light-emitting diodes

Abstract

This invention discloses a light-emitting diode (LED), comprising: a light-emitting epitaxial structure including a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer stacked sequentially; a current spreading layer formed on the surface of the second conductive semiconductor layer and having a plurality of first openings exposing a portion of the second conductive semiconductor layer, wherein the area of ​​the light-emitting epitaxial structure occupied by the current spreading layer is greater than 50% and less than 95%; an insulating layer formed on the current spreading layer and within the first openings of the current spreading layer, and having a plurality of second openings exposing a portion of the current spreading layer, wherein the second openings are offset from the first openings; and a reflective layer formed on the insulating layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a light-emitting diode. Background Technology

[0002] A light-emitting diode (LED) is a semiconductor device that emits light by releasing energy when charge carriers recombine. In particular, flip-chip LEDs have advantages such as no need for wire bonding, high luminous efficiency, and good heat dissipation, and their applications are becoming increasingly widespread.

[0003] Currently, flip-chip LEDs typically use transparent conductive layers (such as conductive metal oxides like ITO) as P-type ohmic contact layers. Although they have high transmittance after high-temperature fusion, they still have some loss, which is not conducive to improving the brightness of the chip. However, if transparent conductive layers are not used as ohmic contact layers, it is difficult to achieve ohmic contact of P-type semiconductor layers. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a light-emitting diode that ensures sufficient ohmic contact with the light-emitting epitaxial structure while improving device brightness.

[0005] The aforementioned light-emitting diode includes: a light-emitting epitaxial structure comprising a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer stacked sequentially; a current spreading layer formed on the surface of the second conductive semiconductor layer and having a plurality of first openings exposing a portion of the second conductive semiconductor layer, wherein the area of ​​the light-emitting epitaxial structure occupied by the current spreading layer is greater than 50% and less than 95%; an insulating layer formed on the current spreading layer and within the first openings of the current spreading layer, and having a plurality of second openings exposing a portion of the current spreading layer, wherein the second openings are offset from the first openings; and a reflective layer formed on the insulating layer.

[0006] In some embodiments, a plurality of first openings adjacent to the same second opening form a regular polygon.

[0007] Preferably, the diameter of the first opening is 2~50 μm. In some embodiments, the light-emitting diode is a miniature LED chip, for example, the cross-sectional area of ​​the LED chip can be 62500 μm. 2 The diameter of the first opening can be 2~10μm; in some embodiments, the light-emitting diode is a medium or large-sized LED chip, for example, the cross-sectional area of ​​the LED chip can be 90000μm. 2The diameter of the first opening can be 2~5μm, 5~10μm, 10~20μm, or more than 20μm. Preferably, the diameter of the first opening is 1~20μm, which can better balance VF (voltage) and LOP (brightness).

[0008] Preferably, the spacing between adjacent first openings is 1~20μm.

[0009] Preferably, the area occupied by the plurality of first openings in the light-emitting epitaxial structure is 5% to 50%.

[0010] Preferably, the three adjacent second openings form an isosceles triangle.

[0011] Preferably, the area occupied by the plurality of second openings in the light-emitting epitaxial structure is 3% to 50%.

[0012] Preferably, the ratio of the number of the first opening to the number of the second opening is between 2:1 and 20:1.

[0013] Preferably, the plurality of second openings are arranged at equal intervals.

[0014] Preferably, the plurality of first openings have at least two different spacings.

[0015] Preferably, the insulating layer further comprises a plurality of third openings that expose a portion of the second conductive semiconductor layer.

[0016] In some embodiments, the insulating layer is silicon nitride, silicon oxide, or aluminum oxide.

[0017] In some embodiments, the insulating layer is a Bragg reflective layer, which may be formed by alternating stacks of light-transmitting materials with high and low refractive indices.

[0018] Preferably, the insulating layer covers the sidewalls of the light-emitting epitaxial structure.

[0019] In some embodiments, the reflective layer includes a metal layer comprising a metal reflective layer and a metal blocking layer.

[0020] In some embodiments, the insulating layer further comprises a plurality of third openings exposing a portion of the second conductive semiconductor layer. A portion of the reflective layer contacts the current spreading layer through the plurality of second openings and contacts the second conductive semiconductor layer through the plurality of third openings. By forming a third opening structure in the insulating layer, the reflective layer is made in direct contact with the light-emitting epitaxial structure, thereby improving the problem of poor adhesion between the reflective layer (such as a metal reflective layer) and the insulating layer and enhancing the reliability of the LED device.

