JPH04299882A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To improve heat dissipation from an element surface, and enhance element characteristics and reliability, by forming constant undulations on the side wall part or the slant part of a second stripe mesa, and providing an electrode formed on the undulations with unevenness. CONSTITUTION:On an N-type InP substrate 11, the following are formed in order; an N-type InP clad layer 12, an N-type GaAsP active layer 13, and an N-type InGaAsP optical guide layer 14. After a diffraction grating having a specified pitch is formed on a wafer wherein the above layers are subjected to crystal growth, a first stripe mesa is formed by performing mesa etching in a stripe type. A P-type InP clad layer 15 is formed on the substrate 11 and the first stripe mesa. A second stripe mesa is formed so as to reflect the form of the first stripe mesa. A slant surface having inclination to the surface of an active layer and undulations is formed on the second stripe mesa. Said undulations are reflected on a P-type InGaAs contact layer 16. Further, an N-type ohmic electrode 18 is formed on the contact layer 16.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor laser devices used in optical communications and information processing, and more particularly to semiconductor laser devices with improved leakage current and heat dissipation characteristics.

0002

2. Description of the Related Art In recent years, semiconductor lasers using various compound semiconductor materials have been developed as light sources for information processing and optical communications, and it is desired to improve their performance. In particular, there is a strong demand for low threshold characteristics and high reliability, and research and development in these areas is actively conducted. In order to simultaneously ensure low threshold values and high reliability, in addition to reducing leakage current,
It is essential to prevent heat generation and increase the diffusion of the generated heat. Currently, buried structure lasers are being actively developed as structures that minimize leakage current, lower threshold values, and suppress excess heat generation.

The prior art will be briefly explained below with reference to FIG. FIG. 4 shows a buried structure laser, and is a perspective cross-sectional view of the vicinity of the active layer. In the figure, 41 is an n-type InP substrate, 42 is an n-type InP cladding layer, and 43 is an InP substrate.
GaAsP active layer, 44 is InGaAsP light guide layer,
45 is a p-type InP cladding layer, which is formed in the first crystal growth and then processed into an inverted mesa stripe shape.

Reference numeral 46 denotes a high-resistance InP block layer, which is formed during the second crystal growth so as to fill the sides of the mesa. 47 and 48 are electrodes. A laser constructed with the above composition has an emission wavelength of 1.5 μm, and is employed as a light source for optical communications using optical fibers.

In this type of buried structure laser, selective mesa etching is performed when processing the crystal layer formed in the first crystal growth into a stripe shape, but since the etching rate differs depending on the crystal plane orientation, It has a so-called inverted mesa shape as shown in 4. Therefore, it is difficult to precisely control the width of the active layer 43 when the width of the active layer 43 is processed to be thinner than the mask pattern prepared in advance, and the thickness of the n-type and p-type cladding layers is approximately 2 μm. be.

Furthermore, since the crystal surface and the electrode 47 have a flat structure, the heat generated in the vicinity of the active layer is not diffused from the laser surface, but is mostly radiated from the pedestal through the electrode 48. In this case, the InP substrate 41 has a thickness of approximately 100 μm.
It has a thickness of 1.5 m, and cannot be said to be sufficient in terms of heat dissipation from the element. Therefore, this causes characteristic deterioration that can be said to be fatal to lasers, such as fluctuations in the oscillation wavelength and optical output saturation. Furthermore, heat generation shortens the life of the element, and in the worst case, the laser becomes unreliable. That is, heat dissipation is an extremely important issue for lasers, and in the conventional structure, heat dissipation at the element surface was incomplete.

FIG. 5 shows another conventional example of a buried structure laser, and is a sectional view of the vicinity of the active layer viewed from the optical waveguide direction. In the figure, 51 is an n-type InP substrate, and 52 is an n-type InP substrate.
P buffer layer (or cladding layer), 53 is InGa
The As active layer 54 is an InGaAsP optical waveguide layer, which is formed in the first crystal growth and then processed into an inverted mesa stripe shape.

55 is a p-type InP cladding layer;
During the second crystal growth, the mesa portion is formed to be buried. 5
6 is a high resistance InP layer, 57 is an n-type InP layer, and the third
Formed during the second crystal growth. 58 is an insulating film, 61, 6
2 is an electrode. A laser constructed with the above composition has a 1.5
It has an emission wavelength of μm and is used as a light source for optical communications using optical fibers.

