WO2025200077A1 - 一种硅基红外波段雪崩光电探测器及其制备方法 - Google Patents

一种硅基红外波段雪崩光电探测器及其制备方法

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Publication number
WO2025200077A1
WO2025200077A1 PCT/CN2024/090322 CN2024090322W WO2025200077A1 WO 2025200077 A1 WO2025200077 A1 WO 2025200077A1 CN 2024090322 W CN2024090322 W CN 2024090322W WO 2025200077 A1 WO2025200077 A1 WO 2025200077A1
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Prior art keywords
film layer
silicon
layer
photodetector
top metal
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English (en)
French (fr)
Inventor
张程
李孝峰
黄炳林
吴乘焓
王绍军
陈泽锋
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Suzhou University
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Suzhou University
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Priority to US19/278,218 priority Critical patent/US20250351589A1/en
Publication of WO2025200077A1 publication Critical patent/WO2025200077A1/zh
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H10F71/121—The active layers comprising only Group IV materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
    • H10F30/22—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes
    • H10F30/225—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier working in avalanche mode, e.g. avalanche photodiodes
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
    • H10F30/22—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes
    • H10F30/227—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier being a Schottky barrier
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation
    • H10F30/22—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes
    • H10F30/227—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier being a Schottky barrier
    • H10F30/2275—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation the devices having only one potential barrier, e.g. photodiodes the potential barrier being a Schottky barrier being a metal-semiconductor-metal [MSM] Schottky barrier
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to the field of photoelectric detection technology, and in particular to a silicon-based infrared band avalanche photoelectric detector and a preparation method thereof.
  • Silicon-based photodetectors due to their advantages such as mature complementary metal oxide semiconductor (CMOS) manufacturing processes, room-temperature operation, and low production costs, have found widespread application in communications, sensing, industrial detection, and medical fields. With the miniaturization and integration of optoelectronic devices, the development of monolithic silicon-based photodetectors for infrared wavelengths based on mature CMOS technology is a significant step forward in the development of silicon photonics. While silicon-based photodetectors are widely used in the visible spectrum (0.4-0.7 ⁇ m), they are not suitable for detecting near-infrared light with wavelengths greater than 1.1 ⁇ m.
  • CMOS complementary metal oxide semiconductor
  • hot electron photodetection technology is used. Metal materials absorb light to generate hot carriers, which are then injected into semiconductors to generate photocurrent. Since the Schottky energy barrier is lower than the semiconductor band width, hot electron detection technology can be used to expand the photodetection band.
  • This type of hot electron device has the advantages of room temperature self-driving, compatibility with silicon-based processes, adjustable working wavelength, detection bandwidth and polarization sensitivity.
  • the device efficiency is always less than 1%. It is difficult to achieve commercial level, which limits the practical application of such thermal electron devices. Therefore, how to effectively improve the responsivity of photodetectors while expanding the photodetection band is the key to promoting the commercialization of thermal electron photodetectors.
  • the present invention provides a silicon-based infrared band avalanche photodetector and a preparation method thereof.
  • the photodetector has a simple structure and consists of a bottom electrode layer, a silicon film layer and a top metal film layer.
  • the photodetector can form a planar Fabry-Perot cavity structure to achieve narrowband light detection.
  • a strong electric field can be excited in the silicon thin film to induce photoconductivity gain and avalanche effect, thereby improving the light response of the device by 3-4 orders of magnitude, and the narrowband peak wavelength can be adjusted by regulating the thickness of the silicon film layer.
  • a first aspect of the present invention provides a silicon-based infrared band avalanche photodetector, the photodetector comprising a bottom electrode layer, a silicon film layer, and a top metal film layer stacked in sequence;
  • the top metal film layer forms a Schottky contact with the silicon film layer
  • the thickness of the silicon film layer is 10 nm-5 ⁇ m.
  • the silicon-based infrared band avalanche photodetector provided by the present invention consists only of a bottom electrode layer, a silicon film layer and a top metal film layer.
  • the top metal film layer absorbs near-infrared light, and the transition metal layer forms a Schottky junction with the silicon.
  • the photoexcited hot carriers generated cross the Schottky barrier and are injected into the silicon film layer.
  • the hot carriers are then collected by the bottom electrode layer to form a photocurrent, thereby realizing the detection of infrared light below the energy band gap of silicon.
  • the bottom electrode layer forms an ohmic contact with the silicon film layer, which is beneficial for collecting photogenerated carriers; at the same time, the bottom electrode layer acts as an optical reflector to improve the light absorption efficiency of the top metal film layer.
  • the material of the bottom electrode layer is one or more of aluminum, noble metals and transition metals, preferably one or more of titanium, gold, silver, copper, chromium and aluminum.
  • the thickness of the bottom electrode layer is preferably greater than 30 nm, for example, 50-200 nm.
  • the bottom electrode layer is formed by stacking a titanium film layer, a gold film layer, and an aluminum film layer in sequence, with the aluminum film layer being bonded to the silicon film layer. More preferably, the titanium film layer has a thickness greater than 2nm, the gold film layer has a thickness greater than 40nm, and the aluminum film layer has a thickness greater than 30nm.
  • the bottom electrode layer formed by stacking the above three metal films, with the aluminum film layer bonded to the silicon film layer reduces the contact barrier between the bottom electrode layer and the silicon film layer. Furthermore, the stacked titanium and gold film layers increase the reflection of light from the bottom electrode layer, thereby improving the light absorption efficiency of the top metal film layer.
  • the material of the silicon film layer is a lightly doped n-type crystalline silicon material or a lightly doped p-type crystalline silicon material; when the silicon film layer is a lightly doped n-type or p-type silicon film, the silicon film layer forms an ohmic contact with the aluminum film layer; more preferably, the resistivity of the silicon film layer is preferably 0.1-100 ⁇ cm.
  • the thickness of the silicon film layer can be any value within the range of 10-100nm, 100-200nm, 200-300nm, 300-400nm, 400-500nm, 500nm-1 ⁇ m, 1-2 ⁇ m, 2-3 ⁇ m, 3-4 ⁇ m, 4-5 ⁇ m, and more preferably 10nm-1 ⁇ m.
  • the silicon film layer of the silicon-based photodetector protected by the present invention is much smaller than the thickness of the silicon substrate in the existing silicon-based photodetector (several hundred microns). More preferably, the thickness of the silicon film layer is smaller than the depletion layer width of the Schottky junction formed by the silicon film layer and the top metal film layer. It is beneficial for the bottom electrode layer to collect carriers.
  • the material of the top metal film layer is selected from one or more of gold, silver, titanium, copper, chromium, aluminum, titanium nitride, and alloys containing at least two of the above metal elements, and is used to absorb near-infrared light. It forms a Schottky contact with the silicon film layer, and is capable of injecting photoexcited hot carriers generated by light exposure into the silicon film layer across the Schottky barrier.
