Preparation method of light-emitting diode for improving brightness

Abstract

The invention discloses a preparation method of a light emitting diode capable of improving brightness. The preparation method sequentially comprises the steps of performing desorption treatment on a substrate, and growing an AlN buffer layer, a u-GaN layer, a Si heavily-doped n-GaN layer, a Si lightly-doped n-GaN layer, an InGaN / GaN stress adjusting layer, a multi-quantum well layer, an AIGaN layer, a Mg-doped p-GaN layer and a heavily-doped p-GaN contact layer on the substrate. The Ag nanoparticles and the air cavity structure are formed in the multi-quantum well layer, the local surface plasma frequency generated by the Ag nanoparticles is effectively coupled with the multi-quantum well, the luminous efficiency of the LED is enhanced, the propagation path of photons generated by the multi-quantum well is changed by refraction and reflection of the photons by the air cavity, and the luminous efficiency of the LED is improved. And the luminous efficiency is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a method for preparing a light emitting diode with improved brightness. Background Art

[0002] Light-Emitting Diode (LED) is a semiconductor electronic device that converts electrical energy into light energy. As a new type of efficient, environmentally friendly and green solid-state lighting source, LED has been widely used in traffic lights, car lights, indoor and outdoor lighting, and display screens. In addition to lighting, the application of LED has also involved other fields, including sterilization, medical treatment, biomedicine, polymer printing, barcode verification, body fluid detection, identification and analysis, water sterilization, and optical sensors and other instruments.

[0003] At present, the photoelectric conversion efficiency of LED in mid-to-high-end application fields such as display screens, sterilization, medical treatment, polymer printing, etc. is still relatively low. If its luminous efficiency can be improved, LED will usher in greater development space.

[0004] Therefore, providing a method for manufacturing a light-emitting diode with improved brightness and improving the luminous efficiency of the LED to meet the application requirements of the LED is a technical problem that needs to be solved urgently in the technical field. Summary of the invention

[0005] The present application forms Ag nanoparticles and an air cavity structure inside the multi-quantum well layer, utilizes the localized surface plasma frequency generated by the Ag nanoparticles to effectively couple with the multi-quantum wells, thereby enhancing the luminous efficiency of the LED. At the same time, the refraction and reflection of photons by the air cavity are used to change the propagation path of the photons generated by the multi-quantum wells, thereby further improving the luminous efficiency.

[0006] The present invention discloses a method for preparing a light-emitting diode with improved brightness, which is characterized by comprising the following steps:

[0007] Step 1: placing the substrate into the MOCVD reaction chamber for desorption treatment;

[0008] Step 2: growing an AlN buffer layer, a u-GaN layer, a Si heavily doped n-GaN layer, and a Si lightly doped n-GaN layer on the substrate in sequence;

[0009] Step 3: growing an InGaN / GaN stress adjustment layer on the Si lightly doped n-GaN layer, and controlling the molar content of In atoms to gradually decrease during the growth process to reduce stress during the material growth process;

[0010] Step 4, growing a multi-quantum well layer on the InGaN / GaN stress adjustment layer;

[0011] Step 5, taking out the substrate with the multi-quantum well layer from the MOCVD reaction chamber, firstly forming a circular pattern on the surface of the multi-quantum well layer by a photolithography process, and then etching the pattern after photolithography by an ICP etching process to form holes on the multi-quantum well layer;

[0012] Step 6: Fill the holes on the multi-quantum well layer with Ag nanoparticles, and control the volume of the portion above the hole that is not filled with Ag nanoparticles to be between one third and one half of the total volume of the hole, specifically:

[0013] Ag nanoparticles are filled into the holes by spin coating, and the Ag nanoparticles are attached to the side walls of the holes and are in close contact with the multi-quantum wells. Then, an alcohol cotton swab is used to wipe the surface of the multi-quantum well layer to ensure that no residual Ag nanoparticles remain on the surface of the multi-quantum well layer and that the Ag nanoparticles in the holes are effectively retained to reduce the loss of light output.

[0014] Step 7: grow an AIGaN layer on the multi-quantum well layer with holes formed inside. During the growth process, control the lateral growth rate to be greater than the vertical growth rate to bury the holes inside the multi-quantum well layer to achieve rapid merging of the AIGaN layer, thereby forming an air cavity inside the multi-quantum well layer.

[0015] Step 8: A Mg-doped p-GaN layer and a heavily-doped p-GaN contact layer are sequentially grown on the AIGaN layer to form a light-emitting diode having Ag nanoparticles and an air cavity inside, thereby improving the light-emitting efficiency.

[0016] Furthermore, the substrate is a substrate suitable for epitaxial growth of sapphire, silicon, silicon carbide, gallium nitride and aluminum nitride.

[0017] Furthermore, the step 3 of controlling the molar content of In atoms to decrease gradually is as follows:

[0018] During the growth process, the In atomic molar content was controlled to decrease uniformly from 3% to 0.5%.

