Light-emitting diode and light-emitting device

Abstract

The present invention provides a light-emitting diode and a light-emitting device. The light-emitting diode includes: a semiconductor layer sequence including a first mesa and a second mesa, where the second mesa is a light-emitting mesa, i.e., the light-emitting region of the second mesa; a first contact electrode formed on the first mesa and electrically connected to the first semiconductor layer; a second contact electrode formed on the second mesa and electrically connected to the second semiconductor layer; the first mesa is a patterned structure having a densely distributed concavo-convex structure, and the concavo-convex structure has a first surface, a second surface higher than the first surface, and a side surface connecting the first surface and the second surface, wherein the first surface exposes the first semiconductor layer, and the first contact electrode is formed on this patterned structure and contacts the first surface, the second surface, and the side wall. The light-emitting diode of the present invention can effectively improve the light-emitting effect.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a light-emitting diode and a light-emitting device. Background Art

[0002] Semiconductor devices including compounds such as GaN, AlGaN, etc. have many advantages, such as a wide and easily adjustable bandgap energy, etc., and can be used differently as light-emitting devices, light-receiving devices, various diodes, etc.

[0003] In recent years, the great application value of ultraviolet LEDs has attracted great attention and become a new research hotspot. Ultraviolet LEDs use group III nitride semiconductor materials containing an Al component. However, the resistivity of nitrides semiconductors containing Al is relatively high, so that in the case of being used for an n-type semiconductor layer, the carrier injection efficiency is low. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a light-emitting diode and a light-emitting device, which can improve the injection efficiency of carriers of the light-emitting diode and improve the brightness.

[0005] In some embodiments, the present invention provides a light-emitting diode, comprising: a semiconductor layer sequence including a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, the semiconductor layer sequence having a first mesa and a second mesa, wherein the second mesa is a light-emitting region; a first contact electrode formed on the first mesa and electrically connected to the first semiconductor layer; a second contact electrode formed on the second mesa and electrically connected to the second semiconductor layer; the first mesa having a patterned structure, the patterned structure having a densely distributed concavo-convex structure, the concavo-convex structure having a first surface, a second surface protruding above the first surface, and a side surface connecting the first surface and the second surface, wherein the first surface exposes the first semiconductor layer, and the first contact electrode is formed on the patterned structure and contacts the first surface, the second surface, and the side wall. In some embodiments, a light-emitting diode includes: a semiconductor layer sequence including a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, an upper surface of the semiconductor layer having a patterned region, the patterned region being distributed with regularly arranged concavo-convex structures, the concavo-convex structures having a first surface, a second surface protruding above the first surface, and a side surface connecting the first surface and the second surface, wherein the first surface exposes the first semiconductor layer, the concavo-convex structures include a series of holes formed on the second surface or a series of columns formed on the first surface, a diameter of the concavo-convex structures being 1 to 20 μm and a pitch being 2 to 15 μm; a first contact electrode formed on the patterned structure and contacting the first surface, the second surface, and the side wall and electrically connected to the first semiconductor layer; a second contact electrode formed on the second semiconductor layer and electrically connected to the second semiconductor layer.

[0006] In some embodiments, the light-emitting diode includes a semiconductor layer sequence, which includes a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer between the first semiconductor layer and the second semiconductor layer. The upper surface of the semiconductor layer has a patterned region, and the patterned region is distributed with regularly arranged concavo-convex structures. The concavo-convex structures have a first surface, a second surface higher than the first surface, and a side surface connecting the first surface and the second surface. The first surface exposes the first semiconductor layer. The concavo-convex structures include a series of holes extending from the second surface to the first surface or a series of columns formed on the first surface. The diameter of the concavo-convex structures is 1-20 μm, and the pitch is 2-15 μm. A first contact electrode is formed on the patterned structure and is in electrical connection with the first semiconductor layer by contacting the first surface, the second surface, and the side wall. A second contact electrode is formed on the second semiconductor layer and is in electrical connection with the second semiconductor layer.

[0007] In some embodiments, the light-emitting diode includes: a semiconductor layer sequence, which includes a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer between the first semiconductor layer and the second semiconductor layer. The upper surface of the semiconductor layer has a patterned region, and the patterned region is distributed with regularly arranged concavo-convex structures. The concavo-convex structures have a first surface, a second surface higher than the first surface, and a side surface connecting the first surface and the second surface. The first surface exposes the first semiconductor layer. The concavo-convex structures include a series of holes extending from the second surface to the first surface or a series of columns formed on the first surface. A first contact electrode is formed on the patterned structure and is in electrical connection with the first semiconductor layer by contacting the first surface, the second surface, and the side wall. A second contact electrode is formed on the second semiconductor layer and is in electrical connection with the second semiconductor layer. The first semiconductor layer includes a first sub-layer having a first doping concentration and a second sub-layer having a second doping concentration. The first contact electrode contacts the first sub-layer, and the first surface is located in the first sub-layer, where the first doping concentration is greater than the second doping concentration.

[0008] The present invention also provides a light-emitting device, which includes any one of the foregoing light-emitting diodes.

[0009] Other features and beneficial effects of the present invention will be described in the following specification. And, partly, they will become apparent from the specification or be understood by implementing the present invention. The objectives and other beneficial effects of the present invention can be achieved and obtained through the structures specifically pointed out in the specification, claims, and other contents. Description of the Drawings

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings; in the following description of the positional relationship in the drawings, unless otherwise specified, the directions of the components shown in the drawings are taken as the reference.

