CN111564544B - Ultraviolet LED chip epitaxial structure, preparation method thereof and chip - Google Patents
Ultraviolet LED chip epitaxial structure, preparation method thereof and chip Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
- H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
- H01L2933/0008—Processes
- H01L2933/0025—Processes relating to coatings
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Abstract
The invention discloses an ultraviolet LED chip epitaxial structure, which comprises: a substrate; an epitaxial layer disposed on the substrate; the epitaxial layer comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially arranged on the substrate; a refractive layer provided on the second semiconductor layer; a current spreading layer disposed on the refraction layer; the refractive index of the refractive layer is smaller than that of the second semiconductor layer. The invention also discloses a preparation method of the ultraviolet LED chip epitaxial structure and an LED chip applying the epitaxial structure. By implementing the invention, the total reflection effect of the ultraviolet LED chip can be effectively reduced, and the light efficiency is improved.
Description
Technical Field
The invention relates to the technical field of photoelectron manufacturing, in particular to an ultraviolet LED chip epitaxial structure, a preparation method thereof and a chip.
Background
The ultraviolet LED chip is a novel solid ultraviolet light source, and compared with a traditional ultraviolet mercury lamp, the ultraviolet LED has the advantages of small volume, light weight, low power consumption, long service life, environmental friendliness, continuous and adjustable luminous wavelength and the like, so that the ultraviolet LED chip has a wide interest in the ultraviolet related application field, and particularly in the disinfection field.
However, since the energy level of ultraviolet light is high, it is easily absorbed by other materials, and total reflection is easily generated, so that the external efficiency is poor and the brightness is much lower than that of light sources of other wave bands. So that the violet light emitted by the mercury lamp cannot be completely replaced.
Disclosure of Invention
The invention aims to solve the technical problem of providing an ultraviolet LED chip epitaxial structure which can effectively improve the light efficiency of an ultraviolet LED chip.
The invention also solves the technical problem of providing a preparation method of the ultraviolet LED chip epitaxial structure.
The invention also solves the technical problem of providing an LED chip.
In order to solve the above technical problems, the present invention provides an ultraviolet LED chip epitaxial structure, which includes:
A substrate;
An epitaxial layer disposed on the substrate; the epitaxial layer comprises a first semiconductor layer, an active layer and a second semiconductor layer which are sequentially arranged on the substrate;
A refractive layer provided on the second semiconductor layer;
A current spreading layer disposed on the refraction layer;
the refractive index of the refractive layer is smaller than that of the second semiconductor layer.
As an improvement of the above technical scheme, the refractive layer is formed by oxidizing the second semiconductor layer by oxygen plasma, and doping the metal element in the current spreading layer by annealing.
As an improvement of the above technical solution, the refractive layer is made of one or more of GaO, ga 2O、Ga2O3, or MgO;
The current spreading layer at least comprises one of Si, ti, sn, zn, ge, cu, ni, au or Ru.
As an improvement of the technical scheme, the thickness of the refraction layer is 1-20 nm, the refractive index is 1.75-2.2, the energy level is 4.2-5.1 eV, the essential wavelength is 245-280 nm, and the electron mobility is 400-1000 m 2/(V.s);
the thickness of the current expansion layer is 10-50 nm.
Correspondingly, the invention also discloses a preparation method of the ultraviolet LED chip epitaxial structure, which comprises the following steps:
(1) Providing a substrate;
(2) Forming an epitaxial layer on the substrate; the epitaxial layer sequentially comprises a first semiconductor layer, an active layer and a second semiconductor layer;
(3) Forming a refractive layer on the second semiconductor layer;
(4) And forming a current expansion layer on the refraction layer to obtain a finished product of the ultraviolet LED chip epitaxial structure.
As an improvement of the above technical solution, the step (2) includes:
(2.1) sequentially forming a first semiconductor layer, an active layer and a second semiconductor layer on the substrate to obtain an epitaxial layer;
(2.2) the substrate with the epitaxial layer was sequentially cleaned with 511 cleaner, BOE cleaner, acetone and isopropyl alcohol.
