WO2022045913A1 - Photovoltaic infrared radiation detector from iv-vi polycrystalline semiconductors - Google Patents

Photovoltaic infrared radiation detector from iv-vi polycrystalline semiconductors Download PDF

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WO2022045913A1
WO2022045913A1 PCT/RS2020/000012 RS2020000012W WO2022045913A1 WO 2022045913 A1 WO2022045913 A1 WO 2022045913A1 RS 2020000012 W RS2020000012 W RS 2020000012W WO 2022045913 A1 WO2022045913 A1 WO 2022045913A1
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film
electrode
semiconductor
temperature
detector
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PCT/RS2020/000012
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French (fr)
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Jovana STANOJEV
Jovan Matovic
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Institut Biosens - Istrazivacko Razvojni Institut Za Informacione Tehnologije Biosistema
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Priority to EP20788910.6A priority Critical patent/EP4205183A1/en
Priority to PCT/RS2020/000012 priority patent/WO2022045913A1/en
Publication of WO2022045913A1 publication Critical patent/WO2022045913A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—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 at least one potential-jump barrier or surface barrier, 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 or surface barrier
    • H01L31/103—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the PN homojunction type
    • H01L31/1037—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier or surface barrier the potential barrier being of the PN homojunction type the devices comprising active layers formed only by AIVBVI compounds
    • 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
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • 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
    • H01L31/02—Details
    • H01L31/0232—Optical elements or arrangements associated with the device
    • H01L31/02327—Optical elements or arrangements associated with the device the optical elements being integrated or being directly associated to the device, e.g. back reflectors
    • 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
    • H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
    • H01L31/0324—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIVBVI or AIIBIVCVI chalcogenide compounds, e.g. Pb Sn Te
    • H01L31/0325—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIVBVI or AIIBIVCVI chalcogenide compounds, e.g. Pb Sn Te characterised by the doping material

Definitions

  • the present invention relates to photovoltaic detector of infrared radiation. In another aspect the invention relates to methods for fabrication such detectors.
  • the invention is classified to the field of semiconductor electrical engineering, i.e. to the primary class HO IL and the secondary class H01L 21/04, H01L 31/00, H01L 31/0272, H01L 31/103 and H01L 31/18.
  • the technical problem solved by described invention is fabrication of polycrystalline photovoltaic detector of infrared radiation sensitive in 1 - 5 pm range, which operates at room temperatures. Formation of P-N homojunction, the main structure of the described photovoltaic detectors in an IV - VI semiconductor class with narrow band-gap of ⁇ 0.3 eV at ambient temperatures in a technically simple and affordable manner is still an unsolved challenge.
  • Infrared detectors based on IV- VI lead compounds (lead selenide, lead sulfide, lead telluride) are known in the Art for a long time and described as an example in “METHOD OF PRODUCTION OF LEAD SELENIDE PHOTODETECTOR CELLS” U.S. Pat. 2,997.409, 1961 that discloses the photoconductive detector based on N - type lead selenide. Since then, the design and performance of the detectors have been improved evolutionarily, but successful devices essentially remain unchanged for decades.
  • P - type semiconductor poly crystalline film of IV- VI lead compound around 1 pm thick is deposited between two planar contact electrodes, preferably from gold, subsequently non-selective doped of the entire film with oxygen, or oxygen/halogen dopants, and thereby converts the P - type film into N - type semiconductor, which is sensitive to infrared radiation.
  • Performances of the detector which operates at ambient temperatures, are remarkably high for a photoconductive device sensitive in 1 - 5 pm wavelengths, due to a suppression of the Auger recombination mechanism in the polycrystalline film, although the exact mechanism of the suppression has not yet been fully elucidated.
  • the presented invention disclose a fabrication method of photovoltaic infrared detector by formation of P-N homojunction in P - type polycrystalline film consisting of the IV-VI semiconductor group, more specifically from lead compounds of sulphur, selen or tellurium (PbS, PbSe or PbTe), in the manner that only a layer in the cross-section of that film is converted to N - type semiconductor by precisely controlled heating of one surface of the film to reach a temperature range allowing dopants, oxygen, or mixture of oxygen and halogen elements, to diffuse into the film to predefined depth and concentration, while the portion of the film underneath does not change, i.e. remains P - type semiconductor.
  • PbS, PbSe or PbTe lead compounds of sulphur, selen or tellurium
  • the formed layer of the N-type semiconductor forms core-shell ⁇ .-structure, where the core of the grains remain P-type and the shell of the grains are converted into N-type, preserving the Auger recombination suppression centers, a crucial structure responsible for a high performance of contemporary photoconductive detectors from IV-VI compounds.
