JP2000312032A - Compound semiconductor epitaxial wafer, method of manufacturing the same, and light emitting diode manufactured using the same - Google Patents

Abstract

(57) Abstract: Provided is an epitaxial wafer having an epitaxial layer containing at least Ga as a constituent element for realizing high light output, and an LED using the same. In an epitaxial wafer having an epitaxial layer containing at least gallium (Ga) as a constituent element, a pn junction is doped with at least nitrogen, and a surface of the epitaxial layer separated from the pn junction by at least 1 μm is provided. It is characterized by having a region of 2 μm or more in which the concentration of nitrogen is lower than that of the pn junction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a compound semiconductor epitaxial wafer, a method of manufacturing the same, and a light emitting diode (hereinafter, “LED”) manufactured using the same.

[0002]

2. Description of the Related Art LEDs using a semiconductor crystal as a constituent material are now widely used as display elements. Especially III-V
Most of group III compound semiconductors are used as materials for manufacturing LEDs.

[0003] III-V group compound semiconductors have been applied to light emitting devices because of their band gaps corresponding to the wavelengths of visible light and infrared light. Among them, GaAsP is L
Demand for ED is great. The emission output is the most important characteristic of the LED, and improvement of the quality from such a viewpoint has been required.

In the following, GaAs _1-x P _x (0.45 ≦ x <
Consider the case where 1) is an epitaxial layer. GaAs
LED with s _1-x P _x (0.45 ≦ x <1) as a light emitting layer
In order to improve luminous efficiency, nitrogen (N) is doped as an isoelectronic trap to improve light output about 10 times.

In general, after growing only an n-type layer by a vapor phase growth method using a quartz reactor, zinc (Zn) is diffused on the surface of the light emitting layer to form a p-type layer to form a pn junction. It is formed so that the LED can be stably obtained.

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 continuously reduce the difference in lattice constant between the substrate and the uppermost layer. A GaAs _1-x P _x grade composition layer 21 changed to x ₀ , a GaAs _1-x0 P _x0 constant composition layer 22, and a GaAs _1-x0 P _x0 low carrier concentration constant composition layer 23 doped with nitrogen (N) are sequentially formed. It has a structure grown epitaxially.

[0007] is the uppermost epitaxial wafer low carrier concentration constant composition layer 23 is a light emitting layer has a constant composition x ₀ to obtain an emission wavelength of LED, nitrogen (N)
And n-type dopant, tellurium (Te) or sulfur (S), is doped to a predetermined carrier concentration. Usually, x for red emission (wavelength 650 nm)
₀ = about 0.55.

When nitrogen (N) is doped into GaAsP, it becomes an isoelectronic trap which becomes a light emission center. Isoelectronic traps are electrically inactive and do not contribute to carrier concentration. By doping the light emitting layer with nitrogen (N), the light emitting efficiency is increased about 10 times.

A hydride method is generally used as a vapor phase growth method. Hydrogen is generally used as a carrier gas.
Metallic Ga is used as the group III raw material. Hydrochloric acid gas HCl
And supplied as GaCl.

A hydride is used as the group V raw material, and arsine A is used.
sH ₃ and phosphine PH ₃ are used.

In general, in vapor phase growth, the above-mentioned epitaxial layers are all n-type, and in a subsequent processing step, a constant composition layer doped with nitrogen (N) is diffused from the surface of the epitaxial layer to a depth of about 4 to 10 μm from the surface of the epitaxial layer. Zn is diffused to a concentration to form a p-type layer.

In the diffusion method, a good ohmic contact can be stably obtained because the p-type layer has a high carrier concentration. However, the quality of the crystal of the epitaxial layer is deteriorated due to the thermal damage of the diffusion, and the light output of the LED is lowered due to the increase in the light absorption of the p-layer.

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 an LED with a high light output, the carrier concentration must be 3.5. It may be set to 8.8 × 10 ¹⁵ cm ^-3 (Japanese Patent Publication No. 58-1539).

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).

