Light emitting device

Abstract

The invention concerns a light emitting device comprising a semiconductor layer stack with 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 light emitting device further comprises a bottom contact layer arranged on a bottom surface of the semiconductor layer stack electrically contacting the second layer, a first electric contact electrically contacting the bottom contact layer, and a second electric contact electrically contacting the first layer. On or above a top surface of the semiconductor layer stack opposite the bottom surface a converter layer is arranged being configured to convert light of a first wavelength generated in the active region into light of a second wavelength. The light emitting device further comprises measures to physically reduce the area where light escapes from the semiconductor layer stack into the converter layer, such that the converter layer can be designed smaller, in particular smaller than the lateral dimensions of the top surface.

Description

[0001] LIGHT EMITTING DEVICE

[0002] The present application claims priority from German patent application DE 10 2023 127 201 . 2 filed on October 05 , 2023 , the disclosure of which is incorporated by way for reference in its entirety .

[0003] The present invention concerns a light emitting device , in particular a p-LED with a converter layer arranged on top, wherein the light emitting device provides an improved performance regarding colour homogeneity and light emitting directionality . In addition, the present invention concerns a method for manufacturing a light emitting device .

[0004] BACKGROUND

[0005] The conversion of for example blue light emitted from a p-LED into white light is a common approach for several applications . This is favourable to be done as cost-effective as possible , as homogeneous as possible in colour over location and beam angle , and as efficient as possible .

[0006] For in particular applications in which such p-LEDs are to be arranged in a transparent medium such as for example a glass window, the transmission of the transparent medium should be as large as possible and therefore the shading area ( p-LED size incl . converter ) should be as small as possible . In addition for most of the applications only an emission of light into one direction is favoured which is why a backward emission of the p-LED should be avoided .

[0007] To date p-LEDs are known which comprise a side and backside mirror to prevent backward emission . For conversion of the light emitted by such p-LEDs the p-LEDs are transferred from a source wafer onto an intermediate carrier, on which a light conversion layer is applied to the p-LEDs completely encapsulating the p-LEDs . In order to get a homogeneous colour over location and beam angle of the emitted light , the conversion layer must thereby protrude over the whole p-LED so that in particular light emitted with a small angle sideways of the p-LED is not or to only a small degree unconverted . Such in a converter encapsulated p-LEDs are however large in size and additional processes are needed for applying the conversion layer onto the p-LEDs on the intermediate carrier .

[0008] It is thus an obj ect of the present application to counteract at least one of the aforementioned problems and to provide a light emitting device with a converter layer arranged on top , wherein the light emitting device provides an improved performance regarding colour homogeneity and light emitting directionality . It is further to be provided a method for manufacturing such a light emitting device .

[0009] SUMMARY OF THE INVENTION

[0010] This and other obj ects are addressed by the subj ect matter of the independent claims . Features and further aspects of the proposed principles are outlined in the dependent claims .

[0011] The concept , the inventors propose , is to physically reduce the area where light escapes from the epi structure of a pixel of a light emitting device into a converter layer , by introducing an optical aperture on a top surface of the semiconductor layer stack or by confinement of the current applied to the semiconductor layer stack such that emission of light is only possible / takes place within only a central region of the interface between the p-LED' s epi surface and the converter layer . By doing so , the converter layer can be designed smaller, in particular smaller than the lateral dimensions of the p- LED / the top surface of the light emitting device on which the converter layer is arranged . Due to this , the converter layer can be already provided on the semiconductor layer stack already at a point of time where the semiconductor layer stack is still arranged on the source wafer and thus on wafer level .

[0012] In one aspect , a light emitting device is provided comprising a semiconductor layer stack with 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 for example be a semiconductor layer that is n-doped, whereas the second layer can for example be a semiconductor layer that is p-doped . The two layers can thus form a pn- j unction with the active region arranged in-between . The active region can for example comprise a quantum well or multi quantum well structure , or can for example comprise quantum dots .

[0013] The light emitting device further comprises a bottom contact layer arranged on a bottom surface of the semiconductor layer stack electrically contacting the second layer, a first electric contact electrically contacting the bottom contact layer, and a second electric contact electrically contacting the first layer . By means of the first and second electric contact , the light emitting device can for example be applied with a supply current .

[0014] In addition, a converter layer is arranged on or above a top surface of the semiconductor layer stack opposite the bottom surface , which is configured to convert light of a first wavelength generated in the active region into light of a second wavelength . The converter layer can for example be formed of or comprise Ce : YAG, x : YAG, Nitride , In Siloxane , a silicon matrix comprising light conversion particles , or any other suitable light conversion material .

[0015] To provide , that the area where light escapes from the semiconductor layer stack into a converter layer is an area smaller than a top surface of the semiconductor layer stack opposite the bottom surface , according to some aspects , an optical aperture is arranged between the converter layer and the top surface exposing only a central portion of the top surface such that light generated in the in the active region can exit the light emitting device only through the central region . It is then possible that the converter layer covers at least the central portion and in particular extends beyond the central portion but must not extend over the white light emitting device or even encapsulate the whole light emitting device . By this the area where light escapes from the semiconductor layer stack into the converter layer , is limited effectively to increase the colour homogeneity and light emitting directionality of the light emitting device while keeping the footprint of the light emitting device small . The optical aperture can in particular be formed of or comprise Al , Ag , a dielectric mirror, a metal and a dielectric mirror , or any other material being absorbent or reflective for light generated in the active region .

