WO2017041812A1

WO2017041812A1 - Optoelectronic device, comprising a waveguide and a semiconductor nanowire array, and method of manufacturing thereof

Info

Publication number: WO2017041812A1
Application number: PCT/EP2015/001835
Authority: WO
Inventors: Ivano GIUNTONI; Lutz GEELHAAR; Henning Riechert; Jürgen BRUNS
Original assignee: Forschungsverbund Berlin E.V.
Priority date: 2015-09-11
Filing date: 2015-09-11
Publication date: 2017-03-16

Abstract

An optoelectronic device (100) comprises a waveguide device (10) being arranged for guiding light fields (1), an array (20) of semiconductor nanowires (21), which stand with a mutual spacing on the waveguide device (10), wherein the positions and spacing of the nanowires (21) are selected such that the array (20) of semiconductor nanowires (21) provides an optical grating coupler optically coupling the waveguide device (10) and the semiconductor nanowires (21), and first and second contact sections (31, 32) for electrically contacting the array (20) of semiconductor nanowires (21). Furthermore, a method of manufacturing the optoelectronic device is described.

Description

Optoelectronic device, comprising a waveguide and a semiconductor nanowire array, and method of manufacturing thereof

Technical field

The present invention relates to an optoelectronic device, comprising a waveguide and an optoelectronic component, like a light emitter or a light detector, e. g. a photodiode, optically coupled with the waveguide. Furthermore, the present invention relates to a method of manufacturing the optoelectronic device. Applications of the invention are available e. g. in the fields of optical data processing, monolithically integrated optics, optoelectronics and/or light sensing.

Technical background In the present specification, reference is made to the following prior art illustrating the technical background of the invention, in particular with regard to optoelectronic devices including Si-based waveguides and epitaxial growth of semiconductor nanowires. It is noted that the citations provided are exemplary since a large number of papers has been published in the present field.

[1] T. Mitze et al . in "IEEE J. Sel. Top. Quantum Electron" vol. 12, p. 983 (2006) ;

[2] B. Snyder et al. in "J. Light. Technol." vol. 31, p.

3934 (2013);

[3] M. E. Groenert et al . in "J. Appl . Phys . " vol. 93, p.

362 (2003); [4] A. Y. Liu et al. in "Appl . Phys . Lett." vol. 104, p.

041104 (2014);

[5] D. Van Thourhout et al. in "IEEE J. Sel. Top. Quantum

Electron." vol. 16, 1363 (2010);

[6] S. R. Jain et al. in "J. Light. Technol." vol. 30, p.

671 (2012);

[7] E. Dimakis et al. in "Nano Lett." vol. 14, p. 2604

(2014); and

[8] D. Taillaert et al. in "IEEE J. of Quantum Electron." vol. 38, p. 949 (2002) .

In silicon based microelectronics, interconnection constitutes one of the major limitations of Moore's law, since it does not scale at the same rate as transistors. Hence, optical interconnects have been proposed for future technology generations. The complexity involved in these applications requires an integration of optics and electronics on the same substrate. For optical purposes, silicon is actually an ideal material for providing a waveguide for light fields e. g. in the range of wavelengths used for optical communication, since it is transparent, exhibits low absorption and a high refractive index (~ 3.5). This permits to realize low-loss waveguides with sub-wavelength dimensions. These waveguides require the employment of silicon-on-insulator (SOI) substrates, which enable a vertical light confinement.

However, silicon as a standalone material is not sufficient for the achievement of active components, like light sources or fast light detectors. Thus, the combination with other ma terials is still favourable in order to integrate optoelectronic components, like light sources and detectors, on the silicon platform. In particular, the compound semiconductor classes of group-III-V- semiconductors, in particular group- III-arsenides and group-III-phosphides are under considera- tion, since they offer direct bandgaps of suitable energy. But also group II-VI semiconductor compounds with direct bandgap can be considered, and well as silicon nitride as a waveguiding material. However, these compound semiconductors have a substantial limitation as planar epitaxial growth of these materials on silicon has to cope with the generally strong mismatch in lattice constants and thermal expansion coefficients. This mismatch leads to the generation of a large number of dislocations that degrade device performance.

