Flip light-emitting diode and preparation method thereof

Abstract

The invention provides a flip light-emitting diode and a preparation method thereof, and belongs to the technical field of photoelectron manufacturing. The light-emitting diode comprises a substrate, a light-emitting core particle and a reflecting layer, wherein the light-emitting core particle and the reflecting layer are respectively positioned on two opposite surfaces of the substrate; the surface of the reflecting layer is provided with a light-transmitting hole exposed out of the substrate, and the orthographic projection of the light-transmitting hole on the surface of the substrate is located in the orthographic projection of the light-emitting core particles on the surface of the substrate. According to the embodiment of the invention, the light-emitting diode can form a circular light-emitting surface, and the light pattern requirement of the vehicle lamp is met.

Description

Technical Field

[0001] The present disclosure relates to the field of optoelectronic manufacturing technology, and in particular to a flip-chip light emitting diode and a preparation method thereof. Background Art

[0002] Light emitting diodes (LEDs) are a highly influential new product in the optoelectronics industry. They have the characteristics of small size, long service life, rich colors, and low energy consumption. They are widely used in lighting, display screens, signal lights, backlight sources, toys and other fields.

[0003] In related technologies, automotive lighting and other terminals also use light-emitting diodes as light sources. These lighting applications have specific requirements for light pattern, and the light emitted by LEDs requires light distribution. Currently, LED chips primarily have square light-emitting surfaces, which hinder light distribution. A circular light-emitting surface, on the other hand, offers a wider and more continuous light-emitting angle coverage, enabling full-angle illumination. Therefore, a circular light-emitting surface facilitates light distribution.

[0004] Because the light-emitting surface of a flip-chip LED is the surface of the sapphire substrate, and the sapphire substrate needs to be cut after the LED is manufactured, it is difficult to form a circular light-emitting surface on the sapphire substrate. The only option is to design the LED's epitaxial layer into a circular pattern, but the light emitted by the epitaxial layer is mixed by the sapphire substrate, resulting in poor light output. Summary of the Invention

[0005] The present disclosure provides a flip-chip light-emitting diode and a method for manufacturing the same, which can form a circular light-emitting surface on the light-emitting diode, thus meeting the light pattern requirements of vehicle lamps. The technical solution is as follows:

[0006] On the one hand, an embodiment of the present disclosure provides a light-emitting diode, which includes a substrate, a light-emitting core and a reflective layer, wherein the light-emitting core and the reflective layer are respectively located on opposite surfaces of the substrate; the surface of the reflective layer has a light-transmitting hole exposing the substrate, and the orthographic projection of the light-transmitting hole on the surface of the substrate is located within the orthographic projection of the light-emitting core on the surface of the substrate.

[0007] In an implementation of the present disclosure, the orthographic projection of the light-transmitting hole on the surface of the substrate is circular.

[0008] In yet another implementation of the present disclosure, the axial cross-section of the light-transmitting hole is trapezoidal in shape, and the end of the light-transmitting hole with a larger size is away from the substrate.

[0009] In yet another implementation of the present disclosure, the angle between the generatrix of the light-transmitting hole and the central axis is 30° to 70°.

[0010] In another embodiment of the present disclosure, the light-transmitting hole includes a first hole segment and a second hole segment coaxially connected, the diameter of the first hole segment is smaller than the diameter of the second hole segment, and the first hole segment is located on a side of the reflective layer close to the substrate.

[0011] In yet another implementation of the present disclosure, the thickness of the reflective layer is 1 μm to 4 μm.

[0012] In yet another implementation of the present disclosure, the reflective layer includes at least one of a metal layer and a distributed Bragg reflector layer.

[0013] In another embodiment of the present disclosure, the distributed Bragg reflector layer includes a plurality of first material layers and a plurality of second material layers alternately stacked, the refractive index of the first material layer is different from the refractive index of the second material layer, the first material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer, and the second material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer.