[0019] Furthermore, the diameter of the circular pattern in step five is 1-2 um, and the distance between the centers of two adjacent circular patterns is 4-8 um.

[0020] Furthermore, the diameter of the hole in step five is 1-2 um and the depth is 200-500 nm.

[0021] Furthermore, the Ag nanoparticles in step six have a diameter of 40-60 nm and a relatively rough surface.

[0022] Furthermore, the step 7 of controlling the lateral growth speed to be greater than the vertical growth speed is specifically as follows:

[0023] Control the lateral growth rate to 2-4 times the vertical growth rate.

[0024] Compared with the prior art, the method for preparing a light-emitting diode with improved brightness of the present invention achieves the following beneficial effects:

[0025] 1. The present application forms Ag nanoparticles and an air cavity structure inside the multi-quantum well layer, on the one hand, utilizes the localized surface plasma frequency generated by the Ag nanoparticles to effectively couple with the multi-quantum wells, thereby achieving the enhancement of the LED luminous efficiency. Since the Ag nanoparticles have a relatively rough surface, this rough surface can ensure that the energy coupled to the localized surface plasma loses momentum, thereby effectively extracting photons from the metal / semiconductor interface, thereby improving the luminous efficiency. In addition, due to the large difference in refractive index between GaN (n=2.5) and air (n=1), the critical angle is only 23.6°, resulting in that only the part of the photons generated from the multi-quantum well layer with an exit angle less than the critical angle can escape and be emitted into the air, and some other photons are difficult to be emitted into the air even after being reflected by the substrate. After the introduction of the air cavity structure, this part of the photons is reflected by the air cavity during the downward propagation process, and the original propagation path is changed, and then after multiple reflections or refractions of the substrate or material, it is emitted into the air, thereby improving the light extraction efficiency.

[0026] 2. By growing an InGaN / GaN stress adjustment layer before growing a multi-quantum well layer and controlling the gradual reduction of the molar content of In atoms during the growth process, the stress and defects caused by lattice mismatch or thermal mismatch can be reduced, dislocation derivatives can be blocked, and dislocations derived from the bottom layer can be reduced, thereby improving the crystal quality, and then improving the luminous efficiency of the LED, while enhancing the anti-static ability.

[0027] 3. After filling the holes with Ag nanoparticles, the surface of the multi-quantum well layer is wiped with an alcohol swab to ensure that no residual Ag nanoparticles remain on the surface of the multi-quantum well layer, and the Ag nanoparticles in the holes are effectively retained, which can effectively reduce the loss of light output and thus help improve the luminous efficiency of the LED.

[0028] Of course, any product implementing the present invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0029] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0031] Figure 1 Shown is a structural diagram of a method for preparing a light-emitting diode with improved brightness according to an embodiment of the present application.

[0032] Marking description: 1. Substrate, 2. AlN buffer layer, 3. u-GaN layer, 4. Si heavily doped n-GaN layer, 5. Si lightly doped n-GaN layer, 6. InGaN / GaN stress adjustment layer, 7. Multi-quantum well layer, 8. Ag nanoparticles, 9. AIGaN layer, 10. Air cavity, 11. Mg-doped p-GaN layer, 12. Heavily doped p-GaN contact layer. DETAILED DESCRIPTION

[0033] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention unless otherwise specifically stated.

[0034] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0035] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0036] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0037] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0038] The method for manufacturing a light emitting diode with improved brightness described in this embodiment comprises the following steps:

[0039] Step 101: Place the sapphire substrate 1 into a MOCVD reaction chamber for desorption treatment.

[0040] Step 102: On the sapphire substrate 1, an AlN buffer layer 2, a u-GaN layer 3, a Si heavily doped n-GaN layer 4, and a Si lightly doped n-GaN layer 5 are sequentially grown.

[0041] Step 103 , growing an InGaN / GaN stress adjustment layer 6 on the Si lightly doped n-GaN layer 5 , and controlling the molar content of In atoms to uniformly decrease from 3% to 0.5% during the growth process to reduce stress during the material growth process.

[0042] Step 104, growing a multi-quantum well layer 7 on the InGaN / GaN stress adjustment layer 6;

[0043] Step 105, take out the sapphire substrate 1 with the multi-quantum well layer 7 grown thereon from the MOCVD reaction chamber, first form a circular pattern with a diameter of 1-2um and a center distance of 4-8um on the surface of the multi-quantum well layer 7 by a photolithography process, and then etch the pattern after photolithography by an ICP etching process to form holes with a diameter of 1-2um and a depth of 200-500nm on the multi-quantum well layer 7.

