JP2009117604A - Nitride semiconductor light-emitting diode element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting diode element having high luminous efficiency. <P>SOLUTION: The nitride semiconductor light-emitting element includes an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer. The element has a metallic layer formed on the p-type nitride semiconductor layer. The active layer includes at least one well layer. A distance between the surface of the p-type nitride semiconductor layer of the well layer located nearest to the p-type nitride semiconductor layer among the well layers in the active layer and a surface of the metallic layer on the side of the p-type nitride semiconductor layer is 70 nm or less. The p-type nitride semiconductor layer includes a p-type Al-containing nitride semiconductor layer which contains Al. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor light emitting diode device, and more particularly to a nitride semiconductor light emitting diode device having high luminous efficiency.

In Non-Patent Document 1, a metal layer made of Ag is formed after laminating a GaN barrier layer having a thickness of 10 nm on an active layer having an InGaN / GaN quantum well structure, and a metal layer is formed in a region very close to the active layer. It is reported that the active layer with high luminous efficiency was realized by amplifying the spontaneous emission of the active layer by photoluminescence (PL) due to the plasmon effect peculiar to the metal in the metal layer.
Koichi Okamoto et al., “Surface plasmon enhanced spontaneous emission rate of InGaN / GaN quantum wells probed by time-resolved photoluminescence spectroscopy”, APPLIED PHYSICS LETTERS 87, 071102 (2005)

  However, in order to obtain the plasmon effect of the metal layer in the structure of an actual nitride semiconductor light emitting diode element, in order to position the metal layer at a distance of several tens of nm or less from the active layer, it is several tens of nm. It is necessary to stack a p-type nitride semiconductor layer having a layer thickness smaller than the following distance.

  In the nitride semiconductor light-emitting diode device having the p-type nitride semiconductor layer having such a thin layer thickness, the p-type nitride semiconductor having a high carrier concentration is caused by the low carrier activation rate of the p-type nitride semiconductor layer. Since it is difficult to obtain a layer, the entire p-type nitride semiconductor layer is depleted, and holes cannot be supplied to the active layer, which makes it difficult to emit light.

  In view of the above circumstances, an object of the present invention is to provide a nitride semiconductor light-emitting diode element having high luminous efficiency.

  The present invention is a nitride semiconductor light-emitting diode element including an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer, and has a metal layer formed on the p-type nitride semiconductor layer. The active layer includes at least one well layer, a well layer located closest to the p-type nitride semiconductor layer among the well layers in the active layer, a surface on the p-type nitride semiconductor layer side, and a metal layer The p-type nitride semiconductor layer is a nitride semiconductor light-emitting diode element including a p-type Al-containing nitride semiconductor layer containing Al and having a distance from the surface on the p-type nitride semiconductor layer side of 70 nm or less. is there.

  Here, in the nitride semiconductor light-emitting diode element of the present invention, the distance is preferably 30 nm or more.

  In the nitride semiconductor light-emitting diode device of the present invention, it is preferable that the p-type nitride semiconductor layer has a structure in which a p-type AlGaN layer and a p-type GaN layer are stacked in this order from the active layer side.

  In the nitride semiconductor light emitting diode element of the present invention, the Al composition ratio of the p-type AlGaN layer is preferably 10% or less.

  The nitride semiconductor light-emitting diode device of the present invention includes an undoped AlGaN layer between a well layer located closest to the p-type nitride semiconductor layer among the well layers in the active layer and the p-type nitride semiconductor layer. It is preferable.

  In the nitride semiconductor light emitting diode element of the present invention, the metal layer is preferably made of at least one selected from the group consisting of Ag, Ag alloy, Al and Pt.

  ADVANTAGE OF THE INVENTION According to this invention, the nitride semiconductor light-emitting diode element which has high luminous efficiency can be provided.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

<Embodiment 1>
FIG. 1 shows a schematic cross-sectional view of an example of the nitride semiconductor light-emitting diode element of the present invention. In this nitride semiconductor light emitting diode element, a metal layer 5, a p-type nitride semiconductor layer 4, an active layer 3, an n-type nitride semiconductor layer 2, a translucent conductive substrate 1, and a negative electrode 7 are provided on a positive electrode 6. It has the structure laminated | stacked in this order. In this nitride semiconductor light emitting diode element, the light emitted from the active layer 3 to the metal layer 5 side is reflected by the metal layer 5 and is emitted from the active layer 3 to the translucent conductive substrate 1 side. Together with light, the light is extracted from the translucent conductive substrate 1 side.

