JPH0677592A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To perform an operation with low threshold value and an operation at a special temperature or higher by using an oblique board in which an OFF angle is set optimally even in a special oscillation wavelength range, and manufacturing a strain MQW structure in which a strain amount, a QW layer width and number of layers to be introduced to the QW layer are set to optimum ranges thereon. CONSTITUTION:A distortion multiple quantum well structure active layer 13 having a periodic structure of a quantum barrier layer interposed between photoconductive layers 3 and 14 having large forbidden band widths and grown on a semiconductor substrate 1 and a quantum well layer (AlXGa1-X)rIN1-rP (0<=x<y1<y2<=1, 0.1<r<9.8) is formed. A composition (r) of the well layer is altered to a composition which is not lattice-aligned with the substrate 1, and a distortion amount is introduced. A lattice misalignment is set to a range from 0.3 to 2.5% in a range of 0.1<r<0.5 for introducing a compression distortion. A lattice misalignment is set to a range of 0.3 to 1.8% in a range of 0.5<<0.8 for introducing a tensile distortion, the well layer is repeated, and number of layers is set to a range of 2 to 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short wavelength visible semiconductor laser device suitable for an optical information terminal or a light source for optical application measurement.

[0002]

2. Description of the Related Art In the prior art, with the goal of lowering the threshold value in the short wavelength region, quaternary A in AlGaInPLD is used.
It is possible to introduce compressive strain by setting a composition in which the lattice constant does not match the GaAs substrate for the lGaInP quantum well (QW) layer, for example, in the prior art "Electronic Letters", 1992, 28, 628 (Electron. .Lett., 28,628 (1992)
Are described in.

However, regarding low threshold and high temperature operation in the short wavelength region, no details are given regarding the optimization of the width and the number of ternary and quaternary quantum well layers and the introduction of strain amount, and the tilted substrate Multiple quantum wells on
(MQW) Does not mention the content of the design of the structure.

[0004]

In the above prior art, the details of the strain QW width and the number of layers and the strain amount to be introduced in the strained multiple quantum well active layer are not described, and for example, in the 630 nm band oscillation wavelength. No mention is made of low threshold operation or improvement of temperature characteristics.

An object of the present invention is to provide a strained MQW structure active layer on a tilted substrate to optimize the strained QW layer width and the number of layers, so that a threshold current in the 630 nm band or a shorter wavelength region can be made higher than that in the prior art. It is to reduce the temperature and stably realize a high temperature operation of 50 ° C. or higher. Further, by defining the off-angle of the tilted substrate to be used, it is intended to shorten the oscillation wavelength and expand the margin regarding the MQW structure design.

[0006]

Means for achieving the above object will be described below.

First, it is necessary to assume the oscillation wavelength of the target laser element and perform device manufacturing conditions and structural design according to the wavelength range. In the 630 nm oscillation wavelength band where the carrier overflow becomes remarkable, it becomes difficult to achieve a low threshold and a high temperature operation. Therefore, the optimization of the above device manufacturing conditions and structural design is particularly important. There are two effective means to use, one is using a tilted substrate having a plane orientation off from the (001) plane in the [110] [-1-10] or [1-10] [-110] direction, A basic double hetero structure is formed on the semiconductor laser device by a crystal grown at a relatively high temperature of 660 to 780 ° C. thereon. Here, the minus sign in parentheses indicates the negative direction of the axis. The other is that the active layer structure is an MQW structure, and strain is introduced into each QW layer to form a strained MQW active layer. The strain amount, the QW layer width, and the number of layers to be introduced into the QW layer are set. It is to optimize. The former is mainly effective for high temperature operation, and the latter is important for lowering the threshold value.

[0008]

The operation of the above means for achieving the object will be described.

From the (001) plane used in the present invention [-1-10]
The action of a tilted substrate having a plane orientation off in the [110] or [1-10] [-110] direction will be described. On the above tilted substrate, it was considered difficult in AlGaInP mixed crystal with high Al composition 1
Since a p-type carrier concentration on the order of × 10 ¹⁸ cm ^-3 can be easily realized, it is possible to increase the hetero barrier against electrons overflowing into the p-type AlGaInP cladding layer. As a result, the conventional CW laser operation was difficult.
Even in a high temperature range of 0 ° C. or higher, the effect of mainly confining electrons occurs, and it becomes possible to secure the threshold carrier density in the active layer, and the high temperature operation is improved. If the off-angle of the tilted substrate is 5 ° or more, the hole concentration can be set to the order of 1 × 10 ¹⁸ cm ⁻³ depending on the amount of p-type impurities, and if the off-angle is further increased, the carrier activation rate of p-type impurities can be increased. It turned out to improve.

