A photothermal electric detector of heterostructure and a preparation method thereof

Abstract

The application belongs to the technical field of photothermal electric detection devices, and discloses a heterostructure photothermal electric detector and a preparation method thereof. The photothermal electric detector comprises, from bottom to top, a bottom electrode, a P-type Si substrate, a ZnO dielectric layer, an Ag2Se absorption layer and a top electrode. The ZnO dielectric layer and the Ag2Se absorption layer form a Type-II heterojunction. The photothermal electric detector has high efficient light absorption capacity in a wider spectral range, can generate electric charges autonomously to meet energy demand, has simple preparation process, reduces external energy dependence and energy consumption, and has high response and high sensitivity to specific waveband light signals.

Description

Technical Field

[0001] This invention belongs to the field of photothermal detector technology, and particularly relates to a heterogeneous photothermal detector and its fabrication method, which has a wide spectral response characteristic and achieves photothermal detection based on self-powered power supply. Background Technology

[0002] Against the backdrop of global energy transition and the deep integration of information technology, the development of novel photothermal and electrical devices that combine high efficiency, low cost, and environmental friendliness has become an urgent need for cutting-edge research. Traditional silicon-based photovoltaic devices are limited by inherent defects such as weak near-infrared light absorption due to wide bandgap and high fabrication energy consumption. While emerging perovskite materials have excellent photoelectric conversion efficiency (PCE), they face application bottlenecks due to poor stability and lead toxicity. To address these issues, heterojunction devices based on narrow bandgap semiconductors have become an important breakthrough due to their ability to expand the spectral response range and improve conversion efficiency. Among them, wide bandgap zinc oxide, as a high electron mobility and non-toxic ultraviolet-sensitive material, can theoretically construct an ideal platform for full-spectrum detection from ultraviolet to near-infrared when formed with narrow bandgap silver selenide to form a Type-II heterojunction. Furthermore, it can drive efficient carrier separation through a strong built-in electric field. However, the practical development of this system is limited by three core contradictions: carrier recombination loss induced by interface defects, weakening of the built-in electric field strength due to non-ideal bandgap arrangement, and environmental instability of Ag₂Se. Existing wet chemical methods are further hampered by interface contamination caused by component inhomogeneity and organic residues, making large-area homogeneous preparation difficult. Meanwhile, high-energy particle bombardment in conventional vacuum sputtering processes easily causes structural damage and stoichiometric imbalances in narrow bandgap materials. Therefore, there is an urgent need to develop a low-damage heterojunction controllable preparation technology that can synergistically address interface defect control, energy level matching optimization, and environmental stability improvement, in order to achieve wide-spectral response and high-sensitivity photothermal-electric detection.

[0003] It should be noted that the information disclosed in the background section above is for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0004] To address the issues of insufficient sensitivity and wide-spectrum response in existing photothermal detectors, this invention provides a heterostructure photothermal detector and its fabrication method. The detector spontaneously generates a photogenerated voltage signal through the built-in electric field of the Ag2Se / ZnO Type-II heterojunction, enabling wide-band detection in the ultraviolet-near-infrared range without external bias, thereby significantly reducing noise interference and improving environmental adaptability.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a heterostructure photothermal detector, comprising a bottom electrode, a P-type Si substrate, a ZnO dielectric layer, an Ag2Se absorption layer and a top electrode arranged sequentially from bottom to top; the ZnO dielectric layer and the Ag2Se absorption layer form a Type-II heterojunction.

[0006] The bottom electrode material is Ag, and the top electrode material is an ITO transparent electrode layer.

[0007] The thickness of the ZnO dielectric layer is 200-300 nm, and the thickness of the Ag2Se absorber layer is 300-400 nm.

[0008] The bottom electrode has a thickness of 1-2µm, the P-type Si substrate has a thickness of 625±20µm, and the top electrode has a thickness of 150nm.

[0009] Furthermore, the present invention also provides a method for fabricating a heterostructure photothermal detector, comprising the following steps:

[0010] Step 1: Pre-treat the P-type Si substrate;

[0011] Step 2: A ZnO dielectric layer is formed on the surface of a P-type Si substrate using radio frequency sputtering. The sputtering power is 20-80W, the dynamic gas pressure is 0.5-3Pa, the deposition time is 60-120min, and the temperature is ≤30℃. Then, vacuum annealing is carried out at 200-400℃ to optimize the interface electron tunneling characteristics.

