JP2012060023A - Semiconductor light-emitting element and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GaN-based semiconductor light-emitting element having an SDH structure and a manufacturing method of the same.SOLUTION: A sapphire substrate with a principal plane being (1-102) plane (R-plane), or a GaN substrate with a principal plane being (11-20) plane (A-plane), or an Si substrate with a principal plane being (111) plane is used as a substrate 10. A mesa-shaped protrusion 11 is formed on the substrate 10 by utilizing a mask layer 17, and a current block layer 15 is formed on sides of the mesa-shaped protrusion 11 by utilizing a difference in crystal growth rate.

Description

  The present invention relates to a GaN-based semiconductor light emitting device having an SDH (Separated Double Hetero Junction) structure and a method for manufacturing the same.

  An SDH structure is known as one means for reducing the threshold current of a semiconductor light emitting device. With an AlGaAs-based material, selective growth and selective etching are easy, and therefore it is extremely easy to create an SDH structure (see Patent Document 1).

Japanese Patent No. 3011938

  However, it is very difficult to create an SDH structure with a GaN-based material, as will be described later. For example, it is conceivable to create an SDH structure by laminating GaN-based materials by crystal growth and then selectively etching them by dry etching or the like. However, in such a case, defects occur due to deterioration of crystallinity, and the SDH structure cannot be realized.

  The present invention has been made in view of such problems, and an object thereof is to provide a GaN-based semiconductor light-emitting element having an SDH structure and a method for manufacturing the same.

The manufacturing method of the 1st semiconductor light-emitting device of this invention includes the following two processes.
(A1) After forming a mask layer having an opening extending in a predetermined direction on the main surface of the substrate whose main surface is the R-plane or A-plane, the mask layer includes a first cladding layer and an active layer, and has a predetermined A first step (A2) of forming a GaN-based mesa-like projection composed of a plurality of crystal planes on the main surface of the substrate exposed in the opening by crystal growth (A2) The mask layer is removed, and the main surface of the substrate A GaN-based current blocking layer is formed by crystal growth in the non-mesa-shaped projection formation region, and then a GaN-based second cladding layer is formed by crystal growth so as to cover the portion including the active layer of the mesa-shaped projection. Second step

  In the first method for manufacturing a semiconductor light emitting device of the present invention, mesa-shaped protrusions are formed on the main surface of the substrate whose main surface is the R surface or the A surface using a mask layer, and the crystal growth rate is further increased. Using the difference, current blocking layers are formed on both sides of the mesa protrusion. Thus, in the present invention, crystal growth is performed in a specific plane orientation, not a general plane orientation such as the C plane of the sapphire substrate or the A plane of the GaN substrate.

The manufacturing method of the 2nd semiconductor light-emitting device of this invention includes the following two processes.
(B1) By forming a GaN-based semiconductor layer including a first cladding layer, an active layer, and a current blocking layer on a main surface of a substrate having a convex portion extending in a predetermined direction on the main surface by crystal growth. And forming a mesa protrusion including at least a first cladding layer and an active layer and having a plurality of predetermined crystal planes on an upper surface of the protrusion, and the protrusion and a portion of the mesa protrusion not including the active layer, Step (B2) of Forming a Buried Layer Embedding In The Second Step of Forming a GaN-Based Second Cladding Layer by Crystal Growth to Cover the Part Containing the Active Layer in the Mesa-Shaped Protrusions

  In the second method for producing a semiconductor light emitting device of the present invention, mesa-like projections are formed on the upper surface of the convex portion of the substrate having irregularities (convex portions) on the main surface using the difference in crystal growth rate, Current blocking layers are formed on both sides of the mesa protrusion. As described above, in the present invention, crystal growth is performed on a substrate (structure substrate) having unevenness.

  The first semiconductor light emitting device of the present invention comprises a GaN-based semiconductor layer in contact with the main surface of the substrate whose main surface is the R-plane or A-plane. Here, the GaN-based semiconductor layer includes a mesa protrusion including the first cladding layer and the active layer in order from the main surface side, a current blocking layer formed on both sides of the mesa protrusion, and an active layer of the mesa protrusions. And a second cladding layer formed so as to cover the portion including the first cladding layer.

  In the first semiconductor light emitting device of the present invention, mesa protrusions are formed on the main surface of the substrate whose main surface is the R surface or the A surface, and current blocking layers are formed on both sides of the mesa protrusions. It is formed. Thus, in the present invention, crystal growth is performed in a specific plane orientation, not a general plane orientation such as the C plane of the sapphire substrate or the A plane of the GaN substrate.

  The second semiconductor light emitting device of the present invention comprises a GaN-based semiconductor layer in contact with the main surface of a substrate having a convex portion extending in a predetermined direction on the main surface. Here, the GaN-based semiconductor layer includes the first cladding layer and the active layer in order from the main surface side, and is formed on both sides of the mesa protrusions formed in contact with the upper surface of the convex portion and the mesa protrusions. A current blocking layer and a second cladding layer formed so as to cover a portion of the mesa protrusion including the active layer.

