JP2000077713A - Semiconductor light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with a P-type transparent electrode in which a high controllability is required. SOLUTION: This element is a semiconductor light-emitting element constituted into a structure, wherein an n-type GaN semiconductor layer 3, a GaN semiconductor luminous layer 4, a P-type AlGaN semiconductor layer 5 and a P-type GaN semiconductor layer 6 are laminated on a substrate 2 consisting of an N-type 4H or 2H-SiC film At the same time, an N-type electrode 8 and a P-type electrode 7 are respectively formed on the substrate 7 and the layer 6. Here, the electrode 8 is arranged at the corner of the substrate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor light emitting device.

[0002]

2. Description of the Related Art GaN (gallium nitride) -based and SiC (silicon carbide) -based materials attract attention as materials suitable for blue light emission, and various techniques have been proposed at present.

[0003] For example, in JP-A-8-64910,
As shown in FIG. 5A, an n-type SiC cladding layer 11, an InGaN active layer 12, a p-type S
An iC cladding layer 13 is sequentially stacked, an Al electrode 14 is formed in the upper center of the p-type SiC cladding layer 13, and a Ni electrode 15 is formed in the lower center of the n-type SiC substrate 10. Conventional structure A) has been proposed.

[0004] Further, the same publication discloses, as its prior art,
As shown in FIG. 5B, on the sapphire substrate 20, A
lGaN buffer layer 21, n-type GaN layer 22, n-type Al
GaN cladding layer 23, InGaN active layer 24, p-type A
An lGaN cladding layer 25, a p-type GaN layer 26, and a p-type transparent electrode 27 are sequentially stacked. Further, a p-type electrode 28 is provided on the p-type transparent electrode 27, and an n-type electrode 29 is provided on a part of the n-type GaN layer 22. A semiconductor light-emitting device capable of emitting blue light (hereinafter, referred to as a conventional structure B) formed with is also disclosed.

In the conventional structure A, low-temperature growth (about 80
(0 ° C.) on the InGaN active layer 12 at a high temperature (14
During the growth of the p-type SiC cladding layer 13, in order to grow the p-type SiC cladding layer 13
There is a problem that N in the GaN active layer 12 is easily detached to cause lattice defects, good crystals cannot be obtained, and device characteristics are deteriorated.

Further, in the conventional structure B, since sapphire, which is an insulator, is used for the substrate 20, it is not possible to conduct electrical conduction in the vertical direction of the element through the substrate 20. In addition, since a GaN-based layer having a lattice constant of 3.11 to 3.16 ° is laminated on the sapphire substrate 20 having a lattice constant of 4.76 °, crystal defects are likely to occur in the GaN-based layer due to lattice mismatch. There are issues.

In consideration of such a point, n-type SiC having a lattice constant substantially similar to that of a GaN-based semiconductor is used as the substrate 30 as in the semiconductor light emitting device shown in FIG. A GaN-based layer, that is, an n-type GaN layer 31 doped with Si, a GaN light emitting layer 3 doped with Si and Zn.
2, Mg-added p-type AlGaN semiconductor (cladding) layer 3
3, p-type GaN semiconductor (contact) layer 34 with Mg added
Is formed, and a transparent p-type electrode 35 and a p-type pad electrode 36 are formed thereon to solve the problems of the conventional structures A and B (hereinafter, structure C).

[0008]

However, the structure C
Also, in the p-type AlGaN semiconductor (cladding) layer 3
3, p-type GaN semiconductor (contact) layer 34 with Mg added
Has a high specific resistance of several ohm-cm, and a sufficiently low-resistance p-type layer cannot be obtained. Therefore, it is necessary to separately provide a transparent electrode 35 for spreading the current, which complicates the manufacturing process. There is. In general, it is necessary to form the transparent electrode 35 by forming a light-shielding metal material so as to be thin enough to transmit light, so that a high controllability is required in a process for forming the transparent electrode 35. There is.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and its basic feature is that GaN is provided on a substrate.
In a semiconductor light emitting device in which a semiconductor layer including a semiconductor light emitting layer is laminated, a transparent and conductive SiC substrate for an emission wavelength is used as a substrate, and an opaque pad electrode connected to this SiC substrate is formed on the SiC substrate. It is arranged at the corner avoiding the center.

Since a transparent and conductive SiC substrate for the emission wavelength is used as the substrate, the substrate is arranged so that the substrate is located on the upper side, and light is extracted through this substrate, so that the transparent electrode, which has been conventionally required, can be formed. It can be unnecessary. Since a transparent electrode is not required, the number of manufacturing steps and cost can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to a semiconductor light emitting device (light emitting diode) suitable for blue light emission shown in FIG.
1 will be described as an example.

This semiconductor light emitting device 1 has a GaN-based compound semiconductor layer on a substrate 2 made of an n-type SiC semiconductor.
That is, an n-type GaN semiconductor layer 3 doped with Si as an impurity, and an n-type GaN semiconductor layer 3 doped with Si and Zn as an impurity.
aN semiconductor light-emitting layer 4, p doped with Mg as an impurity
It has a structure in which a p-type GaN semiconductor contact layer 6 doped with Mg as an impurity and a p-type GaN semiconductor contact layer 6 are sequentially crystal-grown and stacked. Since the light-emitting layer 4 uses a direct transition type GaN-based semiconductor, the light-emitting efficiency can be increased. can do.

