Method for producing an electrical contact of a semiconductor layer and semiconductor device with electrical contact

Abstract

Method for producing an electrical contact of a semiconductor layer (2) comprising the steps: a) Provision of the semiconductor layer; b) Forming a plurality of contact bars (3) on the semiconductor layer, wherein - the contact bars are formed by means of a first material (31) and a second material (32), - the first material is applied to the semiconductor layer and the second material is applied to the first material, - a lateral structure of the first material is formed in a self-organized manner, and - the contact rods are made of a metal or a TCO material; c) Forming a filler layer (4) on the contact bars and in the spaces (5) between the contact bars; and d) Exposing the contact rods.

Description

[0001] The present application relates to a method for producing an electrical contact of a semiconductor layer and a semiconductor device with an electrical contact.

[0002] The publication US 2006 / 0 086 942 A1 describes a light-emitting diode structure based on gallium nitride.

[0003] Document US 2013 / 0 248 877 A1 describes a light-emitting semiconductor element based on gallium nitride, a light source and a method for producing a non-uniform structure.

[0004] In optoelectronic semiconductor devices such as light-emitting diodes (LEDs), an electrical contact is often desired that enables a uniform charge carrier distribution in the lateral direction while simultaneously exhibiting low absorption losses. For example, transparent conductive oxides (TCOs) are used, which are applied to the semiconductor layer to be contacted. However, even such materials can cause a non-negligible radiation absorption.

[0005] One task is to specify a method for creating electrical contacts in a semiconductor device with low absorption losses and simultaneously efficient charge carrier distribution. Furthermore, a semiconductor device characterized by high efficiency in radiation generation or reception should be specified.

[0006] These tasks are solved, among other things, by a method or a semiconductor device according to the independent patent claims. Further embodiments and advantages are the subject of the dependent patent claims.

[0007] A method for creating an electrical contact in a semiconductor layer is described.

[0008] According to the process, a semiconductor layer is provided. For example, the semiconductor layer is a p-type or n-type doped semiconductor layer intended for the fabrication of an optoelectronic semiconductor device, such as a radiation emitter or radiation receiver.

[0009] According to the method, a plurality of contact bars are formed on the semiconductor layer. The contact bars are therefore arranged outside the semiconductor layer. Advantageously, the contact bars are free of semiconductor material, particularly over their entire vertical extent. The contact bars are advantageously designed to be electrically conductive and are electrically connected to the semiconductor layer. For example, the contact bars are metallic or contain at least a metal.

[0010] The contact bars can be directly adjacent to the semiconductor layer. Alternatively, an intermediate layer, particularly an electrically conductive one, can be arranged between the contact bars and the semiconductor layer. The contact bars are arranged side by side, for example, along a lateral direction, i.e., a direction parallel to a principal plane of extension of the semiconductor layer, and are at least partially spaced apart from one another. The term "contact bar" does not imply any restriction regarding the basic geometric shape of the contact bar's base. The base of the contact bars can be polygonal, for example, triangular, square, or hexagonal, or curved completely or at least partially, for example, circular or elliptical.Furthermore, the vertical extent, i.e., the extent of the contact bars perpendicular to the principal plane of extension of the semiconductor layer, does not necessarily have to be greater than the maximum lateral extent of the contact bars. Additionally, the cross-sectional area of ​​the contact bars can be constant or vary along the vertical direction.

[0011] According to the method, a filler layer is formed. For example, the filler layer borders directly on the semiconductor layer or, if applicable, the intermediate layer in certain areas. The filler layer is formed in the spaces between the contact bars. For example, the filler layer completely fills the spaces between the contact bars. For example, the filler layer borders directly on the contact bars. Furthermore, the filler layer is also formed on the contact bars. For example, the filler layer is applied in such a way that it completely covers at least two adjacent contact bars and the space between them. The filler layer can also completely cover all contact bars.

[0012] In particular, the filler layer can have a larger maximum extent in the vertical direction than the contact bars.

[0013] According to the method, the contact bars are exposed. For example, material from the filler layer, particularly material from the side of the contact bars facing away from the semiconductor layer, is removed. This removal is carried out, for example, by chemical and / or mechanical methods, such as etching, polishing, or chemical-mechanical polishing. After the exposure is complete, the contact bars extend completely through the filler layer in a vertical direction. Following the exposure of the contact bars, the filler layer and the contact bars are flush on the side facing away from the semiconductor layer.