[0011] Figure 1 It is a cross-sectional view of a light-emitting diode according to an exemplary embodiment of the present invention.

[0012] Figure 2 It is a top view of an exemplary embodiment of the present invention.

[0013] Figure 3 It is Figure 2 a partial enlarged view of area A in

[0014] Figure 4 It is a top view of a semiconductor layer sequence according to an exemplary embodiment of the present invention.

[0015] Figure 5 It is a top view of a patterned structure on a first mesa according to an exemplary embodiment of the present invention.

[0016] Figure 6 It is a cross-sectional view of a light-emitting diode according to an exemplary embodiment of the present invention.

[0017] Figure 7 It is Figure 5 a top view of the pad electrode of the light-emitting diode shown in

[0018] Figure 8 It is a cross-sectional view of a light-emitting diode according to an exemplary embodiment of the present invention.

[0019] Figure 9 It is a top view of an exemplary embodiment of the present invention.

[0020] Figure 10 It is a partial enlarged view of samples with four different designs.

[0021] Figure 11 It is the light output power distribution map (LOP Mapping in English) of different samples.

[0022] Figure 12 It is a cross-sectional view of a light-emitting diode according to an exemplary embodiment of the present invention.

[0023] Figure 13A cross-sectional view of a light-emitting diode according to an exemplary embodiment of the present invention.

[0024] Figure 14 A cross-sectional view of a light-emitting device according to an exemplary embodiment of the present invention.

[0025] The reference numerals in the figure denote the following:

[0026] 100: Light-emitting diode chip; 110: Substrate; 111: Aluminum nitride bottom layer; 120 Semiconductor layer sequence; 121: First semiconductor layer; 121a: First sub-layer; 121b: Second sub-layer; 121c: Third sub-layer; 121d: Fourth sub-layer; 122: Active layer; 123: Second semiconductor layer; 131: Isolation region; 132: Conductive region; 133: Pattern structure; 141: First contact electrode; 142: Second contact electrode; 151: First connection electrode; 152: Second connection electrode; 160: Insulating layer; 171: First pad; 172: Second pad; 200: Light-emitting device; 210: Encapsulation substrate; 221: First conductive layer; 222: Second conductive layer; M1: First mesa; M2: Second mesa; S11: First surface of the first mesa; S12: Second surface of the first mesa; S13: Sidewall of the first mesa; S20: Lower surface of the first semiconductor layer. Detailed implementation manners

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The technical features designed in different implementation manners of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0028] Figure 1 and 2 is a schematic structural diagram of a light-emitting diode disclosed in the first exemplary embodiment of the present invention, where Figure 2 is a top view, Figure 1 is a longitudinal cross-sectional schematic diagram taken along the Figure 2 cutting line A-A. The light-emitting diode includes a substrate 110, a semiconductor layer sequence formed on the upper surface of the substrate, and contact electrodes 141\142, where the semiconductor layer sequence has a first mesa M1 and a second mesa M2.

[0029] Specifically, the substrate 110 is used to support the semiconductor layer sequence. The substrate 110 is, for example, a sapphire substrate, and may also be a growth substrate capable of forming a III-nitride semiconductor film. Preferably, a layer of aluminum nitride is formed on the upper surface of the substrate 110 as the bottom layer 111, and the bottom layer 111 is in direct contact with the surface of the substrate. The thickness of the aluminum nitride layer 111 may be between 10 nm and 4 μm.

[0030] The semiconductor layer sequence 120 is formed on the aluminum nitride bottom layer 111, and sequentially includes a first semiconductor layer 121, a second semiconductor layer 123, and an active layer 122 located therebetween. For example, the first semiconductor layer 121 is an N-type layer, and the second semiconductor layer 123 is a P-type layer, and the two may also be inverted. In a specific embodiment, the first semiconductor layer 121 is, for example, an n-type AlGaN layer; the active layer 122 is a layer that emits a specific wavelength, and has a well layer and a barrier layer; the second semiconductor layer 123 is, for example, a p-type AlGaN layer or a p-type GaN layer, or a layer formed by laminating a p-type AlGaN layer and a p-type GaN layer.

[0031] Please refer to Figure 2 and 3 , where Figure 3 is Figure 2 a partial enlarged view of the A region of Figure 1 and 3 . In a specific embodiment, the semiconductor layer sequence 120 has a first mesa M1, a second mesa M2, and an isolation portion 131 located therebetween, so as to separate the first mesa M1 and the second mesa M2. The first mesa M1 is used to fabricate the first ohmic electrode 141, and the second mesa M2 serves as the light-emitting region. In some embodiments, the isolation groove can be formed as the isolation portion 131 by removing the second semiconductor layer 123 and the active layer 122 between the first mesa M1 and the second mesa M2, as shown in

[0032] In one embodiment, the light-emitting layer of the light-emitting diode emits ultraviolet light between 210 and 360 nm. The first semiconductor layer 121 is an Al-containing n-type semiconductor layer, and its current diffusion ability is weak. Therefore, in the plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the first mesa M1 to the projected area of the second mesa M2 is preferably 1:5 or more and 1:1 or less, and the first mesa M1 is preferably relatively uniformly distributed in the semiconductor layer sequence. In this way, the current uniformity of the n-type semiconductor layer can be improved, which is beneficial to improving the internal quantum efficiency of the light-emitting diode and helps to reduce the forward voltage of the light-emitting diode. When the area of the first mesa M1 region is too large, it will cause excessive loss of the active region area of the light-emitting diode, which is not conducive to the improvement of the light-emitting efficiency of the light-emitting diode.Figure 4 shows the layout of the first mesa M1 and the second mesa M2 of an exemplary embodiment of the present invention, wherein the first mesa M1 surrounds the second mesa M2 and has a plurality of finger-like structures extending into the interior of the second mesa M2, which helps to improve the current uniformity of the light-emitting diode. Of course, the distribution of the first mesa M1 is not limited to Figure 4 as shown and can be designed according to the actual chip size and shape.

