JP2012212932A - Semiconductor light-emitting element manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element having high light extraction efficiency.SOLUTION: A manufacturing method of a semiconductor light-emitting element including a first semiconductor layer 120, a second semiconductor layer 140, a light-emitting layer 130 provided between the first semiconductor layer 120 and the second semiconductor layer 140, a first electrode 160 connected to the first semiconductor layer 120, and a second electrode 150 provided on the second semiconductor layer 140 with a side facing the second semiconductor layer 140 being composed of at least either one of silver or a silver alloy, comprises: forming a conductive film to be the second electrode 150 on the second semiconductor layer 140; and forming air gap with a width of an emission wavelength or less of the light-emitting layer on a surface of the conductive film facing the second semiconductor layer 140 by causing self organization by migration of the conductive film.

Description

  The present invention relates to a method for manufacturing a semiconductor light emitting device.

  In order to improve the luminance of the semiconductor light emitting device, it is important to improve the light extraction efficiency. As an example of a structure that is expected to have high heat dissipation and high light extraction efficiency in a semiconductor light emitting device, the light emitting layer side of the wafer is brought into contact with the heat sink side, and the emitted light is reflected directly or by a reflective film and taken out from the substrate side. There is a flip chip type structure.

The light emitted in the semiconductor light emitting element changes its optical path according to the incident angle with respect to the interface having a difference in refractive index. When the incident angle is deep such that the incident angle of light is nearly perpendicular to the interface, the light is taken out of the semiconductor element. When the incident angle is shallow, the light is totally reflected and returns to the inside of the semiconductor light emitting element.
In the case of a flip-chip type semiconductor light emitting device, in order to improve the light extraction efficiency, it is conceivable to process the light extraction surface of the substrate into a dome shape or to form a nano uneven structure having a diffraction function. However, for example, in the case of a semiconductor light emitting device in which a nitride semiconductor is formed on a sapphire substrate, the difference in refractive index between the substrate and the semiconductor layer is large, so that light emitted from the semiconductor layer is reflected at the interface and confined in the semiconductor layer. It has a structure that is easy to handle. For this reason, even if the light extraction surface of the substrate is devised, there is room for improvement in improving the light extraction efficiency.

  In order to improve the light extraction efficiency, for example, by processing the surface of the substrate on which the semiconductor layer is formed, forming a non-flat layer in the semiconductor layer, or processing the surface of the semiconductor layer on which the reflective film is formed, It is also conceivable to form a structure. However, both methods require advanced techniques, and there is a possibility that the crystal growth conditions for forming the concavo-convex structure and the crystal growth conditions for improving the characteristics of the semiconductor light emitting device are not highly compatible. That is, the crystal quality is lowered by forming the concavo-convex structure, and there is a concern that the electrical characteristics and the optical characteristics are deteriorated due to this.

  Patent Document 1 proposes a structure in which an electrode that also functions as a high-efficiency reflective film has a region with a width that is 1/2 or less of the wavelength of the emitted light from the light-emitting layer.

JP 2007-5591 A

  The present invention provides a method for manufacturing a semiconductor light emitting device with high light extraction efficiency.

  According to one embodiment of the present invention, a first semiconductor layer, a second semiconductor layer, a light emitting layer provided between the first semiconductor layer and the second semiconductor layer, and the first semiconductor layer A first electrode connected to the semiconductor layer, a second electrode provided on the second semiconductor layer and facing the second semiconductor layer, the second electrode comprising at least one of silver and a silver alloy, A method of manufacturing a semiconductor light-emitting device having the above-described structure, wherein a conductive film to be the second electrode is formed on the second semiconductor layer, and self-organization is caused by migration of the conductive film. A method of manufacturing a semiconductor light emitting device is provided, wherein a gap having a width equal to or smaller than the emission wavelength of the light emitting layer is formed on a surface facing the second semiconductor layer.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a semiconductor light-emitting device with high light extraction efficiency is provided.

1 is a schematic view illustrating the configuration of a semiconductor light emitting element according to a first embodiment of the invention. FIG. 3 is an enlarged schematic view illustrating the structure of the main part of the semiconductor light emitting element according to the first embodiment of the invention. It is a schematic diagram which illustrates the space | gap of the semiconductor light-emitting device concerning the 1st Embodiment of this invention. 1 is a schematic cross-sectional view illustrating the configuration of a semiconductor light emitting element according to a first example of the invention. It is a flowchart figure which illustrates the manufacturing method of the semiconductor light-emitting device concerning the 2nd Embodiment of this invention. FIG. 10 is a schematic cross-sectional view in order of the processes, illustrating a method for manufacturing a portion of the semiconductor light emitting element according to the second example of the invention. It is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing a semiconductor light emitting element according to the second example of the invention. FIG. 8 is a schematic cross-sectional view in order of the steps, following FIG. 7. It is a schematic diagram which shows the behavior of the crystal grain at the time of the heat processing in the manufacturing method of the semiconductor light-emitting device concerning the 2nd example of the present invention. It is a cross-sectional schematic diagram which illustrates the structure of the semiconductor light emitting element of a 1st comparative example. FIG. 6 is a schematic cross-sectional view in order of the process of the main part illustrating the method for manufacturing the semiconductor light emitting element of the first comparative example. 3 is a scanning electron micrograph illustrating the structure of the surface of the second electrode of the semiconductor light emitting device according to the first example of the invention and the semiconductor light emitting device of the first comparative example. It is a cross-sectional schematic diagram which illustrates the structure of the semiconductor light-emitting device which concerns on the 3rd Embodiment of this invention. FIG. 10 is a schematic cross-sectional view in order of the process of the main part illustrating the method for manufacturing a semiconductor light emitting element according to the third example of the invention. It is a scanning electron micrograph which illustrates the structure of the surface of the 2nd electrode of the semiconductor light-emitting device which concerns on the 3rd Example of this invention. It is a graph which illustrates the relationship between the heat processing temperature in the semiconductor light-emitting device concerning the 3rd Example of this invention, and the area ratio of the space | gap of a semiconductor light-emitting device. It is a graph which illustrates the relationship between the heat processing temperature in the semiconductor light-emitting device concerning the 3rd Example of this invention, and the optical output of a semiconductor light-emitting device. FIG. 11 is a schematic cross-sectional view in order of the process of the main part illustrating the method for manufacturing the semiconductor light emitting element of the second comparative example. It is a schematic cross-sectional view in order of the process of the principal part illustrating the method for manufacturing the semiconductor light emitting element of the third comparative example. It is a scanning electron micrograph which illustrates the structure of the surface of the 2nd electrode of the semiconductor light-emitting device of a 2nd, 3rd comparative example. It is a scanning electron micrograph which illustrates the structure of the surface of the 2nd electrode of the semiconductor light-emitting device based on the 4th Example of this invention. It is a cross-sectional schematic diagram which illustrates the structure of the semiconductor light-emitting device concerning the 4th Embodiment of this invention. It is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing a semiconductor light emitting element according to the fourth embodiment of the invention. FIG. 10 is a schematic view illustrating the configuration of a semiconductor light emitting element according to a fifth embodiment of the invention. It is a cross-sectional schematic diagram which illustrates the structure of the semiconductor light-emitting device which concerns on the 6th Embodiment of this invention. FIG. 10 is a schematic cross-sectional view illustrating the configuration of another semiconductor light emitting element according to the sixth embodiment of the invention. It is a cross-sectional schematic diagram which illustrates the structure of the semiconductor light-emitting device which concerns on the 7th Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic view illustrating the configuration of a semiconductor light emitting element according to the first embodiment of the invention.
1B is a schematic plan view illustrating the configuration of the semiconductor light emitting device according to the first embodiment of the invention. FIG. 1A is a cross-sectional view taken along line AA ′ of FIG. It is a line section schematic diagram.
As shown in FIGS. 1A and 1B, the semiconductor light emitting device 10 according to the first embodiment of the present invention includes a first semiconductor layer 120, a second semiconductor layer 140, and a first semiconductor layer 120. On the light emitting layer 130 provided between the semiconductor layer 120 and the second semiconductor layer 140, the first electrode 160 provided on the first semiconductor layer 120, and the second semiconductor layer 140 And a second electrode 150 provided.

That is, the semiconductor light emitting device 10 according to this embodiment includes the semiconductor layer 148 including the first semiconductor layer 120, the second semiconductor layer 140, and the light emitting layer 130 sandwiched therebetween. For the semiconductor layer 148, for example, a nitride semiconductor such as Al _x Ga _1-xy In _y N (x ≧ 0, y ≧ 0, x + y ≦ 1) can be used. However, the present invention is not limited to this.
A semiconductor having n-type conductivity can be used for the first semiconductor layer 120, and a semiconductor having p-type conductivity can be used for the second semiconductor layer 140.

In addition, as illustrated in FIG. 1, the semiconductor layer 148 (the first semiconductor layer 120, the light emitting layer 130, and the second semiconductor layer 140) can be formed over the substrate 110. At this time, a method for forming the semiconductor layer 148 is not particularly limited, and for example, a technique such as a metal organic chemical vapor deposition method or a molecular beam epitaxial growth method can be used.
The substrate 110 can be made of a material such as sapphire, SiC, GaN, GaAs, or Si. When a material that transmits light emitted from the light emitting layer 130 is used, such as sapphire, light can be extracted through the substrate 110. On the other hand, in the case where the substrate 110 is formed using a material that does not transmit light emitted from the light-emitting layer 130, the light can be reflected at the interface between the semiconductor layer 148 and the substrate 110 and extracted outside. The substrate 110 may be removed during or after the manufacture of the semiconductor light emitting element. In that case, light emitted from the light-emitting layer 130 can be extracted from the lower surface of the semiconductor layer 148 (the lower surface in FIG. 1A).

For the second electrode 150, for example, at least one of silver and a silver alloy can be used. However, the present invention is not limited to this, and the second electrode 150 only needs to be made of at least one of silver and a silver alloy on the side facing the second semiconductor layer 140.
The material of the conductive film to be the first electrode 150 may be a silver single layer film or a silver alloy layer containing silver and a metal other than silver. The reflection efficiency of many metal single layer films other than silver in the visible light band tends to decrease as the wavelength becomes shorter in the ultraviolet region of 400 nm or less, but silver is also high for light in the ultraviolet region of 370 nm to 400 nm. Reflective efficiency characteristics. For this reason, by using silver or a silver alloy for the second electrode 150, light generated in the light emitting layer 130, particularly light in the ultraviolet band, can be reflected with high efficiency, and the semiconductor light emitting device 10 with high luminance can be realized. it can.
In the ultraviolet light emitting semiconductor light emitting element, when the conductive film to be the second electrode 150 is formed of a silver alloy, the second semiconductor layer 140 side of the conductive film is made of silver as compared with other portions. A higher component ratio is preferred. The film thickness of the conductive film to be the second electrode 150 is preferably thicker than the reciprocal of the absorption coefficient of silver, and more preferably 100 nm or more, in order to ensure light reflection efficiency.

