Cross-band photodetector structure and preparation method thereof

Abstract

This invention relates to the technical field of semiconductor devices, and in particular to a cross-band photodetector structure and its fabrication method. The cross-band photodetector structure includes a substrate and an Al2O3 dielectric layer. The Al2O3 dielectric layer is deposited on the substrate. A Ga2O3 thin film is disposed on the Al2O3 dielectric layer. A VO2 thin film is disposed on the Ga2O3 thin film. Nanoparticles are disposed on the VO2 thin film. Plasmon resonance occurs at the interface between the nanoparticles and the VO2 thin film. This invention enables cross-band optical response in the long-wave infrared and solar-blind ultraviolet bands, adapting to complex multi-band application scenarios.

Description

Technical Field

[0001] This invention relates to the technical field of semiconductor devices, and in particular to a cross-frequency photodetector structure and its fabrication method. Background Technology

[0002] Photodetectors are core devices that convert light signals into electrical signals, and their applications permeate almost all modern technological fields, such as optical communication, optical imaging, medical and biotechnology, and industrial security. MOS (Metal-Oxide-Semiconductor) photodetectors are optoelectronic devices based on MOS materials (such as ZnO, VO2, Ga2O3, WO3, etc.). They achieve photoelectric conversion by generating electron-hole pairs at the oxide interface or within the semiconductor through the photoconductive or photovoltaic effects. Their core advantages lie in combining high sensitivity and fast response speed, low fabrication cost, high process repeatability, and high compatibility with CMOS (Complementary Metal-Oxide-Semiconductor) processes, making them suitable for large-scale integrated production.

[0003] Due to differences in material properties, photodetectors made from different MOS materials operate in different wavelength ranges. For example, VO2 detectors are more sensitive to infrared light. Although ultraviolet photons have high energy (around 6 eV), they are absorbed by VO2 and converted into heat rather than directly exciting electron transitions. Furthermore, VO2's optical bandgap (0.7 eV) does not match the energy of ultraviolet photons, resulting in almost no absorption in the ultraviolet band. Conversely, Ga2O3-based photodetectors have higher responses in the deep ultraviolet and X-ray bands, but due to Ga2O3's wide bandgap (4.9 eV), it has almost no response to visible and infrared light (cutoff wavelength -280 nm). In other words, photodetectors based on a single MOS material are limited by the material properties, making it difficult to broaden the response spectrum and adapt to some complex multi-band applications.

[0004] In addition, VO2 films have low absorption efficiency for infrared light, especially in the long-wave infrared band of 8-14 μm where the transmittance will exceed 60%, which will greatly weaken the detection capability of the detection structure for infrared light.

[0005] In actual production, due to the unintentional introduction of shallow donor levels during the preparation of thin film materials, they often have a high concentration of free electrons, resulting in a high dark current level in the device. Summary of the Invention

[0006] In order to simultaneously respond to light in the 8-14µm long-wave infrared band and the solar-blind ultraviolet band, this invention provides a cross-band photoelectric detection structure and its fabrication method.

[0007] This invention provides a cross-frequency band photoelectric detection structure, employing the following technical solution:

[0008] A cross-frequency photoelectric detection structure includes a substrate and an Al2O3 dielectric layer. The Al2O3 dielectric layer is deposited on the substrate. A Ga2O3 thin film is disposed on the Al2O3 dielectric layer. A VO2 thin film is disposed on the Ga2O3 thin film. Nanoparticles are disposed on the VO2 thin film. Plasmon effect is generated at the interface between the nanoparticles and the VO2 thin film.

[0009] In one specific implementation, the Ga2O3 film thickness is 90-110 nm.

[0010] In one specific implementation, the VO2 film thickness is 70-90 nm.

[0011] This invention also provides a method for fabricating a cross-frequency band photoelectric detection structure, employing the following technical solution:

[0012] A method for fabricating a cross-frequency band photodetector structure, comprising the following steps:

[0013] The Al2O3 dielectric layer was deposited on the substrate by atomic deposition.

