JP3274710B2 - Distributed feedback semiconductor laser device and method of manufacturing distributed feedback semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a distributed feedback semiconductor laser device used as a light source for optical information processing and optical measurement.

[0002]

2. Description of the Related Art In recent years, with the practical use of semiconductor lasers having the advantages of small size, high output, and low cost, the application of lasers to general industrial equipment and consumer equipment, for which use of laser light sources has been difficult in the past, has been advanced. . Above all, remarkable progress has been made in fields such as optical information processing and optical measurement, and it is considered that semiconductor lasers will be applied to more fields in the future. Under such circumstances, the development of semiconductor lasers intended for application to, for example, high-speed laser printers and the like has been promoted. In this application, a so-called transverse mode control laser controlled to oscillate in the fundamental transverse mode is required. For example, in an optical system using a hologram or the like, a semiconductor laser that oscillates in a single longitudinal mode in addition to the fundamental transverse mode is required.
As a structure for obtaining a single longitudinal mode oscillation by controlling the longitudinal mode of emitted light, a distributed feedback type (Distr.
ibuted Feedback (DFB) structure or distributed reflection type (Distribut
There is an ed Bragg Reflector (DBR) structure. GaAs and InP semiconductor lasers having such a structure are being actively developed.

As a method of manufacturing a distributed feedback type semiconductor laser device having a structure for controlling a longitudinal mode and a structure for controlling a transverse mode, for example, a diffraction grating can be easily formed in a device by two crystal growth steps. A method of producing the same has been reported (JP-A-2-206191). FIG. 7 shows a schematic structure of a semiconductor laser device manufactured by this method. This semiconductor laser device is manufactured as follows.

First, as shown in FIG. 8, in a first crystal growth step, n-In _0.5 (Ga _0.3 ) is formed on an n-GaAs substrate 30 by metal organic chemical vapor deposition (MOCVD) under reduced pressure. Al _0.7 ) _0.5 P
First cladding layer 31, non-doped In _0.5 Ga _0.5 P active layer 32, p
An -In _0.5 (Ga _0.7 Al _0.3 ) _0.5 P optical waveguide layer 33 and an n-GaAs current blocking layer 34 are sequentially grown.

[0005] Next, as shown in FIG. 9, p-In _0.5 (Ga) is etched by a chemical etching method using a photoresist mask.
Until the _0.7 Al _0.3 ) _0.5 P optical waveguide layer 33 is exposed, the n-GaAs current blocking layer 34 is removed by etching to form a stripe groove.

After the photoresist mask is removed with an appropriate solvent, p-In _0.5 (Ga _0.7 Al _0.3 ) inside the stripe groove is removed.
Another photoresist mask is formed on the _0.5 P optical waveguide layer 33. Then, periodic unevenness is imprinted on the photoresist mask by a two-beam interference exposure method. Next, p-In was formed by a chemical etching method using this photoresist mask.
_The periodic irregularities are transferred onto the surface of the _0.5 (Ga _0.7 Al _0.3 ) _0.5 P optical waveguide layer 33 to form a diffraction grating 37 (see FIG. 7).

Subsequently, as shown in FIG. 10, in the second crystal growth step, the p-In _0.5 (Ga _0.7 Al _0.3 ) _0.5 P optical waveguide layer 33 and n
P-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P second on -GaAs current blocking layer 34
After growing the cladding layer 35, a p-GaAS contact layer 36 is grown thereon. Finally, a p-side electrode 38 is formed on the surface of the p-GaAs contact layer 36, and n-side electrode 38 is formed on the back of the n-GaAs substrate 30.
The side electrode 39 is formed, and then the wafer is cleaved and divided into chips, thereby obtaining a distributed feedback semiconductor laser device as shown in FIG.

In the semiconductor laser device having the above structure,
The current blocking layers provided on both sides of the stripe groove have a light absorbing function. The transverse mode of the light oscillated in this portion is controlled, and the longitudinal mode is controlled by the diffraction grating.

