OPTOELECTRONIC ARRANGEMENT AND METHOD FOR ITS OPERATION

Abstract

The invention relates to an optoelectronic arrangement for optical data communication, comprising a plurality of optoelectronic components, in particular microLEDs, each having a main emission area that can be attached to one or more optical fibers; wherein the plurality of optoelectronic components each comprise a semiconductor layer stack with an active area configured to emit light of a first wavelength. A light source is configured to emit excitation light of a second wavelength, the second wavelength being shorter than the first wavelength and arranged to illuminate the active areas and thereby generate photoluminescent light.The optoelectronic arrangement is configured to modulate the generation of photoluminescent light by individually supplying a particularly inverted voltage and / or current signal to the semiconductor layer stack of the multitude of optoelectronic components.

Description

[0001] The present application claims priority from German application DE 10 2023 111 339.9, which was filed with the German Patent and Trade Mark Office on May 2, 2023, and whose disclosure content is hereby fully incorporated by reference.

[0002] The present invention relates to an optoelectronic arrangement for optical data communication and a method for operating one or more optoelectronic components in an arrangement for optical data communication, wherein the one or more optoelectronic components are attached to one or more optical fibers and the one or more optoelectronic components are configured so that they can be individually supplied with a voltage and / or current signal. BACKGROUND

[0003] The use of micro-LEDs for optical and data communication offers several advantages. Beyond their small size, which facilitates easier integration with optical fibers, these vertical optoelectronic components, typically implemented as micro-LEDs, provide improved scalability and can be easily mass-produced and integrated into existing designs. In this context, a micro-LED is an optoelectronic component with a diameter, or more generally, a dimension of less than 50 µm, and specifically less than 20 µm. In some specialized applications, a micro-LED can have a diameter between 2 pm and 10 µm.

[0004] Compared to conventional LEDs with larger dimensions, microLEDs require very little current, resulting in lower overall power consumption and thus reducing heat generated during operation. This not only saves energy, making it particularly suitable for short- and medium-distance connections, but also simplifies the requirements for the heat transfer layer, enabling a dense arrangement of such optoelectronic components.

[0005] Therefore, arrays of such µLEDs have been proposed as a source for optical data communication, in which light signals from several µLEDs are coupled into an arrangement of several optical fibers.

[0006] Aside from the requirement of high quantum efficiency to provide sufficient light, data communication also requires high switching capability, or more generally, a large amplitude modulation depth at high frequencies. Current optical data communication ranges from several hundred megahertz to several gigahertz, for example, in the range between 10 GHz and 50 GHz.

[0007] Consequently, current microLEDs within this frequency range must be switched on and off, or at least their emission amplitude modulated. Given that a light pulse requires a certain length to be detected at the receiver, such high frequencies necessitate a radiative recombination lifetime in the range of a few tens of picoseconds or less. The radiative recombination lifetime is the time the minority charge carriers need to recombine under radiation after the current through the microLEDs has been switched off. Similarly, when the microLED is switched on, the depletion region in the active region must be filled with charge carriers, which then recombine. This results in a specific rise time for the emitted light pulse.

[0008] Several measures have been proposed to reduce the rise and fall times during pulse- or amplitude-modulated emission, as current µLEDs are limited in this respect, resulting in a switching time of only a few hundred megahertz and rise and fall times of 100 ps or more.

[0009] For example, background doping can be implemented in the quantum barriers of the respective optoelectronic components to increase the charge carrier density. While this is suitable in some cases, it requires precise control during the epitaxial growth of the quantum barriers. Alternatively, non-radiative defect centers can be provided within the active region to enhance non-radiative recombination, which competes with the radiative recombination of the charge carrier. However, due to the diffusion of dopants or defect centers and other properties, these induced measures are subject to reliability issues and are difficult to control during device manufacturing.

[0010] Consequently, there is a need for optoelectronic devices or optoelectronic components with a higher switching speed to provide the required rise and fall time for high-speed optical data communication. SUMMARY OF THE INVENTION

[0011] These 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.

[0012] The inventor recognized that a significant portion of the recombination time for charge carriers in the active region is determined by charge carrier injection and transport time through the doped layers and into the active region. All minority carriers must be removed from the active region of the microLED when the microLED's state switches from "ON" to "OFF." This typically occurs through recombination of the minority carriers, either radiatively or non-radiatively. Likewise, all minority carriers must diffuse through the respective doped layers of the microLED into and populate the active region before recombinating there, emitting light. Therefore, both the rise time and the fall time of a light pulse emitted by the microLED depend significantly on the time required to clear or populate the active region.

[0013] Consequently, the inventors propose generating the respective minority carriers directly within the active region, thus bypassing charge carrier diffusion into the region during the forward voltage of the microLED. This approach is achieved by optically pumping the active region of the microLED, generating charge carriers in the form of electron-hole pairs through the absorption of excitation light (with an energy slightly larger than the band gap of the active region) within the active region. The charge carriers then recombine after a short time, emitting light, with the wavelength now corresponding to the band gap energy.

[0014] To switch the microLEDs from the "ON" state to the "OFF" state, a reverse bias signal is applied to the active region, which depletes the induced and generated charge carriers (i.e., the electron-hole pairs are separated so they can no longer recombine). In other words, a reverse electric field is applied, spatially separating the induced charge carriers and thus preventing their recombination. This results in a modulation of the photoluminescence generation, as the charge carriers are separated.

[0015] The proposed principle leads to a significantly higher switching speed because the aforementioned charge carrier injection and transport time from the contact or doped layers into the active region can be neglected and is therefore irrelevant. Optical pumping ensures that charge carriers are present in the active region. Switching the respective microLED to "ON" and "OFF," i.e., activating or deactivating the radiative recombination of the induced charge carriers (i.e., the generation of photoluminescence), is achieved by an electric field instead of charge carrier injection via a current.

