Diamond-based gallium oxide heterojunction avalanche photodetector and preparation method thereof

Abstract

The present application relates to a kind of diamond-based gallium oxide heterojunction avalanche photodetector and its preparation method, adopt p + Diamond substrate, sequentially epitaxial p ‑ Diamond multiplication layer, n ‑ Ga2O3 charge layer, i-Ga2O3 absorption layer and n + Ga2O3 contact layer, form separate absorption multiplication II-type heterojunction mesa structure;Through ICP etching exposure substrate, and utilize BOE wet etching and nitrogen annealing repair side wall damage;Finally, ohmic contact electrode is formed at top and bottom respectively.Under reverse bias, heterojunction built-in electric field and mesa edge local electric field cooperate, realize carrier avalanche multiplication, can realize single-photon level detection to ≤280nm solar blind waveband.Diamond substrate high thermal conductivity significantly inhibits Ga2O3 thermal accumulation, improves device stability and life.Process is fully compatible with MPCVD / MOCVD and standard semiconductor process, applicable to deep ultraviolet weak light imaging and other fields.

Description

Technical Field

[0001] This invention relates to the field of wide bandgap compound semiconductor devices and deep ultraviolet photodetector technology, specifically to a diamond-based gallium oxide heterojunction avalanche photodetector (p-type diamond / n-type gallium oxide heterojunction solar-blind single-photon avalanche photodetector) and its fabrication method. Background Technology

[0002] Ultraviolet photodetectors are key devices that convert ultraviolet signals into electrical signals. They are widely used in military defense (such as missile early warning), secure communication (such as short-range encrypted transmission), and environmental monitoring (such as ozone concentration detection). Among them, solar-blind ultraviolet detectors (for the <280nm band) have become a core research direction because they are less affected by sunlight interference.

[0003] With technological advancements, traditional low-gain ultraviolet detectors can no longer meet the demands of weak light detection. While photomultiplier tubes (PMTs) offer ultra-high gain, they suffer from drawbacks such as high cost, large size, and high power consumption. Avalanche photodiodes (APDs), based on wide-bandgap semiconductors, are gradually replacing PMTs due to their advantages of low cost, simple manufacturing process, and high gain. Their core principle utilizes the strong electric field under reverse bias of a PN junction to cause collisional ionization and avalanche multiplication of photogenerated carriers. Single-photon avalanche diodes (SPADs) further leverage this effect to achieve single-photon-level detection of weak signals.

[0004] Currently, most ultraviolet APDs utilize third-generation wide-bandgap semiconductor materials (such as SiC, GaN, and AlGaN). However, the response wavelengths of SiC (bandgap 3.23 eV) and GaN (bandgap 3.4 eV) are concentrated in the 300-365 nm range, exceeding the solar-blind band (<280 nm), thus failing to meet the selectivity requirements for solar-blind detection. Fourth-generation ultra-wide-bandgap semiconductors (such as gallium oxide (Ga2O3, bandgap 4.9 eV) and diamond (bandgap 5.5 eV)) have become a new direction due to their suitability for the solar-blind band, but gallium oxide-based devices face significant bottlenecks.

[0005] First, Ga2O3 lacks an effective p-type doping mechanism, making it difficult to form a stable PN junction to achieve avalanche multiplication;

[0006] Secondly, its thermal conductivity is extremely low (only about 10 W / mK), which makes it prone to heat accumulation in high electric field avalanche mode, leading to a surge in dark current and device failure.

[0007] Third, single-photon detection performance is still in its early stages, limited by epitaxial growth quality and processing technology.

[0008] Therefore, developing a solar-blind ultraviolet single-photon avalanche photodetector with high selectivity, high gain, and high stability remains a pressing technical challenge. Summary of the Invention

[0009] The purpose of this invention is to address the problems in existing technologies where third-generation wide-bandgap semiconductors cannot accurately cover the solar-blind band, and gallium oxide-based solar-blind ultraviolet detectors suffer from poor heat dissipation due to the lack of p-type doping, making it difficult to achieve high-gain and high-stability single-photon level detection. This invention provides a diamond-based gallium oxide heterojunction avalanche photodetector and its fabrication method. By constructing a type II heterojunction using p-type diamond and n-type gallium oxide, and designing a separated absorption multiplication (SAM) structure and a mesa structure, a solar-blind single-photon avalanche photodetector is fabricated. High selectivity, high gain, and efficient heat dissipation are achieved through material properties and structural optimization.

