
为了解决上述技术问题提出本发明，通过镓原子和硼原子的共掺杂，利用镓原子和硼原子在锗材料中分凝系数的差异，获得均匀的载流子浓度和电阻率的分布。
具体而言，本发明的目的通过调整锗单晶片中共掺杂元素硅、硼和镓的量，共掺杂元素镓、硼和硅的比例以及锗单晶生长的温度梯度和速率实现。
更具体而言，本发明涉及如下技术方案。
本发明提供一种锗单晶片，其中，锗单晶片中包含掺杂剂元素硅、硼和镓，硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc。
在本发明的锗单晶片的一个优选实施方案中，硅原子浓度为 4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc。
在本发明的锗单晶片的一个更优选实施方案中，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
在本发明锗单晶片的一个优选的实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为8:1至1:240。
在本发明锗单晶片的一个更优选的实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为5:1至1:170。
在本发明锗单晶片的一个特别优选的实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为3:1至1:100。
在本发明锗单晶片的一个优选的实施方案中，锗单晶片的硅原子浓度与镓原子浓度比例为4:1-100。
在本发明锗单晶片的一个更优选的实施方案中，锗单晶片的硅原子浓度与镓原子浓度比例为3:1-80。
在本发明锗单晶片的一个特别优选的实施方案中，锗单晶片的硅原子浓度与镓原子浓度比例为2:1-50。
在本发明锗单晶片的一个优选的实施方案中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
在本发明锗单晶片的一个优选的实施方案中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
本发明还提供一种制备锗单晶片的方法，所述方法包括：
1)由包含元素硅和镓的锗单晶棒切割出锗单晶初始晶片，其中，切割得到的锗单晶片初始晶片中硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc，初始晶片的厚度为200-800μm；
2)对步骤1)得到的锗单晶初始晶片进行磨边处理；
3)对步骤2)中进行磨边处理之后的锗单晶初始晶片进行表面处理，和
4)对在步骤3)中表面处理之后的锗单晶初始晶片进行粗抛光， 然后进行精抛光，得到锗单晶片产品，其中，所得到的锗单晶片产品厚度为100-700μm。
在本发明的制备锗单晶片的方法的一个优选实施方案中，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc。
在本发明制备锗单晶片的方法的一个更优选实施方案中，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
在本发明制备锗单晶片的方法的一个优选实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为8:1至1:240。
在本发明制备锗单晶片的方法的一个更优选实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为5:1至1:170。
在本发明制备锗单晶片的方法的一个特别优选的实施方案中，锗单晶片的硼原子浓度和镓原子浓度的比例为3:1至1:100。
在本发明制备锗单晶片的方法的一个优选的实施方案中，硅原子浓度与镓原子浓度比例为4:1-100。
在本发明制备锗单晶片的方法的一个更优选的实施方案中，硅原子浓度与镓原子浓度比例为3:1-80。
在本发明制备锗单晶片的方法的一个特别优选的实施方案中，硅原子浓度与镓原子浓度比例为2:1-50。
在本发明锗单晶片的方法的一个优选实施方案中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
在本发明的制备锗单晶片的方法的一个优选实施方案中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
进一步地，本发明一种制备锗单晶棒的方法，所述方法包括：
1)将第一锗原料、共掺杂剂元素硅和镓以及任选的液封剂一并装入坩埚中，所述坩埚带有晶种槽，晶种槽事先装有高纯锗单晶晶种；
2)将第二锗原料装入装载容器中，第二锗原料用于补充第一锗原料，所述装载容器中任选地装有液封剂；
3)将第1)步所述坩埚和第2)步所述装载容器置于石英管内，并 在真空下密封石英管；
4)将第3)步的密封有坩埚和装载容器的石英管放入具有可移动的石英管支座的晶体生长熔炉中，所述支座用于支承石英管；
5)使第一锗原料和第二锗原料熔融，分别形成第一熔体和第二熔体，然后使得装载容器中的熔融的第二锗原料完全注入坩埚；
6)冷却第5)步得到的坩埚中的熔体，同时控制熔体的温度梯度和冷却速率，使熔体与晶种接触时结晶生长锗单晶棒；和
7)冷却锗单晶棒；
其中，第1)步中添加的掺杂剂元素硅和镓的量使得制得的锗单晶棒在有效长度内硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，且硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc。
在本发明的制备锗单晶棒的方法的一个优选实施方案中，锗单晶棒在有效长度内硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc。
在本发明的制备锗单晶棒的方法的一个更优选实施方案中，锗单晶棒在有效长度内硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
在本发明的制备锗单晶棒的方法的一个优选实施方案中，锗单晶棒在有效长度内硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
在本发明制备锗单晶棒的方法的一个优选实施方案中，晶棒头部硼原子浓度和镓原子浓度的比例为8-5:1，优选为7-4:1，更优选为5-3:1，晶棒尾部硼原子浓度和镓原子浓度比例为1:100-240，优选为1:130-210，更优选为1:160-180。
在本发明的制备锗单晶棒的方法的一个优选的实施方案中，硅原子浓度与镓原子浓度比例为4:1-100。
在本发明的制备锗单晶棒的方法的一个更优选的实施方案中，硅原子浓度与镓原子浓度比例为3:1-80。
在本发明的制备锗单晶棒的方法的一个特别优选的实施方案中， 硅原子浓度与镓原子浓度比例为2:1-50。
在本发明的制备锗单晶棒的方法的一个优选实施方案中，锗单晶棒为横向截面为圆形的晶棒，其圆形横截面的直径不超过10英寸。
在本发明的制备锗单晶棒的方法的一个优选实施方案中，在第6)步使熔体与晶种接触时结晶生长成锗单晶棒的过程中，在晶棒生长区建立0.3-4.0℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个更优选的实施方案中，晶棒生长区建立0.5-3.5℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个特别优选的实施方案中，晶棒生长区建立1.0-3.0℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个优选的实施方案中，在第6)步使熔体与晶种接触时结晶生长成锗单晶棒的过程中，在晶种端建立0.2-1.5℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个更优选的实施方案中，在晶种端建立0.2-1.0℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个特别优选的实施方案中，在晶种端建立0.2-0.5℃/cm的温度梯度。
