JPH10223978A - Semiconductor laser and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a window structure which is free from reactive currents by radiating plasma having a specific quantity of energy upon at least one of the end faces forming a resonator from the end face side after a clad layer having a first conductivity, an active layer containing quantum wells, and a clad layer having a second conductivity are formed on a semiconductor substrate. SOLUTION: A clad layer 3 having a first conductivity, an active layer 4, and a clad layer 5 having a second conductivity are formed on a semiconductor substrate 1. When a laser is formed in a bar-like shape and Ar plasma having an average quantity of energy of 25-300eV is radiated upon both end faces of the laser in a vacuum after an electrode 12 is formed, the crystals near the active layer 4 in the vicinities of the end faces are broken and disordered. Therefore, a window structure can be formed, because quantum wells near the end faces are disordered and the parts near the end faces become transparent at the oscillation wavelength of the laser. Since carriers are inactivated and the resistance of each layer increases, currents hardly flow through the layers when the layers are exposed to the plasma and no current are injected into the layers from the end faces. Therefore, reactive current problems, etc., do not arise and a window structure which is free from reactive currents can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser. The laser of the present invention is suitably used for applications requiring both high output and long life, such as an excitation light source for an optical fiber amplifier and a light source for optical information processing.

[0002]

2. Description of the Related Art In recent years, progress in optical information processing technology and optical communication technology has been remarkable. For example, high-density recording using a magneto-optical disk and two-way communication using an optical fiber network have no spare time. For example, in the telecommunications field, Er ^{3+ is used} as an amplifier for signal amplification that has flexibility in the transmission system, as well as a large-capacity optical fiber transmission line corresponding to the future of the multimedia age.
Optical fiber amplifier (EDF) doped with rare earth such as
The research of A) is being actively conducted in various fields. And
It is an essential element as a component of EDFA,
The invention of a highly efficient semiconductor laser for an excitation light source is awaited.

[0003] In principle, there are three types of oscillation wavelengths of an excitation light source that can be used for EDFA applications.
80 nm and 1480 nm. From the characteristics of the amplifier, it is known that pumping at 980 nm is most desirable in consideration of gain, noise, and the like. It is desired that such a laser having an oscillation wavelength of 980 nm satisfies the contradictory characteristics of a high output and a long life as an excitation light source. Wavelengths in the vicinity,
For example, at 890-1200 nm, an SHG light source,
There is also a demand as a heat source for a laser printer, and development of a laser with high output and high reliability is also straddled in various other applications.

For example, in this band, a semiconductor laser has been developed that can withstand continuous use for about two years at an optical output of about 50-100 mW, but the operation at a higher optical output causes a rapid deterioration, and the reliability is not high. It is enough. One of the causes is caused by deterioration of the emission end face of the laser light exposed to a very high light density. GaAs
As is well known in GaAs / InGaAlP-based semiconductor lasers, there are many surface levels near the laser end face, but these levels absorb laser light. It is described that the temperature in the vicinity becomes higher than the temperature inside the laser, and that this temperature rise further narrows the band gap in the vicinity of the end face, and further causes positive feedback such that laser light is easily absorbed. This phenomenon is called catastrophic optical damage (COD), which is observed when a large current flows instantaneously.
e) Sudden deterioration of the device due to a decrease in the COD level during a long-term energization test is a common problem in many semiconductor laser devices.

As a countermeasure against these phenomena, various methods have been proposed to make the band gap of the active layer region near the end face transparent to the oscillation wavelength and to suppress the light absorption near the end face. Lasers with these structures are generally window-structured lasers or NAMs (non-absorbing).
It is called a “mirror” structure laser, and is very effective when high output is required.

There are various methods for creating a window structure, for example,
Various methods have been proposed, such as a method of epitaxially growing a semiconductor material transparent to an emission wavelength on a laser end face, and a method of intentionally diffusing Zn or Si or the like as an impurity in an active layer near an end face of the laser to disorder. I have.