[0016] Consequently, depletion can be easily achieved by applying a reverse bias signal to the microLED, while occupancy of the active region is achieved by simply switching off the reverse bias during illumination of the active region by the excitation or pumping light. In this respect, it is possible to switch the microLED not only between 0 V and the reverse bias, but actually between a small forward voltage (smaller than the threshold voltage of the active region) and the reverse signal. A small forward voltage assists the transition from the "OFF" state to the "ON" state, thus further reducing the rise time (i.e., increasing the speed). The small forward voltage can be reduced once the microLED is in the "ON" state.

[0017] In this context, it might also be useful to place a filter in front of an optical fiber to prevent pump light from entering the fiber. However, such a solution is not necessary if the optical fiber itself is selective for the light emitted from the active region and not for the pump light, or if a detector on the other side of the optical fiber is wavelength-selective.

[0018] In some aspects, the inventors therefore propose an optoelectronic arrangement for optical data communication. This optoelectronic arrangement comprises a variety of optoelectronic components. Each of these components, which can be implemented as a microLED, includes a main emission surface that can be attached to one or more optical fibers. In this respect, the one or more optical fibers can comprise a multi-core fiber optic array. The optoelectronic components further include a semiconductor layer stack configured to be individually supplied with a voltage or current signal.

[0019] The term “µLED” refers to an optoelectronic component with a diameter of less than 50 µm, for example, in the range of 2 µm to approximately 20 µm. µLEDs can be implemented as vertical or horizontal optoelectronic components. In this respect, a “vertical optoelectronic component” or vertical µLED comprises two contact surfaces arranged on opposite sides, one of which may also be the main emission surface of the respective optoelectronic component and µLED. A horizontal optoelectronic component or horizontal µLED refers to a component or µLED that has the contact surfaces on the same side and preferably opposite the main emission surface. Furthermore, and although not explicitly mentioned, a “surface emitter” is an optoelectronic component that emits its light essentially through a single main emission surface.In contrast, a so-called volume emitter emits light throughout its entire volume. The present application relates primarily to surface emitters, although the proposed principle is not limited to this type of emitter and can also be implemented with volume emitters.

[0020] According to the proposed principle, each semiconductor layer stack comprises a first doped layer with a first doping type, a second doped layer with a second doping type that differs from the first doping type, and an active region located between the first and second doped layers. The active region is also configured to emit light of the first wavelength.

[0021] In some aspects, the doped layer can comprise a variety of sublayers. For example, in some aspects, the doped layers may include charge carrier barrier layers to prevent charge carriers induced by optical pumping from diffusing out of the active region. In other aspects, the doped layers may include undoped cladding layers directly adjacent to the active region. These undoped cladding layers prevent unwanted diffusion of dopants into the active region.

[0022] According to the proposed principle, the optoelectronic arrangement includes a light source configured to emit excitation light with a second wavelength. This second wavelength is shorter than the first. The light source is configured and positioned to illuminate the active regions of each semiconductor layer stack of the multiple optoelectronic components. This illumination of the semiconductor layer stacks causes photoluminescent light to be generated by the active regions of each stack, which is directed at least partially toward the main emission surface.

[0023] Therefore, according to the proposed principle, the optoelectronic components are not actively driven by a current to generate light, but rather illuminated by an excitation light source that provides pump light. This pump light is absorbed by the active region of the semiconductor layer stacks of the multiple optoelectronic components, thereby generating charge carriers in the form of electron-hole pairs in the active regions. The minority charge carriers recombine in the active region, producing photoluminescent light of the first wavelength, some of which is directed onto the main emission surface and subsequently collected by the optical fibers attached to it.

[0024] The optoelectronic arrangement is now configured to modulate the generation of photoluminescent light by means of individual supply signals for the multitude of optoelectronic components. By applying an inverted bias signal to the optoelectronic components, which supplies an inverted voltage to each individual component, the components can be switched on and off, thereby modulating the photoluminescent light signal with the first wavelength.

[0025] In other words, the excitation light itself is not modulated, but rather the generation of photoluminescent light is modulated by signals to the optoelectronic components and their semiconductor layer stacks. The switching speed provided by a reverse voltage is significantly higher compared to the charge recombination time in conventional devices and exhibits steep rise and fall times. It can be limited either by the charge carrier recombination time or by the switching time itself (i.e., by the driver circuitry). Consequently, the switching speed is significantly improved, achieving rise and fall times on the order of a few picoseconds.

[0026] In some aspects, the supply voltage or power supply signals are configured to individually apply a blocking bias to the respective semiconductor layer stacks.

[0027] Consequently, the light source can be configured to illuminate several of these optoelectronic components simultaneously, while modulation is achieved by individually applying a blocking bias signal to the respective semiconductor layer stacks. Therefore, multiple such optoelectronic components can be individually addressed and switched according to the data to be transmitted via optical data communication.

[0028] Several aspects concern the implementation of the numerous optoelectronic components. In some aspects, the optoelectronic components are electrically connected to a common substrate. The common substrate comprises one or more control and driver circuits configured to provide the voltage and / or current signal to individually power the semiconductor layer stacks of the multiple optoelectronic components, and in particular, to apply a blocking voltage or current signal to them to reduce the charge carriers injected into the active area during illumination.

[0029] In some aspects, the one or more control and driver circuits can be configured to switch off the light source during data communication when the multitude of optoelectronic components are also switched off. This further reduces power consumption and prevents accidental and unwanted detection of residual light either from the light source or a portion of the excitation light that is not blocked by the reverse voltage. In some aspects of this arrangement, multiple light sources can be provided, with each light source associated with a multitude of optoelectronic components. Therefore, the arrangement can comprise an array of optoelectronic components and multiple light sources, with each light source associated with a subset of the array of optoelectronic components. This allows for the operation of subsets of the arrangement, thereby reducing overall power consumption.To separate the subsets, a blocking structure can be provided to avoid unwanted illumination.