[0012] Step 3: An Ag₂Se absorber layer is formed on the surface of the ZnO dielectric layer using radio frequency sputtering. The sputtering power is 30-80W, the sputtering pressure is 1-2Pa, and the deposition time is 30-60min. An Ag₂Se composite target is used to obtain a roughness of <5nm and a carrier mobility >100 cm⁻¹. 2 / V·s Ag2Se absorption layer;

[0013] Step 4: Form the top electrode on the surface of the Ag2Se absorber layer using radio frequency sputtering;

[0014] Step 5: Apply highly conductive silver paste to the bottom of the P-type Si substrate and let it solidify to form an ohmic contact bottom electrode. At the same time, lead out the bottom electrode through the solidified silver paste, and lead out the top electrode through silver wire to complete the external circuit connection.

[0015] In step two, a ZnO ceramic target is used to deposit a thin film with a thickness of 200-300 nm under the conditions of an argon-oxygen mixed gas ratio of 9:1, a sputtering power of 80W, and a working pressure of 1.5Pa.

[0016] In step three, an Ag2Se composite target with an atomic ratio of Ag:Se=2:1 is used, the sputtering power is 60W, the sputtering pressure is 1.5Pa, and the sputtering atmosphere is pure argon.

[0017] Steps three and four employ in-situ continuous sputtering to avoid interface oxidation.

[0018] In step four, the top electrode material is ITO, and a 150 nm thick ITO film is sputtered and deposited using a target with a mass ratio of In2O3:SnO2=90:10 to form the top electrode.

[0019] In step four, sputtering is performed at 50W power under an argon atmosphere of 2.0 Pa, followed by vacuum annealing at 300°C for 120 minutes.

[0020] In step five, after applying highly conductive silver paste, it is cured at 80°C for 1 hour to form the bottom electrode with ohmic contact.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention provides a heterostructure photothermal detector and its fabrication method. The sensor combines a ZnO dielectric layer and an Ag2Se absorption layer to construct a Type-II band structure. The p-type Si substrate provides a self-powered electric field to drive carrier separation, while the band arrangement of the Ag2Se / ZnO heterojunction broadens the spectral response to 220~1550 nm. Furthermore, the ITO top electrode and sputtered densification packaging are used to synergistically suppress Ag2Se environmental degradation, solving the core contradiction of weak near-infrared absorption and instability of narrow bandgap materials in traditional silicon-based devices. Therefore, this invention synergistically utilizes the built-in electric field-driven directional carrier separation and the strong infrared absorption capability of narrow bandgap Ag2Se to improve the detector's sensitivity and responsiveness in the ultraviolet-visible-near-infrared broadband band.

[0023] 2. This invention utilizes radio frequency sputtering to prepare ZnO and Ag₂Se thin films. The sequential design of depositing a wide-bandgap ZnO dielectric layer followed by a narrow-bandgap Ag₂Se absorber layer, combined with annealing, achieves atomic-level matching and efficient carrier separation at the heterojunction interface, ultimately yielding a photothermal detector with broad spectral response, self-powered operation, and high sensitivity. This photothermal detector exhibits efficient light absorption across a wide spectral range, can autonomously generate charge to meet energy demands, reducing dependence on external energy sources and energy consumption. Simultaneously, it demonstrates high response and high sensitivity to specific wavelengths of optical signals. The fabrication process is simple and scalable, with broad application prospects in fields such as optical communication, imaging, and photovoltaic power generation, providing new possibilities for the further development of optoelectronic technology. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a heterogeneous photothermal detector provided in an embodiment of the present invention;

[0025] Figure 2 The current curve of the photothermal detector obtained in the embodiment of the present invention under a broadband ultraviolet-near infrared spectrum;

[0026] In this diagram, 1 is the bottom electrode, 2 is the P-type Si substrate, 3 is the ZnO dielectric layer, 4 is the Ag2Se absorber layer, and 5 is the top electrode. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] like Figure 1 As shown, Embodiment 1 of the present invention provides a photothermal detector with a heterostructure, including a bottom electrode 1, a P-type Si substrate 2, a ZnO dielectric layer 3, an Ag2Se absorption layer 4, and a top electrode 5 arranged sequentially from bottom to top; the ZnO dielectric layer 3 and the Ag2Se absorption layer 4 form a Type-II heterojunction.

[0030] Specifically, in this embodiment, the bottom electrode 1 is made of Ag, and the top electrode 5 is made of ITO transparent electrode layer.

[0031] Furthermore, in this embodiment, the thickness of the ZnO dielectric layer 3 is 200-300 nm, and the thickness of the Ag2Se absorber layer 4 is 300-400 nm.

