JP2003282925A - Method of manufacturing light receiving element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light receiving element having a large area and a high sensibility. <P>SOLUTION: The method of manufacturing the light receiving element comprises a process of forming, on a substrate, a base structure having a single or a plurality of semiconductor layers; and a process of forming, on the base structure, a device structure having a single or a plurality of semiconductor layers, each including a light receiving region formed of a group III nitride. The base structure is formed by a metal organic vapor phase growth method, while the group III nitride associated with the formation of at least the light receiving region of the device structure is formed by molecular beam epitaxy. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a light receiving element, and more particularly to a deposition technique used when forming a light receiving element having a multilayer structure.

[0002]

2. Description of the Related Art Conventionally, a light receiving element using a group III nitride semiconductor has been manufactured. Since these group III nitride semiconductors are direct transition type semiconductors and their bandgap energy is wide enough to absorb light in the ultraviolet region, they can also be used as the light receiving region of the ultraviolet light receiving element. However, when a highly sensitive light receiving element is required, it is required that the crystal quality of the group III nitride semiconductor for forming the light receiving region is good.
There is a problem that the lattice constant (lattice interval) is mismatched between the group I nitride semiconductor and the underlying substrate (generally a sapphire substrate). If a lattice constant mismatch exists between the two, dislocations are generated in the group III nitride semiconductor growing on the substrate, and photocarriers are trapped by the levels due to the dislocations, resulting in a decrease in photosensitivity. The problem occurs.

In order to overcome the above problems, that is, to improve the crystal quality of the group III nitride semiconductor for forming the light receiving region, the metal organic chemical vapor deposition (MOCV) method is used.
First, an AlN layer deposited at a low temperature (about 600 ° C.), a GaN layer as a crystal improvement layer, and an AlN layer deposited at a low temperature are sequentially formed on a sapphire substrate by using the D method). A structure is provided, and, for example, an n-type semiconductor layer, an i-type semiconductor layer (light receiving region), a p-type semiconductor layer, and the like are sequentially stacked on the underlying structure by using metal organic vapor phase epitaxy (MOVPE method), A device structure in which a light receiving region is formed by one or a plurality of semiconductor layers among them is provided. When such an element structure including a substrate, a base structure, and a device structure is adopted, the influence of lattice mismatch existing between the group III nitride semiconductor and the substrate for forming the device structure may be adversely affected. The crystal quality of the group III nitride semiconductor, which is relaxed and is related to the formation of the light receiving region included in the device structure, can be made relatively good.

Here, metal organic chemical vapor deposition (MOCVD)
Method and MOVPE method), GaN, AlN, Al
As a raw material used for growing a group III nitride semiconductor such as GaN or InAlGaN, trimethylgallium: TMGa is used as a Ga source, trimethylaluminum: TMAl is used as an Al source, and
It was common to use trimethylindium: TMIn as the n source.

[0005]

Here, when the light receiving element is used as a flame sensor, only the light from the flame is received separately from the room light from the sunlight and various lighting devices. It is required to have wavelength selectivity. Specifically, it is required that the sensitivity in the wavelength range of the light to be detected in the flame light is 10,000 times or more the sensitivity in the wavelength range of the light not to be detected and has a certain level of wavelength selectivity. . In the description in this specification, “sensitivity (unit: A / W)” means how much photocurrent (A) is generated with respect to the light intensity (W) applied to the light receiving element. It can be said that the sensitivity is higher as the photocurrent generated is larger when irradiated with light of the same intensity.

As described above, a high performance light receiving element is required to have high wavelength selectivity.
Impurity levels are formed by incorporating carbon atoms contained in each metal-organic compound used as a raw material in the metal-organic vapor phase epitaxy adopted when manufacturing the light-receiving element into each deposited film. It Then, due to the light absorption by the impurity level, there occurs a problem that the sensitivity appears in the wavelength range not to be detected, and thus the sensitivity in the wavelength range of the light to be detected is in the wavelength range of the light not to be detected. There is a problem that it becomes difficult to increase the sensitivity to 10,000 times or more.

[0007] When performing the growth of the semiconductor layer using the CVD device, usually set the pressure in the reaction chamber the growth of the semiconductor layer is performed at about 10 ³ Pa to about 10 ⁵ Pa, in which case the However, since the lateral growth of the semiconductor layer is suppressed, there is a problem that the area of the light receiving region and the crystal quality cannot be made uniform.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a light receiving element having a large area and high sensitivity.

[0009]

The first characteristic constitution of the method for producing a light-receiving element according to the present invention for solving the above-mentioned problems is to provide a substrate on a substrate as described in claim 1 of the scope of claims. A step of forming a base structure including one or more semiconductor layers, and forming a device structure including one or more semiconductor layers including a light receiving region made of a group III nitride on the base structure. At a point where the underlying structure is formed by metalorganic vapor phase epitaxy, and at least the group III nitride relating to the formation of the light receiving region in the device structure is formed by molecular beam epitaxy. is there.

A second characteristic configuration of the method for producing a light-receiving element according to the present invention for solving the above-mentioned problems is, as described in claim 2 of the scope of the claims, made of a boride of a group IVA element. Group III nitriding according to the formation of at least the light receiving region of the device structure, the method including forming a device structure comprising one or more semiconductor layers including a light receiving region made of a Group III nitride on a substrate. Things are at the point where they are formed by molecular beam epitaxy.

A third characteristic configuration of the method for manufacturing a light-receiving element according to the present invention for solving the above-mentioned problems is, in addition to the second characteristic configuration, as set forth in claim 3 of the scope of claims. And the boride is ZrB ₂ .

A fourth characteristic construction of the method for producing a light-receiving element according to the present invention for solving the above-mentioned problems is the second or third characteristic as described in claim 4 of the claims section. In addition to the configuration, prior to the step of forming the device structure, a step of forming a base structure including one or a plurality of semiconductor layers on the substrate by a metal organic chemical vapor deposition method is included.

