Preparation method of doped Ga2O3-based photoelectric detector based on PIN junction

Abstract

The invention discloses a preparation method of a doped Ga2O3-based photoelectric detector based on a PIN junction. The preparation method comprises the following steps: firstly, performing high-temperature activation on an epitaxial Mg-doped GaN substrate slice on sapphire to form a good P-type conductive layer; then, an anode electrode is formed on the GaN surface, and good ohmic contact is formed through rapid thermal annealing treatment; sequentially preparing an I layer (intrinsic layer) and an N layer Zn-doped Ga2O3 by using atomic layer deposition equipment, and defining an active region, wherein the material of the I layer is unintentionally doped Ga2O3, Al2O3 or AlN; and finally, preparing a cathode electrode by adopting an electron beam evaporation process to obtain the PIN junction type doped Ga2O3-based photoelectric detector. According to the invention, the PIN structure is utilized to realize the high-sensitivity detection of the specific wave band of the ultraviolet light.

Description

Technical Field

[0001] This invention belongs to the field of detector technology, specifically relating to a method for fabricating a photodetector based on a PIN junction and doped Ga2O3. Background Technology

[0002] Ga2O3, as a fourth-generation semiconductor material, has significant advantages such as ultra-wide bandgap, high breakdown field strength, and excellent chemical and thermal stability. Therefore, it is considered one of the most ideal materials for preparing highly selective and highly sensitive ultraviolet photodetectors.

[0003] Atomic layer deposition (ALD) offers excellent atomic-level thickness control and a self-limiting surface reaction, where only one atomic layer can grow per reaction cycle, ensuring uniformity and consistency in large-area film growth. The relatively low growth temperature (typically 150-350 °C) reduces lattice defects and interface states caused by high temperatures. Furthermore, by introducing additional precursor pulses, precise atomic-level doping can be easily achieved. Using ALD to dope Zn into Ga₂O₃ films can enhance the material's electrical transport properties, modulating the film bandgap, improving thermal stability, and enhancing device response.

[0004] A PIN junction is formed by inserting an intrinsic semiconductor layer between P-type and N-type semiconductors, creating a PIN structure. The I-layer is the main region for photogenerated carriers. Because it lacks a high concentration of dopants, there are few carrier recombination centers, resulting in high light absorption efficiency. Increasing the thickness of the I-layer allows more photons to be absorbed and generate electron-hole pairs, significantly improving the device's quantum efficiency. Under reverse bias, the entire thick I-layer is almost completely depleted, forming a very wide depletion region. This causes photogenerated carriers to be generated primarily in the strong internal electric field region and rapidly swept out by the electric field, greatly reducing diffusion time and resulting in a high response speed.

[0005] Currently, research on Ga2O3-based ultraviolet photodetectors is still in its early stages of development, limited by issues such as thin film quality and defects, trade-offs between high responsivity and fast response time, and difficulties in preparation with heteroelement doping. Therefore, further improvements are needed to address these problems. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies, the present invention aims to provide a method for fabricating a PIN junction-based Ga2O3-based photodetector. The present invention prepares unintentionally doped Ga2O3 and Zn-doped Ga2O3-based thin films using atomic layer deposition technology, and constructs a PIN-type photodetector together with P-type GaN, thereby further improving the photodetector sensitivity and response speed in the ultraviolet band.

[0007] This invention is achieved through the following technical solution.

[0008] This invention provides a method for fabricating a photodetector based on a PIN junction and doped Ga2O3, comprising the following steps: (1) Clean the sapphire-epitaxial GaN substrate; (2) The clean GaN substrate is annealed at high temperature in an inert atmosphere to activate holes and serve as a good P-type active region. (3) An anode electrode is formed on the surface of the activated GaN substrate using electron beam evaporation, and then annealed to form a good ohmic contact; (4) Atomic layer deposition process is used to deposit I region material, and then Zn-doped Ga2O3 material is grown in situ as N region material. After photolithography, wet etching, stripping and annealing, the active region is defined. Among them, I region material is selected from any one of unintentionally doped Ga2O3, Al2O3 or AlN. (5) A cathode electrode is prepared on the surface of the N-region material using electron beam evaporation.

