Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
  • H01L31/0264—Inorganic materials
  • H01L31/0296—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe
  • H01L31/02966—Inorganic materials including, apart from doping material or other impurities, only AIIBVI compounds, e.g. CdS, ZnS, HgCdTe including ternary compounds, e.g. HgCdTe
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
  • H01L31/0264—Inorganic materials
  • H01L31/0304—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds
  • H01L31/03046—Inorganic materials including, apart from doping materials or other impurities, only AIIIBV compounds including ternary or quaternary compounds, e.g. GaAlAs, InGaAs, InGaAsP
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by 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
  • H01L31/0693—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 the devices including, apart from doping material or other impurities, only AIIIBV compounds, e.g. GaAs or InP solar cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/544—Solar cells from Group III-V materials
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/547—Monocrystalline silicon PV cells

Definitions

• This invention relates to new materials for photovoltaic devices and more specifically multiband semiconductors for high power conversion efficiency solar cells.
• Various materials that are suitable for photovoltaic devices are known, such as tetrahedral amorphous semiconductors (e.g., amorphous silicon, amorphous silicon germanium and amorphous silicon carbide) as well as poly- and mono-crystalline semiconductors including group IV (Si), II- VI compound semiconductors, (e.g., CdTe), and III-V group compound semiconductors, (e.g., GaAs, GalnP, GaAlAs).
• a conventional solar utilizes the pn junction formed by ion implantation or thermal diffusion of impurities into a substrate of single crystal of silicon (Si) or gallium arsenide (GaAs), or by epitaxial growth of an impurity-doped layer on a substrate of such single crystal.
• Si silicon
• GaAs gallium arsenide
• Such single junction solar cells have only limited efficiency because they are sensitive to a limited part of the total solar spectrum. The efficiency can be improved by using stacks of p/n junctions formed with semiconductors with different energy gaps that are sensitive to different parts of solar spectrum. This concept has been realized in multijunction or tandem solar cells (J. M. Olson, T. A. Gessert, and M. M. Al- Jasim, Proc.
• III-V alloys in which group V anions are partially replaced with the isovalent N [Semiconductor Science and Technology 17, 2002, Special Issue: III-N-V Semiconductor Alloys, the contents of which are hereby incorporated by reference in its entirety] or H-VI alloys in which group VI anions are partially replaced with O [K. M. Yu, W. Walukiewicz, J. Wu, J. W. Beeman, J. W. Ager, E. E. Haller, I. Miotkowski, A. K. Ramdas, and P. Becla, Appl. Phys. Lett. 80, 1571 (2002), the contents of which are hereby incorporated by reference in its entirety, ] are the well known examples of the HMAs.
• GaNjAs;.* exhibits a strong reduction of the band gap by 180 meV when only 1% of the As atoms is replaced by N. It has been predicted and experimentally demonstrated that the electronic band structure of such HMAs is determined by the anticrossing interaction between localized O or N states and the extended states of the semiconductor matrix [W. Walukiewicz, W. Shan, K. M. Yu, J. W. Ager III, E. E. Haller, I. Miotlowski, M. J. Seong, H. Alawadhi, and A. K. Ramdas, Phys. Rev. Lett. 85, 1552 (2000), the contents of which are hereby incorporated by reference in its entirety].
• BRD2F SUMMARY OF THE INVENTION The present invention provides a new class of multiband gap semiconductor materials.
• This class of multiband material can be used for the design of high efficiency solar cells.
• the materials in accordance with the present invention comprise group II- VI compound semiconductor in which a fraction of the group VI atoms have been replaced with oxygen atoms forming TJ-O x -VI 1-x alloys.
• the materials can be fabricated using ion implantation followed by pulsed laser melting and/or thermal annealing.
• the materials can be also synthesized as epitaxial films using Pulsed Laser Deposition and a variety of epitaxial growth techniques including Molecular Beam Epitaxy and Metalorganic Chemical Vapor Deposition.
• the solar cells are fabricated by forming a single p/n junction in the aforementioned materials.
• BRffiF DESCRIPTION OF THE DRAWINGS The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings:
• FIG 1 displays photomodulated reflectance (PR) spectra obtained from a series of 3.3% OAmplanted Zno. 88 Mno. ⁇ 2 Te samples followed by pulsed laser melting with increasing energy fluence from 0.04-0.3 J/cm 2 .
• FIG 3 shows the energy positions of E. and E + for the Zno .88 Mno. 12 O x Te 1-x alloys with different x.
• FIG 4 schematically displays the optical transitions between different bands in Zno. 88 Mn 0.