  Here, the translucent conductive substrate 1 can be used without particular limitation as long as it is conductive and can transmit light emitted from the active layer 3.

Further, as the n-type nitride semiconductor layer 2, for example, a nitride semiconductor crystal represented by a formula of Al _x1 In _y1 Ga _1-x1-y1 N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1) A material doped with an n-type dopant such as can be used. Here, the n-type nitride semiconductor layer 2 may be composed of a single layer or a plurality of layers. In the above formula, Al represents aluminum, In represents indium, Ga represents gallium, and N represents nitrogen. In the above formula, x1 represents an Al composition ratio, y1 represents an In composition ratio, and 1-x1-y1 represents a Ga composition ratio.

  Further, as the active layer 3, one having a quantum well structure including at least one well layer is used, and in this embodiment, MQW (Multi-layer) in which a plurality of well layers 3b and barrier layers 3a are alternately stacked. Those having a Quantum Well structure are used. However, as the active layer 3 used in the present invention, an SQW (Single Quantum Well) including one well layer may be used.

The well layer 3b constituting the active layer 3 is made of, for example, a nitride semiconductor crystal represented by the formula of Al _x2 In _y2 Ga _1-x2-y2 N (0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1). can do. The barrier layer 3a constituting the active layer 3 is, for example, consists of _{Al x3 In y3 Ga 1-x3} -y3 N (0 ≦ x3 ≦ 1,0 ≦ y3 ≦ 1) nitride semiconductor crystal represented by the formula can do. Further, at least one of the well layer 3b and the barrier layer 3a constituting the active layer 3 may be doped with an n-type dopant such as Si and / or a p-type dopant such as Mg to be n-type or p-type. .

  In the above formula, Al represents aluminum, In represents indium, Ga represents gallium, and N represents nitrogen. In the above formula, x2 and x3 each indicate an Al composition ratio, y2 and y3 each indicate an In composition ratio, and (1-x2-y2) and (1-x3-y3) each indicate a Ga composition ratio. Show.

The p-type nitride semiconductor layer 4 can be used without particular limitation as long as it includes at least one p-type Al-containing nitride semiconductor layer containing Al. As the p-type Al-containing nitride semiconductor layer, for example, a nitride semiconductor crystal represented by the formula of Al _x4 In _y4 Ga _1-x4-y4 N (0 <x4 ≦ 1, 0 ≦ y4 ≦ 1) may be made of Mg or the like. What doped the p-type dopant etc. can be used. Further, when the p-type nitride semiconductor layer 4 includes a layer other than the p-type Al-containing nitride semiconductor layer, for example, Al _x5 In _y5 Ga _1-x5-y5 N (0 ≦ x5 ≦ 1, at least one layer in which a nitride semiconductor crystal represented by the formula of 0 ≦ y5 ≦ 1) is doped with a p-type dopant such as Mg. In the above formula, Al represents aluminum, In represents indium, Ga represents gallium, and N represents nitrogen. In the above formula, x4 and x5 each represent an Al composition ratio, y4 and y5 each represent an In composition ratio, and (1-x4-y4) and (1-x5-y5) represent a Ga composition ratio, respectively. Show.

  In order to obtain a nitride semiconductor light-emitting diode element having high luminous efficiency, the metal layer 5 should be a metal layer made of at least one selected from the group consisting of Ag, Ag alloy, Al and Pt. However, in order to obtain a higher plasmon effect, the metal layer 5 is preferably a metal layer made of Ag or an Ag alloy.

  The positive electrode 6 can be used without any particular limitation as long as it functions as a positive electrode, and the negative electrode 7 can be used without any particular limitation as long as it functions as a negative electrode.

  Here, in the nitride semiconductor light emitting diode device of the present invention, in order to obtain a higher plasmon effect in the metal layer 5, it is preferable that the p-type nitride semiconductor layer 4 has a smaller layer thickness. The width of the depletion layer formed on the semiconductor layer 4 side is calculated by the following formula (1).

Wd = ((2κε ₀ / q) × (1 / Na) × φ _bi ) ^1/2 (1)
In the above formula (1), Wd indicates the width of the depletion layer formed on the p-type nitride semiconductor layer 4 side, φ _bi indicates the internal potential of the p-type nitride semiconductor layer 4, and κ is the p-type. The relative dielectric constant of the nitride semiconductor layer 4 is represented, ε ₀ represents the vacuum dielectric constant of the p-type nitride semiconductor layer 4, q represents the charge of electrons, and Na represents the p-type ionization in the p-type nitride semiconductor layer 4. Indicates impurity concentration.

