EP0248881A1 - Structure et procede de fabrication d'un photodetecteur a mode de piegeage - Google Patents

Structure et procede de fabrication d'un photodetecteur a mode de piegeage

Info

Publication number
EP0248881A1
EP0248881A1 EP19870900401 EP87900401A EP0248881A1 EP 0248881 A1 EP0248881 A1 EP 0248881A1 EP 19870900401 EP19870900401 EP 19870900401 EP 87900401 A EP87900401 A EP 87900401A EP 0248881 A1 EP0248881 A1 EP 0248881A1
Authority
EP
European Patent Office
Prior art keywords
region
photodetector
type
conductivity type
conductivity
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19870900401
Other languages
German (de)
English (en)
Inventor
Paul R. Norton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Co
Original Assignee
Santa Barbara Research Center
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Santa Barbara Research Center filed Critical Santa Barbara Research Center
Publication of EP0248881A1 publication Critical patent/EP0248881A1/fr
Ceased legal-status Critical Current

Links

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
    • H01L31/08—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 in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—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 in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/109—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN heterojunction type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/024—Group 12/16 materials
    • H01L21/02411—Tellurides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02551—Group 12/16 materials
    • H01L21/02562—Tellurides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/0257—Doping during depositing
    • H01L21/02573—Conductivity type
    • H01L21/02576—N-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/0257—Doping during depositing
    • H01L21/02573—Conductivity type
    • H01L21/02579—P-type
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02625—Liquid deposition using melted materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02628—Liquid deposition using solutions
    • 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
    • H01L31/08—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 in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—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 in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/103—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN homojunction type
    • H01L31/1032—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN homojunction type the devices comprising active layers formed only by AIIBVI compounds, e.g. HgCdTe IR photodiodes

