JP2001345519A - Laser element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser element where generation of pulsation of optical output emitted from the laser element can be prevented, even at high output operation. SOLUTION: This laser element is a nitride semiconductor laser element, having an N-type clad layer, an active layer and a P-type clad layer. In the laser element, an optical guide layer composed of InfGa1-fN (0<=f<1) is formed at least between the active layer and the N-type or the P-type clad layer. Film thickness of the optical guide layer is at most 0.05 μm. A nondoped layer which is not doped with impurities is formed at least on the N-type clad layer side or the P-type clad layer side of the active layer. The nondoped layer, which is formed on the side where the optical guide layer is formed is formed between the optical guide layer and the clad layer on the side, where the optical guide layer is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride semiconductor (e.g. _{In x Al y Ga 1- x -} y N, 0 ≦ x, 0 ≦ y, x + y ≦
More specifically, the present invention relates to a laser device capable of preventing pulsation of light output.

[0002]

2. Description of the Related Art In recent years, with the development of the information-oriented society, a storage device for storing a large amount of information is required, and a laser light source of a short wavelength is used as a light source for a large-capacity recording medium such as a DVD or a light source for communication. The development is eagerly awaited. In order to realize such a short-wavelength laser, much research and development has been conducted on nitride semiconductor laser devices, and various nitride semiconductor laser devices are known.

[0003] For example, the present inventors have proposed a practical laser device as described in Jpn. J. Appl. Phys. Vol. 37 (1998) pp. L309.
-L312, Part2, No.3B, 15 March 1998, ELOG (Epitaxially late) on top of sapphire substrate
(rally overgrown GaN) 20 μm
Then, GaN is grown to a thickness of 100 μm, and then the sapphire substrate is removed.
A GaN substrate having reduced μm dislocations was obtained,
A nitride semiconductor laser device in which a plurality of nitride semiconductor layers forming a laser device structure are stacked on a substrate has been announced. And, as this laser device, a nitride semiconductor laser device capable of continuous oscillation at room temperature for 10,000 hours or more was announced.

FIG. 10 is a schematic sectional view similar to the laser device shown in the above-mentioned JJAP. As shown in FIG. 10, a ridge shape is formed by partially etching from a p-type contact layer made of p-GaN to a p-type clad layer having a superlattice structure of p-Al _0.14 Ga _0.86 N / GaN. The ridge-shaped stripe thus formed has a side surface of Si for insulation of the device.
A nitride semiconductor laser device in which an insulating film made of O ₂ is formed, a p-electrode is formed on the stripe, and a resonance surface is formed by cleavage. Further, in this laser element, a p pad electrode is formed so as to cover the p electrode.

[0005]

However, in the obtained laser device, when the injection current Iop is increased to increase the optical output to about 30 mW, the injection current Iop is constant during the direct current (CW) operation even though the injection current Iop is constant. Light output frequency 500M
Pulsations that fluctuate between Hz and 5 GHz occur, causing a problem that the optical output becomes unstable. Fluctuations in optical output due to such pulsations cause problems such as reading and writing errors of the recording medium and data communication errors during optical communication. In particular, an optical output of 30 mW corresponds to an optical output value required for rewriting data of a DVD or the like, and a fluctuation of the optical output at the time of high output becomes a serious problem in rewriting data of a DVD or the like. Further, in order to always obtain a stable optical output at an optical output of about 30 mW, the optical output should be 50 to 6
It is important that pulsation does not occur up to around 0 mW.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a laser device which can prevent pulsation of light output from the laser device even during high-power operation.

[0007]

To achieve the above object, according to an aspect of the laser device of the present invention, the nitride semiconductor laser device having an n-type cladding layer and the active layer and the p-type cladding layer, an In _f Ga _{1- An} optical guide layer made of fN (0 ≦ f <1) is formed at least between the active layer and the n-type or p-type clad layer, and the optical guide layer has a thickness of 0.05 μm or less. It has a certain configuration.

Further, in the laser device of the present invention, the non-doped layer which is not doped with the impurity has at least n of the active layer.
The non-doped layer formed on the mold clad layer side or the p-type clad layer side and formed on the side where the light guide layer is formed is the light guide layer and the clad layer on the side where the light guide layer is formed. Is formed between

In the laser device according to the present invention, the thickness of the non-doped layer is 0.5 μm or less.

[0010] The laser device of the present invention, the non-doped layer is _{In c Ga 1-c N (} 0 ≦ c ≦ 1) first undoped layer consisting of the _{Al d Ga 1-d N (} 0 <d ≦ 1 ) Has a superlattice structure composed of a second non-doped layer.

Further, in the laser device according to the present invention, the active layer includes a well layer made of In _x Ga ₁ -xN (0 <x ≦ 1) and an active layer made of In _x Ga ₁ -xN.
_It has a multiple quantum well structure with a barrier layer made of _y Ga _1-y N (0 ≦ y <1, y <x), and is in contact with the active layer on the side of the p-type cladding layer, and Al _z Ga _1-z N An upper barrier layer made of (0 <z ≦ 1) is further formed.

Further, the laser device of the present invention is configured such that the total film thickness of the active layer, the upper barrier layer, the light guide layer and the non-doped layer is 1 μm or less.

Further, in the laser device of the present invention, the n-type and p-type cladding layers are composed of _{a first} cladding layer made of In _a Ga _1-a N (0 ≦ a ≦ 1) and an Al _b Ga _1-b N ( 0 <b ≦ 1)
And a second clad layer made of a superlattice structure having at least one of the first and second clad layers doped with n-type and p-type impurities, respectively.

Further, in the laser device of the present invention, a p-type nitride semiconductor layer is further formed on the p-type cladding layer, and at least the p-type nitride semiconductor layer is formed from the p-type nitride semiconductor layer side.
A part of the mold cladding layer is etched to form a striped waveguide.

In the laser device according to the present invention, the width of the stripe is 1 μm or more and 3 μm or less.

Further, the laser device of the present invention comprises an n-type nitride semiconductor layer, a lower non-doped layer made of a nitride semiconductor, an active layer made of a nitride semiconductor, an upper non-doped layer made of a nitride semiconductor layer, and a p-type nitride. In a laser device having a semiconductor layer, a film thickness from a boundary between the n-type nitride semiconductor and the lower non-doped layer to a boundary between the upper non-doped layer and the p-type nitride semiconductor layer is 0.2 μm or more and 1 μm or more.
The following configuration can be adopted.

