CN216213515U - LED light-emitting device based on flip-chip structure - Google Patents

Abstract

The utility model discloses an LED light-emitting device based on a flip structure, which is characterized by comprising a distributed Bragg reflector DBR, an Indium Tin Oxide (ITO) buffer layer, a P-pole grating layer, a multi-quantum well MQW layer, an N-pole grating layer and a Sapphire substrate Sapphire layer which are sequentially overlapped from bottom to topA group of SiO with cone shape distributed in uniform array shape is arranged on the upper surface of the Sapphire substrate Sapphire layer facing outwards₂And the cone is provided with an N electrode N-nad and a P electrode P-nad at the same positions of the outer edges of the N-pole grating layer and the P-pole grating layer respectively. The device can avoid the metal shielding effect, optical parameters are easier to match, the LED luminous efficiency can be improved, and the heat radiation performance is good.

Description

A LED light-emitting device based on flip-chip structure

technical field

The utility model relates to the technical field of optical communication, in particular to solve the problems of light extraction efficiency and heat dissipation by using a flip-chip LED structure, in particular to an LED light-emitting device based on the flip-chip structure.

Background technique

LED (light emitting diode, LED for short) is a semiconductor solid-state light-emitting device that has risen rapidly in recent years. Compared with traditional incandescent lamps and fluorescent lamps, it has the advantages of small size, good vibration resistance, compact structure, less heat generation, and high brightness. , luminous response speed, long life, low operating voltage and other advantages. However, in the process of use, it is found that there are still some problems affecting the application of LEDs, the most important of which is the problem of low light extraction efficiency. The main reason for the low light extraction efficiency of LEDs is that the refractive index difference between the GaN material in the LED and the surrounding air is too large. When the light is incident from the optically dense dielectric material GaN to the air, total reflection will occur. In order to improve the total reflection between the GaN layer and the air. For the critical angle, many researchers have proposed different methods, such as: surface roughening technology, subwavelength grating technology, LED flip-chip technology, bionic technology for making moth-eye structure, photonic crystal technology, etc. Among them, inverted pyramid LED can solve the problem of critical angle. The total emission caused by the difference in refractive index between the substrate and the air increases the light extraction efficiency by 1.22 times. The flip-chip LED structure can solve the problem of low light emitting efficiency of the chip and the problem of poor heat dissipation. Compared with the front-mounted structure, the light-emitting characteristics are improved by backside light emission without metal shielding, and the heat dissipation of direct metal electrodes instead of the sapphire substrate, thereby improving its heat dissipation and reliability.

At present, the mass-produced GaN-based LEDs on the market are mainly positive and vertical structures. The LED flip-chip technology changes the sapphire substrate into a light-emitting surface, which avoids the absorption of photons by the electrode layer on the P-GaN layer. The flip-chip LED structure improves its light-emitting characteristics through backside emission without metal shielding. Compared with the current mass-produced front-mounted structure on the market, it can solve the problem of low light-emitting efficiency and poor heat dissipation; Not a sapphire substrate, which improves its heat dissipation and reliability.

For the traditional front-mounted structure, in order to improve the current uniformity of the P-GaN layer, metal electrodes are evaporated on the P-GaN to improve the current expansion. Since the metal electrodes are made of opaque materials, it will cause a metal shielding effect, which will cause the chip to emit light. The efficiency is too low. In addition, the thermal conductivity of the sapphire material is very low, so it is not conducive to the heat dissipation of the chip. The lateral current expansion effect inside the front-mounted structure LED is easy to cause current crowding; although the vertical structure can solve the problem of the same side of the metal electrode, the preparation process is complicated and the product yield is low.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an LED light-emitting device based on a flip-chip structure in view of the deficiencies of the prior art. The device can avoid the metal shielding effect, the optical parameters are easier to match, the LED luminous efficiency can be improved, and the heat dissipation performance is good.

