JP2005317931A - Semiconductor light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting diode improving a light extraction efficiency. <P>SOLUTION: An n-type semiconductor layer 2, a light emitting layer 3, and a p-type semiconductor layer 3, are laminated in this order. It is so constituted that each electrode is connected to the n-type semiconductor layer 2 and the p-type semiconductor layer 3, respectively. The electrode connected to the p-type semiconductor layer 3 comprises a lower layer ITO film 5, an upper layer ITO film 6 which is formed on the lower layer ITO film 5 so that a part of a front surface of the lower layer ITO film 5 may be exposed, and a metal film 7 disposed only on the upper layer ITO film 6. The electrode connected to the n-type semiconductor layer 2 is configured by an ITO film 8 and a metal film 9 disposed on the ITO film 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device having an electrode made of a conductive oxide.

Conventionally, a structure in which a p-type semiconductor layer and an n-type semiconductor layer are stacked on a substrate and an electrode electrically connected to each of the p-type and n-type semiconductor layers is formed as a semiconductor light emitting device. Yes. Further, as an electrode electrically connected to the p-type semiconductor layer, a structure is known in which an electrode made of a translucent material is formed on the entire surface of the p-type semiconductor layer, and a metal electrode is formed thereon.
In the semiconductor light emitting device having such a configuration, a transparent metal thin film such as a Ni / Au electrode or a conductive oxide film such as ITO, ZnO, In ₂ O ₃ or SnO _{2 is used} as the entire surface electrode on the p-type semiconductor layer. (For example, Patent Documents 1 and 2).
However, since the metal thin film has a low light transmittance, there is a limit to improving the light extraction efficiency.

In addition, since conductive oxides such as ITO have translucency, light extraction efficiency is generally good, but sufficient light extraction efficiency can be obtained depending on the film thickness and film quality. There is a problem that you can not.
Usually, a pad electrode made of metal is formed on an electrode made of a conductive oxide for connection to the outside such as a wire.
However, since the pad electrode is relatively thick and does not transmit light, not only the light emitted in the area where the pad electrode is formed cannot be extracted, but also the light is absorbed by the presence of the pad electrode, There is also a problem that the light extraction loss increases.

JP 2000-164922 A JP 2001-210867 A

  The present invention has been made in view of the above problems, and by using a transparent conductive oxide film, while improving the light extraction efficiency from the light emitting layer, the metal film is usually used as a pad electrode. Absorption of light emitted from the light emitting layer can be minimized, and light extraction efficiency from the entire surface of the light emitting layer can be further improved by maximizing the reflection of light by the metal film. An object is to provide a semiconductor light emitting device.

  The semiconductor light emitting device according to the present invention includes a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer laminated in this order, and electrodes are connected to the first conductive type and the second conductive type semiconductor layer, respectively. The electrode connected to the second conductivity type semiconductor layer is a lower conductive oxide film and the lower conductive oxide film on the surface of the lower conductive oxide film. An upper conductive oxide film formed so as to have a region where a part of the upper conductive oxide film is exposed, and a metal film disposed only on the upper conductive oxide film, and connected to the first conductive semiconductor layer. The electrode comprises a conductive oxide film and a metal film disposed on the conductive oxide film, and the upper and lower conductive oxide films and the conductive oxide film are made of zinc (Zn), indium (In), tin (Sn) and magnesium (Mg) Characterized by comprising the oxides containing at least one element that is.

In this semiconductor light emitting device, the lower conductive oxide film has the formula (1)
A ・ λ / 4n ₁ ± X (1)
(In the formula, A is an odd number, λ is the wavelength of light (Å) generated from the light emitting layer, n ₁ is the refractive index of the lower conductive oxide film, and X is a film of 0 to 20% of the optical thin film (λ / 4n)) Thick (Å).)
It is formed with the film thickness.
Further, the upper conductive oxide film and the conductive oxide film are formed by the same process using the same type and film thickness.

Further, the upper conductive oxide film and / or the conductive oxide film has the formula (2)
B ・ λ / 4n ₂ + α / 2 (2)
(In the formula, B is an even number, n ₂ is the refractive index of the upper conductive oxide film, α is the phase shift distance (Å), and λ is as defined above.)
It is formed with the film thickness.

The lower conductive oxide film is a film having a lower density than the surface side in the vicinity of the interface with the second conductivity type semiconductor layer.
Further, the upper conductive oxide film and the conductive oxide film are films higher than the density of the lower conductive oxide film in the vicinity of the interface with the second conductive type semiconductor layer.
The upper and lower conductive oxide films and the conductive oxide film are ITO.
Further, the metal film is formed of a single layer film or a laminated film of W, Rh, Ag, Pt, Pd, and Al.
The first conductivity type semiconductor layer is an n-type semiconductor layer, and the second conductivity type semiconductor layer is a p-type semiconductor layer.
Furthermore, the first conductive type and the second conductive type semiconductor layer are made of a nitride semiconductor.

Further, the first conductive type semiconductor layer is formed on the substrate, and at least part of the interface between the substrate and the first conductive type semiconductor layer has irregularities. In particular, the irregularities are at least the upper conductive oxide. It is preferably formed on the substrate surface below the metal film formed on the film.
Furthermore, the electrode connected to the first conductivity type semiconductor layer and the electrode connected to the second conductivity type semiconductor layer are formed on the same surface side, and the first conductivity type semiconductor layer is viewed from the electrode formation surface side. A first region provided with a semiconductor stacked structure having upper and lower conductive oxide films and a second region different from the first region, and the second region has a plurality of irregularities. In particular, the uneven protrusions provided in the second region are made of the same material as the semiconductor layer of the first region, and the tops of the protrusions are made of the same material as the lower conductive oxide film. It is preferable to consist of these films.

  The semiconductor light emitting device of the present invention includes a specific conductive oxide film on an electrode, and the electrode connected to the second conductive type semiconductor layer includes a lower conductive oxide film and a lower conductive oxide. An upper conductive oxide film formed on the film so as to have a region where a part of the surface of the lower conductive oxide film is exposed, and a metal film disposed only on the upper conductive oxide film Since the electrode connected to the first conductive semiconductor layer is composed of a conductive oxide film and a metal film disposed on the conductive oxide film, the second conductive type semiconductor layer is formed on the lower layer. In a region where the conductive oxide film is formed and the metal film is not disposed, light emitted from the light emitting layer can be efficiently extracted. Further, in the region where the metal film is disposed, reflection at the interface between the metal film and the upper conductive oxide film can be improved, and the light extraction efficiency can be further improved. In addition, the upper and lower conductive oxide films and the conductive oxide film contain at least one element selected from the group consisting of zinc (Zn), indium (In), tin (Sn), and magnesium (Mg). Therefore, since the translucency can be improved while ensuring the conductivity, the above effect becomes more remarkable.

In particular, when the lower conductive oxide film is formed with a specific film thickness represented by the formula (1), the lower conductive oxide film emits light in a region where the metal film is not disposed. Since it functions as a non-reflective film for light of a wavelength, light can be transmitted efficiently, and the above-described light extraction efficiency can be further improved.
In addition, when the upper conductive oxide film and the conductive oxide film are formed of the same type and film thickness in the same process, the manufacturing process is simplified, resulting in low cost and reliability. A semiconductor light emitting device having a high height can be obtained.

  Furthermore, when the upper conductive oxide film and / or the conductive oxide film is formed with a specific film thickness represented by the formula (2), the upper conductive oxide film is a metal film. In the arranged region, it functions as a reflective film having a high reflectance with respect to light of the emission wavelength, so that light can be efficiently reflected at the interface between the metal film and the upper conductive oxide film. It is possible to further improve the light extraction efficiency.

  Further, when the lower conductive oxide film is a film having a lower density than the surface side in the vicinity of the interface with the second conductive type semiconductor layer, the upper conductive oxide film and the conductive oxide film further include: When the film is higher than the density of the lower conductive oxide film in the vicinity of the interface with the second conductive type semiconductor layer, the current density between the second conductive type semiconductor layer and the lower conductive oxide film is increased. And the ohmic property can be further improved by reducing the Schottky barrier. Moreover, on the surface side of the lower conductive oxide film, the density is higher than that in the vicinity of the interface and it exists as a region with good crystallinity, so that the current can be spread uniformly in the lateral direction and light scattering is reduced. Therefore, the transmittance for visible light can be improved, and the function as a transparent electrode can be sufficiently exhibited.

Furthermore, when the upper and lower conductive oxide films and the conductive oxide film are ITO, the conductivity and translucency can be improved while ensuring the adhesion with the second conductivity type semiconductor layer. Therefore, the light extraction efficiency can be further improved.
Further, when the metal film is formed of a single layer film or a laminated film of W, Rh, Ag, Pt, Pd, and Al, the adhesion between the upper conductive oxide film and the conductive oxide film is improved. Since it is favorable, supply of current to the semiconductor layer can be sufficiently ensured, and since the reflectance is high, the light extraction efficiency from the light emitting layer can be further improved.

In addition, when the first conductive type semiconductor layer is formed on the substrate and at least part of the interface between the substrate and the first conductive type semiconductor layer has irregularities, light traveling in the lateral direction in the semiconductor layer is transmitted. Since the light is scattered or diffracted by the unevenness and proceeds in the vertical direction, the light extraction efficiency can be further improved.
In particular, when the unevenness is formed on the substrate surface below the metal film formed on the upper conductive oxide film, the light traveling in the lateral direction is scattered or diffracted by the unevenness and changed in the vertical direction. As a result, the light incident on the interface between the metal film and the upper conductive oxide film can be further increased, so that the light extraction efficiency can be further improved.

Furthermore, the electrode connected to the first conductivity type semiconductor layer is formed on the same surface side as the electrode connected to the second conductivity type semiconductor layer, and a plurality of electrodes are formed in the second region on the first conductivity type semiconductor layer. By providing the unevenness, the light traveling in the lateral direction inside the first conductivity type semiconductor layer, that is, the light traveling while repeating total reflection, is taken into the convex portion, and from the top or side surface of the convex portion, Light can be efficiently extracted in the vertical direction, particularly in the emission observation surface side.
Further, when the uneven protrusions provided in the second region are made of the same material as the semiconductor layer of the first region, or the tops of the protrusions are made of the same material as the lower conductive oxide film Therefore, it becomes possible to extract the light taken into the convex portion more efficiently.

  The semiconductor light-emitting device of the present invention usually has a first conductive semiconductor layer, a light-emitting layer, and a second conductive semiconductor layer on a substrate, optionally through one or more layers such as a buffer layer and an intervening layer. The electrodes are sequentially stacked, and electrodes are respectively connected to the first and second conductive semiconductor layers. Examples of the semiconductor light emitting element include elements known in the art such as LEDs and laser diodes. Here, the first conductivity type semiconductor layer means n-type or p-type, and the second conductivity type semiconductor layer means a conductivity type different from that of the first conductivity type semiconductor layer. In this specification, the first conductivity type semiconductor layer may be referred to as n-type and the second conductivity type semiconductor layer may be referred to as p-type.