  In the second semiconductor light emitting device of the present invention, mesa-like projections are formed on the upper surface of the convex portion of the substrate having irregularities (convex portions) on the main surface by utilizing the difference in the crystal growth rate. Current blocking layers are formed on both sides. As described above, in the present invention, crystal growth is performed on a substrate (structure substrate) having unevenness.

  According to the first semiconductor light emitting device and the method of manufacturing the same of the present invention, crystal growth is performed in a specific plane orientation, not a general plane orientation, such as a C plane of a sapphire substrate or an A plane of a GaN substrate. As a result, crystallinity does not deteriorate and defects do not occur. Therefore, a light emitting element having a GaN-based BH / SDH structure can be realized.

  According to the second semiconductor light emitting device and the method of manufacturing the same of the present invention, the crystal growth is performed on the substrate having the unevenness (structure substrate), so that the crystallinity is not deteriorated and the defect does not occur. . Therefore, a light emitting element having a GaN-based BH / SDH structure can be realized.

1 is a cross-sectional view of a semiconductor light emitting element according to a first embodiment of the present invention. It is sectional drawing which shows an example of the manufacturing process of the semiconductor light-emitting device of FIG. It is sectional drawing of the semiconductor light-emitting device based on the 2nd Embodiment of this invention. FIG. 4 is a cross-sectional view showing an example of a manufacturing process of the semiconductor light emitting device of FIG. 3. It is sectional drawing of the semiconductor light-emitting device based on the 3rd Embodiment of this invention. FIG. 6 is a cross-sectional view showing an example of a manufacturing process of the semiconductor light emitting device of FIG. 5. It is sectional drawing of the semiconductor light-emitting device based on the 4th Embodiment of this invention. FIG. 8 is a cross-sectional view showing an example of a manufacturing process of the semiconductor light emitting device of FIG. 7.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The description will be given in the following order.

1. First embodiment (FIGS. 1 and 2)
1. An example in which an SDH structure having a (11-20) plane is formed on a flat substrate. Second embodiment (FIGS. 3 and 4)
2. An example in which an SDH structure having a (1-100) plane is formed on a flat substrate. Third embodiment (FIGS. 5 and 6)
3. Example in which an SDH structure having a (11-22) plane is formed on a flat substrate Fourth embodiment (FIGS. 7 and 8)
Example in which an SDH structure having a (11-20) plane is formed on a structural substrate

<First Embodiment>
[Structure of Semiconductor Light Emitting Element 1]
FIG. 1A shows an example of a cross-sectional configuration of the semiconductor light emitting device 1 according to the first embodiment of the present invention. FIG. 1B is an enlarged view of the cross-sectional configuration of the mesa projection 11 (described later) in FIG. FIGS. 1A and 1B are schematic representations, and are different from actual dimensions and shapes.

  The semiconductor light emitting device 1 includes a GaN-based semiconductor layer including a BH (Buried Hetero) / SDH structure on a flat substrate 10. Here, the BH / SDH structure is a DH (Double Hetero) structure provided not only in the stacking direction but also in the lateral direction (left and right direction in FIG. 1A), and a current block for current confinement. Refers to a layer. Further, the GaN-based refers to a III-V group nitride semiconductor such as GaN.

Here, the “III-V nitride semiconductor” means at least one of the group 3B elements in the short period periodic table, and at least N of the group 5B elements in the short period periodic table. Points to things that contain Examples of the III-V nitride semiconductor include gallium nitride compounds containing Ga and N. Examples of the gallium nitride compound include GaN, Al _x1 Ga _1-x1 N (0 <x1 <0.5), Al _x2 In _x3 Ga _1-x2-x3 N (0 <x2 <0.5, 0 < x3 <0.2), _{Inx4Ga1 -x4N} (0 <x4 <0.5), and the like. For group III-V nitride semiconductors, an n-type impurity of a group IV or VI element such as Si, Ge, O, or Se, or a group II or group IV element such as Mg, Zn, or C, if necessary. A p-type impurity is doped.

  The substrate 10 is, for example, a hexagonal substrate, a GaN substrate, or a Si substrate. Here, examples of the hexagonal substrate include sapphire and SiC. The main surface of the substrate 10 is, for example, a (1-102) plane (R plane) when the substrate 10 is a hexagonal substrate, and (11-20) when the substrate 10 is a GaN substrate. Surface (A surface). Further, the main surface of the substrate 10 is, for example, the (111) surface when the substrate 10 is a Si substrate.

  The semiconductor light emitting device 1 includes striped mesa protrusions 11 on a substrate 10. The mesa protrusion 11 forms an optical waveguide together with portions on both sides of the mesa protrusion 11, performs lateral light confinement using the lateral refractive index difference, and is injected into the semiconductor light emitting device 1. Current to be confined. As will be described later, since the active layer 13 is provided in the mesa protrusion 11, the entire active layer 13 corresponds to the current injection region, and the entire active layer 13 becomes a light emitting region.

  The mesa protrusion 11 is formed in contact with the upper surface (main surface) of the substrate 10 and extends, for example, in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 1A). It has a band shape. For example, as shown in FIG. 1B, the mesa projection 11 has (000-1) plane and (33-62) plane on the side surface, and (11-20) plane on the top surface. is doing. The cross section of the mesa projection 11 has a trapezoidal shape surrounded by the above three crystal planes and the upper surface of the substrate 10, for example.

