JP5309949B2 - Compound semiconductor substrate, light emitting element, compound semiconductor substrate manufacturing method, and light emitting element manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound semiconductor substrate which has various superior characteristics of luminance, life etc., and excellent quality, to provide a light emitting element, to provide a method of manufacturing the compound semiconductor substrate, and to provide a method of manufacturing the light emitting element. <P>SOLUTION: The compound semiconductor substrate has at least a double-hetero-structure formed of (Al<SB>x</SB>Ga<SB>1-x</SB>)yIn<SB>1-y</SB>P (where 0&lt;x&lt;1, 0&lt;y&lt;1) on a GaAs substrate, wherein respective layers constituting the double-hetero-structure have lattice constants matched with the GaAs substrate so that a lattice mismatch rate at room temperature is &ge;0% to &le;0.02%, and the carrier concentration of the GaAs substrate is 1 to 2.5&times;10<SP>18</SP>/cm<SP>3</SP>. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to a compound semiconductor substrate and a light-emitting element, and more particularly, a compound semiconductor substrate, a light-emitting element, and a compound semiconductor in which a double heterostructure composed of (Al _x Ga _1-x ) _y In _1-y P quaternary mixed crystal is formed. The present invention relates to a method for manufacturing a substrate and a method for manufacturing a light emitting element.

In recent years, for example, since it is easy to obtain light with relatively high luminance over a range from green to red, as a light emitting element, (Al _x Ga _1-x ) _y In _1-y P (hereinafter simply referred to as AlGaInP) is formed on a GaAs substrate. A material manufactured from a compound semiconductor substrate obtained by epitaxial growth of a light-emitting layer made of a quaternary mixed crystal is often used.

  However, when a light emitting layer having a lattice constant different from that of GaAs such as AlGaInP is formed on a GaAs substrate, the larger the difference in the lattice constant, the greater the influence on the luminance and life of the light emitting element, for example. The characteristics had deteriorated. Further, warpage and dislocation may occur in the compound semiconductor substrate.

Therefore, conventionally, as disclosed in, for example, Patent Document 1, the composition of AlGaInP is adjusted to form a light emitting layer so that the lattice constants of AlGaInP and GaAs match at the temperature at which AlGaInP is epitaxially grown. The way was done.
In addition, the lattice constant of the epitaxially grown AlGaInP layer can be changed to the lattice constant of GaAs by forming a layer whose mixed crystal ratio gradually changes from GaAs to the lattice constant of AlGaInP or by forming a layer that relaxes mismatch. An attempt was made to bring it closer to.

  However, only the conventional manufacturing method in consideration of the lattice constant at the epitaxial growth temperature or the manufacturing method in which a layer for reducing the difference in lattice constant between AlGaInP and GaAs is formed between the manufactured light-emitting elements ( Various characteristics such as luminance and life of the compound semiconductor substrate) are unstable, or satisfactory results have not been obtained.

  Moreover, such instability has been suppressed by adjusting the carrier concentration of the GaP window layer (not at a high concentration), but this method has its limitations.

JP-A-9-186360

  The present invention has been made in view of such problems, and provides a high-quality compound semiconductor substrate and a light-emitting element having excellent characteristics such as luminance and life, a method for manufacturing the compound semiconductor substrate, and a method for manufacturing the light-emitting element. The purpose is to provide.

To achieve the above object, the present invention is, at least, on a GaAs substrate _{(Al x Ga 1-x)} y In 1-y P ( However, 0 <x <1,0 <y <1) a double consisting A compound semiconductor substrate in which a terror structure and an epitaxially grown GaP current diffusion layer are formed, and each layer constituting the double hetero structure has a lattice mismatch rate of 0% at room temperature with respect to the GaAs substrate. Provided is a compound semiconductor substrate characterized in that the lattice constant is matched so that it is 0.02% or less and the carrier concentration of the GaAs substrate is 1 to 2.5 × 10 ¹⁸ / cm ³ .

Thus, each layer constituting the double heterostructure is a compound semiconductor substrate whose lattice constant is matched such that the lattice mismatch rate at room temperature is 0% or more and 0.02% or less with respect to the GaAs substrate. If there is, the difference in lattice constant between GaAs and AlGaInP at room temperature can be made extremely small, and the effects on various characteristics such as luminance and life of the substrate caused by the difference in the lattice constant can be effectively suppressed. Is possible. By matching the lattice constant within the above range at room temperature as in the present invention, a compound semiconductor substrate with higher luminance and longer life can be obtained.
Further, by setting the carrier concentration of the GaAs substrate to 1 to 2.5 × 10 ¹⁸ / cm ³ , the warpage of the compound semiconductor substrate can be controlled within a predetermined range, and handling is easy when forming a light emitting element or the like later. Can be.

At this time, the room temperature at which the lattice constant is matched so that the lattice mismatch rate between each layer constituting the double heterostructure and the GaAs substrate is 0% or more and 0.02% or less is 25 ° C. Can do .
Thus, it is sufficient if the room temperature at which the lattice constant is matched so that the lattice mismatch rate between each layer constituting the double heterostructure and the GaAs substrate is 0% or more and 0.02% or less is 25 ° C. In addition, a high-quality and long-life compound semiconductor substrate can be obtained.

