RC-Micro LED device and preparation method thereof

Abstract

The application relates to the technical field of photoelectric devices, in particular to an RC-Micro LED device and a preparation method thereof, which comprises, from bottom to top, a second substrate, a metal conductive support layer, a metal electrode layer, a first mirror layer, a transparent conductive layer, a gallium nitride epitaxial layer and a second mirror layer; the gallium nitride epitaxial layer is in a convex mesa structure, an insulating layer is covered on the sidewall of the convex mesa structure; the first mirror layer and the second mirror layer are oppositely arranged to form a Fabry-Perot resonant cavity structure. The RC-Micro LED device can meet the transmission requirement of high-speed short-distance optical interconnection.

Description

Technical Field

[0001] This application relates to the technical field of optoelectronic devices, and in particular to an RC-Micro LED device and its fabrication method. Background Technology

[0002] Currently, Micro-LEDs (micro-light-emitting diodes) have attracted widespread attention in the field of visible light communication due to their advantages such as high brightness and fast response. However, the full width at half maximum (FWHM) of the emission spectrum of traditional Micro-LEDs is typically above 20-30 nm, with a Lambertian beam distribution and a large divergence angle. The modulation bandwidth is limited by factors such as the spontaneous recombination lifetime of charge carriers, making it difficult to meet the transmission requirements of high-speed, short-distance optical interconnects. RC-Micro LEDs (resonant cavity micro-light-emitting diodes) construct a Fabry-Perot resonant cavity structure by placing mirrors above and below the active region. This allows the light generated in the active region of MQWs to form a standing wave gain, improving the light emission morphology and effectively reducing the recombination lifetime of charge carriers. This effectively increases the device bandwidth and communication rate, becoming an effective way to improve the performance of Micro-LED optical communication.

[0003] In related technologies, the fabrication of RC-Micro LEDs typically involves epitaxially growing gallium nitride (GaN) material on a sapphire substrate, removing the sapphire substrate using a laser lift-off process, and then thinning the GaN layer using chemical mechanical polishing (CMP) to control the cavity length. However, during the laser lift-off process, the high-energy laser pulse acts on the interface between GaN and sapphire, generating gallium (Ga) metal particles on the GaN surface and introducing thermal damage, resulting in a rough and uneven GaN surface after lift-off. The rough GaN surface makes the initial conditions for subsequent CMP inconsistent. Furthermore, the thickness control precision of CMP is typically on the micrometer scale. The combined effect of these two factors leads to poor uniformity and low precision in the final GaN epitaxial layer thickness, making it difficult to precisely control the cavity length to a shorter range. Deviations in cavity length directly result in resonant wavelength shift, decreased quality factor, and weakened Purcell enhancement effect, leading to low yield and severely limiting the performance improvement of RC-Micro LED devices.

[0004] Regarding the aforementioned technologies: due to the insufficient precision of existing fabrication processes, the cavity length of RC-Micro LED resonators is difficult to control precisely to a shorter range, the Purcell enhancement effect is not significant, and the modulation bandwidth of the device is still insufficient to meet the transmission requirements of high-speed short-distance optical interconnects. Summary of the Invention

[0005] To meet the transmission requirements of high-speed short-distance optical interconnects, this application provides an RC-Micro LED device and its fabrication method.

[0006] Firstly, this application provides an RC-Micro LED device, which adopts the following technical solution:

[0007] An RC-Micro LED device, comprising:

[0008] The second substrate, the metal conductive support layer, the metal electrode layer, the first reflective mirror layer, the transparent conductive layer, the gallium nitride epitaxial layer, and the second reflective mirror layer are arranged sequentially from bottom to top.

[0009] The gallium nitride epitaxial layer has a convex mesa structure, and the sidewalls of the convex mesa structure are covered with an insulating layer.

[0010] The first reflector layer and the second reflector layer are arranged opposite to each other to form a Fabry-Perot resonant cavity structure.

[0011] By adopting the above technical solution, the bottom first reflective mirror layer and the top second reflective mirror layer form an FP resonant cavity structure. The Purcell effect of the resonant cavity is used to enhance the spontaneous emission rate and shorten the carrier recombination lifetime, thereby improving the modulation bandwidth of the device. At the same time, the mode selection effect is used to achieve narrow linewidth emission and small divergence angle directional light emission to meet the transmission requirements of high-speed short-distance optical interconnects.

[0012] Optionally, the gallium nitride epitaxial layer includes a p-GaN layer, an MQWs quantum well active layer, and an n-GaN layer arranged sequentially from bottom to top. The p-GaN layer is disposed on the side of the transparent conductive layer away from the first reflective mirror layer, and the second reflective mirror layer is in direct contact with the surface of the n-GaN layer away from the MQWs quantum well active layer.

[0013] By employing the above technical solution, a p-GaN layer, an MQWs quantum well active layer, and an n-GaN layer are sequentially arranged from bottom to top in the gallium nitride epitaxial layer. The p-GaN layer is disposed on the side of the transparent conductive layer facing away from the first reflector layer, and the second reflector layer is disposed on the side of the n-GaN layer facing away from the MQWs quantum well active layer. Thus, when a voltage is applied to the device, electrons are injected from the n-GaN layer, and holes are injected from the p-GaN layer. These electrons meet and recombine in the MQWs quantum well active layer, thereby achieving light emission. The MQWs quantum well active layer provides a suitable energy trap, effectively confining charge carriers and improving carrier recombination efficiency, thereby enhancing the device's luminous efficiency. Simultaneously, this layered structure facilitates carrier transport and recombination, enabling the device to more efficiently convert electrical energy into light energy, achieving high-efficiency light emission and providing strong support for realizing low-power, high-bandwidth optical interconnects.

[0014] Optionally, the center peak reflectivity of the first reflector layer is different from that of the second reflector layer, wherein the center peak reflectivity of the side with higher reflectivity is greater than 95%, and the center peak reflectivity of the side with lower reflectivity is 80%-95%, and light is emitted from the side with lower reflectivity.

[0015] By adopting the above technical solution, the center peak reflectivity of the first reflector layer and the second reflector layer are set differently. The center peak reflectivity of the side with higher reflectivity is greater than 95%, while the center peak reflectivity of the side with lower reflectivity is 80%-95%. Light is emitted from the side with lower reflectivity. In the resonant cavity, due to the difference in reflectivity, standing wave gain can be achieved, which enhances the light of a specific wavelength in the cavity, thereby improving the light output efficiency. At the same time, it effectively reduces the carrier lifetime and increases the device bandwidth.

[0016] Optionally, the center peak reflectivity of the second reflector layer is less than that of the center peak reflectivity of the first reflector layer, and the p-type metal electrodes in the metal electrode layer completely cover the surface of the convex mesa structure facing the first reflector layer, so that the device emits light from the side where the second reflector layer is located.

[0017] By adopting the above technical solution, a device structure with front-side light emission (light emission from the second reflector layer side) was realized. The p-type metal electrodes in the metal electrode layer completely cover the bottom surface of the convex mesa structure, which not only provides uniform current injection, but also forms a high reflectivity side with the first reflector layer, which is beneficial for emitting light from the second reflector layer side on the top surface.

[0018] Optionally, the center peak reflectivity of the second reflector layer is greater than that of the center peak reflectivity of the first reflector layer, the metal electrode layer covers the edge region of the convex mesa structure facing the first reflector layer, the middle region of the convex mesa structure is exposed, the second substrate is a light-transmitting substrate, and the device emits light from the side where the second substrate is located.

