JP3213428B2 - Semiconductor laser device and method of manufacturing the same - Google Patents

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 capable of operating at a low threshold current and a method of manufacturing the same.

[0002]

2. Description of the Related Art Semiconductor laser devices are required to have good optical characteristics in many application fields. In order to obtain such good optical characteristics, the semiconductor laser device often employs a refractive index waveguide structure. As the refractive index waveguide structure, a structure called a self-aligned structure manufactured by a crystal growth method such as a molecular beam epitaxy (MBE) method or a metal organic chemical vapor deposition (MOCVD) method is well known.

FIG. 9 shows a conventional semiconductor laser device having the self-aligned structure. The manufacturing process of the self-aligned semiconductor laser device will be described below.

First, an MOC is placed on an n-type GaAs substrate 701.
By the VD method, the n-type GaAs buffer layer 702 (layer thickness: 0.5 μm) and the n-type AlyGa _1- yAs first cladding layer 703 are formed.
(y = 0.45, layer thickness 1 μm) and AlxGa ₁ -xAs active layer 7
04 (x = 0.13, layer thickness 0.08 μm) and p-type AlyGa _1- y
As second cladding layer 705 (layer thickness 0.2 μm) and n-type GaAs
A current blocking layer 706 (layer thickness 1 μm) is formed in order. next,
The current blocking layer 70 is formed by photolithography or the like.
6 is removed in a stripe shape and a groove shape with a width of 3 to 4 μm to form a defective portion 720.

After that, the p-type AlyGa is again formed on the current blocking layer 706 including the deficient portion 720 by MOCVD.
_1- yAs third cladding layer 708 (layer thickness 1 μm) and p-type GaAs
By sequentially forming the cap layer 709 (layer thickness 1 μm), a semiconductor laser device having the structure shown in FIG. 9 is obtained.

[0006] In the semiconductor laser device, the current blocking layer 70
The defective portion 720 formed by removing 6 in a stripe shape becomes a current path. The current blocking layer 70
6 has a light absorbing function, the deficient portion 720 not only serves as the current path but also forms a refractive index waveguide mechanism.

[0007] In the semiconductor laser device, the current blocking layer 70
Due to the refractive index light absorption effect based on the light absorption effect of No. 6, the loss for the higher-order transverse mode is much larger than the loss for the fundamental transverse mode. Therefore, according to the self-aligned structure of the semiconductor laser device, an extremely stable fundamental transverse mode operation can be obtained.

In the semiconductor laser device having the self-aligned structure, the current is confined in the groove-shaped defective portion 720 formed in the current blocking layer 706 to realize a low current operation.

[0009]

However, in the above-described conventional semiconductor laser device, the current confined sufficiently narrowly by the current blocking layer 706 moves in the second cladding layer 705 in the lateral direction (the direction parallel to the active layer 704). ). And
Due to the spread of the current, a reactive current is generated, and there is a problem that a sufficiently low current operation cannot be realized in practice.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor laser device which can realize not only stable fundamental transverse mode oscillation but also a sufficiently low current operation, and a method of manufacturing the same.

[0011]

In order to achieve the above object, the present invention provides at least a semiconductor device of the first conductivity type on a semiconductor substrate of the first conductivity type.
The first conductive type first cladding layer, the active layer, and the second conductive type
A second clad layer of an electric type,
The first conductor having a stripe-shaped and groove-shaped defect on the layer
An electric current blocking layer is stacked, and the stripe-shaped defect is formed.
At least a third cladding layer of the second conductivity type is formed on the portion.
Semiconductor laser device, wherein the second cladding layer
Is a high-concentration portion facing the defective portion of the current blocking layer;
Facing the non-defective portion of the current blocking layer, and
And a low concentration portion having a lower impurity concentration than
At least the impurities in the second cladding layer are
It is characterized by having impurities which are harder to diffuse than impurities of the layer .

[0012]

[0013]

[0014]

[0015]

[0016]

Further, according to the present invention, in the above-described semiconductor laser device, the third clad layer is provided in the high-concentration portion of the second clad layer.
The second cladding layer
The degree portion is characterized in that you do not contain impurities third cladding layers.

Further, the present invention, there is provided a semiconductor laser device described above is characterized in that an impurity of a low concentration portion of the second cladding layer is <br/> carbon.

[0019] In the method for manufacturing a semiconductor laser device for producing a semiconductor laser device described above, formed on a semiconductor substrate, at least a first cladding layer, an active layer, a second cladding layer, a current blocking layer in this order A first step of forming a striped groove-shaped defect in the current blocking layer; and a second step of forming a striped groove-shaped defect in the current blocking layer.
At least a third step of forming a third cladding layer; and diffusing impurities from the third cladding layer into at least the second cladding layer via a defective portion of the current blocking layer;
The impurity concentration of the second cladding layer in the region facing the defective portion is adjusted to the second concentration of the region facing the non-defective portion of the current blocking layer.
A fourth step of making the impurity concentration higher than the impurity concentration of the cladding layer, wherein the impurity existing in the second cladding layer before the impurity is diffused from the third cladding layer to the second cladding layer,
It is characterized in that impurities are hardly diffused compared to the impurities diffused from the third clad layer to the second clad layer.

