Red light LED chip preparation method and red light LED chip

Abstract

The invention provides a red light LED chip preparation method and a red light LED chip. The method comprises the following steps: providing a substrate; growing an epitaxial structure comprising a DBR reflecting layer on the substrate to prepare a red light LED chip; wherein the DBR reflecting layer comprises a plurality of composite layers which are arranged in a stacked mode and are composed of first AlGaAs layers and second AlGaAs layers, the component proportion of Al in the first AlGaAs layers is smaller than the component proportion of Ga, and the number of the composite layers is 25-28. 22 pairs of DBR layers in a conventional red light LED are improved to 25-28 layers, so that the basic brightness of epitaxy is improved, the component proportion of Al in the DBR layers is further controlled to enable the component proportion of Al to be smaller than the component proportion of Ga to form the first AlGaAs layer, oxidation of the component Al can be effectively controlled in cooperation with the second AlGaAs layer arranged in a stacked mode, dark cracks caused by oxidation of the epitaxial layer in the later manufacturing process are reduced, and the brightness of the epitaxial layer is improved. And the product yield is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of LED chips, and in particular to a method for preparing a red light LED chip and a red light LED chip. Background Art

[0002] Hongguang's regular products, commonly known as "AS" products, are usually prepared through epitaxial growth, CB (current blocking layer) etching, ITO coating, PAD electrode production, grinding, back gold, cutting and other processes to complete the chip process.

[0003] In the existing technology, the number of DBR reflective layers of conventional red light LED devices in the industry is 22 pairs. In principle, the basic brightness of the epitaxial layer can be increased by increasing the number of DBR reflective layers to achieve an overall brightness improvement of the device. However, as the number of pairs of DBR layers increases, the DBR layer is prone to oxidation, resulting in dark cracks in the entire DBR layer, thereby affecting the product yield. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing a red light LED chip and a red light LED chip, aiming to solve the technical problem in the prior art that the DBR layer is easily oxidized, resulting in dark cracks in the entire DBR layer.

[0005] In order to achieve the above object, the present invention is implemented by the following technical solution: a method for preparing a red light LED chip, comprising the following steps: providing a substrate; Growing an epitaxial structure including a DBR reflective layer on the substrate to prepare a red light LED chip; The DBR reflective layer includes a plurality of stacked composite layers consisting of a first AlGaAs layer and a second AlGaAs layer, the Al component ratio in the first AlGaAs layer is less than the Ga component ratio, and the number of the composite layers is 25-28 layers.

[0006] Compared with the prior art, the beneficial effects of the present invention are as follows: by increasing the 22 pairs of DBR layers in a conventional red light LED to 25-28 layers, the basic brightness of the epitaxy is improved, and further by controlling the Al component ratio in the DBR layer to be less than the Ga component ratio to form a first AlGaAs layer, and in conjunction with a stacked second AlGaAs layer, the oxidation of the Al component can be effectively controlled, thereby reducing dark cracks caused by oxidation of the epitaxial layer in the post-process, improving the product brightness while ensuring the product yield.

[0007] According to one aspect of the above technical solution, the ratio of Al component to Ga component in the first AlGaAs layer is 96:104.

[0008] According to one aspect of the above technical solution, the specific steps of growing an epitaxial structure including a DBR reflective layer on the substrate include: A DBR reflective layer is grown on the substrate, and an N-type semiconductor layer, a light-emitting layer, a P-type semiconductor layer and a current spreading layer are sequentially grown on the DBR reflective layer to form an epitaxial structure on the substrate.

[0009] According to one aspect of the above technical solution, the specific steps of preparing the current spreading layer include: The preparation of the current blocking layer on the surface of the P-type semiconductor layer is cancelled, and an ITO film with a thickness of 700 angstroms to 900 angstroms is evaporated on the surface of the P-type semiconductor layer based on the first process parameters by electron beam evaporation technology to prepare the current spreading layer.

[0010] According to one aspect of the above technical solution, the first process parameter includes controlling the oxygen flow rate to be 6 sccm-8 sccm.

