A tunable broadband photodetector based on a Schottky junction and its fabrication method

Abstract

This invention discloses a tunable broadband photodetector based on a Schottky junction, comprising: an N-type silicon substrate, a gate ferroelectric dielectric, a gate electrode, a source electrode, and a drain electrode; the source electrode, gate ferroelectric dielectric, and drain electrode are sequentially disposed on the N-type silicon substrate, and the gate electrode is disposed on the gate ferroelectric dielectric; the gate ferroelectric dielectric is made of hafnium oxide, a ferroelectric material, and the gate ferroelectric dielectric and the gate electrode together constitute a ferroelectric gate; the gate electrode is made of a transparent metal oxide. This invention utilizes silicon CMOS manufacturing technology and a simple device structure, greatly reducing the fabrication difficulty of silicon-based infrared detectors, and by leveraging the characteristic that the polarization intensity of ferroelectrics weakens under infrared light, extends the detection long-wavelength limit of silicon-based infrared detectors to the near-infrared band. This invention also discloses a method for fabricating and applying a tunable broadband photodetector based on a Schottky junction.

Description

Technical Field

[0001] This invention relates to the field of semiconductor optoelectronic device technology, and in particular to a tunable broadband photodetector based on a Schottky junction and its fabrication method. Background Technology

[0002] Since the Third Industrial Revolution, especially with the rapid development of integrated circuits and information technology, human society's demand for the detection and processing of natural information has been increasing. By detecting and processing information such as light, sound, and electricity, various machines have acquired sensory organs similar to those of humans. Photodetectors, devices that convert light signals into electrical signals, have been widely used in optical communication, optical interconnection, imaging technology, and disaster early warning. Today, the information society characterized by the "Internet of Things" and "big data" demands further development of electronic and optoelectronic technologies, particularly in the telecommunications and communications fields. As the receiving end, the photodetector is one of the most important components in such optical communication networks. 850nm, 1310nm, and 1550nm wavelengths have almost zero absorption 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 its high thermal stability and mature processing technology have led to its widespread application in the integrated circuit field. If near-infrared detection could be achieved using silicon, the cost of photodetectors would be significantly reduced. However, the wavelength of light absorbed by a detection material typically depends on its bandgap. Silicon has a bandgap of 1.12 eV, supporting only wavelengths up to approximately 1100 nm. This means that the detection of commonly used near-infrared wavelengths like 1310 nm and 1550 nm in near-infrared communication cannot be directly achieved using widely available and inexpensive silicon materials and silicon-based CMOS processes. While infrared detection can be achieved by selecting other infrared detection materials, realizing low-cost infrared detection using mature silicon CMOS processing technology remains a key objective.

[0004] Black silicon and heavily doped processes have some application potential in extending the long-wavelength detection limit, but they only have partial compatibility with CMOS processes. The femtosecond lasers and chemical etching processes commonly used require further research and optimization to adapt to large-scale production. Furthermore, heavily doped processes require precise control of doping concentration and annealing conditions, and are prone to performance degradation and material inhomogeneity under high-temperature conditions. The increased surface area leads to severe surface recombination, which is detrimental to the fabrication of high-performance devices. While growing a passivation layer on the microstructure surface can effectively reduce surface recombination, it hinders the formation of good device contacts.

[0005] Silicon-based thermionic detectors suffer from high energy loss, limited absorption efficiency, and low detection efficiency. Furthermore, they exhibit high dark current, resulting in relatively poor performance. Hot carrier injection can also negatively impact device lifetime, leading to reduced device parameters and reliability issues.

[0006] While directly using infrared detection materials can effectively detect infrared light, these materials are often incompatible with silicon CMOS processes, or are difficult to obtain, leading to high costs. Furthermore, some high-performance InGaAs detectors require cryogenic cooling to reduce dark current and noise, increasing system complexity and power consumption. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, this invention provides a tunable broadband photodetector based on a Schottky junction and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0008] The first aspect of the present invention provides a tunable broadband photodetector based on a Schottky junction, comprising: 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 disposed on the N-type silicon substrate, and the gate electrode is disposed on the gate ferroelectric dielectric; the gate ferroelectric dielectric and the gate electrode constitute a ferroelectric gate.

