Light-emitting diode

Abstract

The light-emitting diode disclosed in the present application includes: a semiconductor stack including a first semiconductor layer, a second semiconductor layer, and an active layer located therebetween, which are sequentially stacked; a first electrode and a second electrode, which are respectively formed on the first semiconductor layer or the second semiconductor layer, and the first electrode and the second electrode have a first surface in contact with the first semiconductor layer or the second semiconductor layer, a second surface opposite to the first surface, and a side surface connecting the first surface and the second surface; an insulating layer including being formed on the second surface and the side surface of the first electrode or the second electrode, and the insulating layer has a plurality of first openings exposing a part of the second surface of the first electrode or the second electrode; a protection electrode, which is in contact with the second surface of the first electrode or the second electrode through the first opening and covers the insulating layer formed on the side surface of the first electrode or the second electrode.

Description

Technical Field

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

[0002] A light emitting diode (abbreviation: LED, English: Light Emitting Diode) is a semiconductor device that forms light by releasing energy during carrier recombination. The LED has many advantages such as low power consumption, pure chromaticity, long lifespan, small size, fast response time, energy conservation and environmental protection, and is widely used in lighting, visible light communication, light emitting display and other scenarios.

[0003] In the structure of a light emitting diode, silicon dioxide (SiO2) is generally used as the surface insulating layer, but the insulating layer does not have high density and has poor adhesion to metal. During application, water vapor and electrolytes can penetrate in, which will cause the insulating layer to peel off from the electrode in the long term, resulting in the deterioration of the coverage of the metal electrode. Further, the metal atoms lose the blocking protection effect of the insulating layer and are extremely likely to migrate under the action of an electric field. The migration direction is from the P electrode to the N electrode, that is, consistent with the direction of the electric field, as Figure 1 shown in the common metal migration phenomenon. Relatively active Cr, Al in the metal electrode and even the most abundant Au will migrate. The continuous migration is extremely likely to cause leakage at the edge of the quantum well or even short circuit the light emitting diode. Further, the aggravation of the migration of Cr and Al leads to the peeling off of the electrode. Therefore, how to prevent the insulating layer from peeling off from the electrode is extremely important. Summary of the Invention

[0004] The light emitting diode according to an embodiment disclosed in the present application includes: a semiconductor stack including a first semiconductor layer, a second semiconductor layer stacked in sequence, and an active layer located therebetween; a first electrode and a second electrode respectively formed on the first semiconductor layer or the second semiconductor layer, the first electrode and the second electrode having a first surface in contact with the first semiconductor layer or the second semiconductor layer, a second surface opposite to the first surface, and a side surface connecting the first surface and the second surface; an insulating layer including formed on the second surface and the side surface of the first electrode or the second electrode, the insulating layer having a plurality of first openings exposing a part of the second surface of the first electrode or the second electrode; a protection electrode in contact with the second surface of the first electrode or the second electrode through the first opening and covering the insulating layer formed on the side surface of the first electrode or the second electrode. Brief Description of the Drawings

[0005] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show certain embodiments of the present application, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0006] Figure 1 SEM diagram of an existing product;

[0007] Figure 2 Cross-sectional schematic diagram of an embodiment of a light-emitting diode in the present invention;

[0008] Figure 3 is Figure 2 Enlarged schematic diagram of partial A;

[0009] Figure 4 Cross-sectional schematic diagram of another embodiment of a light-emitting diode in the present invention;

[0010] Figure 5 Cross-sectional schematic diagram of another embodiment of a light-emitting diode in the present invention.

[0011] Reference numerals:

[0012] 110 Substrate; 120 Semiconductor stack; 121 First semiconductor layer; 122 Active layer; 123 Second semiconductor layer; 130 Current spreading layer; 141 First electrode; 142 Second electrode; 141a, 142a First metal layer; 141b, 142b Second metal layer; 141c, 142c Third metal layer; 141d, 142d Fourth metal layer; 150 Insulating layer; 160 Protection electrode; 161 First layer; 162 Second layer; 160a First part; 160b Second part; OP1 First opening; S1 First surface; S2 Second surface; S3 Side surface. Detailed implementation manners

[0013] Please refer to Figure 2 , Figure 2 which is a cross-sectional schematic diagram of an embodiment of a light-emitting diode in the present invention. An embodiment of the present invention provides a light-emitting diode, which may include a substrate 110, a semiconductor stack 120, a current spreading layer 130, a first electrode 141, a second electrode 142, an insulating layer 150, and a protection electrode 160.