In the laser device of the present invention, the n-type and p-type nitride semiconductor layers have an n-type and a p-type cladding layer, respectively, and the n-type and the p-type cladding layers are In _a
A first cladding layer made of Ga _{1 -aN} (0 ≦ a ≦ 1) and A
l _b Ga _1-b made of N (0 <b ≦ 1) and a second cladding layer is constituted by a superlattice structure, n-type and p-type impurity, respectively at least one of said first and second cladding layer The structure is doped.

Further, in the laser device according to the present invention, the p-type nitride semiconductor layer has a p-type cladding layer in contact with an upper non-doped layer, and at least one of the p-type cladding layers is arranged from the p-type nitride semiconductor layer side. The portion is etched to form a striped waveguide.

Further, the laser element of the present invention has a configuration in which the width of the stripe is 1 μm or more and 3 μm or less.

Further, in the laser device of the present invention, an n-type cladding layer, an active layer, an upper barrier layer, and a p-type cladding layer are sequentially laminated, and at least one of the p-type cladding layers is disposed above the p-type cladding layer. A n-type cladding layer formed of In _a Ga ₁ -aN (0 ≦ a ≦ 1) and a first cladding layer made of Al. _b Ga _1-b N (0 <b ≦ 1)
Having a superlattice structure composed of a second cladding layer made of at least one of the first and second cladding layers doped with an n-type impurity.
The upper barrier layer is formed in contact with the mold cladding layer.
1 _z Ga _{1 -zN} (0 <z ≦ 1), formed in contact with the active layer, and the p-type cladding layer is made of In _a Ga ₁ -aN.
A first cladding layer composed of (0 ≦ a ≦ 1) and Al _b Ga _1-b
A superlattice structure composed of a second cladding layer made of N (0 <b ≦ 1), wherein at least one of the first and second cladding layers is doped with a p-type impurity; May be formed in contact with the substrate.

Further, the laser element of the present invention has a configuration in which the width of the stripe is 1 μm or more and 3 μm or less.

[0022]

FIG. 1 shows an embodiment of the present invention.
First, the C surface (000) of the sapphire substrate 1 which is a heterogeneous substrate
1) A buffer layer (not shown) made of GaN grown at a low temperature is grown to a thickness of 200 to 300 °.
On this buffer layer, a GaN layer grown at a temperature higher than the growth temperature of the buffer layer is formed to form an underlayer 2. On top of this, a stripe width of 10 μm and a stripe interval (window) of 2 μm
An m ₂ SiO ₂ film 3 is formed. Further, after forming the SiO ₂ film 3, the nitride semiconductor substrate 4 made of non-doped GaN is
It is grown to a thickness of 0 μm.

Next, on the nitride semiconductor substrate 4, Al doped with _{Si xc Ga 1-xc N (} 0 ≦ xc ≦ 1) n -type contact layer 5 made of GaN is formed to a thickness of 4 [mu] m.
Next, a crack preventing layer 6 made of In _xp Ga _1-xp N (0 ≦ xp ≦ 1) is formed with a thickness of 0.15 μm. The crack prevention layer can be omitted.

Next, Al _b Ga _{1 -b as} the first cladding layer
A layer made of N (0 <b <1) is formed to a thickness of 25 Å, and an n-type In _a Ga _1-a N (0 ≦ a ≦ 1) doped with Si as a second cladding layer is formed thereon. Is formed with a thickness of 25 Å. The total film thickness having a superlattice structure in which those layers are alternately laminated is 0.5 to
A 1.2 μm n-type cladding layer 7 is formed. Also Si
And the like may be doped into the second cladding layer.
It is also possible to dope both the first and second cladding layers.

Next, a lower non-doped layer 8 is formed in contact with the n-type cladding layer 7. The first non-doped layer made of non-doped Al _d Ga _1-d N (0 <d <1) is 25
A non-doped In _c Ga _{1 -c} N (0 ≦ c ≦
A layer consisting of 1) is formed with a thickness of 25 Å. The lower non-doped layer 8 having a superlattice structure in which these layers are alternately laminated is formed with a total film thickness of 0.5 μm or less, more preferably 0.3 μm or less.

It is preferable that the total thickness of the n-type cladding layer 7 and the lower non-doped layer 8 be 0.7 to 1.2 μm in order to reduce the threshold current. When the absorption of laser light in the n-type cladding layer 7 is sufficiently small, the lower non-doped layer 8 may be omitted. Further, the composition ratio c of the first non-doped layer in the lower non-doped layer 8 to n
It is preferable that the composition ratio a of the first cladding layer in the type cladding layer 7 is substantially the same, and similarly, the composition ratio d of the second non-doping layer in the lower non-doping layer 8 and the composition ratio d of the second cladding layer in the n-type cladding layer 7. It is preferable that the composition ratio b be approximately the same.

Next, non-doped _{In f Ga 1-f N (} 0 ≦ f
The lower light guide layer 9 of <1) is formed with a thickness of 0.05 μm or less. The lower light guide layer 9 may be doped with an n-type impurity as long as the absorption of the laser light is sufficiently small. The lower light guide layer 9 can be omitted when the lower non-doped layer 8 and the n-type cladding layer 7 sufficiently confine laser light in the vertical and transverse modes. The lower light guide layer 9 is preferably larger than the band gap of the well layer in the active layer 10, and is particularly preferably made of GaN.

Further, as described above, the thickness of the light guide layer is set to 0.1.
When the thickness is equal to or less than 05 μm, the effective refractive index in the vertical and horizontal directions in the waveguide is reduced, and the distribution range of light in the vertical and horizontal directions can be increased. By this, NF
The size of the P (near field pattern) in the vertical and horizontal directions increases, and as a result, the size of the FFP (far field pattern) in the vertical and horizontal directions can be reduced, and the aspect ratio can be improved.

Next, In _y Ga _1-y N (0 ≦ y <1, y <
A barrier layer made of x) is formed with a thickness of 100 Å, and a well layer made of In _x Ga ₁ -xN (0 <x ≦ 1) is formed with a thickness of 40 Å. An active layer 10 having a multiple quantum well structure (MQW) having a total film thickness of 380 Å is formed by alternately laminating the barrier layer and the well layer twice and finally ending with the barrier layer.

[0030] Next is a larger band gap energy than the upper optical guide layer 12, an upper barrier layer composed of that 1 × 10 ²⁰ / cm ³ doped with Mg p-type _{Al z Ga 1-z N (} 0 <z ≦ 1) 11 is formed with a thickness of 100 angstroms.