  • the thickness of the top metal film layer is 5-100 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, etc., including but not limited to the thickness values listed above, and can also be other thickness values within the above range. More preferably, the thickness of the top metal film layer is less than the mean free path of electrons, thereby absorbing most infrared light.
  • the photodetector can achieve a responsivity of 0.1-0.35A/W to the near-infrared band of 1200-2000nm under an applied bias voltage of 1-10V, preferably below 5V (the bias voltage is generally below 5V).
  • a bias voltage When a bias voltage is applied, a high-intensity electric field can be formed in the silicon film between the upper and lower metal film layers, and the carriers gain energy in the electric field to accelerate and produce photoconductivity gain and avalanche multiplication effect, thereby increasing the photocurrent by 3-4 orders of magnitude and improving the photoelectric responsivity.
  • the bias voltage that the photodetector can withstand is related to the thickness of the silicon film. The thicker the silicon film, the greater the bias voltage it can withstand.
  • the bias voltage applied to the photodetector with a silicon film layer thickness of 10nm-5 ⁇ m is preferably 1-10V, and more preferably below 5V.
  • the material of the top metal film layer is one or more of titanium, chromium, and titanium nitride, for example titanium
  • broadband absorption of the 1200-2000nm near-infrared band can be achieved, and the responsivity of the photodetector in the 1200-2000nm band reaches 0.1-0.35A/W, which is comparable to the performance of commercial infrared photodetectors based on germanium and indium gallium arsenide materials.
  • the top metal film layer and the bottom electrode layer form a Fabry-Perot cavity
  • the silicon film layer is the dielectric layer in the Fabry-Perot cavity. Narrowband optical absorption at different infrared wavelengths is achieved by adjusting the thickness of the silicon film layer.
  • an adhesion layer is provided between the top metal film layer and the silicon film layer.
  • the material of the adhesion layer is preferably one or more of titanium, chromium, aluminum, and silver, so as to improve the adhesion between the top metal film layer and the silicon film layer. Adhesion between silicon film layers.
  • Narrowband silicon-based optoelectronic devices have been widely used in various fields due to their ability to selectively respond to specific wavelengths of light while ignoring other wavelengths.
  • current narrowband photodetectors primarily integrate inorganic semiconductors with optical filters, resulting in complex equipment and limiting the detector array's image density.
  • Filter-free narrowband photodetectors constructed using materials with narrowband absorption, leveraging plasmon effects to enhance absorption within a selected wavelength range, or controlling internal quantum efficiency through charge collection and narrowing, suffer from low sensitivity and the complex fabrication of the required micro-nanostructures.
  • the silicon-based photodetector provided by the present invention has a simple structure.
  • the top metal film layer and the bottom electrode layer can form a Fabry-Perot cavity. This allows optical resonance to enhance the optical absorption efficiency of the top metal film layer without the need for micro-nanostructures.
  • the absorption peak wavelength can be controlled by regulating the thickness of the silicon film in the dielectric layer, achieving narrowband light absorption in the infrared band.
  • the photodetector effectively improves the device's responsivity while maintaining its narrowband characteristics.
  • a second aspect of the present invention provides a method for preparing the silicon-based infrared band avalanche photodetector according to the first aspect, comprising the following steps:
  • a top metal film layer and a bottom electrode layer are respectively prepared on the upper and lower surfaces of the silicon film layer by physical and/or chemical methods.
  • the pretreatment includes a process of ultrasonically cleaning the silicon on the insulating layer with an organic solvent and water in sequence;
  • the physical and/or chemical method includes magnetron sputtering deposition and electron beam evaporation.
  • the present invention places the silicon on the insulating layer in a hydrofluoric acid solution and uses the hydrofluoric acid to dissolve the insulating layer (such as silicon dioxide), thereby obtaining an ultra-thin silicon film on the surface of the silicon on the insulating layer.
  • a hydrofluoric acid solution uses the hydrofluoric acid to dissolve the insulating layer (such as silicon dioxide), thereby obtaining an ultra-thin silicon film on the surface of the silicon on the insulating layer.
  • the present invention has the following beneficial effects:
  • the present invention provides a silicon-based infrared band avalanche photodetector, which consists only of a bottom electrode layer, a super It consists of a thin silicon film layer and a top metal film layer. It has a simple structure and is easy to prepare. It is suitable for mass production. It is light and thin, meeting the needs of device miniaturization. And by selecting the material of the top metal film layer, it can achieve broadband or narrowband absorption of the near-infrared band, thereby meeting different application requirements.
  • the silicon-based infrared avalanche photodetector provided by this invention has a planar multilayer structure that is insensitive to polarization and angle of incidence. When used as a broadband absorption device, the tolerance for the thickness of the multilayer thin film structure is relatively large. When the bottom electrode layer, ultrathin silicon film layer, and top metal film layer form a Fabry-Perot cavity, it can achieve narrowband light absorption in the infrared band. The narrowband center wavelength can be controlled by adjusting the thickness of the silicon film, making it suitable for use as a narrowband absorption device.
  • a broadband photodetector prepared by the present invention can achieve a photoresponsivity of nearly 0.3 A/W at 1600-1800 nm under a bias of -2 V, which is an improvement of more than three orders of magnitude compared to the photoresponsivity at zero bias.
  • a narrow-band photodetector prepared by the present invention can achieve a photoresponsivity of 0.2 A/W at 1550 nm under a bias of 1.9 V. By regulating the thickness of the silicon film layer of the device, the narrow-band peak absorption wavelength can be adjusted to 1780 nm.
  • the device's responsivity reaches 0.12 A/W, which is an improvement of more than three orders of magnitude compared to the photoresponsivity at zero bias, and is comparable to the performance of commercial infrared photodetectors based on germanium and indium gallium arsenide materials.
  • FIG2 is a flow chart of preparing a silicon-based infrared band avalanche photodetector according to Example 1;
  • FIG3a is the absorption/reflection spectrum of the silicon-based infrared band avalanche photodetector prepared in Example 1, wherein the solid line is the absorptivity curve and the dotted line is the reflectivity curve;
  • FIG3b is the absorption/reflection spectrum of the photodetector Dark state current-voltage curve;
  • FIG4 is a photocurrent-time curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 under laser irradiation of different wavelengths at zero bias;
  • FIG4 b is a responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 to the wavelength range of 1200 nm to 2000 nm at zero bias;
  • FIG5 is a photocurrent-time curve of the silicon-based infrared band avalanche photodetector prepared in Example 1 at different wavelengths under different bias voltages, wherein FIG5a: -1V bias voltage, FIG5b: -2V bias voltage;
  • FIG7 is a schematic diagram of the structure of a silicon-based infrared band avalanche photodetector prepared in Example 2, wherein 1 is a bottom electrode layer, 2 is a silicon film layer, 3 is an adhesion layer, and 4 is a top metal film layer;
  • FIG8 is a flow chart of preparing a silicon-based infrared band avalanche photodetector according to Example 2;
  • FIG10 is a dark-state current-voltage curve of the silicon-based infrared band avalanche photodetector prepared in Example 2;
  • FIG14 is a responsivity curve of the silicon-based infrared band avalanche photodetector prepared in Example 3 to different wavelengths under zero bias;
  • This embodiment relates to the preparation of a silicon-based infrared band avalanche photodetector with broadband absorption.
