JP2002176197A - Substrate for photonic device and its fabricating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for obtaining a photonic device, and its fabricating method, in which an AlGaInN buffer layer having excellent crystallinity is formed on a sapphire substrate with no crack, and an AlGaInN device multilayer film having excellent crystallinity is formed thereon with no crack. SOLUTION: In the photonic device where an AlGaInN device multilayer film is deposited to satisfy a relation AlxGayInzN (x+y+z=1, x, y, z>=0) on a substrate comprising a sapphire substrate body and an AlGaInN buffer layer formed on the surface thereof, minimum Al composition in the buffer layer is set not lower than the Al composition of the thickest layer in the device multilayer film and Al composition x of the buffer layer is decreased continuously or stepwise toward the device multilayer film from the opposite side thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photonic device substrate formed by depositing a multilayer thin film of a III-V nitride semiconductor material by epitaxial growth and a method of manufacturing the same.

[0002]

2. Description of the Related Art As the above-mentioned group III-V nitride semiconductor _{materials, Al x Ga y In z N} (x + y + z = 1, x,
(y, z ≧ 0) is widely used. Such Al _x
The Ga _y In _z N (x + y + z = 1, x, y, z ≧ 0) film is formed by epitaxial growth by MOCVD. As a group III source gas, when forming an AlN film, TMA is used. (Trimethylaluminum), TMG (trimethylgallium) is used when forming a GaN film, and trimethylindium is used when forming an InN film. As a raw material gas, NH ₃ (ammonia) is generally used, and N ₂ and H ₂ are used as carrier gases.

[0003] In _{general, Al x Ga y In z N} (x + y +
z = 1, x, y, z ≧ 0) When a film is formed, the supply ratio of the above-mentioned group III source gas is controlled to control the I
It is intended to obtain a II-V nitride semiconductor thin film.
The band gap Eg of 1N is 6.2 eV and GaN
Is 3.4 eV, the band gap of InN is 1.9 eV, and there is a relationship of λ = 1240 / Eg between the emission wavelength λ and the band gap Eg. The wavelength of light emitted from the light emitting device using the material is approximately 200 n each.
m, 365 nm and 653 nm. Further, in the light receiving device using these nitride semiconductor materials, light having the above-mentioned wavelength or less can be detected.

Further, by adjusting the mixing ratio of the above-mentioned group III source gas, the composition of the nitride semiconductor material thin film to be formed can be controlled, whereby a desired emission wavelength or light reception wavelength can be obtained. be able to. For example, TM
When A and TMG are mixed to form an Al _x Ga ₁ -xN mixed crystal thin film, the band gap Eg becomes approximately 6.2.
x + 3.4 (1-x), and the emission wavelength λ is 12
40 / {6.2x + 3.4 (1-x)}.
Therefore, for example, if x = 0.3, the emission wavelength λ
Is approximately 292 nm. Similarly, the light receiving wavelength has sensitivity at a wavelength equal to or less than the wavelength defined by the above-described formula.

[0005] As described above, a group III-V nitride semiconductor material _{Al x Ga y In z N (} x + y + z = 1, x,
y, z ≧ 0) In manufacturing a photonic device having a multilayer thin film structure, M is formed on a C-plane of a sapphire substrate.
When direct _Al x _Ga y In _z N film is epitaxially grown by _{OCVD, Al x Ga y In z} N film contains many defects, crystallinity becomes very bad, efficiency becomes extremely low .

Accordingly, Al _x G is applied to the surface of the sapphire substrate.
It has been proposed to form a GaN film serving as a buffer layer by low-temperature CVD epitaxial growth without directly forming a device multilayer film of a _y In _z N (x + y + z = 1, x, y, z ≧ 0). Such low temperature CVD
By interposing the buffer layer formed by the epitaxial growth according to the present invention, a difference of 10% or more between the lattice constant of the sapphire substrate and the lattice constant of the device multilayer film is compensated, and a device multilayer film having good crystallinity is formed. be able to. It has also been proposed to form an AlN film as a buffer layer by low-temperature CVD epitaxial growth instead of a GaN film.

[0007] Conventional light-emitting devices have a long-wavelength emission wavelength λ of 400 nm or more, but as described above, in order to emit short-wavelength blue light or ultraviolet light, the Al composition in the device multilayer film must be adjusted. Need to increase. Also, in a conventional light emitting device of green to blue, in order to efficiently confine light in the light emitting layer, A
l The composition must be increased. Thus aluminum-rich _{Al x Ga y In z N (} x + y + z = 1, x, y,
z ≧ 0) as described above.
When a film is formed on the buffer layer formed by the epitaxial growth using D, cracks are generated and crystallinity is significantly deteriorated.

