FR3144404A1 - Three-dimensional light-emitting diode optoelectronic device - Google Patents

Abstract

Three-dimensional light-emitting diode optoelectronic device The present description relates to an optoelectronic device (5) comprising a first light-emitting diode (GLED) comprising three-dimensional semiconductor elements, each corresponding to a microwire, a nanowire, or a conical or frustoconical element of micrometric or nanometric size, and an active zone covering each three-dimensional semiconductor element, the first light-emitting diode being configured to emit radiation (RL) with an emission spectrum for which the light intensity is greater than 80% of the maximum light intensity of the spectrum over a first length range d waves greater than 30 nm and for which the light intensity is greater than 50% of the maximum light intensity over a second wavelength range less than the first range increased by 30 nm; and a band-pass optical filter (F_LED) covering the first light-emitting diode. Figure for abstract: Fig. 3

Description

Three-dimensional light-emitting diode optoelectronic device

The present application relates to an optoelectronic device, in particular a display pixel for a display screen or for a backlight panel, comprising three-dimensional light-emitting diodes based on semiconductor materials, and its manufacturing method.

A light-emitting diode based on semiconductor materials generally comprises an active zone which is the region of the light-emitting diode from which the majority of the electromagnetic radiation provided by the light-emitting diode is emitted. The structure and composition of the active zone are adapted to obtain electromagnetic radiation having the desired properties. In particular, it is generally sought to obtain electromagnetic radiation with a narrow spectrum, ideally substantially monochromatic.

The subject of particular interest here is optoelectronic devices with three-dimensional light-emitting diodes, i.e. light-emitting diodes each comprising a three-dimensional semiconductor element of micrometric or nanometric size extending in a preferred direction, for example a microwire or a nanowire, and the active zone of which covers the three-dimensional semiconductor element. In particular, a three-dimensional light-emitting diode is said to be of the radial type when its active zone extends at least over the side walls of the three-dimensional semiconductor element.

The central wavelength of the radiation emitted by a three-dimensional radial-type light-emitting diode depends in particular on the diameter of the three-dimensional semiconductor element on which the active zone of the light-emitting diode rests.

A method of manufacturing optoelectronic devices comprises forming radial three-dimensional light-emitting diodes on a wafer and cutting the wafer to separate the optoelectronic devices. With known methods of manufacturing radial three-dimensional light-emitting diodes including epitaxial growth steps, when the growth conditions should in theory lead to obtaining on the same wafer three-dimensional semiconductor elements light-emitting diodes of the same dimensions, a significant overall dispersion of the diameters of the three-dimensional semiconductor elements over the entire wafer is observed in practice, even if the local dispersion may remain reduced. This results in a significant overall dispersion of the central wavelengths of the radiation emitted by the light-emitting diodes formed from the same wafer, which can reach 20 nm.

For the manufacture of an optoelectronic device such as a pixel for a display screen or for a backlight panel, a dispersion of the central wavelength of the radiation emitted by the optoelectronic device of less than 2 nm is generally required. It is then necessary to test the optoelectronic devices formed from the same wafer to select those which have the desired properties. These steps increase the manufacturing cost of the optoelectronic devices.

One embodiment overcomes all or part of the drawbacks of known three-dimensional light-emitting diode optoelectronic devices.

An object of one embodiment is to precisely control the central wavelength of the radiation emitted by the optoelectronic device.

An object of one embodiment is to reduce, or even eliminate, the steps of selecting optoelectronic devices formed from the same wafer.

One embodiment provides an optoelectronic device comprising a first light-emitting diode comprising three-dimensional semiconductor elements, each corresponding to a microwire, a nanowire, or a conical or truncated element of micrometric or nanometric size, and an active zone covering each three-dimensional semiconductor element, the first light-emitting diode being configured to emit electromagnetic radiation (RL) with an emission spectrum for which the light intensity is greater than 80% of the maximum light intensity of the spectrum over a first wavelength range greater than 30 nm and for which the light intensity is greater than 50% of the maximum light intensity over a second wavelength range less than the first range increased by 30 nm; and a band-pass optical filter covering the first light-emitting diode. This advantageously allows the optoelectronic device to have a narrow emission spectrum while the light-emitting diode has a broad emission spectrum, thereby reducing the manufacturing constraints of the light-emitting diode.

