JP3525704B2 - Gallium arsenide arsenide epitaxial wafers and light emitting diodes - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention resides in a phosphide arsenide epitaxial wafer and a light emitting diode (hereinafter "LED").

[0002]

2. Description of the Related Art LEDs having a semiconductor crystal as a constituent material are currently widely used as display elements.
III-V group compound semiconductors are used as most of the materials. Since III-V group compound semiconductors have a bandgap corresponding to the wavelengths of visible light and infrared light, they have been applied to light emitting devices. Among them, GaAsP is in great demand for LEDs, and light emission output and life are the most important characteristics of LEDs, and improvement of this quality has been required.

An LED using GaAs _1-x P _x (0.45 ≦ x ≦ 1) as a light emitting layer is doped with nitrogen (N) as an isoelectronic trap to improve the light output in order to increase the light emission efficiency. There is. Generally, 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 the N-type GaP single crystal substrate 20, a homolayer 24 having the same composition as the substrate, and a mixed crystal ratio x of 1.0 to x are continuously set in order to reduce the difference in lattice constant between the substrate and the uppermost layer. 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 has a structure in which epitaxial growth is sequentially performed.
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 x ₀ for obtaining the emission wavelength of the LED, and contains nitrogen and tellurium (Te) or sulfur (N type dopant). 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 in GaAsP, it becomes an isoelectronic trap that serves as a light emission center. The isoelectronic trap is electrically inactive and does not contribute to the carrier concentration. By doping the light emitting layer with nitrogen, the light emitting efficiency is increased about 10 times.

In order to use the GaAsP epitaxial wafer in which the N type epitaxial layer is formed on the N type single crystal substrate as an LED as described above, 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. 2, an ohmic electrode 18 is formed on the surface of the epitaxial wafer in which the PN junction 17 is formed in the epitaxial layer 16 and on the GaP substrate side, and the elements are separated.
Is manufactured.

In order to minimize the destruction of the crystal integrity of the light emitting layer and prolong the life of the injected carriers to obtain an LED with high light output, the carrier concentration is 3.5.
Up to 8.8 × 10 ¹⁵ cm ^-3 (Japanese Patent Publication No. 58-1)
539). Furthermore, the carrier concentration is 3 × 10 ¹⁵ cm
If it is ^-3 or less, improvement of light output and extension of life can be realized at the same time (Japanese Patent Laid-Open No. 6-196756). However, as a result of further study, it was found that when the concentration was 0.5 × 10 ¹⁵ cm ⁻³ or less, the forward voltage of the LED increased, which might cause a defect. Therefore, the carrier concentration should be higher than this. Is preferred.

The epitaxial layers other than the light emitting layer are 0.5 to 5 × 10 ¹⁷ in order to reduce the resistance when the LED is formed.
The carrier concentration is generally about cm ⁻³ .
Below this, the forward voltage of the LED increases, and above this, 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]

Up to now, a high light output and a long life have been realized by optimizing the carrier concentration of the light emitting layer. However, due to the diversification of demand, even longer life is required. For example,
It is impossible to frequently replace the LEDs when mounted on a vehicle, and it is natural that the demand for reliability becomes even more severe in terms of driving safety. Due to the diversification of applications of LEDs, LEDs with extremely high reliability are required. At present, due to technological advances, high light output has already been obtained. Rather than improving the light output of the LED,
Rather, the quality that requires the reliability of the LED is required.

