KR102351100B1 - Light-emitting diode and method for manufacturing same - Google Patents

Abstract

The light emitting diode according to the present invention includes a bulk substrate made of aluminum nitride (AlN), a buffer layer formed by growing the aluminum nitride on the bulk substrate, and a light emitting structure formed on the buffer layer, and an empty space between the bulk substrate and the buffer layer may further include.

Description

Light-emitting diode structure and manufacturing method thereof

The present invention relates to a structure of a light emitting diode and a method for manufacturing the same. More specifically, the present invention relates to a structure for a high-quality ultraviolet light-emitting diode (UV-LED) and a method for manufacturing the same.

As the technology of light emitting diodes (LED) develops, cost reduction and energy saving are experienced. In addition, devices using light emitting diodes (LEDs) are becoming more diverse. Although LEDs in the visible region are being actively applied to applications including lighting today, ultraviolet (UV) light sources are widely used in science/industrial, medical/environmental, and semiconductor industries, and the range will expand further in the future. For example, a protective film of a product produced using a light emitting diode (LED) is created, or a coating film for decoration or protection is formed on nails or toenails. In fact, the UV light emitting diode can replace the UV lamp used in the past.

In the case of using a substrate in which aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) are grown on a sapphire substrate when manufacturing a deep ultraviolet (DUV) light emitting diode (LED), a growth substrate and a compound semiconductor layer are used. Due to the lattice constant difference between the two, defects such as dislocation are generated in the compound semiconductor layer, and ultimately, the crystallinity of the compound semiconductor layer is deteriorated, thereby deteriorating the electrical or optical characteristics of the electronic device. In addition, the difference in lattice constant and thermal expansion coefficient between the growth substrate and the compound semiconductor layer causes stress. That is, the balance between the compressive strain during growth of compound semiconductors and the tensile strain upon cooling to room temperature after growth is out of balance, resulting in cracks or growth in the compound semiconductor layer. The board is broken.

In order to overcome this disadvantage, when epitaxial growth is attempted on a bulk substrate of aluminum nitride (AlN), the difference in lattice constant and thermal expansion coefficient between aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) is used. Due to this, there is a problem in that a low current yield and reliability are deteriorated because a hillock is generated in which the material is piled up like a hill due to self-diffusion, grain boundary diffusion, and the like.

The present invention provides a short-wavelength ultraviolet light emitting diode (DUV-LED) using a bulk substrate of aluminum nitride (AlN).

In addition, the present invention has an internal quantum efficiency (IQE) of a short-wavelength ultraviolet light emitting diode (DUV-LED) formed by growing aluminum nitride (AlN) or aluminum gallium nitride (AlGaN) rather than indium gallium nitride (InGaN). In order to overcome the problem of being more sensitive to threading dislocation density (TDD), a void is formed between the substrate and the buffer layer.

In addition, the present invention can improve light extraction efficiency (LEE) through the void formed between the substrate and the buffer layer and relieve strain, thereby suppressing the generation of hillocks. can do.

In addition, in the present invention, since a void is formed through an Epitaxial Lateral Overgrowth (ELOG) technique after a trench is formed in the substrate, a phenomenon in which dislocations are bent by horizontal epitaxial growth (Dislocation Bending) ) occurs, and the potential at the bottom can be partially blocked by the void.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. will be able

A light emitting diode according to an embodiment of the present invention includes a bulk substrate made of aluminum nitride (AlN), a buffer layer formed by growing the aluminum nitride on the bulk substrate, and a light emitting structure formed on the buffer layer, the bulk substrate and an empty space between the buffer layer and the buffer layer.

In addition, the empty space may be positioned below the upper surface of the bulk substrate.

Also, the empty space may be generated by covering an upper portion of the trench with the buffer layer in a trench made by etching the bulk substrate.

In addition, the width of the empty space may be in the range of 0.3 μm to 2 μm, the height may be in the range of 0.3 μm to 4 μm, and the interval between adjacent empty spaces may be in the range of 0.3 μm to 5 μm.

In addition, the buffer layer may be formed to a thickness of 0.2 μm to 10 μm.

In addition, the lower portion of the empty space may be characterized in that the valley (valley) shape.

In addition, the buffer layer may be formed from the bulk substrate by an epitaxial lateral overgrowth (ELOG) method.

In addition, at least one of polystyrene (PS) balls and quantum dots (QDs) may be further included in the empty space.

In addition, the size of the quantum dots may be formed in the range of about 5 ÅA ~ 10nm.

In addition, the size of the polystyrene particles may be formed in the range of about 100nm ~ 1.5㎛.