[0009]

According to the above manufacturing method, only two semiconductor laser devices each having a structure for controlling the longitudinal mode and a structure for controlling the transverse mode of the oscillated light are provided.
It can be formed in two crystal growth steps. However, in the above method, it is very difficult to uniformly apply a resist for engraving a diffraction grating to the bottom of a narrow stripe groove sandwiched between thick current blocking layers. For example, in a portion near the current blocking layer at the bottom of the stripe groove, the resist is likely to be formed thick. In addition, since this portion is hardly exposed due to the presence of the side wall of the current blocking layer, and the applied resist is not irradiated with ultraviolet rays, a diffraction grating may be formed in the vicinity of the current blocking layer at the bottom of the stripe groove. Can not. If an attempt is made to form a uniform diffraction grating over the entire area of the stripe groove bottom, the width of the stripe groove serving as a waveguide must be 10
It must be formed in a width as wide as μm or more. When the waveguide width is widened in this way, spatial hole burning in the waveguide easily causes deformation of the transverse mode of the oscillated light, which adversely affects the characteristics of the semiconductor laser device.

In the semiconductor laser device manufactured by the above-described manufacturing method, the thickness of the optical waveguide layer near the side wall of the current blocking layer is larger than the thickness of the optical waveguide layer below the center of the stripe groove bottom. Therefore, in the optical waveguide layer, the equivalent refractive index of a portion near the side wall of the current blocking layer becomes large. Since light is guided to a portion having a large refractive index, the light intensity distribution in the portion of the optical waveguide layer near the side wall of the current blocking layer becomes large. Therefore, the loss of light due to the light absorbing action of the current blocking layer is large, and the loss of the fundamental transverse mode in the waveguide becomes excessive.

As described above, when a semiconductor laser device is manufactured by using a conventional manufacturing method, it is difficult to obtain a device having excellent quality, and therefore, there is a disadvantage that the yield is inferior.

The present invention has been made to solve the above-mentioned drawbacks, and the object of the present invention is to manufacture a product with a very high yield.
It consists configured to be Rukoto is to provide a distributed feedback semiconductor laser device having a structure for controlling the structure and transverse mode for controlling the longitudinal mode of the oscillation light.

[0013]

