JP7112262B2 - Semiconductor optical device and optical transmission module - Google Patents

Description

The present invention relates to a semiconductor optical device, its manufacturing method, and an optical transmission module.

Semiconductor lasers, which are one of semiconductor optical devices, are used in various applications such as optical communication, information processing, and light sources, and are required to be low cost, low power consumption, small size, high optical output, and high reliability. . Generally, a semiconductor optical device has a semiconductor crystal forming a pn junction and a metal forming an electrode.

Among semiconductor optical devices, a buried-heterostructure (BH) has a semiconductor crystal forming a pn junction in a mesa structure, and the sides of the mesa structure are buried in a semi-insulating semiconductor buried layer. Therefore, the electrodes are arranged over the upper surface of the mesa structure (the upper exposed surface of the contact layer) and the upper surface of the buried layer.

A metal forming an electrode of a semiconductor optical device is generally deposited on a semiconductor crystal layer by a high-temperature process such as electron beam evaporation. When the temperature of the deposited metal is lowered from high temperature to room temperature, stress is generated in the semiconductor crystal due to the difference in thermal expansion coefficient between the semiconductor and the metal. Such stress is known to adversely affect the performance of semiconductor optical devices. Therefore, various proposals have been made so far for alleviating such stress.

Patent Document 1 reports the relationship between the stress generated in the semiconductor crystal by Pt constituting the electrode and the reliability in a double-channel planar buried heterostructure (DC-PBH) type semiconductor laser. . For example, Patent Literature 1 proposes cutting TiPtAu ohmic electrodes along the mesa portion near both outsides of the mesa structure.

Patent Document 2 reports the relationship between the stress of a semiconductor crystal caused by a metal and the characteristic variation of a laser active layer or a light absorption layer in a ridge type semiconductor laser. For example, Patent Literature 2 proposes adding stress-reducing slits to the electrodes on the mesa structure.

Japanese Laid-Open Patent Publication No. 2002-100002 proposes to relax the stress of the active layer directly under the ridge by the electrode in the ridge type semiconductor laser. For example, Patent Document 3 proposes a structure in which cavities are provided in the sidewall portion of the contact layer above the ridge and the sidewall portion of the semiconductor ridge structure immediately below the contact.

In Patent Document 4, in the ridge type structure of a nitride semiconductor laser, the relationship between the reliability and the stress of the nitride semiconductor layer formed by the electrode and the ridge is reported. For example, Patent Document 4 proposes a structure in which a gap is provided between a protective film on a semiconductor layer and an electrode on the protective film in a ridge base portion.

JP-A-64-28884 JP 2012-256712 A JP 2012-94564 A JP 2012-59890 A

In the BH structure described above, the upper surface of the mesa structure and the upper surface of the buried layer are generally flush with each other. There is In such a semiconductor optical device in which a portion of the mesa structure protrudes from the buried layer, electrodes are also formed on the side surfaces of a portion of the protruding mesa structure. Therefore, in the mesa structure, the electrode stress is felt not only from the top surface but also from the side surface. As a result, the top-protruding mesa structure is more affected by the electrode than the non-top-protruding mesa structure. Therefore, we have found that stress relaxation is particularly important in a BH semiconductor laser in which the upper portion of the mesa structure protrudes.

However, the stress relaxation disclosed in Patent Document 1 relaxes the stress of the BH structure in which the contact layer is not exposed from the buried layer. The stress relaxation disclosed in Patent Documents 2 to 4 is stress relaxation for a ridge type semiconductor laser, not for a BH structure type semiconductor laser. Therefore, there is a possibility that the stress relaxation methods disclosed in Patent Documents 1 to 4 may not achieve sufficient stress relaxation for the BH structure semiconductor laser.

