Bipolar response dual-color detector, method of making and use thereof

Abstract

The application discloses a dual-color detector with bipolar response, a preparation method and application thereof. The detector comprises a first light absorption layer capable of absorbing light in a first wavelength domain and forming photo-generated carriers based on a photovoltaic effect; a second light absorption layer capable of absorbing light in a second wavelength domain and forming photo-generated carriers based on a photothermoelectric effect, the second light absorption layer cooperating with the first light absorption layer to form a pn heterojunction; a first electrode in electrical contact with the first light absorption layer, and the first electrode being spaced apart from the second light absorption layer; and a second electrode in electrical contact with the second light absorption layer. The dual-color detector has the advantages of high integration, bipolar response, low energy consumption, simple operation, high accuracy, and great significance for simplifying the design of an optical communication system and realizing an efficient signal modulation scheme.

Description

Technical Field

[0001] This application relates to an ultraviolet-infrared dual-color detector, specifically a semiconductor heterojunction bipolar response dual-color detector, its fabrication method and application, belonging to the field of optoelectronic technology. Background Technology

[0002] The research and application of optoelectronic information is an important part of the fields of electronic information, optics, and semiconductor technology. It is also a core technology that drives the information technology revolution and national economic development. Photodetectors are the foundation for human beings to utilize optoelectronic information. In particular, infrared detectors and ultraviolet detectors have been widely used in all aspects of people's lives.

[0003] With the development of technology and the increasing complexity of detection environments, monochromatic detectors are no longer sufficient to meet application needs in many scenarios. For example, when single-infrared detection technology uses infrared imaging to detect targets, it is easily interfered with by other targets, such as roads and buildings, especially the strong reflection of sunlight from the ground, making false alarms very likely. On the other hand, the strong absorption and scattering of ultraviolet light by the atmosphere limits the range of single-ultraviolet detection. When the ultraviolet component of the target is weak, the disadvantage in detection range is further amplified. Therefore, in order to effectively suppress the influence of background complexity on the detector and improve the detector's detection performance against blurred backgrounds or constantly changing targets, researchers have integrated infrared and ultraviolet detectors to create infrared-ultraviolet dual-color detectors that can simultaneously detect ultraviolet and infrared bands. This has become an important direction in the development of photoelectric detectors.

[0004] Currently, commercially available ultraviolet and infrared detectors rely on the integration of circuits from detectors of different wavelengths, combining ultraviolet and infrared detection circuits into the same detection system. This structure presents certain challenges for circuit design, and the integration of different circuits results in a large detection system with low integration density. Furthermore, since ultraviolet detection technology often relies on the photomultiplication effect requiring high voltage, it leads to high energy consumption and related safety issues.

[0005] In recent years, some scholars have proposed using heterogeneous integration of ultraviolet and infrared photosensitive materials to achieve detection of different wavelengths by a single detector through the photovoltaic effect. For example, researchers have integrated a multilayer heterojunction structure of zinc oxide (ZnO) and reduced graphene oxide (RGO) onto the same device, achieving detection of different wavelengths. This device achieved a responsivity of 0.13 AW under 365 nm ultraviolet light irradiation. -1Furthermore, it exhibits significant photoresponse capabilities in both the visible light band (412-519 nm) and the infrared band (>780 nm). Other researchers have also implemented a dual-band heterogeneous detector combining ultraviolet and infrared wavelengths using black phosphorus (BP), a two-dimensional infrared photosensitive material with high hole mobility and a tunable bandgap, and gallium oxide (Ga2O3), a naturally solar-blind ultraviolet material with strong radiation resistance. This device achieves 88.4 mA W in the ultraviolet (254 nm) and infrared (1030 nm) bands, respectively. -1 and 1.24mA W -1 While these photovoltaic-based dual-band detector designs can significantly reduce device power consumption and improve device integration, they cannot distinguish the wavelength of incident light. Therefore, in digital applications such as optical communication systems, they still need to be used with filters, which greatly inhibits their application advantages and development. Summary of the Invention

[0006] The main objective of this application is to provide a bipolar response dual-color detector, its fabrication method, and its application, in order to overcome the shortcomings of the prior art.