[0014] The Ga2O3 thin film is deposited on the Al2O3 dielectric layer;

[0015] The VO2 film is deposited on the Ga2O3 film;

[0016] Nanoparticles are deposited on the VO2 film to form a composite structure;

[0017] The composite structure is then subjected to post-annealing.

[0018] Ti and Au electrodes are deposited on the VO2 thin film.

[0019] In one specific implementation, when depositing the Al2O3 dielectric layer on the substrate, the temperature is 180-220°C, the deposition cycle is 1500-2500, and the final thickness of the Al2O3 dielectric layer is 180-230 nm. During the deposition process, argon gas is introduced to remove excess precursors and byproducts from the deposition process.

[0020] In one specific implementation, when depositing the Ga2O3 thin film on the Al2O3 dielectric layer, the temperature is 180-220℃, the deposition cycle is 3500-4500 times, and the thickness of the final Ga2O3 thin film is 90-110nm. During the deposition process, argon gas is introduced to remove excess precursors and byproducts.

[0021] In one specific implementation, when depositing the VO2 film on the Ga2O3 film, the temperature is 130-170℃, the deposition cycle is 3500-4500 times, and the thickness of the final VO2 film is 70-90nm. Argon gas is introduced during the deposition process to remove excess precursors and byproducts.

[0022] In one specific implementation, when depositing nanoparticles on the VO2 film, the sputtering power is 90-110W, the sputtering pressure is 0.4-0.6Pa, the sputtering time is 1-4 minutes, the substrate tray is rotated during the deposition process at a speed of 5-15 r / min, and argon gas is introduced during the deposition process to remove excess precursors and byproducts.

[0023] In one specific feasible implementation, when the composite structure is post-annealed, the furnace temperature is 430-470℃, the furnace pressure is 3-4mbar, the post-annealing time is 1.5-2.5 hours, and a 2%-4% H2 / Ar mixed protective gas is continuously introduced during the post-annealing process.

[0024] In one specific implementation, when depositing the Ga2O3 thin film on the Al2O3 dielectric layer, the gallium source is trimethylgallium, metallic gallium, or triisopropylgallium.

[0025] When depositing the VO2 film on the Ga2O3 film, the vanadium source is triisopropoxide vanadium, vanadium acetate, tetramethylethylenediamine vanadium, or trimethyl vanadium phosphate.

[0026] When nanoparticles are deposited on the VO2 film, the nanoparticles are platinum, lead, silver or gold.

[0027] In summary, the present invention has the following beneficial effects:

[0028] 1. VO2 materials are sensitive to infrared light, while Ga2O3, due to its wide bandgap characteristics, has a higher response in the deep ultraviolet band. A composite thin film of VO2 and Ga2O3, fabricated using a cross-band photodetector structure, can achieve cross-band optical response in both long-wave infrared and solar-blind ultraviolet bands. This overcomes the limitation of limited response bands in photodetectors based on single metal oxide semiconductor materials, making it suitable for complex multi-band applications.

[0029] 2. By depositing nanoparticles on VO2 films, a plasmon effect is generated at the interface with VO2, which can effectively improve the absorption efficiency of VO2 films for 8-14µm long-wave infrared light, thereby improving the response level in the long-wave infrared band.

[0030] 3. Ga2O3 thin films can act as a barrier layer to impede the migration of majority carriers, thereby suppressing dark current between electrodes. Conversely, when the detector operates in the solar-blind ultraviolet band, VO2 thin films act as a barrier layer to suppress dark current.

[0031] 4. The photoelectric sensor prepared by the method of cross-frequency band photoelectric detection structure has better anti-interference, anti-radiation characteristics and thermal stability. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a cross-frequency band photoelectric detection structure.

[0033] Figure 2 These are the results of continuous stability tests of the cross-frequency photoelectric detection structure in the 8µm band. Detailed Implementation

[0034] The following combination Figures 1-2 The present invention will be described in further detail below.