  • the exposed surface of the film is heated by irradiation using pulses of electromagnetic energy in range of ultraviolet, visible, or infrared radiation.
  • the wavelength of radiation, pulse duration, pulse frequency, process duration and specific pulse energy are selected in such way, that only thin semiconductor layer just below the irradiated surface reaches the temperature required for diffusion of the dopants in the film, which ranges from 300 to 600 °C.
  • This process in a simple and technically feasible way, forms a P-N barrier in the IV-VI semiconductor film and can be used to fabricate a photovoltaic infrared radiation detector.
  • the second aspect the present invention discloses the detector of infrared radiation consisting of polycrystalline lead sulfide, lead selenide, or lead telluride thin film, which comprises a P- N junction within the cross-section of the film, and the film situated between first nontransparent infrared and reflecting electrode attached to a substrate with proper mechanical and thermal expansion properties, and partially transparent second electrode atop.
  • Figure 1 shows the flow-chart of processes for fabrication of the photovoltaic infrared detector.
  • Figure 2 shows a deposited P-type semiconductor film composed of compound IV-VI, side view.
  • Figure 3 shows the temperature on the exposed surface of the film during irradiation of the film with a pulsed radiation source, results of the model.
  • Figure 4 shows the temperature gradient along the cross section of the film created during irradiation if the exposed surface of the film with a pulsed radiation source, results of the model.
  • Figure 5 shows a formed photovoltaic infrared detector with a P-N homojunction, side view.
  • Figure 6 shows schematically formation of P-N homojunction irradiated with a defocused laser beam.
  • Figure 7 shows the top view of the photovoltaic infrared detector with P-N homojunction.
  • Figure 8 shows the current- voltage curves of a photovoltaic detector in the dark and illuminated by infrared radiation.
  • the detector shown in Figure 5 consists of a substrate 200, a first contact electrode 201, which simultaneously serves as a mirror of incoming infrared radiation, a P-type semiconductor layer 500 of lead sulfide, lead selenide or lead telluride, connected to the N- type layer of that semiconductor 501 to form a P - N homojunction and second contact partially transparent electrode 502.
  • the process of making such a detector consists of steps according to Figure 1.
  • the first step in the fabrication process 100 is preparation of the substrate for deposition of the first electrode.
  • Non-conductive materials such as glass, ceramics, polymers and composite materials and like can be used for the substrate, as well as conductive materials, such as metals or alloys including silicon, copper, silver, gold, tungsten, tantalum, or various alloys.
  • the substrate 200 Prior to the electrode deposition, the substrate 200 is treated with a series of polar solvents, such as ethyl alcohol, isopropyl alcohol or acetone, deionized water, and finally treated in plasma, a common process in the Art.
  • polar solvents such as ethyl alcohol, isopropyl alcohol or acetone, deionized water
  • the next step is the deposition of the first electrode consisting of gold 201, purity of 98% to 99.99%, by physical or chemical deposition in a thickness range from 100 to 500 nm. Thicknesses over 500 nm do not improve performances of the device. If the substrate material, such as silicon, glass or polymer, has a poor adhesion to gold, a 10 nm thick adhesive layer, such as aluminum, titanium or chromium about may be applied to the substrate 200, which represents a common process in the Art, Figure 2.
  • the next step 102 is deposition of a 0.2 - 20 pm thick semiconductor film over the electrode 201, by physical deposition process, thermal vaporization, electron gun, sputtering, plasma deposition, or chemical deposition from a solution common in the Art.
  • Deposited semiconductor film 202 is a P-type polycrystalline film, regardless of the deposition method.
  • Figure 2 shows the structure of the detector after the film deposition. This structure consists of the substrate 200, the first electrode 201, and the semiconductor film 202.
  • the next step 103 is formation of P-N homojunction in the deposited film.
  • the exposed surface of the film 203 in Figure 2 is irradiated by short and strong pulses of electromagnetic radiation from ultraviolet, visible, or infrared radiation at wavelengths shorter than 5 pm. During the irradiation, the absorbed electromagnetic energy is converted into the thermal energy that heats up the exposed surface of the film 203 and the generated heat flows by conduction into the film below the exposed surface 203.
  • the semiconductor Since the semiconductor is nontransparent for wavelengths shorter than 5 pm, i.e. has a high absorption coefficient to the incoming radiation, the radiation is converted into the heat which is predominantly generated just below the exposed surface 203.
  • An important novelty of this process is that the parameters of the pulse source are setup to heat the surface 203 and the layer just below the surface to a temperature range from 300 to 600°C, which is required for controlled diffusion of the dopants into the top part of the film 202.
