JP2010080937A - Aluminum gallium arsenic supporting substrate and manufacturing method therefor, epitaxial wafer and manufacturing method therefor, and light-emitting diode and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an aluminum gallium arsenic (AlGaAs) supporting substrate and its manufacturing method reduced in cost and eliminated in warpage; an epitaxial wafer and its manufacturing method; and a light-emitting diode (LED) and its manufacturing method. <P>SOLUTION: The AlGaAs supporting substrate 10 includes: a GaAs substrate 11 having a main surface 11a and a back surface 11b in the back of the main surface 11a; a first Al<SB>x</SB>Ga<SB>(1-x)</SB>As layer 12 formed on the main surface 11a of the GaAs substrate 11; and a second Al<SB>y</SB>Ga<SB>(1-y)</SB>As layer 13 formed on the back surface 11b of the GaAs substrate 11. The method of manufacturing the AlGaAs supporting substrate 10 includes: a step of preparing the GaAs substrate 11; a step of forming the first Al<SB>x</SB>Ga<SB>(1-x)</SB>As layer 12 on the main surface 11a by means of a liquid-phase growth method; and a step of forming the second Al<SB>y</SB>Ga<SB>(1-y)</SB>As layer 13 on the back surface 11b by means of the liquid-phase growth method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an AlGaAs support substrate manufacturing method, an epitaxial wafer manufacturing method, an LED manufacturing method, an AlGaAs support substrate, an epitaxial wafer, and an LED.

LED (Light Emitting Diode) using an Al _a Ga _(1-a) As (0 <a <1) (hereinafter also referred to as AlGaAs (aluminum gallium arsenide)) substrate is widely used as an infrared light source. It is used. Infrared LEDs as an infrared light source are used for optical communication, spatial transmission, and the like, and there is a demand for improvement in output with an increase in transmission data capacity and transmission distance. .

Such a method of manufacturing an AlGaAs support substrate is disclosed in, for example, Japanese Patent No. 3937290 (Patent Document 1) and Japanese Patent No. 3996788 (Patent Document 2). Patent Documents 1 and 2 describe that the following steps are performed. Specifically, first, a high carrier concentration layer made of Al _0.26 Ga _0.74 As is formed on the main surface of a GaAs (gallium arsenide) substrate, which is a temporary substrate, by an LPE (Liquid Phase Epitaxy) method. A low carrier concentration layer is grown in this order. Thereafter, the GaAs substrate is removed by etching to produce a support substrate made of AlGaAs.

  Japanese Laid-Open Patent Publication No. 63-31629 (Patent Document 3) discloses a method of manufacturing an AlGaAs support substrate including a GaAs layer and an AlGaAs layer formed on the GaAs layer. Patent Document 3 describes that the following steps are performed. Specifically, first, a Zn-doped p-type AlGaAs epitaxial layer and an undoped GaAs layer are sequentially formed on a p-type GaAs substrate by the LPE method. Thereafter, the p-type GaAs substrate is completely removed by mechanical polishing or chemical etching, and an epitaxial wafer (AlGaAs support substrate) including a GaAs layer and an AlGaAs layer formed on the GaAs layer is manufactured.

Japanese Patent No. 3937290 Japanese Patent No. 3996788 JP-A-63-312629

  In Patent Documents 1 and 2, if the high-concentration layer and the low-concentration layer made of AlGaAs are not grown to a predetermined thickness or more, when the epitaxial layer is formed on the support substrate by the vapor phase growth method, Handling becomes a problem. In addition, the cost for growing a thick AlGaAs layer composed of a high carrier concentration layer and a low carrier concentration layer is high. For this reason, in the said patent documents 1 and 2, there exists a problem that the cost for manufacturing an AlGaAs support substrate is high.

  The AlGaAs support substrate of Patent Document 3 includes a GaAs layer and an AlGaAs layer formed on the GaAs layer. Since the AlGaAs layer contains Al, there is a problem that warpage of the AlGaAs support substrate increases due to Al composition (composition ratio) of the AlGaAs layer. If the warpage becomes large, the AlGaAs support substrate cannot be held by the susceptor used in the vapor phase growth method. In addition, when the growth is performed by the vapor phase growth method, the AlGaAs support substrate is detached from the susceptor. For this reason, if the warp of the AlGaAs support substrate is large, an epitaxial layer cannot be formed on the surface of the AlGaAs layer opposite to the surface on which the GaAs layer is formed by vapor deposition.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an AlGaAs support substrate manufacturing method, an epitaxial wafer manufacturing method, an LED manufacturing method, an AlGaAs support substrate, an epitaxial wafer, and an LED with reduced cost and reduced warpage. .

The manufacturing method of the AlGaAs support substrate of the present invention includes the following steps. A GaAs substrate having a main surface and a back surface opposite to the main surface is prepared. A first Al _x Ga _(1-x) As layer (0 <x <1) (hereinafter also referred to as a first AlGaAs layer) is formed on the main surface side of the GaAs substrate by a liquid phase growth method. A second Al _y Ga _(1-y) As layer (0 <y <1) (hereinafter also referred to as a second AlGaAs layer) is formed on the back side of the GaAs substrate by a liquid phase growth method.

The AlGaAs support substrate of the present invention includes a GaAs substrate having a main surface and a back surface opposite to the main surface, and a first Al _x Ga _(1-x) As layer formed on the main surface side of the GaAs substrate ( 0 <x <1) and a second Al _y Ga _(1-y) As layer (0 <y <1) formed on the back side of the GaAs substrate.

  According to the AlGaAs support substrate manufacturing method and the AlGaAs support substrate of the present invention, the first and second AlGaAs layers are formed on the main surface and the back surface of the GaAs substrate. Thereby, stress in the same direction can be applied to the main surface and the back surface of the GaAs substrate. For this reason, it can suppress that the curvature by the difference of Al composition x and y of a GaAs substrate and a 1st and 2nd AlGaAs layer generate | occur | produces.

  In addition, an AlGaAs support substrate having a GaAs substrate is manufactured. For this reason, the GaAs substrate bears the thickness required for the AlGaAs support substrate for epitaxial growth by vapor phase epitaxy on the AlGaAs support substrate. Since the GaAs substrate is less expensive than the cost required to form the AlGaAs layer, the cost required to manufacture the AlGaAs support substrate can be reduced.

  The AlGaAs support substrate preferably has a warp of 200 μm or less. As described above, stress in the same direction can be applied to the main surface and the back surface of the GaAs substrate. For this reason, an AlGaAs support substrate having a small warp of 200 μm or less can be realized.

The AlGaAs support substrate preferably has a residual strain having an average value of 1.5 × 10 ⁻⁵ or less. As a result, it is possible to realize a crystal that is less prone to crystal cracking and causes less slip in the epitaxially grown epitaxial layer.

The AlGaAs support substrate preferably has a residual strain having a maximum value of 2 × 10 ⁻⁵ or less. As a result, it is possible to realize a crystal that is less prone to crystal cracking and that causes less slip in the epitaxially grown epitaxial layer.

  The AlGaAs support substrate preferably has a diameter of 50 mm or more. Conventionally, when the diameter is large, the residual strain at the outer peripheral portion becomes large, so it has been difficult to produce an AlGaAs support substrate having the residual strain and a diameter of 50 mm or more. However, since the AlGaAs support substrate of the present invention includes the second AlGaAs layer, an AlGaAs support substrate having the residual strain and a diameter of 50 mm or more can be realized. By making the diameter 50 mm or more, the device area can be increased, which is advantageous in terms of cost.

Preferably, in the method of manufacturing the AlGaAs support substrate, the step of forming the second Al _y Ga _(1-y) As layer is performed after the step of forming the first Al _x Ga _(1-x) As layer. .

  Thus, one of the first and second AlGaAs layers can be formed as a layer for growing an epitaxial layer by vapor deposition, and the other can be formed as a layer for reducing warpage. For this reason, it can form so that formation of an oxide film can be suppressed by reducing the composition of Al of the layer for growing an epitaxial layer. In this case, an epitaxial layer with improved characteristics can be formed on the layer for growing the epitaxial layer. Further, the cost can be further reduced by increasing the Al composition of the layer for reducing the warpage and reducing the thickness.

Preferably, in the method of manufacturing the AlGaAs support substrate, the step of forming the first Al _x Ga _(1-x) As layer and the step of forming the second Al _y Ga _(1-y) As layer are performed simultaneously. Do.

  Thereby, the first and second AlGaAs layers having the same characteristics can be formed. For this reason, the same amount of stress can be applied in the same direction to the main surface and the back surface of the GaAs substrate. Therefore, an AlGaAs support substrate with reduced warpage can be manufactured.

Preferably, in the method of manufacturing the AlGaAs support substrate, at least one of the first Al _x Ga _(1-x) As layer and the second Al _y Ga _(1-y) As layer is in contact with the GaAs substrate. And a step of polishing the surface on the opposite side.

  Thereby, the unevenness | corrugation of the grind | polished surface can be reduced and thickness can be made uniform. For this reason, when epitaxial growth is performed on the polished surface by a vapor phase growth method, an epitaxial layer having uniform crystallinity and composition can be formed.

Preferably, in the AlGaAs support substrate manufacturing method, in the polishing step, polishing is performed so that the surface roughness Ra of the surface on the opposite side of the first Al _x Ga _(1-x) As layer is 50 nm or less.

  Thereby, when epitaxial growth is performed on this surface by vapor phase growth, an epitaxial layer with more uniform crystallinity and composition can be formed.

Preferably, in the method of manufacturing the AlGaAs support substrate, in the polishing step, polishing is performed so that the surface roughness Ra of the surface on the opposite side of the second Al _y Ga _(1-y) As layer is 5 μm or less.

  Thereby, the adhesiveness of this surface and a susceptor can be improved more. For this reason, when forming the epitaxial layer by the vapor phase growth method, the growth temperature in the AlGaAs support substrate surface becomes uniform, and the composition and carrier concentration in the surface become uniform.

