KR101118844B1 - Semiconductor laser diode and fabricating method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser diode and a method of manufacturing the same, wherein a multilayered film structure in which an insulating layer and an absorbing layer are repeatedly stacked on a side surface of a ridge structure and a p-clad layer is provided.

According to the present invention, the laser light generated in the active layer can be more efficiently constrained in the ridge structure to increase the Far Field Horizontal (FFH) and thus the Far Field Vertical (FFV) / Far Field Horizontal (FFH). By reducing the ratio, it is possible to generate more circular beams.

In addition, since the absorbing layer is located closer to the active layer where the laser light is generated, it is possible to more effectively suppress the generation of the high-dimensional mode in the lateral direction, thereby increasing the kink level under high power.

Kink, FFH, FFV, Leakage Current, Laser, Diode, Ridge

Description

Semiconductor laser diode and manufacturing method thereof

1 is a cross-sectional view of a conventional ridge wave guide type nitride semiconductor laser diode.

2 is a cross-sectional view of a ridge wave guide type nitride semiconductor laser diode including a Si absorption layer.

3 is a cross-sectional view showing an embodiment of a semiconductor laser diode of the present invention.

4 is a cross-sectional view comparing the state of the conventional insulating film-absorbing layer structure with the multilayer film structure of the present invention.

5 is a graph showing a state diagram of Si and Au.

6 is a cross-sectional view showing another embodiment of the semiconductor laser diode of the present invention.

7 is a sectional view showing yet another embodiment of a semiconductor laser diode of the present invention.

8A to 8E are sectional views showing an embodiment of the method of manufacturing a semiconductor laser diode of the present invention.

Explanation of symbols on the main parts of the drawings

100: n-clad layer 110: active layer

120: p-clad layer 130: p- contact layer

140: multilayer film structure 143: insulating layer

146: absorption layer 150: p-electrode

The present invention relates to a light emitting device, and more particularly, to a semiconductor laser diode and a method of manufacturing the same.

Recently, research and development of an optical storage device using a semiconductor laser diode as a light source have been widely progressed in accordance with the pursuit of higher density of the optical storage device.

In particular, GaN-based semiconductor laser diode is a direct transition method with a high probability of laser oscillation, and has a wide energy band gap to provide a short wavelength oscillation wavelength from the ultraviolet region to the green region. Is attracting attention.

The semiconductor laser diode used as the light source of the optical storage device must satisfy the single mode and high power characteristics. To this end, a ridge wave guide is provided to limit the injected current, thereby lowering the threshold current and gaining only the single mode. To have.

1 is a cross-sectional view of a conventional ridge wave guide type nitride semiconductor laser diode.

As shown therein, the n-GaN layer 11, the n-contact layer 12, the n-clad layer 13, the active layer 14, and the p-clad layer 15 on the sapphire substrate 10. , the p-contact layers 16 are sequentially stacked,

A mesa is etched from the p-contact layer 16 to a portion of the n-contact layer 12 to expose a portion of the n-contact layer 12 from the top, and the p-clad layer 15 The upper region 15a and the p-contact layer 16 form a ridge structure 25.

In addition, an insulating film 17 is formed to surround the lower region 15b of the p-clad layer 15 and the side surface of the ridge structure 25. The insulating film 17 and the p-contact layer 16 are formed. The p-electrode 18 is formed on the n-electrode 19, and the n-electrode 19 is formed on the n-contact layer 12 exposed by the mesa etching.

The semiconductor laser diode formed as described above has an advantage that the threshold current value for laser oscillation is reduced because the resonance width is limited by limiting the current injected by the ridge structure 25.

In addition, the insulating layer 17 formed surrounding the lower region 15b of the p-clad layer 15 and the side surface of the ridge structure 25 is transparent to the laser light generated in the active layer 14 to be absorbed. It rarely happens, so the waveguide losses are small.

However, as the applications are expanded, high power devices are increasingly required, and since the FFH (Far Field Horizontal) value is large and no kink is generated in the region of the high power level, a laser beam having a circular shape is obtained. It is required. As such, when the laser beam having the circular shape is used, light can be used more efficiently in an optical storage device, a laser display, and the like.

