A barium titanate-gallium oxide heterojunction pyroelectric photodetector and a preparation method thereof

Abstract

This invention discloses a barium titanate / gallium oxide heterojunction pyroelectric photodetector and its fabrication method, comprising: a substrate, wherein a gallium oxide light-absorbing layer is disposed on the substrate, the thickness of the gallium oxide light-absorbing layer being 5 nm-500 nm, and the crystal phase being any one of α phase, β phase, γ phase, δ phase, and ε phase; a barium titanate pyroelectric layer is disposed on the gallium oxide light-absorbing layer, the thickness of the barium titanate pyroelectric layer being 5 nm-100 nm, and the crystal phase being tetragonal; a first electrode is disposed on the upper surface of the gallium oxide light-absorbing layer; and a second electrode is disposed on the upper surface of the barium titanate pyroelectric layer. This invention constructs a barium titanate / gallium oxide heterojunction, utilizing the gallium oxide layer to efficiently absorb solar-blind ultraviolet light, while simultaneously coupling the pyroelectric effect of the barium titanate layer with the photovoltaic effect of the heterojunction, achieving effective separation and transport of photogenerated carriers, enabling the device to operate at zero bias voltage, and possessing advantages such as self-powered operation, high responsivity, and fast response.

Description

Technical Field

[0001] This invention relates to a barium titanate and gallium oxide heterojunction pyroelectric photodetector and its fabrication method, belonging to the field of photoelectric detection technology. Background Technology

[0002] Solar-blind deep ultraviolet photodetectors have important applications in fields such as flame early warning, corona discharge monitoring, and secure communication. Traditional solar-blind detection materials such as silicon require complex filters, while wide bandgap alloys such as AlGaN and MgZnO face challenges such as compositional inhomogeneity, lattice mismatch, and epitaxial growth difficulties. Ultra-wide bandgap semiconductor β-gallium oxide (β-Ga2O3) has become an ideal candidate material due to its intrinsic solar-blind absorption (~260 nm) and ease of substrate fabrication.

[0003] However, single gallium oxide devices suffer from drawbacks such as high dark current and slow response speed, and introducing heterojunctions is a common improvement strategy. Existing gallium oxide heterojunctions (such as those combined with NiO, GaN, ZnO, etc.) generally suffer from defects such as large band mismatch, high interface defect density, difficulty in depletion region control, and poor process compatibility, resulting in low photogenerated carrier separation efficiency and difficulty in achieving both dark current suppression and high responsivity. Summary of the Invention

[0004] The purpose of this invention is to provide a self-powered photodetector based on a barium titanate and gallium oxide heterojunction and its fabrication method. This invention utilizes the photovoltaic and pyroelectric effects of the heterojunction to achieve self-powered photodetection; the photodetector fabrication method is simple and low in cost.

[0005] The first aspect of the present invention provides a pyroelectric photodetector based on a barium titanate and gallium oxide heterojunction and a method for fabricating the same, comprising: a substrate, a gallium oxide light-absorbing region disposed on the surface of the substrate, a barium titanate pyroelectric functional region disposed on the gallium oxide layer, and a first electrode and a second electrode respectively connected to the gallium oxide light-absorbing region and the barium titanate pyroelectric functional region.

[0006] The gallium oxide light-absorbing region and the barium titanate pyroelectric functional region form a heterojunction interface. The gallium oxide light-absorbing region is used to absorb deep ultraviolet light and generate photogenerated carriers, and the heterojunction interface provides a photovoltaic built-in electric field to separate the photogenerated carriers; the barium titanate pyroelectric functional region generates a pyroelectric response when the temperature changes caused by light illumination, and couples with the heterojunction photovoltaic response to output an electrical signal.

[0007] Optionally, the thickness of the gallium oxide light-absorbing layer is 5 nm - 500 nm, preferably 100 nm. The crystal phase is any one of α phase, β phase, γ phase, δ phase, and ε phase.