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

[0011] The gate electrode is made of a transparent metal oxide.

[0012] Specifically, when a positive or negative voltage pulse is applied to the ferroelectric gate, infrared light is irradiated onto the gate ferroelectric dielectric to weaken the polarization intensity of the gate ferroelectric dielectric, thereby increasing or decreasing the channel dark current.

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

[0014] In one 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, thereby increasing the channel dark current.

[0015] In one 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, thereby reducing 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] A second aspect of this invention provides a method for fabricating a tunable broadband photodetector based on a Schottky junction, comprising the following steps:

[0018] Step 1: N-type doping of the silicon substrate is performed by ion implantation to obtain an N-type silicon substrate;

[0019] Step 2: After selective photolithography of the gate electrode region, the gate electrode processing window is exposed, and hafnium oxide is deposited on the gate electrode processing window to prepare the gate ferroelectric dielectric of the ferroelectric material.

[0020] Step 3: After selective photolithography of the gate electrode region, the gate electrode processing window is exposed. A transparent metal oxide is deposited on the gate ferroelectric dielectric of the gate electrode processing window to prepare the gate electrode.

[0021] Step four: Prepare source and drain electrodes on both sides of the gate ferroelectric dielectric on the product prepared in step three, and prepare gate electrode connection metal on the gate electrode.

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

[0023] In one embodiment of the present invention, the gate electrode is made of 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] A third aspect of the present invention provides an infrared camera, characterized in that the sensor of the infrared camera includes a plurality of tunable broadband photodetectors based on Schottky junctions provided in the first aspect of the present invention, which form an array structure.

[0026] The beneficial effects of this invention are:

[0027] This invention utilizes the characteristic that the polarization intensity of ferroelectric materials decreases when spontaneously polarized and residually polarized under infrared light irradiation. This transformation of polarization intensity is converted into the regulation of channel carrier concentration, thereby extending the detection limit of silicon to the near-infrared range. Simultaneously, by designing the contact electrode type and adjusting the Schottky junction to achieve unipolar transport in the device's source and drain, and by utilizing different polarization states of the ferroelectric material, a switchable positive and negative response of the detector is achieved, thus realizing a tunable broadband photodetector from ultraviolet to near-infrared.

[0028] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

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

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 A schematic diagram of a tunable broadband photodetector based on a Schottky junction is provided in an embodiment of the present invention.

[0032] Figure 2 A schematic diagram of the energy band of a tunable broadband photodetector based on a Schottky junction operating in the ultraviolet to 1100 nm light range, provided for an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the band structure of a tunable broadband photodetector based on a Schottky junction operating in the 1100 nm to near-infrared band under a positive voltage pulse, provided for an embodiment of the present invention.

[0034] Figure 4 A schematic diagram illustrating the positive response of a tunable broadband photodetector based on a Schottky junction, provided as an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the band structure of a tunable broadband photodetector based on a Schottky junction operating in the 1100 nm to near-infrared band under a negative voltage pulse, provided for an embodiment of the present invention.

[0036] Figure 6 A schematic diagram illustrating the generation of a negative response in a broadband photodetector based on a tunable Schottky junction, provided as an embodiment of the present invention;

[0037] Figure 7 A schematic diagram of two raw frame data in one working cycle of a tunable broadband photodetector array based on a Schottky junction, provided for an embodiment of the present invention;

[0038] Figure 8 This is a schematic diagram of event camera output data provided in an embodiment of the present invention. Detailed Implementation

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

[0040] like Figure 1 As shown, the first aspect of the present invention provides a tunable broadband photodetector based on a Schottky junction, comprising: 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 gate ferroelectric dielectric 2 is made of a ferroelectric material, which is hafnium oxide; the gate ferroelectric dielectric 2 and the gate electrode 3 together constitute a ferroelectric gate, and the gate electrode 3 is made of a transparent metal oxide.

