Nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photoelectric detector and application thereof

Abstract

The invention belongs to the technical field of partial discharge ultraviolet detection, and particularly relates to a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photoelectric detector and application thereof. The invention discloses a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photoelectric detector, and the detector comprises an aluminum oxide substrate; the zinc gallate epitaxial layer grows on the aluminum oxide substrate through metal organic chemical vapor deposition; the lithium-doped p-type nickel oxide layer grows on the zinc gallate epitaxial layer through a pulse laser deposition technology; and the titanium / gold metal electrode layer is deposited on the lithium-doped p-type nickel oxide layer. The device has a high rectification ratio of 106, an ultralow dark current of 0.1 pA under a bias voltage of 6V, an excellent detection rate of 7.1 * 10 < 18 > Jones and an extremely low noise equivalent power of 2.56 * 10 <-19 > W / Hz < 1 / 2 >, so that the device becomes an ideal candidate material for partial discharge detection, security monitoring, environmental monitoring, space exploration and other applications.

Description

Technical Field

[0001] This invention belongs to the field of partial discharge ultraviolet detection technology, specifically relating to a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector and its application. Background Technology

[0002] With increasing voltage levels, power equipment discharge is a phenomenon that is difficult to completely avoid during normal operation of electrical equipment. Fault discharge is the most common form of gas discharge. When a conductor has a sharp point with a small radius of curvature, the local electric field strength exceeds the ionization field strength of the gas, causing electrons in the air to continuously gain and release energy. When electrons release energy, they release ultraviolet light, which can be used as a characteristic quantity for analyzing the discharge phenomenon. In this process, nitrogen, the main component of air, plays a major role, with its corresponding spectral range mostly between 280 and 400 nm, and a small portion below 280 nm, i.e., within the solar blind zone. This portion of solar ultraviolet radiation is almost completely depleted in the atmospheric ozone layer, so very little solar-blind ultraviolet light reaches the Earth's surface. Detecting this band has advantages such as low noise and high sensitivity.

[0003] Solar-blind ultraviolet detectors have attracted much attention due to their excellent dual-use potential, including deep ultraviolet imaging, ozone layer degradation assessment, forest fire monitoring, munitions interception, space exploration, and security. Early research on solar-blind ultraviolet detectors mainly focused on photodetection and electrochemical cells, particularly using vertically oriented p-aluminum gallium nitride / n-gallium nitride pn heterojunction nanowire electrolyte systems.

[0004] Schottky photodetectors are core components in optoelectronic circuit systems that enable radiation-to-charge conversion. Unlike traditional photodetectors, which are limited to a specific wavelength range, broadband photodetectors have achieved broad-spectrum detection capabilities from ultraviolet to infrared, which is crucial for applications such as optical imaging sensing, optical communication, and environmental monitoring. In recent years, broadband photodetector technology has made progress using various semiconductor materials. Gallium nitride (GaN) and aluminum gallium nitride (AlGaN) detectors have achieved significant breakthroughs in this field due to their excellent photoelectric properties. However, with increasing aluminum doping, AlGaN exhibits performance degradation and increased defects due to crystallinity issues. This limitation has prompted researchers to continuously search for new materials that can achieve stable and efficient deep ultraviolet (DUV) detection.

[0005] A major current challenge is that most broadband photodetectors cannot distinguish between different wavelengths and have a low light-to-dark-current ratio, which is particularly critical for applications requiring precise spectral information, such as astronomical detection and information storage. Therefore, the industry urgently needs photodetector devices that can cover a wide spectrum while distinguishing specific wavelengths. Breakthroughs in this area will drive leapfrog development in fields such as medical diagnostics, security systems, and advanced imaging technologies. Summary of the Invention

[0006] The present invention aims to at least solve one of the technical problems existing in the prior art or related technologies. To this end, a first aspect of the present invention provides a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector, comprising:

[0007] Alumina substrate;

[0008] A zinc gallate epitaxial layer is grown on the alumina substrate by metal-organic chemical vapor deposition;

[0009] A lithium-doped p-type nickel oxide layer is grown on the zinc gallate epitaxial layer by pulsed laser deposition technology;

[0010] A titanium / gold metal electrode layer is deposited on the lithium-doped p-type nickel oxide layer, wherein the titanium layer is closer to the lithium-doped p-type nickel oxide layer than the gold layer.

