JP2001345516A - Semiconductor optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor optical device of a self-alignment type where reliability is high at high output. SOLUTION: This semiconductor optical device is provided with a substrate 11, a first conductivity-type clad layer 12 formed on the substrate, an active layer 13 formed on the first conductivity type-clad layer, a first clad layer 14 of a second conductivity type which is formed on the active layer, a current block layer 17 formed on the first clad layer of a second conductivity-type and has an aperture part 16, and a second clad layer 19 of a second conductivity-type, which is formed in the aperture part and at least on a part of the current block layer on both sides of the aperture part. In a section perpendicular to the longitudinal direction of the aperture part, the side surface of the aperture part 16 is represented by a curved line.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor optical device useful as a semiconductor laser or the like, and more particularly to a semiconductor optical device having high reliability in high-power operation.

[0002]

2. Description of the Related Art Semiconductor optical device devices are widely used for light-emitting devices and amplifiers. Among them, semiconductor lasers have characteristics such as robustness, high efficiency, a wide wavelength selection range, and durability. R & D is ongoing. FIG. 4 is a cross-sectional view of a typical semiconductor optical device having a self-aligned waveguide inner stripe structure (hereinafter referred to as “self-aligned type”). In FIG. 4, a first conductivity type cladding layer 42, an active layer 43, and a second conductivity type first cladding layer 44 are sequentially formed on a substrate 41. A current blocking layer 46 having an opening 45 is formed on the second conductive type first cladding layer 44 in the shape shown in the figure, and a second conductive type second cladding layer 47 and a contact layer 48 are further formed thereon in that order. Is formed. In such a self-aligned semiconductor optical device, a current block layer 46 is formed on the second conductivity type second cladding layer 44 by epitaxial growth, and then a part is removed by etching to have a regular mesa-shaped cross section. An opening 45 is formed. At this time, an etching solution having a plane orientation dependence is used for the purpose of forming the bottom and side surfaces of the opening 45 linearly and flatly.

[0003]

However, a self-aligned semiconductor optical device having an opening with a regular mesa cross section as described above causes a problem in the reliability of the device. For example, in a conventional manufacturing process of a semiconductor optical device, deterioration may occur in a clad layer laminated on an opening formed by etching. Such deterioration has a problem that the reliability and reproducibility of the semiconductor optical device are reduced, and the yield is reduced. In addition, the deterioration of the quality of crystal growth of the cladding layer in the opening causes a problem that the electric resistance in the opening is increased and the thermal resistance is increased, and further, the light loss in the opening is increased. Also, there has been a problem that the operating current increases. The increase in thermal resistance and operating current promotes bulk deterioration during high-power operation, and optical damage (hereinafter, “COD” (Catastr), which is output saturation or irreversible destruction.
optical Optical Damage)
Therefore, a reduction in thermal resistance and operating current in the device is indispensable for maintaining high performance and reliability of the optical device device.

Therefore, even in the case of a self-aligned semiconductor optical device having an opening formed by etching, a reliable device free from the above-mentioned problems, particularly, has good reproducibility of the device and is capable of performing high-power operation. Development of a semiconductor optical device having high reliability has conventionally been desired. Thus, the present invention has been made in view of the above-described problems of the prior art, and has a high reliability even at a high output even in a self-aligned semiconductor optical device device in which an opening is formed by etching. It is an object to provide a device device.

[0005]

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, by bending the side surface of the opening, a semiconductor optical device having high reliability at the time of high-power operation is obtained. The inventors have found that an apparatus can be provided, and have completed the present invention. That is, the current blocking layer in the semiconductor optical device is etched with an etchant having no plane orientation dependence to make the side surface of the opening a predetermined curved line. As a result, the epitaxial growth of the cladding layer on the side surface of the opening becomes favorable. Further, the inventors have found that the crystallinity of the cladding layer can be prevented from deteriorating, and have provided a semiconductor optical device of the present invention which is highly reliable even during high-output operation.

A semiconductor optical device according to the present invention comprises a substrate,
A first conductivity type cladding layer formed on the substrate, an active layer formed on the first conductivity type cladding layer, a second conductivity type first cladding layer formed on the active layer, A current blocking layer having an opening formed on the first cladding layer; and a second conductivity type second cladding layer formed inside the opening and at least on a part of the current blocking layer on both sides of the opening. A semiconductor optical device device, wherein a side surface of the opening is represented by a curved line in a cross section orthogonal to a longitudinal direction of the opening.

In a preferred aspect of the semiconductor optical device of the present invention, in a cross section orthogonal to the longitudinal direction of the opening, an absolute value of a slope of a straight line connecting a lower end and an upper end of a side surface of the opening is 0.3. An aspect in which the absolute value of the inclination of the tangent to the curved line is 0.05 to 5 at the lower end of the side surface in a cross section orthogonal to the longitudinal direction of the opening; A cross section perpendicular to the curved line, the absolute value of the inclination of the tangent of the curved line is 0.5 to 50 at the upper end of the side surface; a cross section perpendicular to the longitudinal direction of the opening, the tangent of the curved line An aspect in which the absolute value of the inclination continuously increases from the lower end to the upper end of the side surface; an aspect in which the main surface of the substrate is a (100) plane and the longitudinal direction of the opening is a [01-1] direction. The active layer is InGa an aspect comprising an s quantum well; an aspect in which the current blocking layer is formed of a semiconductor layer having a refractive index smaller than that of the second conductivity type second cladding layer; an aspect in which the current blocking layer has at least a first conductivity type or a high conductivity type. An embodiment in which the current blocking layer is made of AlGaAs or AlGaAsP; one or more layers of etching stop between the second conductive type first cladding layer and the current blocking layer; An embodiment having a layer;
An embodiment in which the etching stop layer is transparent to a light emission wavelength emitted by the active layer;
An embodiment in which a current is injected from the opening into the active layer; an embodiment in which the opening is formed by etching the current block layer with a phosphoric acid / hydrogen peroxide-based etchant An embodiment in which the opening is a stripe-shaped opening extending to both ends; the opening is an opening extending to one end but not extending to the other end; An aspect in which the optical output of the semiconductor optical device is 30 mW or more; an aspect in which the semiconductor optical device is used as a light source for exciting an optical fiber amplifier; the semiconductor optical device is used as an optical fiber amplifier An embodiment characterized by the following. In this specification, “to” means a range that includes numerical values described before and after it as a minimum value and a maximum value, respectively.

