JP2024014143A - Optical conduction switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical conduction switch which can suppress the cost and heat generation at the time of the operation more effectively.

SOLUTION: According to an embodiment, an optical conduction switch 1 includes: a semiconductor layer 10 made of an oxide gallium-based semiconductor, the semiconductor layer including Fe and thus having a higher resistance; an anode electrode 12 and a cathode electrode 13 connected to the upper surface of the semiconductor layer 10; a first n⁺ region 11a as a region including a doner impurity in the semiconductor layer 10, the first n⁺ region 11a being connected to an anode electrode 12; and a second n⁺ region 11b as the region including the doner impurity in the semiconductor layer 10, the second n⁺ region 11b connected to the cathode electrode 13 and being separate from the first n⁺ region 11a.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to photoconductive switches.

Conventionally, photoconductive switches that can be switched from an off state to an on state by irradiation with light are known (see Non-Patent Document 1). A photoconductive switch has an excellent response speed, which is much faster than, for example, a MOSFET switch.

In the photoconductive switch described in Non-Patent Document 1, SiC whose resistance has been increased by adding V (vanadium) is used as a semiconductor layer. In a photoconductive switch, in order to ensure breakdown voltage, the breakdown voltage maintenance region (the region between the n ⁺ region to which the anode electrode is connected and the n ⁺ region to which the cathode electrode is connected) is adjusted according to the resistivity of the semiconductor layer. The length and cross-sectional area are set.

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, p.p. 1837- 1842.

Conventionally known photoconductive switches, including the photoconductive switch using SiC described in Non-Patent Document 1, cannot generate enough carriers without using a very powerful and expensive laser due to the volume of their breakdown voltage maintenance area. However, there is a problem in that the channel cannot be generated, resulting in increased conduction loss and increased heat generation. That is, it has been difficult to put the conventional photoconductive switch into practical use from the viewpoint of cost or heat generation.

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

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

[1] A semiconductor layer made of a gallium oxide-based semiconductor and made highly resistive by containing Fe, an anode electrode and a cathode electrode connected to the upper surface of the semiconductor layer, and a donor impurity in the semiconductor layer. a first n ⁺ region connected to the anode electrode; and a region containing donor impurities in the semiconductor layer, separated from the first n ⁺ region and connected to the cathode electrode. a second n ⁺ region.
[2] The photoconductive switch according to [1] above, wherein a light reflective film is provided on the lower surface of the semiconductor layer.
[3] The above [1] or the distance between the first n ⁺ region and the second n ⁺ region 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 [2].
[4] A first n ⁺ layer made of a gallium oxide semiconductor containing donor impurities, a high resistance layer made of a gallium oxide semiconductor containing Fe on the first n ⁺ layer, and the high resistance layer a second n ⁺ layer made of a gallium oxide semiconductor containing donor impurities, a transparent electrode on the second n+ layer, and a second n ⁺ layer connected to the second n ⁺ layer through the transparent electrode. A photoconductive switch comprising a connected anode electrode and a cathode electrode formed on the lower surface of the first n ⁺ layer and serving as a light reflection film.
[5] In the above [4], 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 with the first n ⁺ layer as a base. Photoconductive switch as described.
[6] The above [4] or the distance between the first n ⁺ layer and the second n ⁺ layer 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 [5].

According to the present invention, it is possible to provide a photoconductive switch that can more effectively suppress costs and heat generation during operation.

FIGS. 1A and 1B are vertical cross-sectional views of a photoconductive switch according to a first embodiment of the present invention. In FIG. 2, the cross-sectional area of the breakdown voltage maintaining region is 1 cm ² and has a semiconductor layer made of Ga ₂ O ₃ , 6H-SiC, GaAs, or Si, and the breakdown voltage is defined as the voltage when the leakage current reaches 10 μA. 2 is a graph showing the relationship between the breakdown voltage maintenance region length and the breakdown voltage value in the photoconductive switch. FIGS. 3A and 3B are vertical cross-sectional views of a photoconductive switch according to a second embodiment of the present invention. FIGS. 4(a) and 4(b) are vertical sectional views of a photoconductive switch according to a third embodiment of the present invention.