  • the structure is shown in FIG1 , which includes, from bottom to top:
  • Bottom electrode layer 1 5nm thick titanium film layer, 70nm thick gold film layer, and 70nm thick aluminum film layer are stacked in sequence from bottom to top;
  • Silicon film layer 2 100 nm thick
  • Top metal film layer 3 20 nm thick titanium film layer.
  • a polished silicon oxide wafer with a top silicon oxide layer of 300 nm thickness is used as a substrate to support the photodetector.
  • FIG2 The preparation process of the above-mentioned photodetector is shown in FIG2 , and is specifically as follows:
  • SOI silicon-on-insulator
  • step (2) The ultra-thin silicon film layer prepared in step (1) was transferred to the surface of the substrate spin-coated with PMMA and air-dried; then, a 70 nm thick aluminum film layer was deposited on the surface of the ultra-thin silicon film layer using magnetron sputtering technology (pre-sputtering was performed for 5 minutes before film deposition, the deposition vacuum was 5 ⁇ 10-4 Pa, and the parameters of magnetron sputtering included: the target material was an aluminum target, the power was 50 W, argon gas was introduced during sputtering, and the pressure in the chamber was 1 Pa.).
  • magnetron sputtering technology pre-sputtering was performed for 5 minutes before film deposition, the deposition vacuum was 5 ⁇ 10-4 Pa, and the parameters of magnetron sputtering included: the target material was an aluminum target, the power was 50 W, argon gas was introduced during sputtering, and the pressure in the chamber was 1 Pa.
  • the film was then transferred to acetone and allowed to stand to obtain a composite film 1 suspended in an organic solvent, which was then transferred to a titanium electrode and air-dried to obtain a composite film 2 comprising a bottom electrode layer and a silicon film layer; wherein the titanium electrode was prepared on a substrate by electron beam evaporation (pre-sputtering for 5 minutes before film deposition, and the parameters of electron beam evaporation included: the evaporation material was titanium particles, the evaporation rate was 0.5 A/s, the pre-evaporation power was 30%, the evaporation power was 30%, the working vacuum was 5e -4 Pa, and the working temperature was 20 degrees.).
  • a layer of photoresist is applied on the silicon film layer of the composite film 2, and a window smaller than the silicon film is exposed using an ultraviolet exposure system. Then, a 20 nm thick titanium metal film layer is deposited using electron beam evaporation technology (pre-sputtering is performed for 5 minutes before film deposition.
  • the parameters of electron beam evaporation include: the evaporation material is titanium gold particles, the evaporation rate is 0.5 A/s, the working vacuum is 5e -4 Pa, and the working temperature is 20 degrees.). Then, the device is immersed in an acetone solution, left to stand for a period of time, taken out and air-dried to prepare a silicon-based photodetector.
  • the thickness of each metal film layer can be ensured to be uniform by controlling various parameters in the deposition process.
  • the test results are shown in FIG3 a .
  • the average absorption rate of the silicon-based photodetector prepared in this embodiment exceeds 50% in the near-infrared band of 1200-2000 nm. This shows that the silicon-based photodetector can achieve broadband absorption in this band.
  • Figure 4a is a photocurrent curve of the photodetector under zero bias voltage when the light is turned on and off over time to near-infrared light of different wavelengths.
  • the wavelength range is from 1100nm to 2000nm, with an interval of 100nm.
  • the photodetector has an electrical photoresponse to near-infrared light of 1100nm to 2000nm; and by measuring the photocurrent of the photodetector with a smaller wavelength interval and the corresponding optical power of the laser light, the response curve of the photodetector in the near-infrared band of 1200nm to 2000nm as shown in Figure 4b is obtained, further illustrating that the photodetector prepared in this embodiment achieves broadband absorption in the band of 1200nm to 2000nm.
  • Figure 5 shows the photocurrent-time curves of the photodetector under different bias voltages and laser irradiation of different wavelengths, with wavelengths ranging from 1100nm to 2000nm, with intervals of 100nm.
  • Figure 5a shows the photocurrent-time curve under a -1V bias voltage.
  • the photocurrent at 1600nm is 150 ⁇ A, a 154-fold gain compared to the 1 ⁇ A photocurrent at 1600nm under a 0V bias voltage.
  • Figure 5b shows the photocurrent-time curve under a -2V bias voltage.
  • the photocurrent at 1600nm is 1.492mA, a 1492-fold gain compared to the 1 ⁇ A photocurrent at 1600nm under a 0V bias voltage.
  • the dark current of the sample is relatively stable at high gain.
  • a polished silicon oxide wafer with a top silicon oxide layer of 300 nm thickness is used as a substrate to support the photodetector.
  • FIG8 The preparation process of the above-mentioned photodetector is shown in FIG8 , and is specifically as follows:
  • SOI silicon-on-insulator
  • step (2) The ultra-thin silicon film layer prepared in step (1) was transferred to the surface of the substrate spin-coated with PMMA and air-dried; then, a 70 nm thick aluminum film layer was deposited on the surface of the ultra-thin silicon film layer using magnetron sputtering technology (pre-sputtering was performed for 5 minutes before film deposition, the deposition vacuum was 5 ⁇ 10-4 Pa, and the parameters of magnetron sputtering included: the target material was an aluminum target, the power was 50 W, argon gas was introduced during sputtering, and the pressure in the chamber was 1 Pa.).
  • magnetron sputtering technology pre-sputtering was performed for 5 minutes before film deposition, the deposition vacuum was 5 ⁇ 10-4 Pa, and the parameters of magnetron sputtering included: the target material was an aluminum target, the power was 50 W, argon gas was introduced during sputtering, and the pressure in the chamber was 1 Pa.
  • the film was then transferred to acetone and allowed to stand to obtain a composite film 1 suspended in an organic solvent, which was then transferred to a titanium electrode and air-dried to obtain a composite film 2 comprising a bottom electrode layer and a silicon film layer; wherein the titanium electrode was prepared on a substrate by electron beam evaporation (pre-sputtering for 5 minutes before film deposition, and the parameters of electron beam evaporation included: the evaporation material was titanium particles, the evaporation rate was 0.5 A/s, the pre-evaporation power was 30%, the evaporation power was 30%, the working vacuum was 5e -4 Pa, and the working temperature was 20 degrees.).
