Single-chip array arrangement vertical pyramid structure full-color Micro LED and preparation method thereof

Abstract

The invention discloses a single-chip array arrangement vertical pyramid structure full-color Micro LED and a preparation method thereof. The problems that an existing Micro LED device is low in production efficiency and high in cost are mainly solved. The full-color Micro LED comprises a TFT (Thin Film Transistor) back plate and pyramid structure LEDs which are arranged on the TFT back plate in an array; the pyramid structure LED comprises a substrate and an epitaxial layer. The epitaxial layer is located on the substrate; the epitaxial layer comprises a dielectric layer and a pyramid structure, the dielectric layer is deposited on the substrate, and the dielectric layer is provided with hole structures which are arranged in a periodic array; the pyramid structure grows in the hole opening area on the substrate, fills the hole structure and continues to grow to form the pyramid structure. According to the method, a plane nitride thin film does not need to be grown on the substrate firstly, then selective area epitaxy of the GaN pyramid is achieved through patterning of the nitride thin film, the GaN-based vertical pyramid LED is directly grown on the opening area of the substrate in an epitaxial mode, the production efficiency is greatly improved, and the production cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology. Specifically, it relates to a single-chip array arranged vertical pyramid structure full-color Micro LED and a preparation method thereof. Background Art

[0002] With the evolution of displays, since LCD successfully replaced CRT TVs, the appearance of displays has undergone significant changes. Subsequently, from LCD to OLED and then to Micro LED, the image quality can be greatly improved. Currently, most of the backlights used in flat panel displays are LEDs, which are better than OLEDs using organic materials with limited lifetimes in terms of brightness, contrast, saturation, power consumption, and response time.

[0003] Currently, the mainstream GaN-based LED epitaxial technology route generally selects inexpensive sapphire substrates. However, due to the large lattice mismatch and thermal mismatch between sapphire and GaN, the GaN / InGaN thin films epitaxially grown on them often have large stress and defects. Moreover, since the sapphire substrate is non-conductive and has poor thermal conductivity, the lateral expansion of current will accumulate a large amount of heat in the device, seriously reducing the efficiency and lifetime of the device. Therefore, the problems of defects and stress of GaN thin films can be solved by growing GaN pyramids.

[0004] If LEDs are thinned, miniaturized, and arrayed, more excellent Micro LED displays can be manufactured. However, there are still quite a few technical challenges to overcome at present. Among them, to ensure the precise "Mass Transfer" micro-assembly technology has become an important key for Micro LED to stand out. And the pyramid structure LEDs arranged in a single-chip array can provide a way for mass transfer and can directly splice the chips to manufacture large-size display screens. Summary of the Invention

[0005] The purpose of the present invention is to provide a single-chip array arranged vertical pyramid structure full-color Micro LED and a preparation method thereof, mainly to solve the problems of low production efficiency and high cost of existing Micro LED devices.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A single-chip array arranged vertical pyramid structure full-color Micro LED includes a TFT backplane and pyramid structure LEDs arrayed on the TFT backplane;

[0008] The pyramid - structured LED includes a substrate and an epitaxial layer; the epitaxial layer is located above the substrate; the epitaxial layer includes a dielectric layer and a pyramid structure. The dielectric layer is deposited on the substrate, and has a periodic array of hole structures thereon; the pyramid structure grows in the open - hole area on the substrate, fills the hole structures and continues to grow to form a pyramid - type structure.

[0009] Further, in the present invention, the substrate is a wide - bandgap β - Ga 2 O 3 substrate with a lattice mismatch of 1% - 15% with GaN. The material of the dielectric layer is SiO 2 , and its thickness is 10 - 200 nm; the hole - structure pattern of the dielectric layer is a regular hexagon; the pyramid structure is an n - type GaN hexagonal pyramid structure with (1 - 100) planes on the side and (0001) plane on the top, with a height of 2 - 10 μm and a width of 10 - 50 μm. The doping element in the pyramid structure is Si, and the doping concentration is 10 18 ~10 20 cm -3 .