According to the present invention, there is provided a distributed feedback semiconductor laser device having a first stacked structure including a first conductive type cladding layer , an active layer , and a second conductive type optical waveguide layer. A structure, and a stripe groove formed on the first laminated structure;
A second stacked structure including a first conductivity type current blocking layer on the surface of the first multilayer structure, the bottom area of the stripe groove
Luo has said current and diffraction gratings formed over the lower region of the blocking layer, and a third multilayer structure comprising a second conductivity type cladding layer formed on the stripe groove and on the current blocking layer, wherein the first with second conductivity type cladding layer is positioned in the lowermost layer of the third multilayer structure, grating epi
A support layer is not disposed on the outermost surface of the diffraction grating.
The diffraction grating and the second conductivity type cladding layer are made of AlGaAs.
Grating / Epi support
The layer is made of GaAs, which achieves the above object. Another distributed feedback semiconductor laser device according to the present invention has a first
Conductive cladding layer , active layer, and second conductive type optical waveguide layer
And a first laminated structure including:
A first conductivity type current blocking layer formed and having a stripe groove.
A second laminated structure including: a surface of the first laminated structure
And from the bottom region of the stripe groove to a region below the current blocking layer.
A diffraction grating formed over an area, and the stripe
A second conductivity type cladding formed on the groove and on the current blocking layer;
And a third stacked structure including a pad layer.
A mold cladding layer located at the lowermost layer of the third laminated structure.
And the grating epi support layer
Disposed on the outermost surface of the diffraction grating, and the second
The conductivity type of the outermost layer of the laminated structure is lower than that of the third laminated structure.
The same as the conductivity type of the layer, thereby achieving the above purpose.
Is done. The distributed feedback semiconductor laser device of the present invention
The serial grating epi-support layer said diffraction grating
Formed on the top of the irregularities that make up the
Objective is achieved. Distributed feedback semiconductor laser element of the present invention
The grating epi support layer is
It is formed over the entire surface of the folded lattice,
The above object is achieved. The distributed feedback semiconductor laser of the present invention
The method of manufacturing a laser element includes a first step of forming a first laminated structure including a first conductive type clad layer , an active layer , and a second conductive type optical waveguide layer, and a surface of the first laminated structure. a second step of forming a diffraction grating, on the first stacked structure including the diffraction grating, the second containing a first conductivity type current blocking layer
A third step of forming a laminated structure, a fourth step of forming a stripe groove by selectively removing some or all of the layers of the second laminated structure,
The second stack structure on the containing method der distributed feedback semiconductor laser device comprising a fifth step, the forming the third laminate structure including a second conductivity type cladding layer as a lowermost layer
Thus, after the first step or after the second step
A grating on the second conductive type optical waveguide layer.
Forming an epi support layer, and the diffraction grating; and
The cladding layer of the second conductivity type is made of an AlGaAs-based material.
The rating epi support layer is made of GaAs,
Thereby, the above object is achieved. Other distribution attributes of the present invention
The method of manufacturing the semiconductor laser device of the first conductivity type
A first layer including a doped layer, an active layer, and a second conductive type optical waveguide layer.
A first step of forming a laminated structure, and the first laminated structure
A second step of forming a diffraction grating on the surface of
A current blocking layer of a first conductivity type on a first laminated structure including
A third step of forming a second laminated structure including:
Selectively remove some or all of the layers in layered structure 2
A fourth step of forming a stripe groove by the said scan
The second conductivity type cladding is formed on the second laminated structure including the trip groove.
Forming a third stacked structure including a pad layer as a lowermost layer
Of a distributed feedback semiconductor laser device including the steps of:
A method comprising: after the first step or after the second step;
After the step, the grating is placed on the second conductive type optical waveguide layer.
Forming a growing epi support layer, and forming the second product
The conductivity type of the outermost layer of the layered structure is the lowermost layer of the third laminated structure.
The above purpose is achieved by the same conductivity type
Is done.

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

After forming periodic irregularities to be a diffraction grating on the surface of the optical waveguide layer, a stripe groove for controlling the transverse mode is formed by etching so that the diffraction grating is at the groove bottom. A uniform diffraction grating is formed over the entire bottom. As a result, a distributed feedback semiconductor laser device having excellent transverse mode stability and oscillating in a single longitudinal mode can be easily manufactured with a very high yield.

[0022]

Embodiments of the present invention will be described below.
In this embodiment, an AlGaAs-based semiconductor was used as a semiconductor material.

Embodiment 1 FIG. 1 shows a schematic structure of a distributed feedback semiconductor laser device manufactured in this embodiment.

This semiconductor laser device has an n-Al _0.5 Ga _0.5 As first cladding layer 11 (1.0 μm thick) on an n-GaAs substrate 10.
Non-doped Al _0.13 Ga _0.87 As active layer 12 (thickness 0.08 μm), p
-Al _{0 .5} Ga _0.5 As carrier barrier layer 13 (thickness 0.05 .mu.m),
p-Al _0.25 Ga _0.75 As optical waveguide layer 14 (thickness 0.15 μm), p-GaA
An s-grating epi-support layer 15 (thickness: 3 nm) is laminated, and periodic irregularities serving as the diffraction grating 21 are formed on the entire surface of the p-Al _0.25 Ga _0.75 As optical waveguide layer. ing. In this embodiment, the p-GaAs grating epi support layer 15 is formed only on the top of the diffraction grating 21. On this structure, an n-Al _0.6 Ga _0.4 As etching stop layer 16 (0.02 to _0.05 μm in thickness), an n-GaAs current blocking layer 17 (0.5 μm in thickness), an n-Al _0.05 Ga _0.95 As A support layer 18 (0.1 μm thick) is laminated, and the etching stop layer 16, current blocking layer 17,
In the center of the support layer 18, a stripe groove is formed. This has p-Al _0.7 Ga _{0 .3} As second cladding layer 19 on the interior of the stripe groove of the diffraction grating 21 and the current blocking layer 17 (thickness 2 [mu] m) is laminated, further p-GaAs contact thereon A layer 20 (1 μm thick) is formed. And p
A p-side electrode 22 is formed on the surface of the -GaAs contact layer 20,
On the back surface of the n-GaAs substrate 10, an n-side electrode 23 is formed.