According to one embodiment, the overall dispersion of the equivalent diameters of the three-dimensional semiconductor elements of the first light-emitting diode is between 2% and 100%, preferably between 3% and 25%, more preferably between 5% and 25%, of the average equivalent diameter of the three-dimensional semiconductor elements of the first light-emitting diode. The overall dispersion may be greater than that due only to the manufacturing processes, which makes it possible to simplify the constraints for the manufacturing of the three-dimensional semiconductor elements.

According to one embodiment, the central wavelengths of the radiation emitted by the active zones of the first light-emitting diode of the optoelectronic device are between 400 nm and 480 nm. This makes it possible to produce light-emitting diodes with three-dimensional elements emitting in the blue.

According to one embodiment, each three-dimensional semiconductor element has an equivalent diameter between 0.05 µm and 2 µm.

In one embodiment, the optical bandpass filter has a half-maximum bandwidth of less than 50 nm. In one embodiment, the optical bandpass filter has a transmission maximum at a wavelength between 430 nm and 480 nm.

According to one embodiment, the optoelectronic device comprises a second light-emitting diode having the same structure as the first light-emitting diode, and a block of a first photoluminescent material covering the second light-emitting diode. This allows the production of a display pixel.

According to one embodiment, the optical band-pass filter does not cover the second light-emitting diode. The efficiency losses due to the optical band-pass filter therefore only concern the first light-emitting diode.

According to one embodiment, the anode of the first light emitting diode is not common with the anode of the second light emitting diode and/or the cathode of the first light emitting diode is not common with the cathode of the second light emitting diode. The first and second light emitting diodes can be controlled separately.

According to one embodiment, the optical bandpass filter has a transmission maximum at a wavelength between 430 nm and 480 nm, and the block of the first photoluminescent material is configured to absorb radiation emitted by the second light-emitting diode and convert it into radiation at a wavelength between 510 nm to 570 nm.

According to one embodiment, the optoelectronic device comprises a third light-emitting diode having the same structure as the first light-emitting diode, and a block of a second photoluminescent material, different from the first photoluminescent material, covering the third light-emitting diode.

According to one embodiment, the optical bandpass filter does not cover the third light-emitting diode.

According to one embodiment, the anode of the first light emitting diode is not common with the anode of the third light emitting diode and/or the cathode of the first light emitting diode is not common with the cathode of the third light emitting diode.

According to one embodiment, the optical bandpass filter has a transmission maximum at a wavelength between 430 nm and 480 nm, and the block of the second photoluminescent material is configured to absorb the radiation emitted by the third light-emitting diode and convert it into radiation at a wavelength between 600 nm to 720 nm.

According to one embodiment, the three-dimensional semiconductor elements of the first light-emitting diode are based on a III-V or II-VI compound.

An embodiment also provides a method of manufacturing optoelectronic devices comprising the following steps:
- forming on a plate first light-emitting diodes each comprising three-dimensional semiconductor elements each corresponding to a microwire, a nanowire, or a conical or truncated element of micrometric or nanometric size, and an active zone covering each three-dimensional semiconductor element, each first light-emitting diode being configured to emit radiation with an emission spectrum for which the light intensity is greater than 80% of the maximum light intensity of the spectrum over a first wavelength range greater than 30 nm and for which the light intensity is greater than 50% of the maximum light intensity over a second wavelength range less than the first range increased by 30 nm;
- forming a bandpass optical filter covering the first light-emitting diode for each optoelectronic device; and
- cut the plate to separate the first light-emitting diodes.

This advantageously allows optoelectronic devices formed on the same wafer to have the same narrow emission spectrum while light-emitting diodes have broad, possibly offset, emission spectra, thereby reducing manufacturing constraints on light-emitting diodes.

The first light-emitting diodes are formed by epitaxial growth. According to one embodiment, the method comprises a step of forming on the plate a mask comprising openings, and a step of growing the three-dimensional semiconductor elements in the openings, in which the overall dispersion of the equivalent diameters of the openings is between 2% and 100% of the average equivalent diameter of the three-dimensional semiconductor elements of the first light-emitting diode.

