JPH10107369A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a useful semiconductor laser device which has a clad layer that is sufficiently enhanced in forbidden band width, so as to restraind useless current induced by carrier leakage from an active layer into the clad layer and lessen in operating current by a method wherein the clad layer is made to contain Al. SOLUTION: A semiconductor laser device is equipped with a first conductivity-type first clad layer 2, an active layer 5, and a second conductivity- type second clad layer 7 formed on a first conductivity-type GaAs substrate 1, a mesa stripe 9 formed in a region which comprises the active layer 5 and the second clad layer 7, and a first, a second, and a third current stop layer, 10, 11, and 12, provided outside the mesa stripe 9, wherein the active layer 5 is formed of Al-free InGaAsP, and the clad layers 2 and 7 contain Al. A first guide layer 4 and a second guide layer 6 which are smaller than the clad layers 2 and 7 in forbidden band width or a protecting layer 3 smaller than the first clad layer 2 in forbidden band width is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor laser device used for an optical disk, a laser beam printer, an optical transmission and the like.

[0002]

2. Description of the Related Art In a semiconductor laser device used for an optical disk, a near-infrared wavelength band (.lambda. = 0.75 to 0.88 .mu.m) is generally used so that a light can be focused on a minute spot by a lens. For this purpose, an Al _x Ga _{1 -x} As active layer (x = 0.01) having a double heterostructure is formed on a GaAs substrate.
.0.20), and a stripe structure is used for confining current and light. Furthermore, in order to reduce the operating current of semiconductor lasers for optical discs, buried heterostructure lasers have been used, in which a mesa stripe is formed in the region including the active layer and buried growth is performed in the semiconductor layer to form a heterojunction. Has been proposed.

FIG. 6 shows a conventional example of a buried heterostructure laser. On an n-GaAs substrate 1, n-Al _x Ga _1-x
As (x = 0.3 to 0.35) First cladding layer 2, n−
Al _xg Ga _1-xg As (xg = 0.25 to 0.3) guide layer 4, Al _x1 Ga _1-x1 As (x1 = 0.01 to 0.0)
6) Active layer 5, p- _{Alx2Ga1 -x2As} (x2 = 0.3
5 to 0.4) is grown a second cladding layer 7, to form a mesa stripe 9 reaching the substrate 1 in the growth layer including an active layer 5, the outside _{p-Al x3 Ga 1-x3} As the mesa stripe 9
(X3 = 0.27 to 0.32) First current blocking layer 10, n
-Al _x3 Ga _1-x 3As (x3 = 0.27 to 0.32)
The second current blocking layer 11 is grown, a Zn diffusion layer 31 is selectively formed on the surface of the mesa stripe 9 and a SiO ₂ film 32 is formed on the surface other than the mesa stripe, and electrodes 14 and 15 are formed on the substrate 1 side and the growth layer surface. Form.

In this conventional example, an oscillation threshold current of 20 mA is reported.

In this conventional example, a carrier can be efficiently confined inside the active layer 5 by the heterojunction of the active layer 5 composed of the mesa-shaped stripe 9 and the buried layers 10 and 11 outside the active layer 5. Therefore, it is possible to prevent an increase in operating current due to diffusion of carriers injected into the active layer 5 to the outside of the light emitting region, and to reduce operating current.

[0006]

In the conventional semiconductor laser device, a double heterostructure including an AlGaAs active layer 5 is grown on a GaAs substrate 1, and a mesa stripe 9 is formed in a region including the active layer 5 in the atmosphere. I do. The active layer 5 has A
The active layer on the side of the mesa is oxidized. When the outside of the mesa stripe 9 is buried with a semiconductor layer to form a double heterojunction, it is difficult to remove oxygen from the active layer 5 on the side surface of the mesa stripe 9. Non-radiative recombination levels are formed. In this state, when carriers are injected into the active layer 5 to cause laser oscillation, the active layer 5 on the side surface of the mesa stripe 9 causes non-radiative recombination of the carriers, thereby generating a reactive current that does not contribute to laser oscillation. . Further, a crystal defect occurs based on the non-radiative recombination level formed in the active layer 5 on the side surface of the mesa stripe 9 during energization, and the reactive current further increases.