[0042] Specifically, when a positive or negative voltage pulse is applied to the ferroelectric gate, infrared light is irradiated onto the gate ferroelectric dielectric 2 to weaken the polarization intensity of the gate ferroelectric dielectric 2, thereby increasing or decreasing the channel dark current.

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

[0044] In this embodiment, ferroelectricity is integrated into a silicon Schottky junction device as a gate dielectric, and the silicon channel is modulated using a ferroelectric polarization field. Utilizing the pyroelectric effect of the ferroelectric material, the detection limit of the silicon material is extended to the near-infrared, and a switchable positive and negative infrared response is achieved, which can be applied to an infrared event camera. The structure and fabrication of the photodetector in this embodiment are very simple and can be fabricated entirely using silicon-based CMOS technology.

[0045] The working principle of the photodetector of this invention is that the Schottky barrier formed by the contact between the source electrode 4 (metal), the drain electrode 5 (metal), and the N-type silicon can create a built-in electric field, which helps to separate electron-hole pairs generated by silicon absorption of light in the ultraviolet to 1100nm light range. Figure 2 As shown. Due to the presence of the Schottky barrier, photogenerated electrons are blocked, while photogenerated minority carrier holes can be absorbed by the metal electrode, thereby generating a photocurrent.

[0046] For the near-infrared band from 1100 nm to further, silicon materials cannot absorb these wavelengths, but they can be detected by utilizing the polarization changes of ferroelectricity. Applying a large positive voltage pulse (5V to 10V) to the ferroelectric gate can induce a downward polarization state in the gate ferroelectric dielectric 2. In this state, the Si channel is modulated into an N-I-N type, such as... Figure 3As shown in the left figure, the carrier concentration is lowest in the v region. Due to the extremely high resistivity of the I region, the device exhibits very low dark current even under source-drain bias. When infrared light, such as 1550nm, irradiates the gate ferroelectric 2, it causes a decrease in the polarization intensity of the gate ferroelectric 2. This weakens the downward polarization intensity, and the gate ferroelectric 2 is unable to maintain the Si channel in a depletion state. The entire channel is modulated into an N~N configuration. - ~N type, such as Figure 3 As shown in the right figure, N - The carrier concentration in region N is less than that in region N. - The resistivity of the region is greatly reduced compared to the previous region I, which leads to an increase in channel current. Figure 4 This diagram illustrates the positive response of a photodetector. By leveraging the effect of illumination on the polarization state under ferroelectric downward polarization, the detection limit of the Si detector is extended to the near-infrared range of 1550 nm, thus achieving a positive response in the near-infrared band.

[0047] When a large negative voltage pulse is applied to the ferroelectric gate, the device operates in the opposite manner. The gate ferroelectric dielectric 2 acquires an upward polarization state, at which point the channel of the Si material is modulated to N~N0. + ~N type, such as Figure 5 As shown in the left figure, N + The carrier concentration in region N is greater than that in region N. + The resistivity of the region is extremely low, allowing the device to achieve a relatively large dark current under source-drain bias. When the same infrared light irradiates the gate ferroelectric 2, it also causes a decrease in the polarization intensity of the gate ferroelectric 2, which weakens the upward polarization intensity, such as... Figure 5 As shown in the right figure, the gate ferroelectric 2 cannot maintain the Si channel in N-mode. + This achieves an ultra-low resistivity state, meaning a reduction in channel current. This state enables the detector to have a negative response in the near-infrared band. Figure 6 A schematic diagram illustrating the negative response generated by a photodetector.

[0048] By utilizing these two states, an infrared photodetector with tunable positive and negative responses is realized, and this characteristic can be used to design infrared event cameras. In fields such as security, traditional cameras record information for every frame, which consumes a significant amount of storage space. Event cameras, on the other hand, can record an event only when the scene changes. The infrared camera based on this invention greatly simplifies the design complexity of event cameras.

