JP3476636B2 - Nitride semiconductor laser device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a nitride semiconductor (In
_X Al _Y Ga _1-XY N, 0 ≦ X, 0 ≦ Y, X + Y ≦ 1).

[0002]

2. Description of the Related Art Nitride semiconductors have recently been put to practical use as materials for high-brightness blue LEDs and pure green LEDs in full-color LED displays, traffic lights and the like. Further, the present applicant recently announced a laser oscillation of 410 nm at room temperature in pulse current using this material (for example, Reference A: Jpn.J.Appl.Phys. Vol.35 (1996) pp.L2.
17-L220, Reference B: Appl. Phys. Lett. 69 (10), 2 Sep. 1996.
pp.1477-1479 etc.)

The cavity surface of a laser device made of a nitride semiconductor is generally formed by using a technique such as etching or cleavage. In Reference A, the nitride semiconductor is etched to form the opposing resonance planes, and in Reference B, the nitride semiconductor is grown on the sapphire A surface, and R of the sapphire is grown.
The plane of cleavage forms a resonance plane. However, the output of these laser devices is still low and unsatisfactory.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above circumstances, and its main object is to provide a laser device made of a nitride semiconductor with improved output and a method for manufacturing the same. To provide.

[0005]

In a nitride semiconductor laser device of the present invention, a nitride semiconductor including an active layer is laminated on a substrate, and the nitride semiconductor layer end face has nitride surfaces having mutually opposing resonance surfaces. In the semiconductor laser device, one of the resonance surfaces is an etching surface of a nitride semiconductor and the other resonance surface is a cleavage surface of a nitride semiconductor, and the etching surface and the cleavage surface are respectively nitrided with laser light. A reflecting mirror for reflecting is formed in the object semiconductor layer, and the reflectance of the reflecting mirror on the etching surface side is adjusted to be higher than the reflectance of the reflecting mirror on the cleavage surface side.

In the nitride semiconductor laser device of the present invention, the cleavage plane is the M plane of the nitride semiconductor.

[Outside 2] Is desirable. The M-plane is a quadrangular surface corresponding to the side surface when the nitride semiconductor is approximated by a hexagonal columnar hexagonal system. The M plane can be indicated by 6 kinds of plane orientations along the side surface of the hexagonal column, but in the present specification,

[Outside 3] Indicates the plane orientations of all M planes.

In the nitride semiconductor laser device of the present invention, the laser light of the laser device is extracted mainly from the cleavage plane side. Laser light is emitted from both resonance surfaces, but in the present invention, "mainly taken out from the cleavage plane side" means
This means that the laser light emitted from the cleavage plane is used as various light sources for reading, writing, and the like. The laser beam emitted from the other etching surface is detected by a photodetector such as a photodetector to control the laser element. The laser beam emitted from this etching surface side is Does not mean the "mainly removed" side.

Hereinafter, in this specification, the reflecting mirror formed on the etching surface side may be referred to as a first reflecting mirror.

Further, in this specification, the reflecting mirror formed on the cleavage plane side may be referred to as a second reflecting mirror.

Further, it is usually desirable to form a multilayer film made of a dielectric material on the reflecting mirror.

The nitride semiconductor laser device according to the present invention comprises:
It can be manufactured by the following manufacturing method. That is, in the manufacturing method, a step of stacking a nitride semiconductor layer including an active layer on a substrate (hereinafter referred to as a stacking step).
And a step of etching the nitride semiconductor layer to form a resonance surface on each of the opposite etching end surfaces of the nitride semiconductor layer (hereinafter referred to as an etching step). A step of cleaving the nitride semiconductor between the surface and the surface (hereinafter referred to as a cleaving step).

In the manufacturing method, after the etching step and before the cleaving step, a step of forming continuous reflecting mirrors (first reflecting mirrors) made of a dielectric material on their resonance surfaces (hereinafter referred to as the first reflecting mirror). (Refer to mirror forming step).

Further, in the above manufacturing method, after the cleaving step, another reflecting mirror (second reflecting mirror) having a lower reflectance of the emission wavelength of the active layer than the reflecting mirror formed on the etching surface is formed.
A step of forming on the cleavage plane (hereinafter referred to as a second reflecting mirror forming step) is included.

