JPH10163531A - Light-emitting diode having electrode at periphery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the reduction of the light-emitting output and lower the forward voltage. SOLUTION: A light-emitting diode having an electrode at the periphery comprises a nitride semiconductor layer, including a light-emitting layer on a square flat substrate, and a pair of p and n-electrodes 5, 4, formed on the surface on which the nitride semiconductor layer, is formed. The diode has a square flat shape, as seen from the electrodes disposed at the corners of the diode along its diagonal line. One of the paired p and n-electrodes 5, 4 is connected to a peripheral electrode 7 disposed at the periphery of the diode, and the other is connected to a transparent electrode 6 disposed inside the peripheral electrode 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting diode, and more particularly, to a light emitting diode capable of reducing an operating voltage. In this specification, "light emitting diode" is used in a broad sense including a laser diode.

[0002]

2. Description of the Related Art FIG. 1 is a plan view of a light-emitting diode having a nitride semiconductor layer provided with a p-electrode and an n-electrode on the same surface of an insulating substrate, and FIG. The light emitting diode of this figure has an n-type nitride semiconductor layer 2
Type nitride semiconductor layer 3. The p-type nitride semiconductor layer 3 is provided in a portion excluding a corner where the n-electrode 4 is provided,
An n-electrode 4 is provided at a corner where no p-type nitride semiconductor layer 3 exists. The transparent electrode 6 is laminated on the surface of the p-type nitride semiconductor layer 3, and the p-electrode 5 is connected to a corner of the transparent electrode 6.

The light emitting diode shown in FIG.
Can be diffused by the transparent electrode 6 and flow over the entire surface of the p-type nitride semiconductor layer 3. Therefore, p
There is a feature that light emitted at the n-junction can be efficiently extracted to the outside from the transparent electrode 6. However, in a light emitting diode using a light emitting layer as a nitride semiconductor layer, a voltage applied to a p electrode and an n electrode to flow a specified current, that is, a forward voltage Vf is high. The red light emitting diode has a forward voltage Vf of approximately 2 V at which a rated current of 20 mA flows. On the other hand, in the light emitting diode of the nitride semiconductor layer, the forward voltage Vf for flowing the same current is about 3.5V. Forward voltage V
High f may, for example, severely limit battery-powered applications. For this reason, it is desired that the light emitting diode of the nitride semiconductor layer have the forward voltage Vf as low as possible.

[0004] The forward voltage Vf of a light emitting diode can be reduced by a structure in which electrodes are provided along the outer periphery, as described in, for example, JP-A-54-6787. As shown in FIG. 3, the light-emitting diode described in this publication has a pair of electrodes disposed on the entire outer periphery and the center thereof. In the light emitting diode having this electrode structure, the insulating substrate 1 has a square planar shape, and a ring-shaped peripheral electrode 7 is provided on one surface thereof, and the other electrode 8 is provided at the center of the peripheral electrode 7.

[0005]

In the light emitting diode of this structure, the forward voltage Vf can be lowered, but the insulating substrate 1
Since the four corners cannot emit light, there is a disadvantage that the light emission output is reduced as a whole. Further, since the peripheral electrode 7 is formed in a narrow ring shape, there is a disadvantage that wire bonds cannot be reliably connected. Furthermore, if the center electrode 8 is enlarged for wire bonding, there is a disadvantage that the light emitting area is reduced and the light emitting output as a whole is reduced.

That is, as shown in FIG. 1, a light emitting diode in which electrodes to be wire-bonded are arranged diagonally is
Although the light emitting area can be widened to increase the light emitting output, the forward voltage Vf increases. As shown in FIG. 3, when electrodes are provided at the center and the periphery thereof, the forward voltage Vf can be reduced, but there is a disadvantage that the light emitting region is narrowed and the light emitting output is weakened.

[0007] The present invention has been developed for the purpose of eliminating these disadvantages. An important object of the present invention is
It is an object of the present invention to provide a light emitting diode in which a decrease in light emission output, which is a characteristic contradictory to each other, can be minimized and the forward voltage Vf can be reduced.

[0008]

According to a first aspect of the present invention, there is provided a light emitting diode having the following configuration to achieve the above object. In the light emitting diode, a nitride semiconductor layer including a light emitting layer is laminated on a substrate 1 having a square planar shape, and a p electrode 5 is provided on the same surface side of the nitride semiconductor layer.
And a pair of electrodes consisting of an n-electrode 4.

