WO2023169203A1 - 一种光电探测器、接收端设备和工作模式的切换方法 - Google Patents

一种光电探测器、接收端设备和工作模式的切换方法 Download PDF

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Publication number
WO2023169203A1
WO2023169203A1 PCT/CN2023/077327 CN2023077327W WO2023169203A1 WO 2023169203 A1 WO2023169203 A1 WO 2023169203A1 CN 2023077327 W CN2023077327 W CN 2023077327W WO 2023169203 A1 WO2023169203 A1 WO 2023169203A1
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layer
photodetector
electrode
working mode
electrical signal
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PCT/CN2023/077327
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English (en)
French (fr)
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沈红明
赵彦立
李达攀
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华为技术有限公司
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Publication of WO2023169203A1 publication Critical patent/WO2023169203A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/489—Gain of receiver varied automatically during pulse-recurrence period
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/109—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier being of the PN heterojunction type

Definitions

  • the present application relates to the field of semiconductor devices, and in particular, to a photodetector, a receiving end device and a working mode switching method.
  • Lidar usually performs ranging based on Time of Flight (TOF).
  • TOF Time of Flight
  • One of the core components of Lidar is the detector. Its working principle is: the laser pulse emitted by the laser reaches the target object after passing through the light transmitting module. The echo pulse signal reflected by the target object passes through the light receiving module and is received by the detector. The signal processing unit determines the target by measuring the time interval between transmitting and receiving the laser pulse. Object distance information and three-dimensional point cloud images.
  • avalanche photodiode is generally used as the detector.
  • the echo power may be too small and be submerged in the noise, thus affecting the signal detection capability.
  • the current working mode of the detector is relatively single, and it is difficult to meet the needs of long-distance and short-distance detection at the same time.
  • Embodiments of the present application provide a method for switching a photoelectric detector, a receiving end device, and a working mode, which improves the detection range of the photoelectric detector and can meet both long-distance and short-distance detection requirements.
  • inventions of the present application provide a photodetector.
  • the photodetector includes a lower contact layer, a multiplication layer, a charge electrode layer, an absorption layer and an upper contact layer arranged in sequence from the bottom layer to the top layer.
  • a first electrode is formed on the lower contact layer
  • a second electrode is formed on the upper contact layer
  • a third electrode is formed on the charge electrode layer.
  • the charge electrode layer is used for electric field control.
  • the photodetector has a first working mode and a second working mode. When the first voltage is applied to the second electrode and the third electrode, the photovoltaic detector is in the first working mode. When the second voltage is applied to the first electrode and the second electrode, the photovoltaic detector is in the second working mode.
  • the gain of the electrical signal output by the photodetector in the first operating mode is smaller than the gain of the electrical signal output in the second operating mode.
  • the photodetector can be in a low-gain working mode in a close-range strong light detection scenario, and the photodetector can be in a high-gain working mode in a long-distance weak light detection scenario, whether it is at a short distance or
  • the signal detection capability can be ensured in long-distance detection scenarios, and the detection range of the photoelectric detector is improved, which can meet both long-distance and short-distance detection needs.
  • the photodetector provided by this application has a compact structure, smaller size, and lower cost.
  • the photodetector does not require an external attenuator, which reduces system power consumption.
  • this application uses a highly doped charge electrode layer.
  • the charge electrode layer The doping concentration of the charge electrode layer is higher than that of the absorption layer, and the doping concentration of the charge electrode layer is higher than that of the multiplication layer.
  • the more impurities are incorporated the stronger the conductivity of the semiconductor material, which is beneficial to improving the performance of the photodetector.
  • the doping type of the lower contact layer and the charge electrode layer is N-type doping
  • the doping type of the upper contact layer is P-type doping.
  • the doping type of each layer structure in contact with the electrode is provided, which enhances the realizability of this solution.
  • the lower contact layer is in ohmic contact with the first electrode
  • the upper contact layer is in ohmic contact with the second electrode
  • the charge electrode layer is in ohmic contact with the third electrode, which facilitates the input and output of current.
  • the photodetector further includes a diffusion barrier layer located between the absorption layer and the upper contact layer.
  • the diffusion barrier layer is used to inhibit the back diffusion of hole carriers to the depletion region, helping to improve the performance of the photodetector.
  • the depletion region refers to the interface region in the semiconductor PN junction where the energy band bending near the interface is caused by the difference in the original chemical potential of the semiconductors on both sides of the interface, resulting in a decrease in the concentration of electrons or holes in the energy band bending region.
  • the photodetector further includes a gradient layer located between the absorption layer and the diffusion barrier layer.
  • the gradient layer is used to slow down the hysteresis of carrier transmission between the absorption layer and the diffusion barrier layer, which helps to improve the performance of the photodetector.
  • the lower contact layer includes a substrate and a buffer layer, the buffer layer is located on the substrate, and the first electrode is formed on the substrate or the buffer layer.
  • the substrate plays a supporting and fixing role, making the overall structure of the photodetector more stable.
  • the charge electrode layer includes an electrode layer and a charge layer.
  • the electrode layer is located on the charge layer.
  • a third electrode is formed on the electrode layer.
  • the charge layer is used for electric field control, which enhances the flexibility of this solution.
  • the photodetector also includes a waveguide structure, and light is incident from one end of the waveguide structure and transmitted along the waveguide structure to the absorbing layer. This implementation is more conducive to achieving high-performance detection and optoelectronic integration.
  • the upper contact layer uses a narrow bandgap highly doped material
  • the lower contact layer and the charge electrode layer use a wide bandgap highly doped material to facilitate ohmic contact and reduce contact resistance
  • the material of the lower contact layer includes indium phosphorus (InP)
  • the material of the multiplication layer includes indium aluminum arsenic (InAlAs)
  • the material of the charge electrode layer includes InAlAs and InP
  • the material of the absorption layer includes indium gallium arsenide.
  • the material of the upper contact layer includes indium gallium arsenide phosphorus (InGaAsP).
  • the photodetector can be mainly used for detection in the mid-short infrared band (800nm-1700nm). Since the multiplication layer uses InAlAs low-noise multiplication material, tunneling dark current can be suppressed, achieving high gain, low noise, and good temperature stability.
  • the material of the lower contact layer, multiplication layer, charge electrode layer, absorption layer and upper contact layer includes silicon (Si).
  • the photodetector can be mainly used for detection in the short infrared band and the visible band (300nm-1000nm), for example, it can be used in cameras, lidar and charge coupled devices (Charge Coupled Device, CCD), etc.
  • This implementation uses a silicon photonic process platform, which has the advantages of lower cost, wide dynamic range, and high pixels.
  • the materials of the lower contact layer, multiplication layer, charge electrode layer and upper contact layer include Si
  • the material of the absorber layer includes germanium (Ge).
  • the photodetector can be mainly used for detection in the short and medium infrared band (800nm-1700nm), and is also compatible with the silicon photonics process platform. This embodiment has a lower cost.
  • embodiments of the present application provide a receiving end device.
  • the receiving end device includes a signal processor, a driving power supply, and a photodetector as described in any embodiment of the first aspect.
  • the photodetector is used to convert the input optical signal into an electrical signal and output the electrical signal to the signal processor.
  • the signal processor is used to adjust the voltage output by the driving power supply to the photodetector according to the electrical signal, and select the electrode on the photodetector for loading voltage according to the electrical signal to control the photodetector between the first working mode and the second working mode. switch between.
  • the driving power supply outputs a first voltage to the second electrode and the third electrode of the photodetector
  • the signal processor is specifically configured to detect the intensity of the electrical signal. If the intensity of the electrical signal is less than the threshold, the driving power supply is adjusted to output a second voltage to the first electrode and the second electrode of the photodetector to control the photodetector to switch from the first operating mode to the second operating mode.
  • a specific scenario for switching the working mode of the photodetector is provided, which enhances the practicability of this solution.
