Quantum dot photoelectric detector and preparation method thereof

Abstract

The invention discloses a quantum dot photoelectric detector and a preparation method thereof, and belongs to the technical field of semiconductors. The quantum dot photoelectric detector comprises a substrate, wherein a blind hole is formed in the surface of the substrate; the quantum dot layer is arranged in the middle area in the blind hole; the hole transport layer and the electron transport layer are oppositely arranged on the side walls of the two sides of the quantum dot layer in a covering manner; the first electrode layer covers the side wall, far away from the quantum dot layer, of the hole transport layer; and the second electrode layer covers the side wall, far away from the quantum dot layer, of the electron transport layer. The functional layer of the detector is arranged in the blind hole of the substrate in a horizontal structure mode, all the layers are tightly combined, the functional layer of the detector can be better protected and is not prone to aging and degradation, and then the stability of the detector can be remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of photodetector fabrication technology, specifically relating to a quantum dot photodetector and its fabrication method. Background Technology

[0002] Quantum dot photodetectors, due to their excellent photoelectric properties and tunable spectral response characteristics, have broad application prospects in photoelectric detection, imaging, and communication. Traditional quantum dot photodetectors typically employ a vertical structure, where functional layers (such as electrodes, transport layers, and quantum dot layers) are vertically stacked on a substrate. While this structure is simple, it presents numerous challenges in practical fabrication.

[0003] First, in the fabrication of vertical quantum dot photodetectors, the order and method of fabricating each functional layer have a significant impact on the final device performance. For example, when depositing electron transport layers or hole transport layers on quantum dot films, high-energy fabrication methods such as magnetron sputtering can damage the quantum dot film, leading to the loss of its photogenerated carrier function. To solve this problem, a protective layer is usually deposited on the quantum dot film, which undoubtedly increases the complexity and cost of fabrication. Second, in practical applications, poor interfacial contact between functional layers in vertical quantum dot photodetectors can easily lead to reduced carrier transport efficiency, affecting the overall performance of the device. Third, during long-term use, the interfaces between functional layers in vertical quantum dot photodetectors are prone to aging and degradation, further affecting the stability and lifespan of the device. Finally, in the fabrication of vertical quantum dot photodetectors, the thickness and uniformity of each functional layer have a significant impact on the final device performance. For example, the thickness and uniformity of the quantum dot film directly affect its light absorption and photogenerated carrier generation efficiency, while the thickness and uniformity of the electron transport layer and hole transport layer directly affect the carrier transport efficiency. Therefore, how to achieve precise control and optimization of each functional layer in a vertical structure has always been a challenge in the fabrication of quantum dot photodetectors. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a quantum dot photodetector and a method for its fabrication.

[0005] In a first aspect, the present invention provides a quantum dot photodetector, comprising: A substrate, wherein a blind hole is formed on the surface of the substrate; A quantum dot layer is disposed in the central region within the blind hole; Hole transport layer and electron transport layer are disposed opposite to each other on the two sidewalls of the quantum dot layer; A first electrode layer is disposed on the sidewall of the hole transport layer away from the quantum dot layer; The second electrode layer is disposed on the sidewall of the electron transport layer away from the quantum dot layer.

[0006] Secondly, the present invention provides a method for fabricating a quantum dot photodetector, comprising the following steps: S1: Plan the corresponding positions of the first electrode layer, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the substrate; wherein: the hole transport layer and the electron transport layer are respectively located on two opposite sidewalls of the quantum dot layer, the first electrode layer is located on the sidewall of the hole transport layer away from the quantum dot layer, and the second electrode layer is located on the sidewall of the electron transport layer away from the quantum dot layer. S2: Coat a layer of photoresist on the substrate to obtain a photoresist layer; remove the photoresist at the corresponding position of the first electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the first electrode layer. After deposition, remove the photoresist to obtain a substrate containing the first electrode layer. S3: Coat a layer of photoresist on the substrate containing the first electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the second electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the second electrode layer. After deposition, remove the photoresist to obtain a substrate containing the second electrode layer. S4: Coat a photoresist layer on the substrate containing the second electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the hole transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the hole transport layer. After deposition, remove the photoresist to obtain a substrate containing the hole transport layer. S5: Coat a layer of photoresist on a substrate containing a hole transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the electron transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the electron transport layer. After deposition, remove the photoresist to obtain a substrate containing an electron transport layer. S6: Coat a layer of photoresist on a substrate containing an electron transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the quantum dot layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching to obtain a pit; after removing the photoresist, fill the pit by inkjet printing quantum dot ink to obtain a quantum dot photodetector.

