JP2002246692A - Semiconductor laser and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a determined horizontal spread angle without increasing a resistive value while suppressing the absorption loss of laser light and stabilizing a fundamental transversal mode. SOLUTION: A light trapping layer 6 is made of an InAlP-based material, and a difference in effective refractive index between inside and outside of a stripe is set at a value in a range of 0.007-0.014.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser and a method for manufacturing the same, and more particularly, to a semiconductor laser having an optical output of 15 mW or less and suitable for application to a real refractive index semiconductor laser.

[0002]

2. Description of the Related Art Bar code readers, light sources for measurement, DVDs
600nm as a light source for high density optical discs such as
InGaAlP-based semiconductor lasers having an oscillation wavelength region in a band have been put to practical use. In particular, a transverse mode control laser oscillating in a fundamental transverse mode is used as a light source for a high-density optical disc.

FIG. 7 is a sectional view showing an example of a conventional transverse mode control semiconductor laser. In FIG. 7, n-type GaAs
On the s substrate 1, n-type In _0.5 (Ga _0.27 Al
_{0.7 3} ) _0.5 P cladding layer 2, MQW (multiple quantum well) active layer 3 and p-type In _{0 . 5} (Ga _0.27 Al
_0.73 ) _0.5 P cladding layer 4 is sequentially formed, and the p-type In _0.5 (Ga _0.27 Al _0.73 ) _0.5 P cladding layer 4 is provided with a stripe-shaped ridge portion RG. Have been. Here, the ridge portion RG is formed by wet etching mainly using phosphoric acid in order to suppress damage to the crystal. For this reason, the shape of the ridge portion RG is trapezoidal due to the anisotropy of the crystal with respect to the wet etching, and the width w2 above the ridge portion RG is smaller than the stripe width w1.

On the ridge portion RG, a p-type In _0.5
A Ga _0.5 P hetero buffer layer 5 is formed, and n-type GaAs light confinement layers 11 are formed on both sides of the ridge RG. A p-type GaAs contact layer 7 is formed on the p-type In _0.5 Ga _0.5 P heterobuffer layer 5 and the n-type GaAs optical confinement layer 11, and the p-type G
A p-side electrode 8 is formed on the aAs contact layer 7, and an n-side electrode 9 is formed on the back surface of the n-type GaAs substrate 1.
Are formed.

Here, p-type In _0.5 (Ga _0.27 A
l _0.73 ) _0.5 The thickness d2 of the ridge portion RG of the P cladding layer 4 is about 1.0 μm, while the ridge portion RG
In the other region, p-type In _0.5 (Ga _0.27 Al
_0.73 ) _{0.5 Since} the thickness of the P cladding layer 4 is set to about 0.1 μm, the distance h between the MQW active layer 3 and the n-type GaAs optical confinement layer 11 becomes about 0.1 μm.

Therefore, in a region other than the ridge portion RG,
Since the laser light is absorbed by the n-type GaAs light confinement layer 11 and the laser light is confined in the stripe, the transverse mode can be stabilized.

The n-type GaAs light confinement layer 11
Also functions as a current blocking layer, and the ridge RG
By providing the n-type GaAs optical confinement layers 11 on both sides of the substrate, the current supplied from the p-side electrode 8 can be guided to the ridge portion RG to perform current confinement, and the threshold current can be reduced. Become.

[0008]

However, n-type G
In the method of stabilizing the transverse mode by providing the aAs light confinement layer 11, the laser light is absorbed by the n-type GaAs light confinement layer 11, so that a current loss occurs and astigmatism is as large as about 10 μm. There was a problem.

On the other hand, in order to eliminate light absorption in the n-type GaAs light confinement layer 11, InAl is used instead of GaAs.
A real refractive index laser using P as a light confinement layer has been proposed (1997 Spring Institute of Applied Physics: 31a-NG-3,
31a-NG-4, 1998 Spring Society of Applied Physics: 29a
-ZH-5, 29a-ZH-6).

In this real refractive index laser, since laser light is not absorbed, waveguide loss is small, low threshold current, high efficiency laser oscillation is possible, and astigmatism is 1 μm.
m and small. In the case of a real refractive index laser, 1998
Spring Institute of Applied Physics: As described in 29a-ZH-6, the refractive index difference Δn between the inside and outside of the stripe is 0.004.
By setting it to about 0.005, stable fundamental transverse mode oscillation can be realized.

