Ultraviolet photoelectric detector, preparation method and application in programmable logic gate

Abstract

The invention relates to an ultraviolet photoelectric detector, a preparation method and application in a programmable logic gate. The apparatus includes: a support base; the ultraviolet band optical response unit comprises an optical substrate and an inorganic quantum dot photosensitive layer, and at least a PN junction is formed between the inorganic quantum dot photosensitive layer and the optical substrate; the charge transmission layer is located on the inorganic quantum dot photosensitive layer and at least forms atomic-scale heterogeneous contact with the inorganic quantum dot photosensitive layer, during photoelectric detection, target ultraviolet light irradiates on the charge transmission layer, and the charge transmission layer is electrically connected with the inorganic quantum dot photosensitive layer based on the detection light intensity state of the target ultraviolet light. The photo-generated current polarity of the ultraviolet photoelectric detector under the target ultraviolet light is regulated and controlled; the detection light intensity state at least comprises a comparison state between the light intensity of the target ultraviolet light and the detection critical light intensity. According to the invention, bipolar ultraviolet photoelectric detection under single-wavelength power modulation can be realized, and the reconfigurable polymorphic logic gate application can be effectively realized.

Description

Technical Field

[0001] This invention relates to a photodetector, particularly an ultraviolet photodetector, its fabrication method, and its application in programmable logic gates. Background Technology

[0002] Optoelectronic logic gates (OELGs) perform logical operations through the interaction between optical signals and electronic components to convert optical inputs into digital signal outputs, thereby facilitating high-speed data processing and communication. The basic logic operations performed by OELGs (AND, OR, NOT, NAND, and NOR) are fundamental operations of integrated circuits in advanced computing systems. Compared to traditional silicon-based logic devices, which are limited by electronic and material properties, OELGs, by integrating optoelectronic components that utilize light for information transmission, can achieve lower power consumption, faster processing speeds, and higher bandwidth, which is beneficial for applications in next-generation optical computing, high-performance computing, and real-time data-intensive tasks (such as the Internet of Things and deep neural networks). Furthermore, the unique memory functionality of OELGs allows them to manage stored data simultaneously while performing logical operations.

[0003] In its early research, OELG primarily used device architectures such as PN, PIN, and avalanche photodiodes. These devices employ unidirectional photogenerated carrier transport, limiting their application to single-device, single-logic operations. Typically, these photodetectors only generate current in the presence of light and not in the absence of light; the presence or absence of light determines the current flow, and the lack of an effective mechanism to regulate the current quantity and direction restricts their performance for various logic operations.

[0004] The second-generation optoelectronic logic gates aim to solve the limited logic operation capabilities of a single device and the difficulty of independently controlling the response to multiple optical inputs. Typically, multiple OLEGs are connected in a specific arrangement within the circuit to allow each OLEG to operate as an independent optical element based on the optical input, thus forming an OLEG-in-circuit system. Specifically, the OLEG-in-circuit system can perform diverse logic operations by adjusting the positions of phototransistors and photodiodes, expanding the broad prospects for the commercialization of OLEG chips.

[0005] Once the aforementioned OELG-in-circuit system is designed and manufactured, the number of executable logic operations is fixed. Simultaneously, the size of the light spot determines the logic gate density per unit area on the OELG chip, raising the possibility of potential interference from the binary outputs of multiple photonic elements. Reconfigurable logic systems, such as Field-Programmable Gate Arrays (FPGAs), allow reversible programming of the internal interconnections of basic logic units, and can actively modify operations even within a defined circuit. Therefore, OELG-based reconfigurable logic systems are not constrained by device structure and circuit design, and can actively convert logic operations using additional stimuli such as electric or light fields. Consequently, they are considered to have broad prospects in the application of third-generation optoelectronic logic gates.

[0006] To achieve multi-state logic computing capabilities on a single device, there is an urgent need to develop optoelectronic devices that can freely control the direction of photogenerated carrier transport. Currently, researchers are implementing complex logic functions on a single device by optimizing device structure and using new materials to improve the integration of OELG-based devices and enhance their processing capabilities in optical communication and data sources. However, there is still a lack of effective solutions for comprehensively modulating the photocurrent amplitude, operating speed, and current direction of OELG devices solely through optical modulation. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ultraviolet photodetector, a preparation method, and its application in programmable logic gates. It can realize bipolar ultraviolet photodetection under single-wavelength power modulation and effectively has the application of reconfigurable multi-state logic gates.

[0008] According to the technical solution provided by the present invention, an ultraviolet photodetector is provided, the ultraviolet photodetector comprising:

[0009] Supporting base;

[0010] An ultraviolet-band optical response unit, located on a supporting substrate, includes an optical substrate capable of absorbing ultraviolet-band light and an inorganic quantum dot photosensitive layer located on the optical substrate, wherein at least a PN junction is formed between the inorganic quantum dot photosensitive layer and the optical substrate;

[0011] A charge transport layer is located on the inorganic quantum dot photosensitive layer and forms at least an atomic-level heterogeneous contact with the inorganic quantum dot photosensitive layer, wherein...

[0012] During photoelectric detection, the target ultraviolet light irradiates the charge transport layer, and the polarity of the photocurrent generated by the ultraviolet photodetector under the target ultraviolet light is adjusted based on the detection light intensity state of the target ultraviolet light.

[0013] The detected light intensity state includes at least the comparison state between the light intensity of the target ultraviolet light and the detection critical light intensity;

[0014] The detection critical light intensity is based at least on the formation of the charge transport layer.

[0015] The optical substrate comprises a p-type GaN layer, and the inorganic quantum dot photosensitive layer comprises an inorganic n-type aluminum quantum dot layer, wherein...

[0016] An inorganic N-type aluminum quantum dot layer is fabricated on a P-type GaN layer, thereby enabling the inorganic N-type aluminum quantum dot layer and the P-type GaN layer to form an effective type II heterojunction contact state.

[0017] When the inorganic quantum dot photosensitive layer is an inorganic N-type aluminum quantum dot layer, the thickness of the inorganic N-type aluminum quantum dot layer is 40nm to 120nm.

[0018] Inorganic N-type aluminum quantum dot layers are prepared on P-type GaN layers by at least one deposition method.

[0019] The charge transport layer includes at least a light-bearing graphene layer, and the light-bearing graphene layer prepared on the inorganic quantum dot photosensitive layer is a few-layer graphene.

[0020] It also includes a photoelectric detection electrode unit, in which,

[0021] The photoelectric detection electrode unit includes a first photoelectric detection electrode disposed on the charge transport layer and a second photoelectric detection electrode disposed on the optical substrate, wherein the first photoelectric detection electrode is electrically connected to the charge transport layer and the second photoelectric detection electrode is electrically connected to the optical substrate.

[0022] A method for fabricating an ultraviolet photodetector, used to fabricate the ultraviolet photodetector described above, wherein the fabrication method includes:

[0023] A support substrate is provided, and an optical substrate is fabricated on the support substrate;

[0024] Inorganic quantum dot photosensitive films are prepared on the aforementioned optical substrate. In preparing the inorganic quantum dot photosensitive film, an inorganic quantum dot solution for forming the inorganic quantum dot photosensitive film is first prepared. Subsequently, the inorganic quantum dot solution is deposited on the optical substrate to form the desired inorganic quantum dot photosensitive film.

[0025] A charge transport film is prepared on the aforementioned inorganic quantum dot photosensitive film, wherein the charge transport film is prepared on the inorganic quantum dot photosensitive film at least by a transfer method.

[0026] After the charge transport film is prepared, a photodetector electrode unit is prepared. In the process of preparing the photodetector electrode unit, an inorganic quantum dot photosensitive layer is formed based on the inorganic quantum dot photosensitive film, and a charge transport layer is formed based on the charge transport film. The charge transport layer and the optical substrate are electrically led out by the photodetector electrode unit.

