Photonically integrated circuit with integrated micro-LED

Abstract

The invention relates to a photonically integrated circuit comprising an elongated waveguide with a light coupling surface and an optoelectronic component arranged adjacent to or integrated into the waveguide and optically coupled to it. The optoelectronic component comprises a semiconductor layer stack consisting of a first layer of a first conductivity type, a second layer of a second conductivity type, and an active region between the first and second layers, wherein the first layer forms a bottom and the second layer a top of the semiconductor layer stack, and wherein side faces of the semiconductor layer stack connect the top and bottom. The photonically integrated circuit further comprises a reflective lower contact element covering the bottom and a reflective upper contact element covering at least a portion of the top.The light coupling surface borders at least one first side surface of the semiconductor layer stack, and the optoelectronic component is configured to emit light through the at least one first side surface of the semiconductor layer stack into the waveguide.

Description

[0001] The present application claims priority from German patent application DE 10 2023 113 827.8, filed on May 25, 2023, the disclosure of which is incorporated in its entirety by reference.

[0002] The present invention relates to a photonically integrated circuit with an integrated optoelectronic component such as a µ-LED and a method for manufacturing such a photonically integrated circuit. BACKGROUND

[0003] Due to the significantly lower price of light-emitting diodes (LEDs) compared to lasers, it would be desirable to use LED light in photonic integrated circuits (PICs). However, since LEDs do not emit directional radiation but rather a broad angular distribution, even approaching the Lambertian distribution, the coupling efficiency of LEDs in PIC structures has so far been very low. Furthermore, LED light has a broader spectrum compared to lasers, which in turn contributes to the coupling problem, as typical coupling grating structures are wavelength-sensitive. This, combined with the fact that it is generally difficult to design a coupling structure capable of capturing incident light with a wide range of incidence angles and guiding it into a single waveguide, has meant that expensive lasers have been used as light sources for PICs until now.

[0004] One objective of the present application is to overcome at least some of the problems mentioned above and to provide an improved photonically integrated circuit and a method for its fabrication. SUMMARY OF THE INVENTION

[0005] This and other objectives are addressed by the subject matter of the independent claims. Features and further aspects of the proposed principles are set forth in the dependent claims.

[0006] The present invention enables the efficient use of LED-based light sources in combination with PIC structures. The low coupling efficiency of LED light into a PIC structure is overcome by directly integrating a side-emitting and optionally asymmetrically shaped micro-LED into the PIC. Thus, the micro-LED emits directly in the plane of a PIC waveguide environment, usually in a guided manner. The micro-LED is designed to emit only from certain surfaces, while the other surfaces are coated with reflectors. The shape of the micro-LED itself can be asymmetrical (e.g., triangular or parabolic), so that a collimating effect also occurs within the micro-LED, resulting in a narrower angular distribution of the emitted light within the waveguide plane. In principle, the side-emitting micro-LEDs can be directly connected to a ridge waveguide bus.However, these µ-LEDs can also initially emit into a slab waveguide environment with an adiabatic transition region to further improve coupling efficiency.

[0007] The main advantages of such a photonically integrated circuit can be, for example: - Highly efficient coupling of LED light into ridge waveguides; - The use of cost-effective light sources (µ-LEDs) is possible. - Avoiding the use of complex coupling grid nanostructures; - The light reflected from the side surfaces of the µ-LED is deflected via its asymmetrically arranged reflective surfaces within the µ-LED, resulting in a more directional emitted light and thus a higher coupling efficiency with the PIC structure; - The technology can be combined with CMOS technology to connect µ-LEDs directly to electronic components. - The design of metallic reflectors makes it possible to use them directly as electrical contacts. - A similar design can be used as a detector with all the aforementioned advantages.

[0008] According to a first aspect, a photonically integrated circuit is provided. The photonically integrated circuit comprises an elongated waveguide with a light coupling surface and an optoelectronic component located alongside or integrated within the waveguide. The optoelectronic component is optically coupled to the waveguide and comprises a semiconductor layer stack consisting of a first layer of a first conductivity type, a second layer of a second conductivity type, and an active region between the first and second layers. The first layer forms the bottom of the semiconductor layer stack opposite the active region, and the second layer forms the top of the semiconductor layer stack opposite the active region. Furthermore, side faces of the semiconductor layer stack connect the top and bottom surfaces.

