LED chip and manufacturing method thereof

Abstract

According to the LED chip and the manufacturing method thereof provided by the invention, the DBR reflector is grown between the second type semiconductor layer and the transition layer, and the DBR reflector is etched to have the plurality of openings to expose part of the second surface of the epitaxial laminated layer, so that the patterned DBR reflector can be obtained; the light emitted to the second type semiconductor layer is reflected by the DBR reflector and then is emitted from one side of the first type semiconductor layer, so that a reversed polarity structure is obtained; meanwhile, through the arrangement of the opening and the transition layer, the contact between the second type semiconductor layer and the current expansion layer is not hindered while the transition of crystal lattices and / or band gaps from the DBR reflector to the current expansion layer is ensured, so that the current diffusion can be better realized, and the electrical requirement of the LED is ensured. Namely, the beneficial effects are realized at the epitaxial end, so that the LED chip has relatively high light emitting efficiency while ensuring the electrical property requirement of the LED. And the method is particularly suitable for high-power LEDs and small-size (such as Mini and Micro) LEDs.

Description

Technical Field

[0001] The present invention relates to the field of LED chips, and in particular to an LED chip and a manufacturing method thereof. Background Art

[0002] With the rapid development of LED technology and the gradual improvement of LED lighting efficiency, the application of LED is becoming more and more extensive, and people are paying more and more attention to the development prospects of LED in display screens. As the core component of LED lamps, the function of LED chips is to convert electrical energy into light energy. Specifically, they include epitaxial wafers and N-type electrodes and P-type electrodes respectively arranged on the epitaxial wafers. The epitaxial wafer includes a P-type semiconductor layer, an N-type semiconductor layer, and an active layer located between the N-type semiconductor layer and the P-type semiconductor layer. When current passes through the LED chip, the holes in the P-type semiconductor and the electrons in the N-type semiconductor will move to the active layer and recombine in the active layer, so that the LED chip emits light.

[0003] At present, LED semiconductor chips are developing towards high power, small size (such as Mini LED, Micro LED), and high brightness. The two main aspects that affect the luminous efficiency of LEDs are internal quantum efficiency and external quantum efficiency. External quantum efficiency is the light extraction efficiency. The optimization direction is mainly to reduce the light absorption of each epitaxial layer and increase the effective light extraction area and angle. Take AlGaInP-based red LED as an example: due to the light absorption of GaAs substrate and other epitaxial layers and insufficient heat dissipation, the light extraction efficiency is limited, affecting the electro-optical conversion efficiency of the device; therefore, AlGaInP-based red LEDs are mostly designed with a reverse polarity chip structure to improve this problem. At the same time, the brightness can be improved by thinning the epitaxial stack or reducing the doping of the N-type semiconductor layer. However, the thinning of the doped area will cause the voltage of the LED to rise, which will also affect its ESD performance.

[0004] In view of this, the inventor specially designed an LED chip and a method for manufacturing the same, which resulted in this case. Summary of the invention

[0005] The object of the present invention is to provide an LED chip and a method for manufacturing the same, so as to improve the light extraction efficiency of the LED chip while ensuring the electrical requirements of the LED.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An LED chip, comprising:

[0008] An epitaxial stack, the epitaxial stack comprising a first-type semiconductor layer, an active layer and a second-type semiconductor layer, and having a first surface and a second surface opposite to each other, wherein the first surface is a light-emitting surface;

[0009] A DBR reflector, which is disposed on the second surface side of the epitaxial stack and has a plurality of openings to expose a portion of the second surface of the epitaxial stack;

[0010] A transition layer, which is disposed on the surface of the DBR reflector and the exposed area of ​​the second surface;

[0011] A current spreading layer, which is arranged on the surface of the transition layer, and the transition layer is used to achieve the transition of the lattice and / or band gap from the DBR reflector to the current spreading layer;

[0012] The substrate is integrated with the epitaxial stack by embedding the conductive bonding layer into each of the openings.

[0013] Preferably, the bottom surface of the opening is located in the epitaxial stack, the bottom surface area of ​​the opening is S, the horizontal laying area of ​​the epitaxial stack is A, then A / 50≤S≤A / 2.

[0014] Preferably, the openings are distributed in an array.

[0015] Preferably, the conductive bonding layer comprises a metal bonding layer.

