Solar blind ultraviolet photoelectric detector and preparation method thereof

Abstract

The invention discloses a solar-blind ultraviolet photoelectric detector and a preparation method thereof. The solar-blind ultraviolet photoelectric detector comprises a substrate, an AlN layer, a first unintentionally doped AlGaN layer, a Si-delta doped n-type AlGaN layer, a second unintentionally doped AlGaN layer and a metal interdigital electrode pair which are sequentially stacked, wherein the Al components in the first unintentionally doped AlGaN layer, the Si-delta doped n-type AlGaN layer and the second unintentionally doped AlGaN layer are gradually reduced layer by layer. The detector is simple in structure and low in preparation difficulty, the Si-delta doped n-type AlGaN layer serves as the photoconductive layer, and photoconductive gain is achieved under illumination; and the Al components of the three different AlGaN layers are gradually reduced, so that a strain polarization field is constructed, the light current output of the photoconductive layer is improved, the detection capability of the whole detector is improved, and high gain and high sensitivity of the photoelectric detector are realized.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric detection, and in particular to a solar-blind ultraviolet photoelectric detector and a preparation method of the solar-blind ultraviolet photoelectric detector. Background Art

[0002] Sunlight needs to penetrate the atmosphere to reach the earth's surface. The ozone layer in the atmosphere has a strong absorption effect on sunlight with a wavelength between 200nm and 280nm, making it almost impossible for sunlight in this band to reach the earth's surface. This band is called the "solar-blind ultraviolet" band. Compared with visible light and infrared light photoelectric detectors, photoelectric detectors working in this "solar-blind ultraviolet" band are less affected by the background radiation of the sun, and can achieve efficient and accurate detection and imaging of non-natural ultraviolet radiation on the earth's surface; solar-blind ultraviolet photoelectric detectors have broad application prospects and huge market demand in the military and civilian fields.

[0003] The photon energy in the solar-blind ultraviolet band is much greater than that in the visible and infrared bands, which means that at the same radiation power, the number of solar-blind ultraviolet photons is much less than that of visible and infrared photons, and the solar-blind ultraviolet photons interact with molecules and suspended particles in the atmosphere to produce scattering and absorption, causing the solar-blind ultraviolet light signal to decay rapidly. These factors result in the solar-blind ultraviolet light emitted from the detected source to be effectively detected. The light signal is extremely weak, which poses a severe challenge to the sensitivity of the solar-blind ultraviolet detector. Only high-gain, low-noise detectors can meet the detection requirements of this extremely weak solar-blind ultraviolet light signal.

[0004] The traditional high-gain solar-blind ultraviolet photodetector is mainly based on the photocathode photomultiplier tube (PMT), which needs to rely on a solar-blind ultraviolet bandpass filter with a high cutoff ratio. The detection capability is severely limited by the transmittance of the filter. The transmittance of the best solar-blind ultraviolet filter in the world is less than 20%. The AlGaN ternary alloy semiconductor material with a direct bandgap has a bandgap of 3.4eV to 6.2eV at room temperature, and the corresponding spectral range covers 200-365 nm. It is an ideal material for the development of solar-blind ultraviolet photodetectors. The existing solar-blind ultraviolet photodetectors prepared based on AlGaN-based semiconductor materials are mainly gain-free photodetectors with PIN structures, which cannot meet the needs of weak signal detection. The gain-type AlGaN solar-blind ultraviolet photodetector is mainly based on avalanche photodiodes with a separation-absorption-multiplication structure, and has defects such as complex material structure, high material defect density, and high signal-to-noise ratio. Summary of the invention

[0005] The purpose of the present invention is to provide a solar-blind ultraviolet photoelectric detector and a preparation method thereof, which can reduce the complexity of the detector material structure while ensuring the high-gain and high-sensitivity detection performance of the solar-blind ultraviolet photoelectric detector, thereby reducing the difficulty of preparing the detector.

[0006] In order to solve the above technical problems, the present invention provides a solar-blind ultraviolet photodetector, comprising: a substrate, an AlN layer, a first unintentionally doped AlGaN layer, a Si-δ doped n-type AlGaN layer, a second unintentionally doped AlGaN layer and a metal interdigital electrode pair stacked in sequence;

[0007] The Al components in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decrease layer by layer.

[0008] In an optional embodiment of the present application, the AlN layer includes a patterned AlN layer and an epitaxial AlN layer formed by secondary growth on the patterned AlN layer;

[0009] The patterned AlN layer includes a plurality of regular hexagonal AlN layers arranged in a flat pattern, the diameter of the regular hexagonal AlN layer is 3 μm-5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers are parallel to each other and the spacing is 1 μm-3 μm.