[0030] Several aspects relate to the multitude of optoelectronic components. In some aspects, the components are implemented as individual components arranged separately on the common substrate. In other aspects, the multitude of optoelectronic components are arranged as an array or monolithically integrated and may include a common contact surface for applying a common potential to the individual optoelectronic components. The common contact surface can be a transparent conductive contact surface and further includes the main emission surfaces of the multitude of optoelectronic components. A transparent conductive contact surface can, for example, comprise a transparent conductive oxide such as ITO. This enables the processing of a multitude of optoelectronic components in a common device array with the multitude of components arranged in rows and columns and essentially isolated from one another.The main exit surface is formed by a transparent conductive contact as a common contact for each of the individually addressable components.

[0031] In this respect, the light source can be formed between adjacent optoelectronic components, which also share the common contact surface as a supply for the common potential.

[0032] In some embodiments, a reflector can be provided between adjacent optoelectronic components, configured to reflect light of the first wavelength towards the main emission surface. In some embodiments, for example, the reflector is mounted directly on the semiconductor layer stack as a reflective mirror. In another embodiment, a reflector can be configured to reflect light of the second wavelength towards the active region of the multiple optoelectronic components. Such a reflector improves the efficiency of the excitation light by reflecting the excitation light towards the active region to generate the electron-hole pairs in the active region.

[0033] In this respect, the semiconductor layer stacks of the multiple optoelectronic components can be embedded in a common insulating layer material, particularly a common insulating layer material that is at least partially transparent to the second wavelength. The common insulating layer material protects the optoelectronic components from potential damage or environmental influences.

[0034] In several other aspects, the optoelectronic arrangement comprises one or more reflective elements positioned between two adjacent semiconductor layer stacks of the multiple optoelectronic components within the common insulating layer material. The one or more reflective elements are configured to deflect light of the second wavelength to the semiconductor layer stacks and, in particular, to their active region.

[0035] The active region of each semiconductor layer stack can comprise a quantum well structure or a multiple quantum well structure. Both structures can be implemented with one or more doped quantum well layers and / or one or more doped barrier layers. Doping in the quantum well layers as well as in the barrier layers increases the charge carrier density and improves the rate of charge carrier recombination, thereby further improving the switching speed. In some aspects, the semiconductor layer stack can comprise a multitude of quantum dots.

[0036] In some further aspects, the semiconductor layer stack can include a mesa-etched structure, which is optionally suited to couple second-wavelength light into the active region to further improve quantum efficiency. It can be advantageous for the active region material to have a larger band gap adjacent to both its perimeter and the mesa facets. A larger band gap is achieved, for example, by using quantum well mixing during the fabrication process. Alternatively, the mesa-etched structure is covered with a regrowth layer that has a larger band gap, resulting in band diffraction of the active region material adjacent to its perimeter.In both cases, an electrical potential is generated within the active region, trapping the charge carriers in the central part and keeping them away from the outer periphery, thereby improving quantum efficiency during optical pumping. Several other aspects concern the arrangement and implementation of the light source. In some aspects, the light source comprises at least two optoelectronic devices configured to illuminate the active region of the plurality of optoelectronic components from different locations. In other aspects, the at least two optoelectronic devices are configured to emit light from different directions, and in particular from directions other than those of the one or more optical fibers. In other words, the at least two optoelectronic devices corresponding to the light source can illuminate the plurality of optoelectronic components from above, i.e., from the sides.The excitation light is directed towards the main emission surface of these components, and not from their respective back faces. This approach is useful to prevent excitation light from being coupled into the optical fibers. In this respect, the coupling of excitation light through the main emission surface into the active region can be improved by appropriate structuring or roughening of the surface.

[0037] In some aspects, the optoelectronic arrangement includes a filter positioned downstream of the main emission surface of the multiple optoelectronic components. The filter is essentially transparent to light of the first wavelength and reflective or absorbent to light of the second wavelength. The filter may be positioned upstream of one or more optical fibers to prevent light from the light source from being coupled into the optical fibers. The filter may, for example, include a DBR mirror.

[0038] In some aspects, the light source comprises a semiconductor layer stack with an active region, positioned laterally between the multiple optoelectronic components and the one or more optical fibers. This semiconductor layer stack can cover multiple optoelectronic components and serve as a common semiconductor layer stack for the pump light for each of them. The aforementioned filter can be implemented as a DBR mirror positioned between one of the semiconductor layer stacks of the light source and the one or more optical fibers. Depending on the geometry and arrangement of the one or more optoelectronic components, the semiconductor layer stack can be interrupted between them, so that the layer stack essentially emits light directly in front of the optoelectronic components, further improving efficiency.If the interrupted layer stack can still be addressed individually, the multiple optoelectronic components can be grouped together that can be switched all at once by simply turning off the pump light.

[0039] Alternatively, if the semiconductor layer stack of the multiple optoelectronic components is configured to emit light over its entire surface, reflective elements can be arranged between and beside the optoelectronic components on the common substrate.

[0040] In some aspects, the semiconductor layer stack of the light source and each semiconductor layer stack of the multiple optoelectronic components can share a common contact surface. This common contact surface comprises a conductive transparent material, for example, a conductive transparent oxide such as ITO, and serves as a common contact for supplying a ground or reference potential.

[0041] The semiconductor stack of the light source can include an active region containing a quantum well or multiple quantum well structure. The light source material can be, for example, gallium nitride (GaN) or gallium phosphide (GaP), as well as ternary and quaternary systems based on GaN or GaP, including but not limited to InGaN, InGaP, AlInGaN, and AlGaInP. Similarly, the optoelectronic components can comprise similar material systems, differing in their smaller band gap, which allows them to emit light with a longer wavelength. However, if the light source and the optoelectronic components are manufactured differently and separately, a common contact surface, a transparent oxide, or another suitable means can be selected to connect the semiconductor stack of the light source to the common contact surface of the multiple optoelectronic components.Such a connection can be made using transparent adhesive or a transparent conductive oxide material, as mentioned above.

