KR100710956B1 - Laser diode having spot size converter and fabricaing method therefor - Google Patents

Abstract

The present invention relates to a laser diode having an optical mode size converter and a method of manufacturing the same.

According to the present invention, an active layer having a predetermined length having a passive waveguide layer on a substrate, and an optical mode size conversion region gradually narrowing while going to one end to transfer the optical mode to the passive waveguide layer, and laminated around the active layer A laser diode having a current blocking layer, a cladding layer formed to cover the active layer and the current blocking layer, and a p-type electrode for injecting current into the active layer, the cladding layer and the current blocking layer adjacent to the active layer. A U-shaped channel is formed on both sides of the active layer to form a ridge structure as a whole, and the p-type electrode extends to the upper surface of the clad layer covering the bottom surface and the inner wall of the U-shaped channel. .

In addition, according to the present invention, a first step of sequentially forming a lower buffer layer, a passive waveguide layer and an upper buffer layer on a substrate; A second step of forming an active layer having a predetermined length on the upper buffer layer having an optical mode size conversion region gradually narrowing toward one end; A third step of etching the active layer in a mesa pattern; A fourth step of growing a current blocking layer around the active layer; Forming a clad layer to cover the active layer and the current blocking layer; Forming a U-shaped channel by etching both sides of the active layer such that the cladding layer and the current blocking layer adjacent to the active layer form a ridge structure as a whole; And a seventh step of forming an electrode by depositing an electrode material on a bottom surface and an inner wall of the U-shaped channel and an upper surface of the clad layer.

Optical Mode Size Converter, Passive Waveguide Layer, Active Layer, Ridge, Polyimide

Description

LASER DIODE HAVING SPOT SIZE CONVERTER AND FABRICAING METHOD THEREFOR}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a perspective view partially showing a configuration of an SSC type laser diode according to the prior art;

2 to 4 are sectional views showing the manufacturing process of the SSC type laser diode according to the prior art.

5 is a perspective view partially showing a configuration of an SSC type laser diode according to a preferred embodiment of the present invention.

6 and 7 are sectional views showing the manufacturing process of the SSC type laser diode according to the preferred embodiment of the present invention.

<Description of main reference numerals in the drawings>

100 ... bottom InP buffer layer 100 '... top InP buffer layer

101 Passive optical waveguide layer 102 Active layer

102a ... Optical mode size conversion area 103 ... U-shaped channel

104 ... electrode layer 105 ... p-InP current blocking layer

106 ... n-InP current blocking layer 107 ... cladding layer

108 Ridge Structure

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser diode and a method of manufacturing the same, and more particularly to a laser diode of a planar buried heterostructure (PBH) equipped with an optical mode size converter (SSC). The present invention relates to a laser diode having an improved structure and a method of manufacturing the same.

Recently, as the price competition for the construction of the optical subscriber network is intensifying, the packaging method of the optical components using the passive alignment is drawing attention.

In general, the packaging method of the manual sorting method is a method of manually aligning the waveguide and the laser diode by using a process such as flip chip bonding, there is an advantage that it is easy to mass production and lower the cost.

However, on the other hand, the passive alignment packaging method has a disadvantage in that the optical coupling efficiency is lowered due to the mode mismatch between the laser diode and the waveguide. Generally, the mode size of a laser diode is 1 to 2 μm, and the silica waveguide has a size of about 5 to 6 μm. Therefore, in order to increase the optical coupling efficiency and to increase the alignment tolerance, the size of the output light mode of the laser diode is increased. It is important.

Figure 1 shows in part the configuration of an SSC type laser diode provided in accordance with this requirement.

Referring to FIG. 1, a conventional SSC type laser diode includes a lower InP buffer layer 10, a passive waveguide layer 11, an upper InP buffer layer 10 ′, and an optical mode size conversion region on a predetermined InP substrate (not shown). The active layer 12 having the 12a is sequentially stacked, and a polyimide layer 13 is filled on both sides of the ridge structure (see 16 in FIG. 2) including the active layer 12.

In the active layer 12, the optical mode size converting region 12a is formed to have a width gradually narrowing toward one end, and the other regions serve as an active optical waveguide.

The optical mode size converting region 12a is generally configured to have a two-step gradient pattern in which the width is narrowed down sharply and then narrowed down gradually to reduce the radiation loss. The optical mode, which has been advanced through the active optical waveguide of the active layer 12, is released from the optical mode size converting region 12a and is eventually transferred to the passive waveguide layer 11. Therefore, the finally emitted optical mode is light constrained due to the thin thickness of the passive waveguide layer 11, the distribution of the optical mode is increased. In this way, when the distribution of the optical mode increases, the radiation angle decreases, thereby reducing the optical coupling loss with the waveguide.

