Residual liquid metal processing during LED manufacturing

Abstract

The present disclosure generally includes a method for forming a light emitting diode (LED) element, the method including: removing a carrier substrate from the LED element using laser irradiation; oxidizing a residual liquid metal layer formed by the laser irradiation by immersing the LED element in heated deionized water; the deionized water on the LED element is washed away; and drying the LED element using a drying process.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure generally relate to methods for forming light-emitting diode (LED) elements. More particularly, embodiments of the present disclosure relate to removing a residual liquid metal layer formed during LED element fabrication. BACKGROUND

[0002] Light-emitting diode (LED) panels use an array of LEDs having individual LEDs that each control an individual pixel element. LED panels can be used for computer monitors, televisions, smartphone screens, and the like. Typically, the individual LEDs are gallium nitride (GaN)-based and formed on a carrier substrate. After the LEDs are fabricated on the carrier substrate, the LEDs can be attached (i.e., transferred) to a backplane or interposer of the LED panel and the carrier substrate is removed. However, removing the carrier substrate can damage the LED material and / or the backplane / interposer or leave a residual liquid metal layer in the place of the carrier substrate. The reflectivity of the residual liquid metal layer can reduce the light emission efficiency of the LEDs. Thus, there is a need in the art for a method of removing a carrier substrate with reduced damage to the LED panel and / or reduced hindrance to its performance. SUMMARY

[0003] The present disclosure generally includes a method for forming a light-emitting diode (LED) element, the method comprising removing a carrier substrate from the LED element using laser irradiation; oxidizing a residual liquid metal layer formed by the laser irradiation by soaking the LED element in heated deionized water; rinsing off the deionized water from the LED element; and drying the LED element using a drying process.

[0004] Embodiments of the present disclosure can further provide a method for forming a light-emitting diode (LED) element, the method comprising removing a carrier substrate from the LED element using laser irradiation, the carrier substrate having a gallium nitride (GaN) LED formed on a carrier surface of the carrier substrate; oxidizing a Ga residual layer formed by the laser irradiation by soaking the LED element in heated deionized water; rinsing off the deionized water from the LED element; and drying the LED element using a drying process.

[0005] Embodiments of the present disclosure can further provide an apparatus, the apparatus comprising: a backplane having backplane electrodes; and a plurality of light-emitting diodes (LEDs) coupled to the backplane, the plurality of LEDs comprising: a transparent layer formed on a first side of an epitaxial layer; and LED electrodes formed on a second side of the epitaxial layer, the LED electrodes coupled to the backplane electrodes. Attached Figure Description

[0006] To gain a more detailed understanding of the features described above, a more specific description of the present disclosure, which has been briefly summarized above, can be obtained by referring to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only exemplary embodiments of the present disclosure and should not be construed as limiting its scope, and other equally effective embodiments are permissible.

[0007] Figure 1 This is a flowchart of a method for coupling an LED to a backplate of a display panel using a direct die-transfer process, according to one or more embodiments.

[0008] Figures 2A to 2H This is a schematic diagram illustrating the treatment of a residual liquid metal layer formed on an LED element manufactured using a single mold transfer process, according to one or more embodiments.

[0009] Figure 3 This is a flowchart of a method for treating a residual liquid metal layer formed on an LED element manufactured using a dual-mold transfer process, according to one or more embodiments.

[0010] Figures 4A to 4H This is a schematic diagram illustrating the treatment of a residual liquid metal layer formed on an LED element manufactured using a dual-mold transfer process, according to one or more embodiments.

[0011] Figure 5 It is a cross-sectional view of pixel 500 according to one or more embodiments.

[0012] To facilitate understanding, the same reference numerals are used to denote common elements in the figures where possible. Elements and features of one embodiment are contemplated to be advantageously incorporated into other embodiments without further description. Detailed Implementation

[0013] Embodiments of this disclosure generally relate to the formation of light-emitting diode (LED) elements. More specifically, embodiments of this disclosure relate to using laser irradiation to treat residual liquid metal layers formed on the LED element due to the removal of a carrier substrate, in order to improve the performance of the LED element.