[0032] Furthermore, in this embodiment, the thickness of the bottom electrode 1 is 1-2µm, the thickness of the P-type Si substrate 2 is 625±20µm, and the thickness of the top electrode 5 is 150nm.

[0033] Example 2

[0034] Embodiment 2 of the present invention provides a method for fabricating a heterostructure photothermal detector as described in Embodiment 1, comprising the following steps:

[0035] Step 1: Pre-treat the P-type Si substrate 2.

[0036] Specifically, in this embodiment, a (100) crystal orientation p-type single crystal silicon wafer with a resistivity of 1-10 Ω·cm is selected as the substrate. It is then ultrasonically cleaned with acetone and anhydrous ethanol for 10 minutes each to remove organic contaminants. After being immersed in 10% hydrofluoric acid solution for 1 minute to peel off the surface oxide layer, it is rinsed with ultrapure water, dried with nitrogen, and immediately sent into the magnetron sputtering chamber.

[0037] Subsequently, with a vacuum degree ≤ 5 × 10 -4 Under the conditions of Pa and a constant base temperature of 30°C, high-purity argon and high-purity oxygen are used as working gases.

[0038] Step 2: A ZnO dielectric layer 3 is formed on the surface of a P-type Si substrate 2 using radio frequency sputtering technology. The sputtering power is 20-80W, the dynamic gas pressure is 0.5-3Pa, the deposition time is 60-120min, and the temperature is ≤30℃. Then, vacuum annealing is carried out at 200-400℃ to optimize the interface electron tunneling characteristics.

[0039] Specifically, in step two, a ZnO ceramic target is used for deposition under conditions of an argon-oxygen mixed gas ratio of 9:1, a sputtering power of 60W, and a working pressure of 1.5Pa, resulting in a thickness of 200-300nm and a conduction band offset ΔE. c A ZnO thin film with a voltage greater than 0.3 eV is designated as ZnO dielectric layer 3. The conduction band offset ΔE of the ZnO dielectric layer can be adjusted by controlling the sputtering oxygen partial pressure through the ratio of the argon-oxygen mixture. c Make it satisfy ΔE c >0.3eV.

[0040] Step 3: An Ag₂Se absorber layer 4 is formed on the surface of the ZnO dielectric layer 3 using radio frequency sputtering. The sputtering power is 30-80W, the sputtering pressure is 1-2Pa, and the deposition time is 30-60min, resulting in a thickness of 300-400nm, a roughness of <5nm, and a carrier mobility >100 cm⁻¹. 2 The Ag2Se thin film with a density of / V·s is called Ag2Se absorber layer 4.

[0041] Specifically, in step three, an Ag2Se composite target with an atomic ratio of Ag:Se=2:1 is used, the sputtering power is 60W, the sputtering pressure is 1.5Pa, and the sputtering atmosphere is a pure argon atmosphere.

[0042] Step 4: The top electrode 5 is formed on the surface of the Ag2Se absorber layer 4 using radio frequency sputtering. The sputtering is performed at 50W radio frequency power in an argon atmosphere of 2.0 Pa, followed by vacuum annealing.

[0043] In step four, the top electrode 5 is made of ITO. A 150 nm thick ITO film is sputtered and deposited using a target with a mass ratio of In2O3:SnO2 = 90:10 to form the top electrode 5. During the formation of the top electrode 5, low-pressure sputtering reduces damage from high-energy particle bombardment. Combined with annealing to repair interface defects and improve carrier mobility, high transmittance and low resistance are achieved, providing a non-destructive ohmic contact for the heterojunction. Simultaneously, sputtering densification enhances overall environmental stability.

[0044] In step four, the vacuum annealing parameters are: vacuum annealing at 300°C for 120 minutes.

[0045] Specifically, steps three and four employ in-situ continuous sputtering to avoid interface oxidation.

[0046] Step 5: Apply highly conductive silver paste to the bottom of the P-type Si substrate 2 and cure it at 80°C for 1 hour to form the bottom electrode 1 with ohmic contact. At the same time, lead out the bottom electrode 1 through the silver paste and lead out the top electrode 5 through the silver wire, thereby completing the external circuit connection.

