JP2005276899A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element that can be improved fully in current diffusing effect, even if the thickness of a current diffusing layer is small and, furthermore, can uniformly energize the light-emitting layer section. <P>SOLUTION: The light-emitting element 100 is constituted of the light-emitting layer 24 composed of a compound semiconductor, and the current diffusing layer 91 composed of a compound semiconductor layer 24 having a thickness larger than that of the light-emitting layer 24 and laminated upon the light-emitting layer 24. In addition, a current diffusing quantum well layer 8 is provided in the current diffusing layer 91. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting element.

JP-A-5-275740 JP 2001-68731 A

  Energization of the light emitting layer portion of the light emitting element is performed through an electrode formed on the element surface. However, since the electrode acts as a light shielding body, for example, it is formed so as to cover only the central portion of the main surface of the light emitting layer portion, and light is extracted from the surrounding electrode non-formation region.

  In this case, reducing the area of the electrode as much as possible can increase the area of the light extraction region formed around the electrode, which is advantageous from the viewpoint of improving the light extraction efficiency. Conventionally, attempts have been made to increase the light extraction amount by effectively spreading the current in the element by devising the electrode shape, but in this case as well, an increase in the electrode area is unavoidable anyway, and the light extraction area On the contrary, it falls into a dilemma where the amount of light extraction is limited by the decrease. In addition, the carrier concentration of the dopant in the clad layer, and thus the conductivity, is kept somewhat low in order to optimize the light emission recombination of carriers in the active layer, and the current tends not to spread in the in-plane direction. . This leads to concentration of current density in the electrode covering region and a substantial light extraction amount in the light extraction region. Therefore, a method of forming a current diffusion layer between the light emitting layer portion and the electrode is employed. As disclosed in Patent Document 1 and Patent Document 2, the current diffusion layer can also be used as an element substrate by being formed thick.

  In order to obtain a sufficient current spreading effect, the current spreading layer needs to be set to a certain thickness. However, the device is reduced in height and size, the light emitting layer is protected from the heat history of layer growth, or the electrode is formed. In view of the convenience of the above, there are cases where the thickness of the current diffusion layer cannot always be ensured to be large. If the thickness of the current diffusion layer is insufficient, it is difficult to uniformly energize the light emitting layer portion, which may lead to deterioration in light emission efficiency and light extraction efficiency.

  An object of the present invention is to provide a light-emitting element that can sufficiently enhance the current diffusion effect even if the thickness of the current diffusion layer is small, and that enables uniform current supply to the light-emitting layer portion.

Means and actions / effects for solving the problems

  In order to solve the above problems, a light emitting device of the present invention includes a light emitting layer portion made of a compound semiconductor, and a current diffusion layer laminated on the light emitting layer portion made of a compound semiconductor layer thicker than the light emitting layer portion. And a current diffusion quantum well layer is provided in the current diffusion layer.

  The quantum well layer is lattice-matched between a well layer and a barrier layer having different band gaps so that at least the thickness of the well layer is an electron mean free path or less (generally, one atomic layer to several nm). In order to promote the light emission recombination process using the carrier confinement effect in the layer thickness direction and to improve the internal quantum efficiency, it has been often used in the light emitting layer part in the past. . In the present invention, focusing on the movement of the majority carriers in the layer thickness direction in such a quantum well layer, on the other hand, the degree of freedom of movement in the in-plane direction is increased. Incorporation into the inside can promote the movement of the carriers in the in-plane direction even with a thin current diffusion layer, and a good current spreading effect can be obtained.

  The quantum well layer for current diffusion is formed by alternately stacking well layers and barrier layers each having a film thickness of a compound semiconductor having a band gap energy larger than the band gap energy corresponding to the peak emission wavelength from the light emitting layer portion. Can be. Thereby, absorption of the emitted light flux in the current spreading quantum well layer is suppressed, and the light extraction efficiency of the device can be increased.

  In the current spreading layer, increasing the effective carrier concentration as much as possible leads to an improvement in the current spreading effect, but in order to do so, it is also necessary to increase the amount of dopant added to the current spreading layer. However, since the dopant atoms also act as scattering sites for the generated carriers, it is difficult to sufficiently reduce the in-plane electrical resistivity (so-called sheet resistance) of the thin current diffusion layer only by increasing the dopant concentration. On the other hand, to increase the freedom of carrier movement in the in-plane direction of the quantum well layer, it is effective to configure the quantum well layer as a non-doped layer, but the quantum well layer itself does not function as a carrier generation source. Therefore, the sheet resistance of the current diffusion layer cannot be sufficiently reduced by itself. Therefore, the current spreading layer is formed by forming the current spreading quantum well layer as a non-doped layer, and is disposed in contact with the current spreading quantum well layer, and has a band gap larger than that of the barrier layer of the current spreading quantum well layer. It may be configured to have a main body layer having a large energy and a higher effective carrier concentration than the well layer and the barrier layer. In this structure, the main body layer cannot be expected to have much current diffusion effect in the plane itself, but since the dopant concentration is high, it functions as a generation source of majority carriers. It is injected into the well layer. Since the dopant concentration is low in the quantum well layer, the high-concentration majority carriers injected from the main body layer move quickly in the plane without being greatly affected by scattering. In addition, since the band gap energy of the barrier layer of the quantum well layer for current diffusion is smaller than the band gap energy of the main layer, majority carriers injected from the main layer are spatially separated from the main layer having a high dopant concentration. The effect of being separated is increased. As a result, the current spreading effect of the entire layer can be greatly enhanced. This effect is more conspicuous when the current diffusion layer is configured to have a structure in which the current diffusion quantum well layer is sandwiched between two main body layers.