Here, in the optical system of the optical pickup, the horizontal divergence angle θ 前後 is generally required to be around 9 degrees (8 to 10 degrees) due to the relationship between the NA of the collimator lens and the objective lens. Therefore, in order to stabilize the fundamental transverse mode oscillation and satisfy the requirement of the horizontal spread angle θ‖ = about 9 degrees, the stripe width w1 needs to be about 3 μm.

However, when the stripe width w1 is 3 μm
In this case, since the ridge portion RG has a trapezoidal shape, the width w2 above the ridge portion RG becomes 1.5 μm or less. For this reason, the current path above the ridge portion RG becomes narrow, the resistance value increases, and the operating voltage increases.
There is a problem that the high-frequency superposition characteristics are deteriorated.

Therefore, an object of the present invention is to stabilize the fundamental transverse mode while suppressing the absorption loss of laser light,
An object of the present invention is to provide a semiconductor laser capable of obtaining a predetermined horizontal spread angle without increasing a resistance value, and a method for manufacturing the same.

[0014]

According to the first aspect of the present invention, a first conductive type clad layer formed on a first conductive type substrate and the first conductive type clad layer are provided. An active layer formed on the mold cladding layer, a second conductivity type cladding layer formed on the active layer, transparent to laser light, and having an effective refractive index difference between the inside and outside of the stripe of 0.007 to 0.007.
And a light confinement layer having a refractive index smaller than that of the second conductivity type cladding layer.

[0015] This makes it possible to suppress the absorption loss of the laser light at the time of confining the light, and even when the stripe width is increased, the predetermined horizontal spread angle can be maintained without deteriorating the stability of the basic transverse mode. Can be obtained. For this reason, it is possible to prevent the deterioration of the high-frequency superposition characteristics while satisfying the requirements from the optical system of the optical pickup.

According to the second aspect of the present invention, the second conductivity type cladding layer has a ridge portion corresponding to the stripe, and the light confinement layer is a second conductivity type cladding layer other than the ridge portion. It is characterized by being formed above.

As a result, the refractive index other than the ridge portion can be easily controlled, so that the laser beam can be confined in the stripe, the fundamental transverse mode can be stabilized, and the current confinement can be achieved. Thereby, the threshold current can be reduced.

According to the third aspect of the present invention, the light confinement layer is formed in the second conductivity type cladding layer at a predetermined distance from the active layer, and has an opening corresponding to the stripe. It is characterized by having.

This makes it possible to easily control the refractive index other than the opening, so that the laser beam can be confined in the stripe, the fundamental transverse mode can be stabilized, and the current confinement can be achieved. Thereby, the threshold current can be reduced.

According to the invention described in claim 4, the distance between the light confinement layer and the active layer is 0.08 μm to 0.08 μm.
It is characterized by a range of 0.15 μm.

Thus, the effective refractive index difference inside and outside the stripe can be set in the range of 0.007 to 0.014 only by controlling the thickness of the second conductivity type cladding layer outside the stripe.

According to a fifth aspect of the present invention, the width of the stripe is in a range of 3.5 μm to 5.5 μm.

As a result, the horizontal spread angle θ‖ is 8 to 1
Since the current path can be widened while being set to 0 degrees, it is possible to prevent the deterioration of the high-frequency superposition characteristics while satisfying the requirements from the optical system of the optical pickup.

According to the invention, the first conductivity type substrate is made of GaAs, the first conductivity type, and the second conductivity type substrate.
The conductivity type cladding layer is InGaAlP, and the active layer is InGaAlP.
GaAlP or InGaP or a quantum well structure thereof, wherein the light confinement layer is InGaAlP or InGaP.
It is characterized by being AlP.

This makes it possible to easily control the refractive index inside and outside the stripe while suppressing the absorption of the laser light by the light confinement layer. It can be stabilized. In addition, current confinement can be performed using a hetero barrier formed between the cladding layer and the optical confinement layer, and the threshold current can be reduced.