The epitaxial layers other than the light-emitting layer are 0.5 to 30 × 10
^In general, the carrier concentration is about ¹⁷ cm ^-3 .

Below this, the forward voltage of the LED increases, and above that, the crystal defects increase as the carrier concentration increases, and the emitted light is absorbed and the light output of the LED decreases.

On the other hand, the N concentration at the pn junction is also important for the light output of the LED. The present inventors have studied that the N
The concentration is usually 0.6 to 5 × 10 ¹⁸ cm ⁻³ ,
Necessary for high light output of LED (JP-A-8-33571)
No. 6).

As described above, usually, the epitaxial wafer immediately after the vapor phase growth has an n-type conductivity type for both the epitaxial layer and the GaP substrate.

The fact that a pn junction can be formed during vapor phase growth can be expected to provide a good pn junction with few crystal defects and an LED with high light output. recently,
Even higher light output has been required for LEDs, and improvement of light output has reached its limit by simply forming a pn junction by a simple vapor deposition method.

Considering the example of FIG. 3 showing a sectional structure of a light emitting diode, in general, Zn is diffused into the constant composition layer 23 of FIG.

Light is emitted from pn near the surface of the epitaxial layer.
Much of the emitted light generated at the junction is extracted out of the LED chip through the p-layer. Therefore, in order to increase the light output of the LED, it is only necessary to suppress the absorption of light in the p-layer as much as possible and to increase the light extraction efficiency from the p-layer.

As described above, it is already known that the p-layer is grown simultaneously during the vapor phase growth. However, conventionally, the p-layer is doped with nitrogen (N) using ammonia gas. Since the p-layer has a high carrier concentration, the amount of light absorption is large.

Further, when nitrogen (N) is doped, the crystal has an increased light absorption due to the deep order of formation of nitrogen (N) and crystal defects caused by doping with nitrogen (N).

Therefore, in order to improve the light output of the LED, the light absorption in the p-layer may be reduced. In the prior application (Japanese Patent Application Laid-Open No. 8-335715), the inventors of the present invention have proposed a method of vapor phase growth. It has been proposed to form a p-layer by the method. This indicates that either the same amount of N doping as that of the pn junction in the p layer or no doping may be performed.

In Japanese Patent Application Laid-Open No. 2-94557,
In order to suppress light absorption in the p-layer, the p-layer remote from the pn junction is not doped with N, so that the light output of the LED is reduced by 3%.
It is described to improve by ~ 5%. However, the improvement in the light output was small, and even if the inventor performed an experiment of reproduction, the effect was hardly seen.

[0026]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an LED capable of realizing a higher light output, an epitaxial wafer having an epitaxial layer containing at least gallium (Ga) as a constituent element thereof, and a method of manufacturing the same. It is to provide a method.

It is another object of the present invention to provide a GaAs _1-x
An object of the present invention is to provide an epitaxial wafer of P _x (0.45 ≦ x <1) or GaP and a method of manufacturing the same.

[0028]

Means for Solving the Problems The present inventor has conducted intensive studies to solve the above-mentioned problems, and as a result, while suppressing the Si concentration, p
It has been found that the conventional problem can be solved by providing a layer in which the N concentration is reduced below the pn junction in the layer.

More specifically, the pn junction is a homo-junction and is a high-quality junction.
It has been found that the problem can be solved by providing a portion in which the N concentration is reduced in the p layer which is 1 μm or more away from the pn junction.

Such a structure can also be realized by epitaxially growing only the n-type layer in advance and then diffusing Zn on the surface of the epitaxial layer. For more stable production, it is effective to form not only the n-layer but also the p-layer during vapor phase growth. At the same time, a layer having a reduced N concentration in the p layer can be easily manufactured.

As the p-type dopant, Zn, Mg, B
Although there are e, Cd, etc., Zn and Mg are useful because of their toxicity. The doping gas can be easily doped by using an organic metal gas of the same dopant metal.