Further, the second electrode 150 has a gap 210 having a width equal to or smaller than the light wavelength of the light emitting layer 130 on the surface facing the second semiconductor layer 140.
As will be described later, this gap 210 can change the optical path of light generated in the light emitting layer 130, suppress the light confinement effect due to total reflection at the interface having a refractive index difference, and has high light extraction efficiency. Can be provided.

  The gap 210 may be provided at least on the interface side of the second electrode 150 with the second semiconductor layer 140, and the gap 210 is provided on the interface of the second electrode 150 with the second semiconductor layer 140. At the same time, the second electrode 150 may be provided on the interface opposite to the second semiconductor layer 140. Further, the gap 210 may be provided in the layer of the second electrode 150 at the same time as being provided at the interface between the second electrode 150 and the second semiconductor layer 140. Further, the gap 210 may be provided through the thickness direction of the second electrode 150. In other words, the gap 210 may be provided at least at the interface of the second electrode 150 on the second semiconductor layer 140 side where light from the semiconductor layer 148 enters.

  Further, the gap 210 of the second electrode 150 can be formed by self-organization by silver migration by high-temperature heat treatment.

  Note that as the material of the first electrode 160, various conductive single-layer films or multilayer films that can be used as the ohmic electrode of the first semiconductor layer 120 can be used as the material of the first electrode 160. A method for forming the first electrode 160 is not particularly limited, and for example, a sintering process may be performed after forming a multilayer structure by an electron beam evaporation method. In the case of performing the sintering process, it is preferable to separately provide a pad on the first electrode 160 in order to improve bondability.

  Note that a pad may be separately provided on the second electrode 150 in order to improve bondability of wire bonding, improve die shear strength when forming gold bumps by a ball bonder, and apply to flip chip mounting. . The film thickness of the pad can be selected between 100 nm and 10,000 nm, for example.

FIG. 2 is an enlarged schematic view illustrating the structure of the main part of the semiconductor light emitting device according to the first embodiment of the invention.
2 and the subsequent drawings, the same reference numerals are given to the same elements as those described above with reference to the previous drawings, and detailed description will be omitted as appropriate.
As shown in FIG. 2, in the semiconductor light emitting device 10 according to the first embodiment of the present invention, the light emitted from the light emitting layer 130 toward the second electrode 150 is incident on a portion other than the gap 210. The reflected light is specularly reflected in accordance with geometric optics like light L. On the other hand, since the width of the gap 210 is smaller than the emission wavelength, the light incident on the gap 210 exhibits a behavior explained by wave optics such as scattering and diffraction. As a result, for example, light X1, X2, and X3 that are scattered and reflected are generated.

As described above, in the semiconductor light emitting device 10 according to this embodiment, by providing the second electrode 150 with the gap 210 having a width equal to or smaller than the wavelength, the interface between the second electrode 150 and the second semiconductor layer 140 is provided. A region of scattering characteristics (diffuse reflection characteristics) can be formed. As a result, light of various angles (for example, light X1, X2, and X3) is generated, and the incident angle with respect to the interface having a difference in refractive index (for example, the interface between the semiconductor layer 148 and the substrate) is shallow, and the inside of the semiconductor light emitting device 10 The incident angle of a part of the light confined in the light can be changed, and the light can be effectively taken out.
Thereby, the semiconductor light emitting device 10 according to the present embodiment can provide a semiconductor light emitting device with high light extraction efficiency.
In general, as the width of the gap 210 becomes smaller than the emission wavelength, the wave nature of the light increases and the component of the light that is scattered and reflected increases. As a result, the light extraction efficiency of the semiconductor light emitting device 10 is improved.

  Here, “specular reflection” refers to reflection with the same incident angle and reflection angle of light as explained by geometric optics, and “diffuse reflection” means that light is omnidirectional as explained by wave optics. It is a scattered reflection.

  In the case of a semiconductor light emitting element using a sapphire substrate, since the difference in refractive index between the substrate 110 and the semiconductor layer 148 is large, most of the emitted light is reflected at the interface and is easily confined inside the semiconductor layer 148. On the other hand, according to the semiconductor light emitting device 10 according to the present embodiment, the light extraction efficiency is improved because the emitted light can be effectively extracted outside the semiconductor layer 148 by diffusely reflecting the emitted light. Is done. Thus, it is effective to apply the semiconductor light emitting device 10 according to the present embodiment to a semiconductor light emitting device using a sapphire substrate.

FIG. 3 is a schematic view illustrating the gap of the semiconductor light emitting element according to the first embodiment of the invention.
That is, FIGS. 3A and 3B illustrate the size (width) of the space when the space has an elliptical shape and a shape other than the elliptical shape, respectively.
As shown in FIG. 3, in the semiconductor light emitting device 10 according to the first embodiment, the width of the gap 210 is the cross-sectional shape of the gap 210 at the interface between the gap 210 and the second semiconductor layer 140. In the case of (FIG. 3A), the major axis S is indicated, and in other cases (FIG. 3B), the linear distance T in the longest gap 210 is indicated.
The width of the gap 210 is the above-described major axis S or linear distance T in the planar shape of the gap 210 in the cross section of the surface of the second electrode 150 facing the second semiconductor layer 140.

It is preferable that the width of the gap 210 be equal to or less than the emission wavelength. The emission spectrum of the semiconductor light emitting device 10 has a half width of about several tens of nanometers. The emission wavelength refers to a peak emission wavelength at which the light output becomes a maximum value with a specified operating current.
When an action body such as the air gap 210 is sufficiently larger than the wavelength of light, the light is treated as a light beam traveling straight, and the behavior of light is explained by geometrical optics including Snell's law. On the other hand, when the effector has the same size as the wavelength of light, the light becomes more waveable, causing a phenomenon that cannot be explained by geometric optics. The light is also bent due to the wave nature of diffraction and scattering. This wave property appears remarkably in the region where the size of the effector is not more than the wavelength. In this region, the behavior of light cannot be calculated strictly based on electromagnetics.

  In general semiconductor light emitting devices, there is a method of forming a non-planar surface (uneven structure) by processing the substrate surface, the semiconductor layer surface, and the surface of the semiconductor layer in contact with the reflective film in order to improve the light extraction efficiency. The surface formed by these methods is a concavo-convex structure having an order of magnitude larger than the wavelength of light, and has a specular reflection characteristic according to geometrical optics when viewed microscopically. On the other hand, in the semiconductor light emitting device 10 according to the present embodiment, the size of the air gap 210 is equal to or less than the wavelength of light, and has wave characteristics that are not explained by geometric optics as described above. Thereby, it is possible to provide a semiconductor light emitting device having high light extraction efficiency that cannot be obtained by other methods.

Note that the higher the density and area ratio of the voids 210 at the interface between the second electrode 150 and the second semiconductor layer 140, the higher the light extraction efficiency. However, if the density and area ratio of the voids 210 are too high, the contact area between the second electrode 150 and the second semiconductor layer 140 may be reduced, and the operating voltage may be increased.
At this time, as in the semiconductor light emitting device 10 illustrated in FIG. 1, when the second electrode 150 and the first electrode 160 are laterally energized such that they are substantially on the same plane, Since current tends to concentrate in a region where the distance from the first electrode 160 is minimized, the decrease in the contact area between the second electrode 150 and the second semiconductor layer 140 due to the gap 210 is as much as the decrease. Does not affect the operating voltage.
In consideration of the balance with the operating voltage, the area ratio of the gap 210 to the total area of the second electrode 150 is preferably 10% or less, and more preferably 5% or less. In the case where a plurality of gaps 210 are provided in the second electrode 150, it is desirable that the majority of the gaps 210 have a width equal to or smaller than the wavelength of the emitted light. By doing so, more than half of the voids 210 cause diffraction and scattering based on the wave nature of light as described above, and the light extraction efficiency can be improved. Further, when a plurality of gaps 210 are provided in the second electrode 150, the average value of the widths of the gaps 210 may be equal to or less than the wavelength of the emitted light. Even in this case, many of the gaps 210 cause diffraction and scattering based on the wave nature of light, and the light extraction efficiency can be improved.

(First embodiment)
Hereinafter, a first example according to the present embodiment will be described.
FIG. 4 is a schematic cross-sectional view illustrating the configuration of the semiconductor light emitting element according to the first example of the invention.
As shown in FIG. 4, the semiconductor light emitting device 11 according to the first example of the present invention has the same structure as the semiconductor light emitting device 10 according to the first embodiment illustrated in FIG.
The planar structure can be the same as that of the semiconductor light emitting device 10 according to this embodiment illustrated in FIG.

The semiconductor light emitting device 11 according to the present example has a high carbon concentration first AlN buffer layer 122 (carbon concentration 3 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ²⁰ cm ⁻³ ) having a film thickness of 3 nm to 20 nm on a substrate 110. ), High-purity second AlN buffer layer 123 (carbon concentration 1 × 10 ¹⁶ cm ^{−3 to} 3 × 10 ¹⁸ cm ⁻³ ) having a thickness of 2 μm, non-doped GaN buffer layer 124 having a thickness of 3 μm, and Si-doped n having a thickness of 4 μm. Type GaN contact layer 125 (Si concentration 1 × 10 ¹⁶ cm ⁻³ to 1 × 10 ¹⁹ cm ⁻³ ), 0.02 μm thick Si-doped n-type AlGaN cladding layer 126 (Si concentration 1 × 10 ¹⁶ cm ⁻³ ) , Si-doped n-type AlGaN barrier layer (Si concentration 1 × ¹⁰ 19 ^{cm -3)} and GaInN light-emitting layer (peak emission wavelength 380nm when the current injection) and three cycles are alternately The light emitting layer 130 having a thickness of 0.075 μm, the non-doped AlGaN spacer layer 142 having a thickness of 0.02 μm, and the Mg-doped p-type AlGaN cladding layer 143 having a thickness of 0.02 μm (Mg concentration 1 × 10 ¹⁹ cm ⁻³ ), a 0.1 μm-thick Mg-doped p-type GaN contact layer 144 (Mg concentration 1 × 10 ¹⁹ cm ⁻³ ), a 0.02 μm-thick Mg-doped p-type GaN contact layer 145 ( A semiconductor layer 148 in which an Mg concentration of 2 × 10 ²⁰ cm ⁻³ ) is stacked.

The semiconductor light emitting device 11 includes a second electrode (p-side electrode) 150 provided with a gap 210 having a width equal to or smaller than the wavelength of light.
Thereby, a semiconductor light emitting device with high light extraction efficiency can be provided.

In the above, the first AlN buffer layer 122, the second AlN buffer layer 123, the non-doped GaN buffer layer 124, the Si-doped n-type GaN contact layer 125, and the Si-doped n-type AlGaN cladding layer 126 are connected to the first semiconductor layer 120. Become.
The non-doped AlGaN spacer layer 142, the Mg-doped p-type AlGaN cladding layer 143, the Mg-doped p-type GaN contact layer 144, and the high-concentration Mg-doped p-type GaN contact layer 145 serve as the second semiconductor layer 140.
The Mg-doped p-type GaN contact layer 144 and the high-concentration Mg-doped p-type GaN contact layer 145 become the p-type GaN contact layer 146.

  Note that the first AlN buffer layer 122 having a high carbon concentration serves to alleviate lattice mismatch with the substrate 110, and particularly reduces screw dislocations.