Here, when the p-type nitride semiconductor layer 4 is composed of a single p-type GaN layer that does not contain Al, for example, φ _bi ≈3.4 (V), κ = 9.5, ε _0. = 8.85 × 10 ⁻¹⁴ (F / cm), q = 1.6 × 10 ⁻¹⁹ (C), and Na = 1 × 10 ¹⁸ (pieces / cm ³ ). Substituting into (1) results in Wd≈60 nm. Therefore, in this case, when the thickness of the p-type nitride semiconductor layer 4 is 60 nm or less, the entire p-type nitride semiconductor layer 4 is depleted and holes cannot be supplied to the active layer 3.

Further, when the p-type ionized impurity concentration Na in the p-type nitride semiconductor layer 4 which is a single p-type GaN layer is 1 × 10 ¹⁸ (pieces / cm ³ ) or more, the p-type nitride semiconductor layer 4 Although it is possible to reduce the width Wd of the depletion layer formed on the side, considering the activation rate of carriers in the p-type nitride semiconductor layer 4 made of a single p-type GaN layer, the value of Na is 1 × It is difficult to increase it to 10 ¹⁸ (pieces / cm ³ ) or more.

  Further, a barrier layer 3 a is inserted between the well layer 3 b in the active layer 3 and the p-type nitride semiconductor layer 4 in order to suppress the diffusion of the p-type dopant from the p-type nitride semiconductor layer 4 to the active layer 3. It is preferable to suppress the decrease in luminous efficiency, and the layer thickness of the barrier layer 3a is required to be at least 10 nm. Therefore, the surface 100 on the p-type nitride semiconductor layer 4 side of the well layer 3b located closest to the p-type nitride semiconductor layer 4 in the active layer 3, and the surface on the p-type nitride semiconductor layer 4 side of the metal layer 5 It is difficult to set the distance D to 101 to 70 nm or less when the p-type nitride semiconductor layer 4 is a single p-type GaN layer.

  Therefore, the p-type nitride semiconductor layer 4 includes at least one Al-containing nitride semiconductor layer made of a nitride semiconductor crystal containing Al, particularly, the p-type AlGaN layer and the p-type GaN layer from the active layer 3 side. Are stacked in this order so that a piezoelectric field generated at the interface between the active layer 3 and the p-type AlGaN layer and the interface between the p-type AlGaN layer and the p-type GaN layer causes the p-type nitride semiconductor layer 4 side to The width Wd of the depletion layer formed on the substrate can be reduced. Thereby, the surface 100 on the p-type nitride semiconductor layer 4 side of the well layer 3b located closest to the p-type nitride semiconductor layer 4 in the active layer 3 and the p-type nitride semiconductor layer 4 side of the metal layer 5 are arranged. When the distance D from the surface 101 is 70 nm or less (the thickness of the p-type nitride semiconductor layer 4 is 60 nm or less, and the well layer 3b located closest to the p-type nitride semiconductor layer 4 in the active layer 3) Even when the thickness of the barrier layer 3a disposed between the p-type nitride semiconductor layer 4 and the p-type nitride semiconductor layer 4 is 10 nm, holes can be supplied to the active layer 3.

  Here, from the viewpoint of obtaining a nitride semiconductor light-emitting diode element having high luminous efficiency, the p-type nitride semiconductor layer 4 is composed of a p-type AlGaN layer and a p-type GaN layer in this order from the active layer 3 side. A laminated structure is preferable.

  In the present invention, when the p-type nitride semiconductor layer 4 has a configuration in which a p-type AlGaN layer and a p-type GaN layer are stacked in this order from the active layer 3 side, the Al composition of the p-type AlGaN layer The ratio and the Ga composition ratio are not particularly limited. From the viewpoint of effectively generating a piezoelectric field generated at the interface between the active layer 3 and the p-type AlGaN layer and the interface between the p-type AlGaN layer and the p-type GaN layer, the p-type. The Al composition ratio of the AlGaN layer is preferably 10% or more.