The semiconductor layers in the first and second conductivity type semiconductor layers and the light emitting layer are not particularly limited, and include elemental semiconductors such as silicon and germanium, III-V group, II-VI group, VI-VI group, etc. A compound semiconductor etc. are mentioned. A nitride semiconductor, in particular, a gallium nitride compound semiconductor such as In _X Al _Y Ga _1-XY N (0 ≦ X, 0 ≦ Y, X + Y ≦ 1) is preferably used.
Each of the semiconductor layer and the light emitting layer may have a single layer structure, but may have a stacked structure of layers having different compositions and film thicknesses, a superlattice structure, or the like. In particular, the light emitting layer preferably has a single quantum well or multiple quantum well structure in which thin films that produce quantum effects are stacked. In general, the semiconductor layer and the light emitting layer may be configured as a homostructure, a heterostructure, a double heterostructure, or the like having a MIS junction, a PIN junction, or a PN junction. The semiconductor layer and the light emitting layer can be formed by a known technique such as MOVPE, metal organic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), or molecular beam epitaxy (MBE). Moreover, the film thickness of a semiconductor layer and a light emitting layer is not specifically limited, The thing of various film thickness is applicable.

As a substrate for forming the semiconductor light emitting device of the present invention, for example, a known insulating substrate or conductive substrate such as sapphire, spinel, SiC, nitride semiconductor (for example, GaN), GaAs or the like can be used. Of these, an insulating substrate is preferable.
When the insulating substrate is not finally removed, both the p electrode and the n electrode are usually formed on the same surface side of the semiconductor layer. In this case, it may be used for either face-up mounting (that is, the semiconductor layer side is the main light extraction surface) or flip chip mounting (face-down mounting, that is, the substrate side opposite to the electrode is the main light extraction surface). It is appropriate to use face-up mounting. A metallized layer (bump: Ag, Au, Sn, In, Bi, Cu, Zn, etc.) for connection to an external electrode or the like is formed on the p electrode and the n electrode, respectively, and this metallized layer is formed on the submount. Are connected to a pair of positive and negative external electrodes provided on the substrate, and wires and the like are further wired to the submount.
When the insulating substrate is finally removed or the conductive substrate is used, as described above, both the p electrode and the n electrode may be formed on the same surface side of the semiconductor layer, or different surfaces. May be formed respectively.

  The electrode formed on the second conductive type semiconductor layer of the present invention is formed, for example, on the second conductive type semiconductor layer via a contact layer, and serves as an ohmic electrode, for example, a lower conductive oxide film, As a pad electrode, an upper conductive oxide film and a metal film are laminated in this order.

The contact layer is used to make a good contact with the electrode electrically connected to the second conductivity type semiconductor layer, and is usually formed of a layer having a lower resistance than the second conductivity type semiconductor layer. The As described above, the contact layer is formed, for example, by appropriately selecting from the materials exemplified for the second conductivity type semiconductor layer. The contact layer may have a function as a clad layer or other layers. In the contact layer, a second conductivity type, for example, a p-type dopant may be diffused to reduce the resistance. The dopant is not particularly limited, and it is appropriate to use an element exhibiting p-type conductivity depending on the material of the contact layer. For example, the contact layer is a nitride semiconductor, i.e., GaN, AlN, InN or mixed crystals of these _{(e.g., In x Al y Ga 1-} xy N, 0 ≦ x, 0 ≦ y, x + y ≦ 1) when it is like Examples of the p-type impurity include Mg, Zn, Cd, Be, Ca, Ba, and the like. Among these, Mg is preferable. The doping concentration is, for example, about 1 × 10 ¹⁸ cm ⁻³ or more, preferably about 1.5 × 10 ²⁰ to 1 × 10 ²² cm ⁻³ . Impurity doping may be performed simultaneously with film formation, or may be performed by vapor phase diffusion, solid phase diffusion, ion implantation, or the like after film formation, or diffused from an adjacent p-type semiconductor layer. But you can.

The upper and lower conductive oxide films are made of an oxide containing at least one element selected from the group consisting of zinc, indium, tin and magnesium. Specific examples include ZnO, In ₂ O ₃ , SnO ₂ , ITO (a composite oxide of In and Sn), MgO, and the like. Of these, an ITO film is preferable. Note that the upper and lower conductive oxide films may be films made of different materials, but are preferably films made of the same material.

The film thickness of the lower conductive oxide film is not particularly limited as long as the transparency is ensured, but for example, the formula (1)
A ・ λ / 4n ₁ ± X (1)
(In the formula, A is an odd number, λ is the wavelength of light (Å) generated from the light emitting layer, n ₁ is the refractive index of the lower conductive oxide film, and X is a film of 0 to 20% of the optical thin film (λ / 4n)) Thick (Å).)
The thing represented by these is preferable. As a result, the lower conductive oxide film minimizes reflection on the surface of the lower conductive oxide film (interface between the conductive oxide film and air) with respect to light from the light emitting layer, and transmits the light. Can be maximized. As a result, the light extraction efficiency can be improved.

Since the lower conductive oxide film transmits light from the light emitting layer to the maximum extent, it is preferable that the lower conductive oxide film has a thickness that is an odd multiple of the optical thin film represented by λ / 4n. That is, a film thickness such that X is zero is preferable. However, since light enters from the light emitting layer into the lower conductive oxide film at random from the direction of 180 °, a film thickness variation of about ± X is allowed in consideration of them. As the film thickness variation, that is, variation, X is, for example, 0 of λ / 4n ₁ .
About 20% is mentioned.

The film thickness of the upper conductive oxide film is, for example, the formula (2)
B ・ λ / 4n ₂ + α / 2 (2)
(In the formula, B is an even number, n ₂ is the refractive index of the upper conductive oxide film, α is the phase shift distance (Å), and λ is as defined above.)
The thing represented by these is preferable. As a result, the upper conductive oxide film maximizes the transmission of the upper and lower conductive oxide films with respect to the light from the light emitting layer, and at the interface between the upper conductive oxide film and the metal film. The reflection can be maximized and the light extraction efficiency can be improved. In equation (2), α may be zero or any value from zero to the phase shift distance, but is preferably substantially equal to the value of the phase shift distance. The phase shift distance is usually such that the phase of light reflected at the interface between the upper conductive oxide film and the metal film is delayed with respect to the phase of light incident on this interface. Therefore, α is normally a value of zero or less. Thereby, the reflection at the interface between the upper conductive oxide film and the metal film can be maximized.

Here, the phase shift distance α is calculated by the following equation (3).
α = λ · θ / 2π (3)
(In the formula, λ is the wavelength (Å) of light generated from the light emitting layer, and θ is the phase shift angle (rad).)
Note that the phase shift takes into account the reflection (reciprocation) of light on the metal film, and ½ of the phase shift distance is increased or decreased from the film thickness of the upper conductive oxide film.
The phase shift angle θ is usually determined by the refractive index of the conductive oxide film and the complex refractive index of the metal film. For example, it is calculated by the following equation (4) according to Section 3.5 Reflection and Optical Constants (published by Katsuaki Sato and Asakura Shoten) of “Revised Light and Magnetics”.

（式中、ｎ₀は酸化物膜の屈折率、ｎは金属膜の屈折率、ｋは金属膜の減衰係数である。）

(Where n ₀ is the refractive index of the oxide film, n is the refractive index of the metal film, and k is the attenuation coefficient of the metal film.)

  Specifically, although it varies depending on the type of metal film formed on the upper conductive oxide film, when the metal film is platinum, the refractive index n is 1.87 and the attenuation coefficient k is 3.20. For this reason, the phase difference is -0.95 (rad), the phase shift distance (optical path difference) is -336 mm, and therefore α / 2 is calculated to be about -168 mm. Similarly, in the case of Rh, the refractive index n = 1.73, the attenuation coefficient k = 4.50, the phase difference is −0.77 (rad), and the phase shift distance is −275 mm, so α / 2 is In the case of W, the refractive index n = 3.31, the attenuation coefficient k = 2.55, the phase difference is −0.67 (rad), the phase shift distance is −239 mm, and α / 2 is about −119 mm. In the case of Ag, the refractive index n = 0.14, the attenuation coefficient k = 2.56, the phase difference is −1.35 (rad), and the phase shift distance is −481 mm. α / 2 is about −240 mm.

  Thus, by considering the phase shift distance in the film thickness of the upper conductive oxide film, reflection occurring at the interface between the upper conductive oxide film and the metal film can be set to a high state. Moreover, by setting the interface between the upper conductive oxide film and the metal film at or near the maximum point in the light wave, it is possible to minimize the variation in phase shift due to the reflection of light from the light emitting layer. And the light extraction efficiency can be further improved.

The upper and lower conductive oxide films constituting the electrode are not only visible light, but also, for example, light generated from the above-described gallium nitride compound semiconductor light emitting layer, that is, a wavelength of about 360 nm to 650 nm, preferably 380 nm to 560 nm or 400 nm. It is preferable that the light can be efficiently transmitted without absorbing light having a wavelength of ˜600 nm, for example, at a transmittance of 90% or higher, 85% or higher, or 80% or higher. Thereby, it can utilize as an electrode of the semiconductor light emitting element of the intended wavelength. Furthermore, it is preferable that the upper and lower conductive oxide films have, for example, a specific resistance of 1 × 10 ⁻⁴ Ωcm or less, and further about 1 × 10 ⁻⁴ to 1 × 10 ⁻⁶ Ωcm. Thereby, it can utilize effectively as an electrode.

The upper and lower conductive oxide films can be formed by a method known in the art. For example, sputtering method, reactive sputtering method, vacuum deposition method, ion beam assisted deposition method, ion plating method, laser ablation method, CVD method, spray method, spin coating method, dipping method or a combination of these methods and heat treatment Various methods can be used.
Of the upper and lower conductive oxide films, the lower conductive oxide film preferably has a lower density than, for example, the surface side and further the upper conductive oxide film at the interface with the p-side contact layer. In other words, it is preferable to be in a porous state in the vicinity of the interface with the second conductivity type semiconductor layer. Examples of the porous state include a state where a plurality of pores having a diameter of about 20 to 200 nm are present uniformly or non-uniformly. Examples of the density include about 90 to 30% of the surface side and / or the upper conductive oxide film. The state of such a lower conductive oxide film is, for example, a method of observing a cross section by transmission electron microscopy (TEM), a method of observing by scanning electron microscopy (SEM), a method of measuring an electron diffraction pattern, It can be measured by a method of observing with an ultra-thin film evaluation apparatus.

  In this case, the surface side of the lower conductive oxide film and the upper conductive oxide film are transparent films having good crystallinity. On the other hand, the second conductive semiconductor layer side of the lower conductive oxide film may have a partially amorphous region, but it is not a completely amorphous state but is a transparent film or a substantially transparent film. It is preferable that it is formed as.

  The low-density region in the lower conductive oxide film exists, for example, from 10 to 100%, preferably 10 to 50% of the total thickness of the lower conductive oxide film from the interface with the p-side contact layer. Is appropriate. In this way, the lower conductive oxide film has lower interface density with the second conductive semiconductor layer than the surface and upper conductive oxide film, thereby ensuring ohmic contact with the p-side contact layer. However, the translucency can be improved.

