JP7351241B2 - Compound semiconductor epitaxial wafer and its manufacturing method - Google Patents

Description

The present invention relates to a compound semiconductor epitaxial wafer for light emitting diodes and a method for manufacturing the same.

A light emitting diode made of a III-V group compound semiconductor, for example, gallium phosphide arsenide GaAs _1-x P _x (0.45≦x≦1.0), is an n-type gallium phosphide (GaP) Alternatively, multiple epitaxial layers of n-type gallium arsenide GaAs _1-x P _x (or gallium phosphide) are formed on a single crystal substrate of gallium arsenide (GaAs), and Zn is further added to the top layer of this epitaxial layer. It can be obtained by thermally diffusing p-type impurities such as, to form a pn junction and forming a light-emitting layer portion.

Alternatively, after forming an epitaxial layer of n-type gallium arsenide phosphide GaAs _{1- x P} A pn junction can also be formed by forming P _x (or gallium phosphide).

By selecting the mixed crystal ratio x, a wavelength range ranging from red through orange to yellow can be realized, and a light emitting diode with a light emitting layer of GaAs _1-x P _x (0.45≦x≦1.0) usually has a high luminous efficiency. In order to increase the optical output, nitrogen (N) is doped as an isoelectronic trap to increase the optical output by about 10 times.

Light emitting diodes are required to have high brightness, and the brightness of the light emitting diodes does not decrease during use, that is, they are required to have a long life. Conventionally, in order to extend the life of light emitting diodes, measures have been taken such as lowering the carrier concentration of epitaxial wafers.

For example, as disclosed in Patent Document 1, the carrier concentration of the nitrogen-doped gallium arsenide phosphide GaAs _1-x P _x layer is set to 1×10 ¹⁵ to 3×10 ¹⁵ (atoms/cm ³ ). Accordingly, it is possible to prevent a decrease in crystallinity due to impurities and extend the life of brightness.

Furthermore, as disclosed in Patent Document 2, by optimizing the nitrogen concentration and its profile of the gallium arsenide phosphide GaAs _{1-x P} As electricity continues to flow through the light-emitting element, the deterioration mechanism in which nitrogen moves to non-light-emitting sites can be prevented, and the lifetime of brightness can be extended.

However, as disclosed in Patent Document 1, even if the carrier concentration of the nitrogen-doped gallium arsenide phosphide GaAs _1-x P _x layer is 1×10 ¹⁵ to 3×10 ¹⁵ (atoms/cm ³ ), Its life characteristics cannot be said to be sufficiently good. In particular, there is a problem in that the movement of nitrogen between sites as disclosed in Patent Document 3 is more likely to occur as the concentration is lower (the site is more vacant).

On the other hand, optimizing the nitrogen concentration and its profile alone as disclosed in Patent Document 2 may not necessarily have a sufficient effect when there are non-luminescent sites generated from crystals during epitaxial growth. do not have.

Japanese Unexamined Patent Publication No. 6-196756 Japanese Patent Application Publication No. 2002-329884 Patent No. 3791672

As described above, epitaxial wafers manufactured by conventional methods as shown in the prior art and light emitting diodes manufactured using the wafers have a problem in that their lifetime characteristics are not sufficient.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a compound semiconductor epitaxial wafer with good lifetime characteristics and a method for manufacturing the same.

The present invention was made to achieve the above object, and consists of a p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45 ≦x≦1.0) layer, a pn junction interface forming a light emitting part is formed, and a region including the pn junction interface is formed with a constant nitrogen concentration. hand,
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. The present invention provides a compound semiconductor epitaxial wafer in which doping is gradually decreased in the direction of the p-type GaAs _1-x P _x layer.

A light emitting device manufactured from such a compound semiconductor epitaxial wafer can have good lifetime characteristics.

Further, a p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45≦x≦1.0) layer were formed on the substrate by hydride vapor phase epitaxy. 0) A method for manufacturing a compound semiconductor epitaxial wafer in which a pn junction interface forming a light emitting part is formed by a layer,
doping nitrogen into a portion including the pn junction interface to form a region where the nitrogen concentration is constant;
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. A method for manufacturing a compound semiconductor epitaxial wafer is provided, in which doping is gradually reduced in the direction of the p-type GaAs _1-x P _x layer.