[0016] To provide , that the area where light escapes from the semiconductor layer stack into a converter layer is an area smaller than a top surface of the semiconductor layer stack opposite the bottom surface , according to some aspects , the bottom contact layer comprises lateral dimensions which are smaller than the lateral dimensions of the converter layer . By this a current applied to the bottom contact layer is confined to the lateral size of the bottom contact layer such that a generation of light only takes place within a central region of the active region and in turn an emission of light is also limited to a central region of an interface between the p-LED' s epi surface and the converter layer . It is then possible that the converter layer covers at least the central portion and in particular extends beyond the central portion but must not extend over the white light emitting device or even encapsulate the whole light emitting device . By this the area where light escapes from the semiconductor layer stack into the converter layer, is limited effectively to increase the colour homogeneity and light emitting directionality of the light emitting device while keeping the footprint of the light emitting device small .

[0017] The term "central" area shall in this context not be understood as an area only in the very centre of the top surface / the semiconductor layer stack but can also be located distant from the circumference of the top surface / the semiconductor layer stack with for example different distances to for example opposing edges of the top surface / the semiconductor layer stack .

[0018] In some embodiments , the central region is at least 5% , 10% , or 15 % smaller by length than a proj ection of the active region when viewing in a direction perpendicular to the top surface .

[0019] The light emitting device can in particular be a small light emitting component / element such as a small LED or p-LED . A p-LED can in particular be a very small LED with edge lengths down to 40 pm, down to 10 pm, down to 5 pm or even less . Such small LEDs can be free of a growth substrate and require a special handling and processing to improve their IQE and light outcoupling efficiency . One exemplary approach to improve the IQE of the p-LED is to cover side surfaces of the semiconductor layer stack with a regrowth layer .

[0020] In some aspects , the converter layer comprises lateral dimensions which are smaller than the lateral dimensions of the top surface . The converter layer in particular does not or at least not substantially protrude the top surface in a lateral direction . By this , the footprint of the light emitting device can be kept small .

[0021] In some aspects bottom contact layer can for example comprise or consist of a transparent conductive oxide (TCO ) such as indium tin oxide ( ITO ) . The bottom contact layer can for example also comprise or consist of a transparent conductive oxide (TCO ) such as indium tin oxide ( ITO ) combined with a gold (Au ) germanium (Ge ) alloy layer .

[0022] In some aspects , the first and / or second electric contact can comprise a gold (Au ) , platin ( Pt ) and / or titanium (Ti ) layer as well as a titanium ( Ti ) , platin ( Pt ) , gold-indium-tin (AulnSn ) , NilnSn, AuSn, InSn and / or a gold (Au ) based solder material as a contact pad .

[0023] In some aspects , the top surface comprises a roughened structure , in particular in the area of the central portion . By means of this , an outcoupling of light through the top surface in particular in the central region can be further enhanced . In some embodiments , the roughened structure provides a better outcoupling of light , generated in the active region, from the top surface into the converter layer compared to an unroughened interface . By this the area where light escapes from the semiconductor layer stack into the converter layer is additionally limited . The roughened structure can for example comprise a nanostructure , a cylindrical roughening or any other roughened structure enhancing the outcoupling efficiency of the top surface . In some aspects , the top surface comprises a roughened structure in the area of the central portion as well as an unroughened structure surrounding the central portion . The unroughened area can at the same time due to different refractive indexes of the semiconductor layer stack and the converter layer act as a reflector, in particular for light incident on the top surface at shallow angles . This can in addition further promote the effect of limiting the area where light escapes from the semiconductor layer stack into the converter layer .

[0024] In some aspects , the light emitting device further comprises a passivation layer arranged between the top surface and the converter layer or covering the converter layer . The passivation layer can in particular be to passivate the material of the semiconductor layer stack from external influences after being structured in a desired way . The passivation layer can therefore for example cover the whole top surface to passivate the top side of the semiconductor layer stack or can cover the converter layer as well as remaining exposed portions of the top surface passivating the top side of the semiconductor layer stack as well as all layers / components arranged on the top surface .

[0025] In some aspects , the passivation layer covers at least portions of the optical aperture on a side facing away from the top surface . In particular the optical aperture can be arranged directly on the top surface and the passivation layer can cover the top surface in the central portion where the top surface is exposed and extend on and over the optical aperture . The passivation layer can however also cover / enclose the converter layer and extend on and over the optical aperture on which the converter layer is arranged .

[0026] The passivation layer can for example be of A12O3, SiO2, SiNx, a combination thereof , or any other suitable passivating material .