[0021] Preferably, the ratio of the number of the second opening to the number of the third opening is between 5:1 and 50:1.

[0022] Preferably, the first opening and the second opening are arrayed, and the third opening is annular or strip-shaped.

[0023] In some embodiments, at least one side length of the light-emitting epitaxial structure is 300 μm or more.

[0024] Furthermore, the light-emitting diode also includes a local defect region located on a portion of the second conductive semiconductor layer and extending downward to the first conductive semiconductor layer to form a mesa structure, wherein the mesa structure exposes the sidewalls of the light-emitting epitaxial structure.

[0025] In some embodiments, the reflective layer is an insulating reflective layer covering the sidewalls of the light-emitting epitaxial structure, and has a first through-hole and a second through-hole. Preferably, the light-emitting diode further includes a first electrode and a second electrode, wherein the first electrode is electrically connected to the first conductive semiconductor layer through the first through-hole, and the first electrode spans a portion of the surface of the insulating reflective layer; the second electrode is electrically connected to the second conductive semiconductor layer through the second through-hole structure, and the second electrode spans a portion of the surface of the insulating reflective layer.

[0026] In some embodiments, at least one side length of the light-emitting epitaxial structure is less than 300 μm.

[0027] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0028] The features and advantages of the invention will be more clearly understood by referring to the accompanying drawings, which are illustrative and should not be construed as limiting the invention in any way.

[0029] Figure 1 This is a schematic diagram of the structure of the light-emitting diode mentioned in Example 1.

[0030] Figure 2 This is a planar schematic diagram showing the distribution of the current spreading layer and the insulating layer.

[0031] Figure 3 This is a schematic diagram of the structure of the light-emitting diode mentioned in Example 2.

[0032] Figures 4-13 This is a schematic diagram illustrating the structure of the LED fabrication method shown in Example 2, where... Figure 5 for Figure 4 (Top view of LED chip unit) Cross-sectional view along the AA direction. Figure 7 for Figure 6 (Top view of LED chip unit) Cross-sectional view along the AA direction. Figure 9 for Figure 8 (Top view of LED chip unit) Cross-sectional view along the AA direction. Figure 11 for Figure 10 (Top view of LED chip unit) Cross-sectional view along the AA direction. Figure 12 In order to be in Figure 11 The diagram shown is a schematic of the structure after an insulating protective layer has been formed on it. Figure 13 In order to be in Figure 12 The diagram shows the structure after the first electrode layer has been fabricated.

[0033] Figure 14 This is a planar schematic diagram showing the patterns of the current spreading layer and the insulating layer in Embodiment 3.

[0034] Figure 15 This is a planar schematic diagram. Figure 14 A partially enlarged view of the schematic diagram shown.

[0035] Figures 16-17 This is a partial structural schematic diagram of the light-emitting diode mentioned in Example 4.

[0036] Figure 18 This is a side sectional view showing a schematic diagram of the structure of the light-emitting diode mentioned in Embodiment 5.

[0037] Figure 19 This is a side sectional view showing a schematic diagram of the structure of the light-emitting diode mentioned in Embodiment Six.

[0038] Figure 20 This is a planar schematic diagram showing the current spreading layer pattern of the light-emitting diode shown in Embodiment 6. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Example 1

[0040] This embodiment discloses the following LED chip, such as... Figure 1 The cross-sectional schematic diagram shown includes the following stacked layers: transparent substrate 110, light-emitting epitaxial structure, current spreading layer 130, insulating layer 141, metal reflective layer 151, first electrode 171, and second electrode 172.

[0041] The transparent substrate 110 can be a growth substrate for growing light-emitting epitaxial layers, or it can be a transparent substrate bonded to the light-emitting epitaxial layers through a transparent adhesive layer. Specifically, it includes planar sapphire substrates, patterned sapphire substrates, silicon carbide substrates, gallium nitride substrates, etc. In this embodiment, the transparent substrate 110 is selected as a patterned sapphire substrate. In other embodiments, the substrate can be thinned or removed to form a thin-film LED chip.

