Vertical photoconductive switch and manufacturing method thereof

Abstract

The invention discloses a vertical photoconductive switch and a manufacturing method thereof, and the vertical photoconductive switch comprises a substrate made of a photoconductive material, the substrate is constructed to be in a quadrilateral geometrical shape, the substrate is provided with a first surface and a second surface which are oppositely arranged, and four side surfaces located between the first surface and the second surface, the input surface and the output surface are positioned on a group of opposite angles of the quadrilateral-like geometrical substrate, the input surface is used for receiving light, and the output surface is used for emitting the light received by the input surface; the first electrode is formed on the first surface; and a second electrode formed on the second surface. According to the vertical photoconductive switch and the manufacturing method thereof, the problem of non-uniform current distribution can be effectively relieved, and the light utilization rate and the voltage resistance of the vertical photoconductive switch are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and in particular relates to a vertical photoconductive switch and a manufacturing method thereof. Background Art

[0002] Gallium nitride (GaN) is one of the most promising third-generation semiconductors with many excellent physical properties, such as a bandgap of 3.4eV, a critical breakdown field of 3.3MV / cm, and a saturated electron migration velocity of 2.5×10 7 cm / s, direct bandgap structure, etc., which ensures that it has broad application prospects in high frequency, high power, optoelectronic devices and other fields.

[0003] Iron-doped semi-insulating gallium nitride (SI-GaN:Fe) is a type of gallium nitride that can be used as an isolation layer between devices to improve breakdown characteristics and as a substrate for devices, so it has been widely studied. In addition, it is known as the most promising semiconductor material for studying high-frequency, high-power photoconductive switches due to its excellent light state (low on-resistance), dark state (low leakage current) and light-dark conversion performance (short carrier lifetime).

[0004] Photoconductive semiconductor switches (PCSS) are semiconductor switches triggered by specific excitation light sources. They have excellent characteristics such as small size, low loss, high output power, fast response speed, and high repetition frequency. They have broad application prospects in the fields of medicine, military, aerospace, etc. Photoconductive switch devices can be roughly divided into two types: vertical type and planar type.

[0005] Among them, the vertical structure can give full play to the advantages of SI-GaN:Fe materials. The critical breakdown field strength of the device is greater, the withstand voltage performance is better, and the service life is longer. However, the vertical structure also has its disadvantages. For example, the incident light of the vertical photoconductive switching device is usually incident from one side, which leads to a large number of photogenerated carriers at the light incident surface and uneven current distribution. This makes it difficult for the device to dissipate heat, which can easily lead to local overheating of the electrode close to the light incident surface, affecting the withstand voltage performance and service life of the device.

[0006] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0007] The object of the present invention is to provide a vertical photoconductive switch and a manufacturing method thereof, which can effectively alleviate the problem of uneven current distribution and significantly enhance the light utilization rate and voltage resistance performance of the vertical photoconductive switch.

[0008] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0009] A vertical photoconductive switch, comprising:

[0010] A substrate of a light-guiding material, the substrate being configured into a quadrilateral-like geometric shape, the substrate having a first surface and a second surface disposed opposite to each other, four side surfaces located between the first surface and the second surface, and an input surface and an output surface located at a set of diagonal corners of the substrate of the quadrilateral-like geometric shape, the input surface being used to receive light, and the output surface being used to emit light received via the input surface;

[0011] A first electrode formed on the first surface; and

[0012] The second electrode is formed on the second surface.

[0013] In one or more embodiments of the present invention, the input surface is configured as a concave surface; and / or,

[0014] The output surface is configured as a concave surface.

[0015] In one or more embodiments of the present invention, the concave surface has a curved shape selected from cylindrical or spherical.

[0016] In one or more embodiments of the present invention, the input surface is configured as a plane; and / or,

[0017] The output surface is designed to be flat.

[0018] In one or more embodiments of the present invention, an anti-reflection film is provided on the input surface; and / or,

[0019] A high reflection film is arranged on the output surface.