[0009] In this invention, in step (1), the sapphire-epitaxy GaN substrate consists of a sapphire substrate and epitaxially grown Mg-doped GaN, with the Mg-doped GaN having a thickness of 4 ± 0.5 μm and a doping concentration of 2 × 10⁻⁶. 17 cm -3 When cleaning the surface of the GaN substrate, it is washed with acetone, isopropanol and deionized water in sequence, and finally dried with nitrogen.

[0010] In this invention, in step (2), the annealing conditions are: in a nitrogen atmosphere, the cavity pressure is 1×10⁻⁶. 3 Under conditions of Pa and furnace temperature of 680-700℃, the GaN substrate was subjected to high-temperature annealing treatment for 2-4 minutes using a rapid thermal annealing (RTP) device.

[0011] In this invention, in step (3), the anode electrode is a Ni / Au multilayer metal with a ring structure; the anode electrode forms a closed loop, which can uniformly collect or inject charge carriers from all directions, reducing the path resistance and inductance of current converging to a single point, and providing a more uniform transverse electric field overall than a non-enclosed electrode. More preferably, the Ni layer metal thickness is 50 nm; the Au layer metal thickness is 50 nm.

[0012] In this invention, in step (3), the anode electrode is fabricated on the surface of the GaN substrate by photolithography, electron beam evaporation, and lift-off processes. The specific fabrication process is as follows: First, a ring electrode region is defined on the surface of a GaN substrate using photolithography. Then, a Ni / Au multilayer metal is deposited using electron beam evaporation. Next, the photoresist is dissolved in acetone and stripped. Then, the substrate is cleaned with isopropanol and deionized water, and finally dried with nitrogen to complete the fabrication of the ring-shaped anode electrode.

[0013] In this invention, in step (3), the annealing conditions are: annealing for 2-4 minutes at an O2 flow rate of 380-420 sccm and a temperature of 550-580 ℃ to form a good ohmic contact.

[0014] In this invention, in step (4), the thickness of the I-region material layer is 30-80 nm, and the thickness of the N-region material layer is 40-60 nm. Atomic layer deposition, tube furnace annealing, photolithography, and wet etching processes are used to define the active region consisting of unintentionally doped Ga2O3 I-region material and in-situ grown Zn-doped Ga2O3 N-region material; step (4) specifically includes: First, using trimethylgallium and oxygen plasma as precursors, unintentionally doped Ga2O3 in region I was grown by atomic layer deposition. Then, trimethylgallium and oxygen plasma were used as precursors for Ga2O3, and diethylzinc and H2O were used as precursors for ZnO. During the thin film deposition process, one supercycle was a superposition of one Ga2O3 subcycle and one ZnO subcycle. That is, after completing one atomic layer deposition cycle of Ga2O3, another atomic layer deposition cycle of ZnO was grown. The growth was carried out in an alternating cycle, and Zn-doped Ga2O3 material was grown in situ on the surface of the material layer in region I. Next, the active region is defined by photolithography on the thin film obtained by in-situ deposition of I-region and N-region materials, which is located inside the annular anode electrode. The I-region and N-region thin films not covered by photoresist are etched away. The photoresist is then dissolved in acetone for stripping, and the film is cleaned with isopropanol and deionized water. Finally, it is dried with nitrogen and the resulting film is annealed in a tube furnace at 395-405 °C for 50-70 min in an oxygen atmosphere to complete the definition of the active region.

[0015] In this invention, in step (4), the atomic layer deposition conditions are as follows: the growth temperature is 180-250℃, the radio frequency power is set to 80-120 W, the pressure in the reaction chamber is maintained between 0.8-1.8 torr, and the pressure difference between the reaction chamber and the outer chamber is stable between 6-8 torr.

