Si-based gallium oxide avalanche photodetector, method of making same, and fire detection system

Abstract

The application discloses a Si-based avalanche photodetector, a preparation method thereof and a fire detection system. The detector comprises an n-type silicon substrate and layers arranged on the substrate in sequence. The buffer layer is used to relieve the lattice mismatch, and the energy band engineering is used to regulate the electric field, so that the avalanche multiplication is realized, and the deep ultraviolet detection sensitivity is improved. The device adopts MOCVD epitaxy and conventional semiconductor micro-nano processing technology, has strong compatibility and is easy to mass produce. The fire detection system carrying the detector has signal conditioning, multi-stage filtering, state judgment and MQTT wireless communication functions, and can realize real-time monitoring of the flame state. The application is oriented to the solar blind ultraviolet detection demand, and is especially suitable for early fire warning in industrial, building and other scenes.

Description

Technical Field

[0001] This invention relates to the field of deep ultraviolet photodetectors, and more particularly to a Si-based... Avalanche photodetector, its preparation method and fire detection system. Background Technology

[0002] The deep ultraviolet (200nm-280nm) wavelength range is affected by absorption by the atmospheric ozone layer, creating a "solar blind zone" in the ground environment. Based on this characteristic, deep ultraviolet photodetectors are immune to solar radiation interference in ground applications and have extremely high signal-to-noise ratios. Especially in the field of early fire warning, deep ultraviolet detectors are an ideal choice for fire detection because flames emit weak deep ultraviolet signals.

[0003] In the deep ultraviolet detector material system, gallium oxide (GaN) With an ultrawide bandgap of 4.4-5.3 eV, it can directly respond to solar-dead ultraviolet light without doping. Compared to GaN, SiC, and ZnO, It possesses irreplaceable advantages such as a higher breakdown electric field, superior thermal stability, and simpler thin film fabrication process. However, As a novel semiconductor, its optoelectronic devices still face key bottlenecks in application: target signals are extremely weak in scenarios such as early-stage fires, and conventional methods... Photodetectors lack an internal gain mechanism, have limited responsivity, and are prone to false negatives.

[0004] Avalanche photodetectors (APDs) can multiply their internal current through collisional ionization of charge carriers, which is an effective way to improve the sensitivity of weak light detection. However, in current technologies, the fabrication... Avalanche detectors typically use insulating substrates, resulting in poor heat dissipation and inability to integrate with existing Si-based readout circuits, thus limiting their large-scale application. Silicon substrates offer advantages such as low cost, high thermal conductivity, and compatibility with CMOS processes, but heterogeneous growth on Si substrates... Achieving a stable avalanche multiplication effect still faces challenges related to lattice mismatch and interface defects. Therefore, a Si-based gallium oxide avalanche photodetector is urgently needed to address the difficulties in detecting weak deep ultraviolet signals and the low integration density of Si-based technologies in existing methods. Summary of the Invention

[0005] To address the aforementioned issues, this application discloses a Si-based gallium oxide avalanche photodetector, its fabrication method, and a fire detection system, aiming to effectively improve the performance and sensitivity of deep ultraviolet photodetectors and enable real-time monitoring of flames.

[0006] To achieve the above objectives, the first technical solution of this application discloses a Si-based gallium oxide avalanche photodetector, comprising:

[0007] n-type silicon substrate;

[0008] In addition, an ultra-wide bandgap semiconductor thin film is disposed on the n-type silicon substrate, the ultra-wide bandgap semiconductor thin film comprising sequentially stacked... Layers and Layer, the The layer is disposed on the n-type silicon substrate and the Between layers.

[0009] Furthermore, the n-type silicon substrate is an n-type double-polished silicon substrate.

[0010] Furthermore, the aforementioned The thickness of the layer is 15–25 nm, the The thickness of the layer is 200–300 nm.

[0011] Furthermore, the ultrawide bandgap semiconductor thin film is prepared by the following method:

[0012] Provide n-type silicon substrates;

[0013] Metal-organic chemical vapor deposition was used to grow on the n-type silicon substrate. layer;

[0014] Using metal-organic chemical vapor deposition, in the Layer growth layer.

