JP3339049B2 - Nitride semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor (In _X
The present invention relates to a laser device composed of Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1). The present invention relates to a nitride semiconductor laser device that can be integrated with a photodiode or the like.

[0002]

2. Description of the Related Art A nitride semiconductor laser device has a layer structure in which an active layer is sandwiched between light confinement layers (cladding layers), and light naturally emitted from the active layer is totally reflected between the p-side and n-side cladding layers. While being amplified in the waveguide layer having the active layer, and using the amplified light as stimulated emission light, an end surface of the active layer (resonance surface)
Release from

For example, the present inventors have proposed a nitride semiconductor laser device capable of continuously oscillating short-wavelength laser light having a wavelength of 410 nm (for example, Appl. Lett. 69). (1996) 30
34, Appl. Phys. Lett. 69 (199
6) described in 4056).

[0004]

However, the above nitride semiconductor laser device does not have a sufficiently satisfactory far field pattern. As a result of various studies of the problem, the present inventors have found that the light confinement of the cladding layer is not sufficient, and that the light passing through the n-side cladding layer is sandwiched between the n-side cladding layer and the sapphire substrate having a low refractive index. It was thought that the laser light was emitted from the end surface of the n-side nitride semiconductor layer guided through the n-side nitride semiconductor layer. Since light has a property of guiding light through a layer having a high refractive index, n is formed between an n-side cladding layer having a low refractive index and a substrate.
Light leaked from the waveguide layer having the active layer is guided in the n-side nitride semiconductor layer having a higher refractive index than the side cladding layer and the substrate. Incidentally, the refractive index of each nitride semiconductor layer constituting the nitride semiconductor laser device is, in order from the largest, an active layer, an intermediate layer (such as GaN), a cladding layer, a substrate (such as sapphire, spinel) and the like. .

In order to prevent the disturbance of the far-field pattern, it is conceivable to further reduce the refractive index of the cladding layer and increase the refractive index of light. However, from the viewpoint of the physical properties of the material of the cladding layer, it is necessary to adjust the refractive index. There is a limit. Also, if the cladding layer is laminated thick enough to prevent light from leaking out, light passing through the cladding layer will be attenuated in the cladding layer, and light will not be guided between the n-side cladding layer and the substrate. However, when the clad layer is thickly laminated, cracks are easily formed, and when cracks are formed, new problems such as deterioration of the performance of the nitride semiconductor laser device are easily generated. If the light in the active layer cannot be sufficiently confined in this way, it is difficult to make the far-field pattern a sufficiently good single mode. Therefore, the laser light obtained from the nitride semiconductor laser device is sufficiently satisfactory as a DVD light source that requires a smaller laser beam diameter or a light used in an optical communication field that requires a single mode light. I can't let it.

SUMMARY OF THE INVENTION An object of the present invention is to provide a nitride semiconductor laser device having a good far-field pattern of laser light and capable of obtaining a single-mode laser light.

[0007]

That is, the present invention can achieve the object of the present invention by the following constitutions. (1) A first waveguide layer having at least an active layer sandwiched between an n-side cladding layer and a p-side cladding layer on a substrate, and one or more nitride layers laminated on the substrate side of the n-side cladding layer. A metal thin film and / or a dielectric that does not emit light from the first waveguide layer on at least one of the end faces of the first waveguide layer having a resonance surface. An emission surface which has an opaque film made of a body multilayer film, suppresses light emission from the resonance surface, and can emit laser light in a direction parallel to the resonance surface, is formed on an end surface of the second waveguide layer. The thickness of the second waveguide layer is 0.1 to 1.0 μm;
A nitride semiconductor laser device, wherein an n-electrode is formed on the n-side cladding layer. (2) The said each layer is a 1st waveguide layer, a 2nd waveguide layer, an n-side and a p-side cladding layer, and a board | substrate in order of a refractive index, The said (1) characterized by the above-mentioned. Nitride semiconductor laser device. (3) a first waveguide layer having at least an active layer sandwiched between an n-side cladding layer and a p-side cladding layer on a substrate, and at least one nitride layer laminated on the substrate side of the n-side cladding layer; A metal thin film and / or a dielectric that does not emit light from the first waveguide layer on at least one of the end faces of the first waveguide layer having a resonance surface. An emission surface which has an opaque film made of a body multilayer film, suppresses light emission from the resonance surface, and can emit laser light in a direction parallel to the resonance surface, is formed on an end surface of the second waveguide layer. Wherein the second waveguide layer has the same thickness and the same refractive index as the first waveguide layer. (4) The opaque film formed on the end face of the first waveguide layer having the resonance surface is a film having a reflectance of 90% to 100%. The nitride semiconductor laser device according to any one of the above items.