  The mesa protrusion 11 includes, for example, a lower cladding layer 12 and an active layer 13 in order from the substrate 10 side. For example, as shown in FIG. 1A, the active layer 13 may be located on the upper surface of the mesa-like projections 11 or may be located inside the mesa-like projections 11 although not shown. When the active layer 13 is located inside the mesa protrusion 11, the same conductivity type GaN-based semiconductor layer as the upper clad layer 16 described later (for example, the same material as the material of the buried layer 14 described later) Is preferably formed in contact with the upper surface of the active layer 13.

  The semiconductor light emitting device 1 further includes a buried layer 14, a current blocking layer 15 and an upper cladding layer 16 around the mesa protrusion 11. The mesa protrusion 11 is embedded by a buried layer 14, a current blocking layer 15 and an upper cladding layer 16. The buried layer 14, the current blocking layer 15, and the upper cladding layer 16 are stacked in this order from the substrate 10 side. The buried layer 14 and the current blocking layer 15 are formed in a region where the mesa protrusion 11 is not formed on the upper surface (main surface) of the substrate 10. The upper clad layer 16 is formed in contact with at least the upper surface of the mesa protrusion 11 and the upper surface of the current blocking layer 15, and covers, for example, the upper portion of the mesa protrusion 11 (the portion including the active layer 13). Yes. That is, the active layer 13 is sandwiched between the lower cladding layer 12 and the upper cladding layer 16 (or a GaN-based semiconductor layer having the same conductivity type as the upper cladding layer 16) in the stacking direction, and in the lateral direction, It is sandwiched between the upper cladding layers 16.

  Here, the lower cladding layer 12 is made of, for example, n-type AlGaN. The refractive index of the lower cladding layer 12 is smaller than the refractive index of the active layer 13, and the forbidden band width of the lower cladding layer 12 is smaller than the forbidden band width of the active layer 13. The active layer 13 has a multiple quantum well structure in which, for example, well layers and barrier layers formed of GaInN having different composition ratios are alternately stacked. The upper cladding layer 16 is made of, for example, p-type AlGaN. The refractive index of the upper cladding layer 16 is smaller than the refractive index of the active layer 13, and the forbidden band width of the upper cladding layer 16 is smaller than the forbidden band width of the active layer 13.

  The buried layer 14 is made of, for example, p-type AlGaN. The refractive index of the buried layer 14 is smaller than the refractive index of the active layer 13, and the forbidden band width of the buried layer 14 is smaller than the forbidden band width of the active layer 13. The current block layer 15 is made of n-type AlGaN, for example. The refractive index of the current blocking layer 15 is smaller than the refractive index of the active layer 13, and the forbidden band width of the current blocking layer 15 is smaller than the forbidden band width of the active layer 13.

  In addition, the conductivity type of each semiconductor layer is not restricted to the conductivity type illustrated above, All the conductivity types illustrated above may be reversed. For example, the lower cladding layer 12 and the current blocking layer 15 may be p-type, and the buried layer 14 and the upper cladding layer 16 may be n-type.

  An upper electrode (not shown) is provided on the upper surface of the upper cladding layer 16 (the upper surface of the contact layer when a contact layer is present on the upper surface of the upper cladding layer 16). The upper electrode is formed by, for example, laminating Ti, Pt, and Au in this order, and is electrically connected to the upper clad layer 16. On the other hand, a lower electrode (not shown) is provided on the back surface of the substrate 10. This lower electrode is formed by, for example, laminating an alloy of Au and Ge, Ni and Au in order from the substrate 10 side, and is electrically connected to the substrate 10. When the substrate 10 is a high resistance substrate, for example, a buffer layer having the same conductivity type as that of the lower cladding layer 12 is provided between the substrate 10 and the lower cladding layer 12 and the buried layer 14. A lower electrode is provided in contact with the buffer layer and the like.

[Method of Manufacturing Semiconductor Light Emitting Element 1]
The semiconductor light emitting device 1 of the present embodiment can be manufactured as follows, for example.

2A to 2D illustrate an example of a cross-sectional configuration of an element in a manufacturing process. First, as the substrate 10, a sapphire substrate whose main surface is a (1-102) plane (R plane), a GaN substrate whose main surface is a (11-20) plane (A plane), or a main surface is A Si substrate having a (111) plane is prepared. Next, on the main surface of the substrate 10, for example, a mask layer 17 having a strip-shaped opening 17A extending in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 1A) is formed. (FIG. 2 (A)). The mask layer 17 is made of an insulating material such as SiO ₂ , SiN, TiO ₂ , for example.

  Next, for example, by performing selective growth of a GaN-based material, a lower cladding layer 12 and an active layer 13 are sequentially formed on a portion of the main surface of the substrate 10 exposed in the opening 17A (see FIG. 2 (B)). As a result, a protrusion having a trapezoidal cross section having (000-1) plane and (33-62) plane on the side surface and (11-20) plane on the upper surface is formed.