[0015] Furthermore, the growth of the described Layers and During the layering process, the growth temperature is 650–850℃, the oxygen flow rate is 80 sccm, and the reaction chamber pressure is 35–100 Torr.

[0016] Furthermore, the growth of the described During the layering process, a trimethylgallium source and a trimethylaluminum source are introduced; the layer is then grown. During the layering process, a trimethylgallium source is introduced.

[0017] The second technical solution of this application discloses a method for fabricating a Si-based gallium oxide avalanche photodetector as described in the first technical solution, comprising:

[0018] Regarding the The layers are photolithographically and etched to form device mesas;

[0019] In the Electrodes are fabricated on the surface of the layer away from the n-type silicon substrate and on the surface of the n-type silicon substrate away from the ultra-wide bandgap semiconductor thin film.

[0020] Furthermore, the etching employs inductively coupled plasma etching, and the etching gas includes... And Ar.

[0021] The third technical solution of this application discloses a fire detection system, including:

[0022] The photosensitive module includes a Si-based gallium oxide avalanche photodetector as described in the first technical solution, used to convert flame radiation into an electrical signal;

[0023] A signal conditioning module, connected to the photosensitive sensor module, is used to convert the electrical signal into a voltage signal;

[0024] The data acquisition and processing module, connected to the signal conditioning module, is used to digitally acquire and filter the voltage signal and determine whether a flame exists.

[0025] A human-computer interaction module, connected to the data acquisition and processing module, is used to display the judgment result; and:

[0026] A remote communication module is connected to the data acquisition and processing module and is used for remotely reporting data.

[0027] Furthermore, the data acquisition and processing module includes a 24-bit ADC and a microcontroller. The microcontroller is used to sequentially perform median filtering, IIR low-pass filtering, and moving average filtering on the digitized signal, and determine whether there is a flame based on the comparison result between the filtered signal and a preset threshold.

[0028] Beneficial effects

[0029] 1. For Si-based gallium oxide avalanche photodetectors, this invention employs an n-type silicon substrate and sequentially sets [the following structures] on it. Layers and Layers, forming / Heterogeneous structure. Due to With more A wider bandgap, in A barrier layer is formed between the absorption region and the n-type silicon substrate, which effectively prevents electron transport towards the substrate; simultaneously, ultraviolet light... The electron-hole pairs are absorbed in the absorption layer, and the charge carriers are then injected into the high electric field. Collision ionization occurs in the region, resulting in avalanche multiplication. Therefore, this detector can achieve an internal gain on the order of 10⁶ even under weak deep ultraviolet signals, solving the problem of conventional... The technical problems of photodetectors include a lack of internal gain and limited responsivity.

[0030] because The introduction of the layer on the silicon substrate and A buffer transition layer is formed between them, which alleviates the lattice mismatch between silicon and gallium oxide and reduces the interface defect density. Thus, while ensuring the stability of the avalanche multiplication effect, Si-based... The fabrication of vertical structure devices allows the detector to be integrated with existing Si-based CMOS readout circuits, and fully utilizes the advantages of low cost and high thermal conductivity of silicon substrates.

[0031] In addition, due to and All of them have an ultra-wide bandgap of 4.4-5.3 eV. The detector has a selective response to solar blind ultraviolet light in the 200 nm–280 nm region, while having almost no response to sunlight, thus achieving an extremely high signal-to-noise ratio in the surface environment, and is particularly suitable for the detection of deep ultraviolet radiation from flames.

[0032] 2. Regarding the fabrication method of Si-based gallium oxide avalanche photodetectors, this invention employs metal-organic chemical vapor deposition to grow them in situ on an n-type silicon substrate. Layers and The two layers are deposited continuously using the same growth system, resulting in a dense interface and uniform elemental distribution between them. This avoids severe defect recombination at the heterogeneous interface, which helps reduce device dark current and improve avalanche multiplication stability.

