Conversion element and radiation-emitting semiconductor device with such a conversion element

Abstract

Conversion element (1) with - an active region (13) formed with a semiconductor material and comprising a variety of barriers (131) and quantum wells (132), - a plurality of first structural elements (14) arranged on a top surface (1a) of the conversion element (1), and - a plurality of second structural elements (15) and / or third structural elements (16) arranged on one side of the active area (13) facing away from the plurality of first structural elements (14), wherein - the multitude of first structural elements (14) is formed in the active area (13), - the conversion element (1) is free of electrical connections, and - the diameter of the first structural elements (14) is smaller than the diameter of the second (15) and / or third (16) structural elements.

Description

[0001] A conversion element is specified.

[0002] Publication WO 2008 / 092437 A1 describes an arrangement and a method for generating mixed light. This arrangement uses an oxynitride- or silicate-based luminescence conversion element to generate green light.

[0003] Conversion elements and radiation-emitting semiconductor components with such conversion elements are known from the documents US 2010 / 0 283 074 A1 and US 2012 / 0 058 586 A1.

[0004] One problem to be solved is to specify a conversion element with which colored light can be generated particularly efficiently by optical pumping of the conversion element.

[0005] The conversion element is particularly designed for optical pumping of the conversion element by a pump source. This means that secondary radiation having a longer wavelength than the pump radiation is generated in the conversion element, preferably by pumping with primary radiation. For example, the conversion element can be pumped with UV radiation or blue light and emit longer-wavelength light, in particular green or red light, as secondary radiation. The conversion element can be designed both to generate mixed radiation from the secondary radiation and the primary radiation and to emit primarily secondary radiation. In this case, the conversion element is configured for what is known as full conversion of the primary radiation.

[0006] According to at least one embodiment of the conversion element, the conversion element comprises an active region formed with a semiconductor material. The active region comprises a plurality of barriers and quantum wells.

[0007] For example, the active region is formed in the InGaN material system to generate green secondary radiation, or in the InGaAlP material system to generate red secondary radiation. The active region comprises a quantum well structure with a multitude of barriers and quantum wells. The secondary radiation emitted by the conversion element during operation is generated by the recombination of charge carriers in the quantum wells. The charge carriers are generated by the absorption of primary radiation that has a shorter wavelength than the secondary radiation, for example, in the barriers.

[0008] The active region can be produced, for example, by epitaxial growth, for example, in a MOVPE (metal organic vapor phase epitaxy) system. This means that the active region can comprise epitaxially grown layers or consist of epitaxially grown layers.

[0009] According to at least one embodiment of the conversion element, the conversion element comprises a plurality of first structural elements arranged on an upper side of the conversion element. The first structural elements are, for example, depressions and elevations arranged on the upper side of the conversion element. For example, the first structural elements can be formed on the active region or in the active region. The first structural elements preferably have structural sizes that enable the secondary radiation generated in the conversion element during operation to be influenced by scattering. The structural size of the first structural elements is preferably between at least 100 nm and at most 10 µm, in particular between at least 0.5 µm and 1.5 µm.The structural size can be, for example, the distance between two elevations, the diameter of a elevation, the diameter of a depression, the distance between two depressions, the height of a elevation and / or the depth of a depression of a first structural element.

[0010] According to at least one embodiment of the conversion element, the conversion element comprises a plurality of second structural elements and / or third structural elements which are arranged on a side of the active region facing away from the plurality of first structural elements.

[0011] The second and third structural elements can, for example, also be depressions and / or elevations. The first and / or second structural elements preferably each have structural sizes that enable the structural elements to scatter the primary radiation entering the conversion element. For example, the structural size of the second and / or third structural elements is between at least 100 nm and at most 10 µm, in particular between at least 0.5 µm and 5 µm. The structural size can, for example, be the distance between two elevations, the diameter of a projection, the diameter of a depression, the distance between two depressions, the height of a projection, and / or the depth of a depression.

[0012] According to at least one embodiment of the conversion element, the conversion element comprises an active region formed with a semiconductor material and comprising a plurality of barriers and quantum wells, a plurality of first structural elements arranged on a top side of the conversion element, and a plurality of second structural elements and / or third structural elements arranged on a side of the active region facing away from the plurality of first structural elements.