The following different methods have been proposed for the integration of active I I I-V-semiconductor based optoelectronic components with silicon waveguides. Firstly, with the so- called hybrid integration, prefabricated optoelectronic com- ponents are combined with silicon waveguides using solder bumps. The light coupling between waveguide and active optoelectronic components occurs directly, by aligning the facets thereof. The adjustment occurs mechanically using pick-and- place equipment [1, 2]. Since the placing accuracies are lim- ited to around 1 μπι, the coupling efficiency cannot be optimized well. Furthermore, this process is time consuming and does not permit a large scale integration.

Furthermore, the monolithic integration of different III-V laser structures on Si has been demonstrated using buffer layers with graded composition to reduce the dislocation density in the actual device [3, 4]. However, these additional matching layers do not prevent the formation of dislocations completely, and they exhibit a thickness of some hundreds of nanometers which would impair the optical coupling with waveguides.

With a wafer bonding based process, wafers or dies of the desired material are placed on top of the SOI substrate using adhesive layers or molecular bonding. After thinning, they are further processed to achieve the desired device, including guiding structures [5, 6]. This method exhibits a high alignment accuracy as provided by the adjustment tolerances of the different lithographic steps. A separation between the two materials of only a few tens of nanometers can be

achieved. Therefore an evanescent light coupling can occur. However, a disadvantage of the wafer bonding technique is that the required heterostructures have to be grown epitaxi- ally on the full surface of an expensive substrate (InP or GaAs ) which is subsequently removed by thinning.

In summary, the above conventional approaches for integrating active optoelectronic components on Si have the disadvantage of being inadequate for large scale integration (hybrid integration) , exhibiting a difficult light coupling to waveguides (hybrid integration, buffer layers) or high costs (wafer bonding) . These limitations occur not only for the coupling of Si and III/V-semiconductors, but also for other material combinations with a lattice mismatch, like Ge/Si and different III/V and II/VI semiconductors.

Infrared light emitters integrated on the Si technology platform are described in [7]. The light emitters comprise free- standing GaAs-based nanowires as building blocks for the emission of light with micrometer wavelength that are mono- lithically integrated on Si substrates. This technique was restricted to the use of the nanowires as light emitters. Objective of the invention

The objective of the invention is to provide an improved optoelectronic device including a waveguide and an optoelectronic component, being capable of avoiding disadvantages of conventional techniques. In. particular, the objective of the invention is to provide the optoelectronic device allowing an integration of at least one active optoelectronic component on the waveguide and offering an improved compact light cou- pling, an improved process efficiency of manufacturing the optoelectronic device, lower costs, improved surface usage, and/or increased integration scale. Furthermore, the objective of the invention is to provide an improved method of manufacturing optoelectronic device, being capable of avoid- ing disadvantages of conventional techniques.

Summary of the invention

According to a first general aspect of the invention, the above objective is solved by an optoelectronic device, comprising a waveguide device for guiding light fields, at least one optoelectronic component, in particular for creating and/or sensing light fields, being optically coupled with the waveguide device, and contact sections for electrically con- tacting the at least one optoelectronic component. According to the invention, the optoelectronic component comprises an array of semiconductor nanowires (nanowire array) , which are provided with a mutual spacing as an upright standing arrangement on the waveguide device. The semiconductor nan- owires provide a regular array with mutual spacing between neighbouring nanowires. The nanowires are positioned such that the semiconductor nanowire array provides an optical grating coupler optically coupling the waveguide device and the semiconductor nanowires.

According to a second general aspect of the invention, the above objective is solved by a method of manufacturing an optoelectronic device according to the above first general aspect of the invention, comprising the steps of providing the waveguide device, growing the array of semiconductor nano- wires on the waveguide device, and contacting the array of semiconductor nanowires with contact sections. Advantageous key characteristics of the overall fabrication are: Firstly, the optical alignment between waveguide and active optoelectronic component (nanowire array) is achieved by lithography. Secondly, the array is monolithically integrated on the waveguide platform. Finally, all involved processing steps are standard for semiconductor technology. They take place on the wafer level, and can be upscaled. Therefore, the invention provides a new generation of compact integrated systems offering functionalities that are presently not obtainable.