[0033] In device-level fabrication, inductively coupled plasma etching is used to... The layer is etched with a mesa and then sputtered using magnetron sputtering. Ti / Pt / Au electrodes are fabricated on the surface of the layer away from the substrate and on the surface of the substrate away from the thin film, forming good ohmic contacts and vertical conductive channels. This fabrication process is compatible with existing Si-based semiconductor processes, which is beneficial for large-scale production and reduces manufacturing costs.

[0034] 3. For the fire detection system, the fire detection system provided by the present invention uses the above-mentioned Si-based gallium oxide avalanche photodetector as the photosensitive sensing module. By utilizing the detector's high sensitivity response to weak deep ultraviolet flame radiation, combined with a transimpedance amplifier, a 24-bit ADC, and a hardware 50 / 60 Hz filter, high-precision and low-noise acquisition of weak photocurrent signals is achieved.

[0035] Because the system employs a multi-level digital filtering algorithm that combines median filtering, IIR low-pass filtering, and moving average filtering, and is coupled with a flame detection state machine and hysteresis mechanism, it can effectively suppress random environmental noise and transient interference, reduce false alarm rate and missed alarm rate, and improve the reliability of fire early warning.

[0036] In addition, the system uses OLED to display the local status and remotely reports the judgment results and real-time data to the IoT cloud platform via the MQTT protocol, realizing distributed and real-time monitoring of the flame status and meeting the needs of early fire warning for response speed and remote management. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 Provided in the embodiments of the present invention and XRD pattern;

[0039] Figure 2 The Si / provided in the embodiments of the present invention / EDS plot;

[0040] Figure 3 This is a schematic diagram of a Si-based gallium oxide avalanche photodetector provided in an embodiment of the present invention;

[0041] Figure 4 The IV curve and corresponding gain curve of the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention;

[0042] Figure 5 IV curves of different light intensities for a Si-based gallium oxide avalanche photodetector provided in an embodiment of the present invention;

[0043] Figure 6 The responsivity of the Si-based gallium oxide avalanche photodetector with different light intensities provided in the embodiments of the present invention;

[0044] Figure 7 The noise current and detectivity of a Si-based gallium oxide avalanche photodetector with different light intensities are shown in the embodiments of the present invention; wherein (left) represents the noise current and (right) represents the detectivity with different light intensities.

[0045] Figure 8 The IT stability diagram of a Si-based gallium oxide avalanche photodetector provided in an embodiment of the present invention;

[0046] Figure 9 The image shows the response time curve of a single cycle of a Si-based gallium oxide avalanche photodetector provided in an embodiment of the present invention.

[0047] Figure 10 A flowchart illustrating the application of a Si-based gallium oxide avalanche photodetector in fire detection, provided as an embodiment of the invention. Detailed Implementation

[0048] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0049] The first embodiment of this application discloses a Si-based gallium oxide avalanche photodetector, comprising: an n-type silicon substrate; and an ultra-wide bandgap semiconductor thin film disposed on the n-type silicon substrate. The ultra-wide bandgap semiconductor thin film includes... Layers and Layer, the The layer is disposed on the n-type silicon substrate and the Between layers.

[0050] The "n-type silicon substrate" provides mechanical support and conductive channels for the device and serves as the lattice basis for epitaxial growth. In a preferred embodiment, the n-type silicon substrate is an n-type double-polished silicon substrate, meaning both sides are polished to reduce surface roughness and nucleation defects during epitaxial growth.

[0051] The term "ultra-wide bandgap semiconductor thin film" refers to a semiconductor material thin film with a bandgap greater than 3.4 eV. In this invention, it specifically refers to... Layers and The thin film is integrally deposited on an n-type silicon substrate, forming a Si / / Heterogeneous structure. Due to The band gap is approximately 4.8-4.9 eV. The band gap increases with increasing Al content (up to 5.3 eV or more), and both are located in the solar blind zone (200 nm-280 nm), making the detector almost unresponsive to sunlight, but highly selective to deep ultraviolet signals from flame radiation.

