JP3548442B2 - Gallium nitride based compound semiconductor light emitting device - Google Patents

Description

[0001]
[Industrial applications]
The present invention is a light emitting diode, n-type gallium nitride compound is used in an electronic device such as a laser diode semiconductor _{(In X Al Y Ga 1-} X-Y N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1, the following nitride The present invention relates to a gallium nitride-based compound semiconductor light-emitting device using a crystal of a gallium-based compound semiconductor).
[0002]
[Prior art]
Blue laser diode that emits ultraviolet, nitride semiconductor as a material for light emitting diodes _{(In X 'Al Y' Ga} 1-X'-Y 'N, 0 ≦ X', 0 ≦ Y ', X' + Y '≦ 1 ), And a blue light emitting diode having a luminous intensity of 1 cd has recently been put to practical use with this material. As shown in FIG. 1, this blue light emitting diode has a buffer layer 2 made of GaN, an n-type layer 3 made of GaN, an n-type cladding layer 4 made of AlGaN, and an InGaN An active layer 5, a p-type clad layer 6 made of AlGaN, and a p-type contact layer 7 made of GaN are sequentially laminated.
[0003]
In general, a nitride semiconductor layer is formed on a substrate surface by a vapor phase growth method such as MOVPE (organic metal vapor phase epitaxy), MBE (molecular beam epitaxy), or HDVPE (hydride vapor phase epitaxy). It is obtained by laminating. Materials such as sapphire, ZnO, SiC, GaAs, and MgO are used for the substrate. On the surface of the substrate, an n-type nitride semiconductor (In _X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1, particularly n-type GaN, n-type AlGaN is often grown). When a substrate having a lattice constant close to that of a nitride semiconductor such as SiC or ZnO is used, an n-type nitride semiconductor may be directly grown on the substrate without forming a buffer layer. Basically, an n-type nitride semiconductor layer is first grown on the surface of a substrate to produce a nitride semiconductor device such as a light emitting device and a light receiving device.
[0004]
For example, according to the MOVPE method, as a nitride semiconductor, an organic metal compound gas serving as a Ga source, an Al source, and an In source and an ammonia gas serving as an N source are used as source gases. The source gas is decomposed by bringing these source gases into contact with the heated substrate surface, and a nitride semiconductor is epitaxially grown on the substrate. As the buffer layer, GaN, AlN, GaAlN, or the like is usually selected and grown at a temperature of 300 ° C. to 900 ° C. with a thickness of 10 Å to 0.1 μm. The n-type nitride semiconductor layer grown on the buffer layer is grown at a temperature of 900 ° C. or higher, usually with a film thickness of 1 μm or more and 4 μm or less.
[0005]
[Problems to be solved by the invention]
It is known that a nitride semiconductor is a crystal that is extremely difficult to epitaxially grow because there is no substrate that is perfectly lattice-matched. Therefore, conventionally, a substrate close to the lattice constant of a nitride semiconductor to be grown, such as a SiC substrate, has been used, or epitaxial growth has been forcibly performed via a buffer layer for reducing lattice mismatch.
[0006]
FIG. 2 shows, as an example, a schematic cross-sectional view of an n-type nitride semiconductor crystal grown on the surface of a substrate that does not lattice match. This is quoted from the Journal of Crystal Growth, Journal of Crystal Growth, 115, (1991) P628-633, in which n-type GaN is epitaxially grown on the surface of a sapphire substrate via a buffer layer made of AlN, and its cross section is obtained. Is measured by TEM (transmission electron microscopy), and the structure of the crystal is schematically shown from the TEM image. According to this figure, a buffer layer with poor orientation is grown on the substrate in a columnar shape, and when GaN is epitaxially grown on the buffer layer, a part of the buffer layer plays a role like a seed crystal. This shows that the GaN layer with improved crystallinity is grown by gradually adjusting the orientation of GaN.
[0007]
However, it is difficult to grow GaN completely free from crystal defects, and many crystal defects as shown by broken lines in FIG. 2 extend from the interface between the buffer layer and the GaN layer until reaching the GaN layer surface. Some of these defects stop inside the crystal, but those reaching the GaN layer surface are, for example, 10 ⁷ to 10 ⁹ / cm ^{2 at} the surface. Similarly, in the light emitting diode element of FIG. 1, the same phenomenon occurs in the crystal of the n-type layer 3.
