Avalanche photodetector and preparation method thereof

Abstract

The invention provides an avalanche photodetector and a preparation method thereof, and the avalanche photodetector comprises a first electrode layer, a substrate, an absorption layer, a multiplication layer, an ohmic contact layer and a second electrode layer which are sequentially stacked from bottom to top. Wherein the material of the absorption layer comprises indium gallium oxide, and the material of the multiplication layer comprises gallium oxide. A light absorption process and a carrier multiplication process are effectively separated in space and an electric field, so that multiplication noise is effectively reduced, device gain and responsivity are remarkably improved, and a solar blind spectral response range is widened by indium gallium oxide.

Description

Technical Field

[0001] This disclosure relates to the field of photodetector technology, and in particular to an avalanche photodetector and its fabrication method. Background Technology

[0002] Solar-blind ultraviolet (200-280nm) detection has important applications in military, civilian, and scientific research fields, such as missile warning, flame detection, space communication, ozone layer monitoring, biomedical imaging, and evaluation of ultraviolet disinfection effects. Traditional silicon-based photodetectors, due to their narrow bandgap, respond to both visible and near-ultraviolet light. In solar-blind ultraviolet applications, they require expensive and complex filters to suppress background noise, increasing device cost and system complexity.

[0003] Avalanche photodiodes (APDs) achieve highly sensitive detection of weak light signals through an internal gain mechanism, and are widely used in fields such as optical communication and lidar.

[0004] However, research on gallium oxide-based APDs is still in its early stages, and significant technical challenges remain in achieving efficient and low-noise avalanche multiplication. Particularly noteworthy is that, due to the immaturity of p-type gallium oxide material preparation and doping techniques, most existing gallium oxide APD structures are limited to simple heterojunction forms. These structures often struggle to simultaneously optimize multiple performance aspects, including light absorption efficiency, gain multiplication, and noise suppression. This limitation severely restricts the full potential of gallium oxide APDs, making it difficult to achieve the ideal low-noise, high-gain performance.

[0005] Therefore, how to design a high-performance, low-noise gallium oxide-based solar-blind ultraviolet APD is a key problem that urgently needs to be solved in the field of gallium oxide photodetectors. Summary of the Invention

[0006] This disclosure provides an avalanche photodetector and its fabrication method, thereby at least solving the above-mentioned technical problems existing in the prior art.

[0007] According to a first aspect of this disclosure, an avalanche photodetector is provided, wherein the avalanche photodetector comprises: The layers stacked sequentially from bottom to top are: a first electrode layer, a substrate, an absorber layer, a multiplication layer, an ohmic contact layer, and a second electrode layer; wherein... The absorber layer is made of indium gallium oxide, and the multiplication layer is made of gallium oxide.

[0008] In one possible embodiment, the material of the absorbent layer is (In x Ga 1-x )2O3, of which 0 <x≤0.2。

[0009] In one possible implementation, it further includes: a window penetrating the second electrode layer, the ohmic contact layer, and a portion of the multiplication layer; A passivation layer covering the bottom and sidewalls of the window, as well as a portion of the surface of the second electrode layer.

[0010] In one embodiment, the conductivity type of the multiplication layer is n-type; the carrier concentration range in the multiplication layer is 8E16 cm⁻¹. -3 ~1E18 cm -3 ; The thickness of the multiplication layer ranges from 100 nm to 200 nm.

[0011] In one embodiment, the absorber layer is a lightly doped n-type layer; the carrier concentration in the absorber layer is in the range of 1E15 cm⁻¹. -3 ~1E16 cm -3 .

[0012] In one embodiment, the thickness of the absorption layer ranges from 150 nm to 400 nm; The bandgap of the absorption layer is 4.42. ~4.75 .

[0013] In one embodiment, the material of the ohmic contact layer includes at least one of NiO, Ir2O3, Cu2O, SnO, CuGaO2, or CuAlO2; The conductivity type of the ohmic contact layer is p-type; The carrier concentration range of the ohmic contact layer is 1E19 cm⁻¹. -3 ~1E21 cm -3 ; The thickness of the ohmic contact layer ranges from 100 nm to 200 nm.

