JP2002270969A - Nitride semiconductor light emitting element and optical device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light emitting element in which crystallinity and emission efficiency are enhanced by suppressing a crystal system separation and phase separation caused by adding As, P or Sb to an InGaN based well layer. SOLUTION: The nitride semiconductor light emitting element comprises an emission layer 107 formed by combining a plurality of well layers and one or a plurality of barrier layers wherein the well layer is composed of a nitride represented by a formula InAlGaN1-x-y-z Asx Py Sbz (where, 0<=x<=0.1, 0<=y<=0.2, 0<=z<=0.05, x+y+z>0). The compositional ratio of As, P or Sb added to the InGaN based well layer is set within a specified range and Al is added additionally thus suppressing the crystal system separation and phase separation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor light emitting device and an optical device using the same, and more particularly to a nitride semiconductor light emitting device having a multiple quantum well structure and a high luminous efficiency, and a semiconductor light emitting device using the same. About.

[0002]

2. Description of the Related Art As a semiconductor laser emitting near blue light, a semiconductor laser having an InGaN active layer has been developed.
In this semiconductor laser, the oscillation wavelength can be shifted to the longer wavelength side by increasing the amount of In. But I
The nGaN layer originally has a large lattice mismatch with the underlying layer, and if the composition ratio of In is increased, the crystallinity of the layer is reduced, and a non-light emitting region having a high In content and a region having a low In content can be formed. As a result, the luminous efficiency decreases.

Japanese Patent Application Laid-Open No. 11-204880 discloses that
For such a problem, In_1-yGa_yN _zAs_1-zConsisting of
A semiconductor laser having a subwell active layer is disclosed. Publication
According to the conventional InGaN active layer, As is slightly contained.
Oscillation due to the so-called Boeing effect
The wavelength is increased, and As is added to the InGaN active layer.
By slightly including the GaN optical waveguide layer,
The amount of lattice mismatch can be reduced.

[0004]

However, Japanese Patent Application Laid-Open No. H11-204880 discloses that the amount of As added is
The document only states that "As is slightly contained", and specifically does not disclose how much As should be added to obtain a desired effect. In fact, In
When a light emitting device is manufactured using a quantum well layer made of a GaNAs crystal, if the content of As in the well layer is increased, N
A hexagonal region having a high (nitrogen) content and a cubic region having a low N content are easily formed. (Hereinafter, a phenomenon in which such regions having different crystal systems are formed in the same layer is referred to as “crystal system separation”.) In addition, if the nitride semiconductor crystal that has undergone the crystal system separation contains In, it is considered that In is contained. , A region having a high In composition and a region having a low In composition are easily formed. (Hereinafter, the phenomenon that such regions having different compositions are formed in the same layer is referred to as "phase separation.") These cause a decrease in crystallinity and luminous efficiency, and cause a nitride semiconductor having a multiple quantum well structure. This makes it difficult to manufacture a light-emitting element. Such crystal system separation and phase separation occur when not only As but also P or Sb is added.

Thus, an object of the present invention is to solve the above-mentioned problems caused by adding As, P or Sb to an InGaN-based well layer, to suppress crystal system separation and phase separation, and to improve crystallinity and luminous efficiency. An object of the present invention is to provide a nitride semiconductor light emitting device and an optical device using the same.

[0006]

Means for Solving the Problems When the InGaN nitride semiconductor is used for the multiple quantum well structure of the nitride semiconductor light emitting device, the present inventors set the composition ratio of As, P or Sb within a predetermined range. , And further by adding Al,
It has been found that crystal separation and phase separation can be suppressed.

Thus, according to the present invention, a plurality of well layers and one well layer are formed.
One or nitride semiconductor light emitting device and a plurality of barrier layers has a light-emitting layer in combination is provided, the element is well layer, wherein _{InAlGaN 1-xyz As x P y} Sb z ( wherein 0
≦ x ≦ 0.1, 0 ≦ y ≦ 0.2, 0 ≦ z ≦ 0.05, x
+ Y + z> 0).

Particularly, in the present invention, A in the well layer
l content is 1 × 10¹⁹/ Cm^ThreePreferably more than
New In the present invention, the well layer has the formula In_aAl_b
Ga _1-abN_1-xyzAs_xP_ySb_z(Where 0 <a ≦
0.5, 0 <b ≦ 0.2, 0 ≦ x ≦ 0.1, 0 ≦ y ≦
0.2, 0 ≦ z ≦ 0.05, x + y + z> 0)
It is preferable to be made of nitride. In the present invention, the well
Total content of As, P and Sb in the door layer (As, P
Or when any of Sb is contained, the total content thereof
And any combination of As, P and Sb.
The total content of the combined elements) is 10¹⁸/ C
m^ThreeThe above can be considered.

In the present invention, the barrier layer may be made of a III-V compound semiconductor containing at least Ga as a group III element and containing only N as a group V element. Alternatively, the barrier layer is formed of a group III-V compound semiconductor containing at least Ga as a group III element and at least one element selected from the group consisting of As, P, and Sb as a group V element and N. It may be.

[0010] Typically, in the present invention, the light emitting layer exists between two adjacent layers. At least one of these two layers is preferably made of a nitride containing Al and N.

In the present invention, the number of the well layers constituting the light emitting layer is preferably 2 or more and 10 or less, and the thickness of the well layer is preferably 0.4 nm or more and 20 nm or less. The thickness of the barrier layer is 1 nm to 20 nm.
The following is preferred.

In a preferred embodiment of the present invention, the well layer and / or the barrier layer includes Si, O, S, C, Ge, Z
At least one element selected from the group consisting of n, Cd and Mg is added. The content of such an additional element is preferably 1 × 10 ¹⁶ to 1 × 10 ²⁰ / cm ³ .

The device according to the present invention may have a light emitting layer formed on a GaN substrate.

According to the present invention, there is provided an optical device such as an optical pickup device using the nitride semiconductor light emitting device.

In the present specification, the “light-emitting layer” is
It is a layer directly involved in the function of emitting light, and is defined as being composed of a well layer and a barrier layer. Here, it is assumed that the relationship of the band gap energy of the well layer <the band gap energy of the barrier layer holds. Typically, the main crystal system of the light emitting layer in the present invention is a hexagonal system.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Effects of Al Addition to Well Layer) In a growth process of an InGaN-based crystal containing As, a hexagonal system having a high N content and a cubic system having a low N content are used. (Crystal sphalerite structure). Further, In, which could not be combined well with N and As, which are Group V elements, easily segregates and easily forms metal droplets. When such segregation occurs, phase separation occurs in which a region having a high In composition and a region having a low In composition occur. This means that the luminous efficiency decreases and the FWHM of the luminous wavelength increases (color spots).
Cause. The phenomena of crystal system separation and phase separation become particularly remarkable when the content of As in the well layer is 1 × 10 ¹⁸ / cm ³ or more.

The above-described crystal system separation and phase separation are performed by using In
Since it occurs not only in the GaNAs well layer but also in the InGaNP well layer and the InGaNSb well layer, InGaP
It is considered that crystal system separation and phase separation occur when at least one of the group V elements of As, P and Sb is contained in the well layer in the N crystal. This includes
In the reaction between group III atoms In and Ga and group V atoms N and As, P or Sb, the bonding force between Ga and As, P or Sb is much stronger than the bonding force between other atoms. This is considered to be due to the fact that the volatility of N is extremely higher than that of As, P or Sb (N escapes from the crystal). Therefore, in order to suppress these crystal system separation and phase separation, N
It is important to efficiently incorporate Si into the crystal and to reduce the bonding force between Ga and As, P or Sb.

In the present invention, crystal system separation and phase separation are suppressed by adding Al to an InGaN-based crystal containing at least one of As, P and Sb. In particular, the well layer _{InAlGaN 1-xyz As x P y} S
b _z (0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.2, 0 ≦ z ≦ 0.
05, x + y + z> 0) The crystal system separation and the phase separation are suppressed by using a nitride crystal represented by the following formula (1). Since Al has high reactivity and can efficiently incorporate N into the crystal, the nitride crystal represented by the formula 1 can be easily grown. The nitride containing Al exists stably even at a high temperature (for example, 1000 ° C.). Al, which is a highly reactive group III atom, effectively prevents N from leaving the crystal. Furthermore, since the bonding force between Ga and As, P or Sb can be reduced by Al, In can be efficiently incorporated into the nitride semiconductor crystal. It is considered that this also leads to suppression of crystal system separation and phase separation.

