Micro-LED configured for operation at wavelengths in far UVC spectrum

Abstract

A light emitting diode (LED) includes a semiconductor structure including at least one epitaxial layer configured to generate far UVC light; and respective electrical contacts on the first surface and the second surface of the semiconductor structure. One or more dimensions of the at least one epitaxial layer in the lateral direction are within an order of magnitude of a thickness of the at least one epitaxial layer in the vertical direction. A primary light extraction surface may include at least one sidewall of the semiconductor structure extending between the first surface and the second surface and configured to emit the far UVC light. Related devices, arrays thereof, and methods of manufacture are also discussed.

Description

Priority claim

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 320,379 filed with the U.S. Patent and Trademark Office on March 16, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The present application relates to UV light sources, and more particularly, to far-UVC light sources and related apparatus and methods. Background Art

[0003] For many applications, a compact and efficient ultraviolet (UV) light source in the wavelength range of about 200 nm to about 400 nm may be desirable. For example, there is an emerging market for germicidal UV (GUV) products. UVC light (e.g., having a wavelength of about 200 nm to about 280 nm; also known as UV-C) including photons in the UVC wavelength range can be used to disinfect airborne and surface pathogens while maintaining safety for human exposure. With regard to human safety, far-UVC light (having a wavelength from about 200 nm to about 240 nm) may not penetrate the dead cell layer on the surface of the skin or the tear layer of the human eye. In particular, far-UVC light can efficiently cause permanent physical damage to DNA and / or proteins, which can prevent bacteria, viruses, and fungi from replicating. Therefore, human-safe far-UVC light can effectively kill or inactivate pathogens with little risk to humans because these wavelengths can be heavily absorbed by the stratum corneum (the top layer of dead skin cells in the epidermis) or the tear layer of the eye. That is, light in the far-UVC wavelength range may be able to quickly kill microscopic pathogens (such as bacteria) and inactivate viruses, but cannot penetrate human skin deeply enough to pose a threat of harm to humans. This could allow the use of UV light to disinfect air and surfaces in the presence of humans.

[0004] However, there may be challenges in operating in the far-UVC wavelength range. For example, few available light sources can be configured for operation under the far-UV. Some conventional far-UVC light sources have been implemented by gas discharge lamps, which generate light from excimers formed in transient plasmas. For example, a KrCl excimer lamp can generate light at 222nm. Solid-state sources of far-UVC light (e.g., light-emitting diodes (LEDs), using phosphor-based wavelength conversion in some instances) may be desirable for reducing costs and / or increasing reliability and other benefits. Although LEDs can be widely deployed and developed as solid-state light sources, such light sources typically have short operating life and poor performance at emission wavelengths shorter than about 265nm. Therefore, LEDs emitting in the far-UVC wavelength range may not be commercially available. Summary of the invention

[0005] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure including at least one epitaxial layer configured to generate far-UVC light. One or more dimensions of the at least one epitaxial layer in a lateral direction are within an order of magnitude of a thickness of the at least one epitaxial layer in a vertical direction.

[0006] In some embodiments, the semiconductor structure includes a first surface and a second surface having respective electrical contacts thereon; and at least one sidewall extending between the first surface and the second surface and configured to emit the far-UVC light.

[0007] In some embodiments, the at least one sidewall comprises opposing sidewalls of the at least one epitaxial layer extending between the first surface and the second surface, and the one or more dimensions comprise a distance between the opposing sidewalls.

[0008] In some embodiments, the at least one sidewall is configured to direct the far-UVC light into a beam or into a distributed pattern.

[0009] In some embodiments, the at least one sidewall slopes between the first surface and the second surface.

[0010] In some embodiments, at least one of the respective electrical contacts is at least partially opaque to the far-UVC light.

[0011] In some embodiments, the substrate includes the semiconductor structure on a front surface thereof. The substrate is different from a native substrate on which the semiconductor structure is formed.

[0012] In some embodiments, the substrate includes one or more optical redirection structures facing the at least one sidewall of the semiconductor structure and configured to change the propagation direction of the far-UVC light emitted from the at least one sidewall into one or more directions.

[0013] In some embodiments, the one or more optical redirection structures are attached to the front surface of the substrate adjacent to the semiconductor structure.

[0014] In some embodiments, the one or more optical redirection structures are integral to the substrate, and the surface of the substrate including the semiconductor structure thereon is recessed relative to the one or more optical redirection structures.

[0016] In some embodiments, the substrate includes a rear surface opposite the front surface and having a backside contact thereon, and at least one conductive via extending through the substrate and electrically connecting at least one of the corresponding electrical contacts of the semiconductor structure to the backside contact.

[0017] In some embodiments, the LED is free of a native substrate of the semiconductor structure.

[0018] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure configured to generate far-UVC light, the semiconductor structure including a first surface and a second surface; corresponding electrical contacts on at least one of the first surface and the second surface; and a primary light extraction surface, the primary light extraction surface including at least one sidewall of the semiconductor structure extending between the first surface and the second surface and configured to emit the far-UVC light.

[0019] In some embodiments, the at least one sidewall includes opposing sidewalls of one or more epitaxial layers of the semiconductor structure extending between the first surface and the second surface, and a distance between the opposing sidewalls is less than about 100 microns.

[0020] In some embodiments, the distance between the opposing sidewalls is less than about 50 μm.

[0021] In some embodiments, the one or more epitaxial layers of the semiconductor structure have a thickness of about 10 μm or less.

[0022] In some embodiments, the distance between the opposing sidewalls is within an order of magnitude of the thickness of the one or more epitaxial layers of the semiconductor structure.

[0023] In some embodiments, the at least one sidewall slopes between the first surface and the second surface.

[0024] In some embodiments, at least one of the respective electrical contacts is at least partially opaque to the far-UVC light.

[0025] In some embodiments, at least a portion of the first surface and / or the second surface comprises a light extraction surface configured to emit the far-UVC light.

[0026] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure configured to generate light including a wavelength in a far UVC wavelength range. The semiconductor structure includes a first surface and a second surface having respective electrical contacts thereon and one or more lateral surfaces extending between the first surface and the second surface. The total surface area of ​​the one or more lateral surfaces is within 10 times the corresponding surface area of ​​the top surface or the bottom surface.

[0027] According to some embodiments, a light emitting diode (LED) array includes a common support substrate; and a plurality of LEDs as described herein, the plurality of LEDs being arranged on a surface of the common support substrate. An optical redirection structure may be provided on the surface of the common support substrate between adjacent LEDs in the plurality of LEDs.

[0028] In some embodiments, the semiconductor structure of any of the LEDs described herein is further configured to generate UVC light.

[0029] Upon reviewing the following drawings and detailed description, other devices, apparatuses and / or methods according to some embodiments will become apparent to those skilled in the art. In addition to any and all combinations of the above-described embodiments, it is intended that all such additional embodiments are included in this specification, within the scope of the invention, and protected by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1A and Figure 1B Schematic perspective and plan views, respectively, illustrating the configuration of a conventional macro LED light source providing light emission in the far UVC spectrum.