[First embodiment]
(Configuration of photoconductive switch)
FIGS. 1A and 1B are vertical 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 including a semiconductor layer made of a gallium oxide semiconductor. FIG. 1(a) shows an off state in which the photoconductive switch 1 is not irradiated with light, and FIG. 1(b) shows an on state in which the photoconductive switch 1 is irradiated with light L. .

The photoconductive switch 1 includes a semiconductor layer 10 made of a gallium oxide-based semiconductor, which has a 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 containing donor impurities in the semiconductor layer 10, which is separated from the first n ⁺ region 11a and connected to the anode electrode 12, and a region containing donor impurities in the semiconductor layer 10, which is separated from the first n ⁺ region 11a. , and a second n ⁺ region 11b connected to the cathode electrode 13.

The gallium oxide semiconductor refers to Ga ₂ O ₃ or Ga ₂ O ₃ to which elements such as Al and In are added. For example, a gallium oxide semiconductor has a composition expressed as (Ga _x Al _y In _(1-x-y) ) ₂ O ₃ (0<x≦1, 0≦y≦1, 0<x+y≦1). have When Al is added to Ga ₂ O ₃ , the band gap is widened, and when In is added, the band gap is narrowed.

Impurities that can increase the resistance of the semiconductor layer 10 made of a gallium oxide semiconductor include Fe, Mg, Zn, H, Li, Be, Na, K, Ca, Rb, Sr, Ba, Cu, Ni, Mn, Examples include Cr and V. Among them, Fe, Mg, and Zn are impurities that have been widely used in the production of high-resistance gallium oxide. In particular, it has been demonstrated that Fe imparts high resistivity to gallium oxide semiconductors, and when the semiconductor layer 10 contains Fe, the resistivity of the semiconductor layer 10 can be increased from 1×10 ¹¹ to 5×10 depending on the Fe concentration. It can be controlled within a range of ¹² Ωcm.

Fe added to a gallium oxide semiconductor forms an impurity level near the conduction band between the conduction band and the valence band of the gallium oxide semiconductor and traps electrons. Become a resistance. Therefore, the portion of the semiconductor layer 10 where the first n ⁺ region 11a and the second n ⁺ region 11b are not provided has a high resistance, and when the light L is not irradiated, the first n ⁺ region No current flows between 11a and second n ⁺ region 11b.

Here, the off-performance of a photoconductive switch is determined by the length and cross-sectional area of the breakdown voltage maintenance region (the region between the n ⁺ region to which the anode electrode is connected and the n ⁺ region to which the cathode electrode is connected), and the resistance of the semiconductor layer. determined by the rate. In the photoconductive switch 1, since the gallium oxide semiconductor constituting the semiconductor layer 10 has a high resistivity, for example, higher resistivity than SiC, the length of the breakdown voltage maintenance region, that is, the first n ⁺ region 11a and the The distance d1 between the two n ⁺ regions 11b can be significantly shortened.

By shortening the length of the breakdown voltage maintenance region, in the photoconductive switch 1, sufficient carriers can be generated in the breakdown voltage maintenance region without using a high-intensity, expensive laser transmitter or the like as a light source for the light L. Therefore, the conduction loss in the on state, that is, the loss of the current flowing through the channel 15, can be greatly reduced, and heat generation can be suppressed. Moreover, by shortening the length of the breakdown voltage maintenance region, the area of the photoconductive switch 1 can be reduced.