The high-purity second AlN buffer layer 123 is a layer for flattening the surface at an atomic level and reducing defects in the non-doped GaN buffer layer grown thereon, and for this purpose, the thickness may be thicker than 1 μm. preferable. In addition, 4 μm or less is desirable to prevent warping due to distortion. The high-purity second AlN buffer layer is not limited to AlN, and may be Al _x Ga _1-x N (0.8 ≦ x ≦ 1) and can compensate for wafer warpage.

  Further, the non-doped GaN buffer layer 124 plays a role of reducing defects by three-dimensional island growth on the high purity second AlN buffer layer 123. In order to flatten the growth surface, the average film thickness of the non-doped GaN buffer layer 124 needs to be 2 μm or more. From the viewpoint of reproducibility and warpage reduction, the total film thickness of the non-doped GaN buffer layer 124 is suitably 4 to 10 μm.

  By adopting these buffer layers, it is possible to realize a defect reduction of about 1/10 compared to conventional low-temperature grown AlN buffer layers. With this technique, a highly efficient semiconductor light emitting device can be produced while being highly concentrated Si doped into the n-type GaN contact layer (Si-doped n-type GaN contact layer) 125 and emitting light in the ultraviolet band.

That is, in the case of a general nitride semiconductor layer formed on a sapphire substrate, defects existing in the semiconductor layer 148, low-temperature growth buffer layers that are amorphous or polycrystalline, etc. are light absorbers. There is a loss of light because it is absorbed while the light is reflected.
At this time, by using the single crystal AlN buffer layer (the first AlN buffer layer 122, the high purity second AlN buffer layer 123, and the non-doped GaN buffer layer 124) as in the semiconductor light emitting device 11 according to the present embodiment, Not only is absorption difficult to occur, but defects in the semiconductor layer 148 are reduced, the cause of light absorption in the semiconductor layer 148 can be reduced as much as possible, and loss can be reduced. Thus, by using the single crystal AlN buffer layer, high light extraction efficiency can be obtained even if the density and area ratio of the voids 210 are reduced.

  As described above, the semiconductor light emitting device 11 of this example uses the second electrode (p-side electrode) 150 provided with the gap 210 having a width equal to or smaller than the wavelength of light, and uses a single crystal AlN buffer layer. Thus, not only the absorption in the buffer layer is difficult to occur, but also defects in the semiconductor layer are reduced, and the cause of light absorption in the semiconductor layer can be reduced as much as possible, and a semiconductor light emitting device with high light extraction efficiency is provided. be able to.

In the semiconductor light emitting device 11 of the present embodiment, when the Mg concentration of the Mg-doped p-type GaN contact layer 144 is set as high as 10 ²⁰ cm ⁻³ , the p-type GaN contact layer 146 and the second electrode 150 are set. And ohmic properties are improved. However, in the case of a semiconductor light-emitting diode, unlike the semiconductor laser diode, the distance between the Mg-doped p-type GaN contact layer 144 and the light-emitting layer 130 is short, and thus the Mg concentration of the Mg-doped p-type GaN contact layer 144 is increased. In such a case, there is a concern about deterioration of characteristics due to Mg diffusion. However, in the case of a semiconductor light emitting diode, since the current density at the time of operation is low, by suppressing the Mg concentration to 10 ¹⁹ cm ⁻³ , it is possible to prevent the diffusion of Mg without greatly impairing the electrical characteristics, and the light emitting characteristics. Can be improved.

  Also, by using a single crystal AlN buffer layer, unlike a low temperature growth AlN buffer layer that is amorphous or polycrystalline, the buffer layer is less likely to be an absorber for emitted light, and defects in the semiconductor layer 148 are reduced. Thus, the cause of light absorption in the semiconductor layer 148 can be reduced as much as possible. As a result, the emitted light can be reflected many times at the substrate 110-epitaxial layer interface and the epitaxial layer-p-side electrode 150 interface, so that the emitted light is confined in the epitaxial layer and easily affected by the gap 210. Therefore, even if the density and area ratio of the voids 210 are low, a high effect can be obtained.

(Second Embodiment)
Next, a method for manufacturing a semiconductor light emitting element according to the second embodiment of the present invention will be described.
FIG. 5 is a flowchart illustrating the method for manufacturing the semiconductor light emitting device according to the second embodiment of the invention.
As shown in FIG. 5, in the method for manufacturing a semiconductor light emitting device according to the second embodiment of the present invention, first, a conductive film that becomes the second electrode (p-side electrode) 150 on the semiconductor layer 148. Is formed (step S110). The conductive film can include at least one layer of silver and a silver alloy.
Then, at least one of water and an ionized substance is adhered to the conductive film (step S120).
The conductive film is subjected to high-temperature heat treatment to create a gap in the grain boundary of the conductive film, and at least on the surface of the conductive film facing the second semiconductor layer 140, the wavelength of the light emitted from the semiconductor light emitting element. A gap 210 having the following width is formed (step S130).

As described above, according to the method for manufacturing the semiconductor light emitting device of this embodiment, the conductive film to be the second electrode 150 is migrated, thereby creating a gap in the grain boundary of the conductive film and conducting it in a self-organizing manner. It is possible to provide a manufacturing method in which a gap 210 having a width equal to or smaller than the wavelength of emitted light can be easily formed in the film, and a semiconductor light emitting device having high light extraction efficiency can be easily manufactured.
Note that as described later, a drying step for removing moisture attached to the surface of the semiconductor layer 148 and the like can be provided before the conductive film to be the second electrode 150 is formed. Further, as will be described later, the generation of the gap 210 can be controlled by controlling the temperature condition of the high temperature heat treatment and the temperature lowering rate after the high temperature heat treatment.

(Second embodiment)
Hereinafter, a method for manufacturing a semiconductor light emitting element according to the second example of the embodiment will be described. That is, the second example is an example of a method for manufacturing the semiconductor light emitting device 11 according to the first example.
FIG. 6 is a schematic cross-sectional view in order of the processes, illustrating a method for partially manufacturing a semiconductor light emitting element according to the second example of the invention.
FIG. 6A is a diagram of the first process, and FIGS. 6B and 6C are diagrams following the previous diagram.
As shown in FIG. 6A, in the method for manufacturing the semiconductor light emitting device 11 according to the second embodiment of the present invention, first, the surface is made of sapphire c-plane by using metal organic vapor phase epitaxy. On the substrate 110, a high carbon concentration first AlN buffer layer 122, a high purity second AlN buffer layer 123, a non-doped GaN buffer layer 124, a Si-doped n-type GaN contact layer 125, a Si-doped n-type AlGaN cladding layer 126, a Si-doped Light emitting layer 130 having a multiple quantum well structure in which n-type AlGaN barrier layers and GaInN light emitting layers are alternately stacked three periods, non-doped AlGaN spacer layer 142, Mg-doped p-type AlGaN cladding layer 143, Mg-doped p-type GaN contact layer 144, a high-concentration Mg-doped p-type GaN contact layer 145 was laminated in this order. The film thicknesses of these layers and the concentrations of carbon, Si, and Mg are as described in the first embodiment.

  Then, as shown in FIG. 6B, the p-type semiconductor layer is formed by dry etching using a mask until the n-type contact layer 125 is exposed on the surface in a part of the semiconductor layer 148. (Second semiconductor layer) 140, light emitting layer 130, and Si-doped n-type AlGaN cladding layer 126 were removed.

Then, as shown in FIG. 6C, a thermal CVD (Chemical Vapor Deposition) apparatus is used for the entire semiconductor layer 148 including a part of the exposed n-type semiconductor layer (first semiconductor layer) 140. The SiO ₂ film 310 was laminated with a film thickness of 400 nm.

  Then, the p-side electrode 150 is formed thereon. A method for forming the p-side electrode 150 will be described in detail below. That is, hereinafter, only the region 300 where the p-side electrode 150 is formed as illustrated in FIG. 6C will be described.

FIG. 7 is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing a semiconductor light emitting device according to the second example of the invention.
FIG. 7A is a diagram of the first step, and FIGS. 7B, 7C, and 7D are diagrams following the previous diagram.
FIG. 8 is a schematic cross-sectional view in order of the processes following FIG.

FIG. 7A is an enlarged schematic cross-sectional view of the region 300 in which the SiO ₂ film 310 is formed on the semiconductor layer illustrated in FIG.
First, as illustrated in FIG. 7B, a lift-off resist 320 is formed in a predetermined pattern on the semiconductor layer 148 on which the SiO ₂ film 310 is formed, and the p-type GaN contact layer 146 is formed on the p-type GaN contact layer 146. A part of the SiO ₂ film 310 was removed by an ammonium fluoride treatment, and water on the wafer (in this case, the substrate 110, the semiconductor layer 148, and the SiO ₂ film 310) was blown off by air blow or a spin dryer.
At this time, as shown in FIG. 7C, when the moisture on the wafer is just blown off, a slight amount of moisture remains on the wafer surface in an uncontrolled state.
Therefore, thereafter, as shown in FIG. 7D, the moisture on the wafer was sufficiently dried and removed.

Then, as shown in FIG. 8A, silver (Ag), platinum (Pt), and titanium (Ti) are formed in this order in a total thickness of 200 nm on the entire wafer by a vacuum deposition apparatus, and p A conductive film 151 for forming the side electrode 150 was formed. Note that the conductive film 151 can be formed using at least one of silver and a silver alloy.
Then, as shown in FIG. 8B, the resist 320 is dissolved with an organic solvent, and only the conductive film 151 formed on the resist 320 is removed, washed sufficiently with ultrapure water, and then heated at 120 ° C. The wafer was thoroughly dried on the plate. In this way, the p-side electrode 150 was formed in the region where the SiO ₂ film 310 was removed.
Then, as shown in FIG. 8C, the sample is left in a clean room in which the temperature and humidity are controlled at 25 ° C. ± 1 ° C. and 50% ± 1% for 24 hours, respectively, on the surface of the formed p-side electrode 150. A slight amount of water (moisture) 330 and ionized substance 340 were attached.
Then, as shown in FIG. 8D, using a rapid thermal annealing (RTA) apparatus, the temperature of the wafer is raised to 800 ° C. at 5 ° C./second in a nitrogen atmosphere, and in a nitrogen atmosphere at 800 ° C. An air gap 210 was formed at the interface between the p-type GaN contact layer 146 and the p-side electrode 150 by performing heat treatment for 1 minute and lowering the temperature to 0.5 ° C./second to room temperature. That is, migration was generated in the conductive film 151, gaps were formed in the grain boundaries of the conductive film 151, and the voids 210 could be formed.

Thereafter, in order to form the first electrode (n-side electrode) 160, a patterned lift-off resist (not shown) is formed on the semiconductor layer, and the n-type contact layer 125 exposed from the resist is formed. The SiO ₂ film 310 was removed by an ammonium fluoride treatment.
Then, a thin film made of Ti / Pt / Au was formed on the entire wafer with a film thickness of 500 nm by a vacuum deposition apparatus, and an n-side electrode 160 was formed in a region where the SiO ₂ film 310 was removed by a lift-off method.
Thereafter, the back surface of the substrate 110 was polished and cleaved or cut with a diamond blade or the like to form the semiconductor light emitting device 11.

