JP2001135889A - Semiconductor laser and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new window structure wherein increase of a threshold current and operation current density is restrained, long term reliability is highly held, and in the other side, high output can be realized by improving COD level, in a BH type semiconductor laser. SOLUTION: In a window region arranged on an end surface of a BH type semiconductor laser, the same semiconductor material layers as an upper and a lower clad layers constituting a stripe optical wave guide are arranged at the same vertical direction positions and used instead of an active layer or an active layer and an optical guide later. As a result, a structure wherein the layers of the semiconductor material having a band gap greater than oscillation laser light energy are arranged is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser having a BH type light emitting layer provided with a window structure for transmitting an oscillating laser beam on a light emitting end face, and a method of manufacturing the same. More specifically, the present invention relates to a semiconductor laser having a structure in which a window structure provided on a light emitting end face is formed of a semiconductor having a band gap larger than energy corresponding to oscillation laser light, and a method for forming the window structure.

[0002]

2. Description of the Related Art Optical damage (COD: catas) on an end face of an edge emitting semiconductor laser caused by an oscillation laser beam itself.
Trophic optical damage) is one of the issues that must be overcome when achieving high output, long life, and high reliability. Optical damage (COD) is a phenomenon in which an edge-emitting type semiconductor laser causes crystal damage such as melting on the end face due to light absorption at an interface between the end face mirror and the semiconductor forming the optical resonator and accompanying heat generation. It is. The oscillation laser light intensity level (CO
One of the means for improving the D level is a window structure (non absorbing) using a semiconductor having a band gap larger than the energy corresponding to the oscillating laser light at the light emitting end face.
There is a method of forming a mirror structure (NAM structure). This NAM structure is formed by a method in which a portion having a window structure is removed by etching and then a semiconductor having a large band gap is buried and regrown (Japanese Patent Laid-Open No. 63-3164).
95, JP-A-64-42884, etc.). For example, a current block layer is buried and grown for horizontal / lateral mode control and current confinement, and a BH (Buried-H
In a semiconductor laser that forms a stripe waveguide of the (eterostructure) type, when forming a BH structure, etching is performed including the portion that becomes the window structure, and then a semiconductor having a larger band gap than the active layer or the light guide layer of the light emitting layer. A method of burying and regrowing a material is adopted (Electron Letters, Vol. 21, No. 30, p. 1766 (19
1994)). In addition, a window stripe structure for deep diffusion of impurities reaching the active layer of the semiconductor laser or, on the contrary, a partial ion implantation near the end face to effectively remove the semiconductor material used for the active layer of the semiconductor laser. There is also a method of widening the band gap and using it as a window structure.

[0003] The end face transparent structure (NAM structure) using the buried regrowth is different from the window structure using the impurity diffusion or ion implantation, and the energy difference between the band gap of the semiconductor material used for the window layer and the oscillation laser light energy. Has the advantage that the COD level can generally be increased. In addition, the heat treatment process accompanying the impurity diffusion and ion implantation may cause a new crystal defect at the growth interface inside the active layer or in the vicinity thereof, which may be a factor of reducing reliability. Since the formation of the window structure using the buried regrowth is performed together with the buried growth of the current block layer forming the BH structure, an extra heat treatment step which may cause the above-described reliability deterioration is not required. .

In a conventional window structure using buried regrowth, a portion to be a window region is etched until it reaches a substrate, and buried regrowth is performed in the groove portion, but the regrown surface is not necessarily flat. Was something. In particular,
As the window area becomes shorter, the width / depth ratio of the groove becomes smaller, and accordingly, it becomes more difficult to make the regrown surface topography more flat. Therefore,
The step of cleaving the center of the buried regrowth portion to form an end face mirror is not always easy. Further, since etching is performed until the light reaches the substrate, a structure that performs a light confinement function in the optical waveguide, specifically, a clad layer disposed above and below the active layer or the light guide layer serving as a light emitting layer, and a BH type stripe There is essentially no structure in the window region, such as a current blocking layer formed in the horizontal horizontal direction of the optical waveguide, for confining light in the optical waveguide direction by a difference in refractive index. Further, the window region is, like the current blocking layer, buried and grown with a semiconductor material having a different refractive index from the active layer or the light guide layer serving as the light emitting layer. Undergoes refraction and scattering. As a result, the ratio of the light reflected by the end face mirror formed by cleavage or the like returning to the inside of the BH type optical waveguide decreases as the window region becomes longer.
This effective decrease in end face reflectivity causes a decrease in laser oscillation efficiency and an increase in threshold current. In order to suppress the effective decrease in the end face reflectance to an acceptable range, the length of the window region should not exceed about twice the width (stripe width) of the active layer and the light guide layer in the BH type optical waveguide. There is a need to. In the BH type semiconductor laser, the upper limit of the stripe width is set to 1.
Since it is about 5 μm, the conventional window region length needs to be 3 μm or less. For this reason, the above-described manufacturing difficulty is further increased, and it is not easy to achieve and maintain a high yield, and there are also many opportunities to increase the manufacturing cost due to a decrease in the yield.

In a BH type semiconductor laser, when the upper limit of the stripe width is set to about 1.5 μm, the current ratio leaking into the current block layer formed in the horizontal and horizontal direction of the BH type stripe optical waveguide is such that the stripe width becomes narrow. As
Get higher. Compared with this type of ridge waveguide type semiconductor laser in which the leakage current is essentially small, the BH type semiconductor laser has a relatively high current density at the same light output, but has an effective effect in the buried growth window structure. The lower end face reflectivity further increases the current density at the same light output.
Although the window structure of the conventional buried growth is very suitable for improving the COD level, an increase in the threshold current, an increase in the operating current density in the narrow stripe, and the like are caused by an increase in the device temperature during continuous operation, particularly in the stripe. This raises the temperature of the active layer and the vicinity thereof, which is a factor that promotes thermal degradation.
That is, it includes factors that cause a reduction in the device life and long-term reliability in continuous operation.

[0006]

As described above, BH
When a window structure using conventional buried regrowth is provided in a semiconductor laser, high output can be achieved by improving the COD level, but on the other hand, long-term reliability can be improved by increasing the threshold current and operating current density. The decline was a concern. Therefore, in a BH type semiconductor laser, it is desired to propose a new window structure capable of suppressing an increase in the threshold current and the operating current density and maintaining high long-term reliability, while achieving high output by improving the COD level. ing.