A method of setting the distance d1 in order to obtain a predetermined breakdown voltage in the photoconductive switch 1 will be described below. First, the following equation (1) holds true according to Ohm's law. Here, V is the voltage applied between the first n ⁺ region 11a and the second n ⁺ region 11b (between the anode electrode 12 and the cathode electrode 13), and I is the voltage applied between the first n + region 11a and the second n ⁺ region 11b. and the second n ⁺ region 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, that is, the length of the first n+ region 11a and the second n ⁺ region 11a. The distance d1 is between the second n ⁺ regions 11b, and S is the cross-sectional area of the breakdown voltage maintenance region perpendicular to the voltage application direction.

As described above, when the semiconductor layer 10 contains Fe, the resistivity ρ of the semiconductor layer 10 can be controlled within the range of 1×10 ¹¹ to 5×10 ¹² Ωcm depending on the concentration of Fe. Therefore, according to equation (1), for example, when the applied voltage V when a leakage current J (=I/S) of 10 μA/cm ² flows is defined as the withstand voltage, the distance d1 to obtain a withstand voltage of 10 kV is is 2 to 100 μm if the resistivity ρ is within the range of 1×10 ¹¹ to 5×10 ¹² Ωcm. Furthermore, when the applied voltage V when a leakage current J (=I/S) of 10 μA/cm ² flows is defined as the withstand voltage, the distance d1 to obtain a withstand voltage of 50 kV is the resistivity ρ of 1×10 ¹¹ If it is within the range of ~5×10 ¹² Ωcm, it will be 10 to 500 μm.

In FIG. 2, the cross-sectional area of the breakdown voltage maintaining region is 1 cm ² and has a semiconductor layer made of Ga ₂ O ₃ , 6H-SiC, GaAs, or Si, and the breakdown voltage is defined as the voltage when the leakage current reaches 10 μA. 2 is a graph showing the relationship between the breakdown voltage maintenance region length and the breakdown voltage value in the photoconductive switch. Ga ₂ O ₃ , 6H-SiC, GaAs, and Si are all assumed to have high resistance by adding impurities, and their respective resistivities are set to 3.0×10 ¹² Ωcm and 1.0×10 ¹¹ Ωcm, 1.0×10 ⁸ Ωcm, and 1.0×10 ⁷ Ωcm.

Here, the applied voltage when a leakage current of 10 μA flows is defined as the "breakdown voltage", and the length of the breakdown voltage maintenance region necessary to maintain the breakdown voltage (the first n ⁺ region 11a and the second (corresponding to the distance d1 between the n ⁺ regions 11b) is defined as the "withstand voltage maintenance region length".

FIG. 2 shows that the length of the breakdown voltage maintenance region for obtaining a predetermined breakdown voltage in a photoconductive switch having a semiconductor layer made of Ga ₂ O ₃ is the same as that of a photoconductive switch having a semiconductor layer made of 6H-SiC, GaAs, or Si. This shows that it is much smaller than that in .

The semiconductor layer 10 is typically a substrate made of a gallium oxide 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 ¹⁸ cm ⁻³ or more and 1×10 ²⁰ cm ⁻³ or less.

In addition ^, in ^the photoconductive switch 1, as shown in FIG. By irradiating L from above, electrons in a region between the first n ⁺ region 11a and the second n ⁺ region 11b on the surface of the semiconductor layer 10 are excited, and a channel 15 is formed. This allows current to flow between the first n ⁺ region 11a and the second n ⁺ region 11b via the channel 15.

Here, the light L irradiated to the photoconductive switch 1 is light with energy larger than the bandgap of the gallium oxide semiconductor constituting the semiconductor layer 10, for example, when the semiconductor layer 10 is made of Ga ₂ O ₃ , the wavelength is is light with a wavelength of 250 nm or less. In this case, since the irradiated light L is absorbed by the semiconductor layer 10, the channel 15 is formed only near the surface thereof.

As described above, in the photoconductive switch 1, the length of the breakdown voltage maintenance region can be significantly shortened. As the length of the breakdown voltage maintenance region becomes shorter, the volume of the region to which the light L is irradiated to form the channel 15 becomes smaller, so that the energy of the irradiated light L can be reduced by an order of magnitude.

