JP2001060719A - Nitride semiconductor light emitting diode - Google Patents

Abstract

An object of the present invention is to provide a nitride semiconductor device which emits light in an ultraviolet region having a light emission peak wavelength of 380 nm or less with high light emission efficiency and good light emission output. SOLUTION: An element structure made of a nitride semiconductor having an emission peak wavelength of 380 nm or less is formed on a nitride semiconductor substrate 1 having a dislocation density of 10 ⁶ / cm ² or less.

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 380 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 reached a practical level. 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. This ultraviolet LED has an emission output of 5 mW when the emission peak wavelength is 371 nm.

[0003]

However, the ultraviolet L
In order to expand the range of application of the ED, it is desired to further shorten the wavelength. However, when the emission peak wavelength is shorter than 371 nm, the emission output sharply decreases. Although the reason for this is not clear, it is considered that the luminous efficiency of the active layer is extremely reduced in a state where the amount of In is very small or no In is contained. If the luminous efficiency of an ultraviolet LED, particularly an LED having an emission peak wavelength shorter than 371 nm, can be improved, many applications including an excitation light source are possible.

An object of the present invention is to provide a nitride semiconductor device which emits light in an ultraviolet region having a light emission peak wavelength of 380 nm or less with high light emission efficiency and good light emission output.

[0005]

That is, the present invention can achieve the object of the present invention by the following constitutions (1) and (2). (1) A nitride semiconductor light emitting diode comprising a nitride semiconductor substrate having an emission peak wavelength of 380 nm or less formed on a nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less. (2) The nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less is formed on a heterogeneous substrate or a nitride semiconductor substrate made of a material different from the nitride semiconductor by utilizing lateral growth of the nitride semiconductor. The nitride semiconductor device according to the above (2), which is grown.

That is, according to the present invention, by forming an element structure on a nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less, an emission peak wavelength having good luminous efficiency of 380 nm or less is obtained. A nitride semiconductor device can be provided.

Conventionally known blue and green LEDs have high luminous efficiency and have already been commercialized. This blue and green L
EDs are grown on sapphire substrates having different lattice constants, and have good luminous efficiency despite the presence of many threading dislocations due to lattice constant mismatch. on the other hand,
Ultraviolet LEDs, like blue and green LEDs, are grown on sapphire substrates. However, as described above, the luminous output is low due to poor luminous efficiency, and the luminous output is extremely low particularly at wavelengths shorter than 371 nm. .

As a result of various studies on such a difference in luminous efficiency, the present inventor thought that there is a great difference in the luminescence mechanism depending on the In composition ratio of the active layer. The difference in the light emission mechanism is described in the aforementioned Applied Physics,
The blue LED described in Vol. 8, No. 2 shifts blue as the forward current increases, but the UV LE
In the case of D, it can be inferred from the fact that the red shift occurs as the forward current increases. In addition, at the threading dislocation due to the lattice constant mismatch with the sapphire substrate, the carriers injected into the active layer are non-radiatively recombined and do not participate in light emission. In the case of a blue or green LED, inhomogeneous In composition probably occurs in the active layer, the band gap energy of the portion containing a large amount of In decreases, and a potential valley is formed. It is considered that the carriers confined in the valley of the potential are well confined, and the carriers confined in the valley of the potential have high luminous efficiency because of good radiative recombination. On the other hand, in the case of an ultraviolet LED, since the In content of the active layer is very small, the potential valley generated due to non-uniform In composition is shallow, and the density of the potential valley is small. The effect of confining the carriers injected into the layer is small, and as a result, a part of the carriers injected into the active layer reaches the non-radiative recombination center by diffusion and non-radiative recombination, so that the luminous efficiency deteriorates. Conceivable.

Therefore, the present inventor has made a study based on the consideration as described above as to whether the cause of the decrease in luminous efficiency in the active layer may be due to the formation of non-radiative recombination centers due to threading dislocations. By using a nitride semiconductor having a small number of threading dislocations as a non-radiative recombination center as a substrate, it is possible to achieve good radiative recombination of carriers and improve luminous efficiency. The present invention solves the problem that the luminous efficiency is extremely reduced in the case of an LED having an emission peak wavelength of 380 nm or less, by using a nitride semiconductor having a very small or almost no dislocation density as a substrate. The efficiency can be improved. In the present invention, the method for measuring the dislocation density is based on observation with a transmission electron microscope (T
EM method). According to this TEM method, the dislocation density is 10
^When a nitride semiconductor substrate having a density of ⁶ / cm ² or less is used, luminous efficiency can be improved satisfactorily. Dislocation density is 10 ⁶
/ Cm ² or less indicates a state where the dislocation density is almost zero or no dislocation exists.

