Semiconductor light-emitting element and preparation method thereof

Abstract

The present invention discloses a semiconductor light-emitting element comprising a semiconductor epitaxial stack having a first surface, a second surface opposite the first surface, and a sidewall connecting the first and second surfaces. The semiconductor layer comprises a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and an active layer positioned between the first and second conductivity type semiconductor layers. The sidewalls of the second conductivity type semiconductor layer have a roughness greater than that of the active layer. The present invention employs a two-step etching method to segmentally etch the sidewalls of the semiconductor epitaxial stack, effectively alleviating leakage issues caused by sidewall roughening.

Description

Technical Field

[0001] The present invention relates to a semiconductor light-emitting element and a preparation method thereof, belonging to the field of semiconductor optoelectronic devices and technology. Background Art

[0002] Light-emitting diodes (LEDs), with their advantages of high luminous intensity, high efficiency, compact size, and long life, are considered one of the most promising light sources. In recent years, LEDs have been widely used in everyday applications such as lighting, signal displays, backlighting, automotive lighting, and large-screen displays. These applications, however, place increasing demands on LED brightness and luminous efficiency.

[0003] Improving luminous efficiency can be achieved through several methods, including improving the quality of epitaxial growth and increasing the probability of electron-hole combination to improve the internal quantum efficiency (IQE). On the other hand, if the light generated by the LED cannot be effectively extracted, some of the light will be confined to the LED due to total internal reflection, reflecting or refracting back and forth, and ultimately absorbed by the electrodes or light-emitting layer, preventing the brightness from being increased. Therefore, surface roughening or changing the geometric shape of the structure can be used to improve the external quantum efficiency (EQE), thereby improving the brightness and luminous efficiency of the LED.

[0004] Existing LEDs improve light extraction efficiency and brightness by roughening the mesas and sidewalls of the semiconductor epitaxial stack. However, during the roughening process, impurities can easily remain on the sidewalls of the active layer, causing leakage in the LEDs and thus affecting product performance. Summary of the Invention

[0005] In order to solve the above problems, the present invention proposes a semiconductor light-emitting element, which comprises: a semiconductor epitaxial stack having a first surface and a second surface opposite to the first surface and a side wall connecting the first surface and the second surface, including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer located between the first conductive semiconductor layer and the second conductive semiconductor layer; characterized in that: the roughness of the side wall of the second conductive semiconductor layer is greater than the roughness of the side wall of the active layer.

[0006] Preferably, the roughness of the sidewall of the second conductive type semiconductor layer is 200-500 nm.

[0007] Preferably, the roughness of the sidewall of the active layer is 0-20 nm.

[0008] Preferably, the ratio of the roughness of the sidewall of the second conductive type semiconductor layer to the roughness of the sidewall of the active layer is 20:1 to 500:1.

[0009] Preferably, the upper surface of the second conductive type semiconductor layer away from the active layer has an uneven structure.

[0010] Preferably, the roughness of the uneven structure of the upper surface of the second conductive type semiconductor layer away from the active layer is in the range of 0-50 μm.

[0011] Preferably, the upper surface of the second conductive type semiconductor layer away from the active layer includes a rough area and a flat area.

[0012] Preferably, the light emitting surface of the semiconductor light emitting element is located on a side of the second conductive type semiconductor layer away from the active layer.

[0013] Preferably, it further comprises a substrate and a bonding layer between the semiconductor epitaxial stack and the substrate.

[0014] Preferably, it further comprises a reflective layer located between the bonding layer and the semiconductor epitaxial stack.

[0015] The present invention also proposes a method for preparing a semiconductor light-emitting element, which is characterized by: 1. forming a semiconductor epitaxial stack, including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer located between the first conductive semiconductor layer and the second conductive semiconductor layer; 2. forming a mesa by dry etching; 3. etching the side of the semiconductor epitaxial stack by a two-stage etching method, wherein the roughness of the side wall of the second conductive semiconductor layer is greater than the roughness of the side wall of the active layer.

