JP2001044563A - Semiconductor laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a red color semiconductor laser having little waveguide absorption loss where optical damages in the resonator end surface is suppressed. SOLUTION: By forming an AlGaInP optical waveguide layer 09 on a GaInP etching-stop layer 106 in a tripe region, a real refractive index of the stripe region increases, and a real refractive index waveguide type semiconductor laser can be constituted. A current block layer on the outside of the stripe region is formed with AlGaInP, whose band gap is larger than that of an active layer 105, so that absorption loss of laser beam can be reduced. Furthermore, Al composition of AlGaInP current block layers 107 and 108 is almost equal to the Al composition of a second conductivity-type AlGaInP clad layer 110, so that the Al composition is not increased and that the optical damage level of a laser resonator end surface also will not increase.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a semiconductor laser device that oscillates at 0 nm.

[0002]

2. Description of the Related Art In recent years, DVDs (Digital Video or Ve
as a light source for reading and writing of an optical disc recording / reproducing apparatus such as a rsatile disk).
Of a red semiconductor laser device has been developed. In order to increase the writing speed of an optical disk device, it is necessary to increase the output of a semiconductor laser.

[0003] Various configuration examples of the conventional red semiconductor laser in such a situation will be described below.

A. Prior Art 1 FIG. 5 shows an AlG as disclosed in JP-A-11-26880.
1 shows a cross-sectional structural view of an aInP-based red semiconductor laser. FIG.
In this case, an n-type GaAs substrate is
Layer 2, n-type AlGaInP cladding layer 3, AlGa
Quantum well active in which InP layers and GaInP layers are alternately stacked
Layer 4, low carrier concentration (2 to 6 × 10 ¹⁷cm^-3) Al
GaInP cladding layer 5, p-type GaInP etching stopper
The stop layer 6 is laminated. 10 is the etching stop layer 6
P-type AlGaInP carrier formed partially on the surface
A diffusion suppressing layer 7 and a high concentration (4 to 15 × 10¹⁷cm^-3)
The p-type AlGaInP cladding layer 8 and the p-type GaInP
Ridge structure in which
You. 11 is a ridge structure on the surface of the etching stopper layer 6.
N-type GaAs current blocking layers formed in portions other than 10
And 12 indicates the current blocking layer 11 and band discontinuity relaxation.
This is a p-type GaAs contact layer formed on the layer 9.
13 is a p-type electrode formed on the surface of the contact layer 12
And 14 is an n-type electrode formed on the back surface of the substrate 1.
You.

In this semiconductor laser, current constriction is performed using a ridge structure 10 sandwiched between n-type GaAs current blocking layers 11 as a current path. At the same time, since the GaAs current confinement layer 11 absorbs light from the quantum well active layer 4, an effective refractive index difference is formed inside and outside the ridge to confine the light. However, there is a problem that the operating current increases due to light absorption loss in the GaAs current confinement layer 11.

B. Prior Art 2 FIG. 6 shows a cross-sectional structure diagram of a red semiconductor laser disclosed in Japanese Patent Application Laid-Open No. 9-172222. As shown in FIG.
An n-type GaAs buffer layer 16, an n-type AlGaInP cladding layer 17, and a GaInP
An active layer 18, a p-type AlGaInP cladding layer 19, and a p-type GaInP intermediate layer 20 are epitaxially grown. Then, a pair of stripe-shaped grooves is formed at a depth traversing the intermediate layer 20 and reaching the p-type cladding layer 19, and a stripe-shaped ridge 21 is formed between the grooves. Then, an n-type AlGaAs current confinement layer 22 is formed so as to fill the trench, and a p-type GaAs cap layer 23 is further epitaxially grown on the entire surface.

In this semiconductor laser, the current confinement layer 22 is
The active layer 18 is made of lGaAs.
Is selected so as to be larger than the band gap. For example, when the wavelength of the active layer is 650 nm, A
The l-composition is 0.39 or more, and is 0.45 or more when the wavelength is 630 nm. Therefore, AlG
The aAs current confinement layer 22 is transparent to laser light,
Waveguide loss can be reduced.