[0042] The light-emitting epitaxial structure is located on the transparent substrate 110 and includes a first conductive semiconductor layer 121, an active layer 122, and a second conductive semiconductor layer 123 stacked sequentially. For example, the first conductive semiconductor layer 121 can be an N-type GaN layer, the active layer 122 can be a GaN-based quantum well layer, and the second conductive semiconductor layer 123 can be a P-type GaN layer. Of course, other types of epitaxial structures can be selected according to actual needs, and are not limited to the examples listed here.

[0043] The local defect region 1211 is located on a portion of the second conductive semiconductor layer 123 and extends downward to the first conductive semiconductor layer 121 to form a mesa structure. The mesa structure exposes the sidewalls of the epitaxial structure. Specifically, the mesa structure exposes the mesa of the first conductive semiconductor layer 121 and the sidewalls of the first conductive semiconductor layer 121, the active layer 122, and the second conductive semiconductor layer 123. It should be noted that the number of local defect regions 1211 is at least one, and can be increased depending on the structure and area of ​​the LED chip.

[0044] The current spreading layer 130 can be made of a metal oxide that is transparent to light emitted from the active layer, such as indium tin oxide, zinc oxide, zinc indium tin oxide, indium zinc oxide, zinc tin oxide, gallium indium tin oxide, indium gallium oxide, zinc gallium oxide, aluminum-doped zinc oxide, fluorine-doped tin oxide, etc. Structurally, the transparent conductive layer located on the surface of the light-emitting epitaxial layer is preferably "recessed" to facilitate the subsequent insulating reflective layer to be coated on the sidewalls of the current spreading layer. The current spreading layer 130 uses a metal conductive oxide, which has good current spreading characteristics and can form a good ohmic contact with the semiconductor layer. However, metal conductive oxides have a certain light absorption for wavelengths below 520nm, and the light absorption becomes more severe as the wavelength decreases. Taking ITO as an example, its light absorption rate can reach about 3-15% in the 400-460nm wavelength range, and its light absorption rate is even more severe in the ultraviolet light below 400nm. In this embodiment, the current spreading layer 130 has multiple first openings 161 that expose a portion of the second conductive semiconductor layer 123. By controlling the size and density of these first openings, the area occupied by the current spreading layer of the light-emitting epitaxial structure is greater than 50% and less than 95%. This ensures sufficient ohmic contact between the current spreading layer 130 and the second conductive semiconductor layer 123 while reducing the area of ​​the current spreading layer 130, thereby improving the brightness of the light-emitting diode. Preferably, the area occupied by the current spreading layer of the light-emitting epitaxial structure is 70-90%. Specifically, the first openings 161 are arranged in an array with a diameter of 2-50 μm, and the spacing between adjacent first openings 161 is 1-20 μm. In this embodiment, the diameter of the first opening is selected to be 2-10 μm, and the spacing is 5-20 μm. Preferably, the thickness of the current spreading layer 130 is 5-60 nm. When the thickness is less than 5 nm, the forward voltage (Vf) of the LED chip is easily increased, and when it exceeds 60 nm, the light absorption effect will increase significantly. The thickness of the current spreading layer 130 is more preferably 10-30 nm, for example, 15 nm or 20 nm.

[0045] The insulating layer 141 is formed on the current spreading layer 130 and within the first opening 161 of the current spreading layer, and encloses the sidewalls of the current spreading layer 130 and the sidewalls of the light-emitting epitaxial structure. Further, the insulating layer 141 has a plurality of second openings 162 exposing a portion of the current spreading layer 130. These second openings 162 serve as reserved windows for the second electrode and are offset from the first openings 161. Figure 2As shown. The total cross-sectional area of ​​the second opening 162 accounts for 3% to 50% of the cross-sectional area of ​​the light-emitting epitaxial structure (LED chip unit), preferably 5% to 20%, more preferably 10%. If the ratio is too low, the contact area between the metal reflective layer 151 and the current spreading layer 130 through the second opening 162 is too small, which is not conducive to voltage control. If the ratio is too high, it will affect the reflection effect of the current spreading layer, the insulating layer (such as a low refractive index layer), and the metal reflective layer forming an all-around reflective layer structure. The insulating layer 141 is made of silicon oxide, silicon nitride, or aluminum oxide. Preferably, the second openings 162 are evenly spaced. Preferably, the light transmittance of the light-transmitting insulating layer 141 is higher than that of the current spreading layer 130, and its thickness is greater than that of the current spreading layer 130, preferably 50 nm or more.

