JPH09237935A - Semiconductor laser element and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a current-block layer from widely covering a mask film by providing a light-confinement layer and a current-blocking layer formed thereon as an antioxidant layer for specifying a layer thickness of a first conductive type. SOLUTION: After etching a p-type clad layer 7 into a shape consisting of a flat part 7a and a ridge part 7b in a state through a mask film 21 by wet etching, an n-type light-confinement layer 10 and an n-type current-blocking layer 11 are continuously grown in this order in a state through the mask film 21 by an MOCVD method. Since an n-type GaAs current-blocking layer 11 is formed on a mask film 21 in a state of being scatteredly dotted with undesired materials, some GaAs grows with dotted materials as nuclei, however, since the layer thickness of the n-type GaAs current block layer 11 does not exceed 0.4μm, the GaAs layer existing on the mask layer 21 does not reach a half region of the mask layer 21 so as to prevent covering in the wide range.

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 and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, AlGaInP-based semiconductor laser devices have been actively researched and developed as semiconductor laser devices having an oscillation wavelength in a red range. In particular, this AlGaInP-based semiconductor laser device can oscillate in the 630 to 680 nm band, and since this wavelength band has high visibility, such a device is used for laser pointers, line markers, etc. Since the oscillation wavelength is shorter than that of a semiconductor laser device, it is expected as a light source for high density recording.

In such a semiconductor laser device, a GaAs layer is generally used as a current blocking layer. For example, IEEE J
OURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS,
VOL. 1, NO. 2, JUNE 1995 p723 to p727 have AlInP layers (optical confinement layers) and GaA as current blocking layers.
An example of a ridge type semiconductor laser device adopting a two-layer structure composed of s layers is shown.

In this document, the semiconductor laser device provided with the current blocking layer having the two-layer structure has an oscillation threshold current and slope efficiency higher than those of a general semiconductor laser device in which the current blocking layer has a single-layer structure of a GaAs layer. It has been reported that can be improved.

Such a ridge type semiconductor laser device is
Usually, after etching is performed through a mask film made of a dielectric material such as a SiO ₂ film to form a ridge portion,
It is manufactured through a step of forming a current blocking layer using a vapor phase growth method such as a metal organic chemical vapor deposition method (MOCVD method) with the mask film left.

[0006]

However, when a current blocking layer made of a material having a high Al composition ratio such as an AlInP layer is grown without introducing a corrosive gas such as HCl, which is unfavorable to the manufacturing apparatus, the growth conditions are set as follows. Even if selected, the material having a high Al composition ratio is scattered and formed on the mask film made of a dielectric material. As a result, when a current blocking layer made of a GaAs layer is subsequently grown, a material having a high Al composition ratio in which the GaAs layers that do not grow on the dielectric material are scattered is usually used as a nucleus to cover a wide area on the mask film. Since it is formed in the region, it becomes difficult to remove the mask film by wet etching or dry etching using a reactive gas after forming the current blocking layer. As a result, part of the mask film remains in the completed semiconductor laser device, which causes a problem that the device yield deteriorates.

Further, even when the above problems are solved,
Regardless of the AlGaInP-based semiconductor laser device, the semiconductor laser device is required to further improve the oscillation threshold current and the slope efficiency.

Among these, the AlGaInP-based semiconductor laser device is inferior to the AlGaAs-based semiconductor laser device in the characteristics of oscillation threshold current and slope efficiency due to problems peculiar to the material, and further improvement in characteristics is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor laser device having an optical confinement layer which does not use a corrosive gas and has a good yield, and a manufacturing method thereof. A further object is to provide a semiconductor laser device having good characteristics of oscillation threshold current and slope efficiency, and a method for manufacturing the same.

[0010]

A semiconductor laser device of the present invention comprises a first conductivity type cladding layer, an active layer formed on the first conductivity type cladding layer, and an active layer formed on the active layer. A second conductivity type cladding layer having a conductivity type opposite to that of the first conductivity type having a striped ridge portion serving as a current path, and the second conductivity type cladding layer covering a side surface of the ridge portion. A band gap ( _Eg : E) having a smaller refractive index than the second conductive type cladding layer formed above and having an energy larger than the energy of oscillated light (hν: h is Planck's constant, ν is the frequency of oscillated light). Al with _g > hν)
And a first conductive type current blocking layer as an antioxidant layer formed on the light confining layer, the layer thickness of the first conductive type current blocking layer is It is characterized by being 0.4 μm or less.