[0008] The reason is that (a small lattice _constant) aluminum-rich _{Al x Ga y In z N (} x + y + z = 1, x,
y, z ≧ 0) thin film with aluminum composition a small (lattice constant larger) tensile stress device multilayer film when deposited on the buffer layer is generated cracks, aluminum-rich Al _x Ga _y In _z N (x + y + z = 1, x,
y, z ≧ 0) the lateral growth rate of the thin film is slow, poor crystallinity low-temperature buffer _{layer, Al x Ga y In z N} (x + y +
This is considered to prevent the improvement of the crystallinity of the device multilayer film (z = 1, x, y, z ≧ 0). Even in a light receiving device that receives ultraviolet light, there is a problem that the light receiving sensitivity is deteriorated due to such deterioration of crystallinity.

In order to solve such a defect, for example, Japanese Patent Application Laid-Open No. 9-64477 discloses an Al _x Ga ₁ -xN (1 ≧ x> 0) film formed on a sapphire substrate as a buffer layer. then, aluminum rich on the _Al x _Ga y I
_{n z N (x + y +} z = 1, x, y, z ≧ 0) emitting device which was formed a device multilayer film has been proposed.

Further, Japanese Patent Application Laid-Open No. 5-291618 discloses
Is the Ga on the sapphire substrate body._1-xyIn_xA
l_yN (1 ≧ x ≧ 0, 1 ≧ y ≧ 0) thin film is formed, and
By changing the composition x and / or y, finally Ga
_1-abIn_aAl _bN (1 ≧ a ≧ 0, 1 ≧ b ≧ 0)
A buffer layer is formed to have a composition of
And Ga_1-abIn_aAl_bN (1 ≧ a ≧ 0,1 ≧
b> 0)
Has been disclosed.

[0011]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 9-6447.
In the technique described in 7 JP, high temperature AlGaN by using a substrate having a buffer layer, an aluminum-rich _Al x thereon _{Ga y In z N (x +} y + z = 1, x,
(y, z ≧ 0) can be formed as having good crystallinity, and the generation of cracks in the device multilayer film can be suppressed.

However, it is necessary to increase the film forming temperature for forming the AlGaN buffer layer to 1300 ° C. or higher. After the formation of the AlGaN buffer layer,
It is necessary to perform annealing at a high temperature of about 0 ° C. As described above, since high-temperature processing is required, the burden on the heater of the MOCVD apparatus becomes very large, maintenance becomes very troublesome, and there is a drawback that the manufacturing cost increases.

In particular, as described above, light having a short wavelength is emitted.
Or to realize photonic devices that receive light
Is an aluminum-rich Al_xGa _yIn
_zN (x + y + z = 1, x, y, z ≧ 0) layers must be provided.
It is important that the aluminum-rich layer
Because the growth rate is slow, the deposition temperature needs to be very high
And there is a problem that the load on the device becomes particularly large.
You.

If the film formation temperature is lowered to about 1200 ° C., cracks occur in the buffer layer at a thickness of about 0.3 μm, and the crystallinity of the buffer layer is insufficient. It becomes impossible to form a device multilayer film having the above.

In addition, the above-mentioned Japanese Patent Application Laid-Open No. 5-291618
In the technology described in the publication, Ga_1-xyIn_xAl
_yN (1 ≧ x ≧ 0, 1 ≧ y ≧ 0) Composition x
And / or y to finally change Ga_1-abI
n_aAl_bN (1 ≧ a ≧ 0, 1 ≧ b ≧ 0)
A substrate is formed as described above, and Ga _1-abI
n_aAl_bDevice consisting of N (1 ≧ a ≧ 0, 1 ≧ b ≧ 0)
Device multi-layer film
Improves crystallinity and effectively suppresses cracking
Has been stopped. Furthermore, the film formation temperature of the buffer
Since the temperature is as low as 0 ° C, the load on the heater is small.
Is getting worse.

However, in this known technique,
The composition is controlled so that the buffer layer and the device multilayer film are continuously connected. As described above, when the composition is continuously connected at the interface between the buffer layer and the device multilayer film, a current leaks from the device multilayer film to the buffer layer, and a loss due to resistance occurs at that portion, There is a disadvantage that the efficiency is reduced.

[0017] Accordingly, an object of the present invention, a sapphire substrate, SiC substrate, on such a GaN substrate, no cracks, excellent crystallinity _{Al x Ga y In z N (} x + y +
z = 1, x, y, z ≧ 0) a buffer layer, no crack by epitaxial growth thereon, excellent crystallinity _{Al x Ga y In z N (} x + y + z = 1, x,
(y, z ≧ 0) It is an object of the present invention to provide a substrate capable of obtaining a highly efficient photonic device by forming a device multilayer film and a method capable of manufacturing such a photonic device substrate.