[0007]

However, in the method of epitaxially growing a semiconductor material transparent to the emission wavelength on the end face of the laser, an electrode to be formed later is used to perform the epitaxial growth on the end face with the laser in a so-called bar state. The process becomes very complicated. In the case of a method of intentionally diffusing Zn or Si or the like as impurities into the active layer near the end face of the laser to make the active layer disorder, the diffusion is generally performed from the epitaxial direction of the laser element toward the substrate. However, there is a problem in the controllability and the controllability of the lateral diffusion with respect to the cavity direction, so that it is difficult to make a stable production. In addition, there is a problem that generation of a reactive current accompanying a decrease in resistance in the diffusion region increases a threshold current and a driving current of the laser.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor laser having a high-performance window structure which can be manufactured by a simple method and has no reactive current or the like. It is in.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, when the end face is treated by irradiating plasma having energy in an optimized range from the end face, There is no problem of controllability of diffusion depth and control of lateral diffusion with respect to the cavity direction as in the case of impurity diffusion, and there is no problem that electrode formation becomes difficult as in the case of epitaxial growth on the end face. The present invention has been found that the end face can be easily made transparent, and furthermore, there is no problem that the resistance near the end face decreases and a reactive current flows, and that a semiconductor laser having both high output and long life can be obtained. did.

That is, the gist of the present invention is to provide a semiconductor laser having a first conductivity type cladding layer, an active layer including a quantum well, and a second conductivity type cladding layer on a semiconductor substrate.
A semiconductor laser characterized by irradiating at least one end face forming a resonator with plasma having energy of 25 eV or more and 300 eV or less from the end face side, and forming a first conductivity type clad layer and a quantum well on a semiconductor substrate. In the method of manufacturing a semiconductor laser having an active layer and a second conductive type clad layer including the first conductive type clad layer on the semiconductor substrate, forming an active layer including a quantum well and a second conductive type clad layer, A method for manufacturing a semiconductor laser, characterized in that at least one end face forming a resonator is irradiated with plasma having an energy of 25 eV to 300 eV from the end face side.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The semiconductor laser of the present invention has a first conductivity type cladding layer on a semiconductor substrate, an active layer having a quantum well structure and a second conductivity type cladding layer, and a semiconductor laser using an end face as a resonator structure. Although the details of the structure are not particularly limited, the following, as an example of a specific structure, has a refractive index waveguide mechanism, the second conductivity type cladding layer is divided into first and second two layers, the second conductivity type A semiconductor laser having a structure in which a current injection region is formed by a second clad layer and a current block layer will be described. Such a semiconductor laser has an oscillation wavelength of 98 nm including an InGaAs quantum well in an active layer, which is desired as an excitation light source for an optical fiber amplifier used for optical communication.
This is preferable as a laser structure near 0 nm, that is, 900 to 1200 nm, more preferably 900 to 1100 nm.

FIG. 2 is a schematic example of a groove type semiconductor laser as an example of the epitaxial structure in the semiconductor laser of the present invention. In the semiconductor laser of the present invention, a so-called group III-V compound single crystal substrate (wafer) is usually used as the semiconductor substrate. The group III-V compound single crystal substrate is composed of a group IIIb element and a group Vb of the periodic table.
It is obtained by cutting out from a bulk crystal of a compound with a group element. As a material of the wafer, GaP, GaAs, InP
Are appropriately selected depending on the desired wavelength, the material of the active layer, the desired light output, and the like. InGaAs for active layer
When s quantum wells are included, GaAs is particularly preferably used.

The buffer layer (2) is preferably provided to alleviate incompleteness of the substrate bulk crystal and facilitate the formation of an epitaxial thin film having the same crystal axis. The buffer layer (2) is preferably made of the same compound as the substrate (1). The active layer includes an InGaAs quantum well, and when a GaAs substrate is used, GaAs is usually used.
Is used.

The first conductivity type cladding layer (3) is, for example,
When the buffer layer (2) is made of a material having a refractive index smaller than the average refractive index of the active layer (4) and GaAs is used as the buffer layer (2), the AlGaAs-based material (Al _V Ga
_1-V As) or In _0.49 Ga _0.51 P is used. A
The mixed crystal ratio of the lGaAs-based material is appropriately selected so that the refractive index satisfies the above condition.

The structure of the active layer (4) is a structure having a quantum well, and a single quantum well (SQW) structure, a double quantum well (DQW) structure, a multiple quantum (MQW) structure or the like is appropriately adopted. be able to. In the quantum well structure, an optical guide layer is usually used in combination, and if necessary, a barrier layer is also used for separating the quantum well. The structure of the active layer is such that a light guide layer is provided on both sides of the quantum well (S
CH structure), a structure (GRIN-S) in which the refractive index is continuously changed by gradually changing the composition of the light guide layer.
CH structure) can be adopted. However, as the thickness of the quantum well is smaller than the thickness of the entire active layer, the effect of the end face treatment tends to be more remarkable.