[0011] According to one aspect of the above technical solution, the specific steps of preparing the current spreading layer further include: The LED chip after the ITO film is evaporated is annealed based on the second process parameters to prepare the current spreading layer, wherein the second process parameters include an annealing temperature of 390° C.-400° C. and an annealing time of 10s-20s.

[0012] According to one aspect of the above technical solution, after the step of forming an epitaxial structure on the substrate, the method further includes: An electrode is prepared on the current spreading layer.

[0013] According to one aspect of the above technical solution, the N-type semiconductor layer includes an N-type confinement layer and an electron blocking layer which are sequentially arranged on the DBR reflective layer.

[0014] According to one aspect of the above technical solution, the P-type semiconductor layer includes a hole blocking layer and a P-type confinement layer which are sequentially arranged on the light-emitting layer.

[0015] On the other hand, the present invention further provides a red LED chip, which is prepared by the red LED chip preparation method described in the above technical solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of the method for preparing a red LED chip in the first embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a red LED chip in the first embodiment of the present invention; Substrate 100, DBR reflective layer 200, N-type semiconductor layer 300, light emitting layer 400, P-type semiconductor layer 500, current spreading layer 600, electrode 700; The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0017] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0020] Embodiment 1 See also Figure 1 , which is a flow chart of a method for preparing a red LED chip in the first embodiment of the present invention. As shown in the figure, the method includes the following steps: Step S100, providing a substrate. The substrate is the basic material for preparing the red LED chip, and is used to support and fix the epitaxial structure. Common substrate materials include sapphire, silicon, silicon carbide, etc., and their selection depends on the growth requirements of the epitaxial layer and the performance requirements of the final device.

[0021] Step S200, growing an epitaxial structure including a DBR reflective layer on the substrate to prepare a red LED chip; The DBR reflective layer includes a plurality of stacked composite layers consisting of a first AlGaAs layer and a second AlGaAs layer, wherein the Al content of the first AlGaAs layer is less than the Ga content, and the number of the composite layers is 25 to 28. In this embodiment, the number of the composite layers is preferably 26.

[0022] A red LED chip is a semiconductor light-emitting device that can emit red light. It is widely used in various display devices, lighting equipment, and indicators, and produces red light by stimulating electron transitions in semiconductor materials through electrical signals. The DBR (Distributed Bragg Reflector) reflective layer is a multilayer structure that achieves enhanced reflection of light of a specific wavelength through the periodic arrangement of materials with different refractive indices. In a red LED chip, the DBR reflective layer is used to improve the efficiency of light extraction from the chip and reduce light loss. The DBR layer is usually prepared by epitaxial growth technology, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE).

[0023] AlGaAs (aluminum gallium arsenide) is a semiconductor material composed of aluminum (Al), gallium (Ga) and arsenic (As). In red LED chips, AlGaAs layers are often used in DBR reflective layers. The refractive index of the material is changed by adjusting the composition ratio of Al and Ga, thereby achieving control over the reflection of light. AlGaAs materials are also prepared by epitaxial growth techniques, such as metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE), which can accurately control the growth rate and composition ratio of AlGaAs on the substrate, thereby preparing high-quality AlGaAs films.

[0024] By increasing the 22 pairs of DBR layers in conventional red light LEDs to 25-28 layers, the basic brightness of the epitaxy is improved. By further controlling the Al component ratio in the DBR layer to make it smaller than the Ga component ratio to form a first AlGaAs layer, and coordinating the stacked second AlGaAs layer, the oxidation of the Al component can be effectively controlled, thereby reducing dark cracks caused by oxidation of the epitaxial layer in the post-process, improving product brightness while ensuring product yield.

[0025] Preferably, in this embodiment, the ratio of Al component to Ga component in the AlGaAs structure is 96:104. That is, by reducing the Al material component in AlGa and replacing it with Ga, the lattice of the AlGaAs structure itself does not change.

[0026] Specifically, in this embodiment, the specific steps of growing an epitaxial structure including a DBR reflective layer on the substrate include: A DBR reflective layer is grown on the substrate, and an N-type semiconductor layer, a light-emitting layer, a P-type semiconductor layer and a current spreading layer are sequentially grown on the DBR reflective layer to form an epitaxial structure on the substrate.

