JPH0834336B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor laser device suitable for a light source for long-distance optical communication and a method for manufacturing the same, and in particular, it oscillates in a single basic horizontal transverse mode and has a low current. The present invention relates to a semiconductor laser device that operates stably and a manufacturing method thereof.

(Prior Art) A semiconductor laser device that oscillates in a wavelength region of 1 μm band (1.1 to 1.7 μm) has been actively studied as a light source for optical communication in the field of high-speed long-distance communication. This is because the propagation loss of the silica glass fiber for optical communication in this wavelength band is extremely low. In particular, a low-loss silica glass fiber using a high-purity material has no material dispersion in the wavelength range of 1.3 μm. Therefore, by using a semiconductor laser that emits a laser beam in this wavelength range, it is possible to achieve a high value exceeding 1 GHz · km. The cutoff frequency is obtained.

FIG. 4 shows a cross-sectional view of a conventional semiconductor laser device used as a light source for 1.3 .mu.m band optical communication. This semiconductor laser device has an indented double hetero structure.

As can be seen from FIG. 4, the n-type In is formed on the semiconductor substrate 21.
P-clad layer 22, non-doped InGaAsP active layer 23, p-type InP
A clad layer 24 and a p-type InGaAsP cap layer 25 are stacked in this order from the substrate 21 side to provide a double hetero structure mesa stripe structure. On the substrate 21 in the region other than the region where the mesa stripe structure is provided, p-type In
A buried layer in which the P current blocking layer 26 and the n-type InP current blocking layer 27 are stacked in this order from the substrate 21 side is provided. The buried layer covers the side surface of the mesa stripe structure. An AuZn electrode 28 is provided on the n-type InP current blocking layer 27 and the p-type InGaAsP cap layer 26, and an AuGe electrode 29 is provided on the back surface of the substrate 21.
Are formed.

In the semiconductor laser device of FIG. 4, the side surface of the mesa stripe structure including the active layer 23 is covered with a buried layer. Therefore, a laser beam that oscillates in a single fundamental horizontal transverse mode can be obtained. Further, when a voltage is applied in the forward direction to the double hetero structure in order to oscillate laser light, a reverse bias is applied to the pn junction provided in the buried layer. For this reason, the reactive current flowing through the buried layer is reduced, and the current is concentrated and efficiently flows in the mesa stripe structure. Therefore, the threshold current is reduced, and stable laser oscillation at low current is realized.

Next, a conventional method of manufacturing the semiconductor laser device of FIG. 4 will be described.

First, the n-type InP clad layer 22, the non-dove InGaAsP active layer 23, the p-type InP clad layer 24, and the p-type InGaAsP cap layer 25 are formed on the semiconductor substrate 21 in this order by the LPE method.
Stack from side 1.

Next, an etching mask having a mesa stripe pattern of a predetermined width is formed on the p-type InGaAsP cap layer 25 in order to form a portion in which the burying layer is buried in a later step, and the etching mask is not covered with the etching mask. P-type In of region
GaAsP cap layer, p-type InP clad layer 24, undoped In
The GaAsP active layer 23, n and the InP cladding layer 22 are etched. Thus, the InP clad layer 22, the InGaAsP active layer 23,
A mesa stripe structure including an InP clad layer 24 and a p-type InGaAsP cap layer is formed on the substrate 21. The pattern of the etching mask at this time determines the width of the active layer 23.

By the above etching, the n-type InP clad layer 22, the non-dove InGaAsP active layer 23, the p-type InP clad layer 24, and the p-type InP clad layer 24 are formed.
On the substrate 21 in the region where the InGaAsP cap layer was removed,
By the PE method, the p-type InP current blocking layer 26 and the n-type InP current blocking layer 27 are stacked in this order from the substrate 21 side. At this time, the buried layer covers the side surface of the mesa stripe structure, and the height of the interface (pn junction surface) between the p-type InP current blocking layer 26 and the n-type InP current blocking layer 27 is equal to that of the active layer 23. Match or be slightly higher than height.

After removing the etching mask, the p-type InGaAsP cap layer 25
And the AuZn electrode 28 on the n-type InP current blocking layer 27, the substrate 2
An AuGe electrode 29 is formed on the back surface of 1.

(Problems to be Solved by the Invention) However, the above-described conventional technology has the following problems.

