DE102008039790B4 - Optoelectronic component and method for its production - Google Patents

Abstract

Optoelectronic component (1), comprising: - an epitaxially grown layer sequence (10) which comprises a partial layer (13) suitable for light emission, the layer sequence (10) having a first main side which faces the main emission direction of emitted light and one of the main emission direction has a second main side facing away;- a carrier substrate (40), transparent to the light emitted in the main emission direction, for mechanical stabilization of the epitaxially grown layer sequence (10), which is arranged on the first main side and is connected to the epitaxially grown layer sequence (10) and the layer sequence in carries the component (1);- at least two connection contacts (20, 21) for supplying charge carriers to partial layers (11, 11a, 12, 13) of the epitaxially grown layer sequence (10), both connection contacts (20, 21) being on the second main side are arranged; - one on the second main side of the epitaxially grown layer sequence (10) arranged insulating layer (14); - a first trench in the insulating layer (14), which exposes a region of an underlying first partial layer (12) of the layer sequence (10); - a second trench (22) in the insulating layer (14 ), in the first partial layer (12) and in the partial layer (13) suitable for light emission, which exposes a region of a second partial layer (11) of the layer sequence (10);- a conductive material in the first and second (22) trench, which contacted in each case one of the at least two connection contacts (20, 21), wherein the carrier substrate (40) comprises at least one Bragg reflection layer.

Description

The invention relates to an optoelectronic component and a method for producing one.

The pamphlet U.S. 2006/0 202 105 A1 relates to a wavelength-converted semiconductor light-emitting device. The pamphlet U.S. 2005/0 287 687 A1 relates to a method for manufacturing an AlGaInP light-emitting diode and its structure. The pamphlet U.S. 6,803,603 B1 relates to a semiconductor light emitting element. The pamphlet DE 10 2007 003 282 A1 relates to a light-emitting diode chip.

Optoelectronic components, often referred to simply as light-emitting diodes, have a large number of different possible applications in the field of light generation. For example, optoelectronic components are characterized, among other things, by the fact that they can also emit light of different wavelengths. Mixed colors and, in particular, white light can be realized in a simple manner by an additional combination of optoelectronic components with dyes. The diverse design and manipulation options allow applications as illuminants in the automotive sector as well as in industrial and domestic areas. In addition, optoelectronic components can also be used as projection light sources. Their low power consumption, long service life and industrial production in large quantities mean that the demand for such components is increasing.

However, complex production is necessary for the production of highly efficient optoelectronic components. For example, a growth substrate is used for production, which is mechanically detached again in subsequent processes after production of the optoelectronic component or application of light-emitting layers of the optoelectronic component. Auxiliary carriers are then used for further processing, to which the light-emitting layers are applied with the growth substrate in order to subsequently remove the growth substrate.

The light-emitting layers must also be provided with electrical contacts to supply the necessary charge carriers. This is done, for example, from the top of the optoelectronic component or from its rear. While it is particularly easy to form electrical contacts on the front side, that is to say on the light-emitting side, this arrangement has the disadvantage of reducing the light yield due to shadowing effects. Correspondingly, contacts are increasingly being made on the rear side of the optoelectronic component in order to make electrical contact with the light-emitting layers.

However, rear connections require vias to be formed in the submount. This is a tedious and error-prone process. For example, a high degree of planarity is required, since otherwise cavities remain after the auxiliary carrier has been connected to the light-emitting layers, which cavities can be the starting points for a reinforced chip mount. In addition, with regard to a lateral positioning of the two elements to be connected, a sufficiently precise adjustment is required in order, for example, to precisely align existing via contacts in the auxiliary carrier.

There is therefore a need, on the one hand, for an inexpensive optoelectronic component and, on the other hand, for a production method which is suitable for the production of optoelectronic components in a cost-effective manner.

This need is met by the subject matter of the independent patent claims, which also define the invention. Further developments and refinements of the invention result from the dependent claims.

In the following, parts of the description and drawings that relate to embodiments or exemplary embodiments that are not covered by the claims are not presented as embodiments or exemplary embodiments of the invention, but as examples that are useful for understanding the invention.

The invention proposes arranging a mechanically stabilizing and at the same time transparent auxiliary carrier not on the side facing away from the main emission direction, but rather on the outcoupling side of a layer sequence suitable for light emission. For this purpose, a production process for the layer sequence is carried out, in which the layer sequence is applied to the growth substrate, for example epitaxially deposited or grown on. Before the growth substrate is detached, a temporary auxiliary carrier is attached to the rear side, which allows the growth substrate to be detached. A standard surface texturing of the uncovered layer, which is continuous over the entire wafer, can then be carried out in order to maximize the light output. The actual, transparent carrier mechanically stabilizing the layer sequence is now on this side applied to the substrate and the temporary auxiliary carrier removed again. Contacting on the back and isolation can then take place.