The present invention solves the above problems,
An object of the present invention is to provide a BH waveguide type semiconductor laser with a window structure having a high end face breakdown level and excellent long-term reliability, and a method of manufacturing the same. In particular, a BH waveguide type semiconductor laser with a window structure, which has a structure with a high end face breakdown level and excellent long-term reliability, and can be manufactured with high productivity, and a manufacturing method suitable for improving the productivity Is to provide.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has made intensive studies to find out what causes the increase in threshold current and operating current density in a conventional window structure using buried regrowth. , Conducted a detailed study. As a result of the study, it was understood that the effective reduction of the end face reflectance in the window structure of the buried growth occurs by the following mechanism. First, since the film thickness of the active layer and the light guide layer is much smaller than the width thereof, when light is emitted from the optical waveguide to the window region, the light beam spreads due to diffraction due to the effective refractive index difference. Mainly the vertical spread is large. Accordingly, the ratio of the light reflected by the end face mirror which reenters the optical waveguide decreases. Similarly, there is a spread in the horizontal direction, but the effect is much smaller than the decrease in the effective reflectivity caused by the vertical spread.

As a result of conducting research based on the results of the study, the present inventor has found that the reduction of the effective reflectivity can be greatly reduced by suppressing the phenomenon that the light beam spreads in the vertical direction mainly by diffraction in the window region. Was found. In addition, in the window region, the same semiconductor material layers as the upper and lower cladding layers constituting the stripe optical waveguide are arranged at the same vertical position, and the active layer or the active layer and the light guide layer are replaced with an oscillating laser beam. With a structure in which a layer of a semiconductor material having a band gap larger than the energy is arranged, it has been found that, when light is emitted from the optical waveguide to the window region, the phenomenon in which the light beam spreads in the vertical direction due to diffraction can be largely suppressed. Thus, the present invention has been completed.

That is, the semiconductor laser of the present invention has a BH
Type stripe waveguide semiconductor laser, wherein the BH type stripe waveguide has an active layer, or an active layer and an optical guide layer attached thereto, and a refractive index higher than that of the active layer or the active layer and the optical guide layer. It has a cladding layer formed above and below it formed of a small first semiconductor material, and at least one end surface functions as a mirror surface forming an optical resonator, and is buried and grown on the end surface functioning as the mirror surface. A window structure is formed using the semiconductor material to be formed, wherein the window structure has the same first semiconductor material layer as the cladding layer in the stripe waveguide, and the first and second layers are arranged vertically. A band larger than the oscillation laser light energy of the semiconductor laser between the active layer or the active layer and the light guide layer, The second layer of semiconductor material having a cap is at least as wide as the active layer, characterized in that it is a structure which is provided in a region which extends from the end of the active layer to the mirror surface. The second semiconductor material layer,
It is preferable to use a semiconductor material having a smaller refractive index than the active layer, and more preferably, the effective refractive index of the second semiconductor material layer in the window structure exceeds the refractive index of the cladding layer itself.

In the semiconductor laser according to the present invention, the width of the first semiconductor material layer in the window structure is substantially smaller than the width of the cladding layer in the stripe waveguide. Preferably, the structure is selected to be equal to or larger than the width of the active layer. Further, the width of the first semiconductor material layer in the window structure portion is substantially equal to or less than the difference between the width of the cladding layer and the width of the active layer in the stripe waveguide, and the width of the stripe waveguide More preferably, the structure is selected to be equal to or larger than the width of the active layer. On the other hand, it is preferable to select a structure in which the end face on which the window structure is formed is formed by cleavage or formed by dry etching with high perpendicularity.

It is preferable that the length of the window structure in the stripe direction is selected so as not to substantially exceed twice the width of the active layer in the stripe waveguide. In addition, a cap layer made of a semiconductor material having a higher refractive index than the semiconductor material forming the first semiconductor material layer and the clad layer is formed on at least a part of the upper surface of the upper clad layer. It is preferable to have a structure. At least the second semiconductor material layer preferably has a structure formed of a semiconductor material having substantially the same lattice constant as the semiconductor material forming the cladding layer. In this case, it is more preferable that the second semiconductor material layer has a structure formed of a semiconductor material composed of substantially the same element as that of the semiconductor material constituting the clad layer.

The above-described semiconductor laser of the present invention can be manufactured, for example, by a manufacturing method described below. That is, the method for manufacturing a semiconductor laser according to the present invention uses the semiconductor material formed by burying growth on the end surface functioning as the mirror surface at least one end surface of which functions as an optical resonator. What is claimed is: 1. A method for manufacturing a BH-type striped waveguide semiconductor laser having a window structure formed therein, comprising at least an active layer or an active layer and an optical guide layer attached thereto used in the BH-type striped waveguide. And forming a DH structure semiconductor laminated film on a substrate, the semiconductor layer being formed of the first semiconductor material having a lower refractive index than the active layer or the active layer and the light guide layer, and including a cladding layer provided above and below the active layer. Forming an etching mask on the surface of the semiconductor laminated film having the DH structure for etching into a predetermined stripe waveguide shape. Step, At that time, the etching mask, the width in the window structure portion is smaller than the width in the stripe waveguide portion, and is selected to be equal to or more than the width of a predetermined active layer, using the etching mask, at least the Until the lower clad layer is reached, a step of forming a stripe mesa shape using a highly perpendicular etching means, from the formed stripe mesa side wall surface, compared with the semiconductor material constituting the clad layer, Using an etching solution having a high selectivity to the active layer or the semiconductor material forming the active layer and the light guide layer, selectively use the stripe waveguide portion so that the width of the active layer becomes the predetermined width. Semiconductor material that forms the active layer or the active layer and the light guide layer in the window structure at the same time as performing the etching. Is removed by the selective etching, and then, using a selective growth mask having the same shape as the etching mask, a semiconductor material having a band gap larger than the oscillation laser light energy of the semiconductor laser is removed from the window structure portion. A step of burying and growing a predetermined film thickness sufficient to fill the gap occupied by the active layer or the active layer and the light guide layer that has been lost in the step, and then forming a predetermined current block layer on both sides of the stripe mesa. And a step of burying and growing a layer comprising the steps of:

