CN115249890A - A terahertz signal detection device and preparation method thereof - Google Patents

Abstract

The invention provides a terahertz signal detection device and a preparation method thereof, wherein the terahertz signal detection device comprises the following steps: a substrate; the first electrode is formed on the substrate and is located on one side of the substrate. The second electrode is formed on the substrate and is disposed symmetrically with the first electrode about a center of the substrate. The first semiconductor layer is formed between the first electrode and the second electrode, and connects the first electrode and the second electrode. The insulating layer is formed on the first semiconductor layer. The third electrode is formed on the insulating layer and is located on one side of the insulating layer. The fourth electrode is formed on the insulating layer and is arranged symmetrically with the third electrode with respect to the center of the substrate. The second semiconductor layer is formed between the third electrode and the fourth electrode, and connects the third electrode and the fourth electrode. And the central connecting line of the first electrode and the second electrode is vertical to the central connecting line of the third electrode and the fourth electrode. The terahertz signal detection device and the preparation method thereof provided by the invention are novel in structure, simple in preparation and have production and application values.

Description

A terahertz signal detection device and preparation method thereof

technical field

The invention relates to the technical field of detection, in particular to a terahertz signal detection device and a preparation method thereof.

Background technique

Terahertz waves are electromagnetic waves with frequencies in the range of 0.1 to 10 THz, which can cover the characteristic spectrum of substances such as semiconductors, organisms, and biological macromolecules. Limited by factors such as the low output power of the terahertz radiation source and the high background noise of thermal radiation in the terahertz frequency range, various terahertz detection devices are required to complement each other in different applicable environments and working ranges.

Terahertz signal detection technology is divided into coherent pulse time domain continuous wave detection technology and incoherent direct energy detection technology. The terahertz signal detection technology based on incoherent technology absorbs thermal radiation energy for detection, and generally can only measure the terahertz radiation intensity, but cannot provide its phase information.

SUMMARY OF THE INVENTION

In view of the above-mentioned defects of the prior art, the present invention proposes a terahertz signal detection device and a preparation method thereof, which improves the absorption rate of the detection device to infrared and terahertz radiation, thereby achieving polarization insensitivity, fast response, high sensitivity, and wide bandwidth. Wide, low signal-to-noise ratio and room temperature working environment and other advantages, improve work efficiency.

In order to achieve the above purpose and other purposes, the present invention proposes a terahertz signal detection device, comprising:

substrate;

a first electrode, formed on the substrate, and located on one side of the substrate;

a second electrode, formed on the substrate, and arranged symmetrically with the first electrode about the center of the substrate;

a first semiconductor layer formed between the first electrode and the second electrode and connecting the first electrode and the second electrode;

an insulating layer formed on the first semiconductor layer;

a third electrode, formed on the insulating layer, and located on one side of the insulating layer;

a fourth electrode, formed on the insulating layer, and arranged symmetrically with the third electrode about the center of the substrate;

a second semiconductor layer formed between the third electrode and the fourth electrode and connecting the third electrode and the fourth electrode;

Wherein, the center line connecting the first electrode and the second electrode is perpendicular to the center line connecting the third electrode and the fourth electrode.

In one embodiment of the present invention, the substrate includes a silicon-based base and a base covering layer, and the base covering layer covers the upper surface of the silicon-based base.

In an embodiment of the present invention, the first electrode, the second electrode, the third electrode and the fourth electrode are arranged in a fan shape.

In an embodiment of the present invention, the structures and dimensions of the first electrode, the second electrode, the third electrode and the fourth electrode are the same.

In an embodiment of the present invention, the radius of the first electrode ranges from 80 μm to 120 μm.

In an embodiment of the present invention, the opening angle of the first electrode ranges from 60° to 90°.

In an embodiment of the present invention, the thickness of the first electrode ranges from 20 nm to 300 nm.

In an embodiment of the present invention, the orthographic projections of the first electrode, the second electrode, the third electrode and the fourth electrode on the substrate do not overlap.

In one embodiment of the present invention, the insulating layer covers the first semiconductor layer.