An epitaxial wafer manufacturing method according to the present invention includes an AlGaAs support substrate manufacturing process according to the AlGaAs support substrate manufacturing method described above, and an epitaxial layer formed on the first Al _x Ga _(1-x) As layer by vapor deposition. Forming a step.

An epitaxial wafer according to one aspect of the present invention includes the AlGaAs support substrate and an epitaxial layer formed on the first Al _x Ga _(1-x) As layer.

  Since the AlGaAs support substrate with reduced warpage is used, it is possible to suppress the AlGaAs support substrate from being detached from the susceptor during epitaxial growth on the AlGaAs support substrate. Further, since the AlGaAs support substrate with reduced cost is used, the cost of the epitaxial wafer provided with the epitaxial layer formed on the AlGaAs support substrate by the vapor phase growth method can be reduced.

Preferably, the method for manufacturing an epitaxial wafer further includes a step of removing the second Al _y Ga _(1-y) As layer and the GaAs substrate.

An epitaxial wafer according to another aspect of the present invention includes a first Al _x Ga _(1-x) As layer and an epitaxial layer formed on the first Al _x Ga _(1-x) As layer. .

  Thereby, since the fall of the transmittance | permeability by a GaAs substrate can be suppressed, the epitaxial wafer which can improve the characteristic of LED formed with an electrode is realizable.

  Preferably, the method for manufacturing an epitaxial wafer further includes a step of forming a substrate on a surface of the epitaxial layer opposite to the surface in contact with the AlGaAs support substrate.

Preferably, the epitaxial wafer according to one and other aspects of the present invention further includes a substrate formed on a surface opposite to the surface in contact with the first Al _x Ga _(1-x) As layer in the epitaxial layer. .

  As a result, when a substrate having good conductivity, heat dissipation, and high reflectivity is formed, heat dissipation performance and high directivity performance are improved when an epitaxial wafer is used for an LED.

  Preferably, the epitaxial wafer according to the above and the other aspects has a warp of 200 μm or less. Thereby, an epitaxial wafer with good crystallinity can be realized.

Preferably, the epitaxial wafer according to the above and the other aspects has a residual strain having an average value of 5 × 10 ⁻⁵ or less. As a result, an epitaxial wafer including an epitaxial layer with less slippage can be realized even if the active layer is intentionally strained.

Preferably, the epitaxial wafer according to the above-described one and still other aspects has a residual strain having a maximum value of 1 × 10 ⁻⁴ or less. Thereby, even if the active layer is intentionally strained, it is possible to realize an epitaxial wafer including an epitaxial layer with less occurrence of slip.

  The manufacturing method of LED of this invention is equipped with the process of manufacturing an epitaxial wafer with the manufacturing method of the epitaxial wafer in any one of the said, and the process of forming an electrode in the surface and back surface of an epitaxial wafer, respectively.

  The LED of the present invention includes any one of the above epitaxial wafers and electrodes formed on the front surface and the back surface of the epitaxial wafer.

  According to the LED manufacturing method and the LED of the present invention, an AlGaAs supporting substrate with reduced warpage is used and an epitaxial wafer with improved characteristics is used. Therefore, an LED with improved characteristics can be manufactured. Since an AlGaAs support substrate with reduced costs is used, an LED with reduced costs can be manufactured.

  According to the present invention, there is provided an AlGaAs support substrate manufacturing method, an epitaxial wafer manufacturing method, an LED manufacturing method, an AlGaAs support substrate, an epitaxial wafer, and an LED with reduced cost and reduced warpage.

It is sectional drawing which shows schematically the AlGaAs support substrate in Embodiment 1 of this invention. It is a schematic diagram for demonstrating the curvature of the AlGaAs support substrate in Embodiment 1 of this invention. It is a flowchart which shows the manufacturing method of the AlGaAs support substrate in Embodiment 1 of this invention. It is sectional drawing which shows schematically the GaAs substrate in Embodiment 1 of this invention. It is sectional drawing which shows schematically the state which grew the 1st AlGaAs layer in Embodiment 1 of this invention. It is sectional drawing which shows schematically the epitaxial wafer in Embodiment 2 of this invention. It is a flowchart which shows the manufacturing method of the epitaxial wafer in Embodiment 2 of this invention. It is sectional drawing which shows schematically the epitaxial wafer in Embodiment 3 of this invention. It is a flowchart which shows the manufacturing method of the epitaxial wafer in Embodiment 3 of this invention. It is sectional drawing which shows roughly the epitaxial wafer in Embodiment 4 of this invention. 10 is a flowchart showing a method for manufacturing an epitaxial wafer in a fourth embodiment. It is sectional drawing which shows schematically the epitaxial wafer in Embodiment 5 of this invention. It is a flowchart which shows the manufacturing method of the epitaxial wafer in Embodiment 5 of this invention. It is sectional drawing which shows schematically LED in Embodiment 6 of this invention. It is a flowchart which shows the manufacturing method of LED in Embodiment 6 of this invention. It is sectional drawing which shows schematically LED in Embodiment 7 of this invention. It is a flowchart which shows the manufacturing method of LED in Embodiment 7 of this invention. It is sectional drawing which shows schematically LED in Embodiment 8 of this invention. It is a flowchart which shows the manufacturing method of LED in Embodiment 8 of this invention. It is sectional drawing which shows schematically LED in Embodiment 9 of this invention. It is a flowchart which shows the manufacturing method of LED in Embodiment 9 of this invention. It is a top view for demonstrating the measuring method of the curvature of the AlGaAs support substrate of an Example. It is a figure which shows the curvature amount of the AlGaAs support substrate of the example 1 of this invention. It is a figure which shows the curvature amount of the AlGaAs support substrate of the comparative example 1. It is sectional drawing which shows roughly the epitaxial wafer of this invention example 1-6. It is a figure which shows distribution of the residual distortion of the AlGaAs support substrate of the example 1 of this invention. It is a figure which shows distribution of the residual strain of the AlGaAs crystal substrate of the comparative example 1 whose average value of a residual strain exceeds 5.0 * 10 < ^-5 >. AlGaAs average of supporting residual strain in the substrate is a diagram schematically showing a slip in the epitaxial wafer in the case of using the AlGaAs support substrate is ^{4.0 × 10 -6 ~6.0 × 10 -6} . It is a figure which shows typically the slip in an epitaxial wafer at the time of using the AlGaAs support substrate whose average value of the residual strain in an AlGaAs support substrate is 1.0 * 10 < ^-5 >. It is a figure which shows typically the slip in an epitaxial wafer at the time of using the AlGaAs support substrate whose average value of the residual strain in an AlGaAs support substrate is 1.5 * 10 < ^-5 >. It is a figure which shows the relationship between the thickness of the 1st and 2nd AlGaAs layer, and the composition of Al.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a cross-sectional view schematically showing an AlGaAs support substrate in the present embodiment. First, the AlGaAs support substrate in the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the AlGaAs support substrate 10 includes a GaAs substrate 11, a first AlGaAs layer 12, and a second AlGaAs layer 13.

  The GaAs substrate 11 has a main surface 11a and a back surface 11b opposite to the main surface 11a. The first AlGaAs layer 12 is formed on the main surface 11 a side of the GaAs substrate 11. The second AlGaAs layer 13 is formed on the back surface 11 b side of the GaAs substrate 11.

  The GaAs substrate 11 may or may not have an off angle. The surface of the GaAs substrate 11 may be a mirror surface or a rough surface.

  The first AlGaAs layer 12 is a layer for forming an epitaxial layer by a vapor phase growth method. When the first AlGaAs layer 12 is used in an LED, the first AlGaAs layer 12 serves as a window layer that diffuses current and transmits light from the active layer, for example.

The first AlGaAs layer 12 is composed of an Al _x Ga _(1-x) As layer (0 <x <1). The composition (composition ratio) x is a molar ratio of Al. The composition (1-x) is a molar ratio of Ga.

  The first AlGaAs layer 12 has a main surface 12a and a back surface 12b opposite to the main surface 12a. The back surface 12 b is in contact with the GaAs substrate 11.

The second AlGaAs layer 13 is a layer for relaxing the warp of the AlGaAs support substrate 10. The second AlGaAs layer 13 is composed of an Al _y Ga _(1-y) As layer (0 <y <1). The composition (composition ratio) y is the molar ratio of Al. The composition (1-y) is a molar ratio of Ga.

  The second AlGaAs layer 13 has a main surface 13a and a back surface 13b opposite to the main surface 13a. The back surface 13 b is in contact with the GaAs substrate 11.

  The Al composition x of the main surface 12 a of the first AlGaAs layer 12 is preferably smaller than the Al composition y of the main surface 13 a of the second AlGaAs layer 13. Since Al has the property of being easily oxidized, it is advantageous to reduce the composition of Al present on the main surface 12a of the first AlGaAs layer 12. This means that the formation of an insulating oxide layer on the main surface 12a of the first AlGaAs layer 12 can be suppressed.

  From the viewpoint of improving the permeability of the first AlGaAs layer 12, it is preferable that the Al composition is high. For this reason, in order to suppress the formation of an oxide layer on the main surface 12a and to improve the permeability, in the first AlGaAs layer 12, the Al composition x of the back surface 12b is made of Al of the main surface 12a. It is preferably higher than the composition x. Further, in the first AlGaAs layer 12, it is preferable that the Al composition x monotonously decreases from the back surface 12b to the main surface 12a. Monotonic decrease means that the composition x is always the same or decreasing from the back surface 12b of the first AlGaAs layer 12 toward the main surface 12a (toward the growth direction), and the main surface 12a is more than the back surface 12b. Means that the composition x is low. That is, the monotonic decrease does not include a portion where the composition x increases in the growth direction.