[0014] According to a second aspect of this disclosure, a method for fabricating an avalanche photodetector is provided, wherein the method includes: Provide substrate; An absorption layer is formed on the substrate, the material of the absorption layer including indium gallium oxide; A multiplication layer is formed on the absorption layer, wherein the material of the multiplication layer includes gallium oxide; An ohmic contact layer is formed on the multiplication layer; A second electrode layer is formed on the ohmic contact layer; A first electrode layer is formed beneath the substrate.

[0015] In one possible embodiment, the material of the absorbent layer is (Inx Ga 1-x )2O3, of which 0 <x≤0.2。

[0016] In one possible implementation, the method further includes: A window is formed, the window penetrating the second electrode layer, the ohmic contact layer, and a portion of the multiplication layer; A passivation layer is formed covering the bottom and sidewalls of the window, as well as a portion of the surface of the second electrode layer.

[0017] The avalanche photodetector and its fabrication method disclosed herein separate the light absorption function and the avalanche multiplication function by fabricating the absorption layer and the multiplication layer separately. By setting the multiplication layer to gallium oxide, the high breakdown electric field characteristics of gallium oxide are utilized to achieve efficient avalanche multiplication, thereby obtaining significant internal gain and greatly improving the detection sensitivity and responsivity to weak solar-blind ultraviolet light signals. Furthermore, by setting the absorption layer to indium gallium oxide (IGNO), which has a narrower bandgap, the detection range is extended to the entire solar-blind band. The IGNO absorption layer can also maintain a low electric field, effectively suppressing collisional ionization in this region, thereby significantly reducing the excess noise of the device, improving the signal-to-noise ratio, solving the performance bottleneck of traditional gallium oxide APDs, and improving the overall performance of the device.

[0018] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0019] The above and other objects, features, and advantages of this disclosure will become readily apparent from the following detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings. Several embodiments of this disclosure are illustrated in the drawings by way of example and not limitation, in which: In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts.

[0020] Figure 1 This is a schematic diagram of the structure of the avalanche photodetector provided in an embodiment of this disclosure; Figure 2 This is a diagram showing the electric field intensity distribution of the avalanche photodetector disclosed herein. Figure 3 A flowchart illustrating the fabrication method of the avalanche photodetector provided in this embodiment of the disclosure; Figures 4a to 4d This is a schematic diagram of the fabrication process of the avalanche photodetector provided in the embodiments of this disclosure. Detailed Implementation

[0021] To make the objectives, features, and advantages of the present disclosure more apparent and understandable, the following will clearly and completely describe the technical solutions in the embodiments of the present disclosure in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present disclosure.

[0022] An avalanche photodetector is provided in an embodiment of the present disclosure. Figure 1 The following is a schematic structural diagram of the avalanche photodetector provided in the embodiment of the present disclosure. As Figure 1 shown, the avalanche photodetector includes: A first electrode layer 11, a substrate 12, an absorption layer 13, a multiplication layer 14, an ohmic contact layer 15, and a second electrode layer 16 stacked in sequence from bottom to top; wherein, The material of the absorption layer 13 includes indium gallium oxide, and the material of the multiplication layer 14 includes gallium oxide.

[0023] In one embodiment, the substrate 12 is a (010)-oriented β-Ga2O3 single crystal substrate. The substrate 12 is n-type conductive through Sn (tin) doping, and the carrier concentration is 2E18 cm -3 ~1E20 cm -3 , preferably, the carrier concentration is 5E18 cm -3 .

[0024] The substrate 12 serves as the mechanical support of the device and simultaneously acts as a good ohmic contact interface for the electron collection layer and the bottom electrode.

[0025] Below the substrate 12 is the first electrode layer 11, and the first electrode layer 11 is the bottom electrode.

[0026] The first electrode layer 11 is a Ti / Au (titanium / gold) metal stack structure.

[0027] The absorption layer 13 is located above the substrate 12. The material of the absorption layer 13 includes indium gallium oxide ((In x Ga 1-x )2O3), where 0 < x < 1. In a preferred embodiment, 0 < x ≤ 0.2.