In the following, the term “carrier substrate” is understood to mean a carrier to which the layer sequence produced in the previous production steps is connected, so that it is stabilized against further mechanical loads. The element thus carries the sequence of layers, both in subsequent process steps and after completion. The carrier substrate comprises a transparent material, since the carrier substrate is arranged on the coupling-out side of the layer sequence.

In one embodiment of the invention, an optoelectronic component has an epitaxially grown layer sequence with a partial layer suitable for light emission. The layer sequence has a first main side, which faces the first main emission direction of emitted light, and a second main side, which faces away from the main emission direction. The first main page is called the decoupling page. The optoelectronic component also includes a carrier substrate that is transparent to the light emitted in the main emission direction, designed to mechanically stabilize the epitaxially grown layer sequence. This is arranged on the first main side and thus the side facing the main emission direction and is connected to the epitaxially grown layer sequence.

At least two connecting contacts for supplying charge carriers to partial layers of the epitaxially grown layer sequence. The at least two connection contacts are arranged on the second main side and thus the side facing away from the main emission direction.

The transparent carrier substrate applied to the first main side or the coupling-out side brings about complete and sufficient mechanical stabilization of the epitaxially grown layer sequence. As a result, subsequent manufacturing process steps can be carried out particularly easily at the wafer level. At the same time, the carrier substrate remains on the layer sequence even after the component has been completed, ie it is not removed again.

The connection contacts arranged on the rear allow a good thermal connection of the optoelectronic component to a circuit board, since only thin soldering pads are present between the epitaxially grown layer sequence or the connection contacts and the circuit board.

It is possible to arrange a mirror layer on that side of the layer sequence which is remote from the coupling-out side. In this way, light that is emitted toward the back of the component is reflected by the mirror layer toward the outcoupling side. The mirror layer can contain, for example, silver or another material with a high reflection coefficient. In addition, the mirror layer can also take on other functional tasks, for example serving as a current spreading layer.

In one configuration of the invention, the epitaxially grown layer sequence is structured on the first main side in order to increase the outcoupling of light. In one configuration, one or more functional layers are applied on the first main side of the epitaxially grown layer sequence in order to increase the outcoupling of light.

In another configuration, the transparent carrier substrate can have a multiplicity of additional functional layers to improve the coupling out of light from the epitaxially grown layer sequence on the main side.

In a further embodiment, the functional layers can also contain conversion layers with a light conversion material. This serves to convert the wavelength of the light emitted by the partial layer of the epitaxially grown layer sequence during operation of the optoelectronic component. In this way, mixed colors can be easily generated. In one embodiment, a conversion material is provided which, from light with a wavelength in the blue range, generates light in a wavelength in the yellow range, so that the optoelectronic component generates white light during operation.

A transparent adhesive layer can be provided between the carrier substrate and the layer sequence to connect the first main side of the epitaxially grown layer sequence or functional layers on the epitaxially grown layer sequence and the carrier substrate. In a cured state, the adhesive layer preferably has a refractive index which essentially corresponds to a refractive index of the carrier substrate or a refractive index of a layer connected to the adhesive. This further improves the decoupling behavior, since reflection between the individual layers is reduced due to different refractive indices.

Depending on the desired application, the preferred light emission can be different when the optoelectronic component is in operation. To this end, in one embodiment provided by the invention to form the carrier substrate with different geometric dimensions with respect to its two main sides. The carrier substrate can thus be designed in the form of a polyhedron with two main sides arranged essentially in parallel, one of the two main sides being connected to the output side of the epitaxially grown layer sequence. The two main sides of the carrier substrate can have different dimensions. As a result, the side surfaces of the carrier substrate are inclined, resulting in a wedge, an obelisk, a tetrahedron, a truncated pyramid or another geometric shape. In a further embodiment, the carrier substrate can be in the form of a lens in order to shape the light emission of the optoelectronic component.

The connection contacts of the optoelectronic component are attached on the side facing away from the main emission direction. This is referred to as the back of the optoelectronic component.

In one configuration, the rear side comprises an insulating layer, which is arranged on the epitaxially grown layer sequence and electrically insulates the underlying, conductive layers. The insulating layer can be made of a material with a high reflection coefficient. First and second trenches are now formed in the insulating layer, so that regions of an underlying first partial layer of the layer sequence are uncovered by the first trench. Areas of a second partial layer of the layer sequence are uncovered by the second trench, which passes through the first partial layer and the partial layer suitable for light emission to form the epitaxially grown layer sequence. The partial layer of the layer sequence that faces the coupling-out side is thus contacted through the second trench filled with an electrically conductive material. The partial layer suitable for light emission lies between the first and the second partial layer. This is usually formed by a pn junction.

