An integrated semiconductor photodetector and a method of fabricating the same

Abstract

An integrated semiconductor photodetector and its fabrication method are disclosed, relating to the field of integrated photodetector technology. This invention addresses the problems of existing detectors, such as limited functionality, insufficient responsivity, low integration, and difficulty in achieving synergistic miniaturization and high performance improvement. The method involves depositing a Cr conductive layer on the front side of a superlens substrate, uniformly coating the conductive layer surface with photoresist, pre-baking to prepare a dot-matrix mask pattern, developing and fixing followed by Ni deposition, and then stripping to obtain the Ni dot-matrix mask. ICP etching is used to remove the surface conductive layer, and a nanopillar array superlens structure is then fabricated. A photodetector layer is transferred to the back side of the substrate. Positive photoresist is spin-coated onto the substrate surface, pre-baking to prepare a source / drain electrode pattern, developing and fixing followed by sequential deposition of an adhesion layer metal and an electrode body metal layer. The metal layer in the non-electrode region is then stripped to obtain the metal electrode in contact with the photodetector layer, completing the detector fabrication. This invention can be applied to polarization imaging, space remote sensing, airborne detection, and optical communication.

Description

Technical Field

[0001] This invention relates to the field of integrated photodetector technology, and more specifically to an integrated semiconductor photodetector and its fabrication method. Background Technology

[0002] III-V compound semiconductor materials possess excellent properties such as high carrier mobility, high photoelectric absorption coefficient, and tunable direct bandgap, giving them significant advantages in the fabrication of high-speed, low-power, and high-sensitivity optoelectronic devices. They have been widely applied in key technology areas such as photoelectric detection, nanolasers, solar cells, and quantum communication. Among these, the photodetector, as the core device for photoelectric conversion, directly determines the performance ceiling of the entire optoelectronic system through its responsivity, response speed, integration density, and functional diversity.

[0003] Polarization is an inherent physical property of light. During transmission, reflection, scattering, and interaction with matter, the polarization state of light undergoes regular changes. These changes directly reflect key information such as the material properties, surface morphology, structural features, and spatial orientation of a target object, making polarization detection technology irreplaceable in fields such as remote sensing imaging, target recognition, environmental monitoring, biological detection, and quantum information processing. In recent years, with the rapid development of integrated optics and micro / nano fabrication technologies, there has been an urgent demand for miniaturization, monolithic design, low power consumption, and high integration in polarization detection systems.

[0004] Traditional polarization detection schemes typically employ a cascaded architecture of bulk optical elements, composed of multiple discrete components such as bulk polarizers, waveplates, lenses, and birefringent crystals. This approach suffers from problems such as large size, complex structure, high assembly precision requirements, high losses, and limited controllability, making it difficult to adapt to the highly integrated development trend of modern optoelectronic systems. Meanwhile, traditional III-V semiconductor photodetectors, limited by material structure and device architecture, generally suffer from insufficient light absorption efficiency, low responsivity, and single functionality, making it difficult to simultaneously achieve high-sensitivity photoelectric conversion and high-precision polarization detection. This fails to meet the demands of high-end applications for multifunctional, high-performance, and miniaturized integrated devices.

[0005] Therefore, developing a novel semiconductor photodetector that highly integrates superlens focusing, polarization modulation, and photoelectric detection functions, and possesses high responsivity, fast response, and polarization sensitivity at the micro-nano scale, has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This invention proposes an integrated semiconductor photodetector and its fabrication method. In order to solve the problems of existing traditional photodetectors, such as single function, insufficient responsivity, complex structure of polarization detection system, low integration, and difficulty in achieving miniaturization and high performance synergistic improvement, this invention proposes an integrated semiconductor photodetector and its fabrication method.

