CN115663087A - Light emitting diode and preparation method thereof - Google Patents
Light emitting diode and preparation method thereof Download PDFInfo
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- CN115663087A CN115663087A CN202211575968.8A CN202211575968A CN115663087A CN 115663087 A CN115663087 A CN 115663087A CN 202211575968 A CN202211575968 A CN 202211575968A CN 115663087 A CN115663087 A CN 115663087A
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- 238000000034 method Methods 0.000 claims abstract description 58
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Abstract
The invention provides a light-emitting diode and a preparation method thereof, wherein the light-emitting diode comprises a substrate, an epitaxial layer and an ITO layer which are sequentially stacked from bottom to top; the ITO layer comprises a plurality of ITO thin film layers which are sequentially stacked from bottom to top, and the compactness of each ITO thin film layer is smaller than that of the adjacent upper ITO thin film layer. The ITO thin film layer with different compactness forms the ITO layer, so that the sheet resistance of the ITO layer is gradually increased from bottom to top, and the low sheet resistance has a current blocking effect to the conduction of the high sheet resistance, so that the current can be further transversely expanded in the axial conduction process, and the current can flow to the edge area far away from the electrode, and the transverse expansion capability of the current of the LED chip is greatly improved.
Description
Technical Field
The invention relates to the technical field of light emitting diodes, in particular to a light emitting diode and a preparation method thereof.
Background
At present, gaN-based light emitting diodes have been widely applied to the solid state lighting field and the display field, and attract more and more people to pay attention. GaN-based leds have been produced industrially and have applications in backlights, lighting, landscape lamps, and the like. However, since the hole concentration of the P-type GaN material is low and tends to cause current crowding, people are continuously searching for effective current spreading materials to solve the above problems, wherein Indium Tin Oxide (ITO) materials are found to have a better current spreading capability, so Indium Tin Oxide (ITO) is widely used as a current spreading layer of an LED chip, however, the current spreading capability of the current spreading material tends to decrease with the increase of the current spreading distance. Therefore, in some large-sized chips, the current spreading is often ensured by increasing the electrode area, but this will sacrifice the light emitting efficiency.
Disclosure of Invention
Based on this, the present invention provides a light emitting diode and a method for manufacturing the same, so as to improve the lateral expansion capability of the current of the LED chip without sacrificing the light emitting efficiency.
The invention provides a light-emitting diode which comprises a substrate, an epitaxial layer and an ITO layer which are sequentially stacked from bottom to top;
the ITO layer comprises a plurality of ITO thin film layers which are sequentially stacked from bottom to top, and the compactness of each ITO thin film layer is smaller than that of the adjacent upper ITO thin film layer.
The invention also provides a preparation method of the light-emitting diode, which comprises the following steps:
providing a substrate;
growing an epitaxial layer on the substrate;
placing the substrate on which the epitaxial layer grows on a slide glass tray of an electron beam evaporation machine, and controlling the slide glass tray to rotate;
controlling an evaporation source to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, wherein the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and is gradually adjusted to be parallel to the surface of the epitaxial layer in the evaporation process, so that a plurality of ITO thin film layers with different compactness are grown on the upper surface of the epitaxial layer, and the compactness of each ITO thin film layer is smaller than that of the adjacent ITO thin film layer.
Preferably, the step of placing the substrate on which the epitaxial layer is grown on a slide glass tray of an electron beam evaporation machine and controlling the slide glass tray to rotate specifically comprises:
and controlling the slide disc to gradually increase to a preset rotating speed at a rotating speed of 0 r/min.
Preferably, the preset rotating speed is 25 to 35r/min, and the step of the rotating speed change is 2r/min.
Preferably, the preset evaporation rate is 2-4A/s.
Preferably, the preset inclination angle is 70 to 80 degrees.
Preferably, the step of irradiating the evaporation source on the surface of the epitaxial layer at a preset inclination angle and gradually adjusting the evaporation source to be parallel to the surface of the epitaxial layer in the evaporation process specifically includes:
controlling an evaporation source to evaporate the surface of the epitaxial layer for a preset time at a preset inclination angle so as to grow an ITO film layer on the surface of the epitaxial layer;
and controlling an evaporation source to carry out multi-stage evaporation for different durations on the surface of the ITO film layer at different inclination angles until an ITO layer with a preset thickness grows on the upper surface of the epitaxial layer, wherein the inclination angle of the evaporation source in each stage is smaller than that of the adjacent previous stage, and the reaction duration of each stage is longer than that of the adjacent previous stage.