[0007] To achieve the aforementioned objectives, the technical solution adopted in this application includes:

[0008] One aspect of this application provides a bipolar response dual-color detector, comprising:

[0009] The first light-absorbing layer is capable of absorbing light in the first wavelength domain and forming photogenerated carriers based on the photovoltaic effect.

[0010] The second light absorption layer is capable of absorbing light in the second wavelength domain and forming photogenerated carriers based on the photothermoelectric effect. The second light absorption layer and the first light absorption layer are stacked together and the two work together to form a pn heterojunction. The first wavelength domain is different from the second wavelength domain.

[0011] The first electrode is electrically in contact with the first light-absorbing layer, and the first electrode and the second light-absorbing layer are disposed at a distance.

[0012] The second electrode is in electrical contact with the second light-absorbing layer.

[0013] Another aspect of this application provides a method for fabricating the bipolar response dual-color detector, comprising:

[0014] The first light-absorbing layer is grown on the substrate.

[0015] A second light-absorbing layer is disposed on a second region of the surface of the first light-absorbing layer, and the first region of the surface of the first light-absorbing layer is exposed.

[0016] A first electrode is disposed on a first region of the surface of the first light-absorbing layer, and

[0017] A second electrode is disposed on the second light absorption layer.

[0018] Another aspect of this application provides the use of the bipolar response dual-color detector in the fields of optical detection and optical communication.

[0019] Compared with existing technologies, the bipolar response dual-color detector provided in this application has a semiconductor heterogeneous integrated structure with high integration. Furthermore, the detector achieves light detection in different wavelength bands based on the photovoltaic effect and photothermal effect. No additional power supply is required during the detection process, resulting in low energy consumption. Moreover, the wavelength of the incident light can be determined simply by judging the direction of the current generated within the device during the detection process. It is simple to operate and highly accurate, which is of great significance for simplifying the design of optical communication systems and realizing high-efficiency signal modulation schemes. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a bipolar response dual-color detector according to an embodiment of this application;

[0022] Figure 2 This is a schematic diagram of the fabrication process of a bipolar response dual-color detector in one embodiment of this application;

[0023] Figure 3 This is a schematic diagram of the electron concentration distribution within a bipolar response dual-color detector according to one embodiment of this application;

[0024] Figure 4 This is a schematic diagram of the built-in potential distribution of a bipolar response dual-color detector in one embodiment of this application;

[0025] Figure 5 This is a transient response test diagram of a bipolar response dual-color detector according to an embodiment of this application;

[0026] Figure 6 This is a dark current test diagram of a bipolar response dual-color detector according to one embodiment of this application. Detailed Implementation

[0027] This application will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of this application are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary and that this application may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as a representative basis for teaching those skilled in the art to employ this application differently in any suitable detailed embodiment.

[0028] Some embodiments of this application provide a bipolar response dual-color detector, including:

[0029] The first light-absorbing layer is capable of absorbing light in the first wavelength domain and forming photogenerated carriers based on the photovoltaic effect.

[0030] The second light absorption layer is capable of absorbing light in the second wavelength domain and forming photogenerated carriers based on the photothermoelectric effect. The second light absorption layer and the first light absorption layer are stacked together and the two work together to form a pn heterojunction. The first wavelength domain is different from the second wavelength domain.

[0031] The first electrode is electrically in contact with the first light-absorbing layer, and the first electrode and the second light-absorbing layer are disposed at a distance.

[0032] The second electrode is in electrical contact with the second light-absorbing layer.

[0033] In one embodiment, the photogenerated electromotive force of the dual-color detector is in the opposite direction to the thermoelectric electromotive force.