[0016] Preferably, the etching gases introduced into the first etching method are Cl and BCl3 gases, and the etching gases introduced into the second etching method are Cl, BCl3, and HBr gases.

[0017] Preferably, the flow ratio of the etching gases Cl, BCl3 and HBr in the second etching method is in the range of 4:10:20 to 4:10:80.

[0018] Preferably, the method further comprises bonding the semiconductor epitaxial stack to a substrate via a bonding layer.

[0019] Preferably, the method further comprises forming a reflective layer located between the bonding layer and the semiconductor epitaxial stack.

[0020] Preferably, the method further comprises roughening the surface of the second conductive type semiconductor layer away from the active layer to form an uneven structure.

[0021] The present invention also proposes a semiconductor light-emitting element, a semiconductor epitaxial stack, having a first surface and a second surface opposite to the first surface and a sidewall connecting the first surface and the second surface, including a first conductive semiconductor layer, a second conductive semiconductor layer and an active layer located between the first conductive semiconductor layer and the second conductive semiconductor layer; characterized in that: the roughness of the sidewall of the active layer ranges from 0 to 20 nm.

[0022] Preferably, it is characterized in that: the semiconductor epitaxial stack is made of a material of the aluminum gallium indium phosphide series.

[0023] Preferably, the upper surface of the second conductive type semiconductor layer away from the active layer has an uneven structure.

[0024] Preferably, the light emitting surface of the semiconductor light emitting element is located on a side of the second conductive type semiconductor layer away from the active layer.

[0025] Preferably, the method further comprises a substrate and a bonding layer between the semiconductor epitaxial stack and the substrate.

[0026] Preferably, a reflective layer is further included between the bonding layer and the semiconductor epitaxial stack.

[0027] The present invention further provides a light emitting diode package, comprising a mounting substrate and at least one semiconductor light emitting element mounted on the mounting substrate, wherein at least one or more or all of the semiconductor light emitting elements are any one of the aforementioned semiconductor light emitting elements.

[0028] The present invention performs segmented etching on the sidewalls of the semiconductor epitaxial stack through a two-step etching method. The roughness of the sidewalls of the second conductive semiconductor layer is greater than that of the active layer sidewalls, which can effectively improve the leakage problem caused by sidewall coarsening.

[0029] 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.

[0030] Although the present invention will be described below in conjunction with some exemplary implementations and methods of use, it should be understood by those skilled in the art that it is not intended to limit the present invention to these embodiments. On the contrary, it is intended to cover all substitutes, modifications and equivalents within the spirit and scope of the present invention as defined by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In addition, the accompanying drawings are for description only and are not drawn to scale.

[0032] Figure 1 This is a schematic cross-sectional view of the semiconductor light-emitting element mentioned in Example 1.

[0033] Figure 2 This is a schematic diagram of the epitaxial structure provided in the manufacturing process mentioned in Example 2. The epitaxial structure includes a semiconductor epitaxial stack.

[0034] Figure 3 This is a schematic diagram of a structure obtained by transferring the semiconductor epitaxial stack provided in the manufacturing process mentioned in Example 2 to a substrate through a bonding process and removing the growth substrate.

[0035] Figure 4 This is a schematic diagram of the structure obtained after forming a front electrode on the second conductive semiconductor layer in the manufacturing process mentioned in Example 2.

[0036] Figure 5 This is a schematic diagram of the structure for roughening the mesa and sidewalls of the semiconductor epitaxial stack in the manufacturing process mentioned in Example 2.

[0037] Figure 6 This is a schematic diagram of the structure of forming a back electrode on the back side of the substrate in the manufacturing process mentioned in Example 2.