[0016] In this invention, in step (5), the cathode electrode is a Ti / Au multilayer metal, which is a fishbone-shaped electrode. The specific shape of its structure can improve the collection efficiency of photogenerated carriers. The cathode electrode is fabricated by photolithography, electron beam evaporation and stripping technology, as follows; ① A fishbone-shaped electrode region is defined on the surface of the N-region material using photolithography; ② A multilayered metal Ti / Au was deposited on the structure obtained in step ① using electron beam evaporation. The photoresist was then dissolved in acetone and stripped. The electrode was cleaned with isopropanol and deionized water and finally dried with nitrogen to complete the electrode fabrication.

[0017] The present invention also provides a photodetector based on a PIN junction and doped Ga2O3, which is prepared by the above-described method.

[0018] In this invention, the Mg-doped GaN epitaxial substrate on sapphire is first activated at high temperature to form a good P-type conductive layer. Then, an anode electrode is formed on the GaN surface and rapidly thermally annealed to form a good ohmic contact. Next, an I-layer Ga2O3 and an N-layer Zn-doped Ga2O3 are prepared using atomic layer deposition equipment to define the active region. Finally, a cathode electrode is prepared using electron beam evaporation to obtain a PIN junction type Ga2O3-based photodetector.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention adopts a PIN structure, which significantly improves the sensitivity of the photodetector: the reverse leakage current is extremely low, and it operates under a high reverse bias voltage, which further enhances the electric field and improves the carrier collection efficiency, thereby improving the sensitivity; it has good linearity, and the output photocurrent and incident light power maintain a good linear relationship over a wide range.

[0020] 2. This invention uses atomic layer deposition (ALD) technology to prepare unintentionally doped Ga2O3 in region I, and then grows Zn-doped Ga2O3 in N region in situ. Its advantages are: (1) large-area growth of thin film with excellent uniformity and consistency; the Ga2O3 material in region I is dense and uniform with few defects; (2) the growth of doped thin film by atomic layer deposition can achieve precise growth of doped film by adjusting the ratio of dopant precursor cycle to host material cycle; (3) high lattice matching degree between Ga2O3 and Zn-doped Ga2O3, and lattice matching is the ideal starting point for constructing high-quality heterojunctions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the photodetector based on a PIN junction and doped Ga2O3 in this invention; wherein, 1 is a sapphire substrate; 2 is a Mg-doped GaN epitaxial layer; 3 is a Ni / Au ohmic contact annular anode; 4 is an I-layer unintentionally doped Ga2O3; 5 is an N-layer Zn-doped Ga2O3; and 6 is a Ti / Au ohmic contact fishbone-shaped cathode.

[0022] Figure 2This is a flowchart of the PIN junction-type Ga2O3-based photodetector of the present invention; a is the epitaxial Mg-doped GaN thin film on a sapphire substrate, b is the Ni / Au 50 / 50nm thin film after photolithography and electron beam evaporation, c is the ring electrode formed after lift-off, d is the unintentionally doped Ga2O3 thin film in the I region and the Zn-doped Ga2O3 thin film in the N region after atomic layer deposition, e is the active region within the ring electrode defined after photolithography and wet etching, and f is the fishbone-shaped electrode formed after photolithography, electron beam evaporation and lift-off.

