Longitudinal photoconductive switch with electrode expansion structure and preparation method thereof

Abstract

The invention provides a longitudinal photoconductive switch with an electrode expansion structure and a preparation method thereof, and relates to the technical field of semiconductor devices. Comprising metal electrodes formed on side surfaces of two ends of a substrate layer; the zinc oxide aluminum-doped layer is formed at the anode position of the substrate layer and symmetrically distributed on a part of the light incident surface and a part of the backlight surface of the substrate layer; and the silicon nitride layers are formed at the anode position and the cathode position of the substrate layer and are symmetrically distributed on a part of the light incident surface and a part of the backlight surface of the substrate layer, and the silicon nitride layer at the anode position is also symmetrically distributed on the zinc oxide aluminum-doped layer. Therefore, by arranging the zinc oxide aluminum-doped layer and the silicon nitride layer on the metal electrode and the substrate layer, the absorption efficiency of the photoconductive switch is improved. Meanwhile, the aluminum-doped zinc oxide is used as an expansion structure, the current density of the metal electrodes is dispersed, the silicon nitride layer is used as a passivation layer, surface flashover between the metal electrodes is inhibited, and the voltage endurance capability of the switch is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to a longitudinal photoconductive switch with an electrode extension structure and a preparation method thereof. Background Art

[0002] Pulse power technology is a technology that compresses energy in time and space to obtain high energy density output. Pulse power technology is widely used in many fields of national defense technology and civil industry such as controlled nuclear fusion, high-power microwave, agriculture and food processing. With the development of high repetition rate pulse power and semiconductor technology, power semiconductor devices gradually replace or replace traditional switching devices. Compared with other power switches, photoconductive switches have the advantages of fast switching speed, photoelectric isolation, compactness and strong breakdown field. Photoconductive switches are composed of ultrafast pulse lasers and optoelectronic semiconductors. The principle is to use lasers of specific wavelengths to control the "on" and "off" of the device, thereby realizing the output of pulses. As a third-generation semiconductor material, silicon carbide has the characteristics of large bandgap width, high breakdown field strength, high thermal conductivity, large saturated electron velocity, high hardness and chemical corrosion resistance, making silicon carbide suitable as a substrate for photoconductive switches.

[0003] At present, the structures of photoconductive switches mainly include horizontal photoconductive switches and vertical photoconductive switches. For horizontal photoconductive switches, although the electrode gap can be controlled, the incident light energy and area can be controlled, the electric field tends to concentrate on the cathode and anode near the middle side, reducing the switch's withstand voltage. For vertical photoconductive switches, they have better electric field homogenization capabilities, but their withstand voltage is limited by the thickness of the substrate, and the application of single switches in high voltage and high power applications is limited. Summary of the invention

[0004] The purpose of the embodiment of the present invention is to provide a longitudinal photoconductive switch with an electrode extension structure and a preparation method thereof, which solves the problem that the withstand voltage of the photoconductive switch in the prior art is limited by the thickness of the substrate and the application of a single switch is limited in high voltage and high power situations.

[0005] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0006] A first aspect of the present invention provides a longitudinal photoconductive switch with an electrode extension structure, comprising a substrate layer, a metal electrode, a zinc oxide doped aluminum layer and a silicon nitride layer;

[0007] Metal electrodes are formed on the sides of both ends of the substrate layer;

[0008] The zinc oxide doped aluminum layer is formed at the anode position of the substrate layer and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer, and the anode position is the position on one side of the substrate layer;

[0009] The silicon nitride layer is formed at the anode position and the cathode position of the substrate layer, and is symmetrically distributed on part of the light-incident surface and part of the backlight surface of the substrate layer. The silicon nitride layer at the anode position is also symmetrically distributed on the zinc oxide doped aluminum layer, and the cathode position is the position on the other side of the substrate layer.

[0010] In some modified embodiments of the first aspect of the present invention, the metal electrode includes a first metal electrode, a second metal electrode and a third metal electrode, and the first metal electrode, the second metal electrode and the third metal electrode are sequentially stacked on the side surfaces at both ends of the substrate layer.

[0011] In some modified embodiments of the first aspect of the present invention, the material of the first metal electrode is nickel material, and the thickness of the first metal electrode ranges from 180 to 220 nm. The material of the second metal electrode is titanium material, and the thickness of the second metal electrode ranges from 100 to 140 nm. The material of the third metal electrode is gold material, and the thickness of the third metal electrode ranges from 50 to 150 nm.

[0012] In some modified implementations of the first aspect of the present invention, the metal electrode, the zinc oxide doped aluminum layer and the silicon nitride layer at the cathode position are all rectangular in shape.

[0013] In some modified embodiments of the first aspect of the present invention, the material of the substrate layer includes silicon carbide material, and the resistivity of the substrate layer is greater than 10 9 Ω·cm, thickness range is 1mm-2mm.

