JP2001135895A - Semiconductor light emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To offer a high performance of semiconductor light emitting device which can maintain a low threshold current and a high efficiency and which is free from COD(Catastrophic Optical Damage) even when the optical output is high. SOLUTION: The semiconductor light emitting device comprises a compound semiconductor layer including an active layer on a substrate, a protective film having an opening and being formed on the compound semiconductor layer, and another compound semiconductor layer of ridge type which has a smaller refractive index than the active layer and is formed on the opening. In the both ends of an optical waveguide path, a bandgap of the active layer becomes larger than that of a current injected region in the center of the optical waveguide path.

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 useful as a semiconductor laser or the like, and more particularly to a semiconductor laser having high reliability in high-power operation.

[0002]

2. Description of the Related Art In a conventional semiconductor laser device, when the light output is increased, the light density at the emission end face increases, the temperature rises due to light absorption at the end face, and irreversible destruction (hereinafter referred to as irreversible destruction).
"COD" (Catastrophic Optica)
l Damage)), and the laser oscillation stops.

In order to obtain high output while preventing such COD, the following two lasers are mainly used at present. One is a broad area laser, which enlarges the light emitting area to increase the total light output while keeping the light density low. However, since the broad area laser has a large light emitting area, it is difficult to operate stably in a single mode.

The other is a laser device in which a non-absorbing region that does not substantially absorb light is provided on an end face, and a reflecting mirror portion on the end face is a non-absorbing area (NAM area).
Normal NAM laser (Non-Absorbing Mi)
rr). Since the NAM laser can prevent light absorption at the end face, COD can be completely suppressed. In addition, the structure near the active layer where stimulated emission is performed is not limited as in the case of the broad area laser, and can be freely designed independently of the non-absorbing region on the end face. Can be operated.

As a typical example of manufacturing such a NAM laser, (1) Disordering process of quantum well structure in edge region (H. Nakashima et al., Japanese Journal of Appl.
iedPhysics, vol.24, No.8, L647 (1985)) and (2) Active layer burying process in the edge region (H. Naito et a
l., IEEE Journal Quantum Electronics, vol.QE-25, 1
495 (1989)).

The above (2) has an advantage that excellent laser characteristics can be realized, but has a disadvantage that the element structure and the manufacturing process are complicated. In the above (1), there is an advantage that the manufacturing process is easy because impurity diffusion or vacancy diffusion of constituent elements is used. However, in the case of impurity diffusion, the internal loss increases due to the high concentration of impurities in the active layer. On the other hand, in the case of vacancy diffusion of constituent elements, a relatively high-temperature process is required, so that process damage to the active layer is caused. Is concerned.

A window structure laser having a ridge structure, which is manufactured by using the quantum well structure disordering process in the end region described in (1), is described in Japanese Patent Application Laid-Open No. Hei 2-203585. As a result, a high output laser having a high COD level can be realized. JP-A-10-2900
In the conventional window structure laser device described in Japanese Patent No. 43-43, a first conductive type clad layer, an active layer, and a second conductive type clad layer are formed on a substrate, and impurities are formed in an end region including a laser light emitting surface. The active layer is formed by diffusing (zinc (Zn)) to form a mixed crystal in the active layer. However, there is a problem that a considerably complicated structure is required to suppress a leak current at an end portion.

On the other hand, the thickness of the cladding layer above the active layer in the non-ridge portion is determined using the crystal growth rate during crystal growth,
A method of forming a protective film on a non-ridge portion and regrowing the ridge portion has been proposed (JP-A-5-121822, JP-A-9-199791, JP-A-10-32).
6934-8, JP-A-10-326945, etc.). This selective ridge growth (SRG; Selective)
Since an eRidge Growth laser can be basically manufactured by only two crystal growths, an element can be easily manufactured. Specifically, when the ridge portion is formed, selective regrowth is performed on the stripe-shaped window using the protective film as a mask, and the anisotropy of the growth rate with respect to the plane orientation causes the cladding layer to have a trapezoidal shape or the like. Contact layers are sequentially stacked. According to such a method, the thickness of the cladding layer above the active layer in the non-ridge portion can be precisely controlled, and the control of the effective refractive index becomes easy.
However, recently, there is a demand for manufacturing a higher performance selective ridge growth laser by a simple and highly reproducible process.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems of the prior art. That is, an object of the present invention is to provide a high-performance semiconductor light emitting device which does not perform COD even at a high output while maintaining a low threshold current and high efficiency. Another object of the present invention is to provide a semiconductor light emitting device that can be manufactured by a simple and highly reproducible process.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, in producing a window structure laser in which the band gap of the active layer at the end of the optical waveguide is increased. Based on the selective ridge growth structure,
An excellent semiconductor light emitting device showing the expected effect by forming an impurity diffusion layer in the upper portion near the active layer, thereby improving the position controllability of the impurity diffusion front and reducing the leak current at the end. Have been obtained, and the present invention has been provided.

That is, the present invention provides a compound semiconductor layer including an active layer on a substrate, a protective film having an opening formed on the compound semiconductor layer, and a protective film formed on the opening and having a refractive index higher than that of the active layer. It has a small ridge type compound semiconductor layer,
A semiconductor light emitting device is provided, wherein the band gap of the active layer at both ends of the optical waveguide is larger than the band gap of the active layer in a current injection region at the center of the optical waveguide.

In a preferred aspect of the present invention, the ridge type compound semiconductor layer is formed inside the opening and at least on a part of the protective film on both sides of the opening;
An embodiment in which the compound semiconductor layer including the active layer includes a layer having a lower refractive index than the active layer above and below the active layer; a layer on the substrate side among layers having a lower refractive index than the active layers above and below the active layer; Is a first-conductivity-type clad layer, and the other layer is a second-conductivity-type first clad layer; an embodiment having protective films at both ends of an optical waveguide on the second-conductivity-type first clad layer; An embodiment having an antioxidant layer at least in the opening on the second conductive type first cladding layer; an embodiment having the active layer having a quantum well structure; a quantum well in the active layer at both ends of the optical waveguide A mode in which the layer is mixed crystal; a mode in which impurities are diffused into the active layer at both ends of the optical waveguide; and a pn junction at both ends of the optical waveguide due to the diffusion of the impurities is at least in the first conductivity type clad layer. Into shape The active layer has a single well layer; the active layer has a plurality of well layers and a barrier layer sandwiched between the well layers, and the thickness of the barrier layer Is larger than the well layer; the well layer is compressively strained; the constituent element of the well layer contains In; the constituent element of the barrier layer or the guide layer sandwiching the well layer is In. An embodiment in which Al is included in the constituent elements of the barrier layer or the guide layer sandwiching the well layer; an embodiment in which a current blocking layer is provided outside the protective film having the opening; Is constituted by at least a semiconductor layer of a first conductivity type or a high resistance; an embodiment having at least one etching stop layer between the first cladding layer of the second conductivity type and the current blocking layer; Having a compound semiconductor layer formed on the opening of the protective film having a lower refractive index than the active layer; the refractive index of the active layer is smaller than the refractive index of the protective film having the opening A mode in which the width of the opening is wider than the central portion of the device near the device end face; a mode in which the width of the opening is narrower than the central portion of the device near the device end face; An embodiment in which the opening is a stripe-shaped opening extending to one end; an embodiment in which the opening is an opening extending to one end but not extending to the other end; An embodiment in which an electric current is injected from the opening into the active layer; an embodiment in which the surface of the substrate has an off-angle with respect to a low-order plane orientation; An aspect that is a peak; both ends of the optical waveguide Wherein the active layer has a band gap that is transparent to light generated in the active layer in the current injection region at the center of the optical waveguide; the active layer has at least GaAs, AlGaAs, InGaAs, and AlGas.
InAs, GaInP, AlGaInP, GaInAs
P, AlGaInAsP, GaN or InGaN; the side wall of the current block layer is (111) B
A mode in which the current blocking layer is formed by selective growth; a mode in which the current blocking layer is formed by selective growth; a mode in which the impurity diffusion layer is formed in a crystal growth apparatus; An embodiment in which the crystal growth apparatus is an organometallic vapor phase epitaxy apparatus; an aspect in which the surface is locally heated to form a mixed crystal; a method in which the surface is locally heated to a high temperature;
A mode using electron beam or laser beam irradiation; a mode in which a ridge-type compound semiconductor layer is selectively grown on the opening by performing metal organic chemical vapor deposition while adding a gas containing a halogen element. An aspect in which the direction in which the opening extends is selected such that the contact layer is formed on substantially the entire surface of the ridge shape;
0) plane or a plane which is crystallographically equivalent thereto, wherein the direction in which the opening of the protective film extends is the [01-1] direction or a direction which is crystallographically equivalent thereto; the ridge type compound semiconductor There may be mentioned an embodiment in which at least a part of the side surface of the layer is in contact with the electrode.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and manufacturing method of a semiconductor light emitting device according to the present invention will be described below in detail.
The semiconductor light emitting device according to the present invention includes a compound semiconductor layer including an active layer, a protective film having an opening formed on the compound semiconductor layer, a protective film inside the opening and at least on both sides of the opening. And a ridge-type compound semiconductor layer having a smaller refractive index than the active layer formed on a part of the active layer. It is characterized in that it is larger than. The semiconductor light emitting device of the present invention may appropriately have layers usually formed in the semiconductor light emitting device in addition to these layers.

In this specification, the expression “B layer formed on the A layer” refers to the case where the B layer is formed such that the bottom surface of the B layer is in contact with the upper surface of the A layer, In which one or more layers are formed and a B layer is formed on the layer. Further, the upper surface of the layer A and the bottom surface of the layer B are partially in contact with each other,
The case where one or more layers exist between the layer and the layer B is also included in the above expression. Specific aspects are apparent from the following description of each layer and specific examples of the examples.

FIG. 1 is a perspective view of an example of a semiconductor light emitting device according to the present invention, and FIG.
FIG. 3 is a cross section taken along the line III-III of FIG. 1. The structure of an example of a semiconductor light emitting device is schematically shown on a substrate 21 made of a compound semiconductor, a first conductive type first clad layer 22, a first conductive type second clad layer 23, an active layer 24, and a second conductive type. A first clad layer 25 is laminated, and a protective film 27 is formed on the first clad layer 25. The protective film 27 is opened in a stripe shape via an oxidation prevention layer (etching prevention layer) 26. Further, a second conductive type second clad layer 28 selectively grown from the opening 32 of the protective film 27 is formed, and a contact layer 29 and an electrode 30 are formed on the second conductive type second clad layer 28. . The electrode 31 is also formed on the bottom side of the substrate 21.

In the semiconductor light emitting device, window regions are formed at both ends of the optical waveguide, in which the band gap of the active layer 24 is larger than the band gap of the active layer 24 in the current injection region at the center of the optical waveguide. .
This window region is a region disordered by impurity diffusion, and the end face of the optical waveguide of the active layer 24 is a mixed crystal region. In FIGS. 1 to 3, a region indicated by oblique lines is a region where impurity diffusion is performed. Normally, the active layer 24 has a multiple quantum well (MQW) structure like the triple quantum well structure of the present example and thus shows a band gap as shown in FIG. 6B. However, the window region is disordered by impurity diffusion. Therefore, as shown in FIG.
Is larger than the band gap. For this reason, in the semiconductor light emitting device of this example, absorption of photons at the laser end surface can be suppressed, and COD can be prevented beforehand.