在本发明的制备锗单晶棒的方法的一个优选的实施方案中，在第6)步中，炉温以0.2℃/h至0.6℃/h的速率冷却。
在本发明的制备锗单晶棒的方法的一个更优选的实施方案中，在第6)步中，炉温以0.3℃/h至0.5℃/h的速率冷却。
在本发明的制备锗单晶棒的方法的一个优选实施方案中，制得的锗单晶棒的头部晶片的平均位错密度为低于80cm 2，尾部晶片的平均位错密度低于75cm 2。
本发明还提供本发明的锗单晶片、由本发明的制备锗单晶片的方法制得的锗单晶片、以及由本发明的制备锗单晶棒的方法制得的锗单晶棒切割得到的锗单晶片用于增加多节太阳能电池开路电压的用途。
本发明通过锗单晶的镓、硼和硅共掺杂，制备电学性能均匀的锗单晶棒，这样既能增加锗(Ge)单晶片多节太阳能电池开路电压、同时制备的锗单晶片的载流子浓度和电学性能在整个锗单晶棒范围内分布更加均匀，从而可以获得性能更均匀的基于锗单晶片的多节太阳能电池。
本发明的获得的锗单晶片具有改进的电学性能，特别是具有更小的电阻率差和载流子浓度差。具体而言，本发明的锗单晶片的电阻率差不超过 2倍。
本发明的获得的锗单晶片还能够提高太阳能电池的开路电压，进而提高太阳能电池的光电转化效率和电力输出。
本发明通过控制、减少和消除光生载流子的复合位置增加太阳能电池器件开路电压Voc。
本发明通过在锗单晶棒也就是单晶衬底中加入一定量的痕量共掺杂剂元素增加多节太阳能电池的开路电压。开路电压增加的原因是在锗衬底上外延生长的多节太阳能电池的底电池界面上的反相畴界的减少和消除，从而减少了底电池界面上光生载流子的非辐射复合。
附图说明
图1是示出现有技术掺镓的锗单晶棒从头到尾电阻率(Res)分布，该图中的横坐标从左到右代表晶棒从头到尾的长度，纵坐标为对应为位置的电阻率；其中，头部电阻率1.5E-02Ohm.cm是尾部电阻率2.54E-03Ohm.cm的5.9倍。
图2示出现有技术掺硼的锗单晶棒从头到尾电阻率分布，该图中的横坐标从左到右代表晶棒从头到尾的长度，纵坐标为对应为位置的电阻率；其中，尾部电阻率2.98E-02Ohm.cm是头部电阻率6.3E-03Ohm.cm的4.7倍。
图3示出本发明的掺硅、硼和镓的晶棒头部的电阻率为3.34E-2Ohm.cm，晶棒尾部的电阻率为3.07E-2Ohm.cm；该图中的横坐标从左到右代表晶棒从头到尾的长度，纵坐标为对应为位置的电阻率；其中，晶棒中最大电阻率为4.94E-2Ohm.cm，最大电阻率的值是最小电阻率的值的1.6倍。
图4示出本发明的掺硅、硼和镓的晶棒头部的电阻率为5.84E-3Ohm.cm，晶棒尾部的电阻率为3.87E-3Ohm.cm；该图中的横坐标从左到右代表晶棒从头到尾的长度，纵坐标为对应为位置的电阻率；其中，晶棒中最大电阻率为7.40E-3Ohm.cm，最大电阻率的值是最小电阻率的值的1.9倍。
图5在锗(100)单晶衬底上外延生长III-V族形成的反相畴示意图。
图6是用于锗单晶生长的密封容器的主视图。
图7是包含密封容器的晶体生长设备的截面图。
图8是从锗原料开始通过使用图6中所示的密封容器和单晶生长设备 进行锗单晶棒生长的全过程流程图。
图9是锗衬底三节太阳能电池示意图。
图10为本发明晶片制备方法的晶棒固定装置半包围石墨的示意图。
图11为本发明晶片制备方法的晶片倒角的示意图，其中图11-1a倒角为圆弧状，图11-1b倒角为坡形。
图12为用于实施本发明的晶片制备方法的研磨、抛光步骤的设备的一个实例。
具体实施方式
在本发明中，如无其他说明，所有操作均在室温、常压进行。
在本发明中，晶片的直径应作如下理解：在晶片为圆形时，是指圆形的直径；在晶片为其他形状(如不规则圆形、正方形、长方形等)时，是指以晶片的中心为圆心画圆、使圆包括晶片所有部分所形成的圆的直径。
在本发明中，术语“有效长度”意指晶棒可以用于切割为晶片的实际长度。
在本发明中，共掺杂剂元素意指除元素锗以外的元素，特别是元素硅(Si)、硼(B)和镓(Ga)。
在本发明中，电阻率采用GB/T 26074-2010《锗单晶电阻率直流四探针测量方法》所述方法进行。
晶片
本发明提供一种锗单晶片，其中，锗单晶片中包含掺杂剂元素硅、硼和镓，硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc。
在本发明的锗单晶片中，硅原子浓度优选为4×10 14atoms/cc至8×10 18atoms/cc，更优选为5×10 14atoms/cc至7×10 18atoms/cc；硼原子浓度优选为2×10 16atoms/cc至8×10 18atoms/cc，更优选为4×10 16atoms/cc至7×10 18atoms/cc；且镓原子浓度优选为2×10 16atoms/cc至9×10 19atoms/cc，更优选为2×10 16atoms/cc至8×10 19atoms/cc。
在本发明中，单位“atoms/cc”意为“原子/立方厘米”。
或者，在本发明的锗单晶片中，硅原子浓度为基于锗的量计的0.5-25ppm，硼原子浓度为基于锗的量计的0.1-200ppm，且镓原子浓度为基于 锗的量计的1-100ppm。
或者，在本发明的锗单晶片中，硅原子浓度优选为基于锗的量计的2-20ppm，更优选为基于锗的量计的3-15ppm；硼原子浓度为基于锗的量计的5-180ppm，更优选为基于锗的量计的10-160ppm；且镓原子浓度优选为基于锗的量计的10-80ppm，更优选为基于锗的量计的20-60ppm。
在本发明的锗单晶片中，硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
本发明通过镓原子和硼原子的共掺杂，利用镓原子和硼原子在锗材料中分凝系数的差异，获得锗单晶片间以及锗单晶棒内均匀的载流子浓度和电阻率的分布。这是因为，作为和镓同一族的硼原子也可以作为锗单晶的P型掺杂剂，且硼原子在锗单晶中的分凝系数为18，在锗单晶生长过程中，硼原子在固相中富集，剩余液相中的硼原子浓度越来越少，电阻率越来越大。
在本发明的锗单晶片中，硼原子浓度和镓原子浓度的比例为8:1至1:240，优选为5:1至1:170，更优选为3:1至1:100。
在本发明的锗单晶片中，硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
本发明的锗单晶片的厚度为100-700μm，优选100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
本发明锗单晶片由锗单晶棒切割制成，锗单晶棒为横向截面为圆形的晶棒(简称圆形晶棒)，其长度方向的截面为长方形或正方形，其圆形横截面的直径通常不超过10英寸，优选为1-8英寸，优选为2-6英寸，甚至更优选为2-4英寸。当然，锗单晶棒也可以是横向截面为其他形状的晶棒，例如由圆形晶棒经过处理而得的横向截面为方形(正方形或长方形)的锗单晶棒，此时，所切割出的晶片为非圆形的锗单晶片。
本发明的锗单晶片优选通过下文所述的晶棒的制备方法制得的晶棒切割而成。
元素硅和锗基体是无限互溶的，令人惊奇地，本发明发现，通过在锗原料中添加硅和镓的基础上进一步添加硼所产生的共掺杂效应可以显著改进锗单晶的电学特性。具体而言，本发明的共掺杂的锗单晶片间的电阻率差更小，并且，用于制备多级太阳能电池时，能够显著增加太阳能电池的开路电压。
制备晶片的方法
本发明还提供一种制备锗单晶片的方法，所述方法包括：
1)由包含元素硅和镓的锗单晶棒切割出锗单晶初始晶片，其中，切割得到的锗单晶片初始晶片中硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc，初始晶片的厚度为200-800μm；
2)对步骤1)得到的锗单晶初始晶片进行磨边处理；
3)对步骤2)中进行磨边处理之后的锗单晶初始晶片进行表面处理，和
4)对在步骤3)中表面处理之后的锗单晶初始晶片进行粗抛光，然后进行精抛光，得到锗单晶片产品，其中，所得到的锗单晶片产品厚度为100-700μm。