[0016] Preferably, the DBR reflector comprises a plurality of groups of alternately grown low-refractive index material layers and high-refractive index material layers, and the low-refractive index material layers and / or the high-refractive index material layers comprise undoped semiconductor material layers.

[0017] Preferably, the opening has sloping side walls.

[0018] Preferably, the inclined side wall forms an angle with the horizontal surface of the epitaxial stack, and the angle is in the range of 5° to 90°, including endpoint values.

[0019] Preferably, the LED chip comprises an AlGaInP-based LED chip.

[0020] Preferably, the first-type semiconductor layer comprises an N-type AlInP confinement layer, the second-type semiconductor layer comprises a P-type AlInP confinement layer, and the current spreading layer comprises a P-GaP layer.

[0021] Preferably, the DBR reflector comprises a plurality of groups of alternately grown AlGaAs layers and AlAs layers; and the transition layer comprises an AlGaInP layer.

[0022] The present invention also provides a method for manufacturing an LED chip, comprising:

[0023] S01, providing a growth substrate;

[0024] S02, forming an epitaxial stack on the surface of the growth substrate, wherein the epitaxial stack includes a first-type semiconductor layer, an active layer, and a second-type semiconductor layer epitaxially grown in sequence;

[0025] S03, growing a DBR reflector, wherein the DBR reflector is arranged on the surface of the epitaxial stack;

[0026] S04, performing photolithography on the DBR reflector to form a plurality of openings exposing a portion of the second surface of the epitaxial stack;

[0027] S05, growing a transition layer, which is disposed on the surface of the DBR reflector and the exposed area of ​​the second surface;

[0028] S06, growing a current spreading layer, which is disposed on the surface of the transition layer;

[0029] S07, providing a substrate, and embedding the substrate into each of the openings through a conductive bonding layer to form a whole with the epitaxial stack;

[0030] S08, peeling off the growth substrate.

[0031] Preferably, the bottom surface of the opening is located in the epitaxial stack, the bottom surface area of ​​the opening is S, the horizontal laying area of ​​the epitaxial stack is A, then A / 50≤S≤A / 2.

[0032] It can be known from the above technical scheme that the LED chip provided by the present invention includes: an epitaxial stack, wherein the epitaxial stack includes a first-type semiconductor layer, an active layer and a second-type semiconductor layer, and has a first surface and a second surface relative to each other, wherein the first surface is a light emitting surface; a DBR reflector, which is arranged on the second surface side of the epitaxial stack and has a plurality of openings to expose part of the second surface of the epitaxial stack; a transition layer, which is arranged on the surface of the DBR reflector and the exposed area of ​​the second surface; a current spreading layer, which is arranged on the surface of the transition layer, and the transition layer is used to realize the transition of the lattice and / or band gap from the DBR reflector to the current spreading layer; and a substrate, which is integrated with the epitaxial stack by embedding each of the openings with a conductive bonding layer. Based on the above arrangement, by growing a DBR reflector between the second-type semiconductor layer and the transition layer, etching the DBR reflector so that it has multiple openings to expose part of the second surface of the epitaxial stack, a patterned DBR reflector can be obtained, so that the light directed to the second-type semiconductor layer is reflected by the DBR reflector and then emitted from the first-type semiconductor layer side, thereby obtaining a reverse polarity structure; at the same time, through the arrangement of the openings and the transition layer, while ensuring the transition from the DBR reflector to the lattice and / or band gap of the current spreading layer, the contact between the second-type semiconductor layer and the current spreading layer is not hindered, and thus the current diffusion can be better achieved, thereby ensuring the electrical requirements of the LED. That is, the present application realizes the above-mentioned beneficial effects at the epitaxial end, thereby enabling the LED chip to have a higher light extraction efficiency while ensuring the electrical requirements of the LED. It is particularly suitable for high-power LEDs and small-size (such as Mini, Micro) LEDs.

[0033] Secondly, by setting A / 50≤S≤A / 2, wherein the bottom area of ​​the opening is S and the horizontal laying area of ​​the epitaxial stack is A; while ensuring that the patterned DBR reflector improves the light extraction efficiency, the current expansion effect is better achieved through the cooperation between the opening, the second-type semiconductor layer and the current expansion layer.

