KR20200066992A - Multi-wavelength light emitting device comprising strain-appled layer - Google Patents

Abstract

The present invention relates to a multi-wavelength light emitting element including a strain-applied layer which outputs light of various wavelengths in accordance with intensity of a current applied to one light emitting element. According to the present invention, the multi-wavelength light emitting element has a structure in which the strain-applied layer is interposed between an active layer of a multi-quantum well structure and a second semiconductor layer. The strain-applied layer is formed on an uppermost quantum well layer of the active layer. Since an indium composition ratio of the strain-applied layer is greater than the composition ratio of an uppermost quantum barrier layer, a compressive strain is generated at the interface with the quantum barrier layer, thereby outputting light of various wavelengths in accordance with the intensity of the applied current.

Description

A multi-wavelength light emitting device comprising strain-appled layer

The present invention relates to a light emitting device, and more particularly, to a multi-wavelength light emitting device including a strain applying layer for outputting light of various wavelengths according to the intensity of the current applied to one light emitting device.

As a medical light source for the treatment of skin diseases, gas lasers and semiconductor light sources such as LEDs (light emitting diodes) or LDs (laser diodes) are used. Gas lasers and LDs are close to destructive methods and are suitable for treating scars and local skin diseases, but not suitable for a wide range of diseases. Therefore, most of the optical medical devices for the treatment of skin diseases use a single LED light source suitable for the treatment of non-destructive skin diseases in a large area.

Treatment of skin diseases such as acne, inflammation, atopic dermatitis, erythema, hair loss and skin aging using LED light was generally performed using a single light source, but the relationship between skin disease and effective light source has not been clearly revealed. no.

A light therapy device equipped with a commercially available medical LED light source is composed of a module that applies a single wavelength or two wavelength LED light sources. However, the existing light treatment device has a hassle of using a different LED light source and system for each skin disease.

For example, a light source effective for acne treatment is generally blue-based, and a 415 nm light source is used as a representative wavelength, but it is known that some 405 nm, 420 nm, or 630 nm wavelengths are effective. Therefore, in order to obtain an accurate and safe treatment effect, treatment using each wavelength is required, and the light irradiator must be replaced whenever the wavelengths are different.

And even if it is the same disease, the effective wavelength of the light source can vary depending on the skin color (eg, Asian or Western) of the person and the degree of the disease. Does not.

As described above, the treatment of skin diseases using the LED light source has a very complex element, and thus light sources and control technologies of various wavelengths are required.

And even in the same disease, since the treatment effect using the LED light source varies depending on the object, there is a problem in that it is necessary to mount a number of light sources having an effective wavelength in order to solve this. For example, 17 kinds of LED light sources (405nm, 406nm, 407nm, 408nm, 409nm, 410nm, 411nm, 412nm, 413nm, 414nm, 415nm, 416nm, 416nm, 416nm, which correspond to the wavelength range of 405~420nm for acne treatment light therapy devices) If 417nm, 418nm, 419nm, 420nm) is to be used, a large number of LED light sources having a main emission wavelength and a controller for controlling each LED light source are required.

In addition, since light treatment has to be performed while replacing the light irradiator whenever the wavelength is different, there is a problem in that it is inconvenient even for user particles and takes a long time for light treatment.

Registered Patent Publication No. 10-0972984 (registered on July 23, 2010)

Accordingly, an object of the present invention is to provide a multi-wavelength light-emitting device including a strain application layer that outputs light of various wavelengths from one light-emitting device.

In order to achieve the above object, the present invention is a substrate; A first semiconductor layer formed on the substrate; An active layer formed on the first semiconductor layer and having a multi-quantum well structure in which a plurality of quantum well layers and a plurality of quantum barrier layers are alternately stacked and an uppermost quantum well layer is disposed at the end; A strain application layer formed on the uppermost quantum well layer of the active layer and having a larger indium composition ratio than the uppermost quantum barrier layer so that a compressive strain occurs at an interface with the uppermost quantum barrier layer; And a second semiconductor layer formed on the strain application layer.

The indium composition ratio of the strain application layer is lower than that of the quantum well layer of the active layer.

The strain application layer is In _x Ga _1-x N (0.15 _{≤ x ≤} 0.24), and has a thickness of 15 to 50 nm.

The first semiconductor layer is an n-type semiconductor layer in which u-GaN and n-GaN are sequentially stacked.

The second semiconductor layer is a p-type semiconductor layer made of p-GaN.

The active layer is made of In _x Ga _1-x N (0<x<1), but the indium composition ratio of the plurality of quantum well layers is 0.24<x<1, and the indium composition ratio of the uppermost quantum barrier layer is 0<x <0.15.