[0009] The photonically integrated circuit further comprises a reflective lower contact element covering the underside and a reflective upper contact element covering at least part of the top side. The optoelectronic component is arranged such that the light coupling surface adjoins at least one first side face of the semiconductor layer stack, and the optoelectronic component is configured to emit light through at least the first side face of the semiconductor layer stack into the waveguide.

[0010] Due to the arrangement or integration of the optoelectronic component with respect to / into the waveguide, whereby the optoelectronic component emits at least some light through its side surface into the waveguide, the low coupling efficiency of LED light into a PIC structure can be overcome. The optoelectronic component is therefore designed to emit only from certain surfaces, while the other surfaces are coated with reflectors, so that the optoelectronic component emits directly in the plane into the waveguide, usually in a guided manner.

[0011] In some aspects, the active region extends substantially parallel to a principal direction of extension of the elongated waveguide. The optoelectronic component can be arranged, particularly with respect to the waveguide, such that the principal direction of extension of the elongated waveguide forms an angle between 60° and 120° with the first side face or is substantially perpendicular to the first side face. The active region can simultaneously extend substantially parallel to the top and / or bottom face. This ensures that the optoelectronic component emits the light generated in the active region into the waveguide at least through its side face.

[0012] In some aspects, the reflective top contact element completely covers the top surface. This means that the light generated in the active region can only be emitted through the side surface(s) of the semiconductor layer stack. However, if the reflective top contact element only covers part of the top surface, the light generated in the active region can also be emitted through the uncovered portion of the top surface.

[0013] In some embodiments, the reflective upper contact element covers not only at least a portion of the top surface but also a second side surface of the semiconductor layer stack, opposite the first side surface. This allows the light generated in the active region to be emitted only through the other side surface(s) of the semiconductor layer stack and, in particular, to be guided directly into the main direction of the elongated waveguide. However, it is also conceivable that the second side surface is provided with a separate reflective coating that is not part of the upper contact element.

[0014] In some embodiments, the reflective upper contact element covers all side faces of the semiconductor layer stack except for the first side face. This allows the light generated in the active region to be emitted only through the first side face of the semiconductor layer stack and, in particular, to be guided directly into the main direction of extension of the elongated waveguide. However, it is also conceivable that the surfaces, with the exception of the first side face, are provided with a separate reflective coating that is not part of the upper contact element.

[0015] In the case of an optoelectronic component with only one side surface, such as a cylindrical semiconductor stack, it is also conceivable that the first side surface, formed by the lateral surface of the semiconductor stack, is partially coated with the reflective top contact element or a separate reflective coating that is not part of the top contact element. For example, only a lateral front region of the lateral surface can be coated with the reflective top contact element or a separate reflective coating that is not part of the top contact element. This allows the light generated in the active region to be emitted only through this lateral front region of the semiconductor stack and, in particular, to be guided directly into the main direction of the elongated waveguide.

[0016] In some aspects, the light coupling surface borders all side faces of the semiconductor layer stack that are not covered with a reflective coating / structure, and / or the portion of the top surface that is not covered with a reflective coating / structure. The light coupling surface can therefore be not only a single flat surface, but also a surface structure consisting of several "separate" surfaces. Furthermore, the optoelectronic component can then be configured to emit light through all these surfaces of the semiconductor layer stack, via the light coupling surface, and into the waveguide.

[0017] In some aspects, a dielectric material layer is positioned between the reflective upper contact element and the side face(s) of the semiconductor layer stack. This prevents a short circuit within the optoelectronic component that could be caused by the reflective upper contact element if it comes into electrical contact with the lower contact element, or if it electrically connects the first and second layers or the upper and lower contact elements.

[0018] In some aspects, a light coupling element is positioned between the optoelectronic component and the light coupling surface. This light coupling element can be, for example, an essentially transparent adhesive that attaches the optoelectronic component to the light coupling surface, and can be made of an index-matched material to increase the coupling efficiency between the optoelectronic component and the waveguide. The index-matched material can be, for example, a substance such as a liquid, cement (adhesive), or gel whose refractive index is very close to that of the waveguide. When two substances with the same index are in contact, light passes from one to the other without reflection or refraction.

