JP3115006B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device using a compound semiconductor material.
The present invention relates to a semiconductor laser device using an AlP-based material.

[0002]

2. Description of the Related Art InGaAlP-based materials exclude nitrides
It has the largest band gap among III-V compound semiconductor mixed crystals, and attracts attention as a light emitting device material in the 0.5 to 0.6 μm band. In particular, a semiconductor laser having a double heterostructure using GaAs as a substrate and InGaAlP lattice-matched to the substrate as an active layer and a cladding layer can oscillate at room temperature.
It becomes a visible light laser of 0.6 μm band, and various applications not available in semiconductor lasers in the infrared region are possible.

Such a semiconductor laser can provide a small beam spot because of its short oscillation wavelength, and can be a light source that enables high-density recording of an optical disk. However, for this purpose, it is necessary to operate stably with an optical output of 30 mW or more.

A factor limiting the optical output of a semiconductor laser is the occurrence of a kink in the current-optical output characteristics (the linearity of the current-optical output characteristics is impaired and a bend occurs). When the kink occurs, the transverse mode is deformed and the beam characteristics are deteriorated, so that it is difficult to use the light source as a light source for an optical disk or the like. Therefore, a semiconductor laser with a high kink level is required to obtain a high optical output while maintaining good beam characteristics.

Another factor that limits the optical output of a semiconductor laser is so-called catastrophic optical damage (COD: Catalytic Damage).
strophic Optical Damage). This is because the active layer itself absorbs the oscillated laser light, and the generated electron-hole pairs generate heat when non-radiative recombination occurs, resulting in a rise in temperature, and further reduction in the energy gap further increases the light absorption. When the positive feedback occurs, the crystal is melted near the laser end face having a high light density and the laser is destroyed. The occurrence of COD depends on the light density, and the higher the light confinement amount in the active layer or the narrower the lateral mode width, the lower the light output, the higher the COD light density, and the more the COD light density is destroyed. Therefore, to obtain a high optical output, a semiconductor laser having a high COD level is required.

Usually, in order to increase the COD level, the active layer is made thinner to reduce the light density in the active layer. However, in the semiconductor laser using the InGaAlP system, when the active layer is thinned, it is difficult to use a clad layer having a sufficiently large energy gap as a clad layer located on both sides of the active layer and having a role of confining injected carriers. . That is, when the active layer is made thin, the threshold current density increases, and carriers having high energy contribute to oscillation, so that the equivalent band gap of the active layer increases. As a result, the energy gap difference between the cladding layer and the cladding layer becomes small, and the injected carriers cannot be effectively confined. Furthermore, if the operating temperature rises,
The decrease in light output became remarkable, and high output operation was difficult.

Conventionally, when an InGaAlP-based material whose lattice constant changes depending on its mixed crystal composition is used for a semiconductor laser, the difference in lattice constant between the substrate and the substrate between the use temperature of room temperature and the temperature at which the crystal is grown is reduced. It has been considered necessary. This is because, when the difference in lattice constants becomes large, misfit dislocations are generated, and the extension of defects due to the occurrence of stress is promoted, so that the characteristics are easily deteriorated. In particular, in a semiconductor laser having a high injection current density and a high optical density, characteristic degradation is remarkably caused by misfit dislocations and extension of defects.

In a general semiconductor laser, the difference in lattice constant between the substrate and the active layer (the degree of lattice mismatch) Δa / a is defined as Δa / a = (a−a ₀ ) / a ₀ , Was assumed to be about 0.2% or less. Where a is InGaAl
Lattice constant of the P layer, a ₀ represents the lattice constant of the substrate.

FIG. 12 shows a conventional transverse mode control structure InG.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an aAlP semiconductor laser.
In the figure, 90 is an n-GaAs substrate, 91 is an n-GaAs buffer layer, 92 is an n-InGaAlP cladding layer, 93 is an InGaP active layer, 94 is a p-InGaAlP cladding layer, 97 is a p-InGaP cap layer, and 99 is p -Ga
This is an As contact layer. This laser has a p-cladding layer 94 having a ridge shape, and a p-cladding layer 94 formed only on the ridge.
The cap layer 97 and the p-contact layer 99 functioning as a light absorbing layer for the buried emission wavelength constitute a mechanism for controlling current confinement and a transverse mode (for example, Applied).
Physics Letters, Vol.56, No.18, 1990, pp1718-171
9).