  As a method of forming a lower conductive oxide film having a different density or an upper and lower conductive oxide film having different densities, for example, a lower conductive oxide film or an upper conductive oxide film by a sputtering method, for example, When forming a two-layer ITO film, a method of switching from a gas having a low or zero oxygen partial pressure to a gas having a large oxygen partial pressure or gradually increasing the oxygen partial pressure as a sputtering gas, a target for ITO film formation In addition to this, a method using a target with a large amount of In or a target with a small amount of oxygen and switching to a target with a large amount of In or a target with a small amount of oxygen in the middle, and increasing the input power of the sputtering apparatus gradually or rapidly can be achieved. Examples include a film forming method. In addition, when forming the upper and lower conductive oxide films by vacuum deposition, a method of rapidly or gradually increasing or decreasing the temperature of the semiconductor layer, a method of rapidly decreasing the deposition rate, oxygen using an ion gun The method etc. which irradiate ion from the middle of film-forming are mentioned.

  Furthermore, when the lower conductive oxide film or upper and lower conductive oxide films are formed by the ion plating method, oxygen gas is turned into plasma from the middle of the film formation, and this oxygen plasma is taken into the ITO film. In a film forming method, ITO fine particles of ITO are dissolved or dispersed in a solvent, suspended, and formed into a film by a spray method, a spin coating method, a dipping method, or the like. Control the flow rate of oxygen gas or raw material oxygen-containing gas when using two types of solutions with varying amounts, or controlling the atmosphere, temperature, etc. during drying or firing, or when forming an ITO film by CVD The method of doing is mentioned.

  In addition, after forming the lower conductive oxide film or the upper conductive oxide film, for example, reducing gas (specifically, carbon monoxide, hydrogen, argon, etc., or a mixed gas of two or more of these) Examples of the method include annealing at a temperature of about 200 to 650 ° C. for a predetermined time according to the film thickness. Further, a multi-stage heat treatment may be used, such as forming a lower conductive oxide film halfway, then heat-treating, and subsequently forming and heat-treating. Examples of the heat treatment method include a lamp annealing process and an annealing process using a heating furnace. Further, as the processing after forming the ITO film, electron beam irradiation or laser ablation may be used. Furthermore, these methods may be arbitrarily combined.

  The lower conductive oxide film described above is normally formed as a full-surface electrode that covers substantially the entire surface of the second conductive semiconductor layer, but it is difficult to obtain ohmic properties on the p-side contact layer made of the p-type semiconductor layer. There is a case. However, as described above, a good ohmic property with the p-type semiconductor layer and / or the p-side contact layer can be obtained by using a conductive oxide film having a low density on the semiconductor layer side. The lower conductive oxide film is preferably formed uniformly on substantially the entire surface of the second conductivity type semiconductor layer, but may have, for example, a dot-like or stripe-like opening. These openings may be regularly distributed or randomly distributed.

  The upper conductive oxide film is formed on the lower conductive oxide film. Only a part of the upper conductive oxide film may be arranged on the lower conductive oxide film and a part may be directly arranged on the p-type semiconductor layer, but the whole is on the lower conductive oxide film. It is appropriate that the second conductive type semiconductor layer is not directly in contact with the second conductive type semiconductor layer. The upper conductive oxide film may be formed so as to cover almost all of the lower conductive oxide film, but the upper conductive oxide film is disposed so that a part of the surface of the lower conductive oxide film is exposed. Is preferred. That is, it is preferable that the upper conductive oxide film is disposed only in a region where a metal film described later is disposed on the lower conductive oxide film. The shape of the upper conductive oxide film is not particularly limited, and can be, for example, a polygon such as a circle, a triangle, or a rectangle, or an indeterminate shape. The size is not particularly limited, and it is appropriate that the metal film described later can be connected to the upper conductive oxide film or the lower conductive oxide film through the upper conductive oxide film. Especially, it is preferable that it is the same shape and magnitude | size as the metal film mentioned later.

  The metal film constituting the electrode connected to the second conductivity type semiconductor layer can function as an electrode bonded by soldering or wire bonding. The kind and form of the metal film are not particularly limited, and any metal film can be used as long as it is normally used as an electrode. For example, zinc (Zn), nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), osmium (Os), iridium (Ir), titanium (Ti), zirconium (Zr) ), Hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), cobalt (Co), iron (Fe), manganese (Mn), molybdenum (Mo), chromium (Cr), tungsten (W ), Lanthanum (La), copper (Cu), silver (Ag), gold (Au), yttrium (Y), and other metals, alloy single layer films or laminated films. Among them, those having low resistance are preferable, and specific examples include single layer films or laminated films of W, Rh, Ag, Pt, Pd, Al, and the like. Further, an upper conductive oxide film, for example, a film having good adhesion to an ITO film, specifically, a single layer film or a laminated film of W, Rh, and Pt is preferable. Moreover, the thing with favorable reflective characteristics, specifically, the single layer film or laminated film of Ag and Rh is preferable.

  As the metal film, for example, Rh (or Al) / Pt / Au electrode in which each of Rh or Al, Pt, and Au is sequentially laminated from the semiconductor layer side by sputtering (the film thickness is, for example, 100 nm / 200 nm, respectively) Pt / Au electrode in which each of Pt and Au is sequentially laminated by sputtering (its film thickness is, for example, 20 nm / 700 nm, respectively). By using Au as the uppermost layer of the metal film, it is possible to ensure good connection with a conductive wire or the like mainly composed of Au. Further, by stacking Pt between Rh and Au, diffusion of Au or Rh can be prevented, and highly reliable electrical connection as an electrode can be obtained. Furthermore, Rh is excellent in light reflectivity and barrier property, and can be suitably used because light extraction efficiency is improved. Of these, a laminated film of Pt / Au (in the case of face-up) is preferable.

  The metal film is formed only on the upper conductive oxide film. That is, the entire metal film is placed on the upper conductive oxide film and is formed so as not to directly contact the lower conductive oxide film. The shape of the metal film is not particularly limited, and can be, for example, a polygon such as a circle, a triangle, or a rectangle, or an indefinite shape corresponding to the shape of the upper conductive oxide film. The size is not particularly limited, but it is necessary that the size be such that current can be efficiently applied to the upper and lower conductive oxide films, and thus the second conductive semiconductor layer, The size of the light emitting layer needs to be small enough to absorb light emitted from the light emitting layer and be efficiently extracted. Specifically, it is appropriate that the size has an area of about 30 to 70% with respect to the area of the light emitting surface.

  For example, the metal film can have a shape having an extended conductive portion as shown in FIGS. Thereby, current can be efficiently injected into the entire light emitting layer, and light can be emitted efficiently. This is particularly effective when the semiconductor light emitting device of the present invention is mounted face up.

  Specifically, as shown in FIG. 2, the p-electrode connected to the p-type semiconductor layer 52 includes a lower conductive oxide film 54 formed on almost the entire surface of the p-side contact layer 52 and an n-electrode 53. It is composed of an upper conductive oxide film (not shown) formed at a position adjacent to the side facing the adjacent side, and a metal film 55 formed in substantially the same shape as this. The upper conductive oxide film and the metal film 55 extend outward from both sides of the upper conductive oxide film and the metal film 55 as two linear extended conductive portions 56. Thereby, the light emitting layer located between the metal film 55 and the n electrode 53 can emit light efficiently. Furthermore, since the extended conductive portion 56 extending from the metal film 55 is electrically well connected to the lower conductive oxide film 54, current is effectively diffused throughout the p-type semiconductor layer, and the entire light emitting layer Can be made to emit light efficiently. In addition, light emission with high luminance can be obtained at the periphery of the metal film 55 and the extended conductive portion 56.

  The extended conductive portion 56 is preferably spaced from the edge of the p layer so as to ensure the peripheral portion from which light emission with high luminance described above can be obtained. . When the sheet resistance RnΩ / □ of the n-side contact layer 51 and the sheet resistance RpΩ / □ of the lower conductive oxide film 54 satisfy the relationship of Rp ≧ Rn, the extension conductive portion 56 and the edge of the p layer Is preferably about 20 to 50 μm. This is because if the interval is smaller than 20 μm, a sufficient peripheral region where light emission with high luminance can be obtained cannot be secured (the region where light emission with high luminance should be obtained protrudes outside). A portion having a low emission luminance is formed along the line, resulting in a decrease in luminance as a whole.

The two extended conductive portions 56 may be formed in a straight line shape, or may be formed in an arc shape so as to be equidistant from the n electrode 53 as shown in FIG. In particular, it is preferable to form in an arc shape because a more uniform light emission distribution can be obtained.
Further, an n-electrode 53 connected to an n-type semiconductor layer described later is formed so as to be close to at least one side of the semiconductor light emitting element. For example, in the central portion of one side, a p-type semiconductor layer and a part of the light emitting layer are removed by etching to provide a notch 51a in which the n-side contact layer 51 is exposed, and is formed in the notch 51a. . The n-electrode 53 is configured by forming a metal film having the same shape on a conductive oxide film (not shown).

Further, as shown in FIGS. 3 and 4, an n-electrode 63 to be described later is provided at one corner of the semiconductor light emitting element so as to be close to two sides, and an upper conductive oxide film constituting a p-electrode. The metal film 65 (not shown) and the metal film 65 are preferably provided at other corners that are diagonally opposite to the corners where the n-electrode 63 is adjacent.
In addition, the two extended conductive portions 66 extending from the metal film 65 are preferably formed in an arc shape so as to be equidistant from the n electrode 63. Thereby, higher luminance and uniform light emission can be obtained. In this case, the distance between the extended conductive portion 66 and the edge of the p layer is preferably about 20 to 50 μm.

In the semiconductor light emitting device of the present invention, usually, in the partial region of the semiconductor light emitting device, the second conductivity type semiconductor layer and the light emitting layer, and optionally the depth direction of the first conductivity type semiconductor layer are removed. The surface of the first conductivity type semiconductor layer is exposed. An electrode is formed on the exposed surface of the first conductivity type semiconductor layer (hereinafter referred to as “second region”). For example, this electrode is formed on the first conductive type semiconductor layer via the first conductive type contact layer, and is configured by laminating a conductive oxide film and a metal film in this order.
The electrode connected to the first conductivity type semiconductor layer may be formed on the back surface side of the first conductivity type semiconductor layer via the first conductivity type contact layer or the like. In particular, when the semiconductor light emitting element is formed on a conductive substrate, the conductive substrate and the first conductive type semiconductor layer are usually electrically connected. Are electrically connected to the first conductive type semiconductor layer via a conductive substrate or the like.

As the first conductive type semiconductor layer and the first conductive type contact layer, those exemplified as the second conductive type semiconductor layer can be applied except that the conductive types are different.
Here, the second region refers to a second layer in which an upper and lower conductive oxide film and a metal film are formed in a stacked structure of first and second conductivity type semiconductor layers constituting one semiconductor light emitting element. It means a region other than the surface region (first region) of the conductive semiconductor layer.

  In the present invention, since it is necessary to provide a conductive oxide film in a region where light propagating from the light emitting layer is likely to hit directly, the upper and lower conductive oxide films are formed on at least the second conductivity type semiconductor layer. If it is, the conductive oxide film is not necessarily provided on the first conductive type semiconductor layer, and a form in which only the metal film is formed is allowed, but it is allowed to be connected to the first conductive type semiconductor layer. The electrode is preferably composed of a conductive oxide film and a metal film.