According to the seventh aspect of the present invention, the first
Forming a first conductivity type cladding layer on the conductivity type substrate, forming an active layer on the first conductivity type cladding layer, and forming a second conductivity type cladding layer on the active layer; Forming a stripe-shaped mask on the cladding layer of the second conductivity type; and forming the second mask through the mask.
A step of etching the conductive cladding layer to a predetermined thickness, and a step of selectively forming a light confinement layer in a region other than the mask by performing crystal growth through the mask, and removing the mask, Forming a contact layer.

This makes it possible to form the light confinement layer while leaving the cladding layer serving as the ridge on the active layer, thereby preventing the crystal quality of the ridge near the active layer from being impaired. As a result, the formation of the second conductivity type cladding layer can be completed only once, and the manufacturing process can be simplified.

According to the eighth aspect of the present invention, the first
Forming a first conductive type clad layer on the conductive type substrate, forming an active layer on the first conductive type clad layer, and forming a first second conductive type clad layer on the active layer. Forming; forming a light confinement layer on the second conductivity type cladding layer; forming a stripe-shaped opening in the light confinement layer; and forming a light-emitting layer on the opening and the light confinement layer. The method is characterized by comprising a second step of forming a second conductive type clad layer and a step of forming a contact layer on the second conductive type clad layer.

As a result, the refractive index inside and outside the stripe can be controlled without providing a ridge portion in the cladding layer, and the current path can be prevented from being narrower than the stripe width. The high frequency superimposition characteristics can be improved while setting the horizontal spread angle θ‖ to about 8 to 10 degrees.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a semiconductor laser according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a semiconductor laser according to the first embodiment of the present invention. In FIG.
On the n-type GaAs substrate 1, n-type In _0.5 (Ga
_0.27 Al _0.73 ) _0.5 P clad layer 2, MQW
(Multiple quantum well) Active layer 3 and p-type In _0.5 (Ga
_0.27 Al _0.73 ) _0.5 P cladding layer 4 is sequentially formed, and p-type In _0.5 (Ga _0.27 Al _0.73 )
_{The 0.5} P cladding layer 4 has a stripe-shaped ridge R
G is provided. On the ridge RG, a p-type I
An n _0.5 Ga _0.5 P heterobuffer layer 5 is formed,
On both sides of the ridge portion RG, In _0.5 Al _0.5 P light confinement layers 6 are formed. These p-type In _0.5 G
a _0.5 P heterobuffer layer 5 and In _0.5 Al
_{On the 0.5} P light confinement layer 6, a p-type GaAs contact layer 7 is formed. On the p-type GaAs contact layer 7, a p-side electrode 8 is formed, and a back surface of the n-type GaAs substrate 1 is formed. Is formed with an n-side electrode 9. In addition,
The p-type In _0.5 Ga _0.5 P hetero buffer layer 5 is
It is intended to alleviate the mismatch of the hetero barrier between the type In _0.5 (Ga _0.27 Al _0.73 ) _0.5 P cladding layer 4 and the p-type GaAs contact layer 7.

[0032] Here, _{an In} 0.5 _{Al 0} instead of n-type GaAs light confinement layer 11 of _{FIG. 5} P light confinement layer 6
By using, it is possible to control the effective refractive index difference between the inside and outside of the stripe while ensuring transparency to laser light, and to stabilize the fundamental transverse mode while suppressing light absorption loss.

_Further, In _{0.5 Al} 0.5 P light confining layer 6 and the p-type _{In 0.5 (Ga 0.2 7 Al 0.73} )
_The current supplied from the p-side electrode 8 can be made to flow only to the central stripe ridge portion RG by using the hetero barrier formed between the _0.5 P cladding layer 4 and the current can be confined. .

The effective refractive index difference between inside and outside of the stripe is:
The distance h between the light confinement layer 6 and the active layer 3 is preferably set in the range of 0.007 to 0.014, and
It is preferably in the range of μm to 0.15 μm. The width w1 of the stripe is preferably in the range of 3.5 μm to 5.5 μm.

As a result, the horizontal spread angle θ‖ of 8 to 10 degrees can be secured and the stripe width w1 can be increased without impairing the stability of the basic transverse mode. Therefore, while satisfying the requirements from the optical system of the optical pickup,
It is possible to prevent an increase in the resistance value and to prevent deterioration of the high-frequency superposition characteristics.