[0013] In the conversion element described here, the active region in which the secondary radiation is generated during operation of the conversion element is arranged at least between the first structural elements and the second or third structural elements. The first structural elements are provided to scatter radiation emerging from the conversion element, in particular secondary radiation. The second and third structural elements are predominantly provided to scatter radiation entering the conversion element, in particular primary radiation with which the conversion element is pumped during operation. In this way, the plurality of first structural elements makes it possible to increase the probability of electromagnetic radiation escaping from the conversion element.The plurality of second and / or third structural elements increases the probability of primary radiation, which is intended for optical pumping of the conversion element, entering the active region.

[0014] The conversion element described here is based on the following considerations, among others: For example, to generate green light, it is possible to use InGaN-based LEDs that directly generate green light. However, these LEDs exhibit an increased forward voltage relative to the physical band gap. In addition, they have a significantly sublinear light-current dependence. Both problems lead to a reduction in efficiency to approximately 50 to 60 percent compared to blue-emitting LEDs. Furthermore, such green-emitting LEDs exhibit very poor charge carrier confinement, which leads to a loss of charge carriers in the active zone. Due to this fact, LEDs that directly emit green light exhibit lower efficiency, particularly at high temperatures.

[0015] In principle, it is possible to generate colored non-blue light, such as green light, via phosphor conversion. This involves using a conversion element comprising an organic or inorganic, particularly ceramic, phosphor. This enables the generation of green light, for example, with high efficiency, but is associated with a very broad emission spectrum, which is disadvantageous for applications where good color rendering is desired.

[0016] The conversion element described here uses a semiconductor material as the active region, which comprises a plurality of barriers and quantum wells. Optical pumping of the active region is provided. Optical pumping of the active region significantly reduces the charge carrier density per quantum well compared to electrical injection of charge carriers.

[0017] This allows for both improved high-current efficiency and a significantly narrower spectral half-width compared to phosphor conversion. The conversion element described here is therefore characterized by particularly high efficiency and a particularly narrow linewidth of the generated light.

[0018] Surprisingly, it has now been shown that the efficiency of a conversion element in which the active region is formed with a semiconductor material and comprises a multitude of barriers and quantum wells can be significantly increased by a combination of coupling and decoupling structures. Surprisingly, it was discovered that arranging the active region between a multitude of first structural elements on one side and a multitude of second and / or third structural elements on another side allows for an increase in efficiency of more than 30 percent compared to conversion elements that do not include any structural elements, for example, smooth outer surfaces within the manufacturing tolerance.

[0019] The conversion element is free of electrical connections. This means that the conversion element is an electrically inactive component that is not intended for electrical operation. In particular, the conversion element does not comprise any electrical contact layers or connection surfaces. Therefore, during operation of the conversion element, no electrical injection of charge carriers into the active region occurs; instead, these are generated solely by optical pumping of the conversion element, in particular the active region.

[0020] According to at least one embodiment, the conversion element is free of a carrier. A carrier, which is used, for example, for growing a semiconductor body of the conversion element, can be detached from the carrier in this case. For example, the carrier is detached from the semiconductor body using mechanical and / or chemical methods and / or a laser separation process. Non-transparent materials can then also be used for the carrier. Such a conversion element, which is free of a carrier, consists, for example, of epitaxially grown semiconductor material.

[0021] According to at least one embodiment of the conversion element, the conversion element comprises a carrier formed from a radiation-permeable material. The carrier is formed, in particular, from an electrically insulating material. This is possible in the present case because the conversion element is, in particular, electrically inactive and not intended for electrical operation.

[0022] The carrier can, for example, be a substrate that is attached to the active region after the active region has been fabricated. The substrate can then be made of a radiation-transparent material such as glass, sapphire, or AlN, or at least contain one of these materials.

[0023] Furthermore, it is also possible that the carrier is part of a growth substrate used in the fabrication of the active region of the conversion element. In this case, the active region is epitaxially grown on the growth substrate, and the carrier and the active region are monolithically bonded together.