Since the well layer of the present invention contains at least one of As, P and Sb, the effective mass of electrons or holes can be reduced. The nitride represented by Formula 1 typically comprises I as a Group III element.
III- containing n, Al and Ga, and containing at least one of As, P and Sb and N as a group V element.
A group V compound semiconductor, in which the ratio (atomic percentage) of the number of As atoms to the total number of atoms of the group V element is 1
0% or less, and the ratio of the number of P atoms (atomic percentage) is 20%.
% Or less, and the ratio of the number of Sb atoms (atomic percentage) is 5%.
It is as follows. When the ratio of the number of As atoms exceeds 10%, A
By the addition of l, the crystal system separation and phase separation cannot be sufficiently suppressed. Similarly, the ratio of the number of P atoms and S
When the ratio of the number of b atoms exceeds 20% and 5%, respectively, it becomes impossible to sufficiently suppress crystal system separation and phase separation by adding Al. By using the nitride having the composition represented by the formula 1 in the multiple quantum well structure, a light emitting device such as a laser with low power consumption, high output, and long life can be obtained.

(Regarding the Multiple Quantum Well Structure) In the formation of the multiple quantum well structure, if a crystal system separation or a phase separation occurs in the well layer, the interface between the well layer and the barrier layer in contact with the well layer becomes rough, and the barrier of the well layer becomes rough. The next layer in contact with the layer (for example, a well layer)
Will also be affected. As a result, the crystallinity and the emission intensity decrease. In contrast, the well layer of the present invention
A light emitting device having a multiple quantum well structure is easily formed. According to the present invention, as described above, the crystal system separation and the phase separation of the well layer can be suppressed. Therefore, the interface between the well layer and the barrier layer is not roughened, and even if the well layers are stacked, the crystallinity is low. A light-emitting element with high light-emission intensity is obtained because of its high intensity.

As can be seen from FIG. 14, the emission intensity is composed of a plurality of well layers (for example, two or more layers and ten layers or less) as compared with a single quantum well structure composed of only one well layer. It can be seen that the light emission intensity is higher in the multiple quantum well structure. FIG. 5 shows the relationship between the number of well layers constituting the light emitting layer (multiple quantum well structure) and the laser threshold current density. In the drawing, the mark を indicates a sapphire substrate, and the mark ● indicates a laser threshold current density when a GaN substrate is used. When the number of well layers is 10 or less, the threshold current density becomes 10 kA / cm ² or less, and continuous oscillation at room temperature is possible. In order to further reduce the oscillation threshold current density, two or more layers and five layers or less are preferable. Also, the tendency that the threshold current density was lower when a GaN substrate was used than when a sapphire substrate was used was observed.

Thus, according to the present invention, InAlG
_{aN 1-xyz As x P y} Sb z (0 ≦ x ≦ 0.1,0 ≦ y ≦
0.2, 0 ≦ z ≦ 0.05, x + y + z> 0) By using a well layer, a well layer having a small ratio of crystal system separation and phase separation can be formed, and thus an interface between the well layer and the barrier layer is obtained. Is not roughened, the crystallinity is improved, and a multiple quantum well structure can be easily manufactured. The light emitting layer used in the present invention can provide a light emitting device with low power consumption, high output and long life.

(Preferable composition and structure of well layer)
What is the degree of As, P or Sb
It was investigated whether the phenomenon occurs depending on the amount of addition. As a result, InG
1 × 10 As, P or Sb in aN crystal ¹⁸/ Cm^Three
When added, crystal separation begins to occur (percentage of crystal separation)
About 2 to 3%), and the atomic percentage in the entire group V element
As composition ratio is about 10%, P composition ratio is about 20%, Sb
When the composition ratio becomes about 5%, the crystal separation becomes about 23 to 25.
%. In addition, As, P,
Or Sb is added, and the ratio of crystal system separation becomes about 3%.
5% of In in the crystal (I
n), phase separation occurs.
(The phase separation ratio is about 1-2%)
As the separation rate increases, the phase separation rate gradually increases.
I went. When the crystal separation becomes about 23-25%,
The ratio of separation is about 13 to 15%. Where the crystalline component
The rate of separation and the rate of phase separation
Part where crystal system separation or phase separation has occurred (applicable part)
And the other part (the part composed of the average composition ratio)
Is determined as the ratio of the corresponding part to the unit volume.
Desired.

FIG. 2 shows the ratio of crystal separation caused by adding Al to the In _0.01 Ga _0.99 N _0.92 P _0.08 well layer and the emission intensity of the light emitting device.
In FIG. 2, the horizontal axis indicates the amount of Al added, the left vertical axis indicates the percentage of crystal system separation (%), and the right vertical axis indicates the emission intensity. In addition, ○ indicates the relationship between the amount of Al added and the ratio of crystal system separation, and ● indicates the relationship between the amount of Al added and the emission intensity. The emission intensity in FIG. 2 is standardized with the emission intensity when Al is not added as 1.

Referring to FIG. 2, the rate of crystal system separation (%) starts decreasing from around 5 × 10 ¹⁸ / cm ³ , and becomes 3% when the amount becomes 1 × 10 ¹⁹ / cm ³ or more. It became the following. On the other hand, the emission intensity was 5 × 10 ¹⁸ /
It started to increase from around ³ cm ³ and increased to about 10 times when it exceeded 1 × 10 ¹⁹ / cm ³ . From these relationships, it was found that there was a correlation between the crystal system separation and the emission intensity.

FIG. 2 describes the In _0.01 Ga _0.99 N _0.92 P _0.08 crystal, but In _a Ga _{1 -a} N _{1 -xyz} As _x P _y
Sb _z (0 <a ≦ 0.5, 0 ≦ x ≦ 0.1, 0 ≦ y ≦
0.2, 0 ≦ z ≦ 0.05, x + y + z> 0) When the crystal was used, the same characteristics as in FIG. 2 were obtained by adding Al. On the other hand, when the composition ratio of Al exceeds 20%, the crystallinity deteriorates, and the luminous efficiency tends to decrease.

The following relationship is observed between the crystal system separation and the phase separation. In _{In 0.01 Ga 0. 99 N 0.92 P} 0.08 well layers, the addition amount of Al is less than 5 × 10 ¹⁸ / cm ^3, the crystal system separation had occurred about 7-9%. At this time, about 4 to 5% of phase separation had occurred. Also, by adding Al in an amount of about 1 × 10 ¹⁹ / cm ³ , the rate of crystal separation is about 3%, and the rate of phase separation is about 1%.
%. This phase separation occurs due to segregation of In remaining from the crystal bond in the region where the crystal system separation has occurred. Therefore, it is understood that there is a correlation between the crystal system separation and the phase separation. Then, it can be seen that by suppressing the occurrence of crystal system separation as much as possible, the ratio of In remaining in the bond is reduced, and the occurrence of phase separation can be suppressed.

In the phase separation, a region having a high In composition tends to emit no light, which causes a decrease in luminous efficiency and an increase in half width (color spot). Therefore, it is desirable that the ratio of phase separation in the well layer be kept as low as possible (eg, 3% or less).

Summarizing the above, in order to obtain a well layer having a multiple quantum well structure having high emission intensity (high emission efficiency), the ratio of crystal system separation is 3% or less and the ratio of phase separation is 3% or less. % Is desirable. In order to obtain such a rate of crystal system separation and a rate of phase separation, as described above, it is more effective to set the addition amount of Al to 1 × 10 ¹⁹ / cm ³ or more. Also, since the crystallinity is reduced when the content of Al with respect to group III atoms is high, the Al composition ratio (percentage of the number of Al atoms with respect to the total number of group III atoms)
Is preferably 20% or less.

[0030] Thus, in a preferred embodiment of the present invention, the well _{layer, In a Al b Ga 1-} a- b N 1-xyz As x P y
Sb _z . It can be composed of a nitride represented by Al (formula 2), and the amount of Al added at the doping level is:
When it is 1 × 10 ¹⁹ / cm ³ or more and Al is added at the composition ratio level, the composition ratio b in the formula is 0 <b ≦
0.2. Further, in Expression 2, 0 <a ≦ 0.5, 0 ≦ x
≦ 0.1, 0 ≦ y ≦ 0.2, 0 ≦ z ≦ 0.05, x + y
+ Z> 0. Further, the number of well layers is preferably 2 or more and 10 or less as described above.

In the present invention, the well layer is made of a conventional InG
Even if it is thicker than the aNAs well layer, since the crystal system separation and the phase separation hardly occur, the thickness can be reduced to about 300 nm. However, when considered as a light emitting device having a multiple quantum well effect, an effective and preferable well layer thickness is 0.4 nm or more and 20 nm or less. When the thickness of the well layer is less than 0.4 nm, the level of confinement of carriers due to the quantum well effect becomes too high, and the luminous efficiency may be reduced. On the other hand, when the well layer thickness is larger than 20 nm, it becomes difficult to obtain the quantum well effect.

