JPH10145003A - Semiconductor laser and optical communication system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser having high performance by reducing a strain of an active quantum well layer under the condition of sufficiently ensuring an electron and hole confinement energy of a long wave length band semiconductor laser. SOLUTION: An active layer 7 is made to have a quantum well structure, a nitrogen system V group mixed crystal semiconductor such as GaInNAs is used for a well layer 6, and a semiconductor of stretching strain for barrier layers (light guide layers) 4 and 5. GaNAs or GaNPAs is preferable for the semiconductor having stretching strain. Electron and positive hole confinement energy can be sufficiently ensured by using the nitrogen based V group mixed crystal semiconductor for both the well layer 6 and the barrier layers 4 and 5. Also each layer's strain of the quantum well active layer and the total strain can be simultaneously reduced by stress compensation by the well layer 6 and the barrier layers 4 and 5. By this means a semiconductor laser having a high performance can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor laser technology, and more particularly, to a high-performance semiconductor laser in which the design tolerance of a long-wavelength semiconductor laser is increased and an optical communication system using the same.

[0002]

2. Description of the Related Art Semiconductor lasers for optical communication systems currently in practical use are all fabricated on an InP substrate, and use GaInPAs or AlGaInAs mixed crystal semiconductor for the active layer. Extremely high performance is achieved by employing a quantum well structure and a refractive index waveguide structure. However, it has a major drawback in that the characteristics are greatly deteriorated during high-temperature operation. In mainline optical fiber communication, semiconductor lasers are used while being cooled by Peltier heating elements, but in the future subscriber optical fiber communication, in which optical fiber communication is introduced to homes and offices and to computers, semiconductor lasers will be used. It is essential to reduce the cost and power consumption of the transmission module, and there is a strong demand for a semiconductor laser for an optical communication system which does not require a cooling element and has excellent temperature characteristics.

Recently, a new material, GaInNAs, is expected to greatly improve the temperature characteristics of a semiconductor laser for an optical communication system.
A semiconductor laser using a laser was reported (Kondo et al., No. 43).
Proceedings of the Annual Conference of Japan Society of Applied Physics (1,046 pages). In addition, it is clear that when the N composition is changed while the composition of the group III element is kept constant, the bandgap of the N-containing III-V mixed crystal semiconductor decreases and then increases again. It has become. Jpn. J. App
l. Phys. vol. 35 (1996) pp. 127
Third, by using gallium indium nitrogen arsenide (GaInNAs) having such physical properties for the active layer of the semiconductor laser, a semiconductor laser for optical communication having excellent temperature characteristics on a gallium arsenide (GaAs) substrate can be realized. Have been described. Here, being able to be formed on a GaAs substrate means that it is advantageous for forming a surface emitting laser because of the ease of forming a semiconductor multilayer reflector. Note that the optical communication system referred to here does not indicate only long-distance communication, but also includes short-distance transmission such as optical interconnection.

[0004]

The semiconductor laser reported above has a quantum well active layer using GaInNAs as a quantum well layer and GaAs as a barrier layer (light guide layer). The band lineup of GaInNAs and GaAs will be described with reference to FIG. In the right half of FIG.
The band lineup of nAs is shown in the left half, and the band lineup of GNAs is shown in the left half. GaInAs and GaNAs
In order to show the band lineup in the same figure, the horizontal axis is scaled by the amount of lattice distortion. Therefore, GaAs is on the y-axis. It can be seen from the figure that when In is added to GaAs to form a GaInAs mixed crystal semiconductor, that is, when + strain (compression strain) is increased, the conduction band is lowered and the valence band is raised.
On the other hand, when N is added to GaAs to form a GaNAs mixed crystal semiconductor, that is, when the strain (extension strain) is increased, the conduction band,
It can be seen that both valence bands fall. GNAs
In the case of (1), the rate of decrease in the conduction band is greater than the rate of decrease in the valence band. Therefore, if N is added to increase the tensile strain, the band gap decreases.