The substrate 2 constituting the semiconductor light emitting device of the present invention
1 is not particularly limited in its conductivity and material as long as it can grow a crystal having a double hetero structure thereon. Preferred is a conductive substrate. Specifically, G is suitable for growing a crystalline thin film on a substrate.
aAs, InP, GaP, ZnSe, ZnO, Si, A
It is preferable to use a crystal substrate such as l ₂ O ₃ , particularly a crystal substrate having a zinc blende structure. In this case, the substrate crystal growth surface is preferably a low-order plane or a plane crystallographically equivalent thereto, and most preferably a (100) plane. In this specification, the (100) plane is not necessarily strictly (10).
0) It is not necessary that the surface be exactly the same, and the case where the off-angle is up to about 30 ° is included. The upper limit of the off-angle is preferably 30 ° or less, more preferably 16 ° or less. The lower limit is preferably 0.5 ° or more, more preferably 2 ° or more, still more preferably 6 ° or more, and most preferably 10 ° or more.

The substrate 21 may be a hexagonal type substrate, for example, a substrate made of Al ₂ O ₃ , 6H—SiC or the like. On the substrate 21, a thickness of 0.2 μm is usually used so that defects of the substrate are not introduced into the epitaxial growth layer.
It is preferable to form a buffer layer of about 2 μm.

On the substrate, a compound semiconductor layer including the active layer 24 is formed. The compound semiconductor layer includes layers having a lower refractive index than the active layer above and below the active layer, of which the layer on the substrate side is a first conductive type clad layer and the other epitaxial side layer is a second conductive type clad layer. Function. In addition, a layer functioning as a light guide layer may be included. The magnitude relationship between the refractive indices can be adjusted by appropriately selecting the material composition of each layer according to a method known to those skilled in the art. For example, Al _x Ga _1-x As, (Al _x
The refractive index can be adjusted by changing the Al composition such as Ga _1-x ) _0.5 In _0.5 P and Al _x Ga _1-x N.

The first conductivity type cladding layer is formed of a material having a lower refractive index than the active layer. Further, it is preferable that the refractive index of the first conductive type clad layer is larger than the refractive index of the second conductive type clad layer. For example, first conductivity type GaI
nP, AlGaInP, AlInP, AlGaAs, A
lGaAsP, AlGaInAs, GaInAsP, G
aN, AlGaN, AlGaInN, BeMgZnS
e, MgZnSSe, CdZnSeTe, etc.
II-V and II-VI semiconductors can be used. The lower limit of the carrier concentration of the first conductivity type cladding layer is 1
It is preferably at least 10 ¹⁸ cm ^-3, more preferably at least 3 10 ¹⁸ cm ^-3, most preferably at least 5 10 ¹⁸ cm ^-3 . The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less, and 5 × 10
^It is more preferably ¹⁹ cm ^-3 or less, most preferably 3 × 10 ¹⁸ cm ^-3 or less.

The first conductivity type cladding layer is composed of a single layer.
When it is, preferably 0.5 to 4 μm, more preferably
It has a thickness of about 1-3 μm, but as in this example
The first conductivity type cladding layer is a first conductivity type first cladding layer 22.
And a plurality of first conductive type second cladding layers 23
It may be. Specifically, GaInP, A
a cladding layer made of lGaInP or AlInP;
AlGaAs or Al of the first conductivity type on the substrate side of the layer of
An embodiment in which a cladding layer made of GaAsP is formed
Examples can be given. At this time, the thickness of the layer on the active layer side
Is preferably thin, and the lower limit of the thickness is 0.0
1 μm or more is preferable, and 0.05 μm or more is more preferable.
No. The upper limit is preferably 0.5 μm or less, and 0.3 μm or less.
μm or less is more preferable. Also, the carrier in the layer on the substrate side
The concentration is lower limit 2 × 10¹⁷cm^-3~ Or more preferred, 5 ×
10¹⁷cm^-3The above is more preferable. Upper limit is 3 × 10¹⁸c
m ^-3The following is preferable, and 2 × 10¹⁸cm^-3Less preferred
New

The structure of the active layer 24 constituting the semiconductor light emitting device of the present invention is not particularly limited, and has a triple quantum well structure (TQW) in this embodiment. Specifically, the triple quantum well structure (TQW) has a light confinement layer (non-doped) 51, a quantum well layer (non-doped) 52, a barrier layer (non-doped) 53, a quantum well layer (non-doped) 54,
It has a structure in which a barrier layer (non-doped) 55, a quantum well layer (non-doped) 56, and a confinement layer (non-doped) 57 are sequentially stacked. In addition to the triple quantum well structure, for example, a single quantum well structure (SQW) including a quantum well layer and a light confinement layer sandwiching the quantum well layer from above and below, a plurality of quantum well layers and a barrier sandwiched therebetween Double quantum well structure (DQ) comprising an optical confinement layer stacked above the uppermost quantum well layer and below the lowermost quantum well layer.
W) or a multiple quantum well structure (MQW) having four or more quantum well layers. When the active layer has a quantum well structure, a shorter wavelength (630 nm to 660 nm) and a lower threshold can be achieved as compared with a single bulk active layer.

The material of the active layer 24 is GaAs, A
lGaAs, GaInP, AlGaInP, GaInA
s, AlGaInAs, GaInAsP, GaN, Ga
InN can be exemplified. When the material contains Ga and In as constituent elements, a natural superlattice is easily formed, so that the effect of suppressing the natural superlattice by using an off-substrate becomes large.

In the case where the active layer 24 has a quantum well structure, from the viewpoint of the easiness of mixed crystal formation: (1) The amount of change in composition before and after mixed crystal formation can be increased. (2) In the case where the active layer has a plurality of well layers (multiple quantum well), it is necessary to reduce the band gap near the center of the mixed crystal region. In order to suppress, the thickness of the barrier layer sandwiched between the mixed crystal composition well layers is larger than the thickness of the well layer. (4) I easily diffuses into the constituent elements of the well layer at a relatively low temperature.
(5) Constituent elements of the barrier layer or the guide layer sandwiching the well layer do not include In for reducing the band gap. (6) Constituent elements of the barrier layer or the guide layer sandwiching the well layer. Preferably contains Al for increasing the band gap.

Most of the ridge type compound semiconductor layer including a layer having a lower refractive index than the active layer 24 formed on the opening of the protective film 27 is generally composed of a second cladding layer of the second conductivity type. In addition, a layer functioning as a light guide layer may be included. It is preferable that a substantially entire surface is made of a low-resistance contact layer. The cladding layer, the active layer and the contact layer are not particularly limited, either.
AlGaInAs, AlGaInP, GaInAsP,
AlGaInN, BeMgZnSe, MgZnSSe,
General group III-V such as CdZnSeTe, II-V
Using a group I semiconductor, a double hetero structure in which an active layer is sandwiched between two cladding layers may be manufactured. At this time, a material having a smaller refractive index than that of the active layer is selected for the cladding layer, and a material having a band gap smaller than that of the cladding layer is usually selected for the contact layer. A low carrier resistance and a suitable carrier density (cm ^-3 ), that is, the lower limit is preferably 1 × 10 ¹⁸ or more, more preferably 3 × 10 ¹⁸ or more, and more preferably 5 × 10 ¹⁸
Most preferably ¹⁸ or more. The upper limit is preferably 2 × 10 ²⁰ or less, more preferably 5 × 10 ¹⁹ or less, and most preferably 3 × 10 ¹⁸ or less.

The protective film 27 is not particularly limited, either.
In order to perform current injection only in the region of the active layer below the ridge formed on the opening 32 of the protective film 27, the protective film on both sides of the opening needs to have an insulating property to perform current confinement. The active layer has a refractive index difference between the ridge portion and the non-ridge portion in the horizontal direction to stabilize the transverse mode of laser oscillation. It is preferably smaller than. However, in practice, if the refractive index difference between the protective film and the clad layer is too large, the effective refractive index step in the lateral direction in the active layer is likely to be large. The thickness must be increased, which causes a problem that the leakage current increases in the lateral direction. On the other hand, if the refractive index difference between the protective film and the cladding layer is too small, light tends to leak to the outside of the protective film, so that the protective film needs to be thickened to some extent. Occurs. Taking these facts into consideration, the lower limit of the refractive index difference between the protective film and the cladding layer is preferably 0.3 or more, more preferably 0.2 or more, and most preferably 0.5 or more. The upper limit is 3.0
Or less, more preferably 2.5 or less, and most preferably 1.8 or less. There is no particular problem with the thickness of the protective film as long as it has sufficient insulation properties and does not leak light to the outside of the protective film. The lower limit of the thickness of the protective film is preferably 10 nm or more, more preferably 30 nm or more, and most preferably 50 or more. Upper limit is 500n
m or less, more preferably 300 nm or less, and 2
00 nm or less is most preferable.

The protective film 27 is preferably made of a dielectric material, specifically, a SiNx film, a SiO ₂ film, a SiON film.
Film, Al ₂ O ₃ film, ZnO film, SiC film, and amorphous Si. The protective film 27 is used when the ridge is formed by selective regrowth using MOCVD or the like as a mask, and is also used for the purpose of current constriction. For simplicity of the process, it is preferable to use the same composition for the protective film for current confinement and the protective film for selective growth. However, if necessary, layers having different compositions may be formed in multiple layers.

When a zinc blende type substrate is used and the substrate surface is a (100) plane or a plane crystallographically equivalent to the (100) plane, a contact layer 29 described later must be protected to facilitate growth on the side surface of the ridge portion. The stripe region defined by the opening 32 of the film 27 preferably extends in the [01-1] direction or a direction crystallographically equivalent thereto. In that case, most of the side surfaces of the ridge often become the (311) A plane, and the contact layer 29 can be grown on substantially the entire surface of the second conductive type second cladding layer 28 that forms the ridge. . The tendency is that the second conductivity type second cladding layer 28 is made of AlGaAs, particularly AlAs mixed crystal ratio of 0.2 to 1.0, preferably 0.3 to 0.9, and most preferably 0.4 to 0.8.
This is particularly noticeable at the time. The direction of the off angle is preferably within ± 30 °, more preferably within ± 7 °, from the direction perpendicular to the direction in which the stripe extends,
Directions within ± 2 ° are most preferred. When the plane orientation of the substrate is (100), the direction of the stripe region is [0−
11] or a direction equivalent thereto, and the off-angle direction is ± 30 ° from the [011] direction or a direction equivalent thereto.
Direction is preferable, a direction within ± 7 ° is more preferable, and a direction within ± 2 ° is most preferable. In this specification, the term “[01-1] direction” refers to (10 −10) in general III-V and II-VI semiconductors.
[11-1] existing between the 0) plane and the [01-1] plane
The [01-1] direction is defined such that the plane is a plane on which a group V or group VI element appears, respectively.