[0023] Figure 3 The figures show the test results of the electrical and photoelectric properties of the PIN junction-type doped Ga2O3-based photodetector in this invention; a represents the PIN under dark conditions, at 0.1 mW / cm². 2 IV curves under illumination of 254 nm and 365 nm, and IV curves of the PIN junction under dark conditions, with b = 0.1 mW / cm². 2 Photocurrent and photoresponsivity at 0 bias under different intensity bands. The inset shows a comparison of the photoresponsivity of PN junction and PIN junction devices at different intensity bands under 0 bias. c represents the photocurrent and photoresponsivity at different light intensities under 0 bias at the 365 nm band. d represents the photoelectric dynamic characteristic curve of the device under 0 bias. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0025] Example 1

[0026] This embodiment provides a photodetector based on a PIN junction and doped Ga2O3, with the structure as follows: Figure 1 As shown, from bottom to top, the layers are: 1. Sapphire substrate; 2. Mg-doped GaN epitaxial layer; 3. Ni / Au ohmic contact annular anode; 4. I layer unintentionally doped Ga2O3; 5. N layer Zn-doped Ga2O3; 6. Ti / Au ohmic contact fishbone-shaped cathode.

[0027] like Figure 2 As shown, the specific fabrication method of the PIN junction-type doped Ga2O3-based photodetector is as follows: (1) such as Figure 2 a. Clean the Mg-doped GaN substrate 2 on the sapphire by the following steps: immerse in acetone for 5 min, then immerse in isopropanol for 5 min, then rinse with deionized water for 5 min, and finally dry with nitrogen. (2) Place the substrate treated in step (1) into a rapid thermal annealing apparatus, under a nitrogen atmosphere and a chamber pressure of 1×10⁻⁶. 3Under the conditions of Pa and furnace temperature of 680℃, the GaN substrate was subjected to high-temperature annealing treatment for 3 min using a rapid thermal annealing (RTP) device to activate holes and serve as a good P-type active region. (3) such as Figure 2 b. In the structure described in step (2), a ring electrode region is defined on the GaN surface using photolithography; then, a Ni / Au 50 / 50 nm stacked metal is deposited using electron beam evaporation. (4) such as Figure 2 c. The photoresist was dissolved in acetone and stripped, then cleaned with isopropanol and deionized water, and finally dried with nitrogen. The structure was then placed in a rapid thermal annealing furnace and annealed for 3 minutes at an O2 flow rate of 400 sccm and a temperature of 570°C to form a Ni / Au ohmic contact annular anode 3. (5) such as Figure 2 d. The unintentionally doped Ga2O3 in region I, grown by atomic layer deposition in the structure described in step (4), has a thickness of 50 nm and a growth temperature of 200 ℃. The precursor is trimethylgallium and oxygen plasma. The radio frequency power during the deposition process is set to 100 W, the pressure in the reaction chamber is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. The trimethylgallium precursor is introduced into the reaction chamber, and N2 is used as the purge gas. The purge time is a certain duration to remove reaction residues and gaseous byproducts. The O2 plasma precursor is introduced, and N2 is used to purge and remove the byproducts generated by the previous pulse reaction. Zn-doped Ga2O3 is grown in situ on this structure. Trimethylgallium and oxygen plasma is used as the precursors for Ga and O, and diethylzinc and H2O are used as the precursors for Zn and O. The radio