  It should be noted that the thickness of the barrier layer is set larger than the thickness of the well layer, specifically, the tunnel thickness of the majority carriers (for example, 50 nm or more) or more, so that the well layer is formed as a two-dimensional electron gas layer. It becomes possible to function, and the current spreading effect can be further enhanced.

  More specifically, the light emitting device of the present invention can be configured as follows. That is, the current diffusion layer is disposed on the second main surface side of the light emitting layer portion, the first main surface of the semiconductor laminate including the light emitting layer portion and the current diffusion layer is defined as a light extraction surface, From the first main surface to the midway position in the thickness direction of the current diffusion layer, a cutout portion is formed by cutting out in a partial region of the first main surface. A light extraction side electrode for applying a driving voltage to the light emitting layer portion is disposed so as to cover a part of the light extraction surface, while the light emitting layer portion is formed on the bottom surface of the notch portion located in the current diffusion layer. A counter electrode for applying a driving voltage is disposed on the substrate.

  According to the above configuration, since the light extraction electrode and the counter electrode having different polarities can be formed on the same main surface side of the element, the electrode formation process can be simplified. However, in this structure, since the current diffusion layer is notched halfway in the layer thickness direction and the counter electrode is formed on the bottom surface of the notch, the thin region that forms the bottom of the notch must be the current constriction. However, it is particularly difficult to uniformly diffuse the current in the plane of the current diffusion layer. Thus, by disposing the current spreading layer in the current spreading layer as in the present invention, a sufficient current spreading effect can be achieved even with the current spreading layer thus cut out. In this case, when a light emission driving voltage is applied between the light extraction side electrode and the counter electrode, an electric field gradient serving as a carrier movement driving force is generated in the section from the first main surface of the current diffusion layer to the bottom surface of the notch. Since it can be generated relatively large, the injection of majority carriers into the current diffusion quantum well layer can be promoted by arranging the current diffusion quantum well layer in the section, and consequently the in-plane current diffusion effect Can be further enhanced.

  The light-emitting element having the above structure includes a second current diffusion layer provided on the first main surface side of the light-emitting layer portion and a current diffusion quantum well layer on the second main surface side of the light-emitting layer portion. A structure in which a current spreading layer is provided can be employed. By providing a current diffusion layer also on the first main surface side of the light emitting layer portion, the current diffusion effect can be further enhanced, and the side surface area of the element is increased, so that the light extraction efficiency from the side surface can be improved. In this case, the element structure can be simplified by not providing the quantum well layer for current diffusion for the first current diffusion layer that does not have a notch and does not cause a problem of current bypass. .

  In addition, a current diffusion layer having a quantum well layer for current diffusion needs to form a fine layered structure of a well layer and a barrier layer by an epitaxial growth process on the main body layer by vapor phase epitaxy, etc. It is advantageous to perform the process in a separate process from the growth of the layer part because it is not easily restricted by the manufacturing process of the light emitting element. In this case, the semiconductor stacked body may be manufactured by bonding a current diffusion layer having a current diffusion quantum well layer to the light emitting layer portion.

  Next, in the light emitting device of the present invention, the cross-sectional area of the laminate body is defined by a plane perpendicular to the thickness direction, with the portion located on the light extraction surface side from the bottom surface of the cutout portion of the semiconductor laminate. However, it can be formed by inclining the side surface of the laminate body so as to increase as it approaches the light extraction surface. According to this structure, since the side surface of the laminate body is an inclined surface, the reflection efficiency is increased, and the extracted light flux toward the light extraction surface side can be increased, so that a high-luminance light-emitting element can be realized. it can. The inclined side surface of the laminate body can be further covered with a metal reflective film. Thereby, the reflection efficiency of the emitted light beam on the inclined side surface can be further increased. On the other hand, the light emitting layer portion forming the pn junction is exposed on the inclined side surface of the laminate body, and if this is directly covered with the metal reflection film, the pn junction may be short-circuited. In order to solve this problem, it is desirable to dispose an insulating film between the metal reflective film and the inclined side surface portion.

  When the light emitting layer portion is made of AlGaInP, a light absorbing GaAs substrate is used as the substrate for growing the light emitting layer portion. In order to suppress the adverse effect of light absorption by the GaAs substrate, the GaAs substrate can be removed after the light emitting layer portion is grown. The GaAs substrate can be removed relatively easily by grinding or chemical etching. The main surface of the light emitting layer portion on the side from which the GaAs substrate is removed can be used as a light extraction surface (that is, the first main surface) or as a back surface (that is, the second main surface). In any case, since there is no growth GaAs substrate on the second main surface of the light emitting layer portion, the second main surface of the current diffusion layer disposed on the second main surface side of the light emitting layer portion is reflected back. It is easy to cover with layers. Thereby, the luminous flux directed toward the second main surface of the current diffusion layer can also be efficiently reflected to the light extraction surface side, and the light extraction efficiency of the element can be increased.

