GaN photomultiplier tube based on multilayer ceramic linear array anode structure and preparation method thereof

Abstract

The invention discloses a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure and a preparation method thereof, the photomultiplier tube is composed of a cathode assembly, an electron multiplier, an anode assembly and a metal ceramic tube shell, the cathode assembly comprises an input light window and a GaN photoelectric cathode, two microchannel plates are stacked to form the electron multiplier, and the metal ceramic tube shell comprises a metal ceramic tube shell and a metal ceramic tube shell. And the anode assembly is an array anode of a multilayer ceramic process and is used as a core component of the ultraviolet detection system. The photomultiplier tube designed and manufactured by the invention has the characteristics of high sensitivity and high gain, and meanwhile, the anode of the photomultiplier tube is a 1 * 16 linear array anode, so that the position information of a detection signal can be reserved, and more detailed analysis on a signal source is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of ultraviolet detection, and in particular relates to a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure and a preparation method thereof. Background Art

[0002] The photomultiplier tube is a vacuum type photoelectric detection device, which is mainly composed of an input light window, a photocathode, a microchannel plate (MCP) and an anode. When the photomultiplier tube is working, photons are incident on the photocathode through the transparent input light window and absorbed by the photocathode. The electrons in the photocathode are excited by the photons to form photoelectrons, which are emitted into the photomultiplier tube. After the photoelectrons enter the MCP, the number of electrons is greatly increased through the multiplication of the MCP. Finally, the electrons are received by the anode to form an electrical signal to be analyzed. In the above process, an external power supply is required to provide voltage to each component through the metal ceramic tube shell, so that a bias is generated inside the photomultiplier tube, thereby guiding the photoelectrons to move between the various components. At the same time, as the outer shell of the photomultiplier tube, the metal ceramic tube shell also provides a high vacuum environment for the photomultiplier tube. Ultraviolet light signals are mainly concentrated in the 100nm-400nm band. When a photomultiplier tube is used to detect signals in this band, this photomultiplier tube belongs to an ultraviolet photomultiplier tube.

[0003] After years of development, the preparation process of Cs2Te and Rb2Te photocathodes has become very mature and low-cost. Although single-anode photomultiplier tubes based on Cs2Te and Rb2Te photocathodes have been widely equipped on various platforms, they still have certain disadvantages during use.

[0004] In the application of lidar wind measurement, the laser emits a 355nm ultraviolet laser to detect wind speed and direction. Based on the photomultiplier tube mentioned above, when detecting the reflected signal, the sensitivity of the Cs2Te and Rb2Te photocathodes is low, and they also respond to signals in other bands, which limits the detection accuracy to a certain extent. In addition, the single anode output structure loses the image information of the target during the signal acquisition process. The development of GaN ultraviolet photomultiplier tubes with array anode structure can better solve the above problems. First of all, as a semiconductor material that can respond to ultraviolet signals, GaN has a higher quantum efficiency than traditional Cs2Te and Rb2Te photocathodes, which can effectively improve the detection distance and accuracy of ultraviolet photomultiplier tubes, and has good cutoff characteristics, which can eliminate interference from signals in other bands. In addition, the use of a linear array anode structure can detect signals in different areas of the surface separately, retain more image information of the target signal, and facilitate subsequent analysis. Summary of the invention

[0005] The present invention aims to provide a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure and a preparation method thereof, which improves sensitivity and gain.

[0006] In order to achieve the purpose of the present invention, on the one hand, the present invention provides a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure, including a cathode assembly 10, a metal ceramic tube shell 20, an electron multiplier 30 and an anode assembly 40;

[0007] The anode assembly 40 and the cathode assembly 10 are located on both sides of the electron multiplier 30 and are sealed with the metal ceramic shell 20 as a whole; the anode assembly 40, the cathode assembly 10, the metal ceramic shell 20, and the electron multiplier 30 form a coaxial structure;

[0008] The cathode assembly 10 includes a GaN epitaxial wafer 101 and an input light window 102, wherein the front side of the input light window 102 faces the inside of the photomultiplier tube and the back side faces the outside of the photomultiplier tube, and the substrate of the GaN epitaxial wafer 101 is sapphire;

[0009] The metal ceramic tube shell 20 is composed of a metal ring and a ceramic ring;

[0010] The electron multiplier 30 is composed of MCP;

[0011] The anode assembly 40 is a 1×16 linear array anode structure.