Thereafter, in the step of forming the BH-type stripe waveguide semiconductor laser, the end face is formed by cleavage at the portion where the window structure is formed, or by dry etching with high perpendicularity. Preferably, the mirror surface forms a resonator. The selective growth mask having the same shape as the etching mask used for forming the stripe mesas is preferably a mask made of a dielectric film. In the buried growth on the dielectric film,
This is preferable because no growth occurs.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The BH-type stripe waveguide semiconductor laser according to the present invention is provided with a window structure against end face damage to make the end face transparent, thereby improving the COD level. The window structure used is such that the same first semiconductor material layer as the clad layer in the region (gain region) where the active layer of the stripe waveguide is left is disposed above and below, and the second semiconductor material layer is formed between the active layer and the active layer, or The structure is such that it is formed in an arrangement corresponding to the active layer and the light guide layer. Therefore, the laser beam incident on the window region from the end of the active layer of the stripe waveguide has an optical beam spread in the vertical direction due to the refractive index difference between the first semiconductor material layer and the second semiconductor material layer. It is limited to a range delimited by one semiconductor material layer.
Part of this laser light is reflected by the mirror surface formed on the end face, and is returned to the gain region again from the end of the active layer of the stripe waveguide. This reflected light is also mostly confined to the area delimited by the first semiconductor material layer. Due to this effect, a decrease in the effective reflectance at the end face having the window structure is suppressed, so that a decrease in the oscillation efficiency,
The increase in the threshold current is effectively suppressed. In addition, in the lateral direction, a current blocking layer is formed on the side surface of the window region in the same manner as the BH-type stripe waveguide, so that an effective refractive index difference is formed. Although the effect is not so remarkable as in the vertical direction, the light beam spread of the laser light incident on the window region is suppressed.

Further, the width of the active layer of the stripe waveguide can be made smaller than the width of the clad layer, and the gain region can be formed by burying the second semiconductor material on the side of the active layer and growing it. . Therefore, also in the gain region, a difference in the refractive index can be formed in the horizontal direction between the second semiconductor material and the active layer. Further, there is a band gap difference between the second semiconductor material and the active layer, so that current confinement is more effectively performed. Therefore, the width of the active layer itself can be reduced while keeping the width of the cladding layer in the stripe waveguide wide. The current is injected into the active layer through the cladding layer by the current blocking layer structure on the side of the stripe waveguide. At this time, the width of the cladding layer can be increased, so that the resistance derived from the cladding layer can be reduced and the resistance can be reduced. Is also reduced. As described above, the width of the stripe waveguide itself can be widened while maintaining the controllability of the horizontal and transverse modes, so that unnecessary heat generation can be reduced, the effect of further reducing the threshold current, and the thermal degradation during continuous operation. Can be further suppressed.

Further, since the window structure is formed by using buried growth, there is a surplus such as a window stripe structure in which a deep impurity is diffused into the active layer in the gain region and a transparent end face due to high resistance by ion implantation. Need not be subjected to thermal treatment. Therefore, there is no induction of crystal defects in the active layer and the like and no disturbance of the interface due to the above-mentioned excessive thermal treatment, and it is possible to reduce the factor for shortening the element life as much as possible.

In addition, in the window structure, the same first semiconductor material layer as the gladding layer in the stripe waveguide is left, and the flatness of the surface is maintained even after the buried growth. Therefore, when forming an end face mirror in this window structure part, it is preferable to form the end face by cleavage or to form it by dry etching with high perpendicularity. It is much easier than with a window structure.

Due to these effects, the BH type stripe waveguide semiconductor laser of the present invention has an improved COD level,
It also has excellent laser characteristics and long-term reliability, and also has high reproducibility and high yield in its manufacture.

Hereinafter, the configuration of the semiconductor laser of the present invention will be described more specifically. FIG. 4 is a cross-sectional view schematically showing an example of a configuration of (A) a stripe waveguide portion serving as a gain region and (B) a configuration of a window structure portion in the semiconductor laser of the present invention. The example shown in FIG. 4 employs a configuration in which a second semiconductor material layer is disposed instead of the active layer in the window structure. The window structure shown in FIG.
The same first semiconductor material layer as the cladding layer of the stripe waveguide portion, the same layer as the light guide layer inside the same, and the second semiconductor material layer formed by burying growth are formed at the center. This second semiconductor material layer is made of the same semiconductor material as the first layer of the current blocking layer in the BH type stripe waveguide. That is, in the stripe waveguide portion shown in FIG. 4A, the semiconductor material is the same as the first layer of the current blocking layer grown so as to bury the side surface of the active layer at the center. The width of the first semiconductor material layer in the window structure portion is smaller than the width of the cladding layer in the stripe waveguide portion and is selected to be larger than the width of the active layer. Therefore, the laser light incident on the window structure from the end of the active layer of the stripe waveguide travels to a region corresponding to the second semiconductor material layer and the light guide layers disposed above and below the second semiconductor material layer. Cladding layer and the first semiconductor material layer, the optical guide layer, the active layer, the first layer and the refractive index of the second semiconductor material layer of the current blocking layer, respectively _{n c, n g, n a} , and n _b . At this time, in order to confine light within the optical waveguide in the stripe waveguide, n _a > n _g > n _c is selected. On the other hand, in the BH-type striped waveguide, n _a > n _b because a difference in refractive index is provided even in the horizontal and horizontal directions.

[0021] For example, when n _g> n _b> n _c become like second semiconductor material (the current blocking layer a first layer of) selecting, in the vertical direction of the stripe waveguide shown in FIG. 4 (A) The refractive index distribution is as shown in FIGS. 5 (a) and 5 (b).
FIG. 5A shows a refractive index distribution of a portion indicated by a dotted line a in FIG. 4A and a gain region where an active layer is provided. In this region, since the active layer and the light guide layer are present, the equivalent refractive index is
the β _1. Light is mainly distributed in the active layer and the light guide layer, and n _a
> Β ₁ > _ng . FIG. 5B shows the refraction of the region indicated by the dotted line b in FIG. 4A, that is, the region where the first layer (second semiconductor material layer) of the current blocking layer is buried and grown instead of the active layer. The rate distribution is shown. Also in this region, light is mainly distributed to the light guide layer and the second semiconductor material layer, and the equivalent refractive index is β ₂
Becomes Accordance light distribution and thickness, and _{n g> β 2> n b} . Therefore, when the equivalent refractive index distribution in the horizontal direction in the stripe waveguide shown in FIG. 4A is schematically shown, FIG.
It becomes what is shown in. In the waveguide, in the gain region where the active layer is located, the equivalent refractive index β ₁ , on both sides thereof, the equivalent refractive index β ₂ , outside the waveguide, only the first layer of the current blocking layer, and the refractive index n _b and β ₁ > β ₂ > n _b .
Based on this refractive index distribution, control is performed in a horizontal transverse mode having a center at the center of the waveguide.