  In this case, since the counter electrode is provided on the bottom surface of the notch, the back reflective layer disposed on the second main surface of the current diffusion layer does not necessarily have a function as an electrode. Therefore, a bonding alloying layer for reducing contact resistance can be not disposed between the back reflective layer and the current diffusion layer. In a conventional configuration of a light emitting element of a type in which a current diffusion layer is also provided on the second main surface side of the light emitting layer portion, as in Patent Document 2, for example, a back surface reflection layer that also serves as an electrode on the second main surface of the current diffusion layer Therefore, a bonding alloying layer for reducing the contact resistance with the electrode is dispersedly formed on the second main surface of the current diffusion layer. The joining alloyed layer is formed by alloying a metal for reducing contact resistance with the current diffusion layer by heat treatment (so-called sinter treatment), so that the reflectance is low. However, by adopting the present invention, the bonded alloying layer can be eliminated from between the back surface reflection layer and the current diffusion layer, and the reflection efficiency by the back surface reflection layer can be further increased.

  For the AlGaInP light-emitting layer, a current diffusion layer made of GaP, GaInP, or AlGaAs is thickened to a thickness of 50 μm or more and 200 μm or less by bonding or hydride vapor phase epitaxy (HVPE). It is also easy to form. Therefore, by removing the GaAs substrate, it is possible to increase the thickness of the current diffusion layer on the second main surface side of the light emitting layer (having the current diffusion quantum well layer) to 50 μm or more and 200 μm or less, The current spreading effect and the light extraction efficiency from the device side surface can be further improved.

  On the other hand, in the light-emitting device of the present invention, the light-emitting layer portion can be composed of InGaAlN, which is a group III nitride. The light emitting layer portion made of InGaAlN can be formed by epitaxial growth on a substrate such as sapphire or SiC by metal-organic vapor phase epitaxy (MOVPE). In particular, a sapphire substrate can easily obtain a substrate with good crystallinity. However, unlike a GaAs substrate, a sapphire substrate is very hard and chemically stable, and thus is difficult to remove by grinding, chemical polishing, or the like, and often remains as an element substrate even in a final light emitting element. Therefore, a current diffusion layer is disposed on the second main surface side of the light emitting layer portion, and a growth sapphire substrate for epitaxial growth of the current diffusion layer and the light emitting layer portion is left on the second main surface side of the current diffusion layer. It is possible to adopt a structure that has been adapted. Although the sapphire substrate is insulative, by forming a notch that reaches the current diffusion layer and disposing the counter electrode on the bottom surface of the notch, light emission drive energization becomes possible without any problem. Further, since the sapphire substrate is transparent, it is possible to take out the luminous flux from the side surface of the sapphire substrate. In this case, if a back surface reflection layer is provided on the second main surface of the sapphire substrate, the light extraction efficiency can be further improved.

  The current spreading layer can be formed of, for example, a group III nitride such as GaN, but the group III nitride is difficult to grow a thick film of 50 μm or more because it is formed by the MOVPE method. However, by incorporating a current diffusion quantum well layer as in the present invention, a good current diffusion effect can be obtained even in a thin film. In order to make the current diffusion effect remarkable, it is desirable to secure a thickness of 1 μm or more for the current diffusion layer including the current diffusion quantum well layer.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The light emitting device 100 in FIG. 1 includes a semiconductor stacked body 50 in which a second current diffusion layer 91 made of a compound semiconductor, a light emitting layer portion 24, and a first current diffusion layer 90 are stacked in this order. The first current diffusion layer 90 is made of a compound semiconductor that is transparent to the luminous flux from the light emitting layer portion 24, has a main light extraction surface EA formed on the first main surface side, and has a light emission driving voltage applied to the light emitting layer portion 24. Is formed so as to cover a part of the first main surface of the first current diffusion layer 90.

The light emitting layer portion 24 includes the active layer 5 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) mixed crystal. , P-type (Al _z Ga _1-z ) _y In _1-y P (where x <z ≦ 1) and n-type (Al _z Ga _1-z ) _y In _1-y P It has a structure sandwiched between n-type cladding layers 4 (x <z ≦ 1), and the emission wavelength is changed from green to red region (the emission wavelength (peak emission wavelength) varies depending on the composition of the active layer 5). 550 nm to 670 nm). In the light emitting element 100, the p-type AlGaInP clad layer 6 is disposed on the light extraction side electrode 9, and the n-type AlGaInP clad layer 4 is disposed on the residual substrate portion 1 side. Therefore, the light extraction side electrode 9 is positive in the energization polarity. In the present invention, “non-dope” means “no active addition of a dopant”, and contains a dopant component inevitably mixed in a normal manufacturing process (for example, 10 ¹³ to 10 ¹⁶ / cm ³ to a maximum extent) is not excluded also. Moreover, you may form the active layer 5 as what has a quantum well structure.

