JP2002190644A - Semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element which has a ridge structure and an edge current non-injection region and can improve reliability under high output oscillation. SOLUTION: An n-GaAs buffer layer 2, an n-AlGaAs lower clad layer 3, an n- or i-InGaP lower optical waveguide layer, an InGaAsP quantitative well active layer 5, a p- or i-InGaP upper optical waveguide layer 6, a p-AlGaAs first upper clad layer 7, a p or i-InGaP etching blocking layer 8, a p-AlGaAs second upper clad layer 9, and a p-GaAs contact layer 10 are grown on an n-GaAs substrate. Resist 20 is coated on the substrate, two ridge groove parts are opened to etch into grooves, the resist 20 around an element is removed to selectively remove the contact layer, and then the resist 20 is removed. An SiO2 film 12 is formed on the entire surface of the substrate, an opening is made in the ridge part, and thereafter a p-electrode is formed in a region other than the element periphery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device having a ridge structure and a current non-injection region near a cavity end face, a method of manufacturing the same, and a solid-state laser device having the semiconductor laser device. .

[0002]

2. Description of the Related Art In a semiconductor laser device, the current density at the end face increases under high-power oscillation, so that a non-radiative recombination current increases and end face destruction occurs, so that high reliability can be obtained. It has become difficult. For this reason, many structures for preventing current injection near the resonator end face have been proposed.

[0003] For example, IEEE PHOTONICS TECHNOLOGY LETT
In ERS, vol. 12, No. 1 Jan. 2000, p. 13-15, a semiconductor laser device in which no current is injected without forming an electrode near an end face on a contact is reported. However, in this structure, the current spreads through the contact layer near the end face, so that the non-current injection at the end face is incomplete.

In Japanese Patent Application Laid-Open No. 11-354880, an etching stop layer and a contact layer are laminated on a clad layer, and a contact layer near an end face is removed until an underlying etch stop layer is exposed. A semiconductor laser device on which an electrode is formed up to an end surface has been proposed. Also in this structure, the electrode is in contact with the underlying etching stop layer near the end face, and current non-injection at the end face is incomplete.

On the other hand, in the case of forming a current non-injection region as described above in a semiconductor laser device having a ridge structure, a step of forming a ridge groove and a step of removing a contact layer in order to eliminate end face current non-injection. Must be performed,
The process is complicated. When photolithography is performed again after the formation of the ridge groove, a resist material is formed in the exposed etching groove by spin coating so as to be thicker than the flat portion, and further, NH ₃ : H for selectively etching the contact layer. _Since the resist is cured by the ₂ O ₂ mixed aqueous solution, the resist stripping property is reduced and the resist remains in the groove. If the resist remains, there is a problem that the groove is contaminated and the adhesiveness of the insulating film is reduced, and a cavity or the like is formed in a later electrode sintering heat treatment step or the like, so that the heat dissipation during laser driving is reduced. Further, there is a problem that, after forming the groove, if the layer is left for a long time, the layer exposed on the side surface of the groove is oxidized, crystal defects increase, and laser driving stops. In particular, when the composition of the layer exposed on the groove side surface is AlGaAs, the layer is easily oxidized.

[0006]

In order to solve the above-mentioned problems, the order of the step of forming the ridge groove and the step of removing the contact layer for non-injection of the end face current is first changed. It is conceivable to form the ridge groove after removing the contact layer.However, after removing the contact layer near the end face, the underlying cladding layer is oxidized, and the reproducibility of the etching depth of the ridge groove etching is reduced. There is a problem that it is not good. Since the groove depth determines the equivalent refractive index step ΔNeff related to the profile of the laser beam, it is not preferable to employ this process in which reproducibility cannot be obtained.

In view of the above circumstances, the present invention provides a semiconductor laser device having a ridge structure and an end face current non-injection structure and having high reliability from a low output to a high output, and obtaining the semiconductor laser device with a high yield and a simple process. It is an object of the present invention to provide a manufacturing method and a solid-state laser device having the semiconductor laser element and having high reliability under high output oscillation.