In order to satisfy this, as shown in FIG. 2, a semiconductor laser diode having a Si absorption layer 32 interposed between the insulating film 31 and the p-electrode 34 has been proposed. That is, the absorption layer 32 made of Si is formed on the insulating film 31 formed on the upper portion of the p-clad layer 30 and the side surface of the ridge structure 45, and the p-contact layer is formed on the absorption layer 32. A p-electrode 34 in contact with 33 was formed.

The semiconductor laser diode configured as described above absorbs the high dimensional mode of the laser generated from the center of the active layer in the absorbing layer 32 to suppress the generation of the high dimensional mode, in which the Si of the absorbing layer 32 absorbs the laser light. It is to use the characteristics.

In addition, the laser light generated in the active layer is well confined in the ridge structure 45 with a large refractive index difference in the lateral direction to increase the FFH to generate a laser light having a circular shape. .

That is, in the 400 nm wavelength region, the refractive indices of the p-clad layer 30 made of GaN, the insulating film 31 made of SiO _2, and the absorbing layer 32 made of Si are GaN = 2.5, SiO ₂ = 1.47, and Si =. It can be seen that the difference in refractive index between GaN and Si and absorption of light occurs in Si, so that light can be confined within the ridge structure 45 as compared with only the insulating film 31 made of SiO ₂ . do.

When the light is constrained well in the ridge structure 45, the FFH becomes large. In this case, the FFV (Far Field Vertical) / FFH (Far Field Horizontal) ratio is reduced to generate a laser beam having a circular shape.

However, as the speed competition progresses, there is an urgent need for devices that are closer to circular beams and do not generate kinks even at high power.

Accordingly, an object of the present invention is to form a multi-layered film structure in which an insulating layer and an absorbing layer are repeatedly stacked on the side of the ridge structure and the p-clad layer, thereby more effectively suppressing the laser light in the high-dimensional mode generated in the active layer and kink. The present invention provides a semiconductor laser diode and a method of manufacturing the same, which raise a level and constrain light generated in an active layer within a ridge structure to generate a more circular beam.

In an embodiment of the semiconductor laser diode of the present invention, an active layer, a p-clad layer, and a p-contact layer are stacked on an n-clad layer, and the p-contact layer and a part of the p-clad layer are etched. A laminate structure forming a ridge structure, a multilayer film structure formed by repeatedly stacking an insulating layer and an absorbing layer on side surfaces of the p-clad layer and the ridge structure, and p formed on the multilayer film structure and the p-contact layer -Characterized in that it comprises an electrode.

Another embodiment of the semiconductor laser diode of the present invention is an n-contact layer formed under the n-clad layer of the laminated structure, a portion of which is mesa-etched and exposed from the top, and the n-contact layer And a n-electrode formed on the buffer layer formed below, the substrate formed under the buffer layer, and the n-contact layer exposed through the mesa etching.

Another embodiment of the semiconductor laser diode of the present invention further comprises a buffer layer formed under the n-clad layer of the stacked structure, a substrate formed under the buffer layer, and an n-electrode formed under the substrate. do.

According to an embodiment of the method of manufacturing a semiconductor laser diode of the present invention, the p-contact layer is formed by sequentially stacking an n-contact layer, an n-clad layer, an active layer, a p-clad layer, and a p-contact layer on a substrate. Mesa etching a portion of the n-contact layer, etching a portion of the p-contact layer and the p-clad layer to form a ridge structure, and the p-clad layer Repeatedly forming an insulating layer and a protective layer on side surfaces of the ridge structure to form a multilayer structure, forming a p-electrode on the multilayer structure and the p-contact layer, and n-exposed by being exposed to the mesa. Forming an n-electrode on the contact layer.

Hereinafter, the semiconductor laser diode of the present invention and a manufacturing method thereof will be described in detail with reference to FIGS. 3 to 8. 3 is a cross-sectional view showing an embodiment of a semiconductor laser diode of the present invention.

