JP2005244201A - Semiconductor luminous element and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor luminous element where light-extraction efficiency is high and a radiating pattern is excellent without using a microscopic lithography technology and a dry etching technology. <P>SOLUTION: An n-type GaN layer 2, an InGaN multi-quantum well active layer 3, a p-type AlGaN electronic barrier layer 4, a p-type AlGaN/GaN strain superlatticed layer 5 and a p-type GaN contact layer 6 are sequentially formed on a sapphire substrate 1. A p-type ohmic electrode 7 is formed to have an opening on the light-extraction part of the p-type GaN contact layer 6. A porous area 9 is formed by wet etching using a mixture of methanol, a hydrofluoric acid and a hydrogen peroxide in a light-extraction section of the p-type GaN contact layer 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device represented by a light emitting diode (hereinafter referred to as LED) that can be used as, for example, various displays, a backlight for a liquid crystal display, a light source for solid state illumination, and the like.

  In recent years, the performance of LEDs has been improved, and application fields are rapidly expanding. In particular, with the advent of nitride-based compound semiconductors typified by gallium nitride (hereinafter referred to as GaN), LEDs that cover the entire visible range from the ultraviolet range can be realized. In addition, it has been attracting attention as an illumination light source to replace fluorescent lamps and incandescent lamps.

  One of the major challenges of current LEDs is the improvement of light extraction efficiency. The reason is that in a simple LED chip produced by cutting a substrate made of a semiconductor wafer having a multilayer structure on the surface into a substantially rectangular chip shape by dicing, most of the light emitted from the active layer This is because total reflection occurs at the interface between the semiconductor and air or resin and the light is trapped in the LED chip, so that only a part of the light can be extracted. Usually, in such a simple LED structure, the light extraction efficiency, that is, the ratio of the light that can be extracted outside the LED chip out of the light generated in the active layer is supposed to be about 20%.

  For this reason, various efforts have been made to improve the light extraction efficiency by processing the light extraction surface of the LED. Regarding processing of this light extraction surface, for example, there is processing as described in Patent Document 1 or Non-Patent Document 1.

  FIG. 14 shows a cross-sectional structure of a conventional LED in which the light extraction efficiency is improved by processing the light extraction surface. As shown in FIG. 14, an n-type GaN layer 102, an InGaN multiple quantum well active layer 103, a p-type AlGaN barrier layer 104, and a p-type GaN contact layer 105 are sequentially formed on the sapphire substrate 101. Here, regular irregularities are provided on the surface of the p-type GaN contact layer 105 by a lithography technique and a dry etching technique. A p-side ohmic electrode 106 is provided on the p-type GaN contact layer 105 via a transparent electrode 107. Note that the n-side ohmic electrode formation region in the stacked structure of each semiconductor layer is removed by etching so that the n-type GaN layer 102 is exposed, and the n-side GaN layer 102 is exposed on the n-side. An ohmic electrode 108 is formed.

According to the conventional LED shown in FIG. 14, the light emitted from the active layer 103 can be prevented from being totally reflected on the surface of the GaN contact layer 105 serving as a light extraction surface, thereby doubling the light extraction efficiency. Can be increased.
JP 2000-196152 A Orita et al., Improvement of light extraction of blue GaN LED by long-period photonic crystal, Fall of 2003 (Heisei 15), 64th Japan Society of Applied Physics, Japan Society of Applied Physics, 2003 8 30th Month, 3rd volume, p.938 Diaz et al., Morphology and luminescence of porous GaN generated via Pt-assisted electroless etching, Journal of Vacuum Science and Technology (J.Vac.Sci.Technol.), November 2002, Vol. B20, No. 6, p. 2375-2383

  However, in the conventional technology as described above, regular irregularities are formed on the light extraction surface, so that the radiation pattern of light emitted from the LED chip becomes stronger in a specific direction due to interference between diffracted lights. There was a problem of practical use. Further, since dry etching is used to form irregularities in the p-type GaN layer that becomes the light extraction surface, the p-type GaN layer is damaged, and as a result, an ohmic electrode is formed on the p-type GaN layer. There is a problem that the light is absorbed and light is absorbed in a deep level generated in the p-type GaN layer.

  In addition, when the emission wavelength from the active layer becomes short, light absorption in the p-type GaN layer cannot be ignored. Therefore, it is necessary to form this layer using a material such as AlGaN having a larger band gap energy than GaN. Will arise. However, in this case, when the above-described conventional technique is used, a material having a large band gap energy generally has a strong bond and is hard, so that there is a problem that etching for forming unevenness becomes difficult. In addition, there is a problem that it becomes more difficult to form an ohmic electrode on a layer made of a material having a large band gap energy.

  Further, the above-described conventional technique has a problem in that the yield is deteriorated because it is necessary to use a fine lithography technique in order to form irregularities with a short pitch on the light extraction surface.

  In view of the above, an object of the present invention is to provide a semiconductor light emitting device having high light extraction efficiency and a good radiation pattern without using a fine lithography technique or a dry etching technique.

  In order to achieve the above object, a semiconductor light-emitting device according to the present invention is a semiconductor light-emitting device in which a plurality of semiconductor layers including an active layer are stacked, in order to extract light from the active layer among the plurality of semiconductor layers. At least a part of the semiconductor layer having a surface serving as a light extraction surface is made porous.

  In the present application, being porous means porous, that is, a large number of micropores (voids) having various shapes are present irregularly.

  According to the semiconductor light emitting device of the present invention, since a large number of voids are irregularly formed in the semiconductor layer having the surface serving as the light extraction surface, the light emitted from the active layer is the surface of the semiconductor layer serving as the light extraction surface. Therefore, it is possible to suppress the total reflection, thereby improving the light extraction efficiency. In addition, since a large number of voids are irregularly formed due to the porous structure, it is possible to avoid a situation in which a specific radiation pattern is generated due to interference between diffracted lights in the radiation pattern of light emitted from the element. Therefore, it is possible to realize a semiconductor light emitting device with high light extraction efficiency and good radiation pattern.

  In addition, according to the semiconductor light emitting device of the present invention, the porous layer can be formed by wet etching on the semiconductor layer having the surface serving as the light extraction surface, so that the semiconductor layer is damaged due to dry etching. The problem can be avoided.

  In addition, according to the semiconductor light emitting device of the present invention, the light absorption edge wavelength (wavelength at which the light absorption coefficient sharply decreases) of the porous semiconductor layer is shorter than that before the porous structure. Shifting reduces the absorption of light from the active layer and, as a result, further increases the light extraction efficiency.

  Further, in the production of the semiconductor light emitting device of the present invention, it is not necessary to use advanced photolithography technology, so that the yield can be improved.

  In the semiconductor light emitting device of the present invention, it is preferable that the bottom of each void in the porous region of the semiconductor layer forms irregularities. Here, it is more preferable that the height difference of the unevenness is about 10 nm or more.