[0014] On the other hand, an embodiment of the present disclosure also provides a method for preparing a light-emitting diode, the method comprising: preparing a light-emitting core on one surface of a substrate; forming a reflective layer on the other surface of the substrate, the surface of the reflective layer having a light-transmitting hole exposing the substrate, the orthographic projection of the light-transmitting hole on the surface of the substrate being located within the orthographic projection of the light-emitting core on the surface of the substrate.

[0015] In another implementation of the present disclosure, forming a reflective layer on the other surface of the substrate includes: evaporating a distributed Bragg reflector layer on the entire surface of the substrate; etching the distributed Bragg reflector layer to form circular light-transmitting holes, wherein the light-transmitting holes correspond one-to-one to the light-emitting core particles, and the light-transmitting holes are opposite to the corresponding light-emitting core particles.

[0016] The beneficial effects of the technical solutions provided by the embodiments of the present disclosure include at least:

[0017] The light-emitting core of the light-emitting diode provided by the embodiment of the present disclosure is arranged on one surface of the substrate, and a reflective layer is also arranged on the other surface of the substrate, that is, the light-emitting core and the reflective layer are respectively arranged on two opposite surfaces of the substrate. By arranging a light-transmitting hole exposing the substrate on the surface of the reflective layer, the orthographic projection of the light-transmitting hole on the surface of the substrate is located within the orthographic projection of the light-emitting core on the surface of the substrate. That is, the light-transmitting hole is directly opposite to the light-emitting core, and the size of the light-transmitting hole is smaller than the size of the light-emitting core. In this way, when the light emitted by the light-emitting core is emitted from the substrate, if the light is emitted to the reflective layer, it is reflected back to the substrate by the reflective layer; if the light is emitted to the light-transmitting hole, it passes through the light-transmitting hole and is emitted from the light-emitting diode. Therefore, the shape of the light-emitting surface of the light-emitting diode is determined by the shape of the light-transmitting hole. In this way, the light-emitting diode can form a light-emitting surface of the designed shape without processing the substrate, and the light-emitting effect can also be guaranteed to meet the light type requirements of automotive lamps. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 is a top view of a light emitting diode provided by an embodiment of the present disclosure;

[0020] Figure 2 yes Figure 1 An AA cross-sectional view is provided;

[0021] Figure 3 is a structural schematic diagram of a light emitting diode provided by an embodiment of the present disclosure;

[0022] Figure 4 is a structural schematic diagram of a light emitting diode provided by an embodiment of the present disclosure;

[0023] Figure 5 Schematic diagram of the structure of a light-emitting core particle provided by an embodiment of the present disclosure;

[0024] Figure 6 is a flow chart of a method for preparing a light emitting diode provided by an embodiment of the present disclosure;

[0025] Figure 7 This is a diagram showing the preparation state of a light-emitting diode provided by an embodiment of the present disclosure;

[0026] Figure 8 This is a diagram of the preparation state of a light-emitting diode provided in an embodiment of the present disclosure.

[0027] The descriptions of the marks in the figure are as follows:

[0028] 10. Substrate;

[0029] 2. Luminescent core particles;

[0030] 20. epitaxial layer; 21. first semiconductor layer; 22. multi-quantum well layer; 23. second semiconductor layer; 24. first electrode; 25. second electrode;

[0031] 30, reflecting layer; 31, light-transmitting hole; 311, first hole segment; 312, second hole segment;

[0032] 40. Temporary substrate. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0034] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by a person of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," "third," and similar words used in the patent specification and claims of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish between different components. Similarly, terms such as "a" or "an" do not indicate a quantitative limitation, but rather indicate the presence of at least one. Terms such as "include" or "comprise" mean that the elements or objects preceding "include" or "comprises" encompass the elements or objects listed after "include" or "comprises," and their equivalents, and do not exclude other elements or objects. Terms such as "connected" or "connected" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," "right," "top," and "bottom" are used only to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0035] Figure 1 This is a top view of a light emitting diode provided by an embodiment of the present disclosure. Figure 2 yes Figure 1 An AA cross-section diagram is provided. Figure 1 、 2 As shown, the light emitting diode includes a substrate 10 , a light emitting core 2 and a reflective layer 30 . The light emitting core 2 and the reflective layer 30 are respectively located on two opposite surfaces of the substrate 10 .

