Gallium oxide solar-blind ultraviolet detector based on asymmetric surface etched nanopore structure

Abstract

The invention provides a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface etched nanopore structure. The gallium oxide solar-blind ultraviolet detector comprises a substrate (4) and a gallium oxide thin film (3), the bottom surface of the gallium oxide thin film is in contact with the substrate, and the top surface of the gallium oxide thin film is a light incident region; a nanopore structure (2) formed by periodically arranging a plurality of nanopores is arranged at the light incident region, and is used for enhancing the surface electric field and magnetic field of a semiconductor material of the gallium oxide thin film and increasing the effective optical path length and the service life of incident photons; according to the invention, the performance of the device is greatly improved by etching the nanopores in the gallium oxide film and optimizing the structural parameters.

Description

Technical Field

[0001] The present invention relates to the field of solar-blind ultraviolet detection technology and nanomaterial preparation technology, in particular to a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure. Background Art

[0002] As we all know, the main source of ultraviolet light on Earth is the sun, which emits ultraviolet radiation with wavelengths ranging from 10-400 nm. The UVC band (200-280 nm) is strongly absorbed by ozone, or triatomic oxygen, in the atmosphere. This means that detection of this band on the ground will not be affected by solar radiation, which brings the inherent advantage of low background noise. Therefore, this band is also vividly called the "solar-blind band." Solar-blind ultraviolet detectors (SBUV-PDs) are widely used in infrastructure, military equipment and scientific research fields, such as flame monitoring, missile warning and ozone hole detection. Compared with narrow-bandgap semiconductors, wide-bandgap (WBG) semiconductor light detection has the advantage of corresponding to the solar-blind band, thereby avoiding the use of optical filters and reducing cost and volume. In addition, WBG semiconductors have higher radiation resistance, which can increase the service life of the device.

[0003] A variety of WBG semiconductors have been studied for the design of UV photodetectors. Diamond, AlxGa1−xN, and ZnxMg1−xO are commonly used in SBUV-PDs. However, the composition of the metal catalyst used during diamond growth significantly influences the properties of the synthesized diamond, particularly its semiconductor properties. Furthermore, nitrogen impurities are inevitably introduced into the growth environment, resulting in high nitrogen concentrations that can compromise optoelectronic applications. Variations in the elemental content of the ternary alloys AlxGa1−xN and ZnxMg1−xO can significantly affect film quality. High-Al content AlxGa1−xN requires a critical growth temperature above 1350°C, while ZnxMg1−xO with Mg exceeding 37% undergoes phase segregation from wurtzite to rock-salt structure, further introducing defects that compromise overall performance. β-Ga2O3, with its natural wide bandgap of 4.7–4.9 eV and high electron drift velocity, is a preferred material for the fabrication of SBUV-PDs. The metal-semiconductor-metal (MSM) structure, a common structure, has attracted attention due to its simple preparation, ease of integration, and low capacitance per unit area. However, insufficient light absorption leads to low photocurrent and responsivity. To improve absorption, researchers have used transparent electrodes such as graphene to increase responsivity, but this poses high cost challenges.

[0004] In response to the deficiencies of the prior art described above, the present invention proposes a structure and preparation method for enhancing the light absorption of gallium oxide solar-blind ultraviolet detectors. Periodic micro / nanostructures can effectively change the properties of materials and have applications in many areas, while surface periodic structures can greatly improve anti-reflection capabilities, achieve near-field enhancement, and enhance overall absorption. At the same time, a number of studies have shown that the rational design of micro-nanostructures can provide a new path for the development of optoelectronic devices. To this end, the present invention designs a periodic asymmetric etched grating Ga2O3MSM-PD structure. The results show that the PD with optimized structural parameters has higher absorption efficiency and optical response. Summary of the Invention

[0005] The present invention proposes a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure. By etching nanopores on a gallium oxide film and optimizing structural parameters, the device performance is greatly improved.

[0006] The present invention adopts the following technical solutions.