In the distributed feedback semiconductor laser device having such a structure, the current blocking layer 17 disposed close to the active layer 12 functions as a light absorbing layer, so that the complex refractive index is formed inside and outside the stripe groove. , Thereby realizing light confinement in the horizontal direction. In addition, the current blocking layer
According to 17, current constriction is performed without generating a leakage current, so that oscillation at a low threshold current is possible.

Further, only the light in the resonator direction is amplified by the diffraction grating 21 provided inside the stripe groove, and laser oscillation occurs when the light reaches a certain threshold. The oscillation wavelength λ at that time is expressed by the following equation.

Λ = 2 · n _eff · Λ / m (m = 1, 2, 3,...) Where n _eff represents an equivalent refractive index, and Λ represents a period of the diffraction grating. As is clear from this relational expression, the period of the diffraction grating Λ
Is changed, the oscillation wavelength λ can be changed.

Next, a method for manufacturing the distributed feedback semiconductor laser device of this embodiment will be described with reference to FIGS.

First, in the first crystal growth step, as raw materials, an organic metal growth containing a group III element (trimethylgallium and trimethylaluminum) and a hydride containing a group V element (arsine and phosphine) are used.
By metalorganic vapor phase (MOCVD) method under reduced pressure (100torr)
As shown in FIG. 2, a first clad layer 11, an active layer 12, a carrier barrier layer 13, an optical waveguide layer
14 and a grating epi support layer 15 are sequentially grown.

Subsequently, as shown in FIG. 3, a photoresist film 24 (having a thickness of 10
After that, a diffraction grating having a period of, for example, 3468 angstroms is formed on the photoresist film 24 by a two-beam interference exposure method. Then, by the chemical etching method,
The periodic irregularities of the photoresist film 24 are transferred to the optical waveguide layer 14 to form a diffraction grating 21 having a depth of 0.1 μm. The photoresist film 24 is removed using an appropriate solvent. At this time, the grating epi support layer 15 remains on the top of the diffraction grating 21.

Next, as shown in FIG. 4, as a second crystal growth step, etching is again performed on the optical waveguide layer 14 on which the diffraction grating 21 is formed and the grating epi-support layer 15 by MOCVD. -The stop layer 16, the current blocking layer 17, and the epi support layer 18 are sequentially grown.

Subsequently, as shown in FIG. 5, a photoresist film 25 (thickness: 300 nm) is formed on the epi support layer 18 by coating, and the central portion thereof is stripped by photolithography and etching. Using the photoresist film 25 as a mask, the current blocking layer 17 and the epi support layer 18 are removed by etching until the etching stop layer 16 is exposed by a chemical etching method using an ammonia-based etchant. When the etching stop layer 16 is formed, the optical waveguide layer 1 thereunder is formed.
4 can be prevented, which is preferable.

Subsequently, the etching stop layer 16 is etched away by a chemical etching method using hydrogen fluoride (HF) so that the optical waveguide layer 14 is exposed. Thus, a stripe groove having a bottom width of 4 μm is formed. At this time, the diffraction grating 21 appears at the bottom of the stripe groove. The photoresist film 25 is removed using an appropriate solvent.