[0007]

In order to solve the above-mentioned problems, a semiconductor laser device according to the present invention comprises a first conductivity type GaAs.
On the s substrate, at least a first cladding layer of the first conductivity type, an active layer, and a second cladding layer of the second conductivity type,
At least a region including the active layer and the second cladding layer is formed of a mesa region, and a current blocking region is provided outside the mesa region. In the semiconductor laser device, the active layer is formed of InGaAsP containing no Al. , The first,
The second cladding layer is characterized by containing at least Al.

In the above, the first and second guide layers each having a smaller forbidden band width than the first and second cladding layers on both sides of the active layer, or further, on the first cladding layer, A protective layer having a smaller band gap than the first cladding layer may be provided.

Further, it is desirable that the forbidden band width of the protective layer is substantially equal to the forbidden band width of the active layer, and the current blocking region outside the mesa region is at least the first current blocking layer and the second current blocking layer. A second current blocking layer formed outside the first current blocking layer, wherein the forbidden band width of the first current blocking layer is larger than the forbidden band width of the active layer; The band width is preferably smaller than the forbidden band width of the active layer.

In the semiconductor laser device of the present invention, by providing an active layer made of InGaAsP containing no Al on the GaAs substrate as described above, the reactive current caused by the oxidation of Al on the active layer surface on the side of the mesa stripe is reduced. Generation can be suppressed, and the operating current can be reduced. At the same time, by making the cladding layer a layer containing Al, the forbidden band width of the cladding layer can be made sufficiently large and the generation of reactive current due to leakage from the active layer to the cladding layer can be suppressed.

Further, a layer having a smaller Al composition ratio than the first and second cladding layers or a layer containing no Al, that is, a guide layer having a smaller forbidden band width than the respective cladding layers is provided adjacent to the active layer. Thus, the generation of reactive current due to the oxidation of Al on the surface of the guide layer on the side surface of the mesa stripe is suppressed, and the operating current can be reduced.

Further, a protective layer having a smaller Al composition ratio than the first clad layer or a protective layer containing no Al, that is, a protective layer having a smaller forbidden band width than the first clad layer is formed on the first clad layer. When provided on the bottom surface of the mesa stripe, generation of reactive current due to oxidation of Al can be suppressed,
The operating current can be reduced.

The protective layer can function as an etching stop layer at the time of forming the mesa stripe, and is useful because the thickness of the buried growth layer outside the mesa stripe can be precisely controlled.

Further, in the semiconductor laser device of the present invention, by setting the forbidden band width of the protective layer to be substantially equal to the forbidden band width of the active layer, the protective layer can have the effect of the saturable absorbing layer. Return light noise due to self-excited oscillation can be reduced.

When a protective layer having a saturable absorption effect exists only inside the stripe, the saturable absorption effect is reduced due to the saturation of carriers generated by light absorption, and self-excited oscillation is less likely to occur. Become. On the other hand, when the protective layer having the saturable absorption effect is provided inside and outside the stripe as described above, carriers generated by light absorption inside the stripe can be efficiently diffused outside the stripe. . For this reason, carrier absorption saturation is unlikely to occur, and self-sustained pulsation is likely to occur. Further, when the protective layer having the saturable absorption effect exists only inside the stripe, the light absorption of the fundamental transverse mode increases, and mixed oscillation of higher-order transverse modes occurs. On the other hand, when the protective layer having the saturable absorption effect is provided inside and outside the stripe, the fundamental transverse mode and the high-order transverse mode are simultaneously affected by light absorption. Since the gain of the layer is large, selective oscillation of the fundamental transverse mode can be caused.

Further, in the semiconductor laser device of the present invention, the forbidden band width of the first current blocking layer in the current blocking region outside the mesa stripe is larger than the forbidden band width of the active layer, and (2) The forbidden band width of the current blocking layer is preferably smaller than the forbidden band width of the active layer. That is, in general, when the basic lateral mode is compared with the higher-order lateral mode, the higher-order lateral mode has a larger spread outside the stripe. Therefore, by configuring as described above, the higher-order transverse mode is more susceptible to light absorption in the second current blocking layer than the fundamental transverse mode, and therefore, fundamental transverse mode oscillation with less light absorption occurs. Thus, fundamental transverse mode oscillation which is practically important can be realized.