  • a layer of photoresist is applied on the silicon film layer of the composite film 2, and a window smaller than the silicon film is exposed using an ultraviolet exposure system. Then, a 5 nm thick titanium film layer and a 14 nm thick gold film layer are deposited using electron beam evaporation technology (pre-sputtering is performed for 5 minutes before film deposition.
  • the parameters of electron beam evaporation include: the evaporation material is titanium or gold particles, the evaporation rate is 0.5 A/s, the pre-evaporation power is 30%, the evaporation power is 30%, the working vacuum is 5e -4 Pa, and the working temperature is 20 degrees.). Then, the device is immersed in an acetone solution, left to stand for a period of time, taken out and air-dried to prepare a silicon-based photodetector.
  • the thickness of each metal film layer can be ensured to be uniform by controlling various parameters in the deposition process.
  • the test results are shown in FIG9 .
  • the reflectivity of the silicon-based photodetector prepared in this embodiment at 1550 nm in the near-infrared band is only 20%, the absorption rate can reach 80%, and the half-width of the absorption wavelength is 200 nm. It can be seen that the silicon-based photodetector can achieve narrow-band absorption in this band.
  • FIG10 is a current-voltage curve of the photodetector between -1 V and 1 V.
  • the top metal film and the silicon film form a Schottky junction
  • the silicon film and the aluminum film in the bottom electrode layer form an ohmic contact.
  • Figure 11 shows the responsivity curve of the photodetector in the near-infrared band of 1200nm to 2000nm under zero bias.
  • the narrow-band response curve is consistent with the trend of the optical reflectance spectrum, further demonstrating that the photodetector can achieve narrow-band absorption at a wavelength of 1550nm.
  • Figure 12 shows the responsivity curve of the photodetector in the near-infrared band of 1200nm to 2000nm under a bias of 1.9V.
  • the wavelength of the highest response is still at 1550nm, and the half-width of the narrow-band response remains at 200nm, indicating that applying a bias does not change the narrow-band absorption characteristics of the photodetector; in addition, the responsivity of the photodetector at 1550nm under a bias of 1.9V reaches 0.2A/W, which is 3 orders of magnitude higher than the responsivity gain under a bias of 0V, which is comparable to the performance of commercial detectors based on germanium and indium gallium arsenide materials.
  • This embodiment relates to a silicon-based infrared band avalanche photodetector with narrow-band absorption.
  • the only difference from Example 2 is that the thickness of the silicon film layer is 190 nm, and the rest are the same.
  • the test results are shown in Figure 13.
  • the reflectivity of the silicon-based photodetector prepared in this embodiment at 1780 nm in the near-infrared band is 35%, the absorption rate reaches 65%, and the half-maximum width of the absorption wavelength is 220 nm, indicating that the silicon-based photodetector prepared in this embodiment can achieve narrow-band absorption in the 1780 nm band.
