Semiconductor structure for micro LED

Abstract

The proposed solution relates to a semiconductor structure (80) for a micro light emitting diode (micro LED) comprising an epitaxial wafer (10) and a plurality of InGaN lamellas (100) monolithically grown on the epitaxial wafer. Each InGaN wafer includes a QW layer. The plurality of InGaN flakes include individual InGaN flakes configured for red, green, and blue light emissions, respectively. The QW layers are disposed at different heights (hB, hG, hR) above the epitaxial wafer surface in a respective InGaN wafer (100), where the heights are related to emission wavelengths. The solution further relates to a micro LED device (800) comprising the semiconductor structure, and a method of manufacturing the semiconductor structure.

Description

Technical Field

[0001] This technology relates to the field of semiconductor structures, particularly microLEDs (micro-light-emitting diodes) used in display and lighting applications. This field focuses on improving the efficiency, performance, and manufacturing processes of microLEDs, which are renowned for their high brightness, low power consumption, long lifespan, and very fast response time and high modulation speed.

[0002] background MicroLEDs have emerged as a promising technology for high-resolution displays in various applications, such as augmented reality (AR), virtual reality (VR), mixed reality (MR), smartwatches, and head-up displays (HUDs). These applications require small pixel sizes (typically less than 10 μm) to achieve high resolution and a compact form factor. Using microLEDs offers several advantages over competing technologies such as liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs), including higher brightness, longer lifespan, and lower power consumption.

[0003] However, at small pixel sizes, several challenges exist related to the fabrication and performance of microLEDs. A significant issue is the sharp decline in external quantum efficiency as pixel size decreases. This efficiency loss is primarily due to the increased impact of sidewall damage caused by dry etching. Therefore, developing highly efficient microLEDs with pixel sizes below 10 μm remains a challenge. Another issue is red-emitting microLEDs, where nitride and AlInGaP microLEDs are unsatisfactory in terms of both efficiency and brightness.

[0004] Another challenge in the fabrication of microLEDs is the assembly of red, green, and blue (RGB) pixels for high-resolution displays. Currently, these three colors are fabricated on separate wafers using epitaxial methods, and these wafers need to be picked up and placed onto the display's backplane / driving circuitry to build the array of RGB pixels. Various techniques exist to achieve this, many of which are not yet technically mature. To date, no pick-and-place method has been successfully used to produce displays with pixel sizes smaller than 10 μm.

[0005] For small displays, such as AR / VR / MR and smartwatches, one possibility is to directly bond the LED chip to the Si CMOS active driver circuitry. This still requires assembling all three colors into RGB pixels. For pixel sizes larger than 10 μm, this can be achieved through several methods, including pick-and-place methods, mechanical stacking of all three color sources, or multi-junction epitaxial layers connected during epitaxy, such as tunnel junctions. However, these methods are not suitable for pixel sizes smaller than 10 μm.

[0006] Several approaches have been proposed to address these challenges, such as directly growing red, green, and blue LEDs on the same epitaxial wafer (i.e., a semiconductor wafer with a common growth layer), which avoids the massive pick-and-place transfer and instead allows LEDs to be attached to CMOS chips using a single-step wafer bonding process. However, a technique is still lacking to achieve RGB epitaxial wafers with pixel sizes below 10 μm and even smaller than 1 μm for all three colors with external quantum efficiencies in the double-digit range.

[0007] In Bi, Gustafsson, and Samuelson's paper, "Bottom-up approaches to microLEDsemitting red, green, and blue light based on GaN nanowires and relaxed InGaN platelets," published December 8, 2022, *Chin. Phys. B*, 2023, Vol. 32(1): 018103, Special Issue: Physics in MicroLEDs and Quantum Dot Devices, Special Review—Physics in MicroLEDs and Quantum Dot Devices, the authors discuss the miniaturization of LEDs. This paper provides a review of efforts to realize microLEDs through direct bottom-up growth based on selective region metal-organic vapor phase epitaxy. In our approach, individual LEDs based on GaN nanowires or InGaN plates are smaller than 1 μm. Such nanoLEDs can serve as building blocks in arrays for assembling microLEDs of different sizes, avoiding sidewall damage caused by dry etching encountered in top-down methods. InGaN lamellae technology is particularly interesting because by changing the indium content in InGaN lamellae, InGaN quantum wells emitting red, green, and blue light can be grown on such lamellae at low strain levels.

[0008] US2022246797A1 discusses a method for fabricating an InGaN semiconductor template, comprising growing an InGaN pyramid with a tilted surface on a semiconductor substrate; processing the pyramid by removing semiconductor material to form a truncated pyramid with a first upper surface; and growing InGaN on the first upper surface to form an InGaN template layer having a c-plane crystal plane constituting the top surface. This InGaN semiconductor template is suitable for further fabrication of semiconductor devices, such as microLEDs configured to emit red, green, or blue light.

[0009] In Gustafsson, Bi, and Samuelson's "From InGaN pyramids to micro-LEDs characterized by cathodoluminescence," published March 1, 2021, in Nano Express 2(1), the authors present a study of the optical properties of each step in a method for fabricating μ-LEDs based on quantum wells embedded in micrometer-sized InGaN lamellae. While the study focuses on structures for red emission, the technique is equally applicable to less technically demanding blue and green emitting μ-LEDs. The starting point is the growth of InGaN pyramids on a hexagonal substrate with submicrometer dimensions. These pyramids are planarized to produce a flat top c-face for subsequent InGaN quantum well growth. The planarized lamellae serve as templates for growing low-strain single quantum wells in both heterostructures and full-LEDs. Invention Overview The proposed solutions relate to apparatus and methods as outlined in the independent claims. Additional aspects and features are summarized below and are set forth in at least part of the dependent claims.

[0011] According to a first aspect of this disclosure, a semiconductor structure for microLEDs is provided. The structure includes an epitaxial wafer and a plurality of InGaN wafers grown through mask openings in the epitaxial wafer. Each InGaN wafer includes a quantum well layer, which may contain a plurality of quantum wells. Optionally, each InGaN wafer has a top c-plane surface connectable to a driving circuit to generate light emission. The quantum well layer may be formed in the InGaN wafer and may be sandwiched between two InGaN layers, such as a lower n-InGaN portion and an upper p-InGaN portion. The quantum well layer may be configured at a height in the InGaN wafer related to the emission wavelength.

[0012] The proposed solution is based on the inventors' research showing that when the quantum well layer is formed closer to the top portion of the pyramid (where its diameter is also smaller), the quantum well grows thicker and may also have a higher concentration of indium, meaning its emission is shifted to a longer wavelength. The proposed solution thus involves the fabrication of microLEDs for emitting a certain wavelength, configured through careful, selective epitaxial growth of the quantum well layer at a specific height. Specifically, this is used for monolithic growth of RGB triplets from a common epitaxial wafer, where InGaN wafers with quantum well layers at different heights at least partially determine the emission color.

[0013] InGaN wafers can be grouped on an epitaxial wafer for red, green, and blue light emission. The InGaN wafers can be arranged in a triangular pattern, and InGaN wafers configured for emission of the same color can be arranged in a hexagonal pattern. The InGaN wafers can be grouped for different emission wavelengths, and the emission wavelength of the InGaN wafers can increase with increasing spacing within the group. InGaN wafers configured for red light emission can have a base layer of InGaN with a first indium concentration adjacent to the epitaxial wafer, and a buffer layer of InGaN with a second indium concentration higher than the first indium concentration between the base layer and the quantum well layer.