With such a method for manufacturing a compound semiconductor epitaxial wafer, it is possible to easily manufacture a compound semiconductor epitaxial wafer that provides a light emitting element with good lifetime characteristics at low cost.

As described above, a light emitting element manufactured from the compound semiconductor epitaxial wafer of the present invention can be a light emitting element with good lifetime characteristics. Further, with the method for manufacturing a compound semiconductor epitaxial wafer of the present invention, a compound semiconductor epitaxial wafer that provides a light emitting element with good lifetime characteristics can be easily manufactured at low cost.

1 shows an example of a schematic cross-sectional view of a compound semiconductor epitaxial wafer manufactured by the method for manufacturing a compound semiconductor epitaxial wafer of the present invention. 1 is a flowchart of an example of a method for manufacturing a compound semiconductor epitaxial wafer of the present invention. 1 is a cross-sectional view of an example of a manufacturing apparatus that can be used in the method for manufacturing a compound semiconductor epitaxial wafer of the present invention. 3 is a diagram showing a SIMS profile in Example 1. FIG. 3 is a diagram showing a SIMS profile in Comparative Example 2. FIG.

As mentioned above, it has been desired to develop a GaAsP light emitting device with good lifetime characteristics.

The present inventors repeatedly investigated GaAsP light emitting devices with good lifetime characteristics, and found that in a region where the nitrogen concentration is constant, Te as an n-type dopant is 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms It was found that a light-emitting element with good lifetime characteristics could be obtained by using a compound semiconductor epitaxial wafer doped with doping in the range of 0.25%/cm ³ ) while gradually decreasing from the n-type layer to the p-type layer, and the present invention was completed based on this finding. .

That is, the compound semiconductor epitaxial wafer of the present invention is
A p-n light-emitting section is formed by a p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45≦x≦1.0) layer. A compound semiconductor epitaxial wafer in which a bonding interface is formed and a region where the nitrogen concentration is constant is formed in a portion including the pn junction interface, the compound semiconductor epitaxial wafer comprising:
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. This is a compound semiconductor epitaxial wafer in which doping is gradually decreased in the direction of the p-type GaAs _1-x P _x layer.

Further, the method for manufacturing a compound semiconductor epitaxial wafer of the present invention includes:
A p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45≦x≦1.0) layer are formed on the substrate by hydride vapor phase epitaxy. A method for manufacturing a compound semiconductor epitaxial wafer in which a layer forms a pn junction interface forming a light emitting part, the method comprising:
doping nitrogen into a portion including the pn junction interface to form a region where the nitrogen concentration is constant;
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. This is a method for manufacturing a compound semiconductor epitaxial wafer in which doping is gradually reduced in the direction of the p-type GaAs _1-x P _x layer.

Hereinafter, the present invention will be explained in detail with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic cross-sectional view of an example of a compound semiconductor epitaxial wafer of the present invention. For the compound semiconductor epitaxial wafer 1, a GaP substrate or a GaAs substrate, which is an n-type single crystal substrate, can be used as a substrate, for example. In the example shown in FIG. 1, a first n-type GaP buffer layer 3 is formed on an n-type GaP substrate 2, and a second n-type GaAs _1-y P _y layer 4 (composition change layer 4) is formed on the buffer layer 3. , a third n-type GaAs _1-x P _x layer 5 (n-type constant composition layer 5) on the composition change layer 4, and a fourth p-type GaAs _1-x P _x layer 6 on the n-type constant composition layer 5. (p-type constant composition layer 6) is formed. At this time, a light emitting section is formed by the third layer n-type GaAs _1-x P _x layer 5 (n-type constant composition layer 5) and the fourth layer p-type GaAs _1-x P _x layer 6 (p-type constant composition layer 6). A pn junction interface 7 is formed. Further, a nitrogen-doped layer 8 is formed in a portion including the pn junction interface 7, having a region where the nitrogen concentration is approximately constant.

The buffer layers on the substrate are not particularly limited and may be the same or different. For example, it can have the same composition as the substrate. That is, in the case of the n-type GaP substrate 2, the buffer layer 3 can be made of n-type GaP.