A fifth characteristic constitution of the method for manufacturing a light receiving element according to the present invention for solving the above-mentioned problems is, as described in claim 5 of the scope of claims, the above-mentioned first to fourth characteristics. In addition to the configuration, a step of forming antireflection means for reducing the reflectance of incident light in the device structure on the light incident surface side of the device structure is included.

A sixth characteristic constitution of the method for manufacturing a light-receiving element according to the present invention for solving the above-mentioned problems is, as described in claim 6 in the section of the claims, the above-mentioned first to fifth characteristics. In addition to the constitution, the band gap energy of the group III nitride for forming the light receiving region is 3.6 eV or more.

A seventh characteristic constitution of the method for manufacturing a light receiving element according to the present invention for solving the above-mentioned problems is, in addition to the sixth characteristic constitution, as described in claim 7 of the scope of claims. In addition, the band gap energy of the group III nitride relating to the formation of the light receiving region is 4.0 eV or less.

An eighth characteristic constitution of the method for manufacturing a light-receiving element according to the present invention for solving the above-mentioned problems is, in addition to the sixth characteristic constitution, as described in claim 8 of the scope of claims. In addition, the band gap energy of the group III nitride relating to the formation of the light receiving region is 4.1 eV or more.

A ninth characteristic configuration of the method for manufacturing a light-receiving element according to the present invention for solving the above-mentioned problems is, in addition to the eighth characteristic configuration, as described in claim 9 of the scope of claims. In addition, the band gap energy of the group III nitride for forming the light receiving region is 4.4 eV or more.

The characteristic configuration of the flame sensor according to the present invention for solving the above-mentioned problems is set forth in claim 1 of the scope of claims.
As described in 0, it is produced by using the method for producing the light receiving element according to any one of claims 6 to 9.

The operation and effect will be described below. According to the first characteristic configuration of the method for manufacturing a light-receiving element according to the present invention,
Since the step of forming the group III nitride relating to the formation of the light receiving region is performed by molecular beam epitaxy, it is possible to form a light receiving element in which carbon hardly exists in the light receiving region. Therefore, when incorporated in a Group III nitride,
Since there is almost no carbon in the film that acts as an impurity level that contributes to the absorption of light and gives unnecessary sensitivity to the light-receiving element, the wavelength selectivity is good and weak light is generated. It is possible to provide a light receiving element that can be detected with high sensitivity even when irradiated. Further, since the light receiving region is formed by molecular beam epitaxy, it is possible to achieve a large area of the light receiving region and uniform crystal quality of the light receiving region. Further, since it is possible to increase the area of the light receiving region and make the crystal quality of the light receiving region uniform, it is also possible to obtain a large number of light receiving elements from a single wafer with a high yield. Even if the speed is low, the total cost required when manufacturing the light receiving element can be reduced.

According to the second characteristic configuration of the method for manufacturing a light receiving element according to the present invention, since the step of forming the group III nitride for forming the light receiving area is performed by molecular beam epitaxy, carbon is formed in the light receiving area. It is possible to form a light receiving element in which there is almost no. Therefore, when incorporated in the group III nitride, there is almost no carbon in the film, which forms an impurity level that contributes to light absorption and has an unnecessary sensitivity to the light receiving element. Therefore, it is possible to provide a light receiving element which has good wavelength selectivity and can detect with high sensitivity even when weak light is irradiated. Further, since the light receiving region is formed by molecular beam epitaxy, it is possible to achieve a large area of the light receiving region and uniform crystal quality of the light receiving region. Further, since it is possible to increase the area of the light receiving region and make the crystal quality of the light receiving region uniform, it is also possible to obtain a large number of light receiving elements from a single wafer with a high yield. Even if the speed is low, the total cost required when manufacturing the light receiving element can be reduced.

Further, a device structure including a light receiving region is I
Since it is formed on a substrate made of a boride of a group IVB element (titanium, zirconium, hafnium, etc.) having a lattice constant equivalent to that of a group II nitride, it improves the crystal quality of the device structure including the light receiving region. be able to.

According to the third characteristic constitution of the method for producing a light-receiving element according to the present invention, Zr in the boride of the group IVA element is used.
Since B ₂ is used as the substrate material, the lattice constant of the group III nitride and the lattice spacing of the crystal growth plane of ZrB ₂ can be made almost equal. As a result, the crystal quality of the device structure (group III nitride semiconductor) formed on the substrate can be improved.

According to the fourth characteristic configuration of the method for manufacturing a light receiving element according to the present invention, the device structure is formed after the semiconductor layer to be the buffer layer is formed on the substrate by the metal organic chemical vapor deposition method. Therefore, the crystal quality of the device structure can be improved.

According to the fifth characteristic configuration of the method for manufacturing a light receiving element according to the present invention, since the antireflection means is provided on the incident light side on the light receiving region, the antireflection means is not provided. In comparison, the amount of light (energy amount) incident on the light receiving region can be increased. As a result, it is equivalent to an increase in photoelectric conversion efficiency in the light receiving region, so that it is possible to provide a light receiving element that can detect with high sensitivity even if the intensity of light from the flame is weak.

According to the sixth characteristic configuration of the method for manufacturing a light-receiving element according to the present invention, the bandgap energy of the light-receiving region is 3.6 eV or more, which results in a wavelength of about 344 nm.
Light with a wavelength of (3.6 eV) or less, that is, a wavelength of about 344 n
It is possible to obtain a light receiving element capable of selectively detecting flame light appearing in a wavelength range of m or less by the light receiving region.