Now, N is added to GaInAs to obtain GaInN.
Consider the case of an As mixed crystal semiconductor. In FIG. 2, the conduction band descends from point A to points B and C. Similarly, the valence band falls from point D to points E and F. The ratio of the rise / fall of the valence band to the strain amount is GaInAs and GaNAs.
GaInNAs lattice-matched with GaAs
, The point F coincides with the level of the GaAs valence band. Therefore, in a quantum well structure using GaInNAs lattice-matched to GaAs for the quantum well layer and GaAs for the barrier layer, electrons cannot be confined but holes cannot be confined.

In order to solve this problem, the above report reports that GaIn
This is dealt with by moving the valence band of NAs to point E in FIG. In other words, the valence band is raised by using GaInNAs as the compression strain layer, and an energy difference from the valence band of GaAs is created. To obtain the hole confinement energy (50 meV or more) required for laser oscillation, GaInNAs must be distorted by + 1.5% or more. In order to suppress the occurrence of crystal defects in a GaInNAs quantum well layer under a high strain, the thickness and the number of the GaInNAs quantum well layers are greatly restricted, which is an obstacle in designing a laser. Accordingly, a first object of the present invention is to provide a structure which sufficiently secures the confinement energy of electrons and holes and reduces the strain of the quantum well layer, thereby allowing the design of a long wavelength band semiconductor laser. It is an object of the present invention to provide a high-performance semiconductor laser with an increased degree and an optical communication system using the semiconductor laser.

Further, in the above-mentioned report, GaInNAs
Laser oscillation at room temperature has been reported in semiconductor lasers for optical communication using GaN as an active layer. The active region has a single quantum well structure in which the light guide layer is GaAs and the well layer is GaInNAs. A GaInNAs single film having a thickness of 7 nm is used for a well layer which is a light emitting region. The N composition of GaInNAs in this report is 1% or less. With such an active layer structure, the oscillation wavelength is 1.3 μm.
To produce a high-performance laser suitable for the m band or the 1.55 μm band, an N composition of about 1 to 4% is required.

N has an atomic radius much smaller than that of a conventionally used III-V semiconductor material.
It is difficult to mix well with other elements constituting InNAs. Therefore, similarly to the conventional structure, the well layer is formed of GaIn.
In the case of a single NAs film, as the N composition increases, the crystallinity may decrease, and the laser performance may deteriorate. Actually, in the quantum well using GaInNAs for the well layer, deterioration of the photoluminescence characteristic due to an increase in the nitrogen composition has been observed. In particular, this problem is remarkable in a 1.55 μm band semiconductor laser that requires an N composition of 3% or more. Therefore, a second object of the present invention is to provide Ga
An object of the present invention is to provide an active layer structure that oscillates at a long wavelength exceeding 1.55 μm in a long wavelength semiconductor laser for optical communication using InNAs for an active layer and having excellent temperature characteristics even if the N composition is 1% or less.

[0009]

SUMMARY OF THE INVENTION The first object of the present invention is to provide a long wavelength band semiconductor laser having a quantum well structure as an active layer, using a compressively strained semiconductor for the well layer, and forming a barrier layer (optical guide layer). This is achieved by using a semiconductor having a tensile strain and providing them on a GaAs substrate. It is preferable to use a nitrogen-based group V mixed crystal semiconductor as the semiconductor having the compressive strain and to use GaNAs or GaNPAs as the semiconductor having the tensile strain.

Referring to FIG. 3, the well layer is made of GaInNAs,
The case where the barrier layer is made of GaNAs will be described. GNA
The conduction band of s is the S point, and the valence band is the T point. Now 50me
Consider obtaining the confinement energy of V holes. When the barrier layer is GaAs, the valence band of GaInNAs is E
It must be a point, but if the barrier layer is GaNAs, it may be at the Y point. Therefore, the strain of GaInNAs can be reduced. In that case, the tensile strain of GaNAs barrier layer
The compressive strain of the InNAs well layer can be canceled (compensated), and the strain of the entire quantum well structure can be greatly reduced. The electron is S point and X
It is confined by the energy difference between points. GaInN
In order to maintain good temperature characteristics of the As laser, it is important to keep the difference at 150 meV or more. For example,
The confinement energy of electrons is 150 meV or more, and the confinement energy of holes is 50 meV or more.