The optoelectronic component according to the proposed principle is produced by epitaxially growing a layer sequence on a growth substrate, which includes a partial layer suitable for light emission. For this purpose, one configuration provides for arranging differently doped semiconductor layers on top of one another, so that a pn junction is formed at the interface of the two semiconductor layers. This represents the partial layer of the epitaxially grown layer sequence that is suitable for light emission. The layer sequence has a first main side, which faces the main emission direction of an emitted light. Furthermore, it includes a second main side facing away from the main emission direction, which can be referred to as the rear side.

A temporary auxiliary carrier is now applied to the second main side of the epitaxially grown layer sequence. This is designed to be able to subsequently detach the growth substrate and still ensure adequate mechanical stability of the epitaxially grown layer sequence. After detaching the growth substrate, the first main side is structured to increase the light output. A carrier that is transparent to the light emitted by the partial layer is then applied to the first main side and attached to the first main side. This forms the carrier substrate, which ensures sufficient mechanical stability of the component. The temporary auxiliary support on the second main page can now be removed without further ado. Finally, electrical connection contacts are formed on the second main face.

In the method proposed here, after the application of the transparent substrate carrier on the first main side, the rear side of the epitaxially grown layer sequence can be structured and processed in further process steps due to the great mechanical stability. For example, electrical connection contacts can now be formed on the second main side in a simple manner. These allow good thermal connection to a circuit board and thus adequate cooling when the component is in operation.

Alternatively, it is also possible, after the production of the epitaxially grown layer sequence, to form the electrical connection contacts on the second main side and only then to apply the temporary auxiliary carrier to the electrical connection contacts. In this context, it is conceivable that part of the material of the connection contacts forms a sacrificial layer in order to facilitate subsequent detachment of the auxiliary carrier.

After the growth substrate has been detached but before the transparent substrate carrier is applied to the first main side, it can be structured or further processed. For example, the surface of the first main side or a partial layer of the epitaxially grown layer sequence forming the first main side can be roughened in order to improve the coupling out of light. It is also possible to apply different functional layers to improve light extraction or to convert the emitted light into a different wavelength.

In these cases, after the structuring of the second main side, an adhesive layer is applied to the structured main side and then the substrate carrier is arranged on it. The adhesive layer is then cured in order to achieve an intimate bond between the substrate carrier and the structured second main side and thus the epitaxially grown layer sequence. In a cured state, the adhesive layer preferably has a refractive index which essentially corresponds to the refractive index of the carrier substrate. If necessary, this reduces light reflection between the carrier substrate and the adhesive layer.

Alternatively, the carrier substrate is designed with additional functional layers that can correspond to those mentioned above. For example, dielectric mirror layers, Bragg mirrors, but also conversion layers can form part of the substrate carrier. This allows separate manufacture. In addition, the sequence of layers can be measured with regard to their emission characteristics in order to then vary the additional functional layers depending on this.

The invention is explained in detail below using various exemplary embodiments with reference to the drawings.

• 1 ein erstes Ausführungsbeispiel der Erfindung,
• 2 ein Diagramm zur Darstellung der Abhängigkeit der Auskoppeleffizienz zum Brechungsindex des Trägersubstrates,
• 3 ein zweites Ausführungsbeispiel der Erfindung,
• 4 ein drittes Ausführungsbeispiel der Erfindung,
• 5 eine Darstellung zum Vergleich optoelektronischer Bauelemente mit unterschiedlich strukturierten Oberflächen,
• 6 ein viertes Ausführungsbeispiel der Erfindung,
• 7 ein fünftes Ausführungsbeispiel der Erfindung,
• 8 ein sechstes Ausführungsbeispiel der Erfindung,
• 9A bis 9K ein Ausführungsbeispiel eines Verfahrens zur Herstellung eines Bauelementes nach dem vorgeschlagenen Prinzip.

Show it:

• 1 a first embodiment of the invention,
• 2 a diagram showing the dependence of the decoupling efficiency on the refractive index of the carrier substrate,
• 3 a second embodiment of the invention,
• 4 a third embodiment of the invention,
• 5 a representation for the comparison of optoelectronic components with differently structured surfaces,
• 6 a fourth embodiment of the invention,
• 7 a fifth embodiment of the invention,
• 8th a sixth embodiment of the invention,
• 9A until 9K an embodiment of a method for producing a component according to the proposed principle.

In the embodiments and figures, components that are the same or have the same effect are provided with the same reference symbols. The figures and the proportions of the elements shown in the figures are not to be regarded as true to scale. Individual elements, such as layers, can be shown in an exaggerated size or thickness for the purpose of clarification and better understanding as well as for ease of representation. Individual aspects of the various embodiments can easily be combined with one another and exchanged within the framework of the technology used.

