JP2008205005A - Gallium-nitride-based light emitting device element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GaN-based LED element in the structure for mitigating shield of light and/or absorption of light by a pad electrode. <P>SOLUTION: The GaN-based LED element 1 includes a conductive substrate 11 and a laminated body 12 formed of a plurality of GaN-based semiconductor layers. The laminated body 12 includes an n-type layer 12-3 arranged at the location furthest from the conductive substrate 11, a light-emitting layer 12-2 arranged between the n-type layer and the conductive substrate 11, and a p-type layer 12-1 arranged to sandwich the light-emitting layer 12-2 in combination with the n-type layer 12-3. A pad electrode P14 is formed on the n-type layer 12-3 and a flat hole H1 having the bottom surface H11 is formed, on the surface in the side of the conductive substrate 11 of the laminated body 12, at least in the depth reaching the light-emitting layer 12-2 in opposition to the pad electrode P14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a GaN-based LED element having a light-emitting element structure using a GaN-based semiconductor.

A GaN-based semiconductor is a compound semiconductor represented by the chemical formula Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ a + b ≦ 1), and is a group III nitride semiconductor Also called a nitride-based semiconductor. A GaN-based LED element in which a light-emitting element structure such as a pn junction structure, a double hetero structure, or a quantum well structure is formed of a GaN-based semiconductor can generate green to near-ultraviolet light. It has been put to practical use in applications such as equipment. At present, research and development for applying GaN-based LED elements to lighting applications are actively performed, but higher output is required for practical use.

A conductive substrate, and a laminate composed of a plurality of GaN-based semiconductor layers formed on the substrate, and the laminate includes an n-type layer disposed at a position farthest from the substrate, and the n-type layer A GaN-based LED element including a light-emitting layer disposed between a mold layer and the substrate and a p-type layer disposed so as to sandwich the light-emitting layer between the n-type layer is known ( Patent Document 1, Patent Document 2, Non-Patent Document 1). In a GaN-based LED element having such a configuration, the pad electrode formed on the n-type layer hinders the extraction of light emitted from the light emitting layer, which has been pointed out as one of the factors hindering the high output of the LED element. (Patent Document 2). Note that the pad electrode is an electrode to which a material used for connection to an external electrode such as a bonding wire, a conductive paste, a brazing material (for example, solder, eutectic metal) or the like is bonded.
US Patent Publication No. 2006/0154389 JP 2004-193338 A Japanese Journal of Applied Physics, Vol. 45, No. 39, 2006, pp. L1045-L1047 (Japan Journal of Applied Physics, Vol. 45, No. 39, 2006, pp. L1045-L1047)

The present invention has been made in view of the above circumstances, and a main object thereof is to provide a GaN-based LED element having a structure capable of reducing light shielding and / or absorption by a pad electrode.

