JP2002270894A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a light-emitting efficiency by improving injected/diffused state of holes in a quantum well structure (MQW structure, SQW structure) of a light-emitting element. SOLUTION: A semiconductor light-emitting element comprises a light- emitting layer 1 having the MQW structure, which is constituted so that the hole is liable to remotely transfer the hole from the side of a p-type semiconductor layer 3 to the side of an n-type semiconductor layer 1, at least two layers among the band gaps of barrier layers 21 to 26 in the MQW structure are different from each other, and there preferably exists a part in which multilayers are stepwisely lowered from the p-type side to the n-type side. The light-emitting element comprises a light-emitting layer 2 having SQW structure, which is formed so that the barrier layer of the p-type side is inclined in it composition, and the band gap is lowered going from the p-type side toward the n-type side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light-emitting device (hereinafter, also simply referred to as "light-emitting device"), and more particularly, to a light-emitting layer having a multi-quantum well.
well (hereinafter, also referred to as “MQW”) structure or a single-quantum well (hereinafter, also referred to as “SQW”) structure.

[0002]

2. Description of the Related Art An SQW structure and an MQW structure are known as one structure of a light emitting layer in a light emitting device. FIG.
FIG. 1 is a diagram schematically illustrating an example of an MQW structure in a conventional GaN-based LED by a schematic band diagram. As shown in the example of FIG.
And the p-type AlGaN cladding layer 60
Are sandwiched, and the light emitting layer 50 is formed as an MQW structure. The MQW structure has an n-type GaN cladding layer 40.
Side, the barrier layer (Barrier layer) 51 / well layer (Well)
A quantum well structure in which a well layer is sandwiched between barrier layers, such as 52) / barrier layer / well layer /... / Well layer / barrier layer, is formed in multiple layers. Usually, the number of pairs of barrier layers / well layers is about 2 to 20 pairs.

[0003] By forming the light emitting layer into an MQW structure,
Compared to the simple double heterostructure in which the active layer is formed, each layer is thinner than the critical thickness (thickness at which dislocations due to misfit vary significantly from the value). When the crystallinity is remarkably improved and the recombination probability of carriers is also improved, the emission intensity is increased and the color purity of the emission spectrum is also improved.

Similarly, in the case of the SQW structure, since the thickness of the well layer is less than the critical thickness, the crystallinity is remarkably improved, the emission intensity is increased, and the color purity of the emission spectrum is increased. Also improve.

[0005]

However, the present inventors examined the light emission state in the conventional MQW structure and examined the distribution state of carriers. As a result, holes were diffused and injected uniformly into each well layer. However, it was found that the density was higher in the well layer on the p-type semiconductor layer side, and the density was lower as the distance from the well layer to the n-type side. Therefore, it has been found that the MQW structure originally designed with the optimum layer structure has a large unevenness in the distribution of carriers (holes), so that the original light emitting performance and light emitting efficiency are not sufficiently obtained. . In addition, the overflow of electrons becomes remarkable, which causes a reduction in luminous efficiency.

On the other hand, also in the SQW structure, holes are not efficiently injected into the well layer, and it is considered that there are many holes that disappear before recombination with electrons. It turned out that there was a problem that it was not obtained sufficiently.

[0007] The above-mentioned problems relating to the quantum well structure are as follows.
In particular, it was found to be remarkable in a GaN-based semiconductor material. In this material system, for example, the average free path of the holes injected into the active layer having the DH structure is said to be several tens of nm, so that the holes are difficult to diffuse. Therefore, in the MQW structure,
As the distance from the p-type semiconductor layer increases, the hole density decreases sharply, and the above-described problem caused by the bias appears more prominently.
Further, also in the SQW structure, the number of holes that disappear before contributing to light emission increases, and the above problem also appears more remarkably.

An object of the present invention is to solve the above-mentioned problems, to improve the injection / diffusion state of holes in a multiple quantum well structure and a single quantum well structure of a light emitting device, and to improve luminous efficiency.

[0009]

SUMMARY OF THE INVENTION The present invention has the following features. (1) A light emitting layer formed as a multiple quantum well structure, a p-type semiconductor layer and an n-type semiconductor layer sandwiching the light emitting layer, and at least two of the barrier layers in the multiple quantum well structure are mutually A semiconductor light emitting device, wherein a material is selected so as to have a different band gap.

(2) The material according to (1), wherein the material of the barrier layer is selected such that the band gap becomes smaller as the distance from the p-type semiconductor layer increases in a specific section of the multiple quantum well structure. Semiconductor light emitting device.