[0014] According to a second aspect of this disclosure, a method for fabricating a semiconductor structure for microLEDs is provided. The method includes epitaxially growing an InGaN pyramid through a mask window of an epitaxial wafer, truncating the InGaN pyramid, for example, by etching or annealing, to form a truncated InGaN pyramid, and growing a separate quantum well layer on the truncated pyramid to form a separate InGaN wafer. The originally grown InGaN pyramids may be grown simultaneously with a common composition and thus have the same indium concentration. The truncated pyramids (which include the remainder of the truncated original grown pyramids) form a corresponding substrate layer for forming the respective and separate monolithically grown InGaN wafers. Optionally, the method may include growing a buffer layer on each substrate layer prior to growing the quantum well layer. The indium concentration of the corresponding buffer layer may be customized for the emission color of the corresponding InGaN wafer. A selective mask for the InGaN wafer may be used for the epitaxial growth of the quantum well layer and the optional buffer layer for emission in one of the red, green, and blue wavelength regions. The growth of quantum well layers can be performed on an epitaxial wafer at a height related to the desired emission wavelength. The formation of quantum well layers for different emission wavelengths on InGaN wafers can be performed using common epitaxial processes.

[0015] The proposed solution thus provides a semiconductor structure having multiple InGaN wafers monolithically grown from a common epitaxial wafer, wherein the InGaN wafers can be used to form RGB pixels. The proposed solution further provides a microLED device comprising a semiconductor structure connected to a driving circuit.

[0016] The proposed solution offers significant advantages over existing technologies. In existing LED growth techniques, monochromatic LEDs of blue, green, or red can be fabricated on a single wafer (or in a single growth run). To fabricate full-color microLED displays, mass transfer is required to transfer the sub-pixels of the R, G, and B microLEDs. This is a highly challenging step, particularly impractical for microLEDs smaller than 10 μm. In contrast, the proposed solution provides RGB sub-pixels by continuously growing them on the same wafer. Thus, each full RGB pixel containing three R / G / B sub-pixels can be directly bonded to the driving circuitry, avoiding the need for mass transfer. This enables monolithic integration of RGB wafer-level microLEDs via epitaxial methods such as metal-organic chemical vapor deposition (MOCVD).

[0017] Overview of the attached figures Figure 1 Three epitaxially grown semiconductor structures in the form of hexagonal InGaN pyramids are schematically illustrated, based on which various implementations of the proposed solution can be obtained.

[0018] Figure 2 An example of an InGaN wafer with a single quantum well according to one embodiment is illustrated schematically.

[0019] Figure 3 An example of a single quantum well, sandwiched between two InGaN layers with low indium content and close to the top c-face, is illustrated schematically according to one embodiment.

[0020] Figure 4 The first example of a process flow for manufacturing red, green, and blue InGaN wafers on the same epitaxial wafer (i.e., from the same growth layer) according to the proposed solution is illustrated.

[0021] Figure 5 A second example of a process flow for fabricating red, green, and blue InGaN wafer LEDs on the same epitaxial wafer is illustrated schematically.

[0022] Figure 6 The schematic diagram illustrates the composition of an InGaN wafer for RGB growth based on an example of the proposed solution.

[0023] Figure 7An example of the proposed solution is shown, including a center-to-center spacing design of growth mask apertures on an epitaxial wafer for localized adjustment of growth rate and the resulting emitted light color.

[0024] Figure 8A A top view shows the arrangement of contacts on a semiconductor structure for attachment to a driving circuit, according to one example.

[0025] Figure 8B A side view illustrating the contacts to a semiconductor structure is shown schematically, based on an example.

[0026] Figure 8C A semiconductor device according to one example is schematically shown, wherein the semiconductor structure is connected to a driving circuit to generate RGB light emission.

[0027] Figure 9 A hexagonal InGaN RGB wafer array design according to one embodiment is illustrated schematically.

[0028] Figure 10A It shows the basis Figure 9 The first instance of the RGB pixels of the pattern.

[0029] Figure 10B It shows the basis Figure 9 The second instance of the RGB pixels of the pattern.

[0030] Figure 11 Displayed based on Figure 10A An example pixel array layout for a display. Invention Details The detailed description set forth below provides information and examples of the disclosed technology with sufficient detail to enable those skilled in the art to implement this disclosure.

[0032] Ternary InGaN alloys are widely used as active layers (or quantum wells) in nitride LEDs and laser diodes. The thickness of the InGaN active layer is typically no more than 3 nm, primarily to confine the effects of the quantum confined Stark effect (QCSE), which reduces the spatial overlap between the electron and hole wave functions in the quantum well. Another reason is that when the layer is grown thicker, the crystal quality of InGaN can deteriorate rapidly, partly due to the large miscibility gap between GaN and InN, but mainly due to strain effects from growth on a mismatched substrate. However, thick and relaxed InGaN films are highly desirable as substrates for nitride optoelectronic devices, where high indium content InGaN active layers are required.

[0033] Selective region growth has been widely used in the fabrication of GaN to reduce dislocation density caused by lattice mismatch between the substrate and the epitaxial GaN layer. If the mask aperture is made small enough, such as 200 nm or smaller, dislocation-free GaN structures including nanowires and pyramids can be grown.

[0034] Figure 1 The figure shows three epitaxially grown semiconductor structures in the form of hexagonal InGaN pyramids, which can be used as the basis for various implementations of the proposed solution. The figure illustrates the semiconductor structures that, according to the proposed solution, can be fabricated and used as starting structures for manufacturing InGaN wafers. For example, a sapphire or Si base substrate 1 has one or more layers of c-oriented GaN as the growth layer 2, such as a (0001) oriented GaN film. For example, SiN... x A mask layer 3 is formed on top of the GaN layer. Holes (or windows / or apertures) 4 are provided in the mask layer. Holes 4 can be fabricated using various types of photolithography, such as EBL (electron beam lithography), nanoimprint lithography, DUV (deep ultraviolet) lithography, etc. Holes 4 can be very narrow, for example, having a diameter of 20-200 nm, 50-150 nm, or 60-100 nm. Optionally, a seed crystal of a Group III nitride material (such as GaN) can be grown. In a subsequent step, hexagonal pyramids 5 of InGaN are epitaxially grown on the holes from the growth layer (optionally from the seed crystal). Growth occurs where gallium and indium primarily diffuse from the SiN mask surface to the holes, without any nucleation on the mask surface. Thus, the growth of InGaN pyramids with a composition of up to 20% indium has been achieved, as determined by photoluminescence (PL) measurements. InGaN pyramids can be grown with selective doping, resulting in negatively doped n-InGaN pyramids. Figure 1 Various examples and aspects related to the prefabrication of structures are disclosed in WO2020187986A1, which is incorporated herein by reference.

[0035] Hexagonal InGaN pyramids with a diagonal base size of several hundred nanometers (e.g., >400 nm) can be used. These pyramids have {101̅1} lateral faces and occasionally a small flat (0001) apex. Each pyramid is a homogeneous InGaN semiconductor structure. In some instances, one or more pyramids can be epitaxially grown in two or more epitaxial stages with different (e.g., gradually increasing) indium concentrations, as will be described.

