JP2001024223A - Nitride semiconductor light emitting diode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor element which emits high-quality having a light emitting peak wavelength of 370 nm or shorter, by improving the light emitting efficiency of the element by preventing self-absorption by paying attention to the deterioration of ohmic contact and the occurrence of cracks. SOLUTION: The active layer 5 of a nitride light emitting diode is composed of a nitride semiconductor layer having a light emitting peak wavelength of <=370 nm, and the n-type contact layer 3 of the diode which is in contact with an n-electrode 9 contains AlaGa1-aN(0<a<0.1). In addition, the p-type contact layer 7 of the diode which is in contact with a p-electrode 8 contains AlbGa1-bN (0<b<0.1). It is preferable that the contact layer 7 contains a p-type impurity at a rate between 1×1018/cm3 and 1×1021/cm3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor device (In _X Al _Y Ga ₁ ) used for a light emitting device such as a light emitting diode (LED), a laser diode (LD), a solar cell, an optical sensor, and a light receiving device. _-XY N, 0 ≦ X, 0 ≦ Y, X
+ Y ≦ 1), especially when the emission peak wavelength is 370 nm.
The present invention relates to the following nitride semiconductor device that emits light in the ultraviolet region.

[0002]

2. Description of the Related Art In recent years, ultraviolet LEDs have become practical. For example, Applied Physics, Vol. 68, No. 2 (199
9) On p152 to p155, on a sapphire substrate,
GaN buffer layer, n-type GaN contact layer, n-type Al
GaN cladding layer, undoped InGaN active layer (I
n composition is almost zero), p-type AlGaN cladding layer,
A nitride semiconductor device in which a p-type GaN contact layer is laminated is described. Under a certain condition, this ultraviolet LED has an emission output of 5 mW when the emission peak is 371 nm, whereas the n-type and p-type contact layers have GaN when the emission wavelength is shorter than this. It is described that self-absorption occurs due to the fact that the emission output sharply decreases. Further, in order to prevent the emission output from lowering and shorten the oscillation wavelength, n
It has been suggested that self-absorption can be prevented by using AlGaN for the type and p-type contact layers.

[0003]

However, simply,
The contact layer should be made A to the extent that self-absorption can be sufficiently prevented.
When growing with AlGaN containing l, it is difficult to obtain ohmic contact with the electrode. Further, the cladding layer is made of AlG containing Al to confine carriers of the active layer.
Since it is made of aN, Al is formed on the p-type clad layer containing Al.
When a p-type contact layer containing Al is grown, or when an n-type clad layer containing Al is grown on an n-type contact layer containing Al, cracks tend to occur in the n-type clad layer and the p-type contact layer. is there. Thus, the conventional Ga
When the n and p-type contact layers made of N are grown as AlGaN, self-absorption in the contact layer can be prevented. However, as described above, the light emission output is sufficiently reduced due to a decrease in ohmic contact and generation of cracks. Difficult to improve.

Accordingly, an object of the present invention is to improve the light extraction efficiency by preventing self-absorption while taking into account the decrease in ohmic contact and the occurrence of cracks.
An object of the present invention is to provide a nitride semiconductor device having good emission output of 0 nm or less.

[0005]

That is, the present invention can achieve the object of the present invention by the following constitutions (1) to (4). (1) In a nitride semiconductor device having at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer on a substrate, the active layer comprises a nitride semiconductor layer having an emission peak wavelength of 370 nm or less. , An n-type contact layer in contact with the n-electrode as an n-type nitride semiconductor layer is formed of Al _a Ga _{1 -a}
N (0 <a <0.1), and as a p-type nitride semiconductor layer, a p-type contact layer in contact with a p-electrode is formed of Al _b
A nitride semiconductor device comprising Ga _{1 -bN} (0 <b <0.1). (2) The p-type contact layer contains 1 × 1 p-type impurities.
The nitride semiconductor device according to (1), wherein the nitride semiconductor device contains 0 ¹⁸ to 1 × 10 ²¹ / cm ³ . (3) The n-type contact layer contains 1 × 1 n-type impurities.
The nitride semiconductor device according to the above (1), which contains 0 ¹⁷ to 1 × 10 ¹⁹ / cm ³ . (4) Al is provided between the active layer and the n-type contact layer.
_a first nitride semiconductor layer containing eGa _{1 -eN} (0 <e <0.3); and an Al _d Ga ₁₋ between the active layer and the p-type contact layer. _{d N (0 <d <0.4} ) above, wherein further comprising a second nitride semiconductor layer comprising the (1) to (3) the nitride semiconductor device according to any one of.