(3) The semiconductor light emitting device according to the above (1), wherein the material of the barrier layer is selected such that the band gap is minimized at the center of the multiple quantum well structure.

(4) Among the barrier layers, the barrier layer closest to the p-type semiconductor layer is formed as a structure having a composition gradient such that the band gap becomes smaller as the distance from the p-type semiconductor layer increases within the layer. The above (1) to (3)
The semiconductor light emitting device according to any one of the above.

(5) The semiconductor light emitting device according to any one of (1) to (4), wherein the multiple quantum well structure is made of a GaN-based semiconductor.

(6) It has a light emitting layer formed as a single quantum well structure, a p-type semiconductor layer and an n-type semiconductor layer sandwiching the light emitting layer, and among the barrier layers in the single quantum well structure, p A semiconductor light emitting device, wherein a barrier layer on the side of a type semiconductor layer is formed as a composition-graded structure such that the band gap becomes smaller as the distance from the p-type semiconductor layer increases in the layer.

(7) The semiconductor light emitting device according to (6), wherein the single quantum well structure is made of a GaN-based semiconductor.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The light emitting device according to the present invention may be a light emitting diode (LED), a semiconductor laser (LD) or the like, and the material system is not limited, but the usefulness of the present invention is particularly remarkable as described later. A light-emitting element using a GaN-based material (an LED is an example of an element)
The present invention will be described.

First, an embodiment in which the light emitting layer has an MQW structure will be described. In the example shown in FIG. 2, on a sapphire C-plane substrate B1, a GaN buffer layer B2 grown at a low temperature, a GaN layer B3 with no addition, an n-GaN contact layer 1 with Si, a light emitting layer (MQW structure) 2, Mg Addition of p-AlGa
N cladding layer 3, Mg-added p-GaN contact layer 4
Are sequentially stacked by crystal growth, an n-type electrode P1 is provided on an exposed portion of the n-GaN contact layer 1, and a p-type electrode P2 is provided on the surface of the p-GaN contact layer 4, respectively, to form a GaN-based LED. ing.

The light emitting device according to the present invention has a
As shown in FIG. 1 as an example of a band diagram, the W structure has a barrier so that more holes injected from the p-type side can reach the well layer on the n-type side. At least two of the layers are layers having different band gaps. In particular, the band gap is gradually changed from the p-type side to the n-type side so that holes can easily move farther from the p-type end to the n-type side. It is configured so that there is a part that becomes lower toward the end.

In the conventional MQW structure, all of the barrier layers have the same band gap, and all of the well layers have the same band gap. That is, the MQW structure of the conventional light emitting device has a structure in which the same quantum well is repeatedly multiplexed. This is because the difference in the distribution of carriers in each well layer was not focused on, and there was no idea to treat each well layer independently.

On the other hand, in the light emitting device of the present invention, as described above, the distribution state of the hole density, which is intensively increased on the p-type side in the MQW structure, is shifted to the n-type side. In this case, the band gap of the barrier layer is changed. For example, in a specific section from the p-type endmost barrier layer, the band gap of each barrier layer is gradually reduced. With this structure, the MQW from the p-type side
Holes injected into the structure are more likely to move beyond the first well layer to the next barrier layer and from there to the next barrier layer beyond the next well layer. It becomes easier to reach the well layer on the mold side, and the extreme bias of the hole density distribution in the MQW structure is improved. As a result, overflow of electrons is also suppressed, and higher luminous performance and luminous efficiency can be obtained.

In the present invention, the thickness of each well layer of the MQW structure is selected from the range of 2 nm to 3.5 nm. 2 nm
As the thickness becomes smaller, the influence of the interface becomes stronger,
When the thickness is more than 3.5 nm, the recombination probability of carriers decreases due to the influence of the piezoelectric field, and when the thickness is further increased, the crystallinity is remarkably deteriorated beyond the critical thickness.

Further, the thickness of each barrier layer of the MQW structure in the present invention ranges from approximately the same thickness as the well layer to 25 nm.
Degree, preferably in the range of 4 nm to 10 nm. However, the thickness of the outermost p-type barrier layer is MQW
During the heating process after the growth of the structure and during the growth of the Mg-added layer,
In order to protect the well layer from thermal damage to the well layer, the thickness is set to be thicker than a barrier layer sandwiched between the well layers and 5 nm to 2 nm.
It is selected in the range of 5 nm.

