JPH09214044A - Nitride semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower a threshold current of a laser device composed of nitride semiconductor by providing a current stopping layer having a striped through- hole and composed of p or i type nitride semiconductor between an n type contact layer and an active layer composed of nitride semiconductor having a quantum structure. SOLUTION: An active layer 14 of a laser device has a quantum structure. The quantum structure means a single quantum well structure and a multiple quantum well structure, etc., each of which emits light owing to quantum effect thereof. The active layer is preferably a multiple quantum well structure. Nitride semiconductor lases by constructing the active layer as the quantum structure. Furhtrer, the laser device includes between an n type contact layer 11 and the active layer a current stopping layer 20 having a striped through-hole and composed of p or i nitride semiconductor. The current stopping layer 20 is formed between the n type contact layer 11 and the active layer 14 to hereby narrow a current between the stripes and form an optical waveguide.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a nitride semiconductor (In _{XA).
l Y Ga 1-XY N,} 0 ≦ X, 0 ≦ Y, a laser element made of X + Y ≦ 1).

[0002]

2. Description of the Related Art Nitride semiconductors have been studied as a material for short wavelength lasers, and we have recently reported pulse oscillation at room temperature using this material (for example, Nikkei Electronics 1995.1.15 (No. 653) p13 to p15). Although the reported laser device is an electrode stripe type laser device, it has a threshold current density of 4 kA / cm ^2, and it is necessary to further reduce the threshold current for continuous oscillation at room temperature.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to reduce the threshold current of a laser device made of a nitride semiconductor and aim for continuous oscillation at room temperature.

[0004]

According to the present invention, there is provided a laser device comprising:
An n-type contact layer made of an n-type nitride semiconductor and an active layer made of a nitride semiconductor having a quantum structure are provided on at least a substrate, and a p layer is provided between the n-type contact layer and the active layer. Type or i-type nitride semiconductor is provided, and the current blocking layer is provided with stripe-shaped through holes. However, the through hole described in the present specification is not a through hole having a hollow inside, but is made of a nitride semiconductor different from the current blocking layer inside.

The laser device of the present invention is characterized in that an optical confinement layer made of an n-type nitride semiconductor containing at least aluminum is provided between the current blocking layer and the active layer. Furthermore, it is more desirable to provide an optical guide layer made of n-type In _X Ga _{1 -X} N (0 ≦ X ≦ 1) between the active layer and the light confinement layer.

Further, in the laser element of the present invention, the through hole has a wide stripe width on the active layer side and a narrow stripe width on the n-type contact layer side. Most preferably, the through holes are V-groove shaped stripes.

The current blocking layer is formed in contact with the n-type contact layer. More preferably, the n-type contact layer is made of Al _Y Ga _1-Y N (0 ≦ Y ≦ 1), and the current blocking layer is made of Al _{Y ′} Ga _{1-Y ′} N (0 ≦ Y ′ ≦ 1). .

Further, in the laser device of the present invention, the p-type contact layer made of at least a p-type nitride semiconductor is provided on the outermost surface of the nitride semiconductor layer facing the n-type contact layer with the active layer interposed therebetween. The positive electrode is provided on almost the entire surface of the p-type contact layer.

[0009]

FIG. 1 is a schematic sectional view showing one structure of the laser device of the present invention. 10 is a substrate, 11 is an n-type contact layer, 20 is a current blocking layer, 12 is an n-type optical confinement layer, 13
Is an n-type light guide layer, 14 is an active layer, 15 is a p-type light guide layer, 16 is a p-type light confinement layer, and 17 is a p-type contact layer. The active layer 14 of the laser device of the present invention has a quantum structure. The quantum structure is a structure that emits light by a quantum effect such as a single quantum well structure and a multiple quantum well structure, and the active layer preferably has a multiple quantum well structure. When the active layer has a quantum structure, the nitride semiconductor oscillates. Further, the laser device of the present invention has a current blocking layer 20 having a stripe-shaped through hole made of a p-type or i-type nitride semiconductor between the n-type contact layer 11 and the active layer 14. There is. This current blocking layer 20 is n
By being formed between the mold contact layer 11 and the active layer 14, a current can be narrowed between the stripes to form a waveguide. Moreover, the n-type contact layer 11
And the active layer 14, the nitride semiconductor having good crystallinity can be grown. The stripe width of the through hole is 10
It is adjusted to be not more than μm, more preferably not more than 5 μm, most preferably not more than 3 μm. If it is larger than 10 μm, it is difficult to concentrate light on the active layer, and the threshold current increases. The lower limit of the stripe width is not particularly limited, but is usually 0.0
1 μm or more is desirable.