[0027] In some aspects , a reflective structure is arranged on at least one side surface of the semiconductor layer stack, the side surface connecting the top and the bottom surface with each other . 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 can be configured to reflect light generated in the active region in the direction of the top surface , to enhance the light emitting efficiency of the light emitting device . In addition, the reflective structure can be configured to reflect light , reflected at the optical aperture or the unroughened surface , to the central portion or roughened surface to again enhance the light emitting efficiency of the light emitting device and to ensure that the light blocked at the first moment by the optical aperture or the unroughened surface nevertheless finds its way out of the light emitting device via the central portion into the converter layer .

[0028] In some aspects , a reflective structure is arranged on the bottom surface of the layer stack, the reflective structure surrounding the first electric contact . The reflective structure can be configured to reflect light generated in the active region in the direction of the top surface , to enhance the light emitting efficiency of the light emitting device . In addition, the reflective structure can be configured to reflect light , reflected at the optical aperture or the unroughened surface , to the central portion or roughened surface to again enhance the light emitting efficiency of the light emitting device and to ensure that the light blocked at the first moment by the optical aperture or the unroughened surface nevertheless finds its way out of the light emitting device via the central portion into the converter layer .

[0029] A possible output luminance penalty compared to providing a structure that emits light over the whole top surface of the light emitting device can in particular be minimized by improving the reflectivity of the side surfaces of the semiconductor layer stack and / or the bottom surface of the semiconductor layer stack . The reflectivity of the reflective structure on the side wall ( s ) and / or the bottom surface can for example be improved by choosing a less lossy material for the reflective structure ( for example aluminium or silver ) and additionally applying a single-layer coating ( e . g . Si02 ) that is thick enough to allow total internal reflectance with minimal loss . As an alternative , a multilayer coating that functions as a distributed Bragg mirror can be applied to improve the reflectance over all incoming angles .

[0030] In some aspects , the reflective structure comprises a conductive material and is electrically coupled to the first layer and wherein the reflective structure is isolated from the active region, the second layer, the bottom contact layer and the first electric contact . By means of the reflective structure , for example an electric contact can be provided from the top surface along the side surfaces of the semiconductor layer to the bottom surface while being electrically isolated from the active region, the second layer, the bottom contact layer and the first electric contact . By means of this , a horizontal contactable light emitting device can be provided with the second electric contact being arranged on the side of the light emitting device opposite the top surface and thus on the same side as the first electric contact . The reflective structure can therefore comprise several layers of conductive and non-conductive , for example dielectric material layers extending from the top surface along the side surfaces of the semiconductor layer stack onto the bottom surface .

[0031] The light emitting device can however also be of a vertical type , with the second electric contact being arranged on the same side as the top surface . For example , the optical aperture can be of a conductive material and act as the second electric contact . Still the reflective structure can be designed and arranged in the same way as already described with however not providing or connecting an electric contact on the side of the bottom side of the light emitting device . The light emitting device can thus for example also be contactable from two opposing sides .

[0032] According to a further aspect , a method for manufacturing a light emitting device is provided . The method can in particular be a method for manufacturing a light emitting device according to at least some of aforementioned aspects . Hence all aspects already described for the light emitting device can in the same way be applied to the method for manufacturing the same . According to some aspects , the method for manufacturing a light emitting device comprises the following steps :

[0033] Providing a semiconductor layer stack with 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 ;

[0034] Structuring the semiconductor layer stack thereby forming a bottom surface as well as side surfaces extending from the bottom surface into a direction away from the bottom surface ;

[0035] Providing a bottom contact layer on the semiconductor layer stack electrically contacting the second layer;

[0036] Providing a first electric contact electrically contacting the bottom contact layer;

[0037] Removing the growth substrate thereby exposing a top surface of the semiconductor layer stack opposite the bottom surface ; and

[0038] Providing a converter layer on or above the top surface being configured to convert light of a first wavelength generated in the active region into light of a second wavelength .

[0039] To provide , that the area where light escapes from the semiconductor layer stack into a converter layer is an area smaller than a top surface of the semiconductor layer stack opposite the bottom surface , according to some aspects , the method comprises a further step of providing an optical aperture arranged between the converter layer and the top surface exposing only a central portion of the top surface such that light generated in the in the active region can exit the light emitting device only through the central region . It is then possible that the converter layer covers at least the central portion and in particular extends beyond the central portion but must not extend over the whole light emitting device or even encapsulate the whole light emitting device . By this the area where light escapes from the semiconductor layer stack into the converter layer, is limited effectively to increase the colour homogeneity and light emitting directionality of the light emitting device while keeping the footprint of the light emitting device small . To provide , that the area where light escapes from the semiconductor layer stack into a converter layer is an area smaller than a top surface of the semiconductor layer stack opposite the bottom surface , according to some aspects , the method comprises that the bottom contact layer is provided and / or structured such that it comprises lateral dimensions which are smaller than the lateral dimensions of the converter layer . By this a current applied to the bottom contact layer is confined to the lateral size of the bottom contact layer such that a generation of light only takes place within a central region of the active region and in turn an emission of light is also limited to a central region of an interface between the p-LED' s epi surface and the converter layer . It is then possible that the converter layer covers at least the central portion and in particular extends beyond the central portion but must not extend over the white light emitting device or even encapsulate the whole light emitting device . By this the area where light escapes from the semiconductor layer stack into the converter layer, is limited effectively to increase the colour homogeneity and light emitting directionality of the light emitting device while keeping the footprint of the light emitting device small .

