KR101161875B1 - Method for fabricating semiconductor laser diode - Google Patents

Abstract

The present invention relates to a method for manufacturing a semiconductor laser diode, by removing the interface having a sudden difference in hardness by interposing a composition change layer inside the epi layer of the semiconductor laser diode, thereby suppressing the warpage of grains generated on the cleaved surface, thereby improving the quality of the cleaved surface. By improving the efficiency and the performance of the device can be improved.

Laser, diode, hardness, deflection, composition, change

Description

Method for fabricating semiconductor laser diode

1A to 1D are cross-sectional views illustrating a manufacturing process of a nitride semiconductor laser diode according to the prior art.

2A to 2H are cross-sectional views illustrating a manufacturing process of a semiconductor laser diode according to a first embodiment of the present invention.

Figure 3 is a schematic cross-sectional view for explaining in detail the n-AlGaN composition change layer interposed in accordance with the first embodiment of the present invention

4 is a cross-sectional view illustrating a manufacturing process of a semiconductor laser diode according to a second embodiment of the present invention.

5 is a cross-sectional view illustrating a GaN layer formed between an n-InGaN composition change layer and an n-AlGaN composition change layer according to the second embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: sapphire substrate 110: gallium nitride thin film

110a and 110b: Seed layer 130: Gallium nitride layer

200: semi-substrate 210: n-GaN electrode layer

215: InGaN cracking prevention layer 220: n-AlGaN composition change layer

221: n-InGaN composition change layer 222: n-GaN layer

223 n-AlGaN composition change layer 240 n-GaN wave guide layer

250: InGaN quantum well active layer 260: p-AlGaN electron flood prevention layer

270: p-GaN wave guide layer 280: p-AlGaN cladding layer

290: p-GaN electrode layer 300: ridge structure

310 oxide film 320 p-electrode

330 n-electrode

The present invention relates to a method for manufacturing a semiconductor laser diode, and more particularly, to suppress the warpage of crystals generated on the cleaved surface by removing an interface having a sudden hardness difference by interposing a composition change layer inside the epi layer of the semiconductor laser diode. The present invention relates to a method for manufacturing a semiconductor laser diode that can improve the quality of the cleaved surface to improve the performance and yield of the device.

In general, a blue laser diode is a device based on a nitride semiconductor, and has been developed for the purpose of a large capacity data storage device and a light source for a high resolution laser printer.

This blue laser diode has made significant technological advancements through active research and development activities over the past few years, but it is still difficult to ensure reliability due to its higher resistance than other materials.

To date, there are many companies that have not introduced them to mass production because there are many solutions regarding reliability and yield.

1A to 1D are cross-sectional views illustrating a manufacturing process of a nitride semiconductor laser diode according to the related art, and include a plurality of seed layers 11a and 11b spaced apart from each other by a gallium nitride thin film on the sapphire substrate 10. To form (FIG. 1A).

Next, a gallium nitride layer 13 is formed on the seed layers 11a and 11b (FIG. 1B).

Here, the gallium nitride layer 13 is formed by coalescing while growing laterally on the seed layers (11a, 11b).

The sapphire substrate 10, the seed layers 11a and 11b, and the gallium nitride layer 13 serve as quasi-substrates 20 for manufacturing a semiconductor laser diode.

A void 12 is formed between the seed layers 11a and 11b of the semi-substrate 20, and the gallium nitride layer on the void 12 may be defined as a wing region. For example, the dislocation density of gallium nitride in the wing region is relatively lower than that of gallium nitride in the seed layer.

Subsequently, an n-GaN electrode layer 21, an n-InGaN cracking prevention layer 22, an n-AlGaN cladding layer 23, and an n-GaN wave guide layer on the gallium nitride layer 13 of the quasi-substrate 20. 24), the InGaN quantum well active layer 25, the p-AlGaN electron flood prevention layer 26, the p-GaN wave guide layer 27, the p-AlGaN cladding layer 28 and the p-GaN electrode layer 29 in sequence Lamination (FIG. 1C).

Then, except for the central region, the p-GaN electrode layer 29 is etched to a part of the p-AlGaN cladding layer 28 to form a ridge structure 30, and the p-AlGaN cladding layer 28 Mesa-etched up to a portion of the n-GaN electrode layer 21, and then exposing a portion of the upper portion of the ridge structure 30 and the mesa-etched n-GaN electrode layer 21, and the p-AlGaN cladding layer 28 An oxide film 35 is formed on the upper side, the mesa-etched sidewall, the ridge structure 30 sidewall, and the n-GaN electrode layer 21, and the p-electrode 41 is formed to surround the exposed ridge structure 30. In addition, an n-electrode 42 surrounding the exposed n-GaN electrode layer 21 is formed.