[0027] When the inorganic quantum dot photosensitive film is an inorganic N-type aluminum quantum dot film, the methods for preparing the inorganic quantum dot solution include:

[0028] A metal precursor and a surfactant are provided, and the metal precursor and the surfactant are added to a photosensitive membrane solvent to react under a first preset reaction condition of the photosensitive membrane and form a first reaction solution of the photosensitive membrane, wherein the photosensitive membrane solvent includes anhydrous xylene.

[0029] A reducing agent was added to the first reaction solution of the photosensitive membrane described above, and the solution was cooled to room temperature after the reaction was completed. Then, an antisolvent for extraction was added and centrifuged. After centrifugation, rotary evaporation was performed to form inorganic N-type aluminum quantum dots.

[0030] The inorganic N-type aluminum quantum dots formed above are dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

[0031] Methods for preparing inorganic quantum dot solutions also include:

[0032] Inorganic N-type aluminum quantum dots are dispersed in a nonpolar solvent, and a polydentate ligand polar solution is added to the nonpolar solvent so that the N-type aluminum quantum dots react with the polydentate ligand solution to form an N-type aluminum quantum dot-polydentate ligand solution.

[0033] The N-type aluminum quantum dot-polydentate ligand solution formed above was centrifuged and washed to form an N-type aluminum quantum dot-polydentate ligand.

[0034] The formed N-type aluminum quantum dots-polydentate ligands were dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

[0035] The polydentate ligand includes ethylenediaminetetraacetic acid or ethylenediamine;

[0036] The photosensitive film deposition solvent includes ethanol or dimethylformamide.

[0037] An application of an ultraviolet photodetector in a programmable logic gate, wherein the ultraviolet photodetector described above, or the ultraviolet photodetector prepared above, when applied in a programmable logic gate, includes at least:

[0038] The target ultraviolet light is used as the logic input of the ultraviolet photodetector. The logic output of the programmable logic gate is generated based on the photocurrent state of the ultraviolet photodetector. The critical light intensity at which the photocurrent reverses is used as the reference light intensity.

[0039] When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "1".

[0040] When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "0".

[0041] The photocurrent state of the ultraviolet photodetector includes at least the amplitude and / or direction of the photocurrent.

[0042] Advantages of this invention: The ultraviolet optical response unit includes an optical substrate and an inorganic quantum dot photosensitive layer. The optical substrate is a P-type GaN layer, and the inorganic quantum dot photosensitive layer is an inorganic N-type aluminum quantum dot layer. The inorganic N-type aluminum quantum dot layer and the P-type GaN layer form an effective type II heterojunction, which significantly improves the photogenerated carrier separation efficiency and response performance of the deep ultraviolet detector in the 200–400 nm band. It can achieve efficient separation and transport of photogenerated carriers in the 200–400 nm band, effectively extending the response band of the GaN-based ultraviolet detector to the deep ultraviolet band (<280 nm).

[0043] When the charge transport layer adopts a light-bearing graphene layer, it not only effectively passivates the surface defects of the inorganic N-type aluminum quantum dot layer and improves the carrier migration efficiency, effectively enhancing the responsivity and response speed of the ultraviolet photodetector in the ultraviolet band; but also realizes the multi-state logic output function under single-wavelength optical control by controlling its Fermi level, endowing the ultraviolet photodetector with a composite function of detection and logic operation, providing a feasible solution for building a new generation of high-response, high-bandwidth, and low-power optoelectronic logic systems.

[0044] The fabrication process of ultraviolet photodetectors is simple, which greatly reduces the cost of device fabrication and is conducive to the integration and application of large-scale devices. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of one embodiment of the ultraviolet photodetector of the present invention.

[0046] Figure 2 This is a schematic diagram of an embodiment of the ultraviolet photodetector of the present invention under different illumination conditions, wherein the thickness of the inorganic N-type aluminum quantum dot layer inside the ultraviolet photodetector is 40 nm.

[0047] Figure 3This is a schematic diagram of an embodiment of the ultraviolet photodetector of the present invention under different illumination conditions, wherein the thickness of the inorganic N-type aluminum quantum dot layer inside the ultraviolet photodetector is 40 nm.

[0048] Figure 4 This is a schematic diagram of an embodiment of the photocurrent extracted by the ultraviolet photodetector of the present invention under different light densities, wherein the thickness of the inorganic N-type aluminum quantum dot layer in the ultraviolet photodetector is 40 nm.

[0049] Figure 5 This is a schematic diagram of an embodiment of the responsivity of the ultraviolet photodetector under different optical power densities according to the present invention, wherein the thickness of the inorganic N-type aluminum quantum dot layer inside the ultraviolet photodetector is 40 nm.

[0050] Figure 6 This is a schematic diagram of an embodiment of the transient light response of the ultraviolet photodetector of the present invention, wherein the thickness of the inorganic N-type aluminum quantum dot layer inside the ultraviolet photodetector is 40 nm.

[0051] Figure 7 This is a schematic diagram of an embodiment of the ultraviolet photodetector of the present invention under different illumination conditions, wherein the thickness of the inorganic N-type aluminum quantum dot layer inside the ultraviolet photodetector is 120 nm.

[0052] Figure 8 This is a schematic diagram of an embodiment of the present invention, in which the ultraviolet photodetector implements an XOR gate under single-wavelength modulation of 254nm.

[0053] Figure 9 This is a schematic diagram of an embodiment of the present invention, in which an ultraviolet photodetector implements an OR gate under single-wavelength modulation of 254nm.

[0054] Figure 10 This is a schematic diagram of an embodiment of the present invention, in which the ultraviolet photodetector implements a NAND gate under single-wavelength 254nm wavelength modulation.

[0055] Figure 11 This is a schematic diagram of an embodiment of the present invention, in which the ultraviolet photodetector implements a NOR gate under single-wavelength modulation of 254nm.

[0056] Figure 12 This is a schematic diagram of an embodiment of the present invention, in which the ultraviolet photodetector implements a NOT gate under single-wavelength modulation of 254nm.

[0057] Figure 13 This is a schematic diagram of an embodiment of the present invention, in which an ultraviolet photodetector implements an AND gate under single-wavelength modulation of 254nm.

[0058] Explanation of reference numerals in the attached figures: 1-Supporting substrate, 2-Optical substrate, 3-Inorganic quantum dot photosensitive layer, 4-Charge transport layer, 5-Second electrode for photodetector, 6-First electrode for photodetector. Detailed Implementation

[0059] The present invention will be further described below with reference to specific accompanying drawings and embodiments.

[0060] To achieve bipolar ultraviolet photodetector under single-wavelength power modulation, this invention provides an ultraviolet photodetector, specifically, the ultraviolet photodetector includes:

[0061] Supporting substrate 1;

[0062] An ultraviolet optical response unit is located on a supporting substrate 1, including an optical substrate 2 capable of absorbing ultraviolet light and an inorganic quantum dot photosensitive layer 3 located on the optical substrate 2, wherein at least a PN junction is formed between the inorganic quantum dot photosensitive layer 3 and the optical substrate 2.

[0063] The charge transport layer 4 is located on the inorganic quantum dot photosensitive layer 3 and forms at least an atomic-level heterogeneous contact with the inorganic quantum dot photosensitive layer 3, wherein...

[0064] During photoelectric detection, the target ultraviolet light irradiates the charge transport layer 4, and the polarity of the photocurrent generated by the ultraviolet photodetector under the target ultraviolet light is adjusted based on the detection light intensity state of the target ultraviolet light.

[0065] The detected light intensity state includes at least the comparison state between the light intensity of the target ultraviolet light and the critical light intensity for detection;

[0066] The detection critical light intensity is formed at least based on the charge transport layer 4.