According to the seventh characteristic configuration of the method for manufacturing a light-receiving element according to the present invention, light having an energy of 3.6 eV or more and 4.0 eV or less is absorbed in the light-receiving region, so that a wavelength of about 310 nm ( 4.0 eV) to 344 nm
It is possible to satisfactorily detect the light having a wavelength in the range of (3.6 eV), that is, the light emission peak due to the light emission of the OH radical, which is observed when the compound containing the hydrocarbon is burned in the light of the flame. It is possible to obtain a light receiving element that can be obtained.
In particular, when the light receiving element is installed in a closed space such as the inside of an engine, when it is installed outdoors, there must be light such as indoor light and sunlight from various lighting devices that are observed at the same time. Therefore, only the light of the flame can be satisfactorily detected.

According to the eighth characteristic construction of the method for manufacturing a light-receiving element according to the present invention, the bandgap energy of the light-receiving region is 4.1 eV or more, so that the wavelength is about 300 nm.
It is possible to obtain a light receiving element capable of detecting light having a wavelength of (4.1 eV) or less, that is, light of flame, by the light receiving region. Further, since the light receiving region is not sensitive to light having a wavelength of more than about 300 nm, that is, room light from various lighting devices, the light receiving element is selectively sensitive to flame light. Can be obtained.

According to the ninth characteristic construction of the method for manufacturing a light-receiving element according to the present invention, since the bandgap energy of the light-receiving region is 4.4 eV or more, the wavelength is about 280 nm.
It is possible to obtain a light receiving element capable of detecting light having a wavelength of (4.4 eV) or less, that is, light of flame, by the light receiving region. Further, since the light receiving region is not sensitive to light having a wavelength of more than about 280 nm, that is, indoor light and sunlight (natural light) from various lighting devices, it is selective to flame light. It is possible to obtain a light receiving element having sensitivity to.

According to the characteristic configuration of the flame sensor according to the present invention, the band gap energy of the group III nitride for forming the light receiving region is adjusted to a value having a selective sensitivity to the light of the flame, At the same time, there is provided a flame sensor having a reduced content of carbon in the film, which acts to give unnecessary sensitivity to the light receiving element. Therefore, the sensitivity in the wavelength range to be detected (range in which flame light is included),
A flame sensor with a large sensitivity difference with the sensitivity in the wavelength range that is not the detection target (range that includes ambient light such as sunlight and room light) can be obtained. Even if there is, it can be detected with high sensitivity by distinguishing its presence from ambient light.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION A method of manufacturing a light receiving element according to the present invention will be described below with reference to the drawings. FIG. 1 exemplifies the configuration of a film forming apparatus for forming a semiconductor layer forming a light receiving element. This film forming apparatus includes a CVD (vapor deposition method) apparatus 1 and an MBE (molecular beam epitaxy) apparatus 2.
Are connected by a tunnel 3, and the substrate on which the film is deposited is transported through the tunnel 3. Therefore, the film obtained by using the CVD apparatus 1 is transferred to the MBE apparatus 2 without exposing to the atmosphere,
A film forming process in which the film is further deposited by using the apparatus 2, or a film forming process in the CVD apparatus 1 after the film forming by the MBE apparatus 2 can be performed.

As the CVD apparatus 1 used in this embodiment, a general apparatus capable of forming a film by a metal organic chemical vapor deposition method is used. Specifically, a carrier gas is caused to flow to vaporize a liquid organometallic raw material, and the raw material is supplied as a carrier gas into the reaction chamber. Then, the supplied raw material can be deposited on the substrate provided in the reaction chamber to obtain a desired film. When the raw material is gas,
The raw materials may be directly supplied into the reaction chamber without using a carrier gas. Specifically, GaN, AlN, AlGa
When it is desired to form a group III nitride semiconductor such as N, InGaN, or InAlGaN, trimethylgallium (TMGa) or TEGa (triethylgallium) is used as a gallium source, and trimethylaluminum (TMAl) or TEAl (triethyl) is used as an aluminum source. Aluminum) is used, trimethylindium (TMIn), TEIn (triethylindium) are used as the indium source, and ammonia is commonly used as the nitrogen source.

Therefore, a raw material tank for storing liquid TMGa or TEGa, a raw material tank for storing liquid TMAl or TEAl, a raw material tank for storing liquid TMIn or TEIn, and a raw material tank for storing gaseous ammonia are prepared respectively. And then TMGa or TEG
a, TMAl or TEAl, and TMIn or T
EIn is vaporized by using a carrier gas (nitrogen, hydrogen, etc.) and the flow rate supplied to the reaction chamber is adjusted. Ammonia is directly supplied to the reaction chamber by adjusting the gas flow rate.

The source gas supplied into the reaction chamber of the CVD apparatus 1 is deposited on the crystal growth surface of the substrate by the source gas activation means provided in the reaction chamber. Heating means, plasma generating means, etc. are typical means for activating the raw material gas. When the supplied raw material gas contains a plurality of kinds of elements, each activated element forms a compound. Then, it is deposited and grown on the crystal growth surface of the substrate. The degree of activation varies depending on the type of raw material gas, and there are organometallic materials that are decomposed near the surface of the substrate and organometallic materials that are decomposed before reaching the surface of the substrate.

When an impurity semiconductor is produced using a dopant, disilane or silane is used as a dopant in the case of Si doping, and MeCp ₂ Mg (bismethylcyclopentane magnesium) or EtCp ₂ as a dopant in the case of Mg doping. Mg (bisethylcyclopentane magnesium) can be used, and Cp ₂ Be (cyclopentane beryllium) or MeCp ₂ Mg (bismethyl cyclopentane beryllium) can be used as a dopant in the case of Be doping.

