Micro LEDs configured for operation at wavelengths in the far UVC spectrum

Abstract

The 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 first and second surfaces of the semiconductor structure. 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. A primary light extraction surface extends between the first and second surfaces and may include at least one sidewall of the semiconductor structure configured to emit far UVC light. Related devices, arrays thereof, and methods of manufacture are also discussed.

Description

[Technical field]

[0001] Claiming priority 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 entire disclosure of which is incorporated herein by reference.

[0002] This application relates to UV light sources, and in particular to deep UVC light sources and related devices and methods. [Background technology]

[0003] A compact and efficient ultraviolet (UV) light source in the wavelength range of about 200 nm to about 400 nm may be desirable for many applications. For example, there is an emerging market for germicidal UV (GUV) products. UVC light, including photons in the UVC wavelength range (e.g., wavelengths of about 200 nm to about 280 nm, also called UV-C), can be used to disinfect airborne and surface disease-causing pathogens while remaining safe for human exposure. With regard to human safety, far-UVC light (wavelengths of about 200 nm to about 240 nm) cannot penetrate the dead cell layer on the skin surface or the tear layer of the human eye. Specifically, far-UVC light can efficiently cause permanent physical damage to DNA and / or proteins, which can prevent the replication of bacteria, viruses, and fungi. Thus, human-safe far-UVC light may effectively kill or inactivate disease-causing pathogens with little or no risk to humans, as these wavelengths may be largely 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 may not penetrate deep enough into human skin to pose a harmful threat to humans. This may allow UV light to be used to sterilize air and surfaces in the presence of humans. Summary of the Invention [Problem to be solved by the invention]

[0004] However, operation in the far-UVC wavelength range can pose challenges. For example, there are few available light sources that can be configured for operation in the far UV. Some conventional far-UVC light sources are implemented with gas discharge lamps that generate light from excimers formed in a transient plasma. For example, KrCl excimer lamps can generate light at 222 nm. To reduce cost and / or improve reliability, among other advantages, a solid state source of far-UVC light (e.g., light emitting diodes (LEDs), in some cases using phosphorus-based wavelength conversion) may be desirable. Although LEDs can be a widely deployed and developed solid-state light source, such sources typically have short operating lifetimes and poor performance at emission wavelengths below about 265 nm. Thus, LEDs that emit in the far-UVC wavelength range are not commercially available. [Means for solving the problem]

[0005] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure including at least one epitaxial layer configured to generate deep UVC light, wherein 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 first and second surfaces having respective electrical contacts thereon, and at least one sidewall extending between the first and second surfaces and configured to emit far-UVC light.

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

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

[0009] In some embodiments, at least one sidewall is sloped 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 deep UVC light.

[0011] In some embodiments, the substrate includes a semiconductor structure on a front side thereof, the substrate being distinct from the native substrate on which the semiconductor structure is formed.

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

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

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

[0015] In some embodiments, the substrate comprises a back surface opposite the front surface having a backside contact thereon, and at least one conductive through via extending through the substrate and electrically connecting at least one of the respective electrical contacts of the semiconductor structures to the backside contact.

[0016] In some embodiments, the LED is devoid of a native substrate for the semiconductor structure.

[0017] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure configured to generate far-UVC light, the semiconductor structure having first and second surfaces, respective electrical contacts on at least one of the first and second surfaces, and a primary light extraction surface extending between the first and second surfaces and including at least one sidewall of the semiconductor structure configured to emit far-UVC light.

[0018] In some embodiments, the at least one sidewall comprises opposing sidewalls of one or more epitaxial layers of the semiconductor structure extending between the first surface and the second surface, wherein the distance between the opposing sidewalls is less than about 100 microns.

[0019] In some embodiments, the distance between opposing sidewalls is less than about 50 μm.

[0020] In some embodiments, the epitaxial layer or layers of the semiconductor structure have a thickness of about 10 μm or less.

[0021] In some embodiments, the distance between the opposing sidewalls is within an order of magnitude of a thickness of one or more epitaxial layers of the semiconductor structure.

[0022] In some embodiments, at least one sidewall is sloped between the first surface and the second surface.

[0023] In some embodiments, at least one of the respective electrical contacts is at least partially opaque to deep UVC light.

[0024] In some embodiments, at least a portion of the first and / or second surface comprises a light extraction surface configured to emit far-UVC light.

[0025] According to some embodiments, a light emitting diode (LED) includes a semiconductor structure configured to generate light including wavelengths in the far UVC wavelength range. The semiconductor structure includes first and second surfaces having respective electrical contacts thereon, and one or more lateral surfaces extending between the first and second surfaces. A collective surface area of ​​the one or more lateral surfaces is within 10 times the surface area of ​​each of the top or bottom surfaces.

[0026] According to some embodiments, a light emitting diode (LED) array includes a common support substrate and a plurality of LEDs as described herein disposed on a surface of the common support substrate, and an optical redirection structure may be provided between adjacent LEDs of the plurality of LEDs on the surface of the common support substrate.

[0027] In some embodiments, the semiconductor structure of any of the LEDs described herein is further configured to generate UVC light.

[0028] Other devices, apparatus, and / or methods according to some embodiments will become apparent to one of ordinary skill in the art upon review of the following figures and detailed description. Any and all combinations of the above embodiments, as well as all such additional embodiments, are intended to be included within this description and protected by the following claims, which are within the scope of the present invention. [Brief description of the drawings]