These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in connection with the attached figures, among which:

there represents, for several plates, the median wavelength of the radiation emitted by the light-emitting diodes of the plate as a function of the median diameter of the light-emitting diodes of the plate;

there represents, for several plates, the maximum wavelength of the radiation emitted by the light-emitting diodes of the plate as a function of the median diameter of the light-emitting diodes of the plate;

there is a partial and schematic sectional view of an embodiment of an optoelectronic device with light-emitting diodes;

there is a partial, schematic, sectional view of one embodiment of a light-emitting diode;

there is a partial and schematic top view of an embodiment of the arrangement of the light-emitting diodes of the optoelectronic device shown in ;

there schematically represents a curve showing the evolution of the luminous intensity of the radiation emitted by the light-emitting diodes of the optoelectronic device of the ;

there schematically represents the curve of the evolution of the luminous intensity of the radiation emitted by the light-emitting diodes represented in on which is superimposed the response curve of the optical filter of the optoelectronic device of the ;

there schematically represents a curve showing the evolution of the luminous intensity of the radiation emitted by the optoelectronic device of the ;

there is a partial, schematic, sectional view of another embodiment of an optoelectronic device with light-emitting diodes; and

there , there , there , there , and the are cross-sectional views of structures obtained at successive stages of an embodiment of a method of manufacturing the optoelectronic device of the .

The same elements have been designated by the same references in the different figures. In particular, the structural and/or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties. For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed. In particular, the electrical connections of the light-emitting diodes of an optoelectronic device are not described.

Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

In the following description, when absolute positional qualifiers, such as "front", "back", "top", "bottom", "left", "right", etc., or relative positional qualifiers, such as "above", "below", "upper", "lower", etc., or orientational qualifiers, such as "horizontal", "vertical", etc., are referred to, unless otherwise specified, the orientation of the figures or an optoelectronic device in a normal position of use are referred to. Furthermore, unless otherwise specified, the terms "insulator" and "conductor" are herein deemed to mean "electrically insulating" and "electrically conductive", respectively.

Unless otherwise specified, the expressions "approximately", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

In the remainder of the description, the internal transmittance of a layer corresponds to the ratio between the intensity of the radiation leaving the layer and the intensity of the radiation entering the layer. The absorption of the layer is equal to the difference between 1 and the internal transmittance. In the remainder of the description, a layer is said to be transparent to radiation when the absorption of the radiation through the layer is less than 60%. In the remainder of the description, a layer is said to be absorbent to radiation when the absorption of the radiation in the layer is greater than 60%. When radiation has a spectrum of general "bell" shape, for example of Gaussian shape, having a maximum, the wavelength of the radiation, or central or main wavelength of the radiation, is called the wavelength at which the maximum of the spectrum is reached. In the remainder of the description, the refractive index of a material corresponds to the refractive index of the material for the wavelength range of the radiation emitted by the optoelectronic device. Unless otherwise stated, the refractive index is considered substantially constant over the wavelength range of the useful radiation, for example equal to the average of the refractive index over the wavelength range of the radiation emitted by the optoelectronic device.

The present invention relates to the manufacture of optoelectronic devices comprising at least one light-emitting diode formed from three-dimensional semiconductor elements of nanometric or micrometric size, in particular microwires, nanowires, or conical or truncated elements of micrometric or nanometric size, in particular pyramids.

By three-dimensional semiconductor element of nanometric or micrometric size, we mean a three-dimensional structure of elongated shape, for example cylindrical, in a preferred direction, of which at least two dimensions, called minor dimensions, are between 5 nm and 2.5 µm, preferably between 50 nm and 2.5 µm. The third dimension, called major dimension, is greater than or equal to 1 time, preferably greater than or equal to 5 times and even more preferably greater than or equal to 10 times, the largest of the minor dimensions. In certain embodiments, the minor dimensions may be less than or equal to approximately 1 µm, preferably between 100 nm and 1 µm, more preferably between 100 nm and 800 nm. In certain embodiments, the height of the three-dimensional semiconductor element may be greater than or equal to 500 nm, preferably between 1 µm and 50 µm. The term "microwire" or "nanowire" refers to a three-dimensional semiconductor element of cylindrical or substantially cylindrical shape. In the remainder of the description, the term "wire" is used to mean "microwire or nanowire".

The cross-section of the wires may have various shapes, for example, an oval, circular or polygonal shape, including triangular, rectangular, square or hexagonal. It will be understood that the term "equivalent diameter" used in relation to a cross-section of a wire means a quantity associated with the area of the wire in that cross-section, corresponding, for example, to the diameter of the disk having the same area as the cross-section of the wire.