[0046] Preferably, the first opening 161 and the second opening 162 form an array. In one specific embodiment, in the array formed by the first opening 161 and the second opening 162, the diameters of the first opening 161 and the second opening 162 are the same, and the ratio of the number of first openings 161 to second openings is preferably 2:1 to 20:1, for example, 2:1, 3:1, or 5:1. Further, six first openings 161 adjacent to the same second opening 162 form a hexagon D1, with the second opening 162 located at the center of the hexagon, and the three closest second openings forming an isosceles triangle, such as... Figure 2 As shown.

[0047] A metal reflective layer 151 is formed on the surface of the insulating layer 141 and contacts the current spreading layer 130 through the second opening 162. As an example, when the metal reflective layer is made of Al or Ag high-reflectivity metal as a mirror, it is preferable to further coat the surface of the metal reflective layer with a metal protective layer 152, which can be made of TiW, Cr, Pt, Ti, etc. The metal protective layer 152 can completely cover the metal mirror layer to protect the metal reflective layer 151.

[0048] Furthermore, a second insulating layer 142 is applied over the metal protective layer 152, completely covering the metal protective layer 152. The material of the second insulating layer 142 can be the same as or different from that of the insulating layer 141. Insulating layers 141 and 142 form a first via 181 in the local defect region 1211 and a second via 182 above the second conductive semiconductor layer. As an example, from a top view, the area of ​​the second via is greater than or equal to the area of ​​the first via, and the number of first and second via structures is roughly equal. The shape of the second via can differ from that of the first via; for example, the second via may be circular with an extension strip, while the first via is circular. That is, when the area of ​​the second via is greater than the area of ​​the first via, it is easier to visually distinguish the positive and negative electrical properties of the second and first electrodes. Generally, the number of first via structures is roughly equal to the number of local defect regions, and the area of ​​the local defect regions is greater than the area of ​​the first vias, to facilitate the insulating layer wrapping the sidewalls of the light-emitting epitaxial structure.

[0049] The first electrode 171 is electrically connected to the first conductive semiconductor layer 121 through the first through-hole 181, and the first electrode spans a portion of the surface of the second insulating layer 142. Specifically, the first electrode 171 is formed in the first through-hole 181 and spans a portion of the surface of the second insulating layer 142. The second electrode 172 is electrically connected to the second conductive semiconductor layer 23 through the second through-hole structure 182, and the second electrode spans a portion of the surface of the second insulating layer 142. As an example, it is preferable that the areas of the first electrode and the second electrode are comparable, and that the first electrode and the second electrode are symmetrical, which can be axially symmetrical or rotationally symmetrical, etc. Further, it is preferable that the area of ​​the first electrode spanning a portion of the surface of the insulating layer accounts for more than 90% of the area of ​​the first electrode, and the area of ​​the second electrode spanning a portion of the surface of the insulating layer accounts for more than 90% of the area of ​​the second electrode. This helps to achieve the overall flatness of the top surfaces of the first electrode and the second electrode, which is beneficial for the die bonding of the flip-chip LED, improves the packaging push level, and enhances reliability. Furthermore, from a top view, it is preferable that the area of ​​the first electrode is larger than the area of ​​the local defect region. Furthermore, the area of ​​the first electrode located above the surface of the light-emitting epitaxial structure / current extension surface is larger than the area of ​​the first electrode located above the local defect region. This helps to minimize the reduction in light-emitting area caused by the local defect region, while also ensuring the flatness of the top surface of the first electrode and reducing the height difference of the first electrode. Example 2

