JP2007227652A - Two-wavelength semiconductor light-emitting device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-wavelength semiconductor light-emitting device capable of improving the condensation characteristics of light beams having two wavelengths and preventing deterioration in the manufacturing process of an active layer in a light-emitting element at a long-wavelength side in the two-wavelength semiconductor light-emitting device in which n and p electrodes are provided on the same surface side, and to provide a method for manufacturing the two-wavelength semiconductor light-emitting device. <P>SOLUTION: Semiconductor lasers D1, D2 are integrated and formed as two light-emitting elements having different light-emitting wavelengths on a common substrate 1. A semiconductor laminate A is laminated on an n-type contact layer 21 in the semiconductor laser D1 while a semiconductor laminate B is laminated in the semiconductor laser D2. The semiconductor laminates A, B have different layer structures. Two n electrodes 11a, 11b corresponding to the semiconductor lasers D1, D2 are formed on the substrate 1 while sandwiching the semiconductor laminates A, B. Crystal growth is made from the semiconductor laminate A at a short-wavelength side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a two-wavelength semiconductor light-emitting device in which two light-emitting elements that emit light of different wavelengths are formed on the same substrate, and a method for manufacturing the same.

  In recent years, development of short-wavelength semiconductor lasers has been focused on for the purpose of application to high-density optical disk recording and the like. For the short wavelength semiconductor laser, a hexagonal compound semiconductor (hereinafter simply referred to as a nitride semiconductor) containing nitrogen such as GaN, AlGaN, InGaN, InGaAlN, GaPN, or the like is used.

  In addition, with the rapid increase in communication traffic due to the explosive spread of the Internet, optical communication technology that enables high-speed and large-capacity communication, high-speed transfer and large-capacity optical disks, and optical devices such as high-efficiency LED light-emitting elements The expectations of have increased greatly. For example, in order to support both rewritable CD and rewritable DVD systems, development of an element equipped with two different semiconductor lasers, a two-wavelength semiconductor laser compatible with multiplexed communication, and the like has become active.

  Therefore, as described in Patent Document 1, an n-GaN buffer layer is formed on a substrate, and each of the two wavelengths of light emitted on the n-GaN buffer layer is formed using the n-GaN buffer layer as a common semiconductor layer. There has been proposed a semiconductor light emitting device in which an n-type semiconductor layer, an active layer, a p-type semiconductor layer, and the like of an element are stacked and a p electrode and an n electrode of each light emitting element are opposed to each other with a substrate interposed therebetween.

In addition, in the semiconductor light emitting device described in Patent Document 1, a light emitting element that oscillates monolithically at two wavelengths is manufactured. A semiconductor layer made of hexagonal nitride formed with a plane parallel to the main surface and an inclined surface inclined from the main surface is formed on the main surface of the semiconductor substrate, respectively, on the plane and the inclined surface of the semiconductor layer. When the active layer is crystal-grown on it, active layers each containing In at different composition ratios are formed, and can oscillate at two wavelengths.
JP 2003-101156 A

  However, in the above conventional configuration, the p-electrode and n-electrode of each light-emitting element with two wavelengths are opposed to each other with the substrate interposed therebetween, so that each light-emitting element can be formed relatively close to each other. When the electrode and the n electrode are provided on the same surface side of the substrate, the n electrode needs to be provided on the n-GaN buffer layer, so that the n electrode is provided between the light emitting elements. Since the distance between the active layers of the two light emitting elements is increased and the distance between the light beams having two wavelengths is increased, there is a problem that the light condensing property is deteriorated.

  In addition, a method for manufacturing a light-emitting element that oscillates monolithically at two wavelengths is capable of simultaneously growing crystals of two-wavelength active layers and reduces the number of manufacturing steps, but is provided so as to sandwich the active layers. Since the light guide layer and the clad layer are monolithically formed of two light emitting elements, there is a problem that device characteristics are deteriorated. That is, since the refractive index of each semiconductor layer such as the light guide layer and the cladding layer depends on the wavelength of light, when the emission wavelength changes, the refractive index of each semiconductor layer with respect to the emitted light changes, and the light guide having the same composition. In the layer and the clad layer, the light confinement effect is different for each of the two light emitting elements, and a semiconductor light emitting device with good performance cannot be manufactured.