Further, as shown in FIG. 6, as a third crystal growth step, a second cladding is formed on the optical waveguide layer 14 and the epi support layer 18 inside the stripe groove by liquid phase epitaxy (LPE). After growing the layer 19, a contact layer 20 is subsequently grown thereon. The grating epi support layer 15 remains on the diffraction grating 21, and the epi layer
Since the support layer 18 exists, the second clad layer 19
Can be easily grown inside the stripe groove.

Finally, a p-side electrode 24 is formed on the surface of the contact layer 20, and an n-side electrode 23 is formed on the back surface of the n-GaAs substrate 10. Then, the wafer is cleaved and divided into chips. Thus, a distributed feedback semiconductor laser device as shown in FIG. 1 is obtained.

The semiconductor laser device having the above structure was formed with a cavity length of 250 μm. The threshold current of this element is 4
It was 0 mA, and oscillated stably in single longitudinal mode even at 10 mW or more.

In the semiconductor laser device having the above structure,
The conductivity type of the semiconductor layer to be regrown and the conductivity type of the underlying layer may be the same.

That is, in the second crystal growth step, the conductivity type of the etching stop layer 16 is the same p-type as that of the optical waveguide layer 14 which is the underlying layer, and in the third crystal growth step, the The conductivity type of the support layer 18 is the same p-type as the second cladding layer 19 to be grown thereon.

With such a structure, at the interface between the two regrowths formed in the second crystal growth step and the third crystal growth step, the conductivity type of the underlying layer is grown and the layer is grown thereon. The conductivity type of the regrowth layer is the same, and the conductivity type of the two regrowth intervening surfaces is the same p type.
Thereby, the occurrence of defects at the regrowth interface is significantly reduced as compared with the case where the conductivity type of the underlying layer is different from the conductivity type of the regrown layer. Therefore, a leakage current flowing through the current blocking layer through crystal defects is eliminated, and a distributed feedback semiconductor laser device having excellent characteristics with a small oscillation threshold can be manufactured.

(Example 2) An example of manufacturing another semiconductor laser device using the manufacturing method of the present invention will be described with reference to FIGS. FIG. 11 substantially corresponds to the laminate shown in FIG.
5 shows the laminate immediately before the stripe groove is formed by etching.

In the laminated body shown in FIG. 11, an n-type substrate 40 has an n-type first cladding layer 41, an active layer 42, a carrier barrier layer 43, and a p-type optical waveguide layer 44 formed thereon. The diffraction grating 51 is formed on the entire surface of the substrate 44.

The optical waveguide layer 44 on which the diffraction grating 51 is formed
On the upper surface, a grating epi support layer 45 having a substantially uniform thickness is formed so as to cover the entire surface, and an etching stop layer 46, a current blocking layer 47, and an epi support layer 48 are further formed. . On the epi support layer 48, a photoresist film 55 is formed.
The central portion of the photoresist film 55 is stripped. Each of the above layers corresponds to the layer having the same name in Example 1, and can be formed using the same material.

This laminate is formed as follows. First, in the first crystal growth step, the layers from the first cladding layer 41 to the optical waveguide layer 44 are grown on the substrate 40, and the diffraction grating 51 is formed on the optical waveguide layer 44. Thereafter, in a second crystal growth step, the above-mentioned grating epi-support layer 45 is grown on the entire surface of the diffraction grating 51, and the etching stop layer 46 and the current blocking layer 4 are further grown.
7 and the epi support layer 48 are grown. The method for growing each semiconductor layer and the method for forming the diffraction grating 41 can be the same as in the first embodiment. In the second embodiment, the grating epi-support layer 45 is formed in the second growth step. Form.

The same method as that of the first embodiment is used for forming the photoresist film 55, and the laminated body shown in FIG.
By using this photoresist film 55, FIG.
As shown in the figure, a stripe groove having a width of 3 μm at the bottom is formed by etching, and the grating
The support layer 45 is exposed.