[0033] In Figure 1 the light-emitting diode shown, the first mesa M1 includes a current conduction portion 132 and a patterned structure 133 located above the current conduction portion 132. The patterned structure 133 is a series of concavo-convex structures formed on the current conduction portion 132 and densely distributed. Specifically, the concavo-convex structure has a first surface S11 and a second surface S12 higher than the first surface. A part of the first mesa M1 removes the second semiconductor 123 and the active layer 122, exposing the surface S11 of the first semiconductor layer 121, forming a series of densely distributed hole structures 133, and the hole structures 133 constitute the concavo-convex structure, where the bottom surface of the hole is the first surface S11 of the first mesa.

[0034] The patterned structure 133 of the first mesa has a first surface S11 and a second surface S12 higher than the first surface. Control the distance D1 between the second surface S2 and the first surface S1 to be greater than or equal to more than half of the thickness of the first semiconductor layer, so that when carriers are injected into the light-emitting diode, they do not directly migrate to the active layer of the second mesa, but are transmitted to the first semiconductor layer of the second mesa through the current conduction portion of the first mesa, and then are fully expanded through the first semiconductor layer under the active layer of the second mesa, thereby mobilizing the carriers under the first semiconductor layer to participate in the movement, enabling more carriers in the n-type semiconductor layer to be effectively utilized, and further improving the injection efficiency of carriers. Preferably, the D1 can be between 60% and 95% of the thickness of the first semiconductor layer. The distance D1 is preferably greater than or equal to 0.6 μm, so that the carriers injected through the second surface of the first mesa flow into the corresponding first semiconductor layer under the second mesa through the current conduction portion, are fully expanded first, and finally uniformly flow into the active layer of the second mesa. In a specific embodiment, the D1 can take values of 0.5 - 3 μm, such as 600 nm, 1.2 μm, 1.8 μm, 2 μm or 2.5 μm.

[0035] The current conduction part 132 is located below the patterned structure 133 and is composed of the first semiconductor layer 121, and is used to transfer the carriers injected from the first mesa to the second mesa. The height D2 of the current conduction part 132 in the thickness direction of the semiconductor layer sequence can be adjusted according to the depth of the isolation part 131, so as to control the efficiency of carrier injection into the second mesa. In some embodiments, the height D2 of the current conduction part is preferably between 1 / 5 and 1 / 2 of the thickness of the first semiconductor layer 121. When the height D2 of the current conduction part 132 is too small, it will cause congestion when the carriers reach the current conduction part 131, thus reducing the injection of carriers; when the height of the current conduction part in the thickness direction is too large, it is not conducive to the expansion of carriers. In some embodiments, the doping concentration of the current conduction part 132 is 5×10 18 / cm 3 or more, and its height D2 in the thickness direction can be 0.2~1μm, for example, it can be 0.3~0.6μm. In the structure shown in Figure 1 , the bottom of the isolation part 131 is between the active layer 122 and the first surface S11 and higher than the first surface S11. When the light-emitting diode is powered on, among the carriers injected through the first mesa M1, the part in the area near the second mesa can directly migrate through the first semiconductor layer 121 under the isolation part to the first semiconductor layer of the second mesa. Therefore, the height D2 of the current conduction part 132 can be appropriately reduced (that is, the depth of the hole 133 is increased). At this time, D2 is preferably 200~500nm (for example, 300nm). In this way, on the one hand, it is beneficial to increase the contact area between the contact electrode 141 and the first semiconductor layer 121, and at the same time, the carriers injected through the second surface S12 of the first mesa are fully expanded first, and then flow into the corresponding first semiconductor layer under the second mesa through the current conduction part, and finally uniformly flow into the active layer of the second mesa. In some other embodiments, the bottom of the groove 131 is basically at the same height as the first surface S11. When the light-emitting diode is powered on, all the carriers injected through the first mesa M1 need to be transferred to the second mesa through the current conduction part 132 under the patterned structure 133. At this time, the height D2 of the current conduction part 132 is preferably 400~900nm, for example, it can be 600nm or 800nm.

[0036] In the above-mentioned light-emitting diode, the diameter and spacing of the holes 133 are controlled so as to be densely distributed on the first mesa M1. Specifically, on a plane perpendicular to the thickness direction of the semiconductor layer sequence 120, the ratio of the projected area of the first surface S11 to the projected area of the first mesa M1 is preferably greater than 0.3, the diameter of the hole 133 can be 1~10μm, and the spacing between adjacent holes is 2~15μm. In a specific embodiment, the ratio of the projected area of the first surface S11 to the projected area of the first mesa M1 can be 0.5 to 0.8, the diameter of the hole 133 can be 1.5 to 4μm, and the spacing between the holes is 5μm, which is conducive to forming a good hole structure and helps to form a contact electrode 141 in the hole.