  • the second layer 204 of the film 202 Just underneath the top part, the second layer 204 of the film 202, remains at a temperature below the diffusion temperature, since it is thermally connected to the substrate 200 that has a thermal capacity 100 - 1000 times greater than the thermal capacity of the film.
  • Such mismatch of thermal capacities is sufficient to dissipate the heat generated on the surface 203, Figure 2.
  • the process can be adjusted to keep temperature of the surface 203 relatively constant in the range sufficient for dopant diffusion, Figure 3 (modeling results).
  • the temperature gradient is formed along the cross section of the semiconductor film 202.
  • Figure 4 shows the temperature profile across the film 202, obtained by modeling of the heat flow within the film, and described under "detector fabrication example”. Heating of the exposed surface 203 is performed in the atmosphere of dopant, oxygen or a mixture of oxygen and a halogen element, iodine or bromine.
  • the film layer 501 is converted into the N-type semiconductor, while the remaining part of the film 500, as thermally firmly connected to the substrate, does not reach the temperature required for dopant diffusion, i.e. remains the P-type semiconductor, thus forming a P-N homojunction in the film 202.
  • an additional heat sink for example a cooler, Peltier element, or forced fluid flow, could be installed during the detector fabrication.
  • the slope of the temperature gradient that determines the depth of the P-N homojunction, the width of the depleted region and the dopant concentration, can be adjusted by irradiation parameters: wavelength, pulse duration, pulse frequency, process duration, and the specific pulse energy. Additionally, the parameters of the P-N homojunction can be adjusted by selecting the thickness of the layer 202, thermal capacity and thermal conductivity of the substrate 200, as well as the heat dissipation methods in order to optimize the infrared detector performance, but the invention disclosed here is not limited by the selection of process parameters.
  • Disclosed photovoltaic detector consists of the semiconducting polycrystalline film 202 of the lead salt from IV - VI compounds, which in its cross-section contains a P-type semiconducting layer 500, N - type semiconducting layer 501 hence forming P - N junction in the polycrystalline material, and embedded between first gold collecting electrode 201, which also serves as a mirror for incoming infrared radiation which pass through the semiconducting film 202, and a partially transparent second collecting electrode 502.
  • the entire structure is situated on a substrate of conduction or non-conducting material with thermal expansion coefficient around 10" 5 /°C.
  • Silicon substrate 200 650 pm thick, was prepared by cleaning with ethanol, isopropyl, deionized water and treatment in plasma, in the manner customary in the Art.
  • the adhesion intermediate layer of titanium of 10 nm thickness was applied to the silicon substrate, and subsequently the gold electrode 201 was deposited by physical deposition at 200 nm thickness.
  • the surface of the semiconductor 203 was irradiated with defocused laser beam, Figure 6.
  • a Nd: YAG diode laser was used, which emits at wavelength of 1064 nm.
  • the laser beam emitted from the laser head 600 was directed by optical lens 601 adjusted in such a way that the focus of the laser beam was out of the exposed film surface 203, i.e. the focus of the laser beam focus was formed in the focal plane 604, Figure 6.
  • the area of irradiated surface of the semiconductor 203 had a diameter of about 2 mm 602, and the surface 203 was heated evenly ( Figure 3).
  • the laser beam energy was sufficient to heat the surface to the temperature required for oxygen diffusion into the layer underneath.
  • Figure 4 shows that the temperature on the surface 203 reached 450 °C, which was sufficient for diffusion of dopants into the film to a depth of 0.1 pm, while the remaining part of the film stayed under 350 °C, i.e no diffusion of dopant occurred (modeling results).
  • Pulsed radiation was emulated by moving the laser beam in the x - y direction with a wipe speed of 3 mm/s.
  • Other process parameters were: laser current 28 A, process duration between 10-15 min. In this process the P-N homojunction 0.1 pm beneath of the surface 203 was formed, Figure 4.
  • the second contact electrode, 502 in the form of a grid, was applied to the second surface of the formed N-type semiconductor 501, Figure 7.
  • Figure 8 shows the measured current-voltage dependence of the detector made in this way, which shows the presence of P-N homojunction in the structure.
  • Curve 1 in Figure 8 is a typical U/I characteristic of a diode
  • curve 2 represents the U/I dependence when the diode is irradiated with an infrared radiation source, which proves that a P-N compound is obtained in the structure and that the device is sensitive to infrared radiation.