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

[0010]

Therefore, as a result of earnest studies to solve the above problems, the present inventor considers that reducing the heat generation of the PN junction portion is effective for extending the life of the LED in order to improve the life of the LED. In particular, it was thought that the 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 the heat generation of the PN junction, it is necessary to suppress the heat generation due to the series resistance of the LED. When Zn, which is a P-type dopant, is diffused into the low-constant-constant-constant-composition layer 23 that is a light-emitting layer to form an LED, since the carrier concentration is 1 × 10 ¹⁹ cm ⁻³ or more, the P-type layer of Resistivity does not matter. As described above, the light emitting layer is 9 in order to obtain high light output.
It is difficult to dope to a concentration outside the range of ^{x10 15} cm ^-3 or less. As a result of the examination, it was revealed that the GaAsP crystal is a mixed crystal, and therefore, the resistivity is several times higher than that of a GaP or GaAs single crystal substrate at the same carrier concentration. It was found that the carrier concentration in 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, the layers other than the light emitting layer,
It was considered that a long-life LED can be obtained by increasing the carrier concentration higher than the conventional 0.5 to 5 × 10 ¹⁷ cm ⁻³ .

That is, the gist of the present invention is to provide a gallium arsenide arsenide epitaxial wafer having an N-type GaAs _1-x P _x (0 ≦ x ≦ 1) epitaxial layer on an N-type single crystal substrate. At the surface side of the epitaxial layer, the carrier concentration is less than 6.5 × 10 ¹⁷ cm ⁻³ and the layer thickness is 2
It has a low carrier concentration region of μm or more and has a carrier concentration of 6.5 × adjacent to the substrate side of the low carrier concentration region.
10 ¹⁷ cm ^-3 phosphide gallium arsenide epitaxial wafer characterized by having a high carrier concentration region above the layer thickness 3μm is more than, and consists in emitting diodes, characterized in that creating from such an epitaxial wafer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the epitaxial wafer and the light emitting diode of the present invention will be described in detail below with reference to FIG. Normally, GaP or GaAs is selected for the single crystal substrate 10, but the low carrier concentration region 13 serving as the light emitting layer is GaAs _1-x P _x (0.45 <x <
In the case of 1), it is preferable that the single crystal substrate 10 is GaP because it 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.
It is 0 ¹⁷ cm ^-3 .

The epitaxial layer in the present invention is
The carrier concentration is 6. on the surface side, that is, on the side opposite to the substrate.
5 x 10¹⁷cm^-3Low carrier concentration of less than 2μm or more
And a base of the low carrier concentration region 13
Adjacent to the plate side, the carrier concentration is 6.5 × 10¹⁷cm^-3
Or more, preferably 6.5 × 10¹⁷~ 30 × 10¹⁷cm ^-3
Has a high carrier concentration region 15 having a layer thickness of 3 μm or more
It

On the other hand, when the GaAs _1-x P _x (0 ≦ x ≦ 1 and 0 <x <1 in some cases) epitaxial layer is viewed from the viewpoint of composition, not carrier concentration, it is usually at least the grade composition layer 11 And a constant composition layer 12. In addition, the homo layer 13 having the same crystal as the single crystal substrate 10 can be formed without particular formation, but the homo layer 14 is 0.1 to 100 μm, preferably 0.5 to 10 μm in order to suppress the occurrence of misfit dislocations. The thickness of 15 μm is preferable because high brightness can be stably obtained. The carrier concentration of the homolayer 14 is preferably approximately the same as the growth starting point of the grade composition layer 11. The layer thickness of the grade composition layer 11 is preferably 2
˜100 μm, more preferably 10 to 35 μm.

The boundary between the low carrier concentration region 13 and the high carrier concentration region 15 usually exists in the constant composition layer 12, but may also exist in the grade composition layer 11 or the boundary between the grade composition layer 11 and the constant composition layer. Even if they match, the thickness of the high carrier concentration region 12 may be 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. The boundary between the low carrier concentration region 15 and the low carrier concentration region 13 is preferably in the constant composition layer, and in particular, it is preferable that the high carrier concentration region 15 has a constant composition on the surface side of about 2 to 25 μm.