In addition, the light emitting structure may include an n-type layer, an active layer, and a p-type layer.

In addition, the light emitting structure may output deep ultraviolet (DUV) having a wavelength in the range of 100-280 nm.

Aspects of the present invention are only some of the preferred embodiments of the present invention, and various embodiments in which the technical features of the present invention are reflected are detailed descriptions of the present invention that will be described below by those of ordinary skill in the art can be derived and understood based on

The effect on the device according to the present invention will be described as follows.

The present invention can provide a high-quality short-wavelength ultraviolet light emitting diode (DUV-LED) using a bulk substrate of aluminum nitride (AlN).

According to the present invention, low current and reliability characteristics of a light emitting diode (LED) may be improved through a void formed between a substrate and a buffer layer, and dislocation density may be lowered.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the following description.

The accompanying drawings are provided to help understanding of the present invention, and provide embodiments of the present invention together with detailed description. However, the technical features of the present invention are not limited to specific drawings, and features disclosed in each drawing may be combined with each other to form a new embodiment.
1 illustrates a short-wavelength ultraviolet light emitting diode (DUV-LED) according to an embodiment of the present invention.
Fig. 2 explains the empty space shown in Fig. 1;
3 illustrates a short-wavelength ultraviolet light emitting diode (DUV-LED) according to another embodiment of the present invention.

Hereinafter, an apparatus and various methods to which embodiments of the present invention are applied will be described in more detail with reference to the drawings.

In the description of the embodiment, in the case where it is described as being formed on "up (above) or under (below)" of each component, the upper (upper) or lower (lower) means that the two components are in direct contact with each other or One or more other components are all formed by being disposed between two components. In addition, when expressed as “upper (upper) or lower (lower)”, a meaning of not only an upper direction but also a lower direction based on one component may be included.

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.

1 illustrates a short-wavelength ultraviolet light emitting diode (DUV-LED) according to an embodiment of the present invention.

As shown, the short-wavelength ultraviolet light emitting diode (DUV-LED) includes a substrate 110 , a buffer layer 115 formed on the substrate, and a light emitting structure 120 .

Typically, a substrate used for a light emitting diode may be formed of a material suitable for semiconductor material growth, a carrier wafer. It may be formed of a material having excellent thermal conductivity, and may be a conductive substrate or an insulating substrate. For example, the substrate is sapphire (Al ₂ O ₃ ), SiC, Si, GaAs, GaN, ZnO, GaP, InP, Ge, and Ga ₂ 0 ₃ At least one of them can be used. However, in the short-wavelength ultraviolet light emitting diode according to an embodiment of the present invention, a bulk substrate made of aluminum nitride (AlN) is used.

The short-wavelength ultraviolet light emitting diode outputs deep ultraviolet (DUV). The wavelength range of ultraviolet (UV) has a wide range of wavelengths ranging from 400 to 10 nm, and it is characterized by strong chemical action. For example, short-wavelength ultraviolet (DUV) output from the light emitting structure 120 may have a wavelength in the range of about 100-280 nm, and may be understood as UV-C (Ultraviolet C) or ultraviolet (germicidal) having sterilizing power. Ultraviolet light emitting diodes can be realized because nitride semiconductors are wide bandgap semiconductors, and nitride materials and epi-growth are important technologies in short-wavelength ultraviolet light emitting diodes.

The short-wavelength ultraviolet light emitting diode according to an embodiment of the present invention may use a wafer made of aluminum nitride (AlN). In general, aluminum nitride (AlN) is obtained by sintering high-purity alumina nitride powder at a high temperature, and may have a low coefficient of thermal expansion (about 1.5x10 ^-6 m) and high thermal conductivity (about 150W/mk). In addition, aluminum nitride (AlN) has strong properties against thermal shock and corrosion resistance against fluorine gas. On the surface of the wafer made of such aluminum nitride (AlN), an aluminum polarization (Al-polar) or nitrogen polarization (N-polar) material may be epitaxially grown. When a wafer made of aluminum nitride (AlN) is used, the ultraviolet light emitting diode can have the same function as killing bacteria with radiation therapy, so it can be applied to various sterilization systems including air purifiers and water purifiers.

In order to form the empty space 130 in the substrate 110 , a trench is first formed. The etching process for forming the trench may be performed by forming a hard mask pattern on the substrate 110 , then etching the substrate 110 using a dry etching method and removing the remaining hard mask pattern. For example, physical and chemical techniques among dry etching methods may be used to etch the substrate 110 .

