LED epitaxial structure and preparation method thereof, LED chip and preparation method thereof

Abstract

The present invention discloses an LED epitaxial structure and a preparation method thereof, an LED chip and a preparation method thereof, wherein the LED epitaxial structure comprises: a growth substrate; a current spreading layer, arranged above the growth substrate, the current spreading layer sequentially comprising a first sublayer and a second sublayer in the thickness direction of the growth substrate, the band gap of the first sublayer being higher than the band gap of the second sublayer; an epitaxial layer, arranged above the second sublayer, and the epitaxial layer sequentially comprising a first semiconductor layer, an active layer and a second semiconductor layer in the thickness direction of the growth substrate. The current spreading layer of the present invention can increase the lateral diffusion capacity of the current, improve the brightness and antistatic capacity of the LED epitaxial structure, improve the forward voltage of the LED epitaxial structure, and is beneficial to the reliability of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and in particular to an LED epitaxial structure and a preparation method thereof, an LED chip and a preparation method thereof. Background Art

[0002] Light Emitting Diode (LED) is a semiconductor device that can directly convert electrical energy into light energy, and is a solid-state cold light source. The inherent physical properties of LED enable it to work at low voltage / current, and it has the characteristics of high luminous efficiency, small size, long life, and energy saving. Therefore, LED has now become the core light-emitting device in the fields of traffic display, medical lighting, military communications, etc. At present, with years of technical research and development, the red light LED chip technology is becoming more and more mature.

[0003] Red LED chips are generally made of AlGaInP (aluminum gallium indium phosphide) quaternary materials. The epitaxial technology of red LEDs is mainly to grow AlGaInP materials on GaAs substrates. Since the lattice matching between AlGaInP and GaAs is good, fewer dislocations are generated during the epitaxial growth process, and the quantum efficiency inside the AlGaInP material exceeds 95%. However, the current red light epitaxial structure is prone to current crowding due to poor lateral expansion of current, which not only restricts the utilization of the light-emitting area but also causes the local temperature of the chip to rise, accelerating the aging of the chip. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an LED epitaxial structure and a preparation method thereof, an LED chip and a preparation method thereof, so as to improve the problem of poor lateral expansion of current.

[0005] In order to achieve the above-mentioned object and other related objects, the present invention provides an LED epitaxial structure, comprising:

[0006] Growth substrate;

[0007] A current spreading layer is disposed above the growth substrate, the current spreading layer sequentially comprising a first sublayer and a second sublayer in the thickness direction of the growth substrate, the band gap of the first sublayer being higher than the band gap of the second sublayer;

[0008] The epitaxial layer is arranged above the second sublayer, and the epitaxial layer includes a first semiconductor layer, an active layer and a second semiconductor layer in sequence in the thickness direction of the growth substrate.

[0009] Optionally, the thickness of the first sub-layer is smaller than the thickness of the second sub-layer.

[0010] Optionally, the thickness of the first sublayer is between 0.5 μm and 1.5 μm, and the thickness of the second sublayer is between 1.5 μm and 3 μm.

[0011] Optionally, the material of the current spreading layer is (Al X Ga 1-X ) Y In 1-Y P, wherein 0≤X≤1, 0≤Y≤1; the Al content in the first sublayer is greater than the Al content in the second sublayer.

[0012] Optionally, the Al content in the material of the first sub-layer is between 0.5 and 0.7, and the Al content in the material of the second sub-layer is between 0.25 and 0.4.

[0013] Optionally, the material of the first sublayer is Al 0.6 Ga 0.4 InP, the material of the second sublayer is Al 0.3 Ga 0.7 InP.

[0014] Optionally, a first diffusion barrier layer is arranged between the first semiconductor layer and the active layer of the epitaxial layer, and a second diffusion barrier layer is arranged between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to prevent the doped elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer.

[0015] Optionally, the LED epitaxial structure radiates red light.

[0016] The present invention also provides an LED chip, comprising:

[0017] substrate;

[0018] An epitaxial layer is located above the substrate, and the epitaxial layer includes a second semiconductor layer, an active layer and a first semiconductor layer in sequence in a thickness direction of the substrate;

[0019] The current spreading layer is located above the first semiconductor layer, and the current spreading layer includes a second sublayer and a first sublayer in sequence in the thickness direction of the substrate, and the band gap of the first sublayer is higher than the band gap of the second sublayer.