Next, non-doped _{In f Ga 1-f N (} 0 ≦ f
The upper light guide layer 12 of <1) is formed with a thickness of 0.05 μm or less. The upper light guide layer 12 may be doped with a p-type impurity as long as the absorption of the laser light is sufficiently small. The upper light guide layer 12 can be omitted when the upper non-doped layer 13 and the p-type clad layer 14 sufficiently confine laser light in the vertical and transverse modes. Further, the upper light guide layer 12 is preferably larger than the band gap of the well layer.
It preferably comprises

Next, an upper non-doped layer 13 is formed in contact with the light guide layer 12. The first non-doped layer made of non-doped Al _d Ga _1-d N (0 <d <1) is 25
A non-doped In _c Ga _{1 -c} N (0 ≦ c ≦
A layer consisting of 1) is formed with a thickness of 25 Å. The upper non-doped layer 13 having a superlattice structure in which these layers are alternately stacked is formed with a total thickness of 0.5 μm or less, more preferably 0.3 μm or less.

When the absorption of laser light in the p-type cladding layer 14 is sufficiently small, the upper non-doped layer 13
May be omitted. Further, it is preferable that the total thickness of the p-type cladding layer 14 and the upper non-doped layer 13 is 0.3 to 1 μm in order to reduce the threshold current.

The total thickness of the active layer, the upper barrier layer, the light guide layer and the non-doped layer is preferably 1 μm or less. This makes it possible to reduce light absorption in the waveguide without increasing the threshold current Ith required for laser oscillation. In particular, the film thickness from the boundary between the n-type clad layer as the n-type nitride semiconductor layer and the first non-doped layer to the boundary between the second non-doped layer and the p-type clad layer as the p-type nitride semiconductor layer is 0. 5 μm or more and 1 μm
It is more preferred that:

Next, Al _b Ga _{1 -b as} the first cladding layer
A layer made of N (0 <b <1) is formed with a thickness of 25 Å, and a second clad layer of Mg-doped p-type In _a Ga _1-a N (0 ≦ a ≦ 1) is formed thereon. Is formed with a thickness of 25 Å. A total film thickness of 0.1 to 10 having a superlattice structure in which those layers are alternately laminated
A 0.5 μm p-type cladding layer 14 is formed. Also M
A p-type such as g may be doped into the second cladding layer, or it may be doped into both the first and second cladding layers. The composition ratios a and b in the n-type and p-type cladding layers may be substantially the same.

Since the clad layer and the non-doped layer have a superlattice structure in this manner, the Al composition ratio of the entire clad layer and the non-doped layer can be increased, so that the refractive indices of the clad layer and the non-doped layer themselves are reduced. This is effective for confining light in the waveguide.
In particular, when the light guide layer is omitted, it is important that the clad layer and the non-doped layer have a super lattice structure. Further, since the band gap energy becomes large, it is very effective in lowering the threshold value. Furthermore, since the superlattice structure reduces the number of pits generated in the cladding layer itself as compared with the non-superlattice structure,
The occurrence of short-circuit can be suppressed low.

When the light guide layer and the non-doped layer are omitted, it is preferable that an n-type clad layer, an active layer, an upper barrier layer, and a p-type clad layer are sequentially formed. The light guide layer may be omitted from only one of the upper and lower guide layers. Similarly, the non-doped layer may be omitted from only one of the upper and lower non-doped layers.

Finally, on the p-type cladding layer 14,
Contact layer 15 made of p-type GaN doped with P
Is formed with a thickness of 150 Å.

Then, etching is performed using RIE (reactive ion etching) to expose the surface of the n-type contact layer 5 where the n-electrode is to be formed.

Next, the p-type contact layer 15 and the p-type cladding layer 14 are etched to form a waveguide region (in this case, a ridge stripe) in which stripe-shaped protrusions are formed. By being formed in the ridge structure, it is possible to sufficiently confine horizontal and horizontal modes,
Further, it is preferable that the stripe width be 1 μm or more and 3 μm. When a stripe is formed, it is highly preferable that the cross-sectional shape of the stripe be a forward mesa shape because the transverse mode becomes a single mode. If it is less than 1 μm, it becomes difficult to form a stripe-shaped ridge structure in manufacturing, and the yield tends to decrease. If it exceeds 3 μm, it tends to be difficult to control the horizontal and lateral modes.

In the etching of the height of the projection, that is, the ridge portion, the semiconductor layer formed above the upper barrier layer is formed by etching the semiconductor layer having a thickness of 500 Å or more, preferably 500 Å or more and 0.35 μm or less, more preferably 5 Å or less.
That is, the depth is to be left in the range of not less than 00 angstroms and not more than 1000 angstroms. This is the film thickness 50
If the remaining depth is 0 Å or more, the upper barrier layer 11 is hardly etched deeply, and a convex portion is formed with good accuracy. 0.35μ
If it is not less than m, the threshold current Ith described above increases, and the controllability of the transverse mode tends to be poor.

