Photoconductive switch

Abstract

To provide a photoconductive switch that can more effectively reduce costs and heat generation during operation. [Solution] In one embodiment, a first n is made of a gallium oxide semiconductor containing donor impurities. + Layer 31a and the first n + A high-resistance layer 30 made of a gallium oxide semiconductor containing Fe is located on layer 31a, and a second n is located on the high-resistance layer 30, made of a gallium oxide semiconductor containing donor impurities. + Layer 31b and the second n + The transparent electrode 34 on layer 31b and the second n + The anode electrode 32 is connected to layer 31b via a transparent electrode 34, and the first n + The present invention provides a photoconductive switch 3 comprising a cathode electrode 33, which also serves as a light-reflecting film, formed on the lower surface of layer 31a.

Description

[Technical Field]

[0001] This invention relates to a photoconductive switch. [Background technology]

[0002] Conventionally, photoconductive switches that can switch from an off state to an on state by light irradiation are known (see Non-Patent Literature 1). Photoconductive switches have excellent response speed, and are significantly faster than, for example, MOSFET switches.

[0003] The photoconductive switch described in Non-Patent Literature 1 uses SiC as the semiconductor layer, with its resistance increased by the addition of V (vanadium). In the photoconductive switch, in order to ensure breakdown voltage, a breakdown voltage maintenance region (where the anode electrode is connected) is defined according to the resistivity of the semiconductor layer. + The region and the cathode electrode are connected n + The length and cross-sectional area of ​​the regions (between the regions) are set. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Qilin Wu et al., “The Test of a High-Power, Semi-Insulating, Linear-Mode, Vertical 6H-SiC PCSS”, IEEE TRANSACTIONS ON ELECTRON DEVICES, APRIL 2019, VOL. 66, NO. 4, pp 1837-1842. [Overview of the project] [Problems that the invention aims to solve]

[0005] Conventional photoconductive switches, including the photoconductive switch using SiC described in Non-Patent Document 1, cannot generate a channel having sufficient carriers without using a very high-intensity and expensive laser from the volume of the breakdown voltage maintenance region, and there is a problem that the conduction loss increases and the heat generation increases. That is, conventional photoconductive switches have been difficult to put into practical use from the viewpoints of cost or heat generation.

[0006] An object of the present invention is to provide a photoconductive switch that can more effectively suppress cost and heat generation during operation.

Means for Solving the Problems

[0007] One aspect of the present invention provides the following photoconductive switch in order to achieve the above object.

[0008] [1] A first n + layer made of a gallium oxide-based semiconductor containing donor impurities, a high-resistance layer made of a gallium oxide-based semiconductor containing Fe on the first n + layer, and a second n + layer made of a gallium oxide-based semiconductor containing donor impurities on the high-resistance layer, a transparent electrode on the second n + layer, an anode electrode connected to the second n + layer through the transparent electrode, and a cathode electrode that also serves as a light reflection film formed on the lower surface of the first n + layer, a photoconductive switch. [2] The first n + layer is made of a substrate, and the high-resistance layer and the second n + layer are made of an epitaxial film having the first n + layer as a base, the photoconductive switch according to [1] above. [3] The distance between the first n + layer and the second n + layer is within a range of 2 μm or more and 100 μm or less, or within a range of 10 μm or more and 500 μm or less, the photoconductive switch according to [1] or [2] above.

Effects of the Invention

[0009] According to the present invention, it is possible to provide a photoconductive switch that can more effectively reduce costs and heat generation during operation. [Brief explanation of the drawing]

[0010] [Figure 1] Figures 1(a) and 1(b) are vertical cross-sectional views of a photoconductive switch according to a first embodiment of the present invention. [Figure 2] Figure 2 is a graph showing the relationship between the breakdown voltage maintenance region length and the breakdown voltage value in a photoconductive switch having a semiconductor layer made of Ga2O3, 6H-SiC, GaAs, or Si, with a breakdown voltage maintenance region cross-sectional area of ​​1 cm2, and defined as the voltage when the leakage current reaches 10 μA. [Figure 3] Figures 3(a) and 3(b) are vertical cross-sectional views of a photoconductive switch according to a second embodiment of the present invention. [Figure 4] Figures 4(a) and 4(b) are vertical cross-sectional views of a photoconductive switch according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0011] [First Embodiment] (Configuration of a photoconductive switch) Figures 1(a) and 1(b) are vertical cross-sectional views of a photoconductive switch 1 according to a first embodiment of the present invention. The photoconductive switch 1 is a horizontal photoconductive switch equipped with a semiconductor layer made of a gallium oxide semiconductor. Figure 1(a) shows the off state in which no light is irradiated onto the photoconductive switch 1, and Figure 1(b) shows the on state in which light L is irradiated onto the photoconductive switch 1.