[0031] Figure 2A and Figure 2B Schematic perspective and plan views, respectively, illustrating configurations of micro LED light sources providing far-UVC light generation according to some embodiments of the present disclosure.

[0032] Figure 3A and Figure 3B is a schematic cross-sectional view illustrating a configuration of a micro LED light source including sidewalls configured to direct far-UVC light in one or more desired directions according to some embodiments of the present disclosure.

[0033] Figure 4A and Figure 4B is a schematic cross-sectional view illustrating a configuration of a micro LED light source on a substrate including an optical redirection structure configured to direct far-UVC light in one or more desired directions according to some embodiments of the present disclosure.

[0034] Figure 5A and Figure 5B is a schematic cross-sectional view illustrating a configuration of a micro LED light source on a substrate including a recessed surface and sidewalls configured to direct far-UVC light in one or more desired directions according to some embodiments of the present disclosure.

[0035] Fig. 6A and Figure 6B is a schematic cross-sectional view illustrating a configuration of a micro-LED light source on a substrate including a recessed surface, sidewalls configured to direct far-UVC light in one or more desired directions, and through-hole electrical connections extending therethrough according to some embodiments of the present disclosure.

[0036] Fig. 7A and Figure 7B is a schematic side view illustrating a method of manufacturing a micro LED light source on a non-native substrate according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0037] Embodiments of the present disclosure provide devices for generating electromagnetic radiation in the far UVC wavelength range (about 200nm to 240nm, such as about 207nm to 222nm), which can be useful for many applications, including (but not limited to) sterilization applications for disinfecting airborne and surface pathogens, and detecting trace chemical or biological species in various field environments (air, water, etc.), while maintaining safety for human exposure and complying with human safety regulations and requirements. As used herein, "far UVC" or "Far UVC" wavelength band or range refers to wavelengths greater than about 200nm (such that the radiation is non-ionizing in the atmosphere) and less than about 240nm, for example, wavelengths of about 200nm to 230nm.

[0038] In particular, embodiments of the present disclosure provide configurations for enhancing the performance (i.e., light output) of inorganic LEDs that emit light in the far UVC portion of the electromagnetic spectrum, particularly light having wavelengths less than about 240 nm. While some custom designed LEDs and research laboratories have demonstrated LEDs having wavelengths from 260 nm down to nearly 230 nm, the efficiency of such devices drops rapidly and therefore may not be commercially viable.

[0039] Several challenges may hinder the development of LEDs configured to emit light at wavelengths below about 250 nm, many of which may be related to extracting light from the device itself. In fact, due to the difficulty in extracting light, the external quantum efficiency (EQE) of UVC LEDs may remain below 10%.

[0040] One such challenge may involve the top and bottom electrical contacts. In particular, as electrical doping levels increase, the contact to the p-side of the LED pn junction (also referred to as a p-contact) may be difficult to form with optical transparency for light in the shorter wavelength range (e.g., at about 200 nm to 230 nm or 240 nm). That is, while higher doping may be required to reduce resistance (and increase efficiency), higher doping levels may reduce optical transparency, which may make it more difficult for photons to leave the LED due to absorption by the electrical contacts. Efficiency may thereby suffer due to the opacity of the contacts. The embodiments described herein recognize tradeoffs, including design changes, which can alleviate the need for high doping levels or can benefit the efficiency of the LED by extracting photons through the surface.

[0041] Another challenge with regard to reducing wavelength may be related to the directionality of the light generated inside the LED. For example, as the aluminum content of the AlGaN material increases, the band gap may increase (and the emission wavelength of the generated light may decrease). Accompanying these changes may be a departure from the isotropic generation of photons, and toward a situation in which the optical transition dipoles inside the material may become increasingly vertical (relative to the crystal plane of the semiconductor material). The closer the transition dipole is to the ideal vertical dipole, the more anisotropic the generation of photons. Transverse electric (TE) polarization may dominate in InGaN / GaN-based blue LEDs, while transverse magnetic (TM) polarization may dominate in AlGaN / GaN UV LEDs. More clearly, as the emission wavelength decreases, the light generated inside the LED may propagate primarily at transverse angles (i.e., have greater intensity) relative to the plane of the active region (i.e., (one or more) quantum wells) of the semiconductor material. Light propagating at transverse angles (i.e., within the critical angle of total internal reflection (TIR)) is more likely to be waveguided to the edge and less likely to be emitted from the top or bottom surface of the device. As used herein, propagation can refer to the direction of travel of light (or photons) inside or outside of a semiconductor material, while emission can refer to the output of light (or photons) from a semiconductor material. Further confusing performance, the length scale for a photon to reach the edge of a macroscopic LED can be thousands of times greater than the distance it takes for a photon to reach the top or bottom surface.

[0042] Embodiments of the present disclosure can address the above and other issues by: (i) removing constraints on optical transparency or light absorption of the top or bottom (e.g., p) electrical contacts, which can simplify the design, increase internal quantum efficiency (IQE), and thus increase overall efficiency, and (ii) addressing polarization issues that may occur for shorter wavelength light (particularly, wavelengths less than about 240 nm, such as far-UVC light) by shortening the optical path to the light extraction surface, taking advantage of the fact that for wavelengths less than about 240 nm, as the Al content in the AlGaN multiple quantum wells increases, shorter wavelength light primarily propagates through the semiconductor material at lateral angles, which can significantly increase EQE. This challenge can be referred to as light extraction efficiency (LEE), where EQE = IQE × LEE. Embodiments of the present disclosure can thereby improve IQE and LEE, resulting in an overall improvement in EQE.

[0043] Embodiments of the present disclosure as described herein relate to the use of micro-scale dimensions for each individual LED (which may be referred to herein as a micro-LED or μLED) in order to achieve performance enhancements over prior art macro-scale LED designs (which may be referred to herein as macro-LEDs or macroLEDs). The benefits may come from geometry: by manufacturing LEDs with microscopic lateral dimensions (i.e., within one or two orders of magnitude of their microscopic thickness dimensions), the relative contribution of the LED edges may be much higher. In addition, due to the shorter length scale, the average contact resistance may be reduced. As an example, the embodiments described herein may be particularly suitable for UVC or far-UVC LEDs based on AlGaN semiconductor materials, but are not limited to AlGaN materials, and may also be implemented by other materials. Such materials may include (but are not limited to) boron nitride (BN), gallium nitride (GaN), silicon carbide (SiC), aluminum nitride (AlN), or other III-nitride or solid-state semiconductor materials configured to provide light emission in the far-UVC spectrum.