[0027] Specifically, the light-emitting layer is the core part of the LED chip. When electrons and holes recombine in the light-emitting layer, energy is released and emitted in the form of light. In red LED chips, the light-emitting layer is usually composed of semiconductor materials that can emit red light. The current spreading layer is a thin film layer used to improve the current distribution in the LED chip. In red LED chips, the current spreading layer is usually located above the P-type semiconductor layer, which improves the luminous efficiency and stability of the LED by reducing contact resistance and improving current uniformity. Common current spreading layer materials include ITO (indium tin oxide) and the like.

[0028] Specifically, the N-type semiconductor layer includes an N-type confinement layer and an electron blocking layer sequentially disposed on the DBR reflective layer, and the P-type semiconductor layer includes a hole blocking layer and a P-type confinement layer sequentially disposed on the light emitting layer.

[0029] Furthermore, the specific steps of preparing the current spreading layer include: The preparation of the current blocking layer on the surface of the P-type semiconductor layer is cancelled, and an ITO film with a thickness of 700 angstroms to 900 angstroms is evaporated on the surface of the P-type semiconductor layer based on the first process parameters by electron beam evaporation technology to prepare the current spreading layer.

[0030] The main function of the current spreading layer is to make the current more evenly distributed in the LED device, thereby improving the external quantum efficiency of the LED. The current distribution in LED devices is usually uneven, especially near the electrodes, where the current density is high, while in areas far away from the electrodes, the current density is low. This uneven current distribution will lead to a decrease in the luminous efficiency of the LED device. The current spreading layer improves the luminous efficiency by providing a low-resistance path so that the current can flow more evenly through the active layer of the LED.

[0031] ITO (Indium Tin Oxide) transparent conductive material as the current spreading layer has good conductivity and transparency, which can effectively spread the current and reduce light loss.

[0032] For ease of understanding, after the conventional process prepares the P-type semiconductor layer, it is necessary to control the current from flowing under the electrode (i.e., the electrode shielding) through the process CB layer (current blocking layer), so that the current flows to the four sides of the chip to trigger holes and recombination in the edge area, thereby improving the brightness of the chip. However, the cost of this process is very high, and it is necessary to prepare a graphic current blocking layer through dry etching, degumming, etc. In this embodiment, by eliminating the preparation of the current blocking layer, and using electron beam evaporation technology, based on the first process parameters, an ITO film with a thickness of 700 angstroms to 900 angstroms is evaporated on the surface of the P-type semiconductor layer to improve the brightness of the chip and reduce the cost of the chip preparation process. Specifically, in this embodiment, the thickness of the above-mentioned ITO film is preferably 800 angstroms.

[0033] Further, in this embodiment, the first process parameter includes controlling the oxygen flow rate to be 6sccm-8sccm. It is easy to understand that, compared with the conventional coating process, this solution can improve the transmittance of the ITO film by controlling the oxygen flow rate to be 6sccm-8sccm, that is, increasing the oxygen flow rate. Specifically, in this embodiment, the oxygen flow rate is preferably 7sccm.

[0034] Furthermore, in this embodiment, the specific steps of preparing the current spreading layer further include: The LED chip after the ITO film is evaporated is annealed based on the second process parameters to prepare the current spreading layer, wherein the second process parameters include an annealing temperature of 390°C-400°C and an annealing time of 10s-20s. Specifically, in this embodiment, the annealing temperature is preferably 395°C and the annealing time is 15s.

[0035] Specifically, in this embodiment, after the step of forming an epitaxial structure on the substrate, the method further includes: Electrodes are prepared on the current spreading layer. The electrode is the interface between the LED chip and the external circuit, and is used to input electrical energy into the LED chip, thereby stimulating the light-emitting layer to emit light. In a red light LED chip, electrodes are usually prepared on the current spreading layer, including positive and negative electrodes, to achieve lighting and control of the LED chip.

[0036] It can be understood that after the preparation of the electrode is completed, the chip is then ground and back-gold evaporated to complete the ohmic contact, and finally the final core particle is produced through back-side cutting, core particle sorting and other actions.