The portion indicated by the dotted line c in FIG.
(A) has a laminated structure substantially the same as that indicated by the dotted line b in FIG.
is there. Therefore, the refractive index distribution is shown in FIG.
And the equivalent refractive index β_cIs β_TwoIs substantially equal to Figure
4 (B) is a portion indicated by a dotted line d in the current blocking layer.
There is only one layer, and as shown in FIG. _b
It is. Thus, even in the window structure, the first semiconductor material
The region sandwiched between the material layers is a region having a higher refractive index than the surroundings.
Light is mainly applied to the light guide layer and the second semiconductor material layer.
Distribute. As a result, the gain region of the stripe waveguide
Of the laser light beam propagating from
Can be suppressed.

FIG. 5 schematically shows an equivalent refractive index distribution in the horizontal direction at the center of the second semiconductor material layer of the window structure.
(F). The equivalent refractive index β _c = β ₂ in a region between the window regions sandwiched between the first semiconductor material layers, and the refractive index outside the region is n _b . Therefore, the window structure portion has a higher refractive index β _c > n _b than the surroundings, and the spread of the light distribution in the horizontal direction is suppressed.

As described above, when the layer corresponding to the light guide layer is left in the window region, the relationship of β ₁ > β ₂ > nb needs to be satisfied in the stripe waveguide to control the horizontal and transverse modes. At that time, even in the window region, β ₂ = β _c > n _b
Is satisfied, and the spread of the light distribution in the horizontal direction is suppressed. Specifically, if satisfied relationship n _g> n _b, the condition is sufficiently satisfied. Note that when the n _c> n _b, the relationship of the β ₂ = β _c> n _b is not necessarily satisfied, selecting a range of n _g> n _b> n _c preferable.

FIG. 6 shows a semiconductor laser according to the present invention.
FIG. 9A is a cross-sectional view schematically illustrating another example of the configuration of the stripe waveguide portion serving as a gain region and FIG. The example shown in FIG. 6 employs a configuration in which the light guide layer is not provided in the stripe waveguide, and the second semiconductor material layer is disposed in place of the active layer in the window structure. This second semiconductor material layer is made of the same semiconductor material as the first layer of the current blocking layer in the BH type stripe waveguide. That is, in the stripe waveguide portion shown in FIG. 6A, the semiconductor material is the same as the first layer of the current block layer grown so as to bury the side surface of the active layer at the center. The width of the first semiconductor material layer in the window structure portion is smaller than the width of the cladding layer in the stripe waveguide portion and is selected to be larger than the width of the active layer. Cladding layer and the first semiconductor material layer, the active layer, the first layer and the refractive index of the second semiconductor material layer of the current blocking layer, respectively n _c, n _a, and n _b. At that time, in order to confine light in the optical waveguide in the stripe waveguide, n _a > n _c is selected. On the other hand, B
In the H-type stripe waveguide, n _a > n _b because a difference in refractive index is provided even in the horizontal and horizontal directions.

[0026] For example, when n _g> n _b> n _c become like second semiconductor material (the current blocking layer a first layer of) selecting, in the vertical direction of the stripe waveguide shown in FIG. 6 (A) The refractive index distribution is as shown in FIGS. 7A and 7B.
FIG. 7A shows a refractive index distribution of a portion indicated by a dotted line e in FIG. 6A and a gain region where an active layer is provided. In this region, since the active layer and the cladding layer exist, the equivalent refractive index is
β _e . The active layer has a center of light distribution, and n _a > β _e >
a n _c. FIG. 7B shows the refraction of the region indicated by the dotted line f in FIG. 6A and the region where the first layer (second semiconductor material layer) of the current blocking layer is buried and grown instead of the active layer. The rate distribution is shown. In this region, the center of the light distribution is in the second semiconductor material layer, the equivalent refractive index is a beta _f. Accordance light distribution and thickness, and _{n b> β f> n c} . Therefore, FIG.
FIG. 7C schematically shows the equivalent refractive index distribution in the horizontal direction in the stripe waveguide shown in FIG. In the waveguide, in the gain region where the active layer is located, the equivalent refractive index is β ₁ , and on both sides, the equivalent refractive index is β _f and β _e
> The relation of β _f. Based on this refractive index distribution, control is performed in a horizontal transverse mode having a center at the center of the waveguide.

The part shown by the dotted line g in FIG.
The laminated structure is substantially the same as that shown by the dotted line b in FIG. Therefore, the refractive index distribution is as shown in FIG. 7D, and the equivalent refractive index β _g is substantially equal to β _f . The portion indicated by the dotted line h in FIG. 6B is only the first layer of the current blocking layer, and as shown in FIG.
It is. Also in the window structure portion, the second semiconductor material layer is a region having a higher refractive index than the first semiconductor material layer sandwiching the second semiconductor material layer, and light is mainly distributed to the second semiconductor material layer. As a result, the spread of the laser light beam propagated from the gain region of the stripe waveguide in the vertical direction is suppressed.

On the other hand, the horizontal equivalent refractive index distribution in the center of the second semiconductor material layer of the window structure is schematically shown in FIG.
(F). In a region of the window region sandwiched between the first semiconductor material layers, the equivalent refractive index β _g = β _f and the refractive index outside the region is n _b . In the horizontal direction, the region of the window region sandwiched between the first semiconductor material layers has a lower equivalent refractive index. However, the length of the window region is not so long, and the spread of the light beam in the lateral direction remains within a range not much different from the window structure of the conventional buried growth. At least, since the spread of the light beam in the vertical direction, which has a greater influence, is suppressed, the ratio of the light reflected on the end face returning to the active layer is improved. In particular, when the width of the first semiconductor material layer in the window region is wider than the width of the active layer, the spread of the light beam in the lateral direction becomes smaller, which gives a favorable result.

In the striped waveguide, a light guide layer is provided, the active layer and the light guide layer are removed by selective etching, and a second semiconductor material (first layer of the current blocking layer) is formed.
Is also similar to the example shown in FIGS. 6 and 7. In any case, since the spread of the light beam in the vertical direction is suppressed, the operation and effect of suppressing the decrease in the oscillation efficiency and the increase in the threshold current of the present invention are sufficiently achieved. In addition, since the window structure has the first semiconductor material layer corresponding to the cladding layer, the flatness after the buried growth can be maintained. Therefore, the end face is formed by cleavage, or The yield at the time of formation by high dry etching is comparable to that of a BH type semiconductor laser having no window structure by buried growth.

In the semiconductor laser of the present invention, the active layer or the active layer and the optical guide layer are removed by selective etching at the side of the window structure and the stripe waveguide, and buried growth is performed at the portion. Except for this point, the manufacturing can be performed essentially according to the conventional manufacturing process of this type of BH type stripe waveguide semiconductor laser.