The embodiment of the present invention is not limited to the case where the above-mentioned stripe region is in the [01-1] direction. Hereinafter, other embodiments will be described. When the stripe region extends in the [011] direction or a direction crystallographically equivalent thereto, for example, the growth rate can have anisotropy depending on the growth conditions, and the growth speed is high in the (100) plane and (111). It can be made to hardly grow on the B side. In this case, when the growth is performed selectively on the (100) surface of the stripe-shaped window portion, a ridge-shaped second conductivity type second clad layer having the (111) B surface as a side surface is formed. Also in this case, the next time a contact layer is formed, by selecting a condition under which a more isotropic growth occurs, the entire ridge side surface composed of the (111) B surface as well as the ridge top surface of the (100) surface is contacted. A layer is formed.

For the same reason, when a wurtzite type substrate is used, the direction in which the stripe region extends is, for example, [11-20] or [1-1] on the (0001) plane.
00] is preferred. HVPE (Hydride Vap
or Phase Epitaxy), either direction may be used, but in MOVPE, the [11-20] direction is more preferable.

On the active layer, a second conductivity type clad layer is formed. One or more second conductivity type cladding layers of the present invention are formed. In the description of the present embodiment, a preferred embodiment having two layers of the second conductivity type first cladding layer 25 and the second conductivity type second cladding layer 28 formed by selective growth in order from the side closer to the active layer will be described as an example. .

The second conductive type first cladding layer 25 is formed of a material having a lower refractive index than the active layer. For example, the second
Conductivity type AlGaInP, AlInP, AlGaAs,
AlGaAsP, AlGaInAs, GaInAsP,
AlGaInN, BeMgZnSe, MgZnSSe,
General group III-V such as CdZnSeTe, II-V
Group I semiconductors can be used. When the second-conductivity-type cladding layer is made of a group III-V compound semiconductor containing Al, GaAs, G
It is preferable to cover with a group III-V compound semiconductor containing no Al such as aAsP, GaInAs, GaInP, and GaInN because surface oxidation can be prevented.

The lower limit of the carrier concentration of the second conductive type first cladding layer 25 is preferably 2 × 10 ¹⁷ cm ⁻³ or more, and 5 ×
10 ¹⁷ cm ^-3 or more is more preferable, and 7 × 10 ¹⁷ cm ^-3 or more is most preferable. The upper limit is preferably 5 × 10 ¹⁸ cm ⁻³ or less, more preferably 3 × 10 ¹⁸ cm ⁻³ or less, and 2 × 10 ¹⁸ cm ⁻³ or less.
Most preferably ¹⁸ cm ^-3 or less. The lower limit of the thickness is 0.
It is preferably at least 01 μm, more preferably at least 0.05 μm, most preferably at least 0.07 μm. The upper limit is preferably 0.5 μm or less, more preferably 0.3 μm or less, and most preferably 0.2 μm or less.

The first cladding layer 25 of the second conductivity type comprises the active layer 2
4 is formed. In a preferred embodiment of the present invention, the refractive index of the second conductive type first cladding layer 25 is smaller than the refractive index of the first conductive type cladding layer. By adopting such an embodiment, the light distribution (near-field image) can be controlled so that light effectively seeps from the active layer to the light guide layer side. Further, since the optical waveguide loss from the active region (the portion where the active layer is present) to the impurity diffusion region can be reduced, the laser characteristics and the reliability in high-power operation can be improved.

The second conductive type first cladding layer 25 has a second
By forming the antioxidant layer (etching stop layer) 26 functioning as a conductive type cap layer, when the second conductive type second clad layer 28 is regrown at least in the opening 32, the passage resistance is formed at the regrowth interface. Can be easily prevented from being generated in the high resistance layer.

The material of the antioxidant layer 26 is not particularly limited as long as it is hardly oxidized or easily cleaned even if oxidized. Specifically, III-V having a low content of an easily oxidizable element such as Al (about 0.3 or less)
Group compound semiconductor layers. It is preferable that light from the active layer is not absorbed by selecting a material and a thickness. The material of the cap layer is generally selected from materials having a larger band gap than the material of the active layer. However, even a material having a small band gap has a thickness of 50 nm or less, more preferably 30 nm or less, and most preferably 10 nm. Below, light absorption can be substantially ignored, so that it can be used.

The method for forming the window region in the semiconductor light emitting device of the present invention is not particularly limited. A preferred method is to perform a process for forming a window region from above the active layer 24. For example, there is an impurity diffusion method as one method for manufacturing the window region.
By forming an impurity diffusion layer on the upper part of 4, the window region can be easily formed. In particular, in the semiconductor light emitting device having the configuration of the present invention, the impurity can be diffused from a location above the active layer 24 and relatively short from the active layer. For example, in the example shown in FIG. 1, impurity diffusion can be performed from above the oxidation preventing layer 26. At this time, the impurity reaches the active layer 24 through the oxidation prevention layer 26 having a relatively small thickness and the first cladding layer 25 of the second conductivity type, so that the position controllability of the impurity diffusion front is improved and the leakage at the end portion is improved. The current can be easily reduced.

If the distance from the active layer to the impurity diffusion layer in the optical waveguide is too short, the impurity concentration in the active layer becomes too high, and the optical waveguide is liable to be affected by quality deterioration due to the regrowth interface. On the other hand, if the distance is too long, there is a problem that the controllability of the diffusion front position is reduced and the leak current at the end is increased. In particular, if the impurity diffuses into a layer having a relatively small band gap below the first conductivity type cladding layer, the leakage current increases and the performance as a light emitting element is greatly impaired. Further, when the active layer contains In (further As), if the diffusion distance is long, high-temperature or long-time diffusion is required. The quality of the active layer may be deteriorated due to disturbance or thermal damage. Considering these, the lower limit of the distance from the active layer to the impurity diffusion layer in the optical waveguide is 0 μm.
m or more, more preferably 0.05 μm or more,
Most preferably, it is 0.1 μm or more. The upper limit of the diffusion distance is 0.
It is preferably at most 5 μm, more preferably at most 0.45 μm, most preferably at most 0.4 μm. Since the diffusion distance of the impurity is relatively short, there is also an advantage that the impurity can be diffused at a relatively low temperature. The impurity diffusion temperature is 8
It is preferably at most 50 ° C, more preferably at most 770 ° C, even more preferably at most 730 ° C.

In consideration of ease of production and controllability, it is preferable that the growth of the layer having the diffusion source and the annealing process be performed consistently in the thin film growth apparatus as the impurity diffusion process. Further, it is preferable to remove the impurity diffusion layer at least by the end of the laser chip manufacturing process in order to reduce the leakage current at the end. The diffusion front of the impurity at the end must be lower than the quantum well layer in the active layer in order to perform the mixed crystal, and the first conductivity type clad having a larger band gap than the active layer is required. It is preferable to be formed in a layer from the viewpoint of suppressing current leakage.

The impurities to be diffused preferably have a large diffusion constant from the viewpoint of reducing the diffusion process temperature, and examples thereof include zinc (Zn), tin (Sn), lithium (Li), and copper (Cu). Further, from the viewpoint of preventing an increase in internal loss in the optical waveguide, an n-type impurity is preferable,
For example, for a III-V group semiconductor, silicon (S
i), germanium (Ge), tin (Sn), sulfur (S), selenium (Se), tellurium (Te), etc .;
For a group VI semiconductor, nitrogen (N), chlorine (Cl), and the like can be given. From the viewpoint of reducing the leakage current at the end, an impurity capable of increasing the resistance is preferable. For example, transition elements such as copper (Cu), iron (Fe), and chromium (Cr), and hydrogen (H), For a III-V semiconductor, boron (B), oxygen (O), and the like can be given.

As a method for doping impurities into the window region, for example, an ion implantation method may be employed in addition to the above-mentioned preferable method. After the ion implantation, heat treatment is performed to diffuse the impurities, thereby enabling the crystal structure of the quantum well structure to be mixed. However, implanting impurities with high energy or a large mass number is not preferable because a large number of defects (especially, when the dose is large) are generated. In particular, the active layer 24
When the implanted impurities reach the upper limit, defects are generated inside the active layer, which is not preferable. From the viewpoint of reducing damage to the active layer, the implantation depth is reduced, and the peak of the implanted impurity profile is formed at the upper part of the active layer. Preferably, there is. As the implanted impurities, silicon (Si), fluorine (F), aluminum (Al), boron (B), carbon (C),
Nitrogen (N), phosphorus (P), sulfur (S), arsenic (As), gallium (Ga) and the like are preferable. From the viewpoint of damage reduction, B, C, F, Al, Si, and the like having relatively small mass are preferable. In the case of injecting into an all-V semiconductor, it is preferable to use N, F, As, Al, Ga or the like which does not work as a carrier from the viewpoint of eliminating the influence of absorption of free carriers. Although it does not directly contribute to the mixed crystal formation, the injection of hydrogen (H), argon (Ar), or the like can reduce the activation rate of carriers and form a high-resistance layer.

No impurities are used (impurity free)
By the method, it is possible to produce an end window structure. For example, by forming a dielectric film such as SiO _{2 on} the surface and treating it at a high temperature (which requires a relatively high temperature than impurity diffusion), base atoms such as Ga on the surface side move into the dielectric film, There is a method in which the vacancies generated at this time are diffused in the film, and the quantum well is mixed. Also at this time, as described above, since the diffusion distance of the vacancy can be reduced by forming the dielectric film on the upper portion near the active layer, the process can be performed at a relatively lower temperature and in a shorter time than the conventional structure. . This makes it possible to suppress damage to the active layer and disorder of the doping profile in a region (for example, a current injection region) that does not need to be mixed-crystallized.

Further, the mixed crystal may be locally heated to a high temperature by using a laser beam, an electron beam or the like to form the window region. This method is used not only when no impurity is used but also when an impurity is used, from the viewpoint of suppressing damage to the active layer and disorder of the doping profile in a region (for example, a current injection region) that does not need to be mixed. Is also effective.

On the impurity diffusion layer formed for impurity diffusion, a surface protective layer is formed for the purpose of preventing evaporation of impurities from the surface, suppressing surface oxidation, preventing contamination by a process, protecting damage, and the like. You may.

In order to improve the controllability of the process, the second
It is preferable that the lower part of the conductive-type clad layer be the second conductive-type first clad layer. In addition, a protective film (current blocking layer) 27 formed on the second conductivity type first cladding layer.
Is more preferably inserted at the interface with the second conductivity type first cladding layer by one or more etching stopper layers.

The protective film 27 constituting the semiconductor light emitting device of the present invention is formed on the second conductivity type first clad layer and has an opening. Basically, a current is injected from the opening 32 into the active layer. The material of the protective film 27 is not particularly limited.
The protective film 27 may be a dielectric or a semiconductor. However, in general, the protective film 27 is preferably a dielectric because it is used for selective growth.
₂ film, SiON film, Al ₂ O ₃ film, ZnO film, SiC film, and amorphous Si. This protective film is used when it is formed by selective regrowth using MOCVD or the like as a mask. When a dielectric is used as the protective film 27, there is an advantage that a layer having a low refractive index and excellent insulating properties can be formed. On the other hand, heat dissipation is poor due to low thermal conductivity, and cleavage is poor. It also has disadvantages such as being difficult to assemble at the junction down because it is difficult to flatten. On the other hand, when a semiconductor is used as the material of the protective film 27, the heat conductivity is higher than that of the dielectric film, so that the heat dissipation is good, the cleavage is good, and the flattening is easy, so that the junction is easy to assemble. ,
Although the contact layer is easily formed on the entire surface, there is an advantage that the contact resistance is easily lowered. On the other hand, when a high Al composition compound such as AlGaAs or AlInP is required to reduce the refractive index, measures such as surface oxidation are required. There are drawbacks such as

The protective film 27 controls the light distribution (particularly the light distribution in the lateral direction) and improves the current blocking function.
It may be formed from two or more layers having different refractive indices, carrier concentrations or conductivity types. By forming a surface protective layer on the protective film 27, surface oxidation can be suppressed or the surface can be protected in the process. Although the conductivity type of the surface protective layer is not particularly limited, the current blocking function can be improved by using the second conductivity type.