When GaNPAs is used for the barrier layer, P
By adjusting the mixed crystal composition of the GaInNAs well layer, the strain amount of the GaInNAs well layer can be further reduced while keeping the confinement energy of electrons and holes large. The well layer is GaIn
NAs may contain Al, P, or Sb to some extent. The above-described object of the present invention is achieved by a nitrogen-based group V mixed crystal semiconductor containing a group V element and nitrogen and another group V atom at the same time.

A second object of the present invention is to provide a semiconductor device having an active layer for generating light on a semiconductor substrate, a cladding layer for confining light, and a resonator structure for obtaining laser light from the generated light. In a laser, an active layer has a quantum well type structure formed of a barrier layer and a well layer, and a first semiconductor layer of a III-V mixed crystal semiconductor containing nitrogen in a well layer and a III-V group containing nitrogen. This is achieved by using a superlattice structure in which second semiconductor layers made of a mixed crystal semiconductor are alternately laminated one by one atomic layer.

More specifically, as shown in FIG. 5, gallium nitrogen arsenide: GaN (0.0085) As (0.9915) is formed in a well layer of a semiconductor laser having a quantum well structure as an active layer.
1 / Indium nitrogen arsenic: InN (0.0085) As (0.9915)
One superlattice is used. At this time, by setting the composition ratio of N in each layer to 0.0085, the oscillation wavelength of the device can be adjusted to 1.55 μm. That is, 1%
Even with the following low N composition, an active layer that emits light at a wavelength of 1.55 μm can be formed.

Also, Appl. Phys. Lett. v
ol. 59 (1991) pp. 2688, (GaA
s) Photoluminescence at 1.34 μm exceeding 1.3 μm at room temperature was observed at room temperature in a strained quantum well using GaAs as a barrier layer using a 1 / (indium arsenide: InAs) 1 superlattice as a well layer. Have been. As described in the above report, (GaAs) 1 / (I
The reason that the nAs) 1 superlattice emits light of a longer wavelength than a disordered Ga (0.5) In (0.5) As single film similarly formed on a GaAs substrate is that the superlattice is disordered due to an artificially introduced periodic structure. This is explained by the fact that the band structure of Ga (0.5) In (0.5) As in the state changes and the band gap narrowing substantially occurs.

The band gap narrowing due to such a periodic structure is based on gallium indium phosphide Ga (0.5) In (0.
5) Observed during the formation of a natural superlattice in P.
Further, the superlattice structure is changed to Ga (0.5) In (0.5)
It has been confirmed by photoluminescence measurement that the crystallinity does not decrease even when the layers are stacked thicker than the critical thickness of As. An effect similar to that described so far is (GaNA
s) Since 1 / (InNAs) 1 superlattice can be used in the case of using a well layer, the N introduction amount is kept at 1% or less.
Light emission at a long wavelength exceeding 1.55 μm can be realized. As described above, by using the structure of the present invention, it is possible to manufacture an optical communication semiconductor laser having excellent temperature characteristics that oscillates in a wavelength band of 1.55 μm even when the N composition is reduced to 1% or less. Note that a similar effect can be obtained with GaNAs, InN
In addition to As, AlNAs, GaNP, InNP, AlN
It is also obtained when a superlattice structure is manufactured using P, GaNSb, InNSb, and AlNSb.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. Embodiments for achieving the first object of the present invention include the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. (First Embodiment) In a first embodiment, the present invention is applied to an edge emitting semiconductor laser having an inverted mesa structure. Hereinafter, this embodiment will be described in detail with reference to FIG. FIG.
FIG. 1A shows a cross-sectional structure of the semiconductor laser of this embodiment, which is shown in FIG.
(B) is an enlarged view of the active layer of this embodiment.

Next, a method for fabricating the device will be described in detail with reference to FIG. First, on an n-type GaAs substrate 1,
n-type GaAs buffer layer 2, n-type Al (0.4) Ga (0.6) A
s clad layer 3, stress-compensated strained quantum well active layer 7, p-type Al (0.4) Ga (0.6) As clad layer 8, p-type Ga (0.5)
In (0.5) P etching stop layer 9, p-type Al (0.4) Ga
(0.6) As clad layer 10, p-type GaAs cap layer 1
1 are sequentially formed by actinic ray epitaxy. At this time, the strain amount of the GaInNAs strained quantum well layer is + 1%.