  • Infrared detectors based on IV- VI semiconductors are the most widely used detectors for the range 1 - 5 pm due to their high sensitivity when working at room temperature and relatively low cost. These detectors are used in spectroscopy, food and gas analysis, as well as missile guidance. The new detector, described here, would find application in the same areas, but would have superior performance than current devices in terms of speed, sensitivity, specific detectivity (D*) and low operating voltage.

Abstract

A photovoltaic infrared radiation detector is provided by forming a P-N homojunction in the film (202) of polycrystalline IV-VI P- type semiconductor by heating one surface (203) of the film to a temperature at which it comes to the diffusion of dopant, oxygen or a mixture of oxygen and halogen element while the opposite surface of that film is maintained at a temperature lower than the temperature required for diffusion. In this way, in the cross section of the semiconductor film, a temperature gradient is formed, so that the surface of the irradiated film and a layer below it is converted into N- type semiconductor layer (501) while the remaining part forms a P- type semiconductor layer (500). Heating is performed by irradiating the surface of the semiconductor with pulses of electromagnetic energy in the region of ultraviolet, visible or infrared radiation, whereby the electromagnetic radiation is converted into heat which heats the surface (203) of the semiconductor and the layer below the surface to the required temperature. The parameters of the radiation pulse are selected so that only a narrow zone below the surface of the irradiated semiconductor reaches a temperature for dopant diffusion which ranges from 300 to 600 ° C. Thereby, a photodiode with a P - N homojunction in the film cross section is provided which is sensitive to infrared radiation in the wavelength range from 1 to 5 pm.

Description

PHOTOVOLTAIC INFRARED RADIATION DETECTOR FROM IV- VI POLYCRYSTALLINE SEMICONDUCTORS
Technical Field
The present invention relates to photovoltaic detector of infrared radiation. In another aspect the invention relates to methods for fabrication such detectors.
According to the International Patent Classification, the invention is classified to the field of semiconductor electrical engineering, i.e. to the primary class HO IL and the secondary class H01L 21/04, H01L 31/00, H01L 31/0272, H01L 31/103 and H01L 31/18.
Background Art
The technical problem solved by described invention is fabrication of polycrystalline photovoltaic detector of infrared radiation sensitive in 1 - 5 pm range, which operates at room temperatures. Formation of P-N homojunction, the main structure of the described photovoltaic detectors in an IV - VI semiconductor class with narrow band-gap of ~ 0.3 eV at ambient temperatures in a technically simple and affordable manner is still an unsolved challenge. In this invention we describe simple and reliable method for fabrication of the photovoltaic detector consisting of lead salts from IV - VI group of elements with specific detectivity (D*) approaching to the theoretical limit of (D*) = 1.2 1011 cmHz1/2/ W.
Infrared detectors based on IV- VI lead compounds (lead selenide, lead sulfide, lead telluride) are known in the Art for a long time and described as an example in “METHOD OF PRODUCTION OF LEAD SELENIDE PHOTODETECTOR CELLS” U.S. Pat. 2,997.409, 1961 that discloses the photoconductive detector based on N - type lead selenide. Since then, the design and performance of the detectors have been improved evolutionarily, but successful devices essentially remain unchanged for decades. P - type semiconductor poly crystalline film of IV- VI lead compound around 1 pm thick is deposited between two planar contact electrodes, preferably from gold, subsequently non-selective doped of the entire film with oxygen, or oxygen/halogen dopants, and thereby converts the P - type film into N - type semiconductor, which is sensitive to infrared radiation. Performances of the detector, which operates at ambient temperatures, are remarkably high for a photoconductive device sensitive in 1 - 5 pm wavelengths, due to a suppression of the Auger recombination mechanism in the polycrystalline film, although the exact mechanism of the suppression has not yet been fully elucidated. The state of the art of the detector is expressly described in review paper "INTRODUCTION TO LEAD SALT INFRARED DETECTORS" U.S. Pat. ARMY ARMAMENT RESEARCH, DEVELOPMENT AND ENGINEERING CENTER, Feb. 1993.
It is known in the Art that photovoltaic detectors have theoretically better specific detectivity (D*) and faster response time than photoconductive detectors from the equivalent material. However, the fabrication of a photovoltaic detector with a high quality P - N homojunction in IV - VI semiconductor compounds, with poses a narrow band-gap of ~ 0.3 eV, and which operates at ambient temperature, is still an issue US. Pat. “METHOD FOR MAKING AND USING A GROUP IV-VI SEMCONDUCTOR” 4,080,723, 1978, discloses formation of P - N homojunction structure of the detector fabricated by epitaxial process. Due to monocrystalline structure i.e. the absence of the specific mechanism suppression of the Auger recombination, the detector works efficiently only at 77K.