In the present invention, a nitride semiconductor having a dislocation density of 10 ⁶ / cm ² or less as a substrate is placed on a heterogeneous substrate or a nitride semiconductor substrate made of a material different from the nitride semiconductor. Growth using growth in the direction (EL
OG growth (epitaxially laterally overgrown GaN growth) is preferable in that dislocation density can be reduced favorably, non-radiative recombination at threading dislocations is prevented, and luminous efficiency is improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A nitride semiconductor device of the present invention is formed by growing on a nitride semiconductor substrate having at least an emission peak wavelength of 380 nm or less and a dislocation density of 10 ⁶ / cm ² or less. If it is, there is no particular limitation. Specific preferred elements include, for example, the element shown in FIG. FIG. 1 is a schematic sectional view of a nitride semiconductor device according to one embodiment of the present invention. FIG. 1 shows that on a GaN substrate 1 having a dislocation density of 10 ⁶ / cm ² or less,
Buffer layer 2, n-type contact layer 3 containing Al _a Ga _1-a N (0 ≦ a <0.1), Al _e Ga _1-e N (0 <e
<N-type cladding layer 4 comprising 0.3), In _f Ga
Active layer 5 of _1-fN (0 ≦ f <0.1), Al _d Ga _1-d N
P-type cladding layer 6 containing (0 <d <0.4), A
_{l b Ga 1-b N (} 0 ≦ b <0.1) are stacked grow a p-type contact layer 7 comprising becomes, the emission peak wavelength of 3
A nitride semiconductor device of 80 nm or less is described. An n-electrode is formed on the n-type contact layer 3, and a p-electrode is formed on the p-type contact layer 7.

Hereinafter, a nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less for forming an element structure will be described. [Nitride Semiconductor Substrate 1] In the present invention, as the nitride semiconductor substrate 1 for forming an element structure, a nitride semiconductor made of GaN having a dislocation density of 10 ⁶ / cm ² or less can be mentioned. GaN with a dislocation density of 10 ⁶ / cm ² or less
Is not particularly limited, and any growth method may be used as long as at least the dislocation density is reduced. For example, preferably, a growth method (ELOG growth) in which vertical growth of a nitride semiconductor is at least partially temporarily stopped and dislocations can be suppressed by utilizing horizontal growth can be given.

For example, as a specific example of ELOG growth, a protective film made of a material on which a nitride semiconductor does not grow or hardly grows is partially formed on a heterogeneous substrate made of a material different from that of a nitride semiconductor. The nitride semiconductor grows from a portion where the protective film is not formed by growing the nitride semiconductor from the above, and the nitride semiconductor grows in a lateral direction toward the protective film by continuing the growth, thereby forming a thick nitride semiconductor. (ELOG substrate). As such a growth method, for example, Japanese Patent Application No.
-275826, Japanese Patent Application No. 10-119377, Japanese Patent Application No. 10-146431, Japanese Patent Application No. 11-37826,
The method described in each specification is mentioned.

Another specific example of ELOG growth is a method without using a protective film. In this method, irregularities are formed on a nitride semiconductor grown on a heterogeneous substrate made of a material different from that of the nitride semiconductor. A growth method for obtaining a nitride semiconductor (ELOG substrate) by growing a nitride semiconductor again from above. In addition, there is a method in which the surface of the nitride semiconductor is partially modified without using a protective film so that the lateral growth of the nitride semiconductor is intentionally performed. As such a growth method, for example, Japanese Patent Application No. 11-378227.
No., Japanese Patent Application No. 11-168079, Japanese Patent Application No. 11-142
No. 400, the method described in each specification.

Further, a nitride semiconductor obtained by the above-described ELOG growth or the like is used as a substrate, and the above-described protective film is used on the nitride semiconductor, or a method such as forming unevenness is used. There is a growth method for obtaining a nitride semiconductor in which dislocation is favorably reduced by repeating ELOG growth. As such a growth method, for example, Japanese Patent Application No.
80288.

The above-mentioned ELOG growth is preferably a method of growing without using a protective film, and a method of growing ELOG on a nitride semiconductor. Such a method is preferable in terms of reducing dislocations, and it is preferable to form an element structure on an ELOG substrate in which dislocations are reduced in terms of reduction in threshold current density and improvement in life characteristics. The details of the ELOG growth method mentioned above are as described in the above-listed specifications, but a preferred example is shown below. However, the present invention is not limited to this.

An embodiment of a preferred ELOG growth that can be used in the present invention will be described below with reference to FIG. FIG. 2 (a-1 to a-4) is a schematic view showing stepwise an embodiment of a nitride semiconductor growing method. First, in the first step of FIG.
1 is grown on the first nitride semiconductor 42, and FIG.
In the second step of 2), irregularities are formed on the first nitride semiconductor 42. Subsequently, in the third step of FIG. 2A-3, the first nitride semiconductor 42 having the irregularities is formed. above,
The second nitride semiconductor 43 is grown under normal pressure or higher pressure conditions.

Hereinafter, each of the above steps will be described in more detail with reference to FIG. (First Step) FIG. 2A-1 is a schematic step view in which a first step of growing a first nitride semiconductor 42 on a heterogeneous substrate 41 is performed. In the first step, as the heterogeneous substrate 41 that can be used, for example,
Surface, and sapphire to either the main surface of the surface A, the insulating substrate such as spinel _{(MgA1 2 O 4), SiC} (6
H, 4H, 3C), ZnS, ZnO, GaAs,
Si, and oxide substrates lattice-matched with nitride semiconductors, etc.
A substrate material different from a conventionally known nitride semiconductor can be used. Preferred heterosubstrates include sapphire and spinel. When sapphire is used as a dissimilar substrate, the orientation of the nitride semiconductor on the upper portion of the projection and the side surface of the depression when the unevenness is formed tends to be specified depending on which surface is the main surface of the sapphire. Because the growth rate of nitride semiconductors is slightly different,
The main surface may be selected such that a plane orientation that facilitates growth is provided on the side surface of the concave portion.