[0034] In one embodiment, the first light-absorbing layer is an n-type semiconductor layer, the second light-absorbing layer is stacked on the first light-absorbing layer, and the doping concentration of the first light-absorbing layer is matched with the hole concentration of the second light-absorbing layer, so that the second light-absorbing layer can fully deplete the electrons in the region of the first light-absorbing layer located directly below the second light-absorbing layer, thereby forming a lateral depletion region in the first light-absorbing layer.

[0035] In one embodiment, the doping concentration of the first light-absorbing layer is 5e15 to 5e16 cm⁻¹. -3 .

[0036] In one embodiment, the doping concentration of the second light-absorbing layer is 1e17 to 1e18 cm⁻¹. -3 .

[0037] In one embodiment, the thickness of the second light-absorbing layer is 300–350 nm.

[0038] In one embodiment, the first electrode and the second light absorption layer are respectively disposed on a first region and a second region on the surface of the first light absorption layer, and the distance between the first electrode and the second light absorption layer is 1 to 2 μm.

[0039] In one embodiment, the first light-absorbing layer is disposed on a high-resistivity substrate. Preferably, the high-resistivity substrate and the first light-absorbing layer are homogeneous, i.e., homogeneous substrates are used to improve the quality of the first light-absorbing layer.

[0040] In one embodiment, the first electrode forms an ohmic contact with the first light-absorbing layer.

[0041] In one embodiment, the region on the surface of the first light-absorbing layer that is bonded to the first electrode has a roughened structure, and its root mean square roughness is preferably above 8 nm, for example, 8 to 40 nm.

[0042] The light in the first wavelength domain is ultraviolet light (preferably, 0 < first wavelength domain < 254nm), and the light in the second wavelength domain is infrared light (preferably 800~1033nm).

[0043] In one embodiment, the first light-absorbing layer is made of a semiconductor material with a band gap greater than 4.42 eV and less than or equal to 6.0 eV, such as AlGaN with high Al content, diamond, gallium oxide, etc., and is not limited thereto. Gallium oxide is preferred because it has a suitable band gap and good stability.

[0044] Furthermore, Si or other donor elements can be used to dope the first light-absorbing layer, making it an n-type semiconductor material.

[0045] In one embodiment, the second electrode covers the second light-absorbing layer and is capable of selectively blocking light in the first wavelength range while allowing light in the second wavelength range to pass through. Preferably, the second electrode completely covers the second light-absorbing layer.

[0046] In one embodiment, the material of the second light-absorbing layer is an infrared photosensitive material, preferably a thermoelectric material with a Seebeck coefficient higher than 661 μV / K, such as any one or more combinations of tin sulfide (SnS), strontium titanate (SrTiO3), barium titanate (BaTiO3), and antimony selenide (Sb2Se3), but not limited thereto.

[0047] In one embodiment, the material of the first electrode includes metals, such as Ti, Au, or combinations thereof, but is not limited thereto.

[0048] In one embodiment, the material of the second electrode includes ITO, but is not limited thereto.

[0049] This application discloses a bipolar response dual-color detector, a self-actuated device combining photovoltaic and photothermal effects. The photovoltaic effect relies on the built-in electric field between a pn heterojunction of a first light-absorbing layer (e.g., formed of an ultraviolet photosensitive material) and a second light-absorbing layer (e.g., formed of an infrared photosensitive material), while the photothermal effect is achieved through the thermal effect of thermoelectric materials and light in the second wavelength domain. By controlling parameters such as the doping concentration of the first light-absorbing layer, the film thickness of the second light-absorbing layer, and the size and spacing of the electrodes, particularly by designing the doping concentration of the first light-absorbing layer, the distribution and magnitude of the built-in electric field are designed, achieving a balance between the built-in potential difference and the thermoelectric potential. When the built-in potential difference and the thermoelectric potential are in opposite directions, photocurrents of different polarities (different directions) will be obtained under different illuminations.

[0050] Some embodiments of this application provide a method for preparing the bipolar-response dual-color detector, including:

[0051] The first light-absorbing layer is grown on the substrate.

