DE102013103605A1 - Optoelectronic component - Google Patents

Abstract

The invention relates to an optoelectronic component having a semiconductor layer sequence (105, 205). The semiconductor layer sequence (105, 205) has an optoelectronically active zone (112, 212) based on at least one III-V compound semiconductor material, and a layer (111, 211) based on at least one II-VI compound semiconductor material. The invention further relates to a method for producing such a component.

Description

The invention relates to an optoelectronic component having a semiconductor layer sequence which has an optoelectronically active zone.

Known optoelectronic components are formed based on III-V compound semiconductor materials, ie compounds with chemical elements of the 3rd and 5th main group of the periodic table. These include, for example, light-emitting diodes (LED). These devices have a semiconductor layer sequence with an active zone for generating a light radiation, which may include III-V materials such as InGaAlP, AlGaAs and / or GaAs. The layer sequence has current spreading layers arranged on both sides of the active zone in order to achieve a homogeneous current density distribution. For example, a front side current spreading layer may be formed of the III-V compound semiconductor InAlP.

The performance of conventional light-emitting diodes is limited by different effects. Impairment may result from high propagation resistance of the III-V based current spreading layers. Another disadvantage is low extraction efficiency.

One currently used method of improving the performance of light-emitting diodes is to form the current spreading layers with a high doping. However, too high a doping results in a reduction of the charge carrier mobility and thus an increase of the resistance. Measures for improving the extraction efficiency are, for example, forming the semiconductor layer sequence having a surface structure, and using a lens made of a material having a high refractive index. As a result, the light extraction from the semiconductor layer sequence can be promoted. However, a total reflection within the semiconductor layer sequence continues to lead to a reduction of the extraction efficiency.

Further devices having III-V compound semiconductors are solar cells. These components have a semiconductor layer sequence with an active zone, by means of which charge carriers generated by absorption can be separated to obtain electrical energy. The active zone is located in a transition region of a base and an emitter. In order to limit recombination of minority carriers at the upper interface of the emitter, a window layer for surface passivation is provided adjacent to the emitter. This layer is formed of a III-V compound semiconductor such as InAlP.

A disadvantage of solar cells is a high absorption of light radiation in the III-V-based window layer, whereby this proportion of radiation is lost for the generation of electrical energy. Another disadvantage is a low transverse conductivity or a high propagation resistance, and a high refractive index of the window layer, which has a high reflection of light radiation result. Furthermore, there is a small valence band offset between the window layer and the emitter, whereby the passivation is insufficient.

A currently used method for improving the efficiency of solar cells is to form the InAlP window layer with a high aluminum content and with a high doping. However, an aluminum content that is too high leads to mechanical stresses, caused by a lattice mismatch between the window layer and underlying layers, which are based for example on a GaAs or Ge grid. Excessive doping results in a decrease in carrier mobility and an increase in conduction band offset between the window layer and the emitter, resulting in a reduction in the current that can be transported across the window layer.

The object of the present invention is to provide a solution for an improved optoelectronic component.

This object is solved by the features of the independent claims. Further advantageous embodiments of the invention are specified in the dependent claims.

According to one aspect of the invention, an optoelectronic component with a semiconductor layer sequence is proposed. The semiconductor layer sequence has an optoelectronically active zone which is based on at least one III-V compound semiconductor material. The semiconductor layer sequence further comprises a layer based on at least one II-VI compound semiconductor material.

According to a further aspect of the invention, a method for producing such an optoelectronic component is proposed. In the method, a semiconductor layer sequence is formed which has an opto-electronically active zone based on at least one III-V compound semiconductor material, and a layer based on at least one II-VI compound semiconductor material.

In the case of the optoelectronic component, the active zone is based on at least one III-V compound semiconductor material, that is, on one or more different compounds with chemical elements of the third and fifth main groups of the periodic table. In particular, an area of the semiconductor layer sequence encompassing the active zone may be formed in this way in the component. In this regard, further subregions or layers of the semiconductor layer sequence may also comprise a III-V compound semiconductor material. This allows the active zone and other areas of the semiconductor layer sequence to perform their respective functions with high reliability and efficiency. The II-VI-based layer, which is based on at least one II-VI compound semiconductor material, ie on one or more different compounds with chemical elements of the second and sixth main group of the periodic table, offers the possibility of electrical and / or optical disadvantages, in particular, to prevent or at least limit the impairments that occur with known components.

In one possible embodiment, the optoelectronic component is a light-emitting diode, in particular a light-emitting diode chip. In this embodiment, the optoelectronically active zone is designed to generate a light radiation. The active zone may, for example, have a quantum well structure, in particular a multiple quantum well structure. For the optoelectronic component in the form of the light emitting diode, the further embodiments described below can be considered.

In another embodiment, the II-VI based layer is a current spreading layer. The current spreading layer may be n-doped, for example. With the aid of the current spreading layer, a homogeneous current density distribution can be achieved during operation of the optoelectronic component. The II-VI-based current spreading layer can be formed with a high doping or with a doping density, whereby compared with a conventional III-V-based current spreading layer a lower layer and thus propagation resistance can be present. In this way, the device designed as a light-emitting diode can have a lower forward voltage and thus higher efficiency.

In a further embodiment, the II-VI-based layer is arranged in the region of a front side of the semiconductor layer sequence. The optoelectronic component furthermore has a front-side, in particular metallic contact structure, which is connected to the II-VI-based layer. The light radiation generated during operation of the component can be emitted via the front side (light exit side). With the aid of the II-VI-based layer, an effective electrical contact between the contact structure and the semiconductor layer sequence can be produced.

The use of the II-VI-based layer also offers the possibility of forming the contact structure arranged thereon from a material which causes no or negligible absorption of light radiation. An example is a TiPtAu contact structure which has good adhesion to II-VI semiconductor material.

The II-VI-based layer also makes it possible to reduce a radiation reflection within the semiconductor layer sequence. In this connection, according to a further embodiment, it is provided that the II-VI-based layer is adjacent to the radiation-generating active zone or at a distance from the active zone which is at most several tens of nanometers, preferably at most forty nanometers. With this embodiment, a small (re) occurring in this area reflection or multiple reflection of light radiation, and thus absorption and reabsorption of light radiation in the active zone, possible. It is exploited that the II-VI-based layer may have a lower refractive index than a III-V-based layer, whereby in the region of an interface of the active zone may have a larger critical angle for total reflection. This is associated with a higher extraction efficiency.

The lower refractive index of the II-VI-based layer also makes it possible to reduce a radiation reflection occurring at a front side of the semiconductor layer sequence.

As a result, an improvement in the extraction efficiency is possible in the same way.

In a further embodiment, the optoelectronic component is a solar cell. In this embodiment, the III-V-based optoelectronically active zone serves to cause a separation of charge carrier pairs (electron-hole pairs) generated by absorption, so that electrical energy can be obtained.

In the solar cell, the active zone is a space charge zone whose electric field causes the charge carrier separation. The space charge zone is located in the transition region of layers with different doping, which are also referred to as base and emitter. In this case, for example, a p-n junction, a p-i-n junction, or a heterojunction may be present. For example, the base may be p-doped, and the emitter may be n-doped. The active zone forming layers are III-V based and have one or different III-V compound semiconductor materials.

The solar cell may be a multiple solar cell, for example a triple solar cell (triple cell). In this case, the semiconductor layer sequence comprises a plurality of (or three) sub-cells, each of which has its own active zone. The subcells can be designed to use different spectral ranges of the light radiation. For this purpose, the individual sub-cells may be formed of different materials.

