Light-emitting device

Abstract

The invention relates to a light-emitting device (1) which comprises a light-generating structure. The light-generating structure comprises a semiconductor layer stack (2) having a first layer (3) of a first doping type, a second layer (4) of a second doping type, and an active region (5) between the first and the second layer. In addition, the light-generating structure has a first contact layer (7), which is provided on the lower face (9) of the semiconductor layer stack (2) and electrically contacts the second layer (4), and a second contact layer (18), which is provided at least partly on a lateral surface of the semiconductor layer stack (2), electrically contacts the first layer (7), and is electrically insulated from the active region (5) and the second layer (4). The light-generating structure is equipped with at least one cavity (22), which extends from the upper face (11) of the light-generating structure, said upper face lying opposite the first contact layer, in the direction of the first contact layer (7). The light-emitting device (1) additionally has a first electrical contact (6), which electrically contacts the first contact layer (7), and a second electrical contact (8), which electrically contacts the second contact layer (18). In addition, a converter layer (10) is provided in the at least one cavity (22), said converter layer being designed to convert light of a first wavelength, which is generated in the active region (5), into light of a second wavelength.

Description

[0001] LIGHT-EMITTING DEVICE

[0002] This application claims priority from German patent application No. 10 2024 104 316 . 4 of February 15, 2024, the disclosure of which is hereby incorporated by reference into this application.

[0003] The present invention relates to a light-emitting device, in particular a p-LED with a converter layer, wherein the light-emitting device has improved performance with regard to color homogeneity and light emission direction. Furthermore, the present invention relates to a method for producing a light-emitting device.

[0004] BACKGROUND

[0005] The conversion of, for example, blue light emitted by a p-LED into white light is a common approach for various applications. It is advantageous if this is done as cost-effectively as possible, with as much color homogeneity as possible across location and beam angle, and as efficiently as possible.

[0006] Especially for applications where such p-LEDs are to be arranged in a transparent medium, such as a glass window, the transmission of the transparent medium should be as high as possible, thus keeping the shadowing area (p-LED size including converter) as small as possible. Furthermore, for most applications, only one-directional light emission is desired, which is why backward emission from the p-LED should be avoided.

[0007] Previously, p-LEDs were known which had a side and rear mirror to prevent backward emission. To convert the light emitted by such p-LEDs, the p-LEDs are transferred, for example, from a production wafer to an intermediate carrier, on which a light conversion layer is applied to the p-LEDs, completely encapsulating the p-LEDs. To achieve a homogeneous color across the location and beam angle of the emitted light, the conversion layer is arranged such that it extends over the entire p-LED, so that in particular light emitted at a small angle to the side of the p-LED is also converted.

[0008] However, such p-LEDs encapsulated in a converter are very large and additional processes are required to apply the conversion layer to the p-LEDs on the intermediate carrier.

[0009] It is therefore an object of the present application to counteract at least one of the aforementioned problems and to provide a light-emitting device with a converter layer, wherein the light-emitting device has improved performance with regard to color homogeneity and light emission direction. Furthermore, a method for producing such a light-emitting device is to be provided.

[0010] SUMMARY OF THE INVENTION

[0011] This need is met by the subject matter of the independent patent claims. Further developments and embodiments of the proposed principle are specified in the subclaims.

[0012] The inventors' concept consists in physically integrating the region in which light emerges from the epi structure of a pixel of a light-emitting device into a converter layer into the light-emitting device or a light-generating structure of the light-emitting device. For this purpose, at least one cavity in which the converter layer is arranged is provided in the light-emitting device or a light-generating structure of the light-emitting device. This allows the converter layer to be made smaller, in particular smaller than the lateral dimensions of the p-LED / the top side of a light-generating structure of the light-emitting device in which the converter layer is arranged. In addition, this allows the converter layer to be provided at a time when the semiconductor layer stack is still arranged on the production wafer and thus at wafer level.In one aspect, a light-emitting device is provided that has a light-generating structure with a semiconductor layer stack. The light-generating structure comprises a first layer of a first doping type, a second layer of a second doping type, and an active region arranged between the first and the second layer. The first layer can be, for example, an n-doped semiconductor layer, while the second layer can be, for example, a p-doped semiconductor layer. The two layers can thus form a pn junction, between which the active region is located. The active region can, for example, comprise a quantum well or multi-quantum well structure or, for example, quantum dots.

[0013] The light-generating structure further comprises a first contact layer which is arranged on an underside of the semiconductor layer stack and makes electrical contact with the second layer. In addition, the light-generating structure comprises a second contact layer which is arranged at least partially on a side surface of the semiconductor layer stack, which makes electrical contact with the first layer and which is electrically insulated from the active region and the second layer. In addition, at least one cavity is formed in the light-generating structure and extends from an upper side of the light-generating structure opposite the first contact layer in the direction of the first contact layer.

[0014] The light-emitting device further comprises a first electrical contact that electrically contacts the first contact layer, and a second electrical contact that electrically contacts the first layer and / or the second contact layer. By means of the first and second electrical contacts, the light-emitting device can be supplied with a supply current, for example.

[0015] In addition, a converter layer is arranged in the at least one cavity, which converter layer is designed such that it converts light of a first wavelength, which is generated in the active region, into light of a second wavelength. The converter layer can, for example, be formed from or comprise Ce:YAG, x:YAG, nitride, In-siloxane, a silicon matrix with light conversion particles or another suitable light conversion material. The converter layer can, for example, comprise or consist of quantum dots, which are optionally embedded in a matrix material. The converter layer can, however, also comprise, for example, extremely small phosphorus crystals (crystallites) which are embedded in a matrix material.

[0016] The lateral dimensions of the at least one cavity are in particular smaller than the lateral dimensions of a top side of the light-emitting structure. This can result in particular from the fact that the at least one cavity is produced in the light-emitting structure or the semiconductor layer stack in such a way that at least regions of the light-emitting structure remain as edge regions, i.e. boundaries for the converter layer. In this way, the region in which light escapes from the semiconductor layer stack into the converter layer is effectively limited in order to increase the color homogeneity and the light emission direction of the light-emitting device and at the same time to keep the footprint of the light-emitting device small.