[0017]

Embodiments of the present invention will be described below.

Embodiment 1 FIG. 1 shows a sectional view of a semiconductor laser device of Embodiment 1.

On a p-GaAs substrate 1, p-Al _0.6 G
a _0.4 As first clad layer 2 (layer thickness 1.2 μm), p-G
aAs protective layer 3 (layer thickness 0.007 μm), undoped I
n _0.48 Ga _0.52 P first guide layer 4 (layer thickness 0.01 μm)
m), undoped In _0.35 Ga _0.65 As _0.40 P _0.60 strained quantum well active layer 5 (layer thickness 0.005 μm), undoped I
n _0.48 Ga _0.52 P second guide layer 6 (layer thickness 0.01 μm)
m), n-Al _0.6 Ga _0.4 As second cladding layer 7 (layer thickness 1.2 μm), n-GaAs cap layer 8 (layer thickness 0.1
.mu.m) are sequentially grown by metal organic chemical vapor deposition (MOCVD), and the etching is stopped on the surface of the p-GaAs protective layer 3 by selective etching.
(1 μm bottom width).

The n-Al _0.6 Ga _0.4 As first current blocking layer 10 (layer thickness: 0.2 μm) and the p-GaAs second current blocking layer 11 (layer thickness: 0.6 μm) are buried outside the mesa stripe 9. , N-GaAs third current blocking layer 12 (layer thickness 0.5 μm) is sequentially grown by MOCVD.

N-GaAs cap layer 8, n-GaAs
An n-GaAs contact layer 13 (2 μm thick) is grown by MOCVD so as to bury the third current blocking layer 12.

On the surface of the p-GaAs substrate 1 and the surface of the n-GaAs contact layer 13, a p-type electrode 14 and an n-type electrode 15 are formed. The cavity length was adjusted to 100 μm, the reflectivity at the end face of the cavity on the light emission side was 30%, and the reflectivity at the rear side was 65%.
An Al ₂ O ₃ film and a Si film are formed so that

In the device of this embodiment, when a forward voltage is applied between the p-type electrode 14 and the n-type electrode 15, the oscillation wavelength is 0.1 mm.
The operating current of 78 μm, the threshold current of 0.5 mA, the slope efficiency of the current-light output characteristics of 1.0 W / A, and the light output of 3 mW is 3.5 mA. Ambient temperature 70 ° C, constant light output 3m
Examining the change in the operating current at W, the running time at which the operating current increases by 20% in the initial stage is 10,000 hours or more. The emitted light of the element of this embodiment is a single-peak circular beam having a radiation angle of 25 degrees in the direction parallel to the pn junction and a radiation angle of 25 degrees in the vertical direction, and the fundamental transverse mode operation can be realized. Further, the return light noise of the element of this embodiment is a reference required for the optical disk device, that is, -130 dB / Hz.
The following is sufficiently applicable to an optical disk device.

In the device according to the present embodiment, the InGaAsP active layer 5 lattice-matched to GaAs is formed on the p-GaAs substrate 1 and the composition ratio of the active layer 5 is adjusted. An oscillation wavelength of 0.78 μm is obtained. Further, the cladding layers 2 and 7 have an Al band gap that is at least 300 meV or more larger than that of the active layer 5 containing Al.
In order to use GaAs, the active layer 5 to the cladding layer 2,
7 can be suppressed from generating a reactive current due to carrier leakage.

In the device of this embodiment, the InGaAsP active layer 5, the InGaP first guide layer 4, the InGaP second guide layer 6, and the p-GaAs protective layer 3 on the bottom of the mesa stripe 9 are all on the side of the mesa stripe 9. It is formed of a semiconductor layer containing no Al. Therefore, when the mesa stripe 9 is formed in the atmosphere, the oxidation caused by Al, that is, the bond between Al and oxygen can be suppressed.
The constituent elements other than Al in each layer are Ga, As, In, and P, and bond with oxygen in the atmosphere occurs. However, the bond is much weaker than Al and has no practical effect.