In the semiconductor laser device of the present invention, when the optical confinement layer is formed by the vapor phase epitaxy method through the mask film made of the dielectric material for forming the ridge portion in the manufacturing process, the light is confined on the mask film. Even if the material for the confinement layer is formed in a scattered manner, the current blocking layer formed thereafter has a layer thickness of 0.4 μm or less, so that the current blocking layer does not cover the wide area of the mask film. Therefore, this mask film can be easily removed by normal wet etching or dry etching using a reactive gas, so that the manufacturing yield can be improved without using a corrosive gas.

In particular, the current blocking layer is formed on the light confining layer in order to prevent oxidation of the light confining layer during the manufacturing process, to improve crystal growth on the light confining layer, and to obtain a sufficient current blocking effect. It is preferably formed with a layer thickness of 0.2 μm or more over the entire region.

In particular, the light confinement layer is of the first conductivity type, and the impurity concentration of at least the active layer side of the light confinement layer is 5 × 10 ¹⁷ cm ⁻³ or less. Further, the optical confinement layer is characterized in that the impurity concentration is 5 × 10 ¹⁷ cm ⁻³ or less over the entire area.

In such a semiconductor laser device, the characteristics of oscillation threshold current and slope efficiency are improved.

Particularly, the impurity concentration is 3 × 10 ¹⁷ cm
^-3 or less.

In this case, the characteristics of oscillation threshold current and slope efficiency are improved.

Further, the impurity concentration is 2 × 10 ¹⁷ cm
^-3 or less.

In this case, the characteristics of oscillation threshold current and slope efficiency are further improved.

The impurity concentration is 5 × 10 ¹⁶ cm
^-3 or more.

In this case, the entire light confinement layer or at least the active layer side of the light confinement layer can be a low resistance region capable of having a sufficient carrier concentration, and thus the low resistance region and the second conductivity type can be formed. Since the current blocking effect is preferably obtained by the pn junction with the cladding layer, the characteristics of oscillation threshold current and slope efficiency can be improved.

Further, the impurity concentration is 1 × 10 ¹⁷ cm
^-3 or more.

In this case, the entire optical confinement layer or at least the active layer side of the optical confinement layer can be a low resistance region capable of having a more sufficient carrier concentration, and thus, this region and the second conductivity type clad. Since the current blocking effect is preferably obtained by the pn junction with the layer, the characteristics of oscillation threshold current and slope efficiency can be improved. Moreover, this one
Since the concentration control of the 0 ¹⁷ cm ⁻³ unit is easier than the concentration control of the 10 ¹⁶ cm ⁻³ unit, the manufacturing yield is improved.

The first conductivity type clad layer is (A
l _x1 Ga _1-x1 ) _y1 In _1-y1 P, and the second
The conductivity type clad layer is (Al _x2 Ga _{1 -x2} ) _y2 In _{1 -y2} P
And the optical confinement layer is (Al _x3 Ga _{1 -x3} )
_y3 In _1-y3 P (1 ≧ x3>x1> 0, 1 ≧ x3>x2>
0, 1>y1> 0, 1>y2> 0, 1>y3> 0), and x3 is 1 ≧ x3 ≧ 0.9, x1,
x2 is more preferably 0.7 ≧ x1 ≧ 0.5, 0.7 ≧ x2 ≧ 0.5, and further preferably, a GaAs substrate of the first conductivity type is used as the substrate, and a clad layer of the first conductivity type, Two
The conductive clad layer and the optical confinement layer are made of GaA, respectively.
s Substrate is substantially lattice-matched (Al _x1 Ga _{1- x1} ) _0.5 In _0.5
P, (Al _x2 Ga _{1 -x2} ) _0.5 In _0.5 P, (Al _x3 Ga
_1-x3 ) _0.5 In _0.5 P.

In this case, the flat portion has a thickness of 0.01-0.
13 μm is preferable, preferably 0.03 to 0.08 μm, and the thickness of the optical confinement layer is 0.3 to 1 μm, preferably 0.4 to 0.85 μm, and more preferably 0.5.
Is about 0.75 μm. In addition, the optical confinement layer is (Al _x3
In the case of Ga _1-x3 ) _y3 In _1-y3 P, the ternary system has better thermal conductivity than the quaternary system, and the refractive index can be maximized. Therefore, the Al composition ratio x3 is most preferably 1. .

In this case, AlG is used as the active layer.
A single or multiple quantum well structure layer made of aInP or GaInP or a non-quantum well layer made of AlGaInP or GaInP is used.

