JP2012175005A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device with an increased amount of light emission which suppresses increase of forward voltage.SOLUTION: A semiconductor light-emitting device 1 comprises: a substrate 110; an intermediate layer 120 stacked on the substrate 110; a ground layer 130 stacked on the intermediate layer 120; an n-type semiconductor layer 140 stacked on the ground layer 130; a light-emitting layer 150 stacked on the n-type semiconductor layer 140; a p-type semiconductor layer 160 stacked on the light-emitting layer 150; and a translucent electrode 170 that is stacked on the p-type semiconductor layer 160 and has translucency to light emitted from the light-emitting layer 150. In the translucent electrode 170, through holes 180 are provided so that a ratio (an opening ratio) in which the surface of the p-type semiconductor layer 160 is exposed is different from a region (C) adjacent to a first-type electrode 190 and a region (A) adjacent to a second-type electrode 200.

Description

  The present invention relates to a semiconductor light emitting device.

In recent years, the progress of semiconductor light emitting devices has been remarkable. In particular, light-emitting diodes using a light-emitting layer of GaInN, AlGaInP, or GaAlAs semiconductor materials with high luminous efficiency have been put into practical use. Group III nitride semiconductors such as gallium nitride (GaN) are attracting attention.
In such a semiconductor light emitting device using a group III nitride semiconductor, a laminated semiconductor layer having a light emitting diode (LED) structure including an n-type semiconductor layer, a light emitting layer, and a p-type semiconductor layer is formed on a substrate, A translucent electrode (translucent electrode) is formed on the p-type semiconductor layer, and light emission is taken out through the translucent electrode.

  In Patent Document 1, a GaN-based semiconductor light-emitting device including an n-type GaN-based semiconductor layer and a p-type GaN-based semiconductor layer includes a translucent electrode formed on the p-type GaN-based semiconductor layer. A GaN-based semiconductor light-emitting element is described that has a plurality of through-holes for light emission reaching the p-type GaN-based semiconductor layer, thereby reducing the absorbance of the light-transmitting electrode and improving the emission efficiency. ing.

JP 2005-123501 A

By the way, when the through-holes are uniformly provided in the translucent electrode on the p-type semiconductor layer of the group III nitride semiconductor in order to increase the emitted light amount (radiant energy) of the semiconductor light emitting device, ohmic contact with the p-type semiconductor layer is achieved. Therefore, the contact area with the translucent electrode is reduced, and the forward voltage of the semiconductor light emitting device is increased. As a result, the driving voltage of the semiconductor light emitting element increases, and as a result, the light emission efficiency of the semiconductor light emitting element decreases.
Further, the ratio of the area of the through hole to the area of the p-type semiconductor layer (opening ratio) controls the resistance of the translucent electrode, and as a result, controls the flow of current. However, in the conventional technique, a uniform current supply to the light emitting layer has not been made. For example, the current is concentrated in the vicinity of the electrode (region close to the electrode), and the current is concentrated in a part of the light emitting layer, so that the light emission efficiency is lowered.
Therefore, it is required to supply a uniform current to the entire light emitting layer of the semiconductor light emitting element to increase the amount of emitted light and to suppress an increase in forward voltage.
In particular, in a rectangular semiconductor element, it is a big problem to supply a uniform current to the entire light emitting layer.

  It is an object of the present invention to provide a semiconductor light emitting device with high luminous efficiency that increases the amount of emitted light and suppresses an increase in forward voltage.

The semiconductor light emitting device to which the present invention is applied is, for example, a first semiconductor layer of a III-V semiconductor having a first conductivity type, and is provided on and in contact with the first semiconductor layer on the first semiconductor layer, and emits light when energized. A light emitting layer of a group III-V semiconductor, a second semiconductor layer of a group III-V semiconductor provided on the light emitting layer in contact with the light emitting layer and having a second conductivity type opposite to the first conductivity type, A translucent electrode provided on the two semiconductor layers in contact with the second semiconductor layer and having transparency to the light emitted from the light emitting layer; and a part of the translucent electrode in contact with the translucent electrode The other terminal connected to the first electrode and the first semiconductor layer, which is provided as one terminal for energizing the light emitting layer, and provided on the same side as the first electrode, for energizing the light emitting layer A translucent electrode on either the first electrode or the second electrode. The contact area, a plurality of through holes where the surface of the second semiconductor layer through the thickness direction so exposed is provided.
Note that the region close to the first electrode or the second electrode is a region close to one of the electrodes within a range not exceeding the midpoint between the first electrode and the second electrode.
The ratio (opening ratio) at which the surface of the second semiconductor layer is exposed in a region where a plurality of through holes close to either the first electrode or the second electrode is provided is 10% to 30%. Can be a feature.
In such a semiconductor light emitting device, the translucent electrode has a plurality of through holes in the thickness direction so that the surface of the second semiconductor layer is exposed in a region adjacent to either the first electrode or the second electrode. A through hole is further provided, and the ratio (opening ratio) at which the surface of the second semiconductor layer is exposed is smaller than the region adjacent to one of the through holes.
Furthermore, the aperture ratio in a region close to either the first electrode or the second electrode can be 15% or less.
Furthermore, the translucent electrode includes a plurality of penetrating in the thickness direction so that the surface of the second semiconductor layer is exposed in an intermediate region between the region adjacent to the first electrode and the region adjacent to the second electrode. Further through holes are further provided.
And the aperture ratio by the several through-hole provided in a translucent electrode can change along the line which connects a 1st electrode and a 2nd electrode, It can be characterized by the above-mentioned. This change may be a gentle change or a step-like change.
The planar shape of such a semiconductor light emitting device is a rectangle whose long side is twice or more the length of the short side, and the first electrode and the second electrode are at both ends in the longitudinal direction of the rectangle. Each may be provided.
Further, the aperture ratio can be characterized by being set by the density or size of the plurality of through holes.
And a translucent electrode can be characterized by being comprised with the oxide electrically-conductive material.
The first conductivity type may be n-type, and the second conductivity type may be p-type.
At this time, the first semiconductor layer includes a contact layer connected to the second electrode and a clad layer in contact with the light emitting layer, and the product of the impurity concentration of the contact layer and the thickness of the contact layer is 1 × 10 ¹⁴ cm ⁻² to 1 × 10 ¹⁶ cm ⁻² , and the sheet resistance of the translucent electrode is 5Ω / □ to 50Ω / □.
Here, the aperture ratio of the region close to the first electrode may be larger than the aperture ratio of the region close to the second electrode.
The aperture ratio 1 of the area close to the first electrode is larger than the aperture ratio 2 of the area close to the second electrode, and the opening of the intermediate area between the area close to the first electrode and the area close to the second electrode The ratio 3 can be characterized by being between an aperture ratio of 1 and an aperture ratio of 2.
Further, the second semiconductor layer is composed of a contact layer in contact with the translucent electrode and a clad layer in contact with the light emitting layer, and the portion of the contact layer in contact with the translucent electrode is more Mg than the portion of the contact layer in contact with the clad layer. This is characterized in that a large amount of is added.
Further, the group III-V semiconductor may be a group III nitride semiconductor.
Furthermore, the width of the through hole may be 1 μm to 10 μm.
Furthermore, the thickness of the translucent electrode may be 50 nm to 400 nm.