The stress-compensated strained quantum well active layer 7 is
FIG. 1 (a) shows an enlarged view of the GaN (0.02) A
An s (0.98) barrier layer (optical guide layer) (layer thickness 150 nm) 4 and 5 and a Ga (0.80) In (0.20) N (0.02) As (0.98) well layer (layer thickness 7 nm) 6 .

Next, a ridge as shown in FIG. 1A is formed by wet etching using a photo-etching process using the oxide film as a mask. Etching is p-type Ga
(0.5) In (0.5) P Stop at the etching stop layer 9. The ridge width at this time is 1 to 15 μm. next,
Using the oxide film used as an etching mask as a mask for selective growth, as shown in FIG. 1A, n-type Al (0.4) Ga
(0.6) As current confinement layer 12 is selectively grown. Thereafter, the wafer is taken out from the growth furnace, and the oxide film used as the selective growth mask is removed by etching. After that, a p-type GaAs contact layer 13 is formed.

Finally, after forming a p-side electrode 14 on the p-type GaAs contact layer 13 and an n-side electrode 15 on the n-type GaAs substrate 1, a laser device having a cavity length of about 900 μm was obtained by a cleavage method. After that, λ / 4 is applied to the front of the laser device.
(Λ: oscillation wavelength) of a low reflection film of SiO ₂
On the rear surface of the device, a high-reflection film composed of a four-layer film made of SiO ₂ and amorphous Si was formed. Thereafter, the laser element was bonded on a heat sink with the bonding surface facing down.

The prototype device is a device having a ridge width of 3 μm.
It oscillated continuously at room temperature with a threshold current of about 10 mA, and its oscillation wavelength was about 1.3 μm. The characteristic temperature T ₀ in the range of 25 ° C. to 85 ° C. was 150K. Also,
This laser has a long element life of 100,000 hours or more because the amount of strain in the active layer is small.

(Second Embodiment) In a second embodiment, the present invention is applied to a surface-emitting type semiconductor laser. Hereinafter, this embodiment will be described in detail with reference to FIG. FIG. 4A shows a cross-sectional structure of the present embodiment, and FIG. 4B shows an enlarged view of the active layer of the present embodiment. Next, a method for manufacturing an element will be described in detail with reference to FIG. First, the n-type GaAs substrate 1
An n-type semiconductor multilayer mirror 20, a GaAs spacer layer 21, a triple quantum well active layer 24, a GaAs spacer layer 25, and p-type Ga (0.5) In lattice-matched to a GaAs substrate are formed thereon.
(0.5) P cladding layer 26, p-type GaAs contact layer 2
7 are sequentially formed by a metalorganic vapor phase epitaxy method.

As shown in FIG. 4B, the triple quantum well active layer 24 has a GaN (0.02) As (0.9
8) Barrier layer (layer thickness 5 nm) 22 and Ga (0.80) In (0.20) N
It is composed of a (0.02) As (0.98) well layer (layer thickness 5 nm) 23. The triple quantum well active layer 24 has a stress compensation type quantum well structure.

The semiconductor multi-layer film reflecting mirror 20 is a semiconductor mirror.
屈折 wavelength thick GaAs layer with high refractive index and １ ／
It is formed by alternately laminating AlInP layers having a wavelength and a low refractive index, and the number of laminated reflective mirror layers is set to 15 pairs in order to make the reflectivity 99% or more. Note that the semiconductor multilayer film reflecting mirror 20 only needs to alternately stack high-refractive index layers and low-refractive index layers. For example, GaAs and AlAs, and GaAs and GaI
Other material systems such as nP or GaInNAs and AlAs may be used.

Next, a circular SiO 2 film having a diameter of 10 μm (not shown in the figure for removal in a later step) is formed by a chemical vapor deposition step and a photoresist step, and this is used as a mask to form an n-type semiconductor. The multi-layer reflector 20 is wet-etched halfway to form a mesa. Thereafter, an SiO ₂ protective layer 28 is formed by a chemical vapor deposition process while leaving the SiO ₂ film serving as a mask, and a polyimide 29 is formed thereon.
Is applied and cured. Then, the polyimide 29 until the SiO ₂ mask is exposed by reactive ion beam etching is etched, it is a flat surface to remove the upper portion of the SiO ₂ mask mesa as illustrated in FIG. Is obtained.