The GaAs substrate preferably has n-type conductivity .
Thus, when the conductivity type of the GaAs substrate is n-type, a compound semiconductor substrate generally used as a high-luminance light emitting element can be obtained.

And it is preferable that the magnitude | size of the curvature of the said compound semiconductor substrate is -50--400 micrometers .
As described above, if the compound semiconductor substrate has a warpage of −50 to −400 μm, it is possible to strongly suppress, for example, difficulty in handling when manufacturing a light-emitting element. It can suppress strongly that productivity falls.

  Furthermore, if it is a light emitting device manufactured from the above compound semiconductor substrate (Claim 5), the difference in lattice constant at room temperature between each layer constituting the double hetero structure of the light emitting layer and the GaAs substrate is extremely small, It is possible to suppress the influence caused by the difference in the lattice constant and to obtain a light emitting element having excellent characteristics such as luminance and life.

Further, in the present invention, at least, on a GaAs substrate _{(Al x Ga 1-x)} y In 1-y P ( However, 0 <x <1,0 <y <1) is a double hetero structure and the epitaxial growth consisting of A compound semiconductor substrate having a GaP current diffusion layer formed thereon, wherein the GaAs substrate has a carrier concentration of 1 to 2.5 × 10 ¹⁸ / cm ³ and the double heterostructure X and y are adjusted (Al _x Ga ₁₎ so that the lattice constants are matched with the GaAs substrate at a lattice mismatch rate of 0% to 0.02% at room temperature. _{-x) y} in _{1-y P} a is epitaxially grown to provide a manufacturing method of a compound semiconductor substrate, characterized in that to form.

In this way, each of the layers constituting the double heterostructure, which is a light emitting layer, is arranged such that the lattice constant is matched with the GaAs substrate so that the lattice mismatch rate is 0% or more and 0.02% or less at room temperature. If y is adjusted to form (Al _x Ga _1-x ) _y In _1-y P by epitaxial growth, the difference in lattice constant between GaAs and AlGaInP at room temperature can be made extremely small. Therefore, the compound semiconductor substrate having higher brightness and longer life can be obtained.
Further, by using a GaAs substrate having a carrier concentration of 1 to 2.5 × 10 ¹⁸ / cm ³ , the size of the warp of the manufactured compound semiconductor substrate becomes difficult to handle when forming an element. This can be suppressed, that is, the compound semiconductor substrate can be easily handled.

At this time, the adjustment of x and y is performed when the lattice constant of GaAs is s _room and the lattice constant of (Al _x Ga _1-x ) _y In _1-y P is a _{room. room -s room) / s room ×} 100 [%] it is, can be carried out by adjusting and calculated so that 0 to 0.02.
As described above, the adjustment of x and y is performed when the lattice constant of GaAs is s _room and the lattice constant of (Al _x Ga _1-x ) _y In _1-y P is a _{room. room -s room) / s room ×} 100 [%] it is, can be carried out by adjusting and calculated so that 0 to 0.02, can be easily obtained a composition having a desired AlGaInP.

Further, the epitaxial growth of the (Al _x Ga _1-x ) _y In _1-y P can be performed by the MOVPE method .
_Thus, it is possible to _{(Al x Ga 1-x)} y In 1-y P epitaxial growth can be carried out by the MOVPE method, the epitaxial growth of AlGaInP having a desired composition.

At this time, the room temperature lattice mismatch ratio between the GaAs substrate and the layers constituting the heterostructure the double lattice constant is matched with 0.02% to 0%, it is possible to 25 ° C..
Thus, by setting the room temperature at which the lattice mismatch between the layers constituting the double heterostructure and the GaAs substrate is 0% or more and 0.02% or less and the lattice constant is matched, the temperature is sufficiently high. A long-lived compound semiconductor substrate can be obtained.

The GaAs substrate is preferably an n-type conductivity type .
As described above, when the conductivity type of the GaAs substrate is n-type, it is possible to obtain a general compound semiconductor substrate as a high-luminance light emitting element.

Furthermore, it is preferable that the magnitude | size of the curvature of the said compound semiconductor substrate shall be -50--400 micrometers .
Thus, if the magnitude | size of curvature of the produced compound semiconductor substrate is -50--400 micrometers, conveyance of a board | substrate etc. will become difficult when manufacturing an element using the produced compound semiconductor substrate. Can be suppressed.

In addition, if the light emitting device is manufactured from the compound semiconductor substrate manufactured by the above method for manufacturing a compound semiconductor substrate, the lattice constant at room temperature between each layer constituting the double hetero structure of the light emitting layer and the GaAs substrate Thus, a light-emitting element having excellent characteristics such as luminance and life can be obtained by suppressing the influence of the difference in lattice constant.

As described above, according to the present invention, the difference in the lattice constant between the GaAs substrate and AlGaInP at room temperature is made extremely small to effectively suppress the influence on the characteristics caused by the difference in the lattice constant, and the carrier concentration. By using a GaAs substrate having a thickness of 1 to 2.5 × 10 ¹⁸ / cm ³ , the warpage of the compound semiconductor substrate can be reduced, and therefore, a high-quality compound semiconductor having higher luminance and longer life. A substrate and a light-emitting element can be obtained.