[0008] Optionally, the barium titanate pyroelectric layer has a thickness of 5 nm to 100 nm and a tetragonal crystal phase.

[0009] Optionally, the thickness of the first electrode and the second electrode is 20 nm to 300 nm, and the structure is square.

[0010] Optionally, the substrate may be made of any one of sapphire, silicon, silicon oxide, etc., and its size is 1×1cm. 2 .

[0011] Optionally, the first electrode may be one of gold, platinum, nickel, titanium, or aluminum electrodes, or a composite electrode composed of two or more of these.

[0012] Optionally, the second electrode may be one of gold, platinum, nickel, titanium, or aluminum electrodes, or a composite electrode composed of two or more of these.

[0013] Secondly, a method for fabricating a barium titanate / gallium oxide heterojunction pyroelectric photodetector specifically includes:

[0014] Step 1: Clean the substrate sequentially with acetone, ethanol and deionized water using ultrasonic cleaning, and then dry it with nitrogen.

[0015] Step 2: Ga2O3 thin films are grown on the cleaned substrate by magnetron sputtering at room temperature to obtain any one of the α phase, β phase, γ phase, δ phase, and ε phase Ga2O3 thin films. The films are then annealed after deposition.

[0016] Step 3: BaTiO3 thin film is grown on gallium oxide layer by magnetron sputtering, and the tetragonal phase BaTiO3 thin film is obtained by room temperature deposition and annealing after deposition.

[0017] Step 4: Electrodes are deposited on the surface of the gallium oxide layer and the barium titanate layer respectively using mask-assisted electron beam evaporation.

[0018] Step 5: Apply an external electric field to polarize the barium titanate layer.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Self-powered detection capability: This invention utilizes the ferroelectric pyroelectric effect of barium titanate to generate spontaneous polarization under photothermal action, forming a strong built-in electric field, enabling the detector to work under zero bias conditions, realizing self-powered solar-blind ultraviolet detection, and significantly reducing system power consumption.

[0021] (2) High responsivity and fast response: The polarization electric field generated by the barium titanate layer effectively promotes the separation of photogenerated electron-hole pairs in the gallium oxide layer and suppresses carrier recombination, thereby significantly improving the responsivity of the detector. At the same time, the presence of the built-in electric field accelerates the carrier transport process, which greatly improves the response speed of the device (response time ≤ 200 ms) and makes it more sensitive to weak light signals.

[0022] (3) Realize pyroelectric-photovoltaic coupling response: After the gallium oxide light-absorbing region absorbs deep ultraviolet light, it generates a steady-state photogenerated carrier response, while the barium titanate pyroelectric functional region generates a transient pyroelectric current during the temperature change caused by the modulation of light. The coupling of the two can improve the device's sensitivity to pulsed deep ultraviolet signals.

[0023] (4) Simple structure and compatible process: The detector structure of the present invention is reasonably designed and the manufacturing process is compatible with existing semiconductor process lines, making it easy to achieve large-scale production. It has broad application prospects in ultraviolet light communication, flame detection, missile early warning and other fields. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a barium titanate and gallium oxide heterojunction pyroelectric photodetector according to the present invention.

[0025] Figure 2 This is a photocurrent response curve of the photodetector under 0 V bias voltage in an embodiment of the present invention.

[0026] Figure 3 This is a response time curve of the photodetector in an embodiment of the present invention.

[0027] Figure 4 This is the It curve of the photodetector under zero bias voltage in an embodiment of the present invention.

[0028] The markings in the figure are: 1-first electrode, 2-barium titanate pyroelectric layer, 3-gallium oxide light-absorbing layer, 4-substrate layer, and 5-second electrode. Detailed Implementation

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

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] This invention introduces a barium titanate and gallium oxide heterojunction pyroelectric photodetector, the structure of which is as follows: Figure 1 As shown, it includes: a substrate 4, a gallium oxide light-absorbing layer 3 disposed on the substrate 4, a barium titanate pyroelectric layer 2 disposed on the gallium oxide light-absorbing layer 3, a first electrode 1 disposed on the upper surface of the gallium oxide light-absorbing layer 3, and a second electrode 5 disposed on the upper surface of the barium titanate pyroelectric layer 2.

