JP2003309288A - Light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting element which can raise intensity. <P>SOLUTION: The light-emitting element comprises: an n-type layer 3; a light emitting layer 4; and a p-type layer sequentially laminated on a substrate 1; a Pt layer 61 and an Rh layer 62 laminated on the layer 5. In this element, the film thickness of the Pt layer 61 is set to 1 to 5 nm. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device (LED, LD) used in electronic devices, displays, lighting, backlights and the like.

[0002]

2. Description of the Related Art FIG. 2 is a side view showing a conventional light emitting device.

In FIG. 2, 11 is a substrate, and the substrate 11 is configured to be transparent or semi-transparent. 12 is an n-type layer provided on the substrate, 13 is a light-emitting layer provided on the n-layer 12, 14 is a p-type layer provided on the light-emitting layer 13, and 15 is provided on the p-layer 14. The p-side electrode 15 includes a Pt layer 16, a Rh layer 17, and an Au layer 18.
The mold layers 14 are sequentially laminated from the mold layer 14 side. 19 is n
An n-side electrode electrically connected to the layer 12, the n-side electrode 19
Is formed by sequentially stacking a Ti layer 20 and an Au layer 21 from the n-type layer side.

In the light emitting element thus constructed, the p-side electrode 15 and the n-side electrode 1 are formed on the electrode patterns 23 and 24 provided on the mounting substrate 22 such as a circuit board and a mounting member, respectively.
9 is surface-mounted with a bonding material such as solder. Of the light emitted from the light emitting layer 13, the light emitted to the substrate 11 side is directly emitted to the outside, and the light emitted to the p-side electrode 15 side is the Rh layer 17 of the p-side electrode 15 and the like. By being reflected by the substrate 11 side, the brightness was improved.

As a prior art example, Japanese Patent Laid-Open No. 11-22016
No. 8 publication and the like are listed.

[0006]

However, in the above-mentioned conventional structure, it is difficult to increase the brightness even if the same drive voltage is used to increase the brightness.

The present invention solves the above-mentioned problems.
The present invention relates to a light emitting device capable of increasing brightness.

[0008]

In order to achieve the above object, the present invention provides a substrate capable of transmitting light, an n layer and ap layer provided on the substrate, and an n layer and a p layer. What is claimed is: 1. A light-emitting device having a light-emitting layer provided between them, and an n-side electrode and a p-side electrode provided in the n-layer and the p-layer, respectively, wherein the p-side electrode is a Pt layer and a Rh layer at least from the p layer side. The Pt layer had a thickness of 1 nm to 5 nm while being laminated in this order.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The invention according to claim 1 is characterized in that a substrate capable of transmitting light, an n layer and ap layer provided on the substrate, and an n layer and ap layer are provided. A light emitting device having a light emitting layer, and an n-side electrode and a p-side electrode provided in the n-layer and the p-layer, respectively, wherein the p-side electrode is laminated at least from the p-layer side in the order of Pt layer and Rh layer. In addition, the light-emitting element is characterized in that the Pt layer has a film thickness of 1 nm to 5 nm, whereby it is possible to prevent light incident on the Pt layer from being absorbed by the Pt layer itself.
Moreover, since the Rh layer can be sufficiently reflected, the brightness can be improved only by improving the electrode structure, and the p-side electrode and the p layer can be sufficiently electrically connected to each other, so that the driving voltage can be reduced. It doesn't have to be high.

According to a second aspect of the present invention, the n layer, the p layer, and the light emitting layer are composed of a semiconductor layer containing at least Ga and N. It is possible to emit light of a short wavelength such as blue or violet.

According to a third aspect of the present invention, the first surface on which the p layer is provided in the n layer and the second surface which is stepped down from the first surface and is oriented in the same direction as the first surface. And the n-side electrode is provided on the second surface, whereby the p-side electrode and the n-side electrode are electrically connected in the same plane direction. It is possible to obtain a surface-mountable light emitting device.