Thereafter, a buffer layer 115 is formed on the substrate 110 in which the trench is formed by using an epitaxial growth method. At this time, an empty space 130 is created by connecting the upper portions of the substrates 110 separated from each other due to the trenches by using the horizontal epitaxial growth method (ELOG). In this case, since the empty space 130 is formed by etching the substrate 110 , it may be located below the upper surface of the substrate 110 . The empty space 130 formed in the substrate 110 induces diffuse reflection of light on the surface of the substrate to improve the light extraction efficiency of the light emitting structure. In addition, the empty space 130 may relieve strain, thereby suppressing the generation of hillocks.

The buffer layer 115 formed on the substrate 110 may be made of aluminum nitride (AlN), which is the same material as the substrate 110 . In addition, according to the embodiment, in order to alleviate the lattice mismatch and difference in the coefficient of thermal expansion of the material between the substrate 110 and the conductive semiconductor layer, the material of the buffer layer 115 is a III-V compound semiconductor, for example, GaN, It may be formed of at least one of InN, InGaN, AlGaN, InAlGaN, and AlInN.

In addition, growing aluminum nitride (AlN) or aluminum gallium nitride (AlGaN), which has a problem that Internal Quantum Efficiency (IQE) is more sensitive to Threading Dislocation Density (TDD) than indium gallium nitride (InGaN) However, the empty space 130 formed between the substrate 110 and the buffer layer 115 may prevent the threading dislocation 134 from proceeding from the bottom of the substrate 110 to the top. In addition, when the buffer layer 115 is formed by using the horizontal epitaxial growth method (ELOG), the dislocation bending phenomenon (Dislocation Bending, 132)-empty space 130 proceeds from the lower part of the substrate 110 to the upper direction. Bending the threading dislocation in the horizontal direction occurs. Accordingly, the dislocation density of the short-wavelength ultraviolet light emitting diode using the aluminum nitride (AlN) substrate can be reduced.

An undoped semiconductor layer (not shown) may be formed on the buffer layer 115 , but is not limited thereto.

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 may be formed on the substrate 110 or the buffer layer 115 .

The light emitting structure 120 may be formed by, for example, metal organic chemical vapor deposition (MOCVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), or molecular beam growth. It may be formed using a method such as Molecular Beam Epitaxy (MBE) or Hydride Vapor Phase Epitaxy (HVPE), but is not limited thereto.

The first conductivity type semiconductor layer 122 may be implemented with a group III-V group or group II-VI compound semiconductor, and may be doped with a first conductivity type dopant. The first conductivity type semiconductor layer 122 has _{a composition formula of Al x} In _y Ga _(1-xy) N (0≤≤x≤≤1, 0≤≤y≤≤1, 0≤≤x+y≤≤1) It may be formed of any one or more of a semiconductor material having AlGaN, GaN, InAlGaN, AlGaAs, GaP, GaAs, GaAsP, and AlGaInP.

When the first conductivity-type semiconductor layer 122 is an n-type semiconductor layer, the first conductivity-type dopant may include an n-type dopant such as Si, Ge, Sn, Se, Te, or the like. The first conductivity type semiconductor layer 122 may be formed as a single layer or a multilayer.

The first conductivity-type semiconductor layer 122 is a silane gas (SiH) containing n-type impurities such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N _{2 ), and silicon (Si) in a chamber. 4} ) can be formed by injection.

A current diffusion layer (not shown) may be formed on the first conductivity-type semiconductor layer 122 of the light emitting structure. The current diffusion layer may be an undoped GaN layer, but is not limited thereto. In addition, an electron injection layer (not shown) may be formed on the current diffusion layer, and the electron injection layer may be a first conductivity type gallium nitride layer. Also, a strain control layer (not shown) may be formed on the electron injection layer. _{For example, a strain control layer formed of In y} Al _x Ga _(1-xy) N (0≤x≤1, 0≤y≤1)/GaN or the like may be formed on the electron injection layer. The strain control layer may relieve stress caused by a lattice mismatch between the first conductivity type semiconductor layer 122 and the active layer 124 .

An active layer 124 may be formed on the first conductivity-type semiconductor layer 122 or the strain control layer.

The active layer 124 may be disposed between the first conductivity-type semiconductor layer 122 and the second conductivity-type semiconductor layer 126 .

The active layer 124 is a layer in which electrons and holes meet each other to emit light having energy determined by an energy band unique to the active layer (light emitting layer) material. When the first conductivity-type semiconductor layer 122 is an n-type semiconductor layer and the second conductivity-type semiconductor layer 126 is a p-type semiconductor layer, electrons are injected from the first conductivity-type semiconductor layer 122 and the second Holes may be injected from the conductive semiconductor layer 126 .