Further, it was revealed that the Al composition steepness was remarkably improved at the AlGaInP hetero interface and the interface flatness was also improved on the tilted substrate. In particular, the above effect is remarkable for the MQW structure in which the Al composition is periodically changed, and it is effective for increasing the density of states of carriers in the QW layer, improving the emission efficiency, and reducing the emission width.
In addition, on the tilted substrate, III which is peculiar to AlGaInP material system
It is possible to suppress the formation of an ordered array structure of group elements (Al, Ga and In). It has been known that the band gap energy is reduced on the (001) just substrate even in the same composition in the AlGaInP mixed crystal in which the ordered arrangement structure of the group III elements is generated. On the other hand, the use of the tilted substrate suppresses the ordered arrangement structure of the group III elements in the crystal layer grown thereon and keeps the band gap energy relatively large. This is effective for shortening the laser oscillation wavelength, and is important for optimal design of the MQW structure. The off angle of the tilted substrate was set to 15.8 ° (11
5) Using a substrate, the growth temperature is relatively high at 660-780
When the temperature is set to ℃, preferably 740 to 780 ℃, it is possible to completely eliminate the ordered arrangement structure of the group III element. As a result, the off angle was set to 15.8 ° (115)
It can be said that it is preferable to use the substrate because the band gap energy can be set to the maximum. Although determined in consideration of the growth temperature, the off-angle of the tilted substrate is set to be larger than 0 ° and within the range of 54.7 ° of the (111) plane, preferably 5 ° or more and 30 ° or less.

It will be described below that it is effective to adopt an MQW structure as the active layer provided on the tilted substrate and introduce strain into each QW layer to optimize the strain amount, the QW layer width and the number of layers. . When optimally designing a strained MQW structure, the oscillation wavelength must be first considered. For example, when the oscillation wavelength is set in the range of 630 to 640 nm, carrier overflow becomes remarkable, and therefore, when designing the strained MQW structure, the range of parameters to be set is sufficiently taken into consideration to reduce the threshold value. There is a need. The oscillation wavelength is 630-6
Distorted MQW that can achieve a low threshold value assuming a range of 40 nm
Regarding the structure, the optimum range of the above parameters will be described below separately for the case of introducing compressive strain and the case of introducing tensile strain.

When introducing compressive strain in the (Al _x Ga _1-x ) _α In _1-α P quantum well layer (0.1 <α <0.5), the band gap of the material forming the QW layer is Since the energy is low, a thin QW layer is required, which causes a decrease in carrier confinement. Therefore, the quaternary AlGaInP layer, which has a larger bandgap energy than the ternary GaInP layer, causes QW.
It is desirable to form a layer because the QW layer width can be widened at the same oscillation wavelength and carrier confinement can be improved.
Even on a (115) substrate that can completely suppress the ordered array structure of Group III elements, the strain-free ternary GaInPQW layer width needs to be 5 to 6 nm in order to realize the above oscillation wavelength, and compressive strain If it is introduced, the QW layer width becomes less than that, which is disadvantageous. In the quaternary AlGaInP QW layer, when the Al composition x is increased to 0.1, the QW layer width is 0.7 to 8 nm and the lattice mismatch is 0.
A compressive strain of 7-0.8% can be introduced. When the Al composition x of the quaternary QW layer is set to 0.2, a compressive strain of lattice misregistration of 1.2 to 1.4% can be introduced within the same QW layer width range. Regarding the amount of strain that can be introduced into the MQW structure, it is desirable to set the compressive strain within the range of 0.5 to 2.0% in lattice irregularity in consideration of the critical film thickness. Regarding the number of QW layers, if the number of layers is small, MQW
Carrier confinement in the active layer decreases, and if the number of layers is too large, non-uniform injection of holes with a large effective mass is caused, resulting in an increase in threshold current. In consideration of the above, it is advantageous to use a quaternary QW layer in the MQW structure introducing compressive strain, the Al composition x is in the range of 0 <x ≦ 0.2, and the QW layer width is in the range of 6 to 9 nm. And the number of QW layers is 10 or less, the optimum range is 3 to 7 layers, and when the compression strain is set to a range of 0.5 to 2.0% of lattice misalignment in this range, the threshold value becomes lower than the conventional one. Became possible.