The material and structure of the active layer (4) are appropriately selected depending on the intended emission wavelength and output. A material containing at least In or Ga tends to form a natural superlattice, and from this viewpoint, it can be said that this kind of material is easily ordered depending on the film forming conditions.
For this reason, the effect of disorder by plasma irradiation is large.
In addition, even in the case of a quantum well structure formed of a material that does not form a natural superlattice, mixing between the barrier layer and the quantum well layer can be caused, so that the effect of plasma irradiation can be sufficiently expected. Specifically, a GaAs material,
AlGaAs-based material, InGaAs-based material, InGaAs
sP-based materials, InGaAlP-based materials, and the like, preferably a material containing In and Ga, and most preferably, a material containing In and Ga.
_{n q Ga 1 -q As (0} <q <1) of such an In, 980 nm vicinity having an active layer made of a material containing Ga and As, i.e., preferably the semiconductor laser emission wavelength of about 890~1200nm Act on. The composition of the barrier layer is preferably Al _x Ga _{1 -x} As (0 ≦ x ≦ 1).

The second conductive type first cladding layer (5) is made of a material having a refractive index smaller than the average refractive index of the active layer (4). The refractive index of the second conductive type first cladding layer (5) is usually the same as that of the first conductive type cladding layer (3). Therefore, as the material of the second conductive type first clad layer (5), the same material as that of the first conductive type clad layer (3) is used, and its mixed crystal ratio is the first conductive type clad layer (3). Is usually the same as

FIG. 2 shows two types of etching stop layers and cap layers. These layers are employed in a preferred embodiment of the present invention, and the formation of the current injection region can be performed accurately and easily. Effective to do. The second etching stop layer (6) is made of Al _a Ga _1-a As (0 ≦ a ≦
1) Although it is composed of a material, usually GaAs is preferably used. This is because when the second conductive type second clad layer and the like are regrown by MOCVD or the like, they can be laminated with good crystallinity. The thickness of the second etching stop layer (6) is usually preferably 2 nm or more.

The first etching stopper layer (7) is made of In _b G
A layer represented by a _1-b P (0 ≦ b ≦ 1) is preferable.
When aAs is used as a substrate, b = 0.45 is usually used in a system without distortion. The thickness of the first etching stop layer is usually 5 nm or more, preferably 10 nm or more. If the thickness is less than 5 nm, etching may not be able to be prevented due to disorder of the film thickness or the like. On the other hand, depending on the film thickness, a strain system can be used,
It is also possible to use b = 0, b = 1, and the like.

The cap layer (10) is used as a protective layer for the current blocking layer (9) in the first growth and at the same time to facilitate the growth of the second conductive type second clad layer (8). Before the device structure is obtained, some or all of them are removed. Since it is necessary for the current blocking layer (9) to literally block the current and not substantially flow, the conductivity type is preferably the same as that of the first conductivity type cladding layer (3) or undoped. In addition, it is preferable that the refractive index is smaller than that of the second conductive type second clad layer (8), which is usually made of the same material as the second conductive type first clad layer (5). Usually, the current blocking layer (9) is made of Al _z Ga _{1 -z} As (0 <z ≦ 1), so that the second conductive type second cladding layer (8) has a mixed crystal ratio of Al.
_{In the case of v} Ga _1-v As material, z ≧ v, In _0.49 Ga _0.51 P
In the case of x, it is preferable that x <0.45 and z> 0.5. Further, in relation to the above-described barrier layer, x <v ≦ z
It is preferable that

It is preferable to provide a contact layer (11) on the second conductive type second clad layer (8) for the purpose of lowering the contact resistivity of the electrode. Contact layer (11)
Is usually made of a GaAs material. In this layer, the carrier concentration is usually made higher than the other layers in order to lower the contact resistivity with the electrode. The thickness of the buffer layer (2) is usually 0.1 to 1 μm, the thickness of the first conductivity type cladding layer (3) is 0.5 to 3 μm, and the quantum well and light The guide layer and the barrier layer have a thickness of 0.0002 to 0.2 μm per layer, and the thickness of the second conductive type first cladding layer (5) is 0.05 to 0.4 μm. ) Has a thickness of 0.5 to 3 μm, the thickness of the cap layer (10) is 0.005 to 0.5 μm, the thickness of the current blocking layer (9) is 0.3 to 2 μm, and the thickness of the contact layer is It is selected from the range of 0.3 to 10 μm.

