KR101198761B1 - Nitride based light emitting diode - Google Patents
Nitride based light emitting diode Download PDFInfo
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- KR101198761B1 KR101198761B1 KR20060070212A KR20060070212A KR101198761B1 KR 101198761 B1 KR101198761 B1 KR 101198761B1 KR 20060070212 A KR20060070212 A KR 20060070212A KR 20060070212 A KR20060070212 A KR 20060070212A KR 101198761 B1 KR101198761 B1 KR 101198761B1
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- quantum well
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Abstract
The present invention relates to a nitride-based light emitting device, and more particularly to a nitride-based light emitting device that can improve the luminous efficiency and reliability of the light emitting device. The present invention provides a light emitting device comprising: a light emitting layer including a quantum well layer and a quantum barrier layer; Preferably, the light emitting layer includes a stress relaxation layer positioned on at least one side of the quantum well layer.
Nitride, semiconductor, GaN, light emitting layer, stress.
Description
1 is a cross-sectional view showing an example of a conventional light emitting device structure.
2 is a cross-sectional view showing an embodiment of a light emitting device structure of the present invention.
3 is a cross-sectional view showing another embodiment of the light emitting device structure of the present invention.
Figure 4 is an enlarged cross-sectional view showing a stress relaxation layer of the present invention.
5 is an energy band diagram of an embodiment of the invention.
6 is an energy band diagram of another embodiment of the present invention.
7 is a cross-sectional view showing a horizontal light emitting device of the present invention.
8 is a cross-sectional view showing a vertical light emitting device of the present invention.
<Brief description of the main parts of the drawing>
10: n-type semiconductor layer 20: light emitting layer
21: quantum well layer 22: quantum barrier layer
30: p-type semiconductor layer 40: stress relaxation layer
41: first layer 42: second layer
50 substrate 60 n-type electrode
70 p-
The present invention relates to a nitride-based light emitting device, and more particularly to a nitride-based light emitting device that can improve the luminous efficiency and reliability of the light emitting device.
Light Emitting Diodes (LEDs) are well-known semiconductor light emitting devices that convert current into light.In 1962, red LEDs using GaAsP compound semiconductors were commercialized, along with GaP: N series green LEDs. It has been used as a light source for display images of electronic devices, including.
The wavelength of light emitted by such LEDs depends on the semiconductor material used to make the LEDs. This is because the wavelength of the emitted light depends on the band-gap of the semiconductor material, which represents the energy difference between the valence band electrons and the conduction band electrons.
Gallium nitride compound semiconductors (Gallium Nitride (GaN)) have high thermal stability and wide bandgap (0.8 to 6.2 eV), which has attracted much attention in the development of high-power electronic components including LEDs.
One reason for this is that GaN can be combined with other elements (indium (In), aluminum (Al), etc.) to produce semiconductor layers that emit green, blue and white light.
In this way, the emission wavelength can be adjusted to match the material's characteristics to specific device characteristics. For example, GaN can be used to create white LEDs that can replace incandescent and blue LEDs that are beneficial for optical recording.
Due to the advantages of these GaN-based materials, the GaN-based LED market is growing rapidly. Therefore, since commercial introduction in 1994, GaN-based optoelectronic device technology has rapidly developed.
The brightness or output of the LED using the GaN-based material as described above is large, the structure of the active layer, the light extraction efficiency to extract light to the outside, the size of the LED chip, the type and angle of the mold (mold) when assembling the lamp package , Fluorescent material and the like.
On the other hand, one of the reasons why the growth of GaN-based semiconductors is more difficult than other III-V compound semiconductors is that there are no high-quality substrates, that is, wafers made of materials such as GaN, InN, and AlN.
Therefore, the LED structure is grown on a heterogeneous substrate such as sapphire, and many defects are generated, and these defects have a great influence on the LED performance.
As shown in FIG. 1, the basic structure of the LED of GaN-based material is a quantum well structure between the n-type semiconductor layer 1 as the electron injection layer and the p-
In general, the
In this multi-quantum well structure, the
In this case, the
Therefore, in order to implement a high-brightness light emitting device, electrons and holes should be transported well to the
As a result, thin film crystallinity of the
Currently, the most representative quantum well structure of a nitride semiconductor light emitting device is composed of a gallium nitride (GaN) quantum barrier layer (5) and an indium gallium nitride (InGaN) quantum well layer (4).
However, GaN and InGaN described above inherently have very large crystal lattice mismatch. Therefore, the InGaN
This compressive stress deforms the energy band structure in the quantum well layer, thereby greatly reducing the luminescence properties, and also lowers the interfacial characteristics between the quantum barrier layer and the quantum well layer, and ultimately greatly reduces the luminous efficiency of the light emitting device. there was.
An object of the present invention is to provide a nitride-based light emitting device that can improve the reliability characteristics by controlling or suppressing the strain and crystal defects of the light emitting device, and by effectively constraining electrons and holes in the active layer.
In order to achieve the above technical problem, the present invention provides a light emitting device comprising: a light emitting layer including a quantum well layer and a quantum barrier layer; Preferably, the light emitting layer includes a stress relaxation layer positioned on at least one side of the quantum well layer.
The light emitting layer and the stress relaxation layer, the quantum barrier layer, the stress relaxation layer, and the quantum well layer is repeatedly laminated in order, or the quantum barrier layer, stress relaxation layer, quantum well layer, and stress relaxation layer is repeated in order It is preferable to laminate | stack.
The stress relaxation layer may have an average planar lattice constant greater than the lattice constant of the quantum barrier layer and less than the lattice constant of the quantum well layer.
The stress relaxation layer may be a superlattice layer in which semiconductor layers having different lattice constants are stacked.
