JP2003188474A - Semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser capable of increasing the response speed of output light to an injection current and quickly modulating the output light. <P>SOLUTION: A p type AlInP capacity reduced layer 100 of which the impurity concentration is lower than that of a p type AlGaInP 1st upper clad layer 14 is formed between the layer 14 and an n type AlInP current block layer 102. An AlInP capacity reduced layer 101 of which the impurity concentration is lower than that of the layer 102 is formed between both the layers 100, 102. Consequently a parasitic capacity generated between the layers 14, 102 can be reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor laser.

[0002]

2. Description of the Related Art In recent years,
The AlGaInP-based semiconductor laser is used as a light source for recording and reading in optical information processing systems such as magneto-optical disks and optical disks. Particularly, the semiconductor laser of the emitted light of the wavelength of 650 nm is DVD (Digital Universal Disc) -R / RW, DVD + R / RW, DVD-RAM.
It has an important position as a key device for realizing a high-density magneto-optical disk such as.

When a semiconductor laser is used as a light source of such an optical information processing system, a shorter wavelength is required for higher density and higher output and higher speed modulation are required for faster rewriting. It is said that Especially DVD-R / R
W performs writing by pulse modulation, and
As the rewriting speed increases from 1 × speed to 2 × speed and 4 × speed, the required pulse width also becomes smaller.

A conventional refractive index waveguide type semiconductor laser will be described below together with its manufacturing method.

6 to 9 are process diagrams of the method for manufacturing the semiconductor laser.

In the method of manufacturing a semiconductor laser described above, first,
As shown in FIG. 6, MBE is formed on the n-type GaAs substrate 11.
N-type AlGaInP lower clad layer 12, AlG
aInP first optical guide layer 43, multiple quantum well active layer 4
1, AlGaInP second optical guide layer 42, p-type AlGa
An InP first upper clad layer 14, a p-type GaInP etching stop layer 15, a p-type AlGaInP second upper clad layer 16, a p-type GaInP intermediate bandgap layer 17,
The p-type GaAs first contact layer 18 is sequentially laminated.

The n-type AlGaInP lower cladding layer 12 is
Si is set to be doped at 1 × 10 ¹⁸ cm ⁻³ , and the p-type AlGaInP first upper cladding layer 14 and the p-type AlGaInP second upper cladding layer 16 are doped with Be at 1 × 10 ¹⁸ cm ^−3. Is set to be done.
Usually, when the Be doping amount is set to 1 × 10 ¹⁸ cm ⁻³ ,
The actual Be concentration is 0.8 × 10 ¹⁸ cm ^{−3 to} 1.5 × 10.
It varies within the range of about ¹⁸ cm ^-3 . In addition, the above AlGa
The InP first light guide layer 43, the multiple quantum well active layer 41, and the AlGaInP second light guide layer 42 are non-doped.

Next, the p-type GaAs first contact layer 18
An Al ₂ O ₃ film 19 is vapor-deposited as a mask layer on the
The l ₂ O ₃ film 19 is patterned into a stripe shape by photolithography.

After that, wet etching is performed using the striped Al ₂ O ₃ film 19 as a mask. Then, the p-type AlGaInP second upper cladding layer 16 and the p-type GaInP are formed.
The portions corresponding to both sides of the Al ₂ O ₃ film 19 of the intermediate band gap layer 17 and the p-type GaAs first contact layer 18 are removed, and the mesa portion 31 is formed immediately below the Al ₂ O ₃ film 19. The mesa portion 31 is composed of a p-type AlGaInP second upper cladding layer 16, a p-type GaInP intermediate bandgap layer 17, and a p-type GaAs first contact layer 18.

The p-type AlGaInP clad layer 16
When a part of is removed, selective etching with the p-type GaInP etching stop layer 15 is performed to surely stop the etching.

Next, the n-type AlInP current blocking layer 20 is provided on both sides of the mesa portion 31 by performing the second MBE growth. This n-type AlInP current blocking layer 2
Stripe 2 made of n-type AlInP with 0 growth
1 grows on the Al ₂ O ₃ film 19.

Next, the n-type AlInP current blocking layer 20 is formed.
A photoresist is applied on the stripes 21 and the stripes 21 and photolithography is performed to form openings 23 in the photoresist 32 as shown in FIG. As a result, the upper surface of the stripe 21 is exposed through the opening 23 of the photoresist 23.