[0014] In some modified implementations of the first aspect of the present invention, the edge angle of the zinc oxide doped aluminum layer is a 90° arc.

[0015] In some modified embodiments of the first aspect of the present invention, the doping concentration of the zinc oxide doped aluminum layer is in the range of 1×10 14 -1x10 17 cm -3 , the resistivity of the zinc oxide doped aluminum layer ranges from 10Ω·cm to 100Ω·cm, and the thickness ranges from 100 to 200nm.

[0016] In some modified embodiments of the first aspect of the present invention, the resistivity of the silicon nitride layer is greater than 10 6 Ω·cm, thickness range is 100-200nm.

[0017] A second aspect of the present invention provides a method for preparing a longitudinal photoconductive switch having an electrode extension structure, comprising:

[0018] The substrate layer is cleaned using the RCA standard cleaning method, and the material of the substrate layer is silicon carbide material;

[0019] Using magnetron sputtering or electron beam evaporation, a first metal electrode is prepared on the sides of both ends of the substrate layer in the electrode region of the substrate layer, and the material of the first metal electrode is nickel material;

[0020] The first metal electrode and the substrate layer are formed into a nickel-silicon alloy by a RTP rapid annealing method;

[0021] Using magnetron sputtering or electron beam evaporation, a second metal electrode and a third metal electrode are sequentially grown on the first metal electrode after rapid annealing on both sides, wherein the material of the second metal electrode is titanium material, and the material of the third metal electrode is gold material;

[0022] Adjusting the placement direction of the current device after the third metal electrode is grown so that the placement direction of the current device is perpendicular to the placement direction of the substrate layer, and growing a zinc oxide doped aluminum layer on the surface of the substrate layer on both sides of the anode position of the substrate layer by magnetron sputtering or electron beam evaporation, wherein the anode position is a position on one side of the substrate layer;

[0023] Silicon nitride layers are grown on the surfaces of the zinc oxide-doped aluminum layers on both sides, the substrate layers on both sides at the anode position, and the substrate layers on both sides at the cathode position of the substrate layer by using magnetron sputtering or electron beam evaporation, and the cathode position is the position on the other side of the substrate layer;

[0024] Nano-silver paste is coated on the third metal electrode and connected to a copper strip, and high-temperature sintering is performed under preset temperature conditions to form silver contact between the third metal electrode, the nano-silver paste and the copper strip, and the device after the silver contact is formed is packaged with epoxy resin to complete the preparation of a longitudinal photoconductive switch with an electrode extension structure.

[0025] In some modified embodiments of the second aspect of the present invention, the doping concentration of the zinc oxide doped aluminum layer is in the range of 1×10 14 -1x10 17 cm -3 The resistivity of the zinc oxide doped aluminum layer ranges from 10Ω·cm to 100Ω·cm, the thickness ranges from 100-200nm, and the resistivity of the silicon nitride layer is>10 6 Ω·cm, thickness range is 100-200nm.

[0026] Compared with the prior art, the present invention provides a longitudinal photoconductive switch with an electrode extension structure and a preparation method thereof. The longitudinal photoconductive switch with an electrode extension structure includes a substrate layer, a metal electrode, a zinc oxide doped aluminum layer and a silicon nitride layer; the metal electrode is formed on the side surfaces at both ends of the substrate layer; the zinc oxide doped aluminum layer is formed at the anode position of the substrate layer and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer, and the anode position is the position on one side of the substrate layer; the silicon nitride layer is formed at the anode position and the cathode position of the substrate layer and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer, the silicon nitride layer located at the anode position is also symmetrically distributed on the zinc oxide doped aluminum layer, and the cathode position is the position on the other side of the substrate layer. In this way, by arranging a zinc oxide-doped aluminum layer and a silicon nitride layer on the metal electrode and the substrate layer, the electrode edge electric field is dispersed, reducing the risk of switch breakdown, so that the longitudinal photoconductive switch with an electrode extension structure can absorb more photons to generate photogenerated carriers, thereby improving the absorption efficiency of the photoconductive switch; at the same time, zinc oxide-doped aluminum is used as an extension structure to disperse the current density of the metal electrode, and the silicon nitride layer is used as a passivation layer to suppress surface flashover between the metal electrodes, thereby improving the switch's voltage resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] By reading the detailed description below with reference to the accompanying drawings, the above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0028] Figure 1 The schematic diagram of the structure of a longitudinal photoconductive switch with an electrode extension structure is schematically shown;

[0029] Figure 2 A flow chart schematically shows a method for preparing a longitudinal photoconductive switch having an electrode extension structure;

[0030] Figure 3 The schematic diagram of the preparation process of the longitudinal photoconductive switch with an electrode extension structure is schematically shown;

[0031] Figure 4 The electric field intensity distribution diagram of the longitudinal photoconductive switch with an electrode extension structure under illumination is schematically shown;

[0032] Figure 5 The electric field intensity distribution diagram of the lateral out-of-plane photoconductive switch under illumination conditions is schematically shown;

[0033] Figure 6 The diagram schematically shows a comparison of the measured output signals of a longitudinal photoconductive switch and a transverse out-of-plane photoconductive switch with an electrode extension structure under the same conditions.