[0007] The specific technical solution of the present invention is as follows: This invention first provides a method for fabricating an integrated semiconductor photodetector, comprising the following steps: S1. Construct a 0~2π phase library for circular nanopillars through FDTD simulation, deduce the nanopillar array arrangement based on the target focal length, and complete the metasurface cylindrical lens design. S2. After cleaning and drying the superlens substrate, a Cr layer is deposited on the front side as a conductive layer. S3. A positive photoresist is uniformly coated on the surface of the conductive layer using a spin coating process. After pre-baking, an electron beam exposure system is used to prepare a dot matrix mask pattern. After development and fixing, Ni is evaporated and then stripped with acetone to obtain a dot matrix Ni mask. S4. First, the surface conductive layer is removed by ICP etching, and then the nanopillar array superlens structure is prepared by ICP etching. S5. Mechanically transfer linear or thin-film semiconductor material or heterojunction structure to the back side of the superlens substrate corresponding to the array center position of the superlens as a photoelectric detection layer. S6. A positive photoresist is spin-coated on the substrate surface. After pre-baking, the source and drain electrode pattern is prepared by exposure using a direct-write lithography machine. After development and fixing, the adhesion layer metal and the electrode body layer metal are deposited sequentially by electron beam evaporation. After peeling off the metal layer in the non-electrode area, the metal electrode in contact with the photodetector layer is obtained, thus completing the fabrication of the integrated semiconductor photodetector.

[0008] Preferably, the superlens substrate is made of materials such as sapphire or diamond, and has a thickness of 300μm to 2mm.

[0009] Preferably, the photodetector layer is a group III-V material, such as GaAs, GaAs, GaAs / InGaAs, GaN, perovskite / GaAs, Ga2O3, MoS and other semiconductor materials, with a linear or thin film structure; it can also be selected from heterojunction structures, such as GaAs / GaN heterojunction, InGaAs / InAlAs / GaAs heterojunction, etc.

[0010] Preferably, the cleaning and drying process in step S2 is as follows: ultrasonic cleaning with acetone solution and anhydrous ethanol for 5 minutes each, followed by rinsing with deionized water and drying with nitrogen gas. The thickness of the superlens substrate is 300μm~2mm.

[0011] Preferably, the conductive layer in step S2 is prepared by electron beam thermal evaporation with an evaporation rate of 0.1 nm / s and a deposition thickness of 10 nm; the Ni mask is prepared by electron beam thermal evaporation with an evaporation rate of 0.2 nm / s and a deposition thickness of 50 nm.

[0012] Preferably, the positive photoresist in step S3 is PMMA950K-A4, which forms a photoresist film with a thickness of 240 nm after spin coating; the pre-baking temperature is 150°C and the time is 300 s.

[0013] Preferably, the overall size of the mask pattern of the dot matrix structure in step S3 is 200nm×200nm, and it is composed of 160,000 units with a size of 65nm~430nm; the development and fixing are completed by immersion in pr56 developer for 150s and immersion in isopropanol solution for 30s.

[0014] Preferably, the process parameters for ICP etching to remove the surface conductive layer in step S4 are: Power=300W, RF=50W, O2 flow rate=6sccm, Cl2 flow rate=24sccm, pressure=0.3Pa, and etching time=10s; The process parameters for preparing the nanopillar structure by ICP etching are: Power=700W, RF=100W, O2 flow rate=30sccm, pressure=0.65Pa, and etching time=100s.

[0015] Preferably, the photoresist in step S6 is positive photoresist AZ5214, which forms a photoresist film with a thickness of 1μm after spin coating; the pre-baking temperature is 100℃ and the time is 180s; the development is completed by immersing in ZX238 developer for 20s and rinsing with deionized water.

[0016] Preferably, the specific parameters of the electron beam evaporation process in step S6 are as follows: first, a 10 nm thick adhesion layer metal is deposited at a rate of 0.2 nm / s, and then a 900 nm thick electrode body layer metal is deposited at a rate of 0.1 nm / s; the channel length of the source / drain structure electrode is 2 μm, and the size of a single electrode is 2 μm to 500 μm.

[0017] Preferably, the metal electrode is made of one of Au / Cr, Au / Ti, Ag / Cr, and Cu / Cr, and the spacing between the electrodes is 2μm-3μm.

[0018] Preferably, the nanopillar units in the nanopillar array superlens structure are isotropic or anisotropic nanopillar units.

[0019] The present invention also provides an integrated semiconductor photodetector, which is prepared by the above-described method; Specifically, the integrated semiconductor photodetector includes a superlens substrate, a nanopillar array superlens structure, a photodetector layer, and a metal electrode; the nanopillar array superlens structure is formed on the front side of the superlens substrate, the photodetector layer is disposed on the back side of the superlens substrate and corresponds to the focusing spot position of the nanopillar array superlens structure, and the metal electrode forms an ohmic contact with the photodetector layer.