Here, the ridge structure 30 is a core region of the semiconductor laser diode in which laser oscillation is generated by effectively generating light by concentrating the applied current in a small area, and is formed in the wing region of the quasi-substrate having a low dislocation density.

The ridge structure directly affects the main laser diode characteristics such as oscillation start current, quantum efficiency, and mode characteristics, and the width of the ridge must be miniaturized for stable single mode and high power operation.

In addition, a SiC substrate and a GaN substrate other than the sapphire substrate may be used, and the dielectric layer may be used for passivation and transverse mode control for removing leakage current.

In addition, the various layers constituting the semiconductor laser diode have different lattice constants, which inevitably accumulates compressive strain and stretch strain in the semiconductor laser diode, thereby causing cracking. Is high.

The n-cracking prevention layer is used for the purpose of suppressing cracking, which mainly uses InGaN material to balance the compressive strain and the stretch strain.

On the other hand, the cleaved surface forming the mirror surface of the semiconductor laser diode is formed by scribing.

The loss caused by the mirror depends on the quality and angle of the cleaved surface, which directly affects the characteristics of the main laser diode such as starting current and quantum efficiency.

The cleaved surface of the laser diode is formed by the nitride semiconductor cracking along the <1-100> plane through a scribing process.

In this case, surface undulation occurs on the surface of the cleaved surface of the seed region of the semi-substrate, while the floating wing region has a high-quality surface without grain.

However, in the conventional semiconductor laser diode structure, the cleaved surface from the interface between the InGaN n-cracking prevention layer and the AlGaN n-clad layer, which has the largest hardness, to the ridge area where the laser oscillation occurs during scribing, Roughness causes a problem of degrading the characteristics of the device.

In order to solve the problems as described above, by removing the interface having a sudden hardness difference by interposing a composition change layer inside the epi layer of the semiconductor laser diode, the quality of the cleaved surface is suppressed by suppressing the warpage of the grain generated on the cleaved surface. It is an object of the present invention to provide a method for manufacturing a semiconductor laser diode that can improve the performance and yield of the device by improving the efficiency.

According to a preferred aspect of the present invention, there is provided a method of forming a gallium nitride thin film on a substrate;

Selectively etching the gallium nitride thin film to form a plurality of seed layers spaced apart from each other;

Forming a gallium nitride layer on the seed layer;

N-GaN electrode layer, n-AlGaN composition change layer, n-AlGaN cladding layer, n-GaN wave guide layer, InGaN quantum well active layer, p-AlGaN electron flood prevention layer, p-GaN wave guide layer on the gallium nitride layer, sequentially stacking the p-AlGaN cladding layer and the p-GaN electrode layer;

Etching away from the p-GaN electrode layer to a portion of the p-AlGaN clad layer except for a central region to form a ridge structure;

Mesa-etching a portion of the p-AlGaN cladding layer from the n-AlGaN composition change layer to expose the n-GaN electrode layer;

Exposing an upper portion of the ridge structure and a portion of the n-GaN electrode layer, and forming an oxide film on the p-AlGaN cladding layer, a mesa etched sidewall, a ridge structure sidewall, and an upper portion of the n-GaN electrode layer;

A method of manufacturing a semiconductor laser diode is provided, which includes forming a p-electrode surrounding the exposed ridge structure and forming an n-electrode surrounding the exposed n-GaN electrode layer.

Another preferred aspect for achieving the above object of the present invention is the step of forming a gallium nitride thin film on the substrate;

Selectively etching the gallium nitride thin film to form a plurality of seed layers spaced apart from each other;

Forming a gallium nitride layer on the seed layer;

N-GaN electrode layer, InGaN cracking prevention layer, In and Al composition change layer, n-AlGaN cladding layer, n-GaN wave guide layer, InGaN quantum well active layer, p-AlGaN electron flood prevention layer, p-GaN on the gallium nitride layer Sequentially stacking the wave guide layer, the p-AlGaN cladding layer and the p-GaN electrode layer;

Etching away from the p-GaN electrode layer to a portion of the p-AlGaN clad layer except for a central region to form a ridge structure;

Mesa-etching a portion from the p-AlGaN cladding layer to an In and Al composition changing layer to expose the n-GaN electrode layer;

Exposing an upper portion of the ridge structure and a portion of the n-GaN electrode layer, and forming an oxide film on the p-AlGaN cladding layer, a mesa etched sidewall, a ridge structure sidewall, and an upper portion of the n-GaN electrode layer;

A method of manufacturing a semiconductor laser diode is provided, which includes forming a p-electrode surrounding the exposed ridge structure and forming an n-electrode surrounding the exposed n-GaN electrode layer.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

2A to 2H are cross-sectional views illustrating a manufacturing process of a semiconductor laser diode according to a first exemplary embodiment of the present invention, in which a gallium nitride thin film 110 is formed on an sapphire substrate 100 (FIG. 2A).