In the conventional example shown in FIG. 4, in order to form the active layer 23 having a predetermined width, a multilayer film including the active layer 23 is formed on the entire surface of the substrate 21, and then a predetermined region of the multilayer film is highly accurately formed. A step of etching to form a mesa stripe structure having a predetermined width is required. In order to stabilize the horizontal transverse mode of laser oscillation, it is necessary to control the deviation of the width of the active layer 23 from a predetermined value to about 0.1 μm or less. According to the above-mentioned conventional technique, the mesa stripe structure is formed by deeply etching a predetermined portion of the multilayer film formed on the entire surface of the wafer. Therefore, the width of the active layer 23 is determined with good reproducibility with such accuracy. Is difficult. Therefore, the width of the active layer 23 varies greatly.

In addition, in order to reduce the reactive current, in the buried layer
The layer thickness of each layer must be controlled so that the height of the pn junction matches the height of the active layer. If a large deviation occurs between the height of the pn junction and the height of the active layer 23, the reactive current flowing through the buried layer without flowing through the active layer 23 increases. Therefore, the oscillation threshold of the semiconductor laser device becomes high.

Further, since a process such as an etching process is required between the crystal growing process for forming the double hetero structure and the crystal growing process for forming the buried layer, the process is complicated. Further, during the above crystal growth step, impurities may be mixed into the crystal layer from the atmosphere.

A semiconductor laser device improved from the conventional example described above (Japanese Patent Laid-Open No. 64-64-
(Disclosed by No. 25590) is shown in FIG.

In this improved example, an n-type InP substrate having a plane orientation (100) is used.
Mesa-shaped ridge (width 5 μm, height 2.2 μm) 3 on 31
2 are provided along the <011> direction (resonator direction, perpendicular to the drawing).

On the substrate 31, an n-type InP buffer layer 33, an n-type InP cladding layer 34, a non-doped InGaAsP active layer 35, and a p-type InP cladding layer 36 are laminated in this order from the substrate 31 side. On the ridge portion, in particular, a mesa stripe-shaped laminated structure having a triangular cross section is formed. The side surface of this laminated structure is the (111) B surface, and the angle between the side surface and the surface of the substrate 31 is 54.7 degrees. As described above, the side faces of the mesa-stripe-shaped laminated structure serve as facets having a specific plane orientation because each of the above layers is grown under the condition that crystal growth does not easily occur on the (111) B plane. In this improved example, the etching step for forming the mesa stripe laminated structure is not necessary.

It should be noted that a multilayer film having a laminated structure similar to the mesa stripe laminated structure is also formed on the substrate 31 in the region other than the region where the mesa stripe laminated structure is provided.

The n-type InP barrier layer 41 and the p-type InP are further formed on the wafer.
The clad layer 42 and the p-type InGaAsP contact layer 43 are laminated in this order from the substrate side. A p-side electrode 44 is formed on the p-type InGaAsP contact layer 43, and an n-side electrode 45 is formed on the back surface of the substrate 31.

The above-described improved example has an advantage that an etching step is not required between the crystal growth step for forming the mesa stripe-shaped laminated structure and the crystal growth step for forming the buried layer during manufacturing. are doing. Further, since the above-described two types of crystal growth steps can be performed in one continuous step, there is little possibility that impurities will be mixed into the crystal layer from the atmosphere.

However, this improved example has a problem that it is difficult to form the ridge 32 having a predetermined width with a high yield because the ridge 32 is formed by deeply etching the substrate 31.

Further, since the double hetero structure is formed on the ridge 32, the difference in the wafer surface before forming the buried layer is large,
It is also difficult to flatten the wafer surface by forming a buried layer. If the upper surface of the wafer is not flat, there arises a problem that when the semiconductor laser element is mounted on the heat sink or the like, it is impossible to realize the arrangement in which the heat sink or the like and the upper surface of the wafer are in contact with each other.

Furthermore, in this improved example, the layer thickness of each layer must be controlled accurately so that the height of the pn junction in the buried layer matches the height of the active layer, which reduces the manufacturing yield. There is also the problem of being lost.

 FIG. 6 shows another improved example.

In this improved example, an n-type InP substrate having a plane orientation (100) is used.
On top of 51, a laminated structure having a structure similar to the mesa-stripe-shaped laminated structure of FIG. 5 is formed in the <011> direction (resonator direction,
(Perpendicular to the drawing). In this laminated structure, a SiO ₂ film having a rectangular opening whose long side extends along the <011> direction is formed on the n-type InP substrate 51, and then MOC is formed.
The n-type InP buffer layer 52, n is formed only in the opening by the VD method.
The p-type InP clad layer 53, the non-doped InGaAsP active layer 54, and the p-type InP clad layer 55 are sequentially and selectively grown. The side surface of the laminated structure thus formed is the (111) B surface, as in the modified example.

