Light emitting device and method for making same

Abstract

To provide LED structures and processes that can provide more efficient LEDs capable of emission in the UVC spectrum.SOLUTION: A device comprises a substrate and a patterned layer. The patterned layer comprises multiple mask regions on the substrate. Exposed portions of the substrate are disposed between the mask regions. Multiple nanostructures are disposed on the exposed portions of the substrate and over the mask regions, the multiple nanostructures being a single-crystal semiconductor and comprising a core tip. An active layer is disposed over the multiple nanostructures. The active layer has a quantum well structure and comprises at least one material chosen from AlN, AlGaN and GaN. A p-doped layer is disposed over the active layer. Both the active layer and the p-doped layer are conformal to the multiple nanostructures so as to form an emitter tip over the core tip.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure is directed to devices for emitting light, and in particular, to devices for emitting light in the UVC spectrum. [Background technology]

[0002] LED devices that emit radiation in the UVC band have a variety of potential commercial applications. However, such UVC LED devices are not commonly available commercially due to low wall plug efficiency. Previous experimental UVC LED devices also suffer from low external quantum efficiency. This is especially true for LEDs that emit wavelengths shorter than 250 nm. Furthermore, most LED devices have output emission wavelengths (e.g., typically longer than 300 nm) that are too long for short-wavelength UVC applications. Furthermore, many LED devices use InGaN as the active material, which does not emit light in the UVC wavelength range, but instead emits light in the visible spectrum.

[0003] Known methods for forming UVC LED devices include using nanometer-scale selective area epitaxy with circular openings to grow vertically oriented nanowires. An optically active AlGaN layer is then deposited partway through, and then finally capped with additional materials for doping and surface passivation. X. Liu et al., Optics Express 25, 30494 2017. In Liu et al., the authors are able to demonstrate emission across the entire c-band with good internal quantum efficiency, due in part to a core-shell structure that reduces non-radiative recombination. The main achievement here is the use of nanowires to relieve strain, allowing for active layers with large Al content to reach shorter wavelengths. However, the reduction in strain comes at the expense of a reduced area fraction of the emitter layer. Also, these layers are still nominally aligned along the c-plane, so the problems of reduced oscillator strength and TM-polarized emission still remain.

[0004] Other methods for creating UVC LED devices use etching techniques to define the growth areas, as described in Appl. Phys. Lett. 2017 by X. Liu et al. AlGaN is grown on the sidewalls of GaN vertical fins, the arrays of which are formed by dry etching. Dry etching causes surface damage and also requires a wet etching step. The growth of these fins addresses the problem of TM polarized output, and in this case the authors state that the vertical orientation of the fins allows more TM polarized light to be extracted from these structures. However, these fins are spaced about 2um apart, which significantly reduces the emitter area fraction and limits the maximum achievable brightness. Furthermore, this minimum width between fins requires the material to penetrate to the base.

[0005] Thus, there is a need in the art for LED structures and processes that can provide more efficient LEDs capable of emitting in the UVC spectrum. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] X. Liu et al., Optics Express 25, 30494 2017 [Non-Patent Document 2] X. Liu et al., Appl.Phys.Lett.2017 Summary of the Invention [Means for solving the problem]

[0007] The present disclosure is directed to a light emitting device for emitting UVC radiation. The device comprises a substrate and a patterned layer. The patterned layer comprises a plurality of masked regions on the substrate. An exposed portion of the substrate is disposed between the masked regions. A plurality of nanostructures are disposed on the exposed portion of the substrate and on the masked regions, the plurality of nanostructures being single crystal semiconductors and comprising a core tip. An active layer is disposed on the plurality of nanostructures. The active layer is a quantum well structure and comprises at least one material selected from AlN, AlGaN, and GaN. A p-doped layer is disposed on the active layer. Both the active layer and the p-doped layer are conformal to the plurality of nanostructures to form an emitter tip on the core tip.

[0008] The present disclosure is also directed to a method of making a UVC light emitting device. The method includes forming a patterned layer including a plurality of mask regions on a substrate, with exposed portions of the substrate disposed between the mask regions. A plurality of nanostructures are epitaxially grown on the exposed portions of the substrate and on the mask regions, with the plurality of nanostructures comprising a core-tip. An active layer is epitaxially grown on the plurality of nanostructures, with the active layer being a quantum well structure and including at least one material selected from AlN, AlGaN, and GaN. A p-doped layer is deposited on the active layer, with both the active layer and the p-doped layer conformal to the plurality of nanostructures to form an emitter tip on the core-tip.