[0019] By adopting the above technical solution, when the reflectivity of the central peak of the second reflector layer is greater than that of the central peak of the first reflector layer, light will be emitted from the side of the first reflector layer with lower reflectivity. The metal electrode layer covers the edge region of the convex mesa structure facing the first reflector layer, while the middle region is exposed, which reduces obstruction of the light-emitting area and improves light extraction efficiency. Simultaneously, the use of a transparent second substrate allows light to pass smoothly through it, avoiding absorption and loss of light within the substrate, thereby improving the device's light-emitting performance and the efficiency of optical communication.

[0020] Optionally, the first reflector layer is one of a metal reflector, a DBR reflector, or a photonic crystal reflector, and the second reflector layer is one of a DBR reflector or a photonic crystal reflector.

[0021] By adopting the above technical solution, multiple options for different reflector types are provided. The first reflector layer can be a metal reflector to obtain broadband high reflectivity, or a DBR reflector or a photonic crystal reflector to obtain high reflectivity at a specific wavelength. The second reflector layer uses a DBR reflector or a photonic crystal reflector, which combines high reflectivity and light transmission, making it suitable for the light-emitting side.

[0022] Optionally, the total thickness of the gallium nitride epitaxial layer is less than 2 μm.

[0023] By adopting the above technical solution, the total thickness of the gallium nitride epitaxial layer can be controlled within 2μm, which can shorten the cavity length of the resonant cavity, expand the free spectral range, enhance the Purcell effect, and help improve the modulation bandwidth of the device.

[0024] Secondly, this application provides a method for fabricating an RC-Micro LED device, employing the following technical solution:

[0025] A method for fabricating an RC-Micro LED device includes the following steps:

[0026] S1: A u-GaN layer, a gallium nitride epitaxial layer, and a transparent conductive layer are sequentially epitaxially grown on the first substrate;

[0027] S2: Etch the u-GaN layer, the gallium nitride epitaxial layer, and the transparent conductive layer to form a convex mesa structure, and deposit an insulating layer on the sidewall of the convex mesa structure;

[0028] S3: The first reflective mirror layer is prepared on the transparent conductive layer;

[0029] S4: Deposit a mask layer on the device surface, the mask layer covering the device body region and the anchor region, the anchor region being located at the edge of the device body region and connected to the device body region, the device body region and the edge region outside the anchor region being exposed, and then dry etching through the u-GaN layer and the gallium nitride epitaxial layer exposed at the edge region, and etching into the first substrate to form a trench structure, immerse the device in an etching solution, and wet etch through the sidewalls of the trench structure to remove the first substrate below the u-GaN layer, so that the device body region is suspended and supported on the first substrate by the anchor region formed by the unetched epitaxial layer below the anchor region;

[0030] S5: Prepare a metal electrode layer on the device, peel the device off the first substrate and flip it over using a flexible material, place the metal electrode layer face down on a second substrate with a preset metal conductive support layer, heat to make the metal conductive support layer adhere to the metal electrode layer and remove the flexible material;

[0031] S6: Remove the u-GaN layer on the top surface of the device and thin the gallium nitride epitaxial layer, and fabricate a second mirror layer on the gallium nitride epitaxial layer. The first mirror layer and the second mirror layer constitute a Fabry-Perot resonant cavity structure.

[0032] By employing the above technical solution, the first substrate is removed using anchor etching. A trench structure is formed at the device edge, and wet etching is used to selectively remove the substrate material beneath the u-GaN layer. This allows the device to be suspended and transferred to the second substrate using a flexible material. This helps avoid damage to the gallium nitride epitaxial layer caused by laser lift-off. The surface of the u-GaN layer is smooth and flat after wet etching, providing a good foundation for subsequent precise thinning and mirror fabrication. Precise removal of the u-GaN layer and thinning of the gallium nitride epitaxial layer using dry etching enables sub-micron-level cavity length control precision, resulting in a significant Purcell effect in the resonant cavity, reducing carrier lifetime, and effectively improving the device's modulation bandwidth.

[0033] Optionally, the gallium nitride epitaxial layer includes an n-GaN layer, an MQWs quantum well active layer, and a p-GaN layer epitaxially grown sequentially on the u-GaN layer, and the second mirror layer is located on the side of the n-GaN layer opposite to the MQWs quantum well active layer;

[0034] In step S2, the transparent conductive layer, the p-GaN layer and the MQWs quantum well active layer are sequentially etched through, and a portion of the n-GaN layer with a thickness of 100-300 nm is etched to form the convex mesa structure;

[0035] In step S4, the dry etching depth into the first substrate is 500nm-2μm. The first substrate is a Si substrate. The etching solution is a KOH solution. The KOH solution performs wet etching through the sidewall of the Si substrate exposed by the trench structure.

[0036] By employing the above technical solution, the specific layer sequence of the gallium nitride epitaxial layer and the specific depth of mesa etching were clarified. During mesa etching, a 100-300 nm thick n-GaN layer was retained, ensuring the integrity of the convex mesa structure and providing an n-type contact surface for subsequent electrode fabrication. A combination of Si substrate and KOH solution was used, leveraging the differential etching rate of KOH on Si with different crystal orientations to achieve selective removal of the Si substrate, while the gallium nitride epitaxial layer remained unaffected by KOH etching. The etching depth of 500 nm-2 μm into the Si substrate ensured that the KOH solution could contact the Si substrate through the sidewalls of the trench structure and perform lateral etching.

[0037] Optionally, in step S6, the u-GaN layer is removed by ICP dry etching and the gallium nitride epitaxial layer is thinned to a total thickness of less than 2 μm.

[0038] By adopting the above technical solution, the u-GaN layer is removed by ICP dry etching and the gallium nitride epitaxial layer is thinned to a total thickness of less than 2μm, so that the cavity length of the resonant cavity is controlled within an extremely short range, which can generate a significant Purcell effect, effectively enhance the spontaneous emission rate, reduce the carrier lifetime, and improve the modulation bandwidth.

[0039] Optionally, in step S5, the process of peeling and flipping the device from the first substrate using a flexible material includes: spin-coating a first flexible material layer on the surface of the device, peeling the device from the first substrate after curing, flipping the device and spin-coating a second flexible material layer on the other side of the device, removing the first flexible material layer after curing, and placing the metal electrode layer face down on the second substrate.

[0040] By adopting the above technical solution, the device can be non-destructively peeled off and flipped by transferring two flexible material layers, avoiding the thermal damage and surface roughening of the gallium nitride epitaxial layer caused by traditional laser peeling, and ensuring the process basis for subsequent thinning and mirror fabrication.