In the present invention, the Al composition ratio is calculated by the following equation (2). In the following formula (2), Al represents aluminum, In represents indium, and Ga represents gallium.
Al composition ratio (%) = 100 × (number of Al atoms in p-type AlGaN layer) / {(number of Al atoms in p-type AlGaN layer) + (number of Ga atoms in p-type AlGaN layer) + ( Number of In atoms in p-type AlGaN layer)} (2)
Further, when the p-type nitride semiconductor layer 4 includes an Al-containing nitride semiconductor layer, the p-type nitride semiconductor of the well layer 3b located closest to the p-type nitride semiconductor layer 4 in the active layer 3 is used. The lower limit of the distance D between the surface 100 on the layer 4 side and the surface 101 on the p-type nitride semiconductor layer 4 side of the metal layer 5 can be 30 nm. Therefore, in the present invention, the surface 100 on the p-type nitride semiconductor layer 4 side of the well layer 3 b located closest to the p-type nitride semiconductor layer 4 in the active layer 3 and the p-type nitride semiconductor of the metal layer 5. The distance D between the surface 101 on the layer 4 side is preferably 30 nm or more and 70 nm or less.

  Further, from the viewpoint of effectively preventing the diffusion of the p-type dopant from the p-type nitride semiconductor layer 4, the well layer 3b located closest to the p-type nitride semiconductor layer 4 in the active layer 3 and the p-type nitride An undoped AlGaN layer is preferably provided as the barrier layer 3a between the semiconductor layer 4 and the semiconductor layer 4. In this case, both functions as a layer that efficiently generates a piezo electric field and a layer that suppresses the diffusion of a p-type dopant such as Mg are more effective than when an undoped GaN layer is provided as the barrier layer 3a. It tends to improve.

  As shown in FIG. 1, the nitride semiconductor light-emitting diode element is preferably mounted so as to be a flip chip type in which the n-type nitride semiconductor layer 2 side is the light extraction side with respect to the active layer 3.

  Further, in the nitride semiconductor light-emitting diode element shown in FIG. 1, the metal layer 5 and the positive electrode 6 are made of, for example, Ti (titanium), W (tungsten), Ta (tantalum), and Mo (molybdenum). A protective layer made of at least one metal selected from the group may be formed.

  As described above, in the nitride semiconductor light emitting diode element shown in FIG. 1, the p-type nitride semiconductor layer 4 includes the p-type Al-containing nitride semiconductor layer containing Al, and is the most p-type nitride in the active layer 3. The distance D between the surface 100 of the well layer 3b located on the p-type nitride semiconductor layer 4 side of the well layer 3b and the surface 101 of the metal layer 5 on the p-type nitride semiconductor layer 4 side is 70 nm or less. Therefore, the plasmon effect of the metal layer 5 can be effectively obtained, and high luminous efficiency is expressed by the plasmon effect of the metal layer 5.

<Embodiment 2>
FIG. 2 shows a schematic cross-sectional view of another example of the nitride semiconductor light-emitting diode element of the present invention. In this nitride semiconductor light-emitting diode element, an insulating substrate 1001 such as a sapphire substrate that can transmit light emitted from the active layer 3 but is not conductive is used as a substrate, and the negative electrode 7 Is in contact with the n-type nitride semiconductor layer 2.

  Even when an insulating substrate 1001 such as a sapphire substrate is used as the substrate and the negative electrode 7 is in contact with the n-type nitride semiconductor layer 2 as in the present embodiment, the p-type nitride semiconductor layer 4 Has a configuration including a p-type Al-containing nitride semiconductor layer (particularly, a configuration in which a p-type AlGaN layer and a p-type GaN layer are stacked in this order from the active layer 3 side), and is the most p-type nitride semiconductor in the active layer 3 By setting the distance D between the surface 100 on the p-type nitride semiconductor layer 4 side of the well layer 3b located on the layer 4 side and the surface 101 on the p-type nitride semiconductor layer 4 side of the metal layer 5 to 70 nm or less. The plasmon effect of the metal layer 5 can be effectively obtained, and high luminous efficiency can be expressed by the plasmon effect of the metal layer 5.

  In the present embodiment also, a protective layer made of at least one metal selected from the group consisting of Ti, W, Ta, and Mo is formed between the metal layer 5 and the positive electrode 6, for example. May be. Also in the present embodiment, the lower limit of the distance D can be set to 30 nm. Since other explanations are the same as those in the first embodiment, the explanation is omitted.

<Embodiment 3>
FIG. 3 shows a schematic cross-sectional view of another example of the nitride semiconductor light-emitting diode element of the present invention. This nitride semiconductor light-emitting diode element is characterized in that it is manufactured by separately preparing a conductive substrate 9 on the surface and affixing the conductive substrate 9 to the metal layer 5 via the adhesive metal layer 8. .

