WO2023072409A1 - Optoelectronic device with nanowire electrode - Google Patents

Optoelectronic device with nanowire electrode Download PDF

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Publication number
WO2023072409A1
WO2023072409A1 PCT/EP2021/080216 EP2021080216W WO2023072409A1 WO 2023072409 A1 WO2023072409 A1 WO 2023072409A1 EP 2021080216 W EP2021080216 W EP 2021080216W WO 2023072409 A1 WO2023072409 A1 WO 2023072409A1
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Prior art keywords
layer
optoelectronic device
electrically conductive
metallic nanowires
nanowires
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PCT/EP2021/080216
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French (fr)
Inventor
Tobias HUEBNER
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Ams-Osram International Gmbh
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Priority to PCT/EP2021/080216 priority Critical patent/WO2023072409A1/en
Publication of WO2023072409A1 publication Critical patent/WO2023072409A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/40—Materials therefor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/38—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes with a particular shape
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/36—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the electrodes
    • H01L33/40—Materials therefor
    • H01L33/42—Transparent materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
    • H01L2933/0008—Processes
    • H01L2933/0016—Processes relating to electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2933/00—Details relating to devices covered by the group H01L33/00 but not provided for in its subgroups
    • H01L2933/0091—Scattering means in or on the semiconductor body or semiconductor body package
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0095—Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/025—Physical imperfections, e.g. particular concentration or distribution of impurities
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
    • H01L33/145—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure with a current-blocking structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/44—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the coatings, e.g. passivation layer or anti-reflective coating

Definitions

  • the present invention concerns an optoelectronic device and a method for manufacturing an optoelectronic device .
  • Optoelectronic devices also referred to as lighting diodes or LEDs require a supply of energy for illumination .
  • the charge carriers introduced in an active zone of the optoelectronic device recombine under the emission of light . From this internally produced light , only a small share can be outcoupled from the LED via direct emission from the active zone or internal reflections .
  • the other part of the internally produced light is trapped within the structure of the LED and must be decoupled from the LED for example by means of suitable outcoupling structures .
  • the obj ect of the invention is thus to counteract the aforementioned problems and to provide an optoelectronic device with an enhanced light extraction of the light generated in the active zone of the optoelectronic device . It is a further obj ect of the invention to provide a method for manufacturing an optoelectronic device with an enhanced light extraction .
  • the concept is to provide an electrically conductive outcoupling structure on a functional layer stack together forming a small optoelectronic device .
  • the electrically conductive outcoupling structure comprises a plurality of metallic nanowires configured on the one hand to outcouple light generated in an active region of the functional layer stack and on the other hand to electrically contact the functional layer stack .
  • the nanowires can thereby act as light scattering centers while also being electrically conductive .
  • the dimensions of the outcoupling structure can be varied according to the desired application to such an extent that also micro-LED dimensions can be served .
  • an electrically conductive outcoupling structure comprising a plurality of metallic nanowires , an enhanced light extraction of the light generated in the active zone can be provided even for small optoelectronic devices such as LEDs , in particular p- LEDs , whose size lies in the area or less than 1000 pm 2 and can go down to about 10 pm 2 .
  • an optoelectronic device with a functional layer stack comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer , and a second layer with a dopant of a second conductivity type arranged on the active region .
  • the optoelectronic device further comprises an electrically conductive contact layer arranged on the first layer as well as an electrically conductive outcoupling structure for light generated in the active region arranged on the second layer .
  • the electrically conductive outcoupling structure comprises a plurality of metallic nanowires configured to electrically contact the second layer .
  • the electrooptical characteristics of the outcoupling structure can be optimized according to the desired application and to the dimensions of the optoelectronic device used .
  • An increase of the density of the metallic nanowires within the outcoupling structure for example leads to a lower sheet resistance of the outcoupling structure thus providing a good electrical contact for the optoelectronic device , while at the same time leads to a worse direct light transmission through the outcoupling structure making it more difficult for light to directly travel through the outcoupling structure .
  • a decrease of the density of the metallic nanowires within the outcoupling structure leads to a lower scattering ratio of light to be outcoupled from the optoelectronic device
  • an increase of the density of the metallic nanowires within the outcoupling structure leads to a higher scattering ratio and can thus lead to a higher indirect light transmission through outcoupling structure due to a scattering of the light
  • the same applies to the thickness of the outcoupling structure as well as the dimensions length, with and cross section of the outcoupling structure whereas the thickness of the outcoupling structure can for example be defined by the number of layers of nanowires that are arranged on top of each other within the outcoupling structure .
  • the optical and electrical properties of the outcoupling structure can be adj usted to the desired needs and combined with various other parameters to improve the electrical conductivity of the contact areas , the outcoupling parameters and light intensity .
  • the proposed outcoupling structure can be applied to the functional layer stack with a lower thickness such that for example a desired aspect ratio of the optoelectronic device can still be provided .
  • the optoelectronic device can comprise an aspect ratio of a length of the optoelectronic device to the height of the optoelectronic device of greater than 1 , in particular greater than 2 , and even more particular within the range of 2 to 3 . 5 .
  • the height of the optoelectronic device should in any case be smaller than a length of the optoelectronic device .
  • the plurality of metallic nanowires form a plurality of light scattering centers or at least act as a plurality of light scattering centers , such as mie-scattering centers , for scattering light generated in the active region . Due to the light scattering centers , most of the internally produced light which is trapped within the functional layer stack can be outcoupled from the functional layer stack .
  • the outcoupling results thereby partially by a "direct" outcoupling of light from the interface between the functional layer stack and the outcoupling structure in regions where the functional layer stack and nanowires of the outcoupling structure are in direct contact .
