JP2001196629A - Semiconductor light emitting device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a current blocking layer without increasing the number of epitaxial growth steps, and allow an emitted light to be taken out efficiently. SOLUTION: A p-type SiC region 11 is formed as a current blocking region at a corresponding position on an n-type SiC substrate 10 to the bottom of a p-type Ohmic electrode 21. If the p-type SiC region 11 is thus formed as a current blocking region on the n-type SiC substrate 10, a current blocking region can be formed by e.g. ion implantation without using the epitaxial growth process. This enables the forming of a current blocking layer without increasing the epitaxial growth steps, and emitted lights can be taken out efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used as a semiconductor light emitting element and a method of manufacturing the same, and more particularly, to a light emitting diode (hereinafter, referred to as LED).
It is suitable to be applied to.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, an LED has a plurality of layers 32 to 36 formed on a conductive substrate 30.
An n-diode is formed, and electrodes 40 and 41 are provided on the front and back surfaces. Then, light is emitted from the surface by passing a current between the electrodes 40 and 41. In such an LED, light is emitted from the surface, so that an electrode provided on the surface side is formed small. However, even with such a structure, the active layer 34 below the surface electrode 41 is formed. However, there is a problem that the light emitted from the LED is reflected by the surface electrode 41 and cannot be efficiently emitted to the outside of the LED.

[0003] To solve this problem, for example,
A structure disclosed in Japanese Patent Application Laid-Open No. 4-229665 has been proposed. In this publication, the light that is not emitted to the outside is reduced by adjusting the relative positional relationship between the light emitting unit and the electrode, and the luminous efficiency is improved. Specifically, the current blocking layer is provided between the surface electrode and the upper cladding layer so that the current flows to the active layer avoiding the current blocking layer, and the active layer is not located under the surface electrode. To emit light. This prevents light from being blocked by the surface electrode and allows light to be emitted outside.

[0004]

However, in order to form the above-mentioned structure, it is necessary to perform epitaxial growth once, form a current blocking layer by processing, and perform epitaxial growth again. Therefore, since the epitaxial growth step has to be performed twice, there arise problems such as an increase in the number of steps, a decrease in yield, and an increase in cost.

In view of the above, the present invention provides a semiconductor light emitting device capable of forming a current blocking layer without increasing the number of epitaxial growth steps and efficiently extracting emitted light to the outside, and a method of manufacturing the same. With the goal.

[0006]

In order to achieve the above object, according to the first to ninth aspects of the present invention, a semiconductor substrate (1) is provided.
0), a current blocking region (11) is formed at a position corresponding to a lower portion of the first electrode (21). For example, the current blocking region is made of the second conductivity type semiconductor.

As described above, when the current blocking region is formed in the semiconductor substrate, the current blocking region can be formed by, for example, ion implantation without depending on the epitaxial growth step. Therefore, the current blocking layer can be formed without increasing the number of epitaxial growth steps, and the emitted light can be efficiently extracted to the outside.

According to a third aspect of the present invention, the resistivity of the low-resistance semiconductor layer is smaller than the resistivity of the first semiconductor layer. Thereby, the first
The current from the electrode spreads further outside the first electrode in the low-resistance semiconductor layer, and the current can flow over a wide range. Thereby, light emission in the active layer located below the first electrode can be almost eliminated, and the light emitting region can be further expanded.

According to the present invention, the diffusion constant of the impurity forming the current blocking region in the semiconductor substrate is smaller than the diffusion constant of the impurity forming the low resistance semiconductor layer in the low resistance semiconductor layer. Is also smaller. Thus, when a semiconductor light emitting layer serving as a light emitting portion is formed on a semiconductor substrate, a structure in which the previously formed current blocking region does not abnormally diffuse at a temperature at the time of forming the semiconductor light emitting layer (for example, an epitaxial growth temperature). can do. Therefore, there is no variation in the structure, and stable characteristics can be obtained.

According to a fifth aspect of the present invention, the semiconductor substrate is made of silicon carbide, and the active layer is made of a nitride-based compound semiconductor. According to this structure, since the silicon carbide is transparent, light emitted from the active layer is not absorbed by the semiconductor substrate and can be effectively extracted to the outside.

According to a sixth aspect of the present invention, the current blocking region is formed in a surface portion of the semiconductor substrate. By forming the current blocking region in the surface layer of the semiconductor substrate in this manner, a region where no current flows becomes closer to the active layer, and the current path can be further expanded. For this reason, light emission in the active layer located below the first electrode is significantly reduced, and the emitted light can be efficiently extracted to the outside.