  Hereinafter, an example of a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 3 will be described with reference to the schematic cross-sectional views of FIGS. 4 (a) to 4 (d).

  First, as shown in FIG. 4A, an n-type nitride semiconductor layer 2, a well layer 3b, and a barrier layer are formed on an insulating substrate 1001 such as a sapphire substrate by, for example, MOCVD (Metal Organic Chemical Vapor Deposition). Active layers 3 and p-type nitride semiconductor layers 4 alternately stacked with 3a are formed in this order. Then, after the metal layer 5 is formed on the surface of the p-type nitride semiconductor layer 4 by, for example, a vacuum deposition method or a sputtering method, the first adhesive metal layer 8a is formed on the metal layer 5.

  Further, as shown in FIG. 4B, the second adhesive metal layer 8b is formed on the conductive substrate 9 by, for example, a vacuum deposition method or a sputtering method.

  Subsequently, as shown in FIG. 4C, the first adhesive metal layer 8a on the insulating substrate 1001 manufactured as described above and the second adhesive metal layer 8b on the conductive substrate 9 face each other. Then, a wafer in which the first adhesive metal layer 8a and the second adhesive metal layer 8b are joined is formed by eutectic bonding or the like.

  4D, the insulating substrate 1001 is peeled off by melting a part of the n-type nitride semiconductor layer 2 by irradiating a laser beam from the insulating substrate 1001 side of the wafer or the like. To do. Then, after forming the negative electrode 7 on the surface of the n-type nitride semiconductor layer 2 exposed by the peeling of the insulating substrate 1001, the wafer is divided into chips, whereby the nitride semiconductor light emitting diode having the configuration shown in FIG. An element is obtained. Here, the adhesive metal layer 8 is a layer in which the first adhesive metal layer 8a and the second adhesive metal layer 8b shown in FIG. 4C are joined.

  Also in the present embodiment, the p-type nitride semiconductor layer 4 includes at least one p-type Al-containing nitride semiconductor layer (particularly, the p-type AlGaN layer and the p-type GaN layer are arranged in this order from the active layer 3 side). The surface 100 of the well layer 3b located on the p-type nitride semiconductor layer 4 side closest to the p-type nitride semiconductor layer 4 side in the active layer 3 and the p-type nitride semiconductor layer 4 of the metal layer 5 By setting the distance D between the side surface 101 to 70 nm or less, the plasmon effect of the metal layer 5 can be effectively obtained, and high luminous efficiency can be exhibited by the plasmon effect of the metal layer 5.

Also in the present embodiment, the lower limit of the distance D can be set to 30 nm. Further, in the present embodiment, a protective layer and / or a part made of at least one metal selected from the group consisting of Ti, W, Ta and Mo, for example, between the metal layer 5 and the adhesive metal layer 8. In particular, a SiO ₂ layer may be formed.

  In addition, when a conductive semiconductor substrate such as an n-type Si substrate is used as the conductive substrate 9, an ohmic contact layer may be provided between the conductive substrate 9 and the adhesive metal layer 8. For example, when the conductive substrate 9 is made of Si, a layer made of a metal such as Ti or W can be used as the ohmic contact layer. Further, a protective layer made of a metal such as Pt may be formed between the ohmic contact layer and the second adhesive metal layer 5b.

  In the present embodiment, Au or the like can be used as the first adhesive metal layer 8a, and AuSn, AuGe, AuSi, or the like can be used as the second adhesive metal layer 8b.

  Since other explanations are the same as those in the first embodiment, explanations thereof are omitted.

<Example 1>
In Example 1, a nitride semiconductor light-emitting diode element having the configuration shown in FIG. 5 was produced. Here, in Example 1, a plurality of nitride semiconductor light emitting diode elements in which the layer thickness of the p-type GaN contact layer 17 was changed in the range of 10 nm to 100 nm were manufactured.

As shown in FIG. 5, the nitride semiconductor light-emitting diode device manufactured in Example 1 has an ohmic electrode layer 22, a second bonding metal layer 23, and a first bonding metal on a conductive substrate 21. Layer 20, protective layer 19, reflective layer 18, p-type GaN contact layer 17, p-type AlGaN cladding layer 16, active layer 15 in which In _0.25 Ga _0.75 N well layers 15b and GaN barrier layers 15a are alternately stacked, n The type GaN contact layer 14, the n-type GaN foundation layer 13, and the negative electrode 24 are stacked in this order. In this nitride semiconductor light emitting diode element, the conductive substrate 21 functions as a positive electrode.