Based on the above understanding, the inventors of the present application examined the stress relaxation disclosed in Patent Documents 1 to 4. As a result, the inventors of the present application have found that the stress relaxation disclosed in Patent Documents 1 to 4 does not affect the SMSR (Side Mode Suppression Ratio) characteristics of a BH structure semiconductor laser in which the contact layer is partially or entirely exposed from the buried layer. It has been found that the adverse effects exerted are not sufficiently mitigated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to reduce stress applied from an electrode layer to the side surfaces of the mesa structure upper portion protruding from the buried layer in a BH structure semiconductor laser in which the upper portion of the mesa structure protrudes from the buried layer.

(1) A semiconductor optical device of the present application comprises a substrate having a first conductivity type, an active layer provided on the substrate, and a second conductivity type provided on the active layer different from the first conductivity type. a mesa structure including a cladding layer and a contact layer having a second conductivity type provided on the cladding layer; a burying layer provided on the substrate and burying the mesa structure; an electrode layer comprising at least two layers provided on the layer. In the semiconductor optical device, the upper portion of the mesa structure is exposed from the buried layer, and one of the electrode layers deposited on the mesa structure and the buried layer and/or on the one layer Another layer to be deposited separates the upper sidewalls of the mesa structure.

(2) In the semiconductor optical device of (1), the thickness of the other layer is thicker than the thickness of the portion where the upper part of the mesa structure is exposed from the buried layer, and the other layer is on the contact layer. on the buried layer, and the one layer is separated by the upper sidewall of the mesa structure.

(3) In the semiconductor optical device of (1), the thickness of the one layer is thicker than the thickness of the portion where the upper part of the mesa structure is exposed from the buried layer, and the one layer is on the contact layer. on the buried layer, and the other layers are separated by upper sidewalls of the mesa structure.

(4) In the semiconductor optical device of (1), the region of the mesa structure exposed from the buried layer is part of the contact layer.

(5) In the semiconductor optical device of (1), the total thickness of the one layer and the other layer is thinner than the thickness of the upper portion of the mesa structure exposed from the buried layer.

(6) In the semiconductor optical device according to any one of (1) to (4), the total thickness of the one layer and the other layer is the thickness at which the upper portion of the mesa structure is exposed from the buried layer. thicker than

(7) In the semiconductor optical device according to any one of (1) to (3), the region of the mesa structure exposed from the buried layer is the entire contact layer.

(8) In the semiconductor optical device according to any one of (1) to (7), one of the electrode layers is Ti and the other electrode layer is Pt.

(9) An optical transmission module of the present application includes the semiconductor optical device according to any one of (1) to (8).

(10) An optical transceiver module of the present application comprises the semiconductor optical device according to any one of (1) to (8).

According to the present invention, in a BH structure semiconductor laser in which the upper portion of the mesa structure protrudes from the buried layer, the side surface of the upper portion of the mesa structure protruding from the buried layer receives stress from the electrode layer.

1 shows an optical transceiver module comprising an optical transmitter module according to an embodiment of the invention; 1 shows an optical transmission module equipped with a semiconductor optical device according to an embodiment of the present invention; 1 shows a top view of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows a cross-sectional view of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows an enlarged cross-sectional view of a mesa structure of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows an enlarged cross-sectional view of a mesa structure of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows an enlarged cross-sectional view of a mesa structure of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows an enlarged cross-sectional view of a mesa structure of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 shows an enlarged cross-sectional view of a mesa structure of a semiconductor optical device according to an embodiment of the present invention; FIG. 1 illustrates a method of manufacturing a semiconductor optical device according to an embodiment of the present invention; 1 illustrates a method of manufacturing a semiconductor optical device according to an embodiment of the present invention; 1 illustrates a method of manufacturing a semiconductor optical device according to an embodiment of the present invention; 1 illustrates a method of manufacturing a semiconductor optical device according to an embodiment of the present invention;

[First embodiment]
FIG. 1 shows an optical transceiver module comprising an optical transmitter module according to an embodiment of the present application. The optical transceiver module 100 includes a housing 101, a printed circuit board 103 provided in the housing 101 and provided with an edge connector 102, an optical transmitter module 106 (TOSA: Transmitter Optical Sub Assembly), and an optical receiver module 107 (ROSA: Receiver Optical Sub Assembly) and optical fiber connectors 108 a and 108 b attached to the housing 101 . A printed circuit board 103 has an integrated circuit 104 on it.

