Photoconductive switch and preparation method thereof
By setting a reflective dielectric film on the lower surface and an antireflective dielectric film on the upper surface of the photoconductive switch wafer, the problem of short light absorption path is solved, thereby improving light absorption efficiency and output capability.
Patent Information
- Application Number
- CN202511019689.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-11-07
AI Technical Summary
In the normal incidence mode, the light absorption path of the photoconductive switch is relatively short, resulting in low light absorption efficiency and consequently, low device output capability.
A reflective dielectric film is placed on the lower surface of the wafer to reflect unabsorbed photons back into the wafer for multiple reflections. An antireflective dielectric film is placed on the upper surface of the wafer to increase transmittance, extend the light absorption path, and improve light absorption efficiency.
By extending the light absorption path, the light absorption efficiency and output capability of the photoconductive switch are improved.
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Figure CN120916533A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor, and in particular to a photoconductive switch and a preparation method thereof. BACKGROUND
[0002] As an ultrafast optoelectronic device integrating laser technology and semiconductor technology, the photoconductive switch has great application potential in the field of ultra-high voltage and high power due to its advantages of high power, fast response speed and small size, and has played a positive role in promoting the development of the field.
[0003] In order to achieve the performance requirements of high breakdown voltage and high power, the photoconductive switch usually adopts a double-sided electrode structure, among which the opposite electrode structure is widely used. In the working process, the side-in light mode is generally adopted. However, this side-in light mode has obvious defects: the area of the light absorption surface is too small, which leads to high concentration of light energy and easily causes device damage, thereby adversely affecting the further improvement of the device performance.
[0004] In order to solve the above problems, the normal-in light mode is proposed. The normal-in light mode can effectively increase the light absorption area and reduce the light energy density per unit area, thereby improving the reliability of the device. However, at the same time, the normal-in light mode also brings new problems: the light absorption path is short under the normal-in light mode, which leads to low light absorption efficiency, and thus the output capacity of the device is low. SUMMARY
[0005] Embodiments of the present application provide a photoconductive switch and a preparation method thereof to solve the problem that the light absorption path is short under the normal-in light mode, which leads to low light absorption efficiency and thus the output capacity of the device is low.
[0006] In a first aspect, embodiments of the present application provide a photoconductive switch, comprising: a wafer, a front electrode, a ring-shaped contact electrode, a reflective dielectric film and an electroplated thickening layer.
[0007] The upper surface of the wafer is provided with the front electrode;
[0008] The lower surface of the wafer is provided with the ring-shaped contact electrode and the reflective dielectric film, and the reflective dielectric film is located inside the ring of the ring-shaped contact electrode.
[0009] The electroplated thickening layer covers the ring contact electrode and the reflective dielectric film; the reflectivity of the reflective dielectric film is greater than the reflectivity of the lower surface of the wafer.
[0010] In a possible implementation, further comprising: an anti-reflection dielectric film;
[0011] The anti-reflection dielectric film is arranged on the remaining area of the upper surface of the wafer which is not covered by the front electrode.
[0012] The transmittance of the antireflection medium film is greater than the transmittance of the upper surface of the wafer.
[0013] In a possible implementation, the thickness of the antireflection medium film and / or the reflective medium film ranges from 3000 to 10000 A.
[0014] In a possible implementation, the material of the antireflection medium film and / or the reflective medium film is SiN or SiO.
[0015] In a possible implementation, the electrode edge of the front electrode and the upper surface of the antireflection medium film are both coated with a polyimide material.
[0016] and / or
[0017] The edge of the electroplated thickening layer, the exposed part of the annular contact electrode, and the remaining area of the lower surface of the wafer not covered by the electroplated thickening layer are all coated with a polyimide material.
[0018] In a possible implementation, the electroplated thickening layer is trapezoidal in the thickness direction.
[0019] In a possible implementation, the front electrode includes an annular sub-electrode and a grid-shaped sub-electrode.
[0020] The grid-shaped sub-electrode is arranged inside the annulus of the annular sub-electrode and is connected to the annular sub-electrode.
[0021] In a possible implementation, the grid-shaped sub-electrode includes a plurality of horizontal electrodes and a plurality of vertical electrodes; the plurality of horizontal electrodes and the plurality of vertical electrodes form a grid-shaped structure.
[0022] The electrode width of the horizontal electrode and / or the vertical electrode ranges from 10 to 50 μm.