[0038] Explanation of component numbers in the figure: 10: growth substrate; 100: base plate; 101: bonding layer; 102: reflective layer; 103: dielectric layer; 104: first conductive type semiconductor layer; 105: active layer; 106: second conductive type semiconductor layer; 107a: pad electrode; 107b: extension electrode; 108: insulating layer; 109: opposite electrode. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0041] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. Example 1

[0042] The present invention provides a semiconductor light emitting element as follows: Figure 1 The cross-sectional schematic diagram shown includes the following stacked layers: 100: substrate; 101: bonding layer; 102: reflective layer; 103: dielectric layer; 104: first conductive type semiconductor layer; 105: active layer; 106: second conductive type semiconductor layer; 107a: pad electrode; 107b: extended electrode; 108: insulating layer; 109: opposite electrode.

[0043] Each structural stacking layer is described in detail below.

[0044] The substrate 100 is a conductive substrate, which can be silicon, silicon carbide, or a metal substrate. The metal substrate is preferably a copper, tungsten, or molybdenum substrate. To provide sufficient mechanical strength to support the semiconductor epitaxial stack 1, the thickness of the substrate 100 is preferably greater than 50 μm. In addition, to facilitate mechanical processing of the substrate 100 after bonding to the semiconductor epitaxial stack 1, the thickness of the substrate 100 is preferably no more than 300 μm. In this embodiment, the substrate 100 is preferably a silicon substrate.

[0045] The bonding layer 101 is a bonding metal material used to adhere one side of the semiconductor epitaxial stack to the substrate 100, such as gold, tin, titanium, nickel, platinum and other metals. The bonding layer 101 can be a single-layer structure or a multi-layer structure, and can be a combination of multiple materials.

[0046] Reflective layer 102 is disposed on the side of bonding layer 101 proximal to the semiconductor epitaxial stack. Reflective layer 102 can be formed from a metal or alloy containing at least one of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, Au, and Hf. Reflective layer 102 can reflect light radiated from the semiconductor epitaxial stack toward the substrate 100, returning it to the semiconductor epitaxial stack and radiating it out the light-emitting side. The light-emitting surface of the semiconductor light-emitting element is located on the side of the second conductive type semiconductor layer 106 away from the active layer 105.

[0047] The dielectric layer 103 is located on a side of the first conductive semiconductor layer 104 away from the active layer 105 and has multiple openings extending therethrough. The dielectric layer 103 can be formed from an insulating material having a lower conductivity than the reflective layer 102, a material having a lower conductivity, or a material that forms a Schottky contact with the first conductive semiconductor layer 104. For example, the dielectric layer 103 can be composed of at least one of a fluoride, a nitride, or an oxide, specifically at least one of ZnO, SiO2, SiOx, SiOxNy, Si3N4, Al2O3, TiOx, MgF, or GaF. The dielectric layer 103 is composed of at least one layer or a combination of multiple layers of dielectric materials having different refractive indices. The dielectric layer 103 is preferably a light-transmitting dielectric layer, allowing at least 50% of light to pass through it. More preferably, the refractive index of the dielectric layer 103 is lower than that of the semiconductor epitaxial stack.

[0048] An ohmic contact layer (not shown in the figures) may also be included between the reflective layer 102 and the dielectric layer 103. The ohmic contact layer, by filling at least the multiple openings in the dielectric layer 103, forms multiple regions of ohmic contact with the first conductive semiconductor layer 104. This ensures uniform current transfer from the reflective layer 102 and bonding layer 101 to the semiconductor epitaxial stack. Therefore, the ohmic contact layer does not contact one side of the first conductive semiconductor layer 104 across its entire surface. The ohmic contact layer can be formed from a transparent conductive layer such as at least one of ITO, IZO, IZTO, IAZO, IGZO, IGTO, AZO, and ATO. Alternatively, the ohmic contact layer may be formed from a light-transmitting conductive layer and a metal. The metal is preferably an alloy material such as gold-zinc, gold-germanium, gold-germanium-nickel, or gold-beryllium. The ohmic contact layer may have a single-layer or multi-layer structure.