[0014] In at least one embodiment of the method for producing an electrical contact of a semiconductor layer, the semiconductor layer is provided. A plurality of contact bars are formed on the semiconductor layer. A filler layer is formed on the contact bars and in the spaces between the contact bars. The contact bars are then exposed.

[0015] According to at least one embodiment of the method, after the contact rods have been exposed, a contact layer is applied which electrically connects at least some of the contact rods to one another. The contact layer is advantageously electrically conductive. In particular, the contact layer covers all contact rods on the side facing away from the semiconductor layer.

[0016] The contact layer can be single-layered or multi-layered. For example, the contact layer, or a sublayer of the contact layer facing the semiconductor layer, can be designed as a mirror layer. This mirror layer might consist of materials such as silver, aluminum, rhodium, nickel, or chromium. These materials are characterized by high reflectivity in the visible spectrum. Gold, for example, exhibits high reflectivity in the infrared spectrum.

[0017] According to the method, the contact rods are formed using a first material and a second material, wherein the first material is applied to the semiconductor layer and the second material is applied to the first material.

[0018] In particular, the thickness of the second material can be greater than the thickness of the first material. For example, the thickness of the second material is at least five times, and preferably at least ten times, the thickness of the first material. The second material can be located on the side of the first material facing away from the semiconductor layer or between the semiconductor layer and the first material.

[0019] According to at least one embodiment of the method, the first material is structured according to a predetermined lateral structure. For example, the first material is applied as a layer over a large area and subsequently structured photolithographically. Alternatively, the semiconductor layer can be partially covered with a mask layer made of material not intended to be covered by the first material. After the first material has been applied, the mask layer, along with the first material deposited on it, can be removed, leaving the first material with the desired lateral structure.

[0020] According to this process, a lateral structure of the first material forms spontaneously. Therefore, structuring, for example using a photolithographic process, is not required.

[0021] A self-organized lateral structure makes it possible to achieve particularly small lateral structures. For example, the maximum lateral extent of a structural element lies below the resolution limit of lithographic processes.

[0022] According to at least one embodiment of the method, the first material is applied in the form of clusters. For example, the clusters are metallic clusters. For example, the clusters contain gold.

[0023] The lateral extent of the clusters can subsequently be reduced so that the clusters are at least partially laterally spaced from one another. This can be achieved, for example, by dry chemical etching. For instance, the individual clusters exhibit a lateral extent between 100 nm and 1 µm.

[0024] After reducing the lateral extent, the individual clusters can, for example, have a lateral extent between inclusive 30 nm and inclusive 100 nm.

[0025] According to at least one embodiment of the method, the second material is applied by electroplating. Electroplating is characterized, in particular compared to other deposition methods such as sputtering or vapor deposition, by a high deposition rate. Furthermore, deposition only occurs at the locations where the first material is present. The thickness of the contact rods to be produced can be adjusted by varying the duration of the electroplating process.

[0026] According to at least one embodiment of the method, the second material is formed by crystal growth starting from the first material. This can be achieved, for example, based on the VLS (Vapour Liquid Solid) mechanism. The second material can be applied, for example, by catalyst-assisted chemical vapor deposition. Single-crystal or multi-crystal contact bars can form in this process. Such crystal bars are also referred to as "whiskers." This growth is self-adjusting and occurs only at the locations where the first material is present.

[0027] For example, the second material of the contact rods can form between the first material and the semiconductor layer. The first material can act as a catalyst in this process. As the process continues, the first material moves away from the semiconductor layer in a vertical direction.

[0028] According to at least one embodiment of the method, an intermediate layer is applied to the semiconductor layer before the contact rods are formed. The contact rods can then be applied to the intermediate layer. For example, the intermediate layer contains a TCO material.

[0029] TCO materials are transparent, conductive materials, typically metal oxides such as zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide, or indium tin oxide (ITO). In addition to binary metal-oxygen compounds, such as ZnO, SnO₂, or In₂O₃, ternary metal-oxygen compounds, such as Zn₂SnO₄, CdSnO₃, ZnSnO₃, MgIn₂O₄, GaInO₃, Zn₂In₂O₅, or In₄Sn₃O₄, are also included. 12 or mixtures of different transparent conductive oxides belong to the group of TCOs. Furthermore, TCOs do not necessarily have a stoichiometric composition and can also be p- or n-doped.