The first current diffusion layer 90 is made of GaP (or GaAsP or AlGaAs), and the light extraction side electrode 9 is made of, for example, an Au electrode. A region around the light extraction side electrode 9 on the first main surface of the first current diffusion layer 90 forms a main light extraction surface EA. The first current spreading layer 90 is, for example, equal to or more than the cladding layer 6 and has an effective carrier concentration of about 2 × 10 ¹⁸ / cm ³ or less, and is 10 μm or more and 200 μm or less (preferably 40 μm or more and 200 μm). In the thick film described below, the extracted light flux from the side surface of the layer is also increased, and the luminance (integrated sphere luminance) of the entire light emitting element is also increased. Further, the first current diffusion layer 90 is formed of a III-V group compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux from the light emitting layer portion 24 (that is, transparent). By doing so, absorption with respect to the luminous flux is also suppressed. In addition, between the light extraction side electrode 9 and the 1st electric current diffusion layer 90, the joining alloying layer 9a for reducing both contact resistance is formed, for example using AuBe alloy etc.

  On the other hand, the second current spreading layer 91 includes a main body layer 91m made of a III-V group compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak wavelength of the luminous flux emitted from the light emitting layer portion 24, and the main body. Current spreading quantum well layer 8 disposed in contact with layer 91m. In the present embodiment, the current spreading quantum well layer 8 is sandwiched between two main body layers 91m and 91m. The main body layer 91m has a band gap energy larger than that of the barrier layer 8b of the current spreading quantum well layer 8 and an effective carrier concentration higher than that of the well layer 8w and the barrier layer 8b. In the present embodiment, the main body layer 91m is made of GaP. The thickness of the second current diffusion layer 91 including the current diffusion quantum well layer 8 is not less than 1 μm and not more than 200 μm. In particular, when the thickness is not less than 50 μm and not more than 200 μm, from the side surface of the second current diffusion layer 91 The light extraction efficiency can be increased.

As shown in FIG. 2, the current diffusion quantum well layer 8 is formed by alternately stacking well layers 8w and barrier layers 8b. Both layers 8w and 8b are made of a compound semiconductor having a band gap energy larger than the photon energy corresponding to the peak emission wavelength from the light emitting layer portion 24. If the main layer 91m is GaP layer, the well layer 8w and the barrier layer 8b, for example, _{Ga 1-x} In x P and can be constituted by a GaAs _y P _1-y. When using Ga _1-x In _x P, the band gap energy decreases as the InP mixed crystal ratio x increases. Therefore, the InP mixed crystal ratio in the well layer 8w _{x w,} the InP mixed crystal ratio of barrier layer 8b as _{x b,} are set to _{1> x w>} x _b. When GaAs _y P _1-y is used, the band gap energy decreases as the GaAs mixed crystal ratio y increases. Accordingly, 1> y _w > y _b is set, where y _w is the GaAs mixed crystal ratio of the well layer 8w and y _b is the GaAs mixed crystal ratio of the barrier layer 8b.

  The thickness of the well layer 8w can be set to 0.5 nm or more and 10 nm or less in order to enhance the carrier confinement effect in the layer thickness direction. The thickness of the barrier layer 8b is preferably 0.5 nm or more and 20 nm or less. In particular, when the well layer 8w is to be configured as a two-dimensional electron gas layer, it is preferably 10 nm or more and 20 nm or less. The well layer 8w and the barrier layer 8b are preferably configured as non-doped layers. The current spreading quantum well layer 8 may have a multiple quantum well structure having a plurality of well layers 8w or a single quantum well structure having only one well layer w.

  Returning to FIG. 1, a notch JK is formed by notching a part of the first main surface from the first main surface of the semiconductor stacked body 50 to a middle position in the thickness direction of the current diffusion layer 91. . A counter electrode 15 made of an Au electrode or the like for applying a driving voltage to the light emitting layer portion is disposed on the bottom surface of the notch portion JK located in the current diffusion layer 91. Further, a bonding alloying layer 15a for reducing contact resistance is disposed between the main body layer 91m forming the bottom surface of the notch JK and the counter electrode 15. In the present embodiment, the main body layer 91m is n-type, and the bonding alloyed layer 9a is made of an AuGeNi alloy or the like.

  In the present embodiment, the notch JK is formed along the periphery of the rectangular first main surface of the light emitting element 100 as shown in FIG. 3, and the counter electrode 15 extends over substantially the entire bottom surface of the notch JK. Is formed. In addition, the light extraction side electrode 9 is formed substantially at the center of the light extraction surface EA. As shown in FIG. 4, a sub electrode 9 s (which can be formed in a radial shape, a dendritic shape, or a network shape) that partially covers the light extraction surface EA can be provided integrally with the light extraction side electrode 9. In FIG. 4, the width of the counter electrode 15 is set smaller than the width of the notch JK formed along the periphery of the first main surface, and the corners where the counter electrodes 15 on each side intersect are A metal pad 15c for wire bonding is formed. The notch JK is not necessarily formed along the entire circumference of the first main surface. For example, as shown in FIG. 5, the notch JK can be selectively formed at a corner of the first main surface.