[0011] Wide-bandgap zinc gallate (ZnGa₂O₄) is considered an ideal candidate material for high-performance solar-blind ultraviolet detectors due to its controllable carrier concentration, tunable direct bandgap of 4.6-5.3 eV, and excellent structural and thermal stability. Currently, most solar-blind detection systems use zinc gallate crystals grown at temperatures above 700℃ to construct photoconductive devices, primarily planar photoconductive detectors and metal-semiconductor-metal (MSM) structures, and require an external power supply. Single-crystal zinc gallate detectors exhibit highly competitive response characteristics in the solar-blind ultraviolet band, while heterojunction structures can further improve detector sensitivity and response speed, especially in weak signal detection and self-powering—the junction interface electric field under illumination can effectively separate photogenerated electron-hole pairs.

[0012] Although zinc gallate / Si heterojunction photodetectors have been reported, their photoresponse performance is limited by the low rectification ratio in the visible light band due to significant lattice mismatch and unfavorable device structure (the radiation absorption rates of the two heterojunction materials are similar). Nickel oxide (NiO), as a wide-bandgap p-type oxide semiconductor with a voltage range of 3.2-3.8 eV, exhibits low-temperature crystallization. Combining NiO with zinc gallate can promote the separation and migration of photogenerated carriers. Furthermore, since both components of this heterojunction are oxides, it avoids the process limitations of device oxidation. Compared to amorphous thin films, epitaxially grown NiO / zinc gallate films offer significant advantages in fabricating high-performance ultraviolet detectors: the well-defined crystal structure minimizes interface states caused by lattice mismatch, ensuring stable device performance required for industrial applications. Therefore, this invention employs epitaxial NiO / zinc gallate films to construct a single-crystal pn heterojunction detector.

[0013] Meanwhile, this unipolar photodiode exhibits unique dual-mode operation: under forward bias, it displays a positive photoconductivity (PPC) effect across the entire spectrum; under reverse bias, it can simultaneously detect ultraviolet light via PPC and visible light via negative photoconductivity. This unique performance enables selective detection, with rectification ratios of 10 for ultraviolet and visible light, respectively. 5 The 74 provides an innovative solution for advanced photoelectric detection applications that require precise differentiation between solar blindness and visible light.

[0014] As a preferred embodiment, the growth conditions for the zinc gallate epitaxial layer of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector include: using triethylgallium, diethylzinc, and oxygen as precursors for gallium, zinc, and oxygen, respectively, with the molar fluxes of each precursor being:

[0015] Triethylgallium: (3.0-5.0)×10 -5 mol / min;

[0016] Diethylzinc: (2.5-4.0)×10 -5 mol / min;

[0017] Oxygen: (3.0-4.0)×10 -2 mol / min;

[0018] Optionally, the following conditions must be met: nitrogen is used as the main gas flow for metal-organic chemical vapor deposition, while high-purity argon is used as the carrier gas for triethylgallium and diethylzinc.

[0019] As a preferred embodiment, the growth conditions for the zinc gallate epitaxial layer of the aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector include:

[0020] The growth temperature is 700-800℃, the pressure is 20-30 Torr, and the growth time is 20-40 minutes.

[0021] As a preferred embodiment, the growth conditions for the lithium-doped p-type nickel oxide layer in the aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector include:

[0022] The deposition process uses a laser pulse frequency of 8-12Hz, a single pulse energy of 500-700mJ, and a laser energy density of 2-4J / cm³. 2 A total of 24,000-30,000 pulses;

[0023] The deposition rate of p-nickel oxide is

[0024] As a preferred embodiment, in the lithium-doped p-type nickel oxide layer of the aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector, lithium is doped at 0.5-2 wt%.