[0014] The semiconductor stack 120 includes a first semiconductor layer 121, an active layer 122 (also referred to as a light-emitting layer 122 or an active layer 122), and a second semiconductor layer 123 that are sequentially stacked on the substrate 110 along the stacking direction.

[0015] The substrate 110 may be an insulating substrate, preferably made of a transparent material, a translucent material, or an opaque material. In the illustrated embodiment, the substrate 110 is a sapphire (Al2O3) substrate. In some embodiments, the substrate 110 may be a patterned sapphire substrate, but is not limited thereto. The substrate 110 may also be made of a conductive or semiconductor material. For example, the substrate 110 may be at least one of silicon carbide (SiC), silicon (Si), magnesium aluminate (MgAl2O4), magnesium oxide (MgO), lithium aluminate (LiAlO2), lithium gallate (LiGaO2), and gallium nitride (GaN). In some embodiments, the substrate 110 may be thinned or removed to form a thin-film LED light-emitting diode.

[0016] In some embodiments, the upper surface of the substrate 110 may have a patterned structure (not shown in the figure), which can improve the external light extraction efficiency and crystallinity of the semiconductor stack 120. Optionally, the patterned structure on the upper surface of the substrate 110 may be formed in various shapes, such as a platform, a cone, a triangular pyramid, a hexagonal pyramid, a conical-like shape, a triangular pyramid-like shape, or a hexagonal pyramid-like shape, etc. Additionally, the patterned structure on the upper surface of the substrate 110 may be selectively formed in each region or may be omitted. The material of the patterned structure may be the same as the material of the substrate 110 or may be different from the material of the substrate 110. For example, selecting a material with a refractive index lower than that of the substrate 110 for the patterned structure is more beneficial for light extraction, and it may be SiO2 or the like.

[0017] Further, in this specification, the upper and lower positions are defined with the position of the substrate 110 as the boundary. It is assumed that the direction close to the substrate 110 is downward, and the direction away from the substrate 110 is upward. The setting of the upper and lower positions in this specification is only for explaining the positional relationship of each component in the illustrated embodiment and does not represent an indication or imply that it must have a specific orientation.

[0018] The semiconductor stack 120 may be formed on the substrate 110 by methods such as metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy (HVPE), physical vapor deposition, or ion plating methods. Specifically, the substrate 110 has opposite upper and lower surfaces, and the semiconductor stack 120 is formed on the upper surface of the substrate 110. Among them, the first semiconductor layer 121 may grow from the upper surface of the substrate 110, and the active layer 122 and the second semiconductor layer 123 are sequentially stacked and grown on the upper surface of the first semiconductor layer 121. In some other embodiments, the semiconductor stack 120 may also be formed on the substrate 110 through a bonding layer, and the bonding layer is preferably a light-transmissive material.

[0019] The semiconductor stack 120 can provide light with a specific central emission wavelength, such as blue light, green light, red light, violet light, or ultraviolet light. In the illustrated embodiment, the semiconductor stack 120 providing blue light is taken as an example for illustration. In the illustrated embodiment, the first semiconductor layer 121 in the semiconductor stack 120 is an N-type semiconductor layer, which can provide electrons to the active layer 122 under the action of a power supply. In some embodiments, the N-type semiconductor layer in the first semiconductor layer 121 includes an N-type doped nitride layer. The N-type doped nitride layer may include N-type impurities of one or more Group IV elements. The N-type impurities can be one or a combination of Si, Ge, and Sn.

