Photoconductive switch based on total internal reflection and preparation method thereof

Abstract

The invention provides a photoconductive switch based on total internal reflection and a preparation method thereof, the photoconductive switch comprises a square substrate, a first side surface, a laser incident surface, a second side surface, a third side surface and a fourth side surface which are connected in sequence are formed on the substrate along the circumferential direction of the substrate, the first side surface is parallel to the third side surface, and the fourth side surface is parallel to the laser incident surface. The second side surface is parallel to the fourth side surface; the substrate is provided with a first surface and a second surface which are opposite along the height direction of the substrate; the first ohmic electrode and the second ohmic electrode are arranged on the first surface and / or the second surface; wherein a first preset angle is formed between the laser incident surface and the first side surface, and a second preset angle is formed between the laser incident surface and the second side surface. According to the photoconductive switch, the laser incident surface, the first side surface, the second side surface, the third side surface and the fourth side surface of the substrate form the total internal reflection structure, and the total internal reflection structure increases the path of laser passing through the interior of the substrate, thereby facilitating the increase of the light on-state current of the photoconductive switch.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a photoconductive switch based on total internal reflection and a preparation method thereof. Background Art

[0002] A semiconductor photoconductive switch is an ultrafast optoelectronic device that integrates laser and semiconductor technologies. Based on the photoelectric effect of semiconductor materials, ultrafast laser pulses alter the number of photogenerated carriers within the switch semiconductor, causing a change in conductivity. The switch can be turned on and off in nanoseconds or even picoseconds. Compared to other switches, photoconductive switches offer a simpler structure, high-voltage resistance, fast switching speed, minimal trigger jitter, superior optical isolation, immunity to electromagnetic interference, and all-solid-state miniaturization. They hold broad application prospects in high-power, ultra-wideband pulse generation and ultrafast electronics.

[0003] Photoconductive switching systems typically consist of lasers and semiconductor chips. The semiconductor is the core functional component, primarily composed of semi-insulating or high-intrinsic resistivity optoelectronic semiconductor materials. Third-generation wide-bandgap and ultra-wide-bandgap semiconductors, such as GaN, SiC, and diamond, have garnered significant attention in recent years due to their high withstand voltage and high saturation drift velocity, which promise to enable higher pulse powers and switching frequencies.

[0004] Photoconductive switches are divided into two types: intrinsic absorption mode and extrinsic absorption mode, depending on the different photon absorption modes. In the intrinsic absorption mode, the non-uniform distribution of current density will lead to local overheating, which can easily cause premature breakdown or failure of the device, thereby reducing the withstand voltage of the photoconductive switch; in the extrinsic absorption mode, the absorption coefficient is small, and the propagation path of the laser inside the material is only a few hundred microns to a few millimeters. The laser energy is transmitted out before it is fully utilized, resulting in the photocurrent of the photoconductive switch device being usually relatively low. Summary of the Invention

[0005] In view of this, the present invention provides a photoconductive switch based on total internal reflection and a preparation method thereof, which are used to solve the problem that the existing photoconductive switch has low absorption rate of incident laser and causes low output current.

[0006] A first aspect of an embodiment of the present invention provides a photoconductive switch based on total internal reflection, comprising:

[0007] A substrate, wherein the substrate is a square body, and along the circumferential direction of the substrate, the substrate is formed with a first side surface, a laser incident surface, a second side surface, a third side surface, and a fourth side surface connected in sequence, the first side surface and the third side surface are parallel to each other, and the second side surface and the fourth side surface are parallel to each other; along the height direction of the substrate, the substrate has a first surface and a second surface opposite to each other;

[0008] A first ohmic electrode and a second ohmic electrode are provided on the first surface and / or the second surface;

[0009] The laser incident surface forms a first preset angle with the first side surface, and the laser incident surface forms a second preset angle with the second side surface.

[0010] According to an embodiment of the present invention, a distance between the first side surface and the third side surface is equal to a distance between the second side surface and the fourth side surface.

[0011] According to an embodiment of the present invention, the first ohmic electrode is disposed on the first surface, and the second ohmic electrode is disposed on the second surface.

