JP3876023B2 - Semiconductor laser element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser element used for optical discs, laser beam printers, optical transmission, and the like.
[0002]
[Prior art]
In a semiconductor laser element used for an optical disc, a near-infrared wavelength band (λ = 0.75 to 0.88 μm) is generally used so that a lens can focus on a minute spot. Therefore, an Al _x Ga _1-x As active layer (x = 0.01 to 0.20) having a double hetero structure is formed on a GaAs substrate, and a stripe structure is used for current and optical confinement. Furthermore, in order to reduce the operating current of a semiconductor laser for optical discs, a buried heterostructure laser in which a mesa stripe is formed in a region including an active layer and a heterojunction is formed by performing buried growth in the semiconductor layer has been hitherto. Has been proposed.
[0003]
FIG. 6 shows a conventional example of a buried heterostructure laser. on n-GaAs substrate _{1, n-Al x Ga 1} -x As (x = 0.3~0.35) first cladding layer _{2, n-Al xg Ga 1} -xg As (xg = 0.25~ 0.3) guide layer _{4, Al x1 Ga 1-x1} As (x1 = 0.01~0.06) active layer _{5, p-Al x2 Ga 1} -x2 As (x2 = 0.35~0.4) The second cladding layer 7 is grown, a mesa stripe 9 reaching the substrate 1 is formed on the growth layer including the active layer 5, and p-Al _x3 Ga _1-x3 As (x3 = 0.27) is formed outside the mesa stripe 9. 0.32) performs growth of the first current blocking layer _{10, n-Al x3 Ga 1} -x 3As (x3 = 0.27~0.32) second current blocking layer 11, selectively in the mesa stripe 9 surface in the SiO ₂ film 32 is formed in addition to the Zn diffusion layer 31 and the mesa stripe surface to form an electrode 15 on the substrate 1 side and the growth layer surface
[0004]
In this conventional example, an oscillation threshold current of 20 mA is reported.
[0005]
In this conventional example, carriers can be efficiently confined inside the active layer 5 by the heterojunction of the active layer 5 composed of the mesa stripes 9 and the buried layers 10 and 11 outside thereof. Therefore, an increase in operating current due to diffusion of carriers injected into the active layer 5 out of the light emitting region can be prevented, and the operating current can be reduced.
[0006]
[Problems to be solved by the invention]
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. Since the active layer 5 contains Al, the active layer on the side surface of the mesa is oxidized. When the outside of the mesa stripe 9 is filled 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, so that the active layer 5 near the junction interface is caused by oxidation. Non-radiative recombination levels are formed. In this state, when carrier injection is performed in the active layer 5 to cause laser oscillation, in the active layer 5 on the side surface of the mesa stripe 9, carriers are non-radiatively recombined, so that a reactive current that does not contribute to laser oscillation is generated. . Furthermore, a crystal defect is generated 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 is further increased.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems, a semiconductor laser device according to the present invention includes at least a first conductivity type first cladding layer, an active layer, and a second conductivity type second cladding on a first conductivity type GaAs substrate. In the semiconductor laser device, a region including at least the active layer and the second cladding layer is a mesa region, and a current blocking region is provided outside the mesa region. The first and second cladding layers contain at least Al, and the Al composition ratio is smaller than that of the first cladding layer or between the first cladding layer and the active layer, or Al. Ri Na provided first guide layer containing no, between the first guide layer and the first cladding layer, a protective layer containing no small or Al of the Al composition ratio than the first cladding layer Region above the protective layer is characterized Rukoto such from the mesa region.
[0008]
In the above, the first and second guide layers having a forbidden band width smaller than that of the first and second cladding layers on both sides of the active layer, respectively, or further on the first cladding layer. A protective layer having a forbidden bandwidth smaller than that of the layer may be provided.
[0009]
Further, the forbidden band width of the protective layer is preferably substantially equal to the forbidden band width of the active layer, and at least the current blocking region outside the mesa-shaped region includes at least the first current blocking layer and the first current blocking layer. A second current blocking layer formed outside the 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 It is desirable that the width is smaller than the forbidden band width of the active layer.