[0041] Thirdly, this application provides a method for fabricating an RC-Micro LED device, employing the following technical solution:

[0042] A method for fabricating an RC-Micro LED device includes the following steps:

[0043] S1: A u-GaN layer, a gallium nitride epitaxial layer, and a transparent conductive layer are sequentially epitaxially grown on the first substrate;

[0044] S2: Etch the u-GaN layer, the gallium nitride epitaxial layer, and the transparent conductive layer to form a convex mesa structure, and deposit an insulating layer on the sidewall of the convex mesa structure;

[0045] S3: The first reflective mirror layer is prepared on the transparent conductive layer;

[0046] S4: Deposit a mask layer on the device surface, the mask layer covering the device body region and the anchor region, the anchor region being located at the edge of the device body region and connected to the device body region, the device body region and the edge region outside the anchor region being exposed, and then dry etching through the u-GaN layer and the gallium nitride epitaxial layer exposed at the edge region, and etching into the first substrate to form a trench structure, immerse the device in an etching solution, and wet etch through the sidewalls of the trench structure to remove the first substrate below the u-GaN layer, so that the device body region is suspended and supported on the first substrate by the anchor region formed by the unetched epitaxial layer below the anchor region;

[0047] S5: Fabricate a metal electrode layer on the device, and peel the device off from the first substrate using a flexible material;

[0048] S6: Flip the device, remove the u-GaN layer and thin the gallium nitride epitaxial layer;

[0049] S7: Place the device on a second substrate, on which a metal conductive support layer and a pre-prepared second reflector layer are disposed. Heat the metal conductive support layer to bond it with the metal electrode layer. The first reflector layer and the second reflector layer constitute a Fabry-Perot resonant cavity structure.

[0050] By employing the above technical solution, the u-GaN layer is removed and the gallium nitride epitaxial layer is thinned before transferring the device to the second substrate. The device is then placed on the second substrate on which the second mirror layer has been pre-fabricated. The advantage of this solution is that the second mirror layer is pre-fabricated on the second substrate, allowing for independent optimization of the mirror fabrication process and quality, unaffected by the device transfer process. Simultaneously, the thinning step is completed before transfer to the second substrate, avoiding the potential impact of high-energy etching on the metal conductive support layer and bonding interface on the second substrate.

[0051] In summary, this application includes at least one of the following beneficial technical effects:

[0052] 1. By placing a gallium nitride epitaxial layer between the first and second mirror layers to form a Fabry-Perot resonant cavity structure, the Purcell effect is used to enhance the spontaneous emission rate and reduce the carrier lifetime, effectively improving the modulation bandwidth of the RC-MicroLED device, reducing driving power consumption, and meeting the transmission requirements of high-speed short-distance optical interconnects.

[0053] 2. The first substrate is removed by anchor etching. After wet etching, the surface of the u-GaN layer is smooth and flat. Combined with dry etching to accurately thin the gallium nitride epitaxial layer, submicron-level cavity length control precision can be achieved, enabling the resonant cavity to produce a significant Purcell effect.

[0054] 3. Two fabrication methods, flip-chip and upright, are provided, as well as two device structures, front-emitting and back-emitting, suitable for different application scenarios and process requirements. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the overall structure of an RC-Micro LED device in this application.

[0056] Figure 2 This is a flowchart of the fabrication process for the flip-chip method.

[0057] Figure 3 This is a flowchart of the manufacturing process for the standard packaging solution.

[0058] Explanation of reference numerals in the attached figures:

[0059] 01. Second substrate; 02. Metal conductive support layer; 03. Metal electrode layer; 031. p-type metal electrode; 032. n-type metal electrode; 04. First reflector layer; 05. Transparent conductive layer; 06. Gallium nitride epitaxial layer; 061. p-GaN layer; 062. MQWs quantum well active layer; 063. n-GaN layer; 07. Second reflector layer; 08. Insulating layer; 09. First substrate; 10. u-GaN layer; 11. Mask layer; 12. First flexible material layer; 13. Second flexible material layer. Detailed Implementation

[0060] The following is in conjunction with the appendix Figure 1-3 This application will be described in further detail.

[0061] This application discloses an RC-Micro LED device.

[0062] It should be noted that, in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0063] Reference Figure 1An RC-Micro LED device includes, from bottom to top, a second substrate 01, a metal conductive support layer 02, a metal electrode layer 03, a first reflector layer 04, a transparent conductive layer 05, a gallium nitride epitaxial layer 06, and a second reflector layer 07. The first reflector layer 04 and the second reflector layer 07 are disposed opposite to each other, and the gallium nitride epitaxial layer 06 is located between the first reflector layer 04 and the second reflector layer 07 to form a Fabry-Perot resonant cavity structure, which realizes standing wave gain and resonant filtering effect, while achieving low power consumption and high bandwidth optical interconnection.

[0064] The gallium nitride epitaxial layer 06 has a convex mesa structure, and an insulating layer 08 covers the sidewalls of the convex mesa structure. In this embodiment, the insulating layer 08 can be made of materials such as SiO2, Al2O3 or SiN, and is deposited on the sidewalls of the convex mesa structure by plasma-enhanced chemical vapor deposition (PECVD). Its function is to prevent current leakage from the sidewalls and improve the efficiency of the device.

[0065] A transparent conductive layer 05 is disposed between the gallium nitride epitaxial layer 06 and the first reflective mirror layer 04. The transparent conductive layer 05 is an indium tin oxide thin film layer (ITO layer), which has good conductivity and transparency. This allows it to form an ohmic contact with the gallium nitride epitaxial layer 06 to achieve current injection, while also allowing light to propagate without significant absorption loss. In this embodiment, the transparent conductive layer 05 is indium tin oxide and is formed on the gallium nitride epitaxial layer 06 through a deposition process.

[0066] The gallium nitride epitaxial layer 06 includes, from bottom to top, a p-GaN layer 061, an MQWs quantum well active layer 062, and an n-GaN layer 063. The p-GaN layer 061 is disposed on the side of the transparent conductive layer 05 facing away from the first reflective mirror layer 04, that is, the lower surface of the p-GaN layer 061 is in contact with the upper surface of the transparent conductive layer 05. The second reflective mirror layer 07 is disposed on the side of the n-GaN layer 063 facing away from the MQWs quantum well active layer 062.

[0067] The p-GaN layer 061 provides holes, and the n-GaN layer 063 provides electrons. The MQW quantum well active layer 062 is located between the p-GaN layer 061 and the n-GaN layer 063, serving as the light-emitting layer of the device. The MQW quantum well active layer 062 typically consists of multiple InGaN / GaN quantum well cycles, with the number of quantum wells typically ranging from 3 to 10. The thickness of each quantum well is typically 2-4 nm, and the thickness of the barrier layer is typically 8-15 nm.

[0068] The thinner the total thickness of the gallium nitride epitaxial layer 06, the shorter the cavity length of the resonant cavity, the more significant the Purcell effect, and the higher the modulation bandwidth. In this embodiment, the total thickness of the gallium nitride epitaxial layer 06 is less than 2 μm. Specifically, the thickness of the n-GaN layer 063 can be 0.5-1.5 μm, the thickness of the MQWs quantum well active layer 062 can be 100-200 nm, and the thickness of the p-GaN layer 061 can be 100-300 nm.

[0069] The center peak reflectivity of the first reflector layer 04 is different from that of the center peak reflectivity of the second reflector layer 07. The center peak reflectivity of the side with higher reflectivity is greater than 95%, while the center peak reflectivity of the side with lower reflectivity is 80%-95%. Light is emitted from the side with lower reflectivity.

[0070] In the front-emitting light scheme, the center peak reflectivity of the second reflector layer 07 is lower than that of the first reflector layer 04. The first reflector layer 04 serves as the high-reflectivity side (center peak reflectivity greater than 95%), and the second reflector layer 07 serves as the low-reflectivity side (center peak reflectivity 80%-95%). Light is emitted from the second reflector layer 07 side (i.e., the top surface of the device). Furthermore, in this scheme, the second substrate 01 can be a metal substrate or a Si substrate.