For the selective growth, for example, an epitaxial crystal growth method such as MOCVD (Metal Organic Chemical Vapor Deposition) method is used. Moreover, as a raw material of the GaN-based material used in the above selective growth, for example, TMA (trimethylaluminum), TMG (trimethylgallium), TMIn (trimethylindium), NH ₃ (ammonia) or the like is used. For example, DMZn (dimethylzinc) is used as the p-type dopant, and for example, H ₂ Se (hydrogen selenide) is used as the n-type dopant. During the selective growth of the lower cladding layer 12, the growth rate is, for example, 0.5 to 8 μm / h, the flow rate of the group III element material (for example, TMG, TMIn, etc.) is, for example, 10 to 90 sccm, and the nitrogen material (for example, NH ₃ ). The flow rate was 5 to 39 slm, the growth temperature was 800 to 950 ° C., the growth source V / III ratio was 1000 to 15000, and the growth pressure was 0.01 to 1 atm, for example. In the selective growth of the active layer 13, the growth rate is, for example, 0.5 to 8 μm / h, the flow rate of the Group III element material (for example, TMG, TMIn, etc.) is, for example, 10 to 90 sccm, and the nitrogen material (for example, NH ₃ ). For example, the growth temperature was 600 to 800 ° C., the growth raw material V / III ratio was 1000 to 15000, and the growth pressure was 0.01 to 2 atmospheres, for example.

Next, after removing the mask layer 17 (FIG. 2C), the buried layer 14 and the current blocking layer 15 are sequentially formed (FIG. 2D). At this time, epitaxial growth by MOCVD is unlikely to occur on the (000-1) plane and (33-62) plane, which are the side surfaces of the protrusions. Is likely to occur. Therefore, the buried layer 14 and the current blocking layer 15 hardly grow on the side surface of the trapezoidal protrusion, and only on the region where the lower cladding layer 12 is not formed and the upper surface of the active layer 13 in the main surface of the substrate 10. They are selectively divided from each other (FIG. 2D). In the selective growth of the buried layer 14 and the current blocking layer 15, in order to obtain a flat surface, the growth rate is, for example, 0.5 to 8 μm / h, and the flow rate of the group III element material (for example, TMG, TMIn, etc.) is, for example, 10 ～90Sccm, nitrogen source (e.g., NH ₃₎ flow rate, for example 5~39sml of the growth temperature, for example: 950 ° C., the V / III ratio growth material for example 1,000 to 15,000, the growth pressure for example 0.01 Atmospheric pressure.

  Next, the upper cladding layer 16 is formed on the surface of the current blocking layer 15 and the upper surface of the mesa protrusion 11 (FIG. 1A). In this way, the mesa protrusion 11 is buried by the buried layer 14, the current blocking layer 15 and the upper cladding layer 16. Thereafter, although not shown, an upper electrode and a lower electrode are formed as necessary. In this way, the semiconductor light emitting device 1 of the present embodiment is manufactured.

[Operation and Effect of Semiconductor Light-Emitting Element 1]
Next, the operation and effect of the semiconductor light emitting device 1 of the present embodiment will be described.

  In the semiconductor light emitting device 1 of the present embodiment, when a predetermined current is supplied to the upper electrode and the lower electrode, the current confined by the current blocking layer 15 is injected into the active layer 13 in the mesa protrusion 11, This causes light emission due to recombination of electrons and holes. As a result, the light emitted from the active layer 13 is emitted to the outside.

  By the way, in the present embodiment, the substrate 10 is a sapphire substrate whose main surface is the (1-102) plane (R plane), and GaN whose main surface is the (11-20) plane (A plane). A substrate or a Si substrate whose principal surface is a (111) plane is used. A mesa protrusion 11 is formed on the substrate 10 using the mask layer 17, and a current blocking layer 15 is formed on both sides of the mesa protrusion 11 using the difference in crystal growth rate. Is done. As described above, in the present embodiment, crystal growth is performed on the substrate 10 having a peculiar plane orientation on the main surface, not a general plane orientation such as the C plane of the sapphire substrate or the A plane of the GaN substrate. . Thereby, since crystallinity does not deteriorate or a defect does not occur, a light-emitting element having a GaN-based BH / SDH structure can be realized.

<Second Embodiment>
[Structure of Semiconductor Light Emitting Element 2]
FIG. 3A illustrates an example of a cross-sectional configuration of the semiconductor light emitting element 2 according to the second embodiment of the present invention. FIG. 3B is an enlarged view of the cross-sectional configuration of the mesa protrusion 21 (described later) in FIG. 3A and 3B are schematic representations, and are different from actual dimensions and shapes.

  Similar to the semiconductor light emitting device 1, the semiconductor light emitting device 2 includes a GaN-based semiconductor layer including a BH / SDH structure on a flat substrate 10, and is common to the configuration of the semiconductor light emitting device 1 in that respect. However, the semiconductor light emitting device 2 is different from the configuration of the semiconductor light emitting device 1 in that the cross-sectional shape of the striped mesa protrusions 21 on the substrate 10 is different from the cross-sectional shape of the mesa protrusions 11. Hereinafter, differences from the configuration of the semiconductor light emitting device 1 will be mainly described, and description of the same configuration as the semiconductor light emitting device 1 will be omitted as appropriate.