[0020]

According to the present invention , the impurity in the second cladding layer is
Contains impurities that are more difficult to diffuse than impurities in the cladding layer
Therefore, impurities are introduced from the third cladding layer to the second cladding layer.
When diffusing, it is in the second cladding layer before this diffusion
The diffusion of impurities can be suppressed, and impurities between the cladding layers can be reduced.
There is an effect that the controllability of material diffusion is improved. Also missing
The impurity concentration of the second cladding layer in the region facing the damaged portion is
The second crack in the region facing the non-defective portion of the current blocking layer
It is easier to make the height higher than that of the metal layer. In addition, the second class
Of reactive current due to current spreading in the pad layer
Thus, a low threshold current operation is realized. That is, in this invention
Controls the impurity distribution in the second cladding layer,
There is an effect that the work can be realized .

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

Further, according to the semiconductor laser device of the present invention, the p-type impurity of the second cladding layer 5 is carbon C, so that the effect of preventing the second cladding layer from diffusing impurities can be further enhanced. Therefore, in the present invention, the controllability of the impurity distribution of the second cladding layer is further improved, and the low-current operation can be realized more reliably.

Further, according to the method of manufacturing a semiconductor laser device according to the present invention, before diffusing impurities from the third cladding layer into the second cladding layer, the impurities in the second cladding layer are removed from the third cladding layer. The impurities are hardly diffused compared to the impurities diffused from the layer into the second cladding layer.

Therefore, when the impurities are diffused from the third cladding layer to the second cladding layer, the diffusion of the impurities existing in the second cladding layer before the diffusion can be suppressed.

Therefore, according to the present invention, the impurity concentration of the second cladding layer in the region facing the deficient portion is made higher than the impurity concentration of the second cladding layer in the region facing the non-defective portion of the current blocking layer. It is easy to raise the height.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows a first example of the semiconductor laser device of the present invention.
1 shows a cross section of an example. The structure of the first embodiment will be described with reference to FIG. This first embodiment is an n-type GaAs substrate
(Carrier concentration: 2 × 10 ¹⁸ cm ⁻³ ) An n-type GaAs buffer layer (layer thickness: 0.5 μm, carrier concentration: 1 × 10 ¹⁸ cm ^-3 )
^-3 ) 2 and n-type AlyGa _1- yAs first cladding layer (y = 0.
5, a layer thickness of 1 μm, a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ ) 3 and a non _- doped AlxGa ₁ -xAs active layer (x = 0.14, layer thickness of 0.0
9 μm) 4 and p-type AlyGa _1- yAs second cladding layer (0.3 μm).
m, 1 × 10 ¹⁷ cm ⁻³ ) 5 and an n-type GaAs current blocking layer (layer thickness: 0.8 μm, carrier concentration: 5 × 10 ¹⁸ cm ⁻³ ) 6 are sequentially stacked.

Further, in the first embodiment, as shown in FIG. 1, the current blocking layer 6 has a defective portion 10 formed by removing the current blocking layer 6 in the form of a stripe-shaped groove. A current is injected into the active layer 4 through the deficient portion 10.

Further, in the first embodiment, the p-type AlyGa _1-
yAs third cladding layer (layer thickness 1 μm, carrier concentration 1.5 ×
10 ¹⁸ cm ⁻³ ) 7 and a p-type GaAs cap layer (layer thickness 2 μm, carrier concentration 5 × 10 ¹⁸ cm ⁻³ ) 8 are sequentially stacked. Further, in the first embodiment, the n-side electrode 1 is provided on the substrate 1 side.
1 is formed, and the p-side electrode 12 is formed on the cap layer 8 side.

Further, in the above embodiment, the impurity is diffused from the third cladding layer 7 through the deficient portion 10, and this diffusion causes the diffusion region from the second cladding layer 5 to the active layer 4. Are formed. This diffusion region is opposed to the defect portion 10. The second cladding layer 5 in the diffusion region forms a high-concentration portion having a higher impurity concentration than the second cladding layer 5 in the region facing the non-defective portion of the current blocking layer 6.

Next, a method of manufacturing the semiconductor laser device of the first embodiment will be described. This manufacturing method first,
As shown in FIG. 8A, an n-type GaAs buffer layer 2 is formed on an n-type GaAs substrate 1 by molecular beam epitaxy.
N-type AlyGa ₁ -yAs first cladding layer 3, non-doped active layer 4, p-type AlGaAs second cladding layer 5, n-type Ga
The As current blocking layer 6 is sequentially grown to form a growth layer.

At this time, the n-type dopant is Si, p
Be is used as the type dopant. Also, the Si doping concentration of the buffer layer 2 and the first cladding layer 3 is about 1 × 10 ¹⁸ cm ⁻³ , the Be doping concentration of the second cladding layer 5 is about 1 × 10 ¹⁷ cm ⁻³ , and the current blocking layer 6
Was made to have a Si doping concentration of about 5 × 10 ¹⁸ cm ⁻³ .

Next, after growing the growth layer shown in FIG. 8A, the growth layer (wafer) is taken out of the MBE apparatus, and
As shown in FIG. 8B, a stripe-shaped and groove-shaped defective portion 10 having a width of about 3.5 μm is formed in the current blocking layer 6 by using a photolithography method or the like. The groove depth of the deficient portion 10 is set so that the thickness of the bottom of the deficient portion 10 becomes about 0.05 μm.

Next, the wafer is introduced into a liquid phase growth apparatus, and the GaAs layer (the rest of the current blocking layer 6) at the bottom of the defective portion 10 is melted back by the liquid phase growth (LPE) method. Then, on the current blocking layer 6 including the deficient portion 10,
A p-type AlGaAs third cladding layer 7 and a p-type GaAs cap layer 8 are sequentially grown (see FIG. 8C).