Furthermore, in the above-mentioned manufacturing method, a step of laminating a nitride semiconductor layer including an active layer on a substrate, and etching the nitride semiconductor layer to form an etching end face of the opposing nitride semiconductor layer, respectively. The method may include a step of forming a resonance surface and a step of forming a continuous reflection mirror made of a dielectric material on the surface of the nitride semiconductor layer and the resonance surface after forming the resonance surface.

[0015]

1 is a perspective view showing the shape of a laser device of the present invention, and FIG. 2 is a schematic view of the laser device of FIG. 1 cut in parallel with the resonance direction at a position indicated by a chain line. FIG. The basic structure is a double hetero structure in which an n-type layer, an active layer, and a p-type layer made of a nitride semiconductor are stacked on a substrate, and end faces of these nitride semiconductor layers have resonances facing each other. Has a face. The resonance surfaces have different reflectances at the emission wavelength of the active layer. As a specific resonance surface, one is an etching surface of a nitride semiconductor and the other is a cleavage surface of a nitride semiconductor.

There are methods such as wet etching and dry etching for etching the nitride semiconductor.
Dry etching is preferably used to form a smooth surface that serves as a resonance surface. Dry etching includes, for example, devices such as reactive ion etching (RIE), reactive ion beam etching (RIBE), electron cyclotron etching (ECR), and ion beam etching. All of them can be selected by appropriately selecting an etching gas. The nitride semiconductor can be etched to form the resonance surface. For example, Japanese Patent Application Laid-Open No. 8-17803 previously disclosed by the present applicant discloses a specific etching method for a nitride semiconductor.

On the other hand, in order to form a resonance surface on the end surface of the nitride semiconductor by cleavage, for example, the C plane of sapphire as disclosed in Japanese Patent Application Laid-Open No. 8-153931 previously filed by the present applicant. After growing a C-axis oriented nitride semiconductor, there is a method of dividing the sapphire substrate by the M plane. In addition, as described in the above-mentioned document B, there is a method of growing a nitride semiconductor on the sapphire A surface and cleaving at the R surface of the sapphire. In the laser device of the present invention, the plane orientation of the cleavage plane of the nitride semiconductor is not particularly limited, but when the M plane of the nitride semiconductor is used as a resonance plane, a very good yield and a resonance plane close to a mirror surface can be obtained. To be The term "resonant surface" as used in the present invention refers to a resonant surface formed on the end surface of the active layer, as indicated by the arrow in FIG.

As described above, by making one resonance surface of the nitride semiconductor an etching surface and the other resonance surface an etching surface, the reflectance of the resonance surface of the laser element can be made different. It is possible to improve the output of the laser light emitted from the resonance surface having a low reflectance. In particular, as shown in FIGS. 1 and 2, when a first reflecting mirror that reflects the emission wavelength of the active layer is formed on the resonance surface on the etching surface side, the reflectance on the cleavage surface side is further reduced, so that the laser is more effective than the cleavage surface. Since the light is directly emitted, a laser device with high output can be obtained.

Furthermore, when the resonance surface is formed by etching, as shown in FIG.
The plane of the n-layer in a position substantially perpendicular to the resonance plane is exposed. This plane reflects the laser light on its surface and disturbs the far-field pattern of the laser light. That is, if there is a plane projecting from the resonance surface on the laser emission light side, the shape of the laser light is disturbed on that plane. On the other hand, if it is a cleavage plane, since there is no protruding portion, laser light of a constant shape close to an ellipse can be obtained. Therefore, in the laser device of the present invention, it is desirable that the laser light emitted from the cleavage plane side be mainly taken out and used as various light sources.

