JPH0722648A - Silicon carbide light emitting diode device - Google Patents

Abstract

PURPOSE:To increase luminous intensity by forming a surface which is not parallel with the surface of a P-type SiC layer, in the part which is positioned on the side opposite to a P-type side electrode of an N-type SiC substrate and faces the electrode. CONSTITUTION:An N-type SiC single crystal substrate 2 has one main surface 2a and the other main surface (non-parallel surface) 2b inclined at an angle theta1 to the main surface 2a. Thereby emitted light is outputted outside an element 1, while the frequency of reflection from the other main surface 2b of the substrate 2 or the surface (upper surface) of a P-type SiC single crystal layer 4 is small, that is, while the absorption in the element 1 is small. Hence the luminous intensity of the element can be increased.

Description

Detailed Description of the Invention

[0001]

This invention relates to silicon carbide light emitting diode devices.

[0002]

2. Description of the Related Art In general, silicon carbide (SiC) has been attracting attention as an environment-resistant semiconductor material because of its excellent heat resistance and mechanical strength and physical and chemical properties such as resistance to radiation.

Moreover, the SiC crystal is an indirect transition type IV-IV compound, and the SiC crystal is 3C type, 4H type, 6H type, 1
There are various crystalline polymorphs such as 5R type, and the forbidden band width is 2.
From a wide range of 4 to 3.3 eV, p-type and n-type crystals are obtained and a pn junction can be formed,
It can be used as a light emitting diode material that emits visible light in all wavelength ranges from red to blue. Above all, 6H type SiC having a forbidden band width of about 3 eV at room temperature
Crystals are used as materials for blue light emitting diodes.

An example of such a silicon carbide light emitting diode element is shown in the magazine "Electronics", Vol. 26, No. 14, pp. 128-129, 1984.

FIG. 5 is a sectional view showing a silicon carbide light emitting diode device using a conventional silicon carbide light emitting diode element.

In the figure, 51 is a silicon carbide light emitting diode element, and 52 is a conductive metal stem on which the light emitting diode element 51 is mounted.

This silicon carbide light emitting diode element 51
Is an n-type SiC layer 54 serving as a light-emitting layer formed on one main surface of the n-type SiC substrate 53, a p-type SiC layer 55 formed on the n-type SiC layer 54, and a p-type SiC layer 55. And n-type SiC substrate 53 on the other main surface thereof, and a p-type side electrode and n-type side electrodes 56 and 57, respectively.

On the other hand, the stem 52 is composed of a mounting surface 52a on which the light emitting diode element 51 is mounted, and a reflecting surface 52b surrounding the light emitting diode element 51 and reflecting light emitted from this element 51 to the upper side of the device. ing.

In the light emitting diode element 51, the mounting surface 52a of the stem 52 on the substrate 53 side is formed using silver paste 58.
And the n-type side electrode 57 and the stem 52 are electrically connected. The p-type side electrode 56 is electrically connected to an electrode terminal (not shown) with a conductive wire.

[0010]

In such a SiC light emitting diode element, light is emitted in a region of the n-type SiC layer 54 which is substantially proportional to the electrode area of the p-type side electrode 56 near the pn junction (light-emitting layer). Occurs. Of this emitted light, p-type Si
Light that goes vertically to the C layer 55 side and the mounting surface 52 of the stem 52
The light traveling vertically to the a side is absorbed while being multiple-reflected by the other main surface of the substrate 53 and the surface of the p-type SiC layer 55, so that there is a problem that sufficient light cannot be extracted from the device. there were.

Therefore, according to the present invention, SiC having high emission intensity is used.
It is an object to provide a light emitting diode device.

[0012]

A SiC light emitting diode device of the present invention comprises an n-type SiC substrate, an n-type SiC layer formed on the n-type SiC substrate, and an n-type SiC layer. a p-type SiC layer, a p-type side electrode formed on a part of the p-type SiC layer, and an n-type side electrode formed on the opposite side of the n-type SiC substrate from the p-type side electrode, And a surface non-parallel to the surface of the p-type SiC layer is provided in a portion of the n-type SiC substrate opposite to and facing the p-type side electrode.