The above crystal growth does not occur on the SiO ₂ film. The SiO ₂ film is removed from the substrate 51 by etching after the selective crystal growth described above.

On the substrate 51 from which the SiO ₂ film has been removed, p
Type InP buried layer 56, n type InP buried layer 57, and p type InP buried layer 5
8 and the p-type InGaAsP cap layer 59 are laminated in this order from the substrate 51 side. The growth of these layers flattens the surface of the wafer. A p-type InP buried layer 56 and an n-type InP buried layer 57 for reducing the reactive current flowing through the buried layer.
The height of the interface (pn junction surface) is controlled to approximately match the height of the active layer 54.

On the p-type InGaAsP cap layer 59, the p-side electrode 60 is formed on the substrate 5
An n-side electrode 61 is formed on the back surface of 1.

In this improved example, since the ridge is not formed on the surface of the substrate 51, the level difference on the wafer surface before forming the embedded layer is relatively small, and it is relatively easy to flatten the wafer surface by forming the embedded layer. Has been done.

However, it is difficult to accurately control the thickness of the buried layer so that the pn junction in the buried layer is formed near the active layer 54. Therefore, the manufacturing yield is reduced.

Further, when the SiO ₂ film is removed from the substrate 61 by etching using a hydrofluoric acid-based etching solution or the like, there is a problem that the mesa stripe-shaped laminated structure is also damaged by etching. This etching damage reduces the manufacturing yield and reliability of the semiconductor laser device.

The present invention has been made to solve the above problems, and an object of the present invention is to reduce the threshold current, in which the width of the active layer is controlled with high accuracy and stable oscillation occurs in a single basic horizontal mode. To provide a semiconductor laser device and a method for manufacturing the same.

Another object of the present invention is to provide a semiconductor laser device which does not need to control the layer thickness of the buried layer with high precision and which can be easily planarized, and a method for manufacturing the same.

(Means for Solving the Problems) A semiconductor laser device of the present invention includes a semiconductor substrate, a dielectric film formed on the semiconductor substrate, and a groove formed in the dielectric film and reaching the substrate. , A mesa-stripe-shaped laminated structure provided on the substrate in the groove, and buried layers provided on both sides of the laminated structure, and the main surface of the substrate is (10
0) plane, the groove is a groove along the <011> direction, and the laminated structure has a lower portion including an active layer and a semiconductor layer having a refractive index smaller than that of the active layer. And a side surface of the lower portion is a facet having a {111} plane, and a side surface of the active layer is covered with the semiconductor layer, whereby the above object is achieved. It

 Further, the embedded layer may be an SOG film.

The manufacturing method of the present invention comprises a step of forming a dielectric film on a semiconductor substrate having a (100) plane as a main surface, and forming a groove along the <011> direction in the dielectric film so as to reach the substrate. And a step of selectively growing a mesa-stripe-shaped multilayer film including an active layer only on the substrate in the trench, and removing the dielectric film from the refractive index of the active layer. And a step of forming a semiconductor layer having a small refractive index so as to cover the side surface of the active layer, whereby the above object is achieved.

(Example) Hereinafter, the present invention will be described with reference to Examples.

 FIG. 1 shows a sectional view of the first embodiment of the present invention.

Plane orientation (100) n-type InP substrate (carrier concentration n ~ 2 x
An amorphous dielectric film 2 made of a SiO ₂ film is provided on 10 ¹⁸ cm ⁻³ ) 1. The dielectric film 2 is provided with a groove 12 having a width of 5 μm which reaches the substrate 1 along the [011] direction (resonator direction, perpendicular to the drawing). Since the groove 12 reaching the substrate 1 is provided in the dielectric film 2, a drive current flows between the electrodes via the groove 12.