The number of pairs of the barrier layer / well layer may be any number as long as it can function as a light emitting element.
６6 pairs is a preferred number of pairs.

The change pattern of the band gap of the barrier layer may be any pattern in which holes are more easily diffused. The following is a representative example of the change pattern. The example of FIG. 1 shows a monotonically decreasing pattern of the band gap in a specific section. In this section, the band gap of the barrier layer gradually decreases as the distance from the p-type semiconductor layer increases. This monotonous decreasing pattern may be formed in any section of the entire barrier layer of the MQW structure, but from the viewpoint of eliminating the bias of holes, as shown in FIG. It is preferable that the band gap is gradually reduced from the barrier layer 26 and monotonically decreases to the immediately preceding barrier layer 22 of the n-type side barrier layer 21. In the example shown in the figure, the barrier layer 21 closest to the n-type has the same band gap as the barrier layer 26 closest to the p-type. this is,
When the band gap is minimized in each barrier layer by increasing the In content of the barrier layer 21 as compared with the immediately preceding layer, holes accumulate here, which is solved. And to promote the diffusion of electrons from the n-type side.

The monotonous decreasing pattern as described above may be linear or curved, but in terms of maximizing luminous efficiency, the decreasing rate of the band gap decreases as the distance from the p-type side increases. A curved shape is preferred. If the monotonous band gap reduction pattern is linear,
The minimum band gap is 4 times the band gap of the well layer.
What is necessary is just to set it so that it may become larger than 00meV, and to make it decrease substantially linearly from the band gap of the part which contacts the well layer of the outermost barrier layer.

FIG. 3 shows a variation pattern in which the band gap is minimized at the center of the MQW structure. With such a pattern, the diffusion of electrons and the diffusion of holes can be balanced. The central portion here is the third portion in the case where the MQW structure has five pairs, for example.
It does not mean only the central one layer such as only the first layer. For example, when the MQW structure has 20 pairs, the remaining layers at the center excluding the first to third barrier layers at both ends are the 14th to 18th layers. As described above, the concept includes a mode in which the central barrier layer has a wide band gap having the same minimum value. Also,
The layer having the minimum band gap may be biased toward either the p-type or the n-type.

When the band gap is minimized at the central portion of the MQW structure, the increase / decrease curve of the band gap is shown in FIG.
, A V-shaped pattern that decreases / increases linearly, or a variation pattern that decreases / increases by drawing an arbitrary curve.

The barrier layer closest to the p-type semiconductor layer among the barrier layers of the MQW structure may be a homogeneous layer, but as shown in FIG.
A layer having a composition gradient such that the band gap becomes smaller as the distance from the layer increases. FIG.
The change may be a continuous change in a straight line or curve as shown in the barrier layer 26 of FIG. 4A or a discontinuous change in a step form as shown in the barrier layer 26 of FIG.

By imparting the above-described band gap gradient to the barrier layer closest to the p-type semiconductor layer,
The injected holes can be efficiently delivered to the well layer.
Similarly, in the case of the SQW structure described later (FIG. 5), the inclination of the band gap in one barrier layer is similar to that of the cladding layer (particularly, the Al layer) before and after the start of the layer growth.
This can be easily achieved by raising the temperature to the growth temperature of the GaN cladding layer). For example, at 750 ° C., In _0.05 Ga
_When gaseous growth of _0.95 N is performed, and only the temperature is changed from the start of growth to 1000 ° C. while the supply gas source is kept as it is, GaN is substantially grown and the composition change of In decreases approximately exponentially ( The band gap increases).

Next, an embodiment in which the light emitting layer has the SQW structure will be described. In this embodiment, as shown in FIG.
Of the pair of barrier layers 21 and 22 constituting the QW structure 2,
The barrier layer 22 on the p-type semiconductor layer side has a feature.
However, it is characterized in that it is formed as a composition-graded structure such that the band gap becomes smaller as the distance from the p-type semiconductor layer 3 increases. This composition gradient is
As in the case of the MQW structure, the barrier layer 22 shown in FIG.
The continuous change in a straight line or curve as shown in FIG.
A step-like discontinuous change as shown in the barrier layer 22 of FIG.

By imparting the above-mentioned band gap gradient to the barrier layer on the p-type semiconductor layer side in the SQW structure, the injected holes can be provided in the same manner as the operation and effect described in the embodiment of FIG. Can be efficiently delivered to the well layer.