With this configuration, even during high-power operation, light can be sufficiently confined in the horizontal and transverse modes, and the light density in the waveguide of the laser element in the vertical and transverse modes can be averaged. FIG. 2 is a schematic diagram showing the vicinity of the ridge portion, which can prevent pulsation of the light output emitted from the laser element without causing an increase in the threshold current Ith required for laser oscillation. Here, illustration of the insulating film and the electrodes is omitted. In the example of FIG. 2, the upper barrier layer 11, the upper light guide layer 12, the upper non-doped layer 13, the p-type cladding layer 1 are provided above the active layer 10.
4 and a p-type contact layer 15 are sequentially formed, and a portion of the p-type cladding layer 14 from the p-type contact layer 15 is removed by etching to form a ridge-shaped convex portion. In an example of another embodiment of the present invention shown in FIG. 3, an upper barrier layer 11, an upper light guide layer 12, an upper non-doped layer 13, a p-type cladding layer 14, and a p-type contact layer 15 are provided above the active layer 10. The p-type contact layer 15 and a part of the p-type cladding layer 14 and the upper non-doped layer 13 are sequentially removed by etching to form a ridge-shaped convex portion. In an example of another embodiment of the present invention shown in FIG. 4, an upper barrier layer 11, a non-doped layer 13, a p-type clad layer 14, and a p-type
The mold contact layer 15 is sequentially formed, and a portion of the p-type contact layer 15 to a part of the p-type clad layer 14 is removed by etching to form a convex portion of a ridge structure. This etching may be performed from the p-type contact layer 15 to the p-type cladding layer 14 and the upper non-doped layer 13.
In another embodiment of the present invention shown in FIG.
Above the upper barrier layer 11, the upper light guide layer 12, p
A mold cladding layer 14 and a p-type contact layer 15 are sequentially formed, and a portion of the p-type contact layer 15 to a part of the p-type cladding layer 14 is removed by etching to form a convex portion of a ridge structure. In an example of another embodiment of the present invention shown in FIG. 6, an upper barrier layer 11 is provided above an active layer 10.
A p-type cladding layer 14 and a p-type contact layer 15 are sequentially formed, and a portion of the p-type cladding layer 14 from the p-type contact layer 15 is removed by etching to form a convex portion of a ridge structure.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a nitride semiconductor laser device according to the present invention will be described below. [Embodiment 1] FIG. 1 is a schematic sectional view showing a structure of a laser device according to an embodiment of the present invention, and is a view when cut in a direction perpendicular to a stripe waveguide. Hereinafter, the first embodiment will be described with reference to FIG. (Underlayer 2) A heterogeneous substrate 1 made of sapphire having 1 inch φ and a C-plane as a main surface is set in a MOVPE reaction vessel, the temperature is set to 500 ° C., and trimethylgallium (TM)
G) Using ammonia (NH ₃ ), a GaN buffer layer is grown to a thickness of 200 Å. After the growth of the buffer layer, the temperature is raised to 1050 ° C., and an underlayer 2 also made of GaN is grown to a thickness of 4 μm. This underlayer forms a protective film partially on the surface and then acts as an underlayer for selectively growing a nitride semiconductor substrate. (Protective film 3) After growing the underlayer, the wafer is taken out of the reaction vessel, a stripe-shaped photomask is formed on the surface of the underlayer, and a stripe width of 10 μm is formed by a PVD apparatus.
A protective film 3 made of SiO ₂ having a thickness of m and a stripe interval (window portion) of 2 μm is formed. (Nitride semiconductor substrate 4) After forming the protective film, the wafer was set again in the MOVPE reaction vessel, and the temperature was set to 1050 ° C.
Using TMG and ammonia, non-doped GaN
A nitride semiconductor substrate 4 is grown to a thickness of 20 μm. Since this nitride semiconductor substrate is grown laterally above the protective film 3, the number of crystal defects is 10 ⁵ / cm ² or less, which is two orders of magnitude less than that of the underlayer 2. (N-type contact layer 5) Next, the nitride semiconductor substrate 1 was formed using ammonia and TMG, and silane gas as an impurity gas.
An n-type contact layer 5 made of GaN doped with 3 × 10 ¹⁸ / cm ³ of Si at 1050 ° C. is grown to a thickness of 4 μm. (Crack prevention layer 6) Next, a crack prevention layer 6 of In _0.06 Ga _0.94 N is grown to a thickness of 0.15 μm using TMG, TMI (trimethyl indium), and ammonia at a temperature of 800 ° C. The crack prevention layer can be omitted. (N-type cladding layer 7) Subsequently, at 1050 ° C., using TMA (trimethylaluminum), TMG, and ammonia,
A layer of undoped Al _0.16 Ga _0.84 N is grown to a thickness of 25 Å, followed by stopping TMA,
By flowing a silane gas, a layer made of n-type GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si is grown to a thickness of 25 Å. These layers are alternately laminated to form a superlattice layer, and an n-type clad layer 7 composed of a superlattice having a total film thickness of 0.9 μm is grown. (Lower non-doped layer 8) Then, at 1050 ° C., TMA
Using (trimethylaluminum), TMG, and ammonia, a layer made of non-doped Al _0.16 Ga _0.84 N is grown to a thickness of 25 Å, then TMA is stopped, and a layer made of non-doped GaN is grown to a thickness of 25 Å. Let it. These layers are alternately laminated to form a superlattice layer, and a lower non-doped layer 8 composed of a superlattice having a total film thickness of 0.125 μm is grown. (Lower light guide layer 9) Subsequently, the silane gas is stopped and 10
At 50 ° C., a lower optical guide layer 8 made of non-doped GaN is grown to a thickness of 0.025 μm. The lower light guide layer 9 may be doped with an n-type impurity. (Active Layer 10) Next, at a temperature of 800 ° C., a barrier layer made of Si-doped In _0.05 Ga _0.95 N is grown to a thickness of 100 Å, and subsequently made of non-doped In _0.2 Ga _0.8 N at the same temperature. A well layer is grown to a thickness of 40 Å. A barrier layer and a well layer are alternately laminated twice, and finally an active layer having a multiple quantum well structure (MQW) having a total thickness of 380 Å is grown, ending with the barrier layer. (Upper barrier layer 11) Next, the temperature is increased to 1050 ° C.
MG, TMA, ammonia, Cp ₂ Mg (cyclopentadienyl magnesium), and a bandgap energy larger than that of the upper optical guide layer 12.
An upper barrier layer 11 made of p-type Al _0.3 Ga _0.7 N doped with 0 ²⁰ / cm ³ is grown to a thickness of 100 Å. (Upper light guide layer 12) Subsequently, Cp ₂ Mg and TMA are stopped, and the upper light guide layer 12 made of non-doped GaN having a band gap energy smaller than that of the p-type cap layer 10 at 1050 ° C. is formed to a thickness of 0.025 μm. Grow with. (Upper non-doped layer 13) Subsequently, a layer made of non-doped Al _0.16 Ga _0.84 N is grown at 1050 ° C. to a thickness of 25 Å, Cp ₂ Mg and TMA are stopped, and a layer made of non-doped GaN is formed at 25 Å. An upper non-doped layer composed of a superlattice layer having a total thickness of 0.125 μm is grown. (P-type cladding layer 14) Subsequently, a layer made of non-doped Al _0.16 Ga _0.84 N is grown at 1050 ° C. to a thickness of 25 Å, and then TMA is stopped and Cp ₂ Mg
And a layer made of Mg-doped GaN is grown to a thickness of 25 Å, and a p-type cladding layer 14 made of a superlattice layer having a total thickness of 0.3 μm is grown. (P-type contact layer 15) Finally, at 1050 ° C., a p-type contact layer 15 made of p-type GaN doped with Mg at 1 × 10 ²⁰ / cm ³ is formed on the p-type cladding layer 9 to a thickness of 150 Å. Grow with.

The wafer on which the nitride semiconductor has been grown as described above is taken out of the reaction vessel, and a protective film made of SiO ₂ is formed on the surface of the uppermost p-type contact layer.
Etching is performed by SiCl ₄ gas using RIE (reactive ion etching) to expose the surface of the n-type contact layer 5 on which the n-electrode 23 is to be formed. In order to deeply etch the nitride semiconductor in this way, SiO ₂ is optimal as a protective film.