That is, according to the present invention, the light generated in the first waveguide layer having the active layer is not emitted from the resonance surface of the first waveguide layer, but passes through the n-side cladding layer. End face of a second waveguide layer formed on the substrate side of the substrate and capable of guiding light passing through the n-side cladding layer, for example, a nitride semiconductor layer such as an n-side contact layer between the substrate and the n-side cladding layer. By forming an emission surface on the surface and using light emitted from the emission surface as the main laser light, the laser light can be in a single mode, and the far-field pattern can be improved.

In a conventionally known nitride semiconductor laser device, the structure of the nitride semiconductor laser device is studied so that light emitted from an end face (resonance surface) of a waveguide layer having an active layer is used as main laser light. I've been. However, as described above, the light leaked from the waveguide layer having the active layer is, for example, n
Since the light is guided in the n-side nitride semiconductor layer sandwiched between the side cladding layers and is emitted from the end face of the n-side nitride semiconductor layer, the main laser beam from the end face of the waveguide layer having the active layer can be favorably irradiated. One mode was difficult.

On the other hand, according to the present invention, an opaque film is provided on an end face having a resonance surface of a first waveguide layer having an active layer to suppress emission of laser light from the resonance surface. Mainly emits light that has been emitted through the second waveguide layer, which has been considered as unnecessary light that disturbs the far-field pattern, and that can guide light on the side opposite to the active layer of the n-side cladding layer. It is possible to improve the far-field pattern by a surprising idea which cannot be predicted from the conventional technology using the laser beam.

Further, according to the present invention, the thickness of the second waveguide layer is
When the thickness is 0.1 μm to 1.0 μm, light leaked from the first waveguide layer is easily guided by the second waveguide layer, and a better single-mode laser beam can be obtained. . Further, according to the present invention, in order to suppress the emission of laser light from the resonance surface of the first waveguide layer, the opaque film formed on the end face of the first waveguide layer has a high reflection ratio of 90 to 100%. When the film has a high ratio, the far-field pattern becomes good and the threshold value is lowered, which is preferable. The opaque film may be formed on at least one end face of the first waveguide layer having a resonance surface. Preferred for lowering.

Further, in the present invention, it is preferable that an n-electrode is provided on the n-side cladding layer. This means that the light leaked from the first waveguide layer can be guided well through the second waveguide layer.
When adjusting the total film thickness of the n-side nitride semiconductor layer laminated on the substrate side of the n-side cladding layer, for example, the n-side contact layer, the crack prevention layer, etc.
This is because it tends to be difficult to etch the n-side contact layer to expose the n-electrode formation surface in order to reduce the thickness of the side contact layer. In the case where an n-electrode is provided on the n-side cladding layer, it is preferable to increase the concentration of the n-type impurity, for example, the Si concentration, on the surface of the n-side cladding layer in contact with the n-electrode because the resistance can be reduced. Here, the second waveguide layer guides light generated in the active layer and passed through the n-side cladding layer without adjusting the thickness thereof according to the thickness of the first waveguide layer or the emission wavelength. Therefore, it is not necessary to adjust the film thickness of the second waveguide layer according to the wavelength of the laser beam. In this case,
An n electrode can be provided on the n-side contact layer.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The nitride semiconductor laser device of the present invention will be described below in more detail with reference to FIG. FIG.
FIG. 2A is a schematic cross-sectional view showing an embodiment of a nitride semiconductor laser device of the present invention, taken from a stripe in a direction parallel to a stripe direction of a ridge-shaped stripe, and FIG. FIG. 2 is a schematic cross-sectional view of FIG. 1 cut in a direction perpendicular to a stripe direction. FIG.
A second waveguide layer 103 including a buffer layer 11, an n-side contact layer 12, and a crack prevention layer 13 is provided thereon, and an n-side cladding layer 14, an n-side light guide layer 15, an active layer 16, and a cap layer are provided thereon. A first waveguide layer 102 comprising a p-side light guide layer 18 and a p-side cladding layer 19 and a p-side contact layer 20 which are laminated to form a first waveguide having a resonance surface formed by etching; As shown in FIG. 1, the end face of the first waveguide layer 102 and the planar n-side cladding layer 14 continuous with the end face are formed with the light-impermeable film 30 so as to suppress light emission from the end face of the wave layer 102. End face (outgoing face) of the second waveguide layer 103 that has a resonance surface formed in a direction parallel to the resonance surface.
1 shows a nitride semiconductor laser device formed by emitting laser light from a laser diode. Further, as shown in FIG. 2, the p-electrode 21 is formed on the ridge-shaped stripe, and the n-
An electrode 23 is formed, an insulating film 25 is formed between the p and n electrodes, and a p pad electrode 22 and an n pad electrode 24 are formed so as to cover the p and n electrodes with the insulating film 25 interposed therebetween. I have. Although light is generated and amplified in the first waveguide layer 102 in FIG. 1, the light amplified as laser light is not emitted because an opaque film is formed on the end face of the first waveguide layer 102. A part of the light amplified by the first waveguide layer 102 passes through the n-side cladding layer 14 and is guided through the second waveguide layer 103. (Emission surface) is emitted as main laser light. Incidentally, when each layer is listed in descending order of the refractive index in FIG. 1, a first waveguide layer having an active layer, a second waveguide layer having an n-side contact layer and a crack preventing layer, an n-side and a p-side cladding are shown. A layer and a substrate (FIG. 1 shows a case of a different kind of substrate different from the nitride semiconductor, for example, sapphire or the like).