[0029] [Figure 1A] FIG. 1 is a schematic perspective view showing the configuration of a conventional macroLED light source providing emission in the far UVC spectrum. [Figure 1B] FIG. 1 is a schematic plan view showing the configuration of a conventional macroLED light source providing emission in the far UVC spectrum. [Figure 2A] FIG. 1 is a schematic perspective view illustrating a configuration of a microLED light source providing far-UVC emission according to some embodiments of the present disclosure. [Figure 2B]1 is a schematic plan view illustrating a configuration of a microLED light source providing far-UVC emission according to some embodiments of the present disclosure. [Figure 3A] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources including sidewalls configured to direct far-UVC light in one or more desired directions, according to some embodiments of the present disclosure. [Figure 3B] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources including sidewalls configured to direct far-UVC light in one or more desired directions, according to some embodiments of the present disclosure. [Figure 4A] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources on a substrate including optical redirection structures configured to direct far-UVC light in one or more desired directions, according to some embodiments of the present disclosure. [Figure 4B] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources on a substrate including optical redirection structures configured to direct far-UVC light in one or more desired directions, according to some embodiments of the present disclosure. [Figure 5A] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources 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. [Figure 5B] 1A-1C are schematic cross-sectional views illustrating configurations of microLED light sources 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. [Figure 6A] FIG. 1 is a schematic cross-sectional view illustrating the configuration of a microLED light source on a substrate including a recessed surface, a sidewall configured to direct far-UVC light in one or more desired directions, and a through-via electrical connection extending through the sidewall, in accordance with some embodiments of the present disclosure. [Figure 6B]FIG. 1 is a schematic cross-sectional view illustrating the configuration of a microLED light source on a substrate including a recessed surface, a sidewall configured to direct far-UVC light in one or more desired directions, and a through-via electrical connection extending through the sidewall, in accordance with some embodiments of the present disclosure. [Figure 7A] 1A-1D are schematic side-view diagrams illustrating a method for fabricating a microLED light source on a non-native substrate according to some embodiments of the present disclosure. [Figure 7B] 1A-1D are schematic side-view diagrams illustrating a method for fabricating a microLED light source on a non-native substrate according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] Examples of the present disclosure provide devices that generate electromagnetic radiation in the far UVC wavelength range (about 200 nm to 240 nm, e.g., about 207 nm to 222 nm) that may be desirable for numerous applications, including (but not limited to) germicidal applications for disinfecting airborne and surface disease-causing pathogens, and detection of trace chemical or biological species in various field environments (air, water, etc.), while remaining safe 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 200 nm (such that the radiation is non-ionizing in the atmosphere) and less than about 240 nm, e.g., about 200 nm to 230 nm.

[0031] Specifically, 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, specifically wavelengths less than about 240 nm. Although some custom designed LEDs and laboratories have demonstrated LEDs with wavelengths from 260 to around 230 nm, the efficiency of such devices decreases rapidly and therefore may not be commercially viable.

[0032] Several challenges may hinder the development of LEDs configured to emit light at wavelengths less than about 250 nm, many of which may be related to extracting the light from the device. Indeed, the external quantum efficiency (EQE) of UVC LEDs may remain below 10% due to the difficulty of extracting the light.

[0033] One such challenge may be related to the top and bottom electrical contacts. Specifically, as electrical doping levels increase, it may be difficult to form a contact to the p-side of the LED pn junction (also referred to as a p-contact) with optical transparency for light in the shorter wavelength range (e.g., from about 200 nm to 230 nm or 240 nm). That is, higher doping may be required to reduce resistance (improve efficiency), but higher doping levels may decrease optical transparency, making it more difficult for photons to exit the LED due to absorption by the electrical contacts. Efficiency may thereby be affected due to the non-transparent nature of the contacts. The embodiments described herein recognize that tradeoffs, including design modifications, that may alleviate the need for high doping levels or the need to extract photons through the surface may benefit the efficiency of the LED.

[0034] Another challenge with decreasing wavelength may be related to the directionality of the light generated inside the LED. For example, as the aluminum content of AlGaN material increases, the band gap may increase (and the emission wavelength of the generated light may decrease). Accompanying this change may be a deviation from isotropic generation of photons towards a situation where the optical transition dipole inside the material may be increasingly perpendicular (to the crystal planes of the semiconductor material). The closer the transition dipole is to an ideal perpendicular dipole, the more anisotropic the photon generation becomes. Transverse electric (TE) polarization may dominate in InGaN / GaN-based blue LEDs, whereas transverse magnetic (TM) polarization may dominate in AlGaN / GaN UV LEDs. More specifically, as the emission wavelength decreases, the light generated inside the LED may propagate predominantly (i.e., at higher brightness) at angles transverse to the plane of the active region (i.e., quantum well) of the semiconductor material. Light propagating at lateral angles (i.e., within the critical angle for total internal reflection (TIR)) is more likely to be guided to the edge and less likely to be emitted out the top or bottom of the device. As used herein, propagation may refer to the direction of travel of light (or photons) in or out of the semiconductor material, and emission may refer to the output of light (or photons) from the semiconductor material. A further confounding feature, the length scale for photons to reach the edge of a macroscopic LED may be thousands of times larger than the distance for photons to reach the top or bottom surface.

[0035] The embodiments of the present disclosure may address these and other issues by (i) removing limitations on optical transparency or absorption for the top or bottom (e.g., p) electrical contacts, which may simplify the design and improve the internal quantum efficiency (IQE), and therefore the overall efficiency, and (ii) addressing polarization issues that may arise for short wavelength light (specifically, wavelengths less than about 240 nm, such as deep UVC light) by shortening the optical path to the light extraction surface, taking advantage of the fact that as the Al composition increases in AlGaN multiple quantum wells for wavelengths less than about 240 nm, short wavelength light propagates predominantly at lateral angles through the semiconductor material, which may significantly increase the EQE. This issue is sometimes referred to as Light Extraction Efficiency (LEE), where EQE=IQE×LEE. The embodiments of the present disclosure may thereby improve the IQE and LEE, resulting in an overall improvement in EQE.

[0036] The embodiments of the present disclosure described herein relate to the use of microscale dimensions for each individual LED (sometimes referred to herein as microLEDs or μLEDs) to achieve improved performance over state-of-the-art macroscale LED designs (sometimes referred to herein as macroscopic LEDs or macroLEDs). Benefits may be derived from the geometry: by fabricating 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's edges may be much higher. Furthermore, due to the shorter length scale, the average contact resistance may be reduced. The embodiments described herein are particularly suited for UVC or deep UVC LEDs based on AlGaN semiconductor materials, for example but not limited to AlGaN materials, but may also be implemented with 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 semiconductor materials configured to provide emission in the deep UVC spectrum.

[0037] 1A and 1B are perspective and plan views, respectively, illustrating the configuration of a conventional LED light source that provides emission 105 in the far UVC spectrum. Specifically, FIGS. 1A and 1B illustrate a conventional macroscopic LED 10 that includes a semiconductor material 100′ (e.g., an AlGaN layer) with respective electrical contacts 1, 2 (e.g., an n-contact and a p-contact) on a top and bottom surface of the semiconductor material 100′. The macroscopic LED 10 has a length dimension (e.g., along the x-axis or y-axis) that is larger (e.g., tens or thousands of times) than a thickness T of the macroscopic LED 10. For example, the thickness T may be about 50 μm or less, and the length dimension (e.g., along the x-direction) may be about 1 millimeter (mm) or more. Thus, the macroscopic LED 10 is typically 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 due, for example, to the directional nature of the far UVC light 105 generated within the LED semiconductor material 100' (e.g., having higher brightness along the horizontal or lateral direction) and difficulties with the degree or amount of transparency of the electrical contacts 1, 2 to the far UVC light 105. In particular, as discussed above, it can be difficult to form a p-contact 1 that has both the desired electrical properties (e.g., low resistance) and the desired optical properties (e.g., transparency to light in the far UVC spectrum).