According to the present invention, the current blocking region has an area equal to or larger than the first electrode when viewed from a direction perpendicular to the surface of the semiconductor substrate. It is characterized by having. As a result, the current flowing in the active layer spreads outside the first electrode,
A current can flow in a wide range. For this reason, light emission in the active layer located below the first electrode is significantly reduced, and the emitted light can be efficiently extracted to the outside.

[0013] The invention according to claim 8 is characterized in that the resistivity of the current blocking region is higher than the resistivity of a portion of the semiconductor substrate adjacent to the current blocking region. As a result, the current can be prevented from flowing into the current blocking region, and the current can be easily flowed over a wide range. For this reason, light emission in the active layer located below the first electrode is significantly reduced, and the emitted light can be efficiently extracted to the outside.

According to a ninth aspect of the present invention, the current blocking region is made of a second conductivity type semiconductor. As a result, the current can be prevented from flowing into the current blocking region, and the current can be easily flowed over a wide range. For this reason, light emission in the active layer located below the first electrode is significantly reduced, and the emitted light can be efficiently extracted to the outside.

In the invention according to claim 10, the first aspect
A step of preparing a conductive semiconductor substrate (10); a step of forming a current blocking region (11) by introducing an impurity into a first predetermined region of the semiconductor substrate; A step of forming a light emitting layer (12 to 16) and a step of forming a first electrode (21) in a second predetermined area on the semiconductor light emitting layer by setting a position corresponding to an upper part of the current blocking area as a second predetermined area And a second on the back side of the semiconductor substrate.
Forming the electrode (20).

As described above, since the current blocking region is formed by introducing impurities into the semiconductor substrate, the semiconductor light emitting device can be manufactured by performing a normal epitaxial process on the semiconductor substrate to form a semiconductor light emitting layer. Can be formed. Therefore, the manufacturing process can be simplified, and the cost can be reduced.

In the eleventh aspect of the present invention, since the current blocking region is formed by introducing the second conductivity type impurity, the current blocking region can be easily formed.

According to a twelfth aspect of the present invention, the current blocking region and the first electrode are formed using a photomask having the same pattern. Thus, the same mask can be used, and the current blocking region and the first electrode can be formed without mask displacement.

Note that the reference numerals in parentheses of the above means indicate the correspondence with specific means described in the embodiments described later.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment shown in the drawings will be described below.

FIG. 1 is a schematic sectional view of an LED as a semiconductor light emitting device according to the first embodiment of the present invention. Hereinafter, the structure of the LED will be described with reference to FIG.

As shown in FIG. 1, n as a semiconductor substrate
A p-type SiC region 11 is formed in a predetermined region of the type SiC substrate 10 as a current blocking region. This p-type SiC
The region 11 is formed with a depth of about 0.5 μm.

Further, n-type S including p-type SiC region 11
On the iC substrate 10, an n-type nitride semiconductor layer (semiconductor layer)
12, an n-type AlGaN layer 13 as a first cladding layer, and an InGaN layer 1 of a nitride-based compound semiconductor as an active layer
4. A p-type AlGaN layer 15 as a second cladding layer and a p-type GaN layer 16 as a low resistance semiconductor layer are sequentially stacked.

The n-type SiC substrate 10 has n
A type ohmic electrode 20 is formed, and a p-type ohmic electrode 21 is formed on the surface of the p-type GaN layer 16.

In this embodiment, the p-type ohmic electrode 21
Is formed above p-type SiC region 11 in substantially the same shape as p-type SiC region 11. When the p-type ohmic electrode 21 and the p-type SiC region 11 are viewed from above the substrate (perpendicular to the substrate surface), the respective areas are equal, or the p-type SiC region 11 is larger than the p-type ohmic electrode 21. It is configured to have an area.

In this embodiment, the p-type GaN layer 16
Is set to be lower than that of the n-type nitride semiconductor layer 12. Also, p-type Si as a current blocking region
The diffusion constant of the impurity forming the C region 11 in the n-type SiC substrate 10 is determined by the p-type of the impurity forming the p-type GaN layer 16.
It is set to be smaller than the diffusion constant in the type GaN layer 16.

The operation of this semiconductor light emitting device will be described with reference to the operation explanatory diagram shown in FIG. First, when a current is applied by applying a voltage in the forward direction between the p-type ohmic electrode 21 and the n-type ohmic electrode 20, the current flows from the p-type ohmic electrode 21 to the p-type GaN layer 16, the p-type AlGaN layer 15, the InGa
It flows through the N layer 14, the n-type AlGaN layer 13, the n-type nitride semiconductor layer 12, and the n-type SiC substrate 10, and reaches the n-type ohmic electrode 20. During this time, since the p-type SiC region 11 is formed below the p-type ohmic electrode 21, the current is
As shown by the arrow in FIG. 2, it does not flow below the p-type ohmic electrode 21 but spreads out so as to avoid the p-type SiC region 11. Therefore, light emission below the p-type ohmic electrode 21 is suppressed. As a result, the ratio of light that is not extracted to the outside can be significantly reduced, and the luminous efficiency can be significantly improved. In particular, if the area of the p-type SiC region 11 is equal to or larger than the p-type ohmic electrode 21 when viewed from above the substrate as in this embodiment, the p-type ohmic electrode 21 Light that will not be lost can be almost eliminated. Then, the p-type SiC region 11 is
Is formed in the surface layer portion, the region where no current flows becomes close to the active layer (InGaN layer 14), and the current path can be further expanded. For this reason, the light emission in the active layer located below the p-type ohmic electrode 21 is significantly reduced, and the emitted light can be efficiently extracted to the outside.

