JPH11121794A - Gallium phosphoarsenide epitaxial wafer and light emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an LED having a very long life on a GaAsP epitaxial wafer, without great optical output reduction that causes a practical problem. SOLUTION: The Ga epitaxial wafer has an n-type GaAs1-x Px (0<=x<=1) epitaxial layer on an n-type single crystal substrate 10. This epitaxial layer has a low-concn. carrier region 13 having a thickness of 2 μm or more and carrier concn. of less than 6.5×10<17> cm<-3> and high-concn. carrier region 15 having a thickness of 3 μm or more and carrier concn. of 6.5×10<17> cm<-3> or more. This region 15 is adjacent to the region 13 at the single crystal substrate side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention resides in arsenic arsenide epitaxial wafers and light emitting diodes (hereinafter "LEDs").

[0002]

2. Description of the Related Art LEDs using a semiconductor crystal as a constituent material are currently widely used as display elements.
III-V compound semiconductors are used as most of the materials. III-V compound semiconductors have band gaps corresponding to the wavelengths of visible light and infrared light, and thus have been applied to light-emitting elements. Among them, GaAsP is in great demand for use in LEDs, and emission characteristics and life are the most important characteristics of LEDs, and improvement in this quality has been demanded.

An LED having a light emitting layer of GaAs _1-x P _x (0.45 ≦ x ≦ 1) is doped with nitrogen (N) as an isoelectronic trap to improve light output in order to increase luminous efficiency. I have. In general, after growing only an N-type layer by a vapor phase growth method using a quartz reactor,
Zinc is diffused on the surface of the light emitting layer to form a P-type layer to form a PN junction, thereby stably obtaining an LED.

FIG. 2 shows a general structure of a GaAsP epitaxial wafer. As an example, a case where the single crystal substrate is GaP will be described. In FIG. 2, on an N-type GaP single crystal substrate 20, a homo layer 24 having the same composition as the substrate, and a mixed crystal ratio x of 1.0 to x in order to alleviate the difference in lattice constant between the substrate and the uppermost layer are continuously set. GaAs _1-x P _x grade composition layer 21 changed to ₀ , GaAs _1-x0 P _x0 constant composition layer 22, nitrogen doped GaAs _1-x0 P _x0 low carrier concentration constant composition layer 2
3 is sequentially grown epitaxially.
Low carrier concentration constant composition layer 23 which is the uppermost layer of the epitaxial wafer is made and the light-emitting layer has a constant composition x ₀ to obtain an emission wavelength of LED, nitrogen and an N-type dopant tellurium (Te) or sulfur ( S) is doped to have a predetermined carrier concentration. Usually, for red light emission (wavelength 640 nm), x ₀ = about 0.60.
When nitrogen (N) is doped into GaAsP, it becomes an isoelectronic trap serving as a light emission center. Isoelectronic traps are electrically inactive and do not contribute to carrier concentration. The luminous efficiency is increased about 10 times by doping the light emitting layer with nitrogen.

As described above, in order to form an LED on a GaAsP epitaxial wafer having an N-type epitaxial layer formed on an N-type single crystal substrate, a PN junction is first formed. Normally, zinc (Z
Although n) is thermally diffused to form a PN junction, a P-type GaAsP epitaxial layer can be newly formed on the surface while introducing a P-type dopant. Then, FIG.
As shown in FIG. 3, an ohmic electrode 18 is formed on the surface of the epitaxial wafer having a PN junction 17 formed in the epitaxial layer 16 and on the side of the GaP substrate.
Is manufactured.

In order to minimize the destruction of the crystal integrity of the light-emitting layer, prolong the life of the injected carriers, and obtain an LED with a high light output, the carrier concentration must be 3.5.
8.8 × 10 ¹⁵ cm ^-3 (Japanese Patent Publication No. 58-1)
No. 539). Further, the carrier concentration is 3 × 10 ¹⁵ cm.
^By setting the value to ^-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 the subsequent examination, it was found that when the density is 0.5 × 10 ¹⁵ cm ⁻³ or less, the forward voltage of the LED increases, which may cause a defect. Is preferred.

[0007] The epitaxial layers other than the light-emitting layer are formed in an amount of 0.5 to 5 × 10 ¹⁷ to reduce the resistance when the LED is formed.
In general, the carrier concentration is about cm ^-3 .
Below this, the forward voltage of the LED 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 LED.