[0035] Reference Figure 1 The cross-frequency photodetector structure includes a substrate, which can be an n-type doped silicon substrate, a sapphire substrate, or a silicon substrate. An Al₂O₃ dielectric layer with a thickness of 180-230 nm, preferably 200 nm, is deposited on the substrate. A Ga₂O₃ thin film with a thickness of 90-110 nm, preferably 102 nm, is deposited on the Al₂O₃ dielectric layer. A VO₂ thin film with a thickness of 70-90 nm, preferably 77 nm, is deposited on the Ga₂O₃ thin film. Nanoparticles are deposited on the VO₂ thin film, and a plasmon effect is generated at the interface between the nanoparticles and the VO₂ thin film. Specifically, the nanoparticles can be Pt, Pb, Ag, and Au nanoparticles. Ti electrodes and Au electrodes are deposited on the VO₂ thin film.

[0036] VO2 thin films are sensitive to infrared light, while Ga2O3 thin films, due to their wide bandgap characteristics, exhibit a high response in the deep ultraviolet band. By combining Ga2O3 and VO2 thin films, cross-band optical response can be achieved in both long-wave infrared and solar-blind ultraviolet bands, overcoming the limitation of limited response bands in photodetectors based on single metal oxide semiconductor materials, and adapting to complex multi-band application scenarios. Furthermore, VO2 thin films can be directly heated under far-infrared light irradiation, compared to depositing VO2 thin films first and then Ga2O3 thin films, where light needs to pass through the Ga2O3 film to heat the VO2 film, resulting in a faster response speed.

[0037] At the interface between deposited Pt nanoparticles and VO2, a plasmon effect is generated, causing collective oscillations of free electrons on the surface of the metal nanostructure. When photons are incident on the metal-semiconductor interface, the free electrons couple with the incident light, forming localized surface plasmons (LSPs). These oscillation modes can localize the light field to the nanoscale, thereby significantly enhancing the intensity of the local light field. Compared with conventional MOS photodetector structures, this invention has higher absorption efficiency for long-wavelength infrared light in the 8-14µm range, thus improving the response level of this invention in this wavelength band to a certain extent.

[0038] When this invention operates in the long-wave infrared band, the Ga2O3 layer acts as a barrier layer to hinder the migration of majority carriers, thereby suppressing dark current between electrodes. Conversely, when operating in the solar-blind ultraviolet band, VO2 acts as a barrier layer to suppress dark current. Compared to conventional MOS photodetector structures, this invention exhibits a lower dark current level, solving the problem of high dark current caused by the introduction of shallow donor levels during the fabrication of metal oxide semiconductor thin films. Compared to depositing a VO2 thin film first and then a Ga2O3 thin film, where long-wave infrared light needs to penetrate the Ga2O3 film before being absorbed by the VO2 film, and the generated carriers need to overcome potentially high potential barriers or defect states at the Ga2O3 / VO2 interface to be effectively separated and collected, this invention allows direct absorption by the VO2 film, resulting in higher separation efficiency for photogenerated carriers.

[0039] Combination Figure 2 The results of the continuous stability test of this invention in the 8µm band show that the output current tends to stabilize after about 450s, with only a small fluctuation, indicating good anti-interference, anti-radiation characteristics and thermal stability.

[0040] This invention also discloses a method for fabricating a cross-frequency band photodetector structure, which includes the following steps:

[0041] S1, an Al2O3 dielectric layer is deposited on a silicon substrate using atomic deposition (ALD).

[0042] A silicon substrate is placed in an ALD chamber at 180-220°C. Trimethylaluminum (TMA) is used as the aluminum source, and ozone as the oxygen source to deposit an Al₂O₃ dielectric layer. The deposition cycle is 1500-2500 times to obtain an Al₂O₃ dielectric layer with a thickness of approximately 180-230 nm, which serves as the gate. High-purity argon gas is continuously introduced during the deposition process at a flow rate of 50-70 sccm to remove excess precursors and byproducts.

[0043] Understandably, the aluminum source can also be aluminum isopropoxide or aluminum tri-oxooxide (ATSB). The substrate can also be an n-type doped silicon substrate or a sapphire substrate.

[0044] S2, Ga2O3 thin film is deposited on Al2O3 dielectric layer by atomic deposition method.

