KR102155544B1 - Multi-wavelength light emitting device comprising strain-appled layer - Google Patents

Abstract

The present invention relates to a multi-wavelength light-emitting device including a strain application layer, and is intended to output light of various wavelengths according to the intensity of a current applied to one light-emitting device. The multi-wavelength light emitting device according to the present invention has a structure in which a strain applying layer is interposed between an active layer having a multi-quantum well structure and a second semiconductor layer. Since the strain application layer is formed on the uppermost quantum well layer of the active layer and has a larger indium composition ratio than the uppermost quantum barrier layer, the strength of the applied current by causing a compressive strain to occur at the interface with the quantum barrier layer. It allows light of various wavelengths to be outputted according to.

Description

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 that outputs light of various wavelengths according to the intensity of a current applied to one light-emitting device.

As medical light sources for the treatment of skin diseases, gas lasers and semiconductor light sources such as LED (light emitting diode) or LD (laser diode) are used. Gas lasers and LDs are close to destructive methods, which cause scarring and are suitable for the treatment of local skin diseases, but are not suitable for large areas of disease. Therefore, most of the optical medical devices for the treatment of skin diseases are commercialized using a single LED light source suitable for the treatment of non-destructive skin diseases in a wide 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 diseases and effective light sources is still clearly revealed. no.

The phototherapy device equipped with a medical LED light source, which is currently commercially available, is composed of a module to which an LED light source of single wavelength or two wavelengths is applied. However, conventional phototherapy devices are cumbersome to use different LED light sources and systems for each skin disease.

For example, an effective light source for acne treatment is generally a blue series, and a 415nm light source is used as a representative wavelength, but it is known that wavelengths of 405nm, 420nm or 630nm are also effective in some. 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 wavelength is different.

And, even with the same disease, the effective wavelength of the light source may vary depending on the color of the skin (for example, Asians or Westerners) and the severity of the disease, so it is suitable to be applied to all subjects as a light therapy device equipped with a single LED light source currently commercially available. Not.

In this way, the treatment of skin diseases using an LED light source has a very complex element, and thus various wavelength light sources and control technologies are required.

In addition, even for the same disease, the treatment effect using the LED light source varies depending on the target, so in order to solve this problem, it is troublesome to mount many light sources of effective wavelengths. For example, 17 kinds of LED light sources (405nm, 406nm, 407nm, 408nm, 409nm, 410nm, 411nm, 412nm, 413nm, 414nm, 415nm, 416nm, 416nm, corresponding to the wavelength range of 405 ~ 420nm, 417nm, 418nm, 419nm, 420nm), 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 the light treatment must be performed while replacing the light irradiator whenever the wavelength is different, there is a problem in that it is inconvenient for user particles and that light treatment takes a lot of time.

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 multiple 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 applying layer formed on the uppermost quantum well layer of the active layer and having a higher indium composition ratio than the uppermost quantum barrier layer to generate a compressive strain at an interface with the uppermost quantum barrier layer; It provides a multi-wavelength light emitting device including a strain applying layer including; and a second semiconductor layer formed on the strain applying layer.

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.

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), wherein 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 applied current has an intensity of 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 applying 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 laminating the strain applying layer on the active layer, the wavelength of the emission spectrum of the output light can be changed. The strain application 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 condition of the phototherapy 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 different LED light sources and systems according to the state of the phototherapy subject as in the past.

In addition, since the multi-wavelength light emitting device according to the present invention can change the wavelength range of the output light by adjusting the intensity of the applied current, light treatment is possible by selecting an effective wavelength according to the condition of the phototherapy subject with one light source. 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 the emission spectrum according to the current applied to the multi-wavelength light emitting device of FIG. 1.

In the following description, it should be noted that only parts necessary for understanding the embodiments of the present invention will be described, and descriptions of other parts will be omitted without distracting the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to a conventional or dictionary meaning, and the inventor is appropriate as a concept of terms in order to describe his own invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention on the basis of the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent all the technical spirit of the present invention, and various equivalents that can replace them at the time of application And it should be understood that there may be variations.

Hereinafter, embodiments of the present invention will be described in more 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 the present embodiment includes a substrate 10, a first semiconductor layer 30, an active layer 40, a strain applying 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, but at the end the uppermost quantum well layer 41a is disposed. It has a multiple quantum well structure. The strain applying layer 50 is formed on the uppermost quantum barrier layer 43a of the active layer 40, and compared to the uppermost quantum barrier layer 43a so that a compressive strain occurs at the interface with the active layer 40. The composition ratio of indium is large. In addition, the second semiconductor layer 70 is formed on the strain applying layer 50. In addition, the multi-wavelength light emitting device 100 according to the present exemplary embodiment includes a buffer layer 20, a first electrode 80, and a second electrode 90.

The substrate 10 is sapphire (Al ₂ O ₃ ), silicon carbide (SiC), zinc oxide (ZnO), silicon (Si), spinel, gallium arsenide (GaAs), gallium phosphorus (GaP), lithium-alumina. (LiAl ₂ O ₃ ), boron nitride (BN), aluminum nitride (AlN), gallium nitride (GaN), zinc oxide (ZNO) 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 lattice mismatch between the substrate 10 and the first semiconductor layer 30 and a difference in coefficient of thermal expansion. The buffer layer 20 may be formed of low-temperature grown GaN (LT-GaN) or AlN.