Within the high carrier concentration region 15, the carrier concentration may fluctuate somewhat. In the present invention, a carrier concentration of 6.5 × 10 ¹⁷ cm ⁻³ is defined as a boundary, and an upper part is defined as a high carrier concentration region and a lower part is defined as a low carrier concentration region. The carrier concentration of is often inferior. High carrier concentration region 1
The transition of the carrier concentration from 5 to the low carrier concentration region 13 is usually sharp, but may be stepwise. In the case of stepwise transition, an intermediate carrier concentration region (such a region is also classified as either a high carrier concentration region or a low carrier concentration region in the present invention) is 20
If the thickness is less than or equal to μm, preferably less than or equal to 10 μm, the effect of improving the life is easily obtained. If the carrier concentration of the high carrier concentration region 15 is 30 × 10 ¹⁷ cm ⁻³ or less, the crystallinity is deteriorated and crystal defects occur on the surface of the epitaxial layer, and the light output of the LED is reduced. None preferred. Further, when the layer thickness is 3 μm or more, a remarkable effect of improving the life is seen, and when it is 60 μm or less, it is preferable because there is no problem that the light output of the LED decreases.

The low carrier concentration region 13 preferably has an average carrier concentration of 9 × 10 ¹⁵ cm ⁻³ or less, but 0.5 × 1.
If it is 0 ¹⁵ cm ^-3 or less, it may be difficult to control the carrier concentration, or the specific resistance may increase and the forward voltage of the LED may increase. Therefore, the preferable average carrier concentration is 0.5 to 9 × 10 5. ^{It is 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 on the P-type epitaxial layer, or when the P-type epitaxial layer is already formed. When the PN junction is formed in the low carrier concentration region by diffusion, the diffusion depth is usually 4 to 15 μm, so the layer thickness in the low carrier concentration region is 5 μm.
At least μm is required. Higher concentration region 1 when exceeding 50 μm
It is not preferable because it is too far from 5. That is, it is preferable to form the PN junction so that the low carrier concentration region is left to be about 2 to 35 μm.

When the composition of the constant composition layer 12 in the low carrier farming range is 0.45 <x <1, it has an indirect transition type band structure, so that the constant composition layer of at least the low carrier concentration is provided in order to enhance the luminous efficiency. It is common to dope with nitrogen. However, if the carrier concentration of all 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 the crystallinity decreases. If the crystallinity deteriorates, not only will the light output decrease,
Levels of crystal defects that absorb light are generated in the band gap, further increasing the light absorption. Epitaxial growth greatly affects the first half of the growth and the latter half of the growth. Therefore, it is preferable for crystallinity to lower the carrier concentration as much as possible especially in the first half of epitaxial growth.

Further, in order to obtain a high light output, the carrier concentration of the grade composition layer 11 increases substantially 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, This can be achieved by providing a structure having a carrier concentration profile having a high carrier concentration region 15 having the maximum high carrier concentration in the 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 latter 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.

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 conductivity type dopant, usually zinc, is formed into a constant composition layer in the low carrier concentration region from the surface. A PN junction is formed by diffusing. Although a GaAsP epitaxial wafer is usually manufactured by a vapor phase growth 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 diethyl zinc ((C By introducing ₂ H ₅ ) ₂ Zn), Z
You may dope n and may form a PN junction.

Further, in order to obtain the carrier concentration profile from the start of the grade composition layer 11 to the end point or inside the adjacent constant composition layer 12, if the dopant gas is grown while being generally increased, a predetermined carrier concentration profile is obtained. Can be easily obtained. The flow rate of the dopant gas may be continuously increased, but there is no problem even if it is increased stepwise in one step or a plurality of steps. The dopant gas flow rate is preferably increased 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 with the same carrier concentration, from the latter half of the grade composition layer 11 to the vicinity of the end point,
A maximum dopant flow rate is preferred. The composition grade layer has the same effect not only when the composition changes continuously but also when the composition changes in a plurality of steps, 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 the CV method after obliquely polishing the epitaxial layer, producing a Schottky barrier diode on the surface thereof. Also, like the Polaron UK Simiconductor profile plotter,
The same measurement can be performed by a method in which the epitaxial layer is directly etched while being etched with an electrolytic solution.