In particular, a first impurity concentration, that is, a carrier concentration, on the light confinement layer is higher than that on the light confinement layer.
It is characterized by having a conductive type current blocking layer.

In this case, the function of the optical confinement layer as the current blocking layer is that the current blocking effect may be small because the impurity concentration (carrier concentration) is small, but the current block having a large impurity concentration (carrier concentration) may be present. The layer can sufficiently supplement the current blocking effect.

In particular, the current blocking layer is made of GaAs.

In this case, GaAs has no fear of being oxidized and has favorable advantages in manufacturing, and AlGaInP
It is preferable because it has better thermal conductivity than that of AlInP and AlInP.

Further, the carrier concentration of at least the active layer side of the optical confinement layer is about 5 × 10 ¹⁶ cm ⁻³ or more.

In this case, at least the active layer side of the optical confinement layer can be a low resistance region, and the current blocking effect can be preferably obtained by the pn junction between this region and the second conductivity type cladding layer, so that the oscillation threshold current And the characteristics of slope efficiency can be improved.

In particular, the light confinement layer is a low resistance layer.

In this case, the optical confinement layer is a low resistance layer, and the current blocking effect by the pn junction with the second conductivity type clad layer is preferably obtained, so that the characteristics of oscillation threshold current and slope efficiency are remarkably excellent. become. The carrier concentration of the low resistance layer is preferably about 5 × 10 ¹⁶ c
m ^-3 or more, more preferably about 1 × 10 ¹⁷ cm ^-3 or more.

The semiconductor laser device manufacturing method of the present invention comprises a step of growing a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer on a semiconductor substrate, and the second conductivity type cladding layer. A mask film made of a dielectric material is formed on the clad layer of the second type, and the ridge portion is formed by etching the second conductive type clad layer with the mask film interposed therebetween; The second conductive type clad layer having the ridge portion is interposed with Al containing a bandgap having an energy smaller than that of the second conductive type clad layer and larger than the energy of the oscillation light. Forming a light confinement layer formed by vapor phase epitaxy, and a layer thickness of 0.4 as an antioxidant layer on the light confinement layer.
The method is characterized by including a step of forming a first-conductivity-type current blocking layer having a thickness of μm or less by a vapor deposition method, and a step of removing the mask film by an etching method. The conditions for vapor phase growth of the light confinement layer are set so that the material of the light confinement layer is discretely formed on the mask film, or preferably is hardly formed. In addition, the vapor phase growth method is usually used also in the step of growing the first conductivity type cladding layer, the active layer, and the second conductivity type cladding layer on the semiconductor substrate.

In the manufacturing method of the present invention, when the light confinement layer is formed through the mask film made of a dielectric material, the light confinement layer is made of a material containing Al, so Even if the material for the confinement layer is formed in a scattered manner, the layer thickness of the current blocking layer formed thereafter is 0.4.
Since the thickness is less than μm, the current blocking layer does not cover the wide area of the mask film. Therefore, since this mask film can be easily removed by ordinary wet etching or dry etching using a reactive gas, the manufacturing yield can be increased without using a corrosive gas.

The mask film is, for example, a silicon oxide film or a silicon nitride film, and MO is used as a vapor phase growth method.
The CVD method, MBE method (molecular beam epitaxy method) or the like is used.

In the case of an AlGaAs semiconductor laser device, the Al composition ratio of the first and second conductivity type cladding layers is preferably selected to be 0.4 to 0.6, and the Al composition ratio of the optical confinement layer is selected. Is larger and preferably 0.42
~ 0.62 is selected.

When the first and second conductivity type cladding layers contain Al as described above, the Al composition ratio of the optical confinement layer is selected to be larger than the Al composition ratio of these cladding layers. An optical confinement layer having an Al composition ratio selected to be larger than the Al composition ratio of the clad layer will be spot-grown on the mask film.

Further, the second conductivity type clad layer may include other layers such as an etching stop layer.

The current blocking layer preferably has a bandgap whose energy is smaller than that of the oscillation light.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention, Al
A GaInP-based semiconductor laser device will be described with reference to the drawings.
1 and 2 are a schematic cross-sectional structure diagram of such a semiconductor laser device and a schematic band structure diagram in the vicinity of the active layer and the current block layer, respectively.