[0019] In some embodiments, the optoelectronic component is arranged in a cavity within the waveguide or waveguide material. The waveguide can be arranged, in particular, at one of its ends or at another point along its principal direction of extension, with the cavity extending from a top surface of the waveguide at least to a waveguide medium of the waveguide. The optoelectronic component can be arranged, in particular, within the cavity of the waveguide such that it emits light into the waveguide through at least the first side surface of the semiconductor layer stack. The light coupling surface can be formed, in particular, by one, several, or all of the boundary surfaces of the cavity.

[0020] In some aspects, the cavity is filled with an encapsulation material, in particular a reflective encapsulation material that surrounds the optoelectronic component located in the cavity. Specifically, the encapsulation material can serve as the aforementioned reflective coating of the side face(s) of the semiconductor layer stack and / or the portion of the top surface not covered by the reflective top contact element. The encapsulation material can cover all side faces except the first, only the side faces adjacent to the first, but not the first and an opposing second side face, and / or the encapsulation material can cover the top surface not covered by the reflective top contact element if light emission from the respective side face(s) and / or the top surface is undesirable.

[0021] In some aspects, the waveguide comprises a light guide core as the light guide medium, which includes a material with a high refractive index, such as SiN, and a light guide cladding layer that surrounds the light guide core in the circumferential direction, the light guide cladding layer comprising a material with a lower refractive index, such as SiO2.

[0022] In some aspects, the light coupling surface borders a second face of the semiconductor layer stack opposite the first face. In this case, the optoelectronic component is configured to also emit light through the second face into the waveguide. This can be the case, in particular, if light is to be directed in two different directions from the optoelectronic component in the middle. Specifically, the waveguide in the middle may have a cavity along its main direction of extension, and the optoelectronic component may be configured to emit light into both adjacent waveguide sections. However, it is also conceivable that a second waveguide is arranged adjacent to the second face of the semiconductor layer stack and that the optoelectronic component is configured to emit light through the second face into the second waveguide.Thus, no cavity within the waveguide would be required. However, it is understood that light emission via the optoelectronic component in two different directions, and therefore into two different waveguides / waveguide sections, is only an example, and light emission via the optoelectronic component in three, four, five, ... directions, and therefore into three, four, five, ... different waveguides / waveguide sections, is also possible. In such a case, the optoelectronic component could, for example, be located in the center and configured to emit light in a star-shaped pattern from its respective side faces into the respective different waveguides / waveguide sections.

[0023] In some aspects, the light coupling surface borders at least a portion of the top surface, and the optoelectronic component is configured to emit light through this portion into the waveguide. In this case, the portion of the top surface is not covered by the reflective top contact element or a reflective coating, and the optoelectronic component is directly integrated into the waveguide. The light emitted through this portion of the top surface enters the waveguide and, due to internal reflection within the waveguide, is guided directly within the waveguide along its principal direction of propagation.

[0024] In some aspects, the semiconductor layer stack of the optoelectronic component has a cross-section that increases in size towards the waveguide when viewed from above and / or from the side. The semiconductor layer stack can, for example, be conical, wedge-shaped, or ellipsoidal. In particular, the semiconductor layer stack / optoelectronic component can be asymmetrically designed to provide a structure which, when coated with a reflective material / contact element on its respective outer surfaces (side, bottom, and top surfaces), already improves light guidance within the semiconductor layer stack / optoelectronic component.The semiconductor layer stack / optoelectronic component can, for example, together with the reflective contact elements and / or the reflective coating, form a reflector-like structure configured to emit light into the waveguide in an improved manner, at least through the first side surface.

[0025] In some aspects, the photonically integrated circuit further comprises a substrate, in particular an integrated circuit, on which the waveguide and the optoelectronic component are arranged. The substrate particularly includes a top surface on which the waveguide and the optoelectronic component are arranged and along which the waveguide extends.

[0026] In some aspects, the optoelectronic component is a micro-LED. Specifically, a micro-LED can be a component with edge lengths smaller than 100 µm, 500 µm, 20 µm, 10 µm, or 5 µm, configured to emit light of a desired wavelength. However, the optoelectronic component can also be a micro-detector. Specifically, a micro-detector can be a component with edge lengths smaller than 100 µm, 500 µm, 20 µm, 10 µm, or 5 µm, configured to detect light of a desired wavelength. In some aspects, however, the optoelectronic component can also be an LED or mini-LED or a detector or mini-detector with edge lengths greater than 500 µm, configured to emit / detect light of a desired wavelength.