In order to achieve the above object, the present invention provides a GaN-based LED element having the following characteristics.
(1) It has a conductive substrate and a laminate composed of a plurality of GaN-based semiconductor layers formed on the conductive substrate, and the laminate is disposed at a position farthest from the conductive substrate. And an n-type layer, a light-emitting layer disposed between the n-type layer and the conductive substrate, and a p-type layer disposed so as to sandwich the light-emitting layer between the n-type layer and the n-type layer. In the GaN-based LED element, a pad electrode is formed on the n-type layer, and a flat surface having a bottom surface is provided on a surface of the laminate on the conductive substrate side so as to face the pad electrode. A GaN-based LED element, wherein the hole is formed at a depth reaching at least the light emitting layer.
(2) The GaN-based LED element according to (1), wherein the flat hole is formed to a depth at which the light emitting layer is completely removed.
(3) When viewed from above the n-type layer, the pad electrode or the main body of the pad electrode is formed so as to fit inside the outer peripheral line of the bottom surface of the flat hole, (1) or The GaN-based LED element according to (2).
(4) The GaN-based LED element according to any one of (1) to (3), wherein the bottom surface of the flat hole is textured.
(5) The GaN-based material according to any one of (1) to (4), wherein a light reflecting recess is formed in addition to the flat hole on the surface of the laminate on the conductive substrate side. LED element.
(6) The concave portion for light reflection has a depth reaching at least the light emitting layer, and a cross-sectional area when the concave portion is cut along a plane perpendicular to the stacking direction of the laminate is the conductive substrate. The GaN-based LED element according to (5), wherein the GaN-based LED element is a concave portion whose side wall surface is inclined so as to decrease as the distance from the surface increases.
(7) The end surface of the laminate is configured such that the area of the surface of the laminate on the side of the conductive substrate is smaller than the area of the surface of the laminate on the side opposite to the surface of the conductive substrate. The GaN-based LED element according to any one of (1) to (6), wherein at least a part is inclined.
(8) The end face of the light emitting layer is made so that the area of the surface of the laminate on the side of the conductive substrate is smaller than the area of the surface of the laminate on the side opposite to the surface of the conductive substrate. The GaN-based LED element according to (7), which is inclined.
(9) The GaN-based LED element according to any one of (1) to (8), wherein the conductive substrate is made of metal.
(10) The GaN-based LED element according to any one of (1) to (8), wherein the conductive substrate is made of a semiconductor.

Since the GaN-based LED element according to the embodiment of the present invention is excellent in light emission output, it can be suitably used in applications that require high output, such as illumination applications.

(Embodiment 1)
A GaN-based LED element according to a preferred embodiment of the present invention includes a conductive substrate and a stacked body composed of a plurality of GaN-based semiconductor layers formed on the conductive substrate. The n-type layer disposed farthest from the conductive substrate, the light-emitting layer disposed between the n-type layer and the conductive substrate, and the n-type layer sandwich the light-emitting layer. And a p-type layer disposed on the n-type layer, a pad electrode is formed on the surface of the laminate on the conductive substrate side. The flat hole having the bottom surface is formed at a depth reaching at least the light emitting layer so as to face the pad electrode. FIG. 1 shows a cross-sectional structure of the GaN-based LED element according to Embodiment 1 of the present invention configured as described above. A GaN-based LED element 1 shown in FIG. 1 has a conductive substrate 11 made of metal and a laminated body 12 made of a plurality of GaN-based semiconductor layers formed thereon. The laminate 12 includes a p-type layer 12-1, a light emitting layer 12-2, and an n-type layer 12-3 in this order from the conductive substrate 11 side. A pad electrode P14 is formed on the n-type layer 12-3. A flat hole H1 having a bottom surface H11 is formed on the surface of the multilayer body 12 on the conductive substrate 11 side so as to face the pad electrode P14, to a depth reaching the n-type layer 12-3. A contact layer P11 is formed on the surface of the p-type layer 12-1. An insulating film P12 is formed on the surface and the end surface of the laminate 12 on the conductive substrate 11 side except for the region where the contact layer P11 is formed. A thin film metal layer P13 is sandwiched between the surfaces of the contact layer P11 and the insulating film P12 and the holding substrate 11.

In the GaN-based LED element 1, since the conductive substrate 1 is made of metal and does not transmit light, the light emitted from the light emitting layer 12-2 is emitted from the surface side of the n-type layer 12-3. Taken out. A flat hole H1 is formed on the surface of the laminate 12 on the side of the conductive substrate 11 so as to face the pad electrode 14 so that light emission does not occur immediately below the pad electrode 14. When light emission directly under the pad electrode is allowed, the generated light is strongly shielded and absorbed by the pad electrode, so it cannot be efficiently taken out of the LED element, and the energy consumed for this light emission is Loss. In the GaN-based LED element 1, loss is reduced and output is improved by preventing light emission just below the pad electrode.