The hydride method is most effective in terms of mass productivity and practical use. The same effect is obtained by the chloride method and the metal organic vapor phase method (MOCVD).

[0026]

EXAMPLES The present invention will be described in more detail below with reference to examples.
As will be apparent, the present invention is implemented as follows unless the gist thereof is exceeded.
It is not limited by example. (Examples 1 to 3 and Comparative Examples 1 to 3) First, Example 1 will be explained.
Reveal GaP substrate and high-purity gallium (Ga)
a Epitaxial reactor with a quartz boat for storage
It was installed in each place. GaP substrate is sulfur
Yellow (S) is 2-10 × 10¹⁷Atom / cm³Added,
It is a circle with a diameter of about 50 mm and is [001] from the (100) plane.
A GaP substrate having a surface displaced by 10 ° in the direction was used. This
They were placed on a holder that rotates at the same time. Next
Elementary (N₂) Introducing gas into the reactor for 15 minutes and air
After sufficiently replacing and removing the high-purity water as carrier gas
Elementary (H₂) Is introduced at 9600 cc / min, N₂Stop the flow of
The temperature rising process was started. Installation part of the above-mentioned Ga-containing quartz boat and
And the temperature of the GaP single crystal substrate installation part is 800 each.
It was confirmed that the temperature was kept constant at ℃ and 850 ℃.
Later, GaAs with 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.
Is introduced at a rate of 120 cc / min, GaCl as a Group III element component of the periodic table is produced to generate 369 cc / min, high-purity hydrogen chloride gas (HCl) is blown into the Ga reservoir in the quartz boat, and It was blown out from the surface. On the other hand, while introducing 750 cc / min of hydrogen phosphide (PH ₃ ) diluted with H ₂ to a concentration of 10% as a group V element element of the periodic table, the first layer (the homo layer in FIG. 1) was introduced for 20 minutes. The GaP epitaxial layer of 14) was grown on a GaP single crystal substrate.

Next, the introduction amount of hydrogen arsenide (AsH ₃ ) diluted with H ₂ to a concentration of 10% was changed without changing the introduction amounts of the gases HCl, PH _{3, and} (C ₂ H ₅ ) ₂ Te. , 0 cc / min
To 480 cc / min, and the second GaAs _1-x P _x epitaxial layer is first applied for 90 minutes.
Was grown on the GaP epitaxial layer. For the next 20 minutes, the amount of (C ₂ H ₅ ) ₂ Te, HCl, PH ₃ , and AsH ₃ introduced is kept unchanged and the third GaAs is maintained.
_0.4 P _0.6 Epitaxial layer (constant composition layer) as the second Ga
It was grown on an As _1-x P _x epitaxial layer.

During the final 50 minutes, 0.5 cc of (C ₂ H ₅ ) ₂ Te was introduced per minute to give a fourth layer (G in FIG. 1).
aAs _1-x0 P _x0 N-doped constant composition layer 13) so that the carrier concentration of the low-doped layer is adjusted to HCl, P
While introducing H ₃ and AsH ₃ without changing the introduction amounts thereof, a high-purity ammonia gas (N
H ₃ ) is introduced by introducing 420 cc / min to add a fourth GaAs _1-x P _x epitaxial layer to the third GaAs _1-x
The growth was completed by growing it on the P _x epitaxial layer.