[0032] The structure of the epitaxial wafer of the present invention according to the above-described gist is firstly an epitaxial wafer in which an epitaxial layer containing at least gallium (Ga) as one of the constituent elements is formed on a single crystal substrate, and a pn junction portion Is doped with at least nitrogen, and has, on the surface side of the epitaxial layer at least 1 μm or more away from the pn junction, a region having a nitrogen concentration of the pn junction 2 μm or more.

Preferably, in the first aspect, the pn
The junction is GaAs _1-x P _x (0.45 ≦ x <1) or GaP, and the p layer is doped with at least nitrogen and the nitrogen concentration is 90% or less of the nitrogen concentration of the pn junction. The second feature is to have a portion that is

More preferably, in the above-mentioned feature, a third feature is that a portion in the p-layer has a nitrogen concentration of 50% or less of a nitrogen concentration of the n-layer of the pn junction.

Preferably, in the above feature, the carrier concentration on the n-layer side forming the pn junction is 0.5
A ~10 × 10 ¹⁵ cm ^-3, and the nitrogen concentration of the pn junction and the fourth being a 0.3~9 × 10 ¹⁸ cm ^-3.

Still further, in any of the above features,
The carrier concentration of the p-layer is 0.3 to 30 × 10 ¹⁸ cm ^−3.
The sixth feature is that the thickness of the p-layer is 4 to 300 μm.

Preferably, in the above feature, the conductivity type on the surface side of the epitaxial layer is a p-type, and the carrier concentration is 1 to 30 × 10 ¹⁸ cm ⁻³ .

Further, preferably, in the above-mentioned feature, the single crystal substrate is GaP.

Still preferably, in the above feature,
The single crystal substrate is made of GaAs.

Further, the light emitting diode according to the present invention comprises:
It is characterized by being manufactured using an epitaxial having the above-mentioned features.

Further, in the method of manufacturing an epitaxial wafer having any of the above characteristics, the epitaxial layer is grown by a vapor phase growth method, and the p-layer is formed using an organometallic compound of a p-type dopant as a doping gas. The nitrogen concentration is reduced by reducing the supply amount of ammonia gas during the formation of the p-layer.

Further, in the method of manufacturing an epitaxial wafer having any of the above characteristics, the epitaxial layer is grown by a hydride method, and the p-layer is formed using an organometallic compound of a p-type dopant as a doping gas. The method is characterized in that the nitrogen concentration is reduced by reducing the supply amount of ammonia gas during the formation of the p-layer.

Further features of the present invention will become apparent from the description of embodiments of the present invention described with reference to the following drawings.

[0044]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of an epitaxial wafer according to the present invention and a light emitting diode manufactured using the same will be described in detail with reference to the drawings. In the drawings, the same or similar components will be described with the same reference numerals.

FIG. 1 is a diagram showing one configuration of an epitaxial wafer according to the present invention. In FIG. 1, the epitaxial layer grown on the single crystal substrate 10 is grown using at least gallium (Ga) as one of the constituent elements.

In general, the demand for LEDs is large.
The epitaxial layer is GaAs _1-x P _x (0 ≦ x ≦ 1) or GaP. As a typical example, the pn junction is GaAs.
_{The case where 1-x} P _x (0.45 ≦ x <1) is described.

The single crystal substrate 10 is usually made of GaP or GaAs.
Is selected. An n-layer 13 forming a pn junction has GaAs _1-x P having an indirect transition type band gap.
_x (0.45 ≦ x <1), the single crystal substrate 1
0 is preferably GaP because it is transparent to the emission color of the LED and a high light output is obtained.

When the GaAs _1-x P _x (0.45 ≦ x ≦ 1) epitaxial layer is viewed from the viewpoint of composition, it generally has at least a grade composition layer 11 and a constant composition layer 12. .

Since the lattice constant difference between the single crystal substrate 10 and the epitaxial layer is large, the use of the grade composition layer 11 makes it possible to obtain a constant composition layer 12 with less crystal defects. In addition, the homo layer 14 made of the same crystal as that of the single crystal substrate 10 is not necessarily formed. However, in order to suppress the occurrence of misfit dislocations, 0.1-10
It is preferable to form the homo layer 14 having a thickness of 0 μm, preferably 0.5 to 15 μm, because high brightness can be stably obtained.