As an improvement of the above technical solution, in the step (3), the second semiconductor layer is processed by using a plasma cleaning machine to form a refraction layer; wherein, the DC power is 30-100W, and the RF power is 80-150W; the working gas is O 2, and the flow rate of the working gas is 30-50 sccm; the cleaning time is 5-20 min.
As an improvement of the above technical solution, the step (4) includes:
(4.1) forming a current spreading layer on the refractive layer;
and (4.2) annealing at 450-600 ℃ for 10-30 min to obtain the ultraviolet LED chip epitaxial structure finished product.
Correspondingly, the invention also discloses an LED chip, which comprises the ultraviolet LED chip epitaxial structure.
As an improvement of the technical scheme, the LED chip is a forward-mounted LED chip, a flip-chip LED chip or a vertical LED chip.
The implementation of the invention has the following beneficial effects:
1. The invention introduces the refractive layer in the ultraviolet LED chip epitaxial structure, and the refractive index of the refractive layer is smaller than that of the second semiconductor layer. The epitaxial structure can effectively prevent the ultraviolet light from generating full emission at the junction of the epitaxial structure and the ITO layer, and effectively improve the light efficiency of the ultraviolet LED chip. Meanwhile, the refraction layer has the characteristic of high energy band, can not absorb ultraviolet light, and further improves the light emitting effect.
2. The refraction layer is formed by oxidizing the second semiconductor by oxygen plasma, and the technology is simple. And the contact resistance (< 10 -2 omega) of the refraction layer can be effectively reduced and the light efficiency is improved by doping metal elements in the refraction layer through annealing. In addition, by oxidation of the oxygen plasma, the second semiconductor layer can be planarized, and defects of the second semiconductor layer can be reduced.
3. The invention is formed by an oxygen plasma cleaning and annealing process. The process can be well integrated with the traditional epitaxial layer preparation, so that the process is reduced, and the efficiency is improved.
Drawings
FIG. 1 is a schematic diagram of an epitaxial structure of an ultraviolet LED chip according to an embodiment of the present invention;
FIG. 2 is an electron microscope image of a second semiconductor layer that has not been oxidized by oxygen plasma;
FIG. 3 is an electron microscope image of a second semiconductor layer after oxygen plasma oxidation;
FIG. 4 is a schematic diagram of an epitaxial structure of an ultraviolet LED chip according to another embodiment of the present invention;
FIG. 5 is a flow chart of a method for fabricating an epitaxial structure of an ultraviolet LED chip according to the present invention;
FIG. 6 is a schematic diagram of an LED chip according to an embodiment of the present invention (front-loading);
FIG. 7 is a schematic diagram of an LED chip (flip chip) according to another embodiment of the present invention;
Fig. 8 is a schematic structural view (vertical) of an LED chip according to another embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent. It is only stated that the terms of orientation such as up, down, left, right, front, back, inner, outer, etc. used in this document or the imminent present invention, are used only with reference to the drawings of the present invention, and are not meant to be limiting in any way.
The ultraviolet light emitted by the ultraviolet LED chip has short wavelength, high light energy level, easy absorption and easy total reflection between the epitaxial structure and the ITO layer, so that the light efficiency is low. To this end, the present invention provides an ultraviolet LED chip epitaxial structure, see fig. 1, comprising a substrate 1, an epitaxial layer 2, a refractive layer 3 and a current spreading layer 4; wherein the epitaxial layer 2 sequentially comprises a first semiconductor layer 21, an active layer 22 and a second semiconductor layer 23 which are arranged on the substrate 1; the refractive layer 3 is provided on the second semiconductor layer 23, and the current spreading layer 4 is provided on the refractive layer 3. Wherein the refractive index of the refractive layer < the refractive index of the second semiconductor layer. The epitaxial structure can effectively prevent the ultraviolet light from generating full emission at the junction of the epitaxial structure and the ITO layer, effectively improve the light efficiency of the ultraviolet LED chip, enable the ultraviolet LED chip to replace mercury lamps, be applied to the field of daily disinfection, and widen the application range of the ultraviolet LED chip.
