ARRANGEMENT, METHODS FOR PRODUCING AN ARRANGEMENT AND OPTOELECTRONIC DEVICE

Abstract

An arrangement is disclosed. The arrangement comprises at least one semiconductor structure configured to convert a primary radiation into a secondary radiation; an encapsulation layer covering the at least one semiconductor structure; and at least one reflective layer arranged on the encapsulation layer. The semiconductor structure is arranged in a center of the arrangement, and a lateral extent of the arrangement is chosen such that an optically resonant condition is fulfilled for a wavelength of the secondary radiation in the encapsulation layer. Methods for producing an arrangement and an optoelectronic device are also disclosed.

Claims

1. An arrangement comprising: at least one semiconductor structure configured to convert a primary radiation into a secondary radiation; an encapsulation layer covering the at least one semiconductor structure; at least one reflective layer arranged on the encapsulation layer; wherein the semiconductor structure is arranged in a center of the arrangement; and wherein a lateral extent of the arrangement is chosen such that an optically resonant condition is fulfilled for a wavelength of the secondary radiation in the encapsulation layer.

2. The arrangement according to claim 1, wherein the arrangement comprises exactly one semiconductor structure and, wherein the arrangement is spheroidal.

3. The arrangement according to claim 1, wherein the at least one semiconductor structure is a semiconductor nanocrystal.

4. The arrangement according to claim 1, wherein the at least one semiconductor structure is an agglomerate of a plurality of semiconductor nanocrystals.

5. The arrangement according to claim 4, wherein the agglomerate comprises at least two semiconductor nanocrystals.

6. The arrangement according to claim 1, wherein the encapsulation layer comprises a metal oxide.

7. The arrangement according to claim 1, wherein the at least one reflective layer comprises Ag, Al, Au, Pt, Pd, alloys thereof, or Ni—P alloys.

8. The arrangement according to claim 1, wherein the at least one reflective layer comprises a Bragg stack.

9. The arrangement according to claim 8, wherein the Bragg stack has a good reflectivity for the secondary radiation and a high transmittance for the primary radiation.

10. The arrangement according to claim 1, wherein the arrangement is formed as a layer, and wherein the arrangement comprises at least two reflective layers and a plurality of semiconductor structures.

11. The arrangement according to claim 10, wherein the arrangement comprises at least one monolayer of semiconductor structures arranged in the encapsulation layer between the at least two reflective layers, and wherein each semiconductor structure has essentially the same distance to both reflective layers.

12. A method for producing an arrangement, comprising: providing a semiconductor structure; applying an encapsulation layer on the semiconductor structure surrounding the semiconductor structure; applying a reflective layer on the encapsulation layer surrounding the encapsulation layer; wherein the semiconductor structure is arranged in a center of the arrangement; and wherein a lateral extent of the arrangement is chosen such that an optically resonant condition is fulfilled for a wavelength of the secondary radiation in the encapsulation.

13. The method according to claim 12, wherein the semiconductor structure is a semiconductor nanocrystal or an agglomerate of a plurality of semiconductor nanocrystals.

14. The method according to claim 12, wherein a thickness of the reflective layer is adjusted such that the quantum efficiency has a maximum value.

15. A method for producing an arrangement, comprising: providing a first reflective layer; arranging a first part of an encapsulation layer on the first reflective layer; arranging at least one monolayer of semiconductor structures on the first part of the encapsulation layer; arranging a second part of the encapsulation layer on the at least one monolayer of the semiconductor structures; arranging a second reflective layer on the second part of the encapsulation layer; wherein the first part and the second part of the encapsulation layer form the encapsulation layer; and wherein a lateral extent of the arrangement is chosen such that an optically resonant condition is fulfilled for a wavelength of the secondary radiation in the encapsulation layer.

16. The method according to claim 15, wherein the semiconductor structures are semiconductor nanocrystals or agglomerates of a plurality of semiconductor nanocrystals.

17. The method according to claim 15, wherein a thickness of the reflective layer is adjusted such that the quantum efficiency has a maximum value.

18. The method according to claim 15, wherein at least five monolayers of semiconductor structures are arranged on the first part of the encapsulation layer.

19. An optoelectronic device comprising: a semiconductor chip configured to emit a primary radiation; a conversion element configured to convert at least part of the primary radiation into a secondary radiation; wherein the conversion element comprises or consists of at least one arrangement according to claim 1.

20. The optoelectronic device according to claim 19, wherein the primary radiation is in the visible or UV wavelength range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The foregoing and other objects, features and advantages disclosed herein will be apparent from the following description of particular embodiments disclosed herein, as illustrated in the accompanying drawings.

