Optoelectronic Components and Lasers

Abstract

The optoelectronic component comprises a stack including a photonic crystal (1) and a gain medium (3). The gain medium comprises a layer sequence of at least two quantum wells (30) and at least one tunnel junction (31) and is configured to emit electromagnetic waves. The photonic crystal is electromagnetically coupled to the gain medium. The stack is arranged on a substrate (5). Alternatively or additionally, the gain medium comprises at least one quantum well. The photonic crystal is structured in a dielectric layer and is electromagnetically coupled to the gain medium.

Description

[Technical field]

[0001] Optoelectronic components and lasers are described. [Background technology]

[0002] Due to their small size and power spectrum, semiconductor lasers are used in a wide range of applications, for example in integrated sensor solutions. Semiconductor lasers can generally be divided into two classes: edge-emitting lasers, where the laser light propagates parallel to the wafer surface of the semiconductor chip and is reflected or coupled at the cleaved edge, and surface-emitting lasers, where the light propagates perpendicular to the surface of the semiconductor wafer. A less common category of surface-emitting lasers is configured in which the laser light propagates in a cavity substantially along the wafer surface (in-plane lasers). One realization of this kind of laser is the photonic crystal surface-emitting laser (PCSEL), where an in-plane laser resonator with a photonic crystal structure is realized. The same structure also reflects a part of the light to form the output beam. Here, single-frequency operation can be achieved, which can be important for applications in, for example, 3D sensing and optical data transmission.

[0003] Photonic crystal surface-emitting lasers, or PCSELs, can be realized, for example, by a stack of functional layers. In contrast to edge-emitting lasers, the lasers can and should be equipped with coupling waveguides depending on the application in order to simplify the manufacturing and to tailor the laser properties to the specific application. At the same time, high quality components, such as the photonic crystals used, are required. Summary of the Invention [Problem to be solved by the invention]

[0004] One objective is to specify optoelectronic components and lasers that allow for easier fabrication and improved laser performance. [Means for solving the problem]

[0005] These problems are solved by an optoelectronic component and a laser according to the independent claims. Further embodiments of the optoelectronic component and the laser are the subject of the dependent claims.

[0006] According to one embodiment of the optoelectronic component, the optoelectronic component comprises a stack including a photonic crystal and a gain medium. The gain medium comprises a layer sequence of at least two quantum wells and at least one tunnel junction. The stack is arranged on a transparent substrate in a region where the electromagnetic waves are emitted. The gain medium is configured to emit the electromagnetic waves. The photonic crystal is electromagnetically coupled to the gain medium.

[0007] To increase the brightness of lasers, especially photonic crystal surface emitting lasers, PCSELs, optoelectronic components with stacks can be advantageous. Unlike other semiconductor lasers with multiple junctions, which are also possible and often necessary, to couple the waveguides. This allows, for example, to omit implementing a photonic crystal layer for each waveguide.

[0008] By combining the waveguides, it is possible to create large-area lasers with high power density with only diffraction-limited beam collimation. Furthermore, the stacks can be placed into superwaveguides.

[0009] With the help of tunnel junctions, individual quantum wells can be coherently coupled across a small space. This concept is easier to fabricate because only one photonic crystal layer is required, and nanostructuring only has to be done after the deposition of the quantum wells and tunnel junctions, thus not introducing additional defects into the most sensitive layers of the device.

[0010] In one embodiment, the optoelectronic component comprises a stack including a photonic crystal and a gain medium. The gain medium includes at least one quantum well and is configured to emit electromagnetic waves. The photonic crystal is structured in a dielectric layer and is electromagnetically coupled to the gain medium. The stack is placed on a substrate. The substrate may be transparent in the region of the electromagnetic wave, for example to couple the electromagnetic wave. Alternatively, the substrate may be opaque in the region of the electromagnetic wave, for example if the electromagnetic wave is not coupled from this side.

[0011] Due to the high collimation quality of the PCSEL, no significant beam broadening occurs even when coupling to a substrate, i.e. the optical properties of optoelectronic components used as lasers are not compromised by "thick" substrates, e.g. >100 μm, and it is therefore also possible to manufacture components using much thicker substrates than previously proposed.

[0012] To realize this approach with high-quality photonic crystal structures, the photonic crystals can not be structured directly inside the semiconductor material, but rather in an additionally inserted layer close to the active zone. This layer comprises, for example, a dielectric material in combination with another dielectric material and / or a transparent conductive material such as indium tin oxide (ITO). Materials with good optical properties and at the same time a high thermal conductivity are particularly suitable as dielectric materials, while other dielectric materials with relatively poor thermal properties are also suitable in principle.

[0013] One advantage of this approach over alternative concepts is that only relatively thin layers of semiconductor material are required, which results in significantly shorter processing times for the corresponding epitaxial layers, thus enabling low-cost components with relatively simple architectures. Structuring the dielectric can reduce or even avoid semiconductor defects.