[0010]
The semiconductor laser device of the present invention suppresses generation of reactive current due to Al oxidation on the active layer surface on the side of the mesa stripe by providing an active layer made of InGaAsP not containing Al on the GaAs substrate as described above. The operating current can be reduced. At the same time, by making the clad layer contain Al, the forbidden band width of the clad layer can be made sufficiently large to suppress the generation of reactive current due to leakage from the active layer to the clad layer.
[0011]
Further, adjacent to the active layer, by providing a layer having a smaller Al composition ratio than the first and second cladding layers, or a layer not containing Al, that is, a guide layer having a forbidden band width smaller than each cladding layer, The generation of reactive current due to the oxidation of Al on the guide layer surface on the side of the mesa stripe can be suppressed, and the operating current can be reduced.
[0012]
Further, a protective layer having a smaller Al composition ratio than the first cladding layer or a protective layer not containing Al, that is, a protective layer having a forbidden band width smaller than that of the first cladding layer is formed on the first cladding layer. When provided on the bottom surface, the generation of reactive current due to oxidation of Al can be suppressed, and the operating current can be reduced.
[0013]
In addition, this protective layer can serve as an etching stop layer when the mesa stripe is formed, and is useful because the thickness of the buried growth layer outside the mesa stripe can be precisely controlled.
[0014]
Furthermore, in the semiconductor laser device of the present invention, by setting the forbidden band width of the protective layer substantially equal to the forbidden band width of the active layer, the protective layer can have the effect of a saturable absorption layer, and self-excited oscillation The return light noise due to can be reduced.
[0015]
When a protective layer having a saturable absorption effect exists only inside the stripe, saturation of the carriers generated by light absorption reduces the saturable absorption effect and makes it difficult for self-excited oscillation to occur. On the other hand, when the protective layer having a saturable absorption effect is present 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, absorption saturation of the carrier hardly occurs and self-excited oscillation is likely to occur. In addition, when a protective layer having a saturable absorption effect exists only inside the stripe, light absorption in the fundamental transverse mode is increased and mixed oscillation in higher order transverse modes occurs. On the other hand, similarly, if the protective layer having the saturable absorption effect described above is present inside and outside the stripe, the fundamental transverse mode and the higher order transverse mode are simultaneously affected by light absorption, but the activity inside the stripe is not affected. Since the gain of the layer is large, selective oscillation in the fundamental transverse mode can be caused.
[0016]
Furthermore, 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 the second current blocking outside the first current blocking layer. The forbidden band width of the layer is preferably smaller than the forbidden band width of the active layer. That is, in general, when the basic transverse mode and the higher order transverse mode are compared, the higher order transverse 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. The fundamental transverse mode oscillation which is important for practical use can be realized.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Examples of the present invention will be described below.
[0018]
Example 1
FIG. 1 shows a cross-sectional view of the semiconductor laser device of Example 1.
[0019]
On the p-GaAs substrate 1, a p-Al _0.6 Ga _0.4 As first cladding layer 2 (layer thickness 1.2 μm), a p-GaAs protective layer 3 (layer thickness 0.007 μm), undoped In _0.48 Ga _0.52 P first Guide layer 4 (layer thickness 0.01 μm), undoped In _0.35 Ga _0.65 As _0.40 P _0.60 strain quantum well active layer 5 (layer thickness 0.005 μm), undoped In _0.48 Ga _0.52 P second guide layer 6 (layer thickness 0. 01 μm), n-Al _0.6 Ga _0.4 As second clad layer 7 (layer thickness 1.2 μm), n-GaAs cap layer 8 (layer thickness 0.1 μm) are sequentially formed by metal organic chemical vapor deposition (MOCVD method). Growing and etching is stopped on the surface of the p-GaAs protective layer 3 by selective etching to form a mesa stripe 9 (bottom width 1 μm).
[0020]
N-Al _0.6 Ga _0.4 As first current blocking layer 10 (layer thickness 0.2 μm), p-GaAs second current blocking layer 11 (layer thickness 0.6 μm), n − so as to embed the outside of the mesa stripe 9. A GaAs third current blocking layer 12 (layer thickness: 0.5 μm) is sequentially grown by MOCVD.