The printed circuit board 103 is connected to the optical transmission module 106 and the optical reception module 107 by the flexible circuit board 105 respectively. The fiber optic connectors 108a, 108b are optically aligned with the optical transmitter module 106 and the optical receiver module 107, respectively.

The integrated circuit 104 has a signal reproduction function and an amplification function. The optical transmission module 106 has the function of converting electrical signals into optical signals. The optical receiver module 107 has a function of converting an optical signal into an electrical signal.

The edge connector 102 outputs electrical signals from the optical receiver module 107 to a host device (not shown) and outputs electrical signals from the host device (not shown) to the optical transmitter module 106 . The optical fiber connectors 108 a and 108 b function as input/output means of the optical transceiver module 100 . That is, the input light is input to the optical receiving module 107 via an optical fiber (not shown) connected to the optical fiber connector 108b, and the output light is an optical fiber (not shown) connected to the optical fiber connector 108a. ) from the optical transmission module 106 .

FIG. 2 shows an optical transmitter module according to an embodiment of the present application. The optical transmission module 106 has a chip carrier 109 , a semiconductor optical device 110 mounted on the chip carrier 109 , and a convex lens 111 .

The semiconductor optical device 110 emits light. The convex lens 111 converts the light emitted from the semiconductor optical device 110 into parallel light or converging light.

FIG. 3 shows a top view of a semiconductor optical device according to an embodiment of the present application. The illustrated semiconductor optical device 110 is an electro-absorption modulator-distributed feedback laser (EA-DFB). The semiconductor optical device 110 has a laser section 112 , a waveguide section 113 , a modulator section 114 and a mesa structure (mesa stripe) 115 .

An electrode 116 is provided above the laser section 112 . Electrode 116 may include at least two metal layers. Laser portion 112 is preferably a DFB laser element, but may be other types of laser elements. An electrode 116 and an electrode pad 117 are provided above the modulator section 114 . Modulator section 114 is preferably an EA optical modulator, but may be other types of optical modulators.

FIG. 4 shows a cross-sectional view along line A-A' of semiconductor optical device 110 according to an embodiment of the present invention. The illustrated semiconductor optical device 110 is a BH structure type semiconductor laser embedded with a semi-insulating semiconductor. The cross-sectional view shown in FIG. 4 is not limited to the cross-section taken along the line AA' in FIG. 3, and any cross-section of the laser section 112 has the structure shown in FIG.

The semiconductor optical device 110 includes a substrate 118 having a first conductivity type, a mesa structure 115 provided on the surface of the substrate 118, an embedding layer 122 embedding the mesa structure 115, and a passivation layer provided on part of the embedding layer 122. The film 123, the Ti layer 124 covering the mesa structure 115, the buried layer 122, and the passivation film 123, the Pt layer 125 provided on the Ti layer 124, the Au layer 126 provided on the Pt layer 125, and the substrate 118. It has an electrode 127 having a first conductivity type formed on the back surface.

The mesa structure 115 includes an active layer 119, a clad layer 120 provided on the active layer 119 and having a second conductivity type different from the first conductivity type, and a clad layer 120 provided on the clad layer 120 and having the second conductivity type. It has a contact layer 121 . The Ti layer 124, the Pt layer 125, and the Au layer 126 constitute the electrode layer 116 having the second conductivity type. The mesa structure 115 has a striped resonator structure in the vertical direction in FIG. 4 in this embodiment. Although omitted in this description, the mesa structure 115 may include other layers such as an SCH layer and a diffraction grating layer. However, the top layer of the mesa structure 115 is the contact layer. In this embodiment, the substrate 118 is an n-type InP substrate, the active layer 119 is a multiple quantum well containing InGaAsP, the cladding layer 120 is a p-type InP layer, and the contact layer 121 is a p-type InGaAs layer. Furthermore, the resonator structure of the mesa structure 115 is a λ/4 shift diffraction grating structure.