Hereinafter, although an embodiment is described about the present invention, the present invention is not limited to these.
When forming each layer of AlGaInP constituting a double hetero structure on a GaAs substrate as a light emitting layer, conventionally, for example, in order to reduce the difference between the lattice constant of GaAs and AlGaInP, a relaxation layer between them is used. The method of forming was performed.

As another method, the epitaxial growth of AlGaInP is performed by adjusting the composition of AlGaInP so that the lattice constants of AlGaInP and GaAs are matched at the temperature at which AlGaInP is epitaxially grown (for example, about 650 to 800 ° C.). It was broken.
In order to effectively prevent warpage and dislocations in the compound semiconductor substrate (light emitting device), it has been natural to match the lattice constant at the epitaxial growth temperature.

  However, in these conventional methods, various properties such as luminance and life of the obtained compound semiconductor substrate (light emitting device) are deteriorated, and sufficiently good characteristics cannot be obtained.

  Therefore, the present inventors conducted extensive research on the compound semiconductor substrate and the light-emitting element. As a result, the lattice constants of GaAs and AlGaInP were matched at room temperature. It has been found that if the matching rate is formed to be an extremely small value of 0% or more and 0.02% or less, the above-described characteristics can be effectively prevented from being deteriorated.

  As described above, in the past, it was believed that the luminance and life characteristics would decrease when the lattice constants of GaAs and AlGaInP were matched, and when the dislocations increased, the occurrence of such dislocations would be prevented or warped. In order to effectively prevent this, it has been common knowledge to perform epitaxial growth with a composition of AlGaInP that matches the lattice constant at the temperature during the epitaxial growth of AlGaInP.

However, the present inventors first found that the occurrence of dislocations does not actually affect the above characteristics so much, and the occurrence of cracks can be sufficiently prevented by devising the processing method.
Further, in order to obtain a compound semiconductor substrate and a light emitting device with better brightness and life, the lattice mismatch rate between GaAs and AlGaInP is 0 at room temperature instead of being based on the temperature during epitaxial growth as in the prior art. It has been found that it is important to perform epitaxial growth with a composition of AlGaInP so that it is not less than 0.02% and not more than 0.02%.

However, the compound semiconductor substrate manufactured by lattice matching in the above-described range may be warped, which causes a problem that it may be difficult to handle when forming a light emitting element.
In order to suppress this warpage, further earnest studies were conducted, and it was found that the magnitude of the warpage was related to the carrier concentration of the GaAs substrate.
In order to investigate the relationship between the carrier concentration of the GaAs substrate and the curvature of the compound semiconductor substrate, the compound semiconductor substrate is manufactured by changing the carrier concentration of the GaAs substrate from 1 × 10 ^{17 to} 3 × 10 ¹⁸ / cm ^3. As a result of investigating the relationship by measuring the magnitude of the warpage, as shown in FIG. 3, when the carrier concentration of the GaAs substrate is between 1 and 2.5 × 10 ¹⁸ / cm ³ , the GaAs substrate When the warpage of the compound semiconductor substrate formed above is almost within the range of 0 to −400 μm, which does not cause a practical problem, and the carrier concentration is less than 1 × 10 ¹⁸ / cm ³ , the size of the warpage exceeds -400Myuemu, also when the carrier concentration is greater than 2.5 × ¹⁰ 18 / cm ^3, on the opposite side size of the warp of the compound semiconductor substrate exceeds the 0μm Heading the Rukoto, it has led to the completion of the present invention from the above findings.

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings.
FIG. 1 shows an example of a compound semiconductor substrate of the present invention.
As shown in FIG. 1A, the compound semiconductor substrate 1 of the present invention includes, for example, a GaAs substrate 2, a buffer layer 7, a double hetero structure 3, and a current diffusion layer 8.
Heterostructure 3 to the double at least the lower cladding layer 4, active layer 5, a light emitting layer formed of the upper cladding layer 6, each of the layers from the _{(Al x Ga 1-x)} y In 1-y P It has become.

Here, each layer 4, 5, 6 constituting the _{(Al x Ga 1-x)} y In 1-y heterostructures 3 P a double consisting are all relative to the GaAs substrate 2, the lattice at room temperature mismatch The lattice constants are matched so that the rate is 0% or more and 0.02% or less.

  That is, the difference in lattice constant at room temperature is extremely small between the GaAs substrate 2 and the layers 4, 5, 6 constituting the double heterostructure 3. Therefore, since the influence on the various characteristics of the compound semiconductor substrate 1 caused by the difference in lattice constant in these layers can be sufficiently suppressed, the characteristics are unlikely to deteriorate, and high characteristics can be obtained. is there.

  This is because the lattice constant is matched at room temperature rather than the lattice constant matched to the epitaxial growth temperature of AlGaInP as in the case of a conventional compound semiconductor substrate, which reduces the characteristics in actual use. This can be prevented more effectively, resulting in a compound semiconductor substrate of higher quality than before.