上述针对锗单晶片的优选、更优选等的相关技术方案同样适用本发明的制备锗单晶片的方法，在此不再赘述。
本发明制备锗单晶片的方法中所用锗单晶棒优选通过下文所述的晶棒的制备方法制得。
在本发明制备锗单晶片的方法中，步骤1)的切割采用切割机进行。切割机通常使用本领域已知的外圆切割机、内圆切割机或多线切割机进行。由于多线切割机具有好的生产效率和出片率，因此优选多线切割机。本发明可用的多线切割机例如购自日本小松NTC的多线切割机MWM442DM。
在使用切割机切割晶棒时，使用本领域已知的切割机用泥浆和钢线进行切割。所述泥浆可由粉末状物质和切割油配置而成。所述粉末状物质为本领域已知且市售可得，可以是例如钻石粉、碳化硼和碳化硅。一般而言，可选择粉末状物质粒径，原则上可以使用粒径为5-15微米的用于配置半导体晶棒切割用泥浆的粉末状物质。所述粉末状物质的粒径优选为6-13微米，更优选为8-12微米。所述切割油同样是本领域已知的且市售可得，可以是植物油(例如橄榄油和大豆油)、矿物油。在本发明中，粉末状物质优选为碳化硅，切割油优选为矿物油。
在本发明制备锗单晶片的方法中，粒径可通过市售已知的粒度仪测定，例如使用Malvern的
Figure PCTCN2020090402-appb-000001
激光衍射粒度分析仪测定。
在本发明中，为了降低锗单晶棒晃动，提高表面质量，可将锗单晶棒固定。固定方式并无特别限制，只要能够在切割过程中有效防止锗单晶棒晃动即可。优选采用半包围结构的固定装置固定锗单晶棒，以在后续步骤中方便地使其与晶片分离。制备半包围结构固定装置的材料并无特别限制，只要能够在切割过程中不至于发生形变或对切割的晶片产生不利影响的材料均可使用，例如可使用石墨。本发明优选的半包围结构固定装置为半包围石墨(如图10所示)。
在本发明制备锗单晶片的方法中，对锗单晶初始晶片进行磨边处理，即对锗单晶初始晶片进行边缘倒角处理(如图11-1a和图11-1b所示)，这为了使晶片边缘获得合适的圆弧(图11-1a)或坡度(图11-1b，其中α优选为45±10°)。图11-1a和11-1b为晶片倒角前后的横截面图示。优选地，使得锗单晶片边缘的横截面具有圆弧状的边缘(图11-1a)，由此可以减少或避免后续步骤中锗单晶片破损的风险。所述倒角处理通常使用倒角机进行，任何现有技术的倒角机均可用于该步骤。在用倒角机倒角时，优选将倒角机的进刀量设置在0.4毫米以内，优选设置在0.3毫米以内。
在本发明制备锗单晶片的方法中，对磨边后的锗单晶初始晶片进行表面处理，表面处理可以使用研磨机研磨经磨边的锗单晶初始晶片。如果需要研磨经磨边的锗单晶初始晶片的两面，则可以在一面研磨后再研磨另一面。研磨加工是为了消除切片工序中锗单晶初始晶片表面的锯纹损伤，获得足够的晶片平整度，为后续的抛光工序作准备。所述研磨可以本领域已知的任何方法进行，例如可在一种已知的研磨设备(例如类似图12的设备)中进行，锗单晶初始晶片置于一个支承垫中，上下两侧垫有研磨垫(通常为聚酯类研磨垫)，研磨过程使用研磨液(可用已知的研磨液)。例如，在采用上下盘式的研磨设备(上下盘反向旋转)时，研磨过程中，晶片所受压力为0.03-0.18千克/平方厘米，优选0.05-0.15千克/平方厘米。上盘转速2-12转/分钟，优选3-10转/分钟；下盘转速5-20转/分钟，优选8-15转/分钟。研磨液量为60-120ml/m 2研磨盘面积/分钟(按设备盘单面计)。研磨时间为20-50分钟，优选25-40分钟。
此外，在本发明制备锗单晶片的方法中，表面处理还可以通过化学法进行。此情况下，例如，可以将锗单晶初始晶片浸泡在刻蚀液中，或者使用刻蚀液冲洗锗单晶初始晶片。所述刻蚀液可以为本领域用于 对锗单晶初始晶片进行表面处理的常规刻蚀液。
当然，根据需要，可以结合使用研磨机和化学表面处理法，例如先使用研磨机处理，然后进行化学表面处理。
在本发明制备锗单晶片的方法中，优选仅使用刻蚀液对经切割的锗单晶初始晶片进行化学表面处理。所述化学表面处理的条件为：温度在室温以上、优选在30℃以上、更优选在35℃以上；处理时间为5-20秒，优选8-18秒，更优选为10-15秒。优选地，刻蚀液为包含NH 3和过氧化氢的水溶液。在刻蚀液中，NH 3为0.1-5摩尔％；过氧化氢为5-15摩尔％；余量为水。在上述条件下表面处理后的晶片表面无药印。
在本发明制备锗单晶片的方法中，还包括对经表面处理的锗单晶片进行粗抛光，然后进行精抛光。
对于粗抛光，也即机械化学抛光，使用的粗抛光溶液，除水以外，还包括二氯代异氰尿酸盐、磺酸盐、焦磷酸盐、碳酸氢盐和硅溶胶。在本发明的一种优选实施方案中，粗抛光溶液中除水以外的成分按它们的重量百分比计(基于除水之外的成分的总量计)，包括二氯代异氰尿酸盐8.0-22.0％、磺酸盐0.01-0.30％、焦磷酸盐4.5-19.0％、碳酸氢盐3.0-13.0％和硅溶胶55.0-72.0％，各组分含量总和为100％。上述各组分溶于水后的总重量百分比以不对晶片产生不利影响为限，可以为任何浓度，但是优选不高于6.0％。
对于粗抛光，在采用上下盘式的抛光设备(上下盘反向旋转)时，抛光过程中，晶片所受压力为0.04-0.15千克/平方厘米，优选0.05-0.12千克/平方厘米。上盘转速10-45转/分钟，优选12-35转/分钟；下盘转速5-40转/分钟，优选8-30转/分钟。抛光液流量为60-120升/cm 2晶片面积/小时。抛光时间为20-70分钟，优选25-60分钟。
对于精抛光，也即化学机械抛光，使用的精抛光溶液，除水以外，包括二氯代异氰尿酸盐、磺酸盐、酸式焦磷酸盐、碳酸氢盐和碳酸盐。在本发明的一个优选实施方案中，除水之外，按重量百分比计(基于除水之外的成分的总量计)，精抛光溶液包括二氯代异氰尿酸盐29.00-40.00％、磺酸盐0.20-0.45％、酸式焦磷酸盐18.00-35.00％、碳酸氢盐17.00-24.00％和碳酸盐15.00～23.00％，各组分含量总和为100％。上述各组分溶于水后的总重量百分比以不对晶片产生不利影响为限，可以为任何浓度，但是优选不高于3.0％。
对于精抛光，在采用上下盘式的抛光设备(上下盘反向旋转)时， 抛光过程中，晶片所受压力为0.05-0.15千克/平方厘米，优选0.06-0.12千克/平方厘米。上盘转速20-60转/分钟，优选25-50转/分钟；下盘转速10-35转/分钟，优选12-25转/分钟。抛光液流量为0.5-1.0ml/cm 2晶片面积/分钟。抛光时间为3-20分钟，优选5-15分钟。
在本发明的各抛光溶液中，二氯代异氰尿酸盐、(酸式)焦磷酸盐、碳酸氢盐和碳酸盐可以使用它们各自的水溶性盐类之一。优选的是，二氯代异氰尿酸盐、(酸式)焦磷酸盐、碳酸氢盐和碳酸盐为各自的水溶性的碱金属盐之一或为铵盐，特别优选为各自的钠盐或铵盐。
对于硅溶胶，可以使用常规的硅溶胶，例如市售的硅溶胶，或者是使用现有技术方法制备的硅溶胶。
对于磺酸盐，可以使用水溶性磺酸盐，优选水溶性碱金属盐之一或为铵盐，特别优选为钠盐或铵盐。优选的是，磺酸盐为例如C 6-16芳基(即含6-16个碳原子的芳基，包括取代的芳基)的单磺酸盐或二磺酸盐(例如C 4-10烷基-苯磺酸盐、苯磺酸盐、萘磺酸盐、蒽磺酸盐、C 4-10烷基-苯基二磺酸二盐、苯基二磺酸二盐、萘基二磺酸二盐或蒽基二磺酸二盐，例如1,2-苯二磺酸二盐、1,3-苯二磺酸二盐、苯磺酸盐或萘磺酸盐)、烷基磺酸盐(优选为4-10个碳原子烷基的磺酸盐，例如丁烷基磺酸盐、戊烷基磺酸盐、己烷基磺酸盐、庚烷基磺酸盐、辛烷基磺酸盐、壬烷基磺酸盐和癸烷基磺酸盐等)和酚磺酸盐之一，进一步优选1,3-苯二磺酸盐、苯磺酸盐、萘磺酸盐或己烷基磺酸盐。
由于粗抛光和精抛光本身可以采用现有技术的方法进行，因此不作进一步赘述。在本发明中，优选进行单面抛光。
经过粗抛光和精抛光，锗单晶片的表面微粗糙度不高于0.5纳米，平整度为3-7微米，优选3-5微米。
经过粗抛光和精抛光，锗单晶片的表面粗糙度和晶片平整度能够满足本领域的使用需求。
任选地，本发明制备锗单晶片的方法还包括：对精抛后的锗单晶片进行表面清洗处理。