According to a fourth aspect of the present invention, n which can transmit light is used.
-Type conductive substrate and p provided on the n-type conductive substrate
Layer, a light emitting layer provided between the n-type conductive substrate and the p layer, and a light emitting device having an n-side electrode and a p-side electrode provided on the n-type conductive substrate and the p layer, respectively. In addition, the p-side electrode is laminated at least from the p-layer side in the order of Pt layer and Rh layer, and the thickness of the Pt layer is 1
By adopting a light emitting element characterized by having a thickness of 5 nm to 5 nm, it is possible to prevent light incident on the Pt layer from being absorbed by the Pt layer itself, and moreover, it is possible to sufficiently reflect the light on the Rh layer. Therefore, the brightness can be improved only by improving the electrode structure, and the electric connection between the p-side electrode and the p-layer can be sufficiently performed. Therefore, it is not necessary to increase the driving voltage. Further, an element with low driving voltage can be manufactured, and an element with low power consumption can be obtained.

The invention according to claim 5 is an n-type conductive substrate,
5. The light emitting device according to claim 4, wherein the p layer and the light emitting layer are composed of a semiconductor layer containing at least Ga and N, and emit light having a short wavelength such as green, blue, and violet. it can.

According to a sixth aspect of the present invention, the first surface on which the p layer is provided on the n-type conductive substrate and the first surface which is oriented in the same direction as the first surface are stepped down. 5. The light emitting device according to claim 4, further comprising a second surface, wherein an n-side electrode is provided on the second surface. It is possible to obtain a light-emitting element that can be surface-mounted and can be mechanically joined.

According to a seventh aspect of the invention, the Rh layer has a thickness of 5
By using the light emitting device according to any one of claims 1 to 6 having a thickness of nm to 2000 nm, desired reflection characteristics can be obtained and productivity can be improved.

The invention according to claim 8 is a light emitting device comprising a light emitting portion provided between an n-type conductive portion and a p-type conductive portion, and a p-side electrode electrically connected to the p-type conductive portion. And the p-side electrode is laminated at least from the p-type conductive portion side in this order to the Pt layer and the Rh layer, and the thickness of the Pt layer is 1 nm.
By using a light emitting device characterized by having a thickness of ˜5 nm, it is possible to prevent light incident on the Pt layer from being absorbed by the Pt layer itself, and moreover, it is possible to sufficiently reflect the light on the Rh layer. The brightness can be improved only by improving the electrode structure, and the electrical connection between the p-side electrode and the p layer can be sufficiently performed. Therefore, it is not necessary to increase the driving voltage.

According to a ninth aspect of the present invention, an electrode pattern is provided on the mounting member, and the light emitting device according to any one of the first to eighth aspects is surface-mounted on the electrode pattern of the mounting member. By adopting the mounting structure of the light emitting element,
A high-brightness LED or the like can be easily manufactured.

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

In FIG. 1, as the substrate 1, a substrate having a transparency that allows at least light to pass therethrough is used. As a constituent material of the substrate 1, a sapphire substrate, Si
A C substrate, a GaN substrate or the like is used.

Reference numeral 3 denotes an n-type layer provided directly on the substrate 1 or via a buffer layer (not shown). The n-type layer 3 is composed of a semiconductor layer containing at least Ga and N.
Moreover, Si, Ge, or the like is preferably used as the n-type dopant. The n-type layer 3 has a film thickness of 4 μm.

Reference numeral 4 denotes a light emitting layer provided on the n-type layer 3,
The light emitting layer 4 is laminated directly on the n-type layer 3 or via a semiconductor layer containing at least Ga and N. The light emitting layer 4 is made of a semiconductor containing at least Ga and N, and a suitable amount of In when necessary to obtain a desired emission wavelength. Also,
Although the light emitting layer 4 has a single-layer structure in FIG. 1, for example, a multi-quantum well structure in which at least one pair of InGaN layers and GaN layers are alternately laminated is used to further improve the brightness.