In the first step, the heterogeneous substrate 41
Before growing the first nitride semiconductor 42 thereon, a buffer layer (not shown) may be formed on the heterogeneous substrate 41. AlN, GaN, AlG
aN, InGaN or the like is used. The buffer layer is 90
At a temperature of 0 ° C. or less and 300 ° C. or more, a film thickness of 0.5 μm to 10 μm
Growing in Angstrom. Thus, the heterogeneous substrate 1
When the buffer layer is formed thereon at a temperature of 900 ° C. or lower, the lattice constant between the heterogeneous substrate 41 and the first nitride semiconductor 42 is reduced, and the crystal defects of the first nitride semiconductor 42 tend to be reduced. .

In the first step, as the first nitride semiconductor 42 formed on the heterogeneous substrate 41, undoped GaN, S
GaN doped with n-type impurities such as i, Ge, and S can be used. The first nitride semiconductor 42 is grown on the heterogeneous substrate 41 at a high temperature, specifically, higher than about 900 ° C. to 1100 ° C., preferably 1050 ° C. When grown at such a temperature, first nitride semiconductor 42 becomes a single crystal. Although the thickness of the first nitride semiconductor 42 is not particularly limited, the thickness of the first nitride semiconductor 42 can be adjusted so that the growth in the vertical direction inside the concave portion can be suppressed and the growth in the horizontal direction can be promoted. And preferably at least 50
The film is formed to have a thickness of 0 Å or more, preferably 5 μm or more, more preferably 10 μm or more.

(Second Step) Next, FIG. 2A-2 shows that after the first nitride semiconductor 42 is grown on the heterogeneous substrate 41, the first nitride semiconductor 42 is partially roughened. Is formed, and the first nitride semiconductor 42 is exposed on the side surface of the concave portion.

In the second step, the step of partially forming the unevenness means that the first nitride semiconductor 4 is formed at least on the side surface of the concave portion.
A recess may be formed in the direction of the heterogeneous substrate 41 from the surface of the first nitride semiconductor 42 so that 2 is exposed. Irregularities may be provided in the first nitride semiconductor 42 in any shape. For example, they can be formed in random depressions, stripes, grids, or dots. A preferable shape is a stripe shape, and this shape is preferable because it has less abnormal growth and is buried more flat. First nitride semiconductor 4
2 are partially provided on the first nitride semiconductor 4.
Etching up to the middle of 2, the depth reaching the heterogeneous substrate, or the depth reaching the heterogeneous substrate, the etching depth is 50
0-3000 angstroms (preferably 1000-
2000 angstrom), preferably a depth such that a heterogeneous substrate is exposed, or a shape obtained by shaving a heterogeneous substrate at the above-described depth. More preferably, the heterogeneous substrate is formed at the above-described depth. The shape shaved off is preferable.

The shape of the concavities and convexities is not particularly limited, such as the length of the side surface of the concave portion, the width of the upper portion of the convex portion and the width of the bottom portion of the concave portion. It is preferable that the second nitride semiconductor 43 grown in the film is adjusted so as to grow laterally from the side surface of the concave portion. When the shape of the unevenness is a stripe shape, the shape of the stripe is not particularly limited. For example, the stripe width (width of the upper portion of the convex portion) is 1 to 20 μm, preferably 1 to 10 μm, and the stripe interval (width of the lower portion of the concave portion). Is 10 to 40 μm, preferably 15 to 35 μm. Having such a stripe shape is preferable in terms of reducing dislocations and improving the surface state. Increasing the portion of the second nitride semiconductor 43 that grows from the opening of the concave portion can be achieved by increasing the width of the bottom portion of the concave portion and decreasing the width of the upper portion of the convex portion, thereby reducing dislocations. Can be more. When the width of the bottom of the recess is increased, it is preferable to increase the depth of the recess in order to prevent the growth in the vertical direction that may grow from the bottom of the recess.

As a method of providing irregularities in the second step,
Any method may be used as long as the first nitride semiconductor 42 can be partially removed, and examples thereof include etching and dicing. When unevenness is formed partially (selectively) on the first nitride semiconductor 42 by etching, using a mask pattern of various shapes in photolithography technology, a photomask such as a stripe shape or a grid shape is used. Fabricate the resist pattern first
Formed on the nitride semiconductor 2 and then etched. The photomask is removed after etching to form irregularities. When dicing is performed, for example, it can be formed in a stripe shape or a grid shape.

The method of etching the nitride semiconductor in the second step includes wet etching, dry etching, and the like. To form a smooth surface, dry etching is preferably used. Dry etching includes, for example, devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and ion beam etching. It can be formed by etching a nitride semiconductor. For example, a specific nitride semiconductor etching means described in Japanese Patent Application Laid-Open No. H8-17803 previously filed by the present applicant can be used. In the case where unevenness is formed by etching, the etched surface (the side surface of the concave portion) is formed as shown in FIG.
As shown in 2), there may be a shape in which the end face is substantially perpendicular to the heterogeneous substrate, a forward mesa shape or an inverted mesa shape, or a shape formed in a step shape. Preferably, from the viewpoint of reduction of dislocation and good surface condition,
Inverse mesas, forward mesas, and more preferably vertical.

