KR102319813B1 - Light Emitting Device - Google Patents

Abstract

An embodiment relates to a light emitting device, comprising: a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer; a light-transmitting substrate disposed on the first surface of the light emitting structure and having a surface roughness on the surface; a roughness reducing layer disposed on the surface of the light-transmitting substrate; and a reflective layer disposed on a surface of the roughness alleviating layer.

Description

Light Emitting Device

The embodiment relates to a light emitting device, and more particularly, a light emitting device in which a reflective layer can be deposited with a uniform thickness on the substrate by smoothing the surface roughness formed on the substrate of the light emitting device during a grinding process when manufacturing the light emitting device is about

Light emitting devices such as light emitting diodes and laser diodes using group 3-5 or group 2-6 compound semiconductor materials of semiconductors are developed in various colors such as red, green, blue, and ultraviolet rays due to the development of thin film growth technology and device materials. By using fluorescent materials or combining colors, high-efficiency white light can be realized, and compared to conventional light sources such as fluorescent and incandescent lamps, low power consumption, semi-permanent lifespan, fast response speed, safety, and environmental friendliness are possible. have an advantage

With the development of these technologies, a light emitting diode backlight, fluorescent or incandescent light bulb that replaces Cold Cathode Fluorescence Lamp (CCFL) constituting the backlight of LCD (Liquid Crystal Display) display devices, as well as display devices as well as transmission modules of optical communication means. Its application is expanding to white light emitting diode lighting devices, automobile headlights, and traffic lights that can replace them.

Here, the light emitting device is light having energy determined by an energy band unique to the material constituting the active layer (light emitting layer) when electrons injected through the first conductivity type semiconductor layer and holes injected through the second conductivity type semiconductor layer meet each other. emits

1 is a view showing a conventional light emitting device.

As shown in FIG. 1 , the conventional light emitting device 1 includes a first electrode pad 22a, a first conductivity type semiconductor layer 22, an active layer 24 and a second conductivity type semiconductor layer 26. The light emitting structure 20 , the second electrode pad 26a , the indium tin oxide (ITO) layer 27 disposed between the second conductivity type semiconductor layer 26 and the second electrode pad 26a , the light-transmitting substrate 40 . ), and a buffer layer 21 provided on the light-transmitting substrate 40 . In addition, the reflective layer 80 is disposed on the light-transmitting substrate 40 in order to increase the reflectivity of light emitted from the light emitting device.

In order to optimize the light extraction efficiency of the light emitting device, the substrate of the light emitting device is ground to a predetermined thickness in a post-processing step during the manufacturing process of the light emitting device. At this time, a surface roughness is formed on the surface of the ground substrate, and when the reflective layer 80 is deposited on the surface of the substrate 40 having non-uniform flatness as described above, the thickness of the reflective layer 80 is uniformly deposited. There is a problem in that it is not possible to emit light with a desired reflectivity.

The embodiment has been devised to solve the above problems, and an object of the present invention is to provide a light emitting device capable of depositing a reflective layer with a uniform thickness on the substrate surface of a light emitting device having a surface roughness formed after a post hole.

In order to achieve the above object, an embodiment provides a light emitting structure including a first conductivity type semiconductor layer, an active layer and a second conductivity type semiconductor layer; a light-transmitting substrate disposed on the first surface of the light emitting structure and having a surface roughness on the surface; a roughness reducing layer disposed on the surface of the light-transmitting substrate; and a reflective layer disposed on a surface of the roughness alleviating layer.

In an embodiment, the light-transmitting substrate may include sapphire.

In addition, the average surface roughness height of the light-transmitting substrate may be 1 μm to 3 μm.

In addition, the roughness alleviating layer may be a spin-on dielectric (SOD) thin film.

In addition, the spin-on dielectric thin film may include perhydropolysilazane (PHPS).

The thickness of the roughness alleviating layer may be 0.5 μm to 5 μm.

Meanwhile, the reflective layer may be a Distributed Bragg Reflector Layer (DBR).

And, the thickness of the reflective layer may be 2.2㎛ to 2.6㎛.

According to the above-described embodiment, since the reflective layer can be deposited with a uniform thickness on the surface of the substrate of the light emitting device, light can be emitted with a desired reflectivity.