[0010] In an optional embodiment of the present application, the metal interdigitated electrode is a composite metal layer formed by sequentially depositing a Ti metal layer, an Al metal layer, a Ti metal layer and an Au metal layer;

[0011] The interdigital spacing of the metal interdigital electrode is 100 μm to 500 μm, and the interdigital length is 500 μm to 5 mm.

[0012] In an optional embodiment of the present application, the Si-δ doped n-type AlGaN layer comprises a multilayer structure layer in which Si uniformly doped n-type AlGaN layers and Si-δ layers are periodically alternately arranged, and the number of periods is 15 to 30.

[0013] In an optional embodiment of the present application, the total thickness of the single-layer Si uniformly doped n-type AlGaN layer and the single-layer Si-δ layer is 8nm-10nm;

[0014] The thickness of the first unintentionally doped AlGaN layer is 300nm-500nm;

[0015] The thickness of the second unintentionally doped AlGaN layer is 50 nm to 80 nm.

[0016] In an optional embodiment of the present application, the first unintentionally doped AlGaN layer is Al x Ga 1-x N layers, where 0.75 ≥ x ≥ 0.65;

[0017] The Si uniformly doped n-type AlGaN layer has a carrier concentration greater than or equal to 3×10 18 / cm 3 Si-δ doped n-type Al y Ga 1-y N layers, where 0.65>y>0.58;

[0018] The second unintentionally doped AlGaN layer is Al z Ga 1-z N layers, where 0.58 ≥ z ≥ 0.5.

[0019] A method for preparing a solar-blind ultraviolet photoelectric detector, used for preparing the solar-blind ultraviolet photoelectric detector as described in any one of the above items, the preparation method comprising:

[0020] epitaxially growing an AlN layer on a substrate;

[0021] Depositing a first unintentionally doped AlGaN layer on the AlN layer;

[0022] Growing a Si-δ doped n-type AlGaN layer on the first unintentionally doped AlGaN layer;

[0023] Depositing a second unintentionally doped AlGaN layer on the Si-δ doped n-type AlGaN layer; wherein the Al content in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decreases layer by layer;

[0024] A pair of metal interdigital electrodes is formed on the second unintentionally doped AlGaN layer.

[0025] In an optional embodiment of the present application, growing a Si-δ doped n-type AlGaN layer on the first unintentionally doped AlGaN layer comprises:

[0026] A growth method in which Al source and Ga source are periodically interrupted and dopant silane is continuously supplied is adopted to form a periodic alternating structure of n-type AlGaN layer uniformly doped with Si and Si-δ layer.

[0027] In an optional embodiment of the present application, epitaxially growing an AlN layer on a substrate includes:

[0028] Epitaxially growing an AlN thin layer with a thickness of 100 nm to 300 nm on the substrate;

[0029] The AlN thin layer is patterned to form a patterned AlN layer; wherein the patterned AlN layer comprises a plurality of regular hexagonal AlN layers arranged in a flat pattern, the diameter of the regular hexagonal AlN layer is 3 μm to 5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers are parallel to each other and the spacing is 1 μm to 3 μm;

[0030] A secondary epitaxial AlN layer is deposited on the patterned AlN layer.

[0031] In an optional embodiment of the present application, forming a metal interdigital electrode pair on the second unintentionally doped AlGaN layer includes:

[0032] Preparing a photoresist layer having a predetermined metal finger pattern on the second unintentionally doped AlGaN layer;

[0033] Depositing a Ti metal layer, an Al metal layer, a Ti metal layer, and an Au metal layer in sequence to form a composite metal layer;

[0034] The composite metal layer in the area covered by the photoresist layer on the second unintentionally doped AlGaN layer is etched away to form the metal interdigitated electrode pair, wherein the interdigital spacing of the metal interdigitated electrodes is 100 μm to 500 μm, and the interdigital length is 500 μm to 5 mm.

[0035] The present invention provides a solar-blind ultraviolet photodetector and a preparation method thereof. The solar-blind ultraviolet photodetector comprises: a substrate, an AlN layer, a first unintentionally doped AlGaN layer, a Si-δ doped n-type AlGaN layer, a second unintentionally doped AlGaN layer and a metal interdigital electrode pair stacked in sequence; wherein the Al component in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decreases layer by layer.