Definitions

  • This invention relates to photodetectors for producing detectable signals from incident radiation such as infrared radiation having wavelengths in the range of about 1 to about 25 microns, or more, particularly where the radiation appears in low background level energy fields, such as, for example, fields with background flux levels less than about 10 17 photons/cm2-sec.
  • incident radiation such as infrared radiation having wavelengths in the range of about 1 to about 25 microns, or more, particularly where the radiation appears in low background level energy fields, such as, for example, fields with background flux levels less than about 10 17 photons/cm2-sec.
  • a photodetector can be, for example, a bar of semiconductor material having electrical contacts at its ends.
  • the photodetector is connected in series with a direct current voltage source and a load resistor.
  • the change in conductivity of the detector in response to incident radiation is sensed in one of two ways. If the resistance of the load resistor exceeds the resistance of the detector, the device operates in the
  • the constant current mode finds wider use in detectors made from semiconductor materials having low resistivity.
  • Photodetectors and particularly arrays of such detectors, have many applications.
  • One application is in the detection of infrared radiation.
  • Infrared sensitive photodetector arrays are used for various heat and object sensing applications.
  • mercury cadmium telluride which consists of a mixture of cadmium telluride and mercury telluride.
  • mercury telluride is a semi-metal having a "negative energy gap" of about minus 0.3eV.
  • the energy gap of the alloy varies monotonically with x, the mole fraction of cadmium telluride in the alloy, Hg, Cd Te.
  • mercury cadmium telluride detectors having a peak response at any of a wide range of infrared wavelengths.
  • Mercury cadmium telluride photodetector arrays are now made by mounting a mercury cadmium telluride crystal on substrates with an epoxy. The thickness of the mercury cadmium telluride is then reduced to about 10 microns by lapping, polishing and etching. The detectors are then delineated and isolated by masking, and then cutting or etching. Electrical leads are attached to opposite ends of each of the individual detector elements, or to one end of each and a common.
  • the photodetectors of this invention produce detectivities close to the theoretical maximum detectivity of 2.52 x is the quantum efficiency, and Q is the background photon flux, and fl is the wavelength of the radiation incident on the detector, and at least about 2 x lO 17 ⁇ ( ⁇ /Q ⁇ ) crnHz'/Watt, where the radiation incident on the detectors is in the range of about 1 microns to about 25 microns or more, more parti- cularly in the range of about 10.microns to about 25 microns or more.
  • detectors are particularly effec ⁇ tive in producing signals from such incident radiation under low background radiation conditions, meaning radiation flux levels of less than about 10 17 photons/ cm 2-sec, and where the temperature under which the detector operates is sufficiently low to minimize thermal generation and recombination of excess carriers.
  • the duration of the signals produced by the new photodetectors at background levels in the range of about 10 10 to about 1013 photons/cm2-sec is at least about 50 microseconds and ranges as high as 100 microseconds or higher.
  • the new photodetectors comprise a substrate that is electrically insulating, such as a dielectric or wide band-gap semiconductor, attached to a body of semi ⁇ conductor material comprising a region of first conductivity type and a region of a second, opposite conductivity type where the first region overlies the second.
  • the region of first conductivity type has a narrow energy band-gap.
  • the region of second, opposite conductivity type may have an energy band-gap substan- tially the same as, or different from the region of first conductivity type.
  • This region of second type may have an energy band-gap that is substantially uniform and the same as or larger than the energy band-gap in the first region, or may vary, linearly or non-linearly, within the second region.
  • the method for making these new photodetectors comprises growing (depositing) a body of photoconductive material, epitaxially, on a substrate, and then annealing the epitaxially-grown photoconductive material to form the regions of first and second conductivity types atop the substrate.
  • the photodetectors are made of mercury cadmium telluride material
  • the annealing takes place in a mercury vapor for a time sufficient to fill mercury vacancies in the portion of the semiconductor material referred to as the region of first conductivity type.
  • the body of semiconductor material can be separated into a plurality of detectors by etching or other suitable technique.
  • an additional layer can be grown, epitaxially, atop the body of semiconductor material, to function as a means for minimizing diffusion of minority carriers to electrical contacts affixed to the top of the detectors.
  • Fig. 1 shows a preferred embodiment of the method for making the new photodetectors of this invention
  • Figs. 2 and 3 illustrate the structure and behavior of two preferred embodiments of the new photodetectors of this invention.
  • Fig. 4 shows a cross-sectional view of a detector array of the present invention.
  • the methods for making photodetectors of the kind shown in the drawings preferably utilize a tellurium- rich or mercury-rich melt including mercury telluride and cadmium telluride in molten form.
  • Photodetectors made from such melts comprise mercury cadmium telluride having the general formula Hg, Cd Te, where x is in the range of about 0.95 to about 0.13. While this detailed description speaks in terms of mercury cadmium telluride photo- conductors, the methods of the invention and/or the structures produced are applicable to the manufacture of photodetectors from other substances, such as III-V, II-VI and IV-VI semiconductor alloys, particularly those having narrow band-gap detecting layers. Fig.
  • a dielectric or wide band-gap semiconductor substrate (such as a cadmium telluride substrate) of relatively high resistivity, meaning a resistivity in the range of about 10 3 to about 108 ohm-cm, is covered with a tellurium melt solution including a predetermined amount of mercury and cadmium. This tellurium melt solution is permitted to cool on the substrate to a temperature where the melt is supersaturated, thereby forming an epitaxial layer of mercury cadmium telluride thereon.
  • the epitaxially-deposited layer of mercury cadmium telluride has an excess of tellurium atoms or a deficiency of mercury atoms (mercury vacancies) in the crystal layer such that its electrical type is dominated by hole carriers (p-type) .
  • the p-type concen- tration, as grown, is typically in the 10 -10 /cm range.
  • a mercury melt solution may be used to grow the layer having the same properties.
  • the sub ⁇ strate carrying the semiconductive, epitaxially grown layer is annealed, preferably in a vapor comprising mercury, at a temperature in the range of about 200°C to about 300°C, for a time in the range of about 0.1 to about 100 hours, or at least for a time sufficient to form an n-type detector layer at the surface of the epitaxial semiconductor body, while retaining a p-type layer beneath the n-type detector layer, and with the PN junction of the two layers extending substantially along the length of the p-type layer (i.e., the p-type trapping region underlies the entire n-type detection layer) .
  • the detector By controlling the time and temperature of annealing, the detector can be made with greatest sensitivity to incident radiation. Time and temperature of the annealing can be adjusted, depending upon the ratio of mercury to cadmium, the thickness of the epitaxial layer, the temperature of growth, and other factors, to achieve maximum practicable sensitivity.
  • the n-type detector layer is lightly doped, meaning that the concentration of electrons is 5 x
  • the p-type region may lie substantially within a compositionally graded interface between the surface of the epitaxial layer and the substrate.
  • an addi- tional layer may be deposited, epitaxially, on the surface of the n-type detector layer.
  • This additional surface layer has a wider band-gap than the first epitaxial layer and can also be made of mercury cadmium telluride, preferably from a mercury melt solution including cadmium and tellurium, or may be made of cadmium telluride or other materials so that the layer prevents or minimizes diffusion of minority carriers to electrodes attached to the top of the detectors of this invention.
  • the body of semiconductor material can be divided into a plurality of arrays by etching, or other known techniques. Thereafter, electrodes can be attached to each of the discrete detectors, or to as many as desired, to form a system including a plurality of the kind of detector shown in Fig. 4. Insulating layers may be added to this structure to control the surface elec ⁇ trical and optical properties.
  • an electrical bias may be applied to a detector by connecting the two electrodes on the detector in series with a battery and load resistor.
  • the electrical bias may be applied by other means, a few examples of which are a pulsing direct current source, an alternating current source, direct connection to a transistor, a microwave generator or from an integrated circuit multiplexer readout chip.
  • Figs. 2 and 3 illustrate the electrical charac ⁇ teristics of the n-type and p-type layers in the photo- conductors in their preferred mercury cadmium telluride embodiments.
  • the n-type detector region atop the detectors has a small, relatively uniform energy band-gap which can be on the order of about 0.1 electron the n-type region. This low concentration produces a wide depletion layer at the PN junction which minimizes para ⁇ sitic tunneling ⁇ leakage currents between the p-type and n-type regions.
  • the binding energy of the p-type region is substantially equal to the full energy band-gap of the detector layer, and may effectively be higher by virtue of being located within the compositionally graded interface between the surface of the epitaxial layer and the substrate. Accordingly, detectors made with this structure and by this method are less susceptible to performance degradation caused by tunneling leakage across the PN junction because of their wider depletion layers; less susceptible to surface leakage since the p-type layer may be more highly doped and located within a wider band-gap portion of the epitaxial layer; and more temperature stable because of the wider band-gap in the trapping p-type layer.
  • One or more of these features, embodied in the new detectors makes them superior to known detectors such as those disclosed in the '223 patent.

