JP2008103759A - Light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting element capable of enhancing luminance. <P>SOLUTION: In order to achieve the above object, the light emitting element includes a light transmitting substrate 1, an n-layer 3 and a p-layer 5 provided on the substrate 1, an emission layer 4 provided between the n-layer 3 and the p-layer 5, and an n-side electrode 7 and a p-side electrode 6 provided on the n-layer 3 and the p-layer 5, respectively. The p-side electrode 6 is formed by laminating at least a Pt layer 61, an Ag layer 62, and an Mo layer 63, from the p-layer 5 side in this order. The invention relates to the light emitting element is capable of enhancing luminance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light emitting element (LED, LD) used for an electronic device, a display, illumination, a backlight, and the like.

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

  In FIG. 2, reference numeral 11 denotes a substrate, and the substrate 11 is configured to be transparent or translucent. 12 is an n layer provided on the substrate, 13 is a light emitting layer provided on the n layer 12, 14 is a p layer provided on the light emitting layer 13, and 15 is provided on the p layer 14. The p-side electrode 15 is configured by laminating a Pt layer 16, an Ag layer 17, a Ni layer 18, and an Au layer 19 in this order from the p-layer 14 side. Reference numeral 20 denotes an n-side electrode electrically connected to the n-layer 12, and the n-side electrode 20 is configured by sequentially laminating a Ti layer 21 and an Au layer 22 from the n-layer side.

  The light-emitting element configured in this manner has the p-side electrode 15 and the n-side electrode 20 on the electrode patterns 24 and 25 provided on the mounting substrate 23 such as a circuit board and a mounting member, respectively, with a bonding material such as solder. Implemented. Of the light emitted from the light emitting layer 13, the light emitted to the substrate 11 side is emitted outward as it is, and the light emitted to the p side electrode 15 side is the Ag layer 17 of the p side electrode 15 or the like. As a result, the luminance is improved.

As a prior example, Patent Literature 1 and the like can be cited.
Japanese Patent Laid-Open No. 11-220168

  However, in the conventional configuration, even if it is attempted to further increase the luminance with the same driving voltage, it has been difficult to increase the luminance.

  The present invention solves the above-described problems, and relates to a light-emitting element capable of increasing luminance.

  In order to achieve the above object, the present invention provides a substrate capable of transmitting light, an n layer and a p layer provided on the substrate, and a light emitting layer provided between the n layer and the p layer. And a light-emitting element having 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 the Pt layer, the Ag layer, and the Mo layer. The film thickness of the Pt layer was set to 0.5 nm to 5 nm.

  A substrate capable of transmitting light, an n layer and a p layer provided on the substrate, a light emitting layer provided between the n layer and the p layer, and provided on the n layer and the p layer, respectively. A light-emitting element having an n-side electrode and a p-side electrode, wherein the p-side electrode is laminated at least from the p-layer side in the order of the Pt layer, the Ag layer, and the Mo layer, so that the light incident on the Pt layer Since it can be absorbed by itself and can be sufficiently reflected by the Ag layer, the luminance can be improved only by improving the electrode structure, and the electrical property between the p-side electrode and the p layer can be improved. Since the connection can be made sufficiently satisfactorily, it is not necessary to increase the drive voltage.

  The invention according to claim 1 is a substrate capable of transmitting light, an n layer and a p layer provided on the substrate, a light emitting layer provided between the n layer and the p layer, and the n layer A light emitting device having an n-side electrode and a p-side electrode provided on each of the p layers, wherein the p-side electrode is laminated at least from the p-layer side in the order of the Pt layer, the Ag layer, and the Mo layer, and the Pt layer By making a light emitting element characterized by having a film thickness of 0.5 nm to 5 nm, it is possible to prevent light incident on the Pt layer from being absorbed by the Pt layer itself, and the Ag layer is sufficient. Therefore, the luminance can be improved only by improving the electrode structure, and the electrical connection between the p-side electrode and the p-layer can be made satisfactorily. good.

  By using a light-emitting element in which the n-layer, the p-layer, and the light-emitting layer are formed of a semiconductor layer containing at least Ga and N, light having a short wavelength such as green, blue, or purple can be emitted.

  a first surface on which the p layer is provided in the n layer; and a second surface stepped down from the first surface facing the same direction as the first surface, and the second surface has n By using a light-emitting element having a side electrode, the p-side electrode and the n-side electrode can be electrically joined in the same plane direction, and a surface-mountable light-emitting element can be obtained. .