[0009] The present disclosure is also directed to a method of disinfecting a surface. The method includes contacting the surface with UVC radiation emitted from a light emitting device. The device includes a substrate and a patterned layer. The patterned layer includes a plurality of masked regions on the substrate. An exposed portion of the substrate is disposed between the masked regions. A plurality of nanostructures is disposed on the exposed portion of the substrate and on the masked regions, the plurality of nanostructures being single crystal semiconductors and having a core tip. An active layer is disposed on the plurality of nanostructures. The active layer is a quantum well structure and includes at least one material selected from AlN, AlGaN, and GaN. A p-doped layer is disposed on the active layer. Both the active layer and the p-doped layer are conformal to the plurality of nanostructures to form an emitter tip on the core tip.

[0010] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed.

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the present teachings and, together with the description, serve to explain the principles of the present teachings. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view of a light emitting device for emitting UVC radiation according to an example of the present disclosure. [Diagram 2] FIG. 2 is a perspective view of a plurality of nanostructures in the form of hexagonal pyramids that can be used to fabricate a light emitting device according to one example of the present disclosure. [Diagram 3] FIG. 1 is a perspective view of a plurality of nanostructures in the form of corrugated ridges that can be used to fabricate a light emitting device according to one example of the present disclosure. [Figure 4] 1 is a schematic diagram of a light emitting device having corrugated ridges that can be used to emit UVC radiation according to one example of the present disclosure. [Diagram 5]FIG. 2 shows an image taken by scanning electron microscopy of a top view of two parallel wavy ridges according to an example of the present disclosure. [Figure 6] FIG. 2 shows an image taken by scanning electron microscopy of an angled top view of a single wavy ridge according to an example of the present disclosure. [Figure 7] FIG. 2 shows a scanning electron microscopy image of a top view of a GaN hexagonal prism according to an example of the present disclosure. [Figure 8] FIG. 1 is a schematic top view of a layout of hexagonal pyramids arranged in a hexagonal grid array (e.g., honeycomb pattern) according to one example of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] It should be noted that some details in the figures have been simplified and are drawn for ease of understanding rather than maintaining strict structural accuracy, detail, and scale.

[0014] Reference will now be made in detail to the present teachings, examples of which are illustrated in the accompanying drawings, in which like reference numerals are used throughout to refer to identical elements. In the following description, reference is made to the accompanying drawings which form a part hereof, and in which specific examples embodying the present teachings are shown by way of illustration. Accordingly, the following description is by way of example only.

[0015] Problems with radiation emitted by LEDs in the UVC range, especially those with wavelengths in the 200 nm to 300 nm range, are low power (e.g., 10 microwatts or less, although what is considered low power can vary widely with device size) or low overall external quantum efficiency (e.g., low quantum efficiency can range below 10%). Causes of low efficiency output include, but are not limited to, 1) non-radiative recombination centers due to defects in the active layer growth, 2) weak dipole moments due to built-in crystal electric fields, and 3) transverse-magnetic mode polarized emission (electric field oscillating perpendicular to the top surface), which reduces photon collection efficiency. The present disclosure addresses these three major problems via selective area epitaxial growth of active layers (e.g., AlGaN quantum wells) on n+ doped nanostructures.

[0016] Selective area epitaxial growth refers to growth on pre-patterned wafers, where growth can occur only in areas predefined via a mask. As discussed in more detail herein, selective area growth redirects defect propagation and provides a non-polar surface on which active regions (e.g., AlGaN quantum wells) can be grown, thus reducing the built-in electric field that separates the wave functions of carriers in the wells, as well as angling transverse magnetic (TM) polarized emission toward the apex of the triangular ridge, thereby improving the light emitting efficiency of the light emitting device.

[0017] Referring to FIG. 1, the present disclosure is directed to a light emitting device 100 for emitting UVC radiation. The light emitting device 100 comprises a substrate 102. A patterned layer 103 comprising a plurality of mask regions 104 is disposed on the substrate 102. An exposed portion 106 of the substrate 102 is disposed between the mask regions 104. A plurality of nanostructures 108 is disposed on the exposed portion 106 of the substrate 102 and over the mask regions 104. The plurality of nanostructures 108 comprises a single crystal semiconductor and optionally includes a core tip 110. The core tip 110, and subsequently formed emitter tip, may be sharp (e.g., no c-axis material at the tip) or truncated (e.g., a small amount of c-axis material at the tip, as shown at 132 in FIG. 7). An active layer 112 comprising at least one material selected from AlN, AlGaN, and GaN is disposed over the plurality of nanostructures 108. A p-doped layer 114 is disposed on the active layer 112, and both the active layer and the p-doped layer are conformal to the plurality of nanostructures to form an emitter tip 118 above the core tip 110. As will be described in more detail below, there are advantages to growing the active layer 112 on the sloped sidewalls of the plurality of nanostructures 108.