[0037] The first ohmic contact electrode 141 is formed on the plurality of first mesas M1, and contacts the upper surface S12 of the first mesas M1, and the bottom and sidewall of the hole 133, and forms an ohmic contact with the first semiconductor layer 121. The second contact electrode 142 is formed on the second semiconductor layer 123, and forms an ohmic contact with the second semiconductor layer 123. In some embodiments, on a plane perpendicular to the thickness direction of the semiconductor layer sequence 120, the ratio of the projected area of the first contact electrode 141 to the projected area of the first mesas M1 is preferably greater than 0.4 and less than 0.9, so that the contact area between the first contact electrode 141 and the first semiconductor layer 121 can be ensured, and the photoelectric performance of the light-emitting diode can be improved.

[0038] In a specific embodiment, the first contact electrode 141 is formed on the first table M1 in contact, and forms an ohmic contact with the first surface S11 of the first table. The first contact layer 131 is selected from one or more of Cr, Pt, Au, Ni, Ti, and Al. Since the first semiconductor layer has a high Al component, the first contact electrode 141 needs to be fused at high temperature to form an alloy after being deposited on the table, so as to form a good ohmic contact with the first semiconductor layer, for example, it can be Ti-Al-Au alloy, Ti-Al-Ni-Au alloy, Cr-Al-Ti-Au alloy, Ti-Al-Au-Pt alloy, etc. The second contact electrode 142 is formed on the surface S3 of the second table M2 in contact, and forms an ohmic contact with the second semiconductor layer. Preferably, the material of the contact electrode 142 can be an oxide transparent conductive material or a metal alloy such as NiAu, NiAg, NiRh, etc., and its thickness is preferably less than 30nm, so as to reduce the light absorption rate of the layer as much as possible. In a preferred embodiment, the wavelength emitted by the active layer is below 280nm, the contact electrode 142 is ITO, and the thickness is 5-20nm, for example, 10-15nm. At this time, the absorption rate of the ITO layer for the light emitted by the active layer can be reduced to less than 40%.

[0039] In the above light-emitting diode, the semiconductor layer sequence 120 is divided into a first mesa M1 and a second mesa M2, and a groove is provided between the first mesa M1 and the second mesa M2 as the isolation portion 131. The upper surface S12 of the first mesa M1 is substantially flush with the upper surface of the second mesa M2. A series of hole structures 133 extending from the upper surface S12 to the first semiconductor layer are formed on the first mesa M1. The hole structures are densely distributed and penetrate into the first semiconductor layer 121. In a specific embodiment, the thickness of the first semiconductor layer 121 may be 1.5 - 3.5 μm, and the distance between the bottom surface S12 of the series of holes 133 and the upper surface of the first semiconductor layer is preferably greater than 500 nm, such as 1.2 μm, 1.8 μm, 2 μm, 2.5 μm or 3 μm. Preferably, the distance is greater than 1 - 3 μm, so that the carriers injected through the second surface are fully expanded first, and then flow into the corresponding first semiconductor layer below the second mesa through the current conduction portion 132, and finally uniformly flow into the active layer of the second mesa, thereby improving the photoelectric conversion efficiency of the light-emitting diode.

[0040] See the appendix Figure 6 , in some embodiments, the light-emitting diode 100 is a flip-chip light-emitting diode. The light-emitting diode 100 may further include a first connection electrode 151, a second connection electrode 152, an insulating layer 160, a first pad 171 and a second pad 172, as Figure 8 shown. The first connection electrode 151 is formed on the first contact electrode 141, and the second connection electrode 152 is formed on the second contact electrode 142. The connection electrode is preferably a multi-layer metal stack, for example, an adhesion layer, a conductive layer, etc. are sequentially deposited on the contact electrode. Preferably, the first connection electrode 151 completely covers the first contact electrode 141, which can increase the height of the mesa area on the one hand and protect the first contact electrode 141 on the other hand.

[0041] The insulating layer 160 is formed on the connection electrode 152 and the side surface of the semiconductor layer sequence to insulate the first connection electrode 151 and the second connection electrode 152. The insulating layer 160 has openings to expose the first connection electrode 151 and the second connection electrode 152.

[0042] The first pad 171 and the second pad 172 are located on the insulating layer 160 and are electrically connected to the first connection electrode 151 and the second connection electrode 152 through openings respectively. The first pad electrode 171 and the second pad 172 can be formed together using the same material in the same process, so they can have the same layer structure. The materials of the first and second pads can be selected from one or more of Cr, Pt, Au, Ni, Ti, Al, and AuSn. Preferably, the first pad 171 is located above the first mesa, and the second pad 172 is located above the second mesa. Since the upper surface S12 of the first mesa is flush with the upper surface of the second mesa, the thrust of the pad electrodes can be increased, improving the reliability of the light-emitting diode. As Figure 7 shown, in some embodiments, the projection of the first pad 171 on the semiconductor layer sequence 120 is a rectangle, and the projection of the second pad 172 on the semiconductor layer sequence 120 includes a main body portion and several arm portions extending towards the first pad. This avoids the overlap or intersection of the second pad 172 and the first contact electrode 141 in the thickness direction, which is beneficial to improving the reliability of the light-emitting diode.

[0043] Figure 9 shows a schematic structural diagram of a light-emitting diode disclosed in the second exemplary embodiment of the present invention, and its top view can be referred to Figure 9 .