Since the p-type AlGaN semiconductor layer 5 and the p-type GaN semiconductor contact layer 6 have a large specific resistance, if necessary, a temperature of about 800 ° C. after the crystal growth is used to reduce the resistance. For a predetermined time. By such processing, the specific resistance value is several ohms.
cm, but this value is, for example, p
About 10 times larger than the specific resistance value of the SiC layer of
It is difficult to obtain a current spread as in the case of a p-type SiC layer.

The SiC substrate is 6H-S, which is the easiest to manufacture.
Although it is common to use iC, as shown in FIG.
This 6H-SiC has a light absorption edge of 428 nm, and a light emission peak wavelength of the light emitting layer 4 (425 to 430 nm).
And becomes opaque to the emission wavelength. Therefore, the SiC substrate 2 has a light absorption edge shorter than the light emission peak wavelength of the light emitting layer 4 and is transparent to the light emission wavelength.
iC or 2H-SiC is used. Where S
As the iC substrate 2, it is preferable to use 4H-SiC which is easier to manufacture than 2H-SiC.

The p-type GaN semiconductor (contact) layer 6 has a p-type electrode 7 made of Si, Al, and Au at its center.
Are formed, and an n-type electrode 8 made of Ni and Au for a pad is formed on the SiC substrate 2. This light emitting element 1
As shown in FIG. 2, since the SiC substrate 2 is used upside down so as to be positioned above, the p-type electrode 7 arranged on the element mounting surface T has a relatively large area.
Since the n-type electrode 8 for the pad to be wire-bonded is thick and opaque, it is arranged at a corner of the substrate 2 so as not to block light emitted from the substrate 2, avoiding the center of the substrate 2. ing.

The element 1 constructed as described above is turned upside down so that the substrate 2 is located on the upper side, as shown in FIG. 2, and the p-type electrode 7 is attached with a conductive adhesive S or the like to a lead electrode or the like. It is fixedly arranged on the surface T. Then, a thin line Y such as gold is wire-bonded to the pad n-type electrode 8 located on the upper side. The element 1 is assembled as shown in FIG. 2 as a light emitting device. At this time, the light extraction efficiency can be increased by covering the periphery with a transparent resin or the like.

A voltage is applied to change the p-type electrode 7 to the n-type electrode 8
When a predetermined current is applied to the inside of the element 1 toward the light emitting device 1, light having a light emission peak wavelength of 425 to 430 nm is generated in the light emitting layer 4. This light is emitted to the outside from the periphery of the light emitting layer 4 including the n-type GaN semiconductor layer 3 and the SiC substrate 2 which are transparent to the emission wavelength. Here, p-type GaN for which it is difficult to reduce the resistance value
Since the large-area p-type electrode 7 is formed in the system semiconductor layer 6, the driving voltage can be reduced and the light emitting area can be enlarged. Further, the n-type SiC substrate 2
Since the resistance value is sufficiently smaller than that of the p-type GaN-based semiconductor layer as well as the p-type SiC, the current easily spreads,
Even if the electrodes are arranged at the corners, the problem of uneven distribution of the light emitting portion does not occur. Therefore, the n-type SiC substrate 2 where the current easily spreads
The n-type electrode 8 is disposed at a corner of the SiC substrate 2 to prevent light emitted to the outside via the SiC substrate 2 from being blocked by the n-type electrode 8.

As described above, since the SiC substrate 2 which is transparent to the emission wavelength and has conductivity is disposed on the upper side, and the pad electrodes 8 are provided at the corners of the SiC substrate 2,
Light can be efficiently extracted through the iC substrate 2. For this reason, it is not necessary to use a transparent electrode as in the related art as the p-type electrode 7 connected to the GaN-based p-type layer for which it is difficult to reduce the resistance, and the configuration of the p-type electrode and the manufacturing process are simplified. be able to.

As shown in FIG. 3, in order to prevent short-circuiting due to the rise of the conductive adhesive S, as shown in FIG. 3, the oxidation is performed so as to cover a part of the substrate 2 and the exposed surfaces of the layers 3 to 6 thereon. An insulating film 9 such as silicon (SiO ₂ ) or silicon nitride (SiN _x ) can be formed.

In the above embodiment, the light emitting layer 4 is made of S
Although the case where an n-type GaN semiconductor material doped with i and Zn as impurities is used has been described as an example, the present invention provides, as the light emitting layer 4, for example, an In doped with Si and Zn doped as impurities.
InGaN semiconductor materials such as a GaN semiconductor layer, an undoped InGaN semiconductor layer, or an InGaN multiple quantum well layer having a different In composition ratio can also be used. In such a case, the emission wavelength is longer (44) than GaN.
0 nm or more), an n-type 6H SiC substrate can be used as a substrate transparent to the emission wavelength, in addition to the n-type 4H or 2H SiC substrate.