[0030] The intermediate layer can function as a current-expansion layer. Such an intermediate layer is particularly suitable for a semiconductor layer exhibiting very low transverse conductivity, for example, p-type semiconductor material based on nitride compound conductor material.

[0031] In this context, "based on nitride compound semiconductors" means that the semiconductor layer, for example as part of a sequence of semiconductor layers, which has an active region for radiation generation or radiation reception, is a nitride compound semiconductor material, preferably Al x In y Ga 1-x-yN is present or consists of, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and x+y ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the formula above. Rather, it may, for example, contain one or more dopants as well as additional components. For the sake of simplicity, however, the formula above only includes the essential components of the crystal lattice (Al, Ga, In, N), even though these may be partially replaced and / or supplemented by small amounts of other substances.

[0032] According to at least one embodiment of the method, the filler layer contains a dielectric material. The filler layer, for example, functions as a dielectric mirror. In the simplest case, the filler layer is a single layer. Alternatively, the filler layer comprises multiple dielectric layers, with adjacent layers exhibiting different refractive indices. For example, a Bragg mirror is formed by means of the dielectric layers.

[0033] According to at least one embodiment of the method, the filler layer contains a TCO material. In particular, the filler layer can comprise a sublayer and a further sublayer, wherein the sublayer contains a dielectric material and the further sublayer contains a TCO material. Advantageously, the further sublayer is arranged closer to the semiconductor layer than the sublayer. In particular, the further sublayer borders directly on the semiconductor layer or, optionally, on the intermediate layer. The sublayer and / or the further sublayer can themselves each be multilayered.

[0034] A filler layer containing a TCO material can itself contribute to current expansion. Dielectric materials, on the other hand, can be characterized by particularly high transparency in the visible spectral range.

[0035] The described method can achieve, in particular, the following effects.

[0036] A large number of contact bars can be formed, each with a small lateral dimension, so that despite the large number of contact bars, the overall shadowing of the semiconductor layer being contacted is minimal. A filler layer can be introduced between the contact bars; this filler layer does not need to be electrically conductive itself. Therefore, the filler material can be selected with a view to minimizing radiation absorption in the relevant spectral range for the semiconductor device being manufactured, for example, in the visible, ultraviolet, or infrared spectral range.

[0037] In particular, compared to a process where a dielectric layer is first deposited on the semiconductor layer and vias are subsequently formed through the dielectric layer, the contact bars can be arranged very close to each other and at a high density. This reduces the requirements for the transverse electrical conductivity of a current-expansion layer outside the semiconductor layer. With the same thickness of a current-expansion layer, such as an intermediate layer in the form of a TCO layer, a higher current density can be introduced homogeneously across the semiconductor device. Alternatively, a thinner intermediate layer can be used to maintain the same current density. This reduces brightness losses due to absorption in the intermediate layer.

[0038] The contact rods are made of either metal or a TCO material. Due to the large number of contact rods, the current flowing through each individual rod is comparatively low. Therefore, in addition to metal, a material with lower electrical conductivity, such as a TCO material, is also suitable for the contact rods. This further reduces absorption losses.

[0039] In particular, the method is suitable for the electrical contacting of semiconductor material that itself has a comparatively low electrical conductivity, for example p-type doped semiconductor material based on nitride compound semiconductors.

[0040] However, the method is also suitable for other semiconductor materials, in particular other III-V compound semiconductors or also for n-type semiconductor material based on nitride compound semiconductors.

[0041] Furthermore, the method is also suitable for the electrical contacting of semiconductor components that are not intended for generating radiation, but for receiving radiation, for example for solar cells or photodetectors.

[0042] A semiconductor device has an electrical contact, wherein the electrical contact is arranged on a semiconductor layer and comprises a plurality of contact bars. The spaces between the contact bars are filled with a filler material. The contact bars are electrically connected to each other on one side facing away from the semiconductor layer via a contact layer.

[0043] For example, the semiconductor component is designed as an optoelectronic semiconductor component, in particular as a luminescent diode, a photodetector or a solar cell.

[0044] The contact bars have a density of at least 1,000,000 pieces per square millimeter, at least in some areas. The higher the density, the lower the current flowing through each individual contact bar can be, thus reducing the requirements for the current-carrying capacity of the individual contact bars.

[0045] The average distance between adjacent contact bars is preferably between 300 nm and 10 µm.