[0037] In summary, the method for preparing a red LED chip in the above embodiment of the present invention increases the 22 pairs of DBR layers in a conventional red LED to 25-28 layers, thereby improving the basic brightness of the epitaxy, and further controls the Al component ratio in the DBR layer to be less than the Ga component ratio to form a first AlGaAs layer, and cooperates with a stacked second AlGaAs layer to effectively control the oxidation of the Al component, thereby reducing dark cracks caused by oxidation of the epitaxial layer in the post-process, thereby improving the product brightness and ensuring the product yield.

[0038] Embodiment 2 The second embodiment of the present invention provides a red LED chip, which is prepared by the red LED chip preparation method in the first embodiment.

[0039] Specifically, the red LED chip in this embodiment includes: Substrate 100; An epitaxial structure grown on the substrate 100 includes a DBR reflective layer 200, wherein the DBR reflective layer 200 includes a plurality of stacked composite layers consisting of a first AlGaAs layer and a second AlGaAs layer, the Al component ratio in the first AlGaAs layer is less than the Ga component ratio, and the number of the composite layers is 25-28 layers.

[0040] Preferably, in this embodiment, the ratio of Al component to Ga component in the AlGaAs structure is 96:104.

[0041] Preferably, in this embodiment, the epitaxial structure specifically includes: A DBR reflective layer 200 is grown on the substrate 100 , and an N-type semiconductor layer 300 , a light emitting layer 400 , a P-type semiconductor layer 500 and a current spreading layer 600 are sequentially grown on the DBR reflective layer 200 .

[0042] Specifically, the N-type semiconductor layer 300 includes an N-type confinement layer and an electron blocking layer sequentially disposed on the DBR reflective layer 200 , and the P-type semiconductor layer 500 includes a hole blocking layer and a P-type confinement layer sequentially disposed on the light emitting layer 400 .

[0043] Preferably, in this embodiment, the current spreading layer 600 is an ITO film with a thickness of 700 angstroms to 900 angstroms.

[0044] Specifically, in this embodiment, the red LED chip further includes an electrode 700 disposed on the current spreading layer 600 .

[0045] In summary, the red LED chip in the above embodiment of the present invention increases the 22 pairs of DBR layers in the conventional red LED to 25-28 layers, thereby improving the basic brightness of the epitaxy, and further controls the Al component ratio in the DBR layer to be less than the Ga component ratio to form a first AlGaAs layer, and cooperates with the stacked second AlGaAs layer to effectively control the oxidation of the Al component, thereby reducing dark cracks caused by oxidation of the epitaxial layer in the post-process, improving the product brightness while ensuring the product yield.

[0046] Embodiment 3 The third embodiment of the present invention provides a method for preparing a red LED chip. The process steps of the method are basically the same as those of the first embodiment, except that: In this embodiment, the number of the composite layers is 25, and the thickness of the ITO film on the surface of the P-type semiconductor layer is 700 angstroms.

[0047] The oxygen flow rate in the first process parameter is 6 sccm; the annealing temperature in the second process parameter is 390° C., and the annealing time is 10 s.

[0048] Embodiment 4 The fourth embodiment of the present invention provides a method for preparing a red LED chip. The process steps of the method are basically the same as those of the first embodiment, except that: In this embodiment, the number of the composite layers is 28, and the thickness of the ITO film on the surface of the P-type semiconductor layer is 900 angstroms.

[0049] The oxygen flow rate in the first process parameter is 8 sccm; the annealing temperature in the second process parameter is 400° C., and the annealing time is 20 s.

[0050] Comparative Example 1 This comparative example 1 provides a method for preparing a red LED chip. The process steps of the method are basically the same as those in the first embodiment, except that: In this comparative example, the oxygen flow rate in the first process parameter is 12 sccm.

[0051] Comparative Example 2 This comparative example 2 provides a method for preparing a red LED chip. The process steps of the method are basically the same as those in the first embodiment, except that: In this comparative example, the oxygen flow rate in the above-mentioned first process parameter is 3 sccm.

[0052] Comparative Example 3 This comparative example 3 provides a method for preparing a red LED chip. The process steps of the method are basically the same as those in the first embodiment, except that: In this comparative example, the thickness of the ITO film on the surface of the P-type semiconductor layer is 2800 angstroms.