FIG. 7 is a schematic cross-sectional view showing a partial structure of the nitride semiconductor wafer in each step for explaining each step of the method of forming stripes and electrodes of the nitride semiconductor laser device of FIG. is there. The cross-sectional view shown in FIG. 7 shows a cross section taken in a direction perpendicular to the stripe waveguide formed by etching, that is, in a direction parallel to the resonance surface.

Next, as shown in FIG. 7A, a first protective film 61 made of Si oxide (mainly SiO ₂ ) is formed on almost the entire surface of the uppermost p-type contact layer 15 by a PVD apparatus. Is formed in a thickness of 0.5 μm, a mask having a predetermined shape is applied on the first protective film 61, and a third protective film 63 made of photoresist is formed with a stripe width w2 μm.
m and a thickness of 1 μm.

Next, as shown in FIG. 7B, after the formation of the third protective film 63, an RIE (reactive ion etching) device is used, using CF ₄ gas and using the third protective film 63 as a mask. The first protective film 61 is etched into a stripe shape. Thereafter, by treating with an etchant to remove only the photoresist, a stripe width of 2 μm is formed on the p-type contact layer 15 as shown in FIG.
The first protective film 61 can be formed.

Further, as shown in FIG. 7D, after the first protection film 61 in the form of a stripe is formed, S is again formed by RIE.
Using iCl ₄ gas, the p-type contact layer 15 and the p-type clad layer 14 are etched to form a stripe-shaped waveguide region (ridge stripe in this case). When a stripe is formed, it is highly preferable that the cross-sectional shape of the stripe be a forward mesa shape as shown in FIG.

Thereafter, the wafer is transferred to a PVD device,
As shown in FIG. 7E, Zr oxide (mainly ZrO
₂ ) forming a second protective film 62 on the first protective film 61 and the p-type clad layer 14 exposed by etching;
Is continuously formed with a film thickness of 0.5 μm.

Next, the wafer was immersed in hydrofluoric acid,
As shown in (f), the first protective film 61 is removed by a lift-off method.

Next, as shown in FIG. 7 (g), the first protective film 61 on the p-type contact layer 15 is removed and the exposed surface of the p-type contact layer is made of Ni / Au.
An electrode 21 is formed. However, the p-electrode 21 has a stripe width of 100 μm, and as shown in FIG.
Over the protective film 62 of FIG.

Next, continuously over the entire surface on the p-electrode 21, T
A first thin film layer made of i is formed with a thickness of 1000 angstroms, and further, as shown in FIG. On the continuously formed first thin film layer, a size that does not match the cleavage plane at the time of forming a resonance plane by cleavage in a later step, that is, an upper part of the cleavage plane is intermittently formed. Then, a second thin film layer made of Au is formed to a thickness of 8000 angstroms, and a p-pad electrode 22 consisting of the first thin film layer and the second thin film layer is formed.

After the formation of the p-pad electrode 22, an n-electrode 23 made of Ti / Al is formed on the surface of the n-type contact layer 5 first exposed in a direction parallel to the stripe. An n pad electrode 24 of Pt / Au is formed.

As described above, the sapphire substrate of the wafer on which the n-electrode 23, the n-pad electrode 24, the p-electrode 21, and the p-pad electrode 22 are formed is polished to 70 μm, and then the sapphire substrate is perpendicular to the stripe-shaped electrodes. In the direction, the substrate is cleaved in a bar shape from the substrate side, and a resonator is formed on a cleavage plane (11-00 plane, a plane corresponding to a side surface of a hexagonal columnar crystal = M plane). A dielectric multilayer film composed of SiO ₂ and TiO ₂ is formed on the resonator surface, and finally the bar is cut in a direction parallel to the p-electrode to obtain a structure shown in FIG.
The laser element shown in FIG. The resonator length is 300
It is desirable to set it to 500 μm.

This laser element is placed on a heat sink,
Wire bond each electrode and let it rest at room temperature.
Laser oscillation, the oscillation wavelength was 405 nm,
Flow density 2.3 kA / cm^TwoGood continuous oscillation at room temperature
Is shown. The threshold current was 45 mA. Also, drive current
 Pulsation at 130mA and 90mW light output
No outbreak was observed. [Embodiment 2] Lower light guide layer 9 and upper part shown in FIG.
4 shows an embodiment of a laser device in which the light guide layer 12 is omitted.
You. (N-type cladding layer 7) The same until the formation of the crack prevention layer 6
Then, at 1050 ° C., TMA (trimethyl alcohol)
Luminium), TMG, ammonia, non-doped
Al_0.16Ga _0.8425 angstroms of N layer
Growth, and then stop TMA, silane gas
And Si is 1 × 10¹⁹/cm^ThreeDoped n-type GaN
A layer of 25 Å in thickness
You. These layers are alternately stacked to form a superlattice layer, and the total film
Growing n-type cladding layer 7 consisting of a superlattice having a thickness of 0.9 μm
Let it. (Non-doped layer 8) Subsequently, at 1050 ° C.
Methylaluminum), TMG, ammonia
Doped Al_0.16Ga_0.8425 Angstroms of N layer
Growing at the thickness of the trome, then stopping TMA,
25 Å film made of doped GaN
Grow in thickness. These layers are alternately stacked to form a superlattice layer.
Non-dose composed of a superlattice having a total film thickness of 0.15 μm
The growth layer 8 is grown. (Active Layer 10) Next, the temperature is set to 800 ° C.
In_0.05Ga_0.95100 angstrom barrier layer made of N
Growing at the thickness of the troem, followed by non-doping at the same temperature
Group In_0.2Ga_0.840 angstrom well layer made of N
Grow with a ROHM film thickness. Interchange the barrier layer and the well layer twice
Stacked on top of each other, finally ending with barrier layer, total thickness 380 on
Gstrom's multiple quantum well structure (MQW) active layer
Let it grow. (Upper barrier layer 11) Next, the temperature is increased to 1050 ° C.
MG, TMA, ammonia, Cp_TwoMg (cyclopentane
Dienyl magnesium) and the upper light guide layer 12
High bandgap energy, Mg 1 × 1
0²⁰/cm^ThreeDoped p-type Al_0.3Ga_0.7Above N
The partial barrier layer 11 is grown to a thickness of 100 Å.
Let (Non-doped layer 13) Subsequently, Cp_TwoStop Mg, then continue
And non-doped Al at 1050 ° C_0.16Ga_{0.8 Four}More than N
Layer is grown to a thickness of 25 Å, followed by
Cp_TwoStops Mg and TMA and is made of non-doped GaN
The layer is grown to a thickness of 25 Å and the total thickness
The p-type cladding layer 14 composed of a 0.15 μm superlattice layer is
Let it grow. (P-type cladding layer 14)
Al_0.16Ga_0.8425 angstrom for N layer
Growth with a film thickness of T_TwoMg
And the layer made of Mg-doped GaN is 25 angstrom.
Superlattice layer with a total thickness of 0.3 μm, grown with ROHM film thickness
A p-type cladding layer 14 is grown.