[0042] In some aspects, the semiconductor layer stack of the light source can comprise one of the materials mentioned above, while the material of the semiconductor layer stack of the multiple optoelectronic components is based on a material system using GaAs, AlGaAs, or a combination thereof. It is also possible to implement the light source in materials such as AlGaAs, but in the latter case with a different and higher aluminum content to provide light with more energy. Consequently, the light source can emit red light in some aspects, while the layer stack of the multiple optoelectronic components is configured to emit light in the infrared spectrum.

[0043] In several other aspects, the control circuit is configured to supply a pulse- or amplitude-modulated blocking voltage to a variety of optoelectronic components. The rise and fall times of such a pulse-modulated signal can be in the range of a few picoseconds, which is sufficient and can be directly converted into corresponding rise and fall times of the light pulses from the numerous optoelectronic components.

[0044] Another aspect concerns a method for operating one or more optoelectronic components in an optical or data communication system. The one or more optoelectronic components are attached to one or more optical fibers and configured so that they can be individually supplied with a voltage and / or current signal and controlled. The one or more optoelectronic components further comprise a semiconductor layer stack with an active region configured to emit light of a first wavelength.

[0045] According to the proposed principle, the active regions of the layer stack of one or more optoelectronic components are illuminated with light of a second wavelength, where the second wavelength is shorter than the first. This light is absorbed by the active region of the semiconductor layer stack, generating charge carrier or electron-hole pairs that typically recombine to produce photoluminescence. Consequently, photoluminescence is generated in the active regions of the layer stack in response to the illumination, with at least a portion of the photoluminescent light being directed onto one or more of the optical fibers.

[0046] A modulated reverse electric field is applied to the active regions of the layer stack to modulate the generation of photoluminescent light and thus implement a modulated optical signal for data communication. The modulation by the reverse electric field is then switched off due to the separation of the induced charge carriers by illumination. Portions of the modulated photoluminescent light are then coupled into one or more optical fibers.

[0047] The modulation is not achieved directly by modulating the current through the optoelectronic component and the microLEDs, but rather by modulating the generation of photoluminescence. This is accomplished by reducing or enabling the recombination of optically induced charge carriers within the active region. In some aspects, the modulated electric field is created by individually applying a reverse-biased voltage and / or current signal to one or more optoelectronic components.

[0048] In some aspects, the step of illuminating the active regions can involve illuminating them from different locations and / or directions, and specifically not in the direction of one or more optical fibers. This can improve the overall quantum yield and the total amount of photoluminescent light.

[0049] In this respect, second-wavelength light reflected towards the beam path of one or more optical fibers can be suppressed or absorbed, for example, by a suitable filter placed in front of the optical fibers. Such a filter can include a wavelength-selective DBR mirror. In some cases, the optical fibers are adjusted to prevent coupling of second-wavelength light.

[0050] The proposed principle can be used in a system for optical data communication with a switching speed in the range of several tens of GHz or more, with rise and fall times of the signal pulses between 1 ps and 50 picoseconds, and in particular below 30 ps. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] 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. shows an embodiment of an optical arrangement according to some aspects of the proposed principle; Fig. a second embodiment of an optoelectronic arrangement according to some aspects of the proposed principle; Fig. a third embodiment of an optoelectronic arrangement according to some aspects of the proposed principle; Fig. a fourth embodiment of an optoelectronic arrangement according to some aspects of the proposed principle; Fig. a fifth embodiment of an optoelectronic arrangement according to some aspects of the proposed principle; Fig. a sixth embodiment of an optoelectronic arrangement according to some aspects of the proposed principle is shown; Fig. shows an embodiment of an optoelectronic component that is used for an optoelectronic arrangement according to some aspects of the proposed principle. DETAILED DESCRIPTION

[0052] 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 exhibit a regular structure or shape. It should be noted that in practice, minor differences and deviations from the ideal may occur without contradicting the inventive concept.

[0053] Furthermore, the individual illustrations and aspects are not necessarily shown at the correct size, nor do the proportions between the individual elements have to be essentially correct. Some aspects are emphasized by magnification. However, terms such as "above," "over," "below," "under," "larger," "smaller," and the like are correctly represented in relation to the elements in the illustrations. Thus, it is possible to deduce such relationships between the elements from the illustrations.

[0054] Fig. Figure 1 shows a system for optical data communication using two arrangements according to the proposed principle. The optical data communication system is arranged on a printed circuit board, a mainboard, or the like, and connects a plurality of optical fibers 50, configured as a multicore fiber system, to a plurality of outputs of optoelectronic components that form part of the two optoelectronic arrangements.

[0055] More precisely, several optoelectronic components 10a, 10b to 10e are arranged separately on a substrate 20.

[0056] The optoelectronic components 10a to 10e are arranged in rows and columns, essentially forming an arrangement that is divided into several subgroups or sub-arrangements separated from each other by an element 60. More precisely, a first subgroup is formed using the optoelectronic components 10a and 10b, while the second subgroup of the arrangement is realized by the electronic components 10c, 10d, and 10e, respectively. The substrate 20 includes several signal and supply lines 21, which are connected to control and driver circuits 23. Each subgroup of the arrangement of optoelectronic components is connected via a supply line 21 to a corresponding control circuit 23 in order to address and supply the respective optoelectronic components of each subgroup individually.

[0057] In the present embodiment, the optoelectronic components 10a to 10e are configured as horizontal microLEDs, the respective contact surfaces of which are located on the main surface opposite their emission surface. The microLEDs are configured as surface emitters, with their emission surface facing the optical fibers 50. The optoelectronic components 10a to 10e are connected by their contact surfaces to corresponding areas on the surface of the substrate 20 via a solder material (not shown). The contact surfaces on the substrate 20 are connected to the control circuits 23 via supply lines, so that the optoelectronic components of each subgroup are supplied and controlled by one of the control and driver circuits 23.