Further, the InGaAsP active layer 5 of this embodiment
In this case, pinning of the Fermi level inside the InGaAsP active layer at the regrowth interface on the side of the mesa stripe or at the interface with the end face reflection film is less likely to occur than in the conventional AlGaAs active layer, so that carrier recombination is suppressed. As a result, it is possible to reduce the operating current and improve the reliability accompanying the suppression of the reactive current.

Further, in the device of this embodiment, the forbidden band width of the protective layer 3 is set substantially equal to the forbidden band width of the active layer 5. Therefore, in the present embodiment, since the protective layer 3 has a saturable absorption effect, self-pulsation occurs and return light noise can be reduced. In addition, since the protective layer 3 exists inside and outside the stripe 9, carriers generated by light absorption inside the stripe 9 are efficiently diffused outside the stripe 9. For this reason, carrier absorption saturation is unlikely to occur in the protective layer 3, self-sustained pulsation is likely to occur with an increase in optical output, and low noise characteristics can be realized. Furthermore, in the device of the present embodiment, since the protective layer 3 having the saturable absorption effect exists inside and outside the mesa stripe 9, the fundamental transverse mode and the higher-order transverse mode are simultaneously affected by light absorption. Since the gain of the active layer inside the stripe is large, selective oscillation in the fundamental transverse mode is possible.

Further, in the device according to the present embodiment, the forbidden band width of the first current blocking layer 10 in the current blocking region outside the mesa stripe 9 is larger than the forbidden band width of the active layer 5. The forbidden band width of the external second current blocking layer 11 is smaller than the forbidden band width of active layer 5. Comparing the basic transverse mode and the higher-order transverse mode, the higher-order transverse mode has a larger spread to the outside of the stripe 9, and the higher-order transverse mode is more affected by light absorption in the second current blocking layer 11 than the fundamental transverse mode. More easily. Therefore, the fundamental transverse mode oscillation with little light absorption occurs, and the fundamental transverse mode oscillation that is practically important can be realized.

Embodiment 2 FIG. 2 shows a sectional view of a semiconductor laser device of Embodiment 2.

On an n-GaAs substrate 1, n- (Al _0.5
Ga _0.5 ) _0.5 In _0.5 P first cladding layer 2 (layer thickness 1.2
μm), undoped In _0.23 Ga _0.77 As _0.57 P _0.43 active layer 5 (layer thickness 0.07 μm), p- (Al _0.5 Ga _0.5 )
_0.5 In _0.5 P second cladding layer 7 (layer thickness 1.2 μm), p
A GaAs cap layer 8 (layer thickness 0.7 μm) is sequentially grown by molecular beam epitaxy (MBE),
The etching is stopped on the surface of the InGaAsP active layer 5 by the selective etching, and a mesa stripe 9 having a width of 2 μm is formed.

[0031] so as to bury the outer mesa stripe _{9, p- (Al 0.4 Ga 0.6} ) 0.5 In 0 .5 P first current blocking layer 10 (thickness 0.6μm), n-GaAs second current blocking layer 11 (Thickness: 0.6 μm) and a p-GaAs third current blocking layer 12 (thickness: 0.7 μm) are sequentially grown by MOCVD. The p-GaAs contact layer 1 is formed on the surfaces of the p-GaAs cap layer 8 and the p-GaAs third current blocking layer 12.
3 is grown by MOCVD. n-GaAs substrate 1
N-type electrode 1 on the surface and p-GaAs contact layer 13
4 and a p-type electrode 15 are formed. The cavity length is adjusted to 200 μm by a cleavage method, and an Al ₂ O ₃ film is formed so that the reflectance of the cavity end face becomes 30%.