In the remainder of the description, embodiments will be described in the case of an optoelectronic device with light-emitting diodes comprising three-dimensional semiconductor elements corresponding to wires. However, it is clear that these embodiments may relate to an optoelectronic device with light-emitting diodes whose three-dimensional semiconductor elements are conical or truncated elements of micrometric or nanometric size, in particular pyramids.

Tests were performed to characterize the dispersion of the central wavelength of the radiation emitted by light-emitting diodes formed on 200 mm diameter semiconductor wafers. For the tests, the light-emitting diodes are of the radial type and are formed by metal-organic chemical vapor deposition (MOCVD). In addition, the three-dimensional semiconductor elements of the light-emitting diodes are wires. The light-emitting diodes, and in particular the wires, are formed under identical growth conditions for all the wafers so that the light-emitting diodes should theoretically have the same structure and dimensions.

There and the represent, for several plates as a function of the median diameter Dmed of the wires of the light-emitting diodes of the plate, respectively the median wavelength λmed and the maximum wavelength λmax of the radiation emitted by all the light-emitting diodes of the plate. In Figures 1 and 2, each point corresponds to a plate. The median diameter Dmed is determined from one hundred wires located at the center of the plate. In Figures 1 and 2, the lines D1 and D2 were obtained by linear regression. Figures 1 and 2 illustrate the dispersion on the wavelengths which results from the processes of forming light-emitting diodes by epitaxial growth.

There is a partial and schematic sectional view of an embodiment of an optoelectronic device 5 with nanowires or microwires. The optoelectronic device 5 comprises from bottom to top in :
- a substrate 10 comprising opposite faces 12 and 14, the upper face 12 preferably being flat at least at the level of the light-emitting diodes;
- a germination layer 16 made of a material promoting the growth of threads and arranged on the face 12, which may not be present;
- an insulating layer 18 covering the seed layer 16 and comprising openings 20 exposing portions of the seed layer 16;
- at least one light-emitting diode GLED comprising elementary light-emitting diodes LED (a single light-emitting diode GLED comprising six elementary light-emitting diodes is shown as an example in ), each elementary light-emitting diode LED each emitting radiation R_LED, each elementary light-emitting diode LED being in contact with the seed layer 16 through one of the openings 20;
- an insulating layer 24 extending over the lateral sides of a lower portion of each elementary light-emitting diode LED and extending over the insulating layer 18 between the elementary light-emitting diodes LED;
- a layer 26 transparent to the electromagnetic radiation R_LED emitted by the elementary light-emitting diodes LED, forming an electrode covering each elementary light-emitting diode LED and further extending over the insulating layer 24 between the elementary light-emitting diodes LED;
- a conductive and reflective layer 28, extending over the layer 26 between the elementary light-emitting diodes LED, the conductive layer 28 being able, as a variant, to be interposed between the electrode layer 26 and the insulating layer 24 between the elementary light-emitting diodes LED;
- an encapsulation layer 34 transparent to the electromagnetic radiation R_LED emitted by the elementary light-emitting diodes LED, extending over the layers 26 and 28, in physical contact with the layers 26 and 28, completely covering the elementary light-emitting diodes LED, and comprising an upper face 35, preferably flat; and
- an optical filter F_LED resting on the face 35 and covering the elementary light-emitting diodes LED, and adapted, in operation, to carry out a band-pass type wavelength filtering of the radiation RL emitted by the light-emitting diode GLED, to provide radiation R which escapes from the optoelectronic device 5.

The GLED light-emitting diode includes all the elementary LED light-emitting diodes connected together. , the elementary light-emitting diodes LED of the GLED light-emitting diode are connected in parallel. Generally, the elementary light-emitting diodes LED of the GLED light-emitting diode can be connected in series and/or in parallel. The radiation RL emitted by the GLED light-emitting diode corresponds to the sum of the radiations R_LED emitted by the elementary light-emitting diodes LED of the GLED light-emitting diode.

The optoelectronic device 5 may comprise additional layers not shown, in particular moisture and/or airtight protective layers, an anti-reflection layer, etc. Alternatively, the encapsulation layer 34 may not be present. In this case, the optical filter F_LED extends over the layers 26 and 28, in physical contact with the layers 26 and 28, and completely covers the light-emitting diodes LED.