US Pat. 9.887.309.B2 “Photovoltaic lead-salt semiconductor detectors” discloses a heterojunction of Pb salt/Non-Pb salt detector in the aim to provide a high quality P-N heterojunction, preserving the mechanism of suppression of the Auger recombination, however the fabrication method of those detectors is quite complex.
Disclosure of the Invention
In one aspect the presented invention disclose a fabrication method of photovoltaic infrared detector by formation of P-N homojunction in P - type polycrystalline film consisting of the IV-VI semiconductor group, more specifically from lead compounds of sulphur, selen or tellurium (PbS, PbSe or PbTe), in the manner that only a layer in the cross-section of that film is converted to N - type semiconductor by precisely controlled heating of one surface of the film to reach a temperature range allowing dopants, oxygen, or mixture of oxygen and halogen elements, to diffuse into the film to predefined depth and concentration, while the portion of the film underneath does not change, i.e. remains P - type semiconductor. The formed layer of the N-type semiconductor forms core-shell ^.-structure, where the core of the grains remain P-type and the shell of the grains are converted into N-type, preserving the Auger recombination suppression centers, a crucial structure responsible for a high performance of contemporary photoconductive detectors from IV-VI compounds.
The exposed surface of the film is heated by irradiation using pulses of electromagnetic energy in range of ultraviolet, visible, or infrared radiation. The wavelength of radiation, pulse duration, pulse frequency, process duration and specific pulse energy are selected in such way, that only thin semiconductor layer just below the irradiated surface reaches the temperature required for diffusion of the dopants in the film, which ranges from 300 to 600 °C. This process, in a simple and technically feasible way, forms a P-N barrier in the IV-VI semiconductor film and can be used to fabricate a photovoltaic infrared radiation detector.
The second aspect the present invention discloses the detector of infrared radiation consisting of polycrystalline lead sulfide, lead selenide, or lead telluride thin film, which comprises a P- N junction within the cross-section of the film, and the film situated between first nontransparent infrared and reflecting electrode attached to a substrate with proper mechanical and thermal expansion properties, and partially transparent second electrode atop.
Brief Description of the Drawings
Figure 1 shows the flow-chart of processes for fabrication of the photovoltaic infrared detector.
Figure 2 shows a deposited P-type semiconductor film composed of compound IV-VI, side view. Figure 3 shows the temperature on the exposed surface of the film during irradiation of the film with a pulsed radiation source, results of the model.
Figure 4 shows the temperature gradient along the cross section of the film created during irradiation if the exposed surface of the film with a pulsed radiation source, results of the model.
Figure 5 shows a formed photovoltaic infrared detector with a P-N homojunction, side view.
Figure 6 shows schematically formation of P-N homojunction irradiated with a defocused laser beam.
Figure 7 shows the top view of the photovoltaic infrared detector with P-N homojunction.
Figure 8 shows the current- voltage curves of a photovoltaic detector in the dark and illuminated by infrared radiation.
Best Mode for Carrying Out of the Invention
Before disclosing the details of the invention, it is important to understand and emphasize that the present invention is not limited to the construction details illustrated and described below. The terms used in the description of the invention serve to understand the invention and not to limit it.
The detector shown in Figure 5, consists of a substrate 200, a first contact electrode 201, which simultaneously serves as a mirror of incoming infrared radiation, a P-type semiconductor layer 500 of lead sulfide, lead selenide or lead telluride, connected to the N- type layer of that semiconductor 501 to form a P - N homojunction and second contact partially transparent electrode 502. The process of making such a detector consists of steps according to Figure 1.
The first step in the fabrication process 100 is preparation of the substrate for deposition of the first electrode. Non-conductive materials such as glass, ceramics, polymers and composite materials and like can be used for the substrate, as well as conductive materials, such as metals or alloys including silicon, copper, silver, gold, tungsten, tantalum, or various alloys.
Prior to the electrode deposition, the substrate 200 is treated with a series of polar solvents, such as ethyl alcohol, isopropyl alcohol or acetone, deionized water, and finally treated in plasma, a common process in the Art.
The next step is the deposition of the first electrode consisting of gold 201, purity of 98% to 99.99%, by physical or chemical deposition in a thickness range from 100 to 500 nm. Thicknesses over 500 nm do not improve performances of the device. If the substrate material, such as silicon, glass or polymer, has a poor adhesion to gold, a 10 nm thick adhesive layer, such as aluminum, titanium or chromium about may be applied to the substrate 200, which represents a common process in the Art, Figure 2. The next step 102 is deposition of a 0.2 - 20 pm thick semiconductor film over the electrode 201, by physical deposition process, thermal vaporization, electron gun, sputtering, plasma deposition, or chemical deposition from a solution common in the Art.