[0053] Comparative Example 4 This comparative example 4 provides a method for preparing a red LED chip. The process steps of the method are basically the same as those in the first embodiment, except that: In this comparative example, the ratio of Al component to Ga component in the AlGa structure is 1:1.

[0054] The photoelectric properties of the red LED chips prepared in Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4 were tested, and the test results are shown in Table 1 below.

[0055]

[0056] Table 1 The brightness data in Table 1 uses the brightness data of the conventional LED red light chip in the prior art as the standard value (100%). It can be seen from the test results that the red light LED chips prepared in the first and second embodiments are improved compared with the conventional red light LEDs, indicating that the high-layer number setting of the DBR reflective layer improves the brightness of the LED chip, while the oxygen intake in the second comparative example is lower than that in the present embodiment, resulting in a decrease in the transmittance of the ITO film, thereby affecting the brightness of the chip. Although the oxygen intake in the first comparative example is higher than that in the present embodiment, this is because although an increase in the oxygen flow rate within a certain value range will lead to a decrease in the square resistance of the ITO film, an excessive intake will lead to an increase in the square resistance; and although the increase in the film thickness in the third comparative example will reduce the square resistance of the ITO film, it will relatively affect the brightness of the source, indicating that the parameters and film thickness in this solution have beneficial effects.

[0057] 1000 red LED chips prepared in Example 1 and Comparative Example 4 were taken respectively, and a lighting performance test was carried out for 1000 hours in a high temperature environment. The test results are shown in Table 2 below.

[0058]

[0059] Table 2 The test results show that the yield of the red LED chip prepared in Example 1 is much higher than that of the red LED chip prepared in Comparative Example 1, which indicates that the ratio of the Al component to the Ga component in this solution has a beneficial effect.

[0060] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0061] The above-described embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a red light LED chip, characterized in that: The following steps are involved: providing a substrate; Growing an epitaxial structure including a DBR reflective layer on the substrate to prepare a red light LED chip; The DBR reflective layer includes a plurality of stacked composite layers consisting of a first AlGaAs layer and a second AlGaAs layer, the Al component ratio in the first AlGaAs layer is less than the Ga component ratio, and the number of the composite layers is 25-28 layers.

2. The method for preparing a red LED chip according to claim 1, characterized in that: The ratio of Al component to Ga component in the first AlGaAs layer is 96:

104.

3. The method for preparing a red LED chip according to claim 1, characterized in that: The specific steps of growing an epitaxial structure including a DBR reflective layer on the substrate include: A DBR reflective layer is grown on the substrate, and an N-type semiconductor layer, a light-emitting layer, a P-type semiconductor layer and a current spreading layer are sequentially grown on the DBR reflective layer to form an epitaxial structure on the substrate.

4. The method for preparing a red LED chip according to claim 3, characterized in that: The specific preparation steps of the current spreading layer include: The current spreading layer is prepared by depositing an ITO film with a thickness of 700 angstroms to 900 angstroms on the surface of the P-type semiconductor layer based on first process parameters by electron beam evaporation technology.

5. The method for preparing a red LED chip according to claim 4, characterized in that: The first process parameter includes controlling the oxygen flow rate to be 6 sccm-8 sccm.

6. The method for preparing a red LED chip according to claim 5, characterized in that: The specific preparation steps of the current spreading layer also include: The LED chip after the ITO film is evaporated is annealed based on the second process parameters to prepare the current spreading layer, wherein the second process parameters include an annealing temperature of 390° C.-400° C. and an annealing time of 10s-20s.

7. The method for preparing a red LED chip according to claim 3, characterized in that: After the step of forming an epitaxial structure on the substrate, the method further comprises: An electrode is prepared on the current spreading layer.

8. The method for preparing a red LED chip according to claim 3, characterized in that: The N-type semiconductor layer includes an N-type confinement layer and an electron blocking layer which are sequentially arranged on the DBR reflective layer.

9. The method for preparing a red LED chip according to claim 3, characterized in that: The P-type semiconductor layer includes a hole blocking layer and a P-type confinement layer which are sequentially arranged on the light-emitting layer.

10. A red light LED chip, characterized in that: The red LED chip is prepared by the red LED chip preparation method according to any one of claims 1 to 9.

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