frequency power during the deposition process was set to 100 W, the pressure in the reaction chamber was maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber was stabilized at 7.0 torr. The element doping ratio was set to 1:1 for atomic layer deposition cycle growth. Therefore, one supercycle in the thin film deposition process is the superposition of one Ga2O3 subcycle and one ZnO subcycle. That is, after completing one atomic layer deposition cycle of Ga2O3, another atomic layer deposition cycle of ZnO is grown. This cycle is repeated until the thickness reaches 50 nm. (6) For example Figure 2 e. Define the active region of the structure described in step (5) by photolithography. The active region is located inside the ring electrode. Use a 1:50 BOE:H2O solution for etching. After 20 s, etch away the I and N region films that are not covered by the photoresist. Then use acetone to dissolve the photoresist for stripping. After that, clean with isopropanol and deionized water. Finally, dry with nitrogen. Anneal the obtained film at 400 °C in an oxygen atmosphere using a tube furnace for 1 hour to complete the definition of the active region. (7) For example Figure 2f, In step (6), the radio frequency power during the doping deposition process using photolithography is set to 100 W, the reaction chamber pressure is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. A fishbone-shaped electrode region is defined on the surface, and then a Ti / Au 20 / 50 nm stacked metal is deposited using electron beam evaporation technology, with a deposition chamber pressure of 4.5 × 10⁻⁶. -4 Pa, high voltage of 7.54kV, then use acetone to dissolve the photoresist for stripping, clean with isopropanol and deionized water, and finally blow dry with nitrogen to complete the preparation of the fishbone-shaped electrode. (8) Finally, the photoelectric properties of the sample were characterized using a semiconductor analyzer and a continuous xenon lamp light source. The results showed that the reverse current of the PIN device remained in the pA range under dark conditions, and the on / off ratio reached 10. 7 Compared to PN junction devices, the reverse dark current is reduced by nearly five orders of magnitude at -1V. PIN junction devices further increase the dark current by 0.1mW / cm at 254 nm and 365 nm, respectively. 2 Intense ultraviolet light irradiation can clearly show an increase in current, generating photocurrent, such as... Figure 3 As shown; at 0.1mW / cm 2 Under illumination of different wavelengths with varying intensities, at zero bias, photocurrent was generated in the 250-400 nm band, while no significant photoresponse was observed in the 400-1000 nm band. The optimal response band was 300 nm, with a photoresponse of 20 mA / W, demonstrating excellent self-powered photodetector characteristics in the ultraviolet band. Compared to the PN type, the PIN type photodetector showed a significant reduction in reverse dark current due to the increased I-region, with the dark current decreasing by nearly five orders of magnitude at -1V. This resulted in a five-order-of-magnitude improvement in the device's on / off ratio and a substantial increase in photoresponse. At zero bias in the 365 nm band, the photocurrent exhibited a good linear relationship with the light intensity under different illumination intensities. At zero bias in the 365 nm band, the photodetector's rise time was 46 ms and fall time was 4 ms, indicating a fast photoresponse speed, achieved through illumination switching.