The semiconductor optical device of the present invention has a structure in which the current block layer has an opening, and the side surface of the opening is represented by a curved line in a cross section orthogonal to the longitudinal direction of the opening. Therefore, according to the semiconductor optical device of the present invention, the crystal growth on the side surface of the cross section of the second conductive type second clad layer in the opening becomes good, and the second conductive type second clad layer is deteriorated. There is an advantage that the occurrence of the phenomenon can be suppressed. Further, in the semiconductor optical device of the present invention, since the quality of the crystal growth of the second conductivity type second cladding layer on the side surface of the opening is improved, the electric resistance in the opening is reduced, and the thermal resistance is reduced. There is an advantage that generation can be suppressed. For this reason, the semiconductor optical device of the present invention has an advantage that the occurrence of output saturation and COD during high-output operation can be prevented with a high probability. Furthermore, in the case of the semiconductor optical device device of the present invention, since the opening is etched with an etchant having no plane orientation,
Since the uniformity of the opening width of the opening can be improved and the opening can be manufactured with a high yield in the manufacturing process, there is an advantage that the opening can be used particularly for a semiconductor optical device device having a small structural design margin.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a semiconductor optical device according to the present invention will be described below in detail. The semiconductor optical device of the present invention comprises a substrate, a first conductivity type clad layer formed on the substrate, an active layer formed on the first conductivity type clad layer, and a second layer formed on the active layer. A conductive type first cladding layer, a current blocking layer having an opening formed on the second conductive first cladding layer, formed inside the opening and at least on a part of the current blocking layer on both sides of the opening; A second conductive type second cladding layer, wherein a side surface of the opening is represented by a curved line in a cross section orthogonal to a longitudinal direction of the opening. The semiconductor optical device of the present invention comprises:
In addition to these layers, a layer usually formed in a semiconductor optical device may be appropriately provided.

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 layer B is further formed on that layer. The above expression also includes the case where the upper surface of the A layer and the bottom surface of the B layer are partially in contact with each other and one or more layers exist between the A layer and the B layer in other portions. 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 optical device according to the present invention, and FIG. 2 is an explanatory view in which the shape of an opening in the example is perspectively shown and an enlarged view of a part thereof. In FIG. 1, the structure of an example of the semiconductor optical device of the present invention is schematically shown as a substrate 1 made of a compound semiconductor.
1, a first conductivity type clad layer 12, an active layer 13, and a second conductivity type first clad layer 14 are laminated, and a current blocking layer 17 opened in a stripe shape via an etching stopper layer 15 thereon. And a surface protection layer 18. Further, a second conductive type second clad layer 19 is formed so as to be stacked on the opening 16 of the current block layer 17, and a contact layer 20 is formed on the second conductive type second clad layer 19.
Are formed.

In the semiconductor optical device according to the present invention, the second conductive type second cladding layer 19 is formed inside the opening having a curved side surface and at least partially on the current blocking layer 17 on both sides of the opening. It is an alignment type. Therefore,
The present invention requires a smaller number of times of growth and does not require a special technique such as selective growth as compared with a ridge-type semiconductor optical device device described in, for example, JP-A-10-290043 (particularly, Al). It is difficult to selectively grow a compound containing a large amount of).

In FIG. 1, the conductivity and material of the substrate 11 constituting the semiconductor optical device are not particularly limited as long as a crystal having a double hetero structure can be grown thereon. . Preferred is a conductive substrate. Specifically, GaAs, InP, GaP, ZnSe, and GaAs suitable for growing a crystal thin film on a substrate
It is preferable to use a crystal substrate of ZnO, Si, Al ₂ O ₃ or the like, 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 a (100) just plane, but includes a case having an off-angle of about 30 ° at the maximum. 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.

Further, the substrate 11 may be a hexagonal substrate, for example, a substrate made of Al ₂ O ₃ , 6H—SiC or the like.

On the substrate 11, a thickness of 0.2 to 2 μm is usually used so that defects of the substrate are not introduced into the epitaxial growth layer.
About m buffer layers may be formed in advance.

On the substrate 11, a compound semiconductor layer including the active layer 13 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. 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 cladding layer 12 of the first conductivity type comprises an active layer 13
It is formed of a material having a lower refractive index than that of the material. Further, the refractive index of the first conductivity type cladding layer 12 is preferably larger than the refractive index of the second conductivity type cladding layer. For example, first conductivity type GaInP, AlGaInP, AlInP, Al
GaAs, AlGaAsP, AlGaInAs, GaI
nAsP, GaN, AlGaN, AlGaInN, Be
General group III-V and group II-VI semiconductors such as MgZnSe, MgZnSSe, and CdZnSeTe can be used. The carrier concentration of the first conductivity type cladding layer 12, the lower limit is preferably 1 × 10 ¹⁷ cm ^-3 or more, 3 × 10 ¹⁷ cm
^-3 or more is more preferred, and 5 × 10 ¹⁷ cm ^-3 or more is most preferred. The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less,
It is more preferably 10 ¹⁹ cm ^-3 or less, and most preferably 5 × 10 ¹⁸ cm ^-3 or less.