  • the thickness of the silicon film layer in the photodetector prepared in Example 2 can achieve narrow-band absorption of different wavelength bands.
  • Figure 14 shows the responsivity curve of the photodetector in the near-infrared band of 1400nm to 2000nm under zero bias.
  • the narrow-band response curve obtained is consistent with the trend of the optical reflectance spectrum, further demonstrating that the photodetector can achieve narrow-band absorption at a wavelength of 1780nm.
  • the silicon-based photodetector provided by the present invention can achieve broadband or narrowband absorption of near-infrared light by adjusting the material of the top metal film layer, thereby meeting different application requirements. Furthermore, when biased, this silicon-based photodetector can generate an avalanche multiplication effect, significantly improving the device's photoresponsivity, bringing the responsivity of the silicon-based photodetector to a level comparable to that of commercial detectors based on germanium and indium gallium arsenide materials.

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Abstract

本发明公开了一种硅基红外波段雪崩光电探测器及其制备方法，包括依次叠层设置的底部电极层、硅膜层以及顶部金属膜层，其中，底部电极层与硅膜层形成欧姆接触，顶部金属膜层与硅膜层形成肖特基接触；该光电探测器通过顶部金属膜层吸收近红外光，产生热载流子注入到硅膜层中，然后被底部电极层收集形成光电流，从而实现了对低于硅能量带隙的红外光的探测；且通过调整硅膜层的厚度以及顶部金属膜层的种类，可实现不同红外波长处的宽带或窄带光学高吸收。此外，该光电探测器在施加3V以下偏压时，可产生光电导增益和雪崩效应，将光电响应度提高3-4个数量级，在1200-2000nm波段的响应度达到0.1-0.35A/W，与商用锗和铟镓砷红外光电探测器性能相当。

Description

一种硅基红外波段雪崩光电探测器及其制备方法 技术领域
本发明涉及光电探测技术领域，具体涉及一种硅基红外波段雪崩光电探测器及其制备方法。
背景技术
硅基光电探测器因具有成熟的互补金属氧化物半导体(CMOS)制造工艺、室温工作、生产成本低等优势在通信、传感、工业检测以及医疗等领域都有着广泛的应用。随着光电器件向着小型化、集成化发展，基于成熟的CMOS技术开发单片上集成的、用于红外波长的硅基光电探测器是硅光子技术发展的重要一步。虽然在可见光谱范围(0.4-0.7μm)中硅基光电探测器已经得到广泛应用，但它们不适合探测波长大于1.1μm的近红外光，这是因为这些近红外光子能量不足以克服硅带隙(1.12eV)并诱导电子-空穴对的光产生，即不产生光电流。为应对硅不吸收红外光这一问题，硅光子学行业提出的一种解决方案是利用低带隙的锗(0.67eV)与硅结合，或者用晶圆键合技术在硅片上集成III-V、II-VI、VI-VI族化合物半导体。因此商用红外光电探测器多采用基于锗、锑化铟、铟镓砷和碲镉汞材料，虽然能够实现红外波段的光探测，但是器件需要用到复杂的制备工艺，并且使用的III-V、II-VI、VI-VI族材料与硅基CMOS数字读出电路不兼容，且材料与器件稳定性差。
为克服上述问题，采用热电子光电探测技术，利用金属材料吸收光产生热载流子，然后注入到半导体中产生光电流，由于肖特基能量势垒低于半导体能带宽度，因此可利用热电子探测技术来拓展光电探测波段。这类热电子器件具有室温自驱动，与硅基工艺兼容，工作波长、探测带宽以及偏振敏感度可调等优点。然而因为热电子光电探测中存在各种能量损耗，器件效率始终低于1％， 难以达到商用水平，从而限制了此类热电子器件的实际应用。因此如何在拓展光电探测波段的同时有效提高光电探测器的响应度，是推动热电子光电探测器商业化的关键。
目前为提高这类热电子光电探测器的响应度，Cheng Zhang等人设计了金包裹的硅纳米锥结构[Adv.Funct.Mater.2023,2304368]，沿锥形针尖的混合等离子体模式提供了巨大的场增强和宽带响应。Ilya Goykhman等人报道了一种片上集成金属石墨烯-硅等离子体肖特基光电探测器[Nano Lett.2016,16,3005-3013]，在3V的反向偏置下实现了雪崩倍增，响应率为0.37A/W。这类光电探测器虽在一定程度上提高了响应度，但独特的纳米结构对加工要求高，不适于实际生产，且探测波段受限，很少能探测到红外波段。
基于此，亟需一种结构简单，可探测波长大于1.1μm的近红外光，且性能与商用锗和铟镓砷等红外光电探测器相当的硅基室温工作的红外光电探测器。
发明内容
为解决上述技术问题，本发明提供了一种硅基红外波段雪崩光电探测器及其制备方法，该光电探测器的结构简单，由底部电极层、硅膜层以及顶部金属膜层组成，可探测1200-2000nm波段的近红外光，且在施加小偏压下即可在硅薄膜中激发强电场引发光电导增益和雪崩效应，使得器件响应度与商用锗和铟镓砷等红外光电探测器相当；此外，通过对顶部金属膜层材料的选择，可使光电探测器形成平面法布里-珀罗腔结构，实现窄带光探测，在施加小偏压条件下可使硅薄膜中激发强电场引发光电导增益和雪崩效应，将器件的光响应度提高3-4个数量级，且可通过调控硅膜层的厚度，实现对窄带峰值波长的调节。
本发明提供以下技术方案：
本发明第一方面提供了一种硅基红外波段雪崩光电探测器，所述光电探测器包括依次叠层设置的底部电极层、硅膜层以及顶部金属膜层；