The present invention also provides a preparation method of a terahertz signal detection device, comprising:

provide a substrate;

forming a first electrode on the substrate, located on one side of the substrate;

forming a second electrode on the substrate, symmetrically arranged with the first electrode about the center of the substrate;

forming a first semiconductor layer between the first electrode and the second electrode, connecting the first electrode and the second electrode;

forming an insulating layer on the first semiconductor layer;

forming a third electrode on the insulating layer, located on one side of the insulating layer;

forming a fourth electrode on the insulating layer, which is symmetrically arranged with the third electrode about the center of the substrate;

forming a second semiconductor layer between the third electrode and the fourth electrode, connecting the third electrode and the fourth electrode;

Wherein, the center connection line between the first electrode and the second electrode is perpendicular to the center connection line between the third electrode and the fourth electrode.

In summary, the present invention proposes a terahertz signal detection device and a preparation method thereof, which have the following beneficial effects: the antenna is designed into a special vertical cross-shaped structure, the response time is improved, and the high sensitivity and wide bandwidth of the detection device are realized. wide and low signal-to-noise ratio. Compared with the traditional field effect structure, the terahertz signal detection device provided by the present invention has novel structure, excellent performance, simple preparation, and can work in the infrared and terahertz bands.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

Figure 1 is a schematic diagram of a log-periodic antenna.

FIG. 2 is a longitudinal sectional view of a log-periodic antenna.

FIG. 3 is a plan view of a log-periodic antenna.

FIG. 4 is a schematic diagram of a log-periodic antenna angle.

FIG. 5 is a partial enlarged view of the center of the log-periodic antenna channel.

FIG. 6 is a top view of the butterfly antenna.

FIG. 7 is a top view of the strip antenna.

Figure 8 is a flow chart of the preparation process.

FIG. 9 is a graph of the local electric field enhancement of the log-periodic antenna channel obtained by electromagnetic simulation.

FIG. 10 is the local electric field enhancement diagram of the butterfly antenna channel obtained by electromagnetic simulation.

FIG. 11 is the local electric field enhancement diagram of the strip antenna channel obtained by the electromagnetic simulation.

Label description:

1 detection device; 2 substrate; 21 silicon base; 22 silicon dioxide layer; 3 first electrode; 4 second electrode; 5 first semiconductor layer; 6 insulating layer; 7 third electrode; 8 fourth electrode; 9 the second semiconductor layer.

Detailed ways

The embodiments of the present invention are described below through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

It should be noted that the drawings provided in this embodiment are only to illustrate the basic concept of the present invention in a schematic way, so the drawings only show the components related to the present invention rather than the number, shape and the number of components in actual implementation. For dimension drawing, the type, quantity and proportion of each component can be changed at will in actual implementation, and the component layout may also be more complicated.

The invention provides a terahertz signal detection device and a preparation method thereof. The antenna is designed into a special vertical cross-shaped structure, which improves the response time and realizes the high sensitivity, wide bandwidth and low signal-to-noise ratio of the detection device. Compared with the traditional field effect structure, it has excellent performance, simple preparation, and can work in the infrared and terahertz bands.

Referring to Fig. 1 , in an embodiment of the present invention, the terahertz signal detection device includes a substrate 2, and the substrate 2 includes, for example, a silicon-based base 21 and a base covering layer 22. The silicon-based base 21 may have a rectangular parallelepiped structure, and is arranged at the bottom as a support. The bottom surface of the base covering layer 22 is in contact with the upper surface of the silicon-based base 21 . The base covering layer 22 may completely cover the upper surface of the silicon-based base 21 . The thickness of the substrate 2 ranges from 50 μm to 500 μm, for example. The material of the substrate 2 can be high-resistance silicon, silicon carbide, quartz, glass resin, sapphire, polyimide, etc., and the base cover layer can be set as a silicon dioxide layer with a thickness ranging from 100nm to 300nm.