[0008]

Hitherto, high light output and long life have been realized by optimizing the carrier concentration of the light emitting layer. However, diversifying demands have required even longer lifespans. For example,
When mounted on an automobile, it is impossible to frequently change the LED, and it is natural that the demand for reliability is further strict in terms of driving safety. The diversification of the uses of LEDs has led to the demand for LEDs with particularly high reliability requirements. At present, high light output has already been obtained due to advances in technology. Rather than improving the LED light output,
Rather, a quality that requires the reliability of the LED is required.

An object of the present invention is to provide an LED which can achieve a longer life and a GaAs _1-x P _x (0.45
<X <1) To provide an epitaxial wafer.

[0010]

The present inventor has conducted intensive studies to solve the above-mentioned problems. As a result, if the reduction in heat generation at the PN junction is considered to be effective for prolonging the life of the LED, the life of the LED can be improved. In particular, it was considered that a high carrier concentration region 15 having a particularly high carrier concentration should be formed near the PN junction.

Considering the example of FIG. 2, in order to suppress heat generation at the PN junction, it is necessary to suppress heat generation due to the series resistance of the LED. When Zn, which is a P-type dopant, is diffused into the low-concentration constant composition layer 23, which is a light-emitting layer, to form an LED, the carrier concentration is 1 × 10 ¹⁹ cm ⁻³ or more. Specific resistance does not matter. As described above, the light-emitting layer needs to be 9 in order to obtain a high light output.
It is difficult to dope to a concentration outside the range of 10 ¹⁵ cm ^-3 or less. As a result of the study, it has been revealed that, since the GaAsP crystal is a mixed crystal, the specific resistance is several times higher than that of a single crystal substrate of GaP or GaAs at the same carrier concentration. It has been found that the carrier concentration of layers other than the light-emitting layer should be increased in order to efficiently suppress the heat generation of the PN junction and reduce the series resistance. Specifically, layers other than the light-emitting layer,
It has been considered that an LED having a long life can be obtained by increasing the carrier concentration to a value higher than the conventional value of 0.5 to 5 × 10 ¹⁷ cm ⁻³ .

That is, the gist of the present invention is to provide a gallium arsenide phosphide epitaxial wafer having an N-type GaAs _1-x P _x (0 ≦ x ≦ 1) epitaxial layer on an N-type single crystal substrate. In the above, the epitaxial layer has a carrier concentration of less than 6.5 × 10 ¹⁷ cm ⁻³ and a layer thickness of 2
a low carrier concentration region of at least μm and a carrier concentration of 6.5 × adjacent to the substrate side of the low carrier concentration region.
A gallium arsenide phosphide epitaxial wafer characterized by having a high carrier concentration region having a layer thickness of 3 μm or more of 10 ¹⁷ cm ⁻³ or more, and a light emitting diode characterized by being produced from such an epitaxial wafer.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the epitaxial wafer and the light emitting diode of the present invention will be described in detail with reference to FIG. The single crystal substrate 10 is usually selected from either GaP or GaAs, but the low carrier concentration region 13 serving as the light emitting layer is made of GaAs _1-x P _x (0.45 <x <
In the case of 1), it is preferable that the single crystal substrate 10 is GaP, since the single crystal substrate 10 is transparent to the emission color of the LED and obtains a high light output as the LED. The carrier concentration is 0.5 to 30 × 10 ¹⁷ cm ^-3 , preferably 2 to 10 × 1
0 ¹⁷ cm ^-3 .

In the present invention, the epitaxial layer
On the front side, that is, on the side opposite to the substrate, the carrier concentration is 6.
5 × 10¹⁷cm^-3Less than 2μm layer thickness and low carrier concentration
A low carrier concentration region 13
Adjacent to the plate side, the carrier concentration is 6.5 × 10¹⁷cm^-3
Above, preferably 6.5 × 10¹⁷~ 30 × 10¹⁷cm ^-3
Has a high carrier concentration region 15 having a layer thickness of 3 μm or more.
You.

On the other hand, when the GaAs _1-x P _x (0 ≦ x ≦ 1, in some cases 0 <x <1) epitaxial layer is viewed not from the carrier concentration but from the viewpoint of composition, at least the grade composition layer 11 And a constant composition layer 12. In addition, the homo layer 13 made of the same crystal as the single crystal substrate 10 can be formed without particular formation. However, in order to suppress the occurrence of misfit dislocation, the homo layer 14 is formed to have a thickness of 0.1 to 100 μm, preferably 0.5 to 100 μm. The thickness of 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 the growth start point of the grade composition layer 11. The thickness of the grade composition layer 11 is preferably 2
１００100 μm, more preferably 10-35 μm.

