JP2002033513A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the luminous efficiency of a GaN-based compound semiconductor light emitting element. SOLUTION: This P-N junction light emitting element is formed by sequentially forming an N-type GaN layer 12, an N-type GaN-based layer 14, and a P-type GaN-based layer 16 on a sapphire substrate 10. The layer 14 is constituted in a superlattice structure by alternately laminating GaN and AlGaN upon another, and the luminous efficiency of the light emitting element is improved by doping the GaN with Si and In and AlGaN with In. In addition, the layer 14 is caused to emit light by forming SiN in the interface between GaN and AlGaN and increasing the resistance value of the layer 14, and then, injecting holes into the layer 14. It is also possible to cause the injected electrons to make Bragg reflection by adjusting the thickness of the P-type GaN-based layer 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-emitting element,
The present invention relates to an improvement in luminous efficiency of a light-emitting element formed by laminating N and AlGaN.

[0002]

2. Description of the Related Art Blue (emission wavelength: 450 n) using GaN
m) to green (emission wavelength: 500 nm) light emitting diode (LED) is considered to be applied to traffic signals, outdoor displays, and the like. The material of this LED is specifically InGaN. However, in order to shorten the emission wavelength and obtain light emission in, for example, an ultraviolet region, it is necessary to reduce the In composition and approach GaN. However, it is known that when the composition of In is reduced, the luminous efficiency is significantly deteriorated, and an LED having a wavelength shorter than 370 nm and having practical efficiency has not yet been developed.

[0003] An LED that emits light in the ultraviolet region is expected to be applied to many fields, and is expected to be used, for example, as a light source for optical recording and reproduction or as a light source for optical communication.

[0004]

On the other hand, GaN and AlG
It has been reported that the emission wavelength can be shortened to 340 nm without lowering the emission efficiency by employing a multilayer structure in which aN is laminated. In the case where InGaN is used as the light emitting layer, the luminous efficiency is extremely high despite the extremely high dislocation density due to the fluctuation of the composition of In. As described above, the shortest wavelength is obtained when the In composition is 0,
Since the composition fluctuation does not occur in GaN, the luminous efficiency is significantly reduced due to the influence of dislocation. AlG with In replaced with Al
In the case of aN, although the emission wavelength is shortened, the composition efficiency of Al does not fluctuate, so that the emission efficiency is reduced. However, since the superlattice structure is formed by alternately laminating very thin (about 2-3 nm) GaN and AlGaN, the thickness of each layer slightly fluctuates, so that the same effect as the composition fluctuation is obtained. ,
It is considered that the luminous efficiency does not deteriorate unlike the single-layer AlGaN.

As described above, the superlattice structure in which GaN / AlGaN is stacked is considered promising. However, as described above, in order to be put to practical use as a light source for optical communication or a reading light source for a recording medium, it is necessary to further improve the structure. Improvement in luminous efficiency or luminous intensity is required.

In particular, when a light-emitting device is configured with a GaN / AlGaN structure, it is necessary to form a PN junction, and a structure that enhances luminous efficiency or a structure that effectively extracts emitted light to the outside is required. .

The present invention has been made in view of the above-mentioned problems of the related art, and an object of the present invention is to provide a light emitting device having excellent luminous efficiency.

[0008]

In order to achieve the above object, the present invention relates to a light emitting device comprising a GaN-based compound semiconductor and a PN junction, wherein the N-type semiconductor layer comprises GaN and AlG.
aN are alternately stacked, and the GaN
SiN is discretely formed at an interface between AlGaN and AlGaN. Since an N-type semiconductor layer formed by alternately stacking GaN and AlGaN has a high luminous efficiency, it is preferable to inject holes into this layer when a PN junction is formed to cause luminescence within this layer. By forming SiN, which is an insulator, at the interface between GaN and AlGaN, the resistance value of the N-type semiconductor layer can be increased, and electrons and holes can be taken in and recombined in this layer to emit light. Note that SiN discretely formed at the interface between GaN and AlGaN causes fluctuation of the band gap in GaN or AlGaN formed thereon, and can itself improve the luminous efficiency of the N-type semiconductor layer.