[0028] Example 2

[0029] This embodiment provides a photodetector based on a PIN junction and doped Ga2O3, with the structure as follows: Figure 1 As shown, from bottom to top, the layers are: 1. Sapphire substrate; 2. Mg-doped GaN epitaxial layer; 3. Ni / Au ohmic contact annular anode; 4. I layer unintentionally doped AlN; 5. N layer Zn-doped Ga2O3; 6. Ti / Au ohmic contact fishbone-shaped cathode.

[0030] like Figure 2 As shown, the specific fabrication method of the PIN junction-type doped Ga2O3-based photodetector is as follows: (1) such as Figure 2 a. Clean the Mg-doped GaN substrate 2 on the sapphire by the following steps: immerse in acetone for 5 min, then immerse in isopropanol for 5 min, then rinse with deionized water for 5 min, and finally dry with nitrogen. (2) Place the substrate treated in step (1) into a rapid thermal annealing apparatus, under a nitrogen atmosphere and a chamber pressure of 1×10⁻⁶. 3 Under the conditions of Pa and furnace temperature of 680℃, the GaN substrate was subjected to high-temperature annealing treatment for 3 min using a rapid thermal annealing (RTP) device to activate holes and serve as a good P-type active region. (3) such as Figure 2 b. In the structure described in step (2), a ring electrode region is defined on the GaN surface using photolithography; then, a Ni / Au 50 / 50 nm stacked metal is deposited using electron beam evaporation. (4) such as Figure 2 c. The photoresist was dissolved in acetone and stripped, then cleaned with isopropanol and deionized water, and finally dried with nitrogen. The structure was then placed in a rapid thermal annealing furnace and annealed for 3 minutes at an O2 flow rate of 400 sccm and a temperature of 580°C to form a Ni / Au ohmic contact annular anode 3. (5) such as Figure 2 d. The unintentionally doped AlN in region I, grown by atomic layer deposition in the structure described in step (4), has a thickness of 60 nm and a growth temperature of 200 °C. The precursor is trimethylaluminum and ammonia plasma. The radio frequency power during the deposition process is set to 100 W, the pressure in the reaction chamber is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. The trimethylaluminum precursor is introduced into the reaction chamber, and N2 is used as the purge gas. The purge time is a certain duration to remove reaction residues and gaseous byproducts. The NH3 plasma precursor is introduced, and N2 is used to purge and remove the byproducts generated by the previous pulse reaction. Zn-doped Ga2O3 is grown in situ on this structure. Trimethylgallium and oxygen plasma are used as precursors for Ga and O, and diethylzinc and H2O are used as precursors for Zn and O. The radio frequency power during the deposition process was set to 100 W, the pressure in the reaction chamber was maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber was stabilized at 7.0 torr. The element doping ratio was set to 1:1 for atomic layer deposition cycle growth. Therefore, one supercycle in the thin film deposition process is the superposition of one Ga2O3 subcycle and one ZnO subcycle. That is, after completing one atomic layer deposition cycle of Ga2O3, another atomic layer deposition cycle of ZnO is grown. This cycle is repeated until the thickness reaches 60 nm. (6) For example Figure 2e. Define the active region of the structure described in step (5) by photolithography. The active region is located inside the ring electrode. Use a 1:50 BOE:H2O solution for etching. After 10 s, etch away the N region film not covered by the photoresist. Then use 40 wt% KOH for 3 min to etch away the I region AlN film. Then use acetone to dissolve the photoresist for stripping. Then clean with isopropanol and deionized water. Finally dry with nitrogen. Anneal the obtained film at 400 °C in an oxygen atmosphere using a tube furnace for 1 hour to complete the definition of the active region. (7) For example Figure 2 f, In step (6), the radio frequency power during the doping deposition process using photolithography is set to 100 W, the reaction chamber pressure is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. A fishbone-shaped electrode region is defined on the surface, and then a Ti / Au 20 / 50 nm stacked metal is deposited using electron beam evaporation technology, with a deposition chamber pressure of 4.5 × 10⁻⁶. -4 Pa, high voltage of 7.54kV, then acetone is used to dissolve the photoresist for stripping, followed by cleaning with isopropanol and deionized water, and finally drying with nitrogen to complete the fabrication of the fishbone-shaped electrode.

[0031] Example 3

[0032] This embodiment provides a photodetector based on a PIN junction and doped Ga2O3, with the structure as follows: Figure 1 As shown, from bottom to top, the layers are: 1. Sapphire substrate; 2. Mg-doped GaN epitaxial layer; 3. Ni / Au ohmic contact annular anode; 4. I layer unintentionally doped Al2O3; 5. N layer Zn-doped Ga2O3; 6. Ti / Au ohmic contact fishbone-shaped cathode.