The refractive layer 3 is formed by oxygen plasma bombardment, oxidizing the second semiconductor 23, and doping the metal element of the current spreading layer 4 by post annealing. The forming method can be well integrated with the traditional epitaxial preparation process, and has simple process and high efficiency. And the metal element is doped in the refraction layer 3 through an annealing process, so that the contact resistance (< 10 -2 Ω) of the refraction layer can be effectively reduced, and the light efficiency is improved. Further, by oxidation of the oxygen plasma, the second semiconductor layer can be planarized, and defects of the second semiconductor layer can be reduced (see fig. 2 and 3).
The refraction layer 3 is made of one or more of GaO, ga 2O、Ga2O3 or MgO; preferably, the refractive layer 3 is made of a mixture of one or more of GaO, ga 2O、Ga2O3 and MgO; further preferably, there is a mixture of GaO and MgO. The GaO and MgO are formed during oxygen plasma oxidation. The refractive index of the refractive layer made of the material is 1.75-2.2, so that the total reflection phenomenon of the ultraviolet LED chip can be effectively relieved; the energy level is 4.2-5.1 eV, the essential wavelength is 245-280 nm, and therefore, the ultraviolet light is not absorbed, and the light can be emitted without absorbing light.
The thickness of the refraction layer 3 is 1-20 nm; when the thickness is less than 1nm, the film is easy to tunnel; when the thickness is more than 20nm, the contact resistance of the refraction layer is too high, and the light efficiency is affected. Preferably, the thickness of the refraction layer 3 is 5-10 nm; exemplary are 4nm, 5nm, 7nm, 8nm, 10nm, but are not limited thereto.
Since the refractive layer 3 is made of GaO, ga 2O、Ga2O3, or the like, its electron mobility is low [ 300m 2/(v·s) ], and the contact resistance is high. Therefore, the current spreading layer 4 is formed on the surface of the refraction layer 3, and the metal element in the current spreading layer 4 is doped into the refraction layer 3 by an annealing process. Through the process, the electron mobility of the refraction layer 3 can be improved to 400-1000 m 2/(V.s), the contact resistance is reduced to below 10 -2 omega, and the light efficiency of the ultraviolet LED chip is improved.
The current spreading layer 4 is a transparent conductive film including at least one element of Si, ti, sn, zn, ge, cu, ag, au or Ru. Preferably, the current spreading layer 4 comprises at least one element of Ni, au, rh, sn. For example, in one embodiment of the present invention, the current spreading layer 4 may be a transparent conductive film containing Sn, such as an ITO film. In another embodiment of the present invention, the current spreading layer 4 includes a first current spreading layer 41 and a second current spreading layer 42; wherein, the first current expansion layer 41 is a Ni film, and the second current expansion layer 42 is an Au film. In still another embodiment of the present invention, the current spreading layer 4 includes a first current spreading layer 41 and a second current spreading layer 42; wherein, the first current expansion layer 41 is a Rh film, and the second current expansion layer 42 is a Au film.
The thickness of the current expansion layer 4 is more than 10nm; preferably, the thickness is 10 to 50nm. When the thickness is more than 50nm, the contact resistance can be effectively improved, but the current diffusion capability can be reduced, so that the current is concentrated in a certain area, and the light efficiency is not improved. It is further preferable that the thickness of the current spreading layer 4 is 15 to 30nm, and is exemplified by 12nm, 18nm, 24nm, 25nm, 27nm, but not limited thereto.
Specifically, in the present embodiment, the epitaxial layer 2 includes a first semiconductor layer 21, an active layer 22, and a second semiconductor layer 23 sequentially provided on the substrate 1; specifically, the first semiconductor layer 21 is an N-GaN layer or an N-AlGaN layer, but is not limited thereto; preferably, the first semiconductor layer 21 is an N-GaN layer having a thickness of 2 to 5 μm. The active layer 22 is a layer including a plurality of Al xGa1-x N quantum well layers and Al yGa1-y N barrier layers stacked on each other. The second semiconductor layer 23 is a P-GaN layer or a P-AlGaN layer, but is not limited thereto; preferably, the second semiconductor layer 23 is a P-GaN layer having a thickness of 1 to 5 μm.