[0014] Typically, LEDs are manufactured on a carrier substrate. After LED formation, the LED is transferred (attached) to a mold. The LED can be transferred to a backplane in a direct mold transfer process, or to an interposer in a dual mold transfer process. After attaching the LED to the mold, the carrier substrate is removed.

[0015] The carrier substrate can be removed by laser irradiation. However, laser irradiation removal can leave a residual liquid metal layer. The composition of the residual liquid metal layer is based on the composition of the LED. For example, gallium nitride (GaN)-based LEDs can leave residual gallium (Ga). Problematically, the reflectivity of the residual liquid metal layer reduces the light emission efficiency of the LED. Embodiments disclosed herein are directed to treating the residual liquid metal layer to increase its transparency and improve the performance of the LED.

[0016] Figure 1 is a flowchart of a method 100 for treating a residual liquid metal layer formed on an LED element manufactured using a single-mold transfer process, in accordance with one or more embodiments. Figures 2A to 2H is a schematic diagram of an LED element 200 for treating a residual liquid metal layer formed on the LED element manufactured using a single-mold transfer process, in accordance with one or more embodiments. To facilitate understanding, will be explained in conjunction with Figure 1 and FIG. 2.

[0017] At operation 102, as shown, a carrier substrate 210 is removed from the LED element 200 using laser irradiation 212 (e.g., laser lift-off). Figure 2A

[0018] The LED element 200 includes a carrier substrate 210 having a plurality of LEDs formed or grown overlying a carrier surface of the carrier substrate 210. For example, the carrier substrate 210 can have a diameter of any suitable size, such as 50 mm to 100 mm. The carrier substrate 210 can include at least one of sapphire, silicon carbide (SiC), gallium nitride (GaN), silicon, quartz, gallium arsenide (GaAs), aluminum nitride (AIN), and glass. In one example, the plurality of LEDs includes LED 208a and LED 208b. Although the carrier substrate 210 includes two LEDs as shown, it should be understood that the carrier substrate 210 can have hundreds, thousands, millions, or more LEDs. Further, each of the LEDs formed on the carrier substrate 210 can be a conventional LED, a PSS LED, or a combination thereof. For example, as shown in FIG. 2, the LED 208a is a conventional LED and the LED 208b is a PSS LED. Figure 2A ​As shown, LED 208b can be a PSS LED. Each of LEDs 208A-B can be a macro LED, a mini LED, a micro LED, or any other size LED. LEDs 208A-B can be fabricated by growing multiple layers onto a carrier surface of carrier substrate 210. LEDs 208a-b can each include an epitaxial layer 208 formed on carrier substrate 210 that serves as an electrical component that generates light. Epitaxial layer 207 can include a first surface 207a that contacts the carrier surface of carrier substrate 210, and a second surface 207b opposite the first surface 207a. Epitaxial layer 207 overlying carrier substrate 210 can include any number of materials and / or layers. In some embodiments, epitaxial layer 207 can be fabricated using layers of Group III to Group V films. In one embodiment, epitaxial layer 207 can be gallium nitride (GaN) based. For example, epitaxial layer 207 can be a gallium and nitrogen containing LED structure formed epitaxially on carrier substrate 210. Although epitaxial layer 207 is illustrated as a single layer in these figures, it should be understood that epitaxial layer 207 can actually be formed using multiple successive layers built on carrier substrate 210. For example, epitaxial layer 207 can include an n-doped GaN layer and a p-doped GaN layer. Further, epitaxial layer 207 can include a multiple-quantum-well (MQW) region between the n-doped GaN layer and the p-doped GaN layer.

[0019] One or more electrodes can be disposed onto epitaxial layer 207. As an example, a plurality of LED electrodes 206 can be formed on the second surface 207b of epitaxial layer 207. LED electrodes 206 can comprise a first material including, but not limited to, gold (Au), indium (In), indium tin oxide (ITO), or the like.