[0036] The photosensitive layer in the solar-blind ultraviolet photodetector of the present application is composed of three structural layers: a first unintentionally doped AlGaN layer, a Si-δ doped n-type AlGaN layer, and a second unintentionally doped AlGaN layer. The three structural layers are essentially of the same type of material structure, which is simple to prepare and easier to prepare to form a high-quality material structure. The Si-δ doped n-type AlGaN layer is used as the photoconductive layer, so that photoconductive gain can be achieved under illumination. At the same time, the doping difficulty of the n-type doped AlGaN layer is low, and the entire photodetector only needs to adopt a metal-semiconductor-metal (MSM) electrode structure, which makes the preparation of the photodetector simple. The preparation difficulty is low; on this basis, the Al components in the three structural layers of the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decrease successively, that is, the lattice constants between the three structural layers increase successively, so that a strain polarization field with a specific polarization direction is formed at the heterogeneous interface between the three structural layers, so that when the photosensitive layer receives day-blind ultraviolet light, the strain polarization field can promote the separation of photogenerated electron-hole pairs, and then help to improve the photocurrent output of the photodetector, thereby improving the detection capability of the entire detector and achieving high gain and high sensitivity of the photodetector. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] FIG1 is a schematic cross-sectional structure diagram of a solar-blind ultraviolet photodetector provided in an embodiment of the present application;

[0039] FIG2 is a schematic diagram of the structure of an imaged AlN layer in an AlN layer provided in an embodiment of the present application;

[0040] FIG3 is a schematic diagram of a partial cross-sectional structure of an AlN layer provided in an embodiment of the present application;

[0041] FIG4 is a schematic diagram of the structure of a Si-δ doped n-type AlGaN layer provided in an embodiment of the present application;

[0042] FIG5 is a coordinate diagram of the electrical performance of a solar-blind ultraviolet photodetector provided in an embodiment of the present application;

[0043] FIG6 is a coordinate diagram of the optical performance of a solar-blind ultraviolet photodetector provided in an embodiment of the present application;

[0044] FIG. 7 is a schematic flow chart of a method for preparing a solar-blind ultraviolet photodetector provided in an embodiment of the present application. DETAILED DESCRIPTION

[0045] The core of the present invention is to provide a solar-blind ultraviolet photoelectric detector and a preparation method thereof, which can reduce the difficulty of preparing the detector while improving the detection capability of the detector.

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0047] As shown in FIG. 1 , FIG. 1 is a schematic diagram of the cross-sectional structure of a solar-blind ultraviolet photodetector provided in an embodiment of the present application.

[0048] In a specific embodiment of the present application, the solar-blind ultraviolet photodetector may include:

[0049] A substrate 1, an AlN layer 2, a first unintentionally doped AlGaN layer 3, a Si-δ doped n-type AlGaN layer 4, a second unintentionally doped AlGaN layer 5 and a metal interdigital electrode pair 6 are stacked in sequence;

[0050] The Al components in the first unintentionally doped AlGaN layer 3 , the Si-δ doped n-type AlGaN layer 4 and the second unintentionally doped AlGaN layer 5 decrease layer by layer.

[0051] As shown in FIG. 1 , in the actual process of preparing the solar-blind ultraviolet photodetector, an AlN layer 2, a first unintentionally doped AlGaN layer 3, a Si-δ doped n-type AlGaN layer 4, a second unintentionally doped AlGaN layer 5 and a metal interdigital electrode pair 6 can be sequentially grown on the substrate.

[0052] Among them, the substrate 1 in this embodiment can be C-plane sapphire; and the AlN layer 2 can be a thin layer of AlN material layer formed by depositing and growing on the substrate 1 using the MOCVD method, and the thickness of the AlN layer 2 can be 100nm~300nm, specifically, the thickness can be 100nm, 200nm or 300nm.

[0053] On this basis, as shown in Figures 2 and 3, Figure 2 is a schematic diagram of the structure of an imaged AlN layer in the AlN layer provided in an embodiment of the present application; Figure 3 is a schematic diagram of the local cross-sectional structure of the AlN layer provided in an embodiment of the present application.

[0054] In an optional implementation of the present embodiment, the AlN layer 2 may include a patterned AlN layer and an epitaxial AlN layer 22 formed by secondary growth on the patterned AlN layer; the patterned AlN layer includes a plurality of regular hexagonal AlN layers 21 arranged in a flat pattern, the diameter of the regular hexagonal AlN layer 21 is 3 μm to 5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers 21 are parallel to each other and the spacing is 1 μm to 3 μm.