  Below, an example of the manufacturing method of the nitride semiconductor light emitting diode element of Example 1 is demonstrated. First, as shown in the schematic cross-sectional view of FIG. 6, a sapphire substrate 11 was prepared, and the sapphire substrate 11 was set in a reactor of a MOCVD apparatus. Then, while flowing hydrogen into the reactor, the temperature of the sapphire substrate 11 was raised to 1050 ° C., and the surface (C surface) of the sapphire substrate 11 was cleaned.

  Next, the temperature of the sapphire substrate 11 is lowered to 510 ° C., hydrogen as a carrier gas, ammonia and TMG (trimethyl gallium) as a source gas are flown into the reactor, and as shown in the schematic cross-sectional view of FIG. A non-doped GaN buffer layer 12 was grown on the surface (C-plane) of the sapphire substrate 11 to a thickness of about 20 nm by the MOCVD method.

Next, the temperature of the sapphire substrate 11 is raised to 1050 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are flown into the reactor, and n-type GaN made of GaN doped with Si Underlayer 13 (carrier concentration: 1 × 10 ¹⁸ / cm ³ ) was grown on GaN buffer layer 12 to a thickness of 6 μm by MOCVD.

Subsequently, the n-type GaN contact layer 14 is formed to a thickness of 0.5 μm by MOCVD in the same manner as the n-type GaN underlayer 13 except that Si is doped so that the carrier concentration becomes 5 × 10 ¹⁸ atoms / cm ³ . A thickness was grown on the n-type GaN foundation layer 13.

Next, the temperature of the sapphire substrate 11 is lowered to 700 ° C., hydrogen as a carrier gas, ammonia, TMG, and TMI (trimethylindium) as a source gas are flown into the reactor, as shown in the schematic cross-sectional view of FIG. Further, an In _0.25 Ga _0.75 N well layer 15b having a thickness of 2.5 nm and a GaN barrier layer 15a having a thickness of 10 nm are alternately grown by MOCVD for six periods on the n-type GaN contact layer 14 to obtain multiple layers. An active layer 15 having a quantum well structure was formed on the n-type GaN contact layer 14. Needless to say, when the active layer 15 is formed, TMI is not allowed to flow into the reactor when the GaN barrier layer 15a is grown.

Next, the temperature of the sapphire substrate 11 is increased to 950 ° C., hydrogen as a carrier gas, ammonia, TMG and TMA (trimethylaluminum) as source gases, and CP2Mg (cyclopentadienylmagnesium) as impurity gases are flowed into the reactor. 9, a p-type AlGaN cladding layer 16 made of Al _0.15 Ga _0.85 N doped with Mg at a concentration of 1 × 10 ²⁰ / cm ³ is formed to a thickness of 20 nm by MOCVD. To grow on the active layer 15.

Next, while maintaining the temperature of the sapphire substrate 11 at 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and CP2Mg as an impurity gas are allowed to flow into the reactor, and Mg is 1 × 10 ²⁰ pieces / cm 2. ^A p-type GaN contact layer 17 made of GaN doped at a concentration of ³ was grown on the p-type AlGaN cladding layer 16 by MOCVD. Here, the p-type GaN contact layer 17 was grown by changing the layer thickness in the range of 10 nm to 100 nm every time the nitride semiconductor light emitting diode element was manufactured.

  Next, the temperature of the sapphire substrate 11 was lowered to 700 ° C., and annealing was performed by flowing nitrogen as a carrier gas into the reaction furnace.

  Next, after the above-described annealing, as shown in the schematic cross-sectional view of FIG. 10, the reflective layer 18 made of an Ag film having a thickness of 150 nm and the protection made of an Mo film having a thickness of 50 nm are formed on the p-type GaN contact layer 17. A first bonding metal layer 20 made of an Au film having a layer 19 and a layer thickness of 3 μm was formed in this order by an EB (Electron Beam) vapor deposition method.

  Next, as shown in the schematic cross-sectional view of FIG. 11, a Ti film with a thickness of 15 nm and an Al film with a thickness of 150 nm are formed on a conductive substrate 21 made of conductive Si with a thickness of 120 μm by EB vapor deposition. And a second bonding metal layer 23 in which an Au film having a thickness of 100 nm and an AuSn film having a thickness of 3 μm are laminated in this order were formed in this order.

