Patent ID: 12206041

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure will be further described below by means of particular examples with reference to the accompanying drawings.

As shown inFIG.6, a method for monolithic integration preparation of a full-color nitride semiconductor micro-LED array was performed as follow in this example:1) Preparation of a composite conductive substrate:1-a) A sapphire substrate was provided to serve as a transparent insulating substrate3, wherein the sapphire substrate had a bandgap greater than 5.0 eV and did not absorb ultraviolet light with a wavelength greater than 250 nm.1-b) An n-type conductive monocrystalline silicon wafer2with a thickness of 430 micrometers, a size of 4 inches, and a resistivity less than 0.001 ohm cm was provided, wherein an outer periphery of the n-type conductive monocrystalline silicon wafer had a same shape as an outer periphery of the transparent insulating substrate: polishing was performed on one side of the n-type conductive monocrystalline silicon wafer until a surface roughness of 0.2 nm was achieved on its upper surface: a non-polished surface of the n-type conductive monocrystalline silicon wafer was thinned to 5 μm, and the n-type conductive monocrystalline silicon wafer was attached onto the transparent insulating substrate, with the polished surface facing upwards, to form the composite conductive substrate1.2) Provision of an insulating template:The insulating template was a flat panel made of an electrically insulating material. An outer periphery of the insulating template had a same shape as an outer periphery of the composite conductive substrate. The insulating template was divided into a plurality of two-dimensional closely arranged through hole units. An outer periphery of each through hole unit was in a square plane shape with a side length (i.e., a) of 5 μm. Each through hole unit included four circular through holes inside with a depth equal to a thickness of the insulating template and a diameter of 0.2a (i.e., 1 μm), namely, one green-light region through hole, one blue-light region through hole, and two red-light region through holes. The green-light region through hole and the blue-light region through hole were respectively located at a pair of diagonal corners of the square, and the two red-light region through holes were respectively located at the other pair of diagonal corners of the square.3) Preparation of a template substrate:3-a) The insulating template was overlaid onto the composite conductive substrate in a completely aligned manner.3-b) The insulating template was spin-coated with a photoresist to prepare a protective layer, such that the protective layer was formed on the n-type conductive monocrystalline silicon wafer in areas corresponding to the circular through holes of the insulating template, while no protective layer was formed in areas not corresponding to the circular through holes.3-c) The insulating template was removed, and ion implantation was performed on the n-type conductive monocrystalline silicon wafer, such that ions were implanted into areas of the n-type conductive monocrystalline silicon wafer which were not covered by the protective layer, thereby increasing resistivity and making these areas electrically insulating, and then the insulating template was removed.3-d) Chemical cleaning was performed on the composite conductive substrate after ion implantation to remove the protective layer, wherein the areas corresponding to the circular through holes of the insulating template remained conductive, while remaining areas became electrically insulating, thus completing modification of the n-type conductive monocrystalline silicon wafer to obtain the template substrate.3-e) Corresponding to the insulating template, a plurality of closely arranged two-dimensional pixel regions4were provided on the n-type conductive monocrystalline silicon wafer of the template substrate, wherein each pixel region4included four circular conductive regions, namely, two red-light conductive regions7, one green-light conductive region6, and one blue-light conductive region5, and the rest being an insulating region8, as shown inFIG.1.4) Preparation of a customized template graphene substrate:4-a) Monocrystalline graphene with a thickness of 6 atomic layers and a size of 4 inches was provided, wherein an outer periphery of the monocrystalline graphene had a same shape as the template substrate.4-b) The monocrystalline grapheme was overlaid onto the template substrate in a completely aligned manner.4-c) The insulating template was overlaid onto the monocrystalline graphene in a completely aligned manner, wherein one green-light region through hole, one blue-light region through hole, and two red-light region through holes of each through hole unit of the insulating template were respectively precisely aligned with the one green-light conductive region, the one blue-light conductive region, and the two red-light conductive regions of in each pixel region of the n-type conductive monocrystalline silicon wafer.4-d) The monocrystalline grapheme was thinned