[0036] Pre-fabrication steps via epitaxial growth from the mask aperture yield InGaN pyramids with no or virtually no dislocations. This avoids emission inhomogeneities caused by dislocations between pixels (individual semiconductor devices). This contributes positively to achieving high quantum efficiencies, such as greater than 10%. Furthermore, very thin GaN buffer / growth layers can be used, resulting in very low wafer warpage. This provides the benefit of high-yield processing.

[0037] Various aspects of the proposed solution are based on creating quantum wells (QWs) embedded within InGaN pyramids or truncated InGaN pyramids to obtain InGaN wafers configured to operate as microLEDs, each microLED configured to emit one of red, green, and blue light. In some implementations, each such InGaN wafer is fabricated from a substantially identical array of InGaN pyramids (i.e., for each color) by simultaneously growing from corresponding mask apertures in an epitaxial process.

[0038] According to some aspects, InGaN pyramids are arranged / grown on a carrier in a first triangular pattern, wherein each InGaN lamella has six adjacent InGaN lamellas at equal distances. This achieves uniformity in the growth of the InGaN pyramids, upon which the InGaN lamellas are formed. In such embodiments, RGB triples can be defined, for example, in a straight line or in a triangular arrangement.

[0039] The use of epitaxially grown InGaN pyramids, grown from small holes to a common growth layer, provides the advantages of high crystal quality and high fabrication efficiency for InGaN lamellae.

[0040] Based on several examples, the pyramidal shape of the starting structure is advantageously used based on the understanding that truncating it to produce a top c-face with different truncated pyramid heights (i.e., at different elevations on the carrier or epitaxial wafer) will also provide a basis for fabricating QWs that emit at different wavelengths (different colors) in relation to the surface dimensions of the c-face. This example provides the possibility of growing QW layers of all three colors (each QW layer containing one or more QWs and associated layers) in a common growth process step.

[0041] According to some examples, pre-arranging individual InGaN pyramids for each pixel based on the growth mask provides an efficient basis for individually masking or not masking the selected pyramids, thereby removing material or epitaxially growing the selected InGaN wafers to produce InGaN wafers for emitting light in the desired wavelength (such as red, green, or blue).

[0042] According to some examples, the pyramid can be configured with a custom pattern defined by the arrangement of mask vias on the epitaxial wafer. In some examples, the pattern can define groups of pixels of the same color (i.e., configured to emit light of the same color), with a pre-configured pixel spacing within each group, wherein the pixel spacing varies depending on the color. Specifically, the pixel spacing PP (e.g., the center-to-center distance of the mask vias) within each group is pre-configured to facilitate different growth of QW layers for different color groups. In this way, two or three groups of QW layers can be grown simultaneously in the same epitaxial process.

[0043] Figure 2 and 3 Different types of InGaN flakes, i.e. InGaN pyramids, based on various instances of the proposed solution, are shown, which have been truncated and subjected to subsequent epitaxial growth to form a QW layer and an upper p-InGaN growth.

[0044] Figure 2 An example of an InGaN wafer 100 comprising a QW layer 110 having a single QW, according to one embodiment, is shown. The InGaN wafer 100 has a truncated pyramidal shape with a substantially flat top surface 120. The InGaN wafer 100 is fabricated from a pyramid grown onto a growth layer 2 through a mask window, a portion of which is shown. The QW layer 110 is formed in the InGaN wafer 100 and configured at a height related to the desired emission wavelength. The figure shows an example of an InGaN wafer having a single QW sandwiched between two InGaN layers with lower indium content. Light emission from the QW is approximately 620 nm.

[0045] Figure 3 An example of an InGaN wafer 100 with a QW layer 110 is shown, the QW layer 110 comprising a single QW sandwiched between two InGaN layers with low indium content and close to the top c-face. Figure 2 In comparison, due to the thicker QW and higher indium content, the light emission from the QW has shifted to 750 nm, indicating that for fixed growth conditions, the emission wavelength can shift depending on the distance to the tip / apex of the pyramid.

[0046] The proposed solution includes a method for manufacturing semiconductor devices comprising InGaN wafers configured for red, green, and blue (RGB) emission on the same carrier, which is a common semiconductor substrate, also referred to herein as an epitaxial wafer. Each InGaN wafer is thus configured to operate as a microLED when connected to a driving circuit.

[0047] By employing bottom-up growth instead of using existing plasma etching techniques to remove InGaN material to form InGaN mesas of a certain pixel size, the risk of damaging the remaining material of the pixel is minimized, which provides high efficiency.

[0048] Figure 4 The presents various stages of a first example of a process flow for fabricating red, green, and blue InGaN wafers 100 on the same epitaxial wafer 10, according to the proposed solution. The process includes, or succeeds in, epitaxially growing InGaN pyramids 5 through mask apertures 4 of the epitaxial wafer 10. In this case, it can be noted that the epitaxial wafer 10 (or carrier) at least includes a mask layer 3, while the underlying growth layer 2 used for growing the InGaN pyramids through the mask apertures can be removed or thinned after the InGaN wafer is completed.

[0049] This process involves truncating InGaN pyramids to form truncated InGaN pyramids and growing a QW layer to form truncated InGaN wafers 100 (100B, 100G, 100R). In the proposed solution, truncation can be achieved using one or more of various types of processes for material removal or rearrangement to obtain the truncated pyramid shape. Etching is one example, while chemical mechanical polishing (CMP) is another.

[0050] The top image depicts an InGaN pyramid with a specific indium content (e.g., 8-12%, such as 10%). This can correspond to... Figure 1 The intermediate image shows the result after progressive truncation to define a group of three truncated pyramids 40B, 40G, and 40R with exposed top c-faces at three different truncation heights, i.e., with exposed c-faces at different elevations above the carrier (e.g., above the top surface of mask layer 3). Truncation involves material removal, such as by back-side etching, annealing, or polishing.

[0051] In some instances (such as referring to) Figure 5 and 6 This involves truncating all the pyramids to leave a corresponding substrate layer with a common height (e.g., 80-120 nm, or approximately 100 nm) on the top surface of the carrier. An additional buffer layer can then be grown on the corresponding substrate layer. This provides an improvement to the upper c-face surface prior to QW growth. The indium concentration of the buffer layer can be customized according to the desired emission color.

[0052] The intermediate image thus shows a set of three truncated pyramids 40B, 40G, and 40R with exposed top c-faces at three different cut-off heights, i.e., exposed c-faces at different elevations above the carrier (e.g., above the top surface of mask layer 3). In this paper, all lamellar crystals are thus processed to expose the c-faces at three different heights; having a height h... B The truncated pyramid 40B is configured to form a QW layer for blue emission, having a height h G The truncated pyramid 40G is configured to form a QW layer for green emission and has a height h R The truncated pyramid 40R is configured to form a QW layer for red emission.

[0053] Quantum well layers 111, 112, and 113 can then be epitaxially grown in a single step on truncated InGaN pyramids 40B, 40G, and 40R with different height / top c-face dimensions, with the aim of having RGB microLEDs fabricated in a common epitaxial process. In other words, for all colors RGB, the same formulation can be used to prepare layers included in the QW, including an additional InGaN overlay layer above the QW, which saves processing time.