[0071] In the back-emitting light scheme, the center peak reflectivity of the second reflector layer 07 is greater than that of the first reflector layer 04. The second reflector layer 07 serves as the high-reflectivity side (center peak reflectivity greater than 95%), while the first reflector layer 04 serves as the low-reflectivity side (center peak reflectivity 80%-95%). Light is emitted from the first reflector layer 04 side (i.e., the bottom surface of the device). Furthermore, in this scheme, the second substrate 01 is a transparent substrate, such as glass, sapphire, or SiC, to allow light to exit from the bottom surface.

[0072] The first reflector layer 04 can be one of a metal reflector, a DBR reflector (distributed Bragg reflector), or a photonic crystal reflector. The second reflector layer 07 can be one of a DBR reflector or a photonic crystal reflector. In this embodiment, the first reflector layer 04 is a metal reflector, and the second reflector layer 07 is a DBR reflector.

[0073] Metal mirrors can be made of Al or Ag, with a thickness greater than 50 nm. Al has high reflectivity (greater than 90%) in the ultraviolet to visible light range, while Ag has even higher reflectivity (greater than 95%) in the visible light range. The advantages of metal mirrors are simple fabrication processes and wide reflectivity bandwidth, but they suffer from some absorption loss.

[0074] DBR mirrors are composed of alternating layers of high-refractive-index and low-refractive-index films, with each layer having an optical thickness of one-quarter of the target wavelength. Material combinations for DBR mirrors can include TiO2 and SiO2, TiO2 and Ta2O5, or SiN and SiO2. 2或 One of GaN and SiO2. DBR mirrors typically have 12-20 pairs; the more pairs, the higher the reflectivity. For example, for a blue RC-Micro LED with a center wavelength of 450nm, a TiO2 / SiO2 DBR mirror can be used. Each TiO2 layer is approximately 45nm thick, and each SiO2 layer is approximately 78nm thick; 16 pairs are sufficient to achieve a center peak reflectivity greater than 99%.

[0075] Photonic crystal mirrors are composed of periodically arranged nanostructures, such as nanopore arrays or nanostrip arrays. The materials used in photonic crystal mirrors can be TiO2, SiN, or GaN. By adjusting the period, duty cycle, and depth of the nanostructures, high reflectivity within a specific wavelength range can be achieved. Compared to DBR mirrors, photonic crystal mirrors have a thinner profile and a wider angular response range.

[0076] The metal electrode layer 03 provides a current loop for the device, enabling its electrical drive. The metal electrode layer 03 includes a p-type metal electrode 031 and an n-type metal electrode 032. The p-type metal electrode 031 forms an ohmic contact with the p-GaN layer 061 through the transparent conductive layer 05. The n-type metal electrode 032 forms an ohmic contact with the exposed n-GaN layer 063 around the convex mesa structure, and the n-type metal electrode 032 is disposed on the surface of the exposed n-GaN layer 063 around the convex mesa structure.

[0077] In this embodiment, the metal system of the p-type metal electrode 031 can be Ni / Au to provide good hole injection capability; the metal system of the n-type metal electrode 032 can be Ti / Al / Ti / Au.

[0078] In another preferred embodiment, the metal systems of the p-type metal electrode 031 and the n-type metal electrode 032 can also be unified as a Ti / Al / Cr / Pt / Au metal system, which can also effectively inject electrons and holes.

[0079] In the front-emitting light scheme, the p-type metal electrode 031 completely covers the surface of the convex mesa structure facing the first reflective mirror layer 04, that is, the p-type metal electrode 031 fully covers the bottom surface of the convex mesa structure, providing uniform current injection.

[0080] In the back-side light emission scheme, the p-type metal electrode 031 covers the edge region of the convex mesa structure facing the first reflective mirror layer 04, while the middle region of the convex mesa structure is exposed to allow light to pass through from the bottom surface. The second substrate 01 is a light-transmitting substrate, such as a glass substrate or a sapphire substrate, to allow light to exit from the bottom surface.

[0081] A conductive metal support layer 02 is disposed on the upper surface of the second substrate 01, and the material of the conductive metal support layer 02 can be a Ni / Sn alloy or solder. The conductive metal support layer 02 includes a first conductive support portion and a second conductive support portion. The first conductive support portion is bonded to a p-type metal electrode 031, and the second conductive support portion is bonded to an n-type metal electrode 032, with a gap between the first conductive support portion and the second conductive support portion.

[0082] In another preferred embodiment, there are multiple RC-Micro LED devices, which are arranged adjacently to form an array structure. The metal electrode layers 03 of adjacent RC-Micro LED devices can be electrically connected in series or in parallel. The metal conductive support layer 02 can be disposed at the edge of the array structure and connected to the metal electrode layers 03 of each device through metal leads.

[0083] The implementation principle of an RC-Micro LED device according to an embodiment of this application is as follows: a Fabry-Perot resonant cavity structure is formed by placing a gallium nitride epitaxial layer 06 between a first reflective mirror layer 04 and a second reflective mirror layer 07. When a forward bias voltage is applied to the device, current is injected into the active layer 062 of the MQW quantum well through the metal electrode layer 03, and spontaneous emission is generated in the active region. The Purcell effect of the resonant cavity enhances the spontaneous emission rate coupled with the cavity mode and shortens the spontaneous emission lifetime, thereby improving the modulation bandwidth of the device. At the same time, the resonant cavity structure narrows the spectral width of the emitted light, enhances its directionality, and reduces the driving power consumption.

[0084] This application also discloses a method for fabricating an RC-Micro LED device.

[0085] Example 1: Refer to Figure 1 and Figure 2 A method for fabricating an RC-Micro LED device includes the following steps:

[0086] S1: A u-GaN layer 10, a gallium nitride epitaxial layer 06, and a transparent conductive layer 05 are sequentially epitaxially grown on the first substrate 09.

[0087] Specifically, the first substrate 09 is a Si substrate, preferably a Si substrate with a <111> crystal orientation. A u-GaN layer 10 (undoped GaN buffer layer) is first grown on the Si substrate using a metal-organic chemical vapor deposition (MOCVD) method. The thickness of the u-GaN layer 10 is typically 1-2 μm, which is used to buffer the lattice mismatch and the difference in thermal expansion coefficient between the Si substrate and the gallium nitride epitaxial layer 06.

[0088] The gallium nitride epitaxial layer 06 comprises an n-GaN layer 063, an MQWs quantum well active layer 062, and a p-GaN layer 061 sequentially grown on the u-GaN layer 10. The n-GaN layer 063 has a thickness of approximately 2-4 μm; the MQWs quantum well active layer 062 is an InGaN / GaN multiple quantum well with a thickness of approximately 100-200 nm; and the p-GaN layer 061 has a thickness of approximately 100-300 nm. Finally, a transparent conductive layer 05 is deposited on the surface of the p-GaN layer 061 by electron beam evaporation or magnetron sputtering. The transparent conductive layer 05 typically has a thickness of 50-200 nm and is an indium tin oxide (ITO) thin film layer.

[0089] S2: Etch u-GaN layer 10, gallium nitride epitaxial layer 06 and transparent conductive layer 05 to form a convex mesa structure, and deposit insulating layer 08 on the sidewall of the convex mesa structure.