  • the driving power supply outputs a second voltage to the first electrode and the second electrode of the photodetector
  • the signal processor is specifically configured to detect the intensity of the electrical signal. If the intensity of the electrical signal is greater than or equal to the threshold, the driving power supply is adjusted to output a first voltage to the second electrode and the third electrode of the photodetector to control the photodetector to switch from the second operating mode to the first operating mode.
  • another specific scenario for switching the working mode of the photodetector is provided, which enhances the flexibility of the solution.
  • embodiments of the present application provide a working mode switching method, which is applied to the photodetector described in any of the embodiments of the first aspect.
  • the method includes: receiving an electrical signal output by a photodetector.
  • the voltage output to the photodetector is adjusted according to the electrical signal, and the electrode for loading the voltage on the photodetector is selected according to the electrical signal to control the photodetector to switch between the first working mode and the second working mode.
  • a first voltage is loaded on the second electrode and the third electrode of the photodetector, and controlling the photodetector to switch between the first working mode and the second working mode includes: detecting the intensity of the electrical signal. If the intensity of the electrical signal is less than the threshold, a second voltage is output to the first electrode and the second electrode of the photodetector to control the photodetector to switch from the first operating mode to the second operating mode.
  • a second voltage is loaded on the first electrode and the second electrode of the photodetector, and controlling the photodetector to switch between the first working mode and the second working mode includes: detecting the intensity of the electrical signal. If the intensity of the electrical signal is greater than or equal to the threshold, the first voltage is output to the second electrode and the third electrode of the photodetector to control the photodetector to switch from the second operating mode to the first operating mode.
  • a vertical structure photodetector including a lower contact layer, a multiplication layer, a charge electrode layer, an absorption layer and an upper contact layer arranged in sequence from the bottom layer to the top layer.
  • electrodes are provided on the lower contact layer, the upper contact layer and the charge electrode layer.
  • the photodetector has two working modes: high gain and low gain. Specifically, when voltage is applied to the electrodes on the charge electrode layer and the upper contact layer, the photodetector is in a low gain mode, and when voltage is applied to the electrodes on the lower contact layer and the upper contact layer, the photodetector is in a high gain mode.
  • the photodetector can be in a low-gain working mode in a close-range strong light detection scenario, and the photodetector can be in a high-gain working mode in a long-distance weak light detection scenario, whether it is close or long distance.
  • the detection capability of the signal can be ensured in all detection scenarios, and the detection range of the photoelectric detector is improved, which can meet the detection needs of long distance and short distance at the same time.
  • the structure of the photodetector provided by this application Compact structure, smaller size and lower cost.
  • the photodetector does not require an external attenuator, which reduces system power consumption.
  • Figure 1 is a possible structural diagram of a lidar device
  • Figure 2 is a schematic structural diagram of a photodetector in an embodiment of the present application.
  • Figure 3 is a schematic structural diagram of a photodetector in an embodiment of the present application.
  • Figure 4 is a schematic diagram of the first electric field distribution of the photodetector
  • Figure 5 is a schematic diagram of the second electric field distribution of the photodetector
  • Figure 6 is a schematic diagram of the third electric field distribution of the photodetector
  • Figure 7 is a schematic structural diagram of a receiving end device in an embodiment of the present application.
  • Figure 8 is another structural schematic diagram of a receiving end device in an embodiment of the present application.
  • Figure 9 is a schematic diagram of an embodiment of the working mode switching method in this application.
  • Embodiments of the present application provide a method for switching a photoelectric detector, a receiving end device, and a working mode, which improves the detection range of the photoelectric detector and can meet both long-distance and short-distance detection requirements.
  • the terms "first”, “second”, “third”, etc. (if present) in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific sequence. Or sequence. It is to be understood that the data so used are interchangeable under appropriate circumstances so that the embodiments described herein can be practiced in sequences other than those illustrated or described herein.
  • spatial relationship terms may be used herein, such as “under,” “under,” “under,” “on” , “up”, etc. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, terms such as “below” may include both upper and lower orientations. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatial descriptors herein interpreted accordingly.
  • FIG. 1 is a schematic diagram of a possible structure of a lidar device.
  • the lidar device includes: laser, light transmitting module, light receiving module, photodetector and signal processor.
  • the laser pulse output by the laser is transmitted to the target object after passing through the light emitting module.
  • the echo pulse signal reflected by the target object will be transmitted to the photodetector through the light receiving module.
  • the photodetector converts the received echo pulse signal into an echo electrical signal and outputs the echo electrical signal to the signal number processor.
  • the signal processor can determine the distance information of the target by measuring the time interval between sending and receiving laser pulses.
  • this application provides a vertically structured photodetector, which has two working modes: high gain and low gain.
  • the signal processor can also adjust the working mode of the photodetector according to the characteristics of the echo electrical signal.
  • the photodetector In the close-range strong light detection scenario, the photodetector can be placed in a low-gain working mode. In the long-distance weak light detection scenario, the photodetector can be placed in a low-gain working mode.
  • the photodetector is in a high-gain working mode, which ensures signal detection capabilities in both short-range and long-range detection scenarios.
  • the photodetector provided by this application is introduced in detail below.
  • FIG. 2 is a schematic structural diagram of a photodetector in an embodiment of the present application.
  • the photodetector includes a lower contact layer 1, a multiplication layer 2, a charge electrode layer 3, an absorption layer 4 and an upper contact layer 5 arranged in sequence from the bottom layer to the top layer.
  • the N1 electrode is formed on the lower contact layer 1
  • the N2 electrode is formed on the charge electrode layer 3
  • the P electrode is formed on the upper contact layer 5 .
  • the doping type of the lower contact layer 1 and the charge electrode layer 3 is N-type doping
  • the doping type of the upper contact layer 5 is P-type doping
  • the lower contact layer 1 is in ohmic contact with the N1 electrode
  • the charge electrode layer 3 It is in ohmic contact with the N2 electrode
  • the upper contact layer 5 is in ohmic contact with the P electrode.
  • the charge electrode layer 3 is also used to realize electric field control.
  • the charge electrode layer 3 is used to control the electric field distribution between the absorption layer 4 and the multiplication layer 2.
  • the absorption layer 5 is used to absorb light.
  • the multiplication layer 2 is an undoped intrinsic layer, and its function is to multiply electrons within it to generate gain.
  • the photodetector in addition to the front-illuminated (light is input from the upper contact layer) or back-illuminated (light is input from the lower contact layer) photodetectors introduced above, can also adopt a waveguide structure. , light is input from one end of the waveguide and transmitted to the absorption layer of the photodetector through the waveguide. The propagation and absorption of the incident light is along the direction of the waveguide and perpendicular to the transport direction of carriers, which is more conducive to achieving high-performance detection and Optoelectronic integration.
  • the photodetector can have two working modes: high gain and low gain. Specifically, when the V1 voltage is applied to the P electrode and the N1 electrode, the photovoltaic detector is in a high-gain working mode, and when the V2 voltage is applied to the P electrode and the N2 electrode, the photovoltaic detector is in a low-gain working mode. Among them, the high-gain operating mode and the low-gain operating mode have their respective corresponding voltage value ranges, which are not limited here.
  • the value range of V1 voltage is 40V-200V
  • the value range of V2 voltage is 0V-20V.
  • the photodetector outputs electrical signals through the P electrode and the N1 electrode.
  • the photodetector outputs electrical signals through the P electrode and the N2 electrode.
  • the electrical signal is output through the P electrode and the N2 electrode.
  • the gain of the signal is greater than the gain of the electrical signal in the low-gain operating mode. That is to say, in the low-gain operating mode, a PN junction is formed between the charge electrode layer 3 and the upper contact layer 5.
  • the photodetector can be regarded as a low-gain photodiode (Photo Diode, PD).
  • PD Photo Diode
  • a PN junction is formed between the lower contact layer 1 and the upper contact layer 5.
  • the photodetector can be regarded as a high-gain avalanche photodiode (APD).
  • charge electrode layer 3 is named based on the function of this layer structure. In practical applications, this layer structure can also have other naming methods. As long as it is a structure that can realize the functions of electric field control and electrode contact, it belongs to This application introduces the charge electrode layer.