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  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Electromagnetism (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Light Receiving Elements (AREA)

Abstract

Des photodétecteurs, qui produisent des détectivités proches de la détectivité maximum théorique, comprennent un substrat à isolation électrique portant un corps de matériau semiconducteur qui comprend une région d'un premier type de conductivité et une région d'un second type de conductivité, où la région d'un premier type de conductivité surplombe et recouvre la jonction avec la région d'un second type de conductivité, et/ou la jonction entre la première et la seconde région sépare les porteurs minoritaires situés dans le région d'un second type de conductivité des porteurs majoritaires situés dans la région d'un premier type de conductivité. Lesdits photodétecteurs produisent des détectivités élevées, où le rayonnement arrivant sur les détecteurs comportent des longueurs d'ondes situées entre environ 1 et environ 25 microns ou davantage, en particulier dans de mauvaises conditions d'environnement.
EP19870900401 1985-12-05 1986-11-24 Structure et procede de fabrication d'un photodetecteur a mode de piegeage Ceased EP0248881A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US80471985A 1985-12-05 1985-12-05
US804719 2004-03-19

Publications (1)

Publication Number Publication Date
EP0248881A1 true EP0248881A1 (fr) 1987-12-16

Family

ID=25189655

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19870900401 Ceased EP0248881A1 (fr) 1985-12-05 1986-11-24 Structure et procede de fabrication d'un photodetecteur a mode de piegeage

Country Status (2)

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EP (1) EP0248881A1 (fr)
WO (1) WO1987003743A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4753684A (en) * 1986-10-31 1988-06-28 The Standard Oil Company Photovoltaic heterojunction structures
US5241196A (en) * 1991-10-15 1993-08-31 Santa Barbara Research Center Photoresponsive device including composition grading and recessed contacts for trapping minority carriers
US5268570A (en) * 1991-12-20 1993-12-07 Litton Systems, Inc. Transmission mode InGaAs photocathode for night vision system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3949223A (en) * 1973-11-01 1976-04-06 Honeywell Inc. Monolithic photoconductive detector array
GB2107930B (en) * 1981-10-21 1985-06-12 Secr Defence Photoconductive strip detectors

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8703743A1 *

Also Published As

Publication number Publication date
WO1987003743A1 (fr) 1987-06-18

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