The invention provides a monolithic integration of standing nanowires, preferably made of a III-V-compound semiconductor, with a planar waveguide, preferably made of silicon. Advantageously, this allows circumventing problems related to lattice mismatch, and further allows direct light coupling between the materials of the nanowires and the waveguide. More specifically, the nanometer-scaled footprint and the high aspect ratio of the nanowires relax the matching requirements because strain can elastically relax at the free sidewall surfaces and dislocations likely terminate there. Furthermore, the provision of the nanowires on the waveguide device such that the refractive index in the waveguide is periodically modulated by the regular array of nanowires, creates the optical grating coupler coupling light field modes in the waveguide device and light field modes in the nanowire. Thus, optical coupling is obtained.

Waveguide photonics is a planar technology, where light is transported along the waveguide in a substrate plane (e. g. spanned by x-y axes of a Cartesian coordinate system) . In contrast, the nanowires are grown extending from the sub- strate plane, e. g. along z-direction (vertical growth) or inclined relative to the z-direction (inclined growth). Advantageously, by utilizing all three spatial dimensions in^¬ stead of restricting oneself to planar configurations, the inventors pursue a new approach for the direct integration of active optoelectronic components on the mature waveguide platform. This new integration leads to compact optoelectronic systems that have not been possible so far. Preferably, the nanowires are created by an epitaxial growth of a compound semiconductor on the waveguide. The epitaxial growth may comprise e. g. a direct epitaxial growth (growth directly from the vapor phase) or a VLS-based (VLS: vapor liquid solid) epitaxial growth (growth from a liquid phase) . As an alternative, a mask-based deposition can be applied, using a thick structured masking layer. Contrary to the conventional hybrid technique, mechanical adjustment of optoelectronic components can be avoided. Furthermore, contrary to the conventional buffer layer and wafer bonding techniques, optical coupling is improved and processing costs are reduced. As a further essential advantage, the above growth mechanisms facilitate providing a desired composition and/or doping profile along an axial or radial direction of the nanowires. Accordingly, the function of the optoelectronic com- ponent provided by the nanowire array can be set, e. g. by creating at least one heterostructure during the nanowire growth .

The contact sections comprise layers or pads being provided for electrically connecting the at least one optoelectronic component, e. g. with a power source, an amplifier circuit or a digital signal processor circuit. According to a preferred embodiment of the invention, the contact sections for electrically contacting the optoelectronic component include a first contact section being connected with the waveguide device, and a second contact section being connected with the semiconductor nanowires. Advantageously, driving the optoelectronic component, sensing an electrical output thereof and/or processing electrical signals is facilitated as only one single contact section connected with the nanowires is required. Preferably, the waveguide device has a doped portion carrying the semiconductor nanowires and providing electrical contact between the semiconductor nanowires and the first contact section. Accordingly, the nanowires are contacted via the material of the waveguide device.

According to a further preferred feature of the invention, the second contact section is connected with end portions, particularly preferred the tips of the semiconductor nanowires. Various materials are available for providing the contact sections, which can be made of e. g. a metal, like TiAu. In particular, the second contact section preferably is made of a transparent material, like a transparent metal lay- er or a semiconductor layer, like indium tin oxide (ITO).

If according to a further particularly preferred embodiment of the invention, the semiconductor nanowires are included in a transparent embedding layer, advantages in terms of a plane upper surface and mechanical stability of the nanowires are obtained, while the optical function of the optoelectronic component is kept. The embedding layer is made of polymer, like Benzocyclobutene (BCB) or Hydrogen silsesquioxane (HSQ) , or a resin, or spin-on glass. The material of the embedding layer can be supplied to the surface of the waveguide device in a precursor liquid state, such that the nanowires are included in the precursor liquid, and subsequently can be hardened, e. g. by drying, and/or heating. Preferably, the embedding layer has a thickness matched to a perpendicular height of the nanowires relative to the supporting waveguide device. Accordingly, the semiconductor nanowires cross the upper surface of the embedding layer. The tips of the nanowires are exposed at the upper surface. With this embodiment, the em- bedding layer advantageously fulfils a third function in terms of carrying the second contact section.