As described above, in the method for manufacturing a semiconductor light emitting device of this example, the gap 210 is self-organized by silver migration by high-temperature heat treatment at least on the interface side of the p-side electrode 150 with the second semiconductor layer 140. Can be formed.
That is, the high-temperature heat treatment of the p-side electrode 150 generates a thermal stress due to a difference in thermal expansion coefficient between different materials, the stress concentrates on the grain boundary, and attempts to relieve the stress. As the pores diffuse and move, voids 210 are formed along the grain boundaries.

At this time, in order to improve the reproducibility of formation of the size and density of the gap 210, it is necessary to control the migration of the p-side electrode 150 (conductive film 151).
For this reason, the adhesion of moisture and ionized substances to the wafer, which has an effect of promoting migration, is controlled.

  In the manufacturing method of the present embodiment, moisture and an ionizing substance (migration promoting substance) that promote migration are attached with good reproducibility by leaving the wafer in a space where temperature and humidity are controlled for a certain period of time. In addition, the method of leaving it in the constant temperature and humidity chamber which can control temperature and humidity may be used. Note that specific conditions for adhesion of these migration promoting substances vary depending on the characteristics of the conductive film 151 and the semiconductor layer 148 used, the processing conditions of the wafer, and the like, and are appropriately determined based on these conditions.

  In each step before and after the formation of the p-side electrode 150, the adhesion of the migration promoting substance (water or ionized substance) is prevented as much as possible. Specifically, for example, after each wet treatment step before and after the formation of the p-side electrode 150, the substrate is sufficiently washed with ultrapure water and sufficiently dried. In addition, air blow and spin dryer performed after cleaning seemed to be able to remove moisture on the wafer, but some moisture or moisture remaining on the wafer surface remained, and resist was formed. When heat treatment is performed in a state immediately before the formation of the conductive film 151 using a hot plate or an oven, the organic solvent evaporates from the resist and adheres to the surface of the semiconductor layer 148, and reproduction of migration of the p-side electrode 150 formed thereon is reproduced. Therefore, the drying method needs to be devised as described above.

  Further, as described above, the formation of the gap 210 by migration is performed with high reproducibility by slowing the high temperature heat treatment and the temperature drop rate after the heat treatment.

As described above, in the method for manufacturing a semiconductor light emitting device of this example, the adhesion of moisture and ionized substances to the wafer, which has the effect of promoting migration, is controlled, and the high temperature heat treatment and the temperature drop rate after the heat treatment are slowed down. By doing so, the gap 210 having a width equal to or smaller than the wavelength can be formed with good reproducibility.
The migration promoting substance includes, for example, water, an ionized substance (a substance having a relatively high ionization tendency and various compounds thereof), and various organic substances derived from, for example, a resist.

Hereinafter, the mechanism for forming the void 210 by heat treatment will be described in detail.
FIG. 9 is a schematic diagram showing the behavior of crystal grains (grains) during heat treatment in the method for manufacturing a semiconductor light emitting device according to the second embodiment of the present invention.
As shown in FIG. 9, a material that easily migrates, such as silver, exhibits a behavior that minimizes the surface area during heat treatment, as well as the surface tension that is a property of liquid.

  That is, when the conductive film 151 (silver or silver alloy thin film) formed on the semiconductor layer 148 is heat-treated, a thermal stress is generated due to a difference in thermal expansion coefficient between different materials, and metal atoms try to relieve the stress. Moving. At that time, since the metal atoms in the crystal grains 220 try to attract each other and condense, the metal atoms in the vicinity of the grain boundary 230 diffuse and move to the center of the crystal grain 220, and a void 210 is generated in the grain boundary 230.

The surface roughness of the conductive film 151 is, for example, about 1.5 nm before the heat treatment, but increases to, for example, about 2.5 nm because the crystal grains 220 rise slightly after the heat treatment. Increasing the heat treatment temperature increases the diffusion rate of metal atoms according to Arrhenius' law, but the stress due to thermal stress decreases. In addition, since another equilibrium reaction occurs in which the crystal grains 220 are bonded to each other, the width of the gap 210 and the density of the gap 210 in the surface of the p-side electrode 150 have maximum values at a certain heat treatment temperature.
The width of the air gap 210 and the density and area ratio in the surface of the p-side electrode 150 are the state of the migration promoting substance (that is, the conditions of the standing process for a certain period of time before the heat treatment, etc.), the heat treatment conditions (heat treatment temperature, time, temperature increase / decrease rate). Etc.), and the type, film thickness, laminated structure, and the like of the conductive film 151 can be controlled.

As described above, when a laminated structure using silver or a silver alloy that is easily migrated is used at least on the interface side with the semiconductor layer 148 as the p-side electrode 150, the void 210 is formed on the interface on the semiconductor layer 148 side. Can do.
As already described, since the light output varies depending on the density and area ratio of the gaps 210, the above manufacturing conditions can be changed in consideration of productivity and light output efficiency.

  Thus, by adopting an electrode sintering process (high-temperature heat treatment process) in which silver contained in the p-side electrode 150 is likely to cause migration, the diffuse reflection region (void 210) can be formed by self-organization. A low-cost semiconductor light emitting device can be realized.

(First comparative example)
Next, the structure of the semiconductor light emitting device of the first comparative example and the manufacturing method thereof will be described.
FIG. 10 is a schematic cross-sectional view illustrating the configuration of the semiconductor light emitting element of the first comparative example.
As shown in FIG. 10, in the semiconductor light emitting device 91 of the first comparative example, the gap 210 is not provided in the second electrode 150. The rest is the same as the semiconductor light emitting device 11 of the first embodiment illustrated in FIG.

Hereinafter, a method for manufacturing the semiconductor light emitting device 91 of the first comparative example will be described. The manufacturing method of the semiconductor light emitting device of the first comparative example can be the same as the manufacturing method of the semiconductor light emitting device of the second embodiment until the step of forming the semiconductor layer 148. A manufacturing method will be described.
FIG. 11 is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing the semiconductor light emitting element of the first comparative example.
FIG. 11A is a diagram of the first step, and FIGS. 11B to 11E are diagrams following the previous diagram.
FIG. 11A is an enlarged view of the region 300 in which the SiO ₂ film 310 is formed on the semiconductor layer.
First, as shown in FIG. 11B, as in the first embodiment, a lift-off resist 320 is formed in a predetermined pattern on the semiconductor layer 148 on which the SiO ₂ film 310 is formed. A part of the SiO ₂ film 310 on the GaN contact layer 146 was removed by ammonium fluoride treatment, and water on the wafer was blown off by air blow, spin dryer or the like.
In this state, as illustrated in FIG. 11C, a slight amount of moisture remains uncontrolled on the wafer surface.
Then, as shown in FIG. 11D, a conductive film 151 for forming a p-side electrode by forming a film with a total thickness of 200 nm in the order of Ag, Pt, and Ti on the entire wafer by a vacuum evaporation apparatus. Formed.
Then, as shown in FIG. 11E, the resist 320 is dissolved with an organic solvent, only the conductive film 151 formed on the resist 320 is removed, washed with ultrapure water, and dried to obtain SiO _2. A p-side electrode 150 was formed in the region where the film 310 was removed.
Then, using an RTA apparatus, the temperature was raised to 350 ° C. at 5 ° C./second in a nitrogen atmosphere, heat treatment was performed for 1 minute in a nitrogen atmosphere at 350 ° C., and the temperature was lowered to room temperature at 5 ° C./second. In this way, the semiconductor light emitting device 91 of the first comparative example illustrated in FIG. 10 was formed.

  That is, in the manufacturing method of the semiconductor light emitting device 91 of the first comparative example, the conductive film 151 for the p-side electrode 150 illustrated in FIG. 7D in the manufacturing method of the second embodiment of the present invention is formed. The drying step before film formation and the migration promoting substance attaching step illustrated in FIG. 8C are omitted.

Hereinafter, evaluation results of the semiconductor light emitting device 11 of the first example formed as described above and the semiconductor light emitting device 91 of the first comparative example will be described.
FIG. 12 is a scanning electron micrograph illustrating the structure of the surface of the second electrode of the semiconductor light emitting device according to the first example of the invention and the semiconductor light emitting device of the first comparative example.
12A corresponds to the semiconductor light emitting element 11 of the first example, and FIG. 12B corresponds to the semiconductor light emitting element 91 of the first comparative example.
As shown in FIG. 12B, the second electrode (p-type electrode) 150 in the semiconductor light emitting device 91 of the first comparative example cannot confirm any characteristic image, and has almost the same surface as before the heat treatment. It was in a state. That is, no gap was formed in the p-side electrode 150 of the semiconductor light emitting device 91. And in evaluation of the surface roughness with an atomic force microscope, it was about 1.7 nm which is substantially equivalent to that before the heat treatment.

  On the other hand, as shown in FIG. 12A, a granular image (a portion with low luminance in the drawing) 291 was observed on the p-side electrode 150 of the semiconductor light emitting device 11 of the first example. The size of the granular image 291 in plan view was about 0.3 μm in diameter on average. As a result of further analysis using a scanning electron microscope, an atomic force microscope, or the like, the upper side of the granular image 291 (the opposite surface of the second semiconductor layer 120) is relatively flat, and the upper side of the portion of the granular image 291. The surface roughness of this surface is about 2.6 nm, which is the same as the region other than the granular image 291, and the granular image 291 is formed in the gap 210 formed at the interface of the second semiconductor layer 140 of the p-side electrode 150. I found out. It was found that the upper side of the gap 210 (the side opposite to the second semiconductor layer 140) was capped by the p-side electrode 150.

  The void 210 was formed at the grain boundary 230 of the silver alloy of the p-side electrode 150.

In the semiconductor light emitting device 11 according to this example, the p-side electrode 150 uses a conductive film 151 made of Ag, Pt, and Ti. Although Ag and Pt mutually diffuse due to the high temperature heat treatment, a metal layer mainly composed of titanium remains on the surface, and voids 210 are formed in the grain boundaries 230 due to migration of the silver alloy.
The area ratio of the void 210 in the surface of the p-side electrode 150 was about 0.9%.

Note that a flat region without a gap 210 (a halftone portion of luminance in the figure) 292 shows ohmic characteristics and high-efficiency specular reflection characteristics, and the gap 210 shows diffuse reflection characteristics. The void 210 contains nitrogen gas in a vacuum or a heat treatment atmosphere, and the refractive index is considered to be almost 1 in any case. Therefore, the refractive index difference with the p-type GaN contact layer 146 is large and total reflection is easy. Structure.
Further, since there is no light absorber in the gap 210, there is little absorption loss due to repeated reflection. Further, it is considered that there is almost no moisture or ionized substance in the gap 210, and the deterioration of the p-side electrode 150 is suppressed, so that the reliability is improved.
Due to these effects, according to the semiconductor light emitting device 11 according to the first embodiment, it is possible to provide a semiconductor light emitting device with high light extraction efficiency and high reliability.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described.
FIG. 13 is a schematic cross-sectional view illustrating the configuration of a semiconductor light emitting element according to the third embodiment of the invention.
As shown in FIG. 13, in the semiconductor light emitting device 30 according to the third embodiment of the present invention, the gap 210 of the second electrode (p-side electrode) 150 is only at the interface with the second semiconductor layer 140. The p-side electrode 150 is continuously provided up to the opposite surface of the second semiconductor layer 140. That is, the gap 210 is provided through the layer of the p-side electrode 150 in the layer thickness direction. Except for the shape of the gap 210, the semiconductor light emitting device 10 has the same structure as that of the semiconductor light emitting device 10 according to the first embodiment illustrated in FIG. 1, and the planar structure of the semiconductor light emitting device 30 is the same as that of the semiconductor light emitting device 10. Since it can do, explanation is omitted.

