JP2000183396A - Epitaxial wafer and led manufactured using the wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the light output of a LED by allowing the carrier density of a graded composition layer in an epitaxial layer to have such a carrier density profile that may have the maximum value at a place within the graded composition layer a specified distance away from the termination point within the graded composition layer. SOLUTION: This epitaxial wafer has an n-type GaAsP epitaxial layer 16 on an n-type single crystalline substrate 20. The epitaxial layer 16 at least comprises a graded composition layer 21 and fixed composition layers 22 and 23. The carrier density of the graded composition layer 21 has such a carrier density profile that may have the maximum value at a place within the graded composition layer (including the termination point) 2 μm or more away from the termination point within the graded composition layer. The start point and the termination point of an epitaxial layer such as the graded composition layer mean a start point and a finish point of growth of the layer respectively. For example, the maximum value of the n-type carrier density is 2-30×1017 cm-3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an epitaxial wafer made of gallium arsenide phosphide or the like, and a light emitting diode (LED) manufactured using the same.

[0002]

2. Description of the Related Art Light emitting diodes using a semiconductor crystal as a constituent material are currently widely used as display elements.
In particular, III-V compound semiconductors are used as materials for most light emitting diodes.

That is, since III-V compound semiconductors have a band gap corresponding to the wavelength of visible light and infrared light, they have been applied to light emitting devices. Among them, gallium arsenide arsenide (GaAsP) is in great demand as a material for light emitting diodes.

The most important characteristic of a light emitting diode is a light emitting output. Therefore, gallium arsenide phosphide (GaAs)
There has been a demand for an improvement in the light emission characteristics with respect to P). A light-emitting diode having gallium arsenide arsenide (GaAs _1-x P _x ) having a light-emitting layer of 0.45 <x <1 has a light output by doping nitrogen (N) as an isoelectronic trap to increase luminous efficiency. It is improved about 10 times.

In general, an n-type epitaxial layer is grown on a single crystal substrate by a vapor phase growth method using a quartz reactor, and then zinc (Zn) is diffused on the surface of the light emitting layer to form a p-type layer. Then, a stable light emitting diode is obtained by using an epitaxial wafer on which a pn junction is formed.

FIG. 4 shows a general layer structure of a gallium arsenide arsenide (GaAsP) epitaxial wafer used for manufacturing a light emitting diode. Such a layer structure is the same as that described in, for example, JP-A-9-186361.

The technique described in Japanese Patent Application Laid-Open No. 9-186361 is one proposal of a combination of an n-type carrier concentration profile in the thickness direction and an n-type carrier concentration and a nitrogen concentration.

In FIG. 4, as an example, a single crystal substrate 20
Is gallium phosphide (GaP). On a single crystal substrate 20 of n-type gallium phosphide (GaP), a homo layer 24 having the same composition as the substrate 20 is epitaxially grown.

Further, on the homo layer 24, a single crystal substrate 20
Gallium arsenide phosphide (GaAs _1-x P _x) grade composition layer 21 in which the mixed crystal ratio x for reducing the difference between the lattice constants of the upper layer and the uppermost layer is continuously changed in the layer thickness direction from 1.0 to x0. Gallium arsenide phosphide (GaAs _1-x0 P _x0 ) with constant mixed crystal ratio
The constant composition layer 22 and the gallium arsenide phosphide (GaAs)
_A gallium arsenide phosphide (GaAs _1-x0 P _x0 ) low carrier concentration constant composition layer 23 doped with nitrogen (N) is sequentially formed on the ( _1-x0 P _x0 ) constant composition layer 22 by epitaxial growth.

The low carrier concentration constant composition layer 23, which is the uppermost layer of the epitaxial wafer, becomes a light emitting layer, has a constant composition x0 for obtaining an emission wavelength of a light emitting diode, and contains nitrogen N and n-type dopant tellurium (Te). ) Or sulfur (S) is doped to a predetermined carrier concentration.