The boundary between the low carrier concentration region 13 and the high carrier concentration region 15 usually exists within the constant composition layer 12, but may be within the grade composition layer 11, or the boundary between the grade composition layer 11 and the constant composition layer. Even if they match, it is sufficient that the thickness of the high carrier concentration region 12 is 3 μm or more. However, in order to reduce the influence of crystal defects such as misfit dislocations generated in the grade composition layer 11 and obtain the low carrier concentration region 13 having better crystallinity, as shown in FIG. It is preferable that the boundary between the low carrier concentration region 15 and the low carrier concentration region 13 is in the constant composition layer, and it is particularly preferable that the high carrier concentration region 15 has a constant composition of about 2 to 25 μm on the surface side.

In the high carrier concentration region 15, the carrier concentration may fluctuate slightly. In the present invention, a high carrier concentration region above the carrier concentration of 6.5 × 10 ¹⁷ cm ⁻³ and a low carrier concentration region below the boundary are mechanically defined. The carrier concentration is often different. High carrier concentration region 1
The transition of the carrier concentration from 5 to the low carrier concentration region 13 is usually steep, but may be stepwise. In the case where the transition is performed stepwise, a region having an intermediate carrier concentration (the region is also classified as a high carrier concentration region or a low carrier concentration region in the present invention) is 20%.
If the thickness is not more than 10 μm, preferably not more than 10 μm, the effect of improving the life can be easily obtained. If the carrier concentration of the high carrier concentration region 15 is 30 × 10 ¹⁷ cm ⁻³ or less, problems such as deterioration of crystallinity to cause crystal defects on the surface of the epitaxial layer and decrease in light output of the LED occur. Preferred. Further, when the layer thickness is 3 μm or more, a remarkable effect of improving the life can be seen.

The low carrier concentration region 13 preferably has an average carrier concentration of 9 × 10 ¹⁵ cm ⁻³ or less,
When the carrier concentration is 0 ¹⁵ cm ⁻³ or less, the carrier concentration may be difficult to control, or the specific resistance may increase, leading to an increase in the forward voltage of the LED. ¹⁵ cm ^-3 . The layer thickness is 2 μm
That is all. However, this layer thickness is the minimum necessary thickness when a P-type epitaxial layer is further grown and formed thereon, or when such a P-layer is already formed, and is the necessary thickness of the P-type dopant. When a PN junction is formed in a low carrier concentration region by diffusion, the layer thickness of the low carrier concentration region is 5 since the diffusion depth is usually 4 to 15 μm.
μm or more is required. If it exceeds 50 μm, high 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 a low carrier concentration region of about 2 to 35 μm.

When the composition of the constant composition layer 12 in the low carrier fertility region is 0.45 <x <1, it has an indirect transition type band structure. It is common to dope nitrogen therein. However, if the carrier concentration of all the layers outside the low carrier concentration region is increased, the emitted light is absorbed. As the light absorption increases, the light output of the LED decreases. Also, from the viewpoint of crystallinity, if the carrier concentration is excessively increased, point defects and the like increase and crystallinity decreases. Poor crystallinity not only reduces light output,
Levels of crystal defects that absorb light occur in the band gap, further increasing light absorption. Epitaxial growth greatly affects the influence of the first half of growth. Therefore, it is preferable to lower the carrier concentration as much as possible in the first half of the epitaxial growth, in view of crystallinity.

Further, in order to obtain a high light output, the carrier concentration of the grade composition layer 11 generally increases from the single crystal substrate 10 side toward the constant composition layer 12, and from the latter half of the grade composition layer 11 to the end point, and This can be achieved by providing a structure having a carrier concentration profile having a high carrier concentration region 15 having a maximum high carrier concentration in an adjacent constant composition layer. Specifically, the carrier concentration in the first half of the grade composition layer 11 is lower than the carrier concentration in the second half, and the carrier concentration at the start of the grade composition layer 11 is approximately 0.5 × 10 ^{17 to} 5 × 10 ¹⁷ cm ⁻³ . do it.

After the constant composition layer in the low carrier concentration region 13 is epitaxially grown adjacent to the surface of the epitaxial layer, a P-type conductive type dopant, usually zinc, is added from the surface to the constant composition layer in the low carrier concentration region. By diffusing, a PN junction is formed. A GaAsP epitaxial wafer is usually manufactured by a vapor phase epitaxy method. As described above, a constant composition layer having a low carrier concentration is grown, and during the growth, for example, Zn is added to a growth gas such as diethyl zinc ((C By introducing ₂ H ₅ ) ₂ Zn), Z
A PN junction may be formed by doping n.