[0038]

[0013] Embodiments of the present disclosure provide "micro" LEDs in which the lateral length scales of the LEDs (e.g., in the x and / or y directions) are reduced, which may address and / or eliminate the above and / or other challenges. Figures 2A and 2B are perspective and top views, respectively, illustrating configurations of a microLED light source 20 providing far-UVC light 105, in accordance with some embodiments of the present disclosure. Although described primarily with reference to producing far-UVC light, the light output 105 of the microLED light source is not limited to the far-UVC wavelength range, and some embodiments may include or be configured to produce light including wavelengths in the broader UVC wavelength range (also referred to herein as UVC light).

[0039] 2A and 2B show a microLED 20 according to some embodiments of the present disclosure, including differences compared to the macroLED 10 shown in FIGS. 1A and 1B. In either case, the thickness of the LED 10, 20 may be determined by the thickness T, t of the semiconductor structure 100′, 100. In a microLED 20 according to some embodiments of the present disclosure, the thickness t may range from about 0.1 micrometers (μm) to about 20 μm, such as from about 0.1 μm to about 10 μm, or from about 0.5 μm to about 5 μm. 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. The semiconductor material may be formed (e.g., epitaxially grown) on a source substrate or wafer (referred to herein as a native substrate), and in some embodiments, the source substrate or wafer may or may not be removed from the LED light source described herein.

[0040] In the macroscopic LED 10 shown in Figures 1A and 1B, the lateral dimensions (e.g., along the x-direction and / or y-direction) of the epitaxial layers may exceed the thickness T by a ratio of more than about 1000:1. This may pose a challenge for photons emitted in-plane, since LED materials may typically reabsorb the emitted photons. The probability that a photon will reach the 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 in this orientation. Due to this issue, the macroscopic LED 10 may include features on the top and / or bottom surfaces 1, 2 to enhance the coupling of light out of the LED through these surfaces. Doing so may improve the efficiency of light extraction from the LED (where photonic extraction efficiency = EQE / IQE).

[0041] In contrast to the macroscopic LED 10 shown in FIGS. 1A and 1B, a microLED 20 according to some embodiments of the present disclosure may have a semiconductor light emitting layer (e.g., an epitaxial layer) having one or more lateral dimensions (e.g., in the horizontal (x and / or y) directions or along the surfaces of the contacts 110, 120 in the figures) that are on the same scale as the thickness of the device semiconductor light emitting layer (e.g., in the vertical (z) direction of the figures perpendicular to the lateral direction). A lateral dimension may refer to a length, width, diameter, major axis, etc., depending on the shape defined by the semiconductor light emitting layer. That is, a microLED described herein may have an epitaxial layer having one or more lateral dimensions x, y that are on the order of magnitude (e.g., less than, greater than, or approximately equal, or within at least one order of magnitude, or at least two orders of magnitude) of its thickness dimension t in the vertical direction. For example, a microLED may include a semiconductor structure 100 having semiconductor epitaxial layers with a collective thickness t of about 15 or 20 μm or less (e.g., about 0.1 to 10 μm, or about 0.5 μm to about 5 μm) and may include one or more lateral dimensions x, y of less than about 500 μm (e.g., less than about 100 μm, about 50 μm, or about 1 to 10 μm). In some embodiments, the epitaxial layers of the semiconductor structure 100 (after removal from the native substrate, e.g., via laser lift-off) may have a thickness t of about 7 μm to about 12 μm and lateral dimensions x, y between about 3 μm and about 50 μm. Edges or sidewalls 115 (also referred to as lateral surfaces) of the semiconductor structure 100 of the microLED 20 may provide a primary light extraction surface 115.

[0042] The advantage of such lateral dimensions may arise from the recognition that the physical distance a given photon must travel to reach the edge or sidewall of the device for outcoupling may be an order of magnitude shorter than some macroscopic designs. As shown in Figures 2A and 2B, the semiconductor structure 100 is configured to generate photons in the far-UVC wavelength range that propagate predominantly at an angle approximately lateral to the active region of the semiconductor material (shown along the horizontal or lateral direction in the figures). As shown by the dashed lines in Figures 2A and 2B, the brightness of the generated far-UVC light 105 drops significantly with deviation from the lateral direction. The lateral dimensions of the semiconductor active layer of the microLED 20 are configured to reduce the optical path length for the output of the photons (i.e., the far-UVC light 105) at the light extraction surface 115 of one or more sidewalls 115 of the semiconductor structure 100. The reduced physical distance or optical path length of a microLED 20 including an epitaxial layer having lateral dimensions x, y according to some embodiments of the present disclosure may enable an exponentially higher probability of photon extraction at far UVC wavelengths and thus may be essential to improving quantum efficiency to sufficient levels for viability.

[0043] More specifically, Figures 2A and 2B show a semiconductor structure 100 including a first surface 101, a second surface 102, and electrical contacts 110, 120 (e.g., n-contact and p-contact) on the first and second surfaces 101, 102, respectively. At least one sidewall 115 extends between the first surface 101 and the second surface 102 to provide a primary light extraction surface 115 configured to emit far-UVC light 105. In some embodiments, multiple (e.g., opposing) sidewalls 115 of an epitaxial layer of the semiconductor structure 100 can provide the primary light extraction surface 115, and the distance between opposing sidewalls 115 along a lateral direction can be on the order of (e.g., within one or two orders of magnitude) of a thickness t of the epitaxial layer of the semiconductor structure 100 along a vertical direction. For example, the distance between opposing sidewalls 115 along a lateral direction can be less than about 100 microns (e.g., less than about 50 μm, or about 1 to 10 μm). Thus, a MicroLED 20 that includes sidewalls or lateral surfaces 115 for primary light extraction may be considered an edge-emitting device.