[0044] Figure 1A and Figure 1B 1 and 2 are perspective and plan views, respectively, illustrating the configuration of a conventional LED light source that provides light emission 105 in the far UVC spectrum. In particular, Figure 1A and Figure 1BA conventional macro-LED 10 is shown, which includes a semiconductor material 100' (e.g., an AlGaN layer) having corresponding electrical contacts 1, 2 (e.g., n-contacts and p-contacts) on the top and bottom surfaces of the semiconductor material 100'. The macro-LED 10 has a length dimension (e.g., along the x-axis or y-axis) that is greater than the thickness T of the macro-LED 10 (e.g., tens or thousands of times the thickness T). For example, the thickness T can be about 50 μm or less, while the length dimension (e.g., along the x-direction) can be about 1 millimeter (mm) or greater. Therefore, the macro-LED 10 is generally configured to couple light out of the top (or bottom) surface as a light extraction surface. However, such outcoupling can be challenging for light in the far-UVC spectrum, for example due to difficulties related to the directionality of the far-UVC light 105 generated in the LED semiconductor material 100' (e.g., having greater intensity along the horizontal or lateral direction) and the degree or amount of transparency of the electrical contacts 1, 2 to the far-UVC light 105. In particular, as described above, it can be difficult to form a p-contact 1 that has both desirable electrical properties (eg, low resistance) and desirable optical properties (eg, transparency to light in the far UVC spectrum).

[0045] Embodiments of the present disclosure provide "micro" LEDs, in which the lateral length scale (eg, in the x and / or y directions) of the LED is reduced, which may address and / or eliminate the above-noted and / or other challenges. Figure 2A and Figure 2B 1 and 2 are perspective and plan views, respectively, illustrating a configuration of a micro-LED light source 20 that provides far-UVC light 105 generation according to some embodiments of the present disclosure. Although primarily described with reference to the generation of far-UVC light, the light output 105 of the micro-LED light source is not limited to the far-UVC wavelength range, and in some embodiments, may include or may be configured to generate light including wavelengths in a wider UVC wavelength range (also referred to herein as UVC light).

[0046] Figure 2A and Figure 2B The micro LED 20 according to some embodiments of the present disclosure includes Figure 1A and Figure 1B. In both cases, the thickness of the LEDs 10, 20 may be determined by the thickness T, t of the semiconductor structure 100', 100. In the micro-LED 20 according to some embodiments of the present disclosure, the thickness t may be in the range of about 0.1 micrometers (μm) to about 20 μm, for example, in the range of about 0.1 μm to about 10 μm, or in the range of about 0.5 μm to about 5 μm. As used herein, the semiconductor structure 100 may include one or more layers of semiconductor material configured to generate light in the far UVC wavelength range, also referred to as far UVC light 105. In some embodiments, the semiconductor material may be formed (e.g., epitaxially grown) on a source substrate or wafer (referred to herein as a native substrate), which may or may not be removed from the LED light source described herein.

[0047] For Figure 1A and Figure 1B In the macro-LED 10 shown in FIG. , the lateral dimensions of the epitaxial layers (e.g., along the x and / or y directions) can exceed the thickness T by a ratio of more than about 1000:1. This presents a challenge for photons emitted in-plane, since the LED material can typically reabsorb emitted photons. The probability of a photon reaching an edge or sidewall 15 of the semiconductor structure 100' may decrease exponentially with (a) the distance to the edge and (b) the relative strength of the transition dipole at that orientation. Because of this problem, the macro-LED 10 can include features in the top and / or bottom surfaces 1, 2 to enhance the coupling of light out of the LED through these surfaces. Doing so can increase the extraction efficiency of light from the LED (where photon extraction efficiency = EQE / IQE).

[0048] and Figure 1A and Figure 1BCompared to the macro-LED 10 shown in FIG. 1 , the micro-LED 20 according to some embodiments of the present disclosure may have (one or more) semiconductor light emitting layers (e.g., epitaxial layers) having one or more lateral dimensions (e.g., in the (one or more) horizontal (x and / or y) directions in the figure or along the surface of the contacts 110, 120, also referred to as the lateral direction) that are approximately the same scale as the thickness of the (one or more) semiconductor light emitting layers of the device (e.g., in the vertical (z) direction perpendicular to the (one or more) lateral directions in the figure). The lateral dimension may refer to the length, width, diameter, major axis, etc., depending on the shape defined by the semiconductor light emitting layer. That is, the micro-LED as described herein may have (one or more) epitaxial layers having one or more dimensions x, y in the lateral direction, the one or more dimensions x, y being of the order of magnitude of its thickness dimension t in the vertical direction (e.g., having similar dimensions or within at least one order of magnitude or several orders of magnitude, including less than, greater than, or substantially equal to). For example, the microLED may include a semiconductor structure 100 having (one or more) semiconductor epitaxial layers, wherein the total thickness t of the semiconductor epitaxial layers is about 15 or 20 μm or less (e.g., about 0.1 to 10 μm, or about 0.5 to 5 μm), and the microLED may include one or more lateral dimensions x, y of less than about 500 μm (e.g., less than about 100 μm, less than about 50 μm, or about 1 to 10 μm). In some embodiments, the (one or more) epitaxial layers of the semiconductor structure 100 may have a thickness t of about 7 μm to about 12 μm (after removal from a native substrate, such as via laser lift-off), and may have lateral dimensions x, y between about 3 μm and about 50 μm. The (one or more) edges or (one or more) sidewalls 115 (also referred to as (one or more) lateral surfaces) of the semiconductor structure 100 of the microLED 20 may provide a primary light extraction surface 115.

[0049] The benefit of such lateral dimension(s) may come from the realization that the physical distance any given photon must traverse before reaching an edge or sidewall of the device to be outcoupled may be orders of magnitude shorter than some macroscopic designs. Figure 2A and Figure 2B As shown in , semiconductor structure 100 is configured to generate photons in the far UVC wavelength range that propagate primarily at substantially lateral angles relative to the active region of the semiconductor material (shown in the figure in a horizontal or lateral direction). Figure 2A and Figure 2BAs shown by the dashed lines in , the intensity of the generated far-UVC light 105 decreases significantly with deviation from the lateral direction. The lateral dimensions (one or more) of the semiconductor active layer (s) of the micro-LED 20 are configured to shorten the optical path length of the output photons (i.e., far-UVC light 105) at the light extraction surface 115 at one or more sidewalls 115 of the semiconductor structure 100. According to some embodiments of the present disclosure, the reduced physical distance or optical path length of the micro-LED 20 including the epitaxial layer having lateral dimensions x, y can provide an exponentially higher probability of photon extraction at the far-UVC wavelength, and therefore, can be critical to increasing the quantum efficiency to a level sufficient to be feasible.

[0050] More specifically, Figure 2A and Figure 2B A semiconductor structure 100 is shown including a first surface 101, a second surface 102, and respective electrical contacts 110, 120 (e.g., n-contacts and p-contacts) on the first and second surfaces 101, 102. At least one sidewall 115 extends between the first and second surfaces 101, 102 and provides a primary light extraction surface 115 configured to emit far-UVC light 105. In some embodiments, multiple (e.g., opposing) sidewalls 115 of (one or more) epitaxial layers of the semiconductor structure 100 may provide the primary light extraction surface 115, and the distance between the opposing sidewalls 115 along the lateral direction may be of the order of magnitude (e.g., within one or two orders of magnitude) of the thickness t of (one or more) epitaxial layers of the semiconductor structure 100 along the vertical direction. For example, the distance between the opposing sidewalls 115 along the lateral direction may be less than about 100 microns (e.g., less than about 50 μm, or about 1 to 10 μm). Therefore, a micro-LED 20 including a sidewall or lateral surface 115 for primary light extraction may be considered an edge emitting device.