  In this way, light from the active layer can be more effectively scattered in the porous region of the semiconductor layer, thereby improving the light output while realizing a good radiation pattern without a specific interference peak. be able to.

  In the semiconductor light emitting device of the present invention, it is preferable that the porous region of the semiconductor layer has a plurality of remaining semiconductor portions, each of which forms an unevenness. Here, it is more preferable that the height difference of the unevenness is about 10 nm or more.

  In this way, light from the active layer can be more effectively scattered in the porous region of the semiconductor layer, thereby improving the light output while realizing a good radiation pattern without a specific interference peak. be able to.

  In the semiconductor light-emitting device of the present invention, the plurality of semiconductor layers have other non-porous semiconductor layers provided between the active layer and the semiconductor layer and serving as current diffusion layers, and the non-porous semiconductor layer It is preferable that an electrode is provided on the materialized region, and it is more preferable that the current spreading layer has at least one heterointerface.

  In this way, carriers that are difficult to diffuse laterally in the semiconductor layer due to the presence of the porous structure can be easily diffused laterally by other semiconductor layers, that is, current diffusion layers. Can be obtained.

  In the semiconductor light emitting device of the present invention, the light absorption edge of the porous region of the semiconductor layer is caused by a quantum effect when the distance between adjacent voids of the porous region of the semiconductor layer is 20 nm or less. The wavelength is shorter than the light absorption edge wavelength of the non-porous region of the semiconductor layer. Here, when the emission wavelength (center wavelength) of the active layer is about or less than the forbidden band wavelength of the semiconductor layer, the light absorption edge wavelength of the porous region of the semiconductor layer is the light emitted from the active layer. Since the light emitted from the active layer becomes shorter than the center wavelength of the light without being absorbed by the semiconductor layer, the light extraction efficiency can be further improved.

  In the semiconductor light emitting device of the present invention, it is preferable that the effective refractive index in the porous region of the semiconductor layer decreases as the distance from the active layer increases.

  If it does in this way, light extraction efficiency can be raised more. The “effective refractive index in the porous region of the semiconductor layer” means a refractive index obtained by averaging the refractive index of the semiconductor portion and the refractive index of the void portion in consideration of the volume ratio of each portion.

  In the semiconductor light emitting device of the present invention, the proportion of voids per unit volume in the porous region of the semiconductor layer is preferably increased as the distance from the active layer increases.

  In this case, the effective refractive index of the porous region of the semiconductor layer gradually decreases as it moves away from the active layer (that is, from the substrate side to the surface side), so that the light extraction efficiency can be further increased. .

  In the semiconductor light emitting device of the present invention, it is preferable that the band gap energy of the semiconductor layer decreases stepwise or continuously as the distance from the active layer increases.

  In this way, the proportion of voids per unit volume in the porous region of the semiconductor layer can be increased as the distance from the active layer increases. As a result, the effective refractive index of the porous region of the semiconductor layer is increased. Since it gradually decreases from the substrate side toward the surface side, the light extraction efficiency can be further increased.

  In the semiconductor light emitting device of the present invention, it is preferable that the semiconductor surface in contact with each void in the porous region of the semiconductor layer is oxidized.

  In this way, the semiconductor surface in the porous region is not directly exposed to the atmosphere, so that the reliability of the device is greatly improved.

  In the semiconductor light emitting device of the present invention, the surface side of the porous region of the semiconductor layer is preferably covered with a protective film.

In this way, the semiconductor surface in the porous region is not directly exposed to the atmosphere, so that the reliability of the device is greatly improved. At this time, as the protective film, for example, a film made of SiO ₂ , Al ₂ O ₃ , SiN, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ or Ga ₂ O ₃ can be used.

  In the semiconductor light emitting device of the present invention, the surface side of the porous region of the semiconductor layer is preferably covered with a transparent electrode.

  In this way, the semiconductor surface in the porous region is not directly exposed to the atmosphere, so that the reliability of the device is greatly improved. In addition, since the carrier can be injected more uniformly, the light emission efficiency can be further improved.

  In the semiconductor light emitting device of the present invention, the semiconductor layer is preferably an n-type semiconductor layer.

  In this case, the p-side electrode having a contact resistance larger than that of the n-side electrode can be formed over the entire surface of the p-type semiconductor layer, which is the opposite surface of the light extraction surface in the plurality of semiconductor layers. Can be reduced.

  In the semiconductor light emitting device of the present invention, the plurality of semiconductor layers are formed on the substrate, and a reflective film having a metal or dielectric multilayer structure is formed on the main surface of the substrate on which the plurality of semiconductor layers are not formed. Preferably it is formed.

  If it does in this way, since the light radiated | emitted from the active layer to the direction of a board | substrate will be reflected efficiently by the said reflecting film, the light extraction efficiency from a light extraction surface can further be improved.

  In the semiconductor light emitting device of the present invention, a reflective film made of a metal or dielectric multilayer structure may be formed on the surface of another semiconductor layer having a surface opposite to the light extraction surface of the plurality of semiconductor layers. preferable.

  In this case, light emitted from the active layer in the direction of the other semiconductor layer is efficiently reflected by the reflective film, so that the light extraction efficiency from the light extraction surface can be further improved.

In the semiconductor light-emitting device of the present invention, as a material of the plurality of semiconductor layers of the, for example, _{B x Al y In z Ga 1} -xyz N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1,0 A nitride compound semiconductor represented by ≦ x + y + z ≦ 1) may be used.

  In the semiconductor light emitting device of the present invention, when the wavelength of light emitted from the active layer is shorter than 430 nm, a white LED can be realized.

In the semiconductor light emitting device of the present invention, a nitride compound semiconductor represented by, for example, Al _x Ga _1-x N (0 ≦ x ≦ 1) may be used as the material of the semiconductor layer.

  A method for manufacturing a semiconductor light emitting device according to the present invention includes a step of sequentially forming an n-type semiconductor layer, a semiconductor layer to be an active layer, and a p-type semiconductor layer on a substrate, and separating the multilayer structure of each semiconductor layer from the substrate. And a step of making at least a part of the n-type semiconductor layer having a surface to be a light extraction surface for extracting light from the active layer in the multilayer structure porous.

  According to the method for manufacturing a semiconductor light emitting device of the present invention, since the semiconductor layer having the surface serving as the light extraction surface is made porous, the light emitted from the active layer is totally reflected on the surface of the semiconductor layer serving as the light extraction surface. This can be suppressed, and thereby the light extraction efficiency can be improved. In addition, since a large number of voids are irregularly formed due to the porous structure, it is possible to avoid a situation in which a specific radiation pattern is generated due to interference between diffracted lights in the radiation pattern of light emitted from the element. Therefore, it is possible to realize a semiconductor light emitting device with high light extraction efficiency and good radiation pattern.