[0033] like Figure 2 As shown, the specific fabrication method of the PIN junction-type doped Ga2O3-based photodetector is as follows: (1) such as Figure 2 a. Clean the Mg-doped GaN substrate 2 on the sapphire by the following steps: immerse in acetone for 5 min, then immerse in isopropanol for 5 min, then rinse with deionized water for 5 min, and finally dry with nitrogen. (2) Place the substrate treated in step (1) into a rapid thermal annealing apparatus, under a nitrogen atmosphere and a chamber pressure of 1×10⁻⁶. 3 Under the conditions of Pa and furnace temperature of 700℃, the GaN substrate was subjected to high-temperature annealing treatment for 3 min using a rapid thermal annealing (RTP) device to activate holes and serve as a good P-type active region. (3) such as Figure 2b. In the structure described in step (2), a ring electrode region is defined on the GaN surface using photolithography; then, a Ni / Au 50 / 50 nm stacked metal is deposited using electron beam evaporation. (4) such as Figure 2 c. The photoresist was dissolved in acetone and stripped, then cleaned with isopropanol and deionized water, and finally dried with nitrogen. The structure was then placed in a rapid thermal annealing furnace and annealed for 3 minutes at an O2 flow rate of 400 sccm and a temperature of 560°C to form a Ni / Au ohmic contact annular anode 3. (5) such as Figure 2 d. The unintentionally doped AlN in region I, grown by atomic layer deposition in the structure described in step (4), has a thickness of 80 nm and a growth temperature of 200 °C. The precursor is trimethylaluminum and oxygen plasma. The radio frequency power during the deposition process is set to 100 W, the pressure in the reaction chamber is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. The trimethylaluminum precursor is introduced into the reaction chamber, and N2 is used as the purge gas. The purge time is a certain duration to remove reaction residues and gaseous byproducts. The O2 plasma precursor is introduced, and N2 is used to purge and remove the byproducts generated by the previous pulse reaction. Zn-doped Ga2O3 is grown in situ on this structure. Trimethylgallium and oxygen plasma is used as the precursors for Ga and O, and diethylzinc and H2O are used as the precursors for Zn and O. The radio frequency power during the deposition process was set to 100 W, the pressure in the reaction chamber was maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber was stabilized at 7.0 torr. The element doping ratio was set to 1:1 for atomic layer deposition cycle growth. Therefore, one supercycle in the thin film deposition process is the superposition of one Ga2O3 subcycle and one ZnO subcycle. That is, after completing one atomic layer deposition cycle of Ga2O3, another atomic layer deposition cycle of ZnO is grown. This cycle is repeated until the thickness reaches 80 nm. (6) For example Figure 2 e. Define the active region of the structure described in step (5) by photolithography. The active region is located inside the ring electrode. Use a 1:50 BOE:H2O solution for etching. After 10 s, etch away the N-region film in the area not covered by the photoresist. Then use 85 wt% nitric acid, heat to 120 ℃, and etch away the I-region Al2O3 film after 2 min. Then use acetone to dissolve the photoresist for stripping. Then clean with isopropanol and deionized water. Finally dry with nitrogen. Anneal the obtained film at 400 ℃ in an oxygen atmosphere using a tube furnace for 1 hour to complete the definition of the active region. (7) For example Figure 2f, In step (6), the radio frequency power during the doping deposition process using photolithography is set to 100 W, the reaction chamber pressure is maintained at 1.0 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized at 7.0 torr. A fishbone-shaped electrode region is defined on the surface, and then a Ti / Au 20 / 50 nm stacked metal is deposited using electron beam evaporation technology, with a deposition chamber pressure of 4.5 × 10⁻⁶. -4 Pa, high voltage of 7.54kV, then acetone is used to dissolve the photoresist for stripping, followed by cleaning with isopropanol and deionized water, and finally drying with nitrogen to complete the fabrication of the fishbone-shaped electrode.

[0034] The above-described embodiments are preferred embodiments of the present invention. However, the embodiments of the present invention are not limited to the embodiments described. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for fabricating a photodetector based on a PIN junction and doped Ga2O3, characterized in that, Includes the following steps: (1) Clean the sapphire-epitaxial GaN substrate; (2) The clean GaN substrate is annealed at high temperature in an inert atmosphere to activate the holes; (3) An anode electrode is formed on the surface of the activated GaN substrate using electron beam evaporation, and then annealed to form a good ohmic contact; (4) Atomic layer deposition process is used to deposit I region material, and then Zn-doped Ga2O3 material is grown in situ as N region material. After photolithography, wet etching, stripping and annealing, the active region is defined. Among them, I region material is selected from any one of unintentionally doped Ga2O3, Al2O3 or AlN. (5) A cathode electrode is prepared on the surface of the N-region material using electron beam evaporation.