[0008]

According to a semiconductor laser device of the present invention, a substrate, a semiconductor layer including an active layer, a clad layer, and a contact layer are laminated in this order, and are continuously formed from one of two cavity facets to the other. Two exposed portions having a depth to expose the semiconductor layer are formed side by side, a ridge portion is formed between the two exposed portions, and a current injection window is formed on the ridge portion. Semiconductor laser device,
At least one of the resonator end faces of the ridge portion has a contact layer near the end face removed, and a region other than the current injection window on the contact layer, and a clad layer exposed on the contact layer near the end face removed and exposed. An insulating film is formed so as to cover the portion, and an electrode is formed at least on the contact layer exposed at the current injection window.

The uppermost layer in the stacking direction of the semiconductor layers is an etching stopper layer, a cladding layer is provided on the etching stopper layer, and the layer exposed at the bottom of the exposed portion is the etching stopper layer. Is also good.

The cladding layer may be made of AlGaAs, and the contact layer may be made of GaAs.

Further, the etching stop layer may be made of InGaP.

Further, further below the etching stopper layer,
Another cladding layer having the same conductivity as that of the cladding layer and substantially the same refractive index and lattice-matching to the substrate may be provided. In the case where the other cladding layer is not provided and the lower layer of the etching stop layer is an optical waveguide layer,
This optical waveguide layer is preferably made of InGaP.

[0013] The position of the side surface of the contact layer exposed at the exposed portion may be a position retreated from a surface extending from the side surface of the clad layer toward the contact side.

The region where the contact layer near the end face is removed is 5 μm or more from the end face toward the inside of the device including the end face.
It is desirable that the thickness be within the range of 0 μm or less.

The method for manufacturing a semiconductor laser device according to the present invention comprises:
A step of laminating a cladding layer and a contact layer in this order on the semiconductor layer including the active layer, and forming a resist having two rod-shaped openings continuous from one end of the resonator end face to the other on the contact layer; A step of forming two grooves by etching the cladding layer and the contact layer using the resist as a mask to form a ridge between the two grooves; and forming at least one of the ridges in the resist. Forming an opening near the cavity end face, using the resist as a mask,
A step of selectively etching and removing the contact layer near the end face; and a step of removing the resist.

When the cladding layer is made of AlGaAs and the contact layer is made of GaAs, the contact layer is made of N
It is desirable to perform etching with a mixed aqueous solution of H ₃ : H ₂ O ₂ .

The solid-state laser device according to the present invention comprises: an excitation light source;
A solid-state laser device comprising a solid-state laser crystal that emits laser light when excited by the excitation light from the excitation light source, wherein the excitation light source comprises the semiconductor laser device of the present invention having the above-described configuration.

The region from which the contact layer is removed is
The “at least one of the resonator end faces of the ridge portion” may be both of the two resonator end faces, and may be removed not only by the ridge portion but also by the width of the element, or The contact layer near the four end faces of the resonator end face and the end face orthogonal to the resonator end face, that is, the contact layer around the element may be removed.

[0019]

According to the semiconductor laser device of the present invention, since the contact layer is removed near the end face and the insulating film is formed thereon, no current is injected near the end face of the optical resonator. The current density at the end face can be reduced, and the heat generation at the end face can be reduced. Therefore,
Since end face destruction or the like due to heat generation due to non-radiative recombination current can be suppressed, a highly reliable beam from low output to high output can be obtained.

The uppermost layer in the stacking direction of the semiconductor layers is an etching stopper layer, and the cladding layer is provided on the etching stopper layer, so that the etching for forming the ridge groove can be stopped accurately. Highly controllable groove width.

When the cladding layer is made of AlGaAs and the contact layer is made of GaAs, the etchant is N
By selecting a mixed aqueous solution of H ₃ : H ₂ O ₂ , only the contact layer can be selectively etched.

Since the etching stopper layer is made of InGaP, the composition of the upper layer is made to have a selectivity to InGaP, so that the etching can be accurately stopped on the etching stopper layer. Especially when the cladding layer is made of AlGaAs and the contact layer is made of GaAs, the selectivity is high.

The position of the side surface of the contact layer exposed at the exposed portion is a position retracted from the surface of the cladding layer extending toward the contact side, so that the side of the insulating film on the groove side surface of the insulating film is formed. High coverage.

The area from which the contact layer is removed is preferably in the range from 5 μm to 50 μm from the end face to the inside of the device, including the end face. It is not preferable because the current injection region cannot be formed and the end face is deteriorated due to heat generation. On the other hand, when it is larger than 50 μm, light loss due to light absorption in the non-current injection region increases, and the light output decreases.