[0052] A second light-absorbing layer is disposed on a second region of the surface of the first light-absorbing layer, and the first region of the surface of the first light-absorbing layer is exposed.

[0053] A first electrode is disposed on a first region of the surface of the first light-absorbing layer, and

[0054] A second electrode is disposed on the second light absorption layer.

[0055] In one embodiment, the preparation method specifically includes: sequentially growing a first light-absorbing layer and a second light-absorbing layer on a substrate, then removing a first portion of the second light-absorbing layer while retaining a second portion of the second light-absorbing layer, wherein the first portion and the second portion of the second light-absorbing layer are respectively disposed on a first region and a second region on the surface of the first light-absorbing layer, thereby exposing the first region on the surface of the first light-absorbing layer.

[0056] The first light-absorbing layer can be grown on the substrate using chemical and / or physical deposition methods such as MOCVD (metal-organic chemical vapor deposition) and PECVD (plasma-enhanced chemical vapor deposition), but is not limited to these methods. Furthermore, homoepitaxial growth of the first light-absorbing layer is preferred.

[0057] Among them, the second light-absorbing layer can be heteroepitaxially grown on the first light-absorbing layer by means of radio frequency magnetron sputtering, thermal evaporation, sol-gel selenization, vapor transport deposition, etc.

[0058] In one embodiment, the preparation method specifically includes:

[0059] The second light-absorbing layer is etched to remove a first portion of the second light-absorbing layer, thereby exposing a first region on the surface of the first light-absorbing layer.

[0060] Then, the first region on the surface of the first light-absorbing layer is etched until a roughened structure is formed.

[0061] In addition, the etching of the second light absorption layer and the first light absorption layer can also be achieved through dry etching processes such as inductively coupled plasma etching technology or wet etching processes.

[0062] In this process, by etching the first region on the surface of the first light-absorbing layer and forming a roughened structure, dangling bonds can be generated on the gallium oxide surface. These dangling bonds are easy to form alloys with metals, thereby further reducing the contact resistance between the first light-absorbing layer and the first electrode.

[0063] Some embodiments of this application also provide a light detection method, which includes: illuminating the light-receiving surface of the bipolar response dual-color detector with light to be detected, and determining the wavelength of the light to be detected based on the direction of the current generated in the detector.

[0064] Some embodiments of this application also provide an optical communication system including the aforementioned bipolar response dual-color detector. Specifically, the signal receiving end of the optical communication system includes the bipolar response dual-color detector. The photodetector of this application requires no external power supply during operation, has low energy consumption, and is distinguishable between infrared and ultraviolet light. When applied to an optical communication system, it can significantly simplify the system structure, improve system integration, significantly reduce system size, and optimize signal transmission efficiency.

[0065] The following will provide a further explanation of the technical solution, its implementation process, and its principles, in conjunction with the accompanying drawings.

[0066] Please see Figure 1 This embodiment provides a bipolar response dual-color detector based on Ga2O3 and Sb2Se3, comprising an Fe-doped Ga2O3 substrate 1, a Si-doped Ga2O3 thin film 2, an Sb2Se3 thin film 3, a Ti / Au electrode 4, and an ITO electrode 5. The Si-doped Ga2O3 thin film is deposited on the Fe-doped Ga2O3 substrate, and the Sb2Se3 thin film is deposited on a local area of ​​the surface of the Si-doped Ga2O3 thin film (which can be defined as a second region). Another local area of ​​the surface of the Si-doped Ga2O3 thin film (which can be defined as a first region) is where the Ti / Au electrode is disposed and forms an ohmic contact with the Si-doped Ga2O3 thin film. The ITO electrode is electrically bonded to the Sb2Se3 thin film and completely covers the Sb2Se3 thin film.