Preferably, after the step of controlling the evaporation source to evaporate the ITO layer on the surface of the epitaxial layer at a preset evaporation rate, the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and gradually adjusts to be parallel to the surface of the epitaxial layer in the evaporation process, so that a plurality of ITO thin films with different densities are grown on the upper surface of the epitaxial layer, and the density of each ITO thin film is smaller than that of an adjacent ITO thin film, the method further comprises:
and putting the substrate plated with the ITO layer into an annealing furnace for RTA annealing treatment.
Preferably, the preset thickness of the ITO layer is 60-200nm.
Preferably, the evaporation source includes In 2 O 3 And SnO 2 Wherein, the In 2 O 3 And said SnO 2 The ratio of (1) to (9).
Compared with the prior art, the invention has the beneficial effects that: the ITO thin film layer with different compactness forms the ITO layer, so that the surface resistance of the ITO layer is gradually increased from bottom to top, and the low surface resistance has a current blocking effect to conduct the high surface resistance, so that the current can be transversely expanded farther in the axial conduction process, and the current can flow to the edge area farther away from the electrode, and the transverse expansion capability of the current of the LED chip is greatly improved.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic view of a layered structure of a light emitting diode according to a first embodiment of the present invention;
FIG. 2 is a flow chart of a method for manufacturing a light emitting diode according to a second embodiment of the present invention;
FIG. 3 is a schematic view of a partial structure of an electron beam evaporation machine according to a second embodiment of the present invention;
FIG. 4 is a diagram illustrating an ITO layer effect obtained by a continuous spin coating method according to a third embodiment of the present invention;
FIG. 5 is a diagram illustrating an effect of an ITO layer obtained by a step-wise spin deposition method according to a third embodiment of the present invention;
the following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Several embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The embodiment of the invention aims to provide a light-emitting diode, which is applied to the technical field of light-emitting diodes. Particularly, with the rapid development of LEDs, light emitting chips based on GaN are more and more widely used, and current crowding is easily caused due to the low hole concentration of P-type GaN materials. In short, the current density at the periphery of the electrode is higher, while the current density at the position far away from the center electrode is low, which seriously affects the uniform expansion of the current, and causes the defects of uneven light emission of the chip, shortened service life of the chip and the like. Therefore, in some large-sized chips, the current spreading is often ensured by increasing the electrode area, but this will sacrifice the light emitting efficiency.
In order to solve the technical problems of the conventional light emitting diode, the embodiment of the invention aims to provide the light emitting diode, the density of an ITO thin film layer is controlled by controlling the evaporation angle and the rotating speed of an epitaxial wafer, so that an ITO layer with gradually changed density is formed, further ITO gradually changed film layers with different surface resistances are formed on the surface of a chip, and a certain current blocking effect is generated in the normal direction, so that the transverse expansion of current is improved and flows to the edge area far away from an electrode, and the transverse expansion capability of the current of the LED chip is greatly improved.
Specifically, the light emitting diode according to the embodiment of the present invention includes a substrate 10, and an epitaxial layer 20 and an ITO layer 30 sequentially grown on the substrate 10; the ITO layer 30 is provided with a plurality of ITO thin film layers which are sequentially stacked from bottom to top, and the compactness of each ITO thin film layer is smaller than that of the adjacent upper ITO thin film layer. The ITO thin film layer with different compactness forms the ITO layer, so that the sheet resistance of the ITO layer is gradually increased from bottom to top, and the low sheet resistance has a current blocking effect to the conduction of the high sheet resistance, so that the current can be further transversely expanded in the axial conduction process, and the current can flow to the edge area far away from the electrode, and the transverse expansion capability of the current of the LED chip is greatly improved.
Example one
Referring to fig. 1, a light emitting diode according to a first embodiment of the present invention includes a substrate 10, and an epitaxial layer 20 and an ITO layer 30 sequentially grown on the substrate 10;
the ITO layer 30 is provided with a plurality of ITO thin film layers which are sequentially stacked from bottom to top, and the compactness of each ITO thin film layer is smaller than that of the adjacent upper ITO thin film layer.
It can be understood that the compactness of the ITO thin film layer and the surface resistance of the ITO thin film layer are in a certain linear relationship, and the larger the compactness is, the larger the surface resistance is, so that the surface resistance can be changed by modifying the compactness of the film layer, and the transverse expansion capability of the current is increased.