[0017] The light-emitting device may in particular be a small light-emitting component / element such as a small LED or p-LED. A p-LED may in particular be a very small LED with edge lengths of up to 40 pm, down to 10 pm, down to 5 pm or even less. Such small LEDs may be free of a growth substrate and require special handling and processing to improve their internal quantum efficiency (IQE) and light extraction efficiency. An exemplary approach to improving the IQE of the p-LED is to coat the side surfaces of the semiconductor layer stack with a regrowth

[0018] layer to cover .

[0019] The light-emitting device can in particular have a thickness in the range between 1 pm and 10 pm, or in the range between 2 pm and 5 pm. The thickness of the converter layer can in this case be in a range between 0.5 pm and 8 pm, for example. In particular, the component can be designed to be as thin as possible, since the material of the semiconductor layer stack in particular is relatively expensive and costs can therefore be saved accordingly. In order to ensure that even a shallow cavity is sufficient to provide the converter layer, quantum dot converters can be used for the converter layer, which achieve a high degree of conversion with a small thickness. This in turn means that the entire light-emitting device and accordingly also the expensive semiconductor layer stack can be designed to be particularly thin.

[0020] In some aspects, the converter layer has lateral dimensions that are smaller than the lateral dimensions of the top side of the light-emitting structure. In particular, the converter layer does not protrude, or at least does not significantly protrude, beyond the top side in the lateral direction. This allows the footprint of the light-emitting device to be kept small.

[0021] In some cases, the first contact layer may, for example, comprise or consist of a transparent conductive oxide (TCO) such as indium tin oxide (ITO). The first contact layer may, for example, also comprise or consist of a transparent conductive oxide (TCO) such as indium tin oxide (ITO) in combination with a gold (Au)-germanium (Ge) alloy layer.

[0022] In some cases, the first and / or second electrical contact may comprise a gold (Au), platinum (Pt) and / or titanium (Ti) layer as well as a titanium (Ti), platinum (Pt), gold-indium-tin (AuInSn), NiInSn, AuSn, InSn and / or a gold (Au) based solder material as the contact surface.

[0023] In some aspects, the converter layer is substantially flush with the top side of the light-emitting structure. The at least one cavity can in particular be filled with the converter layer in such a way that it is substantially flush with the top side of the light-emitting structure. Accordingly, a top side of the converter layer and the top side of the light-emitting structure can lie substantially in the same plane. However, the at least one cavity can also be filled with the converter layer in such a way that the at least one cavity is slightly underfilled or overfilled, so that a top side of the converter layer and the top side of the light-emitting structure differ slightly from one another.In particular, however, the at least one cavity can also be filled with the converter layer in such a way that an upper side of the converter layer and the upper side of the light-emitting structure lie substantially in the same plane at least in an edge region of the upper side of the converter layer, in particular an edge region in which the upper side of the converter layer adjoins the upper side of the light-emitting structure.

[0024] In some aspects, the light-emitting device further comprises a passivation layer that covers exposed regions of the semiconductor layer stack on the top side. The passivation layer can in particular serve to passivate the material of the semiconductor layer stack against external influences after a desired structuring. The passivation layer can therefore, for example, cover any exposed parts of the top side in order to passivate the top side of the semiconductor layer stack, as well as to passivate all layers / components arranged on the top side. In some cases, the passivation layer additionally or alternatively covers the converter layer. In particular, the passivation layer can cover the converter layer and, together with the light-emitting structure, enclose the converter layer.

[0025] The passivation layer can be made of, for example, AI2O3, SiO2, SiN x, a combination thereof or another suitable passivation material .

[0026] In some aspects, the light-emitting device further comprises an optical aperture arranged on the upper side and exposing a central region of the upper side. The optical aperture is designed and arranged such that the at least one cavity and the central region at least partially overlap. The optical aperture can in particular consist of Al, Ag, a dielectric mirror, a metal and a dielectric mirror, or another material that is absorbent or reflective for the light generated in the active region.

[0027] The term "central" region in this context is not to be understood as a region that is only located in the middle of the top side / semiconductor layer stack, but can also be located away from the periphery of the top side / semiconductor layer stack, e.g., with different distances to opposite edges of the top side / semiconductor layer stack.

[0028] In some embodiments, the lateral dimensions of the central region are at least 5%, 10%, or 15% smaller than the lateral dimensions of a projection of the active region when viewed in a direction perpendicular to the top surface.

[0029] In some aspects, the light-emitting device further comprises a first dielectric layer which covers at least parts of the underside and / or the first contact layer and which is arranged between a side surface of the semiconductor layer stack and the second contact layer and in particular extends in regions to the top side.

[0030] In some aspects, the light-emitting device further comprises a second dielectric layer that covers at least parts of the bottom side and / or the first contact layer and / or the first dielectric layer that encapsulates the second contact layer, and that in particular extends to the top side.

[0031] In some aspects, the second contact layer, in particular together with the first and second dielectric layers, forms a reflective structure which is designed to reflect light of the first and / or second wavelength emitted by the side surfaces and the underside of the semiconductor layer stack in the direction of the top side of the light-generating structure. In some aspects, a reflective structure is arranged on at least one side surface of the semiconductor layer stack, wherein the side surface runs from the underside of the semiconductor layer stack in the direction of the top side of the light-emitting structure. The reflective structure can in particular surround / enclose the semiconductor layer stack and can thus be arranged on all side surfaces of the semiconductor layer stack.The reflective structure may be configured to reflect light generated in the active region toward the top surface to increase the light emission efficiency of the light-emitting device.

[0032] In some aspects, the reflective structure is disposed on the bottom surface of the semiconductor layer stack, wherein the reflective structure surrounds the first electrical contact. The reflective structure may be configured to reflect the light generated in the active region toward the top surface to improve the light emission efficiency of the light-emitting device.