2. The preparation method according to claim 1, characterized in that, In step (1), the sapphire-epitaxy GaN substrate consists of a sapphire substrate and epitaxially grown Mg-doped GaN. The thickness of the Mg-doped GaN is 4 ± 0.5 μm, and the doping concentration is 2 × 10⁻⁶. 17 cm -3 When cleaning the surface of the GaN substrate, it is washed with acetone, isopropanol and deionized water in sequence, and finally dried with nitrogen.

3. The preparation method according to claim 1, characterized in that, In step (2), the annealing conditions are: in a nitrogen atmosphere, the chamber pressure is 1×10⁻⁶. 3 Under conditions of Pa and furnace temperature of 680-700℃, the GaN substrate was subjected to high-temperature annealing treatment for 2-4 minutes using a rapid thermal annealing (RTP) device.

4. The preparation method according to claim 1, characterized in that, In step (3), the anode electrode is a Ni / Au multilayer metal with a ring structure; the anode electrode is fabricated on the surface of the GaN substrate by photolithography, electron beam evaporation and lift-off processes, and the specific fabrication process is as follows: First, a ring electrode region is defined on the surface of a GaN substrate using photolithography. Then, a Ni / Au multilayer metal is deposited using electron beam evaporation. Next, the photoresist is dissolved in acetone and stripped. Then, the substrate is cleaned with isopropanol and deionized water, and finally dried with nitrogen to complete the fabrication of the ring-shaped anode electrode.

5. The preparation method according to claim 1, characterized in that, In step (3), the annealing conditions are: annealing for 2-4 min at an O2 flow rate of 380-420 sccm and a temperature of 550-580 ℃ to form a good ohmic contact.

6. The preparation method according to claim 1, characterized in that, In step (4), the thickness of the material layer in region I is 30-80 nm, and the thickness of the material layer in region N is 40-60 nm.

7. The preparation method according to claim 1, characterized in that, Step (4) specifically includes: First, using trimethylgallium and oxygen plasma as precursors, unintentionally doped Ga2O3 in region I was grown by atomic layer deposition. Then, trimethylgallium and oxygen plasma were used as precursors for Ga2O3, and diethylzinc and H2O were used as precursors for ZnO. During the thin film deposition process, one supercycle was a superposition of one Ga2O3 subcycle and one ZnO subcycle. That is, after completing one atomic layer deposition cycle of Ga2O3, another atomic layer deposition cycle of ZnO was grown. The growth was carried out in an alternating cycle, and Zn-doped Ga2O3 material was grown in situ on the surface of the material layer in region I. Next, the active region is defined by photolithography on the thin film obtained by in-situ deposition of I-region and N-region materials, which is located inside the annular anode electrode. The I-region and N-region thin films not covered by photoresist are etched away. The photoresist is then dissolved in acetone for stripping, and the film is cleaned with isopropanol and deionized water. Finally, it is dried with nitrogen and the resulting film is annealed in a tube furnace at 395-405 °C for 50-70 min in an oxygen atmosphere to complete the definition of the active region.

8. The preparation method according to claim 7, characterized in that, The atomic layer deposition conditions are as follows: growth temperature is 180-250℃, radio frequency power is set to 80-120 W, reaction chamber pressure is maintained between 0.8-1.8 torr, and the pressure difference between the reaction chamber and the outer chamber is stabilized between 6-8 torr.

9. The preparation method according to claim 1, characterized in that, In step (5), the cathode electrode is a Ti / Au multilayer metal, which is a fishbone-shaped electrode; the cathode electrode is fabricated by photolithography, electron evaporation and lift-off technology, as follows; ① A fishbone-shaped electrode region is defined on the surface of the N-region material using photolithography; ② A multilayered metal Ti / Au was deposited on the structure obtained in step ① using electron beam evaporation. The photoresist was then dissolved in acetone and stripped. The electrode was cleaned with isopropanol and deionized water and finally dried with nitrogen to complete the electrode fabrication.

10. A photodetector based on a PIN junction and doped Ga2O3, characterized in that, It is prepared by any one of the preparation methods according to claims 1-9.

Images