The first n ⁺ region 11a and the second n ⁺ region 11b are formed by, for example, implanting donor impurities such as Si or Sn into the semiconductor layer 10. The donor concentration of the first n ⁺ region 11a and the second n ⁺ region 11b is, for example, 5×10 ¹⁸ cm ⁻³ or more.

The anode electrode 12 and the cathode electrode 13 are made of, for example, Ti, Al, Ti/Al, or Ti/Au. Further, in order to prevent the occurrence of interface leakage current and damage to the semiconductor layer 10 due to application of a high voltage between the anode electrode 12 and the cathode electrode 13, it is preferable to provide a passivation film 14 covering the surface of the semiconductor layer 10. The passivation film 14 is made of an insulator such as SiO ₂ .

[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 reflecting film 20 is provided on the lower surface of the semiconductor layer 10. different from. Descriptions of the same points as in the first embodiment will be omitted or simplified.

(Configuration of photoconductive switch)
FIGS. 3A and 3B are vertical cross-sectional views of a photoconductive switch 2 according to a second embodiment of the invention. The photoconductive switch 2 is a horizontal photoconductive switch including a semiconductor layer made of a gallium oxide semiconductor. 3(a) shows an off state in which the photoconductive switch 2 is not irradiated with light, and FIG. 3(b) shows an on state in which the photoconductive switch 2 is irradiated with light L. .

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 the light L traveling through the semiconductor layer 10 toward the lower surface. The light reflecting film 20 is made of a metal such as Ag, Pd, Cu, or Au, for example.

The light L irradiated to the photoconductive switch 2 has an energy smaller than the bandgap of the gallium oxide semiconductor constituting the semiconductor layer 10, and has an energy that is smaller than the bandgap of the gallium oxide semiconductor constituting the semiconductor layer 10, and is located between the lower end of the conduction band of the gallium oxide semiconductor and the impurity contained in the semiconductor layer 10. This is light whose energy is greater than the energy difference with the impurity level (trap level). For example, when the semiconductor layer 10 is made of Ga ₂ O ₃ and contains Fe, the light L has a wavelength of 300 nm or more and 1550 nm or less.

Therefore, the light L does not excite electrons from the valence band to the conduction band of the gallium oxide semiconductor, but it moves electrons from the impurity level in the band gap of the gallium oxide semiconductor to the conduction band of the gallium oxide semiconductor. is excited to form a channel 15. In this case, the irradiated light L travels through the semiconductor layer 10 while being gradually absorbed. Then, by being reflected by the light reflection film 20 on the lower surface of the semiconductor layer 10, the light L spreads over a wide range of the semiconductor layer 10, and forms a channel 15 over a wide range of the semiconductor layer 10.

The longer the wavelength of the light L, the lower the manufacturing cost of the laser oscillator that emits the 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 the like, and high-intensity laser oscillators in this wavelength range are easily available. Therefore, the depth of the impurity level from the lower end of the gallium oxide semiconductor conductor is preferably shallower than 1.46 eV. As described above, Fe added to the gallium oxide based 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 based semiconductor. For example, Fe contained in Ga ₂ O ₃ forms an impurity level at a position approximately 0.7 to 0.9 eV from the lower end of the conduction band of Ga ₂ O ₃ . For this reason, it is preferable that the semiconductor layer 10 contains Fe.

In the photoconductive switch 2, since the channel 15 is formed over a wide range, for example, the entire semiconductor layer 10, the conduction resistance in the on state can be more effectively reduced.

[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. Descriptions of the same points as in the first embodiment will be omitted or simplified.

(Configuration of photoconductive switch)
FIGS. 4A and 4B 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 including a semiconductor layer made of a gallium oxide semiconductor. 4(a) shows an off state in which the photoconductive switch 3 is not irradiated with light, and FIG. 4(b) shows an on state in which the photoconductive switch 3 is irradiated with light L. .