[0033] A possible loss of luminance can be minimized in particular by improving the reflectivity of the side surfaces of the semiconductor layer stack and / or the underside of the semiconductor layer stack. The reflectivity of the reflective structure on the sidewall(s) and / or the underside can be improved, for example, by choosing a lower-loss material for the reflective structure (e.g. aluminum or silver) and additionally applying a single-layer coating (e.g. SiO2) that is thick enough to enable total internal reflection with minimal loss. Alternatively, a multi-layer coating can be applied that functions as a distributed Bragg mirror to improve the reflectivity over all angles of incidence.

[0034] By means of the reflective structure or the second contact layer, for example, a second electrical contact can be provided from the top side along the side surfaces of the semiconductor layer stack in the region of the bottom side, while being electrically insulated from the active region, the second layer, the first contact layer and the first electrical contact. In this way, a horizontally contactable light-emitting device can be provided, wherein the second electrical contact is arranged on the side of the light-emitting device opposite the top side and thus on the same side as the first electrical contact. For this purpose, the reflective structure can comprise a plurality of layers of conductive and non-conductive, e.g. dielectric, material layers which extend from the top side along the side surfaces of the semiconductor layer stack to the bottom side.

[0035] However, the light-emitting device can also be designed so that it can be contacted vertically, with the second electrical contact being arranged on the same side as the top side. For example, the optical aperture can be made of a conductive material and serve as a second electrical contact. The reflective structure can, however, be designed and arranged in the same way as already described, but with no electrical contact provided or connected on the bottom side of the light-emitting device. The light-emitting device can thus, for example, also be contactable from two opposite sides.

[0036] In some aspects, the at least one cavity borders at least partially directly on the reflective structure or the second contact layer and / or the first dielectric layer. In particular, the at least one cavity borders the reflective structure or the second contact layer and / or the first dielectric layer in such a way that at least partially no material of the semiconductor layer stack is arranged between the reflective structure or that at least partially no material of the semiconductor layer stack is arranged between the second contact layer and the converter layer and / or between the first dielectric layer and the converter layer. In particular, any material of the semiconductor material can be removed in the region of the at least one cavity, and the cavity can be formed only by the reflective structure or by the second contact layer and / or the first dielectric

[0037] Layer may be limited. In some aspects, a bottom surface of the at least one cavity has a roughened structure. This makes it possible to achieve homogeneous light conversion and homogeneous coupling of light through the top surface. In some aspects, the roughened structure ensures better coupling of light generated in the active region into the converter layer compared to a non-roughened interface. In particular, this can also limit the region in which light escapes from the semiconductor layer stack into the converter layer. The roughened structure can, for example, comprise a nanostructure, a cylindrical roughening or another roughened structure that increases the coupling-out efficiency from the semiconductor layer stack into the converter layer.

[0038] In order to ensure that the region in which light escapes from the semiconductor layer stack into the converter layer is smaller than an upper side of the light-emitting structure opposite the underside of the semiconductor layer stack, the first contact layer, according to some aspects, has lateral dimensions that are smaller than the lateral dimensions of the converter layer. As a result, a current applied to the first contact layer is limited to the lateral size of the first contact layer, so that light generation only takes place in a central region of the active region and light emission is in turn limited to a central region of an interface between the semiconductor layer stack and the converter layer. It is then possible for the converter layer to cover at least the central region and, in particular, to extend beyond the central region.In this way, the area in which light escapes from the semiconductor layer stack into the converter layer is effectively limited in order to increase the color homogeneity and the light emission direction of the light-emitting device.

[0039] In some aspects, the light-generating structure has a multiplicity of cavities which extend from the upper side of the light-generating structure in the direction of the first contact layer. The converter layer can also have a multiplicity of subregions, each of which is arranged in one of the multiplicity of cavities. The converter layer can accordingly also be formed by a non-continuous layer, but rather by subregions which are separated from one another and are arranged in a multiplicity of cavities in the light-generating structure. The cavities can be arranged at a defined distance from one another, can be arranged in a desired pattern, can have identical sizes or different sizes, or can overlap at least in regions.

[0040] According to a further aspect, a method for producing a light-emitting device is provided. The method may, in particular, be a method for producing a light-emitting device according to at least some of the aforementioned aspects. Thus, all aspects already described for the light-emitting device can be applied equally to the method for producing the same.

[0041] In some aspects, the method of manufacturing a light-emitting device comprises the following steps:

[0042] Providing a semiconductor layer stack having a first layer of a first doping type, a second layer of a second doping type and an active region arranged between the first and the second layer on a growth substrate;

[0043] Structuring the semiconductor layer stack, thereby forming a bottom surface and side surfaces of the semiconductor layer stack that extend from the bottom surface in a direction away from the bottom surface;

[0044] Providing a first contact layer on the underside of the semiconductor layer stack that electrically contacts the second layer;

[0045] Providing a second contact layer which is arranged at least partially on the side surfaces of the semiconductor layer stack, which electrically contacts the first layer, and which is electrically insulated from the active region and the second layer;

[0046] Providing a first electrical contact that electrically contacts the first contact layer;

[0047] Removing the growth substrate and exposing a top side opposite the bottom side of the semiconductor layer stack; creating at least one cavity extending from the top side in the direction of the first contact layer; and

[0048] Providing a converter layer in the at least one cavity, which is designed to convert light of a first wavelength, which is generated in the active region, into light of a second wavelength.

[0049] In some aspects, the step of providing the converter layer comprises at least one of the following steps:

[0050] squeegeeing;

[0051] Jetting;

[0052] inkjet printing;

[0053] Spray coating; electro-hydrodynamic printing;

[0054] evaporation;

[0055] grinding; and etching.