[0010] Further, in the present invention, it further includes:

[0011] An InGaN pre - strain layer, grown on the side of the pyramid structure;

[0012] A multi - quantum - well light - emitting layer, grown on the InGaN pre - strain layer;

[0013] A p - type AlGaN electron - blocking layer, grown on the multi - quantum - well light - emitting layer;

[0014] A p - type GaN layer, grown on the p - type AlGaN electron - blocking layer;

[0015] A transparent conductive layer, prepared on the p - type GaN layer.

[0016] Further, in the present invention, the material of the multi - quantum - well light - emitting layer is: 1 to 5 periods of In X1 Ga 1-X1 N / GaN, where the value of X1 is 0.12 - 0.18, corresponding to a blue - light quantum well; 1 to 5 periods of In X2 Ga 1-X2 N / GaN, where the value of X2 is 0.20 - 0.25, corresponding to a green - light quantum well; 1 to 5 periods of In X3 Ga 1-X3 N / GaN, where the value of X3 is 0.30 - 0.40, corresponding to a red - light quantum well; the thickness of the InGaN layer in all quantum wells is 1 - 3 nm; the thickness of the GaN layer is 7 - 15 nm.

[0017] Furthermore, in the present invention, along a certain arrangement direction of the array of the pyramid structure, the multi-quantum well light-emitting layer is etched and the blue light quantum well, the green light quantum well, the red light quantum well, or all of the red, green, and blue light quantum wells are successively retained.

[0018] Furthermore, in the present invention, the p-type GaN layer is obtained by doping with Mg element, and the doping concentration is ~3×10 19 cm -3 ; the transparent conductive layer is ITO, wherein the p / n electrodes of the full-color Micro LED are respectively prepared on the transparent conductive layer and the bottom surface of the substrate.

[0019] The present invention also provides a preparation method for a single-chip array arranged vertical pyramid structure full-color Micro LED, comprising the following steps:

[0020] Step S1: First, prepare a patterned substrate, that is, deposit a dielectric layer on the substrate, and make the dielectric layer into a patterned mask with a periodic hole structure. On the basis of the patterned mask, fill the hole structure and continue to grow to form a pyramid structure;

[0021] Step S2: Then, put the patterned substrate with a mask into the MOCVD reaction chamber. First, control the temperature at 480 - 650 °C, and grow a GaN or AlN nucleation layer in an N 2 atmosphere, and then raise the temperature to 900 - 1200 °C, and grow GaN in an H 2 atmosphere to form a pyramid structure;

[0022] Step S3: Grow an InGaN pre-strained layer on the pyramid structure, grow a multi-quantum well light-emitting layer on the InGaN pre-strained layer, and grow a p-type AlGaN electron blocking layer and a p-type GaN layer on the multi-quantum well light-emitting layer;

[0023] Step S4: Evaporate a transparent conductive layer on the p-type GaN layer; prepare p / n electrodes on the transparent conductive layer and the bottom surface of the substrate respectively.

[0024] Step S5: Transfer the array arranged pyramid structure LED to a TFT backplane corresponding to the pyramid size to complete the fabrication of the device.

[0025] Furthermore, in the step S1, the patterning method is photolithography, colloidal lithography, electron beam exposure or nanoimprinting.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention adopts the MOCVD method that can be quantitatively produced industrially. It does not require growing a planar nitride film on the substrate first and then realizing the selective area epitaxy of GaN pyramids through patterning the nitride film. Instead, it directly epitaxially grows GaN-based vertical pyramid LEDs in the open areas on the substrate, providing a single-chip array arrangement of vertical pyramid structure LEDs, and offering a technical route for the technical problem of mass transfer in Micro LED production, which will greatly improve production efficiency and reduce production costs.

[0028] (2) The size of the array arrangement of vertical pyramid LEDs prepared by the method adopted in the present invention is 10 - 50 μm, which is much smaller than the single-pixel size of Micro LEDs prepared by traditional methods. Therefore, it has a higher resolution. And because the light emission angle of the LEDs in the special vertical pyramid structure in the present disclosure has a greater expansion, the viewing angle of the display screen can be increased. Description of the Drawings

[0029] Figure 1 It is a schematic diagram of the vertical pyramid LED structure provided by the present invention.

[0030] Figure 2 It is a flow chart of the preparation method of the multi-quantum well light-emitting layer of the vertical pyramid LED provided by the present invention.

[0031] Figure 3 It is a schematic plan view of the flow chart of the preparation method of the multi-quantum well light-emitting layer of the array arrangement of vertical pyramid LEDs provided by the present invention.