[0034] The present invention also provides a method for manufacturing an LED chip, which has a simple manufacturing process and is conducive to productization while achieving the above-mentioned beneficial effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0036] Figure 1A schematic diagram of the structure of an LED chip provided by an embodiment of the present invention;

[0037] Figures 2 to 10 A structural schematic diagram corresponding to the method for manufacturing an LED chip provided in an embodiment of the present invention;

[0038] Explanation of symbols in the figure:

[0039] 1. Growth substrate;

[0040] 2. Epitaxial stacking;

[0041] 3. DBR reflector;

[0042] 4. Transition layer;

[0043] 5. Current expansion layer;

[0044] 6. Conductive bonding layer;

[0045] 7. Substrate;

[0046] 21. A first type semiconductor layer;

[0047] 22. Active layer;

[0048] 23. Second type semiconductor layer;

[0049] 31. Low refractive index material layer;

[0050] 32. High refractive index material layer;

[0051] 33. Speak. DETAILED DESCRIPTION

[0052] To make the content of the present invention clearer, the content of the present invention is further described below in conjunction with the accompanying drawings. The present invention is not limited to this specific embodiment. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0053] like Figure 1 As shown, an LED chip comprises:

[0054] An epitaxial stack 2, the epitaxial stack 2 comprising a first-type semiconductor layer 21, an active layer 22 and a second-type semiconductor layer 23, and having a first surface and a second surface opposite to each other, wherein the first surface is a light-emitting surface;

[0055] A DBR reflector 3, which is disposed on the second surface side of the epitaxial stack 2 and has a plurality of openings 33 to expose a portion of the second surface of the epitaxial stack 2;

[0056] A transition layer 4, which is arranged on the surface of the DBR reflector 3 and the exposed area of ​​the second surface;

[0057] A current spreading layer 5, which is arranged on the surface of the transition layer 4, and the transition layer 4 is used to achieve a transition from the DBR reflector 3 to the lattice and / or band gap of the current spreading layer 5;

[0058] The substrate 7 is integrated with the epitaxial stack 2 by embedding the conductive bonding layer 6 into each of the openings 33 .

[0059] Based on the above, in one embodiment of the present application, the bottom surface of the opening 33 is located at the epitaxial stack 2, the bottom surface area of ​​the opening 33 is S, and the horizontal laying area of ​​the epitaxial stack 2 is A, then A / 50≤S≤A / 2.

[0060] Based on the above, in one embodiment of the present application, the openings 33 are distributed in an array.

[0061] Based on the above content, in one embodiment of the present application, the conductive bonding layer 6 includes a metal bonding layer.

[0062] Based on the above, in one embodiment of the present application, the DBR reflector 3 includes several groups of alternatingly grown low refractive index material layers 31 and high refractive index material layers 32, and the low refractive index material layers 31 and / or the high refractive index material layers 32 include undoped semiconductor material layers.

[0063] Based on the above, in one embodiment of the present application, the opening 33 has an inclined sidewall.

[0064] Based on the above, in one embodiment of the present application, the inclined sidewall forms an angle with the horizontal surface of the epitaxial stack 2, and the angle is in the range of 5° to 90°, including endpoint values.

[0065] Based on the above content, in one embodiment of the present application, the LED chip includes an AlGaInP-based LED chip.

[0066] Based on the above, in one embodiment of the present application, the first-type semiconductor layer 21 includes an N-type AlInP confinement layer, the second-type semiconductor layer 23 includes a P-type AlInP confinement layer, and the current spreading layer 5 includes a P-GaP layer.

[0067] Based on the above content, in one embodiment of the present application, the DBR reflector 3 includes several groups of alternately grown AlGaAs layers and AlAs layers; and the transition layer 4 includes an AlGaInP layer.

[0068] Based on the above content, the substrate 7 includes a silicon substrate 7 .

[0069] The embodiment of the present invention further provides a method for manufacturing an LED chip, comprising:

[0070] S01, such as Figure 2 As shown, a growth substrate 1 is provided;

[0071] In one embodiment of the present application, the growth substrate 1 includes a GaAs substrate.

[0072] S02, such as Figure 3 As shown, an epitaxial stack 2 is formed on the surface of the growth substrate 1, and the epitaxial stack 2 includes a first-type semiconductor layer 21, an active layer 22, and a second-type semiconductor layer 23 which are epitaxially grown in sequence;

[0073] In one embodiment of the present application, the first-type semiconductor layer 21 includes an N-type AlInP confinement layer, and the second-type semiconductor layer 23 includes a P-type AlInP confinement layer.