In the MBE apparatus 2 used in this embodiment, the metal material such as Ga, Al, In, etc. to be formed can be supplied by sputtering using a metal target. Alternatively, TMGa,
Organometallics such as TEGa, TMAl, TEAl, TMIn, TEIn can also be used as gas sources. As the nitrogen material, ammonia gas or nitrogen ions can be used. Further, when an impurity semiconductor is manufactured using a dopant, Si, Mg, B serving as a dopant is used.
Impurities can be supplied by sputtering using a simple metal such as e or a metal compound as a metal target.

The structure of the light receiving element formed by using the above CVD apparatus 1 and MBE apparatus 2 is shown in FIG.
For example.

The light receiving element 30 shown in FIG. 2 is formed by sequentially depositing a base structure and a device structure on the substrate 10. The underlying structure is the low temperature deposition buffer layer 1 on the substrate 10.
It is obtained by sequentially depositing No. 1, the crystal improvement layer 12, and the low temperature deposition intermediate layer 13. In the device structure, an n-type semiconductor layer 14, an i-type semiconductor layer 15 acting as a light receiving region, a p-type semiconductor layer 16, and a p-type contact layer 17 are sequentially deposited on the underlying structure, and these An electrode 18 (negative electrode) is provided on the surface of the n-type semiconductor layer 14 exposed by partially etching the deposited layer, and the p-type contact layer 17 is provided.
It is obtained by providing the electrode 19 (positive electrode) on the surface of the.

As the materials of the substrate, the underlying structure, and the device structure described above, for example, the substrate 10 is sapphire, the low-temperature deposition buffer layer 11 is AlN (thickness 20 nm), and the crystal improvement layer 12 is GaN (thickness). 1 μm), the low temperature deposition intermediate layer 13 is AlN (thickness 20 nm), n
-Type semiconductor layer 14 (thickness 1 μm), i-type semiconductor layer 15 (thickness 100 to 200 nm), and p-type semiconductor layer 16 (thickness 80)
nm) and a single crystal _{In x Al y Ga 1-xy} N (0 ≦ x ≦
1, 0 ≦ y ≦ 1). In addition, the p-type contact layer 17
Is p-GaN or Al having a small aluminum composition ratio y
_y Ga _1-y N (thickness 20 nm). Further, the electrodes 18 and 19 are formed using a metal such as Ti, Ni, Al, Au. In addition, the electrode 18 and the n-type semiconductor layer 14
And the electrical characteristics between the electrode 19 and the p-type contact layer 17 are in an ohmic state. Further, since the light is configured to enter the i-type semiconductor layer 15 from the electrode 19 side, the electrode 19 needs to have a structure capable of transmitting the light. Therefore, the electrode 19 is
It is manufactured in the form of a mesh electrode or a transparent conductive electrode. The above-mentioned film thickness value can be changed to another value according to the application.

The role of the underlying structure is to improve the crystal quality of the device structure. _{In x Al y Ga 1-xy} N (0 ≦ x ≦ 1 constituting the lattice spacing in the crystal growth surface of the sapphire substrate 10, the device structure,
There is a large difference with the lattice constant of 0 ≦ y ≦ 1), but the lattice mismatch is relaxed by the underlying structure,
The stress due to the lattice mismatch applied when growing the aN layer can be made extremely small. As a result, the crystal quality of the AlGaN layer in the device structure can be improved.

By configuring the light receiving element as described above,
The light emitted from the electrode 19 side is incident on the i-type semiconductor layer 15 which functions as a light receiving region, absorbs the light having the energy corresponding to the bandgap energy of the i-type semiconductor layer 15, and generates photocarriers. Then, the electrode 18 and the electrode 1
The photocarrier is extracted as a photocurrent by the reverse bias voltage applied during 9, and the intensity of the received light is derived from the magnitude of the current.

Next, a method for forming each layer of the light receiving element shown in FIG. 2 will be described. When the light-receiving element having the structure illustrated in FIG. 2 is manufactured, each of the low-temperature deposition interference layer 11, the crystal improvement layer 12, and the low-temperature deposition intermediate layer 13 forming the underlying structure is a metal organic chemical vapor deposition using the CVD apparatus 1. Formed by the method. The n-type semiconductor layer 14, the p-type semiconductor layer 16, and the p-type contact layer 17 can be formed by metalorganic vapor phase epitaxy using the CVD apparatus 1 or epitaxial growth using the MBE apparatus 2. N-type semiconductor layer 1 adjacent to i-type semiconductor layer 15 relating to the formation of
It is preferable that the 4 and p-type semiconductor layers 16 are formed by epitaxial growth using the MBE device 2 so that the film does not contain carbon.

Therefore, since the i-type semiconductor layer 15 formed by using the MBE device 2 contains almost no carbon capable of forming an impurity level, this light receiving element originates from the impurity level due to carbon. It is possible not to show the sensitivity. As a result, it is possible to provide a light-receiving element having good wavelength selectivity and capable of detecting with high sensitivity even when weak light is irradiated. Especially when using this light receiving element as a flame sensor used in a situation where the light intensity in the wavelength range to be detected is weak, the sensitivity in the wavelength range of the light to be detected and the light not to be detected Since it is required that there is a large difference between the sensitivity and the sensitivity in the wavelength range of, the significance of the present embodiment is large. Further, since the light receiving region is formed by the MBE device 2, it is possible to increase the area of the light receiving region and make the crystal quality of the light receiving region uniform.