  When the Al composition of the second AlGaAs layer 13 is high, the lattice constant increases when the Al composition y is large, and the strain from the degree of lattice matching with the GaAs substrate 11 increases. This increases the stress from the second AlGaAs layer 13 to the GaAs substrate 11. For this reason, since the thickness of the second AlGaAs layer 13 formed so as to have the same magnitude of stress as that of the first AlGaAs layer 12 can be reduced, the cost of the second AlGaAs layer 13 can be reduced. .

  As a result of diligent research, the present inventor has found that the warp of the AlGaAs support substrate 10 can be alleviated even when the thickness of the second AlGaAs layer 13 is reduced, particularly by satisfying the following relationship.

Specifically, the lowest Al composition in each of the first and second AlGaAs layers 12 and 13 is Al _L and the highest Al composition in each of the first and second AlGaAs layers 12 and 13. Is Al _H, and the average value of the Al composition in the first and second AlGaAs layers 12 and 13 in the depth direction is Al _ave . Al _ave is obtained by (Al _L + Al _H ) / 2. Furthermore, the Al _ave ratio X as (Al _ave second Al _ave / first AlGaAs layer 12 of the AlGaAs layer 13), the thickness ratio Y (thickness / of the second AlGaAs layer 13 first AlGaAs layer 12 Thickness). In this case, it is preferable to satisfy the relationship of 0.7 ≦ X <4.0 and −X + 1.3 ≦ Y ≦ −X + 4.0, 0.8 ≦ X ≦ 3.7, and −X + 1.5 ≦ Y It is more preferable to satisfy the relationship of ≦ −X + 4.0.

  The surface roughness Ra of the main surface 12a of the first AlGaAs layer 12 is preferably 50 nm or less, more preferably 0.1 nm or more and 2 nm or less. In the case of 50 nm or less, an epitaxial layer having a more uniform crystallinity and composition can be formed by epitaxial growth by vapor phase epitaxy on the main surface 12a. When the thickness is 2 nm or less, an epitaxial layer with more uniform crystallinity and composition can be formed. The surface roughness Ra is preferably as small as possible, but the lower limit is, for example, 0.1 nm for manufacturing reasons.

  Polishing is performed so that the surface roughness Ra of the main surface 13a of the second AlGaAs layer 13 is preferably 5 μm or less, more preferably 0.05 μm or more and 3 μm or less. In the case of 5 μm or less, the adhesion between the main surface 13a and the susceptor can be further improved. For this reason, when forming the epitaxial layer by a vapor phase growth method, it can suppress more that the AlGaAs support substrate 10 remove | deviates from a susceptor. In the case of 3 μm or less, it is possible to further suppress the AlGaAs support substrate 10 from being detached from the susceptor when the epitaxial layer is grown. On the other hand, the smaller the surface roughness Ra, the better. However, the lower limit is, for example, 0.05 μm from the viewpoint of reducing the cost.

  Here, the surface roughness Ra is a value measured in accordance with, for example, JIS (Japanese Industrial Standards) B0601.

  The compositions of the first and second AlGaAs layers 12 and 13 may be the same or different. The thicknesses of the first and second AlGaAs layers 12 and 13 may be the same or different.

  The warp of the AlGaAs support substrate 10 is preferably 200 μm or less, and more preferably 50 μm or less. When the thickness is 200 μm or less, it is possible to prevent the AlGaAs support substrate 10 from being detached from the susceptor when epitaxial growth is performed on the AlGaAs support substrate 10 by vapor deposition. In the case of 50 μm or less, the AlGaAs support substrate 10 can be more easily held on the susceptor of the growth apparatus, and an epitaxial wafer in which an epitaxial layer is formed on the AlGaAs support substrate 10 by vapor phase growth, and another (attached) substrate Pasting can also be performed easily. The warp of the AlGaAs support substrate 10 is preferably as small as possible, but for manufacturing reasons, the lower limit value of the warp of the AlGaAs support substrate 10 is, for example, 0.001 μm.

  Here, as shown in FIG. 2, the warp is a surface (for example, the back surface) where the space of the AlGaAs support substrate 10 is formed when the AlGaAs support substrate 10 is placed on a parallel platform so as to be convex. The difference in distance h between the highest position (for example, the central portion) of the space to be formed and the lowest position (the end portion on the back surface of the AlGaAs support substrate 10). FIG. 2 is a schematic diagram for explaining warpage of the AlGaAs support substrate 10 in the present embodiment.

The average value of the residual strain of the AlGaAs support substrate 10 is preferably 1.5 × 10 ⁻⁵ or less, and more preferably 6.0 × 10 ⁻⁶ or less. The average value of residual strain of the AlGaAs support substrate 10 is preferably 1.5 × 10 ⁻⁵ or less, and the maximum value is preferably 2 × 10 ⁻⁵ or less. Further, it is particularly effective when the diameter of the AlGaAs support substrate 10 is 50 mm or more.

  The residual strain is evaluated by, for example, Appl. Phys. Lett. 47 (1985) p. It can be carried out based on the photoelastic method described in 365-367. Specifically, for example, the residual strain in the AlGaAs support substrate 10 can be evaluated by calculating the residual strain existing in the AlGaAs support substrate 10 by a photoelastic method. In such a calculation method, the residual strain of the AlGaAs support substrate 10 can be calculated by the absolute value | Sr−St | of the difference between the radial strain Sr and the tangential strain St. In this calculation, | Sr-St | is defined as the following equation (1).

Here, λ is the wavelength of light used for measurement, d is the thickness of the AlGaAs support substrate used for measurement, n ₀ is the refractive index, δ is the phase difference caused by the birefringence of the sample, ψ is the main vibration azimuth, and p ₁₁ , P ₁₂ and p ₄₄ represent photoelastic constants.

  According to this photoelastic method, | Sr-St | in the AlGaAs support substrate can be easily obtained by measuring only the phase difference δ and the main vibration azimuth angle ψ caused by the birefringence of the sample.

  The present inventor strongly correlated the amount of residual strain of the AlGaAs support substrate 10 obtained based on this evaluation method with crystal cracking that occurs during crystal processing such as slicing and polishing, and subsequent epitaxial growth and device processes. I found out. The inventor has also found that slip (crystal defects) generated in an epitaxially grown thin film crystal layer is greatly influenced by the amount of residual strain of the AlGaAs support substrate 10 used as a base in epitaxial growth and device processes.

  By finding the correlation as described above, a high quality AlGaAs support substrate 10 more suitable for the manufacture of semiconductor devices such as LEDs is completed as the present invention. It has become possible to provide users with stable generation of crystals.

When the average value of the residual strain in the AlGaAs support substrate 10 of the present invention is 1 × 10 ⁻⁵ or less, crystal damage such as slip is extremely introduced during the crystal processing such as slicing and polishing, and the subsequent epitaxial growth and device process. It becomes difficult. Moreover, since good crystallinity can be obtained by epitaxial growth, device characteristics are improved. Further, if the maximum value of the residual strain in the AlGaAs support substrate 10 is 2 × 10 ⁻⁵ or less, crystal damage such as slip is less likely to occur, and better device characteristics can be obtained.

  Next, a method for manufacturing the AlGaAs support substrate 10 in the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing a method for manufacturing the AlGaAs support substrate in the present embodiment.

  FIG. 4 is a cross-sectional view schematically showing the GaAs substrate 11 in the present embodiment. As shown in FIGS. 3 and 4, first, a GaAs substrate 11 having a main surface 11a and a back surface 11b opposite to the main surface 11a is prepared (step S1).

FIG. 5 is a cross-sectional view schematically showing a state in which the first AlGaAs layer 12 is grown in the present embodiment. As shown in FIGS. 3 and 5, next, the first Al _x Ga _(1-x) As layer 12 (0 <x <1) is formed on the main surface 11a side of the GaAs substrate 11 by the LPE method. (Step S2).

  In step S2 for growing the AlGaAs layer 12, it is preferable to grow the AlGaAs layer 12 in which the Al composition x at the interface (back surface 12b) with the GaAs substrate 11 is higher than the Al composition x on the main surface 12a.

Next, the second Al _y Ga _(1-y) As layer 13 (0 <y <1) is formed on the back surface 11b side of the GaAs substrate 11 by the LPE method (step S3).

  The LPE method used in steps S2 and S3 is not particularly limited, and a slow cooling method, a temperature difference method, or the like can be used. The LPE method is a method for epitaxially growing an AlGaAs crystal from a liquid phase. The slow cooling method is a method of growing a crystal such as AlGaAs by gradually lowering the temperature of a raw material solution. The temperature difference method is a method in which a temperature gradient is created in a raw material solution and a crystal such as AlGaAs is epitaxially grown.

  Note that step S3 of forming the second AlGaAs layer 13 may be performed after step S2 of forming the first AlGaAs layer 12. In addition, after step S3 for forming the second AlGaAs layer 13, step S2 for forming the first AlGaAs layer 12 may be performed. Further, the first AlGaAs layer 12 and the second AlGaAs layer 13 may be formed simultaneously.

  When one of step S2 and step S3 is performed first, the first AlGaAs layer 12 and the second AlGaAs layer 13 can be formed to have different characteristics. For example, the first and second AlGaAs layers 12 and 13 are formed so that the Al composition x of the first AlGaAs layer 12 is lower than the Al composition y of the second AlGaAs layer 13. In this case, since the formation of an oxide layer on the main surface 12a of the first AlGaAs layer 12 can be suppressed, the first AlGaAs layer 12 is formed as a layer for growing an epitaxial layer by vapor deposition. Can do. The second AlGaAs layer 13 can be applied with the same stress in the same direction as the first AlGaAs layer 12 even if the thickness is reduced. For this reason, the cost required to form the second AlGaAs layer 13 can be reduced. Therefore, the second AlGaAs layer 13 can be formed as a layer for relaxing warpage. As a manufacturing method for forming the first AlGaAs layer 12 in a layer where an epitaxial layer is formed and forming the second AlGaAs layer 13 in a layer for reducing warpage, the first AlGaAs layer 12 is formed at a temperature. Preferably, the second AlGaAs layer 13 is formed by a slow cooling method.