优选进行湿法表面清洗处理。对清洗处理的过程无特别限制，只要其能使晶片表面达到所需的清洁程度即可。就湿法清洗处理而言，可根据所制备的锗单晶片，套用现有技术的方法。
优选地，表面湿法清洗处理在不低于1000级的洁净室中进行。所述洁净室等级的定义参考美国联邦标准209D洁净室规格(见下表1)。 在此，通常只考察微尘粒子数，例如，千级洁净室一般指，每立方英尺中，≥0.5微米的颗粒数≤1000颗；≥5.0微米的颗粒数≤10颗。优选地，经过步骤4)的表面清洗处理，在光照下目测，晶片表面无颗粒、无白雾。并且晶片表面金属Zn和Cu残余量分别≤10×10 10原子/cm 2。这样，本发明方法的锗单晶片不需要再进行任何外延前的处理，可达到开盒即用的水平。由于清洗可以采用现有技术的方法，在此不作进一步赘述。
表1美国联邦标准209D洁净室规格
Figure PCTCN2020090402-appb-000002
制备晶棒的方法
本发明还提供一种制备锗单晶棒的方法，所述方法包括：
1)将第一锗原料、掺杂剂元素硅和镓以及任选的液封剂一并装入坩埚中，所述坩埚带有晶种槽，晶种槽事先装有高纯锗单晶晶种；
2)将第二锗原料装入装载容器中(如图6、图7和图8所示)第二锗原料用于补充第一锗原料，所述装载容器中任选地装有液封剂；
3)将第1)步所述坩埚和第2)步所述装载容器置于石英管内，并在真空下密封石英管；
4)将第3)步的密封有坩埚和装载容器的石英管放入具有可移动的石英管支座的晶体生长熔炉中，所述支座用于支承石英管；
5)使第一锗原料和第二锗原料熔融，分别形成第一熔体和第二 熔体，然后使得装载容器中的熔融的第二锗原料完全注入坩埚；
6)冷却第5)步得到的坩埚中的熔体，同时控制熔体的温度梯度和冷却速率，使熔体与晶种接触时结晶生长锗单晶棒；
7)冷却锗单晶棒；
其中，第1)步中添加的掺杂剂元素硅和镓的量使得制得的锗单晶棒在有效长度内硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc，初始晶片的厚度为200-800μm。
在本发明的锗单晶片中，硅原子浓度优选为4×10 14atoms/cc至8×10 18atoms/cc，更优选为5×10 14atoms/cc至7×10 18atoms/cc；硼原子浓度优选为2×10 16atoms/cc至8×10 18atoms/cc，更优选为4×10 16atoms/cc至7×10 18atoms/cc；且镓原子浓度优选为2×10 16atoms/cc至9×10 19atoms/cc，更优选为2×10 16atoms/cc至8×10 19atoms/cc。
或者，在本发明的锗单晶片中，硅原子浓度为基于锗的量计的0.5-25ppm，硼原子浓度为基于锗的量计的0.1-200ppm，且镓原子浓度为基于锗的量计的1-100ppm。
或者，在本发明的锗单晶片中，硅原子浓度优选为基于锗的量计的2-20ppm，更优选为基于锗的量计的3-15ppm；硼原子浓度为基于锗的量计的5-180ppm，更优选为基于锗的量计的10-160ppm；且镓原子浓度优选为基于锗的量计的10-80ppm，更优选为基于锗的量计的20-60ppm。
在本发明的制备锗单晶棒的方法中，锗单晶棒在有效长度内，晶棒头部硼原子浓度和镓原子浓度的比例为8-5:1，优选为7-4:1，更优选为5-3:1，晶棒尾部硼原子浓度和镓原子浓度比例为1:100-240，优选为1:130-210，更优选为1:160-180。
在本发明的制备锗单晶棒的方法中，锗单晶棒在有效长度内硅原子浓度为与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
在本发明的制备锗单晶棒的方法中，锗单晶棒在有效长度内硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
本发明的制备晶棒的方法所用锗原料为高纯锗原料。在本发明中，“高纯锗”意指，电阻率可达4000Ω·m，纯度为99.999％以上的锗。掺杂剂含量超低的高纯锗原料确保了锗晶片期望的特性和性能的重复 可控性，从而确保了锗衬底制备太阳能电池器件的稳定性。高纯锗原料为市售可得的，市售的高纯锗原料通常呈块状或粉末状。本发明优选使用块状高纯锗原料，例如购自中诺新材(北京)科技有限公司的块状高纯锗。
锗单晶棒生长的容器可以用合适的坩埚材料制备，例如热解氮化硼(PBN)坩埚，这种坩埚稳定性相对较好，不会污染锗原料，也不会在锗熔点(938℃)以上100℃的条件下与锗熔体发生反应。单晶生长的容器或坩埚包括可以呈圆柱形的主体部分，圆柱形主体的直径略大于所要制备锗单晶棒的直径(条件是可以完全容纳锗单晶棒且锗单晶棒不接触圆柱形主体的器壁)，底部是小直径晶种槽，底部晶种槽和圆柱形主体之间有一个圆锥形过渡区(如图6所示)。晶种槽用于放置高纯锗单晶制备的圆柱形晶种。
晶种的上端面的晶向就是期望获得的锗单晶衬底的表面晶向例如(100)或相对于(100)晶向偏转到相邻晶向轴一定角度的表面晶向。将合适形状的锗多晶料块装入晶种腔上面的生长坩埚中。
如果需要，将合适的液封剂例如三氧化二硼和锗原料一起放入位于下部的坩埚中(也称“生长坩埚”，如图6与图7所示)。液封剂可以起到把坩埚内壁和锗熔体或单晶生长过程中的固体锗晶棒表面隔离开的作用，减少所生长的锗晶棒表面和坩埚内壁的粘连，更容易获得完整的锗单晶棒。液封剂的用量为本领域常规用量。
由于生长坩埚中的锗原料熔化后不能充满整个坩埚，所以在生长坩埚的上方再放置一个容纳有相同锗原料装载容器，装载容器底部设有孔，其中的锗原料熔化后滴入生长坩埚中，使得生长坩埚中充满熔融的锗原料，如图6所示。装载容器可以是坩埚，此情况下，装载容器又称补料坩埚。
在本发明中，锗单晶棒由垂直梯度冷凝法熔体生长技术生长。实施本发明的锗单晶棒制备方法所用的锗单晶生产装置描述于美国专利US 8,506,706B2中，所述文献的说明书全文在此以参引的方式纳入本说明书。
以下结合附图示例性阐释本发明。
图7示出锗晶体生长装置的一个实例的横切面视图。该装置为垂直梯度冷凝生长法通常使用的熔炉，可包括一个位于熔炉1中的石英管支座11，其中加热器2由多个区组成，每一区由受控制系统控制的 一台计算机单独控制。调节每一区的温度，以提供控制熔体固化所需的温度分布和温度梯度，调整炉中温度分布和温度梯度，使结晶界面按预期向上移动惯穿熔熔体，例如在晶棒生长区建立0.3-4.0℃/cm、优选0.5-3.5℃/cm且更优选1.0-3.0℃/cm的温度梯度，且在晶种端建立更低的0.2-1.5℃/cm、优选0.2-1.0且更优选0.2-0.5℃/cm的温度梯度。石英管支座11提供对含有坩埚12(生长坩埚)的石英管3的物理支持并对其进行热梯度控制，石英管中的坩埚12有一个晶种槽18用于存放晶种。在熔炉运行时，所述石英管支座11可在晶体生长过程中轴向上下移动。坩埚12可含有一个晶种17，晶体沿晶种顶部生长出单晶。在一个实施方案中，坩埚12可为一个热解氮化硼结构体，具有一个圆筒状晶体生长部分13、一个较小直径的晶种槽圆筒18和一个锥形过渡部分7。晶体生长部分13在坩埚12的顶部是开放的，其直径等于所需晶体产物的直径。在一个示例性实施方案中，在坩埚12的底部的晶种槽圆筒18可具有封闭的底部和稍大于优质晶种17的直径，例如约6-25mm，以及约30-100mm的长度。圆筒状晶体生长部分13和晶种槽圆筒18可具有直壁，或锥形向外逐渐扩张约1-30度，以利于移出坩埚12中的晶体。生长部分13和晶种槽圆筒18之间的锥形过渡部分7具有一个倾斜例如约45-60度的带倾角的侧壁，其较大的直径等于生长区的直径并连接生长区的壁，较小的直径等于晶种槽的直径并连接晶种槽的壁。该带倾角的侧壁也可以为比45-60度更陡或陡度更小的其他角度。
石英管3具有一个类似于坩埚12的形状。石英管3在晶种生长区域19为圆筒状——在石英管3的晶种槽区域19中圆筒具有狭小直径，并且在所述两区域之间具有一个锥形过渡区域8。坩埚12适配于石英管3的内部并且在它们之间具有一个狭窄空隙。作为装载容器(补料坩埚)，位于顶部的装载容器4置于石英基座6上。石英基座6封装在石英管3的中间部分。在本发明的一个实施方案中，补料坩埚4由PBN制成。大部分锗原料5(例如基于生长坩埚和补料坩埚中锗原料计的60-80重量％，优选60-70重量％)装入补料坩埚4中。在加热过程中，锗原料熔化并从补料坩埚4的底部孔滴入坩埚12中。石英管3在其晶种槽区域19的底部是封闭的，并在装入坩埚和原料之后在顶部密封。