According to the method of manufacturing a semiconductor laser device of the present invention, the resist used for forming the ridge groove includes:
By forming an opening for removing the contact layer near the end face and performing double exposure, it is possible to prevent the above-described hardening of the resist inside the groove or oxidation of the groove side wall. A highly accurate non-injection region can be manufactured, and a highly reliable semiconductor laser device up to high output can be provided.

When the cladding layer is made of AlGaAs and the contact layer is made of GaAs, the contact layer is made of N
By etching with an H ₃ : H ₂ O ₂ mixed aqueous solution, only the contact layer can be selectively removed by etching.

According to the solid-state laser device of the present invention, in a solid-state laser device comprising an excitation light source and a solid-state laser crystal excited by the excitation light from the excitation light source to emit laser light, Since the semiconductor laser device is provided, the reliability under high output oscillation is high.

[0028]

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

A semiconductor laser device according to an embodiment of the present invention will be described along the manufacturing process. FIG. 1 is a perspective view showing a process of manufacturing the semiconductor laser device.

As shown in FIG. 1A, n-G is deposited on a (1.0.0) n-GaAs substrate 1 by metal organic chemical vapor deposition.
aAs buffer layer 2, n-Al _0.65 Ga _0.35 As lower cladding layer 3, n or i-In _0.5 Ga _0.5 P lower optical waveguide layer 4, In _0.12 Ga _0.88 As _0.75 P _0.25 quantum well active layer 5, p or i- In _0.5 Ga _0.5 P upper optical waveguide layer 6, p-Al _0.65 Ga _0.35 As first upper cladding layer 7,
p or i-In _0.5 Ga _0.5 P etching stop layer 8,
p-Al _0.65 Ga _0.35 As second upper cladding layer 9, p-
A GaAs contact layer 10 is grown. The thickness of the first upper cladding layer 7 is set so that the waveguide in the groove at the center of the resonator can achieve high-index-refractive-index waveguide.

Thereafter, a resist 20 (not shown) is applied, and is held on a hot plate at 100 ° C. for one minute, and baking is performed. A resist 20 was applied at a light exposure of 100 mJ through a mask (see FIG. 2) in which grooves 21 having a width of 10 μm were opened at intervals of 50 μm so as to be parallel to the orientation flat and perpendicular to the cleavage plane of the laser. An opening is formed in the resist 20 by irradiating the wafer and dissolving the resist 20 in the irradiated area with a developing solution.

Next, as shown in FIG. 1B, the p-GaAs contact layer 10 and the p-AlG
The aAs second upper cladding layer 9 is removed by etching. Etching stops automatically at the InGaP etching stop layer 8 which is insoluble in tartaric acid.

Next, as shown in FIG.
A non-implanted region 31 is used for a photomask to be exposed.
Placed evenly on the end line and the element separation line
And illuminate with an exposure of 100 mJ.
And then dissolve the resist 20 in the irradiated area with a developing solution.
Then, a non-implanted region 31 is opened in the resist 20. N at room temperature
H _Three: H₂O₂= 1: 50 Wafer in mixed aqueous solution for 10 seconds
Immersion to select the p-GaAs contact layer 10 in the non-implanted region 31.
Selectively etch. p-GaAs contact layer 10
At the time of etching, at the same time, the p-GaAs
The side surface of the tact layer 10 recedes. Resist 20
Dissolve in solution.

Next, as shown in FIG. 1C, the P-CV
A 150 nm SiO ₂ insulating film 12 is formed by a D apparatus. p
Since the side wall inside the groove of the -GaAs contact layer 10 recedes, the coverage of the insulating film 12 is improved. Next, the SiO
_{(2) A} resist is applied on the insulating film 12 and an opening is formed in a region of a ridge portion having a width of 50 μm, 3 μm (a in the figure) from the non-implanted region, and 3 μm (b in the diagram) from an end of the ridge. Photomask is superimposed on the wafer, and UV light is
Irradiate with an exposure of 0 mJ. The resist in the irradiation area is dissolved with a developing solution to open the resist. Opening Si with BHF solution
After dissolving the O ₂ film 12, the resist is dissolved with an organic alkali solution. The p-side electrode 13 is formed by a lift-off method in a region excluding the non-injection region and the vicinity of the element isolation cleavage end face.