  When step S2 and step S3 are performed simultaneously, the first and second AlGaAs layers 12 and 13 having the same characteristics can be formed. For this reason, stress of the same magnitude is applied to the main surface 11a and the back surface 11b of the GaAs substrate 11 in the same direction. Therefore, the AlGaAs support substrate 10 with further reduced warpage can be manufactured. In this case, the first and second AlGaAs layers 12 and 13 are preferably formed by a slow cooling method.

  When growing a layer having a constant Al composition x in the AlGaAs layer 12 in step S2, a temperature difference method and a slow cooling method are used to grow a layer in which the Al composition x decreases upward (growth direction). In some cases, it is preferable to use a slow cooling method. It is particularly preferable to use the slow cooling method because of its excellent mass productivity and low cost. Moreover, you may combine them.

  Compared with the vapor deposition method, the LPE method can easily form the first and second AlGaAs layers 12 and 13 having a large thickness. Specifically, the first and second AlGaAs layers 12 and 13 having a thickness of preferably 10 μm or more and 1000 μm or less, more preferably 20 μm or more and 140 μm or less are grown. The thickness at this time is the smallest thickness in the thickness direction of the first and second AlGaAs layers 12 and 13.

  The first and second AlGaAs layers formed in steps S2 and S3 may be a single layer or a plurality of layers.

  Steps S2 and S3 include a p-type dopant such as Zn (zinc), Mg (magnesium), and C (carbon), and an n-type dopant such as Se (selenium), S (sulfur), and Te (tellurium). In this manner, the first and second AlGaAs layers 12 and 13 may be grown.

  Next, in at least one of the first AlGaAs layer 12 and the second AlGaAs layer 13, the surface (main surface 12a, 13a) opposite to the surface (back surface 12b, 13b) in contact with the GaAs substrate 11 is polished. (Step S4). The main surfaces 12a and 13a of the first and second AlGaAs layers 12 and 13 are preferably polished.

  In step S4, polishing is performed so that the surface roughness Ra of the main surface 12a of the first AlGaAs layer 12 is preferably 50 nm or less, more preferably 0.1 nm or more and 2 nm or less. In the case of 50 nm or less, an epitaxial layer having more uniform crystallinity and composition can be formed by epitaxial growth on the main surface 12a. When the thickness is 2 nm or less, an epitaxial layer with more uniform crystallinity and composition can be formed. In the case of 0.1 nm or more, it can be easily produced.

  In step S4, polishing is performed so that the surface roughness Ra of the main surface 13a of the second AlGaAs layer 13 is preferably 5 μm or less, more preferably 0.05 μm or more and 3 μm or less. In the case of 5 μm or less, the adhesion between the main surface 13a and the susceptor can be further improved. When the thickness is 3 μm or less, it is possible to further suppress the separation from the susceptor when the epitaxial layer is grown. In the case of 0.05 μm or more, the cost can be reduced.

  The method for polishing is not particularly limited, and mechanical polishing, chemical mechanical polishing, electropolishing, chemical polishing, and the like can be used, and mechanical polishing or chemical polishing is preferable from the viewpoint of ease of polishing. This step S4 may be omitted.

  The AlGaAs support substrate 10 shown in FIG. 1 can be manufactured by the above steps S1 to S4.

  As described above, according to the AlGaAs support substrate 10 and the manufacturing method thereof in the present embodiment, the first and second AlGaAs layers 12 and 13 are formed on the main surface 11a and the back surface 11b of the GaAs substrate 11, respectively. Yes. As the Al composition x, y of the AlGaAs layers 12 and 13 increases, the lattice constant increases, and distortion occurs due to the degree of lattice matching with the GaAs substrate 11. However, in the present embodiment, tensile stress can be applied to the main surface 11a and the back surface 11b of the GaAs substrate 11 by the first and second AlGaAs layers 12 and 13. Therefore, it is possible to suppress the occurrence of warpage due to the difference in the Al composition x between the GaAs substrate 11 and the first and second AlGaAs layers 12 and 13. Further, the GaAs substrate 11 bears the thickness required for the AlGaAs support substrate 10 for epitaxial growth on the AlGaAs support substrate 10. For this reason, there is no restriction | limiting that the thickness of the 1st and 2nd AlGaAs layers 12 and 13 is enlarged. Since the GaAs substrate is less expensive than the cost required to form the AlGaAs layer, the cost required to manufacture the AlGaAs support substrate 10 can be reduced.

  In the AlGaAs support substrate 10, the Al composition x of the first AlGaAs layer 12 is preferably smaller than the Al composition y of the second AlGaAs layer 13. In this case, since the formation of the oxide layer by Al is suppressed on the main surface 12a of the first AlGaAs layer 12, the first AlGaAs layer 12 is formed as a layer for forming the epitaxial layer by the vapor phase growth method. Can do. Even if the thickness of the second AlGaAs layer 13 is smaller than that of the first AlGaAs layer 12, the same stress can be applied to the GaAs substrate 11 in the same direction as the first AlGaAs layer 12. For this reason, the second AlGaAs layer 13 can be formed as a layer for reducing the warpage.

(Embodiment 2)
FIG. 6 is a cross-sectional view schematically showing an epitaxial wafer in the present embodiment. With reference to FIG. 6, epitaxial wafer 20a in the present embodiment will be described.

  As shown in FIG. 6, the epitaxial wafer 20a includes an AlGaAs support substrate 10 shown in FIG. 1 in the first embodiment and an epitaxial layer 21 formed on the main surface 12a of the first AlGaAs layer 12 by a vapor phase growth method. And. That is, the epitaxial wafer 20a includes the second AlGaAs layer 13, the GaAs substrate 11 formed on the second AlGaAs layer 13, the first AlGaAs layer 12 formed on the GaAs substrate 11, and the first And an epitaxial layer 21 formed on the AlGaAs layer 12.

  The epitaxial layer 21 formed by vapor deposition includes an active layer. The active layer has a smaller band gap than the first AlGaAs layer 12. The active layer has a quantum well structure including, for example, a well layer and a barrier layer. As the material of the well layer, for example, GaAs, AlGaAs, InGaAs (indium gallium arsenide), AlInGaAs (aluminum indium gallium arsenide), or the like can be used. As the material of the barrier layer, for example, AlGaAs, InGaP, AlInGaP, or the like can be used.

  In addition, the epitaxial layer formed by the vapor deposition method may include only the active layer, and may further include other layers such as a cladding layer and an undoped layer.

  The warp of the epitaxial wafer 20a is preferably 200 μm or less, and more preferably 50 μm or less. When the thickness is 200 μm or less, a general epitaxial layer can be successfully grown. Note that the amount of warpage allowed depends on the equipment of the vapor phase growth method. In the case of 50 μm or less, since cracking can be suppressed when the epitaxial wafer 20a and the substrate are bonded together, the LED can be successfully formed. Although the warpage of epitaxial wafer 20a is preferably as small as possible, for manufacturing reasons, the lower limit of the warpage of epitaxial wafer 20a is, for example, 0.001 μm.

  Here, the warp of the epitaxial wafer 20a is the highest position (epitaxial) of the space formed on one surface when the epitaxial wafer 20a is placed on a plane, as in the method of measuring the warp of the AlGaAs support substrate 10. This is a difference in distance h between the lowest position (the end portion on the back surface of the epitaxial wafer 20a) and the lowest position.

The average value of the residual strain of the epitaxial wafer 20a is preferably 5 × 10 ⁻⁵ or less, and more preferably 1.5 × 10 ⁻⁵ or less. The average value of the residual strain of the epitaxial wafer 20a is preferably 5 × 10 ⁻⁵ or less and the maximum value is preferably 1 × 10 ⁻⁴ or less. This is particularly effective when the diameter of the epitaxial wafer 20a is 50 mm or more.

  Subsequently, a method for manufacturing epitaxial wafer 20a in the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing a method for manufacturing epitaxial wafer 20a in the present embodiment.

  As shown in FIG. 7, first, the AlGaAs support substrate 10 is manufactured by the method of manufacturing the AlGaAs support substrate 10 in the first embodiment (steps S1 to S4).

  Next, the epitaxial layer 21 is formed on the first AlGaAs layer 12 by vapor deposition (step S11). In this step S 11, the epitaxial layer 21 as described above is grown on the first AlGaAs layer 12.

  The vapor phase growth method used in step S11 is not particularly limited. For example, HVPE (Hydride Vapor Phase Epitaxy) method, MBE (Molecular Beam Epitaxy) method, MOCVD (Metal Organic Chemical Vapor Deposition: Metalorganic chemical vapor deposition) or the like can be used. In particular, it is preferable to use at least one of the MOCVD method and the MBE method. The MOCVD method grows the epitaxial layer 21 by the thermal decomposition reaction of the source gas on the first AlGaAs layer 12, and the MBE method grows the epitaxial layer 21 by a method that is non-equilibrium and does not involve a chemical reaction process. Compared to the LPE method, the MOCVD method and the MBE method can easily control the thickness of the epitaxial layer 21.

  In step S11, the Al composition of the surface in contact with the first AlGaAs layer 12 in the epitaxial layer 21 is higher than the Al composition x of the surface in contact with the epitaxial layer 21 in the first AlGaAs layer 12 (main surface 12a). Thus, it is preferable to form the epitaxial layer 21. Further, the Al composition of the thickest layer in the epitaxial layer 21 is preferably higher than the Al composition x of the first AlGaAs layer 12 on the surface (main surface 12a) in contact with the epitaxial layer 21.

  By performing the above steps S1 to S11, the epitaxial wafer 20a shown in FIG. 6 can be manufactured.

