A heterojunction photodetector and a preparation method thereof

Abstract

This invention discloses a heterojunction photodetector and its fabrication method, belonging to the field of semiconductor optoelectronic device technology. The heterojunction photodetector, from bottom to top, comprises: a substrate, a two-dimensional material layer disposed on the substrate, an interdigitated electrode layer disposed on the two-dimensional material layer, an interface modification layer disposed on the surface of the two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a quantum dot layer covering the surface of the interface modification layer, and an encapsulation layer covering the surfaces of the quantum dot layer and the interdigitated electrode layer. The heterojunction photodetector of this invention, by introducing an interface modification layer between the two-dimensional material layer and the quantum dot layer, can efficiently passivate defect states at the two-dimensional material / quantum dot interface, suppress carrier recombination, and simultaneously optimize the interface energy level structure, promoting unidirectional and efficient injection of photogenerated carriers from the quantum dot layer to the two-dimensional material layer, significantly improving carrier separation and transport efficiency.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor optoelectronic device technology, specifically relating to a heterojunction photodetector and its fabrication method. Background Technology

[0002] As core devices for converting optical signals to electrical signals, photodetectors play a crucial role in optical communication, image sensing, environmental monitoring, and biomedicine. With the continuous upgrading of application demands, the market is placing more stringent comprehensive requirements on high-performance photodetectors, needing to simultaneously achieve high responsivity, high detectivity, fast response speed, wide spectral coverage, low-cost manufacturing, and long-term operational stability. However, existing mainstream photodetector technologies all face varying degrees of performance bottlenecks and application limitations. While silicon-based detectors have advantages such as mature technology, low cost and excellent stability, due to the indirect bandgap characteristics of silicon materials (bandgap width of about 1.12eV), their spectral response range is mainly limited to the visible light band. The photon response efficiency in the near-infrared region (especially wavelengths greater than 900nm) is drastically reduced, making it difficult to meet the needs of near-infrared applications such as fiber optic communication and night vision imaging.

[0003] Although III-V compound semiconductor detectors (such as InGaAs) exhibit excellent photoelectric conversion performance in the near-infrared band, their fabrication heavily relies on advanced epitaxial growth technologies such as molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). The huge investment in equipment, high process complexity, and high production costs severely restrict their widespread application in the large-scale civilian market and consumer electronics field.

[0004] While organic / polymer detectors possess unique advantages such as flexibility, solution processing, and large-area fabrication, their intrinsic carrier mobility is low, their response speed is slow, and their molecular structure is sensitive to water and oxygen environments, making them prone to performance degradation in air. As a result, they are difficult to meet the practical application requirements of high speed and high stability.

[0005] Perovskite detectors have developed rapidly in recent years, demonstrating extremely high photoelectric conversion efficiency in the laboratory stage. However, lead, a heavy metal in traditional lead-based perovskite materials, has significant biotoxicity, and its crystal structure has poor resistance to moisture, oxygen, and thermal stress, posing serious challenges to long-term operational stability and reliability, thus remaining far from commercial application.

[0006] To overcome the performance limitations of single materials, two-dimensional material / quantum dot heterojunction structures have become a research hotspot in recent years. Theoretically, this structure can combine the ultra-high carrier mobility of two-dimensional materials such as graphene with the complementary advantages of quantum dots, such as tunable bandgap and high optical absorption coefficient, to achieve synergistic effects of rapid charge transport and efficient photon capture. However, existing technologies mostly employ simple physical stacking methods to construct the heterojunction interface, leading to the following key problems: A significant interface defect state density exists between the two-dimensional material and the quantum dot layer. These defects become non-radiative recombination centers for photogenerated carriers, severely inhibiting exciton separation and charge extraction efficiency; simultaneously, energy level misalignment between the two forms a high carrier injection barrier, hindering the effective transport of photogenerated carriers. These interface problems collectively result in high dark current, photoresponsivity and detectivity far below theoretical expectations, and difficulties in ensuring batch-to-batch uniformity and environmental stability of device performance, thus limiting the practical application value of this heterojunction structure. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide a heterojunction photodetector and its fabrication method.