[0012] The photoconductive switch 1 consists of a gallium oxide-based semiconductor, a semiconductor layer 10 with high resistance due to the inclusion of impurities, an anode electrode 12 and a cathode electrode 13 connected to the upper surface of the semiconductor layer 10, and a region within the semiconductor layer 10 containing donor impurities, and a first n connected to the anode electrode 12. +Region 11a and a region containing donor impurities in the semiconductor layer 10, the first n + Region 11a is separated and the second n connected to the cathode electrode 13 + Region 11b and, are provided.

[0013] The gallium oxide-based semiconductor refers to Ga2O3 or Ga2O3 to which elements such as Al and In are added. For example, the gallium oxide-based semiconductor has a composition represented by (Ga x Al y In (1-x-y) )2O3 (0 < x ≤ 1, 0 ≤ y ≤ 1, 0 < x + y ≤ 1). When Al is added to Ga2O3, the bandgap widens, and when In is added, the bandgap narrows.

[0014] Examples of impurities that can increase the resistance of the semiconductor layer 10 made of a gallium oxide-based semiconductor include Fe, Mg, Zn, H, Li, Be, Na, K, Ca, Rb, Sr, Ba, Cu, Ni, Mn, Cr, and V. Among them, Fe, Mg, and Zn are impurities that have a lot of achievements in the production of high-resistance gallium oxide. In particular, Fe has been demonstrated to impart a high resistivity to the gallium oxide-based semiconductor. When the semiconductor layer 10 contains Fe, the resistivity of the semiconductor layer 10 can be controlled within the range of 1 × 10 11 ~5 × 10 12 Ωcm.

[0015] Fe added to the gallium oxide-based semiconductor forms an impurity level near the conduction band between the conduction band and the valence band of the gallium oxide-based semiconductor and traps electrons, thereby increasing the resistance of the gallium oxide-based semiconductor. Therefore, the portion where the first n + region 11a and the second n + region 11b are not provided is highly resistive, and in a state where the light L is not irradiated, no current flows between the first n + region 11a and the second n + region 11b.

[0016] Here, the off performance of the photoconductive switch is the withstand voltage maintenance region (n to which the anode electrode is connected+ The region and the cathode electrode are connected n + It is determined by the length and cross-sectional area of ​​the region between the regions and the resistivity of the semiconductor layer. In the photoconductive switch 1, since the gallium oxide semiconductor constituting the semiconductor layer 10 has a high resistivity, for example, a higher resistivity than SiC, the length of the breakdown voltage maintenance region, i.e., the first n + Region 11a and the second n + The distance d1 between regions 11b can be significantly shortened.

[0017] By shortening the length of the voltage-bearing region, the photoconductive switch 1 can generate sufficient carriers in the voltage-bearing region without using an expensive, high-intensity laser oscillator as the light source L. This significantly reduces conduction loss in the ON state, i.e., the loss of current flowing through channel 15, and suppresses heat generation. Furthermore, shortening the length of the voltage-bearing region allows for a reduction in the area of ​​the photoconductive switch 1.

[0018] The following describes how to set the distance d1 in the photoconductive switch 1 to obtain a predetermined withstand voltage. First, according to Ohm's law, the following equation (1) holds true. Here, V is the first n + Region 11a and the second n + This is the voltage applied between region 11b (between the anode electrode 12 and the cathode electrode 13), where I is the first n + Region 11a and the second n + This is the current flowing between regions 11b, ρ is the resistivity of the semiconductor layer 10 in which the channel 15 is formed, and L is the length of the breakdown voltage maintenance region, i.e., the first n + Region 11a and the second n + d1 is the distance between regions 11b, and S is the cross-sectional area perpendicular to the voltage application direction of the breakdown voltage maintenance region.