In this type of buried structure laser, when processing the crystal layer formed in the first crystal growth into a stripe shape, it is necessary to take it out of the crystal growth apparatus and selectively perform mesa etching. After processing, a p-type InP cladding layer is formed by second buried crystal growth, but the following problem always occurs.

That is, the buffer layer 52, the active layer 53, and the optical waveguide layer 54 have different compositions and have a so-called heterojunction structure. Therefore, when mesa etching is performed with a mixed acid when processing into a stripe shape, unevenness is formed at the edge of the hetero interface due to the dependence of the etching rate on the composition. In particular, when the active layer 53 has a quantum well structure, the side surfaces of the active layer 53 are not flattened because the etching rate differs depending on each composition. Therefore, many dislocations occur in the buried layer near the side surfaces of the active layer. This causes leakage current and scattering loss and increases the threshold current.

Furthermore, if the stripe direction is set to the <110> direction and stripes are formed using a mixed acid, a specific crystal plane will be exposed in the <111> direction. In particular, (10
0) plane is the principal plane of the laser, for example, (100
) plane and the (-1-1-1) plane form a corner A. This corner A is a ridge along the optical waveguide direction. When the p-type InP cladding layer 55 is buried and formed so as to surround the stripe having the corner portion A, an abnormal crystal portion B is generated inside the cladding layer 55. This abnormal crystal part B is connected to the interface C between the active layer 53 and the optical waveguide layer 54 and the cladding layer.

[0012] It has been experimentally found that the abnormal crystal portion B occurs because the crystal growth rate differs between specific surrounding crystal planes formed during stripe processing. It has also been found that this abnormal crystal part B is the cause of laser leakage current. Leakage current through the abnormal crystal portion B and the crystal interface C causes deterioration that can be said to be fatal to the laser, such as an increase in threshold current, a decrease in quantum efficiency, and a low optical output.

[0013]

As described above, in conventional buried structure semiconductor lasers, heat radiation from the element surface side has been incomplete, which has been a factor in deteriorating element characteristics and reliability. Further, when forming a buried layer after processing the mesa portion, abnormal crystal portions are generated due to the influence of the corners of the mesa portion, which causes an increase in leakage current.

The present invention has been made in consideration of the above circumstances, and aims to improve heat dissipation from the element surface while reducing leakage current. An object of the present invention is to provide a semiconductor laser device whose characteristics and reliability can be improved.

Another object of the present invention is to provide a semiconductor laser device that can prevent an increase in leakage current caused by abnormal crystal portions at mesa corners and can reduce the threshold value. be.

[0016]

[Means for Solving the Problems] In order to achieve the above problems, the present invention employs the following configuration.

That is, the present invention (claim 1) provides a first stripe mesa formed in a stripe shape on one main surface of a semiconductor substrate and including at least an active layer and a light guide layer; In a semiconductor laser device including a second striped mesa formed on a mesa and including at least a cladding layer, the second striped mesa is embedded so as to reflect the shape of the first striped mesa, and the sidewall portion or The slope portion is formed to have undulations,
The electrode formed on the second striped mesa is characterized in that it has irregularities reflecting the undulations of the side wall portion or sloped portion of the mesa.

The present invention (claim 2) also provides a striped mesa portion including at least an active layer and an optical waveguide layer, which is provided in a stripe shape on the main surface of a semiconductor substrate, and a striped mesa portion that is embedded in the mesa portion. In a semiconductor laser device equipped with a buried crystal layer formed in It is characterized by having an upwardly convex curve.

[0019]

According to the present invention (claim 1), by providing a certain undulation on the side wall portion or the inclined portion of the second striped mesa, it is possible to form irregularities on the electrode formed thereon. Therefore, the surface area on the element surface side becomes larger, and heat dissipation from the element surface near the active layer becomes better, thereby making it possible to improve the element characteristics and reliability.

Further, according to the present invention (claim 2), etching is performed so that no corners are formed when processing the mesa portion, and the interface between the mesa portion and the buried crystal layer is curved, thereby forming a buried crystal layer. It is possible to prevent abnormal crystal portions from occurring in the layer. This makes it possible to prevent an increase in leakage current due to the mesa corners and to reduce the threshold current.