[0044] Please refer to Figure 9 . Different from Embodiment 1, the first mesa M1 of this light-emitting diode has a first surface S11 that exposes the first semiconductor layer and densely distributed columns 133 formed on the first surface. The top surface of the column constitutes the second surface S12 of the first mesa. Preferably, the diameter of the column 133 is 2 - 20 μm, for example, it can be 3 - 10 μm, and the spacing between adjacent columns can be 2 - 15 μm. On the one hand, it increases the contact area between the first contact electrode 141 and the first semiconductor layer 121, improving the current injection efficiency. On the other hand, it can act as a light guide column to scatter the light reflected from the substrate, enhancing the light extraction efficiency of the light-emitting diode. Further, in a plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the first surface to the projected area of the first mesa is 0.5 or more, preferably between 0.5 and 0.85, to ensure the contact area between the first contact electrode 141 and the first surface S11.

[0045] In this embodiment, the distance D1 between the first surface and the second surface of the first mesa is preferably 1 to 2.5 μm, ensuring that after the carriers injected through the first surface S11 of the first mesa flow into the corresponding first semiconductor layer below the second mesa through the current conduction portion, they are fully expanded first and then uniformly flow into the active layer of the second mesa. When the distance D1 is too small, when the light-emitting diode injects carriers, it is easy for the carriers to directly migrate to the active layer of the second mesa, and it is difficult to effectively improve the carrier injection efficiency; when the distance D1 is too large, it will cause congestion of the carriers injected from the first mesa when passing through the current conduction portion, reducing the carrier injection efficiency.

[0046] In some embodiments, the first semiconductor layer 121 has an n-type doping and may include a highly doped layer and a lowly doped layer, where the lowly doped layer is located between the active layer and the highly doped layer, thereby better confining the carriers in the active layer. The doping concentration of the lowly doped layer is preferably less than 1×10 18 / cm 3 , for example, it can be 2×10 17 / cm 3 to 1×10 18 / cm 3 and its thickness can be between 20 and 100 nm. The doping concentration of the highly doped layer is usually 5×10 18 / cm 3 or more, preferably 1×10 19 / cm 3 or more, for example, it can be 1×10 19 / cm 3 ~5×10 19 / cm 3 . The first surface S11 of the first mesa is preferably located in the highly doped layer, which is beneficial to forming a good ohmic contact between the first contact electrode 141 and the first semiconductor layer 121 on the first surface S11. Further, an extended layer can be inserted between the lowly doped layer and the highly doped layer. The doping concentration of the extended layer is 2×10 18 / cm 3 or more, for example, it can be 5×10 18 / cm 3 ~3×10 19 / cm 3 , which can better balance the crystal quality of the first semiconductor layer and the carrier expansion ability. The carriers injected from the first surface of the first mesa are transmitted to the highly doped layer of the second mesa through the current conduction portion, then laterally expanded through the extended layer, and finally uniformly flow into the active layer.

[0047] The light-emitting diodes disclosed in the above exemplary embodiments can improve the carrier injection efficiency of the n-type AlGaN semiconductor layer, thereby improving the light-emitting efficiency. Next, the light output efficiencies of different embodiments are compared. First, four samples ST, RD1 to RD3 with different structures are fabricated on the same epitaxial wafer and tested. Specifically, these four samples have the same distribution of the second mesa M2 (the distribution diagram is referenced Figure 4 ), where ST is a conventional light-emitting diode, and its first mesa M1 is a platform structure that exposes the first semiconductor layer. The first mesas M1 of RD1 and RD2 both adopt the structure shown in Figure 1 , and the first mesa M1 of RD3 adopts the structure shown in Figure 8 . Figure 10 is a partial enlarged view of the four samples, which shows the pattern of the first mesa. Among them, the diameter of the hole 133 in RD1 is about 1.8 μm, and the pitch is about 2 μm; the diameter of the hole 133 in RD2 is about 5 μm, and the pitch is about 6 μm; the diameter of the cylinder 133 in RD3 is about 5 μm, and the pitch is about 6 μm. Further, the influence of different depths of the first surface of the first mesa of the above four designs on the light output efficiency is respectively compared. Here, the depth refers to the height difference between the first surface S11 and the second surface S12. In the ST structure, the depth is the height difference between the upper surface of the first mesa and the upper surface of the second semiconductor layer.

[0048]

[0049] Table 1 shows the differences in the light output efficiencies of different samples. It can be seen that compared with the ST structure of the prior art, the light output efficiencies of the RD1 to RD3 structures are all improved. Further, it can be seen that in the exemplary embodiment shown in Figure 1 , the holes 133 on the first mesa are arranged more densely, which is more conducive to improving the light output efficiency of the light-emitting diode. At the same time, the improvement of the light output efficiency of the light-emitting diode is also related to the position of the first surface of the first mesa. Compared with the light-emitting diode shown in Figure 8 , appropriately increasing the depth of the first surface of the first mesa in the light-emitting diode shown in Figure 1 is more conducive to improving the light output efficiency of the light-emitting diode.

[0050] Figure 11 illustrates the light output power distribution diagram (abbreviated as LOP Mapping in English) of the LEDs of the above four samples. Among them, the shade of gray represents the magnitude of the brightness, and the darker it is, the greater the brightness. It can be seen from the figure that the light output power of sample RD2 is improved compared with sample ST, and the light output powers of samples RD1 and RD3 are significantly improved.