The photoconductive switch 3 includes a first n ⁺ layer 31a made of a gallium oxide semiconductor containing donor impurities, and a high resistance layer 30 made of a gallium oxide semiconductor containing impurities on the first n ⁺ layer 31a. , a second n ⁺ layer 31b made of a gallium oxide semiconductor containing donor impurities on the high resistance layer 30, a transparent electrode 34 on the second n ⁺ layer 31b, and a second n ⁺ layer 31b. The anode electrode 32 is connected to the substrate via a transparent electrode 34, and the cathode electrode 33 is formed on the lower surface of the first n ⁺ layer 31a and serves as a light reflecting film.

Similar to the semiconductor layer 10 of the photoconductive switch 1 according to the first embodiment, the high resistance layer 30 made of a gallium oxide semiconductor containing impurities for high resistance has high resistance and is not irradiated with light L. In this state, no current flows between the first n ⁺ layer 31a and the second n ⁺ layer 31b. The resistivity of the high resistance layer 30 is, for example, 1×10 ¹¹ to 5×10 ¹² Ωcm when the high resistance layer 30 contains Fe.

In the photoconductive switch 3, as in the photoconductive switch 1, the gallium oxide semiconductor constituting the high resistance layer ³⁰ has high electrical resistance. The distance d2 between the second n ⁺ layers 31b can be significantly shortened.

By shortening the length of the breakdown voltage maintenance region, the photoconductive switch 3 can generate a channel 35 with sufficient carriers without using a high-intensity, expensive laser oscillator or the like as a light source for the light L. Therefore, the conduction loss in the on state, that is, the loss of the current flowing through the channel 35, can be greatly reduced, and heat generation can be suppressed. Moreover, by shortening the length of the breakdown voltage maintenance region, the thickness of the photoconductive switch 3 can be reduced.

The distance d2 for obtaining a predetermined breakdown voltage in the photoconductive switch 3 can be set similarly to the distance d1 of the photoconductive switch 1 according to the first embodiment. That is, it can be calculated from equation (1) by setting the length L of the breakdown voltage maintenance region to the distance d2.

When the high resistance layer 30 contains Fe, the resistivity ρ of the high resistance layer 30 can be controlled within the range of 1×10 ¹¹ to 5×10 ¹² Ωcm depending on the Fe concentration. Therefore, according to formula (1), for example, when the applied voltage V when a leakage current J (=I/S) of 10 μA/cm ² flows is defined as the withstand voltage, the distance d2 required to obtain a withstand voltage of 10 kV is is 2 to 100 μm if the resistivity ρ is within the range of 1×10 ¹¹ to 5×10 ¹² Ωcm. Furthermore, when the applied voltage V when a leakage current J (=I/S) of 10 μA/cm ² flows is defined as the withstand voltage, the distance d2 to obtain a withstand voltage of 50 kV has a resistivity ρ of 1×10 ¹¹ If it is within the range of ~5×10 ¹² Ωcm, it will be 10 to 500 μm.

Further, the relationship between the breakdown voltage maintenance region length and the breakdown voltage value shown in FIG. 2 also holds true in a vertical photoconductive switch 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 Ga ₂ O ₃ is different from that in a photoconductive switch having a semiconductor layer made of 6H-SiC, GaAs, or Si. It's much smaller in comparison. 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.

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.

In addition, in the photoconductive switch 3, as shown in FIG. 4(b), the high resistance layer 30 is irradiated with light L such as a laser beam from above through the transparent electrode 34 and the second n ⁺ layer 31b. , electrons in the high resistance layer 30 are excited and a channel 35 is formed. This allows current to flow between the second n ⁺ layer 31b and the first n ⁺ layer 31a via the channel 35. At this time, the current flowing out from the anode electrode 32 spreads in the plane direction via 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.