[0044] Although described herein with reference to the sidewall or lateral surfaces 115 of the semiconductor structure 100 as the primary light extraction surfaces 115, it will be understood that embodiments of the present disclosure are not limited to light extraction only from the sidewall or lateral 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 provide a secondary light extraction surface.

[0045] The advantage of such lateral dimensions may also arise from the recognition that the relative amount of surface area contributed by the lateral edges of a microLED (e.g., the ends of the microLED compared to the surface area of ​​the top and / or bottom faces) may be much higher than that of a macroLED (where the top / bottom faces have a much larger surface area 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 top or bottom area of ​​about 0.1 to about 2000 μm2 Thus, in some embodiments, the collective surface area of ​​one or more lateral surfaces 115 of semiconductor structure 100 may be within 10 times (e.g., within about 5 times, or within about 5 to 10 times) of the surface area of ​​the top or bottom surface of semiconductor structure 100, respectively. That is, microLEDs described herein may include epitaxial layers having one or more lateral dimensions x, y on the order of (e.g., within an order of magnitude, or within 5 times) their thickness dimension t, and / or lateral edge surface area on the order of their top / bottom areas.

[0046] Furthermore, by increasing the contribution of the lateral edge surfaces of the device to light emission, microLEDs according to some embodiments of the present disclosure may separate the photon extraction surface from the surfaces where current is introduced (usually the top and bottom surfaces 101, 102 having electrical contacts 110, 120 thereon). Thus, the trade-off between optical transparency (for efficiency) and doping level (i.e., contact resistance) may be completely avoided, thereby achieving improved efficiency in the far UVC spectrum. In some embodiments, one or more of the electrical contacts 110, 120 may be formed from materials and / or doping levels with no optical transparency requirements to achieve reduced electrical resistance and / or ohmic contact to the semiconductor structure 100. In particular, one or more of the electrical contacts 110, 120 may be partially (e.g., more than 10%, more than 25%, or more than 30%), or substantially (e.g., more than 50%, more than 75%, or more than 90%), or completely (100%) opaque to the far-UVC light 105. That is, microLEDs including the lateral light extraction surfaces 115 described herein may enable the use of (semi-)opaque electrical contacts 110 and / or 120 to achieve both higher light extraction efficiency and reduced electrical resistance.

[0047] For example, in semiconductor contacts, the electrical resistance is the contact resistance (ohm cm 2 ) / area(cm 2 By reducing the lateral dimensions x, y of the LEDs described herein, the area (cm 2) may be reduced by several orders of magnitude, which may increase the contact resistance. While this may pose challenges, the microLEDs described herein may provide a primary light extraction surface on one or more sidewalls 115 of the device, which may allow electrical contacts that are not limited by optical transparency requirements (e.g., the electrical contacts may be partially or completely opaque to far-UVC light), which may reduce resistance and improve efficiency even at any doping level. Some embodiments may provide far-UVC emitting LEDs that have a contact resistance that is less (e.g., less than 2x, less than 10x) than may be achievable with some macroLEDs (due to optical transparency requirements for electrical contacts of macroLEDs for top and / or bottom emission). For example, a far-UVC emitting LED that includes electrical contacts 110, 120 that are substantially or completely opaque to far-UVC light as described herein may have a contact resistance of about 3x10 in some embodiments. -3 ohms / cm 2 The contact resistance may be less than 100 .mu.m.

[0048] 2A and 2B illustrate general embodiments of the present disclosure, specifically the inventive concepts in a shorter length / lateral dimension (e.g., where the epitaxial layers of the microLED have one or more lateral dimensions x, y of less than 500 μm (e.g., less than about 100 μm, less than about 50 μm, or about 1 to 10 μm) or on the order of their thickness). Additional illustrative embodiments include (but are not limited to) providing a p-contact on the bottom surface of the microLED (rather than the top surface) and providing an n-contact on the top surface (rather than the bottom surface); patterning the p-contact and n-contact on the top and bottom surfaces of the microLED (e.g., on less than the entire surface area of ​​the top and bottom surfaces of the epitaxial layers of the semiconductor structure 100) rather than forming the p-contact and n-contact by blanket coverage of the top and bottom surfaces of the semiconductor structure 100; The method may include one or more of forming the epitaxial layers of the semiconductor structure 100 from materials such as gallium nitride (GaN), silicon carbide (SiC), pure aluminum nitride (AlN), other III-nitrides, solid semiconductor materials, 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 other than 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 microLED configurations (e.g., 20, 30, 40, 40b, 50, 60a, 60b, 70) described herein may be included in a larger array (e.g., hundreds, or thousands, or tens of thousands of microLEDs), and the number of microLEDs in the array may be selected to achieve an overall desired amount of light output from the light source.

[0049] Other embodiments described herein illustrate exemplary modifications of some elements of the microLED device shown in Figures 2A and 2B to improve or change performance. For example, Figures 3A and 3B are schematic cross-sectional views illustrating configurations of microLED 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.

[0050] Specifically, in FIGS. 3A and 3B, the semiconductor structure 100 of the microLED 30a, 30b includes a sidewall or lateral surface 115′ that is slanted or angled (i.e., non-perpendicular to the surface 101, 102 having the electrical contacts 110, 120 thereon). The sidewall or lateral surface 115′ may be optimized or configured to direct the far-UVC light 105 upwards (e.g., away from the native substrate 300a or non-native substrate 300b) out of the plane of the array. In some embodiments, each sidewall 115 may include multiple slope angles (e.g., may be multi-faceted as it extends between the top and bottom surfaces of the semiconductor structure 100). In other embodiments, the sidewall may have a more complex structure to improve the light output fraction or modify the far-field pattern angular distribution of the output light. Another example of modifying the sidewalls 115 for emission of the far-UVC light 105 in one or more desired directions can be achieved by varying or altering the crystal orientation of the semiconductor material (e.g., by providing a sidewall 115' that is off-cut relative to one or more crystal axes of the semiconductor material) and / or the surface roughness of the sidewall. Optical modifications to the sidewalls 115' of the microLED can be optimized or configured to diffuse the light into a particular distribution pattern 105p (as shown in FIG. 3B) or to direct the light as or into a beam 105b (as shown in FIG. 3A), for example, by providing a coating or pattern 315 on the sidewall 115'. More generally, one or more of the sidewalls 115' of the semiconductor structure 100 can be configured to provide a light extraction surface that directs the far-UVC light 105 into the beam 105b or the distributed light pattern 105p.