[0032] (Configuration of the barrier layer in the present _{invention) In a Al b Ga 1-} ab N 1-xyz As x P y Sb z (0 <a
≦ 0.5, 0 <b ≦ 0.2, 0 ≦ x ≦ 0.1, 0 ≦ y ≦
0.2, 0 ≦ z ≦ 0.05, x + y + z> 0, where the addition amount of Al is 1 × 10 ¹⁹ / cm ³ or more) For the well layer, the most preferable barrier layers are As, P and Sb. This is a barrier layer made of a nitride semiconductor containing no. This is because crystal separation does not occur unless the barrier layer itself contains As, P, and Sb, and thus does not hinder the fabrication of the multiple quantum well structure.

As a nitride semiconductor not containing As, P and Sb, for example, InGaN, GaN, AlGaN,
And InAlGaN. Of these, the most preferred material for the barrier layer is InGaN. This is because by containing In, the growth temperature of the barrier layer can be lowered to about the same as that of the well layer, and the crystallinity can be improved. However, the InGaN In
The composition ratio (percentage of the number of In atoms to the total number of group III atoms) is preferably 15% or less. If the In composition ratio exceeds 15%, the crystallinity is deteriorated, and the luminous efficiency may be reduced. Therefore, a more preferred composition of the barrier layer can be represented by the formula In _x Ga ₁ -xN (where 0 <x ≦ 0.15).

For the barrier layer, the next preferred material is Ga
N. Because it does not contain In and Al, there is no concern about deterioration of crystallinity due to them. However, if the growth temperature is not increased, the crystallinity will deteriorate,
It is important to keep the growth temperature as high as possible. The next preferred material is AlGaN. When this is used, the crystallinity deteriorates unless it is grown at a high temperature.
As low as possible (Al to group III element
Is preferably 10% or less in atomic percentage) and the growth temperature is preferably as high as possible (but 900 ° C. or less).

The InAlGaN barrier layer exists stably even at a high growth temperature because it contains Al. Generally A
If the nitride semiconductor crystal containing l does not grow at a high temperature (1000 ° C. or higher), the crystallinity will decrease. However, by including In, the growth temperature can be lowered to the same level as that of the well layer. However, since Al has high reactivity, when As, P or Sb is not contained, Al
And N are easily bonded, and In remaining in the bonding reaction segregates to form metal droplets, which may cause phase separation. When the ratio of the phase separation exceeds 10%, the function as a barrier layer is hindered, and the luminous efficiency is reduced. Therefore, it is not preferable to use InAlGaN for the barrier layer. However, InAlG
When it is desired to use an aN crystal for the barrier layer, it is desirable to reduce the composition ratio of In and Al to Group III atoms as much as possible. For example, the Al composition ratio (atomic percentage) to the total number of group III atoms is preferably 5% or less, and the In composition ratio (atomic percentage) is preferably 5% or less. That is, In _x Al _y Ga _1-xy N (0 <x ≦ 0.05, 0
<Y ≦ 0.05) is preferably used for the barrier layer. If this composition ratio is satisfied, the rate of phase separation can be suppressed to 10% or less.

In the present invention, a nitride semiconductor containing at least one of As, P and Sb may be used for the barrier layer. There are two main advantages to including As, P or Sb in the barrier layer. First, since the barrier layer containing these elements can be grown at substantially the same temperature as the well layer, the crystallinity of the light emitting layer is improved. Secondly, by containing As, P or Sb, the refractive index can be increased, the light confinement efficiency can be improved, the laser oscillation threshold current density can be reduced, and the optical characteristics can be improved. As, P,
Nitride semiconductors for barrier layers containing Sb or a combination thereof include, for example, InAlGaNAs, I
nAlGaNP, InAlGaNSb, InAlGaN
AsP, InAlGaNAsPSb, AlGaNAs,
AlGaNP, AlGaNSb, AlGaNAsP, A
lGaNAsPSb, GNAs, GNP, GANS
b, GNAsP, GNAsPSb, InGaNA
s, InGaNP, InGaNSb, InGaNAs
P, InGaNAsPSb.

Of the above, the most preferred material for the barrier layer is
InAlGaNAs, InAlGaNP, InAlGa
NSb, InAlGaNAsP or InAlGaNA
sPSb. In the present invention, since these have the same constituent elements as the well layer, they can be formed at the same growth temperature as the well layer, and can provide the same effect as the well layer. In the present invention, the composition ratio of each of these constituent elements in the barrier layer can be in the same range as in the well layer.

The next preferred barrier layer material is AlGaN
As, AlGaNP, AlGaNSb, AlGaNAs
P or AlGaNAsPSb. These are A
Since s, P or Sb is contained, the growth temperature can be reduced to the same degree as that of the well layer. Further, the ratio of crystal system separation can be suppressed to about 3% because of containing Al. Also, phase separation does not occur because it does not contain In. AlGaNAs constituting a barrier layer,
In AlGaNP, AlGaNSb, AlGaNAsP or AlGaNAsPSb, the respective composition ratios of Al, As, P and Sb can be the same as those of the well layer of the present invention.

The next preferred barrier layer material is GNA.
s, GaNP, GaNSb, GaNASP or GaN
AsPSb. Although the growth temperature of the GaN crystal must be as high as possible, the growth temperature can be reduced to the same extent as that of the well layer by adding As, P, or Sb. However, when As, P, or Sb is contained in a nitride semiconductor crystal that does not contain Al, the above-described crystal system separation may occur. Therefore, it is desirable to reduce the composition ratio of As, P and Sb as much as possible. The composition ratio of As, P and Sb (percentage of the group V atoms to the total number of atoms) is 5% or less for As,
In the case of 10% or less in the case of Sb and 2% or less in the case of Sb, the ratio of crystal system separation can be about 12 to 14%. If the percentage of crystal system separation in the barrier layer is 15% or less, even when a GaNAs crystal, a GaNP crystal, a GaNSb crystal, a GaNasP crystal, or a GaNasPSb crystal is used for the barrier layer, the emission intensity is hardly affected. Since the barrier layer does not directly contribute to light emission,
If the ratio of crystal system separation is 15% or less, it is considered that the function as a barrier layer is not hindered.

The next preferred barrier layer material is InGaNA
s, InGaNP, InGaNSb, InGaNAsP
Or InGaNAsPSb. Since these contain In and As, P or Sb, the growth temperature can be lowered to the same degree as the well layer. However, since they do not contain Al, they can cause crystal system separation. Further, phase separation may be caused due to the inclusion of In. Therefore, it is desirable to reduce the composition ratio of In, As, P, and Sb as much as possible. The In composition ratio (atomic percentage) to the total number of group III atoms is 15% or less, the composition ratio (atomic percentage) to the total number of group V atoms is 5% or less for As, 10% or less for P, and 2% for Sb. If it is below, the ratio of crystal system separation can be suppressed to about 12 to 14%, and the ratio of phase separation can be suppressed to about 7 to 9%. If the ratio of crystal separation in the barrier layer is 15% or less and the ratio of phase separation is 10% or less, I
nGaNAs crystal, InGaNP crystal, InGaNSb
Crystal, InGaNAsP crystal or InGaNAsP
Even if the Sb crystal is used for the barrier layer, the emission intensity is hardly affected. Since the barrier layer is not a layer directly contributing to light emission, it is considered that the function as the barrier layer will not be affected if the above composition ratios are satisfied.

The thickness of the barrier layer is preferably 1 nm or more and 20 nm or less. Even if the barrier layer is thinner than 1 nm,
This is because the interface between the well layer and the barrier layer starts to be rough even if the thickness is larger than m. The number of barrier layers can be set according to the number of well layers.

(Layer Adjacent to Light Emitting Layer) Typically, in the device according to the present invention, two nitride semiconductor layers are adjacent to the light emitting layer. At least one of the two adjacent layers is a nitride semiconductor containing Al and N, for example, Al
Preferably, it is made of GaN. Typically, the device according to the present invention comprises a substrate made of a nitride semiconductor crystal, or a substrate having a structure in which a nitride semiconductor crystal film is grown on another crystal material, and a nitride film formed on the substrate. An n-type layer and a p-type layer made of a semiconductor, and a light-emitting layer disposed between the n-type layer and the p-type layer. In that case, it is preferable that at least one of the n-type layer and the p-type layer adjacent to the light emitting layer is made of a nitride semiconductor containing Al and N, for example, AlGaN. In the present invention, by providing such a layer containing Al adjacent to the light emitting layer, the amount of shift from the design wavelength can be suppressed small, or the light emission intensity can be increased.