When the first conductivity type cladding layer 12 is a single layer, it preferably has a thickness of about 0.4 to 5 μm, more preferably about 1 to 3 μm.

The first conductivity type cladding layer 12 may be composed of a plurality of layers.
a cladding layer made of nP, AlGaInP or AlInP, and a first conductivity type AlGaAs on the substrate side of the cladding layer.
Alternatively, an embodiment in which a cladding layer made of AlGaAsP is formed can be exemplified. At this time, the thickness of the layer on the active layer side is preferably reduced, and the lower limit of the thickness is preferably 0.01 μm or more, and more preferably 0.05 μm or more. The upper limit is preferably 0.5 μm or less, more preferably 0.3 μm or less. The lower limit of the carrier concentration of the layer on the substrate side is preferably 2 × 10 ¹⁷ cm ⁻³ or more, and more preferably 5 × 10 ¹⁷ cm ⁻³ or more. The upper limit is preferably 2 × 10 ²⁰ cm ⁻³ or less, and 5 × 10
^It is more preferably ¹⁹ cm ^-3 or less.

The structure of the active layer 13 constituting the semiconductor optical device of the present embodiment is not particularly limited, and the example of FIG. 1 has a double quantum well (DQW) structure.
The double quantum well (DQW) structure has a light confinement layer (non-doped) 51 and a quantum well layer (non-doped) 5
2. It has a structure in which a barrier layer (non-doped) 53, a quantum well layer (non-doped) 54, and a confinement layer (non-doped) 55 are sequentially stacked. In addition to the double quantum well (DQW) structure, for example, a single quantum well structure (SQ) including a quantum well layer and a light confinement layer sandwiching the quantum well layer from above and below.
QW) or a multi-quantum well structure having three or more quantum well layers and a barrier layer sandwiched between them, and an optical confinement layer stacked above the uppermost quantum well layer and below the lowermost quantum well layer. There may be. When the active layer 13 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 13 is GaAs, A
lGaAs, GaInP, AlGaInP, GaInA
s, AlGaInAs, GaInAsP, GaN, Ga
InN can be exemplified. In particular, when the active layer 13 is made of an InGaAs quantum well layer, a natural superlattice is easily formed, so that the effect of suppressing the natural superlattice by using an off-substrate can be increased.

On the active layer 13, a second conductivity type clad layer is formed. Two or more second conductivity type cladding layers of the present invention are formed.

The second conductive type first cladding layer 14 is formed of a material having a smaller refractive index than the active layer 13. For example,
Second conductivity type AlGaInP, AlInP, AlGaAs
s, AlGaAsP, AlGaInAs, GaInAs
P, AlGaInN, BeMgZnSe, MgZnSS
e, general III-V group such as CdZnSeTe, II-VI
Group semiconductors can be used. When the second conductivity type cladding layer is made of a group III-V compound semiconductor containing Al, GaAs or GaAs can be formed on substantially the entire surface on which it can grow.
Al such as sP, GaInAs, GaInP, and GaInN
It is preferable to cover with a group III-V compound semiconductor containing no, since surface oxidation can be prevented.

The lower limit of the carrier concentration of the second conductive type first cladding layer 14 is preferably 1 × 10 ¹⁷ cm ⁻³ or more, and 3 × 10 ¹⁷ cm ⁻³ or more.
More preferably 10 ¹⁷ cm ^-3 or more, and most preferably 5 × 10 ¹⁷ cm ^-3 or more. 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 0.4 μm or less, and most preferably 0.2 μm or less.

The first cladding layer 14 of the second conductivity type comprises the active layer 1
3 is formed. In a preferred embodiment of the present invention, the refractive index of the second conductive type first cladding layer 14 is smaller than the refractive index of the first conductive type cladding layer 12. 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.

By forming the first etching stopper layer 15 on the second conductive type first cladding layer 14, the second conductive type second cladding layer 19 is regrown at least in the opening 16. This makes it possible to easily prevent the generation of a high-resistance layer that increases the passage resistance at the interface.

The etching stopper layer 15 can be made so as not to absorb light from the active layer by selecting a material and a thickness, and is preferably transparent to the emission wavelength emitted by the active layer 13. The material of the etching stopper layer 15 is not particularly limited as long as it is hardly oxidized or easy to clean even if oxidized. Specifically, Al _X Ga _{1 -X} As (0 ≦ X ≦ 1), ln _{Y Gal LY} P
A group III-V compound semiconductor layer having a low content of an easily oxidizable element such as Al (0 ≦ Y ≦ 1) (about 0.3 or less) is exemplified. The etching stop layer 15 is generally selected from a material having a larger band gap than the material of the active layer. However, even if the material has a small band gap, the lower limit of the thickness is 2 nm or more, more preferably 5 nm.
If the upper limit is 50 nm or less, more preferably 30 nm or less, and most preferably 10 nm or less,
It can be used because the absorption of light is substantially negligible.