The conductivity type of the protective film 27 is the first conductivity type or high resistance (undoped or doped with impurities (O, Cr, Fe, etc.) that form a deep order), or these two.
Any one of the combinations may be used, and it may be formed from a plurality of layers having different conductivity types or compositions. For example, a protective film 27 formed in the order of a semiconductor layer of the second conductivity type or high resistance and a semiconductor layer of the first conductivity type from the side near the active layer can be preferably used. Further, if the thickness is too small, there is a possibility that current blocking may be hindered. Therefore, the thickness is preferably 0.1 μm or more.
More preferably, it is 5 μm or more. In consideration of the size of the element, it is preferable to select from the range of about 0.1 to 3 μm.

A second-conductivity-type second cladding layer 28 is formed on at least a part of the opening of the protective film 27. Second
The conductivity type second cladding layer 28 is normally formed so as to cover the entire upper surface of the opening 32. The lower limit of the carrier concentration of the second conductive type second cladding layer 28 is 5 × 10 ¹⁷ cm.
^-3 or more, more preferably 7 × 10 ¹⁷ cm ^-3 or more, and most preferably 1 × 10 ¹⁸ cm ^-3 or more. The upper limit is 1 ×
It is preferably 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and most preferably 3 × 10 ¹⁸ cm ⁻³ or less.

The thickness of the second conductive type second cladding layer 28 is as follows.
If the thickness is too small, the light confinement will be insufficient, and if the thickness is too large, the passage resistance will increase, and the lower limit is preferably 0.5 μm or more, more preferably 1.0 μm or more. The upper limit is preferably 3.0 μm or less, and 2.0 μm or less.
m or less is more preferable. After forming the protective film 27 and the second conductive type second cladding layer 28, before forming an electrode, a contact layer 29 having a low resistance (high carrier concentration) is formed in order to reduce the contact resistance with the electrode material. Is preferred. In particular, it is preferable to form an electrode after forming a contact layer on the entire surface of the uppermost layer on which an electrode is to be formed. In order to further increase the contact area with the electrode, it is preferable that at least a part of the side surface of the ridge type compound semiconductor layer is in contact with the electrode.

At this time, the material of the contact layer 29 is usually selected from materials having a smaller band gap than that of the cladding layer, and preferably has low resistance and appropriate carrier density in order to obtain ohmic contact with the metal electrode. . The lower limit of the carrier density is preferably 1 × 10 ¹⁸ cm ⁻³ or more,
More preferably 10 ¹⁸ cm ^-3 or more, and most preferably 5 × 10 ¹⁸ cm ^-3 or more. The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less, more preferably 5 × 10 ¹⁹ cm ⁻³ or less, and 3 × 1
It is most preferably 0 ¹⁸ cm ^-3 or less. The thickness of the contact layer 29 is preferably 0.1 to 10 μm, more preferably 1 to 8 μm, and most preferably 2 to 6 μm.

Next, an opening 32 formed in the protective film 27 is formed.
Will be described. It is preferable that the opening 32 of the protective film 27 be smaller on the lower side (active layer side) than on the upper side (contact layer side) from the viewpoint of reducing the passage resistance (reducing the operating voltage and the heat generation). preferable. By forming the protective film 27 on the end window structure region (for example, the impurity diffusion region), it is possible to eliminate the leak current in the end window structure region. In addition, by forming the protective film 27 further inside the end window structure region, current injection to the end of the active layer 27 can be suppressed. Thereby, deterioration (particularly, valve deterioration) in the end region having the regrowth interface can be reduced.

The opening 32 of the protective film 27 may be a stripe-shaped opening extending to both ends, or extending to one end but extending to the other end. There may be no opening or an opening that does not extend to both ends. In the case where the opening is a stripe-shaped opening extending to both ends, light control in the end window structure region becomes easier, and the spread of light in the lateral direction on the end face can be reduced.
On the other hand, if the opening is formed in a portion that is somewhat inside from the end face, current can be made non-injected near the end face, preventing recombination of current at the end face and preventing the cladding layer etc. Can be minimized. It is preferable that the structure of the opening is appropriately determined according to the purpose of use while taking such advantages into consideration.

The direction of the off angle is preferably within ± 30 °, more preferably within ± 7 °, from the direction perpendicular to the direction in which the opening 32 formed in the protective film 27 extends (longitudinal direction). , ± 2 ° is most preferable. The direction of the opening is such that the plane orientation of the substrate is (100).
In the case of the direction [0-11] or a direction equivalent thereto, the off-angle direction is preferably within ± 30 ° from the [011] direction or a direction equivalent thereto, more preferably within ± 7 °, and ± 5 °. Directions within 2 ° are most preferred.
In this specification, the “[01-1] direction” exists between the (100) plane and the [01-1] plane in general III-V and II-VI semiconductors. The [01-1] direction is defined such that the [11-1] plane is a plane where a group V or group VI element appears, respectively.

The embodiment of the present invention is not limited to the case where the opening 32 is in the [01-1] direction. For example, when the opening extends in the [011] direction or a direction crystallographically equivalent thereto, for example, the growth rate can have anisotropy depending on the growth conditions, and the growth rate is high in the (100) plane.
It can be made to hardly grow on the (111) B plane. In that case, the second side having the (111) B surface as a side surface
A conductive type second cladding layer is formed. Also in this case, the next time the contact layer is formed, by selecting a condition under which a more isotropic growth occurs, the contact layer is entirely formed on the side surface composed of the (111) B plane as well as the top of the (100) plane. It is formed.

For the same reason, when a wurtzite type substrate is used, the direction in which the opening extends is, for example, (0
On the (001) plane, [11-20] or [1-100] is preferable. HVPE (Hydride Vapor P
Hase epitaxy) may be in either direction, but in MOVPE, the [11-20] direction is more preferable.

In designing the semiconductor light emitting device of the present invention, first, the thickness of the active layer and the composition of the cladding layer are determined in order to obtain a desired vertical spread angle. Usually, when the vertical divergence angle is reduced, light seepage from the active layer to the cladding layer is promoted, the light density at the end face is reduced, and the optical damage (COD) level at the output end face can be improved. When high-output operation is required, it is set relatively narrow, but the lower limit is to suppress an increase in oscillation threshold current due to a reduction in light confinement in the active layer and a decrease in temperature characteristics due to carrier overflow. There is a limit, and the lower limit is preferably 15 ° or more, more preferably 17 ° or more, and most preferably 19 ° or more. The upper limit is preferably 33 ° or less, more preferably 31 ° or less, and most preferably 30 ° or less.

Next, when the vertical divergence angle is determined, the structural parameters that largely govern the high output characteristics are the distance dp between the active layer and the current blocking layer and the width at the bottom of the opening (hereinafter referred to as “opening width”) W Becomes When only the second conductivity type first cladding layer exists between the active layer and the current blocking layer, dp is the thickness of the second conductivity type first cladding layer. When the active layer has a quantum well structure, the distance between the active layer closest to the current block layer and the current block layer is dp.

The upper limit of dp is preferably 0.50 μm or less, more preferably 0.45 μm or less, and 0.45 μm or less.
0 μm or less is most preferable. The lower limit is preferably 0.03 μm or more, more preferably 0.1 μm or more, and 0.1
5 μm or more is most preferable. However, if the purpose of use (where the spread angle is set, etc.), material system (refractive index, resistivity, etc.) is different, the above-mentioned optimum range is slightly shifted. It should also be noted that this optimum range affects each of the above structural parameters.

The upper limit of the opening width W at the bottom of the opening is 1
It is preferably at most 00 μm, more preferably at most 50 μm. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more,
Most preferably, it is 2 μm or more. Further, in order to make the transverse mode a single mode (transverse light intensity distribution of a single peak), W cannot be made too large from the viewpoint of cutoff of a higher-order mode and prevention of spatial hole burning. The upper limit of W is preferably 7 μm or less,
6 μm or less is more preferable.

To realize a high output operation, it is effective to increase the opening width W at the bottom of the opening from the viewpoint of reducing the light density at the end face. However, in order to reduce the operating current, the opening width is reduced. Is preferable from the viewpoint of reducing the waveguide loss. Therefore, the opening width W2 near the center serving as the gain region
Is relatively narrow, and the opening width W1 near the end is relatively wide, so that a low operation current and a high output operation can be realized at the same time, and high reliability can be secured (FIG. 10 (a)). That is, the upper limit of the edge (cleavage plane) width W1 is preferably 1000 μm or less, more preferably 500 μm or less. The lower limit is preferably 2 μm or more, more preferably 3 μm or more. The upper limit of the center width W2 is preferably 100 μm or less, and more preferably 50 μm or less. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more, and most preferably 2 μm or more. The upper limit of the difference between the end width W1 and the center width W2 is 1000 μm.
m or less, and more preferably 500 μm or less. The lower limit is preferably 0.2 μm or more, and 0.5 μm
The above is more preferable.

In order to make the transverse mode a single mode, the upper limit of the end width W1 is preferably 7 μm or less.
6 μm or less is more preferable. The upper limit of the center width W2 is 6
μm or less is preferable, and 5 μm or less is more preferable. The upper limit of the difference between the end width W1 and the center width W2 is preferably 5 μm or less, more preferably 3 μm or less, and most preferably 2 μm or less. The lower limit is preferably 0.2 μm or more, more preferably 0.5 μm or more.

In order to achieve a laser with a nearly circular beam while maintaining high reliability, it is necessary to control the above dp and W within an appropriate range with good controllability. In order to realize a nearly circular beam, it is effective to reduce the aperture width. However, when the aperture width is reduced, the injection current density is not preferable from the viewpoint of suppressing bulk deterioration. Therefore, by reducing the width of the central portion W2, which is the gain region, to a relatively large value and the portion near the end portion to a relatively small value, beam spot reduction and low operating current can be realized at the same time, and high reliability is secured. (FIG. 10B). That is, the upper limit of the end (cleavage plane) width W1 is preferably 10 μm or less, more preferably 5 μm or less,
It is most preferably 3 μm or less. Lower limit is 0.5μ
m or more, more preferably 1 μm or more. The upper limit of the center width W2 is 100
μm or less, and more preferably 50 μm or less. The lower limit is preferably 1 μm or more, more preferably 1.5 μm or more, and 2 μm or more.
Most preferably, it is at least m. The upper limit of the difference between the end width W1 and the center width W2 is preferably 100 μm or less, more preferably 50 μm or less. The lower limit is preferably 0.2 μm or more, more preferably 0.5 μm or more.