[0018] The substrate 102 includes at least one material selected from an insulator, a semiconductor material, and combinations thereof. Examples of materials include silicon, silicon carbide (SiC), sapphire (Al2O3), gallium nitride (GaN), and aluminum nitride (AlN). Silicon offers the advantage of acting as a reflector of the emitted UV light, thereby potentially improving the efficiency of the light emitting device 100. Any other substrate material suitable for growing the plurality of nanostructures 108 may also be used. As an example, the substrate may include a single crystal material for the top surface having a crystal orientation of (0001) for SiC, Al2O3, GaN, and AlN, and a crystal orientation of (111) for silicon. In one example, the substrate is n-type and may include one or more n-type dopants that provide an adequate supply of electrons to the active layer, as is well known in the art. Alternatively, the substrate may be an insulating material and the electrons may be supplied by planar injection, as is well known in the art. Optionally, the substrate can be removed and replaced with a second substrate, such as a flexible substrate, an insulating substrate, or any other desired type of substrate. Techniques for removing and replacing substrates are well known in the art.

[0019] The mask region 104 includes at least one material selected from an insulator, a metal, or other material that allows for the growth of a plurality of nanostructures 108. For example, the source material used for epitaxial growth of the nanostructures may not tend to adhere to the selected mask material, and instead adhere to the exposed portions 106 of the substrate 102 to grow the nanostructures. Additionally, the mask material must be able to withstand the temperatures used in subsequent processing and have the ability to be patterned onto the substrate 102. By way of example, the mask region 104 may include at least one material selected from silicon oxide (e.g., SiO2), SiN, Ti, and TiW. Other suitable mask materials may also be used.

[0020] The mask regions 104 have dimensions that allow the mask regions 104 to be completely covered by the plurality of nanostructures 108. For example, the mask regions have a width in a range of about 50 nm to about 1000 nm. The exposed portions 106 between the mask regions 104 have dimensions suitable to provide the desired dimensions of the plurality of nanostructures 108. As an example, the exposed portions 106 have a width in a range of about 50 nm to about 1000 nm. The plurality of nanostructures 108 grown from exposed portions 106 having such dimensions can be narrow enough that photons can more easily escape therefrom compared to much wider structures.

[0021] The plurality of nanostructures 108 provide a suitable surface for the growth of the active layer 112 and comprise a single crystal material that can be epitaxially grown. Examples include at least one material selected from AlN, GaN, and AlGaN. The material can have a hexagonal close-packed crystal orientation. The nanostructures 108 can be n-doped to provide electrons to the active layer.

[0022] The plurality of nanostructures 108 have a three-dimensional shape selected from, for example, prisms, nanowires, fins, and mesas (e.g., hexagonal mesas or other shaped mesas 124 as shown in FIG. 2). In another example, as shown in FIG. 3, the plurality of nanostructures 108 are ridges 126 that are corrugated and have a length to width ratio (L:W) greater than 3:1, for example, from about 5:1 to about 100,000:1 or greater. FIG. 4 shows a perspective view of an example of the device of FIG. 1 including the corrugated ridges 126. The ridges 126 can have core tips 110, as in the case of the triangular cross-section shown in FIG. 3. The plurality of nanostructures 108 may be contiguous or spaced apart. FIG. 3 shows an example of the plurality of nanostructures 108 in the form of contiguous triangular ridges, while FIG. 2 shows non-contiguous hexagonal pyramids. See also Figures 5 and 6, which show scanning electron microscopy of the top view of two parallel triangular GaN ridges (Figure 5), and one triangular ridge (Figure 6). Other materials such as AlN or AlGaN may be used instead of or in addition to GaN. The ridges in Figures 5 and 6 are grown through a mask and are not contiguous. Figure 7 shows scanning electron microscopy of the top view of GaN hexagonal pillars, which could also include AlN or AlGaN. Figure 8 shows a top view of a schematic layout of how hexagonal pyramids like those in Figure 7 could be arranged in a hexagonal grid array (honeycomb pattern) to increase the fill factor.

[0023] The angled faces of the plurality of nanostructures 108 can provide a relatively large emission area, allowing photons to escape more easily from the subsequently grown active layer 112 than from a grown active layer having a surface (e.g., a c-axis surface) parallel to the surface of the substrate 102. Techniques for epitaxially growing nanostructures having three-dimensional shapes with suitable angled faces are well known in the art. Three-dimensional shapes with tips or apexes can avoid a relatively large amount of c-axis material at the surface, which can allow for improved photon emission compared to c-axis material alone. In one example, the ratio of the non-c-axis surface area to the c-axis surface area of ​​the three-dimensional shape is at least 5, such as from about 10 to about 1000.

