JP2823187B2 - Semiconductor laser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to a semiconductor laser,
In particular, it relates to a high-power semiconductor laser. [0002] 2. Description of the Related Art In increasing the output of semiconductor lasers,
Optical loss at the emission end face, so-called COD (Catastro
phic Optical Damage) is a problem. This COD break
In order to achieve goodness, various ideas have been used in the past.
Is being done. That is, a conventional double heterojunction semiconductor
The body laser is, for example, as shown in FIG.
On a GaAs substrate 1, for example, n-type Al of the same conductivity type
A first cladding layer 2 made of GaAs and an n-type or p-type
An active layer 3 of type or intrinsic, for example GaAs;
A second conductive type different from that of the first cladding layer 2, for example, a p-type
Clad layer 4 and cap layer 5 of the same conductivity type
The active layer 3 is sequentially epitaxially grown, and
Heterojunction between the two cladding layers 2 and 4 respectively
Is formed. The half shown in FIG.
The conductor laser is an example of an electrode stripe type configuration.
5, a stripe formed in the insulating layer 6 formed on the insulating layer 6
One electrode 7 is connected to the cap layer 5 through the electrode window 6a.
Is adhered to. 8 is provided on the substrate 1
The other electrode is shown. FIG. 5 shows the vicinity of the active layer of this semiconductor laser.
Shows the energy band gap Eg distribution of
The energy band of the active layer 3 is sandwiched by the active layer 3.
Cap Eg₁Larger energy band gap than
Eg_TwoFirst and second cladding layers 2 and 4 having
And the active layer 3 and the first and second cladding layers
There is a required gap difference ΔEg between 2 and 4
The carrier is confined in the active layer 3
The active layer 3 and the first and second cladding layers 2 and 4
Light is confined by the difference in refractive index between
It is trying to happen. In such a double junction type semiconductor laser,
In this regard, a typical example of improving COD is light closing.
The confinement and carrier confinement are performed separately,
Widening is performed to reduce the light intensity of the active layer
The so-called SCH (Separate Confinment Heterostructur)
e). FIG. 6 shows the energy of the SCH type semiconductor laser.
This shows the energy band gap distribution.
In this case, the active layer 3 and the first and second cladding layers 2 and
4, the difference ΔEg between the energy band gaps of the two.
With a smaller difference ΔEgs, closed for carriers
It has the effect of confining, but light can seep out
First and second light exuding layers 9 and 10
Is provided. As another example, as shown in FIG.
In the usual double junction type configuration, the thickness of the active layer 3 is set to 3
The thickness of the active layer 3 is substantially reduced to about
In some cases, light is exuded from the light. FIG. 7 shows the distribution of the band gap.
As schematically shown, 250 to 450 on both sides of the active layer 3
Thin first and second barrier layers 11 and 12 of Å
Causes substantial seepage due to light penetration
Was also proposed (Applied
Box Letter, Appl. Phys. Lett. 38 (11). 1 June 1981
See). [0009] SUMMARY OF THE INVENTION
In the SCH type semiconductor laser of No. 6, the carrier is
Exudation due to heat is generated because it is not sufficiently confined in the active layer
The threshold current Ith has a large temperature dependency.
There is a title. In addition, the above-mentioned thinning of the active layer,
The barrier layer having a large energy gap described with reference to FIG.
In the provisions, the thin epitaxy
Forming a growth layer, especially in the latter
In the case of obtaining a large energy gap, for example, A
It is necessary to increase the amount of Al added in lGaAs
Technical problems in obtaining a layer with good crystallinity
is there. Then, these thin layers are formed by the active layer itself or the active layer.
Because it is a layer adjacent to the conductive layer,
There is a problem in reliability and reproducibility. The present invention aims to improve COD and improve reliability.
Semiconductor laser with high output and excellent stability and stability
obtain. [0012] SUMMARY OF THE INVENTION The present invention provides a first clutch.
Layer, an active layer, and a second cladding layer are sequentially provided.