[0028] By precisely adjusting the content x of the In component, (In x Ga 1-xThe band gap of In₂O₃ is smaller than that of Ga₂O₃, and the band gap of the absorption layer can be flexibly adjusted, thereby enabling efficient absorption of solar-blind ultraviolet light in the 200-280 nm range. This significantly broadens the optical response range and optimizes absorption in specific solar-blind ultraviolet bands, allowing the detector to optimize the absorption wavelength for different solar-blind ultraviolet application scenarios and improve quantum efficiency. For example, in one specific embodiment, x can be set to 0.15, resulting in a band gap of 4.59 eV, corresponding to an absorption edge of approximately 270 nm. Furthermore, this disclosure controls the absorption layer (In₂O₃) to achieve this. x Ga 1-x The low indium content in Ga2O3 ensures a high degree of lattice mismatch with the Ga2O3 substrate. This low mismatch material system design fundamentally guarantees the high crystallinity of the epitaxial layer and significantly reduces the intrinsic defect density of the material. Compared with heterostructures with large lattice mismatch, the epitaxial layer disclosed in this invention has fewer defects and better quality, which directly translates into lower device dark current and higher operating stability.

[0029] In this disclosure, the material of the absorption layer is indium gallium oxide (IGNO), which has a narrower bandgap, extending the detection range to the entire solar blind band. The IGNO absorption layer can also maintain a low electric field, effectively suppressing collisional ionization in this region, thereby significantly reducing the excess noise of the device, improving the signal-to-noise ratio, solving the performance bottleneck of traditional IGNO APDs, and improving the overall performance of the device.

[0030] In one embodiment, the absorber layer 13 is a lightly doped n-type layer; the carrier concentration of the absorber layer 13 is in the range of 1E15 cm⁻¹. -3 ~1E16 cm -3 .

[0031] The thickness of the absorption layer 13 ranges from 150 nm to 400 nm. In a preferred embodiment, the thickness of the absorption layer 13 is 200 nm.

[0032] The bandgap of the absorption layer 13 is 4.42. ~4.75 This is to achieve effective absorption of ultraviolet light across the entire solar blind band.

[0033] The multiplication layer 14 is located above the absorption layer 13, and the material of the multiplication layer 14 includes gallium oxide (Ga2O3).

[0034] In this disclosure, by setting the multiplication layer material to gallium oxide, and utilizing the high breakdown electric field characteristics of gallium oxide itself, efficient avalanche multiplication is achieved, thereby obtaining significant internal gain and greatly improving the detection sensitivity and responsivity of weak solar-blind ultraviolet light signals.

[0035] Under the action of external reverse bias, the multiplication layer 14 will form a high electric field region, which will induce collisional ionization of photogenerated carriers and achieve avalanche multiplication.

[0036] Multiplication layer 14 is a lightly doped n-type Ga2O3 thin film, achieving n-type conductivity through Si (silicon) charge carriers. The carrier concentration in multiplication layer 14 ranges from 8E16 cm⁻¹. -3 ~1E18 cm -3 In a preferred embodiment, the carrier concentration is 2E17 cm⁻¹. -3 .

[0037] The thickness of the multiplication layer 14 ranges from 100 nm to 200 nm. In a preferred embodiment, the thickness of the multiplication layer 14 is 200 nm.

[0038] Gallium oxide (Ga₂O₃), a wide-bandgap semiconductor material, is an ideal material for solar-blind detection due to its inherent wide bandgap (approximately 4.8 eV), intrinsic absorption wavelength of 258 nm, and insensitivity to visible light. Furthermore, Ga₂O₃ is considered a promising material for developing high-performance solar-blind ultraviolet detectors due to its excellent physicochemical properties, such as ultra-wide bandgap, high breakdown electric field strength, good chemical stability, and the potential for easy fabrication of large-size substrates. In addition, indium gallium oxide (IGGaO), as an alloy of Ga₂O₃, has a smaller bandgap than pure Ga₂O₃, and its bandgap can be precisely tuned by adjusting the In content (x). This allows IGGaO to effectively extend the detector's photoresponse range, enabling efficient absorption and coverage of the entire solar-blind ultraviolet spectrum (200-280 nm), thus achieving wider-band and more efficient solar-blind ultraviolet detection.