[0010] To achieve the aforementioned objectives, in a first aspect, the present invention employs the following technical solution: a diamond-based gallium oxide heterojunction avalanche photodetector comprises, from bottom to top, stacked as follows:

[0011] p + Diamond substrate;

[0012] Formed from p + p on diamond substrate - Type II diamond multiplier layer;

[0013] Formed from p - n on a type of diamond multiplier layer - Type Ga2O3 charge layer;

[0014] Formed from n - i-type Ga2O3 absorber layer on the i-type Ga2O3 charge layer;

[0015] n formed on the type i Ga2O3 absorber layer + Type Ga2O3 contact layer;

[0016] Formed from n + The top electrode on the Ga2O3 contact layer; and

[0017] Formed from p + Bottom electrode on the back side of the diamond substrate;

[0018] Where, p - Type II diamond multiplier layer and n - The Ga2O3 charge layer forms a type II heterojunction, and the detector as a whole is a discrete absorption multiplication structure, and a mesa structure is formed by etching.

[0019] Furthermore, p + The doping concentration of the diamond substrate is 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 .

[0020] Furthermore, p- The doping concentration of the diamond multiplication layer is 1×10⁻⁶. 15 cm -3 -2×10 15 cm -3 The thickness is 200±20nm.

[0021] Furthermore, n - The doping concentration of the Ga2O3 charge layer is 3 × 10⁻⁶. 17 cm -3 -5×10 17 cm -3 The thickness is 200±20 nm; the doping concentration of the i-type Ga2O3 absorber layer is 1×10⁻⁶. 15 cm -3 -2×10 15 cm -3 The thickness is 400±20nm; n + The doping concentration of the Ga2O3 contact layer is 1×10⁻⁶. 19 cm -3 -2×10 19 cm -3 The thickness is 200±20nm.

[0022] Furthermore, the top electrode is a Ti / Al / Ni / Au multilayer metal with layer thicknesses of 10±1nm, 80±1nm, 20±1nm, and 100±1nm, respectively; the bottom electrode is a Ni / Au multilayer metal with layer thicknesses of 20±1nm and 80±1nm, respectively.

[0023] Secondly, the present invention also provides a method for fabricating a diamond-based gallium oxide heterojunction avalanche photodetector, comprising the following steps:

[0024] (1) Provide p + Diamond substrate, for p + The diamond substrate is cleaned and dried;

[0025] (2) Microwave plasma chemical vapor deposition was used on p + p grown on diamond substrate - Type II diamond multiplier layer;

[0026] (3) Using metal-organic chemical vapor deposition on p - n-type diamond multiplication layers are grown sequentially - Type I Ga2O3 charge layer, Type II Ga2O3 absorber layer, n + Type Ga2O3 contact layer;

[0027] (4) The pattern is defined by photolithography, and inductively coupled plasma etching is used. +Type I Ga2O3 contact layer, Type II Ga2O3 absorber layer, n - Type Ga2O3 charge layer and p - Type II diamond multiplication layer to expose p + A diamond substrate is used to form a mesa structure.

[0028] (5) Anneal and wet treatment are performed on the etched sidewalls to repair the etched damage;

[0029] (6) In n + The top electrode is deposited on the type Ga2O3 contact layer, in p + A bottom electrode is deposited on the back side of a diamond substrate and formed into an ohmic contact through rapid thermal annealing.

[0030] Further, in step (1), the cleaning is performed by ultrasonic cleaning with acetone, isopropanol and deionized water for 5 minutes in sequence, and then dried with nitrogen gas.