[0056] In some aspects, the step of providing the converter layer takes place such that the converter layer is substantially flush with the upper side. The step can in particular take place such that the at least one cavity is filled with the converter layer such that it is substantially flush with the upper side of the light-emitting structure. Accordingly, an upper side of the converter layer and the upper side of the light-emitting structure can lie substantially in the same plane. However, the at least one cavity can also be filled with the converter layer such that the at least one cavity is slightly underfilled or overfilled, so that an upper side of the converter layer and the upper side of the light-emitting structure differ slightly from one another.In particular, however, the at least one cavity can also be filled with the converter layer in such a way that an upper side of the converter layer and the upper side of the light-emitting structure lie substantially in the same plane at least in an edge region of the upper side of the converter layer, in particular an edge region in which the upper side of the converter layer adjoins the upper side of the light-emitting structure. In some aspects, the step of providing the converter layer comprises providing the converter layer with lateral dimensions that are smaller than the lateral dimensions of the upper side. Therefore, the resulting converter layer can in particular be designed such that it does not protrude laterally beyond the upper side.

[0057] In some aspects, the method further comprises providing a passivation layer on the converter layer and / or on exposed regions of the top side, in particular such that any regions of the semiconductor layer stack on the top side of the light-generating structure are covered by either the converter layer, an optical aperture or the passivation layer.

[0058] In order to ensure that the region in which light emerges from the semiconductor layer stack is limited to the region of the converter layer, the method according to some aspects comprises a further step of providing an optical aperture on the upper side, which only exposes a central part of the upper side, so that light generated in the active region can only leave the light-emitting device through the central region and thus only through the converter layer. In this way, the region in which light escapes from the semiconductor layer stack is effectively limited in order to increase the color homogeneity and the light emission direction of the light-emitting device. The optical aperture is in particular designed and arranged such that the at least one cavity and the central region at least partially overlap.

[0059] In some aspects, the method further comprises a step of providing a reflective structure covering at least parts of the bottom side and / or the first contact layer and covering the side surfaces, wherein the reflective structure comprises the second contact layer and a first and second dielectric layer that electrically isolate the second contact layer from the active region, the second layer, the first contact layer, and the first electrical contact. In this way, a reflector cavity can be provided that prevents backside emission of light from the light-emitting device.In some aspects, the method further comprises providing a first dielectric layer on at least parts of the bottom side and / or the first contact layer, wherein the first dielectric layer is arranged between a side surface of the semiconductor layer stack and the second contact layer and in particular extends in regions to the top side.

[0060] In some aspects, the method further comprises providing a second dielectric layer on at least parts of the bottom side and / or the first contact layer and / or the first dielectric layer, wherein the second dielectric layer encapsulates the second contact layer and in particular extends to the top side.

[0061] In some aspects, the step of creating the at least one cavity is carried out in such a way that the at least one cavity is at least partially directly adjacent to the second contact layer and / or the first dielectric layer. In particular, the at least one cavity is adjacent to the reflective structure or the second contact layer and / or the first dielectric layer in such a way that at least partially no material of the semiconductor layer stack is arranged between the reflective structure or that at least partially no material of the semiconductor layer stack is arranged between the second contact layer and the converter layer and / or between the first dielectric layer and the converter layer.In particular, the step of creating the at least one cavity may comprise removing any material of the semiconductor layer stack in the region of the at least one cavity, and the cavity is delimited only by the reflective structure or by the second contact layer and / or the first dielectric layer.

[0062] In some aspects, the method further comprises roughening a bottom surface of the at least one cavity to obtain a roughened structure. This can improve the outcoupling of light into the converter layer. The roughened structure can bring about better outcoupling of light generated in the active region into the converter layer compared to a non-roughened interface. This can additionally limit the region in which light escapes from the semiconductor layer stack into the converter layer.

[0063] In some aspects, the step of creating the at least one cavity comprises creating a plurality of cavities that extend from the top side toward the first contact layer. Furthermore, the step of providing the converter layer comprises providing a plurality of subregions of the converter layer, each of which is arranged in one of the plurality of cavities.

[0064] In some aspects, the method further comprises providing a second electrical contact on the side of the underside, which is electrically connected to the first layer, for example, via the reflective structure or the second contact layer. In this way, a horizontally contactable light-emitting device can be provided.

[0065] In order to ensure that the area in which light escapes from the semiconductor layer stack into the converter layer is less than or equal to the area of ​​the converter layer, the method according to some aspects comprises providing and / or structuring the first contact layer such that it has lateral dimensions that are less than or equal to the lateral dimensions of the converter layer. As a result, a current applied to the first contact layer is limited to the lateral size of the first contact layer, such that light generation only takes place in a central area of ​​the active area and light emission is in turn limited to a central area of ​​an interface between the semiconductor layer stack and the converter layer.In this way, the area in which light escapes from the semiconductor layer stack into the converter layer is effectively limited in order to increase the color homogeneity and the light emission direction of the light-emitting device.

[0066] BRIEF DESCRIPTION OF THE DRAWINGS Further aspects and embodiments according to the proposed principle will become apparent with reference to the various embodiments and examples which are described in detail in conjunction with the accompanying drawings.

[0067] Fig. 1A and 1B show a cross-sectional view and a plan view of an embodiment of a light-emitting device according to some aspects of the proposed principle;

[0068] Fig. 2 to 15 show steps of a method for manufacturing a light-emitting device in accordance with some aspects of the proposed principle;

[0069] Fig. 16A and 16B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle;

[0070] Fig. 17 shows a cross-sectional view of another embodiment of a light-emitting device according to some aspects of the proposed principle;

[0071] Fig. 18A and 18B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle;

[0072] Fig. 19A and 19B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle; Fig. 20A and 20B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle;

[0073] Fig. 21A and 21B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle;

[0074] Fig. 22A to 22C show cross-sectional views of further embodiments of a light-emitting device according to some aspects of the proposed principle; and

[0075] Fig. 23A to 24B show a cross-sectional view and a plan view of another embodiment of a light-emitting device according to some aspects of the proposed principle as well as a possible assembly of the light-emitting device in cross-section and in plan view.