The active layer 40 is formed on the first semiconductor layer 30 and has a multiple 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 higher than that of the uppermost quantum barrier layer 43a and lower than the indium composition ratio of the quantum well layer 41 of the active layer 40.

This is because if the indium composition ratio of the strain application layer 50 is greater than the indium composition ratio of the quantum well layer 41, light emitted from the active layer 40 may be absorbed by the strain application layer 50. Therefore, the indium composition ratio of the strain application layer 50 is higher than the indium composition ratio of the uppermost 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 uppermost quantum barrier layer 43a and It can be configured so that a compressive strain occurs at the interface of and that light emitted from the quantum well layer 41 is not absorbed in the strain applying layer 50.

By adjusting the indium composition ratio or thickness of the strain applying layer 50, the range and width of the spectrum of the emission wavelength can be adjusted. For example, the strain application layer 50 may be 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 is The indium composition ratio may be 0<x<0.15.

When the strain applying layer 50 is stacked on the active layer 40 as described above, the wavelength band of the emission spectrum can be enlarged even under application of a low current. In a typical light emitting device, a thin film layer is formed to take less strain, but in the present embodiment, the band of the emission wavelength is enlarged by using the strain in reverse.

The second semiconductor layer 70 is formed on the strain applying 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≤ ₎ containing indium doped with a p-type dopant. 1) can be made.

In addition, a first electrode 80 may be formed on the first semiconductor layer 30, and a 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 applying 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 applying layer 50 on the active layer 40, the wavelength of the emission spectrum of the output light can be changed. The strain applying layer 50 can easily change the wavelength of the emission spectrum even at a low applied current.

Accordingly, the multi-wavelength light-emitting device 100 according to the present exemplary embodiment continuously changes and outputs the emission spectrum according to the intensity of the applied current, thereby performing treatment according to the state of the phototherapy subject. Accordingly, the multi-wavelength light-emitting device 100 according to the present exemplary embodiment can eliminate the hassle of using different LED light sources and systems according to the state of the phototherapy subject as in the past.

In addition, since the multi-wavelength light-emitting device 100 according to the present embodiment can change the wavelength range of the output light by adjusting the intensity of the applied current, one light source selects an effective wavelength according to the condition of the phototherapy subject. There is an advantage that phototherapy is possible.

In order to check whether the multi-wavelength light-emitting device according to the present embodiment outputs light of various wavelengths, light-emitting devices according to Examples and Comparative Examples were manufactured as shown in Tables 1 and 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, the single wavelength light emitting device 200 according to the comparative example excludes that a barrier layer 60 made of GaN material is interposed between the active layer 40 and the second semiconductor layer 70 instead of the strain applied layer. The lower surface has the same structure as the multi-wavelength light emitting device according to the embodiment. In Comparative Examples and Comparative Examples, a sapphire substrate was used as the substrate 10.

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

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

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

Additionally, when the indium composition ratio (x) of the strain application layer is 0 to 0.04, it can be confirmed that light of a single wavelength is 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 greater than the indium composition ratio of the quantum barrier layer.

Next, the emission spectrum of the output light was measured by varying the intensity of the current applied to the light emitting device according to Comparative Examples and Examples. The measurement results are shown in FIGS. 3 and 4. 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 the emission spectrum according to the current applied to the multi-wavelength light emitting device of FIG. 1.

Referring to FIG. 3, even when a current of 20mA to 350mA is applied to the single wavelength light emitting device according to the comparative example, it can be seen that the change in the light emitting wavelength is very narrow at about 4nm. 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 FIG. 4, in the multi-wavelength light emitting device according to the embodiment, when a current of 20mA to 350mA is applied, the change in the emission wavelength is 63nm, and the change in the comparative example is greatly expanded. That is, the emission wavelength of the example was measured to be 542 nm at 20 mA and 479 nm at 350 mA.

As described above, the multi-wavelength light-emitting device according to the present embodiment adds a strain application layer to the structure of a general light-emitting device, so that from the green area (535 nm) to the blue area (475 nm) through one light-emitting device according to the intensity of the applied current. Variable is possible.

On the other hand, the embodiments disclosed in the specification and drawings are only presented specific examples to aid understanding, and are not intended to limit the scope of the present invention. It is obvious to those of ordinary skill in the art that other modifications based on the technical idea of the present invention may 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: uppermost quantum barrier layer
50: strain applied 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 including indium and a plurality of quantum barrier layers including indium are alternately stacked, and the uppermost quantum well layer is disposed at the end;
It is formed as a single layer directly on the uppermost quantum well layer of the active layer, and the indium composition ratio is higher than that of the uppermost quantum barrier layer so that a compressive strain occurs at the interface with the uppermost quantum barrier layer under the uppermost quantum well layer. A strain applied layer that is large and lower than the indium composition ratio of the quantum well layer of the active layer; And
A second semiconductor layer formed on the strain applying layer;
Multi-wavelength light emitting device comprising a strain application layer comprising a. delete The method of claim 1,
The strain application layer is In _x Ga _1-x N (0.15≤x≤0.24), a multi-wavelength light emitting device including a strain application layer, characterized in that the thickness is 15 to 50nm. The method of 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 made of In _x Ga _1-x N (0<x<1), wherein 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 applying layer, characterized in that <0.15. The method of claim 1,
A multi-wavelength light-emitting device including a strain applying layer, wherein a band of a light-emitting wavelength changes according to an intensity of a current applied between the first semiconductor layer and the second semiconductor layer. The method of claim 5,
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, light in a wavelength band of 480nm to 540nm is output.

Images