[0049] The reflective layer 102 and the dielectric layer 103 form an ODR reflective structure, which returns the light radiated from the semiconductor epitaxial stack toward the substrate 100 to the semiconductor epitaxial stack and radiates it out from the light emitting side, thereby improving the light extraction efficiency.

[0050] The semiconductor epitaxial stack has a first surface, a second surface opposite the first surface, and sidewalls connecting the first and second surfaces. The semiconductor epitaxial stack is grown using MOCVD or other growth methods and is made of a semiconductor material capable of providing conventional radiation, such as ultraviolet, blue, green, yellow, red, or infrared light. Specifically, it can be a material with a wavelength of 200 to 950 nm, such as a common nitride, specifically a gallium nitride-based semiconductor epitaxial stack. Gallium nitride-based epitaxial stacks are often doped with elements such as aluminum and indium, primarily providing radiation in the 200 to 550 nm band; or a common aluminum gallium indium phosphide-based or aluminum gallium arsenide-based semiconductor stacked layer, primarily providing radiation in the 550 to 950 nm band. The semiconductor epitaxial stack primarily includes a first conductivity-type semiconductor layer 104, a second conductivity-type semiconductor layer 106, and an active layer 105 located between the first and second conductivity-type semiconductor layers 104 and 106. The first and second conductive semiconductor layers 104 and 106 can be n-doped or p-doped, respectively, to provide at least electrons or holes, respectively. The n-type semiconductor layer can be doped with n-type dopants such as Si, Ge, or Sn, while the p-type semiconductor layer can be doped with p-type dopants such as Mg, Zn, Ca, Sr, or Ba. The first, active, and second conductive semiconductor layers 104, 105, and 106 can be made of materials such as aluminum gallium indium nitride (AlGaInN), gallium nitride (GaN), aluminum gallium nitride (AlGaN), aluminum indium phosphide (AlInP), AlGaInP, gallium arsenide (GaAs), or aluminum gallium arsenide (AlGaAs). The first and second conductive semiconductor layers 104 and 106 can include capping layers that provide electrons or holes, as well as other layers such as current spreading layers, window layers, or ohmic contact layers. These layers can be configured as multiple layers based on doping concentrations or component content. The active layer 105 is the region that provides light radiation for electron and hole recombination. Different materials can be selected based on the wavelength of the emitted light. The active layer 105 can have a periodic structure consisting of a single quantum well or multiple quantum wells. Light of different wavelengths can be radiated by adjusting the composition ratio of the semiconductor materials in the active layer 105. In this embodiment, the semiconductor epitaxial stack is preferably made of AlGaInP-based materials.

[0051] The front electrode is configured on the light-emitting side of the semiconductor exo-die stack. The front electrode includes a pad electrode 107a and an extension electrode 107b. The pad electrode 107a is primarily used for external wiring during packaging. The pad electrode 107a can be designed into various shapes based on actual wiring requirements, such as a cylinder, a square, or other polygonal shape. The extension electrode 107b can be formed in a predetermined pattern and can have various shapes, such as a strip.

[0052] The semiconductor light-emitting element further includes a counter electrode 109. In this embodiment, the counter electrode 109 is formed entirely on the back side of the support substrate 100. The substrate 100 in this embodiment is a conductive support substrate, and the front electrode and the counter electrode 109 are formed on both sides of the substrate 100 to ensure that current flows perpendicularly through the semiconductor epitaxial stack, providing uniform current density.

[0053] The front electrode and the counter electrode 109 are preferably made of metal materials. At least the pad electrode portion and the extended electrode portion of the front electrode may also include a metal material that forms a good ohmic contact with the semiconductor epitaxial stack.