The band of the emission wavelength changes according to the intensity of the current applied between the first semiconductor layer and the second semiconductor layer.

When a current of a specific intensity is applied between the first semiconductor layer and the second semiconductor layer, light in two wavelength bands is output.

In addition, when the intensity of the applied current is 20mA to 350mA, light in a wavelength band of 480nm to 540nm is output.

Since the multi-wavelength light emitting device according to the present invention includes a strain application layer together with an active layer, it is possible to output light of various wavelengths according to the intensity of current applied to one light emitting device. That is, by stacking the strain application layer on the active layer, the wavelength of the light emission spectrum of the output light can be changed. The strain applied layer can easily change the wavelength of the emission spectrum even at a low applied current.

For this reason, the multi-wavelength light emitting device according to the present invention can perform treatment according to the state of a light therapy subject by continuously changing and irradiating the emission spectrum according to the intensity of the applied current. Therefore, the multi-wavelength light emitting device according to the present invention can eliminate the hassle of using each different LED light source and system according to the state of the light treatment subject as before.

In addition, the multi-wavelength light emitting device according to the present invention can vary the wavelength range of the output light by adjusting the intensity of the applied current. There is an advantage.

1 is a cross-sectional view showing a multi-wavelength light emitting device including a strain applying layer according to an embodiment of the present invention.
2 is a cross-sectional view showing a single wavelength light emitting device according to a comparative example.
3 is a table measuring a light emission spectrum according to a current applied to a single wavelength light emitting device according to a comparative example.
4 is a table measuring a light emission spectrum according to a current applied to the multi-wavelength light emitting device of FIG. 1.

It should be noted that in the following description, only parts necessary for understanding the embodiments of the present invention are described, and descriptions of other parts will be omitted without detracting from the gist of the present invention.

The terms or words used in the present specification and claims described below should not be construed as being limited to ordinary or lexical meanings, and the inventor is appropriate as a concept of terms to describe his or her invention in the best way. It should be interpreted as a meaning and a concept consistent with the technical idea of the present invention based on the principle that it can be defined as such. Therefore, the configuration shown in the embodiments and drawings described in this specification is only a preferred embodiment of the present invention, and does not represent all of the technical spirit of the present invention, and various equivalents that can replace them at the time of this application It should be understood that there may be and variations.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a multi-wavelength light emitting device including a strain applying layer according to an embodiment of the present invention.

Referring to FIG. 1, the multi-wavelength light emitting device 100 according to the present embodiment is a light emitting device that outputs light of various wavelengths according to the intensity of an applied current. The multi-wavelength light emitting device 100 according to this embodiment includes a substrate 10, a first semiconductor layer 30, an active layer 40, a strain application layer 50, and a second semiconductor layer 60. The first semiconductor layer 30 is formed on the substrate 10. The active layer 40 is formed on the first semiconductor layer 30, and a plurality of quantum well layers 41 and a plurality of quantum barrier layers 43 are alternately stacked, and at the end, the uppermost quantum well layer 41a is disposed. It has a multi-quantum well structure. The strain application layer 50 is formed on the upper quantum barrier layer 43a of the active layer 40, and is formed on the upper quantum barrier layer 43a so that a compressive strain occurs at the interface with the active layer 40. The indium composition ratio is large. In addition, the second semiconductor layer 70 is formed on the strain application layer 50. In addition, the multi-wavelength light emitting device 100 according to the present embodiment includes a buffer layer 20, a first electrode 80 and a second electrode 90.

The substrate 10 includes sapphire (Al ₂ O ₃ ), silicon carbide (SiC), zinc oxide (ZnO), silicon (Si), spinel, gallium arsenide (GaAs), gallium phosphorus (GaP), and lithium-alumina (LiAl ₂ O ₃ ), boron nitride (BN), aluminum nitride (AlN), gallium nitride (GaN), zinc oxide (ZNO) may be a substrate, but is not limited thereto. The substrate 10 may be variously selected according to the material of the first and second semiconductor layers 30 and 70 formed thereon.

The first semiconductor layer 30 is an n-type semiconductor layer formed on the substrate 10 and made of GaN doped with an n-type dopant of about several μm. For example, the first semiconductor layer 30 may be a GaN structure layer in which unintentionally doped GaN (u-GaN) and n type doped GaN (n-GaN) are sequentially deposited. In addition, the first semiconductor layer 30 may be formed of Al _x In _y Ga _(1-xy) N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) containing indium. .