[0040] In some aspects , the step of providing the converter layer comprises a step of providing a structured mas k as well as a step of depositing a converter material into an opening of the structured mask . The step of depositing the converter material may thereby in particular comprise at least one of : doctor blading; j etting ; ink j etting; spray coating; stencil printing; screen printing ; compression molding ; and slot nozzle coating ; the converter material into the opening of the structured mas k and onto the top surface or another layer ( s ) arranged on the top surface . In some aspects , the method further comprises a step of roughening at least a portion of the top surface , to receive a roughened structure , in particular in at least in the area of the central portion . By means of this , an outcoupling of light through the top surface in particular in the central region can be further enhanced . The roughened structure can provide a better outcoupling of light , generated in the active region, from the top surface into the converter layer compared to an unroughened interface . By this the area where light escapes from the semiconductor layer stack into the converter layer can additionally be limited .

[0041] In some aspects , the step of providing the converter layer comprises providing the converter layer with lateral dimensions which are smaller than the lateral dimensions of the top surface . Hence the resulting converter layer can in particular be designed to not laterally protrude the top surface to keep the footprint of the light emitting device small .

[0042] In some aspects , the method further comprises a step of providing a passivation layer between the top surface and the converter layer or covering the converter layer , wherein optionally the passivation layer in addition covers at least portions of the optical aperture on a side facing away from the top surface .

[0043] In some aspects , the method further comprises a step of providing a reflective structure covering at least portions of the bottom surface and / or the bottom contact layer and covering the side surfaces , wherein optionally the reflective structure comprises a conductive material and is electrically coupled to the first layer while being isolated from the active region, the second layer , the bottom contact layer and the first electric contact . By means of this a reflector cavity can be provided preventing a backside emission of light of the light emitting device .

[0044] In some aspects , the method further comprises a step of providing a second electric contact on the side of the bottom surface being electrically connected to the first layer via for example the reflective structure . By means of this a horizontal contactable light emitting device can be provided .

[0045] SHORT DESCRIPTION OF THE DRAWINGS

[0046] Further aspects and embodiments in accordance with the proposed principle will become apparent in relation to the various embodiments and examples described in detail in connection with the accompanying drawings in which

[0047] Fig . 1A and IB show a cross sectional view and a top view of an embodiment of a light emitting device in accordance with some aspects of the proposed principle ;

[0048] Fig . 2 to 13 show steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle ;

[0049] Fig . 14A to 14 F show further steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle ;

[0050] Fig . 15A to 15H show further steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle ;

[0051] Fig . 16A to 16E show further steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle ;

[0052] Fig . 17A and 17B show a cross sectional view and a top view of another embodiment of a light emitting device in accordance with some aspects of the proposed principle ; Fig . 18A and 18B show a cross sectional view and a top view of another embodiment of a light emitting device in accordance with some aspects of the proposed principle ;

[0053] Fig . 19A and 19B show a cross sectional view and a top view of another embodiment of a light emitting device in accordance with some aspects of the proposed principle ;

[0054] Fig . 20A to 21B show a cross sectional view and a top view of another embodiment of a light emitting device in accordance with some aspects of the proposed principle as well as a possible assembly of the light emitting device in cross section and top view; and

[0055] Fig . 22A to 22D show each a top view of an embodiment of a light emitting device in accordance with some aspects of the proposed principle .

[0056] DETAILED DESCRIPTION

[0057] The following embodiments and examples disclose various aspects and their combinations according to the proposed principle . The embodiments and examples are not always to scale . Likewise , different elements can be displayed enlarged or reduced in size to emphasize individual aspects . It goes without saying that the individual aspects of the embodiments and examples shown in the figures can be combined with each other without further ado , without this contradicting the principle according to the invention . Some aspects show a regular structure or form . It should be noted that in practice slight differences and deviations from the ideal form may occur without , however , contradicting the inventive idea .

[0058] In addition, the individual figures and aspects are not necessarily shown in the correct size , nor do the proportions between individual elements have to be essentially correct . Some aspects are highlighted by showing them enlarged . However , terms such as "above" , "over" , "below" , "under" "larger" , "smaller" and the like are correctly represented with regard to the elements in the figures . So it is possible to deduce such relations between the elements based on the figures .

[0059] Figure 1A and IB show a cross sectional view and a top view of an embodiment of a light emitting device 1 in accordance with some aspects of the proposed principle .

[0060] 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 the second layer . The semiconductor layer stack 2 comprises a bottom surface 9 , a top surface 11 opposite the bottom surface as well as inclined and stepped side surfaces 16 connecting the bottom and the top surface and defining the shape of the semiconductor layer stack 2 .

[0061] A bottom contact layer 7 , in particular of ITO , is arranged on the bottom surface 9 and is electrically coupled to the second layer 4 . The bottom contact layer 7 can in particular act as a current spreading layer to spread the current applied to the bottom contact element 7 via a first electric contact 6 into the second layer 4 .