  • an indirect outcoupling takes place , within the close field of the light at the surface of the semiconductor in the form of near- field-coupling and surface-scattering .
  • the close field of the light at the surface of the semiconductor also causes surface plasmons to facilitate the coupling along the interface between the functional layer stack and the outcoupling structure , that is the nanowires .
  • the metallic nanowires comprise a circular cross section .
  • a non-circular cross section such as an oval cross section or a polygonal cross section is also conceivable .
  • the plurality of metallic nanowires comprises a mean thickness of less than lO Onm, in particular less than 60 nm.
  • the average thickness in particular the average diameter of all nanowires is less than lO Onm, in particular less than 60 nm .
  • the electrically conductive outcoupling structure can comprises several layers of nanowires while still comprising a thickness of less than 300 nm, in particular less than 200 nm.
  • the length of the nanowires can thereby vary inbetween the nanowires and can range from a few pm to a few hundred nm.
  • the metallic nanowires comprise a base material selected from the group consisting of : gold; silver ; platinum; copper ; and nickel .
  • the metallic nanowires comprise in particular a base material which is on the one hand at least electrically conductive and on the other hand resistant against corrosion .
  • the plurality of metallic nanowires are arranged anisotropic in the electrically conductive outcoupling structure .
  • An anisotropic arrangement of the nanowires can for example be desired to promote the electrical properties of the outcoupling structure or to increase the transparency of it .
  • the electrical properties of the outcoupling structure can be promoted by help of an anisotropic arrangement of the nanowires , as due to the anisotropic arrangement more contact points between the nanowires occur .
  • the optoelectronic device is , for example , a radiation-emitting optoelectronic semiconductor chip .
  • the semiconductor chip may be a light emitting diode (LED) chip or a laser chip .
  • the optoelectronic semiconductor chip may generate light during operation .
  • the optoelectronic semiconductor chip generates light in the spectral range from UV radiation to light in the infrared range , in particular visible light .
  • the optoelectronic semiconductor chip is a radiationdetecting semiconductor chip, for example a photodiode .
  • the optoelectronic device may for example comprise edge lengths of less than 100 pm, or less than 40 pm, and in particular less than 10pm .
  • the optoelectronic semiconductor chip can thus for example be a pLED ( LED for light emitting device , pLED for micro-LED ) or a pLED-chip .
  • the optoelectronic device further comprises a dielectric passivation layer arranged on a sidewall of the functional layer stack . Due to manufacturing processes of the electrically conductive outcoupling structure it may occur , that a portion of the plurality of nanowires is not only arranged on the second layer and thus on a top surface of the functional layer stack but may also extend from the top layer to a sidewall of the functional layer stack and contact for example the active region and/or the first layer . The nanowires on the sidewall can thus cause a short in the optoelectronic device which is to be prevented .
  • a dielectric passivation layer can be arranged on the sidewall of the functional layer stack to ensure that later deposited nanowires onto the top surface of the layer stack extending onto the sidewall of the layer stack do not come into contact with the active region and/or the first layer .
  • a portion of the plurality of metallic nanowires extends onto the dielectric passivation layer .
  • the electrically conductive outcoupling structure comprises a light transmission of greater than or equal to 70% , in particular greater than or equal to 80% .
  • a light transmission of greater than or equal to 70% in particular greater than or equal to 80% .
  • the electrically conductive outcoupling structure comprises a haze of greater than or equal to 3% , in particular greater than or equal to 5 % .
  • a haze of greater than or equal to 3% , in particular greater than or equal to 5 % .
  • the haze is dependent on the dimensions ( length, width, cross section of the nanowires ) of the outcoupling structure , the thickness of the outcoupling structure , the surface chemical groups on the nanowires , the density of metallic nanowires within the outcoupling structure as well as the wavelength of light traveling though the outcoupling structure .
  • the haze can be even greater than 5% .
  • the electrically conductive outcoupling structure comprises a sheet resistance of less than 30 Ohm/q, in particular less than 20 Ohm/sq .
  • a comparable transparent electrical contact of for example ITO ( IndiumTinOxide ) with a thickness of 200nm comprises for example a sheet resistance of 44 Ohm/sq .
  • the sheet resistance can thereby for example be measured by means of the 4 -point probes method .
  • the optoelectronic device further comprises a p-type dopant , such as for example Zn ( Zinc ) deposited in an edge region of the active region, causing a quantum well intermixing ( QWI ) thereof .
  • Such QWI occurs in an area belonging to an outer region of the functional layer stack/active region .
  • the QWI enlarges the band gap of the quantum wells in this outer region close to the edges of the sidewall of the device , so that the charge carriers in the quantum wells can no longer reach the outer device surface close to the quantum wells , thus increasing the efficiency of very small InGaAlP LEDs .
  • QWI has provided a significant improvement of efficiency of p-LEDs , especially at low driving currents . However, there are indications that surface recombination is reduced but not completely suppressed .
  • the first layer and/or the second layer comprises a base material selected from the group consisting of :
  • the first layer and/or the second layer in particular comprise epitaxially grown layers .
  • a functional layer stack comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer, and a second layer with a dopant of a second conductivity type arranged on the active region .
  • an electrically conductive contact layer is provided on the first layer, and a plurality of metallic nanowires is deposited on the second layer electrically contacting the second layer .
  • the plurality of metallic nanowires is after depositing them on the second layer baked/ sintered thereby forming an electrically conductive outcoupling structure for light generated in the active region .
  • the step of depositing a plurality of metallic nanowires comprises at least one of inkj et-printing, aerosol- etting, p-scale dispensing, and spin coating .