When the p-GaAs contact layer 10 is etched, the p-GaAs contact layer 10 in the ridge groove is simultaneously formed.
Side surface recedes, and p electrode 13 laminated on SiO ₂ film 12
Is also improved.

Thereafter, the substrate is polished to form an n-side electrode 14. Thereafter, a high-reflectance coat and a low-reflectance coat are applied to the resonator surface of the laser array bar formed by cleaving the sample at the set positions on both end surfaces. The laser array bar is cleaved to each laser element, and bonded to the heat sink with an In brazing material so that the p-plane of the element is in contact with the heat sink.

The semiconductor laser device according to the present embodiment is
If the contact layer around the element was removed and the insulating film 12 was peeled off during cleavage, when the p-side was bonded to the heat sink by junction down, the heat sink and the insulating film were peeled off by the brazing material Even if conduction occurs in the region, no ohmic contact is made and no current flows because the contact layer is removed. The p-electrode is turned up together with the insulating film and covers the side surface of the element, so that even when the p-electrode and the n-type conductive layer of the element come into contact with each other, there is an advantage that a short circuit is unlikely to occur as described above.

In the above embodiment, the case where the n-type GaAs substrate is used is described. However, a p-type conductive substrate may be used. In this case, if the conductivity of each of the above layers is reversed. Good.

As a method for growing each layer, a molecular beam epitaxial growth method using a solid or gas as a raw material may be used.

The width (light emission width) of the ridge is not limited to 50 μm, but can be any width.

The width of the ridge groove is not limited to 10 μm, and the grooves may be formed on both sides of the ridge portion up to the end face at the maximum.

The length of the non-implanted region (that is, the region where the contact layer is removed) is not less than 5 μm and not more than 50 μm from the cleavage plane.
What is necessary is just the following range.

The length of the non-injection region does not have to be formed on the outer periphery of the device as shown in the above embodiment, and is limited to only the current light emitting region (ridge) and not one end but one end. There may be.

The insulating film may be formed by a film forming method other than the P-CVD method. The material is not limited to SiO ₂ , as long as it has insulation and workability. For example, SiN may be used. When SiN is used, the film quality is more dense,
Leakage current due to defects and the like can be reduced, and improvement in yield is expected.

In the above embodiment, the p-electrode is not formed in the non-implanted region. However, since the non-implanted region is formed with an insulating film, no current is injected. May be formed.

Next, an example in which the semiconductor laser device of the above embodiment is provided as an excitation light source of a solid-state laser device will be described. FIG. 3 shows a schematic configuration diagram of the solid-state laser device.

As shown in FIG. 3, the solid-state laser device according to the present embodiment is a solid-state laser device that generates second harmonics. A lens 72 that is provided for an excitation light source and condenses the excitation light emitted from the semiconductor laser element 71, a solid-state laser crystal 73 that oscillates with the condensed excitation light, and a solid-state laser resonator together with the solid-state laser crystal 73. An output mirror 74 consisting of a concave mirror that forms a coating film that has high reflection on the oscillation light of the solid-state laser on the semiconductor laser element side of the solid-state laser crystal 73 and has no reflection on the oscillation light of the semiconductor laser element 76 are formed. The resonator of the solid-state laser is formed by an output mirror 74 composed of the concave mirror and the coating film 76, and converts the wavelength of the laser oscillated from the solid-state laser crystal 73 into a half wavelength in the resonator. It has a KNbO ₃ nonlinear crystal 75 for generating harmonics. The solid-state laser crystal 73 may be made of Nb: YVO ₄ or the like, and the nonlinear crystal 75 may be made of KTP or the like. Further, a semiconductor laser element 71, a solid-state laser crystal 73,
The temperature of the nonlinear crystal 75 is controlled by a Peltier device (not shown).

In this apparatus, a part of the emitted light is branched by a beam splitter 77 to a light receiving element 78, and the optical output of the semiconductor laser element 71 is fed back so that the light intensity becomes constant, and APC (automatic power control) driving is performed. Is what you do.