As described above, the epitaxial wafer 20a and the manufacturing method thereof according to the present embodiment are epitaxial layers formed on the AlGaAs support substrate 10 and the first Al _x Ga _(1-x) As layer 12 by vapor phase growth. Layer 21. Since the AlGaAs support substrate 10 with reduced warpage in the first embodiment is used, the AlGaAs support substrate 10 can be held on the susceptor of the vapor phase growth apparatus in order to perform epitaxial growth on the AlGaAs support substrate 10.

  Furthermore, the AlGaAs support substrate 10 with reduced cost is used. For this reason, the cost of the epitaxial wafer 20a provided with the epitaxial layer 21 formed on this AlGaAs support substrate 10 can be reduced.

  In the present embodiment, the epitaxial layer 21 is formed by vapor phase growth. Since the vapor deposition method can control the film thickness well, the epitaxial layer 21 having a small thickness can be formed.

  In particular, in the first and second AlGaAs layers 12 and 13 of the AlGaAs support substrate 10, the epitaxial layer 21 is preferably formed on the main surface 12a having a low Al composition. That is, since the surface having a low Al composition is not easily oxidized, it is a layer for forming the epitaxial layer 21.

(Embodiment 3)
FIG. 8 is a cross-sectional view schematically showing an epitaxial wafer in the present embodiment. As shown in FIG. 8, the epitaxial wafer 20b in the present embodiment basically has the same configuration as that of the epitaxial wafer 20a shown in FIG. 6 in the second embodiment, but the epitaxial layer 21 has an AlGaAs support substrate. 10 in that it further includes a substrate 22 formed on the surface opposite to the surface in contact with the substrate 10. That is, the epitaxial wafer 20 b includes an AlGaAs support substrate 10, an epitaxial layer 21 formed on the AlGaAs support substrate 10, and a substrate 22 formed on the epitaxial layer 21.

  Specifically, the substrate 22 has conductivity and is provided in order to improve at least one of heat dissipation and high reflection characteristics. The substrate 22 is preferably made of a material having a small difference in thermal expansion coefficient from the epitaxial layer 21. Examples of such materials include Si (silicon), Ga (gallium), As (arsenic), and Ge (germanium).

  A connection layer (not shown) may be provided between the epitaxial layer 21 and the substrate 22. The connection layer is not particularly limited as long as it is a conductive material. For example, eutectic solder may be used.

  Next, with reference to FIG. 9, a method for manufacturing epitaxial wafer 20b in the present embodiment will be described. FIG. 9 is a flowchart showing a method for manufacturing epitaxial wafer 20b in the present embodiment. As shown in FIG. 9, the manufacturing method of the epitaxial wafer 20b in the present embodiment basically has the same configuration as the manufacturing method of the epitaxial wafer 20a of the second embodiment, but the epitaxial layer 21 supports AlGaAs. The difference is that step S12 for forming the substrate 22 on the surface opposite to the surface in contact with the substrate 10 is further provided.

  In step S12 in which the substrate 22 is formed on the surface opposite to the surface in contact with the AlGaAs support substrate 10 in the epitaxial layer 21, the substrate 22 and the epitaxial layer 21 are bonded together using, for example, the connection layer described above. Alternatively, the substrate 22 and the epitaxial layer 21 are bonded together by applying pressure, load, etc. without using the connection layer.

  By performing the above steps S1 to S12, the epitaxial wafer 20b shown in FIG. 8 can be manufactured.

  As described above, according to the epitaxial wafer 20b and the manufacturing method thereof in the present embodiment, the epitaxial layer 21 is further provided with the substrate 22 formed on the surface opposite to the surface in contact with the AlGaAs support substrate 10. Yes. Since the warp of the AlGaAs support substrate 10 is small, it is possible to suppress the formation of cracks, cracks, or the like in the epitaxial layer 21 due to the stress applied in step S12 for attaching the substrate 22. Further, the substrate 22 can be uniformly attached to the epitaxial layer 21. For this reason, in the case where the substrate 22 has good characteristics such as conductivity, heat dissipation, and high reflectivity, the heat dissipation performance and the high directivity performance are improved when the epitaxial wafer 20b is an LED.

(Embodiment 4)
FIG. 10 is a cross-sectional view schematically showing an epitaxial wafer in the present embodiment. Referring to FIG. 10, epitaxial wafer 20c in the present embodiment basically has the same configuration as epitaxial wafer 20b shown in FIG. 8 in the third embodiment, but GaAs substrate 11 and second AlGaAs. The difference is that the layer 13 is not provided. That is, the epitaxial wafer 20 c includes the first AlGaAs layer 12, the epitaxial layer 21 formed on the first AlGaAs layer 12, and the substrate 22 formed on the epitaxial layer 21.

  FIG. 11 is a flowchart showing a method for manufacturing epitaxial wafer 20c in the present embodiment. As shown in FIG. 11, the method for manufacturing epitaxial wafer 20c in the present embodiment has basically the same configuration as the method for manufacturing epitaxial wafer 20b in Embodiment 3, but the second AlGaAs layer. 13 and step S13 for removing the GaAs substrate 11 are different.

  In step S13 for removing, for example, a method such as polishing or etching is used. Polishing refers to mechanically scraping the GaAs substrate 11 and the second AlGaAs layer 13 using a polishing agent such as alumina, colloidal silica, or diamond in a grinding facility having a diamond grindstone. Etching refers to the GaAs substrate 11 and the second AlGaAs layer in a state where the first AlGaAs layer 12, the epitaxial layer 21, and the substrate 22 are protected using an etching solution that is optimally prepared, for example, ammonia, hydrogen peroxide, or the like. 13 is to be removed.

  By performing the above steps S1 to S13, the epitaxial wafer 20c shown in FIG. 10 can be manufactured.

  The order of the processes is not particularly limited, and step S13 for removing GaAs substrate 11 and second AlGaAs layer 13 is performed, for example, between step S11 for growing an epitaxial layer and step S12 for forming substrate 22. Also good.

  As described above, epitaxial wafer 20c and its manufacturing method in the present embodiment further include step S13 for removing second AlGaAs layer 13 and GaAs substrate 11. Thereby, since the light of the active layer can be prevented from being absorbed by the GaAs substrate 11, the epitaxial wafer 20c that can improve the light output characteristics of the LED formed with the electrodes can be manufactured.

  The epitaxial wafer 20 c includes a substrate 22. For this reason, the epitaxial wafer 20c with easy handling can be realized.

  In the present embodiment, among the first and second AlGaAs layers 12 and 13 of the AlGaAs support substrate 10, layers having a low Al composition on the main surfaces 12 a and 13 a (the first AlGaAs layer in the present embodiment). Since the surface of 12) is hardly oxidized, it is used as a layer for forming the epitaxial layer 21. Of the first and second AlGaAs layers 12 and 13, the layer having a high Al composition on the main surfaces 12 a and 13 a (second AlGaAs layer 13 in the present embodiment) alleviates the warp of the AlGaAs support substrate 10. Thus, the sacrificial layer is removed when the epitaxial wafer 20c is formed.

(Embodiment 5)
FIG. 12 is a cross-sectional view schematically showing an epitaxial wafer in the present embodiment. Referring to FIG. 12, epitaxial wafer 20d in the present embodiment has basically the same configuration as that of epitaxial wafer 20a shown in FIG. 6 in the second embodiment. The difference is that the AlGaAs layer 13 is not provided. That is, the epitaxial wafer 20 d includes the first AlGaAs layer 12 and the epitaxial layer 21 formed on the first AlGaAs layer 12.

  FIG. 13 is a flowchart showing a method of manufacturing epitaxial wafer 20d in the present embodiment. As shown in FIG. 13, the manufacturing method of epitaxial wafer 20d in the present embodiment basically has the same configuration as the manufacturing method of epitaxial wafer 20a in the second embodiment, but the second AlGaAs layer. 13 and step S13 for removing the GaAs substrate 11 are different. Since step S13 to be removed is the same as that in the fourth embodiment, description thereof will not be repeated.

  As described above, epitaxial wafer 20d and the method for manufacturing the same in the present embodiment further include step S13 for removing second AlGaAs layer 13 and GaAs substrate 11. Thereby, since the light from the active layer can be prevented from being absorbed by the GaAs substrate 11, the epitaxial wafer 20 d capable of improving the light output characteristics of the LED formed with the electrodes can be manufactured.

(Embodiment 6)
FIG. 14 is a cross-sectional view schematically showing the LED in the present embodiment. With reference to FIG. 14, LED30a in this Embodiment is demonstrated. As shown in FIG. 14, LED 30a in the present embodiment includes epitaxial wafer 20a shown in FIG. 6 in the second embodiment, and electrodes 31 and 32 formed on the front surface and the back surface of epitaxial wafer 20a, respectively. ing. That is, the LED 30a includes the second AlGaAs layer 13, the GaAs substrate 11 formed on the second AlGaAs layer 13, the first AlGaAs layer 12 formed on the GaAs substrate 11, and the first AlGaAs layer. 12, an epitaxial layer 21 formed on the epitaxial layer 21 by vapor phase growth, an electrode 31 formed on the epitaxial layer 21, and an electrode 32 formed below the second AlGaAs layer 13.

  Specifically, the electrode 31 provided in contact with the surface of the epitaxial wafer 20a is a p-type electrode made of an alloy with, for example, Au (gold) Zn (zinc). The electrode 32 provided in contact with the main surface 13a of the second AlGaAs layer 13 is an n-type electrode made of, for example, an alloy of Au, Ge (germanium), and Ni (nickel).

  The LED 30a in the present embodiment is an infrared LED. The first AlGaAs layer 12 is for improving light extraction in the direction perpendicular to the energizing direction.

  Then, with reference to FIG. 15, the manufacturing method of LED30a in this Embodiment is demonstrated. In addition, FIG. 15 is a flowchart which shows the manufacturing method of LED30a in this Embodiment.

  First, the epitaxial wafer 20a is manufactured by the method for manufacturing the epitaxial wafer 20a in the second embodiment (steps S1 to S11).