[0051] It will be appreciated that while described herein with reference to the sidewalls or side surfaces 115 of the semiconductor structure 100 as the primary light extraction surface 115, embodiments of the present disclosure are not limited to light extraction only from the sidewalls or side surfaces 115. For example, in some embodiments, at least a portion of the first and / or second surfaces 101, 102 having respective electrical contacts 110, 120 thereon may also provide a light extraction surface configured to emit far-UVC light 105, and thus may provide a secondary light extraction surface.

[0052] The benefit of such lateral dimension(s) may also come from the recognition that the relative amount of surface area contributed by the lateral edges of the microLED (e.g., on opposite ends of the microLED, compared to the surface area of ​​the top and / or bottom surfaces) may be much higher than for a macroLED (where the top / bottom surfaces have significantly larger surface areas than the lateral edges). For example, a microLED having lateral dimensions of about 1 μm×1 μm to about 50 μm×50 μm may have a surface area of ​​about 1 to about 2500 μm. 2 , and a lateral surface 115 having a total area of ​​about 0.1 to about 2000 μm. Thus, in some embodiments, the total surface area of ​​one or more lateral surfaces 115 of the semiconductor structure 100 can be within 10 times (e.g., within about 5 times, or within about 5 times to 10 times) of the corresponding surface area of ​​the top surface or bottom surface of the semiconductor structure 100. That is, a micro-LED as described herein may include an epitaxial layer having one or more lateral dimensions x, y and / or a lateral edge surface area, wherein the one or more lateral dimensions x, y are of the order of magnitude of its thickness dimension t (e.g., within the order of magnitude of or within 5 times of), and the lateral edge surface area is of the order of magnitude of its top / bottom surface area.

[0053] In addition, by increasing the contribution of the lateral edge surfaces of the device to light emission, the micro-LED according to some embodiments of the present disclosure can decouple the photon extraction surface from the surface on which the current is introduced (typically the top and bottom surfaces 101, 102 having the electrical contacts 110, 120 thereon). In this way, the issues of optical transparency (for efficiency) and doping level (i.e., contact resistance) and the trade-offs therebetween can be completely avoided, thereby providing improved efficiency in the far-UVC spectrum. In some embodiments, one or more of the electrical contacts 110, 120 can be formed of a material and / or doping level without optical transparency requirements to provide a reduced resistance and / or ohmic contact to the semiconductor structure 100. In particular, one or more of the electrical contacts 110, 120 can be partially (e.g., greater than 10%, greater than 25%, or greater than 30%) or substantially (e.g., greater than 50%, greater than 75%, or greater than 90%) or completely (100%) opaque to the far-UVC light 105. That is, a micro-LED including a lateral light extraction surface 115 as described herein may allow for the use of (semi-)opaque electrical contacts 110 and / or 120 in order to achieve both greater light extraction efficiency and reduced electrical resistance.

[0054] For example, for semiconductor contacts, the resistance may include the contact resistance (Ohm cm 2 ) / Area(cm 2 By reducing the lateral dimensions x, y, area (cm) of the LED as described herein 2) can be reduced by several orders of magnitude, which can increase contact resistance. Although this may present challenges, micro-LEDs as described herein can provide primary light extraction surfaces at one or more sidewalls 115 of the device, which can allow electrical contacts that are not constrained by optical transparency requirements (e.g., the electrical contacts can be partially or completely opaque with respect to far-UVC light), which can allow for reduced resistance and can also further improve efficiency at any doping level. Some embodiments can provide far-UVC emitting LEDs in which the contact resistance is less than (e.g., less than one-half of, or less than more than an order of magnitude of) the contact resistance achievable in some macro-LEDs (due to optical transparency requirements for electrical contacts of macro-LEDs that emit light from the top and / or bottom surfaces). For example, in some embodiments, a far-UVC emitting LED including electrical contacts 110, 120 can have a contact resistance of less than about 3×10 -3 Ohm / cm 2 The electrical contacts 110 , 120 may be substantially or completely opaque to far-UVC light as described herein.

[0055] Figure 2A and Figure 2BGeneral embodiments of the present disclosure are shown, and in particular, inventive concepts of shorter length / lateral dimensions are shown (e.g., wherein (one or more) epitaxial layers of a micro-LED have one or more lateral dimensions x, y that are less than 500 μm (e.g., less than about 100 μm, less than about 50 μm, or about 1 to 10 μm) or are on the order of their thickness t). Additional example embodiments may include, but are not limited to, one or more of the following: providing a p-contact on a bottom surface of the microLED (rather than on a top surface), and providing an n-contact on a top surface (rather than on a bottom surface); patterning the p- and n-contacts on the top and bottom surfaces of the microLED (e.g., over an entire surface area less than the top and bottom surfaces of the epitaxial layer(s) of the semiconductor structure 100), rather than forming the p- and n-contacts by blanket-covering the top and bottom surfaces of the semiconductor structure 100; forming the epitaxial layer(s) of the semiconductor structure 100 from a material such as hexagonal boron nitride or gallium nitride (GaN) or silicon carbide (SiC) or pure aluminum nitride (AlN) or other Group III nitride or solid-state semiconductor material, the material being configured to provide light emission in the far-UVC spectrum; providing at least one lateral dimension of up to about 100 μm; and / or removing the native growth substrate of the semiconductor structure 100 (i.e., providing the semiconductor structure 100 on a substrate different from the native growth substrate on which the semiconductor structure 100 was formed; also referred to herein as a non-native substrate). It will also be understood that light sources according to embodiments of the present disclosure based on any of the micro-LED configurations as described herein (e.g., 20, 30a, 30b, 40a, 40b, 50, 60a, 60b, 70) can be included in large arrays (e.g., hundreds or thousands or tens of thousands of micro-LEDs), where the number of micro-LEDs in the array can be selected to achieve a total amount of desired light output from the light source.

[0056] Other embodiments described herein illustrate Figure 2A and Figure 2B Examples of modifications of some elements of the micro-LED device shown in FIG. 1 to improve or change performance. For example, Figure 3A and Figure 3B is a schematic cross-sectional view illustrating a configuration of micro LED light sources 30a, 30b including sidewalls 115' configured to direct far-UVC light 105 in one or more desired directions, according to some embodiments of the present disclosure.