[0021]
An n-GaAs contact layer 13 (layer thickness: 2 μm) is grown by MOCVD so as to embed the n-GaAs cap layer 8 and the n-GaAs third current blocking layer 12.
[0022]
A p-type electrode 14 and an n-type electrode 15 are formed on the surface of the p-GaAs substrate 1 and the surface of the n-GaAs contact layer 13. The resonator length is adjusted to 100 μm, and the Al ₂ O ₃ film and the Si film are formed so that the reflectance of the light emitting side end surface of the resonator end surface is 30% and the reflectance of the rear side is 65%.
[0023]
In the element of this example, when a forward voltage is applied between the p-type electrode 14 and the n-type electrode 15, the oscillation wavelength is 0.78 μm, the threshold current is 0.5 mA, and the slope efficiency of current-light output characteristics is 1.0 W. / A, the operating current of 3 mW optical output is 3.5 mA. Examining the change in operating current at an ambient temperature of 70 ° C. and a constant light output of 3 mW, the running time during which the operating current increases by 20% in the initial period 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 parallel to the pn junction and a radiation angle of 25 degrees in the vertical direction, and a fundamental transverse mode operation can be realized. Further, the return light noise of the element of the present embodiment is a standard required for the optical disk apparatus, that is, −130 dB / Hz or less, and is sufficiently applicable to the optical disk apparatus.
[0024]
In the element of this embodiment having the above-described configuration, the InGaAsP active layer 5 lattice-matched with GaAs is formed on the p-GaAs substrate 1, and the composition ratio of the active layer 5 is adjusted, whereby the oscillation wavelength 0 .78 μm is obtained. Also contains at least Al in the cladding layer 2, 7, to the forbidden band width than the active layer 5 using a large AlGaAs least 300 meV, generated from the active layer 5 of the reactive current due to carrier leakage to the cladding layer 2, 7 Can be suppressed.
[0025]
In the device of this embodiment, the InGaAsP active layer 5, the InGaP first guide layer 4, the InGaP second guide layer 6 on the side surface of the mesa stripe 9, and the p-GaAs protective layer 3 on the bottom surface of the mesa stripe 9 all contain Al. The semiconductor layer is not formed. Therefore, when the mesa stripe 9 is formed in the atmosphere, oxidation caused by Al, that is, bonding between Al and oxygen can be suppressed. Constituent elements other than Al in each layer are Ga, As, In, and P, and bonds with oxygen in the atmosphere occur. However, the bonds are much weaker than Al and have virtually no effect.
[0026]
Further, in the case of the InGaAsP active layer 5 of this embodiment, pinning of the Fermi level inside the InGaAsP active layer is less likely to occur at the regrowth interface on the side surface of the mesa stripe or the interface with the end face reflection film, as compared with the conventional AlGaAs active layer. Therefore, surface recombination of the carrier is suppressed, and it becomes possible to reduce the operating current and improve the reliability accompanying the suppression of the reactive current.
[0027]
Furthermore, in the device of this example, the forbidden band width of the protective layer 3 is set to be approximately equal to the forbidden band width of the active layer 5. Therefore, in this embodiment, since the protective layer 3 has a saturable absorption effect, self-excited oscillation 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 saturation in the protective layer 3 is unlikely to occur, and self-excited oscillation is likely to occur as the light output increases, thereby realizing low noise characteristics. Furthermore, in the element of this example, since the protective layer 3 having a 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.
[0028]
Furthermore, in the element of this 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, and the first band outside the first current blocking layer 10. 2 The forbidden bandwidth of the current blocking layer 11 is smaller than the forbidden bandwidth of the active layer 5. Comparing the fundamental 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 has an effect of light absorption in the second current blocking layer 11 than the fundamental transverse mode. It becomes easy to receive. Therefore, fundamental transverse mode oscillation with little light absorption occurs, and fundamental transverse mode oscillation that is practically important can be realized.
[0029]
FIG. 2 shows a cross-sectional view of a semiconductor laser device of a reference example .