First, second, third and third epitaxial films
The film thickness of the 4 epitaxial layers is approximately 5μ
m, 30 μm, 8 μm, and 21 μm. The fourth epi
The carrier concentration of the axial layer is the epitaxy before diffusion.
A Schottky barrier diode on the wafer surface
The carrier concentration is 3 to 5 × as measured by the CV method.
10¹⁵cm^-3Met. The first, second, and highly doped layers
The carrier concentration of the third epitaxial layer is epitaxy.
By lapping and etching the layer at an angle of about 1 °
After removing diagonally, the Schottky barrier diode is removed.
It produced 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 is 38 μm.
Is 6.5 × 10¹⁷cm^-3Higher concentration area
It was The carrier concentration is almost constant in the second and third layers.
Yes, but from the first layer to the third layer within the grade second layer
Towards 7.5 × 10¹⁷cm^-3From 9 × 10¹⁷cm^-3Loose
, And it was constant in the second layer. 4th 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 x 10¹⁷cm^-3Met. Epitaxial growth
ZnAs₂Zn, which is a P-type impurity, as a diffusion source
With nothing vacuum in quartz ampoule
Encapsulate and make a depth of 4 μm from the surface at a temperature of 760 ° C.
Spread in. The light output was measured by the light method. continue,
220 μm in diameter x 1 by forming electrodes by vacuum evaporation
A mesa-type LED of 80 μm (thickness) is formed to test the life.
Test was carried out. The energization condition of the life test is the TO-18 header
Mount the LED chip on the screen and 240A / cm at room temperature
²DUTY (effective energization time rate) = 1/2 of 50 Hz
Pulse driving was performed for 168 hours. Furthermore, with Examples 2-3
As Comparative Examples 1 to 3, epitaxy from the first layer to the third layer
(C₂H_Five)₂The introduction amount of Te is 1 per minute
5cc, 40cc / min, 80cc / min, 200c / min
c, the same as above, except 260 cc / min,
Additional epitaxial growth was repeated 5 times in total.
It was (C₂H_Five)₂The amount of Te introduced is 200 cc / min,
In the case of 260 cc, there is no problem in practical use,
Pyramidal crystal defects are formed on the surface of the epitaxial layer.
Appeared separately. All epitaxial layer thickness and
The carrier concentration of the fourth layer was almost the same as in Example 1.
It was 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 is the same as
Were determined. The comparative example without the high-concentration region 15 is the same as the example 1.
Similarly, the entire third layer adjacent to the fourth layer and the third layer
Average carrier concentration in the range of 15 μm near the end point of
The degree is defined as the carrier concentration of the high concentration region 15. L in FIG.
ED life test Light output residual rate after energization and high optical output
The relationship between carrier concentrations in the concentration region 15 is shown. Dotted line in Figure 3
Is the light output of the LED before the life test.
However, the residual rate of light output indicated by the solid line is the same as before the life test.
It was defined as the ratio of the light output of the LED after driving under the conditions. The survival rate is
Conventional high concentration area is 3 × 10¹⁷cm^-387% against
6.5 ~ 30 × 10¹⁷cm^-392-98% and most
it was high. Light output is 3 × 10¹⁷cm^-3Light output 6
5 to 9 to 30 × 10 ¹⁷cm^-3With a light output of 48
It was. In practice, if the light output is 35 or more, there is no problem at all,
Higher light output, especially for LEDs requiring long life
Power is gained. Light output is the carrier concentration of the 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 other emission color ranges. (Example 4) The amount of (C ₂ H ₅ ) ₂ Te introduced was 40 cc / min during the epitaxial growth of the first layer, and 40 cc / min to 2 cc during the epitaxial growth of the second layer.
The epitaxial growth was completed in the same manner as in the above example except that the third layer was gradually increased to 200 cc and the third layer was epitaxially grown to 200 cc per minute. There were no pyramid-shaped crystal defects, and a good epitaxial layer surface was obtained.

Similarly, the carrier concentration of each layer is the same as in Examples 1 to 3.
Was measured in the same manner as in Comparative Examples 1 to 3. The carrier concentration profile is shown in FIG. The carrier concentration of the grade composition layer is 2.5 × 10 ¹⁷ cm ⁻³ near the homo layer, and gradually increases to reach the maximum of 1.5 × 10 ¹⁸ cm ⁻³ near the end point of the second layer (grade composition layer). Met. When the light output and life test of the LED were conducted, the light output was 55, and the residual ratio of the light output was 94%. By arranging the high-concentration regions adjacent to each other, we were able to realize a longer life and higher light output.