Further, in order to obtain the carrier concentration profile from the start of the grade composition layer 11 to the end point or in the adjacent constant composition layer 12, the dopant gas is grown while increasing the dopant gas substantially. Can be easily obtained. The flow rate of the dopant gas may be continuously increased, but may be increased one step or a plurality of steps. It is preferable to increase the flow rate of the dopant gas between the grade composition layer 11 and the constant composition layer 12.

Since the grade composition layer 11 has many crystal defects such as misfit dislocations, the mobility of carriers (electrons) is low. Since the specific resistance increases even at the same carrier concentration, from the latter half of the grade composition layer 11 to the vicinity of the end point,
It is preferred to have the maximum dopant flow. The effect of the composition grade layer is the same even if the composition grade layer is not only a continuous composition change but also a plurality of stepwise composition changes, because the resistivity of the epitaxial layer is mainly determined by the carrier concentration.

The carrier concentration profile in the epitaxial layer can be measured by obliquely polishing the epitaxial layer, forming a Schottky barrier diode on the surface thereof, and measuring it by the CV method. Also, like Polaron's Simicon Conductor Profile Plotter,
The measurement can be performed in the same manner by 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).

[0026]

The present invention will be described in more detail with reference to the following examples.
As will be described, the present invention will
It is not limited by the example. (Examples 1 to 3 and Comparative Examples 1 to 3) First, Example 1 will be described.
I will tell. A GaP substrate and high-purity gallium (Ga)
aEpitaxial reactor with quartz boat for reservoir
Each was set in a predetermined place inside. GaP substrate is sulfur
Yellow (S) 2-10 × 10¹⁷Atom / cm^ThreeAdded
It is a circle with a diameter of about 50 mm and is [001] from the (100) plane.
A GaP substrate having a plane deviated by 10 ° in the direction was used. This
They were placed on a holder that rotated simultaneously. Next
Element (N_Two) Gas is introduced into the reactor for 15 minutes and air
After sufficient replacement, high-purity water is used as the carrier gas.
Elementary (H_Two) Is introduced at 9600 cc per minute, and N_TwoStop the flow of
The heating process was started. The above-mentioned Ga-containing quartz boat installation part and
And the temperature of the GaP single crystal substrate installation part is 800
And 850 ° C.
Then, GaAs having a peak emission wavelength of 640 ± 5 nm (red)
_1-xP_xThe vapor phase growth of the epitaxial film was started.

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 120 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 GaCl as a Group III element of the periodic table. It was blown out from the surface. On the other hand, while introducing 750 cc / min of hydrogen phosphide (PH ₃ ) diluted to a concentration of 10% with H ₂ as a Group V element of the periodic table, the first layer (the homo layer in FIG. 14) A GaP epitaxial layer was grown on a GaP single crystal substrate.

Next, the amount of hydrogen arsenide (AsH ₃ ) diluted to a concentration of 10% with H ₂ was determined without changing the amount of each of HCl, PH _{3 and} (C ₂ H ₅ ) ₂ Te. , 0cc per minute
To 480 cc / min, and the second GaAs _1-x P _x epitaxial layer is
Was grown on the GaP epitaxial layer. For the next 20 minutes, the third GaAs is maintained without changing the amounts of (C ₂ H ₅ ) ₂ Te, HCl, PH ₃ , and AsH ₃ introduced.
_0.4 P _0.6 epitaxial layer (constant composition layer)
As it is grown on _1-x P _x epitaxial layer.

In the last 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, P is adjusted so that the carrier concentration of the low-doped layer, which is an aAs _1-x0 P _x0 N-doped constant composition layer 13), becomes the same.
While introducing the H ₃ and 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 ) at a rate of 420 cc / min to add a fourth GaAs _{1-x Px} epitaxial layer to a third GaAs _1-x
Grown on the P _x epitaxial layer, to complete the growth.