所述顶部金属膜层与所述硅膜层形成肖特基接触；
所述硅膜层厚度为10nm-5μm。
本发明所提供的一种硅基红外波段雪崩光电探测器仅由底部电极层、硅膜层以及顶部金属膜层组成，其中通过顶部金属膜层吸收近红外光，过渡金属层与硅形成肖特基结，顶部金属膜层受光照后产生的光激发热载流子越过肖特基势垒注入到硅膜层中，然后被底部电极层收集形成光电流，从而实现了对低于硅能量带隙的红外光的探测。
进一步地，所述底部电极层与所述硅膜层形成欧姆接触，有利于收集光生载流子；同时底部电极层作为光学反射器可提高顶部金属膜层对光的吸收效率。
进一步地，所述底部电极层的材料为铝、贵金属和过渡金属中的一种或多种，优选为钛、金、银、铜、铬、铝中一种或多种。
进一步地，所述底部电极层的厚度优选大于30nm，例如50-200nm。
进一步地，所述底部电极层由钛膜层、金膜层以及铝膜层依次叠层得到，所述铝膜层与所述硅膜层相贴合；更优选地，所述钛膜层的厚度大于2nm，金膜层的厚度大于40nm，铝膜层的厚度大于30nm。由以上三种金属膜叠层得到的底部电极层，且铝膜层与硅膜层相贴合，一方面降低底部电极层与硅膜层之间的接触势垒，同时叠加的钛膜层及金膜层可提高底部电极层对光的反射，从而提高顶部金属膜层对光的吸收效率。
进一步地，所述硅膜层的材料为轻掺杂的n型晶体硅材料或轻掺杂的p型晶体硅材料；当硅膜层为轻掺杂的n型或p型硅膜时，硅膜层与铝膜层形成欧姆接触；更优选地，所述硅膜层的电阻率优选为0.1-100Ω·cm。
进一步地，所述硅膜层的厚度可以为10-100nm、100-200nm、200-300nm、300-400nm、400-500nm、500nm-1μm、1-2μm、2-3μm、3-4μm、4-5μm内的任一值，更优选为10nm-1μm。本发明所保护的硅基光电探测器的硅膜层远小于现有硅基光电探测器中硅基底的厚度(几百微米)，更优选地，所述硅膜层的厚度小于所述硅膜层与所述顶部金属膜层形成的肖特基结的耗尽层宽，有 利于底部电极层对载流子的收集。
进一步地，所述顶部金属膜层的材料选自金、银、钛、铜、铬、铝、氮化钛及包含上述至少两种金属元素的合金中的一种或多种，用以吸收近红外光，且与硅膜层形成肖特基接触，能够将受光照后产生的光激发热载流子越过肖特基势垒注入到硅膜层中；优选地，所述顶部金属膜层的厚度为5-100nm，例如10nm、20nm、30nm、40nm、50nm、60nm、70nm、80nm、90nm等，包括但不限于上述所列举的厚度值，也可为上述范围内其它的厚度值。更优选地，所述顶部金属膜层的厚度小于电子平均自由程，从而可吸收大部分红外光。
进一步地，所述光电探测器在施加1-10V偏压下，优选为5V以下，对1200-2000nm近红外波段的响应度可达0.1-0.35A/W(偏压一般在5V以下)。当施加偏压时，在上下金属膜层之间的硅薄膜中可形成高强度电场，载流子在电场中获得能量加速产生光电导增益和雪崩倍增效应，从而将光电流提高3-4个数量级，提高光电响应度。但光电探测器可承受的偏压大小与硅薄膜的厚度有关，硅薄膜厚度越大可承受的偏压越大，当硅薄膜厚度较小时，施加偏压过大会将器件击穿，无法工作，硅膜层厚度为10nm-5μm的光电探测器施加的偏压优选为1-10V，更优选为5V以下。
进一步地，当所述顶部金属膜层的材料为钛、铬、氮化钛中的一种或多种时，例如钛，可实现对1200-2000nm近红外波段的宽带吸收，且光电探测器在1200-2000nm波段的响应度达到0.1-0.35A/W，与商用的基于锗和铟镓砷材料的红外光电探测器性能相当。
进一步地，当所述顶部金属膜层的材料为金、银、铜、铝及包含上述至少两种金属元素的合金中的一种或多种时，所述顶部金属膜层与所述底部电极层形成法布里-珀罗腔，所述硅膜层为所述法布里-珀罗腔中的介质层，通过调整所述硅膜层的厚度实现不同红外波长处的窄带光学吸收。优选地，当所述顶部金属膜层为金时，所述顶部金属膜层与所述硅膜层之间设置有黏附层，所述黏附层的材料优选为钛、铬、铝、银中的一种或多种，用以提高顶部金属膜层与 硅膜层之间的粘附力。
窄带硅基光电子器件由于能够选择性地响应特定波长的光而对其他波长的光没有响应，已被广泛应用各领域。但目前窄带光电探测器主要由无机半导体与滤光片集成在一起，存在设备复杂且限制了探测器阵列像数密度；而通过使用具有窄带吸收的材料、利用等离子体效应增强选定波长范围内的吸收或通过电荷收集缩窄控制内部量子效率等方法构建的无滤光片窄带光探测器，存在灵敏度低、所需微纳结构加工工艺复杂等问题。
本发明所提供的硅基光电探测器，结构简单，且通过对顶部金属膜层材料的选择，可使顶部金属膜层与底部电极层形成法布里-珀罗腔，从而在无需借助微纳结构的情况下，即可实现光学共振增强顶部金属膜层的光学吸收效率，且吸收峰波长可通过调控介质层硅薄膜厚度来控制，实现红外波段的窄带光吸收。并且，该光电探测器在施加偏压下，可有效提高器件的响应度，同时能够保持窄带特性。
本发明第二方面提供了一种第一方面所述的硅基红外波段雪崩光电探测器的制备方法，包括以下步骤：
将预处理后的绝缘层上硅基片置于氢氟酸溶液中，去除绝缘层得到所述硅膜层；
通过物理和/或化学方法分别在所述硅膜层的上、下表面制备顶部金属膜层、底部电极层。
进一步地，所述预处理包括用有机溶剂、水依次对绝缘层上硅进行超声清洗的过程；所述物理和/或化学方法包括磁控溅射沉积、电子束蒸镀。
本发明通过将绝缘层上硅置于氢氟酸溶液中，利用氢氟酸溶解绝缘层(例如二氧化硅)，从而获得绝缘层上硅表面的超薄硅膜。
与现有技术相比，本发明的有益效果：
1、本发明提供了一种硅基红外波段雪崩光电探测器，仅由底部电极层、超 薄硅膜层以及顶部金属膜层组成，结构简单易制备，适于批量化生产，质轻且薄，满足器件微型化需求；且可通过对顶部金属膜层材料的选择，实现对近红外波段的宽带吸收或窄带吸收，从而满足不同应用需求。
2、本发明所提供的硅基红外波段雪崩光电探测器具有平面多层结构，对偏振及入射角度不敏感。作为宽带吸收器件时，对多层薄膜结构的允许厚度误差较大。当底部电极层、超薄硅膜层以及顶部金属膜层形成法布里-珀罗腔时，能够在红外波段实现窄带光吸收，且窄带中心波长可以通过调节硅薄膜厚度来控制，可作为窄带吸收器件。
3、在上述光电探测器两端施加偏压时，位于上、下金属膜层之间的硅膜层中会产生强电场，载流子在电场中获得能量加速产生光电导增益和雪崩倍增效应，从而将光电流提高3-4个数量级，大大提高器件对近红外光波长的响应度；且当作为窄带吸收器件使，施加偏压可提高器件的响应度，同时半高宽基本不变，仍可保持窄带特性。例如，本发明制备的一宽带光电探测器，在-2V偏压下，可使器件在1600-1800nm处的光响应度接近0.3A/W，相对于零偏压下的光响应度有3个数量级以上的提高；另外，制备的一窄带光电探测器，在1.9V偏压下，可使器件在1550nm处的光响应度达到0.2A/W，通过调控器件硅膜层的厚度，可将窄带峰值吸收波长调节到1780nm处，在3V偏压下器件的响应度达到0.12A/W，相对于零偏压下的光响应度有3个数量级以上的提高，与商用的基于锗和铟镓砷材料的红外光电探测器性能相当。
附图说明
图1为实施例1制备的硅基红外波段雪崩光电探测器的结构示意图，其中，1为底部电极层、2为硅膜层、3为顶部金属膜层；