  Next, electrodes 31 and 32 are formed on the front and back surfaces of epitaxial wafer 20a (step S21). Specifically, Au, Ge, and Ni are vapor-deposited on the back surface of the epitaxial wafer 20a, for example, by vapor deposition, and alloyed to form the n-electrode 32. Further, Au and Zn are vapor-deposited on the surface of the epitaxial wafer 20a, and then alloyed to form the p-electrode 31.

  Next, this LED 30a is mounted. Specifically, for example, with the electrode 31 side down, die bonding is performed on the stem with a die bond agent such as Ag paste or a eutectic alloy such as AuSn.

  The LED 30a shown in FIG. 14 can be manufactured by performing the above steps S1 to S21.

  As described above, in LED 30a and the manufacturing method thereof in the present embodiment, electrodes 31 and 32 are formed on the front surface and the back surface of epitaxial wafer 20a in the second embodiment, respectively (step S21). The LED 30a can reduce the cost of the LED 30a by using the AlGaAs support substrate 10 with reduced warpage.

(Embodiment 7)
FIG. 16 is a cross-sectional view schematically showing the LED in the present embodiment. As shown in FIG. 16, LED 30b in the present embodiment includes epitaxial wafer 20b shown in FIG. 8 in the third embodiment, and electrodes 31 and 32 formed on the front surface and the back surface of epitaxial wafer 20b, respectively. ing. That is, the LED 30b includes the second AlGaAs layer 13, the GaAs substrate 11 formed on the second AlGaAs layer 13, the first AlGaAs layer 12 formed on the GaAs substrate 11, and the first AlGaAs layer. 12, an epitaxial layer 21 formed on the substrate 12, a substrate 22 formed on the epitaxial layer 21, an electrode 31 formed on the substrate 22, and an electrode 32 formed under the second AlGaAs layer 13. ing.

  LED 30b in the present embodiment is an infrared LED. Since electrodes 31 and 32 are the same as in the sixth embodiment, description thereof will not be repeated.

  FIG. 17 is a flowchart showing a method for manufacturing LED 30b in the present embodiment. The manufacturing method of LED 30b in the present embodiment basically has the same configuration as the manufacturing method of epitaxial wafer 20b in the third embodiment, but electrodes 31 and 32 are provided on the front and back surfaces of epitaxial wafer 20b, respectively. The difference is that it further includes step S21 of forming.

  As described above, in the LED 30b and the manufacturing method thereof in the present embodiment, the electrodes 31 and 32 are formed on the front surface and the back surface of the epitaxial wafer 20b in the third embodiment (step S21). Thereby, LED30b excellent in heat dissipation can be manufactured.

(Embodiment 8)
FIG. 18 is a cross-sectional view schematically showing the LED in the present embodiment. As shown in FIG. 18, LED 30c in the present embodiment includes epitaxial wafer 20c shown in FIG. 10 in the fourth embodiment, and electrodes 31 and 32 formed on the front surface and the back surface of epitaxial wafer 20c, respectively. ing. That is, the LED 30 c includes the first AlGaAs layer 12, the epitaxial layer 21 formed on the first AlGaAs layer 12, the substrate 22 formed on the epitaxial layer 21, and the electrode 31 formed on the substrate 22. And an electrode 32 formed under the first AlGaAs layer 12.

  LED 30c in the present embodiment is an infrared LED. Since electrodes 31 and 32 are the same as in the sixth embodiment, description thereof will not be repeated.

  FIG. 19 is a flowchart showing a method for manufacturing LED 30c in the present embodiment. The manufacturing method of LED 30c in the present embodiment basically has the same configuration as the manufacturing method of epitaxial wafer 20c in the fourth embodiment, but electrodes 31 and 32 are provided on the front and back surfaces of epitaxial wafer 20c, respectively. The difference is that it further includes step S21 of forming.

  As described above, in the LED 30c and the manufacturing method thereof in the present embodiment, the electrodes 31 and 32 are formed on the front surface and the back surface of the epitaxial wafer 20c of the fourth embodiment (step S21). By removing the GaAs substrate 11, it is possible to manufacture an LED 30c that is excellent in light transmittance from the active layer, and that is easy to handle and has excellent heat dissipation performance and high directivity performance by including the substrate 22.

(Embodiment 9)
FIG. 20 is a cross-sectional view schematically showing the LED in the present embodiment. As shown in FIG. 20, LED 30d in the present embodiment includes epitaxial wafer 20d shown in FIG. 12 in the fifth embodiment, and electrodes 31 and 32 formed on the front surface and the back surface of epitaxial wafer 20d, respectively. ing. That is, the LED 30 d is formed under the first AlGaAs layer 12, the epitaxial layer 21 formed on the first AlGaAs layer 12, the electrode 31 formed on the epitaxial layer 21, and the second AlGaAs layer 13. The electrode 32 is provided.

  LED 30b in the present embodiment is an infrared LED. Since electrodes 31 and 32 are the same as in the sixth embodiment, description thereof will not be repeated.

  FIG. 21 is a flowchart showing a method for manufacturing LED 30d in the present embodiment. The manufacturing method of LED 30d in the present embodiment has basically the same configuration as the manufacturing method of epitaxial wafer 20d in the fifth embodiment, but electrodes 31 and 32 are provided on the front and back surfaces of epitaxial wafer 20d, respectively. The difference is that it further includes step S21 of forming.

  As described above, in the LED 30d and the manufacturing method thereof in the present embodiment, the electrodes 31 and 32 are formed on the front surface and the back surface of the epitaxial wafer 20d of the fifth embodiment, respectively (step S21). Thereby, LED30d which improved the characteristic by reducing curvature and reduced cost can be manufactured. Further, by removing the GaAs substrate 11, it is possible to manufacture an LED 30d having excellent light transmission from the active layer.

  In this embodiment, step S2 for forming the first AlGaAs layer 12 on the main surface 11a side of the GaAs substrate 11 and step S3 for forming the second AlGaAs layer 13 on the back surface 11b side of the GaAs substrate 11 are performed. We investigated the effect of the preparation.

(Invention Example 1)
Specifically, according to the method for manufacturing the AlGaAs support substrate 10 in Embodiment 1, the AlGaAs support substrate 10 of Example 1 of the present invention was manufactured.

  More specifically, first, a 2-inch GaAs substrate 11 having a thickness of 270 μm was prepared (step S1).

  Next, first and second AlGaAs layers 12 and 13 were formed on the main surface 11a and the back surface 11b of the GaAs substrate 11 by a slow cooling method (steps S2 and S3), respectively. The growth temperature of the LPE method was 780 ° C., the growth rate was 4 μm / H on average, and Te was used as the dopant. Steps S2 and S3 were performed under the same conditions, and first and second AlGaAs layers 12 and 13 having a thickness of 50 μm were formed, respectively. In the first and second AlGaAs layers 12 and 13, the Al compositions x and y of the back surfaces 12b and 13b are 0.35, respectively, and the Al compositions x and y of the main surfaces 12a and 13a are 0.10 respectively. there were. Further, the Al compositions x and y monotonously decreased from the back surfaces 12b and 13b to the main surfaces 13a and 13b.

  Next, the main surfaces 12a and 13a were cleaned using an acid or alkali cleaning solution, an organic solvent, and pure water, and then polished by chemical mechanical polishing (step S4). As a result, the thickness of the first and second AlGaAs layers 12 and 13 became 40 μm. Further, the surface roughness Ra of the main surfaces 12a and 13a was <1 nm to 20 nm (<1 nm is a measurement lower limit). The Al compositions x and y of the main surfaces 12a and 13a at that time were 0.15.

  Through the above steps S1 to S4, the AlGaAs support substrate 10 in Example 1 of the present invention was manufactured.

(Invention Examples 2-6, Comparative Examples 1 and 2)
The AlGaAs support substrates of Examples 2 to 6 of the present invention performed steps S1 to S4 similar to those of the AlGaAs support substrate of Example 1 of the present invention, and then protected the first AlGaAs layer 12 to the second AlGaAs layer 13 side. Then, etching was performed by the etching amounts shown in Table 1 below. As a result, Examples 1 to 6 of the present invention manufactured an AlGaAs support substrate including the GaAs substrate 11 having the thickness shown in Table 1 below and the first and second AlGaAs layers 12 and 13. In Comparative Examples 1 and 2, an AlGaAs support substrate including a GaAs substrate 11 having the thickness shown in Table 1 below and a first AlGaAs layer 12 was manufactured.

(Evaluation methods)
Further, with respect to the AlGaAs support substrates of Invention Examples 1 to 6 and Comparative Examples 1 and 2, as shown in FIG. 22, on the surface of the epitaxial layer 21, the lateral direction, the longitudinal direction orthogonal to the lateral direction, the lateral direction, and The amount of warpage in four directions with respect to a direction inclined 45 degrees from the vertical direction was measured as shown in FIG. Specifically, the AlGaAs support substrate was arranged on a parallel table, and the gap between the AlGaAs support substrate and the parallel table was measured using a position sensor with the convex surface as the upper surface. The results are shown in Table 2 below, FIG. 23 and FIG. FIG. 22 is a plan view for explaining a method of measuring the warpage of the AlGaAs support substrate of this example. FIG. 23 is a view showing the amount of warpage of the AlGaAs support substrate of Example 1 of the present invention. FIG. 24 is a diagram showing the amount of warpage of the AlGaAs support substrate of Comparative Example 1. 23 and 24, the in-plane distance indicates a distance from the center when the center of the AlGaAs support substrate is zero.