That is, according to the present invention, the n-type and p-type contact layers are made of AlGaN having a specific Al composition ratio, so that good ohmic contact and crack generation can be prevented, and self-absorption in the contact layer can be prevented. Thus, it is possible to provide a nitride semiconductor device having a good emission output with an emission peak wavelength of 370 nm or less. The present inventor has conducted various studies in consideration of prevention of ohmic contact and generation of cracks as well as prevention of self-absorption. As a result, the contact layer is made of AlGaN and has a specific Al composition ratio. And self-absorption can be prevented, and the emission output can be improved. Even if the emission peak wavelength is longer than 370 nm,
Since there is also the following light emission, if the contact layer is made of AlGaN, self-absorption can be prevented and light emission output can be improved. However, when the light emission peak wavelength is 370 nm or less, the n-type and p-type
A more remarkable effect can be obtained by using AlGaN having a 1 composition ratio.

Further, according to the present invention, the p-type contact layer containing Al has a p-type impurity concentration of 1 × 10 ¹⁸ to 1 × 1.
0 ²¹ / cm ³ , preferably 5 × 10 ^{19 to} 5 × 10 ²⁰ / c
m ³ is preferable in terms of improving light emission output while maintaining ohmic contact. As described above, when the Al composition ratio of the p-type contact layer and the p-type impurity concentration are specified and combined, it is more preferable in terms of ohmic contact and crack prevention, and improvement in light emission output.

Further, according to the present invention, the n-type contact layer containing Al has an n-type impurity concentration of 1 × 10 ¹⁷ to 1 × 1.
0 ¹⁹ / cm ³ , preferably 1 × 10 ¹⁸ to 1 × 10 ¹⁹ / c
m ³ is preferable in that ohmic contact is maintained and light emission output is improved. As described above, when the Al composition ratio of the n-type contact layer and the n-type impurity concentration are specified and combined, as in the case of the p-type contact layer, it is preferable in terms of ohmic contact and crack prevention and improvement in light emission output. .

Further, according to the present invention, a first nitride semiconductor layer containing Al _e Ga _{1 -e} N (0 <e <0.3) is provided between the active layer and the n-type contact layer. And between the active layer and the p-type contact layer, Al _d Ga _{1 -dN} (0
By having the second nitride semiconductor layer containing <d <0.4), the confinement of carriers in the active layer can be improved,
It is preferable from the viewpoint of improving light emission output. Further, when the Al composition ratio of each of the first nitride semiconductor layer and the second nitride semiconductor layer is set in the above range and the Al composition ratio and the impurity concentration of the contact layer are combined, the prevention of crack generation,
Ohmic contact can be made favorable, which is preferable in terms of improvement in light emission output. Since the first nitride semiconductor layer and the second nitride semiconductor layer have a function as a clad layer, in the present invention, the first nitride semiconductor layer is hereinafter referred to as an n-type clad layer, The nitride semiconductor layer is a p-type cladding layer. However, it is not limited to this.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to FIG. FIG. 1 is a schematic sectional view of a nitride semiconductor device according to one embodiment of the present invention. In FIG.
On a substrate 1, a buffer layer 2, Al _a Ga _1-a N (0 <a <
0.1), n-type contact layer 3, Al _e Ga
_{1-e N (0 <e} <0.3) comprising an n-type cladding layer _{4, In f Ga 1-f} N (0 ≦ f <0.1) active layer 5, A of
p-type cladding layer 6 containing l _d Ga _1-d N (0 <d <0.4), p-type contact layer containing Al _b Ga _1-b N (0 <b <0.1) 7, a nitride semiconductor device having an emission peak wavelength of 370 nm or less is described. The n-type contact layer 3 has an n-electrode,
A p-type electrode is formed on each of the p-type contact layers 7. First, the n-type contact layer 3 and the p-type contact layer 7 of the present invention will be described.