  Returning to FIG. 1, in the second current diffusion layer 91, the current diffusion quantum well layer 8 is arranged in a section from the first main surface to the bottom surface of the notch JK. The first current diffusion layer 90 is not provided with a current diffusion quantum well layer. The second current diffusion layer 91 having the current diffusion quantum well layer 9 is bonded to the light emitting layer portion 24 by bonding. On the other hand, the first current diffusion layer 90 is also bonded to the light emitting layer portion 24 by bonding, and the first current diffusion layer 90 is grown on the light emitting layer portion 24 as a thick epitaxial layer. Also good.

  The second main surface of the second current diffusion layer 91 (that is, the current diffusion layer disposed on the second main surface side of the light emitting layer portion 24) is covered with the back surface reflection layer 10. The back surface reflection layer 10 is electrically separated from the counter electrode 15 and does not have a function as an electrode. Therefore, a bonding alloying layer for reducing the contact resistance between the two layers is not disposed between the back surface reflection layer 10 and the second current diffusion layer 91. In the present embodiment, the element substrate 12 that also serves as a heat sink is bonded to the second main surface of the back reflective layer 10 via a metal adhesive layer 11 made of Ag paste or the like. The element substrate 12 that also serves as a heat sink can be made of a metal having a good thermal conductivity such as a metal such as Cu or Al, aluminum nitride, silicon carbide, or alumina.

  As a result, it is not necessary to arrange a bonding alloying layer having a low reflectance on the second main surface of the semiconductor laminate 50, and the entire surface of the second main surface can be effectively used as a reflecting surface. The effect can be improved. However, with the adoption of this structure, it is indispensable that the counter electrode 15 normally provided on the second main surface is provided on the bottom surface of the notch JK formed on the first main surface side of the semiconductor stacked body 50. . As a result, in the vicinity of the counter electrode 15, the thickness of the energization path in the second current diffusion layer 91 is reduced by the notch JK, and the electrode covering region is also limited to the notch JK. Compared with the case where electrodes are formed on the entire second main surface of the second current diffusion layer 91, current diffusion in the layer surface becomes considerably difficult. However, in the light emitting device 100 according to the present invention, since the current diffusion quantum well layer 9 is provided in the second current diffusion layer 91, the light emission is performed despite the disadvantageous structure for current diffusion. A current can be supplied uniformly in the plane of the layer portion 24, and the luminous efficiency can be increased. Further, by providing the current diffusion layers 90 and 91 on both surfaces of the light emitting layer portion 24, the light extraction efficiency from the side surface of the element is improved, and an element with high emission intensity is realized.

Hereinafter, a method for manufacturing the light emitting device 100 of FIG. 1 will be described.
First, as shown in Step 1 of FIG. 6, a GaAs buffer layer 2 is grown on the first main surface of a growth substrate 1 made of an n-type GaAs single crystal, and then an n-type AlGaInP is formed as a light emitting layer portion 24. The clad layer 4, the AlGaInP active layer (non-doped) 5, and the p-type AlGaInP clad layer 6 are epitaxially grown in this order by a well-known MOVPE method. Further, a GaP substrate (p type, thickness: 40 μm or more and 200 μm or less (for example, 100 μm)) prepared separately is overlaid on the first main surface of the light emitting layer portion 24, and 350 ° C. or higher while applying pressure as shown in Step 2. The first current diffusion layer 90 is formed by bonding by heat treatment at 700 ° C. or lower and 600 ° C. in this embodiment. Instead of bonding the GaP substrate, the GaP layer may be epitaxially grown using, for example, the HVPE method. Then, the process proceeds to step 3 where the growth substrate 1 and the buffer layer 2 are removed by grinding or chemical etching.

  Proceeding to FIG. 7, a sub-wafer to be the second current diffusion layer 91 is manufactured separately from the above. Specifically, as shown in Step 4, an n-type GaP substrate to be one main body layer 91m is prepared, and a current diffusion quantum well layer 8 is epitaxially grown thereon by the MOVPE method. Thereafter, as shown in step 5, the n-type GaP layer to be the other main body layer 91m is epitaxially grown by the HVPE method or the MOVPE method to form a sub-wafer. Then, as shown in Step 6, this sub-wafer is superposed on the second main surface of the light emitting layer portion 24, and as shown in Step 7, it is 350 ° C. or higher and 700 ° C. or lower while being pressurized, and 600 ° C. in this embodiment. Then, the bonded wafer W is obtained as a second current diffusion layer 91 by heat treatment.

  Next, as shown in FIG. 8, the bonded wafer W is diced in order to separate it into individual element chips. This dicing also serves as a step of forming the notch JK in each chip. Specifically, as shown in Step 8 in FIG. 8, the position of the second current diffusion layer 91 in the thickness direction from the first main surface side of the bonded wafer W, in this embodiment, a current diffusion quantum well. A half dicing groove DG to be the notch JK is formed by using the first dicing blade DB at a depth that divides the layer 8 and reaches a midway position in the thickness direction of the main body layer 91m on the second main surface side. To do. Next, as shown in step 9, a metal layer for forming a bonding alloyed layer is formed by vapor deposition on the region to be the first main surface of each element chip and the bottom of the half dicing groove DG, Thereafter, alloying heat treatment is performed to form bonded alloyed layers 9a and 15a, and the light extraction side electrode 9 and the counter electrode 15 are formed by vapor deposition.