[0063] FIGS. 1, 2, and 3 each show a schematic illustration of an arrangement according to different embodiments.

[0064] FIGS. 4, 5, and 6 each show a schematic illustration of an optoelectronic device according to different embodiments.

[0065] In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better understanding.

DETAILED DESCRIPTION

[0066] FIGS. 1, 2, and 3 each show a schematic illustration of an arrangement 1.

[0067] FIG. 1 shows a spheroidal or spherical arrangement 1 with a semiconductor nanoparticle 2 arranged in the center of the arrangement 1. In this instance, the semiconductor nanocrystal 2 is a semiconductor structure. The semiconductor nanocrystal 2 has a diameter of 5 nm to 20 nm, for example. Optionally, the semiconductor nanocrystal 2 can be oxide coated. The semiconductor nanocrystal 2 is configured to convert a primary radiation into a secondary radiation.

[0068] The semiconductor nanocrystal 2 is surrounded with an encapsulation layer 3. In particular, the encapsulation layer 3 is in direct contact to the semiconductor nanocrystal 2. The encapsulation layer 3 comprises or consists of a metal oxide, for example, silica.

[0069] The encapsulation layer 3 is surrounded with a reflective layer 4. The reflective layer 4 is thin compared to the thickness of the encapsulation layer 3. In particular, the reflective layer 4 is in direct contact to the encapsulation layer 3. The reflective layer 4 comprises or consists of a metal, for example, Ag or Al, a metal alloy, or a Bragg stack.

[0070] The diameter of the spheroidal or spherical arrangement 1 is chosen such that an optically resonant condition is fulfilled for a wavelength of the secondary radiation in the encapsulation layer. For example, the diameter of the spheroidal or spherical arrangement 1 is essentially N.Math.λ/2, wherein λ is a wavelength of the secondary radiation in the encapsulation layer and N is an odd natural number. In other words, the diameter of the arrangement 1 is chosen to be resonant with one emission wavelength. For example, the diameter of the arrangement 1 is resonant with a secondary wavelength in the red wavelength range.

[0071] Compared to the arrangement 1 in FIG. 1, the arrangement 1 in FIG. 2 comprises an agglomerate 5 of at least two semiconductor nanocrystals 2. In this instance, the agglomerate 5 is a semiconductor structure. Optionally, each semiconductor nanocrystal 2 can individually be oxide coated. Alternatively or additionally, the agglomerate 5 can optionally be coated with an oxide.

[0072] The arrangements 1 of FIGS. 1 and 2 can be produced as follows. The semiconductor nanocrystal 2 or the agglomerate 5 are embedded in the encapsulation layer 3 comprising a metal oxide by using wet chemical processes or other methods such as sputtering or ALD either after or during the synthesis of the semiconductor nanocrystal 2 or the agglomerate 5. For example, sol-gel, sputtering, ALD or other metal oxide deposition methods or combinations thereof can be used. The reflective layer 4 can be applied by sputtering, electroless deposition of metals, or sequential deposition of layers of transparent materials with different refractive indices.

[0073] Electroless deposition of metals for applying a reflective layer 4 on an encapsulation layer 3 relies on using metal ions and reducing agents in solution. Semiconductor structures, such as semiconductor nanocrystals 2 or agglomerates 5, encapsulated in an encapsulation layer 3 are suspended in a solvent such as water via sonication. A metal ion source such as silver nitrate is added to the solution of the encapsulated semiconductor structures. Additional reagents may be added to the solution to optimize metal deposition and/or surface charge. A reducing agent such as ammonia or amines is then added to the solution to precipitate a metal layer onto the surface of the encapsulated semiconductor structures.

[0074] Reaction parameters such as temperature and/or concentration of reagents and reactants will be tuned to meet specific metals and coating targets. Importantly, the metal deposition process may be optimized by functionalizing the metal oxide surface with an intermediate layer such as 3-mercaptopropyltrimethoxy silane to enhance metal adhesion.

[0075] FIG. 3 shows a layered arrangement 1. The arrangement 1 comprises two reflective layers 4a, 4b. The reflective layers 4a, 4b comprise or consist of a metal, for example, Ag or Al, a metal alloy, or a Bragg stack.

[0076] An encapsulation layer 3 is arranged between the two reflective layers 4a, 4b. The encapsulation layer 3 is thick compared to the thickness of the reflective layers 4a, 4b. In particular, the encapsulation layer 3 is in direct contact to both reflective layers 4a, 4b. The encapsulation layer 3 comprises or consists of a metal oxide, for example, silica.