[0049] Imaging can be achieved by designing the tunable photodetector of this invention as a detector array. The photodetector operates in a cycle that continuously switches between downward and upward polarization states. One cycle contains one positive response interval and one negative response interval; that is, one operating cycle contains two raw frame data. Figure 7 This is a schematic diagram of two raw frame data. After one working cycle, the two raw frame data are directly added together to obtain the changed part of the two raw frame data. If the changed part of the working cycle is zero, it means that no event has occurred; otherwise, the changed part is recorded as an event. Figure 8 Here is an example of the event camera output, which records the following events: multiple vehicles are moving on the road, some vehicles are turning, the outlines of trees indicate that there should be wind at this time, and the stationary parts are all omitted.

[0050] This invention utilizes silicon CMOS manufacturing technology and a simple device structure, greatly reducing the fabrication difficulty and structural complexity of silicon-based infrared detectors. Furthermore, by leveraging the characteristic that ferroelectric polarization intensity weakens under infrared light, the detection long-wavelength limit of silicon-based infrared detectors is extended to the near-infrared band. This invention achieves tunable positive and negative infrared responses through the polarization state of the gate ferroelectric dielectric 2, significantly simplifying the design of infrared event cameras.

[0051] A second aspect of this invention provides a method for fabricating a tunable broadband photodetector based on a Schottky junction, comprising the following steps:

[0052] Step 1: N-type doping of the silicon substrate is performed by ion implantation to obtain N-type silicon substrate 1, with an N-type doping concentration of 5 × 10⁻⁶. 18 cm -3 ~5×10 19 cm -3 The silicon wafers used are standard N-type doped, and the substrate doping concentration can be adjusted using ion implantation.

[0053] Step two: After selective photolithography of the gate electrode 3 region, the processing window of the gate electrode 3 is exposed. Hafnium oxide is deposited 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 selective photolithography of the gate electrode 3 region, the processing window of the gate electrode 3 is exposed. Transparent indium tin oxide is deposited on the gate ferroelectric dielectric 2 of the processing window of the gate electrode 3 to prepare the gate electrode 3.

[0055] Step four: Source electrode 4 and drain electrode 5 are fabricated on both sides of the gate ferroelectric dielectric 2 on the product prepared in step three. A gate electrode connecting metal is fabricated on the gate electrode 3. The gate electrode connecting metal, source electrode 4, and drain electrode 5 are made of the same metal material. The metals of the source electrode 4 and drain electrode 5 directly contact the N-type silicon substrate 1, forming a Schottky junction. Upon completion, the tunable broadband photodetector based on a Schottky junction of the first aspect of this invention is obtained.

[0056] The method for fabricating a photodetector with a gate ferroelectric dielectric 2 as the gate dielectric of the present invention is entirely fabricated using silicon-based CMOS technology, which has strong process compatibility and saves fabrication costs.

[0057] A third aspect of the present invention provides an infrared camera, the sensor of which includes a plurality of Schottky junction-based tunable broadband photodetectors provided in the first aspect of the present invention, which form an array structure.

[0058] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0059] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0060] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0061] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0063] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A tunable broadband photodetector based on a 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 disposed on the N-type silicon substrate, and the gate electrode is disposed 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 gate electrode is made of a transparent metal oxide. Specifically, when a positive or negative voltage pulse is applied to the ferroelectric gate, infrared light is irradiated onto the gate ferroelectric dielectric to weaken the polarization intensity of the gate ferroelectric dielectric, thereby increasing or decreasing the channel dark current. When a positive voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric acquires a downward polarization state. When infrared light irradiates the gate electrode, the downward polarization intensity of the gate ferroelectric dielectric is weakened, thereby increasing the channel dark current. When a negative voltage pulse is applied to the gate electrode, the gate ferroelectric dielectric acquires an upward polarization state. When infrared light irradiates the gate electrode, the upward polarization intensity of the gate ferroelectric dielectric is weakened, thereby reducing the channel dark current.

2. The tunable broadband photodetector based on a Schottky junction as described in claim 1, characterized in that, The gate electrode is made of transparent indium tin oxide.

3. The tunable broadband photodetector based on a Schottky junction as described in claim 1, characterized in that, The thickness of the gate ferroelectric dielectric is 10nm~15nm.

4. An infrared camera, characterized in that, The infrared camera's sensor comprises multiple Schottky junction-based tunable broadband photodetectors as described in any one of claims 1-3, forming an array structure.

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