[0036] For example, as an example of the optimized parameters, n-type _{In 0.5 (Ga 0.2 7 Al 0.73} )
_0.5 The thickness d1 of the P cladding layer 2 is 1.0 μm and the p-type
n _{0. 5} (Ga _0.27 Al _0.73 ) _0.5 P The thickness d2 of the cladding layer 4 is 1.0 μm, the distance h between the optical confinement layer 6 and the active layer 3 is 0.1 μm, and the width w1 of the stripe is 4 μm.
μm and the effective refractive index difference inside and outside the stripe is 0.011
It can be.

In the above embodiment, the case where InAlP is used for the light confinement layer 6 has been described.
nGaAlP may be used. Further, in the above _embodiment, although an In 0.5 _{Al 0.5} P light confining layer 6 has been described for the case of _{undoped, an In 0.5}
The Al _0.5 P light confinement layer 6 may be doped. In addition, although the method of changing the distance h between the light confinement layer 6 and the active layer 3 to control the effective refractive index difference between inside and outside of the stripe has been described, the composition of the light confinement layer 6 may be changed. .

FIG. 2A is a diagram showing a simulation result of the relationship between the distance h and the effective refractive index difference Δn of the semiconductor laser according to the first embodiment of the present invention. In FIG. 2A, as the distance h increases, the light confinement layer 6
Has a smaller effect on the active layer 3, so that the effective refractive index difference Δn inside and outside the stripe becomes smaller. Here, in order to make the refractive index difference Δn between the inside and outside of the stripe 0.004 to 0.005, the distance h needs to be set to about 0.2 μm. 007
In order to set the distance h to 0.014, the distance h is set to 0.08 μm to 0.
It can be seen that it is necessary to set the range to 15 μm.

FIG. 2B is a diagram showing a simulation result of the relationship between the effective refractive index difference Δn and the horizontal spread angle θ‖ of the semiconductor laser according to the first embodiment of the present invention.
Here, when evaluating the relationship between the effective refractive index difference Δn and the horizontal spread angle θ‖, the stripe width w1 is set to 2.5 to 5.
It was changed to 5 μm.

In FIG. 2B, when the stripe width w1 is reduced, the horizontal divergence angle θ‖ increases. However, even when the effective refractive index difference Δn is increased, the horizontal divergence angle θ‖ increases. Therefore, by increasing the effective refractive index difference Δn, the horizontal spread angle θ 水平 can be increased without reducing the stripe width w1. For example, the refractive index difference Δn between the inside and outside of the stripe is 0.004 to
In the case of 0.005, in order to obtain a horizontal spread angle θ‖ = 9 degrees, it is necessary to set the stripe width w1 to about 2.5 μm, and the resistance value increases so as not to be practical.

On the other hand, the refractive index difference Δ
If n is 0.007 to 0.014, the stripe width w
1 = 3.5 μm or more, and the horizontal spread angle θ‖ = 9
Degree of resistance, and the resistance value can be reduced to a practical level. Here, in order to increase the stripe width, the refractive index difference Δn between the inside and the outside of the stripe is set to 0.007 to 0.
If it is set to 014, the basic lateral mode may be unstable, but by using the optical output at 15 mW or less, the stability of the basic lateral mode can be maintained.

FIG. 2C is a diagram showing a simulation result of a relationship between the distance h of the semiconductor laser and the horizontal spread angle θ‖ according to the first embodiment of the present invention. Here, when evaluating the relationship between the distance h and the horizontal spread angle θ‖,
The stripe width w1 was changed from 2.5 to 5.5 μm. In FIG. 2C, when the stripe width w1 is reduced, the horizontal spread angle θ‖ increases, but when the distance h is reduced, the horizontal spread angle θ 角度 increases. Therefore, by reducing the distance h, the stripe width w1
Can be increased without reducing the horizontal spread angle θ‖.

FIG. 3A is a view showing an experimental result of a relationship between the distance h of the semiconductor laser and the horizontal spread angle θ 角度 according to the first embodiment of the present invention. In this experimental example,
The stripe width w1 was set to 4.0 μm. In FIG. 3A, as in the simulation result of FIG. 2C, when the distance h is reduced, the horizontal spread angle θ‖ increases.

FIG. 3B is a diagram showing an experimental result of a relationship between the distance h of the semiconductor laser according to the first embodiment of the present invention, the threshold current Ith and the operating current Iop. In FIG. 3B, the threshold current Ith and the operating current Iop became minimum around the distance h = 0.1 μm. For this reason, from the viewpoint of the threshold current Ith and the operating current Iop, it is desirable to set the distance h to about 0.1 μm, and the refractive index difference Δn between the inside and outside of the stripe at this time is 0.
011.