Particularly, the non-parallel surface emits light under the p-type side electrode and is at least a part of light traveling in the direction perpendicular to the surface of the p-type SiC layer and toward the substrate. Is set so that an extension line of the traveling optical path immediately after being reflected by the non-parallel surface exists outside the p-type side electrode.

[0014]

According to the structure of the present invention, since the surface of the n-type SiC substrate opposite to and facing the p-type side electrode is provided with a surface that is not parallel to the surface of the p-type SiC layer. The emitted light is emitted to the outside of the device while the number of reflections with the surface of the substrate or the p-type SiC layer is small.

In particular, at least a part of the light whose non-parallel surface emits light under the p-type side electrode and is perpendicular to the surface of the p-type SiC layer and progresses toward the substrate side. Is set so that the extension line of the traveling optical path immediately after being reflected by the non-parallel surface exists outside the p-type side electrode, the amount of light blocked by the p-type side electrode is Less.

[0016]

EXAMPLE A SiC light emitting diode device according to a first example of the present invention will be described with reference to the drawings. FIG. 1 shows S of this embodiment.
It is a schematic cross section of an iC light emitting diode device.

In the figure, 1 is a SiC light emitting diode element, and 2 is an n-type SiC single crystal substrate having a 300 μm square upper surface and a central portion having a thickness of 200 μm, which constitutes this element 1. It has a main surface 2a and another main surface (non-parallel surface) 2b forming an angle θ ₁ with the main surface 2a. In this embodiment, the angle θ ₁ is 37 degrees.

On this one main surface 2a, N serving as a donor is formed.
(Constant) layer thickness 5 doped with Al (aluminum) that becomes an acceptor to the extent that it does not invert to p-type together with (nitrogen)
An n-type SiC single crystal layer (light emitting layer) 3 having a thickness of μm is epitaxially grown. On the n-type SiC single crystal layer 3,
Al (doped) layer thickness of 5μ
The p-type SiC single crystal layer 4 of m is epitaxially grown.

At the center of the p-type SiC single crystal layer 4,
A p-type side electrode 5 having an upper surface of 170 μm square is formed. As such a p-type side electrode 5, Ti-Al having a thickness of about 1 μm is used.
Conventionally known electrodes such as an electrode in which a p-type ohmic electrode made of —Ti and a bonding electrode made of Au—Ti—Pd having a thickness of about 1 μm are formed in this order can be used.

An n-type side electrode 6 is formed on the entire other main surface 2b of the n-type SiC single crystal substrate 2. As such an n-type side electrode 6, Ni having a thickness of about 1 μm is used.
Conventionally known electrodes such as an n-type ohmic electrode made of —Au and a bonding electrode made of Au—Ti—Pd having a thickness of about 1 μm configured in this order can be used.

Reference numeral 7 denotes a conductive metal stem which surrounds the mounting surface 7a on which the light emitting diode element 1 is mounted and the light emitting diode element 1 and reflects light emitted from the element 1 to the upper side of the device. It is composed of a reflecting surface 7b.

The light emitting diode element 1 is fixed to the mounting surface 7a of the stem 7 on the substrate 2 side by a conductive adhesive material 8 such as silver paste, and the n-type side electrode 6 and the stem 7 are electrically connected. It The p-type side electrode 5 is electrically connected to an electrode terminal (not shown) with a conductive wire.

Here, the manufacturing of the light emitting diode element 1 will be described.

First, an n-type SiC single crystal substrate 2 having a constant thickness is prepared. Next, the n-type SiC single crystal layer 3 and the p-type SiC single crystal layer 4 are arranged in this order on the main surface 2a of the substrate 2 in this order by the LPE method (liquid phase epitaxial growth method) or the chemical vapor deposition method (CVD method). ) Is used for epitaxial growth. After that, the surface opposite to the one main surface 2a of the substrate 2 is polished to form another main surface 2 forming an angle θ ₁ with the one main surface 2a.
b is formed. The process is completed by the conventionally known steps.

In the light emitting diode element 1, the other main surface 2b of the substrate 2 is an inclined surface (non-parallel) forming an angle θ ₁ with the surface of the p-type SiC single crystal layer 4 (upper surface of the uppermost layer). Face)
Therefore, the emitted light may be absorbed while the number of reflections with the other main surface 2b of the substrate 2 or the surface (upper surface) of the p-type SiC single crystal layer 4 is small, that is, in the element 1. It is emitted to the outside of the element 1 while the amount is small. As a result, the emission intensity of such an element (device) increases.