Reference numeral 5 denotes a p-type layer laminated directly on the light emitting layer 4 or via a semiconductor layer containing at least Ga and N. The p-type layer 5 is composed of a semiconductor layer containing at least Ga and N. Moreover, Mg or the like is preferably used as the p-type dopant. The p-type layer 5 has a film thickness of 0.2 μm.

Reference numeral 6 denotes a p-side electrode provided on the p-type layer 5, and the p-side electrode 6 is a Pt layer 61 and a Rh layer 6 from the p-type layer 5 side.
2 and Au layer 63 are laminated in this order.

One of the features of the present invention is that the thickness of the Pt layer 61 is set to 1 nm to 5 nm. That is,
The Pt layer 61 has a film thickness of 1 nm or more in order to obtain good electrical connection with the p-type layer 5, and the Pt layer 61 has a thickness of 5 n.
If it is thicker than m, the absorption of light by the Pt layer 61 itself becomes large, and the brightness is lowered.

Further, one of the features of the present invention is that the Rh layer 62
The thickness is set to 5 nm to 2000 nm. That is, when the film thickness of the Rh layer 62 is thinner than 5 nm, sufficient reflection characteristics cannot be obtained, and when it is thicker than 2000 nm, the reflection characteristics do not change and a large amount of evaporation raw material required for film formation is required. In addition, since the time required for this process becomes long, the manufacturing cost becomes high.

Thus, the film thickness of the Pt layer 61 is set to 1 to 5 nm.
Thus, even if the light emitted from the light emitting layer enters the Pt layer 61, the light absorption in the Pt layer 61 itself can be suppressed and the brightness can be improved, and the reflection characteristics of the Rh layer 62 are sufficient. Can be obtained. In the prior art example shown in the related art, since the Pt layer has a thickness of 5 nm or more, a large amount of light absorption occurs, and the brightness decreases.

In the present invention, attention is paid to the fact that the light absorption of the Pt layer 61 itself influences the improvement of brightness, and the thickness of the Pt layer 61 is defined by considering the degree of ohmic junction and the like, and as a result, p The brightness can be improved only by improving the side electrode 6.

The p-side electrode 6 is preferably provided on the entire surface of the p-type layer 5 or 80% or more of the exposed area of the p-type layer 5.

Reference numeral 7 denotes an n-side electrode provided on a part of the n-type layer 3 exposed on the side where the p-type layer 5 is provided. The n-side electrode 7 is a Ti layer 71, an Au layer from the n-type layer 3 side. 72 are laminated in order.

Reference numeral 8 denotes a mounting member on which the light emitting element configured as described above is mounted. As the mounting member 8, a circuit board or a mounting member is preferably used. At least electrode patterns 9 and 10 are provided on the mounting member 8. For example, the Au layer 63 and the Au layer 72 are electrically connected to the electrode patterns 9 and 10 by a conductive bonding material such as solder or lead-free solder. Are joined together.

In the light emitting element having the above-described structure, even if the light emitted from the light emitting layer 4 enters the Pt layer 61, the Pt layer 61
By setting the thickness to 5 nm or less, it is possible to suppress light absorption in the Pt layer 61 itself, and by setting the thickness to 1 nm or more, sufficient electric connection with the p-type layer 5 can be obtained. .

Therefore, since the light emitted from the light emitting layer 4 to the p-side electrode 6 side is efficiently reflected and emitted from the substrate 1, sufficient improvement in luminance can be realized only by improving the p-side electrode 6.

In the present embodiment, the Pt layer, Rh
The layers, Au layers, Ti layers and the like may be composed of each material alone or may be layers containing the element as a main component. That is, for example, in the case of a Pt layer, a material in which a predetermined element is mixed with Pt in a range that does not affect the characteristics may be used.

