Cobalt terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector and preparation method thereof

Abstract

The invention discloses a cobalt terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector and a preparation method thereof, and belongs to the technical field of ultraviolet light detection. The detector comprises a gallium nitride nanowire array located on a substrate, one end, far away from the substrate, of the gallium nitride nanowire array is loaded with cobalt terbium alloy through a magnetron sputtering method, and a heterojunction is formed. The cobalt terbium alloy nano-particles are accurately loaded and wrapped on the top of the gallium nitride nano-wire through the magnetron sputtering method, the process controllability is high, compatibility is good, and the method is suitable for large-scale production. On the aspect of a performance improvement mechanism, on the basis of the magnetic characteristics of cobalt terbium alloy, through the synergistic effect of three core mechanisms including the magnetoelectric effect, interface charge regulation and control and catalytic auxiliary surface state optimization, the problems that a traditional gallium nitride detector is high in carrier recombination rate, low in response speed, insufficient in stability and the like are solved. In the aspect of application value, the performance limitation of a traditional gallium nitride detector is broken through, and the gallium nitride detector can be widely adapted to high-end scenes such as transient ultraviolet signal detection and extreme environment monitoring.

Description

Technical Field

[0001] This invention belongs to the field of ultraviolet light detection technology, specifically relating to a cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector and its preparation method. Background Technology

[0002] GaN-based ultraviolet photodetectors are ultraviolet photoelectric conversion devices constructed using gallium nitride (GaN) and its ternary / quaternary alloys (such as AlGaN and InGaN) as the core sensing materials. Leveraging GaN's unique wide bandgap, excellent physicochemical stability, and controllable photoelectric properties, these detectors have completely overcome the performance bottlenecks of traditional silicon-based and sulfide-based ultraviolet detectors, becoming a core technology solution in the fields of solar-blind ultraviolet (200-280nm) and near-ultraviolet (300-400nm) detection, and are widely used in key scenarios such as environmental monitoring and biomedicine.

[0003] The core advantage of GaN-based heterojunctions lies in the ability to construct strong built-in electric fields and high-mobility carrier channels through band matching of different wide-bandgap semiconductors, thereby achieving efficient separation and transport of photogenerated carriers. Currently, a research landscape has been formed based on AlGaN / GaN, extending to multi-systems such as GaN / ZnO and GaN / SiC, with device structures evolving from simple heterojunctions towards multifunctional integration.

[0004] The performance of ultraviolet (UV) photodetectors needs to be evaluated using a series of quantitative parameters. These parameters are the core basis for device design, selection, and application, and mainly include responsivity (R) and rise time (t). r Fall time (t) f Dark Current (I) d Photocurrent (Light Current, I) l ), spectral response range, etc.

[0005] However, existing ultraviolet detectors have shortcomings, specifically including: 1) The photoelectric response performance is weak. The unmodified gallium nitride surface has many defects and a high recombination rate of photogenerated carriers, resulting in extremely low photocurrent density and responsivity, which makes it difficult to meet the requirements of high-sensitivity detection.

[0006] 2) The response speed is slow, the carrier transport efficiency is low, and the rise / fall time is long, making it unsuitable for detection scenarios of transient ultraviolet signals (such as pulsed ultraviolet light).

[0007] 3) Poor performance stability, lack of precise optimization of the composition ratio of the co-catalyst, and fluctuations in composition can easily lead to significant fluctuations in detector performance. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector and its preparation method, thereby solving the problems in the prior art.

[0009] The objective of this invention can be achieved through the following technical solutions: A cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector includes a gallium nitride nanowire array on a substrate. The end of the gallium nitride nanowire array away from the substrate is loaded with cobalt-terbium alloy by magnetron sputtering to form a heterojunction.

[0010] Furthermore, in the cobalt-terbium alloy, the molar ratio of cobalt to terbium is (72-76):(28-24).

[0011] Furthermore, in the cobalt-terbium alloy, the molar ratio of cobalt to terbium is 74:26.

[0012] Furthermore, the substrate material is Si.

[0013] The above-mentioned method for fabricating a cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector includes the following steps: Gallium nitride nanowire arrays were deposited on the substrate surface using metal-organic chemical vapor deposition. Cobalt-terbium alloy was loaded onto gallium nitride nanowire arrays by magnetron sputtering.

[0014] Furthermore, the process of depositing a gallium nitride nanowire array on the substrate surface includes: After cleaning and drying the substrate, it was placed in the reaction chamber and baked in a hydrogen atmosphere. TMAl and NH3 were introduced into the reaction chamber, and AlN nanoparticles were formed at 800℃ to serve as a catalyst. Raise the temperature of the reaction chamber to 900~1000℃, introduce H2 to purge the air; at the same time, introduce TMGa and NH3. After the growth is completed, first turn off the TMGa source, continue to introduce NH3 to cool down to 500℃, then turn off the NH3 and let it cool naturally to room temperature.

[0015] Furthermore, the molar ratio of NH3 to TMGa is 2000:1.

[0016] Furthermore, the process of loading cobalt-terbium alloy onto gallium nitride nanowire arrays includes: Cobalt-terbium alloy was selected as the target material; The processed gallium nitride nanowire array was fixed on the sample stage, the target material was installed at the corresponding target position, the target-substrate distance was adjusted, and the vacuum chamber was closed.

[0017] Argon gas was introduced into the chamber, and magnetron sputtering was performed to load a cobalt-terbium alloy onto one end of the gallium nitride nanowire array.

[0018] Furthermore, the working pressure of the chamber is 7 mTorr; during magnetron sputtering, the sputtering power of the target is 20 W, the rotation speed is 5 rpm, and the magnetron time is 35 min.

[0019] The above-mentioned cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector is used in environmental monitoring.

[0020] The beneficial effects of this invention are: 1. This invention proposes a method for preparing a gallium nitride detector modified with cobalt-terbium alloy and its performance improvement in ultraviolet light detection. The cobalt-terbium alloy is grown on gallium nitride nanowires by magnetron sputtering. The performance improvement is explained by three core mechanisms: magnetoelectric effect, interface charge regulation, and catalytically assisted surface state optimization. This modified structure can effectively improve the detector's responsivity, increase the separation efficiency of photogenerated carriers, thereby increasing photocurrent and reducing dark current, thus enhancing the efficiency and stability of electrocatalytic reactions.

[0021] 2. Cobalt-terbium alloy-modified gallium nitride detectors have broad application prospects in the field of ultraviolet detection. Combining the magnetoelectric, catalytic, and interface modulation characteristics of magnetic alloys with GaN photoelectric detection provides a new design idea for improving the performance of third-generation semiconductor detectors. It can be extended to the research and development of wide-bandgap semiconductor detectors modified with other rare earth-transition alloys (such as cobalt-neodymium and iron-terbium), promoting technological innovation in photoelectric detection materials and devices, and providing new ideas and methods for sustainable energy conversion.

[0022] 3. By loading CoTb alloy onto the top of gallium nitride nanowires using magnetron sputtering, the catalytic effect of CoTb is utilized to repair surface defects in gallium nitride. Simultaneously, the magnetoelectric effect accelerates carrier separation, resulting in a 7-8 fold increase in photocurrent density and responsivity compared to the original sample. Furthermore, the interfacial interaction between the CoTb alloy and gallium nitride optimizes the carrier transport path, shortening the detector rise time to 2.56 ms and fall time to 1.28 ms, thus adapting to transient signal detection. This invention also clarifies that the optimal performance is achieved when the molar ratio of Co to Tb is 74:26, resolving the performance fluctuation problem caused by component mismatch.

[0023] 4. In the cobalt-terbium alloy of this invention, the molar ratio of cobalt to terbium is (72-76):(24-28). Within this ratio range, the CoTb alloy can well match the interfacial charge characteristics of gallium nitride nanowires, thus clearly defining the optimal composition range and balancing the catalytic properties and interfacial compatibility of the alloy, ultimately ensuring the detector's comprehensive performance in terms of high response, speed, and stability. Furthermore, when the molar ratio of cobalt to terbium is 74:26, the performance reaches its peak (photocurrent density 63.874 μA·cm). -2 (Response rate 88.53 mA / W).

[0024] 6. The substrate material of the gallium nitride nanowires described in this invention is Si. The Si substrate can form a complementary band structure with gallium nitride. The band gap of Si (1.12eV) is much smaller than that of GaN (3.4eV). When GaN nanowires are grown directly on the Si substrate, Si can serve as an indirect conductive substrate, providing a stable carrier collection channel for GaN nanowires and avoiding carrier transport losses caused by insulating substrates (such as sapphire), thereby indirectly improving the photocurrent density and responsivity of the detector.

[0025] 7. In this invention, the molar ratio of NH3 to TMGa during the deposition of gallium nitride nanowires is 2000:1. The high V / III ratio of 2000:1 is a key threshold for achieving a "nanowire array" rather than a "thin film". If the ratio is too low (e.g., <1000:1), the excess Ga atoms will lead to lateral growth dominance, eventually forming a continuous thin film and losing the advantage of the high specific surface area of ​​the nanowires.

[0026] 8. The working pressure of the chamber in this invention is 7 mTorr; during magnetron sputtering, the sputtering power of the target material is 20 W, the rotation speed is 5 rpm, and the magnetron time is 35 min; the pressure of 7 mTorr provides an ideal vacuum environment for low-power sputtering, ensuring efficient and low-damage deposition of the alloy; the low power of 20 W and the low rotation speed of 5 rpm work together to achieve nanoscale dispersion deposition of the alloy at the tip of the nanowire; the 5 min sputtering time precisely controls the load, optimizing the interface performance between the alloy and the GaN nanowire. These parameters together ensure the high-quality construction of the CoTb alloy and GaN nanowire heterojunction, which is the key process support for achieving high photocurrent density, high responsivity, and fast response speed in the detector of Example 1. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of the ultraviolet light detector in this invention; Figure 2 This is a physical image of the ultraviolet light detector used in this invention; Figure 3 This is a field test image of the detector in this invention during an electrochemical experiment; Figure 4 This is a comparison chart of the responsivity of the detectors in this invention; Figure 5 This is a scanning electron microscope (SEM) image of the gallium nitride nanowires in this invention. Figure 6 This is a characterization diagram of the hysteresis loop of the alloy-modified gallium nitride nanowires in this invention. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] like Figure 1 As shown, a cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector includes a gallium nitride nanowire array on a substrate, with a cobalt-terbium alloy loaded at the end of the gallium nitride nanowire array away from the substrate, forming a heterojunction.

[0031] The gallium nitride nanowire array is deposited on the substrate surface using a metal-organic chemical vapor deposition (MOCVD) method; the specific process includes: S11: Select suitable raw materials and equipment, including: substrate (Si), metal-organic source (trimethylgallium™Ga with a purity of 99.999%), nitrogen source (ammonia), catalyst precursor (trimethylaluminum™Al), and MOCVD equipment (equipped with a heating stage and a gas flow control system). S12: Substrate pretreatment. The substrate is ultrasonically cleaned with acetone and ethanol for 10 min in sequence (to remove surface oil), then rinsed with deionized water and dried with nitrogen. The substrate is then placed in the MOCVD reaction chamber and baked at 1000℃ in H2 atmosphere for 30 min (to further remove surface impurities). S13: Catalyst preparation: TMAl and NH3 were introduced, and AlN nanoparticles were formed by growing at 800℃ for 10 min (as a catalyst). S14: GaN nanowire growth. The reaction chamber temperature was raised to 900-1000℃, and H2 (carrier gas) was introduced to purge the air. At a V / III ratio (NH3 / TMGa molar ratio) of 2000, TMGa (flow rate 50-100 sccm) and NH3 (flow rate 100-200 sccm) were simultaneously introduced, maintaining stable temperature and gas flow rates. The growth time was 30-120 min. After growth, the TMGa source was first turned off, and NH3 was continuously introduced to cool the temperature to 500℃ (to prevent GaN oxidation). Then, the NH3 source was turned off, and the sample was allowed to cool naturally to room temperature before removal. The resulting nanowires had lengths of 300-500 nm and a density of approximately 1 × 10¹¹ nanowires / cm². 2 Gallium nitride nanowire arrays.

[0032] In cobalt-terbium alloys, the molar ratio of cobalt to terbium is (72-76):(28-24), preferably 74:26.

[0033] Cobalt-terbium alloys are loaded onto gallium nitride nanowire arrays via magnetron sputtering. The specific process includes: S21: An alloy with a cobalt-terbium molar ratio of (72-76):(24-28) is selected as the target material; S22: Fix the processed gallium nitride material on the sample stage, install the target material into the corresponding target position, adjust the target-substrate distance (100mm), ensure that the target material and the substrate are aligned, and close the vacuum chamber.

[0034] S23: Introduce high-purity argon gas (99.999%) into the chamber, adjust the gas flow rate (usually 20-50 sccm) using a mass flow controller, and control the working pressure of the chamber using a vacuum valve to stabilize it at 7 mTorr.

[0035] S24: Set the sputtering power of the target (cobalt-terbium alloy) to 20W (actual power 18.5W), the rotation speed to 5rpm, and the magnetron sputtering time to 35min; S25: Turn off the sputtering power supply, stop the argon gas supply, continue to maintain the high vacuum state of the vacuum chamber, or slowly fill the chamber with nitrogen to atmospheric pressure, open the chamber, and take out the gallium nitride nanowire array loaded with cobalt terbium alloy, which is the detector.

[0036] The technical solution of the present invention will be described below through the following embodiments and comparative examples.

[0037] Example 1 The fabrication method of a cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector includes the following steps: S1, Gallium nitride nanowire arrays are prepared using metal-organic chemical vapor deposition (MOCVD), specifically including: S11: Select suitable raw materials and equipment: substrate (Si), metal-organic source (trimethylgallium™Ga with a purity of 99.999%), nitrogen source (ammonia), catalyst precursor (trimethylaluminum™Al), MOCVD equipment (equipped with a heating stage and a gas flow control system). S12: Substrate pretreatment. The substrate is ultrasonically cleaned with acetone and ethanol for 10 minutes in sequence (to remove surface oil), then rinsed with deionized water and dried with nitrogen. The substrate is then placed in the MOCVD reaction chamber and baked at 1000℃ in H2 atmosphere for 30 minutes (to further remove surface impurities). S13: Catalyst preparation: TMAl and NH3 were introduced, and AlN nanoparticles were formed by growing at 800℃ for 10 minutes (as a catalyst). S14: GaN nanowire growth was performed by raising the reaction chamber temperature to 900-1000℃ and purging the air with H2 (carrier gas). TMGa (50 sccm flow rate) and NH3 (100 sccm flow rate) were simultaneously introduced at a V / III ratio (NH3 / TMGa molar ratio) of 2000, maintaining stable temperature and gas flow rates for 60 minutes. After growth, the TMGa source was first turned off, and NH3 was continuously introduced to lower the temperature to 500℃ (to prevent GaN oxidation). Then, the NH3 source was turned off, and the sample was allowed to cool naturally to room temperature before removal. The resulting nanowires had lengths of 300-500 nm and a density of approximately 1 × 10¹¹ nanowires / cm². 2 Gallium nitride nanowire arrays.

[0038] S2, a detector is obtained by loading a cobalt-terbium alloy onto the upper end of a nanowire using magnetron sputtering. The specific process includes: S21: An alloy target with a cobalt-terbium molar ratio of 74:26 was selected for loading onto gallium nitride nanowires by magnetron sputtering. S22: Fix the processed gallium nitride nanowire array on the sample stage, install the target material into the corresponding target position, adjust the target-substrate distance (100mm), ensure that the target material and the substrate are aligned, and close the vacuum chamber.

[0039] S23: Introduce high-purity argon gas (99.999%) into the chamber, adjust the gas flow rate (usually 50 sccm) using a mass flow controller, and control the working pressure of the chamber using a vacuum valve to stabilize it at 7 mTorr.

[0040] S24: Set the sputtering power of the cobalt-terbium alloy target to 20W (actual power 18.5W), the rotation speed to 5rpm, and the magnetron sputtering time to 35min; S25: Turn off the sputtering power supply, stop the argon gas supply, slowly fill the chamber with nitrogen to atmospheric pressure, open the chamber, and remove the detector.

[0041] Example 2 The difference between this embodiment and Embodiment 1 is that the ratio of cobalt to terbium components is adjusted to 72:28, while the rest of the preparation process is the same as in Embodiment 1, and the detector is obtained.

[0042] Example 3 The difference between this embodiment and Embodiment 1 is that the ratio of cobalt to terbium components is adjusted to 76:24, while the rest of the preparation process is the same as in Embodiment 1, and the detector is obtained.

[0043] Comparative Example 1 The difference between this comparative example and Example 1 is that no cobalt terbium co-catalyst was added, but the rest of the preparation process was the same as in Example 1, and the detector structure was obtained.

[0044] Comparative Example 2 The difference between this comparative example and Example 1 is that CoTb alloy powder was prepared using a hydrothermal method and then loaded onto a gallium nitride nanowire array via sintering. Specifically, this includes: The first step is to weigh out the following ingredients according to the molar ratio of Co:Tb = 74:26: 0.184g of cobalt acetate (Co(OAc)2・4H2O), 0.109g of terbium nitrate (Tb(NO3)3・6H2O), 0.210g of citric acid, and 0.601g of urea.

[0045] The second step is to add the above raw materials to 20 mL of deionized water in sequence and stir magnetically for 30 minutes to obtain a uniform and clear mixed solution.

[0046] The third step involves transferring the mixed solution to a 50 mL reaction vessel, sealing it, and placing it in an oven at 160°C for 24 hours. After the reaction is complete, the mixture is allowed to cool naturally to room temperature. The product is then separated by centrifugation, washed three times alternately with deionized water and anhydrous ethanol, and subsequently dried in a vacuum drying oven at 60°C for 8 hours to obtain the cobalt-terbium composite hydroxide precursor (the main component of which is Co(OH)2-Tb(OH)3).

[0047] The fourth step involves evenly spreading the dried precursor powder in a quartz boat and placing it in the isothermal zone of a tube furnace. Argon gas (Ar, flow rate 50 sccm) is first introduced to purge the air from the furnace, then the atmosphere is switched to hydrogen (H2, flow rate 80 sccm), and the temperature is increased to 600°C at a rate of 5°C / min, and held at that temperature for 2 hours for reduction. After reduction, the furnace is allowed to cool naturally to room temperature under hydrogen atmosphere (to prevent alloy oxidation), and the product is removed, yielding a CoTb alloy powder with a Co:Tb ratio of 74:26.

[0048] The fifth step involves modifying the cobalt-terbium alloy powder onto the gallium nitride nanowire array using a sintering method. This includes adding the obtained CoTb alloy powder to an appropriate amount of deionized water to prepare a solution of 1 mg / mL and ultrasonically treating it for 30 min to form a homogeneous solution; taking an appropriate amount of the solution, placing it into gallium nitride nanowires, and modifying the catalyst in an oven using a sintering method at a temperature of 80℃ for 2 h.

[0049] The remaining preparation processes were the same as in Example 1, and the detector structure was obtained.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that a cobalt-iron alloy synthesized by a hydrothermal method is used as a co-catalyst. The preparation method of the cobalt-iron alloy includes: The first step involves using cobalt acetate (Co(OAc)2・4H2O) and ferric nitrate nonahydrate (Fe(NO3)3・9H2O) as raw materials. Weigh out 0.124g of cobalt acetate, 0.403g of ferric nitrate nonahydrate, 0.142g of citric acid, and 0.405g of urea. Dissolve cobalt acetate, ferric nitrate nonahydrate, and complexing agent (citric acid) in deionized water and stir until completely dissolved to form a homogeneous metal ion solution.

[0051] The second step is to add a precipitant (urea), stir well, and then transfer it to a metal reactor. React at 120°C for 12 hours.

[0052] The third step involves centrifuging the product after the reaction is complete, washing it three times with deionized water and ethanol, and then vacuum drying it at 80°C for 6 hours to obtain the cobalt iron oxide precursor (CoFe2O4).

[0053] The fourth step involves placing the dried precursor powder in a quartz boat and then into a tube furnace. First, an inert gas (Ar) is introduced to purge the air, and then the atmosphere is switched to a reducing atmosphere (H2 flow rate 50 sccm). The temperature is increased to 500°C at a rate of 10°C / min. After the reduction is complete, the powder is allowed to cool naturally to room temperature (while maintaining the reducing atmosphere to prevent alloy oxidation) to obtain cobalt-iron alloy powder.

[0054] The cobalt-iron alloy was then modified onto the gallium nitride nanowire array by sintering. This process involved adding the obtained cobalt-iron alloy powder to an appropriate amount of deionized water to prepare a 1 mg / mL solution and ultrasonically treating it for 30 min to form a homogeneous solution. An appropriate amount of the solution was then placed into gallium nitride nanowires, and the catalyst was modified by sintering in an oven at 80 °C for 2 h.

[0055] The remaining preparation processes were the same as in Example 1, and the detector structure was obtained.

[0056] Images of the detector are listed as follows Figure 2 As shown, from left to right, there are four different test samples. Example 1 is the detector of the present invention, Comparative Example 1 is the detector without the addition of cobalt-terbium co-catalyst, Comparative Example 2 is the detector for CoTb prepared by hydrothermal method, and Comparative Example 3 is the detector using cobalt-iron alloy as co-catalyst.

[0057] Experimental Test The materials prepared in the above embodiments and comparative examples were subjected to performance testing. Photoelectrochemical testing was performed using an HCH Instruments electrochemical workstation with CHI760E software. The specific testing procedure included: The first step is to build the three-electrode system. Connect the detector to the working electrode (electrode lead-out method: solder a strip of solder to the GaN side of the chip, which is equivalent to creating an electrode for the detector to conduct electricity) and prepare the counter electrode (Pt) and the reference electrode (Ag / AgCl). Place the working electrode, counter electrode, and reference electrode into the electrolytic cell in that order, and add the electrolyte (0.5 mol / L Na2SO4 aqueous solution), ensuring that the three electrodes are immersed in the electrolyte and do not come into contact with each other.

[0058] The second step is to connect the three electrodes to the "Working," "Counter," and "Reference" interfaces of the HCH workstation, respectively. Simultaneously, connect the workstation power supply, turn on the host computer, and launch the CHI760E software.

[0059] The third step is to set the software parameters. In the CHI760E software interface, click "Setup" → "Technique", and select "Amperometry (it curve)" (chronoamperometry, used to record current changes under photoelectric switching). Set the parameters Initial E (initial potential), Sample Interval, Run Time (test time), and Sensitivity to start the test.

[0060] Figure 3 This is a field test diagram of the detector's photoelectric performance. The upper left shows the computer screen running the chi760e software; the lower left shows the HCH instruments electrochemical workstation; and the right side shows the RIGOL signal generator and the three-electrode test system. Tables 1, 2, 3, and 4 are obtained by comparing the test results with those of Example 1, as detailed below: Table 1. Performance comparison of detectors with different cobalt-terbium molar ratios. Table 2. Performance comparison of detectors with and without catalyst modification, with different catalysts, and with catalysts modified by different processes. Table 3. Comparison of detector response times with and without catalyst modification, with different catalysts, and with catalysts modified by different processes. Table 4. Performance comparison of detectors under different bias voltages and light intensities, with and without modified co-catalysts, modified with different co-catalysts, and modified with co-catalysts using different processing methods. Note: Jph Represents photocurrent density Table 1 compares detectors with different CoTb component ratios at "0V bias, 1mW·cm⁻ 2 Photocurrent density (J) under illumination ph The photocurrent density and responsivity (R) of the CoTb alloy are shown. It can be seen that the composition ratio of the CoTb alloy has a significant impact on the detector performance. When the CoTb ratio is 74:26 (Example 1), the photocurrent density and responsivity of the detector are both optimal. Adjusting the composition ratio (increasing the Tb ratio to 28 or decreasing it to 24) will lead to a decrease in photoelectric performance, proving that 74:26 is the optimal composition ratio of the CoTb alloy in this scheme.

[0061] Table 2 compares the performance of different detectors at 0V bias and 1mW·cm⁻. 2 Photocurrent density (J) under illumination conditions ph ) and responsivity (R), J of Example 1 (the detector of the present invention) ph Reaching 63.874 μA·cm⁻ 2 It is the best performing; compared to Example 1 (without CoTb), J... ph Only 8.556 μA·cm⁻ 2 The J value was the lowest among all samples; Comparative Example 2 (hydrothermal CoTb) had the lowest J value. ph 40.323 μA·cm⁻ 2 Approximately 63% of that in Example 1; J of Comparative Example 3 (cobalt-iron alloy) ph 49.533 μA·cm⁻ 2 It is approximately 77.5% of that in Example 1.

[0062] Figure 4 The bar charts for the responsivity of each detector show that the responsivity of Example 1 is significantly better than that of other samples. It is 8.27 times that of Comparative Example 1 (the original sample) and also significantly higher than Comparative Examples 2 and 3 (approximately 1.82 to 1.73 times that of them). This indicates that the scheme corresponding to Example 1 (i.e., the gallium nitride detector modified with cobalt terbium alloy) can significantly improve the response performance of the detector.

[0063] Table 3 compares the rise times (t) of different detectors. r ) and fall time (t d (The shorter the time, the faster the response speed), the t of Example 1 (the detector of the present invention) r The response time was 2.56 ms, making it the fastest among all samples; the response time of Comparative Example 1 (without CoTb) was... r The rise time was 5.12 ms, the slowest; compared to Comparative Example 2 (hydrothermal CoTb), the rise time was... rThe time was 3.47 ms, approximately 35.5% slower than Example 1; the time for Comparative Example 3 (cobalt-iron alloy) was... r The descent time is 3.25 ms, approximately 26.9% slower than Example 1. Regarding the descent time, Example 1's t... d At 1.28ms, it has the fastest response recovery; compared to t in Example 1... d The value is 4.39, indicating the slowest rate of decline; t in Comparative Example 2 d The value was 2.86, approximately 123.4% slower than in Example 1; the value of Comparative Example 3 was t. d The rise time was 2.17 ms, which is about 69.5% slower than that of Example 1. Therefore, the response speed of Example 1 (CoTb alloy modified detector) of the present invention is significantly better than other samples. Compared with Comparative Example 1 without a co-catalyst, the rise time is shortened by about 50% and the fall time by about 70.8%. Compared with Comparative Example 2 (hydrothermal CoTb) and Comparative Example 3 (cobalt-iron alloy), the rise / fall time is also shorter, proving that the CoTb alloy modification scheme of the present invention can effectively accelerate the photoelectric response rate of the detector.

[0064] Table 4 compares the photocurrent density (J / L) of different detectors under different bias voltages and illumination intensities. ph ). We can see the J values ​​for all samples. ph Both increase with increasing light intensity and bias voltage; among them, J of Example 1 (the detector of the present invention) increases. ph It consistently had the highest value among all samples, while Comparative Example 1 (without CoTb) consistently had the lowest. Under the same bias voltage (taking 0V bias voltage as an example) and different light intensities, 1mW·cm⁻ 2 Under light intensity, Example 1 (63.874) was 7.5 times that of Comparative Example 1 (8.556), 1.6 times that of Comparative Example 2 (40.323), and 1.3 times that of Comparative Example 3 (49.533); 5 mW·cm⁻ 2 Under the same light intensity, Example 1 (285.698) was 7.9 times that of Comparative Example 1 (36.239), 1.5 times that of Comparative Example 2 (195.269), and 1.2 times that of Comparative Example 3 (247.584). Under the same light intensity (0.5 mW·cm⁻¹), 2 (For example), under different bias conditions, from 0V to 0.5V bias, J in Example 1 ph The photocurrent density increased from 35.897 to 49.364, an improvement of approximately 37.5%; at the same bias voltage (0.5V), Example 1 (49.364) was 5.4 times that of Comparative Example 1 (9.218), 1.4 times that of Comparative Example 2 (35.576), and 1.2 times that of Comparative Example 3 (41.159). Overall, Example 1 of the present invention (the detector modified with CoTb alloy) showed significantly better photocurrent density than other samples under different bias voltages and light intensities. Compared to Comparative Example 1 without a co-catalyst, Jph The efficiency is increased by 5 to 8 times; compared with Comparative Example 2 and Comparative Example 3 of CoTb synthesized by hydrothermal method, J ph It also maintains an advantage of 1.2 to 1.6 times, proving that the CoTb alloy modification scheme of the present invention can stably enhance the photoelectric response performance of the detector under different working conditions.

[0065] In summary, the modification of the CoTb alloy with an appropriate proportion and the use of magnetron sputtering as a catalyst modification method significantly affect the photoelectric performance of the detector. This is because cobalt plays an important role in the alloy, and the cobalt-terbium alloy is synthesized by magnetron sputtering. Co can change the crystal phase structure of the alloy, causing surface reconstruction in the photoelectrochemical reaction, improving the oxidation ability of the cobalt-terbium alloy as a cocatalyst, thereby enhancing the extraction ability of photogenerated carriers. An appropriate terbium-doped alloy cocatalyst loading can maximize the photoelectric performance of the detector. This is because the magnetic characteristics of the cobalt-terbium alloy form a local magnetic field at the heterojunction interface through the magnetoelectric effect. The Lorentz force can quickly separate the photogenerated electron-hole pairs generated by ultraviolet light excitation in GaN. At the same time, the magnetically ordered structure reduces the charge tunneling barrier, accelerates the transport of carriers from GaN to the alloy layer, significantly reduces the carrier recombination time, directly improves the photoresponse speed of the detector, and solves the technical pain point of response lag in traditional GaN detectors. Meanwhile, the magnetic atomic arrangement of the CoTb alloy exhibits long-range order, which interacts with the conduction-valence band electronic states of GaN through df orbital coupling. At the heterojunction interface of GaN and CoTb alloy, this magnetic order lowers the charge tunneling barrier, accelerating the transfer of photogenerated electrons from the conduction band of GaN to the catalytically active sites of the CoTb alloy. Simultaneously, holes are confined within GaN to participate in subsequent electrochemical processes, achieving highly efficient charge separation. Except for Examples 1, 2, and 3, any change to the preparation conditions will lead to a decrease in detector performance.

[0066] Figure 5 This is a scanning electron microscope (SEM) image of the detector of Embodiment 1 of the present invention. The image shows a one-dimensional nanowire array grown perpendicular to the substrate (the lower part of the image). The nanowires are generally elongated columnar structures with a slight contraction at the top, resembling a "pointed cylinder." The nanowires are densely and relatively uniformly arranged on the substrate, with small gaps between adjacent nanowires. There are no obvious clusters or sparse areas, and the growth orientation is consistent (all perpendicular to the substrate).

[0067] Figure 6 For Co 0.74 Tb 0.26The VSM hysteresis loop of alloy-modified gallium nitride nanowires shows the magnetic field strength (Oe) on the horizontal axis and the magnetization (emu / cc) on the vertical axis. As the external magnetic field increases from -1000 Oe to 1000 Oe, the magnetization increases from approximately -600 emu / cc to approximately 600 emu / cc. The magnetization is symmetrical under both positive and negative magnetic fields, reflecting the fundamental magnetic response characteristics of ferromagnetic materials. This hysteresis loop demonstrates that Co... 0.74 Tb 0.26 After alloy modification, gallium nitride nanowires acquire ferromagnetism, which is the basis for achieving "magnetic-optical" synergistic enhancement of detection performance.

[0068] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector, characterized in that, It includes a gallium nitride nanowire array on a substrate, with a cobalt-terbium alloy loaded at the end of the gallium nitride nanowire array away from the substrate by magnetron sputtering to form a heterojunction.

2. The cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 1, characterized in that, In the cobalt-terbium alloy, the molar ratio of cobalt to terbium is (72-76):(28-24).

3. The cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 1, characterized in that, In the cobalt-terbium alloy, the molar ratio of cobalt to terbium is 74:

26.

4. The cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 1, characterized in that, The substrate material is Si.

5. The method for preparing the cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to any one of claims 1-4, characterized in that, Includes the following steps: Gallium nitride nanowire arrays were deposited on the substrate surface using metal-organic chemical vapor deposition. Cobalt-terbium alloy was loaded onto gallium nitride nanowire arrays by magnetron sputtering.

6. The method for fabricating a cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 5, characterized in that, The process of depositing gallium nitride nanowire arrays on the substrate surface includes: After cleaning and drying the substrate, it was placed in the reaction chamber and baked in a hydrogen atmosphere. TMAl and NH3 were introduced into the reaction chamber, and AlN nanoparticles were formed at 800℃ to serve as a catalyst. Raise the temperature of the reaction chamber to 900~1000℃, introduce H2 to purge the air; at the same time, introduce TMGa and NH3. After the growth is completed, first turn off the TMGa source, continue to introduce NH3 to cool down to 500℃, then turn off the NH3 and let it cool naturally to room temperature.

7. The method for preparing a cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 6, characterized in that, The molar ratio of NH3 to TMGa is 2000:

1.

8. The method for fabricating a cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 5, characterized in that, The process of loading cobalt-tertium alloy onto gallium nitride nanowire arrays includes: Cobalt-terbium alloy was selected as the target material; The processed gallium nitride nanowire array was fixed on the sample stage, the target material was installed at the corresponding target position, the target-substrate distance was adjusted, and the vacuum chamber was closed. Argon gas was introduced into the chamber, and magnetron sputtering was performed to load a cobalt-terbium alloy onto one end of the gallium nitride nanowire array.

9. The method for fabricating a cobalt-terbium alloy-modified gallium nitride nanowire heterojunction ultraviolet detector according to claim 8, characterized in that, The working pressure of the chamber is 7 mTorr; during magnetron sputtering, the sputtering power of the target is 20 W, the rotation speed is 5 rpm, and the magnetron time is 35 min.

10. The application of the cobalt-terbium alloy modified gallium nitride nanowire heterojunction ultraviolet detector according to any one of claims 1-4 in environmental monitoring.

Images