[0014] In one embodiment, the optoelectronic component comprises a stack including a photonic crystal and a gain medium. The gain medium comprises at least one quantum well and is configured to emit electromagnetic waves. The photonic crystal (1) is structured in a conductive layer and is electromagnetically coupled to the gain medium. The stack is arranged on a substrate. The substrate may be transparent in the region of the electromagnetic wave, for example to couple the electromagnetic wave. Alternatively, the substrate may be opaque in the region of the electromagnetic wave, for example if the electromagnetic wave is not coupled from this side.

[0015] This allows for photonic crystal structures on the p-side, e.g., InGaN lasers, etc. The internal realization of a conductive layer, e.g., including ITO, on the p-side allows for a perfectly planarized structure that facilitates coupling via the p-side (AR coating) and allows for thermal coupling via the n-side, for example.

[0016] In at least one embodiment, the layer sequence includes at least two quantum wells and at least one tunnel junction, and a photonic crystal is structured in the electrical layer.

[0017] In at least one embodiment of the optoelectronic component, a photonic crystal is included in the gain medium such that the photonic crystal is arranged in a layer sequence.

[0018] Alternatively, the photonic crystal may be arranged separately from the gain medium, such that the photonic crystal is arranged in an outer layer of the layer sequence.

[0019] In at least one embodiment, the gain medium has one or more claddings disposed in the layer sequence such that the quantum well is spaced from the tunnel junction.

[0020] In at least one embodiment, the distance between the quantum well and the tunnel junction, respectively, is adjusted to allow coupling of the fundamental mode from the gain medium.

[0021] In at least one embodiment, one or more claddings are tuned in distance such that the distance between the quantum well and the tunnel junction is tuned to couple multiple single modes out of the gain medium, respectively, and to couple the single modes by energy transfer.

[0022] In at least one embodiment, the photonic crystal includes a cladding.

[0023] In at least one embodiment, the dielectric layer comprises a first dielectric material, the dielectric layer further comprises a second dielectric material and / or a conductive material that is transparent in the domain of electromagnetic waves.

[0024] In at least one embodiment, the conductive layer comprises a first conductive material, a second conductive material, and / or a dielectric material that is transparent in the region of electromagnetic waves.

[0025] Furthermore, conductive and dielectric layers can be combined by suitable material selection, thus for example providing partially dielectric and partially conductive layers.

[0026] In at least one embodiment, the photonic crystal structure of the photonic crystal comprises a first dielectric material and is fully embedded in a second dielectric material and / or a transparent conductive material, The photonic crystal structure of the photonic crystal may be at least partially unembedded in the second dielectric material and / or the transparent conductive material on a side facing the quantum well.

[0027] In at least one embodiment, the photonic crystal structure of the photonic crystal is in direct contact with the gain medium.

[0028] In at least one embodiment, the photonic crystal is structured in a layer that does not have conductive material.

[0029] In at least one embodiment, the laser includes one or more optoelectronic components according to the concepts described herein, and further includes a pump source configured to excite vibrational emission by the gain medium.

[0030] In at least one embodiment, a method for manufacturing an optoelectronic component includes the following steps: first, a photonic crystal and a gain medium are arranged in a stack; the stack is further arranged on a transparent substrate in the region where the electromagnetic waves are emitted; the gain medium includes at least two quantum wells and at least one tunnel junction in a layer sequence; the gain medium is configured to emit the electromagnetic waves; and finally, the photonic crystal is electromagnetically coupled to the gain medium.

[0031] In at least one embodiment, a method for manufacturing an optoelectronic component includes the following steps: first, arranging a photonic crystal and a gain medium in a stack; the stack is placed on a transparent substrate in a region where electromagnetic radiation is emitted; the gain medium includes at least one quantum well and is configured to emit electromagnetic radiation; and the photonic crystal is structured in a dielectric layer and is electromagnetically coupled to the gain medium.

[0032] Further embodiments and further developments of the optoelectronic component or of the method for manufacturing an optoelectronic component will become apparent from the exemplary embodiments described below in conjunction with figures 1 to 11. In the figures, parts of circuits which are identical, similar or act identically are provided with the same reference signs. [Brief description of the drawings]

[0033] [Figure 1] 1 illustrates an example of an optoelectronic component. [Diagram 2] 1 illustrates an example of an optoelectronic component. [Diagram 3] 1 illustrates an example of an optoelectronic component. [Figure 4] 1 illustrates an example of an optoelectronic component. [Diagram 5] 1 illustrates an example of an optoelectronic component. [Figure 6] 1 illustrates an example of an optoelectronic component. [Figure 7] 1 illustrates an example of an optoelectronic component. [Figure 8] 1 illustrates an example of an optoelectronic component. [Figure 9] 1 illustrates an example of an optoelectronic component. [Figure 10] 1 illustrates an example of an optoelectronic component. [Figure 11] 1 illustrates an example of an optoelectronic component. [Figure 12] 1 illustrates an example of an optoelectronic component. [Figure 13] 1 illustrates an example of an optoelectronic component. [Figure 14] 1 illustrates an example of an optoelectronic component. [Figure 15] 1 illustrates an example of an optoelectronic component. [Figure 16] 1 illustrates an example of an optoelectronic component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] 1 shows an optoelectronic component. In this and the following examples, the optoelectronic component comprises a stack including a photonic crystal 1 and a gain medium 3.