  An n-type conductive substrate capable of transmitting light, a p-layer provided on the n-type conductive substrate, a light-emitting layer provided between the n-type conductive substrate and the p-layer, and the n-type A light-emitting element having an n-side electrode and a p-side electrode provided on a conductive substrate and the p layer, respectively, wherein the p-side electrode is laminated at least from the p layer side in the order of the Pt layer and the Ag layer, By making a light emitting element characterized in that the film thickness of the Pt layer is 0.5 nm to 5 nm, it is possible to suppress the light incident on the Pt layer from being absorbed by the Pt layer itself, and Ag. Since the light can be sufficiently reflected by the layer, the luminance can be improved only by improving the electrode structure, and the electrical connection between the p-side electrode and the p-layer can be made sufficiently good, so that the drive voltage is increased. It is not necessary. Furthermore, an element with a low driving voltage can be manufactured, and an element with low power consumption can be obtained.

  By using a light-emitting element in which the thickness of the Ag layer is 5 nm to 2000 nm, desired reflection characteristics can be obtained and productivity can be improved.

  A light-emitting element mounting structure in which an electrode pattern is provided on the mounting member and the light-emitting element is mounted on the electrode pattern of the mounting member by surface mounting makes it possible to easily produce a high-luminance LED or the like. .

  Embodiments of the present invention will be described below with reference to the drawings.

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

  In FIG. 1, a substrate 1 having a transparency that allows light to pass through is used. As a constituent material of the substrate 1, a sapphire substrate, a SiC substrate, a GaN substrate, or the like is used.

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

  Reference numeral 4 denotes a light emitting layer provided on the n layer 3. The light emitting layer 4 is laminated on the n layer 3 directly 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 containing an appropriate amount of In when necessary to obtain a desired emission wavelength. Further, although the light emitting layer 4 has a single layer structure in FIG. 1, the luminance can be further improved by, for example, a multi-quantum well structure in which at least a pair of InGaN layers and GaN layers are alternately stacked. .

  Reference numeral 5 denotes a p layer laminated on the light emitting layer 4 directly or via a semiconductor layer containing at least Ga and N. The p layer 5 is composed of a semiconductor layer containing at least Ga and N, and is a p-type dopant. As Mg, Mg or the like is preferably used. The p layer 5 has a thickness of 0.3 μm.

  Reference numeral 6 denotes a p-side electrode provided on the p-layer 5, and the p-side electrode 6 is formed by sequentially stacking a Pt layer 61, an Ag layer 62, a Mo layer 63, and an Au layer 64 from the p-layer 5 side. .

  One of the features of the present invention is that the thickness of the Pt layer 61 is 0.5 nm to 5 nm. That is, the Pt layer 61 is formed with a film thickness of 0.5 nm or more in order to obtain a good electrical connection with the p layer 5, and if the Pt layer 61 is thicker than 5 nm, light absorption by the Pt layer 61 itself is performed. Becomes larger and the luminance is lowered.

  One of the characteristics of the present invention is that the thickness of the Ag layer 62 is 5 nm to 2000 nm. That is, if the thickness of the Ag layer 62 is less than 5 nm, sufficient reflection characteristics cannot be obtained. Conversely, if the thickness of the Ag layer 62 is more than 2000 nm, there is no change in the reflection characteristics, and a large amount of evaporation raw material is required to form the film. In addition, since the time required for this process becomes long, the manufacturing cost becomes high.

  Thus, by setting the film thickness of the Pt layer 61 to 0.5 to 5 nm, even if light emitted from the light emitting layer enters the Pt layer 61, light absorption in the Pt layer 61 itself can be suppressed and luminance can be reduced. In addition, the reflection characteristics at the Ag layer 62 can be sufficiently obtained. In the prior art shown in the prior art, since the Pt layer is 5 nm or more, a large amount of light absorption occurs and the luminance decreases.

  The present invention pays attention to the fact that the light absorption of the Pt layer 61 itself affects the luminance improvement, and the thickness of the Pt layer 61 is defined by considering the degree of ohmic junction and the like. As a result, the p-side electrode 6 Luminance can be improved only by improvement.

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

  7 is an n-side electrode provided on a part of the n-layer 3 exposed on the side where the p-layer 5 is provided. The n-side electrode 7 is formed by sequentially laminating a Ti layer 71 and an Au layer 72 from the n-layer 3 side. It is configured.

