Narrow-band znmg o-based ultraviolet detector based on resonant cavity enhancement and preparation method thereof

Abstract

The application relates to the technical field of semiconductor ultraviolet detector preparation, in particular to a narrow-band ZnMgO-based ultraviolet detector based on resonant cavity enhancement and a preparation method thereof. From bottom to top, the ultraviolet detector comprises a substrate, a buffer layer, a bottom light reflection layer, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer and a top light reflection layer; the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is any one of vertical pin heterojunction, pn heterojunction or Schottky heterojunction; the photosensitive layer comprises a ZnMgO layer, the ZnMgO layer is any hexagonal phase with a Mg component of 0-60%, or any cubic phase with a Zn component of 0-90%; the bottom light reflection layer is a nitride DBR layer, an oxide DBR layer or a metal film layer; the top light reflection layer is an oxide DBR layer or a metal film layer; a step structure is arranged at the edge of the photosensitive layer and used for arranging an ohmic electrode. The vertical heterojunction has a high response speed; and the narrow-band ultraviolet detection peak position is adjustable.

Description

Technical Field

[0001] This invention relates to the field of semiconductor ultraviolet detector fabrication technology, and in particular to a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement and its fabrication method. Background Technology

[0002] Ultraviolet (UV) detection technology, developed after visible and infrared detection technologies, is a novel photoelectric detection method that has demonstrated significant military and commercial application potential in numerous fields, including flame detection, space-based early warning, corona detection, biochemical analysis, and UV communication. Based on spectral response bandwidth, UV detectors can be categorized into broadband photodetectors and narrowband photodetectors. Broadband detectors cover a wider UV spectral range, focusing on acquiring the total amount of UV radiation; while narrowband detectors exhibit high sensitivity responses only to specific narrow bands, thus possessing excellent spectral resolution and background noise suppression characteristics. Leveraging this advantage, the demand for narrowband detectors in industrial and scientific research fields is increasing. Scenarios such as UV spectral analysis, photochemical reaction monitoring, and high-precision substance identification all require accurate resolution of characteristic emission lines from UV light sources, further highlighting the crucial value of narrowband devices.

[0003] The resonant cavity enhancement method is considered an ideal method for fabricating high wavelength-selective solar-blind ultraviolet detectors, with advantages such as good wavelength selectivity, tunable response center band, and high overall device performance. Currently, such ultraviolet detectors are mainly based on all-nitride material systems, such as the publicly reported pin-structured AlGaN-based ultraviolet detectors and MSM-structured ZnO ultraviolet detectors: (1) The pin-structured AlGaN-based ultraviolet detector is located in AlN / Al 0.3 Ga 0.7 Between the upper and lower mirrors of the DBR fabricated by N, based on the principle of thin film interference, the Fabry-Perot (FP) resonant cavity composed of mirrors has high wavelength selectivity. Placing the detector part in the resonant cavity constitutes a resonant cavity enhanced detector with narrowband detection capability. Due to the reflection of the upper and lower mirrors, the signal light will pass through the resonant cavity multiple times, so a very thin photosensitive layer can achieve high quantum efficiency. At the same time, the thin photosensitive layer can effectively reduce the transit time of photogenerated carriers and improve the response speed of the detector. (2) The MSM structure ZnO ultraviolet detector is located between the upper and lower mirrors of the DBR fabricated by HfO2 / SiO2, constituting a resonant cavity enhanced narrowband ultraviolet detector. In this scheme, the horizontal MSM structure device requires an external bias voltage to operate, which usually faces a serious continuous photoconductivity problem, resulting in a slow response speed.

[0004] In summary, both existing types of resonant cavity enhanced narrowband ultraviolet detectors have the following technical defects: (1) Epitaxial growth of the all-nitride system DBR requires extremely high substrate temperature. When fabricating the photosensitive layer and top DBR optical structure on the DBR, the high-temperature process will cause severe atomic interdiffusion at the interface of the bottom DBR multilayer film, which will damage the optical reflection performance of the DBR, resulting in spectral selectivity degradation and low yield of the finished product; (2) Traditional ZnO-based lateral MSM resonant cavity detectors rely on external bias voltage and have significant continuous photoconductivity effect, resulting in poor response speed, which cannot meet the requirements of high-speed ultraviolet detection scenarios. Therefore, it is urgent to develop an ultraviolet detector with high-speed self-driven response characteristics. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a narrowband ZnMgO-based ultraviolet detector with resonant cavity enhancement and its fabrication method.