[0035] The photonic crystal 1 consists, for example, of a thin layer of a semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent, i.e. does not absorb or only slightly absorbs, the electromagnetic waves to be emitted. The electromagnetic waves to be emitted are, for example, the infrared, IR, ultraviolet, UV, or visible, VIS, part of the electromagnetic spectrum. The photonic crystal 1 comprises a photonic structure 11, which is a periodic refractive index structure and can guide, filter, and / or reflect the electromagnetic waves in a wavelength-selective manner, for example by optical processes such as diffraction and interference. The periodic photonic structure determines or defines, for example, the radiation direction, wavelength and divergence of the electromagnetic waves that can be emitted from the optoelectronic component.

[0036] The photonic crystal structure 11 comprises a one-dimensional or two-dimensional array of structural elements 12 arranged in a pattern (e.g., a square or triangular pattern) to form a photonic crystal structure extending in a given direction or area. The structural elements can include air holes or dielectric materials. As a two-dimensional photonic crystal structure, it functions as a lateral cavity, so to speak. For example, the photonic structures are characterized by the distance (pitch) between the structural elements or by their filling factor and other parameters. Not shown is the extension of the photonic crystal to one plane, resulting in a two-dimensional distribution of periodic photonic structures. In principle, the photonic crystal can extend along one direction, which results in a one-dimensional distribution of periodic photonic structures.

[0037] The gain medium 3 comprises a layer sequence of a quantum well 30, a tunnel junction 31 and a cladding 32. The quantum well is an active medium and is configured to emit electromagnetic waves by vibration-stimulated emission when suitably excited. The gain medium is defined by two outer claddings. In this example, a photonic crystal is the first outer cladding for the gain medium. The second outer cladding 33 defines the gain medium from a substrate 5 on which the stack is placed. The substrate is transparent to the electromagnetic radiation range. The first outer cladding and the second outer cladding can have different layer thicknesses than the cladding 32 of the gain medium. The stack of gain media forms a common waveguide defined by the first and second outer claddings. In this example, the cladding 32 of the gain medium has equal layer thicknesses. For example, the layer thicknesses are in the range of 100 nm to 500 nm. The cladding comprises a doped semiconductor, for example n-doped or p-doped.

[0038] The stack includes multiple quantum wells, three in this example, but at least two quantum wells. This structure is called a multiple quantum well. The first quantum well is photonically coupled to the photonic crystal. In this example, the photonic crystal is disposed in the first quantum well. The term "photonic coupling" refers to this spatial proximity that allows an evanescent field to form between the photonic crystal and the quantum well when the optoelectronic crystal is in operation (e.g., a laser). This is described in more detail below.

[0039] In this layer sequence, a first quantum well is followed by a further cladding 32, followed by a first tunnel junction 31 and another cladding 32. This sequence is repeated for a second quantum well 30 with a further cladding 32, followed by a second tunnel junction 31 and a further cladding 32. This cladding is followed by a third quantum well 30, which in a sense completes the stack in the direction of the substrate 5. The third quantum well 30 is arranged in a second outer cladding 33.

[0040] The tunnel junction 31 represents, for example, a pn junction. Thus, an advantageous sequence of n-doped and p-doped regions can be adjusted by the layer sequence. In this example, the sequence of the respective quantum wells, claddings and tunnel junctions ensures that only one fundamental mode per quantum well is established by appropriate excitation. By arranging several quantum wells (multiple quantum wells), a "super" fundamental mode is established by superposition, which is determined by the layer thickness and the relative position of the quantum wells. For this purpose, layer thicknesses of less than 1 μm have proven to be advantageous for this purpose, the layer thicknesses representing the sequence of the respective quantum wells, claddings and tunnel junctions. In this way, the quantum wells are photonically coupled to each other, since they are very close to each other, and a "polar" fundamental mode is established. The position of the tunnel junction in the stack has proven to be of little importance, since the fundamental mode does not have a node or the like. Thus, by coupling the photonic crystal structure to a thin active layer (quantum well) below the photonic crystal layer in the evanescent field corresponding to the fundamental mode, laser gain by vibrational emission can be realized.

[0041] The substrate comprises two opposing surfaces. One surface 51 is provided with the outer cladding 33, so that the layer sequence is arranged on the substrate. The opposing surface 52 is optionally provided with a reflective coating 53. This reflective coating comprises, for example, a (metallic) reflector or a Bragg mirror. A reflective coating may also be provided on surface 51. The reflective coating is optional since it is not a component of the resonator or since a high reflectivity at the substrate is not necessarily required for laser activity.

[0042] The optoelectronic component may be operated as part of a laser. A suitable pump source may be electrical or optical, causing a vibration emission in the gain medium. For example, a current for pumping the active region, i.e. the quantum well, is applied to the upper and lower surfaces of the optoelectronic component via metal electrodes, e.g. the surface 52 opposite the photonic crystal and the substrate. The electrodes are not shown. In this example, the laser emission occurs via the upper surface (indicated by the arrows) where the photonic crystal is located. For example, the electrodes cover only a small part of the emission surface, e.g. a rectangular area with dimensions of the order of 10 μm to 100 μm. It is also possible to use a top electrode with a rectangular area removed from the center. This allows pumping of the photonic crystal modes to occur in its outer regions, while output coupling is possible in the central region.