[0020] The backplane 202 can include backplane electrodes 204 coupled thereto. The backplane electrodes 204 can be configured to couple with corresponding LED electrodes 206 to form an electrical connection between the LEDs 208a-b and the backplane 202. The backplane electrodes can comprise a second material including, but not limited to, gold (Au), indium (In), indium tin oxide (ITO), or the like. In certain embodiments, the first material and the second material are different. For example, the circuitry of the backplane 202 can include a TFT active matrix array with a thin-film transistor and storage capacitor (not shown) for each of the LEDs 208a-b, row address lines and column address lines, row drivers and column drivers to drive the LEDs. Alternatively, the LEDs 208a-b can be driven by a passive matrix in the backplane circuitry. The backplane 202 can be fabricated using a known complementary metal-oxide silicon (CMOS) process. Each of the backplane electrodes 204 is configured to couple to a corresponding LED structure. The LED element 200 can be mounted to the backplane by mating the LED electrodes 206 with the backplane electrodes 204. The carrier substrate 210 is then vaporized and removed using the laser irradiation 212 (operation 102) to expose the first surface 207a of the epitaxial layer 207 above the backplane 202. Although only two LEDs 208A-B are included in the LED element 200, it should be understood that this is for purposes of illustration only, and more or less than two LEDs can be included in the LED element 200. Further, although the LEDs 208A-B each have LED electrodes 206 formed on the second surface 207b of the epitaxial layer 207, one of the LEDs can have an LED electrode 206 formed between the epitaxial layer 207 and the carrier surface of the carrier substrate 210. For example, the LED 208b can include an LED electrode disposed on the first surface 207a of the epitaxial layer 207, while the LED 208a includes an LED electrode 206 that can be formed on the second surface 207b of the epitaxial layer 207 (or vice versa).

[0021] However, as Figure 2B shown, although the removal of the carrier substrate 210 using the laser irradiation 212 prevents damage to the LED element 200, a residual liquid metal layer 214 remains on the first surface 207a of the epitaxial layer 207. The residual liquid metal layer 214 is based on the composition of the epitaxial layer 207. For example, if the LEDs 208a-b (epitaxial layer 207) are GaN-based, the residual liquid metal layer 214 can include Ga. Although the residual liquid metal layer 214 is described as including Ga, this is for purposes of illustration only, and the residual liquid metal layer 214 can include other materials.

[0022] The residual liquid metal layer 214 can have a thickness ranging from tens to hundreds of nanometers and reduces the luminous efficiency of the LED element 200 due to the reflective properties of Ga (or any other liquid metal). As mentioned above, it is conventional to use HCl to remove the residual liquid metal layer 214. However, HCl is a harmful acid that can corrode and cause damage to the LEDs 208A to 208B, the backplate 202, the LED electrodes 206, the backplate electrodes 204, and combinations thereof. Embodiments herein describe a method for treating the residual liquid metal layer 214 using deionized (DI) water instead of HCl to protect the integrity of the LED element 200.

[0023] At operation 104, such as Figures 2C to 2D As shown, the residual liquid metal layer 214 is oxidized. In one embodiment, the residual liquid metal layer 214 is oxidized by immersing the LED element 200 in heated deionized (DI) water 213. The heated DI water 213 can be heated to a temperature between 60°C and 100°C, and the LED element 200 can be immersed for a duration between 10 minutes and 3 hours. For example, the LED element 200 is immersed in heated DI water 213 at a temperature of 75°C for one hour. In one embodiment, as... Figure 2D As shown, the residual liquid metal layer 214 interacts with heated DI water 213. The interaction between the heated DI water 213 and the residual liquid metal layer 214 releases hydrogen, thereby transforming the residual liquid metal layer 214 into a transparent layer 216. In one or more instances, the transparent layer 216 is transparent to light with wavelengths in the visible spectrum. In another instance, the transparent layer 216 is transparent to light with wavelengths in the infrared (IR) spectrum. Due to the reaction between the residual liquid metal layer 214 and the heated DI water 213, the residual liquid metal layer 214 can be transformed into gallium oxide (GaOH), gallium hydroxide (GaH), or a combination thereof. In other words, the transparent layer 216 can contain GaOH, GaH, or a combination thereof.