[0024] According to at least one embodiment of the conversion element, the plurality of second structural elements is arranged on an outer surface of the carrier facing the active region and / or the plurality of third structural elements is arranged on an outer surface of the carrier facing away from the active region. If the conversion element comprises, for example, only the first and second structural elements, the second structural elements are arranged between the carrier and the active region. The second structural elements can then, for example, be a structuring of the material of the carrier, or a further material can be applied to the outer surface of the carrier facing the active region to produce the second structural elements and thus arranged between the carrier and the active region.If the conversion element alternatively or additionally comprises a plurality of third structural elements, these are arranged on the outer surface of the carrier facing away from the active region. Again, the third structural elements can be formed from the material of the carrier, or another material can be applied to the carrier to form the third structural elements.

[0025] According to at least one embodiment of the conversion element, the conversion element comprises a carrier formed with a radiation-permeable material, wherein the plurality of second structural elements is arranged on an outer surface of the carrier facing the active region and / or the plurality of third structural elements is arranged on an outer surface of the carrier facing away from the active region.

[0026] According to at least one embodiment of the conversion element, during operation of the conversion element, the plurality of first structural elements increases the probability of electromagnetic radiation escaping from the conversion element, and the plurality of second and third structural elements increases the probability of electromagnetic radiation entering the active region of the conversion element. This means that the first structural elements are, in particular, coupling-out structures designed to guide electromagnetic radiation particularly efficiently out of the conversion element. The second and third structural elements are coupling-in structures designed to guide, in particular, pump radiation into the active region with high efficiency, i.e., in particular while avoiding total internal reflection of pump radiation at the outer surface or in the conversion element.

[0027] According to at least one embodiment of the conversion element, during operation of the conversion element, the plurality of second and third structural elements increases the probability of electromagnetic radiation escaping from the conversion element, and the plurality of first structural elements increases the probability of electromagnetic radiation entering the active region of the conversion element. This means that the second and third structural elements are, in particular, coupling-out structures designed to guide electromagnetic radiation particularly efficiently out of the conversion element. The first structural elements are coupling-in structures designed to guide, in particular, pump radiation into the active region with high efficiency, i.e., in particular while avoiding total internal reflection of pump radiation at the outer surface or in the conversion element.If the first structural elements are directed towards the pump source and serve as coupling structures, this has the further advantage that the active region can, for example, be in indirect contact with the pump source and in this way the heat dissipation of the conversion element during operation is very efficient.

[0028] According to at least one embodiment of the conversion element, the conversion element comprises the plurality of second structural elements and the plurality of third structural elements. This means that in a conversion element of this embodiment, both types of structural elements intended for coupling in electromagnetic radiation are present in the conversion element. This further increases the efficiency of the conversion element compared to a conversion element that has only the second or only the third structural elements.

[0029] According to at least one embodiment, the active region comprises at least 10, in particular at least 35, quantum wells. It has been shown that such a large number of quantum wells enables particularly good absorption of the primary radiation in the active region, so that the conversion element is suitable for the full conversion of the primary radiation into secondary radiation.

[0030] According to at least one embodiment of the conversion element, the plurality of first structural elements is formed by V-defects in the active region. The V-defects are funnel-shaped and / or inverse pyramid-shaped depressions, which, for example, have a hexagonal border. These V-defects can be generated, for example, during the production of the active region by adjusting the growth conditions, for example, by lowering the growth temperature. In particular, the production of thick barriers and the production of a thick active region favor the formation of the V-defects. The production of V-defects is described in another context, for example, in the document WO 2011 / 080219 A1, the disclosure content of which is hereby expressly incorporated by reference.

[0031] According to at least one embodiment of the conversion element, the carrier is part of a growth substrate for the active region, and the plurality of second structural elements is formed by a planar surface with a plurality of elevations arranged on the growth surface of the carrier facing the active region. The planar surface and the elevations can be produced by structuring the material of the carrier. In this case, the carrier can be, for example, a pre-structured sapphire carrier. Such a carrier is described in another context in German patent application DE 10 2015 109 761 A1.

[0032] Alternatively, the elevations can be created as masks or mask islands using an ELOG (epitaxial lateral overgrowth) process. The elevations are then formed with a material such as silicon dioxide or silicon nitride.

[0033] According to at least one embodiment of the conversion element, the plurality of third structural elements is formed by roughening the outer surface of the carrier facing away from the active region. The roughening of the carrier can be produced, for example, by lapping. Furthermore, it is possible for the roughening to be produced by etching with or without an etching mask.