In this case, the thickness of the superlattice layer, or more than 1/3 of the thickness of the quantum barrier layer, or 0.5 to 10nm is preferred, two layers having a different lattice constant may be composed of 2 to 40 pairs.
In addition, the thickness of each layer of the superlattice layer is preferably 1 to 10 atomic layers (monolayer).
The superlattice layer may be configured by alternately stacking AlInGaN materials having different lattice constants and band gaps.
The superlattice layer may further include a first layer formed of GaN; The second layer formed of InGaN or AlInGaN may be alternately stacked.
As another example, the superlattice layer may include a first layer of a material having a larger lattice constant than the quantum well layer; The second layer of a material having a smaller lattice constant than the quantum well layer may be alternately stacked.
On the other hand, it is preferable that the quantum well layer of the light emitting layer is formed of InGaN, wherein the composition of In of InGaN is represented by In x Ga 1-x N, where x is 0.2 to 0.4 (0.2 ≤ x ≤). 0.4).
The first conductive semiconductor layer is located on one side of the light emitting layer, and the second conductive semiconductor layer is preferably located on the other side of the light emitting layer.
In addition, the ohmic electrode formed on any one side of the first conductive semiconductor layer or the second conductive semiconductor layer; A reflective electrode in contact with the ohmic electrode; In contact with the reflective electrode, and further comprising a support layer made of a metal or a conductive semiconductor may form a vertical light emitting device.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 2, the structure of the nitride semiconductor light emitting device is composed of an n-
Among them, the multi-quantum well structure (MQW) has a quantum well layer (well 21) and a quantum barrier layer (barrier 22) repeatedly stacked and injected from the electron injection layer and the hole injection layer, respectively. Electrons and holes combine with each other in the
At this time, at least one side of the
In FIG. 2, an example in which the
FIG. 2 illustrates an embodiment in which the
That is, in the stacking order, after the
In addition, as shown in FIG. 3, the
That is, the
The
More specifically, the average lattice constant of the superlattice layer constituting the
4 shows a
In FIG. 4, the superlattice lattice constant of the
In this way, the superlattice layer can effectively act as the
Each of the
In addition, the superlattice layer may be formed by forming two to 40 pairs of two
As described above, the average lattice constant of the superlattice layer constituting the
That is, the AlInGaN material is composed of the
In addition, the
Meanwhile, the
In this case, when the
That is, when the
In FIG. 5, as in FIG. 2, a band structure in a state in which a
As described above, in FIG. 5, the
Meanwhile, as shown in FIG. 6, the
In addition, in FIG. 6, as shown in FIG. 3, the
In some cases, the band gap of the
Usually, InGaN containing In has a lattice constant larger than GaN, and an energy band gap is smaller than GaN. In addition, AlGaN containing Al has a larger bandgap than GaN. Therefore, by combining such components of In and Al, it is possible to form a
The
Therefore, in order to implement a high-brightness light emitting device, electrons and holes must be transported well to the
As a result, the thin film crystallinity of the
The most representative multi-quantum well structure of the nitride semiconductor light emitting device includes a gallium nitride (GaN)
In order to improve light emission efficiency in the light emitting device structure, the gallium nitride (GaN) and indium gallium nitride (InGaN) are prepared as high quality thin films having excellent crystallinity.
However, these GaN and InGaN inherently has a very large crystal lattice mismatch. This means that the atomic radius of indium (In) is larger than the atomic radius of gallium (Ga), and the bonding force and bond length of indium (In) and nitrogen (N) are greater than the bonding force and bond length of gallium (Ga) and nitrogen (N), Each is weak and long.
Therefore, the InGaN
In addition, the compressive stress lowers the interface characteristics between the GaN
Therefore, the above-described problem can be solved by providing the
In addition, the
7 shows an example of the horizontal light emitting device having the
As shown, it has the structure of the above-mentioned light emitting element which consists of the n-
8 shows an example of the vertical light emitting device having the above-described
The structure of the above-described light emitting element consisting of the n-
The p-
In this case, the
The light emitting device manufactured in such a form can greatly increase the luminous efficiency by mitigating the stress acting on the
The above embodiment is an example for explaining the technical idea of the present invention in detail, and the present invention is not limited to the above embodiment, various modifications are possible, and various embodiments of the technical idea are all protected by the present invention. It belongs to the scope.
The present invention as described above has the following effects.
First, in the light emitting device according to the present invention, the band structure of the quantum well layer may be improved by the stress relaxation layer, thereby greatly improving the internal quantum efficiency.
Second, the stress relaxation layer of the present invention can improve the optical properties by making the stress distribution and the indium composition distribution in the nitride semiconductor quantum well layer grown thereon more uniform.
Third, the luminous efficiency can be greatly improved by improving the interface property between the stress relaxation layer and the quantum well layer of the present invention to greatly reduce the loss of charge at the interface.
Claims (14)
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
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KR20060070212A KR101198761B1 (en) | 2006-07-26 | 2006-07-26 | Nitride based light emitting diode |
US11/878,642 US7977665B2 (en) | 2006-07-26 | 2007-07-25 | Nitride-based light emitting device |
EP07113150.2A EP1883121B1 (en) | 2006-07-26 | 2007-07-25 | Nitride-based semiconductor light emitting device |
TW096127303A TWI451591B (en) | 2006-07-26 | 2007-07-26 | Nitride-based light emitting device |
US13/116,802 US8450719B2 (en) | 2006-07-26 | 2011-05-26 | Nitride-based light emitting device |
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KR20060070212A KR101198761B1 (en) | 2006-07-26 | 2006-07-26 | Nitride based light emitting diode |
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