Active layer and first and second cladding layers
Energy band gap difference ΔEg is 0.35
≦ ΔEg ≦ 0.45 (eV), the first and second
Exuding light to at least one of the cladding layers
A layer is provided. And the energy of this light seeping layer
-The band gap of the active layer
Set larger than Also, the light exuding layer and the active layer
The distance between is selected from 500Å to 5000Å, and light exudes
The thickness of the layer is several hundred square meters. With the above configuration, reliability, stability, reproduction
A semiconductor laser with high light output and excellent characteristics was constructed. This
This is because the energy band gap difference ΔE
A cladding layer having a g of 0.35 to 0.45 eV was provided.
This ensures that carriers are confined in the active layer.
It can actually be done, and it exudes thermal carrier exudation
The threshold current I_thHeat dependence
And stabilize the characteristics.
It depends. At the same time, the active layer
At a distance of 500 to 5000 mm,
100 、 energy band gap compared to active layerButBig
The active layer
Of light in the active layerCloth
Lower peak value and broaden its distribution
COD is less likely to occur due to
The distance between the light exuding layer and the active layer is 500 to 500.
0 mm, and its thickness is several hundred mm.
As a result, the resonance of the generated light is
And the separation between the light oscillation part and the carrier coupling part occurs.
Emission in the active layerLet goInconvenience that hinders vibration
Reliability, stability, and reproducibility
It is thought that a semiconductor laser with excellent light output could be constructed.
It is something that can be done. Further, the distance between the active layer and the light exuding layer,
That is, the cladding layer between the active layer and the light exuding layer
The thickness should be 500 ~ 5000mm, and the thickness of the light seeping layer
By setting it to several hundred square meters,
Can be obtained stably as a semiconductor layer having crystallinity
The thickness, reliability, stability and reproduction
A high-power semiconductor laser with excellent performance.
It is. [0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described with reference to FIG.
As will be described, in FIG. 1, portions corresponding to FIG. 4 are the same.
Assign a sign. Also in this example, for example, n-type GaAs
On the substrate 1, Al of the same conductivity type_xGa_1-xFrom As
A first cladding layer 2 comprising n-type or p-type or intrinsic
Al_yGa_1-yAs active layer 3 and first cladding layer
P-type Al with conductivity type different from 2_xGa_1-xConsisting of As
The second cladding layer 4 is made of GaAs having the same conductivity type as the second cladding layer 4.
And a cap layer 5 formed as described above.
And the second cladding layers 2 and 4,
Al of the same conductivity type_zGa _1-zFirst and second
The light exuding layers 21 and 22 from the active layer 3 are provided.
I can. That is, for example, on the GaAs substrate 1, the first
Lower first cladding layer 2 which becomes a part of the cladding layer 2
A is epitaxially grown, and then a first light
The exudation layer 21 is grown epitaxially, and
The upper first cladding layer which becomes a part of the first cladding layer 2
Layer 2B is epitaxially grown, and an active layer 3
Is epitaxially grown. And on top of this,
Lower second cladding layer which becomes a part of the second cladding layer 4
4A is epitaxially grown and a second light
The exposed layer 22 is epitaxially grown, and a second
Upper second cladding layer 4 which becomes a part of the cladding layer 4 of FIG.
B is epitaxially grown. An insulating layer 6 is deposited on the cap layer 5,
The electrode 7 is ohmic through the electrode window 6a formed in this.
The other electrode 8 is ohmic-coated on the substrate 1.
Be worn. Here, each of the layers 2A, 21B, 3, 4A,
22,4B, 5 are continuously MOCVD (Metalorganic C)
Chemical Vapor Deposition)
By switching the switches. Active layer 3 and first and second cladding layers 2
Energy band gap difference ΔEg between 1 and 22
Is selected to be 0.35 ≦ ΔEg ≦ 0.45 (eV). The energy of the light exuding layers 21 and 22
-The band gap is the energy band gap of the active layer 3.
Set larger than the top. The thickness da of the active layer 3 is several hundred to 1500.
Å, for example, 800Å, and the light exuding layers 21 and 22
, Ie, the upper cladding layer 2
B and the lower second cladding layer 4A each have a thickness d.
_s1And d_s2From 500 to 5000, for example 500
I do. The thickness dc of the light exuding layers 21 and 22
₁And dc_TwoIs set to several hundred degrees, for example, 500 degrees. The thickness of each of the above-mentioned layers, ie, the active layer 3,
First cladding layer 2B, lower second cladding layer 4
A, the light exuding layers 21 and 22 are both epitaxy.