[0024] 1, any of the plurality of nanostructures 108 described herein can comprise at least one facet having an angle θ in the range of about 40 degrees to about 90 degrees relative to a top surface 109 of a substrate (e.g., a c-axis surface of a substrate), such as, for example, about 43 degrees to about 75 degrees, or about 55 degrees to about 65 degrees, or about 57 degrees or about 62 degrees. In one example, all of the top faces 130 of the plurality of nanostructures 108 have an angle θ within the range described herein, except for any c-axis faces 132, such as, for example, shown in FIG. 9. In some cases, the exact angle will depend on the angle naturally formed by the material used in the growth conditions used during epitaxy.

[0025] The dimensions of the mask regions 104 and the epitaxial growth conditions, such as gas flow rates and growth temperature, control the geometry of the plurality of nanostructures 108. One skilled in the art will be able to determine appropriate dimensions of the mask regions and epitaxial growth conditions to provide the desired three-dimensional shape for the plurality of nanostructures 108.

[0026] The plurality of nanostructures 108 provide an advantage for UVC emitting devices. AlGaN and its alloys are difficult to grow using a dielectric-based selective area mask because aluminum atoms or metalorganic precursors tend to adhere to the dielectric mask and therefore do not grow selectively at the exposed portions 106. The nanostructures 108 grow over the masked areas 104 so that the AlGaN precursor is not exposed to any of the masked areas 104. To achieve complete coverage of the masked areas 104, as described herein, the masked areas 104 are selected to be relatively small in width so that the lateral growth rate is typically slow and the dielectric is completely covered.

[0027] The active layer 112 is a quantum well structure including a suitable material for emitting UVC radiation, such as AlN, AlGaN, or GaN. AlN, AlGaN, and GaN can have a hexagonal crystal orientation (e.g., hexagonal close-packed orientation). The quantum well structure of the active layer 112 can be a single quantum well or a multiple quantum well structure. In one example, the active layer 112 includes at least one AlN layer and at least one AlGaN layer, such as a three-layer stack of AlN / AlGaN / AlN to form a quantum well. As another example, multiple stacks of AlGaN / AlN can be grown to form a multiple quantum well structure. In another example, the active layer 112 includes at least one AlN layer and at least one GaN layer, such as a three-layer stack of AlN / GaN / AlN. As another example, multiple stacks of GaN / AlN can be grown to form a multiple quantum well structure.

[0028] The thickness of the active layer 112, and the aluminum concentration therein, determine the emission wavelength. In one example, the active layer has a thickness in the range of about 1 nm to about 2000 nm, such as about 10 nm to 500 nm. In one example, the active layer includes at least 50 mol %, for example, about 60 mol % to about 80 mol % aluminum. Thus, the active layer may include at least 50 mol % aluminum, such as at least 50 mol % aluminum. x Ga (1-x)N material, where x ranges from about 0.5 to about 0.9, such as from about 0.6 to about 0.8 or from about 0.65 to about 0.8. In one example, the active layer does not include indium (In).

[0029] The p-doped layer 114 includes at least one p-doped semiconductor material suitable for supplying holes to the active layer 112. By way of example, the p-doped layer 114 includes at least one of a semiconductor material selected from AlN, AlGaN, and hexagonal boron nitride. The p-doped layer may be deposited by any suitable method, such as by employing epitaxial growth or chemical vapor deposition, by way of example.

[0030] In one example, the p-type dopants of the p-doped layer 114 are selectively or polarization doped. Selective and polarization doping are known techniques for increasing the concentration of holes, which may, among other things, lower the threshold turn-on voltage. Thus, in one example, a method of creating a p-doped layer including a p-type dopant includes introducing the p-type dopant by a polarization doping technique. In one example, the p-doped layer has a graded dopant concentration.

[0031] The completed light emitting device 100 comprises one or more light emitting diodes configured to emit radiation having a wavelength in the UVC range, such as from about 200 nm to about 350 nm, or from about 200 nm to about 300 nm, or from about 200 nm to less than 250 nm.

[0032] Growing the active layer 112 on the plurality of nanostructures 108 has several advantages for UVC emitting devices. First, growing the nanostructures on the mask areas 104 can reduce defects in the active layer 112. Selective area growth is generally known to terminate the propagation of defects and thus result in a higher quality surface for epitaxial growth of the active layer 112. Selective area growth is in contrast to other nanoscale etch-based designs, which generally increase defects in the material.

[0033] The advantage of growing the active layer 112 on the sloping sidewalls of the nanostructures 108 is that it can improve the photon emission efficiency of UVC light emitting devices, since short wavelength (UVC) LEDs employ AlGaN quantum wells with high Al content, x>65 mol % and with the axis normal to the c-plane. x Ga 1-x For N quantum wells, the light emission is dominated by transverse magnetic (TM) polarized emission. TM polarized light propagates in the plane of the quantum well and can be undesirably absorbed within the material or cladding layers before the light can be extracted at the surface. In contrast, transverse electric (TE) polarized light propagates perpendicular to the quantum well, resulting in higher extraction efficiency. By growing the quantum wells on angled facets of the selective area growth ridges of the multiple nanostructures 108, if the facet dimensions are kept small enough to reduce or minimize absorption, the emission can emerge at the apex of the ridge at an angle of, for example, 62 degrees or more. The emission angle is determined, among other things, by the resulting sloping sidewalls of the active layer 112 (e.g., the AlGaN / AlN quantum well stack ridge of the active layer 112). The side facets can be (10-11) facets at 62 degrees to the c-plane. In non-equilibrium conditions, the facet angles change, for example 58 degrees (11-22), and other facets may occur.