Next, as shown in FIG. 8, the stripes 21 on the Al ₂ O ₃ film 19 are removed by selective etching using a sulfuric acid type etching solution. Then, the photoresist 32 is removed. Then, the Al ₂ O ₃ film 19 is etched and removed using a hydrofluoric acid-based etching solution.

Thereafter, as shown in FIG. 9, p-type GaAs
The p-type GaAs second contact layer 104 is grown to a thickness of 2 μm on the upper surfaces of the first contact layer 18 and the current blocking layer 20.

Next, the p-type GaAs second contact layer 10
Electrodes (not shown) are provided on the surface of substrate 4 and the surface of substrate 11, respectively.

In order to operate the output light of the semiconductor laser obtained through the above steps in a pulsed manner, the current flowing through the semiconductor laser is turned on / off in a pulsed manner (direct modulation). At this time, even if the current supplied to the semiconductor laser is sufficiently high, the output light of the semiconductor laser is not modulated at high speed if the response speed of the semiconductor laser is poor.

The factors that hinder the high-speed response characteristics of the semiconductor laser are the series resistance and parasitic capacitance of the semiconductor laser. The parasitic capacitance of this semiconductor laser is p-type AlGaIn.
It occurs between the P first upper cladding layer 14 and the p-type GaAs second contact layer 104. In such a situation, since the width of the chip is as large as 230 μm with respect to the width of 3 μm of the mesa portion 31, the p-type AlGaInP first upper cladding layer 14 is formed.
And the p-type GaAs second contact layer 104 have a large opposing area, and the parasitic capacitance is also large. Specifically, the parasitic capacitance is 50 pF to 90 pF. As a result, there is a problem that the modulation speed of the semiconductor laser becomes slow and the rise time and the fall time of the laser output light become long. In the conventional example, the rise time (10% to 90%) of the light output was about 1.0 ns.

The parasitic capacitance is mainly determined by the capacitance of the pn junction between the n-type AlInP current blocking layer 20 and the p-type AlGaInP first upper cladding layer 14. This n-type AlInP current blocking layer 20, p-type AlGaI
The higher the impurity concentration of the nP first upper cladding layer 14, the narrower the depletion layer width, and the parasitic capacitance increases.

Therefore, in order to reduce the parasitic capacitance,
p-type AlGaInP first upper cladding layer 14, n-type AlI
It can be considered to reduce the impurity concentration of the nP current blocking layer 20. However, if the impurity concentration of the p-type AlGaInP first upper clad layer 14 is reduced, the overflow of electrons from the multiple quantum well active layer 41 increases and the temperature characteristics deteriorate, so that the impurity concentration cannot be reduced.
Further, if the impurity concentration of the n-type AlInP current blocking layer 20 is reduced, the effect of blocking the current is reduced, so
The impurity concentration of the InP current blocking layer 20 cannot be reduced.

Therefore, an object of the present invention is to provide a semiconductor laser in which the response speed of output light with respect to the injection current is fast and the output light can be modulated at high speed.

[0021]

In order to solve the above-mentioned problems, a semiconductor laser of the present invention comprises a first conductivity type lower clad layer, an active layer, and a second conductivity type first upper clad on a first conductivity type substrate. Layer and a ridge-stripe-shaped second upper conductivity type second upper cladding layer are sequentially laminated, and a current blocking layer is provided on both sides of this second conductivity type second upper cladding layer. 1 a second conductivity type capacitance reducing layer which is provided between the upper cladding layer and the current blocking layer and has an impurity concentration lower than that of the second conductivity type first upper cladding layer; It is characterized in that it is provided between the current blocking layer and a first conductivity type capacitance reducing layer having an impurity concentration lower than that of the current blocking layer.

In the semiconductor laser having the above structure, the first conductivity type capacitance reducing layer and the second conductivity type capacitance reducing layer are provided between the second conductivity type first upper cladding layer and the current blocking layer. There is. That is, between the second conductivity type first upper clad layer and the current blocking layer, p with a low carrier concentration is used.
-There is an n-junction. As a result, the spread of the depletion layer increases between the second conductivity type first upper cladding layer and the current blocking layer, and the parasitic capacitance decreases. Therefore, the response speed of the output light with respect to the injection current is increased, and the output light can be modulated at high speed.

Further, since the semiconductor light emitting device having the above structure can modulate the output light at a high speed, for example, the DVD-R.
It can be used for drive devices such as / RW.