Furthermore, the embodiments described below can be considered for the optoelectronic component in the form of the solar cell.

In a further embodiment, the II-VI-based layer is a window layer arranged in the region of a front side of the semiconductor layer sequence, which is connected to an emitter of the semiconductor layer sequence. The front side is the side which faces the light radiation during operation of the solar cell. In a multiple solar cell, the emitter and the window layer arranged thereon can be components of an upper part cell of the multiple solar cell. The window layer has the same type of doping as the emitter, for example an n-type doping.

The window layer serves for the surface passivation of the emitter, in order to bring about the lowest possible recombination speed of minority carriers or holes in the emitter. In the II-VI based window layer, this effect may be more pronounced compared to a conventional III-V based window layer. In this way, a larger number of minority carriers of the emitter can be collected and thereby used for energy.

The better passivation is due, among other things, to a large or larger valence band offset between the II-VI based window layer and the III-V based emitter. In this way, a smaller recombination of minority carriers is possible. The larger valence band offset further results in a larger energy barrier for minority carriers, which results in a smaller minority carrier leakage current from the emitter into the window layer. Another advantage is that the II-VI based configuration of the window layer does not result in an increase in conduction band offset between the emitter and the window layer, or the conduction band offset is even smaller. This promotes the transport of majority charge carriers or electrons from the emitter into the window layer.

Further, the II-VI based window layer may have a larger bandgap compared to a III-V based window layer, resulting in lower absorption of light radiation. The lower absorption also makes it possible to form the II-VI-based layer with a large thickness, so that optimum passivation can be achieved. The II-VI based window layer may also have a lower refractive index than a III-V based layer, resulting in less reflection of light radiation at the front of the solar cell.

It is also possible to form the II-VI-based window layer with a high doping or with a high doping density, whereby a further improvement with respect to the passivation can be achieved. The large band gap and the high doping can cause a large band bending between the window layer and the emitter, whereby a movement of minority carriers of the emitter in the direction of the active zone can be promoted. Furthermore, the combination of window layer and emitter can have a low layer and propagation resistance. As a result, a distribution of current, ie a distribution of majority charge carriers or electrons, which in conventional solar cells takes place essentially via the emitter, can take place to a greater extent over the window layer. The emitter can therefore be formed with a lower doping, resulting in less recombination in the Emitter, and results in improved collection of minority carriers in the direction of the active zone.

In a further embodiment, the component formed as a solar cell has a front-side contact structure, which is connected to the II-VI-based layer. The front-side contact structure may comprise, for example, lattice-shaped contact fingers and adjoining larger contact sections, also referred to as busbars. The use of a II-VI semiconductor material allows high doping and thus the presence of a low propagation resistance in the II-VI-based layer. In this way, there is the possibility of forming the solar cell in comparison to a conventional solar cell with a smaller number and spaced from each other arranged contact fingers. A consequence of this is a lower shading in the area of the front and thus a higher efficiency of the solar cell.

A solar cell usually has an antireflection layer on the front side to prevent or suppress the occurrence of radiation reflection. The antireflection layer may be formed of a plurality of layers of different refractive indices arranged on top of each other, whereby a gradual transition of the refractive index is possible.

In this context, according to a further embodiment, it is provided that the component formed as a solar cell has an antireflection layer, and that the II-VI-based layer is a partial layer of the antireflection layer. This function is made possible by the lower refractive index of the II-VI based layer. The II-VI based layer may have a suitably adjusted thickness for this purpose. By incorporating the II-VI based layer to produce an antireflection effect, a sublayer of an absorbing material such as TiOx used in a conventional antireflection layer can be eliminated. This allows, in addition to a cost savings, a higher efficiency of the solar cell.

In a further embodiment of the component designed as a solar cell, the II-VI-based layer has a structured form and forms an antireflection layer. In this embodiment, the comparatively low radiation absorption of the II-VI-based layer is utilized. As a result, the II-VI based layer can be formed with a large film thickness, and therefore with an antireflective structure. Thereby, a steady transition of the refractive index can be provided, which enables effective suppression of radiation reflection.

This is the case in particular in a further embodiment in which the II-VI-based layer has a moth-eye structure.

For the optoelectronic component, which may be designed in particular as a light-emitting diode or as a solar cell, further embodiments may be considered. For example, the II-VI based layer may be n-type.

In another embodiment, the II-VI based layer comprises a semiconductor material comprising the chemical elements zinc and selenium. In other words, the layer is zinc selenide or ZnSe based. In this way, advantages described above can be achieved with high reliability and effectiveness. It is also possible to combine a ZnSe-based material manufacturing technology with III-V semiconductor materials.

The semiconductor string sequence of the optoelectronic component can be produced, for example, by means of an epitaxy process, in particular by means of an organometallic chemical vapor deposition (MOCVD). Here, the II-VI-based layer can be epitaxially grown together with other III-V-based portions of the semiconductor layer sequence.

Alternatively, it is possible first to grow III-V-based portions of the semiconductor layer sequence in an epitaxial process, and to perform the formation of the II-VI-based layer in a separate downstream epitaxy process. In this way it is possible to carry out the growth of the II-VI-based layer at temperatures which are lower than temperatures in the growth of III-V semiconductor materials. As a result, an impairment of the II-VI-based layer which may occur at higher temperatures can be avoided.

Another alternative is to form the II-VI based layer using another, more cost effective, process, such as a sputtering process. This other process may also be performed after producing III-V based portions of the semiconductor layer sequence to avoid temperature degradation of the II-VI based layer. The previously generated III-V-based subregions can in this case be formed with the aid of an epitaxy process.

In another embodiment, the II-VI based layer comprises a ternary compound semiconductor material. Particularly suitable is a ZnSe-based semiconductor material which comprises, for example, beryllium or sulfur as an additional element. As a result, lattice-matched growth, for example on an epitaxial substrate made of, for example, GaAs or Ge, used for forming the semiconductor layer sequence, or on a layer of a III-V compound semiconductor, for example InGaAlP, can be made possible.

In another embodiment, the II-VI based layer comprises a quaternary compound semiconductor material. Particularly suitable is a ZnSe-based semiconductor material in which, for example, beryllium, magnesium or sulfur are used as additional elements. Possible examples of quaternary compound semiconductor materials are MgZnSSe and BeMgZnSe. Quaternary compound semiconductor materials can have a relatively large bandgap and a relatively small refractive index. As a result, in addition to a lattice-matched growth, the above-mentioned advantages may be even better realized.

The above-explained and / or reproduced in the dependent claims advantageous embodiments and refinements of the invention can - except for example in cases of clear dependencies or incompatible alternatives - individually or in any combination with each other are used.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following description of exemplary embodiments, which will be described in more detail in conjunction with the schematic drawings. Show it:

1 a schematic side view of an embodiment of a light-emitting diode chip, which has a semiconductor layer sequence with an active zone for generating a light radiation, wherein a current distribution within the semiconductor layer sequence is indicated;

2 another lateral representation of the LED chip of 1 wherein an emission of light radiation from the active zone is indicated;

3 a schematic perspective view of a multi-junction solar cell, which has a semiconductor layer sequence with three sub-cells arranged one above the other;

4 a schematic side view of the solar cell of 3 additionally showing contact structures and an antireflection layer;

5 a diagram with values of internal quantum efficiency of a conventional solar cell;

6 a schematic plan view of the solar cell of 3 and 4 to illustrate a front contact structure;

7 an enlarged detail of 6 ;

8th Refractive index profiles of different semiconductor materials; and

9 a schematic side view of an embodiment of an upper part cell of a multi-junction solar cell having a patterned anti-reflection layer.