On the substrate 1 in the groove 12, an n-type InP buffer layer (layer thickness 1
μm, carrier concentration n to 1 × 10 ¹⁸ cm ⁻³ 3, n-type InP clad layer (layer thickness 1 μm, carrier concentration n to 1 × 10 ¹⁸ c)
m ⁻³ ) 4, non-doped InGaAsP active layer (layer thickness 0.2 μm, oscillation wavelength 1.3 μm) 5, and p-type InP clad layer (layer thickness 1.5)
A mesa-stripe-shaped multilayer film in which μm and carrier concentration p˜1 × 10 ¹⁷ cm ⁻³ ) 6 are laminated in this order from the substrate 1 side is provided, and a double hetero structure is formed. The mesa-stripe-shaped multilayer film is the lower portion 13 of the mesa-stripe-shaped laminated structure described later. The cross-sectional shape of the lower portion 13 of this mesa-stripe-shaped laminated structure is triangular, and its side surface is a (111) B-facet. The angle formed by the (111) B plane and the surface of the substrate 1 is 54.7 degrees. Therefore, the width of the active layer 5 geometrically determined by this angle, the width of the groove 12 and the layer thicknesses of the n-type InP buffer layer 3 and the p-type InP clad layer 4 is 2 μm.

A p-type InP layer (layer thickness 2 μm, carrier concentration P˜1 × 10 ¹⁸ cm ⁻³ ) 7 having a refractive index smaller than that of the active layer 5 is formed on the lower portion 13 of the mesa stripe laminated structure. ,
It is formed so as to cover the side surface of the active layer 5.

On the p-type InP layer 7, a p-type InGaAsP cap layer (layer thickness 0.
5 μm, carrier concentration p to 6 × 10 ¹⁸ cm ⁻³ ) 8 are formed.

Thus, the n-type InP buffer layer 3, the n-type InP clad layer 4, the non-doped InGaAsP active layer 5, and the p-type InP clad layer 6 are laminated in this order from the substrate 1 side to form the lower portion 13 of the mesa stripe-shaped laminated structure. , The InP layer 7 and the InGaAsP cap layer 8 together with the upper portion 14 of the mesa stripe laminated structure form a mesa stripe laminated structure.

The cross-sectional shape of the mesa striped laminated structure is hexagonal, as shown in FIG. p-type InP layer 7 and p-type InGaA
The sP cap layer 8 is not formed on the dielectric layer 2 made of SiO ₂ .

As an embedded layer, the insulating property was excellent on the region of the substrate 1 other than the region where the mesa stripe-shaped laminated structure was provided.
An SOG film (Spin On Glass film) 9 is provided so as to cover the side surface of the mesa stripe-shaped laminated structure.

The side surface of the mesa striped laminated structure is filled with the SOG film 9 so that the upper surface of the wafer is flattened. AuZn is on the top surface of these flattened wafers.
An electrode 10 and an AuGe electrode 11 are formed on the back surface of the substrate 1.

As described above, the mesa stripe-shaped laminated structure of the semiconductor laser device of the present embodiment includes the mesa stripe-shaped laminated structure lower portion 13 having the side surface of the (111) B-facet. Since the angle formed by the (111) B-facet and the surface of the substrate 1 is a crystallographically determined value (54.7 degrees), the semiconductor laser device of this embodiment has this angle, the width of the groove 12 and n.
The active layer 5 has a width with a small variation determined by the layer thicknesses of the type InP buffer layer 3 and the n-type InP clad layer 4. Therefore, the horizontal transverse mode of the oscillating laser light is unified and stabilized. Moreover, variations in oscillation characteristics among the elements are reduced.

The side surface of the InGaAsP active layer 5 in the lower portion 13 of the mesa stripe-shaped laminated structure is covered with the p-type InP layer 7 having a lower refractive index than the active layer 5 in the upper portion 14 of the mesa stripe.
Therefore, the laser light generated inside the active layer 5 is effectively confined inside the active layer 5. Further, due to the built-in potential (diffusion potential) generated at the interface between the InGaAsP active layer 5 and the p-type InP layer 7, the carriers injected into the active layer 5 are confined in the active layer 5. As a result, the injected carriers contribute to laser oscillation efficiently, and the threshold current level is reduced.

Further, the lower portion 13 of the mesa-stripe-like laminated structure including the active layer 5 is surrounded by the p-type InP layer 7 having a relatively high thermal conductivity of the upper portion 14 of the mesa-stripe-like laminated structure. The heat generated in 1 is quickly radiated from the lower portion 13 to the buried layer. Moreover, since the thermal expansion coefficient of the InGaAsP active layer 5 and the thermal expansion coefficient of the p-type InP layer 7 are relatively close to each other, a thermal expansion coefficient near the interface between the InGaAsP active layer 5 and the p-type InP layer 7 There is no occurrence of crystal defects due to the difference,
Interface states are hard to form. Therefore, according to the configuration of this embodiment, a long-life semiconductor laser device having excellent temperature characteristics and reliability can be obtained. It is difficult to obtain these excellent characteristics depending on the structure in which the lower portion 13 of the mesa stripe-shaped laminated structure and the SOG film 9 are in direct contact with each other.