Normally, x0 = 0.60 for red emission (wavelength 640 nm). When nitrogen (N) is doped into gallium arsenide arsenide (GaAsP), it becomes an isoelectronic trap serving as a light emission center.

The isoelectronic trap is electrically inactive and does not contribute to the carrier concentration. Light emitting layer 2
By doping 3 with nitrogen (N), the luminous efficiency is increased about 10 times.

As described above, in order to form a gallium arsenide phosphide (GaAsP) epitaxial wafer having the n-type epitaxial layer 16 formed on the n-type single crystal substrate 20 as a light emitting diode, a pn junction is formed. It is necessary.

Normally, zinc Zn is thermally diffused on the surface of an n-type epitaxial layer to form a pn junction. While introducing a p-type dopant, a p-type gallium arsenide phosphide (GaAs) is formed.
sP) It is also possible to newly form an epitaxial layer on the surface.

Here, in order to minimize the destruction of the crystal integrity of the light emitting layer, prolong the life of the injected carriers, and obtain a light emitting diode with a high light output, the carrier concentration is set to 3. It is disclosed that it is better to be within the range of 5 to 8.8 × 10 ¹⁵ cm ^-3 (Japanese Patent Publication No. 58-1539).
No.).

Further, when the carrier concentration is set to 3 × 10 ¹⁵ cm ⁻³ or less, it is possible to simultaneously improve the light output and extend the life (Japanese Patent Laid-Open No. 6-196756). However, as a result of subsequent studies, it has been found that when the density is 0.5 × 10 ¹⁵ cm ⁻³ or less, the forward voltage of the light emitting diode increases, which may cause a defect. Preferably, there is.

The epitaxial layers other than the light emitting layer 23 have a thickness of 0.5 to reduce the resistance when the light emitting diode is used.
Generally, the carrier concentration is about 5 × 10 ¹⁷ cm ⁻³ . Below this, the forward voltage of the light emitting diode increases, and above this, the crystal defects increase as the carrier concentration increases, and the emitted light is absorbed, leading to a decrease in the light output of the light emitting diode.

[0018]

Hitherto, high light output has been realized by optimizing the carrier concentration of the light emitting layer 23 in the layer structure of FIG. However, with the diversification of demand, further higher light output is required. That is, a high light output has been obtained by the progress of the technology so far, but a further improvement in the light output of the light emitting diode is required.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a light emitting diode capable of realizing a higher light output, a gallium arsenide phosphide epitaxial wafer as a material thereof, and a light emitting diode manufactured using the same.

[0020]

Means for Solving the Problems The present inventor has made intensive studies to solve the above problems, and as a result, in order to improve the light output of the light emitting diode, the energizing current is efficiently spread to the pn junction portion. We thought that it would be sufficient to efficiently emit light over the entire pn junction and suppress light absorption by the epitaxial layer while effectively suppressing heat generation. Then, it was conceived to obtain a more ideal carrier concentration profile for that purpose.

That is, considering the example of FIG. 4, in order to improve the current spread in the pn junction 17 and suppress heat generation, it is necessary to suppress heat generation due to the series resistance of the light emitting diode.

When Zn, which is a p-type dopant, is diffused into the low carrier concentration constant composition layer 23, which is a light emitting layer, to form a light emitting diode, the carrier concentration becomes 1 × 10 ¹⁹ cm.
Since the impurity is doped so as to be ⁻³ or more, the resistivity of the p-type layer does not matter.

As described above, it is difficult to dope the light emitting layer to a concentration outside the range of 9 × 10 ¹⁵ cm ^-3 or less in order to obtain a high light output. As a result of the study by the present inventors, gallium arsenide arsenide (GaAsP) crystal is a mixed crystal, so that the same carrier concentration is several times larger than that of a single crystal substrate of gallium phosphide (GaP) or gallium arsenide (GaAs). It became clear that the specific resistance was high. In particular, since the crystal defect density of the grade composition layer 21 increases, the specific resistance further increases.