[0008] In a first aspect, the present invention provides a heterojunction photodetector, comprising, from bottom to top: a substrate, a two-dimensional material layer disposed on the substrate, an interdigitated electrode layer disposed on the two-dimensional material layer, an interface modification layer disposed on the surface of the two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a quantum dot layer covering the surface of the interface modification layer, and an encapsulation layer covering the surfaces of the quantum dot layer and the interdigitated electrode layer.

[0009] The interface modification layer material is one or more of the following: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), spiro-OMeTAD, methyl [6,6]-phenyl-C61-butyrate (PCBM), 1,8-octanedithiol (ODT), polymethyl methacrylate (PMMA), and polystyrene (PS).

[0010] Preferably, the substrate is a silicon substrate with a SiO2 layer.

[0011] Preferably, the two-dimensional material layer material is one or more of graphene, transition metal sulfides, transition metal selenides, and transition metal tellurides.

[0012] More preferably, the transition metal sulfide is one of MoS2 and WS2; the transition metal selenide is one of MoSe2 and WSe2; and the transition metal telluride includes one of MoTe2 and WTe2.

[0013] Preferably, the thickness of the two-dimensional material layer is 0.335~0.800 nm.

[0014] Preferably, the interdigitated electrode layer is a Cr-Au interdigitated electrode layer or a Ti-Au interdigitated electrode layer.

[0015] Preferably, the thickness of the interdigitated electrode layer is 30~60nm.

[0016] Preferably, the interface modification layer material is one or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), methyl [6,6]-phenyl-C61-butyrate (PCBM), and 1,8-octanedithiol (ODT).

[0017] Preferably, the thickness of the interface modification layer is 1~20nm.

[0018] Preferably, the quantum dot layer material is one or more of CdSe QDs, CdTe QDs, PbS QDs, PbSe QDs, Ag2S QDs, Ag2Se QDs, HgTe QDs, and HgSe QDs.

[0019] Preferably, the thickness of the quantum dot layer is 150~250nm.

[0020] Preferably, the encapsulation layer material is Al2O3 and SiN. x One of them, Preferably, the thickness of the encapsulation layer is 0.8~1.2μm.

[0021] Secondly, the present invention provides a method for fabricating a heterojunction photodetector, comprising the following steps: S1: A two-dimensional material layer is prepared on the substrate using a film transfer method and / or a chemical vapor deposition method; S2: An interdigitated electrode layer is deposited on a two-dimensional material layer using a mask method to obtain the interdigitated electrode layer; S3: An interface modification layer is prepared on the two-dimensional material layer in the interdigitated electrode layer and the interdigitated electrode gap by spin coating or impregnation. S4: A quantum dot layer is prepared on the interface modification layer by spin coating; S5: Remove the interface modification layer and quantum dot layer on the interdigitated electrode by laser etching; S6: An encapsulation layer is prepared on the quantum dot layer and the interdigitated electrode layer by ICP-CVD deposition to obtain a heterojunction photodetector.

[0022] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: (1) The heterojunction photodetector of the present invention introduces an interface modification layer between the two-dimensional material layer and the quantum dot layer. The interface modification layer can efficiently passivate the defect states of the two-dimensional material / quantum dot interface, suppress carrier recombination, and optimize the interface energy level structure, thereby promoting the unidirectional and efficient injection of photogenerated carriers from the quantum dot layer to the two-dimensional material layer, which greatly improves the carrier separation and transport efficiency.

[0023] (2) The interface modification layer in this invention also has a charge blocking function, which can effectively suppress the injection of charge carriers into the device by the electrode in the dark state, reduce the dark current density of the device by 1-3 orders of magnitude, and significantly improve the optoelectronic noise ratio of the device. In addition, the encapsulation layer can also serve as a physical barrier layer, effectively isolating the quantum dot layer from water and oxygen in the external environment, avoiding performance degradation of the quantum dot layer due to direct contact with water and oxygen, and greatly improving the storage stability and continuous working stability of the device in the air.

[0024] (3) The high carrier mobility of the two-dimensional material layer in the heterojunction photodetector of the present invention and the efficient interface transmission channel constructed by the interface modification layer can shorten the response time of the device to the microsecond level, which can meet the stringent requirements of high-end applications such as high-speed imaging and optical communication for response speed. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the cross-sectional structure of the heterojunction photodetector of the present invention.