The SOG film 9 which is a buried layer has a higher insulation property and a lower dielectric constant than a semiconductor layer which has been conventionally used as a buried layer, so that the reactive current flowing through the buried layer is reduced, and moreover,
It is possible to exhibit excellent characteristics in high-speed response.

The current-light output characteristics of a semiconductor laser device having a semiconductor layer that emits long-wavelength laser light as an active layer is usually
It easily changes due to temperature changes. In particular, the current-light output characteristics of a semiconductor laser device having a structure in which a pn junction to which a reverse bias voltage is applied is provided in the buried layer is
Since the amount of leakage current of the junction changes depending on the temperature strongly, it becomes even more likely to change due to the temperature change.
Therefore, as in the structure of the present embodiment, SO that does not have a pn junction is used.
The configuration using the embedded layer made of the G film is suitable as a configuration of a semiconductor laser device that oscillates a laser beam having a long wavelength.

Hereinafter, a method for manufacturing the semiconductor laser device shown in FIG. 1 will be described with reference to FIG.

First, a plasma is formed on the n-type InP substrate 1 having a plane orientation (100).
A dielectric film 2 made of a SiO ₂ film was formed by using the CVD method.
Next, a groove 12 having a width of 5 μm was formed in the dielectric film 2 along the [011] direction by a normal photo-etching process (FIG. 2 (a)). The depth of the groove 12 is the substrate 1
The etching conditions were adjusted so that

Next, by selective growth using the MOCVD method, a multi-layer film to be the mesa-stripe-shaped lower portion 13 of the mesa-stripe-shaped laminated structure was selectively grown on the substrate 1 in the groove 12 (FIG. 2 (b)). During crystal growth, the n-type InP buffer layer 3, the n-type InP clad layer 4, the non-doped InGaAsP active layer 5, and the p-type InP clad layer 6 are continuously formed in this order from the substrate 1 side by adjusting the gas species and the like. Grown up. At this time,
The substrate temperature was kept at about 650 ° C and the atmospheric pressure was kept at about 10 Torr. Under this selective growth condition, there is a plane orientation dependence of the growth rate that crystal growth does not occur on the (111) B plane, and (111) B plane facets are formed on the side surfaces of the multilayer film after crystal growth. Was done. Thus, on the groove 12 along the [011] orientation, the mesa-stripe-like laminated structure lower portion 13 whose side surface is the (111) B plane and whose cross-sectional structure is triangular was formed.

Next, the p-type InP layer 7 is formed by the LPE method (growth temperature 600 ° C.).
And a p-type InGaAsP cap layer 8 were sequentially formed to form a mesa stripe-shaped laminated structure (FIG. 2 (c)). Although each of these layers does not grow on the dielectric layer 2 made of SiO ₂ ,
It has grown on the (111) plane of the lower portion 13 of the mesa stripe-shaped laminated structure.

Thus, the side surface of the active layer 5 was covered with the p-type InP layer 7 having a refractive index lower than that of the active layer 5.

Next, the SOG solution was applied onto the wafer by a spin coating method to flatten the surface of the wafer having irregularities formed by the mesa stripe-shaped laminated structure. Used at this time
The SiO ₂ concentration in the SOG solution was 20%. When applying the SOG solution, the wafer was spun at 1000 rpm for 30 seconds. After coating, the wafer was baked at 450 ° C. for 30 minutes. Thus, the glass-like SOG film 9 was formed on the dielectric film 2 so as to fill the outside of the mesa stripe-shaped laminated structure (FIG. 2 (d)).

AuZn electrode 10 on the wafer surface flattened by SOG film 9
Was formed. An AuGe electrode 11 was formed on the back surface of the substrate 1 (Fig. 2 (e)). Thus, the semiconductor laser device of FIG. 1 was formed.