  In addition, for the AlGaAs support substrates of Invention Examples 1 to 6 and Comparative Examples 1 and 2, immediately before the epitaxial growth, the main surfaces 12a and 13a were cleaned using an acid, an alkaline cleaning solution, an organic solvent, and pure water, It was placed on the susceptor of the MOCVD apparatus, and it was confirmed whether the following epitaxial layer 21 could be formed. The results are shown in Table 2 below. In Table 2, when the epitaxial layer was formed, “Allow” indicates that the AlGaAs support substrate was grown without detaching from the susceptor, and “No” indicates that the epitaxial layer could not be formed because the AlGaAs support substrate was detached from the susceptor. "

As the epitaxial layer 21, as shown in FIG. 25, an n-type cladding layer 23, an active layer 24, a p-type cladding layer 25, and a p-type contact layer 26 are formed in this order by the MOCVD method. Growing up. The growth temperature of each layer was 750 ° C. The n-type cladding layer 23 had a thickness of 0.5 μm and was made of Al _0.35 Ga _0.65 As. The active layers 24 of Examples 1 to 4 of the present invention each comprised 20 layers of well layers made of GaAs and barrier layers made of Al _0.30 Ga _0.70 As having a thickness of 5 nm. The active layer 24 of Inventive Example 5 has a well layer made of In _u Ga _(1-u) As (In composition u = 0.1 or more and less than 0.2), a thickness of 5 nm, and GaAs _{( 1-v)} 20 barrier layers each consisting of P _v (P composition v = 0.1 or more and less than 0.2) were included. The active layer 24 of Inventive Example 6 has a well layer made of In _u Ga _(1-u) As (In composition u = 0.2 or more and less than 0.3), a thickness of 5 nm, and GaAs. _(1-v) 20 barrier layers each consisting of P _v (P composition v = 0.2 or more and less than 0.3) were included. The p-type cladding layer 25 had a thickness of 0.5 μm and was made of Al _0.35 Ga _0.65 As. The p-type contact layer 26 had a thickness of 0.05 μm and was made of p-type GaAs. FIG. 25 is a cross-sectional view schematically showing the epitaxial wafer of Examples 1 to 6 of the present invention.

  Further, the warpage of the epitaxial wafers of Invention Examples 1 to 6 was measured by the same method as that for the AlGaAs support substrate. The results are shown in Table 2 below.

  Further, the epitaxial wafers of Invention Examples 1 to 6 were examined for whether or not the substrate 22 made of n-type Si having a thickness of 450 μm could be attached. The specific procedure is shown below. First, Ti (0.1 μm) and Au (1 μm) were deposited in this order on the surfaces of the epitaxial wafers of Invention Examples 1 to 6. Further, Ti (0.1 μm), Pt (0.1 μm) and AuSn (Au: Su = 80%: 20%, 2 μm) were formed in this order on the substrate 22. Next, in a state where these substrates were bonded together, the substrate was bonded by applying a load of 800 kg for 30 minutes while heating the substrate to 300 ° C.

  The results are shown in Table 2 below. In Table 2, the case where the substrate 22 could be pasted without cracking the epitaxial wafer was set as “OK”, and the case where the substrate 22 was cracked was set as “impossible”.

  Moreover, the average value of the residual strain of the AlGaAs support substrates of Invention Examples 1 to 6 and Comparative Examples 1 and 2 was measured by a photoelastic method. The results are shown in the following Table 2, FIG. 26 and FIG. FIG. 26 is a diagram showing the residual strain of the AlGaAs support substrate of Example 1 of the present invention. FIG. 27 is a diagram showing the residual strain of the AlGaAs support substrate of Comparative Example 1. 26 and 27, the vertical axis indicates the amount of residual strain, and the horizontal axis indicates the distance from the center of the substrate. 26 and 27, the distance from the center of the substrate (in-plane distance) indicates the distance from the center when the center of the AlGaAs support substrate is zero.

  Moreover, the slip was observed about the epitaxial wafer of the invention examples 1-6. The results are shown in Table 2 below. In Table 2, it is described which slip state was shown in FIGS.

  Furthermore, electrodes were formed on the front and back surfaces of the epitaxial wafers of Invention Examples 1 to 6 to produce LEDs. The electrodes were formed in this order by vapor deposition using an n electrode of Au, Ge, Ni and a p electrode of Au, Zn. The light output characteristics of this LED were measured. The results are shown in Table 2 below.

(Measurement result)
As shown in Table 2, the warpage of the AlGaAs support substrates of Invention Examples 1 to 6 was 200 μm or less, which was smaller than the warp of the AlGaAs support substrates of Comparative Examples 1 and 2. Further, as shown in FIGS. 23 and 24, it was found that the AlGaAs support substrate of Example 1 of the present invention had less warpage when measured from any direction than the AlGaAs support substrate of Comparative Example 1.

  Moreover, as shown in Table 2, since the warp of the AlGaAs support substrates of Invention Examples 1 to 6 could be reduced to 200 μm or less, an epitaxial layer could be formed. On the other hand, since the warpage of the AlGaAs support substrates of Comparative Examples 1 and 2 was large, the AlGaAs support substrate was detached from the susceptor during the epitaxial growth. For this reason, an epitaxial layer could not be formed on the AlGaAs support substrates of Comparative Examples 1 and 2.

  Further, as shown in Table 2, since the warpage of the AlGaAs support substrates of Invention Examples 1 to 6 was small, when the thin epitaxial layer 21 was formed, the average value of the residual strain of the AlGaAs support substrate is shown. Further, the influence of strain due to the epitaxial layer 21 was small, and the warp of the epitaxial wafer was not affected.

  Further, since the AlGaAs support substrates of Examples 1 and 2 of the present invention had a warp of 50 μm or less, the substrate 22 could be stuck so as not to crack the epitaxial wafer.

Further, as shown in Table 2, the average value of the residual strain of the AlGaAs support substrates of Examples 1 to 6 of the present invention was 1.5 × 10 ⁻⁵ or less. On the other hand, as shown in Table 2, the average value of the residual strain of the AlGaAs support substrates of Comparative Examples 1 and 2 exceeded 5.0 × 10 ⁻⁵ . In the AlGaAs support substrates of Invention Examples 1 to 6, AlGaAs layers are formed on both sides of the GaAs substrate. For this reason, stress in the same direction can be applied to the main surface and the back surface of the GaAs substrate. As a result, the stress applied to the inside of the AlGaAs support substrate could be reduced. Therefore, an AlGaAs support substrate in which the average value of residual strain in the AlGaAs support substrate was 1 × 10 ⁻⁵ or less could be obtained. That is, it was confirmed that the AlGaAs support substrate in which the warpage was suppressed also reduced the residual strain of the crystal.

FIG. 26 is a diagram showing a distribution of residual strain of the AlGaAs support substrate of Example 1 of the present invention having an average value of residual strain of 4.0 × 10 ⁻⁶ . As shown in FIG. 26, in an AlGaAs support substrate having an average value of residual strain in the crystal of 4.0 × 10 ⁻⁶ , the amount of residual strain can be suppressed to approximately the same level on average throughout the AlGaAs support substrate. No significant difference was observed between the amount of residual strain at the outer periphery of the AlGaAs support substrate and the amount of residual strain near the center of the AlGaAs support substrate. Further, the maximum value of the residual strain of the AlGaAs support substrate was 2 × 10 ⁻⁵ or less.

FIG. 27 is a diagram showing a distribution of residual strain of the AlGaAs crystal substrate of Comparative Example 1 in which the average value of residual strain exceeds 5.0 × 10 ⁻⁵ . As shown in FIG. 27, in the AlGaAs support substrate in which the average value of residual strain in the crystal exceeds 5.0 × 10 ⁻⁵ , the amount of residual strain increases from the vicinity of the center of the AlGaAs support substrate toward the outer periphery. A tendency to increase rapidly was recognized remarkably, and the amount of residual strain was around 5 × 10 ⁻⁵ around 18 mm from the vicinity of the center.

Thus, from Table 2, FIG. 26, and FIG. 27, the maximum value of residual strain can be made 2 × 10 ⁻⁵ or less in an AlGaAs support substrate having an average residual strain of 4.0 × 10 ^−6. I understood. For this reason, it was confirmed that the residual strain could be reduced on the entire surface of the AlGaAs support substrate in which the warpage was suppressed.

28 to 30, the average values of residual strain in the AlGaAs support substrate are 4.0 × 10 ^{−6 to} 6.0 × 10 ⁻⁶ , 1.0 × 10 ⁻⁵ and 1.5 × 10, respectively. ^{FIG. 5} is a diagram schematically showing a slip in an epitaxial wafer when each AlGaAs support substrate of ⁻⁵ is used. As shown in FIG. 28, no slip is observed in the epitaxial wafer using an AlGaAs support substrate having an average residual strain of 4.0 × 10 ^{−6 to} 6.0 × 10 ^−6. There wasn't. In addition, as shown in FIG. 29, in the epitaxial wafer in the case of using an AlGaAs support substrate having an average residual strain of 1.0 × 10 ⁻⁵ , slip does not occur or even if it occurs, It remained to the extent that it occurred only slightly on the outer periphery. Further, as shown in FIG. 30, although slip occurred in the epitaxial wafer in the case of using the AlGaAs support substrate having an average value of residual strain of 1.5 × 10 ⁻⁵ , the slip occurred at the outer peripheral portion of the epitaxial wafer. It stayed only slightly. From this, it was confirmed that slip was suppressed in an epitaxial wafer in which warpage and residual strain were suppressed.

Furthermore, when the residual strain of the AlGaAs support substrate was 1.5 × 10 ⁻⁵ or less, the LED light output could be detected. In particular, in the inventive examples 1 and 2 in which the residual strain of the AlGaAs support substrate is 6.0 × 10 ⁻⁶ or less, the occurrence of slip in the outer peripheral portion can be suppressed. The output characteristics were very good.