As shown therein, the active layer 110, the p-clad layer 120, and the p-contact layer 130 are stacked on the n-clad layer 100, and the p-contact layer 130 and the A portion of the p-clad layer 120 is etched to form a ridge structure 135.

On the side of the p-clad layer 120 and the ridge structure 135, a multilayer film structure 140 in which an insulating layer 143 and an absorbing layer 146 are repeatedly stacked is formed, and the multilayer film structure 140 The p-electrode 150 is formed on the top and the p-contact layer 130.

The n-clad layer 100, the active layer 110, the p-clad layer 120, and the p-contact layer 130 may be formed of a GaN-based group III-V nitride compound semiconductor, but the p-contact The layer 130 is formed of GaN, and the n-clad layer 100 and the p-clad layer 120 are preferably formed of AlGaN.

The active layer 110 may be a material capable of lasing, but it is preferable to use a material layer capable of obtaining a laser having a low threshold current value and stable lateral mode characteristics.

A portion of the p-contact layer 130 and the p-clad layer 120 is etched to have a ridge structure 135 protruding in a direction perpendicular to the active layer 110 in a central region. The width of 135 is preferably designed on the order of 1 to 2 μm for single mode and high power operation.

On the side of the p-clad layer 120 and the ridge structure 135, a multilayered film structure 140 in which an insulating layer 143 and an absorbing layer 146 are repeatedly stacked is formed, wherein the insulating layer 143 is formed. Silver SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , SiN _x It is preferably made of any one material selected from among, and the absorption layer 146 is preferably made of Si.

The multilayer film structure 140 is formed to have a thickness of about 1000 to about 2000 mm 3, which corresponds to the thickness of the insulating film-absorption layer structure in FIG. 2. In other words, in order to take advantage of the existing design, the existing insulating film-absorption layer structure is changed into a multilayer film structure in which the insulating film and the absorbing layer are repeatedly stacked.

In the multilayer structure 140 of the present invention, since the insulating layer 143 and the absorbing layer 146 are repeatedly stacked, the interface in which the laser light generated in the active layer 110 is reflected is compared with the existing insulating layer-absorption layer structure. This more presence allows the laser light to be confined within the ridge structure 135 more efficiently.

When the laser light generated by the active layer 110 is more confined within the ridge structure 135, the driving current is reduced, and when the driving current is reduced, less heat is generated to improve the reliability of the device.

In addition, when the multilayer film structure 140 is formed by repeatedly stacking the insulating layer 143 and the absorbing layer 146, the absorbing layer 146 has an active layer in which the laser light is generated as compared with the insulating film-absorbing layer structure in FIG. 2 ( It is located closer to 110, it is possible to more effectively suppress the generation of high-dimensional mode in the lateral direction.

Ie, the old insulation film as shown in Fig. 4 as a distance from the active layer from the Si absorption layer when the absorbent structure from T _1, and in the case of multi-layer film structure of the present invention, the distance from the active layer from the Si absorption layer T ₂ In this case, T ₂ <T ₁ .

As described above, according to the multilayer structure of the present invention, the Si absorption layer 146 for absorbing the laser light in the high dimensional mode generated in the active layer 110 is located closer to the active layer 110 to more effectively suppress the high dimensional mode generation. Thus, it is possible to increase the kink level under high power.

It is preferable to further form a protective layer made of an insulating material on the multilayer film structure 140 in which the insulating layer 143 and the absorbing layer 146 are repeatedly stacked.

The reason is that when the absorbing layer 146 made of Si is repeatedly laminated with the insulating layer 143 and the absorbing layer 146 to become the uppermost layer of the multilayer film structure 140, the p-electrode whose Si is mainly composed of Au In this case, the Si-absorbing layer 146 and the p-electrode 150 composed of Au are intermixed during the die bonding process and the high temperature operation. .

That is, referring to the state diagrams of Au and Si in FIG. 5, when Au and Si are separately placed, the melting point of Au is 1064 ° C., and the melting point of Si is 1414 ° C., but the two materials are in contact with each other. The eutectic reaction occurs at temperatures above 363 ° C and is present in the liquid phase.