The etching stopper layer 15 may be formed of two or more layers. In this case, etching may be performed two or more times to form a groove.
The conductivity type of the etching stop layer 15 is not particularly limited when it is removed from the inside of the groove by etching, and the second conductivity type is preferable when a layer is formed inside the groove. Further, it is preferable that the etching stopper layer 15 is lattice-matched to the substrate.

The current blocking layer 17 constituting the semiconductor optical device of the present invention is formed of the second conductive type first cladding layer 14.
It has an opening 16 formed thereon. Basically, a current is injected from the opening 16 into the active layer 13.

The material of the current blocking layer 17 is preferably a semiconductor. When a semiconductor is used as the material of the current blocking layer 17, 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. Since the contact layer can be easily formed on the entire surface, there is an advantage that the contact resistance can be easily reduced.

The refractive index of the current blocking layer 17 is determined by using AlGaAs or AlGaAsP sandwiched between the current blocking layers 17.
(The real refractive index guide structure). By controlling such a refractive index, it becomes possible to reduce the operating current as compared with the conventional loss guide structure. When the current blocking layer 17 is a compound semiconductor, the lower limit of the refractive index difference between the current blocking layer 17 and the second conductivity type second cladding layer 19 is preferably 0.001 or more, more preferably 0.003 or more, and 0.03 or more. 007 or more is most preferable. The upper limit is 1.0
Is preferably 0.5 or less, more preferably 0.5 or less, and most preferably 0.1 or less. When the current blocking layer 17 is a dielectric, the lower limit is preferably 0.1 or more, more preferably 0.3 or more, and most preferably 0.7 or more. The upper limit is preferably 3.0 or less, more preferably 2.5 or less, and most preferably 1.8 or less.

When the refractive index is made lower than that of the second conductive type second cladding layer 19 and lattice matching with the GaAs substrate is taken into consideration, the material of the current blocking layer 17 is AlGaAs or AlGaAsP, which is a compound semiconductor. Is preferred. However, AlGaAs or AlGaAsP
In the case of (1), when the Al composition becomes too close to AlAs, deliquescence is exhibited. Therefore, the upper limit of the Al composition is preferably 0.95 or less, more preferably 0.92 or less, and most preferably 0.90 or less. Further, since the current blocking layer 17 needs to have a lower refractive index than the second conductivity type cladding layer 19,
The lower limit of the Al composition is preferably 0.3 or more, more preferably 0.35 or more, and most preferably 0.4 or more.

The current blocking layer 17 is formed of two or more layers having different refractive indices, carrier concentrations or conductivity types in order to control the light distribution (particularly the light distribution in the lateral direction) and to improve the current blocking function. May be. The conductivity type of the current blocking layer 17 may be any of the first conductivity type or high resistance (undoped or doped with an impurity (O, Cr, Fe, or the like forming a deep order)), or a combination of the two. It may be formed of a plurality of layers having different conductivity types or compositions. For example, a current blocking layer formed in the order of the second conductivity type or high resistance semiconductor layer and the first conductivity type semiconductor layer from the side close to the active layer 13 can be preferably used. If the thickness is too small, it may cause a problem in blocking the current.
It is preferably at least 0.3 μm, more preferably at least 0.3 μm. On the other hand, if the thickness is too large, the passage resistance increases, so the upper limit is preferably 2 μm or less, more preferably 1 μm or less. Considering the size of the element, etc., 0.3 ~
It is preferable to select from a range of about 1 μm.

By forming the surface protection layer 18 on the current blocking layer, surface oxidation can be suppressed or the surface can be protected in the process. Although the conductivity type of the surface protection layer 18 is not particularly limited, the current blocking function can be improved by using the second conductivity type.

As the upper layer of the current blocking layer 17, the second conductivity type second cladding layer 19 is formed so as to reach the inside of the opening 16 and at least part of the current blocking layer 17 on both sides of the opening 16. Second conductivity type second cladding layer 19
Covers the entire upper surface of the opening 16 and
Is formed so as to extend to at least a part of the current block layer 17 on both sides.

The lower limit of the carrier concentration of the second conductivity type second cladding layer 19 is preferably 3 × 10 ¹⁷ cm ⁻³ or more, and more preferably 5 × 10 ¹⁷ cm ^−3.
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 1 × 10 ¹⁹ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or less, and 3 × 10 cm ⁻³ or less.
Most preferably ¹⁸ cm ^-3 or less.

The thickness of the second conductive type second cladding layer 19 is as follows.
The lower limit is preferably 0.5 μm or more, more preferably 1.0 μm or more, considering that light confinement becomes insufficient when the thickness is too small, and that the passage resistance increases when the thickness is too large. 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 current blocking layer 17 and the second conductivity type second cladding layer 19 and before forming an electrode, a low-resistance (high carrier concentration) contact is formed to reduce the contact resistance with the electrode material. Preferably, the layer 20 is formed. In particular, when the semiconductor optical device is used as a semiconductor light emitting element, it is preferable to form the electrode after forming the contact layer 20 on the entire surface of the uppermost layer on which the electrode is to be formed.

At this time, the material of the contact layer 20 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
0 ¹⁹ cm ^-3 or less is most preferred. The thickness of the contact layer is preferably 0.1 to 10 μm, more preferably 1 to 8 μm, and most preferably 2 to 6 μm.

Next, the opening 16 formed in the current block layer 17 will be described.

In a cross section orthogonal to the direction in which the opening 16 extends (longitudinal direction), the side surface of the opening is represented by a curved line 21 (FIG. 2). The shape of the curved line of the opening side surface 21 may be, for example, a quarter circle, a parabola, a quarter ellipse, or the like.