C. Prior Art 3 FIG. 7 shows a red half shown in JP-A-7-249838.
1 shows a sectional structural view of a conductor laser. In FIG. 7, n-type G
On an As substrate 24, an n-type (Al_0.6Ga_0.4) _0.5In
_0.5P cladding layer 25, AlGaInP layer and GaInP
Active layer 26 having a quantum well structure with a p-type (Al_0.6
Ga_0.4)_0.5In_0.5P inner cladding layer 27, p-type Ga
_0.5In_0.5P etching stopper layer 28, p-type (Al
_0.6Ga_0.4)_{0. Five}In_0.5P outer cladding layer 29, p-type G
a_0.5In_0.5P buffer layer 30, p-type GaAs cap
A layer 31 is formed. And a stripe of 6μm width
Form a silicon nitride mask and wet etch
Etching to the etching stopper layer 28
A sa structure is formed. And an n-type AlInP current block.
A growth layer 32 and an n-type GaAs cap layer 33 are grown. n
The AlInP current block layer 32 is formed on the side of the mesa (shaded area).
Min) has a composition of Al_0.5In_0.5Grown to be P
I have. Then, after removing the silicon nitride mask, the p-type Ga
A As contact layer 34 is grown.

Also in the semiconductor laser shown in FIG. 7, since the current block layer 32 is made of AlInP which is transparent to laser light, waveguide loss is reduced. The AlInP current block layer 32 is made of p-type AlGaIn
Since the refractive index is lower than that of the P inner and outer cladding layers, a real refractive index difference is formed inside and outside the ridge, and a real refractive index guided semiconductor laser is obtained.

[0010]

As described above, FIG.
In the semiconductor laser shown in FIG. 7, the Al composition of the current confinement layer is increased in order to reduce the light absorption loss of the current confinement layer. In FIG. 6, the wavelength of the active layer is 6
When the thickness is 50 nm, the A of the AlGaAs current confinement layer 22
The l composition is 0.39 or more, and in FIG. 7, the Al composition of the AlInP current block layer 32 near the mesa is 0.5. This Al composition is AlGaI
This value is larger than the Al composition 0.35 of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P which is a typical cladding layer material of the nP-based semiconductor laser. A semiconductor layer having a high Al content has many surface states, and non-radiative recombination through the semiconductor layers increases. Therefore, there is a problem that optical damage to the end face of the laser resonator is likely to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a red semiconductor laser device which has a small waveguide absorption loss and suppresses optical damage on a cavity facet.

[0012]

According to the first aspect of the present invention,
A first conductivity type substrate having a lattice constant between GaAs or GaAs and GaP, a first conductivity type AlGaInP cladding layer, a GaInAsP active layer, and a GaInP etching stop layer, and the GaInP on both sides of a stripe region for current injection; AlGaI on the etching stop layer
an nP current blocking layer, and an AlGaInP optical waveguide layer and a second layer on the GaInP etching stop layer in the stripe region and on the AlGaInP current blocking layer.
A conductive type AlGaInP cladding layer is formed, and the Al composition of the AlGaInP current blocking layer is substantially equal to the Al composition of the second conductive type AlGaInP cladding layer.

Therefore, since the AlGaInP optical waveguide layer is formed on the GaInP etching stop layer in the stripe region, the actual refractive index of the stripe region is increased, so that a real index guided semiconductor laser can be formed. The current blocking layer outside the stripe region is made of AlGaInP having a band gap larger than that of the active layer, so that the absorption loss of laser light can be reduced. Further, the Al composition of the AlGaInP current blocking layer is
Since the Al composition is substantially equal to the Al composition of the conductivity type AlGaInP cladding layer and the Al composition has not increased, the optical damage level on the end face of the laser resonator does not increase.

According to a second aspect of the present invention, GaAs and GaP
A first conductivity type AlGaInP cladding layer, a GaInP lower optical waveguide layer, a GaInAsP active layer, and a GaInP upper first optical waveguide layer on a first conductivity type substrate having a lattice constant between An AlGaInP current blocking layer on both sides of the GaInP upper first optical waveguide layer, and an AlGaInP upper second optical waveguide layer and a second layer on the GaInP upper first optical waveguide layer in the stripe region and on the AlGaInP current blocking layer. A two-conductivity type AlGaInP clad layer is formed,
The Al composition of the GaInP current blocking layer is substantially equal to the Al composition of the second conductivity type AlGaInP cladding layer.