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 the lower end of the conduction band of the gallium oxide-based semiconductor and the high-resistance layer 30 This is light whose energy is greater than the energy difference between the impurity level and the impurity level of the impurities contained in the . For example, when the high resistance layer 30 is made of Ga ₂ O ₃ and contains Fe, the light L has a wavelength of 300 nm or more and 1550 nm or less.

Therefore, the light L does not excite electrons from the valence band to the conduction band of the gallium oxide semiconductor, but it moves from the Fe impurity level in the band gap of the gallium oxide semiconductor to the conduction band of the gallium oxide semiconductor. The channel 35 is formed by exciting electrons. In this case, the irradiated light L travels through the high resistance layer 30 while being gradually absorbed. Then, by being reflected by the cathode electrode 33 which also serves as a light reflection film on the lower surface of the first n ⁺ layer 31a, the light L spreads over a wide range of the high resistance layer 30, and forms a channel across a wide range of the high resistance layer 30, for example, the entire high resistance layer 30. form 35.

As described above, in the photoconductive switch 3, the length of the breakdown voltage maintenance region can be significantly shortened. As the length of the breakdown voltage maintenance region becomes shorter, the volume of the region to which the light L is irradiated to form the channel 35 becomes smaller, so that the energy of the irradiated light L can be reduced by an order of magnitude.

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. Moreover, in order to improve the reflection efficiency of the light L, the cathode electrode 33 is preferably formed by combining the above-mentioned materials with Ag, Pd, and Cu.

In order to reduce the distance d2 between the first n ⁺ layer 31a and the second n ⁺ layer 31b, it is necessary to make the high resistance layer 30 thin. In this case, by forming the high resistance layer 30 by epitaxial growth, the thin high resistance layer 30 can be easily obtained. For this reason, it is preferable that the first n ⁺ layer 31a is made of a substrate, and the high resistance layer 30 and the second n ⁺ layer 31b are made of an epitaxial film with the first n ⁺ layer 31a as a base.

(Effects of embodiment)
According to the photoconductive switches 1 to 3 according to the first to third embodiments described above, the length of the breakdown voltage maintenance region can be shortened to effectively suppress cost and heat generation during operation. Furthermore, by shortening the length of the breakdown voltage maintaining region, the size of the element can be reduced.

Although the 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 gist of the invention. Moreover, the constituent elements of the embodiments described above can be arbitrarily combined without departing from the spirit of the invention. Furthermore, the embodiments described above do not limit the claimed invention. Furthermore, it should be noted that not all combinations of features described in the embodiments are essential for solving the problems of the invention.

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 reflective film, 30... High resistance layer, 31a... First n ⁺ layer, 31b... Second n ⁺ layer, 34... Transparent electrode

Claims (6)

a semiconductor layer made of a gallium oxide-based semiconductor and made highly resistant by containing Fe;
an anode electrode and a cathode electrode connected to the upper surface of the semiconductor layer;
a first n ⁺ region that is a region containing donor impurities in the semiconductor layer and connected to the anode electrode;
a second n ⁺ region that is a region containing donor impurities in the semiconductor layer, separated from the first n ⁺ region and connected to the cathode electrode;
A photoconductive switch with a light reflecting film is provided on the lower surface of the semiconductor layer;
A photoconductive switch according to claim 1. The distance between the first n ⁺ region and the second n ⁺ region 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. a first n ⁺ layer made of a gallium oxide semiconductor containing donor impurities;
a high resistance layer made of a gallium oxide semiconductor containing Fe on the first n ⁺ layer;
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 via the transparent electrode;
a cathode electrode that also serves as a light reflecting film, formed on the lower surface of the first n ⁺ layer;
A photoconductive switch with the first n ⁺ layer comprises a substrate;
The high resistance layer and the second n ⁺ layer are made of an epitaxial film with the first n ⁺ layer as a base.
A photoconductive switch according to claim 4. The distance between the first n ⁺ layer and the second n ⁺ layer 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 4 or 5.