[0006] The present invention aims to provide a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement, comprising a substrate, a buffer layer, a bottom light-reflecting layer, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, and a top light-reflecting layer that are tightly stacked from bottom to top. The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is any one of a vertical pin heterojunction, a vertical pn heterojunction, or a vertical Schottky heterojunction; the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer includes a ZnMgO layer, which is an arbitrary hexagonal ZnMgO film with a Mg composition of 0-60%, or an arbitrary cubic ZnMgO film with a Zn composition of 0-90%. The bottom light-reflecting layer is a nitride DBR layer, an oxide DBR layer, or a metal film layer; The top light-reflecting layer is an oxide DBR layer or a metal film layer; A stepped structure is set at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction to set the ohmic electrode.

[0007] Preferably, the ZnMgO layer is an n-ZnMgO layer, wherein the Mg component accounts for 20-40%; the ZnMgO layer is prepared by low-temperature molecular beam epitaxy at 200-500℃. The bottom light-reflecting layer and the top light-reflecting layer work together to form a Fabry-Perot resonant cavity; the bottom light-reflecting layer is a nitride DBR layer, consisting of 15 to 30 pairs of Al... 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 The film is formed by periodically stacking alternating N-layers, with a total thickness of 0.8~2μm; The thickness of the buffer layer is 200~400nm, and the material is AlN.

[0008] Preferably, the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pin heterojunction, consisting of an undoped n-ZnMgO layer, an intrinsic i-ZnMgO layer, and a p-NiO hole transport layer from bottom to top; the n-ZnMgO layer is an n-type ZnO layer. 0.7 Mg 0.3 O, with a thickness of 40~60nm; the intrinsic layer of i-ZnMgO is i-type Zn. 0.7 Mg 0.3 O, with a thickness of 40~60nm; p-NiO hole transport layer with a thickness of 20~40nm.

[0009] Preferably, a stepped structure is provided at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, the n-ZnMgO layer is exposed at the step, and an n-electrode is provided in the exposed area of ​​the n-ZnMgO layer; The top light-reflecting layer is an oxide DBR layer that covers the central region of the p-NiO hole transport layer, and a p electrode is disposed in the exposed area at the edge of the p-NiO hole transport layer.

[0010] Preferably, the oxide DBR layer has an HfO2 / SiO2 structure; The n-electrode and the p-electrode are Ti and Pt electrodes, respectively.

[0011] Preferably, the ZnMgO-based vertical heterojunction UV photosensitive layer is a vertical pn heterojunction, consisting of a p-AlGaN layer and an n-ZnMgO layer from bottom to top; the p-AlGaN layer is a p-type Al 0.3 Ga 0.7 N, with a thickness of 90~110nm; the n-ZnMgO layer is n-type Zn. 0.7 Mg 0.3 O, with a thickness of 80~120nm.

[0012] Preferably, a stepped structure is provided at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, the p-AlGaN layer is exposed at the step, and a p electrode is provided in the exposed area of ​​the p-AlGaN layer; The top light-reflecting layer is an Al metal film.

[0013] Preferably, it is prepared by the following method: S1. The substrate is pretreated by cleaning; a buffer layer is prepared on the substrate using magnetron sputtering. S2. Using a metal-organic chemical vapor deposition process, 15-30 pairs of Al atoms are alternately deposited on the buffer layer. 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 By alternating N layers, a bottom light-reflecting layer with a thickness of 0.8~2μm is obtained; S3. Epitaxial growth of a ZnMgO-based vertical heterostructure ultraviolet photosensitive layer containing a ZnMgO layer; wherein the ZnMgO layer is prepared by molecular beam epitaxy at 200~500℃; S4. A magnetron sputtering process is used to deposit the top light-reflecting layer and electrodes.