[0074] It should be noted that the production of the epitaxial stack 2 may also include sequentially producing a buffer layer, an etching stop layer, and a roughening layer on the surface of the growth substrate 1; the present application does not impose any limitation on this.

[0075] S03, such as Figure 4 As shown, a DBR reflector 3 is grown, and the DBR reflector 3 is arranged on the surface of the epitaxial stack 2;

[0076] In one embodiment of the present application, Figure 5 As shown, the DBR reflector 3 includes a plurality of groups of alternately grown low-refractive index material layers 31 and high-refractive index material layers 32, and the low-refractive index material layers 31 and / or the high-refractive index material layers 32 include non-doped semiconductor material layers.

[0077] Based on the above content, in one embodiment of the present application, the DBR reflector 3 includes several groups of alternately grown AlGaAs layers and AlAs layers.

[0078] S04, such as Figure 6 As shown, the DBR reflector 3 is photolithographically processed to form a plurality of openings 33 exposing a portion of the second surface of the epitaxial stack 2;

[0079] In one embodiment of the present application, the bottom surface of the opening 33 is located at the epitaxial stack 2, the bottom surface area of ​​the opening 33 is S, and the horizontal laying area of ​​the epitaxial stack 2 is A, then A / 50≤S≤A / 2.

[0080] In one embodiment of the present application, the openings 33 are distributed in an array.

[0081] In one embodiment of the present application, the opening 33 has an inclined sidewall.

[0082] In one embodiment of the present application, the inclined side wall forms an angle with the horizontal surface of the epitaxial stack 2, and the angle is in the range of 5° to 90°, including endpoint values.

[0083] S05, such as Figure 7 As shown, a transition layer 4 is grown, which is arranged on the surface of the DBR reflector 3 and the exposed area of ​​the second surface;

[0084] Based on the above content, in one embodiment of the present application, the transition layer 4 includes an AlGaInP layer.

[0085] S06, such as Figure 8 As shown, a current spreading layer 5 is grown and arranged on the surface of the transition layer 4;

[0086] Based on the above content, in one embodiment of the present application, the current spreading layer 5 includes a P-GaP layer.

[0087] S07, such as Fig. 9 As shown, a substrate 7 is provided, and the substrate 7 is integrated with the epitaxial stack 2 by embedding the conductive bonding layer 6 into each of the openings 33 .

[0088] Based on the above content, in one embodiment of the present application, the conductive bonding layer 6 includes a metal bonding layer.

[0089] Based on the above content, in one embodiment of the present application, the substrate 7 includes a silicon substrate 7 .

[0090] S08, such as Fig.10 As shown, the growth substrate 1 is peeled off, and finally the Fig.10 The LED chip shown.

[0091] It should be noted that when a buffer layer and an etching stop layer are provided on the surface of the growth substrate 1, they need to be removed simultaneously.

[0092] It can be known from the above technical scheme that the LED chip provided by the present invention includes: an epitaxial stack, wherein the epitaxial stack includes a first-type semiconductor layer, an active layer and a second-type semiconductor layer, and has a first surface and a second surface relative to each other, wherein the first surface is a light emitting surface; a DBR reflector, which is arranged on the second surface side of the epitaxial stack and has a plurality of openings to expose part of the second surface of the epitaxial stack; a transition layer, which is arranged on the surface of the DBR reflector and the exposed area of ​​the second surface; a current spreading layer, which is arranged on the surface of the transition layer, and the transition layer is used to realize the transition of the lattice and / or band gap from the DBR reflector to the current spreading layer; and a substrate, which is integrated with the epitaxial stack by embedding each of the openings with a conductive bonding layer. Based on the above arrangement, by growing a DBR reflector between the second-type semiconductor layer and the transition layer, etching the DBR reflector so that it has multiple openings to expose part of the second surface of the epitaxial stack, a patterned DBR reflector can be obtained, so that the light directed to the second-type semiconductor layer is reflected by the DBR reflector and then emitted from the first-type semiconductor layer side, thereby obtaining a reverse polarity structure; at the same time, through the arrangement of the openings and the transition layer, while ensuring the transition from the DBR reflector to the lattice and / or band gap of the current spreading layer, the contact between the second-type semiconductor layer and the current spreading layer is not hindered, and thus the current diffusion can be better achieved, thereby ensuring the electrical requirements of the LED. That is, the present application realizes the above-mentioned beneficial effects at the epitaxial end, thereby enabling the LED chip to have a higher light extraction efficiency while ensuring the electrical requirements of the LED. It is particularly suitable for high-power LEDs and small-size (such as Mini, Micro) LEDs.