In the LPE growth, Mg is used as a p-type dopant. And the third cladding layer 7 and
The doping concentration of the cap layer 8 is 1.5 × 10
¹⁸ cm ⁻³ and 5 × 10 ¹⁸ cm ⁻³ . This L
After PE growth, the wafer is kept at a high temperature (about 800 ° C.) in the LPE growth apparatus for about 30 minutes, and the third clad layer 7 is formed.
Impurities from the second cladding layer 5 through the defect 10
(Mg) is diffused to form a diffusion region 13 (FIG. 8).
(D)). Next, after taking out the wafer from the LPE apparatus, the substrate 1 is polished to a thickness of about 100 μm,
The side electrode 12 and the n-side electrode 11 are formed. Finally, the semiconductor laser device of the first embodiment can be obtained by dividing the chip by cleavage.

In the semiconductor laser device of the first embodiment, the second cladding layer 5 in the region facing the non-defective portion of the current blocking layer 6 is a low-concentration portion 5A, and the low-concentration portion 5A has an impurity concentration of 1%. × well as the 10 ¹⁷ cm ^-3, a second clad layer 5 in the diffusion region as the high density portion 5B, and the impurity concentration of the high density portion 5B to 5~8 × 10 ¹⁷ cm ^-3. Therefore, the resistivity of the high-concentration portion 5B is changed to the low-concentration portion 5B.
A can be made smaller than the resistivity of A. Accordingly, the third clad layer 7 to the high concentration portion 5 of the second clad layer 5
The current that has reached B can be prevented from spreading to the low concentration portion 5A. That is, in the second cladding layer 5, the reactive current spreading in the lateral direction (the direction parallel to the active layer 4) can be reduced. Therefore, according to the first embodiment, a low threshold current operation can be realized.

In the first embodiment, the dopant of the second cladding layer 5 is set to Be which is difficult to diffuse as compared with Mg which is the dopant of the third cladding layer 7. When the impurity Mg is diffused into the cladding layer 5, the diffusion of the impurity Be of the second cladding layer 5 can be prevented. Here, p of the second cladding layer 5
When the type impurity is carbon C, the effect of preventing the second clad layer 5 from diffusing impurities can be further enhanced.

Next, FIG. 2 shows a cross section of the second embodiment.
The second embodiment has the same basic structure and manufacturing method as the first embodiment. Therefore, points different from the first embodiment will be mainly described below. This second
In the embodiment, the current blocking layer 6 includes an AlGaAs etching stop layer 16 and a GaAs protection layer 15. That is, when the current blocking layer 6 is formed into a multilayer structure to form the striped and grooved deficient portions 10, selective etching is performed so that the groove depth of the deficient portions 10 can be easily controlled. I have. In the second embodiment, as shown in FIG. 8C, the high-temperature holding time after LPE growth (liquid phase growth) is set to 15 minutes, and the diffusion depth of the impurity Mg is controlled.
The depth of the diffusion region 13 is controlled.

Next, FIG. 3 shows a cross section of the third embodiment.
The third embodiment has the same basic structure and manufacturing method as the second embodiment. Therefore, points different from the second embodiment will be mainly described below. In the third embodiment, as shown in FIG. 8C, the high-temperature holding time after the LPE growth (liquid phase growth) is set to 60 minutes, the diffusion depth of the impurity Mg is controlled, and the diffusion region is formed. 13 is controlled. In the third embodiment, as shown in FIG. 3, the diffusion region 13 has reached the first cladding layer 3. That is, in the third embodiment, the p-type diffusion region 13 and the n-type first
The cladding layer 3 forms a pn junction. That is, the third embodiment includes a remote junction in which a pn junction is formed in the first cladding layer 3. If the pn junction of the remote junction is far away from the active layer 4, the oscillation threshold current may increase. Therefore, it is not preferable that the depth of the diffusion region 13 is too large. According to an experiment, it was found that in the above embodiment, the distance between the active layer 4 and the pn junction needs to be about 0.2 μm or less in order to prevent the oscillation threshold current from increasing.

Next, FIG. 4 shows a cross section of the semiconductor laser device of the fourth embodiment. This fourth embodiment is an n-type GaAs substrate
(Impurity concentration 2 × 10 ¹⁸ cm ⁻³ ) 41, an n-type GaAs buffer layer (layer thickness 0.5 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 4
2, an n-type AlyGa _1- yAs first cladding layer (y = 0.5, a layer thickness of 1 μm, an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ ) 43, and a non _- doped AlxGa _1- xAs active layer (x = 0.14) , Layer thickness 0.09μm)
44 and a lightly doped p-type AlyGa _1- yAs second cladding layer (layer thickness: 0.05 μm, impurity concentration: 0.5 × 10 ¹⁷ cm ⁻³ )
And a highly doped p-type AlyGa _1- yAs second cladding layer (layer thickness:
25 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 45-2, n-type GaAs current blocking layer (layer thickness 0.8 μm, impurity concentration 5 × 10
¹⁸ cm ⁻³ ) 46 are sequentially stacked.

The current blocking layer 46 has a deficient portion 50 which is removed in a stripe shape and a groove shape, and a current is injected into the active layer 44 through the deficient portion 50.