More preferably, as shown in FIG. 1, it is most desirable to form the first reflecting mirror on the etching surface side and not form the reflecting mirror on the cleavage surface side. When the laser light is emitted from the resonance surface, the reflection mirror partially blocks the emission. Therefore, since the reflecting mirror is not formed on the cleavage plane side, the light extraction efficiency is improved and the slope efficiency is also improved, so that a high output laser can be obtained. More preferably, the reflecting mirror is made of a high dielectric material such as SiO ₂ , TiO ₂ , ZrO ₂ , or polyimide, which is very convenient in the manufacturing method of the present invention. That is, in the case of a nitride semiconductor laser device, the p-electrode and the n-electrode are often taken out from the semiconductor layer on the same surface side, so that a short circuit between the electrodes is very careful when forming the electrodes. Requires. However, when the reflecting mirror made of a high dielectric material is formed together with the resonance surface as in the present invention, the reflecting mirror acts as an insulating film for preventing the n and p electrodes from being short-circuited, so that the reliability of the laser device is improved. To do. The operation of the reflecting mirror made of this dielectric will be described in more detail in this embodiment.

In the laser device of the present invention, a second reflecting mirror having a reflectance lower than that of the first reflecting mirror formed on the etching surface side may be formed on the cleavage surface side. Forming the second reflecting mirror has the advantage of lowering the threshold value, but the output of the laser element emitted from the cleavage plane side is
It is slightly lower than that of the case where no reflecting mirror is formed.

[0022]

EXAMPLES Next, the present invention will be described in detail with reference to Examples. FIG. 3 is a schematic cross-sectional view showing one structure of the laser device of the present invention, showing the structure when the device is cut in a direction parallel to the resonance plane. FIG. 4 is a block cell diagram showing the crystal structure of a nitride semiconductor. 5 and 6 are partial cross-sectional views showing the structure of a laser device obtained in one step of the embodiment of the present invention, which are views when the device is cut in a direction parallel to the resonance direction of laser light. Shows. Hereinafter, the laser device and the manufacturing method of the present invention will be described based on these drawings.

[Example 1] A method of manufacturing a laser device having the structure shown in FIG. 3 will be described below. (Lamination process) 1) On a substrate 1 made of 2-inch φ sapphire (C surface) 2) Buffer layer made of GaN 2 3) Contact layer made of Si-doped n-type GaN 3 4) Si-doped n-type In0. 1 Ga0.9N crack prevention layer 5) Si-doped n-type Al0.2 Ga0.8 N n-type cladding layer 5 6) Si-doped GaN n-type optical guide layer 6 7) Si-doped In0.2 Ga0.8 N 25 well layers
An active layer in which a barrier layer made of angstrom and Si-doped In0.01Ga0.95N is laminated in 3 pairs of 50 angstrom and finally a well layer is laminated 7 8) Mg-doped p-type Al0.1Ga0.9N p-type cap layer 8 9) p-type optical guide layer 9 made of Mg-doped p-type GaN 9 10) p-type cladding layer 10 made of Mg-doped p-type Al0.2Ga0.8N 11) p-type contact layer 11 made of Mg-doped p-type GaN in order Stack.

1) In addition to the sapphire C surface, R
It is possible to use sapphire whose main surface is the surface or A surface, or an insulating substrate such as spinel (MgA1 ₂ O ₄ ). Other SiC (including 6H, 4H, 3C), Z
It is also possible to use a semiconductor substrate made of nS, ZnO, GaAs, GaN or the like to form an element having the structure of the present invention.

2) The buffer layer 2 is made of AlN, GaN, A
lGaN or the like can be formed at a temperature of 900 ° C. or less and a film thickness of several tens of angstroms to several hundreds of angstroms. This buffer layer is formed in order to mitigate the lattice constant irregularity between the substrate and the nitride semiconductor.
It may be omitted depending on the type of substrate.

3) The n-type contact layer 3 is made of In _X Al _Y G
a _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1), in particular GaN, InGaN, and among them, GaN doped with Si or Ge has a high carrier concentration n. A mold layer is obtained and a favorable ohmic contact with the n-electrode is obtained.