[0054] In order to achieve Figure 4 Based on the structure of the intermediate image, and the top image, a protective layer of resist or other dielectric material can first be deposited on the sample surface (the top surface of epitaxial wafer 10 and pyramid 5). In some instances, the resist / dielectric protective layer is chosen to have a dry etching rate similar to that of InGaN materials, such as crystalline Al2O3. After depositing the protective layer, the surface can be slightly wavy, following the shape profile of the pyramid. CMP can be used to planarize this protective layer.

[0055] According to some examples, when the buffer layer is not included, another layer of a different type of resist / hard mask can be deposited on the prepared surface for photolithography, and the resist / hard mask can be patterned to create a set of apertures on the top 1 / 3 of the InGaN pyramid. Subsequently, dry etching can be performed to truncate the InGaN pyramid exposed below the apertures to form the top c-face for a monochromatic microLED (such as blue). Selective masking is a known procedure and therefore will not be described or shown in detail.

[0056] In one example, the process can continue by removing the top resist / hard mask and subsequently re-depositing a resist / dielectric layer to cover the truncated pyramids. By repeating the above procedure twice from the CMP, two additional sets of truncated pyramids with different heights can be fabricated for two other colors of microLEDs (green and red). After removing all resist material, the desired result is obtained. Figure 4The structure of the intermediate image.

[0057] In another example, the first step of etching the top 1 / 3 of the InGaN pyramid can be followed by a step of removing the resist to form an aperture on a second set of pyramids, where etching can be performed on both the first and second sets of pyramids. Finally, after all three pyramids have been etched, the remaining pyramids can also be exposed. Figure 4 The intermediate image, the selected time for these three process steps can be configured to obtain the corresponding pyramid to the selected cut-off height at three different heights.

[0058] In instances where all pyramids are first etched on the back side to form the corresponding substrate layer, a selective masking process can be used alternatively to grow the buffer layer.

[0059] To conclude template preparation, the resist / hard mask and protective layer are removed, and the sample is cleaned for subsequent epitaxy.

[0060] Corresponding to Figure 4 The intermediate image shows that the original sample can be loaded back into the MOCVD chamber for epitaxy of QW layers 111, 112, and 113. Each QW layer can contain an n-type InGaN buffer layer, an InGaN QW, a GaN or AlGaN electron blocking layer, and a p-InGaN layer. The smaller the top c-facet during QW layer growth, the higher the indium content can be obtained in the InGaN QW. By adjusting the top c-facet size of these three sets of truncated pyramids 40B, 40G, and 40R (i.e., by configuring the height of the truncated pyramids) and growth conditions, InGaN QWs emitting blue, green, and red light can be obtained in a single epitaxial growth process. It should be noted that each pyramid can undergo epitaxy to grow more than one QW per pyramid.

[0061] Figure 4 The bottom image shows the result after a single epitaxy on all truncated InGaN pyramids 40B, 40G, and 40R, resulting in InGaN wafers 100B, 100G, and 100R with corresponding QW 111, 112, and 113 located at three different heights and configured to emit three different colors: blue, green, and red. It should be noted that a single epitaxy refers to performing the same series of epitaxial growth steps on all truncated pyramids 40B, 40G, and 40R.

[0062] As shown in the bottom image, the QW layer growth process also includes the additional growth of an upper InGaN layer (such as doped p-InGaN). In some instances, the growth of the upper InGaN layer continues until the entire pyramidal shape of each corresponding lamella is achieved. Subsequently, all lamellae are truncated, for example by annealing, etching, or polishing, to obtain the same height for all InGaN lamellae. This provides a simplified final process and also achieves a uniform InGaN height, which simplifies contact with the drive circuitry.

[0063] Figure 5 Another example of a process flow for fabricating red, green, and blue InGaN wafer LEDs on the same epitaxial wafer 10 is shown. This process flow includes the epitaxial growth of a QW layer on the InGaN wafer that selectively masks emission in one of the red, green, and blue wavelength regions.

[0064] This process is based on creating QWs of different colors on the same truncated c-plane height (i.e., the substrate layer), covering the selected wafer, and epitaxially growing on the remaining exposed wafer in three consecutive steps to form R, G, and B LEDs.

[0065] A) A pyramidal structure of n-InGaN with a specific indium content (e.g., 8-12%) is depicted. This can correspond to... Figure 1 .

[0066] B) illustrates the planarization / truncation of InGaN pyramids to the same height (leaving the substrate layer). In this figure, each truncated pyramid 51 is surrounded by an additional spacer layer 52 of the same height. The spacer layer 52 is a dielectric material or at least an inorganic material (not a photoresist polymer) because it needs to withstand high temperatures without degrading and contaminating the InGaN. In various embodiments, the spacer layer 52 comprises SiN. x Al2O3, TiN or other suitable materials.

[0067] C) illustrates adding growth mask 53 material to selected 2 / 3 of all truncated pyramids, followed by epitaxial growth of an LED structure comprising a QW layer 111 intended for a single color (e.g., blue light emission). Optionally, a buffer layer tailored for blue light emission, such as having a 5-10% indium concentration, is grown prior to this, which further provides the benefit of reducing any possible band-tail absorption of the QW light. The growth mask material can be, for example, Al₂O₃ or SiN comprising atomic layer deposition (ALD). x .

[0068] In other words, after truncating the InGaN pyramids using dry etching or CMP to form structure B), the sample surface is covered with a growth mask material layer. A set of truncated pyramids is exposed by photolithography and dry etching for subsequent epitaxy of the QW layer (optionally with a buffer layer grown beforehand) and the upper p-InGaN layer to form a microLED 100B configured to emit a single color (e.g., blue).

[0069] D) shows the previously grown LED structure 100B covered in a growth mask material (i.e., by again using a mask layer, such as ALD Al2O3 or SiN). x The entire sample was covered, and half of the remaining truncated pyramid was exposed using photolithography and dry etching. Subsequently, an LED structure containing a QW layer was epitaxially grown to form a microLED 100G configured to emit a second color (e.g., green light emission).

[0070] E) shows an LED structure 100R with a previously grown LED structure covered in a growth mask and the remaining truncated pyramid exposed, which is then epitaxially grown with a QW intended for the final color (e.g., red light emission).

[0071] In this example, for each color of the pixel, a separate formulation for epitaxy can be used to generate—in particular—the QW and buffer layer. This provides greater operational freedom for the configuration of InGaN wafers for microLEDs of different colors. This example thus truncates all InGaN pyramids in the same manner, and then performs epitaxial growth of three types of microLEDs aimed at obtaining blue, green, and red on selected sets of truncated pyramids, while other sets of truncated pyramids are covered with mask material.

[0072] Figure 6 An example of an InGaN wafer composition for RGB growth according to the proposed solution is shown. The InGaN wafer has a substrate layer 61 adjacent to the surface 11 of the epitaxial wafer (such as the top surface of the mask layer 3). As described above, the substrate layer 61 may be the remaining portion of the original pyramid 5 after truncation. The substrate layer size, substantially equal to the size of the original pyramid substrate, may be in the range of 700-900 nm, such as the point-to-point spacing of its hexagonal shape being approximately 800 nm. The substrate layer is made of InGaN (n-InGaN) with a first indium concentration, such as approximately 10% or 8-12%, and may be approximately 100 nm high or 80-120 nm high. A buffer layer 62 is formed between the substrate layer 61 and the QW layer 110, wherein the buffer layer 62 is made of InGaN with a second indium concentration, which may be different from the first indium concentration.