Embodiments of possible optoelectronic components will be described with reference to the following schematic figures. The components have a semiconductor layer sequence with an optoelectronically active zone. The semiconductor layer sequence is formed based on different material systems. One or more III-V compound semiconductor materials and one or more are used several II-VI compound semiconductor materials, ie materials with elements of the 3rd and 5th main group and elements of the 2nd and 6th main group of the periodic table.

As used herein, the term "III-V based" for a layer or region means that this layer or region is formed from one or more different III-V compound semiconductor materials. When using different III-V semiconductor materials, these may be provided, for example, in different partial areas or partial layers. Likewise, the phrase "II-VI based" for a layer means that this layer is formed of one or more different II-VI compound semiconductor materials. When using different II-VI semiconductor materials, these may be provided, for example, in different partial regions or partial layers.

In the case of the described components, the active zone is arranged in a III-V-based region of the semiconductor layer sequence. The use of (at least) one II-VI compound semiconductor material is for one layer 111 . 211 provided, which is arranged in the region of a front side of the components. The II-VI-based layer, which is used instead of a III-V based layer, allows for improved device performance.

The components described can be produced with the aid of processes known from semiconductor technology and from the production of optoelectronic components of known processes, as well as using conventional materials, so that this is only partially addressed. In the same way, the components, in addition to structures shown and described, may comprise further components, structures and / or layers. Also, layers shown and described in the figures may be constructed of several sublayers. It is further noted that the figures are not to scale. In this regard, components and structures shown in the figures may be exaggerated or oversized for clarity.

1 shows a schematic side sectional view of a possible embodiment of a device, which is a light-emitting diode chip 100 is. The LED chip 100 has a semiconductor layer sequence 105 auf, which is structured in the form of a semiconductor body with oblique side walls. The semiconductor layer sequence 105 includes differently doped semiconductor regions or layers 111 . 113 between which an active zone 112 is arranged. The in the region of a front side of the LED chip 100 arranged semiconductor layer 111 is n-doped, and the other semiconductor layer 113 is p-doped. The active zone 112 is designed to generate a light radiation. For this purpose, during operation of the LED chip 100 a voltage to the semiconductor layers 111 . 113 applied, so that an electric current in the forward direction through the semiconductor layer sequence 105 can flow. The active zone 112 For example, it may have a quantum well structure, in particular a multiple quantum well structure.

In the LED chip 100 are the active zone 112 and the p-type semiconductor layer 113 III-V-based trained. The active zone 112 and the layer 113 Therefore, they form a III-V-based region of the semiconductor layer sequence 105 , The active zone 112 or the multiple quantum well structure provided here can for example be based on the semiconductor material system InGaAlP. Individual partial layers of the multiple quantum well structure can have different proportions of In and Al in this case.

In an alternative embodiment, the active zone 112 also based on different III-V compound semiconductor materials, for example, by sublayers of the active zone 112 have different III-V semiconductor materials. For example, a combination of In-GaAlP and GaAs is possible.

The III-V based p-type semiconductor layer 113 is used for power distribution and for establishing an electrical contact with adjoining sections of a contact layer 121 , For these functions, the p-type semiconductor layer 113 For example, different partial layers, ie, a current spreading layer and a contact layer, include (not shown). The partial layers of the semiconductor layer 113 may comprise different III-V semiconductor materials, for example AlGaAs for the current spreading layer and GaAs for the contact layer.

The n-type semiconductor layer 111 is also used for power distribution, and will therefore also be referred to below as a current spreading layer 111 designated. In contrast to the III-V-based region of the semiconductor layer sequence 105 (active zone 112 , Layer 113 ) is the current spreading layer 111 II-VI-based trained. In this way, the LED chip 100 Compared to conventional LED chips, which have an exclusively III-V-based semiconductor layer sequence, a much greater efficiency exhibit. For details, see the II-VI-based current spreading layer 111 will be discussed in more detail below.

In addition to the semiconductor layer sequence 105 has the LED chip 100 furthermore an electrically conductive carrier substrate 140 on. The carrier substrate 140 consists of a doped semiconductor material, for example Ge or Si. Between the carrier substrate 140 and the semiconductor layer sequence 105 There are several layers, in this case a metallic compound layer 135 , a metallic layer 131 , a passivation layer 125 and the above-mentioned portions of the contact layer 121 , The semiconductor layer sequence 105 is on the passivation layer 125 arranged, which in turn on the metallic layer 131 is arranged. The metallic layer 131 which in the operation of the LED chip 100 acting as a mirror for reflecting light radiation is via the bonding layer 135 with the carrier substrate 140 connected.

The semiconductor layer sequence 105 or their p-type semiconductor layer 113 is formed with recesses, so that the passivation layer 125 a given structure with sections 126 which is opposite to the remaining passivation layer 125 toward the front of the LED chip 105 protrude. The protruding sections 126 can, as in 1 is indicated, essentially to the active zone 112 come close. The metallic layer 131 also has a predetermined thereby form, in this case with an increased layer thickness in the region of the sections 126 , The passivation layer 125 has broken or opened areas in which the portions of the contact layer 121 are arranged. Only at these points is there on the contact layer 121 an electrical connection between the semiconductor layer 113 and the metallic layer 131 , This embodiment of the layers 121 . 125 . 126 serves, on the one hand, the current flow through the semiconductor layer sequence 105 , and on the other hand, the reflection of light radiation at the mirror layer 131 set or control to an effective operation of the LED chip 100 to enable.

The carrier substrate 140 indicates one of the connection layer 135 opposite side a flat metallic backside contact 162 on. The backside contact 162 is over the substrate 140 and the layers 135 . 131 . 121 electrically with the p-type semiconductor layer 113 connected. In the area of the front is on the n-type current spreading layer 111 a textured metallic front side contact 161 which is electrically connected to the current spreading layer 111 is connected.

At the front, the semiconductor layer sequence 105 or the layer 111 furthermore a surface structure 117 , For example in the form of roughening, whereby a better light extraction from the semiconductor layer sequence 105 is possible. The front side is the LED chip 100 with another passivation layer 150 formed to the surface of the semiconductor layer sequence 105 cover. The passivation layer 150 is laterally of the semiconductor layer sequence 105 on the other passivation layer 125 arranged.

During operation of the LED chip 100 can through the contacts 161 . 162 a voltage to the semiconductor layers 111 . 113 be applied, so a current through the semiconductor layer sequence 105 flows and the active zone 112 emits a light radiation. The light radiation is both in the direction of the front and in the direction of the substrate 140 emitted. The one in the direction of the substrate 140 emitted radiation component can at the serving as a mirror metallic layer 131 be reflected. About the front, the generated light radiation from the semiconductor layer sequence 105 be disconnected (light exit side).

In 1 is based on arrows during operation of the LED chip 100 in the semiconductor layer sequence 105 current flow 171 indicated (conventional current direction). In this case, the current flows starting from sections of the contact layer 121 to sections of the front side contact 161 , It is clear from the schematic illustration that the n-type current spreading layer 111 among other things serves to allow an unimpeded lateral flow of the stream. In this way, a homogeneous lateral distribution of the current density can be achieved.