[0007] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: In this invention, the functional layer of the detector is arranged in a horizontal structure within the blind hole of the substrate. The layers are tightly bonded together, which can better protect the functional layer of the detector, making it less prone to aging and degradation, thereby significantly improving the stability of the detector.

[0008] The hole transport layer and electron transport layer of the detector of the present invention are respectively disposed on the sidewall of the quantum dot layer, which causes virtually no damage to the surface of the quantum dot layer, can ensure the activity of the quantum dot layer surface, improve the transport efficiency of charge carriers, and thus improve the overall performance of the device. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of the quantum dot photodetector of the present invention.

[0010] Figures 2-6 This is a process flow diagram illustrating the fabrication process of the quantum dot photodetector of the present invention. Detailed Implementation

[0011] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0012] As mentioned above, in a first aspect, the present invention provides a quantum dot photodetector, comprising: A substrate, wherein a blind hole is formed on the surface of the substrate; A quantum dot layer is disposed in the central region within the blind hole; Hole transport layer and electron transport layer are disposed opposite to each other on the two sidewalls of the quantum dot layer; A first electrode layer is disposed on the sidewall of the hole transport layer away from the quantum dot layer; The second electrode layer is disposed on the sidewall of the electron transport layer away from the quantum dot layer.

[0013] Preferably, the depth of the blind hole is 100~500nm, including but not limited to: 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0014] More preferably, the heights of the quantum dot layer, hole transport layer, electron transport layer, first electrode layer, and second electrode layer along the direction from the opening of the blind hole to the bottom of the hole are all equal to the depth of the blind hole.

[0015] Preferably, the blind hole is a circular blind hole with a diameter of 1000~2400nm, including but not limited to: 1000nm, 1100nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, 2100nm, 2200nm, 2300nm, 2400nm, etc.

[0016] More preferably, the quantum dot layer is a cylindrical quantum dot layer and is coaxial with the blind hole; the diameter of the cylindrical quantum dot layer is 200~500nm, including but not limited to: 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0017] In this invention, the quantum dot layer is designed in a cylindrical shape, which makes the built-in electric fields formed between the quantum dot layer and the hole transport layer, as well as between the quantum dot layer and the electron transport layer, symmetrical. The cylindrical structure design is more conducive to carrier separation than other shapes, thereby improving the overall performance of the detector.

[0018] For example, if the quantum dot layer is cuboid in shape, electric field concentration (point discharge effect) will occur at the corners, which will lead to an increase in leakage current in local areas, resulting in a higher overall dark current than a smooth cylindrical structure. Cylindrical quantum dot layers have uniform circular boundaries, which helps to form a smoother, more uniform lateral electric field, facilitating efficient and uniform separation and collection of charge carriers, thus resulting in higher responsivity. Furthermore, the cylindrical structure avoids stress concentration and defects that may be caused by sharp corners during the fabrication process.

[0019] Preferably, the hole transport layer and the electron transport layer are conformally bonded to the sidewalls corresponding to the quantum dot layer.

[0020] Preferably, the first electrode layer conformally fits to the sidewall of the hole transport layer; the second electrode layer conformally fits to the sidewall of the electron transport layer.

[0021] Preferably, the thickness of the hole transport layer and the electron transport layer is independently 50~200nm, including but not limited to: 50nm, 100nm, 150nm, 200nm, etc.

[0022] Preferably, the thickness of the first electrode layer and the second electrode layer are each independently 300~800nm, including but not limited to: 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, etc.

[0023] Preferably, the material of the quantum dot layer is one of CdSe quantum dots, HgSe quantum dots, HgTe quantum dots, and PbSe quantum dots.

[0024] Preferably, the material of the hole transport layer is one of nickel oxide, molybdenum oxide, copper oxide, and cobalt oxide.