Further, the light-emitting diode of the present invention has a square planar shape when viewed from the electrode side, and the p-electrode 5 and the n-electrode 4 are arranged diagonally at the corners of the square light-emitting diode. ing. A pair of electrodes composed of a p-electrode 5 and an n-electrode 4 has a peripheral electrode 7 connected to one electrode and a transparent electrode 6 connected to the other electrode. The peripheral electrode 7 is provided along the outer peripheral edge of the light emitting diode, and the transparent electrode 6 is provided inside the peripheral electrode 7.

FIG. 4 is a plan view of the light emitting diode according to the first embodiment, and FIG. 5 is a sectional view of the light emitting diode. The light emitting diodes shown in these figures are located at the corners of a square planar shape,
The p-electrode 5 and the n-electrode 4 for diagonal wire bonding are provided. A peripheral electrode 7 is connected to the n-electrode 4,
A transparent electrode 6 is connected to the p-electrode 5. Peripheral electrode 7
Is provided on the outer peripheral edge of the square light emitting diode, and the transparent electrode 6 is disposed inside the peripheral electrode 7.

In the light-emitting diode having this electrode structure, the area of the p-electrode 5 and the n-electrode 4 can be increased so that wire bonding can be performed reliably. In addition, there is a feature that light emitted from the light emitting layer can be efficiently emitted from the transparent electrode 6 to the outside. Further, since the peripheral electrode 7 is provided on the entire circumference, there is a feature that the forward voltage Vf can be reduced.

However, the light emitting diode having this structure is similar to that of FIG.
As compared with the light emitting diode shown in (1), there is a disadvantage that the area of the p-type nitride semiconductor layer 3 and the transparent electrode 6 is reduced, and the light emission output as a whole is reduced. That is, as shown in FIG. 1, when the area of the p-type nitride semiconductor layer 3 and the transparent electrode 6 is increased, the light emission output is increased, but the forward voltage Vf is increased, and as shown in FIG. When the electrode 7 is provided, the forward voltage Vf decreases, but there is a disadvantage that the light emission output decreases.

Further, a light emitting diode which solves this drawback is the light emitting diode according to the second aspect. In the light emitting diode according to the second aspect, in order to achieve the above-mentioned object, the peripheral electrode has a unique configuration as shown in FIG. The peripheral electrode 7 is notched at a corner where an electrode electrically connected to the transparent electrode 6 is provided, and is provided at an outer peripheral portion excluding the corner where the electrode connected to the transparent electrode 6 is provided.

Further, in the light-emitting diode according to the third aspect of the present invention, the peripheral electrode 7 is connected to the n-electrode 4 and the transparent electrode 6 is connected to the p-electrode 5.

In the light emitting diode according to a fourth aspect of the present invention, the shapes of the n-electrode 4 and the p-electrode 5 are different from each other.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify light emitting diodes for embodying the technical idea of the present invention, and the present invention does not specify the light emitting diodes as follows.

Further, in this specification, in order to make it easy to understand the claims, the numbers corresponding to the members shown in the embodiments will be referred to as "claims" and "claims". In the column of “means”. However, the members described in the claims are not limited to the members of the embodiments.

FIGS. 4 to 7 show a light emitting diode according to an embodiment of the present invention. In the light emitting diodes shown in these figures, a nitride semiconductor layer including a light emitting layer is stacked on an insulating substrate 1 having a square planar shape, and the same side of the nitride semiconductor layer as shown in FIGS. , A pair of electrodes including a p-electrode 5 and an n-electrode 4 is provided on the upper surface. The p electrode 5 and the n electrode 4 have different plane shapes from each other. The p-electrode 5 has a square shape, and the n-electrode 4 has a shape in which a lower right corner in the figure is curved.

Further, the light emitting diode shown in the figure has a square planar shape as shown in FIGS. 4 and 6 when viewed from the upper surface on the electrode side. Also, the p electrode 5 and the n electrode 4 are
It is located diagonally and located at the corner of a square light emitting diode. In the illustrated light emitting diode, the n-electrode 4 is disposed at the upper left corner, and the p-electrode 5 is disposed at the lower right corner.

The nitride semiconductor layer including the light emitting layer laminated on the substrate 1 includes an n-type nitride semiconductor layer 2 laminated on the substrate 1 with a buffer layer 9 interposed between the n-type nitride semiconductor layer 2 and the n-type nitride semiconductor layer 2. And multiple semiconductor layers 10 to be stacked. The buffer layer 9 and the n-type nitride semiconductor layer 2 are provided on the entire surface of the square planar insulating substrate 1. Therefore, these layers have a square planar shape having the same outer shape as the substrate 1.

The multiple semiconductor layer 10 is provided in a portion other than a plane on which the n-electrode 4 and the peripheral electrode 7 are provided. further,
The multiple semiconductor layers 10 have n
The electrode 4 and the peripheral electrode 7 are laminated with a certain distance therebetween. The light emitting diode of FIG. 6 has an n-electrode 4 at the upper left corner and a peripheral electrode 7 at the outer peripheral edge excluding the lower right corner. For this reason, the multiple semiconductor layer 10 is laminated on a portion excluding the plane of the upper left corner where the n-electrode 4 is provided and the peripheral portion where the peripheral electrode 7 is provided. Further, in the light emitting diode shown in FIG. 7, the multiple semiconductor layer 10 is formed to have an outer shape located slightly inside the outer peripheral edge of the n-type nitride semiconductor layer 2, and the outer peripheral surface is covered with a protective film 11 of SiO _2. Coated.

A pair of electrodes consisting of a p-electrode 5 and an n-electrode 4 connects a peripheral electrode 7 to one n-electrode 4. A transparent electrode 6 is connected to a p-electrode 5 serving as the other electrode. The peripheral electrode 7 is provided along the outer peripheral edge of the light emitting diode, and the transparent electrode 6 is provided inside the peripheral electrode 7. In the light emitting diode shown in the figure, the peripheral electrode 7 is provided along the outer peripheral edge of the n-type nitride semiconductor layer 2,
The shape is not such that the outer periphery of the n-electrode 4 and the n-type nitride semiconductor layer 2 exactly match. The outer edge of the n-electrode 4 is n
It is arranged so as to substantially coincide with the outside of the type nitride semiconductor layer 2 but to be located slightly inside. In addition to the peripheral electrode 7, the n-electrode 4 and the p-electrode 5 are also arranged slightly inside the outer peripheral edge of the light emitting diode.

Further, the light-emitting diode of FIG. 4 has the peripheral electrode 7 arranged on the entire periphery, but the light-emitting diode of FIG. 6 does not have the peripheral electrode 7 on the entire periphery. The peripheral electrode 7 is cut off at the lower right corner where the p electrode 5 is provided, and is provided on the outer peripheral portion excluding the corner where the p electrode 5 is provided. The light emitting diode of FIG. 6 is provided with a p-electrode 5 at the lower right corner, an n-electrode 4 at the upper left corner, and a periphery along the periphery except for the corner where the p-electrode 5 and the n-electrode 4 are provided. An electrode 7 is provided. The peripheral electrode 7 is provided separately from the p electrode 5 and connected to the n electrode 4 so as not to contact the p electrode 5.

The n-electrode 4 and the peripheral electrode 7 are provided by depositing Al and Ti or Al and W to a thickness of 2 μm on the n-type nitride semiconductor layer 2.

The transparent electrode 6 is provided on the outermost surface of the multiple semiconductor layer 10 by depositing, for example, Pd (palladium) to a thickness of 30 angstroms. After the deposition, the Pd film shows a light-transmitting property. The transparent electrode 6 is formed on almost the entire surface of the multiple semiconductor layer 10 to obtain a good ohmic contact and spread the current uniformly over the entire multiple semiconductor layer 10. After the transparent electrode 6 is provided, a p-electrode 5 containing Au and Ni is formed in a thickness of 2 μm at the lower right corner of the transparent electrode 6. The n-electrode 4 is provided by evaporating the transparent electrode 6 and the p-electrode 5 and then evaporating the exposed n-type nitride semiconductor layer 2. Finally, the transparent electrode 6, the p-electrode 5, and the n-electrode 4 are heat-treated at 400 ° C. or more by an annealing device to be alloyed.

The transparent electrode 6 includes platinum (Pt), rhodium (Rh),
At least one metal selected from the group consisting of ruthenium (Ru), osmium (Os), iridium (Ir), nickel (Ni), and gold (Au) can be included.
The transparent electrode 6 in which these elements are added to Pd can maintain the translucency of the electrode without impairing the ohmic property with the multiple semiconductor layers 10. The electrode structure after the addition may be a laminated structure in which thin films are laminated, may be in a state where the laminated structure is thermally annealed and alloyed, or may be in an alloy state from the beginning. Above all, a transparent electrode in which Au is added to Pd is very preferable because it has good adhesion to a bonding pad electrode containing Au. Transparent electrode 6
Shows a preferable translucency when the film thickness is 50 nm or less, more preferably 20 nm or less.

The n-type nitride semiconductor layer 2 on which the multiple semiconductor layers 10 are stacked is an n-type clad layer and an n-type contact layer. The multiple semiconductor layer 10 laminated on this layer includes an active layer 10A of a nitride semiconductor layer having a single quantum well or a multiple quantum well structure, a p-type cladding layer 10B of a p-type nitride semiconductor layer, and a p-type A GaN p-type contact layer 10C is formed.
% Or more) of the transparent electrode 6.

The substrate 1 is made of sapphire (Al ₂ O ₃ , A surface,
(Including the R plane and the C plane). However, in addition to the sapphire substrate, spinel (MgAl ₂ O ₄ ), SiC (6H, 4
H, 3C), ZnS, Zn0, GaAs, GaN
For example, any material that can grow a nitride semiconductor can be used, but sapphire is often used.

The buffer layer 9 is laminated on the entire surface of the substrate 1. The buffer layer 9 is stacked between the substrate 1 and the nitride semiconductor layer to improve the crystallinity of the nitride semiconductor layer. The buffer layer 9 is made of, for example, GaN, AlN, GaAlN, Zn.
O and the like. The buffer layer 9 has a thickness of typically 5 nm in order to reduce lattice mismatch between the insulating substrate 1 and the nitride semiconductor layer.
It is grown to a thickness of about 0.5 μm. When a substrate having a lattice constant close to that of the nitride semiconductor layer or a substrate having the same lattice constant is used as the insulating substrate, the buffer layer is not necessarily required. This is because a nitride semiconductor layer with few lattice defects can be grown on the surface of the insulating substrate.

An n-type clad layer and an n-type contact layer are also grown on the entire surface of the substrate 1. This layer is composed of In _a Al _b Ga
_This is a nitride semiconductor layer represented by _1-abN (0 ≦ a, 0 ≦ b, a + b ≦ 1). This layer is preferably GaN,
In _a Ga _1-a N with an a value of 0.5 or less, or Al _b Ga _lb N with a b value of 0.5 or less. Although the thickness of the n-type cladding layer is not particularly limited, it is preferable that the n-type cladding layer is grown to a thickness of about 0.5 μm to 5 μm in order to serve also as the n-type contact layer. The nitride semiconductor layer has an n-type property due to nitrogen vacancies formed in the crystal in a non-doped state. However, usually, Si, Ge,
A single impurity such as Se is doped during crystal growth. This is for obtaining a preferable n-type having a high carrier concentration.

The active layer 10A has a single quantum well (SQW:
In _x having a single-quantum-well (MQW) structure or a multi-quantum-well (MQW) structure
Ga ₁ a _{-x N (0 <X ≦ 1} ). With the SQW structure or the MQW structure, a light-emitting element with extremely high output can be obtained. SQW and MQW are active layers that can emit light between quantum levels due to the band energy of InGaN. For example, in SQW, the active layer is formed of a single composition In _x G
a _1-x N (0 <X ≦ 1) This layer has a thickness of 10 nm or less, more preferably 7 nm or less, to obtain strong light emission between quantum levels. The MQW is In _x Ga ₁ -xN (X = 0, X = 1 in this case) having different composition ratios.
Is a multilayer film in which a plurality of thin films are included. The light emitting diode in which the active layer 10A is SQW and MQW realizes light emission of about 365 nm to 660 nm by quantum level light emission.

P-type cladding layer 10 in contact with active layer 10A
B is p-type Al _Y Ga _1-Y N (0 <Y ≦ 1). This layer preferably has a Y value of 0.05 or more. This is because a high-output element is used. Further, AlGaN is easy to obtain a p-type with a high carrier concentration. Further, it is hardly decomposed during growth, and has an effect of suppressing the decomposition of the InGaN active layer. Further, this layer can make the band offset and the refractive index difference larger than those of other nitride semiconductors with respect to the InGaN active layer.

The thickness of the p-type cladding layer 10B is 1 nm or more and 2 μm or less, more preferably 5 nm or more and 0.5
μm or less. If the thickness is less than 1 nm, the state becomes close to a state where the p-type cladding layer does not exist, and the light emission output is reduced. 2
If the thickness is larger than μm, cracks easily occur in the p-type cladding layer itself during crystal growth. To make the nitride semiconductor layer p-type, Mg, Zn, C, Be, Ca, B
Doping with an acceptor impurity such as a. Further, in order to obtain a p-layer having a high carrier concentration, after doping an acceptor impurity, annealing is performed at 400 ° C. or more in an atmosphere of an inert gas such as nitrogen or argon. In addition, the carrier concentration can be increased by irradiating an electron beam instead of annealing.

The p-type contact layer 10C is made of p-type GaN,
Preferably, it is Mg dove p-type GaN. Since the p-type contact layer 10C is a layer that is in contact with the transparent electrode 6, it is important to make ohmic contact with the transparent electrode 6. p-type G
aN easily forms ohmic contact with many metals, and is most preferable as a contact layer.

The nitride semiconductor layer having the above structure can be formed by metal organic chemical vapor deposition (MOVPE) or halide vapor deposition (HDV).
(VPE), molecular beam vapor deposition (MBE), or another vapor phase growth method. MOV among them
According to the PE method, a material having good crystallinity can be obtained quickly.
In the MOVPE method, as a Ga source, TMG (trimethylgallium), TEG (triethylgallium), Al
TMA (trimethylaluminum), T
As EA (triethylaluminum) and In sources, trialkyl metal compounds such as TMI (trimethylindium) and TEI (triethylindium) are often used, and as a nitrogen source, a gas such as ammonia or hydrazine is used. As the impurity source, silane gas for Si, germane gas for Ge, Cp ₂ Mg (cyclopentadienyl magnesium) for Mg,
For Zn, a gas such as DEZ (diethyl zinc) is used. In the MOVPE method, these gases are, for example, 60
The gas is supplied to the surface of the substrate heated to 0 ° C. or higher to decompose the gas, whereby In _x Al _Y Ga _{1- x Y} N (0 ≦ X,
0 ≦ Y, X + Y ≦ 1) can be epitaxially grown.

[0036]

EXAMPLE A well-washed sapphire substrate is set in a reaction vessel, and after sufficiently replacing the inside of the reaction vessel with hydrogen, the temperature of the substrate is raised to 1050 ° C. while flowing hydrogen to clean the sapphire substrate.

Subsequently, the temperature is lowered to 510 ° C., and a buffer layer 9 made of GaN is grown to a thickness of 20 nm on a sapphire substrate using hydrogen as a carrier gas, ammonia and TMG (trimethylgallium) as a source gas. .

After growing the buffer layer 9, only TMG is stopped,
Raise the temperature to 1030 ° C. When the temperature reaches 1030 ° C., TMG and ammonia gas are used as source gases, and silane gas is used as a dopant gas.
An n-type GaN layer doped with 1 × 10 ²⁰ / cm ^{3 of} Si
grow by μm.

After the growth of the n-type GaN layer, the source gas and the dopant gas are stopped, the temperature is set to 800 ° C., and TM is added to the source gas.
Using G, TMI (trimethylindium) and ammonia, the active layer 10A having a single quantum well structure has an In _0.43 G
a. A _0.57 N layer is grown to a thickness of 3 nm.

Next, the source gas and the dopant gas are stopped,
The temperature was raised again to 1020 ° C.
G, TMA (trimethylaluminum), ammonia,
Gp ₂ Mg (cyclopentadienyl magnesium) was used as a dopant gas, and Mg was used as the p-type cladding layer 10B.
Was doped with 1 × 10 ¹⁹ / cm ^{3 to} obtain p-type Al _0.3 Ga _0.7
An N layer is grown to a thickness of 50 nm.

The TMA gas is stopped, and a p-type GaN layer doped with Mg at 1 × 10 ¹⁹ / cm ³ is grown as a p-type contact layer 10C to a thickness of 1 μm.

After the growth of the p-type GaN layer, the substrate is taken out of the reaction vessel, and the substrate is placed in a nitrogen atmosphere by an annealing apparatus.
At 20 ° C. for 20 minutes to form a p-type cladding layer 10.
The resistance of the B and p-type contact layers 10C is further reduced.

A part of the multiple semiconductor layer 10 including the p-type contact layer 10C, the p-type cladding layer 10B and the active layer 10A of the wafer obtained as described above is removed by etching, and the n-type nitride semiconductor layer 2 is removed. And expose
A transparent electrode 6 made of Pd and Au is provided on the multiple semiconductor layer 10 at a thickness of 2 μm, and a p-electrode 5 made of 20 nm and Au is provided at a thickness of 2 μm. An n-electrode 4 made of Ti and Al is formed on the n-type nitride semiconductor layer 2 at a thickness of 2 μm. After a chip having a thickness of 350 μm is provided, the chip is cut into a chip having a thickness of 350 μm.

When the spectrum was measured, it showed a pure green light emission having an emission peak of 525 nm and a half width of 45 nm.
The light emitting diode having the electrode structure shown in FIGS.
(Forward current) At 20 mA, the forward voltage Vf dropped to 3.1 V, and the light emitting diode having the electrode structure shown in FIGS. 6 and 7 dropped to 3.2 V. Incidentally, the light-emitting diode having the conventional electrode structure shown in FIG. 1 was manufactured in the same manner as in Example 1 except that the electrode structure was changed, and when the forward voltage Vf was 20 mA for If (forward current) 20 mA. It was 5V.

[0045]

According to the present invention, the light emitting diode having an electrode on the periphery can minimize the decrease in the light emission output and minimize the forward voltage Vf.
There is a feature that can be reduced. That is, the light emitting diode of the present invention arranges a pair of electrodes consisting of a p electrode and an n electrode on a diagonal line, connects a peripheral electrode to one electrode, connects a transparent electrode to the other electrode, and furthermore, This is because the peripheral electrode is provided along the outer peripheral edge of the light emitting diode, and the transparent electrode is provided inside the peripheral electrode.

Further, in the light-emitting diode according to the present invention, the peripheral electrode is notched at a corner where the electrode electrically connected to the transparent electrode is provided, and the corner where the electrode connected to the transparent electrode is provided. Since the light emitting diode is provided on the outer peripheral portion excluding the portion, the forward voltage Vf can be reduced, and the light emitting output can be further increased as compared with the light emitting diode according to the first aspect.

This feature will be described with reference to FIG. FIG.
The light emitting diode shown in FIG.
Is provided, the forward voltage Vf can be minimized.
This is because the electric resistance between the n-electrode 4 and the n-type nitride semiconductor layer 2 can be reduced by bringing the n-electrode 4 into contact with the n-type nitride semiconductor layer 2 over a wide area. However, in the light emitting diode having this structure, the light emitting region tends to be narrowed by the peripheral electrode 7 provided for lowering the forward voltage Vf, and the light emitting output as a whole tends to be slightly reduced.

The light emitting diode according to the second aspect is characterized in that it is possible to improve the overall light emitting characteristics comprising the forward voltage Vf and the light emitting output. This is because the lower right corner of the peripheral electrode 7 is cut to enlarge the light emitting region, and the p electrode 5 provided at the solid line position is moved to the chain line position. By moving the p-electrode 5 from the position of the solid line to the position of the chain line, the light emitting diode of the present invention has an enlarged light emitting area and improved light emission output. However, in the light emitting diode having this electrode structure, it is assumed that the forward voltage Vf is increased because the entire length of the peripheral electrode is reduced. However, in the light emitting diode having this structure, the forward voltage Vf hardly changes even though the entire length of the peripheral electrode is shortened. This is because the ratio of the peripheral electrode provided on the peripheral edge of the p electrode to lower the forward voltage Vf is smaller than that of other parts. In the p-type contact layer in which the transparent electrode and the p-electrode are laminated, the electric resistance of the portion covered with the p-electrode is considerably higher than that of the portion not covered with the p-electrode. If the electric resistance of the p-type contact layer is large in the portion covered by the p-electrode, almost no current flows between the p-electrode and the peripheral electrode provided on the periphery thereof. If current does not effectively flow between the p electrode and the peripheral electrode, the forward voltage Vf
Does not drop. For this reason, the rate at which the forward voltage Vf can be reduced by providing the peripheral electrode near the p electrode is small. The reason why the electrical resistance of the portion of the p-type contact layer covered with the p-electrode is increased is that the hydrogen is removed from the p-type layer, particularly, the topmost p-type contact layer during annealing because of the film thickness. Is blocked by the thick p-electrode. When growing a p-type contact layer, the hydrogen contained in this layer combines with the dopant doped in the p-type contact layer to increase the electrical resistance of the p-type contact layer.
Hydrogen is removed from the p-type contact layer during annealing with the transparent electrode and the p-electrode laminated. However, in the portion covered with the thick p-electrode, hydrogen is not effectively removed because hydrogen hardly permeates the p-electrode. For this reason,
The portion covered by the p-electrode has a large electric resistance.

According to the light emitting diode of the present invention, a part of the peripheral electrode, which is difficult to effectively work to lower the forward voltage Vf, is cut, and the electrode is provided in this part. Therefore, the forward voltage Vf can be reduced in spite of shortening the peripheral electrode, and further, an extremely excellent feature that the light emitting area can be enlarged and the light emitting output can be increased is realized.

Further, the light emitting diode according to the fourth aspect of the present invention has a planar shape different from that of the p electrode and the n electrode. The light emitting diode of this structure has a feature that a p-electrode and an n-electrode can be accurately identified without mistake by using a device for wire bonding to an electrode. Since the wire bonding apparatus recognizes an image and identifies a p-electrode and an n-electrode, it is difficult to accurately identify the p-electrode and the n-electrode if both electrodes have the same shape. If the planar shape of the n-electrode is different from that of the n-electrode, there is a feature that accurate identification and wire bonding can be performed.

[Brief description of the drawings]

FIG. 1 is a plan view of a conventional light emitting diode.

FIG. 2 is a cross-sectional view of the light emitting diode shown in FIG.

FIG. 3 is a plan view of another conventional light emitting diode.

FIG. 4 is a plan view of a light emitting diode according to an embodiment of the present invention.

FIG. 5 is a sectional view of the light emitting diode shown in FIG. 4;

FIG. 6 is a plan view of a light emitting diode according to an embodiment of the present invention.

FIG. 7 is a sectional view of the light emitting diode shown in FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... N-type nitride semiconductor layer 3 ... P-type nitride semiconductor layer 4 ... N electrode 5 ... P electrode 6 ... Transparent electrode 7 ... Peripheral electrode 8 ... Electrode 9 ... Buffer layer 10 ... Multi-semiconductor layer 10A ... Active Layer 10
B: p-type cladding layer 10C: p-type contact layer 11: protective film

Claims (4)

[Claims] 1. A nitride semiconductor layer including a light-emitting layer is laminated on a square planar substrate (1), and a p-electrode (5) and an n-electrode are formed on the same surface of the nitride semiconductor layer. In the light emitting diode in which a pair of electrodes made of (4) is formed, the light emitting diode has a square planar shape when viewed from the electrode side, and the p electrode (5) and the n electrode (4) are square. A pair of electrodes, which are located at the corners of the light-emitting diode and are arranged diagonally and include a p-electrode (5) and an n-electrode (4), have a peripheral electrode (7) connected to one electrode and the other electrode connected to the other electrode. A transparent electrode (6) is connected to the electrode, the peripheral electrode (7) is provided along the outer peripheral edge of the light emitting diode, and the transparent electrode (6) is provided inside the peripheral electrode (7). A light emitting diode having an electrode on the periphery. 2. A nitride semiconductor layer including a light emitting layer is laminated on a square planar substrate (1), and a p-electrode (5) and an n-electrode are formed on the same surface of the nitride semiconductor layer. In the light emitting diode in which a pair of electrodes made of (4) is formed, the light emitting diode has a square planar shape when viewed from the electrode side, and the p electrode (5) and the n electrode (4) are square. A pair of electrodes, which are located at the corners of the light-emitting diode and are arranged diagonally and include a p-electrode (5) and an n-electrode (4), have a peripheral electrode (7) connected to one electrode and the other electrode connected to the other electrode. A transparent electrode (6) is connected to the electrode, the peripheral electrode (7) is provided along the outer peripheral edge of the light emitting diode, the transparent electrode (6) is provided inside the peripheral electrode (7), Further, the peripheral electrode (7) is cut off at a corner where an electrode electrically connected to the transparent electrode (6) is provided, and the electrode connected to the transparent electrode (6) is cut off. Light emitting diode having an electrode on the periphery, characterized in that thus provided on the outer peripheral portion excluding the corner portions provided. 3. The peripheral electrode according to claim 1, wherein the peripheral electrode (7) is connected to the n-electrode (4) and the transparent electrode (6) is connected to the p-electrode (5). Light emitting diode. 4. The light emitting diode having an electrode on the periphery according to claim 1, wherein the shape of the n-electrode (4) and the shape of the p-electrode (5) are different from each other.