[0014] Preferably, when the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pin heterojunction, step S3 includes: epitaxially growing an n-ZnMgO layer and an i-ZnMgO intrinsic layer sequentially by MBE at 200~500℃; depositing a p-NiO hole transport layer on the surface of the i-ZnMgO intrinsic layer by magnetron sputtering to form a vertical pin heterojunction; and annealing at 200~500℃. Step S4 includes: alternating deposition of HfO2 and SiO2 thin films by magnetron sputtering to form an oxide DBR as the top light reflective layer, with the oxide DBR covering only the middle of the p-NiO layer and the edge of the p-NiO hole transport layer exposed; and using magnetron sputtering, n-electrodes and p-electrodes are prepared in the exposed edge regions of the n-ZnMgO layer and the p-NiO hole transport layer, respectively.

[0015] Preferably, when the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pn heterojunction, step S3 includes: epitaxially growing a p-AlGaN layer on the surface of the bottom light-reflecting layer using a metal-organic chemical vapor deposition process; growing an n-ZnMgO layer by molecular beam epitaxy at 200~500℃, wherein the n-ZnMgO layer covers the middle region of the p-AlGaN layer to form a vertical pn heterojunction; and annealing at 200~500℃. Step S4 includes: depositing an Al metal film on the surface of the n-ZnMgO layer as a top light-reflecting layer using magnetron sputtering; and fabricating a p electrode in the exposed area of ​​the p-AlGaN layer surface using magnetron sputtering.

[0016] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The present invention uses a vertical ZnMgO-based heterojunction as the ultraviolet photosensitive detection structure. The ZnMgO thin film can be prepared by epitaxy and annealing at a low temperature of 200~500℃, avoiding the interdiffusion of atoms at the interface of the underlying DBR multilayer film caused by high temperature process, and reducing the thermal damage to the underlying light reflection structure. At the same time, the vertical heterojunction can effectively suppress the continuous photoconductivity problem of traditional horizontal MSM devices and greatly improve the photoresponse speed of the device. (2) By adjusting the epitaxial thickness of the ZnMgO photosensitive layer, the cavity length of the resonant cavity can be changed, and the response peak position of the solar blind ultraviolet band of 240~300nm can be continuously adjusted. Combined with the Fabry-Perot resonant cavity formed by the upper and lower mirrors, the half width of the device spectrum is less than 10nm, which has excellent narrowband spectral resolution. (3) Pt, Al and other metal films can be used to replace nitride / oxide DBR for both bottom and top light reflective layers. The metal film preparation process is simple and does not require multiple alternating thin film deposition, which can simplify the overall film structure of the device, shorten the preparation process, and reduce the device production and processing cost. Among them, the Al metal film on the top layer of the pn type structure can simultaneously serve as the top reflector and the n-side ohmic electrode, eliminating the need to prepare the n electrode separately and further simplifying the process. (4) The step-by-step layered lead-out of the ohmic electrodes on both sides can be adapted to various vertical heterostructures such as pin, pn, and Schottky. The material system selection is flexible and the applicable scenarios are wider. The device has low crystal defect density, stable optical reflection performance, and excellent comprehensive detection performance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to Embodiment 1 of the present invention.

[0018] Figure 2 The results are the performance analysis results of the bottom and top light reflective layers of the narrow-band ZnMgO-based ultraviolet detector based on resonant cavity enhancement provided in Embodiment 1 of the present invention; (a) in the figure shows the cross-sectional SEM image of the bottom light reflective layer; (b) shows the ultraviolet reflection spectrum curves of the bottom and top light reflective layers; (c) and (d) are the X-ray rocking curves of the (002) crystal plane and (102) crystal plane of the bottom light reflective layer, respectively.

[0019] Figure 3 This is a schematic diagram of the structure of a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to Embodiment 2 of the present invention.

[0020] Figure 4 The results of the photoelectric performance test of the narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement provided in Embodiment 2 of the present invention are shown in the figure. (a) shows the normalized spectral response curve of the device under different resonant cavity lengths (180nm, 200nm, 220nm); (b) shows the characteristic curve of responsivity changing with applied reverse bias under 265nm illumination; and (c) shows the transient response test results.