2 to 4 schematically show a process for manufacturing a laser diode of the SSC type according to the prior art.

First, referring to FIG. 2, a process of sequentially forming the lower InP buffer layer 10, the passive waveguide layer 11, the upper InP buffer layer 10 ′, and the active layer 12 is performed on the active layer 12. After depositing the etching mask, a photolithography process and an undercut etching process are sequentially performed to form a mesa structure.

Next, the p-InP current blocking layer 13 and the n-InP current blocking layer 14 are sequentially formed around the active layer 12 to cover the active layer 12 and the n-InP current blocking layer 14. A process of forming the clad layer 15 is followed.

After the cladding layer 15 is formed, as shown in FIG. 3, the cladding layer 15 adjacent to the active layer 12, the current blocking layers 13 and 14, and the upper InP buffer layer 10 ′ are entirely ridged. Dry etching of both sides of the active layer 12 to form (16), and then forming a polyimide layer 18 on the etching portions on both sides of the ridge structure 16 to obtain a structure as shown in FIG.

In the above manufacturing process, particularly dry etching is to use reactive ion etching (RIE), etc. There is a disadvantage that the process takes too much time due to the characteristics of dry etching.

In addition, the polyimide filled to protect the laminated structure has a very difficult surface planarization process, and there is a problem in that the high temperature characteristics of the device are poor due to the deterioration of the heat dissipation characteristics as the polyimide is filled.

The present invention has been made to solve the above problems, SSC type laser diode and the method of manufacturing a structure in which the surface of the ridge structure is covered with a metal layer and a channel is formed to increase the heat dissipation efficiency The purpose is to provide.

Another object of the present invention is to provide an SSC type laser diode having a structure capable of shortening an etching process time for forming a ridge structure and a method of manufacturing the same.

In order to achieve the above object, the laser diode according to the present invention includes a structure in which a U-shaped channel is formed at both sides of a ridge structure including an optical mode size converter.

A laser diode according to a preferred embodiment of the present invention includes an active layer having a predetermined length having a passive waveguide layer on a substrate and an optical mode size conversion region gradually narrowing in width while going to one end so that the optical mode is transferred to the passive waveguide layer. And a current blocking layer stacked around the active layer, a cladding layer formed to cover the active layer and the current blocking layer, and a p-type electrode for injecting current into the active layer. On both sides of the active layer, a U-shaped channel having a bottom surface is formed on the passive waveguide layer, and the p-type electrode has a bottom surface and an inner wall of the U-shaped channel so that the adjacent cladding layer and the current blocking layer form a ridge structure as a whole. Covering and extending to the clad layer upper surface.

According to another aspect of the invention, a first step of sequentially forming a lower buffer layer, a passive waveguide layer and an upper buffer layer on a substrate; A second step of forming an active layer having a predetermined length on the upper buffer layer having an optical mode size conversion region gradually narrowing toward one end; A third step of etching the active layer in a mesa pattern; A fourth step of growing a current blocking layer around the active layer; Forming a clad layer to cover the active layer and the current blocking layer; A sixth step of forming a U-shaped channel having a bottom surface formed in the passive waveguide layer by etching both sides of the active layer such that the cladding layer adjacent to the active layer and the current blocking layer form a ridge structure as a whole; And a seventh step of forming an electrode by depositing an electrode material on a bottom surface and an inner wall of the U-shaped channel and an upper surface of the clad layer.

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In order to reduce the etching process time, the sixth step is preferably performed by a wet etching process using an isotropic etching solution.

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Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

5 is a partial view showing the configuration of an SSC type laser diode according to a preferred embodiment of the present invention.

Referring to FIG. 5, an SSC type laser diode according to an exemplary embodiment of the present invention may include a lower InP buffer layer 100, a passive waveguide layer 101, and an upper InP buffer layer 100 ′ on a predetermined InP substrate (not shown). And an active layer 102 having the optical mode size conversion region 102a is sequentially stacked, and a U-shaped channel 103 is formed on both sides of the ridge structure including the active layer 102 (see 108 in FIG. 6). Here, the substrate, the buffer layer, and the like are not limited to being formed of InP, and of course, may be formed of various materials.

In the active layer 102, the optical mode size conversion region 102a is formed in a structure in which the width gradually narrows toward one end in the longitudinal direction of the active layer 102, and the optical mode proceeds from the other active optical waveguide. Is transferred to the passive optical waveguide layer 101.

