JPH11354839A - GaN based semiconductor light emitting device - Google Patents

Abstract

(57) [Problem] To provide an optimum mode of a quantum dot for a GaN-based light-emitting device and to provide a more efficient GaN-based light-emitting device. SOLUTION: The following multiple quantum dot structure 3 is provided in a light emitting element as a portion related to light emission. The upper surface of the crystal layer A made of a GaN-based material is used as a base surface, and on the base surface,
Quantum dots d1 made of a GaN-based material are dispersedly formed, and a crystal layer (cap layer) made of a GaN-based material is further formed.
B1 is formed so as to embed the quantum dots therein, and a pair of the quantum dots and the cap layer is formed on the crystal layer A in a repetitive manner using the upper surface of the cap layer as a new base surface (d1, B1) to (d5, B5), a GaN-based multiple quantum dot structure formed by laminating two or more stages. However, the band gap of the dot material in each step is smaller than the band gaps of the cap material in the step and the material of the crystal layer serving as the base surface.

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 using a GaN-based material (hereinafter, also referred to as a "GaN-based light-emitting device"). The present invention relates to a multiple quantum dot structure made of a GaN-based semiconductor material.

[0002]

2. Description of the Related Art GaN-based light-emitting devices have been actively researched in recent years with the realization of high-brightness light-emitting diodes (LEDs). Has become.

[0003] Among GaN-based light-emitting devices, a device using an InGaN quantum well layer for a light-emitting layer (active layer) is known as a device capable of obtaining short-wavelength light emission of green to blue and high luminous efficiency. is there. When a quantum well layer is formed using InGaN, the composition ratio is not uniform over the entire layer due to its thermodynamic instability, and a portion having a different In composition ratio occurs locally in the layer. This part has properties similar to quantum dots. In a light-emitting element using a quantum well layer of InGaN as a light-emitting layer, this quantum dot-like portion exhibits an effect of confining excitons not only in the thickness direction of the layer but also in a three-dimensional direction. It is said that coupled light emission occurs, and this is called InGa
This is one of the factors that enable the N quantum well layer to emit light with high luminous efficiency.

[0004] A quantum dot-like site in the InGaN quantum well layer exists in the layer due to the properties of InGaN itself. On the other hand, among GaAs-based materials, formation of quantum dots utilizing lattice mismatch between a dot material and a substrate material is known. On the other hand, in recent years, by applying a special surface treatment to the surface of a crystal layer made of a GaN-based material, a G layer having good lattice matching with the surface of the crystal layer is formed.
It has been clarified that an aN-based semiconductor can be grown as a quantum dot in a projecting manner (Appl. Phys. Lett. 69 (1996) 4096).
). The mechanism of this quantum dot formation is based on the InG
This is completely different from the formation of quantum dots in aN or GaAs.

[0005]

SUMMARY OF THE INVENTION As described above, GaN
It has been clarified that quantum dots can be formed from a system material. However, in order to form a GaN-based light emitting device using the GaN-based quantum dots, it is still necessary to consider a preferable aspect of the quantum dot structure, individual sizes of the quantum dots, and a degree of distribution of the entire quantum dots. The optimal mode is not disclosed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems,
FIG. 4 shows an optimal embodiment of a quantum dot for an N-based light emitting device;
It is an object of the present invention to provide a GaN-based light emitting device with higher efficiency.

[0007]

The GaN based semiconductor light emitting device of the present invention has the following features. (1) A GaN-based multiple quantum dot structure of the following (i):
A GaN-based semiconductor light-emitting device having a light-emitting portion. (I) The upper surface of the crystal layer (A) made of a GaN-based material is used as a base surface, and quantum dots made of a GaN-based material are dispersedly formed on the base surface. Are formed so as to embed the quantum dots therein, and the formation of the quantum dots and the formation of the crystal layer (B) in which the quantum dots are embedded are repeated in a repetitive manner using the upper surface of the crystal layer (B) as a new base surface. This is repeated, so that two or more layers are formed on the crystal layer (A), with the set of the quantum dots and the crystal layer (B) as one step, and the band gap of the material of the quantum dots in each step. Is a crystal layer material serving as a base surface thereof and a crystal layer (B) embedding the material.
A GaN-based multiple quantum dot structure that is smaller than the band gap of each of the materials.