[0021] Figure label: 1. Substrate; 2. Buffer layer; 3. Nitride DBR layer; 4.n-ZnMgO layer; 5. Intrinsic layer of i-ZnMgO; 6. p-NiO hole transport layer; 7. Oxide DBR layer; 8. n electrodes; 9. p electrode; 10. p-AlGaN layer; 11. Metallic film layer. Detailed Implementation

[0022] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0024] This invention provides a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement, comprising a substrate, a buffer layer, a bottom light-reflecting layer, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, and a top light-reflecting layer stacked tightly from bottom to top; The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer can be any one of a vertical pin heterojunction, a vertical pn heterojunction, or a vertical Schottky heterojunction. Specifically, a double-polished sapphire substrate is selected as the substrate; The buffer layer is used to alleviate lattice mismatch between the substrate and the bottom light-reflecting layer, suppress dislocations, and improve crystal quality. Its thickness is 200~400nm; in some embodiments, the thickness is 300nm and the material is AlN. The bottom light-reflecting layer is a nitride DBR layer, an oxide DBR layer, or a metal film layer (e.g., Pt, Al, etc.), with a thickness of 0.8~2μm, preferably 1.7μm; wherein, the nitride DBR layer consists of 15~30 pairs of Al 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 The film is formed by periodically stacking alternating N-layer films, which serves as a reflector under the Fabry-Perot resonant cavity to achieve high reflectivity in the solar-blind ultraviolet band of 240~290nm. The top light-reflecting layer is an oxide DBR layer or a metal film layer; the oxide DBR layer has an HfO2 / SiO2 structure; the metal film layer is an Al metal film.

[0025] In some embodiments, the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pin heterojunction, consisting of an undoped n-ZnMgO layer, an intrinsic i-ZnMgO layer, and a p-NiO hole transport layer from bottom to top; the n-ZnMgO layer is an arbitrary hexagonal ZnMgO film with a Mg content of 0-60%, or an arbitrary cubic ZnMgO film with a Zn content of 0-90%; preferably, the Mg content in the n-ZnMgO layer is 20-40%; Preferably, the n-ZnMgO layer is n-type Zn. 0.7 Mg 0.3 O, with a thickness of 40~60nm; the intrinsic layer of i-ZnMgO is i-type Zn. 0.7 Mg 0.3 O, with a thickness of 40~60nm; the thickness of the p-NiO hole transport layer is 20~40nm; more preferably, the thicknesses of the n-ZnMgO layer, the i-ZnMgO intrinsic layer and the p-NiO hole transport layer are 50nm, 50nm and 30nm, respectively. A stepped structure is provided at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, exposing the n-ZnMgO layer at the step. An n-electrode is provided in the exposed area of ​​the n-ZnMgO layer. The top light-reflecting layer covers the middle region of the p-NiO hole transport layer, and a p-electrode is provided in the exposed area at the edge of the p-NiO hole transport layer. Preferably, the n-electrode and the p-electrode are Ti electrodes and Pt electrodes, respectively.

[0026] In some embodiments, the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pn heterojunction, consisting of a p-AlGaN layer and an n-ZnMgO layer from bottom to top; the AlGaN layer contains 60-80% Ga and 20-40% Al; the n-ZnMgO layer is an arbitrary hexagonal ZnMgO film with 0-60% Mg content, or an arbitrary cubic ZnMgO film with 0-90% Zn content; preferably, the Mg content in the n-ZnMgO layer is 20-40%. Preferably, the p-AlGaN layer is a p-type Al 0.3 Ga 0.7 N, with a thickness of 90~110nm; the n-ZnMgO layer is n-type Zn. 0.7 Mg 0.3 O, with a thickness of 80~120nm; more preferably, the p-AlGaN layer thickness is 100nm; A stepped structure is provided at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, and a p-AlGaN layer is exposed at the step. A p-electrode is provided in the exposed area of ​​the p-AlGaN layer; preferably, the p-electrode is a Pt electrode. The top light-reflecting layer is an Al metal film, which also serves as the top reflector of the resonant cavity and the n-electrode, eliminating the need for additional independent n-electrode fabrication.

[0027] In some embodiments, the ZnMgO-based vertical heterojunction UV photosensitive layer is a vertical Schottky heterojunction, consisting of an Al metal layer, an n-ZnMgO layer, and a Pt metal layer from bottom to top; the Mg content in the n-ZnMgO layer is 20-40%; preferably, the n-ZnMgO layer is n-type Zn 0.7 Mg 0.3 O.