• FIG 5 displays current-voltage (I/V) characteristics and the spectral dependence of Photo voltage (PV) for a proptotypical p/n junction fabricated on the multiband semiconductor.
• the junction comprises a p- type Zno . ssMno . nTe substrate implanted with O and Cl ions.
• the top implanted layer was pulsed laser melted.
• the O atoms partially replacing Te atoms form additional conduction band.
• FIG 6 shows the calculated power conversion efficiency for a solar cell fabricated from a 3-band Zn 0.88 Mno .12 O x Te 1-x alloy as a function of O content. The solid line is an empirical polynomial fit of the calculated data.
• FIG 7 shows the location of the nitrogen energy, E N level relative to the conduction band energy minima Er and Ex in GaN x As 1-x . y P y .
• FIG 8 shows the energies of the upper conduction E + and intermediate E. band in GaN x As ⁇ -x- o. 6 Po. 4 as functions of the N-content x.
• a semiconductor composition comprising a ternary or quaternary alloy, said alloy comprising a Group II element, a Group VI element, Oxygen and optionally a third element "A", wherein said alloy has a mole fraction composition of (Group IT)( 1 .y)(A) y O x (Group VI)(i -X ), and 0 ⁇ y ⁇ l and 0 ⁇ x ⁇ l and "A" comprises Mg.
• an alloy comprising Zno .88 Ao . ⁇ 2 O x Te 1-x , where 0 ⁇ x ⁇ 0.05.
• x is between about 0.01 and 0.05.
• a semiconductor composition comprising a ternary or quaternary alloy, said alloy comprising a Group II element, a Group VI element, Oxygen and optionally a third element "A", wherein said alloy has a mole fraction composition of (Group JT) ⁇ . y )(A)yO x (Group VI)( 1-X ), and 0 ⁇ y ⁇ l and 0 ⁇ x ⁇ 0.05 and "A" comprises either Mn or Mg, and wherein the Group II element does not comprise Cd.
• x is between about 0.01 and 0.05.
• a semiconductor composition comprising a ternary or quaternary alloy comprising a Group II element, optionally another Group II element "A", S or Se, Oxygen and Tellurium, wherein said alloy has a mole fraction composition of (Group H)( X )(A)( 1-X )(S or Se)( 1-y-2 )(Te)( y )(O) 2 ⁇ and
• a semiconductor composition comprising an alloy comprising GaN x As ⁇ -x . y P y wherein 0.3 ⁇ y ⁇ 0.5 and 0 ⁇ x ⁇ 0.05.
• semiconductor composition comprising an alloy comprising Ga 1-y In y N x P ⁇ -x wherein 0.4 ⁇ y ⁇ 0.6 and 0 ⁇ x ⁇ 0.05. All of the compositions disclosed herein are suitable for films for use in photovoltaic devices.
• Group II- VI compounds and their alloys it is meant to include all compound semiconductor materials composed such as ZnTe, CdTe and all other binary, ternary and quaternary alloys of the respective Group elements.
• Group II elements include Mn, Mg, Zn and Cd.
• Group VI elements include O, S, Se, and Te.
• Group HI elements include B, Al, Ga, In and Tl.
• Group V elements include N, P, As, and Sb. It is understood that the present invention includes semiconductor materials which are doped or undoped (i.e. pure intrinsic semiconductors) and may be arranged to form a variety of semiconductor devices with junctions such as pn, pnp, npn, pin, pip and so forth.
• the materials can be doped in a conventional manner.
• conventional dopants such as B, P, As, In and Al can be used.
• Dopants may be selected from Groups ⁇ , 111, IV, V, VI, etc.
• Mn may be replaced with Mg.
• FIG 1 shows a series of PR spectra from Zno .88 Mn 0.12 Te samples implanted with 3.3% of O + followed by PLM with increasing laser energy fluence from 0.04 to 0.3 J/cm 2 .
• transitions can be attributed to transitions from the valence band to the two conduction subbands, E + (-2.6 eV) and E. (-1.8 eV) formed as a result of the hybridization of the localized O states and the extended conduction band states of ZnMnTe.
• the strong signals at both E. and E + indicates the extended nature of these electronic states and the substantial oscillator strength for the transitions.
• the energy band structure and the density of states for the case of Zno .88 Mno .12 O ⁇ Te 1-x alloy (with x ⁇ 0.01) are shown in Fig 4.
• An O derived narrow band of extended states E. is separated from the upper subband E + by about 0.7 eV.
• a reduction in the energy shifts of both E. and E + can be observed at RTA temperature higher than 350°C. This indicates that the Zno. 88 Mno .12 O x Te ⁇ -x alloys are thermally stable up to ⁇ 350°C.