[0008]
If there are many crystal defects on the surface of the n-type nitride semiconductor layer grown on the surface of the substrate, the defects are inherited by all semiconductor layers such as the cladding layer and active layer growing on the surface of the n-type layer, and There is a problem that the entire structure is adversely affected. An element having many crystal defects has a drawback that, for example, when the above-mentioned light emitting diode is used, the element performance such as light emission output and life is adversely affected.
[0009]
In growing an n-type nitride semiconductor layer on the surface of a substrate, it is very important to grow an n-type crystal with few crystal defects, and if this can be achieved, a cladding layer grown on the n-type crystal Since the number of crystal defects in the active layer and the like is reduced, the performance of any device made of a nitride semiconductor can be improved. Accordingly, the present invention has been made in view of such circumstances, and is intended for use in growing an n-type nitride semiconductor layer on the surface of a substrate that is not completely lattice-matched by a vapor growth method such as MOVPE or MBE. Another object of the present invention is to provide a light emitting device using an n-type nitride semiconductor grown by reducing lattice defects in the n-type nitride semiconductor layer.
[0010]
[Means for Solving the Problems]
The present invention provides a second n-type gallium nitride-based compound containing In _a Ga _1-a N (0 <a ≦ 1) or Al _b Ga _1-b N (0 <b ≦ 1) and acting as a buffer layer An n-type gallium nitride-based compound semiconductor having a structure in which a semiconductor layer is sandwiched between a first n-type gallium nitride-based compound semiconductor layer and a third n-type gallium nitride-based compound semiconductor layer is formed by forming an n-type gallium nitride-based compound semiconductor between a substrate and an active layer. And a combination of the first n-type gallium nitride-based compound semiconductor layer, the second n-type gallium nitride-based compound semiconductor layer, and the third gallium nitride-based compound semiconductor layer constitute a superlattice. However, one of the first n-type gallium nitride-based compound semiconductor layer and the third n-type gallium nitride-based compound semiconductor layer is a negative electrode forming layer.
[0011]
In the light-emitting device of the present invention, the active layer is preferably made of InGaN, and the first gallium nitride-based compound semiconductor layer and the third gallium nitride-based compound semiconductor layer preferably have the same composition. .
[0012]
[Action]
When a second nitride semiconductor layer having a different composition is formed in the n-type nitride semiconductor layer, the second nitride semiconductor functions as a buffer layer, that is, a buffer layer, so that crystal defects can be reduced in the buffer layer. (Hereinafter, the second nitride semiconductor layer is referred to as a second buffer layer in the present specification). More specifically, when an n-type nitride semiconductor layer is grown on a substrate, a large mismatch between the substrate and the nitride semiconductor causes crystal defects as shown by broken lines in FIG. 2 to occur in the crystal during the growth. . However, by interposing a second buffer layer having a different composition from the n-type nitride semiconductor layer to be grown as an intermediate layer, continuous crystal defects of the n-type nitride semiconductor layer cause the second buffer layer having a different composition. Stops temporarily in the buffer layer. Next, when an n-type nitride semiconductor is grown on the surface of the second buffer layer, the n-type nitride semiconductor is grown on the second buffer layer because the second buffer layer acts as a substrate having a small mismatch. It is presumed that the n-type nitride semiconductor has improved crystallinity.
[0013]
The second buffer layer may be formed in one or more layers, and the film thickness per layer is adjusted to be in the range of 10 Å (0.001 μm) or more and 1 μm or less, more preferably 0.001 μm or more and 0.1 μm or less. Is desirable. If the thickness is less than 0.001 μm, it tends to be difficult to stop crystal defects in the second buffer layer. If the thickness is larger than 1 μm, new crystal defects tend to be easily generated from the second buffer layer. The second buffer layer may have a thickness of several tens angstroms, and may be a multilayer film in which two or more layers are stacked.
[0014]
The second buffer layer _{In a Ga 1-a N (} 0 <a ≦ 1), or _{Al b Ga 1-b N (} 0 <b ≦ 1), or a different _{Al b Ga 1-b N (} 0 compositions It is desirable to be a multilayer film in which thin films satisfying ≦ b ≦ 1) are stacked. More preferably a value of 0.5 or less _{In a Ga 1-a} N, or b values grow 0.5 following _{Al b Ga 1-b} N. This is because, in a nitride semiconductor, the ternary mixed crystal has better crystallinity than the quaternary mixed crystal semiconductor layer. _{In a Ga} 1-a _N ternary mixed crystal Among them, the _{Al b Ga 1-b N,} a value, and the buffer layer a b value was adjusted to the range further for good crystallinity is obtained The crystal defects of the second buffer layer are reduced, and the crystal defects of the n-type nitride semiconductor layer grown on the second buffer layer are reduced. Further, when the second buffer layer is a multilayer film, crystal defects can be stopped very well. The most preferable combination is that the n-type nitride semiconductor layer is n-type GaN (GaN has the fewest lattice defects), and the second buffer layer is n-type In _a Ga _1-a N (0 <a ≦ 0.5). or or n-type _{Al b Ga 1-b n (} 0 <b ≦ 0.5) or different _{Al b Ga 1-b n (} 0 ≦ b ≦ 1) multilayer thin film has a stack of compositions (ultra Grid).