The technical scheme that realizes the purpose of the present utility model is:

An LED light-emitting device based on a flip-chip structure includes a distributed Bragg reflector DBR (Distributed Bragg Reflection, DBR for short), an indium tin oxide ITO buffer layer, a P-pole grating layer, and a multiple quantum well that are sequentially stacked from bottom to top. The MQW layer, the N-pole grating layer and the Sapphire layer of the sapphire substrate are provided with a group of conical SiO ₂ cones distributed in a uniform array on the upper surface of the Sapphire layer of the sapphire substrate facing outward. An N electrode N-nad and a P electrode P-nad are respectively provided at the same positions on the outer edges of the grating layer and the P-pole grating layer.

方法合成单分散SiO₂纳米颗粒，采用将氨、TEOS和水的浓度分别设定为0.1、17.0和0.2mol/L，将SiO₂粒子的大小控制在60nm，通过SEM(Scanning Electron Microscope)测量得到的SiO₂颗粒，直径为60nm的SiO₂纳米球在蓝宝石表面进旋压铸造，然后在160℃退火10分钟，将SiO₂纳米球嵌入SiO₂层，将样品放入压力0.667Pa和Cl₂(7.5sccm)和BCl₃(30sccm)的混合物的多重ICP(STS)设备下进行蚀刻干，蓝宝石的蚀刻速率为100nm/min，从本质上讲，球形SiO₂作为掩模通过ICP刻蚀牺牲其厚度在蓝宝石中产生不同的蚀刻深度，从而制备成圆锥型结构，从而形成了圆锥型蓝宝石衬底。The conical SiO ₂ cones distributed in a uniform array form a 6×6 array, wherein the spherical diameter of the SiO ₂ cone is 60nm, and the SiO ₂ cone passes through the ordered SiO ₂ nanospheres with ICP etching technology To texture the sapphire surface, in this method, spinning _SiO2 nanospheres are used as a sacrificial dry etching mask to prepare a sapphire substrate with a conical surface: First, the sapphire surface is covered with a 50 nm-thick layer of polystyrene PS (Polystyrene) To immobilize SiO _nanospheres , the surface was then hydrophilized by exposing it to UV radiation, in the presence of water and ammonia, by hydrolysis of the tetraethyl orthosilicate TEOS (Tetraethyl orthosilicate) in an alcoholic medium, according to

Methods Monodisperse SiO nanoparticles _were synthesized by setting the concentrations of ammonia, TEOS and water to 0.1, 17.0 and 0.2 mol/L, respectively, and controlling the size of SiO particles to 60 nm, which _were measured by SEM (Scanning Electron Microscope). The _SiO2 particles, _SiO2 nanospheres with a diameter of 60 nm were spin-cast on the sapphire surface, and then annealed at 160 °C for 10 min, the _SiO2 nanospheres were embedded in the _SiO2 layer, and the samples were placed under a pressure of _0.667Pa and Cl2 ( 7.5sccm) and _BCl3 (30sccm) were etched under multiple ICP (STS) equipment, the etch rate of sapphire was 100nm/min, essentially, spherical _SiO2 was used as a mask to sacrifice its thickness by ICP etching Different etching depths are produced in the sapphire to prepare a conical structure, thereby forming a conical sapphire substrate.

The thickness of the Sapphire layer of the sapphire substrate is 100-600 nm.

Preferably, the thickness of the Sapphire layer of the sapphire substrate is 130 nm. The thickness of the sapphire substrate layer has an influence on the light extraction efficiency of the surface grating flip-chip LED. The influence of the sapphire substrate thickness on the light extraction efficiency of the surface grating flip-chip LED is related to the thickness of the N-GaN layer. The influence on the light extraction efficiency of the surface grating is similar, all because the thickness of the sapphire substrate has an influence on the F-P cavity standing wave, the coupling strength of the grating and the guided mode. The coupling effect of the modes is strong, so more guided modes are guided into the light extraction angle of the LED, so that more energy is extracted.