[0050] like Figure 3As shown, the difference from Embodiment 1 is that this embodiment is a medium-to-large-sized LED chip with multiple local defect areas 1211. The size of the first opening is preferably 2~50μm, more preferably 2~20μm, for example, it can be 2μm, 5μm, or 10μm. Furthermore, the electrode structure in this embodiment differs from that in the previous embodiment. First, a conductive metal layer 173 is formed on the second insulating layer 142, which contacts the first conductive semiconductor layer through a local defect region 1211. A third insulating layer 143 is formed on the conductive metal layer 173, and a first through hole 181 and a second through hole 182 are reserved. The first through hole exposes part of the surface of the conductive metal layer 173, and the second through hole penetrates the third insulating layer 143, the conductive metal layer 173, and the second insulating layer 142, exposing part of the surface of the metal protective layer 152. The third insulating layer 143 covers the sidewall of the conductive metal layer 173. The first electrode 171 and the second electrode 172 are formed on the third insulating layer 143. The first electrode 171 contacts the conductive metal layer 173 through the first through hole 181, and the second electrode 172 is electrically connected to the metal reflective layer through the second through hole 182.

[0051] The following is in conjunction with the appendix Figures 4-13 right Figure 3 The manufacturing method of the light-emitting diode shown is explained in detail.

[0052] First, an epitaxial structure is provided, comprising a first conductive semiconductor layer 121, an active layer 1122, and a second conductive semiconductor layer 123 stacked sequentially. As an example, the epitaxial structure is formed on the substrate 110 using an MOCVD process. The epitaxial structure may include a buffer layer (not shown in the figure), the first conductive semiconductor layer 121, the active layer 122, and the second conductive semiconductor layer 123, etc. The first conductive semiconductor layer 121 may be an N-type GaN layer, the active layer 122 may be a GaN-based multiple quantum well layer, and the second conductive semiconductor layer 123 may be a P-type GaN layer. Of course, other types of epitaxial structures can be selected according to actual needs, and are not limited to the examples listed here.

[0053] like Figure 4 and 5As shown, a number of local defect regions 1211 are etched from top to bottom in the epitaxial structure to form a mesa structure. The mesa structure exposes the sidewalls of the epitaxial structure. Specifically, the mesa structure exposes the mesa of the first conductive semiconductor layer and the sidewalls of the first conductive semiconductor layer 121, the active layer 122, and the second conductive semiconductor layer 123. For example, ICP etching or RIE etching processes can be used to etch the mesa structure in the epitaxial structure, so that the mesa structure exposes the mesa of the first conductive semiconductor layer 121 and the sidewalls of the first conductive semiconductor layer 121, the active layer 122, and the second conductive semiconductor layer 123. The mesa of the first conductive semiconductor layer is used for the subsequent electrical connection of the first electrode. The number of local defect regions 1211 is at least one, and can also be increased according to the structure, application, and area size of the LED chip, so that the number of local defect regions is comparable to the number of the subsequently fabricated second via structures.

[0054] like Figure 6 and 7 As shown, a patterned current spreading layer 130 is formed on a portion of the surface of the light-emitting epitaxial structure. For example, the current spreading layer 130 can be an ITO transparent conductive layer formed by vapor deposition, or other materials can be used. The current spreading layer forms an ohmic contact with the second conductive semiconductor layer of the light-emitting epitaxial structure through fusion. Further, a portion of the current spreading layer is etched using photolithography and etching processes to form multiple first openings 161, exposing a portion of the surface of the second type semiconductor layer 123, such that the area of ​​the light-emitting epitaxial structure occupied by the current spreading layer is 50-95%. Preferably, the first openings 161 are arranged in an array, with a diameter of 2-50 μm, and the spacing between adjacent first openings 161 is 1-20 μm. In this embodiment, the diameter of the first opening is selected as 2-20 μm, and the spacing is 5-20 μm.

[0055] like Figure 8 and 9As shown, an insulating layer 141 is fabricated on the above structure, filling the first opening 161 and wrapping the sidewalls of the current spreading layer 130 and covering the sidewalls of the adjacent light-emitting epitaxial structure. Further, a portion of the insulating layer 141 is etched using photolithography to form a series of second openings 162. For example, a chemical vapor deposition process can be used to form the insulating layer 141 on a portion of the surface of the epitaxial structure. The insulating layer 141 can be a low-refractive-index material, such as silicon dioxide or magnesium fluoride, or a high-refractive-index material, such as titanium dioxide. Alternatively, the insulating layer can be a distributed Bragg reflector (DBR) layer comprising both high and low refractive-index materials, and is not limited to the examples listed herein. If the insulating layer 141 is made of a low-refractive-index material, SiO2, the refractive index difference between the low-refractive-index insulating layer and the transparent conductive layer can enhance light emission. As an example, the second openings 162 are arrayed, with a size between 1 and 50 μm, preferably between 1 and 20 μm. The total cross-sectional area of ​​the second opening 162 accounts for 3% to 50% of the cross-sectional area of ​​the light-emitting epitaxial structure, preferably 5% to 20%, and more preferably 10%.