In order to efficiently suppress the temperature rise due to the heat generated by the pn junction 17 and reduce the series resistance, it is sufficient to increase the carrier concentration of the layers other than the light emitting layer, but if the carrier concentration is high, the emitted light is absorbed. There was a problem that it became easy to do.

Therefore, it is considered that the carrier concentration should be effectively increased in the grade composition layer 21 in which the specific resistance becomes higher at the same carrier concentration, and the region having a higher carrier concentration should be separated from the pn junction as much as possible. Reached.

That is, the gist of the epitaxial wafer according to the present invention is that an n-type single crystal substrate 20 is provided with an n-type gallium arsenide phosphide (GaAs _1-x P _x ) epitaxial layer. In the epitaxial wafer, the epitaxial layer 16 includes at least a grade composition layer 21 and constant composition layers 22 and 23.

The carrier concentration 20 of the grade composition layer 21
Is characterized by having a carrier concentration profile having a maximum value in a grade composition layer (including a start point) distant from the end point in the grade composition layer by 2 μm or more. In the specification of the present application, the start point and the end point of an epitaxial layer such as a grade composition layer mean a growth start point and a growth end point of the layer, respectively.

In one embodiment, the n-type carrier concentration is
Is 2 to 30 × 10¹⁷cm ^-3And said
In the constant composition layer, the carrier concentration is at least 9 × 10
¹⁵cm^-3Features the following low carrier concentration region
And As still another embodiment, the material having
The low carrier concentration region has a thickness of 2 μm or more.
And

Further, as a preferred embodiment, the position where the n-type carrier concentration has the maximum value is at least 5 μm away from the low carrier concentration region. In a preferred embodiment, the grade composition layer has a thickness of 5 to 120 μm, and the low carrier concentration region has a thickness of 2 to 60 μm.

The low carrier concentration region is made of GaAs.
It is preferable that the material is composed of _1-x P _x (0.45 <x <1) and is characterized by being doped with at least nitrogen.

Preferably, the epitaxial layer is made of GaAs _1-x P _x (0 <x <1).

In one embodiment, the single crystal substrate is Ga
It is made of an As substrate or a GaP substrate.

Further, as a light emitting diode material, a p-type compound semiconductor epitaxial layer is further formed on the n-type compound semiconductor epitaxial layer to have a pn junction.

Preferably, the p-type compound semiconductor epitaxial layer is formed by diffusing Zn into the n-type compound semiconductor epitaxial layer.

Further, the light emitting diode according to the present invention comprises:
An epitaxial wafer having the characteristics described above, wherein the epitaxial wafer is cut from an epitaxial wafer having electrodes formed on the back surface of the single crystal substrate and the surface of the p-type compound semiconductor epitaxial layer, and is formed.

Further features of the present invention will become apparent from the following description of embodiments of the present invention.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an epitaxial wafer according to the present invention and a light emitting diode using the same will be described.

FIG. 1 is an explanatory sectional view of the layer structure of a gallium arsenide phosphide epitaxial wafer of the epitaxial wafer of the present invention. In FIG. 1, as a single crystal substrate 10,
Either gallium phosphide GaP or gallium arsenide GaAs is selected.

However, the low carrier concentration region 1 serving as the light emitting layer
3 is gallium arsenide phosphide _{(GaAs 1- x P x) 0.45} <x
In the case of <1, the single crystal substrate 10 is made of phosphide (GaP).
Is preferable for obtaining a high light output as a light-emitting diode, because the light-emitting diode is transparent to the emission color of the light-emitting diode.

On the single crystal substrate 10, an epitaxial layer is grown. The epitaxial layer is selected from compound semiconductors containing gallium (Ga), arsenic (As), and phosphorus (P) as constituent elements. Gallium arsenide arsenide (GaAs _1-x P _x ) 0 <x <1 is most common for light emitting diode applications.