4) The crack prevention layer 4 is grown from an n-type nitride semiconductor containing In, preferably InGaN, so that an n-type cladding layer containing Al to be grown next can be grown as a thick film. , Very preferred.
In the case of LD, it is necessary to grow the layer serving as the light confinement layer, preferably with a film thickness of 0.1 μm or more. Conventionally, a thick film of AlGaN is directly formed on the GaN and AlGaN layers.
, It was difficult to fabricate the device because the AlGaN grown later had cracks. However, this crack prevention layer prevents the n-type cladding layer containing Al to be grown next from cracking. be able to. The crack prevention layer is preferably grown to a film thickness of 100 angstroms or more and 0.5 μm or less. When the thickness is less than 100 Å, it is difficult to act as a crack preventive as described above, and when the thickness is more than 0.5 μm, the crystal itself tends to turn black. The crack prevention layer is a growth method,
It may be omitted depending on the conditions of the growth apparatus, but L
When producing D, it is preferable to grow it. This crack prevention layer may be grown in the n-type contact layer.

5) The n-type cladding layer 5 acts as a carrier confinement layer and an optical confinement layer, and it is desirable to grow a nitride semiconductor containing Al, preferably AlGaN, and 100 angstroms or more and 2 μm or less, and more preferably. A carrier confinement layer with good crystallinity can be formed by growing it at 500 angstroms or more and 1 μm or less.

6) It is desirable that the n-type light guide layer 6 acts as a light guide layer of the active layer to grow GaN and InGaN, and usually 100 angstrom to 5 μm.
m, more preferably 200 Å to 1 μm
It is desirable to grow with a film thickness of.

7) The active layer 7 includes a well layer made of a nitride semiconductor containing In having a film thickness of 70 Å or less, and a barrier layer made of a nitride semiconductor having a bandgap energy larger than that of the well layer having a film thickness of 150 Å or less. When a multi-quantum well structure in which layers are stacked is used, laser oscillation easily occurs.

8) The cap layer 8 is p-type, but since it is thin, it may be i-type in which carriers are compensated by doping n-type impurities, and most preferably p-type. p
The thickness of the mold cap layer is 0.1 μm or less, more preferably 500 angstroms or less, and most preferably 300 Å.
Adjust to less than Angstrom. This is because if the film is grown to a thickness greater than 0.1 μm, cracks are likely to occur in the p-type cap layer, and a nitride semiconductor layer with good crystallinity is difficult to grow. Also, carriers cannot pass through this energy barrier due to the tunnel effect. If the AlGaN having a higher Al composition ratio is formed thinner, the LD element is likely to oscillate. For example, Al _Y Ga _{1-Y with} Y value of 0.2 or more
If it is N, it is desirable to adjust it to 500 angstroms or less. The lower limit of the film thickness of the p-type cap layer 8 is not particularly limited, but it is desirable to form the p-type cap layer 8 with a film thickness of 10 angstroms or more.

9) It is desirable that the p-type light guide layer 9 is made of GaN or InGaN, like the n-type light guide layer. Further, this layer also acts as a buffer layer when growing the p-type cladding layer, and has a thickness of 100 angstroms or more.
5 μm, more preferably 200 Å to 1
When grown to have a film thickness of μm, it acts as a preferable light guide layer.

10) The p-type clad layer 10 functions as a carrier confinement layer and an optical confinement layer like the n-type clad layer, and is a nitride semiconductor containing Al, preferably A.
It is desirable to grow lGaN, and a carrier confinement layer with good crystallinity can be formed by growing it to 100 angstroms or more and 2 μm or less, more preferably 500 angstroms or more and 1 μm or less. Further, it is preferable to use a nitride semiconductor layer containing Al as described above, because a difference in contact resistance between the p-type contact layer and the p-electrode can be obtained.

In the case of an active layer having a quantum structure having a well layer made of InGaN as in this embodiment, a p-type cap layer containing Al having a film thickness of 0.1 μm or less is provided in contact with the active layer, and its p A p-type optical guide layer having a smaller bad gap energy than the p-type cap layer is provided at a position farther from the active layer than the p-type cap layer, and a p-type light guide layer is provided at a position farther from the active layer than the p-type optical guide layer. P made of a nitride semiconductor containing Al having a band gap larger than that of the optical guide layer
Providing a mold cladding layer is highly preferred. Moreover, p
Since the thickness of the mold cap layer is set as thin as 0.1 μm or less, it does not act as a carrier barrier.
The holes injected from the p-layer can pass through the p-type cap layer due to the tunnel effect, are efficiently recombined in the active layer, and the output of the LD is improved. That is, the injected carriers have a large bandgap energy in the p-type cap layer, so that even if the temperature of the semiconductor element rises or the injection current density increases, the carriers do not overflow the active layer and the p-type Since it is blocked by the cap layer, carriers are stored in the active layer, and it becomes possible to efficiently emit light. Therefore, even if the temperature of the semiconductor element rises, the light emission efficiency is less likely to decrease, so that the LD having a low threshold current can be realized.