In the present invention, the first waveguide layer 102 is composed of at least one nitride semiconductor layer having at least the active layer 16 sandwiched between the p-side cladding layer 19 and the n-side cladding layer 14, The light generated in the active layer 16 can be guided and amplified. The nitride semiconductor layer other than the active layer 16 constituting the first waveguide layer 102 is not particularly limited, and for example, a known layer configuration can be used.
For example, specific examples include the n-side light guide layer 15, the cap layer 17, the p-side light guide layer 18, and the like. Each of the nitride semiconductor layers constituting the first waveguide layer 102 has a value larger than the refractive index of the p- and n-side cladding layers. The method for forming the end face having the resonance surface of the first waveguide layer 102 is formed by etching, and is preferably dry etching, and specifically includes, for example, an etching method such as RIE. When forming the end face having the resonance face of the first waveguide layer 102, the n-electrode formation face may be formed at the same time.
The thickness of the first waveguide layer is determined by the element structure of the laser element.

In the present invention, the second waveguide layer 103 is a substrate 10 of the n-side cladding layer 14 through which light generated in the active layer 16 and leaked from the first waveguide layer 102 can be guided. One or more n-side nitride semiconductor layers formed on the side, and can emit light from the end surface (outgoing surface) of the second waveguide layer 103. Second waveguide layer 10
No particular limitation is imposed on the n-side nitride semiconductor layer that constitutes No. 3; for example, a known layer configuration can be used. For example, a buffer layer of low temperature growth that is in contact with the substrate to reduce lattice constant irregularities 11, an n-side contact layer 12, a crack prevention layer 13, and the like. Second waveguide layer 103
Has a value larger than the refractive index of the n-side cladding layer 14. As with the first waveguide layer 102, various thicknesses of the second waveguide layer 103 can be used depending on the element structure of the laser element. In order to efficiently obtain laser light, it is preferable that the thickness of the second waveguide layer 103 is adjusted so that light guided by the first waveguide layer 102 can be favorably guided. The thickness of the second waveguide layer 103 may be the thickness of a layer structure formed between the substrate and the n-side cladding layer when a laser beam is emitted from a conventional resonance surface. The thickness at which the laser light is easily emitted from the end face of the wave layer is 0.1 to 1.0 μm, preferably 0.1 to 1.0 μm.
0.5 μm, more preferably the same thickness and the same refractive index as the first waveguide layer. It is preferable that the film thickness is in the above range because there is no loss of laser light.

The thickness of the second waveguide layer may be adjusted by setting the thickness of the n-side contact layer within the above range when the second waveguide layer is composed of only the n-side contact layer. If the second waveguide layer includes a buffer layer and a crack prevention layer, the thickness of each layer is adjusted. The composition of the buffer layer, the n-side contact layer, and the anti-crack layer only needs to have a refractive index enough to guide the light leaked from the first waveguide layer. And a layer having a composition formed between the layers.
For example, it is a layer composed of GaN, InGaN, or the like. These layers may contain n-type impurities. The end face of the second waveguide layer is formed by cleavage, etching, dicing, or the like. The end face of the formed second waveguide layer is mirror-like.