In the structure of FIG. 12, when the mixed crystal composition of the active layer 93 and the cladding layers 92 and 94 is set within the above range of lattice mismatch (less than 0.2%), the kink level becomes 40.
mW, which limited the maximum light output that could be used.

As one of the mechanisms of kink generation, a hole burning effect can be considered. This is because, in the transverse mode in the active layer, that is, in the portion where the light density is high in the light density distribution, stimulated emission due to recombination of electrons and holes is performed strongly, the concentration of electrons and holes is reduced, and the active layer in the active layer is reduced. Since the concentration distribution of electrons and holes is deformed, the gain distribution is deformed and the transverse mode is deformed. At this time, it is considered that the electron and hole concentration distributions are less likely to be deformed as the diffusion length of the carriers is larger. In the case of an InGaAlP-based material, the diffusion length of holes is particularly small, and this is considered to be the main cause of the low kink level.

FIG. 13 shows the temperature dependence of the current-light output characteristics in the structure of FIG. By making the active layer 93 thin (for example, to 0.04 μm), the light output 20
Operation up to mW has been realized. COD light output is also 51
A high value of mW was obtained. However, at a high temperature of 40 ° C. or higher, the optical output is significantly reduced, and a practical optical output considering the operating temperature range (around 50 ° C.) is about 10 mW, which limits the maximum optical output that can be used.

[0013]

As described above, the conventional In
In a semiconductor laser having an active layer made of a GaAlP-based material, there is a problem that a kink level is reduced due to a hole burning effect, which limits a maximum usable optical output.

Further, when the active layer is thinned to increase the optical output at which COD occurs, the maximum optical output at high temperatures decreases due to the deterioration of the temperature characteristics due to the increase in the threshold current. There was also the problem of limiting the maximum light output that could be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a semiconductor laser device which can operate at a higher temperature and can improve the maximum usable optical output. It is in.

[0016]

The gist of the present invention is to reduce the band gap of the active layer by increasing the difference between the lattice constant of the active layer and the lattice constant of the substrate, thereby reducing the gap between the cladding layer and the active layer. The purpose is to increase the band gap difference.

[0017]

[0018]

That is, according to the present invention, the compound semiconductor substrate
n _1-y (Ga _1-x Al _x ) _y P-based material (0 ≦ x <1,0
≦ y <1) In a semiconductor laser device having a double heterostructure portion in which an active layer composed of ≦ y <1 is sandwiched between cladding layers, the active layer and the cladding layer are directly joined, and the thickness of the active layer is 0.012 μm.活性 0.04 μm, and the lattice constant of the active layer is 0.5% to 2% higher than the lattice constant of the substrate.
It is characterized in that it becomes larger within the range.

[0020]

According to the present invention, by increasing the lattice constant of the active layer by 0.3% or more with respect to the lattice constant of the substrate, the band gap of the active layer is reduced, and the band gap difference between the active layer and the clad layer is reduced. Can be increased. For this reason, the temperature characteristics can be improved by reducing the overflow of the injected carriers due to the temperature rise, and a semiconductor laser capable of operating at a high optical output up to a high temperature can be realized.

Further, by increasing the lattice constant of the active layer by 0.5% or more with respect to the lattice constant of the substrate, strain is applied to the active layer within a range not so large. Due to this distortion, the band structure of InGaAlP used for the active layer, particularly the effective mass of the valence band, can be reduced in the in-plane direction of the active layer. As a result, the diffusion length of holes in the in-plane direction of the active layer can be increased, the hole burning effect which is a cause of kink generation can be avoided, and oscillation in a stable transverse mode without kink up to high light output can be achieved. It becomes possible.