[0058] The substrate 20 also includes a data input port 22 to supply a variety of data signals to the respective control and driver circuits 23 of each subset. The data signals applied to the data input are digital signals consisting of “0” and “1”, corresponding to a “HIGH” and “LOW” (or vice versa) for the optical signals. Data modulation, convolution, and other aspects are generally well understood. For simplicity, in this application, it is assumed that each of the optical data communication systems in Fig. The data bit to be transmitted corresponds to a pulse of a specific length. However, it is understood that the proposed principle is not limited to this concept, but is more flexible. In particular, PWM signal modulation, wavelength division multiplexing, or other more complex modulation models are possible.

[0059] Each subassembly further comprises a plurality of light sources 30 arranged adjacent to the plurality of optoelectronic components in each subassembly to provide light that is substantially parallel to the optical fibers 50. The light sources 30 are configured to illuminate the respective optoelectronic components, and in particular the active region of the optoelectronic components 10a to 10e in each subassembly, with excitation light. For this purpose, the light sources 30 of each subassembly are embedded in a transparent insulating layer with a reflective material on its surface facing the optical fibers 50. An optical element in front of the light can collimate the excitation light to reduce the amount of excitation light entering the optical fibers 50.

[0060] In addition, the multiple light sources 30 in each subgroup are distributed in each subgroup to ensure uniform illumination of each of the optoelectronic components with excitation light, so that the resulting photoluminescence in the components is essentially the same.

[0061] Each of the optoelectronic components 10a to 10e is arranged such that its emission surface is located near an input of an optical fiber in front of a filter 40, which also serves as the input terminal for the attached multicore fiber 50. The filter 40 is configured to absorb or reflect the excitation light while being transparent to the photoluminescence light from the optoelectronic components 10a to 10e.

[0062] During operation of the data communication system, the light sources 30 required for optical data communication are continuously switched on in the subgroups and deliver light of a specific intensity to the respective optoelectronic components 10a, 10b, and 10c to 10e. The element 60 blocks the light between the different subgroups of the array and reflects it back into the respective subgroup to further improve efficiency. In addition, the Fig. The solution shown allows for the individual switching off of entire subgroups of optoelectronic components at once by switching off the light sources 30 in the respective subgroup, which offers high flexibility and responsiveness to the volume of data to be transmitted.

[0063] The wavelength of the excitation light provided by the light sources 30 is shorter than the wavelengths of the photoluminescent light generated in the active region of the optoelectronic components 10a and 10b, as well as 10c to 10e. Since the absorption efficiency of semiconductor material depends on the energy of the excitation light (photons with excessive energy can lead to the formation of multiple hole pairs, absorption in other regions of the components 10, etc.), the wavelength of the excitation light from the light sources 30 is adjusted accordingly to meet the various requirements. Generally, the energy of the excitation light is higher than the band gap energy difference, but not too high, in order to avoid unnecessary heating of the optoelectronic components.

[0064] The excitation light is absorbed in the active region of the optoelectronic components and their layer stacks, generating charge carriers in the form of electron-hole pairs. These electron-hole pairs typically recombine to produce photoluminescent light, which has a wavelength corresponding to the bandgap energy (to a first approximation). The resulting photoluminescent light is emitted, at least partially, through the main emission surface and collected by the attached multicore optical fiber 50.

[0065] According to the proposed principle, the control driver circuits 23 are configured to modulate the generation of photoluminescent light in the respective optoelectronic components. This is achieved by individually applying a blocking bias voltage, generated by the driver and control circuits in response to the data to be transmitted, to the optoelectronic components via the supply lines 21. The blocking bias voltage, e.g., a blocking voltage signal, causes the generation of an electric field within the active region that is inversely proportional to the forward direction of the active region in the optoelectronic components.

[0066] This spatially separates the charge carriers generated by the incident excitation light from the light sources 30, and removes them from the active region by the electric field provided by the driver and control circuits 23. Applying a voltage and / or current signal to each of the optoelectronic components between 0 volts and a reverse bias modulates the generation of photoluminescent light, where 0 volts corresponds to the generation of photoluminescent light and the reverse bias corresponds to the suppression of photoluminescent light generation. The overall modulation frequency of the photoluminescent light depends essentially on the lifetime of carrier recombination within the active region and on the switching speed provided by the driver and control circuits 23.

[0067] Consequently, unlike conventional solutions, no charge carriers need to be injected into or removed from the active area during normal operation of the optoelectronic components. Instead, the charge carriers are continuously generated by the incident excitation light from the light sources 30 and are either separated by an applied opposing electric field or recombined, generating photoluminescent light.

[0068] In this context, it should be noted that zero voltage for generating photoluminescent light is only one possible solution. In fact, the driver and control circuitry can be configured to switch between the blocking voltage, which suppresses photoluminescent light generation, and a small forward voltage, less than the threshold voltage. Aside from the advantages in implementing the driver and control circuitry, this approach can reduce the recombination lifetime or increase the charge carrier density within the active region, thereby improving the switching speed and increasing the intensity of the photoluminescent light.

[0069] The optoelectronic components for an optoelectronic arrangement according to the proposed principle are implemented with a slightly different layer stack than conventional microLEDs, which require carrier injection sublayers, a multitude of doped layers, and the actual active regions. In particular, the active regions in the semiconductor layer stacks of the optoelectronic components according to the proposed principle can be optimized for the absorption of incident excitation light, where the excitation wavelength is shorter than the wavelength of the photoluminescent light.However, the material system, processing parameters and the structure of the active region of the layer stacks can be adapted to the excitation light (and vice versa, as indicated above) so that absorption efficiency is maximized to improve the generation of photoluminescent light without depositing the additional energy in the crystal lattice and thereby heating the active region.