[0027] In some aspects, the active region comprises a quantum well or multiple quantum well structure. However, the active region can also include quantum dots or any other structure for improved light generation within the active region.

[0028] In some aspects, the photonically integrated circuit further comprises a variety of optoelectronic components that are optically coupled to the same waveguide. For example, a red, green, and blue emitting LED can be optically coupled to one and the same waveguide to provide, for example, white light or light of any other desired color at an output surface of the waveguide by mixing the light. The optoelectronic components can be arranged, configured, and designed in the manner already described above.

[0029] In some aspects, the waveguide includes a light-combining element located adjacent to the multitude of optoelectronic components. This light-combining element can function as an adiabatic transition region formed by the waveguide or the waveguide material itself. The light coupling surface, located adjacent to at least the first faces of the optoelectronic components, can be formed at least partially by the light-combining element.

[0030] In some aspects, the waveguide includes a coupling surface configured to allow coupling with another waveguide. In particular, the photonically integrated circuit of the present application can be a separate module comprising a waveguide / waveguide section with an integrated optoelectronic component according to some of the aspects mentioned above, which can be integrated into a larger and more complex photonically integrated circuit.

[0031] In the present application, the optoelectronic component is usually referred to as an emitter configured to emit light into the waveguide(s). However, it is understood that the above-mentioned embodiments and aspects can also be modified and used such that the optoelectronic component is a detector configured to detect light directed from the waveguide(s) to the detector.

[0032] In some aspects, a method for fabricating a photonically integrated circuit is provided, based on some of the aspects mentioned above. The method includes the following steps: Growth of the elongated waveguide on a support substrate, for example using a plasma-enhanced chemical vapor deposition (PECVD) process; Etching a cavity in the waveguide, for example using plasma etching; Arranging the optoelectronic component in the cavity, for example by means of microtransfer printing; electrically connecting the optoelectronic component to the upper and lower contact elements, for example by means of sputtering and / or lithographic processes; and Encapsulation of the optoelectronic component in the cavity, for example using a PECVD process.

[0033] In some aspects, a further method for fabricating a photonically integrated circuit is provided, based on some of the aforementioned aspects. The method comprises the following steps: Arranging the optoelectronic component on a support substrate; electrical contacting of the optoelectronic component by means of the upper and lower contact elements; and Growth of the elongated waveguide on the support substrate, which encapsulates the optoelectronic component. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further aspects and embodiments according to the proposed principle will become clear with reference to the various embodiments and examples, which are described in detail in connection with the accompanying drawings, in which Fig. 1 shows a photonically integrated circuit according to some aspects of the proposed principle; Fig. 2 shows another embodiment of a photonically integrated circuit according to some aspects of the proposed principle; Fig. 3 and Fig. Four side views of further embodiments of a photonically integrated circuit according to some aspects of the proposed principle are shown; Fig. 5 and Fig. Six top views of further embodiments of a photonically integrated circuit according to some aspects of the proposed principle are shown; Fig. 7 and Fig. 8. Show a side and a top view of a further embodiment of a photonically integrated circuit according to some aspects of the proposed principle; and Fig. Figure 9 shows another embodiment of a photonically integrated circuit according to some aspects of the proposed principle. DETAILED DESCRIPTION

[0035] The following embodiments and examples reveal various aspects and their combinations according to the proposed principle. The embodiments and examples are not always to scale. Likewise, various elements may be enlarged or reduced to highlight individual aspects. It is understood that the individual aspects of the embodiments and examples shown in the figures can readily be combined without contradicting the principle of the invention. Some aspects have a regular structure or shape. It should be noted that in practice, minor differences and deviations from the ideal form may occur without contradicting the inventive concept.

[0036] Furthermore, the individual figures and aspects are not necessarily depicted in the correct size, nor do the proportions between individual elements need to be essentially accurate. Some aspects are emphasized through magnification. However, terms such as "above," "over," "below," "under," "larger," "smaller," and the like are correctly represented in relation to the elements within the figures. Thus, it is possible to deduce such relationships between the elements based on the figures.

[0037] Fig. Figure 1 shows a top view of a first embodiment of a photonically integrated circuit 1 according to some aspects of the proposed principle. The photonically integrated circuit 1 comprises an elongated waveguide 2 (e.g., a SiN ribbed waveguide) and an optoelectronic component 4 integrated into the waveguide 2. The waveguide 2 can be described as elongated because, compared to a perpendicular direction y, it extends predominantly along a principal direction x. Due to its integration into the waveguide 2, the optoelectronic component 4 is optically coupled to the waveguide 2, and light emitted by the optoelectronic component 4 is coupled into the waveguide 2 via a light coupling surface 3 of the waveguide 2. The light coupling surface 3 is directly adjacent to at least one front face of the optoelectronic component 4 due to the integration.The optoelectronic component 4 in the illustrated embodiment has an asymmetrical shape, namely a wedge shape with a top and a bottom surface and three side faces. Light is emitted into the waveguide 2 through the front face, while the other two side faces, as well as the top and bottom surfaces, may have a reflective coating (e.g., a metal layer) to reflect the light internally towards the front face. The asymmetrical shape in the xy-plane, in combination with the reflective coatings, thus helps to collimate the generated light L to ensure that a significant portion of the power is directed into the waveguide 2. The optoelectronic component 4 is, in particular, a micro-LED with a first layer of a first conductivity type, a second layer of a second conductivity type, and an active region between the first and second layers.The µ-LED, for example, is a very small LED with edge lengths of less than 20 µm.

[0038] Fig. Figure 2 shows a side view of another embodiment of a photonically integrated circuit 1 according to some aspects of the proposed principle. The photonically integrated circuit 1 comprises an elongated waveguide 2 and an optoelectronic component 4 integrated into the waveguide 2. The optoelectronic component 4 is a micro-LED and comprises a semiconductor layer stack 5 consisting of a first layer 6 of a first conductivity type, a second layer 8 of a second conductivity type, and an active region 7 between the first and second layers. The semiconductor layer stack 5 is defined by a top surface 10, a bottom surface 9, and side surfaces 11 that connect the top surface and the bottom surface 9, 10, forming a mesa structure in the embodiment shown. Therefore, the side surfaces 11 are inclined with respect to the bottom surface 9 / the top surface 10.

[0039] The waveguide 2 can, in particular, grow around the optoelectronic component 4, meaning that the optoelectronic component 4 is arranged in an ideal cavity 16 that surrounds the optoelectronic component 4 on all sides except one. A reflective lower contact element 12 is arranged on the bottom surface 9, covering the bottom surface 9. A reflective upper contact element 13 is arranged on the top surface, covering only a portion of the top surface 10. The reflective upper contact element 13 extends further from the top surface 10 along a second side surface 11b, completely covering the second surface 11b. To prevent a short circuit within the optoelectronic component 4, a dielectric material layer 14 is arranged between the semiconductor layer stack 5 and the upper contact element 13, at least in regions of the first layer 6 and the active region 7.

[0040] The optoelectronic component 4 is configured to emit light L through both the first side surface 11a, which is opposite the second side surface 11b, and the top surface 10, which is not covered by the upper contact element 13. The surface of the cavity 16 adjacent to the first side surface 11a and the top surface 10 forms a light coupling surface 3 of the waveguide 2, through which light L emitted by the optoelectronic component 4 is coupled into the waveguide 2. Due to the reflective lower contact element 12 and the reflective upper contact element 13, which extends at least along the second side surface 11b, the coupling of the light L into the waveguide 2 is already largely directional.

[0041] The Fig. 3 and Fig. Figure 4 shows a side view of further embodiments of a photonically integrated circuit 1 according to some aspects of the proposed principle. The photonically integrated circuit 1 comprises an elongated waveguide 2 and an optoelectronic component 4 integrated into the waveguide 2. The optoelectronic component 4 is a micro-LED and comprises a semiconductor layer stack 5 consisting of a first layer 6 of a first conductivity type, a second layer 8 of a second conductivity type, and an active region 7 between the first and second layers. The semiconductor layer stack 5 is defined by a top surface 10, a bottom surface 9, and side faces 11 connecting the top surface and the bottom surface 9, 10.