[0034] Furthermore, a radiation-emitting semiconductor component is specified. In particular, a conversion element described here can be used in the radiation-emitting semiconductor component. This means that all features disclosed for the conversion element are also disclosed for the semiconductor component, and vice versa.

[0035] According to at least one embodiment of the radiation-emitting semiconductor component, the radiation-emitting semiconductor component comprises a pump source that generates primary radiation during operation. The pump source can be, for example, a light-emitting diode chip or a laser diode chip. The primary radiation of the pump source is preferably electromagnetic radiation from the spectral range of UV radiation and / or blue light.

[0036] According to at least one embodiment of the radiation-emitting semiconductor component, the radiation-emitting semiconductor component comprises a conversion element as described here, wherein the pump source is mechanically connected to the conversion element. For example, the conversion element is attached to a radiation exit surface of the pump source. The conversion element can, for example, be placed on the pump source and attached there.

[0037] According to at least one embodiment of the radiation-emitting semiconductor component, the plurality of first structural elements of the conversion element are arranged on the side of the active region facing away from the pump source, and at least the plurality of second structural elements or at least the plurality of third structural elements are arranged between the pump source and the plurality of first structural elements. This means that the conversion element is applied to the pump source in such a way that the second structural elements and, if appropriate, the third structural elements are arranged between the pump source and the active region. In this way, the second and third structural elements act as coupling-in structures, whereas the first structural elements act as coupling-out structures.

[0038] Alternatively, it is possible for the plurality of first structures to act as coupling structures and face the pump source. This means that the plurality of first structural elements is then arranged between the pump source and the other structural elements. If the first structural elements are directed toward the pump source and serve as coupling structures, this has the further advantage that the active region can, for example, be in indirect contact with the pump source, thus enabling very efficient heat dissipation of the conversion element during operation.

[0039] According to at least one embodiment of the radiation-emitting semiconductor region, secondary radiation is generated in the active region of the conversion element upon excitation by the primary radiation. The secondary radiation is lower-energy than the primary radiation and encompasses, for example, the spectral range between green and red light.

[0040] According to at least one embodiment of the radiation-emitting component, the radiation-emitting semiconductor component comprises a pump source that generates primary radiation during operation, and a conversion element as described here. The pump source is mechanically connected to the conversion element, the plurality of first structural elements of the conversion element are arranged on the side of the active region facing away from the pump source, and at least the plurality of second structural elements or at least the plurality of third structural elements are arranged between the pump source and the plurality of first structural elements. During operation of the radiation-emitting semiconductor component, secondary radiation is generated in the active region of the conversion element upon excitation by the primary radiation.

[0041] According to at least one embodiment of the radiation-emitting semiconductor component, a connecting region is arranged directly between the conversion element and the pump source, which provides the mechanical connection between the conversion element and the pump source. The connecting region is formed, for example, by a radiation-transparent adhesive, which mechanically and firmly connects the pump source to the conversion element and simultaneously establishes an optical coupling between the conversion element and the pump source.

[0042] In the following, the conversion element described here as well as the radiation-emitting semiconductor component described here are explained in more detail using exemplary embodiments and the associated figures. The Fig. 1A and Fig. 1B show embodiments of a conversion element described here using a schematic sectional view. The Fig. 2A and Fig. 2B show embodiments of a radiation-emitting semiconductor component described here using a schematic sectional view. In conjunction with the schematic representations of the Fig. 3A, Fig. 3B, Fig. 3C shows a further embodiment of a conversion element described here in more detail. In conjunction with the schematic representations of the Fig. 4A, Fig. 4B, Fig. 4C and Fig. 4D shows a further embodiment of a conversion element described here in more detail.

[0043] Identical, similar, or functionally identical elements are provided with the same reference numerals in the figures. The figures and the relative sizes of the elements depicted in the figures are not to be considered to scale. Rather, individual elements may be exaggerated for clarity and / or clarity.