In addition, by disposing a spin-on dielectric (SOD) between the substrate and the reflective layer, the amount of photons passing through the reflective layer can be increased by the difference in refractive index between the substrate and the spin-on dielectric (SOD) and the surface roughness of the substrate. have.

1 is a view showing a conventional light emitting device.
2 is a view showing a light emitting device according to an embodiment.
3A to 3D are views illustrating a manufacturing process of a light emitting device according to an embodiment.
4 is a Fourier Transform Infrared Spectrum (FTIR) graph showing light absorption of a spin-on dielectric thin film according to an embodiment.

Hereinafter, a preferred embodiment of the present invention that can specifically realize the above object will be described with reference to the accompanying drawings.

In the description of the embodiment according to the present invention, in the case where it is described as being formed in "on or under" of each element, above (above) or below (on) or under) includes both elements in which two elements are in direct contact with each other or one or more other elements are disposed between the two elements indirectly. In addition, when expressed as “up (up) or down (on or under)”, it may include not only the upward direction but also the meaning of the downward direction based on one element.

In the drawings, the thickness or size of each layer is exaggerated, omitted, or schematically illustrated for convenience and clarity of description. In addition, the size of each component does not fully reflect the actual size.

2 is a view showing a light emitting device according to an embodiment.

As shown in FIG. 2 , the light emitting device 100 according to the present embodiment includes a light emitting structure 120 , a light transmitting substrate 140 , a roughness alleviating layer 160 , and a reflective layer 180 . In addition, the light emitting device 100 may further include a first electrode pad 122a and a second electrode pad 126a.

In addition, the light emitting structure 120 includes a first conductivity type semiconductor layer 122 , an active layer 124 provided on the first conductivity type semiconductor layer 122 , and a second conductivity type semiconductor layer provided on the active layer 124 . and a semiconductor layer 126 .

Here, the light emitting structure 120 including the first conductivity type semiconductor layer 122 , the active layer 124 , and the second conductivity type semiconductor layer 126 is formed by, for example, a metal organic chemical vapor deposition (MOCVD) method. Deposition), Chemical Vapor Deposition (CVD), Plasma-Enhanced Chemical Vapor Deposition (PECVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE) ) may be formed using a method such as, but is not limited thereto.

In addition, a buffer layer 121 may be grown between the first conductivity-type semiconductor layer 122 and the light-transmitting substrate 140 , in order to alleviate a lattice mismatch of materials and a difference in coefficient of thermal expansion. The material of the buffer layer 121 may be formed of a Group III-5 compound semiconductor, for example, at least one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN. An undoped semiconductor layer may be formed on the buffer layer 121 , but is not limited thereto.

In addition, the first conductivity type semiconductor layer 122 may be formed of a semiconductor compound. In more detail, it may be implemented as a compound semiconductor such as Group III-5, Group II-6, or the like, and may be doped with a first conductivity-type dopant. When the first conductivity-type semiconductor layer 122 is an n-type semiconductor layer, the first conductivity-type dopant is an n-type dopant and may include Si, Ge, Sn, Se, and Te, but is not limited thereto.

And, the first conductivity type semiconductor layer 122 is _{a semiconductor material having a composition formula of Al x} In _y Ga _(1-xy) N (0≤x≤1, 0≤y≤1, 0≤x+y≤1) may include. The first conductivity type semiconductor layer 122 may be formed of any one or more of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP.

Meanwhile, in the active layer 124 , electrons injected through the first conductivity-type semiconductor layer 122 and holes injected through the second conductivity-type semiconductor layer 126 formed later meet each other to form the active layer 124 . A layer that emits light with an energy determined by the energy band of

In addition, the active layer 124 may have a double junction structure, a single quantum well structure, a multi quantum well (MQW) structure, a quantum wire (Quantum-Wire) structure, or a quantum dot (Quantum Dot) structure. It may be formed by at least one of the structures. For example, in the active layer 124, trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and trimethyl indium gas (TMIn) may be injected to form a multi-quantum well structure. It is not limited.

The well layer/barrier layer of the active layer 124 is, for example, any of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN, InAlGaN/InAlGaN, GaAs (InGaAs)/AlGaAs, GaP (InGaP)/AlGaP. It may be formed in one or more pair structures, but is not limited thereto. Here, the well layer may be formed of a material having a band gap lower than that of the barrier layer.