The cladding layer, the light guide layer, the active layer, and the like constituting the BH-type stripe waveguide can be appropriately changed depending on the design. In the window structure, the first layer of the current blocking layer serving as the second semiconductor material layer is selected in the above-described refractive index range, but the remaining current blocking layer and the second layer can be appropriately selected. it can. Accordingly, various semiconductor materials constituting these semiconductor lasers can be appropriately selected according to a target laser oscillation wavelength or the like. The active layer or the active layer and the light guide layer are removed by selective etching. For example, the active layer or the active layer and the light guide layer are made of GaAs or InGaAs.
When AlGaAs having a low s and Al content is used, it is more preferable to use a citric acid-based selective etching solution, for example, a mixed solution of citric acid and hydrogen peroxide, as the selective etching solution.

In the window structure portion and the gain region, a second semiconductor material is buried and grown in place of the active layer removed by the selective etching, or the active layer and the light guide layer. The use of a phase growth method or the like is preferable because good growth is achieved in these narrow gaps. Further, as the growth proceeds, it is preferable to select a growth condition under which lateral growth predominates on the surface. For example, in the case of a III-V compound semiconductor or the like, it is preferable to select the substrate plane orientation as (001) and select a temperature condition or the like in which the movement of the group III atom on the surface proceeds effectively.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a specific example of a BH-type stripe waveguide semiconductor laser of the present invention and a method of manufacturing the same.
This will be described more specifically. The following examples show one example of the best embodiment of the present invention, but the present invention is not limited to these best embodiments.

(Example 1) In this example, the present invention is applied to 980 nm
This is an example applied to a band BH type semiconductor laser. FIG.
It is a figure which shows typically the element structure of the 980-nm band edge emission type semiconductor laser which has the window structure of this example. As the gain region of the BH-type stripe waveguide, n of plane orientation (001) is used.
N-type Al having a film thickness of 2000 nm
_0.3 Ga _0.7 As clad layer 2 (added Si, added concentration 1 ×
10 ¹⁷ cm ^-3 ), 100 nm-thick n-type Al _0.2 Ga _0.8
As light guide layer 3 (Si addition, addition concentration 1 × 10 ¹⁷ cm
^-3 ), In with a well layer thickness of 4.5 nm and a barrier layer thickness of 5 nm
_0.24 Ga _0.76 As / GaAs double quantum well (no addition)
Were added to a 50 nm-thick n-type Al _0.1 Ga _0.9 As layer (Si addition, addition concentration: 1 × 10 ¹⁷ cm ⁻³ ) and a 50 nm-thick p-type Al _0.1 Ga _0.9 As layer (Mg addition, 1 × 1 addition concentration)
0 ¹⁷ cm ^-3 ), an active layer 4 having a thickness of 100 nm, a p-type Al _0.2 Ga _0.8 As optical guide layer 5 having a thickness of 100 nm (Mg added, addition concentration 1 × 10 ¹⁷ cm ^-3 ), and a p-type Al having a thickness of 2000 nm _0.3
Ga _0.7 As clad layer 6 (Mg added, additive concentration 1 × 1
0 ¹⁷ cm ^-3 ) and a 1000 nm-thick p-type GaAs cap layer 7 (added Mg, added concentration 1 × 10 ¹⁷ cm ^-3 ) are sequentially stacked by using a normal pressure MOVPE (metal organic chemical vapor deposition) method. . SiO ₂ thin film 8 used as an etching mask and a selective growth mask later on p-type GaAs cap layer 7
Is deposited to a thickness of 200 nm using a sputtering apparatus.

FIG. 2 is a diagram schematically showing the shape of the etching mask. The width of the window region is smaller than the width of the stripe waveguide portion a. The end face is formed, for example, by cleavage at a position indicated by a straight line b in FIG. On the other hand, separation between adjacent elements is performed in the remaining cleavage direction indicated by a straight line c in FIG. Using a photolithography method, a photoresist mask 9 is coated on the SiO ₂ thin film 8 in the shape shown in FIG. Using the photoresist mask 9, the SiO ₂ thin film 8 is removed by etching with hydrofluoric acid, and the pattern is transferred to SiO ₂ .

FIG. 3 shows the photoresist mask 9 described above.
FIG. 4 is a diagram schematically showing a step of forming a stripe mesa by using a vapor phase etching method by using (and a SiO ₂ mask 8), and then performing a selective etching to remove an active layer 4 in a window region. is there. FIG. 3A schematically shows a process of using a photoresist mask 9 to remove the SiO ₂ thin film 8 by etching with hydrofluoric acid and transferring a pattern to SiO ₂ . The actual SiO ₂ mask 8
Is formed on the entire upper surface of the epitaxially grown film as shown in FIG.

Next, the photoresist mask 9 (and
SiO_TwoReactive ion beam etching using a mask 8)
A stripe mesa shape is formed using a chining device.
FIG. 3B schematically shows the shape after etching in this example.
It is shown in a formula. The reactive ion beam etching method,
Etching mask because of high directivity in the vertical direction
The laminated film is left in a shape corresponding to the above. In this example, the etch
Depth is n-type Al _0.2Ga_0.8Crossing the As light guide layer 3
And n-type Al_0.3Ga_0.7Reach the center of As cladding layer 2
And the depth to be done. That is, n-type Al_0.3Ga_0.7Asku
The n-type GaAs substrate 1 under the lad layer 2 is not exposed
To do. After this, the photoresist mask 9
Means butanone (ethyl methyl ketone), alcohol, etc.
Ultrasonic cleaning is performed using the above organic solvent to remove.

Using a mixed solution of citric acid and hydrogen peroxide, an AlGaAs mixed crystal, an InGaAs mixed crystal and GaAs having an Al composition of less than 0.2 are selectively removed by etching. FIG. 3C schematically shows the shape after etching. The stripe width of the active region is sufficiently larger than the stripe width in the window structure portion. Even when the In _0.24 Ga _0.76 As / GaAs double quantum well active layer 4 in the window structure portion is removed by etching, the active region is removed. In this case, the double quantum well active layer 4 remains in a stripe shape. The etching time is selected so that the width of the active layer 4 remaining only in the active region has a desired value. The etching time is selected so that at least the width of the active layer 4 remaining only in the active region is equal to or less than the stripe width in the window structure. As a result, the shape of the active layer 4 is a stripe having both ends in an arrow shape. In the window structure, p-type GaAs under the SiO ₂ mask 8 is used.
The s cap layer 7 and the double quantum well active layer 4 have been removed. The surface of the SiO ₂ mask 8 is washed with a hydrofluoric acid aqueous solution for 10 seconds, washed with water for 5 minutes, and then dried.