According to one embodiment, the optoelectronic device 5 comprises a density of elementary light-emitting diodes greater than 400/mm ² , preferably greater than 20,000/mm ² , even more preferably greater than 40,000/mm ² .

According to another embodiment, the substrate 10 is only present at intermediate stages of the method of producing the optoelectronic device 5 but is then removed and is not present on the final product.

There represents an embodiment of the elementary light-emitting diodes LED. Each elementary light-emitting diode LED comprises a wire 21 in contact with the seed layer 16 through one of the openings 20 and a shell 22 comprising a stack of semiconductor layers covering the side walls and the top of the wire 21. The assembly formed by each wire 21 and the associated shell 22 constitutes an elementary light-emitting diode LED.

The shell 22 may comprise a stack of several layers including in particular an active layer 23 and a bonding layer 25. The active layer 23 is the layer from which the majority of the radiation provided by the elementary light-emitting diode LED is emitted. According to one example, the active layer 23 may comprise confinement means, such as a single quantum well or multiple quantum wells. The bonding layer 25 may comprise a stack of semiconductor layers of the same material as the wire 21 but of the opposite conductivity type to the wire 21. The thickness of the active layer 23 may be between 2 nm and 100 nm.

There is a partial and schematic top view of an embodiment of the arrangement, called a square mesh, of the wires 21 of the elementary light-emitting diodes LED on the substrate 10, the other elements of the optoelectronic device 5 not being shown. In the arrangement illustrated in , an elementary light-emitting diode LED is located at each intersection of a row and a column, the rows being perpendicular to the columns, three rows of three elementary light-emitting diodes LED being shown for illustration purposes. In the embodiment illustrated in the , each wire 21 has a circular cross section of diameter D in a plane parallel to the face 12. As a variant, each wire 21 may have a cross section that is not circular, for example an oval, circular or polygonal shape, in particular triangular, rectangular, square or hexagonal. In this case, the equivalent diameter of the cross section of the wire 21 as defined above is considered. The pitch according to the rows and/or columns may be between 0.1 µm and 50 µm. As a variant, the elementary light-emitting diodes LED may be arranged in another arrangement, for example in a hexagonal arrangement. According to one embodiment, each elementary light-emitting diode LED is adapted to emit radiation R_LED whose central wavelength is in the range from 380 nm to 480 nm, or in the plate from 500 nm to 570 nm, or in the plate from 590 nm to 650 nm.

According to one embodiment, at least some of the wires 21 of the elementary light-emitting diodes LED making up the light-emitting diode GLED have different equivalent diameters D. The overall dispersion of a physical parameter related to the elementary light-emitting diodes is called the standard deviation of this parameter which is measured by taking into account all the elementary light-emitting diodes of the light-emitting diode GLED, the standard deviation is taken relative to the average of the parameter for all the elementary light-emitting diodes of the light-emitting diode GLED. According to one embodiment, the overall dispersion of the equivalent diameters of the wires 21 of the elementary light-emitting diodes LED of the light-emitting diode GLED is greater than 20 nm, preferably greater than 100 nm, more preferably greater than 300 nm. The average equivalent diameter, which is the average of the equivalent diameters D of the wires 21 can be between 0.05 µm and 4 µm. According to one embodiment, the overall dispersion of the equivalent diameters of the wires 21 is between 2% and 100% of the average equivalent diameter of the wires, preferably between 3% and 25% of the average equivalent diameter of the wires, more preferably between 5% and 25% of the average equivalent diameter of the wires.

The local dispersion of a physical parameter related to the elementary light-emitting diodes is called the standard deviation of this parameter which is measured at a point on the face 12 by taking into account the hundred elementary light-emitting diodes closest to this point, the standard deviation is taken relative to the average of the parameter for these hundred elementary light-emitting diodes. According to one embodiment, the local dispersion of the equivalent diameters of the wires 21 of the elementary light-emitting diodes LED of the light-emitting diode GLED is greater than 20 nm, preferably greater than 100 nm, more preferably greater than 300 nm, at any location on the light-emitting diode GLED.

The local/global dispersions indicated above are strictly greater than those resulting from the process of forming elementary light-emitting diodes by epitaxial growth.