[0062] The semiconductor layer stack 2 is on its bottom surface 9 and along its side surfaces 16 covered / encapsulated by a reflective structure 15 comprising a first isolation layer 19 , a second isolation layer 20 and a conductive layer 18 arranged between the first and second isolation layer . The first isolation layer 19 electrically isolates the conductive layer 18 from the active region 5 , the second layer 4 and the bottom contact layer 7 . The second isolation layer on the other hand passivates the conductive layer 18 as well as electrically isolates the conductive layer 18 from the first electric contact 6 . The conductive layer 18 is electrically coupled to the first layer 3 and guides a contact path along the side surfaces 16 back into the direction of the bottom surface 9 opposite of which a second electric contact 8 is arranged coupled to the conductive layer 18 . By means of such a design, a horizontal contactable light emitting device 1 can be provided . The first and second electric contacts 6 , 8 can thereby act as solder pads for mounting and electrically connecting the light emitting device 1 onto a target substrate .

[0063] On the top surface 11 an optical aperture 14 is arranged exposing a central portion 13 of the top surface and covering portions of the top surface adj acent to the side surfaces 16 . The optical aperture 14 is thereby configured to block light impinging the optical aperture 14 but light in the area of the central region 13 is no affected .

[0064] For better light outcoupling, the top surface 11 comprises a roughened structure 12 in the area of the central portion . Hence an outcoupling of light in the central portion is compared to the side portions possible at all compared to the side portions due to the optical aperture and is even increased due to the roughened structure 12 .

[0065] On the optical aperture 14 as well as on the exposed portion of the top surface 11 , a passivation layer 17 is arranged passivating all exposed areas of the semiconductor layer stack 2 from external influences . The passivation layer 17 thereby follows the underlying structure and in particular the roughened structure 12 and extends along the top surface between opposing side surfaces 16 .

[0066] Yet upon the passivation layer 17 a converter layer 10 is arranged being configured to convert light of a first wavelength LI generated in the active region 5 into light of a second wavelength L2 . The converter layer 10 covers the central portion 13 and extends beyond the central portion 13 but comprises lateral dimensions smaller than the top surface 11 . Due to the arrangement and size of the converter layer 10 can be applied to the light emitting device 1 even on wafer level when manufacturing the light emitting device . By means of the size of the optical aperture 14 compared to the size of the converter layer 10 , a homogenised emission of converted light can be provided by the light emitting device , while the footprint of the light emitting device can be kept small . Figures 2 to 13 show first steps of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle .

[0067] In a first step, as shown in Figure 2 , a growth substrate 21 is provided with a structured semiconductor layer stack 2 epitaxially grown on top . The semiconductor layer stack comprises a first layer 3 of a first conductivity type , a second layer 4 of a second conductivity type as well as an active region 5 between the first and second layer 3 , 4 . The semiconductor layer stack 2 is structured such that it comprises at least the two shown portions 2a, 2b each with a bottom surface 9 and mesa etched side surfaces 16 . The portions 2a, 2b are thereby still connected by means of a continuous residual of the first layer 3 . The number and shape of the portions 2a , 2b is however to be understood as exemplary and can vary in any way .

[0068] In a further step, as shown in figure 3 , a structured bottom contact layer with portions 7a, 7b , is deposited to cover the bottom surfaces of the semiconductor layer stack 2 . The structured bottom contact layer can also form a structured mask which is suitable as a mas k for the previous 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 performed, as shown in Figure 2 . The structured bottom contact layer 7 can for example be of a transparent conductive material such as ITO .

[0069] In a further step, as shown in figure 4 , a first isolation layer 19 is provided on portions of the bottom contact layer 7 as well as on the side surfaces covering all side surface portions of the active region 5 and the second layer 4 as well as some of the side surface portions of the first layer 3 . The first isolation layer 19 is to passivate portions of the bottom contact layer 7 as well as the side surface portions of the active region 5 and the second layer 4 from a later applied conductive layer 18 , as shown in Figure 5 . The conductive layer 18 is applied along the side surfaces 16 to electrically contact the first layer 3 and extends along the first isolation layer 19 but is spaced from an opening through the first isolation layer 19 to not electrically contact the bottom contact layers 7a, 7b . On top of the conductive layer 18 a second isolation layer 20 is applied, as shown in Figure 6 , encapsulating the conductive layer 18 together with the first isolation layer 19 .

[0070] In a subsequent step, as shown in Figure 7 , a first and a second electric contact 6 , 8 are provided on the second isolation layer 20 . The first electric contact 6 electrically contacts the bottom contact layer 7 , whereas the second electric contact 8 electrically contacts the conductive layer 18 in an area of an opening through the second isolation layer 20 . The first and the second electric contacts 6 , 8 serve as later contact pads arranged on the same side of the later light emitting device , by means of which, a horizontal contactable light emitting device can be provided .

[0071] The resulting structure is then covered, as shown in Figure 8 and 9 , by a sacrificial layer 24 , a material layer 25 and a carrier layer 26 in the given order . The sacrificial layer can for example be a layer of SiO2or Si and can be configured to be at a later step be selectively removed / etched to release the later light emitting elements from the underlying structure . The material layer 25 on the other hand can be of an encapsulation material planarizing the underlying structure and forming a substantially planar surface to be able to apply carrier layer 26 .