[0020] In one or more embodiments of the present invention, the vertical photoconductive switch further comprises a passivation layer, the passivation layer comprising a first passivation layer at least disposed on the circumference of the first electrode and a second passivation layer at least disposed on the circumference of the second electrode;

[0021] The first passivation layer extends from the first surface of the substrate along the peripheral surface of the first electrode to the surface of the first electrode away from the first surface;

[0022] The second passivation layer extends from the second surface of the substrate along the circumference of the second electrode to a surface of the second electrode facing away from the second surface.

[0023] In one or more embodiments of the present invention, the optical guide material comprises a GaN single crystal having a first doping source, wherein the first doping source comprises Fe with a doping concentration of 1×10 18 cm -3 ~1×10 19 cm -3 .

[0024] In one or more embodiments of the present invention, the resistivity of the substrate is 1×10 8 Ω·cm~1×10 9 Ω·cm, the carrier concentration is 1×10 8 cm -3 ~1×10 9 cm -3 .

[0025] In one or more embodiments of the present invention, the first electrode comprises a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence on the first surface, the thickness of the first Ti layer is in the range of 5nm to 30nm, the thickness of the Al layer is in the range of 80nm to 130nm, the thickness of the second Ti layer is in the range of 50nm to 100nm, and the thickness of the Au layer is in the range of 50nm to 150nm; and / or,

[0026] The edge corner of the first electrode is configured to be arc-shaped; and / or,

[0027] The second electrode comprises a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence on the second surface, the first Ti layer has a thickness range of 5nm to 30nm, the Al layer has a thickness range of 80nm to 130nm, the second Ti layer has a thickness range of 50nm to 100nm, and the Au layer has a thickness range of 50nm to 150nm; and / or,

[0028] The edge corner of the second electrode is configured to be arc-shaped.

[0029] A method for manufacturing a vertical photoconductive switch, comprising:

[0030] Providing a substrate of a light-guiding material, the substrate being configured in a quadrilateral geometric shape, the substrate having a first surface and a second surface disposed opposite to each other, and four side surfaces located between the first surface and the second surface;

[0031] cutting a set of opposite corners of the quadrilateral geometry substrate to form an input face and an output face perpendicular to the first and second surfaces;

[0032] Soaking the cut substrate in TMAH solution to make the input surface and the output surface smooth;

[0033] forming a first electrode on the first surface, and forming a first passivation layer covering at least a peripheral surface of the first electrode;

[0034] forming a second electrode on the second surface, and forming a second passivation layer covering at least a peripheral surface of the second electrode;

[0035] forming an antireflection film on the input surface;

[0036] A high reflection film is formed on the output surface.

[0037] Compared with the prior art, the vertical photoconductive switch and its manufacturing method of the present invention abandon the traditional side wall incident mode and change to angle incidence. By reflecting the incident light at the other corner of the device and inside the device, it is ensured that the light is evenly distributed inside the device, which can effectively alleviate the problem of uneven current distribution. In addition, multiple reflections increase the optical path and further improve the light utilization rate.

[0038] The vertical photoconductive switch and its manufacturing method of the present invention deposit an anti-reflection film on the input surface and deposit a high-reflection film on the output surface, which can further improve the light utilization rate of the device and significantly enhance the light utilization rate and voltage resistance performance of the photoconductive switch.

[0039] The vertical photoconductive switch and its manufacturing method of the present invention obtain input and output surfaces of suitable shapes by laser cutting, and make the input and output surfaces smooth by high-temperature immersion in TMAH solution, so as to achieve uniform distribution of incident light inside the device and improve the photoelectric performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 A schematic diagram of the structure of a vertical photoconductive switch according to an embodiment of the present invention;

[0042] Figure 2 A top view of the structure of a vertical photoconductive switch according to an embodiment of the present invention;

[0043] Figure 3 FIG. 1 is a light incident principle diagram of a vertical photoconductive switch in one embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions in the present invention, 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, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] As mentioned in the background technology, the existing vertical photoconductive switch adopts the sidewall incident mode, and there are many photogenerated carriers at the light incident surface, and the current distribution is uneven. This makes it difficult to dissipate heat from the device, which easily leads to local overheating of the electrode close to the light incident surface, affecting the device's withstand voltage performance and service life.