The epitaxial layer comprises at least a grade composition layer 11 and a constant composition layer 12. In the present invention, the grade composition layer 11 is formed on the substrate 10 or the homo layer 14 formed by epitaxial growth having the same composition as the substrate 10, and the substrate 10 or the homo layer 14 immediately below the same.
From the above composition to the composition at the starting point of the constant composition layer 12.

The grade composition layer 11 suppresses misfit dislocations generated in the constant composition layer due to a difference in lattice constant between the substrate 10 and the constant composition layer 12 to obtain a good quality constant composition layer with few crystal defects. Things.

On the other hand, the constant composition layer 12 is a layer having a constant composition, and the composition is preferably as constant as possible.

Gallium arsenide phosphide (Ga) of constant composition layer 12
Regarding As _1−x P _x ), even if the change is continuous or on a step, the change is ± 0.05 with respect to the average of the constant composition layer 12.
It is preferable that the change is within the range, since crystal defects such as misfit dislocations can be suppressed. If the change is within ± 0.02, a light emitting diode with a high light output can be obtained stably, which is more preferable.

On the other hand, gallium arsenide arsenide (GaAs)
_1-x P _x ) 0 <x <1 When the epitaxial layer is viewed not from the carrier concentration but from the viewpoint of the composition, it has a grade composition layer 11 and a constant composition layer 12 in FIG.

Homolayer 1 of the same crystal as single crystal substrate 10
4 is possible even if it is not particularly formed. However, in order to suppress the occurrence of misfit dislocation, the homo layer
A thickness of 100 μm, preferably 0.5 to 15 μm is preferable because high brightness can be stably obtained. The carrier concentration of the homo layer 14 is preferably substantially the same as or higher than the carrier concentration at the growth start point of the grade composition layer 11, and the range is 2 to 50 × 10 ¹⁷ cm ⁻³ .

The layer thickness of the grade composition layer 11 is preferably 5 to 120 μm, but is more preferably 10 to 70 μm in order to stably obtain a high output. As described above, the carrier concentration of the grade composition layer 11 is 2 μm from the end point.
It becomes maximum at any position in the grade composition layer separated as described above, and then decreases toward the end point of the grade composition layer 11.

As a feature of the present invention, the carrier concentration of the grade composition layer 11 becomes maximum at any position in the grade composition layer, and then decreases toward the end point of the grade composition layer. The point at which the carrier concentration becomes maximum is preferably a point within 80% in the thickness direction from the starting point of the grade composition layer, and more preferably a point within 60% in order to obtain a high light output. The position showing the maximum carrier concentration is not necessarily required to be constant, but is 1 to 10 μm in thickness.
A maximum carrier concentration of about m may be maintained.
The carrier concentration at an arbitrary position in the adjacent constant composition layer 12 has a carrier concentration profile lower than the maximum value of the carrier concentration in the grade composition layer.

The carrier concentration at an arbitrary position in the adjacent constant composition layer 12 has a carrier concentration profile lower than the maximum value of the carrier concentration in the grade composition layer.

The carrier concentration of the grade composition layer 11 is about 0.5 × 10 ¹⁷ cm ^-3 or more, preferably 1 × 1 ¹⁷ cm ^-3.
0 ¹⁷ cm ^-3 or more, and the maximum value is 2 to 30 × 10 ¹⁷ cm
It is preferably ^-3 . And the grade composition layer 11
Is most preferably about the center of the grade composition layer from the starting point of the grade composition layer 11.

In order to make the forward voltage low and uniform when the light emitting diode is formed, the above grade composition layer 11 is used.
It is more preferable that the maximum value of the carrier concentration is 5 to 20 × 10 ¹⁷ cm ⁻³ . However, when the maximum value of the carrier concentration is 30 × 10 ¹⁷ cm ⁻³ or more, problems such as deterioration of crystallinity and generation of crystal defects on the surface of the epitaxial layer and reduction in light output of the light emitting diode occur. Is not preferred.

The distance from the pn junction may be at least 5 μm from the position where the carrier concentration is maximum, but is preferably at least 12 μm because the light output can be increased.