[0076] DETAILED DESCRIPTION

[0077] The following embodiments and examples show various aspects and their combinations according to the proposed principle. The embodiments and examples are not always to scale. Likewise, various elements can be shown enlarged or reduced in size to emphasize individual aspects. It goes without saying that the individual aspects and features of the embodiments and examples shown in the figures can be easily combined with one another without thereby impairing the inventive principle. Some aspects have a regular structure or shape. It should be noted that in practice slight deviations from the ideal shape can occur without, however, contradicting the inventive idea.Furthermore, the individual figures, features, and aspects are not necessarily shown in the correct size, and the proportions between the individual elements may not always be correct. Some aspects and features are emphasized by being shown enlarged. However, terms such as "top", "above", "below", "below", "larger", "smaller", and the like are correctly represented in relation to the elements in the figures. This makes it possible to infer such relationships between the elements from the figures.

[0078] Figures 1A and 1B show a cross-sectional view and a plan view of an embodiment of a light-emitting device 1 according to some aspects of the proposed principle.

[0079] The light-emitting device 1 comprises a semiconductor layer stack 2 with a first layer 3 of a first doping type, a second layer 4 of a second doping type, and an active region 5 arranged between the first and second layers. The semiconductor layer stack 2 comprises a bottom side 9 and inclined and stepped side surfaces 16 that extend from the bottom side 9 in a direction away from the bottom side 9 and that define the shape of the semiconductor layer stack 2.

[0080] Arranged on the underside 9 is a first contact layer 7, in particular made of ITO, which is electrically coupled to the second layer 4. The first contact layer 7 can act in particular as a current spreading layer in order to conduct a current applied to the first contact layer 7 via a first electrical contact 6 into the second layer 4.

[0081] The semiconductor layer stack 2 is covered / encapsulated on its underside 9 and along its side surfaces 16 by a reflective structure 15, which comprises a first dielectric layer 19, a second dielectric layer 20 and a second contact layer 18 arranged between the first and second dielectric layers. The first dielectric layer 19 insulates the second contact layer

[0082] 18 electrically from the active region 5, the second layer 4 and the first contact layer 7. The second dielectric layer 20, on the other hand, passivates the second contact layer 18 and electrically insulates it from the first electrical contact 6. The second contact layer 18 is electrically coupled to the first layer 3 and leads a contact path along the side surfaces 16 back towards the underside 9, where a second electrical contact 8 is arranged coupled to the second contact layer 18. By means of such a construction, a horizontally contactable lighting device 1 can be provided. The first and second electrical contacts 6, 8 can serve as solder pads for mounting and electrically connecting the light-emitting device 1 on a target substrate.

[0083] The semiconductor layer stack 2 together with the first contact layer 7 and the reflective structure 15 form a light-generating structure which has a top side 11 on a side opposite the first contact layer 7. The top side 11 is formed by the reflective structure 15 in an edge region or comprises the latter. A cavity 22 is introduced into the light-generating structure and extends from the top side 11 in the direction of the first contact layer 7. In the case shown, the cavity 22 is introduced in particular into the semiconductor layer stack 2 and extends from the top side 11 into the first layer. The cavity 22 is designed in particular such that a bottom surface 23 of the cavity 22 is arranged above the active region 5, i.e. the cavity 22 extends only into the first layer 3, but not into the active region 5 or the second layer 4.

[0084] A converter layer 10 is arranged in the cavity 22, which fills the cavity 22 and is designed such that it converts light of a first wavelength, which is generated in the active region 5, into light of a second wavelength. The cavity 22 or the converter layer 10 located therein has lateral dimensions that are smaller than the lateral dimensions of the top side 11. In the case shown, the cavity 22 or the converter layer 10 located therein is designed such that it has lateral dimensions that are smaller than lateral dimensions of an upper region of the semiconductor layer stack 2. The cavity 22 is formed in particular in a central region of the semiconductor layer stack 2, so that the converter layer 10 also extends over a central region of the semiconductor layer stack 2.

[0085] A passivation layer 17 is arranged on the converter layer 10 and on exposed parts of the top side 11, which passivates, in particular, exposed regions of the semiconductor layer stack 2 against external influences. The passivation layer 17 follows the underlying structure and extends along the entire top side 11.

[0086] Due to the arrangement and size of the converter layer 10, the converter layer 10 can be applied at the wafer level during the manufacture of the light-emitting device. Thanks to the converter layer 10 arranged in the cavity 22, light of a first wavelength, which is generated in the active region 5, can be efficiently converted into light of a second wavelength. Furthermore, the proposed arrangement can provide a very compact light-emitting device.

[0087] Figures 2 to 15 show steps of a method for manufacturing a light-emitting device according to some aspects of the proposed principle.

[0088] In a first step, as shown in Figure 2, a growth substrate 21 is provided with a structured semiconductor layer stack 2 epitaxially grown thereon. The semiconductor layer stack comprises a first layer 3 of a first conductivity type, a second layer 4 of a second conductivity type and an active region 5 between the first and second layers 3, 4. The semiconductor layer stack 2 is constructed such that it has at least the two sections 2a, 2b shown, each with a bottom side 9 and mesa-etched side surfaces 16. The sections 2a, 2b are still connected by a continuous remainder of the first layer 3. The number and shape of the sections 2a, 2b are, however, to be understood as examples and can vary as desired.In a further step, as shown in Figure 3, a structured first contact layer with sections 7a, 7b is deposited to cover the undersides 9 of the semiconductor layer stack 2. The structured first contact layer can also form a structured mask that is suitable as a mask for the preceding etching step and can thus be deposited on the semiconductor layer stack 3 before a mesa etching of the semiconductor layer stack 2 has been carried out, as shown in Figure 2. The structured first contact layer 7 can, for example, consist of a transparent conductive material such as ITO or comprise ITO.

[0089] In a further step, as shown in Figure 4, a first dielectric layer 19 is applied to parts of the first contact layer 7 and to the side surfaces comprising the side surface sections of the active region 5 and the second layer 4 as well as some of the side surface sections of the first layer 3. The first dielectric layer 19 serves to passivate parts of the first contact layer 7 and the side surface sections of the active region 5 and the second layer 4 before a later applied second contact layer 18, as shown in Figure 5.