[0067] Figure 1 The diagram illustrates one embodiment of an ultraviolet photodetector. This ultraviolet photodetector can at least detect ultraviolet light, such as detecting ultraviolet light intensity. Specific requirements for ultraviolet light detection can be selected as needed. Figure 1 The ultraviolet photodetector shown includes a support substrate 1. Specifically, the support substrate 1 serves as the support for the ultraviolet photodetector. For example, an ultraviolet optical response unit can be fabricated on the support substrate 1. The support substrate 1 can adopt commonly used forms, such as being made of an alumina substrate. The type of support substrate 1 can be selected as needed, and will not be described in detail here.

[0068] Figure 1The figure illustrates an embodiment of an ultraviolet-band optical response unit. The ultraviolet-band optical response unit may include an optical substrate 2 and an inorganic quantum dot photosensitive layer 3 disposed on the optical substrate 2. The optical substrate 2 is placed on a supporting substrate 1. The optical substrate 2 can realize the absorption of ultraviolet light. At least a PN junction is formed between the inorganic quantum dot photosensitive layer 3 and the optical substrate 2. When forming the PN junction, the optical substrate 2 should form a P-type conductive layer in the PN junction, and the inorganic quantum dot photosensitive layer 3 should form an N-type conductive layer in the PN junction. The PN junction formed between the inorganic quantum dot photosensitive layer 3 and the optical substrate 2 can at least realize the separation and transport of photogenerated carriers.

[0069] In one embodiment of the present invention, the optical substrate 2 comprises a p-type GaN layer, and the inorganic quantum dot photosensitive layer 3 comprises an inorganic n-type aluminum quantum dot layer, wherein...

[0070] An inorganic N-type aluminum quantum dot layer is fabricated on a P-type GaN layer, thereby enabling the inorganic N-type aluminum quantum dot layer and the P-type GaN layer to form an effective type II heterojunction contact state.

[0071] Specifically, since the effective direct bandgap of the P-type GaN layer is 3.6 eV, it has strong optical absorption only in the near-ultraviolet band. Therefore, when the optical substrate 2 adopts the P-type GaN layer, the reliability of the optical substrate 2 in violet light absorption and the accuracy of ultraviolet light detection can be improved.

[0072] Since inorganic N-type aluminum quantum dot layers have a strong optical response in the deep ultraviolet band, when the inorganic quantum dot photosensitive layer 3 adopts an inorganic N-type aluminum quantum dot layer and forms a PN junction with the optical substrate 2 adopting a P-type GaN layer, then: by means of the built-in electric field of the PN junction, the effective separation and transport of photogenerated carriers in the ultraviolet band can be realized; on the other hand, by means of the characteristics of the P-type GaN layer and the inorganic N-type aluminum quantum dot layer respectively, a high-performance optical response in the near-ultraviolet to deep ultraviolet band can be realized, that is, the ultraviolet photodetector has a high-performance optical response.

[0073] In specific implementation, the thickness of the P-type GaN layer can be 800 nm to 50 μm. When the thickness of the P-type GaN layer is relatively thick, the required thickness of the P-type GaN layer can be obtained by epitaxy on the P-type GaN substrate. During epitaxy, homoepitaxial and heteroepitaxial methods can be selected. When heteroepitaxial is used, non-GaN materials are used and grown on the P-type GaN substrate. Non-GaN materials can be selected from p-type silicon, sapphire (Al2O3), silicon carbide (SiC), etc. The type of material can be selected as needed, which will not be elaborated here.

[0074] Specifically, by controlling the doping concentration and thickness of the p-type GaN layer, the built-in electric field based on the formation of the PN junction and the depletion layer thickness of different PN junctions within the ultraviolet photodetector can be controlled, thereby regulating carrier separation and transport. Specifically, in the formed PN junction, a higher carrier concentration in the p-type GaN layer results in a shorter minority carrier diffusion length, leading to a smaller depletion layer width at the PN junction or heterojunction, increased space charge density, and enhanced strength of the local built-in electric field. Optimizing the thickness of the p-type GaN layer can, on the one hand, improve ultraviolet light absorption and increase the number of photogenerated carriers; on the other hand, the thickness of the p-type GaN layer can shorten the charge transport path, facilitating rapid extraction of photogenerated carriers.

[0075] It should be understood that when the inorganic N-type aluminum quantum dot layer and the P-type GaN layer form an effective type II heterojunction contact state, it will be more conducive to the separation and transport of photogenerated carriers. The situation of forming an effective type II heterojunction is consistent with the existing technology, and will not be elaborated here.

[0076] In one embodiment of the present invention, when the inorganic quantum dot photosensitive layer 3 is an inorganic N-type aluminum quantum dot layer, the thickness of the inorganic N-type aluminum quantum dot layer is 40nm to 120nm.

[0077] Inorganic N-type aluminum quantum dot layers are prepared on P-type GaN layers by at least one deposition method.

[0078] Specifically, when the inorganic quantum dot photosensitive layer 3 is an inorganic N-type aluminum quantum dot layer, the physical and chemical properties of the inorganic N-type aluminum quantum dots can be utilized to adjust the size, surface ligands, and thickness of the inorganic N-type aluminum quantum dots, thereby enabling the regulation of the physical properties of the PN junction, such as the built-in electric field and band arrangement, which is beneficial to improving the response speed and sensitivity of the ultraviolet photodetector of the present invention.

[0079] Specifically, the size of aluminum quantum dots directly determines their band width and energy level spacing. Specifically, the smaller the size of inorganic N-type aluminum quantum dots, the stronger the quantum confinement effect, and the positions of their conduction band and valence band undergo a blue shift, thereby changing the band alignment mode (such as step-type or abrupt type) between the inorganic N-type aluminum quantum dot layer and the P-type GaN layer. The change in band structure can further modulate the built-in electric field intensity corresponding to the contact interface between the inorganic N-type aluminum quantum dot layer and the P-type GaN layer, affecting the separation efficiency and recombination behavior of photogenerated carriers, and ultimately improving the responsivity of photodetectors to light of specific wavelengths.

[0080] Furthermore, for inorganic N-type aluminum quantum dot layers, different types of organic or inorganic surface ligands within the inorganic N-type aluminum quantum dot layer not only affect the stability and dispersion of the quantum dots, but also regulate their surface state density and interfacial dipole potential. Appropriate ligand selection can reduce surface defects and trapped states, lower the probability of nonradiative recombination, and modulate the difference in interfacial work function between the inorganic N-type aluminum quantum dot layer and the charge transport layer 4 or P-type GaN layer, thereby changing the degree of interfacial band bending and charge transfer direction, which helps to optimize the carrier injection and extraction process.

[0081] The deposition thickness of the inorganic N-type aluminum quantum dot layer determines its light absorption capacity and lateral electric field distribution. A thinner inorganic N-type aluminum quantum dot layer ensures efficient charge extraction, while an appropriate increase in thickness can help enhance ultraviolet absorption and increase carrier generation density. Furthermore, variations in thickness affect the potential difference and built-in electric field gradient between layers in an ultraviolet photodetector, and also play a crucial role in the separation of photogenerated electron-hole pairs. Therefore, in practical implementation, the thickness of the inorganic N-type aluminum quantum dot layer can be selected according to actual needs. The methods and processes for depositing inorganic N-type aluminum quantum dots on a P-type GaN layer can be found in the following descriptions.

[0082] In one embodiment of the present invention, the charge transport layer 4 includes at least a light-bearing graphene layer, and the light-bearing graphene layer prepared on the inorganic quantum dot photosensitive layer is a few-layer graphene.

[0083] Specifically, the light-receiving graphene layer is used to receive the target ultraviolet light. When the inorganic quantum dot photosensitive layer uses an inorganic N-type aluminum quantum dot layer, the charge transport layer 4 is fabricated on the inorganic N-type aluminum quantum dot layer, and the light-receiving graphene layer corresponds directly to the inorganic N-type aluminum quantum dot layer. When the light-receiving graphene layer uses few-layer graphene, the number of layers in the light-receiving graphene layer is single-layer graphene, double-layer graphene, or triple-layer graphene, that is, single-layer graphene, double-layer graphene, or triple-layer graphene are few-layer graphene in the conventional sense.