The active layer 124 may include any one of a double-hetero structure, a multi-well structure, a single quantum well structure, a multi-quantum well (MQW) structure, a quantum dot structure, or a quantum wire structure.

The active layer 124 uses a III-V group element compound semiconductor material to form a well layer and a barrier layer, for example, AlGaN/AlGaN, InGaN/GaN, InGaN/InGaN, AlGaN/GaN, InAlGaN/GaN, GaAs (InGaAs). It may be formed in any one or more pair structure of /AlGaAs, GaP(InGaP)/AlGaP, but is not limited thereto. The well layer may be formed of a material having an energy band gap smaller than that of the barrier layer.

A conductive cladding layer (not shown) may be formed on and/or below the active layer 124 . The conductive cladding layer may be formed of a barrier layer of the active layer or a semiconductor having a bandgap wider 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.

The second conductivity type semiconductor layer 126 may be formed of a semiconductor compound. The second conductivity type semiconductor layer 126 may be implemented with a group III-V or group II-VI compound semiconductor, and may be doped with a second conductivity type dopant.

For example, the second conductive type semiconductor layer 126 may be _{In x Al y Ga 1 -x- y} N (0≤≤x≤≤1, 0≤≤y≤≤1, 0≤≤x + y≤≤ A semiconductor material having the composition formula of 1), AlGaN, GaN, AlInN, AlGaAs, GaP, GaAs, GaAsP, may be formed of any one or more of AlGaInP, the second conductivity type semiconductor layer 126 is Al _x Ga _{(1-x )} may consist of N.

When the second conductivity-type semiconductor layer 126 is a p-type semiconductor layer, the second conductivity-type dopant may be a p-type dopant such as Mg, Zn, Ca, Sr, or Ba.

The second conductivity type semiconductor layer 126 may be formed as a single layer or a multilayer, and the second conductivity type semiconductor layer 126 is provided in a chamber with trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N _{2 ). ) and bisetyl cyclopentadienyl magnesium (EtCp 2} Mg) {Mg(C ₂ H ₅ C ₅ H ₄ ) ₂ } containing p-type impurities such as magnesium (Mg) are implanted to form a p-type GaN layer may be, but is not limited thereto.

When the second conductivity type semiconductor layer 126 is a p-type semiconductor layer, a semiconductor having a polarity opposite to that of the second conductivity type, for example, an n-type semiconductor layer (not shown) is formed on the second conductivity type semiconductor layer 126 . can be formed Accordingly, the light emitting structure 120 may be implemented as any one of an n-p junction structure, a p-n junction structure, an n-p-n junction structure, and a p-n-p junction structure.

An electron blocking layer (not shown) may be disposed adjacent to the active layer 124 between the active layer 124 and the second conductivity-type semiconductor layer 126 . The electron blocking layer may include AlGaN, and may be doped with a second conductivity type dopant. In addition, the electron blocking layer _{may be formed of a superlattice of Al z} Ga _(1-z) N/GaN (0≤z≤1), but is not limited thereto. The electron blocking layer 125 may effectively block electrons that overflow by implanting p-type ions, and may increase hole injection efficiency.

FIG. 2 illustrates the empty space 130 and the buffer layer 115 shown in FIG. 1 .

As shown, the empty space 130 is formed by covering the buffer layer 115 in a trench located on the substrate 110 . In this case, the width W1 of the empty space 130 may be in the range of 0.3 μm to 2 μm. If the width W1 exceeds 2 μm, there is a possibility that the buffer layer 115 formed through the horizontal epitaxial growth method (ELOG) does not merge, and when the width W1 is smaller than 0.3 μm, the buffer layer 115 During the formation of , the trench may be filled so that the empty space 130 may not be formed.

The height H1 of the empty space 130 may be formed in a range of 0.3 μm to 4 μm. If the height H1 is smaller than 0.3 μm, the trench may be filled in the process of forming the buffer layer 115 so that the empty space 130 may disappear, and ?chen? Making the height H1 larger than 4 μm has difficulties and limitations in the process of actually forming a pattern.

The interval W2 between the empty spaces 130 may be in the range of 0.3 μm to 5 μm. For example, the ratio of the pattern size to the spacing of the trenches formed on the substrate 110 may be 1:1 to 1:2.