In the GaN-based LED element 1, in order to suppress light emission directly under the pad electrode 14, the light emitting layer 12-2 is removed from directly under the pad electrode 14 by forming a flat hole H1. Since the light emitting layer acts as an absorber for the light generated by itself, it is possible to reduce the loss by removing unnecessary portions (portions that do not emit light) from the light emitting layer and improve the light emission output of the LED element. it can. In order to obtain this effect, the flat hole may be formed at a depth reaching at least the light emitting layer. Preferably, the flat hole is formed at a depth reaching the n-type layer as in the GaN-based LED element 1. The light emitting layer in the portion where the flat hole is formed is completely removed. In an LED element having a double heterostructure in which the In (indium) content of the light emitting layer is higher than that of the cladding layer, or the Al (aluminum) content of the light emitting layer is lower than that of the cladding layer, Since a plate-like waveguide structure serving as a core is formed and light tends to be strongly confined in the light emitting layer, an output improvement effect can be obtained by removing unnecessary portions from the light emitting layer as in the GaN-based LED element 1. Especially noticeable.

The depth of the flat hole H1 depends on the thickness of the p-type layer 12-1, but can be, for example, 0.1 μm to 2 μm. On the other hand, the width of the flat hole H1 can be, for example, 10 μm to 200 μm. A flat hole having such a depth can be easily formed on the surface of the GaN-based semiconductor using a dry etching technique such as RIE (reactive ion etching) or a wet etching technique. Due to the shape of the flat hole H1, the effect of reflecting the light propagating in the layer direction inside the stacked body toward the surface side of the n-type layer 12-3 having the pad electrode P14 is small.

In the GaN-based LED element 1, the shape and size of the flat hole H1 and the shape and size of the pad electrode P14 when viewed from above the n-type layer 12-3 are substantially the same, but such a configuration is not essential. . If there is a portion overlapping the flat hole H1 and the pad electrode P14 when viewed from above the n-type layer 12-3, the above output improvement effect is obtained, and the effect increases as the area of the overlapped portion increases. . Therefore, in a preferred embodiment, as shown in FIG. 2A, when viewed from above the n-type layer 12-3, the pad electrode P14 fits inside the outer peripheral line of the bottom surface H11 of the flat hole H1 indicated by a broken line. Configure as follows. With this configuration, even when the side wall surface of the flat hole H1 is inclined, the light reflected by the side wall surface and incident at an angle close to the surface of the n-type layer 12-3 is caused by the pad electrode P14. It can also be prevented from being shielded or absorbed. As shown in FIG. 2B, the pad electrode P14 includes a main body portion P14a mainly used for bonding with a bonding wire, a brazing material, and the like, and an extension portion P14b extending from the main body portion for spreading the current in the surface direction. If it is comprised from these, what is necessary is just to comprise so that the main-body part 14a may be settled inside the outer peripheral line of the bottom face H11 of the flat hole H1.

In a preferred embodiment, as shown in FIG. 3, the bottom surface H11 of the flat hole H1 may be textured. When the bottom surface H11 is textured to form irregularities that are equal to or greater than the wavelength of the light emitted from the light emitting layer 12-2, irregular reflection occurs at the bottom surface H11 (the interface between the n-type layer 12-3 and the insulating film P12). Thus, multiple reflections are suppressed, and the light emission output of the LED element is improved. Taking the case where the emission wavelength of the LED element is 400 nm as an example, the light having a wavelength of 400 nm in air has a wavelength of about 160 nm inside a GaN-based semiconductor having a refractive index of about 2.5. If the surface roughness of the bottom surface H11 of the hole H1 is larger than half of 80 nm, irregular reflection can be preferably generated.