[0015]
Further, it is desirable that the electron carrier concentration of the second buffer layer is adjusted to be substantially the same as or higher than that of the previously formed n-type nitride semiconductor layer. 3 and 4 show that an n-cladding layer 4 ', an active layer 5', a p-cladding layer 6 ', and a p-contact layer 7' are laminated on the n-type nitride semiconductor layer 3 "obtained by the method of the present invention. 3 is a cross-sectional view showing the structure of the light emitting element as an actual light emitting element, wherein the second buffer layer 33 is more active than the etched surface of the n-type layer for forming the negative electrode. 4 differs from FIG. 4 in that the second buffer layer 33 is formed closer to the substrate 1 'than the etched surface, for example, to realize a light emitting device as shown in FIG. In other words, in the case where an element in which the position of the second buffer layer 33 is closer to the active layer side than the etching surface on which the negative electrode is to be formed is realized, the electron carrier concentration of the second buffer layer 33 is increased. Is smaller than the n-type layer 3 ′, n is supplied from n to p in the second buffer layer. When the electron carrier concentration of the second buffer layer 33 is higher than that of the n-type layer 3, the current is hardly allowed to flow from the n-type layer to the p-type layer, thereby deteriorating the performance of the device. The electrons can easily spread evenly in the second buffer layer 33, so that uniform light emission can be obtained, while in the case of the device as shown in Fig. 4, the electron carrier concentration in the second buffer layer 33 is small. However, since the current flows through the n-type layer 3 ″ having a higher electron carrier concentration, it hardly affects the characteristics of the light emitting element. On the contrary, when the electron carrier concentration of the second buffer layer 33 is high, Becomes easier to flow toward the second buffer layer 33, and uniform light emission is obtained. Therefore, the electron carrier concentration of the second buffer layer 33 is preferably adjusted to be substantially the same as or higher than that of the previously formed n-type nitride semiconductor layer.
[0016]
By growing the n-type nitride semiconductor layer thicker than 5 μm, crystal defects reaching the surface can be reduced. In FIG. 2, the broken line stops in the middle of the n-type layer, which indicates that the crystal defect stops in the middle. When the crystal defects stopped in the middle of the process were further studied, it was newly found that many of the n-type nitride semiconductor layers stopped at about 4 μm from the substrate. Therefore, if the same material is continuously grown, it is possible to gradually stop the crystal defects during the growth. Therefore, by growing the n-layer at 5 μm or more, the crystal defects reaching the surface of the n-layer can be obtained. Can be reduced. More preferably, the thickness of the n-type nitride semiconductor layer is 7 μm or more.
[0017]
In the present invention, n-type nitride semiconductor which is grown on the substrate _{(In X Al Y Ga 1-} X-Y N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1) is, Y value is 0 ≦ Y ≦ ranging from _{0.5 Al Y Ga 1-Y N} , more preferably 0.3 or less of _Al Y _{Ga 1-Y} N, and most preferably grow GaN of Y = 0. This is because the ternary mixed crystal nitride semiconductor has fewer crystal defects than the quaternary mixed crystal nitride semiconductor as described above. Further, when an n-type nitride semiconductor is used as an electronic device such as a light-emitting element and a light-receiving element, first, an n-type nitride semiconductor grown on a substrate is made of AlGaN having a larger band gap than InGaN having a small band gap, This is because GaN is more convenient for realizing various structures such as single hetero and double hetero. Among them, particularly, AlGaN tends to have more crystal defects as Al is contained, and GaN tends to grow an n-type nitride semiconductor layer having the fewest crystal defects.