[0024] At operation 106, such as Figures 2E to 2F As shown, heated DI water 213 is rinsed off the LED element 200. Rinsing off the heated DI water 213 from the LED element 200 may include rinsing / soaking the LED element 200 using a first immersion process followed by a second immersion process. The first immersion process may include rinsing / soaking the LED element 200 in a first solvent 220. Figure 2E The first immersion time is reached. The second immersion process may include rinsing / immersing the LED element 200 in the second solvent 222. Figure 2FThe first solvent 220 can be, but is not limited to, acetone. The second solvent 222 can be, but is not limited to, isopropyl alcohol (IPA). The first duration can be between 5 seconds and 60 seconds. The second duration can be between 5 seconds and 60 seconds. Advantageously, the second immersion process, which follows the first immersion process, rinses the LED element 200 with heated DI water 213, providing a more thorough cleaning of the LED element 200 and removing organic residues remaining on the LED element 200.

[0025] However, in some instances, only the first immersion process is used to rinse the heated DI water 213 off the LED element 200. In another instance, only the second immersion process is used to rinse the heated DI water 213 off the LED element 200. Although only one immersion process can be used, the first immersion process is preferred because acetone provides a more thorough cleaning than IPA.

[0026] At operation 108, such as Figures 2G to 2H As shown, the LED element 200 undergoes a drying process. This drying process may include a first drying process followed by a second drying process. The first drying process may include air drying the LED element 200. Figure 2G The third drying time is reached. The second drying process may include the use of heat source 217 ( Figure 2H The LED element 200 is heated or baked at a temperature for a fourth duration. The heat source 217 may include, but is not limited to, a resistive heat source, such as a hot plate or an oven. For example, the second drying process may include drying the LED element 200 by placing it on (i.e., in direct contact with) the resistive heat source or by baking it in an oven. The third duration may range from 1 minute to 5 minutes. The temperature may range from 60°C to 120°C, and the fourth duration may range from 30 seconds to 20 minutes. For example, the LED element 200 may be heated at 80°C for 3 minutes.

[0027] Advantageously, using the first drying process followed by the second drying process helps both dry the surface of the LED element 200 and remove moisture inside the LED element. In some implementations, the LED element 200 can only undergo the first drying process. In another example, the LED element 200 can only undergo the second drying process. In some examples, if only one drying process is to be used, it is preferable to use the second drying process because the second drying process is more effective at completely removing moisture from the LED element 200. However, as described above, the LED element 200 can be dried using only the first drying process. If only the second drying process is used, it is preferable to heat the LED element 200 using a resistive heat source as compared to baking the LED element 200. Heating the LED element 200 on a resistive heat source dries the entire LED element 200 more effectively. However, in some implementations, the LED element 200 can be dried by only baking the LED element 200 in an oven (the second drying process).

[0028] Figure 3 is a flowchart of a method 300 for processing a residual liquid metal layer formed on an LED element manufactured using a dual-mold transfer process, according to one or more implementations. Figures 4A to 4H is a schematic diagram of an LED element 400 for processing a residual liquid metal layer formed on the LED element manufactured using a dual-mold transfer process, according to one or more implementations.

[0029] At operation 302, as shown in Figure 4A the carrier substrate 410 is removed from the LED element 400 using laser irradiation.