[0042] The waveguide 2 can, for example, grow around the optoelectronic component 4; however, the optoelectronic component 4 can also be located at one end of the waveguide 2, optically coupled to an end face of the waveguide that forms the light coupling surface 3. The optoelectronic component 4 can also be only "partially embedded" in the waveguide 2, such that only two opposite faces of the semiconductor layer stack 5 face the waveguide 2. This can be achieved, for example, by creating a cavity in the waveguide 2 at any point along its principal direction x, with the cavity extending over the entire thickness of the waveguide and dividing the waveguide into separate sections. The optoelectronic component 4 can then be placed between the sections of the waveguide within the cavity.

[0043] A reflective lower contact element 12 is arranged on the underside 9, covering the underside 9. A reflective upper contact element 13 is arranged on the top side, covering the top side 10. A second side surface 11b of the semiconductor layer stack 5 is additionally covered with a reflective coating 22. To prevent a short circuit within the optoelectronic component 4, a dielectric material layer 14 is arranged between the semiconductor layer stack 5 and the reflective coating 22.

[0044] The optoelectronic component 4 is configured to emit light L through a first side surface 11a opposite the second side surface 11b. The light coupling surface 3 of the waveguide 2, through which the light L emitted by the optoelectronic component 4 is coupled into the waveguide 2, is located directly next to the first side surface 11a. Due to the reflective lower contact element 12, the reflective upper contact element 13, and the reflective coating of the second side surface 11b, the coupling of the light L into the waveguide 2 is already largely directional, as shown in the figures.

[0045] Compared to Fig. 3 shows the semiconductor layer stack of Fig. 4 has a cross-section that increases in the direction of the waveguide 2 when viewed in the side view / xz-plane. The semiconductor layer stack 5 is specifically semi-ellipsoidal, with the first side face 11a acting as the open end of the ellipsoid through which light L is emitted from the optoelectronic component 4 into the waveguide. This causes the top and bottom surfaces to be curved, acting as a reflector structure that helps to collimate the generated light L, ensuring that a significant portion of the power is directed into the waveguide 2. Fig. 5 and Fig. Figure 6 shows a top view of a further embodiment of a photonically integrated circuit 1 according to some aspects of the proposed principle. The photonically integrated circuit 1 comprises an elongated waveguide 2 and an optoelectronic component 4 integrated into the waveguide 2, both of which are arranged on a support substrate 21. The optoelectronic component 4 is located in a cavity 16 of the support substrate 21 at one end of the waveguide 2. The optoelectronic component 4 is attached with its first side face 11a to a light coupling surface 3 of the waveguide by means of a light coupling element 15, such that the light coupling element 15 is located between the optoelectronic component 4 and the light coupling surface 3.The light coupling element 15 can, for example, be an essentially transparent adhesive that attaches the optoelectronic component 4 to the light coupling surface 3, and can in particular be formed from an index-matched material to increase the coupling efficiency between the optoelectronic component 4 and the waveguide 2.

[0046] As in Fig. As can be seen in Figure 6, the cavity 16 can additionally be filled with an encapsulation material 17, which in the case shown is a reflective encapsulation material (for example, silicone and TiO2) that surrounds the optoelectronic component 4 on all side surfaces except the first side surface 11a. This, in combination with, for example, a reflective upper and lower contact element, can improve the coupling efficiency of light from the optoelectronic component 4 into the waveguide 2.

[0047] The Fig. 7 and Fig. Figure 8 shows a side and a top view of a further embodiment of a photonically integrated circuit 1 according to some aspects of the proposed principle. The photonically integrated circuit 1 comprises an elongated waveguide 2 and an optoelectronic component 4 integrated into the waveguide 2, both of which are arranged on a support substrate 21. The optoelectronic component 4 is arranged in a cavity 16 formed in the waveguide 2. The waveguide 2 comprises a light guide core 18 as the light-guiding medium, which includes a material with a high refractive index, such as SiN, and a light guide cladding layer 19, which surrounds the light guide core 18 in the circumferential direction, wherein the light guide cladding layer 18 is a material with a lower refractive index, such as SiO( 2), comprises. The carrier substrate 21 in the illustrated embodiment is an integrated circuit in the form of an integrated circuit for supplying / operating the optoelectronic component 4.