Examples of the conductive oxide film are the same as the upper and lower conductive oxide films described above. This conductive oxide film may be a single layer or a laminated film of two or more layers. However, the lower conductive oxide film is not necessarily the same as the upper conductive oxide film or the upper conductive oxide film. By forming this conductive oxide film on the first conductive type semiconductor layer, it is possible to improve the adhesion between the first conductive semiconductor layer and the conductive oxide film and obtain an ohmic contact. it can. In particular, when the electrode is composed of a lower conductive oxide film, an upper conductive oxide film, and a metal film, the light transmittance is improved and reflection at the interface between the upper conductive oxide film and the metal film is improved. The efficiency of is also improved.
Further, examples of the metal film include the same metal films as described above. The metal film formed on the first conductivity type semiconductor layer is not necessarily the same as the metal film formed on the second conductivity type semiconductor film.

  The conductive oxide film and / or metal film formed on the first conductivity type semiconductor layer is the same type as the upper oxide film and / or metal film formed on the second conductivity type semiconductor layer. The film thickness is preferably the same. Furthermore, it is preferable that these are formed in the same process. If they are formed with the same laminated structure, they can be formed in the same manufacturing process, so that the manufacturing process is simplified, and as a result, an inexpensive and highly reliable semiconductor light emitting device can be obtained.

In the semiconductor light emitting device of the present invention, as described above, a plurality of irregularities may be formed on a part of the surface of the second region, which is the exposed surface of the first conductivity type semiconductor layer (for example, (See FIG. 5). The unevenness may be formed immediately below the electrode, but is suitably formed in a region other than the region where the electrode is disposed in the second region.
Specifically, it is preferably formed in the outer peripheral region of the light emitting element (the peripheral region of the first region) and / or the peripheral region of the electrode. In particular, as shown in FIG. 5, the periphery of the n-electrode 19 emits relatively strong light. Therefore, by providing a convex portion between the n-electrode 19 and the lower conductive oxide layer 5, the light extraction effect can be improved. Further improvement can be achieved. In addition, for example, a plurality of convex portions are provided at high density in a region with relatively strong light emission such as the n electrode and the vicinity of the first region, and a plurality of convex portions are provided at low density in a region with relatively low light emission in a different region. It may be provided. Considering the intensity of the light emitting region, changing the density of the plurality of convex portions enables more effective light extraction and directivity control.

The height of the convex part top part of an unevenness | corrugation should just be a grade which protrudes from the surface which forms an electrode at least. Thereby, the light extraction effect is improved.
For example, the top of the convex portion only needs to be higher than the interface between the light emitting layer and the n-type semiconductor layer adjacent to the light emitting layer, and the top portion is located on the second conductive semiconductor layer side of the light emitting layer, or the p-type semiconductor layer More preferably, they are substantially the same height (see FIG. 6). As a result, the surface area of the side surface of the convex portion increases, so that the light guided through the n-type semiconductor layer easily hits the side surface of the convex portion and less light is totally reflected inside the convex portion. In addition, the light emitted from the light emitting layer in the side surface direction is directly reflected by the convex portion and changes the traveling direction to the light emission observation surface side, so that the light extraction efficiency to the light emission observation surface side is, for example, 10 to 20%. Can be improved. The reason for this is not clear, but (1) the light guided in the n-type semiconductor layer (for example, the n-side contact layer) is taken into the convex portion from the n-side contact layer, and the top of the convex portion or its Light is extracted from the middle part to the observation surface side, (2) Light emitted from the end surface of the light emitting layer to the outside of the side surface is reflected and scattered by a plurality of convex portions and extracted to the observation surface side, and (3) n-side contact This is because the light guided in the layer is irregularly reflected at the root of the convex portion (the connection portion between the n-side contact layer and the convex portion), and the light is extracted to the observation surface side.

Alternatively, it is more preferable that the convex portion is substantially the same height as the lower conductive oxide film (see FIG. 7). In this case, usually, the top of the convex portion is composed of a lower conductive oxide film. As described above, when the convex top is formed of the lower conductive oxide film having a thickness that allows light to easily pass through, it becomes easy to extract the light taken into the convex from the convex top.
The convex portion may be substantially the same height as the upper conductive oxide film.

In addition, it is preferable that the lower layer conductive oxide film at the top of the convex portion has a plurality of voids or has a lower density than the surface side of the lower layer conductive oxide film in the vicinity of the interface with the p-type semiconductor layer. Thereby, the light which progresses toward a top part inside a convex part can be scattered.
Alternatively, the convex portion may be substantially the same height as the metal film (see FIG. 8). Since the top of the convex portion is formed of a metal film, the light taken into the convex portion from the n-type semiconductor layer is reflected at the interface between the metal film on the top of the convex portion and the semiconductor layer and travels to the substrate side. It is preferable when the substrate side is the main light extraction surface.
The bottom of the concave portion between the convex portions may be at least lower than the interface between the light emitting layer and the second semiconductor layer adjacent thereto, and is preferably formed to be lower than the light emitting layer.

The density of the unevenness is not particularly limited, and in one semiconductor light emitting element, it can be at least 100, more preferably 300, more preferably 500. Note that a ratio of an area occupied by a region where unevenness is formed when viewed from the electrode forming surface side can be 10% or more, preferably 30% or more. Moreover, the area of one convex part can be 3-300 micrometers ^{2 by} the root of a convex part.

  The convex section may have any shape such as a triangle, a quadrangle, a trapezoid, or a semicircle, and the planar shape may be any shape, such as a circle, a rhombus, a triangle, or a hexagon. May be. In particular, it is preferable that the convex portion itself has a truncated cone shape that gradually becomes thinner. In this case, the inclination angle of the convex portion is, for example, 30 ° to 80 °, and preferably 40 ° to 70 °, as shown in FIG. Thereby, the directivity control of light becomes easier, and more uniform light extraction as a whole becomes possible. Moreover, since the surface area of a convex part increases, it is thought that light extraction efficiency improves. Furthermore, since the surface area of the top part of the convex part, that is, the top part becomes narrow by gradually narrowing the convex part, the fact that the light totally reflected by the convex part top part also contributes to the improvement of light extraction. Conceivable.

The irregularities may be subjected to a special process for forming the irregularities by growing the semiconductor layer on the exposed n-type semiconductor layer, or divided into the steps for exposing the n-type semiconductor layer or each chip. In order to achieve this, it is preferable to use a step of thinning a predetermined region.
Specifically, a mask having an opening of a predetermined shape such as a circle, a triangle, or a rectangle is formed on the exposed surface of the n-type semiconductor layer, and RIE (reactive ion etching) is performed using this mask. A recess can be formed. Alternatively, a mask covering a predetermined shape may be formed, and the convex portion may be formed using this mask.
The convex portion is a mask that covers a portion where the light emitting layer that functions as a light emitting element remains after laminating the p-type semiconductor layer, a portion where the electrode on the surface of the n-type semiconductor layer is disposed, and a portion where the convex portion is disposed. It can form by etching using. As a result, the process can be simplified.

  In the semiconductor light emitting device of the present invention, irregularities may be provided on at least a part of the interface between the substrate and the semiconductor layer. As a result, light traveling in the lateral direction in the semiconductor layer can be scattered or diffracted by the concavo-convex portion to change the traveling direction in the vertical direction, so that the surface of the lower conductive oxide film and the metal film and the upper conductive layer Light totally reflected at the interface with the oxide film can be reduced. Here, the unevenness at the interface between the substrate and the semiconductor layer means that the surface of the insulating or conductive substrate itself, such as a buffer layer or an intervening layer when the buffer layer or the intervening layer is formed on the substrate, Concavities and convexities are formed on the surface, which means concavities and convexities resulting from the concavities and convexities.

  In the case of a semiconductor light emitting device having a flat substrate, as shown in FIG. 9A, when light from the light emitting region 3 enters the interface between the p-type semiconductor layer 4 and the electrode or the surface of the substrate 1 at a critical angle or more. , Trapped in the waveguide and propagate in the lateral direction. On the other hand, as shown in FIG. 9B, when the substrate has irregularities, light having a critical angle or more with respect to the interface between the p-type semiconductor layer 4 and the electrode or the surface of the substrate 1 is projected. The light is scattered or diffracted by 122 and enters the interface between the p-type semiconductor layer 4 and the electrode or the surface of the substrate 1 at an angle smaller than the critical angle.

  For example, as shown in FIG. 10, the irregularities are formed by using a C-plane (0001) sapphire substrate having an orientation flat on the A-plane (11-20) as a substrate and forming a repetitive pattern on the surface portion of the sapphire substrate. It can be set as the convex part 122 (or recessed part) made. Further, the concave portion 123 or the convex portion 122 has various shapes such as a dot shape (see FIG. 11A), a lattice shape, a stripe shape, a honeycomb shape, a deformed shape such as a honeycomb or a lattice (see FIG. 11B), and the like. It can be a shape.

  Further, as shown in FIG. 12A, the unevenness may be such that the side surface of the convex portion 122 is inclined or may be hemispherical as shown in FIG. 12B. Further, as shown in FIG. 12C, the n-type semiconductor layer 2, the light emitting region 3, and the p-type semiconductor layer 4 may be uneven due to the influence of the protrusion 122. Thereby, as shown in FIGS. 9C and 9D, light can be extracted efficiently.

  In particular, as shown in FIG. 12 (a), a surface (= concave portion or continuous surface) that is continuous with the surface of the convex portion and the surface of the concave portion with a straight line intersecting with a plane substantially parallel to the growth stable surface of the semiconductor layer as a boundary. By forming the side surface of the convex portion inclining with respect to the stacking direction of the semiconductor, the effect of light scattering or diffraction is remarkably increased, and the light extraction efficiency is remarkably improved. One reason for this is that the number of times that light scattering or diffraction occurs increases by increasing the surface area of the surface (= the side surface of the recess or protrusion) that is continuous with the surface of the recess and the surface of the protrusion. Conceivable. In other words, as shown in FIG. 12 (a), the cross-sectional shape of the irregularities is preferably a trapezoid if it is a convex part, and an inverted trapezoid if it is a concave part. By setting it as such a cross-sectional shape, the probability that the propagating light will be scattered and diffracted increases, and the absorption loss during the propagation of the light can be reduced.

  Such unevenness faces at least the region where the metal film 7 and the upper conductive oxide film 6 are disposed, as viewed from below the metal film 7, that is, from the electrode forming surface side, as shown in FIG. By forming it at the interface between the substrate and the semiconductor layer, or by forming it on the entire surface of the substrate as shown in FIG. Therefore, the light incident on the interface between the metal film 7 and the upper ITO film 6 can be increased, and the light extraction efficiency is improved.

  The depth of the concave portion or the level difference of the convex portion is 50 angstroms or more from the viewpoint of obtaining sufficient light scattering or diffraction and improving the luminous efficiency without affecting the lateral flow of current in the laminated structure. And it is preferable that it is below the thickness of the semiconductor layer grown on a board | substrate. The depth of the concave portion or the step of the convex portion is preferably a depth or step of λ / 4 or more in order to sufficiently scatter or diffract light (λ = emission wavelength, for example, an AlGaInN-based light emitting layer) In this case, the effect of scattering or diffraction can be obtained if the depth or step is 206 nm to 632 nm) or more than λ / 4n (n is the refractive index of the semiconductor layer).

