JP3540605B2 - Light emitting element - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light emitting device, and more particularly, to a light emitting device that emits light from a transparent substrate side using, for example, a transparent substrate.
[0002]
[Prior art]
Conventionally, a light emitting element such as a light emitting diode generally has a structure in which light emitted from a light emitting layer is emitted in a direction opposite to a substrate.
[0003]
However, in this structure, there is a problem that the light transmitting electrode and the pad electrode formed on the semiconductor layer reduce the emitted light.
[0004]
In order to solve this problem, there has been proposed a light emitting device using a transparent substrate such as a sapphire substrate, which has a structure in which light is emitted from the transparent substrate side (Japanese Patent Laid-Open No. 6-120562).
[0005]
As shown in FIG. 8A, the light-emitting device 1 includes a transparent substrate 2, an n-type semiconductor layer 3 formed on the transparent substrate 2, and a p-type semiconductor layer formed on the n-type semiconductor layer 3. 4, an n-side electrode 5 formed on the n-type semiconductor layer 3, and a p-side electrode 6 formed on the p-type semiconductor layer 4.
[0006]
In the light emitting device 1, light emitted from the n-type semiconductor layer 3 and the p-type semiconductor layer 4 passes through the transparent substrate 2 and is emitted in the light emission direction A.
[0007]
[Problems to be solved by the invention]
However, in the above conventional technique, there is a problem that light emitted from the light emitting element 1 is not uniform.
[0008]
FIG. 8B shows the relationship between the position on one main surface of the transparent substrate 2 on the light emission direction A side and the light emission intensity. As is clear from FIG. 8B, in the conventional light emitting device 1, the light emission intensity at the portion corresponding to the n-side electrode 5 is reduced, and uniform light emission intensity cannot be obtained.
[0009]
Therefore, a main object of the present invention is to provide a light emitting element capable of obtaining uniform and high light emission intensity over the entire light emitting element.
[0010]
[Means for Solving the Problems]
In order to solve the above problem, the light emitting device according to claim 1, comprising a transparent substrate, a semiconductor layer of at least one conductivity type and a semiconductor layer of another conductivity type formed on one main surface of the transparent substrate. A light emitting element including a semiconductor layer included in this order from the side, a first electrode connected to the semiconductor layer of one conductivity type, and a second electrode formed on the semiconductor layer of another conductivity type, a portion of a side surface of the substrate, the side surface adjacent to the side surface of the transparent substrate of the side surfaces of the one conductivity type semiconductor layer, forming a substantially flush slope having a predetermined angle with respect to one main surface, wherein A first electrode is formed on the slope, and light emitted from the semiconductor layer is reflected by the first electrode and emitted through a transparent substrate .
[0011]
According to a second aspect of the present invention, in the light emitting element according to the first aspect, the first electrode is formed so as to surround the second electrode.
[0012]
According to a third aspect of the present invention, in the light emitting element according to the first or second aspect, the second electrode is at least one of palladium and nickel formed on a part of the semiconductor layer of another conductivity type. And a semiconductor film of another conductivity type and an aluminum film formed on the metal film.
[0013]
In the light emitting device according to the first aspect, light emitted from the semiconductor layer is reflected by the first electrode on the slope formed by a part of the transparent substrate and the semiconductor layer. Therefore, according to the light emitting device of the first aspect, the light emission intensity does not decrease even at the first electrode portion, and light is confined by the first electrode, so that a uniform and high light emission intensity can be obtained over the entire light emitting device. Can be
[0014]
In the light emitting device according to the second aspect, since the first electrode is formed so as to surround the second electrode, current is uniformly injected from the first electrode and the second electrode into the semiconductor layer. Therefore, according to the light emitting element of the second aspect, uniform light emission can be obtained.
[0015]
In the light emitting device according to the third aspect, the second electrode includes palladium or nickel and an aluminum film, and the aluminum film reflects light emitted from the semiconductor layer with high reflectance. Therefore, according to the light emitting device of the third aspect, a uniform and high emission intensity can be obtained over the entire light emitting device.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
[0017]
FIG. 1A is a plan view of the light emitting element 10 of this embodiment, and FIG. 1B is a front cross-sectional view taken along a line X-Y in FIG.
[0018]
Referring to FIG. 1, light emitting element 10 includes transparent substrate 12, semiconductor layer 14, p-side electrode 16, and n-side electrode 18.