[0057] In particular, Figure 3A and Figure 3BIn the embodiment of the present invention, the semiconductor structure 100 of the micro-LEDs 30a, 30b includes a sidewall or side surface 115' that is tilted or angled (i.e., not perpendicular to the surfaces 101, 102 having the electrical contacts 110, 120 thereon). The sidewall or side surface 115' can be optimized or otherwise configured to direct the far-UVC light 105 upward out of the array plane (e.g., in a direction away from the native substrate 300a or the non-native substrate 300b). In some embodiments, the corresponding sidewall 115 can include multiple tilt angles in some embodiments (e.g., it can be multi-faceted when it extends between the top and bottom surfaces of the semiconductor structure 100). In other embodiments, the sidewall can have more complex structuring to increase the output portion of the light or modify the far-field pattern angular distribution of the output light. Additional examples of modifications to the sidewall 115 that emit far-UVC light 105 in one or more desired directions may be achieved by changing or altering the crystal orientation of the semiconductor material (e.g., by providing a sidewall 115' that is offcut relative to one or more crystal axes of the semiconductor material) and / or the surface roughness of the sidewall. For example, by providing a coating or pattern 315 on the sidewall 115', the optical modification of the sidewall 115' of the micro-LED may be optimized or otherwise configured to propagate light into a particular distribution pattern 105p (e.g., Figure 3B ), or directing the light as or into beam 105b (as shown in Figure 3A ). More generally, one or more of the sidewalls 115 ′ of the semiconductor structure 100 may be configured to provide a light extraction surface that directs the far-UVC light 105 into a light beam 105 b or a distributed light pattern 105 p.

[0058] In some embodiments, the micro-LEDs 30a may be provided on and supported by a native substrate 300a (eg, AlN, sapphire, GaN, or other substrate) for epitaxial growth of semiconductor materials of the semiconductor structure 100, such as Figure 3A In other embodiments, the micro-LEDs 30b may be provided on and supported by a non-native substrate 300b (e.g., a silicon substrate or other substrate) that is different from the material or substrate (e.g., a source wafer) on which the LED semiconductor material or structure 100 is grown or formed. In some embodiments, transferring the micro-LEDs from their native substrate 300a (e.g., a source wafer) to the non-native support substrate 300b may be accomplished by micro-transfer printing, but it will be understood that the embodiments described herein may include a variety of manufacturing methods and may not be limited to any particular manufacturing method.

[0059] There are other embodiments of the present disclosure (for example Figure 4A and Figure 4B) may include configurations in which the micro-LEDs 20, 30a, 30b are accompanied by reflective or other optical redirection structures 415 provided on or by the supporting substrates 300a, 300b. In particular, Figure 4A and 4B 4 is a schematic cross-sectional view showing configurations 40a, 40b of micro LED light sources 20 on substrates 300a, 300b including optical redirection structures 415a, 415b (collectively 415) according to some embodiments of the present disclosure. Figure 2A and Figure 2B Various configurations of the micro-LED 20 are described, but it will be understood that according to embodiments of the present disclosure, the illustrated micro-LED 20 may be replaced with other micro-LED configurations (e.g., micro-LEDs 30a, 30b having inclined sidewalls 115' on native or non-native substrates 300a, 300b).

[0060] The optical redirection structure 415 is disposed on the substrate 300a, 300b facing the light extraction surface 115 provided by the sidewall(s) of the semiconductor structure 100 (e.g., attached to the front surface 300f of the non-native substrate adjacent to the semiconductor structure 100), and is configured to change the propagation direction of the far-UVC light 105 output therefrom. For example, the optical redirection structure 415 can reflect light in the far-UVC wavelength range, and can be shaped or otherwise configured to direct the far-UVC light 105 output from the lateral edges of the micro-LEDs into one or more desired directions or in a desired angular far-field pattern.

[0061] Figure 4A An example configuration 40a is shown in which the optical redirection structure 415a is a patterned reflective structure (e.g., an aluminum structure) that is fabricated with relatively flat or smooth angled edge surfaces that are configured to redirect laterally emitted light from the micro-LEDs into one or more different directions (shown as upward and away from the supporting substrate 300a, 300b) to provide a controlled illumination pattern (e.g., light beam 105b or a desired distributed light pattern 105p). Figure 4B An example configuration 40b is shown in which the optical reflective structure 415b is a patterned reflective structure (e.g., an aluminum structure) including a non-uniform or asymmetric surface to redirect the laterally emitted light from the micro-LEDs into an irregular or otherwise non-uniform illumination pattern in one or more directions away from the supporting substrate 300a, 300b. The supporting substrate 300a, 300b can be a native substrate (e.g., a sapphire substrate of an AlGaN semiconductor structure) or a non-native substrate (e.g., a silicon substrate). Figure 4A and Figure 4BIn Examples 40a, 40b, the optical redirection structure 415 is shown to be formed of a material different from the supporting substrate 300a, 300b and arranged on the surface of the supporting substrate 300a, 300b (e.g., using micro-transfer or other techniques), but the embodiments of the present disclosure are not limited to this.

[0062] For example, further embodiments of the present disclosure may incorporate optical or light redirecting structures into the supporting substrate itself, eliminating the need to add additional features on the top surface of the supporting substrate. Figure 5A and Figure 5B is a schematic cross-sectional view showing a configuration 50 of a micro LED light source 20 on a substrate 500 according to some embodiments of the present disclosure, the substrate 500 including a recessed surface 500r and an adjacent side surface 500s, the recessed surface 500r and the adjacent side surface 500s being configured to direct far-UVC light 105 in one or more desired directions. Thus, the side surface 500s of the substrate 500 can provide an optical redirection structure 415' formed of the same material as the substrate 500 and integral with the substrate 500, wherein a surface of the substrate 500 includes a semiconductor structure 100 recessed thereon relative to the one or more optical redirection structures 415'.

[0063] For example, before placing or arranging the micro LED device 20 on the recessed surface 500r within the pit, a light redirecting structure (under the Figure 5A and Figure 5B 4 and 5). In particular, the non-native substrate 500 can be patterned (e.g., by one or more selective or isotropic etching processes) to form the recessed surface 500r and surrounding side surfaces 500s, such that the side surfaces 500s define an optical redirection structure 415' that is configured to provide increased or improved light extraction.

[0064] like Figure 5A and Figure 5BAs shown in , the side surfaces 500s of the inverted pyramid structure are formed at corresponding angles (relative to the recessed surface) to form an optical redirection structure 415', which is configured to direct light emitted from the edge of the micro-LED 20 out of the plane, or otherwise change the propagation direction of the far-UVC light 105 away from the lateral direction. For example, the side surface 500s can be at an angle of about 45 degrees or less relative to the lateral direction of light emission. The (one or more) materials of the supporting substrate 500 and / or one or more layers thereon can be configured to reflect light in the far-UVC wavelength range. Some embodiments may further provide a reflection enhancing coating or pattern 515 on the angled side surface 500s to enhance the reflection of the far-UVC light 105 (e.g., with respect to efficiency and / or direction).

[0065] In particular, Figure 5A It is shown that a mask 501 (e.g., an oxide or nitride mask) and an etching process (e.g., TMAH or other isotropic etching process) can be used to selectively form one or more recessed surfaces 500r at a depth d relative to the top surface of a substrate 500 (e.g., a silicon substrate). The recessed surface 500r may have a width W greater than the opening formed at the top surface of the substrate 500. top Narrower width W bottom and can be along the {100} crystal plane of the silicon substrate 500 or <100> The etching process may form a side surface 500s in the silicon substrate 500, the side surface 500s being adjacent to or surrounding the recessed surface and being angled relative to the recessed surface 500r along a {111} crystal plane or <111> The shape of the side surface 500s is not limited to Figure 5A The examples shown in , and more generally, may include any features that can be etched or otherwise patterned into the supporting substrate 500 to define an optical redirection structure 415' facing the primary light extraction surface 115 of the micro-LED 20 and configured to change the propagation direction of the far-UVC light 105 emitted therefrom into one or more directions.