In order to keep the threshold current Ith and the operating current Iop within a practical range, the distance h = 0.08
It is preferable to set the range of μm to 0.15 μm.
For this reason, as shown in FIG. 2A, it is preferable that the refractive index difference Δn between the inside and outside of the stripe is set to 0.007 to 0.014.

As described above, the refractive index difference Δ
By setting n in the range of 0.007 to 0.014, it is possible to maintain the stability of the basic transverse mode and to set the horizontal spread angle θ 上 to about 9 degrees without increasing the resistance value. In addition, the advantage that the threshold current Ith and the operating current Iop are minimized is also obtained.

FIG. 3C is a graph showing an experimental result of a relationship between the stripe width w1 and the horizontal spread angle θ‖ of the semiconductor laser according to the first embodiment of the present invention. In this experimental example, the distance h was set to 0.1 μm. FIG. 3 (c)
It can be seen that the horizontal spread angle θ‖ increases as the stripe width w1 decreases. Here, the distance h =
In the case of 0.1 μm, even if the stripe width w1 is increased to 4 μm, the horizontal spread angle θ‖ can be set to 8 °, and the resistance value R can be reduced to a practical level.

FIG. 3D is a view showing an experimental result of a relationship between the stripe width w1 and the resistance value R of the semiconductor laser according to the first embodiment of the present invention. FIG. 3D shows that the resistance value R increases as the stripe width w1 decreases. Here, if the resistance value R is about 20Ω or less, there is no practical problem, and the stripe width w1 is preferably set to 3.5 μm or more. On the other hand, if the stripe width w1 is too wide, the allowable value (θ
(‖ = About 8 to 10 degrees), the stripe width w1 is preferably set to 5.5 μm or less.

FIG. 4 is a sectional view showing a method for manufacturing a semiconductor laser according to the first embodiment of the present invention. FIG. 4 (a)
In was charged with n-type GaAs substrate 1 in the MOCVD reactor, MOCVD by (metal organic vapor deposition) method, for example, n-type _{In 0.5 (Ga 0. 27 Al 0.73} )
_0.5 P cladding layer 2, MQW (multiple quantum well) active layer 3, p-type In _0.5 (Ga _0.27 Al _0.73 )
_0.5 P cladding layer 4 and p-type In _0.5 Ga _0.5
Crystal growth of the P hetero buffer layer 5 is performed sequentially. Note that n
The thickness d1 of the type In _0.5 (Ga _0.27 Al _0.73 ) _0.5 P cladding layer 2 is, for example, 1.0 μm and the p-type I
The thickness d2 of the n _0.5 (Ga _0.27 Al _0.73 ) _0.5 P cladding layer 4 is, for example, 1.0 μm and the p-type In
The thickness of the _0.5 Ga _0.5 P hetero buffer layer 5 can be, for example, 0.05 μm.

Next, as shown in FIG. 4B, the n-type GaAs substrate 1 is taken out of the MOCVD reactor,
The silicon oxide film 10 is formed by the D method or the like. And
The silicon oxide film 10 is patterned in a stripe shape by using a photolithography technique and an etching technique. Note that the stripe width of the silicon oxide film 10 can be, for example, 5 μm.

Next, wet etching is performed using the silicon oxide film 10 as a mask to obtain p-type In _0.5.
While removing the Ga _0.5 P hetero buffer layer 5,
p-type In _0.5 (Ga _0.27 Al _0.73 ) _0.5 P
The p-type In _0.5 (Ga
_A ridge portion RG is formed in the _0.27 Al _0.73 ) _0.5 P cladding layer 4. Note that the stripe width w1 in the ridge portion RG can be, for example, 4.5 μm.

Next, as shown in FIG. 4C, the n-type GaAs substrate 1 is put again into the MOCVD reactor, and
By the CVD method, for example, the In _0.5 Al _0.5 P light confinement layer 6 is crystal-grown. Here, p-type In _0.5
A silicon oxide film 10 is formed on the Ga _0.5 P hetero buffer layer 5.
Is formed, and the crystal does not grow on the silicon oxide film 10. Therefore, the In _0.5 Al _0.5 P light confinement layer 6 can be selectively formed in a region other than the ridge portion RG.
The thickness t of the In _0.5 Al _0.5 P light confinement layer 6
Can be, for example, 0.3 μm.