This function of the current spreading layer 111 can be achieved with high efficiency and reliability by the current spreading layer 111 as mentioned above II-VI-based is formed. Particularly suitable is the use of a compound semiconductor material comprising the chemical elements zinc and selenium (Zn, Se), which can be combined with III-V semiconductor materials in terms of production technology.

To ensure a homogeneous current density distribution, the n-type current spreading layer becomes 111 formed with a high doping density. Compared to a conventional LED chips The N-type layer which is III-V-based and formed, for example, from InAlP enables the II-VI or ZnSe-based configuration of the current spreading layer 111 the presence of a much larger carrier concentration. The charge carrier mobility can be approximately comparable. This results in a much lower layer and thus propagation resistance of the current spreading layer 111 , The LED chip 100 As a result, it can be operated with a lower forward voltage and thus a higher efficiency compared to a conventional LED chip.

To illustrate this advantage, in the following table, values of a carrier concentration C, a carrier mobility M, the product of concentration C and mobility M, and a sheet resistance R for an n-type InAlP layer, and for two differently doped ones are shown n-type ZnSe-based layers are shown: C [cm-3] M [cm2 / vs] C × M [1 / cmVs] R [ohm] InAlP about 2.00E + 18 approx. 50 about 1.30E + 20 about 300 ZnSe 2.00E + 18 200 4.00E + 20 98.5 ZnSe 8.20E + 19 50 4.10E + 21 9.6

With a high doping of the ZnSe-based layer (last line of the table) is compared to the InAlP layer at about the same mobility M by an order of magnitude higher concentration C before. The resistance R is reduced by about a factor of 1/30 compared to the InAlP layer.

The II-VI based current spreading layer 111 further allows an internal radiation reflection within the semiconductor layer sequence 105 to reduce. In this context shows 2 another lateral representation of the LED chip 100 , whereby in addition by means of arrows emission cones 181 . 182 for those out of the active zone 112 are indicated in the direction of the front emitted light radiation. The dashed emission cone 181 refers to the use of a conventional III-V based current spreading layer of, for example, InAlP, and the emission cone 182 on the use of the ZnSe-based current spreading layer 111 , The emission cone 182 is much wider than the emission cone 181 , which therefore also leads to a higher efficiency of the LED chip 100 leads.

This effect is based on the II-VI based current spreading layer 111 may have a lower refractive index than a conventional III-V based layer. Thereby, in a region between the current spreading layer 111 and the active zone 112 a much larger critical angle for total reflection is present. Consequently, less reflection and multiple reflection of light radiation take place in this area. It is therefore possible a more effective and earlier radiation decoupling, resulting in losses in the form of absorption of light radiation and a reabsorption of light radiation in the active zone 112 can be much smaller.

This advantage can be achieved with high reliability in the event that the II-VI based current spreading layer 111 directly to the active zone 112 borders. However, it is also possible such an embodiment, in which between the active zone 112 and the current spreading layer 111 a III-V based interlayer, for example of InGaAlP and / or InAlP, is arranged so that the current spreading layer 111 at a distance to the active zone 112 located (not shown). The advantageous effect can be reliably achieved when the distance between the current spreading layer 111 and the active zone 112 is as small as possible and at most several tens of nanometers, in particular at most forty nanometers.

The small (re) refractive index of the II-VI based current spreading layer 111 allows, moreover, that also at the front of a large or larger critical angle for total reflection can be present. As a result, a radiation reflection occurring at this point is reduced, thereby improving radiation extraction.

By way of illustration, the following table shows for the materials InAlP and ZnSe, with a light radiation with a wavelength W of 615 nm, values of the refractive index n, and the critical angle A, based on an interface of the respective material with the exemplary materials air and silicone: W [nm] n A [°], air A [°], silicone InAlP 615 3427 17 26 ZnSe 615 2585 23 35

ZnSe has a smaller refractive index n, which results in larger critical angles A.

Another advantage is the II-VI based current spreading layer 111 providing a good electrical connection to that on the current spreading layer 111 arranged front side contact 161 , The current spreading layer 111 can therefore simultaneously serve as a reliable contact layer. Conventional light-emitting diode chips generally have a multilayer configuration of the III-V-based n-type layer, ie with a current spreading layer and an additional contact layer for contacting a front-side contact. Such a multi-layered design may be in the LED chip 100 omitted. As a result, a simpler production of the LED chip 100 possible.

The front side contact 161 For example, it may be formed of a layer stack of AuGeNiAu. However, this material can cause absorption of light radiation. The use of the II-VI-based current spreading layer 111 offers in this regard the possibility of the front side contact arranged thereon 161 Alternatively, form of a material which causes no or a negligible absorption of light radiation. An example is a front side contact 161 from a stack of layers of TiPtAu, which has good adhesion to a ZnSe semiconductor material.

The II-VI or ZnSe-based current spreading layer 111 can manufacturing technology with III-V materials, which in the LED chip 100 for the active zone 112 and the semiconductor conductive layer 113 are intended to be combined. The production of the semiconductor layer sequence 105 can be carried out, for example, by means of an epitaxy process, in particular by means of metal-organic chemical vapor deposition (MOCVD). Here, the current spreading layer 111 for example, together with the other III-V-based subareas of the semiconductor layer sequence 105 be grown epitaxially.

Also possible is a separate epitaxial growth of the II-VI-based current spreading layer 111 after growing the III-V based region of the semiconductor layer sequence 105 , As a result, the growth of the Stromaufweitungsschicht 111 at comparatively low temperatures (ie, lower than when growing the III-V based region), so that any degradation of the current spreading layer occurring at higher temperatures may occur 111 can be avoided.

Alternatively, it is also possible to use the II-VI based current spreading layer 111 with the help of another, especially cost-effective process form. In this process, which after the production of the III-V-based region of the semiconductor layer sequence 105 can be performed, for example, it may be a sputtering process. The III-V based region may be formed by, for example, an epitaxy process.

Preferably, the ZnSe-based current spreading layer becomes 111 formed with a few extra percent of the chemical elements Be or S. As a result, grid-adapted growth of the current spreading layer is, for example, carried out together or in the case of epitaxial processes carried out separately 111 possible. For example, depending on the manufacturing process, growth of the current spreading layer may occur 111 on one for forming the semiconductor layer sequence 105 be used epitaxial substrate. The epitaxial substrate may comprise, for example, GaAs or Ge, whereby the layer growth may occur with the lattice parameters of GaAs or Ge. However, it is also possible to grow on a layer of a III-V compound semiconductor material (for example InGaAlP).

In the LED chip 100 of the 1 and 2 For example, a production can take place in that the semiconductor layer sequence 105 grown on an epitaxial substrate. Here, the II-VI or ZnSe-based current spreading layer 111 before the III-V based active zone 112 and the III-V based semiconductor layer 113 be formed. Below can be recesses in the layer 113 (for the sections 126 ), and can the layers 121 . 125 . 131 be generated. In a subsequent transfer process, this arrangement can take place via the connection layer 135 with the carrier substrate 140 get connected. Subsequently, the epitaxial substrate may be removed, and may include other processes for completing the LED chip 100 respectively. This includes forming the surface structure 117 , forming the contacts 161 . 162 , a structuring of the semiconductor layer sequence 105 , and a Forming the passivation layer 150 , It is possible to have a plurality of light-emitting diode chips 100 in a parallel manner. Therefore, additionally a singulation process can be performed.