[0019]

number

[0020] As described above, when the semiconductor layer 10 contains Fe, the resistivity ρ of the semiconductor layer 10 is 1 × 10⁻¹⁰ depending on the concentration of Fe.11 ~5×10 12 It can be controlled within the range of Ωcm. Therefore, according to equation (1), for example, 10 μA / cm 2 When the applied voltage V at which a leakage current J (=I / S) flows is defined as the breakdown voltage, the distance d1 required to obtain a breakdown voltage of 10kV is given by a resistivity ρ of 1 × 10 11 ~5×10 12 Within the range of Ωcm, the range is 2 to 100 μm. Also, 10 μA / cm 2 When the applied voltage V at which a leakage current J (=I / S) flows is defined as the breakdown voltage, the distance d1 required to obtain a breakdown voltage of 50kV is given by a resistivity ρ of 1 × 10⁻¹⁰. 11 ~5×10 12 Within the Ωcm range, the thickness is 10 to 500 μm.

[0021] Figure 2 shows a semiconductor layer made of Ga2O3, 6H-SiC, GaAs, or Si, with a breakdown voltage maintenance region cross-sectional area of ​​1 cm². 2 This graph shows the relationship between the breakdown voltage maintenance region length and the breakdown voltage value in a photoconductive switch where the breakdown voltage is defined as the voltage at which the leakage current reaches 10 μA. Ga2O3, 6H-SiC, GaAs, and Si are all assumed to have high resistance due to the addition of impurities, and their resistivity is set to 3.0 × 10⁻⁶. 12 Ωcm, 1.0 × 10 11 Ωcm, 1.0 × 10 8 Ωcm, 1.0 × 10 7 It is expressed as Ωcm.

[0022] Here, the applied voltage when a leakage current of 10 μA flows is defined as the "withstand voltage," and the length of the withstand voltage maintenance region required to maintain that withstand voltage (the first n in the photoconductive switch 1) is defined as the length of the withstand voltage maintenance region. + Region 11a and the second n + The distance d1 between regions 11b is defined as the "pressure resistance maintenance region length".

[0023] Figure 2 shows that the length of the voltage-bearing region required to achieve a predetermined voltage in a photoconductive switch having a semiconductor layer made of Ga2O3 is significantly smaller than that in a photoconductive switch having a semiconductor layer made of 6H-SiC, GaAs, or Si.

[0024] The semiconductor layer 10 is typically a substrate made of a gallium oxide-based semiconductor. Impurities such as Fe contained in the semiconductor layer 10 are distributed throughout the semiconductor layer 10. The concentration of Fe in the semiconductor layer 10 is, for example, 1 × 10⁻⁶. 18 cm -3 The above is 1 x 10 20 cm -3 The following applies:

[0025] Furthermore, in the photoconductive switch 1, as shown in Figure 1(b), the first n of the semiconductor layer 10 + Region 11a and the second n + By irradiating the region between region 11b and the first n on the surface of the semiconductor layer 10 from above, + Region 11a and the second n + The electrons in the region between region 11b and the first n are excited, forming channel 15. As a result, the first n + Region 11a and the second n + A current will begin to flow between region 11b and the region.

[0026] Here, the light L irradiated onto the photoconductive switch 1 is light with energy greater than the band gap of the gallium oxide semiconductor constituting the semiconductor layer 10. For example, if the semiconductor layer 10 is made of Ga2O3, the light has a wavelength of 250 nm or less. In this case, the irradiated light L is absorbed by the semiconductor layer 10, so the channel 15 is formed only near its surface.

[0027] As described above, in the photoconductive switch 1, the length of the voltage resistance maintenance region can be significantly shortened. When the length of the voltage resistance maintenance region is shortened, the volume of the region to which light L should be irradiated for the formation of the channel 15 becomes smaller, and therefore the energy of the irradiated light L can be reduced by an order of magnitude.

[0028] The first n + Region 11a and the second n + Region 11b is formed by implanting donor impurities such as Si and Sn into the semiconductor layer 10. + Region 11a and the second n + The donor concentration in region 11b is, for example, 5 × 10⁻⁶. 18 cm -3 That's all.

[0029] The anode electrode 12 and cathode electrode 13 are made of, for example, Ti, Al, Ti / Al, or Ti / Au. Furthermore, in order to prevent the generation of interfacial leakage current and damage to the semiconductor layer 10 caused by applying a high voltage between the anode electrode 12 and the cathode electrode 13, it is preferable to provide a passivation film 14 that covers the surface of the semiconductor layer 10. The passivation film 14 is made of an insulator such as SiO2.