In a preferred embodiment, as shown in FIG. 4, a light reflecting recess R <b> 1 may be formed on the surface of the laminate 12 on the conductive substrate 11 side in addition to the flat hole H <b> 1. The main purpose of the light reflecting recess R1 is to reflect the light propagating in the layer direction inside the multilayer body 12 so as to be incident on the surface of the n-type layer 12-3 at an angle smaller than the total reflection critical angle. , Changing its direction of travel. In order to achieve this purpose preferably, in the example of FIG. 4, the cross-sectional area of the light reflecting recess R <b> 1 when cut along a plane perpendicular to the stacking direction of the stacked body 12 decreases as the distance from the conductive substrate 11 increases. As described above, the side wall surface of the light reflecting recess R1 is inclined. This inclination is preferably 30 to 60 degrees, more preferably about 45 degrees (40 to 50 degrees). In particular, an LED element having a double hetero structure has a plate-like waveguide structure having a light emitting layer as a core as described above. Therefore, in order to reflect the light propagating through this core, The recess is preferably formed at a depth reaching at least the light emitting layer, and more preferably formed at a depth reaching the n-type layer beyond the light emitting layer as in the example shown in FIG. In addition, an effect of causing irregular reflection of light can be expected from the light reflecting recess. If there is a surface or interface that can cause diffused reflection of light inside the LED element, multiple reflection is suppressed, so that the light emission output is improved.

The light reflecting recess may be a linear recess (groove) or a dot-like recess (hole). Preferably, if the light reflecting recess is a linear recess, the probability that light propagating in the layer direction in the GaN-based semiconductor layer will encounter the light reflecting recess and receive reflection is increased. Both a linear light reflecting recess and a dot light reflecting recess may be provided. The linear light reflecting recess may be linear, curved, or bent. Further, the linear light reflecting recess may be annular, or may have a branch or an intersection. The light reflecting recess may be formed such that its inner wall surface is continuous with the end face of the laminate. Whether the light reflecting recess is linear or dot-shaped, if the cross-sectional shape is V-shaped, the ratio of the inclined side wall surface occupying the inner wall surface of the light reflecting recess is the largest. The improvement effect of output becomes high. A linear recess having a V-shaped cross section is a so-called V-groove. Moreover, the dot-shaped recessed part which has a V-shaped cross section is a hole of a cone shape (for example, cone shape, a pyramid shape), for example. The cross-sectional shape of the light reflecting recess that is preferred next to the V shape is a trapezoid.

In a preferred embodiment, the end face of the laminate 12 may be inclined as shown in FIG. The inclination is provided so that the area of the surface of the laminate 12 on the conductive substrate 11 side is smaller than the area of the opposite surface (the surface of the n-type layer 12-3). Thereby, the light propagating in the layer direction in the layered body 12 can be reflected by the inclined end face, and can be incident on the surface of the n-type layer 12-3 at an angle within the total reflection critical angle. This inclination is preferably 30 to 60 degrees, more preferably about 45 degrees (40 to 50 degrees). In particular, in the LED element having a double hetero structure, since the plate-like waveguide structure having the light emitting layer as a core is formed as described above, the end face of the light emitting layer is inclined as in the example of FIG. It is preferable.

Next, a method for manufacturing the GaN-based LED element nitride LED1 will be described.
First, as shown in FIG. 6A, a crystal substrate suitable for epitaxial growth of a nitride semiconductor crystal, such as a sapphire substrate, a SiC substrate, a GaN substrate, a Si substrate, or a GaAs substrate, is prepared as a growth substrate 13, and the MOVPE method is used. Then, the n-type layer 12-3, the light emitting layer 12-2, and the p-type layer 12-1 are sequentially grown and laminated by using the HVPE method, the MBE method, or the like to form the laminated body 12. Each layer of the n-type layer 12-3, the light emitting layer 12-2, and the p-type layer 12-3 may have a multilayer structure. The n-type layer 12-3 is preferably formed to a thickness of 2 μm or more so that the crystallinity of the light emitting layer 12-2 grown thereon is good. The n-type layer 12-3 is preferably provided with a high carrier concentration layer (carrier concentration: 1 × 10 ¹⁸ cm ⁻³ or more) having a thickness of 1 μm or more. The light emitting layer 12-2 preferably has a multiple quantum well structure in which a well layer is formed of InGaN, InGaAlN, or the like. The uppermost part of the p-type layer 12-1 is made of GaN, AlGaN or InGaN doped with Mg (magnesium) at a high concentration (5 × 10 ¹⁹ cm ⁻³ or more) so that the contact resistance with the contact layer P11 is low. It is preferable to form. Moreover, about the part adjacent to the light emitting layer 12-2 among the n-type layer 12-3 and the p-type layer 12-1, it is preferable to determine a crystal composition so that a double heterostructure may be comprised. A crystal growth method having an effect of improving crystal quality, such as ELO (Epitaxial Lateral Overgrowth), may be used as appropriate. Various functional layers such as a superlattice layer for strain relaxation can be appropriately introduced into the laminate 12.