[0043] _{Here, In x Al y Ga 1-} xy N (0 ≦ x ≦ 1 constituting the i-type semiconductor layer 15 and n-type semiconductor layer 14 and the p-type semiconductor layer 16, which acts as a light receiving region,
The band gap energy of 0 ≦ y ≦ 1) is adjusted by changing the indium composition ratio x and the aluminum composition ratio y, and the indium composition ratio x and the aluminum composition ratio y are adjusted.
And the band gap energy of InAlGaN are expressed by the relationship shown in FIG. As seen from FIG. 3, by changing the indium composition ratio x and the aluminum composition ratio y, it is possible to adjust the band gap energy of _{In x Al y Ga 1-xy} N from 1.9eV down to 6.2 eV. Alternatively, the wavelength range of light that can be absorbed in the light receiving region is adjustable between about 200 nm and about 650 nm. Further, when the light of the flame is detected by the light receiving element, it is sufficient to form the light receiving region having the band gap energy that can absorb the light emission of the flame as shown in the emission spectrum of FIG. The emission spectrum of the flame shown in FIG. 4 is the spectrum of the flame generated when gas (hydrocarbon) is burned. Also, with the spectrum of sunlight,
At the same time, the spectrum of the room light due to the light from various lighting devices is also shown.

The band gap energy of a preferable light receiving region when used as an ultraviolet light receiving element will be described below. Therefore, in order to increase the band gap energy, description will be made assuming that indium is not included (indium composition ratio x = 0).

[0045] In order to provide wavelength selectivity to the light-receiving element, by adjusting the composition ratio of Al in the light receiving area _{(Al y Ga 1-y N} ), to set the band gap energy to a desired value Done. For example, when it is desired to manufacture a flame sensor capable of selectively receiving flame light that appears with a relatively large intensity in a wavelength range of about 344 nm or less, the bandgap energy of the light receiving region is 3.6 eV.
The aluminum composition ratio y may be set to y = 0.05 or more so as to be the above. Alternatively, light from various lighting devices (room light) included in the wavelength range of about 300 nm or more.
When it is desired to manufacture a flame sensor that receives the light of the flame within the detection target wavelength range without receiving the light, the aluminum composition ratio y = 0 so that the bandgap energy of the light receiving region is 4.1 eV or more. 0.25 or more. Alternatively, when it is desired to manufacture a flame sensor that receives only the light of the flame within the detection target wavelength range without receiving the light from sunlight included in the wavelength range of about 280 nm or more, the light receiving region Of aluminum composition ratio y such that the band gap energy of
= 0.35, or higher.

Alternatively, if the ambient light such as sunlight may be absorbed in the light receiving region as long as the light intensity is weak, the band gap energy of the light receiving region is 4.3 eV or more (wavelength is about 290 nm or less). Thus, the aluminum composition ratio y should be 0.31 or more. When the wavelength is about 290 nm or less, the light intensity of the ambient light becomes very small as shown in FIG. 4, and the light of the flame is large on the other hand, and as a result, the presence of the light of the flame can be detected.

Further, when the light receiving element is installed in an enclosed space such as the inside of the engine and it is desired to detect the light emission of the fuel burned therein, the above-mentioned room light and sunlight are not present, so that they are excluded. It is not necessary to set a large bandgap energy. Therefore, among the light of the flame in the detection target wavelength range, a light emission peak (wavelength of approximately 310 nm (wavelength of about 310 nm ( 310 nm ± 10 nm): 4.0 eV)
Light (light of flame with wavelength of 310nm to 344nm)
When a light receiving element capable of selectively receiving light is produced, the bandgap energy of the light receiving region is 3.6e.
The aluminum composition ratio y may be set to 0.05 or more and 0.23 or less so as to be V or more and 4.0 eV or less.

The relationship between the indium composition ratio x and the aluminum composition ratio y and the bandgap energy of InAlGaN described above is based on the theoretical values, and the indium composition ratio x and the aluminum composition ratio y are the same as the theoretical values. Even if the film is formed as described above, the band gap energy of the InAlGaN layer actually obtained may be different. For example, AlGaN which is a ternary mixed crystal compound
In the case of, the binary compound GaN is easily generated,
As a result, the band gap energy tends to shift to the low energy side (long wavelength side). Therefore, when it is desired to obtain the bandgap energy according to the theoretical value, the aluminum composition ratio may be set to a large value before the film formation.

As described above, the band gap of the light receiving region in the device structure is adjusted to receive the light of the desired wavelength. However, the portion other than the light receiving region (for example, p-type shown in FIG. 2). When the band gap energy of the semiconductor layer and the n-type semiconductor layer) is designed to be equal to or larger than the band gap energy of the light receiving region, another effect can be obtained. In other words, the portion other than the light receiving region can be used as a window for the light receiving region, which has good light transmission characteristics, so that the intensity of light incident on the light receiving region can be secured to be large. Therefore, even if the light applied to the light receiving element from the outside is weak, it is possible to reach the light receiving region without attenuating the light intensity.

In the above embodiment, at least:
The i-type semiconductor layer 15 relating to the formation of the light receiving region is the MBE device 2
A method of manufacturing a light receiving element in which carbon is hardly contained in the light receiving region by forming a film by using has been described. However, even when forming a semiconductor layer (a semiconductor layer located within the diffusion distance of photocarriers from the light receiving region) sandwiching the group III nitride semiconductor (i-type semiconductor layer 15) related to the formation of the light receiving region, the MBE is formed. It is preferable to carry out the film forming method using the apparatus 2 so that the semiconductor layers thereof hardly contain carbon. In that case, in the semiconductor layer adjacent to the light receiving region, almost no photocarriers originating from the impurity level due to carbon are generated,
The obtained light receiving element can increase the difference between the sensitivity in the wavelength range of light to be detected and the sensitivity in the wavelength range of light not to be detected.

The light receiving element illustrated in FIG. 5 is a substrate 20 made of a boride of a group IVA element (Ti, Zr, Hf, etc.).
It is formed by directly depositing a device structure thereon.
This device structure has the same configuration as that described with reference to FIG. 2, and includes an n-type semiconductor layer 14, an i-type semiconductor layer 15 acting as a light receiving region, a p-type semiconductor layer 16, and a p-type semiconductor layer 16.
Type contact layer 17 is sequentially deposited, and an electrode 18 (negative electrode) is provided on the surface of n-type semiconductor layer 14 exposed by partially etching the deposited layers, and an electrode is formed on the surface of p-type contact layer 17. It is obtained by providing 19 (positive electrode).