  In addition, according to the method for manufacturing a semiconductor light emitting device of the present invention, the porous layer can be formed by wet etching on the semiconductor layer having the surface serving as the light extraction surface, so that the semiconductor layer is damaged due to dry etching. Can be avoided.

  Further, according to the method for manufacturing a semiconductor light emitting device of the present invention, the light absorption edge wavelength of the porous semiconductor layer is shifted to the short wavelength side compared with that before the porous layer is formed. As a result, the light extraction efficiency can be further increased.

  In addition, according to the method for manufacturing a semiconductor light emitting device of the present invention, it is not necessary to use an advanced photolithography technique, so that the yield can be improved.

  In addition, according to the method for manufacturing a semiconductor light emitting device of the present invention, a p-side electrode having a contact resistance larger than that of an n-side electrode is generally formed on the surface of the p-type semiconductor layer that is the opposite surface of the light extraction surface in the multilayer structure of the semiconductor layer. Since it can be formed over the entire surface, the operating voltage can be reduced.

  According to the semiconductor light-emitting device of the present invention, since the semiconductor layer having the surface that becomes the light extraction surface is made porous, voids are irregularly formed in the semiconductor layer, which is caused by interference between diffracted lights. The light extraction efficiency can be increased without producing a unique radiation pattern. Further, since the porous processing of the semiconductor layer can be performed by wet etching, the problem of damage associated with dry etching can be solved. In addition, since the light absorption edge wavelength of the porous semiconductor layer is shifted to a shorter wavelength side than before the porous layer, the absorption of light from the active layer is reduced, and the light extraction efficiency can be further increased. it can. Further, since a fine photolithography technique is not required for manufacturing, it can be manufactured with high yield.

(First embodiment)
Hereinafter, a semiconductor light emitting device and a manufacturing method thereof according to a first embodiment of the present invention will be described with reference to the drawings.

  1A and 1B are views showing the structure of the semiconductor light emitting device according to the first embodiment, respectively, FIG. 1A is a plan view, and FIG. 1B is a view in FIG. It is sectional drawing of the II line.

The manufacturing method of the semiconductor light emitting device according to the first embodiment is as follows. As shown in FIGS. 1A and 1B, first, an n-type GaN layer 2 (on a sapphire substrate 1 made of a wafer, for example, using a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method). Thickness about 3.0 μm), InGaN multiple quantum well active layer 3, p-type Al _0.15 Ga _0.85 N electron barrier layer 4 (thickness 10 nm), p-type AlGaN / GaN strained superlattice layer 5 and p-type GaN contact layer 6 (Thickness 50 nm) is formed sequentially. Here, the InGaN multiple quantum well active layer 3 is formed by stacking three layers of an In _0.1 Ga _0.9 N quantum well layer (thickness 2.5 nm) and an In _0.02 Ga _0.98 N barrier layer (thickness 5 nm). Is. In addition, the p-type AlGaN / GaN strained superlattice layer 5 is formed by stacking 50 layers of a p-type Al _0.1 Ga _0.9 N layer (thickness 1.5 nm) and a p-type GaN layer (thickness 1.5 nm). It is a thing.

  Next, after forming the p-side ohmic electrode 7 so as to have an opening on the light extraction portion of the p-type GaN contact layer 6, a wafer on which each of the semiconductor layers described above is laminated, for example, methanol, hydrofluoric acid, and peroxide A porous structure (porous region) 9 is formed in the light extraction portion of the p-type GaN contact layer 6 by immersing in a mixed solution of hydrogen water. Subsequently, after etching the n-side ohmic electrode formation region of the stacked structure of each semiconductor layer described above by dry etching until the n-type GaN layer 2 is exposed, n is formed on the exposed surface of the n-type GaN layer 2. Side ohmic electrode 8 is formed. Here, for comparison with the semiconductor light emitting device of the present embodiment, a semiconductor light emitting device having the same structure as the semiconductor light emitting device of the present embodiment (except that the porous structure 9 is not formed) ( A comparative example is also prepared.

  A line (a) in FIG. 2 shows a current (drive current passed through the p-side ohmic electrode 7) -light output characteristic of the semiconductor light emitting device according to the first embodiment, and a line (b) in FIG. The current-light output characteristics of a semiconductor light-emitting element that is manufactured for comparison and does not include a porous structure are shown. As can be seen from FIG. 2, by using the porous structure 9 of the present invention, the light output was improved about three times.

  FIG. 3 shows a radiation pattern of light emitted from the semiconductor light emitting device according to the first embodiment. In FIG. 3, the angle reference (0 °) indicating the light emission direction is directly above the element (normal direction of the main surface of the wafer). As shown in FIG. 3, according to the semiconductor light emitting device of this embodiment, a good radiation pattern without a specific interference peak is obtained.

  FIG. 4 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type GaN contact layer 6 in the semiconductor light emitting device according to the first embodiment. As shown in FIG. 4, a large number of elongated gaps are formed from the surface side of the p-type GaN contact layer 6 toward the inside of the GaN crystal. In the present embodiment, the reason why the light output is improved while realizing a good radiation pattern having no interference peak is that light is effectively scattered by the porous structure 9 in which voids are irregularly formed. It is believed that there is. In addition, since the porous formation of the GaN layer proceeds irregularly, the surface connecting the bottom portions (that is, the deepest portions) of the voids in the porous structure 9 is not flat, and the height difference is about 10 nm or more. Produces irregularities. Thereby, light scattering occurs more effectively, and as a result, it is considered that the light extraction efficiency is improved. In order to cause light scattering more effectively, it is desirable that an uneven shape is also formed on the surface side of the porous structure 9. Specifically, in the porous structure 9 having a plurality of columnar semiconductor remaining portions, it is preferable that the surface connecting the tips of the semiconductor remaining portions has irregularities with an elevation difference of about 10 nm or more. The irregularities on the surface side or bottom side in the porous structure 9 as described above are obtained by optimizing the porous processing conditions (composition ratio of the mixed solution (wet etching solution), processing temperature, processing time, etc.) or by photolithography. It can be formed by further combining the process and the etching process.

  By the way, in this embodiment, the p-type AlGaN / GaN strained superlattice layer 5 and the p-type AlGaN electron barrier layer 4 are provided between the InGaN multiple quantum well active layer 3 and the p-type GaN contact layer 6. Thus, it is desirable to form one or more heterointerfaces by providing a non-porous semiconductor layer to be a current diffusion layer between the active layer and the contact layer. The reason is as follows. Carriers injected from the p-side ohmic electrode 7 having an opening on the light extraction portion of the p-type GaN contact layer 6, that is, the p-side ohmic electrode 7 formed on the non-porous region of the p-type GaN contact layer 6 are Since the porous structure 9 is difficult to diffuse in the lateral direction (direction parallel to the main surface of the substrate) in the p-type GaN contact layer, it is difficult to obtain uniform light emission from the entire surface of the light extraction surface. . On the other hand, by providing a plurality of heterointerfaces between the active layer and the contact layer as in this embodiment, lateral diffusion of carriers can be promoted, and as a result, more uniform light emission is obtained. be able to.