The thickness of the grade composition layer 11 is preferably 2 to 100 μm, more preferably 10 to 35 μm. Further, the carrier concentration of the grade composition layer 11 is
0.5-30 × 10 ¹⁷ cm ^-3 , preferably 1 × 10 ¹⁷ c
m ⁻³ or more and 30 × 10 ¹⁷ cm ⁻³ or less;
Lowering the forward voltage when it is turned into LED is a high carrier concentration region of 10 × 10 ¹⁷ cm ^-3, so good crystallinity can be obtained.

If the carrier concentration is 30 × 10 ¹⁷ cm ⁻³ or more, the crystallinity is deteriorated, and crystal defects are generated on the surface of the epitaxial layer, and problems such as a decrease in the light output of the LED are not preferred.

The effect of the grade composition layer 11 is the same even when the composition changes not only continuously but also in a plurality of steps, because the specific resistance of the epitaxial layer is determined mainly by the carrier concentration. .

A pn junction 17 is formed adjacent to the constant composition layer 12 in the n layer. GaAs _1-x P having an indirect transition band gap on the n-layer side forming the pn junction 17
_x (0.45 <x <1), n of the pn junction
The layer side becomes the low carrier concentration region 13.

The low carrier concentration region 13 preferably has an average carrier concentration of 10 × 10 ¹⁵ cm ⁻³ or less,
When the density is less than 10 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 LED. Accordingly, a high light output can be obtained, and the most preferable average carrier concentration in the low carrier concentration region 13 for stabilizing the electric characteristics is 0.5 to 0.5.
It is 10 × 10 ¹⁵ cm ⁻³ .

The thickness of the low carrier concentration layer 13 is 1 to 100.
μm, preferably 1 to 50 μm, more preferably 1 to 50 μm.
25 μm. If it exceeds 100 μm, the forward voltage is increased due to the increase in resistance due to the low carrier concentration, which is not preferable.

Grade composition layer 11 and low carrier concentration layer 1
3, the region of the constant composition layer 12 other than the low carrier concentration layer 13 is within the same high carrier concentration region 15 as the grade concentration composition layer 11 for the same reason as for the grade composition layer 11. Is more preferable. The layer thickness in this region is 3 to 50 μm, and the growth time becomes longer.
More preferably, the thickness is set to 20 μm.

The composition of the constant composition layer 12 is desirably as constant as possible in order to suppress crystal defects such as misfit dislocations as much as possible, but the composition should be varied within ± 0.05, preferably ± 0.02.

According to the present invention, a region having a nitrogen concentration lower than that of the pn junction 17 is provided in the p layer 30 at least 1 μm away from the pn junction doped with nitrogen (N), that is, on the surface of the epitaxial layer. It is characterized by.

Thus, the absorption of light by the isoelectronic trap of nitrogen (N) is prevented, and the doping of the Si impurity is prevented, so that the light absorption due to the deep order by the Si impurity is suppressed, and the transparency to the emitted light is improved. It is possible to increase. Therefore, a higher light output can be obtained.

The N concentration at the pn junction is 0.3 to 9 × 10
It is preferably ¹⁸ cm ^-3 . The reason why the range is wider than before is that the amount of light absorption in the p-layer is suppressed. Further, when the density is 0.7 to 5 × 10 ¹⁸ cm ⁻³ , a high light output is obtained, which is more preferable.

In the p layer separated from the pn junction 17 by 1 μm or more, preferably 2 μm or more, a layer 32 doped with at least nitrogen (N) and having a reduced N concentration is included in an amount of 2 μm or more.

The N of the layer 32 in which the carrier concentration is reduced
The effect can be obtained if the concentration is 90% or less of the N concentration of the pn junction portion, but it is preferably 50% or less, and more preferably 20% or less, because transparency is further increased.
The lower limit is not particularly limited as long as a nitrogen doping gas is supplied, but the N concentration is usually 0.1% or more, preferably 0.5% or more.