As a concrete structure, Z is used as a substrate material.
rB ₂ is used. The effect obtained when using a boride of the group IVA element as the substrate material is that the difference between the lattice spacing of the crystal growth surface and the lattice constant of the group III nitride (eg, AlGaN) is very small. It is possible to improve the crystal quality of the group III nitride formed above.

FIG. 6 shows the material A of the light receiving region.
3 is a graph showing changes in the lattice constant when changing the aluminum composition ratio in l _y Ga _{1 -y} N (0 ≦ y ≦ 1) and the lattice spacing of the ZrB ₂ surface that is the crystal growth surface for AlGaN. Also, for some materials (SiC and sapphire: Al ₂ O ₃ ) used as a substrate or an underlayer of AlGaN, the lattice spacing of the crystal growth plane is similarly illustrated. As can be seen from FIG. 6, there is a difference in lattice constant (lattice spacing) between a material such as SiC and sapphire: Al ₂ O ₃ and AlGaN. Therefore, when growing AlGaN on those substrates, Causes a problem that stress is applied to AlGaN and AlGaN with good crystal quality cannot be obtained. Incidentally, in order to alleviate this lattice mismatch, conventionally, a crystal improvement structure (underlying structure) is inserted between the substrate and the device structure (particularly, the layer related to the formation of the light receiving region). An example of this underlayer structure is the same as that described with reference to FIG. 2, and an AlN layer (buffer layer) deposited at a low temperature on the substrate and GaN
A single buffer (SB) structure in which a layer is formed, a low temperature deposited AlN layer (low temperature deposition buffer layer), a GaN layer (crystal improvement layer), and a low temperature deposited A on the substrate.
There is a double buffer (DB) structure in which an IN layer (low temperature deposition intermediate layer) is formed.

On the other hand, when ZrB ₂ is used as the material of the substrate, the composition ratio y of Al _y Ga _1-y N (0 ≦ y ≦ 1) is close to y = 0.29. The lattice constants (or lattice spacing) become equal, and as a result, ZrB ₂
The crystal quality of AlGaN deposited on the substrate can be improved.

FIG. 7 shows that Al _y Ga _1-y N having different aluminum composition ratios y are formed on several substrates or underlayers.
It is a graph which shows the defect density in the AlGaN layer when (0 ≦ y ≦ 1) is deposited. ZrB _{2 on the} substrate
In the case of using, as described above, the aluminum composition ratio y
Is the lattice constant (lattice spacing) of both in the vicinity of y = 0.29
Since the aluminum composition ratio y is in the vicinity thereof, the defect density is extremely low at about 1 × 10 ⁶ cm ^−2, and the aluminum composition ratio y is 0.2 to 0.
The defect density between 4 is also about 1 × 10 ⁶ cm ^-2 .

On the other hand, AlGaN is formed on the underlayer structure described above.
Figure 3 shows a graph with layers deposited. As an example, AlGaN is formed on the above-mentioned single buffer (SB) base structure.
The case where the layer is deposited and the case where the AlGaN layer is deposited on the double buffer (DB) underlying structure are shown. From the figure, it is assumed that the AlGaN layer is grown on the single buffer layer structure and the double buffer layer structure. Also, for example, when the aluminum composition ratio y is 0.2 or more, the defect density of the AlGaN layer is about 6 × 10 ⁹ cm ⁻² or more, which is much larger than that when the ZrB ₂ substrate is used. I understand.

The material and film thickness of the device structure of the light receiving element shown in FIG. 6 are the same as those described with reference to FIG. Further, similarly, at least the i-type semiconductor layer 15 relating to the formation of the light receiving region is formed by using the MBE device 2, thereby providing a light receiving element in which carbon is hardly contained in the light receiving region. it can. Therefore, when incorporated in the group III nitride, there is almost no carbon in the film, which forms an impurity level that contributes to light absorption and has an unnecessary sensitivity to the light receiving element. Therefore, it is possible to provide a light receiving element which has good wavelength selectivity and can detect with high sensitivity even when weak light is irradiated.

The light-receiving element shown in FIG. 5A constructed as described above may be configured so that light is irradiated from the electrode 19 side and the light is incident on the i-type semiconductor layer 15. it can. In that case, the electrode 19 is made in the form of a mesh electrode or a transparent conductive electrode, and light of high intensity
It suffices to reach the type semiconductor layer 15.

Further, the substrate 20 of the light receiving element illustrated in FIG. 5A can be removed so that light is incident from the n-type semiconductor layer 14 side. In that case, the light receiving element in FIG. An example is shown in (b). In the light receiving element illustrated in FIG. 5B, a relatively high quality film is obtained even when the band gap energy is increased (for example, the aluminum composition ratio y is increased in Al _y Ga _{1 -y} N). That is, n-AlGaN capable of obtaining a film with little optical loss
Since light is incident on the i-type semiconductor layer 15 through the light source 14, it is possible to ensure that light of high intensity reaches the i-type semiconductor layer 15. Therefore, it is possible to provide a light receiving element that can reliably detect the presence of light even if the intensity of light applied to the light receiving element is weak. As a preferable application example, a case where this light receiving element is used as a flame sensor can be mentioned.

As a modification of the light receiving element illustrated in FIG. 5B, the light receiving element illustrated in FIG. 8 can be cited. This light receiving element is different from the above-described light receiving element in the arrangement of electrodes. Specifically, the n-type semiconductor layer 14 is formed on the substrate 20.
Is the same as the light receiving element in FIG. 5, except that
This is largely different in that an electrode 21 exhibiting ohmic characteristics is provided on the surface of the n-type semiconductor 14 exposed by removing the substrate 20. Further, it is not necessary to remove all of the substrate 20, and the substrate material may be partially left as long as it is ensured that the irradiated light is incident on the n-type semiconductor layer 14 well. In that case, the electrode 21 may be formed on the surface of the n-type semiconductor layer 14, but may also be formed on the remaining portion of the conductive substrate 21 made of the nitride of the group IVA element (that is, the electrode 21 is And a substrate 20).