The laser device of the present invention comprises a current blocking layer 20.
And the active layer 14, the optical confinement layer 12 made of an n-type nitride semiconductor containing aluminum is provided. The light confinement layer 12 is preferably a binary mixed crystal or a ternary mixed crystal of Al _Y Ga _{1 -Y} N (0 <Y ≦ 1) to obtain a good crystallinity, and the active layer It is effective for confining the longitudinal mode of the laser light by increasing the difference in refractive index between and. This layer is usually preferably grown to a thickness of 0.1 μm to 1 μm. If it is thinner than 0.1 μm, it is difficult to act as a light confining layer, and if it is thicker than 1 μm, cracks are likely to occur in the crystal, and it tends to be difficult to manufacture an element.

Further, in the laser device of the present invention, an n-type In _X Ga _1-X N is formed between the optical confinement layer 12 and the active layer 14.
The optical guide layer 13 made of (0 ≦ X ≦ 1) is provided.
It is usually desirable to grow this layer to a film thickness of 100 angstrom to 1 μm, and particularly by using InGaN or GaN, it becomes possible to easily make the next active layer 5 a quantum well structure.

Next, in the laser device of the present invention, as shown in FIG. 1, the through hole has a wide stripe width on the active layer side and a narrow stripe width on the n-type contact layer side. That is, the current blocking layer 20 has a mesa shape. With such a mesa shape, when a nitride semiconductor is grown on the through hole, it is possible to grow a crystal with a uniform film thickness on the slope portion of the current blocking layer. In particular, since a nitride semiconductor is grown by a vapor phase method such as MOVPE, if the end surface of the through hole is vertical, the gas wraparound becomes nonuniform for crystal growth on that end surface, and a uniform film can be formed. It tends to be difficult. Particularly in the laser device of the present invention, since the active layer has a quantum structure,
It is necessary to severely control the film thickness of the nitride semiconductor forming the quantum structure. Therefore, if it has a mesa shape as described above, the film thickness is controlled and an active layer with good crystallinity can be grown.

Further, the through holes are preferably V-groove shaped stripes. FIG. 2 is an enlarged cross-sectional view showing a portion surrounded by an ellipse of the laser element shown in FIG. 1, and shows a structure closer to reality than that of FIG. As shown in this figure, if the groove is a V groove, the n-type light confinement layer 12, the n-type light guide layer 13, the active layer 14, the p-type light guide layer 15, and the p-type light confinement layer 16 are V-shaped. It becomes easier to enter the groove. The laser light emitted from the active layer has a longitudinal mode controlled by the optical confinement layers above and below the active layer. When the V-shaped groove is formed, a lateral optical confinement layer sandwiching the active layer 15 enters into the groove, whereby the lateral mode of laser light can be controlled and optical confinement can be achieved in the groove. Can be lowered. In other words, the V-groove makes it possible to form a so-called refractive index guided laser element in which the lateral active layer is sandwiched by the clad layers having different refractive indexes.