In an alternative method for producing the LED chip 100 may be the formation of the II-VI based current spreading layer 111 as indicated above be carried out in the context of a separate or downstream process. In this case, the production comprises growing the III-V-based subregions on an epitaxial substrate, carrying out a transfer process in which the arrangement of the III-V-based subregions via the connecting layer 135 with the carrier substrate 140 and removing the epitaxial substrate. Subsequently or before carrying out further of the abovementioned processes, in particular the formation of the surface structure 117 , formation of the II-VI based current spreading layer occurs 111 to the semiconductor layer sequence 105 to complete.

The n-type ZnSe-based current spreading layer 111 may have, as a result of the additional elements Be or S, a ternary compound semiconductor material.

However, an embodiment in which the ZnSe-based current spreading layer is possible is also possible 111 comprising a quaternary compound semiconductor material. The quaternary compound semiconductor material may include elements such as Be, Mg or S in addition to Zn and Se. Possible examples of quaternary compound semiconductor materials are MgZnSSe and BeMgZnSe. Quaternary compound semiconductors can have a relatively large bandgap and a relatively small refractive index. As a result, in addition to the enabled lattice-matched growth, the above-mentioned advantages become more effective.

Another advantage of an embodiment of the current spreading layer 111 Zn and Se semiconductor material is that in this way the conduction band offset between the current spreading layer 111 and the active zone 112 (from eg InGalP) can be relatively small. This allows electrons to the current spreading layer 111 leave and without transport problems in the active zone 112 be injected. An adaptation of the conduction band offset is possible, in particular, by the admixture of further elements described above or by the use of ternary and quaternary compound semiconductor materials.

The current spreading layer 111 , which may serve as a contact layer at the same time, may be formed in the form of a uniform layer. The layer 111 For example, in this regard, it may have only one ZnSe semiconductor material and, for example, be uniformly doped. However, it is also possible that the II-VI-based layer 111 have different subregions or partial layers, which have different II-VI or ZnSe materials, for example ternary and quaternary compound semiconductor materials, and / or different doping densities. This gives the opportunity to the layer 111 possibly even more specific to individual functions (power distribution, electrical connection with the front side contact 161 and with the active zone 112 ) to vote.

The use of an II-VI based n-type current spreading layer 111 in a semiconductor layer sequence 105 , which is a III-V based active zone 112 and a III-V based p-type layer 113 is not on the in the 1 and 2 shown LED chip 100 limited. Such a configuration of the semiconductor layer sequence 105 can be used in an analogous manner with differently constructed LED chips.

These also include, for example, light-emitting diode chips in which no transfer process is carried out during the production, and consequently the epitaxial substrate used for the growth simultaneously serves as a carrier substrate. In this regard, the semiconductor layer sequence 105 be grown on the epitaxial substrate such that the III-V-based semiconductor layer 113 before the III-V based active zone 112 is trained. After forming the active zone 112 (based on InGaAlP, for example), or on a III-V-based intermediate layer, the II-VI-based current spreading layer can be used 111 to be raised. When using a ZnSe-based semiconductor material with the additional elements Be and / or S (and optionally Mg) is again a lattice-matched growth of the current spreading layer 111 possible.

II-VI compound semiconductor materials can also be used in other optoelectronic devices. Based on the following figures, this is shown using the example of a solar cell. It should be understood that reference is made to the foregoing with respect to details relating to like or consistent components and features, possible advantages, and the like, which may be otherwise applied by analogy.

3 shows a schematic perspective view of a multiple solar cell 200 , The multiple solar cell 200 may be a so-called concentrator solar cell. Such solar cells can be combined with optical concentrators (eg, lenses) to concentrate solar radiation incident on a larger area of the solar cells (not shown).

The multiple solar cell 200 has a semiconductor layer sequence 205 which is on an electrically conductive carrier substrate 240 is arranged. The carrier substrate 240 has a doped semiconductor material, for example Ge or GaAs. The multiple solar cell 200 is formed in the form of a triple solar cell, in which the semiconductor layer sequence 205 three sub-cells arranged one above the other 210 . 220 . 230 includes. These are also referred to below as the upper cell 210 , Middle cell 220 and subcell 230 designated. The upper cell 210 is located in the area of a front side of the multiple solar cell 200 which are in operation of the solar cell 200 a light radiation 300 (in particular sunlight) faces. The individual subcells 210 . 220 . 230 are over tie layers 251 . 252 electrically connected in series. The connecting layers 251 . 252 For example, they may include tunnel diodes.

Each of the subcells 210 . 220 . 230 has an active zone, with the help of which by absorption of light radiation 300 generated charge carrier pairs, ie electrons and holes, can be separated from each other for electrical energy production. The individual subcells 210 . 220 . 230 are for absorbing different levels of light radiation 300 , ie from different wavelength ranges formed. For this purpose, the sub-cells 210 . 220 . 230 different semiconductor materials with different band gaps.

The upper cell 210 points as in 3 shown four superimposed layers 211 . 213 . 214 . 215 on, ie a present in the front side window layer 211 , an emitter 213 , One Base 214 and another layer 215 , The window layer 211 and the emitter 213 are n-doped. Here, the window layer 211 higher doped than the emitter 213 , The base 214 and the layer 215 are p-doped. Here, the layer 215 be more highly doped than the base 214 ,

Due to the different kind of doping from base 214 and emitter 213 can be in the transitional range of base 214 and emitter 213 a space charge zone 212 exist, which as an active zone 212 the upper cell 210 serves. In the space charge zone 212 there is an electric field. The electric field causes the above-described separation of pairs of charge carriers, which by radiation absorption in the upper cell 210 be generated. In this case, electrons are essentially in the direction of the window layer 211 , and holes in the direction of the layer 215 emotional.

The base 214 and the emitter 213 For example, they may form a pn junction. It is also possible that between base 214 and emitter 213 an additional lightly doped or undoped layer is arranged so that a pin junction is present (not shown). This allows a larger space charge zone 212 , Optionally, an embodiment in the form of a heterojunction is possible.

The on the emitter 213 arranged window layer 211 serves for surface passivation of the emitter 213 to minimize the rate of recombination of minority carriers or holes in the emitter 213 to effect. In this way, a large number of minority carriers of the emitter 213 collected and used for energy production. The layer 215 may be a so-called BSF layer (Back Surface Field), which acts as an electric mirror for reflecting charge carriers (electrons).

The other two subcells 220 . 230 the multiple solar cell 200 are similar to the top cell 210 formed suitably from layers with a different type of doping. Therefore, these sub-cells have 220 . 230 corresponding space charge zones for charge carrier separation.

The semiconductor layer sequence 205 the multiple solar cell 200 may include further layers such as barrier layers, buffer layers, tie layers, etc. Furthermore, the multiple solar cell 200 as in the schematic side view in FIG 4 shown, front and back contacts 260 . 270 for picking up the in the sub-cells 210 . 220 . 230 generated electric power. The backside contact 270 lies, as in 4 is indicated, in the form of a sheet-like metallic layer. The backside contact 270 is on one of the semiconductor layer sequence 205 opposite side of the carrier substrate 240 arranged, and over the substrate 240 electrically to the semiconductor layer sequence 205 tethered.