Then, the ring-shaped p is lifted off by a lift-off method.
After forming the side electrode 13, a dielectric multilayer film reflecting mirror 30 was formed by sputtering evaporation method, and an n-side electrode 14 was formed on the surface of the n-type GaAs substrate. Dielectric multilayer mirror 30
Is a high-refractive-index amorphous Si layer having a quarter-wave thickness in the dielectric and a low-refractive-index SiO ₂ having a quarter-wave thickness in the dielectric.
It was made by alternately stacking the layers. In order to make the reflectance 99% or more, the number of layers was set to four pairs. Note that the dielectric multilayer film reflecting mirror 30 only needs to alternately stack high-refractive-index layers and low-refractive-index layers. For example, SiN and SiO ₂ , amorphous Si and SiN, or TiO ₂ and SiO ₂ Other material systems may be used.

When a current was injected into the surface emitting laser manufactured as described above, continuous oscillation occurred at room temperature. The laser light was emitted from the dielectric multilayer film reflecting mirror 30 side. The oscillation wavelength was 1.3 μm. The surface emitting laser of this example had a long element life of 100,000 hours or more because the amount of strain in the active layer was small.

GANAs which is one of the embodiments of the present invention
The barrier layer composed of a ternary compound semiconductor of GaN or GaNPAs is particularly effective in confining holes and electrons in a quantum well layer composed of a quaternary compound semiconductor of GaInNAs.

Next, as embodiments for achieving the second object of the present invention, there are a third embodiment shown in FIG. 5 and a fourth embodiment shown in FIG. (Third Embodiment) In a third embodiment, the present invention is applied to an edge emitting semiconductor laser. Hereinafter, this embodiment will be described in detail with reference to FIG. FIG. 5A shows a cross-sectional structure of the semiconductor laser of this embodiment, and FIG. 5B shows an enlarged view of the active layer of this embodiment. The fabrication of this device structure requires precise film thickness control and instantaneous switching of materials.
In order to introduce nitrogen (N), a growth method in a non-equilibrium state is suitable, and a molecular beam epitaxy (MBE) method, a metal organic chemical vapor deposition (MOCVD) method, and the like are suitable. Here, the growth method is a gas source MBE (GS-MBE) method. This is a method that uses a gaseous raw material to supply the V group. In this embodiment, arsenic (A
For s), arsine (AsH ₃ ) is used by thermal cracking, and for N, N ₂ gas is used by RF plasma excitation. An n-type GaAs substrate 51 is used as a semiconductor substrate to be manufactured. In the As atmosphere under the supply of AsH ₃ ,
After removing the oxide film on the substrate surface by thermal cleaning for 10 minutes, an n-type GaAs buffer layer 52 doped with silicon (Si) is grown on the substrate 51.

Thereafter, the n-type AlGaAs cladding layer 5
3. A non-doped GaAs barrier layer (light guide layer) 54 is grown in this order. Next, while supplying N plasma and AsH ₃ , the Ga and In shutters are alternately opened and closed to obtain GaN.
(0.0085) As (0.9915) 1 / InN (0.0085) As (0.9915)
One superlattice layer 55 is grown for one atomic layer for 15 periods.
At this time, the total film thickness is about 9 nm. Thereafter, the supply of N plasma is stopped, and a non-doped GaAs barrier layer (light guide layer) 54 and a p-type AlGaAs cladding layer 56 are formed in this order. Finally, a p-type GaAs cap layer 57 is grown. An oxide film 58 is formed on the film thus manufactured, and after using the mask as a mask to remove the oxide film by a photoetching process, a p-type electrode 59 is formed. continue,
After forming the n-type electrode 60, a laser device having a cavity length of 400 μm was obtained through a cleavage step. Subsequently, a low reflection film was formed on the front surface of the device, and a high reflection film was formed on the rear surface. The prototype device had a stripe width of 5 μm and continuously oscillated at room temperature with a threshold current value of about 50 mA. The oscillation wavelength was 1.55 μm. The characteristic temperature (T ₀ ) in the range of 25 ° C. to 80 ° C.
Was 140K.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. This embodiment is an embodiment in which the structure of the present invention is applied to a surface-emitting type semiconductor laser. Again, the growth method was gas source MBE (GS-MBE). As a semiconductor substrate to be manufactured, an n-type GaAs substrate 61 is used. After removing the oxide film on the substrate surface by thermal cleaning for 10 minutes in an As atmosphere under the supply of AsH _3, a lower multilayer film reflecting mirror 62 of n-type AlAs / n-type GaAs was laminated on the substrate 61 for 25 periods. The film thickness is
Each was made to have a quarter wavelength thickness in the semiconductor. Thereafter, a non-doped GaAs barrier layer (spacer layer) 63 is grown. Next, N plasma and AsH _{3 were used} as well layers.
While the Ga and In shutters are alternately opened and closed while supplying GaN (0.0085) As (0.9915) 1 / InN (0.0085) A.
The s (0.9915) 1 superlattice layer 64 is grown for one atomic layer for 15 periods. At this time, the total film thickness is about 9 nm. Thereafter, the supply of the N plasma is stopped, and the non-doped GaAs barrier layer (spacer layer) 13 and the p-type GaInP clad layer 65 are removed.
Are formed in this order.