[0090] Specifically, firstly, a mesa region is defined on the surface of the transparent conductive layer 05 using photolithography. Then, an inductively coupled plasma (ICP) dry etching process is used to sequentially etch through the transparent conductive layer 05, the p-GaN layer 061, and the MQWs quantum well active layer 062. A portion of the n-GaN layer 063, with a thickness of 100-300 nm, is then etched to form a convex mesa structure and obtain the device's ITO pattern. The lateral dimension of the convex mesa structure is typically 5-100 μm, and the device's ITO pattern refers to the patterned structure formed after the transparent conductive layer 05 is etched.

[0091] Then, an insulating layer 08 is deposited on the sidewalls of the convex mesa structure using plasma-enhanced chemical vapor deposition (PECVD). The insulating layer 08 can be made of SiO2, Al2O3, or SiN, with a thickness of 200-800 nm. After depositing the insulating layer 08, the insulating layer 08 at the device electrode locations and device boundaries is removed by photolithography and etching processes to expose the areas where electrodes need to be fabricated.

[0092] S3: Prepare the first reflective mirror layer 04 on the transparent conductive layer 05.

[0093] Specifically, a first reflective mirror layer 04 is deposited on the surface of the transparent conductive layer 05 using methods such as electron beam evaporation, magnetron sputtering, or atomic layer deposition (ALD). The first reflective mirror layer 04 can be a DBR reflector, a metallic reflector, or a photonic crystal reflector. For example, when the first reflective mirror layer 04 is a DBR reflector, TiO2 and SiO2 layers can be deposited alternately, with the optical thickness of each layer being one-quarter of the target wavelength. Depositing 16 pairs of these layers can achieve a center peak reflectivity greater than 99%. When the first reflective mirror layer 04 is a metallic reflector, Al or Ag with a thickness of 50-200 nm can be deposited.

[0094] S4: Deposit a mask layer 11 on the device surface. The mask layer 11 covers the main device region and the anchor region. The anchor region is located at the edge of the main device region and is connected to the main device region. The edge region outside the main device region and the anchor region is exposed.

[0095] Specifically, a mask layer 11 is first deposited on the device surface using PECVD. The mask layer 11 can be made of SiO2, SiN, or photoresist, and its thickness is typically 500 nm to 2 μm. Then, the device body region and anchor region are defined using photolithography. The mask layer 11 is removed from the edge regions, exposing them. The anchor regions are located at the edges of the device body region and connected to it. Multiple anchor regions can be arranged in an array, and each anchor region can be triangular, trapezoidal, or rectangular. The edge regions are annular or strip-shaped regions surrounding the device body region, with a width typically 2–20 μm.

[0096] The u-GaN layer 10 and n-GaN layer 063 exposed at the edge region are then etched through using ICP dry etching, and the etching continues into the first substrate 09. The depth of the dry etching into the first substrate 09 is 500nm-2μm, forming a trench structure. The u-GaN layer 10 and gallium nitride epitaxial layer 06 below the anchor point region are not etched, forming an anchor region connecting the main device region and the surrounding first substrate 09.

[0097] The device is immersed in an etching solution, and the first substrate 09 beneath the u-GaN layer 10 is removed by wet etching through the sidewalls of the trench structure. Specifically, the etching solution is a KOH solution with a concentration typically of 10-40 wt% and a temperature typically of 40-80°C. Since the first substrate 09 is a Si substrate with a <111> crystal orientation, the KOH solution has an extremely low etching rate on the Si <111> crystal plane, but a higher etching rate on other crystal planes (such as <110> and <100> crystal planes). After the trench structure penetrates the first substrate 09, it exposes Si sidewalls with different crystal orientations than the <111> crystal plane. The KOH solution performs lateral etching through these Si sidewalls with different crystal orientations, gradually removing the Si layer beneath the u-GaN layer 10, thus suspending the main body region of the device. Since gallium nitride is not etched by the KOH solution, the lower surface of the u-GaN layer 10 is exposed after the Si is removed, and the surface is smooth and flat. The main body region of the device is supported on the first substrate 09 by anchor regions, maintaining structural stability.

[0098] S5: Prepare a metal electrode layer 03 on the device, peel the device off from the first substrate 09 and flip it over using a flexible material, place the metal electrode layer 03 face down on the second substrate 01 with a pre-set metal conductive support layer 02, heat to make the metal conductive support layer 02 adhere to the metal electrode layer 03 and remove the flexible material.

[0099] Specifically, a metal electrode layer 03 is first deposited on the device surface by electron beam evaporation or magnetron sputtering. The metal electrode layer 03 includes a p-type metal electrode 031 and an n-type metal electrode 032. The metal system of the p-type metal electrode 031 can be Ni / Au (e.g., 20nm Ni / 200nm Au), and the metal system of the n-type metal electrode 032 can be Ti / Al / Ti / Au (e.g., 20nm Ti / 100nm Al / 20nm Ti / 200nm Au). Alternatively, the metal system of the metal electrode layer 03 can be uniformly Ti / Al / Cr / Pt / Au.

[0100] Then, a first flexible material layer 12 is spin-coated onto the device surface. The material of the first flexible material layer 12 can be one of polydimethylsiloxane (PDMS), fluorinated silicone rubber, thermoplastic polyurethane (TPU), polynorbornene, epoxy resin-based shape memory polymer, polyacrylamide hydrogel, or polymethyl methacrylate (PMMA). After spin-coating, it is cured at an appropriate temperature. After curing, the device is peeled off from the first substrate 09 using the first flexible material layer 12. During the peeling process, the anchor region breaks, and the device detaches from the first substrate 09.

[0101] After flipping the device over, a second flexible material layer 13 is spin-coated onto the other side of the device (i.e., the side that originally faced the first substrate 09, now the surface of the u-GaN layer 10). After curing, the first flexible material layer 12 is removed. At this point, the device is supported by the second flexible material layer 13, with the metal electrode layer 03 facing downwards.

[0102] A conductive metal support layer 02 is pre-deposited on the upper surface of the second substrate 01. The material of the conductive metal support layer 02 can be a Ni / Sn alloy or solder. After aligning the device using a positioning platform, the metal electrode layer 03 is flip-chipped onto the conductive metal support layer 02 on the second substrate 01. The conductive metal support layer 02 is heated to its melting point or softening temperature (typically 150-300°C) to bond it to the metal electrode layer 03, forming a stable mechanical and electrical connection. After heating and bonding, the second flexible material layer 13 is removed. At this point, the device is flip-chipped.

[0103] S6: Remove the u-GaN layer 10 on the top surface of the device and thin the gallium nitride epitaxial layer 06. Prepare a second reflector layer 07 on the gallium nitride epitaxial layer 06. The first reflector layer 04 and the second reflector layer 07 constitute a Fabry-Perot resonant cavity structure.

[0104] Specifically, using ICP dry etching, the u-GaN layer 10 (approximately 1-2 μm thick) on the top surface of the device is first removed. Then, the n-GaN layer 063 is further thinned, reducing the total thickness of the remaining gallium nitride epitaxial layer 06 to within 2 μm. The etching thickness accuracy error of ICP dry etching can be controlled within 100 nm, achieving sub-micron level cavity length control accuracy. Since the surface of the u-GaN layer 10 exposed after wet etching removes the Si layer is smooth and flat, ICP dry etching can uniformly thin it on this smooth surface, further ensuring the flatness of the n-GaN layer 063 surface after thinning.