After the p-type contact layer, the same steps as in the first embodiment are formed.

This laser element is set on a heat sink,
Wire bond each electrode and let it rest at room temperature.
Laser oscillation, the oscillation wavelength was 405 nm,
Flow density 2.5 kA / cm^TwoGood continuous oscillation at room temperature
Is shown. The threshold current was 50 mA. Also, drive current
Pulsation even at 160 mA and light output of 120 mW
No outbreak was observed. [Embodiment 3] The lower non-doped layer 8 shown in FIG.
Example of a laser device in which a part of the non-doped layer 13 is omitted
Show. (N-type cladding layer 7) The same until the formation of the crack prevention layer 6
Then, at 1050 ° C., TMA (trimethyl alcohol)
Luminium), TMG, ammonia, non-doped
Al_0.16Ga _0.8425 angstroms of N layer
Growth, and then stop TMA, silane gas
And Si is 1 × 10¹⁹/cm^ThreeDoped n-type GaN
A layer of 25 Å in thickness
You. These layers are alternately stacked to form a superlattice layer, and the total film
Growing n-type cladding layer 7 of 1.2 μm thick superlattice
Let it. (Lower light guide layer 9) Subsequently, the silane gas is stopped and 10
At 50 ° C., the lower light guide layer 8 made of non-doped GaN is
It is grown to a thickness of 0.05 μm. This lower light guide layer
9 may be doped with an n-type impurity. (Active Layer 10) Next, the temperature is set to 800 ° C.
In_0.05Ga_0.95100 angstrom barrier layer made of N
Growing at the thickness of the troem, followed by non-doping at the same temperature
Group In_0.2Ga_0.840 angstrom well layer made of N
Grow with a ROHM film thickness. Interchange the barrier layer and the well layer twice
Stacked on top of each other, finally ending with barrier layer, total thickness 380 on
Gstrom's multiple quantum well structure (MQW) active layer
Let it grow. (Upper barrier layer 11) Next, the temperature is increased to 1050 ° C.
MG, TMA, ammonia, Cp_TwoMg (cyclopentane
Dienyl magnesium) and the upper light guide layer 12
High bandgap energy, Mg 1 × 1
0²⁰/cm^ThreeDoped p-type Al_0.3Ga_0.7Above N
The partial barrier layer 11 is grown to a thickness of 100 Å.
Let (Upper light guide layer 12) Subsequently, Cp_TwoStop Mg, TMA
At 1050 ° C., the band gap energy is
Made of non-doped GaN smaller than the cap layer 10
The upper light guide layer 12 is grown to a thickness of 0.05 μm.
You. (P-type cladding layer 14)
Al_0.16Ga_0.8425 angstrom for N layer
Growth with a film thickness of T_TwoMg
And the layer made of Mg-doped GaN is 25 angstrom.
Super lattice layer with a total thickness of 0.6μm, grown with ROHM film thickness
A p-type cladding layer 14 is grown.

The steps after the p-type contact layer 15 are formed by the same steps as in the first embodiment.

This laser element is placed on a heat sink,
Wire bond each electrode and let it rest at room temperature.
Laser oscillation, the oscillation wavelength was 405 nm,
Flow density 2 kA / cm^TwoGood continuous oscillation at room temperature
You. The threshold current was 40 mA. The driving current 10
Occurrence of pulsation even at 0 mA and light output of 60 mW
No life was seen. [Embodiment 4] The lower light guide layer 9 shown in FIG.
Doped layer, upper non-doped layer and upper light guide layer 12
This shows an embodiment of the laser element in which is omitted. (N-type cladding layer 7) The same until the formation of the crack prevention layer 6
Then, at 1050 ° C., TMA (trimethyl alcohol)
Luminium), TMG, ammonia, non-doped
Al_0.16Ga _0.8425 angstroms of N layer
Growth, and then stop TMA, silane gas
And Si is 1 × 10¹⁹/cm^ThreeDoped n-type GaN
A layer of 25 Å in thickness
You. These layers are alternately stacked to form a superlattice layer, and the total film
Growing n-type cladding layer 7 of 1.2 μm thick superlattice
Let it. (Active Layer 10) Next, the temperature is set to 800 ° C.
In_0.05Ga_0.95100 angstrom barrier layer made of N
Growing at the thickness of the troem, followed by non-doping at the same temperature
Group In_0.2Ga_0.840 angstrom well layer made of N
Grow with a ROHM film thickness. Interchange the barrier layer and the well layer twice
Stacked on top of each other, finally ending with barrier layer, total thickness 380 on
Gstrom's multiple quantum well structure (MQW) active layer
Let it grow. (Upper barrier layer 11) Next, the temperature is increased to 1050 ° C.
MG, TMA, ammonia, Cp_TwoMg (cyclopentane
Dienyl magnesium) and the upper light guide layer 12
High bandgap energy, Mg 1 × 1
0²⁰/cm^ThreeDoped p-type Al_0.3Ga_0.7Above N
The partial barrier layer 11 is grown to a thickness of 100 Å.
Let (P-type cladding layer 14) Subsequently, Cp_TwoStop Mg, 1
Non-doped Al at 050 ° C_0.16Ga_0.84A layer consisting of N
Grown to a thickness of 25 Å, followed by TMA
Stop and Cp_TwoFlow Mg and consist of Mg-doped GaN
The layer is grown to a thickness of 25 Å and the total thickness
A p-type cladding layer 14 composed of a 0.6 μm superlattice layer is formed.
Lengthen.

After the p-type contact layer, the same steps as in the first embodiment are formed.