[0052] The " The "layer" simultaneously acts as a buffer layer and an avalanche zone. On the one hand, because the Al-O bond length is closer to the Si-O bond length than the Ga-O bond length, Layer on silicon substrate and It acts as a lattice transition and stress buffer between silicon and... Interface defects caused by lattice mismatch (approximately -22%) and differences in thermal expansion coefficients reduce the interface state density, thereby suppressing dark current. On the other hand, due to... Having more With a wider bandgap, the layer can form a high electric field region when the device is reverse biased. Photogenerated carriers entering the region undergo avalanche multiplication through collisional ionization, generating internal current gain.

[0053] In a preferred embodiment, the In this layer, the value of X ranges from 0.1 to 0.5, and the thickness is 15-25 nm (preferably about 20 nm). If X is too small, the buffering and barrier effects are insufficient; if X is too large, the lattice mismatch will be exacerbated, and the growth difficulty will increase. If the thickness is less than 15 nm, it will be difficult to form a continuous buffer layer; if it is greater than 25 nm, the series resistance will increase, and the avalanche electric field distribution may deviate from the optimal state.

[0054] The " The "layer" primarily serves as a light absorption region. Ultraviolet light from the solar blind zone is absorbed in this layer, generating electron-hole pairs. Because... Its direct bandgap characteristics and ultra-wide bandgap allow for extremely high absorption coefficients in the solar blind region, enabling sufficient light absorption even with relatively thin thicknesses. In a preferred embodiment, the... The thickness of the layer is 200-300 nm (preferably about 250 nm). If the thickness is too thin, the light absorption will be insufficient and the quantum efficiency will be reduced; if the thickness is too thick, the transport distance of photogenerated carriers before reaching the avalanche region will increase, the recombination probability will increase, and the device capacitance will increase, which is not conducive to high-speed response.

[0055] The The layer is disposed on the n-type silicon substrate and the Between the layers, a sandwich structure is formed. During device operation, the top electrode (located in...) A reverse bias is applied between the surface of the layer (away from the n-type silicon substrate) and the bottom electrode (located on the surface of the n-type silicon substrate away from the ultra-wide bandgap semiconductor film). Deep ultraviolet light from Incident on one side of the layer, in Photogenerated carriers are generated within the layer; electrons drift towards the n-type silicon substrate under the influence of the electric field and enter the high electric field. Impact ionization occurs behind the layer, resulting in avalanche multiplication; simultaneously... The heterojunction barrier of the layer effectively prevents electrons from being injected into the silicon substrate, thus limiting the multiplication process mainly to the layer. Within the layer, this improves the stability of the gain multiplication and suppresses interface leakage.

[0056] In a further embodiment, the ultrawide bandgap semiconductor thin film is preferably grown using a metal-organic chemical vapor deposition (MOCVD) method, including providing an n-type silicon substrate; and growing the semiconductor film on the n-type silicon substrate using a metal-organic chemical vapor deposition method. Layer; Metal-organic chemical vapor deposition method is used in the layer; growth layer.

[0057] In a specific preferred embodiment, the preparation method includes:

[0058] An n-type silicon substrate is provided and ultrasonically cleaned in acetone, isopropanol, and deionized water in sequence, and then dried with nitrogen gas.

[0059] The substrate is placed on the tray of the MOCVD reaction chamber, evacuated to a baseline vacuum and leak-checked. A carrier gas (such as high-purity N2 or Ar) is introduced, and the exhaust gas treatment is confirmed to be normal. The temperature is raised to the bake temperature (300-400℃) to pretreat the substrate, removing adsorbed oxygen and organic matter from the surface. The temperature is then raised to the growth temperature (650–850℃, preferably 750-800℃), and O2 (flow rate approximately 80 sccm) and a metal-organic source are introduced. Growth begins. During the deposition process, trimethylgallium (TMGa) and trimethylaluminum (TMAl) were simultaneously introduced as gallium and aluminum sources, respectively. The X value was controlled by adjusting the molar flow ratio of the two sources, and the deposition time was approximately 53 seconds. During the deposition process, only TMGa is introduced as the gallium source, and the deposition time is approximately 660 seconds. The reaction chamber pressure is controlled at 35-100 Torr (preferably 50-80 Torr).