[0066] Figure 5BAn arrangement or placement of micro-LEDs 20 on a recessed surface 500r of a substrate 500 is shown. The micro-LEDs 20 may be arranged in the center of the recessed surface 500r (i.e., at a substantially equal distance from the corresponding side surface 500s), or may be offset to one of the side surfaces 500s as shown. The process for arranging or placing the micro-LEDs on the patterned surface of the substrate 500 may be, for example, micro-transfer printing, but it will be understood that the embodiments described herein are not limited to any particular manufacturing method. In addition, some embodiments may provide a single micro-LED on the recessed surface 500r within each pit, while other embodiments may provide multiple micro-LEDs on the recessed surface 500r within the corresponding pit (e.g., such that each recessed surface 500r includes one or more micro-LEDs thereon), wherein the light extraction surface 115 faces the optical redirection structure 415' formed by the side surface 500s of the substrate 500.

[0067] Still other embodiments may provide one or more electrical connections to the electrical contacts 110 , 120 of the micro LEDs 20 via conductive vias 611 extending through the support substrate 500 . Fig. 6A and Figure 6B is a schematic cross-sectional view showing a configuration 60a, 60b of a micro LED light source 20 on a substrate 500 according to some embodiments of the present disclosure, the substrate 500 including a side surface 500s configured to direct far-UVC light 105 in one or more desired directions, a recessed surface 500r, and a through hole 611 electrical connection extending therethrough.

[0068] like Fig. 6A and Figure 6B As shown in FIG, the substrate 500 includes a back surface 500b opposite a front surface 500f having thereon a micro-LED 20. The back surface 500b includes thereon one or more backside contacts 610, 620 that are electrically connected to corresponding electrical contacts 110, 120 (e.g., n-contacts and p-contacts) of the micro-LED 20 through one or more through-wafer vias 611 (also referred to herein as conductive vias 611) and / or other conductive interconnects 612 extending through the substrate 500. Fig. 6A Configuration 60a is shown where each contact includes a single via 611, which in this example contacts the N-type contact or N-terminal of the micro-LED. Fig. 6A As shown in , some embodiments may provide micro LEDs 20 directly on top of the through-holes. In other embodiments, as shown in Figure 6B As shown in , a plurality of through wafer vias 611 extend through the substrate 500 to provide electrical contact with the N terminal and the P terminal of the micro LED 20. Fig. 6A and Figure 6BAs shown in , an interlayer dielectric (ILD) 615 (or other non-conductive coating that is substantially transparent to far-UVC light 105) can be provided to electrically insulate the sidewalls 115 of the micro-LEDs 20 to prevent electrical shorting. Other embodiments can use other implementations (e.g., wire bonding) to provide access and electrical connection to the top electrical contact (e.g., p-contact).

[0069] More generally, the vias 611 can provide electrical connections between the front side and the back side of the support substrate 500 having the micro LEDs 20 thereon. Fig. 6A and Figure 6B In the examples 60a and 60b shown in FIG. 6 , the through hole 611 is combined with Figure 5A and Figure 5B The through hole 611 is implemented with the substrate 500 having an inverted pyramid or pit structure, but it will be understood that the through hole 611 can be used in combination with any of the substrates described herein (e.g., 300a, 300b).

[0070] Fig. 7A and 7B is a schematic side view illustrating a method of manufacturing a micro LED light source 20 on a non-native substrate 500 according to some embodiments of the present disclosure. Fig. 7A and 7B As shown in , in some embodiments, micro-transfer printing techniques can be used as an assembly method for manufacturing micro-LED arrays (e.g., comprising hundreds or thousands) on a common support substrate 500. In micro-transfer printing, the (micro-LED) devices can be removed from their native substrate (i.e., released from the native substrate on which the semiconductor structure 100 is formed) and placed or "printed" onto a different or non-native substrate 500 using an elastomeric or other stamp.

[0071] In particular, Fig. 7A Prior to assembly, a non-native support substrate (e.g., 300b, 500) is provided. The non-native substrate 300b, 500 may include a front surface 300f, 500f configured to support one or more micro-LEDs, and a rear surface opposite the front surface 300f, 500f. The front surface 300f may be a substantially flat surface, and in some embodiments, an optical redirection structure 415' may be arranged or placed on the front surface 300f of the substrate 300b between adjacent micro-LEDs 20 to redirect the propagation direction of the far-UVC light 105 output therefrom into one or more directions away from the substrate. In other embodiments, such as Fig. 7AAs shown in , the front surface 500f of the non-native substrate 500 can be a complex surface, which includes a plurality of recessed surfaces 500r or pits surrounded by protruding side surfaces 500s, and the protruding side surfaces 500s are configured to redirect the propagation direction of the far-UVC light 105 output from one or more micro-LEDs 20 into one or more directions away from the substrate 500.

[0072] Still refer to Fig. 7A , the stamp may include corresponding posts sized to removably adhere one or more micro LEDs 20 thereto. In some embodiments, the elastic transfer stamp may be configured and / or optimized to enable micro-transfer of micro LEDs 20 onto complex or patterned substrates 500 such as those described above. In particular, the elastic transfer stamp 700 may include posts having a height and / or a tapered profile that provides sufficient clearance to extend between the protruding side surfaces 500s of the substrate 500, the protruding side surfaces 500s surrounding the recessed surfaces 500r or pits therein, which may be different from the shape of elastic stamps or posts that are typically used for micro-transfer on smooth, flat substrates.

[0073] For example, stamp posts according to some embodiments of the present disclosure may be shaped as a (nearly) mirror image or otherwise corresponding to a shape of an inverted pyramid or other patterned or non-planar substrate geometry. Fig. 7A and 7B The stamp configuration shown in can allow for overall taller pillars to maintain sufficient strength, for example, with a wider "base" (at the top) that tapers toward the stamping surface to accommodate the topology of a patterned or otherwise non-planar substrate 500. Figure 7B As shown in , the tapered posts of the stamp can be adapted to the dimensions of the patterned substrate 500 so as to transfer the micro-LEDs 20 from their posts to the recessed surface 500r of the substrate 500, in some instances directly to the conductive vias 611 or other conductive interconnects exposed on or at the front surface 500f. Thus, in some embodiments, micro-LEDs can be transferred to a non-native support substrate 500 using an elastic stamp whose posts are designed or otherwise configured to match or approximately correspond to the topology of the (complex) support substrate 500.

[0074] Transferring the microLEDs 20 to a non-native support substrate 500 (by microtransfer or other means) as described herein may be advantageous, at least because providing an array of multiple microLEDs 20 on their native substrates may be difficult to manage. For example, a native substrate may typically be about 400 μm thick, while each microLED 20 may have a corresponding lateral dimension of about 10 μm, which may result in an undesirable aspect ratio and / or poor density or substrate area utilization. In addition, there may not be enough area on top of each microLED 20 for wire bonding (which typically requires a 50 μm-75 μm wide metal bonding pad). In contrast, microLEDs provided on a common non-native support substrate 300b, 500 as described herein may be connected by vias 611 and / or other conductive interconnects 612 (including thin film interconnects) in and / or on the surface of the non-native substrate 300b, 500. In some embodiments, the non-native substrate 300b, 500 may be optically transparent to far UVC light.