Therefore, during the process performed at a temperature of 363 ° C. or more, Si of the absorbing layer 146 and Au of the p-electrode 150 are mixed to reduce high output-high temperature reliability and yield.

In addition, when the absorbing layer 146 made of Si becomes the uppermost layer of the multilayered structure 140, the Si absorbing layer 146 is exposed to the atmosphere before the p-electrode 150 is deposited. According to the degree, the Si absorbing layer 146 is reduced and changed in various shapes and thicknesses.

Therefore, a protective layer made of an insulating material is formed between the multilayer film structure 140 and the p-electrode 150. The protective layer is SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , SiN _x , It is preferably made of any one material selected from HfO, TiO ₂ to have a thickness of about 100 ~ 1000 Å.

Here, since the protective layer is deposited together with the insulating layer 143 and the absorbing layer 146, the absorbing layer 146 made of Si may be oxidized while being exposed to the air, thereby preventing the absorbing layer 146 from being reduced and deformed. Therefore, the absorption layer 146 can be sufficiently controlled.

In addition, since the protective layer is made of an insulating material and is formed between the absorbing layer 146 and the p-electrode 150 to serve as a diffusion barrier, the thermal stability of the absorbing layer 146 may be improved. give.

In addition, when a high temperature process such as a die bonding process is performed in a subsequent process, the phenomenon in which the metal of the Si absorption layer 146 and the p-electrode 150 is easily mixed can be prevented, so that the reliability of the device at high power and high temperature operation can be prevented. It will be possible to improve.

In addition, the protective layer may also serve as an insulating layer to prevent leakage current generated through the side of the ridge structure 135 and the p-clad layer 120 to improve electrical characteristics of the device. Can be.

A p-electrode 150 is formed on the upper portion of the multilayer structure 140 and the p-contact layer 130, and the p-electrode 150 is formed of gold (Au), platinum (Pt), and titanium (Ti). It may be made of any one single layer or two or more multilayers selected from aluminum (Al).

As shown in FIG. 6, the semiconductor laser diode of the present invention is formed under the n-clad layer 200, and a portion of the n-contact layer 210 in which mesa is etched, and the n-contact. A buffer layer 220 formed under the layer 210, a substrate 230 formed under the buffer layer 220, and an n-electrode 240 formed on the n-contact layer 210 exposed through the mesa etching process. It can be made to include more.

As shown in FIG. 7, the buffer layer 270, the substrate 280, and the n-electrode 290 which are sequentially formed below the n-clad layer 260 may be further included.

8A to 8E are cross-sectional views showing an embodiment of a method of manufacturing a semiconductor laser diode of the present invention. As shown in the figure, first, the buffer layer 310, the n-contact layer 320, the n-cladding layer 330, the active layer 340, the p-cladding layer 350, and the p-contact on the substrate 300. Layers 360 are sequentially stacked (FIG. 8A).

Next, mesa etching from the p-contact layer 360 to a portion of the n-contact layer 320 exposes a portion of the n-contact layer 320 from the top (FIG. 8B).

Subsequently, after forming a ridge pattern on the p-contact layer 360 with a PR mask, a portion of the p-contact layer 360 and the p-cladding layer 350 are etched to ridge structure 450. To form (FIG. 8C).

Thereafter, a multi-layered film structure 370 in which an insulating layer and an absorbing layer are repeatedly stacked on the side surfaces of the p-clad layer 350 and the ridge structure 450 is formed (FIG. 8D).

The insulating layer of the multilayer structure 370 is SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , SiN _x It is formed of any one material selected from among, and the absorption layer is formed of Si. The multi-layered film structure 370 is formed to have a thickness of about 1000 ~ 2000 Å.

Here, a protective layer made of an insulating material may be further formed on the multilayer film structure 370. In this case, the protective layer is SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , SiN _x , HfO, TiO ₂ It is preferably made of any one material selected from among, and formed to have a thickness of about 100 ~ 1000 Å.

Next, a p-electrode 380 is formed on the multilayered film structure 370 and the p-contact layer 350, and the n-electrode 390 is disposed on the mesa-etched and exposed n-contact layer 320. ) Is formed (FIG. 8E).