[0031] Further, in step (2), the growth conditions for microwave plasma chemical vapor deposition are: a CH4 / H2 / B2H6 gas mixture is introduced, the temperature is 800-900℃, and the pressure is 20-30 Torr.

[0032] Further, in step (3), the growth conditions for metal-organic chemical vapor deposition are: a gas mixture containing Ga source, PH3 or N2 is introduced, the temperature is 800-950℃, and the pressure is 20-100 Torr.

[0033] Further, in step (4), the gas used for inductively coupled plasma etching is one or a mixture of BCl3 and Ar, wherein the flow rate of BCl3 is 15-40 sccm, the flow rate of Ar is 10-30 sccm, the etching pressure is 10-30 mTorr, the RF power is 10-20 W, the ICP power is 60-100 W, and the etching time is 30-90 s;

[0034] In step (5), annealing is performed in a nitrogen or oxygen atmosphere at 400-500℃ for 10-15 minutes; wet treatment is performed by immersing in a buffer oxide etching solution for 10-30 seconds and then rinsing and drying.

[0035] In step (6), the conditions for rapid thermal annealing are: nitrogen atmosphere, temperature 470℃, and holding time 1 min.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] 1. Significantly improved solar blind selectivity: Based on the ultrawide bandgap characteristics of Ga2O3 (4.9eV) and diamond (5.5eV), it has a strong response only to the <280nm solar blind band and almost no response to the >280nm band, which solves the problem of poor band adaptability of third-generation semiconductors.

[0038] 2. Significantly enhanced heat dissipation capability: Diamond (thermal conductivity of approximately 2200 W / mK) is used as the substrate and multiplication layer to effectively compensate for the heat dissipation defects of Ga2O3, avoid heat accumulation under high electric fields, and significantly improve device stability and lifespan.

[0039] 3. Carrier separation and multiplication efficiency optimization: p-type diamond and n-type Ga2O3 form a type II heterojunction, which induces a strong built-in electric field and promotes the rapid separation and transport of photogenerated carriers; the mesa structure forms a high-intensity local electric field under reverse bias, which enhances the avalanche multiplication effect and achieves single-photon level detection sensitivity.

[0040] 4. High process feasibility: By repairing etching damage (annealing + wet etching) and controlling precise process parameters, leakage current channels are reduced, ensuring high device performance and providing a practical solution for high-gain solar-blind ultraviolet single-photon detection. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the detector structure of the present invention;

[0042] Figure 2 This is a flowchart of the preparation method of the present invention;

[0043] Figure 3 This is the reverse voltage-current diagram of the detector of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0045] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0046] Existing Ga2O3-based solar-blind ultraviolet avalanche devices cannot simultaneously meet the requirements of solar-blind selectivity, single-photon gain, and long-term reliability due to the lack of p-type doping, low thermal conductivity, and leakage current caused by sidewall defects.

[0047] To address this issue, this invention constructs a p-type diamond / n-type gallium oxide SAM (separation absorption and multiplication) type II heterojunction mesa structure and introduces a sidewall damage repair process to achieve a deep ultraviolet avalanche photodetector that combines solar-blind selectivity, single-photon gain, and efficient heat dissipation, thereby solving the problems existing in the prior art.

[0048] Example 1

[0049] like Figure 1 As shown, this diamond-based gallium oxide heterojunction avalanche photodetector comprises, from bottom to top, the following:

[0050] p + Diamond substrate;

[0051] Formed from p + p on diamond substrate - Type II diamond multiplier layer;

[0052] Formed from p - n on a type of diamond multiplier layer - Type Ga2O3 charge layer;

[0053] Formed from n - i-type Ga2O3 absorber layer on the i-type Ga2O3 charge layer;

[0054] n formed on the type i Ga2O3 absorber layer + Type Ga2O3 contact layer;

[0055] Formed from n + The top electrode on the Ga2O3 contact layer; and

[0056] Formed from p + Bottom electrode on the back side of the diamond substrate;

[0057] Where, p - Type II diamond multiplier layer and n - The Ga2O3 charge layer forms a type II heterojunction, and the detector as a whole is a discrete absorption multiplication structure, and a mesa structure is formed by etching.