由于石英管-坩埚组合体具有漏斗形状，需要石英管支座11来适 应该漏斗形状并保持石英管12稳定并直立于熔炉内部。在其他实施方案中，石英管-坩埚组合体可保持不同形状，并且石英管支座11的基本结构将根据不同形状而改变。依据一个实施方案，对石英管及其内容物的稳定和支持强度通过石英管支座11的强力的薄壁圆筒16提供。所述强力的薄壁圆筒16容纳石英管结构3的漏斗状底部。在一个实施方案中，坩埚支座圆筒16由导热材料、优选石英构成。在其他实施方案中，碳化硅或陶瓷也可用于形成坩埚支座圆筒16。所述圆筒16与石英管3圆周接触，其中圆筒16的上部边缘接触石英管的锥形区域8的肩状部分。所述构型导致固体对固体的接触最小化，这样可确保很少的甚至没有不希望的、相对不可控的热传导发生。因此，可用其他更可控的方法加热。
支座圆筒11内部的大部分填充有低密度绝缘材料(例如陶瓷纤维)，仅在所述绝缘材料的约中心处有一个中空的轴心20保持空的状态(未填充任何绝缘材料)，用以容纳石英管3的晶种槽19。
低密度绝缘材料还可包括氧化铝纤维(熔点为1,800℃)、氧化铝-氧化硅纤维(熔点为1,426℃)和/或氧化锆纤维(熔点为2,200℃)。将绝缘材料小心地放在石英管支座11中。石英管3的重量——当其置于圆筒16的顶部时——推动绝缘材料向下并形成倾斜的绝缘材料边缘9。用低密度绝缘体填充圆筒内的大部分能减少空气流动，这可确保很少的或没有不需要的、相对不可控的对流的发生。同传导类似，对流是一种对VGF及其他晶体生长方法不利的不可控的热传递过程。
直径约等于石英管晶种槽19的空芯20，向下伸至石英管晶种槽19底部以下一小段距离。在另一个实施方案中，空芯20从晶种槽的底部穿过坩埚支座延伸至熔炉装置1的底部。空芯20提供一种自晶体中心冷却的途径。该途径有助于晶种槽和所生长晶体中心的冷却。采用该构造，热能可向下逃逸穿过固态晶体和晶种的中心、向下穿过晶体支座11中绝缘材料中的空芯20。没有空芯20的话，所冷却晶棒中心的温度将理所当然地高于接近外表面的晶体材料。在此情况下，晶棒任一水平横切面中的中心将在该晶棒周边已固化后才更迟地结晶。在这样的条件下不可能制备具有均一电性能的晶体。通过在晶体支持方法中包括空芯20，热能向下传导穿过石英管3和空芯20的底部，并由此幅射回并穿出幅射通道10。降低生长晶体中心处的热能很重要，这样才能保持等温层在整个晶体直径方向上的平直。保持平直的晶体-熔 熔体界面能产生具有均一电性能和物理性能的晶体。
圆筒11内的低密度绝缘材料阻碍热辐射从一组熔炉加热元件2流动至石英管3中晶种槽区域19，所以该方法需要形成多个贯穿绝缘材料的水平辐射通道/开口/管道10。辐射通道10贯穿绝缘材料从而提供热辐射出口，以可控地将热量从熔炉加热元件2转移至石英管晶种槽19。辐射通道10的数目、形状和直径根据具体情况而变。辐射通道也可以是倾斜的、弯曲的或波状的。辐射通道也不必是连续的，因为它们可以只部分地穿过绝缘材料。这有助于对流最小化。在一个实施方案中，这些通道的直径较小，约一支铅笔的宽度，所以对流气流不显著。根据本发明的其他实施方案，也可使用横切面面积约6.4516cm 2(1平方英寸)或更大的大孔。穿过绝缘材料的辐射通道10也可和绝缘材料中心的空芯20结合起作用，从而辐射来自晶体中心的热能，并冷却具有二维等温温度梯度层的晶体。辐射通道10能控制温度并直接与晶体生长的产率有关。
在本发明的一个示例性实施方案中，在单晶锗晶棒生长阶段，炉温以约0.2℃/h至约0.6℃/h的速率冷却使单晶锗晶棒得以生长。
图7说明一个示例性的熔化并供给锗的方法。从说明初始状态，其中固态锗存在于装载容器4和坩埚12中。作为新的加热技术特征和方法上的进步，出现锗熔熔体的中间状态，固态锗在坩埚12中已熔化为液态的一种状态，
调整炉子不同加热区加热元件的功率，使位于上部的装载容器得到所需的热量。具体而言，通过对上部的装载容器实施加热：装载容器内的锗料开始熔化，熔化的料沿装载容器3最底端的孔流入坩埚12。在一个示例性实施方案中，在炉内有装载容器的区域温度被加热至940℃到955℃摄氏度范围内，该过程持续进行，直至装载容器内的原料全部注入坩埚12。
图7中所示熔炉1为可用于垂直梯度冷凝(VGF)晶体生长方法的熔炉的一个实例。也可使用其他熔炉和构型，例如垂直布里奇曼方法。在VGF晶体生长方法中，固定热源的结晶温度梯度经电控制方式而移动，而晶体固定。
为实施垂直梯度冷凝生长，需在炉内建立所需的温度梯度分布，而熔炉的加热区功率大小则通过计算机进行分别并单独地控制，该计算机被编程为加热和降温以适合熔炉结晶温度和温度梯度需要。对于 生产锗晶棒，例如，熔炉的温度波动可能需要控制在＜±0.1℃。熔炉准备过程中，将锗多晶原料按所述装载入石英管3中。
如图中所示，将在锥形部分具有一个孔的PBN装载容器4固定在石英管3中，置于由石英制成的、位于坩埚12之上的支座6上。装载容器4使坩埚12将装载更多原料。特别是，锗原料5为固态的块或片，因此不能紧密地填充入坩埚12中进行熔化。因此，所述装载容器用于存放额外的可进行熔化的原料，然后将其向下排至坩埚12中，这使坩埚12中更多的锗装料，从而获得较长的锗晶体。例如，初始时可将约65％的原料装入装载容器4中，将35％的原料直接装入生长坩埚12中。
在一个实施例中，使用硅和镓作为掺杂物。将(100)取向的晶种装入坩埚种槽内，然后再装料。将原料和合适量的掺杂剂装入坩埚中，并将坩埚和装载容器放在石英管3中。将装有坩埚和装载容器的石英管接入抽真空系统，当石英管内真空度达到约2.00×10 -4帕斯卡(1.5×10 -6托)时，将石英管密封。将密封的石英管随即装入熔炉，如图7中所示。开启加热炉，使石英管及其内含物受热，加热速率可为5-40℃/min，优选为10-30℃/min，更优选为15-20℃/min，加热温度为1000±50℃(锗的熔点约为940℃)。结晶界面的温度梯度可根据晶棒的不同位置调为0.2-10℃/cm。调节整个温度分布至使给出1-2mm/h的结晶速率。固化完成之后，将熔炉以20-40℃/h进行冷却。
应用上述示例性生长工艺参数生长的锗单晶棒在整个长度方向上的缺陷密度都很低，并且缺陷分布均匀。从生长的晶体上切取头尾的晶片腐蚀位错密度。头尾晶片的位错密度都很均匀，头部晶片的平均位错密度为可低于80cm 2，或为78/cm 2，或为75/cm 2，或为70/cm 2，或65/cm 2，尾部晶片的平均位错密度可低于75cm 2，或为70/cm 2，或65/cm 2，或为66/cm 2，或在此处所测量或给出的量的10％、20％或30％的其他此类数值窗(numerical number)内。因此采用本发明的工艺，缺陷密度降低了大约15-20％。缺陷密度降低的原因是因为晶体生长过程中添加的共掺掺杂剂元素带来的固溶强化效应。
在本发明中，位错密度采用GB/T5252-2006《锗单晶位错腐蚀坑密度测量方法》所述方法测定。
在另一个实施例中，本发明的装置由其中可嵌入PBN装载容器和坩埚的石英管和用以存放PBN装载容器的支座6构成。所述坩埚的尺寸为： 生长晶体段的直径为约150mm，生长晶体段的长度为160mm，并且籽晶段的直径为7mm。在一个示例性实施方案中，将(100)取向的锗晶种嵌入PBN坩埚的籽晶井中，并将作为液体密封剂的三氧化二硼加入晶种上方的PBN坩埚中。然后，将锗多晶材料分别放入PBN生长坩埚和PBN补料坩埚中，将PBN生长坩埚和PBN补料坩埚均嵌入石英管中，并将该石英管在约2.00×10 -4帕斯卡(1.5×10 -6托)的减压条件下用石英盖密封。然后将密封的石英管装入熔炉中并放置在石英管支座上。
以约270℃/小时的速率加热上述石英安瓿。当温度高于结晶材料的熔点约30℃时，保持加热直至所有多晶材料熔化。
本发明在单晶生长过程中需要满足如下要素：
a)选取适量的掺杂剂元素例如硅、硼与镓放入锗单晶生长的原料中，形成共掺杂；