In the compound semiconductor substrate 1 of the present invention, the carrier concentration of the GaAs substrate 2 is 1 to 2.5 × 10 ¹⁸ / cm ³ .
Thus, when the carrier concentration of the GaAs substrate is 1 to 2.5 × 10 ¹⁸ / cm ³ , the warpage of the compound semiconductor substrate can be made small, and handling in manufacturing a light emitting element or the like is easy. Can be.
More preferably, the carrier concentration of the GaAs substrate is 1 to 1.5 × 10 ¹⁸ / cm ³ . A compound semiconductor substrate using a GaAs substrate having such a carrier concentration range can be a compound semiconductor substrate with less variation and less warpage.

  Further, by providing the buffer layer 7 between the double heterostructure 3 and the GaAs substrate 2, it is possible to effectively prevent impurities from diffusing from the GaAs substrate 2 and to further influence the influence of crystal defects. It is possible to remove it sufficiently.

  A current diffusion layer 8 is formed on the upper cladding layer 6 of the double heterostructure 3. If such a current diffusion layer 8 is formed, the current from the electrode 12 (see FIG. 2) can be diffused, so that light can be efficiently emitted not only near the electrode 12 but also in a wide range. Is possible. Examples of the material of the current spreading layer 8 include GaP, but are not particularly limited, and an appropriate material can be selected each time.

In the above description, the compound semiconductor substrate 1 including only the GaAs substrate 2, the buffer layer 7, the double heterostructure 3, and the current diffusion layer 8 as shown in FIG. Of course, the compound semiconductor substrate 1 of the present invention is not limited to this form.
For example, as shown in FIG. 1B, a DBR layer 9 is formed between the double heterostructure 3 and the buffer layer 7 in order to effectively extract light directed from the light emitting layer toward the GaAs substrate 2. The compound semiconductor substrate 1 ′ may be used. In this way, the light emitted from the double heterostructure 3 can be extracted more efficiently.
In addition, a further current diffusion layer (not shown) may be formed between the current diffusion layer 8 and the upper cladding layer 6. With such a further current diffusion layer, characteristics such as luminance can be further improved.

Further, the conditions in each of the above layers, such as the type of dopant and the thickness of the layer, are not particularly limited, and can be appropriately adjusted so as to obtain desired characteristics.
As described above, if the thickness of the compound semiconductor substrate 1 is large, the occurrence of warpage and cracking can be effectively prevented. Therefore, the thickness of each layer is adjusted in consideration of this. (For example, the thickness of the entire substrate is adjusted to be about 200 to 500 μm).
Moreover, the thing etc. which gave the process for preventing them may be given.

The warpage of the compound semiconductor substrate can be set to −50 to −400 μm.
As described above, by setting the size of the warpage of the compound semiconductor substrate in the above-described range, for example, a dicing process for manufacturing a light emitting element thereon and handling during transfer between the processes can be easily performed. Can be.

Here, +-of the warp in the present invention will be described.
In the present invention, as shown in FIG. 5A, the ± direction of warpage of the compound semiconductor substrate is a case where the GaAs substrate 2 side is convex, that is, the buffer layer 7, the double heterostructure 3 and the current diffusion layer 8 side are concave. As shown in FIG. 5B, the case where the GaAs substrate 2 side is concave, that is, convex toward the buffer layer 7, the double heterostructure 3, and the current diffusion layer 8 side is defined as +.
In other words, the warpage of the compound semiconductor substrate described above being −50 to −400 μm represents that the substrate inner peripheral portion of the GaAs substrate is protruded 50 to 400 μm lower than the substrate outer peripheral portion. .

  In addition, although room temperature here shows 25 degreeC, it is not limited to this 25 degreeC. For example, the temperature may not be in a high temperature range such as when epitaxial growth of AlGaInP such as about 650 to 800 ° C. is performed. Therefore, it can also be made into the range of about 15-35 degreeC, for example.

In addition, as shown in FIG. 2, the light emitting device 10 of the present invention is obtained by forming a contact layer 11 and electrodes 12 and 13 on the compound semiconductor substrate 1 as described above, and forming a device through a dicing process or the like. It is.
As described above, the light-emitting element 10 constitutes the double heterostructure 3, and each layer 4, 5, 6 made of AlGaInP has a lattice mismatch rate of 0% or more and 0. The difference between the lattice constants of these layers is extremely small, and the influence of deteriorating the characteristics can be suppressed, so that the luminance and life characteristics are excellent.

Next, the manufacturing method of the compound semiconductor substrate 1 of the present invention as described above will be described.
First, a GaAs substrate 2 is prepared. The GaAs substrate 2 is not particularly limited in thickness, type of dopant, and the like, and can be appropriately selected so as to obtain a desired compound semiconductor substrate 1.
However, the carrier concentration is 1 to 2.5 × 10 ¹⁸ / cm ³ .
This is to suppress the warpage of the manufactured compound semiconductor substrate from becoming a size that makes it difficult to handle the device later. In addition, even if the current diffusion layer is formed thick (30 μm or more), it is to prevent deterioration of the characteristics as an element such as life.