[0054] To improve the efficiency of light emitted from the active layer 105 of the semiconductor light-emitting element, the surface of the second conductive semiconductor layer away from the active layer 105 is roughened. The surface of the second conductive semiconductor layer 106 away from the active layer 105 has an uneven structure. The surface of the second conductive semiconductor layer 106 away from the active layer 105 includes a flat area and a roughened area. The front electrode 108 is located in the flat area of the second conductive semiconductor layer 106 away from the active layer 105. To improve the efficiency of light emitted from the active layer 105 from the sidewalls of the semiconductor light-emitting element, the sidewalls of the semiconductor light-emitting element are roughened. However, during the roughening process, impurities may be present on the sidewalls of the active layer, causing leakage problems in the semiconductor light-emitting element. To address the leakage problem caused by roughened sidewalls in semiconductor light-emitting devices, the present invention proposes a semiconductor light-emitting device in which the sidewall roughness of the second-conductivity-type semiconductor layer 106 is greater than the sidewall roughness of the active layer 105. Preferably, the sidewall roughness of the second-conductivity-type semiconductor layer 106 is in the range of 200-500 nm, while the sidewall roughness of the active layer 105 is in the range of 0-20 nm. This design of a semiconductor light-emitting device can address the leakage problem caused by roughened sidewalls in semiconductor light-emitting devices.

[0055] The semiconductor light emitting element further includes an insulating layer 108 covering the surface and sidewalls of the second conductive type semiconductor layer of the semiconductor light emitting element away from the active layer to protect the semiconductor light emitting element from environmental damage, such as moisture or mechanical damage. Example 2

[0056] The following is a detailed description of the manufacturing process of the semiconductor light emitting element of the above-mentioned embodiment 1.

[0057] like Figure 2As shown, an epitaxial structure is first provided, which specifically includes the following steps: providing a growth substrate 10, preferably a gallium arsenide substrate, and epitaxially growing a semiconductor epitaxial stack on the growth substrate 10 through an epitaxial process such as MOCVD, and the semiconductor epitaxial stack includes: a first conductive semiconductor layer 104, a second conductive semiconductor layer 106 and an active layer 105 located between the first conductive semiconductor layer and the second conductive semiconductor layer.

[0058] Next, a dielectric layer 103 is prepared on one side of the first conductive semiconductor layer 104. In this embodiment, the dielectric layer is preferably SiO2 or MgF2. An opening is formed in the dielectric layer 103 by masking and etching processes. Then, a reflective layer 102 is formed on the side of the dielectric layer 103 away from the first conductive semiconductor layer 104. A bonding layer 101 is provided on one side of the reflective layer 102 and bonded to the substrate 100 by a bonding process. Next, a wet etching process is used to remove the substrate 100 to obtain the following. Figure 3 The structure shown;

[0059] Then, if Figure 4 As shown, a front electrode is formed on the second conductive semiconductor layer 106, and the front electrode includes a main electrode 107a and an extended electrode 107b of the wiring portion, wherein the main electrode 107a and the extended electrode 107b provide a wiring position and horizontal current expansion respectively.

[0060] Then, if Figure 5As shown, a chip separation process separates the semiconductor light-emitting array into unit chip regions. This separation process uses a dry etching process to expose multiple die regions (not shown) on the substrate 100. The dry etching etchant, such as fluorine, chlorine, or hydrogen bromide gas, etches out the second-conductivity-type semiconductor layer 106 and the active layer 105. The present invention employs a two-stage etching process. The first stage is a conventional etching process, in which Cl and BCl3 gases are introduced to etch to the interface between the second-conductivity-type semiconductor layer 106 and the active layer 105. The second stage involves the use of Cl, BCl3, and HBr gases to etch from the active layer 105 to the interface between the active layer 105 and the first-conductivity-type semiconductor layer 104. During the second dry etching process, the addition of HBr gas smoothes the sidewalls of the active layer. This reduces impurity adsorption, lowers the risk of leakage, and improves product performance while ensuring sidewall light extraction efficiency. In this embodiment, the preferred gas flow ratio of Cl, BCl3, and HBr is 4:10:20 to 4:10:40. By means of a segmented etching method, the roughness of the sidewall of the second conductive semiconductor layer is 200-500 nm, and the roughness of the sidewall of the active layer is 0-20 nm. A roughened surface is formed on the second conductive semiconductor layer 106 by patterning. In this embodiment, a wet etching method is preferably used to form an uneven structure on the surface of the second conductive semiconductor layer away from the active layer. The roughness range of the uneven structure is 0-50 μm. The uneven structure can increase the light extraction efficiency and form a passivation layer 108 at least on the sidewall and light-emitting side of the semiconductor epitaxial stack 1.