The semiconductor optical device 110 is composed of an InGaAsP-based material, but may be composed of other materials. Buried layer 122 is composed of a semi-insulating semiconductor. Here, an InP layer to which Fe is added is used. Since the electrode layer 116 composed of the Ti layer 124, the Pt layer 125, and the Au layer 126 constitutes an ohmic electrode on the upper surface of the contact layer 121, low-resistance electrical connection is sufficiently maintained. In this embodiment, the first conductivity type is n-type and the second conductivity type is p-type, but depending on the embodiment, the first conductivity type may be p-type and the second conductivity type may be n-type.

Considering the conduction and heat dissipation of the semiconductor optical device and post-processes (wire bonding and soldering), it is preferable to use Au as the electrode. However, Au in the electrode layer diffuses into the semiconductor layer in the mesa structure, possibly degrading the reliability and characteristics of the semiconductor optical device. In order to prevent such diffusion of Au into the semiconductor layer, a Pt electrode layer is provided below the Au electrode layer as a barrier layer. The contact layer 121 and the Au layer 126 are not in direct contact, and diffusion of Au into the semiconductor crystal is suppressed by the barrier metal effect of the Pt layer 125 . However, since the adhesion strength of Pt to semiconductors is weak, a Ti layer 124 is provided between the Pt layer 125 and the buried layer 122 and the top of the mesa structure 115 to form an adhesion layer and an ohmic electrode.

As described above, Au needs to spread over areas other than the mesa structure for conduction and heat dissipation. Therefore, even if the stress exerted by the Au electrode layer on the mesa structure is large, the stress exerted by the Au layer on the semiconductor layer is inevitable. However, the Pt layer and the Ti layer are mainly provided for a purpose other than the original function of the electrode, which is to conduct electricity. Therefore, it is preferable that the Pt layer and the Ti layer do not exert stress on the mesa structure.

As a result of intensive studies from the above point of view, the inventors of the present application have found a Pt electrode layer in contact with the side surface of the mesa structure and/or a Pt electrode layer in contact with the upper surface of the mesa structure in order to relax the stress exerted on the mesa structure by the Pt layer and the Ti layer. The idea was to weaken the connection between the electrode layer and/or the Ti electrode layer. Specifically, the inventors of the present application have proposed a semiconductor optical device in which the Pt electrode layer and/or the Ti electrode layer are separated at the upper portion and the side portion of the mesa structure. The Pt layer and/or the Ti layer are preferably formed only on the top of the mesa structure, but in practice they are also formed on the sides of the mesa structure to some extent.

Since the electrode layer of the semiconductor optical device described above is separated at the side of the mesa structure, the stress of the electrode layer on the side of the contact layer, which is the upper part of the mesa structure, is relieved, and the stress of the entire mesa structure is relieved. As a result, the inventors of the present application have found that the SMSR yield of the semiconductor optical device according to the present embodiment is improved by 3%.

FIG. 5 shows an enlarged cross-sectional view of the mesa structure of the semiconductor optical device according to the embodiment of the present application at B in FIG. In this embodiment, the entire contact layer 121 is exposed from the buried layer 122 . That is, in this embodiment, the upper portion of the mesa structure 115 exposed from the buried layer 122 is the contact layer 121 . In this embodiment, both the Ti layer 124 and the Pt layer 125 are separated and discontinuous at the sides of the contact layer 121 . Also, the thickness of the region formed on each contact layer 121 and the thickness of the region formed on the buried layer 122 are substantially equal. Depending on the embodiment, a layer (for example, the cladding layer 120) located below the contact layer 121 may be exposed from the buried layer 122. FIG. In this embodiment, the thickness of the Ti layer 124 is thinner than the thickness (hereinafter referred to as H) of the portion of the contact layer 121 exposed from the embedded layer 122 (Ti layer<H), and the thickness of the Pt layer 125 is also Thinner than the thickness of the exposed part (Pt thickness<H). Furthermore, the total thickness of the Ti layer 124 and the Pt layer 125 is greater than H. Therefore, the Au layer 126 arranged on the Pt layer 125 does not come into contact with the side of the exposed portion (the contact layer 121 which is a semiconductor layer), so there is no fear of Au diffusion. In this embodiment, the thickness of the portion of the contact layer 121 exposed from the buried layer 122 is 200 nm, the thickness of the Ti layer 124 is 100 nm, the thickness of the Pt layer 125 is 150 nm, and the thickness of the Au layer 126 is 1000 nm. .