Deposited semiconductor film 202 is a P-type polycrystalline film, regardless of the deposition method. Figure 2 shows the structure of the detector after the film deposition. This structure consists of the substrate 200, the first electrode 201, and the semiconductor film 202. The next step 103 is formation of P-N homojunction in the deposited film. The exposed surface of the film 203 in Figure 2 is irradiated by short and strong pulses of electromagnetic radiation from ultraviolet, visible, or infrared radiation at wavelengths shorter than 5 pm. During the irradiation, the absorbed electromagnetic energy is converted into the thermal energy that heats up the exposed surface of the film 203 and the generated heat flows by conduction into the film below the exposed surface 203. Since the semiconductor is nontransparent for wavelengths shorter than 5 pm, i.e. has a high absorption coefficient to the incoming radiation, the radiation is converted into the heat which is predominantly generated just below the exposed surface 203. An important novelty of this process is that the parameters of the pulse source are setup to heat the surface 203 and the layer just below the surface to a temperature range from 300 to 600°C, which is required for controlled diffusion of the dopants into the top part of the film 202. Just underneath the top part, the second layer 204 of the film 202, remains at a temperature below the diffusion temperature, since it is thermally connected to the substrate 200 that has a thermal capacity 100 - 1000 times greater than the thermal capacity of the film. Such mismatch of thermal capacities is sufficient to dissipate the heat generated on the surface 203, Figure 2.
In this way, by selecting the pulse source parameters, such as energy density, pulse frequency, process duration, thickness of the film 202, material and dimensions of the substrate 200, the process can be adjusted to keep temperature of the surface 203 relatively constant in the range sufficient for dopant diffusion, Figure 3 (modeling results). Hence, the temperature gradient is formed along the cross section of the semiconductor film 202. Figure 4 shows the temperature profile across the film 202, obtained by modeling of the heat flow within the film, and described under "detector fabrication example”. Heating of the exposed surface 203 is performed in the atmosphere of dopant, oxygen or a mixture of oxygen and a halogen element, iodine or bromine. In this way, the film layer 501 is converted into the N-type semiconductor, while the remaining part of the film 500, as thermally firmly connected to the substrate, does not reach the temperature required for dopant diffusion, i.e. remains the P-type semiconductor, thus forming a P-N homojunction in the film 202. If necessary to maintain the temperature of the film layer 204 below the diffusion temperature, an additional heat sink, for example a cooler, Peltier element, or forced fluid flow, could be installed during the detector fabrication.
The slope of the temperature gradient that determines the depth of the P-N homojunction, the width of the depleted region and the dopant concentration, can be adjusted by irradiation parameters: wavelength, pulse duration, pulse frequency, process duration, and the specific pulse energy. Additionally, the parameters of the P-N homojunction can be adjusted by selecting the thickness of the layer 202, thermal capacity and thermal conductivity of the substrate 200, as well as the heat dissipation methods in order to optimize the infrared detector performance, but the invention disclosed here is not limited by the selection of process parameters. Disclosed photovoltaic detector consists of the semiconducting polycrystalline film 202 of the lead salt from IV - VI compounds, which in its cross-section contains a P-type semiconducting layer 500, N - type semiconducting layer 501 hence forming P - N junction in the polycrystalline material, and embedded between first gold collecting electrode 201, which also serves as a mirror for incoming infrared radiation which pass through the semiconducting film 202, and a partially transparent second collecting electrode 502. The entire structure is situated on a substrate of conduction or non-conducting material with thermal expansion coefficient around 10"5 /°C.
Based on a detailed description, the following text illustrates an example of the detector fabrication.
Silicon substrate 200, 650 pm thick, was prepared by cleaning with ethanol, isopropyl, deionized water and treatment in plasma, in the manner customary in the Art. The adhesion intermediate layer of titanium of 10 nm thickness was applied to the silicon substrate, and subsequently the gold electrode 201 was deposited by physical deposition at 200 nm thickness. A P-type lead selenide film, 202, 2 pm thick, was then applied by thermal deposition, Figure 2. In the next step, the surface of the semiconductor 203 was irradiated with defocused laser beam, Figure 6.