In the device of this embodiment, when a forward voltage is applied between the n-type electrode 14 and the p-type electrode 15, the oscillation wavelength is 0.1 μm.
The operating current is 78 μm, the threshold current is 2 mA, the slope efficiency of the current-light output characteristic is 0.6 W / A, and the light output is 3 mW.
mA. Examining the change in operating current at an ambient temperature of 80 ° C. and a constant light output of 3 mW,
The increase in running time by more than 10000 hours. The emitted light of the device of this embodiment has a radiation angle of 15 degrees in the direction parallel to the pn junction and a radiation angle of 25 degrees in the vertical direction. In the device of this embodiment, InGaAs on the side of the mesa stripe 9 is used.
The P active layer 5 is formed of a semiconductor layer containing no Al. Therefore, when forming the mesa stripe 9,
Oxidation in the air due to Al, that is, bonding between Al and oxygen can be suppressed. The constituent elements other than Al of the active layer are Ga, As, In, and P. For the same reason as described above, the non-radiative recombination level due to oxidation is provided at the regrowth interface of the InGaAsP active layer 5 on the side surface of the mesa stripe 9. Can be very small.

The first and second cladding layers 2 and 7 are (A
l _0.5 Ga _0.5 ) _0.5 In _0.5 P containing Al and the active layer 5
The band gap between the active layer 5 and the cladding layers 2 and 7 is sufficiently suppressed to prevent carrier leakage from the active layer 5, and non-radiative recombination of carriers in the active layer 5 on the side of the mesa stripe 9. Deterioration of reliability due to reactive current and generation of crystal defects can be suppressed, and low current characteristics can be obtained.

Third Embodiment FIG. 3 is a sectional view of a semiconductor laser device according to a third embodiment.

On a p-GaAs substrate 1, p-Al _0.5 G
a _0.5 As first cladding layer 2 (layer thickness 2.0 μm), n−I
n _0.60 Ga _0.40 As _0.18 P _0.82 protective layer 3 (layer thickness 0.02
μm), undoped Al _0.25 Ga _0.75 As first guide layer 4 (layer thickness 0.01 μm), undoped In _0.35 Ga _0.65
As _0.40 P _0.60 well layer (thickness 0.01 μm, 3 layers) and undoped In _0.48 Ga _0.52 P barrier layer (thickness 0.00
7 μm, two layers) are alternately arranged, the strained multiple quantum well active layer 5, the undoped Al _0.25 Ga _0.75 As second guide layer 6, and the n-Al _0.5 Ga _0.5 As second clad layer 7 (layer thickness 1.5 μm) ), A p-GaAs contact layer 13 (layer thickness 0.1 μm) is sequentially grown by MOCVD, and the etching is stopped on the surface of the n-InGaAsP protective layer 3 by selective etching to form a mesa stripe 9 having a width of 3 μm.
(1 μm bottom width).

An oxygen-doped high-resistance AlInP layer 21 and a p-GaAs planarization layer 22 are selectively buried and grown outside the mesa stripe 9. p-GaAs substrate 1 surface and n
Forming a p-type electrode 14 and an n-type electrode 15 on the surface of the GaAs contact layer 13 and the surface of the p-GaAs planarization layer 22; The cavity length is adjusted to 375 μm by the cleavage method, and the Al ₂ O ₃ film and the Si film are formed so that the reflectance of the cavity end face on the light emission side is 12% and the reflectance on the opposite side is 75%.

In the device of this embodiment, when a forward voltage is applied between the p-type electrode 14 and the n-type electrode 15, the oscillation wavelength is 0.1 μm.
78 μm, threshold current 5 mA, slope efficiency of current-light output characteristics of 1.0 W / A, light output 35 mW, operating current is 40
mA. Examination of the change in operating current at an ambient temperature of 70 ° C. and a constant light output of 35 mW reveals that the operating current is the initial 2
The 0% increase in running time is more than 5000 hours. The emitted light of the device of this embodiment has a radiation angle of 12 degrees in the direction parallel to the pn junction and a radiation angle of 24 degrees in the vertical direction. In this embodiment, the current blocking region is formed of an oxygen-doped high-resistance AlInP layer 21.
Although it has a feature in that it is constituted by the p-GaAs flattening layer 22, the same operation and effect as in the first embodiment can be obtained also in the device of the present embodiment.

Fourth Embodiment FIG. 4 is a sectional view of a semiconductor laser device according to a fourth embodiment.