[0105] After thinning, a second reflective mirror layer 07 is fabricated on the surface of the n-GaN layer 063 using evaporation and stripping processes. The first reflective mirror layer 04 and the second reflective mirror layer 07 constitute a Fabry-Perot resonant cavity structure, achieving standing wave gain and resonant filtering effects to obtain the final RC-Micro LED device.

[0106] In this embodiment, the center peak reflectivity of the second reflector layer 07 is greater than 80% but less than the center peak reflectivity of the first reflector layer 04 (greater than 95%), so that the device emits light from the front side of the top second reflector layer 07.

[0107] The implementation principle of Embodiment 1 of this application is as follows: a gallium nitride epitaxial layer 06 is grown on a Si substrate, the Si substrate is removed using anchor etching, a flexible material is used for secondary transfer to achieve device flip-chip bonding, the cavity length is precisely controlled by dry etching, and finally, reflective mirrors are fabricated on the top and bottom sides of the device to form a resonant cavity, realizing a front-emitting RC-Micro LED device. The resonant cavity shortens the carrier recombination lifetime by controlling the standing wave gain and cavity length, significantly increasing the modulation bandwidth to over GHz, and realizing a high-bandwidth optical interconnect with narrow linewidth, low dispersion, small divergence angle, high directionality, high efficiency, and low power consumption.

[0108] Example 2: Refer to Figure 2 The difference between this embodiment and Embodiment 1 is that the device is designed to emit light from the back.

[0109] Reference Figure 1 In step S5, the metal electrode layer 03 covers the edge region of the convex mesa structure of the device facing the first reflective mirror layer 04, and the middle region of the convex mesa structure exposes the light-emitting region to allow light to pass through from the bottom. In this embodiment, the second substrate 01 is a light-transmitting substrate such as sapphire, glass, or SiC.

[0110] In step S6, the center peak reflectivity of the second reflective mirror layer 07 is greater than 95%, and the center peak reflectivity of the first reflective mirror layer 04 is greater than 80% but less than 95%. At this time, light is emitted from the bottom first reflective mirror layer 04 through the middle exposed area of ​​the metal electrode layer 03, the metal conductive support layer 02, and the light-transmitting second substrate 01, realizing back-side light emission.

[0111] It should be noted that in the back-emitting light scheme, there is no metal conductive support layer 02 blocking the main body area of ​​the device. After the light is emitted from the first reflector layer 04, it passes through the middle exposed area of ​​the metal electrode layer 03 and the second substrate 01 before being emitted.

[0112] The implementation principle of Example 2 is as follows: by setting the second reflective mirror layer 07 as the high reflectivity end and the first reflective mirror layer 04 as the low reflectivity end, and by adopting a transparent substrate and edge-covered metal electrode design, a back-emitting RC-Micro LED device is realized, which is beneficial for integration with specific optical systems.

[0113] Example 3: Reference Figure 2 The difference between this embodiment and embodiment 1 is that both the first reflector layer 04 and the second reflector layer 07 are DBR reflectors.

[0114] In step S3, the first reflector layer 04 is a DBR reflector, and the material is a stack of two film systems with high and low refractive index differences, such as TiO2 and SiO2, Ta2O5 and SiO2, SiN and SiO2, or GaN and SiO2, with 12-20 pairs.

[0115] In step S6, the second reflector layer 07 is also a DBR reflector, and the material is a combination of two film systems with high and low refractive index differences, such as TiO2 and SiO2, Ta2O5 and SiO2, SiN and SiO2, or GaN and SiO2, which are stacked alternately.

[0116] In this embodiment, the center peak reflectivity of the first reflector layer 04 and the second reflector layer 07 is set to be high (greater than 95%) and low (greater than 80%), respectively. The device emits light from the side with low reflectivity, forming a Fabry-Perot resonant cavity structure.

[0117] The implementation principle of Example 3 is as follows: a resonant cavity is formed by using two DBR mirrors. The DBR mirrors can precisely control the reflection wavelength and bandwidth. The use of dielectric film mirrors on both sides is conducive to achieving a more precise resonant cavity design and a narrower spectral linewidth.

[0118] Example 4: Reference Figure 2 The difference between this embodiment and embodiment 1 is that the first reflector layer 04 and the second reflector layer 07 are a metal reflector and a DBR reflector, respectively.

[0119] In this embodiment, the first reflector layer 04 is a metal reflector made of Al or Ag, with a thickness greater than 50 nm, exhibiting broadband high reflectivity characteristics and a central peak reflectivity greater than 95%. The second reflector layer 07 is a DBR reflector, made of alternating stacks of two film systems with high and low refractive index differences, such as TiO2 and SiO2, Ta2O5 and SiO2, SiN and SiO2, or GaN and SiO2, with a central peak reflectivity greater than 80% but less than that of the first reflector layer 04. The device emits light from the side of the low-reflectivity second reflector layer 07 (DBR reflector).

[0120] In another preferred embodiment, the first reflector layer 04 may be configured as a DBR reflector, the second reflector layer 07 may be configured as a metal reflector, and the center peak reflectivity of the first reflector layer 04 may be less than the center peak reflectivity of the second reflector layer 07.

[0121] The implementation principle of Example 4 is as follows: a metal reflector is used as the high reflectivity end, which is simple to manufacture and has high reflectivity; a DBR reflector is used as the low reflectivity light output end, which can precisely control the light output wavelength and reflectivity, and realize the complementary advantages of the metal reflector and the DBR reflector.

[0122] Example 5: Refer to Figure 2 The difference between this embodiment and embodiment 1 is that the first reflective mirror layer 04 is a metal reflective mirror and the second reflective mirror layer 07 is a photonic crystal reflective mirror.

[0123] In this embodiment, the first reflector layer 04 is a metal reflector made of Al or Ag, with a thickness greater than 50 nm and a central peak reflectivity greater than 95%. The second reflector layer 07 is a photonic crystal reflector made of materials such as TiO2, SiN, or GaN, composed of periodically arranged nanopores or nanostrips of different sizes. The central peak reflectivity of the second reflector layer 07 is greater than 80% but less than that of the first reflector layer 04. Light is emitted from the low-reflectivity second reflector layer 07 (photonic crystal reflector).

[0124] In another preferred embodiment, the first reflector layer 04 may be configured as a photonic crystal reflector, the second reflector layer 07 may be configured as a metal reflector, and the center peak reflectivity of the second reflector layer 07 is greater than 95%, while the center peak reflectivity of the first reflector layer 04 is greater than 80% but less than the reflectivity of the second reflector layer 07.

[0125] The implementation principle of Example 5 is as follows: Photonic crystal mirrors have the advantages of thinness and flexible design. When used in combination with metal mirrors, the overall thickness of the device can be reduced while ensuring the performance of the resonant cavity.

[0126] Example 6: Refer to Figure 2 The difference between this embodiment and embodiment 1 is that both the first reflector layer 04 and the second reflector layer 07 are photonic crystal reflectors.

[0127] The photonic crystal mirror can be made of materials such as TiO2, SiN, or GaN, and is composed of nanopores or nanostrips of different sizes arranged periodically. The center peak reflectivity of the first mirror layer 04 and the second mirror layer 07 is set to be high (greater than 95%) and low (greater than 80%), respectively, and the device emits light from the side with low reflectivity.