[0012] According to an embodiment of the present invention, a first arc-shaped groove is formed by the first surface being recessed toward the second surface;

[0013] A first arc-shaped portion is formed on one end of the first ohmic electrode facing the first surface. The first arc-shaped portion is adapted to the first arc-shaped groove, and an outer surface of the first arc-shaped portion is in contact with a groove wall of the first arc-shaped groove.

[0014] According to an embodiment of the present invention, a second arc-shaped groove is formed by the second surface being recessed toward the first surface;

[0015] A second arc-shaped portion is formed on one end of the second ohmic electrode facing the second surface. The second arc-shaped portion is adapted to the second arc-shaped groove, and an outer surface of the second arc-shaped portion is in contact with a groove wall of the second arc-shaped groove.

[0016] According to an embodiment of the present invention, the first ohmic electrode is a columnar body; and / or,

[0017] The second ohmic electrode is a columnar body.

[0018] According to an embodiment of the present invention, the material of the substrate includes any one of gallium nitride material, silicon carbide material and diamond material.

[0019] According to an embodiment of the present invention, the resistivity of the substrate is greater than 10 7 Ω·cm.

[0020] A second aspect of an embodiment of the present invention provides a method for preparing a photoconductive switch based on total internal reflection, comprising:

[0021] Provide substrate raw materials;

[0022] Cutting the substrate raw material into a cuboid, and cutting one end of the cuboid to form the substrate, wherein the substrate has a first side surface, a laser incident surface, a second side surface, a third side surface, and a fourth side surface connected in sequence along a circumferential direction of the substrate, the first side surface and the third side surface are parallel to each other, and the second side surface and the fourth side surface are parallel to each other; and along a height direction of the substrate, the substrate has a first surface and a second surface opposite to each other;

[0023] A first ohmic electrode and a second ohmic electrode are respectively prepared on the first surface and the second surface of the substrate.

[0024] According to an embodiment of the present invention, the step of preparing a first ohmic electrode and a second ohmic electrode on the first surface and the second surface of the substrate respectively includes:

[0025] forming a first arc-shaped groove on the first surface and a second arc-shaped groove on the second surface by an etching process;

[0026] The first ohmic electrode having a preset thickness is deposited at the first arc-shaped groove, and the second ohmic electrode having a preset thickness is deposited at the second arc-shaped groove.

[0027] The photoconductive switch based on total internal reflection and the preparation method thereof provided in accordance with the embodiments of the present invention can at least achieve the following technical effects: the laser incident surface, the first side surface, the second side surface, the third side surface and the fourth side surface of the substrate form a total internal reflection structure, and the laser enters the interior of the substrate from the laser incident surface. The total internal reflection structure increases the path of the laser passing through the interior of the substrate, making the laser absorption more sufficient, which is beneficial to improving the photoelectric responsivity and photoelectric conversion efficiency, and increasing the optical on-state current of the photoconductive switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0029] Figure 1 Schematically shows a front view of a photoconductive switch according to an embodiment of the present invention;

[0030] Figure 2 Schematically shows a top view of a photoconductive switch according to an embodiment of the present invention;

[0031] Figure 3 A schematic diagram of a path of total internal reflection of laser light inside a substrate according to an embodiment of the present invention is shown;

[0032] Figure numerals: 1: substrate; 11: first side; 12: laser incident surface; 13: second side; 14: third side; 15: fourth side; 16: first surface; 17: second surface; 2: first ohmic electrode; 21: first arc-shaped portion; 22: first cylindrical portion; 3: second ohmic electrode; 31: second arc-shaped portion; 32: second cylindrical portion. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] In the prior art, photoconductive switches are classified into two types: intrinsic absorption mode and extrinsic absorption mode, depending on the photon absorption method. The basic principle of the intrinsic mode is band-edge absorption, where electrons in the valence band absorb a photon energy greater than or equal to the bandgap width and transition to the conduction band. The intrinsic absorption coefficient of general materials is very high, with an absorption depth on the order of microns. Most photons can be absorbed within a very short distance, meaning that most photons are absorbed at the surface of the material. This causes a disproportionate current to be carried to the surface of the device, resulting in current crowding and surface flashover effects. This uneven distribution of current density can lead to local overheating, which can easily cause premature breakdown or failure of the device, thereby reducing the withstand voltage of the photoconductive switch.