[0021]

Embodiments First, the basic principle of the present invention (claim 1) will be explained.

In the present invention, the active layer is buried as a means for reducing the leakage current of the laser, but in order to improve the processing accuracy of the active layer width, the p-type InP cladding layer is buried as a second layer.
The problem was solved by forming it by second buried growth. In other words, the thickness p necessary to obtain the optical confinement effect is
The mold cladding layer (approximately 1.5 μm) was configured so that no fine pattern was formed. In such a crystal layer structure, the surface area of the p-type cladding layer and contact layer provided particularly near the active layer is approximately twice that of the conventional structure, and the area of the electrode formed on this surface is expanded compared to the conventional structure. This aims to reduce the contact resistance of the electrodes formed near the active layer and improve the heat dissipation effect.

[0023] Normally, to drive a laser, several kA/
It is necessary to inject a current into the active layer so that the current density is on the order of cm2. This means that the active layer has a width of about 1 μm.
The forward bias current of about 00mA is concentrated,
As a result, heat generation in the active layer and its vicinity becomes unavoidable. In addition, in order to effectively apply current to the active layer, the ohmic contact portion of the electrode near the active layer is formed so as to be parallel to the active layer stripes. In other words, the structure is such that the area of the ohmic contact portion is small.

[0024] In a laser having such a configuration, the contact resistance at the electrode portion becomes high, and heat generation at the electrode portion is unavoidable. In this way, the causes of laser heat generation are broadly divided into a component due to the internal resistance of the crystal layer and a component due to the contact resistance of the electrode. Attempts have been made to lower the specific resistance of the intracrystalline resistance component by adjusting the carrier concentration, but there are limits. Furthermore, there is a limit to the reduction in contact resistivity in improving electrodes.

Therefore, the present invention was made in consideration of how to prevent the element from generating heat when a certain amount of heat is generated from the active layer of a certain size. The key point is to dissipate heat closest to the heat source and reduce heat generation due to contact resistance of the electrodes. An effective structure for heat dissipation is to make the surface area as wide as possible in the vicinity of the active layer, but it is difficult to create cooling fins by providing many irregularities on the main surface of the laser in order to increase the surface area due to the manufacturing process. It's impossible.

In order to solve this problem, in the present invention, a stripe mesa including a cladding layer is formed by crystal growth so as to reflect the shape of the active layer, and the surface area in the vicinity of the active layer is expanded. Furthermore, many irregularities were formed on the inclined surface or side wall surface. This configuration makes it possible to further expand the crystal surface area at a distance of several μm from the active layer. In the present invention, as a method to achieve this, MOC
As a result of various crystal growth experiments using VD (vapor phase growth using organic metals), the pitch on the inclined surface was 0.2 to 1.
It was possible to form unevenness of 2 μm.

A contact layer with a small bandgap energy is formed on the thus expanded surface, and further an electrode for ohmic contact is formed. This electrode has a shape that reflects the above-mentioned unevenness, and since the contact area is large, the contact resistance is reduced to 1/2 or less, and heat generation in the electrode portion can be prevented. Additionally, the expanded surface area allows heat to be dissipated from the surface of the laser element.

[0028] The above technical means have the effect of preventing the aforementioned leakage current and heat generation, and further improving heat dissipation.
It is possible to provide a high-performance laser. That is, the gist of the invention is to effectively expand the crystal surface area near the active layer,
By providing an electrode in that area, the heat dissipation and series resistance of the laser are improved, thereby improving the characteristics. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a schematic configuration of a semiconductor laser according to a first embodiment of the present invention. n-type InP
An n-type InP buffer layer (not shown) and an n-type InP buffer layer (not shown) are formed on the substrate 11.
The InP cladding layer 12 has a thickness of 0.2 μm and 1.5 μm, respectively.
Form to a thickness of . Subsequently, after forming an n-type InGaAsP active layer 13 to a thickness of 0.1 μm, an n-type InGaAsP active layer 13 is formed to have a thickness of 0.1 μm.
The sP light guide layer 14 is formed to have a thickness of 0.2 μm. Furthermore, an InP cover layer (not shown) is formed to a thickness of 0.1 μm. This is the first crystal growth of MO
The layered structure is stacked using the CVD method.