[0020] In some embodiments, the active layer 122 can be a multiple quantum wells (MQWs) structure formed by alternately stacking quantum well layers and quantum barrier layers. The active layer 122 can be a single quantum well structure or a multiple quantum well structure. The quantum barrier layer can be a GaN layer or an AlGaN layer. In some embodiments, the active layer 122 can include a multiple quantum well structure of GaN / AlGaN, InAlGaN / InAlGaN, or InGaN / AlGaN. To improve the light emission efficiency of the active layer 122, it can be achieved by changing the depth of the quantum wells, the number of pairs of quantum wells and quantum barrier layers, thickness, and / or other characteristics in the active layer 122.

[0021] The second semiconductor layer 123 in the semiconductor stack 120 is a P-type semiconductor layer, which can provide holes to the active layer 122 under the action of a power supply. In some embodiments, the P-type semiconductor layer in the second semiconductor layer 123 includes a P-type doped nitride layer. The P-type doped nitride layer may include P-type impurities of one or more Group II elements. The P-type impurities can be one or a combination of Mg, Zn, and Be. The second semiconductor layer 123 can be a single-layer structure or a multi-layer structure with different compositions. The setting of the semiconductor stack 120 is not limited to this, and other types of semiconductor stacks 120 can be selected according to actual needs.

[0022] In some embodiments, there may be a buffer layer (not shown in the figure) between the substrate 110 and the semiconductor stack 120 in the light-emitting diode to reduce the lattice mismatch between the substrate 110 and the first semiconductor layer 121. In some embodiments, the buffer layer can include an unintentionally doped GaN layer (undroped GaN, abbreviated as: u-GaN) or an unintentionally doped AlGaN layer (undroped AlGaN, abbreviated as: u-AlGaN).

[0023] The buffer layer may be single-layer or multi-layer. The buffer layer may be formed by metal organic chemical vapor deposition, molecular beam epitaxy, or physical vapor deposition (PVD). Among them, physical vapor deposition may include sputtering methods, such as reactive sputtering methods, or evaporation methods; such as electron beam evaporation methods or thermal evaporation methods. In one embodiment, the buffer layer may include an aluminum nitride (AlN) buffer layer and is formed by sputtering. The aluminum nitride buffer layer is formed on a substrate 110 with a patterned structure surface. The sputtering method can form a dense buffer layer with high uniformity. Therefore, the aluminum nitride buffer layer can be deposited on the patterned structure surface of the substrate 110.

[0024] The current spreading layer 130 is formed on the semiconductor stack 120 and is in contact with the second semiconductor layer 123. The current spreading layer 130 can enhance the diffusion of current and form an ohmic contact with the second semiconductor layer 123. The material of the current spreading layer 130 can be ITO, InO, SnO, CTO, ATO, ZnO, GaP, or a combination thereof. The current spreading layer 130 can be formed by evaporation or sputtering. The thickness of the current spreading layer 130, in this embodiment, is selected from the range of 5 nm to 100 nm. Additionally, it is preferably selected from the range of 10 nm to 50 nm.

[0025] The first electrode 141 and the second electrode 142 are located on the semiconductor stack 120. The first electrode 141 is disposed on the upper surface of the first semiconductor layer 121 and is electrically connected to the first semiconductor layer 121. The second electrode 142 is disposed on the upper surface of the current spreading layer 130 and is electrically connected to the second semiconductor layer 123.

[0026] The materials of the first electrode 141 and the second electrode 142 may include, for example, a highly conductive metal layer formed of a metal material such as Al, Cu, Ag, Au, Pt, etc., and may have high reflection characteristics.

[0027] In one embodiment, the first electrode 141 and the second electrode 142 include a first metal layer 141a, 142a, a second metal layer 141b, 142b, a third metal layer 141c, 142c, and a fourth metal layer 141d, 142d formed in sequence on the semiconductor stack 120. The first metal layer 141a, 142a can be selected from Cr or Ni or Ti or a combination thereof to increase the adhesion of the subsequent metal layer to the semiconductor stack 120. The second metal layer 141b, 142b is located above the first metal layer 141a, 142a and can be selected from Al or Ag or an AlAg alloy as a reflective metal layer. The third metal layer 141c, 142c can be a metal layer such as Ti / Pt or Ni / Pt to coat the second metal layer 141b, 142b and the first metal layer 141a, 142a, protecting the easily oxidized metal Al and preventing the migration of the metal Cr. The fourth metal layer 141d, 142d can be selected from Cr or Ni or Ti or a combination thereof to increase the adhesion to the subsequently formed insulating layer 150.