Referring to FIGS. 1-5 , in an embodiment of the present invention, the first electrode 3 is formed on the substrate 2 . The first electrode 3 is disposed on the upper surface of the substrate 2 and is in contact with the base cover layer 22 . The first electrode 3 is disposed on one side of the upper surface of the substrate 2 as a signal antenna. The first electrode may be a log-periodic antenna, and its shape may be a sector. The fan shape is evenly divided into three equal parts about the center of the fan shape, and the two outer fan shapes are alternately provided with notches along different radius lengths. The second electrode 4 is formed on the substrate 2 and is symmetrically arranged with the first electrode 3 about the center of the substrate 2 . The antenna formed by the first electrode 3 and the second electrode 4 may be perpendicular to the side of the upper surface of the substrate 2 or form a certain angle with the side of the upper surface of the substrate 2 . The first electrode 3 and the second electrode 4 are fabricated by photolithography technology and thin film fabrication technology. The structure, size and material of the second electrode 4 can be the same as those of the first electrode 3 . The material of the second electrode 4 may be a combination of titanium (Ti) and gold (Au) or one of them. The thickness of the first electrode 3 is in the range of 20nm-300nm, the radius is in the range of 80m-120m, the opening angle θ1 is in the range of 60°-90°, and the scale factor τ is in the range of 0.707-0.8.

Referring to FIG. 6 , in an embodiment of the present invention, the first electrode 3 may also be a butterfly antenna structure. The first electrode 3 may be fan-shaped, and the second electrode 4 is formed on the substrate 2 and is symmetrically arranged with the first electrode 3 with respect to the center of the substrate 2 . The longest dimension in the horizontal direction of the antenna formed by the first electrode 4 and the second electrode 4 is smaller than the length of each side of the substrate 2 . The antenna formed by the first electrode 3 and the second electrode 4 may be perpendicular to the side of the upper surface of the substrate 2 or form a certain angle with the side of the upper surface of the substrate 2 . The first electrode 3 and the second electrode 4 are fabricated by photolithography technology and thin film fabrication technology. The structure, size and material of the second electrode 4 can be the same as those of the first electrode 3 . The material of the second electrode 4 may be a combination of titanium (Ti) and gold (Au) or one of them. The thickness of the first electrode 3 ranges from 20nm to 300nm, for example, the radius ranges from 80µm to 120µm, and the opening angle θ2 ranges from 30° to 90°.

Referring to FIG. 7 , in an embodiment of the present invention, the first electrode 3 may also be a strip antenna structure, and the first electrode 3 may be a long strip. A funnel-shaped constriction structure is formed near the center of the substrate 2 . The length of the first electrode 3 is less than half of the length of each side of the substrate 2 . The second electrode 4 is formed on the substrate 2 and is symmetrically arranged with the first electrode 3 about the center of the substrate 2 . The antenna formed by the first electrode 3 and the second electrode 4 may be perpendicular to the side of the upper surface of the substrate 2 or form a certain angle with the side of the upper surface of the substrate 2 . The first electrode 3 and the second electrode 4 are fabricated by photolithography technology and thin film fabrication technology. The structure, size and material of the second electrode 4 can be the same as those of the first electrode 3 . The material of the second electrode 4 may be a combination of titanium (Ti) and gold (Au) or one of them. The thickness of the first electrode 3 ranges from 20 nm to 300 nm, for example.

Referring to FIGS. 1-5 , in an embodiment of the present invention, a first semiconductor layer 5 is formed between the first electrode 3 and the second electrode 4 and connects the first electrode 3 and the The second electrode 4 . The first semiconductor layer 5 is respectively connected to the first electrode 3 and the second electrode 4 by different channel structures, as shown in FIG. 5 . The two-dimensional material of the first semiconductor layer 5 is transferred onto the first electrode 3 and the second electrode 4 by thin film transfer technology using a two-dimensional material transfer platform. The material of the first semiconductor layer 5 may be molybdenum disulfide/graphene, tungsten disulfide/graphene, molybdenum diselenide/graphene and other materials.

Referring to FIGS. 1-5 , in an embodiment of the present invention, an insulating layer 6 is formed on the first semiconductor layer 5 . The insulating layer 6 covers the first semiconductor layer 5 . The channel region of the first semiconductor layer 5 is patterned by electron beam lithography to form a patterned insulating layer 6 region. The patterned substrate 2 is soaked in deionized water, the residual developer is washed away, and the solid film is dried. The insulating layer 6 is grown in the pattern area. In this embodiment, the atomic layer deposition method and the magnetron sputtering method in the thin film manufacturing technology are used. The insulating layer 6 can be formed, for example, by film formation at 150°C using an ALD apparatus. The insulating layer 6 can be made of silicon dioxide, hafnium dioxide, aluminum oxide, boron nitride and other materials. The thickness of the insulating layer 6 is in the range of, for example, 20nm-300nm.