  • the nanowires can therefore be dissolved in a solvent , in particular a high boiling solvent such as for example diethylphthalat , octanol , pentanol or butylbenzoat .
  • the step of depositing a plurality of metallic nanowires comprises in some aspects a deposition of the nanowires dissolved in a solvent , in particular a high boiling solvent such as for example diethylphthalat .
  • the step of baking the plurality of metallic nanowires comprises an evaporating of the solvent and a bonding of the nanowires thereby forming the electrically conductive outcoupling structure .
  • the step of depositing a plurality of metallic nanowires can in some aspects be performed prior to a step of separating the functional layer stack into at least two separate portions later forming two separate optoelectronic devices .
  • the step of depositing a plurality of metallic nanowires can also be performed after a step of separating the functional layer stack into at least two separate portions each forming a separate optoelectronic device after deposition of the nanowires and baking the same .
  • the step of separating the functional layer stack into at least two separate portions can for example be a step of sawing , etching , cutting or the like .
  • the step of separating the functional layer stack into at least two separate portions is performed after deposition of the nanowires on the second layer, not only the functional layer stack is separated into at least two separate portions but also the outcoupling structure arranged on the functional layer stack .
  • Such an order of steps brings the advantage that the nanowires can be deposited on a bigger area, whereas in case of the step of separating the functional layer stack into at least two separate portions is performed prior to the step of depositing the nanowires on the second layer , the nanowires do not have to be separated and can thus not be damaged during the step of separation .
  • the method further comprises a step of separating the functional layer stack into at least two separate portions prior to the step of depositing a plurality of metallic nanowires .
  • the method comprises a step of separating at least two optoelectronic devices after the step of baking the plurality of metallic nanowires .
  • the step of depositing a plurality of metallic nanowires is performed by depositing of a plurality of sub-layers each comprising a portion of the plurality of metallic nanowires .
  • the sub-layers can in in some aspects each be baked/sintered before depositing another sublayer on top of the last sub-layer but can also be deposited on top of each other and then as a whole be baked/sintered .
  • the method further comprises a step of providing a dielectric passivation layer , such as for example AL2O3 , on a sidewall of the functional layer stack prior to the step of depositing a plurality of metallic nanowires , as due to deposition of the nanowires it may occur , that a portion of the nanowires is not only arranged on the second layer and thus on a top surface of the functional layer stack but may also extend from the top layer to a sidewall of the functional layer stack and contact for example the active region and/or the first layer .
  • the nanowires on the sidewall can thus cause a short in the optoelectronic device which is to be prevented . Therefore , a dielectric passivation layer can be provided on the sidewall of the functional layer stack to ensure that later deposited nanowires do not come into contact with the active region and/or the first layer .
  • Fig . 1A and Fig . IB each a cross sectional view of an optoelectronic device comprising a transparent top contact layer ,
  • Fig . 2A a cross sectional view of an optoelectronic device according to some aspects of the invention
  • Fig . 2B a cross sectional view of a further embodiment of an optoelectronic device according to some aspects of the invention
  • Fig . 3 steps of a method for manufacturing at least one optoelectronic device according to some aspects of the invention .
  • Fig . 1A shows a cross-sectional view of an optoelectronic device comprising a layer stack 2 with a first layer 3 with a dopant of a first conductivity type , an active region 4 arranged on the first layer 3 and a second layer 5 with a dopant of a second conductivity type arranged on the active region 4 . Further to this , an electrically conductive contact layer 6 is arranged on the first layer 3 and a planar and transparent top contact layer 9 is arranged on the second layer 5 . By electrically connecting the optoelectronic device , charge carriers are introduced in the active region 4 of the optoelectronic device and recombine under the emission of light .
  • a structured transparent top contact layer as shown in Fig . IB is for very small optoelectronic devices , in particular p-LEDs , whose size lies in the area or less than 1000 pm 2 and can go down to about 10 pm 2 very difficult to be implemented .
  • p-LEDs p-LEDs
  • a stable , reproducible wet-chemical roughening of the top contact layer is hardly / not possible at this small scale and on the other hand an etching via lithographic patterns would require a very thick top contact layer in order to achieve surface structures large enough to cause beam path variations of the light to be outcoupled . This again is problematic to achieve a desired aspect ratio (w/d ) of the optoelectronic device .
  • an electrically conductive outcoupling structure comprising a plurality of metallic nanowires and configured on the one hand to outcouple light generated in an active region of a functional layer stack and on the other hand configured to electrically contact the functional layer stack is a way to overcome aforementioned problems .
  • the nanowires can thereby act as light scattering centers while also being electrically conductive .
  • the dimensions ( length, width, cross section) and the thickness of the outcoupling structure can be varied according to the desired application to such an extent that also micro-LED dimensions can be served .
  • an enhanced light extraction of the light generated in the active zone can be provided even for small optoelectronic devices such as LEDs , in particular p- LEDs , whose size lies in the area or less than 1000 pm 2 and can go down to about 10 pm 2 .
  • Such an optoelectronic device 1 is shown in Fig . 2A in a cross-sectional view .
  • the optoelectronic device 1 comprises a layer stack 2 with a first layer 3 with a dopant of a first conductivity type , an active region 4 arranged on the first layer 3 and a second layer 5 with a dopant of a second conductivity type arranged on the active region 4 .
  • an electrically conductive contact layer 6 is arranged on the first layer 3 and an electrically conductive outcoupling structure 7 comprising a plurality of nanowires 8 is arranged on the second layer 5 .
  • the thickness of the outcoupling structure 7 can thereby be chosen to provide on the one hand the required electrical as well as optical properties to the optoelectronic device 1 and on the other hand maintain a desired aspect ratio (w/d ) of the optoelectronic device 1 .