[0012] On the other hand, the present invention also provides a method for preparing a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure, comprising the following steps:

[0013] Step 1: Using a sapphire substrate as a substrate, using metal organic vapor deposition or molecular beam epitaxy technology to prepare an AlN buffer layer, an AlGaN transition layer and a GaN emission layer, gradually reducing the Al content of the AlGaN transition layer from a level close to the Al content in the AlN buffer layer to 0, and performing p-type doping to increase the hole concentration;

[0014] Step 2: Cut the sapphire substrate into discs of the same size as the convex surface of the input light window, and make GaN epitaxial wafers;

[0015] Step 3: Lay the input light window and the GaN epitaxial wafer together on their backs to ensure that the light-transmitting parts overlap each other, place them in a vacuum degassing furnace, and bond them together using a high-temperature bonding method to form a cathode assembly;

[0016] Step 4: chemically cleaning the cathode assembly to remove the surface oxide layer;

[0017] Step 5: Take the first metal ring, the second metal ring, the third metal ring, the fourth metal ring, the fifth metal ring and four ceramic rings, assemble them in specific positions and place them in a high-temperature brazing furnace to form a metal ceramic shell through a high-temperature brazing process;

[0018] Step 6: injecting solder into the groove of the first metal ring in the metal ceramic shell;

[0019] Step 7: welding a getter wire between the fourth metal ring 205 and the fifth metal ring 206 in the metal ceramic shell after solder injection;

[0020] Step 8: The metal ceramic shell and the anode assembly to which the air intake wire is welded in step 7 are sealed together by laser welding or argon arc welding;

[0021] Step 9: installing an electron multiplier formed by stacking two microchannel plates between the second metal ring and the third metal ring of the metal ceramic tube shell and fixing it;

[0022] Step 10: placing the chemically cleaned cathode assembly and the metal ceramic tube shell with the electron multiplier in an ultra-high vacuum degassing table;

[0023] Step 11: thermally cleaning the cathode assembly after chemical cleaning in an ultra-high vacuum environment to further clean the surface layer of the GaN epitaxial wafer;

[0024] Step 12: Activate the surface layer of the GaN epitaxial wafer with Cs and O in an ultra-high vacuum degassing station;

[0025] Step 13: performing high-temperature baking and degassing on the metal ceramic tube shell and the anode assembly in an ultra-high vacuum degassing table;

[0026] Step 14: electronically cleaning the electron multiplier in an ultra-high vacuum degassing station;

[0027] Step 15: In an ultra-high vacuum degassing station, the cathode assembly that has completed surface activation and the metal ceramic tube shell that has undergone high-temperature degassing are sealed together to form a photomultiplier tube.

[0028] Compared with the prior art, the significant progress of the present invention is that the ultraviolet photomultiplier tube involved in the present invention adopts a GaN photocathode, which has higher sensitivity than the traditional ultraviolet photocathode, and the anode is a 1×16 linear array structure, which can better collect linear image information of the target in one direction.

[0029] In order to more clearly illustrate the functional characteristics and structural parameters of the present invention, further description is given below in conjunction with the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0031] Figure 1 is a schematic diagram of the overall structure of a photomultiplier tube in an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of the structure of a cathode assembly in an embodiment of the present invention;

[0033] Figure 3 is a schematic diagram of the structure of a GaN epitaxial wafer in an embodiment of the present invention;

[0034] Figure 4 Schematic diagram of the metal ceramic shell structure in an embodiment of the present invention;

[0035] Figure 5 is a schematic diagram of an anode assembly in an embodiment of the present invention;

[0036] Figure 6 1 is a photocathode sensitivity curve of a GaN photomultiplier tube in an embodiment of the present invention.