This laser element is set on a heat sink,
When the respective electrodes were wire-bonded and laser oscillation was attempted at room temperature, good continuous oscillation was exhibited at room temperature at an oscillation wavelength of 405 nm and a threshold current density of 3.5 kA / cm ² . The threshold current was 70 mA. No pulsation was observed at a driving current of 160 mA and an optical output of 90 mW. [Embodiment 5] FIG. 8 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention. Hereinafter, Embodiment 5 will be described with reference to FIG. (Nitride semiconductor substrate 40)
After the formation of the striped protective film 3 on the surface of the substrate, the wafer is set again in the MOVPE reaction vessel and the temperature is set to 1050.
℃, using TMG and ammonia, non-doped Ga
N is grown to a thickness of 5 μm. Then, the wafer is
A nitride semiconductor substrate 40 made of non-doped GaN is transferred to a VPE (hydride vapor phase epitaxy) apparatus using Ga metal, HCl gas, and ammonia as raw materials.
It is grown to a thickness of μm. After the nitride semiconductor is grown on the protective film 3 by the MOVPE method, the HVP
When a GaN thick film having a thickness of 100 μm or more is grown by the E method, the number of crystal defects is reduced by one digit or more compared to the first embodiment. After the growth of the nitride semiconductor substrate 40, the wafer is taken out of the reaction vessel, and the sapphire substrate 1, the buffer layer 2, the protective film 3,
The non-doped GaN layer is removed by polishing, leaving the nitride semiconductor substrate 40 alone.

Thereafter, in the same manner as in Example 1, the n-type contact layers 5 to 5 are formed on the nitride semiconductor substrate 40 on the side opposite to the polished side.
The layers up to the p-type contact layer 15 are stacked.

Next, a part of the n-type contact layer 5 is removed from the p-type contact layer 15 by etching to form a stripe structure, and a laser device having a structure as shown in FIG. When forming a resonance plane, the cleavage plane of the nitride semiconductor substrate is the same M plane as in the first embodiment. [Embodiment 6] FIG. 9 is a schematic sectional view showing the structure of a laser device according to another embodiment of the present invention. Embodiment 6 will be described below with reference to FIG.

In the third embodiment, the nitride semiconductor substrate 40
A silane gas is added to the raw material in the HVPE apparatus to produce a nitride semiconductor substrate 50 made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si with a thickness of 200 μm. The Si concentration is 1 × 10 ¹⁷ / cm ^{3 to} 5 × 10 ¹⁹ / c
It is preferably in the range of m ^3. Nitride semiconductor substrate 50
After the growth, the sapphire substrate 1, the buffer layer 2, the protective film 3, and the non-doped GaN layer are polished and removed in the same manner as in Example 3 to obtain the nitride semiconductor substrate 50 alone.

Next, on this nitride semiconductor substrate 50, the crack prevention layer 6 to the p-type contact layer 15 are stacked and grown in the same manner as in the first embodiment.

After the p-type contact layer 15 is grown, a striped first protective film 61 is formed in the same manner as in the first embodiment.
The surface of the n-type cladding layer 7 shown in FIG. Thereafter, in the same manner as in the first embodiment, the second protective film 62 containing ZrO ₂ as a main component.
Is formed on the side surface of the stripe waveguide and the surface of the n-type cladding layer 7, and then the p-electrode 21 is formed via the second protective film.
To form

Next, a first thin film layer made of Ti is formed on the p-electrode 21 so as to have the same length as the stripe length with a thickness of 1000 angstroms and Pt in the same shape as the second thin film layer. A third thin film layer having a thickness of 1000
A p-pad electrode 101 which is formed by sequentially laminating a second thin film layer 32 made of Au with a thickness of Angstroms and a shape shorter than the stripe length with a thickness of 8000 Angstroms.
Is formed as shown in FIG. Although not shown, the third thin film layer is formed in the same shape as the second thin film layer. On the other hand, the n-electrode 21
To form After the electrodes are formed, the substrate is cleaved on the M-plane of the nitride semiconductor substrate to form a resonance surface, and a laser device having a structure as shown in FIG. 9 is obtained. Comparative Example The configuration of the comparative example will be described below. (N-type cladding layer 7) The process up to the formation of the crack preventing layer 6 was performed in the same manner as in Example 1, and subsequently, at 1050 ° C., using TMA (trimethylaluminum), TMG, and ammonia,
A layer of undoped Al _0.16 Ga _0.84 N is grown to a thickness of 25 Å, followed by stopping TMA,
By flowing a silane gas, a layer made of n-type GaN doped with 1 × 10 ¹⁹ / cm ^{3 of} Si is grown to a thickness of 25 Å. These layers are alternately laminated to form a superlattice layer, and an n-type clad layer 7 composed of a superlattice having a total film thickness of 1.2 μm is grown. (Lower light guide layer 9) Subsequently, the silane gas is stopped and 10
A lower optical guide layer 8 made of non-doped GaN is grown at 50 ° C. with a thickness of 0.15 μm. (Active Layer 10) Next, at a temperature of 800 ° C., a barrier layer made of Si-doped In _0.05 Ga _0.95 N is grown to a thickness of 100 Å, and subsequently made of non-doped In _0.2 Ga _0.8 N at the same temperature. A well layer is grown to a thickness of 40 Å. A barrier layer and a well layer are alternately laminated twice, and finally an active layer having a multiple quantum well structure (MQW) having a total thickness of 380 Å is grown, ending with the barrier layer. (Upper barrier layer 11) Next, the temperature is increased to 1050 ° C.
MG, TMA, ammonia, Cp ₂ Mg (cyclopentadienyl magnesium), and a bandgap energy larger than that of the upper optical guide layer 12.
An upper barrier layer 11 of 0 ²⁰ / cm ³ doped p-type Al _0.3 Ga _0.7 N is grown to a thickness of 300 Å. (Upper light guide layer 12) Subsequently, Cp ₂ Mg and TMA are stopped, and the upper light guide layer 12 made of non-doped GaN having a band gap energy smaller than that of the p-type cap layer 10 at 1050 ° C. is formed to a thickness of 0.15 μm. Grow with. (P-type cladding layer 14) Subsequently, a layer made of non-doped Al _0.16 Ga _0.84 N is grown at 1050 ° C. to a thickness of 25 Å, and then TMA is stopped and Cp ₂ Mg
And a layer made of Mg-doped GaN is grown to a thickness of 25 Å, and a p-type clad layer 14 made of a superlattice layer having a total thickness of 0.6 μm is grown.

The steps after the p-type contact layer 15 are formed by the same steps as in the first embodiment.

This laser element is set on a heat sink,
When each electrode was wire-bonded and laser oscillation was attempted at room temperature, continuous oscillation was exhibited at room temperature at an oscillation wavelength of 405 nm and a threshold current density of ² kA / cm ² .
The threshold current was 40 mA. Also, the driving current Iop75
mA, at a light output of 30 mW or more, frequency 500 MH
Generation of pulsation of z to 5 GHz was observed.