  • the light L generated in the active region 4 is then not anymore or at least only to a small extend trapped within the structure of the optoelectronic device but outcoupled via the outcoupling structure 7 .
  • Fig . 2B shows a cross sectional view of a further embodiment of an optoelectronic device 1 according to some aspects of the invention, whereas the left half of Fig . 2B shows an embodiment of a faulty optoelectronic device .
  • a dielectric passivation layer 10 is arranged on a sidewall of the functional layer stack 2 .
  • the dielectric passivation layer 10 has the purpose that nanowires 8 extending from the second layer 5 onto the sidewall of the functional layer stack 2 cannot electrically contact the first layer 3 and the active region 4 causing a short , as indicated with the lightning in the left half of Fig . 2B .
  • Fig . 3 shows steps of a method for manufacturing at least one optoelectronic device according to some aspects of the invention .
  • a functional layer stack is provided comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer , and a second layer with a dopant of a second conductivity type arranged on the active region .
  • an electrically conductive contact layer is provided on the first layer
  • a plurality of metallic nanowires is deposited on the second layer electrically contacting the second layer in a second step S3 .
  • the plurality of metallic nanowires is after depositing them on the second layer in a fourth step S4 baked/ sintered thereby forming an electrically conductive outcoupling structure for light generated in the active region .

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Abstract

The invention concerns an optoelectronic device, comprising a functional layer stack with a first layer with a dopant of a first conductivity type, an active region arranged on the first layer, and a second layer with a dopant of a second conductivity type arranged on the active region. The optoelectronic device further comprises an electrically conductive contact layer arranged on the first layer and an electrically conductive outcoupling structure for light generated in the active region arranged on the second layer. The electrically conductive outcoupling structure comprises a plurality of metallic nanowires configured to electrically contact the second layer.

Description

OPTOELECTRONIC DEVICE WITH NANOWIRE ELECTRODE
The present invention concerns an optoelectronic device and a method for manufacturing an optoelectronic device .
Background
Optoelectronic devices also referred to as lighting diodes or LEDs require a supply of energy for illumination . The charge carriers introduced in an active zone of the optoelectronic device recombine under the emission of light . From this internally produced light , only a small share can be outcoupled from the LED via direct emission from the active zone or internal reflections . The other part of the internally produced light is trapped within the structure of the LED and must be decoupled from the LED for example by means of suitable outcoupling structures .
The recent decrease in size has led to the development of p-LEDs , whose size lies in the area or less than 1000 pm2 and can go down to about 10 pm2 . At such sizes , enhanced light extraction of the light generated in the active zone is very limited due to the small structure of the LED Commonly known outcoupling structures are thus difficult to be implemented as their dimensions , in particular their thickness to provide a desired aspect ratio of the LED, need to be smaller than for conventional LED-sizes .
Commonly known strategies to enhance the ratio of outcoupled light are for example :
A wet-chemical roughening of the top-contact of a LED, however a stable reproducible roughening is hardly / not possible at this small scale ; and
An etching of the top-contact of a LED via lithographic patterns , however such an etching would require a very top-thick contact in order to achieve surface structures large enough to cause beam path variations of the light to be decoupled problematic aspect ratio ) . In addition such high-resolution lithographic patterning is hard to achieve and the resulting rough surface structures are difficult to properly electrically contact afterwards .
However , for both strategies such structures are more difficult to fabricate as the LEDs become smaller .
The obj ect of the invention is thus to counteract the aforementioned problems and to provide an optoelectronic device with an enhanced light extraction of the light generated in the active zone of the optoelectronic device . It is a further obj ect of the invention to provide a method for manufacturing an optoelectronic device with an enhanced light extraction .
Summary
This and other requirements are met by an optoelectronic device having the features of claim 1 and a method for manufacturing an optoelectronic device having the features of claim 15 . Embodiments and further developments of the invention are described in the dependent claims .
The concept , the inventor proposes , is to provide an electrically conductive outcoupling structure on a functional layer stack together forming a small optoelectronic device . The electrically conductive outcoupling structure comprises a plurality of metallic nanowires configured on the one hand to outcouple light generated in an active region of the functional layer stack and on the other hand to electrically contact the functional layer stack . The nanowires can thereby act as light scattering centers while also being electrically conductive . At the same time the dimensions of the outcoupling structure ( length, width, cross section of the nanowires ) , the thickness of the outcoupling structure , and the surface chemical groups on the nanowires of the outcoupling structure can be varied according to the desired application to such an extent that also micro-LED dimensions can be served . Thus , by using an electrically conductive outcoupling structure comprising a plurality of metallic nanowires , an enhanced light extraction of the light generated in the active zone can be provided even for small optoelectronic devices such as LEDs , in particular p- LEDs , whose size lies in the area or less than 1000 pm2 and can go down to about 10 pm2 .
In an aspect , an optoelectronic device is provided, with a functional layer stack comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer , and a second layer with a dopant of a second conductivity type arranged on the active region . The optoelectronic device further comprises an electrically conductive contact layer arranged on the first layer as well as an electrically conductive outcoupling structure for light generated in the active region arranged on the second layer . The electrically conductive outcoupling structure comprises a plurality of metallic nanowires configured to electrically contact the second layer .