[0018]

[MEANS FOR SOLVING THE PROBLEMS] Sapphire, ZnO, S
iC, Si, GaAs, GaN, etc.
_Al x _Ga y _In z N that is deposited on one surface thereof
(X + y + z = 1 , x, y, z ≧ 0) and the buffer layer, _Al was deposited epitaxially grown on the surface of the buffer layer _{x Ga y In z N (x} + y + z = 1, x,
y, z ≧ 0) In a photonic device substrate comprising a device multilayer film, the Al composition in the buffer layer having the minimum Al composition is determined by changing the Al composition of at least the maximum film thickness in the device multilayer film. Al composition or more, the Al composition x of the buffer layer is configured so that the value of the Al composition ratio x decreases continuously or stepwise from the side opposite to the device multilayer film toward the device multilayer film. It is characterized by.

Such a substrate for a photonic device according to the present invention can be used as a substrate for a light emitting device or a light receiving device. In a preferred embodiment of the substrate for a photonic device of the present invention, the Al composition of the buffer layer having the minimum Al composition is represented by Al _x Ga
_y In _z N (x + y + z = 1, 1.0 ≧ x ≧ 0.5), and more preferably 1.0 ≧ x ≧ 0.7. In a preferred embodiment of the photonic device substrate according to the present invention, a portion of the buffer layer closest to the base body has a composition of AlN. This increases the degree of freedom of the composition in the buffer layer, so that a device multilayer film having desired characteristics can be easily realized.

It is preferable that the buffer layer has an interface having a difference in Al composition of 10 atomic% or more. Similarly, it is preferable that a difference in Al composition between the device multilayer film and the buffer layer has an interface of 10 atomic% or more. As described above, the Al
By providing a step in the composition, particularly, dislocations
It does not propagate upward beyond the 1 step. Therefore, the amount of dislocation in the portion above the step of the Al composition can be suppressed, and a device multilayer film having excellent crystallinity can be obtained.

[0021] Further, a substrate for a photonic device according to the invention, in the device multi-layer film, the Al composition in the Al composition up in the layer _{Al x Ga y In z N (} x + y
+ Z = 1, 1.0 ≧ x ≧ 0.3), and is preferably applied to a light-emitting device for short-wavelength light emission, a light-receiving device for short-wavelength light reception, and the like.

Further, the method for manufacturing a substrate for a photonic device according to the present invention is characterized in that sapphire, ZnO, SiC, Si,
GaAs, GaN or the like as the substrate main body, _Al x was deposited on the one surface _{Ga y In z N (x +} y + z
= 1, x, y, z ≧ 0) buffer layer and Al deposited on the surface of this buffer layer by epitaxial growth
_{x Ga y In z N (x} + y + z = 1, x, y, z ≧ 0)
In the method for manufacturing a photonic device substrate comprising a device multilayer film, the Al composition of the buffer layer having a minimum Al composition is at least the Al composition of at least the maximum thickness layer in the device multilayer film. The Al composition x of the buffer layer is continuously or stepwise changed from the opposite side to the device multilayer film toward the device multilayer film.
It is characterized in that the composition ratio x is reduced.

In a preferred embodiment of the manufacturing method according to the present invention, the buffer layer is formed by epitaxial growth by MOCVD at a substrate surface temperature higher than the film forming temperature of the device multilayer film. Specifically, it is preferable that the film formation temperature of the buffer layer be 1100 ° C. or higher.

Further, the _{Al x Ga y In z N (} x + y
+ Z = 1, x, y, z ≧ 0) The flow ratio (hydrogen gas / nitrogen gas) of hydrogen gas and nitrogen gas used as a carrier gas when forming a buffer layer having the composition of It is preferable that the flow rate be larger than a flow ratio of hydrogen gas and nitrogen gas (hydrogen gas / nitrogen gas) used as a carrier gas at the time of film formation.

Further, the _{Al x Ga y In z N (} x + y
+ Z = 1, x, y, z ≧ 0) The flow ratio (Group V source gas / Group III source gas) of the Group V source gas to the Group III source gas used for forming the buffer layer having the composition of: A group V raw material used in forming the device multilayer film, II
It is also preferable to make the flow rate ratio smaller than the group I source material (group V source gas / group III source gas). Where III
The flow rate of the group raw material gas is calculated from the saturated vapor pressure on the assumption that polymerization such as dimerization has not occurred.

Furthermore, when a group III source gas containing Al and a group V source gas are used, the average gas flow rate including the source gas in the reaction tube above the substrate is preferably 1 m / sec or more. The average gas flow velocity in this case is represented by the following equation (1).

[0027]

[Equation 1] 合計 Total gas flow rate converted at 0 ° C. (liter / min) / 60 × 10 ³ × reactor tube cross-sectional area above substrate center (m ² )｝ × {760 / reactor tube pressure (Torr)} ( 1)

That is, the average gas flow velocity increases as the total gas flow rate increases, as the cross-sectional area of the reaction tube decreases, or as the pressure in the reaction tube decreases. Therefore, the reaction of the source gas in the gas phase can be suppressed, and the crystallinity of the buffer layer can be more effectively improved.

