JP3136672B2 - Gallium nitride based compound semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride based compound semiconductor light emitting device which emits blue light.

[0002]

2. Description of the Related Art Conventionally, GaN has been used as a blue light emitting diode.
A device using a system compound semiconductor is known. That G
The aN 2 -based compound semiconductor has attracted attention because of its direct transition, which has high luminous efficiency, and uses blue, which is one of the three primary colors of light, as the luminescent color. In such a light emitting diode using a GaN-based compound semiconductor, an n-layer made of an n-conductivity-type GaN-based compound semiconductor is grown directly on a sapphire substrate or with a buffer layer made of aluminum nitride interposed therebetween. The structure is such that an i-layer made of an i-type GaN-based compound semiconductor is grown by adding a p-type impurity on the n-layer (Japanese Patent Application Laid-Open Nos. 62-119196 and 63-188977). Gazette).

[0003]

As shown in FIG. 7, the i-layer electrode 67 of the light emitting diode 60 is provided directly on the i-layer, and the n-layer electrode 68 is provided on a part of the i-layer. Metals such as Al are deposited by utilizing the insides of the holes thus formed. In order to improve the light emission intensity of the light emitting diode 60, since the light emitting region is located above and near the i-layer electrode 67, the electrode area of the i-layer electrode 67 should be as large as possible. It has been known.
By the way, since the electrode area of the i-layer electrode 67 of the light emitting diode 60 is large for the above-described reason, the inter-electrode distance between the i-layer electrode 67 and the n-layer electrode 68 greatly differs depending on the position of the light emitting region. Will be. The electrodes 67 and 68 of the light emitting diode 60 are bonded and joined to the lead members 71 and 72 of the lead frame 70 via solder bumps. Then, the current supplied to the light emitting diode 60 by the lead members 71 and 72 of the lead frame 70 flows more through a portion with a small resistance where the distance between the i-layer electrode 67 and the n-layer electrode 68 is short. Will be. Therefore, the light emitting diode 60 has uneven light emission in the light emitting region. In such a light emitting state of the light emitting diode 60, there is a problem that the light emitting intensity is not improved much though the electrode area of the electrode 67 of the i layer is formed large.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to eliminate uneven light emission in a blue light-emitting region of a GaN-based compound semiconductor light-emitting diode. The purpose is to improve the emission intensity.

[0005]

The present invention for solving the above-mentioned problems comprises a first layer made of an n-type gallium nitride-based compound semiconductor (Al _X Ga _{1 -X} N; including X = 0). , P
Gallium nitride compound semiconductor (Al _X
A gallium nitride-based compound semiconductor light emitting device having a second layer of Ga _1-X N; including X = 0), wherein the first layer electrode and the second layer electrode are provided on the same surface side. The other electrode is formed all around the one electrode and on the same layer . According to a second structure of the present invention, in the above structure, the first layer is located below the second layer, and an electrode is formed over the entire central portion of the upper surface of the second layer.
Further, a third configuration of the invention is the same as the second configuration of the invention described above.
The electrode of the first layer is formed over the entire central portion of the upper surface of the second layer.
Around the upper surface of the second layer so as to surround the formed second layer electrode.
From the first layer to the side of the first layer.
Features.

[0006]

Operation and Effect The first layer electrode and the second layer electrode are provided on the same surface side, and the other electrode is formed all around one electrode and on the same layer . Thereby, it was possible to eliminate light emission unevenness in the blue light emitting region of the light emitting diode. That is, since the distance between the electrodes of the first layer and the electrodes of the second layer of the light emitting diode can be made substantially equal, the current flowing between the electrodes can be made substantially the same regardless of the position of the light emitting region. By this action, the light emitting diode has improved blue light emission intensity. Also, the first layer electrode is on the second layer
Formed continuously from the outer periphery of the surface to the side surface of the first layer.
As a result, light that tries to escape from the light emitting area to the side
Light from the light emitting diode
Strength is improved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. FIG. 1 shows a light emitting diode 10 according to the present invention. FIG. 1 (a) is a longitudinal sectional view, and FIG. 1 (b) is a plan view seen from an electrode side. In FIG. 1A, a light emitting diode 10 is shown.
Has a sapphire substrate 1 on which a buffer layer 2 of AlN of 500 ° is formed. Under the buffer layer 2, a high carrier concentration n ⁺ layer 3 as a first layer made of GaN having a thickness of 2.2 μm is sequentially formed.
And a low carrier concentration n layer 4 as a first layer made of GaN having a thickness of 1.5 μm, and a second layer made of GaN having a thickness of 0.1 μm under the low carrier concentration n layer 4.
And i layer 5 of are formed. Then, an electrode 7 made of aluminum connected to the center of the i-layer 5 is formed. Further, as shown in FIG. 1B, an electrode 8 made of aluminum is formed around the electrode 7 with the distance between the electrodes being substantially equal and connected to the high carrier concentration n ⁺ layer 3 from the side.