[0048] The optoelectronic component 4 is optically coupled to the waveguide 2 due to its integration within the waveguide 2, and light emitted by the optoelectronic component 4 is coupled into the waveguide 2 via a light coupling surface 3 of the waveguide 2. Due to the integration, the light coupling surface 3 is located adjacent to a first side surface 11a and an opposite second side surface 11b of the optoelectronic component 4. Light is emitted into the waveguide 2 through the first and second side surfaces 11a, 11b, while the top and bottom surfaces, and optionally also the other two side surfaces, have a reflective coating (e.g., a metal layer forming the upper and lower contact elements) to reflect the light internally towards the first and second side surfaces.

[0049] By integrating the optoelectronic component 4 into the waveguide at a position, for example in the middle, along its principal direction of extension and through the cavity 16 within the waveguide 2, the waveguide 2 is divided into two sections. A first section 2a of the waveguide extends from the first side face 11a of the semiconductor layer stack 5 in the principal direction of extension x, while a second section 2b of the waveguide extends from the second side face 11b of the semiconductor layer stack 5 in the opposite direction.

[0050] A light coupling element 15 is arranged between the first and second side surfaces 11a, 11b and the light coupling surface 3 of the first and second sections of the waveguide 2a, 2b, respectively. Light generated within the optoelectronic component 4 is coupled into the waveguide 2 via the first and second side surfaces and the light coupling surface 3 by means of the light coupling element 15.

[0051] The cavity 16 is further enclosed by an encapsulation material 17, which surrounds the optoelectronic component 4 on all sides except the first and second sides 11a, 11b. The encapsulation material 17 also surrounds an upper and a lower contact element 12, 13, which are arranged on the upper and lower surfaces 9, 10, respectively. The upper and lower contact elements 12, 13 are each configured to be reflective to light generated in the optoelectronic component 4 and completely cover the upper and lower surfaces 9, 10, respectively.

[0052] The photonically integrated circuit further comprises a first and a second via 23, 24, which electrically connect the upper and lower contact elements to the substrate 21. The first via extends from the upper contact element 13 through the encapsulation material 17 into the substrate, while the second via 24 extends through a portion of the substrate 21 to the lower contact element 12.

[0053] As in Fig. As shown in Figure 8, the waveguide 2 can include a light-combining section located adjacent to the optoelectronic component 4. This allows the optoelectronic component 4 to be a larger µ-LED while still enabling light from larger µ-LEDs to be coupled into a narrower waveguide 2.

[0054] Fig.Figure 9 shows another embodiment of a photonically integrated circuit 1 according to some aspects of the proposed principle. Here, several optoelectronic components 4a, 4b, 4c are integrated into the photonically integrated circuit 1, which is optically coupled to a single waveguide 2. The optoelectronic components 4a, 4b, 4c can, for example, be configured to emit light with different wavelengths. The light is then coupled into the light coupling area 3 of the waveguide, the waveguide comprising a wider waveguide environment before being focused into the ridge waveguide. The wider waveguide environment acts as a light combining element 20, which is arranged adjacent to the plurality of optoelectronic components 4a, 4b, 4c. REFERENCE SIGN LIST 1 photonically integrated circuit 2, 2a, 2b Waveguide 3 Light coupling area 4 optoelectronic components 5, 5a, 5b, 5c Semiconductor layer stack 6 first shift 7 active area 8 second shift 9 Subpage 10 Top 11, 11a, 11b Side surface 12 lower contact element 13 upper contact element 14 Dielectric material layer 15 Light coupling element 16 Cavity 17 Encapsulation material 18 fiber optic core 19 Optical fiber cladding layer 20 light combination elements 21 Carrier substrate 22 reflective coating 23, 24 through-hole plating x Main direction of extension L light QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2023 113 827.8

[0001]