Further, in the fourth embodiment, the defective portion 5
A p-type AlyGa _1- yAs third cladding layer (layer thickness 1 μm, impurity concentration 1.5 × 10 ¹⁸ cm ⁻³ ) 4 on the current blocking layer 46 containing
7 and a p-type GaAs cap layer (layer thickness 2 μm, impurity concentration 5
× 10 ¹⁸ cm ^-3 ) 48 are laminated. Also, the substrate 4
An n-side electrode 51 and a p-side electrode 52 are formed on one side and the cap layer 48 side, respectively.

Further, in the above embodiment, the impurity is diffused from the third cladding layer 47 through the deficient portion 50, and the diffusion causes the active from the second cladding layers 45-2 and 45-1. A diffusion region 53 reaching the layer 44 is formed. This diffusion region 53 faces the above-described defective portion 50.

The highly doped second cladding layer 45-2 in the diffusion region 53 constitutes a high concentration portion 45-2B immediately below the defective portion. Further, the highly doped second cladding layer 4 in a region opposed to the non-defective portion of the current blocking layer 46.
5-2 constitutes the low concentration portion 45-2A immediately below the non-defective portion.

The lightly doped second cladding layer 45-1 located in a region facing the non-defective portion of the current blocking layer 46.
Constitutes the non-defective portion opposite low concentration portion 45-1A.

Next, a method of manufacturing the semiconductor laser device of the fourth embodiment will be described.

In this manufacturing method, first, an n-type GaAs buffer layer 42 and an n-type AlyGa ₁ -yAs first cladding layer 43 are formed on an n-type GaAs substrate 41 by molecular beam epitaxy.
And a non-doped active layer 44, a lightly doped p-type AlGaAs second cladding layer 45-1, a highly doped p-type AlGaAs second cladding layer 45-2, and an n-type GaAs current blocking layer 46. Then, a growth layer shown in FIG. When forming this growth layer, Si was used as an n-type dopant,
Be is used as the p-type dopant.

The buffer layer 42 and the first
The Si doping concentration of the cladding layer 43 is 1 × 10 ¹⁸ cm
^-3 .

The second cladding layers 45-1 and 45-2 are first formed with a Be doping concentration of 0.5.
After growing and forming a low-doped second cladding layer 45-1 of about 10 ¹⁷ cm ^-3 and a thickness of about 0.05 μm, the temperature of the Be cell is changed to obtain a doping concentration of 1 × 10 ¹⁸ cm ^-3 . A highly doped second cladding layer 45-2 is formed. The Si doping concentration of the current blocking layer 46 is about 5 × 10 ¹⁸ cm ⁻³ .

Next, after the growth layer is grown, the growth layer (wafer) is taken out of the MBE apparatus, and the current blocking layer 6 is formed into a stripe-like and groove-like shape having a width of about 3.5 μm by photolithography or the like. Form a defect 50 (FIG. 8B)
reference). The groove depth of the defective portion 50 is set so that the bottom of the defective portion 50 has a thickness of about 0.05 μm.

Next, this wafer is introduced into a liquid phase growth apparatus, and G at the bottom of the defective portion 50 is formed by a liquid phase growth (LPE) method.
The As layer (remaining part of the current blocking layer 46) is melted back, and thereafter, the p-type Al
GaAs third cladding layer 47 and p-type GaAs cap layer 4
8 are sequentially grown (see FIG. 8C). In this LPE growth, Mg was used as a p-type dopant, and the dopant concentrations of the third cladding layer 47 and the cap layer 48 were about 1.5 × 10 ¹⁸ cm ⁻³ and 5 × 10 ¹⁸ cm ⁻³ , respectively.

After this LPE growth, the wafer is
It is kept at a high temperature (about 800 ° C.) in the LPE growth apparatus for about 0 minutes, and the p-type second cladding layer
Then, the impurity (Mg) is diffused into the substrate, as shown in FIG.
A diffusion region 53 is formed. Next, after taking out the wafer from the LPE apparatus, the substrate 41 side was polished to 100 μm.
The p-side electrode 52 and the n-side electrode 51 are formed to a thickness of about the same. Finally, by dividing the chip by cleavage, the semiconductor laser device of the fourth embodiment can be obtained.

In the fourth embodiment, the second clad layer
It has a two-layer structure of a low-doped second cladding layer 45-1 having a doping concentration of 0.5 × 10 ¹⁷ cm ^-3 and a highly-doped second cladding layer 45-2 having a doping concentration of 1 × 10 ¹⁸ cm ^-3. ,
Further, in the diffusion region 53 formed by diffusing the impurity (Mg) from the third cladding layer 47, the impurity concentration is 8 to 12 × 1.
0 ¹⁷ cm ^-3 or more.

Therefore, the resistivity of the high-doped second cladding layer 45-2 in the diffusion region 53, that is, the high-concentration portion 45-2B immediately below the defect portion, is lower than that of the low-concentration portion 45-2A immediately below the non-deletion portion on both sides thereof. The resistivity of the low-doped second cladding layer 45-1 in the diffusion region 53 is smaller than the resistivity of the non-defective portion opposed low-concentration portion 45-1A on both sides thereof. Further, the resistivity of the low-density portion 45-1A opposed to the non-defective portion is equal to the low-density portion 45
−2A, the second resistive layer is highly doped.
The carriers (holes) spread in the lateral direction (parallel to the active layer 44) in the cladding layer 45-2 are opposed to the non-defective portions 45 of the low-doped second cladding layer 45-1.
-1A acts as a barrier layer, and can prevent the spread carriers from reaching the active layer 44 outside the diffusion region 53. Therefore, according to the fourth embodiment, the reactive current can be reduced, and a low threshold current operation can be realized.