[0037] Extrinsic absorption occurs through the excitation of electrons at impurity / defect energy levels within the material's bandgap. This is sub-bandgap excitation, and the required excitation energy depends on the location of the impurity / defect energy level. This allows for wavelength selection by manipulating doping and defects, allowing the use of low-cost, compact visible or infrared lasers as trigger sources for photoconductive switches. However, the main disadvantage of extrinsic absorption is its very small absorption coefficient, with an absorption depth on the order of millimeters to tens of millimeters. Conventional photoconductive switching devices use laser incident light from the side or front, resulting in a laser propagation path within the material of only a few hundred microns to a few millimeters. This means that the laser energy is transmitted before it is fully utilized. Consequently, the photocurrent of photoconductive switching devices using extrinsic absorption is typically low.

[0038] When a photoconductive switching device operates under high voltage, the electric field reaches a peak at the edge of the electrode. Carriers converge there, and the current density passing through this area is large, generating a large amount of heat. This causes the local temperature of the device to be too high, resulting in thermal breakdown, causing premature damage to the device, and the operating voltage is far lower than the theoretically predicted withstand voltage value.

[0039] The present invention provides a photoconductive switch based on total internal reflection, which adopts a total internal reflection structure to increase the path of laser light passing through the photoconductive switch to increase the output current of the photoconductive switch; and improves the withstand voltage value of the photoconductive switch by optimizing the electrode structure.

[0040] The following combination Figures 1 to 3 A photoconductive switch based on total internal reflection according to an embodiment of the present invention is described.

[0041] like Figure 1 and Figure 2 As shown, the photoconductive switch based on total internal reflection provided by the embodiment of the present invention includes a substrate 1, a first ohmic electrode 2 and a second ohmic electrode 3. The substrate 1 is a square body. Along the circumferential direction of the substrate 1, the substrate 1 is formed with a first side surface 11, a laser incident surface 12, a second side surface 13, a third side surface 14 and a fourth side surface 15 connected in sequence. The first side surface 11 and the third side surface 14 are parallel to each other, and the second side surface 13 and the fourth side surface 15 are parallel to each other; along the height direction of the substrate 1, the substrate 1 has a first surface 16 and a second surface 17 opposite to each other; the first ohmic electrode 2 and the second ohmic electrode 3 are arranged on the first surface 16 and / or the second surface 17; wherein the laser incident surface 12 forms a first preset angle with the first side surface 11, and the laser incident surface 12 forms a second preset angle with the second side surface 13.

[0042] Specifically, the substrate 1 is a square body, and has a first side surface 11, a laser incident surface 12, a second side surface 13, a third side surface 14, and a fourth side surface 15 formed in sequence along the circumferential direction of the substrate 1. The first side surface 11 and the third side surface 14 are parallel to each other, the second side surface 13 and the fourth side surface 15 are parallel to each other, and the first side surface 11 is perpendicular to the fourth side surface 15, the fourth side surface 15 is perpendicular to the third side surface 14, and the third side surface 14 is perpendicular to the second side surface 13. The laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14, and the fourth side surface 15 are all polished.

[0043] A first preset angle is formed between the laser incident surface 12 and the first side surface 11. The first preset angle is an obtuse angle, and the range of the first preset angle is 125 to 145 degrees. The first preset angle can be 135 degrees. A second preset angle is formed between the laser incident surface 12 and the second side surface 13. The second preset angle is an obtuse angle, and the range of the second preset angle is 125 to 145 degrees. The second preset angle can also be 135 degrees. The first preset angle and the second preset angle can be equal, or the angle difference between the first preset angle and the second preset angle can be within a preset angle range, for example, the angle difference between the first preset angle and the second preset angle is within 5 degrees.