Further, the thickness of the active layer is set to 0.02 ± 0.008 μm, and the lattice constant of the active layer is 0.5 to 2 times larger than that of the substrate.
%, It is possible to realize a high light output semiconductor laser capable of operating at a high temperature with a good yield.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a conceptual diagram showing the degree of lattice mismatch of a double heterostructure in a semiconductor laser device according to a first embodiment of the present invention. In the figure, 10 is a GaAs substrate, 1
2 and 14 are InGaAlP cladding layers, and 13 is InGa
An active layer of P or InGaAlP. The mixed crystal composition is set so that the energy gap of the active layer 13 is smaller than that of the cladding layers 12 and 14, and has a double hetero structure in which light and carriers are confined in the active layer 13. The conductivity types of the two cladding layers 12 and 14 are different from each other, and electrons and holes are injected into the active layer 13 respectively. The degree of lattice mismatch Δa / a of each layer with respect to the GaAs substrate 10 is such that the two cladding layers 12 and 14
And the active layer 13 is set to be 0.3 to 2.5% larger.

FIG. 2 shows an example in which the double heterostructure portion set as described above is applied to an InGaAlP semiconductor laser having a lateral mode control structure. In the figure, 20 is an n-GaAs substrate, 21 is an n-GaAs buffer layer, 22 is an n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer, 23 is an In _0.55 a _0.45 P active layer, and 24 is p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer, 25 is a p-In _0.5 Ga _0.5 P etching stop layer, 26 is a p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer, 27 is p-In _0.5 Ga _0.5 P A cap layer, 28 is an n-GaAs current confinement layer, and 29 is a p-GaAs contact layer.

This laser differs from the conventional structure in that the degree of lattice mismatch is increased by changing the composition of the active layer 23. That is, in the conventional laser, In _0.5 Ga is used as an active layer so as to lattice-match with GaAs.
_{Although 0.5} P was used, in this embodiment, In _0.55 Ga
By using _0.45 P, the lattice constant of the active layer 23 is about 0.5% larger than the lattice constant of the substrate 20. This degree of lattice mismatch is determined by the photoluminescence wavelength, X-ray diffraction,
It was confirmed by a transmission electron microscope or the like. Also, the active layer 2
The lattice mismatch of _No. 3 is In _1-y (Ga _1-x Al _x ) _y P
In the notation, about 0.5% was achieved by setting Al composition x = 0 and changing Ga composition y to y = 0.45.

FIG. 3A shows the current-light output characteristics of this laser device. At this time, the thickness of the active layer 23 is 0.02 μm.
m. The compositions of the cladding layers 22 and 24 are the same for both p and n, and x = (In _1−y (Ga _1−x Al _x ) _y P)
0.7 and y = 0.5. The impurity doping of each cladding layer is 1 × 10 ¹⁸ cm for the p-type with Zn as an impurity.
About ^-3, n-type was about 1 × 10 ¹⁷ cm ^-3 in concentration of Si as an impurity.

As shown in FIG. 3A, up to 60 ° C.
An optical output of 0 mW is obtained. Also, in FIG.
The lattice constant of the active layer 23 is set to about 1
5 shows the characteristics of a laser using an active layer made of In _0.62 Ga _0.38 P, which is increased by%. In this case, 40m up to 80 ° C
It can be seen that a light output of W is obtained, and a higher light output can be realized.

FIG. 4 shows changes in the operating current due to the thickness of the active layer 23 and the degree of lattice mismatch. This figure shows 50
The operation current when an optical output of 10 ° C. and 10 mW is obtained is shown. When the degree of lattice mismatch is within about 0.2%, the operating current is large and constant, and when the degree of lattice mismatch exceeds this, the operating current drops sharply. And the degree of lattice mismatch is 0.3%
Above, the operating current is sufficiently small. If the degree of lattice mismatch becomes too large, the operating current becomes large again, but this upper limit depends on the film thickness. For example, when the thickness of the active layer 23 is
At 0.02 μm, the operating current increases when the lattice mismatch exceeds 1%, and when the film thickness is 0.012 μm, the operating current increases when the lattice mismatch exceeds 2%. Although not shown in the figure, it has been confirmed that the operating current decreases to a lattice mismatch of 2.5% when the film thickness is 0.01 μm.

That is, if the lattice constant of the active layer 23 is in the range of 0.3 to 2.5% of the lattice constant of the substrate 20, the same effect as described above can be obtained. Further, the thickness of the active layer 23 is 0.02 μm.
It was found that the above effect was remarkable in the range of 0.5 to 1% for m and 0.75 to 1.5% for 0.015 μm. Active layer 23
The upper limit of the lattice mismatch is determined by the deterioration of the device due to the occurrence of misfit dislocations. The thinner the active layer 23 is, the larger the upper limit is, and the upper limit is 2.5% at a film thickness of 0.01 μm. On the other hand, if the thickness of the active layer 23 is too large, the above effect cannot be obtained.
The upper limit of the film thickness is about 0.1 μm.

In particular, when the thickness of the active layer is shown on the X axis and the degree of lattice mismatch is shown on the Y axis, X = 0.015 μm, Y = 0.3%,
X = 0.04 μm, Y = 0.3%, X = 0.04 μm, Y = 0.5%, X
= 0.015 μm, Y = 1.5%, and the area obtained by connecting each point with a straight line was a preferable place where the operating current can be reduced.

The buffer layer 21 is made of n-InGaP,
The etching stop layer 25 is made of p-InGaAlP, p-
GaAlAs or p-GaAs, and the cap layer 27 is made of p-InGaAlP, p-GaAlAs or p-G.
The same effects as described above can be obtained even when aAs is used, the current confinement layer 28 is semi-insulating GaAs, n-type or semi-insulating GaAlAs, and the p-type cladding layer 24 has a thickness of 0.1 to 0.4 μm. The same effect can be expected even when the active layer 23 has a quantum well structure including a quantum well layer and a barrier layer.

FIG. 5 is a conceptual diagram showing the degree of lattice mismatch of the double heterostructure in the semiconductor laser device according to the second embodiment of the present invention. The lattice mismatch Δa / a of each layer with respect to the GaAs substrate 10 is determined by the two cladding layers 12,
14 is substantially equal to the substrate 10, and the active layer 13 is about 1%
It is set large.

FIG. 6 shows an example in which the double heterostructure portion set as described above is applied to a lateral mode control structure InGaAlP semiconductor laser. In the figure, 20 is an n-GaAs substrate, 21 is an n-GaAs buffer layer, 22 is an n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P cladding layer, 23 is an In _0.62 Ga _0.38 P active layer, and 24 is p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P clad layer, 25 is a p-In _0.5 Ga _0.5 P cap layer, and 26 is a p-GaAs contact layer.

This laser is basically the same as the conventional structure shown in FIG. 12, except that the degree of lattice mismatch is increased by changing the composition of the active layer 23. That is, in the conventional laser, G
Although In _0.5 Ga _0.5 P is used so as to lattice-match with aAs, in this embodiment, by using In _0.62 Ga _0.38 P, the lattice constant of the active layer 23 is set to about 1% of the lattice constant of the substrate 20. I'm making it big.

The current-light output characteristics of this laser device were almost the same as those shown in FIG. The active layer 2
The thickness of No. 3 was 0.04 μm. The composition of the cladding layer is p, n
In both cases, x = 0.7 and y = 0.5 in In _1-y (Ga _1-x Al _x ) _y P. In addition, the cladding layer 2
The impurity doping of 2, 24 is about 1 × 10 ¹⁸ cm ⁻³ with Zn as the impurity for the p-type and 1 × 1 with Si as the impurity for the n-type.
The concentration was about 0 ¹⁷ cm ^-3 .

In the structure of this embodiment, the oscillation wavelength is increased by about 20 nm to 690 nm by increasing the degree of lattice mismatch as compared with the conventional structure. While the kink was generated at 43 mW in the conventional structure, the kink level was improved to 100 mW or more in the structure of the present embodiment. Further, in the structure of this example, it was also recognized that the oscillation threshold current was reduced and the differential quantum efficiency was improved as compared with the conventional structure.

FIG. 7 shows the dependency of the kink level on the degree of lattice mismatch of the active layer 23. Active layer 23
In a device having a thickness d of 0.04 μm, the effect of improving the kink level begins to appear at a lattice mismatch of about 0.5%, increases with an increase in the degree of lattice mismatch, and increases at about 0.6%. It was about 1.5 times that of 0. When the degree of lattice mismatch exceeded 2%, the kink level sharply decreased. This is because the occurrence of misfit dislocations deteriorates device characteristics and makes oscillation difficult. Note that the characteristics in FIG. 7 change depending on the thickness d of the active layer. Thickness d
Becomes larger, the degree of lattice mismatch at which the kink level sharply decreases becomes smaller. However, the degree of lattice mismatch at which the steep improvement of the kink level is recognized is always constant regardless of the thickness d.
It was around 0.5%.

FIG. 8 shows the dependence of the kink level and the maximum operating temperature on the active layer thickness. The kink level improved as the active layer thickness was reduced, but the maximum operable temperature was reduced as the active layer thickness was reduced. On the other hand, in those having a high degree of lattice mismatch, the kink level was high at the same active layer thickness, so that the kink level could be improved without lowering the maximum operating temperature. The maximum operating temperature varies with the oscillation wavelength, and operation at higher temperatures was possible with longer wavelengths.
At the same oscillation wavelength, the degree of lattice mismatch of the active layer is large, and although there is a slight improvement, there is no decrease. The maximum operating temperature of 70 ° C. required for stable operation at 50 ° C. is obtained only when the oscillation wavelength is 690 nm.
Of the active layer was 0.02 μm or more.

On the other hand, if the thickness of the active layer is increased, the oscillation becomes difficult due to the generation of misfit dislocations, so that the kink level sharply decreases. However, this level becomes smaller as the degree of lattice mismatch increases. By the way. Therefore, when the kink level is improved to 0.5% or more, the maximum active layer thickness must be 0.1 μm or less at 0.6%, 0.07 μm or less at 1%, and 0.06 μm or less at 1.5%.

As described above, when the degree of lattice mismatch of the active layer is changed, the energy gap changes and the oscillation wavelength changes accordingly. However, in the InGaAlP-based material, in addition to the lattice mismatch, the oscillation wavelength can be controlled by the Al composition x and the order of atoms that changes depending on the crystal growth conditions. The device characteristics tended to be slightly improved with a large lattice mismatch like the kink level. This remarkably appeared in the reduction of the oscillation threshold value and the improvement of the differential quantum efficiency. It is considered that these effects depend on the fact that the band structure changes due to the strain due to lattice mismatch and the effective mass of holes in the in-plane direction of the active layer decreases as in the case of improving the kink level.

The reason why such an effect appears from the degree of lattice mismatch of about 0.5% is that the energy difference between the band edge of the band having a small effective mass of holes and the band edge of the band having a large effective mass in the in-plane direction of the active layer. This is considered to be due to the necessity of such a degree of distortion due to the degree of lattice mismatch to cause a significant difference in the injected carrier density and the operating temperature. Furthermore, if the lattice mismatch is set to 0.6% or more,
The above effects were obtained reliably.

As described above, according to this embodiment, InGaP
By setting the Ga composition of the active layer 23 to be smaller than 0.5, which is lattice-matched with the GaAs substrate 20, for example, 0.38, the lattice constant of the active layer 23 can be made about 1% larger than the lattice constant of the substrate 20. When the degree of misalignment of the active layer 23 with the substrate 20 increases, strain is applied to the active layer 23, and this strain reduces the effective mass of the valence band of InGaP of the active layer 23 in the in-plane direction of the active layer. it can.

Therefore, the diffusion length of holes in the in-plane direction of the active layer can be increased, and the occurrence of kink caused by the hole burning effect can be reduced. Therefore, the same effect as that of the first embodiment can be obtained, and oscillation in a stable transverse mode without kink can be achieved up to a high optical output, which is used as a laser light source that enables high-density recording of an optical disc. be able to.

FIGS. 9 to 11 are sectional views showing the schematic arrangements of the third to fifth embodiments of the present invention. In the third embodiment shown in FIG. 9, 31 is an n-GaAs substrate, 32 is an n-GaAs buffer layer, 33 is an n-InGaAlP first cladding layer, 34 is an InGaP active layer (Δa / a = 0.3 to 2.5%). 35, p-InGaAlP second cladding layer, 36, p-InGaP etching stop layer, 37, n-InGaAlP current confinement layer, 38, p-InGaAlP light guide layer, 39, p-InGaAlP third cladding layer, 40 Is a p-InGaP intermediate band gap layer, and 41 is a p-GaAs contact layer.