  Next, the back surface reflection layer 10 is formed on the second main surface of the second current diffusion layer 91, and the element substrate 12 is bonded to the second main surface of the back surface reflection layer 10 via the metal adhesive layer 11. . Then, as shown in step 10, the bottom of the half dicing groove DG is fully diced using a second dicing blade DL thinner than the first dicing blade DB, and separated into individual element chips. After the dicing, the final device chip 100 is completed by removing the processing damage layer formed on the dicing surface by chemical etching.

  Hereinafter, various modified examples of the light-emitting element of the present invention will be described (the same reference numerals are given to portions common to the light-emitting element 100 in FIG. 1 and detailed description thereof will be omitted). The light emitting device 200 of FIG. 9 is an example in which the current diffusion quantum well layer 8 is provided in the first current diffusion layer 90, and the current diffusion quantum well layer is omitted from the second current diffusion layer 91. . On the second main surface of the second current diffusion layer 91, the bonding alloying layer 31 serving as a counter electrode is dispersedly formed (therefore, the notch portion JL is not formed). The first current diffusion layer 90 whose in-plane direction current diffusibility is enhanced by the current diffusion quantum well layer 8 is formed to be thinner than the second current diffusion layer 91, thereby reducing the height of the element. Yes.

  10 has a structure close to that of the light emitting element 100 of FIG. 1, but the second current spreading layer 91 having the current spreading quantum well layer 8 is more than the first current spreading layer 90. The device is formed thin, and the height of the device is reduced. In the present embodiment, in the light emitting device 100 of FIG. 1, one of the main body layers 91m, 91m provided on both sides of the current diffusion quantum well layer 8 (here, the light emitting layer portion 24 side) is provided. It is omitted.

  In the light emitting element 400 of FIG. 11, the element substrate 7 is bonded to the second main surface of the second current diffusion layer 91 via the multiple reflection film 70. The multiple reflection film 70 is formed by forming two or more lamination period units composed of a plurality of element reflection layers having different refractive indexes. In order to configure the lamination cycle unit most simply, a two-layer structure of a first element reflection layer and a second element reflection layer having different refractive indexes with respect to the emitted light beam can be used. In this case, the larger the difference in refractive index between the two layers, the more the number of lamination period units required to ensure a sufficiently high heat ray reflectance. Note that the number of element reflection layers constituting the lamination cycle unit may be three or more.

  In order to configure the lamination cycle unit most simply, a two-layer structure of a first element reflection layer and a second element reflection layer having different refractive indexes with respect to the emitted light beam can be used. In this case, the larger the difference between the refractive indexes of the two layers, the more the number of lamination period units required for ensuring a sufficiently high reflectance of the luminous flux can be reduced. Note that the number of element reflection layers constituting the lamination cycle unit may be three or more.

  In particular, of the first element reflection layer and the second element reflection layer, the thickness of the high refractive index layer is set to t1, and the thickness of the low refractive index layer is set to t2. If the thickness of the layer is set to be smaller than the thickness of the low refractive index layer, the reflectance of the specific wavelength band with respect to the luminous flux is further increased. Then, assuming that the refractive index of the high refractive index layer for the luminous flux to be reflected is n1 and the refractive index of the low refractive index layer is n2, t1 × n1 + t2 × n2 is ½ of the wavelength λ of the luminous flux to be reflected. When they are equal, a complete reflection band having a reflectance of almost 100% can be formed in a relatively wide wavelength band including the wavelength.

  A band structure similar to the electron energy in the crystal (hereinafter referred to as photonic band structure) is formed for the photoquantized electromagnetic wave energy in the layer thickness direction of the laminate whose refractive index changes periodically. An electromagnetic wave having a specific wavelength corresponding to the period of rate change is prevented from entering the laminate structure. This phenomenon means that in the photonic band structure, the existence of electromagnetic waves in a certain energy region (that is, a certain wavelength region) is prohibited, and is also called a photonic band gap in relation to the electronic band theory. . In the case of a multilayer film, since the refractive index change is formed only in the layer thickness direction, it is also called a one-dimensional photonic band gap in a narrow sense. As a result, the laminate functions as a reflective layer with improved selective reflectivity with respect to the luminous flux having the wavelength.

  The thickness and the number of periods of each layer for forming the photonic band gap can be calculated or experimentally determined according to the range of the wavelength band to be reflected. The outline is as follows. When the center wavelength of the photonic band gap is λm, the thickness θ of one period of the refractive index change may be 1/2 wavelength (or an integer multiple thereof) of the luminous flux having the wavelength λm. (Represented in the case of ½ wavelength). This is a condition for the emitted luminous flux incident within one period of the layer to form a standing wave, and is the same as the Bragg reflection condition in which an electron wave in the crystal forms a standing wave. In the electron band theory, an energy gap appears at the boundary position of the reciprocal lattice that satisfies the Bragg reflection condition, but this is exactly the same in the photonic band theory.