The combination of the materials constituting the MQW structure and the SQW structure (barrier layer, well layer) may be selected according to the desired emission wavelength for each material system. The change in the band gap of the barrier layer may be achieved by changing the composition ratio. For example, in a GaAs system, (barrier layer, well layer) =
(AlGaAs, AlGaAs), (AlInGaP,
AlInGaP). In the case of the InP system, (barrier layer, well layer) = (InGaAsP, InGaP)
AsP) and the like. In the GaN system, (barrier layer, well layer) = (InGaN, InGaN), (Al
InGaN, AlInGaN) and the like.

The light emitting device according to the present invention is a GaN light emitting device (MQW structure, SQW structure material is a GaN semiconductor)
In the case of, the effect is most remarkable.
This is because, as described as a problem in the description of the related art, holes are particularly difficult to diffuse in a GaN-based semiconductor material, and the unevenness of the hole density is remarkable in the MQW structure. , And MQW structure, S
This is because holes are not efficiently injected into the well layer in the QW structure. GaN-based semiconductor is In _x Ga _YA
l _Z N (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ Z ≦ 1, X + Y
+ Z = 1).

In the above-mentioned GaN system (barrier layer, well layer)
Of the combinations, (InGaN, InGa
In N), the luminous efficiency of the well layer is remarkably high, and the crystal growth of both the well layer and the barrier layer can be performed in substantially the same growth atmosphere. .

The materials of the well layers do not necessarily have to be the same, and may be different from each other.
It may be configured such that light of a plurality of wavelengths can be generated from within the structure.

[0036]

EXAMPLE In the following example, the G of the element structure shown in FIG.
An aN-based LED was manufactured, the light emitting layer was made to have an MQW structure, and the characteristics of each were evaluated by variously changing the change pattern of the barrier layer.

Example 1 In this example, as shown in FIG. 1, the number of barrier layers was six (the number of well layers therebetween was five). The change pattern of the band gaps of the barrier layers 21 to 26 is such that the band gap is sequentially reduced from the position after the p-type barrier layer 26 to the barrier layer 22 immediately before the n-type barrier layer 21. This is a pattern that decreases monotonically and linearly.

A sapphire C-plane wafer substrate B1 having a thickness of 500 μm was set in a normal pressure MOVPE apparatus, and the temperature was raised to 1100 ° C. in a hydrogen-rich gas stream. After performing thermal etching while holding for a predetermined time, the temperature was lowered to 450 ° C., and a low-temperature-grown GaN buffer layer B2 was grown to about 20 nm.
Subsequently, the temperature was raised to 1000 ° C.
An aN layer B3 is grown, and a 3000 nm n-Ga
An N layer (with Si added) 1 was grown. This n-GaN layer 1
Is an n-type contact layer and also an n-type cladding layer.

(Formation of MQW Structure in Light Emitting Layer) Subsequently, the growth temperature was set to 760 ° C., and the MQW structure was formed so that the change pattern of the band gap E of the barrier layer had the following specifications. . The thickness of each barrier layer is 6n.
m. All the well layers have a composition of In _0.35 Ga
_0.65 N (bandgap 2.60 eV) and thickness 2.8 nm. Most n-type barrier layer 21: composition In _0.05 Ga _0.95 N, E
= 3.28 eV. Barrier layer 22: composition In _0.15 Ga _0.85 N, E = 3.04e
V. Barrier layer 23: composition In _0.125 Ga _0.875 N, E = 3.09
eV. Barrier layer 24: composition In _0.1 Ga _0.9 N, E = 3.15 e
V. Barrier layer 25: composition In _0.075 Ga _0.925 N, E = 3.21
eV. Most p-type barrier layer 26: composition In _0.05 Ga _0.95 N, E
= 3.28 eV.

After the growth of the light emitting layer 2, the temperature was raised again to 1000 ° C. to grow a 50 nm Al _0.2 Ga _0.8 N clad layer to which Mg was added.
Was further grown.

After the completion of the crystal growth, when the temperature was lowered to 850 ° C., the ammonia gas and the hydrogen gas were all switched to the nitrogen gas flow, and cooled to near room temperature. Take out the laminate obtained by the above process from the MOVPE device,
Normal photolithography technology, electron beam evaporation technology,
Performs etching, electrode formation, etc. using reactive ion etching (RIE) technology, and finally LE
GaN-based LED according to the present invention processed and divided into D chips
And

[0042] For comparison with Comparative Example 1 above Example product, all the barrier layers in the MQW structure _{In 0.05 Ga 0. 95 N (E} = 3.28eV), except that a thickness of 6 nm, above Examples A GaN-based LED was manufactured in exactly the same structure as the product.