Furthermore, in the following it is often referred to that a layer is arranged “on” or “above” a second layer. This includes both a directly adjacent arrangement of the two layers, but also includes additional intermediate layers arranged between the first and second layers. In addition, the terms "above" or "below" are for representation only in relation to the corresponding figure, but do not stand for a specific indication of direction. In the exemplary embodiments, reference is also made to individual connections or material systems. This does not represent a restriction, rather other material systems and materials can be used depending on the technology used under other external conditions.

1 1 shows an embodiment of an optoelectronic component 1 according to the proposed principle, in which an epitaxially grown layer sequence 10 is fastened with its light decoupling side to a carrier substrate 40 via an adhesive layer 30 . In other words, the optoelectronic component provides for the carrier substrate to be arranged on the coupling-out side of the epitaxially grown layer sequence.

The epitaxially grown layer sequence 10 contains a first partial layer 12, doped with a first charge carrier type, and a second partial layer 11 arranged thereon, doped with a second charge carrier type. A pn junction 13 forms at the boundary surface of the two partial layers. An additional partial layer 11a made of the same material is arranged above the second partial layer 11 and forms a structuring or sacrificial layer. As explained further below, this can be manufactured in the same manufacturing process as the partial layer and can comprise the same material. The partial layer 11a often has a lower doping concentration than the partial layer 11 .

• - an einer der gewünschten Abstrahlseite der strahlungserzeugenden Halbleiterschichtenfolge, bei der es sich insbesondere um eine strahlungserzeugende Epitaxie-Schichtenfolge handeln kann, ist eine reflektierende Schicht aufgebracht oder ausgebildet, die zumindest einen Teil der in der Halbleiterschichtenfolge erzeugten elektromagnetischen Strahlung in diese zurückreflektiert;
• - der Dünnfilm-Leuchtdiodenchip weist ein Trägerelement auf, bei dem es sich nicht um das Wachstumssubstrat handelt, auf dem die Halbleiterschichtenfolge epitaktisch gewachsen wurde, sondern um ein separates Trägerelement, das nachträglich an der Halbleiterschichtenfolge befestigt wurde;
• - die Halbleiterschichtenfolge weist eine Dicke im Bereich von 20 µm oder weniger, insbesondere im Bereich von 10 µm oder weniger auf;
• - die Halbleiterschichtenfolge ist frei von einem Aufwachssubstrat. Vorliegend bedeutet „frei von einem Aufwachssubstrat, dass ein gegebenenfalls zum Aufwachsen benutztes Aufwachssubstrat von der Halbleiterschichtenfolge entfernt oder zumindest stark gedünnt ist. Insbesondere ist es derart gedünnt, dass es für sich oder zusammen mit der Epitaxie-Schichtenfolge alleine nicht freitragend ist. Der verbleibende Rest des stark gedünnten Aufwachssubstrats ist insbesondere als solches für die Funktion eines Aufwachssubstrates ungeeignet; und
• - die Halbleiterschichtenfolge enthält mindestens eine Halbleiterschicht mit zumindest einer Fläche, die eine Durchmischungsstruktur aufweist, die im Idealfall zu einer annähernd ergodischen Verteilung des Lichtes in der Halbleiterschichtenfolge führt, das heißt, sie weist ein möglichst ergodisch stochastisches Streuverhalten auf.

In this embodiment, the optoelectronic component is implemented using thin-film technology. Such a "thin-film light-emitting diode chip" is characterized by at least one of the following characteristic features:

• - A reflective layer is applied or formed on one of the desired emission side of the radiation-generating semiconductor layer sequence, which can in particular be a radiation-generating epitaxial layer sequence, which reflects at least part of the electromagnetic radiation generated in the semiconductor layer sequence back into the latter;
• the thin-film light-emitting diode chip has a carrier element which is not the growth substrate on which the semiconductor layer sequence was epitaxially grown, but a separate carrier element which was subsequently attached to the semiconductor layer sequence;
• - the semiconductor layer sequence has a thickness in the range of 20 μm or less, in particular in the range of 10 μm or less;
• - The semiconductor layer sequence is free of a growth substrate. In the present case, “free of a growth substrate” means that a growth substrate that may be used for growth is removed from the semiconductor layer sequence or is at least greatly thinned. In particular, it is thinned in such a way that it is not self-supporting alone or together with the epitaxial layer sequence. The remainder of the greatly thinned growth substrate is particularly unsuitable as such for the function of a growth substrate; and
• the semiconductor layer sequence contains at least one semiconductor layer with at least one surface which has an intermixing structure which ideally leads to an approximately ergodic distribution of the light in the semiconductor layer sequence, ie it has as ergodic and stochastic a scattering behavior as possible.