[0045] The substrate with the Al2O3 dielectric layer deposited was placed in an ALD chamber at 180-220℃. Using trimethylgallium (TMGa) as the gallium source and ozone as the oxygen source, a Ga2O3 thin film was deposited in the chamber. The deposition cycle was 3500-4500 times to obtain a Ga2O3 film with a thickness of 90-110 nm. High-purity argon gas was continuously introduced during the deposition process at a flow rate of 50-70 sccm to remove excess precursors and byproducts.

[0046] Understandably, the gallium source can also be metallic gallium or triisopropyl gallium.

[0047] S3, VO2 film is deposited on Ga2O3 film by atomic deposition method.

[0048] The substrate with the completed Ga2O3 thin film deposition was placed in an ALD chamber at 130-170℃. Vanadium triisopropoxide (VTIP) dissolved in the organic solvent n-hexane was used as the vanadium source, and deionized water was used as the oxygen source. A VO2 thin film was deposited in the chamber. The deposition cycle was 3500-4500 times, yielding a VO2 film with a thickness of approximately 70-90 nm. High-purity argon gas was continuously introduced during the deposition process at a flow rate of 50-70 sccm to remove excess precursors and byproducts.

[0049] Understandably, vanadium sources can also be vanadium acetate, tetramethylethylenediamine vanadium, or trimethyl vanadium phosphate.

[0050] S4, nanoparticles are deposited on VO2 thin films by magnetron sputtering.

[0051] The substrate with the completed VO2 thin film deposition was placed in a magnetron sputtering chamber at room temperature. Pt nanoparticles were sputtered using a pure platinum target as the platinum source at a sputtering power of 90-110 W, a sputtering pressure of 0.4-0.6 Pa, and a sputtering time of 1-4 minutes. During the deposition process, the substrate tray was rotated at a speed of 5-15 r / min. High-purity argon gas was continuously introduced during the deposition process at a flow rate of 20-50 sccm to remove excess precursors and byproducts.

[0052] Understandably, pure platinum can be replaced with lead, silver, or gold. In steps S3 and S4, the deposition methods for Ga2O3 and VO2 films can also be chemical vapor deposition, magnetron sputtering, and electron beam evaporation.

[0053] S5, perform post-annealing treatment on the composite structure.

[0054] The composite structure obtained in step S4 is placed in a tube furnace for post-annealing. The furnace temperature is 430-470℃, the furnace pressure is 3-4 mbar, and the post-annealing time is 1.5-2.5 hours. During the post-annealing process, a 2%-4% H2 / Ar mixed protective gas is continuously introduced at a flow rate of 40-60 sccm.

[0055] S6, Ti and Au electrodes are deposited on a VO2 thin film by electron beam evaporation.

[0056] The post-annealed composite structure was placed on an electron beam evaporation platform, and the Ti and Au layers of the electrode were evaporated sequentially. The thickness of the Ti layer was 5-15 nm, and the thickness of the Au layer was 40-60 nm. The deposition process was carried out under high vacuum conditions, with a vacuum level of 5 × 10⁻⁶. -6 -5×10 -5 Torr. This allows us to obtain the aforementioned cross-frequency photoelectric detection structure.

[0057] Understandably, in this step, the Ti electrode and Au electrode can also be deposited using magnetron sputtering.

[0058] Example 1:

[0059] A method for fabricating a cross-frequency band photodetector structure, comprising the following steps:

[0060] S1, an Al2O3 dielectric layer is deposited on a silicon substrate using atomic deposition (ALD).

[0061] A square-cut silicon substrate was placed in an ALD chamber at 200°C. Using trimethylaluminum (TMA) as the gallium source and ozone as the oxygen source, an Al₂O₃ dielectric layer was deposited in the chamber, with 2000 deposition cycles, resulting in a 200 nm thick Ga₂O₃ film. High-purity argon gas was continuously introduced into the chamber during the deposition process, with a flow rate controlled at 60 sccm.

[0062] S2, Ga2O3 thin film is deposited on Al2O3 dielectric layer by atomic deposition method.