In the mesa structure shown in FIG. 5, the Ti layer 124 is separated and discontinuous at the sides of the contact layer 121 . Therefore, in the semiconductor optical device according to this embodiment, the stress exerted by the Ti layer 124 on the mesa structure 115 is alleviated compared to the case where the mesa structure 115 is continuous. Furthermore, the Pt layer 125 is similarly discontinuous, and the stress exerted by the Pt layer 125 on the mesa structure 115 is relieved.

[Second embodiment]
FIG. 6 shows an enlarged cross-sectional view of the mesa structure of the semiconductor optical device according to the embodiment of the present application. This embodiment is similar to the first embodiment except that the Pt layer 125 is continuous on the sidewalls of the mesa structure 115 . In this embodiment, the Pt layer thickness is set to 250 nm. Since the Ti layer 124 is separated by the sidewalls of the mesa structure 115, the stress exerted by the Ti layer 124 on the contact layer 121 is relieved. Therefore, the same effect can be obtained in this embodiment as well.

[Third embodiment]
FIG. 7 shows an enlarged cross-sectional view of the mesa structure of the semiconductor optical device according to the embodiment of the present application. This embodiment is similar to the first embodiment except that the Ti layer 124 is continuous on the sidewalls of the mesa structure 115 . In this embodiment, the Ti layer thickness is set to 250 nm. Since the Pt layer 125 separates the sidewalls of the mesa structure 115, the stress exerted on the contact layer 121 is relieved. Therefore, the same effect can be obtained in this embodiment as well.

[Fourth embodiment]
FIG. 8 shows an enlarged cross-sectional view of the mesa structure of the semiconductor optical device according to the embodiment of the present application. This embodiment is the same as the first embodiment except that a part of the contact layer 121 is exposed from the buried layer 122 and the thickness of the Pt layer is different. In this embodiment, the thickness H of the exposed portion is 150 nm, and the Pt layer thickness is 100 nm. Also in this embodiment, even if only a portion of the contact layer 121 is exposed, the Ti layer 124 and the Pt layer 125 are separated by the sidewalls of the mesa structure 115, so that the exposed portion of the contact layer 121 is affected. Stress is relieved. Therefore, the same effect can be obtained in this embodiment as well. Conversely, even if part of the clad layer 120 is exposed in the mesa structure, if the Ti layer 124 and/or the Pt layer 125 are discontinuous, the same effects as in this embodiment can be obtained.

[Fifth embodiment]
FIG. 9 shows an enlarged cross-sectional view of the mesa structure of the semiconductor optical device according to the embodiment of the present application. This embodiment is the same as the first embodiment except that the Ti layer 124 and the Pt layer 125 have different thicknesses. Here, the Ti layer thickness is 50 nm and the Pt layer thickness is 100 nm. The thickness H of the portion of the contact layer 121 exposed from the buried layer 122 is 200 nm. In this embodiment, since the Ti layer 124 and the Pt layer 125 are separated by the sidewalls of the mesa structure 115, the stress applied to the exposed portion of the contact layer 121 is relieved. However, since the total thickness of the Ti layer 124 and the Pt layer 125 is thinner than H, the Au layer 126 is in contact with the side wall of the mesa structure. When the Au layer 126 is in contact with the semiconductor layer (contact layer 121), Au may diffuse into the semiconductor. Therefore, the effects of the present invention can be obtained in this structure as well.