The Si concentration of the layer 32 in which the N concentration has been reduced is
0.8 × 10 ¹⁶ cm ⁻³ or less, and 0.4 × 10 ¹⁶
If it is ¹⁶ cm ^-3 or less, light transmission is improved, which is more preferable.

The layer 32 in which the N concentration has been reduced is the p layer 30.
In this case, a layer not doped with nitrogen (N) or a layer doped with nitrogen (N) outside the above range can be included in the p-layer.

The layer thickness of the p layer 30 may be 4 to 300 μm, preferably 6 to 200 μm or more, and more preferably 6 to 80 μm, because higher light output can be obtained. The carrier concentration of the p layer 30 is 0.1 to 70 × 10 ¹⁸
cm ⁻³ , more preferably 0.1 to 40 × 10 ¹⁸ cm ⁻³ . In particular, if the carrier concentration of the P layer on the surface of the epitaxial layer is 1 to 40 × 10 ¹⁸ cm ⁻³ , It is more preferable because an ohmic electrode can be obtained stably.

The carrier concentration in the p layer 30 is 70 × 10 ¹³
If it exceeds cm ^-3 , crystal defects occur and light is absorbed, which is not preferable.

In the production of the above-mentioned epitaxial wafer, a method is selected from a vapor phase epitaxial growth method capable of producing a complicated epitaxial layer structure. Specifically, a halogen transport method or a metal organic chemical vapor deposition method (MOCV
D) is selected.

The halogen transport method is advantageous because a high-purity epitaxial layer can be obtained and the productivity is high, and the hydride method is particularly common.

The method of doping nitrogen (N) generally uses ammonia gas. The concentration of N to be doped is proportional to the amount of supplied ammonia. Therefore, it is possible to form the layer 32 with reduced N concentration by appropriately changing the epitaxial growth conditions, but it is preferable because it can be easily achieved by reducing the ammonia supply amount.

After growing the n-type layer 32 with reduced N concentration, the p-layer can be formed even by diffusing Zn. In this case, there is a problem that the controllability is small, for example, the diffusion depth is constant over the entire surface of the wafer.

As the p-type dopant, Zn, Mg, C
Although there are d, Be, etc., Cd and Be are not preferred due to toxicity. Zn or Mg is selected because of high light output and low harmfulness. As the dopant gas, a high-purity raw material can be obtained and Zn is diethyl zinc (C ₂ H ₅ ) ₂ Zn because it is easy to use, and Mg is cyclopentadienyl magnesium (C ₅ H ₅ ) Mg (or Cp ₂ Mg). Are used.

In particular, it is more preferable to use Mg as a dopant because it is easier to dope a high concentration of 5 × 10 ¹⁸ cm ⁻³ or more.

For measuring the N concentration, secondary ion mass spectrometry (Secondary Ion Mass Spectrometry) was used.
measurement (hereinafter simply referred to as SIMS) may be practical. The method of 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 Harrier diode is formed on the surface thereof.

Further, a semiconductor profile plotter PN430 manufactured by Japan Bio-Rad Laboratory Co., Ltd.
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.

[0075]

DESCRIPTION OF THE PREFERRED EMBODIMENTS GaP substrate and high-purity gallium (Ga)
Was placed at predetermined locations in an epitaxial reactor having a quartz boat for a Ga reservoir.

The GaP substrate contains 3 to 10 × 10 sulfur (S).
¹⁷ atoms / cm ^{3 are} added, and the diameter is 50 mm,
A GaP substrate having a plane deviated by 10 ° in the [001] direction from the (100) plane was used.

These were simultaneously placed on the holder.
The holder was rotated three times per minute. The following description is made using SCCM as a gas flow unit converted into a standard state. Next, nitrogen N (N ₂ ) gas was introduced into the reactor for 15 minutes, and air was sufficiently replaced and removed. Then, 9600 SCCM of high-purity hydrogen (H ₂ ) was introduced as a carrier gas, and the flow of N ₂ was stopped. The heating process was started.