[0060] After growth, the film is annealed in situ at 750-950℃ (preferably 800-900℃) for 30 minutes to improve the crystallization quality and interface compactness of the film. Finally, it is cooled and removed.

[0061] Optionally, the ultrawide bandgap semiconductor thin film can also be prepared using methods such as pulsed laser deposition (PLD), molecular beam epitaxy (MBE), or atomic layer deposition (ALD). When using PLD, the following methods can be selected: Ceramic targets and Composite targets are deposited in an O2 atmosphere at 600–750°C; when using MBE, solid Ga, Al and radio frequency oxygen plasma sources can be used to grow at higher vacuum levels to obtain steeper interfaces.

[0062] The second embodiment of this application discloses a method for fabricating a Si-based gallium oxide avalanche photodetector; comprising: processing the... The layer undergoes photolithography and etching to form the device mesa; in the... Electrodes are fabricated on the surface of the layer away from the n-type silicon substrate and on the surface of the n-type silicon substrate away from the ultra-wide bandgap semiconductor thin film.

[0063] In one embodiment, the device-level fabrication method includes:

[0064] Photolithography: After growth and The substrate is baked at 110°C for 15 minutes on a heated stage to remove surface moisture. Subsequently, photoresist (e.g., positive photoresist, spin-coating speed 3000–5000 rpm) is applied, followed by baking at 95°C for 90 seconds, exposure (e.g., 8.8 seconds), development (e.g., 45 seconds), rinsing with deionized water, and drying with nitrogen to form an etching mask. It should be noted that the baking temperature, exposure, and development times described above can be conventionally adjusted according to the photoresist type and light intensity, and are not intended to limit the essential technical features of this invention.

[0065] Etching: After photolithography, the back of the substrate is coated with silicone oil to fix it to the tray. Inductively Coupled Plasma (ICP) etching is performed to induce a thermal reaction. The tray is then placed into the reaction chamber and evacuated. The etching gas used is... With Ar (e.g., BCl3 flow rate 10-50 sccm, Ar flow rate 5-20 sccm), source power 500 W, bias power 100 W, etching time approximately 230 seconds, to remove excess... This forms the device mesa. Alternatively, a Cl2 / Ar mixture can be used as the etching gas, or reactive ion etching (RIE) and wet etching (such as hot phosphoric acid or molten KOH) can be used as alternatives. After etching, the substrate is immersed in an alcohol solution to remove the back silicone oil and then dried with nitrogen.

[0066] Photoresist removal and overlay: The etched substrate is immersed in acetone to remove the photoresist (immersion time is, for example, one day, or ultrasonic assistance can be used to shorten the time). It is then cleaned sequentially with acetone and isopropanol, followed by overlay photolithography of the electrode patterns. The overlay process includes: baking at 110°C for 15 minutes, spin-coating photoresist, baking at 95°C for 90 seconds, exposure (e.g., 3 seconds), post-baking at 115°C for 60 seconds, bare exposure (e.g., 43 seconds), development (e.g., 18 seconds), rinsing with deionized water, and drying with nitrogen.

[0067] Electrode fabrication: Electrode fabrication was performed using magnetron sputtering. Ti / Pt / Au electrodes are deposited on the surface of the layer away from the n-type silicon substrate and on the surface of the n-type silicon substrate away from the ultra-wide bandgap semiconductor thin film, respectively. In a preferred embodiment, the Ti layer has a thickness of 10-50 nm and serves as an adhesion layer and ohmic contact layer; the Pt layer has a thickness of 20-100 nm and serves as a diffusion barrier layer; the Au layer has a thickness of 100-300 nm and serves as a conductive and protective layer. Optionally, the electrode material can also adopt a composite structure such as Ti / Au, Ni / Au, Cr / Au, or ITO, and the sputtering power, gas pressure, and time can be conventionally adjusted according to the film thickness requirements.