Here, the conductivity type of the GaAs substrate can be n-type.
As described above, when the conductivity type of the GaAs substrate 1 is n-type, a compound semiconductor substrate which is a general high-luminance light emitting element can be obtained.

  Then, the buffer layer 7 is epitaxially grown on the GaAs substrate 2. By forming such a buffer layer 7 in advance of the double heterostructure 3 described later, it is possible to further suppress the occurrence of dislocations and to effectively diffuse impurities from the GaAs substrate 2, for example. This is effective because it can be prevented. However, in the present invention, the formation of this buffer layer is arbitrary.

Further, on the buffer layer 7, a double heterostructure 3 serving as a light emitting layer is formed. As described above, heterostructure 3 to the double, the lower cladding layer 4, active layer 5, is constituted by the upper cladding layer 6, the layers are both _{(Al x Ga 1-x)} y In 1-y Made of P.
In the manufacturing method of the present invention, this (Al _x Ga _1-1) is matched with the GaAs substrate 2 so that the lattice constant is matched at a room temperature (for example, 25 ° C.) with a lattice mismatch rate of 0% to 0.02%. _x ) _y In _1-y P is adjusted to x and y values, and (Al _x Ga _1-x ) _y In _1-y P is epitaxially grown to form the layers 4, 5, 6.

Here, the adjustment method of said x and y is demonstrated more concretely.
As a method for adjusting these x and y, for example, the lattice constants of GaAs and (Al _x Ga _1-x ) _y In _1-y P are compared at room temperature, and x and y are adjusted so that they match. This can be done by selecting y by calculation or the like. The lattice constant of (Al _x Ga _1-x ) _y In _1-y P at room temperature is estimated as follows by using the known crystal lattice constant (room temperature) as shown in Table 1. be able to.

Transforming composition formula of the _{(Al x Ga 1-x)} y In 1-y P, the _{Al xy Ga (1-x)} y In (1-y) P. Therefore, since this quaternary mixed crystal contains AlP, GaP, and InP shown in Table 1 respectively in xy, (1-x) y, and (1-y), (Al _x Ga _1-x ) _y In at room temperature. The lattice constant a _room of _1-y P is
a _room = 0.54625xy + 0.54512 (1-x) y + 0.58688 (1-y) [nm] (1)
It can be expressed as.
On the other hand, assuming that the lattice constant of GaAs at room temperature is s _room , as shown in Table 1,
s _room = 0.565325 [nm] (2)
It is.

Further, the lattice mismatch rate Δa _room at _room temperature between (Al _x Ga _1-x ) _y In _1-y P and GaAs is expressed by the following equation.
Δa _room = (a _room −s _room ) / s _room × 100 [%] (3)
In the manufacturing method of the present invention, the lattice mismatch ratio Δa _{room at room} temperature between the (Al _x Ga _1-x ) _y In _1-y P and GaAs is set to 0% or more and 0.02% or less. ,
0 ≦ Δa _room ≦ 0.02 [%] (4)
It becomes.

Here, since the Al mixed crystal ratio determines the band gap energy of the AlGaInP quaternary mixed crystal, first, the Al mixed crystal ratio x of the active layer 5 corresponding to the target emission wavelength is selected.
In addition, in the cladding layers 4 and 6, it is necessary to make it larger than the band gap energy of the active layer so as to confine carriers without acting as an absorber with respect to light emission. .
Therefore, the combination of the Al mixed crystal ratio x and the band gap energy Eg of the active layer and the clad layer with respect to the target emission wavelength is, for example, when the target emission wavelength is 620 nm, the Al mixed crystal ratio x = 0 of the active layer with respect to this. .17, band gap energy Eg = 2.00, and in the clad layer, a combination of Al mixed crystal ratio x ≧ 0.7 and band gap energy Eg = 2.28 can be obtained. Of course, the present invention is not limited to this combination, and can be selected each time.

In this way, the value of x selected based on the target emission wavelength and the above equations (1) to (4) can be calculated and selected.
The Al _xy Ga _{(1-x) y of} the lower cladding layer 4, the active layer 5, and the upper cladding layer 6 constituting the double heterostructure 3 with the composition of the combination of x and y selected as described above. In _(1-y) P is epitaxially grown sequentially.

In the above example, the room temperature is set to 25 ° C., and the lattice constants of the respective crystals at 25 ° C. are listed in Table 1 but are not limited thereto. For example 20 ° C., as long as obtaining the _{(Al x Ga 1-x)} y In the lattice constant of such _1-y P at 30 ° C., or 35 ° C. such as disclosed in Patent Document 1, and each crystal By taking into account the linear expansion coefficient, it is possible to newly adjust the values of x and y to obtain the lattice constant of (Al _x Ga _1-x ) _y In _1-y P.

Next, as described above, for example, the current diffusion layer 8 can be formed on the upper cladding layer 6 in order to sufficiently diffuse the current and efficiently emit light in a wider range.
Further, a further current diffusion layer can be formed between the current diffusion layer 8 and the upper cladding layer 6. By further forming such a further current diffusion layer, it is possible to further improve characteristics such as luminance.