[0051] Figure 12Shows a schematic structural diagram of a light-emitting diode disclosed in the third exemplary embodiment of the present invention. For its top view, reference can be made to Figure 9 .

[0052] Please refer to the attached Figure 12 , different from the light-emitting diode shown in Figure 8 : The second surface S12 of the first mesa of the light-emitting diode disclosed in this embodiment is located in the first semiconductor layer 121, that is, the second surface S12 of the first mesa is lower than the upper surface of the second mesa. Specifically, a part of the second semiconductor layer 123 and the active layer 122 in a part of the semiconductor layer sequence 120 can be etched first to expose a part of the first semiconductor layer 121 to form the first mesa M1, and then a part of the first mesa M1 is etched to a certain depth to form a series of pillar structures 133, thereby forming a patterned structure on the first mesa M1. In a specific implementation mode, the upper surface S12 of the first mesa is lower than the lower surface of the active layer, that is, the first mesa is located below the active layer.

[0053] In a specific embodiment, the first semiconductor layer 121 has n-type doping. The first semiconductor layer of the second mesa sequentially includes a first sub-layer 121a with a first doping concentration C1, a second sub-layer 121b with a second doping concentration C2, and a third sub-layer 121c with a third doping concentration C3 from bottom to top, where C1 > C2 > C3. The doping concentration C1 of the first sub-layer 121a is usually 5×10 18 / cm 3 or more, preferably 1×10 19 / cm 3 or more. For example, it can be 1×10 19 / cm 3 ~5×10 19 / cm 3 . The first surface S11 of the first mesa is preferably located in the first sub-layer 121a, which is beneficial to the first contact electrode 141 forming a good ohmic contact with the first semiconductor layer 121 at the first surface S11; the doping concentration of the second sub-layer 121b can be 2×10 18 / cm 3 or more. For example, it can be 5×10 18 / cm 3 ~3×10 19 / cm 3, it can better balance the crystal quality of the first semiconductor layer 121 and the carrier expansion ability, enabling the carriers injected from the first surface S11 of the first mesa M1 to be transmitted to the first sub-layer of the second mesa through the current conduction part, then expanded through the second sub-layer, and finally evenly flow into the active layer; the third sub-layer 121c is located between the second sub-layer 121b and the active layer 122, and is used to preferably confine the carriers in the active layer. The doping concentration C3 of the third sub-layer 121c is preferably lower than 1×10 18 / cm 3 , for example, it can be 2×10 17 / cm 3 to 1×10 18 / cm 3 between, and its thickness can be between 20 and 100 nm.

[0054] In the light-emitting diode described in this exemplary embodiment, by setting the upper surface S12 of the first mesa M1 at a position lower than the active layer, the light absorption effect of the second semiconductor layer and the active layer of the first mesa can be reduced. At the same time, a series of patterned structures are formed on the first mesa. On the one hand, this patterned structure can act as a light guide column to scatter the light reflected from the substrate, improving the light extraction efficiency of the light-emitting diode; on the other hand, the ohmic contact surface between the first contact electrode 141 and the first mesa (i.e., the first surface S11 of the first mesa) is set in the highly doped layer at the bottom of the first semiconductor layer, which can prevent the current injected from the first mesa from directly migrating to the active layer of the second mesa. Instead, it flows into the corresponding first sub-layer below the second mesa through the current conduction part below the first mesa, then undergoes sufficient diffusion through the second sub-layer, and mobilizes the carriers in the second sub-layer to participate in the movement, enabling more carriers in the n-type AlGaN semiconductor layer to be effectively utilized, and finally evenly flowing into the active layer of the second mesa, thereby improving the carrier injection efficiency and the photoelectric conversion efficiency of the light-emitting diode.

[0055] Figure 13 shows a schematic structural diagram of a light-emitting diode disclosed in the fourth exemplary embodiment of the present invention, and its top view can be referred to Figure 2 .

[0056] Please refer to Figure 13 , different from the light-emitting diode shown in Figure 12 : In this embodiment, the patterned structure of the first mesa of the light-emitting diode is a series of hole structures 133 extending downward from the upper surface S12 of the first mesa, and the first contact electrode 141 covers the upper surface S12 of the first mesa, the side walls of the holes, and the bottom surface S11 of the holes.

[0057] In a specific embodiment, the first semiconductor layer has n-type doping. The first semiconductor layer of the second mesa includes, from bottom to top, a first sub-layer 121a, a second sub-layer 121b, a fourth sub-layer 121d, and a third sub-layer 121c. Among them, the first sub-layer, the second sub-layer, and the third sub-layer may be set with reference to the third exemplary embodiment. The fourth sub-layer 121d is located between the second sub-layer and the third sub-layer, and the doping concentration is generally 5×10 18 / cm 3 or more, preferably 1×10 19 / cm 3 or more. For example, it can be 1×10 19 / cm 3 ~5×10 19 / cm 3 . The upper surface of the first mesa is preferably located in the fourth sub-layer, which is beneficial to forming a good ohmic contact between the first contact electrode 141 and the first semiconductor layer 121 on the second surface S12; the bottom surface of the hole (i.e., the first surface S11) is located in the first sub-layer, and the first sub-layer with a higher doping concentration can promote the rapid migration of carriers through the current conduction part 132 to the second mesa. The fourth sub-layer is located between the contact electrode and the current conduction part, and a sufficient thickness (preferably more than 1μm) is required for carrier diffusion. Therefore, a lower doping concentration can better balance the crystal quality of the first semiconductor layer and the carrier expansion ability.