Further, in the photonic device substrate according to the present invention, the buffer layer may be made of sapphire,
Although it can be supported by a substrate body such as SiC or GaN, it is also possible to remove the substrate body after forming the buffer layer.

Further, in the photonic device using a substrate for a photonic device according to the present invention described above, the composition of the Al composition greatest layer in the device multi-layer _{film, Al x Ga y In z N} (x + y + z = 1,1.0 ≧
x ≧ 0.3). In the present invention, since the main object is to realize a photonic device in the ultraviolet region, the Al composition x of the light emitting layer in the device multilayer film becomes large. Therefore, the Al composition of the film stacked therearound further increases. For example, assuming ultraviolet light having a light emission wavelength λ of about 300 nm, the Al composition x is 0.3.

Further, in the present invention, the Al composition in the portion having the minimum Al composition in the buffer layer is set to be equal to or more than the Al composition in the layer having the maximum thickness in the device multilayer film.
This configuration is a condition for suppressing cracks that may occur in the film. The largest stress is generated in the layer portion having the maximum thickness in the device multilayer film, and the portion having the highest probability of crack generation is formed. When a tensile stress is generated in the portion having the maximum film thickness, a crack is generated. In order to suppress the occurrence of cracks by generating a compressive stress in this layer, it is necessary to make the Al composition of the buffer layer larger than that of this layer.

In the present invention, the Al composition x of the buffer layer is configured such that the value of the Al composition ratio x decreases continuously or stepwise from the substrate body side toward the device multilayer film. However, this requirement is the most characteristic of the present invention. The present invention uses the conventional 1300
An object is to form a buffer layer having good crystallinity at a low temperature of about 1200 ° C. without using a high temperature of not less than 1200 ° C. However, Al _x having good crystallinity at a low temperature of about 1200 ° C. _{Ga y In z N (x +} y + z = 1, x, y, z
≧ 0) In order to form the buffer layer, it is necessary to increase the thickness of the buffer layer from about 1 μm to about 2 μm.

However, when the thickness of the buffer layer is increased as described above, there is a problem that cracks occur. The reason for this is that tensile stress is generated when the buffer layer is formed, and the thicker the buffer layer, the larger the lattice constant and the more likely it is for cracks to occur. This will be described in more detail later.

In order to solve such a problem, it is only necessary to change the material of the buffer layer to a material having a large lattice constant before cracking. As described above, the buffer layer _{Al x Ga y In z N (} x + y + z =
By reducing the Al composition of (1, x, y, z ≧ 0) composition, the lattice constant increases, so that the stress inside the buffer layer can be prevented, and as a result, 1200 ° C.
Even at a low temperature, the thickness of the buffer layer can be increased without generating cracks, and the crystallinity can be improved. Also, by adding Ga to the buffer layer, the effect of accelerating the growth rate in the lateral direction is also secondary, and therefore, it also has the effect of suppressing dislocation.

Further, in the present invention, the buffer layer is formed at a substrate surface temperature higher than that of the device multilayer film. This is because the buffer layer has a higher Al composition than the device multilayer film. This is because a high temperature is required for the film formation. Therefore, the buffer layer of the present invention can be called a high-temperature buffer layer.

As described above, when a tensile stress is generated during the formation of the buffer layer, cracks are easily formed. This will be further described.
FIG. 1 shows the AlN on the base body side of the buffer layer on the horizontal axis.
The film thickness of the portion is taken, and the vertical axis shows the half width (FWHM) of the X-ray rocking curve of the (002) peak which is a measure of the crystallinity of this AlN film. It can be seen that the half width decreases as the thickness of the AlN film increases, and the crystallinity improves.

FIGS. 2A and 2B show the AlN film thickness on the horizontal axis and the lattice constants a and b of the AlN film on the vertical axis. Where the lattice constants a and b
Corresponds to the length and height of one side of the bottom surface of the hexagonal prism of the AlN crystal formed on the C-plane of the sapphire substrate body, as shown in FIG. In these figures,
The thick solid line indicates the ideal lattice constant of the AlN film. As is clear from these graphs, as the thickness of the AlN film increases, the lattice constant a increases and the lattice constant c decreases.

From the above, it can be seen that as the thickness of the AlN film increases, the crystallinity improves and the in-plane lattice constant a increases. That is, it is understood that when the thickness of the AlN film is increased, tensile stress acts in the plane, and cracks are easily formed.

Also in the manufacturing method of the present invention, it is preferable that an interface having a difference in Al composition of 10 atomic% or more is formed in the buffer layer, and that an interface between the device multilayer film and the buffer layer is formed. It is preferable to form an interface having a difference in Al composition of 10 atomic% or more.
Thereby, as described above, a device multilayer film having excellent crystallinity can be manufactured.