The composition change layer 4 formed on the buffer layer 3 is a layer whose composition changes depending on the distance from the n-type GaP substrate 2. Specifically, the composition change layer 4 is, for example, a layer of n-type GaAs _1-y P _y (0.45≦y≦1.0), and the mixed crystal ratio y increases as the distance from the n-type GaP substrate 2 increases. It can be configured to decrease from 1. The mixed crystal ratio y is preferably varied within a range of 0.45≦y≦1.0. Since the difference in lattice constant between the substrate and the constant composition layer is large, by forming this composition change layer 4, it is possible to obtain a constant composition layer with fewer crystal defects.

On the composition change layer 4, an n-type GaAs _1-x P _x layer 5 (n-type constant composition layer 5) is formed. The n-type constant composition layer 5 is a layer whose composition (mixed crystal ratio x) is constant. When the constant composition layer 5 is made of GaAs _1-x P _x , the mixed crystal ratio x is selected to have a value corresponding to the emission wavelength of the LED.

Te is used as a dopant in this n-type GaAs _1-x P _x layer 5 (n-type constant composition layer 5).

A p-type GaAs _1-x P _x layer 6 (p-type constant composition layer 6) is formed on the n-type constant composition layer 5. For example, Zn can be used as the p-type dopant.

Then, the interface between the p-type GaAs _1-x P _x layer 6 (p-type constant composition layer 6) and the n-type GaAs _1-x P _x layer 5 (n-type constant composition layer 5), that is, the p-n layer forming the light emitting part. There is a nitrogen-doped layer 8 including the bonding interface 7 and having a region where the nitrogen concentration is substantially constant as an iso-electronic trap. By doping GaAsP, which has an indirect transition type bandgap, with nitrogen, it is possible to improve the optical output of a light emitting element.

Further, in the nitrogen-doped layer 8, Te as the n-type dopant is in the range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ), and the n-type GaAs _1-x P _x layer 5 to the p-type The doping is gradually reduced in the direction of the GaAs _1-x P _x layer 6.

In general, in GaAsP-based light emitting devices, nitrogen, which can act as a luminescent center, occupies specific sites (lattice points) in the semiconductor crystal, and there are sites that cannot contribute to luminescence (non-luminous sites). The mechanism of luminance deterioration is thought to be the movement of nitrogen between sites, and it is important to reduce the number of non-luminous sites in order to improve lifetime characteristics.

When a GaAsP epitaxial wafer is doped with N (nitrogen) at the same time as n-type dopants such as Te (tellurium) and S (sulfur), the nitrogen concentration is lower than when the n-type dopant and nitrogen are not doped at the same time. Become. That is, it is considered that the n-type dopant and nitrogen occupy the same site.

The present invention aims to reduce the movement of nitrogen between sites and improve the lifetime characteristics by occupying non-luminous sites with n-type dopants.

On the other hand, when doping is performed to occupy non-emissive sites with an n-type dopant, if the dopant (impurity) concentration is too high, the crystallinity decreases and the lifetime characteristics deteriorate.

Therefore, in the compound semiconductor epitaxial wafer of the present invention, the n-type dopant is doped in a gradient manner, that is, the n-type dopant near the p-n junction interface is kept at a low concentration, and the n-type dopant is doped in the direction from the p-type layer (junction interface) to the n-type layer. By gradually increasing the n-type dopant concentration, it is possible to simultaneously suppress the movement of nitrogen between sites near the p-n junction interface and prevent the decrease in crystallinity due to the n-type dopant (impurity) concentration, improving the lifetime characteristics. It was realized. Further, the above effect can be obtained by using Te as the n-type dopant.

Next, a method for manufacturing a compound semiconductor epitaxial wafer of the present invention will be explained with reference to FIGS. 1 to 3.