[0043] Laser gain by vibration-stimulated emission is realized by coupling the photonic crystal structure 11 of the photonic crystal 1 in the evanescent field of the mode to the quantum well 30 of the gain medium as the active layer (gain layer) below the photonic crystal layer 11. Here, the cladding adjusts the distance between the quantum well and the tunnel junction, respectively, allowing coupling of the fundamental mode from the gain medium. The active region is separated from the photonic structure by a layer sequence to keep the charge carriers confined in the active region, but is photonically coupled by a sequence of cladding 32 and tunnel junction 31.

[0044] Optically transparent, electrically conductive cladding layers of doped semiconductors (outer cladding 33 and photonic crystal 1) are located above and below the stack. Thus, one fundamental mode per quantum well is established by each quantum well, cladding and tunnel junction sequence. By arranging multiple quantum wells (multiple quantum wells), a "super" fundamental mode is established by superposition, which is determined by the layer thicknesses and relative positions of the quantum wells. A reflective coating 53, e.g. a Bragg reflector (Bragg mirror), on one side of the layer sequence can achieve more efficient power extraction.

[0045] By coupling the waveguides, large area lasers with high power density can be generated with only diffraction-limited beam collimation. Furthermore, optoelectronic components can be placed inside the superwaveguide. Tunnel junctions allow coherent coupling of individual quantum wells with small spatial distances. Since this concept requires only one photonic crystal layer, nanostructuring can be performed only after the deposition of the quantum wells and tunnel junctions, thus making the fabrication even easier, since no additional defects are introduced in the most sensitive layers of the device.

[0046] Figure 2 shows another example of an optoelectronic component, which is based on the previous example and is modified in comparison with Figure 1 only in the following features:

[0047] Now, a reflective coating 53 is placed on the outer surface 12 of the photonic crystal. This reflective coating may comprise, for example, a (metallic) reflector or a Bragg mirror, and is optional as it is not a component of the resonator, nor is high reflectivity necessarily required for laser activity. To aid in the coupling of the laser light in the direction of the substrate 5, an anti-reflective coating 54 may be applied to the surface 52 of the substrate. In this example, the laser emission occurs along the bottom surface of the component (indicated by the arrow), i.e. in the direction of the substrate 5.

[0048] Figure 3 shows another example of an optoelectronic component, which is also a further development of the example of Figure 1, modified only in the following features:

[0049] The gain medium 3 comprises a different layer sequence than that depicted in Fig. 1. In this layer sequence, a first quantum well is first followed by a cladding 32 and then by a tunnel junction 31. This is followed by a further cladding 32. This cladding is followed by a second quantum well 30, which in a sense ends the layer sequence in the direction of the substrate 5. In this example, no third quantum well is provided. Instead, the second quantum well is terminated by an outer cladding 33. The photonic crystal 1 represents another outer cladding.

[0050] Unlike Fig. 1, the cladding 32 has a different layer thickness than the tunnel junction 31 or the quantum well 30, respectively. The layer thickness of the cladding 32 is selected such that the distance between the quantum well and the tunnel junction can be adjusted to couple several single modes from the gain medium. Due to the selected distance, a single mode is coupled by energy transfer.

[0051] Laser gain by vibration-stimulated emission is realized by coupling the photonic crystal structure 11 of the photonic crystal 1 to a quantum well 30 of the gain medium as an active layer (gain layer) below the photonic crystal layer 11 in the evanescent field of the mode. Here, the cladding adjusts the distance between the quantum well and the tunnel junction so that the gain medium is split into two waveguides, each forming a single mode. The active region is separated from the photonic structure in a layer sequence to keep the charge carriers confined in the active region, but is photonically coupled to it by a sequence of claddings 32 and tunnel junctions 31. Optically transparent, electrically conductive cladding layers of doped semiconductors (outer cladding 33 and photonic crystal 1) are located above and below the layer sequence.

[0052] Thus, the sequence of quantum wells, claddings, and tunnel junctions results in one single mode per quantum well or waveguide. By selecting the thickness of the layers of quantum wells (multiple quantum wells), tunnel junctions, and claddings, it can be achieved that the waveguides are coherently coupled. The establishment of single modes overlaps by coupling and exchanges energy. This allows the laser light to be coupled out of the central photonic crystal.

[0053] Figure 4 shows another example of an optoelectronic component, which is based on the previous example and is modified in comparison with Figure 3 only in the following features:

[0054] Now, a reflective coating 53 is disposed on the outer surface 12 of the photonic crystal. This reflective coating may comprise, for example, a (metallic) reflector or a Bragg mirror, and is optional as it is not a component of the resonator, nor is high reflectivity necessarily required for laser activity. To aid in coupling of the laser light in the direction of the substrate 5, an anti-reflective coating 54 may be applied to the surface 52 of the substrate. In this example, the laser emission occurs along the bottom surface of the component (indicated by the arrow), in the direction of the substrate 5.