On an n-GaAs substrate 1, n-Al _0.5 Ga
_0.5 As first cladding layer 2 (layer thickness 1.2 μm), n-I
nGaP protective layer 3 (layer thickness 0.01 μm), undoped I
n _0.60 Ga _0.40 As _0.18 P _0.82 First guide layer 4 (layer thickness 0.02 μm), undoped In _0.52 Ga _0.48 As _0.22
P _0.78 strained quantum well active layer 5, undoped In _0.60 Ga
_0.4 As _0.18 P _0.82 Second guide layer 6 (layer thickness 0.02μ)
m), n-Al _0.5 Ga _0.5 As second cladding layer 7 (layer thickness 1.2 μm), p-GaAs cap layer 8 (layer thickness 0.1
) are sequentially grown by the gas source MBE method, and the etching is stopped on the surface of the n-InGaP protective layer 3 by selective etching, thereby forming a 2 μm-wide mesa stripe 9.

Outside the mesa stripe 9, a SiN dielectric 23 for blocking current and a polyimide burying layer 24 for flattening the surface are formed.

An n-type electrode 14 and a p-type electrode 15 are formed on the surface of the n-GaAs substrate 1 and the surface of the p-GaAs cap layer 8. The resonator length is adjusted to 150 μm, and an Al ₂ O ₃ film is formed so that the reflectance of the resonator end face becomes 30%.

In the device of this embodiment, when a forward voltage is applied between the n-type electrode 14 and the p-type electrode 15, the oscillation wavelength is 0.1 μm.
The operating current at 78 μm, threshold current of 1.0 mA, slope efficiency of current-light output characteristics of 0.6 W / A, and light output of 3 mW is 6.0 mA. Ambient temperature 70 ° C, constant light output 3m
Examining the change in the operating current at W, the running time at which the operating current increases by 20% in the initial stage is 10,000 hours or more. The emitted light of the device of this embodiment has a radiation angle of 15 degrees in the direction parallel to the pn junction and a radiation angle of 25 degrees in the vertical direction.

The element of this embodiment is the same as that of the first embodiment except for the operation and effect in the current blocking region. The element of this embodiment has an advantage that it can be manufactured by one crystal growth. Therefore, re-diffusion of the dopant due to crystal growth for forming the current blocking layer can be suppressed, and generation of reactive current due to the re-diffusion can be suppressed.

Fifth Embodiment FIG. 5 shows a sectional view of a semiconductor laser device of a fifth embodiment.

On a p-GaAs substrate 1, p-Al _0.5 G
a _0.5 As first cladding layer 2 (layer thickness 0.6 μm), p-
Al _0.14 Ga _0.86 As protective layer 3 (layer thickness 0.2 μm), p
-In _0.5 Ga _0.5 P first guide layer 4 (layer thickness 0.6 μm)
m), an undoped In _0.25 Ga _0.75 As _0.5 0P _0.50 active layer 5 (thickness _{0.05μm), n-Al 0.5 Ga} 0.5 As
A second cladding layer 7 (layer thickness 1.2 μm) and a p-GaAs cap layer 8 (layer thickness 0.2 μm) are sequentially grown by MOCVD, and p-AlGaAs is selectively etched.
The etching is stopped on the surface of the protective layer 3 to form a mesa stripe 9 (bottom width 1 μm).

The n-Al _0.6 Ga _0.4 As first current blocking layer 10 (layer thickness 0.2 μm) and the p-GaAs second current blocking layer 11 (layer thickness 0.6 μm) are buried outside the mesa stripe 9. , N-GaAs third current blocking layer 12 (layer thickness 0.5 μm) is sequentially grown by MOCVD. n
N-GaAs contact layer 13 so as to bury GaAs cap layer 8 and n-GaAs third current blocking layer 12
(Layer thickness 2 μm) is grown by MOCVD. p-G
An n-type electrode 14 and a p-type electrode 15 are formed on the surface of the aAs substrate 1 and the surface of the n-GaAs contact layer 13. The resonator length is adjusted to 200 μm, and an Al ₂ O ₃ film and Si are formed so that the reflectance of the resonator end face becomes 65%.