(2) In the GaN-based multiple quantum dot structure, the size of each quantum dot in each stage is set to a height h in the thickness direction of the crystal layer (B), and the crystal layer (B)
When the width of the quantum dots on the base surface of each step is defined as the density ρ,
0.5 nm ≦ h ≦ 50 nm, 0.5 nm ≦ w ≦ 200 n
m, 10 ⁶ cm ⁻² ≦ ρ ≦ 10 ¹³ cm ⁻² , wherein the GaN-based semiconductor light emitting device according to the above (1).

(3) The crystal layer (A) in the GaN-based multiple quantum dot structure is a cladding layer of the first conductivity type, and is further provided on the uppermost crystal layer (B). The GaN-based semiconductor light-emitting device according to (1), wherein the clad layer is provided.

(4) In the GaN-based multiple quantum dot structure, the GaN-based material used for the quantum dots in each stage is hereinafter referred to as “dot material”, and the GaN-based material used for the crystal layer serving as the base surface thereof The following "base material"
Shall be called. At this time, the dot material and the base material have a relationship satisfying the lattice matching of the following (ii), and the surface state of the base surface is changed by the anti-surfactant, so that the dot material becomes a quantum dot on the base surface. The GaN-based semiconductor light-emitting device according to the above (1), which is grown.

(Ii) When the dot material is directly crystal-grown on the base surface without performing a surface treatment for changing the surface condition of the base surface, the dot material is crystallized in a film form on the base surface. Lattice matching between the dot material and the base material that can grow.

[0012]

In the present invention, the quantum dots of each stage constituting the GaN-based multiple quantum dot structure (i) used as the portion relating to light emission are formed on the upper surface of the crystal layer made of the GaN-based material (that is, the above ( G) on the base surface in i)
An aN-based material is grown as a quantum dot.
However, the base material and the dot material have the relationship (ii). That is, when the dot material is grown on the base surface by the conventional crystal growth method and growth conditions without changing the surface state of the base surface at all, as conventionally known, the film is formed on the base surface as a film. It is a material that grows as a crystal layer that covers the entire surface. That is, the base material and the dot material, both of which are GaN-based materials, are at least lattice-matched to that extent.

In a state where the base material and the dot material, both of which are GaN-based materials, have a lattice matching relationship as described above, in order to grow the dot material on the base surface not as a film but as a quantum dot. Then, an anti-surfactant (a substance that changes the surface state of the surface of the GaN-based crystal layer serving as the base surface) acts on the base surface. The change in the surface state of the GaN-based crystal layer surface due to the action of the anti-surfactant has not been elucidated in detail, but is considered to be a change in which the surface free energy is reduced. By changing the surface state of the base surface in this way, the dot material grows as quantum dots on the base surface made of a GaN-based material.

As described above, quantum dots are grown on the base surface, and a crystal layer (B) made of a GaN-based material is grown using the remaining region of the base surface as a starting surface for crystal growth. B) Embedding quantum dots inside itself. According to the present invention, the combination of the quantum dot and the crystal layer (B) in which the quantum dot is embedded is repeatedly grown and stacked in multiple stages as in the above (i) to form an unconventional GaN-based multiple quantum dot structure, This is used for a light emitting element as a structure related to a light emitting phenomenon. The light emission phenomenon here is a phenomenon in which exciton (ethoxy) or an electron and a hole are recombined in a quantum dot by injection of an electron or a hole to emit light.

[0015]

FIG. 1 is a sectional view showing an example of a GaN-based light emitting device according to the present invention, and shows an LED having a simple structure as an example for explanation. In the LED shown in the figure, a crystal layer made of a GaN-based material is sequentially grown and stacked on a crystal substrate 1 to form a stacked body S including a plurality of quantum dot structures 3. It is configured by providing an n-type electrode 7. Multiple quantum dot structure 3
Exemplifies a five-stage structure. Layer 2 is an n-type contact layer, layer 5 is a p-type contact layer, and layer 4 is a p-type cladding layer. Further, in the example of FIG. 3, the crystal layer A providing the first base surface in the multiple quantum dot structure 3 is a layer serving as an n-type cladding layer corresponding to the p-type cladding layer 4. . Layers 2 to 5 are all GaN
It consists of a system material.

In the example of FIG. 1, the vertical position of the conduction type (p-type, n-type) is n-type on the crystal substrate side and p-type on the upper layer side for processing reasons for forming the conduction type. It has become common. Further, in the example of the figure, an insulator (sapphire crystal substrate) is used for the crystal substrate, and the electrode arrangement is such that the upper surface of the layer 2 is exposed and the electrode 7 is provided on the surface. Hereinafter, when describing other aspects of the light emitting device of the present invention, the p / n type upper / lower relationship and electrode arrangement will be described with reference to the same example. However, p /
The n-type upside down mode and the electrode arrangement when the crystal substrate has conductivity may be freely selected.