[0075] According to some embodiments of the present disclosure, micro-LEDs (also referred to as μLEDs) having one or more lateral dimensions x, y less than about 100 microns can provide higher optical efficiency at low (e.g., far UVC) wavelengths, which can produce higher power output based on or including (but not limited to) one or more of the following: higher light extraction efficiency; shorter distance to the edge or between opposing edges of the semiconductor material (i.e., higher perimeter to area ratio) on the order of its thickness t; substantial or majority light extraction through a lateral surface 115 (sidewall or edge) of the LED rather than through a top or bottom surface, which can allow for reduced (or no) transparency requirements for electrical contacts 110, 120 on the top / bottom surfaces; and reduced resistance of the electrical contacts 110, 120 due to shorter lateral dimensions x, y of the surfaces 101, 102 of the epitaxial layer(s) of the semiconductor structure 100 on which the electrical contacts 110, 120 are provided.

[0076] In some embodiments, the micro-LEDs can have lateral dimensions as small as 1 μm and as large as 20 μm (e.g., 1 μm×1 μm, 2 μm×2 μm, 3 μm×3 μm, 10 μm×10 μm, or 20 μm×20 μm), such that the perimeter to area ratio is as high as about 4, or as low as about 0.2.

[0077] In some embodiments, the substrate (eg, native substrate) may be removed to allow light extraction (eg, via flip chip technology) through the bottom or top surface of the semiconductor structure 100. In some embodiments, the top and / or bottom surfaces of the semiconductor structure 100 may be substantially free of light extraction features.

[0078] In some embodiments, a plurality of micro-LEDs as described herein may be arranged in an array configuration and electrically connected on a surface of a non-native substrate. The array may include a plurality of optical redirection structures located on or otherwise protruding from the surface of the non-native substrate between corresponding ones of the micro-LEDs.

[0079] Thus, embodiments of the present disclosure may address issues regarding light extraction efficiency of far-UVC light 105 generated by an LED (e.g., due to absorption by the p-contact and / or the semiconductor structure 100 itself) by recognizing that shorter wavelength photons may propagate primarily at lateral angles (e.g., in a lateral direction as shown in the figure) and configuring the light emitting or light extraction surface 115 of the LED to shorten the optical path length of the output of the photons to increase or maximize the output efficiency.

[0080] Some benefits of embodiments of the present disclosure may include, but are not limited to, improved performance of LEDs operating with light emission at wavelengths in the far UVC wavelength range (approximately 200-240 nm). In particular, LEDs fabricated using aluminum gallium nitride (AlGaN) material systems may benefit, but the benefits as described herein may also apply to other material systems and are not limited to GaN-based or III-nitride-based materials.

[0081] By improving the performance of LEDs in the far-UVC wavelength range (i.e., light output per unit of electrical input), embodiments of the present disclosure may provide new solid-state sources for use in germicidal UV applications, where current AlGaN LED technology may be fundamentally challenged. Commercial applications of far-UVC lighting according to embodiments of the present disclosure may include eliminating pathogens from the air and / or surfaces in any indoor space where humans gather (e.g., airports, schools, hospitals, residential care centers, workplaces, etc.), as well as in transportation vehicles (e.g., subways, trains, taxis, airplanes) and agricultural facilities (e.g., animal production facilities, meat processing facilities, indoor greenhouses, etc.).

[0082] Various embodiments have been described herein with reference to the accompanying drawings in which example embodiments are shown. However, these embodiments may be embodied in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure is thorough and complete and fully conveys the inventive concept to those skilled in the art. Various modifications to the example embodiments and the general principles and features described herein will be readily apparent. In the accompanying drawings, the sizes and relative sizes of layers and regions are not shown to scale and may be magnified in some instances for clarity.

[0083] The example embodiments are described primarily in terms of the specific methods and apparatus provided in a particular implementation. However, the methods and apparatus may operate effectively in other implementations. Phrases such as "example embodiment," "one embodiment," and "another embodiment" may refer to the same or different embodiments as well as multiple embodiments. The embodiments will be described with respect to systems and / or apparatus having certain components. However, the systems and / or apparatus may include fewer or additional components than those shown, and changes to the arrangement and types of components may be made without departing from the scope of the inventive concept.

[0084] The example embodiments will also be described in the context of a particular method with specific steps or operations. However, the methods and apparatus may operate effectively with other methods having different and / or additional steps / operations and steps / operations in a different order that is inconsistent with the example embodiments. Therefore, the inventive concept is not intended to be limited to the embodiments shown, but rather to the widest scope consistent with the principles and features described herein.

[0085] It will be understood that when an element is referred to or shown as being "on another element," "connected" or "coupled" to another element, it can be directly on, connected or coupled to the other element, or intervening elements may be present. Conversely, when an element is referred to as being "directly on another element," "directly connected" or "directly coupled" to another element, there are no intervening elements.

[0086] It will also be understood that although the terms first, second, etc. can be used to describe various elements in this article, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the present disclosure, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element.

[0087] In addition, relative terms (such as "lower" or "bottom" and "upper" or "top") can be used herein to describe the relationship of one element to another element, as shown in the figure. It will be understood that relative terms are intended to include different orientations of the device in addition to the orientation depicted in the figure. For example, if the device in one of the figures is turned over, the element described as being on the "lower" side of the other elements will be oriented on the "upper" side of the other elements. Therefore, the exemplary term "lower" can include both "lower" and "upper" orientations, depending on the specific orientation of the figure. Similarly, if the device in one of the figures is turned over, the element described as being "below" or "below" the other elements will be oriented "above" the other elements. Therefore, the exemplary term "below" or "below" can include both upper and lower orientations.

[0088] The terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification and the appended claims, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0089] It will also be understood that the term "and / or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items. It will also be understood that the terms "include, including" and / or "comprise, comprising" when used in this specification specify the presence of stated features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0090] Embodiments of the present disclosure are described herein with reference to the illustrations, which are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. Therefore, variations from the illustrated shapes will be expected due to, for example, manufacturing techniques and / or tolerances. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of device regions and are not intended to limit the scope of the invention.

[0091] Unless otherwise defined, all terms (including technical and scientific terms) used in the disclosed embodiments have the same meaning as those of ordinary skill in the art to which the present invention belongs, and are not necessarily limited to the specific definitions known when describing the present invention. Therefore, these terms may include equivalent terms created after such a time. It will also be understood that terms (such as those defined in common dictionaries) should be interpreted as having the same meaning as their meanings in the context of this specification and related art, and unless clearly defined in this article, should not be interpreted in an expected or overly formal sense. All publications, patent applications, patents and other references mentioned herein are combined by reference in their entirety.