  FIG. 5 shows a light absorption spectrum of p-type GaN, FIG. 5 (a) shows a light absorption spectrum of p-type GaN having a porous structure, and FIG. 5 (b) shows a state before forming the porous structure. The light absorption spectrum of p-type GaN is shown. As can be seen from FIG. 5, by forming a porous structure in p-type GaN, the light absorption edge wavelength (wavelength at which the light absorption coefficient decreases rapidly) is shifted to the short wavelength side. In other words, the light absorption edge wavelength of the porous region of p-type GaN is shorter than the light absorption edge wavelength of the non-porous region of p-type GaN. This is probably because the size of the p-type GaN left in the porous structure is sufficiently small, thereby causing a quantum effect. Specifically, such a quantum effect appears when the average size of p-type GaN in the porous structure 9 indicated by the symbol t in FIG. 4 is approximately 20 nm or less. In other words, among the voids of the porous structure 9, the distance between adjacent voids is preferably about 20 nm or less. The distance does not become smaller than the minimum width of p-type GaN in the porous structure 9 (about 0.5 nm which is the thickness of one atomic layer).

  Further, the shortening of the light absorption edge wavelength as shown in FIG. 5 is that the emission wavelength (center wavelength) of the active layer is about the forbidden band wavelength of the contact layer (about 365 nm in the case of p-type GaN) or It is particularly useful when: That is, by forming the porous structure as described above in the contact layer, the light absorption edge wavelength of the porous structure in the contact layer can be made shorter than the emission wavelength of the active layer. For this reason, since the light radiated | emitted from the active layer can be taken out without absorption by a contact layer, light extraction efficiency can be improved more.

  As described above, according to the first embodiment, since the porous structure 9 is formed in the p-type GaN contact layer 6 having the surface serving as the light extraction surface, the light is emitted from the InGaN multiple quantum well active layer 3. It is possible to suppress the reflected light from being totally reflected on the surface of the p-type GaN contact layer 6, thereby improving the light extraction efficiency. In addition, since a large number of voids are irregularly formed due to the porous structure, it is possible to avoid a situation in which a specific radiation pattern is generated due to interference between diffracted lights in the radiation pattern of light emitted from the element. Therefore, it is possible to realize a semiconductor light emitting device with high light extraction efficiency and good radiation pattern.

  Further, according to the first embodiment, since the porous processing for the p-type GaN contact layer 6 can be performed by wet etching, the p-type GaN contact layer 6 is damaged due to dry etching. It can be avoided.

  Further, according to the first embodiment, the light absorption edge wavelength of the porous p-type GaN contact layer 6 is shifted to the short wavelength side compared with that before the porous structure, so that the InGaN multiple quantum well activity is increased. Light absorption from the layer 3 is reduced, and as a result, the light extraction efficiency can be further increased.

  In addition, according to the first embodiment, since it is not necessary to use advanced photolithography technology when manufacturing an element, the yield can be improved.

In the first embodiment, a mixed solution of methanol, hydrofluoric acid and hydrogen peroxide solution was used for the porous treatment of the p-type GaN contact layer 6. A mixed liquid of hydrogen oxide water may be used. Further, when an SiC layer is used as the contact layer instead of the p-type GaN layer, a wet etching solution containing HF (hydrofluoric acid) and S ₂ O ₈ ⁴⁻ is used for the porous processing of the SiC layer. It may be used.

  In the first embodiment, a reflective film made of a metal or dielectric multilayer structure is formed on the back surface of the sapphire substrate 1 (the surface opposite to the surface on which the n-type GaN layer 2 and the like are formed). Is preferred. In this way, light emitted from the InGaN multiple quantum well active layer 3 toward the sapphire substrate 1 is efficiently reflected by the reflective film, so that the light extraction efficiency from the light extraction surface can be further improved. it can.

  In the first embodiment, the porous structure 9 is formed in the p-type GaN contact layer 6. Instead, the porous structure 9 is formed in another semiconductor layer provided on the p-type GaN contact layer 6. Even if formed, the same effect can be obtained.

(Modification of the first embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a modification of the first embodiment of the present invention will be described with reference to the drawings. This modification is different from the first embodiment in the cross-sectional structure of the porous structure 9 of the p-type GaN contact layer 6. That is, the basic structure excluding the porous structure 9 of the semiconductor light emitting device according to this modification is the same as that of the first embodiment shown in FIGS.

  FIG. 6 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type GaN contact layer 6 in the semiconductor light emitting device according to this modification.

The method for manufacturing the semiconductor light emitting device according to this modification is as follows. First, an n-type GaN layer 2 (thickness of about 3.0 μm), an InGaN multiple quantum well active layer 3 and a p-type Al _0.15 Ga _0.85 are formed on a sapphire (0001) substrate 1 made of a wafer by using, for example, MOCVD. An N-electron barrier layer 4 (thickness 10 nm), a p-type AlGaN / GaN strained superlattice layer 5 and a p-type GaN contact layer 6 (thickness 50 nm) are sequentially formed. Here, the InGaN multiple quantum well active layer 3 is formed by stacking three layers of an In _0.1 Ga _0.9 N quantum well layer (thickness 2.5 nm) and an In _0.02 Ga _0.98 N barrier layer (thickness 5 nm). Is. In addition, the p-type AlGaN / GaN strained superlattice layer 5 is formed by stacking 50 layers of a p-type Al _0.1 Ga _0.9 N layer (thickness 1.5 nm) and a p-type GaN layer (thickness 1.5 nm). It is what.

  In this modification, in order to increase the crystal defect density of the p-type GaN contact layer 6, the crystal growth conditions at the time of forming the p-type GaN contact layer 6 are shifted from those normally used. Specifically, the crystal growth temperature of the p-type GaN contact layer 6 is set to 900 ° C., which is lower by about 100 ° C. than the crystal growth temperature of normal GaN.

  Next, after forming the p-side ohmic electrode 7 so as to have an opening on the light extraction portion of the p-type GaN contact layer 6, a wafer on which each of the semiconductor layers described above is laminated, for example, methanol, hydrofluoric acid, and peroxide By soaking in a mixed solution of hydrogen water, a porous structure (porous region) 9 is formed in the light extraction portion of the p-type GaN contact layer 6 as shown in FIG. Subsequently, after etching the n-side ohmic electrode formation region of the stacked structure of each semiconductor layer described above by dry etching until the n-type GaN layer 2 is exposed, n is formed on the exposed surface of the n-type GaN layer 2. Side ohmic electrode 8 is formed.