In addition, a conductive cladding layer (not shown) may be formed above and/or below the active layer 124 . The conductive cladding layer may be formed of a barrier layer of the active layer 124 or a semiconductor having a wider bandgap than the bandgap. For example, the conductive clad layer may include GaN, AlGaN, InAlGaN, or a superlattice structure. In addition, the conductivity-type cladding layer may be doped with n-type or p-type.

In addition, the second conductivity type semiconductor layer 126 may be formed of a semiconductor compound. In more detail, it may be implemented as a compound semiconductor such as Group III-5, Group II-6, or the like, and may be doped with a second conductivity-type dopant. For example, it may include a semiconductor material having a compositional formula of _{In x} Al _y Ga _{1-xy N (0≤x≤1, 0≤y≤1, 0≤x+y≤1).} In addition, when the second conductivity-type semiconductor layer 126 is a p-type semiconductor layer, the second conductivity-type dopant is a p-type dopant and may include Mg, Zn, Ca, Sr, Ba, or the like.

On the other hand, in the first electrode pad 122a provided in the light emitting device 100 , a portion of the second conductivity type semiconductor layer 126 , the active layer 124 , and the first conductivity type semiconductor layer 122 are mesa-etched so that a part thereof is exposed. and the second electrode pad 126a is disposed on one side of the top surface of the second conductivity type semiconductor layer 126 . Here, an indium tin oxide (ITO) layer 127 may be further disposed between the top surface of the second conductivity type semiconductor layer 126 and the second electrode pad 126a to increase conductivity.

In addition, the first electrode pad 122a and the second electrode pad 126a may include at least one of aluminum (Al), titanium (Ti), chromium (Cr), nickel (Ni), copper (Cu), and gold (Au). It may be formed in a single-layer or multi-layer structure, including:

In the embodiment, the light-transmitting substrate 140 disposed on the lower surface of the light-emitting structure 120 may be a sapphire substrate or the like, and includes a light-transmitting conductive substrate or an insulating substrate, but is not limited thereto.

In addition, the light-transmitting substrate 140 may be formed of a material having excellent thermal conductivity, and in addition to sapphire (Al ₂ O ₃ ), SiO ₂ , SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, Ga ₂ 0 ₃ At least one of them can be used.

In addition, the first surface of the light-transmitting substrate 140 has a surface roughness 142 . Here, in order to optimize the light extraction of the light emitting device 100, the transmissive substrate 140 is ground using a slurry or the like to make the transmissive substrate 140 to a certain thickness. During this process, the transmissive substrate 140 is ground. A surface roughness 142 is formed on the substrate 140 . Here, the average surface roughness height of the surface roughness 142 may be 1 μm to 3 μm to increase the amount of light passing through the translucent substrate 140 . However, the surface roughness 142 formed in this way has the advantage of increasing the amount of light transmitted through the light-transmitting substrate 140, but in order to emit the light of the light-emitting device with a desired reflectivity in the conventional light-emitting device (Fig. There is a problem in that the reflective layer (80 of FIG. 1 ) disposed on 40 of 1 is not deposited to a uniform thickness on the light-transmitting substrate having surface roughness.

Accordingly, in the present embodiment, the roughness alleviating layer 160 for smoothing the surface roughness may be provided on the first surface of the light-transmitting substrate 140 .

Here, the roughness alleviation layer 160 may be provided as a spin-on dielectric (SOD) thin film on the surface of the light-transmitting substrate 140 on which the surface roughness 142 is formed. In addition, the spin-on dielectric thin film may include perhydropolysilazane (PHPS).

Then, perhydropolysilazane is spin-coated on the surface of the translucent substrate 140 on which the surface roughness is formed, and a thermal process is performed. This thermal process is called a curing process. In this case, the curing process is a dry heat process performed in a furnace, and may be performed at a temperature of 200°C to 300°C. After this process, when the surface of the translucent substrate coated with perhydropolysilazane is immersed in hydrogen peroxide (H2O2), most of the Si-H and Si-N bonds in the perhydropolysilazane are Si-O. replaced by a bond. Accordingly, a silicon oxide film (SiOx) having a general formula of -(SiH2NH)n- (n is a positive integer) is formed on the surface of the light-transmitting substrate 140 having the roughness formed thereon.

