JP2000196203A - Semiconductor laser and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser which can generate the light of two wavelengths with one element. SOLUTION: Light emitting parts 1 and 2 containing double-heterojunction and a current block layer are formed on different substrates 6 and 7. Substrate sides are overlapped and are thermally treated so as to joint them. The respective light emitting parts can arbitrarily select luminous wavelengths decided by materials and respective semiconductor layers can be grown at an optimum temperature. The luminous spots of the respective light emitting parts can be set to the distances of several 10 μm-100 μm. An InGaP system material or an InGaAlP system material is used for the double heterojunction of one light emitting part and a GaAs system material or an AlGaAs system material for the double heterojunction of the other light emitting part. Thus, a semiconductor laser emitting the light of a 650 nm band or a 780 nm band can be 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 used for an optical information recording / reproducing apparatus and a method for manufacturing the same.

[0002]

2. Description of the Related Art A digital versatile disk (DVD), which is a next-generation optical disk, has a recording capacity of 135 images.
Since it is possible to reproduce a moving image of a minute and a capacity of 4.7 Gbytes can be recorded as an information record, it is expected to be developed by inheriting a conventional compact disc (CD).

In this DVD reproducing apparatus, a DVD
(Video recording), DVD-ROM (information recording), DVD-
In addition to the reproduction of R (write once information recording) and data reading, the reproduction of CD (video recording), CD-ROM (information recording), and CD-R (write once information) and data reading are performed. This is also a necessary item for migrating from a conventional CD to a DVD.

[0004] DVDs have two major differences from conventional CDs in the following two respects.

[0005] The first difference is the thickness of the substrate of the optical disk. In the CD, the thickness of the substrate was 1.2 mm.
In VD, it is 0.6 mm. This is because when the numerical aperture NA of the condensing lens is increased in order to improve the recording density, the tolerance for the inclination of the optical disk is increased.

[0006] The second difference is the wavelength of the semiconductor laser used in the pickup. The wavelength of a semiconductor laser is 780 nm for a conventional CD, and 650 nm for a DVD.
Semiconductor laser is used. This is because the size of the focused spot is proportional to the wavelength.

For a pickup that reads information, reading two types of optical discs having different substrate thicknesses requires
Difficult in terms of aberration. Therefore, if a lens system designed to read a substrate thickness of 0.6 mm is used as it is, a disk with a substrate thickness of 1.2 mm cannot be read.

Therefore, various methods have been considered as a method of reading disks having different thicknesses. For example,
As described in "Electronic Materials, June 1996, p. 38", a method of switching between two types of objective lenses for CD and DVD, a method of using a bifocal lens as an objective lens, and a liquid crystal. A method using a shutter, etc. With these methods, it is possible to read two types of disks having different substrate thicknesses, and to read a conventional CD or CD-ROM using a DVD reproducing device.

However, it is difficult for the above method to read CD-Rs currently in circulation. The reason is that the once-written CD-R is 780n as a recording method.
This is because a dye that responds to light having a wavelength of m is used. To read this type of CD-R, a wavelength of 7
An 80 nm semiconductor laser is required.

A DV from which this CD-R can be read
The following configuration can be considered as the pickup for D.

First, it is conceivable to provide a pickup with two pickups, a pickup for CD and a pickup for DVD. In this case, each pickup is independent, and a pickup dedicated to DVD has an emission wavelength of 65 nm.
A semiconductor laser of 0 nm and an objective lens of NA 0.6 are used, and a semiconductor laser with an emission wavelength of 780 nm and an objective lens of NA 0.45 are used for a pickup exclusively for CD. However, this method leads to an increase in size and cost of the reproducing apparatus.

However, since the DVD device has been required to be reduced in price from the beginning of its sale, cost reduction is an important key point. For this purpose, one pickup is mounted on the DVD device, and the emission wavelength is 780 nm and 650 nm.
There is a need for a method using two types of light. So 2
By incorporating a semiconductor laser that generates light of various wavelengths into a pickup, a pickup device that can read all CDs and CD-ROMs including a CD-R at low cost can be obtained. .

As a semiconductor laser capable of generating light of these two wavelengths, the following has been conventionally proposed.