[0039] The ohmic contact layer 15 is located on the multiplication layer 14, which can serve as a good ohmic contact interface between the hole collection layer and the top electrode.

[0040] The ohmic contact layer 15 is a heavily doped p-type semiconductor layer, and its material includes at least one of NiO, Ir₂O₃, Cu₂O, SnO, CuGaO₂, or CuAlO₂, or other suitable p-type oxide semiconductor materials may be selected. The heavily doped ohmic contact layer 15 optimizes the ohmic contact characteristics and improves the device performance.

[0041] The carrier concentration range of the ohmic contact layer 15 is 1E19 cm⁻¹. -3 ~1E21 cm -3 In a preferred embodiment, the carrier concentration is 6E20 cm⁻¹. -3 .

[0042] The thickness of the ohmic contact layer 15 ranges from 100 nm to 200 nm. In a preferred embodiment, the thickness of the ohmic contact layer 15 is 100 nm.

[0043] The second electrode layer 16 is located on the ohmic contact layer 15, and the second electrode layer 16 is the top electrode.

[0044] The second electrode layer 16 is a Ni / Au (nickel / gold) metal stack structure.

[0045] In one embodiment, the avalanche photodetector further includes a window 20 penetrating the second electrode layer 16, the ohmic contact layer 15, and a portion of the multiplication layer 14; A passivation layer 17 covers the bottom and sidewalls of the window 20, as well as part of the surface of the second electrode layer 16.

[0046] In this disclosure, a window 20 is formed that penetrates the second electrode layer 16, the ohmic contact layer 15, and part of the multiplication layer 14, so that light can enter through the window 20.

[0047] The passivation layer 17 covers the bottom surface and sidewalls of the window 20, as well as part of the surface of the second electrode layer 16. It can modify and protect the etched interface, reduce surface states and leakage current, thereby improving the long-term operating stability and reliability of the device.

[0048] The material of the passivation layer 17 includes at least one of Al2O3, SiO2 and Si3N4.

[0049] The working principle of the avalanche photodetector in this embodiment is as follows: When solar-blind ultraviolet light with wavelengths in the range of 200-280 nm is incident through the multiplication layer 14 exposed by the top window 20, photons pass through this layer and are efficiently absorbed, primarily in the absorption layer 13 with its narrow bandgap. The photon energy is greater than the bandgap of the absorption layer 13, causing electrons to jump from the valence band to the conduction band, generating electron-hole pairs.

[0050] A reverse bias voltage is applied across the detector (i.e., a negative voltage is applied to the second electrode layer 16, and the first electrode layer 11 is grounded). Due to the pn junction structure of the device, a depletion region and electric field are formed inside. Since the absorption layer 13 is a lightly doped layer, the electric field in this region is relatively low. Its main function is to effectively separate photogenerated electron-hole pairs and initiate their drift, while effectively suppressing collisional ionization within the absorption layer 13, which is crucial for achieving low noise. Under the influence of the electric field, photogenerated electrons drift towards the n-substrate 12, while photogenerated holes drift towards the ohmic contact layer 15.

[0051] Due to the huge difference in carrier concentration between the ohmic contact layer 15 and the multiplication layer 14, the depletion region is mainly distributed in the multiplication layer 14. Figure 2 This is a diagram showing the electric field intensity distribution of the avalanche photodetector disclosed herein. Figure 2As shown, by carefully designing the carrier concentration and thickness of the multiplication layer 14, the electric field can be made to peak in this layer. When holes drifting from the absorption layer 13 enter the multiplication layer 14, they are rapidly accelerated in this high electric field region, gaining sufficient kinetic energy. These high-energy holes collide with lattice atoms, transferring energy to valence band electrons, causing them to jump to the conduction band and generate new electron-hole pairs. This process is called collisional ionization. The newly generated carriers are further accelerated and trigger new collisional ionization, forming a chain-like "avalanche" effect, causing the photocurrent to increase exponentially, thereby achieving the internal gain of the device.