[0061] like Figure 6 As shown, a back electrode 109 is formed on the back side of the substrate 100 .

[0062] The present invention adopts a two-stage etching method to etch the side walls of the semiconductor light-emitting element. The roughness of the active layer side walls is less than the roughness of the side walls of the second conductive semiconductor layer. This can solve the leakage problem caused by the roughening of the side walls of the semiconductor light-emitting element and improve the yield of the semiconductor light-emitting element.

[0063] It should be noted that the above embodiments are only used to illustrate the present invention, and are not used to limit the present invention. Those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention. The scope of patent protection of the present invention should be limited according to the scope of the claims.

Claims

1. A semiconductor light-emitting element, comprising: a substrate; a semiconductor epitaxial stack located on the substrate, having a first surface and a second surface opposite to the first surface, and a sidewall connecting the first surface and the second surface, comprising a first conductive type semiconductor layer, a second conductive type semiconductor layer, and an active layer located between the first conductive type semiconductor layer and the second conductive type semiconductor layer, wherein a side of the second conductive type semiconductor layer away from the active layer is a light emitting surface; The upper surface of the second conductive type semiconductor layer away from the active layer has an uneven structure; a dielectric layer, located on a side of the first conductive type semiconductor layer away from the active layer, and having a plurality of openings exposing the first conductive type semiconductor layer; an ohmic contact layer filling the opening of the dielectric layer; a reflective layer, disposed on a side of the dielectric layer away from the semiconductor epitaxial stack; It is characterized in that: the refractive index of the dielectric layer is lower than the refractive index of the semiconductor epitaxial stack, and the conductivity of the dielectric layer is lower than the conductivity of the reflective layer; the roughness of the side wall of the second conductive semiconductor layer is greater than the roughness of the side wall of the active layer; the ratio of the roughness of the side wall of the second conductive semiconductor layer to the roughness of the side wall of the active layer is 20:1~500:

1.

2. The semiconductor light emitting element according to claim 1, wherein: The roughness of the sidewall of the second conductive type semiconductor layer is in the range of 200-500 nm.

3. The semiconductor light emitting element according to claim 1, wherein: The roughness of the sidewall of the active layer is in the range of 0-20 nm.

4. The semiconductor light emitting element according to claim 1, wherein: The roughness of the uneven structure of the upper surface of the second conductive type semiconductor layer away from the active layer is in the range of 0-50 μm.

5. The semiconductor light emitting element according to claim 1, wherein: The upper surface of the second conductive type semiconductor layer away from the active layer includes a rough area and a flat area.

6. The semiconductor light emitting element according to claim 1, wherein: The invention also comprises a substrate and a bonding layer between the semiconductor epitaxial stack and the substrate.

7. The semiconductor light emitting element according to claim 1, wherein: The ohmic contact layer does not contact the entire surface of the first conductive semiconductor layer on the side away from the active layer.

8. The semiconductor light emitting element according to claim 1, wherein: The semiconductor epitaxial stack is made of aluminum gallium indium phosphide series materials.

9. A light emitting diode package comprising a mounting substrate and at least one semiconductor light emitting element mounted on the mounting substrate, characterized in that: At least one of the semiconductor light emitting elements is the semiconductor light emitting element according to any one of claims 1 to 8.

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