In the second step, when the unevenness is formed in a stripe shape, the stripe is formed as shown in FIG.
As shown in the figure, the orientation flat surface is, for example, a surface A of sapphire, and either left or right with respect to a vertical axis of the orientation flat surface,
θ = 0.1 ° to 1 °, preferably θ = 0.1 ° to 0.5
It is preferable to form the crystal by shifting the crystal by a good angle because a good crystal having a more flat growth surface can be obtained. By the way, when θ in FIG. 5B is 0 °, the surface may not be flat, and when the element structure is formed on the growth surface in such a state, there is a tendency that the element characteristics are likely to deteriorate. Can be A flat surface is also preferable in terms of improving the yield.

(Third Step) Next, FIG.
First nitride semiconductor 42 having irregularities by etching
On top of the second nitride semiconductor 4
FIG. 13 is a schematic cross-sectional view showing a state where a third step of growing a third layer is performed. As the second nitride semiconductor 43, the same as the first nitride semiconductor 42 can be used. Second
The growth temperature of the nitride semiconductor 43 is the same as that for growing the first nitride semiconductor 42, and the second nitride semiconductor 43 grown at such a temperature is a single crystal. Further, when growing the second nitride semiconductor 43, impurities (for example, Si, Ge, Sn, Be, Zn, Mn, Cr,
And Mg, etc.), or the molar ratio of the group III and group V components (II
It is preferable in that the growth in the lateral direction is promoted as compared with the growth in the vertical direction to reduce dislocations by performing growth while adjusting the molar ratio of I / V, and the like. It is preferable in terms of improving the condition.

The above-mentioned pressurizing condition that is equal to or higher than the normal pressure is a condition in which the device or the like is adjusted from normal pressure (pressure in a state where no pressure is intentionally applied) to intentionally apply a pressure to obtain a pressurizing condition. To perform the reaction. The specific pressure is not particularly limited as long as it is equal to or higher than normal pressure, but is preferably from normal pressure (approximately 1 atm) to 2.5 atm.
Normal pressure to 1.5 atm. It is preferable to grow the second nitride semiconductor under such a pressure condition in that the surface state of the surface of the second nitride semiconductor is improved.

In the third step, it is considered that some of the inside of the concave portion grow laterally from the side surface of the concave portion, and some grow vertically from the bottom portion of the concave portion. The second nitride semiconductors grown from the side surfaces are bonded to each other to suppress the growth from the bottom of the concave portion. As a result, almost no dislocation is seen in the second nitride semiconductor grown from the opening of the concave portion. The growth rate in the vertical direction from the bottom of the concave portion seems to be slower than that in the lateral direction from the side surface of the concave portion. In addition, when the surface of the bottom of the concave portion is a heterogeneous substrate such as sapphire, the growth of the second nitride semiconductor from the bottom of the concave portion is suppressed, and the growth of the second nitride semiconductor from the side surface of the concave portion is improved. It is preferable in terms of reduction of the amount.

On the other hand, in the second nitride semiconductor portion grown from the upper portion of the convex portion, dislocations slightly larger than those grown from the opening portion of the concave portion are observed, but the second nitride semiconductor portion starts growing vertically in the upper portion of the convex portion. The nitride semiconductor also tends to grow in the lateral direction toward the opening of the concave portion rather than in the vertical direction, and dislocations are reduced as compared with the case where the nitride semiconductor is grown in the vertical direction without forming irregularities. Further, by repeating the second and third steps of the present invention, dislocations at the upper portion of the convex portion can be eliminated. In addition, the second nitride semiconductor grown from the upper portion of the convex portion and the inside of the concave portion is joined during the growth process, and becomes as shown in FIG.

Further, in the third step, when growing the second nitride semiconductor, the pressure is adjusted to a pressure condition equal to or higher than the normal pressure, so that the surface of the second nitride semiconductor becomes abnormally grown. A good and flat surface state is obtained.

In the present invention, when the second and third steps are repeated, as shown in FIG.
The second nitride semiconductor is partially formed with projections and depressions such that the projections are located above the depressions formed in the nitride semiconductor and the depressions are located above the projections formed in the first nitride semiconductor. Then, the third nitride semiconductor 4 is grown on the second nitride semiconductor having the unevenness. The third nitride semiconductor 4 is preferably a nitride semiconductor having few dislocations as a whole. As the third nitride semiconductor, the same as the second nitride semiconductor is grown. Further, when the second and third steps are repeated, the second nitride semiconductor is grown slightly thinner than when it is not repeated, and the bottom of the concave portion formed in the second nitride semiconductor is made of sapphire. Etching the second nitride semiconductor so as to form a heterogeneous substrate surface such as that described above is preferable because a third nitride semiconductor having less dislocations and a good surface state can be obtained.

The second nitride semiconductor 43 serves as a substrate on which a nitride semiconductor for forming an element structure is grown. The formation of the element structure is performed after removing a different kind of substrate in advance. In some cases, the process is performed while leaving a different substrate or the like. In some cases, the heterogeneous substrate is removed after the element structure is formed. The thickness of the second nitride semiconductor 5 when removing a heterogeneous substrate or the like is 50 μm or more, preferably 100 μm or more.
m, preferably 500 μm or less. When the thickness is in this range, the second nitride semiconductor 43 is less likely to be broken even when the heterogeneous substrate, the protective film, and the like are polished and removed, so that handling is preferable.