By varying the dimensions ( length, width, cross section of the nanowires ) of the outcoupling structure , the thickness of the outcoupling structure , and the surface chemical groups on the nanowires , as well as in particular by varying the density of metallic nanowires within the outcoupling structure the electrooptical characteristics of the outcoupling structure can be optimized according to the desired application and to the dimensions of the optoelectronic device used . An increase of the density of the metallic nanowires within the outcoupling structure for example leads to a lower sheet resistance of the outcoupling structure thus providing a good electrical contact for the optoelectronic device , while at the same time leads to a worse direct light transmission through the outcoupling structure making it more difficult for light to directly travel through the outcoupling structure . Likewise , a decrease of the density of the metallic nanowires within the outcoupling structure leads to a higher sheet resistance of the outcoupling structure thus providing a poor electrical contact for the optoelectronic device , while at the same time leads to a higher direct light transmission through the outcoupling structure allowing light to directly travel through light the outcoupling structure . It was also found that a change of the surface chemical groups on the nanowires , in particular in dependence on their steric and bonding type , shows a different effect on the electrical conductivity as well as the temperature stability of the outcoupling structure . In a similar manner a decrease of the density of the metallic nanowires within the outcoupling structure leads to a lower scattering ratio of light to be outcoupled from the optoelectronic device , whereas an increase of the density of the metallic nanowires within the outcoupling structure leads to a higher scattering ratio and can thus lead to a higher indirect light transmission through outcoupling structure due to a scattering of the light . The same applies to the thickness of the outcoupling structure as well as the dimensions length, with and cross section of the outcoupling structure , whereas the thickness of the outcoupling structure can for example be defined by the number of layers of nanowires that are arranged on top of each other within the outcoupling structure .
By varying these parameters , the optical and electrical properties of the outcoupling structure can be adj usted to the desired needs and combined with various other parameters to improve the electrical conductivity of the contact areas , the outcoupling parameters and light intensity .
In contrast to conventionally used outcoupling structures , the proposed outcoupling structure can be applied to the functional layer stack with a lower thickness such that for example a desired aspect ratio of the optoelectronic device can still be provided . As a result , the optoelectronic device can comprise an aspect ratio of a length of the optoelectronic device to the height of the optoelectronic device of greater than 1 , in particular greater than 2 , and even more particular within the range of 2 to 3 . 5 . In some aspects , the height of the optoelectronic device should in any case be smaller than a length of the optoelectronic device .
In some aspects , the plurality of metallic nanowires form a plurality of light scattering centers or at least act as a plurality of light scattering centers , such as mie-scattering centers , for scattering light generated in the active region . Due to the light scattering centers , most of the internally produced light which is trapped within the functional layer stack can be outcoupled from the functional layer stack .
The outcoupling results thereby partially by a "direct" outcoupling of light from the interface between the functional layer stack and the outcoupling structure in regions where the functional layer stack and nanowires of the outcoupling structure are in direct contact . In addition, an indirect outcoupling takes place , within the close field of the light at the surface of the semiconductor in the form of near- field-coupling and surface-scattering . In some aspects , the close field of the light at the surface of the semiconductor also causes surface plasmons to facilitate the coupling along the interface between the functional layer stack and the outcoupling structure , that is the nanowires .
In some aspects , the metallic nanowires comprise a circular cross section . However, a non-circular cross section such as an oval cross section or a polygonal cross section is also conceivable .
In some aspects , the plurality of metallic nanowires comprises a mean thickness of less than lO Onm, in particular less than 60 nm. In other words , the average thickness , in particular the average diameter of all nanowires is less than lO Onm, in particular less than 60 nm . Thus , the electrically conductive outcoupling structure can comprises several layers of nanowires while still comprising a thickness of less than 300 nm, in particular less than 200 nm. The length of the nanowires can thereby vary inbetween the nanowires and can range from a few pm to a few hundred nm.
In some aspects , the metallic nanowires comprise a base material selected from the group consisting of : gold; silver ; platinum; copper ; and nickel .
The metallic nanowires comprise in particular a base material which is on the one hand at least electrically conductive and on the other hand resistant against corrosion . In some aspects , the plurality of metallic nanowires are arranged anisotropic in the electrically conductive outcoupling structure . However it can also be desired, to arrange the metallic nanowires isotropic in the electrically conductive outcoupling structure to form a desired pattern as for example a grid, a star, circles or other shapes , or are arranged side by side all pointing into the same direction . An anisotropic arrangement of the nanowires can for example be desired to promote the electrical properties of the outcoupling structure or to increase the transparency of it . In particular the electrical properties of the outcoupling structure can be promoted by help of an anisotropic arrangement of the nanowires , as due to the anisotropic arrangement more contact points between the nanowires occur .
The optoelectronic device is , for example , a radiation-emitting optoelectronic semiconductor chip . For example , the semiconductor chip may be a light emitting diode (LED) chip or a laser chip . The optoelectronic semiconductor chip may generate light during operation . In particular, it is possible that the optoelectronic semiconductor chip generates light in the spectral range from UV radiation to light in the infrared range , in particular visible light . Alternatively, it is possible that the optoelectronic semiconductor chip is a radiationdetecting semiconductor chip, for example a photodiode .
The optoelectronic device may for example comprise edge lengths of less than 100 pm, or less than 40 pm, and in particular less than 10pm . The optoelectronic semiconductor chip can thus for example be a pLED ( LED for light emitting device , pLED for micro-LED ) or a pLED-chip .
In some aspects , the optoelectronic device further comprises a dielectric passivation layer arranged on a sidewall of the functional layer stack . Due to manufacturing processes of the electrically conductive outcoupling structure it may occur , that a portion of the plurality of nanowires is not only arranged on the second layer and thus on a top surface of the functional layer stack but may also extend from the top layer to a sidewall of the functional layer stack and contact for example the active region and/or the first layer . The nanowires on the sidewall can thus cause a short in the optoelectronic device which is to be prevented . Therefore , a dielectric passivation layer can be arranged on the sidewall of the functional layer stack to ensure that later deposited nanowires onto the top surface of the layer stack extending onto the sidewall of the layer stack do not come into contact with the active region and/or the first layer . In some aspects , a portion of the plurality of metallic nanowires extends onto the dielectric passivation layer .