  In this modification, as described above, since the crystal defect density of the p-type GaN contact layer 6 is increased, when the porous region 9 is formed, the etching is different from the GaN etching centering on the crystal defect. As a result, the p-type GaN contact layer 6 is etched in a direction perpendicular to the substrate main surface ((0001) plane). Therefore, as shown in FIG. 6, the side surfaces of the columnar structures of the porous region 9 formed by etching are parallel to each other. In this modification, the average value of the diameters t in the direction along the (0001) plane in each of the columnar structures was about 40 nm.

  In this modification as well, as shown in FIG. 6, since many elongated voids are formed from the surface side of the p-type GaN contact layer 6 toward the inside of the GaN crystal, light is effectively scattered. The light output is improved while realizing a good radiation pattern having no interference peak. In addition, since the GaN layer is made porous, the surface of the porous structure 9 connecting the bottoms (that is, the deepest portions) of the voids is not flat, and the height difference is about 10 nm or more. Produces irregularities. Thereby, light scattering occurs more effectively, and as a result, the light extraction efficiency is improved. In order to cause light scattering more effectively, it is desirable that an uneven shape is also formed on the surface side of the porous structure 9. Specifically, in the porous structure 9 having a plurality of columnar semiconductor remaining portions, it is preferable that the surface connecting the tips of the semiconductor remaining portions has irregularities with an elevation difference of about 10 nm or more. The irregularities on the surface side or bottom side in the porous structure 9 as described above are obtained by optimizing the porous processing conditions (composition ratio of the mixed solution (wet etching solution), processing temperature, processing time, etc.) or by photolithography. It can be formed by further combining the process and the etching process.

  By the way, also in this modification, the p-type AlGaN / GaN strained superlattice layer 5 and the p-type AlGaN electron barrier layer 4 are provided between the InGaN multiple quantum well active layer 3 and the p-type GaN contact layer 6. Thus, it is desirable to form one or more heterointerfaces by providing a non-porous semiconductor layer to be a current diffusion layer between the active layer and the contact layer. The reason is as follows. Carriers injected from the p-side ohmic electrode 7 having an opening on the light extraction portion of the p-type GaN contact layer 6, that is, the p-side ohmic electrode 7 formed on the non-porous region of the p-type GaN contact layer 6 are Since the porous structure 9 is difficult to diffuse in the lateral direction (direction parallel to the main surface of the substrate) in the p-type GaN contact layer, it is difficult to obtain uniform light emission from the entire surface of the light extraction surface. . On the other hand, by providing a plurality of heterointerfaces between the active layer and the contact layer as in the present modification, the lateral diffusion of carriers can be promoted, so that more uniform light emission can be obtained. it can.

  As described above, according to the present modification, the porous structure 9 is formed in the p-type GaN contact layer 6 having the surface serving as the light extraction surface, and thus emitted from the InGaN multiple quantum well active layer 3. It is possible to prevent light from being totally reflected on the surface of the p-type GaN contact layer 6, thereby improving the light extraction efficiency. In addition, since a large number of voids are irregularly formed due to the porous structure, it is possible to avoid a situation in which a specific radiation pattern is generated due to interference between diffracted lights in the radiation pattern of light emitted from the element. Therefore, it is possible to realize a semiconductor light emitting device with high light extraction efficiency and good radiation pattern.

  In addition, according to this modification, the p-type GaN contact layer 6 can be made porous by wet etching, thereby avoiding the problem that the p-type GaN contact layer 6 is damaged due to dry etching. be able to.

  Moreover, according to this modification, the light absorption edge wavelength of the porous p-type GaN contact layer 6 is shifted to the short wavelength side compared with that before the porous structure, so that the InGaN multiple quantum well active layer 3 As a result, the light extraction efficiency can be further increased.

  In addition, according to this modification, since it is not necessary to use advanced photolithography technology when manufacturing the element, the yield can be improved.

In this modification, a mixed liquid of methanol, hydrofluoric acid and hydrogen peroxide water was used for the porous treatment of the p-type GaN contact layer 6, but instead, hydrofluoric acid and hydrogen peroxide. A mixture of water may be used. Further, when an SiC layer is used as the contact layer instead of the p-type GaN layer, a wet etching solution containing HF (hydrofluoric acid) and S ₂ O ₈ ⁴⁻ is used for the porous processing of the SiC layer. It may be used.

  Moreover, in this modification, it is preferable that a reflective film made of a metal or dielectric multilayer structure is formed on the back surface of the sapphire substrate 1 (the surface opposite to the surface on which the n-type GaN layer 2 and the like are formed). . In this way, light emitted from the InGaN multiple quantum well active layer 3 toward the sapphire substrate 1 is efficiently reflected by the reflective film, so that the light extraction efficiency from the light extraction surface can be further improved. it can.

  In this modification, the porous structure 9 is formed in the p-type GaN contact layer 6. Instead, the porous structure 9 is formed in another semiconductor layer provided on the p-type GaN contact layer 6. However, the same effect can be obtained.

(Second Embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a view showing a cross-sectional structure of the semiconductor light emitting device according to the second embodiment. The semiconductor light emitting device according to the second embodiment is different from the first embodiment (see FIGS. 1A and 1B) in that, instead of the p-type GaN contact layer 6, as shown in FIG. In addition, the p-type AlGaN gradient composition contact layer 10 is formed in which the Al composition continuously decreases from, for example, about 10% to 0% from the substrate side to the surface side. Other components are the same as those in the first embodiment including the manufacturing method.

  FIG. 8 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type AlGaN gradient composition contact layer 10 in the semiconductor light emitting device according to the second embodiment. In FIG. 8, a graph showing a change in the Al composition in the AlGaN gradient composition contact layer 10 is shown together with the above-described cross-sectional structure.

  As shown in FIG. 8, in the porous structure 9 of the second embodiment, the size (width) of p-type AlGaN gradually decreases from the substrate side to the surface side. This is because the AlGaN etching rate (etching rate in the same porous processing as in the first embodiment) increases as the Al composition decreases. Thereby, in the porous structure 9, the filling rate of p-type AlGaN gradually decreases from the substrate side toward the surface side. In other words, the ratio of the voids per unit volume in the porous structure 9 increases as the distance from the InGaN multiple quantum well active layer 3 increases. For this reason, since the effective refractive index of the porous structure 9 of the p-type AlGaN gradient composition contact layer 10 gradually decreases from the substrate side to the surface side, the light extraction efficiency is improved as compared with the first embodiment. Can be increased.

