JP2001024271A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high output and improve reliability when a device has stripe structure. SOLUTION: In a package 8 provided with a window 7 for leading out a light, a semiconductor laser element 1 is soldered to a heat sink 2 provided with a thermistor, and the heat sink 2 is soldered to a thermoelectric element 3 by using solder 6. As to the semiconductor element 1, a clad layer 22, an optical guide layer 23, an lnGaAsP tensile distortion barrier layer 24, an InGaAsP quantum well active layer 25, an InGaAsP tensile strain barrier layer 26, an optical guide layer 27, a clad layer 28 and a cap layer 29 are laminated in order on an N-GaAs substrate 21. The degree of lattice mismatch between the barrier layer 24 and the substrate 21 is made -0.7%. The total thickness of the two tensile distortion barrier layers 24, 26 and the two optical guide layers 23, 27 which sandwich the active layer 25 is made 0.7 μm. A reflecting film of 20% is formed on the light output end surface, and a reflecting film of 90% is formed on the opposite end surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device having a wide stripe structure.

[0002]

2. Description of the Related Art In recent years, high-power semiconductor laser devices having a wide light-emitting region have attracted attention for printing equipment, medical use, industrial processing, and excitation of solid-state lasers. This is because semiconductor lasers are smaller, have lower power consumption, and are less expensive than other gas lasers or solid-state lasers.

Since a semiconductor laser device of this type is required to have a very high output, an ordinary single mode laser emits light from an active layer having a width of about 3 μm, while the width of the active layer is increased to 10 μm or more. High output is intended. But,
As described above, since the active layer has a width of 10 μm or more, the oscillated light oscillates in a transverse multimode in which many higher-order transverse modes are mixed. For this reason, when the optical output is increased, the oscillating light easily shifts to a different mode due to spatial hole burning of carriers caused by a high photon density distribution in the resonator. At this time, the near-field image, far-field image, and oscillation spectrum of the oscillating light change, and further, the output changes because the current-light conversion efficiency of each of the different transverse modes is different. In such a wide light emitting region at the end face of the semiconductor laser device, the oscillating light emits in the form of a filament, and may exhibit a very strong light intensity locally. For this reason, the end face of the semiconductor laser device is usually
The load of the average light density obtained by dividing the light output to emit light by the width of the light emitting region is applied, but in reality, the load is further increased. Therefore, the semiconductor laser device as described above is required to have higher reliability performance than a normal single mode laser.

In a semiconductor laser device, two things are important to obtain high output. One is that the performance of the semiconductor laser itself is high, and the other is that it is housed in a package that can fully exploit the performance of the semiconductor laser device. Particularly, in the case of a semiconductor laser device exceeding 1 W, the injection current becomes 1 A or more.
A considerable amount of heat is generated, and this heat causes deterioration of the optical output characteristics of the semiconductor laser device. Therefore, in the conventional package having low heat dissipation, the current-light output characteristics of the semiconductor laser device deteriorate, and it is difficult to obtain a high light output.

[0005]

Therefore, a solid-state laser light-emitting device using the above-described high-power semiconductor laser device as an excitation light source or a light-emitting device in which the semiconductor laser device is coupled to an optical fiber can be used for printing, medical, It has been difficult to use it in fields such as industry.

Conventionally used high power semiconductor laser devices having a wide light emitting region are not sufficient in light output characteristics, and require both a high performance semiconductor laser device and a package for maximizing its performance. .

In view of the above circumstances, it is an object of the present invention to provide a high-output and highly reliable semiconductor laser device having a wide stripe structure and a refractive index waveguide mechanism. It is.

[0008]

According to the semiconductor light emitting device of the present invention, a thermoelectric element is soldered in a sealed container having a window for extracting light, and a heat sink having a thermistor on the thermoelectric element is soldered. In order to form a light emitting region on a heat sink, a first conductivity type AlGaAs cladding layer, a first conductivity type light guide layer, a barrier layer, an InGaAsP layer are formed on at least a first conductivity type GaAs substrate.
A quantum well active layer, a barrier layer, a second conductivity type light guide layer, and a second conductivity type AlGaAs cladding layer are formed of a semiconductor layer laminated in this order, and the width of the light emitting region is 100 μm or more and 300 μm or less. Equipped,
A refractive index waveguide having a refractive index difference in the width direction of the active layer; a total thickness of the two light guide layers and the two barrier layers being 0.5 μm or more and 1.2 μm or less; A semiconductor laser device in which the reflectivity of the light emitting end face of the layer is 10% or more and 30% or less and the reflectivity of the end face opposite to the light emitting end face is 90% or more is soldered. Things.