When a current is injected into the laser configured as described above, the injected current is limited to the current confinement portion 44 because of the pn inversion layer formed by the current confinement layer 37. Light emission occurs in the active layer 34 substantially along the current confinement portion 44 and leads to laser oscillation. Light that has permeated to the current confinement layer 37 is caused by a built-in refractive index difference between the light guide region 45 and the current confinement layer 37. You are trapped. With such a structure, the same effect as in the first embodiment can be obtained.

In the structure shown in FIG.
2, n-InGaP, active layer 34 is InGaAlP, etching stop layer 36 is p-GaAlAs, current confinement layer 37 is n-type or semi-insulating GaAlAs or semi-insulating InGaAlP, and light guide layer 38 is p-GaAl.
As, the intermediate band gap layer 40 may be p-GaAlAs or p-GaAs.

In the cladding layers 33 and 35, In
The Al composition x when expressed as _1-y (Ga _1-x Al _x ) _y P was set to x = 0.7.
What is necessary is just to determine suitably as long as the band gap of 3, 35 becomes sufficiently larger than the active layer 34. Further, the light guide layer 3
The Al composition of 8 is not limited to x = 0.5, but may be any smaller than the cladding layers 33 and 35 and larger than the active layer 34. The Al composition of the current confinement layer 37 is x =
It is not limited to 0.7, but can be changed as appropriate within a range larger than the active layer 34.

The fourth embodiment shown in FIG. 10 is different from the third embodiment described above in that the n-InGaAlP shown in FIG.
The current confinement layer 37 is formed by the fourth clad layer 51 and the cap layer 52.
And the current constriction layer 53. in this case,
The light guide region 45 is made narrower than the width of the current confinement portion 44 limited by the current confinement layer 53, so that light in a region where the current distribution is uniform can be confined, and the astigmatic difference becomes very small. With such a structure, the same effect as in the third embodiment can be obtained.

In the fifth embodiment shown in FIG.
Is an n-GaAs substrate, 62 is an n-GaAs or n-InGaP buffer layer, 63 is an n-InGaAlP first cladding layer, 64 is an n-InGaAlP second cladding layer, 65 is an InGaP or InGaAlP active layer (Δa /
a = 0.3 to 2.5%) 66 is a p-InGaAlP third cladding layer, 67 is a p-InGaP or p-GaAlAs etching stop layer, 68 is a p-InGaAlP fourth cladding layer, 69 is p-InGaP or p-GaAlAs intermediate A band gap layer 70 is an n-GaAs or n-GaAlAs current confinement layer, and 71 is a p-GaAs contact layer.

In the laser configured as described above, the band gap of the second cladding layer 64 is made larger than that of the active layer 65 and smaller than that of the first cladding layer 63.
The light density in the active layer 65 can be reduced. Even with such a structure, the same effect as described above can be obtained.

The Al composition x when expressed as In _1-y (Ga _1-x Al _x ) _y P was set to x = 0.7 and y = 0.5 in the first, third and fourth cladding layers. The Al composition may be appropriately determined within a range where the band gaps of the first, third, and fourth cladding layers are sufficiently larger than the active layer 65 and larger than the second cladding layer 64. Further, the Al composition of the second cladding layer 64 is not limited to x = 0.6.
Any material may be used as long as it is smaller than the first, third, and fourth cladding layers and larger than the active layer 65.

The present invention is not limited to the embodiments described above. In the embodiment, the structure as shown in FIGS. 2, 5, and 9 to 11 has been described as the transverse mode control structure. However, similar effects can be obtained with other transverse mode control structures. In addition, semiconductor lasers of other structures other than this,
For example, the present invention can be applied to a gain waveguide type or wide stripe type semiconductor laser. Further, the substrate is Ga
The material is not limited to As, and any material having a lattice constant relatively close to the lattice constant of GaAs can be used.

The direction of the ridge stripe is (10
0) Stripes on the substrate in <01 1 > direction, <011>
Direction may be used, and from the (100) plane, <01
Substrate turned off in the 1> direction, from the (100) plane to <01 1 >
A substrate turned off in the direction may be used. Here, 1 means that the crystal axis direction is negative. In addition, various modifications can be made without departing from the scope of the present invention.