图2为实施例1制备硅基红外波段雪崩光电探测器的流程图；
图3中：图3a为实施例1制备的硅基红外波段雪崩光电探测器对光的吸收/反射谱图，实线为吸收率曲线，虚线为反射率曲线；图3b为光电探测器的 暗态电流-电压曲线；
图4中：图4a为实施例1制备的硅基红外波段雪崩光电探测器在零偏压下不同波长的激光照射下的光电流时间曲线；图4b为实施例1制备的硅基红外波段雪崩光电探测器在零偏压下对1200nm～2000nm波段的响应度曲线；
图5为实施例1制备的硅基红外波段雪崩光电探测器在不同偏压下不同波长处的光电流时间曲线，其中图5a：-1V偏压、图5b：-2V偏压；
图6中：图6a为实施例1制备的硅基红外波段雪崩光电探测器在不同偏压(-0.5V、-1V、-1.5V、-2V)下的响应度曲线；图6b为实施例1制备的硅基红外波段雪崩光电探测器在不同偏压的光电流增益曲线，以波长1600nm为例；
图7为实施例2制备的硅基红外波段雪崩光电探测器的结构示意图，其中，1为底部电极层、2为硅膜层、3为黏附层、4为顶部金属膜层；
图8为实施例2制备硅基红外波段雪崩光电探测器的流程图；
图9为实施例2制备的硅基红外波段雪崩光电探测器对光的吸收/反射谱图，实线为反射率曲线，虚线为吸收率曲线；
图10为实施例2制备的硅基红外波段雪崩光电探测器的暗态电流-电压曲线；
图11为实施例2制备的硅基红外波段雪崩光电探测器在零偏压下对不同波长的响应度曲线；
图12为实施例2制备的硅基红外波段雪崩光电探测器在1.9V偏压下对不同波长的响应度曲线；
图13为实施例3制备的硅基红外波段雪崩光电探测器对光的吸收/反射谱图，实线为反射率曲线，虚线为吸收率曲线；
图14为实施例3制备的硅基红外波段雪崩光电探测器在零偏压下对不同波长的响应度曲线；
图15为实施例3制备的硅基红外波段雪崩光电探测器在3V偏压下对不同波长的响应度曲线。
具体实施方式
除非另有定义，本文所使用的所有的技术和科学术语与属于本发明的技术领域的技术人员通常理解的含义相同。本文中在本发明的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本发明。本文所使用的术语“及/或”包括一个或多个相关的所列项目的任意的和所有的组合。本发明所述的“包括”或“包含”，意指其除所述组分外，还可以包括或包含其他组分。本发明所述的“包括”或“包含”，还可以替换为封闭式的“为”或“由......组成”。
下面结合实施例及附图对本发明作进一步说明，以使本领域的技术人员可以更好地理解本发明并能予以实施，但所举实施例不作为对本发明的限定。
实施例1
本实施例涉及一种宽带吸收的硅基红外波段雪崩光电探测器的制备，结构如图1所示，由下至上包括：
底部电极层1：5nm厚的钛膜层、70nm厚的金膜层、70nm厚的铝膜层由下至上依次叠层设置；
硅膜层2：100nm厚；
顶部金属膜层3：20nm厚的钛膜层。
采用顶层氧化硅为300nm厚的抛光氧化硅片作为基底承载该光电探测器。
上述光电探测器的制备过程如图2所示，具体如下：
(1)将经过丙酮、乙醇、去离子水超声清洗的商用绝缘层上硅(SOI)基底置于体积百分比为40％的氢氟酸溶液中，去除氧化硅层后，得到悬浮在溶液中的硅薄膜。
(2)把步骤(1)制备的超薄硅膜层转移到旋涂了PMMA的衬底表面，并风干；然后在超薄硅膜层的表面使用磁控溅射技术沉积70nm厚的铝膜层(薄膜沉积前先进行5min预溅射，沉积真空度为5×10-4Pa，磁控溅射的参数包括：靶材为铝靶，功率为50W，溅射时通入氩气，腔内压强为1Pa。)。
(3)然后转移至丙酮中静置，得到悬浮在有机溶剂中的复合薄膜1，将其转移至钛金电极上并风干，制备得到包含底部电极层-硅膜层的复合薄膜2；其中，钛金电极采用电子束蒸镀的方法在基底上制备得到(薄膜沉积前先进行5min预溅射，电子束蒸发的参数包括：蒸发料为钛金颗粒，蒸发速率为0.5A/s，预蒸发功率为30％，蒸发功率为30％，工作真空为5e-4Pa，工作温度为20度。)。
(4)在复合薄膜2的硅膜层上涂一层光刻胶，利用紫外曝光系统曝光出比硅薄膜小的窗口，然后使用电子束蒸镀的技术沉积20nm厚的钛金属膜层(薄膜沉积前先进行5min预溅射，电子束蒸发的参数包括：蒸发料为钛金颗粒，蒸发速率为0.5A/s，工作真空为5e-4Pa，工作温度为20度。)，随后把器件浸泡在丙酮溶液中，静置一段时间后取出并风干，制备得到硅基光电探测器。
通过上述制备方法制备的光电探测器，其中各金属膜层的厚度可通过对沉积工艺中各参数的控制，从而保证金属膜层厚度均匀性。
性能测试：
对本实施例制备的硅基光电探测器的光学及电学性能进行测试，具体如下：
(1)利用光谱仪测试光电探测器的光学吸收率及反射率
测试结果如图3a所示，本实施例制备的硅基光电探测器在近红外波段1200-2000nm内平均吸收率超过50％，由此可知，该硅基光电探测器可实现该波段的宽带吸收。
(2)利用微区测试平台测试光电探测器的电学响应
图3b为光电探测器在电压-2V至2V间的电流-电压曲线，由图可知，顶部金属膜与硅膜形成肖特基结，硅膜与底部电极层中的铝膜为欧姆接触。
(3)研究偏压对光电探测器响应度的影响
图4a为光电探测器在零偏压下对不同波长近红外光随着时间开光关光的光电流曲线，波长范围由1100nm～2000nm，间隔100nm，由图可知，该光电探测器对1100nm～2000nm的近红外光都具有电学上的光响应；并通过测量波长间隔更小的光电探测器的光电流以及对应的激光器出光的光功率，得到如图4b所示的光电探测器在近红外波段1200nm～2000nm内的响应度曲线，进一步说明本实施例制备的光电探测器实现了1200nm～2000nm波段的宽带吸收。
图5为光电探测器在不同偏压下不同波长的激光照射下的光电流时间曲线，波长范围由1100nm～2000nm，间隔100nm。其中，图5a为-1V偏压下的光电流时间曲线，由图可知，1600nm处的光电流有150μA，相较于0V偏压下的1600nm光电流1μA有154倍的增益。图5b为-2V偏压下的光电流时间曲线，由图可知，1600nm处的光电流有1.492mA，相较于0V偏压下的1600nm光电流1μA有1492倍的增益，且样品在高增益下的暗电流较为稳定。
图6a为光电探测器在不同偏压下对不同波长光的光响应度曲线。由图可知，随着偏压的增加，光响应度也明显增加，当偏压增大至-2V时，对1600-1800nm的近红外光的响应度接近0.3A/W。且由图6b(不同偏压下对1600nm波长的光电流相对零偏压下的增益)可知，随着偏压的增加，光电流的增益也随之增加，最高的增益倍数可达3-4个数量级。
实施例2
本实施例涉及一种窄带吸收的硅基红外波段雪崩光电探测器的制备，结构如图7所示，由下至上包括：
底部电极层1：5nm厚的钛膜层、70nm厚的金膜层、70nm厚的铝膜层由下至上依次叠层设置；
硅膜层2：100nm厚；
黏附层3：5nm厚的钛膜层；
顶部金属膜层4：14nm金膜层。
采用顶层氧化硅为300nm厚的抛光氧化硅片作为基底承载该光电探测器。
上述光电探测器的制备过程如图8所示，具体如下：
(1)将经过丙酮、乙醇、去离子水超声清洗的商用绝缘层上硅(SOI)基底置于体积百分比为40％的氢氟酸溶液中，去除氧化硅层后，得到悬浮在溶液中的硅薄膜。