[0034] Description of Reference Numerals

[0035] 1. Substrate layer; 2. Metal electrode; 21. First metal electrode; 22. Second metal electrode; 23. Third metal electrode; 3. Zinc oxide doped aluminum layer; 4. Silicon nitride layer. DETAILED DESCRIPTION

[0036] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0037] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present invention should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0038] The method in the embodiment of the present invention is described in detail below.

[0039] Figure 1 The schematic diagram of the structure of a longitudinal photoconductive switch with an electrode extension structure is schematically shown. The longitudinal photoconductive switch with an electrode extension structure comprises a substrate layer 1, a metal electrode 2, a zinc oxide doped aluminum layer 3 and a silicon nitride layer 4;

[0040] Metal electrodes 2 are formed on the side surfaces of both ends of the substrate layer 1;

[0041] The zinc oxide doped aluminum layer 3 is formed at the anode position of the substrate layer 1 and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer 1. The anode position is the position on one side of the substrate layer 1.

[0042] The silicon nitride layer 4 is formed at the anode position and the cathode position of the substrate layer 1, and is symmetrically distributed on part of the light-incident surface and part of the backlight surface of the substrate layer 1. The silicon nitride layer 4 at the anode position is also symmetrically distributed on the zinc oxide doped aluminum layer 3, and the cathode position is the position on the other side of the substrate layer 1.

[0043] Specifically, the zinc oxide doped aluminum layer 3 and the silicon nitride layer 4 can be referred to as a field plate structure, wherein the field plate structure is located on the upper and lower side surfaces of the metal electrode 2 and part of the upper and lower surfaces of the substrate layer 1 .

[0044] The anode position and the cathode position are located at two relative positions of the substrate layer 1. The substrate layer 1 is placed horizontally along the longest side of the substrate layer, wherein the light incident surface is the upper surface of the substrate layer 1, and the backlight surface is the lower surface of the substrate layer 1. The silicon nitride layer 4 in the anode position completely covers the zinc oxide doped aluminum layer 3. The metal electrodes 2 are symmetrically distributed on the side surfaces at both ends of the substrate layer 1, and the side receiving the laser, i.e., the side of the light incident surface, is located in the middle area of ​​the metal electrodes 2 at both ends.

[0045] The silicon nitride layer 4 is distributed on both sides of the metal electrode 2, which can not only serve as a passivation layer to prevent flashover on the switch surface, but also play a role in increasing transmittance and reducing reflection, thereby improving the current carrying capacity of the photoconductive switch.

[0046] As an optional embodiment of the present invention, the metal electrode 2 includes a first metal electrode 21, a second metal electrode 22 and a third metal electrode 23, which are sequentially stacked on the sides of the substrate layer 1 at both ends.

[0047] As an optional embodiment of the present invention, the material of the first metal electrode 21 is nickel material, and the thickness of the first metal electrode 21 ranges from 180 to 220 nm. The material of the second metal electrode 22 is titanium material, and the thickness of the second metal electrode 22 ranges from 100 to 140 nm. The material of the third metal electrode 23 is gold material, and the thickness of the third metal electrode 23 ranges from 50 to 150 nm.

[0048] Specifically, the thickness of the first metal electrode 21 is preferably 200 nm, the thickness of the second metal electrode 22 is preferably 120 nm, and the thickness of the third metal electrode 23 is preferably 100 nm. The preferred thickness of the first metal electrode 21, the thickness of the second metal electrode 22, and the thickness of the third metal electrode 23 result in a low on-resistance.

[0049] As an optional embodiment of the present invention, the metal electrode 2, the zinc oxide doped aluminum layer 3 and the silicon nitride layer 4 at the cathode position are all rectangular in shape.

[0050] As an optional embodiment of the present invention, the material of the substrate layer 1 includes silicon carbide material, and the resistivity of the substrate layer 1 is greater than 10 9 Ω·cm, thickness range is 1mm-2mm.

[0051] As an optional implementation of the present invention, the edge angle of the zinc oxide doped aluminum layer 3 is a 90° arc.

[0052] As an optional embodiment of the present invention, the doping concentration of the zinc oxide doped aluminum layer 3 is in the range of 1×10 14 -1x10 17 cm -3The resistivity of the zinc oxide doped aluminum layer 3 is in the range of 10Ω·cm-100Ω·cm, and the thickness is in the range of 100-200nm.

