Ultraviolet light-receiving element, ultraviolet ray detection type fire alarm and optical switching transistor

Abstract

To provide an ultraviolet light-receiving element capable of detecting ultraviolet rays such as ultraviolet rays generated from flames with high light reception sensitivity and further capable of performing low voltage operation, and an ultraviolet ray detection type fire alarm using the same.SOLUTION: An ultraviolet light-receiving element comprises: an undoped AlxGa1-xN layer (0≤x<1) 11; an insulator film (13) which is provided on a light-receiving region of the undoped AlxGa1-xN layer; AlyGa1-yN layers (x<y<1) (13) provided on undoped AlxGa1-xN layers (12) in portions on both sides of the insulator film; and a source electrode (15) and a drain electrode (16) provided on the AlyGa1-yN layers in the portions on both the sides of the insulator film. A two-dimensional electron gas (14) is formed in the undoped AlxGa1-xN layer in a portion in the vicinity of a heterointerface between the undoped AlxGa1-xN layer and the AlyGa1-yN layer. An ultraviolet ray detection type fire alarm is configured using the ultraviolet light-receiving element.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet light receiving element, an ultraviolet light detection fire alarm, and an optical switching transistor, and more particularly to an ultraviolet light receiving element using a gallium nitride (GaN) semiconductor suitable for use in detecting ultraviolet light emitted from flames at, for example, a fire scene, an ultraviolet light detection fire alarm using this ultraviolet light receiving element, and an optical switching transistor that controls current using ultraviolet light as an optical signal. [Background technology]

[0002] During a fire, flames emit weak ultraviolet rays. Therefore, if this ultraviolet light from flames can be detected, fires can be detected early and damage caused by fires can be minimized.

[0003] Conventional UV light-receiving elements include pin photodiodes and avalanche photodiodes. However, pin photodiodes have the drawback of low UV sensitivity, while avalanche photodiodes have the drawback of requiring a high reverse bias voltage of several hundred volts. Some UV light-receiving elements have a transistor structure, where light is incident on the gate, acting as an optical gate (see Patent Documents 1 and 2). The UV light-receiving element in Patent Document 1 has a p-type GaN layer in the gate electrode, which suppresses the generation of two-dimensional electron gas directly below the gate electrode and increases the resistance between the source and drain electrodes. When light is irradiated near the gate electrode, carriers are generated, and two-dimensional electron gas is generated directly below the gate electrode, dramatically reducing the resistance between the source and drain electrodes. UV light is detected by this change in resistance. Patent Document 2 describes a structure that reduces the two-dimensional electron gas concentration directly below the AlGaN layer by providing a Schottky junction between the source and drain electrodes. When UV light is irradiated here, carriers are generated, the two-dimensional electron gas concentration increases, and the resistance decreases. However, in the ultraviolet light receiving elements of Patent Documents 1 and 2, the two-dimensional electron gas is depleted by a p-type GaN layer or a Schottky metal, which blocks the area where ultraviolet light is incident, resulting in a problem of reduced light receiving sensitivity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007 / 135739 [Patent Document 2] Patent No. 6506453 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an ultraviolet light receiving element that can detect ultraviolet light, such as ultraviolet light emitted from a flame, with high light receiving sensitivity and that can be operated at a low voltage.

[0006] Another object of the present invention is to provide a high-performance ultraviolet detection fire alarm using the above-mentioned excellent ultraviolet light receiving element.

[0007] A further object of the present invention is to provide an optical switching transistor which can control current by using ultraviolet light as an optical signal and which can operate at a low voltage. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides: Undoped Al x Ga 1-x N layers (0≦x<1) and The above undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al on the N layer y Ga 1-y N layer(x <y<1)と、 The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The above undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x This is an ultraviolet light-receiving element in which two-dimensional electron gas is formed in the N layer.

[0009] In this UV photodetector, undoped Al x Ga1-x The Al composition x of the N layer is determined according to the wavelength of the ultraviolet light to be received within the range of 0 ≦ x < 1. Also, Al y Ga 1-y The Al composition y of the N layer is within the range of x < y < 1, and for undoped Al x Ga 1-x N layer and Al y Ga 1-y In the vicinity of the heterointerface between the N layer and the undoped Al x Ga 1-x N layer, it is determined such that a two-dimensional electron gas (2DEG) is formed. For example, in applications for detecting ultraviolet light generated from a flame, since the emission peak wavelength of the flame overlaps with the short wavelength side of the solar spectrum, it is necessary to receive ultraviolet light near a wavelength of 265 nm, which is shorter than 280 nm where the solar spectrum intensity is almost 0. However, in order to receive ultraviolet light with a wavelength of 265 nm and not absorb ultraviolet light with a wavelength of 300 nm or more, the Al composition x of the undoped Al x Ga 1-x N layer is selected to be about 0.35. Also, in this way, for undoped Al x Ga 1-x When the Al composition x of the N layer is about 0.35, Al y Ga 1-y The Al composition y of the N layer is selected to be about 0.6, for example. The thickness of the undoped Al x Ga 1-x N layer of the light-receiving region is appropriately selected within a range where it can sufficiently absorb ultraviolet light, but generally it is selected to be 0.5 μm or more, for example, about 1 μm. Al y Ga 1-y The thickness of the N layer is selected as needed and is not particularly limited, but generally it is selected to be 10 nm or more, typically 20 nm or more. Al y Ga 1-y The N layer may be undoped, n-type, or p-type (including, for example, the case where a very small amount of Mg is doped as an acceptor (p-type impurity)).