[0036] like Figure 2As shown, the surface of the reflective layer 30 has a light-transmitting hole 31 that exposes the substrate 10. The orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 is located within the orthographic projection of the light-emitting core particle 2 on the surface of the substrate 10.

[0037] The light-emitting diode (LED) provided in the embodiment of the present disclosure has a light-emitting core 2 disposed on one surface of a substrate 10, and a reflective layer 30 disposed on the other surface of the substrate 10. That is, the light-emitting core 2 and the reflective layer 30 are disposed on opposite surfaces of the substrate 10, respectively. A light-transmitting hole 31 is disposed on the surface of the reflective layer 30, exposing the substrate 10, so that the orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 lies within the orthographic projection of the light-emitting core 2 on the surface of the substrate 10. That is, the light-transmitting hole 31 is directly opposite the light-emitting core 2, and the size of the light-transmitting hole 31 is smaller than the size of the light-emitting core 2. Thus, when light emitted by the light-emitting core 2 is emitted from the substrate 10, if the light is emitted from the reflective layer 30, it is reflected back to the substrate 10 by the reflective layer 30; if the light is emitted from the light-transmitting hole 31, it passes through the light-transmitting hole 31 and is emitted from the LED. Therefore, the shape of the light-emitting surface of the LED is determined by the shape of the light-transmitting hole 31. In this way, the LED can form a light-emitting surface of the designed shape without processing the substrate 10, and the light-emitting effect can be guaranteed to meet the light type requirements of the vehicle lamp.

[0038] Alternatively, as Figure 2 As shown, the orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 is a circle.

[0039] Designing light-transmitting aperture 31 as a circular hole allows the light-emitting core 2 to form a circular light-emitting surface. This circular light-emitting surface better meets the light focusing requirements of vehicle lights, allowing for precise control of beam distribution, reducing scattered light interference, and improving lighting efficiency. Furthermore, the circular light-emitting surface creates more uniform light, reducing the abruptness at the interface between light and dark, providing a softer, glare-free lighting effect, especially in low beam and daytime running lights.

[0040] For example, Figure 2 As shown, the diameter of the light-transmitting hole 31 is smaller than the width of the light-emitting core 2. This ensures that the size of the light-transmitting hole 31 does not exceed the size of the light-emitting core 2, so that the light-emitting surface of the light-emitting core 2 is larger than the outline of the light-transmitting hole 31. This is equivalent to using the light-transmitting hole 31 to cut the light-emitting surface of the light-emitting core 2 into a circle, thereby forming a circular light-emitting surface.

[0041] As an example, the orthographic projection of the light-emitting core 2 on the surface of the substrate 10 can be rectangular, while the orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 can be circular. Furthermore, the orthographic projection of the light-transmitting hole 31 is an inscribed circle of the orthographic projection of the light-emitting core 2. This ensures that the majority of light from the light-emitting core 2 is emitted directly from the light-transmitting hole 31 without being reflected by the reflective layer 30, thereby improving the luminous brightness.

[0042] Figure 3 Schematic diagram of the structure of a light emitting diode provided by an embodiment of the present disclosure. Figure 3 As shown, the shape of the axial cross section of the light-transmitting hole 31 is a trapezoid, and the end of the light-transmitting hole 31 with a larger size is away from the substrate 10 .

[0043] By aligning the larger end of the light-transmitting hole 31 with its back facing the light-emitting core 2, light propagates from the narrow end to the wider end, reducing the probability of total internal reflection at the hole's sidewalls and allowing more light to penetrate the thinner reflective layer 30 and exit. Furthermore, the frustum-shaped through-hole structure modulates the light field distribution, reducing light losses due to absorption or scattering within the device. The light-transmitting hole 31 also relieves internal stress in the reflective layer 30, preventing cracks in the reflective layer 30 caused by material brittleness.

[0044] Alternatively, as Figure 3 As shown, the included angle α between the generatrix of the light-transmitting hole 31 and the central axis is 30° to 70°.