  Therefore, even if the number of manufacturing steps increases, it is only necessary to manufacture each of the two-wavelength light-emitting elements in separate steps. However, in a light-emitting element having an active layer composed of a nitride containing In, the active layer contains In. The higher the ratio, that is, the longer the wavelength of the light emitting device, there is a problem that when the active layer is exposed to a high temperature after crystal growth of the active layer, the formed active layer is easily broken.

  The present invention was devised to solve the above-described problem. Even in a two-wavelength semiconductor light emitting device in which an n-electrode and a p-electrode are provided on the same surface side, a two-wavelength light beam is condensed. An object of the present invention is to provide a two-wavelength semiconductor light emitting device and a method for manufacturing the same, which can improve the performance and prevent deterioration in the manufacturing process of the active layer in the light emitting element on the long wavelength side.

  To achieve the above object, according to the present invention, two stacked bodies that emit light of different wavelengths are formed on the same substrate, and n corresponding to the two stacked bodies are formed on the same surface side of the substrate. In the two-wavelength semiconductor light-emitting device in which an electrode and a p-electrode are respectively disposed, two n electrodes corresponding to the two stacked bodies are disposed on the substrate so as to sandwich the two stacked bodies. Is a two-wavelength semiconductor light emitting device.

  In the invention according to claim 2, two stacked bodies that emit light of different wavelengths are formed on the same substrate, and n electrodes and p electrodes corresponding to the two stacked bodies are provided on the same surface side of the substrate, respectively. In the method for manufacturing a two-wavelength semiconductor light-emitting device, wherein the active layer in the two stacked bodies is formed of a nitride layer containing In at a different ratio, the In composition ratio of the two stacked bodies is After crystal growth from the first stacked body including the lower active layer, the second stacked body including the active layer having the higher In composition ratio is grown, and then the first stacked body and the second stacked body are grown. A two-wavelength semiconductor light-emitting device manufacturing method characterized in that two n-electrodes are formed on the substrate so as to sandwich the substrate.

  The invention according to claim 3 is the method of manufacturing a two-wavelength semiconductor light emitting device according to claim 2, wherein the active layer of the second stacked body uses n-type GaN as a barrier layer.

  According to a fourth aspect of the present invention, only an InGaN layer is formed as a p-type semiconductor layer after crystal growth of the active layer of the second stacked body. A method for manufacturing a two-wavelength semiconductor light-emitting device according to claim 1.

  The invention according to claim 5 is characterized in that a Si-based film is formed on the substrate except for a region where the first stacked body is stacked before crystal growth of the first stacked body. It is a manufacturing method of the 2 wavelength semiconductor light-emitting device of any one of Claims 2-4.

  According to a sixth aspect of the present invention, a Si-based film is formed on the first laminate and the substrate except for a region where the second laminate is laminated before crystal growth of the second laminate. 6. The method for manufacturing a two-wavelength semiconductor light-emitting device according to claim 2, wherein the film is formed.

  According to the present invention, two stacked bodies that emit light of different wavelengths are formed on the same substrate, and n electrodes and p electrodes corresponding to the two stacked bodies are formed on the same surface side of the substrate. The two n-electrodes are not formed between the two stacked bodies, but are formed on the substrates on both sides of the two stacked bodies, so that the two stacked bodies can be brought close to each other and short-circuited. Since the active layer on the wavelength side and the active layer on the long wavelength side can be brought close to each other, the light condensing property can be improved.