[0052] Ultimately, the multiplied electron flow is collected by the substrate 12 and output through the first electrode layer 11; while a large number of holes (including original photogenerated holes and holes generated by multiplication) are collected by the ohmic contact layer 15 and output through the second electrode layer 16, forming a photocurrent signal that can be detected by external circuitry. The passivation layer 17 effectively protects the etched edges of the device, reduces surface state recombination and leakage current, and ensures the stability and long-term reliability of the device under reverse high bias.

[0053] In this disclosure, by separating the light absorption region and the avalanche multiplication region spatially and in electric field, and by utilizing the ultra-wide bandgap characteristics of gallium oxide and its alloy material indium gallium oxide, the detector has a natural response blind zone for visible and near-ultraviolet light, eliminating the need for additional filters. This greatly simplifies the device structure and application scenarios, while achieving ultraviolet light detection with high gain, low noise, high responsivity, and excellent solar-blind performance.

[0054] This disclosure also provides a method for fabricating an avalanche photodetector. Figure 3 A flowchart of the fabrication method of the avalanche photodetector provided in the embodiments of this disclosure is shown below. Figure 3 As shown, the method includes: Step 301: Provide a substrate; Step 302: Form an absorption layer on the substrate, the material of which includes indium gallium oxide; Step 303: Form a multiplication layer on the absorption layer, wherein the material of the multiplication layer includes gallium oxide; Step 304: Form an ohmic contact layer on the multiplication layer; Step 305: Form a second electrode layer on the ohmic contact layer; Step 306: Form a first electrode layer under the substrate.

[0055] The fabrication method of the avalanche photodetector provided in this disclosure will be further described in detail below with reference to specific embodiments. Figures 4a to 4d This is a schematic diagram of the fabrication process of the avalanche photodetector provided in the embodiments of this disclosure.

[0056] First, refer to Figure 4a , and perform step 301 to provide a substrate 12.

[0057] The substrate 12 is a (010)-oriented β-Ga2O3 single crystal substrate. The substrate 12 is n-type conductive through Sn (tin) doping, and the carrier concentration is 2E18 cm -3 ~1E20 cm -3 , preferably, the carrier concentration is 5E18 cm -3 .

[0058] The substrate 12 serves as the mechanical support of the device and simultaneously acts as a good ohmic contact interface for the electron collection layer and the bottom electrode.

[0059] Next, continue to refer to Figure 4a , and perform step 302 to form an absorption layer 13 on the substrate 12. The material of the absorption layer 13 includes indium gallium oxide.

[0060] Specifically, the absorption layer 13 can be formed by methods such as molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), or pulsed laser deposition (PLD).

[0061] The material of the absorption layer 13 includes indium gallium oxide ((In x Ga 1-x )2O3), where 0 < x < 1. In a preferred embodiment, 0 < x ≤ 0.2.

[0062] By precisely adjusting the content x of the In component, the bandgap of (In x Ga 1-x )2O3 can be made smaller than the bandgap of Ga2O3, and the bandgap of the absorption layer can be flexibly regulated, so as to efficiently absorb the solar-blind ultraviolet band light of 200 - 280 nm, significantly broaden the light response range and optimize the absorption of a specific solar-blind ultraviolet band, enabling the detector to optimize the absorption wavelength for different solar-blind ultraviolet application scenarios and improve the quantum efficiency. For example, in a specific embodiment, x can be set to 0.15, so that its bandgap is 4.59 eV, corresponding to an absorption edge of about 270 nm. And the present disclosure controls the absorption layer (In x Ga 1-xThe low indium content in Ga2O3 ensures a high degree of lattice mismatch with the Ga2O3 substrate. This low mismatch material system design fundamentally guarantees the high crystallinity of the epitaxial layer and significantly reduces the intrinsic defect density of the material. Compared with heterostructures with large lattice mismatch, the epitaxial layer disclosed in this invention has fewer defects and better quality, which directly translates into lower device dark current and higher operating stability.

[0063] In this disclosure, the material of the absorption layer is indium gallium oxide (IGNO), which has a narrower bandgap, extending the detection range to the entire solar blind band. The IGNO absorption layer can also maintain a low electric field, effectively suppressing collisional ionization in this region, thereby significantly reducing the excess noise of the device, improving the signal-to-noise ratio, solving the performance bottleneck of traditional IGNO APDs, and improving the overall performance of the device.