In summary, in the light emitting diode in the above embodiments of the present invention, the ITO thin film layers with different compactness are used to form the ITO layer, so that the sheet resistance of the ITO layer is gradually increased from bottom to top, and since the low sheet resistance is conducted to the high sheet resistance to have a current blocking effect, the current can be laterally expanded farther in the axial conduction process, and thus can flow to the edge region farther away from the electrode, thereby greatly improving the lateral expansion capability of the current of the LED chip.
Example two
Referring to fig. 2, a flowchart of a method for manufacturing a light emitting diode according to a second embodiment of the invention is shown, the method including:
step S101, providing a substrate;
specifically, the substrate can be selected from sapphire substrate and SiO 2 One of a sapphire composite substrate, a silicon carbide substrate, a gallium nitride substrate and a zinc oxide substrate.
In the embodiment, the substrate is a sapphire substrate, sapphire is the most common GaN-based LED substrate material at present, and most GaN-based LEDs in the market use sapphire as the substrate material. The sapphire substrate has the greatest advantages of mature technology, good stability and low production cost.
Step S102, growing an epitaxial layer on the substrate;
specifically, in this embodiment, a metal chemical vapor deposition MOCVD method may be used to grow an epitaxial layer on a substrate, and high-purity hydrogen is used as a carrier gas, high-purity ammonia is used as a nitrogen source, trimethyl gallium and triethyl gallium are used as gallium sources, trimethyl indium is used as an indium source, silane is used as an N-type dopant, trimethyl aluminum is used as an aluminum source, and magnesium metallocene is used as a P-type dopant, wherein the N-type semiconductor layer is an N-GaN layer, the P-type semiconductor layer is a P-GaN layer, and the light emitting layer is a multi-quantum well active layer, wherein the N-GaN layer has a thickness of 1-3 μm, and the Si doping concentration is 5 × 10 18 -1×10 19 cm -3 (ii) a The thickness of the p-GaN layer is 200-300nm, the doping concentration of Mg is 5 multiplied by 10 17 -1×10 20 cm -3 (ii) a The molar ratio of the In component In the multiple quantum well active layer is 10-35%.
Step S103, placing the substrate on which the epitaxial layer grows on a slide glass tray of an electron beam evaporation machine, and controlling the slide glass tray to rotate;
specifically, referring to fig. 3, a part of the structure of the electron beam evaporation machine is shown, which includes a first motor 100, a slide plate 200, a second motor 300 and an evaporation source emitter 400, wherein the second motor 300 is connected to the slide plate 200 to drive the slide plate 200 to rotate, and the evaporation source emitter 400 is located below the slide plate 200.
And step S104, controlling an evaporation source to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, wherein the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and is gradually adjusted to be parallel to the surface of the epitaxial layer in the evaporation process, so that a plurality of ITO thin film layers with different compactness are grown on the upper surface of the epitaxial layer, and the compactness of each ITO thin film layer is smaller than that of the adjacent ITO thin film layer.
It should be explained that, in the process of electron beam evaporation, the compactness of the ITO film layer can be determined by two modes, one mode is the irradiation angle of an evaporation source, the larger the angle is, the poorer the compactness of the film layer is, the smaller the angle is, and the better the compactness of the film layer is; the other is the autorotation speed of the epitaxial layer in the evaporation process, the higher the rotating speed is, the better the compactness is, and the lower the rotating speed is, the poorer the compactness is. Therefore, the ITO film layer with better compactness needs to be obtained at a low angle and a high rotating speed, and the ITO film layer with poorer compactness only needs to be obtained at a large angle and a low rotating speed.
Specifically, in the present embodiment, the predetermined evaporation rate of the evaporation source is 3A/s, and the predetermined inclination angle of the evaporation source is 75 °. In practical application, the evaporation source emitted by the evaporation source emitter 400 can completely irradiate the epitaxial layer, and the first motor 100 is used for driving the slide tray to turn over, so that the included angle 8709between the evaporation source and the epitaxial layer can be gradually changed from 75 degrees to 0 degrees. Therefore, in the process of electron beam evaporation, the irradiation angle of an evaporation source is controlled to be gradually reduced, so that an ITO layer with gradually increased compactness can be grown on the surface of the epitaxial layer.