[0020] Optionally, a roughening structure is formed on a side of the first sub-layer away from the substrate, and a depth of the roughening structure is less than or equal to a thickness of the first sub-layer.

[0021] Optionally, the thickness of the first sub-layer is smaller than the thickness of the second sub-layer.

[0022] Optionally, the material of the current spreading layer is (Al X Ga 1-X ) Y In 1-Y P, wherein 0≤X≤1, 0≤Y≤1, and the Al content in the first sublayer is greater than the Al content in the second sublayer.

[0023] Optionally, a first diffusion barrier layer is arranged between the first semiconductor layer and the active layer of the epitaxial layer, and a second diffusion barrier layer is arranged between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to prevent the doped elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer.

[0024] The present invention also provides a method for preparing an LED epitaxial structure, comprising:

[0025] providing a growth substrate;

[0026] forming a current spreading layer above the first surface of the growth substrate, wherein the current spreading layer includes a first sublayer and a second sublayer in sequence in a thickness direction of the growth substrate, and a band gap of the first sublayer is higher than a band gap of the second sublayer;

[0027] An epitaxial layer is formed above the second sub-layer, and the epitaxial layer includes a first semiconductor layer, an active layer, and a second semiconductor layer in sequence in a thickness direction of the growth substrate.

[0028] The present invention also provides a method for preparing an LED chip, comprising:

[0029] providing a growth substrate;

[0030] forming a current spreading layer on the growth substrate, wherein the current spreading layer includes a first sublayer and a second sublayer in sequence in a thickness direction of the growth substrate, and a band gap of the first sublayer is higher than a band gap of the second sublayer;

[0031] forming an epitaxial layer above the second sublayer, wherein the epitaxial layer sequentially comprises a first semiconductor layer, an active layer and a second semiconductor layer in a thickness direction of the growth substrate;

[0032] A base plate is formed over the second semiconductor layer, and then the growth substrate is removed.

[0033] Compared with the prior art, the LED epitaxial structure and the preparation method thereof, the LED chip and the preparation method thereof described in the present invention have at least the following beneficial effects:

[0034] The LED epitaxial structure described in the present invention is provided with a current spreading layer between the growth substrate and the epitaxial layer, and the current spreading layer includes a first sublayer and a second sublayer, wherein the band gap of the first sublayer is higher than the band gap of the second sublayer. Due to the setting of the high and low potential barrier differences in the current spreading layer, the lateral diffusion capacity of the current can be increased, the brightness and antistatic capacity of the LED epitaxial structure can be improved, and the forward voltage of the LED epitaxial structure can be improved, which is beneficial to the reliability of the device.

[0035] Furthermore, the epitaxial layer in the LED epitaxial structure described in the present invention is provided with a first diffusion barrier layer between the first semiconductor layer and the active layer, and a second diffusion barrier layer is provided between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to block the doping elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer, thereby preventing the light-emitting effect of the active layer from being affected, and further improving the brightness of the LED epitaxial structure.

[0036] The LED epitaxial structure preparation method, LED chip and preparation method thereof of the present invention all include the LED epitaxial structure, and can also achieve the above effects. In addition, due to the arrangement of the current expansion layer in the epitaxial structure, the LED chip of the present invention does not need to be provided with a metal expansion strip to improve the current expansion, thereby avoiding the absorption of the light emitted by the epitaxial layer by the metal expansion strip, and further improving the luminous efficiency of the LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic structural diagram of the LED epitaxial structure described in Example 1 of the present invention;

[0038] Figure 2 is a schematic diagram of the structure of the LED chip described in Example 2 of the present invention;

[0039] Figure 3 is a schematic diagram of the structure of the LED chip described in Example 2 of the present invention;

[0040] Figure 4 This is a flow chart of the method for preparing the LED epitaxial structure described in Example 3 of the present invention.

[0041] Figure 5 This is a flow chart of the method for preparing the LED chip described in Example 4 of the present invention.