The thickness of the second nitride semiconductor 43 in the case where a different substrate or the like is left is not particularly limited.
It is 0 μm or less, preferably 50 μm or less, more preferably 20 μm or less. Within this range, warpage of the wafer due to the difference in thermal expansion coefficient between the heterogeneous substrate and the nitride semiconductor can be prevented, and a nitride semiconductor having an element structure can be favorably grown on the second nitride semiconductor 45 serving as an element substrate. Can be done.

In the method for growing a nitride semiconductor of the present invention, the method for growing the first nitride semiconductor 42 and the second nitride semiconductor 43 is not particularly limited.
MOVPE (metalorganic vapor phase epitaxy), HVPE (halide vapor phase epitaxy), MBE (molecular beam epitaxy), M
All methods known for growing nitride semiconductors, such as OCVD (metal organic chemical vapor deposition), can be applied. As a preferable growth method, when the film thickness is 100 μm or less, the growth rate can be easily controlled by using the MOCVD method. When the film thickness is less than 100 μm, HVPE has a high growth rate and is difficult to control.

In the present invention, since a nitride semiconductor having an element structure can be formed on the second nitride semiconductor 43, the second nitride semiconductor is used in the specification as an element substrate or a nitride. It may be called a semiconductor substrate.

Further, it is preferable to use a substrate in which the main surface of the material to be the heterogeneous substrate in the first step is off-angled, and further a substrate whose stepped off-angle is used. When a substrate with an off-angle is used, three-dimensional growth is not observed on the surface, and step growth appears, so that the surface tends to be flat. Furthermore, when the direction (step direction) along the step of the sapphire substrate that is off-angled in a step shape is formed perpendicular to the A-plane of sapphire, the step surface of the nitride semiconductor is aligned with the cavity direction of the laser. Matches,
This is preferable because laser light is less likely to be irregularly reflected due to surface roughness.

Further preferred heterogeneous substrates include (000
1) Sapphire whose main surface is plane [C-plane], (112-0)
Sapphire whose main surface is the [A-plane] or spinel whose main surface is the (111) plane. Here, the heterogeneous substrate is (00
01) When the sapphire has the [C-plane] as the main surface, the uneven stripe shape formed on the first nitride semiconductor or the like is different from the (112-0) -plane [A-plane] of the sapphire. [It is preferable to form a stripe in a direction parallel to the (101-0) [M plane] of the nitride semiconductor], and the off angle off angle θ (see FIG. 7). Θ) shown is 0.1 ° to 0.5 °, preferably 0.1 ° to 0.2 °. Also (112-0)
When the sapphire is a sapphire whose main surface is the plane [A-plane], the stripe shape of the irregularities is (11-02) plane of the sapphire.
It is preferable that the spinel has a stripe shape perpendicular to the [R-plane]. When the spinel has a (111) plane as a main surface, the uneven stripe shape is in relation to the (110) plane of the spinel. And preferably have a vertical stripe shape. Here, the case where the irregularities are in the form of stripes is described. However, in the present invention, the nitride semiconductor easily grows in the lateral direction on the A and R planes of sapphire and the (110) plane of spinel. Nitride semiconductor 2 such that an end face of the first nitride semiconductor is formed.
In order to form a step, it is preferable to consider formation of a protective film.

The heterogeneous substrate used in the present invention will be described in more detail with reference to the drawings. FIG. 3 is a unit cell diagram showing the crystal structure of sapphire. First, in the method of the present invention, a case will be described in which sapphire having a C-plane as a main surface is used, and the unevenness has a stripe shape perpendicular to the sapphire A-plane. For example, FIG. 5A is a plan view of a sapphire substrate on the main surface side. In this figure, the sapphire C plane is the main surface, and the orientation flat (orientation flat) surface is the A surface. As shown in the figure, stripes having irregularities are formed in parallel with each other in a direction perpendicular to the A-plane. As shown in FIG. 5A, when a nitride semiconductor is selectively grown on a sapphire C plane, the nitride semiconductor easily grows in a plane parallel to the A plane and grows in a vertical direction. It tends to be difficult. Therefore, if the stripes are provided in a direction perpendicular to the A-plane, the nitride semiconductors between the stripes are connected and grow easily, and it is thought that the crystal growth as shown in FIG. 2 can be easily performed. Details are not clear. Further, as described above, as shown in FIG. 5B, it is preferable to slightly shift the surface state because the surface state becomes good.

Next, when a sapphire substrate having the A surface as the main surface is used, similarly to the case where the C surface is the main surface, for example, if the orientation flat surface is an R surface, the orientation flat surface is perpendicular to the R surface. By forming stripes parallel to each other, a nitride semiconductor tends to grow in the stripe width direction, so that a nitride semiconductor layer with few crystal defects can be grown.