Further, in such a light emitting diode element 1, in the n-type SiC single crystal layer 3 serving as a light-emitting layer, a portion 9 (portion indicated by a dot in the figure) depending on the p-type side electrode 5 mainly emits light. In this embodiment, in particular, the angle θ ₁ of the other main surface 2b is the direction perpendicular to the surface (upper surface) of the p-type SiC single crystal layer 4 which emits light at the portion 9 and Extension lines 10 and 10 of the traveling optical path immediately after being reflected by the other main surface 2b of the light traveling to the substrate 2 side are present outside the p-type side electrode 5 (the p-type side electrode 5 and Since they are set so as not to cross each other, the amount of light blocked by the p-type side electrode 5 is reduced. Therefore, since more light is emitted to the outside of the element 1, the emission intensity of such an element (device) becomes larger.

Next, a SiC light emitting diode device according to a second embodiment of the present invention will be described with reference to the drawings. The present embodiment is different from the first embodiment in the shape of the n-type SiC single crystal substrate, and the same portions or corresponding portions as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. Incidentally, FIG.
FIG. 2A is a sectional view schematically showing the structure of this light emitting diode device, and FIG. 2B is a bottom view of a light emitting diode element used in this light emitting diode device.

In FIG. 2, reference numeral 11 denotes a light emitting diode element, and 12 has a thickness L constituting the element 11 of 200 μm.
m is an n-type SiC single crystal substrate having an upper surface of 300 μm square.
The other main surface 12 opposite to the main surface 12a of the substrate 12
In b, a V-shaped stripe groove 13 having a width larger than the width of the p-type side electrode 5 including the facing portion, for example, 180 μm, is formed. The V-shaped stripe groove 13 is an inclined surface (non-parallel surface) forming the V-shape.
13 a and 13 a form an angle θ ₂ with respect to the one main surface 12 a of the substrate 12, respectively. In the case of the present embodiment, this angle θ ₂ is 37 ° (degrees).

An n-type side electrode 14 similar to that of the first embodiment is formed on the entire other main surface 12b including the V-shaped stripe groove 13.

This light emitting diode element 11 is fixed to the mounting surface 7a of the stem 7 on the substrate 12 side by using a conductive adhesive material 8 such as silver paste as in the first embodiment, and the n-type side electrode 14 is attached. And the stem 7 are electrically connected. The p-type side electrode 5 is electrically connected to an electrode terminal (not shown) with a conductive wire.

Here, the manufacturing of the light emitting diode element 11 will be described.

First, an n-type SiC single crystal substrate 12 having a constant thickness is prepared. Next, the n-type SiC single crystal layer 3 and the p-type SiC single crystal layer 4 are formed on the one main surface 12a of the substrate 12 in this order by the LPE method (liquid phase epitaxial growth method) or the chemical vapor deposition method). Epitaxial growth.
Then, the surface opposite to the one main surface 12a of the substrate 12 is polished to a desired substrate thickness and another main surface 12b parallel to the one main surface 12a is formed. After that, a V-shaped blade-mounted dicing saw is used for V on the other main surface 12b.
The V-shaped stripe groove 13 is formed. Finally, the p-type side and n-type side electrodes 5 and 14 are formed by a conventionally known method.

Even in such a light emitting diode element 11, the p-type S
Since the inclined surfaces 13a, 13a form an angle θ ₂ with respect to the surface of the iC single crystal layer 4 (the upper surface of the uppermost layer), the emitted light is emitted from the inclined surfaces 13a, 13a and the surface of the p-type SiC single crystal layer 4. The light is emitted to the outside of the element 11 while the number of reflections with the (top surface) is small, that is, while the absorption inside the element is small. As a result, the emission intensity of such an element (device) increases.