  As described above, the gap 210 is also generated in the light emitting layer 130 by the gap 210 even by the semiconductor light emitting element 30 provided through the p-side electrode 150 continuously in the thickness direction of the p-side electrode 150. Therefore, the light confinement effect due to total reflection at the interface having a difference in refractive index can be suppressed, and a semiconductor light emitting device with high light extraction efficiency can be provided.

  Also in the semiconductor light emitting device 30 of the present embodiment, it is amorphous or polycrystalline by using the single crystal AlN buffer layer (the first AlN buffer layer 122, the high purity second AlN buffer layer 123, and the non-doped GaN buffer layer 124). Unlike a certain low-temperature grown AlN buffer layer, the buffer layer is unlikely to be an absorber for the emitted light, can reduce defects in the semiconductor layer, and can reduce factors that cause light absorption in the semiconductor layer as much as possible. As a result, the emitted light can be repeatedly reflected many times at the interface between the substrate 110 and the epitaxial layer (semiconductor layer 148) and at the interface between the epitaxial layer (semiconductor layer 148) and the p-side electrode 150. Since light is confined in the epitaxial layer (semiconductor layer 148) and easily affected by the gap 210, high light extraction efficiency can be obtained even if the density and area ratio of the gap 210 are low.

(Third embodiment)
Hereinafter, a method for manufacturing a semiconductor light emitting device having this structure will be described.
The manufacturing method of the semiconductor light emitting device of the third embodiment is a modification of a part of the manufacturing method of the semiconductor light emitting device of the second embodiment illustrated in FIGS. At this time, the heat treatment temperature of the p-side electrode 150 was changed, the density of the gap 210 was changed, and the relationship between the gap 210 and the light output was examined.

FIG. 14 is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing a semiconductor light emitting element according to the third example of the invention.
FIG. 14A is a diagram of the first step, and FIGS. 14B to 14G are diagrams following the previous diagram.
That is, as illustrated in FIG. 14A, after providing the SiO ₂ film 310 on the semiconductor layer 148, the patterned lift-off resist 320 is formed on the semiconductor layer 148 in order to form the p-side electrode 150. A part of the SiO ₂ film formed on the p-type GaN contact layer 146 was removed by an ammonium fluoride treatment.
At this time, as shown in FIG. 14B, when the moisture on the wafer is just blown off, a slight amount of moisture remains on the wafer surface without being controlled.
Thereafter, as shown in FIG. 14C, moisture on the wafer was sufficiently dried and removed.

  Then, as shown in FIG. 14D, an Ag single layer film having a film thickness of 200 nm was formed as the conductive film 151 on the entire wafer by a vacuum deposition apparatus.

Then, as shown in FIG. 14E, the resist 320 is dissolved with an organic solvent, only the conductive film 151 formed on the resist 320 is removed, and sufficiently washed with ultrapure water, and then heated at 120 ° C. The wafer was thoroughly dried on the plate. In this way, the p-side electrode 150 was formed in the region where the SiO ₂ film 310 was removed.
Then, as shown in FIG. 14 (f), it is left in a clean room where the temperature and humidity are controlled at 25 ° C. ± 1 ° C. and 50% ± 1%, respectively, for 24 hours, and on the surface of the formed p-side electrode 150. A small amount of moisture 330 and ionized material 340 were attached.
Then, as shown in FIG. 14G, heat treatment is performed for 1 minute in a nitrogen atmosphere at three temperatures of 450 ° C., 700 ° C., and 800 ° C. using an RTA apparatus, and 0.5 ° C. / By lowering the temperature to room temperature in seconds, a gap 210 was formed at the interface between the p-type GaN contact layer 146 and the p-side electrode 150.

  Thereafter, similarly to the second example, the first electrode (n-side electrode) 160 was formed, and the semiconductor light emitting device of this example was formed.

  That is, in the case of the second embodiment, the p-side electrode 150 is made of Ag, Pt, and Ti, and the heat treatment temperature by RTA is 800 ° C. However, in this embodiment, the p-side electrode 150 is made of Ag alone. It is a layer film, and the heat treatment temperature by RTA is changed to three types of 450 ° C., 700 ° C. and 800 ° C.

FIG. 15 is a scanning electron micrograph illustrating the structure of the surface of the second electrode of the semiconductor light emitting device according to the third example of the invention.
That is, FIG. 15 is a photograph of a scanning electron microscope image of the surface of the p-side electrode 150 of the semiconductor light emitting device formed at a heat treatment temperature of 800 ° C.
As shown in FIG. 15, a granular image 291 having a diameter of about 0.1 μm on average was observed. As a result of further analysis using a scanning electron microscope, an atomic force microscope, or the like, a void 210 such as a hole penetrating from the surface of the p-side electrode 150 to the p-type GaN contact layer 146 is formed in the silver grain boundary 230. I found out. That is, it was found that the silver of the p-side electrode 150 caused migration due to the high-temperature heat treatment, and voids 210 were formed at the grain boundaries 230.

Hereinafter, the evaluation results of the semiconductor light emitting device by the method for manufacturing the semiconductor light emitting device according to the third embodiment will be described.
FIG. 16 is a graph illustrating the relationship between the heat treatment temperature and the area ratio of the gaps in the semiconductor light emitting device in the semiconductor light emitting device according to the third example of the invention.
In FIG. 16, the horizontal axis represents the temperature of the RTA heat treatment, and the vertical axis represents the area ratio of the gap 210 in the p-side electrode 150 plane.

As shown in FIG. 16, in the semiconductor light emitting device of the third example, the area ratio of the gap 210 in the surface of the p-side electrode 150 is 0.5 ° C. at the heat treatment temperatures of 450 ° C., 700 ° C., and 800 ° C., respectively. %, 1.2%, and 0.8%. Thus, the area ratio of the voids 210 showed a maximum value at a heat treatment temperature of 700 ° C.
Increasing the heat treatment temperature increases the diffusion rate of metal atoms according to Arrhenius' law, but the stress due to thermal stress decreases. Since another equilibrium reaction in which the crystal grains 220 are bonded to each other also occurs, the area ratio of the void 210 in the p-side electrode 150 takes a maximum value at a certain temperature. In this example, the area ratio of the voids 210 had a maximum value when the heat treatment temperature was 700 ° C.

FIG. 17 is a graph illustrating the relationship between the heat treatment temperature and the light output of the semiconductor light emitting device in the semiconductor light emitting device according to the third example of the invention.
In FIG. 17, the horizontal axis represents the temperature of the RTA heat treatment, and the vertical axis represents the light output of the semiconductor light emitting device. The data for the heat treatment temperature of 350 ° C. in the figure shows data for a comparative example in which no gap is formed in the p-side electrode 150.
This figure illustrates the light output of the semiconductor light emitting device of the comparative example in which the gap 210 is not formed in the p-side electrode 150 as 1, and the light output of the semiconductor light emitting device of this example as a relative ratio. As shown in FIG. 17, in the semiconductor light emitting device of this example, the light output is larger than that of the comparative example having no gap. By forming the gap 210, the light output is improved by about 30% at the maximum. I found out.
Thus, according to the semiconductor light emitting device of this example, a semiconductor light emitting device with high light extraction efficiency can be provided.

(Second and third comparative examples)
Hereinafter, as a comparative example, a second comparative example in which no gap is formed and a third comparative example in which a huge gap having poor reproducibility is formed will be described.
FIG. 18 is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing the semiconductor light emitting element of the second comparative example.
FIG. 18A is a diagram of the first step, and FIGS. 18B to 18E are diagrams following the previous diagram, respectively.
As shown in FIG. 18A, after the SiO ₂ film 310 is formed on the semiconductor layer 148, a lift-off resist 320 is formed in a predetermined pattern, and the SiO ₂ film on the p-type GaN contact layer 146 is formed. A part of 310 was removed by an ammonium fluoride treatment, and water on the wafer was blown off by air blow or a spin dryer.
At this time, as shown in FIG. 18B, when the moisture on the wafer is just blown away, a slight amount of moisture remains on the wafer surface in an uncontrolled state.
Therefore, thereafter, as shown in FIG. 18C, the moisture on the wafer was sufficiently dried and removed.

Then, as shown in FIG. 18D, after a silver single layer film is formed at 200 nm on the entire wafer by a vacuum deposition apparatus, the resist 320 is dissolved by an organic solvent, and the conductive film formed on the resist 320 is formed. After removing only 151 and sufficiently washing with ultrapure water, the wafer was sufficiently dried on a hot plate at 120 ° C. to form the p-side electrode 150 in the region where the SiO ₂ film 310 was removed.
Then, as shown in FIG. 18E, using an RTA apparatus, the temperature is raised to 800 ° C. at 5 ° C./second in a nitrogen atmosphere, and heat treatment is performed for 1 minute in the nitrogen atmosphere at 800 ° C. The temperature dropped to room temperature in seconds.

  That is, in the method for manufacturing the semiconductor light emitting device of the second comparative example, the step of attaching the migration promoting substance illustrated in FIG. 14F in the method for manufacturing the semiconductor light emitting device of the third embodiment of the present invention is omitted. Has been.

FIG. 19 is a schematic cross-sectional view in order of steps of the main part illustrating the method for manufacturing the semiconductor light emitting element of the third comparative example.
FIG. 19A is a diagram of the first step, and FIGS. 19B to 19D are diagrams following the previous diagram.
As shown in FIG. 19A, after the SiO ₂ film 310 is formed on the semiconductor layer 148, a lift-off resist 320 is formed in a predetermined pattern, and the SiO ₂ film on the p-type GaN contact layer 146 is formed. A part of 310 was removed by an ammonium fluoride treatment, and water on the wafer was blown off by air blow or a spin dryer.
At this time, as shown in FIG. 19B, when the moisture on the wafer is just blown off, a slight amount of moisture remains on the wafer surface in an uncontrolled state.
And as represented to FIG.19 (c), the silver single layer film was formed in 200 nm over the whole wafer with the vacuum evaporation system.

Then, as shown in FIG. 19 (d), the resist 320 is dissolved with an organic solvent, and only the conductive film 151 formed on the resist 320 is removed, washed sufficiently with ultrapure water, and then heated at 120 ° C. The wafer was sufficiently dried on the plate, and the p-side electrode 150 was formed in the region where the SiO ₂ film 310 was removed.
Then, as shown in FIG. 19E, using an RTA apparatus, the temperature is raised to 800 ° C. at 5 ° C./second in a nitrogen atmosphere, and heat treatment is performed for 1 minute in the nitrogen atmosphere at 800 ° C. The temperature dropped to room temperature in seconds.