[0068] The third embodiment of this application discloses a fire detection system, which includes: a photosensitive sensing module, a signal conditioning module, a data acquisition and processing module, a human-computer interaction module, and a remote communication module.

[0069] The photosensitive sensing module includes the aforementioned Si-based gallium oxide avalanche photodetector. Under deep ultraviolet light irradiation from a flame, the detector generates a weak photocurrent (typically in the pA to nA range).

[0070] The signal conditioning module includes a transimpedance amplifier (TIA) for converting the weak photocurrent output by the detector into an analog voltage signal. Because the detector has avalanche gain, the feedback resistor of the TIA can be matched to the gain level to optimize the signal-to-noise ratio.

[0071] The data acquisition and processing module includes a 24-bit analog-to-digital converter (ADC) and a microcontroller (MCU). The ADC digitizes the analog voltage signal at a sampling rate of 20 SPS (Samples Per Second) and incorporates a built-in hardware 50 / 60Hz suppression filter to eliminate power frequency interference. The MCU reads the ADC data via an SPI interface, converting the raw digital values ​​into voltage and photocurrent values. Subsequently, the MCU sequentially performs median filtering (removing impulse noise), IIR low-pass filtering (suppressing high-frequency noise), and moving average filtering (smoothing baseline drift) on the voltage signal to obtain a stable filtered voltage. The flame detection state machine determines the presence of a flame based on a comparison between the filtered voltage and a preset threshold, combined with duration confirmation (e.g., exceeding the threshold for 3 consecutive seconds) and a hysteresis mechanism (e.g., a 10%-20% difference between the upper and lower thresholds to prevent critical jitter). This multi-level filtering and state machine mechanism effectively distinguishes between real flame signals and transient environmental interference (such as electric arcs and lightning), significantly reducing the false alarm rate.

[0072] The human-computer interaction module includes an OLED display screen, which is used to display the flame determination result, photocurrent value and equipment status locally in real time.

[0073] The remote communication module reports the judgment results and real-time data to the IoT cloud platform via the MQTT protocol, enabling remote monitoring and multi-point networking. The communication carrier can be Wi-Fi, 4G / 5G, or LoRa, selected according to the on-site network environment.

[0074] The technical solutions and effects of this application will be described in detail below through specific embodiments.

[0075] Example 1: Fabrication of an ultrawide bandgap semiconductor.

[0076] 1) Place the prepared substrate in acetone, isopropanol, and deionized water in sequence to clean it, and then dry it with nitrogen gas.

[0077] 2) Place the substrate on the tray, insert it into the reaction chamber, close the chamber, evacuate to a basic vacuum, and check for leaks. Introduce carrier gas and confirm that the exhaust gas treatment is functioning correctly. Heat to the bake temperature for substrate pretreatment (300-400℃), then heat to the growth temperature (650-850℃, O2 flow rate 80, pressure 35-100 Torr), introduce TMGa and TMAI sources, and deposit for 53 seconds. Then anneal in situ at 750-950℃ for 30 minutes.

[0078] 3) Keeping the substrate in the reaction chamber, continue heating to 800℃, introducing only the TMGa source, and deposit for 660 seconds. Then, anneal in situ at 750-950℃ for 30 minutes. Finally, cool to room temperature to obtain Si / / Ultra-wide bandgap semiconductor thin films with a specific structure.

[0079] like Figure 1 The ultra-wide bandgap semiconductor provided in the embodiments of the present invention has a β phase The diffraction peaks corresponding to the PDF card indicate a monoclinic crystal structure. Specifically (It is a monoclinic crystal system), indicating that the thin film has good crystallization.

[0080] like Figure 2 As shown, the Si / provided in the embodiments of the present invention / Cross-sectional EDS indicates the formation of a layer grown on silicon via MOCVD. and The thin film is very dense, and the elements are evenly distributed. It can be clearly seen that... The layer is approximately 20 nm thick. The layer is approximately 250 nm.