[0019]
A part of the side surface of the transparent substrate 12 on the side of the semiconductor layer 14 and the side surface of the semiconductor layer 14 form a substantially flat slope 20 having a certain angle with respect to one main surface 12 a of the transparent substrate 12.
[0020]
The light emitting element 10 is 400 μm square, for example, and the slope 20 has a width L in FIG. 1B of 25 μm, for example.
[0021]
The transparent substrate 12 is, for example, a sapphire substrate or the like. Note that the transparent substrate 12 only needs to have a small light absorption coefficient at the wavelength of light emitted from the semiconductor layer 14.
[0022]
The semiconductor layer 14 is formed on the transparent substrate 12 and includes, for example, an n-type GaN contact layer 22, an InGaN light-emitting layer 24, and a p-type GaN contact layer 26 laminated on the transparent substrate 12. The thickness of each semiconductor layer is, for example, 4 μm for the n-type GaN contact layer 22, 10 nm for the InGaN light emitting layer 24, and 0.3 μm for the p-type GaN contact layer 26.
[0023]
The p-side electrode 16 is formed on the p-type GaN contact layer 26. As shown in the schematic cross-sectional view of FIG. 2, the p-side electrode 16 includes a contact electrode portion 16a made of palladium (Pd) formed on a part of the p-type GaN contact layer 26, and the contact electrode portion 16a and the p-type A reflective electrode portion 16b made of aluminum (Al) formed on the GaN contact layer 26. The contact electrode portion 16a is formed of, for example, a plurality of strips of Pd. The thickness of the contact electrode portion 16a is, for example, 200 nm, and the thickness of the reflective electrode portion 16b is, for example, 500 nm.
[0024]
It should be noted that the p-side electrode 16 only needs to be ohmicly connected to the p-side GaN contact layer 26 and have a high reflectance. For example, the contact electrode section 16a may be Ni or an alloy of Pd and Ni.
[0025]
The n-side electrode 18 is formed on the transparent substrate 12 and the n-type GaN contact layer 22 on the slope 20 so as to surround the p-side electrode 16. A metal thin film is used for the n-side electrode 18. For example, from the slope 20 side, Al (thickness 6 nm), Si (thickness 2 nm), Ni (thickness 10 nm), and Al (thickness 0.5 μm) are laminated in this order. It is preferable to use a high-reflectivity metal thin film that has been formed, or a high-reflectivity metal thin film in which Ti (thickness: 2 nm) and Al (thickness: 0.5 μm) are stacked in this order from the slope 20 side.
[0026]
Referring to FIG. 3, an example of a manufacturing process of the light emitting device 10 will be described.
[0027]
First, as shown in FIG. 3A, a semiconductor layer 14 and a mask 28 having a trapezoidal vertical cross section are formed on the transparent substrate 12 in this order. The semiconductor layer 14 includes an n-type GaN contact layer 22, an InGaN light-emitting layer 24, and a p-type GaN contact layer 26, which are sequentially stacked on the transparent substrate 12.
[0028]
The semiconductor layer 14 can be formed by, for example, MOCVD using trimethylgallium, trimethylindium, and ammonia as source gases and silane and cyclopentadienylmagnesium as doping gases.
[0029]
The mask 28 having a trapezoidal vertical cross section is formed, for example, by uniformly depositing 30 μm thick Al on the p-type GaN contact layer 26 by an electron beam evaporation method, and then forming the trapezoidal vertical cross section by a photolithography process and an etching process. It can be formed by processing as follows.
[0030]
Thereafter, as shown in FIG. 3B, the mask 28, the semiconductor layer 14, and the transparent substrate 12 are simultaneously etched to form a concave portion 30 having a V-shaped cross section. The inner surface of the recess 30 becomes the slope 20.
[0031]
The concave portion 30 having a V-shaped cross section can be formed, for example, by performing etching such that the etching rates of the mask 28, the semiconductor layer 14, and the transparent substrate 12 become substantially equal. For example, when a parallel plate type dry etching apparatus is used, discharge power is 300 W, pressure is 5 Torr to 10 Torr, and CF4 gas is used as an etching gas, the mask 28, the semiconductor layer 14, and the transparent substrate 12 can be etched at substantially the same etching rate. .