[0028] The fabrication method of the above-mentioned narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement specifically includes the following steps: S1. The substrate is pretreated by cleaning; an AlN buffer layer is prepared on the substrate using magnetron sputtering. S2. Using a metal-organic chemical vapor deposition (MOCVD) process, 15-30 pairs of Al2O3 layers were alternately deposited on the AlN buffer layer. 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 By alternating N layers, a bottom light-reflecting layer with a thickness of 0.8~2μm is obtained, forming a Fabry-Perot resonant cavity lower reflector with a wavelength of 240~290nm; S3. Epitaxial growth of a ZnMgO-based vertical heterostructure ultraviolet photosensitive layer containing an n-ZnMgO layer; wherein the n-ZnMgO layer is prepared by molecular beam epitaxy (MBE) at 200~500℃; S4. A magnetron sputtering process is used to deposit the top light-reflecting layer and electrodes.

[0029] Specifically, when the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction is a vertical pin heterojunction, step S3 includes: epitaxially growing an n-ZnMgO layer and an i-ZnMgO intrinsic layer sequentially by MBE at 200~500℃; depositing a p-NiO hole transport layer on the surface of the i-ZnMgO intrinsic layer by magnetron sputtering to form a vertical pin heterojunction; and annealing at 200~500℃ to optimize the crystal quality of the ZnMgO thin film. Step S4 includes: S41. HfO2 and SiO2 thin films are alternately deposited by magnetron sputtering to form an oxide DBR as the top light reflective layer. The oxide DBR only covers the middle of the p-NiO layer, and the edges of the p-NiO hole transport layer are exposed. S42. Magnetron sputtering is used to prepare n-electrodes and p-electrodes.

[0030] When the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction is a vertical pn heterojunction, step S3 includes: epitaxially growing a p-AlGaN layer on the surface of the bottom light-reflecting layer using MOCVD; epitaxially growing an n-ZnMgO layer by MBE at 200~500℃, wherein the n-ZnMgO layer covers the middle region of the p-AlGaN layer to form a vertical pn heterojunction; and annealing at 200~500℃ to optimize the crystal quality of the ZnMgO thin film. Step S4 includes: depositing an Al metal film on the surface of the n-ZnMgO layer as a top light-reflecting layer using magnetron sputtering; and fabricating a p electrode in the exposed area of ​​the p-AlGaN layer surface using magnetron sputtering.

[0031] Example 1: like Figure 1 As shown, this embodiment provides a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement, including a substrate 1, a buffer layer 2, a bottom light-reflecting layer 3, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, and a top light-reflecting layer 7, which are stacked tightly from bottom to top. Substrate 1: Double-polished sapphire substrate; The thickness of buffer layer 2 is approximately 300 nm, and the material is AlN; The bottom light-reflecting layer 3 is a nitride DBR layer, consisting of 30 pairs of Al 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 The film is composed of alternating N layers stacked periodically, with a thickness of approximately 1.7 μm. The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, from bottom to top, includes an n-ZnMgO layer 4, an i-ZnMgO intrinsic layer 5, and a p-NiO hole transport layer 6; the n-ZnMgO layer 4 is an n-type ZnO layer. 0.7 Mg 0.3 O, with a thickness of approximately 50 nm; the intrinsic layer 5 of i-ZnMgO is i-type Zn 0.7 Mg 0.3 O, with a thickness of approximately 50 nm; p-NiO hole transport layer 6 has a thickness of approximately 30 nm; A stepped structure is set at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, and the n-ZnMgO layer 4 is exposed at the step. An n electrode 8 is set in the exposed area of ​​the n-ZnMgO layer 4. The top light-reflecting layer covers the middle area of ​​the p-NiO hole transport layer 6, and a p electrode 9 is set in the exposed area at the edge of the p-NiO hole transport layer 6. The top light-reflecting layer 7 has an HfO2 / SiO2 structure.