[0090] The second contact layer 18 is applied along the side surfaces 16 to electrically contact the first layer 3 and extends along the dielectric layer 19, but is spaced from an opening through the dielectric layer 19 so as not to electrically contact the first contact layers 7a, 7b. A second dielectric layer 20 is applied to the second contact layer 18, as shown in Figure 6, which encapsulates the second contact layer 18 together with the first dielectric layer 19.

[0091] In a further step, as shown in Figure 7, a first and a second electrical contact 6, 8 are applied to the second dielectric layer 20. The first electrical contact 6 electrically contacts the first contact layer 7, while the second electrical contact 8 electrically contacts the second contact layer 18 in the region of an opening through the second dielectric layer 20. The first and the second electrical contact 6, 8 serve as later contact surfaces, which are arranged on the same side of the later light-emitting device, whereby a horizontally contactable light-emitting device can be provided.

[0092] The resulting structure is then covered, as shown in Figures 8 and 9, with a sacrificial layer 24, a material layer 25, and a carrier layer 26 in the specified order. The sacrificial layer may, for example, be a layer of SiO2 or Si, which is designed such that it can be selectively removed / etched in a later step in order to detach the later light-emitting devices from the underlying structure. The material layer 25, on the other hand, can consist of an encapsulation material that makes the underlying structure planar and forms a substantially flat surface onto which the carrier layer 26 can be applied.

[0093] The growth substrate 21 can then be removed, as shown in Figure 10, and the continuous remainder of the first layer 3 can be removed, as shown in Figure 11, in order to separate the parts 2a, 2b of the semiconductor layer stack 2 and to expose top sides 11 of the light-generating structures formed by the semiconductor layer stack 2 together with the first contact layer 7 and the reflective structure 15.

[0094] As shown in Figure 12, a cavity 22 is introduced or etched into each of the light-generating structures from the top side 11, said cavity extending from the top side 11 in the direction of the first contact layer 7. In the case shown, the cavities 22 are introduced in particular into the semiconductor layer stack 2 and extend from the top side 11 into the first layer 3. The cavities 22 are designed in particular such that a bottom surface 23 of the cavity 22 is arranged above the active region 5, i.e. the cavities 22 extend only into the first layer 3, but not into the active region 5 or the second layer 4. In addition, in the case shown, the cavities 22 are designed such that they have lateral dimensions that are smaller than lateral dimensions of an upper region of the respective semiconductor layer stack portion 2.The cavities 22 are formed in particular in a central region of the semiconductor layer stack portion 2.

[0095] The cavities 22 are then filled with a converter material that forms a subsequent converter layer 10, e.g., by doctoring, as shown in Figure 13. Furthermore, excess material of the converter material can be removed by curing and / or grinding and / or polishing in order to separate individual converter layers 10 belonging to a light-emitting device, each of which fills one of the cavities 22.

[0096] The cavities 22 can, however, also be filled with a converter material by means of electrohydrodynamic printing, so that a subsequent grinding and / or polishing step can be eliminated, or the cavities 22 can be filled by means of spray coating or spin-coating of the converter material and excess material of the converter material can then be removed again.

[0097] As shown in Figure 14, in a further step, a passivation layer 17 is applied to the converter layer 10 and to exposed parts of the upper side 11, which passivates all exposed regions of the semiconductor layer stack 2 against external influences. The passivation layer 17 follows the underlying structure and extends along the entire upper side 11.

[0098] Subsequently, parts of the sacrificial layer 24 are exposed in order to be able to reach and etch the sacrificial layer 24 for separating the light-emitting devices 1, as shown in Figure 15. The light-emitting devices 1 are then only fixed to the carrier substrate 26 by a small pin made of the material layer 25 serving as a holding structure and can be lifted off the carrier substrate 26, for example using a stamping tool. Figures 16A and 16B show a cross-sectional view and a plan view of another embodiment of a light-emitting device 1 according to some aspects of the proposed principle. In comparison to the embodiment shown in Figures 1A and 1B, the embodiment comprises a plurality of cavities 22 which are filled 10 with partial regions of the converter layer.The converter layer 10 can accordingly also be formed by a discontinuous layer, but rather by partial regions which are separated from one another and are arranged in a multiplicity of cavities 22 in the light-generating structure. The cavities 22 can, as shown, be arranged at a defined distance and in a desired pattern and can essentially have an identical size. The cavities 22, on the other hand, can also be arranged in a random pattern with different distances from one another and / or can have different sizes and / or they can overlap at least in regions. By means of such a configuration, for example, a desired color mixture can be achieved during the light conversion, as well as a particularly homogeneous emission of converted and optionally also unconverted light.

[0099] Figure 17 shows a cross-sectional view of a further embodiment of a light-emitting device 1 according to some aspects of the proposed principle. The light-emitting device 1 has an optical aperture 14 on the top side 11, which exposes a central region 13 of the top side 11 and covers parts of the top side 11 that border the side surfaces 16. The optical aperture 14 is designed such that it blocks the light incident on the optical aperture 14, but the light in the region of the central region 13 is not impaired. By means of such an aperture 14, an emission of unconverted light from the light-emitting device 1 in an edge region in which the converter layer 10 is not formed can be suppressed.

[0100] Figures 18A and 18B and Figures 19A and 19B show a cross-sectional view and a plan view of two further embodiments of a light-emitting device 1 according to some aspects of the proposed principle. In addition to the light-emitting device 1 shown in Figures 1A and 1B, the light-emitting devices 1 have a first contact layer 7 with lateral dimensions that are smaller than or equal to the lateral dimensions of the converter layer 10 in order to ensure that the region in which light exits the semiconductor layer stack 2 into the converter layers 10 is limited to the region of the converter layer 10.As a result, a current applied to the first contact layer 7 is limited to the lateral size of the first contact layer 7, so that light generation takes place only in a central region of the active region 5 and, in turn, light emission is also limited to a central region of an interface between the semiconductor layer stack 2 and the converter layer 10.