FIG. 3 is a schematic sectional view showing the structure of another laser device of the present invention, and the same reference numerals as those in FIGS. 1 and 2 indicate the same members. Although this laser element is not a V-shaped groove, it also has a through hole that allows the current blocking layer to have a mesa shape, and the depth of the through hole reaches the n-type contact layer 11. Even if the through hole of FIG. 3 is enlarged, it becomes the same as the view shown in FIG. 2 and has the same operation as the above. In the present invention, the preferable depth of the through hole or the V groove varies depending on the film thickness of the current blocking layer 20, but most importantly, at least the n-type optical confinement layer 12 and the active layer 14 are in the through hole. And most preferably, the optical confinement structure of the laser including the p-type optical confinement layer 16 is present in the through hole.

Further, the laser element of the present invention is characterized in that the current blocking layer 20 is formed in contact with the n-type contact layer. The current blocking layer is preferably formed of p-type nitride semiconductor. If the current blocking layer 20 is formed between the optical confinement layer 12 and the n-type optical guide layer 13, the transverse mode light of the laser spreads, and the threshold current tends to increase. In addition, as another function, the p-type nitride semiconductor is grown on a layer having good crystallinity, and a thick film can be grown to obtain a p-type crystal having excellent characteristics. for that reason,
The p-type current blocking layer grown on the n-type contact layer having good crystallinity can grow with good crystallinity, and even when n-type optical confinement is grown on the current blocking layer with good crystallinity, A preferable n-type optical confinement layer can be grown by inheriting the crystallinity of the p layer grown in 1.

The n-type contact layer 11 is made of Al _Y Ga.
_1-YN (0 ≦ Y ≦ 1) and the current blocking layer 20 is Al _{Y ′}
It is preferably made of Ga _{1 -Y ′} N (0 ≦ Y ′ ≦ 1). Furthermore, it is preferable that the n-type contact layer 11 and the current blocking layer 20 have the same composition. Since the nitride semiconductors having the same composition have the same lattice constant, the current blocking layer to be grown later can be grown with good crystallinity. The current blocking layer is made of AlGa.
When it is N, it tends to be p-type as compared with GaN. Therefore, the n-type contact layer 11 may be GaN, which is easy to obtain ohmic contact with the electrode, and the current blocking layer 20 may be AlGaN, which is easy to obtain a p-type semiconductor. The p-type nitride semiconductor can be obtained by doping the nitride semiconductor layer with an acceptor impurity made of a group II element such as Zn, Mg, Cd, Be, or Ca during crystal growth. In the case of the layer 20, it is difficult to obtain excellent p-type characteristics. Therefore, in the claims and the detailed description of the present specification, a current blocking layer made of a nitride semiconductor layer containing an acceptor impurity is a p-type or i-type layer. It is defined as a nitride semiconductor layer.

In the laser device of the present invention, the active layer 14
A p-type contact layer 17 made of a p-type nitride semiconductor is provided on the outermost surface of the nitride semiconductor layer facing the n-type contact layer 11 with the p-type contact layer 1 interposed therebetween.
It is characterized in that a positive electrode is provided on almost the entire surface of 7. In the present invention, the current blocking layer 20 formed on the n-type contact layer 11 side concentrates the current related to the active layer. Therefore, since the current blocking layer 20 exists, the positive electrode can be formed on almost the entire surface of the uppermost p-type contact layer, so that the threshold voltage can be lowered.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment] FIG. 4 is a schematic sectional view showing a structure of a laser device according to an embodiment of the present invention, and shows a laser device sectional view taken in a direction parallel to a resonance plane. Hereinafter, a method for producing the laser device of the present invention by the MOVPE method will be described in detail with reference to this drawing.

Substrate 100 whose main surface is the A-side of sapphire
Was placed in a reaction vessel of a MOVPE apparatus, TMG (trimethylgallium) and ammonia were used as source gases, and a buffer layer made of GaN was grown to a thickness of 200 Å on the surface of the sapphire substrate at a temperature of 500 ° C. . Substrate 100 includes sapphire R surface, A surface, and C surface.
Sapphire whose main surface is a main surface can also be used. Besides this, spinel (MgAl ₂ O ₄ , 111 surface), SiC, MgO, S
A conventionally known substrate made of a single crystal such as i or ZnO is used. The buffer layer has a function of alleviating the lattice mismatch between the substrate and the nitride semiconductor.
It is also possible to grow GaN or the like. It is known that by growing this buffer layer, the crystallinity of the n-type nitride semiconductor grown on the substrate is improved, but the buffer layer may not be grown depending on the growth method, the type of the substrate and the like. . The buffer layer is not shown in this figure.