Subsequently, the gallium nitride thin film 110 is selectively etched to form a plurality of seed layers 110a and 110b spaced apart from each other (FIG. 2B).

Thereafter, a gallium nitride layer 130 is formed on the seed layers 110a and 110b.

Here, the gallium nitride layer 130 is grown on the seed layer (110a, 110b) while growing side by side are formed to coalesce each other.

The sapphire substrate 100, the seed layers 110a and 110b and the gallium nitride layer 130 serve as a quasi-substrate 200 for manufacturing a semiconductor laser diode.

Next, the n-GaN electrode layer 210, the n-AlGaN composition change layer 220, the n-AlGaN cladding layer 230, and the n-GaN wave guide on the gallium nitride layer 130 of the quasi-substrate 200. The layer 240, the InGaN quantum well active layer 250, the p-AlGaN electron flood prevention layer 260, the p-GaN waveguide layer 270, the p-AlGaN cladding layer 280 and the p-GaN electrode layer 290. Laminating sequentially (FIG. 2D).

Subsequently, except for the central region, the ridge structure 300 is formed by etching from the p-GaN electrode layer 290 to a part of the p-AlGaN cladding layer 280 (FIG. 2E).

Subsequently, a part of the p-AlGaN cladding layer 280 is mesa-etched from the n-AlGaN composition change layer 220 to expose the n-GaN electrode layer 210 (FIG. 2F).

Next, an upper portion of the ridge structure 300 and a portion of the n-GaN electrode layer 210 are exposed, and an upper portion of the p-AlGaN cladding layer 280, a mesa etched sidewall, a sidewall of the ridge structure 300, and the n An oxide film 310 is formed over the GaN electrode layer 210 (FIG. 2G).

Finally, the p-electrode 320 is formed to surround the exposed ridge structure 300, and the n-electrode 330 is formed to surround the exposed n-GaN electrode layer 210 (FIG. 2H).

As described above, according to the present invention, an n-AlGaN composition change layer is interposed between an n-GaN electrode layer and an n-AlGaN cladding layer to remove an InGaN n-cracking prevention layer as in the prior art, thereby providing an interface with a sudden difference in hardness. By not forming, it is possible to suppress the warpage of the grains generated on the cleaved surface, thereby improving the quality of the cleaved surface, thereby improving the performance and yield of the device.

3 is a schematic cross-sectional view for explaining in detail the n-AlGaN composition change layer interposed in accordance with the first embodiment of the present invention, n-GaN electrode layer 210 and n-AlGaN cladding layer 230 An AlGaN composition change layer 220 is interposed.

The growth start Al composition of the n-AlGaN composition change layer 220 first grown on the n-GaN electrode layer 210 is 0% to 5%, and the n-AlGaN composition is in contact with the n-AlGaN cladding layer 230. The growth finish Al composition of the change layer 220 is 5% to 20%, it is preferable to change the composition so that the growth start Al composition is smaller than the growth finish Al composition.

That is, the Al composition of the n-AlGaN composition change layer 220 is changed so that the growth start region 220a of the n-AlGaN composition change layer 220 is smaller than the growth finish region 220b.

In addition, the thickness T1 of the n-AlGaN composition change layer 220 is preferably 0.01 to 1 μm.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of a semiconductor laser diode according to a second embodiment of the present invention. In the second embodiment, an InGaN cracking prevention layer 215 on the n-GaN electrode layer 210 in FIG. 2B, The In and Al composition changing layer 225 and the n-AlGaN cladding layer 230 are formed to form an In and Al composition changing layer 225 between the InGaN cracking prevention layer 215 and the n-AlGaN cladding layer 230. It is intervening.

That is, the In and Al composition change layer 225 approaches the InGaN cracking prevention layer 215 and the n-InGaN composition change layer 221 and the n-AlGaN cladding layer 230, which increase the composition of In, It can be comprised by the n-AlGaN composition change layer 223 which becomes high in composition.

At this time, in the region where the n-InGaN composition change layer is in contact with the n-AlGaN composition change layer, when the In or Al composition is '0', as shown in FIG. 5, the n-InGaN composition change layer 221 ) And an n-GaN layer 222 may be formed between the n-AlGaN composition change layer 223.

Therefore, by interposing the In and Al composition change layer 225 between the InGaN cracking prevention layer 215 and the n-AlGaN cladding layer 230, an interface with a sudden difference in hardness can be removed even in the second embodiment of the present invention. It is possible to suppress the warpage of the grains occurring on the cleaved surface, and, as a result, to improve the quality of the cleaved surface, thereby improving the performance and yield of the device.

The thickness (T2) of the In and Al composition change layer 225 is preferably 0.01 ~ 1㎛.

