JP4483566B2 - Light emitting device - Google Patents

Description

  The present invention relates to a light emitting element used in a light emitting device. In particular, the present invention relates to a light-emitting device that improves light extraction to the observation surface side of a light-emitting element that is flip-chip mounted on a mount member.

  A light-emitting diode including a nitride semiconductor in a layer structure is widely used as a high-luminance pure green light-emitting LED or blue light-emitting LED in various fields such as a full-color LED display, a traffic signal lamp, and a backlight.

These LEDs generally have a structure in which an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer are sequentially stacked on a substrate such as sapphire. Furthermore, a p-side electrode is disposed on the p-type nitride semiconductor layer, and an n-side electrode is disposed on the n-type nitride semiconductor layer. For example, when the p-side electrode and the n-side electrode are provided on the same surface side, the p-side electrode is disposed on the p-type nitride semiconductor layer, and the p-type nitride semiconductor layer, the active layer, and the n-type nitridation are provided. A part of the physical semiconductor layer is removed by etching or the like, and the n-side electrode is arranged on the exposed n-type nitride semiconductor layer. Further, various LED structures have been proposed for the purpose of improving light extraction (for example, Patent Documents 1 and 2).
JP20046662 JP2004-221529

  However, the conventional structure has a problem that light reaching the side surface of the light-emitting element that is flip-mounted cannot be extracted efficiently.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting device that can efficiently extract light reaching a side surface of a flip-mounted semiconductor light emitting element.

In order to achieve the above object, a light-emitting device according to the present invention includes a p-layer , a light-emitting layer, and an n-layer stacked, and electrically connected to the p-electrode and the n-layer that are electrically connected to the p-layer. A semiconductor light emitting device in which n electrodes to be connected are formed on the same surface side , and the semiconductor light emitting device is flip-mounted on a mount member having a circuit electrically connected to each of the p electrode and the n electrode. The semiconductor light emitting device has an inclined surface from the p layer to the n layer, and the inclined surface has a surface uneven structure that totally reflects the light emitted from the light emitting layer to the light emission observation surface side while diffusing the light. It is a feature.

  The light-emitting device according to the present invention can efficiently extract light reaching the side surface of the light-emitting element that is flip-mounted.

Various nitride semiconductors can be used as each semiconductor layer constituting the light emitting element disposed in the light emitting device according to the present invention. Specifically, In _X Al _Y Ga _1- XYN (0 ≦ X, 0 ≦ Y, X + Y ≦) is formed on the substrate by metal organic vapor phase epitaxy (MOCVD), hydride vapor phase epitaxy (HVPE), or the like. A semiconductor in which a plurality of semiconductors such as 1) are formed is preferably used. In addition, the layer structure includes a homo structure having a MIS junction, a PIN junction or a PN junction, a hetero structure, or a double hetero structure. Each layer may have a superlattice structure, or may have a single quantum well structure or a multiple quantum well structure in which an active layer is formed in a thin film in which a quantum effect is generated.

  The light-emitting element is generally formed by growing each semiconductor layer on a specific substrate. At this time, an insulating substrate such as sapphire is used as the substrate. In this case, normally, both the p-side electrode and the n-side electrode are formed on the same surface side on the semiconductor layer. Of course, it is also possible to perform flip-chip mounting after finally removing the substrate. The substrate is not limited to sapphire, and a known member such as spinel, SiC, GaN, or GaAs can be used.

  Embodiments according to the present invention will be described below with reference to the drawings for nitride semiconductor light emitting devices. However, the embodiment described below exemplifies a light emitting device for embodying the technical idea of the present invention, and the present invention does not specify the light emitting device as follows.

(Embodiment 1)
FIG. 1 is a schematic plan view of a group III nitride compound semiconductor device 100 according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. FIG. 3 is a cross-sectional view of a light emitting device using the group III nitride compound semiconductor element 100.

  The group III nitride compound semiconductor device 100 is a light emitting device having the following configuration. As shown in FIG. 1, each side has a width of 300 μm, a groove 150 having a zigzag shape around the light emitting element, an n-electrode 140 is formed in a part of the groove 150, and A thick reflective p-electrode 110 is disposed on almost the entire surface of the central zigzag island.