In some aspects , the electrically conductive outcoupling structure comprises a light transmission of greater than or equal to 70% , in particular greater than or equal to 80% . Thus at least 70% and in particular at least 80% of the light of the optoelectronic device impinging the outcoupling structure travels through the outcoupling structure without being absorbed or back reflected .
In some aspects , the electrically conductive outcoupling structure comprises a haze of greater than or equal to 3% , in particular greater than or equal to 5 % . Thus at least 3% and in particular at least 5% of the light of the optoelectronic device trapped in the functional layer stack is scattered by the nanowires of the outcoupling structure and thus enables the light for being outcoupled of the functional layer stack . It should be noted that the haze is dependent on the dimensions ( length, width, cross section of the nanowires ) of the outcoupling structure , the thickness of the outcoupling structure , the surface chemical groups on the nanowires , the density of metallic nanowires within the outcoupling structure as well as the wavelength of light traveling though the outcoupling structure . For an outcoupling structure with a high density of metallic nanowires or a great thickness , the haze can be even greater than 5% .
In some aspects , the electrically conductive outcoupling structure comprises a sheet resistance of less than 30 Ohm/q, in particular less than 20 Ohm/sq . A comparable transparent electrical contact of for example ITO ( IndiumTinOxide ) with a thickness of 200nm comprises for example a sheet resistance of 44 Ohm/sq . The sheet resistance can thereby for example be measured by means of the 4 -point probes method . In some aspects , the optoelectronic device further comprises a p-type dopant , such as for example Zn ( Zinc ) deposited in an edge region of the active region, causing a quantum well intermixing ( QWI ) thereof . The efficiency of for example very small InGaAlP optoelectronic devices can thereby be improved . Such QWI occurs in an area belonging to an outer region of the functional layer stack/active region . The QWI enlarges the band gap of the quantum wells in this outer region close to the edges of the sidewall of the device , so that the charge carriers in the quantum wells can no longer reach the outer device surface close to the quantum wells , thus increasing the efficiency of very small InGaAlP LEDs . QWI has provided a significant improvement of efficiency of p-LEDs , especially at low driving currents . However, there are indications that surface recombination is reduced but not completely suppressed .
In some aspects , the first layer and/or the second layer comprises a base material selected from the group consisting of :
- GaN;
- Al GaN;
- AlGalnP;
- AlGalnN; and
- AlGaP .
Other material may also be used . The first layer and/or the second layer in particular comprise epitaxially grown layers .
Some other aspects concern a method for manufacturing at least one optoelectronic device . In a first step a functional layer stack is provided comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer, and a second layer with a dopant of a second conductivity type arranged on the active region . Then an electrically conductive contact layer is provided on the first layer, and a plurality of metallic nanowires is deposited on the second layer electrically contacting the second layer . The plurality of metallic nanowires is after depositing them on the second layer baked/ sintered thereby forming an electrically conductive outcoupling structure for light generated in the active region . In some aspects , surface groups may be burned off as well to form the electrically conductive outcoupling structure . In some aspects , the step of depositing a plurality of metallic nanowires comprises at least one of inkj et-printing, aerosol- etting, p-scale dispensing, and spin coating . The nanowires can therefore be dissolved in a solvent , in particular a high boiling solvent such as for example diethylphthalat , octanol , pentanol or butylbenzoat .
Thus , the step of depositing a plurality of metallic nanowires comprises in some aspects a deposition of the nanowires dissolved in a solvent , in particular a high boiling solvent such as for example diethylphthalat .
In some aspects , the step of baking the plurality of metallic nanowires comprises an evaporating of the solvent and a bonding of the nanowires thereby forming the electrically conductive outcoupling structure .
The step of depositing a plurality of metallic nanowires can in some aspects be performed prior to a step of separating the functional layer stack into at least two separate portions later forming two separate optoelectronic devices . However, the step of depositing a plurality of metallic nanowires can also be performed after a step of separating the functional layer stack into at least two separate portions each forming a separate optoelectronic device after deposition of the nanowires and baking the same . The step of separating the functional layer stack into at least two separate portions can for example be a step of sawing , etching , cutting or the like . In case of the step of separating the functional layer stack into at least two separate portions is performed after deposition of the nanowires on the second layer, not only the functional layer stack is separated into at least two separate portions but also the outcoupling structure arranged on the functional layer stack . Such an order of steps brings the advantage that the nanowires can be deposited on a bigger area, whereas in case of the step of separating the functional layer stack into at least two separate portions is performed prior to the step of depositing the nanowires on the second layer , the nanowires do not have to be separated and can thus not be damaged during the step of separation .
In some aspects the method further comprises a step of separating the functional layer stack into at least two separate portions prior to the step of depositing a plurality of metallic nanowires . Whereas in some aspects the method comprises a step of separating at least two optoelectronic devices after the step of baking the plurality of metallic nanowires .
In some aspects , the step of depositing a plurality of metallic nanowires is performed by depositing of a plurality of sub-layers each comprising a portion of the plurality of metallic nanowires . The sub-layers can in in some aspects each be baked/sintered before depositing another sublayer on top of the last sub-layer but can also be deposited on top of each other and then as a whole be baked/sintered .