  That is, in the method for manufacturing the semiconductor light emitting device of the third comparative example, the conductive film for the p-side electrode 150 illustrated in FIG. 14C in the method for manufacturing the semiconductor light emitting device of the third embodiment of the present invention. The drying step before forming the film 151 and the migration promoting substance attaching step illustrated in FIG. 14F are omitted.

FIG. 20 is a scanning electron micrograph illustrating the structure of the surface of the second electrode of the semiconductor light emitting device of the second and third comparative examples.
That is, FIG. 20A corresponds to the second comparative example, and FIG. 20B corresponds to the third comparative example.
As shown in FIG. 20A, in the semiconductor light emitting device of the second comparative example, a process of sufficiently drying and suppressing migration is performed before the conductive film 151 to be the p-side electrode 150 is formed. Therefore, no voids are formed despite the same electrode structure as in the second embodiment and heat treatment conditions of 800 ° C. The image visible in the figure is the grain boundary 230.

On the other hand, as shown in FIG. 20B, in the semiconductor light emitting device of the third comparative example, the size of the gap (not shown) despite the same electrode structure and the heat treatment condition of 800 ° C. as those of the third example. (Width) extends to about 1 μm. In addition, the semiconductor light emitting device of the third comparative example was created a plurality of times with the same process flow, but there was no reproducibility of the size and density of the gap 210.
This is because in the third comparative example, the conductive film 151 to be the p-side electrode 150 was formed in a state where it was not sufficiently dried, and the heat treatment was performed without sufficiently drying after the lift-off. It is considered that this migration was promoted excessively, and the gap 210 was enlarged. Further, even in the same process flow, when the dry state happened to be good, the size of the gap 210 was suppressed, and as a result, the size of the gap could not be controlled.

  As shown in the semiconductor light emitting devices of the second comparative example and the third comparative example, a drying process before forming the conductive film 151 for the p-side electrode 150, a migration promoting substance attaching process, etc. If no special treatment is performed, the void 210 is not formed or a huge void 210 with low reproducibility is formed. Therefore, when forming the semiconductor light emitting device according to this embodiment, as described in the third example, a drying process before forming the conductive film 151 for the p-side electrode 150 or a migration promoting substance is performed. A special treatment such as an adhesion process is required.

(Fourth embodiment)
The semiconductor light emitting element according to the fourth embodiment will be described below.
The semiconductor light emitting device 31 (not shown) of the present example is obtained by changing the material used for the p-side electrode 150 to Ag and Pt with respect to the third semiconductor light emitting device 30 described above. Since the other parts are the same as those of the third semiconductor light emitting element 30, the description thereof is omitted.

The manufacturing method of the principal part of the semiconductor light emitting element 31 according to the present example is as follows.
First, a part of the SiO ₂ film 310 was removed by ammonium fluoride treatment, and water on the wafer was blown off by air blow, spin dryer, or the like, and then the slight water remaining on the wafer surface was sufficiently dried and removed. Then, in order to form the p-side electrode 150, a thin film (conductive film 151) with a total thickness of 200 nm is formed in the order of Ag and Pt on the entire wafer by a vacuum evaporation apparatus, and the SiO ₂ film 310 is formed by a lift-off method. A p-side electrode 150 was formed in the removed region. Then, it was left in a clean room where the temperature and humidity were controlled at 25 ° C. ± 1 ° C. and 50% ± 1% for 24 hours, respectively, and a migration promoting substance (slight moisture 330 or ionized substance 340) was adhered. Thereafter, using an RTA apparatus, heat treatment was performed in a nitrogen atmosphere at 800 ° C. for 1 minute, and a void 210 was formed in the p-side electrode 150. That is, the semiconductor light emitting device according to this example was manufactured under the same conditions as those of the semiconductor light emitting device of the third example except that the material of the conductive film 151 was changed.

FIG. 21 is a scanning electron micrograph illustrating the structure of the surface of the second electrode of the semiconductor light emitting device according to the fourth example of the invention.
As shown in FIG. 21, in the semiconductor light emitting device 31 according to the fourth example of the present invention, a granular image 291 having a diameter of about 0.2 μm on average was observed. As a result of further analysis using a scanning electron microscope, an atomic force microscope, etc., it was found that voids 210 such as holes penetrating to the p-type GaN contact layer 146 were formed at the grain boundaries of the silver alloy. That is, the gap 210 penetrating the p-side electrode 150 was formed.
Silver and platinum are mutually diffused by high-temperature heat treatment, and voids 210 are formed at the grain boundaries by migration of the silver alloy. The area ratio of the gap 210 in the plane of the p-side electrode 150 was 2.9%.
Also in the semiconductor light emitting device 31 according to the fourth embodiment, a semiconductor light emitting device with high light extraction efficiency can be provided by the gap 210 having a width equal to or smaller than the wavelength of light provided in the p-side electrode 150.

(Fourth embodiment)
FIG. 22 is a schematic cross-sectional view illustrating the configuration of a semiconductor light emitting element according to the fourth embodiment of the invention.
As shown in FIG. 22, the semiconductor light emitting device 40 according to the fourth embodiment of the present invention further includes a transparent electrode 410 provided between the second electrode 150 and the second semiconductor layer 140. Except for the transparent electrode 410, the semiconductor light emitting device 30 according to the third embodiment illustrated in FIG. In the semiconductor light emitting device 40 illustrated in FIG. 22, the second electrode 150 has a gap 210 that penetrates the layer of the second electrode 150. However, the present invention is not limited to this, and the gap 210 may be formed only at the interface of the second electrode 150 on the second semiconductor layer 140 side as in the semiconductor light emitting device 10 illustrated in FIG. .
For the transparent electrode 410, a material having a band gap larger than the emission wavelength of the light emitting layer 130 or a metal film having a thickness sufficiently smaller than the reciprocal of the absorption coefficient at the emission wavelength can be used. For the transparent electrode 410, for example, nickel, indium tin oxide (ITO), zinc oxide, or the like can be used.

  The transparent electrode 410 is in electrical contact with the second semiconductor layer 140 and the second electrode 150. Since the transparent electrode 410 has a role of transmitting light from the light emitting layer 130 and reflecting it by the second electrode 150, the shape in plan view is substantially the same as the second electrode 150. It is preferable that The film thickness of the transparent electrode 410 is not particularly limited, and can be selected from 1 nm to 500 nm, for example.

FIG. 23 is a schematic cross-sectional view in order of the steps of the main part illustrating the method for manufacturing a semiconductor light emitting element according to the fourth embodiment of the invention.
FIG. 23A is a diagram of the first step, and FIGS. 23B to 23G are diagrams following the previous diagram.
That is, as shown in FIG. 23A, after providing the SiO ₂ film 310 on the semiconductor layer 148, a patterned lift-off resist is formed on the semiconductor layer 148 in order to form the first electrode 150. A portion of the SiO ₂ film on the second semiconductor layer 140 is removed by an ammonium fluoride treatment, and ITO is deposited on the region where the SiO ₂ film 310 is removed using a vacuum deposition apparatus to form a 100 nm film. After the lift-off, a transparent electrode 410 is formed by performing a sintering process for 1 minute in a nitrogen atmosphere at 550 ° C. Further, a patterned lift-off resist 320 is formed on the semiconductor layer 148.

At this time, as shown in FIG. 23B, in the state where the moisture on the wafer is just blown off, a slight amount of moisture remains on the wafer surface.
Thereafter, as shown in FIG. 23C, moisture on the wafer is sufficiently dried and removed.
Then, as shown in FIG. 23D, for example, an Ag single layer film having a film thickness of 200 nm is formed as the conductive film 151 to be the second electrode 150 on the entire wafer by a vacuum deposition apparatus.
Then, as shown in FIG. 23 (e), the resist 320 is dissolved with an organic solvent, only the conductive film 151 formed on the resist 320 is removed, and sufficiently washed with ultrapure water. Allow the wafer to dry thoroughly on the plate. In this way, the first electrode 150 is formed in the region where the SiO ₂ film 310 has been removed.
Then, as shown in FIG. 23F, the surface of the formed second electrode 150 is left in a clean room where the temperature and humidity are controlled to 25 ° C. ± 1 ° C. and 50% ± 1% for 24 hours, respectively. Further, a slight amount of moisture 330 or ionized material 340 is attached.
Then, as shown in FIG. 23 (g), by using the RTA apparatus, heat treatment is performed in a nitrogen atmosphere at a temperature of 550 ° C. for 1 minute, and the temperature is lowered to room temperature at 0.5 ° C./second, so that the second A gap 210 is formed at the interface between the semiconductor layer 140 and the second electrode 150.
Then, as already described, the first electrode 160 is formed, and the semiconductor light emitting device 40 according to the present embodiment can be formed.

  Also in the semiconductor light emitting device 40 of this embodiment, which is further provided with the transparent electrode 410 between the second electrode 150 and the second semiconductor layer 140, the second electrode 150 is provided. The gap 210 having a width equal to or smaller than the wavelength of light can provide a semiconductor light emitting device with high light extraction efficiency.

  Note that the width of the gap 210, the density in the second electrode 150 plane, and the area ratio can be changed depending on the heat treatment temperature, the type of metal material to be heat-treated simultaneously with the conductive film 151, the film thickness, and the stacked structure. However, those conditions optimized to improve the light output are not necessarily combined with the optimum electrical characteristics. At this time, like the semiconductor light emitting device 40 according to the present embodiment, the transparent electrode 410 is provided between the second electrode 150 and the second semiconductor layer 140, and the high-efficiency reflective film is interposed via the transparent electrode 410. By providing the second electrode 150 having the above function, it is possible to adopt the formation conditions of the gap 210 that are optimized with emphasis on the light output improvement characteristic, and it is easy to manufacture and has high performance and high light extraction efficiency. A semiconductor light emitting device can be provided.

(Fifth embodiment)
FIG. 24 is a schematic view illustrating the configuration of a semiconductor light emitting element according to the fifth embodiment of the invention.
That is, FIG. 24B is a schematic plan view illustrating the configuration of the semiconductor light emitting device according to the fifth embodiment of the invention, and FIG. 24A is the AA line in FIG. It is a cross-sectional schematic diagram. As illustrated in FIGS. 24A and 24B, the semiconductor light emitting device 50 according to the fifth embodiment of the present invention includes the second gap 210 on the second semiconductor layer 140. An electrode 150 and a third electrode 155 are included. The third electrode 155 is in electrical contact with the second electrode 150.
In addition, the third electrode 155 can have an ohmic property better than that of the second electrode 150.
The position where the third electrode 155 is provided is arbitrary as long as it is on the second semiconductor layer 140, but as illustrated in FIGS. 24A and 24B, the third electrode 155 is provided on the second semiconductor layer 140. When the electrode 150 is provided in contact with the first electrode 160 side, a highly ohmic conductive portion can be disposed in a region facing the first electrode 160, so that stable electrical characteristics can be obtained.