[0047] Radio frequency (RF) sputtering technology boasts low-damage deposition, large-area uniform film formation, and precise stoichiometric control, enabling the controllable fabrication of atomically controlled interfaces and high-crystallinity heterostructures. It excels particularly in addressing the component segregation and contamination issues caused by wet processes. This invention combines a Type-II bandgap structure constructed with an Ag₂Se / ZnO photothermal-electric sensitive layer. By synergistically utilizing the built-in electric field-driven directional carrier separation and the strong infrared absorption capability of the narrow-bandgap Ag₂Se, the sensitivity and responsiveness of the detector across the ultraviolet-visible-near-infrared broad spectrum can be further enhanced, providing a key technological foundation for the innovative design of next-generation self-powered broadband detectors. Furthermore, this invention combines the low interface damage characteristics of RF sputtering technology with the broadband trapping and efficient carrier separation advantages of the Ag₂Se / ZnO Type-II heterojunction, proposing a monolithically integrated photothermal-electric detector device with broad spectral response and self-powered characteristics, along with its controllable fabrication method. This meets the core requirements of modern photothermal-electric systems for high efficiency, low power consumption, and environmental adaptability.

[0048] like Figure 2 The image shown is a spectral data diagram of the heterostructure photothermal detector prepared according to an embodiment of the present invention. Figure 2 It can be seen that the prepared photothermal detector has photothermal response in both ultraviolet and near-infrared, and has a high response at 750nm.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a photothermoelectric detector of a heterostructure, characterized in that, The photothermal electric detector comprises, from bottom to top, a bottom electrode (1), a P-type Si substrate (2), a ZnO dielectric layer (3), an Ag2Se absorption layer (4) and a top electrode (5); the ZnO dielectric layer (3) and the Ag2Se absorption layer (4) form a Type-II heterojunction, and the preparation method comprises the following steps: Step one: pretreating the P-type Si substrate (2); Step two: forming the ZnO dielectric layer (3) on the surface of the P-type Si substrate (2) by using a radio frequency sputtering process, the sputtering power being 20-80 W, the dynamic air pressure being 0.5-3 Pa, the deposition time being 60-120 min, the temperature being ≤30℃, and then vacuum annealing at 200-400℃ to optimize the interface electron tunneling characteristics; Step three: using radio frequency sputtering process to form Ag2Se absorption layer (4) on the surface of ZnO dielectric layer (3), sputtering power is 30-80W, sputtering pressure is 1-2Pa, deposition time is 30-60min, using Ag2Se composite target, roughness is <5nm, carrier mobility is >100 cm 2 / V·s of Ag2Se absorption layer (4); Step four: forming the top electrode (5) on the surface of the Ag2Se absorption layer (4) by using a radio frequency sputtering process; Step five: coating high-conductivity silver paste on the bottom of the P-type Si substrate (2) and solidifying it to form the bottom electrode (1) with ohmic contact, and meanwhile leading out the electrode of the bottom electrode (1) through silver paste solidification, leading out the electrode of the top electrode (5) through silver wire, and completing the external circuit connection.

2. The method of claim 1, wherein the method further comprises: The material of the bottom electrode (1) is Ag, and the material of the top electrode (5) is an ITO transparent electrode layer.

3. The method of claim 1, wherein the method further comprises: The thickness of the ZnO dielectric layer (3) is 200-300 nm, and the thickness of the Ag2Se absorption layer (4) is 300-400 nm.

4. The method of claim 1, wherein the method further comprises: The thickness of the bottom electrode (1) is 1-2 µm, the thickness of the P-type Si substrate (2) is 625±20 µm, and the thickness of the top electrode (5) is 150 nm.

5. The method of claim 1, wherein the method further comprises: In step two, a ZnO ceramic target is used to deposit a thin film with a thickness of 200-300 nm under the conditions of an argon-oxygen mixed gas ratio of 9:1, a sputtering power of 80 W and a working air pressure of 1.5 Pa.

6. The method of claim 1, wherein the method further comprises: In step three, an Ag2Se composite target with an atomic ratio of Ag:Se=2:1 is used, the sputtering power is 60 W, the sputtering air pressure is 1.5 Pa, and the sputtering atmosphere is pure argon atmosphere.

7. The method of claim 1, wherein the method further comprises: In-situ continuous sputtering is used in steps three and four to avoid interface oxidation.

8. The method of claim 1, wherein the method further comprises: In step four, the material of the top electrode (5) is ITO, a target material with a mass ratio of In2O3:SnO2=90:10 is used to sputter and deposit an ITO thin film with a thickness of 150 nm to form the top electrode (5).

9. The method of claim 1, wherein the method further comprises: In step four, the sputtering is carried out in an argon atmosphere at 2.0 pa with a power of 50 W, and then vacuum annealing is carried out, the vacuum annealing parameters being vacuum annealing at 300℃ for 120 minutes; In step five, after coating the high-conductivity silver paste, the bottom electrode (1) with ohmic contact is formed by solidifying it at a temperature of 80℃ for 1 hour.

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