The curved line representing the side surface of the opening has an absolute value of the inclination of a straight line 1 connecting the lower end portion A and the upper end portion B of the side surface of 0.3.
The curve is preferably a curve of 10 to 10, more preferably a curve of 0.5 to 6, and even more preferably a curve of 0.8 to 2.5. Here, the term “inclination of the straight line 1” in this specification means an inclination when the opening bottom surface 22 is a horizontal axis and a direction perpendicular thereto is a vertical axis, and specifically, along the horizontal axis. Horizontal increase (Δ
x), the ratio of the increase in the vertical direction (Δy) (Δy /
Δx) (FIG. 2 (c)).

In a cross section orthogonal to the longitudinal direction of the opening, the absolute value of the inclination of the tangent to the curved line 21 is determined by the lower end A of the side surface.
Is preferably 0.05 to 5, and 0.1 to
3, more preferably 0.2 to 1.5 (tangent m). In a cross section perpendicular to the longitudinal direction of the opening, the absolute value of the inclination of the tangent to the curved line 21 is preferably 0.5 to 50, more preferably 1 to 30, at the upper end B of the side surface. .
Even more preferably, it is 5 to 10 (tangent line n).
In a cross section orthogonal to the longitudinal direction of the opening, it is preferable that the absolute value of the inclination of the tangent to the curved line continuously increases from the lower end A to the upper end B of the side surface. As in the case of the straight line 1, the tangent lines m and n are defined with the opening bottom surface 22 as a horizontal axis and a direction perpendicular thereto as a vertical axis. When the curved line representing the side surface of the opening satisfies the above preferable condition, the crystal growth of the second conductivity type second cladding layer from the side surface of the opening becomes good, and the crystallinity hardly deteriorates.

The opening 16 is preferably formed by etching after forming the current blocking layer 17. The etching of the opening 16 is not particularly limited as long as the opening side surface 21 can be formed into a predetermined curved line.
Examples of the etching method include various types of etching such as wet etching, dry etching, and plasma etching. Preferably, wet etching is used, and more preferably, wet etching using an etchant having no plane orientation dependence. When an etchant having no plane orientation dependence, such as a phosphoric acid / hydrogen peroxide-based etchant, is used in the wet etching, the curved line of the opening side surface 21 is particularly preferable, and the second conductive second surface in the opening side surface 21 is particularly preferable. There is an advantage that the epitaxial growth of the cladding layer 19 becomes good. Further, if the etchant has no plane orientation, the width of the opening 16 can be made uniform, so that the semiconductor optical laser device of the present invention can be manufactured at a high yield and the semiconductor optical device device having a small design margin can be manufactured. Manufacturing is also possible.

It is preferable that the shape of the opening 16 is smaller on the lower side (active layer side) than on the upper side (contact layer side) from the viewpoint of reducing the passage resistance, operating voltage and heat generation. When the current blocking layer 17 is also formed near the end face, the current injection in the opening 16 is performed by the active layer 1.
It can also be suppressed at three ends. Thereby, deterioration in the end region (particularly, end surface deterioration) can be reduced.

The opening 16 of the current block layer 17 may be a stripe-shaped opening extending to both ends, or extending to one end but extending to the other end. The opening may not be provided. If the opening is a striped opening extending to both ends,
The control of light 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 depends on the current blocking layer 1.
The direction is preferably within ± 30 ° from the direction perpendicular to the direction (longitudinal direction) in which the opening 16 formed in 7 extends, and ± 30 ° is preferable.
A direction within 7 ° is more preferable, and a direction within ± 2 ° is most preferable. When the plane orientation of the substrate is (100), the direction of the opening 16 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 preferred, ±
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 the general term 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 existing in the group V is a plane where a group V or group VI element appears.

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 Phase Epitaxy)
May be in either direction, but in MOVPE [11-
20] direction is more preferable.

In designing the semiconductor optical 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 divergence angle. Normally, when the vertical divergence angle is narrowed, light seeping from the active layer to the cladding layer is promoted, the light density at the end face is reduced, and the COD level at the emission end face can be improved. Is set relatively narrow.
The lower limit of the vertical divergence angle is limited because it is necessary to suppress an increase in the oscillation threshold current due to the reduction of light confinement in the active layer and a decrease in temperature characteristics due to overflow of carriers. Is preferably 1
7 ° or more is more preferable, and 19 ° or more is most preferable.
On the other hand, the upper limit of the vertical spread angle 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 0.5 μm or less, more preferably 0.4 μm or less, and 0.3 μm or less.
The following are most preferred. The lower limit of dp is 0.0
It is preferably at least 3 μm, more preferably at least 0.05 μm, most preferably at least 0.07 μm. 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 of the opening width W is 1 μm
m or more, more preferably 1.5 μm or more, and most preferably 2 μm or more. Further, in order to make the transverse mode a single mode (transverse light intensity distribution of a single peak), the aperture width W can be made too large from the viewpoint of cutoff of a higher-order mode and prevention of spatial hole burning. However, the upper limit of the opening width W is preferably 7 μm or less, more preferably 5 μm or less, and most preferably 3 μm or less.

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. 5 (a)). That is, the end (cleavage plane) width W
For 1, the upper limit is preferably 1000 μm or less, more preferably 500 μm or less. The lower limit of the edge width W1 is preferably 2 μm or more, more preferably 3 μm or more. Center width W
As for 2, the upper limit is preferably 100 μm or less, more preferably 50 μm or less. The lower limit of the center width W2 is preferably 1 μm or more, more preferably 1.5 μm or more, and more preferably 2 μm or more.
It is most preferred that this is the case. The upper limit of the difference between the end width W1 and the center width W2 is preferably 1000 μm or less, more preferably 500 μm or less. The lower limit is preferably 0.2 μm or more, more preferably 0.5 μm or more.