A basic principle of a thin-film light-emitting diode chip is described, for example, in the publication I. Schnitzer et al., Appl. physics Latvia 63 (16) 18 October 1993, pages 2174-2176. Examples of thin film light emitting diode chips are in the references EP0905797A2 and WO 02/13281 A1 described. A thin-film light-emitting diode chip is, to a good approximation, a Lambertian surface emitter and is therefore well suited, for example, for use in a headlight, for example a motor vehicle headlight.

In the present case, a III/V compound semiconductor material, namely gallium nitride, is used as the material system, with the first partial layer 12 being p-doped and the partial layers 11, 11a facing the transparent carrier substrate 40 being n-doped. In addition, other material systems can also be used.

A III/V compound semiconductor material has at least one element from the third main group, such as B, Al, Ga, In, and one element from the fifth main group, such as N, P, As. In particular, the term “III/V compound semiconductor material” includes the group of binary, ternary or quaternary compounds that contain at least one element from the third main group and at least one element from the fifth main group, for example nitride and phosphide compound semiconductors. Such a binary, ternary or quaternary compound can also have, for example, one or more dopants and additional components.

Correspondingly, a II/VI compound semiconductor material has at least one element from the second main group, such as, for example, Be, Mg, Ca, Sr, and one element from the sixth main group, such as, for example, O, S, Se. In particular, a II/VI compound semiconductor material comprises a binary, ternary or quaternary compound which comprises at least one element from the second main group and at least one element from the sixth main group. Such a binary, ternary or quaternary compound can also have, for example, one or more dopants and additional components. For example, II/VI compound semiconductor materials include: ZnO, ZnMgO, CdS, ZnCdS, MgBeO.

The optoelectronic component 1 according to FIG 1 further comprises an insulating layer 14, which is arranged on the partial layer 12 of the epitaxially grown layer sequence 10. The insulating layer 14 protects the sub-layer 12 from damage or contamination and electrically insulates it. Two connection contacts 20 and 21 are arranged on the rear side of the layer sequence 10 for contacting the two partial layers 12 and 11 . A first contact 20 is formed in a trench of the insulating layer 14 and electrically contacts the p-doped sub-layer 12 .

A second contact 21 is applied to the insulating sub-layer 14 . In addition, trenches 22 are provided, which extend through the insulating layer 14, the partial layer 12, the pn junction 13 into the partial layer 11. The trenches 22 are filled with an insulating layer 23 and with an electrically conductive material. A short circuit of the connection contact 21 with the p-doped partial layer 12 is avoided by the insulating layer 23 . During operation of the optoelectronic component, charge carriers are injected via the two rear connection contacts 20 and 21, which are emitted under light emission in the pn junction 13 recombine with each other. The direct contacting of the connecting contacts 20 and 21 with highly conductive materials brings about good heat dissipation when the optoelectronic component is operated towards the rear.

The adhesive layer 30 on the structured surface 11b of the partial layer 11a is also transparent like the carrier substrate 40 and has a refractive index which essentially corresponds to the refractive index of the carrier substrate. The structuring of the surface 11b of the partial layer 11a improves the decoupling of light into the adhesive layer 30 and the carrier substrate 40.

Glass with a refractive index in the range of 1.4 is particularly suitable as the transparent carrier substrate.

2 shows the outcoupling efficiency in relation to the refractive index. The maximum of the outcoupling efficiency with approximately 1.19 with a refractive index in the range of 1.4 to 1.43 can be clearly seen. This refractive index essentially corresponds to the refractive index of glass, so that the outcoupling efficiency is at a maximum with a carrier substrate made of glass.

3 shows another embodiment of the invention. In this embodiment, the carrier substrate is in the form of a pyramid 41 whose side faces are in the 3 shown sectional view have the shape of an isosceles triangle. In this exemplary embodiment, too, the carrier substrate is formed from a transparent material, for example from glass or sapphire, and is connected via a transparent adhesive layer 30 to a roughened surface 11b of the n-doped gallium nitride layer 11a. The shape of the carrier substrate influences the efficiency of light extraction and the radiation characteristics. In the illustrated embodiment according to 3 bundling of the emitted light in the forward direction is achieved.

In particular in connection with additional converter layers (not shown here) between the surface 11b of the partial layer 11a and the carrier substrate 41, this type of “angle filtering” is well suited to generating a directional emission characteristic.

A similar embodiment shows 7 , in which the carrier substrate 45 has sloping flanks that converge in the emission direction. This structure, known as ATON-like cut, enables a high degree of efficiency in light extraction.