In the present specification, the first conductivity type means P type or N type. The second conductivity type means N type when the first conductivity type is P type and P type when the first conductivity type is N type.

In the semiconductor laser of one embodiment, the resistivity of the second conductivity type capacitance reducing layer is higher than the resistivity of the second conductivity type second upper cladding layer.

According to the semiconductor laser of the above embodiment, since the resistivity of the second conductivity type capacitance reducing layer is higher than the resistivity of the second conductivity type second upper clad layer, the second conductivity type second upper clad layer is formed. Therefore, it is possible to prevent a current from flowing to the second conductivity type capacitance reducing layer.

In the semiconductor laser of one embodiment, the second conductivity type capacitance reducing layer and the second conductivity type second upper clad layer are made of different materials, and the top of the valence band of the second conductivity type capacitance reducing layer is different. And the energy difference between the top of the valence band of the second conductivity type second upper cladding layer is larger than about 26 meV.

According to the semiconductor laser of the above embodiment, the energy difference between the top of the valence band of the second conductivity type capacitance reducing layer and the top of the valence band of the second conductivity type second upper cladding layer is about 26 meV. Since it is larger, it is possible to prevent current from flowing from the second conductivity type second upper cladding layer to the second conductivity type capacitance reducing layer.

In the semiconductor laser of one embodiment, the second conductivity type first upper clad layer is (Al _x Ga _{1 -x} ) InP.
(0 <x <1), and the second conductivity type capacitance reducing layer is made of AlInP, GaAs or AlGaAs.

In the semiconductor laser of one embodiment, the impurity concentration of the second conductivity type first upper clad layer is 0.8 × 10 ¹⁸ c.
m ^{−3 to} 1.5 × 10 ¹⁸ cm ⁻³ .

In the semiconductor laser of one embodiment, the impurity of the second conductivity type first upper cladding layer is Be.

According to the semiconductor laser of the above embodiment, since the impurity of the second conductivity type first upper clad layer is Be, Be hardly diffuses during growth, and the second conductivity type first upper clad layer is not diffused. Impurities of the layer do not diffuse into the second conductivity type capacitance reducing layer. Therefore, it is possible to prevent the doping concentration of the second conductivity type capacitance reducing layer from increasing.

In the semiconductor laser of one embodiment, the crystal growth of the above layer is carried out by the molecular beam epicapital method.

In the semiconductor laser of one embodiment, the conductivity type of the current block layer is the first conductivity type, the opposing area between the second conductivity type first upper cladding layer and the current block layer is S, and the parasitic When the capacity is C, C / S is 250 pF /
A semiconductor laser having a size of mm ² or less.

[0035]

1 to 4 are process diagrams of a method of manufacturing a refractive index waveguide type semiconductor laser according to an embodiment of the present invention.

A method of manufacturing the above semiconductor laser will be described below with reference to FIGS.

First, as shown in FIG. 1, an n-type GaAs substrate 1 as an example of the first conductivity type substrate is formed by the MBE method.
N-type A as an example of the first conductivity type lower clad layer
lGaInP lower clad layer 12, AlGaInP first optical guide layer 43, multiple quantum well active layer 41 as an example of active layer, AlGaInP second optical guide layer 42, p-type as an example of second conductivity type first upper clad layer AlGaInP
The first upper cladding layer 14 and the p-type GaInP etching stop layer 15 are sequentially stacked. Continued p-type GaIn
On the P etching stop layer 15, p-type AlGaInP is formed.
The second upper cladding layer 16, the p-type GaInP intermediate bandgap layer 17, and the p-type GaAs first contact layer 18 are sequentially stacked.

Next, by depositing an Al ₂ O ₃ film on the p-type GaAs first contact layer, is patterned the the Al ₂ O ₃ film into stripes by photolithography. As a result, a striped Al ₂ O ₃ film 19 is obtained on the p-type GaAs first contact layer.

Then, wet etching is performed using the Al ₂ O ₃ film 19 as a mask to remove parts of the p-type AlGaInP second upper cladding layer, the p-type GaInP intermediate bandgap layer and the p-type GaAs first contact layer. . Then, the mesa portion 31 is obtained immediately below the Al ₂ O ₃ film 19. The mesa portion 31 is a p-type AlGaIn layer as an example of a ridge stripe-shaped second conductivity type second upper cladding layer.
It comprises a P second upper cladding layer 16, a p-type GaInP intermediate bandgap layer 17 and a p-type GaAs first contact layer 18.