The substrate 10 used in the present invention is not particularly limited as long as a nitride semiconductor can be grown on the substrate 10. As a specific example of the substrate 10, for example, C
Sapphire for a plane as a principal, R plane, sapphire having the principal surface A, other, spinel (MgA1 ₂ O ₄₎ other such insulating substrate, SiC (including 6H, 4H, and 3C), A semiconductor substrate of ZnS, ZnO, GaAs, GaN, or the like can be used. Since sapphire and spinel have a low refractive index in the substrate 10, light passing through the n-side cladding layer is reflected by a surface such as sapphire and guided between the n-side cladding layer and the substrate. G having a relatively high refractive index
When an aN or other semiconductor is used as the substrate, the light that has passed through the n-side cladding layer is not reflected by, for example, a GaN substrate, and the laser light can be emitted from the exit surface at the end face of the second waveguide layer. Hateful. In this case, a nitride semiconductor layer having a low refractive index, for example, made of AlGaN is stacked on the GaN substrate with a thickness capable of reflecting light, and an n-side contact layer made of GaN is stacked thereon. The laser light can be satisfactorily emitted from the emission surface formed on the end face of the second waveguide layer. The thickness of the substrate 10 is adjusted depending on the ease of forming the element structure, physical factors, and the like.

The light-impermeable film used in the present invention is not particularly limited as long as it does not emit light from the first waveguide layer. For example, the light-impermeable film formed of a metal thin film and / or a dielectric multilayer film is not used. A light transmitting film may be used. Further, the light-impermeable film has a metal thin film that does not transmit light at least on a surface (outermost surface of the light-impermeable film) opposite to the end surface of the first waveguide layer with which the light-impermeable film is in contact. However, it is preferable because the emission of light can be controlled well. Examples of the metal thin film used in the present invention include metals such as Al, Ag, and Pt that have a high reflectance of light of 500 nm or less. The metal thin film made of these materials has a thickness of 500 to 20,000 angstroms when used alone, and the same thickness when used together with a dielectric multilayer film. Further, as the dielectric multilayer film used in the present invention, for example, SiO ₂ , Ti
Dielectrics such as O ₂ , Al ₂ O ₃ , and ZrO ₂ are mentioned. These dielectric multilayer films are designed so as to reflect laser light, and formed and used as a multi-layered film having a desired film thickness. Here, to design to reflect laser light,
This indicates that the refractive index and the like are adjusted so that the laser light is amplified in the first waveguide layer having the active layer but the laser light is not emitted from the resonance surface. Further, when the opaque film is formed only of the dielectric multilayer film, the p-pad electrode may be formed so as to cover the dielectric multilayer film so that the light transmission from the end face of the first waveguide layer can be achieved. It is preferred to prevent

Since the thickness of the dielectric multilayer film is formed on the end face of the first waveguide layer having the resonance surface, the thickness differs depending on the control of the output power and the threshold value.
And the refractive index (η) of each substance forming the dielectric multilayer film, λ /
4η. For example, in the case of being formed of SiO ₂ / TiO ₂ , assuming that the refractive index of SiO ₂ is η1 and the refractive index of TiO ₂ is η2, the film thickness of the reflecting mirror is λ / 4η1 + λ / 4η.
2. The dielectric multilayer film is made of SiO ₂ / TiO _2.
It is preferable to adjust the film thickness of the dielectric multi-layered film as a pair.

In the present invention, it is more preferable that the light-transmitting film has a reflectivity of 90 to 100% as the light-transmitting film, because the threshold value can be reduced in addition to the control of light emission. . More preferably, the reflectance is 95 to 100.
%, More preferably 99 to 100%. Such adjustment of the reflectance is performed by the above-described design of the dielectric multilayer film. As a method of forming the opaque film, the opaque film is formed on at least one end face of the first waveguide layer by sputtering or vapor deposition. The position where the opaque film is formed is an end face of the first waveguide layer having at least one resonance surface, preferably both end faces of the first waveguide layer having the resonance surface. May be formed on a planar n-side cladding layer continuous with the end face of the second waveguide layer, or on an end face other than the end face of the second waveguide layer of the n-side layer.