Generally, the array of semiconductor nanowires comprises any regular arrangement of nanowires grown on the waveguide de- vice and being capable of providing the optical grating coupling of the nanowires with the waveguide device. According to a preferred embodiment of the invention, the nanowire array comprises a single straight row of nanowires, i. e. a group of nanowires, the footprints of which being arranged as a single row extending along a straight line, preferably parallel to a main extension of the waveguide device. The single row embodiment is preferred if the nanowires are grown with a thickness, e. g. 250 nm, being equal to or having the same order of magnitude like a width, e. g. 500 nm, of the wave- guide device. This variant has advantages in terms of a compact design of the optoelectronic component. Alternatively, the nanowire array comprises multiple, i. e. at least two straight rows of nanowires (regular nanowire matrix) . The matrix embodiment has advantages in terms of increased coupling power and coupling efficiency, thus being capable of providing e. g. an increased emission intensity or detection sensitivity of the optoelectronic component. The matrix embodiment can be preferred if the width of the waveguide device is sufficiently large for accommodating multiple parallel nanowire rows.

Each of the semiconductor nanowires is a crystalline column of a compound semiconductor. Preferably, all nanowires are grown simultaneously, e. g. with a common epitaxial growth process, so that all nanowires have the same geometric

(thickness, axial length) and composition (chemical elements of compound semiconductor, doping) features. Basically, each of the nanowires may have a homogeneous composition along the axial length thereof. Alternatively, according to a preferred embodiment of the invention, the nanowire composition along the axial length and/or in a radial direction of the nanowires is changed, e. g. by adjusting process conditions of the growth mechanism, such that at least one pn junction and/or at least one quantum well element is included in the nanowire. Particularly preferred, all of the semiconductor nanowires are designed to act as a light-emitting diode, a laser diode or a light detector. According to further preferred variants of the invention, which can be provided as alternatives or in combination, the nanowire array has at least one of the following features. The array of the semiconductor nanowires comprises at least 2 semiconductor nanowires, preferably at least 5 semiconductor nanowires. Further, the semiconductor nanowires are made with a composition selected in dependency on the operating wavelength of the waveguide device. According to a particularly preferred embodiment of the invention, the nanowires are made of III-V-semiconductors, like e. g. Group III-As or Group III-P. Advantages in terms of a high coupling efficiency in the wavelengths ranges of IR wavelengths, the semiconductor nanowires preferably have a spacing of at least 100 nm and/or at most 10 pm. Further preferred geometrical features comprise a thickness of at least 10 nm and/or at most 1 μπι, and/or an axial length of at least 10 nm and/or at most 10 μπι.

The term "waveguide device" generally refers to a solid structure including a restricted spatial region being ar- ranged for guiding light, e. g. a planar waveguide or a channel waveguide. Depending on the application of the invention, the waveguide device may include further components, like a substrate, e. g. made of Si02, optical couplers, electronic and/or further optoelectronic components. The upper surface of the waveguide is designed such that the refractive index of the waveguide material is influenced by the nanowires grown on the waveguide. Thus, the material of the waveguide may be exposed for creating a direct contact with the nan- owires, or it can carry a transparent intermediate layer having a thickness still allowing the refractive index change in the waveguide.

According to a further embodiment of the invention, the wave- guide device can be provided with a patterned masking layer including holes each of which accommodating at least a foot section of one of the semiconductor nanowires. The holes define the positions of the nanowires, e. g. as seed sections for the epitaxial growth or as receptacles for the nanowires in a mask-based deposition.