Further, the present invention is a light emitting device comprising a GaN-based compound semiconductor with a PN junction, wherein the N-type semiconductor layer comprises:
It is characterized in that AlGaN doped with Mg is formed at the interface between the GaN and the AlGaN while alternately stacking GaN and AlGaN. Mg-doped AlGaN increases the resistance value of the N-type semiconductor layer, thereby increasing the applied voltage in the N-type semiconductor layer to take in holes and electrons and allow the N-type semiconductor layer to emit light.

Further, the present invention is a light emitting device comprising a GaN-based compound semiconductor with a PN junction, wherein the N-type semiconductor layer comprises:
GaN and AlGaN are alternately laminated, and an interface between the N-type semiconductor layer and the P-type semiconductor layer is made of AlGa.
N is formed. AlGaN formed at the interface between the N-type semiconductor layer and the P-type semiconductor layer acts as an energy barrier for electrons (AlGaN also acts as a barrier to holes, but its size is smaller than electrons). It is possible to suppress the transfer of electrons from the semiconductor layer to the P-type semiconductor layer and promote light emission in the N-type semiconductor layer.

Further, the present invention is a light emitting device in which a GaN-based compound semiconductor is formed by PN junction, wherein the P-type and N-type semiconductor layers are formed by alternately stacking GaN and AlGaN. The thickness of AlGaN is set so as to satisfy the Bragg condition with respect to electrons injected into the P-type semiconductor layer, and is set so as not to satisfy the Bragg condition with respect to holes injected into the N-type semiconductor. It is characterized by the following. The electrons injected into the P-type semiconductor layer have a de Broglie wavelength according to the energy level, and the film thickness of each of the GaN / AlGaN laminated structures (specifically, superlattice) is different from the de Broglie wavelength by the Bragg condition. When satisfies, the electrons are totally reflected at the interface of the superlattice. on the other hand,
Since the holes have an energy level different from that of the electrons, the Bragg condition is not satisfied, the holes move from the P-type semiconductor layer into the N-type semiconductor layer, and recombine with the electrons in the N-type semiconductor layer to emit light. Since the energy level of electrons changes according to the bias voltage applied to the light emitting element, phenomenologically,
It can be said that the film thickness is set so as to Bragg-reflect electrons in the P-type semiconductor layer at the driving voltage V of the light-emitting element and cause recombination in the N-type semiconductor layer. Alternatively, a periodic energy barrier is formed by adjusting the thickness of the P-type semiconductor layer, and Bragg reflection is caused on the energy of electrons injected into the P-type semiconductor layer when a bias voltage is applied. Dominantly (ie, P
It can also be said that recombination occurs (at a greater rate than in the type semiconductor layer).

[0012] In the light emitting device of the present invention, further, a substrate, an N-type AlGaN layer formed on the substrate and adjacent to the N-type semiconductor layer, and a P-type semiconductor layer formed on the P-type semiconductor layer.
Type AlGaN ohmic layer. By forming both the buffer layer and the ohmic layer of AlGaN, absorption of light in the ultraviolet region emitted from the N-type semiconductor layer can be suppressed, and luminous efficiency can be improved.

Further, in the light emitting device of the present invention, further, a substrate, an N-type GaN layer formed on the substrate,
A reflective layer formed on the N-type GaN layer and adjacent to the N-type semiconductor layer, wherein the light emitted from the PN junction can be reflected by the Bragg reflective layer.
Light in the ultraviolet region emitted from the N-type semiconductor layer is reflected by the Bragg reflection layer, and absorption in the GaN layer can be suppressed.