The semiconductor laser device of the present invention can be used as an array type semiconductor laser device or mounted on an integrated circuit or the like, in addition to the excitation light source of the solid-state laser device according to the above embodiment.

Since the semiconductor laser device and the solid-state laser device of the present invention can emit highly reliable laser light from low output to high output, they can be used in the fields of high-speed information / image processing and communication, measurement, medical care, and printing. It can be applied as a light source.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a manufacturing process of a semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a view showing a state of alignment of a mask when opening a non-injection region.

FIG. 3 is a schematic configuration diagram showing a solid-state laser device provided with the semiconductor laser element of the present invention.

[Explanation of symbols]

1 (1.0.0) n-GaAs substrate 2 n-GaAs buffer layer 3 n-Al _0.65 Ga _0.35 As lower cladding layer 4 n or i-In _0.5 Ga _0.5 P lower optical waveguide layer 5 In _0.12 Ga _0.88 As _0.75 P _0.25 quantum well active layer 6 p or i-In _0.5 Ga _0.5 P upper optical waveguide layer 7 p-Al _0.65 Ga _0.35 As first upper cladding layer 8 p or i-In _0.5 Ga _0.5 P etching stop layer 9 p-Al _0.65 Ga _0.35 As second upper cladding layer 10 p-GaAs contact layer 12 SiO ₂ film 13 p electrode 14 n electrode

Claims (10)

[Claims] 1. A substrate, a semiconductor layer including an active layer, a clad layer, and a contact layer are laminated in this order, and the semiconductor layer is continuously exposed from one end to the other of the two resonator end faces. The two parts are formed side by side,
A semiconductor laser device in which a ridge portion is formed between the exposed portions of the book and a current injection window is formed on the ridge portion, wherein at least one of the resonator end surfaces of the ridge portion has the contact near the end surface thereof; An insulating film is formed so as to cover the exposed clad layer and the exposed portion where the layer has been removed, the region excluding the current injection window on the contact layer, and the contact layer near the end face has been removed and exposed. A semiconductor laser device, wherein an electrode is formed on the contact layer exposed at least in the current injection window. 2. The semiconductor device according to claim 1, wherein an uppermost layer of the semiconductor layers in the stacking direction is an etching stopper layer, the cladding layer is provided on the etching stopper layer, and a layer exposed at the bottom of the exposed part is the etching stopper layer. 2. The semiconductor laser device according to claim 1, wherein said semiconductor laser device is a blocking layer. 3. The semiconductor laser device according to claim 1, wherein said cladding layer is made of AlGaAs, and said contact layer is made of GaAs. 4. The semiconductor laser device according to claim 2, wherein said etching stop layer is made of InGaP. 5. Under the etching stopper layer, the cladding layer has the same conductivity as the cladding layer and has substantially the same refractive index;
5. The semiconductor laser device according to claim 2, wherein another clad layer lattice-matched to said substrate is provided. 6. The method according to claim 1, wherein a position of a side surface of the contact layer exposed to the exposed portion is a position retreated from a surface of the cladding layer extending toward the contact side. 5. The semiconductor laser device according to claim 5. 7. A region where the contact layer is removed near the end face includes an end face and extends from the end face toward the inside of the device.
7. The semiconductor laser device according to claim 1, wherein the semiconductor laser device has a range of not less than μm and not more than 50 μm. 8. A step of laminating a cladding layer and a contact layer in this order on a semiconductor layer including an active layer; and forming two rod-shaped openings continuous from one end of the resonator end face to the other on the contact layer. Forming a resist having a mask, using the resist as a mask, etching the cladding layer and the contact layer to form two grooves, and forming a ridge portion between the two grooves; Forming an opening near at least one resonator end face of the ridge portion, using the resist as a mask, selectively etching and removing a contact layer near the end face, and removing the resist. A method for manufacturing a semiconductor laser device, comprising: 9. The semiconductor laser device according to claim 8, wherein said cladding layer is made of AlGaAs, said contact layer is made of GaAs, and said contact layer is etched with an aqueous solution of NH ₃ : H ₂ O _2. Manufacturing method. 10. A solid-state laser device comprising: an excitation light source; and a solid-state laser crystal that emits laser light when excited by the excitation light from the excitation light source, wherein the excitation light source is any one of claims 1 to 7. A solid-state laser device, comprising: a semiconductor laser element.