Next, as shown in FIG. 6B, the stacked body 12 is etched to form a flat hole H1, and a contact layer P11 is formed in a region on the p-type layer 12-1 where the flat hole H1 is not formed. To do. Preferably, the contact layer P11 is formed first, and then the flat hole H1 is formed. The contact layer P11 can be formed of a metal that forms a low contact resistance junction with the p-type nitride semiconductor. Specifically, Ni (nickel), Co (cobalt), Au (gold), platinum group (Pt, Pd, Rh, Ir, Ru, Os) and the like are exemplified. The contact layer P11 may also be formed of a conductive oxide such as ITO (indium tin oxide), indium oxide, tin oxide, IZO (indium zinc oxide), AZO (aluminum zinc oxide), or zinc oxide. it can. As the contact layer P11, a thin film known as an ohmic electrode for a p-type nitride semiconductor can be used.

The flat hole H1 can be formed by dry etching such as RIE (reactive ion etching) or wet etching. In particular, RIE using a substance containing chlorine, such as Cl ₂ , SiCl ₄ , and BCl _3, as an etching gas is preferable. Here, when the contact layer P11 is formed of a polycrystalline conductive oxide film that promotes crystallization, and the RIE process is performed thereon to form the flat hole H1, the bottom surface of the flat hole H1 is textured. be able to. As such a conductive oxide film, for example, an ITO film subjected to heat treatment at 500 ° C. for 10 minutes or more after film formation is exemplified. Since the ITO film has a rough surface, the ITO film acts as a non-uniform etching mask, and as a result, the bottom surface of the flat hole H1 is considered to be textured. In order to shorten the processing time, the thickness of the conductive oxide film may be reduced in advance by acid treatment using hydrochloric acid, aqua regia, or the like, and then RIE treatment may be performed.

When providing the light reflecting recess, the light reflecting recess is formed at this stage. The light reflecting recess can be preferably formed using a dry etching technique.

Next, as shown in FIG. 6C, a mesa structure is formed. That is, in order to separate the adjacent element portions on the wafer, the stacked body 12 is etched from the p-type layer 12-1 side to form a groove reaching the n-type layer 12-3. Preferably, as in this example, the growth substrate 13 is exposed at the bottom of the groove. As an etching method, RIE (reactive ion etching) can be preferably used. By providing a taper at the edge of the etching mask used in RIE, the end face of the stacked body 12 can be inclined. In addition, the end surface of the laminated body 12 can be inclined by cutting using a blade having a V-shaped cross section.

Next, as shown in FIG. 7D, the wafer surface on the stacked body 12 side except the surface of the contact layer P11 is covered with an insulating film P12. The insulating film P12 is formed of a light transmissive material. The insulating film P12 is preferably formed of an inorganic material such as a metal oxide, metal nitride, metal oxynitride, or metal fluoride. Specific examples of the material include silicon oxide, silicon nitride, silicon oxynitride, and oxidation. Examples include aluminum, spinel, zirconium oxide, magnesium oxide, titanium oxide, magnesium fluoride, lithium fluoride, and the like. When the insulating film P12 is formed of a material having a low refractive index such as magnesium fluoride, lithium fluoride, silicon oxide, or aluminum oxide, the light reflectivity at the interface between the stacked body 12 and the insulating film P12 can be improved. The insulating film P12 can also be a multilayer film. Preferably, when the insulating film P12 is formed using a plasma CVD method, the end face of the stacked body 12 can be reliably covered.