[0025] Preferably, the electron transport layer is made of one of bismuth selenide, titanium oxide, tin oxide, and zinc oxide.

[0026] Preferably, the material of the first electrode layer is one or more of silver, aluminum, indium tin oxide, and nickel.

[0027] Preferably, the material of the second electrode layer is one or more of chromium, platinum, gold and copper.

[0028] Secondly, the present invention provides a method for fabricating a quantum dot photodetector, comprising the following steps: S1: Plan the corresponding positions of the first electrode layer, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the substrate; the quantum dot layer is set in the middle region, the hole transport layer and the electron transport layer are respectively set on two opposite sidewalls of the quantum dot layer, the first electrode layer is set on the sidewall of the hole transport layer away from the quantum dot layer, and the second electrode layer is set on the sidewall of the electron transport layer away from the quantum dot layer. S2: Coat a layer of photoresist on the substrate to obtain a photoresist layer; remove the photoresist at the corresponding position of the first electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the first electrode layer. After deposition, remove the photoresist to obtain a substrate containing the first electrode layer. S3: Coat a layer of photoresist on the substrate containing the first electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the second electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the second electrode layer. After deposition, remove the photoresist to obtain a substrate containing the second electrode layer. S4: Coat a photoresist layer on the substrate containing the second electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the hole transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the hole transport layer. After deposition, remove the photoresist to obtain a substrate containing the hole transport layer. S5: Coat a layer of photoresist on a substrate containing a hole transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the electron transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the electron transport layer. After deposition, remove the photoresist to obtain a substrate containing an electron transport layer. S6: Coat a layer of photoresist on a substrate containing an electron transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the quantum dot layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching to obtain a pit; after removing the photoresist, fill the pit with quantum dot ink by inkjet printing to a set thickness to obtain a quantum dot photodetector.

[0029] In the fabrication method of the horizontal structure detector of the present invention, the quantum dot layer can be fabricated separately at the end, which avoids the damage to the quantum dot layer caused by depositing an electron transport layer or a hole transport layer on the quantum dot film during the fabrication process of the traditional vertical structure detector. This can improve the stability of the quantum dot layer film and the performance of photogenerated carriers.

[0030] The fabrication method of this invention can simultaneously and in large quantities prepare substrates containing first and second electrodes and electron-hole transport layers using photolithography and etching processes. Then, the required quantum dot active materials are filled in according to actual needs. Therefore, in industrial production, compared with the cumbersome fabrication process of traditional vertical photodetectors that require layer-by-layer stacking, its fabrication cost and difficulty are lower.

[0031] Preferably, in steps S1 to S6, the depth is set to 100~500nm, including but not limited to: 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0032] Preferably, in steps S1 to S5, the deposition method is independently either thermal evaporation deposition or electron beam deposition.

[0033] Example 1 A schematic diagram of the quantum dot photodetector in this embodiment is shown below. Figure 1As shown, the device includes a silicon substrate with a circular blind hole on its surface. The diameter of the blind hole is 1300 nm and the depth is 300 nm. A cylindrical CdSe quantum dot layer is disposed in the center of the blind hole, and the cylindrical CdSe quantum dot layer is coaxial with the blind hole. The height of the cylindrical CdSe quantum dot layer from the opening of the blind hole to the bottom of the hole is 300 nm, and the diameter is 300 nm. On the two opposite arc-shaped sidewalls of the cylindrical CdSe quantum dot layer, arc-shaped nickel oxide hole transport layers and arc-shaped zinc oxide electron transport layers are respectively disposed. The hole transport layer and the electron transport layer are not in contact with each other; a first arc-shaped silver electrode layer is provided on the sidewall of the hole transport layer away from the quantum dot layer; a second arc-shaped copper electrode layer is provided on the sidewall of the electron transport layer away from the quantum dot layer; wherein: the height of the first electrode layer, the hole transport layer, the electron transport layer and the second electrode layer along the blind hole opening towards the bottom of the hole is 300nm; the width between the inner and outer arcs of the hole transport layer and the electron transport layer is 100nm, and the width between the inner and outer arcs of the first electrode layer and the second electrode layer is 400nm.