[0070] In the embodiment of Fig. In Figure 1, the multiple optoelectronic components 10a to 10e are implemented with separate semiconductor layer stacks, which are then applied to the contact areas of the substrate 20 and soldered to them. However, in some aspects, the optoelectronic components and their layer stacks can be implemented as vertical components with a common contact on one side, for example, corresponding to the main emission surface. The layer stacks can, in turn, be implemented as separate optoelectronic components that are transferred to the substrate 20 and placed on its contact surfaces, or as a monolithically integrated structure. The latter makes it possible to optimize the semiconductor layer stacks of the optoelectronic components and arrange them directly in rows and columns for attachment to a multi-core optical fiber.

[0071] Fig. Figure 1 shows another embodiment in which the optoelectronic components are implemented as vertical components with a common transparent contact that forms their main exit surface. In this respect, the doping types of the contacts can be reversed, so that the embodiment is not limited to this specific embodiment.

[0072] The substrate 20 comprises a driver and control circuit 23, which is connected to corresponding contact areas 13 that form p-contacts for semiconductor layer stacks 11 of the optoelectronic components 10. The layer stacks 11 comprise doped layers for charge carrier transport in the event of modulation of the supply voltage, as well as an intermediate active region. The layer stack 11 of each of the optoelectronic components is embedded in a dielectric material 19. The main surface opposite the p-contacts 13 serves as the main exit surface and is covered with a transparent conductive common n-contact.

[0073] The common n-contact 14 is connected to one or more conductive and doped materials 12, which are embedded in a via through the insulating material 19. The material 12 is connected to another conductive trace 21 within the substrate 20. The common n-contact 14 comprises a transparent conductive oxide, such as ITO, which can be further structured or roughened to facilitate the emission of photoluminescent light with wavelength λ. em) to improve the multicore fiber 50. A light source 30 is arranged next to the multitude of optoelectronic components 10 and provides excitation light with wavelength λ. ex The light source 30 may further include a lens or other optical elements 31 to collimate the light and focus the illumination onto the main emission surface of the respective optoelectronic components.

[0074] Similar to the previous embodiment, the incident excitation light with the excitation wavelength is absorbed in the active region of the layer stacks 11 of the multiple optoelectronic components. By providing a blocking bias signal separately and individually for each of the optoelectronic components and the layer stacks, the generation of photoluminescence is modulated, resulting in a pulse-modulated optical signal that is fed into the multicore fiber 50.

[0075] Fig. Figure 1 shows a further embodiment according to the proposed principle. In this embodiment, the insulating material 19a is transparent to the excitation light emitted by the light source 30 and collimated by the optical arrangement 31. The light source 30 is arranged such that the excitation light is emitted substantially parallel to the common n-contact 14. In contrast to the previous embodiment, the excitation light is emitted substantially laterally to the respective layer stacks and not from the main exit surface. Due to the different refractive indices and the small angle between the excitation light and the n-contact, total internal reflection is achieved, so that the material 19a acts as an optical guide for the excitation light.

[0076] Additionally or as a further alternative, a reflective mirror 40 can be provided between the common n-contact and the insulating material 19a. The reflective mirror, for example a thin metal layer, has openings at the locations of the main exit surfaces of the layer stacks 11. This reduces the amount of light coming from the light source that is reflected on the substrate 20 or the active area stacks 11 towards the multicore fiber, thus preventing excitation light from being fed into the optical fibers.

[0077] Although only a single light source 30 is shown here, it should be noted that a plurality of such light sources can be implemented within the dielectric transparent material 19a. Furthermore, the light source 30 can include an optoelectronic component whose active region is arranged substantially perpendicular to the respective active regions of the semiconductor layer stacks 11. In some embodiments, such light sources can, for example, be arranged between two adjacent optoelectronic components 11 and be completely embedded in the transparent material 19a.

[0078] In another embodiment, the light source 30 can be realized by a large optoelectronic device arranged essentially parallel across the plurality of main emission surfaces of the layer stacks 11. Such an approach has several advantages. For example, the arrangement could be implemented as a monolithic component comprising the plurality of optoelectronic components 10 as well as the light source 30. If implemented as an independent element, the light source 30 can be optimized and attached with an adhesive or bonded to the surface of the layer stacks of the plurality of optoelectronic components.Furthermore, an optoelectronic component can act as a light source 30 with a significantly larger lateral dimension, covering the main emission area of ​​the optoelectronic components and the layer stacks 11, thus providing essentially uniformly distributed light in the direction of the active areas of the layer stacks 11.

[0079] Fig. Figure 1 shows an embodiment in which the light source 30 is implemented as a semiconductor layer stack for providing the excitation light with the excitation wavelength. The layer stack of the light source 30 comprises a first doped layer 31, a second doped layer 33, and an active region 32 arranged between the first doped layer 31 and the second doped layer 33.

[0080] The light source material is based on Gan, with the active region comprising InGaN to shift the excitation wavelength towards the red end of the spectrum. This is because the material for layer stack 11 is GaAs / AlGaAs, which emits in the red region of the spectrum. Due to the bonding with adhesive layer 15, the layer stack can be optimized individually and separately.

[0081] In this particular example, the first doped layer 31 is an n-doped layer connected by a multitude of metallic or highly conductive vias 35. The vias 35 are located in openings through the active region 32, the p-doped layer 33, and the transparent p-contact layer 37. The vias 35 are insulated with a dielectric material 36 to prevent a short circuit between the n-contacts 35 and the p-contact material 37.

[0082] A multitude of p-contacts 38 outside the area of ​​the main emission surfaces of the layer stack 11 are located on the transparent p-contact material 37. The layer stack of the light source 30 is then attached to the common transparent n-contact layer 14 of the multitude of optoelectronic components using a transparent adhesive material 15. The common n-contact layer 14 is roughened to improve the outcoupling of the photoluminescent light towards the multi-core optical fibers 50 and the coupling of the excitation light. Furthermore, the p-contact material 37 is transparent to the photoluminescence of the light and can also be roughened to achieve better coupling towards the multi-core optical fibers 50.