Next, as shown in FIG. 7E, a thin film metal layer P13 is formed so as to cover the entire wafer surface on the laminated body 12 side. The thin metal layer P13 is a plating base layer provided to form the conductive substrate 11 by electroplating in a later step. The thin metal layer P13 is preferably formed also when the conductive substrate 11 is formed by electroless plating. The thin metal layer P13 can be formed of, for example, Cr, Pt, Pt / Au, Cr / Au, Ni / Au, Ti / Au, or TaN / Au. When the conductive substrate 11 is formed by dry plating such as vapor deposition, sputtering, or CVD, the formation of the thin film metal layer P13 is not essential, but even in such a case, the metal constituting the conductive substrate 11 is formed. The thin film metal layer P13 can be formed as a barrier layer for preventing undesired interaction (alloying reaction or the like) from occurring between the contact layer P11 and the contact layer P11. In a preferred embodiment, the contact layer P11 is formed so as to be translucent, and Al, Ag, and platinum function as a highly reflective film between the contact layer P11 and the insulating film P12 and the thin metal layer P13. A metal layer having a silver-white appearance is inserted.

Next, as shown in FIG. 7F, a conductive substrate 11 is formed. The conductive substrate 11 is preferably formed by depositing a metal layer on the thin metal layer P13 by electroplating or electroless plating. When electroless plating is used, a polyimide layer or the like is coated on the wafer surface on the growth substrate 13 side. As a material metal when the conductive substrate 11 is formed by electroplating, it is widely used as an electrodeposition metal in electroforming, such as Au (gold), Ni (silver), Cu (copper), Ag (silver), etc. Preferred examples of the metal are:

Next, as shown in FIG. 8G, the growth substrate 13 is removed. For removing the growth substrate 13, a known method for separating the crystal substrate and the GaN-based semiconductor crystal layer epitaxially grown thereon, such as laser lift-off, wet etching, dry etching, grinding, and polishing, is arbitrarily used. It's okay.

After the growth substrate 13 is removed, as shown in FIG. 8H, a pad electrode P14 is formed on the exposed surface of the n-type layer 12-3 so as to face the flat hole H1. When a high carrier concentration layer is provided inside the n-type layer 12-3, the high carrier concentration layer is exposed by a method such as etching, and then a pad electrode P14 is formed on the surface thereof. A conductive oxide film may be formed on the surface of n-type layer 12-3, and pad electrode P14 may be formed thereon. When the pad electrode P14 is directly formed on the surface of the n-type layer 12-3, the portion in contact with the n-type layer is made of Ti (titanium), Al (aluminum), W (tungsten) so as to reduce the contact resistance. , V (vanadium), etc., or an alloy containing one or more metals selected from these is desirable. When the pad electrode P14 is formed on the conductive oxide film formed on the n-type layer 12-3, the material of the pad electrode P14 is not particularly limited, but is preferably a portion in contact with the conductive oxide film. Is formed using platinum group (Rh, Pt, Pd, Ir, Ru, Os), Ni (nickel), Ti (titanium), W (tungsten), Ag (silver), Al (aluminum), or the like. The pad electrode P14 is provided with a layer made of Ag (silver), Au (gold), Sn (tin), In (indium), Bi (bismuth), Cu (copper), Zn (zinc) or the like as a surface layer. Is preferred. The film thickness of the pad electrode P14 can be, for example, 0.2 μm to 10 μm, and preferably 0.5 μm to 2 μm.

After the formation of the pad electrode P14, an insulating protective film is preferably formed on the wafer surface excluding the region on the pad electrode. Finally, a chip-like LED element (die) can be obtained by cutting the wafer using a known dicing method.