[0010] Undoped Al x Ga 1-xThe insulating film provided on the light receiving region of the N layer is not particularly limited as long as it is transparent to the ultraviolet light to be received, and is selected as needed, for example, an SiO2 film, a SiN film (including an Si3N4 film), an SiON film, etc. The thickness of this insulating film is not particularly limited, and is selected as needed. The planar shape of the insulating film is selected as needed, and is not particularly limited, for example, a stripe shape, a zigzag shape, or an annular shape such as a circle or a polygon (triangle, square, pentagon, hexagon, etc.). When the insulating film has an annular shape, Al y Ga 1-y The N layer is provided on the inside and outside of this insulating film.

[0011] This UV light receiving element has a photo-gate type transistor structure, and when in operation, a voltage is applied between the source electrode and the drain electrode so that the drain electrode side has a higher potential. In this UV light receiving element, when UV light is not incident on the light receiving region, the insulating film and undoped Al x Ga 1-x In this state, there are no carriers at the interface between the N layer and the undoped Al layer on both sides of the insulating film. x Ga 1-x N layer and Al y Ga 1-y Undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x Since there is no electron movement between the two-dimensional electron gas formed in the N layer, no current flows between the source and drain electrodes, and the resistance between the source and drain electrodes is high. x Ga 1-x When ultraviolet light with photon energy exceeding the band gap of the N layer is incident, the ultraviolet light passes through the insulating film and is absorbed by the undoped Al x Ga 1-x The electrons are absorbed by the N layer, generating electron-hole pairs. x Ga 1-x Since a sharp bending of the energy band occurs at the interface between the insulating film and the undoped AlN layer, the holes of the electron-hole pairs thus generated are transported between the insulating film and the undoped AlN layer. x Ga1-x The electrons in the electron-hole pairs move to the interface between the insulating film and the undoped AlN layer, accumulate, and recombine with electrons supplied from the two-dimensional electron gas on the source electrode side. x Ga 1-x The resistance between the source and drain electrodes decreases as a result of the current flowing between the source and drain electrodes due to the electrons being attracted to the drain electrode near the interface with the N layer. By detecting this change in the resistance between the source and drain electrodes, the intensity of the ultraviolet light can be identified.

[0012] The present invention also provides: an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; The ultraviolet light receiving element has the following structure.

[0013] The n-type GaN layer is typically doped with Si as a donor (n-type impurity). The p-type GaN layer is typically doped with Mg as an acceptor (p-type impurity). The thickness of the undoped GaN layer in the light-receiving region is appropriately selected so as to sufficiently absorb ultraviolet light, but is generally selected to be 0.5 μm or more, for example, approximately 1 μm. The thickness of the n-type or p-type GaN layer is selected as needed and is not particularly limited, but is generally selected to be 10 nm or more, typically 20 nm or more.

[0014] This UV detector, like the UV detector described above, has a photo-gate transistor structure. During operation, a voltage is applied between the source and drain electrodes so that the drain electrode is at a higher potential. In this UV detector, when UV light is not incident on the light-receiving region, no carriers exist at the interface between the insulating film and the undoped GaN layer. In this state, electrons do not move between the n-type GaN layers on both sides of the insulating film, and therefore no current flows between the source and drain electrodes, resulting in high resistance between the source and drain electrodes. When UV light with photon energy exceeding the band gap of the undoped GaN layer enters the light-receiving region, the UV light penetrates the insulating film and is absorbed by the undoped GaN layer, generating electron-hole pairs. Because of the sharp energy band bending at the interface between the insulating film and the undoped GaN layer, the holes of the electron-hole pairs thus generated migrate to and accumulate at the interface between the insulating film and the undoped GaN layer. If the n-type or p-type GaN layer is an n-type GaN layer, they recombine with electrons supplied from the n-type GaN layer on the source electrode side. The electrons of the electron-hole pairs are attracted to the drain electrode near the interface between the insulating film and the undoped GaN layer, causing a current to flow between the source and drain electrodes, reducing the resistance between them. The intensity of UV light can be determined by detecting this change in resistance between the source and drain electrodes. On the other hand, if the n-type or p-type GaN layer is a p-type GaN layer, holes are supplied from the p-type GaN layer on the source electrode side to the undoped GaN layer and ultimately flow to the p-type GaN layer on the drain electrode side. The electrons of the electron-hole pairs are attracted to the source electrode near the interface between the insulating film and the undoped GaN layer, where they recombine with the holes in the p-type GaN layer. This current flows between the source and drain electrodes, reducing the resistance between them, allowing the intensity of UV light to be determined in the same manner as described above.

[0015] In the invention of this ultraviolet light receiving element, the same as described above in relation to the invention of the ultraviolet light receiving element applies to matters other than those mentioned above, unless it is contrary to the nature of the invention.

[0016] The present invention also provides: At least one ultraviolet light receiving element is included, The ultraviolet light receiving element is Undoped Al x Ga 1-x N layers (0≦x<1) and The above undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al on the N layer y Ga 1-y N layer(x <y<1)と、 The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The above undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x An ultraviolet light-receiving element in which two-dimensional electron gas is formed in the N layer It is an ultraviolet detection fire alarm.

[0017] The present invention also provides: At least one ultraviolet light receiving element is included, The ultraviolet light receiving element is an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; An ultraviolet light receiving element having It is an ultraviolet detection fire alarm.

[0018] These ultraviolet detection fire alarms can be easily constructed by simply using the ultraviolet light receiving element described above as the ultraviolet light receiving element of a conventionally known ultraviolet detection fire alarm. In these ultraviolet detection fire alarm inventions, the same explanations as in the above ultraviolet light receiving element inventions are also applicable.

[0019] The present invention also provides: Undoped Al x Ga 1-x N layers (0≦x<1) and The above undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al on the N layer y Ga 1-y N layer(x <y<1)と、 The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The above undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x This is an optical switching transistor in which two-dimensional electron gas is formed in the N layer.