(2)把步骤(1)制备的超薄硅膜层转移到旋涂了PMMA的衬底表面，并风干；然后在超薄硅膜层的表面使用磁控溅射技术沉积70nm厚的铝膜层(薄膜沉积前先进行5min预溅射，沉积真空度为5×10-4Pa，磁控溅射的参数包括：靶材为铝靶，功率为50W，溅射时通入氩气，腔内压强为1Pa。)。
(3)然后转移至丙酮中静置，得到悬浮在有机溶剂中的复合薄膜1，将其转移至钛金电极上并风干，制备得到包含底部电极层-硅膜层的复合薄膜2；其中，钛金电极采用电子束蒸镀的方法在基底上制备得到(薄膜沉积前先进行5min预溅射，电子束蒸发的参数包括：蒸发料为钛金颗粒，蒸发速率为0.5A/s，预蒸发功率为30％，蒸发功率为30％，工作真空为5e-4Pa，工作温度为20度。)。
(4)在复合薄膜2的硅膜层上涂一层光刻胶，利用紫外曝光系统曝光出比硅薄膜小的窗口，然后使用电子束蒸镀的技术沉积5nm厚的钛膜层及14nm的金膜层(薄膜沉积前先进行5min预溅射，电子束蒸发的参数包括：蒸发料为钛或者是金颗粒，蒸发速率为0.5A/s，预蒸发功率为30％，蒸发功率为30％，工作真空为5e-4Pa，工作温度为20度。)，随后把器件浸泡在丙酮溶液中，静置一段时间后取出并风干，制备得到硅基光电探测器。
通过上述制备方法制备的光电探测器，其中各金属膜层的厚度可通过对沉积工艺中各参数的控制，从而保证金属膜层厚度均匀性。
性能测试：
对本实施例制备的硅基光电探测器的光学及电学性能进行测试，具体如下：
(1)利用光谱仪测试光电探测器的光学吸收率及反射率
测试结果如图9所示，本实施例制备的硅基光电探测器在近红外波段1550处的反射率仅为20％，吸收率可达80％，且吸收波长半高宽为200nm，由此可知，该硅基光电探测器可实现该波段的窄带吸收。
(2)利用微区测试平台测试光电探测器的电学响应
图10为光电探测器在电压-1V至1V间的电流-电压曲线，由图可知，顶部金属膜与硅膜形成肖特基结，硅膜与底部电极层中的铝膜为欧姆接触。
(3)研究偏压对光电探测器响应度的影响
图11为光电探测器在零偏压下在近红外波段1200nm～2000nm内的响应度曲线，得到与光学反射谱趋势一致的窄带响应曲线，进一步说明该光电探测器可实现波长1550nm处的窄带吸收。
图12为光电探测器在1.9V偏压下在近红外波段1200nm～2000nm内的响应度曲线，响应最高的波长仍在1550nm处，且窄带响应的半高宽仍保持在200nm，说明施加偏压不会改变光电探测器窄带吸收的特性；此外，施加1.9V偏压下光电探测器在1550nm响应度达到0.2A/W，相较于0V偏压下的响应度增益倍数达到3个数量级，这与商用的基于锗和铟镓砷材料的探测器性能相当。
实施例3
本实施例涉及一种窄带吸收的硅基红外波段雪崩光电探测器，与实施例2的区别仅在于：硅膜层的厚度为190nm，其余均一致。
性能测试：
(1)利用光谱仪测试光电探测器的光学吸收率及反射率
测试结果如图13所示，本实施例制备的硅基光电探测器在近红外波段1780处的反射率为35％，吸收率达到65％，吸收波长半高宽为220nm，表明本实施例制备的硅基光电探测器可实现1780nm波段的窄带吸收。由此可知，通过调 整实施例2制备的光电探测器中硅膜层的厚度，可实现对不同波段的窄带吸收。
(2)研究偏压对光电探测器响应度的影响
图14为光电探测器在零偏压下在近红外波段1400nm～2000nm内的响应度曲线，得到与光学反射谱趋势一致的窄带响应曲线，进一步说明该光电探测器可实现波长1780nm处的窄带吸收。
图15为光电探测器在3V偏压下在近红外波段1400nm～2000nm内的响应度曲线，响应最高的波长仍然在1780nm处，响应度达到0.12A/W，窄带响应峰的半高宽保持220nm，增益倍数达到了3个数量级。
综上可知，本发明所提供的硅基光电探测器，可通过调整顶部金属膜层的材料实现对近红外光的宽带吸收或窄带吸收，从而满足不同应用需求。且该硅基光电探测器在施加偏压的情况下，可产生雪崩倍增效应，从而极大地提高器件的光响应度，使硅基光电探测器的响应度与商用基于锗和铟镓砷材料的探测器性能相当。
以上所述实施例仅是为充分说明本发明而所举的较佳的施例，本发明的保护范围不限于此。本技术领域的技术人员在本发明基础上所作的等同替代或变换，均在本发明的保护范围之内。本发明的保护范围以权利要求书为准。

Claims (10)

  1. 一种硅基红外波段雪崩光电探测器，其特征在于，所述光电探测器包括依次叠层设置的底部电极层、硅膜层以及顶部金属膜层；
    所述顶部金属膜层与所述硅膜层形成肖特基接触；
    所述硅膜层厚度为10nm-5μm。
  2. 根据权利要求1所述的硅基红外波段雪崩光电探测器，其特征在于，所述底部电极层与所述硅膜层形成欧姆接触；
    和/或，所述底部电极层的材料为铝、贵金属和过渡金属中的一种或多种，优选为钛、金、银、铜、铬、铝中一种或多种；
    和/或，所述底部电极层的厚度大于30nm。
  3. 根据权利要求2所述的硅基红外波段雪崩光电探测器，其特征在于，所述底部电极层由钛膜层、金膜层以及铝膜层依次叠层得到，所述铝膜层与所述硅膜层相贴合。
  4. 根据权利要求1所述的硅基红外波段雪崩光电探测器，其特征在于，所述硅膜层的材料为轻掺杂的n型晶体硅材料或轻掺杂的p型晶体硅材料；
    和/或，所述硅膜层的电阻率为0.1-100Ω·cm。
  5. 根据权利要求1所述的硅基红外波段雪崩光电探测器，其特征在于，所述顶部金属膜层的材料选自金、银、钛、铜、铬、铝、氮化钛及包含上述至少两种金属元素的合金中的一种或多种；
    和/或，所述顶部金属膜层的厚度为5-100nm。
  6. 根据权利要求1或5所述的硅基红外波段雪崩光电探测器，其特征在于，所述顶部金属膜层的厚度小于电子平均自由程；
    和/或，所述硅膜层的厚度小于所述硅膜层与所述顶部金属膜层形成的肖特 基结的耗尽层宽度。
  7. 根据权利要求1所述的硅基红外波段雪崩光电探测器，其特征在于，当所述顶部金属膜层的材料为金、银、铜、铝及包含上述至少两种金属元素的合金中的一种或多种时，所述顶部金属膜层与所述底部电极层形成法布里-珀罗腔，所述硅膜层为所述法布里-珀罗腔中的介质层，通过调整所述硅膜层的厚度实现不同红外波长处的窄带光学吸收。
  8. 根据权利要求7所述的硅基红外波段雪崩光电探测器，其特征在于，当所述顶部金属膜层的材料为金时，所述顶部金属膜层与所述硅膜层之间设置有黏附层；所述黏附层的材料选自钛、铬、铝、银中的一种或多种。
  9. 一种权利要求1-8任一项所述的硅基红外波段雪崩光电探测器的制备方法，其特征在于，包括：
    将预处理后的绝缘层上硅置于氢氟酸溶液中，去除绝缘层得到所述硅膜层；
    通过物理和/或化学方法分别在所述硅膜层的上、下表面制备顶部金属膜层、底部电极层。
  10. 根据权利要求9所述的制备方法，其特征在于，所述预处理包括用有机溶剂、水依次对绝缘层上硅进行超声清洗的过程；
    所述绝缘层为二氧化硅层；
    所述物理和/或化学方法包括磁控溅射沉积、电子束蒸镀。
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