Therefore, the semiconductor laser has an SCH structure having optical waveguide layers above and below the active layer, and the lower optical waveguide layer and the upper first optical waveguide layer adjacent to the active layer are made of GaInP containing no Al. Therefore, optical damage to the end face of the laser resonator can be suppressed.

According to a third aspect of the present invention, in the semiconductor laser device according to the first or second aspect, the optical waveguide layer formed on the AlGaInP current block layer and on the GaInP layer in the stripe region is made of GaInP.

Therefore, by forming the optical waveguide layer formed on the AlGaInP current block layer and the GaInP layer in the stripe region with GaInP, the second crystal growth can be performed from the layer containing no Al, so that the regrown layer can be formed. Crystal quality can be improved.

According to a fourth aspect of the present invention, GaAs and GaP
A first conductivity type AlGaInP cladding layer, a GaInP lower optical waveguide layer, a GaInAsP active layer, and a GaInP upper first optical waveguide layer on a first conductivity type substrate having a lattice constant between On the GaInP upper first optical waveguide layer on both sides, the Al composition is substantially equal to the Al composition of the second conductivity type AlGaInP cladding layer.
A GaInP current blocking layer, wherein the AlGaInP
The GaInP on the current block layer and in the stripe region
A GaInP upper second optical waveguide layer and the second conductivity type AlGaInP cladding layer are formed on the upper first optical waveguide layer, and the GaInP upper first optical waveguide layer and the GaI
The sum of the layer thicknesses of the nP upper second optical waveguide layer is equal to the layer thickness of the GaInP lower optical waveguide layer.

Therefore, the GaInP upper first optical waveguide layer and the G
When the sum of the layer thicknesses of the aInP upper second optical waveguide layer is equal to the layer thickness of the GaInP lower optical waveguide layer, the refractive index distribution in the vertical direction of the stripe region becomes almost symmetrical. The light confinement coefficient is high in the strong center position, and therefore, the threshold current density of the laser can be reduced.

The invention according to claim 5 is the invention according to claims 1 to 4.
In the semiconductor laser device according to any one of the above, a first conductive type GaAsP thick film formed on the first conductive type GaAs via a first conductive type GaAsP composition gradient layer is used as the first conductive type substrate. .

Therefore, n-type GaAsP is formed on n-type GaAs.
An epitaxial substrate on which an n-type GaAsP thick film formed through a composition gradient layer is grown is commercially available as a substrate for a 660 nm red LED, and the use of this substrate as a laser substrate facilitates laser production.

The invention according to claim 6 is the invention according to claims 1 to 5
In the semiconductor laser device according to any one of the above,
The 1GaInP current block layer is formed by laminating a second conductivity type AlGaInP layer and a first conductivity type AlGaInP layer from the substrate side.

Accordingly, the current blocking layer is formed on the second side from the substrate side.
Conductive type AlGaInP layer and first conductive type AlGaInP
By forming the layers in layers, a pn reverse bias junction is formed outside the stripe region, so that effective current confinement can be achieved.

The invention according to claim 7 is the invention according to claims 1 to 6
In the semiconductor laser device according to any one of the above,
GaInP or Ga on the 1GaInP current block layer
A cap layer made of AsP or GaInAsP is formed.

Therefore, on the AlGaInP current blocking layer, Al-free GaInP or GaAsP or Ga
By forming a cap layer made of InAsP,
Oxidation on the surface of the AlGaInP current block layer can be suppressed,
Regrowth becomes easy.

The invention described in claim 8 is the first invention to the seventh invention.
In the semiconductor laser device according to any one of the above, a stripe width for current injection is smaller than 5 μm.

Therefore, even if the width of the stripe region into which the current is injected is made smaller than 5 μm, the laser light leaking into the current block layer is not absorbed, so that the waveguide loss does not increase and the threshold current can be reduced. it can.

[0028] The ninth aspect of the present invention is the first to eighth aspects.
In the semiconductor laser device according to any one of the above, the first conductivity type cladding layer, the optical waveguide layer, the current blocking layer, or the second conductivity type cladding layer contains As.