[0064] In one embodiment, the absorber layer 13 is a lightly doped n-type layer with a carrier concentration in the range of 1E15 cm⁻¹. -3 ~1E16 cm -3 .

[0065] The thickness of the absorption layer 13 ranges from 150 nm to 400 nm. In a preferred embodiment, the thickness of the absorption layer 13 is 200 nm.

[0066] The bandgap of the absorption layer 13 is 4.42. ~4.75 This is to achieve effective absorption of ultraviolet light across the entire solar blind band.

[0067] Next, see [link / reference] Figure 4a Step 303 is performed to form a multiplication layer 14 on the absorption layer 13. The material of the multiplication layer 14 includes gallium oxide.

[0068] The multiplication layer 14 can be formed by methods such as molecular beam epitaxy (MBE), metal-organic chemical vapor deposition (MOCVD), or pulsed laser deposition (PLD).

[0069] In this disclosure, by setting the multiplication layer material to gallium oxide, and utilizing the high breakdown electric field characteristics of gallium oxide itself, efficient avalanche multiplication is achieved, thereby obtaining significant internal gain and greatly improving the detection sensitivity and responsivity of weak solar-blind ultraviolet light signals.

[0070] Under the action of external reverse bias, the multiplication layer 14 will form a high electric field region, which will induce collisional ionization of photogenerated carriers and achieve avalanche multiplication.

[0071] Multiplication layer 14 is a lightly doped n-type Ga2O3 thin film, achieving n-type conductivity through Si (silicon) doping. The carrier concentration in multiplication layer 14 ranges from 8E16 cm⁻¹. -3 ~1E18 cm -3 In a preferred embodiment, the carrier concentration is 2E17 cm⁻¹. -3 .

[0072] The thickness of the multiplication layer 14 ranges from 100 nm to 200 nm. In a preferred embodiment, the thickness of the multiplication layer 14 is 200 nm.

[0073] Next, see [link / reference] Figure 4a Step 304 is performed to form an ohmic contact layer 15 on the multiplication layer 14. The ohmic contact layer 15 can serve as a good ohmic contact interface between the hole collection layer and the top electrode.

[0074] Specifically, the ohmic contact layer 15 can be deposited using magnetron sputtering or pulsed laser deposition (PLD).

[0075] The ohmic contact layer 15 is a heavily doped p-type semiconductor layer, and its material includes at least one of NiO, Ir₂O₃, Cu₂O, SnO, CuGaO₂, or CuAlO₂, or other suitable p-type oxide semiconductor materials may be selected. The heavily doped ohmic contact layer 15 optimizes the ohmic contact characteristics and improves the device performance.

[0076] The carrier concentration range of the ohmic contact layer 15 is 1E19 cm⁻¹. -3 ~1E21 cm -3 In a preferred embodiment, the carrier concentration is 6E20 cm⁻¹. -3 .

[0077] The thickness of the ohmic contact layer 15 ranges from 100 nm to 200 nm. In a preferred embodiment, the thickness of the ohmic contact layer 15 is 100 nm.

[0078] Next, see [link / reference] Figure 4a Step 305 is executed to form a second electrode layer 16 on the ohmic contact layer 15. The second electrode layer 16 is the top electrode.

[0079] Specifically, the second electrode layer 16 can be formed using photolithography and lift-off processes.

[0080] The second electrode layer 16 is a Ni / Au (nickel / gold) metal stack structure.

[0081] Next, see Figure 4b A window 20 is formed, which penetrates the second electrode layer 16, the ohmic contact layer 15 and part of the multiplication layer 14.

[0082] Specifically, a photoresist layer (not shown in the figure) can be formed on the second electrode layer 16, and then the photoresist layer is patterned to form a window pattern. Next, using the window pattern, the second electrode layer 16, the ohmic contact layer 15, and part of the multiplication layer 14 exposed by the window pattern are further etched away to form a window 20, so that light can enter through the window 20. The window 20 defines the active region of the device.