(Substrate for Light-Emitting Element) In general, the crystal of the nitride semiconductor is a nitride semiconductor such as GaN, sapphire,
It can be grown on a substrate such as H-SiC, 4H-SiC, 3C-SiC, Si, and spinel (MgAl ₂ O ₄ ). In particular, a nitride semiconductor, for example In _a Al _b Ga _c
N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, a + b + c
= 1) can be preferably used.
In the case of a nitride semiconductor laser, a layer having a lower refractive index than the cladding layer needs to be in contact with the outside of the cladding layer in order to make the vertical and transverse modes unimodal, and it is more preferable to use an AlGaN substrate. In addition, hexagonal In _a Al _b Ga
_c N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1, a + b +
c = 1) In the substrate, about 10% or less of the nitrogen element is A
It may be substituted with any element of s, P and Sb. Further, Si, O, Cl, S, C, G
e, Zn, Cd, Mg, Be or the like may be doped. When an n-type nitride semiconductor substrate is used, Si, O, or Cl is particularly preferable among the doping elements.

In the following embodiments, among the above substrates, a C-plane (# 0) such as a sapphire substrate and a nitride semiconductor substrate is used.
001) is exposed on the main surface. However, the plane orientation of the main surface of the substrate is not only the C plane but also the A plane ({11-20} plane), the R plane ({1-102} plane), and the M plane.
Plane ({1-100} plane). In addition, a substrate whose main surface has an off angle of 2 degrees or less from the above plane orientation,
It has good surface morphology and can be used preferably.

(Crystal Growth Method) As a method of growing a nitride semiconductor crystal, a metal organic chemical vapor deposition (MOCV) method is used.
D), molecular beam epitaxy (MBE), and hydride vapor phase epitaxy (HVPE) are common. Among them, in consideration of the crystallinity and productivity of a nitride semiconductor to be formed, it is the most common method to use GaN or sapphire as a substrate and to use MOCVD as a growth method.

Embodiment 1 According to the present invention, a nitride semiconductor laser diode device as shown in FIG. 1 is obtained. This device comprises a C-plane (0001) sapphire substrate 100, a low-temperature GaN buffer layer 101, an n-type GaN layer 102, an n-type In _0.07 Ga _0.93 N crack prevention layer 103, an n-type Al
_0.1 Ga _0.9 N cladding layer 104, n-type GaN light guide layer 105, light emitting layer 106, p-type Al _0.2 Ga _0.8 N shielding layer 1
07, p-type GaN optical guide layer 108, p-type Al _0.1 Ga
_0.9 N cladding layer 109, p-type GaN contact layer 11
0, n electrode 111, p electrode 112, and SiO ₂ dielectric film 113. The device is manufactured by the following process.

First, the sapphire substrate 100 is set in an MOCVD apparatus, and a low-temperature GaN buffer layer 101 is grown at a growth temperature of 550 ° C. using NH ₃ (ammonia) as a group V material and TMGa (trimethylgallium) as a group III material.
Is grown to 25 nm. Next, at a growth temperature of 1050 ° C., SiH ₄ (silane) is added to the raw material to form an n-type GaN layer 1.
02 (Si impurity concentration 1 × 10 ¹⁸ / cm ³ ) is formed with a thickness of 3 μm. Subsequently, the growth temperature is increased from 700 ° C to 80 ° C.
The temperature was lowered to about 0 ° C., and TMIn (trimethylindium) as a group III raw material was supplied, and n-type In _0.07 Ga _0.93
The N crack preventing layer 103 is grown to a thickness of 40 nm. Again, the substrate temperature was raised to 1050 ° C., and a group III raw material of TMAl (trimethylaluminum) was used.
8 μm thick n-type Al _0.1 Ga _0.9 N cladding layer 104 (S
i impurity concentration of 1 × 10 ¹⁸ / cm ³ ), followed by n-type GaN optical guide layer 105 (Si impurity concentration of 1 × 10 ¹⁸ / cm ³ ).
¹⁸ / cm ³ ) with a thickness of 0.1 μm. Thereafter, the temperature of the substrate is lowered to 800 ° C., and the thickness is reduced to 4 cycles for 3 cycles.
A light emitting layer (multiple quantum well structure) 106 composed of, for example, an In _0.05 Al _0.02 Ga _0.93 N _0.98 P _0.02 well layer and a 6 nm-thick In _0.05 Ga _0.95 N barrier layer. / Well layer / barrier layer / well layer / barrier layer. At that time, SiH ₄ (Si impurity concentration is 1 × 10 ¹⁸ / cm ³ ) is added to both the barrier layer and the well layer.

The growth may be interrupted for 1 second to 180 seconds between the barrier layer and the well layer or between the well layer and the barrier layer. As a result, the flatness of each layer is improved, and the emission half width is reduced.

The composition ratio of the well layer can be adjusted according to the desired wavelength of the light emitting device. For example, Tables 1 to 6 show InAlGaNAs mixed crystals, and Tables 7 to 12 show InAlGaNAs.
4 shows the relationship between the emission wavelength and the In composition ratio in a GaNP mixed crystal. By performing crystal growth near the composition ratios shown in Tables 1 to 12, an approximate target emission wavelength can be obtained. The Sb composition ratio (percentage of Sb atoms to the total number of group V atoms) in the InAlGaNSb crystal is about 5%.
It is preferable to optimize the respective composition ratios so as to be within%.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

[Table 7]

[0057]

[Table 8]

[0058]

[Table 9]

[0059]

[Table 10]

[0060]

[Table 11]

[0061]

[Table 12]

After forming the light emitting layer 106, the substrate temperature was raised again to 1050 ° C.
_0.2 Ga _0.8 N shielding layer 107, 0.1 μm thick p-type Ga
N light guide layer 108, 0.5 μm thick p-type Al _0.1 G
a _0.9 N clad layer 109 and 0.1 μm thick p
A type GaN contact layer 110 is grown. Mg as a p-type impurity (using EtCP ₂ Mg (bisethylcyclopentadienyl magnesium) as a Mg source) is 5 ×
It is added at a concentration of 10 ¹⁹ / cm ^{3 to} 2 × 10 ²⁰ / cm ³ .

It is preferable that the p-type impurity concentration of the p-type GaN contact layer 110 be increased as the position where the p-type electrode 112 is formed is increased. This reduces the contact resistance due to the formation of the p-electrode. Also, p
To remove residual hydrogen in the p-type layer that hinders activation of Mg, which is a type impurity, a small amount of oxygen may be mixed during the growth of the p-type layer.

After the growth of the p-type GaN contact layer 110, the inside of the reactor of the MOCVD apparatus is changed to all nitrogen carrier gas and NH ₃ , and the temperature is lowered at 60 ° C./min. When the substrate temperature reaches 800 ° C., the supply of NH ₃ is stopped, the substrate is kept at the substrate temperature for 5 minutes, and then cooled to room temperature. Substrate holding temperature is from 650 ° C to 90
The temperature is preferably between 0 ° C. and the waiting time is preferably 3 minutes or more and 10 minutes or less. Further, the reaching speed of the falling temperature is preferably 30 ° C./min or more.

As a result of evaluating the grown film produced in this manner by Raman measurement, it was found that the p-type annealing was already performed after the growth by the above method without performing the p-type annealing used in the conventional nitride semiconductor. Characteristics. Also,
The contact resistance due to the formation of the p-electrode was also reduced.

Next, a laser diode element is obtained by performing the following process on the wafer having the epitaxial growth layer taken out of the MOCVD apparatus. First,
N-type GaN layer 10 using a reactive ion etching apparatus
2 is partially exposed, and an n-electrode 111 is formed on the exposed portion in the order of Ti / Al. In addition to such an n-electrode material, Ti / Mo, Hf / Al, or the like may be used. The p-electrode portion is etched in a stripe shape along the <1-100> direction of the sapphire substrate, and then a SiO ₂ dielectric film 113 is deposited at a necessary place. And p-type G
Pd / Au is applied to a portion where the aN contact layer 110 is exposed.
To form a ridge stripe-shaped p-electrode 112 having a width of 2 μm. In addition to the above p-electrode material, N
i / Au or Pd / Mo / Au may be used. Finally,
Resonator length 5 using cleavage or dry etching
Fabricate a 00 μm Fabry-Perot resonator. Generally, the resonator length is preferably 300 μm to 1000 μm. The mirror end face of the resonator is formed such that the M plane of the sapphire substrate is the end face (see FIG. 3). For example, cleavage and chip division of the laser element are performed by a scriber from the substrate side along a broken line shown in FIG. As a result, the sharpness of the end face and shavings due to scribing do not adhere to the epitaxial growth surface, so that the yield is good. In addition to the feedback method of the above laser cavity, a generally known DFB
(Distributed Feedback), DBR (Distributed Brag)
g Reflector). After forming the mirror end face of the Fabry-Perot resonator, dielectric mirror films of SiO ₂ and TiO ₂ having a reflectivity of 70% are alternately deposited on the mirror end face to form a dielectric multilayer reflective film. In addition to this dielectric material, SiO ₂ / Al ₂ O ₃ may be used as the dielectric multilayer reflective film.