  The mesa protrusion 21 forms an optical waveguide together with portions on both sides of the mesa protrusion 21, performs lateral light confinement using the lateral refractive index difference, and is injected into the semiconductor light emitting device 2. Current to be confined. As will be described later, since the active layer 13 is provided in the mesa protrusions 21, the entire active layer 13 corresponds to the current injection region, and the entire active layer 13 becomes a light emitting region.

  The mesa protrusions 21 are formed in contact with the upper surface (main surface) of the substrate 10 and extend, for example, in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 3A). It has a band shape. For example, as shown in FIG. 3B, the mesa-shaped protrusion 21 has a [1-100] surface on the side surface and the upper surface. The cross section of the mesa protrusion 21 has, for example, a pentagonal shape surrounded by the crystal face. The mesa-shaped protrusion 21 includes, for example, the lower cladding layer 12 and the active layer 13 in order from the substrate 10 side. For example, as shown in FIG. 3A, the active layer 13 is located on the upper surface (a pair of inclined surfaces) of the mesa protrusion 21.

[Method for Manufacturing Semiconductor Light-Emitting Element 2]
The semiconductor light emitting element 2 of the present embodiment can be manufactured as follows, for example.

  4A to 4D illustrate an example of a cross-sectional configuration of an element in a manufacturing process. First, as the substrate 10, a sapphire substrate whose main surface is a (1-102) plane (R plane), a GaN substrate whose main surface is a (11-20) plane (A plane), or a main surface is A Si substrate having a (111) plane is prepared. Next, on the main surface of the substrate 10, for example, a mask layer 17 having a strip-shaped opening 17A extending in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 4A) is formed. (FIG. 4 (A)).

  Next, for example, by performing selective growth of a GaN-based material, a lower cladding layer 12 and an active layer 13 are sequentially formed on a portion of the main surface of the substrate 10 exposed in the opening 17A (see FIG. 4 (B)). Thereby, a pentagonal projection having a [1-100] plane on the side surface and the upper surface is formed. For the selective growth, for example, the MOCVD method or the like is used under conditions lower in temperature than when the semiconductor light emitting device 1 of the first embodiment is manufactured.

  Next, after removing the mask layer 17 (FIG. 4C), the buried layer 14 and the current blocking layer 15 are sequentially formed (FIG. 4D). At this time, epitaxial growth by MOCVD is unlikely to occur on the [1-100] plane, which is the side surface and top surface of the pentagonal projection, while epitaxial growth by MOCVD tends to occur on the main surface of the substrate 10. Therefore, the buried layer 14 and the current blocking layer 15 hardly grow on the side surface and the upper surface of the trapezoidal protrusion, and are selectively separated from each other only in the region where the lower cladding layer 12 is not formed on the main surface of the substrate 10. (FIG. 4D). The growth conditions for the buried layer 14 and the current blocking layer 15 are substantially the same as those for manufacturing the semiconductor light emitting device 1 of the first embodiment.

  Next, the upper clad layer 16 is formed on the surface of the current blocking layer 15 and the upper surface of the mesa protrusion 21 (FIG. 3A). In this way, the mesa protrusions 21 are embedded by the embedded layer 14, the current blocking layer 15 and the upper cladding layer 16. Thereafter, although not shown, an upper electrode and a lower electrode are formed as necessary. In this way, the semiconductor light emitting element 2 of the present embodiment is manufactured.

[Operation / Effect of Semiconductor Light-Emitting Element 2]
Next, the operation and effect of the semiconductor light emitting device 2 of the present embodiment will be described.

  In the semiconductor light emitting device 2 of the present embodiment, when a predetermined current is supplied to the upper electrode and the lower electrode, the current confined by the current blocking layer 15 is injected into the active layer 13 in the mesa-shaped protrusion 21, This causes light emission due to recombination of electrons and holes. As a result, the light emitted from the active layer 13 is emitted to the outside.

  By the way, in the present embodiment, the substrate 10 is a sapphire substrate whose main surface is the (1-102) plane (R plane), and GaN whose main surface is the (11-20) plane (A plane). A substrate or a Si substrate whose principal surface is a (111) plane is used. A mesa protrusion 21 is formed on the substrate 10 using the mask layer 17, and a current blocking layer 15 is formed on both sides of the mesa protrusion 21 using the difference in crystal growth rate. Is done. As described above, in the present embodiment, crystal growth is performed on the substrate 10 having a peculiar plane orientation on the main surface, not a general plane orientation such as the C plane of the sapphire substrate or the A plane of the GaN substrate. . Thereby, since crystallinity does not deteriorate or a defect does not occur, a light-emitting element having a GaN-based BH / SDH structure can be realized.

<Third Embodiment>
[Structure of Semiconductor Light Emitting Element 3]
FIG. 5A shows an example of a cross-sectional configuration of a semiconductor light emitting element 3 according to the third embodiment of the present invention. FIG. 5B is an enlarged view of the cross-sectional configuration of the mesa protrusion 31 (described later) in FIG. 5A and 5B are schematic representations, and are different from actual dimensions and shapes.