[0044] The laser incident surface 12 has a first edge connected to the first side surface 11 and a second edge connected to the second side surface 13. The vertical distance from the first edge to the second side surface 13 is defined as a first distance, and the vertical distance from the second edge to the first side surface 11 is defined as a second distance. The first distance can be equal to the second distance, or the difference between the first and second distances can be within a preset range. It is understood that the first distance is much smaller than the distance between the second side surface 13 and the fourth side surface 15, and the second distance is much smaller than the distance between the first side surface 11 and the third side surface 14.

[0045] A first preset angle is formed between the laser incident surface 12 and the first side surface 11, a second preset angle is formed between the laser incident surface 12 and the second side surface 13, the vertical distance from the first edge of the laser incident surface 12 to the second side surface 13 is a first distance, and the vertical distance from the second edge of the laser incident surface 12 to the first side surface 11 is a second distance, thereby forming a total internal reflection structure with the laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14 and the fourth side surface 15.

[0046] Along the height direction of the substrate 1, the substrate 1 has a first surface 16 and a second surface 17 relative to each other. The first ohmic electrode 2 and the second ohmic electrode 3 can both be located on the first surface 16; the first ohmic electrode 2 and the second ohmic electrode 3 can also both be located on the second surface 17; alternatively, the first ohmic electrode 2 is located on the first surface 16 and the second ohmic electrode 3 is located on the second surface 17.

[0047] The first ohmic electrode 2 can be a columnar or square body, and the second ohmic electrode 3 can be a columnar or square body. Preferably, the first ohmic electrode 2 and the second ohmic electrode 3 are both columnar bodies. The electrode surface area of ​​the columnar electrode is relatively small, the reaction area is more concentrated, and the sensitivity is high.

[0048] The material of the substrate 1 can be any one of gallium nitride, silicon carbide and diamond. The refractive index of gallium nitride is about 2.4, the refractive index of silicon carbide is about 2.6, and the refractive index of diamond is 2.4-2.5. The refractive index of air is about 1. The resistivity of the substrate 1 is greater than 10 7 Ω·cm.

[0049] like Figure 3 As shown, the reflection path of the laser light inside the substrate 1 is described.

[0050] The laser is arranged relative to the laser incident surface 12. The laser emits laser light. The laser light is incident at a certain angle at point O, and the beam divergence angle is controlled within ∠AOB, or is incident between AB in a fiber-coupled manner. The incident light is shown as OC. The incident angle of the laser light at the third side surface 14 is α. The incident angle α is greater than arcsin(n2 / n1), where n1 is the refractive index of the substrate 1 and n2 is the refractive index of air. The laser light is reflected inside the substrate 1 to meet the total internal reflection condition, and the incident laser light can be confined to the interior of the substrate 1 to the greatest extent. The incident light is shown as OD. When the laser light is incident on the third side surface 14, part of the laser light will be refracted from the third side surface 14, reducing the absorption efficiency of the laser light.

[0051] After the laser is incident from the laser incident surface 12, the laser light is incident into the interior of the substrate 1. The laser first enters the third side surface 14, is reflected from the third side surface 14 to the fourth side surface 15, and then is reflected from the fourth side surface 15 to the first side surface 11, and then is reflected from the first side surface 11 to the second side surface 13. Thus, the laser is reflected multiple times in sequence at the third side surface 14, the fourth side surface 15, the first side surface 11 and the second side surface 13 until the laser is fully absorbed, thereby increasing the light absorption efficiency, making the laser absorption more sufficient and uniform, improving the photoelectric response and the photoelectric conversion efficiency, and increasing the on-state current.

[0052] In an embodiment of the present invention, the laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14 and the fourth side surface 15 of the substrate 1 form a total internal reflection structure. The laser enters the interior of the substrate 1 from the laser incident surface 12. The total internal reflection structure increases the path of the laser passing through the interior of the substrate 1, making the laser absorption more sufficient, which is beneficial to improving the photoelectric responsivity and photoelectric conversion efficiency, and increasing the light-on state current of the photoconductive switch.

[0053] In an optional embodiment, the distance between the first side surface 11 and the third side surface 14 is equal to the distance between the second side surface 13 and the fourth side surface 15 .