Further, in the light emitting device of the present invention, the N
It is preferable that at least either GaN or AlGaN of the type semiconductor layer is doped with Si. The applicant of the present application has confirmed that the light emission intensity of the N-type semiconductor layer is increased by doping with Si, whereby the light emission efficiency of the light emitting element can be improved.

Further, in the light emitting device of the present invention, the N
The GaN of the type semiconductor layer is doped with Si and In,
Preferably, the AlGaN is doped with In. The present applicant has doped GaN with Si and In,
It has been confirmed that doping GaN with In increases the light emission intensity of the N-type semiconductor layer, whereby the light emission efficiency of the light emitting element can be improved.

Further, in the light emitting device of the present invention, the N
It is preferable that Si is formed at the interface between the GaN and the AlGaN in the semiconductor layer. Si formed at the interface between GaN and AlGaN causes lattice mismatch, and GaN / AlGaN
AlGaN causes local thickness fluctuations. As a result, fluctuation of the band gap is caused in GaN / AlGaN, and the luminous efficiency can be improved.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a light emitting device according to this embodiment. N-type Ga on sapphire substrate 10
The N layer 12 is formed, for example, at about 2 μm. The N-type GaN-based layer 1 is further formed on the N-type GaN layer 12 as an N-type semiconductor layer.
4 are formed, and a P-type GaN-based layer 16 is further laminated. A PN junction is formed at the interface between the N-type GaN-based layer 14 and the P-type GaN-based layer 16, and holes are injected from the P-type GaN-based layer 16 into the N-type GaN-based layer 14 by applying a predetermined voltage to emit light. I do. The N-type GaN-based layer 14 is composed of GaN and A
Superlattice structure (SLS strained
layer superlattice). Further, the P-type GaN-based layer 16 can also have a superlattice structure in which GaN and AlGaN are alternately stacked. Of course, P-type GaN
The system layer 16 may not have a super lattice structure. Although not shown, a P-type GaN ohmic layer is formed on the P-type GaN-based layer 16 and is connected to an electrode by an ohmic contact.

FIG. 2 shows the N-type GaN-based layer 1 shown in FIG.
4 are shown. GaN14a and AlGa
In this embodiment, the GaN 14a is doped with In and Si, and the AlGaN 14b is doped with In. Here, “doping” in the specification of the present application means that the material is introduced into the reaction tube during the layer growth process. The specific creation method is as follows. That is, after the substrate is placed in the reaction tube and the N-type GaN layer 12 is formed, TMG, NH ₃ , H _2, In and Si are placed in the reaction tube.
Gas such as TMIn or SiH ₄ is introduced to introduce In
And GaN 14a doped with Si are formed by MOCVD. When forming AlGaN 14b on GaN 14a, TMG and TMAl are introduced into the reaction tube, and a gas containing In, for example, TMIn is introduced to form AlGaN 14b doped with In. I
The introduced amount of n or Si is, for example, TMIn = 1.8 μmol.
/ Min and SiH ₄ = 446 μmol / min. The thicknesses of the GaN 14a and the AlGaN 14b are both about 2 nm, and these sets are formed in a total of about 250 pitches (only three pitches are shown in the figure for simplicity). The thickness of the superlattice layer is determined by the diffusion length of the injected carriers, and when it is less than that, the luminous efficiency decreases. On the other hand, if the thickness of the superlattice exceeds 1 μm, cracks occur.
m, a thickness that does not cause cracks, specifically 10 n
m to 500 nm.

As described above, the N-type GaN-based layer 14 of the light emitting device of this embodiment is formed by doping GaN with In and Si and doping AlGaN with In.
The present applicant has confirmed that the emission intensity is remarkably increased (specifically, about 20 times) as compared with the case where N and AlGaN are not doped at all.