  • the photodetector when the light receiving power of the photodetector is high, the photodetector can be placed in a low-gain operating mode to avoid causing saturation of the photodetector. When the light receiving power of the photodetector is low, the photodetector can be placed in a high-gain operating mode to increase the gain of the signal.
  • the low-gain operating mode determines the upper limit of the light receiving power of the photodetector, for example, the upper limit is higher than 10 dBm.
  • the high-gain operating mode determines the light reception of the photodetector A lower limit for power, for example, below -50dBm. Then, a detection range of more than 60dB can be achieved by switching the working mode of the photodetector.
  • this application uses a highly doped charge electrode layer 3.
  • High doping means that more impurities are doped into the semiconductor material. Generally, the more impurities are doped, the The stronger the conductivity of the semiconductor material, the better the performance of the photodetector.
  • the doping concentration of the charge electrode layer 3 is higher than the doping concentration of the absorption layer 4 , and the doping concentration of the charge electrode layer 3 is higher than the doping concentration of the multiplication layer 2 .
  • the present application can improve the maximum gain in the high-gain operating mode by designing the thickness of the multiplication layer 2.
  • this application does not limit the number of multiplication layers 2. In practical applications, higher gain can also be achieved by designing multiple multiplication layers.
  • this application does not limit the specific structure of the multiplication layer 2.
  • the multiplication layer 2 can adopt a superlattice, quantum well, quantum dot and other structures.
  • photodetectors include but are not limited to several layer structures introduced below.
  • FIG. 3 is a schematic structural diagram of a photodetector in an embodiment of the present application.
  • the photodetector may further include a diffusion barrier layer 6 located between the absorption layer 4 and the upper contact layer 5 .
  • the diffusion barrier layer 6 is used to inhibit the back diffusion of hole carriers to the depletion region.
  • the depletion region refers to the bending of the energy band near the interface due to the difference in the original chemical potential of the semiconductor on both sides of the interface in the semiconductor PN junction. , thereby forming an interface region where the concentration of electrons or holes decreases in the band bending region.
  • the photodetector may also include a gradient layer 7 located between the absorption layer 4 and the diffusion barrier layer 6 .
  • the gradient layer 7 is used to slow down the hysteresis of carrier transmission between the absorption layer 4 and the diffusion barrier layer 6 .
  • the above-mentioned lower contact layer 1 can be specifically composed of a substrate 1a and a buffer layer 1b, wherein the buffer layer 1b is located on the substrate 1a, and the substrate 1a is located at the lowest layer of the photodetector and plays a supporting and fixing role.
  • the N1 electrode may be formed on the substrate 1a or the buffer layer 1b.
  • the charge electrode layer 3 can also be split into two independent structures: the charge layer 3a and the electrode layer 3b.
  • the electrode layer 3b is located on the charge layer 3a, and an N2 electrode is formed on the electrode layer 3b.
  • the charge layer 3a Used to achieve electric field control.
  • materials that can be used for the multiplication layer 2 include, but are not limited to, indium phosphorus (InP), silicon (Si), indium aluminum arsenide (InAlAs), germanium (Ge), gallium nitride (GaN), indium arsenide (InAs), and Mercury cadmium telluride (HgTeCd).
  • Materials that can be used for the absorption layer 4 include, but are not limited to, indium gallium arsenide (InGaAs), Si and Ge.
  • the upper contact layer 5 can be made of a narrow bandgap highly doped material
  • the lower contact layer 1 and the charge electrode layer 3 can be made of a wide bandgap highly doped material to facilitate ohmic contact and reduce contact resistance.
  • Embodiment 1 The material used in the lower contact layer 1 is InP, the material used in the multiplication layer 2 is InAlAs, the material used in the charge electrode layer 3 includes InAlAs and InP, the material used in the absorption layer 4 is InGaAs, and the material used in the upper contact layer 5 is InAlAs.
  • the material is InGaAsP, the material used for the diffusion barrier layer 6 is InP, and the material used for the gradient layer 7 is InGaAsP.
  • Figure 4 is a schematic diagram of the first electric field distribution of the photodetector.
  • the abscissa represents the thickness of the photodetector Degree (unit: um)
  • the thickness is displayed in the direction from the top layer of the photodetector to the bottom layer
  • the ordinate represents the electric field (unit: V/cm). It can be seen that when the photodetector is in the high-gain operating mode, a steep rise in electric field is introduced from the absorption layer 4 to the multiplication layer 2.
  • the electric field of the absorption layer 4 is less than 200000V/cm, and the electric field of the multiplication layer 2 is less than 800000V/cm. cm.
  • the absorption layer is completely depleted, the electric field is low, the light is absorbed to generate electron-hole pairs, and the photogenerated electrons move to the multiplication zone to generate multiplication gain.
  • the photodetector introduced in the above-mentioned Embodiment 1 can be mainly used for detection in the medium and short infrared bands (800nm-1700nm). Since the multiplication layer 2 uses InAlAs low-noise multiplication material, the tunneling dark current can be suppressed, achieving high gain, low noise, and good temperature stability.
  • Embodiment 2 All layers of the photodetector are made of Si.
  • Figure 5 is a schematic diagram of the second electric field distribution of the photodetector. As shown in Figure 5, the abscissa represents the thickness of the photodetector (unit: um), which is shown in the direction from the top layer of the photodetector to the bottom layer, and the ordinate represents the electric field (unit: V/cm). It can be seen that when the photodetector is in the high-gain operating mode, a steep rise in electric field is introduced from the absorption layer 4 to the multiplication layer 2. The electric field of the absorption layer 4 is less than 100000V/cm, and the electric field of the multiplication layer 2 is less than 350000V/cm. cm.
  • the absorption layer is completely depleted, the electric field is low, the light is absorbed to generate electron-hole pairs, and the photogenerated electrons move to the multiplication zone to generate multiplication gain.
  • the photodetector introduced in the above Embodiment 2 can be mainly used for detection in the short infrared band and visible band (300nm-1000nm), for example, can be applied to cameras, lidar and charge coupled devices (Charge Coupled Device, CCD) wait.
  • This implementation uses a silicon photonic process platform, which has the advantages of lower cost, wide dynamic range, and high pixels.
  • Embodiment 3 The materials of each layer in the photodetector except the absorption layer 4 are made of Si, and the material of the absorption layer 4 is Ge.
  • Figure 6 is a schematic diagram of the third electric field distribution of the photodetector. As shown in Figure 6, the abscissa represents the thickness of the photodetector (unit: um), which is displayed in the direction from the top layer of the photodetector to the bottom layer, and the ordinate represents the electric field (unit: V/cm). It can be seen that when the photodetector is in the high-gain operating mode, a steep rise in electric field is introduced from the absorption layer 4 to the multiplication layer 2.
  • the electric field of the absorption layer 4 is less than 100000V/cm, and the electric field of the multiplication layer 2 is less than 380000V/cm. cm. That is to say, in the high-gain operating mode of the photodetector, the absorption layer is completely depleted, the electric field is low, the light is absorbed to generate electron-hole pairs, and the photogenerated electrons move to the multiplication zone to generate multiplication gain.
  • the photodetector introduced in the above-mentioned Embodiment 3 can be mainly used for detection in the mid-to-short infrared band (800nm-1700nm), is also compatible with the silicon photonics process platform, and is lower in cost than the above-mentioned Embodiment 1.
  • the present application provides a vertical structure photodetector, including a lower contact layer, a multiplication layer, a charge electrode layer, an absorption layer and an upper contact layer arranged in sequence from the bottom layer to the top layer.
  • electrodes are provided on the lower contact layer, the upper contact layer and the charge electrode layer.
  • the photodetector has two working modes: high gain and low gain. Specifically, when voltage is applied to the electrodes on the charge electrode layer and the upper contact layer, the photodetector is in a low gain mode, and when voltage is applied to the electrodes on the lower contact layer and the upper contact layer, the photodetector is in a high gain mode.
  • the photodetector can be in a low-gain working mode in a close-range strong light detection scenario, and the photodetector can be in a high-gain working mode in a long-distance weak light detection scenario, whether it is close or long distance.