[0054] Specifically, the spacing between the first side surface 11 and the third side surface 14 is defined as a first spacing, and the spacing between the second side surface 13 and the fourth side surface 15 is defined as a second spacing. The first spacing and the second spacing are equal, so that the laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14 and the fourth side surface 15 can more easily form a total internal reflection structure that meets the total internal reflection conditions.

[0055] like Figure 1 As shown, in an optional embodiment, the first ohmic electrode 2 is disposed on the first surface 16 , and the second ohmic electrode 3 is disposed on the second surface 17 .

[0056] Specifically, the first ohmic electrode 2 is disposed on the first surface 16 of the substrate 1, and the second ohmic electrode 3 is disposed on the second surface 17 of the substrate 1. The first ohmic electrode 2 can be deposited on the first surface 16 by magnetron sputtering or electron beam evaporation, which is conducive to maximizing the size of the first ohmic electrode 2; the second ohmic electrode 3 can be deposited on the second surface 17 by magnetron sputtering or electron beam evaporation, which is conducive to maximizing the size of the second ohmic electrode 3.

[0057] The first ohmic electrode 2 and the second ohmic electrode 3 can be made of a single metal material or an alloy material. The metal material includes gold, silver, aluminum, copper, platinum, molybdenum and the like.

[0058] In the embodiment of the present invention, the first ohmic electrode 2 and the second ohmic electrode 3 are respectively located on the first surface 16 and the second surface 17 of the substrate 1, which is conducive to maximizing the size of the first ohmic electrode 2 and the second ohmic electrode 3, and further conducive to increasing the photoconductive switch's light-on current.

[0059] like Figure 1 As shown, in an optional embodiment, a first arc-shaped groove is formed by being recessed from the first surface 16 toward the second surface 17; a first arc-shaped portion 21 is formed at one end of the first ohmic electrode 2 facing the first surface 16, and the first arc-shaped portion 21 is adapted to the first arc-shaped groove, and the outer surface of the first arc-shaped portion 21 is fitted and connected to the groove wall of the first arc-shaped groove.

[0060] Specifically, a first arc-shaped groove is formed on the first surface 16 by a dry or wet etching process. The first arc-shaped groove is recessed in a direction toward the second surface 17 and is located in a central area of ​​the first surface 16 .

[0061] The first ohmic electrode 2 consists of two parts: a cylindrical portion and a first arcuate portion 21 connected to the cylindrical portion. The outer surface of the first arcuate portion 21 is adapted to fit tightly against the wall of the first arcuate groove. The cylindrical portion of the first ohmic electrode 2 is defined as the first cylindrical portion 22.

[0062] A first arc-shaped groove is formed in the central region of the first surface 16 of the substrate 1 by a dry or wet etching process. Then, a first ohmic electrode 2 of a predetermined thickness is deposited in the first arc-shaped groove by a magnetron sputtering or electron beam evaporation process. The top surface of the first ohmic electrode 2 is higher than the first surface 16. This forms a first arc-shaped portion 21 and a first cylindrical portion 22 of the first ohmic electrode 2. The outer surface of the first arc-shaped portion 21 is tightly connected to the groove wall of the first arc-shaped groove.

[0063] The arc-shaped electrode structure formed by the first arc-shaped portion 21 and the first arc-shaped groove increases the curvature radius at the edge of the first ohmic electrode 2, reduces the peak electric field intensity at the edge of the first ohmic electrode 2, optimizes the electric field distribution, and reduces the premature breakdown of the device caused by local concentration of current density, thereby facilitating the improvement of the withstand voltage of the photoconductive switch.

[0064] like Figure 1 As shown, in an optional embodiment, a second arc-shaped groove is formed by the second surface 17 being recessed toward the first surface 16; a second arc-shaped portion 31 is formed at one end of the second ohmic electrode 3 facing the second surface 17, and the second arc-shaped portion 31 is adapted to the second arc-shaped groove, and the outer surface of the second arc-shaped portion 31 is fitted and connected to the groove wall of the second arc-shaped groove.

[0065] Specifically, a second arc-shaped groove is formed on the second surface 17 by a dry or wet etching process. The second arc-shaped groove is recessed toward the first surface 16 and is located in the middle area of ​​the second surface 17 .