  Except for the third electrode 155, the semiconductor light emitting element 30 according to the third embodiment illustrated in FIG. In the semiconductor light emitting element 50 illustrated in FIG. 24, the second electrode 150 has a gap 210 that penetrates the layer of the second electrode 150. However, the present invention is not limited to this, and the gap 210 may be formed only at the interface of the second electrode 150 on the second semiconductor layer 140 side as in the semiconductor light emitting device 10 illustrated in FIG. .

The semiconductor light emitting device 50 according to this embodiment can be manufactured as follows.
That is, after the second electrode 150 (for example, an Ag single layer film having a thickness of 200 nm) having a predetermined pattern having the gap 210 is formed in the same manner as the method for manufacturing the semiconductor light emitting element 30 illustrated in FIG. For example, an Ag / Pt film for forming the electrode 155 is formed in a predetermined pattern with a film thickness of 200 nm, and heat treatment is performed for one minute in a nitrogen atmosphere at 350 ° C., which is one of the conditions that no void is generated, using an RTA apparatus. I do. Accordingly, no void is generated in the third electrode 155, and the ohmic property can be made higher than that of the second electrode 150.
Then, the semiconductor light emitting device 50 illustrated in FIG. 24 is obtained by forming the first electrode 160 in the same manner as described above.

Note that the width of the gap 210, the density in the second electrode 150 plane, and the area ratio can be changed depending on the heat treatment temperature, the type of metal material to be heat-treated simultaneously with the conductive film 151, the film thickness, and the stacked structure. However, those conditions optimized to improve the light output are not necessarily combined with the optimum electrical characteristics.
Further, in the case of an electrode structure in which current is passed in the lateral direction (parallel to each layer) as in the semiconductor light emitting device of the above embodiment, current is applied to the second electrode 150 on the side facing the first electrode 160. There is a tendency to concentrate. In particular, the effect becomes more prominent as the current density is increased.
At that time, like the semiconductor light emitting device 50 of the present embodiment, the second electrode 150 on the side facing the first electrode 160 is electrically contacted, and the ohmic characteristics are better than the second electrode 150, In addition, by providing the third electrode 155 having high-efficiency light reflection characteristics, both the light extraction efficiency and the electric characteristics can be made highly compatible. That is, various conditions regarding the second electrode 150 are optimized by focusing on improving the light extraction efficiency, and various conditions regarding the third electrode 155 are optimized by focusing on improving electrical characteristics. Can do.

  That is, by providing the third electrode 155 with good ohmic properties as in the semiconductor light emitting device 50 of this embodiment, a semiconductor light emitting device with good electrical characteristics and high light extraction efficiency can be provided.

  Note that the electrical characteristics improve as the area of the third electrode 155 in plan view increases, but saturate when expanded to some extent. On the other hand, in order to improve the light extraction efficiency, the larger the area of the second electrode 150, the higher the effect. In consideration of these effects, the area of the third electrode 155 can be appropriately determined according to the design of the second electrode 150 and the first electrode 160.

  Note that the semiconductor light emitting element 50 illustrated in FIG. 24 has a structure in which the second electrode 150 is formed first, and the third electrode 155 is provided so as to cover a part of the second electrode 150. However, a structure in which the third electrode 155 is formed first and the second electrode 150 is provided so as to cover a part of the third electrode 155 may be employed. In this case, the high temperature heat treatment temperature of the third electrode 155 can be set higher than the high temperature heat treatment temperature of the second electrode 150.

  In the semiconductor light emitting device 50 according to this embodiment, a transparent electrode may be provided at least at a part between at least one of the second electrode 150 and the third electrode 155 and the second semiconductor layer 140. good.

(Sixth embodiment)
FIG. 25 is a schematic cross-sectional view illustrating the configuration of a semiconductor light emitting element according to the sixth embodiment of the invention.
As shown in FIG. 25, in the semiconductor light emitting device 60 according to the sixth embodiment of the present invention, the pad portion 158 is provided on the surface of the second electrode 150 opposite to the second semiconductor layer 140. .
Except for the pad portion 158, the structure is the same as that of the semiconductor light emitting device 30 according to the third embodiment illustrated in FIG. In the semiconductor light emitting device 60 illustrated in FIG. 25, the second electrode 150 has a gap 210 that penetrates the layer of the second electrode 150. However, the present invention is not limited to this, and the gap 210 may be formed only at the interface of the second electrode 150 on the second semiconductor layer 140 side as in the semiconductor light emitting device 10 illustrated in FIG. .

  Note that the pad portion 158 covers a part of the second electrode 150 or the entire surface including the side surface of the second electrode 150 after the second electrode 150 having the gap 210 is formed. For example, it can be formed by forming Pt / Au with a film thickness of 800 nm and patterning it into a predetermined shape. For this patterning, for example, a lift-off method can be used.

It is preferable to use a high melting point material that does not diffuse into the second electrode 150 on the second electrode 150 side of the pad portion 158. Examples of the high melting point material include vanadium (N), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), niobium (Nb), molybdenum (Mo), ruthenium (Ru), and rhodium ( Rh), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and the like. Particularly preferred is rhodium (Rh) or platinum (Pt), which also has a high reflectivity with respect to visible light, and thus functions as a reflective film.
By providing the pad portion 158 as in the semiconductor light emitting device 60 according to the present embodiment, the bondability of wire bonding is improved, the die shear strength at the time of gold bump formation by a ball bonder is improved, and further, flip chip Applicable to mount. Further, the second electrode 150 is isolated from the outside air by the pad portion 158, deterioration of silver or a silver alloy can be suppressed, and reliability is improved. Furthermore, improvement in heat dissipation of the semiconductor light emitting device 60 can also be expected. The pad portion 158 can also be used as a gold (Au) bump. Note that AuSn bumps can be formed instead of Au.

  That is, by providing the pad portion 158 like the semiconductor light emitting device 60 according to the present embodiment, a semiconductor light emitting device that is easy to manufacture, has high reliability, good heat dissipation, and high light extraction efficiency is provided. Can do.

  In the semiconductor light emitting device 60 of the present embodiment, the third electrode 155 that contacts the second electrode 150 may be provided, and at least one of the second electrode 150 and the third electrode 155 may be provided. A transparent electrode may be provided at least at a part between the second semiconductor layer 140 and the second semiconductor layer 140.

FIG. 26 is a schematic cross-sectional view illustrating the configuration of another semiconductor light emitting element according to the sixth embodiment of the invention.
As shown in FIG. 26, in another semiconductor light emitting device 61 according to the sixth embodiment of the present invention, a pad portion 158 is provided on the surface of the second electrode 150 opposite to the second semiconductor layer 140. ing. A part of the gap 210 of the second electrode 150 is filled with a conductive material that becomes the pad portion 158.
That is, in the semiconductor light emitting device 61 illustrated in FIG. 26, for example, the second electrode 150 has the gap 210 penetrating the layer of the second electrode 150 during the manufacturing, but the pad portion 158 thereafter. As a result, a part of the gap 210 is filled.
Except for the structure of the gap 210, the structure is similar to that of the semiconductor light emitting device 60 illustrated in FIG.

  As shown in FIG. 26, in the semiconductor light emitting element 61, a part 210 </ b> A of the gap 210 is filled with the pad portion 158, but a space remains at the interface of the second semiconductor layer 140. ing. On the other hand, in the other part 210 </ b> B of the gap 210, the entire gap is filled with a material that becomes the pad portion 158.

In the part 210 </ b> A of the gap where the space remains at the interface of the second semiconductor layer 140, the light extraction efficiency is improved by the effect as described above.
And in the part 210B of the space | gap where all the space | gap 210 was filled, the light extraction efficiency improves with the following effects.

  That is, by using different conductive materials for the second electrode 150 and the pad portion 158, it is possible to cause a difference in complex refractive index between them, thereby generating diffuse reflection and improving light extraction efficiency. Can be made.

  Note that the wavelength in the medium is a value obtained by dividing the wavelength of the emitted light in free space by the refractive index of the medium, and is shorter than the wavelength in free space. For example, in the case of the semiconductor light emitting device 61 according to the present embodiment, the refractive index of the layer (p-type GsN contact layer 146) on the second electrode 150 side of the second semiconductor layer 140 is 2 with respect to the emission wavelength of 380 nm. .47, the in-medium wavelength is about 150 nm. Therefore, when the gap region is filled with another metal (conductive film that becomes the pad portion 158) as in the semiconductor light emitting device 61, the width of the gap 210 is equal to the wavelength in the medium in order to cause effective diffuse reflection. It is desirable to make it less than about.

  Note that, as in the semiconductor light emitting device 10 illustrated in FIG. 1, the gap 210 is provided only on the interface side of the second electrode 150 with the second semiconductor layer 140, and the gap 210 is the conductive film of the second electrode 150. In the case of the structure passivated by the above, the refractive index in the gap 210 is almost 1 without changing before and after the formation of the pad portion 158, so the width of the gap 210 is less than or equal to the wavelength in free space. I do not care.

Thus, even when part of the gap 210 is embedded with a conductive material (metal) different from the second electrode 150 as in the semiconductor light emitting element 61, diffuse reflection can be caused. A semiconductor light emitting device with high light extraction efficiency can be provided.
In the other semiconductor light emitting device 61 of the present embodiment, the third electrode 155 that contacts the second electrode 150 may be provided, and the second electrode 150 and the third electrode 155 may be provided. The transparent electrode 410 may be provided at least at a part between at least one of the second semiconductor layers 140.

(Seventh embodiment)
Next, a seventh embodiment will be described. The semiconductor light emitting device according to this embodiment is a semiconductor light emitting device in which the semiconductor light emitting devices of the above embodiments and examples are combined with a phosphor.
FIG. 27 is a schematic cross-sectional view illustrating the configuration of a semiconductor light emitting element according to the seventh embodiment of the invention.
As shown in FIG. 27, the semiconductor light emitting device 70 according to the seventh embodiment of the present invention is excited by, for example, the semiconductor light emitting device 30 of the third embodiment and the light emitted from the semiconductor light emitting device 30. A phosphor layer 530 that emits fluorescent light.

That is, as shown in FIG. 27, for example, the reflective film 520 is provided on the inner surface of the container 510 made of ceramics or the like. The reflective film 520 is separately provided on, for example, the reflective film 521 on the bottom surface of the container 510 and the reflective film 522 on the side surface of the container 510. For the reflective film 520, for example, aluminum or the like can be used.
Then, the semiconductor light emitting element 30 is installed via the submount 524 on the reflective film 521 on the bottom surface of the container 510. Gold bumps 528 are formed on the semiconductor light emitting element 30 by a ball bonder, and the semiconductor light emitting element 30 is fixed to the submount 524. Note that the semiconductor light emitting element 30 may be fixed to the submount 524 without using the gold bump 528.
For fixing the semiconductor light emitting element 30, the submount 524, and the reflective film 520, for example, adhesion using an adhesive or soldering can be used.

  The surface of the submount 524 on the semiconductor light emitting element 30 side is patterned so as to be insulated from the second electrode (p side electrode) 150 and the first electrode (n side electrode) 160 of the semiconductor light emitting element 30. These electrodes are formed, and are connected to electrodes (not shown) provided on the container 510 side by bonding wires 526. This connection is made in a portion between the reflection film 522 on the side surface portion and the reflection film 521 on the bottom surface portion.