The first, second, third and third epitaxial films
The thickness of the epitaxial layers of No. 4 is approximately 5 μm each.
m, 30 μm, 8 μm, and 21 μm. 4th episode
The carrier concentration of the epitaxial layer depends on the epitaxy before diffusion.
A Schottky barrier diode on the wafer surface
And the carrier concentration is 3 to 5 ×
10^Fifteencm^-3Met. The first, second, and highly doped layers
The carrier concentration of the third epitaxial layer is
Wrapping and etching at an angle of about 1 °
After obliquely removing the Schottky barrier diode
It was prepared on the surface and measured by the CV method. Measurement
As a result, as shown in FIG. 5, the total thickness of the second and third layers was 38 μm.
Is 6.5 × 10¹⁷cm^-3The above high concentration area
Was. The carrier concentration is substantially constant in the second and third layers.
There is a grade from the first layer to the third layer in the second layer.
7.5 × 10¹⁷cm^-3From 9 × 10¹⁷cm^-3Mild
And it was constant in the second layer. Fourth layer
Across the entire third layer adjacent to and near the end of the third layer.
The average carrier concentration in the range of 15 μm
The carrier concentration was used. The carrier concentration in the high concentration region 15 is
9 × 10¹⁷cm^-3Met. Grown epitaxial
Eha with ZnAs_TwoIs used as a diffusion source and Zn as a P-type impurity
With a vacuum inside the quartz ampule without any coating
Enclose and at a temperature of 760 ° C, a depth of 4 μm from the surface
Spread in. Light output was measured by the light method. continue,
Perform electrode formation by vacuum evaporation, etc.
Forming a mesa-type LED of 80 μm (thickness)
Test was carried out. The energizing condition for the life test is the TO-18 header.
Mount the LED chip on the screen, 240A / cm at room temperature
^TwoDUTY (effective energization time ratio) = 1/2 of 50Hz
The operation was performed for 168 hours by pulse driving. Further, Examples 2-3
As Comparative Examples 1 to 3, the epitaxy of the first to third layers
(C)_TwoH_Five)_TwoThe introduction amount of Te is 1 per minute
5cc, 40cc / min, 80cc / min, 200c / min
c, except that it was 260 cc per minute,
Repeat epitaxial growth 5 times in total
Was. (C_TwoH_Five)_Two200cc per minute, Te per minute
In the case of 260cc, there is no problem in practical use,
Pyramid-shaped crystal defects appear on the epitaxial layer surface
Appeared separately. All epitaxial layer thickness and
The carrier concentration of the fourth layer was almost the same as in Example 1.
Was. Example 1 The carrier concentration in the second layer and the third layer was also determined in Example 1.
And the carrier concentration in the high concentration region 15
Were determined. The comparative example having no high-density region 15 is the same as that of Example 1.
Similarly, the entire third layer adjacent to the fourth layer and the third layer
Carrier concentration in the range of 15 μm over the end point of
The degree was defined as the carrier concentration of the high concentration region 15. L in FIG.
Life test of ED
The relationship of the carrier concentration in the concentration region 15 is shown. Dotted line in FIG.
Is the light output of the LED before the life test.
The residual ratio of light output indicated by the solid line
Under the conditions, the ratio of the light output of the LED after driving was used. Survival rate is
Conventional high concentration area is 3 × 10¹⁷cm^-3At 87%
6.5 to 30 × 10¹⁷cm^-392% to 98%
it was high. Light output is 3 × 10¹⁷cm^-3Light output at 6
9 to 30 × 10 for 5 ¹⁷cm^-3And the light output is 48
Was. In practice, there is no problem if the light output is 35 or more,
High light output especially for LEDs requiring long life
Power is gained. Light output is carrier concentration of highly doped layer
Is 6 × 10¹⁷cm^-3There was little change below.

Although only the red LED has been described in the above invention, it goes without saying that the same effect can be obtained in the range of other luminescent colors. Example 4 The amount of (C ₂ H ₅ ) ₂ Te introduced was set to 40 cc / min in the epitaxial growth of the first layer, and from 40 cc / min to 2 cc / min in the epitaxial growth of the second layer.
The epitaxial growth was completed in the same manner as in the above example, except that the growth rate was gradually increased to 00 cc, and 200 cc / min in the epitaxial growth of the third layer. There were no pyramid-shaped crystal defects, and a good epitaxial layer surface was obtained.

Similarly, the carrier concentration of each layer was determined in Examples 1 to 3.
And were measured in the same manner as in Comparative Examples 1 to 3. FIG. 6 shows the carrier concentration profile. The carrier concentration of the grade composition layer is 2.5 × 10 ¹⁷ cm ⁻³ near the homo layer, gradually increases, and reaches a maximum of 1.5 × 10 ¹⁸ cm ⁻³ near the end of the second layer (grade composition layer). Met. When the light output and the life test of the LED were performed, the light output was 55 and the residual ratio of the light output was 94%. By making the high-concentration regions adjacent to each other, it was possible to achieve a long life and a high light output.