Then, the temperature is raised to 1050 ° C., TMG and ammonia are used as a source gas, and SiH is used as a donor impurity.
_An n-type contact layer 101 made of Si-doped GaN was grown to a thickness of 4 μm using ₄ (silane) gas.
The n-type contact layer 101 is made of In _X Al _Y Ga _1-XY N (0
≦ X, 0 ≦ Y, X + Y ≦ 1), and especially G
aN, InGaN, GaN doped with Si among them
With such a constitution, an n-type layer having a high carrier concentration can be obtained and preferable ohmic contact with the negative electrode can be obtained, so that the threshold current of the laser element can be reduced. Al, Ti, W, Cu, Z
A metal or alloy such as n, Sn, In or the like can provide a preferable ohmic. Although not limited to GaN, nitride semiconductors have the property of becoming n-type due to nitrogen vacancies formed inside the crystal even when non-doped (in a state where impurities are not doped).
By doping a donor impurity such as e or Sn during crystal growth, a nitride semiconductor having a high carrier concentration and exhibiting preferable n-type characteristics can be obtained.

Next, while maintaining the temperature at 1050 ° C., TMG, ammonia was used as a source gas, and Cp 2 Mg was used as an impurity gas, and a current blocking layer 200 made of Mg-doped p-type GaN was grown to a thickness of 0.5 μm. .

After growing the current blocking layer 200, the wafer is taken out of the reaction vessel, and the current blocking layer 20 is mesa-etched in a V-groove shape at a depth reaching the n-type contact layer 101.
Through holes were formed as shown in FIG. The width of the V groove is 5
and a depth of 2.5 μm on the surface of the current blocking layer 200.

Next, the wafer is transferred again to the reaction container,
The temperature was set to 750 ° C., TMG, TMI (trimethylindium), ammonia was used as a source gas, and silane gas was used as an impurity gas, and a crack prevention layer 301 made of Si-doped In0.1Ga0.9N was grown to a thickness of 500 angstroms. . The crack prevention layer 301 includes n containing In
It is very preferable that the n-type optical confinement layer 102 made of a nitride semiconductor containing Al to be grown next can be grown in a thick film by growing the n-type optical semiconductor layer, preferably InGaN. In the case of LD, it is necessary to grow the layers serving as the light confinement layer and the light guide layer to have a film thickness of, for example, 0.1 μm or more. Conventionally GaN, Al
If a thick film of AlGaN is grown directly on the GaN layer,
Although it was difficult to fabricate the device because the AlGaN grown later had cracks, the crack prevention layer 301
It is possible to prevent the optical confinement layer to be grown next from cracking. The crack preventing layer is preferably grown to a thickness of 100 Å or more and 0.5 μm or less. If it is thinner than 100 angstroms, it is difficult to act as a crack prevention as described above.
If it is thicker than 5 μm, the crystals themselves tend to turn black.
The crack prevention layer 301 may be omitted depending on the growing method and growing apparatus.

Next, using TEG, TMA (trimethylaluminum), ammonia as a raw material gas, and silane gas as an impurity gas, an n-type optical confinement layer 102 made of Si-doped n-type Al0.3Ga0.7N having a thickness of 0.5 μm is formed. Grown thick. The n-type optical confinement layer 102 is composed of an n-type nitride semiconductor containing Al, and is preferably a binary mixed crystal or a ternary mixed crystal of Al _Y Ga _{1 -Y} N (0 <Y ≦ 1). ,
It is possible to obtain a crystal having good crystallinity, and it is effective in confining the longitudinal mode of laser light by increasing the difference in refractive index from the active layer. This layer is usually preferably grown to a thickness of 0.1 μm to 1 μm. If it is thinner than 0.1 μm, it is difficult to act as a light confining layer, and if it is thicker than 1 μm, cracks are likely to occur in the crystal, and it tends to be difficult to manufacture an element.