[0020] Compared with existing technologies, this invention integrates a nanopillar array superlens and a photodetector unit monolithically on the same substrate, significantly improving the photoelectric conversion efficiency and response performance of the device without increasing the device size or changing the micro / nano-scale structure, and simultaneously achieving high-precision polarization detection. Specific beneficial effects are as follows: This invention integrates a nanopillar array superlens structure at the front end of the photodetector unit. By utilizing the precise focusing and control of incident light by the superlens, the optical power density and effective absorption efficiency on the surface of the photodetector material are significantly improved. This enables the photodetector to generate a stronger photocurrent signal under the same incident light conditions, significantly improving the device's responsivity and response speed. The overall photoelectric conversion performance is significantly better than that of similar photodetectors without integrated structures.

[0021] This invention supports the design of anisotropic polarization-sensitive superlens structures, enabling superlenses to produce differentiated focused spot intensities and distributions for incident light with different polarization states. Combined with photoelectric detection materials such as GaAs-based nanowires, polarization state identification can be achieved without the need for additional discrete optical components such as polarizers and waveplates. This allows the device to simultaneously possess the triple functions of light focusing, photoelectric conversion, and polarization detection, enabling high-precision detection of the polarization characteristics of incident light in multiple wavelength bands and expanding the application scenarios of the device.

[0022] Employing highly stable substrates such as diamond, and combining a monolithic process for fabricating a front-side superlens and integrating a back-side photoelectric detection unit, the device boasts a compact structure, small size, high stability, and excellent process compatibility. It can be directly integrated with PCB boards, readout circuits, and other modular systems, perfectly meeting the development requirements of modern optoelectronic systems for miniaturization, integration, multifunctionality, and low power consumption. It has outstanding practical value and broad industrialization prospects in fields such as polarization imaging, space remote sensing, airborne detection, and optical communication. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the fabrication process of the superlens portion of the integrated semiconductor photodetector described in Example 1; Figure 2 This is a schematic diagram of the fabrication process of the sensitive device of the integrated semiconductor photodetector described in Example 1; Figure 3This is a schematic diagram illustrating the overall integration and application of the integrated semiconductor photodetector described in Example 1; Figure 4 This is a schematic diagram of the fabrication process of the superlens portion of the integrated semiconductor photodetector described in Example 2; Figure 5 This is a schematic diagram of the fabrication process of the sensitive device of the integrated semiconductor photodetector described in Example 2; Figure 6 This is a schematic diagram illustrating the overall integration and application of the integrated semiconductor photodetector described in Example 2; Figure 7 This is a schematic diagram of the fabrication process of the superlens portion of the integrated semiconductor photodetector described in Example 3; Figure 8 This is a schematic diagram of the fabrication process of the sensitive device of the integrated semiconductor photodetector described in Example 3; Figure 9 This is a schematic diagram of the overall integration and application of the integrated semiconductor photodetector described in Example 3.

[0024] Explanation of reference numerals in the attached figures: 1-Superlens substrate, 2-Photodetector layer, 3-Metal electrode, 4-Nanopillar array superlens structure, 5-Conductive layer, 6-Ni mask. Detailed Implementation

[0025] To make the technical solutions of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following embodiments are only used to better understand the technical solutions of the present invention and should not be construed as limiting the present invention.

[0026] Example 1. This embodiment provides a high-response integrated semiconductor photodetector. The core technology utilizes the focusing control of a diamond superlens and the efficient conversion of GaAs photodetector material to simultaneously improve both the device's responsivity and response speed. The specific fabrication process is as follows: A unit phase library covering 0–2π was constructed using geometric parameters such as the height and radius of the column elements. FDTD was used to simulate the relationship between phase, amplitude, and nanopillar radius. Eight circular nanopillars with high transmittance and different radii were selected as discrete units within the 0–2π phase range to deduce the arrangement of nanopillars in the entire metasurface array, completing the design of a metasurface cylindrical lens with a focal length of 600 μm. A 600 μm thick diamond substrate was selected as the metalens 1. The diamond substrate 1 was ultrasonically cleaned for 5 min each with acetone and anhydrous ethanol, and finally rinsed with deionized water and dried with nitrogen to remove impurities and organic matter from the substrate surface, providing a clean substrate interface for subsequent thin film deposition and patterning.

[0027] Subsequently, the Cr target was heated by electron beam thermal evaporation, and a 10 nm thick Cr layer was deposited on the front side of the substrate as a conductive layer 5 at an evaporation rate of 0.1 nm / s. Cr has both excellent conductivity and substrate adhesion, which can effectively avoid the charge accumulation effect in the subsequent electron beam exposure process and ensure the accuracy and uniformity of the exposure pattern.

[0028] A spin coating process was used to uniformly coat the positive photoresist PMMA950K-A4 onto the surface of the conductive layer 5. By controlling the coating speed r1=600rpm, t1=6s, r2=4000rpm, t2=40s, a uniform photoresist film with a thickness of 240nm was formed. After coating, the film was pre-baked at 150℃ for 300s to fully remove the solvent from the photoresist, enhance the adhesion and mechanical stability of the photoresist layer to the substrate, and avoid problems such as photoresist layer peeling and pattern deformation during subsequent exposure and development. Using an electron beam exposure system, a mask pattern is drawn on the photoresist based on a pre-designed lattice structure pattern in the drawing software. The overall size of the mask pattern is 200nm×200nm, consisting of 160,000 isotropic nanopillar units with sizes ranging from 65nm to 430nm. By gradient control of the nanopillar size, full phase coverage of the incident light from 0 to 2π is achieved, providing a structural basis for the focusing function of the subsequent superlens. After exposure, the substrate is immersed in developer pr56 for 150s to fully dissolve the photoresist in the exposed areas while leaving the photoresist intact in the unexposed areas. After development, the substrate is immersed in isopropanol solution for 30s to remove residual developer, thus completing the preparation of the high-precision mask pattern.

[0029] Ni target material was heated by electron beam thermal evaporation, and a 50 nm thick Ni was deposited as mask 6 at an evaporation rate of 0.2 nm / s. Ni has excellent etching selectivity and structural stability, which can fully protect the substrate of the patterned area during subsequent ICP etching, ensuring the etching depth and morphological accuracy of the nanopillar structure. The substrate with Ni deposition was immersed in acetone for 10 h, so that the Ni layer covering the photoresist pattern window was removed synchronously with the dissolution of the photoresist, leaving only the lattice Ni mask layer corresponding to the mask pattern.

[0030] The superlens structure was fabricated using an ICP dry etching process. The first step involved removing the exposed Cr conductive layer 5. Process parameters were set as follows: Power = 300W, RF = 50W, O2 flow rate = 6 sccm, Cl2 flow rate = 24 sccm, pressure = 0.3 Pa, and etching time = 10 s. These conditions allowed for rapid and precise removal of the Cr layer with minimal damage to the Ni mask, avoiding any impact on subsequent diamond etching. The second step involved diamond nanopillar etching. Process parameters were set as follows: Power = 700W, RF = 100W, O2 flow rate = 30 sccm, pressure = 0.65 Pa, and etching time = 100 s. High-density oxygen plasma was used to break the C / C bonds in the diamond, achieving chemical etching. Simultaneously, the bias power was used to control the vertical bombardment energy of ions, forming a 600 nm high, steeply shaped nanopillar array superlens structure 4. This completed the entire fabrication process of the superlens. Figure 1 As shown.

[0031] The back side of the diamond superlens substrate 1 was ultrasonically cleaned for 5 minutes with acetone solution, ultrasonically cleaned for 5 minutes with anhydrous ethanol, rinsed with deionized water and dried with nitrogen to complete the back side cleaning process. Using a mechanical transfer platform, GaAs nanowires were transferred as photoelectric detection material 2 to the back side of the cleaned diamond superlens and the center position of the superlens array. This position corresponds precisely to the focusing focal plane of the superlens, which allows the light spot focused by the superlens to directly act on the GaAs nanowires, maximizing the light power density at the nanowires.

[0032] A spin coating process was used to uniformly coat the back of the substrate with positive photoresist AZ5214. By controlling the coating speeds r1=600rpm, t1=6s, r2=5000rpm, and t2=40s, a uniform photoresist film with a thickness of 1μm was formed. After coating, the substrate was pre-baked at 100℃ for 180s to remove the solvent and enhance adhesion. Using a direct-write lithography machine, the laser beam scanning path was directly controlled by a computer to draw source and drain electrode patterns on the photoresist. The channel length of the electrode pattern was 2μm, and the size of each electrode was 500μm×500μm, precisely corresponding to the two ends of the GaAs nanowires. After exposure, the substrate was immersed in developer ZX238 for 20s to dissolve the photoresist in the exposed areas. After development, the substrate was rinsed with deionized water to remove residual developer, completing the preparation of the electrode windows.

[0033] Using an ultra-high vacuum electron beam evaporation system, a 10 nm thick Ni target was first deposited at an evaporation rate of 0.2 nm / s. Ni, acting as an adhesion layer, significantly enhanced the adhesion between the subsequent Au layer and the substrate, preventing Au layer detachment. After Ni layer deposition, the gold target boat was replaced, and a 900 nm thick Au layer was deposited at an evaporation rate of 0.1 nm / s. Au possesses excellent conductivity, and as the electrode body, it significantly reduced the series resistance of the detector, minimizing current transmission losses. During deposition, the thickness was monitored in real-time using a quartz crystal oscillating film thickness gauge to ensure film thickness accuracy. The substrate with completed Ni / Au deposition was then immersed in acetone and gently stirred for 10 minutes, causing the Ni / Au layer covering the photoresist pattern window to detach synchronously with the dissolution of the photoresist. Only the Ni / Au metal electrode 3, which is located within the photoresist window and directly contacts both ends of the GaAs nanowire, remained. This completed the entire fabrication process of the detector's sensitive device. Figure 2 As shown.

[0034] An optical path is set up to test the fabricated integrated device. A schematic diagram of the overall device integration and application is shown below. Figure 3 As shown, a diamond superlens is vertically irradiated with a 532nm laser. This superlens forms a linear focused spot at a focal length of 600μm, significantly increasing the light power density received by the GaAs nanowires. This, in turn, greatly improves the photocurrent response and response speed of the detector, enabling highly sensitive detection of weak light signals.

[0035] Example 2. This embodiment provides a polarization-sensitive integrated semiconductor photodetector. Based on the high responsivity integrated architecture of Embodiment 1, this embodiment uses a polarization-sensitive superlens structure design to enable the device to improve responsivity while possessing high-precision polarization light detection capability. The specific fabrication process is as follows: A unit phase library covering 0–2π was constructed using geometric parameters such as the height and dimensions of the column units. FDTD was used to simulate the relationship between phase, amplitude, and nanopillar radius. Within the 0–2π phase range, 64 rectangular nanopillars with high transmittance and different geometric dimensions were selected as discrete units to deduce the arrangement of nanopillars in the entire metasurface array, completing the design of a metasurface polarizing cylindrical lens with a focal length of 600 μm. A 600 μm thick diamond was selected as the metalens substrate 1. The diamond substrate 1 was ultrasonically cleaned for 5 min each with acetone solution and anhydrous ethanol, rinsed with deionized water, and dried with nitrogen to complete the substrate cleaning process. Electron beam thermal evaporation was used to heat the Cr target material, and a 10 nm thick Cr layer 5 was deposited on the front side of the substrate at an evaporation rate of 0.1 nm / s as a conductive layer, providing a conductive path for subsequent electron beam exposure and avoiding charge accumulation that could affect pattern accuracy.

[0036] A spin coating process was used to uniformly coat the positive photoresist PMMA950K-A4 onto the surface of the conductive layer 5. By controlling the coating speed r1=600rpm, t1=6s, r2=4000rpm, and t2=40s, a uniform photoresist film with a thickness of 240nm was formed. Solvent removal and photoresist curing were completed by pre-baking at 150℃ for 300s. Using an electron beam exposure system, a mask pattern was drawn on photoresist using a pre-designed polarization-controlled dot matrix. The overall size of the mask pattern was 200nm × 200nm, consisting of 160,000 anisotropic nanopillar units with sizes ranging from 65nm to 430nm. By designing the long axis / short axis ratio and spatial orientation of the nanopillars, polarization-related phase and amplitude modulation was introduced, enabling the superlens to produce differentiated focusing effects on incident light with different polarization states, providing a structural basis for polarization detection. After exposure, the substrate was immersed in PR56 developer for 150s and then in isopropanol solution for 30s to complete development and fixing, obtaining a high-precision polarization-controlled mask pattern.

[0037] The Ni target was heated by electron beam thermal evaporation, and a 50 nm thick Ni was deposited as a mask 6 at an evaporation rate of 0.2 nm / s. After soaking in acetone for 10 h, the mask was stripped, leaving only the lattice Ni mask layer corresponding to the mask pattern, which provides protection for subsequent ICP etching.

[0038] The polarization-sensitive superlens was fabricated using an ICP dry etching process. The first step involved etching for 10 seconds with parameters of Power=300W, RF=50W, O2 flow rate=6sccm, Cl2 flow rate=24sccm, and pressure=0.3Pa to precisely remove the exposed Cr conductive layer 5. The second step involved etching for 100 seconds with parameters of Power=700W, RF=100W, O2 flow rate=30sccm, and pressure=0.65Pa to form an anisotropic nanopillar array with a pillar height of 600nm on the front side of the diamond substrate, thus completing the fabrication of the polarization-sensitive superlens structure 4. A schematic diagram of the entire fabrication process is shown below. Figure 4 As shown.

[0039] The back side of the diamond superlens substrate 1 was ultrasonically cleaned with acetone and anhydrous ethanol, rinsed with deionized water, and dried with nitrogen. Using a mechanical transfer platform, GaAs nanowires were transferred as photoelectric detection material 2 at the center of the superlens array and at the position corresponding to the focused spot of the polarization superlens, ensuring that the polarization-related light intensity change of the focused spot could be directly captured by the GaAs nanowires.

[0040] A positive photoresist AZ5214 was coated on the back of the substrate using a spin coating process. A uniform 1μm thick photoresist film was formed by step-by-step spin control, followed by pre-baking at 100℃ for 180s. Source / drain electrode patterns were fabricated using a direct-write lithography machine, with a channel length of 2μm and electrode dimensions of 500μm × 500μm, precisely corresponding to both ends of the GaAs nanowires. After development in ZX238 developer for 20s and rinsing with deionized water, a 10nm thick Ni adhesion layer and a 900nm thick Au conductive layer were sequentially deposited using an ultra-high vacuum electron beam evaporation process. After immersion in acetone for 10min with gentle stirring, the layers were peeled off, resulting in a Ni / Au metal electrode 3 forming an ohmic contact with the GaAs nanowires. This completed the fabrication of the polarization-sensitive detector. The entire process is illustrated in the diagram below. Figure 5 As shown.

[0041] The device, fabricated using vertical irradiation with a 532nm laser, can form a linear focused spot at a focal length of 600μm. The intensity of the focused spot changes systematically with the polarization state of the incident light: the focused spot intensity is weakest when horizontally polarized light is incident, resulting in the minimum photocurrent output from the GaAs nanowire; the focused spot intensity is strongest when vertically polarized light is incident, resulting in the maximum photocurrent output from the GaAs nanowire. The device can directly identify the polarization state of the incident light through changes in photocurrent. This improves responsivity and achieves high-precision detection of polarized light without the need for additional discrete optical components such as polarizers or waveplates. A schematic diagram of the overall device integration and application is shown below. Figure 6 As shown.

[0042] Example 3. This embodiment provides an array-integrated semiconductor photodetector. The core technology utilizes the polarization-dependent focusing characteristics of a polarization-sensitive superlens, combined with multiple arrayed GaAs nanowire detectors, to achieve quantitative detection of the polarization state and intensity of incident light. The specific fabrication process is as follows: A phase library covering 0–2π was constructed using geometric parameters such as the height and dimensions of the column units. FDTD was used to simulate the relationship between phase, amplitude, and nanopillar radius. Rectangular nanopillars of different geometric dimensions with high transmittance were selected as discrete units within the 0–2π phase range to deduce the arrangement of nanopillars in the entire metasurface array, completing a metasurface polarizing cylindrical lens with a focal length of 600 μm. A 600 μm thick diamond substrate was selected as the metalens 1. The diamond substrate 1 was ultrasonically cleaned for 5 min each with acetone and anhydrous ethanol, rinsed with deionized water, and dried with nitrogen. A 10 nm thick Cr conductive layer 5 was deposited on the front side of the substrate using electron beam thermal evaporation at an evaporation rate of 0.1 nm / s, providing a conductive path for subsequent electron beam exposure. Figure 7 The steps for substrate pretreatment and conductive layer preparation are shown.

[0043] A spin coating process was used to uniformly coat the positive photoresist PMMA950K-A4 onto the surface of conductive layer 5. A uniform film with a thickness of 240 nm was formed by step-by-step spin rotation control, followed by pre-baking at 150°C for 300 seconds to complete curing. Using an electron beam exposure system, a mask pattern was drawn on the photoresist using a pre-designed polarization-controlled dot matrix pattern. This mask pattern, with an overall size of 200 nm × 200 nm, consists of 160,000 anisotropic nanopillar units ranging from 65 nm to 430 nm. It can generate linear focused spots with continuously varying lengths and intensities for incident light of different polarization states, providing a structural basis for quantitative polarization analysis. After exposure, the mask was developed and fixed by immersion in PR56 developer for 150 seconds and isopropanol solution for 30 seconds, resulting in a high-precision mask pattern. Figure 7 The photolithography exposure and development steps are shown.

[0044] Using electron beam thermal evaporation, a 50 nm thick Ni mask was deposited at an evaporation rate of 0.2 nm / s. After immersion in acetone for 10 hours, the mask was stripped, leaving only the lattice Ni mask layer. Figure 7 The steps for preparing and stripping the metal mask are shown in the figure.

[0045] The polarizing superlens was fabricated using an ICP dry etching process. The first step involved etching for 10 seconds with parameters of Power=300W, RF=50W, O2 flow rate=6sccm, Cl2 flow rate=24sccm, and pressure=0.3Pa to remove the exposed Cr conductive layer 5. The second step involved etching for 100 seconds with parameters of Power=700W, RF=100W, O2 flow rate=30sccm, and pressure=0.65Pa to form a 600nm high nanopillar array polarizing superlens structure 4. A schematic diagram of the entire fabrication process is shown below. Figure 7 As shown.

[0046] The back side of the diamond superlens substrate 1 was ultrasonically cleaned with acetone and anhydrous ethanol, rinsed with deionized water, and dried with nitrogen. Using a mechanical transfer platform, a GaAs nanowire was first transferred along the same straight line at the center of the superlens array, and then another GaAs nanowire was transferred 50 μm above and below the first nanowire. The three nanowires together constitute the photoelectric detection material 2, which corresponds to the center position and the extended positions at both ends of the focused spot of the polarization superlens, respectively, to ensure that the changes in the spot distribution under different polarization states can be captured by the nanowires at different positions.

[0047] A positive photoresist AZ5214 was coated on the back of the substrate using a spin coating process. A uniform 1μm thick photoresist film was formed by step-by-step spin control and pre-baking at 100℃ for 180s. Source / drain electrode patterns corresponding to individual nanowires were fabricated using a direct-write lithography machine. The channel length was 2μm, and the individual electrode size was 20μm×2μm, precisely corresponding to both ends of each nanowire. After development in ZX238 developer for 20s and rinsing with deionized water, a 10nm thick Ni adhesion layer and a 900nm thick Au conductive layer were sequentially deposited using an ultra-high vacuum electron beam evaporation process. After immersion in acetone for 10min and gentle stirring, the layers were peeled off, resulting in independent Ni / Au metal electrodes 3 that form ohmic contacts with the three GaAs nanowires, thus completing the fabrication of the array detector. The entire process is illustrated in the diagram below. Figure 8 As shown.

[0048] The device, fabricated using vertical irradiation with a 532nm laser, exhibits a polarizing superlens capable of forming a linear focused spot at a focal length of 600μm. The length and intensity distribution of this spot change systematically with the incident light polarization angle: when horizontally polarized light is incident, the focused spot has the strongest intensity and a length of 100μm, with the strongest photocurrent response at the center nanowire and extremely weak responses at the two outer nanowires. As the incident light polarization angle changes from horizontal to vertical, the focused spot length gradually increases, the intensity at the center gradually decreases, and the intensity at the extended ends gradually increases. When the incident light polarization angle reaches vertical, the focused spot length is the longest, and the intensity is uniformly distributed across the entire spot, with the photocurrent responses of the three nanowires becoming nearly identical. The device can quantitatively calculate the polarization angle and intensity of the incident light using the ratio of the photocurrent responses of the three nanowires, achieving both high-response photodetection and accurate detection of the full polarization information of the incident light. A schematic diagram of the overall device integration and application is shown below. Figure 9 As shown.

[0049] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for fabricating an integrated semiconductor photodetector, characterized in that, Includes the following steps: S1. Construct a 0~2π phase library for circular nanopillars through FDTD simulation, deduce the nanopillar array arrangement based on the target focal length, and complete the metasurface cylindrical lens design. S2. After cleaning and drying the superlens substrate (1), a layer of Cr is deposited on the front side as a conductive layer (5). S3. Using a spin coating process, positive photoresist is uniformly coated on the surface of the conductive layer (5). After pre-baking, an electron beam exposure system is used to prepare a dot matrix mask pattern. After development and fixing, Ni is evaporated and then stripped with acetone to obtain a dot matrix Ni mask (6). S4. First, the surface conductive layer is removed by ICP etching (5), and then the nanopillar array superlens structure is prepared by ICP etching (4). S5. Mechanically transfer linear or thin-film semiconductor material or heterojunction structure to the back side of the superlens substrate (1) corresponding to the array center position of the superlens as a photodetector layer (2). S6. Spin-coat positive photoresist on the substrate surface, and expose the source and drain electrode pattern by direct writing lithography after pre-baking. After development and fixing, use electron beam evaporation process to deposit the adhesion layer metal and the electrode body layer metal in sequence. After peeling off the metal layer in the non-electrode area, the metal electrode (3) in contact with the photodetector layer (2) is obtained, and the fabrication of the integrated semiconductor photodetector is completed.

2. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The cleaning and drying process described in step S1 is as follows: ultrasonic cleaning is performed for 5 minutes each with acetone solution and anhydrous ethanol, followed by rinsing with deionized water and drying with nitrogen gas. The thickness of the superlens substrate 1 is 300μm~2mm.

3. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The conductive layer (5) in step S2 is prepared by electron beam thermal evaporation process with an evaporation rate of 0.1 nm / s and a deposition thickness of 10 nm; the Ni mask (6) is prepared by electron beam thermal evaporation process with an evaporation rate of 0.2 nm / s and a deposition thickness of 50 nm.

4. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The positive photoresist mentioned in step S3 is PMMA950K-A4, which forms a photoresist film with a thickness of 240 nm after spin coating; the pre-baking temperature is 150°C and the time is 300 s.

5. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The overall size of the mask pattern of the dot matrix structure in step S3 is 200nm×200nm, which is composed of 160,000 units with a size of 65nm~430nm; the development and fixing are completed by immersing in pr56 developer for 150s and isopropanol solution for 30s.

6. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The process parameters for ICP etching to remove the surface conductive layer (5) in step S4 are: Power=300W, RF=50W, O2 flow rate=6sccm, Cl2 flow rate=24sccm, pressure=0.3Pa, and etching time is 10s; The process parameters for preparing the nanopillar structure by ICP etching are: Power=700W, RF=100W, O2 flow rate=30sccm, pressure=0.65Pa, and etching time=100s.

7. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The photoresist mentioned in step S6 is positive photoresist AZ5214, which forms a photoresist film with a thickness of 1μm after spin coating; the pre-baking temperature is 100℃ and the time is 180s; the development is completed by immersing in ZX238 developer for 20s and rinsing with deionized water.

8. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The specific parameters of the electron beam evaporation process in step S6 are as follows: first, a 10 nm thick adhesion layer metal is deposited at a rate of 0.2 nm / s, and then a 900 nm thick electrode body layer metal is deposited at a rate of 0.1 nm / s; the channel length of the source-drain structure electrode is 2 μm, and the size of a single electrode is 2 μm to 500 μm.

9. The method for fabricating an integrated semiconductor photodetector according to claim 1, characterized in that, The nanopillar units in the nanopillar array superlens structure (4) are either isotropic or anisotropic.

10. An integrated semiconductor photodetector, characterized in that, Prepared by the preparation method according to any one of claims 1 to 9; The integrated semiconductor photodetector includes a superlens substrate (1), a nanopillar array superlens structure (4), a photodetector layer (2), and a metal electrode (3); the nanopillar array superlens structure (4) is formed on the front side of the superlens substrate (1), the photodetector layer (2) is disposed on the back side of the superlens substrate (1) and corresponds to the focused spot position of the nanopillar array superlens structure (4), and the metal electrode (3) forms an ohmic contact with the photodetector layer (2).

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