[N-type contact layer 3] In the present invention,
As the n-type contact layer 3, at least Al_aGa_1-a
N (0 <a <0.1, preferably 0.01 <a <0.0
5) A nitride semiconductor layer comprising: Al composition ratio is
When the content is within the above range, the crystallinity and the ohmic property are prevented while the self-absorption is prevented.
This is preferable in terms of sonic contact. Further, the n-type contact
Layer 3 contains 1 × 10 n-type impurities.¹⁷~ 1 × 10¹⁹/ C
m ^Three, Preferably 1 × 10¹⁸~ 1 × 10¹⁹/ Cm^ThreeConcentration of
If contained, maintain ohmic contact and crack
It is preferable in terms of prevention of production and maintenance of crystallinity. Thus n
Composition ratio and n-type impurity concentration of the n-type contact layer
The combination of can prevent self-absorption and
It is preferable from the viewpoint of preventing a mic contact and a crack. n-type impurity
Is not particularly limited, for example, Si, Ge, etc.
And preferably Si. n-type contact layer
The film thickness of No. 3 is not particularly limited, but is preferably 0.1 to 20 μm.
Preferably, it is 1 to 10 μm. Film thickness
Within this range, the vicinity of the interface (for example, with the n-type cladding layer)
Of the crystallinity (as a base) and the decrease in resistivity
It is preferred in that respect.

[P-type contact layer 7] In the present invention,
As the p-type contact layer 7, at least Al _b Ga _1-b
N (0 <b <0.1, preferably 0.01 <b <0.0
5) A nitride semiconductor layer comprising: When the Al composition ratio is within the above range, it is preferable in terms of the prevention of self-absorption and the crystallinity and ohmic contact as in the case of the n-type contact layer. Further, the p-type contact layer 7 contains p-type impurities at 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ , preferably at 5 × 1
A content of 0 ^{19 to} 5 × 10 ²⁰ / cm ³ is preferable in terms of ohmic contact, prevention of crack generation, crystallinity, and bulk resistance. The combination of the Al composition ratio and the n-type impurity concentration constituting the p-type contact layer is preferable in terms of preventing self-absorption and preventing ohmic contact and cracks. The p-type impurity is not particularly limited, but preferably includes, for example, Mg. The thickness of the p-type contact layer 7 is not particularly limited, but may be 0.03
To 0.5 μm, more preferably 0.1 to 0.5 μm.
15 μm. When the film thickness is in this range, the reason is not clear, but it is preferable in terms of light extraction efficiency and light emission output.

Specifying the Al composition ratio of the n-type and p-type contact layers as described above, and further specifying and combining the impurity concentration in addition to the Al composition ratio is preferable from the viewpoint of improving the light emission output.

Further, other layers constituting the device will be described below. [Substrate 1] In the present invention, as the substrate 1, sapphire having a sapphire C-plane, an R-plane or an A-plane as a main surface, an insulating substrate such as spinel (MgA1 ₂ O ₄ ), SiC ( 6H, 4H, 3C), Si, Zn
A semiconductor substrate such as O, GaAs, or GaN can be used.

[Buffer Layer 2] In the present invention, as the buffer layer 2, Ga _g Al _{1 -g} N (where g is 0 <g ≦ 1)
Range. ), The crystallinity of the composition is more remarkably improved as the composition of Al is smaller, and the buffer layer 2 is more preferably made of GaN. The thickness of the buffer layer 2 is 0.002 to 0.5
μm, preferably in the range of 0.005 to 0.2 μm, more preferably 0.01 to 0.02 μm. When the thickness of the buffer layer 2 is in the above range, the crystal morphology of the nitride semiconductor becomes good, and the crystallinity of the nitride semiconductor grown on the buffer layer 2 is improved. The growth temperature of the buffer layer 2 is 200 to 900 ° C., preferably 40 ° C.
Adjust to the range of 0 to 800 ° C. When the growth temperature is in the above range, a favorable polycrystal is formed, and this polycrystal is preferable because the crystallinity of the nitride semiconductor grown on the buffer layer 2 as a seed crystal can be improved. The buffer layer 2 grown at such a low temperature may be omitted depending on the type of the substrate, the growth method, and the like.