The above-mentioned Ga-containing quartz boat installation portion and G
After confirming that the temperature of the aP single crystal substrate installation portion is kept constant at 800 ° C. and 930 ° C., respectively,
Vapor phase growth of a GaAs _1-x P _x epitaxial film with a peak emission wavelength of 649 ± 10 nm was started.

First, diethyltellurium ((C ₂ H ₅ ) ₂ T) which is an n-type impurity diluted with hydrogen gas to a concentration of 50 ppm
e) was introduced at 15 SCCM, and 369 cc / min of high-purity hydrogen chloride gas (HCl) was blown into the Ga reservoir in the quartz boat in order to generate 369 SCCM of GaCl as a raw material of a Group III element of the periodic table. It was blown out from the surface of the reservoir.

On the other hand, H2 as a Group V element component of the periodic table
Hydrogen phosphide (PH ₃ ) diluted to a concentration of 10% with
While introducing 37 SCCM, homo layer 1
A GaP layer, which is the first layer as 0, was grown on a GaP single crystal substrate.

Next, without changing the introduction amounts of (C ₂ H ₅ ) ₂ Te, HCl and PH ₃ , the introduction amount of hydrogen arsenide (AsH ₃ ) diluted to a concentration of 10% with H 2 was 0SCCM
From 60 to 60 SCCM / min.
The temperature of the P substrate is gradually lowered from 930 ° C. to 870 ° C., and the second GaAs _1-x P _x epitaxial layer is formed as a grade layer 11 on the first GaP epitaxial layer for 90 minutes. Grew.

For the next 30 minutes, (C ₂ H ₅ ) ₂ Te, HC
1, PH ₃ , AsH ₃ without changing the introduction amount, that is, 15 SCCM, 369 SCCM, 737 SCC, respectively.
M, 603 SCCM while maintaining the third GaAs _1-x
With the _Px epitaxial layer as part of the constant composition layer 12,
The second layer was grown on the GaAs _1-x P _x epitaxial layer.

In the next 20 minutes, (C ₂ H ₅ ) ₂ Te, HC
1, PH ₃ and AsH ₃ were introduced without changing the introduction amount, and 214 SCCM high-purity ammonia gas (NH ₃ ) was added thereto for adding an N iso-electronic trap to the fourth GaAs _{1-. The x} P _x epitaxial layer was grown on the third GaAs _1-x P _x epitaxial layer as a low carrier concentration layer 13 as a constant composition layer 12.

For the next 10 minutes, (C ₂ H ₅ ) ₂ Te, HC
1. In order to supply p-type dopants without changing the introduction amounts of PH ₃ , AsH ₃ and NH ₃ , H ₂ gas was supplied to a cylinder containing (C ₂ H ₅ ) ₂ Zn which was kept at a constant temperature of 25 ° C. 5
Introduce 0SCCM and include (C ₂ H ₅ ) ₂ Zn vapor,
By introducing the H ₂ gas, the fifth p-type GaAs _1-x P _x
An epitaxial layer grown on the fourth GaAs _1-x P _x epitaxial layer.

For the next 40 minutes, (C ₂ H ₅ ) ₂ Te, HC
1. Without changing the introduction amount of PH ₃ and (C ₂ H ₅ ) ₂ Zn, NH ₃ was first reduced at a stretch to 21 SCCM, and then kept constant to obtain a sixth p-type GaAs _1-x P _x epitaxial. A layer was grown on the fifth GaAs _1-x P _x epitaxial layer to terminate the vapor phase growth.

The thicknesses of the first to sixth epitaxial films thus grown are 4 μm, 38 μm, and 13 μm, respectively.
m, 9 μm, 5 μm and 18 μm.

The epitaxial layer was polished obliquely by about 1 °, and a Schottky barrier diode was formed on the surface thereof and measured.

The measured carrier concentration of the first to third layers was 2
An ~3 × 10 ¹⁷ cm ^-3, the fourth layer corresponds to the low carrier concentration layer 13, the carrier concentration was 3 × 10 ¹⁵ cm ^-3.