  • the detection capability of the signal can be ensured in all detection scenarios, and the detection range of the photoelectric detector is improved, which can meet the detection needs of long distance and short distance at the same time.
  • the photodetector provided by this application has a compact structure, smaller size, and lower cost.
  • the photodetector does not require an external attenuator, which reduces system power consumption.
  • this application also provides a receiving end device.
  • the following is combined with the receiving end device.
  • the equipment introduces the working mode switching of photoelectric detectors.
  • FIG. 7 is a schematic structural diagram of a receiving end device in an embodiment of the present application.
  • the receiving end device includes a photodetector 10 , a driving power supply 20 and a signal processor 30 .
  • the photodetector 10 is used to convert the input optical signal into an electrical signal and output the electrical signal to the signal processor 30 .
  • the signal processor 30 is used to adjust the voltage output by the driving power supply 20 to the photodetector 10 according to the characteristics of the electrical signal, and select the electrodes on the photodetector 10 for loading the voltage according to the characteristics of the electrical signal to control the photodetector 10 in Switch between high gain operating mode and low gain operating mode.
  • the receiving end device further includes a multi-stage amplification module 40 .
  • the multi-stage amplification module 40 is used to perform multi-stage amplification on the electrical signal output by the photodetector 10 and then output it to the signal processor 30 .
  • the signal processor 30 may include a decision unit 301 and a control unit 302.
  • the decision unit 301 is used to make a decision according to the characteristics of the input electrical signal.
  • the control unit 302 is used to adjust the voltage output by the driving power supply 20 according to the decision result and select the photodetector 10 electrodes for applying voltage.
  • the photodetector 10 can be the photodetector introduced in any of the above embodiments, and details will not be described again here. It should also be understood that in practical applications, the receiving end device includes but is not limited to the components listed above. For example, the receiving end device also includes a light receiving component located at the front end of the photodetector 10 and so on. Moreover, the above-mentioned receiving end device can be an independent device or a component of the lidar device. As shown in Figure 1 above, the lidar device also includes a transmitting end device composed of a laser and a light transmitting module.
  • the signal processor 30 can switch the working mode of the photodetector 10 by controlling the switching of the switch, which will be further described below.
  • FIG. 8 is another schematic structural diagram of a receiving end device in an embodiment of the present application.
  • the signal processor 30 is connected to the N1 electrode of the photodetector 10 through the switch S1 and is connected to the N2 electrode of the photodetector 10 through the switch S2.
  • the switch S1 When the switch S1 is turned on, the switch S2 is turned off, and the driving power supply 20 outputs the V1 voltage, the photodetector 10 is in the high-gain operating mode.
  • the switch S1 is turned off, the switch S2 is turned on, and the driving power supply 20 outputs the V2 voltage, the photodetector 10 is in the low-gain operating mode.
  • the working mode of the photodetector 10 can be pre-selected according to the distance range of the target object to be measured, and then it is determined whether the working mode of the photodetector 10 needs to be adjusted based on the actual detection results.
  • the switch S1 is currently turned on, the switch S2 is turned off, and the driving power supply 20 outputs the V1 voltage to the P electrode and the N1 electrode of the photodetector 10, that is, the photodetector 10 is in a high-gain operating mode.