In the above process, the reason for exposing the n-type GaN layer 102 using reactive ion etching is as follows.
This is because the sapphire substrate 100 is electrically insulating.
Therefore, when using a conductive substrate such as a GaN substrate or a SiC substrate, a step of exposing the n-type GaN layer 102 is not required, and an n-type electrode may be directly formed on the back surface of the substrate.

Next, the laser diode chip obtained by the above process can be mounted on a package by the following process. Taking advantage of the characteristics of the laser diode using the above light emitting layer and using it as a blue-violet (410 nm wavelength) high power (50 mW) laser suitable for an optical disk for high-density recording, the sapphire substrate has a low thermal conductivity. Care must be taken. Therefore, for example, using an In solder material,
It is preferable to connect a laser diode chip to the package body. Alternatively, instead of directly attaching a laser diode chip to a package body or a heat sink, Si, AlN, diamond, Mo, CuW, BN
Or the like may be connected via a submount.

On the other hand, instead of a sapphire substrate, a SiC substrate having a high thermal conductivity or a nitride semiconductor substrate (for example, GaN
When manufacturing a nitride semiconductor laser diode having the above-mentioned light emitting layer on a GaN thick film substrate (for example, a substrate 800 shown in FIG. 4 in which the seed substrate 801 is removed by grinding), for example, It is preferable to connect the laser diode chip to the package body by junction up using In solder material. Alternatively, instead of directly attaching to the package body or heat sink,
The connection may be made via a submount of i, AlN, diamond, Mo, CuW, BN, or the like.

As described above, a laser diode using a nitride semiconductor containing As, P, or Sb and containing In and Al in the well layer constituting the light emitting layer is manufactured.

(Regarding Addition of Impurity in Light Emitting Layer) In the first embodiment, Si (raw material: SiH ₄ ) is added as an impurity to both the well layer and the barrier layer, but it may be added to only one of the layers. Laser oscillation was possible without adding both layers. However, the photoluminescence (P
L) According to the measurement, in the light emitting layer (both the barrier layer and the well layer)
When PL was supplied, the PL emission intensity was about 1.2 to 1.4 times stronger than when not supplied. For this reason, in a light emitting diode, it is preferable to add an impurity such as Si to the light emitting layer. InAlGaN
_1-xyz In As _x P _y well layer composed of Sb _z mixed crystal, As, not at all contain P and Sb InG
Since a localized level due to In is less likely to be formed than in the aN crystal, it is considered that the emission intensity strongly depends on the crystallinity of the well layer. Therefore, the crystallinity of the light-emitting layer can be improved by adding an impurity such as Si to the light-emitting layer, so that the emission intensity can be increased by adding the impurity. O, S, C, Ge, Z instead of Si
Similar effects can be obtained by adding n, Cd or Mg. The amount of impurities added to the light emitting layer is about 1 × 10
^It is preferably about ¹⁶ to 1 × 10 ²⁰ / cm ³ . 1 impurity
If it is less than × 10 ¹⁶ / cm ³ , it is difficult to improve the crystallinity. On the other hand, if the amount of impurities is more than 1 × 10 ²⁰ / cm ³ , crystal defects due to the addition of the impurities increase, and the crystallinity may decrease. In general, in the case of a laser diode, performing modulation doping in which an impurity is added only to the barrier layer leads to a decrease in threshold current density because there is no carrier absorption in the well layer, but rather, in the well layer of the present invention, The threshold value of the laser was lower when the impurity was added. When a crystal is grown on a sapphire substrate, there are many crystal defects (threading dislocation density of about 1 × 10 ¹⁰ / cm ² ), and the crystallinity is improved by adding impurities rather than considering the carrier absorption in the well layer. This is considered to be more effective for the laser threshold current density.

(Regarding AlGaN Shielding Layer) The AlGaN shielding layer 107 shown in FIG. 1 is provided between the light emitting layer and the p-type layer so as to be in contact with the light emitting layer. The p-type layer formed on the shielding layer is, for example, a p-type light guide layer in the case of a laser diode, and is, for example, a p-type cladding layer or a p-type contact layer in the case of a light-emitting diode.
According to the PL measurement, the shift amount from the design wavelength was smaller and the PL emission intensity was stronger when there was the shielding layer than when there was the shielding layer. This is because the shielding layer containing Al is provided so as to be in contact with the light emitting layer.
This is considered to be because slight crystal system separation and phase separation generated in the light emitting layer are prevented from propagating to the p-type layer. In particular,
When the light emitting layer has a structure of well layer / barrier layer / well layer... / Barrier layer / well layer (see FIG. 6), the effect of the above-mentioned shielding layer was remarkably observed. From the above, it is important that at least Al is contained as a component of the shielding layer. When the shielding layer is provided on the p-layer side, the polarity of the shielding layer is preferably p-type. This is because if the shielding layer is not p-type, the pn junction position of the carrier in the light emitting layer is shifted, and the luminous efficiency is reduced. On the other hand, an n-type AlGaN shielding layer may be provided between the light emitting layer and the n-type layer so as to be in contact with the light emitting layer. The n-type layer in contact with the n-type shielding layer is, for example, an n-type light guide layer in the case of a laser diode, and an n-type cladding layer or an n-type contact layer in the case of a light-emitting diode. The effect of the n-type AlGaN shielding layer is p-type AlG
It is almost the same as that of the aN shielding layer.

(Regarding Band Gap Structure of Light Emitting Layer)
6 to 10 show specific examples of the band gap structure of the light emitting layer. When the light guide layer and the barrier layer are made of the same nitride semiconductor material, they have the same band gap energy and refractive index. Such a bandgap structure is shown in FIG. In such a case, it is difficult to obtain the multiple quantum well effect due to the sub-band. In the case of a laser diode, the gain decreases (the threshold current density increases). In the case of a light-emitting diode, the half-width of the emission wavelength increases (causes of color spots) And is not very desirable. Therefore, as shown in FIGS. 6 to 9, by making the bandgap energy of the barrier layer smaller than that of the optical guide layer, it becomes easier to obtain the multiple quantum well effect by the subband than in the case of FIG. The refractive index is higher than that of the light guide layer.
Therefore, the light confinement efficiency is increased, and the characteristics (single peak) of the vertical / lateral mode are improved. In particular, As in the barrier layer,
When P and Sb are contained, the refractive index tends to increase, so that such a band gap configuration is preferable.

As shown in FIGS. 6 and 7, there are two types of structures of the light emitting layer for making the barrier layer smaller than the band gap energy of the light guide layer. That is, the light-emitting layer has a configuration in which the light-emitting layer starts with the well layer and ends with the well layer, and a configuration in which the light-emitting layer starts with the barrier layer and ends with the barrier layer. Similarly to the above, the structure of the light emitting layer without the shielding layer is as shown in FIGS.

(Example 2) Combinations of the nitride semiconductor materials forming the well layers and the barrier layers of the light emitting layer are as shown in the following table. Other configurations are the same as in the first embodiment.

[0076]

[Table 13]

In Table 13, circles indicate preferable combinations of the nitride semiconductor materials of the well layer and the barrier layer. On the other hand, the mark “を” indicates a combination of a well layer and a barrier layer which is not so preferable as compared with the mark “○” (for the reason, see the above-mentioned “About the barrier layer”). Although the well layers described in the table are of a quinary system, InAlG
_{aN 1-xyz As x P y} Sb z (0 ≦ x ≦ 0.1,0 ≦ y ≦
0.2, 0 ≦ z ≦ 0.05, x + y + z> 0).

The conditions relating to the light emitting layer, such as the number of well layers constituting the light emitting layer, the thickness of the barrier layer, the thickness of the well layer, and the impurity concentration in the light emitting layer, are the same as those in the first embodiment.

(Embodiment 3) FIG. 11 shows the configuration of this embodiment. In the configuration similar to that of the first embodiment, an n-type GaN substrate 700 ({0001} plane) is used instead of the sapphire substrate.

When a GaN substrate is used, the n-type GaN layer 102 may be grown directly on the GaN substrate without forming the low-temperature GaN buffer layer 101. However, when using a GaN substrate having poor crystallinity and surface morphology, it is preferable to insert the low-temperature GaN buffer layer 101 in order to improve them.

In this embodiment, since the n-type GaN substrate 700 is used, the n-electrode 111 can be taken from the back surface of the GaN substrate. Further, since the cleavage end face of the GaN substrate was very steep, the mirror loss was low, and a Fabry-Perot resonator having a cavity length of 300 μm by cleavage was manufactured. Generally, the resonator length is preferably 300 μm to 1000 μm. The mirror end face of the resonator is the
It is formed so that the 100 ° plane is the end face. Cleavage and chip division of the laser element are performed by a scriber from the substrate side along a broken line shown in FIG. As a result, the sharpness of the end face and shavings due to scribing do not adhere to the epitaxial growth surface, so that the yield is good. In addition to the feedback method of the laser cavity, generally known DFB (Distributed Feedback), DBR (Distribute
d Bragg Reflector). Fabry
After forming the mirror end face of the Perot resonator, 7
SiO ₂ and TiO ₂ dielectric films having a reflectance of 0% are alternately deposited to form a dielectric multilayer reflective film. In addition to the dielectric material, SiO ₂ / Al ₂ O ₃ may be used as the dielectric multilayer reflective film.