[0030] [Second Embodiment] The photoconductive switch 2 according to the second embodiment of the present invention differs from the photoconductive switch 1 according to the first embodiment mainly in that a light-reflective film 20 is provided on the lower surface of the semiconductor layer 10. The same aspects as those of the first embodiment will be omitted or simplified in the explanation.

[0031] (Configuration of a photoconductive switch) Figures 3(a) and 3(b) are vertical cross-sectional views of a photoconductive switch 2 according to a second embodiment of the present invention. The photoconductive switch 2 is a horizontal photoconductive switch equipped with a semiconductor layer made of a gallium oxide semiconductor. Figure 3(a) shows the off state in which light is not irradiated onto the photoconductive switch 2, and Figure 3(b) shows the on state in which light L is irradiated onto the photoconductive switch 2.

[0032] In the photoconductive switch 2, a light-reflecting film 20 is provided on the lower surface of the semiconductor layer. The light-reflecting film 20 is a film for reflecting light L that travels downward through the semiconductor layer 10. The light-reflecting film 20 is made of a metal such as Ag, Pd, Cu, or Au.

[0033] The light L irradiated onto the photoconductive switch 2 has energy less than the band gap of the gallium oxide semiconductor constituting the semiconductor layer 10, and energy greater than the energy difference between the lower end of the conduction band of the gallium oxide semiconductor and the impurity level (trap level) of the impurities contained in the semiconductor layer 10. For example, if the semiconductor layer 10 is made of Ga2O3 and contains Fe, the light L has a wavelength of 300 nm or more and 1550 nm or less.

[0034] Therefore, although the light L does not excite electrons from the valence band to the conduction band of the gallium oxide semiconductor, it excites electrons from impurity levels in the band gap of the gallium oxide semiconductor to the conduction band, forming a channel 15. In this case, the irradiated light L propagates through the semiconductor layer 10 while being gradually absorbed. Then, by being reflected by the light-reflecting film 20 on the lower surface of the semiconductor layer 10, the light L spreads over a wide area of ​​the semiconductor layer 10, forming a channel 15 over a wide area of ​​the semiconductor layer 10.

[0035] The longer the wavelength of light L, the lower the manufacturing cost of the laser oscillator that emits light L. In particular, wavelengths of about 0.85 to 1.55 μm (0.8 to 1.46 eV) are widely used in optical communications and other applications, and high-intensity laser oscillators in this wavelength range are readily available. For this reason, it is preferable that the depth of the impurity level from the lower end of the conduction band of the gallium oxide semiconductor be shallower than 1.46 eV. As described above, Fe added to the gallium oxide semiconductor forms an impurity level at a position close to the conduction band between the conduction band and the valence band of the gallium oxide semiconductor. For example, Fe contained in Ga2O3 forms an impurity level at a position of about 0.7 to 0.9 eV from the lower end of the conduction band of Ga2O3. For this reason, it is preferable that the semiconductor layer 10 contains Fe.

[0036] In the photoconductive switch 2, since channels 15 are formed over a wide area of ​​the semiconductor layer 10, for example, throughout the entire layer, the conduction resistance in the ON state can be reduced more effectively.

[0037] [Third Embodiment] The photoconductive switch 3 according to the third embodiment of the present invention differs from the photoconductive switch 1 according to the first embodiment mainly in that it is a vertical photoconductive switch. The same aspects as those of the first embodiment will be omitted or simplified in the explanation.

[0038] (Configuration of a photoconductive switch) Figures 4(a) and 4(b) are vertical cross-sectional views of a photoconductive switch 3 according to a third embodiment of the present invention. The photoconductive switch 3 is a vertical photoconductive switch equipped with a semiconductor layer made of a gallium oxide semiconductor. Figure 4(a) shows the off state in which the photoconductive switch 3 is not irradiated with light, and Figure 4(b) shows the on state in which the photoconductive switch 3 is irradiated with light L.

[0039] The photoconductive switch 3 is a first n made of a gallium oxide-based semiconductor containing donor impurities. + Layer 31a and the first n + A high-resistance layer 30 made of a gallium oxide semiconductor containing impurities is located on layer 31a, and a second n is located on the high-resistance layer 30, also made of a gallium oxide semiconductor containing donor impurities. + Layer 31b and the second n + The transparent electrode 34 on layer 31b and the second n + The anode electrode 32 is connected to layer 31b via a transparent electrode 34, and the first n + The device comprises a cathode electrode 33, which also serves as a light-reflecting film, formed on the lower surface of layer 31a.