On the other hand, since GaN is doped with Si, the N-type GaN-based layer 14 is of N + type, and when biased in the forward direction with respect to the N + and P− junctions, electrons are contained in N +. Due to the large number of electrons, the number of electrons injected from the N + layer 14 into the P− layer 16 is overwhelmingly larger than the number of holes injected from the P− layer 16 into the N + layer 14. Layer 16 having relatively low luminous efficiency
May occur in In order to emit light in the N + layer 14 having excellent luminous efficiency, a junction with a P-type layer having a high hole concentration may be formed to be N + / P ++. However, a P-type layer having a high hole concentration in a GaN system is formed. It is difficult to do.

Therefore, in the present embodiment, the N-type GaN-based layer 14 having excellent luminous efficiency is adopted,
In order to cause the aN-based layer 14 to emit light, the following configuration is employed.

FIG. 3 shows the N-type GaN in this embodiment.
The configuration of the system layer 14 is shown. The basic structure is the same as the structure shown in FIG.
Although the configuration is such that AlGaN 14b doped with a and In are alternately stacked, SiN 14c is further formed at the interface between GaN 14a and AlGaN 14b. That is, GaN (In and Si doped) / SiN / AlGaN
(In-doped). SiN14c is made of GaN
It is not uniformly formed at the interface between AlGaN 14a and AlGaN 14b, but is formed discretely. The specific formation method is
After forming GaN 14a doped with In and Si,
At a growth temperature of GaN 14a (for example, 1050 ° C.), NH ₃ and SiH ₄ are introduced into the reaction tube for about several seconds. By supplying for only a few seconds, SiN 14c is not formed uniformly on GaN 14a, but is formed discretely.

By forming the SiN 14c, the SiN 1c is formed.
The applicant has confirmed that the luminous efficiency increases as compared with the case where 4c is not formed, and furthermore, since SiN 14c functions as an insulator, the resistance value of the entire N-type GaN-based layer 14 increases. When the resistance value of the N-type GaN-based layer 14 increases, a relatively large voltage is applied to the N-type GaN-based layer 14 when a forward bias is applied to the PN junction, and electrons and holes are drawn from both sides of this layer. Light emission will occur in this layer. That is, in the configuration of FIG. 1, by using the N-type GaN-based layer 14 shown in FIG. 3, it is possible to surely cause the N-type GaN-based layer 14 to emit light and to improve the luminous efficiency.

FIG. 4 shows the structure of another N-type GaN-based layer 14. In FIG. 3, GaN 14a and AlGaN
14b, the SiN 14c is formed between the GaN 14a and the AlGaN 14b.
SiN 14c is also formed between AlGaN 14b and GaN 14a formed thereon. That is, GaN
SiN14c at all interfaces between AlGaN 14b and AlGaN 14b
Are formed. Also with this configuration, the resistance value of the N-type GaN-based layer 14 can be increased, and electrons and holes can be drawn to cause the N-type GaN-based layer 14 to emit light.

Alternatively, a superlattice structure can be formed by stacking a plurality of pitches of GaN (In, Si-doped) / AlGaN (In-doped) / SiN at a plurality of pitches.

FIG. 5 shows the structure of another N-type GaN-based layer 14. 3 and 4, GaN 14
By forming SiN 14c at the interface between a and AlGaN 14b, the luminous efficiency is improved and the resistance value is increased.
In this embodiment, the resistance value is increased by using Mg instead of SiN. That is, it is known that when AlGaN is doped with Mg, the resistance value increases.
AlGaN 14d doped with Mg is formed at the interface between N14a and AlGaN 14b. That is, GaN (I
n, Si doped) 14a / AlGaN (Mg doped) 1
This is a configuration of 4d / AlGaN (In-doped) 14b.
Note that Zn can be doped instead of Mg.