Next, FIG. 5 shows a cross section of the semiconductor laser device of the fifth embodiment. As shown in FIG. 5, in the fifth embodiment, an n-type GaAs buffer layer (layer thickness: 0.5 μm, impurity concentration: 1 × 10 5) is formed on an n-type GaAs substrate (impurity concentration: 2 × 10 ¹⁸ cm ⁻³ ). ¹⁸ cm ⁻³ ) 52 and n-type AlyGa ₁ -yAs first cladding layer (y = 0.5, layer thickness 1 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ )
53 and a non _- doped AlzGa ₁ -zAs first optical guide layer (z:
0.5 → 0.3, layer thickness 0.15 μm) 54, non-doped G
aAs quantum well active layer (layer thickness 0.007 μm) 55 and non _- doped AlzGa ₁ -zAs second optical guide layer (z: 0.3 → 0.3)
5, a layer thickness 0.15 μm) 56 and a p-type AlyGa _1- yAs second cladding layer (layer thickness 0.2 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ )
57 and an n-type GaAs current blocking layer (layer thickness 0.8 μm, impurity concentration 5 × 10 ¹⁸ cm ⁻³ ) 58 are laminated.

The current blocking layer 58 has a defective portion 60 removed in a stripe shape. A current is injected into the active layer 55 through the deficient portion 60.

In the fifth embodiment, the defective portion 6
The third cladding layer of p-type AlyGa _1- yAs (layer thickness 1 μm, impurity concentration 1.5 × 10 ¹⁸ cm ⁻³ ) on the current blocking layer 58 containing zero.
61 and a p-type GaAs cap layer (layer thickness 2 μm, impurity concentration 5 × 10 ¹⁸ cm ⁻³ ) 62 are laminated. An n-side electrode 63 and a p-side electrode 64 are formed on the substrate 51 side and the cap layer 62 side.

Further, in the above structure, the third cladding layer 61, the second cladding layer 57, the second light guide layer 56 and the active layer
5 and the first light guide layer 54 are diffused to form a diffusion region 65. The manufacturing method and procedure of the above embodiment are the same as those of the first embodiment, and the types of impurities are also the same as those of the first embodiment.

In the fifth embodiment, the resistivity of the diffusion region 65 is reduced by the impurity diffusion as compared with the resistivity of the second cladding layer 57 on both sides thereof. In other words, the second cladding layer 57 has a defect-confronting high-concentration cladding 57A facing the defect 60 of the current blocking layer 58, and has a lower impurity concentration than the high-concentration cladding 57A. The low-concentration clad portion 57B facing the non-defective portion is included.

The second light guide layer 56 includes a high concentration guide portion 56 A in the diffusion region 65 and the diffusion region 6.
5 includes a non-doped guide portion 56B.

Therefore, in the fifth embodiment, the resistivity of the second cladding layer 57 inside the diffusion region 65 due to impurity diffusion is smaller than the resistivity of the second cladding layer 57 outside the diffusion region 65 on both sides. It has been reduced. Further, the second light guide layer 56 is also provided with the guide portion 5 in the diffusion region 65.
The resistivity of 6A is lower than that of the non-doped, high-resistance guide portion 56B outside the diffusion region 65.

For this reason, in the second cladding layer 57 and the second optical guide layer 56, the reactive current spreading in the lateral direction (the direction parallel to the growth surface of the active layer 55) is reduced, and as a result, the threshold current is reduced. realizable.

In the fifth embodiment, the impurity diffusion reaches the first light guide layer 54, and the first light guide layer 5
Although a remote junction is formed in 4, the first optical guide layer 54 has a graded composition, so that the remote junction does not lower the carrier injection efficiency into the active layer 55. Therefore, the oscillation threshold current does not increase due to the presence of the remote junction. It goes without saying that the impurity diffusion region can be controlled so that the remote junction is not formed.

In the fifth embodiment, the current blocking layer 58 comprises an etching stop layer 58-2 and a protective layer 58-.
1 and a multi-layer structure capable of selective etching. Therefore, in the fifth embodiment, the controllability of the formation of the structure of the defective portion 60 can be improved.

It is effective to improve the controllability of the formation of the structure of the fourth embodiment by making the current blocking layer of the fourth embodiment the same multilayer structure as the current blocking layer of the fifth embodiment. Needless to say, there is.

Next, FIG. 6 shows a cross section of the semiconductor laser device of the sixth embodiment. This sixth embodiment is an n-type GaAs substrate
(Impurity concentration 2 × 10 ¹⁸ cm ⁻³ ) 71, an n-type GaAs buffer layer (layer thickness 0.5 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 7
2 and an n-type AlyGa _1- yAs first cladding layer (y = 0.5,
A layer thickness of 1 μm, an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ ) 73 and a non _- doped AlxGa ₁ -xAs active layer (x = 0.14, layer thickness of 0.0
9 μm) 74 and an n-type AlyGa ₁ -yAs second cladding layer (layer thickness 0.08 μm, impurity concentration 3 × 10 ¹⁷ cm ⁻³ ) 75-1
And a p-type AlyGa _1- yAs second cladding layer (layer thickness 0.25 μm).
m, impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 75-2, n-type GaAs
Current blocking layer (layer thickness 0.8 μm, impurity concentration 5 × 10 ¹⁸ c
m ^-3 ) 76 are sequentially stacked.