On the other hand, when tensile strain is introduced in the (Al _x Ga _1-x ) _α In _1-α P quantum well layer (0.5 <α <0.8),
Since the bandgap energy of the material forming the QW layer becomes large, even if the QW layer is formed by the ternary GaInP layer, it is possible to design the strained MQW structure having the above oscillation wavelength so as to reduce the threshold value. In the direction of introducing the tensile strain and setting the composition α large, the X point of the indirect transition approaches the band gap energy of the Γ point of the direct transition and the light emission efficiency decreases, so it is not possible to introduce a lattice mismatch of 2.0% or more. It is clearly disadvantageous, and it is desirable to set it to 1.5% or less. In consideration of the above, in the tensile strain MQW structure, the Al composition x of the QW layer is in the range of 0 ≦ x ≦ 0.1, the QW layer width is in the range of 6 to 9 nm, and the number of QW layers is 10 or less. The range of layers was the optimum range, and when the tensile strain was set to a range of 0.4 to 1.2% of lattice misalignment, the threshold value could be made lower than before.

As a result of the above, the oscillation wavelength 632.8 nm of the He-Ne gas laser can be replaced with 630-64.
Even in the 0 nm region, the characteristics of the AlGaInP semiconductor laser, stable operation at 50 ° C. or higher, which was difficult in the past, and long-term reliability were made possible, and CW operation was realized at a lower threshold current than in the past.

In the above, the oscillation wavelength of the laser element is 630 to 6
This is a case where a range of 40 nm is assumed and an operation with an optical output of 3 to 10 mW is targeted. When setting the target oscillation wavelength in the 0.5 μm band on the shorter wavelength side than the above, it is effective to design a strained MQW structure as a GaInP compressive strained QW layer using a GaP substrate with a smaller lattice constant. Details will be described in Example 6.

When the target of the oscillation wavelength can be set to a longer wavelength side than the above or when it is aimed to realize a higher output characteristic than the above in the wavelength range, each of the strained MQW structures described in the claims. It is important to separately optimize the parameter design range.

[0017]

Embodiment 1 An embodiment of the present invention will be described with reference to FIGS. First, in FIG. 1, 15. in the [110] [-1-10] direction from the (001) plane.
An n-type GaAs substrate 1 having a surface inclined by 8 ° is used, on which an n-type GaInP buffer layer 2 (d = 0.5 μm, N _D = 1 × 10 ¹⁸ c
m ^-3 ), n-type (Al _y2 Ga _{1-y 2} ) _α In _1-α P optical waveguide layer 3 (d = 2.0μ
m, N _D = 1 × 10 ¹⁸ cm ^-3 , y ₂ = 0.7, α is a value 0.51 that lattice-matches the GaAs substrate), undoped (Al _x Ga _1-x ) _γ In _{1-γ with} a film thickness of 5 nm
P (X = 0, γ = 0.29, lattice mismatch 1.7%) strained quantum well layer 3 layers,
Undoped (Al _y1 Ga _1-y1 ) _β In _1-β P (y ₁ = 0.5,
β is a value 0.51 that lattice-matches the GaAs substrate) 2 quantum barrier layers,
And the optical isolation confinement layer in which the Al composition is set stepwise on both sides of the quantum well layer (Al composition y ₃ from the barrier layer to the optical waveguide layer is
Undoped (Al _y3 Ga _1-y3 ) _β In _1-β P with each film thickness set to 7 nm by changing it in steps of 0.5 to 0.7 in 0.05 steps
Layers (y ₃ = 0.5,0.55,0.6,0.65, β is a value 0.51 that is lattice-matched to the GaAs substrate) (the conduction band structure around the multiple quantum well layer is shown in Fig. 2) Well active layer 4, p-type (Al _y2 Ga _1-y2 ) _α In _1-α P optical waveguide layer 5 (d = 1.8μ
_{m, N A = 7~8 × 10} 17 cm -3, y 2 = 0.7, α values 0.51 to GaAs substrate and the lattice match), p-type _{Ga 0. 51 In 0. 49} P buffer layer 6 (d =
0.05 μm, N _A = 2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by a metal organic chemical vapor deposition method.
After this, a SiO ₂ mask (film thickness d =
0.2 .mu.m, stripe width 4 .mu.m) is formed, and layers 6 and 5 are removed by chemical etching until the layer 5 is left at 0.1 to 0.2 .mu.m to form a ridge stripe. Next, the n-type GaAs current constriction and light absorption layer 7 (d = 1.3 μm, N _D = 2 × 10 ¹⁸ cm ⁻³ ) is selectively grown while leaving the SiO ₂ mask. Furthermore, p-type GaAs contact layer 8 (d = 2 to 3 μm)
m, N _A = 5 × 10 ¹⁸ to 1 × 10 ¹⁹ cm ^-3 ) after embedding and growing,
The p-electrode 9 and the n-electrode 10 are vapor-deposited. Further, cleavage scribing is performed to cut out the element to obtain an element having the cross section of FIG.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.025 to 0.035. A device having a cavity length of 600 μm operates at a room temperature with a threshold current of 20 to 30 mA and operates as a direct current at 670 to 680.
A laser device having an oscillation wavelength of nm was obtained. The maximum laser oscillation temperature is 130 to 150 ° C, and the operating temperature is 60 ° C.
The long-term reliability of 2000 hours or more was achieved by the constant output operation with the optical output of 50 mW.