Next, a diffraction grating having a pitch of about 240 nm is formed on the above-described crystal-grown wafer, and then mesa etching is performed in a stripe shape. At this time, first, a mask pattern is formed using photoresist stripes using a general method, and selective etching is performed by reactive ion beam etching so as to transfer the shape of the pattern. 1st
The active layer of the striped mesa has a width of 1 μm and a depth of approximately 0.5 μm.
It is formed to have a thickness of ~1.5 μm. In this case, since the active layer 13 is close to the surface of the wafer, the width of the active layer can be easily controlled.

[0031] The selective etching may be performed using a Br-based mixed acid etching solution that has been used in the past. Etching with a mixed acid causes the shape of the striped mesa to be slightly deformed, but there is no particular problem.

Next, a second layer for embedding the active layer 13 is formed.
Perform the second crystal growth. Crystal growth is carried out by the MOCVD method at a growth temperature of 600 to 670°C and a pressure of 70 to 150 To.
rr using a reactive gas such as trimethylindium (TMI), trimethylgallium (TMG), phosphine (PH3), arsine (AsH3), etc.

First, a p-type InP cladding layer 15 with a thickness of about 1.5 μm is formed on the striped mesa. p-type In
The P cladding layer 15 is formed on the substrate 11 and the striped mesa, and a striped mesa is formed to reflect the shape of the striped mesa described above (second striped mesa).
. This striped mesa has an undulating slope slope with respect to the active layer surface. These undulations have a period of 1 μm and a depth of about 0.5 μm, and the undulations are reflected in the p-type InGaAs contact layer 16 that is subsequently grown. That is, the second crystal growth forms irregularities on the sidewalls of the striped mesa.

Next, the p-type ohmic electrode 17 is made of TiP.
It is formed on the contact layer 16 by tAu vapor deposition. Furthermore, an n-type ohmic electrode 18 is formed on the substrate 11 by AuGe deposition.

In the semiconductor laser thus formed, there is no fluctuation in the oscillation wavelength due to the prevention of heat generation and the effective dissipation of the generated heat. For example, when continuously oscillating an optical output of 20 mW, the wavelength fluctuation is different from the conventional one. It became less than 1/2. Furthermore, the saturation point of optical output was approximately twice that of the conventional method, and a high output of 50 mW was obtained. Furthermore, as a measure of reliability, the degree of increase in threshold current through accelerated testing was investigated, and it was found to be approximately 2/3 of that of the conventional device, indicating that the device has an excellent lifespan.

The effects of the present invention are even more effective in a so-called arrayed laser in which a plurality of stripes are formed in one element. That is, for arrayed lasers where excessive heat generation due to excessive current in a limited element volume is a problem, the quality of heat dissipation determines the element life.

Note that the present invention is not limited to the embodiments described above. For example, a first stripe mesa is formed on the substrate 11, and the n-type InP buffer layer, the n-type InP cladding layer 12, the n-type InGaAsP active layer 13, the n-type InGaAsP optical guide layer 14, the p-type I
nP cladding layer 15, p-type InGaAs contact layer 1
6 in succession. Next, p-type ohmic electrode 1
7. By forming the n-type ohmic electrode 18,
You may complete the laser. In this case, it is necessary to selectively remove the active layer 13 crystal-grown on the substrate 11 by etching, leaving the active layer 13 formed above the striped mesa. The laser thus completed has the advantage that it can be produced by one crystal growth on the striped mesa provided in advance. Furthermore, since there is no recrystallization interface, there is no leakage current through the abnormal interface, and the structure exhibits excellent characteristics with a lower threshold current than the buried structure described above.

Furthermore, when the width of the active layer is 1 μm or less or the thickness of the p-type InP layer is 1.5 μm or more, the apex of the second striped mesa has a ridge-like shape, but unevenness is formed on the slope. If this were done, the aforementioned effect would remain the same. Next, the basic principle of the present invention (claim 2) will be explained.