[0066] The second ohmic electrode 3 consists of two parts: a cylindrical portion and a second arcuate portion 31 connected to the cylindrical portion. The outer surface of the second arcuate portion 31 is adapted to fit tightly against the wall of the second arcuate groove. The cylindrical portion of the second ohmic electrode 3 is defined as the second cylindrical portion 32.

[0067] A second arc-shaped groove is formed in the central region of the second surface 17 of the substrate 1 by a dry or wet etching process. Then, a second ohmic electrode 3 of a predetermined thickness is deposited in the second arc-shaped groove by a magnetron sputtering or electron beam evaporation process. The top surface of the second ohmic electrode 3 is higher than the second surface 17. This forms a second arc-shaped portion 31 and a second cylindrical portion 32 of the second ohmic electrode 3. The outer surface of the second arc-shaped portion 31 is tightly connected to the groove wall of the second arc-shaped groove.

[0068] The arc-shaped electrode structure formed by the second arc-shaped portion 31 and the second arc-shaped groove increases the curvature radius at the edge of the second ohmic electrode 3, reduces the peak electric field intensity at the edge of the second ohmic electrode 3, optimizes the electric field distribution, and reduces the premature breakdown of the device caused by local concentration of current density, which is beneficial to improving the withstand voltage value of the photoconductive switch.

[0069] The present invention also provides a method for preparing a photoconductive switch based on total internal reflection, the method comprising:

[0070] Provide substrate raw materials;

[0071] Cutting a substrate raw material into a cuboid, and cutting one end of the cuboid to form a substrate 1, wherein the substrate 1 has a first side surface 11, a laser incident surface 12, a second side surface 13, a third side surface 14, and a fourth side surface 15 connected in sequence along a circumferential direction of the substrate 1, wherein the first side surface 11 and the third side surface 14 are parallel to each other, and the second side surface 13 and the fourth side surface 15 are parallel to each other; and along a height direction of the substrate 1, the substrate 1 has a first surface 16 and a second surface 17 opposite to each other;

[0072] A first ohmic electrode 2 and a second ohmic electrode 3 are respectively formed on the first surface 16 and the second surface 17 of the substrate 1 .

[0073] Specifically, a substrate material of target size is selected. The substrate material can be made of gallium nitride material, silicon carbide material or diamond material. The resistivity of the substrate material is greater than 10 7 Ω·cm.

[0074] A substrate of target size is processed into a rectangular parallelepiped using laser cutting or mechanical cutting. The rectangular parallelepiped has opposing first and second surfaces 16, 17, and four side surfaces. Adjacent side surfaces are perpendicular to each other. First and second surfaces 16, 17 are both squares. The side length of the square is set according to actual needs, for example, 0.2 to 10 mm. The four side surfaces of the rectangular parallelepiped are polished.

[0075] Afterwards, one end of the cuboid is cut at a preset cutting angle, and the cutting area extends from the first surface 16 of the cuboid to the second surface 17. It can be understood that the volume of the cutting area occupies a small part of the volume of the cuboid. The preset cutting angle is set according to actual needs. For example, if the cuboid is cut in a direction at a 45-degree angle to one side, the preset cutting angle can also be 40 degrees, 50 degrees, etc. The preset cutting angle and cutting area satisfy that the substrate 1 formed after cutting has a total internal reflection structure. For example, after cutting, the angle between the laser incident surface 12 and the first side surface 11 is 135 degrees, and the angle between the laser incident surface 12 and the second side surface 13 is also 135 degrees.

[0076] After cutting one end of the cuboid, a substrate 1 having a total internal reflection structure is formed. A first side surface 11, a laser incident surface 12, a second side surface 13, a third side surface 14, and a fourth side surface 15 are sequentially formed along the circumferential direction of the substrate 1. The first side surface 11 and the third side surface 14 are parallel to each other, and the second side surface 13 and the fourth side surface 15 are parallel to each other. The spacing between the first side surface 11 and the third side surface 14 can be equal to the spacing between the second side surface 13 and the fourth side surface 15. The laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14, and the fourth side surface 15 are polished. Along the height direction of the substrate 1, the substrate 1 has a first surface 16 and a second surface 17 that are opposite to each other.