11) The p-type contact layer 11 is a p-type I
n _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1), preferably Mg-doped GaN
Then, the most preferable ohmic contact with the p electrode 20 can be obtained. (End of lamination process)

After the nitride semiconductor layer including the active layer 7 is laminated on the substrate 1 having the above-described structure, the wafer is annealed in a reaction vessel in a nitrogen atmosphere to remove hydrogen contained in the p-type layer. The portion is removed to further reduce the resistance of the p-type layer.

Next, a mask having a predetermined shape is formed on the surface of the uppermost p-type contact layer, and an RIE (reactive ion etching) apparatus is used to form the uppermost p-type contact layer 11 as shown in FIG. And the p-type clad layer 10 are mesa-etched to form a ridge having a stripe width of 4 μm.

After forming the ridge, a mask is formed on the exposed plane of the p-type layer, and as shown in FIG. 3, the plane of the n-type contact layer 22 is exposed by making it symmetrical with respect to the striped ridge. . By thus providing the n-type contact layer 3 for forming the n-electrode 22 symmetrically with respect to the ridge stripe, the current from the n-layer is evenly applied to the active layer, and the threshold value is lowered. .

(Etching Step) Next, a mask having a predetermined shape is formed on the surface of the n-type contact layer 3 and the exposed surface of the p-type layer, and the RIE is used to planarize the n-type contact 3. Etching is performed so as to have almost the same height as the above, and a resonance surface having a resonator length of 700 μm is formed.

Next, the p-type contact layer 1 at the top of the ridge
1, an ohmic p-electrode 20 made of Ni and Au is formed on almost the entire surface. On the other hand, an ohmic n-electrode 22 made of Ti and Al is formed on almost the entire surface of the striped n-type contact layer. It should be noted that the almost entire surface means an area of 80% or more. In this way, the n-electrode is also formed on the entire surface and further symmetrically formed with respect to the ridge, whereby the threshold value is lowered. FIG. 5 is a partial cross-sectional view of the wafer after the formation of the p-electrode 20, and shows a schematic diagram when the wafer is cut from directly above the ridge in a direction parallel to the laser resonance direction.

(First Reflecting Mirror Forming Step) After the electrodes are formed, the wafer is transferred to a CVD apparatus and the p-electrode 20 and the n-electrode 2 are formed.
2, the first reflecting mirror 30 made of a dielectric multilayer film of SiO ₂ and TiO ₂ is formed over all layers exposed from the substrate to the upper surface such as the p-type cladding layer 10. The thickness of each layer of the first reflecting mirror 30 is λ / 4n (λ: emission wavelength of the active layer,
(n: refractive index of material). First reflector 3
A cross-sectional view after forming 0 is shown in FIG. The first reflecting mirror functions as a reflecting mirror that reflects the light emitted from the active layer on the resonance surface side, and further, the n-type contact layer 3 and the p-type cladding layer 10 are provided.
On the surface of, it acts as an insulating film that prevents short circuits between electrodes. As described above, by forming the first reflecting mirror 30 continuously between the resonance surfaces, the element can be manufactured very effectively. Examples of the material of the reflecting mirror include SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , ZnO and M.
A high dielectric material such as gO or polyimide can be used.

After forming the first reflecting mirror 30, the p-electrode 20 and
The first reflecting mirror 30 formed on the surface of the n-electrode 22 is removed. The exposed and removed p-electrode 20 and n-electrode 2
In order to spread the electrode area on the surface of 2 and evenly spread the current, the p pad electrode 21 and the n pad electrode 2 are respectively formed.
2 and 2 are formed to have a structure as shown in FIG. As shown in FIG. 3, the p-pad electrode is formed over the surface of the p-type cladding layer 10 via the first reflecting mirror as an insulating film.