The present invention improves the stripe structure by changing the processing method of the active layer and the optical waveguide layer in order to reduce the leakage current of the laser. That is, the cross-sectional shape of the laser viewed from the optical waveguide direction has a structure in which smooth protruding stripes with no corners are embedded with a p-type InP cladding layer. In other words, the three-dimensional shape of the stripes is a semi-cylindrical or semi-cylindrical shape, and the structure is such that crystal planes in a specific direction are not formed. A second buried crystal growth is performed on this stripe, and the above-mentioned abnormal crystal part is eliminated so that the regrowth interface has a smooth curve.

The key point of the present invention is that stripes with curved surfaces can be easily produced by applying dry etching technology to selective mesa etching. As mentioned above, the abnormal crystal portion of the buried crystal layer is caused by the presence of corners in the stripes, and eliminating these corners prevents laser leakage current. This requires a process that can process crystalline materials with different compositions at approximately the same etching rate. In the present invention, dry etching using ECR or dry etching using an ion beam is used to process the stripes, so that corners are not formed when forming the stripes.

The following method was used for stripe etching. First, photoresist is patterned into stripes with a width of about 1 μm under normal process conditions. Next, in order to use the photoresist as a dry etching mask, a heat process is further performed at a temperature higher than the curing temperature of the resist to transform the resist. This modified form has a semicircular cross section and a smooth protrusion on the surface. Next, by using the deformed resist as a selective etching mask, the active layer and the optical waveguide layer are gradually removed from the surface together with the mask, thereby forming curved stripes as if the cross-sectional shape of the resist mask was transferred. We have newly discovered that abnormal crystal portions do not occur by forming a p-type InP cladding layer on stripes that do not have this specific plane orientation.

This is because when crystals grow on growth planes with different orientations during the second crystal growth, collision points (corresponding to B in FIG. 5) that occur at the ends of each crystal layer are avoided. This eliminates the dislocation. Therefore, it is possible to achieve good crystal growth without including abnormal crystal parts. The above technical means are effective in preventing leakage current and scattering, and can provide a high-performance laser. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a cross-sectional view showing the schematic structure of a semiconductor laser according to a second embodiment of the present invention. On the n-type InP substrate 21, an n-type InP buffer layer (or cladding layer)
22, n-type InGaAsP optical waveguide layer 23, n-type InGa
A mesa portion consisting of an As active layer 24 and an InP cover layer 25 is grown, and p-type InP is grown to bury this mesa portion.
The cladding layer 26 has been removed except in the vicinity of the mesa portion.

The side surface of the InP cladding layer 26 has a high resistance I
It is buried with an nP layer 28 and an n-type InP layer 29, and on top of these is a Si3N4 film 3 having an opening on the mesa part.
0 is formed. Then, a p-type ohmic electrode (TiPtAu) 31 is formed on the cladding 26, and the substrate 1
An n-type ohmic electrode (AuGe) 32 is formed on the lower surface of 1.

FIG. 3 is a sectional view showing the manufacturing process of the above embodiment. First, as shown in FIG. 3A, a diffraction grating with a pitch of 240 nm is formed on an n-type InP substrate 21, and an n-type InP cladding layer 22 with a thickness of 5 nm is formed on the diffraction grating. Next, an n-type InGaAsP optical waveguide layer 23 is formed to a thickness of 100 nm. Next, n-type InGaAs, which has a smaller bandgap energy than the optical waveguide layer 23, is used.
The active layer 24 of P layer or multi-quantum well structure is 100n
Form with a thickness of m.

When the active layer 24 is a multiple quantum well,
Crystal growth is repeated about 10 times with the thicknesses of the InGaAsP barrier layer and InGaAs well layer set to 10 nm and 8 nm, respectively.

Next, the InP cover layer 25 is formed with a thickness of 100 nm.
The crystal layer group formed by the first growth of n-type is formed with a thickness of . In each of the formation methods, crystal growth can be performed with extremely high precision using MOCVD or molecular beam epitaxy (MBE).

Next, as shown in FIG. 3(b), stripe processing is performed. First, photoresist stripes are formed with a width of about 1 μm using a general method, and then 130
Deformation hardening at a temperature of ~180°C. The resist has a soft curved protruding stripe on the surface. Then, E.C.
The above-mentioned protrusion stripes are processed by dry etching using R so as to be transferred to the crystal layer group. By this technical means, the crystal layer groups 22 to 25 due to the first growth are
Form into a kamaboko shape.