In the above embodiment, GaN or In
N-type Ga located on one of the upper and lower sides of the GaN semiconductor light emitting layer 4
Si doped n-type GaN semiconductor layer 3 as an N-based semiconductor layer
And an example in which a Mg-doped p-type AlGaN semiconductor layer 5 and a Mg-doped p-type GaN contact layer 6 are used as p-type GaN-based semiconductor layers located on the other of the upper and lower sides of the light-emitting layer 4. However, the present invention is not limited to this.

For example, as another example of the n-type GaN-based semiconductor layer, an undoped n-type GaN semiconductor layer (an n-type AlGaN semiconductor layer) to which no impurity is added, or Se, Ge, Sn, etc. other than Si as an impurity N-type GaN semiconductor layer (n-type AlGaN semiconductor layer) to which a donor impurity is added can be used. Further, a structure in which an n-type AlGaN semiconductor layer is interposed between the n-type GaN semiconductor layer and the light emitting layer 4 may be employed. Furthermore, the n-type SiC substrate 2
A structure in which only an n-type AlGaN semiconductor layer is interposed between the light-emitting layer 4 and the light-emitting layer 4 may be employed.

As another example of the p-type GaN-based semiconductor layer, a p-type GaN semiconductor layer (p-type AlGaN semiconductor layer) to which an acceptor impurity such as Zn other than Mg is added as an impurity can be used. Further, the light emitting layer 4 and the p-type Ga
A structure in which the p-type AlGaN semiconductor layer interposed between the N semiconductor layers is omitted and a p-type GaN semiconductor layer is provided adjacent to the light emitting layer 4 can be adopted. Furthermore, as a p-type GaN-based semiconductor layer adjacent to the light emitting layer 4, p-type AlGaN
A structure in which only a semiconductor layer is provided can be employed.

In the above embodiment, the n-type SiC substrate 2
Although the case where the n-type GaN-based semiconductor layer is directly formed is illustrated as an example, between the n-type SiC substrate 2 and the n-type GaN-based semiconductor layer,
A GaN-based buffer layer made of an AlGaN semiconductor layer or the like for preventing lattice mismatch between the two can be formed.

[0025]

According to the semiconductor light emitting device of the present invention, a SiC substrate which is transparent and conductive with respect to the emission wavelength is used as a substrate. Therefore, the substrate is arranged so that the substrate is located above and light is transmitted through this substrate. By doing so, it is possible to eliminate the need for a transparent electrode that has been required conventionally. Since a transparent electrode is not required, the number of manufacturing steps and cost can be reduced. Further, since the semiconductor light emitting device of the present invention uses a direct transition type GaN or InGaN semiconductor material for the light emitting layer, the luminous efficiency is kept extremely high as compared with the case where SiC is used for the light emitting layer, and the semiconductor light emitting device uses the SiC substrate. Light emission can be provided by reducing light absorption.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a light emitting device including the semiconductor light emitting element of the same embodiment.

FIG. 3 is a cross-sectional view of a main part of a light emitting device including a semiconductor light emitting element according to another embodiment.

FIG. 4 is a view showing physical constants of materials of the semiconductor light emitting device in the same example.

FIGS. 5A and 5B are cross-sectional views showing the structure of a conventional semiconductor light emitting device, and FIGS. 5C and 5C are cross-sectional views showing the improved structure of FIGS.

[Explanation of symbols]

 Reference Signs List 1 semiconductor light-emitting element 2 n-type SiC substrate 3 n-type GaN semiconductor layer 4 GaN semiconductor light-emitting layer 5 p-type AlGaN semiconductor (cladding) layer 6 p-type GaN semiconductor (contact) layer 7 p-type electrode 8 n-type electrode

Claims (3)

[Claims] 1. A method in which G is placed on a semiconductor substrate made of SiC.
A semiconductor light-emitting device in which semiconductor layers including an aN-based semiconductor light-emitting layer are stacked, wherein a transparent and conductive substrate for an emission wavelength is used as the SiC substrate,
An opaque pad electrode connected to this SiC substrate is
A semiconductor light emitting device, wherein the semiconductor light emitting device is arranged at a corner portion avoiding a center of a substrate. 2. An n-type GaN-based semiconductor layer, a GaN semiconductor light-emitting layer, and a p-type GaN-based semiconductor layer are stacked on an n-type substrate made of 4H or 2H SiC, and an n-type GaN-based semiconductor layer is formed on the SiC substrate. An electrode is formed, and a p-type electrode is formed on the p-type GaN-based semiconductor layer.
A semiconductor light emitting device, wherein the n-electrode is arranged at a corner of a substrate. 3. An n-type 6H, 4H or 2H SiC.
N-type GaN-based semiconductor layer, InGa
A semiconductor light-emitting device comprising: an N semiconductor light-emitting layer; a p-type GaN-based semiconductor layer stacked; an n-type electrode formed on the SiC substrate; and a p-type electrode formed on the p-type GaN-based semiconductor layer. A semiconductor light emitting device wherein an n-electrode is arranged at a corner of a substrate.