  Also, in the manufacturing process, a laminate including an active layer composed of a nitride having a high In content ratio, that is, a laminate on the long wavelength side is epitaxially grown later than a laminate on the short wavelength side. Therefore, the time for which the active layer on the long wavelength side is exposed to a high temperature is shortened, and deterioration of the active layer on the long wavelength side can be prevented.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a two-wavelength semiconductor light emitting device according to the present invention.

  On the same substrate 1, semiconductor lasers D1 and D2 are integrated and formed as two light emitting elements having different emission wavelengths. Specifically, the n-type contact layer 21 is laminated on the growth substrate 20. As the growth substrate 20, a sapphire substrate, a GaN substrate, a SiC substrate, or the like is used. An n-type GaN layer or the like is used for the n-type contact layer 21 common to the semiconductor lasers D1 and D2.

  1 constitutes one chip. Actually, the semiconductor lasers D1 and D2 in FIG. 1 are set as one set, and this is repeated to cut each part of FIG. 1 by dicing or the like. One chip. Moreover, the arrow described in FIG. 1 shows the emission direction of the laser beam.

  In the semiconductor laser D1, a semiconductor stacked body A having a striped ridge portion is stacked on the n-type contact layer 21 of the substrate 1. In the semiconductor laser D2, a striped ridge is also formed on the n-type contact layer 21 of the substrate 1. The semiconductor stacked body B having a portion is stacked. The semiconductor laminate A and the semiconductor laminate B have different layer structures. An insulating film 8 (shaded portion) is formed so as to cover the side surface of the ridge portion of the semiconductor stacked body A and the side surface of the ridge portion of the semiconductor stacked body B. An insulating film 6 (shaded portion) is formed on a part of the n-type contact layer 21 and on each side surface of the semiconductor stacked bodies A and B. Note that regions with the same type of diagonal lines represent the same insulating film.

  Further, a p-electrode 9a is formed so as to cover the upper portion of the ridge portion of the semiconductor stacked body A and the insulating film 8, and similarly, a p-electrode 9b is formed so as to cover the upper portion of the ridge portion of the semiconductor stacked body B and the insulating film 8. Has been. Further, for wire bonding or the like, a p-side pad electrode 12a is formed on the p-electrode 9a of the semiconductor laser D1, and a p-side pad electrode 12c is formed on the p-electrode 9b of the semiconductor laser D2.

  The n electrodes 11a and 11b corresponding to the semiconductor lasers D1 and D2 are disposed on both sides of the semiconductor stacked bodies A and B so as to sandwich the semiconductor stacked bodies A and B, and are formed on the common substrate 1.

For wire bonding or the like, an n-side pad electrode 12b is formed on the n-electrode 11a, and an n-side pad electrode 12d is formed on the n-electrode 11b.

  As described above, in the two-wavelength semiconductor light-emitting device in which the n-electrode and the p-electrode are provided on the same surface side, the n-electrode is not provided between the semiconductor laminates A and B, and the semiconductor laminates A and B are formed. Since the semiconductor stacked bodies A and B can be stacked close to each other because they are arranged so as to be sandwiched, the active layers included in the semiconductor stacked bodies A and B can be formed close to each other, which are different. The condensing property of the light beam having the wavelength can be improved.

  A method of manufacturing the two-wavelength semiconductor light emitting device of FIG. 1 will be described with reference to FIGS. Here, the semiconductor laser D1 is, for example, a blue short wavelength laser, and the semiconductor laser D2 is, for example, a green long wavelength laser. In addition, the wafer including the substrate 1 and the semiconductor layer stacked on the substrate extends in the horizontal direction and the front-rear direction on the paper surface. One chip is shown with D2 as one set. Here, the semiconductor stacked body A corresponds to the first stacked body, and the semiconductor stacked body B corresponds to the second stacked body.

  First, in order to form the short-wavelength semiconductor laser D1, the growth substrate 20 is put into a MOCVD (metal organic chemical vapor deposition) apparatus, and the temperature is raised to about 1050 ° C. while flowing hydrogen gas, so that the growth substrate 20 is thermally Clean it. The temperature is lowered to about 600 ° C., and an Si-doped n-type GaN contact layer 211 is grown on the growth substrate 20 as the n-type contact layer 21 as shown in FIG.