As described above, in this embodiment, the active layer 5 having a predetermined width is used.
In order to form the film with a high yield, a multi-layer film including the active layer 5 was selectively grown on the groove 12 on the substrate 1 in a mesa stripe shape by MOCVD. Thus, (11
1) A facet having a B side was formed. Since the angle formed by the (111) B-facet and the surface of the substrate 1 is a crystallographically determined value (54.7 degrees), it is n-type relative to the width of the groove 12.
The width of the active layer 5 could be controlled with high accuracy by adjusting the layer thicknesses of the InP buffer layer 3 and the n-type InP clad layer 4. In this embodiment, the step of deeply etching a predetermined portion of the multilayer film formed on the entire surface of the wafer as in the conventional case is not necessary. Therefore, even though the design dimension of the width of the active layer 5 is about 2 μm, there is a deviation from this value.
It was easy to suppress the thickness to 0.1 μm or less. Therefore, the width of the active layer 5 can be controlled with good reproducibility.
There is no longer a large variation in width.

Further, since the SOG film 9 provided as the buried layer is a high resistance layer having excellent adhesion to the dielectric film 2, it is possible to manufacture a semiconductor laser device having a good yield and a low threshold current. Further, according to the method of forming the buried layer using the SOG film 9 of this embodiment, a film having a flat surface can be easily formed by the spin coating method, and therefore the buried layer is formed by using the semiconductor layer by the crystal growth method. The wafer surface could be easily planarized as compared with the conventional method of forming the.

FIG. 3 shows a sectional view of a semiconductor laser device of another embodiment.

The direction along the groove of the semiconductor laser device of FIG.
1], the direction of the groove of the semiconductor laser device of this example is the direction indicated by [01]. Therefore, in the present embodiment, the cross-sectional shape of the mesa stripe-shaped laminated structure lower portion 13 selectively grown by the MOCVD method is a hexagon as shown in FIG. The active layer 5 is composed of a layer portion parallel to the substrate 1 and a layer portion inclined with respect to the substrate 1.

The lower part of this example in which a double heterostructure is formed
The side surface of 13 is also similar to the side surface of the lower portion 13 of the above-described embodiment.
It is the {111} plane. An n-type having a lower refractive index than the active layer 5 is formed on the lower portion 13 so as to cover the side surface of the active layer 5.
InP layer 7 is selectively formed, and p-type In is formed on n-type InP layer 7.
A GaAsP cap layer 8 is formed.

Also in this embodiment, the n-type InP buffer layers 3, n
-Type InP clad layer 4, non-doped InGaAsP active layer 5, and p-type InP clad layer 6 are laminated in this order from the side of the substrate 1 and include a mesa stripe-shaped laminated structure lower part 13, an InP layer 7 and an InGaAsP cap layer 8. The upper part 14 of the mesa-stripe laminated structure forms a mesa-stripe laminated structure.

The laser light is confined in the portion of the active layer 5 that is parallel to the surface of the substrate 1. In order to perform laser oscillation in a single basic horizontal transverse mode, the width of the layer of the active layer 5 parallel to the substrate 1 must be set to about 2 μm.
Therefore, it is necessary to make the width of the groove formed in the dielectric layer 2 narrower than the width of the groove of the semiconductor laser device shown in FIG.

Like the semiconductor laser device of the above-described embodiment, the semiconductor laser device of the present embodiment also exhibits excellent temperature characteristics and reliability, small reactive current, and high-speed response.

In each of the above-mentioned embodiments, an example using the InGaAsP / InP-based semiconductor material has been described, but other systems, for example, Ga
A semiconductor laser device using a semiconductor material such as AlAs / GaAs system can also exhibit the same effect as the above embodiment.
At this time, as the semiconductor layer formed on the lower portion 13 of the mesa stripe-shaped laminated structure having the side surfaces of the {111} plane, a semiconductor layer having the same composition as the cladding layer in the lower portion 13 can be used.

As a method of selectively growing the mesa-stripe-like laminated structure lower portion 13 having a {111} facet surface on the substrate in the groove, the MBE method can be used in addition to the MOCVD method.

Regarding the conductivity type of the semiconductor substrate and each semiconductor layer, the conductivity type of the embodiment may be reversed.

As the dielectric layer, other than the SiO ₂ layer, a layer made of another dielectric material, for example, a SiN _X layer, an Al ₂ O ₃ layer, or a resin layer such as a photosensitive polyimide or a resist is suitable.

As the burying layer, a film made of a resin such as a polyimide resin may be used instead of the SOG film.