FIG. 6 shows the structure of another N-type GaN-based layer 14. In FIG. 5, GaN 14a and AlG
AlGaN14d doped with Mg between aN14b
In FIG. 6, GaN 14a and AlGaN are formed.
A doped with Mg not only between AlGaN 14b but also between AlGaN 14b and GaN 14a formed thereon.
lGaN 14d is formed. That is, GaN 14a
A in which Mg is doped at all interfaces between AlGaN and AlGaN 14b
1GaN 14d is formed. Also with this configuration, the resistance value of the N-type GaN-based layer 14 can be increased, and electrons and holes can be drawn to cause the N-type GaN-based layer 14 to emit light.

In the configurations shown in FIGS.
Although it is possible to increase the resistance value of the N-based layer 14,
If the resistance of the N-type GaN-based layer 14 as the active layer is high, PN
The current in the joining surface is likely to be uniform, and the light extraction efficiency is increased.

Further, in the configuration shown in FIGS.
Is doped with In and Si, and AlGaN is doped with In. However, any of GaN and AlGaN may be doped with Si.
Only aN may be doped with Si. GaN and AlGa
Any of N can be doped with Si and In.
When both GaN and AlGaN are doped with Si, the emission intensity is increased by about 17 times as compared with the case where nothing is doped, and when only GaN is doped with Si, the emission intensity is increased by about 13 times.
The present applicant has confirmed that when the AlGaN is doped only with Si, the increase is about 16 times.

Also, instead of the configuration shown in FIGS.
In the superlattice (SLS: strained layer superlattice) structure in which GaN and AlGaN are alternately stacked, a material in which Si is discretely formed at the interface between GaN and AlGaN can be used as the aN-based layer 14. The discretely formed Si has a large lattice mismatch, and if there is a lattice mismatch portion at the interface of the superlattice, a minute roughness is generated on the surface, and the film thickness at the rough portion changes. When the film thickness becomes non-uniform, the quantum level based on the quantum effect changes spatially, so that the band gap fluctuates spatially and the luminous efficiency can be increased by setting the dislocation density or higher (Japanese Patent Application No. 2000-1643).
No. 49). Also in this case, by forming AlGaN doped with SiN or Mg at the interface, the resistance value can be increased and light can be emitted from the N-type GaN-based layer 14.

FIG. 7 shows a configuration of a light emitting device according to another embodiment. In the configuration shown in FIG.
Although the P-type GaN-based layer 16 is formed adjacent to the aN-based layer 14, in this embodiment, the N-type GaN-based layer 14 and the P-type Ga
An AlGaN layer 15 is formed at the interface of the N-based layer 16. A
The lGaN layer 15 is formed thin enough to cause a tunnel effect, and preferably has a thickness of about 1 to 50 nm, more preferably about 2 to 10 nm. As the N-type GaN-based layer 14, the N-type GaN-based layer shown in FIG. 2 can be used. When a forward bias is applied in such a configuration, the N-type G
The band gaps of the aN-based layer 14 and the P-type GaN-based layer 16 are smaller than those of the undoped AlGaN single layer, and the AlGaN layer 15 acts as an energy barrier for electrons. The AlGaN layer 15 acts as an energy barrier not only for electrons but also for holes. However, as shown in FIG. 8, since the barrier for electrons is larger than the barrier for holes, the AlGaN layer 15 has more holes than the P-type GaN-based layer 16 and the N-type. G
It is injected into the aN-based layer 14. Therefore, light can be emitted from the N-type GaN-based layer 14 having high luminous efficiency.

In FIG. 7, instead of the AlGaN layer 15, AlGaN doped with Mg or Zn may be used to increase the resistance.

FIG. 7 shows an N-type GaN-based layer 1.
At the interface between the P-type GaN-based layer 4 and the P-type GaN-based layer 16, the injection of holes is promoted by forming a layer having a larger energy barrier for electrons than for holes. By alternately stacking GaN and AlGaN to form a superlattice structure and adjusting the film thickness of GaN and AlGaN, electrons can be confined in the N-type GaN-based layer 14 and the injection of holes can be promoted.