[0056] like Figure 10 and Figure 11 As shown, a metal reflective layer 151 is formed on the surface of the insulating layer 141. This metal reflective layer 151 contacts the current spreading layer 130 through the second opening 162. Further, a metal protective layer 152 is coated onto the metal reflective layer 151. As an example, when the metal reflective layer 151 is made of a highly reflective metal such as Al or Ag, and serves as a mirror, the metal protective layer 152 can be made of materials such as TiW, Cr, Pt, or Ti.

[0057] like Figure 12 As shown, a second insulating layer 142 is formed on the metal protective layer 152. As an example, the second insulating layer 142 can be formed by chemical vapor deposition. The second insulating layer 142 can be a low refractive index material, such as a silicon dioxide layer or magnesium fluoride, or a high refractive index material, such as titanium dioxide. Alternatively, the insulating layer can be a distributed Bragg reflector layer, and is not limited to the examples listed herein.

[0058] like Figure 13 A conductive metal layer 173 (i.e., PAD 1 layer) is formed on the second insulating layer 142, and the conductive metal layer 173 makes electrical contact with the first conductive semiconductor layer 121 through the local defect region 1211.

[0059] Further, a third insulating layer 143 is formed on the conductive metal layer 172, and a first through-hole 181 and a second through-hole 182 are provided. The first through-hole exposes a portion of the surface of the conductive metal layer 173, and the second through-hole penetrates the third insulating layer 143, the conductive metal layer 173, and the second insulating layer 142, exposing a portion of the surface of the metal protective layer 152. The third insulating layer 143 covers the sidewall of the conductive metal layer 173. Finally, a first electrode 171 and a second electrode 172 are fabricated on the third insulating layer 143. The first electrode 171 contacts the conductive metal layer 173 through the first through-hole 181, and the second electrode 172 is electrically connected to the metal reflective layer through the second through-hole 182, as shown below. Figure 3 As shown. Example 3

[0060] like Figure 14 and 15 As shown, the difference from Embodiment 2 is that the distribution pattern of the first opening 161 and the second opening 162 in this embodiment is different from that in Embodiment 2. In this embodiment, eight first openings 161 adjacent to the same second opening 162 form a square or rectangle, and the second opening is located at the geometric center of the pattern. In this embodiment, the ratio of the number of first openings 161 to the number of second openings 162 is approximately 3:1. Example

[0061] like Figure 16 The difference from Embodiment 2 is that the insulating layer 141 in this embodiment also has a third opening 163, where a portion of the second conductive semiconductor layer 123 is exposed. This third opening 163 is preferably annular or strip-shaped, with a size between 1 and 50 μm, more preferably between 1 and 20 μm, and its number is comparable to the number of local defect regions, with similar shapes. The ratio of the number of second openings 162 to the number of third openings 163 is between 5:1 and 50:1, preferably with a ratio of the number of first through-hole structures to the number of second through-hole structures between 10:1 and 30:1.

[0062] like Figure 17 As shown, the metal reflective layer 151 is formed on the surface of the insulating layer 141, a portion of which contacts the current spreading layer 130 through the second opening 162, and another portion contacts the light-emitting epitaxial structure through the third opening 163, thereby improving the problem of poor adhesion between the metal reflective layer 151 and the insulating layer 141 and enhancing the reliability of the LED device. Example 4

[0063] This embodiment discloses a flip-chip LED, such as Figure 18The cross-sectional schematic diagram shown includes the following stacked layers: a transparent substrate 110, a light-emitting epitaxial structure, a current spreading layer 130, an insulating layer 141, a metal reflective layer 151, an insulating reflective layer 153, a first electrode 171, and a second electrode 172. The current spreading layer 130 and the insulating layer 141 form a first opening 161 and a second opening 162, as per Embodiment 1.