[0058] Preferably, p + The doping concentration of the diamond substrate is 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 ;p - The doping concentration of the diamond multiplication layer is 1×10⁻⁶.15 cm -3 -2×10 15 cm -3 The thickness is 200±20nm; n - The doping concentration of the Ga2O3 charge layer is 3 × 10⁻⁶. 17 cm -3 -5×10 17 cm -3 The thickness is 200±20 nm; the doping concentration of the i-type Ga2O3 absorber layer is 1×10⁻⁶. 15 cm -3 -2×10 15 cm -3 The thickness is 400±20nm; n + The doping concentration of the Ga2O3 contact layer is 1×10⁻⁶. 19 cm -3 -2×10 19 cm -3 The thickness is 200±20nm; the top electrode is a Ti / Al / Ni / Au multilayer metal with thicknesses of 10±1nm, 80±1nm, 20±1nm, and 100±1nm respectively; the bottom electrode is a Ni / Au multilayer metal with thicknesses of 20±1nm and 80±1nm respectively.

[0059] In this embodiment, the detector is based on a SAM (Separated Absorption and Multiplication) structure and is deposited via microwave plasma chemical vapor deposition (MPCVD) at p + A layer of p is grown on a diamond substrate - Type I diamond, and then a layer of n-type diamond is sequentially grown by metal-organic chemical vapor deposition (MOCVD). - Type I Ga2O3 charge layer, one type II Ga2O3 absorber layer, one type III Ga2O3 absorber layer + Type Ga2O3 contact layer. Mesa etching of each layer was performed using photolithography and inductively coupled plasma (ICP) etching, etching down to the substrate layer to expose p-type Ga2O3 contact layers. + Diamond substrate. Sidewall etching damage caused by dry etching is repaired through annealing and wet processing (a control group was used to compare unrepaired and repaired devices, revealing that the repaired devices exhibited superior performance, ensuring thorough repair), reducing sidewall dangling bond leakage channels. Metal electrodes are grown on the top layer via magnetron sputtering and formed into ohmic contacts through rapid thermal annealing (RTA). The back side of the substrate is polished, and metal electrodes are grown on the bottom layer via magnetron sputtering, followed by RTA to form ohmic contacts.

[0060] Preferably, the basic etching steps are as follows: first, use photoresist on n +An etching window is defined on the Ga2O3 contact layer, using a Cl2 / BCl3 / Ar gas combination for n + →i→n - →p - When etching the layer, the etching rate must be controlled to avoid over-etching and damaging the underlying substrate. Etching should be stopped until the p-layer is exposed. + A diamond substrate is used to ensure that the electrodes can contact the bottom, remove photoresist, and clean any residue. The etching channel is located on the side of the device and is a rectangular groove.

[0061] Example 2

[0062] like Figure 2 As shown, based on the same concept, this embodiment proposes a method for fabricating a detector, including the following steps:

[0063] (1) Provide p + Diamond substrate, for p + The diamond substrate was cleaned and dried; the cleaning process involved ultrasonic cleaning with acetone, isopropanol and deionized water for 5 minutes in sequence, followed by drying with nitrogen gas.

[0064] (2) Microwave plasma chemical vapor deposition (MPCVD) was used on p + p grown on diamond substrate - A type-3 diamond multiplication layer was grown; the growth conditions for microwave plasma chemical vapor deposition were as follows: introduction of a CH4 / H2 / B2H6 gas mixture, temperature 800-900℃ (too low a temperature will reduce crystal quality, too high a temperature will reduce doping efficiency), and pressure 20-30 Torr (too high a pressure will affect crystal morphology, too low a pressure will reduce deposition rate). At this time, a p-type diamond multiplication layer was grown. - Type II diamond multiplication layer, doping concentration 1×10 15 -2×10 15 cm -3 Thickness 200 (±20) nm.