[0073] For an InGaN wafer 100R configured to emit red light, the buffer layer 62R can be made of InGaN with a second indium concentration (e.g., 18-20%) higher than the first indium concentration. The buffer layer can be grown to obtain a c-plane surface at a height of approximately 520-550 nm from the surface of the epitaxial wafer.

[0074] According to various embodiments, to minimize lattice stress and defect generation, the n-type bottom lamellar segment (i.e., the substrate 61 closest to the mask layer of the pyramid) is designed with an In composition corresponding to a bandgap emission of 420-430 nm. For the red emitting LED 100R, a buffer layer 62R with 475 nm emission is grown before the QW layer 110, while a 425 nm emission layer can be used for green and blue. This suppresses defect generation.

[0075] In some instances, in the formation of green 100G and blue 100B microLEDs, a buffer layer is not grown, or a buffer layer with the same indium concentration as the substrate 61 is grown.

[0076] However, in other instances, buffer layers 62G and 62B of InGaN (n-InGaN) are also grown on the substrate 61 to form InGaN wafers for green 100G and blue 100B emission.

[0077] For a green InGaN wafer 100G, a buffer layer 62G is formed between the substrate layer 61 and the QW layer 110, wherein the buffer layer 62G is made of InGaN with a second indium concentration that is the same as or higher than the first indium concentration, such as 10-15%. The buffer layer can be grown to obtain a c-plane surface at a height of approximately 360-400 nm from the surface of the epitaxial wafer.

[0078] For the blue InGaN wafer 100B, a buffer layer 62B is formed between the substrate layer 61 and the QW layer 110, wherein the buffer layer 62B is made of InGaN with a second indium concentration that is the same as or lower than the first indium concentration, such as 5-10%. The buffer layer can be grown to obtain a c-plane surface at a height of approximately 240-280 nm from the surface of the epitaxial wafer.

[0079] For each InGaN wafer 100R, 100G, 100B, a further upper InGaN layer (p-InGaN) 63R, 63G, 63B is grown above the QW layer 110. As described, when the initial substrate layer 61 size is in the range of 700-900 nm, such as with a dot-to-dot distance of approximately 800 nm, the overall total height of each InGaN wafer can be in the range of 720-770 nm. According to measurements, after the growth step, the substrate height of the corresponding InGaN wafer can be increased to 900-960 nm.

[0080] Figure 7 An example of the proposed solution is shown, including a center-to-center spacing design of the holes 4 in the growth mask 3 for locally adjusting the growth rate of the epitaxial wafer 10. The accompanying figure schematically shows a top view of the mask layer 3. The holes 4 in the mask layer 3 for growing InGaN wafers are configured in groups for red, green, and blue light emission, respectively. This implementation is based on the understanding that the emission wavelength of the InGaN wafer increases with increasing spacing within the group.

[0081] According to this implementation of the proposed solution, R, G, and BLEDs are fabricated using localized variations in aperture spacing. With this configuration, a single-step epitaxial process can be optionally employed for QW layer formation and top layer growth.

[0082] In this context, the proposed lattice design is based on the concept that for selective regional growth of InGaN, indium incorporation depends on the spacing between the holes 3. In the accompanying figure, this spacing is referred to as the pixel pitch PP. At a spacing of at most 2 μm or larger, growth is controlled by diffusion of adsorbed atoms on the mask surface. All adsorbed atoms falling on the mask surface will diffuse to the nearest InGaN pyramid and contribute to growth there. Thus, growth with a larger spacing implies a locally higher growth rate, resulting in an increased indium content (i.e., pre-configuration for longer wavelengths). By carefully designing the spacing between the holes 4, and thereby designing the pyramids growing from the growth layer 2 through the holes 4, and by adjusting the growth conditions, InGaN pyramids 5 can be grown in a single epitaxial run (and subsequently further truncated and processed to introduce a QW layer), where the indium composition (concentration) is tailored to the target emission wavelength (i.e., blue, green, and red light) based on the spacing between the mask windows. In this case, a larger spacing provides InGaN growth suitable for longer wavelength InGaN lamellae (i.e., towards red). It can be noted that the custom lattice pattern used for this purpose can be achieved through the patterning design of the mask apertures 4 in the mask 3 above the growth layer 2. Grouped triangular apertures with larger cc spacing (pixel spacing between InGaN wafers of the same color) promote higher indium incorporation and longer wavelength emission. Thus, designs with three different cc spacings will yield red, green, and blue wafer LEDs on the same wafer.

[0083] Figure 8A and 8B The contacts of the semiconductor structure 80 according to the proposed solution are schematically shown, while Figure 8C A microLED device 800 is shown, in which a semiconductor structure 80 is connected to a driving circuit. Where reference numerals are not included in Figure 8, it should be noted that they refer to details highlighted in other figures.

[0084] Figure 8A A top view shows an example of a triangular arrangement of RGB microLEDs, where n-contacts are centrally configured within the triangular pixel arrangement. Individual n-contacts to the respective microLEDs are another option.

[0085] Figure 8BA semiconductor structure 80 according to an example of the proposed solution is schematically illustrated. As described and illustrated herein, the semiconductor structure 80 includes an epitaxial wafer 10 in which a plurality of InGaN wafers 100 are grown through mask windows 4 of the epitaxial wafer 10, each InGaN wafer including a QW layer 110 comprising one or more QWs. The InGaN wafers 100 have a truncated pyramidal shape. Each InGaN wafer is configured to emit one color in RGB and is designated as 100B, 100G, 100R. In this figure, the buffer layer 2 is still retained, but this layer may be peeled or thinned before or after contact.

[0086] A contact spacer layer 81 may be applied to InGaN wafers 100B, 100G, 100R, wherein p-contacts 82B, 82G, 82R to the respective InGaN wafers protrude through the contact spacer layer 81 and are bonded to the respective top c-surface surfaces of the InGaN wafers 100B, 100G, 100R. The contact spacer layer 81 is a dielectric layer that allows leads (not shown) to be applied to the p-contacts on the surface of the microLED device. n-contacts 83 (or individual contacts) for pixel groups are formed extending from the base-side surface of the pyramid to the top c-surface side to facilitate connection of driving circuitry. According to the illustrated example, the n-contacts 83 may be metallic connections.

[0087] Figure 8C A microLED device 800 is schematically shown, comprising a semiconductor structure 80 according to the proposed solution. The figures indicate the attachment and connection of the semiconductor structure 80 to the driving circuit 84. Each InGaN wafer 100R, 100G, 100B has a top c-surface surface that can be connected to the driving circuit 84 via corresponding connectors 82R, 82G, 82B to generate light emission.

[0088] The driving circuit 84 is exemplified here as a Si CMOS driving circuit. In some instances, thin-film active transistor drivers may be used alternatively or additionally. Although Figure 8A The top image shows a triangular group of RGB pixels with central n-contact; for simplicity, the bottom image shows a line drawing. Either is possible.

