KR100596380B1 - Semiconductor laser device and method for manufacturing the same - Google Patents

Abstract

Disclosed are a semiconductor laser device capable of minimizing optical loss and a method of manufacturing the same. The disclosed semiconductor laser device includes a substrate, an active waveguide formed in a predetermined portion on the substrate, a passive waveguide including a core layer, and a passive waveguide including a core layer while being formed to abut one side of the active waveguide. A cladding layer formed on the upper portion of the passive waveguide may further include a separated confinement heterostructure (SCH) layer having a different composition from that of the core layer.

Optical waveguide, optical coupling coefficient, optical coupling efficiency, SCH

Description

Semiconductor laser device and method for manufacturing the same

1 is a cross-sectional view illustrating a semiconductor laser device in which a conventional active waveguide and a passive waveguide are integrated.

2 is a graph showing the refractive index of the conventional passive waveguide formation procedure.

3 is a cross-sectional view of a semiconductor laser according to the present invention.

4 is a graph showing the refractive index according to the growth direction in the passive waveguide of the semiconductor laser according to the present invention.

5A to 5D are cross-sectional views of respective processes for explaining a method of manufacturing a semiconductor laser according to the present invention.

6 is a graph showing an optical field distribution confined to a passive waveguide according to the present invention.

(Explanation of symbols for the main parts of the drawing)

100: substrate 115,125: SCH layer of the active waveguide

120: photoactive layer 130: first clad layer

140,150: SCH layer of the passive waveguide 145: core layer

155: second cladding layer 160: third cladding layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly, to a semiconductor laser structure integrated with an active waveguide and a passive waveguide capable of reducing optical loss of an optical waveguide and a method of manufacturing the same.

In order to manufacture various functional optical devices, a technology for integrating a laser diode, a photo detector, and an optical modulator on a single substrate is currently being developed, and the most important variable in the integration of these devices is to maintain their unique characteristics. It is.

In order to minimize this change in characteristics, the effective refractive index of the part of the optical waveguide between two different devices to be integrated is almost matched, thereby minimizing optical scattering loss and reflectance at the two device interfaces, and Minimizing optical losses that may occur.

In addition, in the case of laser diodes (active waveguides), optical field and carrier confinement occur in different regions, and at the same time, to increase optical confinement effect. High quantum efficiency can be obtained by adopting a separated confinement heterostructure (SCH) structure in which semiconductor materials having different bandgaps and refractive indices are stacked on both sides of the active layer.

1 is a cross-sectional view illustrating a semiconductor laser device in which a conventional active waveguide and a passive waveguide are integrated.

 The semiconductor laser device is formed such that the active waveguide x and the passive waveguide y are horizontally placed on the n-type InP substrate 10. At this time, the active waveguide x and the passive waveguide y are in contact with each other.

The active waveguide x includes the first SCH layer 15, the photoactive layer 20, and the second SCH layer 25 to have high quantum efficiency. In this case, the first SCH layer 15, the photoactive layer 20, and the second SCH layer 25 may all be InGaAsP layers, and the first and second SCH layers 15 and 25 may be larger than the photoactive layer 20. The band gap is large.

Passive waveguide y includes a core layer 40. The core layer 40 may be InGaAsP without doping impurities.

The first cladding layer 30, for example, a p-type InP layer, is formed on the active waveguide x, and the second cladding layer 45, for example, is not doped with impurities, on the passive waveguide y. An InP or semi-insulating InP layer is formed. In addition, the third cladding layer 50 is covered on the first and second cladding layers 30 and 45. At this time, the waveguide layer (SCH layer, photoactive layer, core layer, etc.) that substantially guides the light is formed of an InGaAsP material having a single composition so that the waveguided light can be transmitted.

2 is a graph illustrating refractive indexes according to the conventional passive waveguide formation order, and the refractive index of the core layer 40 is relatively higher than that of the substrate 10 and the second cladding layer 45.

However, in the conventional semiconductor laser device, since the core layer 40 of the passive waveguide is formed of a single material, even if it is designed to match the effective refractive index of the two integrated devices (active waveguide and passive waveguide), satisfactory optical It does not have an optical confinement factor. As a result, during optical waveguide, an optical loss occurs due to overlapping of the cladding layer existing on the waveguide.

Accordingly, an object of the present invention is to provide a semiconductor laser device capable of minimizing optical loss.

Another object of the present invention is to provide a method of manufacturing the semiconductor laser device.

In order to achieve the above technical problem to be achieved, the semiconductor laser device according to one aspect of the present invention is a substrate, an active waveguide formed in a predetermined portion on the substrate, the active waveguide is formed to be in contact with the active waveguide on one side. And a passive waveguide including a core layer, and a cladding layer formed on the active waveguide and the passive waveguide, and above and below the core layer of the passive waveguide, a separated confinement heterostructure (SCH) layer having a different composition from that of the core layer. This is further formed.