[0084] It should be noted that when the charge transport layer 4 uses a light-bearing graphene layer, due to the unique Dirac cone band structure and atomic-level film thickness of graphene, on the one hand, it can achieve atomic-level heterogeneous contact with the inorganic N-type aluminum quantum dot layer to passivate the surface defects of the inorganic N-type aluminum quantum dot layer. On the other hand, it can achieve high-speed and efficient charge transport by means of its high carrier mobility. Furthermore, by means of the optical gating effect of graphene to adjust the Fermi level, the polarity of the photocurrent generated by the ultraviolet photodetector of the present invention can be effectively reversed during ultraviolet photodetection. If the light-bearing graphene layer used in the charge transport layer 4 is determined, the detection critical light intensity corresponding to the optical gating effect can be determined. That is, the detection critical light intensity of the ultraviolet photodetector of the present invention is at least based on the formation of the charge transport layer 4.

[0085] During photoelectric detection, the target ultraviolet light irradiates the charge transport layer 4, and the polarity of the photocurrent generated by the ultraviolet photodetector under the target ultraviolet light is adjusted based on the detection intensity state of the target ultraviolet light. The detection intensity state includes at least the comparison state between the intensity of the target ultraviolet light and the detection critical intensity, that is, whether the intensity of the target ultraviolet light is greater than or less than the detection critical intensity. It should be understood that when the intensity of the target ultraviolet light is greater than the detection critical intensity, a photocurrent of the first polarity can be obtained, while when the intensity of the target ultraviolet light is less than the detection critical intensity, a photocurrent of the second polarity will be formed. The first polarity and the second polarity are both current directions characterizing the photocurrent. Generally, the current directions corresponding to the first polarity and the second polarity are completely opposite.

[0086] As explained above, after the light-receiving graphene layer forms an atomic-level contact with the inorganic N-type aluminum quantum dot layer, and the inorganic N-type aluminum quantum dot layer forms a PN junction with the P-type GaN layer, the ultraviolet photodetector of this invention forms a composite heterojunction of graphene layer-aluminum quantum dot-GaN. Graphene, as a material with a unique two-dimensional structure, plays a crucial role in electrical regulation and carrier transport. Specifically, in the composite heterojunction, graphene not only acts as a high-mobility charge transport layer 4, but also passivates the surface defects of the inorganic N-type aluminum quantum dot layer through interfacial interaction with it. It should be noted that the inorganic N-type aluminum quantum dot layer, due to its high specific surface area, is prone to abundant surface trap states, leading to carrier recombination and a decrease in photoresponse efficiency. The tight interface formed by the atomic-level contact between the light-receiving graphene layer and the inorganic N-type aluminum quantum dot layer can effectively passivate these surface defects, reduce the non-radiative recombination rate, and improve the lifetime and transport efficiency of photogenerated carriers.

[0087] Furthermore, graphene's excellent carrier extraction capability facilitates the rapid separation and collection of photogenerated carriers within the inorganic N-type aluminum quantum dot layer, enhancing the photoelectric conversion performance of the ultraviolet photodetector of this invention in the ultraviolet band. Moreover, the Fermi level of graphene can be precisely tuned through external manipulation (such as by an electric field or illumination), thereby endowing the ultraviolet photodetector of this invention with multi-state logic response capabilities, laying the foundation for constructing reconfigurable optoelectronic logic gates.

[0088] In one embodiment of the present invention, a photoelectric detection electrode unit is further included, wherein...

[0089] The photoelectric detection electrode unit includes a first photoelectric detection electrode 6 disposed on the charge transport layer 4 and a second photoelectric detection electrode 5 disposed on the optical substrate 2, wherein the first photoelectric detection electrode 6 is electrically connected to the charge transport layer 4 and the second photoelectric detection electrode 5 is electrically connected to the optical substrate 2.

[0090] To facilitate connection and integration with external circuits, the ultraviolet photodetector of this invention should also include a photodetector electrode unit. Figure 1 The figure shows an embodiment of the photodetector electrode unit. As can be seen from the figure, the photodetector electrode unit may include a first photodetector electrode 6 and a second photodetector electrode 5. That is, the ultraviolet photodetector of the present invention is a two-terminal device. The first photodetector electrode 6 can be electrically connected to the charge transport layer 4, and the second photodetector electrode 5 can be electrically connected to the optical substrate 2. That is, the first photodetector electrode 6 and the second photodetector electrode 5 can form the two terminals of the ultraviolet photodetector. Thereafter, the first photodetector electrode 6 and the second photodetector electrode 5 are connected to the external circuit.

[0091] Depend on Figure 1 As can be seen from the above description, the first photodetector electrode 6 is located above the second photodetector electrode 5. When the first photodetector electrode 6 is projected vertically toward the optical substrate 2, the distance between the projection area of ​​the first photodetector electrode 6 and the second photodetector electrode 5 can be 600μm to 1200μm. The distance is the width of the conductive channel of the ultraviolet photodetector of the present invention.

[0092] In specific implementation, the polarity of the photogenerated current formed above refers to the current direction of the photogenerated current along the first photodetector electrode 6 pointing to the second photodetector electrode 5, or the current direction of the photogenerated current along the second photodetector electrode 5 pointing to the first photodetector electrode 6.

[0093] Regarding the aforementioned ultraviolet photodetector, this invention provides a method for fabricating an ultraviolet photodetector, wherein the fabrication method includes:

[0094] A support substrate 1 is provided, and an optical substrate 2 is fabricated on the support substrate 1;

[0095] An inorganic quantum dot photosensitive film is prepared on the aforementioned optical substrate 2. In preparing the inorganic quantum dot photosensitive film, an inorganic quantum dot solution for forming the inorganic quantum dot photosensitive film is first prepared. Subsequently, the inorganic quantum dot solution is deposited on the optical substrate 2 to form the desired inorganic quantum dot photosensitive film.

[0096] A charge transport film is prepared on the aforementioned inorganic quantum dot photosensitive film, wherein the charge transport film is prepared on the inorganic quantum dot photosensitive film at least by a transfer method.

[0097] After the charge transport film is prepared, a photoelectric detection electrode unit is prepared. In the process of preparing the photoelectric detection electrode unit, an inorganic quantum dot photosensitive layer 3 is formed based on the inorganic quantum dot photosensitive film, and a charge transport layer 4 is formed based on the charge transport film. The charge transport layer 4 and the optical substrate 2 are electrically led out by the photoelectric detection electrode unit.

[0098] Specifically, the provision of the support substrate 1 can be referred to the above description. After providing the support substrate 1, the optical substrate 2 can be fabricated on the support substrate 1. The details of the optical substrate 2 can be referred to the corresponding description above. For example, the optical substrate 2 can be a P-type GaN layer. The thickness and doping concentration of the P-type GaN layer can be referred to the above description. It can be understood that the P-type GaN layer can be fabricated on the support substrate 1 using existing commonly used methods. Generally, the optical substrate 2 corresponds directly to the support substrate 1, that is, the optical substrate 2 completely covers the support substrate 1. Figure 1 As shown.

[0099] After the optical substrate 2 is fabricated on the supporting substrate 1, an inorganic quantum dot photosensitive film should be fabricated on the optical substrate 2. The fabricated inorganic quantum dot photosensitive film covers the optical substrate 2. It should be understood that the inorganic quantum dot photosensitive film is a thin film corresponding to the inorganic N-type aluminum quantum dot layer, that is, an inorganic N-type aluminum quantum dot layer can be formed through the inorganic quantum dot photosensitive film. In specific implementation, when fabricating the inorganic quantum dot photosensitive film, an inorganic quantum dot solution should generally be prepared first. Subsequently, the inorganic quantum dot solution is deposited on the optical substrate 2 so that the desired inorganic quantum dot photosensitive film can be formed on the optical substrate 2 after deposition. The methods for preparing the inorganic quantum dot solution and depositing it on the optical substrate 2 to form the inorganic quantum dot photosensitive film can be referred to the corresponding descriptions below.