in areas corresponding to the blue-light region through holes and green-light region through holes, until a thickness of one atomic layer was achieved, and the monocrystalline graphene was thinned in areas corresponding to the red-light region through holes, until a thickness of 4 atomic layers was achieved.4-e) Uniform nitrogen atom doping was performed on the monocrystalline graphene in areas corresponding to the blue-light region through holes, green-light region through holes, and red-light region through holes, wherein the monocrystalline graphene after the uniform nitrogen atom doping exhibits ultraviolet absorption within a range of 240 to 270 nm.4-f) A pseudo-monocrystalline AlON layer with a thickness of 5 nm was deposited on the monocrystalline graphene in areas corresponding to the blue-light region through holes, such that a nitride epitaxial layer grown thereon had a metal lattice polarity.4-g) Edges of the monocrystalline graphene that correspond to the green-light region through holes, blue-light region through holes, and red-light region through holes was cut by using ultraviolet laser with a wavelength of 255 nm, wherein the cutting was performed only on the monocrystalline graphene: blue-region graphene array elements, green-region graphene array elements, and red-region graphene array elements were formed on the monocrystalline graphene in areas respectively corresponding to the blue-light region through holes, green-light region through holes, and red-light region through holes, and insulating-region graphene array elements were formed among the blue-region graphene array elements, green-region graphene array elements, and red-region graphene array elements, thereby forming graphene array units13each consisting of one blue-region graphene array element9, one green-region graphene array element10, two red-region graphene array elements11, and an insulating-region graphene array element12. The insulating template was removed to obtain a customized template graphene substrate14, wherein the blue-region graphene array element, the green-region graphene array element, and the red-region graphene array elements in each graphene array unit13on the n-type conductive monocrystalline silicon wafer of the customized template graphene substrate have surface properties different from each other, as shown inFIG.2.5) Preparation of a full-color micro-LED array epitaxial wafer:The customized template graphene substrate was placed into a metal organic chemical vapor deposition system, and vertical-structure all-nitride micro-LEDs were formed by deposition, which had the following structure: silicon-doped n-type GaN (with an electron concentration of 3×1019cm−3) with a thickness of 300 nm, an deposited InGaN/GaN multiple-quantum-well structure with 5 periods (in each structure, undoped GaN with a thickness of 15 nm served as a potential barrier and undoped InGaN with a thickness of 2.5 nm served as a potential well, and the structure had a total thickness of 102.5 nm), and deposited magnesium-doped p-type GaN (with a hole concentration of 3×1019cm−3) with a thickness of 300 nm. Due to the different surface properties of the blue-region graphene array element, green-region graphene array element, and red-region graphene array elements of each graphene array unit on the n-type conductive monocrystalline silicon wafer of the customized template graphene substrate, the vertical-structure all-nitride materials grown thereon had different lattice polarities, stress states, and In compositions in the MQW structures, and thereby different central emission wavelengths, and therefore a vertical-structure monocrystalline metal-polar blue-light-emitting nitride, a vertical-structure monocrystalline nitrogen-polar green-light-emitting nitride, and a vertical-structure monocrystalline stress-relaxed nitrogen-polar red-light-emitting nitride were grown respectively on the blue-region graphene array elements, green-region graphene array elements, and red-region graphene array elements, to form a blue-light-emitting micro-LED15, a green-light-emitting micro-LED16, and a red-light-emitting micro-LED17, as well as areas without micro-LEDs, which constituted a micro-LED pixel unit18emitting light in multiple directions. The full-color micro-LED array epitaxial wafer19was obtained by one-step in-situ process, and the blue, green, and red-light-emitting micro-LEDs were micrometer-sized pillars. The MQW structure in the vertical-structure monocrystalline metal-polar blue-light-emitting nitride located on the blue-region graphene array elements had 16% of In composition, and the central emission wavelength of the blue-light-emitting micro-LED15was approximately 459 nm. The MQW structure in the vertical-structure monocrystalline nitrogen-polar green-light nitride located on the green-region graphene array elements had 26% of In composition, and the central emission wavelength of the green-light-emitting micro-LED16was approximately 536 nm. The MQW structure in the vertical-structure monocrystalline stress-relaxed nitrogen-polar red-light-emitting nitride located on the red-region graphene array elements had 35% of In composition, and the central emission wavelength of the red-light-emitting micro-LED17was approximately 620 nm, as shown inFIG.3.6) Packaging:

An AlN film with a thickness of 20 to 50 nm was deposited on sidewalls of each micrometer-sized pillar in the full-color micro-LED array and on an upper surface of the insulating region through masking and physical vapor deposition to form a polycrystalline insulating nitride film20, wherein the polycrystalline insulating nitride film had a bandgap greater than 5.0 eV and a resistivity greater than 1×106ohm cm. A polycrystalline Al film with a thickness of 30 nm was deposited using a total internal reflection metal packaging technology. Gaps among the micrometer-sized pillars of the blue, green, and red-light-emitting micro-LEDs were filled with polymethyl methacrylate21, wherein a filling height was equal to a height of the blue, green, and red-light-emitting micro-LEDs, there was no height variation, and top surfaces of the blue, green, and red-light-emitting micro-LEDs were exposed. Light emission from sidewalls of the blue, green, and red-light-emitting micro-LEDs was prevented, while only light emission in a direction vertical to the top surface was allowed. The micro-LED pixel units18emitting light in multiple directions was transformed into micro-LED pixel units22emitting light only in the vertical direction, thereby obtaining a flat full-color micro-LED array wafer23, as shown inFIG.4.7) Preparation of a transparent electrode:7-a) The flat micro-LED array wafer was acid-etched to separate a lower surface of the n-type conductive monocrystalline silicon wafer from the transparent insulating substrate3, and the lower surface of the n-type conductive monocrystalline silicon wafer was smoothed.7-b) An upper surface of the flat micro-LED array wafer was spin-coated with indium tin oxide having a thickness of 50 to 500 nm to form the transparent electrode.7-c) A surface of the transparent electrode was covered with the insulating template, wherein the circular through holes of the insulating template were respectively aligned with each of blue, green, and red-light-emitting micro-LEDs.7-d) The insulating template was spin-coated with a photoresist to prepare a protective layer, such that the protective layer was formed within the circular through holes of the insulating template, while no protective layer was formed in areas without the circular through boles.7-e) The insulating template was removed, and ion implantation was performed on the transparent electrode, wherein ions were implanted into areas of the transparent electrode which were not covered by the protective layer, such that the areas of the transparent electrode that did not correspond to the blue, green, and red-light-emitting micro-LEDs had increased resistivity and became electrically insulating. This achieved a transparent electrode array on top surfaces of the blue, green, and red-light-emitting micro-LEDs. A single vertically-emitting micro-LED pixel unit28with a transparent electrode included a conductive blue region24above the blue-light-emitting micro-LED, a conductive green region25above the green-light-emitting micro-LED, a conductive red region26above the red-light-emitting micro-LED, and a non-conductive insulating region27among the conductive blue region, conductive green region, and conductive red region.7-f) The drive circuit board30was covered with an aluminum array having a complementary pattern to the insulating template, the aluminum array being a columnar array. The columnar aluminum array had a diameter of 5 μm and a thickness of 20 nm. A position of the aluminum array corresponded to that of the electrode array on the drive circuit board, and the electrode array on the driving circuit board also had a diameter of 5 μm. Vapor deposition was performed using techniques such as magnetron sputtering. Heating was performed to reach a temperature of 500° C. to 600° C., which was held for 3 to 5 minutes, to attach the aluminum array onto an upper surface of the drive circuit board.7-g) The upper surface of the drive circuit board, with the aluminum array thereon, was attached to the lower surface of the n-type conductive monocrystalline silicon wafer, wherein the aluminum array was conductive and reflective, preventing light emission from the bottom surface while achieving electrode bonding on the bottom surface, such that all light was emitted from the top surface, to obtain a vertical-structure full-color nitride micro-LED array29with top light emission, as shown inFIG.5.

Finally, it should be noted that disclosure of the embodiments is intended to help further understand the present disclosure. However, those skilled in the art can understand that various substitutions and modifications may be made without departing from the spirit and scope of the present disclosure and the appended claims. Therefore, the present disclosure should not be limited to the content disclosed in the embodiments, and the scope of protection claimed by the present disclosure is subject to the scope defined by the claims.