The method for manufacturing a compound semiconductor epitaxial wafer of the present invention uses a hydride vapor phase epitaxy (HVPE) method to manufacture a compound semiconductor epitaxial wafer. The following description will be made using an example in which an n-type GaP substrate is used as the single crystal substrate, but the present invention is not limited to this. FIG. 2 shows a flowchart of an example of the method for manufacturing a compound semiconductor epitaxial wafer of the present invention. Further, FIG. 3 shows a cross-sectional view of an example of a vapor phase growth apparatus that can be used in the method of manufacturing a compound semiconductor epitaxial wafer of the present invention. The vapor phase growth apparatus shown in FIG. 3 includes a quartz boat 20, an epitaxial reactor 21, a holder 22, a gas introduction pipe 23, a heater 24, and a gallium (Ga) reservoir 25.

[Preparation process]
First, a single-crystal substrate W and high-purity gallium (Ga) are placed at predetermined locations (the single-crystal substrate W is on the holder 22) in an epitaxial reactor 21 having a quartz boat 20 for storing Ga. As the single crystal substrate, in addition to an n-type GaP substrate, for example, an n-type GaAs substrate can be used.

[First layer n-type GaP buffer layer formation process]
Next, a buffer layer is formed on the n-type GaP substrate. Nitrogen (N ₂ ) gas is introduced into the reactor 21 from the gas introduction pipe 23 to sufficiently replace and remove air, then high-purity hydrogen (H ₂ ) is introduced as a carrier gas, the flow of N ₂ is stopped, and the heater 24 to begin the temperature raising process. After confirming that the temperature of the portion where the Ga-containing quartz boat 20 is installed and the portion where the single crystal substrate W is installed is kept constant at a predetermined temperature, a buffer layer having the same composition as the single crystal substrate W (Fig. Vapor phase growth of the buffer layer 3) of No. 1 is started.

A gas for doping the n-type dopant was introduced into the reactor, and high purity hydrogen chloride gas (HCl) was blown into the Ga reservoir 25 in the quartz boat in order to generate GaCl as a raw material for Group III elements of the periodic table. , the gas is blown out from the upper surface of the Ga reservoir. On the other hand, a buffer layer is formed on the single crystal substrate while introducing diethyl tellurium (DETe) as an n-type dopant doping gas and high purity hydrogen phosphate gas (PH ₃ ) as a Group V element component of the periodic table. .

[Second n-type GaAs _1-y P _y layer (composition change layer) formation process]
After forming the buffer layer, a second n-type GaAs _1-y P _y layer (composition change layer) is formed on the buffer layer. By gradually increasing the amount of high-purity hydrogen arsenide gas (AsH ₃ ) introduced without changing the amount of HCl and DETe introduced, and at the same time decreasing the amount of PH ₃ introduced, the second layer n-type GaAs _{1-y was formed.} A P _y layer (composition change layer) is formed on the buffer layer.

[Third layer n-type GaAs _1-x P _x layer (n-type constant composition layer) formation process]
After forming the compositionally variable layer, a third n-type GaAs _1-x P _x layer (n-type constant composition layer) is formed on the compositionally variable layer. Introducing a gas containing N (nitrogen) for isoelectronic trap addition while gradually decreasing the amount of DETe, which is an n-type dopant gas, without changing the amounts of HCl, PH ₃ , and AsH ₃ introduced. do. As the gas, for example, high purity ammonia gas (NH ₃ ) can be used, but it is not limited thereto.

Next, without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , and NH ₃ , the introduced amount of DETe, which is an n-type dopant gas, was further gradually decreased to form the third n-type GaAs _1-x P _x layer. (n-type constant composition layer) is formed on the second layer n-type GaAs _1-y P _y layer (composition variable layer).

[Fourth p-type GaAs _1-x P _x layer (p-type constant composition layer) formation process]
After forming the n-type constant composition layer, a fourth p-type GaAs _1-x P _x layer (p-type constant composition layer) is formed on the n-type constant composition layer. While gradually increasing dimethyl zinc (DMZn), a p-type dopant gas, to a predetermined flow rate by ramping, without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , and NH ₃ and gradually decreasing the introduced amount of DETe. , a p-type GaAs _1-x P _x layer is formed.