[0023] The spacing between adjacent horizontal electrodes and / or adjacent vertical electrodes ranges from 50 to 100 μm.
[0024] In a second aspect, the embodiments of the present application also provide a preparation method of a photoconductive switch, which includes:
[0025] Preparation of a front electrode on the upper surface of a wafer;
[0026] Sequentially, a photoetching, evaporation, and stripping process is used to prepare an annular contact electrode on the lower surface of the wafer;
[0027] Sequentially, a deposition, photoetching, and etching process is used to prepare a reflective medium film on the lower surface of the wafer; the reflective medium film is located inside the annular structure of the annular contact electrode;
[0028] A plating metal layer is prepared on the annular contact electrode and the reflective dielectric film by using a photolithography and plating process in sequence, so as to obtain the photoconductive switch.
[0029] In a possible implementation, after the front electrode is prepared on the upper surface of the wafer, the method further includes:
[0030] A transmittance dielectric film is prepared on the upper surface of the wafer by using a deposition, photolithography and etching process in sequence; the transmittance dielectric film is arranged on the remaining area of the upper surface of the wafer which is not covered by the front electrode;
[0031] The transmittance of the transmittance dielectric film is greater than the transmittance of the upper surface of the wafer
[0032] The embodiment of the present application mainly considers that when the photons are incident on the wafer in the normal incidence mode, the absorption path of the wafer for the incident light is short due to the thin thickness of the wafer, and thus the wafer cannot effectively absorb the incident light. Therefore, the embodiment of the present application can reflect the photons which are not absorbed after penetrating the lower surface of the wafer to the inside of the wafer again for the wafer to absorb again by arranging the reflective dielectric film on the lower surface of the wafer. Through the reflection of the photons by the reflective dielectric film, the photons can be reflected in the wafer for multiple times, so as to prolong the absorption path of the wafer and effectively improve the light absorption efficiency, and finally achieve the purpose of improving the output capability of the photoconductive switch. BRIEF DESCRIPTION OF DRAWINGS
[0033] Figure 1 is a schematic diagram of transmission of incident light in the photoconductive switch;
[0034] Figure 2 is a schematic diagram of a cross section of the photoconductive switch provided by an embodiment of the present application;
[0035] Figure 3 is a schematic diagram of a bottom surface of the photoconductive switch provided by an embodiment of the present application;
[0036] Figure 4 is a schematic diagram of a front electrode of the photoconductive switch provided by an embodiment of the present application;
[0037] Figure 5 is a schematic diagram of a cross section of the photoconductive switch provided by another embodiment of the present application;
[0038] Figure 6 is a schematic diagram of a cross section of the photoconductive switch provided by still another embodiment of the present application;
[0039] Figure 7 is an implementation flowchart of a preparation method of the photoconductive switch provided by an embodiment of the present application;
[0040] Figure 8 is a preparation flowchart of the photoconductive switch provided by an embodiment of the present application. DETAILED DESCRIPTION
[0041] In order to better understand the present solution, the technical solutions in the embodiments of the present solution will be clearly described below in conjunction with the accompanying drawings in the embodiments of the present solution. Obviously, the described embodiments are part of the embodiments of the present solution, rather than all the embodiments. Based on the embodiments in the present solution, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present solution.
[0042] The term "comprising" and other any variations thereof in the specification and claims of the present solution and the above-mentioned drawings means "including but not limited to", which is intended to cover non-exclusive inclusion and is not limited to the examples listed in the text. In addition, the terms "first" and "second" and the like are used to distinguish different objects, rather than to describe a specific order.
[0043] Referring to Figure 1 In the related art, most of the light guide switches are designed in a normal incidence mode with front light incidence to increase the absorption area of incident light and avoid high concentration of light intensity energy. However, the thickness of the wafer (i.e. the main body of the light guide switch) in the light guide switch is small, i.e. the absorption path of the incident light is short, which makes the incident light incident to the inside of the wafer cannot be effectively absorbed, but will be transmitted from the bottom of the wafer, eventually resulting in low light absorption efficiency and low device output capability.