The first to third embodiments and the fourth and fifth embodiments may be combined as appropriate. The present invention is characterized in that the Ti layer and/or the Pt layer are discontinuously arranged from the top of the mesa to the top of the buried layer in a state where a part of the mesa structure is exposed from the buried layer.

[Method for manufacturing a semiconductor optical device according to the embodiment of the present application]
10, 11, 12 and 13 show a method of manufacturing a semiconductor optical device according to the present embodiment. First, as shown in FIG. 10, an active layer 119 suitable for light emission comprising multiple layers is deposited on a substrate 118, a cladding layer 120 is deposited on the active layer 119, and a p-type InP cladding layer 120 is deposited. A contact layer 121 is deposited thereon. Substrate 118 may be, for example, an n-type InP substrate. Active layer 119 may be, for example, multiple quantum wells. Active layer 119 may also include a grating layer that controls the oscillation state of the laser. Contact layer 121 may be, for example, p-type InGaAs.

An etching process then forms the mesa structure 115 followed by selective deposition of the buried layer 122 to form the BH structure. For example, buried layer 122 may be semi-insulating InP. The width of the mesa structure 115 is preferably determined to satisfy single mode oscillation conditions. The width of mesa structure 115 may be, for example, about 2 microns or less. During the crystal growth of the buried layer 122, since a mask having a width slightly larger than the mesa width is arranged over the mesa, the buried layer 122 has a slightly flat region above the mesa as shown in FIG. After that, it extends obliquely upward along the crystal plane, and a flat part continues. Subsequently, after forming a passivation film 123 on the upper surface of the buried layer 122, the passivation film 123 is etched with a width larger than the width of the mesa structure 115 to create a structure for electrical connection with the mesa structure 115. (Fig. 11).

Thereafter, as shown in FIG. 12, etching is performed so that the sides of contact layer 121 are exposed from buried layer 122 . The contact layer 121 is exposed entirely or partially from the buried layer 122 .

Next, as shown in FIG. 13, a Ti layer 124, a Pt layer 125 and an Au layer 126 are deposited in this order. A p-type electrode is formed as a result. Finally, an n-type electrode 127 is formed on the back surface of the substrate 118 .

With the above structure, the present invention has an electrical connection with a small resistance value by an ohmic electrode made of Ti, Pt, and Au on the upper surface of the contact layer, and the Ti layer 124 and/or the Pt layer 125 are separated on the side of the contact layer. As a result, the stress exerted by the Ti layer 124 and/or the Pt layer 125 on the sides of the contact layer is relaxed. This reduces the stress exerted on the mesa structure 115 . As a result, stress-induced refractive index changes and diffraction grating pitch changes are reduced, thereby improving the SMSR yield.

Although the InGaAsP-based EA-DFB laser has been described in this embodiment, similar effects can be expected for semiconductor lasers using other materials having a BH structure and semiconductor laser integrated devices. Furthermore, it goes without saying that the same effect can be obtained in the optical transmission module 106 and the optical transmission/reception module 100 using this semiconductor optical device 110. FIG.

100 optical transceiver module 101 housing 102 edge connector 103 printed board 104 integrated circuit 105 flexible substrate 106 optical transmitter module 107 optical receiver module 108a, b optical fiber connector 109 chip carrier 110 semiconductor optical device , 111 convex lens, 112 laser section, 113 waveguide section, 114 modulator section, 115 mesa structure, 116 electrode, 117 electrode pad, 118 substrate, 119 active layer, 120 clad layer, 121 contact layer, 122 embedded layer, 123 passivation Membrane, 124 Ti layer, 125 Pt layer, 126 Au layer, 127 electrode.