[0046] Based on this, the present invention provides a vertical photoconductive switch and a manufacturing method thereof, by constructing a substrate of a quadrilateral-like geometric shape, and forming an input surface and an output surface at a set of diagonal portions of the substrate, respectively, and by reflecting light at the diagonal portions of the device and inside the device, it is ensured that light is evenly distributed inside the device, which can effectively alleviate the problem of uneven current distribution. In addition, an anti-reflection film is deposited on the input surface, and a high-reflection film is deposited on the output surface, which can further improve the light utilization rate of the device, and significantly enhance the light utilization rate and voltage resistance performance of the photoconductive switch.

[0047] like Figure 1 and Figure 2 As shown, a vertical photoconductive switch in an embodiment of the present invention includes a substrate 10 of a photoconductive material and a first electrode 20 and a second electrode 30 formed on opposite surfaces of the substrate 10 .

[0048] The substrate 10 is configured in a quadrilateral-like geometric shape. The substrate 10 has a first surface 10a and a second surface 10b that are arranged opposite to each other, and four side surfaces 10c located between the first surface 10a and the second surface 10b. The first surface 10a and the second surface 10b are separated by the four side surfaces 10c. The four side surfaces 10c are arranged perpendicularly to each other, and the four side surfaces 10c are respectively perpendicular to the first surface 10a and the second surface 10b. The first surface 10a and the second surface 10b are both planes, and the four side surfaces 10c are also planes.

[0049] In this embodiment, the length and width of the substrate 10 are substantially the same, and the height is smaller than the length and width.

[0050] Although the quadrilateral geometry is understood to have only six surfaces, the quadrilateral-like geometry of the substrate 10 further includes an input face 11 and an output face 12 located at a set of diagonal corners of the quadrilateral-like geometry substrate. The input face 11 is inserted between two adjacent side faces 10c and the first surface 10a and the second surface 10b for receiving light. The output face 12 is also inserted between the other two adjacent side faces 10c and the first surface 10a and the second surface 10b for emitting the light received through the input face 11.

[0051] The arrangement of the input surface 11 and the output surface 12 can make the incident light A evenly distributed, thereby making the current evenly distributed. The incident light A can preferably be a 532nm laser.

[0052] In this embodiment, the input surface 11 is configured as a concave surface, and the output surface 12 is also configured as a concave surface.

[0053] The concave surface has a curved shape selected from cylindrical or spherical. For example, the concave surface is a partial circumference of a cylinder, which can diffuse the incident light in two directions. Or the concave surface is a spherical circumference, which can diffuse the incident light in multiple directions.

[0054] In this embodiment, the input surface 11 and the output surface 12 have the same shape.

[0055] In other embodiments, the input surface 11 and the output surface 12 may also be configured as planes. In this structure, the input surface 11 and the output surface 12 form an angle of 45 degrees relative to the two side surfaces 10c into which they are inserted.

[0056] In order to further improve the light utilization rate of the device, the input surface 11 of the vertical light guide switch of the present invention is further provided with an anti-reflection film 13, and the output surface 12 is further provided with a high-reflection film 14. The provision of the anti-reflection film 13 can increase the transmission of incident light and reduce the reflection of incident light. The provision of the high-reflection film 14 can increase the reflection of incident light and reduce the transmission of incident light, thereby further improving the light utilization rate.

[0057] The optical guide material is a GaN single crystal with a first doping source, the first doping source is Fe, and the doping concentration of Fe is 1×10 18 cm -3 ~1×10 19 cm -3 , preferably 2×10 18 cm -3 ~5×10 18 cm -3 , for example 5×10 18 cm -3 After Fe doping, the substrate 10 presents a high resistance state, so that the substrate 10 has a semi-insulating property and a high resistance. The resistivity of the substrate 10 at room temperature (300K) is 1×108 Ω·cm~1×10 9 Ω·cm, preferably 1×10 8 Ω·cm, the carrier concentration is 1×10 8 cm -3 ~1×10 9 cm -3 , preferably 6.2×10 8 cm -3 .