[0026] Figure 2 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] In a first aspect, the present invention provides a heterojunction photodetector, comprising, from bottom to top: a substrate, a two-dimensional material layer disposed on the substrate, an interdigitated electrode layer disposed on the two-dimensional material layer, an interface modification layer disposed on the surface of the two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a quantum dot layer covering the surface of the interface modification layer, and an encapsulation layer covering the surfaces of the quantum dot layer and the interdigitated electrode layer. The interface modification layer material is one or more of the following: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), spiro-OMeTAD, methyl [6,6]-phenyl-C61-butyrate (PCBM), 1,8-octanedithiol (ODT), polymethyl methacrylate (PMMA), and polystyrene (PS).

[0030] The heterojunction photodetector of this invention significantly reduces the interface defect state density and improves energy level matching by optimizing the heterojunction interface, thereby achieving extremely high photoresponsivity, detectivity, fast response speed and excellent environmental stability.

[0031] In some implementations, the substrate is a silicon substrate with a SiO2 layer.

[0032] In some implementations, the two-dimensional material layer material is one or more of graphene, transition metal sulfides, transition metal selenides, and transition metal tellurides.

[0033] In some implementations, the transition metal sulfide is one of MoS2 and WS2; the transition metal selenide is one of MoSe2 and WSe2; and the transition metal telluride comprises one of MoTe2 and WTe2.

[0034] In some implementations, the thickness of the two-dimensional material layer is 0.335~0.800nm, including but not limited to: 0.335nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, etc.

[0035] In some implementations, the interdigitated electrode layer is a Cr-Au interdigitated electrode layer or a Ti-Au interdigitated electrode layer.

[0036] In some implementations, the thickness of the interdigitated electrode layer is 30~60nm, including but not limited to: 30nm, 40nm, 50nm, 60nm, etc.

[0037] In some implementations, the interface modification layer material is one or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), methyl [6,6]-phenyl-C61-butyrate (PCBM), and 1,8-octanedithiol (ODT).

[0038] In some implementations, the thickness of the interface modification layer is 1~20nm, including but not limited to: 1nm, 3nm, 5nm, 8nm, 10nm, 12nm, 15nm, 18nm, 20nm, etc.

[0039] In some implementations, the quantum dot layer material is one or more of CdSe QDs, CdTe QDs, PbS QDs, PbSe QDs, Ag2S QDs, Ag2Se QDs, HgTe QDs, and HgSe QDs.

[0040] In some implementations, the thickness of the quantum dot layer is 150~250nm, including but not limited to: 150nm, 180nm, 200nm, 220nm, 250nm, etc.

[0041] In some implementations, the encapsulation layer material is Al2O3 and SiN. x One of them, In some implementations, the thickness of the encapsulation layer is 0.8~1.2μm, including but not limited to: 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, etc.

[0042] Secondly, the present invention provides a method for fabricating a heterojunction photodetector, comprising the following steps: S1: A two-dimensional material layer is prepared on the substrate using a film transfer method and / or a chemical vapor deposition method; S2: An interdigitated electrode layer is deposited on a two-dimensional material layer using a mask method to obtain the interdigitated electrode layer; S3: An interface modification layer is prepared on the two-dimensional material layer in the interdigitated electrode layer and the interdigitated electrode gap by spin coating or impregnation. S4: A quantum dot layer is prepared on the interface modification layer by spin coating; S5: Remove the interface modification layer and quantum dot layer on the interdigitated electrode by laser etching; S6: An encapsulation layer is prepared on the quantum dot layer and the interdigitated electrode layer by ICP-CVD deposition to obtain a heterojunction photodetector.

[0043] The preparation method of this invention is simple in overall process, has controllable cost, and is suitable for large-scale production.

[0044] Example 1 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1 From bottom to top, the structure consists of a SiO2 / Si substrate, a graphene two-dimensional material layer disposed on the SiO2 / Si substrate, a Cr-Au interdigitated electrode layer disposed on the graphene two-dimensional material layer, a PTAA interface modification layer disposed on the surface of the graphene two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a PbSe quantum dot layer covering the surface of the PTAA interface modification layer, and a SiN layer covering the surfaces of the PbSe quantum dot layer and the Cr-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0045] (2) Using copper foil as a carrier and CH4 as a carbon source, a graphene layer (thickness of about 0.335 nm) is chemically vapor-deposited on the copper foil. PMMA is spin-coated on the graphene layer to form a PMMA film. Then, the film is placed in an etching solution to etch the copper foil, leaving the PMMA / graphene film floating on the liquid surface. Water is added to dilute the etching solution. Then, the SiO2 / Si substrate is immersed in it, and the graphene film is attached to the surface of the SiO2 layer of the SiO2 / Si substrate (the graphene layer is attached to the surface of the SiO2 layer). Then, the sample is immersed in hot acetone to dissolve and remove PMMA. After cleaning and drying, a two-dimensional graphene material layer can be obtained on the substrate.