The current blocking layer 76 has a defective portion 80 which is removed in a stripe shape and a groove shape, and a current is injected into the active layer 74 through the defective portion 80.

Further, in the sixth embodiment, the defective portion 8
A third p-type AlyGa _1- yAs cladding layer (layer thickness 1 μm, impurity concentration 1.5 × 10 ¹⁸ cm ⁻³ )
77 and a p-type GaAs cap layer (layer thickness 2 μm, impurity concentration 5 × 10 ¹⁸ cm ⁻³ ) 78 are laminated. The n-side electrode 81 and the p-side electrode 81 are provided on the substrate 71 side and the cap layer 78 side, respectively.
A side electrode 82 is formed.

Further, in the above embodiment, the impurity is diffused from the third cladding layer 77 through the deficient portion 80, and the diffusion causes the active from the second cladding layers 75-2 and 75-1. A diffusion region 83 reaching the layer 74 is formed. This diffusion region 83 faces the above-mentioned defective portion 80.

The second cladding layer 75-2 in the diffusion region 83 forms a p-type portion 75-2B immediately below the defective portion. Further, the second cladding layer 75-2 in a region facing the non-defective portion of the current blocking layer 76 constitutes a p-type portion 75-2A immediately below the non-defective portion.

The second cladding layer 75-1 in the diffusion region 83 forms a p-type portion 75-1B opposed to the defective portion. Further, the second cladding layer 75-1 in a region facing the non-defective portion of the current blocking layer 76 has a non-defective portion facing the non-defective portion.
It constitutes the n-type part 75-1A.

Next, a method of manufacturing the semiconductor laser device of the sixth embodiment will be described.

In this manufacturing method, first, an n-type GaAs buffer layer 72 and an n-type AlyGa ₁ -yAs first cladding layer 73 are formed on an n-type GaAs substrate 71 by molecular beam epitaxy.
, A non-doped active layer 74, an n-type AlGaAs second cladding layer 75-1, and a p-type AlGaAs second cladding layer 75-2.
And an n-type GaAs current blocking layer 76 are grown to form the growth layer shown in FIG. When forming this growth layer, Si is used as the n-type dopant and Be is used as the p-type dopant.

The Si doping concentration of the buffer layer 72 and the first cladding layer 73 was 1.5 × 10 ¹⁸ cm ⁻³ .

The n-type second cladding layer 75-1
Is a Si doping concentration of 3 × 10 ¹⁷ cm ^-3 and a layer thickness of about 0.0
It is made to grow to 8 μm. Thereafter, by switching between the Si cell and the Be cell, the p-type second cladding layer 75 is switched.
-2 is grown at a Be doping concentration of 1 × 10 ¹⁸ cm ⁻³ . The Si doping concentration of the current blocking layer 76 is about 5 × 10 ¹⁸ cm ⁻³ .

Next, after the growth layer is grown, the growth layer (wafer) is taken out from the MBE apparatus, and the current blocking layer 76 is formed to a width of about 3.5 μm by photolithography or the like.
The stripe-shaped and groove-shaped defective portions 80 are formed as shown in FIG.
(B)). The groove depth of the defective portion 80 is set so that the thickness of the bottom of the defective portion 80 becomes about 0.05 μm.

Next, this wafer is introduced into a liquid phase growth apparatus, and G at the bottom of the defect 80 is formed by a liquid phase growth (LPE) method.
The As layer (remaining part of the current blocking layer 76) is melted back, and thereafter, the p-type Al
GaAs third cladding layer 77 and p-type GaAs cap layer 7
8 are sequentially grown (see FIG. 8C). In this LPE growth, Mg was used as a p-type dopant, and the dopant concentrations of the third cladding layer 77 and the cap layer 78 were about 1.5 × 10 ¹⁸ cm ⁻³ and 5 × 10 ¹⁸ cm ⁻³ , respectively.

After the LPE growth, the wafer is kept at a high temperature (about 800 ° C.) in the LPE growth apparatus for about 30 minutes, and the p-type third cladding layer 77 is removed from the p-type second cladding layer 7.
5 is diffused to form a diffusion region 83 as shown in FIG. Next, the above wafer is LP
After removing from the E apparatus, the substrate 71 side is polished to 100
The p-side electrode 82 and the n-side electrode 81 are formed to have a thickness of about μm. Finally, the semiconductor laser device of the sixth embodiment can be obtained by dividing the chip by cleavage.

In the sixth embodiment, the second clad layer 75
Is converted to a second n-type doped layer having a doping concentration of 3 × 10 ¹⁷ cm ⁻³ .
Cladding layer 75-1 and doping concentration of 1 × 10 ¹⁸ cm ⁻³
And a p-type doped second cladding layer 75-2. Further, the impurity (M
In the diffusion region 83 formed by diffusing g), the n-type second cladding layer 75-1 is converted to p-type, and the above-mentioned p facing the defective portion is formed.
It is a mold part 75-1B.

Therefore, a pn junction between the p-type portion 75-2A of the second cladding layer 75-2 outside the diffusion region 83 and the n-type portion 75-1A of the second cladding layer 75-1 is formed. The built-in voltage is higher than the built-in voltage at the junction between the second clad layer 75-2 and the second clad layer 75-1 in the diffusion region 83. Therefore, current injection into the active layer 74 is intensively performed in the region facing the stripe-shaped defective portion 80, and a low threshold current operation can be realized.