[0044] The Fig. 1A shows a schematic sectional view of a first exemplary embodiment of a conversion element described here. The conversion element 1 comprises a carrier 11, which is radiation-permeable, in particular transparent. The carrier 11 is, for example, part of a sapphire growth substrate onto which the subsequent layers have been epitaxially grown. The carrier 11 is therefore monolithically connected to the remaining components of the conversion element. The conversion element 1 further comprises an intermediate region 12, which is formed, for example, with GaN or InGaN or InAlGaN. The electronic band gap is larger in the intermediate region 12 than, for example, in quantum wells of the active region 13. For example, the intermediate region 12 comprises a first subregion 121, which can be a 3 µm thick, nominally undoped GaN layer.

[0045] Furthermore, the intermediate region 12 comprises, for example, a second subregion 122, which directly follows the first subregion 121 on the side facing away from the carrier 11. The second subregion 122 is, for example, a 2 µm thick n-doped GaN layer, which is doped, for example, with silicon. The active region 13 directly follows the side of the intermediate region 12 facing away from the carrier 11. The active region 13 comprises a plurality of InGaN-based quantum wells 132, which are separated from one another by GaN-based, InGaN-based, or InAlGaN-based barriers 131. The active region 13 is, for example, nominally undoped. The active region 13 comprises at least 10, in particular at least 35, for example exactly 40 quantum wells 132.It has been shown that such a large number of quantum wells enables particularly good absorption of the primary radiation in the active region, so that the conversion element is suitable for the full conversion of the primary radiation into secondary radiation.

[0046] The first structural elements 14 are formed on the side of the conversion element 1 facing away from the carrier 11, the top side 1a, which is opposite the bottom side 1b. The first structural elements 14 are, for example, roughened areas produced by etching, whereby the etching can be performed with or without a mask, or structures produced by self-organized growth, for example, V-defects. The first structural elements 14 serve as output structures to increase the probability of escape for secondary radiation generated in the conversion element during operation.

[0047] The conversion element further comprises second structural elements 15 arranged between the carrier and the intermediate layer 12. The second structural elements 15 are, for example, an ELOG mask or ELOG mask islands or the depressions and elevations of the structured substrate surface.

[0048] Furthermore, the conversion element 1 comprises on its underside 1b, which is arranged on the side of the intermediate layer 12 facing away from the active region 13, third structural elements 16, which are, for example, roughenings produced by lapping, periodic structuring or self-organized structuring.

[0049] In contrast to the Fig. 1A, it is also possible for the conversion element not to comprise either the second structural elements 15 or the third structural elements 16.

[0050] In the schematic sectional view of the Fig. 1B shows a conversion element 1 in which the carrier 11 has been removed, for example, by a chemical process, a mechanical process, and / or a laser separation process. In this exemplary embodiment, the conversion element 1 consists exclusively of epitaxially produced layers. Advantageously, the plurality of second structural elements 15 can be produced by a pre-structured carrier 11 or by means of the carrier detachment process. Furthermore, in this embodiment, it is advantageously possible for the carrier to be formed from a non-transparent material. This expands the options for selecting the carrier 1.

[0051] In conjunction with the schematic sectional view of the Fig. Figure 2A illustrates in more detail an embodiment of a radiation-emitting semiconductor component described here. In addition to the conversion element 1, the radiation-emitting semiconductor component comprises the pump source 2, which is mechanically firmly connected to the conversion element 1 via the connecting region 3. In the present case, the pump source 2 is, for example, a blue light-emitting diode chip that emits at least a large portion of the emitted radiation through the outer surface facing the conversion element 1.

[0052] The connecting region 3 is, for example, a radiation-permeable, in particular transparent adhesive, which, in addition to the mechanical connection, also effects an optical coupling of the pump source 2 to the conversion element 1.

[0053] The conversion element 1 can, for example, be the one used in conjunction with the Fig. 1A or Fig. 1B or any other conversion element described here.

[0054] In conjunction with the schematic sectional view of the Fig. Figure 2A illustrates in more detail an embodiment of a radiation-emitting semiconductor component described here. In addition to the conversion element 1, the radiation-emitting semiconductor component comprises the pump source 2, which is mechanically firmly connected to the conversion element 1 via the connecting region 3. In the present case, the pump source 2 is, for example, a blue light-emitting diode chip that emits at least a large portion of the emitted radiation through the outer surface facing the conversion element 1.