[0037] The reference numbers in the figure are: 10-cathode assembly, 20-metal ceramic shell, 30-electron multiplier, 40-anode assembly, 101-GaN epitaxial wafer, 102-input light window, 1011-sapphire substrate, 1012-AlN buffer layer, 1013-AlGaN transition layer, 1014-GaN emission layer, 201-first metal ring, 202-ceramic ring, 203-second metal ring, 204-third metal ring, 205-fourth metal ring, 206-fifth metal ring, 401-kovar sealing pad, 402-multilayer ceramic, 403-metal lead pin, 404-metal electrode, 405-peripheral metal electrode. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0039] Combination Figure 1 , a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure of the present invention comprises a cathode assembly 10, a metal ceramic tube shell 20, an electron multiplier 30 and an anode assembly 40;

[0040] The anode assembly 40 and the cathode assembly 10 are located on both sides of the electron multiplier 30 and are sealed with the metal ceramic shell 20 to maintain the vacuum environment inside the photomultiplier tube; the anode assembly 40, the cathode assembly 10, the metal ceramic shell 20, and the electron multiplier 30 form a coaxial structure;

[0041] Combination Figure 2 The cathode assembly 10 includes a GaN epitaxial wafer 101 and an input light window 102, wherein the front side of the input light window 102 faces the inside of the photomultiplier tube and the back side faces the outside of the photomultiplier tube, and the substrate of the GaN epitaxial wafer 101 is sapphire;

[0042] The metal ceramic tube shell 20 is composed of a metal ring and a ceramic ring;

[0043] The electron multiplier 30 is composed of MCP;

[0044] The anode assembly 40 is a 1×16 linear array anode structure.

[0045] Combination Figure 3 The GaN epitaxial wafer 101 is formed by growing an AlN buffer layer 1012, an AlGaN transition layer 1013, and a GaN emission layer 1014 on a sapphire substrate 1011;

[0046] The AlN buffer layer 1012 is used to reduce lattice mismatch;

[0047] The AlGaN transition layer 1013 gradually reduces the Al content from a level close to the Al content in AlN to 0, so as to reduce the lattice mismatch;

[0048] The GaN emission layer 1014 is used as a photocathode, in which the photoelectric signal conversion of the photomultiplier tube is completed.

[0049] The front side of the input light window 102 is attached to the back side of the GaN epitaxial wafer 101 to ensure that the light-transmitting parts overlap each other, and a high-temperature bonding process is used in a high vacuum environment to bond the two together.

[0050] Combination Figure 4 The metal ceramic tube shell 20 is formed by high-temperature brazing of a first metal ring 201, a second metal ring 203, a third metal ring 204, a fourth metal ring 205, a fifth metal ring 206 and a ceramic ring 202; solder needs to be injected into the groove of the first metal ring 201 for subsequent sealing of the cathode assembly 10 and the metal ceramic tube shell 20.

[0051] The electron multiplier 30 is composed of one MCP or two identical MCPs stacked in a double-layer structure, and is fixed between the second metal ring 203 and the third metal ring 204. The second metal ring 203 and the third metal ring 204 are the input and output electrodes of the electron multiplier 30, providing it with working voltage.

[0052] Combination Figure 5 The anode assembly 40 includes a kovar sealing disk 401, a multilayer ceramic 402, a metal lead pin 403, a metal electrode 404, and a peripheral metal electrode 405; the multilayer ceramic 402 is located on the vacuum side of the photomultiplier tube and is composed of 16 metal electrodes 404 and the peripheral metal electrodes 405 in the peripheral area, forming the 1×16 linear array for receiving electrons emitted by the electron multiplier 30; each metal electrode 404 is led to the metal lead pin 403 on the other side through the passage inside the multilayer ceramic 402, and corresponds one to one, and the 16 metal lead pins 403 placed on the atmospheric side form a 4×4 linear array; the peripheral metal electrode 405 is connected to the kovar sealing disk 401, and is used to collect the remaining electrons emitted by the electron multiplier 30, and conduct them to the metal sealing disk to avoid signal interference.

[0053] Furthermore, the metal ceramic tube shell 20 and the anode assembly 40 are sealed as a whole by laser welding, and the welding point meets the vacuum airtightness requirement.

[0054] Furthermore, the input light window 102 is made of quartz.

[0055] Furthermore, the Kovar sealing disc 401 and the fifth metal ring 206 are sealed by argon arc welding or laser welding;

[0056] Furthermore, the cathode assembly 10 is sealed with the first metal ring 201 through an indium seal.