The length of the above-mentioned gradually increasing portion, gradually decreasing portion, and end portion may be designed according to the desired characteristics, but the length of the gradually decreasing portion is 5 to 5 from the viewpoint of reducing the waveguide loss.
10 μm is preferable, and 10 to 50 μm is more preferable.
The length of the end portion is preferably from 5 to 30 μm, more preferably from 10 to 20 μm, from the viewpoint of cleavage accuracy. However, if necessary, the window may be manufactured as follows. (1) The opening width or length of the end portion, the gradually increasing portion or the gradually decreasing portion is asymmetric on both sides of the chip. (2) An area in which the width of the end is constant is not set, but is gradually increased or decreased to the end. (3) One side of the end face (normally, high-output light extraction (front end face)
Side), the opening width of which gradually increases or decreases. (4) The width of the end opening differs between the front end face and the rear end face. (5) A combination of some of the above (1) to (4). In addition, by not providing an electrode near the end face, suppressing bulk deterioration due to current injection into the opening near the end face and reducing the recombination current at the end face can be achieved with a small spot diameter with high reliability. It is effective from the viewpoint of laser production.

Usually, when the stripe width is determined by etching the semiconductor layer (especially wet etching), a specific surface is likely to be selectively formed. Therefore, if the stripe width is gradually reduced, the stripe edge fluctuates. As a result, the edge of the stripe changes stepwise,
The undulation of the step-like edge easily causes disturbances such as ripples and large side peaks in the horizontal far-field image. On the other hand, in the present invention, since the stripe width gradually increasing or decreasing portion is formed by etching the SiNx amorphous film, the stripe width can be linearly increased or decreased. A simple monomodal peak can be easily obtained.

If the length of the window structure region in the direction of the resonator at the end is too short, it becomes difficult to cleave with good reproducibility, while if it is too long, the loss in the window structure region increases. Laser characteristics such as an increase in threshold current and a decrease in slope efficiency will be degraded. Therefore, the length of the window structure region is, as a lower limit, preferably 1 μm or more, more preferably 5 μm or more. The upper limit is 50μ
m or less, more preferably 30 μm or less.

The window region is preferably formed at both ends, but may be formed only on one side surface.
When formed only on one side, it is preferable to form it on the end face side from which higher-power laser light is emitted. It should be noted that “near the end face” in this specification refers to a portion where such a window structure region is formed.

The method for manufacturing the semiconductor light emitting device of the present invention is not particularly limited. What is manufactured by any method is included in the scope of the present invention as long as it satisfies the requirements of claim 1 described above.

In manufacturing the semiconductor light emitting device of the present invention, a conventionally used method can be appropriately selected and used. The method for growing the crystal is not particularly limited. For the crystal growth of the double hetero structure and the selective growth of the current blocking layer, etc., metal organic chemical vapor deposition (MOCVD) is used.
A known growth method such as molecular beam epitaxy (MBE), hydride or halide vapor phase epitaxy (VPE), and liquid phase epitaxy (LPE) can be appropriately selected and used.

The method for manufacturing a semiconductor light emitting device according to the present invention includes a method of forming a compound semiconductor layer including an active layer on a substrate, a protective film having an opening formed on the compound semiconductor layer, and a method of forming a protective film on the opening. A ridge-type compound semiconductor layer having a smaller refractive index than the active layer formed, and the band gap of the active layer at both ends of the optical waveguide in the current injection region at the center of the optical waveguide at the both ends of the optical waveguide. A method of performing a step of making the gap larger than the gap can be exemplified.

The specific growth conditions and the like of each layer vary depending on the composition of the layer, the growth method, the shape of the apparatus, and the like.
The double hetero structure has a growth temperature of about 650 to 750 ° C,
V / III ratio: about 20 to 60 (in the case of AlGaAs) or about 300 to 600 (InGaAsP, AlGa
In the case of InP), the block region has a growth temperature of 600 to 70.
0 ° C., V / III ratio about 40 to 60 (in the case of AlGaAs) or about 350 to 550 (InGaAsP, A
1GaInP), the impurity diffusion region has a growth temperature of 50
0-650 ° C., V / III ratio about 20-80 (AlGa
As) or about 300-600 (InGaAs)
In the case of sP and AlGaInP), the heat treatment (annealing) is preferably performed at 600 to 800 ° C. within 3 hours.

In particular, the portion selectively grown using the protective film is A
When Al is contained like lGaAs and AlGaInP,
It is very preferable to introduce a small amount of HCl gas during the growth, because the deposition of poly on the mask can be prevented. If the Al composition is higher, or the mask width or the mask area ratio is larger, and other growth conditions are constant, poly deposition is prevented and selective growth is performed only on the exposed portion of the semiconductor surface (selective mode). The amount of HCl introduced required for this increases. On the other hand, if the introduction amount of the HCl gas is too large, the growth of the AlGaAs layer does not occur, and the semiconductor layer is etched instead (etching mode). The amount of HCl introduced required to enter the etching mode increases. Therefore, the optimal amount of HCl introduced largely depends on the supply mole number of the group III raw material containing Al such as trimethylaluminum. Specifically, the ratio of the number of moles of HCl supplied and the number of moles of group III raw material containing Al (HC
l / III) has a lower limit of preferably 0.01 or more,
0.05 or more is more preferable, and 0.1 or more is most preferable. The upper limit is preferably 50 or less, more preferably 10 or less, and most preferably 5 or less. However, when the compound semiconductor layer containing In is selectively grown (in particular, HCl is introduced), it is easy to control the composition.

In the following, another preferred embodiment of the semiconductor light emitting device of the present invention will be described in relation to effects. In the semiconductor light emitting device of the present invention, a compound semiconductor layer including an active layer on a substrate, a protective film having an opening formed on the compound semiconductor layer, and a ridge having a smaller refractive index than the active layer on the opening. At least a contact layer formed on the entire surface of a substantially ridge-shaped compound semiconductor layer, and the width of the opening is 2.2 to 1
The thickness is preferably 000 μm. According to the semiconductor light emitting device, a high output operation can be realized. Further, by providing a sufficient contact area between the electrode adjacent to the contact layer and the second conductive type second cladding layer and the contact layer, the resistance of the entire device can be suppressed low. A part of the side surface and the upper surface of the ridge on which the contact layer is formed can be further covered with a protective film for the purpose of preventing oxidation or the like.
Even in such a case, the resistance of the entire device can be reduced as compared with the case where the protective film is not formed on the side surface of the ridge, and is included in the present invention. In particular, a material having a high specific resistance such as an AlGaInP-based or AlGaInN-based (particularly, p-type) is effective in reducing the resistance of the entire device.

In the present invention, a part of the ridge type compound semiconductor layer having a smaller refractive index than the active layer over the opening overlaps the protective film, that is, the protective film inside the opening and at least on both sides of the opening. It is preferable that the second conductive type second cladding layer 28 is formed on an upper part. The lower limit of the overlapping portion of the second conductive type second cladding layer 28 on the protective film 27 is preferably 0.01 μm, more preferably 0.1 μm or more, and the upper limit is less than 2.0 μm (excluding 2.0 μm). Preferably, it is 1.0 μm or less. By adopting such an embodiment, it is possible to improve the controllability of the light distribution that seeps into the vicinity of the boundary between the protective film 27 and the bottom of the ridge, or to reduce the light absorption of the contact layer formed on the side surface of the ridge. be able to. In this case, like the conventional ridge waveguide type laser, the protective film 2 is
7 is not required, which is effective in simplifying the process and reducing the cost.

In the present invention, the width of the opening 32 is 4 μm.
You can set: By setting the thickness to 4 μm or less, the transverse mode can be made a single mode (transverse light intensity distribution of a single peak). In addition, by being characterized in that the far-field image has a single peak, a laser suitable for a wide range of uses such as information processing and optical communication can be provided.

In the present invention, the thickness of the cladding layer formed between the active layer and the protective film is set to 0.10 to 0.50.
By setting it to μm, it becomes easy to realize a high output operation in the above-mentioned opening width (stripe width).

Further, the protective film 27 is formed of a SiNx film,
iO ₂ film, SiON film, Al ₂ O ₃ film, ZnO film and Si
By using a dielectric such as a C film, it is easy to realize a high output operation under the above conditions. At this time, it is preferable that the difference in the refractive index at the oscillation wavelength between the protective film 27 and the first cladding layer 25 of the second conductivity type is 0.5 to 2.0.

The thickness of the second conductive type second cladding layer 28 is 0.25 to 0.25 with respect to the width W of the protective film opening.
About 2.0 times is preferable. Within this range, there is no remarkable protrusion as compared with the surroundings (a current block layer and a ridge dummy region to be described later). Also, on the contrary, it is preferable because the post-process such as the electrode forming process is not difficult to be performed because it is extremely lower than the surroundings.

In addition to the structure of the present invention, by forming a ridge-shaped clad by regrowth with an oxidation preventing layer provided on the epitaxial surface side of the DH structure, the passage resistance is increased at the regrowth interface. It is possible to easily prevent the generation of a high-resistance layer.

The antioxidant layer is not particularly limited as long as it is a material which is hardly oxidized or easy to clean even if oxidized. Specifically, the content of elements that do not contain easily oxidizable elements such as Al is low (about 0.3 or less).
III-V compound semiconductor layer. In addition, it is preferable that light from the active layer is not absorbed by selection of the material or the thickness, and the material is selected from materials having a larger band gap than the material of the active layer. , More preferably 30
If it is less than nm, most preferably less than 10 nm, it can be used because light absorption can be substantially ignored.

In the present invention, the cladding layer of the regrown portion is grown so as to cover the upper surface of the protective film made of an insulator, and the controllability of the distribution of light seeping into the vicinity of the protective film and the ridge is improved. A contact layer is grown on substantially the entire surface on which the growth can be made on the cladding layer in the growth part, thereby suppressing oxidation of the side surface of the cladding layer and increasing the contact area with the electrode on the epitaxial surface side, thereby making contact with the electrode. It is particularly preferable to reduce the resistance. The growth of the cladding layer and the contact layer of these regrowth portions so as to cover the upper portion of the insulating film may be performed independently, or both may be combined. Furthermore, when the ridge is formed by regrowth, in order to improve the controllability of the composition, carrier concentration and growth rate of the ridge, a ridge dummy layer having a larger area than the ridge to which the current is injected is not used. It is also possible to provide. At this time, a thyristor structure or the like, which is insulated from an oxide film or the like, is formed in the ridge dummy layer in order to prevent the passage of current. Further, when the current injection stripe is formed on the off-substrate in the direction perpendicular to the off-direction by the manufacturing method of the present invention, the ridge for regrowth is asymmetrical in the left and right direction, but more than the conventional semiconductor block layer. The difference in the refractive index between the protective film and the cladding layer in the ridge can be easily increased, or the cladding layer in the regrown portion can be grown so as to cover the upper surface of the protective film by appropriately selecting the stripe direction. As a result, the symmetry of the distribution of light seeping into the vicinity of the protective film and the ridge is good, and stable fundamental transverse mode oscillation up to high output can be obtained. As described above, the present invention is applicable to various ridge stripe type waveguide semiconductor light emitting devices.