Next, as shown in FIG. 3(c), a second crystal growth is performed. First, a p-type InP layer 26 with a thickness of about 1 to 2 μm is formed on the main surface of the substrate. The formation method is MO
This is possible by CVD method or liquid phase crystal growth. Although liquid phase growth is desirable in order to make the stripe surface smoother, the growth surface may not become flat.

Next, after selectively forming a Si3 N4 film 27 on the surface of the grown p-type InP layer 26, etching is performed using a mixed acid using the insulating film as a mask to form a p-type I
The nP layer 26 is selectively left. At this time, side etching is performed to a width equivalent to the thickness of the InP layer 26 to form a canopy-shaped insulating film.

Next, as shown in FIG. 3(d), a third crystal growth is performed. A high-resistance InP layer 28 and an n-type InP layer 29 are formed by MOCVD with the above-described insulating film preserved. The insulating film has the effect of preventing abnormal protrusion growth during the third growth and flattening the surface of the grown crystal.

After this, after removing the Si3 N4 film 27, the Si3 N4 film 30 is selectively formed again on the main surface of the substrate. Next, the p-type ohmic electrode 51 is made of Ti.
An n-type ohmic electrode 52 formed by PtAu vapor deposition
By forming this by AuGe vapor deposition, the structure shown in FIG. 2 is realized.

In the semiconductor laser thus fabricated, the leakage current through abnormal crystal parts and crystal interfaces is reduced to about 1/10 or less of the conventional one, and the threshold current is reduced to 10 mA, about half of the conventional one. Optical output is 100mW, 5 times the conventional one
was realized. In particular, when the active layer has a multiple quantum well structure, scattering can be avoided by preventing unevenness on the side surface of the active layer, which has the effect of further reducing the threshold current.

[0054]

Effects of the Invention As detailed above, the present invention (Claim 1)
According to the above, by providing a certain undulation on the side wall or slope of the second stripe mesa and forming irregularities on the electrode formed on the undulation, the structure reduces leakage current, while reducing leakage current from the element surface. It becomes possible to realize a semiconductor laser device in which heat dissipation can be improved and device characteristics and reliability can be improved.

Further, according to the present invention (claim 2), etching is performed so that no corners are formed during processing of the mesa portion, and the interface between the mesa portion and the buried crystal layer is curved, thereby forming a mesa corner. It is possible to prevent an increase in leakage current due to abnormal crystal portions in the semiconductor laser device, and to realize a semiconductor laser device in which the threshold value can be reduced.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a semiconductor laser according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view showing a schematic configuration of a semiconductor laser according to a second embodiment of the present invention;

FIG. 3 is a sectional view showing the manufacturing process of the second embodiment;

[Figure 4
] A perspective view showing the schematic configuration of a conventional embedded laser,

[Figure 5
]A cross-sectional view for explaining the problems of the conventional structure.

[Explanation of symbols]

11, 21... n-type InP substrate, 12, 22... n-type InP cladding layer, 13... n-type InGaAsP active layer, 14, 23... n-type InGaAsP light guide layer, 15, 2
6...p-type InP cladding layer, 16...p-type InGaAs contact layer, 17, 31...p
side electrode, 18, 32...n side electrode. 24... n-type InGaAs or multiple quantum well active layer, 2
5...p-InP cover layer, 27,30...Si3N4 film, 28...high resistance InP layer, 29...n-type InP layer.

Claims (2)

[Claims] 1. A first stripe mesa formed in a stripe shape on a main surface of a semiconductor substrate and including at least an active layer and an optical guide layer; and a first stripe mesa formed to reflect the shape of the first stripe mesa. a second striped mesa including at least a cladding layer formed to cover the mesa and whose sidewall portion or sloped portion is formed to have undulations; What is claimed is: 1. A semiconductor laser device comprising: an electrode having concavities and convexities reflecting the undulations of an inclined portion; 2. A striped mesa portion including at least an active layer and an optical waveguide layer provided in a stripe shape on a main surface of a semiconductor substrate, and a buried crystal layer formed to bury this mesa portion. The interface between the mesa portion and the buried crystal layer is formed by a curved surface, and the cross-sectional shape of the mesa portion viewed from the optical waveguide direction has a curved line convex upward with respect to the main surface of the substrate. Semiconductor laser equipment.