The SCH layer above and below the core layer has a relatively large band gap and has a relatively low refractive index than the core layer.

In this case, the core layer and the SCH layer above and below the core layer may be formed of an InGaAsP material, and the composition ratio thereof may be different from each other.

The active waveguide includes a first SCH layer formed on the substrate, a photoactive layer formed on the first SCH layer, and a second SCH layer formed on the photoactive layer.

The cladding layer includes a first cladding layer formed on the active waveguide, a second cladding layer formed on the passive waveguide, and a third cladding layer formed on the first and second cladding layers. .

In addition, a method of manufacturing a semiconductor laser according to another aspect of the present invention is as follows. First, the first SCH layer, the photoactive layer, the second SCH layer and the first clad layer for the active waveguide are sequentially stacked on the substrate. Thereafter, a portion of the first clad layer, the second SCH layer, the photoactive layer, the first SCH layer, and the InP substrate are etched to define a passive waveguide region. A first SCH layer, a core layer, a second SCH layer, and a second clad layer for the passive waveguide are formed on the passive waveguide region of the substrate. Then, a third cladding layer is formed on the first and second cladding layers.

At this time, the step of etching the first cladding layer, the second SCH layer, the photoactive layer, the first SCH layer and a portion of the InP substrate to define a passive waveguide region, the passive waveguide region is exposed on the first cladding layer. Forming an insulating mask film so as to etch and etching a portion of the first cladding layer, the second SCH layer, the photoactive layer, the first SCH layer, and the InP substrate using the insulating mask as a mask; The mask may be removed between forming the second clad layer and forming the third clad layer.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and the like of the elements in the drawings are exaggerated to emphasize a more clear description, and the elements denoted by the same reference numerals in the drawings means the same elements. In addition, where a layer is described as being "on" another layer or semiconductor substrate, a layer may exist in direct contact with the other layer or semiconductor substrate, or a third layer therebetween. Can be done.

Figure 3 is a cross-sectional view of a semiconductor laser according to the present invention, Figure 4 is a graph showing the refractive index according to the growth direction in the passive waveguide of the semiconductor laser according to the present invention. 5A to 5D are cross-sectional views of respective processes for explaining a method of manufacturing a semiconductor laser according to the present invention, and FIG. 6 is a graph showing an optical field distribution constrained by a passive waveguide according to the present invention.

As shown in FIG. 3, the semiconductor laser 100 according to the present invention includes a substrate 110, an active waveguide 100a and a passive waveguide 100b formed on the substrate 110. In this case, the active waveguide 100a and the passive waveguide 100b are disposed to abut each other in a horizontal state, and the cladding layers 130, 155, and 160 are disposed on the active waveguide 100a and the passive waveguide 100b. The substrate 110 may be an n-type InP substrate.

Here, the active waveguide 100a includes a first SCH layer 115, a photoactive layer 120, and a second SCH layer 125. In this case, the first SCH layer 115, the photoactive layer 120, and the second SCH layer 125 may all be InGaAsP layers, and the first and second SCH layers 115 and 125 may have a bandgap compared to the photoactive layer 120. It is preferred that this large material is used.

The passive waveguide 100b is disposed on one side of the active waveguide 100a and includes a first SCH layer 140, a core layer 145, and a second SCH layer 150. The first SCH layer 140, the core layer 145, and the second SCH layer 150 for the passive waveguide 100b may all be InGaAsP, and the first and second SCH layers 140 and 150 may be the core layer 145. The composition of InGaAsP may be different from that of the core layer 145 so as to have a relatively large band gap and a relatively small refractive index.

4 is a graph showing the refractive index of the passive waveguide portion in the semiconductor laser device of the present invention. The refractive index increases from the substrate 110 to the core layer 145 and then decreases toward the second clad layer 155. . That is, the refractive index of the core layer 145 is the highest, and the refractive index gradually decreases toward the upper and lower portions thereof.

Meanwhile, a first cladding layer 130, for example, a p-type InP layer, is formed on the active waveguide 100a, and a second cladding layer 155, eg, impurities, is formed on the passive waveguide 100b. An undoped InP layer or a semi-insulated InP layer is formed. In addition, the third cladding layer 160 is covered on the first and second cladding layers 130 and 155. The third clad layer 160 may be a p-type InP layer.

The semiconductor laser device having such a structure can increase the optical coupling coefficient between the active waveguide and the passive waveguide by forming the SCH layers 140 and 150 having a larger band gap and lower refractive index than the core layer above and below the core layer of the passive waveguide. have. As a result, the overall optical properties are improved.

A method of manufacturing the semiconductor laser 100 will be described with reference to FIGS. 5A to 5D.