[0067] In some bipolar response dual-color detector samples of this embodiment, the Fe-doped Ga2O3 substrate can be a commercially available Ga2O3 substrate, with Fe doping to ensure high resistivity. The Si-doped Ga2O3 film has a thickness of approximately 100 nm and a doping concentration of 5e15–5e16 cm⁻¹. -3 Adjustable within a certain range. The thickness of the Sb₂Se₃ film is approximately 300 nm, and the Seebeck coefficient is approximately 661 μVK. -1 The doping concentration is between 1e17 and 1e18 cm⁻¹ -3 Adjustable within a certain range. The Ti / Au electrode can comprise stacked Ti and Au layers, with thicknesses of approximately 20 nm and 100 nm, respectively. The ITO electrode has a thickness of approximately 200 nm and a resistance < 7 Ω / sq. Simulations show that the above doping concentration combinations can extend the lateral depletion region (UV absorption region) to a maximum of 2.85 μm and a minimum of 1.55 μm, which corresponds to the distance between the first electrode and the second light-absorbing layer. The light absorption coefficient of the Sb₂Se₃ thin film is 7e⁴ cm⁻¹. -1 It can absorb 90% of infrared light (880nm); since light decays exponentially in Sb2Se3 thin films, an exponentially distributed temperature gradient and a stable potential difference will be obtained in Sb2Se3 thin films.

[0068] This bipolar response dual-color detector combines photovoltaic and photothermal effects through the heterogeneous integration of ultraviolet and infrared photosensitive materials. The photovoltaic effect refers to the separation of photogenerated carriers using a built-in potential difference, generating a current from the Ga₂O₃ thin film to the Sb₂Se₃ thin film. The photothermal effect refers to the use of the thermoelectric potential of Sb₂Se₃ to generate a current from the Sb₂Se₃ thin film to the Ga₂O₃ thin film. The magnitude of the thermoelectric potential can be calculated using the Seebeck coefficient, and the built-in potential difference can be simulated. By changing the magnitudes of the built-in potential difference and the thermoelectric potential, the dual-color detector can achieve high sensitivity.

[0069] Specifically, in the detector of this embodiment, since gallium oxide is n-type doped and Sb₂Se₃ is p-type doped, when the two combine, a positive space charge region is generated in gallium oxide and a negative space charge region is generated in Sb₂Se₃. The resulting built-in electric field points from gallium oxide to Sb₂Se₃. Photogenerated carriers separate in the built-in electric field, with photogenerated holes drifting towards Sb₂Se₃ and photogenerated electrons drifting towards gallium oxide. This causes the potential of Sb₂Se₃ to increase and the potential of gallium oxide to decrease. The photogenerated electromotive force moves from Sb₂Se₃ to Sb₂Se₃ within the device. The photoelectromotive force (e3) points towards gallium oxide (GaO), generating a photocurrent from GaO to Sb₂Se₃. Because Sb₂Se₃ has a large Seebeck coefficient, when infrared light shines on it, the light intensity exhibits an exponential distribution within the Sb₂Se₃, resulting in an exponentially distributed thermal field. Holes from high-temperature areas flow to low-temperature areas, i.e., from the upper surface of Sb₂Se₃ to GaO, causing the potential of the upper surface of Sb₂Se₃ to decrease and the potential of GaO to increase. The thermoelectric potential then points from GaO to Sb₂Se₃, forming a current from Sb₂Se₃ to GaO. In short, because the photoelectric potential under ultraviolet light and the thermoelectric potential under infrared light are in opposite directions, currents in different directions are generated.

[0070] Please see Figure 2 A method for preparing the bipolar response dual-color detector includes the following steps:

[0071] (1) Cleaning of the high-resistivity Ga2O3 substrate: A Ga2O3 substrate with an orientation of (001) grown using the guided mode method can be selected to grow a high-quality n-type Ga2O3 epitaxial film. The concentration of Fe ions in the Ga2O3 substrate exceeds its background carrier concentration, and the doping concentration is 2 × 10⁻⁶. 17 cm -3 Soak in acetone and isopropanol in sequence, then dry with nitrogen gas for later use.