Therefore, when As is contained in the first conductivity type cladding layer, the optical waveguide layer, the current blocking layer or the second conductivity type cladding layer, generation of hillocks can be suppressed and surface flatness can be improved.

[0030]

FIG. 1 shows a first embodiment of the present invention.
A description will be given based on FIG.

[Structure] FIG. 1 is a sectional structural view of the semiconductor laser of the present embodiment. In FIG. 1, 115 is an n-type G
n-type GaAsP composition gradient layer 10 on aAs substrate 101
2. GaAs having stacked n-type GaAs _0.6 P _0.4 thick film 103
It is an sP substrate.

Reference numeral 104 denotes an n-type GaAs _0.6 P _0.4 thick film 103
Forming n-type on _{(Al 0.5 Ga 0 .5) 0.7} In 0.3 P cladding layer, GaInAsP active layer formed on the n-type cladding layer 104 is 105, Ga is 106 formed on the active layer 105 _0.7 In _0.3 P etching stop layer.

Reference numeral 107 denotes a p-type (Al _0.5 Ga _0.5 ) _0.7 In _0.3 P current block layer formed on the etching stop layer 106 except for a stripe region into which current is injected, and 108 denotes a p-type current block layer 107. forming n-type (Al _0.5 Ga _0.5) is _0.7 in _{0 .3} P current blocking layer.

Reference numeral 109 denotes an (Al _0.1 Ga _0.9 ) _0.7 In _0.3 P optical waveguide layer formed on the n-type current block layer 108 and the etching stop layer 106 in the stripe region.
Reference numeral 110 denotes a p-type (Al _0.5
Ga _0.5 ) _0.7 In _0.3 P cladding layer, 111 is a p-type Ga _0.7 In _0.3 P band discontinuous relaxation layer formed on the p-type cladding layer 110, and 112 is a p-type band discontinuous relaxation layer 11
1 is a p-type GaAs _0.6 P _0.4 cap layer formed on the substrate 1.

Reference numeral 113 denotes a p-side electrode formed on the surface of the p-type cap layer 112, and 114 denotes an n-type GaAs substrate 10.
1 is an n-side electrode formed on the back surface.

[Manufacturing method] Next, the thus constructed
A method for manufacturing a semiconductor laser will be described with reference to FIG.
You. First, as shown in FIG.
5 on the n-type (Al _0.5Ga_0.5)_0.7In_0.3P clad
Layer 104, GaInA having a band gap wavelength of 635 nm
sP active layer 105, Ga_0.7In_0.3P etching stock
Layer 106, p-type (Al_0.5Ga_0.5)_0.7In_0.3P current
Block layer 107, n-type (Al_0.5Ga_0.5)_0.7In_0.3
The P current block layer 108 is sequentially epitaxially grown.
You. Epitaxial growth is performed by metal organic chemical vapor deposition
Was.

Next, a resist mask 201 is formed on the n-type current block layer 108 of the epitaxial substrate, and a stripe window having a width of 6 μm is formed by photolithography. Then, the p-type AlGaInP current blocking layer 107 and the n-type Al
The GaInP current block layer 108 is chemically etched to the surface of the GaInP etching stop layer 106,
A stripe-shaped groove as shown in FIG. 2B is formed. For the etching, a sulfuric acid-based etching solution was used.

Next, after removing the resist mask 201, as shown in FIG. 2C, the (Al _0.1 Ga _0.9 ) _0.7 In _0.3 P optical waveguide layer 109 and the p-type ( Al _0.5 Ga _0.5 ) _0.7 In _0.3 P clad layer 110, p
Ga _0.7 In _0.3 P band discontinuous relaxation layer 111, p-type G
aAs _0.6 P _0.4 cap layer 112 is sequentially epitaxially grown.

Thereafter, a p-side electrode 113 was formed on the surface of the p-type GaAs _0.6 P _0.4 cap layer 112, and after polishing the n-type GaAs substrate 101, an n-side electrode 114 was formed on the back surface of the substrate, as shown in FIG. A semiconductor laser having such a structure is obtained.

[Operation] In the semiconductor laser according to the present embodiment, the AlG is provided outside the stripe region.
The current is confined to the stripe region by the aInP current block layers 107 and 108.