[0040] Similar to the semiconductor layer 10 of the photoconductive switch 1 according to the first embodiment, the high-resistance layer 30, which is made of a gallium oxide-based semiconductor containing impurities for increased resistance, is highly resistive, and in the state where light L is not irradiated, the first n + Layer 31a and the second n + No current flows between layers 31b. The resistivity of the high-resistivity layer 30 is, for example, 1 × 10 if the high-resistivity layer 30 contains Fe. 11 ~5×10 12 It is Ωcm.

[0041] In the photoconductive switch 3, similar to the photoconductive switch 1, the gallium oxide semiconductor constituting the high-resistance layer 30 has high electrical resistance, thus the length of the breakdown voltage maintenance region, i.e., the first n + Layer 31a and the second n + The distance d2 between layers 31b can be significantly shortened.

[0042] By shortening the length of the voltage-bearing region, the photoconductive switch 3 can generate a channel 35 with sufficient carriers without using an expensive, high-intensity laser oscillator as the light source L. This significantly reduces conduction loss in the ON state, i.e., the loss of current flowing through the channel 35, thereby suppressing heat generation. Furthermore, shortening the length of the voltage-bearing region allows for a reduction in the thickness of the photoconductive switch 3.

[0043] The distance d2 required to obtain a predetermined withstand voltage in the photoconductive switch 3 can be set in the same way as the distance d1 in the photoconductive switch 1 according to the first embodiment. That is, the length L of the withstand voltage maintenance region can be used as the distance d2 and calculated from equation (1).

[0044] If the high-resistivity layer 30 contains Fe, the resistivity ρ of the high-resistivity layer 30 will be 1 × 10⁻¹⁰ depending on the concentration of Fe. 11 ~5×10 12 It can be controlled within the range of Ωcm. Therefore, according to equation (1), for example, 10 μA / cm 2 When the applied voltage V at which a leakage current J (=I / S) flows is defined as the breakdown voltage, the distance d2 required to obtain a breakdown voltage of 10kV is given by a resistivity ρ of 1 × 10⁻¹⁰. 11 ~5×10 12 Within the range of Ωcm, the range is 2 to 100 μm. Also, 10 μA / cm 2 When the applied voltage V at which a leakage current J (=I / S) flows is defined as the breakdown voltage, the distance d2 required to obtain a breakdown voltage of 50kV is given by a resistivity ρ of 1 × 10⁻¹⁰. 11 ~5×10 12 Within the Ωcm range, the thickness is 10 to 500 μm.

[0045] In addition, the relationship between the breakdown voltage maintenance region length and the breakdown voltage shown in FIG. 2 also holds for vertical photoconductive switches such as the photoconductive switch 3. That is, the length of the breakdown voltage maintenance region for obtaining a predetermined breakdown voltage in a photoconductive switch having a semiconductor layer made of Ga2O3 is significantly smaller compared to that in a photoconductive switch having a semiconductor layer made of 6H-SiC, GaAs, or Si. Note that the length of the breakdown voltage maintenance region in this case corresponds to the distance d2 between the first n + layer 31a and the second n + layer 31b in the photoconductive switch 3.

[0046] Impurities such as Fe contained in the high-resistance layer 30 are distributed throughout the high-resistance layer 30. The concentration of Fe in the high-resistance layer 30 is, for example, 1×10 18 cm -3 or more and 1×10 20 cm -3 or less.

[0047] In addition, in the photoconductive switch 3, as shown in FIG. 4(b), by irradiating the high-resistance layer 30 with light L such as laser light from above through the transparent electrode 34 and the second n + layer 31b, electrons in the high-resistance layer 30 are excited to form a channel 35. As a result, a current flows between the second n + layer 31b and the first n + layer 31a through the channel 35. At this time, the current flowing out from the anode electrode 32 spreads in the planar direction through the transparent electrode 34 and flows into the entire surface of the first n + layer 31a. The transparent electrode 34 is made of a transparent conductive film such as an ITO (Indium Tin Oxide) film, an IZO (Indium Zinc Oxide) film, or an IGZO (Indium Gallium Zinc Oxide) film.