[0063] A silicon substrate containing an Al₂O₃ dielectric layer was placed in an ALD chamber at 200°C. Using trimethylgallium (TMGa) as the gallium source and ozone as the oxygen source, a Ga₂O₃ thin film was deposited in the chamber. The deposition cycle was 4000 times, yielding a Ga₂O₃ film with a thickness of approximately 102 nm. High-purity argon gas was continuously introduced into the chamber during the deposition process, with a flow rate controlled at 60 sccm.

[0064] S3, VO2 film is deposited on Ga2O3 film by atomic deposition method.

[0065] The prepared structure was placed in an ALD chamber at 150°C. VTIP was dissolved in the organic solvent n-hexane as a vanadium source, and deionized water was used as an oxygen source. A VO2 film was deposited in the chamber after 4000 deposition cycles, yielding a VO2 film with a thickness of 77 nm. High-purity argon gas was continuously introduced into the chamber during the deposition process, with the flow rate controlled at 60 sccm.

[0066] S4, nanoparticles are deposited on VO2 thin films by magnetron sputtering.

[0067] The prepared structure was placed in a magnetron sputtering chamber at room temperature, and Pt nanoparticles were sputtered using a pure platinum target as the platinum source. The sputtering power was 100 W, the sputtering pressure was 0.55 Pa, and the sputtering time was 3 minutes. During the deposition process, the substrate tray was rotated at a speed of 10 r / min. High-purity argon gas was continuously introduced into the chamber during the deposition process, and the flow rate was controlled at 30 sccm.

[0068] S5, perform post-annealing treatment on the composite structure.

[0069] The furnace temperature was controlled at 450℃, the tubular furnace pressure at 3.5 mbar, and the post-annealing time was 2 hours. During the annealing process, a 3% H2 / Ar mixed protective gas was continuously introduced at a flow rate of 50 sccm.

[0070] S6, Ti and Au electrodes are deposited on a VO2 thin film by electron beam evaporation.

[0071] The prepared structure was placed on an electron beam evaporation platform, and the Ti and Au layers of the electrode were evaporated sequentially. The thickness of the Ti layer was 10 nm; the thickness of the Au layer was 50 nm. The deposition process was carried out under high vacuum conditions, with a vacuum level of 1 × 10⁻⁶. -6 Torr. This allows us to obtain the aforementioned cross-band photoelectric detection structure.

[0072] Example 2:

[0073] The difference between Example 2 and Example 1 is that the post-annealing process in step S5 is omitted in Example 2. All other steps and conditions are the same and will not be described again.

[0074] Example 3:

[0075] The difference between Example 3 and Example 1 is that step S4, which involves depositing nanoparticles on the VO2 film, is omitted in Example 3. The other steps and conditions are the same and will not be described again.

[0076] The performance of the cross-band photoelectric detection structures obtained in Examples 1, 2, and 3 was tested, and the results are shown in Table 1 below:

[0077] Table 1

[0078]

[0079] In the table above, responsivity indicates the response level of the photodetector structure to 8-14µm long-wave infrared or solar-blind ultraviolet light during the test. Data is reported as the response level of the photodetector structure in the corresponding frequency band; a higher value indicates better photoelectric performance.

[0080] Response time represents the time it takes for an optoelectronic structure to fully respond at a corresponding frequency band. The rise time is defined as the time from the rising edge of the baseline to 90% of the maximum responsivity, and the fall time is defined as the time from the falling edge of the maximum responsivity to the baseline. A lower value indicates better optoelectronic performance of the structure.

[0081] The cross-band photodetector structures obtained in Examples 1, 2, and 3 were placed under dark conditions, 8µm wavelength illumination, and 254nm wavelength illumination, respectively. The current of the structure under a 1V bias voltage was measured, and the data in Table 1 were obtained. The formula for calculating the responsivity is as follows:

[0082]

[0083] In the formula, This refers to responsiveness;

[0084] It represents the difference between photocurrent and dark current;

[0085] Indicates the incident light power density;

[0086] Indicates the effective irradiated area.

[0087] Comparing the experimental data in Table 1, it can be seen that post-annealing treatment can significantly improve the responsivity of the cross-band photodetector structure and greatly shorten the response time. Depositing nanoparticles on VO2 thin films can also significantly improve the responsivity of the cross-band photodetector structure and shorten the response time.