  Similar to the semiconductor light emitting device 1, the semiconductor light emitting device 3 includes a GaN-based semiconductor layer including a BH / SDH structure on a flat substrate 10, and is common to the configuration of the semiconductor light emitting device 1 in that respect. However, the semiconductor light emitting device 3 is different from the configuration of the semiconductor light emitting device 1 in that the cross-sectional shape of the striped mesa protrusion 31 on the substrate 10 is different from the cross-sectional shape of the mesa protrusion 11. Hereinafter, differences from the configuration of the semiconductor light emitting device 1 will be mainly described, and description of the same configuration as the semiconductor light emitting device 1 will be omitted as appropriate.

  The mesa protrusion 31 constitutes an optical waveguide together with both sides of the mesa protrusion 31, performs lateral light confinement using the lateral refractive index difference, and is injected into the semiconductor light emitting device 3. Current to be confined. As will be described later, since the active layer 13 is provided in the mesa protrusion 31, the entire active layer 13 corresponds to the current injection region, and the entire active layer 13 becomes a light emitting region.

  The mesa protrusion 31 is formed in contact with the upper surface (main surface) of the substrate 10 and extends, for example, in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 5A). It has a band shape. For example, as shown in FIG. 5B, the mesa protrusion 31 has a (000-1) plane and a (0001) plane on the side surface and a (11-22) plane on the upper surface. Yes. The cross section of the mesa protrusion 31 has, for example, a quadrangular shape surrounded by the above three crystal planes and the upper surface of the substrate 10 and having an upper side inclined. The mesa protrusion 31 includes, for example, the lower cladding layer 12 and the active layer 13 in order from the substrate 10 side. For example, as shown in FIG. 5A, the active layer 13 is located on the upper surface (a pair of inclined surfaces) of the mesa protrusion 31.

[Method for Manufacturing Semiconductor Light-Emitting Element 3]
The semiconductor light emitting device 3 of the present embodiment can be manufactured as follows, for example.

  6A to 6D illustrate an example of a cross-sectional configuration of an element in a manufacturing process. First, as the substrate 10, a sapphire substrate whose main surface is a (1-102) plane (R plane), a GaN substrate whose main surface is a (11-20) plane (A plane), or a main surface is A Si substrate having a (111) plane is prepared. Next, on the main surface of the substrate 10, for example, a mask layer 17 having a strip-shaped opening 17A extending in the <11-20> direction of the substrate 10 (direction perpendicular to the paper surface of FIG. 6A) is formed. (FIG. 6 (A)).

  Next, for example, by performing selective growth of a GaN-based material, a lower cladding layer 12 and an active layer 13 are sequentially formed on a portion of the main surface of the substrate 10 exposed in the opening 17A (see FIG. 6 (B)). Thereby, a quadrangular protrusion having a (000-1) plane and a (0001) plane on the side surface and a (11-22) plane on the upper surface is formed. For the selective growth, for example, the MOCVD method or the like is used under conditions lower in temperature than when the semiconductor light emitting device 1 of the first embodiment is manufactured.

  Next, after removing the mask layer 17 (FIG. 6C), the buried layer 14 and the current blocking layer 15 are sequentially formed (FIG. 6D). At this time, epitaxial growth by MOCVD is unlikely to occur on the side surfaces and top surface of the quadrangular protrusions, while epitaxial growth by MOCVD tends to occur on the main surface of the substrate 10. Therefore, the buried layer 14 and the current blocking layer 15 hardly grow on the side surface and the upper surface of the quadrangular protrusion, and are selectively separated from each other only in the region where the lower cladding layer 12 is not formed in the main surface of the substrate 10. (FIG. 6D). The growth conditions for the buried layer 14 and the current blocking layer 15 are substantially the same as those for manufacturing the semiconductor light emitting device 1 of the first embodiment.

  Next, the upper clad layer 16 is formed on the surface of the current blocking layer 15 and the upper surface of the mesa protrusion 31 (FIG. 5A). In this way, the mesa protrusion 31 is embedded by the buried layer 14, the current blocking layer 15 and the upper cladding layer 16. Thereafter, although not shown, an upper electrode and a lower electrode are formed as necessary. In this way, the semiconductor light emitting device 3 of the present embodiment is manufactured.

[Operation / Effect of Semiconductor Light Emitting Element 3]
Next, the operation and effect of the semiconductor light emitting device 3 of the present embodiment will be described.

  In the semiconductor light emitting device 3 of the present embodiment, when a predetermined current is supplied to the upper electrode and the lower electrode, the current confined by the current blocking layer 15 is injected into the active layer 13 in the mesa protrusion 31, This causes light emission due to recombination of electrons and holes. As a result, the light emitted from the active layer 13 is emitted to the outside.