The N-pole grating layer is an N-GaN layer, and the thickness of the N-GaN layer is 100 nm. When the thickness of the Sapphire layer of the sapphire substrate varies uniformly at intervals of 10 nm between 100 and 600 nm, the surface grating flip-chip LED light is extracted. The efficiency oscillates periodically, but the oscillation peak decreases as the thickness increases, and the light extraction efficiency decreases from 30.98% when the thickness is equal to 100 nm to 25.86% when the thickness is equal to 600 nm. Only when the thickness of the N-GaN layer is 100 nm, The coupling strength between the grating and the guided mode in the LED is the highest.

The P-pole grating layer is a P-GaN layer, and the thickness of the P-GaN layer is 100-300 nm.

Preferably, the thickness of the P-GaN layer is 220 nm. When the thickness of the P-GaN layer is uniformly changed at intervals of 10 nm between 100 and 300 nm, the light extraction efficiency of the flip-chip LED and the surface grating flip-chip LED changes periodically. When the P-GaN layer is 220 nm, the light extraction efficiency of both the flip-chip LED and the surface grating LED reaches the maximum.

Both the N-pole grating layer and the P-pole grating layer use metal grating structures, which can not only effectively improve the internal quantum efficiency of LEDs, but also enhance the external quantum efficiency. Gallium Nitride (GaN) is an inorganic substance, which is composed of nitrogen and gallium. The compound, a direct bandgap semiconductor, can be used in high-power, high-speed optoelectronic components, and the LED model uses GaN gratings.

The N-electrode N-nad is made of vapor-deposited metal into an N-type electrode, and the material is arsenic, antimony or phosphorus.

The P electrode P-nad is made of vapor-deposited metal into a P-type electrode, and the material is boron, indium or gallium, and is used as the LED injection current terminal.

The distributed Bragg reflector (DBR) is a special all-dielectric reflective film, which is usually composed of two kinds of high and low refractive index compounds alternately stacked to produce periodic modulation of the refractive index in one dimension of space, resulting in strong interference. phenomenon, and achieve selective light reflection within a certain wavelength range, oxide films with high refractive index include ZnO, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , ZrO ₂ , SiO ₂ , HfO ₂ , MgO, etc., SiO ₂ It is the lowest refractive index material with the best film properties, and SiO ₂ is not easy to decompose, so it is the best low refractive index film for plating. The refractive index of TiO ₂ is high, the refractive index n≈2.5, and the mechanical strength is also high. , but it is transparent in all wavelengths, and combined with SiO ₂ can reduce the absorption and scattering of light, it is a relatively good high and low refractive index material, DBR is made by evaporation method: the first layer is SiO ₂ , and the last layer is also It is SiO ₂ , with TiO ₂ and SiO ₂ intersecting in the middle, so the structure of substrate SiO ₂ -TiO ₂ and SiO ₂ -SiO ₂ is formed. The wavelength of the reflection area of this structure increases with the ratio of high and low refractive index materials. In addition, the reflectivity increases with the increase of the number of TiO ₂ and SiO ₂ cycles, but with the increase of the film layer to a certain extent, the more serious the ripple oscillation on both sides of the high-reflection area, the half-width of the high-reflection area does not increase. If it is large, the reflectivity will not increase. In order to obtain high reflectivity and high bandwidth, and take into account the chip voltage and heat dissipation, the chip preparation of this technical scheme selects 18 cycles of SiO ₂ and TiO ₂ alternately grown DBR as the reflector.

Indium tin oxide ITO layer (Indium Tin Oxides, ITO for short) is a P-type semiconductor material with good conductivity and high light transmittance. The transmittance in the visible light band can reach more than 90% and has good stability. , Using ITO electrodes to replace the P-type electrode chips in traditional LEDs can increase the light extraction rate of the luminous body by 30%-40%, and add an ITO buffer layer between the gratings to further improve the LED luminous intensity.