Excellent reliability and stability in Shall growth technology,
Formed as an excellent crystalline semiconductor layerDoEnough thickness for
It is. In the above composition of each layer, x, y and z
Satisfies y <z <x. FIG. 2 shows each layer in this case.
Of the active layer
3 and the cladding layers 2 and 4
As described above, the difference ΔEg between the loops is 0.35 ≦ ΔEg ≦
0.45 (eV), the active layer 3 and the light seeping layer 2
Energy band gap difference ΔEg between 1 and 22
s is set to ΔEgs <ΔEg. The curve shown by the solid line in FIG.
The degree distribution is shown. The dashed curve in the figure shows the first and second curves.
Light exuding layers 21 and 2 are provided in the lad layers 2 and 4.
Light intensity distribution in the case of the structure of FIG.
As can be seen by comparing both curves,
The light intensity distribution is steep for those without a protruding layer.
In contrast to that of the present invention, the light intensity distribution is broadened,
Its peak value has dropped. The light intensity is weak
COD is less likely to occur, and the amount of integration,
, And thus the power is sufficiently obtained. In the above-described example, AlGaAs
Is the case where the present invention is applied to a system semiconductor laser,
InGaAsP system that emits short wavelength light or long wavelength light
Of InGaAsP based semiconductor lasers
it can. [0027] As described above, according to the present invention, stable
High power semiconductor laser with excellent reproducibility and reproducibility
Came. This is because, as mentioned earlier,
Energy band gap difference ΔEg is 0.35 to 0.45 eV
With the cladding layer of
Carrier can be reliably confined,
Carrier seepage can be effectively suppressed and the threshold current
I_thHeat dependence can be reduced,
This is because we were able to stabilize. Also at the same time
The distance between the cladding layer and the active layer is 500 to 5000.
At the Å position, the energy is several hundred mm thick compared to the active layer.
Luggy band gapButGreat light seeping layer
As a result, seepage of light from the active layer is generated,
Intensity in the conductive layerClothLower peak value and its distribution
COD can be reliably produced
Less likely to occur, moreover, light exuding layer and active layer
At a distance of 500 to 5000 mm, and its thickness
The light exuding layer described above is a few hundred square meters.
Can avoid the resonance of the generated light in the
Separation of the active layer from the junction reduces light emission in the active layer
SaLet goThe inconvenience that hinders vibration is avoided.
, High light output semi-conductor with excellent reliability, stability and reproducibility
It is considered that the body laser could be constructed. Further, the distance between the active layer and the light exuding layer,
That is, the cladding layer between the active layer and the light exuding layer
The thickness should be 500 ~ 5000mm, and the thickness of the light seeping layer
By setting it to several hundred square meters,
Can be obtained stably as a semiconductor layer having crystallinity
The thickness, reliability, stability and reproduction
A high-power semiconductor laser with excellent performance.
It is.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of an example of a semiconductor laser according to the present invention. FIG. 2 is a schematic view of an energy band gap used for describing a semiconductor laser according to the present invention. FIG. 3 is a light intensity distribution curve diagram for describing a semiconductor laser according to the present invention. FIG. 4 is a schematic sectional view of a conventional semiconductor laser. FIG. 5 is a schematic diagram of an energy band gap used for describing a conventional semiconductor laser. FIG. 6 is a schematic diagram of an energy band gap used for describing a conventional semiconductor laser. FIG. 7 is a schematic diagram of an energy band gap used for describing a conventional semiconductor laser. [Description of Signs] 1 Substrate 2 First clad 4 Second clad 3 Active layer 21 First light exuding layer 22 Second light exuding layer 5 Cap layers 7, 8 Electrode

Claims (1)

(57) [Claims] A first cladding layer, an active layer, a second cladding layer are sequentially formed, the active layer and the first and second clad layers, component
Are formed of the same material having different composition ratios , and a difference ΔEg in energy band gap between the active layer and the first and second cladding layers is equal to 0.
35 ≦ ΔEg ≦ 0.45 (eV), wherein a light seepage layer is provided on at least one of the first and second cladding layers, and the energy band gap of the light seepage layer is Is set to be larger than the energy band gap of the active layer, and the distance between the light seeping layer and the active layer is 500 °.
A semiconductor laser, wherein the thickness of the light exuding layer is set to several hundreds of mm.