Next, the introduction amount of NH 3 is gradually decreased and the introduction of NH ₃ is stopped without changing the introduction amounts of HCl, PH ₃ , AsH _{3 ,} DETe, and DMZn. Next, without changing the amounts of HCl, PH ₃ , AsH ₃ , and DETe introduced, the flow rate of DMZn was further gradually increased by ramping to fix the flow rate of DMZn, and the fourth p-type GaAs _1-x P _x layer ( A p-type constant composition layer) is formed on the third n-type GaAs _1-x P _x layer (n-type constant composition layer), and the vapor phase growth is completed.

In the method for manufacturing a compound semiconductor epitaxial wafer of the present invention, growth can be performed by gradually reducing the amount of DETe introduced from 8 sccm to 1 sccm by ramping while controlling the flow rate with a mass flow controller (MFC). It is also possible, for example, to gradually reduce the n-type dopant (Te) concentration using residual gas in the reactor and piping. That is, the supply of DETe is stopped by closing the supply valve, but due to continuous growth, the residual gas in the introduction pipe (the pipe between the DETe outlet and the reactor inlet) is gradually exhausted through the reactor, and as a result, Doping can be performed in the same manner as when flow rate control is performed using MFC.

As described above, the method for manufacturing a compound semiconductor epitaxial wafer of the present invention can manufacture a compound semiconductor epitaxial wafer as shown in the cross-sectional view in FIG.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited thereto.

(Example 1)
An epitaxial wafer was produced by the HVPE method as follows.

[Preparation process]
An n-type GaP single crystal substrate and high-purity gallium (Ga) were placed at predetermined locations in an epitaxial reactor equipped with a quartz boat for storing Ga. The GaP substrate is doped with tellurium (Te) at a concentration of 3 to 10×10 ¹⁷ (atoms/cm ³ ), is circular with a diameter of 50 mm, and has a plane that is deviated from the (100) plane by 10 (°) in the [011] direction. be. These were placed on a holder at the same time, and the holder was rotated 8 times per minute.

Next, nitrogen (N ₂ ) gas was introduced into the reactor for 20 minutes to sufficiently replace and remove air, and then high-purity hydrogen (H ₂ ) was introduced as a carrier gas at 6500 sccm per minute to stop the flow of nitrogen gas and raise the temperature. The process has started. After confirming that the temperatures of the Ga-containing quartz boat installation area and the GaP single crystal substrate installation area were maintained at constant temperatures, vapor phase growth of the GaAs _1-x P _x epitaxial film was started.

[First layer n-type GaP buffer layer formation process]
DETe (diethyl tellurium) is introduced as an n-type dopant gas diluted with hydrogen gas, and high purity hydrogen chloride gas (HCl) is added to the Ga in the quartz boat in order to generate GaCl as a raw material for Group III elements of the periodic table. The gas was blown into the reservoir and blown out from the upper surface of the Ga reservoir. On the other hand, an n-type GaP buffer layer as a first layer was grown on an n-type GaP substrate while introducing high-purity hydrogen phosphide gas (PH ₃ ) as a Group V element component of the periodic table.

[Second n-type GaAs _1-y P _y layer (composition change layer) formation process]
After the buffer layer was formed, introduction of high purity hydrogen arsenide gas (AsH ₃ ) was started without changing the amount of HCl introduced, and the amount introduced was gradually increased. At the same time, the amount of PH ₃ introduced was reduced, and a second n-type GaAs _1-y P _y layer (composition-change layer) was formed on the first n-type GaP buffer layer.

[Third layer n-type GaAs _1-x P _x layer (n-type constant composition layer) formation process]
After forming the composition-change layer, high-purity ammonia gas was added for isoelectronic trap addition while gradually decreasing the amount of DETe, which is an n-type dopant gas, without changing the amounts of HCl, PH ₃ , and AsH ₃ introduced. (NH ₃ ) was introduced. Without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , and NH ₃ , the introduced amount of DETe, which is an n-type dopant gas, was further gradually reduced to form the third n-type GaAs _1-x P _x layer (n-type A constant composition layer) was formed on the composition change layer.