Next, also for spinel (MgAl ₂ O ₄ ), the growth of the nitride semiconductor is anisotropic, the growth surface of the nitride semiconductor is (111) plane, and the orientation flat surface is (11).
When the plane is the 0) plane, the nitride semiconductor tends to grow in a direction parallel to the (110) plane. Therefore, (11
When a stripe is formed in the direction perpendicular to the 0) plane, the nitride semiconductor layer and the adjacent nitride semiconductor are connected to each other at the upper portion of the protective film, and a crystal having few crystal defects can be grown. The spinel is not shown in the figure because it is tetragonal.

In the following, the direction along the steps of the sapphire substrate that has been off-angled corresponds to the A of the sapphire substrate.
The case of being formed perpendicular to the plane will be described with reference to FIG. The dissimilar substrate such as sapphire, which is off-angled in a step shape, has a substantially horizontal terrace portion A and a step portion B as shown in FIG. Terrace part A
Have few surface irregularities and are almost regularly formed.
The step portion having such an off angle θ is desirably formed continuously over the entire substrate, but may be formed particularly partially. Note that the off angle θ
4 indicates the angle between the straight line connecting the bottoms of the plurality of steps and the horizontal plane of the uppermost step as shown in FIG. The off-angle of the heterogeneous substrate is 0.1 ° to 0.5 °, preferably 0.1 ° to 0.2 °. When the off angle is in the above range, the surface of the first nitride semiconductor 42 has a fine streak morphology, and the epitaxial growth surface (the surface of the second nitride semiconductor 43) has a wavy morphology.
The nitride semiconductor device obtained using this substrate is smooth,
Characteristics with long life, high efficiency, high output, and improved yield can be obtained.

Further, when a nitride semiconductor obtained by further performing ELOG growth on the nitride semiconductor substrate obtained by the above-described ELOG growth or the like is used as a substrate having an element structure, reduction in dislocation and reduction in warpage are excellent. Which is preferable for obtaining the effects of the present invention. A preferred embodiment of the present invention is described in Japanese Patent Application No. 11-80288. For example, as a preferable example, a thick film, for example, a third nitride semiconductor having a thickness of, for example, 80 to 500 μm is grown on the second nitride semiconductor 43 obtained by the process shown in FIG. After that, the heterogeneous substrate is removed to make only the third nitride semiconductor, and a fourth nitride semiconductor is grown by HVPE or the like on the surface of the third nitride semiconductor opposite to the surface from which the heterogeneous substrate is removed. Let it. The thickness of the fourth nitride semiconductor is adjusted so that the sum of the thickness of the third nitride semiconductor and the thickness of the fourth nitride semiconductor is, for example, preferably about 400 to 80 μm. Is done. Repeated ELOG growth on such a nitride semiconductor composed of the third and fourth nitride semiconductors can provide a nitride semiconductor substrate with reduced dislocations, which is preferable for obtaining the effects of the present invention. .

When a nitride semiconductor having few dislocations as described above is used as a substrate and an element structure is formed on this substrate, an element having good crystallinity can be obtained, which is preferable from the viewpoint of improving luminous efficiency. Further, it is preferable in terms of reduction of threshold current density and improvement of life characteristics.

Hereinafter, the element structure shown in FIG. 1 will be described. However, according to the present invention, the emission peak wavelength is 380.
The element structure is not particularly limited as long as it has an active layer having a thickness of nm.

[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 <0.5, preferably 0 <a <0.5, more
Nitriding preferably comprising 0.01 <a <0.05)
Semiconductor layer. the n-type contact layer contains Al;
When the Al composition ratio is within the above range, self-absorption can be prevented and at the same time.
This is preferable in terms of crystallinity and ohmic contact. Further
The n-type contact layer 3 has an n-type impurity of 1 × 10¹⁷~ 1 ×
10¹⁹/ Cm ^Three, Preferably 1 × 10¹⁸~ 1 × 10¹⁹/
cm^ThreeAt a concentration of 0.1% to maintain ohmic contact.
Retention, prevention of cracking, and maintenance of crystallinity
No. Thus, the Al composition ratio constituting the n-type contact layer
And n-type impurity concentration can prevent self-absorption
As well as ohmic contact and crack prevention.
New The n-type impurity is not particularly limited.
For example, Si, Ge and the like can be mentioned, and preferably, Si is used.
Although the thickness of the n-type contact layer 3 is not particularly limited,
0.1-20 μm is preferred, and more preferably 1-10
μm. When the film thickness is within this range, the vicinity of the interface (for example,
(Near the interface with the n-type cladding layer)
) Is preferred in terms of lowering the resistivity.

[N-type cladding layer 4]
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 film (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 may be a nitride semiconductor having a composition such that the emission peak wavelength is 380 nm or less, preferably the emission peak wavelength is 370 nm or less. Preferably In _f Ga _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 is almost zero, and may be zero depending on the wavelength. The thickness of the active layer is not particularly limited, but may be a thickness at which a quantum effect can be obtained.
0.01 to 0.01 μm, more preferably 0.003 to 0.01 μm.
０．００0.007 μm. 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 of the active layer is not particularly limited as long as the In peak ratio is such that the emission peak wavelength is 380 nm or less. Can be cited as an approximate value. However, since a wavelength obtained by actually emitting light has a quantum level having a quantum well structure, the energy of the wavelength (Eλ) becomes larger than the band gap energy (Eg) of InGaN, and FIG.
From the emission wavelength obtained from the calculation formula etc. as shown in
It tends to shift to shorter wavelengths.