The quantum well active layer may have a compressive stress therein.

It is preferable that the lattice mismatch Δa between the quantum well active layer and the GaAs substrate is 0.5% <Δa ≦ 1.5%.

[0011] Here, the lattice mismatch of the quantum well active layer and the GaAs substrate △ a is the lattice constant of the quantum well active layer and a _a, when the lattice constant of the GaAs substrate was _{a s,} (a a -
a _s / a _s ) × 100.

Further, the barrier layer may have a tensile stress inside.

It is preferable that the lattice mismatch Δb between the barrier layer and the GaAs substrate is −1.2% ≦ Δb <−0.2%.

[0014] Here, the lattice mismatch of the barrier layer and the GaAs substrate △ b is the lattice constant of the barrier layer and a _b, when the lattice constant of the GaAs substrate was _{a s, (a b -a s} / a _s ) × 10
It is represented by 0.

Further, the semiconductor laser element is In, Sn
Alternatively, it is desirable to be soldered to the heat sink by either InSn.

Further, an intermediate layer made of AlGaAs may be formed between the first conductivity type GaAs substrate and the first conductivity type AlGaAs cladding layer. In this case, the composition ratio of Al in the intermediate layer is the same as that of the first conductivity type AlGaAs cladding layer. It is desirable that the composition ratio of Al in the one-conductivity-type AlGaAs cladding layer is smaller than that of Al.

[0017]

According to the semiconductor light emitting device of the present invention, a thermoelectric element is soldered in a sealed container having a window for extracting light, and a heat sink having a thermistor is soldered on the thermoelectric element. And heat sink,
In order to form the light emitting region, at least the first conductivity type Ga
A first conductivity type AlGaAs cladding layer, a first conductivity type light guide layer, a barrier layer, a quantum well active layer made of InGaAsP, a barrier layer, a second conductivity type light guide layer, a second conductivity type light guide layer,
A conductive type AlGaAs cladding layer is formed of a semiconductor layer laminated in this order, and the width of the light emitting region is 100 μm or more and 300 μm or more.
μm or less, a refractive index guiding mechanism having a refractive index difference in the width direction of the active layer, and the total thickness of the two light guide layers and the two barrier layers is zero. A semiconductor laser device having a reflectance of not less than 0.5 μm and not more than 1.2 μm, a reflectance of the light emitting end face of the semiconductor layer of not less than 10% and not more than 30%, and a reflectance of an end face opposite to the light emitting end face of not less than 90%. , Because it is soldered,
The element characteristics of the semiconductor laser device can be improved, and a highly reliable high-output semiconductor light emitting device can be obtained.

Specifically, the light guide layer thickness is set to 0.5 μm.
By setting the length to m or more and 1.2 μm or less, the light density in the light emitting region can be reduced, and the light output when the end face is broken can be improved.

The active layer contains no aluminum.
Since the nGaAsP material is used, end face destruction due to a defect or the like due to oxidation of the light emitting area on the light emitting surface can be prevented, and reliability can be improved.

Further, the stripe width should be 100 μm or more and 30 μm or more.
By setting the refractive index to 0 μm or less and introducing a refractive index waveguide mechanism, light can be efficiently confined in the active layer, and a high output with controlled transverse mode can be obtained.

Further, since a heat sink having a cooling function is soldered in the hermetically sealed package, heat generated when a high current is injected into the semiconductor laser device can be efficiently released, and deterioration of device characteristics due to poor heat radiation can be suppressed. be able to.

Further, the reflectivity of the light emitting end face is not less than 10% and not more than 3%.
By setting it to 0% or less, light can be emitted efficiently and return light can be efficiently reflected, so that a stable output can be obtained.

When the quantum well active layer has a compressive strain, the carrier injection efficiency can be improved and the driving current can be reduced, so that the output can be improved.