Next, the light receiving element shown in FIG. 9 is a modification of the light receiving element shown in FIG. In this light receiving element, C is formed on a substrate 20 made of a boride of Group IVA element.
The buffer layer 2 is formed by using the metalorganic vapor phase epitaxy with the VD device 1.
2 is deposited and a device structure is formed on the buffer layer 22. As described above, the lattice spacing of the crystal growth surface of the substrate 20 is equal to the lattice constant of the n-type semiconductor layer 14 provided in the lowermost layer of the device structure. However, depending on the composition of the n-type semiconductor layer 14, these values may differ. It can be different. However, by first depositing a buffer layer on the substrate 20 as shown in FIG. 9, the effect of lattice mismatch that exists between the substrate 20 and the n-type semiconductor layer 14 is mitigated and the resulting n-type is obtained. The crystal quality of the semiconductor layer 14 can be improved.

The material of the buffer layer 22 is preferably the same compound as the n-type semiconductor layer 14 (compound having the same lattice constant). For example, when the n-type semiconductor layer 14 is AlGaN, the buffer layer 22 is also preferably AlGaN. Further, the buffer layer 22 may be composed of a plurality of layers.

<Other Embodiments><1> The structure of the light receiving element has been described above. However, there is a problem that the light is reflected on the surface of the element and the intensity of the light incident on the light receiving region becomes small. The provision of the antireflection function for preventing the light receiving element will be described with reference to FIG.

FIG. 10A is a configuration diagram of a light receiving element having an antireflection function, and FIG. 10B is an explanatory diagram of the antireflection function portion shown in FIG. 10A. (C)
FIG. 6 is an explanatory diagram of a comparative example in the case of not having an antireflection function.

First, the light receiving element shown in FIG. 10A has the same element structure as that shown in FIG. The difference is that the structure of the electrode 19 and the light transmission layer 23 that functions as an antireflection means are provided on the portion of the p-type contact layer 17 where the electrode 19 is not provided. The light transmission layer 23 used here is Al _y Ga _1-y N (0 ≦ y ≦ 1),
The refractive index can be adjusted by changing the composition of atoms. Besides, magnesium fluoride (MgF ₂ ), calcium fluoride (CaF ₂ ), silicon dioxide (SiO ₂ ), etc. can be used. When Al _y Ga _1-y N is used, there is an advantage that it can be manufactured in the same film forming process as each semiconductor layer.

FIG. 10B is a diagram for explaining an antireflection function portion provided on the semiconductor structure in the light receiving element shown in FIG. 10A. In the figure, the refractive index in air is n ₀ , the refractive index of the light transmitting layer is n ₁ (n ₁ > n ₀ ), and the refractive index of the p-type contact layer 17 is n ₂ (n ₂ > n ₁ ). . Further, as a comparative example, FIG. 10C illustrates reflection when the antireflection function is not provided.

First, as shown in FIGS. 10A and 10B, the case where the p-type contact layer 17 and the light transmission layer 23 are provided and the light transmission layer 23 is exposed to the air, , 2 cases in which the light transmission layer 23 is not provided and the p-type contact layer 17 is exposed in the air, p
The reflectances R ₁ and R ₂ with respect to the incident light perpendicularly incident on the mold contact layer 17 are shown in the following formulas ₁ and ₂ . Here, the film thickness d ₂₃ of the light transmission layer 23 is a value obtained by dividing a quarter wavelength of incident light by its own refractive index: d ₂₃ = λ (incident light) / 4n
Set to ₁ . The wavelength of the incident light is the wavelength of the light to be transmitted, and for example, 260n corresponding to the flame light.
The wavelength is from m to 280 nm.

[0068]

[Formula 1] R ₁ = (n ₀ · n ₂ −n ₁ ) ² / (n ₀ · n ₂ + n ₁ ) ²

[0069]

## EQU2 ## R ₂ = (n ₀ −n ₂ ) ² / (n ₀ + n ₂ ) ²

Here, the refractive index n of the p-type contact layer 17 is
₂Is the refractive index n of the light transmitting layer 23.₁Is greater than
n₀If = 1, by comparing equation 1 and equation 2, R₂
> R ₁It turns out that Therefore, the light transmission layer 23 is provided.
Intensity of light incident on the p-type contact layer 17 in the case of
Is incident on the p-type contact layer 17 when not provided.
The light conversion efficiency of the light receiving element is
The rate can be increased. As a result, Teru
The emitted light can be efficiently introduced into the light receiving area.
A light receiving element is provided.

<2> In the above embodiment, the electrode 1
8 and electrodes 19 are made of Ti, Ni, Al, Au
Although it has been described that a metal such as the above can be used, other materials may be used. For example, ZrB ₂ can be used as an electrode. ZrB _{2 which} is the material of the electrode is
Ion beam sputtering, laser ablation, CVD
Can be prepared by a vapor deposition method such as Zr [N (C ₂ H ₅ ) ₂ ] ₄ or Zr (BH ₄ ) ₄ as a Zr source.
1 to produce ZrB ₂ using the MOCVD method using trimethylboron as the B source.
There is an advantage that the film forming apparatus described with reference to can be used to form the film in a process similar to that of the group III nitride.
Incidentally, Al on the ZrB ₂ electrode prepared, Au, Ni, T
A metal such as i may be further formed to form a multi-layer electrode that protects the ZrB ₂ electrode.