[0030] The LED element 400 includes a carrier substrate 410 having a plurality of LEDs formed or grown overlying a carrier surface of the carrier substrate 410. For example, the carrier substrate 410 can have a diameter of any suitable size, such as 50 mm to 100 mm. The carrier substrate 410 can include at least one of sapphire, silicon carbide (SiC), gallium nitride (GaN), silicon, quartz, gallium arsenide (GaAs), aluminum nitride (AIN), and glass. In one example, the plurality of LEDs includes a first LED 408A and a second LED 408B. Although the carrier substrate 410 includes two LEDs as shown, it should be understood that the carrier substrate 410 can have hundreds, thousands, millions, or more LEDs. Further, each of the LEDs formed on the carrier substrate 410 can be a conventional LED, a PSS LED, or a combination thereof. For example, as shown in Figure 4AAs shown, the second LED 408b can be a PSS LED. Each of the LEDs 408A-B can be a macro LED, a mini LED, a micro LED, or any other size LED. The LEDs 408A-B can be fabricated by growing multiple layers onto a carrier surface of a carrier substrate 410. The LEDs 408a-b can each include an epitaxial layer 407 formed on the carrier substrate 410 that serves as an electrical component that generates light. The epitaxial layer 407 overlying the carrier substrate 410 can include any number of materials and / or layers. The epitaxial layer 407 can include a first surface 407a that contacts the carrier surface of the carrier substrate 410, and a second surface 407b opposite the first surface 407a. The epitaxial layer 407 overlying the carrier substrate 410 can include any number of materials and / or layers. In some embodiments, the epitaxial layer 407 can be fabricated using layers of Group III to Group V films. In one embodiment, the epitaxial layer 407 can be gallium nitride (GaN) based. For example, the epitaxial layer 407 can be a gallium and nitrogen containing LED structure formed epitaxially on the carrier substrate 410. Although the epitaxial layer 407 is illustrated as a single layer in the figures, it should be understood that the epitaxial layer 407 can actually be formed using multiple successive layers built on the carrier substrate 210. For example, the epitaxial layer 407 can include an n-doped GaN layer and a p-doped GaN layer. Further, the epitaxial layer 407 can include a multiple-quantum-well (MQW) region between the n-doped GaN layer and the p-doped GaN layer.

[0031] One or more electrodes can be disposed onto the epitaxial layer 407. As an example, a plurality of LED electrodes 406 can be formed on the second surface 407b of the epitaxial layer 407 that is opposite the carrier surface of the carrier substrate 410. The LED electrodes 406 can include, but are not limited to, gold (Au), indium (In), indium tin oxide (ITO), or the like. In one or more embodiments, the LED electrodes 406 can be transferred (i.e., attached) to the interposer layer 402. The interposer layer can include, but is not limited to, an adhesive polymer. The carrier substrate 410 is then vaporized and removed using a laser irradiation 412 to expose the first surface 407a of the epitaxial layer 407 above the interposer layer 402 (operation 102). Although only two LEDs 408A-B are included in the LED element 400, it should be understood that this is for purposes of illustration only, and more or less than two LEDs can be included in the LED element 400.

[0032] However, as Figure 4BAs shown, although the removal of the carrier substrate 410 using the laser irradiation 412 prevents damage to the LED element 400, a residual liquid metal layer 414 remains based on the composition of the epitaxial layer 407. For example, if the LEDs 408A-B (epitaxial layer 407) are GaN-based, the residual liquid metal layer 414 can include Ga. Although the residual liquid metal layer 414 is described as a Ga residual layer, this is for illustrative purposes only, and the residual liquid metal layer 414 can include different materials.

[0033] At operation 304, as Figures 4C to 4D shown, the residual liquid metal layer 414 is oxidized. In one embodiment, the residual liquid metal layer 414 is oxidized by soaking the LED element 400 in heated deionized (DI) water 413. The heated DI water 413 can be heated to a temperature between 60 °C and 120 °C, and the LED element 400 can be soaked for a duration between 10 minutes and 3 hours. For example, the LED element 400 can be soaked in heated DI water 413 at 75 °C for 1 hour. In one embodiment, as Figure 4D shown, the residual liquid metal layer 414 interacts with the heated DI water 413. The interaction between the heated DI water 413 and the residual liquid metal layer 414 releases hydrogen, thereby transforming the residual liquid metal layer 414 into a transparent layer 416. In one or more examples, the transparent layer 416 is transparent to light having a wavelength within the visible spectrum. In another example, the transparent layer 416 is transparent to light having a wavelength in the infrared (IR) wavelength spectrum. As a result of the reaction between the residual liquid metal layer 414 and the heated DI water, the residual liquid metal layer 414 can be transformed into gallium oxyhydroxide (GaOH), gallium hydroxide (GaH), or a combination thereof. In other words, the transparent layer 416 can include GaOH, GaH, or a combination thereof.