[0055] The connecting region 3 is, for example, a radiation-permeable, in particular transparent adhesive, which, in addition to the mechanical connection, also effects an optical coupling of the pump source 2 to the conversion element 1.

[0056] In contrast to the embodiment of the Fig. 2A, the conversion element 1 is arranged with the first structural elements 14 facing the pump source 2. In this way, the active region 13 is arranged as close as possible to the pump source 2. This results in improved heat dissipation of the active region 13 and reduced absorption of pump radiation on the way to the active region 13. The first structural elements 14 act as coupling structures for the pump radiation. The second structural elements 15 and optionally the third structural elements 16 act as coupling-out structures. The first structural elements 14 are embodied, for example, as V-defects with a diameter of 0.5 µm. The second structural elements 15 can be produced by structuring the carrier 1 and have, for example, a diameter of 2.8 µm.For example, the diameter of the first structural elements 14 in this embodiment may generally be smaller than the diameter of the second and / or third structural elements 15, 16. For example, the diameter of the second and / or third structural elements 15, 16 is at least 2 times, in particular at least 5 times, the diameter of the first structural elements 14.

[0057] The conversion element 1 can also be the one used in conjunction with the Fig. 1A or Fig. 1B or any other conversion element described here.

[0058] In conjunction with the schematic representations of the Fig. 3A to 3C, a further embodiment of a conversion element 1 described here is explained in more detail. In the conversion element 1, which is shown in conjunction with the schematic sectional view of Fig. 3A is explained, compared to the conversion element of the Fig. 1A, the second structural elements 15 are omitted. This means that the conversion element 1 comprises the first structural elements 14 on the top side 1a of the conversion element and the third structural elements 16 on the bottom side 1b of the conversion element.

[0059] The first structural elements 14 are, for example, V-defects, as they are associated with the Fig. 3B and Fig. 3C are explained in more detail. The arrow marked Up indicates the Fig. 3B shows the growth direction in which the active region 13 is deposited onto the carrier 11. The carrier 11 is, for example, part of a sapphire growth substrate. The subsequent layers are deposited, for example, onto the (0001) growth surface 11a of the substrate.

[0060] By setting suitable growth temperatures, for example a reduced growth temperature, funnel-shaped depressions with a hexagonal border are created, as shown schematically in the Fig. 3B in plan view and in the Fig. 3C are shown in the sectional view, in the active region 13. On the side of the active region 13 facing away from the growth substrate, the V-defects act as coupling-out structures and thus as the first structural elements 14.

[0061] The size, for example, the diameter, of the V-defects correlates with the thickness of the active layer 13 and is approximately 500 nm here. Furthermore, the V-defects are not closed again and remain open. In contrast, when V-defects are used in a conventional light-emitting diode chip, they are (partially) closed again, for example, by the growth of a p-side of the semiconductor body, whereas in this case they are not overgrown.

[0062] In conjunction with the schematic representations of the Fig. 4A to 4D, a variant of the second structural elements 15 is explained in more detail. Fig. 4A shows the carrier 11 in a sectional view, which Fig. 4B and Fig. 4C show a top view of the growth surface 11A of the carrier 11. As in the sectional view of Fig. 4A, the elevations 152 protrude from the plane formed by the flat surface 151. The three-dimensionally shaped elevations 152 extend upwards from the flat surface 151. The cross section of the elevations 152 can be round and in particular circular, as is shown, for example, in the Fig. 4B. The elevations 151 can then be formed, for example, as conical elevations. Alternatively, it is possible for the elevations 151 to be formed as shown in the Fig. 4C, also a square one, for example a hexagonal one, or a triangular one, see Fig. 4D, cross-section such that the elevations 15 are formed as pyramid-shaped elevations on the flat surface 151.