Further, in FIG. 1, when it is considered that an epitaxial layer is formed from the high carrier concentration region 15 and the low carrier concentration region 13, the constant composition layer 12 between the low carrier concentration region 13 and the grade composition layer 11 is formed. Is preferably lower than the maximum value of the grade composition layer 11, preferably substantially equal to or lower than the carrier concentration at the end point of the grade composition layer 11, and is preferably equal to or higher than the low carrier concentration region 13.

In order to reduce the influence of crystal defects such as misfit dislocations generated in the grade composition layer 11, the boundary between the high carrier concentration region 15 and the low carrier concentration region 13 is fixed as shown in FIG. 12, especially 2 to 40 μm on the surface side of the high carrier concentration region 15.
Preferably, m is a constant composition.

Here, the carrier concentration at an arbitrary position is
It is preferable that the carrier concentration is at least lower than the maximum value of the carrier concentration in the grade composition layer 11. Otherwise, a region having a large light absorption is provided near the low carrier concentration region 13 where the pn junction is formed, and the light output is likely to decrease.

The low carrier concentration region 13 preferably has an average carrier concentration of 9 × 10 ¹⁵ cm ⁻³ or less,
If it is less than 0 ¹⁵ cm ^-3 , it may be difficult to control the carrier concentration or the specific resistance may be increased to cause an increase in the forward voltage of the light emitting diode. Therefore, a preferable average carrier concentration is 0.5 to 9 × 10 ¹⁵ cm ⁻³ .

The layer thickness is 2 μm or more. However,
This layer thickness is the minimum necessary thickness when a p-type epitaxial layer is further grown thereon or formed, or when such a p-type layer is already formed, and is the diffusion of the p-type dopant. When the pn junction is formed in the low carrier concentration region 13 by the following method, the diffusion depth is usually 4 to 15 μm.
Therefore, the layer thickness of the low carrier concentration region 13 needs to be 5 μm or more, preferably 8 to 60 μm.

If it exceeds 60 μm, high carrier concentration region 1
It is not preferable because it is too far from 5. That is, the pn junction is preferably formed so as to leave the low carrier concentration region 13 of about 2 to 45 μm.

The composition of the constant composition layer 12 having the low carrier fertility region 13 is gallium arsenide phosphide (GaAs _1-x P _x )
In the case of 0.45 <x <1, it has an indirect transition type band structure.
As described in US Pat. No. 6,361, it is common to dope nitrogen at least in a constant composition layer having a low carrier concentration.

The constant composition layer in the low carrier concentration region 13 is epitaxially grown adjacent to the surface of the epitaxial layer, and then a p-type dopant, usually Zn, is added from the surface to the constant composition layer in the low carrier concentration region 13. To form a pn junction.

The gallium arsenide phosphide (GaAsP) epitaxial wafer is usually manufactured by a vapor phase growth method. As described above, the constant composition layer 13 having a low carrier concentration is grown, and the growth is performed during the growth. An pn junction may be formed by introducing an organometallic gas as a p-type doping gas, for example, Zn into diethyl zinc ((C ₂ H ₅ ) ₂ Zn).

The specific resistance of the epitaxial layer is not limited to the case where the grade composition layer 11 has not only a continuous composition change but also a plurality of stepwise composition changes.
The effect is the same because it is mainly determined by the carrier concentration.

The method for measuring the carrier concentration profile in the epitaxial layer can be measured by a CV method after the epitaxial layer is polished obliquely and a Schottky barrier diode is formed on the surface thereof.

A semiconductor profile plotter PN430 manufactured by Nippon Bio-Rad Laboratories, Inc.
As in the case of 0, the measurement can be similarly performed by a method of directly measuring the epitaxial layer while etching it with an electrolytic solution.

As the manufacturing method, the hydride method is most effective in terms of mass productivity and practical application. The effect is the same in the chloride method and the metal organic chemical vapor deposition (MOCVD).