[0053] Specifically, the resistivity of the zinc oxide doped aluminum layer 3 is between the resistances of the metal electrode 2 and the substrate layer 1, and can act as a buffer layer, reducing the influence of the electric field concentration on the edge of the electrode; at the same time, the zinc oxide doped aluminum layer 3, as a transparent conductive film, can achieve the effect of increasing the transmittance and reducing the reflection of the incident laser, thereby improving the output capacity of the photoconductive switch.

[0054] As an optional embodiment of the present invention, the resistivity of the silicon nitride layer 4 is greater than 10 6 Ω·cm, thickness range is 100-200nm.

[0055] The present invention uses the silicon nitride layer 4 as a passivation layer to suppress the surface flashover between the metal electrodes 2, thereby improving the voltage withstand capability of the switch. At the same time, the silicon nitride layer 4 is used as an electric field buffer to gradually weaken the electric field at the edge of the electrode, thereby improving the voltage withstand performance and life characteristics of the photoconductive switch. In addition, the structure relative to the metal electrode 2 is set to further homogenize the switch electric field distribution, so that the electric field lines pass through the inside of the switch as much as possible, thereby improving the reliability of the switch.

[0056] Based on the above Figure 1 It can be seen from the implementation method that the longitudinal photoconductive switch with an electrode extension structure of an embodiment of the present invention includes a substrate layer 1, a metal electrode 2, a zinc oxide doped aluminum layer 3 and a silicon nitride layer 4; the metal electrode 2 is formed on the side surfaces at both ends of the substrate layer 1; the zinc oxide doped aluminum layer 3 is formed at the anode position of the substrate layer 1, and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer 1, and the anode position is the position on one side of the substrate layer 1; the silicon nitride layer 4 is formed at the anode position and the cathode position of the substrate layer 1, and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer 1, the silicon nitride layer 4 located at the anode position is also symmetrically distributed on the zinc oxide doped aluminum layer 3, and the cathode position is the position on the other side of the substrate layer 1. In this way, by arranging the zinc oxide doped aluminum layer 3 and the silicon nitride layer 4 on the substrate layer 1, the electrode edge electric field is dispersed, and the risk of switch breakdown is reduced, so that the longitudinal photoconductive switch with an electrode extension structure can absorb more photons to generate photogenerated carriers, thereby improving the absorption efficiency of the photoconductive switch; at the same time, the zinc oxide doped aluminum is used as an extension structure to disperse the current density of the metal electrode 2, and the silicon nitride layer 4 is used as a passivation layer to suppress surface flashover between the metal electrodes 2, thereby improving the switch withstand voltage capability.

[0057] Figure 2 The method for preparing a longitudinal photoconductive switch with an electrode extension structure in an embodiment of the present invention is schematically shown. Figure 2 As shown, the method for preparing the longitudinal photoconductive switch with an electrode extension structure may include:

[0058] S201 , cleaning the substrate layer 1 using the RCA standard cleaning method.

[0059] The substrate layer 1 is made of silicon carbide.

[0060] Specifically, clean silicon carbide is obtained by wet chemical cleaning (Radio Corporation of America, RCA) standard cleaning method, or ultrasonic oscillation of acetone, ethanol, and deionized water for 5 mm respectively, and then drying with high-purity nitrogen gas.

[0061] Before using the RCA standard cleaning method to clean the substrate layer 1, it includes: obtaining regular rectangular silicon carbide by diamond knife scribing or laser cutting. The thickness of the silicon carbide is 1-2mm, and the resistivity is greater than>10 9 Ω·cm.

[0062] S202 , using magnetron sputtering or electron beam evaporation to prepare first metal electrodes 21 on the sides of both ends of the substrate layer 1 in the electrode region of the substrate layer 1 .

[0063] The first metal electrode 21 is made of nickel.

[0064] Specifically, Figure 3 The schematic diagram of the preparation process of a longitudinal photoconductive switch with an electrode extension structure is schematically shown, wherein: Figure 3 (a) is a schematic diagram of preparing a first metal electrode 21 on the side of one end of the substrate layer 1 in the electrode region of the substrate layer 1, Figure 3 (b) is a schematic diagram of preparing the first metal electrode 21 on the side of the other end of the substrate layer 1 in the electrode region of the substrate layer 1, and the first metal electrode 21 is prepared on the side of the two ends of the substrate layer 1 in the electrode region of the substrate layer 1 by using a magnetron sputtering method or an electron beam evaporation method. Specifically, it includes: masking with a metal mask or a photoresist, and using a magnetron sputtering method or an electron beam evaporation method to prepare the first metal electrode 21 on the side of one end of the substrate layer 1 in the electrode region of the substrate layer 1, and then flipping the two ends of the substrate layer 1, placing the side of the original one end of the substrate layer 1 on the side of the original other end of the substrate layer 1, and preparing the first metal electrode 21 on the side of the other end of the substrate layer 1 in the electrode region of one end of the substrate layer 1 according to the same method as preparing the first metal electrode 21 on the side of one end of the substrate layer 1, so as to achieve double-sided preparation of the first metal electrode 21.