The multiple quantum dot structure has a structure in which a crystal layer made of a GaN-based material is a lowermost layer, and quantum dots are formed thereon and a crystal layer that embeds the quantum dots therein (hereinafter, this crystal layer is also referred to as a “cap layer”). It has a structure in which sets are stacked in two or more stages. These are all made of GaN-based materials. To explain the example of FIG. 1 in more detail, the crystal layer A made of a GaN-based material is used as the lowermost layer of the multiple structure, and the upper surface is used as the base surface. On the base surface, quantum dots d1 made of a GaN-based material are formed in a dispersed state. A crystal layer (cap layer) B1 made of a GaN-based material is used as a starting surface for crystal growth on a portion of the base surface where the quantum dots d1 are not formed.
Growing up to 1 embedded. The set of the quantum dots and the cap layer is counted as one stage.

Further, quantum dots d2 are formed again using the upper surface of the cap layer B1 as a new base surface, and the cap layers B2 are grown until the quantum dots d2 are embedded. The formation of the cap layer is repeated. By this repetition, on the crystal layer A, pairs of quantum dots and cap layers are stacked up to five levels as (d1, B1) to (d5, B5) to form a multiple quantum dot structure.

The multiple quantum dot structure referred to in the present invention refers to a structure in which quantum dots at each stage are covered by a material having a larger band gap than each dot material. In the example of FIG. 1, the multiple layers from the lowermost crystal layer A to the uppermost crystal layer B5 have a multiple quantum dot structure. In order to use this multiple quantum dot structure as a portion related to light emission, another crystal layer may be added as a layer involved in the light emission mechanism as needed. In addition, the conductivity type of each layer in the multiple quantum dot structure may be freely determined in addition to the following examples according to the desired light emission mechanism of the multiple quantum dot structure.

In the example shown in FIG. 1, the lowermost crystal layer A functions as a first conductivity type (n-type) cladding layer, and is further provided on the multiple quantum dot structure 3 for a light emitting mechanism. A second conductivity type (p-type) cladding layer 4 is added. The layer A is n-type, and each of the layers B1 to B5 is an undoped layer and has a weak n-type.

In the example of FIG. 2A, the lowermost crystal layer A
Is a layer for confining the quantum dots d1 with a material having a larger bandgap. An n-type / p-type cladding layer having a larger bandgap is added, and these layers sandwich the multiple quantum dot structure 3 from above and below. . Each layer from layer A to layer B3 is an undoped layer and has a weak n-type.

FIG. 2B shows a multiple quantum dot structure 3
In this example, the lowermost crystal layer A is an n-type cladding layer, and the uppermost crystal layer B3 is a p-type cladding layer. The layers B1 and B2 are undoped layers and have a weak n-type.

The band gap of the dot material used for the quantum dots in each stage is determined by the band material of the base material of the crystal layer serving as the base plane and the material of the cap layer embedding it (hereinafter referred to as “cap material”). What is necessary is just to be smaller than a gap. This is because electrons and holes are efficiently injected into the quantum dots in each stage, and this portion is used as a more efficient light emitting portion. If the relationship between the band gap of the dot material and the surrounding material satisfies this condition, the band gaps of the respective stages may be different from each other.

G used in the GaN-based light emitting device of the present invention
The aN-based material is represented by the formula In _x Ga _Y Al _Z N (0 ≦ X ≦
1,0 ≦ Y ≦ 1, 0 ≦ Z ≦ 1, X + Y + Z = 1). Among them, GaN, InGa
N and AlGaN are useful. G
In the aN-based multiple quantum dot structure, as a material combination satisfying the above band gap relationship, for example, the base material and the cap material are Al _x Ga _{(1- x)} N, and the dot material is Al _Y Ga _{(1- Y)} Combinations of N (where 0 <X, 0 ≦ Y, and Y <X).

The dot material may be doped with an impurity such as Si for the purpose of, for example, increasing the emission intensity.

One or more of the base material, the dot material, and the cap material further include B, As, P
And at least one element selected from the group consisting of:

The shape of each quantum dot varies depending on the material and growth conditions, but it is polyhedral, columnar, or hemispherical.