(Effect of the Invention) As described above, the semiconductor laser device of the present invention has the mesa-stripe double hetero structure having the {111} face side surface and has the active layer whose width is adjusted to a desired value with high precision. Therefore, it oscillates stably in a single basic horizontal transverse mode.

Since the side surface of the active layer is covered with the semiconductor layer having a refractive index lower than that of the active layer, the laser light generated inside the active layer is effectively confined in the active layer.

Further, due to the built-in potential (diffusion potential) generated at the interface between the active layer and the semiconductor layer, the carriers injected into the active layer are confined in the active layer. As a result, the injected carriers contribute to laser oscillation efficiently, and the threshold current level is reduced. Moreover, since the thermal expansion coefficient of the active layer and the thermal expansion coefficient of the semiconductor layer are relatively close to each other,
In the vicinity of the interface between the active layer and the semiconductor layer, there is no occurrence of crystal defects or the like due to the difference in coefficient of thermal expansion, and it is difficult to form the interface level.

If SOG film is used as the buried layer, SOG with excellent thermal conductivity
Since the film fills the outside of the mesa stripe-shaped laminated structure, good temperature characteristics can be obtained.
Since the SOG film has a high insulating property and a low dielectric constant, the reactive current flowing through the buried layer is reduced, and moreover, it is possible to exhibit oscillation characteristics excellent in high-speed response.

As described above, according to the present invention, there is provided a semiconductor laser device which has excellent temperature characteristics and reliability, has a low oscillation threshold, and oscillates in a single fundamental transverse mode.

According to the manufacturing method of the present invention, it is possible to selectively grow a double hetero structure mesa-stripe-shaped multilayer film having a {111} plane side surface in a groove on a substrate. Therefore, the active layer width can be controlled with high reproducibility and high accuracy, and a large variation in the active layer width does not occur. Therefore, it is possible to form a semiconductor laser device that operates stably in the single basic horizontal transverse mode with a high yield.

When the SOG film is used as the burying layer, the SOG film is a high resistance layer having excellent adhesion to the dielectric film, so that the reactive current flowing through the burying layer is reduced and the yield of semiconductor laser devices with a low oscillation threshold is improved. It can be manufactured. Also, since the SOG film with a flat surface can be easily formed by the spin coating method, it is easier to flatten the wafer surface as compared with the conventional method of forming the buried layer using the semiconductor layer by the crystal growth method. Is.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention, FIGS. 2 (a) to 2 (e) are sectional views for explaining a manufacturing method of the first embodiment, and FIG. 4 is a sectional view showing an embodiment of
FIG. 6 to FIG. 6 are sectional views showing conventional examples. 1 ... n-type InP substrate, 2 ... dielectric film, 3 ... n-type InP buffer layer, 4 ... n-type InP clad layer, 5 ... undoped InGaAsP active layer, 6 ... p-type InP clad layer, 7 ... p
Type InP layer, 8 ... p type InGaAsP cap layer, 9 ... SOG
Membrane, 10 …… AuZn electrode, 11 …… AuGe electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Okumura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Co., Ltd. Incorporated (72) Inventor Haruhisa Takiguchi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (56) Reference JP-A-3-183182 (JP, A) JP-A-58-73175 (JP) , A)

Claims (3)

[Claims] 1. A semiconductor substrate, a dielectric film formed on the semiconductor substrate, a groove formed in the dielectric film to reach the substrate, and provided in the groove on the substrate. A laminated structure having a mesa stripe shape, and embedded layers provided on both sides of the laminated structure, a main surface of the substrate is a (100) surface, and the groove is a groove along the <011> direction, The laminated structure includes a lower portion including an active layer and an upper portion including a semiconductor layer having a refractive index lower than that of the active layer, and a side surface of the lower portion is {111 } Facets, and the side surface of the active layer is covered with the semiconductor layer. 2. The semiconductor laser device according to claim 1, wherein the buried layer is an SOG film. 3. A step of forming a dielectric film on a semiconductor substrate having a (100) plane as a main surface, and a step of forming a groove along the <011> direction on the dielectric film so as to reach the substrate. And a step of selectively growing a mesa-stripe-shaped multilayer film including an active layer only on the substrate in the groove, and a refraction smaller than the refractive index of the active layer without removing the dielectric film. Forming a semiconductor layer having a certain ratio so as to cover the side surface of the active layer, and a method for manufacturing a semiconductor laser device.