[0058] In a modified embodiment, the first mesa M1 of the light-emitting diode includes a complete first semiconductor layer 121 and a part of the active layer 122, that is, the upper surface S12 of the first mesa is located in the active layer 122. Specifically, the active layer 122 may have n-type doping, such as Si doping, and its doping depth is preferably 1×10 18 / cm 3 or more, preferably 1×10 18 / cm 3 to 1×10 19 / cm 3 between. For example, it can be 2×10 18 / cm 3 or 5×10 18 / cm 3 etc. In this modified embodiment, by appropriately adding n-type doping to the active layer, on the one hand, it is beneficial to increase the electron concentration in the active layer and thus improve the internal quantum efficiency, and on the other hand, it enables the active layer to be suitable for directly fabricating the first contact electrode with good ohmic contact. In this variant embodiment, the first semiconductor layer 121 may be set with reference to the third exemplary embodiment.

[0059] The bandgap of 122 is lower than that of the first semiconductor layer 122, which is more conducive to forming a good ohmic contact between the first contact electrode 141 and the upper surface S12 of the first mesa [z1].

[0060] In a specific embodiment, the semiconductor layer sequence may include a confinement layer (not shown in the figure) disposed between the active layer 122 and the second semiconductor layer 123. The confinement layer preferably has a high Al component and is lightly doped or undoped, and its thickness is preferably less than 50 nm, which can limit the diffusion of the doping elements of the second semiconductor layer into the active layer and improve the optoelectronic performance of the light-emitting diode.

[0061] See Figure 14 , this embodiment discloses a light-emitting device 200, in which the die uses the light-emitting diode of the first embodiment above. The light-emitting diode 100 is fixed on the circuit board 210. The circuit board is provided with a first conductive layer 221 and a second conductive layer 222. The first conductive layer and the second conductive layer are isolated from each other. The first pad electrode 171 of the light-emitting diode is disposed on the first conductive layer 221 and is electrically connected to the first conductive layer 221. The second pad electrode 172 of the light-emitting diode is disposed on the second conductive layer 222 and is electrically connected to the second conductive layer 222.

[0062] In this embodiment, increasing the distance between the upper surface of the first mesa and the lower surface of the first semiconductor layer can improve the carrier injection efficiency of the n-type AlGaN semiconductor layer, and thus improve the light-emitting efficiency of the light-emitting device. Further, reducing the height difference between the first mesa and the second mesa can reduce the thrust of the electrodes when fabricating the pad electrodes on the first mesa and the second mesa.

[0063] In this embodiment, the light-emitting diode and the circuit board are taken as a whole. Since the areas of the first pad electrode 171 and the second pad electrode 172 are close, it is beneficial for the overall product to have better thrust and reliability under the same conditions.

[0064] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A light-emitting diode, comprising: A semiconductor layer sequence including a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, the semiconductor layer sequence having a first mesa and a second mesa, wherein the second mesa is a light-emitting region; A first contact electrode formed on the first mesa and electrically connected to the first semiconductor layer; A second contact electrode formed on the second mesa and electrically connected to the second semiconductor layer; Characterized in that: the first mesa has a patterned structure, the patterned structure has a densely distributed concavo-convex structure, the concavo-convex structure has a first surface, a second surface protruding from the first surface, and a sidewall connecting the first surface and the second surface, wherein the first surface exposes the first semiconductor layer, and the first contact electrode is formed on the patterned structure and contacts the first surface, the second surface and the sidewall; The distance between the second surface and the first surface is greater than or equal to half of the thickness of the first semiconductor layer.

2. The light-emitting diode according to claim 1, wherein: The patterned structure of the first mesa is a series of columns formed on the first surface, and the top surface of the columns constitutes the second surface.

3. The light-emitting diode according to claim 2, wherein: The diameter of the columns is 2 to 20 μm, and the distance between adjacent columns is 2 to 15 μm.

4. The light-emitting diode according to claim 1, characterized in that: The patterned structure of the first mesa is a series of holes extending from the second surface to the first surface, the bottom surface of the holes constitutes the first surface, and there is an isolation region between the first mesa and the second mesa to separate the first mesa and the second mesa.

5. The light-emitting diode according to claim 4, characterized in that: The diameter of the holes is 1 to 10 μm, and the distance between adjacent holes is 2 to 15 μm.

6. The light-emitting diode according to claim 1, wherein: The first semiconductor layer has a lower surface away from the active layer, and the distance from the first surface to the lower surface of the first semiconductor layer is 200 to 500 nm.

7. The light-emitting diode according to claim 1, wherein: The first semiconductor layer includes a first sub-layer having a first doping concentration and a second sub-layer having a second doping concentration, the first contact electrode contacts the first sub-layer, and the first surface is located in the first sub-layer, wherein the first doping concentration is greater than the second doping concentration.

8. The light-emitting diode according to claim 1, wherein: The first semiconductor layer includes a first sub-layer having a first doping concentration and a third sub-layer having a third doping concentration. The first contact electrode contacts the first sub-layer. The third sub-layer is located between the first sub-layer and the active layer, and the doping concentration of the third sub-layer is lower than 1×10 18 / cm 3 .