In order for the GaN-based multiple quantum dot structure to emit light with high efficiency, the size of each dot and the degree of distribution of the entire quantum dot on the base surface of the quantum dot in each stage are determined. It is necessary to set the optimum range. In addition, with respect to the entire multiple quantum dot structure, it is a preferable embodiment that the layer thickness, the density of the quantum dots, the composition of the material, and the like are changed for each step. The present invention provides an optimum range for forming these quantum dots and a preferable embodiment as a whole multiplex structure. This is described below.

The size of each quantum dot is an important factor that affects the luminous efficiency in the quantum dot structure, and it is important that the size is such that the quantum confinement effect is sufficiently obtained. The size of each quantum dot is determined by setting the height of the quantum dot in the thickness direction of the cap layer (the distance from the base surface to the top of the quantum dot) as the height h, and the maximum size of the quantum dot in the direction in which the cap layer extends. The preferable range is limited as the width w.

It is preferable that the height h and the width w of the quantum dot are small from the viewpoint of confinement of excitons contributing to light emission. It is preferably 0.5 nm or more. Regarding these maximum dimensions, from the viewpoint of the quantum effect, the height h is 50 nm or less and the width w is 200 n.
m or less is preferable. Therefore, 0.5 nm ≦ h ≦ 50n
m, 0.5 nm ≦ w ≦ 200 nm is a preferable range.

Since the degree of dispersion of the entire quantum dot on the base surface of each step is the density of the light emitting source on the base surface, this is also an important factor affecting the luminous efficiency. The degree of dispersion of the quantum dots is expressed as density (the number of quantum dots per unit area) ρ, and the range is limited.

The density ρ is preferably not less than 10 ⁶ cm ⁻² in consideration of luminous efficiency because light emission from each quantum dot is weak. Further, depending on the size of the quantum dot, the density ρ is 10 ¹³ so that the dots do not touch each other
cm ⁻² or less. Therefore, 10 ⁶ cm
^-2 ≦ ρ ≦ 10 ¹³ cm ⁻² is a preferable range.

The height h, width w, density ρ,
Parameters that determine the specifications of each stage, such as the layer thickness of each stage (that is, the layer thickness of the cap layer), the dot material of each stage, and the composition of the cap material, may be selected to be different between adjacent stages. . For example, when a set of a quantum dot and a cap layer has a three-layer structure, the emission wavelength changes to R (red), G (green), and B (blue) every time the level changes.
The composition of the dot material at each stage, the height h and the width w of the quantum dots,
Setting the density ρ, the layer thickness of the cap layer, and the like can be mentioned.

The mode of change when changing the specifications of each stage may be freely selected according to the purpose other than the above.
The parameter of the specification increases (decreases) monotonically every time the stage changes
Change, two kinds of specifications are alternated, and a step near the center is a change peak. Further, it is also possible to adopt a mode in which the specifications of a plurality of adjacent stages are the same, and the values are changed for each of a plurality of stages, such as not only for each stage but also for every two stages. When the composition of the material is changed, both the dot material and the cap material may be changed, or only one of the materials may be changed, for example, the dot material is kept constant and only the cap material is changed.

The GaN-based multiple quantum dot structure described above and a crystal layer such as a cladding layer added to the GaN quantum dot structure as necessary constitutes one unit. It may be provided. With this structure, it is possible to expand the range of functions of the element, for example, to make the emission wavelength different for each unit.

In order to form a quantum dot on the base surface, as described in the description of the operation, a GaN-based material used for the quantum dot is formed by applying a substance (anti-surfactant) to the base surface to change the surface state. The material is crystal-grown. In order for the anti-surfactant to act on the base surface, the anti-surfactant may be brought into contact with the base surface. The method of contact is not limited, for example,
If GaN quantum dots are formed by MOCVD using the upper surface of the AlGaN crystal layer as a base surface,
After the AlGaN crystal layer is grown in the MOCVD apparatus, a gaseous anti-surfactant may be supplied into the apparatus. After that, a Ga material, an N material and the like are supplied to grow a GaN crystal.

[0037] To supply the anti-surfactant as gaseous, for example, if the tetraethyl silane and the anti-surfactant, a method of supplying by bubbling H ₂ gas into the solution, the H ₂ gas as a carrier gas No.

The substance used as the antisurfactant can be appropriately selected according to the combination of the base material and the dot material, and is not limited. For example, as described above, tetraethylsilane is used as an antisurfactant when GaN is formed as a quantum dot on an AlGaN crystal layer. In addition, SiH ₄ , Si
₂ H ₆ , or a mixed gas thereof, Cp ₂ Mg (biscyclopentadienyl magnesium) or the like can be used.