[0034] Additionally, growing the active layer 112 on multiple nanostructures 108 can enhance oscillator strength. Most nitride-based optically active materials, such as GaN and AlGaN, have a large built-in electric field along the (0001) c-axis and are typically grown primarily in this direction. Thus, dipoles arising in the material will have weak oscillator strength due to the separation of electron / hole wave functions caused by this electric field (e.g., electrons and holes are pulled apart by the strong dipole force, which reduces their ability to recombine and emit light). Growing the active layer 112 on the facets of a tilted ridge addresses this issue by utilizing facets that have a reduced or no electric field compared to the c-axis dipoles. The facets of the ridge can be semi-polar (10-11) or non-polar (11-20) instead of (0001 c-axis) polar planes, which can improve the wave function overlap between electrons and holes and increase the recombination rate. This results in improved internal efficiency.

[0035] The present disclosure is also directed to a method of making a light emitting device 100 for emitting UVC radiation. The method includes forming a patterned layer 103 including a plurality of mask regions 104 on a substrate 102. Exposed portions 106 of the substrate 102 are formed between the mask regions 104. To create a selective area mask on the substrate, a dielectric or metal layer as disclosed herein is deposited on a surface of the substrate 102. The mask is then patterned, for example, by standard optical lithography techniques.

[0036] A plurality of nanostructures are epitaxially grown on the exposed portions 106 of the substrate 102 and on the masked regions 104. The plurality of nanostructures 108 comprise core tips 110. The process may include, for example, loading the substrate 102 patterned with the masked regions 104 into a growth chamber, such as an MOCVD or MBE chamber. Under suitable growth conditions, the plurality of nanostructures 108 will selectively grow on the exposed portions 106 between the plurality of masked regions 104. The growth may be, for example, in the shape of a sloping (e.g., triangular or pyramidal) ridge, or any other shape described herein for a nanostructure. The c-plane is the most rapidly growing plane. When the growth of the sloping ridge causes the c-plane to disappear, the sloping sidewalls will grow laterally above the masked regions 104. The growth process ends when two adjacent sloping ridges merge on the masked regions 104.

[0037] An active layer 112 is epitaxially grown on the sloping ridges of the plurality of nanostructures 108. The active layer 112 includes at least one material selected from AlGaN, AlN, and GaN disposed on the plurality of nanostructures. A p-doped layer 114 is deposited on the active layer 112 by any suitable deposition method, such as epitaxial growth or chemical vapor deposition. Both the active layer 112 and the p-doped layer 114 are conformal to the plurality of nanostructures to form an emitter tip 118 above the core tip 110.

[0038] The present disclosure is also directed to a method of disinfecting a surface. The method includes contacting the surface with UVC radiation emitted from any of the light emitting devices disclosed herein. As an example, the light emitting device 100 includes a substrate 102. The patterned layer 103 includes a plurality of masked regions 104 on the substrate. An exposed portion 106 of the substrate 102 is disposed between the masked regions 104. A plurality of nanostructures 108 is disposed on the exposed portion 106 of the substrate 102 and on the masked regions 104. The plurality of nanostructures 108 is a single crystal semiconductor and includes a core tip 110. The active layer 112 includes at least one material selected from AlGaN, AlN, and GaN disposed on the plurality of nanostructures 108. A p-doped layer 114 is disposed on the active layer. Both the active layer 112 and the p-doped layer 114 are conformal to the plurality of nanostructures 108 to form an emitter tip 118 on the core tip 110.

[0039] Efficient UVC emitters in the 200-350 nm, 200-300 nm, or even less than 200-250 nm ranges would be of benefit to UV-based sanitation facilities in general. Targeting specific wavelengths within these ranges would not only allow for compact and energy-efficient sanitation methods, but also potentially be safe for eyes and skin with respect to human exposure. There is great commercial interest in producing highly efficient UV light sources. The UVC LED devices of the present disclosure provide the desired efficiency and would also have a wide range of commercial applications in addition to disinfection / sterilization, such as 1) lasers for cooling trapped ions, e.g., Mg ions using a 279 nm laser and Hg+ ions using a 281 nm laser for compact atomic clocks or more compact quantum memories; 2) micro-Raman sources, since Raman intensity is proportional to wavelength and this allows short wavelength sources to obtain orders of magnitude more signal than long wavelength sources; 3) lighting and display applications, such as compact and efficient excitation sources for phosphorescent materials. Still other applications may be recognized by those skilled in the art.