Further, by setting the degree of lattice mismatch between the quantum well active layer and the GaAs substrate to be 0.5% or more and 1.5% or less, dislocations due to strain do not occur and carrier injection efficiency is improved. And the driving current can be reduced.

Further, by imparting tensile strain to the barrier layer, the carrier injection efficiency can be improved and the drive current can be reduced, so that the output can be improved.

Also, by setting the degree of lattice mismatch between the barrier layer and the GaAs substrate to be not less than -1.2% and not more than -0.2%, dislocations due to strain are not generated as in the above case.
Carrier injection efficiency can be improved, and drive current can be reduced.

Further, compressive stress is applied to the quantum well active layer,
By applying tensile strain to the barrier layer, the strain stress near the quantum well active layer can be reduced, and even if the active layer has an appropriate composition and a critical thickness exists, the critical thickness is effectively reduced. And the threshold current and the like can be reduced.

A GaAs substrate and a first conductivity type AlG
a composition of Al between the first conductivity type A
By forming an intermediate layer smaller than the Al composition of the lGaAs cladding layer, strain stress between the cladding layer and the GaAs substrate can be reduced, and generation of lattice defects can be prevented, so that a stable output can be obtained. And reliability can be improved.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a semiconductor light emitting device according to a first embodiment of the present invention.

As shown in FIG. 1, the semiconductor light emitting device of the present embodiment has a package 8 having a window 7 for extracting light.
The semiconductor laser element 1 is soldered to a heat sink 2, and the heat sink 2 is soldered to a thermoelectric element 3 by solder 6, and a thermistor 4 for controlling temperature is provided in the heat sink 2. Embedded. A photodetector 5 is fixed on the thermoelectric element 3 for monitoring an optical output. Package 8
The inside of is enclosed with dry air to prevent dew condensation due to temperature change. Light emitted from the semiconductor laser device 1 is extracted to the outside through the window 7. In the semiconductor light emitting device thus configured, since the semiconductor laser element 1 is soldered to a heat sink having the thermistor 4, the temperature can be controlled to a desired temperature.

Next, the semiconductor laser device 1 soldered in the package 8 will be described, and FIG. 2 shows a sectional structure perpendicular to the light emitting direction.

As shown in FIG. 2, the semiconductor light emitting device according to the present embodiment has an n-AlG substrate on an n-GaAs substrate 21.
aAs cladding layer 22, n-InGaP light guiding layer 23, I
nGaAsP tensile strain barrier layer 24, InGaAsP quantum well active layer 25, InGaAsP tensile strain barrier layer 2
6, a p-InGaP light guide layer 27, a p-AlGaAs cladding layer 28, and a p-GaAs cap layer 29 are sequentially laminated. The lattice constant of the barrier layer and a _b, when the lattice constant of the GaAs substrate was a _s, lattice mismatch of the barrier layer and the GaAs substrate △ b is _{△ b = (a b -a s} / a s) × 100 In this semiconductor laser device, this Δb is −
0.7%. The total thickness of the two tensile strain barrier layers 24 and 26 and the two light guide layers 23 and 27 sandwiching the active layer is 0.7 μm.

The semiconductor laser device 1 has a ridge structure, and the ridge structure has a mesa shape with a width of about 200 μm. On both sides of the ridge, etching is performed up to the light guide layer 27 so that the remaining thickness of the p-AlGaAs cladding layer 28 becomes 0 μm, and a refractive index waveguide is formed at the ridge portion so that the refractive index becomes equivalently higher. ing.

An insulating film 30 is formed on the p-GaAs cap layer 29, and an electrode window is formed on the ridge by photolithography. Thereafter, a p-side electrode 31 is formed on the insulating film 30, and an n-side electrode 32 is formed on the back surface of the GaAs substrate 21.

After the semiconductor laser device fabricated as described above is cleaved to a predetermined cavity length, 20%
Reflection film is formed, and 90% is formed on the end face opposite to the light emission face.
Is formed. The reflectivity of the light emitting surface is a high value for this type of semiconductor laser device, because the influence of the return light is taken into consideration. The applicant's research so far has shown that the influence of the returning light can be eliminated by setting the front surface reflectance to 10% or more.