[0042] List of reference numerals:

[0043] 100 Growth substrate

[0044] 101 First Buffer Layer

[0045] 102 Etching sacrificial layer

[0046] 200 Current expansion layer

[0047] 201 First Sublayer

[0048] 202 Second Sublayer

[0049] 300 Epitaxial layer

[0050] 301 First semiconductor layer

[0051] 302 first diffusion barrier layer

[0052] 303 Active layer

[0053] 304 Second Diffusion Barrier Layer

[0054] 305 Second semiconductor layer

[0055] 400 Second buffer layer

[0056] 500 GaP layer

[0057] 600 substrates

[0058] 701 First Electrode

[0059] 702 second electrode DETAILED DESCRIPTION

[0060] The following specific embodiments illustrate the embodiments of the present invention, and those familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0061] It should be noted that the diagrams provided in the embodiments of the present invention are only used to illustrate the basic concept of the present invention in a schematic manner. Although the diagrams only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, the form, quantity and proportion of each component can be changed at will during actual implementation, and the layout of the components may also be more complex. The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions that can be implemented in this application, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by the present invention.

[0062] Example 1

[0063] This embodiment provides an LED epitaxial structure, referring to Figure 1The LED epitaxial structure includes: a growth substrate 100; a current spreading layer 200, which is arranged above the growth substrate 100, and the current spreading layer 200 includes a first sublayer 201 and a second sublayer 202 in the thickness direction of the growth substrate 100, and the band gap of the first sublayer 201 is higher than the band gap of the second sublayer 202; an epitaxial layer 300, which is arranged above the second sublayer 202, and the epitaxial layer 300 includes a first semiconductor layer 301, an active layer 303, and a second semiconductor layer 305 in the thickness direction of the growth substrate 100. Among them, the current spreading layer 200 in the present invention includes a first sublayer 201 and a second sublayer 202, and the band gap of the first sublayer 201 is higher than the band gap of the second sublayer 202. The high and low setting of the band gap can force the current to increase the lateral current spreading ability in the current spreading layer 200, which is helpful to improve the brightness of the LED epitaxial structure and improve the antistatic ability and forward voltage of the LED epitaxial structure.

[0064] Specifically, refer to Figure 1 The material of the growth substrate 100 includes but is not limited to GaAs. In this embodiment, the GaAs growth substrate 100 is taken as an example.

[0065] The current spreading layer 200 is disposed above the growth substrate 100. Optionally, a first buffer layer 101 and an etching sacrificial layer 102 are also disposed between the growth substrate 100 and the current spreading layer 200; the first buffer layer 101 is used to eliminate the influence of the lattice defects of the growth substrate 100 on the epitaxial layer 300. The etching sacrificial layer 102 is used as a stop layer for subsequent chemical etching. Optionally, the etching sacrificial layer 102 is an N-type etching sacrificial layer 102, and the material is N-GaInP. The material of the current spreading layer 200 is (Al X Ga 1-X ) Y In 1-Y P, where 0≤X≤1, 0≤Y≤1, generally, the thickness is between 2 and 4μm. The current spreading layer 200 includes a first sublayer 201 and a second sublayer 202. The band gap of the first sublayer 201 is higher than the band gap of the second sublayer 202. Since the current diffuses slowly in the first sublayer 201, when it is conducted to the second sublayer 202, the difference in high and low band gaps forces the current to expand laterally, thereby improving the brightness of the LED and improving the antistatic performance. Optionally, the Al content in the first sublayer 201 is greater than the Al content in the second sublayer 202; in order to prevent the current spreading layer from being easily oxidized and easily absorbing light, the Al content in the material of the first sublayer 201 is between 0.5 and 0.7, and the Al content in the material of the second sublayer 202 is between 0.25 and 0.4. In this embodiment, the material of the first sublayer 201 is Al 0.6 Ga 0.4 InP, the material of the second sub-layer 202 is Al 0.3 Ga0.7 InP. Optionally, the thickness of the first sublayer 201 is less than the thickness of the second sublayer 202, which can ensure that the forward voltage is appropriately reduced and the brightness of the LED epitaxial structure is improved. Optionally, the thickness of the first sublayer 201 is between 0.5μm and 1.5μm, and the thickness of the second sublayer 202 is between 1.5μm and 3μm. The thickness range and component ratio of the second sublayer can largely avoid the light absorption of the current spreading layer, and achieve higher LED brightness and better forward voltage. In this embodiment, the thickness of the first sublayer 201 is 1.5μm, and the thickness of the second sublayer 202 is 2μm.