[0100] After preparing the inorganic quantum dot photosensitive film, a charge transport film should be prepared on the inorganic quantum dot photosensitive film. It should be understood that the prepared charge transport film can form the aforementioned charge transport layer 4, and the prepared charge transport film should cover the inorganic quantum dot photosensitive film, such as completely covering the inorganic quantum dot photosensitive film. In practice, the charge transport film should generally be prepared first, and then transferred to the inorganic quantum dot photosensitive film.

[0101] After the charge transport film is prepared, a photodetector electrode unit should be prepared. As described above, the photodetector electrode unit should include at least a first photodetector electrode 6 and a second photodetector electrode 5. The second photodetector electrode 5 is electrically connected to the optical substrate 2, and the first photodetector electrode 6 is electrically connected to the charge transport layer 4. In order to prepare the required photodetector electrode unit, after the charge transport film is prepared, the charge transport film and the inorganic quantum dot photosensitive film should be patterned. It should be understood that after patterning the charge transport film and the inorganic quantum dot photosensitive film, a portion of the optical substrate 2 is exposed, while the other portion is covered by the formed inorganic quantum dot photosensitive layer 3 and the charge transport layer 4. That is, when patterning the charge transport film and the inorganic quantum dot photosensitive film, it is necessary to partially remove the inorganic quantum dot photosensitive film and the charge transport film, and form the inorganic quantum dot photosensitive layer 3 and the charge transport layer 4 based on the remaining portions.

[0102] In practice, commonly used techniques in this field can be employed to pattern the charge transport film and the inorganic quantum dot photosensitive film. For example, photolithography can be used to pattern the charge transport film and the inorganic quantum dot photosensitive film. The specific patterning method and corresponding process conditions can be selected as needed to meet the patterning requirements.

[0103] As explained above, when fabricating the photodetector electrode unit, the charge transport film and the inorganic quantum dot photosensitive film should be patterned first. After forming the inorganic quantum dot photosensitive layer 3 and the charge transport layer 4, the photodetector electrode unit should be fabricated, including at least a first photodetector electrode 6 and a second photodetector electrode 5. Specifically, when fabricating the first photodetector electrode 6 and the second photodetector electrode 5, magnetron sputtering can be used to simultaneously fabricate the first photodetector electrode 6 and the second photodetector electrode 5. As explained above, during magnetron sputtering, the second photodetector electrode 5 should be supported on the optical substrate 2 and electrically connected to the optical substrate 2. The first photodetector electrode 6 is located on the charge transport layer 4 and electrically connected to the charge transport layer 4. Specifically, the metal material sputtered by magnetron sputtering can be one or more of Cr, Ti, and Au. The type of metal material can be selected according to actual needs, and will not be listed here.

[0104] The above describes the fabrication process steps for the ultraviolet photodetector of this invention. The following section details a convenient method for fabricating inorganic quantum dots. Specifically,

[0105] In one embodiment of the present invention, when the inorganic quantum dot photosensitive film is an inorganic N-type aluminum quantum dot film, the method for preparing the inorganic quantum dot solution includes:

[0106] A metal precursor and a surfactant are provided, and the metal precursor and the surfactant are added to a photosensitive membrane solvent to react under a first preset reaction condition of the photosensitive membrane and form a first reaction solution of the photosensitive membrane, wherein the photosensitive membrane solvent includes anhydrous xylene.

[0107] A reducing agent was added to the first reaction solution of the photosensitive membrane described above, and the solution was cooled to room temperature after the reaction was completed. Then, an antisolvent for extraction was added and centrifuged. After centrifugation, rotary evaporation was performed to form inorganic N-type aluminum quantum dots.

[0108] The inorganic N-type aluminum quantum dots formed above are dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

[0109] In practice, when preparing the inorganic quantum dot solution, a metal precursor and a surfactant should be provided. The metal precursor can be selected from one or more aluminum halides such as aluminum chloride and aluminum bromide. The surfactant includes, but is not limited to, amine salt cationic surfactants. Then, the metal precursor and the surfactant are added to the photosensitive membrane solvent. The photosensitive membrane solvent can be anhydrous xylene, or other corresponding solvents can be selected, as long as they are compatible with the metal precursor and the surfactant.

[0110] After adding the metal precursor and surfactant to the photosensitive membrane solvent, the metal precursor and surfactant can react under the pre-configured first preset reaction conditions of the photosensitive membrane, and a first reaction solution of the photosensitive membrane can be formed after the reaction. The first preset reaction conditions of the photosensitive membrane may include reaction time, reaction temperature, etc. Specific examples of the first preset reaction conditions of the photosensitive membrane will be given below.

[0111] After obtaining the first reaction solution of the photosensitive membrane, a reducing agent needs to be added to the first reaction solution of the photosensitive membrane. The reducing agent can be an ammonia ethanol solution. After the reduction reaction is completed, the liquid is cooled to room temperature. Then, an antisolvent for extraction is added to the solution and centrifuged. After centrifugation, rotary evaporation is performed to prepare inorganic N-type aluminum quantum dots.

[0112] After obtaining the inorganic N-type aluminum quantum dot body, the inorganic N-type aluminum quantum dot body is dispersed in the photosensitive film deposition solvent to form an inorganic quantum dot solution. Specifically, the photosensitive film deposition solvent can be N,N-dimethylformamide, and the specific type can be selected as needed to meet the requirements for forming the inorganic quantum dot solution.

[0113] In specific implementation, when both the metal precursor and the surfactant are in solution, the concentrations of the metal precursor and the surfactant can be selected between 1:1 and 1:3. Different concentration ratios will regulate the surface morphology of aluminum quantum dots. In addition, the concentrations of the metal precursor and the reducing agent can be selected between 1:1 and 1:4. Different concentration ratios will regulate the size of aluminum quantum dots, thereby further regulating their band structure.

[0114] A feasible specific scheme for preparing inorganic quantum dot solution is as follows: 709 mg (2 mmol) of cationic surfactant and 133 mg (1 mmol) of aluminum halide metal precursor are added to an absolutely dry 250 ml three-necked flask. The surfactant and metal precursor are dispersed by ultrasonication in the three-necked flask, and then degassed in an argon atmosphere for 1 h. Subsequently, the reaction solution in the three-necked flask is heated to 120 °C, and 2 ml (2.0 M) of ammonia ethanol solution is added to the three-necked flask as a reducing agent, wherein the reducing agent is added at a rate of 2 mL / h.

[0115] After reacting with the reducing agent for 4 hours, icy acetone was added to the reaction solution in the three-necked flask to terminate the reaction. Then, methanol / ethyl acetate / water / antisolvent were added to the three-necked flask in the following order for extraction. The volume ratio of methanol, ethyl acetate, water, and antisolvent to the reaction solution in the three-necked flask could be 1 / 1 / 1 / 1 / 4. The white precipitate was removed by centrifugation, and the supernatant was collected and rotary evaporated to remove the organic solvent xylene. The supernatant was then redispersed in dimethylformamide to prepare a colloidal aluminum quantum dot solution, which is the inorganic quantum dot solution of this invention.

[0116] As can be seen from the above description, the first preset reaction conditions for the photosensitive film may include ultrasonic dispersion, degassing in an argon atmosphere for 1 hour, and heating the reaction solution to 120°C. Of course, the first preset reaction conditions for the photosensitive film may also be other cases, which will not be listed here.

[0117] In one embodiment of the present invention, the method for preparing inorganic quantum dot solution further includes:

[0118] Inorganic N-type aluminum quantum dots are dispersed in a nonpolar solvent, and a polydentate ligand polar solution is added to the nonpolar solvent so that the N-type aluminum quantum dots react with the polydentate ligand solution to form an N-type aluminum quantum dot-polydentate ligand solution.