A buffer layer 20 is interposed between the substrate 10 and the first semiconductor layer 30. The buffer layer 20 mitigates a difference in lattice mismatch and thermal expansion coefficient between the substrate 10 and the first semiconductor layer 30. The buffer layer 20 may be formed of low temperature growth GaN (LT-GaN) or AlN.

The active layer 40 is formed on the first semiconductor layer 30 and has a multi-quantum well structure. That is, the active layer 40 has a structure in which at least two quantum well layers 41 and at least two quantum barrier layers 43 are alternately stacked. The active layer 40 may be formed of In _x Ga _1-x N (0<x<1).

The strain application layer 50 is formed on the uppermost quantum well layer 41a of the active layer 40. The indium composition ratio of the strain application layer 50 is larger than that of the uppermost quantum barrier layer 43a, and is lower than that of the quantum well layer 41 of the active layer 40.

Here, if the indium composition ratio of the strain application layer 50 is larger than the indium composition ratio of the quantum well layer 41, it is because light emitted from the active layer 40 can be absorbed by the strain application layer 50. Therefore, the indium composition ratio of the strain application layer 50 is larger than that of the upper quantum barrier layer 43a, and lower than the indium composition ratio of the quantum well layer 41 of the active layer 40, so that the upper quantum barrier layer 43a Compressive strain (compressive strain) is generated at the interface of, and the light emitted from the quantum well layer 41 may be configured to prevent absorption from occurring in the strain application layer 50.

By adjusting the indium composition ratio or thickness of the strain application layer 50, the range and width of the spectrum of the emission wavelength can be adjusted. For example, the strain application layer 50 is made of In _x Ga _1-x N (0.15 _{≤ x ≤} 0.24), and may have a thickness of 15 to 50 nm. The active layer 40 is made of In _x Ga _1-x N (0<x<1), but the indium composition ratio of the plurality of quantum well layers 41 is 0.24<x<1, and the uppermost quantum barrier layer 43a The indium composition ratio may be 0<x<0.15.

When the strain application layer 50 is stacked on the active layer 40 as described above, the band of the wavelength of the emission spectrum can be expanded even under low current application. In general, the light emitting device configures the thin film layer so that strain is less, but in this embodiment, the band of the emission wavelength is extended by using the strain in reverse.

The second semiconductor layer 70 is formed on the strain application layer 50. The second semiconductor layer 70 is a p-type semiconductor layer made of GaN doped with a p-type dopant of about several μm. In addition, the second semiconductor layer 70 includes Al _x In _y Ga _(1-xy) N (0≤x≤1, 0≤y≤1, 0≤x+y≤ including indium doped with a p-type dopant ₎ 1).

In addition, the first electrode 80 may be formed on the first semiconductor layer 30, and the second electrode 90 may be formed on the second semiconductor layer 70. A transparent electrode layer (not shown) for ohmic contact may be formed on the second semiconductor layer 70.

As described above, since the multi-wavelength light emitting device 100 according to the present embodiment includes the strain application layer 50 together with the active layer 40, light of various wavelengths is output according to the intensity of the current applied to one light emitting device. can do. That is, by stacking the strain application layer 50 on the active layer 40, it is possible to change the wavelength of the light emission spectrum of the output light. The strain applying layer 50 can easily change the wavelength of the emission spectrum even at a low applied current.

For this reason, the multi-wavelength light emitting device 100 according to the present embodiment can continuously change the light emission spectrum according to the intensity of the applied current and output the light, thereby performing treatment according to the state of the light treatment subject. Therefore, the multi-wavelength light emitting device 100 according to the present embodiment can solve the hassle of using each different LED light source and system according to the state of the light treatment subject as before.

In addition, since the multi-wavelength light emitting device 100 according to the present embodiment can change the wavelength region of the output light by adjusting the intensity of the applied current, it is possible to select an effective wavelength according to the state of the light treatment subject with one light source. There is an advantage that light therapy is possible.

In order to confirm whether the multi-wavelength light emitting device according to this embodiment outputs light of various wavelengths, light emitting devices according to Examples and Comparative Examples were manufactured as shown in Table 1 and FIG. 2.

The single wavelength light emitting device according to the comparative example was manufactured in a structure as shown in FIG. 2. Referring to FIG. 2, in the single wavelength light emitting device 200 according to the comparative example, a barrier layer 60 made of GaN is interposed between the active layer 40 and the second semiconductor layer 70 instead of the strain application layer. The lower surface has the same structure as the multi-wavelength light emitting device according to the embodiment. In the comparative example and the comparative example, a sapphire substrate was used as the substrate 10.

After applying a current of 20 mA to the light emitting device according to Examples and Comparative Examples, the emission spectrum of the output light was measured.