[0063] The carrier 11 can be a sapphire carrier that is part of a sapphire growth substrate. The flat surface 151 is then preferably formed by a crystallographic c-surface of the sapphire. The second structural elements 15 can be produced, for example, by etching the carrier 11. They act both as optically effective structural elements and to improve the crystal quality during the growth of the subsequent layers of the conversion element, thus increasing the efficiency of the conversion element. List of reference symbols 1 conversion element 1a top 1b bottom 11 carriers 11a Growth area 12 Intermediate area 121 first sub-area 122 second sub-area 13 active area 131 Barrier 132 Quantum Trough 14 first structural elements 15 second structural elements 151 flat surface 152 Survey 16 third structural elements 2 pump source 3 Connection area

Claims

[1] Conversion element (1) with - an active region (13) formed with a semiconductor material and comprising a plurality of barriers (131) and quantum wells (132), - a plurality of first structural elements (14) arranged on an upper side (1a) of the conversion element (1), and - a plurality of second structural elements (15) and / or third structural elements (16) which are arranged on a side of the active region (13) facing away from the plurality of first structural elements (14), wherein - the plurality of first structural elements (14) is formed in the active region (13), - the conversion element (1) is free of electrical connections, and - a diameter of the first structural elements (14) is smaller than a diameter of the second (15) and / or third (16) structural elements. [2] Conversion element (1) according to the preceding claim, which is free of a carrier (11). [3] Conversion element (1) according to claim 1 with - a carrier (11) formed with a radiation-permeable material, wherein - the plurality of second structural elements (15) is arranged on an outer surface of the carrier (11) facing the active region (13), and / or - the plurality of third structural elements (16) are arranged on an outer surface of the carrier (11) facing away from the active region (13). [4] Conversion element (1) according to one of the preceding claims, wherein the plurality of first structural elements (15) increases the probability of electromagnetic radiation escaping from the conversion element (1) and the plurality of second structural elements (15) and third structural elements (16) increases the probability of electromagnetic radiation entering the active region (13). [5] Conversion element (1) according to one of claims 1 to 3, wherein the plurality of second structural elements (15) and / or third structural elements (16) increases the probability of electromagnetic radiation escaping from the conversion element (1) and the plurality of first structural elements (15) increases the probability of electromagnetic radiation entering the active region (13). [6] Conversion element (1) according to one of the preceding claims, comprising the plurality of second structural elements (15) and the plurality of third structural elements (16). [7] Conversion element (1) according to one of the preceding claims, wherein the active region (13) comprises at least 10, in particular at least 35 quantum wells (132). [8] Conversion element (1) according to one of the preceding claims, wherein the plurality of first structural elements (14) are formed by V-defects in the active region (13). [9] Conversion element (1) according to one of the preceding claims, wherein the plurality of first, second and / or third structural elements (14, 15, 16) is formed by at least one etching process. [10] Conversion element (1) according to one of the preceding claims, in which the carrier (11) is part of a growth substrate with a growth surface (11a) for the active region (13) facing the active region (13), and the plurality of second structural elements (15) comprises a flat surface (151) with a plurality of elevations (152) which are arranged on the growth surface (11a) of the carrier (11) facing the active region (13). [11] Conversion element (1) according to one of the preceding claims, in which the plurality of third structural elements (16) is formed by roughening the outer surface of the carrier (11) facing away from the active region (13). [12] Radiation-emitting semiconductor device with - a pump source (2) which generates primary radiation during operation, and - a conversion element (1) according to one of the preceding claims, wherein - the pump source (2) is mechanically connected to the conversion element (1), - the plurality of first structural elements (14) of the conversion element (1) is arranged on the side of the active region (13) facing the pump source (2), - the plurality of first structural elements (14) is arranged between the pump source (2) and the plurality of second structural elements (15) or third structural elements (15), and - secondary radiation is generated in the active region (13) of the conversion element (1) upon excitation by the primary radiation. [13] Radiation-emitting semiconductor device with - a pump source (2) which generates primary radiation during operation, and - a conversion element (1) according to one of the preceding claims, wherein - the pump source (2) is mechanically connected to the conversion element (1), - the plurality of first structural elements (14) of the conversion element (1) is arranged on the side of the active region (13) facing away from the pump source (2), - at least the plurality of second structural elements (15) or at least the plurality of third structural elements (15) are arranged between the pump source (2) and the plurality of first structural elements (14), and - secondary radiation is generated in the active region (13) of the conversion element (1) upon excitation by the primary radiation. [14] Radiation-emitting semiconductor component according to one of the two preceding claims, in which a connecting region (3) is arranged directly between the conversion element (1) and the pump source (2), which connecting region provides the mechanical connection between the conversion element (1) and the pump source (2).

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