In the present invention, the n-side cladding layer, the active layer, and the p-side cladding layer are not particularly limited, and may have any structure, for example, conventionally known ones.

In the present invention, the n-side nitride semiconductor layer forming the n-electrode is not particularly limited as long as it is an n-side layer.
For example, it is formed on any of the n-side contact layer, the crack prevention layer, and the n-side cladding layer shown in FIG. n
The n-side cladding layer is more preferable because it is easily exposed by etching for forming an electrode. FIG. 2 is a cross-sectional view of the device when an n-electrode 24 is formed on the n-side cladding layer 14. In the present invention, when the element structure is a conventionally known element structure, the n-side contact layer constituting the second waveguide layer of the present invention is formed as a thick film. Exposed by etching
Electrodes may be formed. Further, when the second waveguide layer is made thin in order to efficiently guide light in the second waveguide layer, the thickness of the n-side contact layer is reduced, and the thickness of the n-side contact layer is reduced. An n-electrode may be formed on the n-side cladding layer for easy exposure by etching. However, when an n-electrode is formed on the n-side cladding layer, the silicon concentration must be increased at the contact surface of the n-side cladding layer that is in contact with the n-electrode in order to reduce the resistance with the electrode. Is desirable. In the present invention, when an element structure is formed using a GaN substrate, an n-electrode may be formed on a surface of the GaN substrate opposite to the surface having the element structure. In this case, the GaN substrate is doped with an n-side impurity. The GaN substrate can be formed by a known GaN lateral growth method or the like.

In addition, the structure of the nitride semiconductor laser device,
For example, the shapes of the electrodes and elements are not particularly limited, and any known ones may be used.

[0024]

The present invention will be described below in more detail with reference to an embodiment of the present invention. However, the present invention is not limited to this. Embodiment 1 In Embodiment 1 according to the present invention, the nitride semiconductor laser device shown in FIGS. 1 and 2 is manufactured by the following procedure.

(Second Waveguide Layer: Buffer Layer 11 to Crack Prevention Layer 13) First, the substrate 10 made of sapphire (C plane) is set in a reaction vessel, and the inside of the vessel is sufficiently replaced with hydrogen. The substrate temperature is raised to 1050 ° C. while cleaning the substrate, and the substrate is cleaned. Subsequently, the temperature was lowered to 510 ° C., hydrogen was used as a carrier gas, and ammonia (NH ₃ ) and TMG (trimethylgallium) were used as source gases.
And a buffer layer 11 made of GaN on a substrate 10.
Is grown to a thickness of about 200 angstroms. After growing the buffer layer 11, only TMG is stopped and the temperature is set to 105
Raise to 0 ° C. When the temperature reaches 1050 ° C., TMG,
An n-side contact layer 12 of n-type GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si is grown to a thickness of 0.1 μm using silane gas (SiH ₄ ) as an ammonia and impurity gas. More preferably, the n-side contact layer 12 is formed of a super lattice. Next, the temperature was increased to 800 ° C., and TMG, TMI (trimethylindium) and ammonia were used as source gases, silane gas was used as impurity gas, and Si
^A crack preventing layer 13 made of In _0.1 Ga _0.9 N doped with ¹⁸ / cm ³ is grown to a thickness of 500 Å.

Then, the temperature is raised to 1050 ° C. and TMA
(Trimethylaluminum), TMG, ammonia, silane gas and doped with Si at 5 × 10 ¹⁸ / cm ³
A first layer of type Al _0.2 Ga _0.8 N is grown to a thickness of 20 Å, followed by stopping TMA and silane, and a second layer of undoped GaN is grown to a thickness of 20 Å. This operation is repeated 100 times to grow the n-side cladding layer 14 composed of a superlattice layer having a total film thickness of 0.4 μm.