As shown in FIG. 3, the insulating film 4 a is formed on the n-GaN contact layer 211, and the resist 14 is patterned except for the region where the semiconductor stacked body A is formed on the insulating film 4 a. For the insulating film 4a, a Si-based film such as SiO ₂ or Si ₃ N ₄ that cannot grow GaN and is easy to perform wet etching is used. By using this Si-based film, the shape of the semiconductor stacked body A can be obtained simply by stacking the semiconductor layers constituting the semiconductor stacked body A on the wafer, as will be described later. Next, the insulating film 4a in the region where the semiconductor stacked body A is formed is removed by wet etching.

  As shown in FIG. 4, in order to stack the semiconductor stacked body A, the wafer is again introduced into the MOCVD apparatus, the temperature is raised to about 1000 ° C., the Si-doped n-type AlGaN cladding layer 22, the Si-doped n-type GaN The light guide layer 23 is grown.

  Next, the temperature is lowered to about 750 ° C., and the InGaN active layer 24 is grown. Thereafter, the temperature is raised to about 1000 ° C. to 1100 ° C., and an Mg-doped p-type GaN light guide layer 25, an Mg-doped p-type AlGaN cladding layer 26, and an Mg-doped p-type GaN contact layer 27 are sequentially stacked.

  The InGaN active layer 24 may be an InGaN single layer, but may have a multiple quantum well structure. In this case, the well layer is formed of InGaN, the barrier layer (barrier layer) is formed of undoped GaN or InGaN, and the well layer and the barrier layer are formed. Are alternately stacked for several cycles. As described above, since the semiconductor laser having the blue emission wavelength (short wavelength side) is assumed to be D1, it is desirable that the In composition of the InGaN active layer 24 is about 15% and the InGaN well layer is about 30%.

  The Al composition of the n-AlGaN cladding layer 22 is desirably up to 10%, and the film thickness is desirably 1.2 μm or less in order to prevent cracks. The n-GaN light guide layer 23 may be an n-InGaN light guide layer. In this case, the In composition is preferably up to 3%.

  The p-GaN light guide layer 25 may also be a p-InGaN light guide layer. In this case, the In composition is preferably up to 3%. Note that the Al content of the p-AlGaN cladding layer 26 is preferably up to 10% and the film thickness is preferably up to 0.4 μm. Here, the layers from the n-AlGaN cladding layer 22 to the p-GaN contact layer 27 correspond to the semiconductor stacked body A.

Next, as illustrated in FIG. 5, the insulating film 4 b is stacked so as to cover the entire insulating film 4 a and the semiconductor stacked body A. Similarly to the insulating film 4a, the insulating film 4b is made of a Si-based film such as SiO ₂ or Si ₃ N ₄ that cannot grow GaN and is easy to wet-etch. Thus, when forming the semiconductor stacked body B, the shape of the semiconductor stacked body B can be obtained by sequentially stacking the semiconductor layers constituting the semiconductor stacked body B, as will be described later. The mask 6 is patterned except for the region where the semiconductor laminate B is to be formed, and wet etching is performed.

  After the mask 5 is lifted off, the semiconductor stacked body B of the semiconductor laser D2 is stacked in the region where the wet etching is performed in FIG. 5 as shown in FIG. In order to grow the semiconductor stacked body B, the temperature is again raised to about 1000 ° C. in the MOCVD apparatus, and the Si-doped n-type AlGaN cladding layer 32 and the Si-doped n-type are formed on the n-GaN contact layer 211. The GaN light guide layer 33 is crystal-grown. Next, the temperature is lowered to about 750 ° C., and the InGaN active layer 34 is grown. Thereafter, the temperature is raised to about 850 ° C., and the Mg-doped p-type InGaN layer 35 is grown. Here, the n-AlGaN cladding layer 32 to the p-InGaN layer 35 correspond to the semiconductor stacked body B.