[0055] Referring to FIG. 2 , in the actual process of growing and forming the AlN layer 2, a relatively thin AlN layer can be prepared first, and then the AlN layer can be patterned and etched to form a plurality of regular hexagonal AlN layers 21 with the same structure and closely arranged, the diameter D of each regular hexagonal AlN layer 21 is 3 μm to 5 μm, and the side of each regular hexagonal AlN layer 21 is parallel to the side of the adjacent regular hexagonal AlN layer 21, and the spacing l between the sides of two adjacent regular hexagonal AlN layers 21 is 1 μm to 3 μm. It can be understood that the diameter D of each regular hexagonal AlN layer 21 should be greater than the spacing l between the sides of two adjacent regular hexagonal AlN layers 21; for example, when the diameter D of the regular hexagonal AlN layer 21 is 5 μm, the spacing l between the sides of two adjacent regular hexagonal AlN layers 21 can be 2.5 μm.

[0056] As shown in FIG. 3 , after forming the patterned AlN layer, a secondary epitaxial growth may be further performed on the patterned AlN layer to form an epitaxial AlN layer 22 . The growth thickness of the epitaxial AlN layer 22 may be 2 μm to 5 μm, and preferably 4 μm.

[0057] In this embodiment, the patterned AlN layer is used as a growth template to perform secondary epitaxial growth of the epitaxial AlN layer 22, which can form a lateral epitaxial growth effect on the side of each regular hexagonal AlN layer 21 in the patterned AlN layer, which is beneficial to reducing the dislocation density in the first grown patterned AlN layer and improving the crystal quality of the AlN layer 2 finally grown.

[0058] After the AlN layer 2 is prepared, a first unintentionally doped AlGaN layer 3, a Si-δ doped n-type AlGaN layer 4 and a second unintentionally doped AlGaN layer 5 can be further formed on the AlN layer 2; wherein the first unintentionally doped AlGaN layer 3 and the second unintentionally doped AlGaN layer 5 are structural layers formed in a non-doped manner, and the Si-δ doped n-type AlGaN layer 4 is a structural layer formed by doping Al source and Ga source into the Si material structure.

[0059] On this basis, the Al composition in the first unintentionally doped AlGaN layer 3, the Si-δ doped n-type AlGaN layer 4 and the second unintentionally doped AlGaN layer 5 in the present embodiment decreases layer by layer, that is, the Al composition of the first unintentionally doped AlGaN layer 3 is higher than the Al composition of the Si-δ doped n-type AlGaN layer 4, and the Al composition of the Si-δ doped n-type AlGaN layer 4 is higher than the second unintentionally doped AlGaN layer 5.

[0060] In an optional embodiment of the present application, the first unintentionally doped AlGaN layer 3 may be Al x Ga 1-x N layers, where 0.75 ≥ x ≥ 0.65, for example, the value of x may be 0.65;

[0061] The Si-δ doped n-type AlGaN layer 4 may be a Si-δ doped n-type Al y Ga 1-y N layer, wherein 0.65>y>0.58, for example, the value of y may be 0.6; ensuring that the carrier concentration in the Si-δ doped n-type AlGaN layer is greater than or equal to 3×10 18 / cm 3 .

[0062] The second unintentionally doped AlGaN layer 5 may be Al z Ga 1-z N layers; wherein 0.58≥z≥0.5, for example, the z value may be 0.58.

[0063] It should be noted that the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer in this embodiment are essentially of the same type of material structure, so that the preparation steps are simpler in the actual preparation process, and it is also easier to prepare a high-quality material structure. In addition, the Si-δ doped n-type AlGaN layer 4 in this embodiment is used as a photoconductive layer, and its conductivity can change under light, so that photoconductive gain can be achieved, thereby achieving high gain of the day-blind ultraviolet photodetector, and relative to the p-type AlGaN layer with a high Al component, the doping difficulty of the n-type AlGaN layer in this embodiment is smaller, thereby reducing the difficulty of preparing the entire photodetector, thereby forming a detector with a higher signal-to-noise ratio.

[0064] In addition, the Al components in the three structural layers of the first unintentionally doped AlGaN layer 3, the Si-δ doped n-type AlGaN layer 4 and the second unintentionally doped AlGaN layer 5 in this embodiment decrease successively, which means that the lattice constants of the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer increase successively. The difference in lattice constants causes strain to form at the interlayer interfaces between the three structural layers, and a strain polarization field with a specific polarization direction is formed at the heterogeneous interface between the three structural layers. Therefore, when the photosensitive layer composed of the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer receives day-blind ultraviolet light, the strain polarization field can promote the separation of photogenerated electron-hole pairs, thereby helping to improve the photocurrent output of the photodetector, thereby improving the detection capability of the entire detector and achieving high gain and high sensitivity of the photodetector.