[0119] The N-type aluminum quantum dot-polydentate ligand solution formed above was centrifuged and washed to form an N-type aluminum quantum dot-polydentate ligand.

[0120] The formed N-type aluminum quantum dots-polydentate ligands were dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

[0121] In specific implementation, the polydentate ligand includes ethylenediaminetetraacetic acid (EDTA) or ethylenediamine. After determining the type of polydentate ligand, it is dispersed in a polar solution to form a polydentate ligand polar solution. Subsequently, the polydentate ligand solution is added to a solution containing inorganic N-type aluminum quantum dots. After reaction, an N-type aluminum quantum dot-polydentate ligand solution is formed. During the reaction, stirring is generally required for 1 to 3 hours. After stirring, centrifugation is performed to remove the supernatant, thereby forming the N-type aluminum quantum dot-polydentate ligand compound.

[0122] Finally, the formed N-type aluminum quantum dot-polydentate ligand is dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution, wherein the photosensitive film deposition solvent includes ethanol or dimethylformamide. It should be understood that the inorganic N-type aluminum quantum dot layer prepared in this manner should contain a polydentate ligand. When the polydentate ligand is ethylenediaminetetraacetic acid (EDTA), the formed inorganic N-type aluminum quantum dot layer can achieve multi-point anchoring, effectively reducing surface defects. If the polydentate ligand is ethylenediamine (EDA), it can achieve good surface passivation and enhanced electronic coupling. Simultaneously, the work function change and interfacial potential are measured for effective type II heterojunction contact with the P-type GaN layer.

[0123] In one embodiment of the present invention, after preparing the inorganic quantum dot solution, a feasible deposition method for preparing an inorganic quantum dot photosensitive film on a p-type GaN layer includes:

[0124] The P-type GaN layer was ultrasonically cleaned with acetone, isopropanol and deionized water respectively, with each cleaning time being 5 minutes. The cleaning was repeated three times, and then dried on a hot plate at 120°C for later use.

[0125] The p-type GaN layer, after the above drying treatment, is activated by oxygen plasma to achieve a hydrophilic surface. The prepared inorganic quantum dot solution is then deposited onto the clean p-type GaN layer using one or more methods, such as spin coating, spray coating, or blade coating. The thickness of the inorganic quantum dot photosensitive film can be 40 nm-120 nm. Subsequently, it is annealed on a hot plate at 95 °C for 20 min. In specific implementation, once the deposition method is selected, the techniques of this technical field can be used to deposit the inorganic quantum dot solution onto the clean p-type GaN layer, and the thickness of the inorganic quantum dot photosensitive film can be controlled. The specific deposition method and process are detailed here.

[0126] Specifically, when the charge transport layer 4 is made of graphene, the charge transport film is also a graphene film. The specific method for preparing the charge transport film can be as follows:

[0127] Single-layer graphene is transferred onto a substrate using a wet process. The preparation steps for graphene film deposition during the transfer are as follows: A suitable volume of copper-based single-layer graphene film is cut, flattened, and then spin-coated with a 3% (w / w) PMMA solution (anisole solvent) at 500 rpm for 10 s, followed by 1500 rpm for 20 s. The PMMA film is then cured on a hot plate at 100°C. Subsequently, the copper-based graphene coated with the PMMA film is transferred to a 2M ferric chloride solution and etched for 1 hour. After the copper substrate is completely etched, the graphene is lifted from the bottom up using a glass slide and placed in a petri dish containing deionized water to dilute the ferric chloride etching solution. This completes one step of the process, which should generally be repeated three times.

[0128] After cleaning the monolayer graphene using the prepared substrate, hold it vertically and allow the water on the sample surface and in the middle of the graphene to air dry naturally. After air drying, heat the sample on a hot plate at 90°C for one hour, then cool it and immerse it in acetone solution to remove PMMA. Repeat this process three times to completely remove PMMA. After the acetone on the surface has evaporated, store the sample in a dry environment for subsequent processing. Generally, PMMA can be completely removed by repeating the acetone solution removal process multiple times.

[0129] As can be seen from the above description, the charge transport layer 4 can be a few-layer graphene, and the thickness of the inorganic N-type aluminum quantum dot layer can be selected as needed. The following is a detailed description of the ultraviolet photodetector of the present invention based on the number of graphene layers used in the charge transport layer 4 and the thickness of the inorganic N-type aluminum quantum dot layer.

[0130] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 40 nm, Figure 2 The diagram shows the IV curves of the corresponding ultraviolet photodetector under different illumination conditions, where the illumination wavelength is 254 nm, which is also the wavelength of the target ultraviolet light. Figure 2 It can be seen that near the open-circuit voltage, there exists a bipolar photocurrent that varies with light intensity, with a critical optical power density of 44.1 μW / cm². 2 .

[0131] It should be noted that, Figure 2 In the text, "dark" and "10.2" both represent the optical power density of the input light. Specifically, "dark" means that no violet light is illuminating the charge transport layer 4. Figure 2The horizontal axis represents different bias voltages, and the vertical axis represents the photocurrent generated by the photodetector. The bias voltage on the horizontal axis is the bias voltage applied to control the normal operation of the ultraviolet photodetector. Generally, the bias voltage is applied to the ultraviolet photodetector through the first photodetector electrode 6 and the second photodetector electrode 5. The application of the bias voltage is consistent with the prior art. It can be seen that in order to ensure the normal operation of the photodetector, in addition to ultraviolet light shining on the charge transport layer 4, a corresponding bias should also be applied. After that, the corresponding photocurrent can be measured.

[0132] Figure 3 The text shows the relationship with... Figure 2 The graph shows the It curves of the corresponding ultraviolet photodetector under different illumination conditions, where the illumination wavelength is 254 nm. The horizontal axis represents time, the vertical axis represents the photocurrent of the ultraviolet photodetector, and the values ​​on the right represent the corresponding optical power density. Figure 3 It can be seen that the ultraviolet photodetector exhibits a stable switching response to different light power densities, and the ratio of photocurrent to dark current of the ultraviolet photodetector remains consistently at 10. 3 This scale is beneficial for ultraviolet photodetectors to achieve excellent light response.

[0133] also, Figure 3 In the study, the device exhibits a bipolar photocurrent response near the detection critical light intensity. Specifically, when the light intensity is below the detection critical intensity, the photocurrent generated by the ultraviolet photodetector is mainly negative; while when the light intensity is above the detection critical intensity, the photocurrent generated by the ultraviolet photodetector is mainly positive. Therefore, the bipolar photocurrent response characteristic of the ultraviolet photodetector, which is dependent on the single-wavelength light power density, provides a novel approach to multi-state logic gates under single-light modulation.

[0134] Figure 4 It shows the relationship with Figure 2 The relationship between photocurrent and optical power density of the corresponding ultraviolet photodetector under different illumination conditions is shown. To more intuitively illustrate the bipolar response of the device with light intensity, the photocurrent under different illumination conditions was extracted. It can be seen that the detection critical light intensity is 44.1 μW / cm². 2 The photocurrent of the ultraviolet photodetector underwent a significant polarity reversal, proving that the ultraviolet photodetector can achieve bipolar photoelectric response through single-wavelength light intensity modulation.

[0135] Figure 5 It shows the relationship with Figure 2 The graph shows the responsivity of the ultraviolet photodetector under different illumination conditions. As can be seen from the figure, the responsivity of the ultraviolet photodetector first increases and then decreases with increasing optical power density, reaching a minimum at 343 μW / cm². 2Under illumination conditions, a responsivity of up to 134 A / W can be achieved. This shows that the use of composite heterojunctions can effectively improve the photoelectric detection performance of the device and help it expand its application range in practical scenarios.

[0136] Figure 6 It shows the relationship with Figure 2 The transient optical response of the corresponding ultraviolet photodetector is shown in the figure. As can be seen from the figure, an ultrafast photodetector can be realized by irradiation with high-frequency signal light, with a rise time of 1.6 μs and a fall time of 7.5 μs. This demonstrates that a significant improvement in the transient response speed can be achieved by using a composite heterojunction, thus enhancing the application of ultraviolet photodetectors in high-speed detection scenarios.