[0072] The growth substrate 21 can then be removed, as shown in Figure 10 , and the continuous residual of the first layer 3 can be removed, as shown in Figure 11 , to separate the portions 2a, 2b of the semiconductor layer stack 2 .

[0073] As shown in Figure 12 , the top surface 11 is then in central potions 13a, 13b roughened, resulting in a roughened structure 12 to enhance the light outcoupling of the semiconductor layer stack 2 in these areas . In a subsequent step , as shown in Figure 13 , optical apertures 14 are then applied to the top surface 11 in areas outside the central portions 13a, 13b, exposing the central portions . The optical apertures 14 are of a light absorbing or reflective material configured to block / ref lect light impinging the optical apertures 14 . The optical apertures 14 are thereby provided such that they in addition expose portions of the sacrificial layer 24 to be able to later reach and etch the sacrificial layer 24 for separating the light emitting devices .

[0074] Fig . 14A to 14 F show further following steps of a first embodiment of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle .

[0075] As shown in Figure 14A, in a subsequent step , a passivation layer 17 is applied on the optical aperture 14 as well as on the exposed portion of the top surface 11 , passivating all exposed areas of the semiconductor layer stack 2 from external influences . The passivation layer 17 thereby follows the underlying structure and in particular the roughened structure 12 and extends along the top surface between opposing side surfaces 16 .

[0076] Then, a structured mas k 22 is arranged on the passivation layer 17 as shown in Figure 14B . The structured mask 22 comprises openings 23 above the openings of the optical apertures 14 , wherein the openings 23 of the structured mask 22 are larger than the openings of the optical apertures 14 .

[0077] The openings 23 are then filled by means of a converter material forming a later converter layer by for example means of doctor blading , as shown in Figure 14C .

[0078] Due to curing and / or grinding and / or polishing , excess material of the converter material is removed, as shown in Figure 14D, to separate single converter layers 10 each arranged on top of one of the openings of the optical apertures 14 . The structured mask 22 is then removed as shown in Figure 14E and portions of the sacrificial layer 24 are again exposed to be able to reach and etch the sacrificial layer 24 for separating the light emitting devices 1 , as shown in Figure 14 F . The light emitting devices 1 are then fixed to the carrier substrate 26 only by a small pin formed of the material layer 25 acting as a holding structure and can be picked from the carrier substrate by means of for example a stamp tool .

[0079] Fig . 15A to 15H show further steps of a further embodiment of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle following the step shown in Figure 13 .

[0080] Compared to the embodiment described earlier , the converter layers 10 are provided using structured mas k 23 before passivation layer 17 is provided . The steps shown in Figure 15A to 15D differ from the ones shown in Figures 14B to 14E only in that the passivation layer is not yet provided on the top surface 11 and the optical apertures 14 .

[0081] The passivation layer 17 is however provided on the optical apertures 14 and covering the converter layers 10 after the structured mas k 22 has been removed, as shown in Figure 15E . In a first step , as shown in Figure 15E , the passivation layer 17 may also cover the sacrificial layer 24 between the converter layers 10 , which is why this portion of the passivation layer 17 is again be removed using a further structured mask 27 , as shown in Figure 15 F, resulting in exposed portions of the sacrificial layer 24 , as shown in Figure 15G . By this , the sacrificial layer 24 can be reached to etch it for separating the light emitting devices 1 , as shown in Figure 15H . The light emitting devices 1 are then fixed to the carrier substrate 26 only by a small pin formed of the material layer 25 acting as a holding structure and can be picked from the carrier substrate by means of for example a stamp tool .

[0082] Fig . 16A to 16E show further steps of a further embodiment of a method for manufacturing a light emitting device in accordance with some aspects of the proposed principle following the step shown in Figure 13 . Compared to the embodiment described earlier , the converter layers 10 are provided using structured mas k 23 without any passivation layer 17 is provided . The steps shown in Figure 16A to 16E differ from the ones shown in Figures 14B to 14 F only in that the passivation layer is not provided on the top surface 11 and the optical apertures 14 .

[0083] The idea here is that by means of the optical apertures 14 and the converter layers 10 , a sufficient passivation of the top surface may be provided as long as the optical aperture 14 together with the reflective structure 15 covers and closes the transmission region between top surface 11 and side surfaces 16 .

[0084] Figure 17A and 17B show a cross sectional view and a top view of another embodiment of a light emitting device 1 in accordance with some aspects of the proposed principle . The embodiment comprises a different roughened structure 12 compared to the one shown in Figures 1A and IB . In particular the roughened structure 12 comprises a cylindrical roughening . This is however only to be understood exemplary, and any other type of surface structuring / roughening can be applied to the top surface 11 .