[0072] (2) n-type Ga2O3 thin film epitaxy: Homoein epitaxy is performed on a Ga2O3 substrate using metal-organic chemical vapor deposition (MOCVD), and silane is introduced for Si doping. The doping concentration can be controlled to 5e15cm. -3 ~5e16cm -3 .

[0073] (3) Sb2Se3 thin film 3 heteroepitaxial growth: Sb2Se3 thin film was grown on Ga2O3 thin film in argon atmosphere using radio frequency sputtering equipment for 2700s, followed by annealing in nitrogen atmosphere for 1h at 300℃.

[0074] (4) Sb2Se3 thin film ICP etching: The Sb2Se3 thin film was etched using inductively coupled plasma (ICP) etching technology to expose the underlying Ga2O3 thin film. In order to form a good ohmic contact on the Ga2O3 thin film, the Ga2O3 thin film was etched to a certain extent, with an etching depth of about 40 nm.

[0075] (5) Fabrication of Ti / Au ohmic contact: Ti / Au electrode 4 was formed by sequentially depositing metallic Ti (20 nm) and Au (100 nm) on a Ga2O3 thin film using an electron beam evaporation apparatus, followed by annealing in a nitrogen atmosphere for 1 min at a temperature of 475 °C. Since the ultraviolet response of the device depends on the built-in electric field in the depletion region, it is preferable that the distance between the Ti / Au electrode and the Sb2Se3 thin film is 1 μm.

[0076] (6) ITO thin film deposition: ITO is deposited as an electrode on the Sb2Se3 thin film using an optical coating machine. Before depositing the ITO electrode, a photoresist mask is used to cover the Ti / Au metal and the exposed Ga2O3 surface. After the ITO deposition is completed, a stripping process is performed, leaving only the ITO electrode 5 on the Sb2Se3 thin film.

[0077] Please see Figures 3-4 The working principle of the bipolar response dual-color detector (hereinafter referred to as "device") in this embodiment includes:

[0078] Ultraviolet detection principle: The surface of the Sb₂Se₃ thin film in the device is completely covered by an ITO electrode. Since ITO has extremely low transmittance for ultraviolet light at 254 nm, the Sb₂Se₃ thin film will not produce any photoresponse to ultraviolet light. When the hole concentration of Sb₂Se₃ is greater than 1 × 10⁻⁶, the detection will be successful. 17 cm -3When the doping concentration of the Ga2O3 film reaches a certain value, electrons in the Ga2O3 film region directly below the Sb2Se3 film will be fully depleted, and the depletion region will expand laterally by a distance of approximately 1–2 μm. This lateral depletion region can be defined as the optical window for ultraviolet light. When the incident light is ultraviolet light and irradiates the lateral depletion region, the peak value of the photogenerated carrier generation rate coincides with the peak value of the built-in electric field intensity, which is most conducive to the separation and collection of photogenerated carriers. Therefore, the spacing between the Ga2O3 electrode and the Sb2Se3 film mesa is preferably 1–2 μm, because photogenerated carriers outside the depletion region will recombine quickly, leading to a decrease in quantum efficiency. Furthermore, an excessively large spacing will prolong the carrier transit time, reducing both the response speed and the device gain. Under the influence of the built-in electric field, the photogenerated carriers will generate a photocurrent in the direction of I1. By adjusting the Si doping concentration, impurity concentration distribution (Gaussian distribution, uniform distribution, etc.), and film thickness of the Ga2O3 thin film, the magnitude and distribution of the built-in electric field strength and built-in potential difference can be controlled. When the built-in electric field is strong enough and coincides with the peak value of the photogenerated carrier generation rate, it can greatly promote the generation and collection of photogenerated carriers, which is beneficial for realizing a high-sensitivity detector.