Next, a manufacturing process of the light emitting diode 10 having this structure will be described with reference to FIGS. 2, 3 and 4. FIG. The light emitting diode 10 was manufactured by vapor phase growth using a metal organic compound vapor phase epitaxy method (hereinafter referred to as MOVPE). The gases used were NH ₃ , carrier gas H ₂ and trimethylgallium (Ga (CH ₃ ) ₃ ) (hereinafter referred to as TM
G) and trimethylaluminum (Al (CH ₃ ) ₃ )
(Hereinafter referred to as TMA), silane (SiH ₄ ), and diethylzinc (hereinafter referred to as DEZ). First, a single-crystal sapphire substrate 1 having an a-plane as a main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a MOVPE apparatus. Next, the sapphire substrate 1 was subjected to gas phase etching at a temperature of 1100 ° C. while flowing H ₂ into the reaction chamber at a flow rate of 2 l / min at normal pressure. Next, the temperature was lowered to 400 ° C., H ₂ was 20 l / min, NH ₃ was 10 l / min, and TMA was 1.8 l / min.
A buffer layer 2 made of AlN having a thickness of 500 ° was formed by supplying at a rate of × 10 ^-5 mol / min. Next, the temperature of the sapphire substrate 1 was maintained at 1150 ° C., H ₂ was 20 l / min, and NH ₃ was 10 l / min.
/ Min, 1.7 × 10 ^-4 mol / min of TMG and silane (SiH ₄ ) diluted to 0.86 ppm with H ₂ at a rate of 200 ml / min for 30 minutes, a film thickness of 2.2 μm and a carrier concentration of 1.5 × 10 ¹⁸ /cm
^A high carrier concentration n.sup. ⁺ Layer 3 of ³ GaN was formed. Subsequently, the temperature of the sapphire substrate 1 was maintained at 1150 ° C., H ₂ was 20 l / min, NH ₃ was 10 l / min, and TMG was 1.7 l / min.
× 10 ^-4 mol / min at a rate of 20 minutes, and a film thickness of 1.5 μm
A low carrier concentration n layer 4 made of GaN having a carrier concentration of 1 × 10 ¹⁵ / cm ³ was formed. Next, sapphire substrate 1
H ₂ O, 20 l / min, NH ₃ 10 l / min, TM
G was supplied at a rate of 1.7 × 10 ⁻⁴ mol / min and DEZ was supplied at a rate of 1.5 × 10 ⁻⁴ mol / min for 1 minute to form an i-layer 5 made of GaN having a thickness of 0.1 μm. Thus, a multilayer structure as shown in FIG. 2A was obtained. Next, as shown in FIG. 2B, the wafer having the multilayer structure shown in FIG. 2A is diced from the i-layer 5 to the low carrier concentration n-layer 4, A notch is formed in a lattice shape so-called half-cut to the high carrier concentration n ⁺ layer 3, the buffer layer 2, and a part of the upper surface of the sapphire substrate 1. next,
As shown in FIG. 2 (c), the entire surface and the side surface (vertical surface) of the sample were subjected to A deposition by rotating aluminum with rotation of the sample.
The layer 11 was formed to a thickness of 0.3 μm. And that A
A photoresist 12 was applied on the l layer 11, and was patterned by photolithography in a predetermined shape so that the photoresist 12 remained in the electrode portions for the high carrier concentration n ⁺ layer 3 and the i layer 5.

Next, as shown in FIG. 3D, the exposed portion of the lower Al layer 11 is etched with a nitric acid-based
Was removed with acetone to form an electrode 7 of the i-layer 5. still,
FIG. 4 is a plan view of the wafer in a state where the process is completed, as viewed from above. Next, as shown in FIG. 3 (e), dicing using a thin blade (for example, 150 μm thick)
The sapphire substrate 1 on which the l layer 11 was deposited was cut off into individual pieces to form the electrodes 8 of the high carrier concentration n ⁺ layer 3.
Thus, the MIS (Metal Insulat) shown in FIG.
gallium nitride-based light-emitting device having a (or semiconductor) structure.