After the cleavage, the semiconductor laser device 1 is soldered on the heat sink 2 using a GaAs substrate and a reflection-side surface using In. Copper having high thermal conductivity is used as the heat sink material. The heat sink 2 is soldered to the thermoelectric element 3 and a thermistor 4 is embedded in the heat sink 2 so that the temperature can be controlled.

FIG. 3 shows current-light output characteristics of the present invention and a conventional semiconductor light emitting device. In the figure, line a shows the characteristics of the semiconductor light emitting device of the present invention, and line b shows the characteristics of the conventional semiconductor light emitting device. In the conventional semiconductor light emitting device, the barrier layer has no tensile strain, and GaAs
It has a structure lattice-matched to the substrate. As shown by the line b, the conventional semiconductor light emitting device has a drive current of 20
If it exceeds 00 mA, the light output tends to be saturated. However, as shown by the line a, in the semiconductor light emitting device of the present invention, the light output increases almost monotonously as the drive current increases. Therefore, by having a tensile strain in the barrier layer as in the semiconductor light emitting device of the present invention,
A much higher output can be obtained than the conventional one.

FIG. 4 shows the characteristics of the light output when the end face is broken with respect to the total thickness of the barrier layer and the light guide layer of the semiconductor light emitting device. In the conventional semiconductor light emitting device, the total thickness of the barrier layer and the light guide layer was about 0.5 μm and the output was about 5 W. However, in the semiconductor light emitting device of the present invention, the total thickness was 0.5 μm.
By setting it to μm or more, a maximum output of 7 W is obtained.
However, where the diameter is larger than 1.2 μm, the light output tends to decrease. This is because when the total film thickness is larger than 1.2 μm, the internal loss increases and the operating current increases. Therefore, as shown in FIG. 4, reducing the light density in the active layer by setting the total thickness of the barrier layer and the light guide layer to 0.5 μm or more and 1.2 μm is effective for increasing the output. You can see that.

Next, FIG. 5 shows the reliability characteristics of the present invention and the conventional semiconductor light emitting device. In the figure, the solid line a shows the characteristics of the semiconductor light emitting device according to the present invention, and the broken line b shows the characteristics of the conventional semiconductor light emitting device. In a conventional semiconductor light emitting device, the quantum well active layer is made of AlGaAs containing Al.
As shown in FIG. 5B, in the conventional semiconductor light emitting device, elements which suddenly deteriorate during energization were observed, but as shown in FIG. 5A, in the semiconductor light emitting device according to the present invention, the driving time exceeded 1000 hours. At this point, it can be seen that the drive current hardly increased and the drive was stable. It is considered that in the semiconductor light emitting device of the present invention, since the active layer is made of a material containing no Al, deterioration of the end face of the light emitting region due to oxidation of the Al element does not occur.

FIG. 6 shows current-light output characteristics of the semiconductor light emitting device of the present invention having a thermoelectric element in a package and a conventional semiconductor light emitting device having no thermoelectric element in a package. Line a shows the characteristics of the semiconductor light emitting device of the present invention, and line b shows the characteristics of the conventional semiconductor light emitting device. It can be seen that the semiconductor light emitting device of the present invention shown by the line a has a higher light output at the time of high current injection than the conventional semiconductor light emitting device shown by the line b. The conventional semiconductor light emitting device has a strong tendency of light output saturation at the time of high current injection because the conventional semiconductor light emitting device does not have a thermoelectric element inside the package, so the heat radiation ability from the heat sink is small, and
Since the contact between the package and the thermoelectric element is not perfect due to the jig or the like for fixing them, the thermal conductivity from the heat sink to the thermoelectric element outside the package deteriorates. As a result, poor heat radiation occurs and the light output decreases.

Here, a conventional semiconductor light emitting device hermetically sealed in a package will be described, and the figure is shown in FIG.
As shown in FIG. 7, a conventional semiconductor light emitting device includes a semiconductor laser device in a package 78 having a window 77 for extracting light.
A heat sink 72 is soldered to a heat sink 72, and the heat sink 72 is soldered to a package 78 by a solder. The inside of the package 78 is filled with dry air to prevent dew condensation due to temperature change. The light emitted from the semiconductor laser element 71 is
It is taken out from the window 72. As described above, the conventional semiconductor light-emitting device does not include a thermoelectric element whose temperature can be controlled in the package, and thus the element characteristics are deteriorated due to poor heat radiation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a semiconductor light emitting device according to a first embodiment of the present invention;

FIG. 2 is a sectional view of a semiconductor laser device included in the semiconductor light emitting device according to the first embodiment;

FIG. 3 is a graph showing a relationship between a drive current and a light output of a semiconductor light emitting device depending on the presence or absence of a tensile strain barrier layer.