In addition, the size of the concave portion and / or the convex portion (that is, the length of one side serving as the constituent side of the concave portion and / or the convex portion) and the interval between them are set to λ (380 nm to 460 nm) as the emission wavelength in the semiconductor layer. In some cases, the size is preferably at least λ / 4. Thereby, light can be sufficiently scattered or diffracted. However, if there is a size equal to or larger than λ / 4n (n is the refractive index of the semiconductor layer) and the mutual distance, the effect of scattering or diffraction can be obtained.
Note that the semiconductor light-emitting element of the present invention can extract light more effectively by combining both the plurality of unevenness formed in the second region and the unevenness formed at the interface between the substrate and the semiconductor layer. it can.

  In the semiconductor light emitting device of the present invention, the exposed surface of the lower conductive oxide film provided on at least the second conductive type semiconductor layer on the surface of the semiconductor light emitting device may be coated with a resin. For example, when the conductive oxide film is ITO, the refractive index of ITO is approximately 2.0, whereas the refractive index of air is 1.0. By providing a resin such as silicon (refractive index: 1.4 to 1.6) having a refractive index of at least on the exposed surface of the lower conductive oxide film, the resin becomes a buffer material, and the conductive oxide Since less light is reflected at the interface between the film and air, the light can be extracted to the outside more efficiently. When a semiconductor light emitting device is actually used, generally, for example, in order to protect the semiconductor light emitting device from the outside, its periphery is sealed with a sealing resin made of an organic resin such as a silicon resin or an epoxy resin. The Moreover, it is good also as a light conversion layer by making resin contain a light conversion member.

  In the semiconductor light emitting device of the present invention, as shown in FIGS. 16 and 17, the p-side pad electrode 155b made of the upper conductive oxide film and the metal film thereon is branched from the n electrode in a predetermined direction. It may extend in the shape and may be arranged so as to face each other (see 153a and 155a in FIGS. 16 and 17). Hereinafter, the p-side pad electrode 155b may be referred to as a current diffusion electrode, and the n electrode may be referred to as an n line electrode.

The semiconductor light emitting device shown in FIGS. 16 and 17 is configured by laminating an n-type semiconductor layer 2, a light emitting layer 3, and a p-type semiconductor layer 4 made of a nitride semiconductor in this order on a substrate 1. The n-type semiconductor layer 2 has an exposed portion on a part of its surface, and a plurality of n-line electrodes 153 separated from each other are formed in the exposed portion.
That is, in the stacked body including the n-type semiconductor layer 2, the light-emitting layer 3, and the p-type semiconductor layer 4, a part of the p-type semiconductor layer 4 and the light-emitting layer 3 is removed in a line to form a plurality of slits SL. Then, the n-type semiconductor layer is exposed in a line shape, and the n-line electrodes 153 are formed on the n-type semiconductor layer exposed by the slit SL. Further, the n-type semiconductor layer is exposed to a predetermined width along one side parallel to the slit (one side of the light emitting element: hereinafter referred to as the first side), and there is also one n-line electrode there. 153 is formed. Note that the side facing the first side is referred to as the second side.

In this semiconductor light emitting device, the n-line electrode formation region and the plurality of slits SL on the surface where the n-type semiconductor layer is exposed are parallel to each other, and the interval between the n-line electrode formation region and the slit SL and the interval between adjacent slits SL. Are formed to be equal to each other.
Each n-line electrode 153 is provided at one end of an extended conductive portion (hereinafter referred to as an n-side extended conductive portion) 153a composed of a conductive oxide film and / or a metal film, and the n-side extended conductive portion 153a. The n-side pad electrode 153b is composed of a conductive oxide film and / or a metal film. The n-side pad electrode 153b provided at one end of each n-side extended conductive portion is formed along one side (third side) perpendicular to the first side.
In addition, the n-side extended conductive portion 153a is widely formed at one end thereof to form the n-side pad electrode 153b, and the n-side pad electrode 153b is formed thereon.

  The p-electrode has a light-transmitting lower conductive oxide film 5 formed on almost the entire surface of the p-type semiconductor layer, and a plurality of current diffusion electrodes 155 formed on the lower conductive oxide film 5. Consists of. The current spreading electrode 155 includes a plurality of extended conductive portions (hereinafter referred to as p-side extended conductive portions) 155a formed in parallel with the n-side extended conductive portion 153a and a p-side pad provided at one end of the p-side extended conductive portion 155a. And the electrode 155b. The p-side extended conductive portion 155a and the p-side pad electrode 155b are composed of an upper conductive oxide film and a metal film formed in substantially the same shape as this. The interval between the p-side extended conductive portion 155a and the adjacent n-line electrode 153 is formed to be equal to each other, and one of the plurality of p-side extended conductive portions 155a is formed along the second side, Another p-side extended conductive portion 155 a is formed between the n-line electrodes 153. That is, when an n-line electrode is formed along one side (first side) of two opposing sides, the current diffusion electrode 155 is formed along the other side facing the one side. It is configured as follows. Further, each of the p-side pad electrodes 153b provided at one end of each p-side extended conductive portion 155a is along the fourth side facing the third side where the n-pad electrode 153b of the n-electrode is formed. It is formed.

  Such a semiconductor light emitting device improves the light emission efficiency by injecting a current into the entire light emitting region for the following reasons, and emits a nitride semiconductor having a relatively large area (for example, 1000 μm × 1000 μm). Even in the element, uniform light emission is possible over the entire light emitting surface.

First, a metal film 153b is formed on one end of each n-line electrode 153, and a metal film 155b is formed on one end of each p-side extended conductive portion 155a. As a result, the current can be injected almost uniformly into the entire light emitting region.
In this semiconductor light emitting device, the distance from the metal film 153b to the other end of the n-side extension conductive portion 153a can be made substantially equal between the different n-line electrodes 153, and the metal film between the different current diffusion electrodes 155. The distance between 155b and the other end of the p-side extended conductive portion 155a can be made substantially equal, and current can be uniformly injected into the entire light emitting region.
Here, the above-mentioned distances are substantially equal does not mean that the distances are completely the same, but those that do not cause current non-uniformity due to the difference in distances are substantially the same range. Shall be included.

Second, the distance between the adjacent n-line electrode 153 and the current diffusion electrode 155 on the p side is made equal so that current is uniformly injected into the entire light emitting region.
That is, the n-side extended conductive portion 153a and the p-side extended conductive portion 155a are formed in a straight line so that corners and curved portions are not formed in the middle, and electric field concentration and electric field non-conformity at the corners and curved portions are formed. Uniformity is prevented and current non-uniformity associated therewith is prevented.

Also, the other end of the p-side extended conductive portion 155a (the end located on the opposite side of the one end where the p-side pad electrode 155b is formed) and the n-side pad electrode 153b (the n-line electrode where the n-side pad electrode 153b is formed) 153 is set to be approximately equal to the distance between the p-side extended conductive portion 155a and the n-line electrode 153.
Further, the other end of the n-line electrode 153 (the end located on the opposite side of the one end where the n-side pad electrode 153b is formed) and the p-side pad electrode 155b (the p-side extended conductive portion where the p-side pad electrode 155b is formed). The distance between the p-side extended conductive portion 155a and the n-line electrode 153 is set to be approximately equal to the distance between the one end portion of 155a.
As a result, the distance between the current diffusion electrode 155 and the n-line electrode 153 can be made substantially equal in any part, so that current can be injected almost uniformly into the entire light emitting region, and uniform light emission can be achieved.

  Further, in this semiconductor light emitting device, as described above, the n-side contact is formed in the second region by forming a convex portion having the same height as the surface of the lower conductive oxide film on the first region. Light taken from the inside of the layer into the convex portion can be easily extracted from the top of the convex portion, and the light extraction efficiency from the electrode arrangement surface side can be further improved.

Furthermore, as shown in FIG. 18, the semiconductor light emitting device of the present invention may be formed so that the p-type semiconductor layer is divided by the exposed n-type semiconductor layer.
In this semiconductor light emitting device 10c, an n-electrode 73 is formed on the exposed n-type semiconductor layer, and a lower conductive oxide film 5 and a p-side pad electrode 21 are formed on the p-type semiconductor layer. ing. The lower conductive oxide film 5 has a stripe shape, and has a shape wider than the width of the exposed n-type semiconductor layer in the central portion of the semiconductor light emitting device. The number of stripe columns of the lower conductive oxide film 5 is larger than the number of columns of the n electrode 73 on the n-type semiconductor layer.

  Thus, the n-electrode 73 has a constricted shape, whereby the area area of the lower conductive oxide film 5 can be increased, and the amount of current input to the semiconductor light emitting element per unit time can be increased. it can. Furthermore, the light extraction efficiency of the semiconductor light-emitting element can be improved by reducing the area of the n-type semiconductor layer that does not contribute to light emission of the semiconductor light-emitting element and relatively increasing the area of the p-type semiconductor layer on the light-emitting surface. Therefore, this semiconductor light emitting device can achieve high luminance. Further, by providing the lower conductive oxide film 5 as described above, the current input to the semiconductor light emitting element can be uniformly diffused over the entire surface of the semiconductor light emitting element, and thus light emission from the light emitting surface of the semiconductor light emitting element. Can be made uniform.

  An upper conductive oxide film and a metal film are formed on the lower conductive oxide film. When such a semiconductor light emitting device is flip-chip mounted, the upper conductive oxide film and the metal film formed on the lower conductive oxide film reflect light directed from the light emitting layer toward the p-electrode side toward the substrate side. The amount of light extracted from the substrate side can be increased.

  In addition, in the semiconductor light emitting device as shown in FIG. 18, when a convex portion including the n-side contact layer to the metal film is formed on the surface of the n-side contact layer on which the n-electrode is formed, the convex portion is formed from within the n-side contact layer. Since the light taken in can be reflected to the substrate side, the light extraction effect from the substrate side can be further improved. Furthermore, when the film thickness of the lower conductive layer and the upper conductive oxide film of the convex portion is the same as the lower conductive film and the upper conductive oxide film on the light emitting region, the light extraction effect is further improved. .

  The laminated structure of the first conductive semiconductor layer, the light emitting layer, and the second conductive semiconductor layer constituting the semiconductor light emitting device of the present invention is specifically as shown in the following (1) to (5). The thing is mentioned.

(1) A buffer layer made of GaN having a thickness of 200 mm, an n-side contact layer made of Si-doped n-type GaN having a thickness of 4 μm, and a single quantum well structure made of undoped In _0.2 Ga _0.8 N having a thickness of 30 mm. A light-emitting layer, a p-type cladding layer made of Mg-doped p-type Al _0.1 Ga _0.9 N having a thickness of 0.2 μm, and a p-side contact layer made of Mg-doped p-type GaN having a thickness of 0.5 μm.