[0055]

As described in detail above, according to the present invention, since the lattice constant of the active layer is made 0.3% or more larger than the lattice constant of the substrate, it can be operated at high temperatures and the maximum usable optical output can be used. And a semiconductor laser device capable of improving the performance.

When the lattice constant of the active layer is made 0.6% or more larger than the lattice constant of the substrate, in addition to the above effects,
The kink level can be increased by suppressing the hole burning effect, and a semiconductor laser device capable of improving the maximum usable optical output can be realized.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the degree of lattice mismatch of a double heterostructure in a semiconductor laser device according to a first embodiment of the present invention.

2 is a lateral mode control structure InG to which the structure of FIG. 1 is applied.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an aAlP semiconductor laser.

FIG. 3 is a characteristic diagram showing a relationship between current and light output of the laser device of FIG.

FIG. 4 is a characteristic diagram showing a change in operating current due to the thickness of the active layer 23 and the degree of lattice mismatch.

FIG. 5 is a conceptual diagram showing a degree of lattice mismatch of a double heterostructure in a semiconductor laser device according to a second embodiment of the present invention.

6 is a lateral mode control structure InG to which the structure of FIG. 5 is applied.
FIG. 1 is a cross-sectional view illustrating a schematic configuration of an aAlP semiconductor laser.

FIG. 7 is a characteristic diagram showing a relationship between a degree of lattice mismatch and a kink level.

FIG. 8 is a characteristic diagram showing a relationship between an active layer thickness, a kink level, and a maximum operating temperature.

FIG. 9 is a sectional view showing a schematic configuration of a third embodiment of the present invention.

FIG. 10 is a sectional view showing a schematic configuration of a fourth embodiment of the present invention.

FIG. 11 is a sectional view showing a schematic configuration of a fifth embodiment of the present invention.

FIG. 12 is a cross-sectional view showing a schematic configuration of a conventional InGaAlP semiconductor laser having a lateral mode control structure.

13 is a characteristic diagram showing temperature dependence of current-light output characteristics in the structure of FIG.

[Explanation of symbols]

10 GaAs substrate, 12 InGaAlP cladding layer, 13 InGaP or InGaAlP active layer, 14
... InGaAlP cladding layer, 20 ... n-GaAs substrate, 21 ... n-GaAs buffer layer, 22 ... n-InG
aAlP cladding layer, 23 ... InGaP active layer, 24 ...
p-InGaAlP cladding layer, 25 ... p-InGaP
Etching stop layer, 26 ... p-In (GaAl) P
Clad layer, 27 ... p-InGaP cap layer, 28 ...
n-GaAs current confinement layer, 29... p-GaAs contact layer.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideto Sugawara 1st Toshiba Research Institute, Komukai-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Masaki Okajima Toshiba Komukai-shi, Kawasaki-shi, Kanagawa Prefecture No. 1 in Toshiba Research Institute, Inc. (72) Inventor Genichi Hatoshige 1 in Komukai Toshiba, Koyuki-ku, Kawasaki-shi, Kanagawa Prefecture In-Toshiba Research Institute, Inc. (56) References JP-A-60-206081 (JP, A) JP-A-3-270187 (JP, A) JP-A-3-278492 (JP, A) Appl. Phys. Lett Vol. 54 No. 15 (1989) p. 1391− 1392 (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein In _1-y (Ga
_1-x Al _x ) _{y In} a semiconductor laser device having a double heterostructure portion in which an active layer made of a P-based material (0 ≦ x <1, 0 ≦ y <1) is sandwiched between cladding layers, The layers are directly bonded, the thickness of the active layer is set to 0.012 μm to 0.04 μm, and the lattice constant of the active layer is set to be smaller than the lattice constant of the substrate.
A semiconductor laser device which is increased in a range of 0.5 to 2%. 2. The method according to claim 1, wherein the substrate is GaAs, and the cladding layer is G.
In _0.5 (Ga _1-x Al _x ) _0.5 lattice-matched to aAs
P, the active layer is In having a larger lattice constant than GaAs.
_2. The semiconductor laser device according to claim 1, wherein _1-y Ga _y P (y <0.5).