[0032]
Thereafter, as shown in FIG. 3C, after removing the mask 28, the p-side electrode 16 is formed on the p-type GaN contact layer 26. The structure of the p-side electrode 16 is as shown in FIG. The p-side electrode 16 is formed by forming a strip-shaped contact electrode portion 16a made of Ni on the p-type GaN contact layer 26, and then forming a reflective electrode portion 16b made of Al on the p-type GaN contact layer 26 and the contact electrode portion 16b. Can be formed by vapor deposition.
[0033]
The contact electrode portion 16a can be formed by depositing a Ni thin film on the slope 20 and the p-type GaN contact layer 26 by an electron beam evaporation method, and then removing an unnecessary Ni thin film using a photolithography process and an etching process. Similarly, the reflective electrode portion 16b can also be formed by depositing an Al thin film and then removing an unnecessary Al thin film using a photolithography process and an etching process.
[0034]
Thereafter, as shown in FIG. 3D, an n-side electrode 18 is formed on the inclined surface 20 on the transparent substrate 12 and the n-type GaN contact layer 22 and is separated into, for example, 400 μm square elements.
[0035]
The n-side electrode 18 is formed by forming a photoresist except for the portion where the n-side electrode 18 is formed, and after evaporating an Al thin film, a Si thin film, a Ni thin film, and an Al thin film in this order by an electron beam evaporation method, lifts off. Can be formed.
[0036]
Separation for each element can be easily performed by, for example, forming a scribe line on the transparent substrate 12 with a scriber.
[0037]
Thus, the light emitting element 10 is formed.
[0038]
The function of the light emitting element 10 is schematically shown in FIG.
[0039]
Referring to FIG. 4A, in the light emitting device 10, light emitted from the InGaN light emitting layer 24 passes through the transparent substrate 12, or the p-side electrode 16 or the p-side electrode 16 and the n-side electrode 18 And is emitted in the direction of light emission direction A.
[0040]
FIG. 4B shows the relationship between the position on the one main surface 12b of the transparent substrate 12 on the light emission direction A side and the light emission intensity.
[0041]
As is clear from FIG. 4B, according to the light emitting element 10, the decrease in the light emission intensity is small even at the position corresponding to the portion where the n-side electrode 18 is formed. Therefore, according to the light emitting element 10, unlike the light emitting element 1 having the conventional structure shown in FIG. 8, uniform light emission can be obtained.
[0042]
Further, in the light emitting element 10, the n-side electrode 18 is formed at a constant angle with respect to the one main surface 12a, so that the light emitted from the InGaN light emitting layer 24 is prevented from dissipating to the side surface and the light emission direction is reduced. A has the effect of trapping in A. Therefore, according to the light emitting element 10, high light emission intensity can be obtained.
[0043]
Therefore, according to the light emitting element 10, it is possible to obtain a light emitting element having high light emission intensity uniform over the entire light emitting element 10.
[0044]
As shown in FIG. 4 (b), when the angle α (see FIG. 4 (a)) between the one main surface 12a of the transparent substrate 12 and the inclined surface 20 is 70 degrees, the case where α is 10 degrees A more uniform and higher light emission intensity can be obtained.
[0045]
On the other hand, by decreasing α, the slope 20 and the n-side electrode 18 can be easily formed, and the contact area between the n-type GaN contact layer 22 and the n-side electrode 18 can be increased. In particular, when α is set to 45 degrees or less, the slope 20 and the n-side electrode 18 can be easily formed with high accuracy.
[0046]
Therefore, in order to obtain a light emitting device 10 that can obtain uniform light emission intensity and can be easily formed, α is preferably set to 30 degrees to 45 degrees.
[0047]
Furthermore, since the light emitting element 10 has a structure in which the n-side electrode 18 surrounds the periphery of the p-side electrode 16, current is uniformly injected from the p-side electrode 16 and the n-side electrode 18 to the semiconductor layer 14. And a more uniform emission intensity can be obtained.
[0048]
Further, in the light emitting device 10 of the present invention, since the high reflectance metal is used for the p-side electrode 16, light emitted from the InGaN light emitting layer 24 is reflected with a high reflectance.
[0049]
For example, in the structure of the p-side electrode 16 shown in FIG. 2, since the aluminum used for the reflective electrode portion 16b has a high reflectance, the light emitted from the InGaN light emitting layer 24 is reflected with a high reflectance. Therefore, according to the light emitting element 10, high light emission intensity can be obtained.