[0045] When light is incident on the side wall of the light-transmitting hole 31, the inclination angle of the wall of the light-transmitting hole 31 can adjust the reflection path within the above range, so that more light is transmitted through the through hole instead of being completely reflected back into the light-emitting layer, thereby improving the luminous brightness.

[0046] Exemplarily, the included angle between the generatrix of the light-transmitting hole 31 and the central axis is 50°.

[0047] Figure 4 Schematic diagram of the structure of a light emitting diode provided by an embodiment of the present disclosure. Figure 4 As shown, the light-transmitting hole 31 includes a first hole segment 311 and a second hole segment 312 coaxially connected. The diameter of the first hole segment 311 is smaller than that of the second hole segment 312 . The first hole segment 311 is located on a side of the reflective layer 30 close to the substrate 10 .

[0048] like Figure 4 As shown by the middle arrow, if some light is emitted obliquely from the first hole segment 311, this part of the light will be reflected at the side wall of the second hole segment 312, so that more light can be emitted along the light-emitting surface defined by the light-transmitting hole 31, thereby improving the brightness of the light-emitting diode.

[0049] For example, the ratio of the diameter of the first hole section 311 to the diameter of the second hole section 312 is 0.5 to 0.9. For example, the ratio of the diameter of the first hole section 311 to the diameter of the second hole section 312 is 0.6.

[0050] Exemplarily, the ratio of the depth of the first hole section 311 to the depth of the second hole section 312 is less than or equal to 1.

[0051] By setting the depth of the first hole segment 311 to not exceed the depth of the second hole segment 312, the thickness of the reflective layer 30 where the first hole segment 311 is located is sufficiently small to allow some light to be transmitted from the reflective layer 30 into the second hole segment 312. The intensity of this partially transmitted light is lower than that of the light directly emitted from the first hole segment 311. Therefore, a circular light spot with weaker intensity is formed around the circular light spot with greater intensity, resulting in a light output pattern with a bright center and dark surroundings.

[0052] Optionally, the reflective layer 30 has a thickness of 1 μm to 4 μm.

[0053] By setting the thickness of the reflective layer 30 within the above range, it is possible to avoid the reflective layer 30 being too thin to have no reflective effect, and it is also possible to avoid the reflective layer 30 being too thick to increase the preparation cost.

[0054] Exemplarily, the thickness of the reflective layer 30 may be 3 μm.

[0055] Optionally, the reflective layer 30 includes at least one of a metal layer and a distributed Bragg reflector layer.

[0056] For example, the reflective layer 30 may be a metal layer with high reflectivity such as an Ag layer and an Al layer.

[0057] Exemplarily, the distributed Bragg reflector layer includes a plurality of first material layers and a plurality of second material layers alternately stacked, and the refractive index of the first material layer is different from the refractive index of the second material layer.

[0058] The first material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer, and the second material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer.

[0059] Exemplarily, the first material layer includes an aluminum oxide layer, and the second material layer includes a titanium oxide layer. The thickness of the first material layer is 1 / 4 of the optical thickness of the aluminum oxide, and the thickness of the second material layer is 1 / 4 of the optical thickness of the titanium oxide.

[0060] The refractive index of the first material layer and the refractive index of the second material layer are different, so that the reflective layer 30 formed by alternately stacking the first material layer and the second material layer forms a DBR structure.

[0061] The refractive index of aluminum oxide is about 1.76, and the refractive index of titanium oxide is about 2.40, which is significantly different. Due to the contrast between the high and low refractive indices, the Bragg reflection effect is enhanced, and high reflectivity can be achieved within a narrow period, ensuring the reflection effect of the reflective layer 30.

[0062] In addition, aluminum oxide has excellent chemical stability, thermal stability and mechanical strength, so the use of aluminum oxide for the first material layer can improve the stability of the reflective layer 30; aluminum oxide and titanium oxide are both wide-bandgap materials with low light absorption, resulting in less light loss, thereby improving the brightness of the light-emitting diode.