Referring to FIGS. 1-5 , in an embodiment of the present invention, the third electrode 7 is formed on the insulating layer 6 and is located on one side of the insulating layer 6 . The fourth electrode 8 is formed on the insulating layer 6 and is symmetrically arranged with the third electrode 7 with respect to the center of the substrate 2 . The structures, dimensions and materials of the third electrode 7 and the fourth electrode 8 may be the same as those of the first electrode 3 and the second electrode 4 . The third electrode 7 and the fourth electrode 8 are fabricated by photolithography technology and thin film fabrication technology, and the center connection line between the first electrode 3 and the second electrode 4 is perpendicular to the third electrode 7 and the fourth electrode 8's center line. The third electrode 7 and the fourth electrode 8 can be logarithmic periodic antennas, also can be butterfly antenna structures, and can also be strip antenna structures.

Referring to FIGS. 1-5 , in an embodiment of the present invention, a second semiconductor layer 9 is formed between the third electrode 7 and the fourth electrode 8 and connects the third electrode 7 and the Fourth electrode 8 . The second semiconductor layer 9 is respectively connected to the third electrode 7 and the fourth electrode 8 by different channel structures, as shown in FIG. 5 . The two-dimensional material of the second semiconductor layer 9 is transferred onto the third electrode 7 and the fourth electrode 8 by thin film transfer technology using a two-dimensional material transfer platform. The material of the second semiconductor layer 9 can be molybdenum disulfide/graphene, tungsten disulfide/graphene, molybdenum diselenide/graphene and other materials.

Please refer to FIG. 9-FIG. 11. In an embodiment of the present invention, different antenna structures in the shape of a vertical cross are designed in this embodiment, and the result of the electromagnetic simulation pattern can not only determine whether the design meets the needs, but also can use the A hyperhemispheric lens is used to gather infrared and terahertz waves, and the infrared and terahertz waves are coupled to the detection area as much as possible, as shown in Figure 9-Figure 11. The simulation results of different antenna structures show that the different antenna structures designed can meet the technical requirements. .

The present invention also provides a preparation method of a terahertz signal detection device, comprising the following steps:

S1. Provide substrate;

S2, forming a first electrode on the substrate, located on one side of the substrate;

S3, forming a second electrode on the substrate, which is symmetrically arranged with the first electrode about the center of the substrate;

S4, forming a first semiconductor layer between the first electrode and the second electrode, and connecting the first electrode and the second electrode;

S5, forming an insulating layer on the first semiconductor layer;

S6, a third electrode is formed on the insulating layer, located on one side of the insulating layer; a fourth electrode is formed on the insulating layer, and the third electrode is symmetrically arranged with respect to the center of the substrate;

S7, forming a second semiconductor layer between the third electrode and the fourth electrode, and connecting the third electrode and the fourth electrode; wherein, the center of the first electrode and the second electrode The connecting line is perpendicular to the center connecting line of the third electrode and the fourth electrode.

Referring to FIG. 8 , in an embodiment of the present invention, a tin diselenide/graphene heterojunction is used as the material of the first semiconductor layer 5 , and a log-periodic antenna is used as the first electrode 3 . In step S1 of this embodiment, a substrate 2 is provided, and the substrate 2 is cleaned by, for example, a stripping cleaning device and an ultrasonic device. The substrate 2 can be ultrasonically cleaned by using acetone, ethanol, and deionized water for many times, and the range of each ultrasonic time is, for example, 10-15 minutes.