The light emitting diode 10 has electrodes 7, 8
5 are joined to the lead members 21 and 22 of the lead frame 20 via the solder bumps formed on the lead frame 20. As shown in FIG. Then, the distance between the electrode 7 of the i layer 5 and the electrode 8 of the high carrier concentration n ⁺ layer 3 formed therearound is substantially equal. That is, the current flowing between the electrodes of the light emitting diode 10 can be made substantially the same regardless of the position of the light emitting region. Therefore, the light emission unevenness in the blue light emitting region of the light emitting diode 10 can be eliminated and the light emission intensity can be improved. Further, in the light emitting diode 10 of this embodiment, the electrode 8 is formed so as to cover the side surface with aluminum so as to be connected to the high carrier concentration n ⁺ layer 3. For this reason, light that escapes to the side from the light emitting region located above and near the electrode 7 of the i-layer is reflected upward, and the light emitting intensity of the light emitting diode 10 is further improved. You.

FIG. 6 shows a light emitting diode 30 according to another embodiment of the present invention. FIG. 6 (a) is a longitudinal sectional view, and FIG.
Is a plan view seen from the electrode side. Elements having the same layer structure as the light emitting diode 10 described above are denoted by the same reference numerals, and description thereof is omitted. This light emitting diode 30
2 (a), a part of the upper surface of the i-layer 5, the low carrier concentration n-layer 4 and the high carrier concentration n ⁺ layer 3 under the i-layer 5 is dry-etched on the multi-layer wafer shown in FIG. A hole was formed, and an Al layer was formed on the entire surface of the sample by vapor deposition. Then, the Al layer was etched to form an electrode 38 of the high carrier concentration n ⁺ layer 3 and an electrode 37 of the i layer 5. Then, as shown in FIG. 6B, the high carrier concentration n
^The distance between the electrode 38 of the ⁺ layer 3 and the electrode 37 of the i layer 5 formed therearound is substantially equal. That is, the current flowing between the electrodes of the light emitting diode 30 can be substantially the same regardless of the position of the light emitting region. Therefore, it was possible to eliminate the uneven light emission in the blue light emitting region of the light emitting diode 30 and to improve the light emission intensity. Contrary to the electrode arrangement of the light-emitting diode 30, the electrode of the i-layer 5 is formed as wide as possible in the center of the i-layer 5, and the periphery thereof is dry-etched as described above to obtain a high carrier concentration n ^+. A groove reaching the layer 3 is formed, and an electrode of the high carrier concentration n ⁺ layer 3 is formed. At this time, the distance between the electrode of the high carrier concentration n ⁺ layer 3 and the electrode of the i layer 5 is made substantially equal. Then, also in this light emitting diode, the current flowing between the electrodes can be made substantially the same regardless of the position of the light emitting region, and the same effect can be obtained. Note that the light emitting region of the light emitting diode is a central portion above and near the electrode of the i layer 5, and is a peripheral portion in the light emitting diode 30 described above.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a manufacturing process of the light emitting diode according to the embodiment.

FIG. 3 is a vertical sectional view showing a manufacturing step of the light emitting diode according to the embodiment, following FIG. 2;

FIG. 4 is a plan view showing the state of the wafer during the manufacturing process of the light emitting diode according to the example.

FIG. 5 is a partial longitudinal sectional view showing a joint state between the light emitting diode and the lead frame according to the embodiment.

FIG. 6 is a configuration diagram showing another embodiment of the light emitting diode according to the present invention.

FIG. 7 is a partial vertical cross-sectional view showing a conventional light-emitting diode and a lead frame joined state.

[Explanation of symbols]

1-Sapphire substrate 2-Buffer layer 3-High carrier concentration n ⁺ layer 4-Low carrier concentration n layer 5-i layer 7,8-electrode 10-Light emitting diode

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-287675 (JP, A) JP-A-55-9442 (JP, A) JP-A-54-6787 (JP, A) 103666 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50

Claims (3)

(57) [Claims] 1. An n-type gallium nitride compound semiconductor (A)
a first layer composed of l _X Ga _1-X N; including X = 0, and a gallium nitride-based compound semiconductor (Al _X Ga) doped with a p-type impurity.
_A gallium nitride-based compound semiconductor light emitting device having a second layer of _1- XN; including X = 0), wherein the first layer electrode and the second layer electrode are provided on the same surface side; A semiconductor light emitting device, wherein the other electrode is formed all around one electrode and on the same layer . 2. The semiconductor according to claim 1, wherein the first layer is located below the second layer, and an electrode is formed over the entire central portion of the upper surface of the second layer. Light emitting element. 3. The electrode of the first layer is provided on an upper surface of the second layer.
Surrounding the electrode of the second layer formed over the entire central portion of
From the outer periphery of the upper surface of the second layer to the side surface of the first layer.
3. The semiconductor device according to claim 2, wherein:
3. The semiconductor light emitting device according to item 1.