[0063] In the disclosed embodiment, the thickness of each material layer is set to 1 / 4 of the optical thickness of the corresponding material. This allows for a 180° phase difference in the reflected light from adjacent layers when incident vertically, resulting in destructive interference. The reflected light at the Bragg wavelength is superimposed and amplified, maximizing reflectivity.

[0064] For example, the number of the first material layer is 30 to 50, and the number of the second material layer is 30 to 50. By optimizing the number of stacked material layers in the reflective layer 30, the DBR can achieve high reflectivity in a wider spectral range.

[0065] In the embodiment of the present disclosure, the substrate 10 may be a sapphire substrate 10. The sapphire substrate 10 has a relatively high light transmittance, that is, the substrate 10 is a transparent substrate 10. Furthermore, the sapphire material is relatively hard and chemically stable, which enables the light-emitting diode to have good light-emitting effect and stability.

[0066] Figure 5 Schematic diagram of the structure of a light-emitting core particle 2 provided in an embodiment of the present disclosure. Figure 5 As shown, the light emitting core particle 2 may include an epitaxial layer 20 , and the epitaxial layer 20 includes a first semiconductor layer 21 , a multi-quantum well layer 22 , and a second semiconductor layer 23 stacked in sequence.

[0067] One of the first semiconductor layer 21 and the second semiconductor layer 23 is a p-type layer, and the other of the first semiconductor layer 21 and the second semiconductor layer 23 is an n-type layer.

[0068] Exemplarily, the first semiconductor layer 21 is an n-type layer, and the second semiconductor layer 23 is a p-type layer.

[0069] Optionally, the first semiconductor layer 21 is a silicon-doped n-type GaN layer, and the thickness of the n-type GaN layer may be 0.5 μm to 3 μm.

[0070] Optionally, the multi-quantum well layer 22 includes alternately grown InGaN quantum well layers and GaN quantum barrier layers, wherein the multi-quantum well layer 22 may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0071] As an example, in the embodiment of the present disclosure, the multi-quantum well layer 22 includes five periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0072] Optionally, the thickness of the multi-quantum well layer 22 may be 150 nm to 200 nm.

[0073] Optionally, the second semiconductor layer 23 is a magnesium-doped p-type GaN layer, and the thickness of the p-type GaN layer may be 0.5 μm to 3 μm.

[0074] Optionally, the light emitting diode further includes an AlN buffer layer and a u-type GaN layer, the AlN buffer layer and the u-type GaN layer are sequentially stacked on the substrate 10 , and the epitaxial layer 20 is located on the u-type GaN layer.

[0075] Alternatively, as Figure 5 As shown, the light-emitting diode also includes a passivation layer, a first electrode 24 and a second electrode 25. The second semiconductor layer 23 also has a groove exposing the first semiconductor layer 21. The first electrode 24 is located in the groove and is connected to the first semiconductor layer 21. A portion of the second electrode 25 is located on the surface of the second semiconductor layer 23, and another portion of the second electrode 25 is located on the light-absorbing and resistive-increasing layer. The first electrode 24 and the second electrode 25 are used to connect to an external power supply and transmit current to various regions of the epitaxial layer 20.

[0076] The passivation layer is located on the surface and in the groove of the second semiconductor layer 23 and covers the first electrode 24 and the second electrode 25. The passivation layer also has through holes exposing the first electrode 24 and the second electrode 25, so that an external power source can be connected to the electrodes through the through holes.

[0077] Illustratively, the passivation layer may be at least one of a silicon oxide layer, an aluminum oxide layer, and a silicon nitride layer.

[0078] Optionally, the passivation layer may have a thickness of 800 angstroms to 3000 angstroms.

[0079] Alternatively, the first electrode 24 and the second electrode 25 may each include a first Al layer, a first Ti layer, a second Al layer, a second Ti layer, and an Au layer stacked in sequence.

[0080] Figure 6 This is a flow chart of a method for preparing a light emitting diode provided by an embodiment of the present disclosure. Figure 6 As shown, the preparation method comprises:

[0081] S11 : preparing light-emitting core particles 2 on one surface of the substrate 10 .