(1) A method of incorporating two types of semiconductor laser chips inside a semiconductor laser package and emitting two types of light.

(2) As disclosed in JP-A-3-9589, a method in which adjacent semiconductor laser chips on the same wafer are oscillated at different wavelengths by changing the thickness of the coating film.

(3) As disclosed in Japanese Patent Application Laid-Open No. 61-19186, in adjacent semiconductor lasers on the same wafer, if the Al content of the active layer is changed by changing the width of the groove below the active layer. And change the oscillation wavelength.

(4) As disclosed in JP-A-3-30388, a double heterojunction comprising a first active layer and second and third cladding layers is formed on a substrate, and A method for forming a double hetero junction comprising a second active layer and fourth and fifth cladding layers.

[0018]

However, in the above method (1), the distance between the light emitting spots becomes a problem.
When two light beams having different wavelengths are handled by using the same lens system in the pickup, the distance between the light emitting spots needs to be at least 100 μm or less. In a package having a normal shape, the distance between the light emitting spots is 100 μm or more because the semiconductor laser chips are arranged side by side.
Furthermore, by attaching the chip to the package,
An error of about 0 μm occurs.

The above methods (2) and (3) have a problem that a large wavelength difference cannot be obtained. In either method, since each active layer is formed in one growth step, the material system is the same. For example, although there is a slight difference in the Al mixed crystal ratio, AlGaAs is used in the 780 nm band.
It is a system material, and its wavelength difference is at most about 10 nm.
In order to obtain compatibility with a CD-R in a DVD pickup, it is necessary to generate emission wavelengths in the 780 nm band and the 650 nm band. Therefore, in order to generate light in the 650 nm band, GaI is used as an active layer and a cladding layer.
It is necessary to use an nP-based material and an AlGaInP-based material. Therefore, in order to obtain two kinds of wavelengths, it is necessary to form the double hetero junction composed of the active layer and the cladding layer using completely different materials.

Further, the method (4) has the following problem.

First, Japanese Patent Application Laid-Open No. Hei.
The semiconductor laser shown in the embodiment is of a type called a ridge structure. This structure is grown by vapor phase epitaxy (metalorganic vapor phase epitaxy: MOCVD) and molecular beam epitaxy (MBE). According to a similar experiment conducted by the present inventors, in this structure, the surface of the ZnSSe layer after the growth of the ZnSSe layer and removal of SiO ₂ is not flat but convex. MOCVD on it
When a p-GaAs contact layer, a clad layer, an active layer and a clad layer are sequentially grown by the MBE method or the MBE method, the p-GaAs contact layer
Since the growth is performed while maintaining the shape of the layer, the active layer has a curved structure. In such a structure in which the active layer is curved, the reliability when the semiconductor laser is operated at a high temperature is deteriorated, and the semiconductor laser cannot be used by being incorporated in an actual pickup.

Next, Japanese Patent Laid-Open Publication No. Hei.
The semiconductor laser shown in the embodiment is of a type called a VSIS structure. This structure is difficult to manufacture by the vapor phase growth method, so the liquid phase growth method (LPE method)
Grow with. However, with this configuration, it is not possible to obtain the required 650 nm band laser light. The reason is that an AlGaInP layer needs to be used as a cladding layer in a double heterojunction that generates light of a wavelength in the 650 nm band, but AlGaInP cannot be grown by the LPE method.

Another problem of the above method (4) is that
The growth temperature. When the material of the active layer or the cladding layer is different, the optimum growth temperature is usually different. For example, when an active layer and a cladding layer are grown on a semiconductor substrate using a GaInP / AlGaInP-based material and then an active layer and a cladding layer are grown on an AlGaAs-based material, GaInP / A
The optimum growth temperature is about 600 ° C. for the 1GaInP-based material, and about 800 ° C. for the AlGaAs-based material.
° C. Therefore, the active layer or the cladding layer made of the GaInP / AlGaInP-based material is exposed to a temperature higher than the optimum growth temperature. If the temperature is maintained at a temperature higher than the optimum growth temperature for a long time, impurities and the like in the device diffuse to diffuse the device characteristics (threshold current density and reliability).
Is worse.