[0137] It should be noted that the above "with" Figure 2 "Corresponding ultraviolet photodetector" specifically refers to... Figure 2 Similar to the mid-ultraviolet photodetector, such as the charge transport layer 4 formed based on a single layer of graphene, and the thickness of the inorganic N-type aluminum quantum dot layer is 40 nm.

[0138] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 7 The IV curves of the corresponding ultraviolet photodetector at different optical power densities are shown. Figure 7 And the above Figure 2 It can be seen that increasing the open-circuit voltage of the ultraviolet photodetector to 0.5V will facilitate the separation and transport of charge carriers due to the large built-in electric field.

[0139] As can be seen from the above description of the characteristics of the ultraviolet photodetector, the ultraviolet photodetector of the present invention can be used as a programmable logic gate, and thus the following can be obtained:

[0140] An application of an ultraviolet photodetector in a programmable logic gate, wherein the ultraviolet photodetector described above, or the ultraviolet photodetector prepared above, when applied in a programmable logic gate, includes at least:

[0141] The target ultraviolet light is used as the logic input of the ultraviolet photodetector. The logic output of the programmable logic gate is generated based on the photocurrent state of the ultraviolet photodetector. The critical light intensity at which the photocurrent reverses is used as the reference light intensity.

[0142] When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "1".

[0143] When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "0".

[0144] The photocurrent state of the ultraviolet photodetector includes at least the amplitude and / or direction of the photocurrent.

[0145] As described above, the ultraviolet photodetector includes a first photodetector electrode 6 and a second photodetector electrode 5. The first photodetector electrode 6 and the second photodetector electrode 5 can be used to connect the ultraviolet photodetector to an external functional circuit. The target ultraviolet light irradiates the charge transport layer 4 as the logic input of the ultraviolet photodetector. At the same time, a current will be generated in the ultraviolet photodetector under the target ultraviolet light, that is, the photocurrent described above will be generated. It can be understood that in addition to having polarity, the amplitude of the photocurrent will generally also be different. Therefore, the photocurrent state can be obtained based on the amplitude and / or direction of the photocurrent.

[0146] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 40 nm, Figure 8 This diagram illustrates an embodiment of an XOR logic gate (exclusive OR gate) in an analog-digital circuit for an ultraviolet photodetector at 254nm. Specifically, using a current of -20nA as the dividing line, when the current is higher than -20nA, the logic output of the ultraviolet photodetector is determined to be 0; when the current is lower than -20nA, the logic output of the ultraviolet photodetector is determined to be 1. It should be noted that the current here is the photocurrent mentioned above, and all currents mentioned in the following description have the same meaning. Please refer to this description.

[0147] Furthermore, "00" represents no light input, "10" and "01" represent one optical path being open, and "11" represents both optical paths being open simultaneously. The light intensity is 29.3 μW / cm². 2 Using a beam of ultraviolet light as input, under the "00" signal, the output current of the ultraviolet photodetector is -0.2nA, resulting in signal 0; under the "10" and "01" signals, one optical path is open, and the photocurrent generated by the ultraviolet photodetector is -76.3nA, resulting in signal 1; under the "11" signal, both optical paths are open simultaneously, and the photocurrent generated by the ultraviolet photodetector is 155nA, resulting in signal 0. Based on the above signal judgment results, the optical XOR logic operation of the XOR logic gate can be implemented. It should be understood that the "00" signal means that no ultraviolet light shines on the charge transport layer 4, "10" and "01" both indicate the presence of a beam of ultraviolet light as input, and "11" indicates that two beams of ultraviolet light are correspondingly shining on the charge transport layer 4. The corresponding optical inputs described below all represent the same meaning and can be referred to in this explanation.

[0148] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 9 This diagram illustrates an embodiment of an analog-to-digital circuit OR logic gate (or gate) operating at 254 nm using an ultraviolet photodetector, specifically utilizing light intensity of 10.2 μW / cm². 2 As input light, under the "00" signal, the output current of the ultraviolet photodetector is -0.2nA, resulting in signal 0; under "10" and "01" signals, one optical path is open, and the photocurrent generated by the ultraviolet photodetector is -118.52nA, resulting in signal 1; under the "11" signal, both optical paths are open simultaneously, and the corresponding photocurrent generated by the ultraviolet photodetector is -129.92nA, resulting in signal 0. Based on the above signal judgment results, the optical OR logic operation of the OR logic gate can be implemented.

[0149] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 10 This diagram illustrates an embodiment of an analog-to-digital NAND logic gate (AND gate) of an ultraviolet photodetector operating at 254 nm, specifically utilizing light intensity of 29.3 μW / cm². 2 The input light intensity is 1.2 μW / cm. 2 As background modulation light, under the "00" signal, the photogenerated current of the ultraviolet photodetector is -30.53 nA, resulting in signal 1; under "10" and "01" signals, one optical path is open, and the response current of the ultraviolet photodetector is -72.79 nA, resulting in signal 1; under the "11" signal, both optical paths are open simultaneously, and the photogenerated current of the ultraviolet photodetector is 153.96 nA, resulting in signal 0. Based on the above signal determination results, optical NAND logic operations can be implemented for NAND logic gates.

[0150] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 11 This diagram illustrates an embodiment of an analog-to-digital NOR logic gate (or NOT gate) for an ultraviolet photodetector at 254 nm, specifically utilizing a light intensity of 112 μW / cm². 2 The input light intensity is 1.2 μW / cm. 2As background modulation light, under the "00" signal, the photocurrent generated by the ultraviolet photodetector is -30.53 nA, resulting in signal 1; under "10" and "01" signals, one optical path is open, and the photocurrent generated by the ultraviolet photodetector is 572.19 nA, resulting in signal 0; under the "11" signal, both optical paths are open simultaneously, and the photocurrent generated by the ultraviolet photodetector is 1347.37 nA, resulting in signal 0. Based on the above signal judgment results, the optical OR-NOT logic operation of the NOR logic gate can be implemented.

[0151] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 12 The NOT logic gate of the analog-digital circuit of the ultraviolet photodetector at 254 nm is shown. This was achieved using a light intensity of 218 μW / cm². 2 The input light intensity is 1.2 μW / cm. 2 As background modulation light, under a "0" signal, the device output current is -30.53nA, resulting in signal 1; under a "1" signal, one optical path is opened, and the corresponding device current is 1342.499nA, resulting in signal 0. Based on the above signal judgment results, the optical logic gate operation of NOT can be realized.

[0152] For ultraviolet photodetectors, when the charge transport layer 4 is formed based on a single layer of graphene and the thickness of the inorganic N-type aluminum quantum dot layer is 120 nm, Figure 13 This diagram illustrates one embodiment of an analog-to-digital AND logic gate in an ultraviolet photodetector at 254 nm, specifically utilizing light intensity of 0.6 μW / cm². 2 As input light, under the "00" signal, the photocurrent generated by the ultraviolet photodetector is -0.2nA, resulting in signal 0; under "10" and "01" signals, one optical path is open, and the photocurrent generated by the ultraviolet photodetector is -15.25nA, resulting in signal 0; under the "11" signal, both optical paths are open simultaneously, and the corresponding current of the device is -31.19nA, resulting in signal 1. Based on the above signal judgment results, the optical AND logic operation of the AND gate can be implemented.

[0153] It should be noted that the two optical paths mentioned above specifically refer to the existence of two ultraviolet light sources. The ultraviolet light generated by the two ultraviolet light sources is used as a channel. According to the logic operation of the logic gate, the two ultraviolet lights irradiate the charge transport layer 4. If an AND logic operation is implemented, the two ultraviolet lights should irradiate the charge transport layer 4 simultaneously to represent two logic input bits. In addition, the irradiation state of the ultraviolet light on the charge transport layer 4 should be controlled by an electronic control module, such as controlling the frequency and time of ultraviolet light irradiation.