The quantum well in the multi-quantum well MQWS layer is a sandwich structure with a thin layer of semiconductor film in the middle. The structure of the semiconductor film is composed of a composite form of AlGaAs-GaAs-AlGaAs, and the outer side is two isolation layers, namely two N-type GaAs, The photons generated by the spontaneous emission of the LED quantum well QW pass through the GaN layer, and through the effective coupling of the SPPs-QW, the light extraction rate on the surface of the GaN grating is improved.

The device can avoid the metal shielding effect, the optical parameters are easier to match, the LED luminous efficiency can be improved, and the heat dissipation performance is good.

Description of drawings

FIG. 1 is a schematic diagram of the mechanism of the embodiment.

In the figure, 1. Cone 2. Sapphire substrate layer 3. N-pole grating layer 4. N-electrode N-nad 5. Multiple quantum well layer 6. P-electrode P-nad 7. P-pole grating layer 8. Indium tin oxide buffer Layer 9. Distributed Bragg Mirrors.

Detailed ways

The content of the present utility model will be further elaborated below in conjunction with the accompanying drawings and embodiments, but it is not intended to limit the present utility model.

Example:

1, an LED light-emitting device based on a flip-chip structure includes a distributed Bragg reflector DBR9, an indium tin oxide ITO buffer layer 8, a p-pole grating layer 7, and a multiple quantum well MQW layer sequentially stacked from bottom to top. 5. The N-pole grating layer 3 and the sapphire substrate Sapphire layer 2 are provided with a group of conical SiO ₂ cones distributed in a uniform array on the upper surface of the sapphire substrate Sapphire layer 2 facing outward. The N-pole grating layer 3 and the P-pole grating layer 7 are respectively provided with an N-electrode N-nad4 and a P-electrode P-nad6 at the same positions on the outer edges of the N-pole grating layer 3 and the P-pole grating layer 7 .

方法合成单分散SiO₂纳米颗粒，采用将氨、TEOS和水的浓度分别设定为0.1、17.0和0.2mol/L，将SiO₂粒子的大小控制在60nm，通过SEM(Scanning Electron Microscope)测量得到的SiO₂颗粒，直径为60nm的SiO₂纳米球在蓝宝石表面进旋压铸造，然后在160℃退火10分钟，将SiO₂纳米球嵌入SiO₂层，将样品放入压力0.667Pa和Cl₂(7.5sccm)和BCl₃(30sccm)的混合物的多重ICP(STS)设备下进行蚀刻干，蓝宝石的蚀刻速率为100nm/min，从本质上讲，球形SiO₂作为掩模通过ICP刻蚀牺牲其厚度在蓝宝石中产生不同的蚀刻深度，从而制备成圆锥型结构，从而形成了圆锥型蓝宝石衬底。In this example, the conical _SiO2 cones distributed in a uniform array form a 6 × 6 array, in which the spherical diameter of the _SiO2 cones is 60 nm, and the _SiO2 cones are etched by the ordered _SiO2 nanospheres with ICP etching technique to texture the sapphire surface. In this method, spinning _SiO2 nanospheres are used as sacrificial dry etching masks to prepare a sapphire substrate with a conical surface: first, the sapphire is covered with a 50 nm thick layer of polystyrene (PS) surface to immobilize SiO nanospheres, which _were then hydrophilized by exposing them to UV radiation, in the presence of water and ammonia, by hydrolysis of the tetraethyl orthosilicate TEOS (Tetraethyl orthosilicate) in an alcoholic medium, according to

Methods Monodisperse SiO nanoparticles _were synthesized by setting the concentrations of ammonia, TEOS and water to 0.1, 17.0 and 0.2 mol/L, respectively, and controlling the size of SiO particles to 60 nm, which _were measured by SEM (Scanning Electron Microscope). The _SiO2 particles, _SiO2 nanospheres with a diameter of 60 nm were spin-cast on the sapphire surface, and then annealed at 160 °C for 10 min, the _SiO2 nanospheres were embedded in the _SiO2 layer, and the samples were placed under a pressure of _0.667Pa and Cl2 ( 7.5sccm) and _BCl3 (30sccm) were etched under multiple ICP (STS) equipment, the etch rate of sapphire was 100nm/min, essentially, spherical _SiO2 was used as a mask to sacrifice its thickness by ICP etching Different etching depths are produced in the sapphire to prepare a conical structure, thereby forming a conical sapphire substrate.