[0034]

EXAMPLE As a practical example of the present invention, a method for manufacturing the gallium nitride-based compound semiconductor light emitting device shown in FIG. 3 will be described. In the following examples, a metalorganic vapor phase epitaxy method is used as a method for growing a gallium nitride-based compound semiconductor,
The growth method is not limited to this, and a molecular beam epitaxy method, an organometallic molecular beam epitaxy method, or the like can be used.

Example 1 First, a sapphire substrate 1 having a mirror-finished surface was placed on a substrate holder in a reaction tube, and then the temperature of the substrate 1 was kept at 1000 ° C. while flowing nitrogen and hydrogen. By heating 1 for 10 minutes,
Dirt and water such as organic substances adhering to the surface of the substrate 1 were removed.

Next, the temperature of the substrate 1 was lowered to 550 ° C., while supplying nitrogen as a carrier gas, ammonia and TMG were supplied to grow a buffer layer 2 made of GaN with a thickness of 25 nm.

Next, after the supply of TMG is stopped and the temperature is raised to 1050 ° C., while supplying nitrogen and hydrogen as a carrier gas, ammonia, TMG and SiH ₄ are supplied to form n-doped GaN. Mold layer 3 is 4 μm
Grown to a thickness of.

After growing the n-type layer 3, the supply of TMG and SiH ₄ is stopped and the substrate temperature is lowered to 750 ° C.
At a temperature of ° C, while supplying nitrogen as a carrier gas, ammonia, TMG, and TMI are supplied to supply undoped I
The light emitting layer 4 having a single quantum well structure made of nGaN has a thickness of 2 nm.
Grown to a thickness of.

After growing the light emitting layer 4, the supply of TMI is stopped,
While flowing TMG and raising the substrate temperature toward 1050 ° C., undoped GaN (not shown) is continued.
Was grown to a thickness of 4 nm, and when the substrate temperature reached 1050 ° C., while flowing nitrogen and hydrogen as carrier gases,
Supply ammonia, TMG, TMA, Cp ₂ Mg,
A p-type cladding layer 51 made of AlGaN doped with Mg was grown to a thickness of 0.2 μm.

After the p-type clad layer 51 is grown, ammonia and TM are fed while the substrate 1 is kept at 1050 ° C. while flowing nitrogen gas and hydrogen gas as carrier gases.
G, TMA, and Cp ₂ Mg are supplied so that the p-type contact layer 52 made of Mg-doped AlGaN is 0.1.
It was grown to a thickness of μm.

After the growth of the p-type contact layer 52, the supply of TMG, TMA and Cp ₂ Mg is stopped, the temperature of the substrate 1 is cooled to about room temperature while flowing nitrogen gas and ammonia, and The wafer on which the gallium nitride compound semiconductor was laminated was taken out from the reaction tube.

With respect to the laminated structure made of the gallium nitride-based compound semiconductor thus formed, a SiO ₂ film is deposited on the surface thereof by the CVD method without performing additional annealing, and then photolithography and wet etching are performed. To form a SiO ₂ mask for etching. Then, a part of the p-type contact layer 52, the p-type clad layer 51, the intermediate layer, the light emitting layer 4, and the n-type layer 3 is formed at a depth of about 0.4 μm in a direction opposite to the laminating direction by the reactive ion etching method. To expose the surface of the n-type layer 3.

After removing the SiO ₂ mask for etching by wet etching, a photoresist is applied on the surface of the laminated structure, and only the photoresist on the surface of the p-type contact layer 52 is removed by photolithography. 80% of the surface of the p-type contact layer 52
The above is exposed. Then, the laminated structure is mounted in the chamber of the vacuum vapor deposition apparatus, and the inside of the chamber is set to 2 × 10 ⁻⁶ To.
After evacuation to rr or less, a Pt layer 61 having a thickness of 3 nm was deposited on the surface of the p-type contact layer 52 and the photoresist exposed by the electron beam evaporation method. Subsequently, a Rh layer 62 having a thickness of 100 nm is deposited,
Further, an Au layer 63 having a thickness of 1 μm was deposited. Next, the laminated structure is taken out of the chamber, and P on the photoresist is removed.
By removing the t layer 61, the Rh layer 62, and the Au layer 63 together with the photoresist, the p-side electrode 6 in which the Pt layer 61, the Rh layer 62, and the Au layer 63 are sequentially laminated on the surface of the p-type contact layer 52 is formed. Formed.