  By the way, in the present embodiment, the substrate 10 is a sapphire substrate whose main surface is the (1-102) plane (R plane), and GaN whose main surface is the (11-20) plane (A plane). A substrate or a Si substrate whose principal surface is a (111) plane is used. A mesa protrusion 31 is formed on the substrate 10 using the mask layer 17, and the current blocking layer 15 is formed on both sides of the mesa protrusion 31 using the difference in crystal growth rate. Is done. As described above, in the present embodiment, crystal growth is performed on the substrate 10 having a peculiar plane orientation on the main surface, not a general plane orientation such as the C plane of the sapphire substrate or the A plane of the GaN substrate. . Thereby, since crystallinity does not deteriorate or a defect does not occur, a light-emitting element having a GaN-based BH / SDH structure can be realized.

<Fourth embodiment>
[Structure of Semiconductor Light Emitting Element 4]
FIG. 7A shows an example of a cross-sectional configuration of a semiconductor light emitting element 4 according to the fourth embodiment of the present invention. FIG. 7B is an enlarged view of the cross-sectional configuration of the mesa protrusion 41 (described later) in FIG. FIGS. 7A and 7B are schematic representations, and are different from actual dimensions and shapes.

  Unlike the semiconductor light emitting device 1, the semiconductor light emitting device 4 includes a GaN-based semiconductor layer including a BH / SDH structure on a substrate 10 having an uneven surface on the upper surface (main surface). This is different from the configuration of the element 1. Hereinafter, differences from the configuration of the semiconductor light emitting device 1 will be mainly described, and description of the same configuration as the semiconductor light emitting device 1 will be omitted as appropriate.

  The substrate 10 is, for example, a sapphire substrate whose main surface is a (1-102) plane (R plane) or (0001) plane (C plane), and whose main plane is (11-20) plane (A plane) or ( 11-20) a GaN substrate having a (A) surface, or a Si substrate having a (111) main surface. That is, the substrate 10 may be a substrate having a specific plane orientation or a substrate having a general plane orientation.

  The semiconductor light emitting device 4 includes a mesa protrusion 41 on the upper surface of the convex portion 40 </ b> A of the substrate 40. The mesa protrusion 41 constitutes an optical waveguide together with portions on both sides of the mesa protrusion 41, performs lateral light confinement using the lateral refractive index difference, and is injected into the semiconductor light emitting device 4. Current to be confined. As will be described later, since the active layer 13 is provided in the mesa protrusion 41, the entire active layer 13 corresponds to the current injection region, and the entire active layer 13 becomes a light emitting region. The convex portion 40A has, for example, a strip shape extending in the <11-20> direction of the substrate 40 (a direction perpendicular to the paper surface of FIG. 7A).

  The mesa projection 41 is formed in contact with the upper surface of the convex portion 40A, and has, for example, a strip shape extending in the <11-20> direction of the substrate 40. For example, as shown in FIG. 7B, the mesa protrusion 41 has a (000-1) plane and a (33-62) plane on the side surface, and an (11-20) plane on the upper surface. is doing. The cross section of the mesa protrusion 41 is, for example, a quadrangular shape surrounded by the above three crystal planes and the upper surface of the substrate 40. The mesa protrusion 41 includes, for example, the lower cladding layer 12 and the active layer 13 in order from the substrate 40 side. For example, as shown in FIG. 7A, the active layer 13 is positioned on the upper surface of the mesa protrusion 41.

[Method for Manufacturing Semiconductor Light-Emitting Element 4]
The semiconductor light emitting device 4 of the present embodiment can be manufactured as follows, for example.

  8A to 8C illustrate an example of a cross-sectional configuration of the element in the manufacturing process. First, as the substrate 40, a sapphire substrate whose main surface is the (1-102) plane (R plane) or (0001) plane (C plane), and the main plane is the (11-20) plane (A plane) or ( A GaN substrate having a (11-20) plane (A plane) or a Si substrate having a (111) plane as a main surface is prepared. At this time, a convex portion 40A extending in a predetermined direction is formed on the upper surface (main surface) of the substrate 40. Here, the extending direction of the convex portion 40A extends in the A-axis direction when the main surface of the substrate 40 is a C surface, and the main surface of the substrate 40 is an A surface. Extends in the C-axis direction.

  Next, for example, by performing selective growth of a GaN-based material, the lower cladding layer 12 and the active layer 13 are formed on the upper surface of the convex portion 40A of the substrate 40 and the portion of the upper surface of the substrate 40 other than the convex portion 40A. Are sequentially formed (FIG. 8B). Thus, a protrusion having a square cross section having (000-1) and (33-62) surfaces on the side surface and (11-20) surface on the upper surface of the convex portion 40A of the substrate 40. Is formed. For the selective growth, for example, the MOCVD method or the like is used under the same conditions as those for manufacturing the semiconductor light emitting device 1 of the first embodiment.

  At this time, epitaxial growth by MOCVD does not easily occur on the side surface of the convex portion 40A, while epitaxial growth by MOCVD tends to occur on the main surface of the substrate 40 (the upper surface of the convex portion 40A and the skirt of the convex portion 40A). Therefore, the lower cladding layer 12 and the active layer 13 hardly grow on the side surface of the convex portion 40A, and are selectively separated from each other only on the main surface of the substrate 40 (FIG. 8B).