[0046] The maximum lateral extent of the contact bars is preferably between 3% and 20% of the mean distance between adjacent contact bars. This allows a comparatively large number of contact bars to be applied to the semiconductor layer without resulting in significant coverage of the semiconductor layer by contact bars. Absorption losses caused by the contact bars are minimized while maintaining good electrical contactability of the semiconductor layer.

[0047] In particular, especially small distances between the contact bars can be achieved by means of a self-organized design of the arrangement of the contact bars.

[0048] For example, the average distance between adjacent contact bars is between 300 nm and 1 µm. For example, the contact bars have a density of at least 1 million per square millimeter, at least in some areas.

[0049] The maximum lateral extent of the contact rods is preferably between 30 nm and 1000 nm. Particularly in the case of self-organized contact rods, the contact rods can have a maximum lateral extent between 30 nm and 100 nm.

[0050] The method for producing an electrical contact, described above, is particularly suitable for manufacturing the semiconductor device. Features disclosed in connection with the methods can therefore also be used for the semiconductor device, and vice versa.

[0051] Further designs and advantages will become apparent from the following description of the exemplary embodiments in conjunction with the figures.

[0052] They show: The Fig. 1A to 1F represent an embodiment of a method based on intermediate steps shown in sectional and top view; the Fig. 2A to 2E represent an exemplary embodiment of a method based on intermediate steps shown in sectional and top view; the Fig. 3A to 3F show an exemplary embodiment of a method based on intermediate steps illustrated in sectional and top view; the Fig. 4A to 4F show an embodiment of a method based on intermediate steps illustrated in sectional and top view; and the Fig. 5A and Fig. 5B an embodiment of a semiconductor device in schematic sectional view ( Fig. 5A) and in an enlarged view of a section in Fig. 5B.

[0053] Identical, similar, or equivalent elements in the figures are marked with the same reference symbols.

[0054] The figures are schematic representations and therefore not necessarily to scale. Rather, comparatively small elements and especially layer thicknesses may be exaggerated for clarity.

[0055] In the Fig. Figures 1A to 1F show an embodiment of a method for producing an electrical contact, wherein the figures each show a sectional view and a corresponding top view.

[0056] A material layer 310 is applied to an electrically contactable semiconductor layer 2 ( Fig. 1A). The material layer contains a metal, for example nickel. The material layer is directly adjacent to the semiconductor layer 2.

[0057] The material layer 310 is subsequently structured, so that a first material 31 in laterally structured form is present on the semiconductor layer 2 ( Fig. 1B). For example, the first material 31 is in the form of a regular rectangular or hexagonal lattice. The structuring can be achieved, for example, by lithography, such as using a stepper, and subsequent etching of the areas of the material layer to be removed. For example, the individual areas of the first material are circular.

[0058] Alternatively, the first material 31 can also be applied to the semiconductor layer in a structured form. For this purpose, the second semiconductor layer can be covered by a mask layer in areas not to be coated, and the mask layer can be coated with the material layer 310. By removing the mask layer and the material of the material layer 310 applied to it, the first material is formed in a structured form.

[0059] The following will describe how in Fig. As shown in Figure 1C, a second material 32 is formed on the first material. Electroplating is a suitable method for this. Electroplating allows for relatively quick production of large layer thicknesses. Furthermore, deposition only occurs on those areas where the first material 31 is already present. The second material contains a metal, for example, nickel. In the vertical direction, the extent of the second material 32 is significantly greater than that of the first material 31, for example, at least five times greater.

[0060] The following will be described as in Fig. Figure 1D shows the spaces 5 between the contact bars 3 being filled with a filler layer 4, in particular completely, for example by sputtering or vapor deposition. This also covers the contact bars 3 on the side facing away from the semiconductor layer 2. The contact bars 3 are then exposed, for example by a chemical, mechanical, or chemo-mechanical removal process, such as polishing, etching, or chemo-mechanical polishing. For this purpose, the material of the filler layer 4 is preferably removed over a large area, in particular completely, until the contact bars 3 are exposed. Fig. 1E). In this step, part of the contact bars can also be removed. This easily ensures that the contact bars extend completely through the filler layer.

[0061] The contact rods 3 thus formed are metallic. In particular, the contact rods comprise the first material 31 and the second material 32, wherein the first material and the second material each comprise or consist of a metal.