  The InGaN active layer 34 may be a Si-doped n-type InGaN single layer, but may have a multiple quantum well structure. In this case, the well layer is Si-doped n-type InGaN, and the barrier layer is Si-doped n-type GaN. The well layer and the barrier layer may be alternately stacked for several cycles. As described above, since the semiconductor laser having the green emission wavelength (long wavelength side) is assumed to be D2, it is desirable that the In composition of the InGaN active layer 34 is about 20% and the InGaN well layer is about 30%. By using n-type GaN as the barrier layer, it can be grown at a temperature of about 750 ° C. as in the case of the well layer.

  Similar to the semiconductor stacked body A, the Al composition of the n-AlGaN cladding layer 32 is desirably up to 10%, and the film thickness is desirably 1.2 μm or less in order to prevent cracks. The n-GaN optical guide layer 33 may be an n-InGaN optical guide layer, and in this case, the In composition is preferably up to 3%. In addition, the In composition of the p-InGaN layer 35 is up to 3%, and in order to obtain good film quality, the film thickness is preferably 0.5 μm or less.

Conventionally, Al _X Ga _Y N (where X + Y = 1, 0 ≦ X <1, 0 <Y ≦ 1) is used for the p-type current injection layer. However, in order to obtain Al _X Ga _Y N exhibiting good p-type conduction, it is necessary to grow at a temperature exceeding 1000 ° C. However, when p-type Al _X Ga _Y N is grown at a temperature exceeding 1000 ° C., the InGaN active layer 34 on the long-wavelength side having a particularly large In composition tends to deteriorate and break easily. The longer wavelength light emitting element, the composition of In contained in the active layer increases, but as the composition of In increases, the active layer tends to deteriorate because In in the active layer is sublimated and separated at higher temperatures, Further, since it becomes fragile, the InGaN active layer 34 needs to be grown at 900 ° C. or lower.

  If the semiconductor stacked body B is first crystal-grown and p-type AlGaN or GaN is used on the semiconductor stacked body B as well as the semiconductor stacked body A, the InGaN active layer 34 having a large In composition. After the film is formed, the time during which the InGaN active layer 34 is exposed to a high temperature of 1000 ° C. or longer becomes longer. However, by growing the semiconductor laminated body A on the short wavelength side first as in the present invention, the composition of In can be increased. After the formation of the large InGaN active layer 34, the time during which the InGaN active layer 34 is exposed to a high temperature of 1000 ° C. or more can be shortened, and the InGaN active layer 34 can be prevented from being deteriorated.

  Further, in the case of the semiconductor stacked body B, unlike the semiconductor stacked body A, the p-InGaN layer 35 is formed on the InGaN active layer 34 without forming the p-GaN light guide layer and the p-AlGaN cladding layer. Since the layers are stacked, the crystal can be grown at a low temperature of 900 ° C. or less even after the InGaN active layer 34 is formed. In addition, when the InGaN active layer 34 has a quantum well structure, the barrier layer is made of n-type GaN, so that the InGaN active layer 34 can be grown at the same temperature as the well layer. Can be prevented. The p-InGaN layer 35 is a semiconductor layer that also functions as a cladding layer and a contact layer.

  Next, as shown in FIG. 7, after the insulating films 4a and 4b are removed, the insulating film 6 is applied onto the substrate 1, the mask 7 is patterned in a stripe shape, and etching is performed, so that the semiconductor stacked bodies A and B are formed. A striped ridge portion is formed simultaneously. Then, as shown in FIG. 8, light etching is performed by immersing in hydrofluoric acid to dissolve a part of the insulating film 6 and shape the ridge portion.

  As shown in FIG. 9, an insulating film 8 made of a material different from that of the insulating film 6 is formed by sputtering from the side surfaces of the ridges of the semiconductor stacked bodies A and B to the upper surface of the insulating film 6, and again as shown in FIG. In the state immersed in hydrofluoric acid, the insulating film 6 on the ridge portion is completely dissolved, and the mask 7 and the insulating film 8 formed above the ridge portion are removed.