A Nd: YAG diode laser was used, which emits at wavelength of 1064 nm. The laser beam emitted from the laser head 600 was directed by optical lens 601 adjusted in such a way that the focus of the laser beam was out of the exposed film surface 203, i.e. the focus of the laser beam focus was formed in the focal plane 604, Figure 6. Using this defocused laser beam, the area of irradiated surface of the semiconductor 203 had a diameter of about 2 mm 602, and the surface 203 was heated evenly (Figure 3). The laser beam energy was sufficient to heat the surface to the temperature required for oxygen diffusion into the layer underneath. Figure 4 shows that the temperature on the surface 203 reached 450 °C, which was sufficient for diffusion of dopants into the film to a depth of 0.1 pm, while the remaining part of the film stayed under 350 °C, i.e no diffusion of dopant occurred (modeling results). Pulsed radiation was emulated by moving the laser beam in the x - y direction with a wipe speed of 3 mm/s. Other process parameters were: laser current 28 A, process duration between 10-15 min. In this process the P-N homojunction 0.1 pm beneath of the surface 203 was formed, Figure 4. Finally, the second contact electrode, 502, in the form of a grid, was applied to the second surface of the formed N-type semiconductor 501, Figure 7.
Figure 8 shows the measured current-voltage dependence of the detector made in this way, which shows the presence of P-N homojunction in the structure. Curve 1 in Figure 8 is a typical U/I characteristic of a diode, and curve 2 represents the U/I dependence when the diode is irradiated with an infrared radiation source, which proves that a P-N compound is obtained in the structure and that the device is sensitive to infrared radiation.
Industrial Applicability
Infrared detectors based on IV- VI semiconductors are the most widely used detectors for the range 1 - 5 pm due to their high sensitivity when working at room temperature and relatively low cost. These detectors are used in spectroscopy, food and gas analysis, as well as missile guidance. The new detector, described here, would find application in the same areas, but would have superior performance than current devices in terms of speed, sensitivity, specific detectivity (D*) and low operating voltage.

Claims

Claims
1. A method for producing an infrared radiation detector from IV -VI polycrystalline semiconductors of a lead compound, comprising:
(a) preparing the substrate and depositing the first contact electrode of conductive material that provides ohmic contact with the semiconductor film,
(b) deposition of P-type IV-VI polycrystalline film over the first electrode,
(c) heating the exposed surface of the film in an atmosphere of dopants to a temperature at which the dopants partially diffuse through the exposed surface and the top part of the film while maintaining the temperature of the bottom part of that film below the doping temperature, and
(d) deposition of the partially-transparent second contact electrode of conductive material atop the exposed surface of the film.
2. The method according to claim 1, wherein the substrate for electrode deposition is prepared by treatment with a series of polar solvents and followed by the treatment in plasma.
3. The method according to claims 1 or 2, wherein gold with a purity of 98% to 99.99% is applied as the material for the first contact electrode at thickness between 100 and 500 nm, and optionally, an intermediate layer is deposited between gold and the substrate, where the intermediate layer consist from aluminum, chromium or titanium.
4. The method according to any of claims 1, 2 and 3, wherein 0.2 - 20 pm thick semiconductor film of IV-VI compound - lead sulfide, lead selenide or lead telluride, is deposited over the first electrode.
5. The method according to any of claims 1,2,3 and 4, wherein the exposed surface of the film is heated to a temperature between 300-600 °C in the atmosphere of dopants, wherein the dopants diffuse into the semiconductor film in a controlled concentration and a controlled depth through the heated surface only.
6. The method according to any of claims 1 to 5, wherein heating of the exposed surface of the film is performed by irradiating of this surface with pulsed electromagnetic radiation in the ultraviolet, visible or infrared spectrum from a source, such as laser, gas discharge lamp, or other suitable device that can provide the light pulses with required uniformity, frequency, specific energy, and period.
7. The method according to any of claims 1 to 6, wherein the dopants comprise oxygen, a mixture of oxygen and iodine or bromine, or oxygen and a mixture of these halogens, whereby the exposed surface and underlying top layer of the film is converted to N-type polycrystalline semiconductor with core-shell micro crystalline grains, where the crystalline grains shell is N - type semiconductor and the core remains P - type semiconductor.
8. The method according to any of claims 1 to 7, wherein during the heating of the exposed film surface, the generated heat is dissipated from the exposed surface, in such manner that the temperatures of the bottom part of the film remain below the temperature required for the dopants diffusion, preserving P - type semiconductor of the bottom part of the film and consequently forming the P - N homojunction with the top part of the film.
9. The method according to any of claims 1 to 8, wherein the heat generated in the film is extracted naturally, through a substrate having a heat capacity 100-1000 times greater than the capacity of the film, or in a forced manner with a cooler, Peltier element, fluid cooler or a combination of the natural and the forced cooling.
10. The method according to any of claims 1 - 9, wherein the partially-transparent second electrode is applied over the exposed surface of the film by depositing gold with a purity of 98% to 99.99% and thickness of 100 - 500 nm.