  In the second embodiment, the Al composition of the p-type AlGaN gradient composition contact layer 10 is continuously changed. Instead, the Al composition may be changed stepwise. Further, instead of the p-type AlGaN graded composition contact layer 10, another graded composition layer whose band gap energy gradually or continuously decreases as the distance from the InGaN multiple quantum well active layer 3 may be used. Even in this case, the proportion of voids per unit volume in the porous region of the other gradient composition layer can be increased as the distance from the active layer increases. As a result, the other gradient composition layer Since the effective refractive index of the porous region gradually decreases from the substrate side to the surface side, the light extraction efficiency can be further increased.

(Third embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a third embodiment of the present invention will be described with reference to the drawings. The semiconductor light emitting device according to the third embodiment is different from the second embodiment (see FIGS. 7 and 8) in the detailed structure of the porous structure 9 of the p-type AlGaN gradient composition contact layer 10. is there. That is, the element structure of the third embodiment other than the detailed structure is the same as that of the second embodiment.

  FIG. 9 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type AlGaN gradient composition contact layer 10 in the semiconductor light emitting device according to the third embodiment.

As shown in FIG. 9, in this embodiment, an oxide film 11 (specifically, Ga ₂ O _x (specifically) is formed on the semiconductor surface in contact with each void in the porous structure 9 of the p-type AlGaN gradient composition contact layer 10 by thermal oxidation. 0 <x ≦ 3)) is formed. Thereby, since the AlGaN surface in the porous structure 9 is not directly exposed to the atmosphere, the reliability of the device is greatly improved as compared with the second embodiment.

  In the third embodiment, the case where the AlGaN surface in the p-type AlGaN gradient composition contact layer 10 formed with the porous structure 9 is oxidized has been described as an example. However, the present invention is not limited thereto, and the material of the contact layer is GaN. In the case of AlGaInN, InGaN or the like, the same effect can be obtained by oxidizing the semiconductor surface in the porous structure.

(Fourth embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a fourth embodiment of the present invention will be described with reference to the drawings. The semiconductor light emitting device according to the fourth embodiment is different from the first embodiment (see FIGS. 1A, 1B, and 4) in that the porous structure of the p-type GaN contact layer 6 is used. 9 is a detailed structure in FIG. That is, the element structure of the fourth embodiment other than the detailed structure is the same as that of the first embodiment.

  FIG. 10 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type GaN contact layer 6 in the semiconductor light emitting device according to the fourth embodiment.

  As shown in FIG. 10, in this embodiment, the porous structure 9 of the p-type GaN contact layer 6 is covered with a protective film 12 formed by, for example, a CVD (Chemical Vapor Deposition) method or a sputtering method. In this case, as shown in FIG. 10, the protective film 12 is not formed up to the inside of the porous structure 9. That is, the protective film 12 is formed only near the surface of the porous structure 9. However, since the GaN surface in the porous structure 9 is not directly exposed to the atmosphere, the reliability of the device is greatly improved as compared with the first embodiment.

In the fourth embodiment, the type of the protective film 12 is not particularly limited. For example, SiO ₂ , Al ₂ O ₃ , SiN, TiO ₂ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ or Ga ₂ O is used. _A single layer structure or a multilayer structure made of a material selected from _{3 and the} like can be used.

(Fifth embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a fifth embodiment of the present invention will be described with reference to the drawings. The semiconductor light emitting device according to the fifth embodiment is different from the first embodiment (see FIGS. 1A, 1B, and 4) in that the porous structure of the p-type GaN contact layer 6 is used. 9 is a detailed structure in FIG. That is, the element structure of the fifth embodiment other than the detailed structure is the same as that of the first embodiment.

  FIG. 11 is a diagram schematically showing a cross-sectional structure of the porous structure 9 of the p-type GaN contact layer 6 in the semiconductor light emitting device according to the fifth embodiment.

  As shown in FIG. 11, in this embodiment, the porous structure 9 of the p-type GaN contact layer 6 is covered with a transparent conductive film (transparent electrode) 13. Thereby, since the GaN surface in the porous structure 9 is not directly exposed to the atmosphere, the reliability of the device is greatly improved as compared with the first embodiment. In addition, since the carriers can be injected more uniformly from the p-side ohmic electrode 7 (see FIGS. 1A and 1B), the light emission efficiency of the device can be further improved.

In the fifth embodiment, the material of the transparent conductive film 13 is not particularly limited. For example, ITO (In ₂ SnO ₃ ), β-GaO _3, or the like can be used. Further, as the transparent conductive film 13, a laminated film of a Ni film and an Au film that are thinned to a thickness of several nm or less may be used.

(Sixth embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a sixth embodiment of the present invention will be described with reference to the drawings.

  FIG. 12 is a drawing showing a cross-sectional structure of a semiconductor light emitting device according to the sixth embodiment.

The method for manufacturing the semiconductor light emitting device according to the sixth embodiment is as follows. As in the first embodiment, first, an n-type GaN layer 2 (thickness: about 3.0 μm), an InGaN multiple quantum well active layer is formed on a sapphire substrate (not shown) made of a wafer, for example, using MOCVD. 3. A p-type Al _0.15 Ga _0.85 N electron barrier layer 4 (thickness 10 nm) and a p-type GaN contact layer 6 (thickness 50 nm) are sequentially formed. Here, the InGaN multiple quantum well active layer 3 is formed by stacking three layers of an In _0.1 Ga _0.9 N quantum well layer (thickness 2.5 nm) and an In _0.02 Ga _0.98 N barrier layer (thickness 5 nm). Is.

  Next, the p-side ohmic electrode 7 and the Au plating layer 12 are sequentially formed on the p-type GaN contact layer 6 over the entire surface. Thereafter, the sapphire substrate is peeled off from the crystal growth layer (the aforementioned laminated structure of each semiconductor layer) by, for example, irradiating a short pulse ultraviolet laser light from the sapphire substrate side. Thereafter, the n-side ohmic electrode 8 is formed so as to have an opening on the surface of the light extraction portion of the surface of the n-type GaN layer 2 exposed by the substrate peeling. Finally, the n-side ohmic electrode 8 in the n-type GaN layer 2 is formed. A porous structure (porous region) 9 is formed by performing a porous treatment on the portion exposed to the opening. FIG. 12 shows the cross-sectional structure of the device with the n-type GaN layer 2 side up and the p-type GaN contact layer 6 side down after the substrate is peeled off.

  As described above, according to the sixth embodiment, since the porous structure 9 is formed in the n-type GaN layer 2 having the surface serving as the light extraction surface, it is emitted from the InGaN multiple quantum well active layer 3. Can be prevented from being totally reflected on the surface of the n-type GaN layer 2, thereby improving the light extraction efficiency. In addition, since a large number of voids are irregularly formed due to the porous structure, it is possible to avoid a situation in which a specific radiation pattern is generated due to interference between diffracted lights in the radiation pattern of light emitted from the element. Therefore, it is possible to realize a semiconductor light emitting device with high light extraction efficiency and good radiation pattern.