[0040]

FIG. 4 shows an example of a process for manufacturing an embodiment of a substrate for a photonic device according to the present invention. The substrate for the photonic device of this example is
It is a substrate for a light emitting device that emits ultraviolet light. The C-plane sapphire (Al ₂ O ₃ ) substrate main body 1 is introduced into the MOCVD chamber, and the surface temperature of the substrate main body, that is, the film forming temperature is maintained at approximately 1200 ° C., and the film forming pressure is maintained at 15 Torr, and TMA is group III The gaseous growth was performed by introducing ammonia at a total gas flow rate of 10 liters / minute, using ammonia as a group V source gas and hydrogen gas as a carrier gas to form an AlN film 3 of about 0.5 μm. To a film thickness of

The flow ratio (H ₂ flow rate / N ₂ flow rate) of the hydrogen gas and the nitrogen gas used as the carrier gas becomes infinite. The ratio of the flow rate of the group V source gas to the flow rate of the group III source gas (group V source gas flow rate / group III source gas flow rate) is 450, and the supply rate of the source gas is set so that the film forming rate is 1 μm / hour. Controlled. In this case, since a horizontal reaction tube having a reaction tube cross-sectional area of 5 × 10 ⁻³ m ² at the center upper portion of the substrate is used, when the average gas flow rate is calculated from Expression (1),
1.7 m / sec.

In this example, the substrate body 1 of the buffer layer 2 is
Is formed with an AlN film. Next, group III raw materials
Add TMG as gas_0.985Ga
_0.015An N film 4 is formed to a thickness of approximately 0.5 μm.
Further, by changing the flow ratio of the TMA raw material and the TMG raw material,
_0.85Ga_0.15N film 5 to a thickness of approximately 0.5 μm
Form a film. In this manner, the C-
AlN film 3, A having a total thickness of about 1.5 μm on the surface
l_0.985Ga_0.015N film 4 and Al _0.85G
a_0.15Substrate on which buffer layer 2 made of N film 5 is formed
To form

Here, the gas (group V material gas flow rate / III
The flow rate of the gas is not changed from the conditions for forming the AlN film 3 except that the supply rate of the raw material gas is adjusted so as to keep the group gas flow rate constant.

In this case, (00) of the buffer layer
2) Peak rocking curve half width (FWHM) is 5
0 arcsec. Also, the AlGaN films 4 and 5
Since the difference in the Al composition between them is 10% or more, even if the AlGaN film 4 contains a relatively large amount of dislocations, the rate at which the dislocations propagate to the AlGaN film 5 decreases.

FIG. 5 is a sectional view showing the structure of an ultraviolet light emitting device in which a device multilayer film is formed on the surface of the buffer layer 2 of the photonic device substrate according to the present invention formed as described above by epitaxial growth by MOCVD. is there. In this case, as described above, the substrate body 1
Surface may be formed a device multilayer film substrate for a photonic device according to the invention was deposited a buffer layer 2 from the once removed from the MOCVD apparatus, but subsequently _{Al x Ga y In z N (} x + y + z = 1 , X, y, z ≧
The device multilayer film of 0) can also be formed by epitaxial growth.

The substrate surface temperature at the time of film formation is 1050 ° C., which is lower than 1200 ° C. which is the substrate surface temperature at the time of forming the buffer layer 2, and the flow ratio (H ₂₎ of hydrogen and nitrogen gas used as a carrier gas is set. Flow rate / N ₂ flow rate)
When the above-mentioned buffer layer 2 is formed, the flow rate ratio is not more than 1
And the ratio of the flow rate of the group V source gas to the flow rate of the group III source gas (the flow rate of the group V source gas / the flow rate of the group III source gas) when the device multilayer film is formed. Is set to 2000, which is equal to or higher than the flow rate ratio when forming a film.

As described above, the flow ratio of the hydrogen gas and the nitrogen gas used as the carrier gas is set to be equal to or less than the flow ratio in the case of forming the buffer layer 2 because the buffer layer 2 has good crystallinity. _Al x _Ga y _In z N with
This is because in order to form a film (x + y + z = 1, x, y, z ≧ 0), it is desirable to increase the flow rate of hydrogen gas. When the hydrogen gas flow ratio was actually reduced, the crystallinity deteriorated, and the half-width (FWHM) of the (002) peak X-ray rocking curve became 100 arcsec or more. Further, the ratio of the flow rate of the group V source gas to the flow rate of the group III source gas when forming the buffer layer 2 is determined by comparing the flow rate of the group V source gas and the group III source material when forming the device multilayer film. The flow rate ratio is made smaller than the gas flow ratio, which is important for obtaining the buffer layer 2 having good crystallinity.