Next, as shown in FIG. 4D, the n-type GaAs substrate 1 is taken out of the MOCVD reactor, and the silicon oxide film 10 on the p-type In _0.5 Ga _0.5 P heterobuffer layer 5 is formed. Is removed. Then, the n-type GaAs substrate 1
Is again introduced into the MOCVD reactor, and, for example, the p-type GaAs contact layer 7 is crystal-grown by the MOCVD method. Thereafter, the n-type GaAs substrate 1 is taken out of the MOCVD reactor, and the p-side electrode 8 is formed by a method such as vapor deposition.
And an n-side electrode 9 is formed.

This wafer was cleaved so as to have a cavity length of 400 μm, coated with an end face having a front surface reflectivity of 30% and a rear surface reflectivity of 80%, and scribed to produce semiconductor chips. When this semiconductor chip was mounted on a 5.6φ package and the laser characteristics were evaluated, the lasing threshold Ith = 20 mA, lasing wavelength λ = 655 nm, operating voltage = 2.25 V, horizontal spread angle θ 角度 = 9 degrees, vertical The spread angle θ⊥ = 28 degrees was obtained. In addition, current light output characteristics with good linearity were obtained up to an optical output of 15 W, and there was no problem with high-frequency superposition characteristics.

In the embodiment described above, the MOCVD
The method of crystal growth by the method has been described.
E (molecular beam epitaxial growth) or ALE (atomic layer epitaxy) may be used.

FIG. 5 is a sectional view showing the structure of a semiconductor laser according to the second embodiment of the present invention. In the first embodiment described above, in order to control the effective refractive index difference between inside and outside of the stripe, In _0.5 Al is provided on both sides of the ridge portion RG.
_{While the 0.5} P light confinement layer 6 is formed,
In the embodiment, the In _0.5 Al _0.5 P light confinement layer 2
By forming an opening HL in 5, an effective refractive index difference inside and outside the stripe is controlled.

In FIG. 5, on an n-type GaAs substrate 21
Is an n-type In_0.5(Ga_0.27Al_0.73)
_0.5P cladding layer 22, MQW (multiple quantum well) activity
Layer 23 and p-type In_0.5(Ga_0.27Al
_0.73)_0.5P clad layer 24a, In_0.5Al
_0.5P light confinement layer 25, p-type In_0.5(Ga
_0.27Al _0.73)_0.5P clad layer 24b, p
Type In_0.5Ga_0.5P hetero buffer layer 26 and
A p-type GaAs contact layer 27 is sequentially formed.
A p-side electrode is formed on the p-type GaAs contact layer 27.
28 is formed and the back of the n-type GaAs substrate 21 is formed.
An n-side electrode 29 is formed on the surface.

Here, the In _0.5 Al _0.5 P light confinement layer 25 has a thickness h of p-type In _{0.1. 5} (Ga _0.27 A
1 _0.73 ) _0.5 A stripe-shaped opening HL corresponding to the light-emitting region is provided through the P cladding layer 24a. Therefore, an effective refractive index difference is generated inside and outside the stripe, and the effective refractive index inside the stripe can be made larger than the effective refractive index outside the stripe. Therefore, the laser light can be confined in the stripe, and the transverse mode can be stabilized.
Further, since an InAlP-based material is used for the light confinement layer 25, transparency to laser light can be ensured and light absorption loss can be suppressed. Further, by utilizing a hetero barrier formed between the In _0.5 Al _0.5 P light confinement layer 25 and the p-type In _0.5 (Ga _0.27 Al _0.73 ) _0.5 P cladding layers 24a and 24b. , The current supplied from the p-side electrode 28 can be passed only to the central opening HL, and the current can be constricted.

Here, in order to secure a horizontal divergence angle θ‖ of 8 to 10 degrees without deteriorating the stability of the basic transverse mode, the effective refractive index difference inside and outside the stripe is 0.007 to 0.007.
It is preferable to set in the range of 0.014. Further, in order to set the effective refractive index difference inside and outside the stripe to such a range, the distance h between the light confinement layer 25 and the active layer 23 is set.
Is preferably in the range of 0.08 μm to 0.15 μm. In order to suppress an increase in the resistance value, the width w1 of the stripe is preferably in the range of 3.5 μm to 5.5 μm.