[0051] In some embodiments, as shown in FIG. 3A, the microLED 30a may be provided on and supported by a native substrate 300a (e.g., AlN, sapphire, GaN, or other substrate) used for epitaxial growth of the semiconductor material of the semiconductor structure 100. In another embodiment, the microLED 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 LED semiconductor material or material or substrate (e.g., a source wafer) on which the structure 100 was grown or formed. It will be understood that the transfer of the microLED from its native substrate 300a (e.g., a source wafer) to the non-native support substrate 300b may be performed by microtransfer printing in some embodiments, although the embodiments described herein may include various fabrication methods and may not be limited to any particular fabrication method.

[0052] Further embodiments of the present disclosure as shown in Figures 4A and 4B may include configurations in which the microLEDs 20, 30a, 30b are associated with reflective or other optical redirection structures 415 provided on or by the supporting substrate 300a, 300b. Specifically, Figures 4A and 4B are schematic cross-sectional views illustrating configurations 40a, 40b of microLED light sources 20 on substrates 300a, 300b including optical redirection structures 415a, 415b (collectively 415) according to some embodiments of the present disclosure. Although described below with reference to various configurations using the microLED 20 of Figures 2A and 2B, it will be understood that the illustrated microLED 20 may be replaced with other microLED configurations according to embodiments of the present disclosure (e.g., microLEDs 30a, 30b having sloping sidewalls 115' on native or non-native substrates 300a, 300b).

[0053] The optical redirection structures 415 are disposed on the substrates 300a, 300b (e.g., attached to the front surface 300f of a non-native substrate adjacent to the semiconductor structure 100) facing the light extraction surface 115 provided by the sidewalls of the semiconductor structure 100, and configured to change the propagation direction of the far-UVC light 105 output from the light extraction surface 115. For example, the optical redirection structures 415 may be reflective to light in the far-UVC wavelength range, and may be shaped or configured to direct the far-UVC light 105 output from the lateral edges of the microLED in one or more desired directions or in a desired angular far-field pattern.

[0054] 4A shows an example configuration 40a in which the optical redirection structure 415a is a patterned reflective structure (e.g., an aluminum structure) fabricated with a relatively flat or smooth angled edge surface configured to redirect laterally emitted light away from the microLED (shown above and away from the support substrate 300a, 300b) in one or more different directions to provide a controlled illumination pattern (e.g., beam 105b or desired distributed light pattern 105p). FIG. 4B shows an example configuration 40b in which the optical redirection structure 415b is a patterned reflective structure (e.g., an aluminum structure) that includes a non-uniform or asymmetric surface to redirect laterally emitted light away from the microLED in an irregular or non-uniform illumination pattern in one or more directions away from the support substrate 300a, 300b. The support substrates 300a, 300b can be native substrates (e.g., sapphire substrates for AlGaN semiconductor structures) or non-native substrates (e.g., silicon substrates). Although the examples 40a, 40b of Figures 4A and 4B show the optical redirection structures 415 formed from a different material than the support substrates 300a, 300b and disposed on a surface of the support substrates 300a, 300b (e.g., using microtransfer printing or other techniques), embodiments of the present disclosure are not so limited.

[0055] For example, another embodiment of the present disclosure incorporates the optical redirection structure or light redirection structures into the support substrate itself, such that adding additional features to the top surface of the support substrate may not be necessary. Figures 5A and 5B are schematic cross-sectional views illustrating configurations 50 of microLED light sources 20 on a substrate 500 including a recessed surface 500r and adjacent side surfaces 500s configured to direct far-UVC light 105 in one or more desired directions, according to some embodiments of the present disclosure. Thus, the side surfaces 500s of the substrate 500 may provide optical redirection structures 415' formed of the same material as and integral with the substrate 500, and the surface of the substrate 500 includes recessed semiconductor structures 100 thereon relative to the optical redirection structures 415'.

[0056] For example, a light redirection structure (shown by way of example in FIGS. 5A and 5B below with reference to an inverted trapezoidal or "pyramid" structure that defines a recessed surface 500r or "pit" of the substrate 500) may be formed or provided on a top surface of the non-native substrate 500 (e.g., a silicon or other support wafer) prior to placing or configuring the microLED device 20 on the recessed surface 500r within the pit. In particular, the non-native substrate 500 may be patterned (e.g., by one or more selective or isotropic etching processes) to form the recessed surface 500r and surrounding side surfaces 500s, whereby the side surfaces 500s define the optical redirection structure 415' configured to provide enhanced or improved light extraction.

[0057] As shown in FIGS. 5A and 5B, the sides 500s of the inverted pyramid structure are formed at respective angles (relative to the concave surface) to form optical redirection structures 415′ configured to direct light emitted from the edge of the microLED 20 out of plane or to change the propagation direction of the far-UVC light 105 away from the lateral direction. For example, the sides 500s may be angled at about 45 degrees or less relative to the lateral direction of the light emission. The support substrate 500 and / or the material of one or more layers thereon may be configured to be reflective to light in the far-UVC wavelength range. Some embodiments may further provide a reflection-enhancing coating or pattern 515 on the angled sides 500s to enhance (e.g., in terms of efficiency and / or direction) the reflection of the far-UVC light 105.

[0058] 5A illustrates that a mask 501 (e.g., an oxide or nitride mask) and an etching process (e.g., a TMAH or corresponding isotropic etching process) may be used to selectively form one or more recessed surfaces 500r at a depth d relative to a top surface of a substrate 500 (e.g., a silicon substrate). The recessed surfaces 500r are formed on the top surface of the substrate 500 with a width W of an opening formed therein. top Narrower than W bottom The silicon substrate 500 may have a {100} crystal plane or <100> The etching process may be performed adjacent to or surrounding the recessed surface and at an angle to the recessed surface 500r, along the {111} crystallographic planes or <111> 5A , and may form a side surface 500s in the silicon substrate 500 that extends along a crystal direction. The shape of the side surface 500s is not limited to the example shown in FIG. 5A , but more generally may include any feature that may be etched or patterned into the support substrate 500 to define an optical redirection structure 415′ facing the primary light extraction surface 115 of the microLED 20 and configured to change the propagation direction of the far-UVC light 105 emitted from the microLED 20 in one or more directions.