[0062] A contact layer 35 is applied to the side of the contact rods 3 facing away from the semiconductor layer 2, for example by sputtering or vapor deposition. The contact layer electrically connects the individual contact rods to each other. For example, the contact layer 35 is directly adjacent to the contact rods 3.

[0063] The material of the filler layer 4 can be electrically conductive or electrically insulating. Preferably, the filler layer contains a dielectric material, for example an oxide, such as silicon oxide, a nitride, such as silicon nitride, or an oxynitride, such as silicon oxynitride. The filler layer can also be multilayered.

[0064] For example, the filler layer can have a plurality of dielectric layers, with adjacent layers each having different refractive indices, so that the filler layer forms a dielectric mirror in the form of a Bragg mirror. In the simplest case, a single dielectric layer can form a dielectric mirror. In particular, in conjunction with a contact layer 35 designed as a mirror layer, this allows for electrical contacting of the semiconductor layer, characterized by low absorption losses and high reflectivity.

[0065] The spacing between adjacent contact bars 3 is, for example, between 3 µm and 10 µm. The maximum lateral extent of the contact bars is, for example, between 300 nm and 1 µm. Preferably, the maximum lateral extent of the contact bars is between 5% and 20% of the spacing between the contact bars. This simplifies the process by ensuring that only a relatively small area of ​​the semiconductor layer 2 is covered by the contact bars, while simultaneously achieving a uniform current distribution in the semiconductor layer 2 in the lateral direction.

[0066] The vertical extent of the contact rods is, for example, between 200 nm and 1.5 µm. In particular, the vertical extent is preferably between 0.3 and three times the peak wavelength of the radiation to be generated.

[0067] The vertical extent of the contact rods 3 depends in particular on the thickness of the filler layer 4 to be produced. For example, in a single-layer configuration, the filler layer can have a smaller thickness than in a multi-layer configuration, where the filler layer forms a dielectric mirror, such as a Bragg mirror, with high reflectivity.

[0068] Another embodiment of a method is described in the Fig. 2A to 2E are shown schematically using intermediate steps. This embodiment essentially corresponds to the one described in connection with the Fig. The embodiment described in 1A to 1F. In contrast, the first material 31 is applied in a self-organizing manner. For this purpose, as in Fig. Figure 2A shows cluster 311, in particular metallic clusters, deposited onto semiconductor layer 2. For simplified representation, the clusters are shown in Fig. 2A are arranged in a regular hexagonal lattice. However, the clusters are self-organized, so the average distances between neighboring clusters differ, resulting in a non-regular arrangement. For example, the clusters are metal nanoclusters, such as gold nanoclusters.

[0069] Subsequently, the lateral extent of the clusters 311 is reduced so that the remaining material of at least some adjacent clusters is spaced apart from one another. The distance between the individual sub-regions of the first material 31, and thus of the contact rods subsequently produced, is preferably between 300 nm and 1 µm.

[0070] After reducing the lateral extent, the extent of the first material is preferably between 30 nm and 100 nm.

[0071] Starting with the first material 31, a second material 32 is deposited. The second material can be deposited using a crystal growth process, for example, based on the VLS mechanism. The second material grows between the first material 31 and the semiconductor layer 2, so that the first material 31 moves further and further away from the semiconductor layer 2 as the growth time increases. The growth is self-adjusting and occurs only at locations where the first material 31 is present. The growth process continues until the formed contact rods have a length at least equal to the thickness of the dielectric mirror to be produced.

[0072] The second material 32 contains, for example, a metal or a metal oxide, such as a TCO material.

[0073] The further process steps, in particular filling the spaces to produce the dielectric mirror, exposing the contact rods and applying a contact layer, can be described as in connection with the Fig. 1D to 1F are described.

[0074] When exposing the contact rods 3, the first material 31 can in particular be completely removed ( Fig. 2E), so that the first material is no longer present in the finished contact bars. An interface within the contact bars between the first material and the second material 32 can thus be avoided, even though both the first and second materials are used to manufacture the contact bars. Alternatively, the material removal during the exposure of the contact bars can also be stopped earlier, so that at least some of the first material remains in the contact bars.

[0075] By means of the described self-organized design of the contact rods 3, particularly small lateral dimensions of the contact rods and small distances between the contact rods can be achieved, especially in comparison to the formation of contact rods using a lithographic process.