Claims (12)

a substrate having a first conductivity type;
an active layer provided on the substrate, a clad layer provided on the active layer and having a second conductivity type different from the first conductivity type, and a contact layer provided on the clad layer and having a second conductivity type a mesa structure comprising
a burying layer provided on the substrate and burying the mesa structure so that an upper portion of the mesa structure is exposed ;
an electrode layer provided on the upper portion of the mesa structure and on the buried layer;
wherein the electrode layer comprises an adhesion layer contacting the upper portion of the mesa structure, a conductive layer, and a barrier layer between the adhesion layer and the conductive layer;
the adhesion layer has a higher adhesion strength to the upper portion of the mesa structure than any other layer of the electrode layer;
the adhesive layer, the conductive layer, and the barrier layer form an ohmic electrode on the contact layer;
the electrode layer includes one layer of the adhesion layer and the barrier layer and the other layer of the adhesion layer and the barrier layer;
At least one of the one layer and the other layer of the electrode layer provided on the mesa structure and on the buried layer is separated into a portion on the top of the mesa structure and a portion on the buried layer. has been
A semiconductor optical device characterized by: The semiconductor optical device according to claim 1,
the thickness of the other layer is thicker than the thickness of the portion where the upper portion of the mesa structure is exposed from the buried layer;
the other layer is continuously connected from the contact layer to the embedded layer;
the one layer is separated by a sidewall of the upper portion of the mesa structure;
A semiconductor optical device characterized by: The semiconductor optical device according to claim 1,
the thickness of the one layer is thicker than the thickness of the portion where the upper portion of the mesa structure is exposed from the buried layer;
the one layer is continuously connected from the contact layer to the embedded layer;
the other layer is separated by a sidewall of the upper portion of the mesa structure;
A semiconductor optical device characterized by: The semiconductor optical device according to claim 1,
A region of the mesa structure exposed from the buried layer is part of the contact layer,
A semiconductor optical device characterized by: The semiconductor optical device according to claim 1,
the sum of the thicknesses of the one layer and the other layer is less than the thickness at which the upper portion of the mesa structure is exposed from the buried layer;
A semiconductor optical device characterized by: The semiconductor optical device according to any one of claims 1 to 4,
the sum of the thicknesses of the one layer and the other layer is greater than the thickness of the upper portion of the mesa structure exposed from the buried layer;
A semiconductor optical device characterized by: The semiconductor optical device according to any one of claims 1 to 3,
A region of the mesa structure exposed from the buried layer is the entire contact layer,
A semiconductor optical device characterized by: The semiconductor optical device according to any one of claims 1 to 7,
the adhesion layer is Ti,
the barrier layer is Pt;
A semiconductor optical device characterized by: An optical transmission module comprising the semiconductor optical device according to claim 1 . An optical transceiver module comprising the semiconductor optical device according to claim 1 . a substrate having a first conductivity type;
an active layer provided on the substrate, a clad layer provided on the active layer and having a second conductivity type different from the first conductivity type, and a contact layer provided on the clad layer and having a second conductivity type a mesa structure comprising
an embedding layer provided on the substrate and embedding the mesa structure;
an electrode layer comprising at least two layers provided on said contact layer and said buried layer;
has
an upper portion of the mesa structure is exposed from the buried layer;
One of the electrode layers deposited on the mesa structure and the buried layer and/or another layer deposited on the one layer are separated by sidewalls of the upper portion of the mesa structure. ,
the thickness of the one layer is thicker than the thickness of the portion where the upper portion of the mesa structure is exposed from the buried layer;
the one layer is continuously connected from the contact layer to the embedded layer;
the other layer is separated by a sidewall of the upper portion of the mesa structure;
A semiconductor optical device characterized by: a substrate having a first conductivity type;
an active layer provided on the substrate, a clad layer provided on the active layer and having a second conductivity type different from the first conductivity type, and a contact layer provided on the clad layer and having a second conductivity type a mesa structure comprising
an embedding layer provided on the substrate and embedding the mesa structure;
an electrode layer comprising at least two layers provided on said contact layer and said buried layer;
has
an upper portion of the mesa structure is exposed from the buried layer;
One of the electrode layers deposited on the mesa structure and the buried layer and/or another layer deposited on the one layer are separated by sidewalls of the upper portion of the mesa structure. ,
one of the electrode layers is Ti;
the other of the electrode layers is Pt;
A semiconductor optical device characterized by:

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