Further, in such a light emitting diode element 11,
Of the n-type SiC single crystal layer 3 serving as a light-emitting layer, a hanging portion 9 (indicated by a dot in the figure) of the p-type side electrode 5 mainly serves as a light-emitting portion, but in the present embodiment, the inclined surface 13a is used. , 13a, the angle θ _{2 of which} is most of the light that is emitted from the portion 9 and is perpendicular to the surface (upper surface) of the p-type SiC single crystal layer 4 and that travels toward the substrate 12 side. , 13a, the extension lines 20 and 20 of the traveling optical path immediately after being reflected by the light source 13a and 13a are set to be present outside the p-type side electrode 5 (not intersecting with the p-type side electrode 5). The amount of light blocked by the p-type side electrode 5 is reduced. Therefore, the emission intensity of such a device (element) becomes higher.

Next, a SiC light emitting diode device according to a third embodiment of the present invention will be described with reference to the drawings. This example differs from the second example in that an n-type side electrode is not provided on the V-shaped stripe groove and a low refractive index material having a lower refractive index than that of the n-type SiC substrate is provided. Second
The same parts and corresponding parts as those of the embodiment are designated by the same reference numerals and the description thereof will be omitted. 3A is a sectional view schematically showing the structure of the light emitting diode device, and FIG. 3B is a bottom view of the light emitting diode element used in the light emitting diode device.

In the figure, in a V-shaped stripe groove 13 formed on another main surface 12b opposite to one main surface 12a of the n-type SiC single crystal substrate 12, the substrate 12 has a refractive index with respect to emitted light. Refractive index n ₂ (n ₁ > less than refractive index n ₁
A light-transmitting low refractive index material 21 such as an epoxy resin having n ₂ ) is filled.

On the other main surface 12b where the V-shaped stripe groove 13 is not formed, an n-type side electrode 24 similar to that of the first embodiment is formed. This light emitting diode element 11 is fixed to the mounting surface 7a of the stem 7 on the substrate 12 side using a conductive adhesive material 28 such as silver paste as in the second embodiment, and the n-type side electrode 24 and the stem 7 are attached. Are electrically connected. The p-type side electrode 5 is electrically connected to an electrode terminal (not shown) with a conductive wire.

In FIG. 4, the refractive index n ₁ for blue light is 2.
When a transparent low refractive index layer having a refractive index n ₂ for blue light is provided on the lower surface of the SiC single crystal of No. 6, the incident light of blue light is Si
Reflected light reflected at an angle θ _i at an interface other than transmitted light that is incident on the light-transmitting refractive index layer from the C single crystal at the incident angle θ _i (degrees) and then is transmitted to the low refractive index layer at the angle θ _t. The ratio (reflected intensity) of the reflected light to the incident light is shown.

As can be seen from FIG. 4, the incident angle θ _i
When the angle exceeds a certain angle, the reflection intensity rapidly increases, and when the angle increases, total reflection occurs. For example, when the refractive index n ₂ is 1.25, the incident angle θ _i is 28 °.
If it is (degrees) or more, it becomes the pre-reflection (that is, only the reflected light without generating the transmitted light). When the refractive index n ₂ is 1.54, total reflection occurs when the incident angle θ _i is 37 ° or more.

Therefore, the light emitting diode element 11 is
An n-type SiC single crystal substrate 12, which emits blue light and constitutes an element 11, an n-type SiC single crystal layer 3, and a p-type SiC
When the single crystal layer 4 is made of 6H-type SiC single crystal, the refractive index n ₁ (refractive index of the n-type SiC single-crystal substrate 12) is about 2.6, so the angle θ _{2 is set} to 37 °. In this embodiment, the low refractive index material 21 has a refractive index n ₂ of 1.5.
If the material is 4 or less, preferably 1 or more, such as epoxy resin, the emitted light is totally reflected by the inclined surfaces 13a and 13a without passing through the translucent low refractive index material 21, so the second embodiment The emission intensity of the element (device) becomes significantly higher than that of the example.

The present invention is not limited to the above-described embodiments, but is applied to the surface (upper surface) of the p-type SiC layer at a portion of the n-type SiC substrate opposite to and facing the p-type side electrode. If such a non-parallel surface is provided, the number of reflections with respect to the surface (upper surface) of the substrate or the p-type SiC layer decreases, so that the amount of light emitted outside the device can be increased. For example, instead of the V-shaped stripe groove 13 used in the second embodiment, a U-shaped stripe groove (U-shaped surface), or a conical surface having an opening having an area larger than the area of the p-type side electrode ( It is also possible to provide a skirt-like surface).