[0065] (3) Using metal-organic chemical vapor deposition (MOCVD) on p - n-type diamond multiplication layers are grown sequentially - Type I Ga2O3 charge layer, Type II Ga2O3 absorber layer, n + Type Ga2O3 contact layer, with doping concentrations of 3×10 17 cm -3 -5×10 17 cm -3 1×10 15 cm -3 -2×10 15 cm -3 1×10 19 cm-3 -2×10 19 cm -3 The thicknesses are 200 (±20) nm, 400 (±20) nm, and 200 (±20) nm, respectively. The growth conditions for metal-organic chemical vapor deposition are: a gas mixture containing Ga source, PH3 or N2 is introduced, the temperature is 800-950℃ (below 800℃ will produce amorphous or polycrystalline, and above 950℃ will produce volatilization loss), and the pressure is 20-100 Torr (50 Torr is commonly used).

[0066] (4) Define the pattern by photolithography and etch n using inductively coupled plasma (ICP). + Type I Ga2O3 contact layer, Type II Ga2O3 absorber layer, n - Type Ga2O3 charge layer and p - Type II diamond multiplication layer to expose p + A diamond substrate is used to form a mesa structure. The gas used for inductively coupled plasma etching is one or a mixture of BCl3 and Ar, with a BCl3 flow rate of 15-40 sccm, an Ar flow rate of 10-30 sccm, an etching pressure of 10-30 mTorr, an RF power of 10-20 W, an ICP power of 60-100 W, and an etching time of 30-90 s.

[0067] Preferably, the BCl3 flow rate is 25 sccm, the Ar flow rate is 15 sccm, the etching pressure is 15 mTorr, the RF power is 10 W, the ICP power is 60 W, and the etching time is 50 s.

[0068] (5) Annealing and wet treatment are performed on the etched sidewalls to repair the etch damage; annealing is performed in a nitrogen or oxygen atmosphere at 400-500℃ for 10-15 min; wet treatment is performed by soaking in buffer oxide etching solution (BOE) for 10-30 s and then rinsing and drying.

[0069] In this embodiment, the repair method in step (5) is as follows: ultrasonic cleaning with acetone / isopropanol is used to remove photoresist and avoid residual polymer covering the damaged area, which would affect subsequent wet etching; rinsing is done with deionized water and then dried; the sample is gently immersed in BOE solution for 10–30 seconds, gently shaken, and immediately removed, rinsed with deionized water for 3–5 minutes, and dried with N2. The cleaned sample is then placed into a preheated chamber, and high-purity N2 (99.999%) or O2 is introduced at a continuous flow rate ≥200 sccm, with a target temperature of 400–500°C. The temperature is increased at a rate of approximately 10°C / s, held for 10–15 minutes, and then cooled and removed from the furnace. After removing the sample, it is cooled with N2.

[0070] (6) In n +The top electrode is deposited on the type Ga2O3 contact layer, in p + A bottom electrode is deposited on the back side of a diamond substrate, and an ohmic contact is formed by rapid thermal annealing. The conditions for rapid thermal annealing are as follows: ohmic contact is formed by RTP method, nitrogen atmosphere, temperature 470℃, holding time 1 min, using rapid thermal annealing equipment (RTA) or tube annealing furnace equipment.

[0071] In this embodiment, the top and bottom electrodes are formed by electron beam evaporation, thermal deposition, or magnetron sputtering. Preferably, the top metal electrode material is a Ti, Al, Ni, Au multilayer metal with thicknesses of 10nm / 80nm / 20nm / 100nm, respectively, with an error of 1-2nm; the bottom electrode material is Ni / Au with thicknesses of 20nm / 80nm, respectively, with an error of 1-2nm; the materials are not limited here, and functionally equivalent metal materials can also be used.