When the other layers were similarly configured with the lower and upper light guide layers having a thickness of 0.1 μm and the laser oscillation was attempted at room temperature, the oscillation wavelength was 405 nm and the threshold current density was ² kA / cm ² . Indicates continuous oscillation. The threshold current was 40 mA. The driving current Iop80m
A, at a power of 35 mW or more, frequency 500 MHz
Generation of pulsation of セ ー 5 GHz was observed.

[0071]

As described above, the laser device of the present invention can prevent pulsation of the light output emitted from the laser device even during high-power operation.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view showing a part of a laser element according to one embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view showing a part of a laser element according to another embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a part of a laser element according to another embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a part of a laser element according to another embodiment of the present invention.

FIG. 6 is a schematic sectional view showing a part of a laser element according to another embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view illustrating a partial structure of a wafer in each step for explaining each step of a method of forming a stripe-shaped ridge structure.

FIG. 8 is a schematic sectional view showing a laser device according to another embodiment of the present invention.

FIG. 9 is a schematic sectional view showing a laser device according to another embodiment of the present invention.

FIG. 10 is a schematic sectional view showing the structure of a conventional laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Different substrate 2 ... Underlayer 3 ... Protective film for nitride semiconductor substrate growth 4, 40, 50 ... Nitride semiconductor substrate 5 ... N-type contact layer 6 ... Crack Prevention layer 7 n-type clad layer 8 lower non-doped layer 9 lower light guide layer 10 active layer 11 upper barrier layer 12 upper light guide layer 13 Upper non-doped layer 14 ... p-type cladding layer 15 ... p-type contact layer 21 ... p electrode 22 ... p pad electrode 23 ... n electrode 24 ... n pad electrode 31, 32 ...・ Insulating film 61 ・ ・ ・ First protective film 62 ・ ・ ・ Second protective film 63 ・ ・ ・ Third protective film

Claims (15)

[Claims] 1. A n-type nitride semiconductor laser device having a cladding layer and the active layer and the p-type cladding _{layer, In f Ga 1-f N} (0 ≦ f <1) optical guiding layer is at least the activity consisting Layer and the n-type or p-type cladding layer, and the light guide layer has a thickness of 0.0
A laser element having a diameter of 5 μm or less. 2. The non-doped layer which is formed on at least an n-type cladding layer side or a p-type cladding layer side of the active layer, wherein the non-doped layer is formed on the side where the light guide layer is formed. 2. The laser device according to claim 1, wherein the laser element is formed between the light guide layer and the clad layer on the side where the light guide layer is formed. 3. 3. The laser device according to claim 2, wherein said non-doped layer has a thickness of 0.5 μm or less. 4. The non-doped layer is composed of In _c Ga _{1 -c} N (0 ≦
c ≦ 1) and a first non-doped layer comprising Al _d Ga _1-d N
4. A superlattice structure comprising a second non-doped layer composed of (0 <d ≦ 1).
4. The laser device according to item 1. 5. The active layer is formed of In _x Ga ₁ -xN (0 <x ≦
1) and In _y Ga _1-y N (0 ≦ y <1, y
A multi-quantum well structure with a barrier layer made of <x), and Al _z Ga ₁ -zN in contact with the active layer on the side of the p-type cladding layer.
The laser device according to claim 2, further comprising an upper barrier layer (0 <z ≦ 1). 6. The laser device according to claim 5, wherein the total thickness of the active layer, the upper barrier layer, the light guide layer, and the non-doped layer is 1 μm or less. 7. The n-type and p-type cladding layers are formed of In _a G
a _{1 -a} N (0 ≦ a ≦ 1) first cladding layer and Al _b
A second clad layer made of Ga _1-b N (0 <b ≦ 1), and at least one of the first and second clad layers is doped with n-type and p-type impurities, respectively. 2. The method according to claim 1, wherein
7. The laser device according to any one of items 1 to 6. 8. A p-type nitride semiconductor layer is further formed on the p-type cladding layer, and at least a part of the p-type cladding layer is etched from the p-type nitride semiconductor layer side to form a stripe. The laser device according to claim 1, wherein a waveguide is formed. 9. The laser device according to claim 8, wherein the width of the stripe is 1 μm or more and 3 μm or less. 10. A laser device having an n-type nitride semiconductor layer, a lower non-doped layer made of a nitride semiconductor, an active layer made of a nitride semiconductor, an upper non-doped layer made of a nitride semiconductor layer, and a p-type nitride semiconductor layer. The laser, wherein a film thickness from a boundary between the n-type nitride semiconductor and the lower non-doped layer to a boundary between the upper non-doped layer and the p-type nitride semiconductor layer is 0.2 μm or more and 1 μm or less. element. 11. The n-type and p-type nitride semiconductor layers have n-type and p-type cladding layers, respectively, and the n-type and p-type cladding layers are In _a Ga ₁ -aN (0 ≦ a ≦ 1). ) And a second cladding layer made of Al _b Ga ₁ -bN (0 <b ≦ 1), and is provided in at least one of the first and second cladding layers. The laser device according to claim 10, wherein n-type and p-type impurities are respectively doped. 12. The p-type nitride semiconductor layer has a p-type cladding layer in contact with an upper non-doped layer, and at least a part of the p-type cladding layer is etched from the p-type nitride semiconductor layer side to form a stripe. 12. A waveguide having a shape of a circle.
4. The laser device according to item 1. 13. The width of the stripe is not less than 1 μm and not more than 3 μm.
The laser device according to claim 10, wherein: 14. An n-type cladding layer, an active layer, an upper barrier layer,
A laser device in which a p-type cladding layer is sequentially stacked, and at least a part of the p-type cladding layer is etched from above the p-type cladding layer to form a striped waveguide, The cladding layer is made of In _a Ga _1-a N (0 ≦ a ≦ 1).
A first cladding layer made of _{Al b Ga 1-b N (} 0 <b ≦
1) having a superlattice structure composed of a second cladding layer, wherein at least one of the first and second cladding layers is doped with an n-type impurity; formed in contact with, the upper barrier _{layer, Al z Ga 1-z N} (0 <z ≦ 1) is formed in contact with the active layer made of the p-type cladding layer, in _a Ga _1-a A superlattice structure composed of a first cladding layer composed of N (0 ≦ a ≦ 1) and a second cladding layer composed of Al _b Ga _1-b N (0 <b ≦ 1); A laser device, wherein at least one of the second cladding layers is doped with a p-type impurity and is formed in contact with the upper barrier layer. 15. A stripe having a width of 1 μm or more and 3 μm or more.
The laser device according to claim 14, wherein: