JPH09283837A - Semiconductor distributed feedback laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distributed semiconductor feed back laser device capable of oscillating at a single wavelength over a wide temp. range. SOLUTION: The distributed semiconductor feed back laser device has a multiple quantum well active layer 8 composed of five first InGaAsP well layers A (λg=1.40μm) of 6nm thick each lattice-matched with InP and five second InGaAsP well layers B (λg=1.40μm) of 8nm thick each lattice-matched with InP which are alternately disposed in the layer direction, and InGaAsP barrier layers (λg=1.05μm) of 10nm thick each lattice-matched with InP which are each inserted between the first and the second well layers A and B. Such constitution provides a wider wavelength range having a gain than the conventional one and enables a single wavelength oscillation in a wider temp. range than the conventional one.

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 suitable for a light source for optical communication.

[0002]

2. Description of the Related Art A semiconductor distributed feedback type laser is characterized by lasing at a single wavelength, is excellent in high-speed response and has low noise, and is therefore widely used as a light source for optical communication. Normally, in such a semiconductor distributed feedback laser, it is necessary to keep the laser temperature constant in order to stabilize the characteristics, and it is mounted on a temperature control element such as a Peltier cooler and operated at a predetermined temperature. . However, in order to simplify the optical communication system, it is necessary to operate the laser without controlling the temperature. Since the conventional semiconductor distributed feedback laser can realize low threshold current characteristics, high light output characteristics, and high speed modulation characteristics, a multiple quantum well structure formed of a plurality of quantum wells is used in the active layer.

FIG. 12 (a) is a sectional view of a conventional semiconductor distributed feedback laser in the cavity direction. An uneven diffraction grating 102 that causes distributed feedback is formed on an n-type InP substrate 101, and an n-type InGaAsP waveguide layer 103, a multiple quantum well active layer 104, a p-type InGaAsP waveguide layer 105, p-type InP clad layer
106 are stacked. With such a configuration, the effective refractive index in the layer direction periodically fluctuates in the resonator direction, and laser oscillation occurs only at the Bragg wavelength determined by the effective refractive index and the period of the diffraction grating 102. The multiple quantum well active layer is formed of a well layer 107 having the same layer thickness and bandgap energy and a barrier layer 108 having the same layer thickness and bandgap energy.

[0004]

In the semiconductor distributed feedback laser of the conventional example, the ground quantum level formed in each well layer forming the multiple quantum well active layer has the same energy level in all well layers and Light is absorbed and recombined between the ground quantum level formed on the band side and the ground quantum level formed on the valence band side, and a gain is generated. Since the electrons and holes involved in the absorption and recombination of light exist energetically spread, the gain has a peak with respect to the wavelength as shown by the solid line A in FIG. 12 (b). The Bragg wavelength BR1 determined from the effective refractive index and the period of the diffraction grating is set in the wavelength region where the gain exists at the operating temperature. Further, usually, the Bragg wavelength is set near the peak wavelength of the gain in order to realize the low threshold characteristic.

In such a structure, when the ambient temperature of the laser changes, the band gap energy of the compound semiconductor material forming the laser changes. For example, when the ambient temperature rises from room temperature, the band gap energy becomes smaller. When the band gap energy of the well layer becomes small, the peak wavelength of the gain is shown in Fig. 12 (b).
As indicated by the broken line B in FIG. This rate of change is about 0.5 nm / ° C.

On the other hand, the change amount of the effective refractive index with respect to the temperature change is very small, and the period of the diffraction grating does not change. Therefore, as shown in FIG. Very small at 0.1 nm / ° C. For this reason, the gain at the Bragg wavelength BR2 becomes extremely small, laser oscillation does not occur at the Bragg wavelength, and laser oscillation occurs in the Fabry-Perot mode near the gain peak wavelength. When the ambient temperature becomes lower than room temperature, the peak wavelength of gain shifts to the short wavelength side (dashed line C), and similarly, the laser does not oscillate at the Bragg wavelength (BR3), and it oscillates in Fabry-Perot mode near the gain peak wavelength. Resulting in. Therefore, in the semiconductor distributed feedback laser of the conventional example, the temperature range in which single wavelength oscillation at the Bragg wavelength is possible is very narrow, from 0 ° C to 50 ° C.

The present invention has been made in view of the above problems, and provides a semiconductor distributed feedback laser device capable of oscillating a single wavelength in a wider temperature range than before.

[0008]

As shown in FIGS. 1 to 6, the above-mentioned problems are solved by using a multiple quantum well active layer of a semiconductor distributed feedback laser device in a quantum well having at least two different base quantum level levels. It is solved by forming a high gain in a wide wavelength range.

The principle of the present invention will be described with reference to FIGS. 10 and 11. As shown in the energy band diagram of FIG. 10, the band gap energies of the well layers of the multiple quantum well active layer of the semiconductor distributed feedback laser device are all the same, and the well layers have well layer thicknesses of LzA and LzB. It is divided into a plurality of types of well layers A51 and B52. When LzA and LzB have a relationship of LzA> LzB, the ground quantum level level of EcA is formed in the conduction band of the well of the well layer A51 and EvB is formed in the valence band of the well layer A51. Similarly, the well of the well layer B52 has EcA for the conduction band and Ev for the valence band.
B ground quantum level levels are formed. The energy between the ground quantum level levels of the well layer A51 is EgA, and the well layer B52
The energy between the ground quantum level levels of is EgB. At this time, the relationship of EgA <EgB is established due to the difference in quantum size effect.

The gain curve, which is the wavelength dependence of the gain generated by such a multi-quantum well active layer, is as shown by the solid line C in FIG. 11 (b). The solid line A in FIG. 11 (a) is the gain due to the plurality of well layers A51, the solid line B in FIG. 11 (a) is the gain due to the well layer B52, and the gain from the entire multiple quantum well active layer is the solid line A and the solid line. It becomes the solid line C which combined B. The solid line C has a wider wavelength range width having a gain than the solid lines A and B, which are the gains from the plurality of well layers A51 and the plurality of well layers B52, respectively.
The Bragg wavelength BR1 is set at the center of the wavelength range having the gain indicated by the solid line C.

With such a structure, for example, the ambient temperature changes to the high temperature side, and the gain curve shifts to the long wavelength side with respect to the wavelength as shown in FIG. In this case, the gain at the Bragg wavelength (BR2) is sufficient and single wavelength oscillation becomes possible. This is the same when the ambient temperature shifts to the low temperature side.

Further, FIG. 1 shows that the well layers of the multiple quantum well active layer have the same bandgap energy, and each well layer has a well layer thickness of LzA and LzB. Although it is divided into B, the well layer thickness may be two or more types, and in order to have a structure having at least two different base quantum level levels, not only the well layer thickness but also the well layer thickness. The band gap energy may be two or more types, and the band gap energy of the barrier layer may be two or more types.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

(First Embodiment) FIG. 1 is a diagram showing a semiconductor distributed feedback laser device according to a first embodiment of the present invention. 1A is a front view, and FIG. 1B is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm. The semiconductor distributed feedback laser of the present invention comprises an n-type InGaAsP waveguide layer 3 on an n-type InP substrate 1 on which a diffraction grating 2 is formed.
(Thickness 150nm, λg = 1.05μm), multiple quantum well active layer 4, p
-Type InGaAsP waveguide layer 5 (thickness 30 nm, λg = 1.05 μm) is formed in a mesa shape, and p-type InP current block layer 6 and n-type InP current block layer 7 are buried on both sides of these. The p-type InP clad layer 8 and the p-type InGaAsP contact layer 9 (λg = 1.3 μm) are formed on the upper part thereof. n-type InP substrate 1
Au / Sn electrode 10 is formed on the back surface of the p-type InGaAsP contact layer 9, and an SiO2 insulating film 11 having a stripe-shaped window is formed on the p-type InGaAsP contact layer 9, and the Au / Zn electrode 12 is formed on the SiO2 insulating film 11. Is a p-type InG through the striped window of the SiO2 insulating film 11.
It is in contact with the aAsP contact layer 9. In addition, the Au / Zn electrode 12
A Ti / Au electrode 13 is formed on the top.

The multi-quantum well active layer 4 includes a first InGaAsP well layer A14 (λg = 1.40 μm) having a thickness of 6 nm and InP lattice-matched with InP.
The second InGaAsP well layer B15 (λg =
1.40 μm) are alternately arranged in the direction of five layers between the first well layer A and the second well layer B, and a 10 nm-thick InGaAsP barrier layer 16 (λg = 1.05 μm) is arranged.

The energy band diagram of the first embodiment is as shown in FIG. 1C, and the well layer A14 has Ec on the conduction band side (Ec).
A, the base quantum level of EcB is formed in the well layer B15, and EvA and the well layer B15 are formed in the well layer A14 on the valence band side (Ev).
, The ground quantum level level of EvB is formed in (EcA-EvA)>
The relationship is (EcB-EvB).

The composition wavelength of the InGaAsP barrier layer 16 is 1.05 μm, In
The composition wavelength of the GaAsP well layer 14 and the InGaAsP well layer 15 is 1.40μ.
When m, the relationship between the well layer thickness at room temperature and the energy wavelength (λgw) between the ground quantum level levels formed in the well layer is as shown in Fig. 7. When the well layer thickness is 6 nm, λgw = 1.308 μ
When the m well layer thickness is 8 nm, λgw = 1.333 μm. By setting the Bragg wavelength determined by the diffraction grating to wavelengths near the center of 1.308 μm and 1.333 μm, single wavelength oscillation is possible in a wider temperature range than before.

(Second Embodiment) FIG. 2 shows a semiconductor distributed feedback laser device according to a second embodiment of the present invention. 2A is a front view, and FIG. 2B is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm.

The difference from the first embodiment is the structure of the multiple quantum well active layer 4. In constituting the multiple quantum well active layer 4
All the GaAsP well layers are lattice-matched with InP, and the well layer thickness is
6 nm. The composition wavelength λg is 1.4 in the multiple quantum well active layer 4.
0 μm first InGaAsP well layer A17 and composition wavelength λg 1.43 μm
5 second InGaAsP well layers B18 are alternately arranged in the layer direction, and a 10 nm InGaAsP barrier lattice-matched with InP is provided between the first well layer A14 and the second well layer B15. Layer 19 (λg =
1.05 μm) is arranged.

The energy band diagram of the second embodiment is as shown in FIG. 2C, and the well layer A17 has Ec on the conduction band side (Ec).
A, the ground quantum level of EcB is formed in the well layer B18, and EvA in the well layer A17 and the well layer B18 in the valence band side (Ev).
, The ground quantum level level of EvB is formed in (EcA-EvA)>
The relationship is (EcB-EvB).

The composition wavelength of the InGaAsP barrier layer 19 is 1.05 μm, In
When the well layer thickness of the GaAsP well layer is 6 nm, the relationship between the composition wavelength of the well layer at room temperature and the energy wavelength (λgw) between the ground quantum level levels formed in the well layer is as shown in FIG.
When the composition wavelength of the well layer is 1.40 μm, λgw = 1.308 μm, and when the composition wavelength of the well layer is 1.43 μ, λgw = 1.333 μm. The Bragg wavelengths determined by the diffraction grating are 1.308 μm and 1.333.
By setting the wavelength near the center of μm, single wavelength oscillation is possible in a wider temperature range than before.

(Embodiment 3) FIG. 3 is a diagram showing a semiconductor distributed feedback laser device according to Embodiment 2 of the present invention. FIG. 3 (a) is a front view, and FIG. 3 (b) is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm.

The difference from the first embodiment is the configuration of the multiple quantum well active layer 4. In constituting the multiple quantum well active layer 4
All the GaAsP well layers 20 are lattice-matched with InP, the well layer thickness is 6 nm, and the composition wavelength λg is 1.40 μm. n-type InGaAs
The first InGaAsP barrier layer A21 (λg = 1.05 μm) with a thickness of 10 nm which is lattice-matched with InP adjacent to the three well layers from the P barrier layer 3 side
However, the first InGaAsP barrier layer A21 (λg = 1.05 μm) is arranged adjacent to the two well layers from the p-type InGaAsP barrier layer 5 side, and is also lattice-matched with InP adjacent to the other well layers. Thickness 10nm
Second InGaAsP barrier layer B22 (λg = 1.14 μm) is arranged.

The energy band diagram of the third embodiment is as shown in FIG. 3 (c). On the conduction band side (Ec), the well between the barrier layers A21 is EcA in the layer A and the well between the barrier layers B22. The ground quantum level level of EcB is formed in layer B, and it is a well layer on the valence band side (Ev).
EvA is formed in A and EvB is formed in the well layer B, and the relationship is (EcA-EvA)> (EcB-EvB).

When the well layer thickness of the InGaAsP well layer is 6 nm and the composition wavelength is 1.40 μm, the energy wavelength (λgw) between the composition wavelength of the InGaAsP barrier layer and the ground quantum level level formed in the well layer at room temperature is The relationship is as shown in FIG. 9. When the composition wavelength of the barrier layer is 1.05 μm, λgw = 1.308 μm, and when the composition wavelength of the barrier layer is 1.14 μm, λgw = 1.321 μm. By setting the Bragg wavelength determined by the diffraction grating to wavelengths near the center of 1.308 μm and 1.321 μm, single wavelength oscillation is possible in a wider temperature range than before.

(Fourth Embodiment) FIG. 4 is a diagram showing a semiconductor distributed feedback laser device according to a fourth embodiment of the present invention. FIG. 4 (a) is a front view, and FIG. 4 (b) is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm.

The difference from the first embodiment is the configuration of the multiple quantum well active layer 4. P-type InGaA is used for the multiple quantum well active layer 4.
Five first 6nm thick lattice-matched InPs on the sP waveguide layer 3 side
InGaAsP well layer A23 (λg = 1.40 μm) and five second 8 nm thick InGaAsP lattice-matched with InP on the n-type InGaAsP waveguide layer side.
Well layers B24 (λg = 1.40 μm) are arranged, and InGaAsP barrier layers 25 with a thickness of 10 nm lattice-matched with InP are provided between the well layers.
(λg = 1.05 μm) is arranged.

The energy band diagram of the fourth embodiment is as shown in FIG. 4C, and the well layer A23 has Ec on the conduction band side (Ec).
A, the ground quantum level level of EcB is formed in the well layer B24, and EvA and well layer B24 are formed in the well layer A23 on the valence band side (Ev).
, The ground quantum level level of EvB is formed in (EcA-EvA)>
The relationship is (EcB-EvB).

The composition wavelength of the InGaAsP barrier layer is 1.05 μm,
When the composition wavelength of the AsP well layer is 1.40 μm, the relationship between the well layer thickness at room temperature and the energy wavelength (λgw) between the ground quantum level levels formed in the well layer is as shown in Fig. 7. When the thickness is 6 nm, λgw = 1.308 μm, when the well layer thickness is 8 nm, λg
w = 1.333 μm. By setting the Bragg wavelength determined by the diffraction grating to wavelengths near the center of 1.308 μm and 1.333 μm, single wavelength oscillation is possible in a wider temperature range than before.

Further, as a feature of the fourth embodiment, p
Energy DEvA between the barrier layer and the ground quantum level EvA on the valence band side of the n-type InGaAsP waveguide layer 5 side is n-type InGaAsP
It is smaller than the energy DEvB between the barrier layer on the valence band side on the waveguide layer 3 side and the ground quantum level EvB, and is supplied from the p-type InP cladding layer side as compared with the configuration of the first embodiment. Holes are sufficiently supplied to the well layer on the n-type InGaAsP waveguide layer 3 side. As a result, holes are uniformly injected into all the well layers, and laser characteristics such as high-speed response are improved.

(Fifth Embodiment) FIG. 5 is a diagram showing a semiconductor distributed feedback laser device according to a fifth embodiment of the present invention. 5 (a) is a front view, and FIG. 5 (b) is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm.

The difference from the first embodiment is the configuration of the multiple quantum well active layer 4. In constituting the multiple quantum well active layer 4
The GaAsP well layer 26 and the InGaAsP well layer 27 are all lattice-matched with InP, and the well layer thickness is 6 nm. In the multiple quantum well active layer 4, the composition wavelength λg is 1.40 μm on the p-type InGaAsP waveguide layer 5 side.
5 first InGaAsP well layers 26 and n-type InGaAsP waveguide layers 3
Five second InGaAsP well layers with composition wavelength λg of 1.43 μm on the side
27 is disposed, and an InGaAsP barrier layer 28 (λg having a thickness of 10 nm, which is lattice-matched with InP, is provided between the first well layer and the second well layer.
= 1.05 μm) is arranged.

The energy band diagram of the fifth embodiment is as shown in FIG. 5C, and the well layer A26 has Ec on the conduction band side (Ec).
A, the ground quantum level level of EcB is formed in the well layer B27, and EvA and the well layer B27 are formed in the well layer A26 on the valence band side (Ev).
, The ground quantum level level of EvB is formed in (EcA-EvA)>
The relationship is (EcB-EvB).

The composition wavelength of the InGaAsP barrier layer is 1.05 μm,
When the well layer thickness of the AsP well layer is 6 nm, the relationship between the composition wavelength of the well layer at room temperature and the energy wavelength (λgw) between the ground quantum level levels formed in the well layer is as shown in Fig. 8. When the composition wavelength of the layer is 1.40 μm, λgw = 1.308 μm, and when the composition wavelength of the well layer is 1.43 μ, λgw = 1.333 μm. Bragg wavelengths determined by the diffraction grating are 1.308 μm and 1.333 μm
By setting the wavelength near the center of, the single wavelength oscillation is possible in a wider temperature range than the conventional one.

Furthermore, the feature of the fifth embodiment is that p
Energy DEvA between the barrier layer and the ground quantum level EvA on the valence band side of the n-type InGaAsP waveguide layer 5 side is n-type InGaAsP
The energy DEvB between the barrier layer and the ground quantum level EvB on the valence band side on the waveguide layer 3 side is smaller than that on the waveguide layer 3 side, and is supplied from the p-type InP cladding layer side as compared with the configuration of the second embodiment. Holes are sufficiently supplied to the well layer on the n-type InGaAsP waveguide layer 3 side. As a result, holes are uniformly injected into all the well layers, and laser characteristics such as high-speed response are improved.

(Sixth Embodiment) FIG. 6 is a diagram showing a semiconductor distributed feedback laser device according to a sixth embodiment of the present invention. FIG. 6 (a) is a front view, and FIG. 6 (b) is a sectional view taken along the broken line AB in the resonator direction. The semiconductor distributed feedback laser of the present invention is set so that the oscillation wavelength is around 1.31 μm.

The difference from the first embodiment is the configuration of the multiple quantum well active layer 4. In constituting the multiple quantum well active layer 4
All the GaAsP well layers 29 are lattice-matched with InP, the well layer thickness is 6 nm, and the composition wavelength λg is 1.40 μm. n-type InGaAs
Between the well layers on the P waveguide layer 3 side, there are five first InGaAsP barrier layers A30 (λg = λg) lattice-matched with InP and having a thickness of 10 nm.
1.05 μm), but on the p-type InGaAsP waveguide layer 5 side, five second InGaAsP barrier layers B31 (λg = 1.1
4 μm) is arranged.

The energy band diagram of the sixth embodiment is as shown in FIG. 6 (c). On the conduction band side (Ec), the well between the barrier layers A30 is EcA in the layer A and the well between the barrier layers B31. The ground quantum level level of EcB is formed in layer B, and it is a well layer on the valence band side (Ev).
EvA is formed in A and EvB is formed in the well layer B, and the relationship is (EcA-EvA)> (EcB-EvB).

When the well layer thickness of the InGaAsP well layer is 6 nm and the composition wavelength is 1.40 μm, the energy wavelength (λgw) between the composition wavelength of the InGaAsP barrier layer and the ground quantum level level formed in the well layer at room temperature is The relationship is as shown in FIG. 9. When the composition wavelength of the barrier layer is 1.05 μm, λgw = 1.308 μm, and when the composition wavelength of the barrier layer is 1.14 μm, λgw = 1.321 μm. By setting the Bragg wavelength determined by the diffraction grating to wavelengths near the center of 1.308 μm and 1.321 μm, single wavelength oscillation is possible in a wider temperature range than before.

Further, the feature of the sixth embodiment is that p
-Type InGaAsP waveguide layer 5 side, the energy DEvB between the barrier layer and the ground quantum level EvB on the valence band side is n-type InGaAsP
The energy DEvA between the barrier layer on the valence band side and the ground quantum level EvA on the waveguide layer 3 side is smaller than that on the waveguide layer 3 side, and is supplied from the p-type InP cladding layer side as compared with the configuration of the third embodiment. Holes are sufficiently supplied to the well layer on the n-type InGaAsP waveguide layer 3 side. As a result, holes are uniformly injected into all the well layers, and laser characteristics such as high-speed response are improved.

[0041]

As described above, in the semiconductor distributed feedback laser device of the present invention, single wavelength oscillation is possible in a wider temperature range than in the past.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a second embodiment of the present invention.

FIG. 3 is a diagram illustrating Embodiment 3 of the present invention.

FIG. 4 is a diagram illustrating Embodiment 4 of the present invention.

FIG. 5 is a diagram illustrating Embodiment 5 of the present invention.

FIG. 6 is a diagram illustrating a fifth embodiment of the present invention.

FIG. 7 is a diagram for explaining the relationship of the energy wavelength between the well layer thickness and the ground quantum level level formed in the well layer.

FIG. 8 is a diagram for explaining the relationship between the composition wavelength of the well layer and the energy wavelength between the ground quantum level levels formed in the well layer.

FIG. 9 is a diagram illustrating the relationship between the composition wavelength of the barrier layer and the energy wavelength between the ground quantum level levels formed in the well layer.

FIG. 10 is a diagram illustrating a configuration of the present invention.

FIG. 11 is a diagram for explaining the effect of the present invention.

FIG. 12 is a diagram illustrating a conventional example.

[Explanation of symbols]

 1 n-type InP substrate 2 diffraction grating 3 n-type InGaAsP waveguide layer 4 multiple quantum well active layer 5 p-type InGaAsP waveguide layer 6 p-type InP current block layer 7 n-type InP current block layer 8 p-type InP clad layer 9 p Type InGaAsP contact layer 10 Au / Sn electrode 11 SiO2 insulating film 12 Au / Zn electrode 13 Ti / Au electrode 14 First InGaAsP well layer A (thickness 6 nm, λg = 1.40 μm) 15 Second InGaAsP well layer B ( Thickness 8 nm, λg = 1.40 μm) 16 InGaAsP barrier layer (thickness 10 nm, λg = 1.05 μm) 17 First InGaAsP well layer A (thickness 6 nm, λg = 1.40 μm) 18 Second InGaAsP well layer B ( Thickness 6 nm, λg = 1.43 μm) 19 InGaAsP barrier layer (thickness 10 nm, λg = 1.05 μm) 20 InGaAsP well layer (thickness 6 nm, λg = 1.40 μm) 21 First InGaAsP barrier layer A (thickness 10 nm, λg = 1.05 μm) 22 Second InGaAsP barrier layer B (thickness 10 nm, λg = 1.14 μm) 23 First InGaAsP well layer A (thickness 6 nm, λg = 1.40 μm) 24 Second InGaAsP well layer B ( Thickness 8 nm, λg = 1.40 μm) 25 InGaAsP barrier layer (thickness 10 nm, λg = 1.05 μm) 6 First InGaAsP well layer A (thickness 6 nm, λg = 1.40 μm) 27 Second InGaAsP well layer B (thickness 6 nm, λg = 1.43 μm) 28 InGaAsP barrier layer (thickness 10 nm, λg = 1.05 μm) 29 InGaAsP well layer (thickness 6 nm, λg = 1.40 μm) 30 First InGaAsP barrier layer A (thickness 10 nm, λg = 1.05 μm) 31 Second InGaAsP barrier layer B (thickness 10 nm, λg = 1.14 μm) 51 well layer A with well layer thickness LzA 52 well layer with well layer thickness LzB 101 n-type InP substrate 102 diffraction grating 103 n-type InGaAsP waveguide layer 104 multiple quantum well active layer 105 p-type InGaAsP waveguide layer 106 p Type InP clad layer 107 well layer 108 barrier layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Matsui 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (13)

[Claims] 1. A semiconductor laser, comprising a substrate and a multilayer structure formed on the substrate, which emits laser light, wherein the refractive index or the gain is periodically changed in the cavity direction. A lattice, the multilayer structure includes an active layer comprising at least a multi-quantum well structure, the active layer being formed from a quantum well having at least two different ground quantum level levels, and having a high wavelength range. A semiconductor distributed feedback laser device having a gain, a Bragg wavelength determined by the diffraction grating being set within the wavelength range, and capable of oscillating at the Bragg wavelength even when ambient temperature changes. 2. The semiconductor distributed feedback laser device according to claim 1, wherein the multiple quantum well structure forming the active layer has at least two different well layer thicknesses. 3. The semiconductor distributed feedback laser device according to claim 2, wherein the bandgap energies of all the well layers forming the multiple quantum well structure forming the active layer are equal. 4. The semiconductor distributed feedback laser device according to claim 1, wherein the multiple quantum well structure forming the active layer is composed of at least two well layers having different bandgap energies. . 5. The semiconductor distributed feedback laser device according to claim 4, wherein the well layers forming the multiple quantum well structure forming the active layer have the same well layer thickness. 6. The barrier layer adjacent to each well layer forming the multiple quantum well forming the active layer has at least two different band gap energies. Semiconductor distributed feedback laser device. 7. The semiconductor distributed feedback laser device according to claim 6, wherein the well layers constituting the multiple quantum well forming the active layer have the same well layer thickness and bandgap energy. 8. A multi-quantum well structure forming the active layer is formed in at least two or more regions, the well layers included in each region have the same layer thickness, and the band gap of the well layer is different in each region. Energy is different, a region where the band gap energy of the well layer is the largest exists on the p-side electrode side, and a region where the band gap energy of the well layer is the smallest exists on the n-side electrode side. The semiconductor distributed feedback laser device according to claim 4, wherein the injection efficiency is improved. 9. A multi-quantum well structure forming the active layer is formed in at least two regions, and the band gap energies of the well layers included in each region are all the same, and the well layer is formed in each region. There is a region where the thickness of the well layer is the thickest on the p-side electrode side, and a region where the well layer is the thinnest on the n-side electrode side, and the efficiency of hole injection into each well layer is different. 4. The semiconductor distributed feedback laser device according to claim 2, wherein the semiconductor distributed feedback laser device is improved. 10. A multi-quantum well structure forming the active layer is formed in at least two or more regions, and the band gap energy and the layer thickness of the well layers included in each region are all equal, and barriers are provided in each region. The layers have different bandgap energies, the p-side electrode has a region where the barrier layer has the smallest bandgap energy, and the n-side electrode has a region where the barrier layer has the largest bandgap energy. The semiconductor distributed feedback laser device according to claim 6 or 7, wherein the injection efficiency into the well layer is improved. 11. The semiconductor distributed feedback type according to claim 1, wherein the Bragg wavelength is set near the center of a wavelength range in which a gain generated by the active layer exists at room temperature. Laser device. 12. The semiconductor distributed feedback laser device according to claim 1, wherein + 0.5% to + 1.5% compressive strain of the well layer is introduced. 13. The compound semiconductor substrate is InP, the barrier layer of the multiple quantum well structure is InGaAsP, and the well layer is InGaAsP or InGaAs or InAsP. A semiconductor distributed feedback laser device according to.