[0065] It can be seen that in this embodiment, only a single material structure of AlGaN is used, and by controlling the decreasing change of the Al component, three AlGaN layers with different lattice constants can be formed, which not only reduces the difficulty of preparing the photosensitive structure layer of the entire detector, but also can ensure the high gain and high sensitivity of the detector.

[0066] On this basis, as shown in FIG. 4 , FIG. 4 is a schematic diagram of the structure of the Si-δ doped n-type AlGaN layer provided in an embodiment of the present application.

[0067] In an optional embodiment of the present embodiment, the Si-δ doped n-type AlGaN layer may be a multilayer structure layer in which Si uniformly doped n-type AlGaN layers and Si-δ layers are periodically alternately arranged, and a layer of Si uniformly doped n-type AlGaN layer 41 and a layer of Si-δ layer 42 constitute a periodic structure, and the number of periods of the periodic structure in the Si-δ doped n-type AlGaN layer 4 may be 15 to 30.

[0068] In the actual preparation process of forming the Si-δ doped n-type AlGaN layer 4, a Si doping source can be continuously introduced while an Al source and a Ga source are intermittently introduced to finally form a Si-δ doped n-type AlGaN layer 4 in which a Si uniformly doped n-type AlGaN layer 41 and a Si-δ layer 42 are alternately stacked.

[0069] In addition, in a specific implementation of the present embodiment, the total thickness of the single-layer Si uniformly doped n-type AlGaN layer 41 and the single-layer Si-δ layer 42 in the Si-δ doped n-type AlGaN layer 4 is 8nm~10nm, specifically 8nm, 9nm or 10nm; in addition, the thickness of the first unintentionally doped AlGaN layer 3 is 300nm~500nm, specifically 300nm, 350nm, 400nm, 450nm or 500nm; the thickness of the second unintentionally doped AlGaN layer 5 is 50nm~80nm, specifically 50nm, 55nm, 60nm, 65nm, 70nm, 75nm or 80nm.

[0070] After the second unintentionally doped AlGaN layer 5 is formed, a metal interdigital electrode 6 may be further formed on the second unintentionally doped AlGaN layer 5 . The metal interdigitated electrode 6 in the present embodiment can be a composite metal layer formed by sequentially depositing a Ti metal layer, an Al metal layer, a Ti metal layer and an Au metal layer, so that the metal interdigitated electrode in the present embodiment is also a composite metal layer formed by sequentially stacking a Ti metal layer, an Al metal layer, a Ti metal layer and an Au metal layer; on this basis, the interdigitated spacing of the metal interdigitated electrode 6 can be 100μm~500μm, for example, the thickness of the Ti metal layer, the Al metal layer, the Ti metal layer and the Au metal layer can be 30nm, 50nm, 30nm or 200nm respectively, or the total thickness of the metal interdigitated electrode is 100μm, 200μm, 300μm, 400μm or 500μm; the interdigitated length can be 500μm~5mm, for example, the interdigitated length can be 500μm, 600μm, 700μm, 800μm, 900μm, 1mm, 2mm, 3mm, 4mm or 5mm, etc.

[0071] As shown in Figures 5 and 6, Figures 5 and 6 respectively show the electrical and optical properties of a day-blind ultraviolet photodetector with a finger spacing of 200μm and a finger length of 3mm. The horizontal axis in Figure 5 is the bias voltage applied to the metal finger electrode of the day-blind ultraviolet photodetector; the vertical axis is the current value in the photosensitive layer of the day-blind ultraviolet photodetector; thus, the different curves in Figure 5 are the photocurrent change curves of the day-blind ultraviolet photodetector under different wavelengths of light with the change of bias voltage. Based on Figure 5, it can be seen that under the applied bias, the day-blind ultraviolet photodetector presents a large photocurrent, and the ratio of the photocurrent to the dark current reaches at least 2 orders of magnitude, with a good signal-to-noise ratio. In Figure 6, the horizontal axis is the illumination wavelength; the vertical axis is the quantum efficiency; Figure 6 shows the change curve of the quantum efficiency of photoelectric conversion with wavelength under different applied bias voltages. Based on Figure 6, it can be seen that the response band of the day-blind ultraviolet photodetector is between 220nm-260nm, and the quantum efficiency of photoelectric conversion under ±1V external bias voltage exceeds 100%, indicating that the day-blind ultraviolet photodetector has a gain characteristic, and as the external bias voltage increases, the quantum efficiency continues to increase and the gain becomes larger and larger.