Here, also for the formation of the device multilayer film, the flow rate of the hydrogen gas is increased, and
When the flow rate ratio of the group II source gas is reduced, the emission characteristics may be deteriorated. The reason _is, Al _x Ga y _In z N
This is because when the concentration of Ga and In in the film is high, the film is more susceptible to etching by hydrogen gas, and as a result, the crystallinity of the film is deteriorated. For this reason, it is considered that the light emission characteristics and the electric characteristics of the entire device multilayer film deteriorate.

Hereinafter, the case where a light emitting device as a photonic device is formed will be described. As shown in FIG. 5, first, an n-type GaN film 6 having a thickness of 3 μm is formed on the surface of the buffer layer 2 as described above. In this case, Al constituting the uppermost layer of the buffer layer 2
_Since the difference in Al composition between the _0.85 Ga _0.15 N film 5 and the GaN film 6 is 10% or more,
_0.85 Ga _{0. Even if the} 15N film 5 contains a relatively large amount of dislocations, the rate at which these dislocations propagate into the GaN film 6 decreases.

The GaN film 6 has the largest film thickness in the device multilayer film. However, since it does not contain any Al, the minimum value of the Al composition in the buffer layer is smaller than that in the device multilayer film. It satisfies the requirement that the composition be at least equal to the Al composition in the layer having the largest thickness.

Next, an n-type Al
_{A 0.10} Ga _0.90 N film 7 is formed to a thickness of 0.1 μm. Next, an In _0.15 Ga _0.85 N film 8 as a light emitting layer is formed on the Al _0.10 Ga _0.90 N film 7 to a thickness of 0.05 μm. Further, In _0.15 Ga
_{0.85 Al} of p-type on the N layer 8 0.10 _{Ga 0.9} 0 N
After forming the film 9 to a thickness of 0.1 μm, this Al _0.10
On the Ga _0.90 N film 9, a low-resistance p-type GaN film 10 is formed to a thickness of 0.5 μm.

Finally, the GaN film 6 to the p-type GaN film 10
Is partially removed by etching to expose a part of the surface of the GaN film 6. Then, the electrode 11 is formed on the exposed surface of the GaN film 6 and the electrode 12 is also formed on the surface of the low-resistance GaN film 10 to obtain a desired light emitting device.

Further, as a modified example of the above-mentioned light emitting device, the following light emitting device can be exemplified. As shown in FIG. 5, first, on the surface of the buffer layer 2,
An n-type AlGaInN film 6 having an Al composition of 0.8
It is formed to a thickness of μm. The AlGaInN film 6 has the largest thickness in the device multilayer film, but in the present invention, the minimum value of the Al composition of the buffer layer 2 is
The Al composition of the AlGaInN film having the maximum thickness is equal to or more than the Al composition.

Further, as shown in FIG.
On the N film 6, an n-type AlGaI having an Al composition of 0.50
An nN film 7 is formed to a thickness of about 0.5 μm. In this case, since the difference in Al composition between the AlGaInN films 6 and 7 is 10% or more, the AlGaInN
Even if the film 6 contains a relatively large amount of dislocations, the rate at which the dislocations propagate to the AlGaInN film 7 decreases.

Next, an AlGaInN film 8 having an Al composition of 0.4 is formed on the AlGaInN film 7 as a light-emitting layer in a thickness of about 0.1.
The film is formed to a thickness of 1 μm. This light emitting layer, AlGaI
On the nN film 7, a p-type AlGaI having an Al composition of 0.5
An nN film 9 is formed to a thickness of approximately 0.5 μm.
Low-resistance p-type AlGaInN film 1 having a composition of 0.1 or less
0 is formed into a film thickness of approximately 0.5 μm. Finally, AlG
removing a part of the aInN films 6 to 10 by etching to expose a part of the surface of the n-type AlGaInN film 6;
An electrode 11 is formed thereon and a low-resistance p-type AlGa
An electrode 12 is also formed on the InN film 10.

FIG. 6 shows a photonic device according to the present invention.
Pin type with sensitivity to ultraviolet light
FIG. 3 shows an example of a process for manufacturing a photodiode.
You. As shown in FIG. 6, an AlN film 3, A
l_0.985Ga _0.015N film 4 and Al_0.85
Ga_0.15The buffer layer 2 made of the N film 5 was formed.
Thereafter, on the surface of the buffer layer 2, first, the Al composition is set to 0.1.
The n-type AlGaInN film 6 of FIG.
To achieve.

The AlGaInN film 6 has the largest film thickness in the device multilayer film. In the present invention, the minimum value of the Al composition of the buffer layer 2 is set to the value of the AlGaInN film 6 having the largest film thickness. Al composition or more.