[0064] Unlike Embodiment 1, the reflective layer in this embodiment includes a metal reflective layer 151 and an insulating reflective layer 153. The insulating reflective layer 153 simultaneously covers the sidewalls of the light-emitting epitaxial structure. When light radiated from the active layer 122 reaches the surface of the insulating reflective layer 153 through the current spreading layer 130, most of the light can be reflected back into the light-emitting epitaxial stack by the insulating reflective layer 153, and most of the light passes through the transparent substrate 110 side to exit, reducing light loss caused by light passing through the surface and sidewalls of the light-emitting epitaxial stack. Preferably, the insulating reflective layer 153 can reflect at least 80% or further at least 90% of the light intensity radiated from the light-emitting layer reaching its surface. Specifically, the insulating reflective layer 153 may include a Bragg reflector. The Bragg reflector can be formed by repeatedly stacking at least two insulating media with different refractive indices, and can be formed in 4 to 20 pairs. For example, the insulating reflective layer 153 may include TiO2, SiO2, HfO2, ZrO2, Nb2O5, MgF2, etc. In some embodiments, the insulating layer may be an alternating deposition of TiO2 layers / SiO2 layers.

[0065] In the case where the insulating reflective layer 153 includes a Bragg reflector, it further includes an underlayer or interface layer to improve the film quality of the distributed Bragg reflector. For example, the insulating reflective layer comprises an interface layer formed of SiO2 with a thickness of about 0.2 to 1.0 μm, and then TiO2 / SiO2 layers are stacked on the interface layer in a specific period.

[0066] The insulating reflective layer 153 has at least one first through-hole 181 and one second through-hole 182. A first electrode 171 and a second electrode 172 are formed on the surface of the insulating reflective layer 153. The first electrode 171 is electrically connected to the first conductive semiconductor layer 121 through the first through-hole 181. The second electrode 172 is in contact with the metal reflective layer 151 through the second through-hole 182 and is electrically connected to the second conductive semiconductor layer 123 through the second opening 162 and the current spreading layer 130.

[0067] In this embodiment, firstly, a light-transmitting insulating layer 141 and a metal reflective layer 151 are formed above the patterned current spreading layer 130 to constitute an all-around reflective layer. Its reflective effect is superior to conventional metal reflective layers or distributed Bragg reflective layer structures, enhancing the probability of external light extraction from the LED chip and improving the brightness of the LED device. Secondly, an array of openings is formed on the current spreading layer 130, such that the area occupied by the current spreading layer of the light-emitting epitaxial structure is greater than 50% and less than 95%. This ensures sufficient ohmic contact between the current spreading layer 130 and the second conductive semiconductor layer 123 while reducing the impact of the current spreading layer 130 on the light-emitting epitaxial structure. The area is increased, thereby improving the brightness of the light-emitting diode. An insulating reflective layer is covered above the metal reflective layer and on the sidewall of the light-emitting epitaxial structure. On the one hand, it can ensure that it covers the sidewall of the light-emitting epitaxial stack more stably, prevent moisture from entering the area around the light-emitting epitaxial stack, and reduce the risk of leakage. On the other hand, the insulating reflective layer and the metal reflective layer achieve full coverage of the surface of the light-emitting epitaxial stack. When the light radiated by the active layer can be reflected by the omnidirectional reflective layer and the insulating reflective layer 153, most of the light returns to the light-emitting epitaxial stack, and most of the light passes through the second surface of the transparent substrate and exits to the side, reducing the light loss caused by light passing through the surface and sidewall of the light-emitting epitaxial stack. Example 5

[0068] This embodiment discloses a flip-chip LED, such as Figure 19 The cross-sectional schematic diagram shown includes the following stacked layers: a transparent substrate 110, a light-emitting epitaxial structure, a current spreading layer 130, an insulating reflective layer 153, a first electrode 171, and a second electrode 172. Please refer to the attached diagram. Figure 9 The current spreading layer 130 has arrayed first openings 161 exposing the surface of the second conductive semiconductor layer 123. These openings are preferably uniformly distributed, and the area occupied by the first openings in the light-emitting epitaxial structure is preferably 10% to 40%. The diameter of the first openings is 0.1 to 50 μm. In some embodiments, the light-emitting diode is a miniature LED chip, for example, the cross-sectional area of ​​which can be 62500 μm. 2 The diameter of the first opening can be 2~10μm; in some embodiments, the light-emitting diode is a medium or large-sized LED chip, for example, the cross-sectional area of ​​the LED chip can be 90000μm. 2 The diameter of the first opening can be 2~5μm, 5~10μm, 10~20μm, or more than 20μm. Preferably, the diameter of the first opening is 2~20μm, which can better balance VF (voltage) and LOP (brightness), and the spacing between adjacent first opening portions 161 is 1~20μm. In this embodiment, the diameter of the first opening is selected as 2~10μm, and the spacing is 5~20μm.