Finally, a p-type GaAs contact layer 66 is grown. A circular oxide film having a diameter of 10 μm is formed on the film thus manufactured, and a mesa etch is performed using the film as a mask. Subsequently, after forming the oxide film protection layer 67, a polyimide 68 is applied and cured. Next, the polyimide is etched, and the oxide film on the mesa is removed and planarized.
After a ring-shaped p-side electrode 69 is formed on the upper part, SiO ₂
/ TiO ₂ to form a dielectric multilayer film reflecting mirror 70.
The film thickness was set to be 1/4 wavelength thick in the semiconductor. Finally, an n-side electrode 71 was formed on the back surface to complete the device. The prototype device oscillated continuously at room temperature due to current injection. The oscillation wavelength was 1.55 μm.

In the third and fourth embodiments, the first semiconductor layer (Ga) made of a group III-V mixed crystal semiconductor containing nitrogen is formed in the well layer of a semiconductor laser having a quantum well structure.
The effect of band gap narrowing by introducing a periodic structure by using a superlattice structure in which second semiconductor layers (InNAs) made of a group III-V mixed crystal semiconductor containing nitrogen (NAs) and nitrogen are alternately laminated one by one atomic layer. And N of 1% or less
Even with the composition, it is possible to obtain an optical communication semiconductor laser having excellent temperature characteristics oscillating in the wavelength band of 1.55 μm.

As is clear from the description of the first to fourth embodiments, the semiconductor laser of the present invention has a feature in the structure of the active layer. It does not depend on a structure such as a surface emission type or a manufacturing method such as a method using an actinic ray epitaxy method or a method using a metalorganic vapor phase epitaxy method.

[0035]

According to the present invention, by using a nitrogen-based group V mixed semiconductor for both the well layer and the barrier layer, both the confinement energy of electrons and holes can be sufficiently ensured. Also,
By compensating the stress in the well layer and the barrier layer, both the strain in each layer of the quantum well active layer and the entire strain can be reduced. Since the present invention does not depend on the structure and manufacturing method of the semiconductor laser, the design tolerance of the long-wavelength band semiconductor laser can be greatly increased, and a higher-performance semiconductor laser can be provided.

Further, according to the present invention, the well layer of a semiconductor laser having a quantum well structure has a III-
III-V containing nitrogen and first semiconductor layer of group V mixed crystal semiconductor
By using a superlattice structure in which second semiconductor layers made of a group-III mixed crystal semiconductor are alternately laminated one by one atomic layer, the effect of band gap narrowing due to the introduction of the periodic structure is one.
%, It is possible to obtain an optical communication semiconductor laser having excellent temperature characteristics oscillating in a wavelength band of 1.55 μm.

[Brief description of the drawings]

FIG. 1 is a diagram showing an element structure of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a band lineup of GaInNAs / GaAs.

FIG. 3 is a diagram illustrating a band lineup of GaInNAs / GaNAs.

FIG. 4 is a diagram showing an element structure of a semiconductor laser according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an element structure of a semiconductor laser according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an element structure of a semiconductor laser according to a fourth embodiment of the present invention.

[Explanation of symbols]

1: n-type GaAs substrate, 2: n-type GaAs buffer layer,
3: n-type AlGaAs cladding layer, 4, 5: GaNAs
Light guide layer, 6: GaInNAs well layer, 7: stress compensation type strain quantum well active layer, 8: p-type AlGaAs cladding layer, 9: p-type GaInP etching stop layer, 10: p-type AlGaAs cladding layer, 11: p-type GaAs cap layer, 12: n-type AlGaAs current confinement layer, 13: p-type G
aAs contact layer, 14: p-side electrode, 15: n-side electrode, 20: n-type semiconductor multilayer mirror, 21: GaAs spacer layer, 22: GaN barrier layer, 23: GaInN
As well layer, 24: 3 quantum well active layer, 25: GaAs
s spacer layer, 26: p-type GaInP cladding layer, 2
7: p-type GaAs contact layer, 28: SiO ₂ protective layer, 29: polyimide, 30: dielectric multilayer reflector, 5
1: n-type GaAs substrate, 52: n-type GaAs buffer layer, 53: n-type AlGaAs cladding layer, 54: non-doped GaAs barrier layer, 55: superlattice layer, 56: p-type Al
GaAs clad layer, 57: p-type GaAs cap layer,
58: oxide insulating layer, 59: p-type electrode, 60: n-type electrode, 61: n-type GaAs substrate, 62: lower multilayer reflector, 63: non-doped GaAs barrier layer, 64: superlattice layer, 65: p GaInP cladding layer, 66: p-type Ga
As contact layer, 67: oxide protective layer, 68: polyimide, 69: p-side electrode, 70: dielectric multilayer mirror, 7
1: n-side electrode

Continuing on the front page (72) Inventor Ken Kenya 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Hitachi, Ltd.Central Research Laboratories

Claims (11)

[Claims] 1. An active layer for generating light on a GaAs substrate crystal, and a cladding layer (or a spacer layer) for confining light.
And a semiconductor laser having a resonator structure for obtaining laser light from generated light, wherein the active layer has a quantum well structure composed of a well layer and a barrier layer, and the type of strain in the well layer and the barrier layer Wherein the stress compensation type walls are different from each other, and a nitrogen-based Group V mixed crystal semiconductor is used for the well layer. 2. The semiconductor laser according to claim 1, wherein the strain type of said well layer is compressive strain, and said strain type of said barrier layer is extensional strain. 3. The semiconductor laser according to claim 1, wherein said barrier layer is made of GaNAs or GaNPAs. 4. The semiconductor laser according to claim 1, wherein said well layer is made of GaInNAs. 5. The semiconductor laser according to claim 1, wherein the confinement energy of electrons is 150 meV or more, and the confinement energy of holes is 50 meV or more. 6. An active layer for generating light and a cladding layer (or spacer layer) for confining light on a semiconductor substrate.
And a semiconductor laser having a resonator structure for obtaining laser light from generated light, wherein the active layer is formed of a quantum well type structure formed of a barrier layer and a well layer, and the well layer contains nitrogen. A superlattice structure is used in which a first semiconductor layer made of a group-III mixed crystal semiconductor and a second semiconductor layer made of a III-V mixed-crystal semiconductor containing nitrogen are alternately and repeatedly stacked one by one atomic layer. Semiconductor laser. 7. The semiconductor laser according to claim 6, wherein the semiconductor material forming the superlattice structure is GaNA.
s, InNAs, AlNAs, GaNP, InNP, A
A semiconductor laser selected from the group consisting of 1NP, GaNSb, InNSb, and AlNSb. 8. The semiconductor laser according to claim 6, wherein said semiconductor laser has an oscillation wavelength in a 1.55 μm band and contains nitrogen used for a well layer of said semiconductor laser.
The nitrogen composition ratio of the group V mixed crystal semiconductor is 1
% Or less. 9. The semiconductor laser according to claim 1, wherein said semiconductor laser is of an edge emitting type. 10. The semiconductor laser according to claim 1, wherein said semiconductor laser is of a surface-emitting type. 11. An optical communication system using the semiconductor laser according to claim 1.