[0128] The implementation principle of Example 6 is as follows: a resonant cavity is formed by using a dual-photonic crystal mirror. The photonic crystal mirror is thin and flexible in design, which is conducive to realizing ultra-thin RC-Micro LED devices.

[0129] Example 7: Refer to Figure 3 The difference between this embodiment and embodiment 1 is that the second reflective mirror layer 07 is pre-prepared on the second substrate 01, and the device is placed upright.

[0130] The preparation method of this embodiment includes the following steps:

[0131] Steps S1 to S4 are the same as in Example 1.

[0132] Step S5: Device stripping. A p-type metal electrode 031 and an n-type metal electrode 032 are prepared using a vapor deposition and stripping process. Then, a first flexible material layer 12 is spin-coated onto the device surface and covers the sample surface. After curing, the device is stripped from the first substrate 09 using the first flexible material layer 12, obtaining a temporary device temporarily protected by the first flexible material layer 12.

[0133] Step S6: Cavity thickness reduction. Flip the device over and remove the u-GaN layer 10 exposed on the device surface by etching. Continue etching to thin the n-GaN layer 063 until the total thickness of the remaining gallium nitride epitaxial layer 06 is reduced to less than 2 μm.

[0134] Step S7: Substrate Transfer. A metal conductive support layer 02 and a pre-prepared second reflective mirror layer 07 are pre-deposited on the second substrate 01. The size of the second reflective mirror layer 07 is larger than the size of the device mesa. After aligning the device using a positioning platform, it is placed upright on the second substrate 01. Heating causes the metal conductive support layer 02 to adhere to the metal electrode layer 03, and the first flexible material layer 12 is removed.

[0135] The first reflective mirror layer 04 and the second reflective mirror layer 07 constitute a Fabry-Perot resonant cavity structure. In this embodiment, the center peak reflectivity of the second reflective mirror layer 07 and the center peak reflectivity of the first reflective mirror layer 04 are set to be one high (greater than 95%) and the other low (greater than 80%), and the device emits light from the side with low reflectivity.

[0136] The implementation principle of Example 7 is as follows: the second reflector layer 07 is pre-fabricated on the second substrate 01, which can independently optimize the reflector quality and reduce the process difficulty and damage risk of directly fabricating the reflector on the thinned epitaxial layer. The device is placed upright, simplifying the flipping and transfer steps.

[0137] Example 8: Refer to Figure 3 The difference between this embodiment and Embodiment 1 is that the device is ultimately retained on the flexible substrate to form a flexible RC-Micro LED device.

[0138] The preparation method of this embodiment includes the following steps:

[0139] Steps S1 to S4 are the same as in Example 1.

[0140] Step S5: Device stripping. A p-type metal electrode 031 and an n-type metal electrode 032 are prepared using a vapor deposition and stripping process. Then, a first flexible material layer 12 is spin-coated onto the device surface and covers the sample surface. After curing, the device is stripped from the first substrate 09 using the first flexible material layer 12.

[0141] Step S6: Cavity thickness reduction. Flip the device, etch away the u-GaN layer 10 exposed on the device surface, and continue etching to thin the n-GaN layer 063 until the total thickness of the remaining gallium nitride epitaxial layer 06 is reduced to less than 2 μm.

[0142] Step S7: Fabrication of the second reflective layer 07. The second reflective layer 07 is directly deposited on the n-GaN layer 063. The center peak reflectivity of the second reflective layer 07 and the center peak reflectivity of the first reflective layer 04 are set to be one high (greater than 95%) and the other low (greater than 80%). The device emits light from the side with low reflectivity, forming a Fabry-Perot resonant cavity structure. At this time, the first flexible material layer 12 serves as a flexible substrate, thereby obtaining the final flexible substrate RC-Micro LED device.

[0143] The implementation principle of Example 8 is as follows: the device is retained on the flexible substrate and does not need to be transferred to the rigid substrate, which can realize a flexible RC-Micro LED device, suitable for application scenarios such as flexible optical communication and wearable devices.

[0144] Example 9: Refer to Figure 2 The difference between this embodiment and embodiment 1 is that multiple devices are transferred over a large area with multiple anchor points as an array as a whole.

[0145] The preparation method of this embodiment includes the following steps:

[0146] Step S1 is the same as in Example 1. Furthermore, in this example, the first substrate 09 is also a Si substrate.

[0147] Step S2: Fabrication of device mesa and insulating layer 08. Multiple adjacent device ITO patterns and convex mesa structures are formed by etching. Insulating layer 08 is deposited on the sidewalls of the convex mesa structure using plasma-enhanced chemical vapor deposition (PECVD). After depositing insulating layer 08, the insulating layer 08 at the device electrode locations and device boundaries is removed by photolithography and etching processes to expose the areas where electrodes need to be fabricated.

[0148] Step S3: Fabrication of the first reflector. The first reflector layer 04 is deposited on the surface of the transparent conductive layer 05 by methods such as electron beam evaporation, magnetron sputtering, or atomic layer deposition (ALD).

[0149] Step S4: Anchor point etching of the first substrate 09. A mask layer 11 is deposited on the device surface, covering the main area of ​​the device, with the edge areas outside the main area and anchor point areas exposed. Multiple anchor point areas are left at the edge of the array device shape, and each anchor point area is connected to the main body of the array device. The array device is equivalent to a whole, forming a rectangle or circle, with multiple anchor point areas set on its shape edge, and the anchor point areas covering the mask.

[0150] The entire gallium nitride epitaxial layer 06 at the edge of the device is etched through by dry etching and embedded into the first substrate 09. Anchor regions are formed by the remaining unetched gallium nitride layer at the edge, connecting the device to the main body of the array. The device is then immersed in a KOH solution, and the bottom first substrate 09 is wet-etched, leaving the array device suspended and supported only by multiple anchor points at the edge.

[0151] Step S5: Device stripping and transfer. A p-type metal electrode 031 and an n-type metal electrode 032 are fabricated on the device surface using a vapor deposition and stripping process. The electrodes between the array devices are configured in series or parallel. Then, a first flexible material layer 12 is spin-coated onto the device surface. After curing, the device is removed from the first substrate 09 using the first flexible material layer 12, flipped, and then transferred a second time to the second substrate 01.

[0152] The device is placed upside down on a second substrate 01 with a metal conductive support layer 02, which only supports the edges of the array device. After heat bonding, the first flexible material layer 12 is removed. At this point, the device is inverted.

[0153] Step S6: Cavity thickness reduction and fabrication of the second reflective mirror layer 07. Using photolithography and ICP dry etching, the u-GaN layer 10 is removed and the n-GaN layer 063 is thinned until the total thickness of the remaining gallium nitride epitaxial layer 06 is reduced to less than 2 μm. A second reflective mirror layer 07 is fabricated on the n-GaN layer 063 of each mesa of the array device, forming a Fabry-Perot resonant cavity structure, thus obtaining the final array RC-Micro LED device.

[0154] The implementation principle of Example 9 is as follows: the large-area overall transfer of array devices is achieved through multi-anchor point support, which improves the transfer efficiency and is conducive to the large-scale fabrication and array integration application of RC-Micro LED devices.

[0155] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. An RC-Micro LED device, characterized in that, include: The second substrate (01), the metal conductive support layer (02), the metal electrode layer (03), the first reflective mirror layer (04), the transparent conductive layer (05), the gallium nitride epitaxial layer (06), and the second reflective mirror layer (07) are arranged sequentially from bottom to top. The gallium nitride epitaxial layer (06) has a convex mesa structure, and the sidewalls of the convex mesa structure are covered with an insulating layer (08). The first reflector layer (04) and the second reflector layer (07) are arranged opposite to each other to form a Fabry-Perot resonant cavity structure.