  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, a mounting member, or the like is preferably used. At least electrode patterns 9 and 10 are provided on the mounting member 8. For example, an Au layer 64 and an 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, respectively. Are joined together.

  The light emitting device configured as described above suppresses light absorption in the Pt layer 61 itself even if light emitted from the light emitting layer 4 is incident on the Pt layer 61 because the thickness of the Pt layer 61 is 5 nm or less. In addition, a sufficient electrical junction with the p layer 5 can be obtained by setting the film thickness to 0.5 nm or more.

  Therefore, 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, so that a sufficient luminance improvement can be realized only by improving the p-side electrode 6.

  In the present embodiment, the Pt layer, the Ag layer, the Mo layer, the Au layer, the Ti layer, or the like may be formed of each material alone or may be a layer 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 in a range that does not affect the characteristics of Pt may be used.

  As an example of the present invention, a method for manufacturing a gallium nitride-based compound semiconductor light-emitting device shown in FIG. 3 will be described. In the following examples, a method using a metal organic vapor phase growth method is shown as a method for growing a gallium nitride compound semiconductor, but the growth method is not limited to this, and a molecular beam epitaxy method or a metal organic molecule is used. It is also possible to use a line epitaxy method or the like.

(Example 1)
First, after placing a sapphire substrate 1 having a mirror-finished surface on a substrate holder in a reaction tube, the substrate 1 is heated to 1000 ° C. and heated for 10 minutes while flowing nitrogen and hydrogen. Then, dirt and moisture such as organic substances adhering to the surface of the substrate 1 were removed.

  Next, the temperature of the substrate 1 is lowered to 550 ° C., ammonia and trimethylgallium (hereinafter abbreviated as “TMG”) are supplied while flowing nitrogen as a carrier gas, and the buffer layer 2 made of GaN is formed. Growing with a thickness of 25 nm.

Next, after the supply of TMG is stopped and the temperature is raised to 1050 ° C., ammonia, TMG and SiH ₄ are supplied while flowing nitrogen and hydrogen as carrier gases, and the n layer 3 made of Si-doped GaN is formed. The film was grown at a thickness of 4 μm.

After the n-layer 3 is grown, supply of TMG and SiH ₄ is stopped, the substrate temperature is lowered to 750 ° C., and nitrogen, flowing as carrier gas at 750 ° C., ammonia, TMG, trimethylindium (hereinafter “TMI”) The light emitting layer 4 having a single quantum well structure made of undoped InGaN was grown to a thickness of 2 nm.

After the light emitting layer 4 is grown, the supply of TMI is stopped, and the substrate temperature is raised toward 1050 ° C. while flowing TMG, and subsequently, undoped GaN (not shown) is grown to a thickness of 4 nm. Reaches 1050 ° C., while flowing nitrogen and hydrogen as carrier gases, ammonia, TMG, trimethylaluminum (hereinafter abbreviated as “TMA”), cyclopentadienyl magnesium (hereinafter referred to as “Cp ₂ Mg”) (Abbreviated)), a p-type cladding layer 51 made of AlGaN doped with Mg was grown to a thickness of 0.2 μm.

After growing the p-type cladding layer 51, ammonia, TMG, TMA, and Cp ₂ Mg are supplied while flowing nitrogen gas and hydrogen gas as carrier gases while maintaining the temperature of the substrate 1 at 1050 ° C., and Mg A p-type contact layer 52 made of AlGaN doped with is grown to a thickness of 0.1 μm.

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

After the SiO ₂ film is deposited on the surface of the laminated structure made of the gallium nitride compound semiconductor formed in this way by the CVD method without performing any additional annealing, it is roughly processed by photolithography and wet etching. An SiO ₂ mask for etching was formed by patterning into a shape. Then, by reactive ion etching, a part of the p-type contact layer 52, the p-type cladding layer 51, the intermediate layer, the light emitting layer 4 and the n layer 3 is formed at a depth of about 0.4 μm in the direction opposite to the stacking direction. Then, the surface of the n layer 3 was exposed.