After the formation of the stripe grooves, a second cladding layer (not shown), a contact layer (not shown), and an electrode (not shown) are formed in the same manner as in Example 1, and a semiconductor laser device is formed. You.

In the semiconductor laser device manufactured in this embodiment, since the grating epi-support layer 45 having a substantially uniform thickness is formed on the diffraction grating 51, the second cladding layer is formed inside the stripe groove. Can be more easily grown, and the buried growth yield can be improved.

The semiconductor laser device having the above configuration was formed with a cavity length of 250 μm. The threshold current of this element is 4
It was 0 mA, and oscillated stably in single longitudinal mode even at 10 mW or more.

(Embodiment 3) An example of manufacturing a semiconductor laser device by the second manufacturing method of the present invention will be described with reference to FIGS. 13 and 14
Corresponds to the laminate shown in FIGS. 11 and 12 in Example 2, respectively. In this laminate, an n-type first cladding layer 61, an active layer 62, a carrier barrier layer 63, and a p-type optical waveguide layer 64 are formed on an n-type substrate 60, and the entire surface is formed on the optical waveguide layer 64. Is formed with a diffraction grating 71. In the third embodiment, the diffraction grating 71 is formed in a corrugated shape having a square apex.

The optical waveguide layer 64 having the diffraction grating 71 formed thereon
A p-type semiconductor layer 69 which will be a part of a second clad layer which later fills the inside of the stripe groove is formed thereon, and an etching stop layer 66, a current blocking layer 67, and an epi support layer 68 are further formed. Have been. On the epi support layer 68, a photoresist film 75 is formed, and a central portion of the photoresist film 75 is removed in a stripe shape. Each of the above layers corresponds to the layer having the same name in Example 1, and can be formed using the same material.

This laminate is formed as follows. First, in the first crystal growth step, the layers from the first cladding layer 61 to the optical waveguide layer 64 are grown on the substrate 60, and the diffraction grating 71 is formed on the optical waveguide layer 64. Then, in a second crystal growth step, a p-type semiconductor layer 69 which is to be a part of the second clad layer is grown on the diffraction grating 71, and the etching stop layer 66 and the current blocking layer 6 are further formed.
7 and the epi support layer 68 are grown. Further, as the method of growing the semiconductor layer and the method of forming the diffraction grating 71 in the above configuration, the same method as in the first embodiment can be used. The photoresist film 75 is formed in the same manner as in the first embodiment. In the laminated body shown in FIG. 13, stripe grooves are formed by etching using the photoresist film 75 as shown in FIG. The p-type semiconductor layer 69 is exposed.

After the formation of the stripe groove, the remaining portion (not shown) of the second cladding layer is grown inside the stripe groove in the same manner as in Example 1, and further, the contact layer (not shown) and the electrode (not shown) are formed. (Not shown), and a semiconductor laser device is formed.

The semiconductor laser device manufactured in this embodiment has a p-type layer on the diffraction grating 71 which becomes a part of the second cladding layer.
Since the type semiconductor layer 69 is formed, it is possible to prevent the diffraction grating 71 from deteriorating during the burying growth.

The semiconductor laser device having the above configuration was formed with a cavity length of 250 μm. The threshold current of this element is 4
It was 0 mA, and oscillated stably in single longitudinal mode even at 10 mW or more.

In the third embodiment, the same effect as described in the first embodiment can be obtained by setting the conductivity type of the semiconductor layer to be regrown to the same conductivity type as that of the underlying layer. be able to.

[0055]

According to the present invention, since a uniform diffraction grating can be formed over the entire area of the bottom of the stripe groove for controlling the transverse mode, the stability of the transverse mode is excellent, and the distributed feedback oscillating in the single longitudinal mode is achieved. Type semiconductor laser device can be easily manufactured with good yield. The semiconductor laser device manufactured by the present invention has uniform oscillation characteristics and can be provided at a low price, and can be widely used as a light source for optical information processing, optical measurement, and the like.