  According to the present invention, it is possible to provide a semiconductor light emitting element with high luminous efficiency that increases the amount of emitted light and suppresses an increase in forward voltage.

It is a figure explaining an example of a section schematic diagram of a semiconductor light emitting element to which this embodiment is applied. It is a figure explaining an example of the plane schematic diagram of the semiconductor light-emitting device shown in FIG. It is a cross-sectional schematic diagram of a semiconductor light-emitting device when a through hole is not provided in a translucent electrode. It is a figure explaining the experiment example which investigated the relationship between the area | region which provides a through-hole in a translucent electrode, the emitted light quantity Po (mW) of a semiconductor light-emitting device, and the forward voltage Vf (V). It is a figure explaining the other example of the through-hole provided in the translucent electrode. It is a figure explaining the relationship between the emitted light amount Po (mW) of the semiconductor light emitting element of Examples 1-4 and Comparative Examples 1 and 2, and the forward voltage Vf (V).

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is an example of a schematic cross-sectional view of a semiconductor light-emitting element (light-emitting diode) 1 to which the present embodiment is applied, and FIG. 2 is a diagram for explaining an example of a schematic plan view of the semiconductor light-emitting element 1 shown in FIG. is there. 1 is a cross-sectional view taken along the line II of FIG. 2 is a plan view seen from an arrow II in FIG. 1.

(Semiconductor light emitting element 1)
As shown in FIG. 1, the semiconductor light emitting device 1 includes a substrate 110, an intermediate layer 120 stacked on the substrate 110, and a base layer 130 stacked on the intermediate layer 120. In addition, the semiconductor light emitting device 1 includes an n-type semiconductor layer 140 as an example of a first semiconductor layer stacked on the base layer 130, a light-emitting layer 150 stacked on the n-type semiconductor layer 140, and the light-emitting layer 150. And a p-type semiconductor layer 160 as an example of a second semiconductor layer stacked on the substrate. In the following description, the intermediate layer 120, the base layer 130, the n-type semiconductor layer 140, the light emitting layer 150, and the p-type semiconductor layer 160 are collectively referred to as a laminated semiconductor layer 100 as necessary.

In addition, the semiconductor light emitting device 1 includes a translucent electrode 170 that is laminated on the upper surface 160 c of the laminated semiconductor layer 100 and has transparency to the light emitted from the light emitting layer 150.
The semiconductor light emitting device 1 includes the first electrode 190 stacked on a part of the translucent electrode 170, and a part of the p-type semiconductor layer 160, the light-emitting layer 150, and the n-type semiconductor layer 140 cut out. A second electrode 200 stacked on a portion of the exposed n-type semiconductor layer 140 on the semiconductor layer exposed surface 140c.

The translucent electrode 170 includes a plurality of through holes 180 that penetrate in the thickness direction and expose the surface of the p-type semiconductor layer 160. As will be described later, the through hole 180 is a ratio at which the surface of the p-type semiconductor layer 160 is exposed in different regions on the surface of the translucent electrode 170 (region A, region B, and region C in FIGS. 1 and 2). (Aperture ratios) are provided differently.
Further, the semiconductor light emitting element 1 includes a protective layer 210 that covers the surface of the translucent electrode 170, the surface of the laminated semiconductor layer 100, and the side surfaces except for a part of the surfaces of the first electrode 190 and the second electrode 200. Prepare. Note that the protective layer 210 also covers the surface of the p-type semiconductor layer 160 exposed at the bottom of the through hole 180 and the side surface (inner wall) inside the through hole 180 in the through hole 180.

  As shown in FIG. 2, the planar shape of the semiconductor light emitting device 1 is, for example, a rectangle. The first electrode 190 and the second electrode 200 having a circular planar shape are respectively provided at the ends in the longitudinal direction of the rectangle. The planar shape of the semiconductor light emitting element 1 is, for example, 350 μm × 850 μm. The planar shape of the first electrode 190 and the second electrode 200 is, for example, a circle having a diameter of 70 μm. When the ratio of the long side to the short side is twice or more, it is difficult to make the current density uniform, so the effect of the present invention is great.

In the present embodiment, the planar shape of the through hole 180 is, for example, a circle having a diameter d.
The surface of the translucent electrode 170 is divided into three regions: a region A close to the second electrode 200, a region C close to the first electrode 190, and a region B between the regions A and C. The region C adjacent to the first electrode 190 or the region A adjacent to the second electrode 200 is within a range not exceeding the midpoint between the first electrode 190 and the second electrode 200 and is close to any one of the electrodes. It is an area.
And in each area | region, the through-hole 180 is arrange | positioned so that it may be located in the vertex of the some equilateral triangle arranged so that a side may mutually be made common.
The through-hole 180 is located at the apex of an equilateral triangle with a side length pa in the region A, at the apex of an equilateral triangle with a side length pb in the region B, and at the apex of an equilateral triangle with a side length pc in the region C. Is provided. And the length of one side of the equilateral triangle of each area is set so that pa>pb> pc. Therefore, when the through-hole 180 has a diameter d, the rate at which the surface of the p-type semiconductor layer 160 is exposed in the region A is small, and the rate at which the surface of the p-type semiconductor layer 160 is exposed in the region C is large. Region B is intermediate between region A and region C.
The diameter d of the through-hole 180 is, for example, 3 μm, the side length pa of the equilateral triangle in the region A is, for example, 12 μm, the side length pb of the equilateral triangle in the region B is, for example, 9 μm, and the side length pc of the equilateral triangle in the region C is, for example, 6 μm. is there. When the side lengths pa, pb, and pc are not distinguished from each other, they are expressed as one side length p. The arrangement of the through holes 180 is a regular triangle vertex, but may be a polygonal vertex or an irregular arrangement.

Note that the region A where the ratio of the surface of the p-type semiconductor layer 160 exposed is small is a region where the amount of light per unit area is large when the through-hole 180 is not provided, and the ratio of the surface of the p-type semiconductor layer 160 exposed. The region C where the light amount is large is a region where the amount of light is small when the through hole 180 is not provided. This light amount difference is caused by a difference in current (current density) per unit area flowing in the light emitting layer 150.
That is, in the case where the through hole 180 is not provided, the rate at which the surface of the p-type semiconductor layer 160 is exposed is changed by the current density reflecting the amount of light emitted per unit area. A region where the amount of light per unit area is large reduces the rate at which the surface of the p-type semiconductor layer 160 is exposed, and a region where the amount of light per unit area is small increases the rate at which the surface of the p-type semiconductor layer 160 is exposed. In this way, by changing the rate at which the surface of the p-type semiconductor layer 160 is exposed, the amount of light per unit area and the current density can be made uniform.
In addition, the planar shape of the through-hole 180 does not need to be the above-described circle, and may be a square, a rectangle, a triangle, or another shape.

  In this semiconductor light emitting device 1, by passing a current through the p-type semiconductor layer 160, the light-emitting layer 150, and the n-type semiconductor layer 140 via the first electrode 190 that is a positive electrode and the second electrode 200 that is a negative electrode, Light is emitted from the light emitting layer 150. Therefore, when the semiconductor light emitting element 1 is caused to emit light, a voltage is applied to the first electrode 190 and the second electrode 200, so the direction of the electric field is a direction connecting the first electrode 190 and the second electrode 200.