In the figure, 1 is an n-type GaAs semiconductor substrate, and one main surface (crystal growth surface) of the (100) plane is [011].
Angle θ (θ = 5 to 17 degrees, preferably 7 to 1 degrees)
3 degrees: hereinafter, this angle θ is inclined at an off angle θ), and an n-type Ga _0.5 In _0.5 P buffer layer 2 having a layer thickness of 0.3 μm is formed on the one main surface.

A layer thickness of 1.2 μm is formed on the buffer layer 2.
Of n-type _{(Al x1 Ga 1-x1)} 0.5 In 0 .5 P ( in this embodiment x
1 = 0.7: Si-doped), the cladding layer 3 is formed.

As shown in detail in FIG. 2, an undoped (Al _z1 G layer having a layer thickness of 500 Å is formed on the n-type cladding layer 3.
_{a 1-z1) 0.5 In 0.5} P (z1 = 0.5 in this embodiment) optical guide layer 4 is formed.

On the light guide layer 4, a layer thickness of 100 Å
Has tensile strain (Al_pGa_1-p) _qIn_1-qP (1> p
≧ 0, 1> q> 0.51: In this embodiment, p = 0, q = 0.
65) Compression of quantum well layers 5a, 5a, 5a and layer thickness 40Å
Has distortion (Al_rGa_1-r)_sIn_1-sP (1 ≧ r>
0,0 <s <0.51: In this embodiment, r = 0.5, s =
0.45) The quantum barrier layers 5b and 5b are alternately stacked.
Of an undoped strain-compensated multiple quantum well structure
The functional layer 5 is formed.

On this active layer 5, an undoped (Al _z2 Ga _{1 -z 2} ) _0.5 In _0.5 P (z2 = 0.5 in this embodiment) optical guide layer 6 having a layer thickness of 500 Å is formed.

On the light guide layer 6, a flat portion 7a having a layer thickness t and a height of 0.5 to 0.8 μm extending in the direction perpendicular to the plane of the drawing (resonator length direction) approximately at the center of the flat portion 7a, Upper width 2.5
P-type (Al _x2 Ga ₁ -x2) composed of a striped ridge portion 7b having a width of 3.5 μm to a width of 3.5 μm to 4.5 μm.
_0.5 In _0.5 P (x2 = 0.7 in this embodiment: Zn-doped)
A clad layer 7 made of is formed.

A layer thickness of 0.1 μm is formed on the upper surface of the ridge portion 7b.
m p-type Ga _0.5 In _0.5 P cap layer (Zn-doped)
8 and a p-type GaAs cap layer (Z
n-doop) 9 is formed in this order.

These p-type cap layers 8 and 9, ridge portion 7
On the side surface of b and on the flat portion 7a, an n-type layer having a layer thickness of u μm
(Al_x3Ga_1-x3)_0.5In_0.5P (1 ≧ x3> x1, x
2> 0: x3 = 1, Se doped in the present embodiment)
Impurity concentration is 5 × 10¹⁷cm ^-3Current blocking layer below
Optical confinement that also functions as an optical confinement function
The layer 10 and the optical confinement layer 10 have better thermal conductivity and
In this embodiment, the impurity concentration is high and 1 × 10 5.¹⁸cm^-3
N-type G having a layer thickness of 0.4 μm or less, for example 0.3 μm
Current as an antioxidant layer made of aAs (Se-doped)
The block layer 11 is formed in this order. In addition, this
The thickness of the current blocking layer 11 of the
The oxidation of layer 10 is prevented and the current blocking effect is sufficient.
Therefore, 0.2 μm or more is preferable.

The cap layer 9 and the current blocking layer 11
Above the p-type GaAs contact layer (Zn
Dope) 12 is formed.

Au--Cr is formed on the upper surface of the contact layer 12.
The p-type ohmic electrode 13 composed of the n-type GaA
An n-type side ohmic electrode 14 made of Au—Sn—Cr is formed on the lower surface of the s substrate 1.

Such a semiconductor laser device is sandwiched between the cladding layers 3 and 7 having a bandgap having a larger energy than the bandgap of the active layer 5 (that is, the energy (hν) of the oscillation light) and the energy (hν) of the oscillation light. Larger band gap (that is, almost no absorption of oscillating light)
In addition, the optical confinement layer 10 having a smaller refractive index than the cladding layer 7
And a current blocking layer 11 having higher thermal conductivity than the optical confinement layer 10. The optical confinement layer 10
When the conductivity type is the same as that of the cladding layer 7 or it is undoped, the current blocking effect and the current constriction effect are weakened,
Oscillation threshold current and slope efficiency deteriorate, so do not set them.