By using a GaN substrate instead of a sapphire substrate, the thickness of the n-type AlGaN cladding layer and the thickness of the p-type AlGaN cladding layer can be increased without generating cracks in the epitaxial growth layer. Preferably, the thickness of the AlGaN cladding layer is 0.8 μm to 1.0 μm.
μm. As a result, the single-peak vertical and transverse modes and the light confinement efficiency are increased, and the optical characteristics of the laser are improved and the threshold current density of the laser is reduced. Further, as described above, the performance of the light emitting layer strongly depends on the crystallinity (crystal defects) of the well layer. Therefore, when a GaN substrate is used, the crystal defect density (for example, threading dislocation density) in the light emitting layer decreases. Example 1 using a sapphire substrate for laser oscillation threshold current density
Compared with 10% to 20% (see FIG. 5).

In this embodiment, the conditions relating to the light emitting layer, such as the number of well layers constituting the light emitting layer, the thickness of the barrier layer, the thickness of the well layer, and the impurity concentration in the light emitting layer, are the same as in the first embodiment. The nitride semiconductor material of the light emitting layer is the same as in the second embodiment. However, with respect to the impurity concentration in the light emitting layer, the laser threshold current density can be reduced by modulating doping in which an impurity is added only in the barrier layer or by adding an impurity concentration of 3 × 10 ¹⁸ / cm ³ or less to the well layer. Reduced. This is because, as described above, the crystallinity of the light emitting layer is improved as compared with the case where a sapphire substrate is used.

(Embodiment 4) This embodiment is the same as Embodiment 1 or Embodiment 2 except that the sapphire substrate 100 of Embodiment 1 shown in FIG. 1 is replaced with a substrate 800 having a structure as shown in FIG. It is. The substrate 800 shown in FIG.
1, a low-temperature buffer layer 802, an n-type GaN film 803, a dielectric film 804, and an n-type GaN thick film 805. Such a substrate is manufactured by the following process.

First, a low-temperature buffer layer 802 is laminated at 550 ° C. on a seed substrate 801 by MOCVD. Next, 10
1 μm while doping Si at a growth temperature of 50 ° C.
An n-type GaN film 803 is formed. After forming the n-type GaN film 803, the substrate is taken out from the MOCVD apparatus, a dielectric film 804 is formed to a thickness of 100 nm using a sputtering method, a CVD method or an EB vapor deposition method, and the dielectric film 804 is periodically formed by a lithographic technique. Into a striped pattern. In forming a stripe pattern,
A stripe extending in the <1-100> direction is formed on the n-type GaN film 803, and a stripe width of 5 μm and a pitch of 1 in a <11-20> direction perpendicular to this direction.
A periodic stripe pattern of 0 μm was formed. Subsequently, the substrate having the dielectric film 804 processed into a stripe shape is set in an HVPE apparatus, and a growth temperature of 1100 is set.
℃, Si concentration 1 × 10 ¹⁸ / cm ³ , thickness of 350 μm n
Type GaN thick film 805 is laminated. After forming the n-type GaN thick film 805 by the above manufacturing method, the substrate is taken out from the HVPE apparatus, and a laser diode similar to that of Example 1 (FIG. 1) is manufactured. However, the ridge stripe portion of the laser diode corresponds to lines 810 and 81 shown in FIG.
It is manufactured so as not to be located on the upper side of the first. This is for producing a laser element in a portion having a small threading dislocation density (crystal defect). The characteristics of the laser diode thus manufactured are the same as those of the third embodiment.

Further, the seed substrate 80 is polished from the substrate 800 with a polishing machine.
1 may be peeled off, and a laser diode may be manufactured on the obtained substrate. In this case, the obtained substrate includes the low-temperature buffer layer 802 to the n-type GaN thick film 805. Also, all layers below the low-temperature buffer layer 802 are peeled off with a polishing machine,
A laser diode may be manufactured on the obtained substrate.
In this case, the substrate includes the n-type GaN film 803 to the n-type GaN thick film 805. Further, all layers below the dielectric film 804 may be peeled off with a polishing machine, and a laser diode may be manufactured over the obtained substrate. In this case, the substrate is composed of the n-type GaN thick film 805. When the seed substrate 801 or the above-described portion is peeled off, the n-electrode 111 can be taken from the back surface of the substrate as in the third embodiment. Also, the seed substrate 801
May be peeled off after manufacturing the laser diode.

In the manufacture of the substrate 800, the seed substrate 8
01, C-plane sapphire, M-plane sapphire, A-plane sapphire, R-plane sapphire, GaAs, ZnO, MgO,
Spinel, Ge, Si, 6H-SiC seed substrate, 4H-S
Any of an iC seed substrate and a 3C-SiC seed substrate can be used. The low temperature buffer layer 802 is
A low-temperature GaN buffer layer, a low-temperature AlN buffer layer, and a low-temperature Al _x Ga _1-x N buffer layer (0
<X <1), low-temperature In _y Ga _1-y N buffer layer (0 <y ≦
1). n-type GaN film 803
Instead, an n-type Al _z Ga _{1 -zN} film (0 <z <1) may be used. The dielectric film 804 is made of a SiO ₂ film, SiN _x
It can be any one of a film, a TiO ₂ film, and an A1 ₂ O ₃ film. Further, instead of the dielectric film, a metal film such as tungsten or molybdenum may be used, or a portion of the dielectric film may be hollow. Instead of the n-type GaN thick film 805,
An n-type Al _w Ga _1-w N thick film (0 <w ≦ 1) may be used, and the thick film may be 20 μm or more.

(Embodiment 5) In the first embodiment, the light guide layer is composed of a GaN layer for both the n-type layer and the p-type layer, and nitrogen atoms of this GaN layer are replaced with any one of As, P and Sb. It may be replaced by an element. In this embodiment, GaN
_{1-xyz As x P y Sb} z (0 ≦ x ≦ 0.075,0 ≦ y ≦
0.1, 0 ≦ z ≦ 0.025, x + y + z ≠ 0). Other structures are the same as in the first embodiment.

In the conventional AlGaN cladding layer / GaN optical guide layer, even if the Al composition of the cladding layer is increased, the difference in the refractive index between the layers is small, and conversely, the lattice mismatch increases, and the generation of cracks and This causes a decrease in crystallinity. On the other hand, the AlGaN cladding layer and the GaN
For _{1-xyz As x P y Sb} z light guide layer, As, because of the very large bowing effect of P or Sb, AlGa
Compared with the N clad layer / GaN optical guide layer, slight lattice mismatch causes an increase in energy gap difference and an increase in refractive index difference. As a result, the laser light of the nitride semiconductor laser diode can be efficiently confined, and the vertical and transverse mode characteristics (single peak) are improved.

[0090] The _{GaN 1-xyz As x P y} Sb z (0 ≦ x
≦ 0.075, 0 ≦ y ≦ 0.1, 0 ≦ z ≦ 0.025,
x + y + z ≠ 0) Each composition ratio x, y, z of the light guide layer is:
It may be adjusted so that the energy gap is equal to or larger than the energy gap of the barrier layer. For example, in the case of a GaN _1-x As _x light guide layer of a blue-violet laser (410 nm), the composition ratio x of As is 0.015 or less, and in the case of a GaN _{1-y Py} light guide layer, the composition ratio y of P is 0.025 or less, Ga
In the case of the N _1-z Sb _z light guide layer, the composition ratio z of Sb is 0.0
It is preferably 1 or less.

(Embodiment 6) The nitride semiconductor according to the present embodiment
The light emitting diode element is shown in FIGS. FIG.
2 is a sectional view, and FIG. 13 is a top view. As shown in FIG.
The element is a C-plane (0001) sapphire substrate 90
0, low-temperature GaN buffer layer 901 (thickness: 30 nm), n
Type GaN layer 902 (thickness 3 μm, Si impurity concentration 1 × 1
0¹⁸/ Cm ^Three), N-type Al_0.1Ga_0.9N isolation layer and crack
Layer 903 (film thickness 20 nm, Si impurity concentration 1 × 10¹⁸
/ Cm^Three), Light emitting layer 904, p-type Al_0.1Ga_0.9N shielding
Layer / cladding layer 905 (film thickness 20 nm, Mg impurity concentration
6 × 10¹⁹/ Cm^Three), P-type GaN contact layer 906
(Film thickness 200 nm, Mg impurity concentration 1 × 10²⁰/ C
m ^Three), Translucent p-electrode 907, pad electrode 908, n-electrode
It comprises a pole 909 and a dielectric film 910.