[0030]
On an n-GaAs substrate 1, an n- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P first cladding layer 2 (layer thickness 1.2 μm), an 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), and p-GaAs cap layer 8 (layer thickness 0.7 μm) are sequentially grown by molecular beam epitaxy (MBE). The etching is stopped on the surface of the InGaAsP active layer 5 by selective etching to form a mesa stripe 9 having a width of 2 μm.
[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 (layer thickness 0.6 μm) and the p-GaAs third current blocking layer 12 (layer thickness 0.7 μm) are sequentially grown by MOCVD. A p-GaAs contact layer 13 is grown on the surfaces of the p-GaAs cap layer 8 and the p-GaAs third current blocking layer 12 by MOCVD. 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 contact layer 13. 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 is 30%.
[0032]
In the element of this reference example, when a forward voltage is applied between the n-type electrode 14 and the p-type electrode 15, the oscillation wavelength is 0.78 μm, the threshold current is 2 mA, and the slope efficiency of current-light output characteristics is 0.6 W / A. The operating current with an optical output of 3 mW is 6.5 mA. Examining the change in operating current at an ambient temperature of 80 ° C. and a constant light output of 3 mW, the running time during which the operating current increases by 20% of the initial time is 10,000 hours or more. The emitted light of the element of this reference example 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 reference example, the InGaAsP active layer 5 on the bottom surface of the mesa stripe 9 is formed of a semiconductor layer not containing Al. Therefore, when the mesa stripe 9 is formed, oxidation in the atmosphere caused by Al, that is, bonding between Al and oxygen can be suppressed. Constituent elements other than Al in the active layer are Ga, As, In, and P. For the same reason as described above, a non-radiative recombination level due to oxidation is present at the regrowth interface of the InGaAsP active layer 5 on the bottom surface of the mesa stripe 9. Can be very low.
[0033]
The first and second cladding layers 2 and 7 are (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P and contain Al, and the difference in band gap from the active layer 5 is very large. , leakage of carrier leakage to 7 suppressed sufficiently, it is possible to suppress the deterioration in reliability due to the reactive current and crystal defects caused by non-radiative recombination of carriers in the active layer 5 of the mesa stripe 9 bottom surface Low current characteristics can be obtained.
[0034]
Example 2
FIG. 3 shows a cross-sectional view of the semiconductor laser device of the second embodiment.
[0035]
p-Al _0.5 Ga _0.5 As first cladding layer 2 (layer thickness 2.0 μm), p-In _0.60 Ga _0.40 As _0.18 P _0.82 protective layer 3 (layer thickness 0.02 μm), undoped on p-GaAs substrate 1 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 (layer thickness 0.01 μm, 3 layers) and undoped In _0.48 Ga _0.52 P barrier layer (layer) Strained multiple quantum well active layer 5 formed by alternately arranging 0.007 μm thickness, two layers), undoped Al _0.25 Ga _0.75 As second guide layer 6, p- Al _0.5 Ga _0.5 As second cladding layer 7 (layer thickness) 1.5 [mu] m), n -GaAs contact layer 13 (thickness 0.1 [mu] m), was grown by successively MOCVD method, the etching is stopped at p -InGaAsP protective layer 3 surface by selective etching, the width 3μm main Stripe 9 to form a (bottom width 1 [mu] m).
[0036]
An oxygen-doped high-resistance AlInP layer 21 and a p-GaAs planarization layer 22 are selectively embedded and grown outside the mesa stripe 9. A p-type electrode 14 and an n-type electrode 15 are formed on the surface of the p-GaAs substrate 1, the surface of the n-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 facet on the light emission side is 12% and the reflectance on the opposite side is 75%.
[0037]
In the element of this example, when a forward voltage is applied between the p-type electrode 14 and the n-type electrode 15, the oscillation wavelength is 0.78 μm, the threshold current is 5 mA, and the slope efficiency of current-light output characteristics is 1.0 W / A. The operating current at an optical output of 35 mW is 40 mA. Examining changes in operating current at an ambient temperature of 70 ° C. and a constant light output of 35 mW, the running time during which the operating current increases by 20% of the initial time is 5000 hours or more. In addition, the emitted light of the element of this example has a radiation angle of 12 degrees parallel to the pn junction and a radiation angle of 24 degrees in the vertical direction. The present embodiment is unique in that the current blocking region is constituted by the oxygen-doped high-resistance AlInP layer 21 and the p-GaAs planarization layer 22, but the device of this embodiment also has the same characteristics as in the first embodiment. Exactly the same operation and effect can be obtained.