In a preferred embodiment of the present invention, the refractive index of the first cladding layer 25 of the second conductivity type is larger than the refractive index of the second cladding layer 28 of the second conductivity type. As a result, it is possible to suppress the tailing of the light distribution (near-field image) to the ridge portion, improve the symmetry of the vertical spread angle (far-field image), suppress the side peak of the horizontal spread angle (far-field image), Alternatively, laser characteristics and reliability can be improved by suppressing light absorption in the contact layer.

In another preferred embodiment of the present invention, the second
An antioxidant layer is provided at least immediately below the opening of the protective film on the conductive type first cladding layer, that is, in the stripe region and preferably on both sides thereof. Accordingly, when the cladding layer of the ridge portion is formed by regrowth, it is possible to prevent the generation of a high-resistance layer that increases the passage resistance at the regrowth interface. Also, if a large amount of impurities such as oxygen are present at the regrowth interface, light absorption (heat generation) at the interface due to deterioration of crystal quality and diffusion of impurities through defects are promoted, resulting in deterioration of characteristics and reliability. I will.

The present invention can be applied to various ridge waveguide type semiconductor light emitting devices, for example, it can be combined with the following embodiments. (1) By forming a current blocking layer such as a semiconductor and a dielectric on the outer side of the protective film covering both sides of the stripe region, the yield at the time of cleavage and assembling is improved, and the ridge portion at the time of assembling by junction down is improved. The stress is reduced and the life is extended. (2) By setting the width of the opening and the distance between the active layer and the protective film within an appropriate range, and adopting a configuration in which the vertical spread angle of light is within a specific range, etc. Enables excitation oscillation. (3) By forming a structure having a ridge dummy region further outside the protective film covering both sides of the stripe region,
The thickness, composition, and carrier concentration of the stripe portion are easily controlled. As a semiconductor laser device using the semiconductor light emitting device of the present invention, a light source for information processing (usually an AlGaAs system (wavelength 78)
0 nm), AlGaInP system (wavelength 600 nm)
Band), InGaN-based (wavelength around 400 nm)), communication signal light source (normally 1.3 μm band, 1.5 μm band with InGaAsP or InGaAs as active layer) laser, fiber excitation light source (InGaAs strained quantum well active layer / Near 980 nm using GaAs substrate, InGaAs
1480 nm using P strain well active layer / InP substrate
Examples include various devices that require particularly high-output operation, such as a semiconductor laser device for communication such as a laser (for example, in the vicinity). Also, among communication lasers, a laser having a nearly circular shape is effective in increasing the coupling efficiency with a fiber.
A laser having a single peak in the far-field image can be used as a laser suitable for a wide range of uses such as information processing and optical communication.

Further, the present invention can be applied to a light emitting diode (LED) of an edge emitting type or the like other than the semiconductor laser.

[0086]

The present invention will be described in more detail with reference to specific examples. Materials, reagents, ratios, operations, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples.

Example 1 In this example, a semiconductor light emitting device was manufactured by forming each layer in the order shown in FIG. 4 (a) to 4 (f), there are portions where the dimensions are intentionally changed in order to facilitate understanding of the structure, but the actual dimensions are as described in the following text.

On a n-type GaAs (n = 1 × 10 ¹⁸ cm ⁻³ ) substrate 101 having a thickness of 350 μm and a (100) surface, a 2.0 μm-thick n-type Al
_0.35 Ga _0.65 As (Si doped: n = 1 × 10 ¹⁸ c
m ⁻³ ), an n-type cladding layer 102, a double quantum well (DQW) active layer 103, and a p-type Al layer having a thickness of 0.25 μm.
_0.35 Ga _0.65 As (Be doped: p = 1 × 10 ¹⁸ c
m ⁻³ ), a p-type first cladding layer 104 having a thickness of 10 n
m p-type GaAs (Be doped: p = 1 × 10 ¹⁸ c
m- ³ ) An antioxidant layer (etching stop layer) 105 was sequentially laminated. The double quantum well (DQW) active layer 103 includes a GaAs optical confinement layer having a thickness of 30 nm (non-doped), an In _0.2 Ga _0.8 As well layer having a thickness of 6 nm (non-doped), a GaAs barrier layer having a thickness of 8 nm (non-doped), 6n thick
m In _0.2 Ga _0.8 As well layer (non-doped) and a GaAs light confinement layer (non-doped) with a thickness of 30 nm are sequentially laminated.

In order to form an impurity diffusion region,
In addition, a 100 nm thick S
An iNx protective film is deposited by plasma CVD and photo
[0-11] B by lithography and etching
A rectangular SiNx protective film 106 was formed in the direction (FIG. 4).
(A)). Note that the [01-1] B direction is a general II
In the group IV compound semiconductor, the (100) plane and the (01) plane
The (11-1) plane existing between the -1) planes is a group V element.
Define it to be the surface that appears. At this time, SiNx protection
Wet etch such as buffered hydrofluoric acid solution for film etching
Or SF ₆, CF_FourDryer using gas such as
Tching was used. The length of the rectangular SiNx protective film is
700 μm, width 20 μm, side of rectangular protective film
Space spacing in the direction is 330μm, space spacing in the vertical direction
Was set to 40 μm.

A selective growth using the MOCVD method around the stripe-shaped SiNx film 106 has a thickness of 0.3
μm high concentration p-type Al _0.7 Ga _0.3 As (Zn doped: p
= 1 × 10 ²⁰ cm ⁻³ ) Impurity diffusion layer 107, thickness 0.2
μm undoped GaAs cap layer 108 at 580 ° C.
Formed.

After that, annealing (7
(15 ° C., 1 hour) to form a p-type GaAs
Impurities from the surface of the prevention layer 105 to a depth of 0.4 μm.
(Zn) diffusion was performed (FIG. 4B). This impurity diffusion
The annealing step for the
In the same MOCVD apparatus as the selective growth process of the
I went next. This simplifies the manufacturing process
Thus, the reproducibility of the distribution of impurities made of Zn was high.
Due to the annealing step, the impurities are indicated by oblique lines in FIG.
And the diffusion front position on the element end face is n
It reached the inside of the mold cladding layer 102. At this time, FIG.
In the III-III section of (b), the SiNx protective film 10
Impurities diffused into the region except under 6 (FIG. 4C).
Further, the composition profile in the depth direction was not subjected to Ar sputtering.
When analyzed by Auger electron spectroscopy, double quantum
Mixed crystal formation occurs in the well (DQW) active layer 103.
(See FIGS. 7A and 7B).
This is due to the high concentration (~ 1 × 10 ¹⁹cm^-3) For the diffusion of Zn
From In_0.2Ga_0.8As well layer and GaAs barrier layer
And inter-diffusion in the guide layer
Is caused. In addition, photoluminescence (P
L) The emission wavelength from the active layer was measured by the method
8, as shown in FIG.
In the region where the PL peak wavelength is shortened by 40 nm (9
From 70 nm to 930 nm)
Was. That is, the band gap expands (55 meV)
The laser light emitting end face
It was confirmed that the window structure was formed.

Next, the undoped GaAs cap layer 10
8. The high concentration p-type GaAs impurity diffusion layer 107 was removed by etching. At this time, the undoped GaAs cap layer 108 and the high-concentration p-type Al _0.7 Ga _0.3 As impurity diffusion layer 107 are partially removed with a phosphoric acid / hydrogen peroxide-based etchant, and the high-concentration p-type is removed with a hydrofluoric acid-based etchant.
The remainder of the type Al _0.7 Ga _0.3 As impurity diffusion layer 107 was removed, and the etching was stopped on the surface of the p-type GaAs antioxidant layer 105. Then, the rectangular SiNx protective film 106 is formed.
By wet etching such as buffered hydrofluoric acid solution or SF
₆ , removed by dry etching using a gas such as CF ₄ .

Thereafter, a SiNx protective film 109 having a thickness of 100 nm is formed on the surface of the double hetero substrate by plasma CV.
D, and [0-
11] Striped opening 1 whose longitudinal direction is in direction B
10 (the p-type GaAs antioxidant layer 105 was exposed) (FIG. 4D). The width of the striped opening is 2.5
μm, and the horizontal space interval between the stripe-shaped openings was 330 μm.

Thereafter, a thickness of 1.8 μm is formed by MOCVD.
m p-type Al _0.4 Ga _0.6 As (Zn doped: p = 1 × 1
0 ¹⁸ cm ⁻³ ) and a 0.5 μm-thick p-type GaAs (Zn-doped: p = 2 × 1)
A contact layer 112 of 0 ¹⁹ cm ⁻³ ) was grown (FIG. 4E). In the above MOCVD method, III
Group materials include trimethylgallium (TMG), trimethylaluminum (TMA) and trimethylindium (T
MI), arsine and phosphine as group V raw materials, and hydrogen as carrier gas. Dimethyl zinc was used as the p-type dopant, and disilane was used as the n-type dopant. During the growth of the ridge, HCl gas is changed to HCl / I
The group II was introduced such that the molar ratio was 0.2, especially the molar ratio of HCl / TMA was 0.3.

Thereafter, the p-side electrode 113 was deposited and the substrate was thinned to 100 μm, and then the n-side electrode 114 was deposited and alloyed (FIG. 4 (f)). The wafer thus fabricated was cleaved at almost the center of the impurity diffusion region having a width of 40 μm, and cut into chip bars so as to form a laser light emitting end face (primary cleavage), thereby producing an end face window structure laser. The resonator length at this time was 740 μm. After applying an asymmetric coating of 5% front end face-95% rear end face,
It was separated into chips by secondary cleavage. After assembling the chip by junction down, current-light output and current-voltage characteristics were measured at 25 ° C. by continuous conduction (CW).

FIG. 9 shows the current-light output characteristics of the laser device thus manufactured. In the laser having the window structure manufactured according to the present embodiment, the optical output increases with an increase in the operating current, and is kink-free to about 400 mW and about 550 mW.
Light output was obtained without COD up to W. However, even if the operating current is further increased, the light output does not increase, and the light output is limited by heat saturation due to heat generation of the element itself. The oscillation wavelength is 976 nm on average, and the threshold current is 20 m on average.
A, The slope efficiency was 0.8 mW / mA on average, and the characteristics were very good. At 250 mW output, the vertical spread angle is 28 ° on average, and the horizontal spread angle is 8.
5 °. At this time, it was found that the astigmatic difference could be made as very small as 2 μm or less, and the light source would be excellent in optical coupling characteristics with an optical fiber. Furthermore, high reliability (300 ° C at high temperature of 70 ° C, 250mW, high power)
0 hours or more). Further, since the opening for current injection is formed by the etching stop layer, the uniformity of the device structure can be improved, and the above-described semiconductor laser device can be manufactured with high yield.

(Embodiment 2) This embodiment is shown in FIG. 5 (a) to 5 (f), there are portions where the dimensions are intentionally changed in order to facilitate understanding of the structure, but the actual dimensions are as described in the following text.