[0065] Specifically, the substrate layer 1 is placed vertically on the metal mask so that the side of one end of the substrate layer 1 faces upward, and then placed in the revolving disk of the magnetron sputtering device. First, the magnetron sputtering device is evacuated to a low vacuum state, about 10E-1Torr, and then the molecular pump is turned on to evacuate the magnetron sputtering device to a high vacuum state, about 5E-6Torr. The sputtering power is controlled to 100W to obtain a first metal electrode 21 of 180-220nm, i.e., metal nickel. Turn on the magnetron sputtering device, flip the device for preparing metal nickel, and sputter the metal nickel on the side of the other end of the substrate layer 1 according to the same sputtering method.

[0066] S203 , forming a nickel-silicon alloy between the first metal electrode 21 and the substrate layer 1 through a RTP rapid annealing method.

[0067] Specifically, under low vacuum or inert gas protection and rapid high temperature annealing conditions, a rapid thermal processing (RTP) method is used to form a nickel-silicon alloy between metal nickel and silicon carbide to obtain a good ohmic contact.

[0068] The device after preparing the first metal electrode 21 is placed on the annealing table. First, the magnetron sputtering equipment is evacuated to a low vacuum state, and the gas in the chamber is kept as an inert gas such as nitrogen by ventilation. Then, the temperature is maintained at 1000°C for 300 seconds to obtain a nickel-silicon alloy with a contact resistivity of about 10 -4 Ω·cm-10 -5 Ω·cm.

[0069] S204 , using magnetron sputtering or electron beam evaporation, sequentially growing a second metal electrode 22 and a third metal electrode 23 on the first metal electrode 21 after rapid annealing on both sides.

[0070] The second metal electrode 22 is made of titanium, and the third metal electrode 23 is made of gold.

[0071] Specifically, Figure 3 The schematic diagram of the preparation process of a longitudinal photoconductive switch with an electrode extension structure is schematically shown, wherein: Figure 3 (c) is a schematic diagram of sequentially growing the second metal electrode 22 and the third metal electrode 23 on the first metal electrode 21 after rapid annealing on one side. Figure 3(d) is a schematic diagram of sequentially growing the second metal electrode 22 and the third metal electrode 23 on the first metal electrode 21 after rapid annealing on the other side. The second metal electrode 22 and the third metal electrode 23 are sequentially grown on the first metal electrode 21 after rapid annealing on one side by using a metal mask or a photoresist shielding method and a magnetron sputtering method or an electron beam evaporation method; then, one side of the device after the third metal electrode 23 is grown is turned over, and the one side of the device after the third metal electrode 23 is grown is placed on the other side of the device after the third metal electrode 23 is not grown; and the second metal electrode 22 and the third metal electrode 23 are sequentially grown on the first metal electrode 21 after rapid annealing on one side in the same manner as the first metal electrode 21 after rapid annealing on one side, so as to achieve double-sided growth of the second metal electrode 22 and the third metal electrode 23.

[0072] The first metal electrode 21 after rapid annealing is placed vertically on a metal mask, and then placed in a magnetron sputtering revolution disk. First, the magnetron sputtering equipment is evacuated to a low vacuum state, about 10E-1Torr, and then the molecular pump is turned on to evacuate the magnetron sputtering equipment to a high vacuum state, about 5E-6Torr. The sputtering power is controlled to 60W to obtain a 100-140nm second metal electrode 22, namely metal titanium. Then, based on the metal titanium, the sputtering power is controlled to 20W to obtain a 50-150nm second metal electrode 22, namely metal gold. Turn on the magnetron sputtering equipment, flip the device, and sputter the other side of metal titanium and metal gold using the same sputtering method.

[0073] S205. Adjust the placement direction of the current device after growing the third metal electrode 23 so that the placement direction of the current device is perpendicular to the placement direction of the substrate layer 1, and grow a zinc oxide-doped aluminum layer 3 on the surface of the substrate layer 1 on both sides of the anode position of the substrate layer 1 by magnetron sputtering or electron beam evaporation.

[0074] The anode position is the position on one side of the substrate layer 1, and the doping concentration range of the zinc oxide doped aluminum layer 3 is 1x10 14 -1x10 17 cm -3 The resistivity of the zinc oxide doped aluminum layer 3 is in the range of 10Ω·cm-100Ω·cm, and the thickness is in the range of 100-200nm.