[0044] In order to extend the light absorption path, improve the light absorption efficiency, and thus improve the device output capability, the present embodiment sets a reflective dielectric film on the lower surface of the wafer, which can reflect the photons that have penetrated the lower surface of the wafer and have not been absorbed to the inside of the wafer for re-absorption by the wafer. Through the reflection of the reflective dielectric film to the photons, the photons can be reflected multiple times inside the wafer, thereby extending the light absorption path of the wafer, effectively improving the light absorption efficiency, and ultimately achieving the purpose of improving the output capability of the light guide switch.
[0045] The implementation of the present application will be described in detail below in conjunction with specific drawings:
[0046] Figure 2 A cross-sectional view of the light guide switch provided by the present embodiment. Figure 3 A bottom view of the light guide switch provided by the present embodiment. Referring to Figure 2 and Figure 3 The light guide switch comprises a wafer 21, a front electrode 22, a circular ring-shaped contact electrode 23, a reflective dielectric film 24, and an electroplated thickening layer 25.
[0047] The upper surface of the wafer 21 is provided with the front electrode 22;
[0048] The lower surface of the wafer 21 is provided with a circular contact electrode 23 and a reflective dielectric film 24, and the reflective dielectric film 24 is located inside the circular ring of the circular contact electrode 23;
[0049] The electroplated thickening layer 25 covers the circular contact electrode 23 and the reflective dielectric film 24; the reflectivity of the reflective dielectric film 24 is greater than that of the lower surface of the wafer 21.
[0050] Here, the circular arc contact electrode 23, the reflective dielectric film 24, and the electroplated thickening layer 25 together constitute the back electrode of the light guide switch. The electroplated thickening layer 25 is arranged at the bottom of the circular arc contact electrode 23 and the reflective dielectric film 24, covers the circular arc contact electrode 23 and the reflective dielectric film 24, and is used to thicken the circular arc contact electrode 23 to improve the current carrying capacity of the back electrode. Exemplarily, the material of the electroplated metal layer 25 can be Au or Cu. The thickness of the electroplated metal layer 25 can range from 3 to 7 μm.
[0051] In some embodiments, referring to Figure 2 Under the forward viewing angle (i.e., when the upper surface of the wafer is upward), the electroplated thickening layer 25 is trapezoidal in the thickness direction.
[0052] Here, arranging the electroplated thickening layer 25 to be trapezoidal in the thickness direction can reduce the surface field strength, thereby improving the breakdown voltage of the light guide switch. Exemplarily, referring to Figure 2 , the included angle between the trapezoidal electroplated thickening layer 25 and the surface horizontal line of the circular contact electrode 23 ranges from 40 to 60°.
[0053] The reflective dielectric film 24 is arranged on the lower surface of the wafer and located inside the circular ring of the circular arc contact electrode 23. A small part of the photons incident into the wafer is absorbed by the wafer, and most of them pass through the lower surface of the wafer to reach the reflective dielectric film 24. The reflective dielectric film 24 reflects the unabsorbed photons, thereby reflecting them again into the wafer for absorption. Through the reflection of the photons by the reflective dielectric film, the photons can be reflected multiple times in the wafer, thereby prolonging the light absorption path of the wafer and effectively improving the light absorption efficiency, and ultimately achieving the purpose of improving the output capacity of the light guide switch.
[0054] Here, the embodiments of the present application limit the reflectivity of the reflective dielectric film 24 to be greater than that of the lower surface of the wafer 21, so as to ensure that the purpose of prolonging the light absorption path of the wafer and improving the light absorption efficiency can be achieved.
[0055] In some embodiments, referring to Figure 2 The above light guide switch further comprises an anti-reflection dielectric film 26. The anti-reflection dielectric film 26 is arranged on the remaining area of the upper surface of the wafer 21 which is not covered by the front electrode 22.
[0056] The applicant finds that, in addition to the short light absorption path, the transmittance of the upper surface of the wafer is also an important factor limiting the light absorption efficiency of the wafer. See Figure 1 When the incident light reaches the upper surface of the wafer, most of the photons are reflected, and only a small part of the photons are transmitted into the wafer for absorption. Therefore, the present application provides a transmittance increasing medium film in the area of the upper surface of the wafer not covered by the front electrode, so as to increase the transmittance of the upper surface of the wafer, so that more photons can be transmitted into the wafer, thereby further increasing the light absorption efficiency. Here, the transmittance of the transmittance increasing medium film is greater than that of the upper surface of the wafer.
[0057] In some embodiments, the thickness of the transmittance increasing medium film and / or the reflective medium film ranges from 3000 to 10000 A.