First, from the (100) plane, [0-1-
1] 350 μm thick GaAs turned off by 10 ° in the A direction
0.5 μm thick on the s substrate 201 by MOCVD.
m-doped n-type GaAs buffer layer (n = 1 × 10
¹⁸cm^-3) (Not shown), 1.5 μm thick Si-doped
n-type Al_0.75Ga_0.25As first cladding layer (n = 1 × 1
0¹⁸cm^-3) 202, 0.25 μm thick Si-doped n
Type (Al_0.7Ga_0.3) _0.5In_0.5P second cladding layer (n
= 1x10¹⁸cm^-3) 203, 50 nm thick non-doped
(Al_0.5Ga_0.5)_0.5In_0.5P light guide layer or
5 nm thick non-doped (Al_0.5Ga_0.5)_0.5In_0.5
Non-doped Ga having a thickness of 5 to 6 nm sandwiched between P barrier layers
_0.44In_0.56Triple quantum well composed of P well layers (three layers)
(TQW) Active layer 204, Zn-doped with 0.3 μm thickness
p-type (Al_0.7Ga_0.3)_0.5In_0.5P first cladding layer
(P = 7 × 10¹⁷cm^-3) 205, 5 nm thick Zn
P-type Ga_0.5In_0.5P oxidation prevention layer (p = 1 × 10¹⁸
cm^-3) 206 by stacking them sequentially.
A structure was formed.

At this time, it is preferable to select a composition of the antioxidant layer 206 so as not to absorb the light recombined by the active layer in order to reduce the threshold current, but it is intentionally used for self-pulsation. It is also possible to absorb light and use it as a saturable absorption layer. In order to prevent light from being absorbed, the composition of the Ga _x In _{1 -x} P antioxidant layer is changed to the Ga rich side (X = 0.5 to 1), or a small amount of Al is added ((Al _{X Ga 1-X) 0.5 In} 0.5
P, X = about 0.1 to 0.2) is more effective.

In order to form an impurity diffusion region, first,
A 100 nm thick SiN film is formed on the surface of this double hetero substrate.
An x protective film 207 is deposited by plasma CVD, and then [0-11] by photolithography and etching.
A rectangular SiNx film 207 was formed in the direction (FIG. 5
(A)). At this time, the etching of the SiNx protective film 207 was performed by wet etching using a buffered hydrofluoric acid solution or the like or dry etching using a gas such as SF ₆ or CF ₄ . The length of the rectangular SiNx protective film is 470 μm,
The horizontal width was 20 μm, the horizontal space interval of the rectangular protective film was 280 μm, and the vertical space interval was 30 μm.

Around the rectangular SiNx film 207, M
By selective growth using the OCVD method, a 0.3 μm thick high-concentration p-type GaAs (Zn-doped: p = 1 × 10 ²⁰ cm
^-3 ) An impurity diffusion layer 208 and an undoped GaAs cap layer 209 having a thickness of 0.2 μm were formed at 580 ° C.

After that, annealing (7
00 ° C., 1 hour) to obtain p-type Ga_0.5In
_0.50.5 μm deep from the surface of the P oxidation preventing layer 206
Then, impurity (Zn) diffusion was performed (FIG. 5B). this
Due to the annealing process, the impurities are indicated by oblique lines in FIG.
And the diffusion front position on the element end face is n
The mold reaches the inside of the first cladding layer 202. At this time,
5B, the SiNx protective film 2
The impurity diffused into the region except underneath (see FIG. 5).
(C)). At this time, the composition profile in the depth direction is represented by A
It was analyzed by Auger electron spectroscopy while r sputtering
At the same time, the triple quantum well (TQW) activity was the same as in Example 1.
It has been determined that intermixing has occurred in layer 204.
Was. This is due to the high concentration (~ 1 × 10¹⁹cm^-3) Zn expansion
By dispersion, Ga_0.44In_0.56P well layer and (Al _0.5Ga
_0.5)_0.5In_0.5In the As well layer and the guide layer,
This is because mutual diffusion (intermixing) has occurred. Ma
In the photoluminescence (PL) method, the active layer
When the emission wavelengths were measured, Zn diffusion (that is, mixing) was observed.
In the crystallized region, the PL peak wavelength is 30 nm short wave
Elongation (change from 645 nm to 615 nm)
There was found. That is, the band gap is enlarged (94 me
V) The laser light emitting end
You can see that the window structure is formed on the surface
Was.

Next, the undoped GaAs cap layer 20
9. The high concentration p-type GaAs impurity diffusion layer 208 was removed by etching. At this time, the undoped GaAs cap layer 209 and the high-concentration p-type GaAs impurity diffusion layer 208 were removed with a phosphoric acid / hydrogen peroxide-based etchant, and etching was stopped on the surface of the p-type Ga _0.5 In _0.5 P oxidation preventing layer 206. . Then, the rectangular SiNx protective film 207 is formed.
By wet etching such as buffered hydrofluoric acid solution or SF
₆ , removed by dry etching using a gas such as CF ₄ .

Next, an insulating SiNx protective film (refractive index: 1.9, wavelength: around 650 nm) 210 is deposited to a thickness of 200 nm on the surface of the double heterosubstrate. A striped opening 211 having a width of 3.5 μm was opened in the orthogonal [01-1] B direction (FIG. 5D).

An MO 211 is formed in the stripe-shaped opening 211.
By selective growth using the CVD method, a Zn-doped p-type Al _0.77 Ga _0.23 As cladding layer having a height of 2.0 μm at the center of the ridge (p = 1.5 × 10 ¹⁸ cm ⁻³ ; refractive index 3.3, wavelength 655 nm) 212 and Zn-doped G with a thickness of 0.5 μm
A ridge composed of the aAs contact layer 213 was formed (FIG. 5E). At this time, most of the side surfaces of the ridge are often (311) A plane or a plane close to the (311) A plane, and the cladding layer of the regrown portion is grown so as to cover the upper surface of the protective film made of an insulator. A contact layer 213 was grown on substantially the entire surface of the cladding layer on which growth was possible. According to SEM observation, the ridge-shaped p-type second cladding layer 212 is approximately 0.4 μm
It was confirmed that they were formed to overlap. In all stripe widths, the p-GaAs contact layer covered the entire side wall of the ridge. By forming such a structure, the controllability of the distribution of light that seeps into the vicinity of the protective film 212 and the ridge is improved, the surface oxidation due to the exposure of the side surface of the cladding layer is suppressed, and the electrode on the epitaxial surface side is connected. Was increased, and the contact resistance with the electrode was able to be reduced. This tendency is due to the
lGaAs, especially AlAs mixed crystal ratio (Al composition) 0.2 to
0.9, preferably 0.3 to 0.8.

It should be noted that there is no particular problem if the ridge side wall is partially or entirely covered with the SiNx protective film as in the conventional method after the ridge growth, but in this embodiment, the process is simplified and the contact resistance is reduced. In consideration of the above, a protective film made of a dielectric or the like was not formed on the side surface of the ridge. Due to the influence of the off-angle of the substrate, the ridge shape was slightly asymmetric (not shown).

In the above MOCVD method, the group III raw materials include trimethyl gallium (TMG), trimethyl aluminum (TMA) and trimethyl indium (TM
I), arsine and phosphine were used as group V raw materials, and hydrogen was used as a carrier gas. Dimethyl zinc was used as the p-type dopant, and disilane was used as the n-type dopant.
During the growth of the ridge, HCl gas is changed to HCl / III.
The group was introduced such that the molar ratio of the group was 0.2, particularly the molar ratio of HCl / TMA was 0.3.

Thereafter, the p-side electrode 214 was deposited and the substrate was thinned to 100 μm, and then the n-side electrode 215 was deposited and alloyed (FIG. 5 (f)). The wafer thus fabricated was cleaved at substantially the center of the impurity diffusion region having a width of 30 μm, and cut into chip bars so as to form a laser light emitting end face (primary cleavage), thereby forming a laser resonator structure. The resonator length at this time was 500 μm. Front end face 1
0%-After applying an asymmetric coating of 90% of the rear end face,
It was separated into chips by secondary cleavage. After assembling by chip junction down, current-light output and current-voltage characteristics were measured at 25 ° C. by continuous energization (CW). Very good current-voltage characteristics and current-output characteristics were exhibited, and the threshold value was 1.9 V, which was a low value corresponding to the band gap of the active layer, and it was confirmed that no high-resistance layer was present. Further, it was confirmed that the series resistance was as small as 5 to 6Ω and the contact resistance between the p-type contact layer and the p-type electrode was extremely small. The laser of this embodiment can achieve a high output up to an optical output of 200 mW, an oscillation wavelength of 655 nm on average, a threshold current of 20 mA on average, and a slope efficiency of 0.85 m on average.
The characteristics such as W / mA are very good, the vertical divergence angle is 23 ° on average, a far field image (beam divergence angle) of a single peak as designed is obtained, and the control of light distribution is very It was confirmed that it was good. From this result, SiNx
Since the transverse mode is basically controlled by the insulating film,
It is considered that there is no adverse effect on the kink level and the like due to the slightly asymmetric regrowth ridge shape. In the specification of the present application, “single peak” does not necessarily mean that only one peak exists, but means that there is no other peak having an intensity of 1/10 or more of the maximum peak. In addition, even at the horizontal divergence angle, a good single-peaked peak without any ripple or side peak was obtained. From these results, it can be seen that the laser structure of the present invention is used as a light source for writing on an optical disk such as a DVD. In addition, high reliability (60
, A stable operation at a high temperature of 50 mW and a high output for 1000 hours or more). Further, since the openings are formed by selective growth, the uniformity of the opening width can be improved, and the above-described semiconductor laser device can be manufactured with a high yield. Also turned out to be small.

When a semiconductor laser device having a wider stripe-shaped opening than that of this embodiment was manufactured, when the width became 5 μm or more, most of the devices were in a single transverse mode (transverse light with a single peak). It was also found that oscillation did not occur in the intensity distribution. Therefore, in order to realize single transverse mode oscillation, the width of the stripe-shaped opening must be 5
It has been found that the thickness is desirably not more than μm.

Further, as a result of confirming by simulation from a result of the experiment, a region where high-power operation can be performed, the lateral effective refractive index step inside the active layer is 5 × 10 ^{−3 to} 1.3 × 10 ³ .
It turns out that it needs to be set to about ^-2 .

In this embodiment, the n-side cladding layer has a thickness
1.5 μm Si-doped Al_0.75Ga _0.25As the first class
Pad layer (n = 1 × 10¹⁸cm^-3) 202 and thickness 0.2
5 μm Si-doped n-type (Al_0.7Ga_0.3)_0.5In_0.5
P second cladding layer (n = 1 × 10¹⁸cm^-3With 203)
Although it has a two-layer structure, one layer of any composition
It may be structured. At this time, one n-side cladding layer
The thickness can be approximately the same as the thickness of two layers.
Also, in order to perfectly match the lattice with the GaAs substrate, A
A small amount of P is added to the lGaAs layer to form an AlGaAsP layer.
For example, Zn-doped p-type Al_0.75Ga_0.25
As cladding layer (p = 1.5 × 10¹⁸cm ^-3) Is Al
_0.75Ga_0.25As_0.97P_0.03It can also be. this
These modifications can be made appropriately within a range obvious to those skilled in the art.
Noh.

(Comparative Example) A laser device was manufactured in the same process as in Example 1 except that the end region was not formed with a window structure. That is, the laser device of this comparative example is different from the example in that it does not have an impurity diffusion region.
In the laser having this element structure, when the operating current was increased, COD was generated when an optical output of about 350 mW was obtained, and the laser element was broken (FIG. 9).