[0032] Furthermore, the thickness of the gallium oxide light-absorbing layer 3 is 5 nm to 500 nm, and the crystal phase is any one of the α phase, β phase, γ phase, δ phase, and ε phase.

[0033] Furthermore, the barium titanate pyroelectric layer 2 has a thickness of 5 nm to 100 nm and a tetragonal crystal phase.

[0034] Furthermore, the thickness of the first electrode 1 and the second electrode 5 is 20 nm - 300 nm, and the structure is square.

[0035] Furthermore, the substrate 4 is made of any one of sapphire, silicon, silicon oxide, etc., and has a size of 1×1cm. 2 .

[0036] Furthermore, the first electrode 1 and the second electrode 5 are made of one or more of the following materials: gold, platinum, nickel, titanium, and aluminum.

[0037] This invention discloses a method for fabricating a barium titanate and gallium oxide heterojunction pyroelectric photodetector, specifically including:

[0038] Step 1: Substrate cleaning: The substrate is ultrasonically cleaned in acetone, ethanol and deionized water in sequence, and then dried with nitrogen.

[0039] Step 2: Gallium oxide layer growth: Ga2O3 thin films are grown on the cleaned substrate using magnetron sputtering and sol-gel to obtain any one of the α-phase, β-phase, γ-phase, δ-phase, and ε-phase Ga2O3 thin films, which are then annealed after deposition.

[0040] Step 3: Barium titanate layer growth: BaTiO3 thin film was grown on gallium oxide layer by magnetron sputtering, and the tetragonal phase BaTiO3 thin film was obtained by room temperature deposition and annealing after deposition.

[0041] Step 4: Electrode fabrication: Electrodes are deposited on the surface of the gallium oxide layer and the barium titanate layer respectively using mask-assisted electron beam evaporation.

[0042] Step 5: Polarization treatment: Apply an external electric field to polarize the barium titanate layer.

[0043] Example 1:

[0044] This embodiment describes a method for fabricating a barium titanate and gallium oxide heterojunction pyroelectric photodetector, specifically including:

[0045] (1) Substrate cleaning: The silicon oxide substrate was ultrasonically cleaned in acetone, ethanol and deionized water for 10 minutes each, and then dried with nitrogen.

[0046] (2) Gallium oxide layer growth: β-Ga2O3 thin film was grown on the cleaned substrate by magnetron sputtering. The deposition was carried out at room temperature, with a pressure of 0.2 Pa, an Ar flow rate of 30 sccm, and a deposition time of 1 hour, resulting in a β-Ga2O3 thin film with a thickness of approximately 100 nm. After deposition, the film was annealed at 800 °C in a nitrogen atmosphere for 1 hour.

[0047] (3) Barium titanate layer growth: BaTiO3 thin film was grown on gallium oxide layer by magnetron sputtering. Deposition was carried out at room temperature, pressure of 0.3 Pa, Ar flow rate of 30 sccm, and deposition time of 0.5 hours to obtain BaTiO3 thin film with a thickness of about 30 nm. After deposition, it was annealed at 700℃ in nitrogen atmosphere for 1 hour.

[0048] (4) Electrode fabrication: Ti / Al electrodes were deposited on the surface of gallium oxide layer and barium titanate layer respectively using mask-assisted electron beam evaporation with a thickness of 20 / 100 nm. The electrode pattern was square with a side length of 100 μm.

[0049] (5) Polarization treatment: Apply an external electric field to the barium titanate layer to polarize it in order to enhance its pyroelectric effect.

[0050] Example 2:

[0051] This embodiment describes a method for fabricating a barium titanate / gallium oxide heterojunction pyroelectric photodetector. The gallium oxide is prepared using a sol-gel method, with a thickness of 100 nm and an α-phase crystal structure. Specifically, it includes:

[0052] (1) Substrate cleaning: The silicon oxide substrate was ultrasonically cleaned in acetone, ethanol and deionized water for 10 minutes each, and then dried with nitrogen.