Referring to FIG. 8 , in an embodiment of the present invention, in step S2 , nitrogen gas is used to remove moisture on the substrate 2 and dried, and a spin coater is used to spin-coat the positive photoresist on the substrate 2 . In order to ensure that the prepared photoresist film is flat and free of bubbles, the rotational speed used in the spin coating process is, for example, 3000 rpm. After coating, the volatile part of the photoresist is evaporated by heating on a high temperature hot stage, e.g., 100°C for 10-15 minutes to form a cured photoresist film on the substrate 2 . The photoresist-coated substrate 2 is covered with a corresponding reticle, and the photolithography process can be realized, for example, using an ultraviolet exposure machine. The operating wavelength range employed is, for example, 350-450 nm, and the pattern resolution is, for example, 0.2 μm. Ultraviolet light is irradiated on the substrate 2 placed directly under the reticle through the patterned areas in the preset reticle, and reacts with the positive photoresist exposed to the uv light. The exposed photoresist area is washed away with the corresponding developing solution to form a patterned first electrode 3 area. Finally, the patterned substrate 2 is soaked in deionized water, the residual developer is washed away, and the solid film is dried. After drying the solid film, the pattern area is coated. In this embodiment, for example, the magnetron sputtering method in the thin film manufacturing technology is used. The cathode target is made of coating material, and the substrate is used as the anode. Argon gas or other inert gas with a pressure range of 0.1-10Pa is passed into the vacuum chamber, and a glow is generated under the action of a cathode (target) adding a voltage range such as 1-3kV DC negative high voltage or a radio frequency voltage with a frequency such as 13.56MHz discharge. The ionized argon ions bombard the target surface, so that the target atoms are sputtered and deposited on the substrate to form a thin film, and the first electrode 3 is obtained.

Referring to FIG. 8 , in an embodiment of the present invention, in step S3 , the second electrode 4 is obtained, and the patterning process of the second electrode 4 is performed. The patterning process used in this embodiment may include one of ordinary ultraviolet lithography and electron beam lithography, and one of atomic layer deposition, thermal evaporation, and magnetron sputtering. In this embodiment, the electrodes are patterned by electron beam lithography, for example. The positive photoresist was spin-coated on the substrate 2 using a spin coater. In order to ensure that the prepared photoresist film is flat and free of air bubbles, the rotational speed used in the spin coating process is, for example, 3000 rpm. After coating, it is heated on a high temperature hot stage such as 100° C. for 10-15 minutes to evaporate the volatile part of the photoresist to form a cured photoresist film on the substrate 2 . The photoresist-coated substrate 2 is covered with a corresponding reticle, and the photolithography process can be realized by, for example, an ultraviolet exposure machine. The operating wavelength range employed is, for example, 350-450 nm, and the pattern resolution is, for example, 0.2 [mu]m. The UV light is irradiated on the substrate 2 placed directly under the reticle through the patterned areas in the preset reticle, and reacts with the positive photoresist exposed to the uv light. The exposed photoresist area is rinsed off with the corresponding developing solution to form a patterned second electrode 4 area. Finally, the patterned substrate 2 is soaked in deionized water, the residual developer is washed away, and the solid film is dried. After drying the solid film, the pattern area is coated. In this embodiment, for example, the magnetron sputtering method in the thin film manufacturing technology is used. The cathode target is made of coating material, and the substrate is used as the anode. Argon gas or other inert gas whose pressure range is 0.1-10Pa is passed into the vacuum chamber, and glow is generated under the action of cathode (target) adding voltage range such as 1-3kV DC negative high voltage or frequency such as 13.56MHz radio frequency voltage. discharge. The ionized argon ions bombard the target surface, so that the target atoms are sputtered and deposited on the substrate to form a thin film, and the second electrode 4 is obtained.

Referring to FIG. 8, in an embodiment of the present invention, in step S4, a two-dimensional material transfer platform is used to form the first semiconductor layer 5, and the material of the first semiconductor layer 5 is transferred to the first electrode 3 and the second electrode 4 on.

Referring to FIG. 8, in an embodiment of the present invention, in step S5, the insulating layer 6 is obtained on the basis of step S4, and the patterning process of the insulating layer 6 is performed. In practice, the channel region of the first semiconductor layer 5 is patterned by, for example, electron beam lithography. For example, using the same steps in step S2, the patterned insulating layer 6 region is formed. The patterned substrate 2 was immersed in deionized water, the residual developer was washed away, and the solid film was dried. After drying the solid film, the insulating layer 6 needs to be grown on the pattern area. Thus, the insulating layer 6 is formed.