In some aspects , the method further comprises a step of providing a dielectric passivation layer , such as for example AL2O3 , on a sidewall of the functional layer stack prior to the step of depositing a plurality of metallic nanowires , as due to deposition of the nanowires it may occur , that a portion of the nanowires is not only arranged on the second layer and thus on a top surface of the functional layer stack but may also extend from the top layer to a sidewall of the functional layer stack and contact for example the active region and/or the first layer . The nanowires on the sidewall can thus cause a short in the optoelectronic device which is to be prevented . Therefore , a dielectric passivation layer can be provided on the sidewall of the functional layer stack to ensure that later deposited nanowires do not come into contact with the active region and/or the first layer .
Brief description of the drawings
In the following , embodiments of the invention will be explained in more detail with reference to the accompanying drawings . It is shown schematically in
Fig . 1A and Fig . IB each a cross sectional view of an optoelectronic device comprising a transparent top contact layer ,
Fig . 2A a cross sectional view of an optoelectronic device according to some aspects of the invention, Fig . 2B a cross sectional view of a further embodiment of an optoelectronic device according to some aspects of the invention, and
Fig . 3 steps of a method for manufacturing at least one optoelectronic device according to some aspects of the invention .
Detailed description
The present disclosure will now be described more fully hereinafter with reference to the accompanying drawings , in which exemplary embodiments of the disclosure are shown . The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness . Like reference characters refer to like elements throughout the description . The drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the exemplary embodiments of the present disclosure .
Fig . 1A shows a cross-sectional view of an optoelectronic device comprising a layer stack 2 with a first layer 3 with a dopant of a first conductivity type , an active region 4 arranged on the first layer 3 and a second layer 5 with a dopant of a second conductivity type arranged on the active region 4 . Further to this , an electrically conductive contact layer 6 is arranged on the first layer 3 and a planar and transparent top contact layer 9 is arranged on the second layer 5 . By electrically connecting the optoelectronic device , charge carriers are introduced in the active region 4 of the optoelectronic device and recombine under the emission of light . However only a small share from this internally produced light can be outcoupled from the LED via direct emission L from the active region or internal reflections at for example the electrically conductive contact layer 6 . The other part Lo of the internally produced light is trapped within the structure of the optoelectronic device ( indicated by the dotted line ) . A possibility to outcouple the trapped light from the optoelectronic device is shown in Fig . IB . According to Fig . IB , the planar and transparent top contact layer was changed for a structured transparent top contact layer acting as an outcoupling structure 7 . It can be seen from the figure that light L is not anymore trapped within the structure of the optoelectronic device but outcoupled via the outcoupling structure 7 . However, such a structured transparent top contact layer as shown in Fig . IB is for very small optoelectronic devices , in particular p-LEDs , whose size lies in the area or less than 1000 pm2 and can go down to about 10 pm2 very difficult to be implemented . On the one hand a stable , reproducible wet-chemical roughening of the top contact layer is hardly / not possible at this small scale and on the other hand an etching via lithographic patterns would require a very thick top contact layer in order to achieve surface structures large enough to cause beam path variations of the light to be outcoupled . This again is problematic to achieve a desired aspect ratio (w/d ) of the optoelectronic device . In addition to this it is also hard to achieve a required high-resolution lithographic patterning and the resulting rough surface structures are difficult to be properly electrically contact afterwards . In summary such structures are harder to fabricate , the smaller the optoelectronic device becomes .
The inventor however found out , that by providing an electrically conductive outcoupling structure comprising a plurality of metallic nanowires and configured on the one hand to outcouple light generated in an active region of a functional layer stack and on the other hand configured to electrically contact the functional layer stack is a way to overcome aforementioned problems . The nanowires can thereby act as light scattering centers while also being electrically conductive . At the same time the dimensions ( length, width, cross section) and the thickness of the outcoupling structure can be varied according to the desired application to such an extent that also micro-LED dimensions can be served . Thus , by using an electrically conductive outcoupling structure comprising a plurality of metallic nanowires , an enhanced light extraction of the light generated in the active zone can be provided even for small optoelectronic devices such as LEDs , in particular p- LEDs , whose size lies in the area or less than 1000 pm2 and can go down to about 10 pm2 .
Such an optoelectronic device 1 is shown in Fig . 2A in a cross-sectional view . The optoelectronic device 1 comprises a layer stack 2 with a first layer 3 with a dopant of a first conductivity type , an active region 4 arranged on the first layer 3 and a second layer 5 with a dopant of a second conductivity type arranged on the active region 4 . Further to this , an electrically conductive contact layer 6 is arranged on the first layer 3 and an electrically conductive outcoupling structure 7 comprising a plurality of nanowires 8 is arranged on the second layer 5 . The thickness of the outcoupling structure 7 can thereby be chosen to provide on the one hand the required electrical as well as optical properties to the optoelectronic device 1 and on the other hand maintain a desired aspect ratio (w/d ) of the optoelectronic device 1 . The light L generated in the active region 4 is then not anymore or at least only to a small extend trapped within the structure of the optoelectronic device but outcoupled via the outcoupling structure 7 .
Fig . 2B and in particular the right half of Fig . 2B, shows a cross sectional view of a further embodiment of an optoelectronic device 1 according to some aspects of the invention, whereas the left half of Fig . 2B shows an embodiment of a faulty optoelectronic device . According to the right half of Fig . 2B a dielectric passivation layer 10 is arranged on a sidewall of the functional layer stack 2 . The dielectric passivation layer 10 has the purpose that nanowires 8 extending from the second layer 5 onto the sidewall of the functional layer stack 2 cannot electrically contact the first layer 3 and the active region 4 causing a short , as indicated with the lightning in the left half of Fig . 2B .