The present invention has been made to solve such problems of the prior art, and can generate light of two wavelengths, obtain good element characteristics, and can be used in a pickup. It is an object to provide a possible semiconductor laser and a method for manufacturing the same.

[0025]

According to a semiconductor laser of the present invention, a first light emitting portion including a first active layer is provided on a first substrate, and a second active layer is provided on a second substrate. Including the first
A second light emitting unit that emits light having a wavelength different from that of the light emitting unit is provided, and the substrate sides are joined together, the light emitting unit sides are joined, or one substrate side and the other light emitting unit side are joined. This achieves the above object.

The light emitting section may have a double hetero junction in which an active layer is sandwiched between a first conductive type first clad layer and a second conductive type second clad layer.

[0027] The light emitting section may further include a current blocking layer.

The double heterojunction of one of the light emitting portions is InG
aP-based material or InGaAlP-based material, and the double heterojunction of the other light emitting portion is made of GaAs-based material or AlG
It may be made of an aAs-based material.

The p-type impurity of the cladding layer may be Be.

A method for manufacturing a semiconductor laser according to the present invention is a method for manufacturing a semiconductor laser according to the present invention, wherein a first light emitting portion including a first active layer is formed on the first semiconductor substrate. Forming a second light emitting unit including a second active layer on the second semiconductor substrate; and connecting the substrate sides, the light emitting unit sides, or one substrate side and the other light emitting unit side. Superimposing and joining by heat treatment, whereby the object is achieved.

Hereinafter, the operation of the present invention will be described.

In the present invention, light emitting portions including a double hetero junction, a current blocking layer, and the like are formed on separate substrates, and the light emitting portions on the substrate side, the light emitting portions on the other side, or the light emitting portions on one substrate side and the other on the other side. The light emission wavelength determined by the material can be arbitrarily selected in each light emitting portion, and the growth of each semiconductor layer must be performed at an optimum temperature. Can be.

After forming a double hetero junction or a current blocking layer on each semiconductor substrate, the two substrates are overlapped and joined to each other, so that the light emitting spot of each light emitting portion is several tens μm.
From about 100 μm or less.

Further, the double hetero junction and the current blocking layer can be grown on a proven substrate such as a GaAs substrate in the same manner as a normal semiconductor laser. A structure and configuration that have been used in semiconductor lasers can be used. The initial characteristics and reliability of the semiconductor laser can be made similar to those of a normal semiconductor laser.

The positions of the light emitting portion on the first substrate and the light emitting portion on the second substrate can be determined by photolithography by using a specific location on the substrate for positioning. In addition, the bonding of the substrate and the light emitting unit can be performed with high accuracy by using a specific location of the substrate.

The double heterojunction of one of the light emitting sections has InG
An aP-based material or an InGaAlP-based material is used, and a GaAs-based material or an AlGa
By using an As-based material, the 650 nm band and 78
Since a semiconductor laser that emits light in the zero band can be obtained, DV
It can be used for D pickup. With the optical disk pickup using the semiconductor laser, not only DVD disks but also CD disks, CD-ROM disks, and CD-R disks can be read.

When the p-type impurity of the cladding layer is Be, since the diffusion coefficient is lower than that of Zn, the threshold current does not increase by the heat treatment at the time of bonding.

[0038]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 shows a front view of the present invention.

This semiconductor laser has a first substrate 6 provided with a first light emitting section 1 for generating light in a 780 nm wavelength band.
And a second substrate 7 provided with a second light-emitting unit 2 that emits light in a wavelength range of 650 nm.

The first light emitting section 1 comprises an n-type GaAs substrate 6, an n-type cladding layer 8, an active layer 9 and a p-type cladding layer 10.
Is provided. A p-cladding layer 12 is formed thereon via an etching stop layer 11.
And a stripe-shaped mesa portion 24 composed of the p-contact layer 13. Current blocking layers 25 are provided on both sides of the mesa section 24.

The second light emitting section 1 has a double hetero junction comprising an n-cladding layer 21, an active layer 41 and a p-cladding layer 14 provided on an n-GaAs substrate 7. Light guide layers 43 and 42 are provided between the layers. A stripe-shaped mesa portion 31 composed of the p-cladding layer 16, the p-intermediate band gap layer 17, and the p-contact layer 18 is provided thereon via the etching stop layer 11. The current block layers 20 are provided on both sides of the mesa unit 31.