[0066]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. (Example 1 and Comparative Examples 1 and 2) To explain Example 1 of the present invention, first, a gallium phosphide (GaP) substrate and a high-purity gallium (Ga) were prepared by epitaxial growth with a quartz boat for a Ga reservoir. Each was installed at a predetermined location in the reactor.

As a gallium phosphide (GaP) substrate, sulfur (S) is added in an amount of 2 to 10 × 10 ¹⁷ atoms / cm ³ , is a circle having a diameter of about 50 mm, and is 10 ° from the (100) plane in the [001] direction. One having a deviated surface was used.

These were placed on a holder that rotates simultaneously. Next, nitrogen (N ₂ ) gas is introduced into the reactor for 15 minutes.
After the air was sufficiently displaced and removed, 9600 cc of high-purity hydrogen (H ₂ ) was introduced as a carrier gas per minute, the flow of nitrogen (N ₂ ) was stopped, and the temperature was raised.

After confirming that the temperatures of the gallium (Ga) -containing quartz boat installation portion and the gallium phosphide (GaP) single crystal substrate installation portion were kept constant at 800 ° C. and 850 ° C., respectively. , Peak emission wavelength 588 ±
3nm started the vapor phase growth of GaAs _{1- x} P _x epitaxial film of (yellow).

First, diethyl tellurium ((C ₂ H ₅ ) ₂ Te) which is an n-type impurity diluted to 100 ppm with hydrogen gas
At a rate of 30 cc / min, and high-purity hydrogen chloride gas (HCl) is blown into the Ga reservoir in the quartz boat to generate 369 cc / min of gallium chloride (GaCl) as a Group III element of the periodic table. From the Ga reservoir top surface.

On the other hand, H ₂ as a group V element in the periodic table
Hydrogen phosphide (PH ₃ ) diluted to a concentration of 10% with
While introducing 20 cc, a GaP epitaxial layer as the first layer (homolayer 14 in FIG. 1) was grown on a GaP single crystal substrate for 20 minutes.

Next, HCl, without changing the introduction amount of the gas of PH _3, for 90 minutes, a concentration of 10% with H2
Of hydrogen arsenide (AsH ₃ ) diluted to 0 cc / min
To 110 cc per minute, and at the same time (C
The second GaAs corresponding to the grade layer 11 of FIG. 1 is gradually increased to 75 cc in the first 20 minutes of ₂ H ₅ ) ₂ Te, and then gradually reduced to 30 cc per 30 minutes.
The _1-x P _x epitaxial layer grown on the first GaP epitaxial layer.

For the next 20 minutes, (C ₂ H ₅ ) ₂ Te, HC
1, the third GaAs corresponding to the constant composition layer 12 of FIG. 1 while maintaining the introduced amount of PH ₃ and AsH ₃ without changing.
_{A 0.4} P _0.6 epitaxial layer was grown on the second GaAs _1-x P _x epitaxial layer.

In the final 50 minutes, (C ₂ H ₅ ) ₂ Te was introduced at a rate of 0.5 cc / min to thereby form the fourth layer (G in FIG. 1).
HCl, PH is adjusted so that the carrier concentration of the low-doped layer which is the aAs _1-x 0P _x0 N-doped constant composition layer 13) is obtained.
_{3. While} introducing AsH ₃ without changing the introduction amount, a high-purity ammonia gas (N) conventionally used for adding a nitrogen isoelectronic trap is added thereto.
H ₃ ) was introduced by introducing 420 cc per minute. As a result, the fourth GaAs _1-x P _x epitaxial layer becomes the third GaAs _1-x P _x epitaxial layer.
Was grown on the GaAs _1-x P _x epitaxial layer.

The thicknesses of the first, second, third, and fourth epitaxial layers of the epitaxial film were approximately 5 μm, 28 μm, 7 μm, and 20 μm, respectively.

The carrier concentration of the fourth epitaxial layer was measured by a CV method after forming a Schottky barrier diode on the surface of the epitaxial wafer before diffusion, and the carrier concentration was 3 × 10 ¹⁵ cm ⁻³ . .