The carrier concentration in the p-layer is determined by the semiconductor profile profile of Japan Bio-Rad Laboratory.
It was measured by a plotter PN4300. The p-layer carrier concentration of the fifth to sixth layers was 7 × 10 ¹⁸ cm ⁻³ . In the sixth layer in which the N concentration was reduced, the carrier concentration of the p-layer on the surface of the epitaxial layer was 6 × 10 ¹⁸ cm ⁻³ .

Subsequently, as shown in FIG. 3, the formation of the electrode 18 and the like are performed by vacuum evaporation to obtain a 300 μm × 300 μm ×
Forming a prismatic light emitting diode of 280 μm (thickness);
The measurement was performed without the epoxy coat.

For 5 chips, the forward voltage is 1.9 ±
At 0.1 V, the light output was 89 and the peak wavelength was 649 nm. Further, SIMS analysis was performed to measure the Si concentration and the N concentration. The Si concentration in the sixth layer is 0.7 × 10 ¹⁵ cm ⁻³ at the pn junction and 0.8 × 10 ¹⁵ cm ⁻³ in the sixth layer.
And the N concentration at the pn junction is 1.6 × 10 ¹⁸ cm ⁻³ ,
It was 0.16 × 10 ¹⁸ cm ⁻³ in the sixth layer.

[0092]

COMPARATIVE EXAMPLE 1 The vapor phase growth was completed in the same manner as in the example except that the fifth layer was grown for 60 minutes and the sixth layer was not grown. The thicknesses of the first, second, third, fourth, and fifth epitaxial layers of the epitaxial film are 5 μm and 39 μm, respectively.
m, 14 μm, 8 μm and 22 μm.

Except for the sixth layer, the carrier concentrations of the first to fifth layers were measured in the same manner as in Example 1, and were the same. Next, a light emitting diode was formed in the same manner as in Example 1, and the measurement was performed without an epoxy coat.

For 5 chips, a forward voltage of 1.9 ±
The optical output is 74 at 0.1 V, and the peak wavelength is 649 ± 1 n.
m. SIMS analysis was performed to measure Si concentration and N concentration. The Si concentration was 0.7 × 10 ¹⁵ cm ⁻³ in the pn junction and the fifth layer, and 1.6 × 10 ¹⁸ cm ⁻³ in the pn junction and the fifth layer.

[0095]

COMPARATIVE EXAMPLE 2 The vapor phase growth was completed in the same manner as in the example except that the fourth layer was grown for 5 minutes and the supply amount of ammonia was set to 0 SCCM in the sixth layer. The thickness of each of the first to sixth epitaxial layers is 5 μm,
They were 8 μm, 12 μm, 9 μm, 5 μm and 19 μm.

The carrier concentrations of the first to sixth layers were measured and the same as in Example 1. A light emitting diode was formed in the same manner as in Example 1, and the measurement was performed without an epoxy coat. For five chips, the light output was 80 at a forward voltage of 1.9 ± 0.1 V, and the peak wavelength was 649 ± 1 nm.

SIMS analysis was performed to measure Si concentration and N concentration. Si concentration is 0.6 × 10 ¹⁵ cm at the pn junction
^-3 , a high concentration of 3 × 10 ¹⁶ cm ^-3 is detected in the sixth layer, and the N concentration is 1.7 × 10 ¹⁸ cm ^-3 at the pn junction, and
The concentration was below the detection limit in the layer.

[0098]

According to the present invention, as described above with reference to the accompanying drawings, according to the present invention, the GaAsP epitaxial wafer has a nitrogen concentration lower than the pn junction on the epitaxial layer surface side at least 1 μm away from the pn junction. It is configured to have a region of 2 μm or more. As a result, the efficiency of extracting light emission to the outside is improved, and an LED having a high light output can be obtained.

In the description of the embodiments of the present invention, GaP has been described as an example of a semiconductor substrate, but the present invention is not limited to this. In other words, the effect of the present invention remains the same even with GaAs,
This can contribute to a future increase in demand for LEDs using aAsP as a material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a layer structure of a gallium arsenide phosphide epitaxial wafer of the present invention.