Using the SiO ₂ mask 8 as a selective growth mask, a current block layer is laminated by MOVPE. The current blocking layer is made of n-type Al having a thickness of 1000 nm.
_0.3 Ga _{0 .7} As first layer 10 (Si addition, the addition concentration of 1 × 1
0 ¹⁷ cm ^-3 ), p-type Al _0.45 Ga having a thickness of 1000 nm
_0.55 As second layer 11 (Mg added, concentration 1 × 10 ¹⁷ c
m ^-3 ), n-type Al _0.45 Ga _0.55 As with a thickness of 1000 nm
The third layer 12 has an n / p / n three-layer structure with Si added and an added concentration of 1 × 10 ¹⁷ cm ⁻³ . As shown in FIG. 3D, the n / p / n three-layer current blocking layer has an n-type A
The l _0.3 Ga _0.7 As first layer 10 is composed of a gap formed by removing the active layer 4 by the selective etching, the p-type GaAs cap layer 7.
Also grows in the voids where p-type Al and p-type Al
It grows so as to cover the upper surface of the _0.3 Ga _0.7 As clad layer 6. Next, the p-type Al _0.45 Ga _0.55 As second layer 11
Is n in the gap from which the p-type GaAs cap layer 7 is removed.
A type Al _0.3 Ga _0.7 As is grown to cover the first layer 10. At this point, the voids formed by the selective etching are filled, and the n-type Al _0.45 Ga _0.55 As third layer 12 grows to cover the p-type Al _0.45 Ga _0.55 As second layer 11 on the side of the mesa. .

The SiO ₂ mask 8 used as a selective growth mask is removed by immersing it in a hydrofluoric acid aqueous solution for 2 minutes, washed with water for 5 minutes, and dried. Further, the surface of the semiconductor layer is purified with an etching solution of a mixture of phosphoric acid and hydrogen peroxide. A 500 nm-thick p-type GaAs contact layer 1 is formed on the entire surface.
3 (Mg added, concentration 1 × 10 ¹⁷ cm ⁻³ ). The surface of the grown p-type GaAs contact layer 13 is treated with an etching solution of a mixed solution of phosphoric acid and hydrogen peroxide,
Wash and dry. Then, the p-type GaAs contact layer 1
Ti, titanium (Pt), Pt
A p-electrode 14 is formed by laminating (platinum) and Au (gold) in this order. On the other hand, the back side of the substrate 1 is polished to a thickness of 80 μm, treated with an etching solution, washed with water, and dried. Au, Ge (germanium), and Ni (nickel) are laminated on the back surface of the substrate 1 by a sputtering method to form an n-electrode 15.

Thereafter, in the window region, cleavage is performed at a position indicated by a straight line b in FIG. 2 to form an end face. Is cleaved, after the laser bar, the end face, an Al ₂ O ₃ film on the front of the emitting end of the laser light, on the back surface to take out monitor light Al ₂
A dielectric multilayer film made of O ₃ and amorphous Si is formed by a sputtering method. In this example, the film thickness is selected so that the Al ₂ O ₃ film on the front surface has a reflectance of 3% and the dielectric multilayer film on the back surface has a reflectance of 95%. After forming an anti-reflective protective film on the front surface and a reflective film on the back surface and passivating the end surface, the laser bar is cut and divided into each element to obtain a laser element.

Note that, instead of cleavage, it is also possible to form the end face by using dry etching having high perpendicularity. At this time, before the back surface polishing step, the formation of the resonator mirror by dry etching is completed, and thereafter, the back surface polishing step and the formation of the n-electrode are performed, and a laser bar is formed. Further, in addition to the above materials, for example, TiO ₂ , AlN, CaF, Z
It is also possible to use rO or the like.

(Embodiment 2) In this embodiment, the present invention is applied at 980 nm.
This is another example applied to a band BH type semiconductor laser. In this example, a structure in which no light guide layer is provided in the gain region of the BH type stripe waveguide is employed. As shown in FIG. 8, the element structure has a configuration similar to that of the laser of Example 1 shown in FIG. 1 except that this light guide layer is not provided.
First, as a gain region of a BH-type stripe waveguide, a film thickness of 2000 was formed on an n-type GaAs substrate 1 having a plane orientation (001).
n-type Al _0.3 Ga _0.7 As clad layer 2 (adding Si, doping concentration 1 × 10 ¹⁷ cm ⁻³ ), well layer thickness 4.5 n
m, In _0.24 Ga _0.76 As / GaAs with a barrier layer thickness of 5 nm
An s double quantum well (without addition) is made of n-type Al having a thickness of 50 nm.
_0.1 Ga _0.9 As layer (adding Si, doping concentration 1 × 10 ¹⁷ cm
^-3 ) and an active layer 4 sandwiched by a 50 nm-thick p-type Al _0.1 Ga _0.9 As layer (Mg addition, addition concentration: 1 × 10 ¹⁷ cm ⁻³ ), and a 2000 nm-thick p-type Al _0.3 Ga _0.7 As clad layer 6 (Mg added, additive concentration 1 × 10 ¹⁷ cm ⁻³ ) and a 1000 nm-thick p-type GaAs cap layer 7 (Mg added, additive concentration 1 × 10 ¹⁷ cm ⁻³ ) are successively subjected to normal pressure MOVP.
The layers are stacked using an E (metal organic chemical vapor deposition) method. p-type Ga
A 200 nm-thick SiO ₂ thin film to be used as an etching mask and a selective growth mask later is deposited on the As cap layer 7 by using a sputtering apparatus.

FIG. 2 is a diagram schematically showing the shape of the etching mask. The width of the window region is smaller than the width of the stripe waveguide portion a. The end face is formed, for example, by cleavage at a position indicated by a straight line b in FIG. On the other hand, separation between adjacent elements is performed in the remaining cleavage direction indicated by a straight line c in FIG. Using a photolithography method, a photoresist mask is coated on the SiO ₂ thin film in the shape shown in FIG. Using this photoresist mask, the SiO ₂ thin film is removed by etching with hydrofluoric acid, and the pattern is transferred to SiO ₂ .
Then, the photoresist mask (and SiO ₂₎
Using a mask, a stripe mesa is formed by a vapor phase etching method. The actual SiO ₂ mask is formed on the entire upper surface of the epitaxial growth film as shown in FIG.