[0072] The fabrication process of the solar-blind ultraviolet avalanche photodetector based on the SAM-type gallium oxide / diamond heterojunction provided by this invention is simple, and it utilizes p - Diamond and n - The formation of a type II heterojunction with Ga2O3 significantly improves the performance of the photodetector. Firstly, diamond, due to its inherent properties, exhibits excellent solar-blind selectivity, similar to gallium oxide. Secondly, diamond possesses extremely high thermal conductivity, greatly compensating for the low thermal conductivity and insufficient heat dissipation of gallium oxide, thus endowing the device with excellent thermal management capabilities. p-type diamond can form a type II heterojunction with n-type gallium oxide. Its built-in electric field not only effectively promotes the separation and transport of photogenerated carriers, improving the response speed, but also, under reverse bias and in a high-intensity built-in electric field, photogenerated carriers undergo collisional ionization and avalanche multiplication, successfully achieving high-gain ultraviolet solar-blind detection performance, while further improving its single-photon detection performance. This design provides a new approach for the development of high-gain ultraviolet solar-blind avalanche photodetectors, solving the problems of selectivity and weak heat dissipation in the solar-blind band for gallium oxide-based avalanche photodetectors, and has broad application prospects, providing new ideas for the design and optimization of high-gain ultraviolet solar-blind avalanche photodetectors.

[0073] like Figure 3 The diagram shown is the reverse voltage-current plot of the SAM-type gallium oxide / diamond heterojunction solar-blind ultraviolet avalanche detector of the present invention. It can be seen that:

[0074] 1. Low dark current → Process and structural optimization

[0075] Extremely low dark current (<10 in the low bias region) -10 A), confirming:

[0076] Mesh etching + damage repair (annealing + BOE wet etching) effectively reduces sidewall defects and suppresses leakage current;

[0077] The heterojunction interface has high quality (interface compatibility between MPCVD and MOCVD growth), reducing interface state leakage.

[0078] 2. Avalanche Effect → Heterojunctions and Structural Design

[0079] The steep ascent section breached by the avalanche confirms:

[0080] Type II heterojunction (p-type diamond / n-type Ga2O3) induces a strong built-in electric field. After being superimposed with a reverse bias, a high electric field region is formed at the interface between the diamond multiplication layer and the Ga2O3 charge layer (satisfying the collision ionization threshold).

[0081] Separate Absorption Multiplication (SAM) Structure: i-type Ga2O3 is responsible for light absorption, p... - Diamond is responsible for carrier multiplication, and functional partitioning improves efficiency;

[0082] Platform structure: further concentrates the electric field and enhances the avalanche triggering capability.

[0083] 3. Solar blind light response → Material bandgap matching

[0084] The photocurrent in the low-bias region under illumination confirms:

[0085] The ultrawide bandgap of Ga2O3 (4.9eV) + diamond (5.5eV) enables solar-blind selectivity by responding only to photons in the <280nm solar-blind band (carriers can be excited with photon energy >4.9eV) and having no response to long wavelengths (such as visible light and near ultraviolet light).

[0086] 4. Single-photon detection → Avalanches under both illumination and darkness conditions

[0087] The device has a breakdown voltage of 112.5V under illumination and 120.7V under darkness. By utilizing the difference in breakdown voltage, a DC + pulse signal can be selected to build a suitable test circuit and realize the function of single-photon detection.

[0088] This invention achieves low dark current, clear avalanche characteristics, and solar-blind photoresponse through the synergy of "materials-structure-process", laying the foundation for single-photon level detection and solving the core problems of "difficulty in carrier multiplication, poor heat dissipation, and insufficient selectivity" in the background technology.

[0089] The parts of this invention not described in detail are prior art, therefore they are not described in detail here.

[0090] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0091] Although this document uses a considerable amount of technical terminology, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0092] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes made to their shape or structure, any technical solution that is the same as or similar to this invention falls within the protection scope of this invention.