Embodiment 2 Another embodiment of the present invention will be described with reference to FIGS. First, in FIG. 3, 15. from the (001) plane in the [110] [-1-10] direction.
An n-type GaAs substrate 1 having a surface inclined by 8 ° is used, on which an n-type GaInP buffer layer 2 (d = 0.1 μm, N _D = 1 × 10 ¹⁸ c
m ^-3 ), n-type (Al _y2 Ga _{1-y 2} ) _α In _1-α P optical waveguide layer 3 (d = 2.0μ
m, N _D = 1 × 10 ¹⁸ cm ^-3 , y ₂ = 0.7, α is a value that lattice-matches the GaAs substrate 0.51), undoped (Al _x Ga _1-x ) _γ In _{1-γ with} a thickness of 7 nm
P (X = 0.10, γ = 0.24, lattice mismatch 2.0%)) 2 quantum well layers and 10 nm thick undoped (Al _y1 Ga _1-y1 ) _β In _1-β P (y ₁ =
0.5 and β are values that lattice-match with the GaAs substrate 0.51) Quantum barrier layer 1
Layers and quantum well layers Optical separation and confinement layers with Al composition set stepwise (Al composition is increased stepwise from y ₃ = 0.5 to 0.7 by 0.05 from barrier layer to optical waveguide layer)
Undoped (Al _y3 Ga _1-y3 ) _β In _1-β P layer (y ₃ = 0.5,
0.55, 0.6, 0.65, β is a value 0.51 which is lattice-matched to the GaAs substrate) (The conduction band band structure around the quantum well layer is as shown in Fig. 4) Multiple quantum well active layer 11, p-type
(Al _y2 Ga _{1-y 2} ) _α In _1-α P Optical waveguide layer 5 (d = 1.8 μm, N _A = 5 to 7)
× 10 ¹⁷ cm ^-3 , y ₂ = 0.7, α is a value that is lattice-matched with the GaAs substrate 0.
51), p-type _{Ga 0. 51 In 0. 49} P buffer layer _{6 (d = 0.03μm, N A} =
2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by the metal organic chemical vapor deposition method. After that, an element is manufactured in exactly the same manner as in Example 1 to obtain an element having the cross section of FIG.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.015 to 0.025. A device having a resonator length of 600 μm operates at a room temperature with a threshold current of 10 to 20 mA and operates as a direct current at 670 to 680.
A laser device having an oscillation wavelength of nm was obtained. The maximum laser oscillation temperature is 130 to 150 ° C, and the operating temperature is 60 ° C.
The long-term reliability of 2000 hours or more was achieved by the constant output operation with the optical output of 70 mW.

Embodiment 3 Another embodiment of the present invention will be described with reference to FIGS. First, in FIG. 6, 15. from the (001) plane in the [110] [-1-10] direction.
An n-type GaAs substrate 1 having a surface inclined by 8 ° is used, on which an n-type GaInP buffer layer 2 (d = 0.1 μm, N _D = 1 × 10 ¹⁸ c
m ^-3 ), n-type (Al _y2 Ga _1-y21-y2 ) _α In _1-α P optical waveguide layer 3 (d = 1.
1 μm, N _D = 1 × 10 ¹⁸ cm ^-3 , y ₂ = 0.7, α is a lattice matching value with the GaAs substrate 0.51), undoped (Al _x Ga _1-x ) _γ In with a thickness of 5 nm
_1-γ P (X = 0, γ = 0.42, lattice mismatch 0.5%) 8 quantum well layers and 6 nm thick undoped (Al _y1 Ga _1-y1 ) _β In _1-β P (y ₁ =
0.5 and β are values that lattice match the GaAs substrate 0.51) Quantum barrier layer 7
Layers and quantum well layers Optical separation and confinement layers with Al composition set stepwise (Al composition is increased stepwise from y ₃ = 0.5 to 0.7 by 0.05 from barrier layer to optical waveguide layer)
Undoped (Al _y3 Ga _1-y3 ) _β In _1-β P layer (y ₃ = 0.5,
0.55, 0.6, 0.65, β is a value 0.51 that is lattice-matched to the GaAs substrate) (The conduction band band structure around the quantum well layer is as shown in Fig. 6) Multiple quantum well active layer 12, p-type
(Al _y2 Ga _{1-y 2} ) _α In _1-α P Optical waveguide layer 5 (d = 1.1 μm, N _A = 5 to 7)
× 10 ¹⁷ cm ^-3 , y ₂ = 0.7, α is a value that is lattice-matched with the GaAs substrate 0.
51), p-type _{Ga 0. 51 In 0. 49} P buffer layer _{6 (d = 0.03μm, N A} =
2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by the metal organic chemical vapor deposition method. After that, an element is manufactured in exactly the same manner as in Example 1 to obtain an element having a cross section of FIG.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.20 to 0.25. A device with a cavity length of 600 μm operates at a room temperature with a threshold current of 60 to 70 mA, and operates as a direct current at 630 to 640 n.
A laser device having an oscillation wavelength of m was obtained. A maximum laser oscillation temperature of 90 to 100 ° C. was obtained, and long-term reliability of 2000 hours or more was achieved by a constant output operation with an optical output of 5 mW at an operating temperature of 50 ° C.