In the device of this embodiment, when a forward voltage is applied between the n-type electrode 14 and the p-type electrode 15, the oscillation wavelength is 0.1 mm.
The operating current at 78 μm, threshold current of 1.0 mA, slope efficiency of current-light output characteristics of 0.8 W / A, and light output of 3 mW is 4.8 mA. Ambient temperature 70 ° C, constant light output 3m
Examining the change in the operating current at W, the running time at which the operating current increases by 20% in the initial stage is 10,000 hours or more. The emitted light of the device of this embodiment has a radiation angle of 15 degrees in the direction parallel to the pn junction and a radiation angle of 25 degrees in the vertical direction.

In the device of this embodiment, the protective layer 3 contains Al, but the Al composition ratio is 0.12 to 0.16.
Then, since the degree of oxygen in the atmosphere is small, there is no hindrance to the effect that the generation of the reactive current can be suppressed.

In the device according to the present embodiment, the forbidden band width of the protective layer 3 is substantially equal to the forbidden band width 5 of the active layer, and similarly to the first embodiment, the protective layer 3 has a saturable absorption effect. Self-sustained pulsation occurs and return optical noise can be reduced.

It should be noted that the present invention is not limited to the embodiments described above, but includes layer thicknesses, Al composition ratios,
The present invention can be applied to the carrier concentration as long as the effects of the present invention are obtained. As for the growth method, in addition to the MOCVD method, the MBE method, and the gas source MBE method, the LPE method,
The ALE (atomic beam epitaxy) method is also applicable as long as the effects of the present invention are obtained. Although the present invention has been described with reference to a mesa stripe, the present invention is also applicable to a surface emitting laser having a circular mesa-shaped region and emitting laser light from the surface.

[0051]

According to the present invention, the semiconductor laser device is made of GaAs.
By providing an active layer made of InGaAsP that does not contain Al on the substrate, generation of reactive current due to oxidation of Al on the surface of the active layer on the side surface of the mesa stripe can be suppressed, and the operating current can be reduced. At the same time, in the semiconductor laser device of the present invention, by containing Al in the cladding layer, the forbidden band width of the cladding layer is made sufficiently large, and reactive current generation due to leakage of carriers from the active layer to the cladding layer is reduced. It is possible to provide a useful semiconductor laser device capable of suppressing the operation current and reducing the operating current.

[Brief description of the drawings]

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

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

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

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

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

FIG. 6 is a sectional view of a conventional semiconductor laser device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 GaAs substrate 2 1st cladding layer 3 protective layer 4 1st guide layer 5 InGaAsP active layer 6 2nd guide layer 7 2nd cladding layer 10 1st current blocking layer 11 2nd current blocking layer 12 3rd current blocking layer 21 height Resistance layer 23 Dielectric film

Claims (5)

[Claims] 1. A semiconductor device comprising: a first conductivity type GaAs substrate having at least a first conductivity type first cladding layer, an active layer, and a second conductivity type second cladding layer; A semiconductor laser device having a region including the second cladding layer formed of a mesa region and a current blocking region outside the mesa region, wherein the active layer is formed of InGaAsP containing no Al;
A semiconductor laser device according to claim 1, wherein said first and second cladding layers contain at least Al. 2. The semiconductor laser device according to claim 1, wherein first and second guide layers each having a smaller forbidden band width than the first and second cladding layers are provided on both sides of the active layer. A semiconductor laser device characterized by the above-mentioned. 3. The semiconductor laser device according to claim 1, wherein a protective layer having a smaller bandgap than the first cladding layer is provided on the first cladding layer. element. 4. The semiconductor laser device according to claim 3, wherein a forbidden band width of said protective layer is substantially equal to a forbidden band width of said active layer. 5. The semiconductor laser device according to claim 1, wherein the current blocking region outside the mesa-shaped region is at least a first current blocking layer and outside the first current blocking layer. The second formed on
A current blocking layer, wherein the forbidden band width of the first current blocking layer is larger than the forbidden band width of the active layer, and the forbidden band width of the second current blocking layer is smaller than the forbidden band width of the active layer. A semiconductor laser device characterized by the above-mentioned.