[0089] When the microLED device 800 is configured to emit light through the substrate side of the InGaN wafer, the p-contacts 82B, 82G, 82R connected to the upper c-surface of the corresponding InGaN wafer can be reflective to improve light output.

[0090] Remove substrate 1 (see) Figure 1As described, the original GaN growth layer 2 can be further thinned or stripped. The epitaxial wafer 10 of the microLED device 800 thus includes a mask layer 3 and optionally a portion of the growth layer 2.

[0091] Figure 9 Examples of InGaN RGB wafer array designs based on some of the proposed solutions are shown. InGaN wafers are epitaxially grown from holes arranged in a triangle in a growth mask and subsequently formed into QWs (where each InGaN wafer has six adjacent InGaN wafers at a common distance), providing very uniform growth conditions and achieving well-controlled composition.

[0092] As shown in the figure, a hexagonal array is configured for each color. The hexagonal pattern specifies that the same distance / spacing is configured between all InGaN wafers prepared for the same emission wavelength. This is beneficial for growth uniformity. Specifically, by maintaining the triangular symmetry (and the spacing between the centers) of the red, green, and blue wafer LEDs, the color purity and uniformity of each LED color on the wafer are very high.

[0093] Figure 10A This example shows a pixel group configuration where a triplet of RGB InGaN wafers is combined within a single pixel group to achieve any color in the visible spectrum. In this example, a triangular pixel group is configured.

[0094] Figure 10B An example is shown illustrating an alternative arrangement of ternaries for RGB InGaN wafers in a pixel group, capable of achieving any color in the visible spectrum. In this example, a linear combination is configured.

[0095] Figure 11 Examples of multiple pixel RGB groups are shown, each containing data based on... Figure 10A The triplet of the example. The pixel array layout illustrates the arrangement of InGaN wafer 100 for red, green, and blue light emission in a display application.

[0096] The above embodiments provide examples of proposed solutions for semiconductor structures and manufacturing methods for microLEDs. The disclosed techniques minimize defects in crystal formation and improve the external quantum efficiency of microLEDs with pixel sizes below 10 μm. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this disclosure. Various modifications and adaptations can be made by those skilled in the art without departing from the scope of this disclosure as set forth in the appended claims.

[0097] Referring to the above description of the proposed solution, along with its examples and implementation schemes, various further relevant features and examples are outlined below.

[0098] The growth of InGaN pyramids through the mask window 4 of the epitaxial wafer 10 enables the formation of InGaN wafers 100 with specific shapes and configurations. This controlled growth process contributes to the overall quality and performance of the resulting microLEDs because it allows the formation of InGaN wafers with minimal defects and optimized external quantum efficiency.

[0099] The growth mask 3 used for growing InGaN pyramids is preferably made of a dielectric material such as Al2O3 or SiN. x TiN. The holes 4 passing through the openings of the dielectric growth mask are preferably arranged in a triangular lattice, such as... Figure 9-11 As shown, the pore size is in the range of 20-200 nm and is spaced 0.5-10 μm apart.

[0100] The InGaN pyramid 5 is preferably grown as n-type InGaN. The n-type InGaN pyramid can be doped with, for example, Si to a doping level of 1-5 × 10⁻⁶. 18 cm -3 The level.

[0101] According to some examples, InGaN pyramids 5 with the same composition are simultaneously grown into n-type InGaN pyramids with a specific indium concentration, wherein the pyramids are then processed to obtain individual RGB InGaN wafers.

[0102] According to other examples, for blue LEDs, GaN or InGaN pyramids with an indium content of less than 5% (wavelength <380 nm) can be used. For green LEDs, InGaN pyramids with an indium content of approximately 10% (wavelength 420-430 nm) are preferred, and for red LEDs, an indium content of 18%-20% (wavelength 480-500 nm) is preferred. Different indium contents / concentrations can be obtained by growing InGaN pyramids in separate processes.

[0103] In some instances, for example, as referenced Figure 6 The n-type InGaN can be comprised of more than one segment separated in elevation above the epitaxial wafer / mask layer. In some instances, the substrate layer of the InGaN closest to the epitaxial wafer 10 can have the same indium composition as the original InGaN pyramid. However, for Figure 6As shown, this fabrication method can begin with an InGaN pyramid with approximately 10% indium content emitting 420-430 nm light. After truncating the pyramid, the template can be directly used for blue and green microLEDs. For red microLEDs, a buffer InGaN layer (below the active region of the QW layer) with, for example, approximately 18-20% indium content (480-500 nm light) can be grown, followed by the growth of a red InGaN QW to reduce the risk of introducing stacking mismatch boundaries. The variation in indium concentration between the substrate and the buffer layer helps achieve the desired emission wavelength of red light and improves the crystal quality of the InGaN lamellae.

[0104] Following the epitaxial growth of the InGaN pyramid, the fabrication method may involve truncating the InGaN pyramid 5 to form a truncated InGaN pyramid (and possibly further InGaN buffer growth). This process facilitates the production of an InGaN wafer 100 with a truncated pyramid shape, which is advantageous for forming a QW layer parallel to the defined c-plane of the epitaxial wafer and for the overall performance of the microLED.

[0105] When truncating pyramid 5, a protective layer can be applied before LED epitaxy, such as before QW layer growth (and, where appropriate, buffer layer growth). Figure 4 and Figure 5 As shown. The protective layer should preferably be deposited using a dielectric material (Al₂O₃, etc.) similar to the growth mask, because it can be deposited conformally, covering all surfaces with the same thickness. Other deposition methods typically result in different depositions on different surfaces.

[0106] The InGaN wafer 100 includes a QW layer, also known as an active layer, formed within the wafer, which may contain one or more QWs. The QW can be approximately 2-3 nm thick. The compositions (i.e., indium concentrations) used for blue, green, and red LEDs are approximately 10-15%, 25-27%, and 35-40%, respectively. For blue and green LEDs, an electron blocking layer (EBL) of AlGaN with an Al content of 10-25% and a thickness of 10-25 nm can be used. For red LEDs, GaN or AlGaN with an Al content of less than 10% can be used as the EBL.

[0107] According to some examples, the QW layer is configured at a height related to the emission wavelength in the InGaN wafer 100, as shown in the reference. Figure 4 As explained and illustrated. For at least some of the QW layers, this configuration allows QW layers to be formed on InGaN wafers 100 for different emission wavelengths in a common epitaxial process or so-called single epitaxy, which simplifies the manufacturing process and reduces manufacturing costs.

[0108] In some instances, the fabrication method may also include selectively masking the InGaN wafer 100 to epitaxially grow a QW layer for emission in one of the red, green, and blue wavelength regions. This selective masking process enables the individual and specialized creation of semiconductor structures with InGaN wafers configured for different emission wavelengths, allowing the formation of microLEDs capable of emitting red, green, and blue light.