Next, each component of the semiconductor light emitting element 1 will be described in more detail.
<Substrate 110>
The substrate 110 is not particularly limited as long as a III-V group semiconductor crystal is epitaxially grown on the surface, and various substrates can be selected and used. For example, a substrate made of sapphire, SiC, silicon, germanium, GaAs, GaP, GaN, zinc oxide, or the like can be used. Alternatively, after epitaxial growth on the substrate, a substrate made of another material is attached, and the epitaxially grown substrate is removed, so that the attached substrate which is a substrate made of another material can be used as the substrate 110.
In the case of a group III nitride semiconductor crystal, among the above substrates, it is particularly preferable to use a sapphire substrate having a c-plane as a main surface. In the case of using a sapphire substrate, it is desirable to form an intermediate layer 120 (buffer layer) on the c-plane of sapphire because crystals having different lattice constants can be grown with good quality.

<Laminated semiconductor layer 100>
The laminated semiconductor layer 100 is a layer made of a group III nitride semiconductor, and as shown in FIG. 1, on the substrate 110, an intermediate layer 120, a base layer 130, an n-type semiconductor layer 140, a light-emitting layer 150, and a p-type layer. Each layer of the semiconductor layer 160 is laminated in this order.
Further, as shown in FIG. 1, each of the n-type semiconductor layer 140, the light emitting layer 150, and the p-type semiconductor layer 160 may be composed of a plurality of semiconductor layers. Here, the n-type semiconductor layer 140 conducts electricity in the first conductivity type using electrons as carriers, and the p-type semiconductor layer 160 conducts electricity in the second conductivity type using holes as carriers.
Note that although the stacked semiconductor layer 100 can be formed with good crystallinity when formed by the MOCVD method, a semiconductor layer having crystallinity superior to that of the MOCVD method can be formed by optimizing the conditions also by the sputtering method. . Hereinafter, description will be made sequentially.

<Intermediate layer 120>
The intermediate layer 120 is preferably made of polycrystalline _{Al x Ga 1-x N (} 0 ≦ x ≦ 1) , and more preferably those of the single crystal _{Al x Ga 1-x N (} 0 ≦ x ≦ 1) .
As described above, the intermediate layer 120 can be, for example, made of polycrystalline Al _x Ga _1-x N (0 ≦ x ≦ 1) and having a thickness of 0.01 μm to 0.5 μm. If the thickness of the intermediate layer 120 is less than 0.01 μm, the intermediate layer 120 may not sufficiently obtain an effect of relaxing the difference in lattice constant between the substrate 110 and the base layer 130. In addition, when the thickness of the intermediate layer 120 exceeds 0.5 μm, the film forming process time of the intermediate layer 120 becomes longer and the productivity may be lowered, although the function as the intermediate layer 120 is not changed. There is.

  The intermediate layer 120 alleviates the difference in lattice constant between the substrate 110 and the base layer 130. In particular, when the substrate 110 is made of sapphire having a c-plane as a main surface, the (0001) plane (c-plane) of the substrate 110 ) To facilitate the formation of a c-axis oriented single crystal layer on top. Therefore, when the single crystal base layer 130 is stacked on the intermediate layer 120, the base layer 130 with higher crystallinity can be stacked. In the present invention, it is preferable to form an intermediate layer, but the intermediate layer may not be formed.

  The intermediate layer 120 may have a hexagonal crystal structure made of a group III nitride semiconductor. Further, the group III nitride semiconductor crystal forming the intermediate layer 120 may have a single crystal structure, and preferably has a single crystal structure. By controlling the growth conditions, the group III nitride semiconductor crystal grows not only in the upward direction but also in the in-plane direction to form a single crystal structure. Therefore, by controlling the film forming conditions of the intermediate layer 120, the intermediate layer 120 made of a crystal of a group III nitride semiconductor having a single crystal structure can be obtained. When the intermediate layer 120 having such a single crystal structure is formed on the substrate 110, the buffer function of the intermediate layer 120 works effectively, so that the group III nitride semiconductor formed thereon has a good orientation. The crystal film has the property and crystallinity.

  Further, the group III nitride semiconductor crystal forming the intermediate layer 120 can be formed into a columnar crystal (polycrystal) having a texture based on a hexagonal column by controlling the film forming conditions. In addition, the columnar crystal consisting of the texture here is a crystal that is separated by forming a crystal grain boundary between adjacent crystal grains, and is itself a columnar shape as a longitudinal sectional shape. Say.

<Underlayer 130>
As the underlayer 130, Al _x Ga _y In _z N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, x + y + z = 1) can be used, but Al _x Ga _1-x N It is preferable to use (0 ≦ x <1) because the base layer 130 with good crystallinity can be formed.
The film thickness of the underlayer 130 is preferably 0.1 μm or more, more preferably 0.5 μm or more, and most preferably 1 μm or more. When the thickness is increased, the underlayer 130 with good crystallinity can be easily obtained.
In order to improve the crystallinity of the underlayer 130, it is desirable that the underlayer 130 is not doped with impurities. However, when p-type or n-type conductivity is required, a p-type impurity (acceptor) or an n-type impurity (donor) can be added.

<N-type semiconductor layer 140>
As shown in FIG. 1, the n-type semiconductor layer 140 is preferably composed of an n-contact layer 140a and an n-cladding layer 140b. The n contact layer 140a can also serve as the n clad layer 140b. In addition, the base layer 130 described above may be included in the n-type semiconductor layer 140.

The n contact layer 140 a is a layer for providing the second electrode 200. The n contact layer 140a is preferably composed of an Al _x Ga _1-x N layer (0 ≦ x <1, preferably 0 ≦ x ≦ 0.5, more preferably 0 ≦ x ≦ 0.1). .

The n contact layer 140a is preferably doped with an n-type impurity, and the n-type impurity is preferably 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²⁰ / cm ³ , preferably 1 × 10 ¹⁸ / cm ³ to When contained at a concentration of 1 × 10 ¹⁹ / cm ³ , it is preferable in that good ohmic contact with the second electrode 200 can be maintained. Although it does not specifically limit as an n-type impurity, For example, Si, Ge, Sn, etc. are mentioned, Preferably Si and Ge are mentioned.

The film thickness of the n contact layer 140a is preferably 0.5 μm to 5 μm, and more preferably set to a range of 1 μm to 3 μm. When the film thickness of the n contact layer 140a is in the above range, the crystallinity of the light emitting layer 150 and the like is maintained well.
Further, the product (Nd) of the impurity concentration and the film thickness of the n contact layer 140a is inversely proportional to the electrical resistance of the n contact layer 140a, and the current density of the light emitting layer 150 is made uniform, and the forward voltage Vf is A desirable range for lowering is Nd = 1 × 10 ¹⁴ / cm ² to 1 × 10 ¹⁶ / cm ² , preferably 2 × 10 ¹⁴ / cm ^{2 to} 5 × 10 ¹⁵ / cm ² . When the value of this product is too small, the amount of light (current density) in the region (near) close to the second electrode 200 is large and the forward voltage Vf is high. On the other hand, if this product value is too large, the amount of light (current density) on the side closer to the first electrode 190 increases, leading to a decrease in electrostatic breakdown voltage due to a decrease in crystal quality of the n-contact layer 140a.

  An n-clad layer 140b is preferably provided between the n-contact layer 140a and the light emitting layer 150. The n-cladding layer 140b is a layer that injects carriers into the light emitting layer 150 and confines carriers. The n-clad layer 140b can be formed of AlGaN, GaN, GaInN, or the like. Alternatively, a heterojunction of these structures or a superlattice structure in which a plurality of layers are stacked may be used. When the n-cladding layer 140b is formed of GaInN, it is desirable to make it larger than the band gap of GaInN of the light emitting layer 150. In this specification, AlGaN and GaInN may be described in a form in which the composition ratio of each element is omitted.

The thickness of the n-clad layer 140b is not particularly limited, but is preferably 5 nm to 500 nm, and more preferably 5 nm to 100 nm. The n-type impurity concentration of the n-clad layer 140b is preferably 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²⁰ / cm ³ , more preferably 1 × 10 ¹⁸ / cm ³ to 1 × 10 ¹⁹ / cm ³ . An impurity concentration within this range is preferable in terms of maintaining good crystallinity and reducing the operating voltage of the device.

When the n-cladding layer 140b is a layer including a superlattice structure, a detailed illustration is omitted, but an n-side first layer made of a group III nitride semiconductor having a thickness of 10 nm or less; It may include a structure in which an n-side second layer made of a group III nitride semiconductor having a composition different from that of the n-side first layer and having a film thickness of 10 nm or less is stacked.
Further, the n-cladding layer 140b may include a structure in which n-side first layers and n-side second layers are alternately and repeatedly stacked. The GaInN and GaN alternate structures or GaInN having different compositions. It is preferable that they have an alternating structure.

<Light emitting layer 150>
As the light emitting layer 150 stacked on the n-type semiconductor layer 140, it is desirable to adopt a single quantum well structure or a multiple quantum well structure.
In FIG. 1, the light emitting layer 150 is shown in a multiple quantum well structure in which barrier layers 150a and well layers 150b are alternately stacked. In the light emitting layer 150, the side in contact with the n-clad layer 140b and the side in contact with the p-clad layer 160a described later are respectively barrier layers 150a. As the well layer 150b having a multiple quantum well structure, a group III nitride semiconductor layer made of Ga _1-y In _y N (0 <y <0.4) is usually used. The film thickness of the well layer 150b can be set to a film thickness at which a quantum effect can be obtained, for example, 1 nm to 10 nm, and preferably 2 nm to 6 nm in terms of light emission output.
In the case of the light emitting layer 150 having a multiple quantum well structure, the Ga _1-y In _y N is used as the well layer 150b, and Al _z Ga _1-z N (0 ≦ z <0), which has a larger band gap energy than the well layer 150b. .3) is defined as a barrier layer 150a. Impurities may or may not be added to the well layer 150b and the barrier layer 150a depending on the design.

<P-type semiconductor layer 160>
The p-type semiconductor layer 160 is generally composed of a p-cladding layer 160a and a p-contact layer 160b. The p contact layer 160b can also serve as the p clad layer 160a.

The p-cladding layer 160a is a layer that performs confinement of carriers in the light emitting layer 150 and injection of carriers. The p clad layer 160a is not particularly limited as long as it has a composition larger than the band gap energy of the light emitting layer 150 and can confine carriers in the light emitting layer 150. For example, Al _x Ga _1-x N (0 <X ≦ 0.4).

It is preferable that the p-cladding layer 160a is made of such AlGaN from the viewpoint of confining carriers in the light-emitting layer 150. The thickness of the p-cladding layer 160a is not particularly limited, but is preferably 1 nm to 400 nm, more preferably 5 nm to 100 nm.
The p-type impurity concentration of the p-clad layer 160a is preferably 1 × 10 ¹⁸ / cm ³ to 1 × 10 ²¹ / cm ³ , more preferably 1 × 10 ¹⁹ / cm ³ to 1 × 10 ²⁰ / cm ³ . When the p-type impurity concentration is in the above range, a good p-cladding layer 160a can be obtained without reducing the crystallinity.
The p-cladding layer 160a may have a superlattice structure in which a plurality of layers are stacked. In this case, the AlGaN and GaN are alternately structured with different composition ratios or AlGaN and GaN with different compositions. It is preferable.

The p contact layer 160 b is a layer for providing the translucent electrode 170. The p contact layer 160b is preferably Al _x Ga _1-x N (0 ≦ x ≦ 0.4). When the Al composition is in the above range, it is preferable in that good crystallinity and good ohmic contact with the translucent electrode 170 can be maintained.
The p-contact layer 160b contains p-type impurities at a concentration of 1 × 10 ¹⁸ / cm ³ to 1 × 10 ²¹ / cm ³ , preferably 5 × 10 ¹⁹ / cm ^{3 to} 5 × 10 ²⁰ / cm ^3. In this case, it is preferable in terms of maintaining good ohmic contact, preventing the generation of cracks, and maintaining good crystallinity. Although it does not specifically limit as a p-type impurity, For example, Preferably Mg is mentioned.
The thickness of the p contact layer 160b is not particularly limited, but is preferably 10 nm to 500 nm, and more preferably 50 nm to 200 nm. When the film thickness of the p contact layer 160b is within this range, it is preferable in terms of the forward voltage Vf and the amount of emitted light Po.

Further, the p-contact layer 160b is composed of a p-side first layer and a p-side second layer, and the p-side first layer (part) in contact with the p-cladding layer 160a is in the p-side second layer in contact with the translucent electrode 170. Compared to the layer (part), the amount of Mg added may be reduced to reduce the layer resistance (sheet resistance).
The contact resistance (contact resistance) decreases in proportion to the added amount of Mg, but the layer resistance has an appropriate range of the added amount of Mg. If excessive Mg is added, the resistance increases. For this reason, it is desirable to lower both the contact resistance and the layer resistance in two layers.
As a result, the layer resistance of the p-type semiconductor layer 160 can be reduced, and the contact resistance between the p-type semiconductor layer 160 and the translucent electrode 170 can also be reduced.

<Translucent electrode 170>
As shown in FIG. 1, a translucent electrode 170 is stacked on the p-type semiconductor layer 160.
When viewed in plan as shown in FIG. 2, the translucent electrode 170 is substantially the same as the upper surface 160 c of the p-type semiconductor layer 160 from which a part has been removed by means such as etching to form the second electrode 200. It is formed so as to cover the entire surface.

  The translucent electrode 170 preferably has a small contact resistance with the p-type semiconductor layer 160. Further, in this semiconductor light emitting device 1, since the light from the light emitting layer 150 is extracted to the side where the first electrode 190 is formed, the translucent electrode 170 is excellent in light transmittance from the light emitting layer 150. preferable. Furthermore, in order to uniformly diffuse the current over the entire surface of the p-type semiconductor layer 160, it is preferable that the translucent electrode 170 has excellent conductivity.

From the above, an oxide conductive material (oxide conductive material) containing indium (In) is used as the translucent electrode 170. A part of the oxide containing In is preferable in that both light transmittance and conductivity are superior to other transparent conductive films. As the conductive oxide containing In, for example, ITO (indium tin oxide (In ₂ O ₃ —SnO ₂ )), IZO (indium zinc oxide (In ₂ O ₃ —ZnO)), IGO (indium gallium oxide (In _{2 O 3 -Ga 2 O 3)} ), ICO ( indium cerium oxide _{(In 2 O 3 -CeO 2)} ) , and the like. For example, fluorine may be added to these.

  These materials are deposited as a film by means known in this technical field and processed (patterned) by a known means to form a translucent electrode 170 provided with a through hole 180. In addition, after forming the translucent electrode 170, thermal annealing may be performed for the purpose of making the translucent electrode 170 transparent and reducing resistance.

As the translucent electrode 170, a crystallized structure may be used. In particular, ITO or IZO having high transparency and low resistance including In ₂ O ₃ crystal having a hexagonal crystal structure or a bixbite structure is used. It can be preferably used.
For example, when IZO containing hexagonal In ₂ O ₃ crystal is used as the translucent electrode 170, an amorphous IZO film having excellent etching properties is used to pattern into a specific shape provided with the through-hole 180. Further, by changing the structure from an amorphous state to a structure including a crystal by heat treatment or the like, the light-transmitting electrode 170 having a light transmission property superior to that of the amorphous IZO film can be processed.

Further, it is preferable to use a composition having the lowest specific resistance as the IZO film.
For example, the ZnO concentration in IZO is preferably 1% by mass to 20% by mass, and more preferably 5% by mass to 15% by mass. 10% by mass is particularly preferable. The film thickness of the IZO film is preferably in the range of 35 nm to 10000 nm (10 μm) at which low contact resistance and high light transmittance can be obtained. When the film thickness is thinner than 35 nm, the contact resistance increases. From the viewpoint of reduction in light transmittance and production cost, the thickness of the IZO film is preferably 1000 nm (1 μm) or less. Furthermore, 50 to 400 nm with low contact resistance and high light transmittance is optimal.
In order to make the current density uniform, the sheet resistance of the IZO film is desirably in the range of 5 to 50Ω / □. Furthermore, it is desirably 10 to 40Ω / □. When the sheet resistance is high, the forward voltage Vf increases and the light emission efficiency decreases. If the sheet resistance is too low, the current density in the vicinity of the second electrode 200 increases, and the efficiency of the semiconductor light emitting device 1 as a whole decreases.
The width of the through hole 180 is preferably in the range of 1 to 10 μm, and more preferably 2 to 5 μm. When the width is smaller than 1 μm, the variation in the width of the through hole 180 becomes large, and it becomes difficult to obtain a uniform current density. On the other hand, if it is larger than 10 μm, the current density differs between the region of the through hole 180 and the other region, the current supply to the light emitting layer 150 becomes uneven, and the light emission efficiency of the semiconductor light emitting element 1 as a whole decreases.
The patterning of the fine through-hole 180 in the IZO film is desirably performed before the heat treatment. By the heat treatment, the amorphous IZO film becomes a crystallized IZO film, which makes etching difficult compared to the amorphous IZO film. On the other hand, since the IZO film before the heat treatment is in an amorphous state, it can be easily and accurately patterned using an etching solution.

Patterning of the fine through hole 180 of the amorphous IZO film may be performed using a dry etching apparatus. At this time, Cl ₂ , SiCl ₄ , BCl _3, or the like can be used as an etching gas. IZO film in an amorphous state, for example, and was heat-treated in 500 ° C. to 1000 ° C., containing by controlling the conditions IZO film and containing an _In 2 _{O 3} crystal having a hexagonal crystal structure, an _In 2 _{O 3} crystal bixbyite structure An IZO film can be formed. Since an IZO film containing an In ₂ O ₃ crystal having a hexagonal crystal structure is difficult to etch as described above, it is preferable to perform heat treatment after the above patterning.

  In particular, as described above, an IZO film crystallized by heat treatment has better adhesion to the first electrode 190 and the p-type semiconductor layer 160 than an amorphous IZO film, and thus is effective in the embodiment of the present invention. It is.

<First electrode 190>
The first electrode 190 formed on the translucent electrode 170 and in ohmic contact with the translucent electrode 170 is, for example, a conventionally known Au, Al, Ti, V, Cr, Mn, Co, Zn, Ge, Zr, It is made of a material such as Nb, Mo, Ru, Ta, Ni, Pt, or Cu. The structure of the 1st electrode 190 is not specifically limited, A conventionally well-known structure is employable. It can be provided by means conventionally known in this technical field. In order to improve wire bond characteristics, it is desirable not to provide the through hole 180 in the translucent electrode 170 under the first electrode 190.
The thickness of the first electrode 190 is, for example, in the range of 100 nm to 2000 nm, and preferably in the range of 300 nm to 1000 nm.

<Second electrode 200>
The second electrode 200 is in ohmic contact with the n contact layer 140a of the n-type semiconductor layer 140. That is, the second electrode 200 removes part of the p-type semiconductor layer 160, the light emitting layer 150, and the n-type semiconductor layer 140 of the stacked semiconductor layer 100 to form a semiconductor layer exposed surface 140c of the n-contact layer 140a, It is provided on this semiconductor layer exposed surface 140c.
The second electrode 200 may have the same composition and structure as the first electrode 190. The second electrodes 200 having various compositions and structures are conventionally known, and these second electrodes 200 can be used without any limitation. It can be provided by means conventionally known in this technical field.

<Protective layer 210>
The protective layer 210 is formed on the surface of the translucent electrode 170 except for a part of the surfaces of the first electrode 190 and the second electrode 200 in order to suppress the entry of moisture and the like into the semiconductor light emitting element 1. The laminated semiconductor layer 100 is provided so as to cover the surface and side surfaces thereof.
In this embodiment mode, light from the light-emitting layer 150 is extracted through the protective layer 210, and thus the protective layer 210 is preferably excellent in transparency to light emitted from the light-emitting layer 150. In the present embodiment, it constitutes the protective layer 210 with SiO _2. However, it is not limited thereto for the material constituting the protective layer 210, in place of SiO _2, using _{TiO 2, Si 3 N 4,} SiO 2 -Al 2 O 3, Al 2 O 3, AlN , etc. be able to.

(Method for Manufacturing Semiconductor Light-Emitting Element 1)
Next, an example of a method for manufacturing the semiconductor light emitting element 1 according to the present embodiment will be described.
First, a substrate 110 such as a sapphire substrate is prepared and subjected to pretreatment. The pretreatment can be performed by, for example, a method in which the substrate 110 is placed in a chamber of a sputtering apparatus and sputtering is performed before the intermediate layer 120 is formed. The intermediate layer 120 is preferably formed by sputtering, but can also be formed by MOCVD.

After the formation of the intermediate layer 120, a single crystal base layer 130 is formed on the intermediate layer 120. The underlayer 130 may be formed by a known MOCVD method.
After the foundation layer 130 is formed, the n-type semiconductor layer 140 is formed by laminating the n-contact layer 140a and the n-cladding layer 140b on the foundation layer 130. The n contact layer 140a and the n clad layer 140b may be formed by a sputtering method or an MOCVD method.

  The light emitting layer 150 may be formed by a known MOCVD method. Specifically, the barrier layers 150a and the well layers 150b may be alternately and repeatedly stacked, and the barrier layers 150a may be stacked in the order in which the barrier layers 150a are disposed on the n-type semiconductor layer 140 side and the p-type semiconductor layer 160 side. .

  The p-type semiconductor layer 160 may be formed by a known MOCVD method. Specifically, a p-cladding layer 160a and a p-contact layer 160b may be sequentially stacked on the light emitting layer 150.

A film (IZO film, ITO film, etc.) constituting the translucent electrode 170 is deposited on the p-type semiconductor layer 160 by a known means such as a vapor deposition method or a sputtering method, patterned by a known means, and a through hole is formed. A translucent electrode 170 having 180 is formed. Note that the translucent electrode 170 provided with the through hole 180 can be formed by one etching. As the etching, a dry etching method excellent in fine processing is desirable.
Then, a part of the laminated semiconductor layer 100 is removed by a known means, a part of the n contact layer 140a is exposed, and a semiconductor layer exposed surface 140c is formed.

Then, as described above, the first electrode 190 is formed on the translucent electrode 170, and the second electrode 200 is formed on the semiconductor layer exposed surface 140c.
Finally, except for a part (opening) of each surface of the first electrode 190 and the second electrode 200, SiO _{2 is formed} so as to cover the surface of the translucent electrode 170, the surface and the side surface of the laminated semiconductor layer 100. A protective layer 210 made of is formed.
Thus, the semiconductor light emitting element 1 is obtained.

  The semiconductor light emitting device 1 thus obtained may be heat-treated at a temperature in the range of 150 ° C. to 600 ° C., more preferably 200 ° C. to 500 ° C., for example, in an inert atmosphere such as nitrogen. This heat treatment improves the adhesion between the translucent electrode 170 and the first electrode 190, improves the adhesion between the second electrode 200 and the semiconductor layer exposed surface 140c, improves the transmissivity of the translucent electrode 170, low This is done for the purpose of reducing efficiency. This heat treatment may be performed before the protective layer 210 is formed.

(Through hole 180 provided in translucent electrode 170)
Next, the through hole 180 provided in the translucent electrode 170 will be described.
In a state where the through hole 180 is not provided, the light emission efficiency of the light emitting layer 150 is reduced in a region where current concentration occurs. Luminous efficiency is improved by dispersing the concentrated current in the light emitting layer 150 through the through holes 180. That is, by optimizing the aperture ratio and arrangement of the through-holes 180, current flow can be controlled, current can be supplied uniformly to the light emitting layer 150, and the light emission efficiency of the light emitting layer 150 can be increased.
The translucent electrode 170 is provided so as to transmit about 90% or more of the light emitted from the light emitting layer 150, but absorbs a part of the light because the transmittance is not 100%. For this reason, it is desirable that the film thickness of the translucent electrode 170 is small. Furthermore, when the translucent electrode 170 is provided with a through hole 180 to expose the surface of the p-type semiconductor layer 160, the translucent electrode 170 absorbs the film. This also has the effect of suppressing the light to be emitted and increasing the amount of light emitted from the semiconductor light emitting element 1 (radiant energy).
That is, if the light-transmitting electrode 170 is provided with many through-holes 180, light emitted from the p-type semiconductor layer 160 whose surface is exposed is not absorbed by the light-transmitting electrode 170, and thus the amount of light emitted from the semiconductor light emitting element 1 is increased. To increase.
However, if a large number of through-holes 180 are provided in the translucent electrode 170, the contact area between the translucent electrode 170 and the p-type semiconductor layer 160 decreases, and the contact resistance increases. For this reason, the forward voltage Vf of the semiconductor light emitting element 1 increases. And the drive voltage of the semiconductor light emitting element 1 rises, and the light emission efficiency of the semiconductor light emitting element 1 falls.

In the present embodiment, as shown in FIG. 1, the through-hole 180 has a different ratio (aperture ratio) at which the surface of the p-type semiconductor layer 160 is exposed in a plurality of different regions on the surface of the translucent electrode 170. It is provided as follows. The aperture ratio 1 in the region C close to the first electrode 190, the aperture ratio 2 in the region A close to the second electrode 200, and the aperture ratio 3 in the region B (intermediate region) between the region A and the region C are as follows: > Opening ratio 3> Opening ratio 2 The aperture ratio may change continuously from the region A to the region C.
The rate at which the surface of the p-type semiconductor layer 160 is exposed is set as follows. That is, when the through-hole 180 is not provided on the surface of the translucent electrode 170, the region where the amount of light emitted per unit area is large reduces the rate at which the surface of the p-type semiconductor layer 160 is exposed by the through-hole 180. In the region where the amount of light emitted per unit area is small, the ratio at which the surface of the p-type semiconductor layer 160 is exposed by the through hole 180 is increased. In other words, the current density supplied to the light emitting layer 150 is made uniform by changing the aperture ratio in accordance with the direction of the electric field, thereby improving the light emission efficiency. It is desirable to change the aperture ratio along a line connecting the first electrode 190 and the second electrode 200.

In FIG. 1, a region A is a region where the amount of light per unit area is large when the through hole 180 is not provided, and a region C is a region where the amount of light per unit area is small when the through hole 180 is not provided.
FIG. 3 is a schematic cross-sectional view of the semiconductor light emitting device 1 when the translucent electrode 170 is not provided with the through hole 180.
The region A having a large amount of light per unit area is a bright region when viewed from the translucent electrode 170 side, and is a region where a large amount of current flows through the light emitting layer 150 (high current density). That is, as indicated by Ia in FIG. 3, a large amount of current flowing through the semiconductor light emitting element 1 flows in the portion of the light emitting layer 150 corresponding to the region A of the translucent electrode 170. On the other hand, the region C having a small amount of light per unit area is a dark region when viewed from the translucent electrode 170 side, and the current flowing through the light emitting layer 150 is low (current density) as indicated by Ic in FIG. Is low). The current (Ib) flowing through the light emitting layer 150 corresponding to the region B of the translucent electrode 170 is the current Ia flowing through the light emitting layer 150 corresponding to the region A and the current Ic flowing through the light emitting layer 150 corresponding to the region C. The current is between. Note that the currents Ia, Ib, and Ic are schematically shown, and in the actual semiconductor light emitting device 1, the current flows in the light emitting layer 150.
The region A having a large light amount per unit area is a region close to the second electrode 200, and the region C having a small light amount per unit area is a region close to the first electrode 190. As described above, the distribution of the amount of light per unit area of the translucent electrode 170 is such that the current flowing from the first electrode 190 to the second electrode 200 between the first electrode 190 and the second electrode 200 is the semiconductor light emitting device 1. It is determined by the distribution (current distribution).

When the through-holes 180 are uniformly provided in the translucent electrode 170, the contact resistance between the translucent electrode 170 and the p-type semiconductor layer 160 increases uniformly. The influence of the increase in the contact resistance is noticeable in the region A where the current density is high, and the forward voltage Vf of the semiconductor light emitting element 1 becomes high.
On the other hand, in the present embodiment, in the region A where the current density is high, the rate at which the surface of the p-type semiconductor layer 160 is exposed is reduced, and the contact resistance between the translucent electrode 170 and the p-type semiconductor layer 160 is increased. Is suppressed. On the other hand, in the region C where the current density is low, the ratio at which the surface of the p-type semiconductor layer 160 is exposed is increased, and priority is given to extraction of light emitted from the light emitting layer 150 rather than suppressing increase in contact resistance. Yes. Thereby, the emitted light amount Po of the semiconductor light emitting element 1 is increased, and the increase of the forward voltage Vf is suppressed.

The relationship between the through hole 180 of the translucent electrode 170 described above and the forward voltage Vf will be described with an experimental example.
FIG. 4 is a diagram for explaining an experimental example in which the relationship between the region in which the through-hole 180 is provided in the translucent electrode 170, the emitted light amount Po (mW) of the semiconductor light emitting element 1, and the forward voltage Vf (V). . Here, the semiconductor light emitting device 1 having the same configuration as that shown in FIG. 1 is used except for the portion of the through hole 180. The through hole 180 is provided only in one of the regions A and C. The forward current If is 20 mA.
The diameter d of the through hole 180 is 3 μm. In FIG. 4, one side length pa (μm) of the equilateral triangle in which the through holes 180 are arranged in the region A, and one side length pc (μm) of the equilateral triangle in which the through holes 180 are arranged in the region C (pa, −, pc). “-” Indicates that the through hole 180 is not provided. In FIG. 4, the side lengths pa and pc are all 6 μm. Therefore, for example, the case where the through hole 180 is provided only in the region A is denoted as #A (6,-,-).

  And when the through-hole 180 is not provided in the translucent electrode 170 (# 0 of FIG. 4), the area | region A is the brightest (the light quantity per unit area is large), and it becomes dark as it goes to the area | regions B and C ( The amount of light per unit area is small). That is, the current density in the portion of the light emitting layer 150 corresponding to the region A is high, and the current density is lowered as going to the regions B and C.

As shown in FIG. 4, #A (6,-,-) as compared to the case where the through hole 180 indicated by # 0 (-,-,-) is not provided (Po = 20.0 mW, Vf = 3.08 V). In any case of (Po = 21.5 mW, Vf = 3.10 V), #C (−, −, 6) (Po = 21.0 mW, Vf = 3.06 V), the emitted light amount Po (mW) increases. . The forward voltage Vf (V) is obtained when the through hole 180 is provided in the region A (#A) and when the through hole 180 is provided in the region C (#C) and when the through hole 180 is not provided (# 0).
In FIG. 4, the case where the side length p (pa, pb, pc) is 6 μm is shown, but the case where the length is 9 μm and 12 μm is the same.

  That is, also in the experimental example, by reducing the ratio of exposing the surface of the p-type semiconductor layer 160 in the region A where the amount of light per unit area is large and the current flowing through the light emitting layer 150 is large (the current density is high), It shows that an increase in voltage Vf can be suppressed.

FIG. 5 is a diagram for explaining another example of the through hole 180 in the translucent electrode 170.
Here, it is assumed that the region close to the second electrode 200 has a large light amount per unit area and a large amount of current flows through the light emitting layer 150 (the current density is high), and the region close to the first electrode 190 corresponds to the unit area. , And the current flowing through the light emitting layer 150 is small (the current density is low).
In FIG. 5A, the surface of the translucent electrode 170 is divided into two regions (regions A and B). In addition, a through hole is not provided in the region A close to the second electrode 200 where the amount of light per unit area is large, the current flowing through the light emitting layer 150 is large (the current density is high). On the other hand, a through hole 180 is provided in a region B close to the first electrode 190 where the amount of light per unit area is small, the current flowing through the light emitting layer 150 is small (the current density is low).
Even in such a case, the emitted light amount Po of the semiconductor light emitting element 1 can be increased and the increase of the forward voltage Vf can be suppressed.

In FIG. 5B, the surface of the translucent electrode 170 is divided into two regions (regions A and B). The amount of light per unit area is large, the current flowing through the light emitting layer 150 is large (the current density is high), and the ratio of the surface of the p-type semiconductor layer 160 exposed in the region A adjacent to the second electrode 200 is small. The through-hole 180 is provided so that it may become. On the other hand, the amount of light per unit area is small, the current flowing through the light emitting layer 150 is small (the current density is low), and in the region B close to the first electrode 190, the ratio of the surface of the p-type semiconductor layer 160 exposed is large. The through-hole 180 is provided so that it may become.
Even in such a case, the emitted light amount Po of the semiconductor light emitting element 1 can be increased and the increase of the forward voltage Vf can be suppressed.
Note that the region A and the region B in FIGS. 5A and 5B are not necessarily provided by dividing the surface of the translucent electrode 170 into two, and may be set as appropriate.

In FIG. 5C, the surface of the translucent electrode 170 is divided into three regions (regions A, B, and C) as in FIG. In addition, the through hole 180 is not provided in the region A close to the second electrode 200 where the amount of light per unit area is large, the current flowing through the light emitting layer 150 is large (the current density is high). On the other hand, the amount of light per unit area is small, the current flowing through the light emitting layer 150 is small (the current density is low), and the region C adjacent to the first electrode 190 has a high ratio of exposing the surface of the p-type semiconductor layer 160. The through-hole 180 is provided so that it may become. A through hole 180 is provided in a region B between the region A and the region C so that the ratio of the surface of the p-type semiconductor layer 160 exposed is smaller than that in the region C.
Even in such a case, the emitted light amount Po of the semiconductor light emitting element 1 can be increased and the increase of the forward voltage Vf can be suppressed.
Note that the regions A, B, and C are not necessarily provided by dividing the surface of the translucent electrode 170 into three, and may be set as appropriate.

  Further, in FIG. 5, the side length p of the equilateral triangle in which the through hole 180 is arranged is changed to change the exposed ratio of the surface of the p-type semiconductor layer 160. The diameter d of the through hole 180 may be changed to change the exposed ratio of the surface of the p-type semiconductor layer 160. In this case, the diameter d of the through-hole 180 may be set so that the current density flowing in the p-type semiconductor layer 160 whose surface is exposed by the through-hole 180 does not decrease and the emitted light amount Po of the semiconductor light emitting element 1 does not decrease. .

  Further, although not shown, the region close to the first electrode 190 has a large light amount per unit area, and a large amount of current flows through the light emitting layer 150 (the current density is high), and the region close to the second electrode 200 is When the amount of light per unit area is small and the current flowing through the light emitting layer 150 is small (the current density is low), the ratio at which the p-type semiconductor layer 160 is exposed by the through holes 180 shown in FIGS. What is necessary is just to set reverse with respect to an area | region.

  Note that whether the region where the amount of light per unit area is large is the region close to the first electrode 190 or the region close to the second electrode 200 depends on the layer resistance of the n-type semiconductor layer 140 and the p-type semiconductor. This is considered to be determined by the relationship between the layer 160 and the layer resistance of the transparent electrode 170 and the layer resistance. When the layer resistance of the n-type semiconductor layer 140 is larger than the layer resistance of the stacked portion of the p-type semiconductor layer 160 and the translucent electrode 170, as shown in the present embodiment, the portion close to the second electrode 200 is formed. Current concentrates. On the contrary, when the layer resistance of the n-type semiconductor layer 140 is smaller than the layer resistance of the stacked portion of the p-type semiconductor layer 160 and the translucent electrode 170, the current concentrates in a portion close to the first electrode 190.