[0038]
Example 3
FIG. 4 is a cross-sectional view of the semiconductor laser device of Example 3 .
[0039]
On the n-GaAs substrate 1, an n-Al _0.5 Ga _0.5 As first cladding layer 2 (layer thickness 1.2 μm), an n-InGaP protective layer 3 (layer thickness 0.01 μm), undoped In _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 0.02 μm) ), 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 μm) are sequentially grown by the gas source MBE method, and selectively etched. Etching is stopped on the surface of the n-InGaP protective layer 3 to form a mesa stripe 9 having a width of 2 μm.
[0040]
An SiN dielectric 23 is formed outside the mesa stripe 9 to block current, and a polyimide buried layer 24 is formed for planarizing the surface.
[0041]
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 is 30%.
[0042]
In the device of this example, when a forward voltage is applied between the n-type electrode 14 and the p-type electrode 15, the oscillation wavelength is 0.78 μm, the threshold current is 1.0 mA, and the slope efficiency of current-light output characteristics is 0.6 W. / A, the operating current of optical output 3 mW is 6.0 mA. Examining the change in operating current at an ambient temperature of 70 ° C. and a constant light output of 3 mW, the running time during which the operating current increases by 20% in the initial period is 10,000 hours or more. In addition, the emitted light of the element of this example has an emission angle of 15 degrees parallel to the pn junction and an emission angle of 25 degrees in the vertical direction.
[0043]
The element of the present embodiment is the same as that of the first embodiment except that the operation and effect in the current blocking region are different. Note that the element of this embodiment has an advantage that it can be manufactured by a single crystal growth. Therefore, dopant re-diffusion due to crystal growth for forming a current blocking layer can be suppressed, and generation of reactive current due to re-diffusion can be suppressed.
[0044]
Example 4
FIG. 5 shows a cross-sectional view of the semiconductor laser device of Example 4 .
[0045]
On the p-GaAs substrate 1, a p-Al _0.5 Ga _0.5 As first cladding layer 2 (layer thickness 0.6 μm), a 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), undoped In _0.25 Ga _0.75 As _0.5 0P _0.50 active layer 5 (layer thickness 0.05 μm), n-Al _0.5 Ga _0.5 As second cladding layer 7 (layer) A thickness of 1.2 μm) and an n- GaAs cap layer 8 (layer thickness of 0.2 μm) are sequentially grown by MOCVD, and the etching is stopped on the surface of the p-AlGaAs protective layer 3 by selective etching to obtain a mesa stripe 9 ( A bottom width of 1 μm).
[0046]
An n-Al _0.6 Ga _0.4 As first current blocking layer 10 (layer thickness 0.2 μm), a p-GaAs second current blocking layer 11 (layer thickness 0.6 μm), n − so as to embed the outside of the mesa stripe 9. A GaAs third current blocking layer 12 (layer thickness: 0.5 μm) is sequentially grown by MOCVD. An n-GaAs contact layer 13 (layer thickness: 2 μm) is grown by MOCVD so as to embed the n-GaAs cap layer 8 and the n-GaAs third current blocking layer 12. a p-GaAs substrate 1 and the n-GaAs contact layer 13 is formed on the surface of a p-type electrode 14 and the n-type electrode 15. 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 is 65%.
[0047]
In the device of this example, when a forward voltage is applied between the p- type electrode 14 and the n- type electrode 15, the oscillation wavelength is 0.78 μm, the threshold current is 1.0 mA, and the slope efficiency of current-light output characteristics is 0.8 W. / A, the operating current of optical output 3mW is 4.8mA. Examining the change in operating current at an ambient temperature of 70 ° C. and a constant light output of 3 mW, the running time during which the operating current increases by 20% in the initial period is 10,000 hours or more. In addition, the emitted light of the element of this example has an emission angle of 15 degrees parallel to the pn junction and an emission angle of 25 degrees in the vertical direction.