[0007] A gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure comprises a substrate (4) and a gallium oxide film (3); the bottom surface of the gallium oxide film is in contact with the substrate, and the top surface of the gallium oxide film is a light incident area; a nanopore structure (2) formed by a plurality of periodically arranged nanopores is provided at the light incident area, and the nanopore structure is used to enhance the surface electric field and magnetic field of the semiconductor material of the gallium oxide film and increase the effective optical path length and lifetime of the incident photons.

[0008] A metal electrode (1) is provided on the top surface of the gallium oxide film beside the nanopore structure.

[0009] The metal electrode is made of gold.

[0010] The nanopore structure is prepared by etching the surface of the gallium oxide film.

[0011] The substrate is made of aluminum oxide.

[0012] When the gallium oxide solar-blind ultraviolet detector is working, the nanopore structure on the top surface of the gallium oxide film uses its area with a smaller curvature radius to geometrically confine the electron cloud at the light incident area, so that the electron cloud produces a strong charge separation effect.

[0013] When the gallium oxide solar-blind ultraviolet detector is working, the gallium oxide film scatters the incident light with the irregular surface or nanostructure at the nanopore structure to change the light propagation path, and greatly increases the light propagation path in the light incident area through multiple scattering; The light incident area uses the changing electric field at its nanopore to generate a vortex magnetic field, forming a Lorentz force to further affect the carrier motion trajectory, and at the same time uses a higher electric field intensity to increase the energy of the photoelectrons, thereby enhancing the photoelectric conversion efficiency. That is, when photons enter the photodetector, the nanopore accelerates the movement of the photoelectrons through the high-intensity electric field, making it easier for them to pass through the potential barrier of the energy band structure, thereby prompting the photons to be absorbed by higher energy bands, improving the photoelectric conversion efficiency, and thus improving the photocurrent and responsiveness of the detector, enhancing the detector's detection capability, and according to the simulation results, it does not affect the wavelength of the light wave.

[0014] The region of the nanopore structure with a smaller curvature radius is the edge or tip of the nanopore.

[0015] The nanopores are evenly arranged in rows and columns, and are blind holes with a depth of 180 nm, a spacing of 350 nm, and a radius of 80 nm.

[0016] The method for preparing a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure is used to prepare the above-mentioned detector, which is characterized by comprising the following steps: Step 1: Cleaning the substrate with acetone, anhydrous ethanol and deionized water in sequence under ultrasound; Step 2: Using metal organic chemical vapor deposition technology to grow a 300-1000 nm gallium oxide absorption layer on the substrate; Step 3: Use ion implantation technology to heavily dope the gallium oxide absorption layer with n-type, with a doping concentration of 1×10 18 cm -3 ; Step 4: Using electron beam lithography technology, prepare a mask structure with a pitch of 350 nm and a radius of 80 nm; Step 5: using an inductively coupled plasma etching method to etch nanopores with a depth of 180 nm; Step six: prepare metal electrodes using conventional photolithography technology.

[0017] The present invention discloses a day-blind ultraviolet detector based on a gallium oxide nanopore structure etched on an asymmetric surface, and relates to the field of day-blind ultraviolet detection technology and nanomaterial preparation technology. The detector comprises a substrate, a gallium oxide thin film placed on the surface of the substrate, a nanopore structure produced by etching the gallium oxide thin film, and an Au metal electrode. The present invention determines the optimal values of various parameters of the nanopore to solve the problem of light absorption by traditional devices and maximize the use of incident light. The present invention uses periodic micro / nanostructures to utilize mechanisms such as surface plasmon resonance, standing wave effect, and plasmon coupling to effectively change the properties of the material, namely: the surface periodic structure can greatly improve the anti-reflection ability, achieve near-field enhancement, and enhance overall absorption. At the same time, the increase in surface area can effectively enhance the interaction between light and material, thereby greatly improving the photocurrent and responsiveness of the detector, and enhancing the detection capability of the detector.

[0018] The advantages of the present invention compared to the prior art are as follows: 1) Nanopores are used to optimize and enhance the device's electric field distribution, strengthening the electric and magnetic fields on the semiconductor material's surface while increasing the effective optical path length and lifetime of incident photons. In regions with a small radius of curvature, such as the edge or tip of the nanopore, the electron cloud is geometrically confined, resulting in strong charge separation. At the nanoscale, when light encounters irregular surfaces or nanostructures, it scatters, changing its propagation path and undergoing multiple scatterings, significantly increasing the light's path. The changing electric field in the nanopore generates a vortex magnetic field, which further influences the carrier motion trajectory through the Lorentz force. Higher electric field strengths can increase the energy of photoelectrons, thereby enhancing photoelectric conversion efficiency. When photons enter a photodetector, the high electric field intensity accelerates their motion, making it easier for them to cross the potential barriers of the band structure, thereby causing the photons to be absorbed by higher energy bands, improving photoelectric conversion efficiency, significantly increasing the detector's photocurrent and responsivity, and enhancing the detector's detection capability. Simulation results show that this does not affect the wavelength of the light.

[0019] 2) Compared with the gallium oxide solar-blind UV detector reported in existing research, the present invention uses an asymmetric structure to form a dipolar current, thereby expanding the application scenarios of gallium oxide solar-blind UV detectors. Under positive bias, the detector has a high sensitivity and is suitable for use in low-intensity UV environments, such as environmental monitoring and solar radiation monitoring. The negative bias can suppress background radiation interference and provide better stability. It is particularly suitable for strong light environments and occasions that require anti-saturation, such as industrial detection and background radiation suppression. In dynamic monitoring, the alternating response of positive and negative bias can flexibly adapt to different radiation conditions, optimize real-time data acquisition, and be applied to fields such as ultraviolet intensity monitoring and medical health monitoring.

[0020] 3) The conventional Ga2O3MSM-PD was etched to form an asymmetric periodic surface structure to enhance light absorption. -4 W incident power, the PDCR of the device can reach 2.14×10 8 The results show that the responsivity of the film is more than an order of magnitude higher than that of the untreated film, reaching 2.41A / W, which is 4.34 times higher than that of the structure without nanopores. This provides a reference and reference for the application of etched surface structures in photodetection devices, which will contribute to the development of photodetection devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: Attachment Figure 1 This is a schematic structural diagram of the gallium oxide solar-blind ultraviolet detector based on the asymmetric surface-etched nanopore structure described in Example 1, wherein.

[0022] Figure 2 This is a schematic structural diagram of the gallium oxide solar-blind ultraviolet detector without an etching structure described in Comparative Example 1; Figure 3 This is a schematic diagram showing the effect of changes in structural parameters on the electric field intensity in Example 1; Figure 4 Schematic diagram of comparative absorption rate of untreated gallium oxide film without nanopores and with nanopores introduced in Example 1; Figure 5 Schematic diagram of the normalized magnetic field and electric field intensity distribution, light absorption power, and photogenerated carrier distribution near the solar-blind ultraviolet detector of Example 1 (in the figure, area a is a schematic diagram of the normalized electric field in the xz direction; area b is a schematic diagram of the normalized magnetic field in the xz direction; area c is a schematic diagram of the light absorption power in the xy direction; and area d is a schematic diagram of the photogenerated carrier distribution in the xy direction); Figure 6 Schematic diagrams of IV curves, responsivity curves, energy bands, and wavelength-responsivity curves for Example 1 and Comparative Example 1 in the dark and at an ultraviolet wavelength of 250 nm (a is a comparison of the photocurrent and dark current of the untreated and nanopore-introduced samples; b is a schematic diagram of the responsivity curves of the untreated and nanopore-introduced samples; c is a schematic diagram of the energy band diagram and working mechanism of the photodetector with an asymmetric etched surface structure; d is a schematic diagram of the change in responsivity with wavelength of the untreated and nanopore-introduced samples); In the figure: 1-metal electrode, 2-gallium oxide thin film, 3-nanopore structure, 3-gallium oxide thin film, 4-substrate. DETAILED DESCRIPTION

[0023] As shown in the figure, a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure includes a substrate 4 and a gallium oxide thin film 3; the bottom surface of the gallium oxide thin film is in contact with the substrate, and the top surface of the gallium oxide thin film is a light incident area; a nanopore structure 2 composed of a plurality of periodically arranged nanopores is provided at the light incident area, and the nanopore structure is used to enhance the surface electric and magnetic fields of the semiconductor material of the gallium oxide thin film, and increase the effective optical path length and lifetime of the incident photons.

[0024] A metal electrode 1 is provided on the top surface of the gallium oxide film beside the nanopore structure.

[0025] The metal electrode is made of gold.

[0026] The nanopore structure is prepared by etching the surface of the gallium oxide film.

[0027] The substrate is made of aluminum oxide.

[0028] When the gallium oxide solar-blind ultraviolet detector is working, the nanopore structure on the top surface of the gallium oxide film uses its area with a smaller curvature radius to geometrically confine the electron cloud at the light incident area, so that the electron cloud produces a strong charge separation effect.

[0029] When the gallium oxide solar-blind ultraviolet detector is working, the gallium oxide film scatters the incident light with the irregular surface or nanostructure at the nanopore structure to change the light propagation path, and greatly increases the light propagation path in the light incident area through multiple scattering; The light incident area uses the changing electric field at its nanopore to generate a vortex magnetic field, forming a Lorentz force to further affect the carrier motion trajectory, and at the same time uses a higher electric field intensity to increase the energy of the photoelectrons, thereby enhancing the photoelectric conversion efficiency. That is, when photons enter the photodetector, the nanopore accelerates the movement of the photoelectrons through the high-intensity electric field, making it easier for them to pass through the potential barrier of the energy band structure, thereby prompting the photons to be absorbed by higher energy bands, improving the photoelectric conversion efficiency, and thus improving the photocurrent and responsiveness of the detector, enhancing the detector's detection capability, and according to the simulation results, it does not affect the wavelength of the light wave.

[0030] The region of the nanopore structure with a smaller curvature radius is the edge or tip of the nanopore.

[0031] The nanopores are evenly arranged in rows and columns, and are blind holes with a depth of 180 nm, a spacing of 350 nm, and a radius of 80 nm.

[0032] The method for preparing a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure is used to prepare the above-mentioned detector, which is characterized by comprising the following steps: Step 1: Cleaning the substrate with acetone, anhydrous ethanol and deionized water in sequence under ultrasound; Step 2: Using metal organic chemical vapor deposition technology to grow a 300-1000 nm gallium oxide absorption layer on the substrate; Step 3: Use ion implantation technology to heavily dope the gallium oxide absorption layer with n-type, with a doping concentration of 1×10 18 cm -3 ; Step 4: Using electron beam lithography technology, prepare a mask structure with a pitch of 350 nm and a radius of 80 nm; Step 5: using an inductively coupled plasma etching method to etch nanopores with a depth of 180 nm; Step six: prepare metal electrodes using conventional photolithography technology.

[0033] Example: Combined with attachment Figure 1 In this embodiment, a gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure is formed by periodically arranging single nanopores as structural units. The detector structure includes a substrate (4), a gallium oxide film (3) placed on the surface of the substrate (4), a nanopore structure (2) generated by etching the surface of the gallium oxide film (3), and a metal electrode (1).

[0034] The comparative example of this embodiment is combined with the attached Figure 2 Description: This comparative example shows a gallium oxide solar-blind ultraviolet detector without an etching structure, wherein the detector comprises a substrate (3), a gallium oxide thin film (2) disposed on the surface of the substrate (3), and a metal electrode (1) disposed on the surface of the gallium oxide thin film (2).

[0035] Attachment Figure 3 The effect of changes in simulated structural parameters on the electric field strength is demonstrated, where the nanopore parameters under the optimal electric field strength are: depth of 180nm, spacing of 350nm, and radius of 80nm.

[0036] Attachment Figure 4 The following graphs compare the absorption rates of a bare gallium oxide film without electrodes, a gallium oxide film with electrodes but no nanopores, and a gallium oxide film with electrodes and nanopores. Within the 200-400nm wavelength range, the device with the surface structure exhibits a significantly enhanced absorption rate. Gallium oxide exhibits almost no absorption for wavelengths exceeding 275nm. Since electrodes also absorb incident light, the addition of Au electrodes also results in absorption beyond 275nm, with enhanced absorption in the ultraviolet region. By introducing this surface structure, the absorption rate can be significantly increased.