[0058] The first electrode 20 is formed on the first surface 10a of the substrate 10. The first electrode 20 includes a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence. The thickness of the first Ti layer ranges from 5nm to 30nm, preferably 20nm. The thickness of the Al layer ranges from 80nm to 130nm, preferably 130nm. The thickness of the second Ti layer ranges from 50nm to 100nm, preferably 50nm. The thickness of the Au layer ranges from 50nm to 150nm, preferably 150nm.

[0059] The second electrode 30 is formed on the second surface 10b of the substrate 10. The second electrode 30 includes a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence. The thickness of the first Ti layer ranges from 5nm to 30nm, preferably 20nm. The thickness of the Al layer ranges from 80nm to 130nm, preferably 130nm. The thickness of the second Ti layer ranges from 50nm to 100nm, preferably 50nm. The thickness of the Au layer ranges from 50nm to 150nm, preferably 150nm.

[0060] In order to further effectively alleviate the electric field concentration and prevent the first electrode 20 and the second electrode 30 from being broken down, the edge corners of the first electrode 20 and the second electrode 30 are both configured to be arc-shaped.

[0061] In order to isolate the first electrode 20 and the second electrode 30 from air and moisture, in the vertical photoconductive switch of the present embodiment, a first passivation layer 41 is provided on at least the circumference of the first electrode 20, and a second passivation layer 42 is provided on at least the circumference of the second electrode 30, which can effectively avoid device surface breakdown and improve the device's voltage resistance performance.

[0062] The first passivation layer 41 extends from the first surface 10a of the substrate 10 along the circumference of the first electrode 20 to the surface of the first electrode 20 away from the first surface 10a. The second passivation layer 42 extends from the second surface 10b of the substrate 10 along the circumference of the second electrode 30 to the surface of the second electrode 30 away from the second surface 10b.

[0063] refer to Figure 3As shown, in the vertical light guide switch of this embodiment, the incident light A enters from the input surface 11 and propagates inside the device after passing through the anti-reflection film 13. When the light reaches the output surface 12, part of the light passes through the high reflection film 14 and transmits out of the vertical light guide switch, and the other part of the light is reflected at the output surface 12, and after multiple reflections, it returns to the input surface 11 again. This process not only increases the optical path and improves the light utilization rate, but also makes the light distribution uniform, thereby uniformly distributing the current.

[0064] The present invention also provides a method for manufacturing the vertical photoconductive switch, which specifically comprises the following steps:

[0065] A substrate of light-conducting material is provided and cleaned.

[0066] The substrate is configured in a quadrilateral geometric shape, and has a first surface and a second surface that are opposite to each other, and four side surfaces between the first surface and the second surface.

[0067] A set of diagonal corners of a quadrilateral geometric substrate are cut by femtosecond laser to form an input surface and an output surface perpendicular to the first surface and the second surface. The input surface and the output surface can be a plane or a concave curved surface.

[0068] The surface of the substrate after laser cutting will become rough, which will easily affect the performance of the device. Therefore, the cut substrate needs to be soaked in TMAH solution at high temperature. The temperature is 85℃ and the time is 2h. The surface of the substrate becomes smooth after being soaked in TMAH solution at high temperature.

[0069] An ohmic electrode (first electrode) is formed on the first surface of the substrate, and a first passivation layer is formed to cover at least the peripheral surface of the ohmic electrode.

[0070] An ohmic electrode (second electrode) is formed on the second surface of the substrate, and a second passivation layer is formed to cover at least the peripheral surface of the ohmic electrode.

[0071] An antireflection film is formed on the input surface of the substrate, and a high reflection film is formed on the output surface of the substrate.

[0072] Compared with the prior art, the vertical photoconductive switch and its manufacturing method of the present invention abandon the traditional side wall incident mode and change to angle incidence. By reflecting the incident light at the other corner of the device and inside the device, it is ensured that the light is evenly distributed inside the device, which can effectively alleviate the problem of uneven current distribution. In addition, multiple reflections increase the optical path and further improve the light utilization rate.