The semiconductor laser device of the present embodiment operates as a real refractive index guided laser device due to the structure of the optical confinement layer 10 which is transparent to the oscillation light. In order to operate as an index guided type, the difference in actual refractive index between the active layer 5 under the ridge portion 7b region and outside the ridge portion 7b region needs to be a predetermined value or more. In order to operate satisfactorily, the difference in refractive index is preferably required to be 3 × 10 ⁻³ or more.

FIG. 3 shows the result of calculation of the relationship between the layer thickness t of the flat portion 7a and the difference in actual refractive index with respect to the active layer 5 under the ridge portion 7b region and under the ridge portion 7b outer region.

From this FIG. 3, in the present embodiment, the layer thickness t of the flat portion 7a is set so that the actual refractive index difference becomes 3 × 10 ⁻³ or more.
Is selected to be 1300 Å or less, preferably 800 Å or less, which is 5 × 10 ⁻³ or more. And the active layer 5
Alternatively, in the structure in which the light confinement layer 10 is in direct contact with the light guide layer 6, there is a disadvantage that these layers are exposed to the atmosphere during manufacturing, so the layer thickness t should be set to, for example, approximately 100Å as the lower limit.

FIG. 4 shows the relation between the layer thickness u of the optical confinement layer 10 of the semiconductor laser device of this embodiment and the oscillation threshold current, which is obtained by experiment. This characteristic is that the optical confinement layer 10 has an impurity concentration of 1 × 10 ¹⁷ cm ⁻³ and a cavity length L =
It was obtained by continuous oscillation under the conditions of 400 μm, non-coated end face, and room temperature.

From FIG. 4, the layer thickness u of the optical confinement layer 10 is shown.
It is understood that is preferably 0.3 μm or more and 1 μm or less, more preferably 0.4 μm or more and 0.85 μm or less, and still more preferably 0.5 μm or more and 0.75 μm or less.

The reason why the light confinement layer 10 needs to have a certain thickness is as follows. That is, in the present embodiment, since the current blocking layer 11 is made of a material capable of absorbing light, if the thickness of the light confinement layer 10 is small, the current blocking layer 11 strongly absorbs light, and if it is too thick, This is because the light confinement layer 10 has poor heat dissipation and the heat dissipation characteristics of the device deteriorate.

FIG. 5 is a current-optical output characteristic diagram (IL characteristic) of the semiconductor laser device of this embodiment and a conventional loss guide type AlGaInP-based semiconductor laser device in which the current blocking layer has a single-layer structure of a GaAs layer. Figure) is shown. Incidentally, this characteristic also shows that the impurity concentration of the optical confinement layer 10 is 1 × 10 ¹⁷ c
m ^-3 , resonator length L = 400 μm, u = 0.5 μm, t =
It was obtained by continuous oscillation under the conditions of 0.05 μm, non-coated end face, and room temperature.

From FIG. 5, it can be seen that the element of this embodiment has a smaller oscillation threshold current value and better slope efficiency than the conventional element.

Next, FIG. 6 shows the relationship between the impurity concentration (dopant concentration) of the optical confinement layer 10 and the oscillation threshold current and slope efficiency.

From FIG. 6, it can be understood that the light trapping layer 10 has a smaller impurity concentration and a smaller oscillation threshold current and a larger slope efficiency.

Particularly, the impurity concentration of the optical confinement layer 10 is 5
In the case of × 10 ¹⁷ cm ^-3 or less, a loss guide type AlGaI in which the conventional current blocking layer has a single-layer structure of a GaAs layer.
It can be 40 mA or less, which is smaller than the oscillation threshold current of the nP-based semiconductor laser device, and the slope efficiency can be 0.3 W / A or more, which is larger than that of the conventional device.

Further, the impurity concentration is 3 × 10 ¹⁷ cm ^-3.
In the following cases, the oscillation threshold current can be made smaller than 30 mA, and the slope efficiency can be made larger than 0.4 W / A, which is more preferable. In the case of 2 × 10 ¹⁷ cm ^-3 or less, the oscillation threshold current can be 25 mA. It is more desirable because it can be smaller and the slope efficiency can be larger than 0.45 W / A.
In addition, in the case of 1 × 10 ¹⁷ cm ^-3 or less, the oscillation threshold current becomes extremely small and the slope efficiency becomes 0.5 W / A.
As described above, it is very preferable.