  • Signal processor 30 detects the strength of the input electrical signal. If the intensity of the electrical signal is greater than or equal to the threshold, it means that the gain of the signal in the current working mode is too high. Furthermore, the signal processor 30 controls the switch S1 to turn off, the switch S2 to turn on, and controls the driving power supply 20 to output the V2 voltage to the P electrode and N2 electrode of the photodetector 10 to control the photodetector 10 to switch to a low gain operating mode.
  • the switch S1 is currently turned off, the switch S2 is turned on, and the driving power supply 20 outputs the V2 voltage to the P electrode and N2 electrode of the photodetector 10, that is, the photodetector 10 is in a low-gain operating mode.
  • Signal processor 30 detects the strength of the input electrical signal. If the intensity of the electrical signal is less than the threshold, it means that the gain of the signal in the current working mode is too low. Furthermore, the signal processor 30 controls the switch S1 to turn on and the switch S2 to turn off, and controls the driving power supply 20 to output the V1 voltage to the P electrode and N1 electrode of the photodetector 10 to control the photodetector 10 to switch to a high-gain operating mode.
  • the signal processor 30 may detect the average intensity of the input electrical signal within a period of time, and use the average intensity of the electrical signal as a parameter for decision making. In some possible implementations, the signal processor 30 may also make a decision based on other characteristics of the input electrical signal, or make a decision based on multiple characteristics of the input electrical signal, which are not specifically limited here. For example, signal processor 30 responds to input telecommunications The rising edge slope of the signal is used for judgment. If the rising edge slope is greater than or equal to the threshold, the photodetector 10 is controlled to switch to a low-gain operating mode. If the rising edge slope is less than the threshold, the photodetector 10 is controlled to switch to a high-gain operating mode.
  • FIG. 9 is a schematic diagram of an embodiment of the working mode switching method in this application.
  • the working mode switching method includes the following steps.
  • the photodetector can convert the input optical signal into an electrical signal and output the electrical signal to the signal processor.
  • step 902 may be specifically executed by the signal processor in the receiving end device shown in FIG. 7 or FIG. 8 .
  • the specific method of controlling the photodetector to switch the working mode please refer to the relevant introduction of the embodiment shown in FIG. 7 and FIG. 8 above, and will not be described again here.

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Abstract

本申请实施例公开了一种光电探测器、接收端设备和工作模式切换方法，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。光电探测器包括自底层至顶层依次排列的下接触层、倍增层、电荷电极层、吸收层和上接触层。下接触层上形成有第一电极，上接触层上形成有第二电极，电荷电极层上形成有第三电极，电荷电极层用于电场调控。光电探测器具有高增益工作模式和低增益工作模式，光电探测器在低增益工作模式下对电信号的增益小于在高增益工作模式下对电信号的增益。当第二电极和第三电极上加载第一电压时光电探测器处于低增益工作模式。当第一电极和第二电极上加载第二电压时光电探测器处于高增益工作模式。

Description

一种光电探测器、接收端设备和工作模式的切换方法
本申请要求于2022年3月8日提交中国国家知识产权局、申请号为202210227512.6、申请名称为“一种光电探测器、接收端设备和工作模式的切换方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及半导体器件领域，尤其涉及一种光电探测器、接收端设备和工作模式切换方法。
背景技术
激光雷达通常基于飞行时间(Time of Flight，TOF)进行测距，激光雷达的一个核心器件是探测器。其工作原理是：激光器发出的激光脉冲通过光发射模块后达到目标物体，目标物体反射的回波脉冲信号通过光接收模块后被探测器接收，信号处理单元通过测量激光脉冲的收发时间间隔确定目标物体的距离信息及三维点云图像。
目前，在激光雷达系统的接收端，一般采用雪崩光电二极管(Avalanche Photodiode，APD)作为探测器。远距离探测时，回波功率可能会由于太小会淹没在噪声中，从而影响信号的检测能力。若要实现远距离探测往往需要增大发射激光的功率，这样又会导致近距离的回波功率很强，容易引起探测器饱和，也会影响信号的检测能力。也就是说，当前探测器的工作模式较为单一，很难同时满足远距离和近距离的探测需求。
发明内容
本申请实施例提供了一种光电探测器、接收端设备和工作模式的切换方法，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。
第一方面，本申请实施例提供了一种光电探测器。该光电探测器包括自底层至顶层依次排列的下接触层、倍增层、电荷电极层、吸收层和上接触层。其中，下接触层上形成有第一电极，上接触层上形成有第二电极，电荷电极层上形成有第三电极，电荷电极层用于电场调控。光电探测器具有第一工作模式和第二工作模式。当第二电极和第三电极上加载第一电压时光电探测器处于第一工作模式。当第一电极和第二电极上加载第二电压时光电探测器处于第二工作模式。光电探测器在第一工作模式下输出的电信号的增益小于在第二工作模式下输出的电信号的增益。
在该实施方式中，在近距离的强光探测场景中可以让光电探测器处于低增益工作模式，在远距离的弱光探测场景中可以光电探测器处于高增益工作模式，无论是近距离还是远距离探测场景都能保证信号的检测能力，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。另外，本申请提供的光电探测器的结构紧凑，尺寸较小，成本更低。并且，光电探测器无需外加衰减器，降低了系统功耗。