[Fourth p-type GaAs _1-x P _x layer (p-type constant composition layer) formation process]
After forming a layer with a constant n-type composition, DMZn, which is a p-type dopant gas, is gradually ramped to a predetermined flow rate without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , and NH ₃ and while gradually decreasing the introduced amount of DETe. A p-type GaAs _1-x P _x layer was formed while increasing the temperature. Next, without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , DETe, and DMZn, the introduced amount of NH ₃ was gradually decreased and the introduction of NH ₃ was stopped. Next, the DMZn flow rate was further gradually increased by ramping without changing the introduced amounts of HCl, PH ₃ , AsH ₃ , and DETe to fix the DMZn flow rate, and the fourth p-type GaAs _1-x P _x layer ( After forming a p-type (constant composition layer) on the n-type constant composition layer, vapor phase growth was completed, and a compound semiconductor epitaxial wafer was manufactured.

In addition, when manufacturing a compound semiconductor epitaxial wafer, the third layer n-type GaAs _1-x P _x layer (n-type constant composition layer) ~ Fourth layer p-type GaAs _{1-x P} An n-type dopant (Te) is added to the region where the nitrogen concentration is constant (nitrogen concentration region) in the x layer (p-type constant composition layer), and third layer n-type GaAs ₁ A layer (gradient doping) in which doping was gradually decreased in the direction from the _-x P _x layer (n-type constant composition layer) to the fourth p-type GaAs _1-x P _x layer (p-type constant composition layer) was fabricated. Further, the n-type dopant (Te) concentration at this time was controlled to be from 1.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ).

The manufactured compound semiconductor epitaxial wafer had a first n-type GaP buffer layer thickness of approximately 5 μm, a second layer n-type GaAs _1-y P _y layer (composition change layer) thickness of approximately 20 μm, and a third layer n-type GaAs ₁ layer. The thickness of the _-x P _x layer (n-type constant composition layer) was about 15 μm, and the thickness of the fourth p-type GaAs _1-x P _x layer (p-type constant composition layer) was about 15 μm. Further, the constant nitrogen concentration region including the pn junction interface was approximately 15 μm.

[evaluation]
In order to evaluate the lifetime characteristics (residual rate of initial brightness and brightness after energization, i.e. survival rate = (luminance after energization/initial brightness) x 100) of the epitaxial wafer produced in this way, the following procedure was performed. We evaluated the procedures.

The produced compound semiconductor epitaxial wafer was taken out and the back surface was lapped. Thereafter, an n-type electrode was formed on the back surface of the wafer, and a p-type electrode was formed on the epitaxial layer on the front surface. After cutting to a size of 280 μm□, a total of 6 chips were cut, 2 each from the orientation flat part (OF part) around 5 mm from the outer circumference of the wafer, the part on the opposite side of the OF part (anti-OF part), and 3 places at the center of the wafer. I took it out. An LED lamp was made from the chip taken out, and its brightness was measured when a direct current of 20 mA was applied. Thereafter, electricity was applied at 50 mA at 25° C. for 168 hours, and the brightness was measured again. The survival rate was calculated from the brightness immediately after fabrication (initial stage) and the brightness after energization. The results are shown in Table 1.

(Example 2)
The same as Example 1 except that the n-type dopant (Te) concentration in the constant nitrogen concentration region was doped at a gradient from 0.9×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ). The results are also shown in Table 1.

(Example 3)
This is the same as Example 1 except that the n-type dopant (Te) concentration in the constant nitrogen concentration region was doped at a gradient from 0.8×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ). The results are also shown in Table 1.

(Example 4)
This is the same as Example 1 except that the n-type dopant (Te) concentration in the constant nitrogen concentration region was doped at a gradient from 2.0×10 ¹⁶ to 0.4×10 ¹⁶ (atoms/cm ³ ). The results are also shown in Table 1.

(Comparative example 1)
This is the same as Example 1 except that the n-type dopant (Te) concentration in the constant nitrogen concentration region was doped at a gradient from 9.0×10 ¹⁶ to 1.8×10 ¹⁶ (atoms/cm ³ ). The results are also shown in Table 1.

(Comparative example 2)
It is the same as Example 1 except that the n-type dopant (Te) concentration in the constant nitrogen concentration region was flatly doped at 0.4×10 ¹⁶ (atoms/cm ³ ). The results are also shown in Table 1.