[0066] An epitaxial layer 300 is arranged above the current spreading layer 200, and the epitaxial layer 300 includes a first semiconductor layer 301, an active layer 303 and a second semiconductor layer 305 in sequence. In this embodiment, the first semiconductor layer 301 is an N-type confinement layer, the material of which is N-AlInP, and can provide electrons for compound luminescence; the second semiconductor layer 305 is a P-type confinement layer, the material of which is P-AlInP, and can provide holes for compound luminescence. The active layer 303 is a single quantum well or a multi-quantum well, and its material composition is AlGaInP, which can perform compound luminescence of electrons and holes. In this embodiment, the semiconductor epitaxial structure radiates red light. In addition, since the first semiconductor layer 301 is also a high bandgap layer, it forms a high-low-high barrier with the first sublayer 201 and the second sublayer 202, which can further increase the current spreading capability and improve the LED brightness and antistatic performance.

[0067] In an optional embodiment, a first diffusion barrier layer 302 is provided between the first semiconductor layer 301 of the epitaxial layer 300 and the active layer 303, and a second diffusion barrier layer 304 is provided between the second semiconductor layer 305 and the active layer 303. The first diffusion barrier layer 302 and the second diffusion barrier layer 304 are respectively used to prevent the doping elements in the first semiconductor layer 301 and the second semiconductor from diffusing into the active layer 303. Since the first diffusion barrier layer 302 and the second diffusion barrier layer 304 belong to the undoped space region, the luminous effect of the active layer 303 can be prevented from being affected, causing the brightness and reliability of the LED to deteriorate. Optionally, the constituent materials of the first diffusion barrier layer 302 and the second diffusion barrier layer 304 are the same as those of the first semiconductor layer 301 and the second semiconductor layer 305, respectively.

[0068] Optionally, a GaP layer 500 is further provided above the second semiconductor layer 305 of the epitaxial layer 300, and the GaP layer 500 is used to expand the current. Optionally, a second buffer layer 400 is further provided between the GaP layer 500 and the second semiconductor layer 305, and the second buffer layer 400 is used to eliminate the lattice constant difference between the GaP layer 500 and the second semiconductor layer 305, and plays a role of transition connection.

[0069] The LED epitaxial structure described in this embodiment can increase the current expansion while improving the forward voltage, thereby enhancing the brightness and antistatic performance of the LED epitaxial structure by setting the potential barrier difference between the first sublayer and the second sublayer in the current expansion layer.

[0070] Example 2

[0071] The present embodiment provides an LED chip, which includes a substrate 600; an epitaxial layer 300, which is located above the substrate 600, and the epitaxial layer 300 includes a second semiconductor layer 305, an active layer 303 and a first semiconductor layer 301 in sequence in the thickness direction of the substrate 600; a current spreading layer 200, which is located above the first semiconductor layer 301, and the current spreading layer 200 includes a second sublayer 202 and a first sublayer 201 in sequence in the thickness direction of the substrate 600, and the band gap of the first sublayer 201 is higher than the band gap of the second sublayer 202.

[0072] Specifically, refer to Figure 2 , the substrate 600 has a first surface and a second surface arranged opposite to each other, the epitaxial layer 300 is formed on the first surface of the substrate 600, and the substrate 600 may be a SiC substrate, a Ge substrate, or a sapphire substrate, etc. When the second electrode 702 is formed on the second surface of the substrate 600, the substrate 600 is a conductive substrate. In this embodiment, a GaP layer 500 is arranged between the substrate 600 and the epitaxial layer 300.

[0073] An epitaxial layer 300 is disposed above the GaP layer 500. Optionally, in order to eliminate the lattice constant difference between the epitaxial layer 300 and the GaP layer 500, a second buffer layer 400 is generally further disposed between the GaP layer 500 and the epitaxial layer 300. The epitaxial layer 300 includes a second semiconductor layer 305, an active layer 303, and a first semiconductor layer 301 in sequence. The second semiconductor layer 305, the active layer 303, and the first semiconductor layer 301 in the epitaxial layer 300 in this embodiment are the same as those in Embodiment 1, and are not described one by one here.