(Cleaving Step) Next, the wafer is transferred to a polishing apparatus and a diamond polishing agent is used to lap the sapphire substrate on the side where the nitride semiconductor is not formed to a substrate thickness of 50 μm. After lapping, the substrate surface is mirror-finished by polishing with 1 μm with a finer polishing agent. The thickness of the substrate is 70 μm or less, more preferably 60
When the thickness is less than or equal to μm, most preferably less than or equal to 50 μm, the heat dissipation of the element is enhanced and the element has a long life.

After polishing the substrate, scribe the polishing surface side,
At the position indicated by the alternate long and short dash line in FIG. 6, a bar is cleaved in a direction parallel to the resonance surface, and a resonator is produced on the cleavage surface. As a result, the resonator length 55 composed of the cleavage plane and the etching plane is formed.
A resonance surface of 0 μm is produced. The cleavage plane is the M plane of the nitride semiconductor surface grown on the sapphire substrate. Although the M plane has been described above, specifically, as shown in FIG. 4, when a nitride semiconductor is approximated by a hexagonal system of a regular hexagonal prism, a quadrangular plane corresponding to the side face of the hexagonal prism is used. Is a surface corresponding to. In addition, in order to cleave at the M plane, it is necessary to make beforehand the resonance plane to be made the M plane in the etching step. Further, by cutting the wafer at a position parallel to the n-electrode, a laser device having a shape as shown in FIG. 2 is obtained.

By manufacturing a laser device as described above, a device having a structure as shown in FIG. 1 can be manufactured. One of the resonance surfaces of this laser element is formed by cleavage, and no reflection mirror is formed on the cleavage surface. The other resonance surface is formed by etching, and a reflecting mirror is formed on the etching surface. When this laser element was placed face up (the substrate and the heat sink faced each other) on the heat sink and each electrode was wire-bonded and laser oscillation was attempted at room temperature, a threshold current density of 1.5 kA / c
At m ² and a threshold voltage of 6 V, continuous oscillation with an oscillation wavelength of 405 nm was confirmed. The output of the laser light emitted from the cleaved surface side is about twice as high as that obtained by etching both resonance surfaces and forming a reflecting mirror having the same reflectance on the resonance surfaces. Improved. Also, the far-field pattern of the laser light circulated from the cleavage plane side was elliptical and had a very beautiful shape without disturbance.

[Embodiment 2] In Embodiment 1, after the cleavage step, a mask is formed on the surface of the first reflecting mirror other than the cleavage surface, and a dielectric multilayer film of SiO ₂ and TiO ₂ is also formed on the cleavage surface. The second reflecting mirror 31 is formed. The second reflecting mirror 31 is adjusted to 1/10 of the reflectance of the first reflecting mirror by adjusting its film thickness.

After the formation of the second reflecting mirror, the mask was removed, the surfaces of the p-electrode 20 and the n-electrode 22 were exposed in the same manner, and the laser element was similarly produced thereafter. FIG. 7 is a schematic sectional view showing the structure of this laser device. Similarly, this laser element also exhibited continuous oscillation at room temperature, and the output was reduced by about 20% as compared with that of Example 1.

[Embodiment 3] In the etching process of Embodiment 1, etching is performed in the same manner except that the resonator length is 550 μm.

Then, similarly, a p-electrode 20 is formed on the p-type contact layer 11 and an n-electrode 22 is formed on the n-type contact layer 3.

After forming the electrodes, a mask is formed on one of the etching surfaces to be the resonance surface, and then the wafer is transferred to a CVD apparatus to cover all the layers exposed from the substrate to the upper surface in the same manner as in Example 1. Thus, a first reflecting mirror made of a dielectric multilayer film of SiO ₂ and TiO ₂ is formed. As described above, by providing the step of forming the reflecting mirror made of a continuous dielectric material on the surface of the nitride semiconductor layer and the resonant surface after forming the resonant surface, the first reflecting mirror is made of the nitride as described above. It acts as an insulating film formed on the semiconductor surface, prevents short circuits between electrodes, and forms the p pad electrode 21 on the p electrode 20 to expand the substantial electrode area. When the electrode area is increased, the threshold value can be lowered.