[0081] Example 2: Fabrication and Performance Testing of a Si-based Gallium Oxide Avalanche Photodetector

[0082] Preparation method:

[0083] 1) The final growth and The substrate was first baked at 110°C for 15 minutes on a heating stage. It was then placed in a spin coater, three drops of photoresist were added and applied, baked at 95°C for 90 seconds, exposed for 8.8 seconds, developed for 45 seconds, rinsed with deionized water for 4 seconds, and finally dried with a nitrogen gun.

[0084] 2) After photolithography, the substrate is coated with silicone oil on the back and placed on a tray. The III-V inductively coupled plasma etching machine is warmed up first. The tray is placed into the chamber, a vacuum is drawn, and the tray is then sent into the reaction chamber. BCl3 gas and Ar are used, with a source power of 500 W and a bias power of 100 W. After etching for 230 seconds, excess gallium oxide can be removed. Finally, the tray is purged and removed. The substrate on the tray is immersed in an alcohol solution to remove the silicone oil on the back of the substrate and then dried with a nitrogen gun.

[0085] 3) After etching, immerse the substrate in acetone for one day to remove the photoresist; then clean it with acetone and isopropanol in sequence before overlaying the electrode pattern. First, bake the substrate at 110°C for 15 minutes, place it in a spin coater, add three drops of photoresist and coat it, bake at 95°C for 90 seconds, expose for 3 seconds, bake at 115°C for 60 seconds, expose bare for 43 seconds, develop for 18 seconds, and finally place it in an ionized water solution to remove the developer, and finally dry it with a nitrogen gun.

[0086] 4) After overlay etching, Ti / Pt / Au electrodes are deposited on the top of the gallium oxide substrate and the back of the n-type double-polished silicon substrate using magnetron sputtering to obtain the Si-based gallium oxide avalanche photodetector.

[0087] Performance testing:

[0088] like Figure 3 As shown, the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention mainly consists of five parts: a Si back electrode (approximately 200-300 nm), an n-type double-polished Si substrate, Layer (around 15-35nm) Layer (around 200-300 nm). Top electrode of the layer (around 200-300 nm).

[0089] like Figure 4 , Figure 5 As shown, the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention has an ultra-low dark current, with the dark current level remaining below 10 before a reverse bias of 30 V. -14 The photocurrent of this device increases continuously with increasing light intensity, reaching the order of A. At a wavelength of 254 nm and a light intensity of 1 μW / cm², the photocurrent continues to increase. 2 It exhibits good performance under ultraviolet light irradiation, with a photocurrent reaching 10 at a reverse bias of 43 V. -6 At the A-order level, the gain can reach 8.6 × 10⁻⁶. 6 .

[0090] like Figure 6 , Figure 7As shown, the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention operates at a wavelength of 254 nm and a current of 1 μW / cm². 2 It exhibits high detectivity and responsivity under varying light intensity, with a responsivity reaching 2.09 × 10⁻⁶. 4 A / W. Noise equivalent power (NEP) is a key indicator characterizing the sensitivity of a photodetector. The formula can be expressed as: Where i and B represent the noise current and bandwidth, respectively. The detectivity at different light intensities, calculated using the noise current, is shown at a frequency of 100 Hz and a light intensity of 1 μW / cm². 2 The detection rate reached 1.9×10⁻⁶. 14 Jones.

[0091] like Figure 8 As shown, the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention exhibits very stable performance within 900 seconds and shows virtually no attenuation under prolonged illumination.

[0092] like Figure 9 As shown, the Si-based gallium oxide avalanche photodetector provided in the embodiments of the present invention... and The response times are 680 microseconds and 710 microseconds respectively, and their rapid response time will be crucial for future practical applications.

[0093] like Figure 10 As shown, an embodiment of the present invention provides a flame detection system based on a Si-based gallium oxide avalanche photodetector, comprising: a photosensor module, a signal conditioning module, a data acquisition and processing module, a human-machine interaction module, and a remote communication module. The specific steps are as follows:

[0094] Step 1: The photosensitive material generates a photocurrent under flame radiation, which is converted into an analog voltage signal by a transimpedance amplifier;

[0095] Step 2: The 24-bit ADC digitizes the analog voltage signal at a sampling rate of 20 SPS, while using a hardware 50 / 60Hz suppression filter to eliminate power frequency interference.