(First waveguide layer: n-side light guide layers 15 to p)
Side light guide layer 18) Subsequently, at 1050 ° C., undoped G
The n-side light guide layer 15 made of aN is formed to a thickness of 0.1 μm.
Let it grow. Next, TMG, TMI, ammonia, sila
The active layer 16 is grown using a gas. The active layer 16
While maintaining the temperature at 800 ° C., first, 8 × 10¹⁸/cm
^ThreeIn doped with_0.2Ga_0.825 well layers of N
It is grown to a thickness of Å. Next, TMI
8 × 10 at the same temperature only by changing the ¹⁸
/cm^ThreeDoped In_0.01Ga_0.99N barrier layer
It is grown to a thickness of 50 angstroms. This operation
Repeated twice, and finally a total thickness of 175 mm
Layer with multiple quantum well structure (MQW)
Grow 16. Next, raise the temperature to 1050 ° C,
TMG, TMA, ammonia for impurity gas and C for impurity gas
p_TwoFor Mg (cyclopentadienyl magnesium)
Has a larger band gap energy than the active layer,
Mg 1 × 10²⁰/cm^ThreeDoped p-type Al_0.3Ga_0.7
N-side p-side cap layer 17 is 300 angstroms
It grows with the film thickness of the system. Subsequently, at 1050 ° C., the band
Gap energy is smaller than p-side cap layer 17
The p-side light guide layer 18 made of undoped GaN is
It is grown to a thickness of 0.1 μm.

Subsequently, TMG, TMA, ammonia, C
A first layer made of p-type Al _0.2 Ga _0.8 N doped with Mg at 1 × 10 ²⁰ / cm ³ at 1050 ° C. was formed using p ₂ Mg.
P-type GaN doped with Mg at 1 × 10 ²⁰ / cm ³ , grown only with Å thickness
A second layer is grown with a thickness of 20 Angstroms. And this operation is repeated 100 times,
P-side cladding layer 1 composed of a superlattice layer having a total thickness of 0.4 μm
9 is formed. Finally, at 1050 ° C., p-type G doped with 2 × 10 ²⁰ / cm ^{3 of} Mg is formed on the p-side cladding layer 19.
A p-side contact layer 20 made of aN is grown to a thickness of 150 Å.

After the reaction is completed, the temperature is lowered to room temperature, and the wafer is placed in a nitrogen atmosphere in a reaction vessel.
Anneal at ℃ to further reduce the resistance of the p-type layer. After annealing, the wafer is taken out of the reaction vessel, and as shown in FIG. 2, the uppermost p-side contact layer 20 and the p-side cladding layer 19 are etched by an RIE apparatus to form a ridge shape having a stripe width of 4 μm. I do.

Next, a mask is formed on the surface of the ridge, and the surface of the n-side cladding layer 14 is exposed as shown in FIG.
A resonance surface is formed on an end face of the waveguide layer 102 in the direction perpendicular to the stripe-shaped ridge.

Next, a p-electrode 21 made of Ni and Au is formed on almost the entire outermost surface of the stripe ridge of the p-side contact layer 20.
To form On the other hand, an n-electrode 23 made of Ti and Al is formed on almost the entire surface of the stripe-shaped n-side cladding layer 14.

Next, as shown in FIG. 1, the first waveguide layer 1
02 on an end surface having a resonance surface of No. 02 and a planar n-side cladding layer continuous with the end surface by sputtering.
Angstrom SiO ₂ (refractive index is 1.45) and 390 angstrom thick TiO ₂ (refractive index is 2.5
8), two pairs of dielectric multilayer films are formed, and a dielectric multilayer film having a thickness of 0.2 μm is formed.
An opaque film 30 having a reflectance of 98% was formed by forming a metal thin film having a thickness of 0.2 μm and a thickness of 1 μm.

Next, as shown in FIG.
S on the surface of the nitride semiconductor layer exposed between the
An insulating film 25 made of iO ₂ is formed, and the p pad electrode 2 electrically connected to the p electrode 21 via the insulating film 25 is formed.
2 and an n-pad electrode 24 are formed. As described above, the wafer on which the n-electrode and the p-electrode are formed is transferred to a polishing apparatus, and the sapphire substrate 1 on which the nitride semiconductor is not formed is wrapped using a diamond abrasive.
The thickness of the substrate is 100 μm. After lapping, the substrate surface is mirror-finished by polishing with a finer abrasive at 1 μm.

After the substrate is polished, the polished surface side is scribed,
Cleavage is performed in a bar shape in a direction perpendicular to the stripe-shaped electrodes, and a laser light emission surface is formed on a cleavage surface of the second conductive layer 103. Finally, the bar is cut in a direction parallel to the p-electrode to form a laser chip. Next, the chip was placed face-up (with the substrate and the heat sink facing each other) on the heat sink, the electrodes were wire-bonded, and laser oscillation was attempted at room temperature.
At 0 nm, a threshold current density of 2.9 kA / cm ² , and a threshold voltage of 4.4 V, laser light oscillation was observed from the emission surface of the second waveguide layer 103, and the far-field pattern was good. .