Brief description of the drawings

Further details and advantages of the invention are de- scribed in the following with reference to the attached drawings, which show in:

Figure 1: a schematic illustration of an optoelectronic device according to a first embodiment of the inven- tion;

Figure 2: a schematic illustration of an optoelectronic device according to a further embodiment of the invention; Figure 3: a graphical representation of the vertical light out-coupling efficiency from the waveguide in dependency on a spacing of the nanowires in an optoe- lectronic device according to the invention;

Figure 4: a schematic cross-sectional view of an optoelectronic device according to a further embodiment of the invention and amplitude of the computed elec- trie field;

Figure 5: a graphical representation of a light absorption in nanowires in dependency on a spacing of the nanowires in an optoelectronic device according to the invention; and

Figure 6: a graphical representation of the coupling efficiency for a coherent light emission in dependency on a spacing of the nanowires in an optoelectronic device according to the invention.

Preferred embodiments of the invention

Features of preferred embodiments of the invention are de- scribed in the following with particular reference to the integration of an optoelectronic component, comprising a single row nanowire array, on a waveguide. The implementation of the invention is not restricted to the single row embodiment, but correspondingly possible with a matrix nanowire array. Exem- plary reference is made to III/V-semiconductor nanowires grown on a Si waveguide. The implementation of the invention is not restricted to this material combination, but rather possible with other materials, like e.g. II-VI semiconductors and silicon nitride as guiding material. Known details of op- toelectronic devices, like the design and manufacturing of the waveguide or the combination of the optoelectronic device with further components are not described as they can be implemented as with conventional optoelectronic devices.

Figure 1 is a representation of a first embodiment of the inventive optoelectronic device 100 comprising a regular array 20 of free-standing III-V nanowires 21 grown on a waveguide device 10 having a planar silicon waveguide 11. The optoelectronic device 100 is shown without contact sections (see Figure 2) . To improve the mechanical stability the space between the nanowires can be filled with an embedding layer comprising spin-on-glass or a polymer, e.g. benzocyclobutene (BCB) (see Figures 2 and 4) .

The waveguide device 10 comprises a channel waveguide 11 realized on a silicon-on-insulator wafer. A Si0₂ buried layer 12 is placed as a substrate under the Si guiding layer. The further Si carrier substrate under the buried oxide 12 is not shown in the figure. The width and thickness of the channel portion of the waveguide 11 are e. g. 500 nm and 220 nm, resp.. The extension of the waveguide 11 along the substrate plane and the coupling thereof with further components are selected in dependency on the particular application conditions .

The array 20 of nanowires 21 comprises e. g. eight nanowires 21 arranged as a straight row on the waveguide 11. The nanowires 21 have a thickness of e. g. 250 nm, an axial length of e. g. 1 μπι. The array 20 of nanowires 21 provides e. g. a light emitting optoelectronic component. To this end, the nanowires 21 are made e. g. with the following composition: GaAs/ (In, Ga) As. It is noted that Figure 1 shows in a generic way how optoelectronic components based on vertical nanowires can be integrated with a planar silicon waveguide. The key feature of the invention is that with a proper tailoring of the array spacing D and nanowire thickness d it is possible to control the light coupling between waveguide 11 and nanowires 21. The nanowire array 20 produces a modulation of the effective index of the waveguide core, which acts like a grating coupler. The coupling properties are further described with reference to Figure 3 below. Hence, light propagating in the waveguide 21 is vertically out-coupled into the nanowires. By the same mechanism, light generated in the nanowires 21 is coupled into the waveguide 11 and propagates along the plane of the substrate 12. By engineering a heterostructure and doping profile in the nanowires 21, the desired optoelectronic functionality can be achieved, with a broad range of possible devices that can be obtained, including sensors, photodiodes and lasers. Figure 2 is an extended view representation of a further embodiment of the inventive optoelectronic device 100, including a Si waveguide 11 and a nanowire array 20 with contact sections 31, 32. The Si waveguide 11 is arranged on a Si0₂ substrate 12. In the area where the nanowire array 20 is to be provided, a doped portion 13 is created by p-doping Si (e. g. with Boron) of the waveguide core and the surrounding Si layer. Furthermore, the surface of the former is covered with a thin silicon dioxide masking layer 14 for the selective area growth of GaAs nanowires. Small holes 15 are etched into the silicon dioxide masking layer 14 providing a mask where the nanowires 21 are to be grown. Then the nanowire array 20 is created e. g. by epitaxial growth, in particular VLS-based epitaxial growth (as described in [7]) or by an epitaxial growth directly from the vapor phase. As a further alternative, a mask-based deposition includes depositing and structuring a thick masking layer, e. g. a polymer layer, having a thickness equal to the axial lengths of the nanowires and column-shaped holes at the positions of the nanowires to be obtained, and depositing the III/V semiconductor in the holes, e. g. by vapor deposition. Subsequently, the masking layer can be used as an embedding layer 40 as described below.