[0082] S12 : forming a reflective layer 30 on the other surface of the substrate 10 .

[0083] The reflective layer 30 has a light-transmitting hole 31 on its surface that exposes the substrate 10 . The orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 is located within the orthographic projection of the light-emitting core 2 on the surface of the substrate 10 .

[0084] The light-emitting diode fabricated by this method has a light-emitting core 2 disposed on one surface of a substrate 10, and a reflective layer 30 disposed on the other surface of the substrate 10. That is, the light-emitting core 2 and the reflective layer 30 are disposed on opposite surfaces of the substrate 10. A light-transmitting hole 31 is provided on the surface of the reflective layer 30, exposing the substrate 10. The orthographic projection of the light-transmitting hole 31 on the surface of the substrate 10 lies within the orthographic projection of the light-emitting core 2 on the surface of the substrate 10. That is, the light-transmitting hole 31 directly faces the light-emitting core 2, and the size of the light-transmitting hole 31 is smaller than that of the light-emitting core 2. Thus, when light emitted by the light-emitting core 2 exits the substrate 10, if the light strikes the reflective layer 30, it is reflected back to the substrate 10. If the light strikes the light-transmitting hole 31, it passes through the light-transmitting hole 31 and exits the light-emitting diode. Therefore, the shape of the light-emitting surface of the LED is determined by the shape of the light-transmitting hole 31. In this way, the LED can form a light-emitting surface of the designed shape without processing the substrate 10, and the light-emitting effect can be guaranteed to meet the light type requirements of the vehicle lamp.

[0085] The process of preparing the light-emitting core particle 2 in step S11 may include the following steps:

[0086] In the first step, an epitaxial layer 20 is formed on the substrate 10 .

[0087] Exemplarily, the substrate 10 is a sapphire substrate 10, a silicon substrate 10, or a silicon carbide substrate 10. The substrate 10 can be a flat substrate 10 or a patterned substrate 10.

[0088] As an example, in the embodiment of the present disclosure, the substrate 10 is a sapphire substrate 10. The sapphire substrate 10 is a commonly used substrate 10 with mature technology and low cost. Specifically, it can be a patterned sapphire substrate 10 or a sapphire flat sheet substrate 10.

[0089] The sapphire substrate 10 may be pre-treated by placing it in a MOCVD (Metal-organic Chemical Vapor Deposition) reaction chamber and baking it for 12 to 18 minutes. For example, in the embodiment of the present disclosure, the sapphire substrate 10 is baked for 15 minutes.

[0090] Specifically, the baking temperature may be 1000° C. to 1200° C., and the pressure in the MOCVD reaction chamber during baking may be 100 mbar to 200 mbar.

[0091] Growing the epitaxial layer 20 on the substrate 10 may include: first, sequentially forming an AlN buffer layer and a u-type GaN layer on the sapphire substrate 10 by using MOCVD technology.

[0092] Then, a first semiconductor layer 21 , a multi-quantum well layer 22 and a second semiconductor layer 23 are sequentially formed on the sapphire substrate 10 by MOCVD technology.

[0093] Illustratively, the epitaxial layer 20 includes an n-type GaN layer, a multi-quantum well layer 22 and an n-type GaN layer stacked in sequence.

[0094] Optionally, the thickness of the n-type GaN layer may be 0.5 μm to 3 μm.

[0095] The growth temperature of the n-type GaN layer may be 1000° C. to 1100° C., and the growth pressure of the n-type GaN layer may be 100 Torr to 300 Torr.

[0096] Optionally, the multi-quantum well layer 22 includes alternately grown InGaN quantum well layers and GaN quantum barrier layers, wherein the multi-quantum well layer 22 may include 3 to 8 periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0097] When growing the multi-quantum well layer 22, the pressure of the MOCVD reaction chamber is controlled at 200 Torr. When growing the InGaN quantum well layer, the reaction chamber temperature is 760°C to 780°C. When growing the GaN quantum barrier layer, the reaction chamber temperature is 860°C to 890°C.