In addition to the above-described method for manufacturing the GaN-based LED element 1, Patent Document 1 can be referred to.

(Embodiment 2)
FIG. 9 shows a cross-sectional view of a GaN-based LED element according to Embodiment 2 of the present invention. In the GaN-based LED element 2 shown in this figure, a laminated body 22 made of a plurality of GaN-based semiconductor layers is formed on a conductive substrate 21 made of a semiconductor. Bonding of the conductive substrate 21 and the laminated body 22 is performed by direct wafer bonding. The stacked body 22 includes a p-type layer 22-1, a light emitting layer 22-2, and an n-type layer 22-3 in this order from the conductive substrate 21 side. A flat hole H2 having a bottom surface is formed on the surface of the laminate 22 on the conductive substrate 21 side to a depth reaching the n-type layer 22-3. On the n-type layer 22-3, a negative pad electrode P24 is formed so as to face the flat hole H2. On the back surface of the conductive substrate 21, a positive pad electrode P25 is formed. The semiconductor constituting the conductive substrate 21 may be any semiconductor that can be bonded to the nitride semiconductor by direct wafer bonding. Preferably, the semiconductor constituting the conductive substrate 21 is a semiconductor having a band gap energy larger than the band gap energy of the light emitting layer 22-2 so that light generated in the light emitting layer 22-2 is not strongly absorbed. When the emission wavelength of the light emitting layer 22-2 is 400 nm or more, ZnO (zinc oxide) is preferably exemplified as a semiconductor constituting the conductive substrate 21.

In order to manufacture the GaN-based LED element 2, first, a c-plane sapphire substrate is used as a growth substrate, and an n-type layer 22-3, a light emitting layer 22-2, and a p-type layer 22-1 are formed thereon by MOCVD. Are sequentially grown to form an LED wafer in which the laminate 22 is laminated on the sapphire substrate. At this time, it is desirable that the rms roughness when the 5 × 5 μm ² region on the surface of the p-type layer 22-1 is measured with an AFM (atomic force microscope) is 0.55 nm or less.

Next, the laminated body 22 of the LED wafer is etched to form a flat hole H2.

Next, the conductive substrate 21 made of a semiconductor is bonded to the surface of the stacked body 22 by a direct wafer bonding method. Non-patent document 1 can be referred to for the procedure in the case of using a ZnO substrate as the conductive substrate 21. That is, as the ZnO substrate, the rms when the area of 5 × 5 μm ^{2 on} the surface manufactured by hydrothermal method with a film thickness of 500 μm, electric resistance of about 0.2 Ω · cm is measured with an AFM (Atomic Force Microscope). Those having a roughness of 0.75 nm or less can be preferably used. The ZnO substrate is washed with acetone and isopropyl alcohol, rinsed with deionized water, and then dried. The LED wafer is cleaned with acetone and isopropyl alcohol, immersed in an HCl solution for 1 minute, rinsed with deionized water, and dried. Immediately after the cleaning process, the LED wafer and the ZnO substrate are superposed in a clean room, and a heat treatment is performed at 600 ° C. for 1 hour in a nitrogen gas atmosphere with a pressure of 2 MPa applied in a uniaxial direction. In this way, the ZnO substrate can be bonded to the LED wafer laminate 22.

After the wafer bonding, the sapphire substrate used as the growth substrate is removed by using methods such as laser lift-off, wet etching, dry etching, grinding, and polishing. After removing the sapphire substrate, a negative pad electrode P24 is formed on the exposed surface of the n-type layer 22-3 so as to face the flat hole H2, and a positive pad electrode P25 is formed on the back surface of the conductive substrate 21. Form. Then, a chip-like element (die) can be obtained by cutting the wafer using a known dicing method.