[0048]
In the element of this example, the protective layer 3 contains Al. However, if the Al composition ratio is 0.12 to 0.16, the amount of oxygen in the atmosphere is small, so that reactive current is generated. There is no hindrance to the effect that it can be suppressed.
[0049]
In the device of this example, the forbidden band width of the protective layer 3 is substantially equal to the forbidden band width 5 of the active layer, and the protective layer 3 has a saturable absorption effect as in Example 1, so that self-excited oscillation occurs. Occurs, and the return light noise can be reduced.
[0050]
Note that the present invention is not limited to the above-described embodiments, and is applicable to layer thicknesses, Al composition ratios, and carrier concentrations other than the embodiments as long as the effects of the present invention are obtained. In addition to the MOCVD method, the MBE method, and the gas source MBE method, the growth method can be applied to the LPE method and the ALE (atomic beam epitaxy) method as long as the effects of the present invention are obtained. Although the present invention has been described with respect to a mesa stripe, it can also be applied to a surface emitting laser having a circular mesa region and emitting laser light from the surface.
[0051]
【The invention's effect】
In the semiconductor laser device of the present invention, by providing an active layer made of InGaAsP not containing Al on a GaAs substrate, the generation of reactive current due to the oxidation of Al on the active layer surface on the side of the mesa stripe can be suppressed. Reduction can be achieved. 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 sufficiently increased, and reactive current generation due to carrier leakage from the active layer to the cladding layer is generated. It is possible to provide a useful semiconductor laser device that can be suppressed and the operating current can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a semiconductor laser device according to Example 1 of the present invention.
FIG. 2 is a cross-sectional view of a semiconductor laser device according to a reference example .
FIG. 3 is a cross-sectional view of a semiconductor laser device according to Example 2 of the present invention.
FIG. 4 is a cross-sectional view of a semiconductor laser device according to Example 3 of the invention.
FIG. 5 is a cross-sectional view of a semiconductor laser device according to Example 4 of the present invention.
FIG. 6 is a cross-sectional view of a conventional semiconductor laser device.
[Explanation of symbols]
1 GaAs substrate 2 first cladding layer 3 protective layer 4 first guide layer 5 InGaAsP active layer 6 second guide layer 7 second cladding layer 10 first current blocking layer 11 second current blocking layer 12 third current blocking layer 21 high Resistive layer 23 Dielectric film

Claims (6)

On the first conductivity type GaAs substrate, at least a first conductivity type first cladding layer, an active layer, and a second conductivity type second cladding layer are provided, and at least the active layer and the second cladding layer are provided. In the semiconductor laser device comprising a mesa-like region, and including a current blocking region outside the mesa-like region,
The active layer is made of InGaAsP not containing Al, and the first and second cladding layers contain at least Al,
Wherein between the first cladding layer and the active layer, a small Al composition ratio than said first cladding layer, or Ri Na provided first guide layer containing no Al,
A protective layer having an Al composition ratio smaller than that of the first cladding layer or not containing Al is provided between the first cladding layer and the first guide layer, and a region above the protective layer is the mesa-shaped region. Tona semiconductor laser device characterized Rukoto. The semiconductor laser device according to claim 1,
The semiconductor laser device, wherein the forbidden band width of the protective layer is substantially equal to the forbidden band width of the active layer . The semiconductor laser device according to claim 1 or 2,
A semiconductor laser device, wherein a second guide layer having an Al composition ratio smaller than that of the second cladding layer or containing no Al is provided between the active layer and the second cladding layer . In the semiconductor laser device according to claim 1 or 3,
The semiconductor laser device , wherein the first and second cladding layers have a forbidden band width of 300 meV or more larger than that of the active layer . The semiconductor laser device according to any one of claims 1 to 3 ,
The active layer, a semiconductor laser element characterized that you have configured the oscillation wavelength is 780nm band. The semiconductor laser device according to any one of claims 1 to 5 ,
The current blocking region outside the mesa-shaped region has at least a first current blocking layer and a second current blocking layer formed outside the first current blocking layer. band gap greater than the band gap of the active layer, the band gap of the second current blocking layer is a semiconductor laser element characterized that no less than the band gap of the active layer.

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