[0025] As a preferred embodiment, the aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector satisfies the following requirements:

[0026] The thickness of the zinc gallate epitaxial layer is 100-130 nm;

[0027] The thickness of the lithium-doped p-type nickel oxide layer is 130-170 nm;

[0028] The target-substrate distance is 50-70 mm;

[0029] In the titanium / gold metal electrode layer, the thickness of the titanium layer is 70-100nm, and the thickness of the gold layer is 15-30nm.

[0030] As a preferred embodiment, the aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector employs a physical tin metal mask to selectively coat the hetero interface, and then deposits titanium / gold metal electrodes on the thin film surface using an electron beam evaporation process within a vacuum coating system.

[0031] According to the present invention, the above-mentioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector has a photo-dark-current ratio >10 under 200-280nm solar-blind ultraviolet light irradiation. 5 It can reach 10 at a specific voltage. 8 .

[0032] According to the present invention, the alumina substrate of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector is a c-plane (0001) sapphire substrate.

[0033] The aforementioned nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector has 10 6 High rectification ratio, ultra-low dark current of 0.1pA at 6V bias, 7.1×10 18 Jones's exceptional detection rate and 2.56 × 10⁻⁶ -19 W / Hz 1 / 2 Its extremely low noise equivalent power makes it an ideal candidate material for applications such as partial discharge detection, security monitoring, environmental monitoring, and space exploration. Therefore, a second aspect of the present invention provides the application of the above-described nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector in the field of partial discharge detection.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] This invention successfully grows single-crystal zinc gallate on a sapphire substrate using metal-organic chemical vapor deposition (MOCVD) technology and innovatively introduces a nickel oxide / zinc gallate heterojunction to suppress dark current in the device, demonstrating its excellent solar-blind ultraviolet detection performance. To address the reproducibility and stability issues caused by material quality and crystallinity, this invention employs MOCVD technology to epitaxially grow a high-quality single-crystal zinc gallate film on a sapphire substrate. This material forms a heteroepitaxial relationship with the sapphire substrate, exhibiting a precise match between the sixth harmonic symmetry and the sapphire lattice planes. The MOCVD growth process on the sapphire substrate confirms the high crystallinity of zinc gallate, thereby achieving excellent Schottky characteristics: a significant barrier height of 1.23 eV, an ideality factor close to the ideal value (n≈1), and an oxygen vacancy concentration as low as 6.66%. These findings highlight the importance of film uniformity and crystallinity for optimizing the performance of Schottky photodiodes, opening new avenues for large-area fabrication of Schottky photodiodes. Zinc gallate-based photodiodes have shown significant application potential in solar-blind ultraviolet detection, with their unique dual-mode operating mechanism being particularly noteworthy: exhibiting positive photoconductivity under forward bias and achieving ultraviolet-visible selective detection under reverse bias, providing a multifunctional solution for high-performance photodetection. This device features 10... 6 High rectification ratio, ultra-low dark current of 0.1pA at 6V bias, 7.1×10 18 Jones's exceptional detection rate and 2.56 × 10⁻⁶ -19 W / Hz 1 / 2 Its extremely low noise equivalent power makes it an ideal candidate material for applications such as partial discharge detection, security monitoring, environmental monitoring, and space exploration. It exhibits excellent light-to-dark-current ratio, low dark current, fast response / recovery time, high responsivity, and detectivity. Research has confirmed the type II band arrangement of zinc gallate / nickel oxide, and the use of interleaved band diagrams to deeply analyze the internal physical processes of heterojunction devices has significantly improved the rectification ratio in the visible light band. This invention proposes to optimize zinc gallate-based detectors by utilizing the thermoelectric photoelectron effect (PPE) coupled with photon excitation, photo-induced pyroelectric polarization, and semiconductor properties—in the nickel oxide / zinc gallate system, the pyroelectric polarization charge generated by illumination can modulate the carrier dynamics in the junction region, enhancing recombination, separation, generation, and transport processes, thereby improving the performance of self-powered detectors. By constructing a heterojunction structure and utilizing the PPE effect, this research provides a new approach for developing fast-response, high-sensitivity deep ultraviolet detectors, promoting the advancement of photoelectric detection technology.

[0036] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0037] Figure 1 A schematic cross-sectional view of a layered structure for a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector is shown.