[0096] Step 3: The microcontroller reads the ADC sampling data through the SPI interface and converts the raw digital values ​​into voltage and photocurrent values;

[0097] Step 4: The voltage signal is sequentially filtered through median filtering, IIR low-pass filtering, and moving average filtering to obtain a stable filtered voltage;

[0098] Step 5: The flame detection state machine determines whether a flame exists based on the comparison between the filtered voltage and the preset threshold, combined with the duration confirmation and hysteresis mechanism.

[0099] Step 6: The judgment results and real-time data are displayed locally on the OLED screen, and simultaneously reported remotely to the IoT cloud platform via the MQTT protocol to achieve real-time monitoring of the flame status.

[0100] As shown above, the Si-based gallium oxide avalanche photodetector provided by this invention has excellent performance and a fast response time. Furthermore, the flame detection system based on the Si-based gallium oxide avalanche photodetector can monitor the flame status in real time.

[0101] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A Si-based gallium oxide avalanche photodetector, characterized in that, include: n-type Si substrate; In addition, an ultra-wide bandgap semiconductor thin film is disposed on the n-type silicon substrate, the ultra-wide bandgap semiconductor thin film comprising sequentially stacked... Layers and Layer, the The layer is disposed on the n-type silicon substrate and the Between layers.

2. The Si-based gallium oxide avalanche photodetector according to claim 1, characterized in that, The n-type silicon substrate is an n-type double-polished silicon substrate.

3. The Si-based gallium oxide avalanche photodetector according to claim 1, characterized in that, The The thickness of the layer is 15-25 nm, the The thickness of the layer is 200-300 nm.

4. The Si-based gallium oxide avalanche photodetector according to claim 1, characterized in that, The ultrawide bandgap semiconductor thin film is prepared by the following method: Provide n-type silicon substrates; Metal-organic chemical vapor deposition was used to grow on the n-type silicon substrate. layer; Using metal-organic chemical vapor deposition, in the Layer growth layer.

5. The Si-based gallium oxide avalanche photodetector according to claim 4, characterized in that, The growth described Layers and During the layering process, the growth temperature is 650–850℃, the oxygen flow rate is 80 sccm, and the reaction chamber pressure is 35–100 Torr.

6. The Si-based gallium oxide avalanche photodetector according to claim 4, characterized in that, The growth described During the layering process, a trimethylgallium source and a trimethylaluminum source are introduced; the layer is then grown. During the layering process, a trimethylgallium source is introduced.

7. A method for fabricating a Si-based gallium oxide avalanche photodetector as described in claim 1, characterized in that, include: Regarding the The layers are photolithographically and etched to form device mesas; In the Electrodes are fabricated on the surface of the layer away from the n-type silicon substrate and on the surface of the n-type silicon substrate away from the ultra-wide bandgap semiconductor thin film.

8. The preparation method according to claim 7, characterized in that, The etching is performed using inductively coupled plasma etching, and the etching gas includes... And Ar.

9. A fire detection system, characterized in that, include: A photosensitive sensing module, including a Si-based gallium oxide avalanche photodetector as described in any one of claims 1-6, is used to convert flame radiation into an electrical signal; A signal conditioning module, connected to the photosensitive sensor module, is used to convert the electrical signal into a voltage signal; The data acquisition and processing module, connected to the signal conditioning module, is used to digitally acquire and filter the voltage signal and determine whether a flame exists. A human-computer interaction module, connected to the data acquisition and processing module, is used to display the judgment result; as well as: A remote communication module is connected to the data acquisition and processing module and is used for remotely reporting data.

10. The fire detection system according to claim 9, characterized in that, The data acquisition and processing module includes a 24-bit ADC and a microcontroller. The microcontroller is used to sequentially perform median filtering, IIR low-pass filtering, and moving average filtering on the digitized signal, and determine whether there is a flame based on the comparison result between the filtered signal and a preset threshold.

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