[0077] A plurality of semiconductor structures, for example, a plurality of semiconductor nanocrystals 2, is arranged in at least one monolayer 6 in the encapsulation layer 3 in such a way that each semiconductor structure has essentially the same distance to both reflective layers 4a, 4b. The arrangement comprises, for example, more than one monolayer 6 of semiconductor structures. This is indicated in FIG. 3 with dashed lines 6a, 6b, 6c.

[0078] The encapsulation layer 3 can comprise at least two parts 3a, 3b that together form the encapsulation layer 3. In particular, the two parts 3a, 3b of the encapsulation layer 3 are connected to each other by chemical bonds, for example, covalent bonds. As shown in FIG. 3, the encapsulation layer 3 thus embeds the at least one monolayer 6 of semiconductor structures and pervades or penetrates the monolayer 6 in between the individual semiconductor structures. Thus, each semiconductor structure in the monolayer 6 is covered or surrounded by the encapsulation layer 3.

[0079] The arrangement 1 of FIG. 3 can be produced as follows. The first reflective layer 4a is applied on, for example, a radiation emission surface of a semiconductor chip by, for example, sputtering or sequential deposition of layers of transparent materials with different refractive indices. The first part 3a of the encapsulation layer 3 is applied on the first reflective layer 4a by wet or dry chemical processes, for example, sol-gel or sputtering. At least one monolayer 6 of semiconductor structures is applied to the first part 3a of the encapsulation layer 3 by, for example, spin coating. The second part 3b of the encapsulation layer 3 is then applied on the at least one monolayer 6. In particular, the second part of 3b of the encapsulation layer 3 pervades or penetrates the monolayer 6 in between the individual semiconductor structures to form covalent bonds to the first part 3a of the encapsulation layer 3. The second reflective layer 4b is applied on the second part of the encapsulation layer 3.

[0080] FIGS. 4, 5, and 6 each show a schematic illustration of an optoelectronic device.

[0081] FIG. 4 shows an optoelectronic device comprising a semiconductor chip 11 with an active layer stack and an active region (not explicitly shown here). During operation, the semiconductor chip 11 emits a primary radiation, for example, from the radiation emission surface 12. In particular, the primary radiation is electromagnetic radiation in the UV or visible wavelength range, for example, from 300 nm inclusive to 800 nm inclusive.

[0082] A conversion element 13 is arranged on the radiation emission surface 12 of the semiconductor chip 11. In particular, the conversion element is arranged in direct contact to the radiation emission surface 12. The conversion element 13 is configured to convert at least part of the primary radiation into a secondary radiation. The secondary radiation is electromagnetic radiation with a wavelength range at least partially, preferably completely, different from the wavelength range of the primary radiation. For example, the conversion element 13 converts the primary radiation into secondary radiation in the visible or infrared wavelength range, for example, from 450 nm inclusive to 1500 nm inclusive.

[0083] The conversion element 13 comprises or consists of at least one arrangement 1. For example, the conversion element 13 comprises at least one arrangement 1, preferably a plurality of arrangements 1, as shown in conjunction with FIGS. 1 and 2. In particular, the arrangements 1 are embedded in a matrix material such as silicone, polysiloxane or epoxy.

[0084] Alternatively, the conversion element 13 comprises, in particular consists of, an arrangement 1 formed as a layer structure as shown in FIG. 3. In particular, one of the two reflective layers 4a, 4b is arranged in direct contact to the radiation emission surface 12 of the semiconductor chip 11.

[0085] As shown in the exemplary embodiment of FIG. 5, the semiconductor chip 11 and the conversion element 13 are arranged in the recess 15 of a housing 14. In particular, the recess 15 can be filled at least partially, preferably completely with an encapsulation such as silicone, polysiloxane or epoxy. In particular, the semiconductor chip 11 and the conversion element 13 are completely embedded in the encapsulation.

[0086] In contrast to the exemplary embodiment of an optoelectronic device shown in FIG. 5, the conversion element 13 in the exemplary embodiment of an optoelectronic device shown in FIG. 6 is spaced apart from the semiconductor chip 11. For instance, an encapsulation or other layers or elements can be arranged in the recess 15 between the semiconductor chip 11 and the conversion element 13. Alternatively, the recess 15 is free of an encapsulation or other layers or elements.

[0087] Alternatively, the housing 14 can have no side walls and thus no recess 15 and can be formed as a carrier (not shown here).

[0088] The features and exemplary embodiments described in connection with the figures can be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part.

[0089] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.