(2) A buffer layer made of AlGaN having a thickness of about 100 mm, an undoped GaN layer having a thickness of 1 μm, an n-side contact layer made of GaN containing 4.5 × 10 ¹⁸ / cm ³ of Si having a thickness of 5 μm, and 3000 μm undoped. An n-side first multilayer film composed of three layers: a lower layer made of GaN, a middle layer made of GaN containing 4.5 × 10 ¹⁸ / cm ^{3 of} 300 Ｓｉ Si, and an upper layer made of 50 Å undoped GaN (total film thickness) : 3350Å), a nitride semiconductor layer made of a nitride semiconductor layer made of undoped GaN from 40Å undoped an in _0.1 Ga _0.9 a nitride semiconductor layer made of N and the 20Å are stacked ten layers alternately repeated further undoped GaN Barrier made of n-side second multilayer film layer (total film thickness: 640 mm) having a superlattice structure formed with a thickness of 40 mm and an undoped GaN film with a thickness of 250 mm And the film thickness is laminated by six layers alternately repeated and a well layer made of In _0.3 Ga _0.7 N of 30 Å, further thickness light-emitting layer having the multiple quantum well structure barrier composed of undoped GaN of 250Å was formed (total Nitride semiconductor made of In _0.03 Ga _0.97 N containing 40 × and a nitride semiconductor layer made of Al _0.15 Ga _0.85 N containing 5 × 10 ¹⁹ / cm ³ Mg and 5 × 10 ¹⁹ / cm ³ A superlattice structure in which five layers of 25 Å layers are alternately laminated and a nitride semiconductor layer made of Al _0.15 Ga _0.85 N containing 5 × 10 ¹⁹ / cm ^{3 of} Mg is formed to a thickness of 40 さ ら に. A p-side contact layer made of GaN containing 1 × 10 ²⁰ / cm ³ of Mg with a p-side multilayer film layer (total film thickness: 365 mm) and a film thickness of 1200 mm.

(3) A buffer layer made of AlGaN having a thickness of about 100 Å, an undoped GaN layer having a thickness of 1 μm, an n-side contact layer made of GaN containing 4.5 × 10 ¹⁸ / cm ³ of Si having a thickness of 5 μm, An n-side first multilayer film composed of three layers: a lower layer made of undoped GaN, a middle layer made of GaN containing 4.5 × 10 ¹⁸ / cm ^{3 of} 300 ｃｍ Si, and an upper layer made of 50 Å undoped GaN (total film) A thickness of 3350 mm), 40 mm of nitride semiconductor layers made of undoped GaN, and 20 mm of nitride semiconductor layers made of undoped In _0.1 Ga _0.9 N were alternately stacked, and 10 layers of nitride semiconductor layers made of undoped GaN were further stacked. N-side second multilayer film layer (total film thickness) 640 mm) of superlattice structure formed with a film thickness of 40 mm, first undoped with a film thickness of 250 mm The first barrier layer and the thickness of the film thickness subsequently a barrier layer made of aN is the well layers and the film thickness made of In _0.3 Ga _0.7 N of 30Å consisting 100Å of In _0.02 Ga _0.98 N is made of undoped GaN of 150Å A light emitting layer having a multiple quantum well structure (total film thickness of 1930 mm) formed by alternately and alternately stacking 6 layers of the second barrier layer alternately (preferably in the range of 3 to 6 layers repeatedly stacked alternately), 40 を of nitride semiconductor layer made of Al _0.15 Ga _0.85 N containing 5 × 10 ¹⁹ / cm ^{3 of} Mg and 25 Å of nitride semiconductor layer made of In _0.03 Ga _0.97 N containing 5 × 10 ¹⁹ / cm ^{3 of} Mg are repeated. A p-side multilayer layer having a superlattice structure in which nitride semiconductor layers made of Al _0.15 Ga _0.85 N containing 5 × 10 ¹⁹ / cm ^{3 of} Mg and 5 × 10 ¹⁹ / cm ³ are stacked alternately and each having a thickness of 40 mm (total Film thickness 365mm), film thickness is P-side contact layer made of GaN containing Mg of ^{200Å 1 × 10 20 / cm 3} . Further, a lower layer made of 3000 ア ン undoped GaN provided on the n side, a first layer made of 1,500 ア ン undoped GaN from the bottom, a second layer made of GaN containing 5 １０ 10 ¹⁷ / cm ^{3 of} 100 Ｓｉ Si, and 1500 Å By using a lower layer of a three-layer structure composed of a third layer made of undoped GaN, it is possible to suppress the variation in V _{f with} the lapse of the drive time of the light emitting element.

(4) Buffer layer, undoped GaN layer, n-side contact layer made of GaN containing 6.0 × 10 ¹⁸ / cm ^{3 of} Si, undoped GaN layer (the above is an n-type nitride semiconductor layer with a total film thickness of 6 nm), Si 5 × 10 ¹⁸ / cm ^{3 of} GaN barrier layers and InGaN well layers are repeatedly stacked in a multiple quantum well light emitting layer, and the Mg layer having a thickness of 1300 mm is 5.0 × 10 ¹⁸ / A p-type nitride semiconductor layer made of GaN containing cm ³ and an InGaN layer having a thickness of 50 mm may be provided between the light-transmitting conductive layer and the p-type nitride semiconductor layer. When a 50-inch InGaN layer is provided, this layer is in contact with the positive electrode and can be a p-side contact layer. Thus, even a layer not doped with Mg functions as a p-type semiconductor layer for forming a p-electrode if the film thickness is relatively smaller than that of an adjacent p-type semiconductor layer.

(5) Buffer layer, undoped GaN layer, n-side contact layer made of GaN containing 1.3 × 10 ¹⁹ / cm ^{3 of} Si, undoped GaN layer (the above is an n-type nitride semiconductor layer having a total film thickness of 6 nm), Si Is a multiple quantum well light emitting layer (total film thickness: 800 mm) in which 7 layers of GaN barrier layers and InGaN well layers containing 3.0 × 10 ¹⁸ / cm ³ are alternately stacked, and Mg having a film thickness of 1300 mm. A p-type nitride semiconductor layer made of GaN containing 2.5 × 10 ²⁰ / cm ³ and an InGaN layer having a thickness of 50 mm may be provided between the light-transmitting conductive layer and the p-type nitride semiconductor layer. . When a 50-inch InGaN layer is provided, this layer is in contact with the positive electrode and can be a p-side contact layer.

  In addition, the semiconductor light emitting device of the present invention may have a light conversion member that converts part of light from the light emitting device into light having a different wavelength. As a result, a light-emitting device in which light from the light-emitting element is converted can be obtained, and a light-emitting device in white or light bulb color can be obtained by using mixed color light of the light emission from the light-emitting element and converted light.

  As the light conversion member, aluminum containing Al and containing at least one element selected from Y, Lu, Sc, La, Gd, Tb, Eu, and Sm and one element selected from Ga and In And garnet phosphors, and aluminum garnet phosphors containing at least one element selected from rare earth elements. Thereby, even when the light emitting element is used with high output and high heat generation, a light emitting device having excellent temperature characteristics and excellent durability can be obtained.

The light conversion member is (Re _1−x R _x ) ₃ (Al _1−y Ga _y ) ₅ O ₁₂ (0 <x <1, 0 ≦ y ≦ 1, where Re is Y, Gd, La, Lu , Tb, Sm, and at least one element selected from the group consisting of Sb, Tb, and Sm, and R may be Ce or Ce and Pr). Thus, as described above, a high-output light-emitting element can be an element having excellent temperature characteristics and durability. In particular, when the light-emitting layer is InGaN, the temperature characteristic changes along with black body radiation, and white This is advantageous in system light emission.

Furthermore, the light conversion member contains N and is selected from at least one element selected from Be, Mg, Ca, Sr, Ba and Zn, and from C, Si, Ge, Sn, Ti, Zr and Hf. It may be a nitride-based phosphor containing at least one element and activated by at least one element selected from rare earth elements. Specifically, the general formula _{L X Si Y N (2 /} 3X + 4 / 3Y): Eu or _{L X Si Y O Z N (} 2 / 3X + 4 / 3Y-2 / 3Z): Eu (L is Sr or Ca, or any one of Sr and Ca.). As a result, similar to the phosphor described above, excellent temperature characteristics and durability can be obtained in a high-output light emitting device. Of these, a silicon oxynitride compound is preferable. Further, by combining with the above-described aluminum / garnet phosphor, the temperature characteristics of the two interact with each other, and a light emitting device with a small temperature change of the mixed color can be obtained.

Hereinafter, a semiconductor light emitting device of the present invention will be described in detail with reference to the drawings.
Experimental Example A GaN layer of 5.5 μm is formed on a sapphire substrate, an ITO film is formed as a lower conductive oxide film on the entire surface, and an ITO film and a Pt film are formed thereon as an upper conductive oxide film. Were formed with the film thicknesses shown in Table 1, and samples a to d were obtained.
For each of the obtained samples, light having a wavelength of 460 nm was incident vertically from the sapphire substrate side, the reflected light was detected, and the reflectance was measured. The reflectance was measured with a spectrophotometer (UV-2400PC) manufactured by Shimadzu Corporation. The results are also shown in Table 1.

The wavelength of light is 460 nm, A is an odd number 3, and each value of 2.06, which is the refractive index of the ITO film, is substituted into the above-described equation (1), so that the film thickness of the lower ITO film is about 1670cm was set. That is, the thickness of the lower ITO film was 3λ / 4n. Note that the distance of phase shift was not considered.
The upper ITO film was 948 mm in sample a. That is, the film thickness of the upper ITO film is 2λ / 4n + α / 2, the refractive index n of platinum is 1.87, the platinum attenuation coefficient is 3.20, the above-mentioned wavelength, and the refractive index of ITO is expressed by the formula (3 ) And (4), the thickness of the upper ITO film is obtained by subtracting the film thickness corresponding to the phase shift distance (α / 2 = 336 mm) from the odd multiple (1116 mm) of λ / 4n. The total film thickness was set to an odd multiple of λ / 4n.

Sample b was used as a comparative control because no upper ITO film was provided.
In sample c, it was 390 mm. That is, the film thickness of the upper ITO film was set to 1λ / 4n + α / 2, and the total film thickness was set to be a value obtained by subtracting the film thickness causing phase shift from an even multiple of λ / 4n (558 mm).
In sample d, it was 558 mm. That is, the thickness of the upper ITO film was set to 1λ / 4n, and the total film thickness was set to be an even multiple of λ / 4n.

From the results of Table 1, as shown in samples a and b, ITO film is used as the upper and lower conductive oxide films, Pt is used as the metal film, and the total film thickness of the ITO film is an odd multiple of λ / 4n. It was confirmed that the reflectance can be improved when set to be.
In particular, as shown in sample a, in the thickness of the ITO film that can maximize the reflectivity, the phase shift that is influenced by the complex refractive index of the metal film and the refractive index of the ITO film is offset. Thus, it was confirmed that the reflectance generated between the ITO film and the platinum film can be further increased, and the light extraction efficiency can be further improved.

Example 1
The semiconductor light emitting device of this example is shown in FIG.
In this semiconductor light emitting device 10, a buffer layer (not shown) made of Al _0.1 Ga _0.9 N and a non-doped GaN layer (not shown) are stacked on a sapphire substrate 1, and an n-type semiconductor layer 2 is formed thereon. A n-side contact layer made of Si-doped GaN, a superlattice n-type cladding layer in which a GaN layer (40Å) and an InGaN layer (20 積 層) are alternately stacked 10 times, and further, a GaN layer As the light emitting layer 3 and the p-type semiconductor layer 4 having a multiple quantum well structure in which (250 （) and InGaN layers (30Å) are alternately stacked three to six times, an Mg-doped Al _0.1 Ga _0.9 N layer (40Å) and an Mg-doped layer A superlattice p-type cladding layer in which InGaN layers (20Å) are alternately stacked 10 times and a p-side contact layer made of Mg-doped GaN are stacked in this order.