The current blocking layer is formed of p-type (Al
_0.5 Ga _0.5 ) _0.7 In _0.3 P layer 107 and n-type (Al _0.5 G
a _0.5 ) _0.7 In _0.3 P layer 108 is laminated, and a pnpn junction is formed outside the stripe region. Therefore, almost no current flows due to the pn reverse bias junction, and the current can be confined in the stripe region.

In the present embodiment, the current blocking layer is composed of two layers of a p-type AlGaInP layer and an n-type AlGaInP layer, but is formed of two or more layers having different compositions, carrier concentrations, and conductivity types. May be. Or,
It is also possible to use a high resistance or semi-insulating AlGaInP1 layer.

When a current is injected into the GaInAsP active layer 105, light emission of 635 nm corresponding to the band gap is generated. The thin GaIn is formed in the stripe-shaped groove.
Through P etching stop layer 106 on top of the active layer _{105 (Al 0.1 Ga 0.9) 0.} 7 In 0.3 P optical waveguide layer 109
Is provided. The refractive index of the optical waveguide layer 109 is
05 and larger than the cladding layer and the current blocking layer. On the other hand, outside the groove, the optical waveguide layer 109 is located at a position away from the active layer 105. Therefore, the effective refractive index of the stripe groove portion is higher than that of the outside, and an optical waveguide for confining light generated in the active layer is formed.

The horizontal transverse mode, oozes to the outside of the striped groove but, p-type _{(Al 0.5 Ga 0 .5) 0.7} In 0.3 P current blocking layer 107 and the n-type (Al _0.5 Ga _{0.5) 0.7} I
Since the n _0.3 P current blocking layer 108 has a larger band gap than the active layer 105, there is no light absorption. Therefore, the waveguide loss is reduced, and the operating current of the laser can be reduced.

Further, the difference in the effective refractive index of the waveguide is realized by changing the position of the optical waveguide layer instead of reducing the refractive index of the current blocking layer. Therefore, the Al composition of the p-type (Al _0.5 Ga _0.5 ) _0.7 In _0.3 P current blocking layer 107 and the n-type (Al _0.5 Ga _0.5 ) _0.7 In _0.3 P current blocking layer 108 have the same value as the Al composition of the p-type cladding layer 110. Can be. Therefore, it is not necessary to increase the Al composition of the current blocking layer, and the optical damage level on the end face of the laser resonator is not reduced.

The semiconductor laser of the present embodiment has a G
GaAs _0.6 P with lattice constant between aAs and GaP
_0.4 Laminated on a substrate. The band gap wavelength of Ga _0.7 In _0.3 P lattice-matched to GaAs _0.6 P _0.4 is 56
0 nm, and the band gap wavelength of the active layer 105 is 63 nm.
The wavelength is shorter than 5 nm. Therefore, the Ga _0.7 In _0.3 P etching stop layer 106 adjacent to the active layer 105 functions as a carrier block layer having a larger band gap than the active layer, and does not absorb light from the active layer. Since the etching rate of GaInP is much lower than that of sulfuric acid-based etching, selective etching with a current blocking layer made of AlGaInP is facilitated.

The GaAs _0.6 P _0.4 substrate 115 having a lattice constant between GaAs and GaP is an n-type GaAs substrate 10.
1, an n-type GaAsP composition gradient layer 102, an n-type GaAs
It is formed by laminating a _0.6 P _0.4 thick film 103 by a vapor deposition method. Such an epitaxial substrate is commercially available as a substrate for a 660 nm red LED, and the use of the substrate facilitates the production of a laser.

A second embodiment of the present invention will be described with reference to FIG. The same portions as those described in the first embodiment are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments).

[Structure] FIG. 3 is a sectional view showing the structure of a semiconductor laser according to the second embodiment of the present invention.
3, 301 is a Ga _{0. 7} In _0.3 P lower optical waveguide layer formed on the n-type cladding layer 104, 302 formed on the lower optical waveguide layer 301, GaInP and Ga
Reference numeral 303 denotes a quantum well active layer having a strained superlattice structure of InAsP, and reference numeral 303 denotes Ga formed on the quantum well active layer 302.
_0.7 In _0.3 P is the upper first optical waveguide layer. Reference numeral 304 denotes a Ga _0.7 In _0.3 P upper second optical waveguide layer formed on the n-type current block layer 108 and the upper first optical waveguide layer 303 in the stripe region. Other points are the same as the structure of the semiconductor laser shown in the first embodiment.