Moreover, as shown in Table 2, the average value of the residual strain of the epitaxial wafers of Invention Examples 1 to 6 was 5 × 10 ⁻⁵ or less. On the other hand, as shown in Table 2, an epitaxial wafer could not be grown on the AlGaAs support substrates of Comparative Examples 1 and 2. Since the epitaxial wafers of Examples 1 to 6 of the present invention are provided with the AlGaAs support substrate in which the AlGaAs layers are formed on both sides of the GaAs substrate, the stress applied to the inside of the AlGaAs support substrate can be reduced. Therefore, it was possible to obtain an epitaxial wafer in which the average value of residual strain in the epitaxial wafer provided with this AlGaAs support substrate was 5 × 10 ⁻⁵ or less. In Examples 5 and 6 of the present invention, a predetermined distortion was intentionally added, but the output was not greatly reduced. For this reason, it has been found that the epitaxial layer can be strained to such an extent that the light emission characteristics can be controlled.

  As described above, according to the present embodiment, step S2 for forming the first AlGaAs layer 12 on the main surface 11a side of the GaAs substrate 11 and the second AlGaAs layer 13 on the back surface 11b side of the GaAs substrate 11 are formed. It was confirmed that the warpage of the AlGaAs support substrate can be reduced by providing the step S3.

  Furthermore, the manufacturing cost of the AlGaAs support substrates of Invention Examples 1 to 6 that could reduce the warpage was lower than the manufacturing cost of the AlGaAs layer in which the AlGaAs layer having the same thickness was formed on the GaAs substrate and the GaAs substrate was removed.

  In this example, the relationship between the thicknesses of the first and second AlGaAs layers and the Al composition was examined.

(Invention Examples 7 to 11)
Tables 3 to 7 show the configurations of the AlGaAs support substrates of Examples 7 to 11 of the present invention, respectively. The AlGaAs support substrates of Invention Examples 7 to 11 are basically the same as the manufacturing method of Invention Example 1 described above, but as shown in Tables 3 to 7 below, the thickness of the GaAs substrate, the first And the thickness of the second AlGaAs layer and the composition of the first and second AlGaAs layers were different. As shown in Tables 3 to 7, the first and second AlGaAs layers of the AlGaAs supporting substrates of Examples 7 to 11 of the present invention have a monotone Al composition x from the back surfaces 12b and 13b toward the main surfaces 12a and 13a. It was decreasing. Further, the first AlGaAs layer of Invention Example 8 was two layers.

In Tables 3 to 7, the lowest Al composition in the first and second AlGaAs layers 12 and 13 is Al _L, and the highest Al composition in the first and second AlGaAs layers 12 and 13 is used. Was Al _H and the average value of the Al composition in the first and second AlGaAs layers 12 and 13 in the depth direction was Al _ave . Al _ave was determined by (Al _L + Al _H ) / 2. Moreover, in Tables 3-7, the back surface side (2nd AlGaAs layer) is described below. That is, in Tables 3 to 7, the main surface side (first AlGaAs layer) is described above and described as stacked. For this reason, in Tables 3 to 7, the numerical value described on the lower side in the cell with the Al composition ratio is the Al composition at the position on the back surface side in the layer, and the upper side in the cell with the Al composition ratio. The numerical value described is the composition of Al at the position on the main surface side in the layer. For example, in Inventive Example 7 shown in Table 3, the Al composition on the main surface of the first AlGaAs layer was 0.15, and the Al composition on the back surface was 0.35.

(Measuring method)
For the AlGaAs support substrates of Invention Examples 7 to 11, warpage was measured in the same manner as in Example 1. The results are shown in Table 8 below. In Table 8, the Al _ave ratio X as (Al _ave second Al _ave / first AlGaAs layer 12 of the AlGaAs layer 13), the thickness ratio Y (thickness / first second AlGaAs layer 13 Of the AlGaAs layer 12). In Table 8, the first AlGaAs layer is the front and the second AlGaAs layer is the back.

In addition to Invention Examples 7 to 11, a plurality of AlGaAs support substrates having various Al _ave ratios X and thickness ratios Y were prepared, and the Al _ave ratio X, the thickness ratio Y, and the warpage of each AlGaAs support substrate were measured. . The result is shown in FIG. The warpage of the plurality of AlGaAs support substrates shown in FIG. 31 was all 200 μm or less. FIG. 31 is a diagram illustrating the relationship between the _Alave ratio X and the thickness ratio Y in the second embodiment. In FIG. 31, the vertical axis represents the thickness ratio Y, and the horizontal axis represents the _Alave ratio X.

(Measurement result)
As shown in FIG. 31 and Table 8, in the AlGaAs support substrate, 0.7 ≦ X <4.0 and −X + 1.3 ≦ Y ≦ −X + 4.0 (within the dotted line in FIG. 31) When it is satisfied, it has been found that the warp of the AlGaAs support substrate is 200 μm or less. For this reason, warpage can be reduced by forming AlGaAs layers on both sides of the GaAs substrate, and by satisfying the above relational expression, the thickness of the second AlGaAs layer (backside AlGaAs layer) can be reduced while maintaining low warpage. It turned out that cost can be reduced by reducing.

  In particular, when 0.7 ≦ X <4.0 and −X + 2.0 ≦ Y ≦ −X + 2.2 (the vicinity of the solid line in FIG. 31) is satisfied, the warp of the AlGaAs support substrate is less than 20 μm. I understood it.

  As described above, the inventor reduced the thickness of the second AlGaAs layer 13 by satisfying the relationship of 0.7 ≦ X <4.0 and −X + 1.3 ≦ Y ≦ −X + 4.0. Even if it exists, it discovered that the curvature of the AlGaAs support substrate 10 could be eased.

  Although the embodiments and examples of the present invention have been described above, it is also planned from the beginning to appropriately combine the features of the embodiments and examples. The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the embodiments and examples described above but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  10 AlGaAs support substrate, 11 GaAs substrate, 11a, 12a, 13a main surface, 11b, 12b, 13b back surface, 12 first AlGaAs layer, 13 second AlGaAs layer, 20a, 20b, 20c, 20d epitaxial wafer, 21 epitaxial Layer, 22 substrate, 23 n-type cladding layer, 24 active layer, 25 p-type cladding layer, 26 p-type contact layer, 30a, 30b, 30c, 30d LED, 31, 32 electrodes.

Claims (22)

Providing a GaAs substrate having a main surface and a back surface opposite to the main surface;
Forming a first Al _x Ga _(1-x) As layer (0 <x <1) on the main surface side of the GaAs substrate by a liquid phase growth method;
Forming a second Al _y Ga _(1-y) As layer (0 <y <1) on the back side of the GaAs substrate by a liquid phase growth method. The AlGaAs support according to claim 1, wherein the step of forming the second Al _y Ga _(1-y) As layer is performed after the step of forming the first Al _x Ga _(1-x) As layer. A method for manufacturing a substrate. 2. The AlGaAs according to claim 1, wherein the step of forming the first Al _x Ga _(1-x) As layer and the step of forming the second Al _y Ga _(1-y) As layer are performed simultaneously. Manufacturing method of support substrate. At least one of the first Al _x Ga _(1-x) As layer and the second Al _y Ga _(1-y) As layer is polished on the surface opposite to the surface in contact with the GaAs substrate. The manufacturing method of the AlGaAs support substrate of any one of Claims 1-3 further provided with the process. 5. The AlGaAs support substrate according to claim 4, wherein in the polishing step, polishing is performed so that a surface roughness Ra of the opposite surface of the first Al _x Ga _(1-x) As layer is 50 nm or less. Manufacturing method. 6. The AlGaAs according to claim 4, wherein in the polishing step, polishing is performed so that the surface roughness Ra of the opposite surface of the second Al _y Ga _(1-y) As layer is 5 μm or less. Manufacturing method of support substrate. A step of manufacturing an AlGaAs support substrate by the method of manufacturing an AlGaAs support substrate according to any one of claims 1 to 6;
And a step of forming an epitaxial layer on the first Al _x Ga _(1-x) As layer by vapor phase epitaxy.   The method for manufacturing an epitaxial wafer according to claim 7, further comprising a step of forming a substrate on a surface opposite to a surface in contact with the AlGaAs support substrate in the epitaxial layer. The method for manufacturing an epitaxial wafer according to claim 7, further comprising a step of removing the second Al _y Ga _(1-y) As layer and the GaAs substrate. A step of producing an epitaxial wafer by the method for producing an epitaxial wafer according to any one of claims 7 to 9,
Forming an electrode on the front surface and the back surface of the epitaxial wafer, respectively. A GaAs substrate having a main surface and a back surface opposite to the main surface;
A first Al _x Ga _(1-x) As layer (0 <x <1) formed on the main surface side of the GaAs substrate;
An AlGaAs support substrate comprising: a second Al _y Ga _(1-y) As layer (0 <y <1) formed on the back side of the GaAs substrate.   The AlGaAs support substrate according to claim 11, which has a warp of 200 μm or less. The AlGaAs support substrate according to claim 11 or 12, which has a residual strain having an average value of 1.5 × 10 ^-5 or less. The AlGaAs support substrate according to claim 13, which has a residual strain whose maximum value is 2 × 10 ⁻⁵ or less.   The AlGaAs support substrate according to claim 13 or 14, which has a diameter of 50 mm or more. The AlGaAs support substrate according to any one of claims 11 to 15,
An epitaxial wafer comprising: an epitaxial layer formed on the first Al _x Ga _(1-x) As layer. The first Al _x Ga _(1-x) As layer according to any one of claims 11 to 15,
An epitaxial wafer comprising: an epitaxial layer formed on the first Al _x Ga _(1-x) As layer. 18. The epitaxial wafer according to claim 16, further comprising a substrate formed on a surface of the epitaxial layer opposite to a surface in contact with the first Al _x Ga _(1-x) As layer.   The epitaxial wafer according to claim 16, which has a warp of 200 μm or less. The epitaxial wafer according to any one of claims 16 to 19, wherein the average value has a residual strain of 5 x ^10-5 or less. ^21. The epitaxial wafer according to claim 20, having a residual strain having a maximum value of 1 × 10 ⁻⁴ or less. The epitaxial wafer according to any one of claims 16 to 21, and
LED provided with the electrode respectively formed in the surface and the back surface of the said epitaxial wafer.

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