[0033]

According to the present invention, in a GaAsP epitaxial wafer, an LED having a particularly long life is provided.
Can be realized without causing a large decrease in optical output, which is not a problem in practical use. In the present invention, the substrate is GaP as an example.
The same effect is obtained with aAs. This allows GaAsP
LED demand is expected to increase.

[Brief description of drawings]

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

FIG. 2 is an explanatory cross-sectional view of a general layer structure of a gallium arsenide phosphide 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 energization in the life test, and the dotted line shows the relationship between the carrier concentration in the high-concentration region and the light output.

FIG. 4 is an explanatory cross-sectional view of the structure of the light emitting diode of the present invention.

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

FIG. 6 is 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,
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 homolayer A GaP substrate, B homolayer, C grade composition layer, D
High carrier concentration constant composition layer, E low carrier concentration region, F high carrier concentration region

─────────────────────────────────────────────────── --Continued from the front page (56) Reference JP-A-8-335716 (JP, A) JP-A-6-196756 (JP, A) JP-A-59-9984 (JP, A) JP-A-53- 47285 (JP, A) JP 4-328878 (JP, A) JP 59-23578 (JP, A) JP 3-163884 (JP, A) JP 8-335715 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (9)

(57) [Claims] 1. An N-type GaAs on an N-type single crystal substrate.
_{In a} gallium arsenide arsenide epitaxial wafer having a _1-X P _X (0 ≦ x ≦ 1) epitaxial layer, the epitaxial layer has a carrier concentration of 6.
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 has 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. And a high carrier concentration region having a layer thickness of 3 μm or more , and the epitaxial layer is at least graded.
The grade composition layer consists of a composition layer and a constant composition layer.
The carrier concentration increases from the single crystal substrate side toward the constant composition layer.
Increasing, from the latter half of the grade composition layer to the end point and adjacent
The key that gives the highest high carrier concentration in either of the constant composition layers.
A gallium arsenide phosphide epitaxial wafer having a carrier concentration profile . 2. A boundary between the high carrier concentration region and the low carrier concentration region, phosphide gallium arsenide epitaxial wafer according to claim 1, characterized in that resides in the constant composition layer. 3. 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 × 10.
^The gallium arsenide arsenide epitaxial wafer according to claim 1 or 2 , wherein the gallium arsenide arsenide epitaxial wafer is ¹⁷ cm ^-3 . 4. The average carrier concentration in the first half of the grade composition layer is lower than the average carrier concentration in the latter half, and the starting carrier concentration of the grade composition layer is 0.5 × 10 ^{17 to} 5 × 10.
Phosphide gallium arsenide epitaxial wafer according to any one of claims 1 to 3, characterized in that a ¹⁷ cm ^-3. 5. The high carrier concentration region has a layer thickness of 3 to 60 μm.
, And the phosphide gallium arsenide epitaxial wafer according to any one of claims 1 to 4 Low carrier concentration region, wherein the thickness is 5 to 50 [mu] m. 6. The low carrier concentration region is GaAs _1-X P
It consists _{X (0.45 <x <1)} , phosphide gallium arsenide epitaxial wafer according to any one of claims 1 to 5, characterized that at least a nitrogen is doped. 7. A single crystal substrate, phosphide gallium arsenide epitaxial wafer according to any one of claims 1 to 6, characterized in that it consists of GaAs or GaP. 8. The N-type GaAs _1-X P _X (0 ≦ x ≦ 1)
On the epitaxial layer, P-type GaAs _1-X P _X (0
≦ x ≦ 1) The epitaxial wafer according to any one of claims 1 to 8 , which has an epitaxial layer. 9. A light-emitting diode manufactured from the epitaxial wafer according to claim 8 .