[Operation] In the present embodiment, GaI
The SCH structure has the optical waveguide layers 301 and 303 above and below the nAsP / GaInP quantum well active layer 302. The lower optical waveguide layer 301 and the upper first optical waveguide layer 303 are composed of A
It is composed of Ga _0.7 In _0.3 P not containing l. That is, the active layer and the region adjacent to the active layer do not contain Al. Therefore, compared to the first embodiment, it is possible to reduce the oxidation and the surface level of the end face of the laser resonator, and it is possible to suppress the occurrence level of optical damage on the end face.

The upper second optical waveguide layer 304 formed on the n-type current block layer 108 and the upper first optical waveguide layer 303 in the stripe region is made of Ga _0.7 In _0.3 P. Therefore, the second crystal growth can be performed from the layer containing no Al, and the crystal quality of the regrown layer is improved.

Further, in the semiconductor laser according to the present embodiment, the Ga _0.7 In _0.3 P upper first optical waveguide layer 303 and the G _0.7 In _0.3 P
a _0.7 In _0.3 P The sum of the thickness of the upper second optical waveguide layer 304 is G
a _{0. 7} In _0.7 P is configured to be equal to the thickness of the lower optical waveguide layer 301. Accordingly, the refractive index distribution in the vertical direction of the stripe region is substantially vertically symmetric with respect to the quantum well active layer 302. Therefore, the quantum well active layer 302 is located at the position where the light intensity is the strongest in the vertical mode,
The optical confinement coefficient increases. Therefore, the threshold current density of the laser is reduced.

In other respects, the same effects as in the first embodiment can be obtained.

A third embodiment of the present invention will be described with reference to FIG.

[Structure] FIG. 4 shows a semiconductor device according to the present embodiment.
FIG. 3 is a cross-sectional structural view showing a structure of a body laser. Figure 4
And 401 is n-type GaAs_0.6P_0.4Formed on thick film 103
N-type (Al_0.5Ga_0.5)_0.7In_0.3As_0.05P
_0.95It is a cladding layer. 402 is a strike for injecting current.
Formed on the upper first optical waveguide layer 303 excluding the pump region
p-type (Al _0.5Ga_0.5)_0.7In_0.3As_0.05P_0.95Current
A block layer 403; a p-type current block layer 402;
The n-type (Al_0.5Ga_0.5)_0.7In_0.3As
_0.05P_0.95The current block layer 404 is an n-type current block.
Ga formed on the lock layer 403_0.7In_0.3P cap
Layer. 405 is on the upper second optical waveguide layer 304
P-type (Al_0.5Ga_0.5)_0.7In_0.3As
_0.05P_0.95It is a cladding layer. Other points are the second embodiment
This is the same as the semiconductor laser shown in FIG.

[Operation] In the present embodiment, the n-type A
A cap layer made of Ga _0.7 In _0.3 P containing no Al is formed on the lGaInAsP current block layer 403. Therefore, the area where the Al surface, which is easily oxidized on the surface, is exposed on the regrown surface can be reduced, and the quality of the second crystal growth layer can be improved.

The n-type cladding layer 401, p-type current blocking layer 402, n-type current blocking layer 403,
Type cladding layer 405 is made of AlGaI containing about 5% As.
It is composed of an nAsP mixed crystal. A for AlGaInP
By adding a small amount of s, the hillock density and hillock size of a film grown by metal organic chemical vapor deposition can be reduced, and the surface flatness of the device is improved. Thereby, the scattering loss of the guided light is reduced, and the threshold current density and the slope efficiency of the laser are improved.