Here, the thickness of the roughness alleviating layer 160 is formed to a thickness capable of alleviating the roughness of the surface roughness formed on the light-transmitting substrate 140, and when the roughness alleviating layer including the silicon oxide film is deposited too thickly, cracks may occur. Since it may occur, the thickness of the roughness alleviating layer 160 may be applied in a range of 0.5 μm to 5 μm.

Meanwhile, the reflective layer 180 may be disposed on the surface of the roughness alleviating layer 160 to provide a high reflectance of light emitted from the light emitting device 100 to substantially improve luminance.

Also, as described above, the reflective layer 180 may be deposited with a uniform thickness on the light-transmitting substrate 140 by smoothing the surface roughness 142 .

In addition, the reflective layer 180 may be a Distributed Bragg Reflector Layer (DBR), and for high reflectance of light emitted from the light emitting device 100 according to the embodiment, the reflective layer 180 has a thickness of 2.2 μm to It may be 2.6 μm.

3A to 3D are diagrams illustrating a manufacturing process of the light emitting device 100 according to the embodiment.

As shown in FIG. 3A , a light emitting structure 120 including a buffer layer, a first conductivity type semiconductor layer 122 , an active layer 124 , and a second conductivity type semiconductor layer 126 on the light transmitting substrate 140 is formed. Grow. Here, the light emitting structure 120 is, for example, a metal organic chemical vapor deposition (MOCVD) method, a chemical vapor deposition method (CVD; Chemical Vapor Deposition), a plasma chemical vapor deposition method (PECVD; Plasma-Enhanced Chemical Vapor Deposition), It may be formed using a method such as Molecular Beam Epitaxy (MBE) or Hydride Vapor Phase Epitaxy (HVPE), but is not limited thereto.

On the other hand, the light-transmitting substrate 140 may be formed of a material suitable for semiconductor material growth, a carrier wafer, and includes a light-transmitting conductive substrate or an insulating substrate, for example, sapphire (Al ₂ O ₃ ) may be used. In addition, impurities on the surface can be removed by wet cleaning the light-transmitting substrate.

As shown in FIG. 3B , in order to obtain the optimal light extraction efficiency of the light emitting device 100 , a grinding process is performed on the first surface of the light transmitting substrate 140 with a slurry or the like, and the light transmitting substrate 140 is performed. ) to a certain thickness. In this case, a surface roughness 142 is formed on the first surface of the light-transmitting substrate 140 that has undergone the grinding process. Here, the average surface roughness height h1 of the surface roughness 142 may be 1 μm to 3 μm, and the amount of light of the light source passing through the light transmitting substrate 140 can be increased due to the surface roughness 142 . .

Referring to FIG. 3C , a roughness alleviating layer 160 for smoothing the surface roughness may be provided on the surface of the light-transmitting substrate 140 .

Here, the roughness alleviating layer 160 is a spin-on dielectric (SOD) thin film containing perhydropolysilazane (PHPS) on the surface of the light-transmitting substrate 140 on which the surface roughness 142 is formed. can be provided.

In addition, perhydropolysilazane is spin-coated on the surface of the light-transmitting substrate 140 having a roughened surface, and a thermal process is performed at a temperature of 200°C to 300°C. In this case, the perhydropolysilazane may be deposited on the light-transmitting substrate 140 to a thickness t1 of 0.5 μm to 5 μm by controlling the spin coating rate or by performing double coating. In addition, while the above-described roughness alleviating layer 160 is deposited on the surface of the light-transmitting substrate 140 having an average surface roughness of 1 μm to 3 μm, the surface of the light-transmitting substrate 140 may be formed flat.

In addition, when the surface of the translucent substrate 140 coated with perhydropolysilazane is subjected to a process of dipping in hydrogen peroxide (H2O2), most of the Si-H and Si-N bonds in the perhydropolysilazane are Si-O bonds. A silicon oxide film (SiOx) is formed on the surface of the surface transmissive substrate 140 by substitution.

As shown in FIG. 3D , the reflective layer 180 may be disposed on the silicon oxide layer so that light from the light emitting device may be transmitted with a desired reflectivity. Here, the reflective layer 180 may be a Distributed Bragg Reflector Layer (DBR) having a multilayer structure composed of two materials having different refractive indices. In addition, the thickness t2 of the dispersion Bragg reflective layer 180 may be 2.2 μm to 2.6 μm so that light emitted from the active region of the light emitting device can be emitted with high reflectivity.