The buffer layer 115 covering the empty space 130 may be formed to a thickness T1 of 0.2 μm to 10 μm. If the thickness T1 of the buffer layer 115 exceeds 10 μm, the process time is prolonged and economical efficiency is deteriorated. On the other hand, when the thickness T1 of the buffer layer 115 is less than 0.2 μm, the possibility that the buffer layers 115 formed through the horizontal epitaxial growth method (ELOG) are not combined increases.

3 illustrates a short-wavelength ultraviolet light emitting diode (DUV-LED) according to another embodiment of the present invention.

As shown, the short-wavelength ultraviolet light emitting diode includes a substrate 210 and a buffer layer 215 . A light emitting structure as described with reference to FIG. 1 may be positioned on the buffer layer 215 .

An empty space 230 is positioned between the substrate 210 and the buffer layer 215 . The empty space 230 may prevent a threading dislocation 234 from proceeding from the bottom of the substrate 210 to the top. In addition, the use of the horizontal epitaxial growth method (ELOG) when forming the buffer layer 215 is a dislocation bending phenomenon (Dislocation Bending, 232) that proceeds in an upward direction from the bottom of the substrate 210 between the empty space 230. Bending the threading dislocation in the horizontal direction occurs. Accordingly, the dislocation density of the short-wavelength ultraviolet light emitting diode is lowered.

The short-wavelength ultraviolet light emitting diode includes small particles 236 in the empty space 230 . Here, the small particles 236 include at least one of polystyrene (PS) balls and quantum dots (QDs).

In general, quantum dots (QDs) are nanometer (10 ^-9 m) sized crystals. If the radius of the nanocrystal is smaller than the exciton Bohr radius, electrons and holes are restricted from motion in all directions, and quantum effects are applied in all directions. It is felt and the energy level of a substance has discontinuous values in all directions. In particular, quantum dots show optical properties different from those of the same bulk material, and properties can be controlled according to their size. In general, as the size of a quantum dot decreases, the band gap widens and purple appears, and as the size increases, the band gap approaches the bulk (crystal momentum) state and becomes red. In the case of the quantum dots (QD) constituting the small particles 236 of FIG. 3 , they may be formed in a size of about 5 Å to 10 nm.

When the small particles 236 are formed of polystyrene particles (PS balls), the size of the polystyrene particles may be in the range of 100 nm to 1.5 μm. When an electron beam is irradiated to polystyrene (PS) particles, it can emit strong fluorescence of various colors depending on the amount of electron beam irradiation. In addition, when the energy storage property of the polystyrene particles is used, the energy efficiency of the light emitting diode may be improved.

Features, structures, effects, etc. described in the above embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified for other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiment has been described above, it is merely an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains are exemplified above in a range that does not depart from the essential characteristics of the present embodiment. It can be seen that various modifications and applications that have not been made 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.

110: substrate
115: buffer layer
120: light emitting structure
130: empty space
236: small particle

Claims (12)

a bulk substrate made of aluminum nitride (AlN);
a buffer layer formed by growing the aluminum nitride on the bulk substrate; and
It includes a light emitting structure formed on the buffer layer,
an empty space between the bulk substrate and the buffer layer; and
A light emitting diode further comprising at least one of polystyrene (PS) balls and quantum dots (QDs) in the empty space. According to claim 1,
The empty space is a light emitting diode, characterized in that located below the upper surface of the bulk substrate. According to claim 1,
The empty space is a light emitting diode, characterized in that in a trench made by etching the bulk substrate, an upper portion of the trench is covered with the buffer layer. According to claim 1,
The width of the empty space is in the range of 0.3 µm to 2 µm, the height is in the range of 0.3 µm to 4 µm, and the interval between adjacent empty spaces is in the range of 0.3 µm to 5 µm. 5. The method of claim 4,
The buffer layer is a light emitting diode formed to a thickness of 0.2 μm to 10 μm. According to claim 1,
The lower portion of the empty space is a light emitting diode, characterized in that the valley (valley) shape. According to claim 1,
The buffer layer is a light emitting diode, characterized in that formed by a horizontal epitaxial growth (Epitaxial Lateral Overgrowth, ELOG) method from the bulk substrate. delete According to claim 1,
The size of the quantum dots is a light emitting diode formed in the range of 5 Å ~ 10nm. According to claim 1,
The size of the polystyrene particles is a light emitting diode formed in the range of 100nm ~ 1.5㎛. According to claim 1,
The light emitting structure is a light emitting diode including an n-type layer, an active layer, and a p-type layer. According to claim 1,
The light emitting structure is a light emitting diode that outputs deep ultraviolet (DUV) having a wavelength in the range of 100-280 nm.

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