Fig . 3 shows steps of a method for manufacturing at least one optoelectronic device according to some aspects of the invention . In a first step SI a functional layer stack is provided comprising a first layer with a dopant of a first conductivity type , an active region arranged on the first layer , and a second layer with a dopant of a second conductivity type arranged on the active region . Then in a second step S2 an electrically conductive contact layer is provided on the first layer , and a plurality of metallic nanowires is deposited on the second layer electrically contacting the second layer in a second step S3 . The plurality of metallic nanowires is after depositing them on the second layer in a fourth step S4 baked/ sintered thereby forming an electrically conductive outcoupling structure for light generated in the active region .
LIST OF REFERENCES
1 optoelectronic device
2 functional layer stack 3 first layer
4 active region
5 second layer
6 electrically conductive contact layer
7 electrically conductive outcoupling structure 8 nanowire
9 top contact layer
10 dielectric passivation layer
L light
Lo trapped light w length d height
S1...S4 Steps

Claims

CLAIMS An optoelectronic device (1) , comprising:
- a functional layer stack
(2) comprising:
- a first layer (3) with a dopant of a first conductivity type;
- an active region (4) arranged on the first layer (3) ; and
- a second layer (5) with a dopant of a second conductivity type arranged on the active region (4) ;
- an electrically conductive contact layer (6) arranged on the first layer
( 3 ) ; and
- an electrically conductive outcoupling structure (7) for light (L) generated in the active region
(4) arranged on the second layer ( 5 ) ; wherein the electrically conductive outcoupling structure (7) comprises a plurality of metallic nanowires (8) configured to electrically contact the second layer
(5) . The optoelectronic device according to claim 1, wherein the optoelectronic device comprises an aspect ratio of a length (w) of the optoelectronic device to the height (d) of the optoelectronic device of greater than 1, in particular greater than 2. The optoelectronic device according to claim 1 or 2 , wherein the plurality of metallic nanowires (8) form a plurality of light scattering centers for scattering light generated in the active region ( 4 ) . The optoelectronic device according to any one of the preceding claims , wherein the plurality of metallic nanowires (8) comprises a mean thickness of less than lOOnm, in particular less than 60 nm. The optoelectronic device according to any one of the preceding claims, wherein the electrically conductive outcoupling structure (7) comprises a thickness of less than 300 nm, in particular less than 200 nm.
6. The optoelectronic device according to any one of the preceding claims, wherein the metallic nanowires (8) comprise a base material selected from the group consisting of: gold; silver; and platinum.
7. The optoelectronic device according to any one of the preceding claims, wherein the plurality of metallic nanowires (8) are arranged anisotropic in the electrically conductive outcoupling structure.
8. The optoelectronic device according to any one of the preceding claims, further comprising a dielectric passivation layer (10) arranged on a sidewall of the functional layer stack (2) .
9. The optoelectronic device according to claim 8, wherein a portion of the plurality of metallic nanowires (8) extends onto the dielectric passivation layer (10) .
10. The optoelectronic device according to any one of the preceding claims, wherein the electrically conductive outcoupling structure (7) has a light transmission of greater than or equal to 70%, in particular greater than or equal to 80%.
11. The optoelectronic device according to any one of the preceding claims, wherein the electrically conductive outcoupling structure (7) has a haze of greater than or equal to 3%, in particular greater than or equal to 5%.
12. The optoelectronic device according to any one of the preceding claims, wherein the electrically conductive outcoupling structure (7) has a sheet resistance of less than 30 Ohm/sq, in particular less than 20 Ohm/sq.
13. The optoelectronic device according to any one of the preceding claims, further comprising a p-type dopant deposited in an edge - 18 - region of the active region, causing a quantum well intermixing thereof .
14. Optoelectronic device according to any one of the preceding claims, wherein the first layer (3) and/or the second layer (5) comprises a base material selected from the group consisting of :
- GaN;
- Al GaN;
- AlGalnP;
- AlGalnN; and
- AlGaP.
15. Method for manufacturing at least one optoelectronic device (1) , comprising the steps of:
- providing a functional layer stack (2) comprising:
- a first layer (3) with a dopant of a first conductivity type;
- an active region (4) arranged on the first layer (3) ; and
- a second layer (5) with a dopant of a second conductivity type arranged on the active region (4) ;
- providing an electrically conductive contact layer (6) on the first layer (3) ;
- depositing a plurality of metallic nanowires (8) on the second layer (5) electrically contacting the second layer (5) ; and
- baking the plurality of metallic nanowires (8) thereby forming an electrically conductive outcoupling structure (7) for light (L) generated in the active region (4) .
16. The method according to claim 15, wherein the step of depositing a plurality of metallic nanowires (8) comprises at least one of the following processes: inkj et-printing; aerosol- j etting; and p-scale dispensing.
17. The method according to claim 15 or 16, wherein the step of depositing a plurality of metallic nanowires (8) comprises - 19 - depositing the nanowires dissolved in a solvent, in particular a high boiling solvent. The method according to claim 17, wherein the step of baking the plurality of metallic nanowires (8) comprises an evaporating of the solvent and a bonding of the nanowires thereby forming the electrically conductive outcoupling structure (7) . The method according to any one of claims 15 to 18, further comprising a step of providing a dielectric passivation layer (10) on a sidewall of the functional layer stack (2) prior to the step of depositing a plurality of metallic nanowires (8) . The method according to any one of claims 15 to 19, wherein the step of depositing a plurality of metallic nanowires (8) is performed by depositing of a plurality of sub-layers each comprising a portion of the plurality of metallic nanowires. The method according to any one of claims 15 to 20, further comprising a step of separating the functional layer stack (2) into at least two separate portions prior to the step of depositing a plurality of metallic nanowires (8) . The method according to any one of claims 15 to 20, further comprising a step of separating at least two optoelectronic devices (1) after the step of baking the plurality of metallic nanowires (8) .
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