[0072] In summary, the photosensitive layer in the day-blind ultraviolet photodetector of the present application is composed of three structural layers: a first unintentionally doped AlGaN layer, a Si-δ doped n-type AlGaN layer and a second unintentionally doped AlGaN layer. The three structural layers are essentially of the same type of material structure, which is simple to prepare and easier to prepare to form a high-quality material structure; and the Si-δ doped n-type AlGaN layer is used as the photoconductive layer, which can achieve photoconductive gain under illumination, and the doping difficulty of the n-type doped AlGaN layer is low, and the entire photodetector only needs to adopt a metal-semiconductor-metal (MSM) electrode structure, so that the photodetector The preparation difficulty of the device is low; on this basis, the Al components in the three structural layers of the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decrease successively, that is, the lattice constants between the three structural layers increase successively, so that a strain polarization field with a specific polarization direction is formed at the heterogeneous interface between the three structural layers, so that when the photosensitive layer receives day-blind ultraviolet light, the strain polarization field can promote the separation of photogenerated electron-hole pairs, and then help to improve the photocurrent output of the photodetector, thereby improving the detection capability of the entire detector and achieving high gain and high sensitivity of the photodetector.

[0073] Based on the above discussion, the present application further discloses a method for preparing a solar-blind ultraviolet photoelectric detector, which can be used to prepare the solar-blind ultraviolet photoelectric detector of any of the above embodiments. As shown in FIG7 , in a specific embodiment of the present application, the method for preparing the solar-blind ultraviolet photoelectric detector may include:

[0074] S11: epitaxially growing an AlN layer on a substrate.

[0075] The AlN layer in this embodiment may be a thin AlN material layer grown on a C-plane sapphire substrate using a MOCVD (Metal-organic Chemical Vapor Deposition) technique.

[0076] S12: depositing a first unintentionally doped AlGaN layer on the AlN layer.

[0077] The first unintentionally doped AlGaN layer may be Al x Ga1- x N layers, where 0.75 ≥ x ≥ 0.65, and the preferred x value is 0.65;

[0078] The thickness of the first unintentionally doped AlGaN layer may be 300-500 nm, and preferably 450 nm.

[0079] S13: growing a Si-δ doped n-type AlGaN layer on the first unintentionally doped AlGaN layer.

[0080] The Si-δ doped n-type AlGaN layer may be a Si-δ doped n-type Al y Ga1- y N layer, 0.65>y>0.58, the preferred y value is 0.6; Si-δ doped n-type Al y Ga1- y The carrier concentration of N layer is ≥3×10 18 / cm 3 .

[0081] Optionally, the Si-δ doped n-type AlGaN layer can be grown in a manner that the Al source and the Ga source are periodically interrupted and the dopant silane is continuously supplied to form a uniformly Si-doped n-type AlGaN layer. y Ga1- y The N layer and Si-δ layer are periodically alternating structures.

[0082] Single layer Si uniformly doped with n-type Al y Ga 1-y The total thickness of the N layer and the single Si-δ layer can be 8nm~10nm. The Si-doped n-type Al y Ga 1-y The periodic structure formed by the N layer and the Si-δ layer may have a period number of 15 to 30.

[0083] S14: depositing a second unintentionally doped AlGaN layer on the Si-δ doped n-type AlGaN layer.

[0084] The Al components in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decrease layer by layer.

[0085] The second unintentionally doped AlGaN layer may be Al z Ga 1-z N layer, 0.58≥z≥0.5, and the preferred z value is 0.58; the thickness of the second unintentionally doped AlGaN layer is 50nm-80nm, and the preferred thickness is 60nm.

[0086] S15: forming a pair of metal interdigital electrodes on the second unintentionally doped AlGaN layer.

[0087] Based on the above discussion, in an optional implementation of this embodiment, the process of growing an AlN layer on a substrate may further include:

[0088] S111: epitaxially growing an AlN thin layer with a thickness of 100 nm to 300 nm on the substrate.

[0089] Specifically, an AlN thin layer may be formed on the substrate by MOCVD technology, and the thickness of the AlN thin layer may be 100 nm, 200 nm, or 300 nm, preferably 200 nm.

[0090] S112: patterning the AlN thin layer to form a patterned AlN layer; wherein the patterned AlN layer includes a plurality of regular hexagonal AlN layers arranged in a flat pattern, the diameter of the regular hexagonal AlN layer is 3 μm to 5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers are parallel to each other and the spacing is 1 μm to 3 μm.