[0060] For example, as an example of the optimized parameters, n-type _{In 0.5 (Ga 0.2 7 Al 0.73} )
_0.5 P clad layer 22 has a thickness d1 of 1.0 μm and a p-type In _{0 . 5} (Ga _0.27 Al _0.73 ) _0.5 The thickness d3 of the P cladding layer 24b is 1.0 μm, and the light confinement layer 2
5 and the active layer 23. 0.1 μm, the width w1 of the stripe is 4.5 μm, and the effective refractive index difference inside and outside the stripe can be 0.011.

FIG. 6 shows a semiconductor device according to a second embodiment of the present invention.
It is sectional drawing which shows the manufacturing method of a body laser. In FIG. 6 (a)
Then, the n-type GaAs substrate 21 is put into the MOCVD reactor.
And MOCVD, for example, n-type In
_0.5(Ga_0.27Al_0.73) _0.5P clad
Layer 22, MQW (multiple quantum well) active layer 23, p-type In
_0.5(Ga_0.27Al_0.73)_0.5P clad
Layer 24a and In_0.5Al _0.5P light confinement layer 2
5 are sequentially grown. Note that n-type In_0.5(Ga
_0.27Al_0.73)_0.5Thickness of P clad layer 22
d1 is, for example, 1.0 μm, p-type In_0.5(Ga
_0.27Al_0.73)_0.5Thickness of P clad layer 24a
The thickness h is, for example, 0.1 μm, In_0.5Al_0.5P
The thickness t of the light confinement layer 25 is, for example, 0.5 μm.
Can be

Next, as shown in FIG. 6B, the n-type GaAs substrate 21 is taken out of the MOCVD reactor,
The silicon oxide film 30 is formed by a VD method or the like. Then, a stripe-shaped opening is formed in the silicon oxide film 30 by using a photolithography technique and an etching technique. The width of the opening of the silicon oxide film 30 can be, for example, 4.0 μm.

Next, by using the silicon oxide film 30 as a mask, the In _0.5 Al _0.5 P light confinement layer 25 is etched to form an opening in the In _0.5 Al _0.5 P light confinement layer 25. The part HL is formed. The stripe width w1 at the opening HL is, for example, 4.0 μm.
It can be.

Next, as shown in FIG.
Silicon oxide film 3 on _0.5 Al _0.5 P optical confinement layer 25
Remove 0. Then, the n-type GaAs substrate 21 is
Again charged into OCVD reactor by MOCVD, for example, p-type _{In 0.5 (Ga 0. 27 Al 0.73} )
_0.5 P clad layer 24 b, p-type In _0.5 Ga _0.5
The P hetero buffer layer 26 and the p-type GaAs contact layer 27 are crystal-grown. Note that p-type In _0.5 (Ga
The thickness d3 of the _0.27 Al _0.73 ) _0.5 P cladding layer 24 b can be, for example, 1.0 μm. Thereafter, the n-type GaAs substrate 21 is taken out of the MOCVD reactor, and a p-side electrode 28 and an n-side electrode 29 are formed by a method such as vapor deposition.

This wafer was cleaved so as to have a cavity length of 400 μm, coated with an end face having a front surface reflectivity of 30% and a rear surface reflectivity of 80%, and scribed to produce semiconductor chips. When this semiconductor chip was mounted on a 5.6φ package and the laser characteristics were evaluated, the same results as in the embodiment of FIG. 1 were obtained.

[0066]

As described above, according to the present invention,
It is possible to stabilize the fundamental transverse mode while suppressing the absorption loss of laser light, and to obtain a predetermined horizontal spread angle without increasing the resistance value.

[Brief description of the drawings]

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

FIG. 2A is a diagram illustrating a simulation result of a relationship between a distance h and an effective refractive index difference Δn of the semiconductor laser according to the first embodiment of the present invention, and FIG. Effective refractive index difference Δn of the semiconductor laser according to the first embodiment
FIG. 2C shows a simulation result of a relationship between the horizontal spread angle θ‖ and the distance h of the semiconductor laser according to the first embodiment of the present invention. FIG.