11. Photovoltaic infrared radiation detector made of IV- VI poly crystalline semiconductors compounds, wherein the detector consists of a substrate, a first contact electrode, which simultaneously serves as a mirror of the incident infrared radiation, a polycrystalline semiconductor film, comprising a P-type semiconductor layer electrically and optically connected to the first electrode, a N-type semiconductor layer electrically and optically connected to the second electrode, forming in that way P-N homojunction structure in the film.
12. Infrared detector according to claim 11, wherein the substrate is made of non-conductive or conductive material: silicon, glass, ceramic, composite, metal or an alloy to which is deposited the first electrode of gold purity of 98% to 99.99% and thickness of 200 - 500 nm, wherein the first electrode is a contact electrode and a reflective layer for the incident infrared radiation that has not been absorbed in the semiconductor film by passing through.
13. The detector according to claims 11 or 12, wherein a polycrystalline film of PbS, PbSe or PbTe, with thickness of 0.2 - 20 pm contains a P - N homojunction situated within the film cross section in a manner that P- type layer is oriented toward first electrode and the N - type layer is oriented toward second electrode.
14. The detector according to any of claims 11 to 13, wherein the N-type layer consists of microcrystalline grains of core-shell structure, where the grain core is P-type and the grain shell are N-type semiconductor.
15. The detector according to any of claims 11 to 14, wherein the second contact electrode is made of gold with purity of 98% to 99.99% and thickness in range 100 - 500 nm and fabricated in form of a meander, a grid or a mesh.
PCT/RS2020/000012 2020-08-27 2020-08-27 Photovoltaic infrared radiation detector from iv-vi polycrystalline semiconductors WO2022045913A1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2997409A (en) 1959-11-04 1961-08-22 Santa Barbara Res Ct Method of production of lead selenide photodetector cells
US9887309B2 (en) 2012-12-13 2018-02-06 The Board of Regents of the University of Okalahoma Photovoltaic lead-salt semiconductor detectors
WO2018193045A1 (en) * 2017-04-20 2018-10-25 Trinamix Gmbh Optical detector

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2997409A (en) 1959-11-04 1961-08-22 Santa Barbara Res Ct Method of production of lead selenide photodetector cells
US9887309B2 (en) 2012-12-13 2018-02-06 The Board of Regents of the University of Okalahoma Photovoltaic lead-salt semiconductor detectors
WO2018193045A1 (en) * 2017-04-20 2018-10-25 Trinamix Gmbh Optical detector

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
AHMED RASIN ET AL: "Mid-infrared photoresponse of electrodeposited PbSe thin films by laser processing and sensitization", OPTICS AND LASERS IN ENGINEERING, vol. 134, 16 July 2020 (2020-07-16), AMSTERDAM, NL, pages 106299, XP055806364, ISSN: 0143-8166, DOI: 10.1016/j.optlaseng.2020.106299 *
KASIYAN VLADIMIR ET AL: "Infrared detectors based on semiconductor junction of PbSe", JOURNAL OF APPLIED PHYSICS, AMERICAN INSTITUTE OF PHYSICS, US, vol. 112, no. 8, 15 October 2012 (2012-10-15), pages 86101 - 86101, XP012167763, ISSN: 0021-8979, [retrieved on 20121017], DOI: 10.1063/1.4759011 *
MOON-HYUNG JANG ET AL: "Electrical transport properties of sensitized PbSe thin films for IR imaging sensors", SEMICONDUCTOR SCIENCE TECHNOLOGY, IOP PUBLISHING LTD, GB, vol. 34, no. 6, 21 May 2019 (2019-05-21), pages 65009, XP020334609, ISSN: 0268-1242, [retrieved on 20190521], DOI: 10.1088/1361-6641/AB19E7 *
REN Y.X. ET AL: "Fabrication of lead selenide thin film photodiode for near-infrared detection via O2-plasma treatment", JOURNAL OF ALLOYS AND COMPOUNDS, vol. 753, 19 March 2018 (2018-03-19), CH, pages 6 - 10, XP055806362, ISSN: 0925-8388, DOI: 10.1016/j.jallcom.2018.03.227 *
SIMONDS BRIAN J ET AL: "Laser processing for thin film chalcogenide photovoltaics: a review and prospectus", JOURNAL OF PHOTONICS FOR ENERGY, SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 1000 20TH ST. BELLINGHAM WA 98225-6705 USA, vol. 5, no. 1, 19 January 2015 (2015-01-19), pages 50999, XP060053836, DOI: 10.1117/1.JPE.5.050999 *

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