An electrode 34 is provided on the first light emitting portion 1, and a common electrode 50 is provided on an exposed portion of the n-GaAs substrate 6, and the lead wire 3 is connected. An electrode 33 is provided on the second light emitting unit 2 and is fused on the stem 100. Then, the common electrode 50 and the stem 10
By passing a current between 0 and 0, light with a wavelength of 635 nm is emitted. By passing a current between the common electrode 50 and the electrode 34, light with a wavelength of 780 nm is emitted.

This semiconductor laser can be manufactured, for example, as follows.

First, the fabrication of the first light emitting section 1 will be described.

As shown in FIG. 2A, the thickness is 100 μm.
N-GaAs substrate 6 on the n-GaAs substrate 6 by MOCVD.
1GaAs (for example, Al _0.45 Ga _0.55 As) cladding layer 8, AlGaAs (Al _0.15 Ga _0.85 As) active layer 9,
p-AlGaAs (for example, Al _0.45 Ga _0.55 As) cladding layer 10 and p-AlGaAs etching stop layer 1
1. p-AlGaAs (for example, Al _0.45 Ga _0.55 As)
A cladding layer 12 and a p-GaAs contact layer 13 are sequentially grown. The substrate temperature at this time was 800 ° C., Zn was used as a p-type dopant, and S was used as an n-type dopant.
Use i.

Next, by depositing an Al ₂ O ₃ film as a mask layer thereon, is patterned an Al ₂ O ₃ film in a stripe shape by photolithography. At this time, the position of the stripe portion is determined based on the orientation flat of the wafer. Thereafter, wet etching is performed using the Al ₂ O ₃ film as a mask to remove portions of the contact layer 13 and the cladding layer 12 corresponding to both sides of the Al ₂ O ₃ film. Thus, the mesa portion 24 is formed immediately below the Al ₂ O ₃ film. When removing the cladding layer 12, selective etching with the etching stop layer 11 is performed to stop the etching reliably.

After that, a second growth is performed by the MOCVD method to form the n-GaAs current blocking layers 25 on both sides of the mesa portion 24. The growth at this time is n-GaAs.
This is performed under the condition that the s layer is not formed on the Al ₂ O ₃ film.

Next, the fabrication of the second light emitting section 2 will be described.

As shown in FIG. 2B, n- (Al _0.7 Ga _0.3 ) is formed on the n-GaAs substrate 7 by MOCVD.
_0.52 In _0.48 P clad layer 21, (Al _0.5 Ga _0.5 )
_0.52 In _0.48 P optical guiding layer 43, multiple quantum well active layer (four layers) 41, (Al _0.5 Ga _0.5 ) _0.52 In _0.48 P optical guiding layer 42, p- (Al _0.7 Ga _0.3 ) _0.52 In _0.48 P cladding layer 14. , P-GaInP etching stop layer 1
5, p-AlGaInP cladding layer 16 and p-GaI
An nP intermediate band gap layer 17 and a p-GaAs contact layer 18 are sequentially grown. The growth temperature at this time is 74
At 0 ° C., Zn is used as a p-type dopant, and Si is used as an n-type dopant. Here, although the optimum growth temperature differs depending on the material of the active layer and the cladding layer, since each light emitting portion is formed on a separate substrate, it is possible to grow at each optimum temperature.

Next, by depositing an Al ₂ O ₃ film as a mask layer thereon, is patterned an Al ₂ O ₃ film in a stripe shape by photolithography. At this time, the position of the stripe portion is determined based on the orientation flat of the wafer as in the case of manufacturing the light emitting section 1. Thereby, the stripe-shaped mesa portions 24 of the light-emitting portions 1 and 2,
31 can be accurately adjusted. Then A
Using the l ₂ O ₃ film as a mask, wet etching is performed to remove portions of the contact layer 18, the intermediate band gap layer 17, and the cladding layer 16 corresponding to both sides of the Al ₂ O ₃ film. As a result, the mesa portion 31 is formed immediately below the Al ₂ O ₃ film. When removing the cladding layer 16, selective etching with the etching stop layer 15 is performed to stop the etching reliably.