The thickness of the Sapphire layer 2 of the sapphire substrate is 100-600 nm.

In this example, the thickness of the Sapphire layer 2 of the sapphire substrate is 130 nm. The thickness of the sapphire substrate layer 2 has an influence on the light extraction efficiency of the surface grating flip-chip LED. The influence of the sapphire substrate thickness on the light extraction efficiency of the surface grating flip-chip LED is related to the N- The effect of the thickness of the GaN layer on the light extraction efficiency of the surface grating is similar, all because the thickness of the sapphire substrate has an effect on the F-P cavity standing wave, the coupling strength of the grating and the guided mode. When the thickness of the sapphire substrate is 130 nm, the The coupling effect of the guided modes in the LED is strong, so more guided modes are guided into the light extraction angle of the LED, so that more energy is extracted.

In this example, the N-pole grating layer 3 is an N-GaN layer, and the thickness of the N-GaN layer is 100 nm. When the thickness of the Sapphire layer 2 on the sapphire substrate varies uniformly between 100 and 600 nm at intervals of 10 nm, the surface grating is flipped. The light extraction efficiency of LEDs oscillates periodically, but the oscillation peak decreases with the increase of thickness. The light extraction efficiency drops from 30.98% when the thickness is equal to 100nm to 25.86% when the thickness is equal to 600nm. Only the thickness of N-GaN layer 3 When it is 100 nm, the coupling strength between the grating and the guided mode in the LED is the largest.

The P-pole grating layer 7 is a P-GaN layer, and the thickness of the P-GaN layer is 100-300 nm.

In this example, the thickness of the P-GaN layer is 220 nm. When the thickness of the P-GaN layer 7 varies uniformly between 100 and 300 nm at intervals of 10 nm, the light extraction efficiencies of the flip-chip LED and the surface grating flip-chip LED are both periodic. Change, when the P-GaN layer 7 is 220 nm, the light extraction efficiency of the flip-chip LED and the surface grating LED both reach the maximum.

Both the N-pole grating layer and the P-pole grating layer use metal grating structures, which can not only effectively improve the internal quantum efficiency of LEDs, but also enhance the external quantum efficiency. Gallium Nitride (GaN) is an inorganic substance, which is composed of nitrogen and gallium. The compound, a direct bandgap semiconductor, can be used in high-power, high-speed optoelectronic components, and the LED model uses GaN gratings.

The N-electrode N-nad4 is made of vapor-deposited metal into an N-type electrode, and the material is arsenic, antimony or phosphorus.

The P electrode P-nad6 is made of vapor-deposited metal into a P-type electrode, and the material is boron, indium or gallium, and is used as the LED injection current terminal.