[0109] In some instances, various techniques, such as photolithography, electron beam lithography, or nanoimprint lithography, can be used to perform the selective masking process to create a desired mask pattern on the epitaxial wafer 10. The mask material can be selected based on its compatibility with the chosen masking technology and its ability to withstand the epitaxial growth process without degradation or undesirable contamination of the InGaN material. Using selective masking for wavelength region emission in the fabrication of semiconductor structures for microLEDs offers several advantages. By enabling the formation of InGaN wafers 100 with different emission wavelengths on the same epitaxial wafer 10, the selective masking process allows for the creation of microLEDs capable of emitting a full range of colors for display applications. Furthermore, the selective masking process can contribute to improved efficiency with optimized growth conditions for each color and uniformity of the epitaxial growth process, resulting in InGaN wafers 100 with fewer defects and higher external quantum efficiency. Moreover, combining selective masking with a common epitaxial process can help simplify the fabrication method and reduce the overall processing time and cost associated with fabricating semiconductor structures for microLEDs.

[0110] In some instances, InGaN lamellae can incorporate additional layers with varying indium concentrations to further optimize their performance. These additional layers can be located between the substrate and the buffer layer, or between the buffer layer and the QW layer. These additional layers can help reduce strain, improve crystal quality, and customize the emission wavelength of the InGaN lamellae.

[0111] A p-type InGaN top layer is further grown above the QW layer. For blue LEDs, the p-layer can be a p-GaN with a thickness of 100-200 nm or a p-InGaN containing only a few percent (<10% or <5%) of In. For green and red LEDs, p-InGaN with indium contents of 10% and 18% can be used, respectively. For example, a thickness of at least 1 × 10⁻⁶ is used. 19 cm -3 Mg can achieve p-type doping at a certain level. Rapid thermal annealing can be used to activate Mg doping.

[0112] like Figure 8B As shown, the contact spacer layer 81 can be a polymer. Preferably, the dielectric spacer layer is such as PECVD SiO2. xIt should be used in conjunction with CMP to expose the top c-face of the p-InGaN layer. In PECVD SiO x Before growth, a thin layer of ALD Al2O3 can be deposited first to facilitate the deposition of SiO2 via PECVD. x It initially protects the surface from plasma damage and also serves as a surface passivation agent for lamellar surfaces.

[0113] Preferably, such as Figure 8B As shown, n-type contacts to the substrate end of the InGaN wafer (typically to a growth layer on the opposite side of the mask layer, such as a GaN buffer layer) and p-type InGaN contacts can be processed on the wafer side of the epitaxial wafer 10, allowing for convenient bonding to driving circuits, such as CMOS driver chips. In this case, the flat c-plane top surface of the truncated InGaN wafer provides a surface suitable for bonding p-contacts.

[0114] In one example, the InGaN wafers 100 are arranged in groups on the epitaxial wafer 10 for emitting red, green, and blue light. This arrangement enables the fabrication of microLEDs with different emission wavelengths on a single epitaxial wafer 10, which simplifies the manufacturing process and reduces costs.

[0115] In some instances, InGaN wafers 100 are arranged in groups, with the groups configured for different emission wavelengths. The emission wavelength of the InGaN wafers 100 increases with the spacing within the group. This arrangement allows the emission wavelength of the InGaN wafers 100 to be adjusted by varying the spacing within the group, providing flexibility in designing microLEDs with desired emission wavelengths during InGaN pyramid growth.

[0116] In various instances, the InGaN wafers 100 are arranged in a triangular pattern. In some instances, the InGaN wafers 100 configured to emit the same color are further arranged in a hexagonal pattern. These patterns provide an efficient arrangement of the InGaN wafers 100 on the epitaxial wafer 10 for red, green, and blue light emission, which helps improve the external quantum efficiency of microLEDs with pixels smaller than 10 μm.

[0117] Overall, the method for fabricating semiconductor structures for microLEDs described in this paper provides a robust and efficient approach to generating high-quality microLEDs with minimal defects during crystal formation and improved external quantum efficiency. The various steps and optional features of this method contribute to the formation of InGaN wafers with precise control over their shape, configuration, and emission properties, ensuring optimal performance of the resulting microLEDs in a wide range of applications.

[0118] Selective masking of wavelength-region emission offers several advantages in the fabrication of semiconductor structures for microLEDs. By enabling the formation of InGaN wafers 100 with different emission wavelengths on the same epitaxial wafer 10, selective masking allows for the creation of microLEDs capable of emitting a full range of colors for display applications. Furthermore, selective masking can help improve the efficiency and uniformity of the epitaxial growth process, resulting in InGaN wafers 100 with fewer defects and higher external quantum efficiency. Moreover, combining selective masking with a common epitaxial process can help simplify the fabrication method and reduce the overall processing time and cost associated with fabricating semiconductor structures for microLEDs.

[0119] The proposed solution can be configured according to any of the terms set forth below, depending on various aspects.

[0120] Clause 1. A semiconductor structure for a micro light-emitting diode (microLED), comprising: Epitaxial wafer (10); Multiple InGaN wafers (100) monolithically grown on an epitaxial wafer, each containing a quantum well (QW) layer; The plurality of InGaN wafers include individual InGaN wafers configured for red, green and blue light emission, respectively.

[0121] Clause 2. The semiconductor structure of claim 1, wherein the QW layer is disposed at different heights (h) above the epitaxial wafer surface in the respective InGaN wafer (100), wherein the height is related to the emission wavelength.

[0122] Clause 3. The semiconductor structure according to claim 1 or 2, wherein the QW layer is disposed at an increasing height in an InGaN wafer configured for different emission wavelengths in a blue-green-red order.

[0123] Clause 4. The semiconductor structure according to any one of claims 1-3, wherein each InGaN wafer comprises a substrate layer with a first indium concentration adjacent to the epitaxial wafer, and a buffer layer with a second indium concentration between the substrate layer and the QW layer, wherein the second indium concentration is different between InGaN wafers configured for different color emission.

[0124] Clause 5. The semiconductor structure of claim 4, wherein the substrate layer in each InGaN wafer has the same first indium concentration.

[0125] Clause 6. The semiconductor structure according to claim 5, wherein the concentration of the first indium is 8-12%.

[0126] Clause 7. The semiconductor structure according to any one of claims 4-6, wherein in the InGaN wafer configured for blue emission, the second indium concentration is lower than the first indium concentration.

[0127] Clause 8. The semiconductor structure according to any one of claims 4-7, wherein the second indium concentration is 5-10% in the InGaN wafer configured for blue emission.

[0128] Clause 9. The semiconductor structure according to any one of claims 4-8, wherein in the InGaN wafers respectively configured for green and red emission, the second indium concentration is higher than the first indium concentration.

[0129] Clause 10. The semiconductor structure according to any one of claims 4-9, wherein the second indium concentration is 10-15% in the InGaN wafer configured for green emission.

[0130] Clause 11. The semiconductor structure according to any one of claims 4-10, wherein in the InGaN wafer configured for red emission, the concentration of the second indium is 18-20%.

[0131] Clause 12. The semiconductor structure according to any of the preceding claims, wherein the InGaN wafer (100) has a truncated pyramidal shape and a top c-face surface that can be connected to a driving circuit to generate light emission.

[0132] Clause 13. A semiconductor structure according to any of the preceding claims, wherein InGaN wafers (100) configured for the same emission wavelength are arranged in a hexagonal pattern on the epitaxial wafer.

[0133] Clause 14. The semiconductor structure according to any of the preceding claims, wherein the InGaN wafers are arranged in a group adjacent to each other on the epitaxial wafer.

[0134] Clause 15. The semiconductor structure of claim 14, wherein each group comprises a ternary array of adjacent InGaN wafers (100) arranged in a triangular pattern.