[0055] 5 shows another example of an optoelectronic component, in which the photonic crystal is arranged in a layer sequence.

[0056] In further embodiments, photonic crystals may also be placed between the waveguides, for example inside the tunnel junction or inside the intermediate cladding 32. Thin, low-loss tunnel junctions may be advantageous. Photonic crystal structures may also be placed on the substrate side. The structure of the photonic crystal (pitch, fill factor, etc.) determines or defines the emission direction, wavelength and divergence.

[0057] Due to the high collimation quality of the PCSEL, no significant broadening of the beam occurs, even when coupling takes place through the substrate. That is to say, the optoelectronic components themselves are not significantly affected in their optical properties by somewhat "thick" substrates (e.g. >100 μm), and therefore components can be fabricated with significantly thicker substrates than have been proposed up to now. To realize this approach with quality photonic crystal structures, the photonic crystals can be structured in a dielectric layer without being embedded directly inside the semiconductor material. This additionally inserted layer can be placed close to the active region of the gain medium, i.e. the quantum well. This kind of structuring in the dielectric allows defects in the semiconductor to be avoided.

[0058] 6 shows another example of an optoelectronic component. The optoelectronic component includes a stack including a photonic crystal 1 and a gain medium 3. The gain medium includes a quantum well 30 configured to emit electromagnetic waves as the active medium.

[0059] The gain medium is arranged on a transparent substrate 5. The substrate comprises a semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent to the electromagnetic radiation to be emitted, i.e. does not absorb or only slightly absorbs it. The electromagnetic radiation to be emitted is, for example, in the infrared, IR, ultraviolet, UV, or visible, VIS part of the electromagnetic spectrum.

[0060] An anti-reflection coating 54 is applied to the surface 52 of the substrate to aid in coupling of the laser light towards the substrate 5. Furthermore, an electrode 53, e.g. an n-contact, is arranged on the surface 52. In this example, the laser emission occurs along the bottom surface (indicated by the arrow). The electrode is arranged to cover only a small part of the surface 53, e.g. a rectangular area having dimensions of the order of 10 μm to 100 μm. It is also possible to use an electrode with a rectangular area removed from the center. Thereby, pumping of the photonic crystal modes occurs in its outer regions, whereas out-coupling is possible in the central region.

[0061] At another surface 51 of the substrate opposite surface 52, a gain medium is arranged with a layer sequence. The layer sequence comprises differently doped semiconductors surrounding a quantum well 30. In this example, a first semiconductor layer 34 of n-doped GaN is arranged at surface 51, followed by the quantum well 30. A second semiconductor layer 34 of p-doped GaN is in turn arranged in the quantum well.

[0062] Gain media, particularly the layer stack embodiments, can be replaced or extended by the embodiments of FIGS. 1-5, in which case the semiconductor layer 34 can be replaced or complemented by a cladding. In this way, the embodiments of FIGS. 1-5 can be replaced or complemented by the embodiments of FIGS. 6-10.

[0063] The photonic crystal 1 is structured in the dielectric layer 14 and is electromagnetically coupled to the gain medium. In this regard, the dielectric layer 14 includes a first dielectric material, in this example, a first layer 15 containing ITO. The photonic structure 11 is structured in a second layer 16 that also includes the first dielectric material. The structural element 13 includes a second dielectric material. The dielectric layer 14 further includes a third layer 17 that contacts the gain medium.

[0064] The dielectric layer 14 includes a dielectric material combined with another dielectric material and / or a transparent conductive material such as indium tin oxide (abbreviated as ITO). Materials with good optical properties and high thermal conductivity at the same time are particularly suitable as dielectric materials, but other dielectric materials with not-so-good thermal properties are also in principle suitable, although there may be other drawbacks. ITO can be mixed with a TCO, where TCO refers to a transparent conductive oxide. Suitable materials are, for example, the following: ITO / CaF n_TCO>n_dielectric ITO / SiO n_TCO>n_dielectric ITO / MgF n_TCO>n_dielectric ITO / TiO n_TCO<n_dielectric ITO / TaO n_TCO<n_dielectric

[0065] For example, the following refractive indices can be used.

[0066] Further, a second electrode 18, e.g., a p-contact, is placed on the photonic crystal. The electrode comprises, for example, a reflective material for emitting electromagnetic radiation (e.g., Au or Al). Optionally, the electrode can be comprised in an insulator configured in the form of an aperture 19 for providing a current aperture.

[0067] By means of two electrodes, the optoelectronic component can be excited, vibrating and emitting electromagnetic waves as laser radiation. In the proposed structure, a photonic structure made of a dielectric material is completely embedded in a transparent conductive material to form a photonic crystal. The layer thickness of the p-GaN and the directly adjacent closed ITO layer is preferably very thin to ensure a small spacing of the photonic crystal from the quantum well (<300 nm, preferably <100 nm to about 50 nm). The advantage of this approach compared to alternative suspects is that only a relatively thin layer of semiconductor material is required in the gain medium. As a result, the corresponding epitaxial process takes significantly less time, thus enabling low-cost components with a relatively simple architecture.