If the conductivity type of the underlying layer is the same as the conductivity type of the layer to be regrown thereon when the crystal is regrown, the two regrowth interfaces having different conductivity types are present. The occurrence of defects at the regrowth interface can be greatly reduced as compared with the case where Therefore, a leakage current flowing through the current blocking layer through crystal defects is eliminated, and a distributed feedback semiconductor laser device having excellent characteristics with a small oscillation threshold can be manufactured.

If the grating epi-support layer is formed on the diffraction grating, the burying growth yield of the second cladding layer formed inside the stripe groove can be improved. If the thickness of the grating epi support layer is made substantially uniform, the effect can be further increased.

According to the second manufacturing method, the semiconductor layer of the second conductivity type is formed at the bottom of the stripe groove, and the same semiconductor as the semiconductor layer is grown thereon to form the second cladding layer. Therefore, since the diffraction grating is not exposed during the burying growth, the deterioration can be prevented. For this reason, a semiconductor laser device having good transverse mode stability and oscillating in a single longitudinal mode can be manufactured with a very high yield.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view showing a schematic structure of a distributed feedback semiconductor laser device manufactured by a first manufacturing method of the present invention.

FIG. 2 is a partially broken perspective view showing a first crystal growth step in the manufacturing steps of the distributed feedback semiconductor laser device shown in FIG.

FIG. 3 is a partially cutaway perspective view showing a step of forming a diffraction grating on the surface of the optical waveguide layer in the manufacturing steps of the distributed feedback semiconductor laser device shown in FIG.

FIG. 4 is a partially cutaway perspective view showing a second crystal growth step in the process of manufacturing the distributed feedback semiconductor laser device shown in FIG. 1;

FIG. 5 is a partially broken perspective view showing a step of forming a stripe groove in a step of manufacturing the distributed feedback semiconductor laser device shown in FIG. 1;

FIG. 6 is a partial perspective view showing a third crystal growth step in the manufacturing steps of the distributed feedback semiconductor laser device shown in FIG.

FIG. 7 is a partially broken perspective view showing a schematic structure of a conventional distributed feedback semiconductor laser device.

8 is a cross-sectional view showing a first crystal growth step in the manufacturing steps of the conventional distributed feedback semiconductor laser device shown in FIG.

9 is a cross-sectional view showing a step of forming a stripe groove in the process of manufacturing the conventional distributed feedback semiconductor laser device shown in FIG.

10 is a cross-sectional view showing a second crystal growth step in the process of manufacturing the conventional distributed feedback semiconductor laser device shown in FIG.

FIG. 11 is a partially cutaway perspective view showing a second crystal growth step in another distributed feedback semiconductor laser device manufactured by the first manufacturing method of the present invention.

FIG. 12 is a partially cutaway perspective view showing a step of forming a stripe groove in another distributed feedback semiconductor laser device manufactured by the first manufacturing method of the present invention.

FIG. 13 is a partially cutaway perspective view showing a second crystal growth step in another distributed feedback semiconductor laser device manufactured by the second manufacturing method of the present invention.

FIG. 14 is a partially broken perspective view showing a step of forming a stripe groove in another distributed feedback semiconductor laser device manufactured by the second manufacturing method of the present invention.

[Explanation of symbols]

 10, 40, 60 Substrate 11, 41, 61 First cladding layer 12, 42, 62 Active layer 14, 44, 64 Optical waveguide layer 15, 45 Grating / epi support layer 16, 46, 66 Etching stop layer 17, 47, 67 Current blocking layer 18, 48, 68 Epi support layer 19 Second cladding layer 20 Contact layer 21, 51, 71 Diffraction grating 69 P-type semiconductor layer that becomes a part of second cladding layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mototaka Tanaya 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Chinori Nakanishi 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp shares Inside the company (72) Inventor Satoshi Sugawara 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Hiroaki Kudo 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka inside Sharp Corporation (56) Reference Document JP-A-2-206191 (JP, A) JP-A-2-119288 (JP, A) JP-A-63-73683 (JP, A) JP-A-63-263785 (JP, A) 186689 (JP, A) JP-A-2-17885 (JP, A)