[0037] Attachment Figure 5The normalized magnetic field and electric field intensity distributions, light absorption power, and photogenerated carrier distribution of a solar-blind UV detector in an embodiment are shown. The periodic nanopore structure promotes a periodic electric field distribution and also enhances the electric field within the absorber layer compared to that without nanopores. Furthermore, energy from the processing side can be better introduced into the absorber layer.

[0038] Attachment Figure 6 The IV curves, responsivity curves, energy band diagrams, and wavelength-responsivity curves of the examples and comparative examples in the dark and at a 250nm UV wavelength are shown. The photocurrent of the device is significantly improved. In addition, the dark current of the device with the surface structure is also reduced, and the light-to-dark current ratio (PDCR) of the device reaches 2.14×10 8 (Figure (a)), an order of magnitude improvement. Due to the increase in photocurrent, the responsivity is also significantly improved, increasing by about 4.34 times (Figure (b)).

[0039] The above description of the present invention is exemplified in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as such non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure, characterized by: The invention comprises a substrate (4) and a gallium oxide film (3); the bottom surface of the gallium oxide film is in contact with the substrate, and the top surface of the gallium oxide film is a light incident area; a nanopore structure (2) formed by a plurality of periodically arranged nanopores is provided at the light incident area, and the nanopore structure is used to enhance the surface electric field and magnetic field of the semiconductor material of the gallium oxide film and increase the effective optical path length and lifetime of the incident photons.

2. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 1, characterized in that: A metal electrode (1) is provided on the top surface of the gallium oxide film beside the nanopore structure.

3. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 2, characterized in that: The material of the metal electrode is gold.

4. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 1, characterized in that: The nanopore structure is prepared by etching the surface of the gallium oxide film.

5. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 1, characterized in that: The substrate is made of aluminum oxide.

6. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 1, characterized in that: When the gallium oxide solar-blind ultraviolet detector is working, the nanopore structure on the top surface of the gallium oxide film uses its area with a smaller curvature radius to geometrically confine the electron cloud at the light incident area, so that the electron cloud produces a strong charge separation effect.

7. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 6, characterized in that: When the gallium oxide solar-blind ultraviolet detector is working, the gallium oxide film scatters the incident light with the irregular surface or nanostructure at the nanopore structure to change the light propagation path, and greatly increases the light propagation path in the light incident area through multiple scattering; The light incident area generates a vortex magnetic field with the changing electric field at its nanopore, forming a Lorentz force to further affect the carrier motion trajectory, and at the same time increases the energy of the photoelectrons with a higher electric field intensity, thereby enhancing the photoelectric conversion efficiency. That is, when photons enter the photodetector, the nanopore accelerates the movement of the photoelectrons through the high-intensity electric field, making it easier for them to pass through the potential barrier of the energy band structure, thereby prompting the photons to be absorbed by higher energy bands and improving the photoelectric conversion efficiency.

8. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 6, characterized in that: The region of the nanopore structure with a smaller curvature radius is the edge or tip of the nanopore.

9. The gallium oxide solar-blind ultraviolet detector based on an asymmetric surface-etched nanopore structure according to claim 6, characterized in that: The nanopores are evenly arranged in rows and columns, and the nanopores have a depth of 180 nm, a spacing of 350 nm, and a radius of 80 nm.

10. A method for preparing a solar-blind ultraviolet detector of gallium oxide based on an asymmetric surface-etched nanopore structure, used to prepare the detector of claim 9, characterized in that: The following steps are involved: Step 1: Cleaning the substrate with acetone, anhydrous ethanol and deionized water in sequence under ultrasound; Step 2: Using metal organic chemical vapor deposition technology to grow a 300-1000 nm gallium oxide absorption layer on the substrate; Step 3: Use ion implantation technology to heavily dope the gallium oxide absorption layer with n-type, with a doping concentration of 1×10 18 cm -3 ; Step 4: Using electron beam lithography technology, prepare a mask structure with a pitch of 350 nm and a radius of 80 nm; Step 5: using an inductively coupled plasma etching method to etch nanopores with a depth of 180 nm; Step six: prepare metal electrodes using photolithography technology.

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