[0083] Finally, a multitude of filter elements 41 are located on the multi-core optical fibers 50 opposite the main exit surfaces of the layer stacks 11. The filter elements 41 are transparent to the photoluminescent light but reflect the light from the light source 30. The step of attaching the layer stack of the light source 32 to the optoelectronic components can be performed at the chip-to-chip, chip-to-wafer, or wafer-to-wafer level. Furthermore, the process described here in Fig. The illustrated structure for the layer stack of the light source 30 can be reused from existing architectures with transparent p-contacts, including a transparent conductive oxide.

[0084] The light source in the embodiment of Fig. The optoelectronic components are manufactured separately and then attached to the multiple optoelectronic components on the substrate 20 using an adhesive layer 15. However, depending on the material used for the optoelectronic components 10 and the light source 30, the arrangement is realized as a monolithic wafer structure. In such a case, the multiple optoelectronic components and the layer stack of the light source 30 comprise a common n-contact material 14, which is arranged between the layer stack 30 and the multiple optoelectronic components.

[0085] The common n-contact material 14 is electrically connected to an n-contact 12 via the insulating layer 19. In addition, several metal contact tracks 16 are arranged between two adjacent optoelectronic components to distribute the current across the common n-contact, thereby providing a substantially uniform current injection into the layer stack 30 and an equal potential for the layer stack 11 of the optoelectronic components 10.

[0086] On the opposite side of the light source layer stacks, the transparent conductive layer 37 is applied, on which a plurality of metal contact tracks 38 are arranged. Furthermore, a distributed Bragg reflector (DBR) is applied to the transparent p-contact layer 37 and the contacts 38 to reflect the excitation light towards the layer stacks 11. The BPR mirror material 42 comprises several insulating transparent layers with different refractive indices, which are transparent to the photoluminescent light from the optoelectronic components 10 but reflective to the excitation light from the light source 30.

[0087] In another aspect, which in Fig. As shown, several reflective elements, for example in the form of triangles or pyramids, are implemented in the dielectric transparent layer material 19. The side walls of the reflective elements 18 are inclined such that the excitation light from the layer stack of the light source 30 is reflected towards the active region of the layer stacks 11 of the optoelectronic components 10. The reflection of this excitation light further improves the efficiency of the generation of the photoluminescent light and thereby reduces the light wasted by the light source 30.

[0088] Similar to the previous embodiments, the structures can either be implemented as separate elements, including the substrate 20 with a variety of optoelectronic components and layer stacks 11 deposited on it, and the light source 30. Alternatively, both elements can be fabricated together as a monolithic integrated circuit.

[0089] The layer stacks 11 of the multiple optoelectronic components are optimized for the absorption of excitation light to improve the overall quantum yield of the photoluminescence, but not necessarily for charge carrier injection into the active region. This is because there are no requirements for charge carrier injection when the optoelectronic component is forward biased. Rather, the active region should be optimized for charge carrier separation when a reverse bias is applied.

[0090] Fig.Figure 1 shows an embodiment of the layer stack 11 of an optoelectronic component 10. The layer stack 11 comprises a first doped layer 11c, a second doped layer 11a, and the active region 11b located between them. The doping concentration of layers 11a and 11c can be adjusted to either prevent the diffusion of generated charge carriers into the doped layers or prevent the diffusion of dopants from the doped layers 11a and 11c into the active region 11b. The layer stack 11 also includes a mesa-etched structure with a regrown insulating layer 11 deposited on the mesa facets. This reduces the number of non-radiative recombination centers on the mesa facets, thereby improving radiative recombination and the generation of photoluminescent light during operation.

[0091] In this respect, the doped layer 11c can further have a roughened or otherwise structured surface to improve the absorption of the excitation light in the active region 11b. The band gaps of the doped layers 11a and 11c are adjusted so that no absorption of the excitation light occurs in the doped layers themselves, but rather primarily in the intervening active region 11b. Two contacts 13 and 14 are further provided on opposite sides of the layer stack. While layer 14 comprises a transparent conductive oxide used as a common contact layer, contact 13, which, for example, comprises a metal contact area, covers the doped layer 11a. This allows for the individual addressing of multiple layer stacks 11 arranged side-by-side on a common substrate.For stability reasons, but also for light guidance in cases where the excitation light is supplied parallel to layer 14, the layer stacks can be embedded in a dielectric transparent material. REFERENCE MARK LIST 1 Data communication system 10 optoelectronic components 10a, 10b optoelectronic component 10c, 10d optoelectronic component 11 layer stacks 11a, 11c doped layer 11b active area 12 n-contact 14 shared n-contacts 15 Adhesive 16 n-contacts 18 Reflector 19 Dielectric material 19a transparent dielectric material 20 substrate 21 conductor track 22 Data entry 23 Driver and control circuit 30 light sources 31 n-doped layer 32 active area 33 p-doped layer 38 p-contacts 39 optical element 40 filter elements 41 Filter element 42 DBR 50 optical fibers, multi-core fiber 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 111 339.9

[0001]