Claims (6)

(57) [Claims] 1. A first laminated structure including a first conductive type cladding layer , an active layer , and a second conductive type optical waveguide layer, and a stripe groove formed on the first laminated structure. and, a second stacked structure including a first conductivity type current blocking layer on the surface of the first multilayer structure, the bottom surface of the stripe groove
Has a diffraction grating formed over the lower region of the current blocking layer from the region, a third stacked structure including a second conductive-type clad layer formed on the stripe groove and on the current blocking layer, wherein the with the second conductive type cladding layer, positioned in the lowermost layer of the third multilayer structure, grating epi support
And a second conductive type cladding layer is formed on the outermost surface of the diffraction grating.
And the grating epi support layer
It characterized in that it consists of GaAs distributed feedback semiconductor laser device. 2. The first conductive type clad layer, the active layer, and the first conductive type clad layer.
A first laminated structure including a two-conductivity-type optical waveguide layer; and a stripe groove formed on the first laminated structure.
A second stacked structure including a current blocking layer of a first conductivity type; and a bottom surface of the stripe groove on a surface of the first stacked structure.
Circuit formed from the region to the region below the current blocking layer.
Folded grating , formed on the stripe groove and on the current blocking layer
A third stacked structure including a cladding layer of the second conductivity type.
And, the second conductivity type cladding layer, the uppermost of the third multilayer structure
Located in the lower layer,
A layer is disposed on the outermost surface of the diffraction grating, and
The conductivity type of the outermost layer of the second laminated structure is the third product.
Characterized by the same conductivity type as the lowermost layer of the layer structure
Distributed feedback semiconductor laser device. 3. The grating epi support layer
Is formed on the top of the unevenness forming the diffraction grating.
The distributed feedback semiconductor laser device according to claim 1 or 2, wherein: 4. The grating epi support layer
Is formed over the entire surface of the diffraction grating.
The distributed feedback semiconductor laser according to claim 1 or 2,
User element. 5. A method of forming a first stacked structure including a first conductive type clad layer , an active layer , and a second conductive type optical waveguide layer.
Step 1, a second step of forming a diffraction grating on the surface of the first multilayer structure, and a first conductivity type current blocking layer on the first multilayer structure including the diffraction grating. A third step of forming a second laminated structure including: a fourth step of forming a stripe groove by selectively removing a part or all of the layers of the second laminated structure; and the second stack structure on the containing groove, the second conductive
Fifth step and, distributed feedback semiconductor laser device comprising forming a third multilayer structure including a type cladding layer as a lowermost layer
The method according to claim 1 , wherein after the first step or after the second step,
On the second conductivity type optical waveguide layer, a grating
A port layer is formed, and the diffraction grating and the second conductivity type cladding layer are made of an AlGaAs-based material.
And the grating epi support layer
A method for manufacturing a distributed feedback semiconductor laser device comprising GaAs . 6. A first conductive type clad layer, an active layer, and a first conductive type clad layer.
Forming a first stacked structure including a two-conductivity type optical waveguide layer;
Step 1 and a second step of forming a diffraction grating on the surface of the first laminated structure.
Forming a first conductive type on the first stacked structure including the diffraction grating.
Third step of forming a second laminated structure including a current blocking layer
And selectively removing a part or all of the layers of the second laminated structure.
And forming a second conductive layer on the second laminated structure including the stripe groove.
Forming a third laminated structure including the mold clad layer as the lowermost layer
Feedback semiconductor laser device including:
The method according to claim 1 , wherein after the first step or after the second step,
On the second conductivity type optical waveguide layer, a grating
A port layer is formed, and the conductivity type of the outermost layer of the second laminated structure is the third type.
It has the same conductivity type as the lowermost layer of the laminated structure.
Of manufacturing a distributed feedback semiconductor laser device.