[0091] Standard photolithography and lift-off technology can be used to first prepare a patterned metal Al film on the AlN thin layer as a masking layer. The mask layer is a densely arranged regular hexagonal metal Al film. The circumscribed circle diameter of each regular hexagonal metal Al film is 3μm~5μm, and the spacing between the sides of two adjacent regular hexagonal metal Al films is 1μm~3μm.

[0092] Then, the inductively coupled plasma etching (ICP) technology is used to etch the area of ​​the AlN thin layer with a patterned metal Al film on the surface that is not covered by the regular hexagonal metal Al film. The etching depth is equal to the thickness of the AlN thin layer, thereby retaining the regular hexagonal AlN thin layer with the metal Al film covered on the surface; the metal Al film is then removed by a phosphoric acid wet method, and after repeated cleaning with deionized water and isopropanol solution, it is dried at 150°C to obtain a patterned AlN layer; obviously, the patterned AlN layer also includes densely arranged regular hexagonal AlN layers, the diameter of each regular hexagonal AlN layer is 3μm~5μm, and the spacing between the sides of two adjacent regular hexagonal AlN layers is 3μm~5μm, as shown in Figure 2.

[0093] S113: forming an epitaxial AlN layer on the patterned AlN layer.

[0094] After the patterned AlN layer is formed, the MOCVD method can be used again to perform secondary epitaxial growth on the patterned AlN layer to form an AlN layer, that is, to obtain an epitaxial AlN layer. The total thickness of the epitaxial AlN layer and the patterned AlN layer can be 3 μm to 5 μm.

[0095] In this embodiment, an AlN thin layer is first epitaxially grown on a substrate, and then dry-etched to form a patterned AlN layer, and secondary epitaxial growth is performed on the patterned AlN layer, that is, the patterned AlN layer is used as a growth template. During the secondary epitaxial growth process, a lateral epitaxial growth effect is formed on the patterned AlN layer, which is beneficial to reducing the dislocation density in the AlN thin layer grown for the first time and improving the crystal quality of the AlN layer.

[0096] It is understandable that, in practical applications, the present application does not provide a method for forming an AlN layer by one-time processing; in this case, the thickness of the AlN layer formed by one-time molding can be 500 nm to 3 μm.

[0097] In another optional embodiment of the present application, the process of preparing the above-mentioned metal interdigital electrode pair may include:

[0098] S151: preparing a photoresist layer having a predetermined metal finger pattern on the second unintentionally doped AlGaN layer.

[0099] Specifically, a photoresist layer can be coated on the second unintentionally doped AlGaN layer, and the photoresist layer can be pattern-etched according to a set metal finger pattern (i.e., the pattern of the metal finger electrodes to be formed in the end), thereby forming a photoresist layer with a set metal finger pattern.

[0100] S152: depositing a Ti metal layer, an Al metal layer, a Ti metal layer, and an Au metal layer in sequence to form a composite metal layer.

[0101] The metal layers of the composite metal layer can be deposited sequentially on the photoresist layer by thermal evaporation or electron beam evaporation. Optionally, the thicknesses of the Ti metal layer, Al metal layer, Ti metal layer, and Au metal layer in the composite metal layer can be 30nm, 50nm, 30nm, and 200nm, respectively.

[0102] S153: etching and removing the composite metal layer in the area covered by the photoresist layer on the second unintentionally doped AlGaN layer to form a metal interdigital electrode pair.

[0103] Among them, the interdigital spacing of the metal interdigital electrode is 100μm~500μm, and the interdigital length is 500μm~5mm.

[0104] In practical applications, the lift-off process can be used to strip off the composite metal layer in the area covered with the photoresist layer, thereby obtaining a metal interdigitated electrode pair. Obviously, the metal interdigitated electrode pair is an electrode pair formed by stacking multiple metal layers in sequence.

[0105] S154: Annealing the metal interdigital electrode pair at 950° C. in a N 2 atmosphere.

[0106] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "includes", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements are inherent to the elements. In the absence of more restrictions, the elements limited by the sentence "comprising one..." do not exclude the presence of other identical elements in the process, method, article or equipment comprising the elements. In addition, the above-mentioned technical solution provided in the embodiment of the present application is consistent with the corresponding technical solution in the prior art in principle, and the part is not described in detail, so as to avoid too much redundancy.

[0107] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core ideas of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A solar-blind ultraviolet photoelectric detector, characterized in that: include: A substrate, an AlN layer, a first unintentionally doped AlGaN layer, a Si-δ doped n-type AlGaN layer, a second unintentionally doped AlGaN layer and a pair of metal interdigital electrodes are stacked in sequence; The Al components in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decrease layer by layer.

2. The solar-blind ultraviolet photodetector according to claim 1, characterized in that: The AlN layer includes a patterned AlN layer and an epitaxial AlN layer formed by secondary growth on the patterned AlN layer; The patterned AlN layer includes a plurality of regular hexagonal AlN layers arranged in a flat pattern, the diameter of the regular hexagonal AlN layer is 3 μm-5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers are parallel to each other and the spacing is 1 μm-3 μm.

3. The solar-blind ultraviolet photodetector according to claim 1, characterized in that: The metal interdigitated electrode is a composite metal layer formed by sequentially depositing a Ti metal layer, an Al metal layer, a Ti metal layer and an Au metal layer; The interdigital spacing of the metal interdigital electrode is 100 μm to 500 μm, and the interdigital length is 500 μm to 5 mm.

4. The solar-blind ultraviolet photodetector according to claim 1, characterized in that: The Si-δ doped n-type AlGaN layer comprises a multilayer structure layer in which Si uniformly doped n-type AlGaN layers and Si-δ layers are periodically and alternately arranged, and the number of periods is 15-30.

5. The solar-blind ultraviolet photodetector according to claim 4, characterized in that: The total thickness of the single-layer Si uniformly doped n-type AlGaN layer and the single-layer Si-δ layer is 8nm-10nm; The thickness of the first unintentionally doped AlGaN layer is 300nm-500nm; The thickness of the second unintentionally doped AlGaN layer is 50 nm to 80 nm.

6. The solar-blind ultraviolet photodetector according to any one of claims 1 to 5, characterized in that: The first unintentionally doped AlGaN layer is Al x Ga 1-x N layers, where 0.75 ≥ x ≥ 0.65; The Si uniformly doped n-type AlGaN layer has a carrier concentration greater than or equal to 3×10 18 / cm 3 Si-δ doped n-type Al y Ga 1-y N layers, where 0.65>y>0.58; The second unintentionally doped AlGaN layer is Al z Ga 1-z N layers, where 0.58 ≥ z ≥ 0.

5.

7. A method for preparing a solar-blind ultraviolet photodetector, characterized in that: Used to prepare the solar-blind ultraviolet photoelectric detector according to any one of claims 1 to 6, the preparation method comprising: epitaxially growing an AlN layer on a substrate; Depositing a first unintentionally doped AlGaN layer on the AlN layer; Growing a Si-δ doped n-type AlGaN layer on the first unintentionally doped AlGaN layer; Depositing a second unintentionally doped AlGaN layer on the Si-δ doped n-type AlGaN layer; wherein the Al content in the first unintentionally doped AlGaN layer, the Si-δ doped n-type AlGaN layer and the second unintentionally doped AlGaN layer decreases layer by layer; A pair of metal interdigital electrodes is formed on the second unintentionally doped AlGaN layer.

8. The method for preparing a solar-blind ultraviolet photoelectric detector according to claim 7, characterized in that: Growing a Si-δ doped n-type AlGaN layer on the first unintentionally doped AlGaN layer comprises: A growth method in which Al source and Ga source are periodically interrupted and dopant silane is continuously supplied is adopted to form a periodic alternating structure of n-type AlGaN layer uniformly doped with Si and Si-δ layer.

9. The method for preparing a solar-blind ultraviolet photoelectric detector according to claim 7, characterized in that: Epitaxially growing an AlN layer on a substrate, comprising: Epitaxially growing an AlN thin layer with a thickness of 100 nm to 300 nm on the substrate; The AlN thin layer is patterned to form a patterned AlN layer; wherein the patterned AlN layer comprises a plurality of regular hexagonal AlN layers arranged in a flat pattern, the diameter of the regular hexagonal AlN layer is 3 μm to 5 μm, and two adjacent sides of two adjacent regular hexagonal AlN layers are parallel to each other and the spacing is 1 μm to 3 μm; A secondary epitaxial AlN layer is deposited on the patterned AlN layer.

10. The method for preparing a solar-blind ultraviolet photodetector according to claim 7, characterized in that: Forming a metal interdigital electrode pair on the second unintentionally doped AlGaN layer comprises: Preparing a photoresist layer having a predetermined metal finger pattern on the second unintentionally doped AlGaN layer; Depositing a Ti metal layer, an Al metal layer, a Ti metal layer, and an Au metal layer in sequence to form a composite metal layer; The composite metal layer in the area covered by the photoresist layer on the second unintentionally doped AlGaN layer is etched away to form the metal interdigitated electrode pair, wherein the interdigital spacing of the metal interdigitated electrodes is 100 μm to 500 μm, and the interdigital length is 500 μm to 5 mm.

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