After that, a second growth is performed by the MOCVD method to form the n-GaAs current block layers 20 on both sides of the mesa portion 31. The growth at this time is n-GaAs.
This is performed under the condition that the s layer is not formed on the Al ₂ O ₃ film.

Next, the first substrate 6 provided with the light emitting section 1 and the second substrate 7 provided with the light emitting section 2 are joined as follows.

First, H ₂ SO ₄ , H ₂ O ₂ and H ₂
The surfaces of the first substrate 6 and the second substrate 7 are etched with a mixed solution of O, hydrofluoric acid treatment is performed, and then water washing and drying are performed. Then, as shown in FIG. 2C, the first substrate 6 and the second substrate are overlapped with the stripe direction being the same direction for the first substrate 6 and the second substrate 7. At this time, position alignment is performed by adjusting the orientation flat.

Next, the two substrates thus superimposed are placed on a boat 6
1 and 20g / cm on it ^TwoFrom carbon
Put the weight 60 and H_Two30 at 600 ° C under atmosphere
Leave for a minute. Thereby, the n-GaAs substrate 6 and the n-
The GaAs substrate 7 is bonded at the atomic level, and as shown in FIG.
As shown, the light emitting unit 1 and the light emitting unit 2 are joined on the substrate side.
Wafer is obtained.

Next, in order to form the common electrode 50, the n-GaAs current blocking layer 25, the p-AlGaAs etching stop layer 11, and the p-type
-AlGaAs cladding layer 10, AlGaAs active layer 9
And a part of the n-AlGaAs cladding layer 8 is removed.

Then, as shown in FIG.
The electrodes 33 and 34 and the common electrode 50 are formed on the surface of the aAs contact layer 18, on the GaAs substrate 6 exposed by etching, and on the n-GaAs contact 11, respectively.

The manufactured wafer is divided and mounted on a package, and a semiconductor laser device is completed.

In the present embodiment, the threshold value of the light emitting section 1 which emits light at the wavelength of 780 nm is 52 mA, and the wavelength is 650 nm.
The threshold value was 50 mA in the light emitting unit 2 that emits light in nm.
Furthermore, the reliability was tested by conducting an energization test at a constant high temperature output.
An MTTF of 00 hours could be obtained.

Further, only the light-emitting section 1 and the light-emitting section 2 were fabricated to form electrodes, and the oscillation threshold was checked. In the light emitting unit 2, the threshold is 38.
mA. From these results, by performing direct coupling, the threshold value of the light emitting section 2 emitting light at 650 nm is about 12
It can be seen that the mA rises.

Therefore, in the following embodiment 2, the light emitting unit 2
Will be described with reference to an example manufactured by the MBE method.

(Embodiment 2) In this embodiment 2,
The light emitting unit 1 is manufactured in the same manner as in the first embodiment, and the light emitting unit 2 is manufactured as described below. Note that layers having the same function are described with the same reference numerals as in the first embodiment.

An n-type AlGaInP cladding layer 21, an AlGaInP light guide layer 43, a multiple quantum well active layer 41, an AlGaIn
P light guide layer 42, p-AlGaInP clad layer 1
4, p-GaInP etching stop layer 15, p-A
1GaInP cladding layer 16, p-GaInP intermediate band gap layer 17, and p-GaAs contact layer 18
Grow sequentially. The growth temperature at this time is 600 ° C.
Be is used as a p-type dopant, and Si is used as an n-type dopant.

The subsequent manufacturing method is the same as that of the first embodiment. The manufactured wafer is divided and mounted on a package.
The semiconductor laser device is completed.

In this embodiment, the threshold value of the light emitting section 1 emitting light at a wavelength of 780 nm is 51 mA, and the light emitting section 1 has a wavelength of 650 nm.
The threshold value was 39 mA in the light emitting unit 2 that emits light at nm.
Further, the reliability was tested by conducting an electricity test at a constant high temperature output.
An MTTF of 00 hours could be obtained.

When the second embodiment is compared with the first embodiment,
When the light emitting unit 2 emitting light at a wavelength of 650 nm is manufactured by MOCVD, the threshold current (It
h) is increased, but it is considered that it is not affected by the MBE method.