In summary, in the method for manufacturing the light emitting diode in the above embodiment of the invention, the ITO thin film layers with different compactness are adopted to form the ITO layer, so that the sheet resistance of the ITO layer is gradually increased from bottom to top, and the current blocking effect is achieved when the low sheet resistance is conducted to the high sheet resistance, so that the current can be further extended in the axial direction, and can flow to the edge area far away from the electrode, thereby greatly improving the lateral extension capability of the current of the LED chip.
EXAMPLE III
A method for manufacturing a light emitting diode according to a third embodiment of the present invention includes:
step S11, providing a substrate;
specifically, the substrate can be sapphire substrate or SiO 2 One of a sapphire composite substrate, a silicon carbide substrate, a gallium nitride substrate and a zinc oxide substrate.
In the embodiment, the substrate is a sapphire substrate, sapphire is the most common GaN-based LED substrate material at present, and most GaN-based LEDs in the market use sapphire as the substrate material. The sapphire substrate has the biggest advantages of mature technology, good stability and low production cost.
S12, growing an epitaxial layer on the substrate;
specifically, in this embodiment, a metal chemical vapor deposition MOCVD method may be used to grow an epitaxial layer on a substrate, and high-purity hydrogen is used as a carrier gas, high-purity ammonia is used as a nitrogen source, trimethyl gallium and triethyl gallium are used as gallium sources, trimethyl indium is used as an indium source, silane is used as an N-type dopant, trimethyl aluminum is used as an aluminum source, and magnesium metallocene is used as a P-type dopant, wherein the N-type semiconductor layer is an N-GaN layer, the P-type semiconductor layer is a P-GaN layer, and the light emitting layer is a multi-quantum well active layer, wherein the N-GaN layer has a thickness of 1-3 μm, and the Si doping concentration is 5 × 10 18 -1×10 19 cm -3 (ii) a The thickness of the p-GaN layer is 200-300nm, the doping concentration of Mg is 5 multiplied by 10 17 -1×10 20 cm -3 (ii) a The molar ratio of the In component In the multiple quantum well active layer is 10-35%.
S13, placing the substrate with the grown epitaxial layer on a slide plate of an electron beam evaporation machine, and controlling the slide plate to rotate;
specifically, referring to fig. 3, a part of the structure of the electron beam evaporation machine is shown, which includes a first motor 100, a slide plate 200, a second motor 300 and an evaporation source emitter 400, wherein the second motor 300 is connected to the slide plate 200 to drive the slide plate 200 to rotate, and the evaporation source emitter 400 is located below the slide plate 200.
And S14, controlling an evaporation source to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, wherein the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and is gradually adjusted to be parallel to the surface of the epitaxial layer in the evaporation process so as to enable a plurality of ITO thin film layers with different compactness to grow on the upper surface of the epitaxial layer, and the compactness of each ITO thin film layer is smaller than that of the adjacent ITO thin film layer.
It should be explained that, in the process of electron beam evaporation, the compactness of the ITO film layer can be determined by two modes, one mode is the irradiation angle of an evaporation source, the larger the angle is, the poorer the compactness of the film layer is, the smaller the angle is, and the better the compactness of the film layer is; the other is the autorotation speed of the epitaxial layer in the evaporation process, the higher the rotating speed is, the better the compactness is, and the lower the rotating speed is, the poorer the compactness is. Therefore, the ITO film layer with better compactness needs to be obtained at a low angle and a high rotating speed, and the ITO film layer with poorer compactness only needs to be obtained at a large angle and a low rotating speed.
Specifically, in this embodiment, the predetermined evaporation rate of the evaporation source is 3A/s, and the predetermined inclination angle of the evaporation source is 75 °. In practical application, the evaporation source emitted by the evaporation source emitter can completely irradiate the epitaxial layer, and the first motor 100 is used for driving the slide holder 200 to turn over, so that the included angle of 8709between the evaporation source and the epitaxial layer can be gradually changed from 75 degrees to 0 degrees. Therefore, in the process of electron beam evaporation, the irradiation angle of the evaporation source is controlled to be gradually reduced, so that an ITO layer with gradually increased compactness can be grown on the surface of the epitaxial layer.
Further, the step of placing the substrate on which the epitaxial layer grows on a slide plate of an electron beam evaporation machine and controlling the slide plate to rotate specifically comprises the following steps:
and controlling the slide disc to gradually increase to a preset rotating speed at a rotating speed of 0 r/min.