As described above, it can be understood that the oscillation threshold current and slope efficiency of the optical confinement layer 10 improve as the impurity concentration decreases.

This is because, in the conventional element, the current blocking layer blocks the current by the pn junction formed by making the current blocking layer of the conductivity type opposite to that of the clad layer adjacent to this layer, etc. This is a phenomenon opposite to the point where it was considered desirable that the concentration be high.

Although the reason for this is not sufficient, in the case of the semiconductor laser device of the present invention, impurities (dopants) easily move in the optical confinement layer 10 having a larger bandgap (larger Al composition ratio) than the cladding layer 7. It is considered that the impurities (dopant: Se in the present embodiment) from the layer 10 diffuse to the active layer 5 side. Moreover, it is considered that one of the causes is that the device of the present invention has the layer thickness t of the flat portion smaller than that of the conventional semiconductor laser device.

When the impurity concentration (carrier concentration) of the optical confinement layer 10 is extremely low, the current blocking effect and the current constriction effect due to the pn junction with the cladding layer 7 are weakened, and the oscillation threshold current is increased. And the slope efficiency is poor, so this impurity concentration is better than 2 × 10 ¹⁶ cm ^-3 .
It is preferably 5 × 10 ¹⁶ cm ⁻³ or more. In the above-described embodiment, since the activation rate of the dopant is about 100%, the carrier concentration is about 2 × 10 ¹⁶ cm ⁻³ when the impurity concentration is 2 × 10 ¹⁶ cm ^−3. Concentration is 5
The carrier concentration at ^{x10 16} cm ^-3 is approximately 5 x 10 ¹⁶ c
The carrier concentration corresponding to m ⁻³ and the impurity concentration of 1 × 10 ¹⁷ cm ⁻³ corresponds to about 1 × 10 ¹⁷ cm ⁻³ .

Next, an example of a method of manufacturing such a semiconductor laser device will be shown below.

First, as shown in FIG. 7A, n-type G
On the aAs plate 1, an n-type buffer layer 2, an n-type clad layer 3, an optical guide layer 4, an active layer 5, an optical guide layer 6, a p-type clad layer 7, a p-type GaInP cap layer 8, a p-type GaAs.
After the cap layer 9 is continuously grown by MOCVD in this order, a film thickness of 0.2 μm is formed on the p-type GaAs cap layer 9.
Of the SiO ₂ film is formed by a thin film forming method such as a sputtering method, a CVD method, or an electron beam evaporation method, and is formed into a stripe-shaped mask film 2 using a hydrofluoric acid-based etching solution.
1 is formed.

Next, as shown in FIG. 7B, the p-type clad layer 7 is etched into a shape including a flat portion 7a and a ridge portion 7b by wet etching with the mask film 21 interposed therebetween, and then, The n-type optical confinement layer 10 and the n-type current blocking layer 11 are continuously grown in this order by the MOCVD method with the mask film 21 interposed therebetween. In this step, the growth condition of the n-type light confinement layer 10 is set so as to reduce the deposition of the material of the light confinement layer 10 on the mask film 21, but this material is dispersed on the mask film 21. Will be scattered around.

After that, the mask film 21 is removed by wet etching using a hydrofluoric acid-based etching solution, and then the p-type contact layer 12 is formed by the MOCVD method.
The n-type ohmic electrodes 13 and 14 are formed to complete the semiconductor laser device shown in FIG.

In this manufacturing method, the n-type GaAs is formed on the mask film 21 in which the undesired material is scattered in a discrete manner.
Since the current blocking layer 11 is formed, GaAs is slightly crystallized using the scattered material as a nucleus. However, since the layer thickness of the n-type current block layer 11 is 0.4 μm or less, the GaAs layer existing on the mask film 21 does not reach the half of the mask film 21. As a result, when removing the mask film 21 by wet etching,
The etching solution is sufficiently spread to easily remove the mask film 21.

On the other hand, when the layer thickness of the n-type current blocking layer 11 is set to 0.5 μm or more, the GaAs layer is formed in a wide area far beyond the half on the mask film 21,
It becomes difficult to completely remove the mask film 21. As a result, a semiconductor laser device in which the characteristics of the mask film 21 in which some of the mask film 21 remains deteriorated is manufactured.

Similar results were obtained by dry etching using a reactive gas instead of the above wet etching.