In this embodiment, the width W of the stripe region into which the current is injected can be made smaller than 5 μm, for example, 3 μm. When the stripe width is reduced, light leakage to the outside of the stripe region increases in the transverse mode. At this time, when the current blocking layer is made of a light absorbing material, the absorption loss is greatly increased and the slope efficiency is reduced. Further, when the Al composition of the current block layer is high, the light that has leaked into the current block layer is absorbed by the surface states, and optical damage to the end face is likely to occur. On the other hand, in the semiconductor laser according to the present embodiment, the laser light that has leaked into the current blocking layer is not absorbed, so that the waveguide loss does not increase. Further, the Al composition of the current blocking layer is the same as that of the cladding layer, and the optical damage level of the end face does not decrease. And, by reducing the stripe width, the operating current of the element can be reduced.

In other respects, the same effects as in the first and second embodiments can be obtained.

[0060]

According to the first aspect of the present invention, AlG is formed on the GaInP etching stop layer in the stripe region.
Since the aInP optical waveguide layer is formed, the actual refractive index of the stripe region is increased, so that a real refractive index guided semiconductor laser can be formed. The current blocking layer outside the stripe region has a band gap larger than that of the active layer. Large AlGaI
Since it is made of nP, the absorption loss of laser light can be reduced. Further, the Al composition of the AlGaInP current block layer is substantially equal to the Al composition of the AlGaInP cladding layer of the second conductivity type, and the Al composition is not increased, so that the optical damage level on the end face of the laser resonator does not increase. .

According to the second aspect of the present invention, there is provided a semiconductor laser having a SCH structure having optical waveguide layers above and below the active layer, and the lower optical waveguide layer and the upper first optical waveguide layer adjacent to the active layer are formed. Since it is made of GaInP that does not contain Al, it is possible to suppress optical damage to the end face of the laser resonator.

According to the third aspect of the present invention, AlGaI
GaInP on nP current block layer and stripe region
When the optical waveguide layer formed on the layer is formed of GaInP, the second crystal growth can be performed from a layer containing no Al, so that the crystal quality of the regrown layer can be improved.

According to the fourth aspect of the present invention, GaInP
Since the sum of the thicknesses of the upper first optical waveguide layer and the GaInP upper second optical waveguide layer is equal to the thickness of the GaInP lower optical waveguide layer, the vertical refractive index distribution of the stripe region becomes substantially symmetrical. The layer is located at the central position where the light intensity is strongest and the light confinement coefficient is high, so that the threshold current density of the laser can be reduced.

According to the fifth aspect of the present invention, n-type GaAs
An epitaxial substrate on which an n-type GaAsP thick film formed via an n-type GaAsP composition gradient layer was grown on s
It is commercially available as a substrate for a red LED in the nm band, and by using this as a substrate for a laser, the laser can be easily manufactured.

According to the sixth aspect of the present invention, the current blocking layer is formed from the substrate side to the second conductivity type AlGaInP layer and the first current blocking layer.
By forming the conductive type AlGaInP layer by lamination, a pn reverse bias junction is formed outside the stripe region to enable effective current confinement.

According to the seventh aspect of the present invention, AlGaI
By forming a cap layer made of GaInP or GaAsP or GaInAsP containing no Al on the nP current block layer, oxidation of the surface of the AlGaInP current block layer can be suppressed, and regrowth is facilitated.

According to the eighth aspect of the present invention, even if the width of the stripe region into which the current is injected is made smaller than 5 μm, the laser light that has leaked into the current block layer is not absorbed, so that the waveguide loss does not increase. In addition, the threshold current can be reduced.

According to the ninth aspect of the present invention, the first conductive type clad layer, the optical waveguide layer, the current blocking layer or the second conductive type clad layer contains As, thereby suppressing generation of hillocks and flattening the surface. Performance can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional structural view showing a structure of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a sectional structural view showing a manufacturing process of the semiconductor laser.

FIG. 3 is a sectional structural view showing a structure of a semiconductor laser according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a structure of a semiconductor laser according to a third embodiment of the present invention.

FIG. 5 is a cross-sectional structure diagram showing a structure of an AlGaInP-based semiconductor laser according to Prior Art 1.

FIG. 6 is a cross-sectional structure diagram showing the structure of a real refractive index guided semiconductor laser according to Prior Art 2.

FIG. 7 is a sectional structural view showing the structure of a real refractive index guided semiconductor laser of prior art 3.