[0093] Secondly, by setting A / 50≤S≤A / 2, wherein the bottom area of ​​the opening is S and the horizontal laying area of ​​the epitaxial stack is A; while ensuring that the patterned DBR reflector improves the light extraction efficiency, the current expansion effect is better achieved through the cooperation between the opening, the second-type semiconductor layer and the current expansion layer.

[0094] The present invention also provides a method for manufacturing an LED chip, which has a simple manufacturing process and is conducive to productization while achieving the above-mentioned beneficial effects.

[0095] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0096] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0097] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An LED chip, characterized in that: include: An epitaxial stack, the epitaxial stack comprising a first-type semiconductor layer, an active layer and a second-type semiconductor layer, and having a first surface and a second surface opposite to each other, wherein the first surface is a light-emitting surface; A DBR reflector, which is disposed on the second surface side of the epitaxial stack and has a plurality of openings to expose a portion of the second surface of the epitaxial stack; A transition layer, which is disposed on the surface of the DBR reflector and the exposed area of ​​the second surface; A current spreading layer, which is arranged on the surface of the transition layer, and the transition layer is used to achieve the transition of the lattice and / or band gap from the DBR reflector to the current spreading layer; The substrate is integrated with the epitaxial stack by embedding the conductive bonding layer into each of the openings.

2. The LED chip according to claim 1, characterized in that: The bottom surface of the opening is located in the epitaxial stack, the bottom surface area of ​​the opening is S, and the horizontal laying area of ​​the epitaxial stack is A, then A / 50≤S≤A / 2.

3. The LED chip according to claim 1, characterized in that: The openings are distributed in an array.

4. The LED chip according to claim 1, characterized in that: The conductive bonding layer includes a metal bonding layer.

5. The LED chip according to claim 1, characterized in that: The DBR reflector includes a plurality of groups of alternately grown low-refractive index material layers and high-refractive index material layers, and the low-refractive index material layers and / or the high-refractive index material layers include non-doped semiconductor material layers.

6. The LED chip according to claim 1, characterized in that: The opening has a sloped sidewall.

7. The LED chip according to claim 6, characterized in that: The inclined side wall forms an angle with the horizontal surface of the epitaxial stack, and the angle has a value range of 5° to 90°, including endpoint values.

8. The LED chip according to any one of claims 1 to 7, characterized in that: The LED chip includes an AlGaInP-based LED chip.

9. The LED chip according to claim 6, characterized in that: The first-type semiconductor layer includes an N-type AlInP confinement layer, the second-type semiconductor layer includes a P-type AlInP confinement layer, and the current spreading layer includes a P-GaP layer.

10. The LED chip according to claim 7, characterized in that: The DBR reflector includes a plurality of groups of alternately grown AlGaAs layers and AlAs layers; and the transition layer includes an AlGaInP layer.

11. A method for manufacturing an LED chip, characterized in that: include: S01, providing a growth substrate; S02, forming an epitaxial stack on the surface of the growth substrate, wherein the epitaxial stack includes a first-type semiconductor layer, an active layer, and a second-type semiconductor layer epitaxially grown in sequence; S03, growing a DBR reflector, wherein the DBR reflector is arranged on the surface of the epitaxial stack; S04, performing photolithography on the DBR reflector to form a plurality of openings exposing a portion of the second surface of the epitaxial stack; S05, growing a transition layer, which is disposed on the surface of the DBR reflector and the exposed area of ​​the second surface; S06, growing a current spreading layer, which is disposed on the surface of the transition layer; S07, providing a substrate, and embedding the substrate into each of the openings through a conductive bonding layer to form a whole with the epitaxial stack; S08, peeling off the growth substrate.

12. The method for manufacturing an LED chip according to claim 11, characterized in that: The bottom surface of the opening is located in the epitaxial stack, the bottom surface area of ​​the opening is S, and the horizontal laying area of ​​the epitaxial stack is A, then A / 50≤S≤A / 2.

Images