[0059] FIG. 5B illustrates the configuration or arrangement of microLEDs 20 on the recessed surface 500r of the substrate 500. The microLEDs 20 may be configured in the center of the recessed surface 500r (i.e., at approximately equal distances to each side 500s) or may be offset toward one of the side surfaces 500s as shown. The process for configuring or arranging the microLEDs on the patterned surface of the substrate 500 may be, for example, microtransfer printing, although it will be understood that the embodiments described herein are not limited to any particular manufacturing method. Additionally, while some embodiments may provide a single microLED on the recessed surface 500r within each pit, other embodiments may provide multiple microLEDs on the recessed surface 500r within each pit (e.g., whereby each recessed surface 500r includes one or more microLEDs thereon), with the light extraction surface 115 facing the optical redirection structure 415′ formed by the side surfaces 500s of the substrate 500.

[0060] Yet another embodiment may provide one or more electrical connections to the conductive microLED 20 electrical contacts 110, 120 by conductive through vias 611 extending through the supporting substrate 500. Figures 6A and 6B are schematic cross-sectional views illustrating configurations 60a, 60b of a microLED light source 20 on a substrate 500 including a recessed surface 500r, a side surface 500s configured to direct the far-UVC light 105 in one or more desired directions, and a through via 611 electrical connection extending through the side surface 500s, according to some embodiments of the present disclosure.

[0061] As shown in FIGS. 6A and 6B, the substrate 500 includes a front surface 500f having a microLED 20 thereon and an opposing back surface 500b. The back surface 500b includes one or more backside contacts 610, 620 thereon, which are electrically connected to respective electrical contacts 110, 120 (e.g., n-contacts and p-contacts) of the microLED 20 by one or more through-wafer vias 611 (also referred to herein as conductive through vias 611) that extend through the substrate 500 and / or other conductive interconnects 612. FIG. 6A shows a configuration 60a including a single through-via 611 per contact, which in this example contacts the n-type contact or N-terminal of the microLED. As shown in FIG. 6A, some embodiments may provide the microLED 20 directly on top of the through-vias. In another embodiment, as shown in FIG. 6B, a plurality of through-wafer vias 611 extend through the substrate 500 to provide electrical contact to both the N and P terminals of the microLED 20. As shown in FIGS. 6A and 6B, an interlayer dielectric (ILD) 615 (or other non-conductive coating that is substantially transparent to far UVC light 105) may be provided to electrically insulate the sidewalls 115 of the microLED 20 to prevent electrical shorting. Alternate embodiments may provide access to and electrical connection to the top electrical contact (e.g., p-contact) using other implementations, such as wire bonding.

[0062] More generally, the through via 611 may provide an electrical connection between the front and rear sides of a supporting substrate 500 having microLEDs 20 thereon. In the examples 60a, 60b shown in Figures 6A and 6B, the through via 611 is implemented in combination with a substrate 500 including the inverted pyramid or pit structure of Figures 5A and 5B, although it will be understood that the through via 611 may be used in combination with any of the substrates described herein (e.g., 300a, 300b).

[0063] 7A and 7B are schematic side views illustrating a method of fabricating a microLED light source 20 on a non-native substrate 500, according to some embodiments of the present disclosure. As shown in FIGs. 7A and 7B, in some embodiments, a microtransfer printing technique may be used as an assembly method to fabricate an array of microLEDs (e.g., hundreds or thousands) on a common support substrate 500. In microtransfer printing, the (microLED) device may be removed from its native substrate (i.e., released from the native substrate on which the semiconductor structure 100 is formed) and placed or "printed" onto a different substrate or non-native substrate 500 using an elastomeric stamp or other stamp.

[0064] 7A shows that a non-native support substrate (e.g., 300b, 500) is provided prior to assembly. The non-native substrate 300b, 500 may include a front surface 300f, 500f configured to support one or more microLEDs and a back surface opposite the front surface 300f, 500f. The front surface 300f may be a substantially planar surface, and in some embodiments, optical redirection structures 415' may be configured or disposed on the front surface 300f of the substrate 300b between adjacent microLEDs 20 to redirect the propagation direction of far-UVC light 105 output from the microLEDs 20 into one or more directions away from the substrate. In another example, as shown in FIG. 7A , the front surface 500f of the non-native substrate 500 can be a composite surface including a plurality of recessed surfaces 500r or pits surrounded by protruding sides 500s configured to redirect the propagation direction of the far-UVC light 105 output from one or more microLEDs 20 into one or more directions away from the substrate 500.

[0065] 7A, the stamp may include respective posts dimensioned to removably adhere one or more microLEDs 20 thereon. In some embodiments, an elastomeric transfer stamp may be configured and / or optimized to perform microtransfer printing of microLEDs 20 onto a composite or patterned substrate 500 as described above. In particular, the elastomeric transfer stamp 700 may include posts having a height and / or tapered profile that provides sufficient clearance to extend between the protruding side surfaces 500s of the substrate 500 surrounding the recessed surface 500r or pits therein, which may differ from the shape of elastomeric stamps or posts that may typically be used for microtransfer printing onto smooth-sided, flat substrates.

[0066] For example, stamp posts according to some embodiments of the present disclosure may be shaped to (approximately) mirror or correspond to an inverted pyramid or other patterned or non-planar substrate geometry. The stamp configuration shown in FIGS. 7A and 7B may, for example, allow for an overall taller post that maintains sufficient strength, with a wider "base" (at the top) that tapers toward the stamping surface to match the topology of the patterned or other non-planar substrate 500. As shown in FIG. 7B, the tapered post of the stamp may conform to the dimensions of the patterned substrate 500 to transfer the microLEDs 20 from the post of the stamp directly to the recessed surface 500r of the substrate 500, in some examples, on the front surface 500f or onto the conductive through vias 611 or other conductive interconnects exposed on the front surface 500f. Thus, in some embodiments, microLEDs may be transferred to a non-native support substrate 500 using an elastomeric stamp whose posts are designed or configured to match or nearly correspond to the topology of the (composite) support substrate 500.

[0067] Transferring the microLEDs 20 to a non-native support substrate 500 as described herein (by microtransfer printing or other means) may be advantageous at least because providing an array of multiple microLEDs 20 on the native substrate can be unmanageable. For example, the native substrate may typically be about 400 μm thick, while each microLED 20 may have respective lateral dimensions of about 10 μm, resulting in undesirable aspect ratios and / or insufficient density or utilization of substrate area. Furthermore, there may be insufficient area on top of each microLED 20 for wire bonds (wire bonds typically require metal bond pads 50 μm to 75 μm wide). In contrast, microLEDs provided on a common non-native support substrate 300b, 500 as described herein may be connected by through vias 611 and / or other conductive interconnects 612 (including thin film interconnects) within and / or on the surface of the non-native substrate 300b, 500. The non-native substrate 300b, 500 may be optically transparent to deep UVC light in some embodiments.