[Explanation of symbols]

 Reference Signs List 101 n-type GaAs substrate 102 n-type GaAsP composition gradient layer 103 n-type GaAsP thick film 104 n-type AlGaInP cladding layer 105 GaInAsP active layer 106 GaInP etching stop layer 107 p-type AlGaInP current block layer 108 n-type AlGaInP current block layer 109 AlGaInP photoconductor Wave layer 110 p-type AlGaInP cladding layer 111 p-type GaInP band discontinuous relaxation layer 112 p-type GaAsP cap layer 115 GaAsP substrate 301 GaInP lower optical waveguide layer 302 quantum well active layer 303 GaInP upper first optical waveguide layer 304 GaInP upper second Optical waveguide layer 401 n-type AlGaInAsP cladding layer 402 p-type AlGaInAsP current blocking layer 403 n-type AlGaInAsP current blocking layer 404 aInP capping layer 405 p-type AlGaInAsP clad layer

Claims (9)

[Claims] 1. A first conductivity type AlG on a GaAs or a first conductivity type substrate having a lattice constant between GaAs and GaP.
aInP cladding layer, GaInAsP active layer and GaI
an AlGaInP current blocking layer on the GaInP etching stop layer on both sides of the stripe region into which the current is injected; and an AlG on the AlGaInP current blocking layer and the GaInP etching stop layer in the stripe region.
a semiconductor laser device comprising an aInP optical waveguide layer and a second conductivity type AlGaInP cladding layer, wherein an Al composition of the AlGaInP current blocking layer is substantially equal to an Al composition of the second conductivity type AlGaInP cladding layer. . 2. A first conductivity type AlGaInP cladding layer, a GaInP lower optical waveguide layer, a GaInAsP active layer, and a GaInP upper first optical waveguide layer are provided on a first conductivity type substrate having a lattice constant between GaAs and GaP. An AlGaInP current blocking layer on the GaInP upper first optical waveguide layer on both sides of the stripe region into which current is injected, and an AlGaI on the AlGaInP current blocking layer and the GaInP upper first optical waveguide layer in the stripe region.
An nP upper second optical waveguide layer and a second conductivity type AlGaInP cladding layer are formed, and the Al composition of the AlGaInP current blocking layer is substantially equal to the Al composition of the second conductivity type AlGaInP cladding layer. Semiconductor laser device. 3. The optical waveguide layer formed on the AlGaInP current block layer and on the GaInP layer in the stripe region is made of GaInP.
Or the semiconductor laser device according to 2. 4. A first conductivity type AlGaInP cladding layer, a GaInP lower optical waveguide layer, a GaInAsP active layer, and a GaInP upper first optical waveguide layer on a first conductivity type substrate having a lattice constant between GaAs and GaP. The Al composition has a second conductivity type AlGaI on the GaInP upper first optical waveguide layer on both sides of the stripe region into which current is injected.
an AlGaInP current blocking layer substantially equal to the Al composition of the nP cladding layer; and GaInP on the AlGaInP current blocking layer and the GaInP upper first optical waveguide layer in the stripe region.
An upper second optical waveguide layer and the second conductivity type AlGaInP cladding layer are formed, and the sum of the thicknesses of the GaInP upper first optical waveguide layer and the GaInP upper second optical waveguide layer is the GaInP lower optical waveguide layer. A semiconductor laser device having a thickness equal to the thickness of the semiconductor laser. 5. A first conductivity type Ga on a first conductivity type GaAs.
First conductivity type GaAs formed via an AsP composition gradient layer
5. The semiconductor laser device according to claim 1, wherein a P thick film is used as said first conductivity type substrate. 6. The AlGaInP current blocking layer,
From the substrate side, the second conductivity type AlGaInP layer and the first conductivity type A
The semiconductor laser device according to any one of claims 1 to 5, wherein the semiconductor laser device is formed by laminating lGaInP layers. 7. The semiconductor laser device according to claim 1, wherein a cap layer made of GaInP, GaAsP, or GaInAsP is formed on the AlGaInP current block layer. 8. The semiconductor laser device according to claim 1, wherein a stripe width for current injection is smaller than 5 μm. 9. The semiconductor laser device according to claim 1, wherein the cladding layer of the first conductivity type, the optical waveguide layer, the current blocking layer, or the cladding layer of the second conductivity type contains As. .