In order to make the transverse mode a single mode, the upper limit of the end width W1 is preferably 10 μm or less, more preferably 7 μm or less. The upper limit of the center width W2 is preferably 7 μm or less, more preferably 5 μm or less. 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 2 μm or less.
μm or less is most preferred. 0.2 μm for lower limit
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.

It is effective to reduce the aperture width in order to realize a nearly circular beam. However, if 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, the beam spot can be reduced and the low operating current can be realized at the same time, and high reliability is secured. (Figure 5
(B)). That is, the upper limit of the end portion (cleavage plane) width W1 is preferably 10 μm or less, and preferably 5 μm.
Or less, more preferably 3 μm or less, most preferably. As a lower limit of the edge (cleavage plane) width W1,
It is preferably at least 0.5 μm, more preferably at least 1 μm. The upper limit of the center width W2 is preferably 100 μm or less, and more preferably 50 μm or less. The lower limit of the center width W2 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 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. However, 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, it is not necessary to provide an electrode near the end face to suppress bulk deterioration due to current injection into the opening near the end face and to reduce recombination current at the end face. This is effective from the viewpoint of producing a laser having a spot diameter.

The lower limit of the light output of the semiconductor optical device of the present invention is 30 mW or more. At least 3 light outputs
If a long life can be confirmed at 0 mW or more, the reliability of the semiconductor optical device at the time of high-power operation will be high. Even if the light output of the semiconductor light emitting device is 100 mW or more, and even 300 mW or more, it has a long life.

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

The method of manufacturing a semiconductor optical device according to the present invention is as follows. First, a first conductive type clad layer 12 is formed on a substrate 11.
Then, after forming a double hetero structure having the first cladding layer 14 of the second conductivity type and the active layer 13, a current blocking layer 17 is formed on the first cladding layer 14 of the second conductivity type, and the current blocking layer 17 is opened by etching. After the opening 16 is formed, the current blocking layer 1 inside the opening and on both sides of the opening is formed.
The step of forming the second conductivity type second cladding layer 19 on a part of the upper layer 7 can be exemplified. Details of this manufacturing method and other manufacturing methods can be understood from the following examples and related technical documents.

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 device, and the like. When the III-V compound semiconductor layer is grown by MOCVD, a double heterostructure is used. Is a growth temperature of about 600 to 750 ° C., and V
/ III ratio of about 50 to 150 (for GaAs and InGaAs), about 20 to 60 (for AlGaAs) or about 300 to 600 (InGaAsP, AlGaInP).
), The current blocking layer has a growth temperature of 600 to 700
° C, V / III ratio about 40-60 (in case of AlGaAs)
Alternatively, about 350 to 550 (InGaAsP, AlGa
(In the case of InP).

In particular, when the portion to be selectively grown using the surface protection layer 18 contains Al such as AlGaAs or AlGaInP, a small amount of HCl gas is introduced during the growth to prevent poly deposition on the mask. Very preferred because it can be. When the Al composition is higher or the mask width or the mask area ratio is larger, and other growth conditions are kept constant, poly deposition is prevented and selective growth is performed only on the semiconductor surface exposed portion (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). HCl required to enter etching mode
The amount of introduction increases. For this reason, 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 supply mole number of HCl to the supply mole number of the group III raw material containing Al (HCl
/ III) has a lower limit of preferably 0.01 or more, and 0.0
5 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,
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.

Used for self-aligned type formation and selective growth
The surface protective layer 18 is preferably a dielectric,
Specifically, a SiNx film, SiO_TwoFilm, SiON film, A
l_TwoO _ThreeFilm, ZnO film, SiC film and amorphous Si
Selected from the group consisting of: The surface protection layer 18 includes a mask and
And selectively regrow the grooves using MOCVD, etc.
It is used when forming.

As a semiconductor laser device using the semiconductor optical device of the present invention, a light source for information processing (usually AlG
aAs-based (wavelength around 780 nm), AlGaInP-based (wavelength 600 nm band), InGaN-based (wavelength 400 nm)
Signal source for communication (usually InGaAsP or I)
1.3 μm band with nGaAs active layer, 1.5 μm
In particular, communication semiconductor laser devices such as lasers, lasers, and fiber excitation light sources (such as near 980 nm using an InGaAs strained quantum well active layer / GaAs substrate, and near 1480 nm using an InGaAsP strained well active layer / InP substrate) lasers, etc. Various devices that require high output operation can be given. In addition, even for communication lasers,
A laser having a circular shape is effective in increasing the coupling efficiency with the 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 semiconductor optical device of the present invention can be applied not only to a semiconductor laser but also to optical elements such as a semiconductor optical amplifier, a photodetector, an optical modulator, an optical switch, and an integrated device thereof. Further, the present invention is not limited to a semiconductor laser, and may be a light emitting diode (LED) such as an edge emitting type.
It is also applicable as.

[0069]

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.