[0068] According to some embodiments of the present disclosure, microLEDs (also referred to as μLEDs) having one or more lateral dimensions x, y of less than about 100 microns may achieve higher light efficiency at low (e.g., deep UVC) wavelengths, which may result in higher output power based on or including (but not limited to) one or more of the following: higher light extraction efficiency; shorter distances to or between opposing edges of the semiconductor material of about its thickness t (i.e., higher perimeter to area ratio); significant or majority of light extraction through the lateral surfaces 115 (sidewalls or edges) of the LED rather than through the top or bottom surfaces, allowing for reduced (or eliminated) transparency requirements for the top / bottom electrical contacts 110, 120; and reduced electrical resistance of the electrical contacts 110, 120 due to shortened lateral dimensions x, y of the surfaces 101, 102 of the epitaxial layers of the semiconductor structure 100 on which the electrical contacts 110, 120 are provided.

[0069] In some embodiments, microLEDs can have lateral dimensions of only 1 μm to as much 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), and thus a height of as much as about 4, or a circumference-to-area ratio of only about 0.2.

[0070] In some embodiments, a substrate (e.g., a native substrate) may be removed (e.g., via flip-chip techniques) for light extraction through a bottom or top surface of semiconductor structure 100. In some embodiments, the top and / or bottom surfaces of semiconductor structure 100 may be substantially free of light extraction features.

[0071] In some embodiments, a plurality of microLEDs as described herein may be disposed and electrically connected on a surface of the non-native substrate in an array configuration, and the array may include a plurality of optical redirection structures on or protruding from the surface of the non-native substrate between each of the microLEDs.

[0072] Thus, embodiments of the present disclosure may address issues with the light extraction efficiency of the far-UVC light 105 generated by the 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 predominantly at lateral angles (e.g., lateral as shown in the figure) and configuring the emission of the light extraction surface 115 of the LED to shorten the optical path length for the output of the photons to improve or maximize the output efficiency.

[0073] Some advantages of embodiments of the present disclosure may include, but are not limited to, improved performance of LEDs operating with emission at wavelengths in the deep UVC wavelength range (approximately 200-240 nm). In particular, LEDs fabricated using the aluminum gallium nitride (AlGaN) material system may benefit, although the advantages described herein may also apply to other material systems and are not limited to GaN-based or III-nitride-based materials.

[0074] By improving the performance (i.e., light output per unit electrical input) of LEDs in the far UVC wavelength range, embodiments of the present disclosure may provide new solid-state light sources for use in germicidal UV applications where currently AlGaN LED technology may be fundamentally challenged. Commercial applications for far UVC illumination according to embodiments of the present disclosure may include the removal of pathogens from air and / or surfaces in any indoor space where humans congregate (e.g., airports, schools, hospitals, inpatient care centers, workplaces, etc.), as well as in transportation vehicles (e.g., subway cars, trains, taxis, airplanes) and agricultural environments (e.g., livestock facilities, meatpacking facilities, indoor greenhouses, etc.).

[0075] Various embodiments have been described herein with reference to the accompanying drawings in which exemplary embodiments are shown. However, such embodiments may be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, such embodiments are provided so that this disclosure will be thorough, complete, and complete in conveying the concept of the present invention to those skilled in the art. Various modifications to the exemplary embodiments, general principles, and features described herein will be readily apparent. In the drawings, the sizes and relative sizes of layers and regions are not shown to scale and in some instances may be exaggerated for clarity.

[0076] Exemplary embodiments are described primarily in terms of specific methods and devices provided in particular implementations. However, the methods and devices may operate effectively in other implementations. Phrases such as "exemplary embodiment," "one embodiment," "another embodiment," and the like may refer to the same or different embodiments, as well as to multiple embodiments. The embodiments are described in terms of systems and / or devices having several components. However, the systems and / or devices may include fewer or additional components than those illustrated, and variations in the arrangement and type of components may be made without departing from the scope of the inventive concept.

[0077] The illustrative embodiments are also described in the context of a particular method having some steps or actions. However, the methods and devices may effectively operate in other ways having different and / or additional steps / actions and steps / actions in different orders consistent with the illustrative embodiments. Thus, the inventive concept is not intended to be limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and features described herein.

[0078] When an element is referred to or shown as being "on" or "connected" or "coupled" to another element, it will be understood that the element may be directly on, connected to, or coupled to the other element, or intervening elements may be present. In contrast, when an element is "directly on", "directly connected to", or "directly coupled" to another element, there are no intervening elements present.

[0079] It will also be understood that, although terms such as first, second, etc. may be used herein to describe various elements, such elements should not be limited by such terms. Such terms are merely used to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the present disclosure.

[0080] Furthermore, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of an element to another element as shown in the figures. It will be understood that the relative terms are intended to encompass various orientations of the device in addition to the orientation depicted in the figures. For example, if a device in one of the figures is inverted, an element described as being "under" another element would then be oriented "above" the other element. Thus, the exemplary term "lower" encompasses both an orientation of "lower" and "upper", depending on the particular orientation of the figure. Similarly, if a device in one of the figures is inverted, an element described as being "below" or "under" another element would then be oriented "above" the other element. Thus, the exemplary term "lower" or "under" may encompass both an orientation of "up" and "down".

[0081] The terms used in the description herein are merely for the purpose of describing particular embodiments and are not intended to limit the invention. In the description and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0082] It will also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms "include", "including", "comprises" and / or "comprising" as used herein 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 groups thereof.

[0083] Embodiments of the present disclosure are described herein with reference to illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the present invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to represent the actual shape of a region of a device and are not intended to limit the scope of the invention.

[0084] Unless otherwise defined, all terms used in disclosing the embodiments, including technical and scientific terms, have the same meaning as commonly understood by those skilled in the art to which the present invention belongs, and are not necessarily limited to the specific definition known at the time the present invention is described. Thus, such terms may include equivalent terms created after such time. It will be further understood that terms as defined in commonly used dictionaries should be interpreted to have a meaning that is consistent with their meaning in the context of this specification and the related art, and will not be interpreted in an idealized or overly formal sense unless expressly defined herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.