  A phosphor layer 530 is provided so as to cover the semiconductor light emitting element 30 and the bonding wire 526. In the semiconductor light emitting device 70 illustrated in FIG. 27, the phosphor layer 530 is provided on the first phosphor layer 531 including the red phosphor and the first phosphor layer 531, and blue, green Alternatively, a second phosphor layer 532 including a yellow phosphor is provided. On these phosphor layers 530, for example, a lid 512 made of silicon resin is provided.

The first phosphor layer 531 includes a resin and a red phosphor dispersed in the resin. As the red phosphor, for example, Y ₂ O ₃ , YVO ₄ , Y ₂ (P, V) O ₄ can be used as a base material, and trivalent Eu (Eu ³⁺ ) is used as an activator. Include. That is, Y ₂ O ₃ : Eu ³⁺ , YVO ₄ : Eu ^3+, etc. can be used as the red phosphor. The concentration of Eu ³⁺ can be 1% to 10% in terms of molar concentration. As a base material of the red phosphor, LaOS, Y ₂ (P, V) O ₄ or the like can be used in addition to Y ₂ O ₃ and YVO ₄ . In addition to Eu ³⁺ , Mn ⁴⁺ or the like can be used. In particular, by adding a small amount of Bi together with trivalent Eu to the YVO ₄ matrix, absorption at 380 nm increases, so that the luminous efficiency can be further increased. Further, as the resin, for example, silicon resin or the like can be used.

The second phosphor layer 532 includes a resin and at least one of blue, green, and yellow phosphors dispersed in the resin. For example, a phosphor combining a blue phosphor and a green phosphor may be used, or a phosphor combining a blue phosphor and a yellow phosphor may be used, and a blue phosphor, a green phosphor and a yellow phosphor may be used. You may use the fluorescent substance which combined the fluorescent substance.
As the blue phosphor, for example, (Sr, Ca) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , BaMg ₂ Al ₁₆ O ₂₇ : Eu ^2+, or the like can be used.
As the green phosphor, for example, Y ₂ SiO ₅ : Ce ³⁺ , Tb ³⁺ having trivalent Tb as the emission center can be used. In this case, energy is transferred from Ce ions to Tb ions, so that the excitation efficiency is improved. For example, Sr ₄ Al ₁₄ O ₂₅ : Eu ²⁺ can be used as the green phosphor.
For example, Y ₃ Al ₅ : Ce ³⁺ can be used as the yellow phosphor.
Further, as the resin, for example, a silicon resin or the like can be used.
In particular, trivalent Tb exhibits sharp light emission near 550 nm where the visibility is maximized. Therefore, when combined with sharp red light emission of trivalent Eu, the light emission efficiency is significantly improved.

According to the semiconductor light emitting device 70 according to the present embodiment, the 380 nm ultraviolet light generated from the semiconductor light emitting device 30 is emitted to the substrate side of the semiconductor light emitting device 30 and also uses the reflection in the reflection films 521 and 522. The phosphors contained in each phosphor layer can be excited efficiently.
For example, the phosphor having the emission center of trivalent Eu contained in the first phosphor layer 531 is converted into light having a narrow wavelength distribution around 620 nm, and red visible light can be efficiently obtained. is there.
In addition, the blue, green, and yellow phosphors included in the second phosphor layer 532 are efficiently excited, and blue, green, and yellow visible light can be efficiently obtained.
As these mixed colors, white light and various other colors can be obtained with high efficiency and good color rendering.
In addition, although the example using the semiconductor light emitting element 30 according to the third embodiment has been described above, the present invention is not limited thereto, and the semiconductor light emitting elements 10, 11, 40, according to the above embodiment and examples are described. 50, 60, 61 can be used.

Next, a method for manufacturing the semiconductor light emitting device according to this embodiment will be described.
The process of manufacturing the semiconductor light emitting element 30 is as already described.
First, a metal film to be a reflective film is formed on the inner surface of the container 510 by, for example, sputtering, and the metal film is patterned to form the reflective films 521 and 522 on the bottom surface portion and the side surface portion of the container 510, respectively. .
Then, gold bumps 528 are formed on the semiconductor light emitting element 30 by a ball bonder. Then, the semiconductor light emitting element 30 is mounted on the submount 524 having electrodes patterned for the second electrode (p-side electrode) 150 and the first electrode (n-side electrode) 160 of the semiconductor light emitting element 30. The submount 524 is installed on the reflection film 521 on the bottom surface of the container 510 and fixed. It is possible to use adhesion with an adhesive, solder, or the like for these fixations. Further, the semiconductor light emitting element 30 can be directly fixed on the submount 524 without using the gold bump 528 by the ball bonder.

  Next, the first electrode 160 and the second electrode 150 (not shown) on the submount 524 are connected to the electrodes (not shown) provided on the container 510 side by bonding wires 526, respectively. Further, a first phosphor layer 531 is formed so as to cover the semiconductor light emitting element 30 and the bonding wire 526, and a second phosphor layer 532 is formed on the first phosphor layer 531. As a method for forming each phosphor layer, for example, a method in which each phosphor is dispersed in a resin raw material mixed solution is dropped, and heat treatment is performed to thermally polymerize the resin to be used. In addition, the resin raw material mixed solution containing each phosphor is dropped and left standing for a while and then cured, whereby the fine particles of each phosphor settle, and the first phosphor layer 531 and the second phosphor layer 532 The fine particles of each phosphor can be unevenly distributed in the lower part of each layer, and the luminous efficiency of each phosphor can be appropriately controlled. Thereafter, a lid 512 is provided on the phosphor layer, and the semiconductor light emitting device 70 according to this embodiment, that is, a white LED is manufactured. Thus, the manufactured semiconductor light emitting device 70 of the present embodiment can provide a semiconductor light emitting device that generates various colors with high light extraction efficiency and high efficiency.

  In each of the above embodiments, the example in which the first semiconductor layer 120 is an n-type semiconductor layer and the second semiconductor layer 140 is a p-type semiconductor layer has been described. Without limitation, the conductivity types of both semiconductor layers may be reversed.

The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, regarding the specific configuration of each element constituting the semiconductor light emitting device and the manufacturing method thereof, for example, the shape, size, material, arrangement relationship and crystal growth process of each element such as a semiconductor multilayer film, metal film, dielectric film, etc. As long as a person skilled in the art can carry out the present invention by appropriately selecting from the well-known ranges and obtain the same effect, it is included in the scope of the present invention.
Moreover, what combined any two or more elements of each specific example in the technically possible range is also included in the scope of the present invention as long as the gist of the present invention is included.

  In addition, all semiconductor light-emitting devices and methods for manufacturing the same that can be implemented by those skilled in the art based on the semiconductor light-emitting devices and methods for manufacturing the same described above as embodiments of the present invention are also included in the gist of the present invention. As long as it is included, it belongs to the scope of the present invention.

  In addition, in the category of the idea of the present invention, those skilled in the art can conceive of various changes and modifications, and it is understood that these changes and modifications also belong to the scope of the present invention. .

In this specification, “nitride semiconductor” means B _x In _y Al _z Ga _1-xyz N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z ≦ 1) Semiconductors having all compositions in which the composition ratios x, y, and z are changed within the respective ranges are included. Furthermore, in the above chemical formula, those that further include a group V element other than N (nitrogen), and those that further include any of various dopants added to control the conductivity type, etc. Shall be included.

10, 11, 30, 40, 50, 60, 61, 70, 91 Semiconductor light emitting device 110 Substrate 120 First semiconductor layer 122 First AlN buffer layer 123 Second AlN buffer layer 124 Non-doped GaN buffer layer 125 Si-doped n-type GaN contact Layer (n-type contact layer)
126 Si-doped n-type AlGaN cladding layer 130 Light-emitting layer 142 Non-doped AlGaN spacer layer 143 Mg-doped p-type AlGaN cladding layer 144 Mg-doped p-type GaN contact layer 145 High-concentration Mg-doped p-type GaN contact layer 146 p-type GaN contact layer 148 Semiconductor Layer 150 Second electrode (p-side electrode)
155 The third electrode 158 pad portion 160 first electrode 210 voids 210A, part of 210B void 220 grain 230 grain boundaries 291 image 300 region 310 SiO ₂ film 320 resist 330 water (moisture)
340 Ionized material 410 Transparent electrode 510 Container 512 Lid 520, 521, 522 Reflective film 524 Submount 526 Bonding wire 528 Gold bump 530, 531, 532 Phosphor layer

Claims (12)

A first semiconductor layer; a second semiconductor layer; a light-emitting layer provided between the first semiconductor layer and the second semiconductor layer; and a first connected to the first semiconductor layer. And a second electrode provided on the second semiconductor layer and facing the second semiconductor layer, the second electrode comprising at least one of silver and a silver alloy. There,
Forming a conductive film to be the second electrode on the second semiconductor layer;
A semiconductor light emitting device characterized in that a self-organization due to migration of the conductive film is caused and a gap having a width equal to or smaller than a light emission wavelength of the light emitting layer is formed on a surface of the conductive film facing the second semiconductor layer. Manufacturing method.   2. The method of manufacturing a semiconductor light emitting element according to claim 1, wherein moisture is removed before forming the conductive film.   The formation of the void includes forming the void in an interface between the second electrode and the second semiconductor layer and in the layer of the second electrode. The manufacturing method of the semiconductor light-emitting device of description.   2. The void is formed by penetrating through the interface between the second electrode and the second semiconductor layer and in the thickness direction of the second electrode. Manufacturing method of the semiconductor light-emitting device.   The gap is formed by forming the gap at the interface of the second electrode with the second semiconductor layer and the interface of the second electrode opposite to the second semiconductor layer. The method of manufacturing a semiconductor light emitting device according to claim 1, comprising:   The method of manufacturing a semiconductor light emitting element according to claim 1, wherein the second electrode is a silver single layer film. A transparent conductive film that transmits light from the light emitting layer is further formed on the second semiconductor layer,
The method of manufacturing a semiconductor light emitting element according to claim 1, wherein forming the conductive film includes forming the conductive film on the transparent electrode film.   The method of manufacturing a semiconductor light emitting element according to claim 7, wherein the transparent conductive film is made of a material having a band gap larger than an emission wavelength of the light emitting layer.   9. The method for manufacturing a semiconductor light emitting element according to claim 7, wherein the film thickness of the transparent conductive film is thinner than the reciprocal of the absorption coefficient at the emission wavelength of the light emitting layer.   The method for manufacturing a semiconductor light-emitting element according to claim 6, wherein the transparent conductive film includes at least one of nickel, indium tin oxide, and zinc oxide. Forming a third electrode on the second semiconductor layer;
The third electrode according to claim 1, wherein the third electrode is in contact with the second electrode and has an ohmic property higher than that of the second electrode with respect to the second semiconductor layer. The manufacturing method of the semiconductor light-emitting device as described in any one.   The semiconductor light-emitting device according to claim 1, further comprising: forming the first semiconductor layer, the second semiconductor layer, and the light-emitting layer on a sapphire substrate. Method.