Subsequently, the area around the nanowires is partially filled with benzocyclobutene (BCB) forming an embedding layer 40. The first contact section 31, made of e. g. aluminium, is positioned on the doped portion 13, and the top second con- tact section 32 is provided on the embedding layer 40, either by metal or by a layer of indium tin oxide (ITO) if a transparent contact is needed. As an alternative, the first contact section 31 can be provided as a back-contact of the doped portion 13.

Figure 3 illustrates a calculated dependency of the coupling efficiency, i.e. the power of light out-coupled from the waveguide 11 to the nanowire array 20 on top divided by the power of the guided light in the waveguide 11, on the nan- owire spacing D at a wavelength of 1.3 pm. This coupling efficiency curve is obtained from two-dimensional numerical simulations using the finite difference time domain software package "Meep" . An array of twenty nanowires placed on top of a Si waveguide has been considered. They exhibit a height of 800 nm and a thickness of 256 nm. These values have been taken from structures described in [7]. A grating condition is best fulfilled for nanowire spacing D in a range of 0.6 to 1 pm, and light is vertically scattered and out-coupled from the waveguide. At a value of D = 0.8 pm, the maximal out- coupling value is reached, with almost 60% of the input light vertically extracted.

The coupling at D = 0.8 μπι can be visualized as shown in Fig- ure 4, which illustrates a cross-sectional view of an optoelectronic device 100 according to a further embodiment of the invention. The optoelectronic device 100 comprises the waveguide 11 carrying the array 20 of nanowires 21 in the embedding layer 40. Light 1 is vertically scattered and propagates through the nanowires 21 with an axial length of 1 μπι. The phase fronts of the vertically propagating light 1 exhibit a tilt of about 10°, as it is typical for grating couplers directly etched in waveguides, used for light coupling with optical fibers [ 8 ] .

If at least one pn junction is formed in each of the nanowires, e. g. along the axial length thereof, or with a core- shell configuration, the array of nanowires can be designed as a monolithically integrated photodiode. For such a device to be functional, light not only has to be out-coupled from the Si waveguide into the nanowires but needs to be absorbed there. This has been tested by two-dimensional simulations at a wavelength of 1.3 μιη with an example of a linear array of 10 nanowires with varying spacing, having an axial nanowire length of 1 μπι. The assumed core-shell geometry corresponds to what has been described in [7], i. e. 20 nm GaAs core, 50 nm n-GaAs shell, 8 nm radial (In,Ga)As QW and 60 nm p-GaAs shell. As shown in Figure 5, a relative absorption of 0.3 is obtained with 10 nanowires, assuming for the (In,Ga)As shell an absorption coefficient of a = 10⁴ cm^-1, the standard value for bulk material.

Figure 6 illustrates the calculated coupling efficiency for a coherent light emission generated in the nanowires with an axial nanowire length of 1 μπι to the underlying silicon waveguide as function of the spacing D. Since the coupling interface between the waveguide and the nanowires is bidirectional, a light emitter for optical systems on silicon waveguides can be achieved. Light generated in the nanowires can be hence coupled to the waveguide. In Figure 6, the computed coupling efficiency for a coherent emission from the nanowires as function of the nanowire spacing is shown. For a spacing of D = 0.62 nm 40% of the emitted light can couple to the waveguide. The shorter spacing D at which the light coupling occurs compared to the photodiode case can be explained, considering that the light generated in the nanowires experiences a different effective index compared to the waveguide. To achieve such an optical system the nanowires are configured as laser sources, since a coherent emission is required for the coupling interface: the wave fronts have to be in phase at the nanowire/waveguide interface .