[0020] The present invention also provides: an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; The optical switching transistor has the following structure.

[0021] In these optical switching transistors, undoped Al x Ga 1-x Ultraviolet light with photon energy exceeding the band gap of the N layer or undoped GaN layer is used as an optical signal, and this optical signal is made to enter the light-receiving region. In these optical switching transistor inventions, the same as described in relation to the ultraviolet light-receiving element invention above applies except for the above, unless it is contrary to the nature of the invention. [Effects of the Invention]

[0022] According to this invention, in the ultraviolet light receiving element, the undoped Al in the light receiving region x Ga 1-x By providing an insulating film on the N layer or undoped GaN layer and configuring it so that ultraviolet rays are incident through this insulating film, it is possible to realize an ultraviolet light receiving element that can detect ultraviolet rays such as those emitted from flames with high light receiving sensitivity and can also operate at low voltage. Furthermore, using this excellent ultraviolet light receiving element, a high-performance ultraviolet detection type fire alarm can be realized. Also, in the optical switching transistor, the undoped Al in the light receiving region x Ga 1-x By providing an insulating film on the N layer or undoped GaN layer and allowing ultraviolet light to enter through this insulating film, it is possible to realize an optical switching transistor that can control current using ultraviolet light as an optical signal and can also operate at low voltage. [Brief explanation of the drawings]

[0023] [Figure 1A] 1 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 1B] 1 is a plan view showing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view for explaining the operation of the GaN-based ultraviolet light receiving element according to the first embodiment of the present invention. [Figure 3A]1 is a schematic diagram showing an energy band diagram immediately below an insulating film of the GaN-based ultraviolet light receiving element according to the first embodiment of the present invention when not receiving ultraviolet light. [Figure 3B] 1 is a schematic diagram showing an energy band diagram immediately below an insulating film of the GaN-based ultraviolet light receiving element according to the first embodiment of the present invention when receiving ultraviolet light. [Figure 4] FIG. 2 is a schematic diagram for explaining the operation of the GaN-based ultraviolet light receiving element according to the first embodiment of the present invention. [Figure 5A] 1A to 1C are cross-sectional views illustrating a method for manufacturing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 5B] 1A to 1C are cross-sectional views illustrating a method for manufacturing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 5C] 1A to 1C are cross-sectional views illustrating a method for manufacturing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 5D] 1A to 1C are cross-sectional views illustrating a method for manufacturing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 5E] 1A to 1C are cross-sectional views illustrating a method for manufacturing a GaN-based ultraviolet light receiving element according to a first embodiment of the present invention. [Figure 6] FIG. 3 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a second embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a third embodiment of the present invention. [Figure 8] FIG. 10 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a fourth embodiment of the present invention. [Figure 9] FIG. 10 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a fifth embodiment of the present invention. [Figure 10A] FIG. 10 is a cross-sectional view showing a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 10B] FIG. 10 is a plan view showing a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 11A]FIG. 13 is a plan view showing a prototype example of a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 11B] FIG. 13 is a plan view showing the planar shape of a prototype example of a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 12] 13 is a photograph substituted for a drawing showing a prototype example of a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 13] FIG. 13 is a schematic diagram showing a measurement system used to measure a prototype example of a GaN-based ultraviolet light receiving element according to a sixth embodiment of the present invention. [Figure 14] FIG. 20 is a schematic diagram showing current-voltage characteristics before and after ultraviolet irradiation of a prototype example of a GaN-based ultraviolet light receiving element according to the sixth embodiment of the present invention. [Figure 15] FIG. 13 is a cross-sectional view showing a GaN-based optical switching transistor according to a seventh embodiment of the present invention. [Figure 16] FIG. 13 is a cross-sectional view showing a GaN-based optical switching transistor according to an eighth embodiment of the present invention. [Figure 17] FIG. 13 is a cross-sectional view showing a GaN-based optical switching transistor according to a ninth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, modes for carrying out the invention (hereinafter referred to as "embodiments") will be described.

[0025] First Embodiment [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to a first embodiment will be described.

[0026] 1A and 1B show this GaN-based ultraviolet light receiving element, with FIG. 1A being a cross-sectional view and FIG. 1B being a plan view. As shown in FIG. 1A and FIG. 1B, this GaN-based ultraviolet light receiving element is made of undoped Al x Ga 1-xA stripe-shaped insulating film 12 is provided on the light-receiving region of the N layer 11, and undoped Al is formed on both sides of the insulating film 12. x Ga 1-x An insulating film 12 is sandwiched between the Al layer 11 and the N layer 11. y Ga 1-y In FIG. 1A, the undoped Al layer 13 is stacked on the insulating film 12. x Ga 1-x A shallow groove is provided in the N layer 11, and an insulating film 12 is provided in this groove. However, if no such groove is provided, a flat undoped Al x Ga 1-x An insulating film 12 may be provided on the N layer 11. On both sides of the insulating film 12, undoped Al x Ga 1-x N layer 11 and Al y Ga 1-y Undoped Al in the vicinity of the heterointerface with the N layer 13 x Ga 1-x A two-dimensional electron gas (2DEG) 14 (electrons are shown by ● in FIG. 1A) is formed in the N layer 11. When no ultraviolet light is incident, the insulating film 12 and the undoped Al x Ga 1-x There are no carriers near the interface with the N layer 11. y Ga 1-y A source electrode 15 is provided on the N layer 13, and the Al y Ga 1-y A drain electrode 16 is provided on the N layer 13. The source electrode 15 and the drain electrode 16 are formed by insulating film 12 on both sides of the Al y Ga 1-y They are in ohmic contact with the 2DEG 14 via the N layer 13. The source electrode 15 and the drain electrode 16 may basically be made of any material as long as they can make ohmic contact with the 2DEG 14, but for example, they may be made of a Ti / Al / Ti laminated film or a Ti / Al / Ti / Ni / Au laminated film.