[0028] Referring to Figure 3 , Figure 3 is Figure 2 an enlarged schematic view of the partial A. The second electrode 142 has a first surface S1 in contact with the second semiconductor layer 123, a second surface S2 opposite to the first surface S1, and a side surface S3 connecting the first surface S1 and the second surface S2. The first electrode 141 also has a first surface S1 in contact with the first semiconductor layer 121, a second surface S2 opposite to the first surface S1, and a side surface S3 connecting the first surface S1 and the second surface S2.

[0029] In a preferred embodiment, the included angle α between the first surface S1 and the side surface S3 of the first electrode 141 and the second electrode 142 is between 40° and 80°.

[0030] The insulating layer 150 covers the semiconductor stack 120, is located above the second semiconductor layer 123, above the mesa of the first semiconductor layer 121, and above the sidewalls of the semiconductor stack 120, and the insulating layer 150 also covers the current spreading layer 130, the first electrode 141, and the second electrode 142. The insulating layer 150 has a plurality of first openings OP1 located above the first electrode 141 and the second electrode 142 to expose partial surfaces of the first electrode 141 and the second electrode 142. In a specific embodiment, the insulating layer 150 covers a part of the second surface S2 and the side surface S3 of the first electrode 141 and the second electrode 142. The insulating layer 150 is in contact with the fourth metal layer 141d, 142d in the first electrode 141 and the second electrode 142, which can increase the adhesion between the insulating layer 150 and the first electrode 141 and the second electrode 142.

[0031] In a preferred embodiment, the thickness of the insulating layer 150 is between 100 nm and 500 nm. In a further preferred embodiment, the thickness of the insulating layer 150 is between 150 nm and 300 nm.

[0032] The protection electrode 160 is disposed on the insulating layer 150, and contacts the second surfaces S2 of the first electrode 141 and the second electrode 142 through the first opening OP1, and covers the insulating layer 150 formed on the side surfaces S3 of the first electrode 141 and the second electrode 142.

[0033] In one embodiment, the protection electrode 160 includes a first portion 160a and a second portion 160b. The first portion 160a is formed on the first electrode 141 and the second electrode 140 through the first opening OP1 and extends to cover the insulating layer 150. The second portion 160b covers the insulating layer 150 formed on the side surface S3 of the first electrode 141. By disposing the protection electrode 160 on the insulating layer 150, the insulating layer 150 covering the second surface S2 and the side surface S3 of the first electrode 141 is wrapped, which can reduce the probability of the insulating layer 150 peeling off from the side surface S3 of the first electrode 141, enhance the covering effect of the insulating layer 150 on the first electrode 141, and reduce the migration probability of metals, especially Cr and Al, in the first electrode 141.

[0034] The thickness T1 of the first portion 160a is greater than the thickness T2 of the second portion 160b.

[0035] In one embodiment, the protection electrode 160 may include a first layer 161 and a second layer 162. The first layer 161 is located between the insulating layer 150 and the second layer 162. The first layer 161 is disposed on the first electrode 141 and the second electrode 142 through the first opening OP1 and extends to cover the insulating layer 150. The first layer 161 also covers the insulating layer 150 formed on the side surface S3 of the first electrode 141 and the second electrode 142. The first layer 161 can be a metal such as Cr, Ni, Ti, etc. These metals such as Cr, Ni, Ti, etc. have good adhesion to the insulating layer 150, which can reduce the probability of the insulating layer 150 peeling off from the surface of the first electrode 141. Specifically, the fourth metal layers 141d and 142d of the first electrode 141 and the second electrode 142 and the first layer 161 can be made of the same metal material, enhancing the adhesion effect on the insulating layer. The second layer 162 is disposed on the first layer 161. The second layer 162 can be a metal such as Au. The property of Au is relatively stable and it is not easy to react with other substances. Using the Au film as the wire bonding layer at the topmost of the electrode, the stability of the electrode is better. By providing the protection electrode 160 on the insulating layer 150 and the first electrode 141, the insulating layer 150 covering the second surface S2 and the side surface S3 of the first electrode 141 is wrapped, which can reduce the probability of the insulating layer 150 peeling off from the side surface S3 of the first electrode 141, enhance the covering effect of the insulating layer 150 on the first electrode 141, and reduce the migration probability of the metal in the first electrode 141, especially Cr and Al.