[0034] The fabrication method of the quantum dot photodetector in this embodiment includes the following steps: S1: Based on the structure and size of the designed quantum dot photodetector, plan the positions of the first electrode, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the silicon substrate; S2: The process flow for this step is shown below. Figure 2 Specifically, a layer of photoresist is coated on a silicon substrate, and the photoresist at the first electrode position is removed by photolithography to expose the substrate. The exposed substrate is then subjected to dry etching with a depth of 300 nm and a width of 400 nm. After etching, a layer of metallic silver is deposited by thermal evaporation with a deposition height of 300 nm. After deposition, the photoresist is removed by cleaning to obtain a substrate containing a first electrode layer of metallic silver.

[0035] S3: The process flow for this step is shown below. Figure 3 Specifically, a layer of photoresist is coated on a substrate containing a first electrode layer of metallic silver. The photoresist at the second electrode position is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 300 nm and a width of 400 nm. After etching, a layer of metallic copper is deposited by thermal evaporation with a deposition height of 300 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a second electrode layer of metallic copper.

[0036] S4: The process flow for this step is shown below. Figure 4Specifically, a photoresist layer is coated on a substrate containing a copper second electrode layer. The photoresist on the hole transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 300 nm and a width of 100 nm. After etching, a nickel oxide hole transport layer is deposited by electron beam deposition with a deposition height of 300 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a nickel oxide hole transport layer.

[0037] S5: The process flow for this step is shown below. Figure 5 Specifically, a photoresist layer is coated on a substrate containing a nickel oxide hole transport layer. The photoresist on the electron transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 300 nm and a width of 100 nm. After etching, a zinc oxide electron transport layer is deposited by electron beam deposition with a deposition height of 300 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a zinc oxide electron transport layer.

[0038] S6: The process flow for this step is shown below. Figure 6 Specifically, a photoresist layer is coated on a substrate containing a zinc oxide electron transport layer. The photoresist on the quantum dot layer is removed by photolithography, exposing the substrate. The exposed substrate is then dry-etched to a depth of 300 nm. After etching, the photoresist is removed by cleaning, resulting in a device with a cylindrical pit at the quantum dot layer location. The pit is filled with a CdSe quantum dot solution by inkjet printing, thus obtaining a quantum dot photodetector.

[0039] Comparative Example 1 The specific steps for fabricating quantum dot photodetectors using a traditional vertical structure are as follows: S1: A first electrode layer of metallic silver with a thickness of 400 nm is deposited on a silicon substrate by thermal evaporation.

[0040] S2: A nickel oxide hole transport layer with a thickness of 100 nm is deposited on the first electrode layer of metallic silver by electron beam deposition.

[0041] S3: Inkjet print a 300nm thick CdSe quantum dot layer on the nickel oxide hole transport layer.

[0042] S4: A zinc oxide electron transport layer with a thickness of 100 nm was deposited on the CdSe quantum dot layer by electron beam deposition.

[0043] S5: A 400nm thick copper second electrode layer is deposited on the zinc oxide electron transport layer by thermal evaporation to obtain a quantum dot photodetector.

[0044] Example 2 A schematic diagram of the quantum dot photodetector in this embodiment is shown below. Figure 1 As shown, the device includes a silicon substrate with a circular blind via on its surface. The diameter of the blind via is 1900 nm and its depth is 200 nm. A cylindrical HgSe quantum dot layer is disposed in the central region within the blind via, coaxial with the blind via. The height of the cylindrical HgSe quantum dot layer along the direction from the opening of the blind via to the bottom is 200 nm, and its diameter is 500 nm. Arc-shaped copper oxide hole transport layers and arc-shaped [other structures] are sequentially disposed on two opposite arc-shaped sidewalls of the cylindrical HgSe quantum dot layer. The device consists of a titanium dioxide electron transport layer and a hole transport layer that do not contact each other. An arc-shaped indium tin oxide first electrode layer is disposed on the sidewall of the hole transport layer away from the quantum dot layer. An arc-shaped platinum metal second electrode layer is disposed on the sidewall of the electron transport layer away from the quantum dot layer. The height of the first electrode layer, hole transport layer, electron transport layer, and second electrode layer along the direction from the blind hole opening to the bottom of the hole is 200 nm. The width between the inner and outer arcs of the hole transport layer and electron transport layer is 200 nm, and the width between the inner and outer arcs of the first electrode layer and second electrode layer is 500 nm.