在一些可能的实施方式中，本申请采用的是高掺杂的电荷电极层，具体地，电荷电极层 的掺杂浓度高于吸收层的掺杂浓度，且电荷电极层的掺杂浓度高于倍增层的掺杂浓度。通常情况下，掺入的杂质越多，半导体材料的导电性越强，利于提升光电探测器的性能。
在一些可能的实施方式中，下接触层和电荷电极层的掺杂类型为N型掺杂，上接触层的掺杂类型为P型掺杂。在该实施方式中，提供了与电极接触的各层结构的掺杂类型，增强了本方案的可实现性。
在一些可能的实施方式中，下接触层与第一电极欧姆接触，上接触层与第二电极欧姆接触，电荷电极层与第三电极欧姆接触，利于电流的输入与输出。
在一些可能的实施方式中，光电探测器还包括扩散阻挡层，扩散阻挡层位于吸收层与上接触层之间。扩散阻挡层用于抑制空穴载流子反扩散至耗尽区，有助于提升光电探测器的性能。其中，耗尽区指的是在半导体PN结中，由于界面两侧半导体原有化学势的差异导致界面附近能带弯曲，从而形成能带弯曲区域电子或空穴浓度的下降的界面区域。
在一些可能的实施方式中，光电探测器还包括渐变层，渐变层位于吸收层与扩散阻挡层之间。渐变层用于减缓吸收层与扩散阻挡层之间载流子传输的迟滞，有助于提升光电探测器的性能。
在一些可能的实施方式中，下接触层包括衬底和缓冲层，缓冲层位于衬底上，衬底或缓冲层上形成有第一电极。其中，衬底起着支撑和固定的作用，使得光电探测器的整体结构更稳定。
在一些可能的实施方式中，电荷电极层包括电极层和电荷层，电极层位于电荷层上，电极层上形成有第三电极，电荷层用于电场调控，增强了本方案的灵活性。
在一些可能的实施方式中，光无论从上接触层入射还是从下接触层入射都可以实现类似的效果。
在一些可能的实施方式中，光电探测器还包括波导结构，光从波导结构的一端入射并沿着波导结构传输至吸收层，这种实现方式更有利于实现高性能探测和光电集成。
在一些可能的实施方式中，0.1um≤倍增层的厚度≤1um，便于提升高增益工作模式下的最大增益。
在一些可能的实施方式中，上接触层采用窄带隙高掺杂材料，下接触层和电荷电极层采用宽带隙高掺杂材料，便于实现欧姆接触，减少接触电阻。
在一些可能的实施方式中，下接触层的材料包括铟磷(InP)，倍增层的材料包括铟铝砷(InAlAs)，电荷电极层的材料包括InAlAs和InP，吸收层的材料包括铟镓砷(InGaAs)，上接触层的材料包括铟镓砷磷(InGaAsP)。在该实施方式中，光电探测器可主要应用于中短红外波段(800nm-1700nm)的探测。由于倍增层采用了InAlAs的低噪声倍增材料，可抑制隧穿暗电流，实现高增益、低噪声，且温度稳定性好。
在一些可能的实施方式中，下接触层、倍增层、电荷电极层、吸收层和上接触层的材料包括硅(Si)。在该实施方式中，光电探测器可主要应用于短红外波段以及可见波段(300nm-1000nm)的探测，例如，可应用于相机、激光雷达和电荷耦合器件(Charge Coupled Device，CCD)等。该实施方式使用硅光的工艺平台，具备成本更低、宽动态范围和高像素等优点。
在一些可能的实施方式中，下接触层、倍增层、电荷电极层和上接触层的材料包括Si， 吸收层的材料包括锗(Ge)。在该实施方式中，光电探测器可主要应用于中短红外波段(800nm-1700nm)的探测，还能兼容硅光的工艺平台，该实施方式的成本较低。
第二方面，本申请实施例提供了一种接收端设备。该接收端设备包括信号处理器、驱动电源和如上述第一方面任一实施方式介绍的光电探测器。具体地，光电探测器用于将输入的光信号转换为电信号并将电信号输出至信号处理器。信号处理器用于根据电信号调节驱动电源向光电探测器输出的电压，并根据电信号选择光电探测器上用于加载电压的电极，以控制光电探测器在第一工作模式和第二工作模式之间切换。通过上述方式，提供了一种切换光电探测器工作模式的具体实现方式，提高了本方案的可实现性。
在一些可能的实施方式中，驱动电源向光电探测器的第二电极和第三电极输出第一电压，信号处理器具体用于：检测电信号的强度。若电信号的强度小于阈值，则调节驱动电源向光电探测器的第一电极和第二电极输出第二电压，以控制光电探测器从第一工作模式切换到第二工作模式。在该实施方式中，提供了一种切换光电探测器工作模式的具体场景，增强了本方案的实用性。
在一些可能的实施方式中，驱动电源向光电探测器的第一电极和第二电极输出第二电压，信号处理器具体用于：检测电信号的强度。若电信号的强度大于或等于阈值，则调节驱动电源向光电探测器的第二电极和第三电极输出第一电压，以控制光电探测器从第二工作模式切换到第一工作模式。在该实施方式中，提供了另一种切换光电探测器工作模式的具体场景，增强了本方案的灵活性。
第三方面，本申请实施例提供了一种工作模式的切换方法，该工作模式切换方法应用于如上述第一方面任一实施方式介绍的光电探测器。该方法包括：接收光电探测器输出的电信号。根据电信号调节向光电探测器输出的电压，并根据电信号选择光电探测器上用于加载电压的电极，以控制光电探测器在第一工作模式和第二工作模式之间切换。
在一些可能的实施方式中，光电探测器的第二电极和第三电极上加载第一电压，控制光电探测器在第一工作模式和第二工作模式之间切换包括：检测电信号的强度。若电信号的强度小于阈值，则向光电探测器的第一电极和第二电极输出第二电压，以控制光电探测器从第一工作模式切换到第二工作模式。
在一些可能的实施方式中，光电探测器的第一电极和第二电极上加载第二电压，控制光电探测器在第一工作模式和第二工作模式之间切换包括：检测电信号的强度。若电信号的强度大于或等于阈值，则向光电探测器的第二电极和第三电极输出第一电压，以控制光电探测器从第二工作模式切换到第一工作模式。
本申请实施例中，提供了一种垂直结构的光电探测器，包括自底层至顶层依次排列的下接触层、倍增层、电荷电极层、吸收层和上接触层。其中，下接触层、上接触层和电荷电极层上都设置有电极。该光电探测器具有高增益和低增益两种工作模式。具体地，当电荷电极层和上接触层上的电极加载电压时光电探测器处于低增益模式，当下接触层和上接触层上的电极加载电压时光电探测器处于高增益模式。也就是说，在近距离的强光探测场景中可以让光电探测器处于低增益工作模式，在远距离的弱光探测场景中可以光电探测器处于高增益工作模式，无论是近距离还是远距离探测场景都能保证信号的检测能力，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。另外，本申请提供的光电探测器的结 构紧凑，尺寸较小，成本更低。并且，光电探测器无需外加衰减器，降低了系统功耗。
附图说明
图1为激光雷达装置一种可能的结构示意图；
图2为本申请实施例中光电探测器的一种结构示意图；
图3为本申请实施例中光电探测器的一种结构示意图；
图4为光电探测器的第一种电场分布示意图；
图5为光电探测器的第二种电场分布示意图；
图6为光电探测器的第三种电场分布示意图；
图7为本申请实施例中接收端设备的一种结构示意图；
图8为本申请实施例中接收端设备的另一种结构示意图；
图9为本申请中工作模式的切换方法的一个实施例示意图。
具体实施方式
本申请实施例提供了一种光电探测器、接收端设备和工作模式的切换方法，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”、“第三”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的实施例能够以除了在这里图示或描述的内容以外的顺序实施。此外，术语“包括”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
应当理解，如果元件或者层称为在另一元件或者层“上”，那么它可以直接在另一元件或者层上，或者也可以存在中间元件或者层。为了易于说明书描述图中所示的一个元件与另一元件的关系，在这里可以使用空间关系术语，例如“在…之下”、“在…下面”、“下”、“在…之上”、“上”等。应当理解，空间关系术语意图包括除附图描述的方向之外应用或操作中的器件的不同取向。例如，如果翻转附图中的器件，描述为“在其他的元件或者特征下面”或者“在其他的元件或者特征之下”的元件将取向为“在其他的元件或者特征之上”。如此，术语例如“在…下面”可包括上面和下面两个取向。可以另外地定向该器件(旋转90度或者在其他的方向)，而在这里的空间描述符也被相应地理解。
本申请提供的光电探测器可应用于激光雷达、激光探测及成像等各个领域，其中，激光雷达可广泛应用于汽车辅助、自动驾驶、机器人定位导航、手机三维成像、空间环境测绘和安保安防等领域。图1为激光雷达装置一种可能的结构示意图。如图1所示，激光雷达装置包括：激光器、光发射模块、光接收模块、光电探测器和信号处理器。激光器输出的激光脉冲经过光发射模块后向目标物传输。目标物反射的回波脉冲信号会经过光接收模块传输至光电探测器。光电探测器将接收到的回波脉冲信号转换为回波电信号并将回波电信号输出至信 号处理器。信号处理器通过测量激光脉冲的收发时间间隔可以确定目标物的距离信息。
需要说明的是，本申请提供了一种垂直结构的光电探测器，该光电探测器具有高增益和低增益两种工作模式。信号处理器还可以根据回波电信号的特征调节光电探测器的工作模式，在近距离的强光探测场景中可以让光电探测器处于低增益工作模式，在远距离的弱光探测场景中可以光电探测器处于高增益工作模式，无论是近距离还是远距离探测场景都能保证信号的检测能力。下面对本申请提供的光电探测器进行详细介绍。
图2为本申请实施例中光电探测器的一种结构示意图。如图2所示，该光电探测器包括自底层至顶层依次排列的下接触层1、倍增层2、电荷电极层3、吸收层4和上接触层5。其中，下接触层1上形成有N1电极，电荷电极层3上形成有N2电极，上接触层5上形成有P电极。应理解，下接触层1和电荷电极层3的掺杂类型为N型掺杂，上接触层5的掺杂类型为P型掺杂，下接触层1与N1电极欧姆接触，电荷电极层3与N2电极欧姆接触，上接触层5与P电极欧姆接触。还应理解，电荷电极层3除了用于实现电极接触外，还用于实现电场调控。例如，电荷电极层3用于控制吸收层4和倍增层2之间的电场分配。需要说明的是，本申请中无论光从下接触层1入射还是从上接触层5入射，都可以实现类似的效果，具体此处不做限定。吸收层5用于吸收光。倍增层2为无掺杂的本征层，作用是电子在其内倍增从而产生增益。