In the sixth embodiment, the dopant of the p-type second cladding layer 75-2 is added to the p-type third cladding layer 77-2.
Be, which is difficult to diffuse as compared with Mg as a dopant, is used to diffuse the impurity Mg from the third cladding layer 77 to the second cladding layer 75-2.
Can be prevented from diffusing. Here, when the p-type impurity of the second cladding layer 75-2 is carbon C, the effect of preventing the second cladding layer 75-2 from diffusing impurities can be further enhanced.

In the manufacturing method of the sixth embodiment,
When MBE growth is performed on the growth layer shown in FIG.
The whole of the cladding layers 75-1 and 75-2 is doped with n-type, and then the p-type impurity is diffused into the second cladding layer 75 in a region opposed to the stripe-shaped defective portion 80, whereby Region second cladding layer 75
Is inverted to the p-type, the current blocking layer 76 does not function effectively. Moreover, the pn junction on both sides of the diffusion region 83 is formed by the junction between the current blocking layer 76 and the third cladding layer 77. As a result, in the above case, the built-in voltage of the pn junction on both sides of the diffusion region 83 is smaller than that of the semiconductor laser device having the structure shown in FIG.

Next, FIG. 7 shows a cross section of the semiconductor laser device of the seventh embodiment. As shown in FIG. 7, in the seventh embodiment, an n-type GaAs buffer layer (layer thickness: 0.5 μm, impurity concentration: 1 × 10 ³ ) is formed on an n-type GaAs substrate (impurity concentration: 2 × 10 ¹⁸ cm ⁻³ ). ¹⁸ cm ⁻³ ) 92 and n-type AlyGa ₁ -yAs first cladding layer (y = 0.5, layer thickness 1 μm, impurity concentration 1 × 10 ¹⁸ cm)
^-3 ) 93 and the n-type AlzGa _1- zAs first light guide layer (z:
0.5 → 0.3, layer thickness 0.15 μm, impurity concentration about 5 × 10
¹⁷ cm ^-3 ) 94, a non-doped GaAs quantum well active layer (layer thickness 0.007 μm) 95, and an n-type AlzGa ₁ -zAs second light guide layer (z: 0.3 → 0.5, layer thickness 0.5). 15 μm, impurity concentration 5 ×
10 ¹⁷ cm ⁻³ ) 96, a p-type AlyGa ₁ -yAs second cladding layer (layer thickness 0.2 μm, impurity concentration 1 × 10 ¹⁸ cm ⁻³ ) 97, and n
GaAs current blocking layer (layer thickness 0.8 μm, impurity concentration 5 × 1
0 ¹⁸ cm ^-3 ) 98 are laminated.

The current blocking layer 58 has a defective portion 104 which is removed in a stripe shape. This missing portion 104
, A current is injected into the active layer 95.

In the seventh embodiment, the defective portion 1
04 on the current blocking layer 98 containing p-type AlyGa _1- yAs
Cladding layer (layer thickness 1 μm, impurity concentration 1.5 × 10 ¹⁸ c
m ⁻³ ) 99 and a p-type GaAs cap layer (layer thickness 2 μm, impurity concentration 5 × 10 ¹⁸ cm ⁻³ ) 100 are laminated. The n-side electrode 1 is provided on the substrate 91 side and the cap layer 100 side.
01 and a p-side electrode 102 are formed.

Further, in the above structure, the second cladding layer 99 is separated from the second
Diffusion of impurities reaching the cladding layer 97, the second light guide layer 96, the active layer 95, and the first light guide layer 94 is performed, and a diffusion region 103 is formed. The manufacturing method and procedure of the above embodiment are the same as those of the sixth embodiment, and the types of impurities are also the same as those of the sixth embodiment.

In the seventh embodiment, the resistivity of the diffusion region 103 is increased by impurity diffusion so that the second cladding layer
, The resistivity is reduced.

Further, impurities (M
In the diffusion region 103 formed by diffusing g), the n-type second region
The light guide layer 96 is converted to a p-type to form a defective portion facing guide portion 96B.

That is, the second light guide layer 96 is formed of a p-type defect-portion-facing guide portion 96 B in the diffusion region 103.
An n-type guide portion 96A outside the diffusion region 103 is included.

Then, the second cladding layer 97 is formed on the current blocking layer 98 so as to face the defective portion 104 facing the defective portion 104.
It includes a mold clad portion 97B and a p-type non-defective portion facing clad portion 97A facing the non-defective portion of the current blocking layer 98.

Therefore, the built-in voltage due to the pn junction between the p-type portion 97A of the second cladding layer 97 outside the diffusion region 103 and the n-type guide portion 96A of the second optical guide layer 96 is reduced by The first region in the diffusion region 103
The voltage is higher than the built-in voltage due to the junction between the diffusion region 94B of the light guide layer 94 and the non-diffusion region 94A of the first light guide layer 94. Therefore, current injection into the active layer 95 is performed intensively in a region facing the striped defect portion 104, and a low threshold current operation can be realized.

In the seventh embodiment, the impurity diffusion region 103 reaches the first light guide layer 94 and a remote junction is formed in the first light guide layer 94. Since the guide layer 94 has a graded composition, the remote junction does not lower the efficiency of carrier injection into the active layer 95. Therefore, the oscillation threshold current does not increase due to the presence of the remote junction. It goes without saying that the impurity diffusion region can be controlled so that the remote junction is not formed.

