Tunable wide-spectrum photoelectric detector based on Schottky junction and preparation method thereof

Abstract

The invention discloses a tunable wide-spectrum photoelectric detector based on a Schottky junction. The photoelectric detector comprises an N-type silicon substrate, a gate ferroelectric medium, a gate electrode, a source electrode and a drain electrode, the source electrode, the gate ferroelectric medium and the drain electrode are sequentially arranged on the N-type silicon substrate, and the gate electrode is arranged on the gate ferroelectric medium; the gate ferroelectric medium is made of ferroelectric material hafnium oxide, and the gate ferroelectric medium and the gate electrode jointly form a ferroelectric gate; the gate electrode is made of transparent metal oxide. According to the silicon-based infrared detector, the silicon CMOS manufacturing technology and a simple device structure are used, the preparation difficulty of the silicon-based infrared detector is greatly reduced, and the detection long wave limit of the silicon-based infrared detector is expanded to the near-infrared band by means of the characteristic that the polarization intensity of ferroelectricity is weakened when the ferroelectricity is irradiated by infrared light. The invention further discloses a preparation method and application of the tunable wide-spectrum photoelectric detector based on the Schottky junction.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor optoelectronic devices, and particularly to a wide-spectrum photodetector based on a Schottky junction tunable and a preparation method thereof. Background Art

[0002] Since the third industrial revolution, especially with the rapid development of integrated circuits and information technology, the demand of human society for the detection and processing of natural information has been increasing day by day. By detecting and processing information such as light, sound, and electricity, various machines have acquired sensory organs similar to those of humans. A photodetector is a device that converts an optical signal into an electrical signal and has been widely applied in the fields of optical communication, optical interconnection, imaging technology, disaster warning, etc. Nowadays, the information society characterized by "Internet of Things" and "big data" requires the further development of electronic and optoelectronic technologies, especially in the fields of telecommunications and communication. As a receiving end, the photodetector is one of the most important components in such optical communication networks. 850nm, 1310nm, and 1550nm have almost zero absorption characteristics in optical fibers and are the three most commonly used wavelengths in the field of optical communication.

[0003] Silicon (Si) is the second most abundant element in the earth's crust, and has high thermal stability and mature processing technology, and has been widely used in the field of integrated circuits. If near-infrared band detection can be achieved using silicon materials, the cost of photodetectors will be greatly reduced. However, the optical wavelength that a detection material can absorb usually depends on the bandgap width of the material. The bandgap width of silicon material is 1.12eV, which can only support the detection of light with a wavelength of about 1100nm or less, making it impossible to directly use the widely used and low-cost silicon materials and silicon-based CMOS processes for the detection of the two commonly used wavelengths of 1310nm and 1550nm in the field of near-infrared communication. Although infrared detection can be achieved by selecting other infrared detection materials, realizing low-cost infrared detection by means of mature silicon CMOS processing technology is still the goal that people strive for.

[0004] Black silicon and heavy doping processes have certain application potential in expanding the detection long-wave limit, but they are only partially compatible with the CMOS process. The processes such as femtosecond laser and chemical etching commonly used by them need to be further studied and optimized to adapt to large-scale production, and the heavy doping process requires precise control of doping concentration and annealing conditions, and is prone to problems such as performance degradation and non-uniform material properties at high temperatures. It increases its surface area, resulting in serious surface recombination, which is not conducive to the preparation of high-performance devices. Although the surface recombination can be effectively reduced by growing a passivation layer on the microstructure surface, it is not conducive to forming good contacts for the device.

[0005] The hot electron detector of the silicon-based hot electron detector has a high energy loss of the hot electron detector, limited absorption efficiency, and low detection efficiency. Moreover, its dark current is high, the performance is relatively poor, and the injection of hot carriers will affect the device life, resulting in a reduction of device parameters and causing reliability problems.