[0046] (3) A photomask is formed on the graphene two-dimensional material layer by photolithography, and then a Cr metal layer with a thickness of 5 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s, and then an Au metal layer with a thickness of 50 nm is deposited at a deposition rate of 0.5 nm / s. Cr-Au interdigitated electrode layer is deposited on the graphene two-dimensional material layer.

[0047] (4) Dissolve PTAA in chlorobenzene to prepare a solution with a concentration of 2 mg / mL; in a nitrogen glove box, prepare a PTAA thin film layer on the graphene two-dimensional material layer at the Cr-Au interdigitated electrode layer and the interdigitated electrode gap by spin coating (spin coating speed of 3000 rpm and spin coating time of 30 s), and then anneal at 100 °C for 10 min to remove residual solvent to obtain a PTAA interface modification layer (thickness of about 10 nm).

[0048] (5) PbSe QDs were dissolved in octane to prepare a 20 mg / mL PbSe QDs dispersion. The PbSe QDs dispersion was spin-coated (1500 rpm, 60 s) onto the PTAA interface modification layer to form a PbSe quantum dot layer about 200 nm thick.

[0049] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Cr-Au interdigitated electrode. The process parameters of laser etching are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0050] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the chamber pressure was maintained at 8.000 mTorr, and the power was 400 W. SiN was deposited. x As a packaging layer for the device, the thickness of the packaging layer is about 1 μm (calculated with interdigitated electrodes as the substrate), resulting in a heterojunction photodetector.

[0051] Comparative Example 1 The process is basically the same as in Example 1, except that step (4) is not performed, the interface modification layer is not prepared, and the PbSe quantum dot layer is directly prepared on the graphene two-dimensional material layer at the Cr-Au interdigitated electrode layer and the interdigitated electrode gap.

[0052] Example 2 It is basically the same as Example 1, except that in step (4), the thickness of the PTAA interface modification layer is about 2nm.

[0053] Example 3 It is basically the same as Example 1, except that in step (4), the thickness of the interface modification layer is about 20nm.

[0054] Example 4 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1 From bottom to top, the structure consists of a SiO2 / Si substrate, a MoS2 two-dimensional material layer on the SiO2 / Si substrate, a Cr-Au interdigitated electrode layer on the MoS2 two-dimensional material layer, an ODT interface modification layer on the surface of the MoS2 two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, an HgTe quantum dot layer covering the surface of the ODT interface modification layer, and a SiN layer covering the surfaces of the HgTe quantum dot layer and the Cr-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0055] (2) MoO3 and S are used as the source of Mo and the source of S, respectively, and Ar is used as the carrier gas. A two-dimensional MoS2 material layer with a thickness of 0.650 nm is deposited on the SiO2 layer of the SiO2 / Si substrate by chemical vapor deposition.

[0056] (3) A photomask is formed on the MoS2 two-dimensional material layer by photolithography. Then, a Cr metal layer with a thickness of 10 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s, and an Au metal layer with a thickness of 30 nm is deposited at a deposition rate of 0.5 nm / s. A Cr-Au interdigitated electrode layer is obtained on the MoS2 two-dimensional material layer.

[0057] (4) The device obtained in step (3) is immersed in a 10 mM isopropanol solution of 1,8-octanedithiol (ODT) for 12 h at room temperature. After immersion, it is rinsed with pure isopropanol to remove physically adsorbed molecules and then dried with nitrogen gas to form a dense ODT interface modification layer (thickness of about 8 nm) on the surface of the Cr-Au interdigitated electrode layer and the MoS2 two-dimensional material layer at the interdigitated electrode gap.