In the n-InGaN composition change layer 221 described above, the In composition of the n-InGaN composition change layer in which growth starts on the InGaN cracking prevention layer 215 is 2% to 20%, and the n-InGaN composition change in which growth is finished The In composition of the layer is 0% to 10%, and it is preferable to change the composition so that the growth start In composition is larger than the growth finish In composition.

The n-AlGaN composition change layer 223 has an Al composition of 0% to 10% of the n-AlGaN composition change layer at which growth begins, and an Al composition of 5% of the n-AlGaN composition change layer at which growth finishes. 30% and the growth start Al composition is preferably a layer whose composition is changed to be smaller than the growth finish Al composition.

As described above, the present invention removes the interface with the sudden hardness difference by interposing the composition change layer inside the epi layer of the semiconductor laser diode, thereby suppressing the warpage of the texture occurring on the cleaved surface and improving the quality of the cleaved surface. There is an effect to improve the performance and yield.

Although the invention has been described in detail only with respect to specific examples, it will be apparent to those skilled in the art that various modifications and variations are possible within the spirit of the invention, and such modifications and variations belong to the appended claims.

Claims (8)

Forming a gallium nitride thin film on the substrate; Selectively etching the gallium nitride thin film to form a plurality of seed layers spaced apart from each other; Forming a gallium nitride layer on the seed layer; N-GaN electrode layer, n-AlGaN composition change layer, n-AlGaN cladding layer, n-GaN wave guide layer, InGaN quantum well active layer, p-AlGaN electron flood prevention layer, p-GaN wave guide layer on the gallium nitride layer, sequentially stacking the p-AlGaN cladding layer and the p-GaN electrode layer; Etching a portion of the p-AlGaN clad layer from the p-GaN electrode layer to form a ridge structure; Mesa-etching a portion of the p-AlGaN cladding layer from the n-AlGaN composition change layer to expose the n-GaN electrode layer; Exposing an upper portion of the ridge structure and a portion of the n-GaN electrode layer, and forming an oxide film on the p-AlGaN cladding layer, a mesa etched sidewall, a ridge structure sidewall, and an upper portion of the n-GaN electrode layer; Forming a p-electrode surrounding the exposed ridge structure, and forming an n-electrode surrounding the exposed n-GaN electrode layer. The method of claim 1, The growth start Al composition of the n-AlGaN composition change layer first grown on the n-GaN electrode layer is The method of manufacturing a semiconductor laser diode, characterized in that less than the growth finish Al composition of the n-AlGaN composition change layer in contact with the n-AlGaN cladding layer. Forming a gallium nitride thin film on the substrate; Selectively etching the gallium nitride thin film to form a plurality of seed layers spaced apart from each other; Forming a gallium nitride layer on the seed layer; N-GaN electrode layer, InGaN cracking prevention layer, In and Al composition change layer, n-AlGaN cladding layer, n-GaN wave guide layer, InGaN quantum well active layer, p-AlGaN electron flood prevention layer, p-GaN on the gallium nitride layer Sequentially stacking the wave guide layer, the p-AlGaN cladding layer and the p-GaN electrode layer; Etching a portion of the p-AlGaN clad layer from the p-GaN electrode layer to form a ridge structure; Mesa-etching a portion from the p-AlGaN cladding layer to an In and Al composition changing layer to expose the n-GaN electrode layer; Exposing an upper portion of the ridge structure and a portion of the n-GaN electrode layer, and forming an oxide film on the p-AlGaN cladding layer, a mesa etched sidewall, a ridge structure sidewall, and an upper portion of the n-GaN electrode layer; Forming a p-electrode surrounding the exposed ridge structure, and forming an n-electrode surrounding the exposed n-GaN electrode layer. The method of claim 3, wherein The In and Al composition change layer, A method of manufacturing a semiconductor laser diode comprising an n-InGaN composition change layer in which the composition of In is increased when the InGaN cracking prevention layer is approached, and an n-AlGaN composition change layer in which the Al composition is increased when the n-AlGaN clad layer is approached. . The method of claim 4, wherein In the region where the n-InGaN composition change layer and the n-AlGaN composition change layer are in contact, The n-GaN layer is formed between the n-InGaN composition change layer and the n-AlGaN composition change layer. The method of claim 4, wherein The n-InGaN composition change layer, The In composition of the n-InGaN composition change layer in which growth starts above the InGaN cracking prevention layer is larger than the In composition of the n-InGaN composition change layer in which growth ends. The method of claim 4, wherein The n-AlGaN composition change layer, The Al composition of the n-AlGaN composition change layer at which growth begins is smaller than the Al composition of the n-AlGaN composition change layer at which growth occurs. The method of claim 3, wherein The thickness of the In and Al composition change layer is a manufacturing method of a semiconductor laser diode, characterized in that 0.01 ~ 1㎛.

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