[0057] On the other hand, the present invention also provides a method for preparing a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure, comprising the following steps:

[0058] Step 1: Using a sapphire substrate as a substrate, using metal organic vapor deposition or molecular beam epitaxy technology to prepare an AlN buffer layer, an AlGaN transition layer and a GaN emission layer, gradually reducing the Al content of the AlGaN transition layer from a level close to the Al content in the AlN buffer layer to 0, and performing p-type doping to increase the hole concentration;

[0059] Step 2: Cut the sapphire substrate into discs of the same size as the convex surface of the input light window, and make GaN epitaxial wafers;

[0060] Step 3: Lay the input light window and the GaN epitaxial wafer together on their backs to ensure that the light-transmitting parts overlap each other, place them in a vacuum degassing furnace, and bond them together using a high-temperature bonding method to form a cathode assembly;

[0061] Step 4: chemically cleaning the cathode assembly to remove the surface oxide layer;

[0062] Step 5: Take the first metal ring, the second metal ring, the third metal ring, the fourth metal ring, the fifth metal ring and four ceramic rings, assemble them in specific positions and place them in a high-temperature brazing furnace to form a metal ceramic shell through a high-temperature brazing process;

[0063] Step 6: injecting solder into the groove of the first metal ring in the metal ceramic tube shell for subsequent sealing of the cathode assembly and the metal ceramic tube shell;

[0064] Step 7: welding a suction wire for maintaining vacuum in the tube between the fourth metal ring 205 and the fifth metal ring 206 in the metal ceramic tube shell after solder injection;

[0065] Step 8: The metal ceramic shell and the anode assembly to which the air intake wire is welded in step 7 are sealed together by laser welding or argon arc welding, and the welding point meets the vacuum airtightness requirement;

[0066] Step 9: installing an electron multiplier formed by stacking two microchannel plates between the second metal ring and the third metal ring of the metal ceramic tube shell and fixing it;

[0067] Step 10: placing the chemically cleaned cathode assembly and the metal ceramic tube shell with the electron multiplier in an ultra-high vacuum degassing table;

[0068] Step 11: thermally cleaning the cathode assembly after chemical cleaning in an ultra-high vacuum environment to further clean the surface layer of the GaN epitaxial wafer;

[0069] Step 12: Activate the surface layer of the GaN epitaxial wafer with Cs and O in an ultra-high vacuum degassing station to reduce its surface work function and improve the cathode sensitivity of the photomultiplier tube;

[0070] Step 13: performing high-temperature baking and degassing on the metal ceramic tube shell and the anode assembly in an ultra-high vacuum degassing table;

[0071] Step 14: electronically cleaning the electron multiplier in an ultra-high vacuum degassing station to further remove residual gas remaining in the electron multiplier;

[0072] Step 15: In an ultra-high vacuum degassing station, the cathode assembly that has completed surface activation and the metal ceramic tube shell that has undergone high-temperature degassing are sealed together to form a photomultiplier tube.

[0073] The photomultiplier tube prepared by the above process was tested, and its photocathode sensitivity curve was combined with Figure 6 , the performance indicators are shown in the following table:

[0074] Serial number index Test Results 1 Spectral response band 200nm-400nm 2 Radiated sensitivity 50mA / W@360nm 3 Multiplication factor <![CDATA[2.0×10 5 ]]>

[0075] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure, characterized in that: It comprises a cathode assembly (10), a metal ceramic tube shell (20), an electron multiplier (30) and an anode assembly (40); The anode assembly (40) and the cathode assembly (10) are located on both sides of the electron multiplier (30), and are respectively sealed with the metal ceramic tube shell (20) as a whole; the anode assembly (40), the cathode assembly (10), the metal ceramic tube shell (20), and the electron multiplier (30) form a coaxial structure; The cathode assembly (10) comprises a GaN epitaxial wafer (101) and an input light window (102), the front side of the input light window (102) faces the inside of the photomultiplier tube, and the back side faces the outside of the photomultiplier tube, and the substrate of the GaN epitaxial wafer (101) is sapphire; The metal ceramic tube shell (20) is composed of a metal ring and a ceramic ring; The electron multiplier (30) is composed of MCP; The anode assembly (40) is a 1×16 linear array anode structure.

2. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The GaN epitaxial wafer (101) is formed by growing an AlN buffer layer (1012), an AlGaN transition layer (1013), and a GaN emission layer (1014) on a sapphire substrate (1011); The AlN buffer layer (1012) is used to reduce lattice mismatch; The AlGaN transition layer (1013) gradually reduces the Al content from a level close to the Al content in AlN to (0) to reduce the lattice mismatch; The GaN emission layer (1014) is used as a photocathode, in which the photoelectric signal conversion of the photomultiplier tube is completed.

3. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The front side of the input light window (102) is bonded to the back side of the GaN epitaxial wafer (101) to ensure that the light-transmitting parts overlap each other, and a high-temperature bonding process is used in a high vacuum environment to bond the two together.

4. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The metal ceramic tube shell (20) is formed by high-temperature brazing of a first metal ring (201), a second metal ring (203), a third metal ring (204), a fourth metal ring (205), a fifth metal ring (206) and a ceramic ring (202); solder needs to be injected into the groove of the first metal ring (201).

5. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 4, characterized in that: The electron multiplier (30) is composed of a piece of MCP or two identical pieces of MCP stacked together, and is fixed between the second metal ring (203) and the third metal ring (204). The second metal ring (203) and the third metal ring (204) are input and output electrodes of the electron multiplier (30).

6. A GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The anode assembly (40) includes a kovar sealing disk (401), a multilayer ceramic (402), a metal lead pin (403), a metal electrode (404), and a peripheral metal electrode (405); the multilayer ceramic (402) is located on one side of the vacuum inside the photomultiplier tube and is composed of (16) metal electrodes (404) and the peripheral metal electrodes (405) in the peripheral area, forming the (1)×(16) linear array; each metal electrode (404) is led to the metal lead pin (403) on the other side through a passage inside the multilayer ceramic (402); the peripheral metal electrode (405) is connected to the kovar sealing disk (401) and is conducted to the metal sealing disk.

7. The GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The metal ceramic tube shell (20) and the anode assembly (40) are sealed as a whole by laser welding or argon arc welding, and the welding point meets the vacuum airtightness requirement.

8. The GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to claim 1, characterized in that: The input light window (102) is made of quartz.

9. A method for preparing a GaN photomultiplier tube based on a multilayer ceramic linear array anode structure, characterized in that: The preparation method for realizing the GaN photomultiplier tube based on a multilayer ceramic linear array anode structure according to any one of claims 1 to 8 comprises the following steps: Step 1: Using a sapphire substrate as a substrate, using metal organic vapor deposition or molecular beam epitaxy technology to prepare an AlN buffer layer, an AlGaN transition layer and a GaN emission layer, gradually reducing the Al content of the AlGaN transition layer from a level close to the Al content in the AlN buffer layer to 0, and performing p-type doping to increase the hole concentration; Step 2: Cut the sapphire substrate into discs of the same size as the convex surface of the input light window, and make GaN epitaxial wafers; Step 3: Lay the input light window and the GaN epitaxial wafer together on their backs to ensure that the light-transmitting parts overlap each other, place them in a vacuum degassing furnace, and bond them together using a high-temperature bonding method to form a cathode assembly; Step 4: chemically cleaning the cathode assembly to remove the surface oxide layer; Step 5: Take the first metal ring, the second metal ring, the third metal ring, the fourth metal ring, the fifth metal ring and four ceramic rings, assemble them in specific positions and place them in a high-temperature brazing furnace to form a metal ceramic shell through a high-temperature brazing process; Step 6: injecting solder into the groove of the first metal ring in the metal ceramic shell; Step 7: welding a getter wire between the fourth metal ring 205 and the fifth metal ring 206 in the metal ceramic shell after solder injection; Step 8: The metal ceramic shell and the anode assembly to which the air intake wire is welded in step 7 are sealed together by laser welding or argon arc welding; Step 9: installing an electron multiplier formed by stacking two microchannel plates between the second metal ring and the third metal ring of the metal ceramic tube shell and fixing it; Step 10: placing the chemically cleaned cathode assembly and the metal ceramic tube shell with the electron multiplier in an ultra-high vacuum degassing table; Step 11: thermally cleaning the cathode assembly after chemical cleaning in an ultra-high vacuum environment to further clean the surface layer of the GaN epitaxial wafer; Step 12: Activate the surface layer of the GaN epitaxial wafer with Cs and O in an ultra-high vacuum degassing station; Step 13: performing high-temperature baking and degassing on the metal ceramic tube shell and the anode assembly in an ultra-high vacuum degassing table; Step 14: electronically cleaning the electron multiplier in an ultra-high vacuum degassing station; Step 1 5: In an ultra-high vacuum degassing table, the cathode assembly that has completed surface activation and the metal ceramic tube shell that has undergone high-temperature degassing are sealed together to form a photomultiplier tube.

Images