b)在装入锗原料过程中放入掺杂剂元素，然后进行单晶生长；
c)在单晶生长过程中，所用的生长程序需要维持合适的单晶生长速率和温度梯度，避免因为掺杂剂元素的共掺杂造成生长过程中形成多晶。
这些和标准的锗单晶生长工艺相比增加的要素内容都是必须的，以便在单晶生长过程中保持合适的固液界面形状，避免新的晶粒或多晶形核生长，从而生长出完好的锗单晶棒，制备出多节太阳能电池用开路电压增强型锗单晶衬底。多晶的生长可能在晶种附近出现，或在从晶种至等径的锥形转换区出现，也有可能在等径生长过程中出现。多晶的出现将会导致整条单晶棒或部分单晶棒不能用来制备用于多节太阳能电池的锗单晶衬底。
通过本发明制备晶棒的方法制备的晶棒，硅、硼和镓原子浓度在晶棒的轴向上呈变化的，在晶棒的有效长度上，硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，且硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc。硅原子浓度优选为4×10 14atoms/cc至8×10 18atoms/cc，更优选为5×10 14atoms/cc至7×10 18atoms/cc。硼原子浓度优选为2×10 16atoms/cc至8×10 18atoms/cc，更优选为4×10 16atoms/cc至7×10 18atoms/cc。镓原子浓度优选为2×10 16atoms/cc至9×10 19atoms/cc，更优选为2×10 16atoms/cc至8×10 19atoms/cc。
设计的生长程序能够从晶种端直至单晶生长结束(或全部的熔体凝固生长成固态单晶)都能够获得合适生长速率和在固液界面附近获得合适的 温度梯度。相对于不含有掺杂剂的单晶棒的生长而言，含有掺杂剂的锗单晶棒的生长过程要求单晶的生长速率更低，固液界面移动的速率降比正常没有添加掺杂剂元素的锗单晶棒生长要低20％，同时不同温度分区温度下降的速率也降低20％左右。
在这个生长程序和放入适量的掺杂剂元素条件下，在整个晶棒长度范围内都保持了单晶生长。例如，可以生长出直径为4英寸的约200毫米长的锗单晶棒。
当坩埚中所有装入的原料都凝固后，生长的晶棒在控温条件下冷却至室温，在所述的实施例中冷却速率在～20-40℃/h。
锗原料中添加硅和镓所产生的共掺杂效应对锗单晶电学特性的改进，除了上文提及的使锗单晶的电阻率更低，同时，还使锗晶棒从晶种端到尾端沿整个锗晶棒的电阻率分布更加均匀。锗晶棒最大电阻率的值是最小电阻率的值的1.0-3.0倍，优选为1.2-2.5倍，更优选为1.5-2.0倍。
为更好地理解本发明，下文将结合实施例详细描述本发明，但应认识到这些实施例仅为对本发明进行示例说明，而非意在限制本发明。
用途
本发明还涉及本发明的锗单晶片用于增加多节太阳能电池开路电压的用途。
在本发明用途的一个优选实施方案中，使用本发明的锗单晶片的多节太阳能电池的开路电压增加0.4-3.5％(相当于增加10-95mV)，优选增加1.2-3.0％(相当于增加31-81mV)，更优选增加1.5-2.5％(相当于增加40-67mV)。
本发明通过控制、减少和消除光生载流子的复合位置增加太阳能电池器件开路电压。
本发明涉及如下方案：
1.一种锗单晶片，其中，锗单晶片中包含掺杂剂元素硅、硼和镓，硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc；
优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
2.根据实施方案1所述的锗单晶片，其中，锗单晶片的硼原子浓度和镓原子浓度的比例为8:1至1:240，优选为5:1至1:170，更优选为3:1至1:100。
3.根据实施方案1-2任一项所述的锗单晶片，其中，锗单晶片的硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
4.根据实施方案1-3任一项所述的锗单晶片，其中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
5.根据实施方案1-4任一项所述的锗单晶片，其中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
6.本发明还提供一种制备锗单晶片的方法，所述方法包括：
1)由包含元素硅、硼和镓的锗单晶棒切割出锗单晶初始晶片，其中，切割得到的锗单晶片初始晶片中硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc，初始晶片的厚度为200-800μm，
优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc；
2)对步骤1)得到的锗单晶初始晶片进行磨边处理；
3)对步骤2)中进行磨边处理之后的锗单晶初始晶片进行表面处理，和
4)对在步骤3)中表面处理之后的锗单晶初始晶片进行粗抛光，然后进行精抛光，得到锗单晶片产品，其中，所得到的锗单晶片产品厚度为100-700μm。
7.根据实施方案6所述的制备锗单晶片的方法，其中，锗单晶片的 硼原子浓度和镓原子浓度的比例为8:1至1:240，优选为5:1至1:170，更优选为3:1至1:100。
8.根据实施方案6-7任一项所述的制备锗单晶片的方法，其中，硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
9.根据实施方案6-8任一项所述的制备锗单晶片的方法，其中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
10.根据实施方案6-9任一项所述的制备锗单晶片的方法，其中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
11.一种制备锗单晶棒的方法，所述方法包括：
1)将第一锗原料、掺杂剂元素硅、硼和镓以及任选的液封剂一并装入坩埚中，所述坩埚带有晶种槽，晶种槽事先装有高纯锗单晶晶种；
2)将第二锗原料装入装载容器中，第二锗原料用于补充第一锗原料，所述装载容器中任选地装有液封剂；
3)将第1)步所述坩埚和第2)步所述装载容器置于石英管内，并在真空下密封石英管；
4)将第3)步的密封有坩埚和装载容器的石英管放入具有可移动的石英管支座的晶体生长熔炉中，所述支座用于支承石英管；
5)使第一锗原料和第二锗原料熔融，分别形成第一熔体和第二熔体，然后使得装载容器中的熔融的第二锗原料完全注入坩埚；
6)冷却第5)步得到的坩埚中的熔体，同时控制熔体的温度梯度和冷却速率，使熔体与晶种接触时结晶生长锗单晶棒；和
7)冷却锗单晶棒；
其中，第1)步中添加的掺杂剂元素硅、硼和镓的量使得制得的锗单晶棒在有效长度内硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，且硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc；
优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
12.根据实施方案11所述的制备锗单晶棒的方法，其中，晶棒头部硼原子浓度和镓原子浓度的比例为8-5:1，优选为7-4:1，更优选为5-3:1，晶棒尾部硼原子浓度和镓原子浓度比例为1:100-240，优选为1:130-210，更优选为1:160-180。
13.根据实施方案11-12任一项所述的制备锗单晶棒的方法，其中，硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
14.根据实施方案11-13任一项所述的制备锗单晶棒的方法，其中，在第6)步使熔体与晶种接触时结晶生长成锗单晶棒的过程中，在晶棒生长区建立0.3-4.0℃/cm；优选地，在晶棒生长区建立0.5-3.5℃/cm的温度梯度；更优选地，在晶棒生长区建立1.0-3.0℃/cm的温度梯度。