  Here, the wavelength of the luminous flux incident on the element reflection layer becomes shorter in inverse proportion to the refractive index of the layer. When a luminous flux having a wavelength λ is perpendicularly incident on an element reflection layer having a thickness t and a refractive index n, the wavelength is λ / n, and the wave number in the layer thickness direction is n · t / λ. This is the same as when a luminous flux having a wavelength λ is incident on a layer having a refractive index of 1 and a thickness of n · t, and n · t is referred to as an optical thickness of an element reflection layer having a refractive index of n.

  In the luminous flux reflecting material layer, if the refractive index of the high refractive index layer for the luminous flux to be reflected is n1, and the refractive index of the low refractive index layer is n2, the optical thickness of the high refractive index layer is t1 ×. Similarly, the optical thickness of the low refractive index layer is t2 × n2. Therefore, the converted thickness θ ′ for one cycle is represented by t1 × n1 + t2 × n2. When this value is equal to ½ of the wavelength λ of the emitted light beam to be reflected, the above-described high reflectivity band appears remarkably. In particular, when the condition of t1 × n1 = t2 × n2 is satisfied, a complete reflection band is formed in a substantially bilaterally symmetric shape around a wavelength that is twice the converted thickness θ ′ of one cycle.

  In the present embodiment, the element substrate 7 is a silicon substrate, and the multiple reflection film 70 is composed of a high refractive index layer silicon layer and a low refractive index layer stacked alternately on the first main surface of the silicon substrate 7. A photonic band structure is realized as a multilayer film in which two layers of a silica (silicon dioxide) layer are used as a lamination period unit. The difference in refractive index between the silicon layer and the silica layer is very large, and a large reflectance can be achieved with a small number of lamination periods.

  As shown in FIG. 11, an element substrate 1 made of GaAs is used, and a DBR (Distributed Bragg Reflector) layer made of a III-V group compound semiconductor formed by epitaxial growth on the element substrate 1 is multiplexed. The reflective film 170 may be formed.

  In the light emitting device 500 of FIG. 12, the device substrate 7 is a silicon substrate, and the second main surface of the second current diffusion layer 91 is arranged through the back reflective layer 10 made of a metal mainly composed of Au or Ag. It is directly bonded to the substrate 7. Such a structure includes a first metal layer mainly composed of Au or Ag on the second current spreading layer 91 side and a second metal layer mainly composed of Au or Ag on the element substrate 7 side. The first metal layer and the second metal layer are stacked and pressed or heated.

  In the light emitting device 600 of FIG. 13, the side surface of the multilayer body 50 (notch portion JK) is so large that the cross-sectional area of the multilayer body 50 by a plane orthogonal to the thickness direction becomes closer to the light extraction surface EA. It is formed as an inclined side surface portion IP. As a result, it is possible to reflect, on the light extraction surface EA side, the incident light beam that is incident on the side surface of the notch JK at an angle equal to or smaller than the total reflection critical angle, so that the emission light beam is extracted from the light extraction surface EA. Efficiency can be increased. As shown in FIG. 14, the notch JK having the side surface shape inclined as described above replaces the groove DG shown in Step 8 of FIG. 8 with half dicing by the dicing blade DB, and as shown in FIG. It is obtained by forming by grooving using

  The light-emitting element 700 in FIG. 15 corresponds to a structure in which the inclined side surface IP of the light-emitting element 600 in FIG. Thereby, the reflection efficiency of the luminous flux at the inclined side surface portion IP can be further increased. In addition, the luminous flux incident on the inclined side surface portion IP at an angle larger than the total reflection critical angle can also be reflected. The metal reflection film 61 can be, for example, an Au layer or an Ag layer. In addition, the light emitting layer part 24 which forms a pn junction is exposed to the inclined side surface part IP, and if this is directly covered with the metal reflective film 61, there exists a possibility that a pn junction may short-circuit. Therefore, in the present embodiment, an insulating film 60 made of ceramic (eg, silica, alumina, silicon nitride, aluminum nitride, etc.) or resin is disposed between the metal reflective film 61 and the inclined side surface portion IP.

In the light emitting device 800 of FIG. 16, each layer (p-type cladding layer 106, active layer 105, and n-type cladding layer 104) of the light emitting layer portion 124 having a double hetero structure is formed of InGaAlN (In _x Ga _y Al _{1-x. −y} N: 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1) Depending on the composition of the active layer 105, the ultraviolet region is red (the peak emission wavelength is 300 nm to 700 nm: particularly A wide emission wavelength from 380 nm to 480 nm (purple or blue) can be realized. The first current spreading layer 190 and the main body layer 191m of the second current spreading layer 191 are made of GaN, and the well layer and the barrier layer of the current spreading quantum well layer 108 are made of GaAlN having different mixed crystal ratios. ing. The first current diffusion layer 190, the light emitting layer portion 124, and the first current diffusion layer 190 are epitaxially grown on the first main surface of the sapphire substrate 167 by the MOVPE method. Each thickness of the first current diffusion layer 190 and the second current diffusion layer 191 (including the current diffusion quantum well layer 108) is 1 μm or more and less than 50 μm. The second main surface of the sapphire substrate 167 is covered with the back surface reflection layer 10 mainly composed of Au, Ag, or Al.