Photoresist mask (and SiO_TwoMa
A reactive ion beam etching system
When forming a stripe mesa shape using
The ion beam etching method has high directivity in the vertical direction.
So that the laminated film has a shape that matches the etching mask
Is left. In this example, the etching depth is n-type Al
_0.3Ga_0.7The depth reaching the center of the As cladding layer 2 is
You. That is, n-type Al_{0. Three}Ga_0.7As clad layer 2
The underlying n-type GaAs substrate 1 is not exposed.
After this, the photoresist mask is replaced with butanone (E)
Organic solvent such as tyl methyl ketone) and alcohol
And remove it by ultrasonic cleaning.

Using a mixed solution of citric acid and hydrogen peroxide, an AlGaAs mixed crystal, an InGaAs mixed crystal, and GaAs having an Al composition of less than 0.2 are selectively removed by etching. The stripe width of the active region is sufficiently larger than the stripe width in the window structure portion. Even when the In _0.24 Ga _0.76 As / GaAs double quantum well active layer 4 in the window structure portion is removed by etching, the active region is removed. In this case, the double quantum well active layer remains in a stripe shape. The etching time is selected so that the width of the active layer remaining only in the active region has a desired value. The etching time is selected so that at least the width of the active layer remaining only in the active region is equal to or less than the stripe width in the window structure portion. As a result, the shape of the active layer becomes a stripe having both ends in an arrow shape. In the window structure, the p-type GaAs cap layer 7 under the SiO ₂ mask and the double quantum well active layer 4 are removed.
The SiO ₂ mask surface is washed with a hydrofluoric acid aqueous solution for 10 seconds, washed with water for 5 minutes, and then dried.

Using a SiO ₂ mask as a selective growth mask, a current block layer is laminated by MOVPE.
The current blocking layer is made of n-type Al _0.3 G having a thickness of 1000 nm.
a _0.7 As first layer 10 (added Si, added concentration 1 × 10 ¹⁷
cm ⁻³ ), p-type Al _0.45 Ga _0.55 A with a thickness of 1000 nm
s second layer 11 (Mg added, additive concentration 1 × 10 ¹⁷ c
m ^-3 ), n-type Al _0.45 Ga _0.55 As with a thickness of 1000 nm
The third layer 12 has an n / p / n three-layer structure with Si added and an added concentration of 1 × 10 ¹⁷ cm ⁻³ . This n / p / n three-layer current blocking layer is composed of an n-type Al _0.3 Ga _0.7 As first layer 10.
Is the gap from which the active layer was removed by the selective etching, p
It also grows in the gap from which the type GaAs cap layer 7 has been removed, and grows so as to cover the mesa side surface and the upper surface of the p-type Al _0.3 Ga _0.7 As clad layer 2. Next, p-type Al _0.45 Ga
_{The 0.55} As second layer 11 is grown so as to cover the n-type Al _0.3 Ga _0.7 As first layer 10 in the gap from which the p-type GaAs cap layer has been removed. At this point, the void formed by the selective etching is filled, and n-type Al _0.45 Ga _0.55 A
The s third layer 12 is grown so as to cover the p-type Al _0.45 Ga _0.55 As second layer 11 on the side of the mesa.

The SiO ₂ mask used as the selective growth mask is removed by immersing it in a hydrofluoric acid aqueous solution for 2 minutes, washed with water for 5 minutes, and dried. Further, the surface of the semiconductor layer is purified with an etching solution of a mixture of phosphoric acid and hydrogen peroxide. A 500 nm-thick p-type GaAs contact layer 13 is formed on the entire surface.
(Mg addition, addition concentration 1 × 10 ¹⁷ cm ⁻³ ).
The surface of the grown p-type GaAs contact layer 13 is treated with an etching solution of a mixture of phosphoric acid and hydrogen peroxide, washed with water, and dried. After that, the p-type GaAs contact layer 13
On top, Ti (titanium), Pt
A p-electrode 14 is formed by laminating (platinum) and Au (gold) in this order. On the other hand, the back side of the substrate is polished to a thickness of 80 μm, treated with an etching solution, washed with water, and dried. Au, Ge (germanium), and Ni (nickel) are stacked on the back surface of the substrate by a sputtering method to form an n-electrode 15.

Thereafter, in the window region, cleavage is performed at a position indicated by a straight line b in FIG. 2 to form an end face. Is cleaved, after the laser bar, the end face, an Al ₂ O ₃ film on the front of the emitting end of the laser light, on the back surface to take out monitor light Al ₂
A dielectric multilayer film made of O ₃ and amorphous Si is formed by a sputtering method. In this example, the film thickness is selected so that the Al ₂ O ₃ film on the front surface has a reflectance of 3% and the dielectric multilayer film on the back surface has a reflectance of 95%. After forming an anti-reflective protective film on the front surface and a reflective film on the back surface and passivating the end surface, the laser bar is cut and divided into each element to obtain a laser element.

It should be noted that the end face can be formed by dry etching having high perpendicularity instead of cleavage. At this time, before the back surface polishing step, the formation of the resonator mirror by dry etching is completed, and thereafter, the back surface polishing step and the formation of the n-electrode are performed, and a laser bar is formed. Further, in addition to the above materials, for example, TiO ₂ , AlN, CaF, Z
It is also possible to use rO or the like.

[0051]

According to the semiconductor laser of the present invention, since a window structure for making the end face transparent is provided at the light output end face, the COD level can be increased. On the other hand, this window structure
Instead of the active layer, a semiconductor layer having a larger band gap is formed by burying the semiconductor layer in the vertical direction between the semiconductor layers corresponding to the cladding layer, thereby suppressing the spread of the light beam similar to the optical waveguide structure. The effect obtained is obtained. Therefore, with the semiconductor laser of the present invention, the COD level can be increased while maintaining high efficiency, the semiconductor laser is excellent in long-term reliability, and a high output can be achieved.

[Brief description of the drawings]

FIG. 1 illustrates an example of a BH-type stripe waveguide semiconductor laser provided with a window structure according to the present invention, and is a diagram schematically illustrating a configuration of a semiconductor material layer that is buried and grown in a window region.

FIG. 2 is an etching mask used for manufacturing a BH-type stripe waveguide semiconductor laser provided with a window structure according to the present invention;
FIG. 4 is a diagram showing a shape a of a selective growth mask, a position b of an end face formed in a window region, and a separation position c between elements.

FIGS. 3A and 3B show, during a manufacturing process of a BH-type stripe waveguide semiconductor laser provided with a window structure according to the present invention, (a) a process of forming an etching mask and a selective growth mask, (b) a process of etching a stripe mesa, and (c). It is a figure which shows typically the active layer removal process of the window area | region by selective etching, and (d) the end surface shape in the final laser element.