In the structure of the light emitting diode, n-type A
The l _0.1 Ga _0.9 N shielding layer / cladding layer 903 may be omitted. The translucent p-electrode 907 is made of Ni or Pd, the pad electrode 908 is made of Au, and the n-electrode 909 is made of T or Td.
i / Al, Hf / Au, Ti / Mo, or Hf / Al
It is composed of In the light emitting layer of this embodiment, the well layer and the barrier layer are each made of SiH ₄ (Si impurity concentration 5 × 10 ¹⁷ / c).
m ³ ).

The nitride semiconductor materials of the well layers and the barrier layers constituting the light emitting layer are the same as in the second embodiment. Also, instead of the sapphire substrate 900, Ga
When the N substrate is used, the same effect as in the third embodiment is obtained, and when the substrate shown in FIG. 4 is used, the same effect as in the fourth embodiment is obtained. In the case of using a conductive GaN substrate, as shown in FIG. 13, instead of removing both the p and n electrodes from one side, an n electrode from the back side of the GaN substrate and a translucent p electrode from the epi surface side are used. Can be taken. In the present embodiment, the conditions for the light emitting layer, such as the thickness of the barrier layer, the thickness of the well layer, and the impurity concentration, which constitute the light emitting layer, and the crystal growth method are the same as in the first embodiment.

FIG. 14 shows the relationship between the number of well layers constituting the light emitting layer of the light emitting diode and the light emission intensity. FIG.
The light emission intensity of the middle light emitting diode is standardized with the light emission intensity when the conventional InGaN well layer is used as 1 (broken line). In the figure, the mark ○ indicates the emission intensity when a sapphire substrate was used, and the mark ● indicates the light emission intensity when a GaN substrate was used. From this figure, it is preferable that the number of well layers in the light emitting diode is 2 or more and 10 or less. Also,
It can be seen that the emission intensity is improved by using a GaN substrate rather than a sapphire substrate.

(Embodiment 7) The present embodiment provides a nitride semiconductor superluminescent diode device. The crystal growth method and the structure of the element are the same as those of the first embodiment (see FIG. 1). On the other hand, the nitride semiconductor materials of the well layers and the barrier layers constituting the light emitting layer are the same as in the second embodiment. The sapphire substrate 9
When a GaN substrate is used instead of 00, the same effect as in the third embodiment is obtained, and when the substrate shown in FIG. 4 is used, the same effect as in the fourth embodiment is obtained. The conditions relating to the light emitting layer, such as the thickness of the barrier layer, the thickness of the well layer, and the impurity concentration, and the crystal growth method are the same as those in the first embodiment. Also,
The relationship between the number of well layers constituting the light emitting layer of the superluminescence diode and the light emission intensity is the same as in the sixth embodiment.

(Embodiment 8) In this embodiment, the C impurity is added to the well layer and the barrier layer constituting the light emitting layer at 1 × 10 ²⁰ / cm.
^It is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that ^{3 was} added.

(Embodiment 9) In this embodiment, the light emitting layer is formed
1 × 10 Mg impurity in well layer and barrier layer ¹⁶/ C
m^ThreeExcept for the addition, Example 1, Example 3, Example 4,
This is the same as the sixth or seventh embodiment.

(Embodiment 10) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by five periods of In _0.05 Al.
_0.1 Ga _0.85 N _0.98 P _0.02 well layer (2 nm) / Al _0.02
Example 1 except for the Ga _0.98 N barrier layer (4 nm)
This is the same as the third, fourth, sixth or seventh embodiment.

(Embodiment 11) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are composed of 10 cycles of In _0.05 Al.
_0.1 Ga _0.85 N _0.99 As _0.01 well layer (0.4 nm) / G
Except for the aN barrier layer (1 nm), it is the same as Example 1, Example 3, Example 4, Example 6, or Example 7.

(Embodiment 12) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by three periods of In _0.2 Al _0.2
Ga _0.6 N _0.99 P _0.01 well layer (6 nm) / Al _0.1 Ga
Example 1, Example 3, Example 4, Example 6, or Example 7 except that the barrier layer is _0.9 N _0.99 As _0.01 barrier layer (6 nm).
Is the same as

(Embodiment 13) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of four periods of In _0.2 Al _0.2
Ga _0.6 N _0.99 As _0.01 well layer (4 nm) / Al _0.1 Ga
Example 1, Example 3, Example 4, Example 6, or Example 7 except that it is a _0.9 N _0.99 P _0.01 barrier layer (10 nm).
Is the same as

(Embodiment 14) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are composed of two periods of In _0.05 Al.
_0.03 Ga _0.92 N _0.98 P _0.02 well layer (18 nm) / In
_This is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that it is a _0.02 Ga _0.98 N barrier layer (20 nm).

(Embodiment 15) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of six periods of In _0.1 Al.
_0.05 Ga _0.85 N _0.99 As _0.01 Well layer (4 nm) / GaN
Except for the barrier layer (3 nm), Examples 1, 3,
This is the same as the fourth, sixth, or seventh embodiment.

(Embodiment 16) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of four periods of In _0.1 Al.
_0.05 Ga _0.85 N _0.98 P _0.02 well layer (6 nm) / In _0.03
Besides being _{Al 0.0l Ga 0.96 N 0. 99 P} 0.01 barrier layers (3 nm), the Example 1, Example 3, Example 4, the same as in Example 6 or Example 7.

(Embodiment 17) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are composed of five periods of In _0.1 A1.
_0.01 Ga _0.89 N _0.99 As _0.01 well layer (4 nm) / GaN
_It is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that the barrier layer is _0.99 As _0.01 (10 nm).

(Embodiment 18) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of six periods of In _0.02 Al.
_0.03 Ga _0.95 N _0.98 As _0.02 well layer (4 nm) / GaN
Except for the barrier layer (4 nm), Examples 1, 3,
This is the same as the fourth, sixth, or seventh embodiment.

(Embodiment 19) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by three periods of In _0.05 Al.
_0.01 Ga _0.94 N _0.98 Sb _0.02 Well layer (5 nm) / GaN
Except for the barrier layer (5 nm), Examples 1, 3,
This is the same as the fourth, sixth, or seventh embodiment.

(Embodiment 20) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of four periods of In _0.2 Al.
_0.03 Ga _0.77 N _0.97 P _0.03 well layer (4 nm) / In _0.02
Besides being _{Al 0.03 Ga 0.95 N 0. 98 As} 0.02 barrier layers (8 nm) is Example 1, Example 3, Example 4, the same as in Example 6 or Example 7.

Embodiment 21 In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by three periods of In _0.2 Al.
_0.05 Ga _0.75 N _0.98 As _0.02 well layer (15 nm) / In
_It is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that it is a _0.02 Ga _0.98 N _0.98 As _0.02 barrier layer (10 nm).

(Embodiment 22) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by three periods of In _0.1 Al.
_0.01 Ga _0.89 N _0.94 P _0.06 well layer (5 nm) / Al _0.03
Besides being Ga _0.97 N _0.98 Sb _{0. 02} barrier layer (5 nm), the Example 1, Example 3, Example 4, the same as in Example 6 or Example 7.

(Embodiment 23) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are composed of two periods of In _0.1 Al.
_0.03 Ga _0.87 N _0.96 As _0.04 well layer (6 nm) / In
Except a _0.15 Ga _0.85 N _0.97 P _{0. 03} barrier layer (6 nm), Example 1, Example 3, Example 4, the same as in Example 6 or Example 7.

(Embodiment 24) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of four periods of In _0.35 Al.
_0.1 Ga _0.55 N _0.98 As _0.02 well layer (10 nm) / In
Except a _{0.1 Al 0.1 Ga 0.8 N 0. 95} P 0.05 barrier layers (4 nm), Example 1, Example 3, Example 4, the same as in Example 6 or Example 7.

(Embodiment 25) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed of four periods of In _0.35 Al.
_0.05 Ga _0.6 N _0.94 P _0.06 well layer (10 nm) / GaN
_It is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that the barrier layer is _0.95 As _0.05 barrier layer (15 nm).

(Embodiment 26) In this embodiment, the well layer and the barrier layer constituting the light emitting layer are formed by three periods of In _0.2 Al.
_0.02 Ga _0.78 N _0.95 As _0.05 Well layer (20 nm) / Ga
This is the same as Example 1, Example 3, Example 4, Example 6, or Example 7 except that the barrier layer is N _0.9 P _0.1 (20 nm).