After removing the mask, the wafer is cleaved between the resonance planes. In this way, both resonance planes are created by etching, a reflection mirror is formed on one resonance plane, a reflection mirror is not formed on the other resonance plane, and both reflection planes are reflected. Laser elements having different rates can be manufactured. Laser light is extracted from the resonance surface on the side where the reflecting mirror is not formed in this laser element, and continuous oscillation with an oscillation wavelength of 405 nm was confirmed at room temperature with a threshold current density of 1.5 kA / cm ² and a threshold voltage of 6 V. Was done. The output of the laser light emitted from the resonance surface side where no reflecting mirror is formed is compared with the case where both resonance surfaces are formed by etching and a reflecting mirror having the same reflectance is formed on the resonance surface. And it improved 1.3 times.
However, the far-field pattern of the laser light was disturbed because it was not a cleavage plane. However, the flat portion protruding from the resonance surface can be removed by polishing or by cleaving the substrate at a position close to the resonance surface.

[0052]

As described above, the laser device of the present invention can realize a high-power laser device by making the reflectances of the resonance surfaces different from each other. Moreover, if one side is a cleavage plane and the other side is an etching plane, the laser beam emitted from the cleavage side is a laser beam of a very beautiful shape which is almost an ellipse.

Further, according to the manufacturing method of the present invention, since the insulating film can be formed in the step of manufacturing the reflecting mirror, it is possible to prevent a short circuit between the electrodes of the laser elements on the same surface side, which is very reliable. The device can be realized.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing the shape of the laser element shown in FIG.

FIG. 3 is a sectional view showing the structure of the laser device shown in FIG. 2 in detail.

FIG. 4 is a unit cell diagram schematically showing a crystal structure of a nitride semiconductor.

FIG. 5 is a partial cross-sectional view showing a schematic structure of a wafer obtained in one step of the manufacturing method of the present invention.

FIG. 6 is a partial cross-sectional view showing a schematic structure of a wafer obtained in one step of the manufacturing method of the present invention.

FIG. 7 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention.

[Explanation of symbols]

1 ... Sapphire substrate 2 ... Buffer layer 3 ... n-type contact layer 4 ... Crack prevention layer 5 ... n-type clad layer 6 ... n type light guide layer 7 ... Active layer 8: p-type cap layer 9 ... p-type optical guide layer 10 ... p-type clad layer 11 ... p-type contact layer 20 ... p electrode 21 ... p pad electrode 22 ... n electrode 23 ... n pad electrode 30: first reflecting mirror 31 ... second reflecting mirror

Front Page Continuation (72) Inventor Shuji Nakamura 491, Kaminaka-cho, Anan City, Anan City, Tokushima Prefecture Nichia Chemical Industry Co., Ltd. (56) References JP-A-5-315703 (JP, A) JP-A-8-250802 (JP, A) JP-A-3-285380 (JP, A) JP-A-8-153931 (JP, A) JP-A-61-265888 (JP, A) JP-A-8-264886 (JP, A) Kaihei 8-213692 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/10

Claims (2)

(57) [Claims] 1. A nitride semiconductor laser device comprising a substrate, on which a nitride semiconductor including an active layer is laminated, and end faces of the nitride semiconductor layer having resonance surfaces facing each other, wherein one of the resonance surfaces is a nitride semiconductor. Is the etching surface, the other resonance surface is the cleavage surface of the nitride semiconductor, the etching surface, and the cleavage surface is respectively formed with a reflection mirror for reflecting the laser light in the nitride semiconductor layer. A nitride semiconductor laser device characterized in that the reflectance of the reflecting mirror on the etching surface side is adjusted to be higher than the reflectance of the reflecting mirror on the cleavage surface side. 2. The cleavage plane is an M plane of a nitride semiconductor. The nitride semiconductor laser device according to claim 1, wherein: