JPH08186288A - Semiconductor light-emitting element - Google Patents

Abstract

PURPOSE: To provide a semiconductor light-emitting element whose thermal resistance and electrical resistance are low and whose luminous efficiency is high. CONSTITUTION: A low-carrier-concentration layer 8, a p-type clad layer 9, a p-type active layer 6 and an n-type clad layer 2 are grown on a substrate by a liquid phase method or the like. An insulating film is formed on the surface of the n-type clad layer 2, the insulating film in which a p-type electrode 4 is to be formed is etched and removed, Zn is diffused down to a part which reaches at least the active layer 6, and a p-type diffused layer 5 is formed. The substrate is removed selectively, the insulating film is removed additionally, an n-type electrode 3 is formed in the n-type clad layer 2, and the n-type electrode 4 is formed in the p-type diffused layer 5. The shape of the n-type electrode 3 and that of the p-type electrode 4 are formed to be a comb shape, teeth 3a, 4a for the comb shape are formed alternately, and only the surface of the teeth 3a for the comb shape for the n-type electrode 3 is covered with an insulating film 7. A semiconductor light-emitting element 1 is junctiondown mounted on a lead frame or the like.

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 device such as an LED (light emitting diode).

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing an example of a general conventional semiconductor light emitting device. In FIG. 1A, in the semiconductor light emitting device 10, the active layer 11 has a p-type cladding layer 12 and
Forming a double hetero structure sandwiched between the type clad layers 13, a p-type electrode 14 is formed on the lower surface of the p-type clad layer 12, an n-type electrode 15 is formed on the upper surface of the n-type clad layer 13, and a surface of the p-type electrode 14 is formed. Is mounted on a lead frame or the like, wire bonding or the like is connected to the n-type electrode 15 to supply a current, and light is extracted from the upper surface of the n-type cladding layer 13 side.

[0003]

By the way, in order to operate the LED at a high output, it is necessary to increase the maximum operating current. The factor that defines the maximum operating current of the LED is the pn junction temperature Tj. This is because the crystal characteristics of an ordinary LED are deteriorated when it is continuously operated at Tj> 100 ° C. The countermeasures are as follows: 1) To reduce the thermal resistance, mount the pn junction close to the heat sink (junction down). 2) Lower element resistance. Can be considered.

The element resistance R of the LED is expressed by the following equation. R = R1 + R2 + R3 + R4 where R1: contact resistance of p-type electrode R2: resistance of p-type layer (including current spreading resistance due to electrode shape) R3: resistance of n-type layer (including current spreading resistance due to electrode shape) ) R4: n-type electrode contact resistance. In an ordinary LED, R2 >> R1, R3
, R4, and it is important to reduce R2.
In order to reduce R2, (1) reduce the thickness of the p-type layer. (2) Increase the area of the electrode. It is necessary.

With respect to (1), however, it is a practical problem to set the thickness of the p-type layer to 150 μm or less for normal handling. As for (2), FIG.
In the configuration such as the semiconductor light emitting device 10 shown in (a),
When the electrode diameter is increased, light is blocked by the electrode and the light output is reduced. Therefore, it is customary to make the electrode on the upper surface a diameter as small as possible for wire bonding, for example, a circle of hundreds of tens of μm.

Therefore, there is one in which the p-type electrode is taken from the n-type electrode side to reduce the effective p-type layer thickness.
The configuration will be described with reference to FIG.
In the figure, the semiconductor light emitting element 16 is different from the semiconductor light emitting element 10 of FIG. 1A in that a p-type impurity diffusion region 16 is formed in a part of the n-type cladding layer 13 until reaching the active layer 11. The point is that the p-type electrode 14 is formed on the upper surface. Reference numeral 17 denotes an isolation groove 17 for isolating the impurity diffusion region 16 and the n-type layer 13, which has a depth to reach the active layer 11. This semiconductor light emitting element 16 has the n-type electrode 15 and the p-type electrode 14 on the same surface, is junction down-mounted, and has a small distance of current flowing through the p-type layer (effective p-type layer thickness). However, the current spreading resistance is large, and there is a problem that the resistance does not decrease as much as expected.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor light emitting element having low heat resistance and element resistance and high luminous efficiency.

[0008]

As a means for achieving the above object, the present invention provides a second conductivity type which is formed on a semiconductor layer of a first conductivity type and which is opposite to the first conductivity type. A semiconductor layer, and a first conductivity type electrode and a second conductivity type electrode formed on the surface of the first conductivity type semiconductor layer, and from the second conductivity type semiconductor layer side. In the semiconductor light emitting device that outputs light, the first conductivity type electrode and the second conductivity type electrode each have a plurality of gaps, and the other electrode is provided in the gap of one electrode One of the electrodes is formed in the gap portion of the electrode without contact, on the electrode of the second conductivity type, from the surface of the semiconductor layer of the first conductivity type to the semiconductor layer of the second conductivity type. A semiconductor light emitting device having the second conductivity type impurity diffusion region formed until reaching To provide.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor light emitting device according to an embodiment of the present invention will be described below with reference to the accompanying drawings. 1A and 1B are views showing a semiconductor light emitting element according to an embodiment of the present invention, FIG. 1A is a view showing an electrode surface, and FIG. 1B is an enlarged view showing a part of an AB cross section. In the figure, an n-type electrode 3 and a p-type electrode 4 are formed in a comb shape on the surface of the n-type cladding layer 2 of the semiconductor light emitting device 1. n-type clad layer 2 on which p-type electrode 4 is formed
Impurities are diffused from the surface of the p to form the p-type diffusion layer 5 that has changed to the p-type until it reaches the active layer 6. The comb teeth 3a of the n-type electrode 3 and the comb teeth 4a of the p-type electrode 4 are alternately formed without contact with each other, and only the comb teeth 3a of the n-type electrode 3 are made of an insulating film (for example, SiN) 7 Are covered by.

Next, a method of manufacturing the semiconductor light emitting device 1 will be described. First, a low carrier concentration GaAlAs layer 8 (having a film thickness of about 150 μm) having a carrier concentration of 10 × 10 ¹⁷ cm ⁻³ or less is formed on a GaAs substrate (not shown) by a liquid phase method or the like.
p-type GaAlAs clad layer 9 (film thickness of about 10 μm), p
-Type GaAlAs active layer 6 (film thickness: about 1 μm), n-type GaA
The 1As clad layer 2 (film thickness of about 5 μm) is grown.

Subsequently, an insulating film of SiN or the like is formed on the surface of the n-type cladding layer 2, the insulating film in the portion where the p-type electrode 4 is formed is removed by etching, and Zn is diffused at least until the active layer 6 is reached. The mold diffusion layer 5 is formed.

Next, after selectively etching the GaAs substrate and removing the insulating film, the n-type electrode 3 is alternately formed on the surface of the n-type cladding layer 2 and the p-type electrode 4 is alternately formed on the surface of the p-type diffusion layer 5. The comb teeth 3a and 4a are formed in a comb shape without contacting each other with a width of about 5 to 10 μm, and the comb teeth 3a of the n-type electrode 3 are covered with the insulating film 7.

According to this embodiment, the distance between the pn junction position and the electrode is very close to about 5 μm, and the heat generated in the light emitting portion can be efficiently dissipated. In the conventional LED having the p-type electrode on the upper surface of the device, the p-type clad layer that occupies most of the device resistance is very thick, about 150 μm. The thickness (the distance that the current flows through the p-type cladding layer) is about 20 μm, and the element resistance can be significantly reduced. When a device of 400 μm × 400 μm was manufactured with the structure of this example, the device resistance was about 0.7Ω. This is a conventional LE
About 1/4 of the device resistance of D was about 2.5Ω
And is very small.

The semiconductor light emitting device manufactured as described above is junction down mounted. For example, n
The lead frame on the side of the mold electrode 3 is connected to In as far as possible in the exposed portion 3b of the n-type electrode 3 without contacting the p-type electrode 4, and the lead frame on the side of the p-type electrode 4 is n-type. The electrode 3 and the n-type electrode 3 are connected to the p-type electrode 4 by In or the like over a wide range without coming into contact with the lead frame. That is, since the comb tooth 4a of the p-type electrode 4 and the comb tooth 3a of the n-type electrode 3 adjacent to the p-type electrode 4 are insulated by the insulating film 7, the lead frame on the p-type electrode 4 side has the n-type electrode 3 exposed. It suffices to connect the entire surface except the portion 3b. Therefore, it is not necessary for the lead frame to have a complicated shape particularly in accordance with the electrode shape. Further, since it can be connected to the lead frame over a wide range, heat can be efficiently dissipated.