A method for forming the buffer layer 7, the lower cladding layer 4, the active layer 5, the upper cladding layer 6, the current diffusion layer 8 and the like formed on the GaAs substrate 2 is not particularly limited. It can be formed by epitaxial growth by the MOVPE method or the like. The apparatus used for forming each layer can be the same apparatus as in the past.
The thickness of each layer, the type and concentration of the dopant, and the formation conditions such as the temperature and time during formation are not particularly limited, and can be appropriately set so as to obtain a desired compound semiconductor substrate that is lattice-matched at room temperature. it can.

At this time, as described above, in order to prevent the compound semiconductor substrate 1 from warping or cracking more reliably, the formation conditions of each layer may be set so that the compound semiconductor substrate 1 has a sufficient thickness. In addition, when the compound semiconductor substrate 1 is processed, the generation of cracks can also be suppressed by devising a processing method.
As described above, it is desirable to adjust the thickness of the GaAs substrate 2 and the thickness of the current diffusion layer 8 so that the entire substrate has a thickness of 200 to 500 μm, for example.

Moreover, the curvature of the manufactured compound semiconductor substrate can be made into -50--400 micrometers.
Thus, by setting the magnitude of the warpage to be −50 to −400 μm, it is possible to facilitate the subsequent process, for example, handling when manufacturing a light emitting element.

With the manufacturing method as described above, the compound semiconductor substrate 1 that can extract light having a target emission wavelength and has excellent characteristics such as luminance and life can be manufactured.
Then, the contact layer 11 and the electrode 12 are formed on the compound semiconductor substrate 1 thus obtained, and the electrode 13 is also formed on the GaAs substrate 1 side. Thus, the light emitting element 10 of the present invention can be obtained.

EXAMPLES Hereinafter, although the Example and comparative example of this invention are given and demonstrated in detail, this invention is not limited to this.
(Examples 1 and 2)
A double heterostructure or the like is formed on a GaAs substrate, and two types of light emitting devices of the present invention as shown in FIG. The characteristics were measured.
First, an n-type GaAs substrate having a thickness of 250 μm, a plane orientation (100) of 15 degrees off, and a silicon dope (carrier concentration of 1 × 10 ¹⁸ / cm ³ ) was prepared.
A GaAs buffer layer having a silicon doping (carrier concentration of 1 × 10 ¹⁸ / cm ³ ) and a thickness of 0.5 μm was epitaxially grown on the GaAs substrate by MOVPE.

Next, a double heterostructure composed of (Al _x Ga _1-x ) _y In _1-y P was epitaxially grown by the MOVPE method.
At this time, first, the value of x is selected from the band gap energy of the active layer so that the emission wavelength becomes (620 nm), and further, from the range of the lattice mismatch rate at room temperature in the present invention, the above formula (1 ) To (4) were used to calculate and select the value of y.
Table 2 shows specific compositions of (Al _x Ga _1-x ) _y In _1-y P in the active layer, the lower cladding layer, and the upper cladding layer selected by adjusting x and y in this way.

Then, by adjusting the mixing ratio of each source gas in the MOVPE process, an active layer, a lower cladding layer, and an upper cladding layer having the composition shown in Table 2 were sequentially formed on the buffer layer.
Note that TMAl, TMGa, TMIn, Cp ₂ Mg (or DEZn), arsine, phosphine, and monosilane were used as source gases. The furnace pressure was reduced to 200 hPa or less, and the epitaxial growth temperature was set to 700 ° C.

The active layer is non-doped and has a thickness of 1 μm, the lower cladding layer is silicon-doped (carrier concentration 5 × 10 ¹⁷ / cm ³ ) and the thickness is 2 μm, and the upper cladding layer is magnesium-doped (carrier concentration 1 × 10 ¹⁷ / cm ³ ). The thickness was 2 μm.

After forming a double heterostructure as described above, p-type GaP was formed thereon by the MOVPE method.
Further, a p-type GaP layer was epitaxially grown as a current diffusion layer by the HVPE method.
This p-type GaP layer was zinc-doped (carrier concentration 1 × 10 ¹⁸ / cm ³ ) and had a thickness of 50 μm.

  Thereafter, (Au—Be) / Au was deposited to form an ohmic electrode. Further, (Au—Ge) / Au was deposited on the GaAs substrate side to form an ohmic electrode, and a light emitting device of the present invention having a chip size of 250 μm was manufactured through a process such as dicing.

The luminance and life characteristics of the light emitting device of the present invention thus manufactured were measured. The measurement temperature is 85 ° C, the humidity is 45%, the light emission output is measured at a current of 20 mA, the light output is measured again after a current of 50 mA is applied for 100 hours, and the afterglow rate (life) Was calculated. Table 3 shows the measurement results of Examples 1 and 2 together with the measurement results of Comparative Examples 1 to 4 described later.
In addition, as shown in Table 3, the luminance was expressed as a relative value based on the value measured in Example 1.