[0058] (5) Dissolve HgTe QDs in toluene to prepare a 15 mg / mL HgTe QDs dispersion. Spin-coat the HgTe QDs dispersion onto the ODT interface modification layer (spin-coating speed 2500 rpm, spin-coating time 45 s) to form an HgTe quantum dot layer with a thickness of about 150 nm.

[0059] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Cr-Au interdigitated electrode. The process parameters of laser etching are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0060] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the chamber pressure was maintained at 8.000 mTorr, and the power was 400 W. SiN was deposited. x As a packaging layer for the device, the thickness of the packaging layer is approximately 0.9 μm (calculated with interdigitated electrodes as the substrate), resulting in a heterojunction photodetector.

[0061] Comparative Example 2 The process is basically the same as in Example 4, except that step (4) is not performed, the interface modification layer is not prepared, and the HgTe quantum dot layer is directly prepared on the Cr-Au interdigitated electrode layer and the MoS2 two-dimensional material layer at the gap between the interdigitated electrodes.

[0062] Example 5 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1From bottom to top, the structure consists of a SiO2 / Si substrate, a MoTe2 two-dimensional material layer on the SiO2 / Si substrate, a Ti-Au interdigitated electrode layer on the MoTe2 two-dimensional material layer, a PCBM interface modification layer on the surface of the MoTe2 two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a PbS quantum dot layer covering the surface of the PCBM interface modification layer, and a SiN layer covering the surfaces of the PbS quantum dot layer and the Ti-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0063] (2) MoO3 and Te are used as Mo source and Te source respectively, and Ar is used as carrier gas. A MoTe2 two-dimensional material layer with a thickness of 0.700 nm is deposited on the SiO2 layer of the SiO2 / Si substrate by chemical vapor deposition.

[0064] (3) A photomask is formed on the MoTe2 two-dimensional material layer by photolithography. Then, a Ti metal layer with a thickness of 10 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s. Then, an Au metal layer with a thickness of 50 nm is deposited at a deposition rate of 0.5 nm / s. Ti-Au interdigitated electrode layer is obtained on the MoTe2 two-dimensional material layer.

[0065] (4) Dissolve PCBM in chlorobenzene to prepare a solution with a concentration of 15 mg / mL; in a nitrogen glove box, prepare a PCBM thin film layer on the Ti-Au interdigitated electrode layer and the MoTe2 two-dimensional material layer at the interdigitated electrode gap by spin coating (spin coating speed of 4000 rpm and spin coating time of 40 s), and then anneal at 90 °C for 15 min to remove residual solvent to obtain a PCBM interface modification layer (thickness of about 10 nm).

[0066] (5) PbS QDs were dissolved in toluene to prepare a PbS QDs dispersion of 15 mg / mL. The PbS QDs dispersion was spin-coated (spin-coating speed of 2000 rpm, spin-coating time of 50 s) onto the PCBM interface modification layer to form a PbS quantum dot layer of about 250 nm thickness.

[0067] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Ti-Au interdigitated electrode. The laser etching process parameters are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0068] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the chamber pressure was maintained at 8.000 mTorr, and the power was 400 W. SiN was deposited. x As a packaging layer for the device, the thickness of the packaging layer is approximately 1.1 μm (calculated with interdigitated electrodes as the substrate), resulting in a heterojunction photodetector.

[0069] Comparative Example 3 The process is basically the same as in Example 4, except that step (4) is not performed, the interface modification layer is not prepared, and the HgTe quantum dot layer is directly prepared on the Ti-Au interdigitated electrode layer and the MoTe2 two-dimensional material layer at the gap between the interdigitated electrodes.

[0070] Example 6 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1 From bottom to top, the structure consists of a SiO2 / Si substrate, a MoSe2 two-dimensional material layer on the SiO2 / Si substrate, a Cr-Au interdigitated electrode layer on the MoSe2 two-dimensional material layer, a spiro-OMeTAD interface modification layer on the surface of the MoSe2 two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, an Ag2S quantum dot layer covering the surface of the spiro-OMeTAD interface modification layer, and a SiN layer covering the surfaces of the Ag2S quantum dot layer and the Cr-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0071] (2) MoO3 and Se are used as the source of Mo and the source of Se, respectively. Ar is used as the carrier gas. A two-dimensional MoSe2 material layer with a thickness of 0.650 nm is deposited on the SiO2 layer of the SiO2 / Si substrate by chemical vapor deposition.