The carrier concentration of the highly doped first, second and third epitaxial layers is determined by removing the epitaxial layer obliquely at an angle of about 1 ° by lapping and etching to form a Schottky barrier diode on the surface. It was prepared and measured by the CV method.

FIG. 2 shows carrier concentration profiles of the present invention and a comparative example described later. The horizontal axis shows the distance from the boundary between the substrate and the epitaxial layer, and the vertical axis shows the carrier concentration. In FIG. 2, Δ indicates Example 1, □ indicates Comparative Example 1, and Δ indicates Comparative Example 2.

When the above Example 1 was measured, as shown in FIG. 2, the carrier concentration of the second and third layers was 6 μm from the first layer, and the carrier concentration of the maximum value was 4 μm in the second layer. It became × 10 ¹⁷ cm ⁻³ , gradually decreased, and was almost constant at 1.5 × 10 ¹⁷ cm ⁻³ in the third layer.

The grown epitaxial wafer was vacuum-sealed in a quartz ampoule without coating anything with ZnAs ₂ as a diffusion source, and Zn as a p-type impurity was diffused from the surface to a depth of 4 μm at a temperature of 760 ° C.
The light output was measured using a light emitting diode of the form shown in FIG. 3, and the light output was 24.

Comparative Example 1 shows a conventional method, and Comparative Example 2 shows an example in which the carrier concentration is increased near the light emitting layer. In Comparative Examples 1 and 2, the amount of (C ₂ H ₅ ) ₂ Te introduced during the epitaxial growth of the second to third layers was constant at 30 cc / min (Comparative Example 1). Furthermore, during the growth of the second layer, it was gradually increased from 30 cc / min to 75 cc / min, and was constant at 90 cc / min in the third layer (Comparative Example 2). Other processes were the same as in Example 1, and the epitaxial growth was further repeated twice in total.

The thickness of the epitaxial layer and the fourth
The carrier concentration of this layer was almost the same as in Example 1. As a result of the measurement, in Comparative Example 1, the carrier concentration in the second layer and the third layer was approximately constant at 1.5 × 10 ¹⁷ cm ⁻³ .

In Comparative Example 2, as shown in FIG.
2 has a carrier concentration of 1.5 × 10¹⁷cm^-3From
8 × 10¹⁷cm^-3Gradually increase to 8x in the third layer
10 ¹⁷cm^-3Was almost constant.

The light output of each of the comparative examples 1 and 2 was measured, and the light output was measured.
Then there were 17. By this comparison, in the present invention, the light output was increased by 20% compared to Comparative Example 1 of the conventional method. Also, when the carrier concentration near the light emitting layer was increased as in Comparative Example 2, the luminance was reduced by 15%, contrary to the conventional method.
Therefore, the light output of Example 1 is 40% higher than that of Comparative Example 2.

FIG. 4 is a sectional view of a light emitting diode manufactured by using the embodiment of the arsenic arsenide epitaxial wafer manufactured as described above. As shown in FIG.
Pn junction 1 in epitaxial layer 16 formed on
7 are formed on the surface A of the epitaxial layer on which the first electrode 7 is formed and the back surface B of the gallium phosphide (GaP) substrate 10, respectively.
8, 19 are formed. Further, the light emitting diode is manufactured by separating the elements.

[0086]

As described in detail above, according to the present invention, a gallium arsenide arsenide (GaAsP) epitaxial wafer is manufactured, and a light emitting diode having a particularly high light output can be realized. In the present invention, gallium phosphide (GaP) is taken as an example of a single crystal substrate, but gallium arsenide (GaP) is used.
The effect is the same in As).

Thus, gallium arsenide arsenide (GaAs)
The demand for light emitting diodes in P) is expected to increase.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a layer structure of a gallium arsenide phosphide epitaxial wafer of the present invention.

FIG. 2 is a graph showing carrier concentration profiles of epitaxial layers according to an example of the present invention and a comparative example.