The n-type AlGaInP lower cladding layer 12 is
Si is set to be doped at 1 × 10 ¹⁸ cm ⁻³ , and the p-type AlGaInP first upper cladding layer 14 and the p-type AlGaInP second upper cladding layer 16 are doped with Be at 1 × 10 ¹⁸ cm ^−3. Is set to be done.
Usually, when the Be doping amount is set to 1 × 10 ¹⁸ cm ⁻³ ,
The actual Be concentration is 0.8 × 10 ¹⁸ cm ^{−3 to} 1.5 × 10.
It varies within the range of about ¹⁸ cm ^-3 . In addition, the above AlGa
The InP first light guide layer 43, the multiple quantum well active layer 41, and the AlGaInP second light guide layer 42 are non-doped.

When part of the p-type AlGaInP second upper clad layer is removed, selective etching with the p-type GaInP etching stop layer 15 is performed to surely stop the etching.

Next, the second MBE growth is performed to stack a p-type AlInP capacitance reducing layer 100 as an example of the second conductivity type capacitance reducing layer 0.15 μm on both sides of the mesa portion 31. Then, on the p-type AlInP capacitance reducing layer 100, an n-type AlInP capacitance reducing layer 101 having a thickness of 0.15 μm is provided as an example of the first conductivity type capacitance reducing layer. Furthermore, n
An n-type AlInP current blocking layer 102 as an example of a current blocking layer is formed on the type AlInP capacitance reducing layer 101. At this time, p-type AlI is formed on the Al ₂ O ₃ film 19.
nP capacitance reduction layer 100, n-type AlInP capacitance reduction layer 10
The 1 and n-type AlInP current blocking layer 102 materials are stacked. The layer stacked on the Al ₂ O ₃ film 19 in this way is defined as the unnecessary layer 103.

The p-type AlInP capacitance reducing layer 100 has a p-type
2 × 10 Be as an impurity¹⁷cm ^-3Doped, n
2 × 10 of Si is used for the AlInP capacitance reduction layer 101.¹⁷c
m^-3Doping. In addition, the n-type AlInP current block
The lock layer 102 is made of Si of 1 × 10.¹⁸cm^-3doping
is doing.

Next, the n-type AlInP current blocking layer 10
2 and the unnecessary layer 103, a photoresist is applied and photolithography is performed to form an opening 23 in the photoresist 32 as shown in FIG. As a result, the upper surface of the unnecessary layer 103 is exposed through the opening 23 of the photoresist 23.

Next, as shown in FIG. 3, the unnecessary layer 103 is removed by selective etching with respect to the Al ₂ O ₃ film 19 using a sulfuric acid-based etching solution. Then, photoresist 3
Remove 2.

Then, as shown in FIG. 4, the Al ₂ O ₃ film 19 is removed by etching using a hydrofluoric acid type etching solution. After that, the p-type GaAs first contact layer 18, p
A p-type GaAs second contact layer 104 is grown to a thickness of 2 μm on the n-type AlInP capacitance reducing layer 100, the n-type AlInP capacitance reducing layer 101, and the n-type AlInP current blocking layer 102.

Next, the p-type GaAs second contact layer 10 is formed.
An electrode (not shown) is formed on each of the surface of No. 4 and the surface of the substrate 11. Up to this point, the processing in the wafer state is completed.

Next, the completed wafer is divided into a length (= resonator length) of 800 μm in a direction parallel to the mesa portion 31. Then, an end face coating is applied to the front surface and the rear surface of the laser bar obtained by such division.

Next, the laser bar is divided into a length (= chip width) of 230 μm in the direction perpendicular to the mesa portion 31. That is, it is divided into the above laser bar chip states. A semiconductor laser is completed by fixing the laser chip obtained by this division to the stem.

Table 1 below shows the characteristics of the semiconductor laser of the present embodiment (in Table 1, simply referred to as "this example").
Table 1 below shows the conventional semiconductor laser of FIG.
The characteristics of "conventional example" are also shown inside.

[0051]

[Table 1]

As can be seen from Table 1, the capacitance of the semiconductor laser of this embodiment is much lower than that of the conventional semiconductor laser of FIG. This is p-type AlIn
P capacitance reduction layer 100 and n-type AlInP capacitance reduction layer 101
Are formed, the n-type AlInP current blocking layer 102 and the p-type AlGaInP first upper cladding layer 14 are formed.
It means that the capacitance between and is lower than the capacitance component in the conventional semiconductor laser of FIG. Also, the rise time of the light output was improved to 0.6 ns.