[0045] The fabrication method of the quantum dot photodetector in this embodiment includes the following steps: S1: Based on the structure and size of the designed quantum dot photodetector, plan the positions of the first electrode, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the silicon substrate; S2: The process flow for this step is shown below. Figure 2 Specifically, a layer of photoresist is coated on a silicon substrate, and the photoresist at the first electrode position is removed by photolithography to expose the substrate. The exposed substrate is then subjected to dry etching with a depth of 200 nm and a width of 500 nm. After etching, a layer of indium tin oxide is deposited by thermal evaporation with a deposition height of 200 nm. After deposition, the photoresist is removed by cleaning to obtain a substrate containing the indium tin oxide first electrode layer.

[0046] S3: The process flow for this step is shown below. Figure 3 Specifically, a photoresist layer is coated on a substrate containing an indium tin oxide first electrode layer. The photoresist at the second electrode position is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 200 nm and a width of 500 nm. After etching, a layer of platinum is deposited by thermal evaporation with a deposition height of 200 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a platinum second electrode layer.

[0047] S4: The process flow for this step is shown below. Figure 4Specifically, a photoresist layer is coated on a substrate containing a platinum second electrode layer. The photoresist on the hole transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 200 nm and a width of 200 nm. After etching, a copper oxide hole transport layer is deposited by electron beam deposition with a deposition height of 200 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a copper oxide hole transport layer.

[0048] S5: The process flow for this step is shown below. Figure 5 Specifically, a photoresist layer is coated on a substrate containing a copper oxide hole transport layer. The photoresist on the electron transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 200 nm and a width of 200 nm. After etching, a titanium oxide electron transport layer is deposited by electron beam deposition with a deposition height of 300 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a titanium oxide electron transport layer.

[0049] S6: The process flow for this step is shown below. Figure 6 Specifically, the process involves coating a substrate containing a titanium dioxide electron transport layer with a layer of photoresist, removing the photoresist at the quantum dot layer location using photolithography to expose the substrate, performing dry etching on the exposed substrate to a depth of 200 nm, cleaning to remove the photoresist after etching, resulting in a device with a cylindrical pit at the quantum dot layer location, with a diameter of 500 nm, and filling the pit with HgSe quantum dot solution using inkjet printing to obtain a quantum dot photodetector.

[0050] Example 3 A schematic diagram of the quantum dot photodetector in this embodiment is shown below. Figure 1As shown, the device includes a silicon substrate with a circular blind via on its surface. The diameter of the blind via is 1600 nm and its depth is 500 nm. A cylindrical HgSe quantum dot layer is positioned in the center of the blind via, coaxial with the via. The height of the cylindrical HgSe quantum dot layer from the opening of the blind via towards the bottom is 500 nm, and its diameter is 200 nm. On two opposite arc-shaped sidewalls of the cylindrical HgSe quantum dot layer, arc-shaped molybdenum oxide hole transport layers and arc-shaped... The electron transport layer and hole transport layer are not in contact. A first aluminum electrode layer in an arc shape is provided on the sidewall of the hole transport layer away from the quantum dot layer. A second gold electrode layer in an arc shape is provided on the sidewall of the electron transport layer away from the quantum dot layer. The height of the first electrode layer, hole transport layer, electron transport layer and second electrode layer along the direction from the blind hole opening to the bottom of the hole is 500 nm. The width between the inner and outer arcs of the hole transport layer and electron transport layer is 100 nm. The width between the inner and outer arcs of the first electrode layer and the second electrode layer is 600 nm.