The size and shape of each quantum dot and the degree of dispersion of the quantum dot can be controlled by changing the supply amount of the anti-surfactant, the growth temperature of the quantum dot, and the composition of the base material as parameters. The crystal growth method for growing quantum dots is M
OCVD, MBE and the like.

The crystal substrate may be any substrate on which a GaN-based crystal can be grown. For example, sapphire, quartz, SiC which has been widely used for growing a GaN-based crystal has been used.
And the like. Above all, sapphire C side, A side,
A 6H-SiC substrate, particularly a C-plane sapphire substrate, is preferred. In addition, ZnO, MgO for reducing the difference in lattice constant and coefficient of thermal expansion from the GaN-based crystal on the surface of these materials.
A buffer layer such as AlN or AlN may be provided, or a thin film of a GaN-based crystal may be provided on the surface. In the example of FIG. 1, a buffer layer 1 for improving lattice matching is formed on a base sapphire crystal substrate 1a.
The substrate on which b is formed is used as the crystal substrate 1.

[0041]

EXAMPLE In this example, an LED having the structure shown in FIG. 1 was actually manufactured. However, the multiple quantum dot structure 3 is shown as five stages (d1, B1) to (d5, B5) in the figure, but in this embodiment, there are ten stages. Regarding the configuration of the entire multiplex structure, all steps were formed in the same manner without changing the material or changing the specifications of the quantum dots every time the step was changed. The cap material of each stage is Al _0.1 Ga
_0.9 N, and all the dot materials were GaN. Also,
The material of the crystal layer A, which is the n-type cladding layer, and the material of the p-type cladding layer 4 were both Al _0.15 Ga _0.85 N.

[Formation of Crystal Substrate 1] A sapphire C-plane substrate was used as the most basic crystal substrate 1a. First, this sapphire substrate 1a was placed in a MOCVD apparatus, and heated to 1200 ° C. in a hydrogen atmosphere to perform thermal etching. Thereafter, the temperature was lowered to 500 ° C., and trimethylaluminum (hereinafter referred to as TMA) as an Al raw material and ammonia as an N raw material were flown.
The crystal substrate 1 was obtained.

[Formation of n-type contact layer 2] The growth temperature was raised to 1000 ° C., trimethylgallium (TMG) as a Ga source, ammonia as an N source, and silane as a dopant source were flown. 3
μm was grown.

[Formation of Multiple Quantum Dot Structure 3] Formation of Layer A: TMA, T
MG, ammonia, and silane were supplied as dopant materials, and an n-type AlGaN layer A was grown to 0.5 μm. This layer A is a layer that functions as an n-type cladding layer.

Surface treatment of the upper surface of the layer A (base surface): The growth temperature was set to 1000 ° C., tetraethylsilane was supplied using H ₂ gas as a carrier, and the upper surface of the layer A was contacted for 10 seconds.

Formation of the first stage quantum dot d1; TM
G and ammonia were supplied to form GaN quantum dots d1 on the base surface. The average of the height h of each quantum dot was 6 nm, and the average of the width w was 40 nm. The degree of dispersion of the quantum dots on the base surface (density, that is, the number of quantum dots per unit area) ρ is 3 × 10 ⁹ cm.
^-2 .

Formation of first-stage cap layer B1; growth temperature is set to 1100 ° C., TMA, TMG and ammonia are supplied, and a region where quantum dots are not formed on the base surface is used as a starting surface for crystal growth. A 10 nm-thick cap layer B1 was grown so that the dots were embedded inside.

Formation of the second stage or more: By repeating the above steps by using the upper surface of the cap layer as a new base surface, the set of the quantum dots and the cap layer in which the quantum dots are embedded Ten layers were stacked.

[Formation of p-type cladding layer 4]
100 ° C., TMA, TMG, ammonia, biscyclopentadienyl magnesium (Cp ₂ Mg) as a dopant raw material were supplied, and the p-type AlGaN layer
μm was grown.

[Formation of p-type contact layer 5] A p-type GaN contact layer 5 was grown to 1 µm by supplying TMG, ammonia, and Cp ₂ Mg as a dopant material at a growth temperature of 1000 ° C.

[Formation of Electrodes] The sample was taken out of the apparatus and annealed at 800 ° C. for 20 minutes in a nitrogen atmosphere. Finally, a p-type electrode 6 is formed on the p-type contact layer 5, and a part of the p-type layer and the quantum dot structure is removed by etching from the upper surface of the laminate by dry etching.
The upper surface of the n-type contact layer 2 was exposed, and an n-type electrode 7 was formed to complete an LED.