Further, as shown in FIG.
On the N film 6, non-dope AlGa having an Al composition of 0.5
An InN film 7 is formed to a thickness of about 100 °, and
The p-type AlGaInN film 8 having a composition of 0.15
The AlGaInN films 6 to
8 is removed by etching to remove n-type AlGa.
A part of the surface of the InN film 6 is exposed, an electrode 11 is formed thereon, and the electrode 1 is formed on the p-type AlGaInN film 8.
2 is formed to complete a pin type photodiode.

The light receiving surface of the photodiode shown in FIG. 6 can be on the upper side of the figure using the electrode 12 as a transparent electrode, or can be on the substrate side when the substrate 1 is transparent.

As described above, as the conditions for forming the buffer layer 2, the average gas flow rate obtained by the above equation (1) is set to 1 m / sec or more. FIG. 7 shows the average gas flow velocity on the horizontal axis and the half width (FWH) of the X-ray rocking curve representing the crystallinity on the vertical axis.
M). The plot shown in FIG. 7 is data of the average gas flow rate derived from various gas flow rates, the cross-sectional area of the reaction tube, and the pressure in the reaction tube using the equation (1). As is clear from FIG. 7, the average gas flow velocity was 1 m /
The half width FWHM is 90 arcsec
The results are as follows, and it has been confirmed that the buffer layer 2 having good crystallinity can be formed.

The present invention is not limited only to the above-described embodiment, and many modifications and variations are possible. For example, in the above-described embodiment, the substrate main body is formed with sapphire of C-plane, but other crystal plane of sapphire, ZnO
A substrate body formed of an oxide crystal such as SiC, a semiconductor crystal such as SiC, Si, GaAs, or GaN can also be used. Furthermore, in the above-described embodiment, the substrate for a light emitting device that emits ultraviolet light or the substrate for a pin type photodiode is used. However, other types of light emitting diodes such as a laser diode and a light emitting diode that emits light of another color such as blue are used. A substrate for a light emitting device or a substrate for another light receiving device such as a Schottky type photodiode can also be used.

In the above-described embodiment, a buffer layer is formed on the sapphire substrate main body by epitaxial growth to form a substrate for a photonic device, but after forming the buffer layer with a thickness of about 100 μm on the substrate main body. ,
The substrate body can also be removed.

[0063] As described above, in the photonic device substrate and a manufacturing method thereof according to the present invention, there is no occurrence of cracks, Al _x Ga _y with good crystallinity
_{In z N (x + y +} z = 1, x, y, z ≧ 0) having a buffer layer, and thus on _{its, Al x Ga y In z N} (x + y + z = 1, x having a good crystallinity, y, z
≧ 0) can provide a substrate for a photonic device on which a device multilayer film can be formed, and in particular, emits or receives light having a short wavelength ranging from blue light to ultraviolet light,
A substrate for realizing a photonic device with good efficiency and good electrical characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the thickness of an AlN buffer layer and crystallinity.

FIGS. 2A and 2B are graphs showing the relationship between the thickness of an AlN buffer layer and lattice constants a and b.

FIG. 3 is a diagram schematically showing a crystal structure of AlN.

FIG. 4 is a sectional view showing one embodiment of a substrate for a photonic device according to the present invention.

5 is a cross-sectional view showing a light emitting device formed by forming a device multilayer film on the substrate shown in FIG.

FIG. 6 is a cross-sectional view showing a light receiving device formed using the photonic device substrate according to the present invention.

FIG. 7 is a graph showing the relationship between the average gas flow rate and the crystallinity during the formation of a buffer layer.

[Explanation of symbols]

1 C-plane sapphire substrate main body, 2 buffer layer,
3 AlN film, 4, 5 AlGaN film, 6, 7 n-type AlGaInN film, 8 light emitting layer, 9 p-type AlGa
InN film, 10 Low resistance p-type AlGaInN film, 1
1,12 electrodes

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akiyo Nagai 2-56, Suda-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Inside Nihon Insulators Co., Ltd. No. 56 F-term in Nihon Insulators Co., Ltd. (reference) 5F041 AA03 CA22 CA34 CA65 5F045 AA04 AB18 AC08 AC12 AC18 AD15 AD16 AF01 AF02 AF03 AF04 AF07 AF09 BB12 BB13 BB16 CA12 CA19 DA53 DA58

Claims (18)