Also in this Embodiment 2, as shown in FIG. 10, the bottom face H21 of the flat hole H2 can be textured. In addition to the flat hole H2, a light reflecting recess R2 can be formed on the surface of the laminate 22 on the conductive substrate 21 side. Further, at least a part of the end surface of the stacked body 22 can be inclined so that the area of the surface of the stacked body 22 on the conductive substrate 21 side is smaller than the area of the surface on the opposite side.

When the GaN-based LED element 2 is fixed to a mounting base such as a substrate, slag, lead frame, or unit substrate to form a light emitting device, the surface on the side of the GaN-based LED element 2 conductive substrate 21 is the surface of the mounting base. It can be fixed to face. When the conductive substrate 21 is translucent, it can be fixed so that the surface of the n-type layer 22-3 faces the surface of the mounting substrate.

(Other embodiments)
In a GaN-based LED according to an embodiment of the present invention, a conductive substrate and a laminate composed of a plurality of GaN-based semiconductor layers are bonded to each other by a conductive paste, brazing material (including solder, eutectic alloy), or the like. What was joined using the agent may be used.

The present invention is not limited to the embodiments explicitly described in the present specification, and various modifications can be made without departing from the spirit of the invention.

It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention. It is a top view of the GaN-type LED element which concerns on embodiment of this invention. It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention. It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention. It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention. It is a figure for demonstrating the manufacturing method of the GaN-type LED element shown in FIG. It is a figure for demonstrating the manufacturing method of the GaN-type LED element shown in FIG. It is a figure for demonstrating the manufacturing method of the GaN-type LED element shown in FIG. It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention. It is sectional drawing of the GaN-type LED element which concerns on embodiment of this invention.

Explanation of symbols

1, 2 GaN-based LED elements 11, 21 Conductive substrates 12, 22 Laminated bodies H1, H2 Flat holes P14, P24 Pad electrodes

Claims (10)

A conductive substrate, and a laminate composed of a plurality of GaN-based semiconductor layers formed on the conductive substrate, and the laminate includes an n-type disposed at a position farthest from the conductive substrate. A GaN-based layer comprising: a layer; a light-emitting layer disposed between the n-type layer and the conductive substrate; and a p-type layer disposed so as to sandwich the light-emitting layer between the n-type layer In the LED element,
A pad electrode is formed on the n-type layer,
A flat hole having a bottom surface is formed at a depth reaching at least the light emitting layer on the surface of the laminate on the conductive substrate side so as to face the pad electrode.
A GaN-based LED element characterized by the above. The GaN-based LED element according to claim 1, wherein the flat hole is formed at a depth at which the light emitting layer is completely removed. The pad electrode or the body portion of the pad electrode is formed so as to fit inside the outer peripheral line of the bottom surface of the flat hole when viewed from above the n-type layer. GaN-based LED element. The GaN-based LED element according to claim 1, wherein a bottom surface of the flat hole is textured. The GaN-based LED element according to any one of claims 1 to 4, wherein a concave portion for light reflection is formed in addition to the flat hole on a surface on the conductive substrate side of the laminate. The light reflecting recess has a depth that reaches at least the light emitting layer, and the cross-sectional area when the recess is cut along a plane perpendicular to the stacking direction of the stacked body is separated from the conductive substrate. The GaN-based LED element according to claim 5, wherein the GaN-based LED element is a recess having an inclined sidewall surface so as to decrease. At least a part of the end surface of the laminate so that the area of the surface of the laminate on the side of the conductive substrate is smaller than the area of the surface of the laminate on the side opposite to the surface of the conductive substrate. The GaN-based LED element according to claim 1, wherein the GaN LED element is inclined. The end surface of the light emitting layer is inclined so that the area of the surface of the laminate on the side of the conductive substrate is smaller than the area of the surface of the laminate on the side opposite to the surface of the conductive substrate. The GaN-based LED element according to claim 7. The GaN-based LED element according to claim 1, wherein the conductive substrate is made of metal. The GaN-based LED element according to claim 1, wherein the conductive substrate is made of a semiconductor.

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