[0040] While the present teachings have been illustrated with respect to one or more implementations, changes and / or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. Moreover, while certain features of the present teachings may be disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations as may be desired or advantageous for any given or particular function.

[0041] Additionally, the disclosure includes examples according to the following clauses: Clause 1. A light emitting device for emitting UVC radiation, comprising: a substrate; a patterned layer comprising a plurality of mask regions on a substrate, the exposed portions of the substrate being disposed between the mask regions; a plurality of nanostructures disposed on the exposed portions of the substrate and over the mask regions, the plurality of nanostructures being single crystal semiconductors and comprising a core tip; an active layer disposed over the plurality of nanostructures, the active layer being a quantum well structure and comprising at least one material selected from AlN, AlGaN, and GaN; and a p-doped layer disposed over the active layer, the active layer and the p-doped layer both conformal to the plurality of nanostructures to form an emitter tip over the core tip. A light emitting device comprising: Clause 2. The light emitting device of clause 1, wherein the substrate comprises at least one semiconductor selected from silicon, sapphire (Al2O3), silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN). Clause 3. The light emitting device of clause 1 or 2, wherein the mask region comprises at least one material selected from an insulator and a metal. Clause 4. The light emitting device of any one of clauses 1 to 3, wherein the mask region has a width in the range of about 50 nm to about 1000 nm. Clause 5. The light emitting device of any one of clauses 1 to 4, wherein the exposed portions between the mask regions have a width in the range of about 50 nm to about 1000 nm. Clause 6. A light emitting device according to any one of clauses 1 to 5, wherein the plurality of nanostructures comprises at least one material selected from AlN, GaN, and AlGaN, and the material of the plurality of nanostructures is different from the material of the active layer. Clause 7. The light emitting device of any one of clauses 1 to 6, wherein the nanostructure has a three-dimensional shape selected from a prism, a nanowire, and a mesa. Clause 8. A light emitting device according to any one of clauses 1 to 7, wherein the nanostructures are corrugated ridges. Clause 9. The light emitting device of any one of clauses 1 to 8, wherein the nanostructure is a hexagonal mesa. Clause 10. A light emitting device according to any one of clauses 1 to 9, wherein the nanostructures have at least one face having an angle in the range of about 40 degrees to about 90 degrees relative to a top surface of the substrate on which they are formed. Clause 11. The light emitting device according to any one of clauses 1 to 10, wherein the active layer is a multiple quantum well structure comprising at least one AlN layer and at least one AlGaN layer. Clause 12. The light emitting device of any one of clauses 1 to 11, wherein the active layer comprises AlxGa(1-x)N, where x is in the range of 0.5 to about 0.9. Clause 13. The light emitting device of any one of clauses 1 to 12, wherein the active layer has a thickness in the range of about 1 nm to about 2000 nm. Clause 14. A light emitting device according to any one of clauses 1 to 13, wherein the light emitting device comprises one or more light emitting diodes, the one or more light emitting diodes being configured to emit radiation at a wavelength in the range of about 200 nm to about 350 nm. Clause 15. A light emitting device according to any one of clauses 1 to 14, wherein the p-doped layer comprises at least one semiconductor material selected from AlN, AlGaN, and hexagonal boron nitride, the material of the p-doped layer being different from the material of the active layer. Clause 16. The light emitting device of any one of clauses 1 to 15, wherein the p-doped layer has a graded dopant concentration. Clause 17. A light emitting device according to any one of clauses 1 to 16, wherein the substrate is a flexible substrate. Clause 18. A method of making a UVC light emitting device, the method comprising the steps of forming a patterned layer comprising a plurality of mask regions on a substrate, the exposed portions of the substrate being disposed between the mask regions; epitaxially growing a plurality of nanostructures on the exposed portions of the substrate and on the masked areas, the plurality of nanostructures comprising a core tip; epitaxially growing an active layer on the plurality of nanostructures, the active layer being a quantum well structure and comprising at least one material selected from AlN, AlGaN, and GaN; and depositing a p-doped layer on the active layer, both the active layer and the p-doped layer conformal to the plurality of nanostructures to form an emitter tip on the core tip. A method comprising: Clause 19. The method of clause 18, wherein the substrate comprises at least one semiconductor selected from silicon, silicon carbide (SiC), sapphire (Al2O3), gallium nitride (GaN), and aluminum nitride (AlN). Clause 20. The method of clause 18 or 19, wherein the mask region comprises at least one material selected from an insulator and a metal. Clause 21. The method of any one of clauses 18 to 20, wherein the plurality of nanostructures comprises at least one material selected from AlN, GaN, and AlGaN, and the material of the plurality of nanostructures is different from the material of the active layer. Clause 22. The method of any one of clauses 18 to 21, wherein the nanostructure has a three-dimensional shape selected from a prism, a nanowire, and a mesa. Clause 23. The method of any one of clauses 18 to 22, wherein the nanostructures are corrugated ridges. Clause 24. The method of any one of clauses 18 to 23, wherein the nanostructures have at least one face having an angle in the range of about 40 degrees to about 90 degrees relative to a top surface of the substrate on which they are formed. Clause 25. The method of any one of clauses 18 to 24, wherein the active layer comprises AlxGa(1-x)N, where x is in the range of 0.5 to about 0.9. Clause 26. The method of any one of clauses 18 to 25, wherein the active layer has a thickness in the range of about 1 nm to about 2000 nm. Clause 27. The method of any one of clauses 18 to 26, wherein the p-doped layer comprises a p-type dopant, and the method further comprises the step of introducing the p-type dopant by a polarization doping technique. Clause 28. The method of any one of clauses 18 to 27, further comprising removing the substrate and replacing it with a second substrate. Clause 29. A method of disinfecting a surface, the method comprising the steps of contacting the surface with UVC radiation emitted from a light emitting device, the light emitting device comprising: a substrate; a patterned layer comprising a plurality of masked regions on the substrate, where exposed portions of the substrate are disposed between the masked regions; a plurality of nanostructures disposed on the exposed portions of the substrate and on the masked regions, where the plurality of nanostructures are single crystal semiconductors and comprise a core-tip; an active layer disposed on the plurality of nanostructures, where the active layer is a quantum well structure and comprises at least one material selected from AlN, AlGaN, and GaN; and a p-doped layer disposed on the active layer, where both the active layer and the p-doped layer are conformal to the plurality of nanostructures to form an emitter tip on the core-tip. Clause 30. The method of clause 29, wherein the UVC radiation has a wavelength in the range of about 200 nm to about 300 nm. Clause 31. The method of clause 29, wherein the UVC radiation has a wavelength in the range of about 200 nm to less than 250 nm.