  Further, according to the sixth embodiment, since the porous processing for the n-type GaN layer 2 can be performed by wet etching, the problem that the n-type GaN layer 2 is damaged due to dry etching is avoided. be able to.

  In addition, according to the sixth embodiment, the light absorption edge wavelength of the n-type GaN layer 2 that has been made porous shifts to the short wavelength side compared to before the porous structure, so that the InGaN multiple quantum well active layer As a result, the light extraction efficiency can be further increased.

  In addition, according to the sixth embodiment, since it is not necessary to use advanced photolithography technology when manufacturing an element, the yield can be improved.

  Further, according to the sixth embodiment, the p-side ohmic electrode 7 whose contact resistance is generally larger than that of the n-side electrode can be formed over the entire surface of the p-type GaN contact layer 6 without opening, so that the operating voltage is reduced. it can. Specifically, for example, the operating voltage when driving at 20 mA could be reduced from 3.0V to 2.8V.

  Further, according to the sixth embodiment, as a material of the p-type ohmic electrode 7, a material having a large reflectance with respect to the emission wavelength of the InGaN multiple quantum well active layer 3, for example, Pt, Rh, Ag, or the like is used. Since the light emitted from the InGaN multiple quantum well active layer 3 toward the Au plating layer 12 can be efficiently reflected toward the n-type GaN layer 2, the light extraction efficiency can be further improved.

In the sixth embodiment, similarly to the first embodiment, a p-type AlGaN / GaN strained superlattice layer may be provided between the p-type AlGaN electron barrier layer 4 and the p-type GaN contact layer 6. . Here, as the p-type AlGaN / GaN strained superlattice layer, for example, a laminated structure of a p-type Al _0.1 Ga _0.9 N layer (thickness 1.5 nm) and a p-type GaN layer (thickness 1.5 nm) is 50 periods. A part formed can be used.

(Seventh embodiment)
Hereinafter, a semiconductor light emitting device and a method for manufacturing the same according to a seventh embodiment of the present invention will be described with reference to the drawings.

  FIG. 13 is a cross-sectional view of a semiconductor light emitting device according to the seventh embodiment.

The method for manufacturing the semiconductor light emitting device according to the seventh embodiment is as follows. Similar to the sixth embodiment, first, an n-type GaN layer 2 (thickness of about 3.0 μm), an InGaN multiple quantum well active layer is formed on a sapphire substrate (not shown) made of a wafer, for example, using MOCVD. 3. A p-type Al _0.15 Ga _0.85 N electron barrier layer 4 (thickness 10 nm) and a p-type GaN contact layer 6 (thickness 50 nm) are sequentially formed. Here, the InGaN multiple quantum well active layer 3 has a three-period stacked structure of an In _0.1 Ga _0.9 N quantum well layer (thickness 2.5 nm) and an In _0.02 Ga _0.98 N barrier layer (thickness 5.0 nm). Formed.

Next, after forming the transparent electrode 14 and the dielectric multilayer structure 15 made of, for example, ITO over the entire surface of the p-type GaN contact layer 6, the light extraction portion of the n-type GaN layer 2 in the dielectric multilayer structure 15 is formed. The portions other than the region immediately below are removed by photolithography and etching. Here, the dielectric multilayer structure 15 is formed by alternately depositing, for example, SiO ₂ films (film thickness 69 nm) and TiO ₂ films (film thickness 40 nm) for 10 cycles. Then, after forming the Au plating layer 12 on the dielectric multilayer structure 15 and the transparent electrode 14, the sapphire substrate is irradiated with a short pulse ultraviolet laser light from the sapphire substrate side, for example. Layered structure of each semiconductor layer). Thereafter, the n-side ohmic electrode 8 is formed so as to have an opening on the surface of the light extraction portion of the surface of the n-type GaN layer 2 exposed by the substrate peeling. Finally, the n-side ohmic electrode 8 in the n-type GaN layer 2 is formed. A porous structure (porous region) 9 is formed by performing a porous treatment on the portion exposed to the opening. FIG. 13 shows the cross-sectional structure of the element with the n-type GaN layer 2 side up and the p-type GaN contact layer 6 side down after the substrate is peeled off.

  According to the seventh embodiment, in addition to the same effects as in the sixth embodiment, the following effects can be obtained. That is, light emitted from the InGaN multiple quantum well active layer 3 in the direction of the p-type GaN contact layer 6, that is, in the direction of the Au plating layer 12 is efficiently reflected by the dielectric multilayer structure 15. The light extraction efficiency from the surface of the GaN layer 2 can be further improved.

In the seventh embodiment, the dielectric multilayer structure 15 is a SiO ₂ / TiO ₂ laminated structure for 10 cycles. However, the present invention is not limited to this, and the material or film thickness of the dielectric multilayer structure 15 is as follows. It can be set freely so as to obtain a high reflectance with respect to the emission wavelength from the InGaN multiple quantum well active layer 3.

  In the seventh embodiment, the reflective film made of the dielectric multilayer structure 15 is formed on the surface of the p-type GaN contact layer 6 having the surface opposite to the light extraction surface. Alternatively, a reflective film made of metal may be formed.

In the seventh embodiment, a p-type AlGaN / GaN strained superlattice layer may be provided between the p-type AlGaN electron barrier layer 4 and the p-type GaN contact layer 6 as in the first embodiment. . Here, as the p-type AlGaN / GaN strained superlattice layer, for example, a laminated structure of a p-type Al _0.1 Ga _0.9 N layer (thickness 1.5 nm) and a p-type GaN layer (thickness 1.5 nm) is 50 periods. A part formed can be used.

Further, in the seventh embodiment, ITO is used as the material of the transparent electrode 14, but instead of this, for example, β-GaO ₃ or the like may be used. Further, as the transparent electrode 14, a laminated film of a Ni film and an Au film thinned to a thickness of several nm or less, for example, a laminated film of a Ni film having a thickness of 2 nm and an Au film having a thickness of 3 nm may be used. .

Furthermore, in the first to seventh embodiments described above, the InGaN multiple quantum well active layer 3 is used as an active layer, and the GaN contact layer 6 or the AlGaN gradient composition contact layer 10 is used as a layer that forms a porous structure. Although used, the present invention is not limited to this. Specifically, when using a nitride-based compound semiconductor as the material of the semiconductor layers constituting the semiconductor light emitting element of the embodiments of the present invention, for example formula _{B x Al y In z Ga 1} -xyz N (0 ≦ Even if a material represented by x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ x + y + z ≦ 1) is used for each semiconductor layer, the same effect as each embodiment of the present invention can be obtained. it can. At this time, as the material of the active layer, for example, a nitride compound semiconductor represented by the general formula Al _x Ga _1-x N (0 ≦ x ≦ 1) may be used.

  In the first to seventh embodiments, when the wavelength (center wavelength) of light emitted from the InGaN multiple quantum well active layer 3 is 200 nm or more and shorter than 430 nm, a white LED can be realized. .