First, as shown in FIG. 5A, the first SCH layer 115, the photoactive layer 120, and the second SCH layer for an active waveguide are formed on an n-type InP substrate 110 having an active waveguide region and a passive waveguide region defined therein. The 125 is sequentially stacked. As the photoactive layer 120 for the active waveguide, for example, InGaAsP (u-InGaAsP) or InGaAsP / In (Ga) (As) P multi quantum well (MQW) without impurity doping may be used. As the first and second SCH layers 115 and 125, an InGaAsP layer having a band gap larger than that of the photoactive layer 120 may be used. The first clad layer 130 is formed on the second SCH layer 125. As the first cladding layer 130, a p-type InP layer may be used, and the first cladding layer 130 is first crystal-grown by MOCVD.

As shown in FIG. 5B, a mask layer 135 is formed on the first clad layer 130 to expose the passive waveguide region. For example, an insulating film such as a silicon oxide film or a silicon nitride film may be used as the mask layer 135. By using the mask layer 135, the exposed clad layer 130, the second SCH layer 125, the photoactive layer 120, the first SCH layer 115, and predetermined portions of the substrate 110 are etched. The passive waveguide region A is defined. In this case, the etching amount of the substrate 110 may vary fluidly according to the structure of the photoactive layer 120 of the active waveguide.

As shown in FIG. 5C, the first SCH layer 140, the core layer 145, and the second SCH layer 150 for the passive waveguide are sequentially grown on the passive waveguide region A. FIG. Thereafter, the second clad layer 155 is secondarily grown on the second SCH layer 150. In this case, the first SCH layer 140, the core layer 145, and the second SCH layer 150 for the passive waveguide may use an InGaAsP layer that is not doped with impurities, and the composition may be different as described above. Can be. In addition, the second clad layer 155 may be an InP layer not doped with impurities.

Next, as shown in FIG. 5D, the mask layer 135 is removed in a known manner, and then a third cladding layer 160 made of p-type InP is formed on the resultant layer by tertiary crystal growth, thereby forming a semiconductor laser device. Complete (see FIG. 3).

6 is a graph showing an optical field distribution confined to a passive waveguide according to the present invention. The dotted line in the graph is the distribution of the optical field according to the prior art, and the solid line represents the optical field distribution according to the present invention. In addition, the graph shows the optical field based on the center of the passive waveguide by measuring the optical coupling coefficient of the passive waveguide. Looking at the graph, compared to the prior art, the distribution of the optical field according to this embodiment is more widely distributed, thereby constraining a greater amount of light. Thus, the optical coupling efficiency is improved.

 As described in detail above, according to the present invention, in the passive waveguide structure, an SCH layer having a composition different from that of the core layer is interposed above and below the core layer. Accordingly, much higher optical coupling efficiency can be obtained without degrading the optical characteristics.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. .

Claims (7)

Board; An active waveguide formed in a predetermined portion on the substrate; A passive waveguide formed on one side of the active waveguide to be in contact with the active waveguide; And A cladding layer formed on the active waveguide and the passive waveguide, The passive waveguide, A first separated confinement heterostructure (SCH) layer formed on the substrate, A core layer formed on the first SCH layer and having a composition different from that of the first SCH layer; And And a second SCH layer formed on the core layer. The semiconductor laser device of claim 1, wherein the first and second SCH layers have a relatively large bandgap and a relatively low refractive index than the core layer. The semiconductor laser device of claim 1, wherein the first and second SCH layers and the core layer are formed of an InGaAsP material, and have different composition ratios. The method of claim 1, wherein the active waveguide, A first SCH layer formed on the substrate; A photoactive layer formed on the first SCH layer; And And a second SCH layer formed on the photoactive layer. The method of claim 1, wherein the cladding layer, A first cladding layer formed on the active waveguide; A second clad layer formed on the passive waveguide; And a third cladding layer formed on the first and second cladding layers. Sequentially stacking a first SCH layer, a photoactive layer, a second SCH layer and a first clad layer for an active waveguide on a substrate; Etching a portion of the first clad layer, the second SCH layer, the photoactive layer, the first SCH layer, and the InP substrate to define a passive waveguide region; Forming a first SCH layer, a core layer, a second SCH layer, and a second clad layer for the passive waveguide on the passive waveguide region of the substrate; And Forming a third clad layer on the first and second clad layers, Wherein the first and second SCH layers for the passive waveguide have a relatively high bandgap and a low refractive index compared to the core layer. The method of claim 6, wherein the etching of the first cladding layer, the second SCH layer, the photoactive layer, the first SCH layer, and a portion of the InP substrate to define a passive waveguide region includes: Forming an insulating mask layer on the first clad layer to expose a passive waveguide region; And Etching the first cladding layer, the second SCH layer, the photoactive layer, the first SCH layer, and a portion of the InP substrate by using the insulating mask as a mask, And the insulating mask is removed between the forming of the second cladding layer and the forming of the third cladding layer.

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