The light emitting section 2 emitting light at a wavelength of 650 nm is
The difference between the case manufactured by the CVD method and the case manufactured by the MBE method is that the p-type dopant is Be in the MBE method and MO
The point is that it is Zn in the CVD method.

This is probably because the diffusion coefficient of Be is lower than that of Zn. That is, at the junction temperature of the present embodiment, Zn diffuses in the semiconductor and Ith rises, while Be does not diffuse, so that the threshold current is almost the same as that in the case where the semiconductor laser is manufactured with a single light emitting portion. Is obtained.

In the first and second embodiments, n is required for manufacturing the common electrode 50 of the light emitting unit 1 and the light emitting unit 2.
-Although the cladding layer 8 is etched, the contact may be made by etching the n-side semiconductor layer. Specifically, the etching may be stopped at any part between the n-cladding layer 12 and the n-cladding layer 8 to form an electrode and make contact.

As described above, in order to take out the common electrode, G
When a part of the light emitting unit is removed by etching so as to reach the aAs substrate, irregularities are formed on the wafer surface.
Further, since the wafer is as thin as 100 μm or less, the wafer may be broken during the manufacturing process.

Therefore, in the following embodiment 3, an example in which impurity diffusion is performed to produce a common electrode will be described.

(Embodiment 3) In this embodiment 3,
The light emitting unit 1 and the light emitting unit 2 are formed on the GaAs substrate 6 and the GaAs substrate 7, respectively, and are fabricated in the same manner as in the first and second embodiments until the substrate side is joined. The common electrode is fabricated as follows. Do it. Note that layers having the same function are described with the same reference numerals as in the first embodiment.

As shown in FIG. 3A, for a wafer bonded by the substrates 6 and 7 having the light emitting unit 1 and the light emitting unit 2, the wafer is selected in the center between the adjacent stripe-shaped mesa portions 24 of the light emitting unit 1. Zn is implanted by an ion implantation method. At this time, the acceleration voltage is adjusted so that Zn reaches near the active layer 9. Next, by selective ion implantation,
Type. At this time, Si is implanted deeper than Zn. After each impurity is implanted, N
Anneal in _two atmospheres. The impurity diffuses by this annealing, and Zn diffuses more easily.
A p-type impurity diffusion region 15 in which Zn is diffused as shown in FIG.
2 and an n-type impurity diffusion region 153 in which Si is diffused is formed. Here, Si was used as the n-type impurity,
Other impurities can be applied as long as they are n-type impurities. Further, Zn is used as the p-type impurity, but other impurities can be applied as long as they are p-type impurities.

Next, an electrode 33 is formed on the entire surface of the contact layer 18, and a common electrode 50 is selectively formed on the portion where the impurity diffusion has been performed. The electrode 34 is selectively formed over the current blocking layer 25. Common electrode 50 and electrode 3
In order to selectively form 4, a lift-off method can be used in which a photoresist is left on unnecessary portions of the electrodes, an electrode film is formed thereon, and the portions on the photoresist are removed in an organic solvent. .

Thereafter, the manufactured wafer is divided and mounted on a package, and a semiconductor laser device is completed.

The semiconductor laser of the present embodiment has the common electrode 5
When a current flows between the common electrode 51 and the electrode 34, the light-emitting unit 1 oscillates, and when a current flows between the common electrode 51 and the electrode 33, the light-emitting unit 2 oscillates. This semiconductor laser has no irregularities on the wafer surface, and can prevent the wafer from cracking in the manufacturing process, thereby improving the productivity.

In the first to third embodiments, G
Although examples have been given of the aAs-based material and the AlGaInP-based material, other materials such as InGaAsP and ZnSS
Other materials such as e and GaN may be used. The light emitting section 1 is made of an AlGaAs-based material, and the light emitting section 2 is made of AlG
aInP-based material is used.
The light emitting unit 2 may be made of an AlGaAs-based material using an aInP-based material. Furthermore, the growth method is MBE or MOC.
Not limited to the VD method, a method such as the MOMBE method or the CBE method may be used. In the light emitting units 1 and 2, a second contact layer may be formed on the p-contact layer and the current block layer. The structure of the light emitting unit is as described in the first to third embodiments.
However, the present invention is not limited to those described above, and various structures that have been used in the past can be applied.