[0053] (2) Gallium oxide layer growth: α-Ga₂O₃ thin films were grown on the cleaned substrate using a sol-gel method. The solution consisted of Ga(NO₃)₃ dissolved in ethylene glycol, with monoethanolamine used as a complexing agent. 3+ The concentration was 0.5 mol / L, dissolved and stirred at 60℃ for 2 hours, and then aged for 24 hours.

[0054] Gallium oxide thin films were prepared on a cleaned substrate by spin coating at 3000 rpm for 30 s, repeated 5 times. The films were then baked at 350 °C for 10 min. Finally, they were air-annealed at 450 °C for 1 hour.

[0055] (3) Barium titanate layer growth: BaTiO3 thin film was grown on gallium oxide layer by magnetron sputtering. Deposition was carried out at room temperature, pressure of 0.3 Pa, Ar flow rate of 30 sccm, and deposition time of 0.5 hours to obtain BaTiO3 thin film with a thickness of about 30 nm. After deposition, it was annealed at 700℃ in nitrogen atmosphere for 1 hour.

[0056] (4) Electrode fabrication: Ti / Al electrodes were deposited on the surface of gallium oxide layer and barium titanate layer respectively using mask-assisted electron beam evaporation with a thickness of 20 / 100 nm. The electrode pattern was square with a side length of 100 μm.

[0057] (5) Polarization treatment: Apply an external electric field to the barium titanate layer to polarize it in order to enhance its pyroelectric effect.

[0058] Example 3:

[0059] This embodiment describes the performance testing of a barium titanate and gallium oxide heterojunction pyroelectric photodetector. This embodiment uses a probe station and a semiconductor parameter analyzer in conjunction with a 254nm light source to characterize its working performance.

[0060] The detector prepared in Example 1 was subjected to performance testing, and the results are as follows: Figure 2 and Figure 3 As shown. Figure 2 This indicates that the detector can generate a significant photocurrent under a 0V bias voltage, achieving self-powered detection. Figure 3 This indicates that the detector has a response time of ≤200ms, demonstrating its fast response capability.

[0061] The It curve (fourth-order response) under 254nm light illumination at zero bias voltage is shown in the figure below. Figure 4 As shown in the figure, under zero bias, the fourth-order photoresponse dynamics caused by the optical switch can be seen. When the photodetector is in the dark state, there is only dark current, which is the fourth response. When the 254nm light source is turned on, the device generates photogenerated carriers, which are separated by the heterojunction and the ferroelectric-induced built-in electric field, generating photocurrent. At the same time, due to the increase in thermal vibration, the light-induced temperature rise disturbs the random oscillation state of the electric dipoles in the barium titanate ferroelectric film, resulting in a decrease in ferroelectric polarization charge and generating pyroelectric current. Therefore, the first-order response generates both pyroelectric current and photocurrent. When the laser continues to irradiate and the temperature remains constant, the pyroelectric current disappears, leaving only a stable photocurrent, which is the second-order response. When the laser is turned off, the temperature of the photodetector decreases, leading to an increase in bound charge and generating a reverse pyroelectric current, which is the third-order response. As time passes and the temperature remains constant, only the dark current remains, which is the fourth stage.

[0062] Barium titanate is a typical perovskite ferroelectric material with a large spontaneous polarization intensity at room temperature (~26 μC / cm).2 Barium titanate possesses a high dielectric constant and a band gap of approximately 3.2 eV, forming a band complement to gallium oxide. More importantly, barium titanate exhibits excellent pyroelectric effects: it can generate a strong built-in electric field without an external bias voltage, effectively separating photogenerated carriers; and it is sensitive to pulsed photothermal perturbations, generating transient currents synchronized with optical signals. Heterogeneous integration of barium titanate and gallium oxide holds promise for modulating the heterojunction band structure through ferroelectric polarization, reducing the effective interface barrier, and simultaneously overcoming the contradiction between responsivity and response speed in traditional heterojunctions by utilizing the pyroelectric-photovoltaic coupling mechanism.