FIG. 4 is a graph showing the relationship between the total film thickness of the barrier layer and the light guide layer and the light output when the end face is broken.

FIG. 5 is a graph showing a relationship between a driving time and a driving current of a semiconductor light emitting device depending on a difference in composition of a quantum well active layer.

FIG. 6 is a graph showing a relationship between a driving time of a semiconductor light emitting device and an optical output depending on the presence or absence of a thermoelectric element.

FIG. 7 is a diagram showing a conventional semiconductor light emitting device.

[Explanation of symbols]

 1,71 Semiconductor laser device 2,72 Heat sink 3 Thermoelectric device 4 Thermistor 5 Photodetector 6,76 Solder 7,77 Window 8,78 Package 21 n-GaAs substrate 23 n-InGaP optical guide layer 24,26 Tensile strain barrier layer 25 Quantum Well active layer 27 p-InGaP optical guide layer

Continued on the front page (72) Inventor Fujio Akinaga Fuji Photo Film Co., Ltd. 798, Kaisei-cho, Ashigarugami-gun, Kanagawa Prefecture (72) Inventor Hideo Yamanaka 798 Miyadai, Kaisei-cho, Ashigaue-gun, Kanagawa Prefecture, Fuji Photo Photo Co., Ltd. (72) Inventor Takeshi Osato 798, Miyadai, Kaisei-cho, Ashigarashimo-gun, Kanagawa Prefecture, Japan (72) Inventor Masanori Sasao 798, Miyaidai, Kaisei-cho, Ashigara-gun, Kanagawa, Japan F-film (reference) ) 5F073 AA45 AA74 AA83 BA07 BA09 CA13 CB23 EA28 FA25 GA14

Claims (7)

[Claims] 1. A thermoelectric element is soldered in a sealed container provided with a window for extracting light, and a heat sink having a thermistor is soldered on the thermoelectric element. In order to constitute the above, at least the first conductivity type Ga
A first conductivity type AlGaAs cladding layer, a first conductivity type light guide layer, a barrier layer, a quantum well active layer made of InGaAsP, a barrier layer, a second conductivity type light guide layer, a second conductivity type light guide layer,
A conductive type AlGaAs cladding layer is formed of a semiconductor layer laminated in this order, and the width of the light emitting region is 100 μm or more.
It has a stripe structure of not more than 00 μm, has a refractive index guiding mechanism having a refractive index difference in the width direction of the active layer, and has a thickness of the two light guide layers and the two barrier layers. The total is 0.5 μm or more and 1.2 μm or less, the reflectance of the light emitting end face of the semiconductor layer is 10% or more and 30% or less, and the reflectance of the end face opposite to the light emitting end face is 90%.
% Of a semiconductor laser device, which is soldered. 2. The semiconductor light emitting device according to claim 1, wherein said quantum well active layer has a compressive stress therein. 3. The semiconductor light emitting device according to claim 2, wherein the lattice mismatch △ a between the quantum well active layer and the GaAs substrate is 0.5% <△ a ≦ 1.5%. . 4. The semiconductor light emitting device according to claim 1, wherein said barrier layer has a tensile stress therein. 5. The semiconductor light emitting device according to claim 4, wherein a degree of lattice mismatch Δb between the barrier layer and the GaAs substrate satisfies −1.2% ≦ Δb <−0.2%. . 6. The semiconductor light emitting device according to claim 1, wherein said semiconductor laser element is soldered to said heat sink by using any one of In, Sn, and InSn. 7. An AlGaAs intermediate layer is formed between the first conductivity type GaAs substrate and the first conductivity type AlGaAs cladding layer, and the Al composition ratio of the intermediate layer is the first conductivity type. 7. The semiconductor device according to claim 1, wherein the composition ratio is smaller than the Al composition ratio of the AlGaAs cladding layer.
13. The semiconductor light emitting device according to claim 1.