[0034] At operation 306, as Figures 4E to 4FAs shown, the heated DI water 413 is rinsed off the LED element 400. Rinsing the heated DI water 413 off the LED element 400 can include rinsing / soaking the LED element 400 using a first soaking process followed by a second soaking process. The first soaking process includes rinsing / soaking the LED element 400 in a first solvent 420 for a first duration. The second soaking process includes rinsing / soaking the LED element 400 in a second solvent 422 for a second duration. The first solvent 420 can be, but is not limited to, acetone. The second solvent 422 can be, but is not limited to, isopropyl alcohol (IPA). The first duration can be between 5 seconds and 60 seconds. The second duration can be between 5 seconds and 60 seconds. Advantageously, rinsing the heated DI water 413 off the LED element 400 using the first soaking process followed by the second soaking process promotes a more thorough cleaning of the LED element 400 and removes organic residue left on the LED element 200.

[0035] However, in some instances, the heated DI water 413 is rinsed off the LED element 400 using only the first soaking process. In another instance, the heated DI water 413 is rinsed off the LED element 400 using only the second soaking process. Although only one soaking process can be used, the first soaking process is preferred because acetone provides a more thorough cleaning than IPA.

[0036] At operation 308, the LED element 400 is subjected to a drying process, as shown. Figures 4G to 4H The drying process can include a first drying process followed by a second drying process. The first drying process can include air drying the LED element 400 Figure 4G ) for a third duration. The second drying process can include heating or baking the LED element 400 Figure 4H ) at a temperature for a fourth duration using a heat source 417. The heat source 417 can include, but is not limited to, a resistive heat source such as a hot plate or an oven. For example, the second drying process can include heating the LED element 400 by placing the LED element 400 on the resistive heat source (i.e., in direct contact with the resistive heat source) or baking the LED element 400 in the oven, thereby drying the LED element 400. The third duration can range between 1 minute and 5 minutes. The temperature can range between 60 °C and 120 °C, and the fourth duration can range between 30 seconds and 20 minutes.

[0037] Advantageously, using a second drying process following the first drying process helps to dry both the surface of the LED element 400 and remove moisture from the interior of the LED element. In some embodiments, the LED element 400 may undergo only the first drying process. In another instance, the LED element 400 may undergo only the second drying process. In some instances, if only one drying process is desired, the second drying process is preferred because it is more effective at completely removing moisture from the LED element 400. However, as mentioned above, the LED element 400 may be dried using only the first drying process. If only the second drying process is used, heating the LED element 400 with a resistive heat source is preferable to baking the LED element 400. Heating the LED element 400 with a resistive heat source will dry the entire LED element 400 more effectively. However, in some embodiments, the LED element 400 may be dried simply by baking it in an oven (the second drying process).

[0038] For example, LED element 400 can be heated at 80°C for 3 minutes. In one example, LED element 400 may only undergo the first drying process. In another example, LED element 400 may only undergo the second drying process.

[0039] At operation 310, LED element 400 undergoes an additional transfer process. For example, interposer 402 is transferred to the backplane.

[0040] Figure 5 This is a cross-sectional view of pixel 500 according to one or more embodiments. Pixel 500 includes at least four LEDs 504 disposed on a backplate 502. For example, pixel 500 includes two LEDs 208a and two LEDs 208b. Pixel 500 may include LEDs of the same or different types. The LEDs are connected to the backplate 502 via backplate electrodes 204 and LED electrodes 206.