On the other hand, while the present invention has been shown and described with respect to specific preferred embodiments, various modifications and variations of the present invention without departing from the spirit or field of the invention provided by the claims below It will be readily apparent to one of ordinary skill in the art that it can be used.

According to the present invention, by forming a multilayer structure in which an insulating layer and an absorbing layer are repeatedly stacked on the side of the ridge structure and the p-clad layer, laser light generated in the active layer is reflected as compared with the conventional insulating layer-absorbing layer structure. The more interfaces exist, the more efficiently the laser light can be confined within the ridge structure. In this case, the FFH can be increased, thus reducing the FFV / FFH ratio to provide more circular beams. It can happen.

In addition, when the laser light generated in the active layer is more confined within the ridge structure, the driving current is reduced, and when the driving current is reduced, less heat is generated to improve the reliability of the device.

In addition, compared to the conventional insulating film-absorption layer structure, the absorbing layer is located closer to the active layer where the laser light is generated, thereby more effectively suppressing the generation of the high-dimensional mode in the lateral direction, thereby increasing the kink level under high power. Will be.

Claims (13)

delete a stacked structure in which an active layer, a p-clad layer, and a p-contact layer are stacked on an n-clad layer, and a portion of the p-contact layer and the p-clad layer are etched to form a ridge structure; A multilayer film structure in which an insulating layer and an absorbing layer are repeatedly stacked on side surfaces of the p-clad layer and the ridge structure; A p-electrode formed on the multilayer structure and the p-contact layer; An n-contact layer formed under the n-clad layer, a portion of which is mesa-etched and exposed from the top; A buffer layer formed under the n-contact layer; A substrate formed under the buffer layer; And And a n-electrode formed on the mesa-etched and exposed n-contact layer. a stacked structure in which an active layer, a p-clad layer, and a p-contact layer are stacked on an n-clad layer, and a portion of the p-contact layer and the p-clad layer are etched to form a ridge structure; A multilayer film structure in which an insulating layer and an absorbing layer are repeatedly stacked on side surfaces of the p-clad layer and the ridge structure; A p-electrode formed on the multilayer structure and the p-contact layer; A buffer layer formed under the n-clad layer; A substrate formed under the buffer layer; And And a n-electrode formed under the substrate. The semiconductor laser diode according to claim 2 or 3, wherein the insulating layer is made of any one material selected from SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , and SiN _x . The semiconductor laser diode according to claim 2 or 3, wherein the absorption layer is made of silicon (Si). The semiconductor laser diode according to claim 2 or 3, wherein the multilayer film structure has a thickness of 1000 to 2000 GPa. 4. The semiconductor laser diode according to claim 2 or 3, further comprising a protective layer made of an insulating material between the multilayer film structure and the p-electrode. The method of claim 7, wherein the protective layer is SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , SiN _x , A semiconductor laser diode comprising any one selected from HfO and TiO ₂ . The semiconductor laser diode according to claim 7, wherein the protective layer has a thickness of 100 to 1000 kHz. Sequentially depositing an n-contact layer, an n-clad layer, an active layer, a p-clad layer, and a p-contact layer on the substrate, and then mesa etching the p-contact layer to a portion of the n-contact layer; Etching a portion of the p-contact layer and p-clad layer to form a ridge structure; Repeatedly forming an insulating layer and an absorbing layer on side surfaces of the p-clad layer and the ridge structure to form a multilayer structure; And Forming a p-electrode on the multilayer structure and the p-contact layer, and forming an n-electrode on the mesa-etched and exposed n-contact layer. The semiconductor device of claim 10, further comprising forming a protective layer of an insulating material on the multilayer film structure between the forming of the multilayer film structure and the forming of the p-electrode and the n-electrode. Method of manufacturing a laser diode. The method of claim 10, wherein the insulating layer is formed by depositing any one selected from SiO ₂ , Al ₂ O ₃ , AlN, ZrO ₂ , and SiN _x . The method of claim 10, wherein the absorption layer is formed by depositing silicon (Si).

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