The semiconductor light emitting device shown in FIG. 2 is constituted by further forming electrodes (12) and (13). Electrode (1
In the case of p-type, 2) is formed by sequentially depositing, for example, Ti / Pt / Au on the surface of the contact layer (11), followed by alloying. On the other hand, the electrode (13) is formed on the surface of the substrate (1). In the case of an n-type electrode, for example, AuGe / Ni / Au is sequentially deposited on the surface of the substrate (1) and then formed by alloying. You.

The wafer on which the electrodes are formed is cleaved and divided into laser bars, and at least one end face forming a resonator is irradiated with plasma of optimized energy in a vacuum. I do. In the present invention,
End face processing after electrode formation, that is, electrodes can be formed on the wafer before cleavage for exposing the end face, for example, compared to the case where a semiconductor layer is formed on the end face to make it transparent, the laser after cleavage is This eliminates the need for a complicated process of forming electrodes on each of the bars, which is advantageous in manufacturing.

The plasma to be irradiated is 1 such as Ar plasma.
Group 8 element plasma or N ₂ plasma is preferred. The energy of the irradiated Ar plasma is 25 eV or more and 300
eV or less. If it is less than 25 eV, the effect of Ar plasma irradiation is small, and the problem of sudden deterioration under rated output operation of the laser for a long period of time cannot be solved. 30 energy
Above 0 eV, disordering occurs too severely, so that the laser is more likely to break down, leading to a reduction in the maximum output in the initial characteristics. At this time, a preferable condition of the plasma irradiation is a current density of 1 μA / cm.
^The time is ^{2 to 1} mA / cm ² and the time is 15 seconds to 30 minutes.

The end face may subsequently be provided with an asymmetric coating. Normally, a single-layer AlO _x film, SiO _x film, SiN _x film, or the like is formed on the front end face for extracting light to form a low reflection surface, and AlO _x / α-Si, SiO _x /
A high reflection surface is formed by forming a plurality of layers of TiO _x or the like. At this time, the preferred reflectance is 0.5 to
20%, more preferably 2 to 10%, 50 to 50% on the rear end face side
It is 98%, more preferably 85-95%. In the present invention, it is preferable that the asymmetric coating of the end face is performed after the plasma irradiation without breaking the vacuum. A laser bar coated with an asymmetrical end face is divided into chips and used as a laser diode (LD).

FIG. 1 is a perspective view of the semiconductor laser of the present invention. The end face and the area 15 near the end face are high-resistance areas formed by plasma irradiation, whereby the quantum well near the end face is disordered. Therefore, the vicinity of both end faces is made transparent at the laser oscillation wavelength. Also, in the shaded area, each layer is exposed to plasma to inactivate carriers and increase resistance, and current is difficult to flow. There is little deterioration in characteristics.

In a semiconductor laser having a first conductivity type cladding layer, an active layer including a quantum well, and a second conductivity type cladding layer on a semiconductor substrate, the semiconductor laser according to the present invention may be provided on at least one end face forming a resonator. 25 eV or more 3
A plasma having energy of not more than 00 eV is irradiated from the end face side, whereby the semiconductor substrate, the first conductive type clad layer, the active layer including the quantum well, and the second conductive type clad layer are near the end face. In other words, a high-resistance region is formed in the active layer, that is, the region has a higher resistance than an adjacent portion in the same layer that is not affected by plasma irradiation, and the high-resistance region near the end face of the active layer including the quantum well is disordered. However, in such a semiconductor laser, a so-called window structure can be manufactured very easily and stably, and at the same time, a problem such as a reactive current does not occur by manufacturing a high-resistance region. Thus, a semiconductor laser diode having a high output and a long life can be easily realized.

Although the above description relates to a groove type semiconductor laser having a refractive index guiding mechanism, the present invention relates to a ridge type semiconductor laser, a laser having a gain guiding type mechanism, and the like. Instead, the present invention can be similarly applied to any semiconductor laser as long as it has the features described in the claims of the present application.

[0029]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. Example 1 A groove type laser device shown in FIG. 2 was manufactured as follows.