[0041] like Figure 5 As shown above, a transparent layer 216 is formed over the epitaxial layer 207. As described above, after removing the carrier substrate 210, a residual liquid metal layer 214 remains. Conventionally, the residual liquid metal layer 214 can be removed using HCl. However, HCl is a harmful acid that can corrode and cause damage to the LED 504, backplane 502, LED electrode 206, backplane electrode 204, and combinations thereof. Therefore, instead of removing the residual liquid metal layer 214, the residual liquid metal layer 214 is treated with heated DI water 213 (i.e., method 100) to form a transparent layer 216 that protects the integrity of the LED. In other words, each of the LEDs 504 includes a transparent layer 216 formed over the epitaxial layer 207.

[0042] The SI structures 510 are disposed above and, in some embodiments, on the backplane 502. Adjacent SI structures 510 define respective wells 513 of at least three sub-pixels 512. Each LED is disposed in a respective well 513 between adjacent SI structures 510. The width of each well 513 is about 0.5 pm to about 40 pm, such as about 2 pm to about 30 pm. The width of the SI structures 510 is about 0.1 pm to about 15 pm, such as 1 pm to 10 pm. The SI structures 510 can comprise an organic material, such as an epoxy-based photoresist.

[0043] The sub-pixels 512 include a first sub-pixel 512a having a red conversion material 514a disposed in the well 513 of the first sub-pixel 512a, a second sub-pixel 512b having a blue conversion material 514b disposed in the well 513 of the second sub-pixel 512b, and a third sub-pixel 512c having a green conversion material 514c disposed in the well 513 of the third sub-pixel 512c. When the LED 504a of the first sub-pixel 512a is on, the red conversion material 514a converts light emitted from the micro-LED 504a to red light. When the LED 504b of the second sub-pixel 512b is on, the blue conversion material 514b converts light emitted from the LED 504b to blue light. When the LED 504c of the third sub-pixel 512c is on, the green conversion material 514c converts light emitted from the micro-LED 504c to green light. In one embodiment, the pixel 500 includes a fourth sub-pixel 512d. As shown, the fourth sub-pixel 512d does not contain a color conversion material, i.e., no color conversion layer. In some embodiments, the fourth sub-pixel 512d can be subsequently filled with a color conversion material 514 (e.g., a red, green, blue, violet, etc. color conversion material). In another embodiment, the fourth sub-pixel 112d contains a sacrificial material (not shown). In other embodiments, the at least three sub-pixels 512 contain the same color conversion material. The fourth sub-pixel 512d can be subsequently filled with a color conversion material 514. Figure 5

[0044] In some embodiments, the color conversion materials 514 can include quantum dots (QDs). Quantum dots can be sized to produce wavelengths corresponding to different colors. In one embodiment, the red conversion material 514a can include quantum dots sized about 6 nm. The blue conversion material 514b can include quantum dots sized about 4 nm. The green conversion material 514c can include quantum dots sized about 2 nm. In other embodiments, the color conversion materials 514 can include nanostructures, photoluminescent materials, or organic substances.

[0045] ​An encapsulation layer 522 is disposed over the top surface of the SI structures 510 and sub-pixels 512, and in some embodiments, directly on the top surface of the SI structures and the sub-pixels. The encapsulation layer 522 prevents reactions between the color conversion material 514 and other materials in the surrounding environment. The encapsulation layer 522 has a thickness of 10 nm or less, and is one of a metal layer, a metal oxide layer, or a silicon-containing layer. The encapsulation layer includes, but is not limited to, aluminum oxide, titanium oxide, silicon nitride, tantalum (Ta), hafnium (Hf), tantalum oxide, hafnium oxide, titanium (Ti), aluminum (Al), chromium (Cr), copper (Cu), tungsten (W), zirconium (Zr), or a combination thereof. The encapsulation layer 522 can be deposited using a physical vapor deposition (PVD) process, chemical vapor deposition (CVD), or atomic layer deposition (ALD). The PVD process can include pulsed laser deposition (PLD), thermal evaporation, or electron beam evaporation PVD (EBPVD).