[0076] The in the Fig. The embodiment shown in sections 3A to 3F essentially corresponds to that described in connection with the Fig. The embodiment described in sections 1A to 1F differs in that the contact bars 3 are not formed directly on the semiconductor layer 2. Before the contact bars are formed, as described in Fig. Figure 3A shows an intermediate layer 6 applied to the semiconductor layer 2. For example, a TCO material such as indium tin oxide (ITO) or zinc oxide is suitable for the intermediate layer.

[0077] On intermediate layer 6, as in the Fig. 3B and Fig. 3C shows a first material 31 and subsequently a second material 32 applied ( Fig. 3D). These steps, as well as the subsequent filling of the gaps and exposure of the contact bars, and the application of the contact layer, can be described as in connection with the Fig. The processes described in sections 1A to 1F are carried out as follows. Such an intermediate layer is, of course, also suitable for the other embodiments described in this application.

[0078] The lateral current distribution in the semiconductor layer 2 can be further improved by means of the intermediate layer 6. Compared to a current-expansion layer that is not electrically connected to a multitude of contact bars 3, the requirements for the electrical conductivity of the intermediate layer 6 are reduced. Therefore, for the same current densities, a smaller thickness of the intermediate layer or a material characterized by lower electrical conductivity but higher radiation transmittance is sufficient. Alternatively, with the same thickness of the intermediate layer, a higher current density can be introduced into the semiconductor layer 2 due to the contact bars 3.

[0079] For example, the intermediate layer 6 has a thickness between 3 nm inclusive and 20 nm inclusive.

[0080] The in the Fig. The embodiment shown in sections 4A to 4F essentially corresponds to that described in connection with the Fig. The embodiment described in sections 1A to 1F. In contrast, the filler layer 4 has a sublayer 42 and a further sublayer 41. The further sublayer 41 is located closer to the semiconductor layer 2 and is applied in such a way that the contact bars 3 still protrude from the filler layer in a vertical direction ( Fig. 4D). Only with the help of sub-layer 42 are the gaps 5 completely filled.

[0081] The further process steps, and in particular the application of a contact layer 35, can be carried out as described in connection with the Fig. The process is described in sections 1A to 1F. The filler layer 4, which contains a TCO material, can itself contribute to improved lateral current distribution in the semiconductor layer 2. The thickness of the additional sublayer 41 is, for example, between 3 nm and 20 nm. The greater the layer thickness, the greater the transverse conductivity of the additional sublayer 41. However, at the same total thickness of the filler layer 4, the radiation absorption also increases, since TCO materials typically exhibit higher absorption than dielectric materials. Such a filler layer with a TCO material and a dielectric material can also be used in the further embodiments.

[0082] In the Fig. 5A and Fig. Figure 5B shows an embodiment of a semiconductor device 7 in the form of a semiconductor chip with an electrical contact 1. Fig. Figure 5B shows an enlarged view of section 9 of the Fig. 5A. The semiconductor device 7 is, for example, designed as a luminescent diode, in particular as a light-emitting diode for generating radiation in the visible, ultraviolet or infrared spectral range. Alternatively, the semiconductor device can also be configured as a radiation detector or as a solar cell.

[0083] The semiconductor device 7 has a sequence of semiconductor layers 72 with an active region 720 intended for generating radiation, a first semiconductor layer 721 and a second semiconductor layer 722. For example, the second semiconductor layer 722 is p-type and the first semiconductor layer 721 is n-type, or vice versa.

[0084] The first semiconductor layer 721 is electrically connected to a first electrical contact 761 via a first connection layer 731. The second semiconductor layer 722 is electrically connected to a second electrical contact 762 via a second connection layer 732. By applying an external electrical voltage between the first electrical contact 761 and the second electrical contact 762, charge carriers can be injected into the active region from different sides and recombine there, emitting radiation. In a radiation receiver or a solar cell, the charge carriers generated in the active region by the separation of electron-hole pairs can be discharged from the semiconductor device 7 via the contacts 761 and 762.

[0085] The electrical contact 1, which can be produced as described in particular in connection with the preceding embodiments, serves for the electrical contact of the second semiconductor layer 722. The electrical contact 1 is formed by the second terminal layer 732 and, as described in connection with the preceding embodiments, has a plurality of contact bars 3. The contact bars 3 are electrically connected to a contact layer 35 on the side facing away from the semiconductor layer 2. A filler material 4 is arranged between the contact bars 3.