[0075] Specifically, Figure 3 The schematic diagram of the preparation process of a longitudinal photoconductive switch with an electrode extension structure is schematically shown, wherein: Figure 3 (e) is a schematic diagram of growing a zinc oxide doped aluminum layer 3 on the surface of the upper metal electrode. Figure 3(f) is a schematic diagram of growing a zinc oxide doped aluminum layer 3 on the surface of the lower metal electrode, adjusting the placement direction of the current device after the growth of the third metal electrode 23 so that the placement direction of the current device is perpendicular to the placement direction of the substrate layer 1, and shielding with a metal mask or photoresist, using magnetron sputtering or electron beam evaporation to grow the zinc oxide doped aluminum layer 3 on the surface of the upper part of the substrate layer 1 in the anode position of the substrate layer 1; then flipping one side of the device after the zinc oxide doped aluminum layer 3 is grown on the upper side, and growing the zinc oxide doped aluminum layer 3 on the surface of the lower part of the substrate layer 1 in the anode position of the substrate layer 1 in the same way as growing the zinc oxide doped aluminum layer 3 on the surface of the upper metal electrode.

[0076] Adjust the placement direction of the current device after growing the third metal electrode 23, place the current device on the metal mask, and deposit the zinc oxide doped aluminum layer 3 around the anode of the current device by designing the size. The length of the zinc oxide doped aluminum layer 3 is controlled to be 100μm-500μm, and the thickness is controlled to be 100nm-200nm.

[0077] First, the magnetron sputtering device is evacuated to a high vacuum state, and then the substrate layer 1 is heated by a resistance wire. The temperature is maintained at 300°C during the coating process, the sputtering power is controlled to be 90W, and the argon gas flow rate is 15-20sccm. At this time, the pressure in the inner cavity of the magnetron sputtering device is 7mTorr. After growing one side of the zinc oxide doped aluminum layer 3, the magnetron sputtering device is turned on, and the device after growing one side of the zinc oxide doped aluminum layer 3 is turned over, and the other side of the zinc oxide doped aluminum layer 3 is sputtered using the same sputtering method.

[0078] S206, growing a silicon nitride layer 4 on the surfaces of the zinc oxide-doped aluminum layer 3 on both sides, the substrate layer 1 on both sides at the anode position, and the substrate layer 1 on both sides at the cathode position of the substrate layer 1 by using magnetron sputtering or electron beam evaporation.

[0079] The cathode position is the position on the other side of the substrate layer 1 .

[0080] Specifically, Figure 3 The schematic diagram of the preparation process of a longitudinal photoconductive switch with an electrode extension structure is schematically shown, wherein: Figure 3 (g) is a schematic diagram showing the growth of a silicon nitride layer 4 on the surface of the upper metal electrode. Figure 3(h) is a schematic diagram of growing a silicon nitride layer 4 on the surface of the lower metal electrode. The silicon nitride layer 4 is grown on the surfaces of the upper zinc oxide-doped aluminum layer 3, the upper portion of the substrate layer 1 at the anode position, and the upper portion of the substrate layer 1 at the cathode position of the substrate layer 1 by magnetron sputtering or electron beam evaporation through metal mask or photoresist shielding; then one side of the device after the silicon nitride layer 4 is grown on the upper side is turned over, and the silicon nitride layer 4 is grown on the surfaces of the lower zinc oxide-doped aluminum layer 3, the lower portion of the substrate layer 1 at the anode position, and the lower portion of the substrate layer 1 at the cathode position of the substrate layer 1 in the same manner as the silicon nitride layer 4 is grown on the surface of the upper metal electrode.

[0081] Adjust the direction of the device after growing the zinc oxide doped aluminum layer 3, replace the new metal mask, and deposit the silicon nitride layer 4 around the anode and cathode of the device after growing the zinc oxide doped aluminum layer 3 by designing the size. The length of the silicon nitride layer 4 is controlled at 600μm-1000μm, and the thickness is controlled at 50nm-150nm. First, evacuate the magnetron sputtering equipment to a high vacuum state, control the sputtering power to 70-90W, the argon flow rate to 10-15scccm, and introduce 1-3sscm nitrogen at the same time. At this time, the inner cavity pressure of the magnetron sputtering equipment is 7mTorr. After growing one side of the silicon nitride layer 4, turn on the magnetron sputtering equipment, flip the device after growing one side of the silicon nitride layer 4, and sputter the other side of the silicon nitride layer 4 according to the same sputtering method.

[0082] S207, coating nano silver paste on the third metal electrode 23 and connecting the copper strip, sintering under preset temperature conditions to form silver contact between the third metal electrode 23, the nano silver paste and the copper strip, and encapsulating the device after the silver contact is formed with epoxy resin to complete the preparation of the longitudinal photoconductive switch with an electrode extension structure.

[0083] The preset temperature is 230℃.