[0074] A current spreading layer 200 is disposed above the epitaxial layer 300, and the current spreading layer 200 sequentially includes a second sublayer 202 and a first sublayer 201. The first sublayer 201 and the second sublayer 202 in the current spreading layer 200 in this embodiment are the same as those in Embodiment 1, and are not described in detail here.

[0075] A first electrode 701 is also formed on the surface of the first sublayer 201. A roughened structure is formed on the side of the first sublayer 201 away from the substrate 600. The roughened structure is formed on the surface other than the contact surface between the first sublayer 201 and the first electrode 701. The depth of the roughened structure is less than or equal to the thickness of the first sublayer 201. Roughening the surface of the first sublayer with a higher potential barrier is beneficial to the roughening effect of the LED chip. At the same time, the first sublayer 201 is set to 0.5-1.5 μm, and a roughened structure with a roughening depth of 0.5-1.5 μm is obtained. The roughened structure is more beneficial to the light emitting effect of the LED.

[0076] A second electrode 702 is also formed on the second surface of the substrate 600. At this time, the chip is formed into a vertical structure. Figure 2 In an optional embodiment, a step structure is etched on the epitaxial layer 300, the step structure exposes the GaP layer 500, and the second electrode 702 is formed on the GaP layer 500 exposed on the step structure. At this time, the chip is formed into a horizontal structure. Figure 3 .

[0077] The LED chip described in this embodiment includes the LED epitaxial structure in embodiment 1, which can also improve the forward voltage while increasing the current expansion, and improve the brightness and antistatic performance of the LED epitaxial structure. In addition, since the high and low barrier layers in this embodiment can increase the lateral expansion of the current, there is no need to form a metal expansion strip between the electrode and the current expansion layer, which avoids the absorption of light by the metal expansion strip, improves the luminous efficiency, and saves manufacturing process and cost. The LED chip described in this embodiment was tested and found that the brightness of the LED chip can be increased by 10%, the forward voltage can be reduced by 5%, and the antistatic ability can be improved by 20%.

[0078] Example 3

[0079] This embodiment provides a method for preparing an LED epitaxial structure. Figure 4 The specific steps include:

[0080] S101: providing a growth substrate;

[0081] Specifically, refer to Figure 1 , a growth substrate 100 is provided. The growth substrate has a first surface and a second surface arranged opposite to each other. The material of the growth substrate 100 includes but is not limited to GaAs. In this embodiment, the GaAs growth substrate 100 is taken as an example.

[0082] A first buffer layer 101 and an etching sacrificial layer 102 are sequentially formed on the first surface of the growth substrate 100, and specifically, they can be sequentially deposited by chemical vapor deposition. The etching sacrificial layer 102 is an N-type etching sacrificial layer 102, and the material is N-GaInP.

[0083] S102: forming a current spreading layer above the growth substrate, the current spreading layer comprising a first sublayer and a second sublayer in sequence in a thickness direction of the growth substrate, the band gap of the first sublayer being higher than the band gap of the second sublayer;

[0084] Specifically, refer to Figure 1 , a current spreading layer 200 is formed above the etched sacrificial layer 102 of the growth substrate 100 . Specifically, a first sublayer 201 is firstly deposited on the etched sacrificial layer 102 , and then a second sublayer 202 is deposited on the first sublayer 201 .

[0085] S103: forming an epitaxial layer above the second sub-layer, wherein the epitaxial layer includes a first semiconductor layer, an active layer, and a second semiconductor layer in sequence in a thickness direction of the growth substrate.

[0086] Specifically, refer to Figure 1 , an epitaxial layer 300 is formed on the surface of the second sub-layer 202 by chemical vapor deposition, and the epitaxial layer 300 sequentially forms a first semiconductor layer 301, an active layer 303, and a second semiconductor layer 305. In an optional embodiment, forming the epitaxial layer 300 includes: depositing the first semiconductor layer 301, the first diffusion barrier layer 302, the active layer 303, the second diffusion barrier layer 304, and the second semiconductor layer 305 on the surface of the second sub-layer 202 in sequence.