Furthermore, ZrB is used as the electrode material.₂When using
The ohmic characteristics of the underlying semiconductor layer.
It has the advantage that it can be example
For example, use Al, Au, Ni, Ti, etc. as the electrode material.
In these materials, In _xAl_yGa_1-xyN layer
The electrical characteristics between (0 ≦ x ≦ 1, 0 ≦ y ≦ 1)
In order to obtain a strong one, the aluminum composition ratio y
Was required to be small. However, the material of the electrode
ZrB as a fee₂If you use
The composition ratio is not limited, and the aluminum composition ratio y is large.
In this case also, the electrical properties of the interface between the electrode and the InAlGaN layer
The characteristics can be ohmic.

<3> In the above-described embodiment, the description has been given by taking the light receiving element having the PIN diode type device structure as an example. However, in the case of forming another light receiving element such as a PN type, a Schottky type, or a photoconductor. By applying the present invention to the steps of forming the semiconductor layer related to the formation of the respective light receiving regions, the same effect as described above can be obtained.
For example, in the case of a PN diode type, a p-type semiconductor layer and n
Since the depletion region formed at the interface with the type semiconductor layer acts as a light receiving region, both the p-type semiconductor layer and the n-type semiconductor layer are semiconductor layers related to the formation of the light receiving region. It may be formed according to the manufacturing method of the light receiving element according to the present invention. Further, although the case where the contact layer is provided between the semiconductor and the electrode has been described in the present embodiment, the contact layer is not necessarily provided.

<4> FIG. 1 shows an example of a film forming apparatus in which the CVD apparatus 1 and the MBE apparatus 2 are connected by the tunnel 3. However, the method for manufacturing a light receiving element according to the present invention can be carried out. What is possible is not limited to the film forming apparatus illustrated in FIG. For example, the CVD device 1 and the MBE device 2 are independent devices (not connected by a tunnel), and when transferring the substrate (and the semiconductor layer already deposited on the substrate) to each other, it is It may be configured to touch.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a semiconductor growth apparatus.

FIG. 2 is a sectional view of a light receiving element.

FIG. 3 is a graph showing band gap energy of InAlGaN.

FIG. 4 is a graph showing spectra of flame light, sunlight, and room light.

FIG. 5 is a cross-sectional view of another light receiving element.

FIG. 6 is a graph showing lattice constants of AlGaN and ZrB ₂ .

FIG. 7 is a graph showing a defect density in an AlGaN layer.

FIG. 8 is a sectional view of another light receiving element.

FIG. 9 is a cross-sectional view of another light receiving element.

FIG. 10A is a sectional view of another light receiving element,
(B) And (c) is a figure explaining the function of an antireflection means.

[Explanation of symbols]

1 CVD equipment 2 MBE equipment 3 tunnels 10 substrates 11 Low temperature deposition buffer layer 12 Crystal improvement layer 13 Low-temperature deposited intermediate layer 14 n-type semiconductor layer 15 i-type semiconductor layer 16 p-type semiconductor layer 17 p-type contact layer 18 electrodes 19 electrodes 20 substrates 21 electrodes 22 Buffer layer 23 Light transmission layer (antireflection means)

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Ueyama             1-501 Shiogamaguchi, Tenpaku-ku, Nagoya-shi, Aichi             Faculty of Science and Engineering, Jojo University (72) Inventor Hiroshi Amano             1-501 Shiogamaguchi, Tenpaku-ku, Nagoya-shi, Aichi             Faculty of Science and Engineering, Jojo University (72) Inventor Isamu Akasaki             1-501 Shiogamaguchi, Tenpaku-ku, Nagoya-shi, Aichi             Faculty of Science and Engineering, Jojo University F-term (reference) 5F049 MA04 MB07 NA01 NA10 NB10                       PA03 PA04 PA18 SE02 SE09                       SS01 SZ03

Claims (10)

[Claims] 1. A step of forming a base structure comprising a single or a plurality of semiconductor layers on a substrate, and a single or a plurality of semiconductor layers including a light receiving region made of a group III nitride on the base structure. And a step of forming a device structure comprising, the underlying structure is formed by a metal organic chemical vapor deposition method, the group III nitride according to the formation of at least the light-receiving region of the device structure, the molecular beam A method for manufacturing a light-receiving element formed by epitaxy. 2. A method of forming a device structure comprising one or more semiconductor layers including a light receiving region made of a group III nitride on a substrate made of a boride of a group IVA element, the device structure comprising: A method for producing a light-receiving element, wherein at least the group III nitride for forming the light-receiving region is formed by molecular beam epitaxy. Wherein the boride is ZrB ₂ claim 2
A method for manufacturing the light-receiving element according to. 4. The method according to claim 2, further comprising a step of forming an underlayer structure including one or more semiconductor layers on the substrate by a metal organic chemical vapor deposition method prior to the step of forming the device structure. The method for manufacturing the light-receiving element according to claim 3. 5. The method according to claim 1, further comprising a step of forming antireflection means for reducing a reflectance of incident light in the device structure on a light incident surface side of the device structure. Of manufacturing the light receiving element of. 6. The method for producing a light-receiving element according to claim 1, wherein the bandgap energy of the group III nitride for forming the light-receiving region is 3.6 eV or more. 7. The method for manufacturing a light-receiving element according to claim 6, wherein the band gap energy of the group III nitride for forming the light-receiving region is 4.0 eV or less. 8. The method for producing a light-receiving element according to claim 6, wherein the bandgap energy of the group III nitride relating to the formation of the light-receiving region is 4.1 eV or more. 9. The method for producing a light-receiving element according to claim 8, wherein the band gap energy of the group III nitride relating to the formation of the light-receiving region is 4.4 eV or more. 10. A flame sensor manufactured by using the method for manufacturing a light-receiving element according to claim 6.