[0032] Preparation methods include: S1. The substrate is pre-treated by cleaning; a buffer layer with a thickness of approximately 300 nm is prepared on the substrate using magnetron sputtering. S2. Using a metal-organic chemical vapor deposition (MOCVD) process, 30 pairs of Al atoms were alternately deposited on the buffer layer. 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 Alternating N layers were used to obtain a bottom light-reflecting layer with a thickness of approximately 1.7 μm, forming a Fabry-Perot resonant cavity lower mirror; the bottom light-reflecting layer was a nitride DBR layer. S3. An n-ZnMgO layer and an i-ZnMgO intrinsic layer were sequentially epitaxially grown using MBE at 200–500 °C. A p-NiO hole transport layer was deposited globally on the surface of the i-ZnMgO intrinsic layer using magnetron sputtering to form a p-NiO heterojunction. Annealing was performed at 200–500 °C to optimize the crystal quality of the ZnMgO thin film. The n-ZnMgO layer was an n-type ZnO layer. 0.7 Mg 0.3 The intrinsic layer of O,i-ZnMgO is type i Zn. 0.7 Mg 0.3 The thicknesses of the O;n-ZnMgO layer, the i-ZnMgO intrinsic layer, and the p-NiO hole transport layer are approximately 50 nm, 50 nm, and 30 nm, respectively. S4. HfO2 and SiO2 thin films were alternately deposited by magnetron sputtering to form an oxide DBR as the top light-reflecting layer. The oxide DBR only covered the middle of the p-NiO layer, and the edges of the p-NiO hole transport layer were exposed. Ti electrodes and Pt electrodes were prepared by magnetron sputtering as n electrodes and p electrodes, respectively.

[0033] The performance of the bottom and top light-reflecting layers of the fabricated cavity-enhanced narrowband ZnMgO-based ultraviolet detector was analyzed, and the results are as follows: Figure 2 As shown. Among them Figure 2 In the middle (a), the cross-sectional SEM image of the bottom light-reflecting layer shows that the prepared multilayer alternating film interface is clear and steep, the thickness of each single film is uniform, the surface is flat, and there is no obvious interlayer interdiffusion phenomenon. Figure 2(b) shows the ultraviolet reflectance spectra of the bottom and top light reflective layers under different number of periods, where bottom DBR-1 and bottom DBR-2 represent bottom light reflective layers with 30 and 15 periods, respectively (the bottom light reflective layer with 15 periods is used as a control). The results show that the high reflectance bands of the bottom nitride DBR and the top oxide DBR can be tuned in the solar-blind ultraviolet range of 250-290 nm. The reflectance of the bottom nitride DBR can be tuned in the range of 50-90%, and the reflectance of the top oxide DBR can be tuned in the range of 90-99%. The two are matched to form a Fabry-Perot resonator, which can realize the narrowband light resonance enhancement of the target band. Figure 2 (c) and (d) are X-ray rocking curves of the (002) and (102) crystal planes of the nitride DBR structure, respectively. The half-width at half maximum (WHM) of the rocking curve for the (002) crystal plane is 0.054°, and that for the (102) crystal plane is 0.138°. Based on the WHM, the screw dislocation density of this nitride DBR film is calculated to be approximately 7.1 × 10⁻⁶. 7 cm -2 The edge dislocation density is approximately 2.9 × 10⁻⁶. 9 cm -2 This indicates that the DBR thin film has excellent crystal quality and low defect density, which is beneficial for obtaining stable ultraviolet high reflectance characteristics.

[0034] Example 2: like Figure 3 As shown, this embodiment provides a narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement, including a substrate 1, a buffer layer 2, a bottom light-reflecting layer 3, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, and a top light-reflecting layer 7, which are stacked tightly from bottom to top. Substrate 1 is a double-polished sapphire substrate; The thickness of buffer layer 2 is approximately 300 nm, and the material is AlN; The bottom light-reflecting layer 3 is a nitride DBR layer, consisting of 30 pairs of Al 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 The film is composed of alternating N layers stacked periodically, with a thickness of approximately 1.7 μm. The ZnMgO-based vertical heterojunction UV photosensitive layer, from bottom to top, includes a p-AlGaN layer 10 and an n-ZnMgO layer 4; the p-AlGaN layer 10 is a p-type Al 0.3 Ga 0.7 N, the layer thickness is approximately 100 nm; n-ZnMgO layer 4 is n-type Zn. 0.7 Mg 0.3 O, with a thickness of 80~120nm; A stepped structure is set at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction, and a p-AlGaN layer 10 is exposed at the step. A p electrode 9 is set in the exposed area of ​​the p-AlGaN layer 10. The top light-reflecting layer is a metal film layer 11, which completely covers the upper surface of the n-ZnMgO layer 4. It also serves as the dual function of the top reflector of the resonant cavity and the n-side ohmic electrode, without the need to fabricate an additional independent n electrode. The material of the metal film layer 11 is Al.