Since electrons and holes also have wave properties (de Broglie waves or matter waves), they are reflected at each interface in a layer having periodic energy as shown in FIG. When the Bragg condition is satisfied with respect to the de Broglie wavelength whose energy cycle is determined by the energy level of the electrons, the light is totally reflected and cannot move. Since the effective mass and the height of the energy barrier are different between electrons and holes, if the energy barrier and the period of the P-type GaN-based layer 16 are set so as to satisfy the Bragg condition for electrons, the electrons are injected into the P-type GaN-based layer 16. The electrons are totally reflected and cannot move in the P-type GaN-based layer 16, but holes are injected into the N-type GaN-based layer 14 without being totally reflected because the Bragg condition is not satisfied. As described above, GaN and Al in the P-type GaN-based layer 16 are
By setting the thickness of GaN so that the Bragg condition is satisfied with respect to the injected electrons, the N-type GaN-based layer 14 is formed.
This causes recombination of holes and electrons to emit light. The specific conditions are as follows.

[0036]

(Equation 1)

(Equation 2) Where m ^* is the effective mass of an electron or hole,
E is the energy of electrons or holes, L is the thickness of the barrier (B) and well (W), U0 is the energy height of the barrier, h is Planck's constant, and m and n are integers.

The GaN of the P-type GaN-based layer 16 formed by alternately stacking GaN and AlGaN functions as a well layer (subscript w), and AlGaN functions as a barrier layer (subscript B). The specific thickness of GaN and AlGaN varies depending on the Al composition x of AlGaN. For example, x = 0.15, Δ
If Eg = 200 meV and ΔEc = 140 meV,
Lw (thickness of GaN as a well layer) = 1.8 ± 0.5 n
m, LB (thickness of AlGaN as a barrier layer) = 1 ±
It is about 0.5 nm.

FIG. 10 shows the structure of a light emitting device according to still another embodiment. 3 to 6 can be used as the N-type GaN-based layer 14. In the configuration shown in FIG. 1, a PN junction layer is formed on the N-type GaN layer 12, and a GaN ohmic layer is formed thereon. However, GaN is opaque to light in the ultraviolet region (UV). In this case, the light emitted from the active layer is absorbed by GaN, and the efficiency may be reduced.

Therefore, in this embodiment, the luminous efficiency in the active layer is improved, and absorption in a layer adjacent to the active layer is also prevented. Specifically, as shown in FIG.
An AlGaN layer 13 (for example, 1.5 μm) is formed, and a P-type AlGa is formed as an ohmic layer on the PN junction layer.
An N ohmic layer 17 is formed. AlG compared to GaN
Since aN is relatively transparent to UV, it can suppress UV absorption from the active layer.

FIG. 11 shows the structure of a light emitting device according to still another embodiment. 3 to 6 can be used as the N-type GaN-based layer 14.
In the present embodiment, in the configuration of FIG.
A Bragg reflection layer 18 for Bragg-reflecting light emitted at the interface between the substrate and the N-type GaN-based layer 14, and further forming a P-type Ga
A UV transparent P-type AlGaN ohmic layer 17 is formed on the N-based layer 16. The Bragg reflection layer 18 is made of GaN, AlGaN for the wavelength of light (UV) from the active layer.
Is adjusted to １ ／ wavelength, and is laminated to reflect incident light to prevent UV from being absorbed by the lower N-type GaN layer. Further, since the P-type AlGaN ohmic layer 17 is formed on the upper part instead of the GaN ohmic layer, absorption of UV can be prevented.

Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications are possible. For example, as shown in FIG. 1, a sapphire substrate / N-type GaN layer / N-type GaN-based layer / P-type G
An aN-based layer / P-type ohmic layer (the N-type GaN-based layer 14 may be one shown in FIGS. 3 to 6), and then another substrate is attached to the surface to form a sapphire substrate. Alternatively, the N-type GaN layer 12 may be removed by polishing or light irradiation to prevent absorption by the N-type GaN layer 12.