[0068] Figure 7 shows another example of an optoelectronic component. The optoelectronic component corresponds to the example of figure 6, but in this embodiment, in addition to the photonic structure, an aperture 20 is provided. The aperture can be made directly from the same material system as the photonic crystal and / or from another material, such as a metal. For example, the aperture defines a dielectric layer (e.g. layers 16, 17). The aperture can be used to advantageously influence the properties of the laser, such as the beam broadening or divergence.

[0069] Figure 8 shows another example of an optoelectronic component. It corresponds to the example of Figure 6, with the difference that the dielectric layer 14 only includes the first layer 15 and the second layer 16, but not the third layer 17. Instead, the contact to the gain medium is established directly by the second layer 16. Thus, in this setup, the distance between the photonic structure and the quantum well is further reduced by not providing a closed dielectric layer, for example an ITO layer, between the p-GaN and the photonic crystal. Here, it is important that a good charge transport to the active zone can still be achieved. Again, an opening 19 can be structured in the photonic crystal.

[0070] Figure 9 shows another example of an optoelectronic component. The optoelectronic component is a further development of Figure 8 with the difference that the photonic crystal is structured in a dielectric layer 14 that does not contain a conductive material. For example, the dielectric layer comprises two dielectric materials with different refractive indices. Nevertheless, to ensure a good contact, an intermediate layer 35 is inserted in the layer sequence with very good lateral electrical conductivity (e.g. p++ GaN) between the photonic crystal 1 and the gain medium 3.

[0071] Furthermore, a second electrode 18, e.g. a p-contact, is arranged on the photonic crystal. The dielectric layer 14 is embedded with the electrode. The electrode comprises a material (e.g. Au or Al) that is reflective to the emitted electromagnetic radiation. Optionally, the electrode can be included in an insulator configured in the form of a (current) aperture 19 for providing a current aperture. Furthermore, the substrate 5 can also have a (current) aperture 19 on the surface 52, an electrode 55, e.g. an n-contact, and an anti-reflection coating 54.

[0072] Figure 10 shows another example of an optoelectronic component. The optoelectronic component is a further development of the exemplary embodiment of figure 9. In this setup, the photonic crystal is composed of a combination of conductive material (e.g. TCO) and dielectric, e.g. the conductive material is made of two different TCO materials or the TCO is deposited by two different methods. First, a TCO1 film 21 is deposited, e.g. by ALD, to a depth that contacts the GaN p++ of the photonic crystal. In the next step, a planar TCO2 film 22 is deposited, which flatly encapsulates the photonic crystal but does not embed it. Thus, the p-contact is realized from TCO2 and TCO1 through the p-GaN.

[0073] As a result, dielectric layer 14 includes a first layer 15 with embedded structural elements 13. Dielectric layer 15 and the components are covered with a dielectric film 21. Film 22 forms a planar seal to film 21.

[0074] Optoelectronic components can be further developed. For example, photonic crystal structures are fabricated by shaping a shape-preserving layer, such as silicon. The silicon is structured in this process. A dielectric is then deposited, which forms a mold for the silicon. The silicon is then removed again (however, silicon may remain depending on the wavelength / absorption of Si at that wavelength). Further processes can be performed as described in FIG. 10. In general, instead of a dielectric, for example a-Si with a high refractive index can be used. Due to the thin layer, the absorption in Si is acceptable even at, for example, 450 nm (for example, 80% transmission at 450 nm with a thickness of 100 nm). However, the transmission is particularly high (fill factor) since Si only occupies a part of the photonic crystal. a-Si has the advantage over other dielectrics that it can for example be structured very precisely.

[0075] The concept presented here is suitable for GaN-based PC-VCSELs, but is also applicable to GaAs- and InP-based systems. In particular, the advantages become very clear in this case. In principle, a mirror can also be used on the substrate side. This exemplary embodiment can also be configured to couple the laser emission through the top side, for which purpose, for example, the following metallization is adapted: SiO n=1.465 SiN n=2.055 TaO n~2.16 TiO n~2.8 NbO n~2.445 HfO n~1.91 CaF n=1.438 MgF2 n=1.38 AlO n~1.77 AlN n~2.2 ITO n~1.9 (depending on TCO material) GaN n~2.46

[0076] Herein, the term ITO is used to represent a variety of TCO (transparent conductive oxide) materials, of which ITO is one.

[0077] 11 shows another example of an optoelectronic component. The optoelectronic component includes a stack including a photonic crystal and a gain medium. The gain medium includes a quantum well 30, which is an active medium configured to emit electromagnetic radiation.

[0078] The gain medium is arranged on a transparent substrate 5. The substrate comprises a semiconductor material, for example gallium arsenide, GaAs, gallium nitride, GaN, or indium phosphide, InP, which is transparent to the electromagnetic waves to be emitted, i.e. does not absorb or only slightly absorbs them. The electromagnetic waves to be emitted are, for example, the infrared, IR, ultraviolet, UV, or visible, VIS, part of the electromagnetic spectrum. The gain medium comprises two semiconductor layers 34. For example, the first semiconductor layer is p-doped and the second semiconductor layer is n-doped. In this example, the second semiconductor layer faces the gain medium and is n-doped (for example nGaN) and the first semiconductor layer faces the conductive layer 21 and is p-doped (for example pGaN).