In this example, a semiconductor light emitting device, which is one of the semiconductor optical device devices, was manufactured by forming each layer in the order shown in FIG. 3 (a) to FIG.
In (c), there is a part where the dimensions are intentionally changed in order to make it easy to grasp 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 301 having a thickness of 350 μm and a (100) plane, a 2.0 μm-thick n-type Al _0.35 G is formed by MBE.
a _{0. 65} As ^{(Si-doped: n = 1 × 10 18 cm} -3) n -type cladding layer 302 made of, GaAs optical confinement layer having a thickness of 30 nm (non-doped), a thickness of 6 nm an In _0.2 Ga
_0.8 As well layer (non-doped), 8 nm thick GaAs
Barrier layer (non-doped), 6 nm thick In _0.2 Ga _0.8
As well layer (non-doped) and GaAs having a thickness of 30 nm
A double quantum well (DQW) active layer 303 in which light confinement layers (non-doped) are sequentially laminated, p-type Al _0.4 Ga _0.6 As (Be doped: p = 1 × 10 ¹⁸ cm) having a thickness of 0.1 μm
^-3 ) p-type first cladding layer 304, thickness 10 nm
P-type GaAs (Be doped: p = 1 × 10 ¹⁸ cm ⁻³ )
Second etch stop layer 305, 20 nm thick p-type In
_0.49 Ga _0.51 P (Be doped: p = 1 × 10 ¹⁷ cm ⁻³ )
First etching stop layer 305 ', 0.5 μm thick n-type Al _0.35 Ga _0.65 As (Si-doped: n = 1 × 10 ¹⁸ c
m- ³ ), an n-type current block layer 306 having a thickness of 10 n
m n-type GaAs (Si doped: n = 1 × 10 ¹⁸ c
m ⁻³ ) were sequentially laminated (FIG. 3A).

In order to form a current injection region, first, a 100 nm thick SiNx
A surface protective layer was deposited by plasma CVD, and a large number of stripe-shaped openings 308 were formed in the [0-11] B direction by photolithography. Note that the [01-1] B direction is (1) in a general III-V compound semiconductor.
(11-1) exists between the (00) plane and the (01-1) plane.
The plane is defined as the plane where the group V element appears.

Using the SiNx surface protective layer as an etching mask,
The current block layer 306 is removed by etching using a phosphoric acid / hydrogen peroxide-based etchant so that the etching is stopped at the first etching stop layer 305 '.
The formation of the stripe-shaped openings 308 is completed. At this time, the side surface of the cross section of the stripe-shaped opening 308 was a curved line, the width of the bottom surface of the opening 308 was 2.2 μm, and the horizontal space interval was 400 μm. Thereafter, the striped SiNx protective film was removed by wet etching using a buffered hydrofluoric acid solution or by dry etching using a gas such as SF ₆ or CF ₄ . Next, the first etching stop layer 30 immediately below the opening (current injection region) is stopped by stopping the etching at the second etching stop layer 305.
5 'was removed by etching using a hydrochloric acid-based etchant, thereby completing the formation of the striped groove 308 (FIG. 3).
(B)).

Thereafter, a thickness of 2.2 μm was formed by MOCVD.
m p-type Al _0.35 Ga _0.65 As (Zn doped: p = 1 ×
10 ¹⁸ cm ⁻³ ) of p-type second cladding layer 309, and 3.5 μm-thick p-type GaAs (Zn doped: p = 2)
A contact layer 310 of (× 10 ¹⁹ cm ⁻³ ) was grown.

Thereafter, the p-side electrode 311 was deposited and the substrate was thinned to 100 μm, and then the n-side electrode 312 was deposited and alloyed (FIG. 3C). The wafer thus manufactured is cleaved to form a laser light emitting end face (first cleavage).
Then, a semiconductor light emitting device laser was manufactured. The resonator length at this time was 1000 μm. After applying an asymmetric coating of 5% front end face-95% rear end face, the chip 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).

The light output of the semiconductor light emitting device manufactured in this manner increases as the operating current increases.
Light output was obtained without kink free up to about 650 mW and kink free up to mW. 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. Oscillation wavelength is 9 on average
79 nm, the threshold current was 20 mA on average, and the slope efficiency was 0.85 mW / mA on average, and the characteristics were very good. At a power of 300 mW, the vertical spread angle was 28 ° on average, and the horizontal spread angle was 8.5 ° on average.
At this time, it was found that the astigmatic difference can be made as very small as 2 μm or less, and that the light source has excellent light coupling characteristics with an optical fiber. Furthermore, high reliability (70 ° C, 3
It has been found that a stable operation of 3,000 hours or more at a high temperature of 00 mW and high output can be obtained. Further, since the opening for current injection is formed by etching up to the etching stop layer, the uniformity of the element structure can be improved, and the above-described semiconductor laser element can be manufactured with high yield.

COMPARATIVE EXAMPLE The current blocking layer was removed by etching using a tartaric acid / hydrogen peroxide type etching solution to form a stripe-shaped groove, and the side wall was straight facet face (usually (111) A) Near the A-plane), a semiconductor light-emitting device was manufactured by the same steps as in Example 1. SE cross section of semiconductor light emitting device chip
Observation with M revealed that in the comparative example, a region having deteriorated crystallinity was present in the p-type second cladding layer grown from the side wall of the block layer. On the other hand, a region where crystallinity was deteriorated as in the comparative example was not recognized from the curved side wall of the example. In the semiconductor light emitting device having this element structure, the deterioration rate was about 2 to 5 times larger in the long life test than the device of the example. This is considered to be due to the deterioration of crystallinity in the p-type second cladding layer grown from the side wall of the block layer.