[0087] After forming the epitaxial layer 300, a second buffer layer 400 and a GaP layer 500 are sequentially deposited on the surface of the second semiconductor layer 305 of the epitaxial layer 300 to obtain Figure 1 The epitaxial structure shown.

[0088] The method for preparing the LED epitaxial structure described in this embodiment can improve the forward voltage while increasing the current expansion, thereby improving the brightness and antistatic performance of the LED epitaxial structure by setting the potential barrier difference between the first sublayer and the second sublayer.

[0089] Example 4

[0090] This embodiment also provides a method for preparing an LED chip, referring to Figure 5 In addition to steps S101 to S103 in the above embodiment 3, this step also includes:

[0091] S104: forming a substrate above the second semiconductor layer, and then removing the growth substrate.

[0092] Specifically, refer to Figure 2 Or 3, forming a metal bonding layer (not shown in the figure) on the GaP layer 500 , and bonding the metal bonding layer to the first surface of the substrate 600 .

[0093] The growth substrate 100 is thinned by mechanical grinding, and the growth substrate 100 and the first buffer layer 101 are removed by wet etching. The etching stops at the etching sacrificial layer 102, and the etching sacrificial layer 102 is removed by wet etching to expose the first sublayer 201.

[0094] A first electrode 701 is formed on a portion of the surface of the first sub-layer 201. In this embodiment, the first electrode 701 is an N electrode. After the first electrode 701 is formed, the surface of the exposed first sub-layer 201 is patterned so that a roughened structure is formed on the surface of the exposed first sub-layer 201, and the depth of the roughened structure is less than or equal to the thickness of the first sub-layer 201. Since the Al content in the first sub-layer 201 is relatively high, the roughening effect can be ensured.

[0095] A second electrode 702 is formed on the second surface of the substrate 600. The second electrode 702 is a P electrode, forming a vertical chip structure. Figure 2 In an optional embodiment, a step structure is etched on the epitaxial layer 300, the step structure exposes the GaP layer 500, and a second electrode 702 is formed on the GaP layer 500 exposed on the step structure to form a horizontal chip structure, as shown in FIG. Figure 3 shown.

[0096] The method for preparing the LED chip described in this embodiment includes the LED epitaxial structure in embodiment 1, and can also improve the forward voltage while increasing the current expansion, and improve the brightness and antistatic performance of the LED epitaxial structure. In addition, since the high and low barrier layers in this embodiment can increase the lateral expansion of the current, there is no need to form a metal expansion strip between the electrode and the current expansion layer, which avoids the absorption of light by the metal expansion strip, improves the luminous efficiency, and saves the manufacturing process and cost.

[0097] In summary, the LED epitaxial structure described in the present invention is provided with a current spreading layer between the growth substrate and the epitaxial layer, and the current spreading layer includes a first sublayer and a second sublayer, wherein the band gap of the first sublayer is higher than the band gap of the second sublayer. Due to the setting of the high and low potential barrier differences in the current spreading layer, the lateral diffusion capacity of the current can be increased, the brightness and antistatic ability of the LED epitaxial structure can be improved, and the forward voltage of the LED epitaxial structure can be improved, which is beneficial to the reliability of the device.

[0098] Furthermore, the epitaxial layer in the LED epitaxial structure described in the present invention is provided with a first diffusion barrier layer between the first semiconductor layer and the active layer, and a second diffusion barrier layer is provided between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to block the doping elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer, thereby preventing the light-emitting effect of the active layer from being affected, and further improving the brightness of the LED epitaxial structure.

[0099] The LED epitaxial structure preparation method, LED chip and preparation method thereof of the present invention all include the LED epitaxial structure, and can also achieve the above effects. In addition, due to the arrangement of the current expansion layer in the epitaxial structure, the LED chip of the present invention does not need to be provided with a metal expansion strip to improve the current expansion, thereby avoiding the absorption of the light emitted by the epitaxial layer by the metal expansion strip, and further improving the luminous efficiency of the LED chip.