Claims

[1] Optoelectronic arrangement for optical data communication, comprising: - a plurality of optoelectronic components, in particular µLEDs, each having a main emission surface that can be attached to one or more optical fibers; wherein the plurality of optoelectronic components each comprise a semiconductor layer stack; - wherein each semiconductor layer stack comprises a first layer with a first doping type, a second layer with a second doping type that differs from the first doping type, and an active region arranged between the first and second layers, the active region being configured to emit light of a first wavelength; - a light source configured to emit light of a second wavelength, the second wavelength being shorter than the first wavelength; - the light source is arranged such that it illuminates the active regions of each semiconductor layer stack, thereby generating photoluminescent light through the active regions of each semiconductor layer stack, the photoluminescent light being emitted at least partially through the main emission surface; wherein - the optoelectronic arrangement is configured to modulate the generation of photoluminescent light by individually supplying a particularly inverted voltage and / or current signal to the semiconductor layer stack of the multiple optoelectronic components. [2] Optoelectronic arrangement according to one of the preceding claims, further comprising a control circuit configured to supply pulse- or amplitude-modulated blocking voltage signals to the plurality of optoelectronic components. [3] Optoelectronic arrangement according to one of the preceding claims, wherein the multiple optoelectronic components are electrically connected to a common substrate, the common substrate comprising a control circuit configured to provide the voltage and / or current signal to supply the semiconductor layer stacks of the multiple optoelectronic components individually. [4] Optoelectronic arrangement according to one of the preceding claims, wherein the plurality of optoelectronic components comprises at least one of the following elements: - a common contact surface, in particular a transparent conductive contact surface, wherein the transparent contact surface comprises the main emission surfaces of the multiple optoelectronic components; - a reflector configured to reflect light of a first wavelength towards the main emission surface; - a reflector configured to reflect light of a second wavelength towards the active area. [5] Optoelectronic arrangement according to one of the preceding claims, wherein the semiconductor layer stacks of the multiple optoelectronic components are embedded in a common insulating layer material, wherein the common insulating layer material is optionally at least partially transparent to the second wavelength. [6] Optoelectronic arrangement according to one of the preceding claims, further comprising one or more reflective elements arranged between two adjacent semiconductor layer stacks of the multiple optoelectronic components within the common insulating layer material, wherein the one or more reflective elements are configured to deflect light of the second wavelength towards the semiconductor layer stack and in particular its active region and / or to deflect light of the first wavelength towards the optical fibers. [7] Optoelectronic arrangement according to any of the preceding claims, wherein active regions of each semiconductor layer stack comprise at least one of the following elements: - a quantum well structure, optionally with one or more doped quantum well layers and / or with one or more doped barrier layers; - a multiple quantum well structure, optionally with one or more doped quantum well layers and / or with one or more doped barrier layers; - a large number of quantum dots; - a mesa-etched structure in which the material of the active region has a larger band gap adjacent to its perimeter. [8] Optoelectronic arrangement according to one of the preceding claims, wherein the light source comprises at least two optoelectronic components configured to illuminate the active area of ​​the multiple optoelectronic components from different locations and / or from different directions, in particular not in the direction of the one or more optical fibers. [9] Optoelectronic arrangement according to one of the preceding claims, further comprising a filter arranged downstream of the beam path of the main exit surface of the multiple optoelectronic components or upstream of the one or more optical fibers, wherein the filter is configured to be transparent to light of the first wavelength and reflective or absorbing to light of the second wavelength, the filter optionally comprising a DBR structure. [10] Optoelectronic arrangement according to one of the preceding claims, wherein the light source comprises a semiconductor layer stack with an active region arranged between the plurality of optoelectronic components and the one or more fibers, wherein optionally a wavelength-selective filter, in particular a DBR structure, is arranged between the active region of the semiconductor layer stack of the light source and the one or more fibers. [11] Optoelectronic arrangement according to one of the preceding claims, wherein the light source comprises a semiconductor layer stack with an active region covering one or more of the optoelectronic components, and further comprises at least one of the following elements: - an adhesive layer between the semiconductor layer stack and the multitude of optoelectronic components; - a common contact layer between the semiconductor layer stack and the multitude of optoelectronic components. [12] Optoelectronic arrangement according to one of claims 10 to 11, wherein the semiconductor layer stack of the light source and each semiconductor layer stack of the multiple optoelectronic components share a common contact plane, the common contact plane optionally comprising a conductive transparent material. [13] Optoelectronic arrangement according to one of claims 10 to 12, wherein the semiconductor layer stack of the light source comprises an active region containing at least one of the following elements: - a quantum well structure; and - a multiple quantum well structure. [14] Optoelectronic arrangement according to any one of the preceding claims, wherein the material of the semiconductor layer stack of the multiple optoelectronic components comprises one of GaAs, AlGaAs, InAlGaAs and InGaAsSb and combinations thereof; and / or wherein the material of the light sources comprises one of GaN, AlGaN, InAlGaN, GaP, AlP, AlGaP and InGaAlP. [15] Method for operating one or more optoelectronic components in an optical data communication arrangement, wherein the one or more optoelectronic components are attached to one or more optical fibers, wherein the one or more optoelectronic components are configured to be individually supplied with a voltage and / or current signal, wherein the one or more optoelectronic components comprise a semiconductor layer stack with an active region configured to emit light of a first wavelength, wherein the method comprises: - Illuminating the active areas of the layer stacks of one or more optoelectronic components with light of a second wavelength, where the second wavelength is shorter than the first wavelength; - Generating photoluminescence in the active areas of the layer stacks in response to illumination, wherein at least a portion of the photoluminescent light is directed onto one or more optical fibers; - Applying a modulated electric field in reverse direction to the active areas of the layer stacks; - Coupling parts of the modulated photoluminescent light into one or more optical fibers. [16] Method according to claim 15, wherein the illumination of the active areas comprises the step of illuminating the active areas of the layer stacks from different locations and / or from different directions, in particular not in the direction of the one or more optical fibers. [17] Method according to any one of claims 15 to 16, wherein the step comprises applying a modulated electric field: - Modulation, in particular pulse or amplitude modulation of the photoluminescence in the respective active areas by individually applying a reverse biased voltage and / or a current signal to one or more optoelectronic components; [18] Method according to any one of claims 15 to 17, further comprising: - Suppression by absorbing or reflecting light of the second wavelength in the beam path of one or more optical fibers. [19] Method according to any one of claims 15 to 18, wherein the rise and fall time of the reverse bias voltage and / or current signal is in the range between 10 ps and 100 ps and in particular below 50 ps.

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