On the p-type semiconductor layer 4, the lower ITO film 5 (film thickness: 1670 上) is formed almost entirely, and the upper ITO film 6 (film thickness: 948 Å) is formed only in a part of the region on the lower ITO film 5. Furthermore, a metal film 7 (thickness: 2000 mm) made of Pt having the same size as that of the upper ITO film 6 is laminated to form a p-electrode. The interface between the lower ITO film 5 and the p-type semiconductor layer is preferably lower in density than the surface side of the lower ITO film 5 and the upper ITO film 6, or a plurality of voids are formed in the vicinity of the interface. . By forming the lower ITO film 5 in this way, the current density between the p-type semiconductor layer and the lower ITO film 5 can be increased, the Schottky barrier can be reduced, and the ohmic property can be improved. it can.
Moreover, it is preferable that the surface side of the lower ITO film 5 and the upper ITO film 6 have no gap and have a higher density than the vicinity of the interface between the lower ITO film 5 and the p-type semiconductor layer. By forming the surface side of the lower ITO film 5 and the upper layer ITO film 6 in this way, the surface side of the lower layer ITO film 5 and the upper layer ITO film 6 can have good transmittance for visible light. Light can be efficiently reflected by the film.

  In a partial region of the n-type semiconductor layer 2, the light emitting layer 3 and the p-type semiconductor layer 4 stacked thereon are removed, and further, a portion of the n-type semiconductor layer 2 itself in the thickness direction is removed. On the exposed n-type semiconductor layer 2, an ITO film 8 having a thickness of 390 mm and a metal film 9 made of Pt having a thickness of 2000 mm are formed as an n electrode.

Such a semiconductor light emitting device can be formed by the following manufacturing method.
<Formation of semiconductor layer>
First, a sapphire substrate having a diameter of 2 inches and a C-plane as a main surface is set in a MOVPE reaction vessel, and the temperature is set to 500 ° C., and trimethylgallium (TMG), trimethylaluminum (TMA), and ammonia (NH ₃ ) are used. A buffer layer made of Al _0.1 Ga _0.9 N is grown to a thickness of 100 mm.
After forming the buffer layer, the temperature is set to 1050 ° C., and an undoped GaN layer is grown to a thickness of 1.5 μm using TMG and ammonia. This layer acts as a base layer (growth substrate) in the growth of each layer forming the element structure.

Next, an n-side contact layer made of GaN doped with 1 × 10 ¹⁸ / cm ³ of Si at 1050 ° C. using TMG, ammonia, and silane gas as an impurity gas as an n-type semiconductor layer 2 on the base layer. Growing with a film thickness of 2.165 μm.
On top of that, a superlattice n-type cladding layer in which a GaN layer (40 cm) and an InGaN layer (20 cm) are alternately stacked 10 times while the temperature is set to 800 ° C. and trimethylindium is intermittently supplied to the source gas. 5 is grown to a thickness of 640 Å, and further, a light emitting layer 3 having a multiple quantum well structure in which GaN layers (250 Å) and InGaN layers (30 Å) are alternately stacked 3 to 6 times is grown.

As the p-type semiconductor layer 4, a superlattice p-type cladding layer in which Mg-doped Al _0.1 Ga _0.9 N layers (40 Å) and Mg-doped InGaN layers (20 Å) are alternately stacked 10 times is grown by 0.2 μm.
Finally, at 900 ° C. in a hydrogen atmosphere, 4 cc of TMG, 3.0 liters of ammonia, 2.5 liters of hydrogen gas as a carrier gas were introduced, and Mg was added to the p-type cladding layer at 1.5 × 10 ²⁰ / A p-side contact layer made of cm ³ -doped p-type GaN is grown to a thickness of 0.5 μm.
Thereafter, the obtained wafer is annealed in a reaction vessel at 600 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type cladding layer and the p-side contact layer.

<Etching>
After annealing, the wafer is taken out of the reaction vessel, a mask having a predetermined shape is formed on the surface of the uppermost p-side contact layer, and etched from above the mask with an etching apparatus to expose a part of the n-side contact layer.

<Formation of p-electrode and n-electrode>
After removing the mask, a wafer is set in the sputtering apparatus, and an oxide target made of a sintered body of In ₂ O ₃ and SnO ₂ is set in the sputtering apparatus. The wafer is maintained at 300 ° C. in an oxygen gas atmosphere by a sputtering apparatus, and is sputtered with a mixed gas (20: 1) of argon gas and oxygen as a sputtering gas, for example, at an RF power of 10 W / cm ² for 20 minutes. The ITO film 5 is formed with a film thickness of 1670 mm.

Next, a mask having a desired shape made of a resist is formed on the p-side contact layer and the n-side contact layer including the lower ITO film 5, and sintering of In ₂ O ₃ and SnO ₂ is performed thereon. Using an oxide target consisting of a body, the wafer is maintained at 300 ° C. in an oxygen gas atmosphere, and the RF power is changed to 2 W / cm ² with a mixed gas (20: 1) of argon gas and oxygen as a sputtering gas. Then, sputtering is performed for 20 minutes, and the mask and ITO formed thereon are removed by a lift-off method. Thereby, the upper ITO film 6 and the ITO film 8 are formed with a film thickness of 948 mm on a partial region on the lower ITO film 5 and on the n-side contact layer.

Further, the metal film 7 and the metal film 9 are formed with a film thickness of 2000 mm on the upper ITO film 6 and the ITO film 8 by using a lift-off method similar to the above using a Pt target.
Next, heat treatment is performed at about 400 to 600 ° C. in a lamp annealing apparatus.
The semiconductor light emitting element 10 is obtained by dividing the obtained wafer at predetermined locations.

When the cross section of the semiconductor light emitting device formed as described above is observed by STEM, a plurality of holes of about 20 to 200 nm are observed inside the lower ITO film 5 which is the lower conductive oxide film, and the density is low. Can be confirmed. In addition, the upper ITO film 6 that is the upper conductive oxide film and the ITO film 8 that is the conductive oxide film have a high density and a good crystal state. Note that the p-electrode itself is transparent.
In addition, the configuration of the semiconductor light emitting device of the present invention can strengthen both the adhesion between the p electrode and the p side contact and the adhesion between the n electrode and the n side contact layer. By increasing the current density between the lower ITO film, which is the lower conductive oxide film, and the p-side contact layer, the Schottky barrier is reduced and the contact resistance between the lower ITO film and the p-side contact layer is reduced. be able to.
Further, as a comparative example, a semiconductor light emitting device in which the upper ITO film 6 that is the upper conductive oxide film and the ITO film 8 are not formed is manufactured, and the light emission between the semiconductor light emitting device described above and the semiconductor light emitting device of the comparative example is made. When the extraction efficiency is measured, it can be confirmed that the above-described semiconductor light emitting device has higher light extraction efficiency.

Example 2
The semiconductor light emitting device of this example is the same as the semiconductor light emitting device of Example 1 except that the metal film in the p electrode and the metal film in the n electrode are separately formed as follows.
That is, a mask having a predetermined pattern is formed on the upper ITO film 6 with a resist, and a metal film 7 made of Rh (1000 Å) / Pt (2000 Å) / Au (5000 Å) is formed thereon.
Thereafter, a W layer 200 Å, a Pt layer 2000 Å, and an Au layer 5000 積 層 are laminated in this order on the ITO film 8 formed on the n-side contact layer to form the metal film 9.
The obtained semiconductor light emitting device has the same effect as that of Example 1.

  As described above, the configuration of the semiconductor light emitting device of the present invention can strengthen the adhesion between the positive electrode and the p-side contact, and in particular, the lower ITO film which is the first semiconductor film and the p-side contact layer. Is increased, the Schottky barrier can be reduced, and the contact resistance between the lower ITO film and the p-side contact layer can be reduced. In addition, the sheet resistance is low due to the metal film, the current can be spread uniformly in the in-plane direction in the positive electrode, and the current can be spread evenly from the positive electrode to the entire semiconductor layer. The layer can emit light efficiently. In addition, the light extraction efficiency can be improved.

Example 3
In the semiconductor light emitting device of this embodiment, as shown in FIG. 5, the p electrode 20 and the n electrode 19 are provided on the same surface side, and light is transmitted from the electrode forming surface side with the observation surface side as the electrode forming surface side. It is the structure to take out. The semiconductor multilayer structure constituting the semiconductor light emitting device includes a GaN buffer layer 12, a non-doped GaN layer 13, a Si-doped GaN layer 14 serving as an n-side contact layer, a Si-doped GaN layer 15 serving as an n-type cladding layer, on a sapphire substrate 11. The InGaN layer 16 serving as a light-emitting layer, the Mg-doped AlGaN layer 17 serving as a p-type cladding layer, and the Mg-doped GaN layer 18 serving as a p-side contact layer have a layered structure. Further, the Mg-doped GaN layer 18, the Mg-doped AlGaN layer 17, the InGaN layer 16, the Si-doped GaN layer 15, and the Si-doped GaN layer 14 are partially removed by etching or the like, and an n electrode is formed on the exposed surface of the Si-doped GaN layer 14. 19 is formed, and the Mg-doped GaN layer 18 is provided with a p-electrode 20.

  The n electrode 19 is laminated in the order of an ITO film and a metal film from the n-side contact layer side as in the first embodiment. The metal film of the n electrode 19 is formed by laminating W, Pt, and Au in order from the n-side contact layer side. The p electrode 20 includes a lower conductive oxide film 5 formed on almost the entire surface of the p-side contact layer, and an upper conductive oxide film 6 and a metal film 7 that become the p-side pad electrode 21. Further, the metal film 7 of the p electrode is formed by sequentially stacking W, Pt, and Au in the same manner as the n electrode. In this embodiment, the lower conductive oxide film 5 of the p-electrode partially surrounds the n-electrode 19 in order to ensure a wide light-emitting region (first region).

  The n-side contact layer includes a first region provided with a semiconductor multilayer structure having a p-electrode and a second region different from the first region, as viewed from the electrode forming surface side. Are provided with an n-electrode 19 and a plurality of convex portions 29. In addition, each convex portion 29 surrounds the first region. In this semiconductor light emitting device, by surrounding the first region that emits light during driving with a convex portion, the surface area on the electrode forming surface side of the semiconductor light emitting device is effectively used to control light extraction efficiency and light directivity. It can be carried out.

  As shown in FIG. 7, the top of each projection 29 provided in the second region is provided with a lower conductive oxide film, and the top of the projection is the lower layer on the first region that emits light in the cross section. The lower conductive oxide film having substantially the same film thickness as that of the conductive oxide film 5 is formed. Thus, when the convex part is formed so that the convex part has a lower conductive oxide film having a film thickness that allows light to easily pass through, the light taken into the convex part from the n-side contact layer is absorbed. Therefore, the light extraction efficiency is further improved as compared with the semiconductor light emitting device of Example 1.