Hereinafter, an example explains.
In Table 1, as a configuration and evaluation result of the through-hole 180 provided in the translucent electrode 170 of each of the semiconductor light emitting devices 1 of Examples 1 to 4 and Comparative Examples 1 and 2, a forward current If was passed by 20 mA. The emission light amount Po (mW) and the forward voltage Vf (V) at the time are shown. The emission wavelength at this time was 450 nm.
Each of the semiconductor light emitting devices 1 of Examples 1 to 4 and Comparative Examples 1 and 2 has the same configuration as shown in FIG. 1 except for the through hole 180 provided in the translucent electrode 170. .
In Examples 1 to 4, as shown in FIG. 1, the translucent electrode 170 is divided into regions A, B, and C, and each region has a side length p ( Through holes 180 are provided at pa, pb, pc). The diameter d of the through hole 180 is 3 μm. In each of Examples 1 to 4, the ratio of exposing the surface of the p-type semiconductor layer 160 is higher in the region C than in the region A. The ratio (opening ratio) at which the p-type semiconductor layer 160 is exposed is 20% when the side length p (pa, pb, pc) of the equilateral triangle in which the through-hole 180 is disposed is 6 μm, and is 9% when 9 μm. Is 10%, and 5% for 12 μm. In Table 1, it shows in ().
On the other hand, in Comparative Example 1, the translucent electrode 170 is not provided with the through hole 180. In this case, the amount of light per unit area of the region close to the second electrode 200 (region A in Examples 1 to 4) is large, and the region close to the first electrode 190 (region C in Examples 1 to 4). The amount of light per unit area is small.
In Comparative Example 2, the side length p (pa, pb, pc) of the equilateral triangle is 6 μm, and the through-holes 180 are uniformly provided in the translucent electrode 170.

FIG. 6 illustrates the relationship between the emitted light amount Po (mW) and the forward voltage Vf (V) of the semiconductor light emitting devices 1 of Examples 1 to 4 and Comparative Examples 1 and 2 shown in Table 1 as the evaluation results. FIG.
As can be seen from Table 1 and FIG. 6, in Examples 1 to 4, the emitted light amount Po (mW) is 23.8 mW to 22.1 mW, and 20 of Comparative Example 1 in which the through-hole 180 is not provided in the translucent electrode 170. Both are increasing compared to 0.0 mW.
On the other hand, in the comparative example 2 in which the through-holes 180 are uniformly provided in the translucent electrode 170, the emitted light amount Po (mW) is 21.1 mW, and in the comparative example 1 in which the through-holes 180 are not provided in the translucent electrode 170. Compared to 20.0 mW. However, the forward voltage Vf (V) of Comparative Example 2 is 3.14V, which is significantly higher than 3.07V of Comparative Example 1.
On the other hand, in Examples 1 to 4, the forward voltage Vf (V) is maintained at 3.06 V to 3.09 V, which is close to 3.07 V of Comparative Example 1, and the order by providing the through hole 180 is the order. An increase in the directional voltage Vf (V) is suppressed.

  As described above, the surface of the translucent electrode 170 is divided into a plurality of regions, and the ratio of exposure of the surface of the p-type semiconductor layer 160 is changed, thereby increasing the amount of emitted light Po from the semiconductor light emitting element 1. The forward voltage Vf can be suppressed from increasing.

DESCRIPTION OF SYMBOLS 1 ... Semiconductor light emitting element, 100 ... Laminated semiconductor layer, 110 ... Substrate, 120 ... Intermediate layer, 130 ... Underlayer, 140 ... N-type semiconductor layer, 150 ... Light emitting layer, 160 ... P-type semiconductor layer, 170 ... Translucent Electrode 180 ... through hole 190 ... first electrode 200 ... second electrode 210 ... protective layer

Claims (17)

A first semiconductor layer of a III-V semiconductor having a first conductivity type;
A light-emitting layer of a III-V group semiconductor that is provided on the first semiconductor layer in contact with the first semiconductor layer and emits light when energized;
A second semiconductor layer of a III-V group semiconductor provided on the light emitting layer in contact with the light emitting layer and having a second conductivity type opposite to the first conductivity type;
A translucent electrode provided on and in contact with the second semiconductor layer on the second semiconductor layer and having transparency to the light emitted from the light emitting layer;
A part of the translucent electrode is provided in contact with the translucent electrode, connected to the first semiconductor layer and a first electrode serving as one terminal for energizing the light emitting layer, and A second electrode provided on the same side as the first electrode and serving as the other terminal for energizing the light emitting layer;
The translucent electrode is provided with a plurality of through holes penetrating in a thickness direction in a region adjacent to either the first electrode or the second electrode so that the surface of the second semiconductor layer is exposed. A semiconductor light emitting device.   A ratio (aperture ratio) at which the surface of the second semiconductor layer is exposed in a region where the plurality of through holes adjacent to either the first electrode or the second electrode is provided is 10% to 30%. The semiconductor light emitting element according to claim 1.   The translucent electrode further includes a plurality of through-holes penetrating in a thickness direction so that a surface of the second semiconductor layer is exposed in a region close to either the first electrode or the second electrode. The ratio (opening ratio) at which the surface of the second semiconductor layer is exposed in a region adjacent to the other is smaller than that in the region adjacent to the one. Semiconductor light emitting device.   4. The semiconductor light emitting element according to claim 3, wherein the aperture ratio in a region close to the other of the first electrode and the second electrode is 15% or less. 5.   The translucent electrode penetrates in a thickness direction so that a surface of the second semiconductor layer is exposed in an intermediate region between a region close to the first electrode and a region close to the second electrode. The semiconductor light-emitting element according to claim 3, further comprising a plurality of through holes.   6. The semiconductor light emitting device according to claim 5, wherein an aperture ratio of the plurality of through holes provided in the translucent electrode changes along a line connecting the first electrode and the second electrode. element.   The planar shape of the semiconductor light emitting device is a rectangle whose long side is twice or more the length of the short side, and the first electrode and the second electrode are at both ends in the longitudinal direction of the rectangle. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is provided respectively.   The semiconductor light emitting element according to claim 1, wherein the aperture ratio is set according to a density or size of the plurality of through holes.   9. The semiconductor light emitting element according to claim 1, wherein the translucent electrode is made of an oxide conductive material.   10. The semiconductor light emitting device according to claim 1, wherein the first conductivity type is an n-type and the second conductivity type is a p-type. 10. The first semiconductor layer includes a contact layer connected to the second electrode and a cladding layer in contact with the light emitting layer, and a product of the impurity concentration of the contact layer and the thickness of the contact layer is 1 × 10 ¹⁴ cm ^−. 11. The semiconductor light emitting element according to claim 10, which is ² to 1 × 10 ¹⁶ cm ⁻² , and the sheet resistance of the translucent electrode is 5Ω / □ to 50Ω / □.   The semiconductor light emitting device according to claim 11, wherein an aperture ratio of a region adjacent to the first electrode is larger than an aperture ratio of a region adjacent to the second electrode.   The aperture ratio 1 of the area close to the first electrode is larger than the aperture ratio 2 of the area close to the second electrode, and an intermediate area between the area close to the first electrode and the area close to the second electrode 13. The semiconductor light emitting element according to claim 12, wherein the aperture ratio 3 is a value between an aperture ratio of 1 and an aperture ratio of 2.   The second semiconductor layer includes a contact layer in contact with the translucent electrode and a cladding layer in contact with the light emitting layer, and a portion of the contact layer in contact with the translucent electrode is in the cladding layer of the contact layer. 14. The semiconductor light emitting element according to claim 10, wherein the amount of Mg added is larger than that of the contacting portion.   The semiconductor light emitting element according to claim 1, wherein the group III-V semiconductor is a group III nitride semiconductor.   The semiconductor light emitting device according to claim 1, wherein a width of the through hole is 1 μm to 10 μm.   17. The semiconductor light emitting device according to claim 1, wherein the translucent electrode has a thickness of 50 nm to 400 nm.

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