[0042] Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variations thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprising." Furthermore, for purposes of this specification discussion and claims, the term "about" is defined to mean within plus or minus 10% of the stated value, unless the change results in non-compliance of the process or structure for the intended purpose described herein. Moreover, all ranges disclosed herein should be understood to encompass any and all subranges contained therein.

[0043] It will be appreciated that the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications, including various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein, which may subsequently be made by those skilled in the art, and which are also intended to be encompassed by the following claims. [Explanation of symbols]

[0044] 100 Light emitting device 102 Substrate 103 Patterned Layer 104 Mask Area 106 Exposed part 108 Nanostructures 109 Top surface of substrate 110 Core tip 112 Active layer 114 p-doped layer 118 Emitter Tip 124 Mesa 126 Ridge 130 Nanostructured Top Surface 132 c-axis plane

Claims

1. A light emitting device (100) for emitting UVC radiation, comprising: A substrate (102); a patterned layer comprising a plurality of mask regions (104) on the substrate (102), with exposed portions (106) of the substrate (102) disposed between the mask regions (104); a plurality of nanostructures (108) disposed on the exposed portion (106) of the substrate (102) and on the masked area (104), the plurality of nanostructures (108) being a single crystal semiconductor and comprising a core tip (110); an active layer (112) disposed on the plurality of nanostructures (108), the active layer (112) being a quantum well structure and comprising at least one material selected from AlN, AlGaN, and GaN; a p-doped layer disposed on the active layer (112), the active layer (112) and the p-doped layer both conformal to the plurality of nanostructures (108) to form an emitter tip (118) on the core tip (110); Equipped with A light emitting device (100), wherein the substrate (102) comprises at least one semiconductor selected from silicon, sapphire (Al2O3), silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

2. 10. The light emitting device (100) of claim 1, wherein the mask region (104) comprises at least one material selected from an insulator and a metal.

3. The light emitting device (100) of claim 1, wherein the mask region (104) has a width in the range of 50 nm to 1000 nm.

4. 2. The light emitting device (100) of claim 1, wherein the exposed portions (106) between the masked regions (104) have a width in the range of 50 nm to 1000 nm.

5. 2. The light emitting device (100) of claim 1, wherein the plurality of nanostructures (108) comprises at least one material selected from AlN, GaN, and AlGaN, and the material of the plurality of nanostructures (108) is different from the material of the active layer (112).

6. The light emitting device (100) of claim 1, wherein the nanostructure (108) has a three-dimensional shape selected from a prism, a nanowire, and a mesa.