[0085] Figure 18A and 18B as well as Figure 19A and 19B show a cross sectional view and a top view of two further embodiments of a light emitting device 1 in accordance with some aspects of the proposed principle . The light emitting devices 1 compared to the previously shown light emitting devices 1 do not comprise an optical aperture but the bottom contact layer 7 comprises lateral dimensions which are smaller than the lateral dimensions of the converter layer 10 to provide , that the area where light escapes from the semiconductor layer stack 2 into the converter layers 10 is smaller than the top surfaces of the semiconductor layer stack 2 opposite the bottom surface 9 . By this a current applied to the bottom contact layer 7 is confined to the lateral size of the bottom contact layer 7 such that a generation of light only takes place within a central region 13 of the active region 5 and in turn an emission of light is also limited to a central region of an interface between the semiconductor layer stack 2 and the converter layer 10 . Hence the reduction in size of the bottom contact layer 7 has the same or a similar effect as the optical aperture 14 .

[0086] In the embodiment shown in Figures 18A and 18B , the reduction in size of the bottom contact layer 7 is conducted by actually reducing ( only) the size of the bottom contact layer 7 . In the embodiment shown in Figures 19A and 19B, the reduction in size of the bottom contact layer 7 is conducted by reducing the size of the bottom contact layer 7 as well as a portion of the second layer 4 . In particular the later embodiment can provide an even better current confinement to limit the actual emission of light to the central portion 13 .

[0087] Figures 20A and 20B show a cross sectional view and a top view of another embodiment of a light emitting device 1 in accordance with some aspects of the proposed principle as well as Figures 21A and 21B show a possible assembly of the light emitting device 1 in cross section and top view . The light emitting device 1 thereby is configures as a vertical contactable light emitting device 1 with the optical aperture

[0088] 14 acting as the second electric contact 8 . The reflective structure

[0089] 15 therefore does not necessarily comprise the same structure and in particular not a conductive layer but can of course .

[0090] By means of the design of such a vertical contactable light emitting device 1 the size / f ootprint of the light emitting device 1 can further be decreased .

[0091] For electrical contacting, the light emitting device 1 can be arranged on a target substrate 28 with its first electric contact 6 being electrically coupled to a solder pad 29 on a first portion of a metallization layer 30 . The second electric contact 8 and thus the optical aperture 14 can on the other hand be electrically coupled to a second portion of the metallization layer 30 via a contact wire 31 or a planar interconnect .

[0092] Figures 22A to 22D show each a top view of an embodiment of a light emitting device 1 in accordance with some aspects of the proposed principle . In particular Figures 22A to 22D show embodiments of different possible lateral dimensions a , b , c of the central portion 13 relative to the converter element 10 and the top surface 11 . The light emitting devices 1 shown in Figures 22A and 22B thereby comprise an optical aperture 14 , whereas the light emitting devices 1 shown in Figures 22C and 22D do not comprise an optical aperture but a bottom contact element of reduced size .

[0093] Figure 22A shows an embodiment where the lateral dimension a of the central portion 13 is smaller than the lateral dimension b of the converter layer 10 and both the lateral dimension a, b of the central portion 13 and the converter layer 10 is smaller than the lateral dimension c of the top surface 11 .

[0094] Figure 22B shows an embodiment where the lateral dimension a of the central portion 13 is equal to the lateral dimension b of the converter layer 10 and both the lateral dimension a, b of the central portion 13 and the converter layer 10 is smaller than the lateral dimension c of the top surface 11 .

[0095] Figure 22C shows an embodiment where the lateral dimension a of the central portion 13 is slightly smaller than the lateral dimension b of the converter layer 10 and both the lateral dimension a, b of the central portion 13 and the converter layer 10 is smaller than the lateral dimension c of the top surface 11 .

[0096] Figure 22D shows an embodiment where the lateral dimension a of the central portion 13 is smaller than the lateral dimension b of the converter layer 10 and both the lateral dimension a, b of the central portion 13 and the converter layer 10 is smaller than the lateral dimension c of the top surface 11 . LIST OF REFERENCES light emitting device semiconductor layer stack a, 2b separate portions first layer second layer active region first electric contact bottom contact layer a, 7b bottom contact layer second electric contact bottom surface 0 converter layer 1 top surface 2 roughened structure 3 central portion 3a , 13b central portion 4 optical aperture 5 reflective structure 6 side surface 7 passivation layer 8 conductive layer 9 isolation layer 0 isolation layer 1 growth substrate 2 structured mas k 3 opening 4 sacrificial layer 5 material layer 6 carrier layer 7 structured mas k 8 target substrate 9 solder pad 0 metallization layer 1 contact wire 2 filler material LI light with a first wavelength

[0097] LI light with a second wavelength a , b, c width

Claims

CLAIMS1. Light emitting device (1) comprising: 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; a bottom contact layer (7) arranged on a bottom surface (9) of the semiconductor layer stack (2) electrically contacting the second layer (4) ; a first electric contact (6) electrically contacting the bottom contact layer (7) ; a second electric contact (8) electrically contacting the first layer (3) ; a converter layer (10) arranged on or above a top surface (11) of the semiconductor layer stack (2) opposite the bottom surface (9) being configured to convert light of a first wavelength (LI) generated in the active region (5) into light of a second wavelength (L2) ; and an optical aperture (14) arranged between the converter layer (10) and the top surface (11) exposing a central portion (13) of the top surface (11) ; wherein the converter layer (10) covers at least the central portion (13) and in particular extends beyond the central portion (13) .