The features of the invention disclosed in the above description, the drawings and the claims can be of significance both individually as well as in combination or sub-combination for the realization of the invention in its various embodiments.

Claims

Claims 1. Optoelectronic device (100), comprising

- a waveguide device (10) being arranged for guiding light fields (1),

- an array (20) of semiconductor nanowires (21), which stand with a mutual spacing on the waveguide device (10), wherein the positions and spacing of the nanowires (21) are selected such that the array (20) of semiconductor nanowires (21) provides an optical grating coupler optically coupling the waveguide device (10) and the semiconductor nanowires (21), and

- first and second contact sections (31, 32) for electrically contacting the array (20) of semiconductor nanowires (21).

2. Optoelectronic device according to claim 1, wherein

- the first contact section (31) is connected with the waveguide device (10) , and

- the second contact section (32) is connected with the semiconductor nanowires (21).

3. Optoelectronic device according to claim 2, wherein

- the waveguide device (10) has a doped portion (13) carrying the semiconductor nanowires (21) and providing electrical contact between the semiconductor nanowires (21) and the first contact section (31).

4. Optoelectronic device according to one of the claims 2 to 3, wherein

- the second contact section (32) is connected with end portions of the semiconductor nanowires (21) .

5. Optoelectronic device according to one of the claims 2 to 4, wherein

- the second contact section (32) is made of a transparent metal or a transparent semiconductor.

6. Optoelectronic device according to one of the foregoing claims, wherein

- the semiconductor nanowires (21) are included in a transparent embedding layer (40) .

7. Optoelectronic device according to claim 6, wherein

- the embedding layer has a thickness such that the semiconductor nanowires (21) cross an upper surface (41) of the embedding layer (40) , and

- the second contact section is arranged on the upper surface of the embedding layer (40) .

8. Optoelectronic device according to one of the foregoing claims, wherein

- the array (20) of semiconductor nanowires (21) comprises at least one row of the semiconductor nanowires (21).

9. Optoelectronic device according to one of the foregoing claims, wherein

- each of the semiconductor nanowires (21) includes at least one pn junction and/or at least one quantum well element.

10. Optoelectronic device according to one of the foregoing claims, wherein

- all of the semiconductor nanowires (21) are designed to act as a light-emitting diode, a laser diode or a light detector.

11. Optoelectronic device according to one of the foregoing claims, wherein the array (20) of the semiconductor nan- owires (21) has at least one of the features:

- the array (20) of the semiconductor nanowires (21) compris- es at least 2 semiconductor nanowires (21),

- the semiconductor nanowires (21) are made with a composition selected in dependency on the operating wavelength of the waveguide device (10),

- the semiconductor nanowires (21) are made of III-V- semiconductors,

- the semiconductor nanowires (21) have a spacing of at least 100 nm and/or at most 10 μπι,

- the semiconductor nanowires (21) have a thickness of at least 10 nm and/or at most 1 μιη, and

- the semiconductor nanowires (21) have an axial length of at least 100 nm and/or at most 10 μπι.

12. Optoelectronic device according to one of the foregoing claims, wherein the waveguide device (10) has at least one of the features

- the waveguide device (10) is made of silicon,

- the waveguide device (10) carries a patterned masking layer (14) including holes (15) each of which accommodating one of the semiconductor nanowires (21), and

- the waveguide device (10) has a substrate made of Si0₂.

13. Method of manufacturing an optoelectronic device according to one of the foregoing claims, comprising the steps of

- providing the waveguide device (10),

- growing the array (20) of semiconductor nanowires (21) on the waveguide device (10), and

- contacting the array (20) of semiconductor nanowires (21) with the first and second contact sections (31, 32) .

14. Method according to claim 13, wherein

- the growing step includes a direct epitaxial or a vapor- liquid-solid-based growth of the semiconductor nanowires (21) on the waveguide device (10) or a mask-based deposition of the semiconductor nanowires (21) on the waveguide device (10) .

15. Method according to claim 13 or 14, including the step of

- embedding the semiconductor nanowires (21) in a transparent embedding layer (40) .