[0036] The thickness T3 of the first layer 161 is 3 nm to 50 nm, and the thickness T4 of the second layer is 200 nm to 1500 nm.

[0037] As an alternative embodiment, referring to Figure 4 , there is a second layer 162 between the third metal layers 141c and 142c and the fourth metal layers 141d and 142d. The second layer 162 is disposed above the third metal layers 141c and 142c, which can increase the effective contact area of wire bonding metals such as Au and Pt with the first electrode 141 or the second electrode 142.

[0038] As an alternative embodiment, referring to Figure 5 , the second layer 162 can be only located on a partial surface of the first layer 161. For example, the second layer 162 is located above the first opening OP1 and is in electrical contact with the first semiconductor layer 121 or the second semiconductor layer 123.

[0039] The above are only the preferred embodiments of the present application. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present application, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present application.

Claims

1. A light-emitting diode, comprising: A semiconductor stack including a first semiconductor layer, a second semiconductor layer stacked in sequence, and an active layer therebetween; A first electrode and a second electrode respectively formed on the first semiconductor layer or the second semiconductor layer, the first electrode and the second electrode having a first surface in contact with the first semiconductor layer or the second semiconductor layer, a second surface opposite to the first surface, and a side surface connecting the first surface and the second surface; An insulating layer formed on the second surface and the side surface of the first electrode or the second electrode, the insulating layer having a plurality of first openings exposing a part of the second surface of the first electrode or the second electrode, and the insulating layer being silicon dioxide; A protective electrode in contact with the second surface of the first electrode or the second electrode through the first opening and covering the insulating layer formed on the side surface of the first electrode or the second electrode, the protective electrode including a first layer and a second layer, the first layer covering the insulating layer formed on the side surface of the first electrode or the second electrode, the first layer being one or several of chromium, nickel, and titanium, and the second layer being one or several of gold and platinum.

2. The light-emitting diode according to claim 1, wherein, The protective electrode includes a first part and a second part, the first part being in contact with the first electrode or the second electrode through the first opening and extending to cover the insulating layer, and the second part covering the insulating layer formed on the side surface of the first electrode or the second electrode.

3. The light emitting diode according to claim 2, wherein The thickness of the first part is greater than the thickness of the second part.

4. The light-emitting diode according to claim 1, wherein The first layer is at least filled in contact with the first opening and the first electrode or the second electrode, and the second layer is formed on the first layer.

5. The light-emitting diode according to claim 4, wherein, The thickness of the first layer is 3 nm to 50 nm, and the thickness of the second layer is 200 nm to 1500 nm.

6. The light emitting diode according to claim 1, wherein, The included angle between the first surface and the side surface of the first electrode or the second electrode is between 40° and 80°.

7. The light-emitting diode according to claim 1, characterized in that, The thickness of the insulating layer is between 100 nm and 500 nm.

8. The light-emitting diode according to claim 1, characterized in that, The first electrode or the second electrode includes a first metal layer, a second metal layer, a third metal layer, a fourth metal layer, and a fifth metal layer, the fifth metal layer being in contact with the insulating layer, and the protective electrode includes a first layer in contact with the insulating layer, and the fifth metal layer and the first layer are made of the same material.

9. The light-emitting diode according to claim 8, characterized in that, The material of the fifth metal layer and the first layer is titanium or nickel.

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