Specifically, in the embodiment, the preset rotation speed is 30r/min, and the step of the rotation speed change is 2r/min. The method can be understood that in the electron beam evaporation process, the autorotation rate of the epitaxial layer is controlled to be from low to high, the irradiation angle of the evaporation source is controlled to be from large to small, the gradual change effect of the ITO layer can be effectively improved, namely, the ITO thin film layer at the initial part grows at a large angle and a low rotating speed, the ITO thin film layer at the subsequent part grows at a small angle and a high rotating speed, when the included angle between the evaporation source and the epitaxial layer is limited to 8709, and gradually changes from 75 degrees to 0 degree, the slide glass disc stops autorotation, and the growth process of the ITO layer is completed.
Specifically, the step of irradiating the evaporation source on the surface of the epitaxial layer at a preset inclination angle and gradually adjusting the evaporation source to be parallel to the surface of the epitaxial layer in the evaporation process specifically includes:
controlling an evaporation source to evaporate the surface of the epitaxial layer for a preset duration at a preset inclination angle so as to grow an ITO film layer on the surface of the epitaxial layer;
and controlling the evaporation source to perform multi-stage evaporation with different durations on the surface of the ITO thin film layer at different inclination angles until an ITO layer with a preset thickness grows on the upper surface of the epitaxial layer, wherein the inclination angle of the evaporation source in each stage is smaller than that of the adjacent previous stage, and the reaction duration of each stage is longer than that of the adjacent previous stage.
In the actual evaporation process, two evaporation modes are mainly included, one is a continuous rotation evaporation method, and the other is a stepping rotation evaporation method.
The preparation process of the continuous rotary evaporation method comprises the following specific steps:
in the first stage, the included angle 8709between the evaporation source and the epitaxial layer is driven to gradually change from 75 degrees to 0 degrees by the rotation of the first motor 100, meanwhile, the slide plate 200 is driven to rotate by the second motor 300, the slide plate 200 does not stop rotating in the evaporation process and gradually increases from 0r/min to 30r/min at the speed of 2r/min, the evaporation is stopped when the included angle between the evaporation source and the epitaxial layer is gradually adjusted to 0 degrees, the thickness of the finally obtained ITO layer is 60nm, the whole evaporation process is 200s, and the finally obtained ITO layer has the effect that the sheet resistance gradually changes from low to high as shown in FIG. 4.
The preparation process of the stepping rotary evaporation method comprises the following specific steps:
in the first stage, the included angle between the evaporation source and the epitaxial layer is adjusted to be 75 degrees through the rotation of the first motor 100, then the second motor 300 is started to drive the slide plate 200 to rotate, the slide plate does not stop rotating in the evaporation process and gradually increases from 0r/min to 30r/min at the speed of 2r/min, when the first evaporation time reaches 26 seconds, the growth process of the ITO thin film layer in the first stage is completed, at the moment, the first motor 100 adjusts the included angle between the evaporation source and the epitaxial layer to be 70 degrees, the growth process of the ITO thin film layer in the second stage is entered, when the second evaporation time reaches 27.5 seconds, the growth process of the ITO thin film layer in the second stage is completed, in the third stage, the included angle between the evaporation source and the epitaxial layer is adjusted to be 65 degrees and the evaporation time is 29 seconds, in the fourth stage, the included angle between the evaporation source and the epitaxial layer is adjusted to be 60 degrees and the evaporation time is 30.5 seconds on the basis of the third stage, and the whole process is gradually performed. It can be understood that the inclination angle of the evaporation source in each subsequent stage is less than 5 degrees of the previous stage, the reaction time of each stage is 1.5 seconds longer than that in the previous stage, the evaporation is stopped when the included angle between the evaporation source and the epitaxial layer is gradually adjusted to 0 degree, the thickness of the finally obtained ITO layer is 67.5nm, the whole evaporation process is 225 seconds, and the effect of the finally obtained ITO layer is shown as that the sheet resistance is gradually changed from low to high as shown in FIG. 5.
In addition, in the present embodiment, the vapor deposition source is In 2 O 3 And SnO 2 Mixture of (1), in 2 O 3 And SnO 2 The ratio of (1) to (9).
Further, the method comprises the steps of controlling an evaporation source to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, wherein the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and is gradually adjusted to be parallel to the surface of the epitaxial layer in the evaporation process so that a plurality of ITO thin film layers with different compactness are grown on the upper surface of the epitaxial layer, and the compactness of each ITO thin film layer is smaller than that of the adjacent ITO thin film layer, and the method further comprises the following steps:
and putting the substrate plated with the ITO layer into an annealing furnace for RTA annealing treatment.