Next, as shown in FIG. 2, an AlN buffer layer 102 made of aluminum nitride (AlN) and having a thickness of about 15 nm is formed on a sapphire substrate 101 having a thickness of about 300 μm. A non-doped GaN layer 103 is formed, and an n-type contact layer 104 (high carrier concentration n ⁺ layer) having a film thickness of about 5 μm made of GaN doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ is formed thereon. Has been.

On the n-type contact layer 104, an n-type cladding layer 105 having a thickness of about 25 nm made of Al _0.15 Ga _0.85 N doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ is formed. . Further thereon, three pairs of a well layer made of non-doped In _0.2 Ga _0.8 N having a thickness of about 3 nm and a barrier layer made of non-doped GaN having a thickness of about 20 nm are stacked to form a light emitting layer 106 having a multiple quantum well structure. Has been.

Further, a p-type cladding layer (first p layer) 107 made of p-type Al _0.15 Ga _0.85 N having a film thickness of about 25 nm doped with 2 × 10 ¹⁹ / cm ^{3 of} Mg is formed on the light emitting layer 106. Has been. On the p-type cladding layer 107, a p-type contact layer (second p layer) 108 made of p-type GaN having a thickness of about 100 nm doped with 8 × 10 ¹⁹ / cm ^{3 of} Mg is formed.

  A reflective p-electrode 110 formed by metal deposition is formed on the p-type contact layer (second p-layer) 108, and an n-electrode 140 is formed on the n-type contact layer 104. The reflective p-electrode 110 includes a first layer made of rhodium (Rh) having a thickness of about 300 nm, a first layer made of titanium (Ti) having a thickness of about 10 nm and a gold (Au) having a thickness of about 500 nm. It consists of two layers.

The n-electrode 140 having a multilayer structure is composed of a first layer made of vanadium (V) with a thickness of about 20 nm and aluminum (Al) with a thickness of about 100 nm from above a part of the n-type contact layer 104 that is partially exposed. The second layer, a third layer made of titanium (Ti) with a thickness of about 10 nm, and a fourth layer made of gold (Au) with a thickness of about 500 nm are stacked.

The group III nitride compound semiconductor device 100 having the above-described configuration was manufactured as follows. Group III nitride compound semiconductor device 100 was manufactured by metal organic vapor phase epitaxy (hereinafter abbreviated as “MOVPE”). The gases used were ammonia (NH ₃ ), carrier gas (H ₂ and N ₂ ), trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as “TMG”), trimethylaluminum (Al (CH ₃ ) ₃ (Hereinafter referred to as “TMA”), trimethylindium (In (CH ₃ ) ₃ ) (hereinafter referred to as “TMI”), silane (SiH ₄ ) and cyclopentadienyl magnesium (Mg (C ₅ H ₅ ) ₂ ) (Hereinafter referred to as “CP ₂ Mg”).

First, a single crystal sapphire substrate 101 whose main surface is an A surface cleaned by organic cleaning and heat treatment is mounted on a susceptor mounted in a reaction chamber of an MOVPE apparatus. Next, the sapphire substrate 101 was baked at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at normal pressure.

Next, the temperature of the sapphire substrate 101 was lowered to 400 ° C., and H ₂ , NH ₃ and TMA were supplied to form the AlN buffer layer 102 with a thickness of about 15 nm.

Next, the temperature of the sapphire substrate 101 was maintained at 1150 ° C., H ₂ , NH ₃ , and TMG were supplied, and the non-doped GaN layer 103 was formed thereon. Next, H ₂ , NH ₃ , TMG and silane are supplied, and n-type contact layer 104 (high carrier) having a film thickness of about 5 μm made of GaN doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ thereon. Density n ⁺ layer).

Thereafter, the supply amount of H ₂ , NH ₃ , TMG, TMA, and silane is controlled, and an n _0.15 Ga _0.85 N film made of Al _0.15 Ga _0.85 N doped with silicon (Si) at 1 × 10 ¹⁸ / cm ³ is formed. A mold cladding layer 105 was formed.