[0006] Although directly using infrared detection materials can directly and effectively detect infrared light, it is difficult to be compatible with the silicon CMOS process, or the materials themselves are difficult to obtain, and even lead to high costs. In addition, for example, some high-performance InGaAs detectors require cryogenic cooling to reduce dark current and noise, increasing the complexity and power consumption of the system. Summary of the Invention

[0007] In order to solve the above problems existing in the prior art, the present invention provides a Schottky junction-based tunable wide-spectrum photodetector and a preparation method thereof. The technical problems to be solved by the present invention are realized through the following technical solutions:

[0008] The first aspect of the embodiment of the present invention provides a Schottky junction-based tunable wide-spectrum photodetector, including: an N-type silicon substrate, a gate ferroelectric dielectric, a gate electrode, a source electrode, and a drain electrode;

[0009] The source electrode, the gate ferroelectric dielectric, and the drain electrode are sequentially arranged on the N-type silicon substrate, and the gate electrode is arranged on the gate ferroelectric dielectric; the gate ferroelectric dielectric and the gate electrode form a ferroelectric gate;

[0010] The material of the gate ferroelectric dielectric is a ferroelectric material, and the ferroelectric material is hafnium oxide;

[0011] The material of the gate electrode is a transparent metal oxide;

[0012] Wherein, when a positive voltage pulse or a negative voltage pulse is applied to the ferroelectric gate, infrared light irradiates the gate ferroelectric dielectric to weaken the polarization intensity of the gate ferroelectric dielectric, so as to increase or decrease the channel dark current.

[0013] In an embodiment of the present invention, the material of the gate electrode is transparent indium tin oxide.

[0014] In an embodiment of the present invention, when a positive voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric obtains a downward polarization state. When infrared light irradiates the gate electrode, the downward polarization intensity of the gate ferroelectric dielectric is weakened, so as to increase the channel dark current.

[0015] In an embodiment of the present invention, when a negative voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric obtains an upward polarization state. When infrared light irradiates the gate electrode, the upward polarization intensity of the gate ferroelectric dielectric is weakened, so as to decrease the channel dark current.

[0016] In one embodiment of the present invention, the thickness of the gate ferroelectric dielectric is 10 nm to 15 nm.

[0017] The second aspect of the embodiments of the present invention provides a method for preparing a Schottky junction-based tunable wide-spectrum photodetector, including the following steps:

[0018] Step 1, perform N-type doping on a silicon substrate by ion implantation to obtain an N-type silicon substrate;

[0019] Step 2, after performing selective area lithography on the gate electrode region, expose the gate electrode processing window, and deposit hafnium oxide on the gate electrode processing window to prepare the gate ferroelectric dielectric of the ferroelectric material;

[0020] Step 3, after performing selective area lithography on the gate electrode region, expose the gate electrode processing window, and deposit a transparent metal oxide on the gate ferroelectric dielectric in the gate electrode processing window to prepare the gate electrode;

[0021] Step 4, prepare a source electrode and a drain electrode on both sides of the gate ferroelectric dielectric of the product prepared in Step 3, and prepare a gate electrode connecting metal on the gate electrode.

[0022] In one embodiment of the present invention, the metal materials of the gate electrode connecting metal, the source electrode, and the drain electrode are the same.

[0023] In one embodiment of the present invention, the material of the gate electrode is transparent indium tin oxide.

[0024] In one embodiment of the present invention, the thickness of the gate ferroelectric dielectric is 10 nm to 15 nm.

[0025] The third aspect of the embodiments of the present invention provides an infrared camera, characterized in that the sensor of the infrared camera includes a plurality of Schottky junction-based tunable wide-spectrum photodetectors provided in the first aspect of the embodiments of the present invention that form an array structure.

[0026] Advantages of the present invention:

[0027] By utilizing the characteristics that the spontaneous polarization and the remanent polarization of the ferroelectric material decrease in polarization intensity when irradiated by infrared light, the present invention converts the changing polarization intensity into the regulation of the channel carrier concentration, thereby extending the detection limit of silicon to the near-infrared range. At the same time, by designing the type of contact electrodes and adjusting the Schottky junction, the source and drain of the device achieve unipolar transport, and by utilizing different polarization states of the ferroelectric material, the switchable positive and negative responses of the detector are realized, and a tunable wide-spectrum photodetector from ultraviolet to near-infrared is completed.

[0028] Other features and advantages of the present invention will be set forth in the following description, and in part will be obvious from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention may be realized and attained by the structure particularly pointed out in the written description, claims, as well as the drawings.