[0077] After the substrate 1 having the total internal reflection structure is prepared, a first ohmic electrode 2 is prepared on the first surface 16 of the substrate 1 , and a second ohmic electrode 3 is prepared on the second surface 17 of the substrate 1 .

[0078] Specifically, a first arc-shaped groove is formed in the middle area of ​​the first surface 16 of the substrate 1 by a dry or wet etching process, and a second arc-shaped groove is formed in the middle area of ​​the second surface 17 of the substrate 1 by a dry or wet etching process.

[0079] A first ohmic electrode 2 of a preset thickness is deposited on the first arc-shaped groove by magnetron sputtering or electron beam evaporation, and the top surface of the first ohmic electrode 2 is higher than the first surface 16. A second ohmic electrode 3 of a preset thickness is deposited on the second arc-shaped groove by magnetron sputtering or electron beam evaporation, and the top surface of the second ohmic electrode 3 is higher than the second surface 17. After the first ohmic electrode 2 and the second ohmic electrode 3 are deposited, a high-temperature rapid annealing is performed to ensure that the first ohmic electrode 2 and the second ohmic electrode 3 form good ohmic contact with the substrate 1, with a contact resistivity of less than 1×10 2 Ω·cm.

[0080] The first ohmic electrode 2 consists of two parts: a first cylindrical portion 22 and a first arcuate portion 21 connected to the first cylindrical portion 22. The outer surface of the first arcuate portion 21 is tightly connected to the wall surface of the first arcuate groove. The second ohmic electrode 3 consists of two parts: a second cylindrical portion 32 and a second arcuate portion 31 connected to the second cylindrical portion 32. The outer surface of the second arcuate portion 31 is tightly connected to the wall surface of the second arcuate groove.

[0081] The arc-shaped electrode structure formed by the first arc-shaped portion 21 and the first arc-shaped groove increases the radius of curvature at the edge of the first ohmic electrode 2, reduces the peak electric field intensity at the edge of the first ohmic electrode 2, and optimizes the electric field distribution. The arc-shaped electrode structure formed by the second arc-shaped portion 31 and the second arc-shaped groove increases the radius of curvature at the edge of the second ohmic electrode 3, reduces the peak electric field intensity at the edge of the second ohmic electrode 3, and optimizes the electric field distribution.

[0082] The following describes the reflection path of laser light inside the photoconductive switch.

[0083] The laser is incident at a certain angle at point O, and the beam divergence angle is controlled within ∠AOB, or is incident between AB in a fiber-optic coupling manner. The incident light is shown as OC. The incident angle of the laser at the third side 14 is α, and the incident angle α is greater than arcsin(n2 / n1). The laser is reflected inside the substrate 1 to meet the total internal reflection condition, and the incident laser can be confined to the interior of the substrate 1 to the greatest extent.

[0084] After the laser is incident from the laser incident surface 12, the laser light is incident on the inside of the substrate 1. The laser first enters the third side surface 14, is reflected from the third side surface 14 to the fourth side surface 15, and then is reflected from the fourth side surface 15 to the first side surface 11, and then is reflected from the first side surface 11 to the second side surface 13. Thus, it undergoes multiple reflections at the third side surface 14, the fourth side surface 15, the first side surface 11 and the second side surface 13 in sequence until the laser is fully absorbed.

[0085] In summary, the photoconductive switch of the present invention has the following effective effects.

[0086] The laser incident surface 12, the first side surface 11, the second side surface 13, the third side surface 14 and the fourth side surface 15 of the substrate 1 form a total internal reflection structure. The laser enters the interior of the substrate 1 from the laser incident surface 12. The total internal reflection structure increases the path of the laser passing through the interior of the substrate 1, which is beneficial to improving the photoelectric responsivity and photoelectric conversion efficiency, and increasing the light-on current of the photoconductive switch.