Carrier concentration 1 × 10¹⁸cm^-3N-type Ga
Buffer layer (2) on As substrate (1) by MBE method
1 × 10 μm thick carrier concentration 1 × 10¹⁸cm^-3of
n-type GaAs layer, first conductivity type clad layer (3)
μm thick carrier concentration 1 × 10¹⁸cm^-3N-type Al
_0.35Ga_0.65As layer, then 24 nm thick Ando
GaAs light guide layer, 6 nm thick undoped In
_0.2Ga_0.8As quantum well layer, 10 nm thick Ando
GaAs barrier layer, 6 nm thick undoped In _0.2G
a_0.8As quantum well layer and undoped 24 nm thick
Double quantum well in which GaAs light guide layers are sequentially laminated
Active layer (4) having (DQW) structure, second conductivity type first
0.1 μm thick clad layer (5), carrier concentration
1 × 10¹⁸cm^-3P-type Al_0.35Ga_0.65As layer, second
10 nm-thick carrier as etching stop layer (6)
Concentration 1 × 10¹⁸cm^-3P-type GaAs layer, first etchin
20 nm thick and a carrier concentration of 5 × as a blocking layer (7).
10¹⁷cm^-3N-type In_0.49Ga_0.51P layer, current blow
0.5 μm thick, carrier concentration 5 × as a backing layer (9)
10¹⁷cm^-3N-type Al_0.4Ga_0.6As layer, cap layer
(10) thickness 10 nm, carrier concentration 1 × 10¹⁸
cm^-3N-type GaAs layers were sequentially laminated.

Next, a mask of silicon nitride was provided in a portion other than the current injection region of the uppermost layer. In this case, the width of the opening of the silicon nitride mask was 1.5 μm. Etching was performed using the first etching stop layer as an etching stop layer to remove the cap layer (10) and the current block layer (9) in the current injection region. The etchant used at this time was sulfuric acid (98 wt%) and hydrogen peroxide (30 wt%).
Aqueous solution) and water mixed at a volume ratio of 1: 1: 5, and performed at 25 ° C. for 30 seconds.

Then, HF (49%) and NH ₄ F (40
%) In an etching solution mixed at a ratio of 1: 6 to remove the silicon nitride layer for 2 minutes and 30 seconds, and further etch the first etching stop layer in the current injection region using the second etch stop layer as an etch stop layer. It was removed (FIG. 7). The etchant used at this time was hydrochloric acid (35 wt.
%) And water at a ratio of 2: 1 at a temperature of 25%.
C. and the time was 2 minutes.

Thereafter, the second conductive type second layer is formed by MOCVD.
Carrier concentration 1 × 10 as cladding layer (8)¹⁸cm^-3
P-type Al_0.35Ga_0.65Embedded portion of As layer (current injection
Grown to a thickness of 2 μm at the
Contact layer (1) to maintain good contact with the electrode
As 1), the thickness is 3 μm, the carrier concentration is 1 × 10¹⁹cm
^-3Was grown to form a laser device.
The width W of the current injection region of the laser element,
Between the second cladding layer of the second conductivity type and the first cladding layer of the second conductivity type
The width in the plane was 2.2 μm.

Next, after depositing Ti / Pt / Au on the p-side and AuGe / Ni / Au on the n-side in order,
After forming an electrode by alloying for one minute, the laser is turned into a so-called bar state, and both ends are evacuated in vacuum at an average energy of 100 eV and an ion current density of 20 μA /
Irradiated with Ar ² cm ² for 3 minutes. Thereafter, one layer of alumina is continuously formed on the front end face and four layers of alumina / amorphous silicon / alumina / amorphous silicon are formed on the rear end face without breaking the vacuum in the Ar plasma treatment.
% / 90% asymmetric coating was applied. FIG. 3 shows the initial current light output characteristics of the device obtained as a result. 2
The threshold current at 5 ° C. was 21 mA. Also, 20
FIG. 4 shows the life test results in the APC mode at 0 mW output and 70 ° C. Further, one of the fabricated devices was processed into a sample for observation with a transmission electron microscope, and the bulk state was compared with the vicinity of the active layer near the end face.
As a result, it was confirmed that in the vicinity of the end face irradiated with the Ar plasma, the crystallinity near the active layer was broken and disorder occurred. (Comparative Example 1) Except that the Ar plasma irradiation was not performed,
The procedure was exactly the same as in Example 1. FIG. 5 shows the initial current light output characteristics. The threshold current at 25 ° C. was 21 mA. FIG. 6 shows the results of a life test in the APC mode at 200 mW output and 70 ° C. (Comparative Example 2) The energy of the Ar plasma to be irradiated was 20
Except for eV, the procedure was exactly the same as in Example 1. FIG. 7 shows the initial current light output characteristics. The threshold current at 25 ° C. was 21 mA. FIG. 8 shows the life test result in the APC mode at 200 mW output and 70 ° C. (Comparative Example 3) The energy of the Ar plasma to be irradiated was 60
The procedure was exactly the same as in Example 1 except that 0 eV was set. FIG. 9 shows the initial current light output characteristics. The threshold current at 25 ° C. was 23 mA. Also, as shown in FIG.
Since the output did not reach 00 mW, the life test could not be performed. (Example 2) The procedure was the same as that of Example 1 except that N ₂ plasma was irradiated for 2 minutes instead of irradiating Ar plasma for 3 minutes to both end surfaces of the laser bar. FIG. 10 shows the initial current light output characteristics of the device obtained as a result. 25
The threshold current at 21 ° C. was 21 mA. Also, 200
FIG. 11 shows a life test result in the APC mode at a mW output of 70 ° C. Further, one of the fabricated devices was processed into a sample for observation with a transmission electron microscope, and the bulk state was compared with the vicinity of the active layer near the end face.
As a result, it was confirmed that near the end face irradiated with the N ₂ plasma, the crystallinity near the active layer was broken and disorder occurred.