[0044] Step 106: fill the holes on the multi-quantum well layer 7 with Ag nanoparticles 8, and control the volume of the portion above the hole that is not filled with Ag nanoparticles 8 to be between one third and one half of the total volume of the hole, specifically:

[0045] Ag nanoparticles 8 are filled into the holes by spin coating. First, a sapphire substrate sheet 1 with holes formed on the upper surface is fixed on a spin coating machine, and an ethanol solution containing Ag nanoparticles 8 is spin coated on the upper surface of the multi-quantum well layer 7 with holes formed inside. The Ag nanoparticles 8 are filled into the holes by centrifugal force and gravity, and the Ag nanoparticles 8 are attached to the side walls of the holes to make close contact with the multi-quantum wells. Then, an alcohol cotton swab is used to wipe the surface of the multi-quantum well layer 7 to ensure that no residual Ag nanoparticles 8 remain on the surface of the multi-quantum well layer 7, and that the Ag nanoparticles 8 in the holes are effectively retained to reduce the loss of light output.

[0046] Step 107, growing an AIGaN layer 9 on the multi-quantum well layer 7 with holes formed inside, controlling the lateral growth rate to be 2-4 times the vertical growth rate during the growth process, burying the holes inside the multi-quantum well layer 7 to achieve rapid merging of the AIGaN layer 9, thereby forming an air cavity 10 inside the multi-quantum well layer 7.

[0047] Step 108, a Mg-doped p-GaN layer 11 and a heavily-doped p-GaN contact layer 12 are sequentially grown on the AIGaN layer 9 to form a light-emitting diode with a complete structure. Ag nanoparticles and an air cavity structure are formed inside the multi-quantum well layer, and the localized surface plasma frequency generated by the Ag nanoparticles is effectively coupled with the multi-quantum wells to enhance the luminous efficiency of the LED. At the same time, the refraction and reflection of the air cavity on the photons are used to change the propagation path of the photons generated by the multi-quantum wells, thereby further improving the luminous efficiency.

[0048] Although some specific embodiments of the present invention have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present invention. It will be appreciated by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for preparing a light-emitting diode with improved brightness, characterized by comprising the following steps: Step 1: placing the substrate into the MOCVD reaction chamber for desorption treatment; Step 2: growing an AlN buffer layer, a u-GaN layer, a Si heavily doped n-GaN layer, and a Si lightly doped n-GaN layer on the substrate in sequence; Step 3: growing an InGaN / GaN stress adjustment layer on the Si lightly doped n-GaN layer, and controlling the molar content of In atoms to gradually decrease during the growth process to reduce stress during the material growth process; Step 4, growing a multi-quantum well layer on the InGaN / GaN stress adjustment layer; Step 5, taking out the substrate with the multi-quantum well layer from the MOCVD reaction chamber, firstly forming a circular pattern on the surface of the multi-quantum well layer by a photolithography process, and then etching the pattern after photolithography by an ICP etching process to form holes on the multi-quantum well layer; Step 6: Fill the holes on the multi-quantum well layer with Ag nanoparticles, and control the volume of the portion above the hole that is not filled with Ag nanoparticles to be between one third and one half of the total volume of the hole, specifically: Ag nanoparticles are filled into the holes by spin coating, and the Ag nanoparticles are attached to the side walls of the holes and are in close contact with the multi-quantum wells. Then, an alcohol cotton swab is used to wipe the surface of the multi-quantum well layer to ensure that no residual Ag nanoparticles remain on the surface of the multi-quantum well layer and that the Ag nanoparticles in the holes are effectively retained to reduce the loss of light output. Step 7: grow an AIGaN layer on the multi-quantum well layer with holes formed inside. During the growth process, control the lateral growth rate to be greater than the vertical growth rate to bury the holes inside the multi-quantum well layer to achieve rapid merging of the AIGaN layer, thereby forming an air cavity inside the multi-quantum well layer. Step 8: A Mg-doped p-GaN layer and a heavily-doped p-GaN contact layer are sequentially grown on the AIGaN layer to form a light-emitting diode having Ag nanoparticles and an air cavity inside, thereby improving the light-emitting efficiency.

2. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The substrate is a substrate suitable for epitaxial growth of sapphire, silicon, silicon carbide, gallium nitride and aluminum nitride.

3. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The step 3 of controlling the molar content of In atoms to gradually decrease is specifically as follows: During the growth process, the In atomic molar content is controlled to decrease uniformly from 3% to 0.5%.

4. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The diameter of the circular pattern in step five is 1-2 um, and the distance between the centers of two adjacent circular patterns is 4-8 um.

5. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The diameter of the hole in step five is 1-2um and the depth is 200-500nm.

6. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The Ag nanoparticles in step six have a diameter of 40-60 nm and a relatively rough surface.

7. The method for preparing a light emitting diode with improved brightness according to claim 1, characterized in that: The step 7 of controlling the lateral growth rate to be greater than the vertical growth rate is specifically as follows: Control the lateral growth rate to 2-4 times the vertical growth rate.

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