Then, after removing the etching SiO ₂ mask 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 to remove the p-type contact. More than 80% of the surface of the layer 52 was exposed. Then, the laminated structure is mounted in a chamber of a vacuum vapor deposition apparatus, the inside of the chamber is evacuated to 2 × 10 ⁻⁶ Torr or less, and then the surface of the p-type contact layer 52 exposed by the electron beam vapor deposition method and photo A 1 nm thick Pt layer 61 was deposited on the resist. Subsequently, an Ag layer 62 having a thickness of 100 nm was deposited, and a Mo layer 63 having a thickness of 100 nm and an Au layer 64 having a thickness of 1 μm were sequentially deposited. Next, the laminated structure is taken out of the chamber, and the Pt layer 61, the Ag layer 62, the Mo layer 63, and the Au layer 64 on the photoresist are removed together with the photoresist to thereby form the Pt layer 61 on the surface of the p-type contact layer 52. Then, the p-side electrode 6 in which the Ag layer 62, the Mo layer 63, and the Au layer 64 are sequentially laminated is formed.

A photoresist was applied again on the surface of the laminated structure, and only the photoresist on the exposed surface portion of the n layer 3 was removed by photolithography to expose a portion of the surface of the n layer 3. Then, the laminated structure is mounted in a chamber of a vacuum deposition apparatus, the inside of the chamber is evacuated to 2 × 10 ⁻⁶ Torr or less, and then the exposed surface of the n layer 3 and the photoresist by electron beam deposition. On top of this, a Ti layer 71 having a thickness of 100 nm was deposited, and an Au layer 72 having a thickness of 1.5 μm was further deposited. Next, the Ti layer 71 and the Au layer 72 are sequentially laminated on a part of the surface of the n layer 3 by removing the laminated structure from the chamber and removing the Ti layer 71 and the Au layer 72 on the photoresist together with the photoresist. The n-side electrode 7 thus formed was formed.

  Thereafter, the back surface of the substrate 1 was polished and adjusted to a thickness of about 100 μm, and separated into chips by scribing. In this way, the gallium nitride compound semiconductor light emitting device shown in FIG. 3 was obtained.

  This light emitting element was bonded by Au bumps on a Si diode having a pair of positive and negative electrodes with the electrode formation surface side facing down. 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. Thereafter, 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 uniform surface light emission was obtained from the surface opposite to the side where the laminated structure of the substrate 1 was formed. At this time, the forward operating voltage was 3.4 V, and the light emission output was 6.4 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 was changed to 6 nm in Example 1. 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 uniform surface emission was obtained from the surface opposite to the side where the laminated structure of the substrate 1 was formed. The forward operating voltage was 3.4 V, and the light emission output was 4.1 mW.

  The relationship between the film thickness of the Pt layer and the luminance of the light emitting element and the relationship between the film thickness of the Pt layer and the driving voltage described above will be described with reference to FIGS.

  As shown in FIG. 4, when the film thickness of the Pt layer is thicker than 5 nm, the luminance decreases due to the reason that the amount of light absorption in the Pt layer itself is remarkably increased. Further, as can be seen from FIG. 5, when the film thickness of the Pt layer is less than 0.5 nm, an increase in driving voltage that is considered to be caused by the fact that the ohmic junction with the p layer is not reliably performed is observed.

  Therefore, it can be seen that the Pt layer is preferably 0.5 nm to 5 nm in terms of electrical characteristics or luminance.

  The light incident on the Pt layer can be prevented from being absorbed by the Pt layer itself, and can be sufficiently reflected by the Ag layer, so that the luminance can be improved only by improving the electrode structure, It is useful as a light-emitting element used in equipment, displays, lighting, backlights, and the like.

The side view which shows the light emitting element in one embodiment of this invention Side view showing a conventional light emitting device The side view which shows the light emitting element in one embodiment of this invention The graph which shows the relationship between the film thickness of the Pt layer of a light emitting element in one embodiment of this invention, and a brightness | luminance The graph which shows the relationship between the film thickness of the Pt layer of the light emitting element in one embodiment of this invention, and a drive voltage

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Buffer layer 3 n layer 4 Light emitting layer 5 p layer 6 p side electrode 7 n side electrode 8 Mounting member 9, 10 Electrode pattern 51 p type clad layer 52 p type contact layer 61 Pt layer 62 Ag layer 63 Mo layer 64 Au layer 71 Ti layer 72 Au layer

Claims (1)

A substrate capable of transmitting light; an n layer and a p layer provided on the substrate; a light emitting layer provided between the n layer and the p layer; and the n layer and the p layer. A light emitting device having an n-side electrode and a p-side electrode, wherein the p-side electrode is laminated at least from the p-layer side in the order of the Pt layer, the Ag layer, and the Mo layer, and the thickness of the Pt layer is 0.5 nm to A light-emitting element having a thickness of 5 nm.

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