[0098] As an example, in the embodiment of the present disclosure, the multi-quantum well layer 22 includes five periods of alternately stacked InGaN quantum well layers and GaN quantum barrier layers.

[0099] Optionally, the thickness of the multi-quantum well layer 22 may be 150 nm to 200 nm.

[0100] Optionally, the p-type GaN layer may have a thickness of 0.5 μm to 3 μm.

[0101] When growing the p-type GaN layer, the growth pressure of the p-type GaN layer may be 200 Torr to 600 Torr, and the growth temperature of the p-type GaN layer may be 800° C. to 1000° C.

[0102] In the second step, a groove exposing the first semiconductor layer 21 is formed by etching the surface of the second semiconductor layer 23 .

[0103] In the third step, a transparent conductive layer is formed on the surface of the second semiconductor layer 23 .

[0104] The transparent conductive layer has a through hole exposing the second semiconductor layer 23 .

[0105] Exemplarily, the transparent conductive layer is an indium tin oxide layer or an indium zinc oxide layer.

[0106] Exemplarily, the thickness of the transparent conductive layer may be 200 angstroms to 5000 angstroms. For example, the thickness of the transparent conductive layer is 2000 angstroms.

[0107] In the fourth step, a first electrode 24 is formed in the groove, and a second electrode 25 is formed on the transparent conductive layer of the second semiconductor layer 23 .

[0108] The first electrode 24 located in the groove is an n-type electrode, and the second electrode 25 located on the second semiconductor layer 23 is a p-type electrode.

[0109] For example, the first electrode 24 and the second electrode 25 may each be a first Al layer, a first Ti layer, a second Al layer, a second Ti layer, and an Au layer stacked in sequence.

[0110] In the fifth step, a passivation layer is formed on the surface of the second semiconductor layer 23 and in the groove.

[0111] For example, the passivation layer may be a silicon oxide layer, and the thickness of the passivation layer may be 800 angstroms to 3000 angstroms.

[0112] Step S12 may include: evaporating a distributed Bragg reflector layer on the entire surface of the substrate 10 .

[0113] like Figure 7 As shown, the light-emitting core particle 2 is temporarily bonded first. A bonding adhesive such as BCB adhesive is used to bond the side of the light-emitting core particle 2 away from the substrate 10 to the temporary base plate 40, and the substrate 10 is thinned.

[0114] like Figure 8 As shown, a reflective layer 30 is evaporated on the entire surface of the substrate 10 away from the light-emitting core particles 2 .

[0115] Optionally, the thickness of the reflective layer 30 is 1 μm to 4 μm. For example, the thickness of the reflective layer 30 may be 3 μm.

[0116] Optionally, the reflective layer 30 includes at least one of a metal layer and a distributed Bragg reflector layer.

[0117] For example, the reflective layer 30 may be a metal layer with high reflectivity such as an Ag layer and an Al layer.

[0118] Exemplarily, the distributed Bragg reflector layer includes a plurality of first material layers and a plurality of second material layers alternately stacked, and the refractive index of the first material layer is different from the refractive index of the second material layer.

[0119] The first material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer, and the second material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer.

[0120] Exemplarily, the first material layer includes an aluminum oxide layer, and the second material layer includes a titanium oxide layer. The thickness of the first material layer is 1 / 4 of the optical thickness of the aluminum oxide, and the thickness of the second material layer is 1 / 4 of the optical thickness of the titanium oxide.

[0121] For example, the number of the first material layer is 30 to 50, and the number of the second material layer is 30 to 50. By optimizing the number of stacked material layers in the reflective layer 30, the DBR can achieve high reflectivity in a wider spectral range.

[0122] Then, the distributed Bragg reflector layer is etched to form a circular light-transmitting hole 31 .

[0123] Specifically, the method may include etching a portion of the reflective layer 30 to form a light-transmitting hole 31 exposing the substrate 10 .

[0124] like Figure 8 As shown, the light-transmitting holes 31 correspond to the light-emitting core particles 2 one by one, and the light-transmitting holes 31 are opposite to the corresponding light-emitting core particles 2 .