[0018]
Materials such as sapphire, GaAs, Si, ZnO, and SiC can be used for the substrate, but sapphire is generally used. When sapphire is used as a substrate, it is preferable to grow a buffer layer on the substrate. However, depending on the plane orientation of the sapphire substrate, growth can be performed without a buffer layer. By preferably growing the buffer layer, it is possible to obtain a smooth and mirror-like n-type nitride semiconductor crystal capable of measuring lattice defects. The n-type nitride semiconductor can be realized in a non-doped state or by doping during the crystal growth with a donor impurity such as Si, Ge, or C.
[0019]
【Example】
Hereinafter, the method of the present invention by the MOVPE method will be described in detail.
[Example 1]
(1) First, a well-washed sapphire substrate is placed on a susceptor in a reaction vessel. After evacuation of the inside of the container, the substrate is heated at 1050 ° C. for about 20 minutes to remove oxides on the surface while flowing hydrogen gas into the container, and the substrate is cleaned. Thereafter, the temperature of the susceptor was adjusted to 500 ° C., and at 500 ° C., a buffer layer made of GaN was formed to a thickness of 0.02 μm while flowing TMG (trimethyl gallium gas) as a Ga source and ammonia gas as an N source over the substrate surface. Let it grow.
[0020]
(2) Next, the TMG gas is stopped, the temperature is raised to 1050 ° C., and then a TMG gas and a SiH ₄ gas are flowed to grow a Si-doped n-type GaN layer to a thickness of 2 μm.
[0021]
{Circle around (3)} Next, the TMG gas and the SiH ₄ gas are stopped, and the temperature is set to 800 ° C. When the temperature reaches 800 ° C., the carrier gas is switched to nitrogen, TMG gas, TMI (trimethylindium), and SiH ₄ gas are flown, and a Si-doped n-type In0.1Ga0.9N layer having a thickness of 0.01 μm is used as a second buffer layer. Grow with.
[0022]
{Circle around (4)} After growing the In0.1Ga0.9N layer, the temperature is raised again to 1050 ° C., the carrier gas is returned to hydrogen, and TMG gas and SiH ₄ gas are flown. Similarly, the Si-doped n-type GaN layer is a 2 μm film. Grow in thickness. Note that the carrier concentration of the second buffer layer and the carrier concentration of the n-type GaN layer were almost the same.
[0023]
After the growth, the substrate is taken out of the reaction vessel, the surface of the uppermost n-type GaN layer was measured by TEM, than the TEM images, it was measured number of crystal defects per unit area, approximately 1 × 10 ⁴ cells / cm ² .
[0024]
[Example 2]
In steps (2) and ( ₄ ) of the n-type nitride semiconductor layer, Si-doped n-type Al0.3Ga0.7N layers are grown to a thickness of 2 μm using TMG, TMA (trimethylaluminum), and SiH ₄ gas. Except that the second buffer layer is interposed therebetween, the same operation as in the first embodiment is performed. As a result, when measured in the same manner, the number of crystal defects reaching the surface of the Si-doped n-type Al0.3Ga0.7N layer was approximately 5 × 10 ⁵ / cm ² . Note that the electron carrier concentration of the Si-doped n-type Al0.3Ga0.7N layer was substantially the same as that of the second buffer layer.
[0025]
[Example 3]
A Si-doped n-type GaN layer is grown to a thickness of 1 μm in the same manner as in step (2) of the n-type nitride semiconductor layer. Next, a Si-doped n-type In0.1Ga0.9N layer is grown to a thickness of 50 Å as a second buffer layer in the same manner as in the step (3) of the second buffer layer. Further, similarly to the step of the n-type nitride semiconductor layer of (4), similarly, a Si-doped n-type GaN layer is sequentially grown to a thickness of 1 μm.
[0026]
Further, a Si-doped n-type In0.1Ga0.9N layer as a third buffer layer is grown once more on the Si-doped n-type GaN layer with a thickness of 50 Å in the same manner as in the step (3). Finally, a Si-doped GaN layer is grown to a thickness of 2 μm in the same manner as in step (4). That is, in Example 3, the GaN buffer layer 200 Å, the n-type GaN layer 1 μm, the Si-doped n-type In0.1Ga0.9N second buffer layer 50 Å, the n-type GaN layer 1 μm, the Si-doped n-type In0 .1 Ga 0.9 N third buffer layer 50 Å and n-type GaN layer 2 μm were sequentially stacked.
[0027]
As a result, the number of crystal defects reaching the surface of the final Si-doped n-type GaN layer was about 1 × 10 ⁴ / cm ² . The electron carrier concentrations of the second buffer layer, the third buffer layer, and the Si-doped n-type GaN layer were almost the same.