[0101] In the embodiment shown in Figures 18A and 18B, the reduction of the first contact layer 7 is achieved by actually reducing the size of the first contact layer 7. In the embodiment shown in Figures 19A and 19B, the reduction of the first contact layer 7 is achieved by reducing the size of both the first contact layer 7 and a portion of the second layer 4. The latter embodiment, in particular, can provide even better current limitation to limit the actual light emission to a central region of the active region 5.

[0102] Figures 20A and 20B, as well as 21A and 21B, each show a cross-sectional view and a plan view of another embodiment of a light-emitting device 1 according to some aspects of the proposed principle. The embodiments differ from the embodiment shown in Figures 1A and 1B in that the cavity 22 directly adjoins the second contact layer 18 or the first dielectric layer 19. In particular, the cavity 22 adjoins the reflective structure 15 or the second contact layer 18 and the first dielectric layer 19 in such a way that no material of the semiconductor layer stack 2 is arranged between the reflective structure 15 and the cavity 22. When creating the cavity 22, any material of the semiconductor layer stack 2 can be removed, in particular in the region of the cavity 22, and the cavity 22 is only formed by the reflective structure 15 or.bounded by the second contact layer 18 and the first dielectric layer 19.

[0103] For better coupling or decoupling of light from the semiconductor layer stack 2 into the converter layer 10, a bottom surface 23 of the cavity 22 of the embodiment shown in Figures 21A and 21B additionally has a roughened structure 12. This can enhance the coupling or decoupling of light from the semiconductor layer stack 2 into the converter layer 10. However, the type of surface structuring / roughening shown is only to be understood as an example, and any other type of surface structuring / roughening can be introduced into the bottom surface 23.

[0104] Figures 22A to 22C each show a cross-sectional view of a further embodiment of a light-emitting device 1 according to some aspects of the proposed principle. In particular, the embodiments of Figures 22A to 22C illustrate that the cavity 22 can be filled with the converter material such that the resulting converter layer 10 is substantially flush with the upper side (Figure 22A). However, the cavity can also be overfilled or underfilled, resulting in a converter layer 10 which projects beyond the upper side 10 at least in some regions (Figure 22B), or which at least in some regions does not project as far as the upper side 10 but is thinner (Figure 22C).

[0105] Figures 23A and 23B show a cross-sectional view and a plan view of another embodiment of a light-emitting device 1 according to some aspects of the proposed principle, and Figures 24A and 24B show a possible structure of the light-emitting device 1 in cross section and in plan view. The light-emitting device 1 is designed as a vertically contactable light-emitting device 1, wherein the optical aperture 14 acts as a second electrical contact 8. By constructing such a vertically contactable light-emitting device 1, the size / footprint of the light-emitting device 1 can be further reduced. For electrical contacting, the light-emitting device 1 can be arranged on a target substrate 28, wherein its first electrical contact 6 is electrically coupled to a solder pad 29 on a first section of a metallization layer 30.The second electrical contact 8 and thus the optical aperture 14 can, however, be electrically coupled to a second section of the metallization layer 30 via a conductor track 31 or a planar connection.

[0106] LIST OF REFERENCE SYMBOLS

[0107] 1 light-emitting device

[0108] 2 semiconductor layer stacks

[0109] 2a , 2b separate portions

[0110] 3 first layer

[0111] 4 second layer

[0112] 5 active area

[0113] 6 first electrical contact

[0114] 7 first contact layer

[0115] 7a , 7b first contact layer

[0116] 8 second electrical contact

[0117] 9 Bottom

[0118] 10 Converter layer

[0119] 11 Top

[0120] 12 roughened structure

[0121] 13 central area

[0122] 14 optical aperture

[0123] 15 reflective structure

[0124] 16 side surface

[0125] 17 Passivation layer

[0126] 18 second contact layer

[0127] 19 dielectric layer

[0128] 20 dielectric layer

[0129] 21 Growth substrate

[0130] 22 Cavity

[0131] 23 floor area

[0132] 24 sacrificial layer

[0133] 25 material layers

[0134] 26 Carrier layer

[0135] 27 Filler material

[0136] 28 Target substrate

[0137] 29 Solder pad

[0138] 30 Metallization layer

[0139] 31 Conductor track

Claims

PATENT CLAIMS 1. A light-emitting device (1) comprising: a light-generating structure with a semiconductor layer stack (2) comprising a first layer (3) of a first doping type, a second layer (4) of a second doping type, and an active region (5) arranged between the first and the second layer, a first contact layer (7) which is arranged on an underside (9) of the semiconductor layer stack (2) and electrically contacts the second layer (4), a second contact layer (18) which is arranged at least partially on a side surface (16) of the semiconductor layer stack (2), which electrically contacts the first layer (4) and is electrically insulated from the active region and the second layer (4), and at least one cavity (22) which extends from an upper side (11) of the light-generating structure opposite the first contact layer (7) in the direction of the first contact layer (7);a first electrical contact (6) that electrically contacts the first contact layer (7); a second electrical contact (8) that electrically contacts the second contact layer (18); and a converter layer (10) that is arranged in the at least one cavity (22) and is configured to convert light of a first wavelength generated in the active region (5) into light of a second wavelength.

2. The light-emitting device according to claim 1, wherein the converter layer (10) has lateral dimensions that are smaller than the lateral dimensions of the top side (11).

3. The light-emitting device according to any one of the preceding claims, wherein the converter layer (10) is substantially flush with the upper side (11).

4. The light-emitting device according to one of the preceding claims, further comprising a passivation layer (17) covering the converter layer (10) and in particular exposed regions of the top side (11).

5. The light-emitting device according to one of the preceding claims, further comprising an optical aperture (14) arranged on the upper side (11) and exposing a central region (13) of the upper side (11), wherein the at least one cavity (22) and the central region (13) at least partially overlap.