As described above, when a silicon oxide film is coated on the surface of the light-transmitting substrate 140 having a roughened surface, the surface of the light-transmitting substrate 140 becomes flat. 180 may be deposited with a uniform thickness. Accordingly, light from the light emitting device can be emitted with a desired reflectivity.

4 is a Fourier Transform Infrared Spectrum (FTIR) graph showing light absorption of a spin-on dielectric thin film according to an embodiment.

Fourier transform infrared spectroscopy observes a spectrum caused by vibration or rotation of a molecule, and by analyzing the wavelength or intensity of the spectrum, the shape of a molecule, bonding force between atoms, or their composition can be known.

Referring to FIG. 4 , the solid line shows an infrared absorption spectrum of a silicon oxide film (SiOx) deposited on the translucent substrate 140 having a surface roughness formed according to the embodiment, and the graph shown by the dotted line is PVD (Physical Vapor Deposition) ) or CVD (Chemical Vapor Deposition) method shows the infrared absorption spectrum of the conventional silicon oxide film.

From the graph of FIG. 4 , it can be seen that the silicon oxide film (SiOx) according to the present embodiment has higher absorbance than the conventional silicon oxide film (SiOx).

Therefore, the silicon oxide film (SiOx) formed according to the embodiment is a more stable thin film in the process of replacing Si-H and Si-N bonds with Si-O bonds in perhydropolysilazane. It can be seen that a reduced thin film can be formed.

As described above, the step coverage of the spin-on dielectric (SOD) deposited on the substrate after spin-coating the spin-on dielectric (SOD) on the substrate surface of the light emitting device on which the surface roughness is formed after the post hole. By improving the reflective layer, a reflective layer is deposited with a uniform thickness on the substrate surface of the light emitting device, so that light can be emitted with a desired reflectivity.

In addition, by disposing a spin-on dielectric (SOD) between the substrate and the reflective layer, the amount of photons passing through the reflective layer can be increased due to the difference in refractive index between the substrate and the spin-on dielectric and the surface roughness of the substrate. The beam angle of the light emitted from the device is wide, and high light efficiency can be obtained.

One or a plurality of the above-described light emitting devices may be disposed in one light emitting device package.

Here, when the light emitting device is disposed in the light emitting device package, the first electrode and the second electrode of the light emitting device may be electrically connected to the first lead frame and the second lead frame, respectively. In addition, a molding part including silicon or the like is disposed around the light emitting device to protect the light emitting device.

In addition, the above-described light emitting device or light emitting device package may be used as a light source of a lighting system, and may be used, for example, in a backlight unit of an image display device and a lighting device.

When used as a backlight unit of an image display device, it may be used as an edge-type backlight unit or a direct-type backlight unit, and when used in a lighting device, it may be used for a lamp or a bulb-type light source.

Although the embodiment has been described above, it is only an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are not exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications are possible. For example, each component specifically shown in the embodiment can be implemented by modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

1, 100: light emitting device 20, 120: light emitting structure
22, 122: first conductivity type semiconductor layer 24, 124: active layer
26, 126: second conductivity type semiconductor layer 40, 140: light-transmitting substrate
42, 142: surface roughness 80, 180: reflective layer
160: roughness relief layer

Claims (8)

a light emitting structure including a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer;
a light-transmitting substrate having a first surface on which the light emitting structure is disposed, and a second surface opposite to the first surface and having a surface roughness;
a roughness alleviating layer disposed on the second surface of the light-transmitting substrate and having a third surface in contact with the second surface and a fourth surface opposite to the third surface; and
a reflective layer disposed on the fourth surface of the roughness alleviating layer;
The roughness alleviating layer is a spin-on dielectric (SOD) thin film,
The spin-on dielectric thin film is a light emitting device comprising a hydropolysilazane (Perhydropolysilazane: PHPS). delete According to claim 1,
An average surface roughness height of the light-transmitting substrate is 1 μm to 3 μm. delete delete According to claim 1,
The thickness of the roughness alleviating layer is 0.5㎛ to 5㎛ the light emitting device. According to claim 1,
The reflective layer is a Distributed Bragg Reflector Layer (DBR),
The reflective layer has a thickness of 2.2 μm to 2.6 μm. delete

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