[0028]
[Example 4]
In step (3) of the second buffer layer, a Si-doped n-type Al0.3Ga0.7N layer is formed to a thickness of 0.01 μm using TMG, TMA (trimethylaluminum), and SiH ₄ gas without changing the growth temperature. Except that the second buffer layer is formed by growing in the same manner as in the first embodiment. As a result, the number of crystal defects reaching the surface of the Si-doped n-type GaN layer was approximately 1 × 10 ⁴ / cm ² when measured in the same manner. Note that the electron carrier concentration of the second buffer layer was almost the same as that of the Si-doped n-type GaN layer.
[0029]
[Example 5]
In ▲ 3 ▼ step of the second buffer layer, TMG without changing the growth temperature, TMA, using SiH ₄ gas, is grown first, the Si-doped n-type Al0.02Ga0.98N layer with a thickness of 30 angstroms. Next, the TMA gas is stopped, and a Si-doped n-type GaN layer is grown to a thickness of 30 Å. This operation is repeated five times to form a multilayer film in which a 30 Å Si-doped n-type Al0.02Ga0.98N layer and a 30 Å n-type GaN layer are alternately laminated in a five-layer structure. Except for forming the second buffer layer as described above, the same operation as in the first embodiment is performed. As a result, when the lattice defects were measured in the same manner, the number of crystal defects reaching the surface of the Si-doped n-type GaN layer was approximately 5 × 10 ³ / cm ² . Note that the electron carrier concentration of the multilayer film as the second buffer layer was substantially the same as that of the Si-doped n-type GaN layer.
[0030]
[Example 6]
In the process of Example 2, a Si-doped n-type Al0.3Ga0.7N layer was grown in the same manner except that a Si-doped n-type Al0.1GaGa0.9N film was grown to a thickness of 0.01 μm as a second buffer layer. I let it. As a result, the number of lattice defects reaching the outermost n-type Al0.3Ga0.7N layer was about 1 × 10 ⁵ / cm 2. Note that the electron carrier concentration in this example was also substantially the same.
[0031]
[Comparative Example 1]
In Example 1, when the second buffer layer was not grown and a Si-doped n-type GaN layer was continuously grown to a thickness of 4 μm, the number of crystal defects reaching the surface of the n-type GaN layer was approximately It was 1 × 10 ⁷ pieces / cm ² .
[0032]
[Example 7]
An example in which the structure of an actual light emitting element is used will be described.
The following step was added after the step (4) in Example 1.
{Circle around (5)} After the growth of the Si-doped n-type GaN layer, a new TMA (trimethylaluminum) gas is added, and at 1050 ° C., a Si-doped n-type Al0.2Ga0.8N layer having a thickness of 0.1 μm is formed as the n-cladding layer. Let it grow.
[0033]
{Circle around (6)} After growing the n-cladding layer, the TMG, TMA and SiH ₄ gases are stopped, the temperature is again set to 800 ° C., and in addition to the TMG, TMI and SiH ₄ gases, DEZ (diethyl zinc) is flown to form an active layer. A Si and Zn doped In0.05Ga0.95N layer is grown to a thickness of 0.1 μm.
[0034]
{Circle around (7)} After the active layer is grown, the TMG, TMI, SiH ₄ and DEZ gases are stopped, the temperature is set to 1050 ° C., and then TMG, TMA and Cp2Mg (cyclopentadienyl magnesium) gas are flowed to form a p-clad layer doped with Mg. A p-type Al0.1Ga0.9N layer is grown to a thickness of 0.1 μm.
[0035]
{Circle around (8)} After the growth of the p-type Al0.1Ga0.9N layer, the TMA gas is stopped, and an Mg-doped p-type GaN layer is grown at 1050 ° C. as a p-contact layer with a thickness of 0.3 μm.
[0036]
{Circle around (9)} The device obtained as described above is etched to expose the n-type GaN layer grown next to the second buffer layer. Electrodes are formed on the p-contact layer and the exposed Si-doped n-type GaN layer. Was formed. That is, a light emitting diode element having a structure as shown in FIG. 4 was obtained. The device was mounted on a lead frame and molded with resin. This light-emitting diode had a Vf of 3.6 V, an emission wavelength of 450 nm, a luminous intensity of 3.0 cd, and an emission output of 3.5 mW at 20 mA.
[0037]
[Comparative Example 2]
The same process as in Example 7 was performed on the Si-doped GaN layer grown in Comparative Example 1 to obtain a light-emitting diode device having a structure as shown in FIG. 1. The light-emitting diode had a Vf of 3.6 V at 20 mA, Although the emission wavelength was 450 nm, the luminous intensity was 1.0 cd, and the emission output was only 1.2 mW.