(Embodiment 27) In this embodiment, a light emitting layer is formed.
The well layer and the barrier layer are composed of two periods of In._0.1Al_0.1
Ga_0.8N_0.98P_0.02Well layer (5 nm) / Al_0.01Ga
_0.99N_0.95As_0.05A barrier layer (5 nm),
No barrier layer is used between the p-type layer and n-type Al _0.15Ga
_0.85Other than using an N shielding layer between the n-type layer and the light emitting layer
Is the same as Example 1, Example 3, Example 4, Example 6, or
This is the same as the seventh embodiment. Also, n-type Al_{0. 15}Ga_0.85N shield
By using the shielding layer, Example 1, Example 3,
Almost the same effects as in Example 4, Example 6, or Example 7 can be obtained.
Was.

(Example 28) The nitride semiconductor laser of the present invention, which emits ultraviolet light to bluish purple light (oscillation wavelength of 380 nm to 410 nm), has a lower laser oscillation threshold current density than the conventional nitride semiconductor laser. Spontaneous emission of light is reduced, and it is strong against noise. Further, the laser according to the present invention is a laser suitable for an optical disk for high-density recording / reproduction because it operates stably in a high output (50 mW) and high temperature atmosphere. FIG. 15 shows an example of an optical device using the nitride semiconductor laser of the first to fifth embodiments.

The optical device shown in FIG. 15 is an optical disk device as an example of an information recording device. In the apparatus, a laser beam from a laser 150 is modulated by an optical modulator 151 according to input information, reflected by a tracking mirror 153, and recorded on a disk 160 through a lens 154. At the time of reproduction, laser light optically changed by the bit arrangement on the disk 160 is detected by the photodetector 155 through the splitter 152, and becomes a reproduction signal. These operations and the disk motor 157 are controlled by a control circuit 156. Laser output is usually 30m during recording
W and about 5 mW during reproduction.

Further, the laser element according to the present invention is effective for a laser printer, a projector, and the like in addition to the above-mentioned optical disk device. In the projector, a laser diode of three primary colors (blue, green, and red) using the light emitting layer according to the present invention can be used.

(Embodiment 29) The light emitting diode or the super luminescent diode of the embodiment 6 or 7
Applies to white light sources or displays. In this case, light emitting diodes of three primary colors of light (red, green, and blue) or superluminescent diodes are used.

Instead of the halogen light source used in the conventional liquid crystal display, this white light source can be used as a backlight with low power consumption and high luminance. this is,
It can be used as a backlight for a liquid crystal display of a man-machine interface by a portable notebook personal computer, a mobile phone, or the like, and can provide a small-sized and clear liquid crystal display.

[0121]

As described above, the present invention relates to InAl
_{GaN 1-xyz As x P y} Sb z (0 ≦ x ≦ 0.1,0 ≦ y
≦ 0.2, 0 ≦ z ≦ 0.05, x + y + z> 0) is used for the well layer, and if necessary, the composition ratio of each constituent element of the well layer is optimized. By optimizing the constituent elements of the barrier layer and its composition ratio, and further introducing a shielding layer as necessary, it suppresses occurrence of crystal system separation and phase separation, and has excellent crystallinity and high luminous efficiency A nitride semiconductor light emitting device can be provided, and a high-performance optical device can be provided using such a device.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a structure of a laser device according to a first embodiment.

FIG. 2 is a diagram showing the relationship between the additive concentration of Al, the ratio of crystal system separation, and the emission intensity.

FIG. 3 is a schematic diagram illustrating division and cleavage of a chip.

FIG. 4 is a schematic cross-sectional view showing a structure of a substrate using a nitride semiconductor thick film.

FIG. 5 is a diagram showing a relationship between the number of well layers of a laser diode and a threshold current density.

FIG. 6 is a schematic diagram illustrating an example of a band gap energy structure.

FIG. 7 is a schematic view showing another example of the bandgap energy structure.

FIG. 8 is a schematic diagram showing another example of the bandgap energy structure.

FIG. 9 is a schematic view showing another example of the bandgap energy structure.

FIG. 10 is a schematic diagram showing another example of the bandgap energy structure.

FIG. 11 is a schematic sectional view showing an example of a laser structure using a nitride semiconductor substrate.

FIG. 12 is a schematic sectional view showing an example of a light emitting diode structure.

13 is a plan view of the light emitting diode structure shown in FIG.

FIG. 14 is a diagram showing a relationship between the number of well layers and light emission intensity of a light emitting diode.

FIG. 15 is a schematic diagram illustrating an optical disc device as an example of an information recording device.

[Explanation of symbols]

100,900 sapphire substrate, 101,901 low temperature GaN buffer layer, 102,902 n-type GaN layer,
103 n-type In _0.07 Ga _0.93 N crack preventing layer, 10
4 n-type Al _0.1 Ga _0.9 N cladding layer, 105 n-type G
aN light guide layer, 106,904 light emitting layer, 107 p
-Type Al _0.2 Ga _0.8 N shielding layer, 108 p-type GaN optical guide layer, 109 p-type Al _0.1 Ga _0.9 N cladding layer, 11
0,906 p-type GaN contact layer, 111,909
n electrode, 112 p electrode, 113 SiO ₂ dielectric film, 700 n-type GaN substrate, 800 substrate, 801
Seed substrate, 802 Low temperature buffer layer, 803 n-type GaN
Film, 804,910 dielectric film, 805 n-type GaN thick film, 903 n-type Al _0.1 Ga _0.9 N blocking layer and the cladding layer, 905 p-type Al _0.1 Ga _0.9 N blocking layer and the cladding layer, 907 transparent p-electrode , 908 pad electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F041 CA05 CA34 CA40 CA46 CA53 CA54 CA56 CA57 CA65 CA82 CA83 CA88 CA92 FF11 5F045 AA04 AB14 AB17 AC12 AF09 AF13 BB04 BB16 CA11 DA53 DA55 CB19 CB22 DA05 DA24 DA32 EA23

Claims (14)

[Claims] 1. A nitride semiconductor light emitting device having a plurality of well layers and one or more light emitting layers and barrier layers are combined, the well layer, wherein _{InAlGaN 1-xyz As x P y} Sb _z
(Where 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.2, 0 ≦ z ≦
A nitride semiconductor light emitting device comprising a nitride represented by the formula: 0.05, x + y + z> 0). 2. The method according to claim 1, wherein the content of Al in the well layer is 1 ×.
2. The method according to claim 1, wherein the density is 10 ¹⁹ / cm ³ or more.
3. The nitride semiconductor light emitting device according to item 1. Wherein the well layer is of the formula In _a Al _b Ga _1-ab
During _{N 1-xyz As x P y} Sb z ( wherein, 0 <a ≦ 0.5,0 <
b ≦ 0.2, 0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.2, 0 ≦ z
3. The nitride semiconductor light emitting device according to claim 1, wherein the nitride semiconductor light emitting device is made of a nitride represented by ≦ 0.05, x + y + z> 0). 4. The barrier layer according to claim 1, wherein said barrier layer contains at least Ga as a group III element and contains only N as a group V element.
The nitride semiconductor light emitting device according to any one of claims 1 to 3, wherein the nitride semiconductor light emitting device is made of a II-V compound semiconductor. 5. The barrier layer contains at least Ga as a group III element and at least one element selected from the group consisting of As, P and Sb as a group V element and N.
The nitride semiconductor light emitting device according to claim 1, comprising a III-V compound semiconductor comprising: 6. As, P and Sb in the well layer
6. The nitride semiconductor light-emitting device according to claim 1, wherein the total content of is 10 ¹⁸ / cm ³ or more. 7. The light emitting layer according to claim 1, wherein the light emitting layer is present between two adjacent layers, and at least one of the two layers is made of a nitride containing Al and N. 7. The nitride semiconductor light-emitting device according to any one of items 6 to 6. 8. The light emitting device according to claim 1, wherein the number of said well layers constituting said light emitting layer is 2 or more and 10 or less.
8. The nitride semiconductor light-emitting device according to any one of items 7 to 7. 9. The method according to claim 1, wherein the thickness of the well layer is at least 0.4 nm and at least 20.
The nitride semiconductor light emitting device according to any one of claims 1 to 8, wherein the thickness is equal to or less than nm. 10. The barrier layer has a thickness of 1 nm or more and 20 n or more.
10. The nitride semiconductor light emitting device according to claim 1, wherein m is equal to or less than m. 11. The method according to claim 1, wherein at least one element selected from the group consisting of Si, O, S, C, Ge, Zn, Cd, and Mg is added to the well layer and / or the barrier layer. A method according to any one of claims 1 to 10, wherein
Item 3. The nitride semiconductor light emitting device according to item 1. 12. The amount of the element added is 1 × 10 ¹⁶ to 1 ×.
Characterized in that it is a 10 ²⁰ / cm ^3, a nitride semiconductor light emitting device according to claim 11. 13. The nitride semiconductor light emitting device according to claim 1, further comprising a GaN substrate, wherein the light emitting layer is formed on the GaN substrate. 14. An optical device using the nitride semiconductor light emitting device according to claim 1.