[0033]

According to the present invention, an LED having a particularly excellent lifetime in a GaAsP epitaxial wafer is provided.
Can be realized without a significant decrease in optical output, which is not a problem in practical use. In the present invention, the substrate is GaP as an example.
The effect is the same for aAs. Thereby, GaAsP
LED demand 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 an explanatory cross-sectional view of a general layer configuration of a gallium arsenide arsenide epitaxial wafer.

FIG. 3 is a graph showing characteristics of a light emitting diode. The solid line shows the carrier concentration in the high-concentration region and the residual ratio of the light output after the life test is energized, and the dotted line shows the relationship between the carrier concentration and the light output in the high-concentration region.

FIG. 4 is an explanatory sectional view of a configuration of the light emitting diode of the present invention.

FIG. 5 shows a carrier concentration profile of the light emitting diode of the present invention (Example 1).

FIG. 6 shows a carrier concentration profile of the light emitting diode of the present invention (Example 4).

[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,
Reference Signs List 17 PN junction, 18 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 A GaP substrate, B homo layer, C grade composition layer, D
High carrier concentration constant composition layer, E low carrier concentration region, F high carrier concentration region

Claims (11)

[Claims] An N-type GaAs is formed on an N-type single crystal substrate.
_{In a} gallium arsenide phosphide epitaxial wafer having a _1-x P _x (0 ≦ x ≦ 1) epitaxial layer, the epitaxial layer has a carrier concentration of 6.times.
It has a low carrier concentration region of less than 5 × 10 ¹⁷ cm ⁻³ and a layer thickness of 2 μm or more, and a carrier concentration of 6.5 × 10 ¹⁷ cm ⁻³ or more adjacent to the low carrier concentration region on the single crystal substrate side. A gallium arsenide phosphide epitaxial wafer having a high carrier concentration region having a layer thickness of 3 μm or more. 2. The gallium arsenide phosphide epitaxial wafer according to claim 1, wherein said epitaxial layer comprises at least a grade composition layer and a constant composition layer. 3. The gallium arsenide phosphide epitaxial wafer according to claim 2, wherein a boundary between the high carrier concentration region and the low carrier concentration region exists in the constant composition layer. 4. The low carrier concentration region has an average carrier concentration of 9 × 10 ¹⁵ cm ⁻³ or less, and the high carrier concentration region has a carrier concentration of 6.5 × 10 ¹⁷ to 30 × 1.
The gallium arsenide phosphide epitaxial wafer according to any one of claims 1 to ³ , wherein the ^thickness is 0 ¹⁷ cm ^-3 . 5. The carrier concentration of the grade composition layer is as follows:
A carrier concentration profile that increases from the single crystal substrate side toward the constant composition layer, and has a maximum high carrier concentration at any one of an end point and an adjacent constant composition layer from the latter half of the grade composition layer. 5. The gallium arsenide phosphide epitaxial wafer according to any one of 2 to 4. 6. An average carrier in the first half of the grade composition layer.
The concentration is lower than the average carrier concentration in the latter half,
The starting carrier concentration of the composition layer is 0.5 × 10 ¹⁷~ 5 × 1
0¹⁷cm^-3The method according to any one of claims 2 to 5, wherein
Gallium arsenide arsenide epitaxial wafers described in
C. 7. The high carrier concentration region has a layer thickness of 3 to 60 μm.
7. The gallium arsenide phosphide epitaxial wafer according to claim 1, wherein the low carrier concentration region has a layer thickness of 5 to 50 μm. 8. The low carrier concentration region is made of GaAs _1-x P
_The gallium arsenide phosphide epitaxial wafer according to any one of claims 1 to 7, comprising _x (0.45 <x <1) and being doped with at least nitrogen. 9. The gallium arsenide phosphide epitaxial wafer according to claim 1, wherein the single crystal substrate is made of GaAs or GaP. 10. The N-type GaAs _1-x P _x (0 ≦ x ≦
1) P-type GaAs _1-x P _{x is} further formed on the epitaxial layer.
The epitaxial wafer according to claim 1, wherein the epitaxial wafer has an (0 ≦ x ≦ 1) epitaxial layer. 11. A light-emitting diode produced from the epitaxial wafer according to claim 10.