[0027] Undoped Al x Ga 1-xThe Al composition x of the N layer 11 is determined according to the wavelength of the ultraviolet light to be received within the range of 0 ≦ x < 1. Specifically, for example, when the wavelength of the ultraviolet light to be received is 265 nm and ultraviolet light with a wavelength of 300 nm or more is not to be received, x is selected to be about 0.35. Al y Ga 1-y The Al composition y of the N layer 11 is undoped Al within the range of x < y < 1 x Ga 1-x N layer 11 and Al y Ga 1-y In the vicinity of the heterointerface between the N layer 13 and undoped Al x Ga 1-x N layer is determined so that 2DEG14 is formed. For example, undoped Al with x = 0.35 x Ga 1-x For the N layer 11, Al y Ga 1-y The Al composition y of the N layer​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0030] As shown in Fig. 2, in this GaN-based ultraviolet light receiving element, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side has a higher potential. As already mentioned, when ultraviolet light is not incident on the insulating film 12, the insulating film 12 and the undoped Al x Ga 1-x No carriers exist near the interface with the N layer 11. Figure 3A shows the energy band diagram directly below the insulating film 12 in this state. In Figure 3A, the vertical axis represents electron energy, E c is the energy at the bottom of the conduction band, E v is the energy at the top of the valence band, E f As shown in FIG. 2, the insulating film 12 is formed of undoped Al. x Ga 1-x When ultraviolet light having a photon energy exceeding the band gap of the N layer 11 is incident, it passes through the insulating film 12 and is converted into undoped Al. x Ga 1-x The electrons of the electron-hole pairs are thus generated by the incidence of ultraviolet light on the N layer 11, generating electron-hole pairs. In FIG. 2, the electrons of the electron-hole pairs are indicated by ●, and the holes by ○. FIG. 3B shows an energy band diagram directly below the insulating film 12 when electron-hole pairs are thus generated by the incidence of ultraviolet light. FIG. 4 shows a three-dimensional energy band diagram. As shown in FIGS. 3B and 4, the insulating film 12 and the undoped Al x Ga 1-x At the interface with the N layer 11, undoped Al x Ga 1-x Since the energy band of the N layer 11 is sharply bent, the holes of the electron-hole pairs move toward the insulating film 12 and are bonded to the insulating film 12 and the undoped Al x Ga 1-xThese electrons accumulate at the interface between the source electrode 15 and the N layer 11. Electrons supplied from the source electrode 15 via the 2DEG 14 recombine with the holes accumulated at this interface. Meanwhile, the electrons of the electron-hole pairs are attracted to the drain electrode 16 and flow into the drain electrode 16 via the 2DEG 14 directly below the drain electrode 16. This causes a current to flow between the source electrode 15 and the drain electrode 16. As a result, the resistance between the source electrode 15 and the drain electrode 16 is significantly reduced. By detecting this change in resistance, the intensity of the incident UV light can be identified.

[0031] [Manufacturing method for GaN-based UV photodetectors] A method for manufacturing the GaN-based ultraviolet light receiving element shown in Figures 1A and 1B will now be described. This GaN-based ultraviolet light receiving element can be easily manufactured by a conventionally known manufacturing method.

[0032] As shown in FIG. 5A, a low-temperature buffer layer 101 such as a GaN buffer layer or an AlN buffer layer is grown on the entire surface of a base substrate 100 by a conventionally known MOCVD (metal organic chemical vapor deposition) method or the like, and then an undoped AlN buffer layer is grown on the base substrate 100. x Ga 1-x N layer 11 and Al y Ga 1-y The N layer 13 is then grown sequentially. The low-temperature buffer layer 101 may be grown by sputtering. The base substrate 100 may be a general substrate conventionally used for growing GaN layers, such as a C-plane sapphire substrate, a Si substrate, a SiC substrate, an AlN substrate, or a GaN substrate.

[0033] Next, as shown in FIG. 5B, the Al y Ga 1-y The N layer 13 is removed by etching. x Ga 1-x This is continued until the upper part of the N layer 11 is etched. The etching is performed by, for example, inductively coupled plasma (ICP)-reactive ion etching (RIE) using chlorine (Cl)-based gas, or photoelectrochemical etching (PEC) using UV light.

[0034] Next, as shown in FIG. 5C, an insulating film 12 such as an SiO2 film is formed on the entire surface by, for example, a CVD (chemical vapor deposition) method.

[0035] Next, the insulating film 12 is etched back by, for example, the RIE method, so that Al y Ga 1-y The insulating film 12 is left only in the area where the N layer 12 has been removed.

[0036] Next, as shown in FIG. 5E, the Al y Ga 1-y A source electrode 15 and a drain electrode 16 are formed on the N layer 12 .

[0037] In this manner, the desired GaN-based ultraviolet light receiving element is manufactured.