Although it is not clear why the area of the GaAs layer formed on the mask film 21 becomes very small by setting the layer thickness of the n-type current blocking layer 11 to 0.4 μm or less, it is not clear. Usually, in order to form a GaAs layer that is not formed on the mask film 21, it is considered that, in addition to the presence of the nuclei described above, the adhesion strength must be increased by increasing the layer thickness to 0.5 μm or more. Therefore, when the layer thickness is 0.4 μm or less, it is considered that the layer cannot be sufficiently grown in the extending direction even if the nuclei are present. Incidentally, such a phenomenon is also observed in the mask film made of a dielectric material such as a SiN film other than the SiO ₂ film.

In the above description, the active layer having the strain compensation type quantum well structure has been mainly described, but it may have tensile strain, compressive strain, non-strain, or of course, bulk structure. Further, although the above-mentioned active layer is provided with an optical guide layer in order to improve optical confinement in the quantum well layer, a configuration without these optical guide layers is also possible.

[0078] Further, may be used n-type GaAs buffer layer in place of the n-type GaAs semiconductor substrate 1 and the n-type cladding layer 3 n-type is provided between the Ga _{0. 5} In _0.5 P buffer layer 2,
Further, the buffer layer may not be provided.

In the clad layer composed of the ridge portion and the flat portion as described above, for example, an etching stop layer between the both portions, a saturable light absorbing layer in the flat portion or the ridge portion, and the like are provided. It is also possible to adopt a configuration in which the layers are included.

In addition, (Al _x Ga _1-x ) _v In _1-v P (x ≧
0) crystal, v = is 0.51 distortion exactly GaAs semiconductor substrate and lattice-matched to the case of no, since v = 0.51 little distortion even in the vicinity of do not occur, (Al _x G
a _1-x ) _0.5 In _0.5 P is the composition ratio v
Should be around 0.51. In particular, in the present invention, it is preferable that the clad layer and the block layer have substantially no distortion.

Furthermore, in the above embodiment, one main surface of the GaAs semiconductor substrate 1 is a surface inclined from the (100) surface in the [011] direction, but it is desirable that the surface has an equivalent relationship. That is, one major surface (crystal growth surface) of the GaAs substrate
Is a plane tilted from the (100) plane in the [0-1-1] direction, a plane tilted from the (010) plane to the [101] or [-10-1] direction, a [110] plane from the [110] or [-
1-10] direction, that is, {100}
Any surface may be used as long as the surface is inclined in the <011> direction.

In addition, in the above embodiment, the entire layer is covered.
The impurity concentration is 5 × 10¹⁷cm^-3Light confinement that is
Layer was used, but at least the impurity concentration on the active layer side was 5 ×
10 ¹⁷cm^-3The following optical confinement layers can also be used
You. Furthermore, the impurity concentration gradually increases in the optical confinement layer,
It can be changed in steps, and the optical confinement layer can be
You may make it consist of several layers of different composition ratio.

Furthermore, in the above description, the AlGaInP-based semiconductor laser device has been described, but the present invention can be appropriately applied to other material-based semiconductor laser devices, for example, AlGaAs-based semiconductor laser devices.

[0084]

Industrial Applicability It is possible to provide a semiconductor laser device having an optical confinement layer which can be manufactured with a good yield without using a corrosive gas, and a manufacturing method thereof.

Furthermore, it is possible to provide a semiconductor laser device having favorable oscillation threshold current and slope efficiency characteristics.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional structural diagram of a semiconductor laser device that is an embodiment of the present invention.

FIG. 2 is a schematic band structure diagram in the vicinity of an active layer or a current block layer of the semiconductor laser device according to the above embodiment.

FIG. 3 is a diagram showing the relationship between the layer thickness t of the flat portion of the p-type cladding layer and the actual refractive index difference.

FIG. 4 is a diagram showing a relationship between a layer thickness u of an optical confinement layer and an oscillation threshold current.

FIG. 5 is a diagram showing the relationship between the optical output-current characteristics of the semiconductor laser device of the above embodiment and the conventional semiconductor laser device.

FIG. 6 is a diagram showing a relationship between an impurity concentration of an optical confinement layer, an oscillation threshold current, and slope efficiency.