[0078]

According to the semiconductor optical device of the present invention, the side face of the stripe-shaped opening is formed in a curved shape, so that the crystallinity of the clad layer grown from the side face of the opening can be prevented from deteriorating. For this reason, the semiconductor optical device of the present invention has high device reliability during high-output operation. Further, the semiconductor optical device of the present invention can improve the uniformity of the opening width and can be manufactured with a high yield.
This is particularly effective when a laser having a small structural design margin is required. INDUSTRIAL APPLICABILITY The present invention can be applied to a wide range of fields including a semiconductor laser and the like, and is particularly suitable for an optical fiber amplifier pumping light source and an amplifier used in an optical communication system.

[Brief description of the drawings]

FIG. 1 is a perspective view of a semiconductor optical device according to an embodiment of the present invention.

FIG. 2 is a perspective view and an enlarged view of a part of one embodiment of the semiconductor optical device device of the present invention shown in FIG.

FIG. 3 is a process diagram illustrating an example of a manufacturing process of the semiconductor optical device device of the present invention.

FIG. 4 is a cross-sectional view showing a conventional general self-aligned waveguide type stripe structure.

FIG. 5 is a top view of one embodiment of the semiconductor optical device device of the present invention.

[Explanation of symbols]

 11: substrate 12: first conductivity type clad layer 13: active layer 14: second conductivity type first clad layer 15: second etching stop layer 16: opening 17: current blocking layer 18: surface protection layer 19: second Conductive type second cladding layer 20: Contact layer 21: Opening side surface 22: Opening bottom surface 41: Substrate 42: First conductive type cladding layer 43: Active layer 44: Etching stop layer 45: Opening 46: Current block layer 47 : Second conductivity type cladding layer 48: contact layer 51, 55: light confinement layer 52, 54: well layer 53: barrier layer 301: substrate 302: n-type cladding layer 303: active layer 304: p-type first cladding layer 305 : Second etching stop layer 305 ′: first etching stop layer 306: current blocking layer 307: SiNx surface protection layer 308: opening 309: p-type second cladding layer 310: contact layer 311: p-side electrode 312: n-side electrode W1: end width W2: central width

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H079 AA02 AA13 BA01 DA16 EA03 EA07 EA08 EB04 HA11 5F073 AA20 AA53 AA74 AA86 CA07 DA22 EA29

Claims (20)

[Claims] A first conductive type clad layer formed on the substrate; an active layer formed on the first conductive type clad layer; and a second conductive type first layer formed on the active layer. A cladding layer, a current blocking layer having an opening formed on the second conductive first cladding layer, and a second conductive layer formed on the current blocking layer inside the opening and at least on both sides of the opening. A semiconductor optical device having a mold-type second cladding layer, wherein a side surface of the opening is represented by a curved line in a cross section orthogonal to a longitudinal direction of the opening. 2. An absolute value of a slope of a straight line connecting a lower end portion and an upper end portion of a side surface of the opening in a cross section orthogonal to a longitudinal direction of the opening is 0.3 to 10. Item 2. The semiconductor optical device according to item 1. 3. The cross section orthogonal to the longitudinal direction of the opening, wherein the absolute value of the inclination of the tangent to the curved line is 0.05 to 5 at the lower end of the side surface. 3. The semiconductor optical device device according to 2. 4. An absolute value of an inclination of a tangent of the curved line in a cross section orthogonal to a longitudinal direction of the opening is 0.5 to 50 at an upper end portion of the side surface. 3. The semiconductor optical device device according to any one of items 3. 5. The cross section orthogonal to the longitudinal direction of the opening, wherein the absolute value of the inclination of the tangent to the curved line continuously increases from the lower end to the upper end of the side surface. 5. The semiconductor optical device according to any one of items 1 to 4. 6. A main surface of the substrate is a (100) plane,
6. The semiconductor optical device according to claim 1, wherein a longitudinal direction of the opening is a [01-1] direction. 7. The semiconductor optical device according to claim 1, wherein said active layer is made of an InGaAs quantum well. 8. The semiconductor according to claim 1, wherein said current blocking layer is formed of a semiconductor layer having a lower refractive index than said second cladding layer of said second conductivity type. Optical device equipment. 9. The method according to claim 1, wherein the current blocking layer comprises at least a first
9. The semiconductor optical device according to claim 1, wherein the semiconductor optical device is formed of a conductive or high-resistance semiconductor layer. 10. The current blocking layer is made of AlGaAs.
9. The semiconductor optical device according to claim 1, wherein the semiconductor optical device is made of AlGaAsP. 11. The semiconductor optical device according to claim 1, wherein at least one etching stop layer is provided between the second conductivity type first cladding layer and the current blocking layer. apparatus. 12. The semiconductor optical device according to claim 11, wherein the etching stop layer is transparent to a wavelength of light emitted from the active layer. 13. The semiconductor optical device according to claim 11, wherein the etching stop layer is made of GaAs. 14. The semiconductor optical device according to claim 1, wherein a current is injected from said opening into said active layer. 15. The semiconductor light according to claim 1, wherein the opening is formed by etching the current blocking layer with a phosphoric acid / hydrogen peroxide-based etchant. Device equipment. 16. The semiconductor optical device according to claim 1, wherein said opening is a stripe-shaped opening extending to both ends. 17. The method according to claim 1, wherein the opening is an opening extending to one end but not extending to the other end. Semiconductor optical device. 18. The semiconductor optical device according to claim 1, wherein an optical output of said semiconductor optical device is 30 mW or more. 19. The semiconductor optical device according to claim 1, wherein said semiconductor optical device is used as a light source for exciting an optical fiber amplifier. 20. The apparatus according to claim 1, wherein said semiconductor optical device is used as an optical fiber amplifier.
20. The semiconductor optical device device according to any one of items 1 to 19.