[0029] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. Description of the Drawings

[0030] The drawings are used to provide a further understanding of the present invention, and constitute a part of the description. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0031] Figure 1 It is a schematic structural diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention;

[0032] Figure 2 It is a schematic energy band diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention when operating in the ultraviolet to 1100 nm light range;

[0033] Figure 3 It is a schematic energy band diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention when operating in the 1100 nm to near-infrared band range under a positive voltage pulse;

[0034] Figure 4 It is a schematic diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention generating a positive response;

[0035] Figure 5 It is a schematic energy band diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention when operating in the 1100 nm to near-infrared band range under a negative voltage pulse;

[0036] Figure 6 It is a schematic diagram of a Schottky-junction tunable broadband photodetector provided by an embodiment of the present invention generating a negative response;

[0037] Figure 7 It is a schematic diagram of two original frame data in one working cycle of a Schottky-junction tunable broadband photodetector array provided by an embodiment of the present invention;

[0038] Figure 8 It is a schematic diagram of the output data of an event camera provided by an embodiment of the present invention. Detailed Embodiments

[0039] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto.

[0040] As Figure 1 shown, in the first aspect of the embodiment of the present invention, a wide-spectrum photodetector based on a Schottky junction tunable is provided, including: an N-type silicon substrate 1, a gate ferroelectric dielectric 2, a gate electrode 3, a source electrode 4, and a drain electrode 5.

[0041] The source electrode 4, the gate ferroelectric dielectric 2, and the drain electrode 5 are sequentially disposed on the N-type silicon substrate 1, and the gate electrode 3 is disposed on the gate ferroelectric dielectric 2. The material of the gate ferroelectric dielectric 2 is a ferroelectric material, and the ferroelectric material is hafnium oxide; the gate ferroelectric dielectric 2 and the gate electrode 3 together form a ferroelectric gate, and the material of the gate electrode 3 is a transparent metal oxide.

[0042] Among them, when a positive voltage pulse or a negative voltage pulse is applied to the ferroelectric gate, infrared light irradiates the gate ferroelectric dielectric 2 to weaken the polarization intensity of the gate ferroelectric dielectric 2, so as to increase or decrease the channel dark current.

[0043] The thickness of the gate ferroelectric dielectric 2 is 10 nm to 15 nm. The material of the gate electrode 3 is transparent indium tin oxide.

[0044] In this embodiment, the ferroelectric is integrated into the silicon Schottky junction device, used as the gate dielectric, and the ferroelectric polarization electric field is used to modulate the silicon material channel. Utilizing the pyroelectric effect of the ferroelectric material, the detection limit of the silicon material is extended to the near infrared, and a switchable infrared positive and negative response is achieved, and it is applied to an infrared event camera. The structure and preparation of the photodetector in this embodiment are very simple, and it can be completely prepared using a silicon-based CMOS process.

[0045] The working principle of the photodetector of the present invention is that the Schottky barrier formed by the contact of the source electrode 4 metal, the drain electrode 5 metal, and the N-type silicon can form a built-in electric field, which helps the separation of electron-hole pairs generated by silicon absorbing light in the ultraviolet to 1100 nm light range, as Figure 2 shown. Due to the existence of the Schottky barrier, the photo-generated electrons are blocked, while the photo-generated minority carrier holes can be absorbed by the metal electrode, thereby generating a photocurrent.

[0046] For the near-infrared band from 1100 nm to a farther distance, the silicon material cannot absorb it, and the ferroelectric polarization change can be used to detect it. Applying a large positive voltage pulse (5V - 10V voltage) to the ferroelectric gate can make the gate ferroelectric dielectric 2 obtain a downward polarization state. In this state, the Si channel is modulated to an N - I - N type, as Figure 3As shown in the left figure, the carrier concentration in the v region is the lowest. Due to the extremely high resistivity of the I region, even under the action of the source-drain bias voltage, the device has a very low dark current in this state. When infrared light such as 1550 nm irradiates on the gate ferroelectric dielectric 2, it will cause the polarization intensity of the gate ferroelectric dielectric 2 to weaken, which weakens the downward polarization intensity, and the gate ferroelectric dielectric 2 cannot maintain the Si channel in the depletion state, and the entire channel is modulated to N~N - ~N type, as Figure 3 shown in the right figure, the carrier concentration in the N - region is less than that in the N region, and the resistivity of the N - region is greatly reduced compared with the previous I region, which increases the channel current. Figure 4 This is a schematic diagram of the positive response of the photodetector. That is, through the influence of light irradiation on the polarization state in the ferroelectric downward polarization state, the ferroelectric expands the detection limit of the Si detector to the near-infrared of 1550 nm, realizing the positive response of the detector in the near-infrared band.