[0038] Figure 2 The photocurrent-to-dark current ratio of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector of Example 1 under 246 nm solar-blind ultraviolet illumination is shown.

[0039] Figure 3 The photoresponse results of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet detector of Example 1 for different wavelength light signals under different bias voltages (-7V, -10V, -13V) are shown.

[0040] Figure 4 The dark currents of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet detector and the single zinc gallate device of Example 1 under different bias voltages are shown. Detailed Implementation

[0041] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0042] In the embodiments and comparative examples of this invention, the process operations not specifically described are conventional techniques in the art and have little impact on the performance of the resulting products.

[0043] Example 1

[0044] This embodiment provides a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector. See structure below. Figure 1 The diagram shows a cross-sectional schematic of a layered structure for a nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector. It includes: a c-plane (0001) sapphire substrate; a zinc gallate epitaxial layer grown on the alumina substrate via metal-organic chemical vapor deposition; a lithium-doped p-type nickel oxide layer grown on the zinc gallate epitaxial layer via pulsed laser deposition; and a titanium / gold metal electrode layer deposited on the lithium-doped p-type nickel oxide layer, wherein the titanium layer is closer to the lithium-doped p-type nickel oxide layer than the gold layer.

[0045] High-quality zinc gallate epitaxial layers were grown on a c-plane (0001) sapphire substrate (alumina composition) using metal-organic chemical vapor deposition (MOCVD) with triethylgallium (TEGa), diethylzinc (DEZn), and oxygen as Ga, Zn, and O precursors, respectively. The molar fluxes of each precursor were: TEGa 4.2 × 10⁻⁶. -5 mol / min, DEZn 3.1×10 -5 mol / min, oxygen 3.6 × 10 -2 The MOCVD process used nitrogen as the main gas flow and high-purity argon as the carrier gas for both TEGa and DEZn. The growth temperature was set at 760℃ and the pressure at 25 Torr. After 30 minutes of growth, a zinc gallate epitaxial layer with a thickness of 115 nm was obtained.

[0046] At room temperature, with 6×10 -3 A lithium-doped (1 wt%) p-type nickel oxide layer was grown on an n-type zinc gallate film using pulsed laser deposition at an oxygen partial pressure of mbar. The deposition process employed a 10 Hz laser pulse frequency, a single pulse energy of 600 mJ, and a laser energy density of 3 J / cm². 2 A total of 27,000 pulses were generated. With the target-substrate distance set to 60 mm, the deposition rate of p-nickel oxide was... The thickness of the p-nickel oxide film was determined to be 150 nm by energy dispersive spectroscopy (EDX) and stylus profilometry.

[0047] After selectively depositing a film on a heterogeneous interface using a physical tin metal mask, a metal electrode (Au / Ti = 20 / 80 nm) is deposited on the thin film surface using an electron beam evaporation process in a vacuum deposition system. This process significantly improves the adhesion of the metal electrode.

[0048] Figure 2 The photo-dark current ratio of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector of Example 1 under 246nm solar-blind ultraviolet light illumination is shown, and it can be seen that the photo-dark current ratio reaches 10. 8 . Figure 2 In the diagram, "Dark" (the curve marked with "○") indicates dark-state test conditions, that is, the current-voltage characteristics of the device measured in a completely dark environment.

[0049] Figure 3 The photoresponse results of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet detector of Example 1 for different wavelength light signals under different bias voltages (-7V, -10V, -13V) are shown. It can be seen that it has good responsivity in the solar-blind ultraviolet region.

[0050] Figure 4 The dark currents of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet detector and the single zinc gallate device of Example 1 under different bias voltages are shown. It can be seen that the novel structure of the present invention can effectively suppress the photocurrent of the device and improve the detection of the device.

[0051] The zinc gallate thin film forms a heteroepitaxial relationship with the sapphire substrate, exhibiting a precise match between the six-harmonic symmetry and the sapphire lattice plane.

[0052] The MOCVD growth process on sapphire substrates confirmed the high crystallinity of zinc gallate, thereby achieving excellent Schottky characteristics: a significant barrier height of 1.23 eV, an ideal factor close to the ideal value (n≈1), and an oxygen vacancy concentration as low as 6.66%.