Referring to Table 1, the single wavelength light emitting device according to the comparative example, when applying a current of 20mA, it was confirmed that the light of a single wavelength of 456nm is output.

On the other hand, when the multi-wavelength light emitting device according to the present embodiment was applied with a current of 20 mA, it was confirmed that light of dual wavelengths of 454 nm and 536 nm was output.

Additionally, when the indium composition ratio (x) of the strain application layer was 0 to 0.04, it was confirmed that light having a single wavelength was output. That is, it is determined that the dual wavelength light is output only when the indium composition ratio of the strain application layer is larger than the indium composition ratio of the quantum barrier layer.

Next, the light emission spectrum of the output light was measured by varying the intensity of the current applied to the light emitting device according to the comparative example and the example. The measurement results are shown in FIGS. 3 and 4. Here, FIG. 3 is a table measuring a light emission spectrum according to a current applied to a single wavelength light emitting device according to a comparative example. 4 is a table measuring a light emission spectrum according to a current applied to the multi-wavelength light emitting device of FIG. 1.

Referring to FIG. 3, even when a current of 20 mA to 350 mA is applied to a single wavelength light emitting device according to a comparative example, it was found that the change in the emission wavelength is very narrow, about 4 nm. That is, the emission wavelength of the comparative example was measured to be 460 nm at 20 mA and 464 nm at 350 mA.

On the other hand, referring to Figure 4, the multi-wavelength light emitting device according to the embodiment, when applying a current of 20mA to 350mA, the change of the emission wavelength is 63nm, it can be seen that the comparative example and the change width is greatly expanded. That is, the emission wavelength of the example was 542 nm at 20 mA and 479 nm at 350 mA.

As described above, in the multi-wavelength light emitting device according to the present embodiment, by adding a strain application layer to the structure of a general light emitting device, the green area (535 nm) to the blue area (475 nm) through one light emitting device according to the intensity of the applied current. It is variable.

On the other hand, the embodiments disclosed in the specification and the drawings are merely presented as specific examples to help understanding, and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art to which the present invention pertains that other modifications based on the technical spirit of the present invention can be implemented in addition to the embodiments disclosed herein.

10: substrate
20: buffer layer
30: first semiconductor layer
40: active layer
41: quantum well layer
43: quantum barrier layer
43a: upper quantum barrier layer
50: strain application layer
60: barrier layer
70: second semiconductor layer
80: first electrode
90: second electrode
100: multi-wavelength light emitting device
200: single wavelength light emitting device

Claims (7)

Board;
A first semiconductor layer formed on the substrate;
An active layer formed on the first semiconductor layer and having a multi-quantum well structure in which a plurality of quantum well layers and a plurality of quantum barrier layers are alternately stacked and a top quantum well layer is disposed at the end;
A strain application layer formed on the uppermost quantum well layer of the active layer and having a larger indium composition ratio than the uppermost quantum barrier layer so that compressive strain occurs at an interface with the uppermost quantum barrier layer; And
A second semiconductor layer formed on the strain application layer;
Multi-wavelength light emitting device comprising a strain applying layer comprising a. According to claim 1,
A multi-wavelength light-emitting device comprising a strain application layer characterized in that the indium composition ratio of the strain application layer is lower than the indium composition ratio of the quantum well layer of the active layer. According to claim 2,
The strain applying layer is In _x Ga _1-x N (0.15≤x≤0.24), a multi-wavelength light-emitting device comprising a strain applying layer characterized in that the thickness is 15 to 50nm. According to claim 3,
The first semiconductor layer is an n-type semiconductor layer in which u-GaN and n-GaN are sequentially stacked,
The second semiconductor layer is a p-type semiconductor layer made of p-GaN,
The active layer is composed of In _x Ga _1-x N (0<x<1), but the indium composition ratio of the plurality of quantum well layers is 0.24<x<1, and the indium composition ratio of the uppermost quantum barrier layer is 0<x A multi-wavelength light-emitting device comprising a strain application layer, characterized in that <0.15. According to claim 1,
A multi-wavelength light emitting device including a strain applying layer, characterized in that the band of the emission wavelength changes according to the intensity of the current applied between the first semiconductor layer and the second semiconductor layer. The method of claim 5,
A multi-wavelength light-emitting device including a strain applying layer characterized in that when a current of a specific intensity is applied between the first semiconductor layer and the second semiconductor layer, light in two wavelength bands is output. The method of claim 5,
When the intensity of the applied current is 20mA to 350mA, a multi-wavelength light emitting device including a strain applying layer, characterized in that the light of the 480nm to 540nm wavelength band is output.

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