Next, the temperature of the sapphire substrate 101 is lowered to 825 ° C., and the supply amount of N ₂ or H ₂ , NH ₃ , TMG, and TMI is controlled to be made of non-doped In _0.2 Ga _0.8 N with a film thickness of about 3 nm. A light emitting layer 106 having a multiple quantum well structure was formed by laminating three pairs of well layers and barrier layers made of non-doped GaN having a thickness of about 20 nm.

Next, the temperature of the sapphire substrate 101 is maintained at 1050 ° C., and N ₂ or H ₂ , NH ₃ , TMG, TMA and CP ₂ Mg are supplied while being controlled, and Mg is doped 2 × 10 ¹⁹ / cm ³ . A p-type cladding layer (first p layer) 107 made of p-type Al _0.15 Ga _0.85 N having a thickness of about 25 nm was formed. Next, N ₂ or H ₂ , NH ₃ , TMG and CP ₂ Mg are supplied while being controlled, and a p-type contact layer made of p-type GaN having a thickness of about 100 nm doped with 8 × 10 ¹⁹ Mg (the second type) p layer) 108 was formed.
With respect to the sapphire substrate (hereinafter referred to as a wafer) that has undergone the above crystal growth process, a photoresist is applied to the entire surface of the wafer, and the outermost periphery of the group III nitride compound semiconductor device 100 is formed in a zigzag shape by photolithography. The photoresist was removed to form a window, and at the same time, the portion of the photoresist where the n-electrode 140 was formed was removed to form a window.

Subsequently, the group III nitride compound semiconductor p-type contact layer (second p-layer) 108, the p-type cladding layer 107, the active layer 106, the n-type cladding layer 105, and the window portion not covered with the photoresist, A part of the n-type contact layer 104 is etched by reactive ion etching so as to form an uneven side surface 160 having an angle of α = 45 degrees, and the outermost peripheral portion of the group III nitride compound semiconductor device 100 is zigzag-shaped. The n-type contact layer 104 was exposed so that the shape of the n-type contact was formed, and at the same time, the portion of the n-type contact layer 104 where the n-electrode 140 was formed was exposed.
Next, a photoresist is applied to the entire surface of the wafer, a portion of the photoresist where the reflective p-electrode 110 is formed is removed by photolithography, a window is formed, and the p-type contact layer (second p-layer) 108 is exposed. It was. Subsequently, rhodium (Rh) was deposited to 300 nm on the entire surface of the wafer.

Thereafter, the photoresist and rhodium (Rh) on the photoresist were removed, and a rhodium (Rh) film was formed on the p-type contact layer 108 as the reflective p-electrode 110.
Next, a photoresist was applied to the entire surface of the wafer, a portion of the photoresist where the n-electrode 140 was to be formed was removed by photolithography, a window was formed, and the n-type contact layer 104 was exposed. Subsequently, vanadium (V) having a film thickness of about 20 nm and aluminum (Al) having a film thickness of about 100 nm were successively deposited on the entire surface of the wafer. Thereafter, the vanadium (V) and aluminum (Al) laminated film on the photoresist is removed together with the photoresist, and a vanadium (V) / aluminum (Al) laminated film is formed on the n-type contact layer 104 as the n electrode 140. Next, heat treatment is performed at 500 ° C. for about 4 minutes in an N ₂ atmosphere.

  Next, a photoresist was applied to the entire surface of the wafer, and the photoresist was removed from the n-electrode 140 portion and the p-electrode 110 portion by photolithography to form a window, and the n-electrode 140 and the p-electrode 110 were exposed. Subsequently, titanium (Ti) having a film thickness of about 10 nm and gold (Au) having a film thickness of about 500 nm were sequentially deposited on the entire surface of the wafer.

  Thereafter, the laminated film of titanium (Ti) and gold (Au) on the photoresist is removed together with the photoresist, and titanium (Ti) / gold (Au) is formed as a thick film electrode 130 on the n electrode 140 and the reflective p electrode 110. ) A laminated film was formed.

  Thereafter, the individual light emitting element portions are separated by dicing.