[0083] Next, see Figure 4c A passivation layer 17 is formed covering the bottom and sidewalls of the window 20, as well as a portion of the surface of the second electrode layer 16.

[0084] Specifically, the passivation layer 17 can be formed using atomic layer deposition (ALD) technology.

[0085] The passivation layer 17 covers the bottom surface and sidewalls of the window 20, as well as part of the surface of the second electrode layer 16. It can modify and protect the etched interface, reduce surface states and leakage current, thereby improving the long-term operating stability and reliability of the device.

[0086] The material of the passivation layer 17 includes at least one of Al2O3, SiO2 and Si3N4.

[0087] Next, see Figure 4d Step 306 is executed to form a first electrode layer 11 below the substrate 12. The first electrode layer 11 is the bottom electrode.

[0088] Specifically, electrode materials can be deposited on the back side of substrate 12 by methods such as electron beam evaporation, and then formed into good ohmic contacts through rapid thermal annealing.

[0089] The first electrode layer 11 is a Ti / Au (titanium / gold) metal stack structure.

[0090] The specific details of each part of the above method have been described in detail in the product implementation section. For any undisclosed details, please refer to the product implementation section, and therefore will not be repeated here.

[0091] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this disclosure can be achieved, and this is not limited herein.

[0092] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means two or more, unless otherwise explicitly specified.

[0093] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. An avalanche photodetector, characterized in that, The avalanche photodetector includes: The layers stacked sequentially from bottom to top are: a first electrode layer, a substrate, an absorber layer, a multiplication layer, an ohmic contact layer, and a second electrode layer; wherein... The absorber layer is made of indium gallium oxide, and the multiplication layer is made of gallium oxide.

2. The avalanche photodetector according to claim 1, characterized in that, The material of the absorbent layer is (In) x Ga 1-x )2O3, of which 0 <x≤0.2。 3. The avalanche photodetector according to claim 1, characterized in that, Also includes: A window penetrating the second electrode layer, the ohmic contact layer, and a portion of the multiplication layer; A passivation layer covering the bottom and sidewalls of the window, as well as a portion of the surface of the second electrode layer.

4. The avalanche photodetector according to claim 1, characterized in that, The conductivity type of the multiplication layer is n-type; The carrier concentration in the multiplication layer ranges from 8E16 cm⁻¹. -3 ~1E18 cm -3 ; The thickness of the multiplication layer ranges from 100 nm to 200 nm.

5. The avalanche photodetector according to claim 1, characterized in that, The absorption layer is a lightly doped n-type layer; the carrier concentration of the absorption layer is in the range of 1E15 cm⁻¹. -3 ~1E16 cm -3 .

6. The avalanche photodetector according to claim 1, characterized in that, The thickness of the absorption layer ranges from 150 nm to 400 nm; The bandgap of the absorption layer is 4.

42. ~4.75 .

7. The avalanche photodetector according to claim 1, characterized in that, The material of the ohmic contact layer includes at least one of NiO, Ir2O3, Cu2O, SnO, CuGaO2, or CuAlO2; The conductivity type of the ohmic contact layer is p-type; The carrier concentration range of the ohmic contact layer is 1E19 cm⁻¹. -3 ~1E21 cm -3 ; The thickness of the ohmic contact layer ranges from 100 nm to 200 nm.

8. A method for fabricating an avalanche photodetector, characterized in that, The method includes: Provide substrate; An absorption layer is formed on the substrate, the material of the absorption layer including indium gallium oxide; A multiplication layer is formed on the absorption layer, wherein the material of the multiplication layer includes gallium oxide; An ohmic contact layer is formed on the multiplication layer; A second electrode layer is formed on the ohmic contact layer; A first electrode layer is formed beneath the substrate.

9. The method according to claim 8, characterized in that, The material of the absorbent layer is (In) x Ga 1-x )2O3, of which 0 <x≤0.2。 10. The method according to claim 8, characterized in that, The method further includes: A window is formed, the window penetrating the second electrode layer, the ohmic contact layer, and a portion of the multiplication layer; A passivation layer is formed covering the bottom and sidewalls of the window, as well as a portion of the surface of the second electrode layer.

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