[0038] As described above, in the GaN-based ultraviolet light receiving element according to the first embodiment, when ultraviolet light is not incident on the insulating film 12, the insulating film 12 and the undoped Al x Ga 1-x Since no carriers exist near the interface with the N layer 11, and therefore no current flows between the source electrode 15 and the drain electrode 16, the dark current value can be kept low. When ultraviolet light is incident on the insulating film 12, the 2DEG 14 directly below the source electrode 15, the insulating film 12, and the undoped Al x Ga 1-x Current flows efficiently between the source electrode 15 and the drain electrode 16 due to electron-hole pairs generated near the interface with the N layer 11 and the 2DEG 14 directly below the drain electrode 16, resulting in high sensitivity to incident ultraviolet light. Furthermore, this GaN-based ultraviolet light receiving element can be operated satisfactorily with a low voltage, comparable to that of a dry cell, and can be easily manufactured due to its simple structure. This GaN-based ultraviolet light receiving element receives ultraviolet light with a wavelength of 265 nm, for example, and absorbs ultraviolet light with a wavelength of 300 nm or more. x Ga 1-xBy selecting the Al composition x of the N layer 11, ultraviolet rays emitted from flames during a fire can be detected with high light-receiving sensitivity, making it possible to realize a high-performance ultraviolet detection fire alarm at low cost.

[0039] Second Embodiment [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to a second embodiment will be described below, which is shown in FIG.

[0040] As shown in Figure 6, this GaN-based ultraviolet light receiving element differs from the GaN-based ultraviolet light receiving element according to the first embodiment in that the insulating film 12 is formed of a multilayer anti-reflection film in which high-refractive-index insulating films 12a and low-refractive-index insulating films 12b are alternately stacked. Examples of the high-refractive-index insulating film 12a include a SiN film, and examples of the low-refractive-index insulating film 12b include a SiO2 film. Because the insulating film 12 is thus formed of a multilayer anti-reflection film, reflection can be prevented when ultraviolet light is incident on the insulating film 12. Other aspects of this GaN-based ultraviolet light receiving element are the same as those of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0041] [Operation of GaN-based UV photodetectors] The operation of this GaN-based ultraviolet light receiving element is the same as that of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0042] [Manufacturing method for GaN-based UV photodetectors] The manufacturing method of this GaN-based ultraviolet light receiving element is the same as the manufacturing method of the GaN-based ultraviolet light receiving element according to the first embodiment, except that the insulating film 12 is formed of a multilayer antireflection film in which insulating films 12a with high refractive index and insulating films 12b with low refractive index are alternately stacked.

[0043] According to the second embodiment, in addition to being able to obtain the same advantages as the first embodiment, the insulating film 12 is made of a multilayer anti-reflection film, which makes it possible to effectively prevent reflection of incident ultraviolet rays and to effectively utilize the amount of ultraviolet light.

[0044] Third Embodiment [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to the third embodiment will be described below, which is shown in FIG.

[0045] As shown in Figure 7, in this GaN-based ultraviolet light receiving element, a striped insulating film 12 is provided on the light receiving region of a high-resistivity undoped GaN layer 31, and low-resistivity n-type GaN layers 32 are stacked on the undoped GaN layer 31 on both sides of the insulating film 12, sandwiching the insulating film 12. When ultraviolet light is not incident, no carriers are present near the interface between the insulating film 32 and the undoped GaN layer 31. A source electrode 15 is provided on the n-type GaN layer 32 on one side of the insulating film 12, and a drain electrode 16 is provided on the n-type GaN layer 32 on the other side of the insulating film 12. These source electrode 15 and drain electrode 16 are in ohmic contact with the n-type GaN layer 32 on both sides of the insulating film 12.

[0046] [Operation of GaN-based UV photodetectors] The operation of this GaN-based ultraviolet light receiving element will now be described.

[0047] As with the GaN-based UV light receiving element according to the first embodiment, in this GaN-based UV light receiving element, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side has a higher potential. When UV light is not incident on the insulating film 12, no carriers exist near the interface between the insulating film 12 and the undoped GaN layer 31. When UV light with a photon energy exceeding the band gap of the undoped GaN layer 31 is incident on the insulating film 12, it penetrates the insulating film 12 and enters the undoped GaN layer 31, generating electron-hole pairs. The holes of the electron-hole pairs migrate toward the insulating film 12 and accumulate at the interface between the insulating film 12 and the undoped GaN layer 31. Electrons supplied from the source electrode 15 via the n-type GaN layer 32 recombine with the holes accumulated at this interface. Meanwhile, the electrons of the electron-hole pairs are attracted toward the drain electrode 16 and flow into the drain electrode 16 via the n-type GaN layer 32 directly below the drain electrode 16. This allows current to flow between the source electrode 15 and the drain electrode 16. As a result, the resistance between the source electrode 15 and the drain electrode 16 is significantly reduced. By detecting this change in resistance, the intensity of the incident ultraviolet light can be identified.

[0048] [Manufacturing method for GaN-based UV photodetectors] The manufacturing method of this GaN-based ultraviolet light receiving element is undoped Al x Ga 1-x N layer 11 and Al y Ga 1-y The method for manufacturing the GaN-based ultraviolet light receiving element is the same as that of the first embodiment, except that an undoped GaN layer 31 and an n-type GaN layer 32 are grown instead of the N layer 12.

[0049] According to the third embodiment, it is possible to obtain the same advantages as the first embodiment.

[0050] <Fourth embodiment> [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to the fourth embodiment will be described below, which is shown in FIG.

[0051] As shown in FIG. 8, this GaN-based ultraviolet light receiving element has the same configuration as the GaN-based ultraviolet light receiving element according to the third embodiment, except that a p-type GaN layer 33 is used instead of the n-type GaN layer 32.

[0052] [Operation of GaN-based UV photodetectors] The operation of this GaN-based ultraviolet light receiving element will now be described.