FIG. 2 is a diagram illustrating a cross section of a general layer configuration of a gallium arsenide phosphide epitaxial wafer.

FIG. 3 is a diagram illustrating a cross section of a configuration of a light emitting diode to which the present invention is applied.

[Explanation of symbols]

10 single crystal substrate, 11 grade composition layer, 12 constant composition layer, 1
3 Low carrier concentration region, 14 homo layers,
Reference Signs List 15 high carrier concentration region, 16 epitaxial layer, 17 pn junction, 18 electrodes 20 GaP single crystal substrate, 21 GaAs _1-x P _x grade composition layer, 22 G
aAs _1-x0 P _x0 constant composition layer, 23 N doped GaAs
_{1-x0 Px0} Low carrier concentration constant composition layer, 24 GaP homo layer 30 p layer 31 Layer having a larger band gap than pn junction 32 Layer with reduced N concentration in p layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 AA03 CA35 CA37 CA38 CA48 CA49 CA53 CA55 CA57 CA60 CA65 5F045 AA04 AB10 AB11 AB17 AC01 AC09 AC12 AC13 AC19 AD12 AD13 AF04 CA10 DA58 DA59 DQ08 EE12 5F052 KA05

Claims (11)

[Claims] A single crystal substrate is provided with at least gallium (G).
a) an epitaxial wafer having an epitaxial layer containing one of the constituent elements, wherein the pn junction is doped with at least nitrogen, and the nitrogen of the pn junction is located at least 1 μm or more away from the pn junction on the surface of the epitaxial layer. An epitaxial wafer having a region having a concentration lower than that of 2 μm or more. 2. The method according to claim 1, wherein the pn junction is formed of GaAs _1-x P _x (0.
45 ≦ x <1) or GaP, wherein the p layer has a portion doped with at least nitrogen and having a nitrogen concentration of 90% or less of the nitrogen concentration of the pn junction. 2. The epitaxial wafer according to 1. 3. The method according to claim 1, wherein the nitrogen concentration in said p-layer is
3. The epitaxial wafer according to claim 1, wherein the epitaxial wafer has a portion having a nitrogen concentration of 50% or less of an n-layer of a bonding portion. 4. 4. A carrier on an n-layer side forming said pn junction.
The concentration is 0.5- ^Ten× 10¹⁵cm^-3And p
The nitrogen concentration at the n-junction is 0.3 to 9 × 10¹⁸cm^-3Is
4. The method according to claim 1, wherein
Pitaxial wafer. 5. The p-layer has a carrier concentration of 0.1 to 70 ×.
5. The epitaxial wafer according to claim 1, wherein the thickness is 10 ¹⁸ cm ⁻³ , and the thickness of the p-layer is 4 to 300 μm. 6. The epitaxial layer according to claim 1, wherein the conductivity type on the surface side of the epitaxial layer is p-type, and the carrier concentration is 1 to 30 × 10 ¹⁸ cm ^-3. Wafer. 7. The epitaxial wafer according to claim 1, wherein said single crystal substrate is GaP. 8. The epitaxial wafer according to claim 1, wherein said single crystal substrate is GaAs. 9. A light-emitting diode manufactured by using the epitaxial layer according to claim 1. Description: 10. The method for manufacturing an epitaxial wafer according to claim 1, wherein the epitaxial layer is grown by a vapor phase growth method, and the p-type dopant is an organometallic compound as a doping gas. A method for manufacturing an epitaxial wafer, comprising: forming a p-layer; and reducing the nitrogen concentration by reducing the supply of ammonia gas during the formation of the p-layer. 11. The method for manufacturing an epitaxial wafer according to claim 1, wherein said epitaxial layer is grown by a hydride method, and said p-type dopant is an organometallic compound as a doping gas. Forming an epitaxial wafer, and further reducing the supply of ammonia gas during the formation of the p-layer to reduce the nitrogen concentration.