[0072] (3) A photomask is formed on the MoSe2 two-dimensional material layer by photolithography. Then, a Cr metal layer with a thickness of 10 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s, and an Au metal layer with a thickness of 40 nm is deposited at a deposition rate of 0.5 nm / s. A Cr-Au interdigitated electrode layer is obtained on the MoSe2 two-dimensional material layer.

[0073] (4) The device obtained in step (3) is immersed in a 10 mM isopropanol solution of spiro-OMeTAD and soaked for 12 h at room temperature. After soaking, it is rinsed with pure isopropanol to remove physically adsorbed molecules and then dried with nitrogen gas to form a dense spiro-OMeTAD interface modification layer (thickness of about 8 nm) on the surface of the Cr-Au interdigitated electrode layer and the MoSe2 two-dimensional material layer in the interdigitated electrode gap.

[0074] (5) Dissolve Ag2S QDs in toluene to prepare a 15 mg / mL Ag2S QDs dispersion. Spin-coat the Ag2S QDs dispersion (spin-coating speed 2000 rpm, spin-coating time 50 s) onto the spiro-OMeTAD interface modification layer to form an Ag2S quantum dot layer with a thickness of about 250 nm.

[0075] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Cr-Au interdigitated electrode. The process parameters of laser etching are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0076] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the chamber pressure was maintained at 8.000 mTorr, and the power was 400 W. SiN was deposited. x As a packaging layer for the device, the thickness of the packaging layer is approximately 1.0 μm (calculated with interdigitated electrodes as the substrate), resulting in a heterojunction photodetector.

[0077] Example 7 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1From bottom to top, the structure consists of a SiO2 / Si substrate, a graphene two-dimensional material layer disposed on the SiO2 / Si substrate, a Cr-Au interdigitated electrode layer disposed on the graphene two-dimensional material layer, a PMMA interface modification layer disposed on the surface of the graphene two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, an HgSe quantum dot layer covering the surface of the PMMA interface modification layer, and a SiN layer covering the surfaces of the HgSe quantum dot layer and the Cr-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0078] (2) Using copper foil as a carrier and CH4 as a carbon source, a graphene layer (thickness of about 0.335 nm) is chemically vapor-deposited on the copper foil. PMMA is spin-coated on the graphene layer to form a PMMA film. Then, the film is placed in an etching solution to etch the copper foil, leaving the PMMA / graphene film floating on the liquid surface. Water is added to dilute the etching solution. Then, the SiO2 / Si substrate is immersed in it, and the graphene film is attached to the surface of the SiO2 layer of the SiO2 / Si substrate (the graphene layer is attached to the surface of the SiO2 layer). Then, the sample is immersed in hot acetone to dissolve and remove PMMA. After cleaning and drying, a two-dimensional graphene material layer can be obtained on the substrate.

[0079] (3) A photomask is formed on the graphene two-dimensional material layer by photolithography, and then a Cr metal layer with a thickness of 10 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s, and then an Au metal layer with a thickness of 30 nm is deposited at a deposition rate of 0.5 nm / s. Cr-Au interdigitated electrode layer is deposited on the graphene two-dimensional material layer.

[0080] (4) Dissolve PMMA in chlorobenzene to prepare a solution with a concentration of 10 mg / mL; in a nitrogen glove box, prepare a PMMA thin film layer on the graphene two-dimensional material layer at the Cr-Au interdigitated electrode layer and the interdigitated electrode gap by spin coating (spin coating speed of 4000 rpm and spin coating time of 40 s), and then anneal at 90 °C for 15 min to remove residual solvent to obtain a PMMA interface modification layer (thickness of about 10 nm).

[0081] (5) HgSe QDs were dissolved in octane to prepare a 20 mg / mL HgSe QDs dispersion. The HgSe QDs dispersion was spin-coated (2000 rpm, 50 s) onto the PMMA interface modification layer to form a PbSe quantum dot layer with a thickness of about 190 nm.

[0082] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Cr-Au interdigitated electrode. The process parameters of laser etching are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0083] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the cavity pressure was maintained at 8.000 mTorr and the power was 400 W. SiNx was deposited as the encapsulation layer of the device. The thickness of the encapsulation layer was about 1 μm (calculated with interdigitated electrodes as the substrate) to obtain a heterojunction photodetector.