6. The light-emitting device according to claim 5, wherein the second electrical contact (8) comprises the optical aperture (14).

7. The light-emitting device according to one of the preceding claims, further comprising a first dielectric layer (19) which covers at least parts of the underside (9) and / or the first contact layer (7) and which is arranged between a side surface (16) of the semiconductor layer stack (2) and the second contact layer (18) and extends in particular in regions up to the top side (11).

8. The light-emitting device according to one of the preceding claims, further comprising a second dielectric layer (20) which covers at least parts of the underside (9) and / or the first contact layer (7) and / or the first dielectric layer (19) and which encapsulates the second contact layer (18) and in particular extends to the top side (11).

9. The light-emitting device according to one of the preceding claims, wherein the second electrical contact (8) is arranged on a side of the light-emitting device (1) opposite the top side (11).

10. The light-emitting device according to one of the preceding claims, wherein the at least one cavity (22) at least partially directly adjoins the second contact layer (18) and / or the first dielectric layer (19), such that at least partially no material of the semiconductor layer stack (2) is arranged between the second contact layer (18) and the converter layer (10) and / or that at least partially no material of the semiconductor layer stack (2) is arranged between the first dielectric layer (19) and the converter layer (10).

11. The light-emitting device according to one of the preceding claims, wherein a bottom surface (23) of the at least one cavity (22) has a roughened structure (12).

12. The light-emitting device according to one of the preceding claims, wherein the first contact layer (7) has lateral dimensions which are smaller than the lateral dimensions of the converter layer (10).

13. The light-emitting device according to one of the preceding claims, wherein the second contact layer (18), in particular together with the first and second dielectric layers (19, 20), forms a reflective structure (15) which is designed to reflect a light of the first and / or second dielectric layer emitted by the side surfaces (14) and the underside (9) of the semiconductor layer stack (2). Wavelength towards the top side (11) of the light-generating to reflect structure.

14. The light-emitting device according to one of the preceding claims, wherein the light-generating structure has a plurality of cavities (22) which extend from the upper side (11) of the light-generating structure in the direction of the first contact layer (7), and wherein the converter layer (10) has a plurality of subregions, each of which is arranged in one of the plurality of cavities (22).

15. Method for manufacturing a light-emitting device (1) , comprising the steps: Providing a semiconductor layer stack (2) with a first layer (3) of a first doping type, a second layer (4) of a second doping type and an active region (5) arranged between the first and the second layer on a growth substrate (21); Structuring the semiconductor layer stack (2), whereby a bottom side (9) and side surfaces (16) of the semiconductor layer stack (2) are formed, which extend from the bottom side (9) in a direction away from the bottom side (9); Providing a first contact layer (7) on the underside (9) of the semiconductor layer stack (2) which electrically contacts the second layer (4); Providing a second contact layer (18) which is at least partially formed on the side surfaces (16) of the semiconductor layer stack (2) is arranged, which electrically contacts the first layer (4) and which is electrically insulated from the active region () and the second layer (4); Providing a first electrical contact (6) which electrically contacts the first contact layer (7); Removing the growth substrate (21) and exposing an upper side (11) opposite the underside (9) of the semiconductor layer stack (2); Creating at least one cavity (22) extending from the top side (11) in the direction of the first contact layer (7); and Providing a converter layer (10) in the at least one cavity (22) which is designed to convert light of a first wavelength generated in the active region (5) into light of a second wavelength.

16. The method according to claim 15, wherein the step of providing the converter layer (10) comprises at least one of the following steps: squeegeeing; Jetting; inkjet printing; Spray coating; electro-hydrodynamic printing; evaporation; grinding; and Etching .

17. The method according to any one of claims 15 to 16, wherein the step of providing the converter layer (10) is carried out such that the converter layer (10) is substantially flush with the top side (11).

18. The method according to any one of claims 15 to 17, wherein the step of providing the converter layer (10) comprises providing the converter layer (10) with lateral dimensions that are smaller than the lateral dimensions of the top side (11).

19. The method according to any one of claims 15 to 18, further comprising providing a passivation layer (17) on the converter layer (10) and / or on exposed regions of the top side (11).

20. Method according to one of claims 15 to 19, further comprising providing an optical aperture (14) on the upper side (11), wherein the optical aperture (14) exposes a central region (13) of the upper side (11), and wherein the at least one cavity (22) and the central region (13) at least partially overlap.

21. The method according to any one of claims 15 to 20, further comprising providing a first dielectric layer (19) on at least parts of the underside (9) and / or the first contact layer (7), wherein the first dielectric layer (19) is arranged between a side surface (16) of the semiconductor layer stack (2) and the second contact layer (18) and extends in particular in regions to the top side (11).

22. The method according to any one of claims 15 to 21, further comprising providing a second dielectric layer (20) on at least parts of the bottom side (9) and / or the first contact layer (7) and / or the first dielectric layer (19), wherein the second dielectric layer (20) encapsulates the second contact layer (18) and in particular extends to the top side (11).

23. The method according to any one of claims 15 to 22, wherein the step of creating the at least one cavity (22) is carried out such that the at least one cavity (22) is at least partially directly adjacent to the second contact layer (18) and / or the first dielectric layer (19), such that at least partially no material of the semiconductor layer stack (2) is arranged between the second contact layer (18) and the at least one cavity (22) and / or that at least partially no material of the semiconductor layer stack (2) is arranged between the first dielectric layer (19) and the at least one cavity (22).

24. The method according to any one of claims 15 to 23, wherein further comprising roughening a bottom surface (23) of the at least one cavity (22) to produce a roughened structure (12).

25. The method according to any one of claims 15 to 24, wherein the step of producing the at least one cavity (22) comprises producing a plurality of cavities (22) extending from the top side (11) in the direction of the first contact layer (7), and wherein the step of providing the converter layer (10) comprises a Providing a plurality of subregions of the converter layer (10), each of which is arranged in one of the plurality of cavities (22).

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