[0125] For example, Figure 8 As shown, the diameter of the light-transmitting hole 31 is smaller than the width of the light-emitting core particle 2 .

[0126] As an example, the orthographic projection of the light emitting core 2 on the surface of the substrate 10 may be rectangular, and the orthographic projection of the light transmission hole 31 on the surface of the substrate 10 may be circular. The orthographic projection of the light transmission hole 31 is an inscribed circle of the orthographic projection of the light emitting core 2 .

[0127] Exemplarily, the shape of the axial cross section of the light-transmitting hole 31 is trapezoidal, and the end of the light-transmitting hole 31 with a larger size is away from the substrate 10 .

[0128] Optionally, the angle between the generatrix of the light-transmitting hole 31 and the central axis is 30° to 70°. Exemplarily, the angle between the generatrix of the light-transmitting hole 31 and the central axis is 50°.

[0129] Finally, the temporary substrate 40 is removed, and the sapphire substrate 10 is subjected to invisible cutting and cleaving, which can effectively reduce the loss of brightness. Then, the light emitting diode is obtained by testing.

[0130] The above description is merely an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A light emitting diode, characterized in that: The light-emitting diode comprises a substrate (10), a light-emitting core (2) and a reflective layer (30), wherein the light-emitting core (2) and the reflective layer (30) are respectively located on opposite surfaces of the substrate (10); The surface of the reflective layer (30) has a light-transmitting hole (31) exposing the substrate (10), and the orthographic projection of the light-transmitting hole (31) on the surface of the substrate (10) is located within the orthographic projection of the light-emitting core particle (2) on the surface of the substrate (10).

2. The light emitting diode according to claim 1, characterized in that The shape of the orthographic projection of the light-transmitting hole (31) on the surface of the substrate (10) is circular.

3. The light emitting diode according to claim 1, characterized in that The axial cross-section of the light-transmitting hole (31) is in the shape of a trapezoid, and the end of the light-transmitting hole (31) with a larger size is away from the substrate (10).

4. The light emitting diode according to claim 3, characterized in that The included angle between the generatrix of the light-transmitting hole (31) and the central axis is 30° to 70°.

5. The light emitting diode according to claim 1, characterized in that The light-transmitting hole (31) comprises a first hole segment (311) and a second hole segment (312) coaxially connected, the diameter of the first hole segment (311) being smaller than the diameter of the second hole segment (312), and the first hole segment (311) being located on a side of the reflective layer (30) close to the substrate (10).

6. The light emitting diode according to any one of claims 1 to 5, characterized in that: The thickness of the reflective layer (30) is 1 μm to 4 μm.

7. The light emitting diode according to any one of claims 1 to 5, characterized in that: The reflective layer (30) includes at least one of a metal layer and a distributed Bragg reflector layer.

8. The light emitting diode according to claim 7, characterized in that The distributed Bragg reflector layer includes multiple first material layers and multiple second material layers alternately stacked, the refractive index of the first material layer is different from the refractive index of the second material layer, the first material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer, and the second material layer includes an aluminum oxide layer, a titanium oxide layer or a silicon oxide layer.

9. A method for preparing a light emitting diode, characterized in that: The preparation method comprises: Preparing a light-emitting core particle (2) on a surface of a substrate (10); A reflective layer (30) is formed on the other surface of the substrate (10), the surface of the reflective layer (30) having a light-transmitting hole (31) exposing the substrate (10), and the orthographic projection of the light-transmitting hole (31) on the surface of the substrate (10) is located within the orthographic projection of the light-emitting core particle (2) on the surface of the substrate (10).

10. The preparation method according to claim 9, characterized in that Forming a reflective layer (30) on the other surface of the substrate (10) comprises: Vapor-depositing a distributed Bragg reflector layer on the entire surface of the substrate (10); The distributed Bragg reflector layer is etched to form circular light-transmitting holes (31), wherein the light-transmitting holes (31) correspond to the light-emitting core particles (2) one by one, and the light-transmitting holes (31) are opposite to the corresponding light-emitting core particles (2).

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