[0058] In some embodiments, the material of the transmittance increasing medium film and / or the reflective medium film is SiN or SiO.
[0059] The thickness of the transmittance increasing medium film will directly affect its transmittance. As the thickness of the transmittance increasing medium film gradually increases, the transmittance of the transmittance increasing medium film changes in a sinusoidal waveform. Therefore, the present application can determine the thickness corresponding to the peak of the sinusoidal waveform as the thickness of the transmittance increasing medium film. Alternatively, the thickness range corresponding to the peak and its adjacent region in the sinusoidal waveform is determined as the thickness range of the transmittance increasing medium film. Exemplarily, the thickness range of the transmittance increasing medium film ranges from 3000 to 10000 A. The reflective medium film is the same, which will not be described here.
[0060] In some embodiments, see Figure 4 and Figure 5 The front electrode includes a circular ring-shaped sub-electrode 221 and a grid-shaped sub-electrode 222.
[0061] The grid-shaped sub-electrode 222 is arranged inside the circular ring of the circular ring-shaped sub-electrode 221 and is connected with the circular ring-shaped sub-electrode 221.
[0062] The present application can disperse the current in the front electrode by arranging the grid-shaped sub-electrode 222 inside the circular ring-shaped sub-electrode 221, so as to avoid current concentration, so as to avoid device damage caused by current concentration, or adversely affect the performance of the light guide switch.
[0063] Here, the annular sub-electrode 221 includes a front annular contact electrode and a front plating metal layer. The front plating metal layer covers the front annular contact electrode, and is used to improve the current carrying capacity of the electrode. Similar to the plating metal layer in the back electrode, the material of the front plating metal layer can be Au or Cu. The thickness of the plating metal layer can range from 3 to 7 μm. The front plating metal layer is inverted trapezoidal in the thickness direction, and the included angle between the front plating metal layer and the upper surface of the front annular contact electrode ranges from 40 to 60°, which is used to reduce the surface field strength, thereby improving the breakdown voltage of the photoconductive switch.
[0064] In some embodiments, referring to Figure 4 , the grid-shaped sub-electrode 222 includes a plurality of horizontal electrodes and a plurality of vertical electrodes; the plurality of horizontal electrodes and the plurality of vertical electrodes form a grid structure.
[0065] Here, the size and shape of the incident light can be adjusted by adjusting the grid topography, thereby changing the area of the light absorption region. By changing the area of the light absorption region, the contact resistance can be affected, thereby achieving a balanced design between light energy absorption and contact resistance conduction.
[0066] The larger the area of the light absorption region, the more light is absorbed, the concentration of photo-generated carriers increases, and the contact resistance decreases. Here, the grid topography mainly includes grid size and grid line width. The grid size is determined by the distance between adjacent horizontal electrodes and / or adjacent vertical electrodes. The grid line width is the electrode width of the horizontal electrode and / or the vertical electrode. Exemplarily, the electrode width of the horizontal electrode and / or the vertical electrode can range from 10 to 50 μm; the distance between adjacent horizontal electrodes and / or adjacent vertical electrodes can range from 50 to 100 μm.
[0067] Here, the horizontal electrode includes a horizontal contact electrode and a horizontal plating metal layer. The horizontal plating metal layer covers the horizontal contact electrode, and is used to improve the current carrying capacity of the electrode. The material of the horizontal plating metal layer can be Au or Cu. The thickness of the horizontal plating metal layer can range from 3 to 7 μm. The plating metal layer is inverted trapezoidal in the thickness direction, and the included angle between the plating metal layer and the upper surface of the horizontal contact electrode ranges from 40 to 60°. The vertical electrode is the same, and will not be described here.
[0068] It should be noted that, referring to Figure 5 , when the anti-reflection medium film is arranged on the upper surface of the wafer, the area of the upper surface of the wafer in the annular sub-electrode which is not covered by the grid-shaped sub-electrode can also be provided with an anti-reflection medium film to increase the transmission of incident light as much as possible.
[0069] In some embodiments, referring to Figure 6 , the electrode edges of the front electrode and the upper surface of the anti-reflection medium film are coated with a polyimide material 61;
[0070] and / or
[0071] The edge of the electroplated thickening layer, the exposed part of the annular contact electrode, and the remaining area of the lower surface of the wafer not covered by the electroplated thickening layer are coated with a polyimide material 61.