The light emission output (current 20 mA, wavelength 470 nm) of the bare chip state devices obtained in Example 1 and Comparative Example 1 was measured.
W, the comparative product was 5.0 mW, and it was found that the MQW structure of the light emitting device according to the present invention improved the light emission output.

Embodiment 2 In this embodiment, the number of barrier layers in the MQW structure of the light emitting layer is six, and the change pattern of the band gap of the barrier layer is such that the band gap is minimized near the center of the MQW structure. Pattern. More specifically, as shown in FIG. 3, the band gap decreases sequentially from the position next to the barrier layer 26 closest to the p-type side, monotonously decreases to the barrier layer 23 near the center, and the next barrier layer 22, most n It is a change pattern that increases sequentially with the barrier layer 21 on the mold side. Except for the specification of the MQW structure, the GaN LE
D was prepared.

(Formation of MQW Structure in Light Emitting Layer) The change pattern of the band gap of the barrier layer is as follows. Most n-type barrier layer 21: composition In _0.05 Ga _0.95 N, E
= 3.28 eV. Barrier layer 22: composition In _0.075 Ga _0.925 N, E = 3.21
eV. Barrier layer 23: composition In _0.15 Ga _0.85 N, E = 3.04e
V. Barrier layer 24: composition In _0.125 Ga _0.875 N, E = 3.09
eV. Barrier layer 25: composition In _0.075 Ga _0.925 N, E = 3.21
eV. Most p-type barrier layer 26: composition In _0.05 Ga _0.95 N, E
= 3.28 eV.

Light emission output (current: 20 mA, wavelength: 470 nm) of the element in a bare chip state obtained by Example 2
Was found to be 6.1 mW, indicating that the light emission output was improved as compared with the output of the device of Comparative Example 1.

Embodiment 3 In this embodiment, the total number of barrier layers in the MQW structure of the light emitting layer is set to six, and as shown in FIG.
The composition of the barrier layer 26 closest to the p-type semiconductor layer was graded stepwise so that the band gap in the layer 26 became smaller as the distance from the p-type semiconductor layer increased. MQ
The change pattern of the band gap of the barrier layer as the whole W structure is the same as in the second embodiment. Further, the band gap of the next barrier layer is made smaller than the band gap reduced in the barrier layer closest to the p-type semiconductor layer.

The specifications of the MQW structure are the same as those of the second embodiment except for the barrier layer 26 closest to the p-type side. The p-type side barrier layer 26 has an n-type side composition of In _0.05 Ga _0.95 N (E
= 3.28 eV), and the thickness becomes 2n toward the p-type side.
The composition gradient in the layer is stepwise at a rate at which the band gap increases by 22 meV for each m, the composition on the most p-type side is GaN (E = 3.39 eV), and the total thickness of this barrier layer is about 10 nm. And

A GaN-based LED was manufactured in exactly the same structure as in Example 1 except for the specifications of the MQW structure. The light emission output (current: 20 mA, wavelength: 470 nm) of the element in the bare chip state obtained by Example 3 was 6.5 mW, and was found to be 6.5 mW, which was the output of the element of Comparative Example 1 and the output of the element of Example 2 above. It was found that the light emission output was improved as compared with.

Embodiment 4 In this embodiment, as shown in FIG.
A W structure was used, and the barrier layer on the p-type side was a composition gradient layer that continuously changed. The structure of the entire device except for the SQW structure of the light emitting layer, and the manufacturing conditions up to forming a bare chip are the same as those in the first embodiment.

(Formation of SQW Structure) The composition of the barrier layer on the n-type side is In _0.05 Ga _0.95 N (E = 3.28 eV) and the thickness is 10
nm. Composition of well layer: In _0.35 Ga _0.65 N (E = 2.60 e)
V), thickness 2.8 nm. At the start of growth, the p-type side barrier layer has the same composition as the n-type side barrier layer at the same growth temperature as that of the well layer, _ie , In _0.05 Ga _0.95 N.
Was grown to a thickness of 5 nm, and the temperature was raised to the growth temperature (1000 ° C.) of the Mg-added AlGaN layer as the next layer while keeping the composition of the gas phase. By controlling the rate of temperature rise at this time, the InN mixed crystal ratio in the barrier layer is reduced with the temperature rise, and the total thickness is 10 mm.
A nm barrier layer was grown. The change in composition is 5 nm thick
At this point, the In composition starts to decrease and changes to almost GaN when the thickness is 8 nm.