[0073] The vertical photoconductive switch and its manufacturing method of the present invention deposit an anti-reflection film on the input surface and deposit a high-reflection film on the output surface, which can further improve the light utilization rate of the device and significantly enhance the light utilization rate and voltage resistance performance of the photoconductive switch.

[0074] The vertical photoconductive switch and its manufacturing method of the present invention obtain input and output surfaces of suitable shapes by laser cutting, and make the input and output surfaces smooth by high-temperature immersion in TMAH solution, so as to achieve uniform distribution of incident light inside the device and improve the photoelectric performance of the device.

[0075] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0076] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A vertical photoconductive switch, characterized in that: include: A substrate of a light-guiding material, the substrate being configured into a quadrilateral-like geometric shape, the substrate having a first surface and a second surface disposed opposite to each other, four side surfaces located between the first surface and the second surface, and an input surface and an output surface located at a set of diagonal corners of the substrate of the quadrilateral-like geometric shape, the input surface being used to receive light, and the output surface being used to emit light received via the input surface; a first electrode formed on the first surface; as well as The second electrode is formed on the second surface.

2. The vertical optical switch according to claim 1, characterized in that: The input surface is configured as a concave surface; and / or, The output surface is configured as a concave surface.

3. The vertical optical switch according to claim 2, characterized in that: The concave surface has a curved shape selected from cylindrical or spherical.

4. The vertical optical switch according to claim 1, characterized in that: The input surface is configured as a plane; and / or, The output surface is designed as a plane.

5. The vertical optical switch according to claim 1, characterized in that: An anti-reflection film is provided on the input surface; and / or, A high reflection film is arranged on the output surface.

6. The vertical optical switch according to claim 1, characterized in that: Also includes a passivation layer, the passivation layer includes a first passivation layer at least disposed on the peripheral surface of the first electrode and a second passivation layer at least disposed on the peripheral surface of the second electrode; The first passivation layer extends from the first surface of the substrate along the peripheral surface of the first electrode to the surface of the first electrode away from the first surface; The second passivation layer extends from the second surface of the substrate along the circumference of the second electrode to the surface of the second electrode away from the second surface.

7. The vertical optical switch according to claim 1, characterized in that: The optical guide material includes a GaN single crystal having a first doping source, wherein the first doping source includes Fe with a doping concentration of 1×10 18 cm -3 ~1×10 19 cm -3 .

8. The vertical optical switch according to claim 1, characterized in that: The resistivity of the substrate is 1×10 8 Ω·cm~1×10 9 Ω·cm, the carrier concentration is 1×10 8 cm -3 ~1×10 9 cm -3 .

9. The vertical optical switch according to claim 1, characterized in that: The first electrode comprises a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence on the first surface, the first Ti layer has a thickness range of 5nm to 30nm, the Al layer has a thickness range of 80nm to 130nm, the second Ti layer has a thickness range of 50nm to 100nm, and the Au layer has a thickness range of 50nm to 150nm; and / or, The edge corner of the first electrode is configured to be arc-shaped; and / or, The second electrode comprises a first Ti layer, an Al layer, a second Ti layer, and an Au layer stacked in sequence on the second surface, the first Ti layer has a thickness range of 5nm to 30nm, the Al layer has a thickness range of 80nm to 130nm, the second Ti layer has a thickness range of 50nm to 100nm, and the Au layer has a thickness range of 50nm to 150nm; and / or, The edge corner of the second electrode is configured to be arc-shaped.

10. A method for manufacturing a vertical photoconductive switch, characterized in that: include: Providing a substrate of a light-guiding material, the substrate being configured in a quadrilateral geometric shape, the substrate having a first surface and a second surface disposed opposite to each other, and four side surfaces located between the first surface and the second surface; cutting a set of opposite corners of the quadrilateral geometry substrate to form an input face and an output face perpendicular to the first and second surfaces; Soaking the cut substrate in TMAH solution to make the input surface and the output surface smooth; forming a first electrode on the first surface, and forming a first passivation layer covering at least a peripheral surface of the first electrode; forming a second electrode on the second surface, and forming a second passivation layer covering at least a peripheral surface of the second electrode; forming an antireflection film on the input surface; A high reflection film is formed on the output surface.

Images