In the seventh embodiment, the current blocking layer 98 includes the etching stop layer 98-2 and the protective layer 98-.
1 and a multi-layer structure capable of selective etching. Therefore, in the seventh embodiment, the controllability of the formation of the structure of the defective portion 104 can be improved.

[0105]

As is apparent from the above description, the present invention
According to the semiconductor laser device described in the above, the second cladding layer
Impurities in which impurities are less likely to diffuse than impurities in the third cladding layer
From the third cladding layer to the second cladding layer
When diffusing impurities into the layer, the second
Diffusion of impurities in the pad layer can be suppressed. did
As a result, the controllability of impurity diffusion between layers is improved.
There is fruit. In addition, the second cladding in a region facing the defect portion
The impurity concentration of the layer is set so as to face the non-defective portion of the current blocking layer.
Higher than the second cladding layer in the region where
You. Furthermore, there is no noise due to current spreading in the second cladding layer.
The active current is suppressed, and a low threshold current operation is realized. sand
That is, in the present invention, the impurity distribution of the second cladding layer is controlled.
Thus, there is an effect that low-current operation can be realized .

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

Further, according to the semiconductor laser device of the present invention, since the p-type impurity of the second cladding layer 5 is carbon C, the effect of preventing the second cladding layer from diffusing impurities can be further enhanced. Therefore, in this inventions it is,
The controllability of impurities in the second cladding layer is further improved, and low-current operation can be realized more reliably.

Further, according to the method of manufacturing a semiconductor laser device according to the present invention, before diffusing impurities from the third cladding layer into the second cladding layer, the impurities in the second cladding layer are removed from the third cladding layer. The impurities are hardly diffused compared to the impurities diffused from the layer into the second cladding layer. Therefore, when the impurities are diffused from the third cladding layer to the second cladding layer, the diffusion of the impurities existing in the second cladding layer from before the diffusion can be suppressed. Therefore, according to the present invention, the impurity concentration of the second cladding layer in the region facing the non-defective portion of the current blocking layer is reduced. Higher than that. Therefore, reduction of the threshold current of the semiconductor laser device can be promoted.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a second embodiment of the semiconductor laser device of the present invention.

FIG. 3 is a sectional view of a third embodiment of the semiconductor laser device of the present invention.

FIG. 4 is a sectional view of a semiconductor laser device according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a semiconductor laser device according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a semiconductor laser device according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a semiconductor laser device according to a seventh embodiment of the present invention.

FIG. 8 is a process chart for explaining a method of manufacturing the semiconductor laser device according to the first, fourth and sixth embodiments.

FIG. 9 is a sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

1, 41, 51, 71, 91 ... n-type GaAs substrate, 2, 42, 52, 72, 92 ... n-type GaAs buffer layer, 3, 43, 53, 73, 93 ... n-type AlGaAs first cladding layer, 4 , 44, 55, 74, 95 ... active layer, 5, 45, 57, 75, 97 ... AlGaAs second cladding layer, 6, 46, 58, 76, 98 ... n-type GaAs current blocking layer, 7, 47, 61 , 77, 99 ... p-type AlGaAs third cladding layer, 8, 48, 62, 78, 100 ... p-type GaAs cap layer, 10, 50, 60, 80, 104 ... defect part, 11, 51, 63, 81, 101 ... n-side electrode, 12, 52, 64, 82, 102 ... p-side electrode, 13, 53, 65, 83, 103 ... diffusion region.

Continuation of the front page (56) References JP-A-63-192287 (JP, A) JP-A-2-194684 (JP, A) JP-A-2-194681 (JP, A) JP-A-1-138775 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (4)

(57) [Claims] A first conductive type first clad layer, an active layer, and a second conductive type second clad layer laminated on a first conductive type semiconductor substrate; A semiconductor laser in which a first conductivity type current blocking layer having a stripe-shaped and groove-shaped defect is laminated on a layer, and at least a second conductivity-type third cladding layer is formed on the stripe-shaped defect. In the device, the second cladding layer includes a high-concentration portion facing a defective portion of the current blocking layer,
Opposed to the non-defective portion of the flow blocking layer, and from the high concentration portion
A low-concentration portion having a low impurity concentration, wherein at least the impurity of the second cladding layer has an impurity which is more difficult to diffuse than the impurity of the third cladding layer. . 2. The semiconductor laser device according to claim 1,
In the high concentration portion of the second cladding layer, the third cladding layer is expanded.
Scattered impurities, and the low concentration portion of the second cladding layer
3 semiconductor laser device characterized that it will not include impurities cladding layer. 3. A semiconductor laser device according to claim 1 or 2, wherein the impurity of low concentration portion of the second cladding layer is carbon der
The semiconductor laser device, characterized in that that. 4. The method of manufacturing a semiconductor laser device according to claim 1, wherein at least a first cladding layer, an active layer, and a second semiconductor layer are formed on the semiconductor substrate. A first step of sequentially forming a cladding layer and a current blocking layer; a second step of forming a striped groove-shaped defect in the current blocking layer; , At least third
A third step of forming a cladding layer; and diffusing impurities from the third cladding layer through the deficient portion of the current blocking layer to at least the second cladding layer, and forming a third region of the region opposed to the deficient portion. A fourth step of making the impurity concentration of the second cladding layer higher than the impurity concentration of the second cladding layer in a region facing the non-defective portion of the current blocking layer. The semiconductor laser device according to claim 1, wherein the impurities existing in the second cladding layer are made harder to diffuse than the impurities diffusing from the third cladding layer to the second cladding layer before the impurity is diffused. Production method.