[0079] The design of the gain medium, in particular the layer sequence, of this and the following embodiments can be replaced or extended by the embodiments of figures 1 to 10, in which case the semiconductor layer 34 can be replaced or supplemented, for example, by a cladding, thus replacing or supplementing the illustrated exemplary embodiments.

[0080] The photonic crystal is structured in the conductive layer 21 and is electromagnetically coupled to the gain medium. In this respect, the conductive layer 21 comprises a first layer 22 comprising a first conductive material. This can be a TCO, where "TCO" refers to a transparent conductive oxide. In this example, the first conductive material is ITO. The first layer 22 is used to laterally encapsulate the optoelectronic components. The photonic structure is structured in a second layer 23, which also comprises a first conductive material. The photonic structure is formed by structural elements 25 (voids). The structural elements are shown enlarged in the right-hand figure and are, for example, of a similar emission wavelength of the optoelectronic components, for example about 300 nm. The structuring of the second layer 23 and thus of the structural elements 25 is performed, for example, by an edging process. The conductive layer 21 further comprises a third layer 24 in contact with the gain medium 3. In this example, the third conductive layer 24 is arranged planarly on the surface of the gain medium.

[0081] The conductive layer 21 or layers 22, 23, 24, respectively, can be manufactured by different deposition methods, for example atomic layer deposition (ALD), sputtering methods or setting. The variant of overgrown or oversputtered voids 25 has the additional advantage that the etched structures can initially be larger than what is ultimately required (due to partial overgrowth during sputtering). This allows more freedom or further options regarding the structuring process and resolution. In particular, anti-reflective coatings (AR) can be applied to the closed structures.

[0082] Figure 12 shows another example of an optoelectronic component. The optoelectronic component, in particular the conductive layer 21 of figure 11, can be structured by etching and masking. In this process, structural elements 25 of different depths can be produced.

[0083] The left-hand drawing shows a structuring that can be achieved by a combination of two lithography steps, each followed by an etching step. Alternatively, one gray lithography step and one etching step can be performed, which allows a good alignment between the sublattices. Alternatively, structures 26, 27 of different depths can be introduced in the second layer 23. These structures can then be formed by depositing the second layer 23 alone and / or together with the first layer 22 to form the structural elements 25. The right-hand drawing shows the structural elements that are subsequently formed. A conductive material, for example ITO, can be applied by sputtering to encapsulate the structures 26, 27. Furthermore, the first layer 22 can also be deposited in this step and finally planarized.

[0084] Fig. 13 shows a further example of an optoelectronic component. In the left-hand diagram, an optoelectronic component according to Fig. 11 is shown, with additional electrical contacts. An electrode 53, for example an n-contact, is arranged on the surface 52 of the substrate. Optionally, the surface 52 can be provided with an anti-reflection coating to aid in the coupling of the laser light.

[0085] In this example, the laser emission occurs along the bottom surface 52. The electrodes are arranged to cover only a small portion of the surface 52, for example a rectangular area having dimensions of the order of 10 μm to 100 μm. It is also possible to use electrodes with a rectangular area removed from the center. This allows pumping of the photonic crystal modes to occur in the outer regions, while output coupling is possible in the central region.

[0086] Further, a second electrode 18, e.g. a p-contact, is placed on the photonic crystal. The electrode comprises, for example, a reflective material for emitting electromagnetic radiation (e.g. Au or Al). The second electrode 18 can be contacted from the backside. Optionally, the first and second electrodes can be included in an insulator configured in the form of an aperture 19 for providing a current aperture.

[0087] On the right side of the figure, an alternative arrangement of the second electrode 18 is shown. Instead of the surface 52 of the substrate, the electrode is arranged on the semiconductor layer 34 and adjacent to the gain medium, for example on the second n-doped semiconductor layer facing the gain medium. The second electrode 18 thus allows contact from the front side.

[0088] The two electrodes allow the optoelectronic component to be excited and emit electromagnetic waves as laser radiation. In the proposed setup, a photonic structure made of conductive material is completely embedded in a transparent conductive material, thus forming a photonic crystal. The electrodes are configured in such a way that emission occurs on the substrate side by an opening 19 in the first electrode.

[0089] A further example of an optoelectronic component is shown in Fig. 14. On the left side of the figure, an optoelectronic component according to Fig. 12 (left) is shown, in which a reflector 26, in particular an epi-DBR reflector, is additionally arranged on the substrate. The electrodes are configured in such a way that emission occurs on the top side by means of an opening 19 in the first electrode.

[0090] Figure 15 shows another example of an optoelectronic component. This component corresponds to the one shown in figure 11, but the conductive layer 21 is open, i.e. the first layer 21 is not provided to laterally seal the optoelectronic component. The structures 26, 27 remain unencapsulated and thus form the structural elements of the optoelectronic component. A current distribution can be formed laterally in the conductive layer 21, for example in intermediate ridges of ITO.