The distributed Bragg reflector (DBR) is a special all-dielectric reflective film, which is usually composed of two kinds of high and low refractive index compounds alternately stacked to produce periodic modulation of the refractive index in one dimension of space, resulting in strong interference. phenomenon, and achieve selective light reflection within a certain wavelength range, oxide films with high refractive index include ZnO, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , ZrO ₂ , SiO ₂ , HfO ₂ , MgO, etc., SiO ₂ It is the lowest refractive index material with the best film properties, the absorption and scattering are very small, and SiO ₂ is not easy to decompose, so it is the best low-refractive index film for plating. The refractive index of TiO ₂ is high and the refractive index n≈ 2.5, the mechanical strength is also high, but it is transparent in all wavelengths, and combined with SiO ₂ can reduce the absorption and scattering of light, it is a relatively good high and low refractive index material, DBR is made by evaporation method: the first layer It is SiO ₂ , the last layer is also SiO ₂ , and there are many pairs of TiO ₂ and SiO 2 in the middle, so the structure of the substrate SiO ₂ - many pairs of _{TiO 2} and SiO ₂ -SiO ₂ is formed, and the reflective area of this structure is formed. The wave width increases with the ratio of high and low refractive index materials. In addition, the reflectivity increases with the number of cycles of TiO ₂ and SiO ₂ . However, with the increase of the film layer to a certain extent, the ripple oscillation on both sides of the high-reflection area becomes larger. Seriously, the half width of the high reflection area will not increase, and the reflectivity will not increase. In order to obtain high reflectivity and high bandwidth, and take into account the chip voltage and heat dissipation, 18 cycles of SiO ₂ and TiO are used for chip preparation in this example. ₂ DBRs that grow alternately with each other are mirrors.

The indium tin oxide ITO layer 8 (Indium Tin Oxides, ITO for short) is a P-type semiconductor material with good conductivity and high light transmittance. The transmittance in the visible light band can reach more than 90%, with good stability. The use of ITO electrodes to replace the P-type electrode chips in traditional LEDs can increase the light extraction rate of the luminous body by 30%-40%, and add an ITO buffer layer between the gratings to further improve the LED luminous intensity.

The quantum well in the multi-quantum well MQWS layer 5 is a sandwich structure, with a thin layer of semiconductor film in the middle, the structure of the semiconductor film is composed of a composite form of AlGaAs-GaAs-AlGaAs, and two isolation layers on the outside are two N-type GaAs . The photons generated by the spontaneous emission of the LED quantum well QW pass through the GaN layer, and through the effective coupling of the SPPs-QW, the light extraction rate on the surface of the GaN grating is improved.

Claims (9)

1. The LED light-emitting device based on the flip structure is characterized by comprising a distributed Bragg reflector DBR, an Indium Tin Oxide (ITO) buffer layer, a P-pole grating layer, a multi-quantum well (MQW) layer, an N-pole grating layer and a Sapphire substrate Sapphire layer which are sequentially overlapped from bottom to top, wherein a group of SiO which is uniformly distributed in an array shape and is conical is arranged on the outer upper surface of the Sapphire substrate Sapphire layer₂And the cone is provided with an N electrode N-nad and a P electrode P-nad at the same positions of the outer edges of the N-pole grating layer and the P-pole grating layer respectively.

2. The LED lighting device based on the flip-chip structure as claimed in claim 1, wherein the SiO in the form of cone distributed in a uniform array₂The cones are in a 6X 6 array, wherein SiO₂The spherical diameter of the cone is 60 nm.

3. The flip-chip based LED lighting device as claimed in claim 1, wherein the Sapphire substrate Sapphire layer has a thickness of 100-600 nm.

4. The flip-chip structure-based LED light emitting device according to claim 3, wherein the Sapphire substrate Sapphire layer has a thickness of 130 nm.

5. The LED light emitting device based on the flip-chip structure as claimed in claim 1, wherein the N-pole grating layer is an N-GaN layer, and the thickness of the N-GaN layer is 100 nm.

6. The LED light emitting device based on the flip-chip structure as claimed in claim 1, wherein the P-gate layer is a P-GaN layer with a thickness of 100-300 nm.

7. The LED light emitting device based on the flip-chip structure according to claim 5, wherein the thickness of the P-GaN layer is 220 nm.

8. The LED light-emitting device based on the flip-chip structure as claimed in claim 1, wherein the N-nad is made of evaporated metal to form an N-type electrode, and the material is arsenic, antimony or phosphorus.

9. The LED light-emitting device based on the flip-chip structure as claimed in claim 1, wherein the P-nad is made of vapor deposited metal as a P-type electrode, and the material is boron, indium or gallium, which is used as an injection current terminal of the LED.

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