Then, TMG, ammonia, and
Si-doped n-type GaN using silane gas as impurity gas
The n-type light guide layer 103 was made to grow to a film thickness of 500 angstroms. The n-type light guide layer 103 is In
N-type nitride semiconductor containing n or n-type GaN, preferably ternary mixed crystal or binary mixed crystal of In _X Ga _1-X N (0 ≦
X ≦ 1). It is usually desirable to grow this layer to a film thickness of 100 Å to 1 μm.
By using GaN or GaN, the next active layer 104 can be easily formed into a quantum structure.

Next, the source gas is TMG, TMI, and ammonium.
The active layer 104 was grown by using. Active layer
Hold at 750 ℃, first undoped In0.2Ga0.8N
A well layer consisting of 25 angstroms
Let Next, change the TMI molar ratio to the same temperature.
A barrier layer made of non-doped In0.01Ga0.95N.
It is grown to a film thickness of 0 angstrom. This operation 1
Repeat 3 times, and finally grow the well layer to a total film thickness of 0.1μ
Growth of active layer 14 with multiple quantum well structure of m thickness
I let it. The active layer 104 is composed of a nitride semiconductor containing In.
However, ternary mixed crystal In is preferable. _XGa_1-XN (0 <X <
It is desirable to set 1). The ternary mixed crystal InGaN has four
As a crystal with better crystallinity than that of the original mixed crystal can be obtained,
The luminous output is improved. Among them, the active layer is particularly preferable.
To In_XGa_1-XWell layer made of N and van rather than well layer
And a barrier layer made of a nitride semiconductor with a large gap.
Layered multiple quantum well structure (MQW: Multi-quantum-wel)
l). Similarly, for the barrier layer, ternary mixed crystal In_{X '}Ga_{1-X '}
N (0 ≦ X ′ <1, X ′ <X) is preferable, well + barrier + well
Door + ... + Barrier + Layered to form a well layer
Configure a child well structure. In this way, the active layer is made of InGaN.
If MQW is made by stacking the
It is possible to realize a high-power LD between nm and 660 nm.
it can. Furthermore, a barrier made of InGaN is formed on the well layer.
When the layers are stacked, the InGaN barrier layer is GaN,
The crystal is softer than the AlGaN crystal. Because of that
Laser oscillation is possible because the thickness of AlGaN in the saddle layer can be increased.
Can be realized. Furthermore, InGaN and GaN are crystalline
Have different growth temperatures. For example, in the MOVPE method, InGa
N is grown at 600 ° C. to 800 ° C., whereas Ga is grown.
N is grown at a temperature higher than 800 ° C. Therefore, In
After growing a well layer made of GaN, it is made of GaN
If you try to grow the barrier layer, you will raise the growth temperature
There is a need. When the growth temperature is raised, the In grown previously
Well layer with good crystallinity because the GaN well layer is decomposed
Hard to get. Furthermore, the thickness of the well layer is several tens of angstroms.
There is only a strom, and if the thin well layer decomposes, MQW
Is difficult to manufacture. On the other hand, in the present invention,
Since the wall layer is also InGaN, the well layer and the barrier layer have the same temperature.
You can grow in degrees. Therefore, the well layer previously formed is decomposed.
Therefore, it is possible to form MQW with good crystallinity.
it can. This shows the most preferred form of MQW
In addition, the well layer is InGaN, the barrier layer is GaN,
The band gap of the barrier layer is better than that of the well layer like AlGaN.
Any composition may be used as long as the energy is increased.
Further, the active layer 104 is a single well layer composed of only a single well layer.
A single quantum well structure may be used.