[0069] Unlike the LED chip shown in Example 5, an insulating reflective material is used as the reflective layer. Specifically, an extended electrode 175 is formed on a portion of the surface of the current spreading layer 130. At least a portion of the extended electrode 175 contacts the second conductive semiconductor layer 123 through the first opening 161. The contact resistance between the extended electrode 175 and the second conductive semiconductor layer is higher than its contact resistance with the current spreading layer 130, ensuring that the current flowing into the extended electrode is preferably spread through the current spreading layer 130 before entering the second conductive semiconductor layer 123. Therefore, the forward voltage can be reduced and the luminous efficiency can be improved. The insulating reflective layer 153 covers the upper surface and sidewalls of the current spreading layer, the upper surface and sidewalls of the extended electrode, and the sidewalls of the light-emitting epitaxial structure, and fills the remaining first opening. The insulating reflective layer 153 has at least one first through-hole 181 and one second through-hole 182. The first electrode 171 and the second electrode 172 are formed on the surface of the insulating reflective layer 153. The first electrode 171 is electrically connected to the first conductive semiconductor layer 121 through the first through hole 181, and the second electrode 172 is in contact with the extended electrode layer 175 through the second through hole 182 and is electrically connected to the second conductive semiconductor layer 123 through the current extension layer 130.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A light-emitting diode, characterized in that, include: The light-emitting epitaxial structure includes a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer stacked sequentially. The light-emitting epitaxial structure has a local defect region. The local defect is located on a portion of the second conductive semiconductor layer and extends downward to the first conductive semiconductor layer to form a mesa structure. The mesa structure exposes the sidewalls of the light-emitting epitaxial structure. A current spreading layer is formed on the surface of the second conductive semiconductor layer and has a plurality of first openings that expose a portion of the second conductive semiconductor layer; An insulating layer is formed on the current spreading layer and within the first opening of the current spreading layer, and has at least one second opening that exposes a portion of the current spreading layer. The second opening is offset from the first opening, and the ratio of the number of the first opening to the number of the second opening is between 2:1 and 20:

1. The insulating layer also has a third opening that exposes a portion of the second conductive semiconductor layer. A reflective layer is formed on the insulating layer, a portion of which contacts the current spreading layer through the second opening, and another portion of which contacts the second conductive semiconductor layer through the third opening.

2. The light-emitting diode according to claim 1, characterized in that: The six first openings adjacent to the same second opening form a hexagon.

3. The light-emitting diode according to claim 2, characterized in that: The second opening is located at the center of the hexagon, and the three closest second openings form an isosceles triangle.

4. The light-emitting diode according to claim 1, characterized in that: The diameter of the first opening is 2~50μm.

5. The light-emitting diode according to claim 1, characterized in that: The spacing between adjacent first openings is 1~20μm.

6. The light-emitting diode according to claim 1, characterized in that: The first opening is arranged in an array.

7. The light-emitting diode according to claim 1, characterized in that: The thickness of the insulating layer is greater than the thickness of the current spreading layer.

8. The light-emitting diode according to claim 1, characterized in that: The thickness of the current spreading layer is 5~60nm.

9. The light-emitting diode according to claim 1, characterized in that: It also includes a second insulating layer and a first electrode and a second electrode disposed on the second insulating layer. The second insulating layer is disposed on the reflective layer. The second insulating layer forms a first through-hole in a local defect area and a second through-hole above the second conductive semiconductor layer. The first electrode is connected to the first conductive semiconductor layer through the first through-hole, and the second electrode is electrically connected to the second conductive semiconductor layer through the second through-hole.

10. The light-emitting diode according to claim 9, characterized in that: The area of ​​the first electrode located above the current-spreading surface is larger than the area of ​​the first electrode located above the local defect region.

Images