[0084] Example 8 A schematic diagram of the heterojunction photodetector in this embodiment can be seen. Figure 1 From bottom to top, the structure consists of a SiO2 / Si substrate, a graphene two-dimensional material layer disposed on the SiO2 / Si substrate, a Cr-Au interdigitated electrode layer disposed on the graphene two-dimensional material layer, a PS interface modification layer disposed on the surface of the graphene two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a CdTe quantum dot layer covering the surface of the PS interface modification layer, and a SiN layer covering the surfaces of the CdTe quantum dot layer and the Cr-Au interdigitated electrode layer. x Encapsulation layer; The preparation process flow chart of this embodiment can be seen. Figure 2 The specific preparation method is as follows: (1) Provide a silicon wafer (SiO2 / Si) with a 300nm thick SiO2 layer as a substrate.

[0085] (2) Using copper foil as a carrier and CH4 as a carbon source, a graphene layer (thickness of about 0.335 nm) is chemically vapor-deposited on the copper foil. PMMA is spin-coated on the graphene layer to form a PMMA film. Then, the film is placed in an etching solution to etch the copper foil, leaving the PMMA / graphene film floating on the liquid surface. Water is added to dilute the etching solution. Then, the SiO2 / Si substrate is immersed in it, and the graphene film is attached to the surface of the SiO2 layer of the SiO2 / Si substrate (the graphene layer is attached to the surface of the SiO2 layer). Then, the sample is immersed in hot acetone to dissolve and remove PMMA. After cleaning and drying, a two-dimensional graphene material layer can be obtained on the substrate.

[0086] (3) A photomask is formed on the graphene two-dimensional material layer by photolithography, and then a Cr metal layer with a thickness of 10 nm is deposited by electron beam evaporation at a deposition rate of 0.2 nm / s, and then an Au metal layer with a thickness of 30 nm is deposited at a deposition rate of 0.5 nm / s. Cr-Au interdigitated electrode layer is deposited on the graphene two-dimensional material layer.

[0087] (4) Dissolve PS in chlorobenzene to prepare a solution with a concentration of 8 mg / mL; in a nitrogen glove box, prepare a PS thin film layer on the graphene two-dimensional material layer at the Cr-Au interdigitated electrode layer and the interdigitated electrode gap by spin coating (spin coating speed of 4000 rpm and spin coating time of 40 s), and then anneal at 90 °C for 15 min to remove residual solvent to obtain a PS interface modification layer (thickness of about 10 nm).

[0088] (5) CdTe QDs were dissolved in octane to prepare a CdTe QDs dispersion of 20 mg / mL. The CdTe QDs dispersion was spin-coated (spin-coating speed of 2000 rpm and spin-coating time of 50 s) onto the PS interface modification layer to form a CdTe quantum dot layer of about 180 nm thickness.

[0089] (6) Laser etching is used to remove the interface modification layer and quantum dot layer on the Cr-Au interdigitated electrode. The process parameters of laser etching are as follows: the laser etching power is 2% of the actual total output power of the laser equipment, the etching time is 0.2s, the etching frequency is 400kHz, the etching speed is 900mm / s, and the etching line spacing is the width of the interdigitated electrode, until the interdigitated electrode is etched out.

[0090] (7) The encapsulation layer was prepared by ICP-CVD. The specific process parameters of ICP-CVD were as follows: SiH4 and N2 were used as gas sources, with flow rates of 6.5 sccm and 6.0 sccm, respectively; the cavity pressure was maintained at 8.000 mTorr and the power was 400 W. SiNx was deposited as the encapsulation layer of the device. The thickness of the encapsulation layer was about 1 μm (calculated with interdigitated electrodes as the substrate) to obtain a heterojunction photodetector.

[0091] The responsivity, dark current, detectivity, and external quantum efficiency of the devices in Examples 1-5 and Comparative Examples 1-3 were tested, and the results are shown in Table 1.