[0053] Experiments have verified that the device in Example 1 has 10 6 High rectification ratio, ultra-low dark current of 0.1pA at 6V bias, 7.1×10 18 Jones's exceptional detection rate and 2.56 × 10⁻⁶ -19 W / Hz 1 / 2 Extremely low noise equivalent power.

[0054] Test case

[0055] The following shows the dark current, responsivity, and detectivity performance of different device materials. The data are from scientific literature or obtained through conventional testing methods in the field.

[0056] Table 1

[0057] Device Materials Dark current (pA) Response time (A / W) Detectability (Jones) GaN / AlGaN 20 3.6 x 10 7 ]]> 6.53 x 10 18 ]]> Example 1 : NiO / ZnGa2O4 0.1 338 7.1 x 10 18 ]]> ITO / ZnGa2O4 / Pt 10 0.024 PtSe2 / Bi2Te3 / Si ~10 7 ]] 0.625 1.37 x 10 12 ]]> [PdSe2 / Ga2O3] ～100 0.123 1.63 x 10 13 ]] GeSe2 / Si ~10 7 ]] 0.325 2.57 x 10 13 ]] <![CDATA[Ga2O3]]> <![CDATA[10 6 ]]> 9.7 <![CDATA[9×10 13 ]]> <![CDATA[MoS2 / ZnGa2O4]]> 1 288 <![CDATA[4.9×10 18 ]]>

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector, characterized in that, include: Alumina substrate; A zinc gallate epitaxial layer is grown on the alumina substrate by metal-organic chemical vapor deposition; A lithium-doped p-type nickel oxide layer is grown on the zinc gallate epitaxial layer by pulsed laser deposition technology; A titanium / gold metal electrode layer is deposited on the lithium-doped p-type nickel oxide layer, wherein the titanium layer is closer to the lithium-doped p-type nickel oxide layer than the gold layer.

2. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The growth conditions for the zinc gallate epitaxial layer include: using triethylgallium, diethylzinc, and oxygen as precursors for gallium, zinc, and oxygen, respectively, with the following molar flow rates for each precursor: Triethylgallium: (3.0-5.0)×10 -5 mol / min; Diethylzinc: (2.5-4.0)×10 -5 mol / min; Oxygen: (3.0-4.0)×10 -2 mol / min; Optionally, the following conditions must be met: nitrogen is used as the main gas flow for metal-organic chemical vapor deposition, while high-purity argon is used as the carrier gas for triethylgallium and diethylzinc.

3. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The growth conditions for the zinc gallate epitaxial layer include: The growth temperature is 700-800℃, the pressure is 20-30 Torr, and the growth time is 20-40 minutes.

4. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The growth conditions for the lithium-doped p-type nickel oxide layer include: The deposition process uses a laser pulse frequency of 8-12Hz, a single pulse energy of 500-700mJ, and a laser energy density of 2-4J / cm³. 2 A total of 24,000-30,000 pulses; The deposition rate of p-nickel oxide is / pulse.

5. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The lithium-doped p-type nickel oxide layer contains 0.5-2 wt% lithium.

6. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The thickness of the zinc gallate epitaxial layer is 100-130 nm; The thickness of the lithium-doped p-type nickel oxide layer is 130-170 nm; The target-substrate distance is 50-70 mm; In the titanium / gold metal electrode layer, the thickness of the titanium layer is 70-100nm, and the thickness of the gold layer is 15-30nm.

7. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, After selectively depositing a film on the heterogeneous interface using a physical tin metal mask, titanium / gold metal electrodes are deposited on the thin film surface using an electron beam evaporation process in a vacuum deposition system.

8. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The photodetector exhibits a photocurrent-to-dark-current ratio >10 under 200-280nm solar-blind ultraviolet light irradiation. 5 .

9. The nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to claim 1, characterized in that, The alumina is c-face (0001) sapphire.

10. The application of the nickel oxide / zinc gallate heterojunction solar-blind ultraviolet photodetector according to any one of claims 1-9 in the field of partial discharge detection.

Images