In the area of the front one comes on the window layer 211 arranged contact structure 260 for use. The front contact structure 260 may be multi-layered, and one on the window layer 211 arranged layer 261 of a doped semiconductor material, for example a III-V semiconductor material such as GaAs, and a metallic layer arranged thereon 262 exhibit. The layer 261 can the semiconductor layer sequence 205 be attributed. Seen from above, the contact structure 260 in the 6 shown embodiment with different sections 265 . 266 exhibit. At the front or on the window layer 211 is further, as in 4 shown an antireflection coating 281 arranged to suppress a radiation reflection.

For the multiple solar cell 200 is a large or predominant part of the semiconductor layer sequence 205 III-V-based, and therefore has layers or sub-layers of III-V compound semiconductor materials. The passivation of the emitter 213 used n-type window layer 211 is a II-VI based layer. In this way, the solar cell 200 compared to a conventional solar cell, which has a III-V-based window layer, for example of InAlP, for emitter passivation, have a much greater efficiency. This will be discussed in more detail below.

The upper cell 210 , which are down to the window layer 211 III-V based, may be, for example, an InGaP subcell. Here are the basis 214 and the emitter 213 , and thus also the active zone provided thereby 212 , the III-V semiconductor material InGaP. Also the layer 215 may have InGaP. It is also possible to use another III-V semiconductor material in the top cell 210 , for example, InGaAlP, or the combination of various III-V compound semiconductors, for example, InGaP and InGaAlP, for example, to provide a heterojunction.

Also the middle cell 220 may be based on III-V materials, and be, for example, an InGaAs or GaAs subcell. The connecting layers 251 . 252 may also be III-V based layers. The subcell 230 may be a Ge or InGaAs subcell with a higher indium content than the mid cell 220 be.

For the II-VI based n-type window layer 211 the multiple solar cell 200 comes, comparable to the Stromaufweitungsschicht described above 111 of the LED chip 100 , an embodiment with a compound semiconductor material comprising the chemical elements zinc and selenium into consideration. As a result, a good combination with III-V semiconductor materials is possible manufacturing technology.

The production of the semiconductor layer sequence 205 can also with the solar cell 200 for example, by means of an epitaxy process, in particular by means of an MOCVD method. Here, the window layer 211 together with other subregions of the semiconductor layer sequence 205 be grown epitaxially. It is also possible, the window layer 211 separate from other subregions of the semiconductor layer sequence 205 , and therefore at lower temperatures, grow epitaxially.

Alternatively, the II-VI-based window layer 211 be formed with the help of another, in particular cost-effective process. This process, which, for example, after the production of other layers of the semiconductor layer sequence 205 can be performed, for example, a sputtering process. The other layers of the semiconductor layer sequence 205 can be formed for example by means of an epitaxial process.

The ZnSe-based window layer 211 is preferably formed with a few additional percent of the chemical elements Be or S. This results in a lattice-matched growth of the window layer, for example, in a jointly performed, or carried out separately epitaxial processes 211 possible. Forming the semiconductor layer sequence 205 can be carried out on an epitaxial substrate of, for example, GaAs or Ge, so that layers of the semiconductor layer sequence 205 including the window layer 211 grown with the lattice parameters of GaAs or Ge.

The growth process may be performed in inverted or regular fashion on a corresponding epitaxial substrate. In a possible inverted process, the semiconductor layer sequence 205 generated such that the III-V based layer 261 (the later contact structure 260 ) in front of the other layers of the semiconductor layer sequence 205 is formed, and therefore the II-VI or ZnSe-based window layer 211 on the shift 261 , on the window layer 211 the III-V based emitter 213 , etc. grown up. In a subsequent to the growth of the semiconductor layer sequence 205 This transfer process can be performed via the subcell 230 (or a conductive connection layer, not shown) with the carrier substrate 240 get connected. Thereafter, the epitaxial substrate may be removed, and may include other processes for completing the multi-junction solar cell 200 be performed. This is one of them Forming the contact structures 260 . 270 and the antireflection layer 281 , In terms of contact structure 260 can be provided, the metallic layer 262 in structured form on the layer 261 form and as a hard mask for structuring the layer 261 insert before the antireflection coating 281 is produced. It is possible to have a plurality of solar cells 200 in a parallel manner.

Therefore, additionally a singulation process can be performed.

In an alternative inverted process, forming the II-VI based window layer 211 be carried out separately. Here, a layer sequence starting with the emitter 213 , the base 214 , etc. are formed on an epitaxial substrate and on the carrier substrate 240 be transferred. After removal of the epitaxial substrate, the II-VI-based window layer is first formed 211 on the emitter 213 before further processes for finishing the multi-junction solar cell 200 like forming the contact structures 260 . 270 and the antireflection layer 281 be performed. With respect to the front contact structure 260 can be made with either, or alternatively without the III-V based layer 261 be considered. In the second variant, a temperature-induced impairment of the window layer 211 , which may be a consequence of the growth of the layer 261 on the window layer 211 can be avoided. In this embodiment, the contact structure 260 therefore different from 4 only the metallic, and directly on the window layer 211 arranged layer 262 include.

In a regular process, the carrier substrate serves 240 at the same time as epitaxial substrate for growing the semiconductor layer sequence 205 so that no substrate transfer occurs. In this regard, the semiconductor layer sequence becomes 205 starting with the subcell 230 educated. As a result, the II-VI based window layer 211 on the III-V based emitter 213 (for example from InGaP or InGaAlP), and subsequently optionally at the window layer 211 the III-V based layer 261 is grown up. Subsequently, the above-mentioned processes for finishing the multi-junction solar cell 200 ie forming the contact structures 260 . 270 and the antireflection layer 281 Performing a singulation, be carried out in the same way. In the regular process, as with the inverted process, the contact structure may be provided 260 without the III-V based layer 261 form so that the metallic layer 262 directly on the window layer 211 is trained.

The ZnSe-based window layer 211 may have, as a result of the additional elements Be or S, a ternary compound semiconductor material. Also possible is an embodiment in which the window layer 211 comprising a quaternary compound semiconductor material. As a quaternary compound semiconductor material, which in addition to Zn and Se may include elements such as Be, Mg or S, compounds such as MgZnSSe and BeMgZnSe may be used. Quaternary compound semiconductors can have a relatively large bandgap and a relatively small refractive index, which allows high efficiency of the multiple solar cell 200 can result.

The window layer 211 furthermore, comparable to the current spreading layer 111 of the light-emitting diode chip described above 100 be formed in the form of a uniform layer. The window layer 211 For example, in this context, only one ZnSe semiconductor material may be used and, for example, uniformly doped. However, it is also possible that the II-VI-based window layer 211 have different subregions or partial layers, which have different II-VI or ZnSe materials, for example ternary and quaternary compound semiconductor materials, and / or different doping densities. This makes it possible, if necessary, the window layer 211 even more specific to individual functions (passivation, electrical connection with the contact structure 260 and the emitter 211 ) to vote.

The II-VI-based n-type window layer 211 offers the possibility of better passivation of the emitter compared to a conventional window layer (III-V-based, for example of InAlP) 213 to achieve. In particular, a larger number of minority carriers or holes, which in the n-type emitter 213 can be generated by absorption, are used for energy.

Among other things, this advantage is based on the fact that, due to the use of an II-VI compound semiconductor material, a larger valence band offset between the window layer 211 and the emitter 213 may be present. Compared with the use of a III-V-based window layer can in this way a reduced recombination of minority carriers of the emitter 213 be achieved.