[0113]

According to the semiconductor light emitting device of the present invention, since the end face of the optical waveguide has a window structure, deterioration of the end face can be suppressed, so that the reliability of the element in a high output operation can be improved. Therefore, the present invention can be applied to a wide range of fields including a semiconductor laser and the like, and is particularly suitable for a light source for exciting an optical fiber amplifier used in an optical communication system.

In addition, selective ridge growth (SRG; Cell)
By forming an impurity diffusion layer in the upper part near the active layer based on the active Ridge Growth (structure), it is possible to improve the position controllability of the impurity diffusion front and reduce the leakage current at the end.

In the element structure of the present invention, a ridge is formed by selective growth in a stripe region into which a current is injected using a protective film made of an insulator, and no protective film made of an insulator is formed on the side surface of the ridge. Therefore, the stripe width can be linearly increased and decreased. In addition, since the ridge portion grows in the horizontal direction and is less susceptible to the undulation of the ridge in the tapered portion of the stripe, in the horizontal far-field image, good unimodal characteristics without ripples and side peaks Peaks are easily obtained. In addition, a contact layer is formed on substantially the entire surface including the top and side surfaces of the ridge portion formed by the growth, and the contact area between the contact layer and the electrode is increased, so that the contact resistance is reduced and the cladding layer on the ridge side wall is formed. Surface oxidation (especially when Al is included) is also prevented, and laser characteristics and reliability are improved.

Further, even when a substrate having a large off-angle with respect to a low-order plane orientation (such as (100)) is used to shorten the wavelength, as in the case of an AlGaInP / GaInP-based visible laser, the above-described ridge conduction is also improved. A stable fundamental transverse mode can be obtained up to a high-output operation without substantially affecting the left-right asymmetry of the ridge shape in the wave-shaped laser by the left-right asymmetry of the light intensity distribution.

Further, according to the present invention, since the opening can be formed by selective growth, the uniformity of the opening width can be improved, and the above-described semiconductor laser device can be manufactured with a high yield. In particular, the laser manufacturing method of the present invention is effective for manufacturing a laser having a small structural design margin.

[Brief description of the drawings]

FIG. 1 is a perspective view of one embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is a cross-sectional view of one embodiment of the semiconductor light emitting device of the present invention shown in FIG. 1, which is a cross-sectional view taken along the line II-II in FIG.

FIG. 3 is a cross-sectional view of one embodiment of the semiconductor light-emitting device of the present invention shown in FIG. 1, which is a cross-sectional view taken along the line III-III in FIG.

FIG. 4 is a process diagram illustrating an example of a manufacturing process of the semiconductor light emitting device of the present invention.

FIG. 5 is a process diagram illustrating another example of the manufacturing process of the semiconductor light emitting device of the present invention.

6A and 6B are diagrams illustrating a band gap of an active layer of an embodiment of the semiconductor light emitting device according to the present invention, wherein FIG. 6A is a diagram illustrating a band gap of a window region, and FIG. It is a figure showing a gap.

7A and 7B are diagrams showing measurement results using Auger electron spectroscopy in the semiconductor light emitting device of the present invention, wherein FIG. 7A is a diagram showing a device without diffusion for comparison, and FIG. FIG. 4 is a diagram showing a mixed crystal due to impurity diffusion in one embodiment of the semiconductor light emitting device of FIG.

FIG. 8 is a diagram showing a measurement result using a photoluminescence (PL) method in the semiconductor light emitting device of the present invention.

FIG. 9 is a diagram showing the relationship between the operating current and the light output of one embodiment of the semiconductor light emitting device of the present invention and a comparative example.

FIG. 10 is a top view of one embodiment of the semiconductor light emitting device of the present invention.

[Explanation of symbols]

 Reference Signs List 21: substrate 22: first conductivity type cladding layer 23: first conductivity type cladding layer 24: active layer 25: second conductivity type first cladding layer 26: antioxidant layer (etching stop layer) 27: protective layer 28: first 2nd conductivity type second cladding layer 29: contact layer 30: epitaxial side electrode 31: substrate side electrode 32: opening 51, 57: light confinement layer 52, 54, 56: well layer 53, 55: barrier layer 101: substrate 102 : N-type cladding layer 103: Active layer 104: P-type first cladding layer 105: Oxidation prevention layer (etching prevention layer) 106: SiNx protection film 107: Impurity diffusion layer 108: Cap layer 109: SiNx protection film 110: Striped Opening 111: p-type second cladding layer 112: contact layer 113: p-side electrode 114: n-side electrode 201 : Substrate 202: n-type first cladding layer 203: n-type second cladding layer 204: active layer 205: p-type first cladding layer 206: antioxidant layer 207: SiNx protective film 208: impurity diffusion layer 209: cap layer 210 : SiNx protective film 211: striped opening 212: p-type second cladding layer 213: contact layer 214: p-side electrode 215: n-side electrode W1: end width W2: center width

Claims (42)

[Claims] 1. A compound semiconductor layer including an active layer on a substrate, a protective film having an opening formed on the compound semiconductor layer, and a ridge type formed on the opening and having a smaller refractive index than the active layer. Wherein the band gap of the active layer at both ends of the optical waveguide is larger than the band gap of the active layer in the current injection region at the center of the optical waveguide. 2. The semiconductor light emitting device according to claim 1, wherein the ridge type compound semiconductor layer is formed inside the opening and at least on a part of the protective film on both sides of the opening. . 3. The semiconductor light emitting device according to claim 1, wherein the compound semiconductor layer including the active layer includes layers above and below the active layer, each having a lower refractive index than the active layer. 4. A layer having a lower refractive index than the active layers above and below the active layer, the layer on the substrate side is a first conductive type clad layer, and the other layer is a second conductive type first clad layer. The semiconductor light emitting device according to claim 1, wherein: 5. The semiconductor light emitting device according to claim 4, wherein protective films are provided at both end portions of the optical waveguide on the second conductive type first cladding layer. 6. The semiconductor light emitting device according to claim 4, wherein an oxidation preventing layer is provided on at least the opening on the second conductive type first cladding layer. 7. The semiconductor light emitting device according to claim 1, wherein said active layer has a quantum well structure. 8. The semiconductor light emitting device according to claim 1, wherein quantum well layers in said active layer at both ends of said optical waveguide are mixed crystal. 9. The semiconductor light emitting device according to claim 1, wherein impurities are diffused into said active layer at both ends of said optical waveguide. 10. The semiconductor light emitting device according to claim 9, wherein pn junctions at both ends of the optical waveguide are formed at least in the first conductivity type clad layer by the diffusion of the impurity. 11. The semiconductor light emitting device according to claim 1, wherein said active layer has a single well layer. 12. The active layer according to claim 1, wherein the active layer has a plurality of well layers and a barrier layer sandwiched between the well layers, and the thickness of the barrier layer is larger than that of the well layer.
The semiconductor light emitting device according to any one of claims 10 to 10. 13. The semiconductor light emitting device according to claim 11, wherein a compressive strain is applied to the well layer. 14. The semiconductor light emitting device according to claim 11, wherein In is contained in a constituent element of said well layer. 15. The semiconductor light emitting device according to claim 11, wherein In is not contained in a constituent element of a barrier layer or a guide layer sandwiching said well layer. 16. The semiconductor light emitting device according to claim 11, wherein a constituent element of a barrier layer or a guide layer sandwiching said well layer contains Al. 17. The semiconductor device according to claim 1, further comprising a current blocking layer outside the protective film having the opening.
The semiconductor light emitting device according to any one of the above. 18. The method according to claim 18, wherein the current blocking layer has at least a first
18. The semiconductor light emitting device according to claim 17, comprising a semiconductor layer of a conductivity type or a high resistance. 19. The semiconductor light emitting device according to claim 17, wherein one or more etching stop layers are provided between said second conductivity type first cladding layer and said current blocking layer. 20. The semiconductor device according to claim 1, further comprising: a compound semiconductor layer including a layer having a smaller refractive index than an active layer, formed on the opening of the protective film having the opening. 13. The semiconductor light emitting device according to claim 1. 21. The semiconductor light emitting device according to claim 1, wherein a refractive index of the active layer is smaller than a refractive index of the protective film having the opening. 22. The apparatus according to claim 1, wherein the width of the opening is wider in the vicinity of the end face of the apparatus than in the center of the apparatus.
22. The semiconductor light-emitting device according to any one of claims 21 to 21. 23. The apparatus according to claim 1, wherein the width of the opening is smaller in the vicinity of the end face of the apparatus than in the center of the apparatus.
22. The semiconductor light-emitting device according to any one of claims 21 to 21. 24. The device according to claim 1, wherein the opening is a stripe-shaped opening extending to both ends.
24. The semiconductor light-emitting device according to any one of items 23 to 23. 25. The semiconductor according to claim 1, wherein the opening extends to one end but does not extend to the other end. Light emitting device. 26. The semiconductor light emitting device according to claim 1, wherein the opening is an opening that does not extend to both ends. 27. The semiconductor light emitting device according to claim 1, wherein a current is injected from said opening into said active layer. 28. The substrate according to claim 1, wherein the surface of the substrate has an off angle with respect to a low-order plane orientation.
8. The semiconductor light emitting device according to any one of 7. 29. The semiconductor light emitting device according to claim 1, wherein the far field image has a single peak. 30. An active layer at both ends of the optical waveguide has a band gap that is transparent to light generated in the active layer in a current injection region at the center of the optical waveguide. The semiconductor light emitting device according to claim 1. 31. The active layer is formed of at least GaAs, A
lGaAs, InGaAs, AlGaInAs, GaI
nP, AlGaInP, GaInAsP, AlGaIn
31. The semiconductor light emitting device according to claim 1, comprising AsP, GaN, or InGaN. 32. The side wall of the current blocking layer is (11
31. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device comprises a B surface. 33. The semiconductor light emitting device according to claim 1, wherein said current blocking layer is formed by selective growth. 34. The semiconductor light emitting device according to claim 1, which is used as a light source for exciting an optical fiber amplifier. 35. The semiconductor according to claim 1, wherein said impurity diffusion layer is formed in a crystal growth apparatus, and then heat treatment is performed in said crystal growth apparatus. Light emitting device. 36. The semiconductor light emitting device according to claim 35, wherein the crystal growth apparatus is a metal organic chemical vapor deposition apparatus. 37. The semiconductor light-emitting device according to claim 8, wherein the surface is locally heated to cause a mixed crystal. 38. The semiconductor light emitting device according to claim 37, wherein an electron beam or laser light irradiation is used as a method for locally raising the surface temperature. 39. A ridge-type compound semiconductor layer is selectively grown on the opening by performing metal organic chemical vapor deposition while adding a gas containing a halogen element. 39. The semiconductor light emitting device according to any one of 1 to 38. 40. The semiconductor light emitting device according to claim 1, wherein a direction in which the opening extends is selected such that the contact layer is formed substantially over the entire surface of the ridge. 41. A crystal growth plane of the substrate is a (100) plane or a plane crystallographically equivalent thereto, and the direction in which the opening of the protective film extends is a [01-1] direction or a crystallographically equivalent direction. 41. An equivalent direction.
The semiconductor light emitting device according to any one of the above. 42. The semiconductor light emitting device according to claim 1, wherein at least a part of a side surface of the ridge type compound semiconductor layer is in contact with an electrode.