  Subsequently, the buried layer 14 and the current blocking layer 15 are sequentially formed (FIG. 8C). Also at this time, epitaxial growth by MOCVD hardly occurs on the side surfaces of the quadrangular protrusions, while epitaxial growth by MOCVD tends to occur on the upper surface of the active layer 13. Therefore, the buried layer 14 and the current blocking layer 15 hardly grow on the side surfaces of the quadrangular protrusions, and are selectively separated from each other only on the upper surface of the active layer 13 (FIG. 8C). . The growth conditions for the buried layer 14 and the current blocking layer 15 are substantially the same as those for manufacturing the semiconductor light emitting device 1 of the first embodiment.

  Next, the upper clad layer 16 is formed on the surface of the current blocking layer 15 and the upper surface of the mesa protrusion 41 (FIG. 7A). In this way, the mesa protrusion 41 is buried by the buried layer 14, the current blocking layer 15 and the upper cladding layer 16. Thereafter, although not shown, an upper electrode and a lower electrode are formed as necessary. In this way, the semiconductor light emitting element 4 of the present embodiment is manufactured.

[Operation / Effect of Semiconductor Light-Emitting Element 4]
Next, the operation and effect of the semiconductor light emitting device 4 of the present embodiment will be described.

  In the semiconductor light emitting device 4 of the present embodiment, when a predetermined current is supplied to the upper electrode and the lower electrode, the current confined by the current blocking layer 15 is injected into the active layer 13 in the mesa protrusion 41, This causes light emission due to recombination of electrons and holes. As a result, the light emitted from the active layer 13 is emitted to the outside.

  By the way, in this embodiment, mesa-like projections 41 are formed on the upper surface of the convex portion 40A of the substrate 40 having irregularities (convex portions 40A) on the upper surface (main surface) by utilizing the difference in the crystal growth rate. The current blocking layer 15 is formed on both sides of the mesa protrusion 41. Thus, in the present embodiment, crystal growth is performed on the substrate 40 having unevenness. Thereby, since crystallinity does not deteriorate or a defect does not occur, a light-emitting element having a GaN-based BH / SDH structure can be realized.

  DESCRIPTION OF SYMBOLS 1, 2, 3, 4 ... Semiconductor light emitting element 10, 40 ... Substrate 11, 21, 31, 41 ... Mesa protrusion, 12 ... Lower clad layer, 13 ... Active layer, 14 ... Buried layer, 15 ... Current block Layer 16 upper cladding layer 17 mask layer 17A opening 40A convex portion

Claims (9)

A mask layer having an opening extending in a predetermined direction is formed on the main surface of the substrate whose main surface is an R surface or an A surface, and then includes a first cladding layer and an active layer, and a predetermined plurality of A first step of forming a GaN-based mesa-like protrusion made of a crystal face on a portion of the main surface of the substrate exposed in the opening by crystal growth;
The mask layer is removed, and a GaN-based current blocking layer is formed by crystal growth in a region where no mesa protrusion is formed on the main surface of the substrate, and then the portion of the mesa protrusion including the active layer is covered. And a second step of forming a GaN-based second cladding layer by crystal growth. The method for manufacturing a semiconductor light emitting element according to claim 1, wherein the substrate is a sapphire substrate, a GaN-based substrate, or a Si substrate. The method for manufacturing a semiconductor light emitting element according to claim 2, wherein the opening extends in a <11-20> direction. 4. The semiconductor according to claim 1, wherein the mesa protrusion has a (000-1) surface and a (33-62) surface on a side surface and (11-20) on an upper surface. 5. Manufacturing method of light emitting element. 4. The method of manufacturing a semiconductor light emitting element according to claim 1, wherein the mesa protrusion has a [1-100] plane on a side surface and an upper surface. 4. The semiconductor light emitting element according to claim 1, wherein the mesa protrusion has a (000-1) plane and a (0001) plane on a side surface and (11-22) on an upper surface. 5. Manufacturing method. By forming, by crystal growth, a GaN-based semiconductor layer including a first cladding layer, an active layer, and a current blocking layer on a main surface of a substrate having a convex portion extending in a predetermined direction as a main surface. A mesa-like protrusion comprising a first cladding layer and the active layer and having a plurality of predetermined crystal planes is formed on the upper surface of the convex part, and the active layer is included among the convex part and the mesa-like protrusion. A first step of forming a buried layer that embeds a portion that is not present;
And a second step of forming a GaN-based second cladding layer by crystal growth so as to cover a portion of the mesa protrusion including the active layer. A GaN-based semiconductor layer is provided in contact with the main surface of the substrate whose main surface is an R surface or an A surface,
The GaN-based semiconductor layer is
A mesa protrusion including a first cladding layer and an active layer in order from the main surface side;
A current blocking layer formed on both sides of the mesa protrusion;
And a second cladding layer formed so as to cover a portion of the mesa protrusion including the active layer. A GaN-based semiconductor layer is provided in contact with the main surface of the substrate having a convex portion extending in a predetermined direction on the main surface,
The GaN-based semiconductor layer is
Mesa-shaped protrusions including a first cladding layer and an active layer in order from the main surface side and formed in contact with the upper surface of the convex portion;
A current blocking layer formed on both sides of the mesa protrusion;
And a second cladding layer formed so as to cover a portion of the mesa protrusion including the active layer.

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