Specifically, after the ITO layer is plated, the ITO layer is placed into a 550 ℃ annealing furnace for RTA annealing treatment, the annealing time is 15min, and then the subsequent chip manufacturing process is continuously completed to complete the manufacture of the electrode and the passivation layer.
In summary, in the method for manufacturing the light emitting diode in the above embodiment of the invention, the ITO thin film layers with different compactness are adopted to form the ITO layer, so that the sheet resistance of the ITO layer is gradually increased from bottom to top, and the current can be further laterally expanded in the axial conduction process due to the current blocking effect when the low sheet resistance is conducted to the high sheet resistance, so that the current can flow to the edge region farther away from the electrode, thereby greatly improving the lateral expansion capability of the current of the LED chip.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A light-emitting diode is characterized by comprising a substrate, an epitaxial layer and an ITO layer which are sequentially laminated from bottom to top;
the ITO layer comprises a plurality of ITO thin film layers which are sequentially stacked from bottom to top, and the compactness of each ITO thin film layer is smaller than that of the adjacent upper ITO thin film layer.
2. A method for preparing a light emitting diode according to claim 1, wherein the method comprises:
providing a substrate;
growing an epitaxial layer on the substrate;
placing the substrate on which the epitaxial layer grows on a slide glass tray of an electron beam evaporation machine, and controlling the slide glass tray to rotate;
controlling an evaporation source to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, wherein the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle and is gradually adjusted to be parallel to the surface of the epitaxial layer in the evaporation process, so that a plurality of ITO thin film layers with different compactness are grown on the upper surface of the epitaxial layer, and the compactness of each ITO thin film layer is smaller than that of the adjacent ITO thin film layer.
3. The method for preparing the light-emitting diode according to claim 2, wherein the step of placing the substrate on which the epitaxial layer is grown on a slide glass tray of an electron beam evaporation machine and controlling the slide glass tray to rotate specifically comprises:
and controlling the slide disc to gradually increase to a preset rotating speed at a rotating speed of 0 r/min.
4. The method for preparing the light-emitting diode of claim 3, wherein the preset rotation speed is 25 to 35r/min, and the step of the rotation speed variation is 2r/min.
5. The method of claim 2, wherein the predetermined evaporation rate is 2 to 4A/s.
6. The method for manufacturing the light-emitting diode according to claim 2, wherein the predetermined inclination angle is 70 ° to 80 °.
7. The method for preparing the light-emitting diode according to claim 2, wherein the step of irradiating the surface of the epitaxial layer with the evaporation source at a preset inclination angle and gradually adjusting the surface of the epitaxial layer to be parallel to the surface of the epitaxial layer in the evaporation process specifically comprises:
controlling an evaporation source to evaporate the surface of the epitaxial layer for a preset duration at a preset inclination angle so as to grow an ITO film layer on the surface of the epitaxial layer;
and controlling an evaporation source to carry out multi-stage evaporation for different durations on the surface of the ITO film layer at different inclination angles until an ITO layer with a preset thickness grows on the upper surface of the epitaxial layer, wherein the inclination angle of the evaporation source in each stage is smaller than that of the adjacent previous stage, and the reaction duration of each stage is longer than that of the adjacent previous stage.
8. The method for preparing the light-emitting diode according to claim 2, wherein the evaporation source is controlled to evaporate an ITO layer on the surface of the epitaxial layer at a preset evaporation rate, the evaporation source irradiates the surface of the epitaxial layer at a preset inclination angle during evaporation and is gradually adjusted to be parallel to the surface of the epitaxial layer, so that a plurality of ITO thin film layers with different densities are grown on the upper surface of the epitaxial layer, and after the step of reducing the density of each ITO thin film layer to be smaller than that of the ITO thin film layer on the upper surface of the epitaxial layer, the method further comprises:
and (4) putting the substrate plated with the ITO layer into an annealing furnace for RTA annealing treatment.
9. The method for preparing the light-emitting diode according to claim 7, wherein the predetermined thickness of the ITO layer is 60-200nm.
10. The method of claim 2, wherein the evaporation source comprises In 2 O 3 And SnO 2 Wherein, the In 2 O 3 And said SnO 2 The ratio of (1) is 9.
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