An alternative embodiment shows 4 . In this embodiment, the carrier substrate is attached “upside down”, that is to say with the main side with a smaller area, via the adhesive layer 30 to the roughened surface 11b of the partial layer 11a. The underside 42a of the carrier substrate 42 attached to the partial layer 11a has smaller geometric dimensions than the corresponding upper side of the carrier substrate 42. Accordingly, the side edges run away from one another at an angle. Additional adhesive layers 43 in the space created between the surface 42a and the side edges 42b of the carrier substrate 42 running away at an angle cause light to be coupled out to the side. This enables the realization of an optoelectronic component for backlighting, in which the component with the carrier substrate is placed on the object to be illuminated. In addition, there is the possibility of forming the carrier substrate with additional functional layers before it is applied to the surface of the partial layer 11a. Alternatively, it is of course possible, after detaching the growth substrate, to grow additional functional layers next to the adhesive layer on the surface of the partial layer 11a and then to connect them to the carrier substrate.

6 FIG. 1 shows an embodiment in this regard, in which a plurality of functional layers 53, 51, 52 are arranged between a carrier substrate layer 43 and the n-doped partial layer 11a.

In the present exemplary embodiment, the functional layers 51 to 53 and the carrier substrate layer 43 as well as the additional decoupling layer 44 together form the carrier substrate. The carrier substrate is manufactured in separate process steps. As a result, the functional layers 50 with the individual partial layers 51 to 53 can be deposited on the carrier substrate layer 43 in various deposition processes at temperatures above 300 degrees. A conversion layer 52 with a conversion material serves to convert the light emitted by the layer sequence 10 into a different wavelength. Due to the separate production of the carrier substrate with the functional layers 50, the thickness of the converter layer 52 can be significantly reduced.

Alternatively or additionally, it is also possible to introduce converter particles into the adhesive layer 30 . Conversion particles or layers can also be arranged on top of the carrier substrate layer.
In addition to the converter layer 52, the carrier substrate has an additional functional layer 51 in the form of a Bragg mirror. This includes a Multiplicity of laterally structured partial layers arranged one on top of the other to improve the light output and reduce the reflection of light which is emitted by the epitaxial layer sequence in the output direction.

The separate application of the carrier substrate with the converter layers to the layer sequence 10 that has already been produced allows a pre-characterization of the epitaxial layer sequence in order to set the thickness of the converter layer 52 for the carrier substrate as a function thereof. In this way, conversion layers 52 can be deposited individually for epitaxial layer sequences 10 on the carrier substrate layer 43 in order to produce a desired mixed color.

Finally shows 8th an embodiment in which the carrier substrate 46 is designed in the form of a lens and is connected to the layer sequence 10 via the adhesive layer. This allows the light generated and emitted by the epitaxial layer sequence 10 to be focused and emitted in a directed manner. In addition, a lens-shaped silicone layer 47 can be applied to the carrier layer 46 . This improves the stability and at the same time protects the lens-shaped carrier substrate 46.

5 shows a comparison of the decoupling efficiency for different configurations of optoelectronic components in which connection contacts are provided on the back. A light emission thus takes place in the direction of the roughened structured surface. The rear of the components is connected to electrical connections, which also form heat sinks for cooling the component during operation. A decoupling of light on the decoupling side directly into air shows a normalized decoupling efficiency of 1. In contrast, in the component 1 according to the invention, a 0.4 mm thick carrier substrate made of glass is applied via an adhesive layer. Compared to the component 1a, this has an improved decoupling efficiency in the range of 1.19. For comparison with this, an optoelectronic component 1B is shown which is completely surrounded by a silicone lens. Although this shows a slightly improved decoupling efficiency of 1.23, silicone is susceptible to aging processes, so that the decoupling efficiency tends to deteriorate over a longer period of time. In addition, the silicone lens has significantly larger dimensions than the component 1 according to the invention.

the 9A until 9K show an embodiment of a manufacturing method for an optoelectronic component according to the proposed principle.

According to 9A a growth substrate 90 is provided in the first steps. A first partial layer 110, which is doped with a first charge carrier type, is deposited on this. In this case, the sub-layer 110 corresponds to the sub-layers 11a and 11 of the previous embodiments. A small area is therefore intended to be chemically or physically structured or roughened later, in order to improve the outcoupling of light. Accordingly, the sub-layer 110 should have a sufficient thickness. A second partial layer 12 is deposited epitaxially over the partial layer 110 and is doped with a different charge carrier type than the partial layer 110 . As a result, a pn junction 13 is formed at the interface between the two partial layers 12 and 110 .

The two sub-layers 110 and 12 partially shown here can include additional sub-layers such as charge carrier injection layers or charge carrier transport layers. Their doping concentration can vary in individual sub-layers. In one configuration, provision is made, for example, for a lightly doped partial layer of the same charge carrier type to be additionally arranged between the growth substrate 90 and the first partial layer 110 . This can serve as a sacrificial layer for the later detachment of the growth substrate 90 . At the same time, it is also suitable for planarizing the surface of the growth substrate 90 . Alternatively, the partial layer 110 can also be provided with a doping gradient, so that the doping concentration changes across the thickness of the layer.