[0087] The first arc-shaped portion 21 of the first ohmic electrode 2 cooperates with the first arc-shaped groove on the first surface 16 to form an arc-shaped electrode structure, increasing the radius of curvature at the edge of the first ohmic electrode 2. The second arc-shaped portion 31 of the second ohmic electrode 3 cooperates with the second arc-shaped groove on the second surface 17 to form an arc-shaped electrode structure, increasing the radius of curvature at the edge of the second ohmic electrode 3. These two arc-shaped electrode structures reduce the peak electric field intensity at the electrode edges, optimize the electric field distribution, and reduce premature device breakdown caused by localized current density concentration, thereby improving the withstand voltage of the photoconductive switch.

[0088] The foregoing is merely a specific embodiment of the present invention, but the scope of protection of this application is not limited thereto. Any changes or substitutions made within the spirit and principles of the present invention shall be included within the scope of protection of this application. Therefore, the scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A photoconductive switch based on total internal reflection, characterized in that: include: A substrate, wherein the substrate is a square body, and along the circumferential direction of the substrate, the substrate is formed with a first side surface, a laser incident surface, a second side surface, a third side surface, and a fourth side surface connected in sequence, the first side surface and the third side surface are parallel to each other, and the second side surface and the fourth side surface are parallel to each other; along the height direction of the substrate, the substrate has a first surface and a second surface opposite to each other; A first ohmic electrode and a second ohmic electrode are provided on the first surface and / or the second surface; The laser incident surface forms a first preset angle with the first side surface, and the laser incident surface forms a second preset angle with the second side surface.

2. The photoconductive switch based on total internal reflection according to claim 1, characterized in that: The distance between the first side surface and the third side surface is equal to the distance between the second side surface and the fourth side surface.

3. The photoconductive switch based on total internal reflection according to claim 1, characterized in that: The first ohmic electrode is disposed on the first surface, and the second ohmic electrode is disposed on the second surface.

4. The photoconductive switch based on total internal reflection according to claim 3, characterized in that: A first arc-shaped groove is formed by the first surface being recessed toward the second surface; A first arc-shaped portion is formed on one end of the first ohmic electrode facing the first surface. The first arc-shaped portion is adapted to the first arc-shaped groove, and an outer surface of the first arc-shaped portion is in contact with a groove wall of the first arc-shaped groove.

5. The photoconductive switch based on total internal reflection according to claim 3, characterized in that: A second arc-shaped groove is formed by the second surface being recessed toward the first surface; A second arc-shaped portion is formed on one end of the second ohmic electrode facing the second surface. The second arc-shaped portion is adapted to the second arc-shaped groove, and an outer surface of the second arc-shaped portion is in contact with a groove wall of the second arc-shaped groove.

6. The photoconductive switch based on total internal reflection according to any one of claims 1 to 5, characterized in that: The first ohmic electrode is a columnar body; and / or, The second ohmic electrode is a columnar body.

7. The photoconductive switch based on total internal reflection according to any one of claims 1 to 5, characterized in that: The material of the substrate includes any one of gallium nitride material, silicon carbide material and diamond material.

8. The photoconductive switch based on total internal reflection according to any one of claims 1 to 5, characterized in that: The resistivity of the substrate is greater than 10 7 Ω·cm.

9. A method for preparing a photoconductive switch based on total internal reflection, characterized in that: include: Provide substrate raw materials; Cutting the substrate raw material into a cuboid, and cutting one end of the cuboid to form the substrate, wherein the substrate has a first side surface, a laser incident surface, a second side surface, a third side surface, and a fourth side surface connected in sequence along a circumferential direction of the substrate, the first side surface and the third side surface are parallel to each other, and the second side surface and the fourth side surface are parallel to each other; and along a height direction of the substrate, the substrate has a first surface and a second surface opposite to each other; A first ohmic electrode and a second ohmic electrode are respectively prepared on the first surface and the second surface of the substrate.

10. The method for preparing a photoconductive switch based on total internal reflection according to claim 9, characterized in that: The step of preparing a first ohmic electrode and a second ohmic electrode on the first surface and the second surface of the substrate respectively comprises: forming a first arc-shaped groove on the first surface and a second arc-shaped groove on the second surface by an etching process; The first ohmic electrode having a preset thickness is deposited at the first arc-shaped groove, and the second ohmic electrode having a preset thickness is deposited at the second arc-shaped groove.

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