Further, referring to fig. 4, in another embodiment of the present invention, the epitaxial layer 2 further includes a buffer layer 24 disposed between the substrate 1 and the first semiconductor layer 21; and an electron blocking layer 25 provided between the active layer 22 and the second semiconductor layer 23; the buffer layer 24 may be an AlN layer, an AlGaN superlattice layer, or a u-GaN layer, but is not limited thereto. Preferably, the buffer layer 24 is a composite layer of an AlN layer and a u-GaN layer, the AlN layer being disposed on the substrate, and the u-GaN layer being disposed on the AlN layer. The electron blocking layer may be an N-AlGaN layer or a P-AlGaN layer, but is not limited thereto. Preferably, the electron blocking layer is a P-AlGaN layer.
Correspondingly, referring to fig. 5, the invention also discloses a preparation method of the ultraviolet LED chip epitaxial structure, which comprises the following steps:
s1: providing a substrate;
wherein, the substrate is selected from sapphire, siC or spinel, but is not limited thereto.
S2: sequentially forming a first semiconductor layer, an active layer and a second semiconductor layer on a substrate;
Specifically, S2 includes:
s21: sequentially forming a first semiconductor layer, an active layer and a second semiconductor layer on a substrate to obtain an epitaxial layer;
specifically, the first semiconductor layer, the active layer, and the second semiconductor layer are formed using an MOCVD method, a PECVD method, or an MBE method.
Specifically, after the epitaxial layer is formed, annealing can be performed on the epitaxial layer; annealing may not be performed; preferably, no annealing is performed at this step.
S22: the substrate with the epitaxial layer was cleaned sequentially with 511 cleaner, BOE cleaner, acetone and isopropyl alcohol.
Specifically, the 511 cleaning agent is a mixture of sulfuric acid, hydrogen peroxide and water, and sulfuric acid: hydrogen peroxide: water=5:1:1; the BOE cleaning agent is a mixture of hydrofluoric acid and ammonium fluoride, and the ammonium fluoride (40%): hydrofluoric acid (49%) =6:1.
By adopting the cleaning agent for cleaning, pollutants on the surface of the epitaxial layer can be effectively removed, and a good foundation is provided for the bombardment and oxidation of the oxygen plasma in the later stage.
S3: forming a refractive layer on the second semiconductor layer;
specifically, the refractive layer may be formed by an MBE method, a PECVD method, an MOCVD method, or a plasma cleaning method, but is not limited thereto.
Preferably, the second semiconductor layer is processed by a plasma cleaning machine, and oxygen plasma generated by the plasma cleaning machine oxidizes part of the second semiconductor layer to form a refraction layer. The method has the advantages of short preparation process, low cost and capability of being fused with the traditional epitaxial preparation process.
Specifically, the working gas of the plasma cleaning machine is an oxygen-containing gas, such as O 2、O3、H2 O, air, NO, N 2 O, etc., but is not limited thereto; preferably, O 2 is selected. The flow rate of the working gas is 30-50 sccm; exemplary are, but not limited to, 30sccm, 32sccm, 36sccm, 40sccm, 45sccm, 48 sccm.
The DC power of the plasma cleaner is 30-100W, and the RF power is 80-150W. The cleaning time is 5-20 min, and if the cleaning time is more than 20min, the chip voltage is too high.
S4: and forming a current expansion layer on the refraction layer to obtain a finished product of the ultraviolet LED chip epitaxial structure.
Specifically, S4 includes:
S41: forming a current expansion layer on the surface of the refraction layer;
Specifically, the current spreading layer may be formed by vapor deposition, sputtering, or the like, but is not limited thereto.
S42: annealing at 450-600 ℃ for 10-30 min to obtain the ultraviolet LED chip epitaxy structure finished product.
Specifically, by annealing, the metal element in the current spreading layer can be diffused into the refractive layer, so that the contact resistance thereof is reduced.