  Thereafter, as shown in the schematic cross-sectional view of FIG. 12, after the first bonding metal layer 20 on the sapphire substrate 11 is placed on the second bonding metal layer 23 of the conductive substrate 21, the first 13 is a schematic cross-sectional view of FIG. 13 in which the conductive substrate 21 produced above is bonded to the sapphire substrate 11 by bonding the bonding metal layer 20 and the second bonding metal layer 23 by the eutectic bonding method. The nitride semiconductor layer laminated wafer shown was formed. Here, the temperature during the eutectic bonding of the first bonding metal layer 20 and the second bonding metal layer 23 was 290 ° C.

  Subsequently, the GaN buffer layer 12 is melted by irradiating laser light from the side of the sapphire substrate 11 of the nitride semiconductor layer laminated wafer shown in FIG. The surface of the formation 13 was exposed.

  Then, as shown in FIG. 5, a negative electrode 24 composed of a laminate of a Ti film and an Au film is formed at the center of the exposed surface of the n-type GaN foundation layer 13, and then the negative electrode 24 is formed. The nitride semiconductor layer laminated wafer was divided into chips to produce a nitride semiconductor light emitting diode device having the configuration shown in FIG.

  In the nitride semiconductor light-emitting diode element having the configuration shown in FIG. 5, the p-type GaN contact layer 17 is grown by changing the thickness of the p-type GaN contact layer 17 in the range of 10 nm to 100 nm for each production of the nitride semiconductor light-emitting diode element. For each production, the surface 100 of the well layer 15b located closest to the p-type nitride semiconductor layer (p-type AlGaN cladding layer 16 and p-type GaN contact layer 17) in the active layer 15, and the p-type of the reflective layer 18 The distance D between the surface 101 on the side of the nitride semiconductor layer (p-type AlGaN cladding layer 16 and p-type GaN contact layer 17) is different.

  As a result of measuring the luminous efficiency of the nitride semiconductor light emitting diode device, the luminous efficiency is obtained when the thickness of the p-type GaN contact layer 17 is 10 nm or more and 40 nm or less (that is, when the distance D is 40 nm or more and 70 nm or less). Is confirmed to increase.

<Example 2>
In Example 2, a plurality of nitride semiconductor light-emitting diode elements each having a different Al composition ratio of the p-type AlGaN cladding layer 16 of the nitride semiconductor light-emitting diode element having the configuration shown in FIG.

  The fabrication of the nitride semiconductor light-emitting diode element in Example 2 was performed in the same manner as in Example 1 until the active layer 15 was formed.

Next, the temperature of the sapphire substrate 11 is raised to 950 ° C., hydrogen as the carrier gas, ammonia, TMG and TMA (trimethylaluminum) as the source gas, and CP2Mg as the impurity gas flow into the reactor, and the schematic diagram of FIG. As shown in the cross-sectional view, a p-type AlGaN cladding layer 16 made of Al _a Ga _1-a N (0 ≦ a ≦ 0.4) doped with Mg at a concentration of 1 × 10 ²⁰ / cm ³ is formed by MOCVD. To grow on the active layer 15 to a thickness of 20 nm.

  Here, in Example 2, the p-type AlGaN cladding layer 16 was grown by changing the Al composition ratio of the p-type AlGaN cladding layer 16 for each production of the nitride semiconductor light-emitting diode element.

Next, while maintaining the temperature of the sapphire substrate 11 at 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and CP2Mg as an impurity gas are allowed to flow into the reactor, and Mg is 1 × 10 ²⁰ pieces / cm 2. ^A p-type GaN contact layer 17 made of GaN doped at a concentration of ³ was grown on the p-type AlGaN cladding layer 16 to a thickness of 30 nm by MOCVD.

  Thereafter, in the same manner as in Example 1, a plurality of nitride semiconductor light-emitting diode elements were manufactured such that the Al composition ratio of the p-type AlGaN cladding layer 16 was different every time each nitride semiconductor light-emitting diode element was manufactured.

  As a result of measuring the light emission efficiency of the nitride semiconductor light emitting diode element, it was confirmed that the light emission efficiency was increased when the Al composition ratio of the p-type AlGaN cladding layer 16 was 10% or more.

<Example 3>
In Example 3, a plurality of nitride semiconductor light-emitting diode elements were produced in which the material of the reflective layer 18 of the nitride semiconductor light-emitting diode element having the configuration shown in FIG.

  The fabrication of the nitride semiconductor light-emitting diode element in Example 3 was performed in the same manner as in Example 1 until the p-type GaN contact layer 17 was formed.