[0053] In this GaN-based ultraviolet light-receiving element, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side is at a lower potential. When ultraviolet light is not incident on the insulating film 12, no carriers exist near the interface between the insulating film 12 and the undoped GaN layer 31. When ultraviolet light with photon energy exceeding the band gap of the undoped GaN layer 31 is incident on the insulating film 12, it penetrates the insulating film 12 and enters the undoped GaN layer 31, generating electron-hole pairs. The holes of the electron-hole pairs migrate toward the insulating film 12 and accumulate at the interface between the insulating film 12 and the undoped GaN layer 31. The holes supplied to the undoped GaN layer 31 from the p-type GaN layer 33 directly below the source electrode 15 are attracted toward the drain electrode 16 and flow into the drain electrode 16 via the p-type GaN layer 33 directly below the drain electrode 16. Meanwhile, the electrons of the electron-hole pairs are attracted toward the source electrode 15, flow into the p-type GaN layer 33, and recombine with the holes in the p-type GaN layer 33. This causes a current to flow between the source electrode 15 and the drain electrode 16. As a result, the resistance between the source electrode 15 and the drain electrode 16 is significantly reduced. By detecting this change in resistance, the intensity of the incident ultraviolet light can be identified.

[0054] [Manufacturing method for GaN-based UV photodetectors] The manufacturing method of this GaN-based ultraviolet light receiving element is undoped Al x Ga 1-x N layer 11 and Al y Ga 1-yThe method for manufacturing the GaN-based ultraviolet light receiving element is the same as that of the first embodiment, except that an undoped GaN layer 31 and a p-type GaN layer 33 are grown instead of the N layer 12.

[0055] According to the fourth embodiment, it is possible to obtain the same advantages as the first embodiment.

[0056] Fifth Embodiment [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to the fifth embodiment will be described.

[0057] FIG. 9 is a plan view showing this GaN-based ultraviolet light receiving element. The cross section along line AA in FIG. 9 is the same as FIG. 1A. As shown in FIG. 9, in this GaN-based ultraviolet light receiving element, the source electrode 15 and the drain electrode 16 have comb-like portions 15a and 16a, respectively, and these comb-like portions 15a and 16a are combined with each other. In this case, undoped Al x Ga 1-x The light-receiving region of the N layer 11, and therefore the insulating film 12 thereon, has a zigzag shape that reflects the shapes of the comb-like portions 15a, 16a of the source electrode 15 and the drain electrode 16. Other aspects of this GaN-based ultraviolet light-receiving element are the same as those of the GaN-based ultraviolet light-receiving element according to the first embodiment.

[0058] [Operation of GaN-based UV photodetectors] The operation of this GaN-based ultraviolet light receiving element is the same as that of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0059] [Manufacturing method for GaN-based UV photodetectors] The method for manufacturing this GaN-based ultraviolet light receiving element is y Ga 1-y The method for manufacturing the GaN-based ultraviolet light receiving element is the same as that for the first embodiment, except that the planar shapes of the N layer 13, source electrode 15, and drain electrode 16 differ from those of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0060] According to the fifth embodiment, it is possible to obtain the same advantages as the first embodiment.

[0061] Sixth Embodiment [GaN-based ultraviolet light-receiving element] A GaN-based ultraviolet light receiving element according to the sixth embodiment will be described. This GaN-based ultraviolet light receiving element has an insulating film 12, an Al y Ga 1-y The planar shapes of the N layer 13, source electrode 15, and drain electrode 16 differ from those of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0062] 10A and 10B show this GaN-based ultraviolet light receiving element, with FIG. 10A being a cross-sectional view and FIG. 10B being a plan view. As shown in FIG. 10A and FIG. 10B, this GaN-based ultraviolet light receiving element is made of undoped Al x Ga 1-x An annular insulating film 12 is provided on the light receiving region of the N layer 11, and undoped Al is formed on both sides of the insulating film 12, in other words, on the inner and outer parts of the insulating film 12. x Ga 1-x An insulating film 12 is sandwiched between the Al layer 11 and the N layer 11. y Ga 1-y The insulating film 12 has an N layer 13 laminated thereon. x Ga 1-x N layer 11 and Al y Ga 1-y Undoped Al in the vicinity of the heterointerface with the N layer 13 x Ga 1-x The 2DEG 14 is formed in the N layer, similar to the GaN-based ultraviolet light receiving element according to the first embodiment. When ultraviolet light is not incident, the insulating film 12 and the undoped Al x Ga 1-x There are no carriers near the interface with the N layer 11. y Ga 1-y A circular source electrode 15 is provided on the N layer 13, and the Al y Ga 1-yA circular drain electrode 16 is provided on the N layer 13 so as to surround the insulating film 12. A pad portion 15a is extended from the source electrode 15, straddling the circular drain electrode 16. A pad portion 16a is extended from the drain electrode 16 on the opposite side to the pad portion 15a. At the intersection of the pad portion 15a of the source electrode 15 and the drain electrode 16, the pad portion 15a passes over an insulating film (not shown) provided on the drain electrode 16. Other aspects of this GaN-based ultraviolet light receiving element are the same as those of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0063] [Operation of GaN-based UV photodetectors] The operation of this GaN-based ultraviolet light receiving element is the same as that of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0064] [Manufacturing method for GaN-based UV photodetectors] The method for manufacturing this GaN-based ultraviolet light receiving element is y Ga 1-y The method for manufacturing the GaN-based ultraviolet light receiving element is the same as that for the first embodiment, except that the planar shapes of the N layer 13, source electrode 15, and drain electrode 16 differ from those of the GaN-based ultraviolet light receiving element according to the first embodiment.

[0065] According to the sixth embodiment, it is possible to obtain the same advantages as the first embodiment.

[0066] An example will be described.