[N-type contact layer 3] A nitride semiconductor containing AlGaN containing the above-mentioned n-type impurity.

[N-type cladding layer 4] In the present invention, n
The type cladding layer 4 has a composition that is larger than the band gap energy of the active layer 5 and is not particularly limited as long as carriers can be confined in the active layer 5, but a preferable composition is Al _e Ga _{1 -e.} N (0 <e <0.
3, preferably 0.1 <e <0.2). It is preferable that the n-type cladding layer is made of such AlGaN in terms of confining carriers in the active layer. n
The thickness of the mold cladding layer is not particularly limited, but is preferably 0.01 to 0.1 μm, more preferably 0.0 to 0.1 μm.
3 to 0.06 μm. The n-type impurity concentration of the n-type cladding layer is not particularly limited, but is preferably 1 × 10 ¹⁷ to
1 × 10 ²⁰ / cm ³ , more preferably 1 × 10 ¹⁸
１1 × 10 ¹⁹ / cm ³ . It is preferable that the impurity concentration be in this range in terms of resistivity and crystallinity.

The n-type cladding layer may be a multilayer layer (including a superlattice structure) in addition to the single layer as described above. In the case of a multilayer film layer, a multilayer film layer composed of the above Al _e Ga _1-e N and a nitride semiconductor layer having a smaller band gap energy may be used. , In _h Ga _1-h N
(0 ≦ h <1), Al _j Ga _1-j N (0 ≦ j <1, e>)
j). The thickness of each layer forming the multilayer film layer is
Although not particularly limited, in the case of a superlattice structure, the thickness of one layer is 100 angstrom or less, preferably 70 angstrom or less, more preferably 10 to 40 angstrom. It can be a layer composed of a composition. In the case where the n-type cladding layer is a multilayer film layer including a layer having a large band gap energy and a layer having a small band gap energy, at least one of the layer having a large band gap energy and the layer having a small band gap energy is doped with an n-type impurity. May be. When doping both the layer having a large band gap energy and the layer having a small band gap energy, the doping amount may be the same or different.

[Active Layer 5] In the present invention, the active layer 5 includes a nitride semiconductor having a composition such that the emission peak wavelength is 370 nm or less. Preferably an In _f G
a _1-f N (0 ≦ f <0.1) nitride semiconductor; The In composition ratio of the active layer decreases as the emission peak wavelength becomes shorter, but the In composition ratio becomes almost zero. The thickness of the active layer is not particularly limited, but may be a thickness at which a quantum effect can be obtained, for example, preferably 0.001 to 0.01 μm, and more preferably 0.003 to 0.007 μm. is there. It is preferable that the film thickness is in the above range in terms of light emission output.
The active layer consists in addition of a single quantum well structure as described above, the well layer and the In _f Ga _1-f N, a barrier layer having the composition larger bandgap energy than the well layer multiplexing It may be a quantum well structure. The active layer may be doped with impurities.

The adjustment of the In composition ratio in the active layer is not particularly limited as long as the In composition ratio at which the emission peak wavelength becomes 370 nm or less is used. Specific values include, for example, calculation of the following theoretical values. A value obtained from the equation can be given as an approximate value. However, the wavelength obtained by actually emitting light has a quantum level having a quantum well structure, so that the energy of the wavelength (Eλ) is larger than the band gap energy (Eg) of InGaN. There is a tendency to shift to a shorter wavelength side than the required emission wavelength.

[Calculation formula of theoretical value] Eg = (1-χ) 3.40 + 1.95χ-Bχ (1-
χ) wavelength (nm) = 1240 / Eg Eg: band gap energy of InGaN well layer χ: composition ratio of In 3.40 (eV): band gap energy of GaN 1.95 (eV): band gap energy of InN B : Indicates a bowing parameter, which is 1 to 6 eV. The variation of the Boeing parameter like this is
In recent studies, from SIMS analysis and the like, it has been conventionally assumed that the crystal has no distortion, but it is set to 1 eV. It is becoming clear that