[0091] Figure 16 shows further examples of optoelectronic components, which correspond to those shown in Figure 15, with a reflector, in particular an epi-DBR reflector, additionally disposed on the substrate.

[0092] This patent application claims priority from German patent applications nos. 102021113598.2 and 102021128124.5, the disclosures of which are incorporated herein by reference.

[0093] The present invention is not limited thereto by the description based on the exemplary embodiments, but rather, any novel feature and any combination of features, including in particular any combination of features in the claims, is included in the present invention even if this feature or combination itself is not explicitly recited in the claims or in the exemplary embodiments. [Explanation of symbols]

[0094] 1. Photonic Crystals 3 Gain medium 5 Substrate 11 Photonic Structures 12 Photonic Crystal Surface 13 Structural Elements 14 Dielectric layer 15 First Layer 16 Second Layer 17 The Third Layer 18 electrodes 19 (current) aperture 20 aperture 21 Conductive layer 22 First Layer 23 Second Layer 24 The Third Layer 25 Structural Elements 26 Reflector 30 Quantum Well 31 Tunnel Junction 32 Clad 33 Outer Cladding 34 Semiconductor layer 35 Middle Class 51 Surface 52 Surface 53 Reflective Coating 54 Anti-reflective coating 55 electrode

Claims

1. An optoelectronic component comprising a stack including exactly one photonic crystal (1) and a gain medium (3), - said gain medium (3) comprises a layer sequence of quantum wells (30), tunnel junctions (31) and claddings (32) and is configured to emit electromagnetic waves; - said photonic crystal (1) is electromagnetically coupled to said gain medium, said optoelectronic component, said stack being arranged on a substrate (5).

2. An optoelectronic component comprising a stack including a photonic crystal (1) and a gain medium (3), - said gain medium (3) comprises a layer sequence of quantum wells (30), tunnel junctions (31) and claddings (32) and is configured to emit electromagnetic waves; - said photonic crystal (1) is structured in a dielectric layer (14) and is electromagnetically coupled to said gain medium; said optoelectronic component, said stack being arranged on a substrate (5).

3. An optoelectronic component comprising a stack including exactly one photonic crystal (1) and a gain medium (3), the gain medium (3) includes a layer sequence of quantum wells (30), tunnel junctions (31) and claddings (32) and is configured to emit electromagnetic waves; - said photonic crystal (1) is structured in a conductive layer (21) and is electromagnetically coupled to said gain medium; said optoelectronic component, said stack being arranged on a substrate (5).

4. - An optoelectronic component as described in claim 1, wherein the photonic crystal (1) is structured in a dielectric layer (14).

5. 4. An optoelectronic component according to claim 1, wherein the photonic crystal (1) is included in the gain medium (3) such that the photonic crystal is arranged in the layer sequence.

6. 4. An optoelectronic component according to claim 1, wherein the photonic crystal (1) is arranged separately from the gain medium (3) such that the photonic crystal is arranged in an outer layer of the layer sequence.

7. - An optoelectronic component described in any one of claims 1 to 3, wherein the cladding (32) is arranged in the layer sequence so that the quantum well (30) is spaced from the tunnel junction (31).

8. 8. The optoelectronic component of claim 7, wherein the cladding (32) has a thickness different from that of the quantum well (30) or the tunnel junction (31), respectively, to adjust the distance between the quantum well (30) and the tunnel junction (31) to couple a fundamental mode from the gain medium (3).

9. 8. The optoelectronic component of claim 7, wherein the cladding (32) has a thickness different from that of the quantum well (30) or the tunnel junction (31), respectively, to adjust the distance between the quantum well (30) and the tunnel junction (31) to allow coupling of multiple single modes from the gain medium (3), and coupling the single modes by energy transfer.

10. The optoelectronic component of claim 7 , wherein the photonic crystal (1) comprises an outer cladding (33).

11. The dielectric layer (14) is a first dielectric material, - a second dielectric material and / or a conductive material that is transparent in the region of said electromagnetic waves, and / or the conductive layer (21) a first electrically conductive material, An optoelectronic component according to claim 2 or 3, comprising a second electrically conductive material and / or a dielectric material that is transparent in the range of said electromagnetic waves.

12. The optoelectronic component of claim 11, wherein the photonic crystal structure (11) of the photonic crystal (1) comprises the first dielectric material and is completely embedded in the second dielectric material and / or a transparent conductive material.

13. The optoelectronic component of claim 12, wherein the photonic crystal structure (11) of the photonic crystal (1) is not at least partially embedded in the second dielectric material and / or the transparent conductive material on the side facing the quantum well (30).

14. The optoelectronic component according to claim 12, wherein the photonic crystal structure (11) of the photonic crystal (1) is in direct contact with the gain medium (3).

15. 4. An optoelectronic component according to claim 1, wherein the photonic crystal (1) is structured in a layer that does not contain electrically conductive material.

16. A laser, - one or more optoelectronic components according to any one of claims 1 to 3, and said laser comprising a pump source configured to excite vibrational emission by said gain medium.

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