[0035] Preparation methods include: S1. The substrate is pre-cleaned; a buffer layer with a thickness of approximately 300 nm is prepared on the substrate using magnetron sputtering. S2. Using a metal-organic chemical vapor deposition (MOCVD) process, 30 pairs of Al atoms were alternately deposited on the buffer layer. 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 Alternating N-layers were used to obtain a bottom light-reflecting layer with a thickness of approximately 1.7 μm, forming a Fabry-Perot resonant cavity lower mirror; the bottom light-reflecting layer was a nitride DBR layer; S3. A p-AlGaN layer is epitaxially grown on the surface of the bottom light-reflecting layer using MOCVD; an n-ZnMgO layer is epitaxially grown using MBE at 200~500℃, with the n-ZnMgO layer completely covering the middle region of the p-AlGaN layer to form a pn heterojunction; annealing is performed at 200~500℃ to optimize the crystal quality of the ZnMgO thin film; the cavity length of the resonant cavity can be changed by adjusting the thickness of the n-ZnMgO thin film, thus achieving tunable UV response peak position of the device; S4. Using magnetron sputtering, a Pt electrode is deposited in the exposed area of ​​the p-AlGaN layer as the p electrode; an Al metal film is deposited as the top light-reflecting layer, and the Al metal film directly forms an ohmic contact with the n-ZnMgO layer, simultaneously serving as the n electrode.

[0036] The photoelectric performance of the cavity-enhanced narrowband ZnMgO-based pn-type ultraviolet detector (cavity length 200 nm) fabricated in this embodiment was tested. To verify the modulation law of cavity length on detection wavelength, additional devices with total cavity lengths of 180 nm and 220 nm were fabricated as control samples. The performance analysis results of all devices are as follows: Figure 4 As shown. Figure 4 In Figure (a), the normalized spectral response curves of the devices under different resonant cavity lengths are shown. It can be seen that by adjusting the thickness of the n-ZnMgO layer to change the resonant cavity length, the peak response can be tunable in the solar-blind ultraviolet range of 240~300nm. The half-width of the spectral response of each group of devices is less than 10nm, which reflects excellent narrowband detection characteristics. Figure 4Figure (b) shows the characteristic curve of the responsivity of the device in this embodiment under 265nm illumination as a function of the applied reverse bias voltage. When the reverse bias voltage exceeds 2V, the device exhibits a significant photoelectric gain effect. When the reverse bias voltage is 5V, the responsivity exceeds 1A / W, and the responsivity can reach 30A / W under 10V reverse bias. Figure 4 (c) shows the transient response test results of the device in this embodiment. The test results show that the device has a fast optical response speed.

[0037] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0038] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement, characterized in that: It includes a substrate, a buffer layer, a bottom light-reflecting layer, a ZnMgO-based vertical heterojunction ultraviolet photosensitive layer, and a top light-reflecting layer, which are tightly stacked from bottom to top. The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is any one of a vertical pin heterojunction, a vertical pn heterojunction, or a vertical Schottky heterojunction; the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer includes a ZnMgO layer, which is an arbitrary hexagonal ZnMgO film with a Mg composition of 0-60%, or an arbitrary cubic ZnMgO film with a Zn composition of 0-90%. The bottom light-reflecting layer is a nitride DBR layer, an oxide DBR layer, or a metal film layer; The top light-reflecting layer is an oxide DBR layer or a metal film layer; A stepped structure is set at the edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction to set the ohmic electrode.

2. The narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 1, characterized in that: The ZnMgO layer is an n-ZnMgO layer, wherein the Mg component accounts for 20-40%; the ZnMgO layer is prepared by low-temperature molecular beam epitaxy at 200-500℃; The bottom light-reflecting layer and the top light-reflecting layer work together to form a Fabry-Perot resonant cavity; the bottom light-reflecting layer is a nitride DBR layer, consisting of 15 to 30 pairs of Al... 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 The film is formed by periodically stacking alternating N-layers, with a total thickness of 0.8~2μm; The thickness of the buffer layer is 200~400nm, and the material is AlN.