[P-type cladding layer 6]
The type cladding layer 6 is not particularly limited as long as it has a composition larger than the band gap energy of the active layer 5 and can confine carriers in the active layer 5, but is preferably Al _d Ga _{1 -dN.} (0 <d <0.4, preferably 0.15 <d <0.3).
When the p-type cladding layer is made of such AlGaN,
This is preferable in terms of confining carriers in the active layer. The thickness of the p-type cladding layer is not particularly limited, but is preferably 0.01 to 0.15 μm, more preferably 0.01 to 0.15 μm.
4 to 0.08 μm. The p-type impurity concentration of the p-type cladding layer is not particularly limited, but is preferably 1 × 10 ¹⁸ to
1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ¹⁹
５5 × 10 ²⁰ / cm ³ . It is preferable that the p-type impurity concentration is within the above range, since the bulk resistance is reduced without lowering the crystallinity.

The p-type cladding layer may be a multilayer layer (including a superlattice structure) in addition to the single layer described above. In the case of a multilayer film layer, it may be a multilayer film layer composed of the above Al _d Ga _1-d N and a nitride semiconductor layer having a smaller band gap energy. , In _h Ga ₁ -hN (0 ≦ h <1), Al _j
Ga _1-j N (0 ≦ j <1, e> j). The thickness of each layer forming the multilayer film layer is not particularly limited, but in the case of a superlattice structure, the thickness of each layer is 100 Å or less, preferably 70 Å or less, more preferably 10 to 40 Å. In the case of a single layer that does not form a structure, it can be a layer having the above composition. Further, when the p-type cladding layer is a multilayer film layer including a layer having a large band gap energy and a layer having a small band gap energy, at least one of the layer having a large band gap energy and the layer having a small band gap energy is doped with a p-type impurity. May be. When doping both the layer having a large band gap energy and the layer having a small band gap energy, the doping amount may be the same or different.

[P-type contact layer 7] A nitride semiconductor containing AlGaN containing the above-mentioned p-type impurity.

In the present invention, various types of p-electrode and n-electrode can be used, and are appropriately selected from known electrode materials and the like. Specific examples of the electrode include those described in Examples below. Although the present invention has been described with reference to FIG. 1 as an embodiment of the element structure, the emission peak wavelength is 370 nm or less, and both the n-type contact layer and the p-type contact layer are made of AlGaN having a specific Al composition ratio. If this is the case, the effect of the present invention can be obtained. In addition to FIG. 1, other layers may be formed in order to improve element characteristics such as electrostatic withstand voltage, forward voltage, and life characteristics.

In the device of the present invention, an annealing process is performed to make the p-side layer p-type and have a low resistance. The annealing process is described in Japanese Patent No. 2540791.
As described above, after growing a gallium nitride-based compound semiconductor doped with a p-type impurity by a vapor phase growth method, the gallium nitride-based compound semiconductor is heated at 400 ° C. in an atmosphere substantially containing no hydrogen.
There is a method in which a heat treatment is performed at the above temperature to generate hydrogen from a gallium nitride-based compound semiconductor doped with a p-type impurity to make the semiconductor p-type.

[0027]

The present invention will be described below in more detail with reference to examples which are embodiments of the present invention. However, the present invention is not limited to this.

Example 1 In Example 1, the nitride semiconductor device of FIG. 1 is manufactured. (Substrate 1) The surface of the substrate 1 made of sapphire (C plane) is cleaned at 1050 ° C. in a hydrogen atmosphere in a reaction vessel.

(Buffer Layer 2) Subsequently, in a hydrogen atmosphere,
At 510 ° C., a buffer layer 2 made of GaN is grown on the substrate 1 to a thickness of about 200 angstroms using ammonia and TMG (trimethylgallium).

(N-type contact layer 3) Next, at 1050 ° C., using TMG, TMA (trimethylaluminum), ammonia, and silane (SiH ₄ ), Si is formed at 5 × 10 ¹⁸ / c.
An n-type contact layer 3 made of m ³ -doped n-type Al _0.04 Ga _0.96 N is grown to a thickness of 4 μm.

(N-type cladding layer 4) Next, at 1050 ° C., T
Using MG, TMA, ammonia, silane, Si is 5 ×
An n-type cladding layer 4 made of n-type Al _0.18 Ga _0.82 N doped with 10 ¹⁷ / cm ³ is formed to a thickness of 400 Å.