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

[Explanation of symbols]

1 n-type GaAs semiconductor substrate 3 n-type (Al _x1 Ga _1-x1 ) _0.5 In _0.5 P clad layer 5 active layer 7 p-type (Al _x2 Ga _1-x2 ) _0.5 In _0.5 P clad layer 7a flat part 7b ridge part 10 Optical confinement layer (n-type (Al _x3 Ga _{1 -x3} ) _0.5 In
_0.5 P layer) 11 Current blocking layer (n-type GaAs layer)

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koji Yoneda 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Masayuki Shono 2-5 Keihan-hondori, Moriguchi-shi, Osaka No. 5 in Sanyo Electric Co., Ltd. (72) Inventor Akira Ibaraki 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor Keiichi Yoshinari Keihan Hondori, Moriguchi City, Osaka Prefecture 2-5-5 Sanyo Electric Co., Ltd.

Claims (14)

[Claims] 1. A clad layer of the first conductivity type, an active layer formed on the clad layer of the first conductivity type, and a stripe-shaped ridge portion serving as a current path formed on the active layer. A second conductivity type clad layer having a conductivity type opposite to the first conductivity type, and the second conductivity type clad formed on the second conductivity type clad layer so as to cover the side surface of the ridge portion. A light confinement layer having a refractive index smaller than that of the layer and having a bandgap having an energy larger than that of the oscillation light, and a current of the first conductivity type formed on the light confinement layer as an antioxidant layer. A block layer, and the layer thickness of the current blocking layer of the first conductivity type is 0.4.
A semiconductor laser device having a thickness of not more than μm. 2. The layer thickness of the current blocking layer is 0.2 μm.
The semiconductor laser device according to claim 1, wherein the above is the case. 3. The light confinement layer is of a first conductivity type,
3. The semiconductor laser device according to claim 1, wherein the impurity concentration of at least the active layer side of the light confinement layer is 5 × 10 ¹⁷ cm ⁻³ or less. 4. The light confinement layer is non-permeable over the entire area.
Pure substance concentration is 5 × 10 ¹⁷cm^-3Characterized by
The semiconductor laser device according to claim 3, wherein 5. The semiconductor laser device according to claim 3, wherein the impurity concentration is 3 × 10 ¹⁷ cm ⁻³ or less. 6. The semiconductor laser device according to claim 5, wherein the impurity concentration is 2 × 10 ¹⁷ cm ⁻³ or less. 7. The semiconductor laser device according to claim 3, wherein the impurity concentration is 5 × 10 ¹⁶ cm ⁻³ or more. 8. The semiconductor laser device according to claim 7, wherein the impurity concentration is 1 × 10 ¹⁷ cm ⁻³ or more. 9. The cladding layer of the first conductivity type is made of (Al_x1
Ga_1-x1)_y1In_{1- y1}P, and the second conductive
Mold cladding layer is (Al_x2Ga_1-x2)_y2In _1-y2From P
And the optical confinement layer is (Al_x3Ga_1-x3)_y3I
n_1-y3P (1 ≧ x3> x1> 0, 1 ≧ x3> x2> 0,
1> y1> 0, 1> y2> 0, 1> y3> 0)
Claims 1, 2, 3, 4, 5, 6, 7,
Alternatively, the semiconductor laser device according to item 8. 10. The semiconductor laser device according to claim 1, wherein the current blocking layer has a higher impurity concentration than the optical confinement layer. . 11. The current blocking layer is made of GaAs, 1, 2, 3, 4, 5, 6,
7. The semiconductor laser device according to 7, 8, 9 or 10. 12. The carrier concentration of at least the active layer side of the light confinement layer is about 5 × 10 ¹⁶ cm ⁻³ or more, and the carrier concentration is at least 1, 2, 3, 4, 5, 6, 7. ,
8. The semiconductor laser device according to 8, 9, 10, or 11. 13. The light confinement layer is a low resistance layer, as claimed in any one of claims 1, 2, 3, 4, 5, 6, 7,
8. The semiconductor laser device according to 8, 9, 10, 11, or 12. 14. A step of growing a first conductivity type clad layer, an active layer, and a second conductivity type clad layer on a semiconductor substrate, and a dielectric material on the second conductivity type clad layer. A step of forming a ridge portion by etching the second conductivity type clad layer with the mask film interposed, and a second step of forming the ridge portion with the mask film interposed; An optical confinement layer containing Al having a refractive index smaller than that of the second conductivity type clad layer and a bandgap having an energy larger than that of oscillation light is formed on the conductivity type clad layer by a vapor deposition method. And a step of forming a current blocking layer of a first conductivity type having a layer thickness of 0.4 μm or less as an antioxidation layer on the light confinement layer by vapor phase growth, and removing the mask film by etching. The method of manufacturing a semiconductor laser device, comprising the steps, a.