3. The narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 2, characterized in that: The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pin heterojunction, consisting of an undoped n-ZnMgO layer, an intrinsic i-ZnMgO layer, and a p-NiO hole transport layer from bottom to top; the n-ZnMgO layer is an n-type ZnO layer. 0.7 Mg 0.3 O, with a thickness of 40~60nm; the intrinsic layer of i-ZnMgO is i-type Zn. 0.7 Mg 0.3 O, with a thickness of 40~60nm; p-NiO hole transport layer with a thickness of 20~40nm.

4. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 3, characterized in that: The edge of the ultraviolet photosensitive layer of the ZnMgO-based vertical heterojunction is provided with a stepped structure, the n-ZnMgO layer is exposed at the step, and an n-electrode is provided in the exposed area of ​​the n-ZnMgO layer. The top light-reflecting layer is an oxide DBR layer that covers the central region of the p-NiO hole transport layer, and a p electrode is disposed in the exposed area at the edge of the p-NiO hole transport layer.

5. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 4, characterized in that: The oxide DBR layer has an HfO2 / SiO2 structure; The n-electrode and the p-electrode are Ti and Pt electrodes, respectively.

6. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 2, characterized in that: The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pn heterojunction, consisting of a p-AlGaN layer and an n-ZnMgO layer from bottom to top; the p-AlGaN layer is a p-type Al 0.3 Ga 0.7 N, with a thickness of 90~110nm; the n-ZnMgO layer is n-type Zn. 0.7 Mg 0.3 O, with a thickness of 80~120nm.

7. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 6, characterized in that: The ZnMgO-based vertical heterojunction ultraviolet photosensitive layer has a stepped structure at its edge, and the p-AlGaN layer is exposed at the step. A p electrode is set in the exposed area of ​​the p-AlGaN layer. The top light-reflecting layer is an Al metal film.

8. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 1, characterized in that: Prepared by the following method: S1. The substrate is pretreated by cleaning; a buffer layer is prepared on the substrate using magnetron sputtering. S2. Using a metal-organic chemical vapor deposition process, 15-30 pairs of Al atoms are alternately deposited on the buffer layer. 0.75 Ga 0.25 N / Al 0.5 Ga 0.5 By alternating N layers, a bottom light-reflecting layer with a thickness of 0.8~2μm is obtained; S3. Epitaxial growth of a ZnMgO-based vertical heterostructure ultraviolet photosensitive layer containing a ZnMgO layer; wherein the ZnMgO layer is prepared by molecular beam epitaxy at 200~500℃; S4. A magnetron sputtering process is used to deposit the top light-reflecting layer and electrodes.

9. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 8, characterized in that: When the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pin heterojunction, step S3 includes: epitaxially growing an n-ZnMgO layer and an i-ZnMgO intrinsic layer sequentially by MBE at 200~500℃; depositing a p-NiO hole transport layer on the surface of the i-ZnMgO intrinsic layer by magnetron sputtering to form a vertical pin heterojunction; and annealing at 200~500℃. Step S4 includes: alternating deposition of HfO2 and SiO2 thin films by magnetron sputtering to form an oxide DBR as the top light reflective layer, with the oxide DBR covering only the middle of the p-NiO layer and the edge of the p-NiO hole transport layer exposed; and using magnetron sputtering, n-electrodes and p-electrodes are prepared in the exposed edge regions of the n-ZnMgO layer and the p-NiO hole transport layer, respectively.

10. A narrowband ZnMgO-based ultraviolet detector based on resonant cavity enhancement according to claim 8, characterized in that: When the ZnMgO-based vertical heterojunction ultraviolet photosensitive layer is a vertical pn heterojunction, step S3 includes: epitaxially growing a p-AlGaN layer on the surface of the bottom light-reflecting layer using a metal-organic chemical vapor deposition process; growing an n-ZnMgO layer by molecular beam epitaxy at 200~500℃, wherein the n-ZnMgO layer covers the middle region of the p-AlGaN layer to form a vertical pn heterojunction; and annealing at 200~500℃. Step S4 includes: depositing an Al metal film on the surface of the n-ZnMgO layer as a top light-reflecting layer using magnetron sputtering; and fabricating a p electrode in the exposed area of ​​the p-AlGaN layer surface using magnetron sputtering.

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