[0051] The fabrication method of the quantum dot photodetector in this embodiment includes the following steps: S1: Based on the structure and size of the designed quantum dot photodetector, plan the positions of the first electrode, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the silicon substrate; S2: The process flow for this step is shown below. Figure 2 Specifically, a layer of photoresist is coated on a silicon substrate, and the photoresist at the first electrode position is removed by photolithography to expose the substrate. The exposed substrate is then subjected to dry etching with a depth of 500 nm and a width of 600 nm. After etching, a layer of metallic silver is deposited by thermal evaporation, and the thickness of the metallic aluminum deposition is 500 nm. After deposition, the photoresist is removed by cleaning to obtain a substrate containing a metallic aluminum first electrode layer.

[0052] S3: The process flow for this step is shown below. Figure 3 Specifically, a photoresist layer is coated on a substrate containing a first aluminum electrode layer. The photoresist at the second electrode position is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 500 nm and a width of 600 nm. After etching, a layer of gold is deposited by thermal evaporation with a deposition height of 500 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a second gold electrode layer.

[0053] S4: The process flow for this step is shown below. Figure 4Specifically, a photoresist layer is coated on a substrate containing a gold second electrode layer. The photoresist at the hole transport layer location is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 500 nm and a width of 100 nm. After etching, a molybdenum oxide hole transport layer is deposited by electron beam deposition with a deposition height of 500 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a molybdenum oxide hole transport layer.

[0054] S5: The process flow for this step is shown below. Figure 5 Specifically, a photoresist layer is coated on a substrate containing a molybdenum oxide hole transport layer. The photoresist on the electron transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 500 nm and a width of 100 nm. After etching, a tin oxide electron transport layer is deposited by electron beam deposition with a deposition height of 500 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a tin oxide electron transport layer.

[0055] S6: The process flow for this step is shown below. Figure 6 Specifically, a photoresist layer is coated on a substrate containing a tin oxide electron transport layer. The photoresist on the quantum dot layer is removed by photolithography, exposing the substrate. The exposed substrate is then dry-etched to a depth of 500 nm. After etching, the photoresist is removed by cleaning, resulting in a device with a cylindrical pit at the quantum dot layer location. The pit is 200 nm in diameter. The pit is then filled with HgSe quantum dot solution by inkjet printing, thus obtaining a quantum dot photodetector.

[0056] Example 4 A schematic diagram of the quantum dot photodetector in this embodiment is shown below. Figure 1As shown, the device includes a silicon substrate with a circular blind via on its surface. The diameter of the blind via is 2100 nm and its depth is 100 nm. A cylindrical PbSe quantum dot layer is positioned in the center of the blind via, coaxial with the blind via. The cylindrical PbSe quantum dot layer has a height of 100 nm from the opening of the blind via to the bottom, and a diameter of 400 nm. An arc-shaped cobalt oxide hole transport layer and an arc-shaped [other structure] are sequentially arranged on two opposite arc-shaped sidewalls of the cylindrical PbSe quantum dot layer. The device comprises a bismuth selenide electron transport layer, with no contact between the hole transport layer and the electron transport layer; a first arc-shaped nickel electrode layer is provided on the sidewall of the hole transport layer away from the quantum dot layer; a second arc-shaped chromium electrode layer is provided on the sidewall of the electron transport layer away from the quantum dot layer; wherein: the height of the first electrode layer, the hole transport layer, the electron transport layer and the second electrode layer along the blind hole opening towards the bottom of the hole is 100 nm; the width between the inner and outer arcs of the hole transport layer and the electron transport layer is 50 nm, and the width between the inner and outer arcs of the first electrode layer and the second electrode layer is 800 nm.

[0057] The fabrication method of the quantum dot photodetector in this embodiment includes the following steps: S1: Based on the structure and size of the designed quantum dot photodetector, plan the positions of the first electrode, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the silicon substrate; S2: The process flow for this step is shown below. Figure 2 Specifically, a layer of photoresist is coated on a silicon substrate, and the photoresist at the first electrode position is removed by photolithography to expose the substrate. The exposed substrate is then subjected to dry etching with a depth of 100 nm and a width of 800 nm. After etching, a layer of metallic nickel is deposited by thermal evaporation with a deposition height of 100 nm. After deposition, the photoresist is removed by cleaning to obtain a substrate containing a first electrode layer of metallic nickel.