After the growth of the active layer 104, the temperature is set to 1050 ° C., TMG, TMA, ammonia, and Cp 2 Mg (cyclopentadienyl magnesium) as an acceptor impurity source are used, and a p-type cap made of Mg-doped p-type Al 0.2 Ga 0.8 N is used. Layer 302 was grown to a thickness of 100 Angstroms. The p-type cap layer 302 has a thickness of 1 μm or less, more preferably 10 angstroms or more, and 0.1.
InGaN is grown by growing the film to a thickness of 1 μm or less.
P-type nitride semiconductor containing Al on the active layer, preferably Al _Y Ga _{1 -Y} N (0 <Y <1). By growing the p-type cap layer made of, the light emission output is remarkably improved. The film thickness of this p-type cap layer is 1 μm.
If it is thicker than m, the layer itself tends to be cracked, and it tends to be difficult to manufacture the device. The p-type cap layer 302 can also be omitted depending on the growing method, growing apparatus, and the like.

Next, while maintaining the temperature at 1050 ° C., T
Mg-doped p-type G using MG, ammonia, and Cp2Mg
The p-type light guide layer 105 made of aN was grown to a film thickness of 500 angstrom. This p-type light guide layer 105
P-type nitride semiconductor containing In or p-type Ga
N, preferably binary or ternary mixed In _x Ga _1-x
Grow N (0 ≦ X ≦ 1). The light guide layer is usually 1
It is desirable to grow the film with a film thickness of 00 angstrom to 1 μm. In particular, by using InGaN or GaN, the next p-type optical confinement layer 106 can be grown with good crystallinity.

Then, TMG, TMA, ammonia, C
A p-type optical confinement layer 106 made of Mg-doped Al0.3Ga0.7N was grown to a thickness of 0.5 μm using p2Mg. The p-type optical confinement layer 106 is made of a p-type nitride semiconductor containing Al, and is preferably a binary mixed crystal or a ternary mixed crystal of Al _Y Ga _{1 -Y} N (0 <Y ≦ 1). As a result, a crystal having good crystallinity can be obtained. Like the n-type light confinement layer, it is desirable that the p-type light confinement layer be grown to have a film thickness of 0.1 μm to 1 μm, and by using a p-type nitride semiconductor containing Al such as AlGaN, The refractive index difference is increased to effectively act as a light confinement layer.

Then, TMG, ammonia, Cp2Mg
Was used to grow a p-type contact layer 107 made of Mg-doped p-type GaN with a film thickness of 0.5 μm. The p-type contact layer 17 is formed of p-type In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦.
Y, X + Y ≦ 1), especially InGa
When N, GaN, and among them, p-type GaN doped with Mg, a p-type layer having the highest carrier concentration is obtained, good ohmic contact with the positive electrode is obtained, and the threshold current can be reduced. . The material of the positive electrode is Ni,
A metal or alloy having a relatively high work function such as Pd, Ir, Rh, Pt, Ag, and Au is likely to obtain ohmic contact. As described above, the nitride semiconductor layer grown on the current blocking layer 20 having the V-shaped groove (through hole) has the n-type crack prevention layer 301 to the p-type contact layer 10 in the V groove.
7 are all contained, and an element structure corresponding to a refractive index waveguide is manufactured for the active layer 104.

Next, after taking out the wafer in which the nitride semiconductor is laminated on the A surface of the sapphire substrate from the reaction container, the uppermost p layer is formed by a reactive ion etching (RIE) apparatus.
Selective etching was performed from the mold contact layer 107 to expose the plane of the n-type contact layer 101 on which the negative electrode was to be formed. Next, a positive electrode was formed on almost the entire surface of the uppermost p-type contact layer 107, and a striped negative electrode parallel to the V groove was formed on the exposed n-type contact layer 101.