[0092] In conjunction with the above description and the accompanying drawings, many different embodiments have been disclosed herein. It will be understood that literally describing and illustrating every combination and sub-combination of these embodiments would be overly repetitive and confusing. Therefore, this specification, including the accompanying drawings, should be interpreted as constituting a complete written description of all combinations and sub-combinations of the embodiments of the present invention described herein, as well as the manner and process of making and using them, and should support claims directed to any such combination or sub-combination.

[0093] Although the present invention has been described herein with reference to various embodiments, it will be appreciated that further changes and modifications may be made within the scope and spirit of the principles of the present invention. Although specific terms are used, they are used only in a general and descriptive sense, rather than for limiting purposes, and the scope of the present invention is set forth in the following claims.

Claims

1. A light emitting diode (LED), comprising: a semiconductor structure comprising at least one epitaxial layer configured to generate far-UVC light, One or more dimensions of the at least one epitaxial layer in a lateral direction are within the order of magnitude of a thickness of the at least one epitaxial layer in a vertical direction.

2. The LED according to claim 1, wherein The semiconductor structure comprises: a first surface and a second surface having respective electrical contacts thereon; and At least one sidewall extends between the first surface and the second surface and is configured to emit the far-UVC light.

3. The LED according to claim 2, wherein: The at least one sidewall includes opposing sidewalls of the at least one epitaxial layer extending between the first surface and the second surface, and the one or more dimensions include a distance between the opposing sidewalls.

4. The LED according to claim 2, wherein: The at least one sidewall is configured to direct the far-UVC light into a beam or into a distributed pattern.

5. The LED according to claim 2, wherein: The at least one side wall is inclined between the first surface and the second surface.

6. The LED according to claim 2, wherein: At least one of the respective electrical contacts is at least partially opaque to the far-UVC light.

7. The LED according to any preceding claim, further comprising: A substrate includes the semiconductor structure on a front surface thereof, wherein the substrate is different from a native substrate on which the semiconductor structure is formed.

8. The LED according to claim 7, wherein: The substrate includes one or more optical redirection structures facing the at least one sidewall of the semiconductor structure and configured to redirect a propagation direction of the far-UVC light emitted from the at least one sidewall into one or more directions.

9. The LED according to claim 8, wherein: The one or more optical redirection structures are attached to the front surface of the substrate adjacent to the semiconductor structure.

10. The LED according to claim 8, wherein: The one or more optical redirection structures are integral with the substrate, and the surface of the substrate including the semiconductor structure thereon is recessed relative to the one or more optical redirection structures.

11. The LED according to claim 8, wherein: The substrate comprises: a rear surface opposite the front surface and having a backside contact thereon; and At least one electrically conductive via extends through the substrate and electrically connects at least one of the corresponding electrical contacts of the semiconductor structure to the backside contact.

12. An LED according to any preceding claim, wherein The LED is free of a native substrate for the semiconductor structure.

13. An LED according to any preceding claim, wherein The semiconductor structure is also configured to generate UVC light.

14. A light emitting diode (LED), comprising: a semiconductor structure configured to generate far-UVC light, the semiconductor structure comprising a first surface and a second surface; a corresponding electrical contact on at least one of the first surface and the second surface; as well as A primary light extraction surface includes at least one sidewall of the semiconductor structure extending between the first surface and the second surface and configured to emit the far-UVC light.

15. The LED according to claim 14, wherein The at least one sidewall includes opposing sidewalls of one or more epitaxial layers of the semiconductor structure extending between the first surface and the second surface, and a distance between the opposing sidewalls is less than about 100 microns.

16. The LED according to claim 15, wherein The distance between the opposing sidewalls is less than about 50 μm.

17. The LED according to claim 15, wherein: The one or more epitaxial layers of the semiconductor structure have a thickness of about 10 μm or less.

18. The LED according to claim 15, wherein The distance between the opposing sidewalls is within an order of magnitude of the thickness of the one or more epitaxial layers of the semiconductor structure.

19. The LED according to claim 14, wherein: The at least one side wall is inclined between the first surface and the second surface.

20. The LED according to claim 14, wherein At least one of the respective electrical contacts is at least partially opaque to the far-UVC light.

21. The LED according to any one of claims 14 to 20, further comprising: A substrate comprising the semiconductor structure on a surface thereof, wherein the substrate comprises one or more optical redirection structures facing the primary light extraction surface and configured to change the propagation direction of the far-UVC light emitted from the primary light extraction surface into one or more directions.

22. The LED according to claim 21, wherein The one or more optical redirection structures are attached to the surface of the substrate adjacent to the semiconductor structure.

23. The LED according to claim 21, wherein The one or more optical redirection structures are integral with the substrate, and the surface of the substrate including the semiconductor structure thereon is recessed relative to the one or more optical redirection structures.

24. The LED according to claim 21, wherein The substrate includes at least one electrically conductive via extending into the surface of the substrate and in electrical contact with at least one of the corresponding electrical contacts.

25. The LED according to any one of claims 14 to 24, wherein At least a portion of the first surface and / or the second surface comprises a light extraction surface configured to emit the far-UVC light.

26. The LED according to any one of claims 14 to 25, wherein The LED is free of a native substrate for the semiconductor structure.

27. The LED according to any one of claims 14 to 26, wherein The semiconductor structure is also configured to generate UVC light.

28. A light emitting diode (LED), comprising: A semiconductor structure configured to generate light including a wavelength in the far UVC wavelength range, the semiconductor structure including a first surface and a second surface having respective electrical contacts thereon and one or more lateral surfaces extending between the first surface and the second surface, Wherein a total surface area of ​​the one or more lateral surfaces is within 10 times the corresponding surface area of ​​the top surface or the bottom surface.

29. The LED according to claim 28, wherein The one or more lateral surfaces include opposing sidewalls of at least one epitaxial layer of the semiconductor structure extending between the first surface and the second surface, and a distance between the opposing sidewalls is less than about 100 microns.

30. The LED according to claim 29, wherein The distance between the opposing sidewalls is less than about 50 μm, and a thickness of the at least one epitaxial layer is about 10 μm or less.

31. The LED of claim 28, wherein One or more dimensions of the at least one epitaxial layer of the semiconductor structure in a lateral direction are within an order of magnitude of a thickness of the at least one epitaxial layer in a vertical direction.

32. The LED according to any one of claims 28 to 31, wherein The one or more lateral surfaces are inclined between the first surface and the second surface.

33. The LED according to any one of claims 28 to 32, wherein At least one of the respective electrical contacts is at least partially opaque to the far-UVC light.

34. The LED according to any one of claims 28 to 33, further comprising: A substrate comprising the semiconductor structure on a surface thereof, wherein the substrate comprises one or more optical redirection structures facing the one or more lateral surfaces and configured to change the propagation direction of the far-UVC light emitted from the one or more lateral surfaces into one or more directions.

35. The LED of any one of claims 28 to 34, wherein The semiconductor structure is also configured to generate UVC light.

36. A light emitting diode (LED) array comprising: a common supporting substrate; as well as A plurality of LEDs according to any preceding claim, arranged on a surface of the common supporting substrate, Optionally, wherein optical redirection structures are provided on the surface of the common support substrate between adjacent LEDs in the plurality of LEDs.

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