在一些可能的实施方式中，除了上述介绍的正照式(光从上接触层输入)或背照式(光从下接触层输入)的光电探测器，该光电探测器还可以采用波导式的结构，光从波导的一端输入并通过波导传输至光电探测器的吸收层，入射光的传播和吸收是沿着波导方向，且与载流子的输运方向垂直，更有利于实现高性能探测和光电集成。
需要说明的是，本申请引入电荷电极层3的目的在于对光电探测器的电场进行调控。通过引入电荷电极层3可以使得该光电探测器具有高增益和低增益两种工作模式。具体地，当P电极和N1电极上加载V1电压时光电探测器处于高增益工作模式，当P电极和N2电极上加载V2电压时光电探测器处于低增益工作模式。其中，高增益工作模式和低增益工作模式都有各自对应的电压取值范围，具体此处不做限定。例如，V1电压的取值范围是40V-200V，V2电压的取值范围是0V-20V。应理解，在高增益工作模式下光电探测器是通过P电极和N1电极输出电信号，在低增益工作模式下光电探测器是通过P电极和N2电极输出电信号，高增益工作模式下对电信号的增益大于低增益工作模式下对电信号的增益。也就是说，在低增益工作模式中，电荷电极层3与上接触层5之间形成PN结，此时光电探测器可以视为低增益的光电二极管(Photo Diode，PD)。在高增益工作模式中，下接触层1与上接触层5之间形成PN结，此时光电探测器可以视为高增益的雪崩光电二极管(Avalanche Photo Diode，APD)。
应理解，上述电荷电极层3是基于该层结构的功能进行命名的，在实际应用中，这一层结构也可以有其他的命名方式，只要是能实现电场调控和电极接触功能的结构都属于本申请介绍的电荷电极层。
作为一个示例，当光电探测器的光接收功率较高时，可以让光电探测器处于低增益工作模式，避免引起光电探测器的饱和。当光电探测器的光接收功率较低时，可以让光电探测器处于高增益工作模式，以提升对信号的增益。应理解，低增益工作模式决定了光电探测器的光接收功率的上限，例如，该上限高于10dBm。高增益工作模式决定了光电探测器的光接收 功率的下限，例如，该下限低于-50dBm。那么，通过切换光电探测器的工作模式可以实现60dB以上的探测范围。
需要说明的是，本申请不限定上述N1电极、N2电极和P电极的具体形状，上述图2中展示的只是其中一种示例。
在一种可能的实施方式中，本申请采用的是高掺杂的电荷电极层3，高掺杂指的是掺入半导体材料中的杂质较多，通常情况下，掺入的杂质越多，半导体材料的导电性越强，利于提升光电探测器的性能。作为一种具体的实现，电荷电极层3的掺杂浓度高于吸收层4的掺杂浓度，且电荷电极层3的掺杂浓度高于倍增层2的掺杂浓度。
在一种可能的实施方式中，本申请可以通过设计倍增层2的厚度以提升高增益工作模式下的最大增益，优选地，0.1um≤倍增层的厚度≤1um。需要说明的是，本申请不限定倍增层2的数量，在实际应用中，也可以通过设计多个倍增层来实现更高的增益。另外，本申请不限定倍增层2的具体结构，例如，倍增层2可以采用超晶格，量子阱，量子点等结构。
需要说明的是，在上述图2所示光电探测器的基础上，还可以通过增加其他的层结构以实现更多的功能，下面通过一个具体的示例进行介绍。应理解，在实际应用中光电探测器包括但不限于以下介绍的几种层结构。
图3为本申请实施例中光电探测器的一种结构示意图。如图3所示，作为一个示例，光电探测器还可以包括扩散阻挡层6，扩散阻挡层位于吸收层4与上接触层5之间。扩散阻挡层6用于抑制空穴载流子反扩散至耗尽区，其中，耗尽区指的是在半导体PN结中，由于界面两侧半导体原有化学势的差异导致界面附近能带弯曲，从而形成能带弯曲区域电子或空穴浓度的下降的界面区域。
作为另一个示例，光电探测器还可以包括渐变层7，渐变层7位于吸收层4和扩散阻挡层6之间。渐变层7用于减缓吸收层4与扩散阻挡层6之间载流子传输的迟滞。
作为又一个示例，上述下接触层1具体可以由衬底1a和缓冲层1b组成，其中，缓冲层1b位于衬底1a上，衬底1a位于光电探测器的最底层，起着支撑和固定的作用。可选地，N1电极可以形成在衬底1a，也可以形成在缓冲层1b。
作为再一个示例，电荷电极层3也可以拆分成电荷层3a和电极层3b两层独立的结构，其中，电极层3b位于电荷层3a上，电极层3b上形成有N2电极，电荷层3a用于实现电场调控。
需要说明的是，本申请不限定光电探测器的各层结构所采用的材料。例如，倍增层2可以采用的材料包括但不限于铟磷(InP)、硅(Si)、铟铝砷(InAlAs)、锗(Ge)、氮化镓(GaN)、砷化铟(InAs)和汞碲镉(HgTeCd)。吸收层4可以采用的材料包括但不限于铟镓砷(InGaAs)、Si和Ge。优选地，上接触层5可采用窄带隙高掺杂材料，下接触层1和电荷电极层3可采用宽带隙高掺杂材料，便于实现欧姆接触，减少接触电阻。
下面结合各层结构所采用的材料介绍几种具体的实现方式。
实施方式1：下接触层1采用的材料为InP，倍增层2采用的材料为InAlAs，电荷电极层3采用的材料包括InAlAs和InP，吸收层4采用的材料为InGaAs，上接触层5采用的材料为InGaAsP，扩散阻挡层6采用的材料为InP，渐变层7采用的材料为InGaAsP。
图4为光电探测器的第一种电场分布示意图。如图4所示，横坐标表示光电探测器的厚 度(单位：um)，该厚度是从光电探测器的顶层至底层的方向来展示的，纵坐标表示电场(单位V/cm)。可以看出，当光电探测器处于高增益工作模式时，从吸收层4到倍增层2引入了一段电场陡升，其中，吸收层4的电场小于200000V/cm，倍增层2的电场小于800000V/cm。也就是说，光电探测器在高增益工作模式下，吸收层完全耗尽，电场较低，吸收光产生电子空穴对，光生电子运动到倍增区产生倍增增益。
应理解，上述实施方式1介绍的光电探测器可主要应用于中短红外波段(800nm-1700nm)的探测。由于倍增层2采用了InAlAs的低噪声倍增材料，可抑制隧穿暗电流，实现高增益、低噪声，且温度稳定性好。
实施方式2：光电探测器的各层材料均采用Si。图5为光电探测器的第二种电场分布示意图。如图5所示，横坐标表示光电探测器的厚度(单位：um)，该厚度是从光电探测器的顶层至底层的方向来展示的，纵坐标表示电场(单位V/cm)。可以看出，当光电探测器处于高增益工作模式时，从吸收层4到倍增层2引入了一段电场陡升，其中，吸收层4的电场小于100000V/cm，倍增层2的电场小于350000V/cm。也就是说，光电探测器在高增益工作模式下，吸收层完全耗尽，电场较低，吸收光产生电子空穴对，光生电子运动到倍增区产生倍增增益。
应理解，上述实施方式2介绍的光电探测器可主要应用于短红外波段以及可见波段(300nm-1000nm)的探测，例如，可应用于相机、激光雷达和电荷耦合器件(Charge Coupled Device，CCD)等。该实施方式使用硅光的工艺平台，具备成本更低、宽动态范围和高像素等优点。
实施方式3：光电探测器中除吸收层4之外的各层材料均采用Si，吸收层4采用的材料是Ge。图6为光电探测器的第三种电场分布示意图。如图6所示，横坐标表示光电探测器的厚度(单位：um)，该厚度是从光电探测器的顶层至底层的方向来展示的，纵坐标表示电场(单位V/cm)。可以看出，当光电探测器处于高增益工作模式时，从吸收层4到倍增层2引入了一段电场陡升，其中，吸收层4的电场小于100000V/cm，倍增层2的电场小于380000V/cm。也就是说，光电探测器在高增益工作模式下，吸收层完全耗尽，电场较低，吸收光产生电子空穴对，光生电子运动到倍增区产生倍增增益。
应理解，上述实施方式3介绍的光电探测器可主要应用于中短红外波段(800nm-1700nm)的探测，还能兼容硅光的工艺平台，相较于上述实施方式1成本更低。
通过上面的描述，本申请提供了一种垂直结构的光电探测器，包括自底层至顶层依次排列的下接触层、倍增层、电荷电极层、吸收层和上接触层。其中，下接触层、上接触层和电荷电极层上都设置有电极。该光电探测器具有高增益和低增益两种工作模式。具体地，当电荷电极层和上接触层上的电极加载电压时光电探测器处于低增益模式，当下接触层和上接触层上的电极加载电压时光电探测器处于高增益模式。也就是说，在近距离的强光探测场景中可以让光电探测器处于低增益工作模式，在远距离的弱光探测场景中可以光电探测器处于高增益工作模式，无论是近距离还是远距离探测场景都能保证信号的检测能力，提高了光电探测器的探测范围，可以同时满足远距离和近距离的探测需求。另外，本申请提供的光电探测器的结构紧凑，尺寸较小，成本更低。并且，光电探测器无需外加衰减器，降低了系统功耗。
在上述介绍的光电探测器的基础上，本申请还提供了一种接收端设备，下面结合接收端 设备对光电探测器的工作模式切换进行介绍。
图7为本申请实施例中接收端设备的一种结构示意图。如图7所示，接收端设备包括光电探测器10、驱动电源20和信号处理器30。具体地，光电探测器10用于将输入的光信号转换为电信号并将电信号输出至信号处理器30。信号处理器30用于根据电信号的特征调节驱动电源20向光电探测器10输出的电压，并根据电信号的特征选择光电探测器10上用于加载电压的电极，以控制光电探测器10在高增益工作模式和低增益工作模式之间切换。在一些可能的实施方式中，接收端设备还包括多级放大模块40，多级放大模块40用于将光电探测器10输出的电信号进行多级放大后再输出至信号处理器30。信号处理器30可以包括判决单元301和控制单元302，判决单元301用于根据输入电信号的特征进行判决，控制单元302用于根据判决结果调节驱动电源20输出的电压，并选择光电探测器10上用于加载电压的电极。