Claims

[1] A photonically integrated circuit (1) comprising: an elongated waveguide (2) with a light coupling surface (3); an optoelectronic component (4) which is arranged adjacent to or integrated into the waveguide (2) and is optically coupled to the waveguide (2), wherein the optoelectronic component (4) comprises a semiconductor layer stack (5), with a first layer (6) of a first conductivity type; a second layer (8) of a second conductivity type; and an active area (7) between the first and second layer (6, 8); wherein the first layer (6) forms a bottom (9) and the second layer (8) a top (10) of the semiconductor layer stack (5); and wherein side surfaces (11) of the semiconductor layer stack (5) connect the top and bottom surfaces (9, 10); a reflective lower contact element (12) covering the underside (9); and a reflective upper contact element (13) covering at least a part of the top surface (10); wherein the light coupling surface (3) adjoins at least one first side surface (11a) of the semiconductor layer stack (5); wherein the optoelectronic component (4) is configured to emit light through at least the first side surface (11a) of the semiconductor layer stack (5) into the waveguide (2); and wherein the semiconductor layer stack (5) has a cross-section that increases in the direction of the waveguide in top and / or side views. [2] Photonically integrated circuit according to claim 1, wherein the active area (7) extends substantially parallel to a principal extension direction (x) of the elongated waveguide (2). [3] Photonically integrated circuit according to claim 1 or 2, wherein the active area (7) extends substantially parallel to the top and / or bottom surface (9, 10). [4] Photon integrated circuit according to one of claims 1 to 3, wherein the reflective upper contact element (13) completely covers the top surface (10). [5] Photonically integrated circuit according to any one of claims 1 to 4, wherein the reflective upper contact element (13) covers a second side surface (11b) of the semiconductor layer stack (5) opposite the first side surface (11a). [6] Photonically integrated circuit according to any one of claims 1 to 5, wherein the reflective upper contact element (13) covers all side surfaces (11) of the semiconductor layer stack (5) except for the first side surface (11a). [7] Photonically integrated circuit according to any one of claims 1 to 6, wherein a dielectric material layer (14) is arranged between the reflective upper contact element (13) and the side surface(s) (11) of the semiconductor layer stack (5). [8] Photonically integrated circuit according to one of claims 1 to 7, wherein a light coupling element (15) is arranged between the optoelectronic component (4) and the light coupling surface (3). [9] Photonically integrated circuit according to any one of claims 1 to 8, wherein the optoelectronic component (4) is arranged in a cavity (16) in the waveguide (2). [10] Photonically integrated circuit according to claim 9, wherein the cavity (16) is filled with an encapsulation material (17), in particular a reflective encapsulation material. [11] Photonically integrated circuit according to any one of claims 1 to 10, wherein the optoelectronic component (4) is a µ-LED. [12] Photonically integrated circuit according to any one of claims 1 to 11, wherein the waveguide (2) comprises a light guide core (18) made of SiN and a light guide cladding layer (19) made of SiO2 surrounding the light guide core (18) in the circumferential direction. [13] Photonically integrated circuit according to one of claims 1 to 12, wherein the light coupling surface (3) adjoins a second side surface (11b) of the semiconductor layer stack (5) which is opposite the first side surface (11a), and wherein the optoelectronic component (4) is configured to emit light through the second side surface (11b) into the waveguide (2). [14] Photonically integrated circuit according to any one of claims 1 to 13, wherein the light coupling surface (3) adjoins at least a part of the top surface (10) and wherein the optoelectronic component (4) is configured to emit light through the at least part of the top surface (10) into the waveguide (2). [15] Photonically integrated circuit according to any one of claims 1 to 14, further comprising a plurality of optoelectronic components (4a, 4b, 4c) optically coupled to the same waveguide (2). [16] Photonically integrated circuit according to claim 15, wherein the waveguide (2) comprises a light combination element (20) arranged adjacent to the plurality of optoelectronic components (4a, 4b, 4c). [17] Photonic integrated circuit according to any one of claims 1 to 16, wherein the semiconductor layer stack (5) is conical, wedge-shaped or ellipsoidal. [18] Photonically integrated circuit according to one of claims 1 to 17, further comprising a support substrate (21), in particular an integrated circuit, on which the waveguide (2) and the optoelectronic component (5) are arranged. [19] Method for fabricating a photonically integrated circuit (1) according to any one of claims 1 to 18, comprising the following steps: Growth of the elongated waveguide (2) on a support substrate (21); Etching a cavity (16) in the waveguide (2); Arranging the optoelectronic component (4) in the cavity (16); electrical contacting of the optoelectronic component (4) by means of the upper and lower contact elements (12, 13); and Encapsulation of the optoelectronic component (4) in the cavity (16). [20] Method for fabricating a photonically integrated circuit (1) according to any one of claims 1 to 18, comprising the following steps: Arranging the optoelectronic component (4) on a support substrate (21); electrical contacting of the optoelectronic component (4) by means of the upper and lower contact elements (12, 13); and Growth of the elongated waveguide (2) on the support substrate (21) which encapsulates the optoelectronic component (4).

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