  Next, after annealing the sapphire substrate 11 on which the p-type GaN contact layer 17 is formed, the type of the material of the reflective layer 18 on the surface of the p-type GaN contact layer 17 is changed every time each nitride semiconductor light emitting diode element is manufactured. Thus, the reflective layer 18 was produced with a layer thickness of 150 nm. Here, as the material of the reflective layer 18, Ag alloy, Pt, and Al containing Pd and Cu in a content of 1% by mass or less were used.

  Thereafter, in the same manner as in Example 1, a plurality of nitride semiconductor light-emitting diode elements having different materials for the reflective layer 18 were manufactured for each nitride semiconductor light-emitting diode element.

  As a result of measuring the luminous efficiency of the nitride semiconductor light emitting diode element, the nitride semiconductor light emitting diode element using an Ag alloy for the reflective layer 18 is a reflective layer under the condition that the distance D is 70 nm or less. 18 was confirmed to have the same luminous efficiency as that of the nitride semiconductor light emitting diode device fabricated in Example 1 using Ag.

  Note that the nitride semiconductor light-emitting diode element using Pt and Al for the reflective layer 18 has high luminous efficiency, although not as high as the nitride semiconductor light-emitting diode element manufactured in Example 1 using Ag for the reflective layer 18. Was confirmed.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  ADVANTAGE OF THE INVENTION According to this invention, the nitride semiconductor light-emitting diode element which has high luminous efficiency can be provided.

It is typical sectional drawing of an example of the nitride semiconductor light-emitting diode element of this invention. It is typical sectional drawing of another example of the nitride semiconductor light-emitting diode element of this invention. It is typical sectional drawing of another example of the nitride semiconductor light-emitting diode element of this invention. (A)-(d) is typical sectional drawing illustrated about an example of the manufacturing method of the nitride semiconductor light-emitting diode element shown in FIG. It is typical sectional drawing of the nitride semiconductor light-emitting diode element produced in the Example. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing the nitride semiconductor light-emitting diode element shown in FIG. 5.

Explanation of symbols

1 translucent conductive substrate, 2 n-type nitride semiconductor layer, 3,15 active layer, 3a barrier layer, 3b well layer, 4p-type nitride semiconductor layer, 5 metal layer, 6 positive electrode, 7, 24 negative electrode , 8 adhesive metal layer, 8a first adhesive metal layer, 8b second adhesive metal layer, 9, 21 conductive substrate, 11 sapphire substrate, 12 GaN buffer layer, 13 n-type GaN underlayer, 14 n-type GaN contact layer, 15a GaN barrier layer, 15b In _0.25 Ga _0.75 N well layer, 16 p-type AlGaN cladding layer, 17 p-type GaN contact layer, 18 reflective layer, 19 protective layer, 20 first bonding metal layer, 22 ohmic electrode layer, 23 Second metal layer for adhesion, 100, 101 surface, 1001 Insulating substrate.

Claims (6)

A nitride semiconductor light emitting diode element comprising an n-type nitride semiconductor layer, an active layer, and a p-type nitride semiconductor layer,
A metal layer formed on the p-type nitride semiconductor layer;
The active layer includes at least one well layer;
Of the well layer in the active layer, the surface of the well layer located closest to the p-type nitride semiconductor layer side on the p-type nitride semiconductor layer side, and the surface of the metal layer on the p-type nitride semiconductor layer side The distance between and is 70 nm or less,
The nitride semiconductor light emitting diode device, wherein the p-type nitride semiconductor layer includes a p-type Al-containing nitride semiconductor layer containing Al.   The nitride semiconductor light-emitting diode element according to claim 1, wherein the distance is 30 nm or more.   3. The nitriding according to claim 1, wherein the p-type nitride semiconductor layer has a configuration in which a p-type AlGaN layer and a p-type GaN layer are stacked in this order from the active layer side. Semiconductor light-emitting diode element.   The nitride semiconductor light emitting diode device according to claim 3, wherein an Al composition ratio of the p-type AlGaN layer is 10% or more.   The undoped AlGaN layer is included between the well layer located closest to the p-type nitride semiconductor layer among the well layers in the active layer and the p-type nitride semiconductor layer. 5. The nitride semiconductor light-emitting diode device according to any one of items 1 to 4.   6. The nitride semiconductor light-emitting diode element according to claim 1, wherein the metal layer is made of at least one selected from the group consisting of Ag, an Ag alloy, Al, and Pt.

Images