[0154] As can be seen from the above description, when the ultraviolet photodetector of the present invention is used as a programmable logic gate, it can be used as at least an XOR logic gate, an OR logic gate, a NAND logic gate, a NOR logic gate, and an AND logic gate. The specific type of logic gate can be selected as needed, and the corresponding description above can be referred to.

[0155] In summary, the ultraviolet optical response unit of the present invention includes an optical substrate 2 and an inorganic quantum dot photosensitive layer 3. The optical substrate 2 is a P-type GaN layer, and the inorganic quantum dot photosensitive layer 3 is an inorganic N-type aluminum quantum dot layer. The inorganic N-type aluminum quantum dot layer and the P-type GaN layer form an effective type II heterojunction, which significantly improves the photogenerated carrier separation efficiency and response performance of the deep ultraviolet detector in the 200–400 nm band. It can achieve efficient separation and transport of photogenerated carriers in the 200–400 nm band, effectively extending the response band of the GaN-based ultraviolet detector to the deep ultraviolet band (<280 nm).

[0156] When the charge transport layer 4 adopts a light-bearing graphene layer, it not only effectively passivates the surface defects of the inorganic N-type aluminum quantum dot layer and improves the carrier migration efficiency, effectively improving the responsivity and response speed of the ultraviolet photodetector in the ultraviolet band; but also realizes the multi-state logic output function under single-wavelength optical control by controlling its Fermi level, endowing the ultraviolet photodetector with a composite function of detection and logic operation, providing a feasible solution for building a new generation of high-response, high-bandwidth, low-power optoelectronic logic system.

[0157] The fabrication process of ultraviolet photodetectors is simple, which greatly reduces the cost of device fabrication and is conducive to the integration and application of large-scale devices.

Claims

1. An ultraviolet photodetector, characterized in that, The ultraviolet photodetector includes: Supporting base; An ultraviolet-band optical response unit, located on a supporting substrate, includes an optical substrate capable of absorbing ultraviolet-band light and an inorganic quantum dot photosensitive layer located on the optical substrate, wherein at least a PN junction is formed between the inorganic quantum dot photosensitive layer and the optical substrate; A charge transport layer is located on the inorganic quantum dot photosensitive layer and forms at least an atomic-level heterogeneous contact with the inorganic quantum dot photosensitive layer, wherein... During photoelectric detection, the target ultraviolet light irradiates the charge transport layer, and the polarity of the photocurrent generated by the ultraviolet photodetector under the target ultraviolet light is adjusted based on the detection light intensity state of the target ultraviolet light. The detected light intensity state includes at least the comparison state between the light intensity of the target ultraviolet light and the critical light intensity for detection; The detection critical light intensity is based at least on the formation of the charge transport layer.

2. The ultraviolet photodetector according to claim 1, characterized in that: The optical substrate comprises a p-type GaN layer, and the inorganic quantum dot photosensitive layer comprises an inorganic n-type aluminum quantum dot layer, wherein... An inorganic N-type aluminum quantum dot layer is fabricated on a P-type GaN layer, thereby enabling the inorganic N-type aluminum quantum dot layer and the P-type GaN layer to form an effective type II heterojunction contact state.

3. The ultraviolet photodetector according to claim 2, characterized in that: When the inorganic quantum dot photosensitive layer is an inorganic N-type aluminum quantum dot layer, the thickness of the inorganic N-type aluminum quantum dot layer is 40nm to 120nm. Inorganic N-type aluminum quantum dot layers are prepared on P-type GaN layers by at least one deposition method.

4. The ultraviolet photodetector according to claim 1, characterized in that: The charge transport layer includes at least a light-bearing graphene layer, and the light-bearing graphene layer prepared on the inorganic quantum dot photosensitive layer is a few-layer graphene.

5. The ultraviolet photodetector according to any one of claims 1 to 4, characterized in that: It also includes a photoelectric detection electrode unit, in which, The photoelectric detection electrode unit includes a first photoelectric detection electrode disposed on the charge transport layer and a second photoelectric detection electrode disposed on the optical substrate, wherein the first photoelectric detection electrode is electrically connected to the charge transport layer and the second photoelectric detection electrode is electrically connected to the optical substrate.

6. A method for fabricating an ultraviolet photodetector, characterized in that, The method for preparing the ultraviolet photodetector according to any one of claims 1 to 5 includes: A support substrate is provided, and an optical substrate is fabricated on the support substrate; Inorganic quantum dot photosensitive films are prepared on the aforementioned optical substrate. In preparing the inorganic quantum dot photosensitive film, an inorganic quantum dot solution for forming the inorganic quantum dot photosensitive film is first prepared. Subsequently, the inorganic quantum dot solution is deposited on the optical substrate to form the desired inorganic quantum dot photosensitive film. A charge transport film is prepared on the aforementioned inorganic quantum dot photosensitive film, wherein the charge transport film is prepared on the inorganic quantum dot photosensitive film at least by a transfer method. After the charge transport film is prepared, a photodetector electrode unit is prepared. In the process of preparing the photodetector electrode unit, an inorganic quantum dot photosensitive layer is formed based on the inorganic quantum dot photosensitive film, and a charge transport layer is formed based on the charge transport film. The charge transport layer and the optical substrate are electrically led out by the photodetector electrode unit.

7. The method for fabricating an ultraviolet photodetector according to claim 6, characterized in that, When the inorganic quantum dot photosensitive film is an inorganic N-type aluminum quantum dot film, the methods for preparing the inorganic quantum dot solution include: A metal precursor and a surfactant are provided, and the metal precursor and the surfactant are added to a photosensitive membrane solvent to react under a first preset reaction condition of the photosensitive membrane and form a first reaction solution of the photosensitive membrane, wherein the photosensitive membrane solvent includes anhydrous xylene. A reducing agent was added to the first reaction solution of the photosensitive membrane described above, and the solution was cooled to room temperature after the reaction was completed. Then, an antisolvent for extraction was added and centrifuged. After centrifugation, rotary evaporation was performed to form inorganic N-type aluminum quantum dots. The inorganic N-type aluminum quantum dots formed above are dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

8. The method for fabricating an ultraviolet photodetector according to claim 7, characterized in that, Methods for preparing inorganic quantum dot solutions also include: Inorganic N-type aluminum quantum dots are dispersed in a nonpolar solvent, and a polydentate ligand polar solution is added to the nonpolar solvent so that the N-type aluminum quantum dots react with the polydentate ligand solution to form an N-type aluminum quantum dot-polydentate ligand solution. The N-type aluminum quantum dot-polydentate ligand solution formed above was centrifuged and washed to form an N-type aluminum quantum dot-polydentate ligand. The formed N-type aluminum quantum dots-polydentate ligands were dispersed in a photosensitive film deposition solvent to form an inorganic quantum dot solution.

9. The method for fabricating an ultraviolet photodetector according to claim 8, characterized in that, The polydentate ligand includes ethylenediaminetetraacetic acid or ethylenediamine; The photosensitive film deposition solvent includes ethanol or dimethylformamide.

10. An application of an ultraviolet photodetector in a programmable logic gate, characterized in that, When the ultraviolet photodetector according to any one of claims 1 to 5, or the ultraviolet photodetector prepared according to any one of claims 6 to 9, is used in a programmable logic gate, it shall at least include: The target ultraviolet light is used as the logic input of the ultraviolet photodetector. The logic output of the programmable logic gate is generated based on the photocurrent state of the ultraviolet photodetector. The critical light intensity at which the photocurrent reverses is used as the reference light intensity. When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "1". When ultraviolet light from a target source with an intensity higher than the detection threshold shines onto the photodetector, the logic input of the ultraviolet photodetector is set to "0". The photocurrent state of the ultraviolet photodetector includes at least the amplitude and / or direction of the photocurrent.

Images