[0079] Infrared detection principle: When the wavelength of the incident light is greater than 254 nm, the Ga2O3 thin film (band gap of 4.9 eV) shows no response to the incident light; in this case, the Sb2Se3 thin film plays a major role in the photoresponse. This is because the Sb2Se3 thin film has a high absorption coefficient of 0.7 × 10⁻⁶ for near-infrared radiation at 880 nm. 5 cm -1 Infrared light is almost concentrated on the upper surface of the Sb₂Se₃ thin film, thus generating a top-down temperature gradient and thermoelectric potential within the film. Holes move towards Ga₂O₃ under the influence of this thermoelectric potential, generating a photocurrent in the direction of I₂.

[0080] Therefore, when using the device of this embodiment for detection, the wavelength of the incident light can be determined simply by judging the direction (polarity) of the current.

[0081] The device characteristics of a bipolar response dual-color detector sample in this embodiment are as follows: Figures 5-6 As shown. Among them, this Figure 5 The transient response performance of the sample is shown. Before 90 seconds, ultraviolet light was applied with a negative current; after 90 seconds, the light source changed to infrared light with a positive current. This indicates that the device generates currents in different directions for different wavelengths of light. τ r τ is the time it takes for the current in the device to reach its maximum value from the dark current at the instant an optical signal is applied. dThis is the time it takes for the device's current to decrease from its maximum value to its dark current during the instantaneous removal of the light signal. The bipolar response dual-color detector in this embodiment exhibits a millisecond-level fast response speed, which is highly advantageous for applications in high-speed optical communication systems and dual-color imaging systems. Figure 6 The dark current (noise current) characteristics of this sample are shown, i.e., the current value of the device in a dark environment. Testing revealed that the other samples in this embodiment also exhibit similar performance.

[0082] In this embodiment, the light absorption characteristics of Ga2O3 and ITO are used to filter infrared and ultraviolet light respectively, thereby achieving spatial division of the spectral response. This is beneficial for realizing the bipolar response of the device, that is, distinguishing the incident light. This can replace the use of filters, reduce the cost and size of the detection system, and reduce energy consumption.

[0083] In addition, the applicant replaced the aforementioned Sb2Se3 thin film with thermoelectric materials such as tin sulfide (SnS), strontium titanate (SrTiO3), and barium titanate (BaTiO3) to construct a series of bipolar response dual-color detectors, and tested their performance, finding that their performance was quite ideal.

[0084] The bipolar response dual-color detector of this embodiment can be used to detect infrared and ultraviolet light, and can also be used in the signal receiving end of an optical communication system. Utilizing its self-driving and bipolar response characteristics, it can replace external power supplies and filters, thereby significantly improving system integration and reducing system size, complexity, and energy consumption. Furthermore, demodulation of the light source signal can be achieved simply by controlling the wavelength of the incident light and changing the polarity of the detector's output current, thus simplifying the demodulation circuit and improving signal transmission efficiency. The signal modulation modes of the optical communication system include CSK, on / off keying, pulse position modulation, etc., but are not limited to these.

[0085] Although this application has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of this application, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of this application to adapt particular situations or materials to the teachings of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed for carrying out this application, but rather is intended to include all embodiments falling within the scope of the appended claims.

Claims

1. A bipolar response dual-color detector, characterized in that, include: The first light-absorbing layer is capable of absorbing light in the first wavelength domain and forming photogenerated carriers based on the photovoltaic effect. The second light-absorbing layer can absorb light in the second wavelength domain and form photogenerated carriers based on the photothermoelectric effect. The second light-absorbing layer and the first light-absorbing layer cooperate to form a pn heterojunction. The first wavelength domain is different from the second wavelength domain. The first electrode is electrically in contact with the first light-absorbing layer, and the first electrode and the second light-absorbing layer are disposed at a distance. The second electrode is in electrical contact with the second light-absorbing layer; Wherein, the first light-absorbing layer is an n-type semiconductor layer, the second light-absorbing layer is stacked on the first light-absorbing layer, and the doping concentration of the first light-absorbing layer is matched with the hole concentration of the second light-absorbing layer, so that the second light-absorbing layer can fully deplete the electrons in the region of the first light-absorbing layer located directly below the second light-absorbing layer, thereby forming a lateral depletion region in the first light-absorbing layer; and the photogenerated electromotive force in the detector is opposite in direction to the thermoelectric electromotive force.