Example 2 In Example 1, the thickness of each layer of the second waveguide layer was about 100 Å for the buffer layer, 0.1 μm for the n-side contact layer, and 0.1 μm for the crack prevention layer. The film thickness was changed to 0.1 μm, and n
A nitride semiconductor laser device was obtained in the same manner except that the electrode was formed on the surface where the n-side clad was exposed by etching. As a result, almost the same results as in Example 1 were obtained.

Example 3 A nitride semiconductor laser device was obtained in the same manner as in Example 1, except that the reflectance of the light-impermeable film was 90%. As a result, the threshold value is slightly higher than that of the first embodiment, but the far field pattern is good.

Example 4 In Example 1, a GaN substrate was formed on a sapphire substrate by using lateral growth.
An element structure was formed in the same manner as described above except that a layer made of AlGaN was formed on this GaN substrate in a thickness capable of reflecting light instead of the buffer layer 11 of Example 1 on this GaN substrate.
However, the thickness of the n-side contact layer 12 was set to 0.1 μm, and the thickness of the crack prevention layer was set to 0.1 μm. Further, the sapphire substrate and the protective film are removed by polishing and etching, and an n-electrode is formed on a surface of the GaN substrate having no element structure, thereby forming a laser element. As a result, almost the same results as in Example 1 were obtained.

[0038]

According to the nitride semiconductor laser device of the present invention, it is possible to provide a nitride semiconductor laser device having a good far-field pattern shape of laser light and capable of obtaining single-mode laser light.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a nitride semiconductor laser device according to an embodiment of the present invention, cut in a direction parallel to a stripe direction.

FIG. 2 is a schematic sectional view of the nitride semiconductor laser device shown in FIG. 1, which is one embodiment of the present invention, cut in a direction perpendicular to a stripe direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ...... Substrate 11 ... Buffer layer 12 ... N-side contact layer 13 ... Crack prevention layer 14 ... N-side cladding layer (superlattice layer) 15 ... n Side light guide layer 16 Active layer 17 Cap layer 18 Side light guide layer 19 Side clad layer (superlattice layer) 20 Side contact Layer 21 ... P electrode 22 ... P pad electrode 23 ... N electrode 24 ... N pad electrode 25 ... Insulating film 102 ... First waveguide layer 103 ... ..Second layer wave layers

Claims (4)

(57) [Claims] 1. A first waveguide layer having at least an active layer sandwiched between an n-side cladding layer and a p-side cladding layer on a substrate, and at least one layer laminated on the substrate side of the n-side cladding layer. A metal thin film that does not emit light from the first waveguide layer on at least one of the end faces of the first waveguide layer having a resonance surface, and / or
Alternatively, an emission surface which has an opaque film made of a dielectric multilayer film, suppresses emission of light from the resonance surface, and can emit laser light in a direction parallel to the resonance surface, is formed on an end surface of the second waveguide layer A nitride semiconductor laser device comprising: a second waveguide layer having a thickness of 0.1 to 1.0 [mu] m; and an n-electrode formed on the n-side cladding layer. 2. The method according to claim 1, wherein each of the layers has a first refractive index in descending order of refractive index.
2. The nitride semiconductor laser device according to claim 1, wherein: 3. A first waveguide layer having at least an active layer sandwiched between an n-side cladding layer and a p-side cladding layer on a substrate, and at least one layer laminated on the substrate side of the n-side cladding layer. A metal thin film that does not emit light from the first waveguide layer on at least one of the end faces of the first waveguide layer having a resonance surface, and / or
Alternatively, an emission surface which has an opaque film made of a dielectric multilayer film, suppresses emission of light from the resonance surface, and can emit laser light in a direction parallel to the resonance surface, is formed on an end surface of the second waveguide layer The nitride semiconductor laser device, wherein the second waveguide layer has the same thickness and the same refractive index as the first waveguide layer. 4. The light-impermeable film formed on an end face of the first waveguide layer having the resonance surface has a reflectance of 90% to 100%.
The film according to any one of claims 1 to 3, wherein
Item 4. The nitride semiconductor laser device according to item 1.