[0050]
The p-side electrode 16 is not limited to the structure shown in FIG. 2, but may have the structure shown in FIG. The p-side electrode 17 shown in FIG. 5A includes a contact electrode portion 17a made of a Pd thin film formed on the p-type GaN contact layer 26 and a reflective electrode portion 17b made of Al formed on the contact electrode portion 17a. And For the contact electrode portion 17a, nickel (Ni) or an alloy of Pd and Ni may be used instead of Pd.
[0051]
In the structure of the p-side electrode 17 shown in FIG. 5A, the reflectance of the p-side electrode 17 can be improved by reducing the thickness of the contact electrode portion 17a. FIG. 5B shows a change in the light output of the light emitting element 10 when the material and the film thickness of the contact electrode portion 17a and the reflective electrode portion 17b are changed.
[0052]
The light output in FIG. 5B is relative to 100 when the light output is 100 when Pd (thickness: 30 nm) is used for the contact electrode portion 17a and Au (thickness: 200 nm) is used for the reflective electrode portion 17b. Indicates the value. As is clear from FIG. 5B, the light output is maximized when Pd with a thickness of 2 nm is used as the contact electrode portion 17a and Al with a thickness of 200 nm is used as the reflective electrode portion 17b.
[0053]
Therefore, according to the light emitting device 10 using the structure of FIG. 5A, high luminance can be obtained by changing the material and the film thickness of the contact electrode portion 17a and the reflective electrode portion 17b.
[0054]
With reference to FIG. 6, another example of the manufacturing process of the light emitting device 10 is shown. This manufacturing process is different from the manufacturing process shown in FIG.
[0055]
First, as shown in FIG. 6A, a semiconductor layer 14 is formed on a transparent substrate 12, and then a groove 32 is formed. The process of forming the semiconductor layer 14 is the same as that described with reference to FIG. The groove 32 has a depth of, for example, 10 μm from the surface of the semiconductor layer 14 and can be easily formed using a dicing saw or the like.
[0056]
Thereafter, as shown in FIG. 6B, a mask 28 is formed on the p-type GaN contact layer 26 so that the vertical cross section becomes trapezoidal. The step of forming the mask 28 is the same as the step described with reference to FIG.
[0057]
Thereafter, the mask 28, the semiconductor layer 14, and the transparent substrate 12 are etched to form a concave portion 30 having a V-shaped cross section, as shown in FIG. The etching step is the same as the step described with reference to FIG.
[0058]
Thereafter, as shown in FIG. 6D, after removing the mask 28, the p-side electrode 16 and the n-side electrode 18 are formed. The step of forming the p-side electrode 16 and the n-side electrode 18 is the same as the step described with reference to FIGS. 3C and 3D.
[0059]
Thus, the light emitting element 10 is formed.
[0060]
In the manufacturing process shown in FIG. 6, by forming the groove 32, the etching process for forming the recess 30 can be shortened. Therefore, according to the manufacturing process shown in FIG. 6, the manufacture of the light emitting element 10 is easy.
[0061]
FIG. 7 shows an example in which the light emitting element 10 of the present invention is used for a light emitting diode 40.
[0062]
The light emitting diode 40 includes a light emitting element 10, stems 42 and 44, a mount base 46, an insulating member 48, an n-side electrode connecting member 50, a conductive adhesive 52, a gold wire 54, and a transparent resin (FIG. (Not shown).
[0063]
The stems 42 and 44 are made of, for example, metal and are electrically connected to a mount base 46.
[0064]
The mount base 46 is made of metal and is electrically connected to the p-side electrode 16 of the light emitting element 10 by a conductive adhesive 52.
[0065]
The n-side electrode connecting member 50 is made of, for example, a metal, and has a slope 58 formed so as to be in close contact with the n-side electrode 18. The n-side electrode connection member 50 is electrically insulated from the mount base 46 by an insulating member 48, and is electrically connected to the n-side electrode 18 by a conductive adhesive (not shown). The n-side electrode connection member 50 also functions as a reflecting mirror.
[0066]
The stem 44 is electrically connected to the n-side electrode connection member 50 by a gold wire 54.
[0067]
The light emitting element 10 is molded with a transparent resin (not shown), like a normal light emitting diode.