[0042]

According to the present invention, light emission efficiency can be increased by causing light emission in the N-type semiconductor layer at the PN junction. Further, absorption of light emitted from the active layer can be suppressed, and luminous efficiency can be increased.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a light emitting device according to an embodiment.

FIG. 2 is a basic configuration diagram of an N-type GaN-based layer in FIG.

FIG. 3 is a configuration diagram of an N-type GaN-based layer according to the embodiment.

FIG. 4 is a configuration diagram of another N-type GaN-based layer according to the embodiment.

FIG. 5 is a configuration diagram of another N-type GaN-based layer according to the embodiment.

FIG. 6 is a configuration diagram of another N-type GaN-based layer according to the embodiment.

FIG. 7 is an overall configuration diagram of another light emitting element according to the embodiment.

FIG. 8 is an explanatory diagram of bands of electrons and holes.

FIG. 9 is an explanatory diagram showing a relationship between de Broglie waves and a periodic energy barrier.

FIG. 10 is an overall configuration diagram of another light emitting element according to the embodiment.

FIG. 11 is an overall explanatory diagram of another light emitting element according to the embodiment.

[Explanation of symbols]

10 sapphire substrate, 12 N-type GaN layer, 14 N
-Type GaN-based layer, 16P-type GaN-based layer.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 AA11 AA20 BA02 BA08 BA38 BB12 FA10 5F041 AA03 AA11 CA05 CA34 CA40 CA46 CA57 CB15 FF01 FF14 FF16 5F045 AA04 AB14 AB17 AB33 AC01 AC12 AF09 BB16 CA09 DA53 DA54

Claims (9)

[Claims] 1. A light emitting device comprising a GaN-based compound semiconductor and a PN junction, wherein an N-type semiconductor layer is formed by alternately stacking GaN and AlGaN, and is discretely provided at an interface between the GaN and AlGaN. A light-emitting element comprising SiN formed thereon. 2. A light emitting device comprising a GaN-based compound semiconductor and a PN junction, wherein the N-type semiconductor layer is formed by alternately stacking GaN and AlGaN, and Mg is present at an interface between the GaN and AlGaN. A light-emitting device, wherein doped AlGaN is formed. 3. A light emitting device comprising a GaN-based compound semiconductor and a PN junction, wherein the N-type semiconductor layer is formed by alternately stacking GaN and AlGaN, and wherein the N-type semiconductor layer and the P-type semiconductor A light-emitting element wherein AlGaN is formed at an interface between layers. 4. A light emitting device comprising a GaN-based compound semiconductor and a PN junction, wherein the P-type and N-type semiconductor layers are formed by alternately stacking GaN and AlGaN, and the GaN and AlGaN
Is set so as to satisfy the Bragg condition for electrons injected into the P-type semiconductor layer, and not to satisfy the hole injected into the N-type semiconductor layer. Characteristic light emitting element. 5. The light-emitting device according to claim 1, further comprising: a substrate; and N formed on the substrate and adjacent to the N-type semiconductor layer.
A light emitting device comprising: a p-type AlGaN layer; and a p-type AlGaN ohmic layer formed on the p-type semiconductor layer. 6. The light emitting device according to claim 1, further comprising: a substrate; an N-type GaN layer formed on the substrate; and an N-type GaN layer formed on the N-type GaN layer. And a reflection layer adjacent to the mold semiconductor layer, wherein the Bragg reflection layer reflects light emitted from the PN junction. 7. The light emitting device according to claim 1, wherein at least one of GaN and AlGaN of the N-type semiconductor layer is doped with Si. 8. The light emitting device according to claim 1, wherein said GaN of said N-type semiconductor layer is doped with Si and In, and said AlGaN is doped with In. element. 9. The light emitting device according to claim 1, wherein an interface between the GaN and the AlGaN of the N-type semiconductor layer is
A light emitting device, wherein i is formed.