FIG. 3 is a cross-sectional view illustrating a configuration of a light emitting diode manufactured from a gallium arsenide phosphide (GaAsP) epitaxial wafer.

FIG. 4 is a diagram showing a general layer structure of a gallium arsenide phosphide (GaAsP) epitaxial wafer used for manufacturing a light emitting diode.

[Explanation of symbols]

10: single crystal substrate, 11: grade composition layer, 12: constant composition layer, 13: low carrier concentration region, 14: homo layer, 15:
High carrier concentration region, 16: epitaxial layer, 17: p
n junction, 18, 19: electrode, 20: GaP single crystal substrate,
21: GaAs _1-x P _x grade composition layer, 22: GaAs
_1-x0 P _x0 constant composition layer, 23: nitrogen-doped GaAs _1-x0 P
_x0 Low carrier concentration constant composition layer, 24: GaP homo layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G077 AA03 BE48 DB01 EB01 ED06 5F041 AA04 CA02 CA35 CA37 CA38 CA50 CA53 CA55 CA64 CA65 CA67 CA72 FF01 5F045 AA04 AB11 AB17 AC01 AC03 AC09 AC12 AC13 AD12 AF04 AF13 BB12 CA10 DA59 DA

Claims (13)

[Claims] 1. A method according to claim 1, wherein Ga, As, and
An epitaxial wafer having an n-type compound semiconductor epitaxial layer containing P as a constituent element, wherein the n-type compound semiconductor epitaxial layer comprises at least a grade composition layer and a constant composition layer, and the n-type carrier of the epitaxial layer An epitaxial wafer having a profile in which the concentration has a maximum value in the grade composition layer and decreases toward an end point of the grade composition layer. 2. The epitaxial wafer according to claim 1, wherein the maximum value of the n-type carrier concentration exists in the grade composition layer separated from the end point in the grade composition layer by 2 μm or more. 3. The maximum value of the n-type carrier concentration is 2 to 3.
30 × 10¹⁷cm^-3And within the constant composition layer
Means that the carrier concentration is at least 9 × 10¹⁵cm ^-3below
2. A low carrier concentration region.
Or, the epitaxial wafer according to 2. 4. The epitaxial wafer according to claim 3, wherein the low carrier concentration region in the constant composition layer has a thickness of 2 μm or more. 5. The epitaxial wafer according to claim 1, wherein a position where the n-type carrier concentration takes a maximum value is at least 5 μm away from the low carrier concentration region. 6. The grade composition layer has a thickness of 5 to 120 μm.
m, and the low carrier concentration region has a layer thickness of 2 to 60 μm.
The epitaxial wafer according to any one of claims 1 to 5, wherein m is m. 7. The low carrier concentration region includes GaAs _1-x P _x
The epitaxial wafer according to any one of claims 1 to 6, comprising (0.45 <x <1) and being doped with at least nitrogen. 8. The method of claim 1, wherein the epitaxial layer is GaAs _1-x P
_x (0 <x <1).
The epitaxial wafer according to any one of the above. 9. The method according to claim 1, wherein the single crystal substrate is a GaAs substrate or a G substrate.
The epitaxial wafer according to any one of claims 1 to 8, comprising an aP substrate. 10. The semiconductor device according to claim 1, wherein a p-type compound semiconductor epitaxial layer is further formed on said n-type compound semiconductor epitaxial layer to have a pn junction.
10. The epitaxial wafer according to any one of claims 9 to 9. 11. The epitaxial wafer according to claim 10, wherein said p-type compound semiconductor epitaxial layer is formed by vapor phase growth. 12. The epitaxial wafer according to claim 10, wherein said p-type compound semiconductor epitaxial layer is formed by diffusing zinc into an n-type compound semiconductor epitaxial layer. 13. An epitaxial wafer according to claim 10, wherein said epitaxial wafer is formed by forming electrodes on a back surface of said single crystal substrate and on a surface of said p-type compound semiconductor epitaxial layer. A light emitting diode characterized by being made.