[Calculation formula of theoretical value] Eg = (1-（) 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

As described above, although there is a slight difference between the oscillation wavelength considered from the specific In composition ratio obtained from the SIMS analysis of the well layer and the like when actually oscillated, the actual oscillation wavelength is slightly different. The oscillation wavelength is adjusted to be a desired wavelength.

[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
１1 × 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 can be a multilayer film layer (including a superlattice structure) in addition to the single layer as 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]
As the p-type contact layer 7, at least Al _b Ga _1-b
A nitride semiconductor layer containing N (0 ≦ b <0.5, preferably 0 <b <0.1, more preferably 0.01 ≦ b ≦ 0.05). When the p-type contact layer contains Al and the Al composition ratio is in the above range, it is preferable in terms of crystallinity and ohmic contact as well as prevention of self-absorption as in the case of the n-type contact layer. Further, the p-type contact layer 7 contains p-type impurities of 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm.
³ , preferably at a concentration of 5 × 10 ^{19 to} 5 × 10 ²⁰ / cm ³ , is preferable in terms of ohmic contact, prevention of crack generation, crystallinity, and bulk resistance. Thus p
The combination of the Al composition ratio and the n-type impurity concentration constituting the mold contact layer is preferable in terms of preventing self-absorption and preventing ohmic contact and cracking. The p-type impurity is not particularly limited, but is preferably, for example, Mg
Is mentioned. The thickness of the p-type contact layer 7 is not particularly limited, but is preferably from 0.03 to 0.5 μm, and more preferably from 0.1 to 0.15 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.

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.

The device of the present invention is subjected to an annealing treatment in order 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.

[0058]

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. Further, as described in the detailed description of the invention, the value of the formula for calculating the theoretical value of the In composition ratio is different from the actual oscillation wavelength due to a shift to a short wavelength due to the formation of a quantum level having a quantum well structure. Therefore, the In composition ratio of the active layer of the example is an approximate value.

Example 1 As Example 1, a nitride semiconductor light emitting device according to an embodiment of the present invention shown in FIG. 1 is manufactured.

As shown in FIG.
The principal plane is the C-plane that is off-angled in a step shape,
Angle angle θ = 0.15 °, step step about 20 ON
Gustrom, terrace width W about 800 angstroms
With the orientation flat surface as surface A and the step perpendicular to surface A.
Prepare a straight sapphire substrate. This sapphire group
Place the plate in the reaction vessel, raise the temperature to 510 ° C,
Hydrogen for carrier gas, ammonia and TMG for source gas
Limethyl gallium) and Ga on the sapphire substrate.
Low temperature growth buffer layer of N (not shown)
Is grown to a thickness of 200 angstroms. Buff
After layer growth, stop only TMG and raise temperature to 1050 ° C
When the temperature reaches 1050 ° C., TMG
The first of undoped GaN using ammonia
The nitride semiconductor layer 42 is grown to a thickness of 2 μm. Next
On the wafer on which the first nitride semiconductor layer 42 is laminated.
Form a striped photomask and use it for sputtering equipment
The stripe width (the part that becomes the upper part of the projection) is 5 μm,
Putter to 10μm at tripe interval (part to be the bottom of concave part)
SiO_TwoForming a film, followed by an RIE device
By SiO_TwoFirst nitridation of a portion where a film is not formed
The entire semiconductor layer 42 is etched and sapphire is further
Etching to a depth of 200 angstroms to make it uneven
Forming the first nitride semiconductor on the side surface of the concave portion.
The layer 42 is exposed. After forming the irregularities, the Si
O _TwoRemove the film. The stripe direction is shown in FIG.
As shown in the figure, the shape is shifted by 0.3 ° with respect to the orientation flat surface.
To achieve. Next, set in a reaction vessel, at normal pressure,
Using TMG and ammonia for undoped GaN
Grown second nitride semiconductor layer 43 with a thickness of 15 μm
Thus, a nitride semiconductor substrate 1 is obtained. Obtained nitride semiconductor
The following element structure is laminated and grown using the substrate as a nitride semiconductor substrate 1.
(FIG. 2). Of the surface of the obtained nitride semiconductor substrate 1
Observation of dislocations by TEM method shows that
Almost no dislocations are seen, and slightly more dislocations are seen
Was measured. The following layers are formed on the nitride semiconductor substrate 1.
Let it grow.

(N-type contact layer 3) Next, on the obtained nitride semiconductor substrate 1, TMG, TMA
(Trimethylaluminum), ammonia, silane (S
iH ₄ ) and n doped with 5 × 10 ¹⁸ / cm ^{3 of} Si
N-type contact layer 3 of Al _0.04 Ga _0.96 N
It is grown to a thickness of 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 or 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 at 700 ° C. in a reaction vessel in a nitrogen atmosphere,
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 etching, almost 200 angstrom of Ni is formed 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. However, the LED is manufactured such that the active layer that emits light is located above the concave portion of the nitride semiconductor substrate 1 where there is almost no dislocation, and further avoids the central portion of the concave portion and is located, for example, as shown in FIG.

This LED element has an emission peak wavelength of 371 nm at a forward voltage of 10 mA, and Vf is 3.
5V, the output is 2.0 mW. The luminous efficiency of the LED of Example 1 is 5.7%. This data is plotted as ● in FIG.