Due to the larger valence band offset between the window layer 211 and the emitter 213 Furthermore, a larger energy barrier for minority carriers is available, so that a thermionic emission or a flow of minority charge carriers from the emitter 213 in the window layer 211 can be better suppressed. This results in a smaller minority carrier leakage current between the emitter 213 and the window layer 211 ,

The presence of the larger valence band offset is without an increase in conduction band offset between the window layer 211 and the emitter 213 possible. Therefore, the II-VI-based window layer has 211 no impairment of the (intended) transport of majority carriers or electrons from the emitter 213 in the window layer 211 result. Depending on the design or material of the II-VI-based window layer 211 For example, the conduction band offset may be even smaller, and therefore the transport of majority carriers from the emitter 213 in the window layer 211 with a smaller resistance and consequently favored.

As an illustration, in the following table, values of a band gap Eg, a conduction band offset delta Ec, and a valence band offset delta Ev are shown for a ZnSe-based window layer having a sulfur content of six percent and for a conventional InAlP window layer, with the corresponding emitter formed of InGaP, respectively is. InAlP ZnS0.06Se Eg [eV] 2:33 2.75 delta Ec [eV] 0.2 0085 InGaP emitter delta Ev [eV] 12:24 0703 InGaP emitter

In the embodiment with the ZnSe-based window layer, there is a much larger valence band offset, and a smaller conduction band offset.

The II-VI-based window layer 211 Further, it may have a larger bandgap than a conventional III-V based window layer. This is shown, for example, in the table above for the materials ZnS0.06Se and InAlP. The presence of the larger band gap leads to a lower absorption of light radiation 300 in the window layer 211 , In this way, a larger, usable for the generation of electrical energy radiation in the emitter 213 the upper cell 210 be transmitted.

To illustrate this aspect shows 5 a measurement diagram showing values of an internal quantum efficiency (IQE) of a conventional solar cell with an InAlP window layer for different wavelengths W of a light radiation. The internal quantum efficiency reflects the ratio of absorbed photons to generated charge carriers. To recognize is a lowering 315 caused by a radiation absorption taking place below a wavelength W of about 480 nm in the InAlP window layer. One consequence of this is a reduction in internal quantum efficiency. When using the II-VI based window layer 211 In contrast to this, an absorption due to the larger band gap can occur only at relatively long wavelengths W. Therefore, the associated solar cell 200 have a larger internal quantum efficiency.

ZnSe has a band gap of 2.7eV, which is greater than that of InAlP with 2.35eV. The band gap can still be much larger by the window layer 211 comprising a quaternary compound semiconductor material. For example, the use of MgZnSSe with a maximum bandgap of 4.4eV, or of BeMgZnSe with a maximum bandgap of 4.54eV may be provided. Such materials may be grown lattice-matched as stated above along with III-V materials.

The lower absorption of the II-VI based window layer 211 it also makes possible the window layer 211 form with a relatively large thickness. This allows optimal passivation of the emitter 213 be enabled.

The embodiment of the n-type window layer 211 from an II-VI compound semiconductor material also offers the possibility of the window layer 211 form with a high doping density. In this way, the passivating effect of the window layer 211 (additionally) be improved. Because a high doping density can cause a large band bending between the window layer 211 and the emitter 213 cause. In addition, the above-described presence of the large band gap can contribute to this. The large or larger band bending between the window layer 211 and emitter 213 has the consequence that Minority carrier or holes of the emitter 213 faster towards the active zone 212 and thus towards the base 214 be moved, and thereby be available for energy.

In the presence of a high doping, the II-VI or ZnSe-based window layer 211 Compared to a conventional III-V-based window layer have a much larger carrier concentration for majority carriers or electrons. The charge carrier mobility can be approximately comparable. This results in a much lower layer and thus propagation resistance of the window layer 211 ,

To illustrate this advantage, the following table shows values of a carrier concentration C and a carrier mobility M for an n-doped layer of InAlP, and for two differently doped n-type ZnSe-based layers: C [cm-3] M [cm2 / vs] InAlP about 2.00E + 18 approx. 50 ZnSe 2.00E + 18 200 ZnSe 8.20E + 19 50

With a high doping of the ZnSe-based layer (last line of the table) is compared to the InAlP layer at about the same mobility M by an order of magnitude higher concentration C before.

With a high doping of the II-VI-based window layer 211 can the combination of window layer 211 and emitter 213 have a low layer and spreading resistance. This allows the window layer 211 make a major contribution to the distribution of electricity, ie to the distribution of majority charge carriers or electrons. In conventional solar cells, the function of the current distribution is substantially exerted by the emitter, which is formed for this purpose with a high doping density.

The high doping of the II-VI-based window layer 211 As a result, offers the possibility of the emitter 213 in contrast to a conventional solar cell with a lower doping density form. This allows the operation of the multiple solar cell 200 or from their upper cell 210 be improved. Because a lower doping of the emitter 213 results in less recombination of minority carriers in the emitter 213 whereby collecting minority carriers in the direction of the base 214 can be further improved.

The presence of a low propagation resistance further enables a more advantageous embodiment of the front-side contact structure 260 , as described below.

6 shows a schematic plan view of the multiple solar cell 200 , on the basis of which the lateral shape of a possible embodiment of the on the window layer 211 arranged front contact structure 260 becomes clear. An enlarged detail is in 7 shown. The front contact structure 260 has sections in the form of thin linear contact fingers 265 on, which are arranged parallel to each other. At the ends go the contact fingers 265 in two larger and perpendicular to the contact fingers 265 running sections 266 over, which also as busbars 266 be designated. The busbars 266 are used for connecting electrical conductors, for example by soldering (not shown).

In operation of the solar cell 200 flow in the n-type window layer 211 or to the window layer 211 passing electrons (majority charge carriers) to the contact fingers 265 and busbars 266 , In this case, there is also a lateral flow of the stream, as in 7 is indicated. The lower propagation resistance and thus the higher transverse conductivity of the window layer 211 or the combination of window layer 211 and emitter 213 makes an embodiment of the solar cell 200 possible in which the contact fingers 265 have a greater distance from each other, and in which a smaller number of contact fingers 265 is provided. This leads to a lower shading in the front of the solar cell 200 , and thus to a higher efficiency.

For the multiple solar cell 200 can the anti-reflection layer 281 , as in 4 is indicated between sections of the front contact structure 260 on the window layer 211 be arranged. The 6 and 7 show by dashed areas 267 another variant. This is apart from the areas 267 essentially the entire front of the solar cell 200 with the antireflection coating 281 coated, ie that the layer 281 not just the window layer 211 , but also the contact fingers 265 and an edge of the bus bars 266 covered.

Another advantage of the II-VI based window layer 211 is a smaller refractive index than a conventional III-V based window layer. To illustrate shows 8th measured progressions 321 . 322 the refractive index n as a function of the wavelength of light W. The course 321 refers to the III-V compound semiconductor InAlP, and the history 322 on the II-VI compound semiconductor ZnSe. Clearly visible is the lower refractive index n of ZnSe.

The smaller refractive index of the II-VI or ZnSe-based window layer 211 leads to a lower radiation reflection in front of the multiple solar cell 200 , Furthermore, the possibility exists, the window layer 211 specifically used to suppress a radiation reflection, as will be described in more detail below.

For the multiple solar cell 200 can the in 4 antireflection coating shown 281 be formed multi-layered, and a plurality (ie, two or more) stacked sub-layers with different refractive indices include (not shown). As a result, a gradual transition of the refractive index is possible, whereby the antireflective effect is favored. The refractive index is in this case, starting from a "first" layer stepped toward the outside (or top) toward reduced (step-down antireflection layer).