This LED was mounted on a To-18 stem base, and the luminous intensity was measured at 20 mA.
It was 0 mcd.

Comparative Example In Example 1, the combination of the quantum dot and the cap layer was changed to 1
An LED was manufactured in the same manner as in Example 1 except that only the steps were used. About this LED, 20 m
The luminous intensity measured at A was 75 mcd.

[0054]

The GaN-based light-emitting device of the present invention has a quantum dot structure made of a GaN-based material as a portion related to light emission, and has a multistage quantum dot structure as an optimal mode. . Furthermore, the proposal proposes to limit the appropriate range of the height and width of each quantum dot in each stage and the degree of dispersion of the quantum dots, and to give specification changes for each stage even for the entire multi-stage structure. is there. By these aspects of optimization, a GaN-based light-emitting device with higher efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a GaN-based light emitting device of the present invention. In the figure, for the sake of explanation, the thickness of each layer, the dimensions of the quantum dots / electrodes, and the like are exaggerated, and are different from the actual ratios. Also, to distinguish from other layers, electrodes,
The layers A and B1 to B5 are hatched.

FIG. 2 is a cross-sectional view showing another example of a multiple quantum dot structure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 crystal substrate 2 n-type contact layer 3 multiple quantum dot structure A n-type cladding layer d1 to d5 quantum dot of each stage B1 to B5 cap layer of each stage 4 p-type cladding layer 5 p-type contact layer 6 p-type electrode 7 n Type electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoru Tanaka 13-2-3 Miyanomori 1-chome, Chuo-ku, Sapporo-shi, Hokkaido 3-2 Solairard Miyanomori 3-2 (72) Inventor Katsunobu Aoyagi 2-1 Hirosawa, Wako-shi, Saitama RIKEN (72) Inventor Yoichiro Ouchi 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Cable Industries Co., Ltd.Itami Works (72) Inventor Hiroaki Ogawa 4-3-1 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Wire Co., Ltd. Itami Works (72) Inventor Kazuyuki Tadomo 4-3 Ikejiri, Itami-shi, Hyogo Mitsubishi Electric Cable Industry Co., Ltd.

Claims (4)

[Claims] 1. A GaN-based semiconductor light-emitting device having a GaN-based multiple quantum dot structure (i) as a portion related to light emission. (I) The upper surface of the crystal layer (A) made of a GaN-based material is used as a base surface, and quantum dots made of a GaN-based material are dispersedly formed on the base surface. Are formed so as to embed the quantum dots therein, and the formation of the quantum dots and the formation of the crystal layer (B) in which the quantum dots are embedded are repeated in a repetitive manner using the upper surface of the crystal layer (B) as a new base surface. This is repeated, so that two or more layers are formed on the crystal layer (A), with the set of the quantum dots and the crystal layer (B) as one step, and the band gap of the material of the quantum dots in each step. Is smaller than the respective band gaps of the material of the crystal layer serving as the base surface and the material of the crystal layer (B) embedding the same.
N-type multiple quantum dot structure. 2. In the GaN-based multiple quantum dot structure, the size of each quantum dot in each stage is determined by the size of the crystal layer (B).
The height h is in the thickness direction, the width w is in the spreading direction of the crystal layer (B), and the density ρ is the degree of dispersion of the quantum dots on the base surface of each step.
nm ≦ h ≦ 50 nm, 0.5 nm ≦ w ≦ 200 nm, 1
^{0 6 cm -2 ≦ ρ ≦ 10} 13 cm -2, GaN -based semiconductor light-emitting device according to claim 1, wherein a. 3. The crystal layer (A) in the GaN-based multiple quantum dot structure is a first conductivity type clad layer,
2. The GaN-based semiconductor light emitting device according to claim 1, further comprising a second conductivity type cladding layer provided on the uppermost crystal layer (B). 4. In the GaN-based multiple quantum dot structure, a GaN-based material used for quantum dots in each stage is called a dot material, and a GaN-based material used for a crystal layer serving as a base surface is called a base material. As the dot material and the base material have a relationship satisfying the lattice matching shown in (ii) below, the dot state grows as quantum dots on the base surface by changing the surface state of the base surface by anti-surfactant. The GaN-based semiconductor light emitting device according to claim 1, wherein (Ii) When the dot material is directly crystal-grown on the base surface without performing a surface treatment to change the surface state of the base surface, the dot material can grow into a film-like crystal on the base surface. Lattice matching between such dot material and base material.