[Claims] 1. Sapphire, ZnO, SiC, Si, Ga
The as, GaN or the like as the substrate main body, _Al x was deposited on the one surface _{Ga y In z N (x +} y + z =
1, x, y, z ≧ 0) buffer layer and Al _x deposited on the surface of the buffer layer by epitaxial growth
In a substrate for a photonic device including a device multilayer film of Ga _y In _z N (x + y + z = 1, x, y, z ≧ 0), the Al composition of the buffer composition having the minimum Al composition is obtained by: The Al composition of at least the layer having the maximum thickness in the device multilayer film is equal to or more than the Al composition, and the Al composition x of the buffer layer is continuously or stepwise shifted toward the device multilayer film from the side opposite to the device multilayer film. A substrate for a photonic device, characterized in that the ratio x is reduced. Wherein said buffer layer, Al composition of the Al composition of the minimal _{portion, Al x Ga y In z N} (x + y + z =
2. The substrate for a photonic device according to claim 1, wherein (1.0, x ≧ 0.5). 3. The photonic device substrate according to claim 1, wherein a portion of the buffer layer closest to the substrate body has a composition of AlN. 4. forming the buffer layer _Al x _Ga y I
_nz N (x + y + z = 1, x, y, z ≧ 0) is (00
2) FWHM of X-ray rocking curve at peak
The photonic device substrate according to any one of claims 1 to 3, wherein HM is 90 arcsec (ω scan) or less. 5. The photonic device substrate according to claim 1, wherein said buffer layer is formed at a substrate surface temperature higher than that of said device multilayer film. 6. The semiconductor device according to claim 1, wherein a difference in Al composition in the buffer layer or between the buffer layer and the device multilayer film is 1 or more.
The photonic device substrate according to any one of claims 1 to 5, having an interface of 0 atomic% or more. 7. The buffer layer is made of sapphire, ZnO,
The photonic device substrate according to any one of claims 1 to 6, wherein the substrate is supported by a substrate body made of SiC, Si, GaAs, GaN, or the like. 8. The device according to claim 1, wherein the Al composition in the device multilayer film is the largest.
The composition of the layer is Al_xGa _yIn_zN (x + y + z = 1,
1.0 ≧ x ≧ 0.3).
A base for a photonic device according to any one of 1 to 7
Board. 9. Sapphire, ZnO, SiC, Si, Ga
The as, GaN or the like as the substrate main body, _Al x was deposited on the one surface _{Ga y In z N (x +} y + z =
1, x, y, z ≧ 0) buffer layer and Al _x deposited on the surface of the buffer layer by epitaxial growth
In a method for manufacturing a substrate for a photonic device, comprising: a Ga _y In _z N (x + y + z = 1, x, y, z ≧ 0) device multilayer film, an Al composition in a portion of the buffer layer having a minimum Al composition. The Al composition of at least the layer having the maximum thickness in the device multilayer film, and the Al composition x of the buffer layer is continuously or stepwise shifted toward the device multilayer film from the side opposite to the device multilayer film. To Al
A method for producing a substrate for a photonic device, wherein the composition ratio is configured to be small. 10. The photonic device substrate according to claim 9, wherein said buffer layer is formed by epitaxial growth by MOCVD at a substrate surface temperature higher than a film forming temperature of said device multilayer film. Manufacturing method. 11. The substrate surface temperature at the time of forming said buffer layer is 1100 ° C. or higher.
3. The method for producing a substrate for a photonic device according to item 1. 12. The method according to claim 11, wherein the substrate surface temperature at the time of forming the buffer layer is less than 1300 ° C.
3. The method for producing a substrate for a photonic device according to item 1. 13. The method according to claim 1, wherein a flow rate ratio of hydrogen gas and nitrogen gas (hydrogen gas / nitrogen gas) used as a carrier gas when forming the buffer layer is determined as a carrier gas when forming the device multilayer film. The method for manufacturing a substrate for a photonic device according to any one of claims 9 to 12, wherein a flow rate ratio of hydrogen gas and nitrogen gas (hydrogen gas / nitrogen gas) to be used is made larger. 14. A method for forming the buffer layer according to claim 1.
The flow rate ratio of the group V source gas to the group III source gas (group V source gas / group III source gas) is determined by the flow rate of the group V source gas used for forming the device multilayer film to the group III source gas. 14. The method for manufacturing a substrate for a photonic device according to claim 9, wherein the ratio is set to be smaller than the ratio (group V source gas / group III source gas). 15. The method for manufacturing a substrate for a photonic device according to claim 9, wherein an average gas flow rate at the time of forming the buffer layer is 1 m / sec or more. 16. The method according to claim 16, wherein the buffer layer is made of sapphire, Si
The device multilayer film is formed after forming on a surface of a substrate body such as C or GaN, with the buffer layer supported by the substrate body.
5. The method for manufacturing a substrate for a photonic device according to any one of 5. 17. The method according to claim 9, wherein an interface having a difference in Al composition of 10 atomic% or more is formed in said buffer layer or between said buffer layer and said device multilayer film. A method for manufacturing the substrate for a photonic device according to any one of the above. 18. The Al composition in the device multilayer film composition of the largest _{layer, Al x Ga y In z N} (x + y + z =
The method for manufacturing a substrate for a photonic device according to any one of claims 9 to 17, wherein (1, 1.0? X? 0.3).