[0047] When a large negative voltage pulse is applied to the ferroelectric gate, the working principle of the device is reversed. The gate ferroelectric dielectric 2 obtains an upward polarization state. At this time, the channel of the Si material is modulated to N~N + ~N type, as Figure 5 shown in the left figure, the carrier concentration in the N + region is greater than that in the N region, and the resistivity of the N + region is extremely low, and the device can obtain a relatively large dark current under the source-drain bias voltage. When the same infrared light irradiates on the gate ferroelectric dielectric 2, it also causes the polarization intensity of the gate ferroelectric dielectric 2 to weaken, which weakens the upward polarization intensity, as Figure 5 shown in the right figure, the gate ferroelectric dielectric 2 cannot maintain the Si channel in the N + ultra-low resistivity state, that is, the channel current decreases. This state realizes the negative response of the detector in the near-infrared band, Figure 6 which is a schematic diagram of the negative response of the photodetector.

[0048] Using these two states, an infrared photodetector with tunable positive and negative responses is realized, and an infrared event camera can be designed using this feature. In the fields of security and so on, traditional cameras will record the information of each frame, which greatly occupies the storage space, while the event camera can record an event only when the picture changes. Based on the infrared camera of the present invention, the design complexity of the event camera is greatly simplified.

[0049] By designing the tunable photodetector of the present invention into a detector array, imaging can be performed. It is defined that the photodetector operates in a working cycle of continuously switching between the downward polarization state and the upward polarization state. One cycle contains a positive response interval and a negative response interval, that is, one working cycle contains two original frame data,Figure 7 These are schematic diagrams of two original frame data. After one working cycle, the two original frame data are directly added together to obtain the changing part of the two original frame data. If the changing part of this working cycle is zero, it means no event has occurred; otherwise, the changing part is recorded as an event. Figure 8 This is an example of the output of an event camera. The recorded scene events are as follows: there are multiple vehicles moving on the road, some vehicles are turning, the outlines of the trees reveal that there should be wind at this time, and the stationary parts are all omitted.

[0050] The present invention uses silicon CMOS manufacturing technology and a simple device structure, greatly reducing the preparation difficulty and structural complexity of silicon-based infrared detectors. By taking advantage of the characteristic that the polarization intensity of ferroelectric decreases under infrared light illumination, the long-wavelength detection limit of silicon-based infrared detectors is extended to the near-infrared band. The present invention realizes the tunable positive and negative responses of infrared through the polarization state of the gate ferroelectric dielectric 2, greatly simplifying the design difficulty of infrared event cameras.

[0051] The second aspect of the embodiments of the present invention provides a preparation method for a Schottky-junction tunable broadband photodetector, including the following steps:

[0052] Step 1: Perform N-type doping on a silicon substrate by ion implantation to obtain an N-type silicon substrate 1, and the N-type doping concentration is 5×10 18 cm -3 ~5×10 19 cm -3 . The silicon wafer used is a standard N-type doped one, and the doping concentration of the substrate can be adjusted by ion implantation.

[0053] Step 2: After performing selective area lithography on the gate electrode 3 region to expose the processing window of the gate electrode 3, deposit hafnium oxide on the processing window of the gate electrode 3 to prepare the gate ferroelectric dielectric 2 of the ferroelectric material. The thickness of the gate ferroelectric dielectric 2 is 10 nm to 15 nm.

[0054] Step 3: After performing selective area lithography on the gate electrode 3 region to expose the processing window of the gate electrode 3, deposit transparent indium tin oxide on the gate ferroelectric dielectric 2 in the processing window of the gate electrode 3 to prepare the gate electrode 3.

[0055] Step 4: Prepare a source electrode 4 and a drain electrode 5 on both sides of the gate ferroelectric dielectric 2 of the product prepared in Step 3, and prepare a gate electrode connection metal on the gate electrode 3. The metal materials of the gate electrode connection metal, the source electrode 4, and the drain electrode 5 are the same. The metals of the source electrode 4 and the drain electrode 5 are in direct contact with the N-type silicon substrate 1 to form a Schottky junction. After preparation, the Schottky-junction tunable broadband photodetector of the first aspect of the embodiments of the present invention is obtained.