[0063] This invention employs a heterojunction constructed from the ferroelectric material barium titanate (BaTiO3) and gallium oxide. Utilizing the strong built-in electric field generated by the spontaneous ferroelectric polarization of BaTiO3, a photovoltaic effect is formed, effectively separating photogenerated carriers and suppressing recombination, significantly improving the detector's photoresponsivity. Simultaneously, the pyroelectric effect of BaTiO3 generates a transient pyroelectric current under pulsed light illumination. This current superimposes with the photovoltaic current, accelerating the photoresponse process and shortening the response time. Through the coupling mechanism of photovoltaic and pyroelectricity, this invention simultaneously achieves high responsivity and fast response speed, overcoming the problem of mutual constraints between sensitivity and time response in traditional gallium oxide heterojunctions.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A barium titanate and gallium oxide heterojunction pyroelectric photodetector, characterized in that, include: Substrate; Gallium oxide light-absorbing regions are disposed on the surface of the substrate; A barium titanate pyroelectric functional region is disposed on the gallium oxide light-absorbing region; a first electrode and a second electrode; wherein the gallium oxide light-absorbing region and the barium titanate pyroelectric functional region form a heterojunction interface, the first electrode is connected to the gallium oxide light-absorbing region, and the second electrode is connected to the barium titanate pyroelectric functional region; the gallium oxide light-absorbing region is used to absorb deep ultraviolet light and generate photogenerated carriers, the heterojunction interface is used to provide a photovoltaic built-in electric field to separate photogenerated carriers, and the barium titanate pyroelectric functional region is used to generate a pyroelectric response when the temperature changes caused by illumination, and couples with the heterojunction photovoltaic response to output an electrical signal.

2. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The thickness of the gallium oxide light-absorbing layer is 5-500 nm.

3. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The crystalline phase of the gallium oxide light-absorbing region is any one of the α phase, β phase, γ phase, δ phase, and ε phase.

4. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The thickness of the barium titanate pyroelectric layer is 5 nm to 100 nm, preferably 30 nm.

5. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The barium titanate pyroelectric functional region is a tetragonal BaTiO3 thin film.

6. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The thickness of the first and second electrodes is 20 nm - 300 nm, and the structure is square.

7. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The first electrode and the second electrode are made of any one of the following metal materials: gold, platinum, nickel, titanium, and aluminum, or a composite electrode composed of two or more of these materials.

8. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: The substrate is made of any one of sapphire, silicon, or silicon oxide, and has a size of 1×1 cm. 2 .

9. The barium titanate and gallium oxide heterojunction pyroelectric photodetector according to claim 1, characterized in that: Gallium oxide and barium titanate thin films can be prepared by one of the following methods: magnetron sputtering, chemical vapor deposition, sol-gel method, and pulsed laser deposition.

10. A method for fabricating a barium titanate / gallium oxide heterojunction pyroelectric photodetector, characterized in that: Specifically, it includes: Step 1: Clean the substrate sequentially with acetone, ethanol and deionized water using ultrasonic cleaning, and then dry it with nitrogen gas; Step 2: Ga2O3 thin films are grown on the cleaned substrate using magnetron sputtering or sol-gel methods to obtain any one of the α-phase, β-phase, γ-phase, δ-phase, and ε-phase Ga2O3 thin films, and then annealed after deposition; Step 3: BaTiO3 thin film is grown on gallium oxide layer by magnetron sputtering to obtain tetragonal BaTiO3 thin film, and then annealed after deposition; Step 4: Electrodes are deposited on the surface of the gallium oxide layer and the barium titanate layer respectively using mask-assisted electron beam evaporation; Step 5: Apply an external electric field to polarize the barium titanate layer.

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