(Comparative example 3)
Hydrogen sulfide gas (H ₂ S) is used as the n-type dopant gas, and the n-type dopant (S) concentration in the constant nitrogen concentration region is varied from 2.0×10 ¹⁶ to 0.4×10 ¹⁶ (atoms/cm ³ ). It is the same as Example 1 except that it is doped. The results are also shown in Table 1.

(Comparative example 4)
Example except that hydrogen sulfide gas (H ₂ S) was used as the n-type dopant gas, and the n-type dopant (S) concentration in the constant nitrogen concentration region was doped to a flat value of 0.2×10 ¹⁶ (atoms/cm ³ ). Same as 1. The results are also shown in Table 1.

Further, SIMS profiles of Example 1 (gradient doping example) and Comparative Example 2 (flat doping example) are shown in FIGS. 4 and 5.

In Comparative Example 1, the n-type dopant was Te, and the Te concentration was set at a high concentration of 9.0×10 ¹⁶ to 1.8×10 ¹⁶ (atoms/cm ³ ) in a constant nitrogen concentration region including the p-n junction interface. Although gradient doping was performed, the residual brightness did not improve. Further, in Comparative Example 2, although the Te concentration was flatly doped at 0.4×10 ¹⁶ (atoms/cm ³ ), the residual rate of brightness did not improve. In Comparative Example 3, the n-type dopant was S, and the S concentration was gradient-doped from 2.0×10 ¹⁶ to 0.4×10 ¹⁶ (atoms/cm ³ ) in a constant nitrogen concentration region including the p-n junction interface. However, the residual brightness rate did not improve. Further, in Comparative Example 4, the S concentration was flatly doped at 0.2×10 ¹⁶ (atoms/cm ³ ), but the residual brightness did not improve.

On the other hand, in the compound semiconductor epitaxial wafer of the present invention, the n-type dopant is Te, and the Te concentration is set at 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/ By performing gradient doping in the range of 3 cm ³ ), the residual brightness rate was improved.

As described above, the compound semiconductor epitaxial wafer according to the present invention can be a compound semiconductor epitaxial wafer with good life characteristics. In addition, with the method for manufacturing a compound semiconductor epitaxial wafer according to the present invention, a compound semiconductor epitaxial wafer from which a light emitting element with good lifetime characteristics can be obtained can be easily manufactured at low cost.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of.

1... Compound semiconductor epitaxial wafer (present invention),
2...n-type GaP substrate,
3...first layer n-type GaP buffer layer,
4...Second n-type GaAs _1-y P _y layer (composition change layer),
5... Third layer n-type GaAs _1-x P _x layer (n-type constant composition layer),
6... Fourth layer p-type GaAs _1-x P _x layer (p-type constant composition layer),
7... pn junction interface, 8... nitrogen doped layer,
20...Quartz boat, 21...Epitaxial reactor,
22...Holder, 23...Gas introduction pipe, 24...Heater,
25...Ga reservoir, W...single crystal substrate.

Claims (2)

A p-n light-emitting section is formed by a p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45≦x≦1.0) layer. A compound semiconductor epitaxial wafer in which a bonding interface is formed and a region where the nitrogen concentration is constant is formed in a portion including the pn junction interface, the compound semiconductor epitaxial wafer comprising:
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. A compound semiconductor epitaxial wafer characterized in that the p-type GaAs _1-x P _x layer is doped while gradually decreasing in the direction thereof. A p-type GaAs _1-x P _x (0.45≦x≦1.0) layer and an n-type GaAs _1-x P _x (0.45≦x≦1.0) layer are formed on the substrate by hydride vapor phase epitaxy. A method for manufacturing a compound semiconductor epitaxial wafer in which a layer forms a pn junction interface forming a light emitting part, the method comprising:
doping nitrogen into a portion including the pn junction interface to form a region where the nitrogen concentration is constant;
In the region where the nitrogen concentration is constant, Te is added as an n-type dopant in a range of 2.0×10 ¹⁶ to 0.2×10 ¹⁶ (atoms/cm ³ ) from the n-type GaAs _1-x P _x layer. A method for manufacturing a compound semiconductor epitaxial wafer, characterized in that doping is performed while gradually decreasing in the direction of the p-type GaAs _1-x P _x layer.

Images