In this embodiment, the p-type GaN layer 16
Is set to be lower than that of the n-type nitride semiconductor layer 12, the current from the p-type ohmic electrode 21 further spreads outside the p-type ohmic electrode 21 by the p-type GaN layer 16. It is possible to pass a current over a wide range. Therefore, light emission in the active layer located below the p-type ohmic electrode 21 is almost eliminated, and the light emitting region can be further expanded.

The diffusion constant of the impurity forming the p-type SiC region 11 as a current blocking region in the n-type SiC substrate 10 is determined by the impurity of the p-type G
The diffusion constant is set to be smaller than the diffusion constant in the aN layer 16. For this reason, when forming each layer which becomes a light emitting part on the n-type SiC substrate 10, it is considered that the impurity in the p-type SiC region 11 previously formed abnormally diffuses due to the temperature during the epitaxial growth and the like. Can be prevented.

Further, since there is a p-type SiC region 11,
The current avoids the p-type SiC region 11 and the n-type SiC substrate 10
Can flow to the side. Therefore, light emission from the active layer (InGaN layer 14) located below the p-type ohmic electrode 21 is almost eliminated, and light that can be extracted to the outside can be increased.

The semiconductor substrate (n-type SiC substrate 10)
Is made of silicon carbide, and the active layer is made of a nitride-based compound semiconductor. According to such a configuration, since silicon carbide is transparent to most of visible light, light emitted from the active layer is not absorbed by n-type SiC substrate 10 and is effectively extracted to the outside. Can be.

FIG. 3 is a sectional view showing a manufacturing process of the LED shown in FIG. Hereinafter, a method for manufacturing an LED will be described with reference to FIG.

First, as shown in FIG.
A mold SiC substrate 10 is prepared. This n-type SiC substrate 10
In order to form a p-type SiC region 11 as a current blocking layer on the surface of the substrate, a predetermined region is designated by a photolithography process, and after elevating the temperature of the SiC substrate 10 to, for example, 500 degrees or more, B is added as a p-type impurity. Ions are implanted. Thus, as shown in FIG. 3B, a p-type region 11 having a depth of about 0.5 μm is formed in the surface layer of the n-type SiC substrate 10.

Next, as shown in FIG.
The N-type nitride semiconductor layer 12 and the n-type AlGa are formed on the surface of the n-type SiC substrate 10 including the p-type SiC region 11 by the D method.
N layer 13, InGaN layer 14, p-type AlGaN layer 15,
The p-type GaN layer 16 is sequentially epitaxially grown.

At this time, for example, the n-type nitride semiconductor layer 1
2 has an impurity concentration of 0.2 to 2 × 10 ¹⁸cm^-3Degree, n-type
The AlGaN layer 13 has an impurity concentration of 0.5 to 4 × 10¹⁸c
m^-3The p-type AlGaN layer 15 has an impurity concentration of 0.2
~ 1 × 10¹⁸cm^-3The p-type GaN layer 16 has a high impurity concentration.
Degree is 2-6 × 10¹⁸cm^-3It is about to be.

Then, as shown in FIG.
forming an n-type ohmic electrode 20 on the back surface of the iC layer 10;
The p-type ohmic electrode 21 is patterned on the p-type GaN layer 16. Here, when patterning the p-type ohmic electrode 21, the same photomask used to form the p-type SiC region 11 or a photomask having the same pattern (including black and white inversion) is used. For example, when using the same photomask, the p-type ohmic electrode 2
This can be achieved by using a positive resist in one of the patterning step 1 and the step of forming the p-type SiC region 11 and using a negative resist in the other step.
As a result, the mask can be shared, and the p-type SiC region 11 and the p-type ohmic electrode 21 can be formed without mask displacement.