On the epitaxially grown layer sequence is according to 9B furthermore, a partial layer 14 is deposited. This can be an insulating layer, which protects the underlying sub-layers of the epitaxial layer sequence. between the partial layer 14 and the partial layer 12 a reflective and highly conductive layer is additionally arranged.

To 9C A thin adhesive layer 93 is now applied to the insulating layer 14 and a temporary auxiliary carrier 92 is attached thereto, for example by a special 3M process. This serves only for short-term mechanical stabilization and should therefore be reversibly connected to the insulating layer 14 via the adhesive layer 93 . The adhesive layer is removed chemically, mechanically or physically in later process steps in order to detach the temporary auxiliary carrier 92 again.

The temporarily applied auxiliary carrier 92 stabilizes the epitaxially grown layer sequence, so that the growth substrate 90 as in 9D shown can be removed. This is done, for example, by what is known as a laser lift-off process. The uncovered surface of the partial layer 110 is exposed in a subsequent process step according to FIG 9E roughened to increase light extraction. An adhesive layer 30a, which is transparent in the cured state, is then applied to the roughened surface and distributed evenly. The adhesive used can be liquid, for example, and is spun or spun on, so that it is distributed as evenly as possible over the roughened surface 11b. In addition, it is ensured that there are no air pockets between the adhesive layer 30a and the roughened surface 11b of the partial layer 110 .

According to 9F a structured carrier substrate 47, provided with additional functional layers if required, is now applied to the not yet cured adhesive layer 30a, and the adhesive layer 30a is then cured. As a result, the carrier substrate 47 is intimately connected to the epitaxial layer sequence 10 and leads to sufficiently large mechanical stabilization. The adhesive layer 30 in the cured state has a refractive index which essentially corresponds to the adjoining area of the carrier substrate 47'. This reduces or avoids reflection due to a difference in the refractive indices between the adhesive layer 30 and the carrier substrate 47′.
According to 9G the carrier substrate 47' can also be structured, for example by grinding or removing the side edges as shown here.

The temporary subcarrier 92 is now used as shown in 9H removed and the underlying insulating layer 14 exposed. Trenches 80′ and 80, respectively, are now etched in different areas on the rear side of the component in order to make contact with the p-doped or n-doped sublayers 12 and 110, respectively. The trenches 80 ′ reach through the insulating layer 14 and the mirror layer arranged between the insulating layer 14 and the partial layer 12 and are therefore areas within the partial layer 12 uncovered. Correspondingly, the trenches 80 break through the insulating layer 14, the mirror layer, the partial layer 12 and the pn junction 13 and end in the partial layer 110.

In order to prevent short circuits, the trenches 80 in particular are now provided with an insulation layer 23 on their side walls. However, the bottom of the trenches 80 remains free, so that a conductive material therein electrically conductively contacts the partial layer 110 .

The trenches 80' and 80 according to FIG 9K filled with an electrically conductive material and the rear contacts 20 and 21 formed. The mirror layer between the insulating layer 14 and the sub-layer 12 is contacted by the material in the trenches 80' and also serves as a current distribution layer to improve the lateral charge carrier injection into the sub-layer 12. Accordingly, the trenches 80 can end in a region of the sub-layer 110 which has a low lateral resistance and is therefore also well suited for current distribution.

In addition to the method shown here, in which the rear connection contacts and in particular the trenches are produced after the carrier substrate 46 has been applied, it is also possible to form trenches 80′ and 80 in previous method steps. For example, the trenches can be etched into the individual partial layers and filled with electrically conductive material before the temporary auxiliary carrier is applied and the growth substrate 90 is detached. In this embodiment, the temporary submount would be applied and attached to the already patterned and trenched backside.

It is also possible, after the trenches 80' and 80 have been formed and filled, to completely provide the rear side with a thin metal layer and to arrange the temporary auxiliary carrier thereon. After the later structuring of the decoupling side and the application of the carrier substrate, the temporary auxiliary carrier is detached again and then the metallic layer applied to the insulating layer is structured in order to form the rear connection contacts.

The present invention makes it possible to implement a thin-film LED chip with both electrical connections on the side facing away from the emission surface, without having to accept losses in the mechanical stability of the chip. In addition, the manufacturing process can be implemented according to the proposed principle at the wafer level, including the formation of the connection contacts. This is achieved in that the carrier substrate used for mechanical stabilization of the epitaxial layer sequence is transparently connected to the decoupling side of the epitaxially grown layer sequence. As a result, the back of the epitaxial layer sequence can be formed completely, including the connection contacts, without having to form additional vias through the carrier substrate. The chip can thus be processed as a single-die-chip without the need for bonding wires, and it is also no additional package necessary. If encapsulation is nevertheless desired, this can contribute to optimizing light extraction by adapting its refractive index to the refractive index of the substrate carrier.