[0058] S3: The process flow for this step is shown below. Figure 3 Specifically, a layer of photoresist is coated on a substrate containing a first electrode layer of metallic nickel. The photoresist at the second electrode position is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 100 nm and a width of 800 nm. After etching, a layer of metallic chromium is deposited by thermal evaporation with a deposition height of 100 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a second electrode layer of metallic chromium.

[0059] S4: The process flow for this step is shown below. Figure 4Specifically, a photoresist layer is coated on a substrate containing a copper second electrode layer. The photoresist at the hole transport layer location is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 100 nm and a width of 50 nm. After etching, a cobalt oxide hole transport layer is deposited by electron beam deposition with a deposition height of 100 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a cobalt oxide hole transport layer.

[0060] S5: The process flow for this step is shown below. Figure 5 Specifically, a photoresist layer is coated on a substrate containing a cobalt oxide hole transport layer. The photoresist on the electron transport layer is removed by photolithography, exposing the substrate. The exposed substrate is then subjected to dry etching with a depth of 100 nm and a width of 50 nm. After etching, a bismuth selenide electron transport layer is deposited by electron beam deposition with a deposition height of 100 nm. After deposition, the photoresist is removed by cleaning, resulting in a substrate containing a bismuth selenide electron transport layer.

[0061] S6: The process flow for this step is shown below. Figure 6 Specifically, a photoresist layer is coated on a substrate containing a bismuth selenide electron transport layer. The photoresist on the quantum dot layer is removed by photolithography, exposing the substrate. The exposed substrate is then dry-etched to a depth of 100 nm. After etching, the photoresist is removed by cleaning, resulting in a device with a cylindrical pit at the quantum dot layer location. The pit is 400 nm in diameter. The pit is then filled with a PbSe quantum dot solution by inkjet printing, thus obtaining a quantum dot photodetector.

[0062] The response band, cutoff edge, dark current, and responsivity of the quantum dot photodetector in Examples 1-4 and Comparative Example 1 were studied. The test methods are as follows, and the results are shown in Table 1.

[0063] The response band and cutoff edge can be directly measured using an ultraviolet-visible-near-infrared spectrometer. Dark current density can be obtained by placing the detector in a completely black shielded box and measuring it with a semiconductor parameter analyzer. Responsivity can be measured using a halogen lamp and monochromator; the photocurrent is then subtracted from the dark current, and the result is divided by the optical power.

[0064] Table 1 Both the photodetectors in Example 1 and Comparative Example 1 use CdSe quantum dots. From the performance tests, their optical band gaps are similar, resulting in essentially the same response band and cutoff edge. In the traditional vertical structure of Comparative Example 1, the electrode area is large, and the multilayer film stacking easily generates leakage paths such as pinholes and defects, leading to a high dark current. In the horizontal structure of Example 1, the electron and hole transport layers are physically isolated and located on opposite sides of the quantum dot layer. This structure effectively suppresses the possibility of charge carriers tunneling directly from one electrode to another without illumination, thus effectively reducing the dark current. The horizontally separated electrode structure can form an effective transverse electric field within the quantum dot layer, facilitating rapid separation of photogenerated electron-hole pairs and further reducing recombination. Therefore, the responsivity of Example 1 is higher than that of Comparative Example 1.

[0065] Both the photodetectors in Examples 2 and 3 utilize HgSe quantum dots, which have a smaller bandgap than CdSe quantum dots, thus extending the response band into the short-wave infrared region. This demonstrates that the operating wavelength of the detector can be easily adjusted by selecting different types of quantum dot materials. In Example 3, the quantum dot layer is taller and smaller in diameter than in Example 2. The thicker quantum dot layer absorbs more light, while the smaller diameter means a shorter carrier transport path. This combination results in a higher responsivity in Example 3 compared to Example 2. While the greater layer height may slightly increase defects in the quantum dot layer, the dark current in Example 3 remains low due to the suppression of leakage current by the horizontal structure.

[0066] The photodetector in Example 4 uses PbSe quantum dots, which have a smaller band gap than CdSe quantum dots, thus extending the response band into the short-wave infrared region. However, since the quantum dot layer height is relatively low in Example 4, this may lead to insufficient light absorption, resulting in a relatively low responsivity and correspondingly low dark current.