2. Light emitting device (1) comprising: 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; a bottom contact layer (7) arranged on a bottom surface (9) of the semiconductor layer stack (2) electrically contacting the second layer (4) ; a first electric contact (6) electrically contacting the bottom contact layer (7) ; a second electric contact (8) electrically contacting the first layer (3) ; anda converter layer (10) arranged on or above a top surface (11) of the semiconductor layer stack (2) opposite the bottom surface (9) being configured to convert light of a first wavelength (LI) generated in the active region (5) into light of a second wavelength (L2) ; wherein the bottom contact layer (7) comprises lateral dimensions which are smaller than the lateral dimensions of the converter layer (10) .

3. The light emitting device according to claim 1 or 2 , wherein the converter layer (10) comprises lateral dimensions which are smaller than the lateral dimensions of the top surface (11) .

4. The light emitting device according to any one of the previous claims , wherein the top surface (11) comprises a roughened structure (12) , in particular in the area of the central portion (13) .

5. The light emitting device according to any one of the previous claims , further comprising a passivation layer (17) arranged between the top surface (11) and the converter layer (10) or covering the converter layer (10) .

6. The light emitting device according to claim 5, wherein the passivation layer (17) covers at least portions of the optical aperture (14) on a side facing away from the top surface (ID •7. The light emitting device according to any one of the previous claims , further comprising a reflective structure (15) covering at least portions of the bottom surface (9) and / or the bottom contact layer (7) and covering side surfaces (16) of the semiconductor layer stack (2) connecting the bottom and the top surface (9, 11) .

8. The light emitting device according to claim 7,wherein the reflective structure (15) comprises a conductive layer (18) that is electrically coupled to the first layer (3) and wherein the reflective structure (15) is isolated from the active region (5) , the second layer (4) , the bottom contact layer (7) and the first electric contact (6) .

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

10. The light emitting device according to any one of claims 1 to 8, wherein the second electric contact (8) comprises the optical aperture ( 14 ) .

11. 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) thereby forming a bottom surface (9) as well as side surfaces (16) extending from the bottom surface (9) into a direction away from the bottom surface (9) ;Providing a bottom contact layer (7) on the semiconductor layer stack (2) electrically contacting the second layer (4) ;Providing a first electric contact (6) electrically contacting the bottom contact layer (7) ;Removing the growth substrate (21) thereby exposing a top surface (11) of the semiconductor layer stack (2) opposite the bottom surface (9) ;Providing a converter layer (10) on or above the top surface (11) being configured to convert light of a first wavelength (LI) generated in the active region (5) into light of a second wavelength (L2 ) ; andProviding an optical aperture (14) between the converter layer (10) and the top surface (8) exposing a central portion (13) of the top surface (11) ; wherein the converter layer (10) covers at least the central portion (13) and in particular extends beyond the central portion (13) .

12. 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) thereby forming a bottom surface (9) as well as side surfaces (16) extending from the bottom surface (9) into a direction away from the bottom surface(9) ;Providing a bottom contact layer (7) on the semiconductor layer stack (2) electrically contacting the second layer (4) ;Providing a first electric contact (6) electrically contacting the bottom contact layer (7) ;Removing the growth substrate (21) thereby exposing a top surface (11) of the semiconductor layer stack (2) opposite the bottom surface (9) ; andProviding a converter layer (10) on or above the top surface (11) being configured to convert light of a first wavelength (LI) generated in the active region (5) into light of a second wavelength (L2) ; wherein the bottom contact layer (7) comprises lateral dimensions which are smaller than the lateral dimensions of the converter layer(10) .

13. Method according to claim 11 or 12, wherein the step of providing the converter layer (10) comprises providing a structured mask (22) as well as depositing a converter material into an opening (23) of the structured mask (22) , wherein the step of depositing the converter material comprises in particular at least one of:doctor blading; j etting; ink j etting; spray coating; stencil printing; screen printing; compression molding; and slot nozzle coating.

14. Method according to any one of claims 11 to 13, further comprising a step of roughening at least a portion of the top surface (11) .

15. Method according to any one of claims 11 to 14, wherein the step of providing the converter layer (10) comprises providing the converter layer (10) with lateral dimensions which are smaller than the lateral dimensions of the top surface (11) .

16. Method according to any one of claims 11 to 15, further comprising a step of providing a passivation layer (17) between the top surface (11) and the converter layer (10) or covering the converter layer (10) , wherein optionally the passivation layer (17) covers at least portions of the optical aperture (14) on a side facing away from the top surface (11) .

17. Method according to any one of claims 11 to 16, further comprising a step of providing a reflective structure (15) covering at least portions of the bottom surface (9) and / or the bottom contact layer (7) and covering the side surfaces (16) , wherein optionally the reflective structure (15) comprises a conductive layer (18) electrically contacting the first layer (3) and being isolated from the active region (5) , the second layer (4) , the bottom contact layer (7) and the first electric contact (6) .

18. Method according to any one of claims 11 to 17,further comprising a step of providing a second electric contact (8) on the side of the bottom surface (9) .

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