[0038]
As described above, since the light-emitting element of the present invention has the n-type layer with few crystal defects, the number of crystal defects such as a clad layer and an active layer laminated thereon is reduced. In particular, since the thickness of the active layer is as thin as about 0.2 μm or less, it is very important to grow a crystal having few crystal defects. Therefore, by growing a crystal having few crystal defects, it is possible to realize a light emitting diode element having a luminous intensity of 1 cd or more and excellent in luminous output in the related art.
[0039]
Example 8
{Circle around (1)} A buffer layer made of GaN is grown to a thickness of 0.02 μm on the surface of the sapphire substrate in the same manner as in step (1) of the first embodiment.
[0040]
{Circle around (2)} A 10 μm-thick Si-doped n-type GaN layer is grown on the buffer layer in the same manner as in step {circle around (2)} of the first embodiment.
[0041]
After the growth, the substrate was taken out of the reaction vessel, the surface of the n-type GaN layer was measured with a TEM, and the number of crystal defects per unit area was measured from the TEM image, which was about 1 × 10 ⁵ / cm ^2. Was.
[0042]
[Example 9]
Crystal growth was performed in the same manner as in Example 5 except that the thickness of the Si-doped n-type GaN layer was changed to 5 μm. As a result, the number of crystal defects on the surface of the n-type GaN layer was approximately 5 × 10 ⁶ .
[0043]
[Example 10]
In step (2) of Example 5, crystal growth was performed in the same manner as in (2) of Example 2, except that a Si-doped n-type Al0.3Ga0.7N layer was continuously grown to a thickness of 10 μm. Was performed, the number of crystal defects on the surface of the n-type Al0.3Ga0.7N layer was approximately 3 × 10 ⁶ / cm ² .
[0044]
[Example 11]
On the Si-doped GaN layer obtained in Example 5, an n-cladding layer, an active layer, a p-cladding layer, and a p-contact layer were laminated in the same manner as in Example 7 to obtain a light emitting diode. Its characteristics were almost equivalent to those of Example 7.
[0045]
【The invention's effect】
As described above, the light emitting element of the present invention has the n-type nitride semiconductor layer with few crystal defects on the substrate. Therefore, the present invention is very useful because it can be applied to an electronic device such as a light-receiving element, because a crystal having few crystal defects is stacked for a nitride semiconductor light-emitting element having no lattice matching substrate.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing one structure of a conventional light emitting diode element.
FIG. 2 is a schematic cross-sectional view showing a crystal structure when an n-type GaN layer is grown on a surface of a substrate via an AlN buffer layer.
FIG. 3 is a schematic cross-sectional view showing one structure of a light emitting diode device having an n-type nitride semiconductor layer of the present invention.
FIG. 4 is a schematic cross-sectional view showing one structure of a light emitting diode device having an n-type nitride semiconductor layer of the present invention.
[Explanation of symbols]
1, 1 '... substrate 2, 2' ... buffer layer 3, 3 ', 3 "... n-type nitride semiconductor layer 4, 4' ... n-type cladding layer 5, 5 '... -Active layer 6, 6 '... p cladding layer 7, 7' ... p contact layer 33 ... second buffer layer (second nitride semiconductor layer)

Claims (3)

A second n-type gallium nitride-based compound semiconductor layer containing In _a Ga _1-a N (0 <a ≦ 1) or Al _b Ga _1-b N (0 <b ≦ 1) and acting as a buffer layer, An n-type gallium nitride-based compound semiconductor having a structure sandwiched between a first n-type gallium nitride-based compound semiconductor layer and a third n-type gallium nitride-based compound semiconductor layer is provided between a substrate and an active layer. ,
A combination of the first n-type gallium nitride-based compound semiconductor layer, the second n-type gallium nitride-based compound semiconductor layer, and the third gallium nitride-based compound semiconductor layer does not constitute a superlattice; A gallium nitride-based compound semiconductor light emitting device having a double hetero structure in which one of the first n-type gallium nitride-based compound semiconductor layer and the third n-type gallium nitride-based compound semiconductor layer is a negative electrode forming layer. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein the active layer is made of InGaN. The gallium nitride-based compound semiconductor according to claim 1, wherein the first gallium nitride-based compound semiconductor layer and the third gallium nitride-based compound semiconductor layer have the same composition.

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