In the present invention, after the epitaxial layer is formed, a single annealing may be performed, and then after the refractive layer and the current spreading layer are formed, a single annealing may be performed together, that is, a total of two anneals may be performed. It is also possible that no annealing is performed after the formation of the epitaxial layer, and that after the formation of the refractive layer and the current spreading layer, one annealing is performed together, i.e. one annealing is performed in total. It is also possible to anneal after the epitaxial layer is formed and not anneal after the refractive layer and the current spreading layer are formed, i.e. to anneal once in total. In the present invention, it is preferable that the epitaxial layer is not annealed separately, but the refractive layer and the current spreading layer are formed and then annealed together once. The process ensures that the refraction layer and the current expansion layer can be fused with the preparation process of the traditional epitaxial structure, effectively shortens the process, improves the production efficiency and can effectively improve the light efficiency. The above three schemes are tested respectively, and the results are shown in the following table, and as can be seen from the table, the common annealing can be improvedTo 107.5% of the traditional structure; while two anneals may promote/>108.5% Of the traditional structure, and the two are similar.
Correspondingly, in the invention, an LED chip is also disclosed, which comprises the ultraviolet LED chip epitaxial structure.
Specifically, in one embodiment of the present invention, the LED chip is a front-mounted LED chip. Referring to the drawings, it includes an ultraviolet LED chip epitaxial structure 100, a transparent conductive layer 200, a first electrode 300, a second electrode 400, and a passivation layer 500; the ultraviolet LED chip epitaxial structure 100 includes a substrate 110, and an epitaxial layer 120, a refractive layer 130, and a current spreading layer 140 sequentially disposed on the substrate 110. Wherein the epitaxial layer 120 sequentially includes a first semiconductor layer 121, an active layer 122, and a second semiconductor layer 123. In preparing the LED chip, holes penetrating the current spreading layer 140, the refractive layer 130, the second semiconductor layer 123 and the active layer 122 are formed through a photolithography etching process; the first electrode 300 is disposed in the hole and electrically connected to the first semiconductor layer 121. The transparent conductive layer 200 is disposed on the current spreading layer 140, and the second electrode 400 is disposed on the transparent conductive layer 300. The passivation layer 500 is disposed on the first electrode 300, the second electrode 400, the surface of the transparent conductive layer 200, and the exposed sidewalls of the epitaxial layer 120 to protect the LED.
Wherein the transparent conductive layer 300 is made of one or more of Indium Tin Oxide (ITO), fluorine Tin Oxide (FTO), and Aluminum Zinc Oxide (AZO); but is not limited thereto. The first electrode 400 and the second electrode 500 are a stacked structure, which is composed of two or more of Cr, ti, ni, sn, au, pt. The passivation layer 500 is made of one of photoresist, siO 2、SiNx, or Ni.
Specifically, in another embodiment of the present invention, the LED chip is a flip-chip LED chip, which specifically includes: an ultraviolet LED chip epitaxial structure 100 (comprising a substrate 110 and an epitaxial layer 120, a refractive layer 130 and a current spreading layer 140 sequentially disposed on the substrate 110); a transparent conductive layer 200 disposed on the current spreading layer 140, a first electrode 300 and a second electrode 400 disposed on the transparent conductive layer 200; an insulating protection layer 500 provided on the first electrode 300 and the second electrode 400; a reflective layer 600 provided on the insulating protective layer 500, and first and second electrode adhesion layers 700 and 800 provided on the reflective layer 600; wherein the first electrode 300 is electrically connected to the first electrode adhesive layer 700 through a hole penetrating the reflective layer 600 and the insulating protective layer 500; the second electrode 400 is electrically connected to the second electrode adhesive layer 800 through a hole penetrating the reflective layer 600 and the insulating protective layer 500.
Wherein the transparent conductive layer 200 is made of one or more of Indium Tin Oxide (ITO), fluorine Tin Oxide (FTO), and Aluminum Zinc Oxide (AZO); but is not limited thereto. The insulating protective layer 500 is made of SiO 2 or SiN x; but is not limited thereto; the reflective layer 600 includes at least one SiO 2 layer and at least one Ti 3O5 layer, which is preferably stacked by a plurality of SiO 2 layers and Ti 3O5 layers.
Specifically, in yet another embodiment of the present invention, the LED chip is a vertical LED chip. Referring to the drawings, comprising: a second substrate 200; a back metal layer 300 provided on the back of the second substrate; the bonding layer 400, the composite reflecting layer 500, the transparent conductive layer 600, the epitaxial structure 100, the passivation layer 700 and the first electrode 800 are sequentially arranged on the front surface of the second substrate; the epitaxial structure 100 includes a current spreading layer 140, a refractive layer 130, a second semiconductor layer 123, an active layer 122, and a first semiconductor layer 121 sequentially disposed on a transparent conductive layer 300. The first electrode 800 is connected through the passivation layer 700 and the first semiconductor layer 121.