[0135] Clause 16. The semiconductor structure of claim 14 or 15, wherein each group comprises an InGaN wafer (100) configured for blue, green and red emission.

[0136] Clause 17. The semiconductor structure according to any one of claims 1-15, wherein the InGaN wafers (100) are arranged in groups, the groups being configured for the same emission wavelength, and wherein the spacing (PP) between the InGaN wafers within a respective group is related to the emission wavelength for which the InGaN wafers are configured, such that the spacing increases in the order of blue-green-red.

[0137] Clause 18. A micro LED device (800) comprising: The semiconductor structure (80) according to any one of the preceding claims; and The driving circuit (84) is connected via a p-contact to the corresponding top position of each InGaN wafer and via an n-contact to the substrate side of the epitaxial wafer for generating light emission from the respective InGaN wafer.

[0138] Clause 19. A method of manufacturing a semiconductor structure for microLEDs, the method comprising: InGaN pyramids (5) are epitaxially grown through the mask window of the epitaxial wafer (10); The InGaN pyramid is truncated to form a truncated InGaN pyramid with a c-faced top surface; Quantum well (QW) layers are grown on the corresponding truncated InGaN pyramids; and A top InGaN layer is grown on the corresponding QW layer to form separate InGaN wafers configured for red, green and blue light emission, respectively.

[0139] Clause 20. The method of claim 19, wherein the QW layer is grown at different heights (h) above the surface of the epitaxial wafer in the respective InGaN wafer (100), wherein the height is related to the emission wavelength.

[0140] Clause 21. The method of claim 19 or 20, wherein the QW layer is grown at increasing height in an InGaN wafer configured for different emission wavelengths in a blue-green-red order.

[0141] Clause 22. The method according to any one of claims 19-21, wherein the truncated InGaN pyramid forms a corresponding substrate layer having a first indium concentration, the method further comprising: A buffer layer with a second indium concentration is grown on the substrate layer prior to the growth of the QW layer, wherein the second indium concentration is different between InGaN wafers configured for different color emission.

[0142] Clause 23. The method of claim 22, wherein the substrate layer in each InGaN wafer has the same first indium concentration.

[0143] Clause 24. The method according to any one of claims 19 to 23, wherein the growth of quantum well layers on InGaN wafers for different emission wavelengths is carried out in a common epitaxial process.

Claims

1. A semiconductor structure (80) for a micro light-emitting diode (microLED), comprising: Epitaxial wafer (10); Multiple InGaN wafers (100B, 100G, 100R) monolithically grown on an epitaxial wafer each contain quantum well (QW) layers (111, 112, 113); The plurality of InGaN wafers include individual InGaN wafers configured for red, green, and blue light emission, respectively. Its features The QW layer is disposed at different heights (h) above the surface of the epitaxial wafer in the corresponding InGaN wafer (100). B h G h R ( ) where the height is related to the emission wavelength.

2. The semiconductor structure of claim 1, wherein the QW layer is disposed at an increasing height in an InGaN wafer configured for different emission wavelengths in a blue-green-red order.

3. The semiconductor structure according to claim 1 or 2, wherein each InGaN wafer comprises a substrate layer (61) with a first indium concentration adjacent to the epitaxial wafer, and a buffer layer (62B, 62G, 62R) with a second indium concentration between the substrate layer and the QW layer, wherein the second indium concentration is different between InGaN wafers configured for different color emission.

4. The semiconductor structure according to claim 3, wherein the substrate layer in each InGaN wafer has the same first indium concentration.

5. The semiconductor structure according to claim 4, wherein the concentration of the first indium is 8-12%.

6. The semiconductor structure according to any one of claims 3-5, wherein in the InGaN wafer configured for blue emission, the second indium concentration is lower than the first indium concentration.

7. The semiconductor structure according to any one of claims 3-6, wherein in the InGaN wafer configured for blue emission, the concentration of the second indium is 5-10%.

8. The semiconductor structure according to any one of claims 3-7, wherein in the InGaN wafers respectively configured for green and red emission, the second indium concentration is higher than the first indium concentration.

9. The semiconductor structure according to any one of claims 3-8, wherein in the InGaN wafer configured for green emission, the concentration of the second indium is 10-15%.

10. The semiconductor structure according to any one of claims 3-9, wherein in the InGaN wafer configured for red emission, the concentration of the second indium is 18-20%.

11. The semiconductor structure according to any one of the preceding claims, wherein the InGaN wafer (100) has a truncated pyramidal shape and a top c-face surface that can be connected to a driving circuit to generate light emission.

12. The semiconductor structure according to any one of the preceding claims, wherein the InGaN wafers (100) configured for the same emission wavelength are arranged in a hexagonal pattern on the epitaxial wafer.

13. The semiconductor structure according to any one of the preceding claims, wherein the InGaN wafers are arranged in a group adjacent to each other on the epitaxial wafer.

14. The semiconductor structure of claim 13, wherein each group comprises a ternary array of adjacent InGaN wafers (100) arranged in a triangular pattern.

15. The semiconductor structure of claim 13 or 14, wherein each group comprises an InGaN wafer (100) configured for blue, green and red emission.

16. The semiconductor structure according to any one of claims 1-14, wherein the InGaN wafers (100) are arranged in groups, the groups are configured for the same emission wavelength, and wherein the spacing (PP) between the InGaN wafers in the respective groups is related to the emission wavelength for which the InGaN wafers are configured, such that the spacing increases in the order of blue-green-red.

17. A microLED device (800), comprising: The semiconductor structure (80) according to any one of the preceding claims; and The driving circuit (84), connected via p-contacts (82B, 82G, 82R) to the respective top position of each InGaN wafer and via n-contacts (83) to the substrate side of the epitaxial wafer, is used to generate light emission from the respective InGaN wafer.

18. A method for manufacturing a semiconductor structure for microLEDs, the method comprising: InGaN pyramids (5) are epitaxially grown through the mask window of the epitaxial wafer (10); The InGaN pyramid is truncated to form a truncated InGaN pyramid (40B, 40G, 40R) with a c-faced top surface; Quantum well (QW) layers (111, 112, 113) were grown on the corresponding truncated InGaN pyramids; and A top InGaN layer is grown on the corresponding QW layer to form separate InGaN wafers (100B, 100G, 100R) respectively configured for red, green, and blue light emission, characterized in that the QW layer is at different heights (h) above the surface of the epitaxial wafer in the corresponding InGaN wafer (100). B h G h R It grows at a height that is related to the emission wavelength.

19. The method of claim 18, wherein the QW layer is grown at increasing height in an InGaN wafer configured for different emission wavelengths in a blue-green-red order.

20. The method of claim 18 or 19, wherein the truncated InGaN pyramid forms a corresponding substrate layer having a first indium concentration, the method further comprising: Before growing the QW layer, a buffer layer (62B, 62G, 62R) with a second indium concentration is grown on the substrate layer, wherein the second indium concentration is different between InGaN wafers configured for different color emission.

21. The method of claim 20, wherein the substrate layer in each InGaN wafer has the same first indium concentration.

22. The method according to any one of claims 18 to 21, wherein the growth of quantum well layers on InGaN wafers for different emission wavelengths is carried out in a common epitaxial process.

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