9. The light-emitting diode according to claim 1, wherein: The first semiconductor layer sequentially includes a first sub-layer having a first doping concentration C1, a second sub-layer having a second doping concentration C2, and a third sub-layer having a third doping concentration C3, the first contact electrode contacts the first sub-layer, and C1 > C2 > C3.

10. The light-emitting diode according to claim 9, characterized in that: The first semiconductor layer further includes a fourth sub-layer having a fourth doping concentration C4, the fourth sub-layer being located between the second sub-layer and the third sub-layer, and the second doping concentration C2 being 2×10 18 / cm 3 or more; the fourth doping concentration C4 being 5×10 18 / cm 3 or more.

11. The light-emitting diode according to claim 1, characterized in that: The wavelength of the light-emitting diode is 210 nm to 360 nm.

12. The light emitting diode according to claim 1, characterized in that: It further includes an insulating layer, a first pad electrode and a second pad electrode, the insulating layer is formed on the first and second contact electrodes and covers the first mesa and the second mesa, having a first opening and a second opening, the first pad electrode is electrically connected to the first contact electrode through the first opening, and the second pad electrode is electrically connected to the second contact electrode through the second opening.

13. The light-emitting diode according to claim 1, wherein: It further includes a first connection electrode, a second connection electrode, an insulating layer, a first pad electrode, and a second pad electrode. The first connection electrode is electrically connected to the first contact electrode, and the second connection electrode is electrically connected to the second contact electrode. The insulating layer is formed on the first and second connection electrodes and has a first opening and a second opening. The first opening exposes the first connection electrode, and the second opening exposes the second connection electrode. The first pad electrode and the second pad electrode are formed on the insulating layer. The first pad electrode is electrically connected to the first connection electrode through the first opening, and the second pad electrode is electrically connected to the second connection electrode through the second opening.

14. The light-emitting diode according to claim 1, wherein: The first mesa surrounds the second mesa.

15. The light-emitting diode according to claim 1, characterized in that: The height of the patterned structure is 500 to 3000 nm.

16. The light-emitting diode according to claim 1, wherein: The distance from the first surface to the active layer is 500 nm or more.

17. The light emitting diode according to claim 1, wherein: In a plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the first mesa to the projected area of the second mesa is 0.2 or more and 1 or less.

18. The light-emitting diode according to claim 1, wherein: In a plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the first contact electrode to the projected area of the first mesa is 0.4 or more and 0.9 or less.

19. The light-emitting diode according to claim 1, characterized in that: In a plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the first surface to the projected area of the first mesa is 0.3 or more.

20. A light-emitting diode, characterized in that: Comprising: A semiconductor layer sequence including a first semiconductor layer having a first conductivity type, a second semiconductor layer having a second conductivity type different from the first conductivity type, and an active layer between the first semiconductor layer and the second semiconductor layer. The upper surface of the semiconductor layer has a patterned structure, and the patterned structure has regularly arranged concavo-convex structures. The concavo-convex structures have a first surface, a second surface higher than the first surface, and sidewalls connecting the first surface and the second surface. The first surface exposes the first semiconductor layer. The concavo-convex structures include a series of holes extending from the second surface to the first surface or a series of columns formed on the first surface. A first contact electrode formed on the patterned structure and making electrical contact with the first surface, the second surface, and the sidewalls to form an electrical connection with the first semiconductor layer. A second contact electrode formed on the second semiconductor layer and making an electrical connection with the second semiconductor layer.

21. The light-emitting diode according to claim 20, wherein: It further includes a first connection electrode, a second connection electrode, a second insulating layer, a first pad electrode, and a second pad electrode. The first connection electrode is electrically connected to the first contact electrode, and the second connection electrode is electrically connected to the second contact electrode. The second insulating layer is formed on the first and second connection electrodes and has a first opening and a second opening. The first opening exposes the first connection electrode, and the second opening exposes the second connection electrode. The first pad electrode and the second pad electrode are formed on the insulating layer. The first pad electrode is electrically connected to the first connection electrode through the first opening, and the second pad electrode is electrically connected to the second connection electrode through the second opening.

22. The light-emitting diode according to claim 21, wherein: On a plane perpendicular to the thickness direction of the semiconductor layer sequence, the ratio of the projected area of the hole or the column to the projected area of the patterned structure is 0.3 or more.

23. The light emitting diode according to claim 20, wherein: The first semiconductor layer includes at least a first sub-layer having a first doping concentration and a second sub-layer having a second doping concentration. The first contact electrode is in direct contact with the first sub-layer, and the first surface is located in the first sub-layer, where the first doping concentration is greater than the second doping concentration.

24. The light-emitting diode according to claim 20, wherein the diameter of the concavo-convex structure is 1 to 20 μm and the pitch is 2 to 15 μm.

25. The light emitting diode according to claim 23, wherein: The first semiconductor layer further includes a third sub-layer having a third doping concentration, and the third sub-layer is between the first sub-layer and the active layer, and the third doping concentration is lower than the second doping concentration.

26. The light-emitting diode according to claim 25, wherein: The doping concentration of the third sub-layer is equal to or less than 1×10 18 / cm 3 .

27. The light-emitting diode according to claim 23, wherein: The first doping concentration is 5×10 18 / cm 3 or higher; the second doping concentration is 2×10 18 / cm 3 or higher.

28. A light-emitting device, characterized in that, Use the light-emitting diode according to any one of claims 1 to 27.

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