[0067] A GaN-based ultraviolet light receiving element as shown in Figures 11A and 11B was fabricated. This GaN-based ultraviolet light receiving element has the same structure as the GaN-based ultraviolet light receiving element according to the sixth embodiment. Figure 12 is an optical microscope photograph (surface photograph) of the fabricated GaN-based ultraviolet light receiving element. Undoped Al x Ga 1-x The Al composition x of the N layer 11 is 0.35, and the thickness is 1 μm. y Ga 1-y The Al composition x of the N layer 13 is 0.6, and the thickness is 20 nm.y Ga 1-y The diameter of the N layer 13 was set to 100 μm. y Ga 1-y The width of the annular insulating film 12 surrounding the N layer 13 was changed to two levels: 5 μm and 15 μm. The GaN-based ultraviolet light receiving element on the left side of Figure 12 shows the case where the insulating film 12 is 5 μm wide, and the GaN-based ultraviolet light receiving element on the right side shows the case where the insulating film 12 is 15 μm wide. The source electrode 15 had a circular shape, and no pad portion 15a was formed. A single layer of SiO2 film was used as the insulating film 12, but it was not specifically designed to function as an anti-reflection film.

[0068] The measurement system is shown in Figure 13. In this measurement system, a sample 202 was placed on a stage 201, and probes 203 and 204 were set up on the pad portions 16a of the source electrode 15 and the drain electrode 16, respectively (see Figure 11A). A UV lamp 205 was used as a light source of ultraviolet light. The wavelength of the UV lamp 205 was 265 nm, and the output was 40 mW / cm. 2 In this measurement system, the UV lamp 205 cannot be placed directly above the sample 202, so the ultraviolet rays 206 were incident obliquely onto the surface of the sample 202. Since the SiO2 film serving as the insulating film 12 does not function as an anti-reflection film, a considerable proportion of the incident ultraviolet rays 206 is reflected.

[0069] Figure 14 shows the measurement results of a GaN-based ultraviolet light receiving element with an insulating film 12 having a width of 5 μm. An optical microscope photograph of this GaN-based ultraviolet light receiving element is shown in the upper right corner of Figure 14. The horizontal axis of Figure 14 is the voltage applied between the source electrode 15 and the drain electrode 16, i.e., the bias voltage, and the vertical axis is the current (photocurrent) flowing between the source electrode 15 and the drain electrode 16. As shown in Figure 14, in a dark state where no ultraviolet light is irradiated, the current value (dark current value) is 10 -11Although it is in the A range, when ultraviolet light is irradiated, the current value becomes approximately 1 mA at a bias voltage of +50 V, indicating that the resistance between the source electrode 15 and the drain electrode 16 is reduced by more than seven orders of magnitude. Since the source electrode 15 and the drain electrode 16 are on the side where ultraviolet light 206 from the UV lamp 205 is irradiated, the only place where ultraviolet light can penetrate is the region directly below the insulating film 12. If this region is considered to be the active region for photoelectric conversion, and the width of the insulating film 12 is 5 μm, the area of ​​this insulating film 12, and therefore the active region, is 2π × 52.5 [μm] × 5 [μm] = 1648 μm 2 The insulating film 12 is irradiated with 40 mW / cm 2 is irradiated with ultraviolet light, the incident light output at this active region is 6.594×10 -7 From this, the sensitivity is calculated as follows: the photocurrent value at a bias of 10 V is 5.51 × 10 -4 Since it was A, it is 6.594 x 10 -7 / 5.51×10 -4 It can be seen that an extremely high sensitivity of λ / W = 758 A / W is obtained. In reality, taking into consideration that ultraviolet light is incident at an angle and that the SiO2 film used as the insulating film 12 does not function as an anti-reflection film, it is expected that even greater sensitivity can be obtained by making ultraviolet light incident perpendicularly or by using the insulating film 12 as an anti-reflection film.

[0070] Seventh Embodiment [GaN-based optical switching transistor] A GaN-based optical switching transistor according to the seventh embodiment will be described.

[0071] FIG. 15 is a cross-sectional view showing this GaN-based optical switching transistor. The plan view of this GaN-based optical switching transistor is the same as FIG. 1B. As shown in FIG. 15, this GaN-based optical switching transistor has a configuration basically similar to that of the GaN-based ultraviolet light receiving element according to the first embodiment, but an optical signal is used as the gate input. The optical signal is input to an undoped Al x Ga 1-x Ultraviolet light with photon energy exceeding the band gap of the N layer 11 is used.

[0072] [Operation of GaN-based optical switching transistors] The operation of this GaN-based optical switching transistor will now be described.

[0073] Basically, in the same way as the GaN-based ultraviolet light receiving element according to the first embodiment, in this GaN-based optical switching transistor, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side has a higher potential. When no optical signal is incident on the insulating film 12, the insulating film 12 and the undoped Al x Ga 1-x Since there are no carriers near the interface with the N layer 11, no current flows between the source electrode 15 and the drain electrode 16. When an optical signal is incident on the insulating film 12, it passes through the insulating film 12 and is x Ga 1-x As a result of electron-hole pairs being generated by entering the N layer 11, a current flows between the source electrode 15 and the drain electrode 16. In this way, the current flowing between the source electrode 15 and the drain electrode 16 can be controlled by an optical signal.

[0074] [Method of manufacturing GaN-based optical switching transistor] This GaN-based optical switching transistor can be manufactured in the same manner as the GaN-based ultraviolet light receiving element according to the first embodiment.

[0075] According to the seventh embodiment, it is possible to realize a novel GaN-based optical switching transistor that can control current using ultraviolet light as an optical signal and that can operate at a low voltage.

[0076] Eighth Embodiment [GaN-based optical switching transistor] A GaN-based optical switching transistor according to the eighth embodiment will be described.

[0077] Figure 16 is a cross-sectional view showing this GaN-based optical switching transistor. The plan view of this GaN-based optical switching transistor is the same as that of Figure 1B. As shown in Figure 16, this GaN-based optical switching transistor has a configuration basically similar to that of the GaN-based ultraviolet light receiving element according to the third embodiment, but an optical signal is used as the gate input. As the optical signal, ultraviolet light with photon energy exceeding the band gap of the undoped GaN layer 31 is used.