1 is a schematic cross-sectional view illustrating a first example of a light-emitting element of the present invention. The conceptual diagram of the quantum well layer for electric current spreading | diffusion. The top view which shows the 1st example of the formation form of a notch part and a counter electrode. The top view which shows the 2nd example of the formation form of a notch part and a counter electrode. The top view which shows the 3rd example of the formation form of a notch part and a counter electrode. FIG. 3 is an explanatory diagram of a manufacturing process of the light emitting device of FIG. 1. Explanatory drawing following FIG. Explanatory drawing following FIG. The cross-sectional schematic diagram which shows the 2nd example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 3rd example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 4th example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 5th example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 6th example of the light emitting element of this invention. Explanatory drawing which shows an example of the formation method of the notch part of the light emitting element of FIG. The cross-sectional schematic diagram which shows the 7th example of the light emitting element of this invention. The cross-sectional schematic diagram which shows the 8th example of the light emitting element of this invention.

Explanation of symbols

100, 200, 300, 400, 500, 600, 700, 800 Light-emitting element 8, 108 Quantum well layer for current diffusion 9 Light extraction side electrode 10 Back surface reflection layer 15 Counter electrode JK Notch 24, 124 Light-emitting layer 31 Bonding alloy Layer (back electrode)
61 Metal reflection layer 90, 190 First current diffusion layer 91, 191 Second current diffusion layer 91m, 191m Body layer

Claims (14)

  A light-emitting layer portion made of a compound semiconductor; and a current diffusion layer laminated on the light-emitting layer portion made of a compound semiconductor layer thicker than the light-emitting layer portion, and a current diffusion quantum well in the current diffusion layer A light-emitting element provided with a layer.   The quantum well layer for current diffusion is formed by alternately laminating well layers and barrier layers each composed of a compound semiconductor having a band gap energy larger than a band gap energy corresponding to a peak emission wavelength from the light emitting layer portion. The light emitting device according to claim 1, wherein the light emitting device is one.   The current diffusion layer is configured such that the current diffusion quantum well layer is configured as a non-doped layer, and is disposed in contact with the current diffusion quantum well layer, and more than the barrier layer of the current diffusion quantum well layer. 3. The light emitting device according to claim 1, further comprising a main body layer having a large band gap energy and a higher effective carrier concentration than the well layer and the barrier layer.   4. The light emitting device according to claim 3, wherein the current diffusion layer has a structure in which the current diffusion quantum well layer is sandwiched between the two main body layers. The current diffusion layer is disposed on the second main surface side of the light emitting layer portion, and a first main surface of a semiconductor laminate including the light emitting layer portion and the current diffusion layer is defined as a light extraction surface, and the semiconductor laminate From the first main surface of the current diffusion layer to the midway position in the thickness direction of the current diffusion layer is cut out in a partial region of the first main surface, a notch is formed,
A light extraction side electrode for applying a driving voltage to the light emitting layer portion is disposed so as to cover a part of the light extraction surface, and on the bottom surface of the notch portion located in the current diffusion layer, 5. The light emitting device according to claim 1, wherein a counter electrode for applying a driving voltage to the light emitting layer portion is disposed.   6. The light emitting device according to claim 5, wherein the current diffusion quantum well layer is disposed in a section from a first main surface of the current diffusion layer to a bottom surface of the notch.   A first current diffusion layer is provided on the first main surface side of the light emitting layer part, and the current diffusion layer provided on the second main surface side of the light emitting layer part is used as a second current diffusion layer, the first The light emitting device according to claim 6, wherein the current diffusion quantum well layer is not provided in one current diffusion layer.   8. The semiconductor stack according to claim 5, wherein the current diffusion layer having the quantum well layer for current diffusion is bonded to the light emitting layer portion. 9. Light emitting element.   The section located on the light extraction surface side from the bottom surface of the cutout portion of the semiconductor stacked body is a stacked body, and the cross-sectional area of the stacked body by a plane orthogonal to the thickness direction approaches the light extraction surface. The light emitting device according to any one of claims 5 to 8, wherein a side surface of the laminate body is formed to be inclined so as to become larger.   The light emitting device according to claim 9, wherein the inclined side surface of the laminate body is covered with a metal reflective layer with an insulating layer interposed therebetween.   The said light emitting layer part consists of AlGaInP, and the 2nd main surface of the said current diffusion layer arrange | positioned at the 2nd main surface side of this light emitting layer part is covered with a back surface reflecting layer. The light emitting element of any one of Claim 10 thru | or 10.   11. The light emitting device according to claim 5, wherein a thickness of the current diffusion layer disposed on the second main surface side of the light emitting layer portion is 50 μm or more and 200 μm or less. .   The light emitting layer portion is made of InGaAlN, the current diffusion layer is disposed on the second main surface side of the light emitting layer portion, and the current diffusion layer and the light emitting layer portion are epitaxially grown on the second main surface side of the current diffusion layer. The light emitting device according to claim 5, wherein a growth sapphire substrate is left to remain.   15. The light emitting device according to claim 14, wherein the current diffusion layer is formed to have a thickness of 1 μm or more and less than 50 μm by the MOVPE method.

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