(Active layer 5) Next, at 700 ° C. in a nitrogen atmosphere.
Undoped In using TMI, TMG and ammonia
An active layer made of GaN is grown to a thickness of 55 Å. The In composition ratio is so small (almost zero) that it cannot be measured.

(P-type cladding layer 6) Next, in a hydrogen atmosphere,
TMG, TMA, ammonia, Cp ₂ Mg at 1050 ° C
Using (cyclopentadienyl magnesium), a p-type cladding layer 6 made of Al _0.2 Ga _0.8 N doped with Mg at 1 × 10 ²⁰ / cm ³ is grown to a thickness of 600 Å.

(P-type contact layer 7) Subsequently, TMG,
Mg is 1 × 10 ²⁰ with TMA, ammonia and Cp ₂ Mg.
A p-type contact layer 7 of Al _0.04 Ga _0.96 N doped with / cm ³ is grown to a thickness of 0.12 μm.

After the growth is completed, the wafer is annealed in a nitrogen atmosphere in a reaction vessel at 700 ° C.
After further reducing the resistance of the mold layer, the wafer is taken out of the reaction vessel, a mask having a predetermined shape is formed on the surface of the uppermost p-type contact layer 7, and the p-type contact layer is formed by an RIE (reactive ion etching) apparatus. Etching from the side,
As shown in FIG. 1, the surface of the n-type contact layer 3 is exposed.

After the etching, almost 200 angstrom of Ni is deposited on almost the entire surface of the uppermost p-type contact layer 7.
And a translucent p-electrode 8 containing Au and Au, and a p-pad electrode 10 made of Au for bonding on the p-electrode 8.
It is formed with a thickness of 2 μm. On the other hand, an n-electrode 9 containing W and Al is formed on the surface of the n-type contact layer 3 exposed by etching. Finally, after an insulating film made of SiO ₂ is formed to protect the surface of the p-electrode 8, the wafer is separated by scribing to obtain LED elements of 350 μm square.

This LED element has an emission peak wavelength of 370 nm at a forward voltage of 20 mA, and Vf is 3.
8V, output is 1.2 mW. The light extraction efficiency of the LED of the first embodiment is such that the conventional n-type and p-type contact layers
It is almost 1.5 times as large as those not including l.

[0038]

According to the present invention, as described above, by using AlGaN in which the Al composition ratio of the n-type and p-type contact layers is specified, the self-contained structure can be formed while considering the reduction of ohmic contact and the generation of cracks. It is possible to improve the light extraction efficiency by preventing absorption and provide a nitride semiconductor device having a good light output of 370 nm or less. Further, in the present invention, even better effects can be obtained by combining the Mg concentration of the n-type and p-type contact layers and the specific clad layer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an LED according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Buffer layer 3 ... N-type contact layer 4 ... N-type cladding layer 5 ... Active layer 6 ... P-type cladding layer 7 ... P-type contact layer 8 ... p electrode 9 ... n electrode 10 ... pad electrode

Claims (4)

[Claims] 1. A nitride semiconductor device having at least an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer on a substrate, wherein the active layer has an emission peak wavelength of 370 nm or less. The n-type contact layer in contact with the n-electrode comprises Al _a Ga _{1 -aN} (0 <a <0.1), and the p-type nitride semiconductor layer comprises p-type contact layer in contact with the p _{electrode, Al b Ga 1 -b N (} 0 <b <0.1) nitride semiconductor device characterized by comprising. 2. The nitride semiconductor device according to claim 1, wherein said p-type contact layer contains a p-type impurity at 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ . 3. The nitride semiconductor device according to claim 1, wherein said n-type contact layer contains an n-type impurity in an amount of 1 × 10 ¹⁷ to 1 × 10 ¹⁹ / cm ³ . 4. A semiconductor device comprising a first nitride semiconductor layer containing Al _e Ga _{1 -eN} (0 <e <0.3) between the active layer and the n-type contact layer, , Between the active layer and the p-type contact layer, Al _d Ga _{1 -dN} (0 <d <0.
The nitride semiconductor device according to any one of claims 1 to 3, further comprising a second nitride semiconductor layer containing (4).