• At an RTA temperature of 700°C only the original E M transition is observed. This may suggest that the O atoms that resided in the Te sites diffused out of the Te sites, possibly forming O bubbles.
• x decreases with increasing energy fluence higher than the melt threshold (-0.08 J/cm 2 ); possibly due to the longer melt duration and/or dilution through the deeper melt depth.
• the energy positions of the two transitions as predicted by the B AC model are plotted as solid lines.
• TA thermal annealing
• PLM pulsed laser melting
• PLA pulse laser annealing
• PLM pulse melting
• the calculated power conversion efficiency for a solar cell fabricated from a 3-band Zno .88 Mno . ⁇ 2 O x Te 1-x alloy as a function of O content is shown in FIG 6. Note that in the following examples it is preferred that the time period used for the heating be as short as possible. There is generally an inverse relationship between the time for heating and the temperature used. One of ordinary skill in the art can readily optimize the proper parameters for the particular Group II- VI semiconductor. Examples
• the band gap of the compositions and films made in accordance with the present invention was measured at room temperature using photomodulated reflectance (PR). Radiation from a 300 Watt halogen tungsten lamp dispersed by a 0.5 m monochromator was focused on the samples as a probe beam.
• PR photomodulated reflectance
• PR signals were detected by a Si photodiode using a phase-sensitive lock-in amplification system.
• the values of the band gap and the line width were determined by fitting the PR spectra to the Aspnes third-derivative functional form, see D. E. Aspnes, Surf. Sci. 37, 418 (1973), the contents of which are hereby incorporated by reference in its entirety.
• Example 1 (Group ⁇ ) (x) (A) ( ⁇ -x )(S or Se) (1-y-z) (Te) (y )(O) z , and 0 ⁇ x ⁇ l, 0 ⁇ z ⁇ 0.04 and 0 ⁇ y ⁇ 0.2).
• the material may be fabricated as follows. A substrate of ZnSe 1-y Te y (0 ⁇ y ⁇ 0.2) is implanted with 1 to 4% of O. The top layer is melted with a short pulse of a laser light. The top layer, four band layer can be doped n-type to form a p/n junction with the p-type substrate.
• Example 2 Preparation of a solar cell using the semiconductor materials described herein.
• a p-type substrate of Zn ⁇ . y Mn y Te (or similar material) may be implanted with 1 to 4 atomic % of O and 0 to 1 atomic % of Cl. The top implanted layer is then melted with a short laser pulse.
• Example 3 Preparation of a (Group U)(i -y )(A)yO ⁇ (Group VI)( 1-X ), and 0 ⁇ y ⁇ l and 0 ⁇ x ⁇ 0.1 and "A" comprises Mg.
• Example 4 Preparation of GaN x As 1-x-y P y , where 0.3 ⁇ y ⁇ 0.5 and 0 ⁇ x ⁇ 0.05. Multiple energy implantation of N into GaAs 1-y P y (0.3 ⁇ y ⁇ 0.5) single crystals to form a thin layer with relatively constant N concentration corresponding to N mole fractions of 0 ⁇ x ⁇ 0.05.
• the N + -implanted samples are pulsed-laser melted with varying photon fluence.
• GaN x As 1-x-y P y with 0.3 ⁇ y ⁇ 0.5 and 0 ⁇ x ⁇ 0.05 can be also grown using appropriate thin film growth epitaxial techniques including molecular beam epitaxy and metalorganic chemical vapor deposition.
• FIG 7 shows the location of the nitrogen energy, E N level relative to the conduction band energy minima Er and E x in GaN x As 1-x- y P y .
• An intermediate nitrogen derived band is best formed when the E falls below Er and Er is still below E x minimum. As seen in FIG 7 this occurs for 0.4 ⁇ y ⁇ 0.6.
• FIG 8 shows the energies of the upper conduction E + and intermediate E.
• Example 5 Preparation of Ga ⁇ -y In y N x Pi. x wherein 0.4 ⁇ y ⁇ 0.6 and 0 ⁇ x ⁇ 0.05. Multiple energy implantation of N into Ga ⁇ -y In y P (0.4 ⁇ y ⁇ 0.6) single crystals to form a thin layer with relatively constant N concentration corresponding to N mole fractions of 0 ⁇ x ⁇ 0.05. The N + -implanted samples are pulsed-laser melted with varying photon fluence.
• Ga 1-y In y N x P 1-x with 0.3 ⁇ y ⁇ 0.5 and 0 ⁇ x ⁇ 0.05 can be also grown using appropriate thin film growth epitaxial techniques including molecular beam epitaxy and metalorganic chemical vapor deposition.
• BAC band anticrossing

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