FIG. 3A is a view showing an experimental result of a relationship between a distance h and a horizontal spread angle θ‖ of the semiconductor laser according to the first embodiment of the present invention, and FIG. 3B is a view showing the present invention. Of the semiconductor laser according to the first embodiment and the threshold current Ith
FIG. 3C shows an experimental result of the relationship between the stripe width w1 and the horizontal spread angle θ‖ of the semiconductor laser according to the first embodiment of the present invention. FIG. 3D shows the stripe width w1 and the resistance value R of the semiconductor laser according to the first embodiment of the present invention.
FIG. 9 is a view showing an experimental result of a relationship with the above.

FIG. 4 is a sectional view illustrating the method for manufacturing the semiconductor laser according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration of a semiconductor laser according to a second embodiment of the present invention.

FIG. 6 is a sectional view illustrating a method for manufacturing a semiconductor laser according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a configuration of a conventional semiconductor laser.

[Explanation of symbols]

1,21 n-type GaAs substrate 2,22 n-type In _0.5 (Ga _0.27 A
l _0.73 ) _0.5 P cladding layer 3, 23 MQW active layer 4, 24 a, 24 bp p-type In _0.5 (Ga _0.27 A
l _0.73 ) _0.5 P cladding layer _5, 26 p-type In _0.5 Ga _0.5 P heterobuffer layer 6, 25 In _0.5 Al _0.5 P light confinement layer 7, 27 p-type GaAs contact Layer 8, 28 p-side electrode 9, 29 n-side electrode RG Ridge part HL Opening

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Tanaka 1st address, Komukai Toshiba-cho, Saiyuki-ku, Kawasaki-shi, Kanagawa F-term in Toshiba Microelectronics Center Co., Ltd. 5F073 AA13 AA74 AA83 BA04 BA06 CA14 CB02 DA05 DA22 DA32 DA34 EA15 EA19

Claims (8)

[Claims] A first conductive type clad layer formed on the first conductive type substrate; an active layer formed on the first conductive type clad layer; and a second conductive layer formed on the active layer. A light-confining layer which is transparent to laser light, has an effective refractive index difference between the inside and outside of the stripe in the range of 0.007 to 0.014, and has a smaller refractive index than the second conductive type cladding layer. And a semiconductor laser. 2. The method according to claim 2, wherein the second conductive type clad layer includes a ridge corresponding to the stripe, and the light confinement layer is formed on the second conductive type clad layer other than the ridge. Claim 1
A semiconductor laser as described in the above. 3. The light confinement layer is formed in the cladding layer of the second conductivity type at a predetermined distance from the active layer, and has an opening corresponding to the stripe. A semiconductor laser as described in the above. 4. The semiconductor laser according to claim 1, wherein a distance between the light confinement layer and the active layer is in a range of 0.08 μm to 0.15 μm. 5. The method according to claim 1, wherein the stripe has a width of 3.5 μm or less.
5. The range of 5.5 [mu] m.
The semiconductor laser according to any one of the above items. 6. The first conductivity type substrate is made of GaAs, and the first conductivity type and the second conductivity type cladding layers are made of InGaAl.
P, the active layer is InGaAlP or InGaP, or a quantum well structure thereof, and the light confinement layer is In.
6. The semiconductor laser according to claim 1, wherein the semiconductor laser is GaAlP or InAlP. 7. A step of forming a first conductivity type clad layer on a first conductivity type substrate, a step of forming an active layer on the first conductivity type clad layer, and a second conductivity type on the active layer. Forming a cladding layer, forming a stripe-shaped mask on the second conductivity type cladding layer, etching the second conductivity type cladding layer to a predetermined thickness via the mask, A semiconductor comprising a step of selectively forming an optical confinement layer in a region other than the mask by performing crystal growth through a mask; and a step of forming a contact layer by removing the mask. Laser manufacturing method. 8. A step of forming a first conductivity type clad layer on a first conductivity type substrate, a step of forming an active layer on the first conductivity type clad layer, and a first step on the active layer. Forming a second conductivity type clad layer; forming a light confinement layer on the second conductivity type clad layer; forming a stripe-shaped opening in the light confinement layer; A second second pass on the light confinement layer
A method of manufacturing a semiconductor laser, comprising: forming a conductive type clad layer; and forming a contact layer on the second conductive type clad layer.