FIG. 4 is an example of a configuration of a semiconductor laser of the present invention,
(A) shows the relationship between the refractive index of each semiconductor layer in the stripe waveguide gain region and the width of the active layer and the cladding layer;
(B) is a conceptual diagram showing a refractive index of each semiconductor layer in a window region.

5A and 5B are diagrams schematically illustrating a refractive index distribution in a semiconductor laser of the present invention, wherein FIG. 4A shows a dotted line a in FIG.
(B) is a refractive index distribution in a vertical cross section shown in FIG.
Shows a refractive index distribution in a vertical section indicated by a dotted line b, (c) shows a refractive index distribution in a cross section including the active layer, and (d) shows a refractive index distribution in a vertical section indicated by a dotted line c in FIG.
4E shows a refractive index distribution in a vertical section shown by a dotted line d in FIG. 4B, and FIG. 4F shows a refractive index distribution in a horizontal section including the second semiconductor material layer.

FIGS. 6A and 6B show another example of the configuration of the semiconductor laser of the present invention. FIG. 6A shows the relationship between the refractive index of each semiconductor layer in the stripe waveguide gain region and the width between the active layer and the cladding layer, and FIG. It is a conceptual diagram which shows the refractive index of each semiconductor layer in a window area.

7A and 7B are diagrams schematically illustrating a refractive index distribution in a semiconductor laser according to the present invention. FIG. 7A illustrates a dotted line e in FIG.
(B) is a refractive index distribution in a vertical cross section shown in FIG.
Shows a refractive index distribution in a vertical section indicated by a dotted line f, (c) shows a refractive index distribution in a cross section including the active layer, (d) shows a refractive index distribution in a vertical section shown by a dotted line g in FIG.
FIG. 6E shows a refractive index distribution in a vertical section indicated by a dotted line h in FIG. 6B, and FIG. 6F shows a refractive index distribution in a horizontal section including the second semiconductor material layer.

FIG. 8 is a view schematically illustrating another example of a BH-type stripe waveguide semiconductor laser provided with a window structure according to the present invention, and schematically illustrating a configuration of a semiconductor material layer buried and grown in a window region.

[Explanation of symbols]

Reference Signs List 1 n-substrate (n-GaAs) 2 n-cladding layer (n-Al _0.3 Ga _0.7 As) 3 n-light guide layer (n-Al _0.2 Ga _0.8 ) 4 active layer (In _0.24 Ga _0.76 As / GaAs double quantity) 5 p-light guide layer (p-Al _0.2 Ga _0.8 As) 6 p-cladding layer (p-Al _0.3 Ga _0.7 As) 7 p-cap layer (p-GaAs) 8 dielectric film (SiO ₂₎ 9) photoresist 10 n-current blocking layer first layer (n-Al _0.3 Ga _0.7 As) 11 p-current blocking layer second layer (p-Al _0.45 Ga _0.55 As) 12 n-current blocking layer third layer ( n-Al _0.45 Ga _0.55 As) 13 p electrode (Ti / Pt / Au) 14 n electrode (AuGe / Ni)

Claims (6)

[Claims] 1. A BH-type stripe waveguide semiconductor laser, wherein the BH-type stripe waveguide includes an active layer, an active layer and an optical guide layer attached thereto, and the active layer or the active layer and an optical layer. A cladding layer formed of a first semiconductor material having a lower refractive index than the guide layer and provided above and below the first semiconductor material; at least one end face functions as a mirror surface forming an optical resonator; and functions as the mirror surface. A window structure formed by using a semiconductor material formed by burying growth is formed on the end surface, and the window structure has the same first semiconductor material layer as the clad layer in the stripe waveguide. Between the first semiconductor material layer disposed, the active layer, or, instead of the active layer and the light guide layer,
A structure in which a second semiconductor material layer having a bandgap larger than the oscillation laser light energy of the semiconductor laser is provided at least in a region having the same width as the active layer and extending from an end of the active layer to the mirror surface. A semiconductor laser, characterized in that: 2. The width of the first semiconductor material layer in the window structure portion is substantially smaller than the width of the cladding layer in the stripe waveguide, and the width of the active layer in the stripe waveguide. The semiconductor laser according to claim 1, wherein the semiconductor laser has a structure selected as described above. 3. The semiconductor laser according to claim 1, wherein the end face on which the window structure is formed is formed by cleavage or formed by dry etching with high perpendicularity. . 4. A window structure formed by using a semiconductor material formed by burying growth on the end surface functioning as the mirror surface, wherein at least one end surface functions as a mirror surface forming an optical resonator. A method for manufacturing a BH-type stripe waveguide semiconductor laser comprising: an active layer, or at least an active layer and an optical guide layer attached thereto, used for the BH-type stripe waveguide;
And forming, on a substrate, a semiconductor laminated film having a DH structure, which is formed of the first semiconductor material having a lower refractive index than the active layer or the active layer and the light guide layer, and includes cladding layers provided thereon. Forming an etching mask for etching into a predetermined stripe waveguide shape on the surface of the semiconductor laminated film having the DH structure, wherein the etching mask has a width in the window structure rather than a width in the stripe waveguide portion. Is narrowed, and is selected so as to be equal to or larger than the width of the predetermined active layer. Using the etching mask, a stripe mesa shape is formed by using a highly perpendicular etching means at least until reaching the underlying cladding layer. The step of forming, from the formed stripe mesa side wall surface, compared with the semiconductor material constituting the cladding layer, Using an etching solution having a high selectivity to the active layer or the semiconductor material forming the active layer and the light guide layer, the width of the active layer in the stripe waveguide portion is selected to be the predetermined width. Simultaneously etching the active layer or the semiconductor material forming the active layer and the light guide layer in the window structure by the selective etching, and then selecting the same shape as the etching mask. Using a growth mask, a semiconductor material having a band gap larger than the oscillation laser light energy of the semiconductor laser,
A step of burying and growing a predetermined film thickness sufficient to fill the gap occupied by the active layer or the active layer and the light guide layer which have been lost in the window structure, and thereafter, a predetermined thickness is formed on both sides of the stripe mesa. A step of burying and growing a layer to be a current block layer, and performing the above steps as a series. 5. The method according to claim 4, wherein said burying growth is performed by using a metal organic chemical vapor deposition method. 6. The device according to claim 1, wherein the active layer and the light guide layer are made of GaAs,
InGaAs or AlGa having an Al composition of less than 0.2
The method according to claim 4, wherein a citric acid-based etching solution is used as the etching solution having high selectivity when the semiconductor laser is made of a semiconductor material selected from As.