[0035]

According to the semiconductor laser of the present invention, the vicinity of the end face of the active layer including the quantum well is appropriately disordered and has a high resistance, and the semiconductor substrate, the first conductivity type cladding layer,
Since the vicinity of the end surface of the second conductivity type cladding layer is made high in resistance, it has excellent characteristics such as high output and long life without any problem such as loss due to reactive current. The method for manufacturing a semiconductor laser of the present invention is a simple method of irradiating at least one end face forming a resonator with plasma in a specific energy range, and has no problem such as loss due to reactive current, high output, and long life. A semiconductor laser can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a perspective view of a semiconductor laser of the present invention.

FIG. 2 is an explanatory cross-sectional view of a semiconductor laser according to an embodiment of the present invention, as viewed from a cavity direction.

FIG. 3 is a graph showing current light output characteristics of the semiconductor laser of Example 1 of the present invention.

FIG. 4 is a graph showing the results of a life test in the APC mode at 70 ° C. and 200 mW output of the semiconductor laser of Example 1 of the present invention.

FIG. 5 is a graph showing initial current light output characteristics of the semiconductor laser of Comparative Example 1.

FIG. 6 shows a 200 mW output of the semiconductor laser of Comparative Example 1,
It is a graph which shows the result of the life test in APC mode at 0 ° C.

FIG. 7 is a graph showing initial current light output characteristics of the semiconductor laser of Comparative Example 2.

FIG. 8 shows a 200 mW output of the semiconductor laser of Comparative Example 2;
It is a graph which shows the result of the life test in APC mode at 0 ° C.

FIG. 9 is a graph showing the initial current light output characteristics of the semiconductor laser of Comparative Example 3.

FIG. 10 is a graph showing current light output characteristics of the semiconductor laser according to Example 2 of the present invention.

FIG. 11 shows 200 mW of the semiconductor laser according to the second embodiment of the present invention.
It is a graph which shows the output and the result of the life test in APC mode at 70 degreeC.

[Explanation of symbols]

1: semiconductor substrate 2: buffer layer 3: first conductivity type cladding layer 4: active layer 5: second conductivity type first cladding layer 6: second etching stop layer 7: first etching stop layer 8: second conductivity type Second cladding layer 9: current blocking layer 10: cap layer
11: contact layer 12: electrode 13: electrode 14:
Destruction 15: High resistance area

Claims (7)

[Claims] 1. A first conductivity type cladding layer on a semiconductor substrate,
In a semiconductor laser having an active layer including a quantum well and a second conductivity type cladding layer, at least one end face forming a resonator is irradiated with plasma having energy of 25 eV or more and 300 eV or less from the end face side. Semiconductor laser. 2. The semiconductor laser according to claim 1, wherein the vicinity of the end face of the active layer including the quantum well is disordered. 3. The semiconductor laser according to claim 1, wherein the semiconductor substrate is a GaAs substrate, and the active layer contains In or Ga as an element. 4. The semiconductor laser according to claim 1, wherein the plasma is a group 18 element plasma or N ₂ plasma. 5. A first conductivity type clad layer on a semiconductor substrate,
In a method of manufacturing a semiconductor laser having an active layer including a quantum well and a second conductive type clad layer, forming the first conductive type clad layer, an active layer including a quantum well and a second conductive type clad layer on the semiconductor substrate After that, at least one end face forming the resonator is irradiated with plasma having an energy of 25 eV or more and 300 eV or less from the end face side. 6. The method according to claim 5, wherein the plasma is plasma of a group 18 element or N ₂ plasma. 7. The method for manufacturing a semiconductor laser according to claim 5, wherein an anti-reflection film and / or a high-reflection film is formed on the end face without breaking the vacuum after the plasma irradiation.