Further, it is preferable that the emitted light is uniformly emitted in all directions to the outside of the light emitting diode element because the light emitted from the device is not biased. Therefore, the plane that is not parallel to the surface of the p-type SiC layer is preferably provided symmetrically with respect to the p-type side electrode so that the emitted light can be uniformly emitted to the outside of the device. From this point, the light emitting diode element 11 used in the second embodiment is more preferable than the light emitting diode element 1 used in the first embodiment.

Further, when the non-parallel surface is covered with a low-refractive index material having a lower refractive index than the n-type SiC substrate for total reflection on the non-parallel surface, the refractive index n ₁ of the n-type SiC substrate is The surface (upper surface) of the p-type SiC layer changes because it depends on the crystalline polymorph of the substrate, the wavelength range of light emitted by the light emitting diode element, and the like.
The refractive index n ₂ of the low refractive index material that covers the non-parallel surface that forms an angle θ _i with is obtained by n ₁ / n ₂ = sin θ _t / sin θ _i θ _t as 90 degrees in the Snell's equation shown below. It may be selected as n ₂ or less calculated by the following equation.

N ₂ = n ₁ · sin θ _i

[0045]

The SiC light emitting diode element of the present invention is
n-type SiC substrate and n formed on the n-type SiC substrate
-Type SiC layer and the n-type S layer formed on the n-type SiC layer
A p-type SiC layer forming a pn junction with the iC layer, a p-type side electrode formed on a part of the p-type SiC layer, and a side of the n-type SiC substrate opposite to the p-type side electrode. And a surface not parallel to the surface of the p-type SiC layer at a portion of the n-type SiC substrate opposite to and facing the p-type side electrode. Existing SiC
Compared with the light emitting diode element, the emitted light is emitted to the outside of the element while the number of reflections between the substrate and the surface of the p-type SiC layer is small, that is, while being absorbed in the element. Therefore, a sufficient amount of light is emitted outside the device as compared with the conventional device. As a result, the light emission intensity of such an element becomes higher than that of the conventional one, so that the device incorporating this element also has a high light emission intensity.

Particularly, the non-parallel surface emits light under the p-type side electrode and is at least a part of the light which is perpendicular to the surface of the p-type SiC layer and travels to the substrate side. When the extension line of the traveling optical path immediately after being reflected by the reflecting surface is set to exist outside the p-type side electrode, the amount of emitted light blocked by the p-type side electrode is set as follows. Since it can be made small, the amount of light emitted from such an element becomes larger.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a SiC light emitting diode device according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a SiC light emitting diode device according to a second embodiment of the present invention.

FIG. 3 is a diagram schematically showing a SiC light emitting diode device according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a reflection intensity and an incident angle when a low refractive index layer is provided on a lower surface of a SiC crystal.

FIG. 5 is a sectional view schematically showing a conventional SiC light emitting diode device.

[Explanation of symbols]

 2 n-type SiC single crystal substrate 2b Other main surface (non-parallel surface) 3 n-type SiC layer 4 p-type SiC layer 5 p-type side electrode 12 n-type SiC single-crystal substrate 13 V-shaped stripe groove 13a inclined surface (Non-parallel surface) 21 Low refractive index material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junko Suzuki 18-2 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. An n-type silicon carbide substrate, an n-type silicon carbide layer formed on the n-type silicon carbide substrate, a p-type silicon carbide layer formed on the n-type silicon carbide layer, and the p-type silicon carbide layer. A p-type side electrode formed on a part of the n-type silicon carbide layer, and n.
An n-type side electrode formed on the opposite side of the p-type silicon carbide substrate from the p-type silicon carbide substrate.
A silicon carbide light emitting diode element comprising a surface that is non-parallel to the surface of the p-type silicon carbide layer at a portion opposite to and opposite to the mold side electrode. 2. The non-parallel surface is at least a part of light that is emitted from the p-type side electrode depending on a direction perpendicular to the surface of the p-type silicon carbide layer and proceeds to the substrate side. 2. The silicon carbide light emitting diode element according to claim 1, wherein the extension line of the traveling optical path immediately after being reflected by the non-parallel surfaces is set outside the p-type side electrode. .