[0068]
In the light emitting diode 40, when the light emitting element 10 is fixed to the mount base 46 and the n-side electrode connecting member 50 to be electrically connected, the light emitting element 10 is fixed at a predetermined position by the n-side electrode 18 and the inclined surface 58. Is done. Therefore, according to the light emitting diode 40 using the light emitting element 10, when the light emitting element 10 is fixed to the mount base 46 and the n-side electrode connecting member 50 and electrically connected, the p-side electrode 16 and the n-side electrode 18 are connected. And that short circuit can be prevented.
[0069]
That is, in the light emitting diode using the conventional light emitting element 1 (FIG. 8A), the positioning of the light emitting element 1 is not easy, and when the light emitting element 1 is fixed, the n-side electrode 5 and the p-side electrode 6 are connected. Although there was a problem that short-circuit was easily caused, according to the light-emitting diode 40 using the light-emitting element 10, the short-circuit between the p-side electrode 16 and the n-side electrode 18 is difficult, and the production can be performed with higher yield than the conventional one.
[0070]
As described above, the embodiment of the present invention has been described by way of example. However, the above embodiment is merely an example when the present invention is used, and the present invention is not limited to the above embodiment.
[0071]
For example, the semiconductor layer 14 described in the above embodiment may have any structure as long as it functions as a light emitting element. For example, a GaN buffer layer or the like may be formed between the transparent substrate 12 and the n-type GaN contact layer 22, or a clad layer or the like may be formed on both sides of the InGaN light emitting layer. Further, the order of the respective semiconductor layers formed on the sapphire substrate 12 may be reversed.
[0072]
【The invention's effect】
As described above, according to the present invention, since the electrodes are formed on the slope having a certain angle with respect to the main surface of the transparent substrate, it is possible to obtain a light emitting element with uniform and high luminous intensity.
[0073]
Further, since the electrodes formed on the slope are formed so as to surround the other electrodes, current injection is performed uniformly, and a light-emitting element with uniform light emission intensity is obtained.
[0074]
Furthermore, a light-emitting element with high emission intensity can be obtained by using an electrode formed on a semiconductor layer with a metal having a high reflectance.
[Brief description of the drawings]
FIG. 1 is a view showing an embodiment of the present invention, wherein (a) is a plan view and (b) is a front sectional view.
FIG. 2 is a cross-sectional view illustrating an example of a structure of a p-side electrode according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating an example of a manufacturing process of the light emitting device according to the embodiment of the present invention.
FIG. 4 is an illustrative view showing functions of a light emitting element in one embodiment of the present invention;
FIG. 5A is a cross-sectional view showing another example of the structure of the p-side electrode according to an embodiment of the present invention, and FIG. 5B shows the relationship between the contact electrode portion and the reflective electrode portion and the light output. FIG.
FIG. 6 is a cross-sectional view showing another example of the manufacturing process of the light emitting device in one embodiment of the present invention.
FIG. 7 is a front sectional view showing a light emitting diode using a light emitting element according to an embodiment of the present invention.
FIG. 8 is an illustrative view showing a structure and a light emission intensity of a conventional light emitting element.
[Explanation of symbols]
Reference Signs List 10 light emitting element 12 transparent substrate 12a one main surface 14 semiconductor layer 16, 17 p-side electrode 16a, 17a contact electrode portion 16b, 17b reflective electrode portion 18 n-side electrode 20 slope 22 n-type GaN contact layer 24 InGaN light-emitting layer 26 p-type GaN contact layer 28 mask 30 recess 32 groove 40 light emitting diode 46 mount base 50 n-side electrode connection member A light emission direction

Claims (3)

A transparent substrate, a semiconductor layer formed on one main surface of the transparent substrate and including at least one conductive semiconductor layer and another conductive semiconductor layer in this order from the transparent substrate side, and the one conductive semiconductor A light emitting element comprising: a first electrode connected to a layer; and a second electrode formed on the other conductive semiconductor layer,
A part of the side surface of the transparent substrate and a side surface adjacent to the side surface of the transparent substrate among the side surfaces of the one conductivity type semiconductor layer have a substantially flat inclined surface having a certain angle with respect to the one main surface. Wherein the first electrode is formed on the slope, and light emitted from the semiconductor layer is reflected by the first electrode and emitted through the transparent substrate. . The light emitting device according to claim 1, wherein the first electrode is formed to surround the second electrode. The second electrode is formed on a metal film containing at least one of palladium and nickel formed on a part of the other conductive type semiconductor layer, and on the other conductive type semiconductor layer and the metal film. The light emitting device according to claim 1, further comprising: an aluminum film formed.

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