[0072] Here, the polyimide material mainly plays a protective role, which is used to protect the electrode edge from breakdown with air and prevent the device from being scratched.
[0073] For the front surface of the light guide switch, the electrode edge of the front surface electrode and the upper surface of the antireflection medium film can be coated with a polyimide material to protect the front surface electrode and prevent the front surface of the device from being scratched. Here, it should be noted that the upper surface of the antireflection medium film inside the annular sub-electrode does not need to be coated with a polyimide material.
[0074] For the back surface of the light guide switch, referring to Figure 6 , the edge of the electroplated thickening layer, the outer side of the annular contact electrode not covered by the electroplated thickening layer, and the remaining area of the lower surface of the wafer not covered by the electroplated thickening layer are coated with a polyimide material to protect the back surface electrode and prevent the back surface of the device from being scratched.
[0075] Based on the above light guide switch, referring to Figure 7 , the embodiment of the present application also provides a preparation method of a light guide switch, comprising:
[0076] Step 701, preparing a front surface electrode on the upper surface of the wafer.
[0077] Referring to Figure 8 , the front surface annular contact electrode and the front surface grid-shaped contact electrode are made on the upper surface of the wafer by using a photolithography-evaporation-peeling method. Here, the front surface grid-shaped contact electrode includes a plurality of horizontal contact electrodes and a plurality of vertical contact electrodes.
[0078] The electrode thickness of each contact electrode can range from 1000A to 5000A, the electrode width of the horizontal electrode and / or the vertical electrode can range from 10μm to 50μm, and the spacing between adjacent horizontal electrodes and / or adjacent vertical electrodes can range from 50μm to 100μm.
[0079] Then, the metal thickening of each contact electrode is performed by using a photolithography-electroplating method. Here, the metal can be selected from Au or Cu, and the thickness can range from 3μm to 7μm. In order to reduce the surface field strength and improve the breakdown voltage of the device, the plating layer has an inverted trapezoidal structure in the thickness direction, and the angle between the plating layer and the horizontal plane of the contact electrode is 40° to 60°.
[0080] In some embodiments, referring to Figure 8After the front electrode is prepared on the upper surface of the wafer, a deposition, lithography and etching process can be sequentially used to prepare a transmittance enhancement dielectric film on the upper surface of the wafer; the transmittance enhancement dielectric film is arranged on the remaining area of the upper surface of the wafer which is not covered by the front electrode. The transmittance of the transmittance enhancement dielectric film is greater than the transmittance of the upper surface of the wafer.
[0081] Here, the deposition-lithography-etching method can be used to complete the preparation of the transmittance enhancement dielectric film. The material of the transmittance enhancement dielectric film can be SiN or SiO, etc. The thickness of the transmittance enhancement dielectric film can range from 3000 to 10000 A.
[0082] In some embodiments, referring to Figure 8 After the preparation of the transmittance enhancement dielectric film is completed, a layer of polyimide material can be coated on the edge of the front electrode and the transmittance enhancement dielectric film. The coating thickness can range from 3 to 5 μm. Here, the lithography-curing method can be used to protect the edge of the front electrode with the polyimide material, to prevent breakdown from air and to prevent the device from being scratched, thus playing a certain protective role,
[0083] Step 702: a lithography, evaporation and stripping process is sequentially used to prepare a circular ring contact electrode on the lower surface of the wafer;
[0084] Referring to Figure 8 Here, the lithography-evaporation-stripping method can be used to prepare the circular ring contact electrode on the lower surface of the wafer. The electrode thickness of the circular ring contact electrode can range from 1000 to 5000 A.
[0085] Step 703: a deposition, lithography and etching process is sequentially used to prepare a reflection dielectric film on the lower surface of the wafer; the reflection dielectric film is located inside the circular ring structure of the circular ring contact electrode;
[0086] Referring to Figure 8 Here, the deposition-lithography-etching method can be used to complete the preparation of the reflection dielectric film on the lower surface of the wafer. The material of the reflection dielectric film can be SiN or SiO, etc. The thickness of the reflection dielectric film can range from 3000 to 10000 A.
[0087] Step 704: a lithography and electroplating process is sequentially used to prepare an electroplated metal layer on the circular ring contact electrode and the reflection dielectric film, to obtain a light guide switch.