The separate production of the carrier substrate with the functional layer and the subsequent application of the same to the decoupling side of the epitaxial layer sequence allows the epitaxial layer sequence to be characterized in terms of its emission characteristics in an intermediate step during the production process and parameters for the production of the functional layers to be set depending on this.

Claims (12)

Optoelectronic component (1), comprising: - an epitaxially grown layer sequence (10), which comprises a partial layer (13) suitable for light emission, the layer sequence (10) having a first main side facing the main emission direction of emitted light and a second main side facing away from the main emission direction; - A carrier substrate (40) that is transparent to the light emitted in the main emission direction for mechanical stabilization of the epitaxially grown layer sequence (10), which is arranged on the first main side and is connected to the epitaxially grown layer sequence (10) and the layer sequence in the component (1) carries; - At least two connection contacts (20, 21) for supplying charge carriers to partial layers (11, 11a, 12, 13) of the epitaxially grown layer sequence (10), both connection contacts (20, 21) being arranged on the second main side; - An insulating layer (14) arranged on the second main side of the epitaxially grown layer sequence (10); - A first trench in the insulating layer (14), which exposes a region of an underlying first partial layer (12) of the layer sequence (10); - A second trench (22) in the insulating layer (14), in the first part-layer (12) and in the part-layer (13) suitable for light emission, which uncovers a region of a second part-layer (11) of the layer sequence (10); - A conductive material in the first and second (22) trench, which in each case one of the at least two connection contacts (20, 21) makes contact, wherein - The carrier substrate (40) comprises at least one Bragg reflection layer. The component (1) after claim 1 , in which the epitaxially grown layer sequence (10) is structured on the first main side to increase the light extraction. The component (1) according to one of Claims 1 until 2 , in which a transparent adhesive layer (30) for connecting the carrier substrate (40) to the layer sequence (10) is arranged between the epitaxially grown layer sequence (10) and the carrier substrate (40). The component (1) after claim 3 , in which a refractive index of the adhesive (30) essentially corresponds to a refractive index of the carrier substrate (40). The component (1) according to one of Claims 1 until 4 , in which at least one of the following layers is arranged between the carrier substrate (40) and the epitaxially grown layer sequence (10): - a light conversion layer (52) with a conversion dye; - a Bragg reflection layer (51). The component according to one of Claims 1 until 4 , wherein the carrier substrate (40) comprises at least one light conversion layer with a conversion dye, which faces the first main side. The component (1) according to one of Claims 1 until 6 , in which the carrier substrate (40) has a first main side facing the epitaxially grown layer sequence (10) and a second opposite main side, the first and second main sides having different dimensions. Method for producing an optoelectronic component (1), comprising: - providing a layer sequence (10) which is epitaxially grown on a growth substrate (90) and comprises a partial layer (13) suitable for light emission, the layer sequence (10) having a first main side which facing the main emission direction of emitted light, and a second main side facing away from the main emission direction; - applying an auxiliary support (92) to the second main face; - Detaching the growth substrate (90); - structuring of the first main page to increase light extraction; - Application of a transparent for light emitted by the partial layer carrier substrate (47) on the first main side; - detachment of the auxiliary support (92) on the second main side; - forming electrical connection contacts (20, 21) on the second main face, the forming of electrical connection contacts (20, 21) on the second main face prior to the step of applying an auxiliary carrier (92) on the second Main side takes place and wherein the formation of electrical connection contacts (20, 21) comprises: - forming an insulating layer (14) on the second main side of the epitaxially grown layer sequence (10); - Forming a first trench (80') in the insulating layer (14), which exposes a region of an underlying first partial layer (12) of the layer sequence (10); - forming a second trench (80) in the insulating layer (14), in the first part-layer (12) and in the part-layer (13) suitable for light emission, which trench uncovers a region of a second part-layer (110) of the layer sequence (10); - Filling the first and second trenches with a conductive material. procedure after claim 8 , in which the structuring of the first main side comprises at least one of the following steps: - roughening the surface of a partial layer (110) forming the first main side; - Application of a light conversion layer (52); - Application of a Bragg reflection layer (51). Procedure according to one of Claims 8 until 9 , in which the carrier substrate (47) comprises a mechanically stabilizing transparent carrier, in particular a glass carrier and at least one of the following layers, which is adjacent to the first main side: - a light conversion layer having a conversion dye; - a Bragg reflection layer. Procedure according to one of Claims 8 until 10 , in which the application of a carrier substrate (47) comprises: - application of a transparent adhesive layer (30) on the first main side; - Applying the carrier substrate (47) to the adhesive layer (30); - Hardening of the transparent adhesive layer (30). Procedure according to one of Claims 8 until 11 , in which the formation of electrical connection contacts (20, 21) takes place and then the auxiliary carrier (92) is applied to the connection contacts (20, 21) formed in this way.

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