7. The light emitting device (100) of claim 1, wherein the nanostructures (108) are corrugated ridges (126).

8. The light emitting device (100) of claim 1, wherein the nanostructure (108) is a hexagonal mesa.

9. 10. The light emitting device (100) of claim 1, wherein the nanostructures (108) comprise at least one face having an angle in the range of 40 degrees to 90 degrees with respect to a top surface of the substrate (102) on which they are formed.

10. 10. The light emitting device (100) of claim 1, wherein the active layer (112) is a multiple quantum well structure comprising at least one AlN layer and at least one AlGaN layer.

11. The active layer (112) is Al ｘ G （１－ｘ） The light emitting device (100) of claim 1, comprising N, where x is in the range of 0.5 to 0.

9.

12. The light emitting device (100) of claim 1, wherein the active layer (112) has a thickness in the range of 1 nm to 2000 nm.

13. 10. The light emitting device (100) of claim 1, comprising one or more light emitting diodes, the one or more light emitting diodes configured to emit radiation having a wavelength in the range of 200 nm to 350 nm.

14. 10. The light emitting device (100) of claim 1, wherein the p-doped layer comprises at least one semiconductor material selected from AlN, AlGaN, and hexagonal boron nitride, and the material of the p-doped layer is different from the material of the active layer (112).

15. 10. The light emitting device (100) of claim 1, wherein the p-doped layer has a graded dopant concentration.

16. The light emitting device (100) of claim 1, wherein the substrate (102) is a flexible substrate.

17. A method of making a UVC light emitting device (100), the method comprising: forming a patterned layer on a substrate (102) comprising a plurality of mask regions (104), with exposed portions (106) of the substrate (102) disposed between the mask regions (104); epitaxially growing a plurality of nanostructures (108) on the exposed portion (106) of the substrate (102) and on the masked area (104), the plurality of nanostructures (108) comprising a core tip (110); epitaxially growing an active layer (112) on the plurality of nanostructures (108), the active layer (112) being a quantum well structure and comprising at least one material selected from AlN, AlGaN, and GaN; depositing a p-doped layer over the active layer (112), both the active layer (112) and the p-doped layer being conformal to the plurality of nanostructures (108) to form an emitter tip (118) over the core tip (110); Including, The method, wherein the substrate (102) comprises at least one semiconductor selected from silicon, sapphire (Al2O3), silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

18. The method of claim 17, wherein the mask region (104) comprises at least one material selected from an insulator and a metal.

19. 20. The method of claim 17, wherein the plurality of nanostructures (108) comprises at least one material selected from AlN, GaN, and AlGaN, and the material of the plurality of nanostructures (108) is different from the material of the active layer (112).

20. The method of claim 17 , wherein the nanostructure (108) has a three-dimensional shape selected from a prism, a nanowire, and a mesa.

21. The method of claim 17, wherein the nanostructures (108) are corrugated ridges (126).

22. 20. The method of claim 17, wherein the nanostructures (108) comprise at least one face having an angle in the range of 40 degrees to 90 degrees relative to a top surface of the substrate (102) on which they are formed.

23. The active layer (112) is Al ｘ G （１－ｘ） 20. The method of claim 17, comprising N, where x is in the range of 0.5 to 0.

9.

24. The method of claim 17, wherein the active layer (112) has a thickness in the range of 1 nm to 2000 nm.

25. 20. The method of claim 17, wherein the p-doped layer comprises a p-type dopant, the method further comprising introducing the p-type dopant by a polarization doping technique.

26. The method of claim 17, further comprising removing the substrate (102) and replacing it with a second substrate.

27. 1. A method of disinfecting a surface, the method comprising: Contacting the surface with UVC radiation emitted from a light emitting device (100), the light emitting device (100) comprising: A substrate (102); a patterned layer comprising a plurality of mask regions (104) on the substrate (102), with exposed portions (106) of the substrate (102) disposed between the mask regions (104); a plurality of nanostructures (108) disposed on the exposed portion (106) of the substrate (102) and on the masked area (104), the plurality of nanostructures (108) being a single crystal semiconductor and comprising a core tip (110); an active layer (112) disposed on the plurality of nanostructures (108), the active layer (112) being a quantum well structure and comprising at least one material selected from AlN, AlGaN, and GaN; a p-doped layer disposed on the active layer (112), the active layer (112) and the p-doped layer both conformal to the plurality of nanostructures (108) to form an emitter tip (118) on the core tip (110); The method includes the steps of: The method, wherein the substrate (102) comprises at least one semiconductor selected from silicon, sapphire (Al2O3), silicon carbide (SiC), gallium nitride (GaN), and aluminum nitride (AlN).

28. 28. The method of claim 27, wherein the UVC radiation has a wavelength in the range of 200 nm to 300 nm.

29. 30. The method of claim 27, wherein the UVC radiation has a wavelength in the range of 200 nm to less than 250 nm.

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