[0084] Specifically, nano silver paste is coated on the first metal electrode 21, the second metal electrode 22 and the third metal electrode 23, and then a copper strip is placed. Under high temperature sintering conditions of 230°C and 1h, the organic matter in the solvent is evaporated to form a relatively good silver contact. Finally, the device with silver contact is placed in a resin tube shell, filled with epoxy resin AB glue, and a longitudinal photoconductive switch with an electrode extension structure is prepared.

[0085] The present invention provides a method for preparing a longitudinal photoconductive switch with an electrode extension structure. Through the method for preparing a longitudinal photoconductive switch with an electrode extension structure, the prepared photoconductive switch can absorb more photons under the effect of the zinc oxide doped aluminum layer 3 and the silicon nitride layer 4 to increase transmittance and reduce reflection, thereby generating more photogenerated carriers, thereby improving the current flow capacity of the photoconductive switch. In addition, since the resistivity of the zinc oxide doped aluminum layer 3 is between the substrate layer 1 and the metal electrode 2, the curvature radius of the electrode edge is increased, and the current density is dispersed; at the same time, the silicon nitride layer 4, as a passivation layer, can play a role in preventing surface flashover, thereby improving the breakdown capacity of the device from two aspects. In addition, the relative metal electrode 2 structure is set to ensure the uniformity of the electric field distribution, so that the longitudinal photoconductive switch with the electrode extension structure has better stability and reliability.

[0086] Figure 4 The electric field intensity distribution diagram of the longitudinal photoconductive switch with an electrode extension structure under illumination is schematically shown. The horizontal and vertical coordinates are the dimensions of the longitudinal photoconductive switch device in um. Figure 4 This is a simulation of the two-dimensional electric field intensity distribution of a longitudinal photoconductive switch with an electrode extension structure. The bias voltage is set to 5kV and the light energy is 18e5W / cm 2 , the depth of color represents the strength of the electric field. Figure 5 The schematic diagram shows the electric field intensity distribution of the transverse out-of-plane photoconductive switch under illumination conditions. The horizontal and vertical coordinates are the dimensions of the longitudinal photoconductive switch device in um. Figure 5 This is a simulation of the two-dimensional electric field intensity distribution of an existing lateral out-of-plane photoconductive switch, with a bias voltage of 5 kV and a light energy of 18e5 W / cm 2 , the depth of the color represents the magnitude of the electric field strength. Figure 4 The color is more balanced, the electric field distribution is further balanced, and the stability and reliability of the photoconductive switching device are improved.

[0087] Figure 6 The diagram schematically shows a comparison of the measured output signals of a longitudinal photoconductive switch and a transverse photoconductive switch with an electrode extension structure under the same conditions, with the horizontal axis representing time and the vertical axis representing the output pulse voltage amplitude. The red line represents the output signal of the transverse photoconductive switch, and the black line represents the output signal of the longitudinal photoconductive switch with an electrode extension structure of the present invention. The bias voltage of the longitudinal photoconductive switch with an electrode extension structure is 5kV, the output light energy is 17mJ, the load resistance is 100Ω, and the gap between the two electrodes of the switch is 4mm.

[0088] Compared with other existing technologies, the present invention has the following advantages: 1. Through rapid annealing, the metal nickel and the silicon carbide substrate layer 1 form a good ohmic contact. 2. The metal titanium connects the metal gold and the metal nickel well, so that the electrode has relatively good stability and adhesion. 3. The zinc oxide doped aluminum layer 3 is used as the first field plate, first as a transparent conductive film, and under the use of a suitable field plate structure, the electrode edge electric field is dispersed, reducing the risk of switch breakdown. Secondly, by selecting a suitable thickness, the laser can be better enhanced and reduced in reflection, so as to achieve the effect of collecting more photons to generate more photogenerated carriers, thereby improving the ability of the photoconductive switch to absorb lasers. 4. The silicon nitride layer 4 is used as the second field plate, first as a passivation layer, suppressing the surface flashover between the metal electrodes 2, and improving the voltage resistance of the switch; then it can also be used as an anti-reflection film to absorb more photons, thereby improving the current flow capacity of the photoconductive switch. 5. By setting a longitudinal electrode, the electric field distribution is further balanced, thereby improving the stability and reliability of the photoconductive switch device.

[0089] It should be pointed out here that the description of the above embodiment of the method for preparing a longitudinal photoconductive switch with an electrode extension structure is similar to the description of the above embodiment of the longitudinal photoconductive switch with an electrode extension structure, and has similar beneficial effects as the embodiment of the longitudinal photoconductive switch with an electrode extension structure. For technical details not disclosed in the embodiment of the method for preparing a longitudinal photoconductive switch with an electrode extension structure of the embodiment of the present invention, please refer to the description of the embodiment of the longitudinal photoconductive switch with an electrode extension structure of the present invention for understanding.