[0046] In some embodiments, the pixel 500 includes a micro-lens 528 disposed on the encapsulation layer 522 and over each of the wells 513 of the sub-pixels 512. In some embodiments, a passivation layer 526 is disposed on the micro-lens 528. In other embodiments, the micro-lens 528 can be made of a resist material, such as a photoresist material that blocks UV light.

[0047] While the foregoing is directed to examples of the present disclosure, other and further examples of the present disclosure can be devised without departing from the basic scope thereof, and the scope thereof is determined by the recited claims.

Claims

1. A method for forming a light-emitting diode (LED) element, the method comprising: The carrier substrate is removed from the LED element using laser irradiation; The residual liquid metal layer formed by laser irradiation is oxidized by immersing the LED element in deionized water. Rinse off the deionized water from the LED element; and The LED components are dried using a drying process.

2. The method of claim 1, wherein the deionized water is heated to a temperature between 60°C and 100°C.

3. The method of claim 1, wherein the residual liquid metal layer comprises gallium (Ga).

4. The method of claim 3, wherein oxidizing the residual liquid metal layer transforms the residual liquid metal layer into a transparent layer, the transparent layer comprising gallium hydroxy oxide (GaOH), gallium hydroxide (GaH), or a combination thereof.

5. The method of claim 1, wherein rinsing off the deionized water from the LED element comprises: The LED element is rinsed using a first immersion process for a first duration; as well as The LED element is rinsed using a second immersion process for a second duration.

6. The method of claim 5, wherein the first immersion process comprises immersing the LED element in acetone for the first duration, and the second immersion process comprises immersing the LED element in isopropanol (IPA) for the second duration.

7. The method of claim 1, wherein the drying process includes a first drying process and a second drying process.

8. The method of claim 7, wherein the first drying process includes air-drying the LED element for a first duration, and the second drying process includes heating or baking the LED element at a temperature for a second duration.

9. The method of claim 8, wherein the LED element is heated by placing it in direct contact with a resistive heat source, and the LED element is baked in an oven.

10. A method for forming a light-emitting diode (LED) element, the method comprising: The carrier substrate, having a gallium nitride (GaN) LED formed on a carrier surface of the carrier substrate, is removed from the LED element by laser irradiation. The Ga residue layer formed by laser irradiation is oxidized by immersing the LED element in deionized water. Rinse off the deionized water from the LED element; and The LED components are dried using a drying process.

11. The method of claim 10, wherein the deionized water is heated to a temperature between 60°C and 100°C.

12. The method of claim 10, wherein rinsing off the deionized water from the LED element comprises: The LED element is rinsed using a first immersion process for a first duration; as well as The LED element is rinsed using a second immersion process for a second duration.

13. The method of claim 12, wherein the first immersion process comprises immersing the LED element in acetone for the first duration, and the second immersion process comprises immersing the LED element in isopropanol (IPA) for the second duration.

14. The method of claim 10, wherein the drying process includes a first drying process and a second drying process.

15. The method of claim 14, wherein the first drying process includes air-drying the LED element for a first duration, and the second drying process includes heating or baking the LED element at a temperature for a second duration.

16. The method of claim 15, wherein the LED element is heated by placing it in direct contact with a resistive heat source, and the LED element is baked in an oven.

17. The method of claim 9, wherein the Ga oxide residue layer transforms the Ga residue layer into a transparent layer, the transparent layer comprising gallium hydroxy oxide (GaOH), gallium hydroxide (GaH), or a combination thereof.

18. An apparatus comprising: A backplate having backplate electrodes; as well as A plurality of light-emitting diodes (LEDs) coupled to the backplane, the plurality of LEDs comprising: A transparent layer is formed on a first side of the epitaxial layer; as well as LED electrode, which is formed on the second side of the epitaxial layer and coupled to the backplane electrode.

19. The apparatus of claim 18, wherein the transparent layer is transparent to at least one of light with wavelengths in the visible spectrum and light with wavelengths in the infrared (IR) spectrum.

20. The apparatus of claim 18, wherein the transparent layer comprises gallium hydroxy oxide (GaOH), gallium hydroxide (GaH), or a combination thereof.

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