2. The bipolar response dual-color detector according to claim 1, characterized in that, The doping concentration of the first light-absorbing layer is 5e15~5e16 cm⁻¹ -3 .

3. The bipolar response dual-color detector according to claim 1, characterized in that, The doping concentration of the second light-absorbing layer is 1e17~1e18 cm⁻¹ -3 .

4. The bipolar response dual-color detector according to claim 1, characterized in that, The thickness of the second light-absorbing layer is 300~350nm.

5. The bipolar response dual-color detector according to claim 1, characterized in that, The first electrode and the second light absorption layer are respectively disposed on the first region and the second region on the surface of the first light absorption layer, and the distance between the first electrode and the second light absorption layer is 1~2μm.

6. The bipolar response dual-color detector according to claim 1, characterized in that, 0 < first wavelength domain < 254nm, second wavelength domain is 800~1033nm.

7. The bipolar response dual-color detector according to claim 1, characterized in that, The first light-absorbing layer is made of a semiconductor material with a band gap greater than 4.42 eV and less than or equal to 6.0 eV.

8. The bipolar response dual-color detector according to claim 1, characterized in that, The first electrode is made of metal.

9. The bipolar response dual-color detector according to claim 1, characterized in that, The first light-absorbing layer is disposed on a high-resistivity substrate.

10. The bipolar response dual-color detector according to claim 1, characterized in that, The first electrode forms an ohmic contact with the first light-absorbing layer.

11. The bipolar response dual-color detector according to claim 1, characterized in that, The second electrode covers the second light-absorbing layer and can selectively block light in the first wavelength range while allowing light in the second wavelength range to pass through.

12. The bipolar response dual-color detector according to claim 1, characterized in that, The second light-absorbing layer is made of thermoelectric materials with a Seebeck coefficient higher than 661 μV / K.

13. The bipolar response dual-color detector according to claim 12, characterized in that, The thermoelectric material includes any one or more combinations of tin sulfide, strontium titanate, barium titanate, and antimony selenide.

14. The bipolar response dual-color detector according to claim 1, characterized in that, The material of the second electrode includes ITO.

15. The bipolar response dual-color detector according to claim 1, characterized in that, The light in the first wavelength domain is ultraviolet light, and the light in the second wavelength domain is infrared light.

16. A method for fabricating a bipolar response dual-color detector according to any one of claims 1-15, characterized in that, include: A first light-absorbing layer and a second light-absorbing layer are grown sequentially on a substrate. Then, a first portion of the second light-absorbing layer is removed, while a second portion of the second light-absorbing layer is retained. The first portion and the second portion of the second light-absorbing layer are respectively disposed on a first region and a second region on the surface of the first light-absorbing layer, thereby exposing the first region on the surface of the first light-absorbing layer. A first electrode is disposed on a first region of the surface of the first light-absorbing layer; A second electrode is disposed on the second light absorption layer.

17. The preparation method according to claim 16, characterized in that, Specifically, it includes: The second light-absorbing layer is etched to remove a first portion of the second light-absorbing layer, thereby exposing a first region on the surface of the first light-absorbing layer. Then, the first region on the surface of the first light-absorbing layer is etched until a roughened structure is formed.

18. The preparation method according to claim 17, characterized in that, The etching methods include dry etching or wet etching.

19. The preparation method according to claim 17, characterized in that, The root mean square roughness of the roughened structure is 8~40 nm.

20. A photodetector method, characterized in that, include: The light-receiving surface of the bipolar response dual-color detector according to any one of claims 1-15 is illuminated with light to be detected, and the wavelength of the light to be detected is determined according to the direction of the current generated in the detector.

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