Referring to FIG. 8, in an embodiment of the present invention, in step S6, the third electrode 7 and the fourth electrode 8 are formed on the insulating layer 6. After drying the solid film, an insulating layer needs to be applied to the pattern area. 6 Growth. In this embodiment, for example, atomic layer deposition and magnetron sputtering in thin-film manufacturing techniques are used, for example, ALD equipment can be used to form a film at 150°C. And in step S7, a second semiconductor layer 9 is formed between the third electrode 7 and the fourth electrode 8, and a terahertz signal detection is obtained by connecting the third electrode 7 and the fourth electrode 8 device 1.

To sum up, the present invention has the following beneficial effects: the antenna is designed into a special vertical cross-shaped structure, and a heterojunction formed by graphene or boron nitride with excellent electrical properties and some two-dimensional materials, such as diselenide The tin/graphene heterojunction, etc., improves the response time and realizes the high sensitivity, wide bandwidth and low signal-to-noise ratio of the detection device. Compared with the traditional field effect structure, the device has novel structure, excellent performance, simple preparation, can work in the infrared and terahertz bands, and is easy to mass-produce.

The above description is only a preferred embodiment of the application and an illustration of the applied technical principle. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solution formed by the specific combination of the above technical features , and shall also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept, for example, the above features are similar to those disclosed in this application (but not limited to) A technical solution formed by replacing the technical features of the functions with each other.

Except for the technical features described in the specification, the remaining technical features are the known technologies of those skilled in the art, and in order to highlight the innovative features of the present invention, the remaining technical features are not repeated here.

Claims (10)

1. A terahertz signal detection device, characterized in that, comprising: substrate; a first electrode, formed on the substrate, and located on one side of the substrate; a second electrode, formed on the substrate, and arranged symmetrically with the first electrode about the center of the substrate; a first semiconductor layer formed between the first electrode and the second electrode and connecting the first electrode and the second electrode; an insulating layer formed on the first semiconductor layer; a third electrode, formed on the insulating layer, and located on one side of the insulating layer; a fourth electrode, formed on the insulating layer, and arranged symmetrically with the third electrode about the center of the substrate; a second semiconductor layer formed between the third electrode and the fourth electrode and connecting the third electrode and the fourth electrode; Wherein, the center line connecting the first electrode and the second electrode is perpendicular to the center line connecting the third electrode and the fourth electrode. 2 . The terahertz signal detection device according to claim 1 , wherein the substrate comprises a silicon-based base and a base covering layer, and the base covering layer covers the upper surface of the silicon-based base. 3 . 3 . The terahertz signal detection device according to claim 1 , wherein the first electrode, the second electrode, the third electrode and the fourth electrode are arranged in a fan shape. 4 . 4 . The terahertz signal detection device according to claim 1 , wherein the structures and dimensions of the first electrode, the second electrode, the third electrode and the fourth electrode are the same. 5 . 5 . The terahertz signal detection device according to claim 4 , wherein the radius of the first electrode ranges from 80 μm to 120 μm. 6 . 6 . The terahertz signal detection device according to claim 4 , wherein the opening angle of the first electrode ranges from 60° to 90°. 7 . 7 . The terahertz signal detection device according to claim 4 , wherein the thickness of the first electrode ranges from 20 nm to 300 nm. 8 . 8 . The terahertz signal detection device according to claim 1 , wherein the orthographic projections of the first electrode, the second electrode, the third electrode and the fourth electrode on the substrate are different. 9 . coincide. 9 . The terahertz signal detection device according to claim 1 , wherein the insulating layer covers the first semiconductor layer. 10 . 10. A preparation method of a terahertz signal detection device, characterized in that, comprising: provide a substrate; forming a first electrode on the substrate, located on one side of the substrate; forming a second electrode on the substrate, symmetrically arranged with the first electrode about the center of the substrate; forming a first semiconductor layer between the first electrode and the second electrode, connecting the first electrode and the second electrode; forming an insulating layer on the first semiconductor layer; forming a third electrode on the insulating layer, located on one side of the insulating layer; forming a fourth electrode on the insulating layer, which is symmetrically arranged with the third electrode about the center of the substrate; forming a second semiconductor layer between the third electrode and the fourth electrode, and connecting the third electrode and the fourth electrode; Wherein, the center connection line between the first electrode and the second electrode is perpendicular to the center connection line between the third electrode and the fourth electrode.

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