[0048] Here, the light L irradiated to the photoconductive switch 3 has an energy smaller than the bandgap of the gallium oxide-based semiconductor constituting the high-resistance layer 30, and is also larger in energy than the energy difference between the lower end of the conduction band of the gallium oxide-based semiconductor and the impurity level of the impurities contained in the high-resistance layer 30. For example, when the high-resistance layer 30 is made of Ga2O3 and contains Fe, the light L is light having a wavelength of 300 nm or more and 1550 nm or less.

[0049] Therefore, the light L does not excite electrons from the valence band to the conduction band of the gallium oxide-based semiconductor, but forms the channel 35 by exciting electrons from the impurity level of Fe in the bandgap of the gallium oxide-based semiconductor to the conduction band of the gallium oxide-based semiconductor. In this case, the irradiated light L travels while being gradually absorbed in the high-resistance layer 30. Then, at the lower surface of the first n + layer 31a, by being reflected by the cathode electrode 33 that also serves as a light reflection film, the light L spreads over a wide range of the high-resistance layer 30, and forms channels 35 over a wide range of the high-resistance layer 30, for example, throughout.

[0050] As described above, in the photoconductive switch 3, the length of the withstand voltage maintenance region can be significantly shortened. When the length of the withstand voltage maintenance region is shortened, the volume of the region where the light L should be irradiated for forming the channel 35 becomes small, so that the energy of the irradiated light L can be reduced by orders of magnitude.

[0051] The first n + layer 31a and the second n + layer 31b contain donor impurities such as Si and Sn, for example. The donor concentration of the first n + layer 31a and the second n + layer 31b is, for example, 5×10 18 cm -3 or more. The anode electrode 32 and the cathode electrode 33 are made of, for example, Ti, Al, Ti / Al, or Ti / Au. Further, the cathode electrode 33 is preferably formed by combining Ag, Pd, or Cu with the above materials in order to enhance the reflection efficiency of the light L.

[0052] The first n +Layer 31a and the second n + In order to reduce the distance d2 between layers 31b, the high-resistance layer 30 needs to be made thin. In this case, a thin high-resistance layer 30 can be easily obtained by forming the high-resistance layer 30 by epitaxial growth. For this reason, the first n + Layer 31a consists of a substrate, and a high-resistance layer 30 and a second n + Layer 31b is the first n + It is preferable that the material consists of an epitaxial film with layer 31a as a base.

[0053] (Effects of the embodiment) According to the photoconductive switches 1 to 3 of the first to third embodiments described above, the length of the voltage resistance maintenance region can be shortened, effectively reducing costs and heat generation during operation. Furthermore, shortening the length of the voltage resistance maintenance region allows for a reduction in the size of the element.

[0054] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the invention. Furthermore, the components of the above embodiments can be arbitrarily combined without departing from the spirit of the invention. Moreover, the embodiments described above do not limit the invention as claimed. It should also be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. [Explanation of Symbols]

[0055] 1-3...Photoconductive switch, 10...Semiconductor layer, 11a...First n + Region, 11b... Second n + Region, 12, 32... Anode electrode, 13, 33... Cathode electrode, 14... Passivation film, 15... Channel, 20... Light-reflecting film, 30... High-resistivity layer, 31a... First n + Layer, 31b...the second n + Layer, 34...transparent electrode

Claims

1. The first n consists of a gallium oxide-based semiconductor containing donor impurities. ＋ Layers, The first n ＋ A high-resistance layer made of a gallium oxide semiconductor containing Fe is located on top of the layer, A second n made of a gallium oxide-based semiconductor containing donor impurities is placed on the aforementioned high-resistance layer. ＋ Layers, The second n ＋ The transparent electrode on top of the layer, The second n ＋ The layer has an anode electrode connected via the transparent electrode, The first n ＋ A cathode electrode, which also serves as a light-reflecting film, is formed on the lower surface of the layer, A photoconductive switch equipped with [a specific feature].

2. The first n ＋ The layers consist of a substrate, The high-resistance layer and the second n ＋ layer are made of an epitaxial film having the first n ＋ layer as a base. The photoconductive switch according to claim 1.

3. The first n ＋ Layer and the second n ＋ The distance between layers is within the range of 2 μm or more and 100 μm or less, or within the range of 10 μm or more and 500 μm or less. The photoconductive switch according to claim 1 or 2.

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