Claims

1. A diamond-based gallium oxide heterojunction avalanche photodetector, characterized in that, Including those stacked from bottom to top: p + Diamond substrate; Formed in the p + p on diamond substrate - Type II diamond multiplier layer; Formed in the p - n on a type of diamond multiplier layer - Type Ga2O3 charge layer; Formed in the n - i-type Ga2O3 absorber layer on the i-type Ga2O3 charge layer; n formed on the i-type Ga2O3 absorber layer + Type Ga2O3 contact layer; Formed in the n + Top electrode on Ga2O3 contact layer; as well as Formed in the p + Bottom electrode on the back side of the diamond substrate; Wherein, p - Type II diamond multiplier layer and n - A type II heterojunction is formed by a Ga2O3 charge layer. The detector as a whole is a discrete absorption multiplication structure, and a mesa structure is formed by etching. Wherein, p + The doping concentration of the diamond substrate is 1×10⁻⁶. 18 cm -3 -1×10 19 cm -3 The p - The doping concentration of the diamond multiplication layer is 1×10⁻⁶. 15 cm -3 -2×10 15 cm -3 The thickness is 200±20nm; the n - The doping concentration of the Ga2O3 charge layer is 3 × 10⁻⁶. 17 cm -3 -5×10 17 cm -3 The thickness is 200±20 nm; the doping concentration of the i-type Ga2O3 absorber layer is 1×10⁻⁶. 15 cm -3 -2×10 15 cm -3 The thickness is 400±20nm; the n + The doping concentration of the Ga2O3 contact layer is 1×10⁻⁶. 19 cm -3 -2×10 19 cm -3 The thickness is 200±20nm.

2. The diamond-based gallium oxide heterojunction avalanche photodetector according to claim 1, characterized in that, The top electrode is a Ti / Al / Ni / Au multilayer metal with layer thicknesses of 10±1nm, 80±1nm, 20±1nm, and 100±1nm, respectively; the bottom electrode is a Ni / Au multilayer metal with layer thicknesses of 20±1nm and 80±1nm, respectively.

3. A method for fabricating a diamond-based gallium oxide heterojunction avalanche photodetector, characterized in that, Includes the following steps: (1) Provide p + Diamond substrate, for the p + The diamond substrate is cleaned and dried; (2) Microwave plasma chemical vapor deposition was used on the p + p grown on diamond substrate - Type II diamond multiplier layer; (3) Using metal-organic chemical vapor deposition on the p - n-type diamond multiplication layers are grown sequentially - Type I Ga2O3 charge layer, Type II Ga2O3 absorber layer, n + Type Ga2O3 contact layer; (4) The pattern is defined by photolithography, and the n is etched by inductively coupled plasma. + Type I Ga2O3 contact layer, Type II Ga2O3 absorber layer, n - Type Ga2O3 charge layer and p - Type II diamond multiplication layer to expose p + A diamond substrate is used to form a mesa structure. (5) Annealing and wet treatment are performed on the etched sidewalls to repair the etched damage; (6) In the n + A top electrode is deposited on the type Ga2O3 contact layer, in the p + A bottom electrode is deposited on the back side of a diamond substrate and formed into an ohmic contact by rapid thermal annealing. In step (4), the gas used for inductively coupled plasma etching is one or a mixture of BCl3 and Ar, wherein the flow rate of BCl3 is 15-40 sccm, the flow rate of Ar is 10-30 sccm, the etching pressure is 10-30 mTorr, the RF power is 10-20 W, the ICP power is 60-100 W, and the etching time is 30-90 s. In step (5), the annealing is performed in a nitrogen or oxygen atmosphere at 400-500℃ for 10-15 minutes; the wet treatment is performed by immersing in a buffer oxide etching solution for 10-30 seconds and then rinsing and drying.

4. The preparation method according to claim 3, characterized in that, In step (1), the cleaning process involves sequentially ultrasonically cleaning with acetone, isopropanol, and deionized water for 5 minutes, followed by drying with nitrogen gas.

5. The preparation method according to claim 3, characterized in that, In step (2), the growth conditions for microwave plasma chemical vapor deposition are: a CH4 / H2 / B2H6 gas mixture is introduced, the temperature is 800-900℃, and the pressure is 20-30 Torr.

6. The preparation method according to claim 3, characterized in that, In step (3), the growth conditions for metal-organic chemical vapor deposition are: a gas mixture containing Ga source, PH3 or N2 is introduced, the temperature is 800-950℃, and the pressure is 20-100 Torr.

7. The preparation method according to any one of claims 3-6, characterized in that, In step (6), the conditions for rapid thermal annealing are: nitrogen atmosphere, temperature 470℃, and holding time 1 min.

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