  Next, as shown in FIG. 11, after the p-electrode layer 9 is stacked, the mask 10 is patterned in the region where the p-electrode is to be formed, the excess p-electrode layer 9 is removed by etching, and the p-electrodes 9a, 9b Form.

  Thereafter, as shown in FIG. 12, in order to form an n-electrode, the mask 10 is mesa-patterned and etched to remove part of the insulating films 8 and 10. Next, as shown in FIG. 13, the resist 40 is patterned except for the region where the n electrode is laminated, the n electrode layer 11 is laminated by vapor deposition or sputtering, and the resist 40 is lifted off. As shown in FIG. N electrodes 11 a and 11 b corresponding to the lasers D 1 and D 2 are formed on the n-GaN contact layer 211 so as to sandwich the semiconductor stacked bodies A and B.

Next, as shown in FIG. 15, the resist 42 is patterned except for the region where the pad electrode is formed, the pad electrode layer 12 is laminated by vapor deposition or sputtering, and the wafer 42 is immersed in an acetone solution, the resist 42 is dissolved, As shown in FIG. 1, the p-side pad electrode 12a is formed on the p-electrode 9a, the p-side pad electrode 12c is formed on the p-electrode 9b, the n-side pad electrode 12b is formed on the n-electrode 11a, and the n-electrode 11b is formed. The n-side pad electrode 12d is formed to complete a two-wavelength semiconductor light emitting device.

It is a figure which shows schematic structure of the 2 wavelength semiconductor light-emitting device of this invention. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device. It is a figure which shows one manufacturing process of a 2 wavelength semiconductor light-emitting device.

Explanation of symbols

1 substrate 2 semiconductor laminate A
3 Semiconductor stack B
6 Insulating film 8 Insulating film 9a p electrode 9b p electrode 11a n electrode 11b n electrode 12a p side pad electrode 12b n side pad electrode 12c p side pad electrode 12d n side pad electrode 20 growth substrate 21 n-type contact layer

Claims (6)

In the two-wavelength semiconductor light emitting device in which two stacked bodies that emit light of different wavelengths are formed on the same substrate, and an n electrode and a p electrode corresponding to the two stacked bodies are respectively disposed on the same surface side of the substrate.
Two n-electrodes corresponding to the two stacked bodies are arranged on the substrate so as to sandwich the two stacked bodies. Two laminated bodies emitting light of different wavelengths are formed on the same substrate, and n electrodes and p electrodes corresponding to the two laminated bodies are respectively arranged on the same surface side of the substrate, and the two laminated bodies In the method of manufacturing a two-wavelength semiconductor light-emitting device, the active layer in is composed of nitride layers containing In at different ratios.
Crystal growth is performed from the first stacked body including the active layer having the lower In composition ratio of the two stacked bodies, and then the second stacked body including the active layer having the higher In composition ratio is crystal-grown. Then, two n-electrodes are formed on the substrate so as to sandwich the first stacked body and the second stacked body, and the method for manufacturing a two-wavelength semiconductor light emitting device.   3. The method of manufacturing a two-wavelength semiconductor light emitting device according to claim 2, wherein the active layer of the second stacked body uses n-type GaN as a barrier layer.   4. The two-wavelength semiconductor light-emitting device according to claim 2, wherein after the crystal growth of the active layer of the second stacked body, only an InGaN layer is formed as a p-type semiconductor layer. 5. Device manufacturing method.   5. The Si-based film is formed on the substrate excluding a region where the first stacked body is stacked before crystal growth of the first stacked body. 2. A method for producing a two-wavelength semiconductor light-emitting device according to item 1. 3. The Si-based film is formed on the first stacked body and the substrate except for a region where the second stacked body is stacked before crystal growth of the second stacked body. The manufacturing method of the two-wavelength semiconductor light-emitting device of any one of Claims 5-5.

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