[0088] Referring to Figure 8 Here, the lithography-electroplating method can be used to thicken the metal on the circular ring contact electrode and the reflection dielectric film. The metal can be Au or Cu, etc. The thickness can range from 3 to 7 μm. When the lower surface of the wafer faces upward, the electroplated metal layer has a trapezoidal structure.
[0089] In some embodiments, referring to Figure 8After the electroplated metal layer is prepared, a photo-cured method can be used to coat a layer of polyimide material on the lower surface of the wafer. The coating thickness can range from 3 to 5 μm. The polyimide material can protect the edge of the electroplated thickening layer, the outer side of the annular contact electrode not covered by the electroplated thickening layer, and the lower surface of the wafer not covered by the electroplated thickening layer from breakdown with air, and prevent the device from being scratched, thereby playing a certain protective role.
[0090] The above examples are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A light guide switch, characterized by The application relates to a light guide switch, which comprises: a wafer, a front electrode, a ring-shaped contact electrode, a reflective dielectric film and a plating thickening layer; the upper surface of the wafer is provided with the front electrode; the lower surface of the wafer is provided with the ring-shaped contact electrode and the reflective dielectric film, and the reflective dielectric film is located inside the ring of the ring-shaped contact electrode; the plating thickening layer covers the ring-shaped contact electrode and the reflective dielectric film; the reflectivity of the reflective dielectric film is greater than that of the lower surface of the wafer.
2. The photoconductive switch of claim 1, wherein, The application further comprises: an anti-reflection dielectric film; the anti-reflection dielectric film is arranged on the remaining area of the upper surface of the wafer which is not covered by the front electrode; the transmissivity of the anti-reflection dielectric film is greater than that of the upper surface of the wafer.
3. The photoconductive switch of claim 2, wherein, The thickness of the anti-reflection dielectric film and / or the reflective dielectric film ranges from 3000 to 10000 angstroms.
4. A light guide switch as claimed in claim 2 or 3, characterized in that The material of the anti-reflection dielectric film and / or the reflective dielectric film is SiN or SiO.
5. The photoconductive switch of claim 2 or 3, wherein, The electrode edges of the front electrode and the upper surface of the anti-reflection dielectric film are coated with a polyimide material; and / or the edges of the plating thickening layer, the exposed part of the ring-shaped contact electrode and the remaining area of the lower surface of the wafer which is not covered by the plating thickening layer are coated with a polyimide material.
6. The photoconductive switch of any of claims 1-3, wherein, The plating thickening layer is trapezoidal in the thickness direction.
7. The photoconductive switch of any of claims 1-3, wherein, The front electrode comprises a ring-shaped sub-electrode and a grid-shaped sub-electrode; the grid-shaped sub-electrode is arranged inside the ring of the ring-shaped sub-electrode and is connected with the ring-shaped sub-electrode.
8. The photoconductive switch of claim 7, wherein, The grid-shaped sub-electrode comprises a plurality of horizontal electrodes and a plurality of vertical electrodes; the plurality of horizontal electrodes and the plurality of vertical electrodes form a grid-shaped structure; the electrode width of the horizontal electrodes and / or the vertical electrodes ranges from 10 to 50 microns; the interval between adjacent horizontal electrodes and / or the interval between adjacent vertical electrodes ranges from 50 to 100 microns.
9. A method of fabricating a photoconductive switch, comprising: The application further comprises: preparing the front electrode on the upper surface of the wafer; sequentially adopting photoetching, evaporation and stripping processes to prepare the ring-shaped contact electrode on the lower surface of the wafer; sequentially adopting deposition, photoetching and etching processes to prepare the reflective dielectric film on the lower surface of the wafer; the reflective dielectric film is located inside the ring structure of the ring-shaped contact electrode; sequentially adopting photoetching and plating processes to prepare the plating metal layer on the ring-shaped contact electrode and the reflective dielectric film, so as to obtain the light guide switch.
10. The method of claim 9, wherein the photoconductive switch is prepared by the steps of: After the step of preparing the front electrode on the upper surface of the wafer, the application further comprises: sequentially adopting deposition, photoetching and etching processes to prepare the anti-reflection dielectric film on the upper surface of the wafer; the anti-reflection dielectric film is arranged on the remaining area of the upper surface of the wafer which is not covered by the front electrode; the transmissivity of the anti-reflection dielectric film is greater than that of the upper surface of the wafer.