[0085] Many different embodiments have been disclosed herein in connection with the above description and drawings. It will be understood that a literal description and illustration of every combination and subcombination of such embodiments would be unduly repetitive and unclear. Thus, the present specification, including the drawings, is intended to constitute a complete description of every combination and subcombination of the embodiments of the invention described herein, and the manner and process of making and using them, and is intended to support any claim to any such combination or subcombination.

[0086] Although the invention has been described herein with reference to various embodiments, it will be understood that other variations and modifications can be made within the scope and spirit of the principles of the invention. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention is set forth in the following claims.

Claims

1. Semiconductor structure comprising at least one epitaxial layer configured to generate far UVC light - Patent 7222227 A light emitting diode (LED) comprising: A light emitting diode (LED) wherein one or more dimensions of the at least one epitaxial layer in a lateral direction are within an order of magnitude of the thickness of the at least one epitaxial layer in a vertical direction.

2. the semiconductor structure a first surface and a second surface having respective electrical contacts thereon; at least one sidewall extending between the first surface and the second surface and configured to emit the far-UVC light; 10. The light emitting diode (LED) of claim 1, comprising:

3. 3. The light emitting diode (LED) of claim 2, wherein 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 comprises a distance between the opposing sidewalls.

4. 3. The light emitting diode (LED) of claim 2, wherein the at least one sidewall is configured to direct the far UVC light into a beam or a dispersed pattern.

5. 3. The light emitting diode (LED) of claim 2, wherein the at least one sidewall slopes between the first surface and the second surface.

6. 3. The light emitting diode (LED) of claim 2, wherein at least one of the respective electrical contacts is at least partially opaque to the far UVC light.

7. a substrate containing the semiconductor structure on its front side, the substrate being different from the native substrate on which the semiconductor structure is formed; 7. The light emitting diode (LED) of claim 1, further comprising:

8. 8. The light emitting diode (LED) of claim 7, wherein the substrate comprises one or more optical redirection structures facing at least one sidewall of the semiconductor structure and configured to change the propagation direction of the far-UVC light emitted from the semiconductor structure into one or more directions.

9. 9. The light emitting diode (LED) of 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. 9. The light emitting diode (LED) of claim 8, wherein the one or more optical redirection structures are integral with the substrate, and a surface of the substrate containing the semiconductor structure thereon is recessed relative to the one or more optical redirection structures.

11. The substrate is a back surface opposite the front surface and having back contacts thereon; at least one conductive through via extending through the substrate and electrically connecting at least one of the electrical contacts of each of the semiconductor structures to the backside contact; 9. The light emitting diode (LED) of claim 8, comprising:

12. 7. The light emitting diode (LED) of claim 1, wherein the semiconductor structure is free of a native substrate and / or the semiconductor structure is further configured to generate UVC light.

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

14. 14. The light emitting diode (LED) of claim 13, wherein the at least one sidewall comprises opposing sidewalls of one or more epitaxial layers of the semiconductor structure extending between the first surface and the second surface, the distance between the opposing sidewalls being less than 100 microns.

15. 15. The light emitting diode (LED) of claim 14, wherein the distance between the opposing sidewalls is less than 50 μm, or the thickness of the one or more epitaxial layers of the semiconductor structure is 10 μm or less, or 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.

16. 14. The light emitting diode (LED) of claim 13, wherein the at least one sidewall slopes between the first surface and the second surface.

17. 14. The light emitting diode (LED) of claim 13, wherein at least one of the respective electrical contacts is at least partially opaque to the far UVC light.

18. a substrate including a semiconductor structure on a surface thereof, the substrate having one or more optical redirection structures facing a primary light extraction surface and configured to change the propagation direction of the far UVC light emitted from the semiconductor structure into one or more directions; 18. The light emitting diode (LED) of any of claims 13 to 17, further comprising:

19. 20. The light emitting diode (LED) of claim 18, wherein the one or more optical redirection structures are attached to the surface of the substrate adjacent the semiconductor structure.

20. 20. The light emitting diode (LED) of claim 18, wherein the one or more optical redirection structures are integral with the substrate, and the surface of the substrate containing the semiconductor structure thereon is recessed relative to the one or more optical redirection structures.

21. 20. The light emitting diode (LED) of claim 18, wherein the substrate comprises at least one conductive through via extending into the surface of the substrate and electrically contacting at least one of the respective electrical contacts.

22. 18. A light emitting diode (LED) according to any of claims 13 to 17, 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.

23. 23. The light emitting diode (LED) of claim 22, wherein the semiconductor structure is free of a native substrate and / or the semiconductor structure is further configured to produce UVC light.

24. 1. A semiconductor structure configured to produce light including wavelengths 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. A light emitting diode (LED) comprising: A light emitting diode (LED) wherein the collective surface area of ​​said one or more lateral surfaces is within 10 times the surface area of ​​each of the top or bottom surfaces.

25. 25. The light emitting diode (LED) of claim 24, 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, the distance between the opposing sidewalls being less than 100 microns.

26. 26. The light emitting diode (LED) of claim 25, wherein the distance between the opposing sidewalls is less than 50 μm and the thickness of the at least one epitaxial layer is 10 μm or less.

27. 25. The light emitting diode (LED) of claim 24, wherein one or more dimensions of at least one epitaxial layer of the semiconductor structure in a lateral direction are within an order of magnitude of a thickness of at least one epitaxial layer in a vertical direction.

28. 28. A light emitting diode (LED) according to any of claims 24 to 27, wherein the one or more lateral surfaces are sloped between the first surface and the second surface.

29. 28. A light emitting diode (LED) according to any of claims 24 to 27, wherein at least one of the respective electrical contacts is at least partially opaque to the far-UVC light, and / or further comprising a substrate including a semiconductor structure on a surface thereof, the substrate having one or more optical redirection structures facing one or more lateral surfaces and configured to change the propagation direction of the far-UVC light emitted from the semiconductor structure into one or more directions, and / or the semiconductor structure is further configured to generate UVC light.

30. a common support substrate; a plurality of light emitting diodes (LEDs) according to any one of claims 1 to 6, 13 to 17 and 24 to 27, arranged on a surface of the common support substrate; 1. A light emitting diode (LED) array comprising: Optionally, an optical redirection structure is provided between adjacent light emitting diodes (LEDs) of said plurality of LEDs on a surface of said common support substrate.

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