[0056] The preparation method of the photodetector with the gate ferroelectric dielectric 2 of the present invention as the gate dielectric is completely prepared using the silicon-based CMOS process, with strong preparation process compatibility and cost savings in preparation.

[0057] The third aspect of the embodiment of the present invention provides an infrared camera, and the sensor of the infrared camera includes a plurality of the wide-spectrum photodetectors based on Schottky junction tunable provided in the first aspect of the embodiment of the present invention that form an array structure.

[0058] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0059] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more, unless otherwise specifically defined.

[0060] In the present invention, unless otherwise clearly defined and limited, terms such as "mounted", "connected", "connected to", "fixed" and the like should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the first feature being "above", "over" and "on" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under" and "beneath" the second feature includes the first feature being directly below and obliquely below the second feature, or merely indicating that the horizontal height of the first feature is lower than that of the second feature.

[0062] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0063] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these changes and modifications.

Claims

1. A tunable wide-spectrum photodetector based on Schottky junction, characterized in that: include: N-type silicon substrate, gate ferroelectric dielectric, gate electrode, source electrode and drain electrode; The source electrode, the gate ferroelectric dielectric and the drain electrode are sequentially arranged on the N-type silicon substrate, and the gate electrode is arranged on the gate ferroelectric dielectric; the gate ferroelectric dielectric and the gate electrode constitute a ferroelectric gate; The material of the gate ferroelectric dielectric is a ferroelectric material, and the ferroelectric material is hafnium oxide; The material of the gate electrode is a transparent metal oxide; When a positive voltage pulse or a negative voltage pulse is applied to the ferroelectric gate, infrared light irradiates the gate ferroelectric dielectric to weaken the polarization intensity of the gate ferroelectric dielectric, thereby increasing or reducing the channel dark current.

2. A Schottky junction tunable wide spectrum photodetector as claimed in claim 1, characterized in that: The gate electrode is made of transparent indium tin oxide.

3. The Schottky junction tunable wide spectrum photodetector according to claim 1, characterized in that: When a positive voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric obtains a downward polarization state. When infrared light irradiates the gate electrode, the downward polarization intensity of the gate ferroelectric dielectric is weakened to increase the channel dark current.

4. The Schottky junction tunable wide spectrum photodetector according to claim 1, characterized in that: When a negative voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric obtains an upward polarization state. When infrared light irradiates the gate electrode, the upward polarization intensity of the gate ferroelectric dielectric is weakened to reduce the channel dark current.

5. The Schottky junction tunable wide spectrum photodetector according to claim 1, characterized in that: The thickness of the gate ferroelectric dielectric is 10 nm to 15 nm.

6. A method for preparing a tunable wide-spectrum photodetector based on a Schottky junction, characterized in that: The following steps are involved: Step 1, performing N-type doping on the silicon substrate by ion implantation to obtain an N-type silicon substrate; Step 2, after selective photolithography is performed on the gate electrode region, a gate electrode processing window is exposed, and hafnium oxide is deposited on the gate electrode processing window to prepare a gate ferroelectric dielectric of a ferroelectric material; Step 3, after selective photolithography of the gate electrode region, a gate electrode processing window is exposed, and a transparent metal oxide is deposited on the gate ferroelectric dielectric in the gate electrode processing window to prepare a gate electrode; Step 4: Prepare a source electrode and a drain electrode on both sides of the gate ferroelectric dielectric on the product prepared in step 3, and prepare a gate electrode connection metal on the gate electrode.

7. The method for preparing a Schottky junction tunable wide spectrum photodetector according to claim 6, characterized in that: The gate electrode connection metal, the source electrode and the drain electrode are made of the same metal material.

8. The method for preparing a Schottky junction tunable wide spectrum photodetector according to claim 6, characterized in that: The gate electrode is made of transparent indium tin oxide.

9. The method for preparing a Schottky junction tunable wide spectrum photodetector according to claim 6, characterized in that: The thickness of the gate ferroelectric dielectric is 10 nm to 15 nm.

10. An infrared camera, characterized in that: The sensor of the infrared camera comprises a plurality of Schottky junction-based tunable wide-spectrum photodetectors as described in any one of claims 1 to 5 forming an array structure.

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