Table 3 also shows the results of measuring the lattice constants of the active layer of the double heterostructure and the GaAs substrate in Example 1 by the double crystal X-ray diffraction method.
Using CuKα1 ray of wavelength λ = 1.5405４０ as X-ray for measurement, Bragg angles ω and ω ′ at (400) plane of GaAs substrate and AlGaInP active layer are measured, and AlGaInP active layer with respect to diffraction peak of GaAs substrate The difference Δω (= ω′−ω) with respect to the diffraction peak was obtained.
From this Δω, the lattice constant difference Δd can be obtained by the following equation (5) derived from the Bragg reflection condition, and the lattice constant and the lattice mismatch rate can be calculated.
Δd = d′−d = − (λ / 2) · (cos ω / sin ² ω) · Δω (5)
Here, d and d ′ are the lattice constants of the GaAs substrate and the AlGaInP active layer, respectively.

(Comparative Examples 1 and 2)
As shown in Table 2 above, the lattice mismatch rate of (Al _x Ga _1-x ) _y In _1-y P and GaAs at room temperature exceeds 0.02% (Al _x Ga _1-x ) _y Except for changing the composition of In _1-y P, a total of two types of light-emitting elements (Comparative Examples 1 and 2) were manufactured in the same procedure as in Examples 1 and 2, respectively. Measurements were made.
Tables 2 and 3 show the measurement results of the composition and characteristics of (Al _x Ga _1-x ) _y In _1-y P in each example.
Comparative Example 1 (Δω = −100 ″) was manufactured by epitaxially growing AlGaInP with a composition such that the lattice constants of AlGaInP and GaAs matched at the epitaxial growth temperature (700 ° C.) as in the conventional manufacturing method. It is.

  Here, the lattice constant will be described. The lattice constant of the active layer actually measured by the two-crystal X-ray diffraction method (refer to Table 3), the equations (1) to (4), etc. are set in advance before the epitaxial growth. It was consistent with the lattice constant in the composition.

Next, Examples 1 and 2 and Comparative Examples 1 and 2 shown in Tables 2 and 3 are compared.
With respect to the luminance, when Δω measured using the two-crystal X-ray diffraction method is 0 to −50 ″ as in the light-emitting elements of the present invention in Examples 1 and 2, that is, the lattice mismatch rate is 0% or more. It can be seen that the luminance (relative output with respect to Example 1) can be maintained when it is 0.02% or less.
Table 3 shows the lattice mismatch rate at room temperature in the active layer. In Examples 1 and 2, the lattice mismatch rates in the lower cladding layer and the upper cladding layer are also the lattice mismatch rates of the present invention. It was in the range.

  On the other hand, as in Comparative Examples 1 and 2, when Δω becomes a value smaller than −50 ″ (a value larger on the minus side), that is, when the lattice mismatch rate exceeds 0.02%, the high luminance is maintained. Although it was able to be done, it turns out that the afterglow rate worsens.

In addition, with respect to life, in Examples 1 and 2, the afterglow ratio was maintained at 90% or more even after the current was continuously supplied at 50 mA for 100 hours.
On the other hand, in Comparative Examples 1 and 2, the afterglow ratio is lower than 90%, and the light-emitting elements of the present invention in Examples 1 and 2 are more light-emitting than the conventional light-emitting elements in Comparative Examples 1 and 2. It can be seen that the life characteristics are more excellent.

(Comparative Examples 3 and 4)
Except for changing the composition of (Al _x Ga _1-x ) _y In _1-y P as shown in Table 2 above, a total of two types of light-emitting elements were used in the same procedure as in Examples 1 and 2 (each comparative example) 3 and 4) The same characteristics as in Examples 1 and 2 were measured.
Tables 2 and 3 show the measurement results of the composition and characteristics of (Al _x Ga _1-x ) _y In _1-y P in each example.
As shown in Table 3, unlike Examples 1 and 2 and Comparative Examples 1 and 2, Δω is a positive value, that is, in the two-crystal X-ray diffraction method, the Bragg angle ω ′ in epitaxially grown AlGaInP is It was manufactured with a composition that was larger than the Bragg angle ω in the GaAs substrate.

  Thus, in the case of a light emitting device manufactured so that Δω is positive, misfit dislocations are remarkably manifested, and the influence on life and the like becomes extremely large. Therefore, such a light-emitting element has poor luminance and particularly life characteristics, and is difficult to use as a product. For the above reasons, a light emitting element in which AlGaInP is epitaxially grown so that Δω is positive is not normally manufactured.

(Example 3, Comparative Examples 5 and 6)
The carrier concentration of the GaAs substrate was 2 × 10 ¹⁸ / cm ³ (Example 3), 7.5 × 10 ¹⁷ / cm ³ (Comparative Example 5), and 3 × 10 ¹⁸ / cm ³ (Comparative Example 6). A compound semiconductor substrate was manufactured under the same conditions as in Example 1, and the warpage was evaluated. Thereafter, a light emitting device was produced in the same manner, and the same characteristics as in Example 1 were measured, and the afterglow rate (light emission intensity) with respect to the energization time was calculated. The result is shown in FIG.

The warpage of the compound semiconductor substrate of Example 3 was −100 μm, and it was found that the level was not problematic in practice, unlike Comparative Example 5 of −500 μm and Comparative Example 6 of 100 μm.
Further, as shown in FIG. 4, the light emitting device manufactured from the compound semiconductor substrate of Example 3 in which the carrier concentration of the GaAs substrate is 2 × 10 ¹⁸ / cm ³ has a residual efficiency of 90% after 100 hr energization, Both were found to be sufficiently stable light-emitting elements as compared with Comparative Examples 5 and 6, which had a severe deterioration of around 60%.