2. The RC-Micro LED device according to claim 1, characterized in that: The gallium nitride epitaxial layer (06) includes a p-GaN layer (061), an MQWs quantum well active layer (062), and an n-GaN layer (063) arranged sequentially from bottom to top. The p-GaN layer (061) is disposed on the side of the transparent conductive layer (05) away from the first reflective mirror layer (04), and the second reflective mirror layer (07) is in direct contact with the surface of the n-GaN layer (063) away from the MQWs quantum well active layer (062).

3. The RC-Micro LED device according to claim 1, characterized in that: The center peak reflectivity of the first reflector layer (04) is different from that of the second reflector layer (07). The center peak reflectivity of the side with high reflectivity is greater than 95%, while the center peak reflectivity of the side with low reflectivity is 80%-95%. Light is emitted from the side with low reflectivity.

4. The RC-Micro LED device according to claim 3, characterized in that: The center peak reflectivity of the second reflector layer (07) is less than that of the center peak reflectivity of the first reflector layer (04). The p-type metal electrodes (031) in the metal electrode layer (03) completely cover the surface of the convex mesa structure facing the first reflector layer (04), and the device emits light from the side where the second reflector layer (07) is located.

5. The RC-Micro LED device according to claim 3, characterized in that: The center peak reflectivity of the second reflector layer (07) is greater than that of the center peak reflectivity of the first reflector layer (04). The metal electrode layer (03) covers the edge region of the convex mesa structure facing the first reflector layer (04), and the middle region of the convex mesa structure is exposed. The second substrate (01) is a light-transmitting substrate, and the device emits light from the side where the second substrate (01) is located.

6. The RC-Micro LED device according to claim 1, characterized in that: The first reflector layer (04) is one of a metal reflector, a DBR reflector, or a photonic crystal reflector, and the second reflector layer (07) is one of a DBR reflector or a photonic crystal reflector.

7. The RC-Micro LED device according to claim 1, characterized in that: The total thickness of the gallium nitride epitaxial layer (06) is less than 2 μm.

8. A method for fabricating an RC-Micro LED device, characterized in that, Includes the following steps: S1: A u-GaN layer (10), a gallium nitride epitaxial layer (06), and a transparent conductive layer (05) are sequentially epitaxially grown on the first substrate (09). S2: Etch the u-GaN layer (10), the gallium nitride epitaxial layer (06) and the transparent conductive layer (05) to form a convex mesa structure, and deposit an insulating layer (08) on the sidewall of the convex mesa structure. S3: A first reflective mirror layer (04) is prepared on the transparent conductive layer (05); S4: Deposit a mask layer (11) on the device surface. The mask layer (11) covers the main device area and the anchor point area. The anchor point area is located at the edge of the main device area and is connected to the main device area. The main device area and the edge area outside the anchor point area are exposed. Then, the u-GaN layer (10) and the gallium nitride epitaxial layer (06) exposed by the edge area are etched through by dry etching and etched into the first substrate (09) to form a trench structure. The device is immersed in the etching solution. The first substrate (09) below the u-GaN layer (10) is removed by wet etching through the sidewall of the trench structure, so that the main device area is suspended and supported on the first substrate (09) by the anchor area formed by the unetched epitaxial layer below the anchor point area. S5: Prepare a metal electrode layer (03) on the device, peel the device off from the first substrate (09) and flip it over using a flexible material, place the metal electrode layer (03) face down on a second substrate (01) with a preset metal conductive support layer (02), heat to make the metal conductive support layer (02) adhere to the metal electrode layer (03) and remove the flexible material; S6: Remove the u-GaN layer (10) on the top surface of the device and thin the gallium nitride epitaxial layer (06), and prepare a second mirror layer (07) on the gallium nitride epitaxial layer (06). The first mirror layer (04) and the second mirror layer (07) constitute a Fabry-Perot resonant cavity structure.

9. The method for fabricating the RC-Micro LED device according to claim 8, characterized in that: The gallium nitride epitaxial layer (06) includes an n-GaN layer (063), an MQWs quantum well active layer (062), and a p-GaN layer (061) epitaxially grown sequentially on the u-GaN layer (10). The second mirror layer (07) is located on the side of the n-GaN layer (063) away from the MQWs quantum well active layer (062). In step S2, the transparent conductive layer (05), the p-GaN layer (061) and the MQWs quantum well active layer (062) are sequentially etched through, and a portion of the n-GaN layer (063) with a thickness of 100-300 nm is etched to form the convex mesa structure; In step S4, the dry etching depth into the first substrate (09) is 500nm-2μm. The first substrate (09) is a Si substrate. The etching solution is a KOH solution. The KOH solution performs wet etching through the sidewall of the Si substrate exposed by the trench structure.

10. The method for fabricating the RC-Micro LED device according to claim 8, characterized in that: In step S6, the u-GaN layer (10) is removed by ICP dry etching and the gallium nitride epitaxial layer (06) is thinned to a total thickness of less than 2 μm.

11. The method for fabricating the RC-Micro LED device according to claim 8, characterized in that: In step S5, the process of peeling and flipping the device from the first substrate (09) using a flexible material includes: spin coating a first flexible material layer (12) on the surface of the device, peeling the device from the first substrate (09) after curing, flipping the device and spin coating a second flexible material layer (13) on the other side of the device, removing the first flexible material layer (12) after curing, and placing the metal electrode layer (03) face down on the second substrate (01).

12. A method for fabricating an RC-Micro LED device, characterized in that, Includes the following steps: S1: A u-GaN layer (10), a gallium nitride epitaxial layer (06), and a transparent conductive layer (05) are sequentially epitaxially grown on the first substrate (09). S2: Etch the u-GaN layer (10), the gallium nitride epitaxial layer (06) and the transparent conductive layer (05) to form a convex mesa structure, and deposit an insulating layer (08) on the sidewall of the convex mesa structure. S3: A first reflective mirror layer (04) is prepared on the transparent conductive layer (05); S4: Deposit a mask layer (11) on the device surface. The mask layer (11) covers the main device area and the anchor point area. The anchor point area is located at the edge of the main device area and is connected to the main device area. The main device area and the edge area outside the anchor point area are exposed. Then, the u-GaN layer (10) and the gallium nitride epitaxial layer (06) exposed by the edge area are etched through by dry etching and etched into the first substrate (09) to form a trench structure. The device is immersed in the etching solution. The first substrate (09) below the u-GaN layer (10) is removed by wet etching through the sidewall of the trench structure, so that the main device area is suspended and supported on the first substrate (09) by the anchor area formed by the unetched epitaxial layer below the anchor point area. S5: Fabricate a metal electrode layer (03) on the device, and peel the device off from the first substrate (09) using a flexible material; S6: Flip the device, remove the u-GaN layer (10) and thin the gallium nitride epitaxial layer (06). S7: Place the device on the second substrate (01), on which a metal conductive support layer (02) and a pre-prepared second reflector layer (07) are provided. Heat the metal conductive support layer (02) to bond with the metal electrode layer (03). The first reflector layer (04) and the second reflector layer (07) constitute a Fabry-Perot resonant cavity structure.

Images