Wherein the transparent conductive layer 600 is made of one or more of Indium Tin Oxide (ITO), fluorine Tin Oxide (FTO), and Aluminum Zinc Oxide (AZO); but is not limited thereto.
The composite reflective layer 500 includes a reflective layer 510 and an etch stop layer 520. The reflective layer 510 is made of Ag and/or Al, and is effective to reflect light emitted from the epitaxial structure. The etch stop layer 520 may prevent metal ion migration diffusion from occurring in the reflective layer 41. The etch stop layer 520 is a stacked structure consisting of two or more of Cr, pt, ti, au, ni and TiW. Preferably, the etch stop layer 520 is composed of a Cr layer and a TiW layer.
The bonding layer 400 has a stacked structure, which is Cr/Ti/Pt/Au, cr/Ti/Pt/Sn, or Au/Sn/Pt/Sn, but is not limited thereto.
The second substrate 200 is a transfer substrate for an epitaxial structure. Specifically, a copper substrate or a conductive silicon substrate may be selected, but is not limited thereto.
The passivation layer 700 is made of silicon dioxide, which is used to protect the LED chip; the first electrode 800 is a stacked structure, which is composed of two or more of Cr, ti, ni, sn, au, pt. The back metal layer 300 is a stacked structure composed of two or more of Cr, ti, ni, sn, au, pt.
While the foregoing is directed to the preferred embodiments of the present invention, it will be appreciated by those skilled in the art that changes and modifications may be made without departing from the principles of the invention, such changes and modifications are also intended to be within the scope of the invention.
Claims (4)
1. The preparation method of the ultraviolet LED chip epitaxial structure is characterized by comprising the following steps of:
(1) Providing a substrate;
(2) Forming an epitaxial layer on the substrate; the epitaxial layer sequentially comprises a first semiconductor layer, an active layer and a second semiconductor layer;
(3) Forming a refractive layer on the second semiconductor layer; the refraction layer is made of a mixture of MgO and one or more of GaO and Ga 2O、Ga2O3, the thickness of the refraction layer is 1-20 nm, the refractive index is 1.75-2.2, the energy level is 4.2-5.1 eV, the essential wavelength is 245-280 nm, and the electron mobility is 400-1000 m 2/(V.s); the refractive index of the refractive layer is smaller than that of the second semiconductor layer;
(4) Forming a current expansion layer on the refraction layer to obtain a finished product of the ultraviolet LED chip epitaxial structure; the current expansion layer at least comprises one of Si, ti, sn, zn, ge, cu, ni, au or Ru, and the thickness of the current expansion layer is 10-50 nm;
The refraction layer is formed by oxygen plasma bombardment and oxidation of the second semiconductor layer, and metal elements in the current expansion layer are doped through post annealing; by oxidation of the oxygen plasma, the second semiconductor layer can be planarized, and defects of the second semiconductor layer can be reduced.
2. The method of fabricating an ultraviolet LED chip epitaxial structure of claim 1, wherein step (2) comprises:
(2.1) sequentially forming a first semiconductor layer, an active layer and a second semiconductor layer on the substrate to obtain an epitaxial layer;
(2.2) the substrate with the epitaxial layer was sequentially cleaned with 511 cleaner, BOE cleaner, acetone and isopropyl alcohol.
3. The method of fabricating an epitaxial structure of an ultraviolet LED chip according to claim 1, wherein in step (3), the second semiconductor layer is processed by a plasma cleaning machine to form a refractive layer; wherein, the DC power is 30-100W, the RF power is 80-150W, the working gas is O 2, the flow rate of the working gas is 30-50 sccm, and the cleaning time is 5-20 min.
4. The method of fabricating an ultraviolet LED chip epitaxial structure of claim 1, wherein step (4) comprises:
(4.1) forming a current spreading layer on the refractive layer;
and (4.2) annealing at 450-600 ℃ for 10-30 min to obtain the finished product of the ultraviolet LED chip epitaxial structure.
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