  The semiconductor light-emitting device of the present invention can be used not only as a simple indicator lamp but also as an illumination light source in place of a fluorescent lamp or an incandescent lamp.

(A) is a top view of the semiconductor light-emitting device concerning the 1st Embodiment of this invention, (b) is sectional drawing of the II line | wire in Fig.1 (a). It is a figure which shows the electric current-light output characteristic of the semiconductor light-emitting device concerning the 1st Embodiment of this invention. It is a figure which shows the radiation pattern of the light radiated | emitted from the semiconductor light-emitting device concerning the 1st Embodiment of this invention. It is a figure which shows typically the cross-section of the porous area | region of the contact layer in the semiconductor light-emitting device concerning the 1st Embodiment of this invention. (A) is a figure which shows the light absorption spectrum of the porous area | region of the p-type GaN contact layer in the semiconductor light-emitting device concerning the 1st Embodiment of this invention, (b) is a non-porous of this p-type GaN contact layer. It is a figure which shows the light absorption spectrum of a quality area | region. It is a figure which shows typically the cross-sectional structure of the porous area | region of the contact layer in the semiconductor light-emitting device which concerns on the modification of the 1st Embodiment of this invention. It is sectional drawing of the semiconductor light-emitting device based on the 2nd Embodiment of this invention. It is a figure which shows typically the cross-sectional structure of the porous area | region of the contact layer in the semiconductor light-emitting device concerning the 2nd Embodiment of this invention. It is a figure which shows typically the cross-section of the porous area | region of the contact layer in the semiconductor light-emitting device concerning the 3rd Embodiment of this invention. It is a figure which shows typically the cross-sectional structure of the porous area | region of the contact layer in the semiconductor light-emitting device concerning the 4th Embodiment of this invention. It is a figure which shows typically the cross-sectional structure of the porous area | region of the contact layer in the semiconductor light-emitting device concerning the 5th Embodiment of this invention. It is sectional drawing of the semiconductor light-emitting device based on the 6th Embodiment of this invention. It is sectional drawing of the semiconductor light-emitting device based on the 7th Embodiment of this invention. It is sectional drawing of the conventional semiconductor light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sapphire substrate 2 n-type GaN layer 3 InGaN multiple quantum well active layer 4 p-type AlGaN electron barrier layer 5 p-type AlGaN / GaN strained superlattice layer 6 p-type GaN contact layer 7 p-side ohmic electrode 8 n-side ohmic electrode 9 porous Materialized region 10 P-type AlGaN graded composition contact layer 11 Oxide film 12 Protective film 13 Transparent conductive film 14 Transparent electrode 15 Dielectric multilayer structure

Claims (22)

  In a semiconductor light emitting device in which a plurality of semiconductor layers including an active layer are stacked, at least a part of the semiconductor layer having a surface serving as a light extraction surface for extracting light from the active layer is porous among the plurality of semiconductor layers. A semiconductor light emitting device characterized in that the semiconductor light emitting device is characterized.   The semiconductor light emitting element according to claim 1, wherein the bottom of each void in the porous region of the semiconductor layer forms irregularities.   The semiconductor light emitting device according to claim 1, wherein the porous region of the semiconductor layer has a plurality of remaining semiconductor portions, each of which has an unevenness at the tip. The plurality of semiconductor layers include another semiconductor layer that is provided between the active layer and the semiconductor layer and that does not become porous and serves as a current diffusion layer.
The semiconductor light emitting element according to claim 1, wherein an electrode is provided on the non-porous region of the semiconductor layer.   The semiconductor light emitting device according to claim 4, wherein the current diffusion layer has at least one heterointerface.   2. The semiconductor light emitting element according to claim 1, wherein the light absorption edge wavelength of the porous region of the semiconductor layer is shorter than the light absorption edge wavelength of the non-porous region of the semiconductor layer.   2. The semiconductor light emitting element according to claim 1, wherein a light absorption edge wavelength of the porous region of the semiconductor layer is shorter than a center wavelength of light emitted from the active layer.   2. The semiconductor light emitting element according to claim 1, wherein among the voids in the porous region of the semiconductor layer, a distance between adjacent voids is 20 nm or less.   2. The semiconductor light emitting device according to claim 1, wherein an effective refractive index in the porous region of the semiconductor layer decreases as the distance from the active layer increases.   2. The semiconductor light emitting element according to claim 1, wherein a ratio of voids per unit volume in the porous region of the semiconductor layer increases as the distance from the active layer increases.   The semiconductor light emitting device according to claim 1, wherein the band gap energy of the semiconductor layer decreases stepwise or continuously as the distance from the active layer increases.   The semiconductor light emitting element according to claim 1, wherein a semiconductor surface in contact with each void in the porous region of the semiconductor layer is oxidized.   2. The semiconductor light emitting element according to claim 1, wherein the surface side of the porous region of the semiconductor layer is covered with a protective film. The protective _{layer, SiO 2, Al 2 O 3} , SiN, a semiconductor light emitting according to claim 13, characterized in that consisting of _{TiO 2, ZrO 2, Nb 2} O 5, Ta 2 O 5 or Ga ₂ O ₃ element.   The semiconductor light emitting element according to claim 1, wherein the surface side of the porous region of the semiconductor layer is covered with a transparent electrode.   The semiconductor light emitting device according to claim 1, wherein the semiconductor layer is an n-type semiconductor layer. The plurality of semiconductor layers are formed on a substrate;
2. The semiconductor light emitting element according to claim 1, wherein a reflective film made of a metal or dielectric multilayer structure is formed on a main surface of the substrate where the plurality of semiconductor layers are not formed. 3.   2. A reflective film made of a metal or dielectric multilayer structure is formed on the surface of another semiconductor layer having a surface opposite to the light extraction surface of the plurality of semiconductor layers. The semiconductor light-emitting device described in 1. Each of the plurality of semiconductor layers, nitride represented by _{B x Al y In z Ga 1} -xyz N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1,0 ≦ x + y + z ≦ 1) The semiconductor light-emitting device according to claim 1, comprising a physical compound semiconductor.   20. The semiconductor light emitting device according to claim 19, wherein the wavelength of light emitted from the active layer is shorter than 430 nm. 2. The semiconductor light emitting element according to claim 1, wherein the semiconductor layer is made of a nitride compound semiconductor represented by Al _x Ga _1-x N (0 ≦ x ≦ 1). Sequentially forming at least an n-type semiconductor layer, a semiconductor layer to be an active layer, and a p-type semiconductor layer on a substrate;
Separating the multilayer structure of each semiconductor layer and the substrate;
And a step of making at least a part of the n-type semiconductor layer having a surface to be a light extraction surface for extracting light from the active layer out of the multilayer structure. Manufacturing method.

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