[0092] Table 1 As shown in Table 1, the heterojunction photodetector in Example 1 exhibits good responsivity, high detectivity, high external quantum efficiency, and low dark current. Comparative Example 1, without an interface modification layer, shows a significant decrease in responsivity, detectivity, and external quantum efficiency, and a significant increase in dark current compared to Example 1. In Examples 2 and 3, the thickness of the interface modification layer was adjusted compared to Example 1. In Example 2, reducing the thickness of the interface modification layer resulted in a slight decrease in responsivity, detectivity, and external quantum efficiency, and a slight increase in dark current compared to Example 1. This may be because a thinner interface modification layer weakens passivation and limits carrier recombination suppression. In Example 3, increasing the thickness of the interface modification layer resulted in a slight decrease in responsivity, detectivity, and external quantum efficiency, and a slight increase in dark current compared to Example 1. This may be because an excessively thick interface modification layer affects carrier injection.

[0093] The heterojunction photodetector of Example 4 exhibits good responsivity, high detectivity, high external quantum efficiency, and low dark current. Comparative Example 2, without the interface modification layer, shows a significantly reduced responsivity, detectivity, and external quantum efficiency compared to Example 4, and a significantly increased dark current.

[0094] The heterojunction photodetector of Example 5 exhibits good responsivity, high detectivity, high external quantum efficiency, and low dark current. Comparative Example 3, without the interface modification layer, shows a significantly reduced responsivity, detectivity, and external quantum efficiency compared to Example 5, and a significantly increased dark current.

[0095] 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 heterojunction photodetector, characterized in that, From bottom to top, it includes: a substrate, a two-dimensional material layer disposed on the substrate, an interdigitated electrode layer disposed on the two-dimensional material layer, an interface modification layer disposed on the surface of the two-dimensional material layer and located at the electrode gap of the interdigitated electrode layer, a quantum dot layer covering the surface of the interface modification layer, and an encapsulation layer covering the surfaces of the quantum dot layer and the interdigitated electrode layer. The interface modification layer material is one or more of the following: poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], spiro-OMeTAD, methyl [6,6]-phenyl-C61-butyrate, 1,8-octanedithiol, polymethyl methacrylate, and polystyrene.

2. The heterojunction photodetector according to claim 1, characterized in that, The substrate is a silicon substrate with a SiO2 layer.

3. The heterojunction photodetector according to claim 1, characterized in that, The two-dimensional material layer material is one or more of graphene, transition metal sulfides, transition metal selenides, and transition metal tellurides; And / or: the thickness of the two-dimensional material layer is 0.335~0.800nm.

4. The heterojunction photodetector according to claim 3, characterized in that, The transition metal sulfide is one of MoS2 and WS2; the transition metal selenide is one of MoSe2 and WSe2; the transition metal telluride includes one of MoTe2 and WTe2.

5. The heterojunction photodetector according to claim 1, characterized in that, The interdigitated electrode layer is a Cr-Au interdigitated electrode layer or a Ti-Au interdigitated electrode layer; And / or: The thickness of the interdigitated electrode layer is 30~60nm.

6. The heterojunction photodetector according to claim 1, characterized in that, The interface modification layer material is one or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], methyl [6,6]-phenyl-C61-butyrate, and 1,8-octanedithiol.

7. The heterojunction photodetector according to claim 1 or 6, characterized in that, The thickness of the interface modification layer is 1~20nm.

8. The heterojunction photodetector according to claim 1, characterized in that, The quantum dot layer material is one or more of CdSeQDs, CdTeQDs, PbSQDs, PbSeQDs, Ag2SQDs, Ag2SeQDs, HgTeQDs, and HgSeQDs. And / or: the thickness of the quantum dot layer is 150~250nm.

9. The heterojunction photodetector according to claim 1, characterized in that, The encapsulation layer material is Al2O3 and SiN. x One of them; And / or: the thickness of the encapsulation layer is 0.8~1.2μm.

10. The method for fabricating a heterojunction photodetector according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1: A two-dimensional material layer is prepared on the substrate using a film transfer method and / or a chemical vapor deposition method; S2: An interdigitated electrode layer is deposited on a two-dimensional material layer using a mask method to obtain the interdigitated electrode layer; S3: An interface modification layer is prepared on the two-dimensional material layer in the interdigitated electrode layer and the interdigitated electrode gap by spin coating or impregnation. S4: A quantum dot layer is prepared on the interface modification layer by spin coating; S5: Remove the interface modification layer and quantum dot layer on the interdigitated electrode by laser etching; S6: An encapsulation layer is prepared on the quantum dot layer and the interdigitated electrode layer by ICP-CVD deposition to obtain a heterojunction photodetector.

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