[0100] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An LED epitaxial structure, characterized in that: include: Growth substrate; A current spreading layer is disposed above the growth substrate, wherein the current spreading layer includes a first sublayer and a second sublayer in sequence in the thickness direction of the growth substrate, the band gap of the first sublayer is higher than the band gap of the second sublayer, and the thickness of the first sublayer is smaller than the thickness of the second sublayer; The epitaxial layer is disposed above the second sub-layer, and the epitaxial layer includes a first semiconductor layer, an active layer and a second semiconductor layer in sequence in the thickness direction of the growth substrate.

2. The LED epitaxial structure according to claim 1, characterized in that: The thickness of the first sub-layer is between 0.5 μm and 1.5 μm, and the thickness of the second sub-layer is between 1.5 μm and 3 μm.

3. The LED epitaxial structure according to claim 1, characterized in that: The material of the current spreading layer is (Al X Ga 1-X ) Y In 1-Y P, wherein 0≤X≤1, 0≤Y≤1; the content of Al in the first sub-layer is greater than the content of Al in the second sub-layer.

4. The LED epitaxial structure according to claim 3, characterized in that: The Al content in the material of the first sub-layer is between 0.5 and 0.7, and the Al content in the material of the second sub-layer is between 0.25 and 0.

4.

5. The LED epitaxial structure according to claim 4, characterized in that: The material of the first sublayer is Al 0.6 Ga 0.4 InP, the material of the second sub-layer is Al 0.3 Ga 0.7 InP.

6. The LED epitaxial structure according to claim 1, characterized in that: A first diffusion barrier layer is arranged between the first semiconductor layer and the active layer of the epitaxial layer, and a second diffusion barrier layer is arranged between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to prevent the doping elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer.

7. The LED epitaxial structure according to claim 1, characterized in that: The LED epitaxial structure radiates red light.

8. An LED chip, characterized in that: include: substrate; An epitaxial layer, located above the substrate, wherein the epitaxial layer sequentially comprises a second semiconductor layer, an active layer and a first semiconductor layer in a thickness direction of the substrate; A current spreading layer is located above the first semiconductor layer, and the current spreading layer includes a second sublayer and a first sublayer in sequence in the thickness direction of the substrate, the band gap of the first sublayer is higher than the band gap of the second sublayer, and the thickness of the first sublayer is less than the thickness of the second sublayer.

9. The LED chip according to claim 8, characterized in that: A roughening structure is formed on a side of the first sub-layer away from the substrate, and a depth of the roughening structure is less than or equal to a thickness of the first sub-layer.

10. The LED chip according to claim 8, characterized in that: The material of the current spreading layer is (Al X Ga 1-X ) Y In 1-Y P, wherein 0≤X≤1, 0≤Y≤1, and the content of Al in the first sublayer is greater than the content of Al in the second sublayer.

11. The LED chip according to claim 8, characterized in that: A first diffusion barrier layer is arranged between the first semiconductor layer and the active layer of the epitaxial layer, and a second diffusion barrier layer is arranged between the second semiconductor layer and the active layer. The first diffusion barrier layer and the second diffusion barrier layer are respectively used to prevent the doping elements in the first semiconductor layer and the second semiconductor from diffusing into the active layer.

12. A method for preparing an LED epitaxial structure, characterized in that: include: providing a growth substrate; forming a current spreading layer above the growth substrate, wherein the current spreading layer includes a first sublayer and a second sublayer in sequence in a thickness direction of the growth substrate, the band gap of the first sublayer is higher than the band gap of the second sublayer, and the thickness of the first sublayer is less than the thickness of the second sublayer; An epitaxial layer is formed above the second sub-layer, wherein the epitaxial layer sequentially includes a first semiconductor layer, an active layer, and a second semiconductor layer in a thickness direction of the growth substrate.

13. A method for preparing an LED chip, characterized in that: include: providing a growth substrate; forming a current spreading layer above the growth substrate, wherein the current spreading layer includes a first sublayer and a second sublayer in sequence in a thickness direction of the growth substrate, the band gap of the first sublayer is higher than the band gap of the second sublayer, and the thickness of the first sublayer is less than the thickness of the second sublayer; forming an epitaxial layer above the second sublayer, wherein the epitaxial layer sequentially comprises a first semiconductor layer, an active layer, and a second semiconductor layer in a thickness direction of the growth substrate; A base plate is formed over the second semiconductor layer, and then the growth substrate is removed.

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