After the growth of the light emitting layer, p-
An Al _0.2 Ga _0.8 N clad layer and a p-GaN contact layer were grown, and finally processed and divided into LED chips to obtain a GaN-based LED according to the present invention.

Comparative Example 2 For comparison with the device obtained in Example 4 above,
The barrier layer on the p-type side of the SQW structure is changed to In _0.05 Ga _0.95 N (E = 3.28) having no composition gradient similarly to the barrier layer on the n-type side.
eV) A GaN-based LED was manufactured in exactly the same structure as in Example 4 except that the thickness was 10 nm.

The light emission output (current: 20 mA, wavelength: 470 nm) of the element in a bare chip state obtained in Example 4 and Comparative Example 2 was measured.
W was 4.2 mW for the comparative example, and it was found that the SQW structure of the light emitting device according to the present invention improved the light emission output.

[0055]

As described above, by changing the band gap of the barrier layer of the MQW structure and the band gap of the p-type barrier layer of the SQW structure, the hole diffusion state is improved, The luminous efficiency of the well structure was improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing, as a band diagram, an example of a change pattern of a band gap of a barrier layer in an MQW structure of a light emitting device of the present invention. This band diagram is for visually indicating the change pattern of the band gap of the barrier layer to facilitate understanding, and the values of the details are different from the actual band diagrams (the same applies to other figures). Further, in the figure, the change pattern of the band gap is emphasized by a thick dashed line.

FIG. 2 shows a GaN-based LE as an example of the light emitting device of the present invention.
FIG. 4 is a diagram showing an element structure of D. Although the light-emitting layer 2 is not shown like a single layer, it has an MQW structure.

FIG. 3 is a diagram schematically showing another example of a band gap change pattern of a barrier layer in the MQW structure of the light emitting device of the present invention as a band diagram.

FIG. 4 is a diagram schematically showing another example of a change pattern of the band gap of the barrier layer in the MQW structure of the light emitting device of the present invention as a band diagram.

FIG. 5 is a diagram schematically showing an example of a change pattern of a band gap of a barrier layer on a p-type side when a light emitting layer has an SQW structure in the present invention as a band diagram.

FIG. 6 is a diagram schematically showing an example of an MQW structure in a conventional GaN-based LED by a band diagram.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 n-type semiconductor layer 2 light-emitting layer (MQW structure) 21 to 26 barrier layer W well layer 3 p-type semiconductor layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoichiro Ouchi 4-3 Ikejiri, Itami-shi, Hyogo Prefecture Mitsubishi Cable Industries, Ltd. Itami Works (72) Inventor Takashi Tsunekawa 4-3-1 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Wire F-term (reference) in Itami Works 5F041 AA03 CA05 CA34 CA40 CA46 CA57 CA65 CA74 5F045 AA04 AB14 AB17 AD11 AD12 AD13 AD14 AF09 BB04 BB16 CA10 CA12 DA55 DA58

Claims (7)

[Claims] 1. A light-emitting layer formed as a multiple quantum well structure, a p-type semiconductor layer and an n-type semiconductor layer sandwiching the light-emitting layer, wherein at least two of the barrier layers in the multiple quantum well structure are formed. A semiconductor light emitting device, wherein materials are selected such that band gaps are different from each other. 2. The semiconductor according to claim 1, wherein the material of the barrier layer is selected such that the band gap decreases as the distance from the p-type semiconductor layer increases in a specific section of the multiple quantum well structure. Light emitting element. 3. The semiconductor light emitting device according to claim 1, wherein a material of the barrier layer is selected so as to minimize a band gap at a central portion of the multiple quantum well structure. 4. The barrier layer closest to the p-type semiconductor layer among the barrier layers is formed as a composition-graded structure such that the band gap becomes smaller as the distance from the p-type semiconductor layer increases within the layer. Item 4. The semiconductor light emitting device according to any one of Items 1 to 3. 5. The semiconductor light emitting device according to claim 1, wherein said multiple quantum well structure is made of a GaN-based semiconductor. 6. A light-emitting layer formed as a single quantum well structure, and a p-type semiconductor layer and an n-type semiconductor layer sandwiching the light-emitting layer. A semiconductor light emitting device, wherein a barrier layer on the semiconductor layer side is formed as a composition-graded structure such that the band gap becomes smaller as the distance from the p-type semiconductor layer increases within the layer. 7. The semiconductor light emitting device according to claim 6, wherein said single quantum well structure is made of a GaN-based semiconductor.