In the first to third embodiments, the surface to be joined is on the GaAs substrate side. However, the current blocking layer 25 of the light emitting section 1 and the GaAs substrate 7 of the light emitting section 2 may be joined. In that case, the distance between the light emitting portions is substantially equal to the light emitting portion 2
Therefore, the distance between the light emitting spots can be reduced to about 100 μm, which is the thickness of the substrate. Alternatively, the current blocking layer 20 of the light emitting unit 2 and the GaAs substrate 6 of the light emitting unit 1 may be joined. Alternatively, the light emitting unit 1
Current blocking layer 25 of the light emitting section 2
May be joined. In this case, the distance between the light emitting spots can be about 4 μm.

Furthermore, the pickup incorporating the semiconductor lasers of the first to third embodiments can generate 650 nm light and 780 nm light in a single path by using a double focus lens. Becomes Therefore, it is possible to read all DVDs and CD-related discs including the currently distributed CD-R.

[0080]

As described above in detail, in the case of the present invention, the emission wavelength determined by the material can be arbitrarily selected in each light emitting portion, and the growth of each semiconductor layer can be performed at the optimum temperature. It can be carried out. Therefore, it is possible to obtain a semiconductor laser that emits light of two wavelengths and has excellent initial characteristics and reliability.

Further, the light emitting spot of each light emitting portion is set to several tens.
The distance can be from about μm to about 100 μm or less.
Therefore, two different wavelengths of light can be used in the pickup by using the same lens system.

The double heterojunction of the first light emitting section is formed with InG
Using aP-based material or InGaAlP-based material, a GaAs-based material or AlGa
By using an As-based material, the 650 nm band and 78
A semiconductor laser that emits zero band light is obtained. Therefore,
With the optical disk pickup using this semiconductor laser, not only DVD disks but also CD disks,
A CD-ROM disc and a CD-R disc can be read, and a next-generation optical disc, DVD, can be developed.

[Brief description of the drawings]

FIG. 1 is a front view of a semiconductor laser according to a first embodiment.

FIG. 2 is a sectional view illustrating a manufacturing process of the semiconductor laser according to the first embodiment;

FIG. 3 is a sectional view illustrating a manufacturing process of the semiconductor laser according to the third embodiment;

[Explanation of symbols]

 1, 2 light emitting section 3 lead wire 6, 7 n-GaAs substrate 8 n-AlGaAs cladding layer 9 AlGaAs active layer 10, 12 p-AlGaAs cladding layer 11 p-AlGaAs etching stop layer 13, 18 p-GaAs contact layer 14, Reference Signs List 16 p-AlGaInP cladding layer 15 p-GaInP etching stop layer 17 p-GaInP intermediate band gap layer 20, 25 n-GaAs current blocking layer 24, 31 mesa unit 33, 34 electrode 41 multiple quantum well active layer 42, 43 AlGaInP light Guide layer 60 Weight 61 Boat

Claims (6)

[Claims] A first substrate including a first active layer on a first substrate;
A second active layer is provided on the second substrate, and the second active layer emits light of a different wavelength from that of the first light emitting unit.
And a light-emitting portion is provided, and the substrate side is connected to each other, the light-emitting portion sides are connected, or one substrate side and the other light-emitting portion side are joined. 2. The semiconductor laser according to claim 1, wherein the light emitting unit has a double hetero junction in which an active layer is sandwiched between a first cladding layer of a first conductivity type and a second cladding layer of a second conductivity type. 3. The semiconductor laser according to claim 2, wherein said light emitting unit further has a current blocking layer. 4. The double heterojunction of one of the light emitting sections is In
The light emitting portion is made of a GaAs-based material or an AlGaP-based material.
4. The semiconductor laser according to claim 2, wherein the semiconductor laser is made of a GaAs-based material. 5. The semiconductor laser according to claim 2, wherein the p-type impurity of the cladding layer is Be. 6. The method for manufacturing a semiconductor laser according to claim 1, wherein a first light emitting portion including a first active layer is formed on the first semiconductor substrate. Forming a second light emitting unit including a second active layer on the second semiconductor substrate; and connecting the substrate sides, the light emitting units, or one substrate side and the other light emitting unit side. And bonding by heat treatment.