[0067] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A quantum dot photodetector, characterized in that, include: A substrate, wherein a blind hole is formed on the surface of the substrate; A quantum dot layer is disposed in the central region within the blind hole; Hole transport layer and electron transport layer are disposed opposite to each other on the two sidewalls of the quantum dot layer; A first electrode layer is disposed on the sidewall of the hole transport layer away from the quantum dot layer; The second electrode layer is disposed on the sidewall of the electron transport layer away from the quantum dot layer.

2. The quantum dot photodetector according to claim 1, characterized in that, The depth of the blind hole is 100~500nm.

3. The quantum dot photodetector according to claim 1 or 2, characterized in that, The height of the quantum dot layer, hole transport layer, electron transport layer, first electrode layer, and second electrode layer along the direction from the opening of the blind hole to the bottom of the hole is equal to the depth of the blind hole.

4. The quantum dot photodetector according to claim 1 or 2, characterized in that, The blind hole is circular and has a diameter of 1000~2400nm.

5. The quantum dot photodetector according to claim 1 or 2, characterized in that, The quantum dot layer is cylindrical and coaxial with the blind hole; the diameter of the cylindrical quantum dot layer is 200~500nm.

6. The quantum dot photodetector according to claim 1 or 2, characterized in that, The hole transport layer and electron transport layer are conformally bonded to the sidewalls corresponding to the quantum dot layer, respectively. And / or: the first electrode layer conformally fits to the sidewall of the hole transport layer; the second electrode layer conformally fits to the sidewall of the electron transport layer.

7. The quantum dot photodetector according to claim 1 or 2, characterized in that, The widths of the hole transport layer and the electron transport layer are each independently 50~200nm; the widths of the first electrode layer and the second electrode layer are each independently 300~800nm.

8. The quantum dot photodetector according to claim 1 or 2, characterized in that, The quantum dot layer is made of one of CdSe quantum dots, HgSe quantum dots, HgTe quantum dots, and PbSe quantum dots; And / or: the material of the hole transport layer is one of nickel oxide, molybdenum oxide, copper oxide, and cobalt oxide; And / or: the material of the electron transport layer is one of bismuth selenide, titanium oxide, tin oxide, and zinc oxide; And / or: the material of the first electrode layer is one of silver, aluminum, indium tin oxide and nickel; And / or: The material of the second electrode layer is one of chromium, platinum, gold and copper.

9. The method for fabricating a quantum dot photodetector according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Plan the corresponding positions of the first electrode layer, hole transport layer, quantum dot layer, electron transport layer and second electrode layer on the substrate; wherein: the hole transport layer and the electron transport layer are respectively disposed on two opposite sidewalls of the quantum dot layer, the first electrode layer is disposed on the sidewall of the hole transport layer away from the quantum dot layer, and the second electrode layer is disposed on the sidewall of the electron transport layer away from the quantum dot layer. S2: Coat a layer of photoresist on the substrate to obtain a photoresist layer; remove the photoresist at the corresponding position of the first electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the first electrode layer. After deposition, remove the photoresist to obtain a substrate containing the first electrode layer. S3: Coat a layer of photoresist on the substrate containing the first electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the second electrode layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the second electrode layer. After deposition, remove the photoresist to obtain a substrate containing the second electrode layer. S4: Coat a photoresist layer on the substrate containing the second electrode layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the hole transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the hole transport layer. After deposition, remove the photoresist to obtain a substrate containing the hole transport layer. S5: Coat a layer of photoresist on a substrate containing a hole transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the electron transport layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching, and then deposit the electron transport layer. After deposition, remove the photoresist to obtain a substrate containing an electron transport layer. S6: Coat a layer of photoresist on a substrate containing an electron transport layer to obtain a photoresist layer; remove the photoresist at the corresponding position of the quantum dot layer by photolithography to expose the substrate; then etch the exposed substrate to a set depth by dry etching to obtain a pit; after removing the photoresist, fill the pit with quantum dot ink by inkjet printing to a set thickness to obtain a quantum dot photodetector.

10. The method for fabricating a quantum dot photodetector according to claim 9, characterized in that, In steps S1 to S5, the deposition method is independently either thermal evaporation deposition or electron beam deposition.

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