[0088] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A cross-frequency photoelectric detection structure, comprising a substrate and an Al2O3 dielectric layer, wherein the Al2O3 dielectric layer is deposited on the substrate, characterized in that: A Ga2O3 thin film is disposed on the Al2O3 dielectric layer, a VO2 thin film is disposed on the Ga2O3 thin film, and nanoparticles are disposed on the VO2 thin film. Plasmon resonance effect is generated at the interface between the nanoparticles and the VO2 thin film. Ti electrode and Au electrode are deposited on the VO2 thin film. When operating in the long-wave infrared band, the Ga2O3 film acts as a barrier layer to hinder the migration of charge carriers and suppress dark current between electrodes. When operating in the solar-blind ultraviolet band, the VO2 thin film acts as a barrier layer to suppress dark current; The method for fabricating the photoelectric detection structure includes the following steps: The Al2O3 dielectric layer was deposited on the substrate by atomic deposition. The Ga2O3 thin film is deposited on the Al2O3 dielectric layer; The VO2 film is deposited on the Ga2O3 film; Nanoparticles are deposited on the VO2 film to form a composite structure; The composite structure is then subjected to post-annealing. Ti and Au electrodes are deposited on the VO2 thin film.

2. The cross-frequency band photoelectric detection structure according to claim 1, characterized in that: The thickness of the Ga2O3 film is 90-110 nm.

3. The cross-frequency band photoelectric detection structure according to claim 1, characterized in that: The thickness of the VO2 film is 70-90 nm.

4. A method for fabricating a cross-frequency band photoelectric detection structure, characterized in that: The method for preparing the cross-frequency photoelectric detection structure according to any one of claims 1-3 includes the following steps: The Al2O3 dielectric layer was deposited on the substrate by atomic deposition. The Ga2O3 thin film is deposited on the Al2O3 dielectric layer; The VO2 film is deposited on the Ga2O3 film; Nanoparticles are deposited on the VO2 film to form a composite structure; The composite structure is then subjected to post-annealing. Ti and Au electrodes are deposited on the VO2 thin film.

5. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When depositing the Al2O3 dielectric layer on the substrate, the temperature is 180-220℃, the deposition cycle is 1500-2500, and the final thickness of the Al2O3 dielectric layer is 180-230nm. Argon gas is introduced during the deposition process to remove excess precursors and byproducts.

6. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When depositing the Ga2O3 thin film on the Al2O3 dielectric layer, the temperature is 180-220℃, the deposition cycle is 3500-4500 times, and the thickness of the final Ga2O3 thin film is 90-110nm. Argon gas is introduced during the deposition process to remove excess precursors and by-products.

7. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When depositing the VO2 film on the Ga2O3 film, the temperature is 130-170℃, the deposition cycle is 3500-4500 times, and the thickness of the final VO2 film is 70-90nm. Argon gas is introduced during the deposition process to remove excess precursors and by-products.

8. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When depositing nanoparticles on the VO2 film, the sputtering power is 90-110W, the sputtering pressure is 0.4-0.6Pa, the sputtering time is 1-4 minutes, the substrate tray is rotated during the deposition process at a speed of 5-15 r / min, and argon gas is introduced during the deposition process to remove excess precursors and byproducts.

9. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When the composite structure is subjected to post-annealing, the furnace temperature is 430-470℃, the furnace pressure is 3-4mbar, the post-annealing time is 1.5-2.5 hours, and 2%-4% H2 / Ar mixed protective gas is continuously introduced during the post-annealing process.

10. The method for fabricating a cross-frequency band photoelectric detection structure according to claim 4, characterized in that: When depositing the Ga2O3 thin film on the Al2O3 dielectric layer, the gallium source is trimethylgallium, metallic gallium, or triisopropylgallium; When depositing the VO2 film on the Ga2O3 film, the vanadium source is triisopropoxide vanadium, vanadium acetate, tetramethylethylenediamine vanadium, or trimethyl vanadium phosphate. When nanoparticles are deposited on the VO2 film, the nanoparticles are platinum, lead, silver or gold.

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