After forming the electrodes, the wafer is transferred to a polishing apparatus, the sapphire substrate is polished to a thickness of 80 μm to be thin, and then the sapphire substrate surface is nitrided corresponding to the R surface, that is, the direction perpendicular to the stripe electrodes. The semiconductor layer side was scratched, and the substrate was cleaved at the R surface by an external force to produce a semiconductor bar with the cleaved surface exposed. By this operation, the sapphire substrate was cleaved at the R plane, but the cleaved surface of the nitride semiconductor layer was cleaved at a plane at a twist position different from the R plane of the substrate. However, on the cleavage plane of the nitride semiconductor layer,
The cleavage plane of the V groove containing the active layer was a mirror surface, and the cleavage plane was parallel to the cleavage plane. In this example,
The resonance surface was formed by cleavage, but in addition to this, etching,
The resonance surface can also be formed by using a means such as polishing.

After forming a reflecting mirror made of a dielectric multilayer film on the cleaved surface of the semiconductor bar obtained as described above by using a sputtering apparatus, the bar is cut by dicing at a position perpendicular to the R plane. To obtain a laser chip of 500 μm square. Place this laser chip on the heat sink,
Threshold current density of 2k when pulsed at room temperature
It showed a laser oscillation of 410 nm at A / cm ² .

[Embodiment 2] A laser device was manufactured in the same manner as in Embodiment 1 except that the composition of the current blocking layer 200 was Mg-doped p-type Al0.1Ga0.9N. A device could be produced.

[0035]

The laser device of the present invention is provided between the active layer and the n-type contact layer, and the p-type or n-type current blocking layer having the through hole allows the active layer and the active layer in the through hole to be activated. Since the n-type and p-type clad layers sandwiching the layers come into contact with each other and a refractive index waveguide type laser element can be realized, the threshold value of the element is lowered. Since there is a current blocking layer, p
Since the positive electrode can be formed on the entire surface of the layer, the threshold voltage also decreases. As described above, according to the laser device of the present invention, it is possible to realize a refractive index waveguide type laser device in which the threshold value is lowered by the nitride semiconductor, and it is industrially applicable in producing a continuous wave lasing short wavelength laser device. The utility value is enormous.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of a laser device according to one embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the structure of the elliptical portion of FIG.

FIG. 3 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a laser device for explaining an example of the invention.

[Explanation of symbols]

 10 ... Substrate 11 ... N-type contact layer 20 ... Current blocking layer 12 ... N-type optical confinement layer 13 ... N-type optical guide layer 14 ... Active layer 15 ... P-type optical guide layer 16 ... P-type optical confinement layer 17 ... P-type contact layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Nakamura 491, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd.

Claims (8)

[Claims] 1. An n-type contact layer made of an n-type nitride semiconductor and an active layer made of a nitride semiconductor having a quantum structure are provided on at least a substrate, and the n-type contact layer and the active layer are provided. A nitride semiconductor laser device characterized in that a current blocking layer made of a p-type or i-type nitride semiconductor is provided between the two, and the current blocking layer is provided with stripe-shaped through holes. 2. The laser device according to claim 1, further comprising an optical confinement layer made of an n-type nitride semiconductor containing at least aluminum between the current blocking layer and the active layer. 3. An optical guide layer made of n-type In _X Ga _{1 -X} N (0 ≦ X ≦ 1) is provided between the active layer and the light confinement layer. 2. The laser device according to item 2. 4. The through hole has a wide stripe width on the active layer side and a narrow stripe width on the n-type contact layer side, according to any one of claims 1 to 3. Laser device. 5. The laser device according to claim 4, wherein the through hole is V-shaped. 6. The laser device according to claim 1, wherein the current blocking layer is formed in contact with the n-type contact layer. 7. The n-type contact layer is Al _Y Ga _{1 -Y} N
(0 ≦ Y ≦ 1), and the current blocking layer is Al _{Y ′} Ga.
7. The laser device according to claim 1, wherein the laser device is made of _{1-Y ′} N (0 ≦ Y ′ ≦ 1). 8. A p-type contact layer made of at least a p-type nitride semiconductor is provided on the outermost surface of the nitride semiconductor layer facing the n-type contact layer with the active layer interposed therebetween. 8. The laser device according to claim 1, wherein a positive electrode is provided on substantially the entire surface of the layer.