The comparatively low refractive index of the II-VI-based window layer 211 offers the possibility of the multiple solar cell 200 with a multilayer antireflection coating 280 form, wherein the window layer 211 , as in 4 is indicated, such a first sub-layer of the multi-layered and thus stepped anti-reflection layer 280 is. Here it is on the window layer 211 arranged layer 281 another sub-layer of the anti-reflection layer 280 , In addition to the two layers shown 211 . 281 can the anti-reflection layer 280 (at least) one more, on the sublayer 281 having arranged sub-layer. The as part of the antireflection coating 280 serving window layer 211 may for this purpose have a correspondingly optimized thickness. By including the window layer 211 it is possible to dispense with an absorbent material such as TiOx, which can be used in conventional multilayer antireflection layers for a first sub-layer. The inclusion of the window layer 211 therefore enables not only cost savings but also higher efficiency.

The above-described low absorption (due to a large band gap) made possible by using an II-VI compound semiconductor material can further be utilized for the window layer 211 to be used as such as an antireflection layer, wherein no further partial layers are used. Here, the window layer becomes 211 formed with such a thickness that structuring the window layer 211 is possible. The window layer 211 Therefore, it can be formed with a structure having antireflective properties in a broad wavelength range. In this way, a transition of the refractive index which is continuous from the inside to the outside can be made available, which makes it possible to effectively suppress a radiation reflection.

To illustrate shows 9 in a schematic side view of another embodiment of the upper cell 210 the multiple solar cell 200 , The II-VI-based window layer 211 has a suitable structure 285 with protruding structural elements. This may in particular be a moth-eye structure 285 act. In this way, the window layer 211 simultaneously serve as a reliable antireflection coating.

In the 9 shown structured window layer 211 can exert an effective antireflective effect, in particular, when the thickness of the window layer is slightly larger than the maximum wavelength of the solar cell 200 for generating energy usable fraction of the light radiation 300 , In terms of the solar cell 200 can be an optimal thickness of the window layer 211 for example, be in the range of approximately two microns. Due to the material-related low absorption, such a thickness for the II-VI-based window layer 211 be provided. In a conventional III-V based window layer, however, such a thickness would result in an inappropriately high absorption.

The embodiments explained with reference to the figures represent preferred or exemplary embodiments of the invention. In addition to the described and illustrated embodiments, further embodiments are conceivable which show further modifications or combinations of features may include. For example, other materials may be used in place of the materials listed above, and the above figures may be replaced by other data.

It is possible that the optoelectronic components shown and described 100 . 200 may include other or additional structures and layers, and in that inverse conductivities are provided instead of the specified conductivities. Further, optoelectronic devices having a III-V based active region and an II-VI based layer can also be realized with other shapes and with a different structure.

With respect to the LED chip 100 For example, it is possible to form it with an additional lens made of a material having a high refractive index in order to enable improved light extraction. Furthermore, the above-described combination of III-V and II-VI compound semiconductor materials in a semiconductor layer sequence 105 be provided for differently constructed LED chips. For example, light-emitting diode chips may be considered in which a semiconductor layer sequence is penetrated by via contacts. In such embodiments, the semiconductor layer sequence may similarly be formed in accordance with the approaches set forth above (II-VI based current spreading layer, arrangement of the II-VI based current spreading layer adjacent to or at a small distance to a III-V based active region, front-side configuration Contact structure on the II-VI based current spreading layer, etc.).

With respect to solar cells, there are possible modifications, those with a different number of sub-cells or only with a single active zone 212 train. Here, similarly, a front portion according to the above-mentioned approaches (II-VI-based window layer on III-V based emitter, arrangement of a front contact structure on the II-VI-based window layer, multilayer anti-reflection layer with an II-VI-based Window layer as a sub-layer, structured II-VI-based window layer, etc.).

While the invention has been further illustrated and described in detail by way of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

100

 LED chip

105

 Semiconductor layer sequence

111

 Current spreading layer

112

 Active zone

113

 Semiconductor layer

117

 surface structure

121

 contact layer

125

 passivation

126

 section

131

 Metallic layer

135

 link layer

140

 carrier substrate

150

 passivation

161

 Front contact

162

 Back contact

171

 current flow

181, 182

 emission cone

200

 solar cell

205

 Semiconductor layer sequence

210

 Subcell / Upper cell

211

 window layer

212

 active zone

213

 emitter

214

 Base

215

 layer

220

 Partial cell / middle cell

230

 Subcell / subcell

240

 carrier substrate

251, 252

 link layer

260

 Front contact structure

261, 262

 layer

265

 contact fingers

266

 busbar

267

 Area

270

 Back contact

280

 Antireflection coating

281

 Antireflection layer / partial layer

285

 Moth-eye structure

300

 light radiation

310

 Measurement diagram IQE

315

 lowering

321, 321

 Course refractive index

Claims (15)

Optoelectronic component with a semiconductor layer sequence ( 105 . 205 ) comprising: an opto-electronically active region based on at least one III-V compound semiconductor material ( 112 . 212 ); and a layer based on at least one II-VI compound semiconductor material ( 111 . 211 ). Optoelectronic component according to claim 1, wherein the optoelectronic component is a light-emitting diode ( 100 ). Optoelectronic component according to one of the preceding claims, wherein the layer comprises a current spreading layer ( 111 ). Optoelectronic component according to one of the preceding claims, wherein the layer ( 111 ) in the region of a front side of the semiconductor layer sequence ( 105 ), and wherein the optoelectronic component has a front-side contact structure ( 161 ), which with the layer ( 111 ) connected is. Optoelectronic component according to one of the preceding claims, wherein the layer ( 111 ) to the active zone ( 112 ) or at a distance to the active zone ( 112 ), wherein the distance is at most several tens of nanometers, preferably at most forty nanometers. Optoelectronic component according to claim 1, wherein the optoelectronic component is a solar cell ( 200 ). An optoelectronic component according to claim 6, wherein the layer has a layer in the region of a front side of the semiconductor layer sequence ( 205 ) window layer ( 211 ), which with an emitter ( 213 ) of the semiconductor layer sequence ( 205 ) connected is. Optoelectronic component according to one of claims 6 or 7, wherein the optoelectronic component has a front-side contact structure ( 260 ), which with the layer ( 211 ) connected is. Optoelectronic component according to one of claims 6 to 8, further comprising an antireflection coating ( 280 ), the layer ( 211 ) a sub-layer of the antireflection coating ( 280 ). Optoelectronic component according to one of claims 6 to 9, wherein the layer ( 211 ) a structured form ( 285 ) and forms an antireflection layer of the optoelectronic component. An optoelectronic component according to claim 10, wherein the layer ( 211 ) a moth eye structure ( 285 ) having. Optoelectronic component according to one of the preceding claims, wherein the layer ( 111 . 211 ) comprises a semiconductor material comprising the chemical elements zinc and selenium. Optoelectronic component according to one of the preceding claims, wherein the layer ( 111 . 211 ) has a ternary compound semiconductor material. Optoelectronic component according to one of the preceding claims, wherein the layer ( 111 . 211 ) has a quaternary compound semiconductor material. Method for producing an optoelectronic component according to one of the preceding claims, wherein a semiconductor layer sequence ( 105 . 205 ) comprising: an opto-electronically active zone based on at least one III-V compound semiconductor material ( 112 . 212 ); and a layer based on at least one II-VI compound semiconductor material ( 111 . 211 ).

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