Embodiment 4 Another embodiment of the present invention will be described with reference to FIGS. First, in FIG. 7, 15. from the (001) plane in the [110] [-1-10] direction.
An n-type GaAs substrate 1 having a surface inclined by 8 ° is used, on which an n-type GaInP buffer layer 2 (d = 0.5 μm, N _D = 1 × 10 ¹⁸ c
m ^-3 ), n-type (Al _y2 Ga _{1-y 2} ) _α In _1-α P optical waveguide layer 3 (d = 1.2μ
m, N _D = 1 × 10 ¹⁸ cm ^-3 , y ₂ = 0.7, α is a value that lattice-matches the GaAs substrate 0.51), undoped (Al _x Ga _1-x ) _γ In _{1-γ with} a thickness of 7 nm
P (X = 0.10, γ = 0.38, lattice mismatch 1.0%) 5 quantum well layers,
Undoped (Al _y1 Ga _1-y1 ) _β In _1-β P (y ₁ = 0.5,
β is a value 0.51 that lattice-matches the GaAs substrate) 4 quantum barrier layers,
And the optical isolation confinement layer in which the Al composition is set stepwise on both sides of the quantum well layer (Al composition is y from the barrier layer to the optical waveguide layer).
By 0.05 ₃ = 0.5 to 0.7 stepwise increasing undoped that each film thickness _{10nm (Al y3 Ga 1-y3} ) β In 1-β P layer (y ₃ = 0.5,0.5
5, 0.6, 0.65 and β are values 0.51) that are lattice-matched to the GaAs substrate (the outline of the conduction band structure around the quantum well layer is as shown in Fig. 8). Multiple quantum well active layer 13, p-type (Al
_y2 Ga _1-y2 ) _α In _1-α P Optical waveguide layer 5 (d = 1.2 μm, N _A = 5 to 7 × 1
0 ¹⁷ cm ^-3 , y ₂ = 0.7, α is a value 0.5 that lattice-matches the GaAs substrate
1), p-type _{Ga 0. 51 In 0. 49} P buffer layer _{6 (d = 0.03μm, N A} =
2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by the metal organic chemical vapor deposition method. After this, an element is manufactured in exactly the same manner as in Example 1, and an element having the cross section of FIG. 7 is obtained.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.15 to 0.20. A device having a resonator length of 600 μm operates as a direct current with a threshold current of 40 to 50 mA at room temperature, and operates at 630 to 640 n.
A laser device having an oscillation wavelength of m was obtained. A maximum laser oscillation temperature of 100 to 120 ° C. was obtained, and long-term reliability of 2000 hours or more was achieved by a constant output operation with an optical output of 10 mW at an operating temperature of 50 ° C.

Embodiment 5 Another embodiment of the present invention will be described with reference to FIGS. First, in FIG. 9, 1 in the [110] [-1-10] direction from the (001) plane.
An n-type GaAs substrate 1 having a surface inclined at 5.8 ° was used, and an n-type GaInP buffer layer 2 (d = 0.5 μm, N _D = 1 × 10 ¹⁸ c) was formed thereon.
m ^-3 ), n-type (Al _y2 Ga _{1-y 2} ) _α In _1-α P optical waveguide layer 3 (d = 1.5μ
m, N _D = 1 × 10 ¹⁸ cm ^-3 , y ₂ = 0.7, α is a value 0.51) that is lattice-matched to the GaAs substrate, and 8 nm thick undoped (Al _x Ga _1-x ) _γ In _1-γ
P (X = 0, γ = 0.59, lattice mismatch 0.8%) 4 quantum well layers and 7 nm thick undoped (Al _y1 Ga _1-y1 ) _β In _1-β P (y ₁ = 0.5, β
Is a value 0.51 which is lattice-matched with the GaAs substrate) and three optical barrier layers on both sides of the quantum well layer and a stepwise Al composition confinement layer (Al composition is y ₃ = from the barrier layer to the optical waveguide layer).
Undoped (Al _y3 Ga _1- y ₃ ) _β In _1- P _β layer (y ₃ = 0.5,0.55,
0.6, 0.65 and β are values 0.51 which are lattice-matched to the GaAs substrate (the outline of the conduction band structure around the quantum well layer is as shown in FIG. 10). Multiple quantum well active layer 14, p-type (Al
_y2 Ga _{1-y 2} ) _α In _{1 -α} P Optical waveguide layer 5 (d = 1.2 μm, N _A = 5 to 7 × 1
0 ¹⁷ cm ^-3 , y ₂ = 0.7, α is a value 0.5 that lattice-matches the GaAs substrate
1), p-type _{Ga 0. 51 In 0. 49} P buffer layer _{6 (d = 0.03μm, N A} =
2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by the metal organic chemical vapor deposition method. After that, an element is manufactured in exactly the same manner as in Example 1 to obtain an element having the cross section of FIG.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.12 to 0.18. A device having a cavity length of 600 μm operates as a DC device with a threshold current of 30 to 40 mA at room temperature and operates at 630 to 640 n.
A laser device having an oscillation wavelength of m was obtained. A maximum laser oscillation temperature of 100 to 120 ° C. was obtained, and long-term reliability of 2000 hours or more was achieved by a constant output operation with an optical output of 20 mW at an operating temperature of 50 ° C.

Embodiment 6 Another embodiment of the present invention will be described with reference to FIGS. First, in FIG. 11, n is formed on the n-type GaP substrate 15 having a surface inclined by 15.8 ° from the (001) surface in the [110] [-1-10] direction.
-Type GaP optical waveguide layer 16 (d = 2.0 μm, N _D = 1 × 10 ¹⁸ cm ^-3 ), film thickness
5 nm undoped Ga _γ In _1-γ P (γ = 0.7, lattice mismatch 1.7%) strained quantum well layer 2 layers and 8 nm thick undoped Ga _β In _1-β P
(β = 0.9) 1 quantum barrier layer and optical isolation confinement layer on both sides of the strained quantum well layer (undoped Ga _β In _1-β P layer with a thickness of 8 nm)
(β = 0.9) (the conduction band structure around the quantum well layer is as shown in FIG. 12) multiple quantum well active layer 17, p-type GaP optical waveguide layer 18 (d = 1.8 μm, N _A = 7 × 10 ¹⁷
˜2 × 10 ¹⁸ cm ⁻³ ) was epitaxially grown at a growth temperature of 760 ° C. by a metal organic chemical vapor deposition method. After that, a SiO ₂ mask (film thickness d = 0.2 μm, stripe width 4 μm) is formed by photolithography, and the ridge stripe is formed by chemical etching to remove the layer 18 to the extent of leaving 0.1 to 0.2 μm. . Next, with the SiO ₂ mask left, the n-type GaP current confinement layer 19 (d = 1.3 μm, N _D =
Selectively grow 3 × 10 ¹⁸ cm ^-3 ). Further, p-type GaP contact layer 20 was _{(d = 2~3μm, N A =} 5 × 10 18 ~1 × 10 19 cm -3) the burying growth, depositing a p electrode 9 and n electrode 10. In addition, cleaving scribing and cutting out into the shape of the element,
An element having the cross section of FIG. 11 is obtained.

The optical confinement coefficient of the strained multiple quantum well structure active layer in this embodiment is in the range of 0.010 to 0.025. A device having a cavity length of 600 μm operates as a DC device with a threshold current of 40 to 50 mA at room temperature and operates at 530 to 540.
A laser device having an oscillation wavelength of nm was obtained. A maximum laser oscillation temperature of 80 to 90 ° C. was obtained, and long-term reliability of 1000 hours or more was achieved by a constant output operation with an optical output of 10 mW at an operating temperature of 50 ° C.

[0029]

According to the present invention, even in the oscillation wavelength range of 630 to 640 nm where the carrier overflow from the active layer becomes remarkable, the tilted QW layer is formed on the tilted substrate with the off angle set optimally. By producing a strained MQW structure in which the strain amount, the QW layer width, and the number of layers are set in the optimum range, the AlGaInP semiconductor laser characteristics are improved. As a result, the low threshold operation and the high temperature operation at 50 ° C. or higher, which have been difficult in the past in the short wavelength region of 650 nm or less, are enabled.

According to the embodiment of the present invention, the DC operation is performed at room temperature with the threshold current of 30 to 40 mA, and the DC current is 630 to 640 n.
A laser device having an oscillation wavelength of m was obtained. Resonator length 600
Maximum laser oscillation temperature of 100 to 12 in μm device
0 ° C is obtained, and optical output is 20 mW at operating temperature of 50 ° C.
With the constant output operation, the long-term reliability of 2000 hours or more was achieved.

According to another embodiment, a laser device having a lasing wavelength of 530 to 540 nm operating at direct current with a threshold current of 40 to 50 mA at room temperature was obtained. In a device having a cavity length of 600 μm, a maximum laser oscillation temperature of 80 to 90 ° C. was obtained, and long-term reliability of 1000 hours or more was achieved by constant output operation with an optical output of 10 mW at an operating temperature of 50 ° C.

Although the present invention has been described by using the AlGaInP material system, by changing the composition of the other material system, the lattice mismatch with the semiconductor substrate is caused and InGaAs / GaAs forming the strained QW layer is formed.
The present invention can be applied to systems, GaAsP / GaAs systems, GaAsSb / GaAs systems, InGaAsP / InP systems, and the like.

[Brief description of drawings]

FIG. 1 is a sectional view of a device structure showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a strained multiple quantum well conduction band structure according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view of an element structure showing another embodiment of the present invention.

FIG. 4 is a schematic diagram showing a strained multiple quantum well conduction band structure according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view of an element structure showing another embodiment of the present invention.

FIG. 6 is a schematic view showing a strained multiple quantum well conduction band structure according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of an element structure showing another embodiment of the present invention.

FIG. 8 is a schematic diagram showing a strained multiple quantum well conduction band structure according to another embodiment of the present invention.

FIG. 9 is a sectional view of an element structure showing another embodiment of the present invention.

FIG. 10 is a schematic view showing a strained multiple quantum well conduction band structure according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view of an element structure showing another embodiment of the present invention.

FIG. 12 is a schematic view showing a strained multiple quantum well conduction band structure according to another embodiment of the present invention.

[Explanation of symbols]

1 ... n-type GaAs substrate turned off by 15.8 ° in the [110] [-1-10] direction from the (001) plane, 2 ... n-type GaInP buffer layer, 3 ... n
Type (Al _y2 Ga _1-y2 ) _α In _1-α P (y ₂ = 0.7, α is a value 0.51 that lattice-matches the GaAs substrate) Optical waveguide layer, 4… Ga _γ In _1-γ P / (Al _y1 Ga
_1-y1 ) _β In _1-β P Strained multiple quantum well structure active layer, 5 ... p type (A
_{l y2 Ga 1-y2) α} In 1-α P (y 2 = 0.7, α is a value 0.51 to GaAs substrate lattice matched) optical waveguide layer, 6 ... p-type _{Ga 0. 51 In 0. 49} P buffer layer, 7 ... n-type GaAs current constriction and light absorption layer, 8 ... p-type GaAs contact layer, 9 ... p electrode, 10 ... n electrode, 11 ... (Al _x Ga
_1-x ) _γ In _1-γ P / (Al _y1 Ga _1-y1 ) _β In _1-β P Strained multiple quantum well structure active layer, 12… Ga _γ In _1-γ P / (Al _y1 Ga _1-y1 ) _β In _1-β
P-strained multiple quantum well structure active layer, 13 ... (Al _x Ga _1-x ) _γ In
_1-γ P / (Al _y1 Ga _1-y1 ) _β In _1-β P Strained multiple quantum well structure active layer, 14 ... Ga _γ In _1-γ P / (Al _y1 Ga _1-y1 ) _β In _1-β P strained multiple quantum well structure active layer, 15 ... From the (001) plane [110] [-1-1
N-type GaP substrate with 15.8 ° off in the [0] direction, 16 ... n-type G
aP optical waveguide layer, 17 ... Ga _γ In _1-γ P / Ga _β In _1-β P strained multiple quantum well structure active layer, 18 ... p-type GaP optical waveguide layer, 19 ... n
-Type GaP current confinement layer, 20 ... p-type GaP contact layer.

Claims (11)

[Claims] 1. A metal organic chemical vapor deposition (MO) method on a semiconductor substrate.
CVD) or molecular beam epitaxy (MBE) grown optical waveguide layer (Al _y2 Ga _{1 -y2} ) _α In with a large forbidden band width
Multiple quantum well structure (quantum barrier layer (Al _y1 GA _1-y1 ) _β In _1-β P sandwiched by _1-α P (0 <y ₂ ≦ 1, 0.2 <α <0.8)
(0 <y ₁ <y ₂ ≦ 1, 0.1 <β <0.8) and quantum well layer
(Al _x Ga _1-x ) _γ In _1-γ P (0 ≦ x <y ₁ <y ₂ ≦ 1, 0.1 <
γ <0.8)), the amount of strain is introduced by changing the composition γ in the quantum well layer to a composition that does not lattice match with the semiconductor substrate, but compressive strain is introduced.
In the range of γ <0.5, the lattice irregularity is set in the range of 0.3% to 2.5%, preferably 0.5% or more and 2.0% or less, and 0.5 <γ <0.5 for introducing tensile strain. In the range of 8, the lattice irregularity is 0.
Range of 3% to 1.8%, preferably 0.4% or more 1.2
%, And the number of repeating layers of the quantum well layer is set to 2 layers or more and 10 layers or less. 2. The semiconductor laser device according to claim 1, wherein the substrate plane orientation used for the semiconductor substrate is [001]
10] In the [-1-10] direction or the [1-10] [-110] direction, the substrate surface is inclined in the range of 0 ° to 54.7 °, preferably 5 ° or more and 30 ° or less. Semiconductor laser device. 3. The semiconductor laser device according to claim 1, wherein the thickness of each of the quantum barrier layers provided between the quantum well layers is in the range of 5 nm to 30 nm, preferably 8 nm or more and 15 nm or less. A semiconductor laser device, wherein the thickness of each quantum barrier layer is set larger as the amount of strain introduced into the quantum well layer is larger. 4. The semiconductor laser device according to claim 1, 2 or 3, wherein the quantum barrier layer is strain-free or introduces strain, but in a direction opposite to the strain introduced in each of the strained quantum well layers. A semiconductor laser device characterized in that when a strain to which stress is applied is introduced, the strain amount is set to be exactly the same as or more than that of each of the quantum well layers. 5. The semiconductor laser device according to claim 1, 2, 3 or 4, wherein the quantum barrier layer is strain-free or introduces strain. When introducing strain to which stress is applied in the same direction, the amount of strain is set to be smaller than the amount of strain of each of the quantum well layers, and the quantum well layer and the quantum barrier layer in which strain is introduced are repeated. A semiconductor laser device characterized in that the film thickness of the entire multiple quantum well structure is within a range not exceeding the critical film thickness. 6. The semiconductor laser device according to claim 1, 2, 3, 4 or 5, wherein the strain quantum well layer has a thickness of 4 nm to 15 nm, and the strain quantum well layer has a small thickness. A semiconductor laser device characterized in that the number of quantum well layers is increased accordingly in the range of 2 to 10 layers and the optical confinement coefficient is set in the range of 0.01 to 0.30. 7. The semiconductor laser device according to claim 1, 2, 3, 4, 5 or 6, wherein the quantum well layer (Al _x Ga _1-x ) _γ In
_For Al composition x in _1-γ P (0 ≦ x <y ₁ <y ₂ ≦ 1, 0.1 <γ <0.8), 0.1 <γ <0 for introducing compressive strain into the quantum well layer When 0.5, the range is 0 ≦ x ≦ 0.2, and tensile strain is introduced into the quantum well layer, 0.5 <γ <0.5.
A semiconductor laser device characterized in that when 8 is set, the range is 0 ≦ x ≦ 0.1. 8. The semiconductor laser device according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the amount of strain introduced into each of said quantum well and said quantum barrier layer is such that each film thickness has elastic energy. A semiconductor laser device characterized by being within a critical amount that can be maintained and does not generate dislocations or defects. 9. Claims 1, 2, 3, 4, 5, 6, 7 or 8
In the semiconductor laser device according greater the Al composition y ₁ of the quantum barrier layer on the light waveguide layer is gradually increased Al composition to the Al composition y ₂ of GRIN (Graded Index) layer, or stepped A semiconductor laser device characterized in that the step layer described above is provided as an optical waveguide and an optical confinement layer. 10. Claims 1, 2, 3, 4, 5, 6, 7, 8
Alternatively, in the semiconductor laser element according to 9, the material used for the semiconductor substrate is GaAs _1-z P _z (0 ≦ z ≦ 1). 11. Claim items 1, 2, 3, 4, 5,
In the semiconductor laser device according to 6, 7, 8, 9 or 10, each crystal layer provided on the semiconductor substrate has a growth temperature of 6
A semiconductor laser device, which is epitaxially grown in the range of 60 to 780 ° C.