[0032] Figure 4 It is a flow chart of the preparation method of a single-chip array arrangement of vertical pyramid structure full-color Micro LEDs provided by the present invention.

[0033] Among them, the names corresponding to the reference numerals are:

[0034] 1 - Substrate, 2 - Dielectric layer, 3 - Pyramid structure, 4 - InGaN pre-strained layer, 5 - Multi-quantum well light-emitting layer, 6 - p-type AlGaN electron blocking layer, 7 - p-type GaN layer. Detailed Embodiments

[0035] The present invention will be further described below in conjunction with the description of the drawings and embodiments. The implementation manners of the present invention include but are not limited to the following embodiments.

[0036] Embodiment

[0037] As Figures 1 to 3As shown in the figure, a single-chip array-arranged vertical pyramid structure full-color MicroLED disclosed by the present invention includes a TFT backplane and pyramid structure LEDs array-arranged on the TFT backplane; the pyramid structure LEDs include a substrate and an epitaxial layer; the epitaxial layer is located above the substrate; the epitaxial layer includes a dielectric layer and a pyramid structure, the dielectric layer is deposited on the substrate, and the dielectric layer has a periodically arrayed hole structure; the pyramid structure grows in the opening area on the substrate, fills the hole structure and continues to grow to form a pyramid-like structure.

[0038] Among them, the substrate is a wide-bandgap β-Ga 2 O 3 substrate with a lattice mismatch of 1% to 15% with GaN, and the material of the dielectric layer is SiO 2 , with a thickness of 10 to 200 nm; the hole structure pattern of the dielectric layer is a regular hexagon; the pyramid structure is an n-type GaN hexagonal pyramid structure with a (1-100) plane on the side and a (0001) plane on the top, with a height of 2 to 10 μm and a width of 10 to 50 μm. The doping element in the pyramid structure is Si, and the doping concentration is 10 18 ~10 20 cm -3 .

[0039] In this embodiment, there is also an InGaN pre-strained layer 4, a multi-quantum well light-emitting layer 5, a p-type AlGaN electron blocking layer 6, and a p-type GaN layer 7 on the pyramid structure. The InGaN pre-strained layer grows on the side of the pyramid structure; the multi-quantum well light-emitting layer grows on the InGaN pre-strained layer; the p-type AlGaN electron blocking layer grows on the multi-quantum well light-emitting layer; the p-type GaN layer grows on the p-type AlGaN electron blocking layer; a transparent conductive layer is prepared on the p-type GaN layer. Among them, the material of the multi-quantum well light-emitting layer is: In X1 Ga 1-X1 N / GaN for 1 to 5 periods, where the value of X1 is 0.12 to 0.18, corresponding to a blue light quantum well; In X2 Ga 1-X2 N / GaN for 1 to 5 periods, where the value of X2 is 0.20 to 0.25, corresponding to a green light quantum well; In X3 Ga 1-X3 N / GaN for 1 to 5 periods, where the value of X3 is 0.30 to 0.40, corresponding to a red light quantum well; the thickness of the InGaN layer in all quantum wells is 1 to 3 nm; the thickness of the GaN layer is 7 to 15 nm. The multi-quantum well light-emitting layer is etched and reserved in sequence along a certain arrangement direction of the pyramid structure array to retain the blue light quantum well, the blue and green light quantum wells, and all the red, green, and blue light quantum wells. The p-type GaN layer is obtained by doping with Mg element, and the doping concentration is ~3×10 19 cm-3 ; The transparent conductive layer is ITO. Among them, the p / n electrodes of the full-color Micro LED are respectively prepared on the transparent conductive layer and the bottom surface of the substrate.

[0040] The preparation method of this Micro LED is as follows:

[0041] Step 1: Take a (-201)-oriented β-Ga 2 O 3 substrate and put it into a solution prepared by mixing sulfuric acid and hydrogen peroxide in a volume ratio of 3:1 to clean the surface of the substrate;

[0042] Step 2: Through plasma-enhanced chemical vapor deposition, deposit a SiO 2 O 3 dielectric layer on the above-mentioned β-Ga 2 substrate, with a thickness of 50 nm; and use conventional photolithography and dry etching methods to prepare the SiO 2 dielectric layer into a regular hexagon mask with a side length of 6 μm and a periodic hole structure, which provides the necessary conditions for the selective area epitaxial growth of GaN pyramids;

[0043] Step 3: Put the patterned β-Ga 2 substrate with the SiO 2 mask into the MOCVD reaction chamber. First, control the temperature at 480 - 650 °C and grow a low-temperature GaN or AlN nucleation layer for 3 min in an N 3 atmosphere, then raise the temperature to 900 - 1200 °C and grow GaN for 1 hour in an H 2 atmosphere to obtain an n-type GaN pyramid structure with a height of 4 μm, where the n-type GaN layer is obtained by doping with the element Si; 2 atmosphere to grow a 50-nm-thick InGaN pre-strained layer on the n-type GaN pyramid, and control the temperature at 700 - 800 °C, where the In component is 10%.

[0044] Step 4: Grow a 50-nm-thick InGaN pre-strained layer on the n-type GaN pyramid in an N 2 atmosphere, and control the temperature at 700 - 800 °C, where the In component is 10%.

[0045] Step 5: In a further embodiment, the InGaN / GaN multiple quantum well light-emitting layer is grown on the InGaN pre-strained layer: its material is: 5 periods of In 0.12 Ga 0.88 N / GaN, corresponding to the blue light quantum well; 5 periods of In 0.25 Ga 0.75 N / GaN, corresponding to the green light quantum well; 5 periods of In 0.35 Ga 0.65 N / GaN, corresponding to the red light quantum well.

[0046] Step 6: AsFigure 2 , Figure 3 As shown in Figure 3 , the blue light quantum well, green light quantum well, and all red, green, and blue quantum wells are etched and retained in sequence along a certain arrangement direction of the pyramid array. The thickness of the InGaN layer in all quantum wells is 2 nm, and the thickness of the GaN layer is 8 nm. Figure 3 In Figure 3 , blue indicates that all LEDs in that row emit blue light, red indicates LEDs that emit blue and red light, and green indicates LEDs that emit green light. Each pattern in the arrangement in this figure is a pyramid-shaped pattern when magnified.

[0047] Step 7: Grow a p-type AlGaN electron blocking layer and a p-type GaN layer on the multi-quantum well light-emitting layer in sequence; among them, the p-type GaN layer is obtained by doping with the element Mg, the Al component of AlGaN is 0.25, the thickness is 10 nm, and the thickness of the p-type GaN layer is 200 nm;

[0048] Step 8: Evaporate a transparent conductive layer ITO on the p-type GaN layer;

[0049] Step 9: As shown in Figure 4 , the p-electrode is prepared on the transparent conductive layer, and the above-mentioned array arrangement vertical pyramid structure LED is encapsulated and cured using epoxy resin.

[0050] Step 10: Use a patterning method to strip off part of the substrate, leaving a 20-nm-thick substrate under the pyramid LED structure;

[0051] Step 11: Prepare an n-electrode on the surface of the Ga 2 O 3 substrate by combining with a patterning method;

[0052] Step 12: Transfer the array arrangement pyramid structure LED to a TFT backplane corresponding to the pyramid size to complete the fabrication of the device.

[0053] Through the above design, the present invention adopts the MOCVD method that can be quantitatively produced industrially. It does not require growing a planar nitride film on the substrate first and then realizing the selective area epitaxy of GaN pyramids through patterning the nitride film. Instead, it directly grows GaN-based vertical pyramid LEDs in the opening area on the substrate, providing a single-chip array arrangement vertical pyramid structure LED, and providing a technical route for the technical problem of massive transfer in Micro LED production, which will greatly improve production efficiency and reduce production costs.

[0054] The above embodiments are only one of the preferred embodiments of the present invention and should not be used to limit the protection scope of the present invention. Any modification or polishing that has no substantial meaning made on the main design idea and spirit of the present invention and whose solved technical problems are still consistent with the present invention should be included in the protection scope of the present invention.

Claims

1. A single chip array with vertical pyramid structure full-color Micro LED, characterized in that: It includes a TFT back panel, and a pyramid structure LED arrayed on the TFT back panel; The pyramid structure LED includes a substrate and an epitaxial layer; the epitaxial layer is located on the substrate; the epitaxial layer includes a dielectric layer and a pyramid structure, the dielectric layer is deposited on the substrate, and the dielectric layer has a hole structure arranged in a periodic array; the pyramid structure grows in the open area on the substrate, fills the hole structure and continues to grow to form a pyramid structure.

2. The single-chip array vertical pyramid structure full-color Micro LED according to claim 1, characterized in that: The substrate is a wide-bandgap β-Ga2O3 substrate with a lattice mismatch of 1% to 15% with GaN. The material of the dielectric layer is SiO2 with a thickness of 10 to 200 nm. The hole structure pattern of the dielectric layer is a regular hexagon. The pyramid structure is an n-type GaN hexagonal pyramid structure with a side surface of (1-100) and a top surface of (0001), a height of 2 to 10 μm, a width of 10 to 50 μm, and an impurity element in the pyramid structure of Si with an impurity concentration of 10 18 ~10 20 cm -3 .

3. The single-chip array vertical pyramid structure full-color Micro LED according to claim 2, characterized in that: Also includes: InGaN pre-strained layer, grown on the side of the pyramid structure; A multi-quantum well light-emitting layer is grown on the InGaN pre-strained layer; A p-type AlGaN electron blocking layer grown on the multi-quantum well light-emitting layer; A p-type GaN layer grown on a p-type AlGaN electron blocking layer; The transparent conductive layer is prepared on the p-type GaN layer.

4. The single-chip array vertical pyramid structure full-color Micro LED according to claim 3, characterized in that: The material of the multi-quantum well light-emitting layer is: 1 to 5 periods of In X1 Ga 1-X1 N / GaN, where the value of X1 is 0.12 to 0.18, corresponding to the blue light quantum well; 1 to 5 cycles In X2 Ga 1-X2 N / GaN, where the value of X2 is 0.20 to 0.25, corresponding to the green light quantum well; 1 to 5 cycles In X3 Ga 1-X3 N / GaN, where the value of X3 is 0.30-0.40, corresponding to the red light quantum well; the thickness of the InGaN layer in all quantum wells is 1-3 nm; the thickness of the GaN layer is 7-15 nm.

5. The single-chip array vertical pyramid structure full-color Micro LED according to claim 4, characterized in that: The multi-quantum well light-emitting layer is sequentially etched along a certain arrangement direction of the pyramid structure array to retain blue light quantum wells, green light quantum wells, red light quantum wells, or all quantum wells of red light, green light, and blue light.

6. The single-chip array vertical pyramid structure full-color Micro LED according to claim 5, characterized in that: The p-type GaN layer is obtained by doping Mg element, and the doping concentration is ~3×10 19 cm -3 ; The transparent conductive layer is ITO, wherein the p / n electrodes of the full-color Micro LED are respectively prepared on the transparent conductive layer and on the bottom of the substrate.

7. A method for preparing a full-color Micro LED with a vertical pyramid structure arranged in a single chip array, characterized in that: The following steps are involved: Step S1: first prepare a patterned substrate, that is, deposit a dielectric layer on the substrate, and prepare the dielectric layer into a patterned mask with a periodic hole structure, and on the basis of the patterned mask, fill the hole structure and continue to grow to form a pyramid structure; Step S2: placing the patterned substrate with the mask into the MOCVD reaction chamber, first controlling the temperature at 480-650°C, growing a GaN or AlN nucleation layer in a N2 atmosphere, then raising the temperature to 900-1200°C, growing GaN in a H2 atmosphere to form a pyramid structure; Step S3: growing an InGaN pre-strained layer on the pyramid structure, growing a multi-quantum well light-emitting layer on the InGaN pre-strained layer, and growing a p-type AlGaN electron blocking layer and a p-type GaN layer on the multi-quantum well light-emitting layer; Step S4: evaporating a transparent conductive layer on the p-type GaN layer; preparing p / n electrodes on the transparent conductive layer and the bottom surface of the substrate respectively; Step S5: transferring the array-arranged pyramid structure LED to a TFT backplane corresponding to the size of the pyramid to complete the device manufacturing.

8. The method for preparing a full-color Micro LED with a vertical pyramid structure arranged in a single chip array according to claim 7, characterized in that: In the step S1, the patterning method is photolithography, colloidal lithography, electron beam exposure or nanoimprinting.

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