15.根据实施方案11-14任一项所述的制备锗单晶棒的方法，其中，锗单晶棒在有效长度内硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
16.实施方案1-5任一项所述锗单晶片、实施方案6-10任一项所述制备锗单晶片的方法制得的锗单晶片以及实施方案11-15任一项所述制备锗单晶棒的方法制得的锗单晶棒切割得到的锗单晶片用于增加多节太阳能电池开路电压的用途。
实施例
参照一个完整的实施例对本发明进行说明。这里所描述的实施例不代表本发明包括的所有实施案例，仅仅是一个实施的案例。本发明可能包括许多其他的实施例。
原料与设备
高纯锗，块状，纯度99.999％，购自中诺新材(北京)科技有限公司；
三氧化二硼，分析纯，购自南京化学试剂股份有限公司。
抛光机(上下盘直径1.0米)，如图12所示，其中R1和R2为转动轴，11为研磨液或抛光液管，12为设备上盘，13为设备下盘，14为晶片和支承垫，16为研磨垫或抛光垫(研磨垫为购自美国环球光学公司Universal Optics Co.Ltd的聚酯类研磨垫，牌号为LPS研磨垫； 粗抛光垫为购自美国DOW公司的聚氨酯抛光垫，牌号Suba-X Pad；精抛光垫为购自美国DOW公司的聚氨酯抛光垫，牌号POLITEX Pad。下盘也有研磨垫和抛光垫，与上盘的相同，位于晶片和支承垫之下，未示出)。支承垫(研磨和抛光采用同一支承垫)、研磨垫和抛光垫直径为1米；支承垫用于承载晶片的4个孔位于半径方向的中部，沿圆周方向均匀分布。
研磨液，采用日本Fujimi Corporation Fujimi 20T三氧化二铝研磨粉和水的混合液，重量比为1:1，研磨过程中的研磨液流量为每分钟90毫升/平方米设备盘面积(单面计)。
多线切割机，MWM442DM，购自日本小松NTC。
碳化硅，粒径为10微米，购自上海上磨磨料磨具有限公司。
矿物油，C10油，购自安永公司。
万用表，Fluke 28-II，电压量程：0.1mV至1000V，购自美国福禄克(Fluke)公司。
多功能数字式四探针测试仪，ST2258A型，购自苏州晶格电子有限公司。
高分辨二次离子质谱仪，NanoSIMS 50L，购自法国CAMECA公司。
性能测试
所制备锗单晶初始晶片的检测条件如下：目测晶片完整且表面无裂纹为合格。
电阻率，采用GB/T 26074-2010《锗单晶电阻率直流四探针测量方法》所述方法使用上述多功能数字式四探针测试仪测试。
位错密度，采用GB/T5252-2006《锗单晶位错腐蚀坑密度测量方法》所述方法测定。
开路电压使用万用表测试。
掺杂剂元素硅、硼和锗的原子浓度采用上述高分辨二次离子质谱仪测定，测定条件如下：测试Si原子浓度时采用铯离子(Cs+)束为入射离子束，从样品表面溅射到样品内部10微米厚度范围内获得平均Si原子浓度；测试B原子浓度时采用氧离子(O2+)离子束为入射离子束，从样品表面溅射到样品内部10微米厚度范围内获得平均B原子浓度；测试Ga原子浓度时采用氧离子(O2+)束为入射离子束，从样 品表面溅射到样品内部10微米厚度范围内获得平均Ga原子浓度；测试腔室的真空度为10 -7Torr(托)，入射离子束流提强度0.16mA/cm 2，分析区域为250×250平方微米，溅射速率为3.6微米/小时。
制备锗单晶棒
以下实施例中制备的是直径4英寸的增加多节太阳能电池开路电压锗单晶棒，然而，其他直径尺寸的锗单晶棒例如1英寸至8英寸直径或更大的直径的晶棒都可以采用本发明的制备锗单晶棒的方法制备。
按照如下步骤制备锗单晶棒：
使用10kg块状高纯锗原料以及下表2所述量的掺杂剂硅、硼、镓(基于高纯锗原料计)和三氧化二硼液封剂。
1)分别将65％的表2所述量的块状高纯锗以及硅、硼、镓和三氧化二硼装入第一生长坩埚中，第一生长坩埚的晶种槽中预先装有高纯锗单晶晶种；
2)将剩余35％的高纯锗以及硅、硼、镓和三氧化二硼装入第一生长坩埚上方的第二补料坩埚中；
3)将第一生长坩埚和第二补料坩埚装入石英管中，并在真空度为10 -5托的条件下密封石英管；
4)将第3)步得到的密封有第一生长坩埚和第二补料坩埚的石英管放入具有可移动的石英管支座的晶体生长熔炉中，支座用于支承石英管；
5)启动生长熔炉的加热程序，以20℃/min的加热速率加热第一生长坩埚和第二补料坩埚，使其中的第一锗原料和第二锗原料熔融，形成第一熔体和第二熔体，第二熔体加入第一熔熔体；
6)冷却第5)步得到的熔体，同时控制熔体的冷却速率，使熔体与晶种接触时结晶形成锗单晶棒，锗单晶生长的温度梯度以及从晶种端开始锗单晶生长的结晶冷却速率如表2所示；和；
7)单晶生长完成后冷却锗单晶棒至室温，冷却速率为30℃/h。
表2制备锗单晶棒的各掺杂剂投料量及生产参数
Figure PCTCN2020090402-appb-000003
*)基于高纯锗原料计的ppm值。
图3和图4分别为本发明1和2的掺镓、硼和硅的锗单晶棒从头到尾电阻率(Res)分布，最大电阻率和最小电阻率按照作图所得，本发明3-4按照类似方式得到。
制得锗单晶棒的性能如表3所示。
Figure PCTCN2020090402-appb-000004
制备锗单晶片
将上述实施例制备的锗单晶棒按照如下步骤切割为锗单晶片。
切割：锗单晶棒用多线切割机切割为厚度为240μm的锗单晶初始晶片。在切割过程中，使用半包围石墨固定圆形锗单晶棒。切割完成后，人工取出锗单晶初始晶片，操作由同一人员按相同的条件完成。
倒角：使用倒角机对各片圆形晶片进行边缘倒角处理，使其边缘截面成为弧形。
固定：将晶片的一面置于直径5.2厘米圆形的、250微米厚的平坦陶瓷板(Ra<0.5微米)上，轻轻施加压力确保晶片和陶瓷板之间没有气泡。
表面处理：将载有晶片的陶瓷板置于35℃的刻蚀液中12秒，所述刻蚀液的组成为：1摩尔％NH 3、10摩尔％过氧化氢，余量为水。
抛光：然后将载有晶片的陶瓷板放在抛光机的支承垫腔内(紧贴陶瓷板)，固定，先将表4所示的粗抛光溶液用于该抛光设备，在表4所示粗抛条件下抛光60分钟，用去离子水(电阻率大于17.5兆欧姆·厘米——按25℃的值)清洗后，干燥，再将表5所示的精抛光溶液用于该抛光设备，在表5所示精抛条件下抛光6分钟，然后将载有晶片的陶瓷板取出放在加热炉上，使胶熔化，将晶片移出陶瓷板，用去离子水清洗后，干燥。
清洗：a)在10℃，将晶片在含有0.3重量％NH 3、1.3重量％(如无相反说明，以下各溶液均按重量百分比计，基于溶液总重量)过氧化氢的水溶液中浸渍5分钟；b)在10℃，用去离子水冲洗晶片表面3分钟；c)在20℃，将晶片用10重量％过氧化氢溶液浸渍5分钟；d)在15℃，用去离子水冲洗晶片表面3分钟；e)在20℃，将晶片用10重量％氨水溶液浸渍5分钟；f)在15℃，用去离子水冲洗晶片表面3分钟；g)将晶片放入晶片旋转干燥机中用热氮气干燥。
所得锗单晶片的厚度为140μm，所得锗单晶片的性能测试结果如下表6所示。
表4粗抛光溶液的组成及抛光条件
Figure PCTCN2020090402-appb-000005
Figure PCTCN2020090402-appb-000006
表5精抛光溶液的组成及抛光条件
Figure PCTCN2020090402-appb-000007
表 6锗单晶片的性能测试结果
Figure PCTCN2020090402-appb-000008
制备太阳能电池
使用上述切割实施例制备的锗单晶棒得到的锗单晶按照如下步骤制备太阳能电池。
1)将制得的锗单晶衬底放入外延炉中，采用金属有机物化学气相外延的方法生长多节太阳能电池外延层，外延过程中采用的气源和金属有机物源包括高纯氢气、磷烷(PH 3)、砷烷(AsH 3)、三甲基镓(TM-Ga)、 三甲基铟(TM-In)，采用磷做n型掺杂，与锗衬底之间形成PN结；
2)外延生长铟镓砷中间电池层；
3)外延生长铟镓磷顶电池层；
4)沉积减反射层：沉积减反射层的目的在于减少表面反射，增加折射率，使用PECVD淀积SiN，由于PECVD淀积SiN时，不光是生长SiN作为减反射膜，同时生成了大量的原子氢，这些氢原子能对多晶硅片具有表面钝化和体钝化的双重作用，可用于大批量生产；