  Further, as shown in FIG. 5, the semiconductor light emitting device of this example is provided in the first region located between the n electrode and the pad portion of the p electrode as viewed from the electrode arrangement surface side. It is preferable that the obtained semiconductor multilayer structure has a constricted portion from the n-electrode side and a plurality of convex portions in the constricted portion on an extension line of VV ′ connecting the pad portion of the n electrode and the p electrode. Thereby, light extraction and light directivity controllability can be further improved. Although the current mainly flows in the extension line of VV ′, a part of the first area on the extension line of VV ′ in the first area is intentionally removed, and a plurality of convex portions are provided in the removal area. In addition, light extraction efficiency and light directivity control can be effectively improved. As a result, it is possible to spread the current over a wider area of the semiconductor multilayer structure, and relatively strong light emitted from the end face of the semiconductor multilayer structure including the light emitting layer in the area removed from the VV ′ extension line. This is thought to be because it can be effectively extracted to the observation surface side.

Furthermore, by providing a plurality of convex portions in the second region, it is possible to obtain a tendency to improve both the forward and reverse electrostatic withstand voltages. The reason for this is not clear, but is probably related to the fact that a plurality of convex portions are provided and the surface area is increased.
In the present embodiment, the electrode has a rectangular outer shape when viewed from the electrode forming surface side, and an n-electrode and a p-side pad electrode are arranged at substantially the center of both ends in the longitudinal direction. It is not limited to this. For example, an n electrode and a p-side pad electrode may be arranged on a rectangular diagonal.

Example 4
As shown in FIG. 15, the semiconductor light emitting device 10 b of this example has a configuration similar to that of Example 1 except that the interface between the substrate 1 b and the n-type semiconductor 2 has irregularities. In this embodiment, a sapphire substrate having a C-plane (0001) having an orientation flat on the A-plane (11-20) as the main surface is used.

This semiconductor light emitting device can be formed by the following method.
First, an SiO ₂ film serving as an etching mask is formed on the sapphire substrate 1.
Next, a circular photomask having a diameter φ = 5 μm is used, and the SiO ₂ film and the sapphire substrate 1 are etched by 1 μm by RIE. Thereafter, the SiO ₂ film is removed. Thus, a repetitive pattern of convex portions 122 and concave portions 123 having a circular planar shape as shown in FIG. 11A is formed on the surface portion of the sapphire substrate 1b. The top part of the convex part was set to a diameter a = 5 μm, and the distance between the convex part and the convex part b = 2 μm. Further, the inclination angle θb of the convex portion side surface is 120 °.
Moreover, you may form the repeating pattern of the convex part 122 in a 2-step inclined surface (refer FIG. 13). In this case, for example, after removing the SiO ₂ film, the surface of the sapphire substrate 1b is further etched so that the uppermost surface of the convex portion has a diameter a = 3 μm and the distance between the convex portion and the convex portion b = 1.5 μm. Further, the angle θ ₁ of the convex side surface can be set to 70 ° and the angle θ ₂ can be set to 20 °. In this way, when the convex portion 122 is formed with a two-step inclined surface, not only the light extraction effect described later but also the semiconductor element structure grown on the substrate having the convex portion, particularly the crystallinity of the semiconductor layer therein is improved. Thus, the internal quantum efficiency can be increased.

  Next, on the obtained sapphire substrate 1, an AlxGa1-xN (0 ≦ x ≦ 1) low-temperature growth buffer layer is formed as an n-type semiconductor layer 100 by 100 μm, undoped GaN is 3 μm, Si-doped GaN is 4 μm, undoped Next, as a light emitting layer 3 of a multi-quantum well to be a light emitting region, (GaN layer, barrier layer) = (undoped InGaN, Si doped GaN) with respective film thicknesses (60 cm, 250 mm). ) Are stacked alternately so that there are 6 well layers and 7 barrier layers. In this case, the barrier layer to be finally stacked may be undoped GaN. Note that the first layer formed on the low-temperature growth buffer layer is made of undoped GaN, so that the projections 122 can be filled more uniformly.

Thereafter, 200 p of Mg-doped AlGaN, 1000 p. Of undoped GaN, and 200 p. Of Mg-doped GaN are stacked as the p-type semiconductor layer 4. The undoped GaN layer formed as the p-type semiconductor layer 4 exhibits p-type due to diffusion of Mg from the adjacent layer.
Next, from the Mg-doped GaN to the p-type semiconductor layer 4, the light emitting layer 3, and a part of the n-type semiconductor layer 2 are etched to expose the Si-doped GaN layer.
Subsequently, a p-electrode composed of the lower ITO film 5, the upper ITO film 6, and the metal film 7 and an n-electrode composed of the ITO film 8 and the metal film 9 are formed in the same manner as in the first embodiment.
The semiconductor light emitting element 10 is obtained by dividing the obtained wafer at predetermined locations.

  In the semiconductor light-emitting device obtained in this way, light traveling at an angle greater than the critical angle with respect to the interface between the metal film and the upper ITO film or the substrate surface is scattered by unevenness provided at the interface between the substrate and the semiconductor layer. Since it is diffracted and can enter the interface between the metal film and the upper ITO film or the substrate surface at an angle smaller than the critical angle, the light extraction efficiency can be further improved as compared with the semiconductor light emitting device of Example 1. Can do.

  The semiconductor light emitting device of the present invention can be suitably used for a semiconductor light emitting device constituting various light sources such as a backlight light source, a display, illumination, and a vehicle lamp.

It is sectional drawing which shows one Embodiment of the semiconductor light-emitting device in this invention. It is a top view for demonstrating the electrode shape of the semiconductor light-emitting device in this invention. It is a top view for demonstrating another electrode shape of the semiconductor light-emitting device in this invention. It is a top view for demonstrating another electrode shape of the semiconductor light-emitting device in this invention. It is a top view which shows another embodiment of the semiconductor light-emitting device in this invention. FIG. 6 is a partial cross-sectional view taken along line V-V ′ of FIG. 5. It is a fragmentary sectional view showing another embodiment of a semiconductor light emitting element in the present invention. It is a fragmentary sectional view showing another embodiment of a semiconductor light emitting element in the present invention. It is a fragmentary sectional view for explaining a course of light in a semiconductor light emitting element of the present invention. It is a fragmentary sectional view showing another embodiment of a semiconductor light emitting element in the present invention. It is a figure which shows the example of a pattern of the convex part in FIG. It is a fragmentary sectional view showing other embodiments of a semiconductor light emitting element in the present invention. It is sectional drawing which shows the example of an uneven | corrugated shape. It is sectional drawing which shows another embodiment of the semiconductor light-emitting device in this invention. It is sectional drawing in the semiconductor light-emitting device of Example 4 in this invention. It is a top view which shows another embodiment of the semiconductor light-emitting device in this invention. FIG. 17 is a sectional view taken along line XVI-XVI ′ of FIG. 16. It is a top view which shows another embodiment of the semiconductor light-emitting device in this invention.

Explanation of symbols

1, 1a, 1b substrate 2 n-type semiconductor layer 3 light emitting layer 4 p-type semiconductor layer 5 lower ITO film (lower conductive oxide layer)
6 Upper ITO film (Upper conductive oxide layer)
7 Metal film 8 ITO film (conductive oxide layer)
9 Metal film 10, 10a, 10b, 10c Semiconductor light emitting device 11 Sapphire substrate 12 GaN buffer layer 13 Non-doped GaN layer 14, 15 Si-doped GaN layer 16 InGaN layer 17 Mg-doped AlGaN layer 18 Mg-doped GaN layer 19 n-electrode 20 p-electrode 21 P-side pad electrodes 29, 29 a, 29 b Protrusions 51 n-side contact layer 51 a Notch 52 p-type semiconductor layers 53, 63 n-electrodes 54, 64 Transparent electrodes 55, 65 p-side pad electrodes 56, 66 Extended conductive part 73 n electrode 122 convex portion 123 concave portion 153 n line electrode 153a n side extended conductive portion 153b n side pad electrode 155 current spreading electrode 155a p side extended conductive portion 155b p side pad electrode

Claims (14)

A semiconductor light emitting device comprising a first conductive type semiconductor layer, a light emitting layer, and a second conductive type semiconductor layer stacked in this order, and electrodes connected to the first conductive type and the second conductive type semiconductor layer, respectively. ,
The electrode connected to the second conductive type semiconductor layer has a lower conductive oxide film and a region where a part of the surface of the lower conductive oxide film is exposed on the lower conductive oxide film. An upper conductive oxide film formed as described above, and a metal film disposed only on the upper conductive oxide film,
The electrode connected to the first conductive semiconductor layer comprises a conductive oxide film and a metal film disposed on the conductive oxide film, and the upper and lower conductive oxide films and the conductive oxide A semiconductor light emitting device, wherein the physical film is made of an oxide containing at least one element selected from the group consisting of zinc (Zn), indium (In), tin (Sn), and magnesium (Mg). The lower conductive oxide film has the formula (1)
A ・ λ / 4n ₁ ± X (1)
(In the formula, A is an odd number, λ is the wavelength of light (Å) generated from the light emitting layer, n ₁ is the refractive index of the lower conductive oxide film, and X is a film of 0 to 20% of the optical thin film (λ / 4n)) Thick (Å).)
The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting device is formed with a film thickness of 5 nm. The semiconductor light-emitting device according to claim 1, wherein the upper conductive oxide film and the conductive oxide film are formed of the same type and film thickness in the same process. The upper conductive oxide film and / or the conductive oxide film has the formula (2)
B ・ λ / 4n ₂ + α / 2 (2)
(In the formula, B is an even number, n ₂ is the refractive index of the upper conductive oxide film, α is the phase shift distance (Å), and λ is as defined above.)
The semiconductor light emitting element according to claim 3, wherein the semiconductor light emitting element is formed with a film thickness of 5 mm. 3. The semiconductor light emitting element according to claim 1, wherein the lower conductive oxide film is a film having a lower density than the surface side in the vicinity of the interface with the second conductive type semiconductor layer. The upper conductive oxide film and the conductive oxide film are made of a film having a higher density than the lower conductive oxide film in the vicinity of the interface with the second conductive type semiconductor layer. The semiconductor light emitting element as described. The semiconductor light emitting element according to claim 1, wherein the upper and lower conductive oxide films and the conductive oxide film are ITO. The semiconductor light emitting element according to claim 1, wherein the metal film is formed of a single layer film or a laminated film of W, Rh, Ag, Pt, Pd, and Al. The semiconductor light-emitting element according to claim 1, wherein the first conductivity type semiconductor layer is an n-type semiconductor layer, and the second conductivity type semiconductor layer is a p-type semiconductor layer. The semiconductor light emitting element according to claim 1, wherein the first and second conductive semiconductor layers are made of a nitride semiconductor. A first conductivity type semiconductor layer is formed on the substrate;
The semiconductor light-emitting device according to claim 1, wherein at least a part of an interface between the substrate and the first conductivity type semiconductor layer has irregularities. The semiconductor light emitting element according to claim 11, wherein the unevenness is formed on the substrate surface below the metal film formed on at least the upper conductive oxide film. An electrode connected to the first conductivity type semiconductor layer and an electrode connected to the second conductivity type semiconductor layer are formed on the same surface side,
The first conductivity type semiconductor layer includes a first region provided with a semiconductor stacked structure having upper and lower conductive oxide films, and a second region different from the first region, as viewed from the electrode forming surface side. Consists of
The semiconductor light emitting element according to claim 1, wherein a plurality of irregularities are provided in the second region. The uneven protrusion provided in the second region is made of a layer made of the same material as the semiconductor layer of the first region, and the top of the protruded portion is made of a film made of the same material as the lower conductive oxide film. Item 14. A semiconductor light emitting device according to Item 13.

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