Further, in the case of the structure of the semiconductor laser as in this embodiment, part of the driving current is from the p-type AlGaInP second upper cladding layer 16 to the p-type AlInP capacitance reducing layer 10.
It is conceivable that the reactive current may flow through 0 and do not contribute to oscillation. However, in the case of this embodiment, p-type Al
Resistivity of InP capacitance reduction layer 100 (= 10 Ω · cm)
However, since it is higher than the resistivity (= 2Ω · cm) of the p-type AlGaInP second upper cladding layer 16, almost no reactive current flows. As a result, the oscillation start current (Ith), which is one of the characteristics of the semiconductor laser of the present embodiment, is almost the same as that of the conventional semiconductor laser of FIG.

Further, in the present embodiment, all crystal growth is performed by the molecular beam epicapital method (MBE method). The MBE growth method is characterized by a lower growth temperature than other methods, for example, a metal organic chemical vapor deposition method (MOCVD method), and that Be, which is ideal as a P-type dopant, can be used.

Further, according to the present embodiment, p-type AlG
The aInP first upper clad layer 14 is doped at a relatively high concentration of 1 × 10 ¹⁸ cm ⁻³ , but Be hardly diffuses during growth. Specifically, the diffusion of Be is 5
It is less than 00Å. Therefore, the p-type AlGaInP first
Be of the upper clad layer 14 is a p-type AlInP capacitance reducing layer 1
P-type AlInP capacitance reducing layer 1000 without diffusing into
The doping concentration of is kept low, and the parasitic capacitance can be reduced. In the MBE growth method, since the growth temperature is low, diffusion of Be during growth is small.

If a dopant such as Zn or Mg is used as an impurity, the dopant diffuses, and the p-type AlInP capacitance reducing layer 100 does not expand the depletion layer due to the diffused dopant and the parasitic capacitance is not reduced. MOC
The VD growth method has a growth temperature of ~ 6 as compared with the MBE growth method.
The temperature is as high as 00 ° C., and the impurities Zn or Mg easily diffuse.

The parasitic capacitance C of the semiconductor laser is proportional to the chip area. Therefore, it is necessary to consider how much the parasitic capacitance can be reduced per area.

FIG. 5 shows the relationship between the parasitic capacitance C and the area S of the semiconductor laser. The area S is p-type AlGaI.
This is an area where the nP first upper cladding layer 14 and the n-type AlInP current blocking layer 102 face each other.

According to FIG. 5, the C / S of the semiconductor laser of this embodiment is 250 pF / mm ² or less.
On the other hand, the C / S of the conventional semiconductor laser shown in FIG.
Exceeds 250 pF / mm ² . That is, the C / S of the semiconductor laser of this embodiment is smaller than the C / S of the conventional semiconductor laser of FIG.

In the above embodiment, in order to reduce the parasitic capacitance, the p-type AlInP capacitance reducing layer 100 and the n-type AlI are formed.
Although the nP capacitance reducing layer 101 was used, p-type AlInP
0.15 μm p-type GaA instead of the capacitance reducing layer 100
In addition to using the s capacitance reducing layer, an n-type GaAs capacitance reducing layer having a thickness of 0.15 μm may be used instead of the n-type AlInP capacitance reducing layer 101. In this case, the top of the valence band of the p-type AlGaInP second upper cladding layer 16 and the p-type GaAs
Since the energy difference ΔEv from the top of the valence band of the capacitance reducing layer is larger than the distribution width of holes (about 26 meV), it becomes a barrier at the junction surface against holes. As a result, p-type Al
A current does not flow between the GaInP second upper cladding layer 16 and the p-type GaAs capacitance reducing layer, and the generation of a reactive current that does not contribute to oscillation can be prevented.

Further, the p-type GaAs capacitance reducing layer and the n-type Ga
When using the As capacitance reducing layer, an n type GaAs current blocking layer is provided on the n type GaAs capacitance reducing layer.

In the above embodiment, the n-type GaAs substrate 1 is used.
Although 1 is used, a p-type substrate may be used and the conductivity type of each layer may be opposite to the above. In this case, the same effects and advantages as those of the above embodiment can be obtained.

The p-type first upper clad layer made of (Al _x Ga _{1 -x} ) InP (0 <x <1) may be used as the second conductivity type first upper clad layer.