5)形成电极：采用电子束蒸发工艺将金锗镍镀层在太阳电池的正背面，以形成正负电极引线；
6)电池片测试：完成的电池片经过测试分档进行归类。
用万用表测定各太阳能电池的开路电压。
本发明实施例中把锗原料装入坩埚过程中加入适量的硅掺杂剂，同时采用合适的生长程序，装入的原料几乎都长成了单晶材料，几乎整个晶棒都可用于光伏器件外延用衬底材料的制备。在这些晶棒中探测到了硅原子，采用这些晶棒制备的锗单晶衬底材料明显增加了其上外延生长的光伏器件的开路电压。
结果表明，通过共掺杂，可以明显增加基于这些晶棒制备的衬底上外延生长的多节太阳能电池的开路电压，开路电压Voc增加如下表7所示，使得能够增加多节太阳能光伏器件的光电转化效率。
表7所得太阳能电池的开路电压增加情况
实施例编号 开路电压增加
本发明1 1.6％
本发明2 1.2％
本发明3 2.2％
本发明4 1.8％
对比1 0.1％
对比2 0.15％
应注意，用本发明公开的方法/过程制备的任何锗晶体衬底(例如晶锭、晶片等)都明确地在本发明的范围内。此外，包含这种用本发明方法之一制备的锗晶体衬底的任何产品(例如电子设备或光电设备等)也符合本发明。
虽然上述内容已参照本发明的一些具体实施方案进行了说明，但是本 领域技术人员应该理解，在不偏离本发明原则和主旨的情况下可对所述实施方案进行改变，本发明的范围通过所附权利要求书进行限定。

Claims (16)

  1. 一种锗单晶片，其中，锗单晶片中包含掺杂剂元素硅、硼和镓，硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc；
    优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
    更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
  2. 根据权利要求1所述的锗单晶片，其中，锗单晶片的硼原子浓度和镓原子浓度的比例为8:1至1:240，优选为5:1至1:170，更优选为3:1至1:100。
  3. 根据权利要求1-2任一项所述的锗单晶片，其中，锗单晶片的硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
  4. 根据权利要求1-3任一项所述的锗单晶片，其中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
  5. 根据权利要求1-4任一项所述的锗单晶片，其中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
  6. 本发明还提供一种制备锗单晶片的方法，所述方法包括：
    1)由包含元素硅、硼和镓的锗单晶棒切割出锗单晶初始晶片，其中，切割得到的锗单晶片初始晶片中硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，且镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc，初始晶片的厚度为200-800μm，
    优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
    更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼 原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc；
    2)对步骤1)得到的锗单晶初始晶片进行磨边处理；
    3)对步骤2)中进行磨边处理之后的锗单晶初始晶片进行表面处理，和
    4)对在步骤3)中表面处理之后的锗单晶初始晶片进行粗抛光，然后进行精抛光，得到锗单晶片产品，其中，所得到的锗单晶片产品厚度为100-700μm。
  7. 根据权利要求6所述的制备锗单晶片的方法，其中，锗单晶片的硼原子浓度和镓原子浓度的比例为8:1至1:240，优选为5:1至1:170，更优选为3:1至1:100。
  8. 根据权利要求6-7任一项所述的制备锗单晶片的方法，其中，硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
  9. 根据权利要求6-8任一项所述的制备锗单晶片的方法，其中，锗单晶片的厚度为100-700μm，优选为100-500μm，更优选为100-200μm，甚至更优选为120-140μm。
  10. 根据权利要求6-9任一项所述的制备锗单晶片的方法，其中，锗单晶片的硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
  11. 一种制备锗单晶棒的方法，所述方法包括：
    1)将第一锗原料、掺杂剂元素硅、硼和镓以及任选的液封剂一并装入坩埚中，所述坩埚带有晶种槽，晶种槽事先装有高纯锗单晶晶种；
    2)将第二锗原料装入装载容器中，第二锗原料用于补充第一锗原料，所述装载容器中任选地装有液封剂；
    3)将第1)步所述坩埚和第2)步所述装载容器置于石英管内，并在真空下密封石英管；
    4)将第3)步的密封有坩埚和装载容器的石英管放入具有可移动的石英管支座的晶体生长熔炉中，所述支座用于支承石英管；
    5)使第一锗原料和第二锗原料熔融，分别形成第一熔体和第二熔体，然后使得装载容器中的熔融的第二锗原料完全注入坩埚；
    6)冷却第5)步得到的坩埚中的熔体，同时控制熔体的温度梯度 和冷却速率，使熔体与晶种接触时结晶生长锗单晶棒；和
    7)冷却锗单晶棒；
    其中，第1)步中添加的掺杂剂元素硅、硼和镓的量使得制得的锗单晶棒在有效长度内硅原子浓度为3×10 14atoms/cc至10×10 18atoms/cc，且硼原子浓度为1×10 16atoms/cc至10×10 18atoms/cc，镓原子浓度为1×10 16atoms/cc至10×10 19atoms/cc；
    优选地，硅原子浓度为4×10 14atoms/cc至8×10 18atoms/cc，硼原子浓度为2×10 16atoms/cc至8×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至9×10 19atoms/cc；
    更优选地，硅原子浓度为5×10 14atoms/cc至7×10 18atoms/cc，硼原子浓度为4×10 16atoms/cc至7×10 18atoms/cc且镓原子浓度为2×10 16atoms/cc至8×10 19atoms/cc。
  12. 根据权利要求11所述的制备锗单晶棒的方法，其中，晶棒头部硼原子浓度和镓原子浓度的比例为8-5:1，优选为7-4:1，更优选为5-3:1，晶棒尾部硼原子浓度和镓原子浓度比例为1:100-240，优选为1:130-210，更优选为1:160-180。
  13. 根据权利要求11-12任一项所述的制备锗单晶棒的方法，其中，硅原子浓度与镓原子浓度比例为4:1-100，优选为3:1-80，更优选为2:1-50。
  14. 根据权利要求11-13任一项所述的制备锗单晶棒的方法，其中，在第6)步使熔体与晶种接触时结晶生长成锗单晶棒的过程中，在晶棒生长区建立0.3-4.0℃/cm；优选地，在晶棒生长区建立0.5-3.5℃/cm的温度梯度；更优选地，在晶棒生长区建立1.0-3.0℃/cm的温度梯度。
  15. 根据权利要求11-14任一项所述的制备锗单晶棒的方法，其中，锗单晶棒在有效长度内硅原子、硼原子和镓原子浓度之和A的范围为2ppm≤A≤120ppm，优选4ppm≤A≤70ppm，基于锗的量计。
  16. 权利要求1-5任一项所述锗单晶片、权利要求6-10任一项所述制备锗单晶片的方法制得的锗单晶片以及权利要求11-15任一项所述制备锗单晶棒的方法制得的锗单晶棒切割得到的锗单晶片用于增加多节太阳能电池开路电压的用途。
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