[0078] [Operation of GaN-based optical switching transistors] The operation of this GaN-based optical switching transistor will now be described.

[0079] Basically similar to the GaN-based ultraviolet light receiving element according to the first embodiment, in this GaN-based optical switching transistor, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side has a higher potential. When no optical signal is incident on the insulating film 12, no carriers exist near the interface between the insulating film 12 and the undoped GaN layer 31, and therefore no current flows between the source electrode 15 and the drain electrode 16. When an optical signal is incident on the insulating film 12, the optical signal passes through the insulating film 12 and enters the undoped GaN layer 31, generating electron-hole pairs, which causes a current to flow between the source electrode 15 and the drain electrode 16. In this way, the current flowing between the source electrode 15 and the drain electrode 16 can be controlled by the optical signal.

[0080] [Method of manufacturing GaN-based optical switching transistor] This GaN-based optical switching transistor can be manufactured in the same manner as the GaN-based ultraviolet light receiving element according to the third embodiment.

[0081] According to the eighth embodiment, it is possible to obtain the same advantages as the seventh embodiment.

[0082] Ninth Embodiment [GaN-based optical switching transistor] A GaN-based optical switching transistor according to a ninth embodiment will be described.

[0083] FIG. 17 is a cross-sectional view showing this GaN-based optical switching transistor. The plan view of this GaN-based optical switching transistor is the same as FIG. 1B. As shown in FIG. 17, this GaN-based optical switching transistor has a configuration basically similar to that of the GaN-based ultraviolet light receiving element according to the fourth embodiment, but an optical signal is used as the gate input. As the optical signal, ultraviolet light with photon energy exceeding the band gap of the undoped GaN layer 31 is used.

[0084] [Operation of GaN-based optical switching transistors] The operation of this GaN-based optical switching transistor will now be described.

[0085] As with the GaN-based ultraviolet light-receiving element according to the fourth embodiment, in this GaN-based optical switching transistor, a voltage is applied between the source electrode 15 and the drain electrode 16 so that the drain electrode 16 side has a lower potential. When no optical signal is incident on the insulating film 12, no carriers exist near the interface between the insulating film 12 and the undoped GaN layer 31, and therefore no current flows between the source electrode 15 and the drain electrode 16. When an optical signal is incident on the insulating film 12, the optical signal passes through the insulating film 12 and enters the undoped GaN layer 31, generating electron-hole pairs, which causes a current to flow between the source electrode 15 and the drain electrode 16. In this way, the current flowing between the source electrode 15 and the drain electrode 16 can be controlled by the optical signal.

[0086] [Method of manufacturing GaN-based optical switching transistor] This GaN-based optical switching transistor can be manufactured in the same manner as the GaN-based ultraviolet light receiving element according to the fourth embodiment.

[0087] According to the ninth embodiment, it is possible to obtain the same advantages as the seventh embodiment.

[0088] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical concept of the present invention are possible.

[0089] For example, the numerical values, structures, shapes, materials, etc. given in the above-described embodiments are merely examples, and different numerical values, structures, shapes, materials, etc. may be used as needed. [Explanation of symbols]

[0090] 11...Undoped Al x Ga 1-x N layer, 12...insulating film, 13...Al y Ga 1-y N layer, 14... 2DEG, 15... source electrode, 16... drain electrode, 31... undoped GaN layer, 32... n-type GaN layer, 33... p-type GaN layer

Claims

1. Undoped Al x Ga 1-x N layers (0≦x<1); The undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al provided on the N layer y Ga 1-y N layers (x<y<1), The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x An ultraviolet light receiving element in which two-dimensional electron gas is formed in the N layer.

2. The undoped Al x Ga 1-x 2. The ultraviolet light receiving element according to claim 1, wherein the N layer is an undoped GaN layer.

3. 3. The ultraviolet light receiving element according to claim 1, wherein the insulating film has a stripe shape, a zigzag shape, or a ring shape.

4. an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; An ultraviolet light receiving element having

5. 5. The ultraviolet light receiving element according to claim 4, wherein the insulating film has a stripe shape, a zigzag shape, or a ring shape.

6. At least one ultraviolet light receiving element is included, The ultraviolet light receiving element is Undoped Al x Ga 1-x N layers (0≦x<1); The undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al provided on the N layer y Ga 1-y N layers (x<y<1), The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x UV photodetector with two-dimensional electron gas formed in the N layer An ultraviolet detection fire alarm.

7. At least one ultraviolet light receiving element is included, The ultraviolet light receiving element is an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; An ultraviolet light receiving element having An ultraviolet detection fire alarm.

8. Undoped Al x Ga 1-x N layers (0≦x<1); The undoped Al x Ga 1-x an insulating film provided on the light receiving region of the N layer; The undoped Al on both sides of the insulating film x Ga 1-x Al provided on the N layer y Ga 1-y N layers (x<y<1), The Al on both sides of the insulating film y Ga 1-y a source electrode and a drain electrode provided on the N layer; and The undoped Al x Ga 1-x N layer and the above Al y Ga 1-y The undoped Al in the vicinity of the heterointerface with the N layer x Ga 1-x An optical switching transistor in which two-dimensional electron gas is formed in the N layer.

9. an undoped GaN layer; an insulating film provided on a light-receiving region of the undoped GaN layer; n-type or p-type GaN layers provided on the undoped GaN layer on both sides of the insulating film; a source electrode and a drain electrode provided on the n-type or p-type GaN layer on both sides of the insulating film; A light switching transistor having

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