[0086] By means of the electrical contact 1, charge carriers can be efficiently impressed into the second semiconductor layer 722 via the second electrical contact 762. At the same time, the electrical contact can have a high reflectivity, so that radiation generated in the active region 720 and emitted towards the support 75, on which the semiconductor layer sequence 72 is arranged, is deflected towards a radiation transmission surface 710 of the semiconductor device and can exit from it.

[0087] The electrical contact of the first semiconductor layer is made via one or more recesses 725, which extend through the second semiconductor layer 722 and the active region 720 into the first semiconductor layer 721. To prevent an electrical short circuit between the first contact layer 731 and the second semiconductor layer 722, one side surface of the recess 725 is covered with an insulating layer 77, for example, an oxide layer.

[0088] In the illustrated embodiment, the carrier 75 differs from a growth substrate for the semiconductor layer sequence 72, and the semiconductor layer sequence is attached to the carrier by means of a connection layer 78. Of course, the described electrical contacting 1 is also suitable for semiconductor devices in which the carrier 75 is the growth substrate of the semiconductor layer sequence. The arrangement of the electrical contacts can also be varied within wide limits.

[0089] Electrical contacting is particularly suitable for p-type semiconductor layers requiring electrical contact, especially for p-type semiconductor layers based on nitride compound semiconductor material, since such semiconductor layers exhibit comparatively low electrical conductivity. However, electrical contacting is also fundamentally suitable for other semiconductor layers, particularly n-type semiconductor material or other compound semiconductor material.

[0090] This patent application claims priority over German patent application 10 2016 118 241.9, the disclosure content of which is hereby incorporated by reference. Reference symbol list 1 electrical contact 2 Semiconductor layer 3 contact rods 31 first material 310 material layer 311 clusters 32 second material 35 Contact layer 4 Fill layer 41 more sub-shifts 42 sub-shift 5 spaces 6 Intermediate shift 7 Semiconductor device 710 radiation transmission area 72 Semiconductor layer sequence 720 active area 721 first semiconductor layer 722 second semiconductor layer 725 Exclusion 731 first connection layer 732 second connection layer 75 carriers 761 first contact 762 second contact 77 Insulation layer 78 Compound layer 9 Excerpt

Claims

Method for producing an electrical contact of a semiconductor layer (2) comprising the steps: a) providing the semiconductor layer; b) forming a plurality of contact bars (3) on the semiconductor layer, wherein - the contact bars are formed by means of a first material (31) and a second material (32), - the first material is applied to the semiconductor layer and the second material is applied to the first material, - a lateral structure of the first material is self-organized, and - the contact bars comprise a metal or a TCO material; c) forming a filler layer (4) on the contact bars and in spaces (5) between the contact bars; and d) exposing the contact bars. Method according to claim 1, wherein, prior to step b), an intermediate layer (6) is applied to the semiconductor layer and the contact rods are applied to the intermediate layer. Method according to claim 1 or 2, wherein, after step d), a contact layer (35) is applied which electrically connects at least a part of the contact bars to each other. Method according to one of the preceding claims, wherein the first material is structured according to a predetermined lateral structure. Method according to one of the preceding claims, wherein the first material is applied in the form of clusters (311) and, prior to the formation of the second material, a lateral expansion of the clusters is reduced so that the clusters are at least partially laterally spaced apart from one another. Method according to one of the preceding claims, wherein the second material is applied by electroplating. Method according to any one of claims 1 to 5, wherein the second material is formed by crystal growth starting from the first material. A method according to any of the preceding claims, wherein the filler layer contains a dielectric material. Method according to any of the preceding claims, wherein the filler layer contains a TCO material. Method according to one of the preceding claims, wherein the filler layer comprises a sublayer (42) and a further sublayer (41), the sublayer comprising a dielectric material and the further sublayer comprising a TCO material. Semiconductor device (7) with an electrical contact (1) in which the electrical contact is arranged on a semiconductor layer (2) and - the contact has a plurality of contact bars (3); - spaces (5) between the contact bars are filled with a filler material (4); - the contact bars are electrically connected to each other on a side facing away from the semiconductor layer via a contact layer (35); - the contact bars (3) have a density of at least 1,000,000 pieces per mm² at least locally; and - the contact bars are made of a metal or a TCO material. Semiconductor device according to claim 11, wherein the contact bars have a density of at least 10000 pieces per mm2 at least in certain areas. Semiconductor device according to claim 11 or 12, which is manufactured according to a method according to one of claims 1 to 10.

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