应理解，光电探测器10可以是上述任一实施例所介绍的光电探测器，具体此处不再赘述。还应理解，在实际应用中，接收端设备包括但不限于上述列举的组件，例如，接收端设备还包括位于光电探测器10前端的光接收组件等。并且，上述接收端设备可以是一个独立的设备，也可以是激光雷达装置的组成部分，如上述图1所示，激光雷达装置还包括由激光器和光发射模块组成的发送端设备。
需要说明的是，在实际应用中，信号处理器30可以通过控制开关的切换来实现光电探测器10工作模式的切换，下面进行进一步介绍。
图8为本申请实施例中接收端设备的另一种结构示意图。如图8所示，信号处理器30通过开关S1与光电探测器10的N1电极连接，并通过开关S2与光电探测器10的N2电极连接。当开关S1导通，开关S2断开，且驱动电源20输出V1电压时，光电探测器10处于高增益工作模式。当开关S1断开，开关S2导通，且驱动电源20输出V2电压时，光电探测器10处于低增益工作模式。应理解，在实际应用中，可以先根据待测目标物的距离范围为光电探测器10预选工作模式，进而，再根据实际的检测结果判断是否需要调节光电探测器10的工作模式。
作为一个示例，当前开关S1导通，开关S2断开，驱动电源20向光电探测器10的P电极和N1电极输出V1电压，即光电探测器10处于高增益工作模式。信号处理器30检测输入电信号的强度。若电信号的强度大于或等于阈值，则说明当前的工作模式对信号的增益太高了。进而，信号处理器30控制开关S1断开，开关S2导通，并控制驱动电源20向光电探测器10的P电极和N2电极输出V2电压，以控制光电探测器10切换到低增益工作模式。
作为另一个示例，当前开关S1断开，开关S2导通，驱动电源20向光电探测器10的P电极和N2电极输出V2电压，即光电探测器10处于低增益工作模式。信号处理器30检测输入电信号的强度。若电信号的强度小于阈值，则说明当前的工作模式对信号的增益太低了。进而，信号处理器30控制开关S1导通，开关S2断开，并控制驱动电源20向光电探测器10的P电极和N1电极输出V1电压，以控制光电探测器10切换到高增益工作模式。
需要说明的是，考虑到输入信号处理器30的电信号强度可能是波动的，可以通过信号处理器30检测一段时间内输入电信号的平均强度，并将电信号的平均强度作为判决的参量。在一些可能的实施方式中，信号处理器30还可以根据输入电信号的其他特征进行判决，或者综合输入电信号的多个特征进行判决，具体此处不做限定。例如，信号处理器30根据输入电信 号的上升沿斜率进行判决。若上升沿斜率大于或等于阈值，则控制光电探测器10切换到低增益工作模式。若上升沿斜率小于阈值，则控制光电探测器10切换到高增益工作模式。
下面还将介绍本申请提供的一种工作模式的切换方法。该工作模式的切换方法应用于上述任一实施方式介绍的光电探测器。该工作模式的切换方法是基于上述图7或图8所示的接收端设备来实现的。图9为本申请中工作模式的切换方法的一个实施例示意图。在该示例中，工作模式的切换方法包括如下步骤。
901、接收光电探测器输出的电信号。
以上述图7或图8所示的接收端设备为例，光电探测器可以将输入的光信号转换为电信号，并将电信号输出至信号处理器。
902、根据电信号的特征调节向光电探测器输出的电压，并根据电信号的特征选择光电探测器上用于加载电压的电极，以控制光电探测器在高增益工作模式和低增益工作模式之间切换。
本实施例中，步骤902具体可以由上述图7或图8所示接收端设备中的信号处理器执行。控制光电探测器切换工作模式的具体方式可以参考上述图7和图8所示实施例的相关介绍，此处不再赘述。
需要说明的是，以上实施例仅用以说明本申请的技术方案，而非对其限制。尽管参照前述实施例对本申请进行了详细说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (21)

  1. 一种光电探测器，其特征在于，包括自底层至顶层依次排列的下接触层、倍增层、电荷电极层、吸收层和上接触层，所述下接触层上形成有第一电极，所述上接触层上形成有第二电极，所述电荷电极层上形成有第三电极，所述电荷电极层用于电场调控；
    所述光电探测器具有第一工作模式和第二工作模式，当所述第二电极和所述第三电极上加载第一电压时所述光电探测器处于所述第一工作模式，当所述第一电极和所述第二电极上加载第二电压时所述光电探测器处于所述第二工作模式，所述光电探测器在所述第一工作模式下输出的电信号的增益小于在所述第二工作模式下输出的电信号的增益。
  2. 根据权利要求1所述的光电探测器，其特征在于，所述电荷电极层的掺杂浓度高于所述吸收层的掺杂浓度，且所述电荷电极层的掺杂浓度高于所述倍增层的掺杂浓度。
  3. 根据权利要求1或2所述的光电探测器，其特征在于，所述下接触层和所述电荷电极层的掺杂类型为N型掺杂，所述上接触层的掺杂类型为P型掺杂。
  4. 根据权利要求1至3中任一项所述的光电探测器，其特征在于，所述下接触层与所述第一电极欧姆接触，所述上接触层与所述第二电极欧姆接触，所述电荷电极层与所述第三电极欧姆接触。
  5. 根据权利要求1至4中任一项所述的光电探测器，其特征在于，所述光电探测器还包括扩散阻挡层，所述扩散阻挡层位于所述吸收层与所述上接触层之间，所述扩散阻挡层用于抑制空穴载流子反扩散至耗尽区。
  6. 根据权利要求5所述的光电探测器，其特征在于，所述光电探测器还包括渐变层，所述渐变层位于所述吸收层与所述扩散阻挡层之间，所述渐变层用于减缓所述吸收层与所述扩散阻挡层之间载流子传输的迟滞。
  7. 根据权利要求1至6中任一项所述的光电探测器，其特征在于，所述下接触层包括衬底和缓冲层，所述缓冲层位于所述衬底上，所述衬底或所述缓冲层上形成有所述第一电极。
  8. 根据权利要求1至7中任一项所述的光电探测器，其特征在于，所述电荷电极层包括电极层和电荷层，所述电极层位于所述电荷层上，所述电极层上形成有所述第三电极，所述电荷层用于电场调控。
  9. 根据权利要求1至8中任一项所述的光电探测器，其特征在于，光从所述上接触层入射，或者，光从所述下接触层入射。
  10. 根据权利要求1至8中任一项所述的光电探测器，其特征在于，所述光电探测器还包括波导结构，光从所述波导结构的一端入射并沿着所述波导结构传输至所述吸收层。
  11. 根据权利要求1至10中任一项所述的光电探测器，其特征在于，0.1um≤所述倍增层的厚度≤1um。
  12. 根据权利要求1至11中任一项所述的光电探测器，其特征在于，所述上接触层采用窄带隙高掺杂材料，所述下接触层和所述电荷电极层采用宽带隙高掺杂材料。
  13. 根据权利要求1至12中任一项所述的光电探测器，其特征在于，所述下接触层的材料包括铟磷InP，所述倍增层的材料包括铟铝砷InAlAs，所述电荷电极层的材料包括InAlAs和InP，所述吸收层的材料包括铟镓砷InGaAs，所述上接触层的材料包括铟镓砷磷InGaAsP。
  14. 根据权利要求1至12中任一项所述的光电探测器，其特征在于，所述下接触层、所 述倍增层、所述电荷电极层、所述吸收层和所述上接触层的材料包括硅Si。
  15. 根据权利要求1至12中任一项所述的光电探测器，其特征在于，所述下接触层、所述倍增层、所述电荷电极层和所述上接触层的材料包括Si，所述吸收层的材料包括锗Ge。
  16. 一种接收端设备，其特征在于，包括信号处理器、驱动电源和如权利要求1至15中任一项所述的光电探测器；
    所述光电探测器用于将输入的光信号转换为电信号并将所述电信号输出至信号处理器；
    所述信号处理器用于根据所述电信号调节所述驱动电源向所述光电探测器输出的电压，并根据所述电信号选择所述光电探测器上用于加载电压的电极，以控制所述光电探测器在第一工作模式和第二工作模式之间切换。
  17. 根据权利要求16所述的接收端设备，其特征在于，所述驱动电源向所述光电探测器的第二电极和第三电极输出第一电压，所述信号处理器具体用于：
    检测所述电信号的强度；
    若所述电信号的强度小于阈值，则调节所述驱动电源向所述光电探测器的第一电极和第二电极输出第二电压，以控制所述光电探测器从所述第一工作模式切换到所述第二工作模式。
  18. 根据权利要求16所述的接收端设备，其特征在于，所述驱动电源向所述光电探测器的第一电极和第二电极输出第二电压，所述信号处理器具体用于：
    检测所述电信号的强度；
    若所述电信号的强度大于或等于阈值，则调节所述驱动电源向所述光电探测器的第二电极和第三电极输出第一电压，以控制所述光电探测器从所述第二工作模式切换到所述第一工作模式。
  19. 一种工作模式的切换方法，其特征在于，所述工作模式切换方法应用于如权利要求1至15中任一项所述的光电探测器，所述方法包括：
    接收所述光电探测器输出的电信号；
    根据所述电信号调节向所述光电探测器输出的电压，并根据所述电信号选择所述光电探测器上用于加载电压的电极，以控制所述光电探测器在第一工作模式和第二工作模式之间切换。
  20. 根据权利要求19所述的方法，其特征在于，所述光电探测器的第二电极和第三电极上加载第一电压，控制所述光电探测器在第一工作模式和第二工作模式之间切换包括：
    检测所述电信号的强度；
    若所述电信号的强度小于阈值，则向所述光电探测器的第一电极和第二电极输出第二电压，以控制所述光电探测器从所述第一工作模式切换到所述第二工作模式。
  21. 根据权利要求19所述的方法，其特征在于，所述光电探测器的第一电极和第二电极上加载第二电压，控制所述光电探测器在第一工作模式和第二工作模式之间切换包括：
    检测所述电信号的强度；
    若所述电信号的强度大于或等于阈值，则向所述光电探测器的第二电极和第三电极输出第一电压，以控制所述光电探测器从所述第二工作模式切换到所述第一工作模式。
PCT/CN2023/077327 2022-03-08 2023-02-21 一种光电探测器、接收端设备和工作模式的切换方法 WO2023169203A1 (zh)

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