In the manner as described above, the flip chip type group III nitride compound semiconductor device 100 in which light is extracted from the sapphire side opposite to the semiconductor layer side was manufactured.
Next, FIG. 3 shows a light emitting device 200 using the semiconductor element 100 manufactured as described above. The group III nitride compound semiconductor element 100 is fixed to the center of the recess of the resin case 210 having the reflector portion 220 via a gold bump 240, and the p-side electrode 211 formed on the resin case 210 and the group III nitride compound are formed. The reflective p-electrode 110 of the semiconductor element 100, the n-side electrode 212 formed on the resin case, and the n-electrode 140 of the group III nitride compound semiconductor element 100 were electrically connected and fixed by gold bumps 240, respectively. And the sealing material 230, such as a silicone resin which is a transparent material, was filled in the recessed part of the resin case, and the light-emitting device 200 which protected the group III nitride compound semiconductor element 100 was manufactured.

  According to the light emitting device 200 according to Embodiment 1 of the present invention, light is diffused on the side surface 160 in order to form the zigzag unevenness on the side surface 160 of the groove 150 of the group III nitride compound semiconductor element 100. In addition, since the angle α of the side surface 160 is 45 degrees, the light reaching the side surface 160 is totally reflected while being diffused, guided to the sapphire side of the light emitting element, and extracted outside the issuing element. Further, since there is a zigzag uneven surface serving as a reflection surface formed at the same angle (α = 45 degrees) on the opposite side of the groove 150, light leaked from the end surface of the light emitting surface is diffused. It is possible to extract light to the emission observation surface side well.

Note that the shape of the group III nitride compound semiconductor device 100 shown in the embodiment is not particularly limited. For example, the zigzag of the groove 150 provided in the light emitting element 100 can be replaced with a wave shape. The angle α of the side surface 160 is not limited to 45 degrees, but is preferably 30 degrees or more and less than 50 degrees, and more preferably 40 degrees or more and 45 degrees. This is because if the angle is smaller than 30 degrees, the light emitting surface area of the light emitting element is reduced and the light emitting area cannot be obtained. If the angle exceeds 50 degrees, the light is not totally reflected, and the lower side of the light emitting element. This is because there is a risk of being taken out.
(Embodiment 2)
FIG. 42 shows a schematic plan view of a group III nitride compound semiconductor device 300 according to the second embodiment of the present invention.

  The group III nitride compound semiconductor device 300 is manufactured in the same manner as the group III nitride compound semiconductor device 100 except that a connecting portion 330 is formed to connect the remaining portion 320 around the periphery of the group III nitride compound semiconductor device 300 and the central island-shaped portion 310. did.

  According to the group III nitride compound semiconductor device 300 according to the second embodiment of the present invention, since the connecting portion 330 is formed, until the p-layer side of many light emitting devices formed on the same substrate is separated. Since they are electrically connected, they are not charged at the portions that become individual light emitting elements, and therefore, there is an effect that the pn interface is not easily destroyed by static electricity.

FIG. 1 is a plan view of a semiconductor light emitting element according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the semiconductor light emitting element according to the first embodiment of the present invention. FIG. 3 is a sectional view of the light emitting device according to the first embodiment of the present invention. FIG. 4 is a plan view of a semiconductor light emitting element according to the second embodiment of the present invention.

Explanation of symbols

100, 300 Light emitting element 120 p electrode 140 n electrode 150 groove 160 uneven surface 200 light emitting device

Claims (5)

In the light emitting device,
p layer, emission layer and n-layer are laminated semiconductor in which the p-layer and the p electrode and the n layer and electrically connected to and n electrodes are electrically connected are formed on the same side A light emitting element;
The semiconductor light emitting element is flip-mounted on a mount member having a circuit electrically connected to each of the p electrode and the n electrode,
The semiconductor light emitting element has an inclined surface from the p layer to the n layer, and the inclined surface has a surface uneven structure that totally reflects the light emitted from the light emitting layer to the light emission observation surface side while diffusing the light .
A light emitting device characterized by that.   The light emitting device according to claim 1, wherein the slope of the semiconductor light emitting element is formed in a groove shape.   The light emitting device according to claim 1, wherein the concavo-convex structure has a sawtooth shape extending in a front and back direction.   4. The light emitting device according to claim 1, wherein the n electrode has a mesa shape with side surfaces formed by inclined surfaces. 5.   The light emitting device according to any one of claims 1 to 4, wherein the slope of the semiconductor light emitting element is 50 degrees or less and 30 degrees or more.

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