A photoresist is applied again on the surface of the laminated structure, and only the photoresist on the exposed part of the surface of the n-type layer 3 is removed by photolithography.
A part of the surface of the n-type layer 3 was exposed. Then, the laminated structure is mounted in a chamber of a vacuum vapor deposition apparatus, the chamber is evacuated to 2 × 10 ⁻⁶ Torr or less, and then the exposed surface of the n-type layer 3 and the photo layer are exposed by an electron beam vapor deposition method. A Ti layer 71 having a thickness of 100 nm was vapor-deposited on the resist, and an Au layer 72 having a thickness of 1.5 μm was vapor-deposited. Next, the laminated structure is taken out of the chamber, and the Ti layer 71 and the Au layer 72 on the photoresist are removed together with the photoresist, so that the Ti layer 71 and the Au layer 72 are sequentially formed on a part of the surface of the n-type layer 3. Layered n-side electrode 7
Was formed.

Thereafter, the back surface of the substrate 1 is polished to 100 μm.
The thickness was adjusted to about m and the chips were separated by scribing. Thus, the gallium nitride-based compound semiconductor light emitting device shown in FIG. 3 was obtained.

This light-emitting element was placed on a Si diode having a pair of positive and negative electrodes with the electrode formation surface side facing downward.
Bonded by u-bump. At this time, the light emitting element is mounted so that the p-side electrode 6 and the n-side electrode 7 of the light emitting element are connected to the negative electrode and the positive electrode of the Si diode, respectively. Then, the Si diode on which the light emitting element was mounted was placed on the stem with Ag paste, the positive electrode of the Si diode was connected to the electrode on the stem with a wire, and then resin-molded to produce a light emitting diode. When this light emitting diode was driven with a forward current of 20 mA, it emitted blue light with a peak emission wavelength of 470 nm, and the substrate 1
A uniform surface emission was obtained from the surface opposite to the side on which the laminated structure was formed. The forward operating voltage at this time was 3.4 V, and the light emission output was 5 mW.

(Example 2) In Example 2, a light emitting device was manufactured in the same procedure as in Example 1 except that the thickness of the Pt layer 61 in Example 1 was changed to 6 nm.
When this light emitting device was driven with a forward current of 20 mA, it emitted blue light with a peak emission wavelength of 470 nm and emitted blue light with a peak emission wavelength of 470 nm, and was uniform from the surface opposite to the side where the laminated structure of the substrate 1 was formed. However, the forward operation voltage at this time was 3.4 V, and the light emission output was 4.2 mW.

The relationship between the film thickness of the Pt layer and the brightness of the light emitting element and the relationship between the film thickness of the Pt layer and the driving voltage, which have been described above, will be described with reference to FIGS. 4 and 5.

As shown in FIG. 4, the thickness of the Pt layer is 5 nm.
When the thickness is larger than this, the brightness is lowered because the amount of light absorption in the Pt layer itself seems to be remarkably increased. Further, as can be seen from FIG. 5, when the film thickness of the Pt layer is thinner than 1 nm, an increase in the driving voltage, which is considered to be due to the fact that the ohmic contact with the p layer is not reliably performed, is observed.

Therefore, it is understood that the Pt layer preferably has a thickness of 1 nm to 5 nm in terms of electrical characteristics or brightness.