As described above, since the p-type SiC region 11 is formed by introducing the p-type impurity into the n-type SiC substrate 10, the semiconductor is then subjected to a normal epitaxial process on the n-type SiC substrate 10. If the light emitting layers 12 to 16 are formed, an LED can be formed. Therefore, the manufacturing process can be simplified, and the cost can be reduced. (Other Embodiments) The present invention is not limited to the above embodiment. For example, in the above embodiment, SiC was used for the substrate 10, but other materials such as GaN and Zn
O may be used. Further, although the substrate 10 is made n-type,
The conductivity type of each layer constituting the light emitting layer may be reversed. Further, although the p-type GaN layer 16 is used as the low-resistance layer, the p-type InGaN or another nitride semiconductor layer may be used, and two or more nitride compound layers may be used. In addition, the epitaxial layer and the substrate are not limited to the above semiconductor materials, and other semiconductor materials may be used.

Alternatively, a high-resistance region of the same conductivity type may be formed in the n-type or p-type substrate 10 and used as a current blocking region.

Further, MO is used as an epitaxial growth method.
Although the CVD method was used, an MBE (Molecular Beam Epitaxial Growth) method may be used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of an LED according to an embodiment to which the present invention is applied.

FIG. 2 is a diagram showing an operation of the LED shown in FIG.

FIG. 3 is a view showing a manufacturing process of the LED shown in FIG. 1;

FIG. 4 is a diagram showing a cross-sectional configuration of a conventional LED.

[Explanation of symbols]

10 ... n-type SiC substrate, 11 ... p-type SiC region, 12 ...
n-type nitride semiconductor layer, 13 ... n-type AlGaN layer, 14 ...
InGaN layer, 15 ... p-type AlGaN layer, 16 ... p-type G
aN layer, 20 ... n-type ohmic electrode, 21 ... p-type ohmic electrode.

Claims (12)

[Claims] 1. A semiconductor substrate of a first conductivity type, a semiconductor light emitting layer serving as a light emitting portion formed on the semiconductor substrate, and a semiconductor light emitting layer partially formed on the semiconductor layer. In a semiconductor light emitting device provided with a first electrode (21) and a second electrode (20) formed on the back surface of the semiconductor substrate, the semiconductor light emitting device corresponds to a portion of the semiconductor substrate below the first electrode. A semiconductor light emitting device, wherein a current blocking region (11) is formed at a position. 2. A first conductive type semiconductor substrate (10), a first conductive type first semiconductor layer (12) formed on the semiconductor substrate, and a stacked layer formed on the first semiconductor layer in this order. The first conductive type clad layer (13), the active layer (14),
A second cladding layer (15) of the second conductivity type;
A second conductive type low-resistance semiconductor layer (16) formed on the cladding layer, a first electrode (21) partially formed on the low-resistance semiconductor layer, and a back surface of the semiconductor substrate; And a second electrode (20) formed on the side of the semiconductor light emitting device, wherein a current blocking region (11) is formed in the semiconductor substrate at a position corresponding to a lower portion of the first electrode. A semiconductor light emitting device characterized by the above-mentioned. 3. The semiconductor light emitting device according to claim 2, wherein the resistivity of the low-resistance semiconductor layer is smaller than the resistivity of the first semiconductor layer. 4. The diffusion constant of the impurity forming the current blocking region in the semiconductor substrate is smaller than the diffusion constant of the impurity forming the low resistance semiconductor layer in the low resistance semiconductor layer. The semiconductor light emitting device according to claim 2, wherein: 5. The semiconductor substrate is made of silicon carbide.
The semiconductor light emitting device according to claim 2, wherein the active layer is made of a nitride-based compound semiconductor. 6. The semiconductor light emitting device according to claim 1, wherein the current blocking region is formed in a surface layer of the semiconductor substrate. 7. The current blocking region has an area equivalent to that of the first electrode when viewed from a direction perpendicular to the surface of the semiconductor substrate.
7. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device has a larger area than the first electrode. 8. 8. The semiconductor device according to claim 1, wherein the resistivity of the current blocking region is higher than that of a portion of the semiconductor substrate adjacent to the current blocking region. The semiconductor light emitting device according to claim 1. 9. The semiconductor light emitting device according to claim 1, wherein the current blocking region is made of a second conductivity type semiconductor. 10. A step of preparing a semiconductor substrate (10) of a first conductivity type; a step of forming a current blocking region (11) by introducing an impurity into a first predetermined region of the semiconductor substrate; A semiconductor light-emitting layer (12-
16) forming a first electrode (21) in the second predetermined region on the semiconductor light emitting layer, wherein a position corresponding to an upper part of the current blocking region is set as a second predetermined region; Forming a second electrode (20) on the back side of the semiconductor substrate. 11. A method for manufacturing a semiconductor light emitting device, wherein the impurity introduced into the first predetermined region is a second conductivity type impurity. 12. The method according to claim 10, wherein the current blocking region and the first electrode are formed using a photomask having the same pattern.