As described above, as in the present invention, a GaAs substrate having a carrier concentration of 1 to 2.5 × 10 ¹⁸ / cm ³ is used, and the lattice defect between the double heterostructure (AlGaInP) and the GaAs substrate at room temperature. In the case of a light emitting device (compound semiconductor substrate) in which AlGaInP is epitaxially grown so that the lattice constant is matched when the matching rate is 0% or more and 0.02% or less, for example, the above-described lattice constant at the epitaxial growth temperature is used. Thus, it is possible to make the characteristics such as luminance and life superior to those of a light emitting element (compound semiconductor substrate) formed so as to match.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

(A) It is a schematic block diagram which shows an example of the compound semiconductor substrate of this invention. (B) It is a schematic block diagram which shows the other example of the compound semiconductor substrate of this invention. It is a schematic block diagram which shows an example of the light emitting element of this invention. It is the figure which showed the relationship between the carrier density | concentration of a GaAs substrate, and the magnitude | size of the curvature of a compound semiconductor substrate. It is the figure which showed the relationship between the electricity supply time and emitted light intensity of the light emitting element produced using the compound semiconductor substrate of Example 1 and Comparative Examples 5 and 6. FIG. It is a figure explaining the curvature of the compound semiconductor substrate.

Explanation of symbols

1, 1 '... Compound semiconductor substrate of the present invention,
2 ... GaAs substrate 3 ... Double heterostructure,
4 ... lower cladding layer, 5 ... active layer, 6 ... upper cladding layer,
7 ... Buffer layer, 8 ... Current diffusion layer, 9 ... DBR layer,
DESCRIPTION OF SYMBOLS 10 ... Light emitting element of this invention, 11 ... Contact layer, 12, 13 ... Electrode.

Claims (10)

At least, on a GaAs substrate _{(Al x Ga 1-x)} y In 1-y P ( However, 0 <x <1,0 <y <1) GaP current spreading layer heterostructure and is epitaxially grown to a double consisting and A compound semiconductor substrate on which is formed,
Each layer constituting the double hetero structure has a lattice constant matched to the GaAs substrate so that a lattice mismatch rate at room temperature is 0% or more and 0.02% or less, and the carrier of the GaAs substrate. concentration 1~2.5 × ¹⁰ 18 / cm ³ der is,
The compound semiconductor substrate is characterized in that the warpage of the compound semiconductor substrate is −50 to −400 μm .   The room temperature at which the lattice constant is matched so that the lattice mismatch ratio between each layer constituting the double heterostructure and the GaAs substrate is 0% or more and 0.02% or less is 25 ° C. The compound semiconductor substrate according to claim 1.   The compound semiconductor substrate according to claim 1, wherein the GaAs substrate has an n-type conductivity. A light emitting device manufactured from the compound semiconductor substrate according to any one of claims 1 to 3 . At least, on a GaAs substrate _{(Al x Ga 1-x)} y In 1-y P ( However, 0 <x <1,0 <y <1) GaP current spreading layer heterostructure and is epitaxially grown to a double consisting and A method of manufacturing a compound semiconductor substrate on which is formed,
The GaAs substrate having a carrier concentration of 1 to 2.5 × 10 ¹⁸ / cm ³ and each layer constituting the double heterostructure has a lattice mismatch rate of 0 with respect to the GaAs substrate at room temperature. (Al _x Ga _1-x ) _y In _1-y P is formed by epitaxial growth by adjusting the x and y so that the lattice constants are matched in the range of% to 0.02% ,
A method of manufacturing a compound semiconductor substrate, wherein the warpage of the compound semiconductor substrate is set to −50 to −400 μm . Adjustment of the x and y, the lattice constant of _{GaAs s room, (Al x Ga} 1-x) the lattice constant of y _{an In 1-y} P is taken as _{a room room,} the lattice mismatch ratio _{(a room room} -s _{6. The} method for producing a compound semiconductor substrate according to claim 5 , wherein adjustment / calculation is performed such that ( _room ) / s _room × 100 [%] is 0 or more and 0.02 or less. The _{(Al x Ga 1-x)} y In 1-y P-epitaxial growth of a compound semiconductor substrate manufacturing method according to claim 5 or claim 6, wherein the performing by MOVPE. The room temperature lattice mismatch ratio of each layer and the GaAs substrate constituting the heterostructure the double lattice constant is matched with 0.02% to 0%, 5 to claim, characterized in that the 25 ° C. The manufacturing method of the compound semiconductor substrate of any one of Claim 7 . Wherein the GaAs substrate, a compound semiconductor substrate manufacturing method according to any one of claims 5 to claim 8 conductivity type, characterized in that used as the n-type. A method for manufacturing a light-emitting element, comprising manufacturing a light-emitting element from a compound semiconductor substrate manufactured by the method for manufacturing a compound semiconductor substrate according to any one of claims 5 to 9 .

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