[0051]

The substrate capable of transmitting light, the n layer and the p layer provided on the substrate, the light emitting layer provided between the n layer and the p layer, and the n layer and the p layer, respectively. A light-emitting element having an n-side electrode and a p-side electrode provided, wherein the p-side electrode is laminated at least from the p-layer side in this order to the Pt layer and the Rh layer, and the thickness of the Pt layer is 1 nm to 5 nm. By doing so, it is possible to suppress the light incident on the Pt layer from being absorbed by the Pt layer itself, and moreover, it is possible to sufficiently reflect the light on the Rh layer, so that the brightness can be improved only by improving the electrode structure. Since the electric connection between the p-side electrode and the p-layer can be performed sufficiently well, it is not necessary to increase the driving voltage.

[Brief description of drawings]

FIG. 1 is a side view showing a light emitting element according to an embodiment of the present invention.

FIG. 2 is a side view showing a conventional light emitting device.

FIG. 3 is a side view showing a light emitting element according to an embodiment of the present invention.

FIG. 4 shows Pt of a light emitting device according to an embodiment of the present invention.
Graph showing the relationship between layer thickness and brightness

FIG. 5 is a light emitting element Pt according to an embodiment of the present invention.
Graph showing the relationship between the layer thickness and the drive voltage

[Explanation of symbols]

1 substrate 2 buffer layers 3 n layers 4 Light emitting layer 5 p layer 6 p-side electrode 7 n-side electrode 8 mounting members 9, 10 electrode pattern 51 p-type clad layer 52 p-type contact layer 61 Pt layer 62 Rh layer 63 Au layer 71 Ti layer 72 Au layer

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Claims (9)

[Claims] 1. A substrate capable of transmitting light, an n layer and ap layer provided on the substrate, a light emitting layer provided between the n layer and the p layer, the n layer and the p layer. A light emitting device having an n-side electrode and a p-side electrode provided in each layer,
The side electrodes are laminated at least from the p-layer side in this order to the Pt layer and the Rh layer, and the film thickness of the Pt layer is 1 nm to
A light emitting device having a thickness of 5 nm. 2. The n layer, the p layer, and the light emitting layer are at least Ga and N.
The light emitting device according to claim 1, wherein the light emitting device comprises a semiconductor layer containing. 3. A first surface on which an n layer is provided with a p layer, and a second surface, which is stepped down from the first surface and is oriented in the same direction as the first surface, The light emitting device according to claim 1, wherein an n-side electrode is provided on the second surface. 4. An n-type conductive substrate capable of transmitting light;
P layer provided on the type conductive substrate, a light emitting layer provided between the n type conductive substrate and the p layer, and n side provided on the n type conductive substrate and the p layer, respectively. A light-emitting element having an electrode and a p-side electrode, wherein the p-side electrode is laminated at least from the p-layer side in the order of Pt layer and Rh layer, and the Pt layer has a thickness of 1 nm to 5 nm. Characteristic light emitting element. 5. The light emitting device according to claim 4, wherein the n-type conductive substrate, the p layer, and the light emitting layer are composed of a semiconductor layer containing at least Ga and N. 6. An n-type conductive substrate is provided with a first surface on which a p layer is provided, and a second surface which is oriented in the same direction as the first surface and which is stepped down from the first surface. The light emitting device according to claim 4, wherein an n-side electrode is provided on the second surface. 7. The light emitting device according to claim 1, wherein the Rh layer has a thickness of 5 nm to 2000 nm. 8. A light-emitting device comprising a p-side electrode electrically connected to the p-type conductive part, wherein a light-emitting part is provided between the n-type conductive part and the p-type conductive part. A light-emitting device having a structure in which at least a Pt layer and a Rh layer are stacked in this order from the p-type conductive portion side, and the Pt layer has a film thickness of 1 nm to 5 nm. 9. A mounting structure of a light emitting element, wherein an electrode pattern is provided on a mounting member, and the light emitting element according to claim 1 is surface-mounted on the electrode pattern of the mounting member. .