The shape of the electrode is not limited to this,
It is sufficient if the n-type electrode 3 and the p-type electrode 4 are configured so as to have a large number of adjacent portions over a wide range on the surface of the n-type cladding layer 2, and the n-type electrode on the surface on which the p-type electrode is formed is formed. The type clad layer is impurity-diffused as described above to form a p-type diffusion layer. Further, in this embodiment, n
Although the mold electrode is covered with the insulating film, the p-type electrode may be covered. FIG. 2 shows examples of other electrode shapes in three patterns ((a) to (c) in the figure). In the figure, 3 is a first conductivity type electrode, 4 is a second conductivity type electrode, and if necessary, 2
An insulating film as described above that separates the two electrodes is formed.

If necessary, a separation groove from the surface of the n-type cladding layer 2 to the p-type layer may be formed at the boundary between the p-type diffusion layer 5 and the n-type cladding layer 2. For example, it is formed when the band gap difference between the clad layer and the active layer is small to prevent a current from flowing directly from the p-type clad layer to the n-type clad layer without passing through the active layer.

In this embodiment, an LED having a GaAlAs double hetero structure has been described as an example, but the same applies to a general homo structure or a single hetero structure, and the material is GaA.
Not specific to lAs.

[0018]

As described above, according to the light emitting device of the present invention, the following effects can be obtained. The pn junction position can be configured to be very close to the electrode, and the heat generated in the light emitting portion can be efficiently dissipated due to the electrode shape in which the p-type electrode and the n-type electrode are widely formed on the same surface. Therefore, the thermal resistance is very small. Further, the effective thickness of the p-type cladding layer, which greatly affects the element resistance, can be made extremely thin, and the element resistance can be greatly reduced. Further, since the p-type electrode and the n-type electrode are formed on the same surface and a part of one of the electrodes is insulated by the insulating film, it is possible to easily mount the junction down and to mount the lead frame. The shape does not need to match the shape of the electrode particularly precisely, and the electrode can be connected in a wide range, and heat can be efficiently released. Furthermore, since the semiconductor layer has a low carrier concentration and light is extracted from the upper surface, light absorption due to free carrier absorption is small, and since there is no electrode on the upper surface, light is not blocked and light extraction efficiency is improved. high.

[Brief description of drawings]

FIG. 1 is a diagram showing a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an electrode shape of a semiconductor light emitting device according to another embodiment of the present invention.

FIG. 3 is a sectional view showing an example of a conventional semiconductor light emitting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Semiconductor light emitting element 2 n-type GaAlAs clad layer (n-type clad layer) 3 n-type electrode 4 p-type electrode 5 p-type diffusion layer 6 p-type GaAlAs active layer (active layer) 7 insulating film 8 low carrier concentration GaAlAs layer (low) Carrier concentration layer) 9 p-type GaAlAs clad layer (p-type clad layer)

Claims (5)

[Claims] 1. A semiconductor device formed on a semiconductor layer of a first conductivity type,
A semiconductor layer of a second conductivity type opposite to the first conductivity type; an electrode of a first conductivity type and an electrode of a second conductivity type formed on the surface of the semiconductor layer of the first conductivity type; In the semiconductor light emitting device that outputs light from the second conductive type semiconductor layer side, the first conductive type electrode and the second conductive type electrode each have a plurality of gaps. , The other electrode is formed in the gap portion of the one electrode without contacting the one electrode in the gap portion of the other electrode, and the first conductivity type is formed on the electrode of the second conductivity type. 2. The semiconductor light emitting device having the impurity region of the second conductivity type formed from the surface of the semiconductor layer to the semiconductor layer of the second conductivity type. 2. A semiconductor layer of a first conductivity type formed on the semiconductor layer,
A semiconductor layer of a second conductivity type opposite to the first conductivity type; an electrode of a first conductivity type and an electrode of a second conductivity type formed on the surface of the semiconductor layer of the first conductivity type; In the semiconductor light-emitting element having the second conductivity type semiconductor layer side and outputting light, a plurality of the first conductivity type electrodes and the second conductivity type electrodes are formed adjacent to each other. The second conductivity type impurity diffusion region formed on the second conductivity type electrode from the surface of the first conductivity type semiconductor layer to the semiconductor layer of the second conductivity type. A semiconductor light-emitting device comprising: 3. The first-conductivity-type and second-conductivity-type electrodes have a comb shape, and a plurality of comb teeth of the electrodes having different conductivity types are alternately formed. Item 3. The semiconductor light emitting device according to item 1 or 2. 4. A part of the surface of either the first conductivity type electrode or the second conductivity type electrode is covered with an insulating film. One of
A semiconductor light-emitting device according to item. 5. A semiconductor layer having a low carrier concentration is provided on the side of the second conductivity type semiconductor layer.
The semiconductor light emitting element according to claim 4.