As shown in more detail in FIGS. 6 and 7, the ridge structure 108 includes an active layer 102, a cladding layer 107 adjacent to the top of the active layer 102, and adjacent to both sides of the active layer 102. Current blocking layers 105 and 106 are included, and U-shaped channels 103 are formed on both sides of the ridge structure 108.

Here, the inner wall and the bottom surface of the U-shaped channel 103 is covered by the electrode layer 104 of the metal material. In this case, the electrode layer 104 extends to the upper surface of the cladding layer 107 to perform the function of the p-type electrode. According to this structure, the InP exposed surfaces of the cladding layer 107, the current blocking layers 105 and 106 are protected by the electrode layer 104, and heat can be smoothly released into the U-shaped channel 103 by the metal material. The heat dissipation efficiency can be improved.

Preferably, the portion of the electrode layer 104 on the bottom surface of the U-shaped channel 103 may be formed to contact the passive waveguide layer 101.

Next, the process of performing the SSC type laser diode manufacturing process according to the preferred embodiment of the present invention will be described with reference to FIGS. 6 and 7 again.

First, referring to FIG. 6, a process of sequentially forming the lower InP buffer layer 100, the passive waveguide layer 101, the upper InP buffer layer 100 ′, and the active layer 102 is performed, and then on the active layer 102. After depositing the etching mask, a photolithography process and an undercut etching process are sequentially performed to form a mesa structure.

Next, the p-InP current blocking layer 105 and the n-InP current blocking layer 106 are sequentially formed around the active layer 102 to cover the active layer 102 and the n-InP current blocking layer 106. A process of forming the clad layer 107 is followed.

After the cladding layer 107 is formed, both sides of the active layer 102 such that the cladding layer 107 adjacent to the active layer 102, the current difference monolayers 105 and 106, and the upper InP buffer layer 100 ′ form a ridge structure 108 as a whole. Etching to form a U-shaped channel 103 is performed. Here, the etching of the U-shaped channel 103 is preferably performed by for example a wet etching process by the isotropic etching solution H ₂ 0, H ₂ O _2, and HBr mixed.

After the etching of the U-shaped channel 103 is finished, the etching mask is removed, and a SiNx film is deposited again, followed by a photolithography process and an etching process to form an upper surface of the clad layer 107, which is a part where the electrode layer 104 is to be formed. A process of selectively removing the SiNx of the bottom surface and the inner wall of the U-shaped channel 103 proceeds. Subsequently, when the electrode material 104 is formed by depositing the electrode material on the portion from which the SiNx is removed, a structure as shown in FIG. 7 is manufactured.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

As described above, the SSC type laser diode according to the present invention provides the following effects.

First, since the U-shaped channels are formed on both sides of the ridge structure, the heat dissipation space can be secured sufficiently, the heat dissipation efficiency of the metal electrode layer formed on the surface of the U-shaped channel can be improved, and the surface of the ridge structure can be protected. have.

Second, the wet etching process is used to form the U-shaped channel, which reduces the process time, which is suitable for mass production.

Third, unlike the prior art in which both sides of the ridge structure are filled with polyimide, a planarization process is not required.

Claims (5)

An active layer having a passive waveguide layer on the substrate, an optical mode size conversion region gradually narrowing toward one end to transition the optical mode to the passive waveguide layer, a current blocking layer stacked around the active layer, and the active layer A laser diode having a cladding layer formed to cover an overcurrent blocking layer and a p-type electrode for injecting current into the active layer, On both sides of the active layer, a U-shaped channel having a bottom surface thereof is formed on the passive waveguide layer so that the cladding layer and the current blocking layer adjacent to the active layer form a ridge structure as a whole. And the p-type electrode extends to the top surface of the clad layer covering the bottom surface and the inner wall of the U-shaped channel. delete A first step of sequentially forming a lower buffer layer, a passive waveguide layer, and an upper buffer layer on the substrate; Forming an active layer on the upper buffer layer, the active layer having an optical mode size conversion region gradually narrowing toward one end; A third step of etching the active layer in a mesa pattern; A fourth step of growing a current blocking layer around the active layer; Forming a clad layer to cover the active layer and the current blocking layer; A sixth step of forming a U-shaped channel having a bottom surface formed in the passive waveguide layer by etching both sides of the active layer such that the cladding layer adjacent to the active layer and the current blocking layer form a ridge structure as a whole; And And forming an electrode by depositing an electrode material on a bottom surface and an inner wall of the U-shaped channel and an upper surface of the clad layer. delete The method of claim 3, The sixth step is a laser diode manufacturing method, characterized in that performed by a wet etching process using an isotropic etching solution.

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