[0090] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A longitudinal photoconductive switch with an electrode extension structure, characterized in that: It includes a substrate layer, a metal electrode, a zinc oxide doped aluminum layer and a silicon nitride layer; The metal electrodes are formed on the side surfaces at both ends of the substrate layer; The zinc oxide doped aluminum layer is formed at the anode position of the substrate layer and is symmetrically distributed on part of the light incident surface and part of the backlight surface of the substrate layer, and the anode position is a position on one side of the substrate layer; The silicon nitride layer is formed at the anode position and the cathode position of the substrate layer, and is symmetrically distributed on part of the light-incident surface and part of the backlight surface of the substrate layer. The silicon nitride layer located at the anode position is also symmetrically distributed on the zinc oxide doped aluminum layer, and the cathode position is the position on the other side of the substrate layer.

2. The longitudinal photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The metal electrode comprises a first metal electrode, a second metal electrode and a third metal electrode, and the first metal electrode, the second metal electrode and the third metal electrode are sequentially stacked on the side surfaces at both ends of the substrate layer.

3. The longitudinal photoconductive switch with an electrode extension structure according to claim 2, characterized in that: The material of the first metal electrode is nickel material, and the thickness of the first metal electrode ranges from 180 to 220 nm. The material of the second metal electrode is titanium material, and the thickness of the second metal electrode ranges from 100 to 140 nm. The material of the third metal electrode is gold material, and the thickness of the third metal electrode ranges from 50 to 150 nm.

4. The longitudinal photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The metal electrode, the aluminum-doped zinc oxide layer and the silicon nitride layer at the cathode position are all in rectangular shapes.

5. The vertical photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The material of the substrate layer includes silicon carbide material, and the resistivity of the substrate layer is greater than 10 9 Ω·cm, thickness range is 1mm-2mm.

6. The longitudinal photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The edge angle of the zinc oxide doped aluminum layer is a 90° arc.

7. The vertical photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The doping concentration of the zinc oxide doped aluminum layer is in the range of 1×10 14 -1x10 17 cm -3 The resistivity of the zinc oxide doped aluminum layer is in the range of 10Ω·cm-100Ω·cm, and the thickness is in the range of 100-200nm.

8. The vertical photoconductive switch with an electrode extension structure according to claim 1, characterized in that: The resistivity of the silicon nitride layer is>10 6 Ω·cm, thickness range is 100-200nm.

9. A method for preparing a longitudinal photoconductive switch having an electrode extension structure, characterized in that: The longitudinal photoconductive switch with an electrode extension structure applicable to any one of claims 1 to 8 comprises: Cleaning the substrate layer using an RCA standard cleaning method, wherein the substrate layer is made of silicon carbide material; Using magnetron sputtering or electron beam evaporation, prepare first metal electrodes on the sides of both ends of the substrate layer in the electrode region of the substrate layer, wherein the material of the first metal electrode is nickel material; The first metal electrode and the substrate layer are formed into a nickel-silicon alloy by a RTP rapid annealing method; Using magnetron sputtering or electron beam evaporation, sequentially growing a second metal electrode and a third metal electrode on the first metal electrode after rapid annealing on both sides, wherein the material of the second metal electrode is titanium material, and the material of the third metal electrode is gold material; Adjusting the placement direction of the current device after the third metal electrode is grown, so that the placement direction of the current device is perpendicular to the placement direction of the substrate layer, and growing a zinc oxide-doped aluminum layer on the surface of the substrate layer on both sides of the anode position of the substrate layer by using the magnetron sputtering method or the electron beam evaporation method, wherein the anode position is a position on one side of the substrate layer; Using the magnetron sputtering method or the electron beam evaporation method, a silicon nitride layer is grown on the surfaces of the zinc oxide doped aluminum layer on both sides, the substrate layer on both sides of the anode position, and the substrate layer on both sides of the cathode position of the substrate layer, wherein the cathode position is the position on the other side of the substrate layer; Nano-silver paste is coated on the third metal electrode and connected to a copper strip, and sintering is performed under preset temperature conditions to form silver contact between the third metal electrode, the nano-silver paste and the copper strip, and the device after the silver contact is formed is packaged with epoxy resin to complete the preparation of the longitudinal photoconductive switch with an electrode extension structure.

10. The method for preparing a longitudinal photoconductive switch with an electrode extension structure according to claim 9, characterized in that: The doping concentration of the zinc oxide doped aluminum layer is in the range of 1×10 14 -1x10 17 cm -3 The resistivity of the zinc oxide doped aluminum layer is in the range of 10Ω·cm-100Ω·cm, the thickness is in the range of 100-200nm, and the resistivity of the silicon nitride layer is>10 6 Ω·cm, thickness range is 100-200nm.

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