As the second conductivity type capacitance reducing layer, Al is used.
A p-type capacitance reducing layer made of any of InP, GaAs and AlGaAs may be used.

[0065]

As is apparent from the above, the semiconductor laser of the present invention has an impurity concentration higher than that of the second conductivity type first upper cladding layer between the second conductivity type first upper cladding layer and the current blocking layer. Since the second conductivity type capacitance reducing layer having a low concentration is provided, and the first conductivity type capacitance reducing layer having an impurity concentration lower than that of the current blocking layer is provided between the second conductivity type capacitance reducing layer and the current blocking layer, The parasitic capacitance between the conductivity type first upper cladding layer and the current blocking layer is reduced. Therefore, the response speed of the output light with respect to the injection current is increased, and the output light can be modulated at high speed.

[Brief description of drawings]

FIG. 1 is a schematic manufacturing process diagram of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is a schematic manufacturing process diagram of the semiconductor laser.

FIG. 3 is a schematic manufacturing process diagram of the semiconductor laser.

FIG. 4 is a schematic manufacturing process diagram of the semiconductor laser.

FIG. 5 is a graph showing the relationship between the parasitic capacitance and the area of the semiconductor laser.

FIG. 6 is a schematic manufacturing process diagram of a conventional semiconductor laser.

FIG. 7 is a schematic manufacturing process diagram of the conventional semiconductor laser.

FIG. 8 is a schematic manufacturing process diagram of the conventional semiconductor laser.

FIG. 9 is a schematic manufacturing process diagram of the conventional semiconductor laser.

[Explanation of symbols]

11 n-type GaAs substrate 12 n-type AlGaInP clad layer 14 p-type AlGaInP first upper cladding layer 16 p-type AlGaInP second upper cladding layer 41 Multiple quantum well active layer 100 p-type AlInP capacitance reduction layer 101 n-type AlInP capacitance reduction layer 102 n-type AlInP current blocking layer 110 p-type GaAs capacitance reduction layer 111 n-type GaAs capacitance reduction layer

Claims (8)

[Claims] 1. A first conductivity type lower clad layer, an active layer, a second conductivity type first upper clad layer, and a ridge stripe-shaped second conductivity type second upper clad layer are sequentially laminated on a first conductivity type substrate. In the semiconductor laser in which the current blocking layers are provided on both sides of the second conductivity type second upper cladding layer, the second laser diode is provided between the second conductivity type first upper cladding layer and the current blocking layer. The second conductivity type capacitance reducing layer having an impurity concentration lower than that of the second conductivity type first upper cladding layer, and the impurity concentration higher than that of the current blocking layer are provided between the second conductivity type capacitance reducing layer and the current blocking layer. A semiconductor laser having a low first conductivity type capacitance reducing layer. 2. The semiconductor laser according to claim 1, wherein the resistivity of the second conductivity type capacitance reducing layer is higher than the resistivity of the second conductivity type second upper clad layer. 3. The semiconductor laser according to claim 1, wherein the second conductivity type capacitance reducing layer and the second conductivity type second upper cladding layer are made of different materials, and the value of the second conductivity type capacitance reducing layer is different. The top of the electronic band and the second above
A semiconductor laser, wherein the energy difference between the conductivity type second upper cladding layer and the top of the valence band is larger than about 26 meV. 4. The semiconductor laser according to claim 1, wherein the second conductivity type first upper cladding layer is (Al _x Ga _{1 -x} ) In.
P (0 <x <1), and the second conductivity type capacitance reducing layer is made of any one of AlInP, GaAs and AlGaAs. 5. The semiconductor laser according to claim 1, wherein the impurity concentration of the second conductivity type first upper cladding layer is 0.8.
A semiconductor laser having a size of × 10 ¹⁸ cm ^{-3 to} 1.5 × 10 ¹⁸ cm ^-3 . 6. The semiconductor laser according to claim 1, wherein the impurity of the second conductivity type first upper cladding layer is Be. 7. The semiconductor laser according to claim 1, wherein crystal growth of the layer is performed by a molecular beam epi-capital method. 8. The semiconductor laser according to claim 1, wherein the conductivity type of the current blocking layer is a first conductivity type, the second conductivity type first upper clad layer and the current. When the area facing the block layer is S and the parasitic capacitance is C, C / S
Is 250 pF / mm ² or less, a semiconductor laser.