Example 2 An LED is manufactured in the same manner as in Example 1, except that the In composition ratio of the active layer is adjusted so that the emission peak wavelength becomes 360 nm and 377 nm. The luminous efficiency of the obtained LED is such that the luminous peak wavelength is 3
In the case of 60 nm, 0.59%, the emission peak wavelength is 377.
In the case of nm, it is 5.85%. These data are plotted as ● in FIG.

Comparative Example 1 An LED was manufactured in the same manner as in Example 1, except that the In composition ratio of the active layer was adjusted so that the emission peak wavelength became 470 nm and 520 nm. The luminous efficiency of the obtained LED is 6.0%,
3.0%. These data are plotted as ● in FIG.

[Comparative Example 2] Further, in Example 1, a sapphire substrate was used in place of the nitride semiconductor substrate 1, and a GaN buffer layer was grown on the sapphire substrate at 550 ° C. at 300 Å. On the layer, an element structure consisting of a plurality of layers such as a contact layer similar to that of the first embodiment is grown.
D is made. However, by adjusting the In composition ratio of the active layer,
Emission peak wavelength is 360 nm, 371 nm, 377 n
m, 470 nm, and 520 nm are produced as comparative LEDs. The luminous efficiencies of the obtained comparative LEDs were 0.25%, 4.8%, 5.1%, 6.0%, and 3.0%, respectively.
Becomes These data are plotted as ■ in FIG.

(Comparison of Luminous Efficiency of LED of Example and Comparative Example) FIG. 6 shows the value of the luminous efficiency [●] of the LED using a nitride semiconductor substrate due to the change of the luminous peak wavelength and the sapphire substrate 5 is a graph plotting luminous efficiency values [■] according to changes in the luminous peak wavelength of each LED. Hereinafter, the values [data of wavelength and luminous efficiency] obtained in the above-described example and comparative example shown in FIG. 6 are summarized in a list.

[0073]

Table 1 Wavelength (nm) Luminous efficiency (%) Nitride semiconductor substrate Sapphire substrate---------------------------------- --------------------------------------------------------------------------- 0.5 0.50 0.25 371 5.70 4.80 377 5.85 5.10 470 6 .00 6.00 520 3.00 3.00 −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−

The change in luminous efficiency due to the difference in the substrate and the difference in the emission peak wavelength will be discussed below with reference to FIG. First, emission peak wavelengths are 470 nm and 520 nm.
In the case of, the LED using the nitride semiconductor substrate
[●: Comparative Example 1] and LE using sapphire substrate
D [■: Comparative Example 2] has the same luminous efficiency. When the emission peak wavelength changes from 470 nm to 380 nm, the luminous efficiency of these LEDs gradually decreases. Such a gradual decrease is smaller in the LED [●] using the nitride semiconductor substrate with less dislocation than in the LED [■] using the sapphire substrate. This means that LEDs using nitride semiconductor substrates
[●] indicates that it is easier to maintain high luminous efficiency. Further, when the emission peak wavelength is 380 nm or less, both tend to sharply decrease the luminous efficiency.

However, the LE using the sapphire substrate
As compared with D [■: Comparative Example], the LED [●: Example] using the nitride semiconductor substrate has higher luminous efficiency. For example, when the emission peak wavelength is 360 nm, the LED using the nitride semiconductor substrate shows 2.36 times the luminous efficiency as compared to the LED using the sapphire substrate.

As described above, in the case of an ultraviolet LED that emits light in the ultraviolet region, the luminous efficiency is improved favorably by using a nitride semiconductor substrate having a low dislocation density. And
By improving the luminous efficiency, the luminous output can be improved.

[0077]

According to the present invention, the emission peak wavelength is 380 nm.
By growing a nitride semiconductor device emitting light in the following ultraviolet region on a nitride semiconductor substrate having a very low dislocation density, luminous efficiency can be improved satisfactorily.

[Brief description of the drawings]

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

FIG. 2 shows an ELOG that can be used in the present invention.
It is a typical sectional view showing the structure of each process of one embodiment of growth.

FIG. 3 is a unit cell diagram showing a plane orientation of sapphire.

FIG. 4 is a schematic cross-sectional view showing a partial shape of an off-angled heterogeneous substrate.

FIG. 5 is a plan view of the main surface of the substrate for explaining the stripe direction of the unevenness.

FIG. 6 is a graph showing the relationship between the luminous efficiency and the wavelength of the LEDs of Examples and Comparative Examples.

FIG. 7 is a schematic cross-sectional view showing band gap energy (Eg) of a well layer of an active layer and energy (Eλ) of an oscillation wavelength due to formation of a quantum level.

[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 (2)

[Claims] 1. A nitride semiconductor device comprising: a nitride semiconductor device having a light emission peak wavelength of 380 nm or less formed on a nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less. . ^2. A nitride semiconductor substrate having a dislocation density of 10 ⁶ / cm ² or less is formed by utilizing lateral growth of a nitride semiconductor on a heterogeneous substrate or a nitride semiconductor substrate made of a material different from a nitride semiconductor. The nitride semiconductor device according to claim 2, wherein the nitride semiconductor device is grown by growing.