According to one embodiment, the local and/or global dispersion of the equivalent diameters indicated above is obtained by providing openings 20 whose equivalent diameters are different. According to one embodiment, the global dispersion of the openings 20 of the light-emitting diode GLED is greater than 20 nm. The average equivalent diameter of the openings 20 can be between 0.01 µm and 4 µm. According to one embodiment, the local dispersion of the openings 20 of the light-emitting diode GLED is greater than 10 nm, at any location on the light-emitting diode GLED.

According to one embodiment, the local and/or global dispersion of the equivalent diameters indicated above is obtained by arranging the wires 21 in an irregular arrangement. Indeed, the diameter of the wires depends in particular on the pitch of the mesh. According to one embodiment, the global dispersion of the pitch of the wires 21 of the light-emitting diode GLED is greater than 10 nm. According to one embodiment, the local dispersion of the pitch of the wires of the light-emitting diode GLED is greater than 10 nm, at any location on the light-emitting diode GLED.

There schematically represents, as a function of the wavelength λ, a curve of evolution C1 of the luminous intensity I of the radiation RL emitted by the light-emitting diode GLED, which corresponds to the sum of the radiations R_LED emitted by the elementary light-emitting diodes LED of the light-emitting diode GLED of the , that is to say before filtering by the optical filter F_LED obtained when the local dispersion of the equivalent diameters of the wires 21 of the elementary light-emitting diodes LED of the light-emitting diode GLED is greater than 80 nm.

The curve C1 has a general "plateau" shape, that is to say that it has, over a first range of wavelengths Δλ greater than 30 nm, preferably greater than 40 nm, more preferably greater than 50 nm, a luminous intensity of between 80% of the maximum intensity Imax and the maximum intensity Imax of the layer C1 and that it has over a second range Δλ2 of wavelengths less than the first range Δλ1 increased by 30 nm, preferably increased by 20 nm, more preferably increased by 15 nm, a luminous intensity of between 50% of the maximum intensity Imax and the maximum intensity Imax of the layer C1. The evolution curve C1 has a significantly flatter shape than the curve representing the luminous intensity of the radiation R_LED emitted by a single elementary light-emitting diode LED of the light-emitting diode GLED which has a "bell" shape with a maximum at the central wavelength of the elementary light-emitting diode LED. This is due to the fact that, since the wires 21 have different diameters, the central wavelengths of the radiation R_LED emitted by the elementary light-emitting diodes LED of the light-emitting diode GLED are different, the radiation RL emitted by the light-emitting diode GLED corresponding to the sum of the radiation R_LED emitted by all the elementary light-emitting diodes LED of the light-emitting diode GLED.

According to one embodiment, the overall dispersion of the central wavelengths of the radiation emitted by the elementary light-emitting diodes of the GLED light-emitting diode is greater than 40 nm. According to one embodiment, the local dispersion of the central wavelengths of the radiation emitted by the elementary light-emitting diodes of the GLED light-emitting diode is greater than 40 nm.

A method of manufacturing the optoelectronic device 5 comprises forming the three-dimensional elementary light-emitting diodes LED on a wafer, and cutting the wafer to separate the optoelectronic device from the rest of the wafer. The formation of the three-dimensional elementary light-emitting diodes on the wafer notably comprises epitaxial growth steps. Several examples of the optoelectronic device 5 can be produced simultaneously on the same wafer, then separated.

There schematically represents, in a solid line, the evolution curve C1 represented in of the intensity of the RL radiation emitted by the GLED light-emitting diode of the , on which is superimposed, in short dotted lines, the response curve F of the optical filter F_LED of the optoelectronic device 5 of the . The F curve has a peak at a wavelength λ ₀ . According to one embodiment, the bandwidth of the F curve at half-height for the peak at the wavelength λ ₀ is less than 50 nm, preferably less than 30 nm. According to one embodiment, the wavelength λ ₀ is between 430 nm and 480 nm.

In , we have shown, in long dotted lines, a curve of evolution C1' of the luminous intensity I of the radiation emitted by the light-emitting diode of an optoelectronic device having the same structure as the optoelectronic device 5 of the and which was manufactured on the same wafer. The C1' curve has the same shape as the C1 curve but can be shifted in wavelength relative to the C1 curve. This shift results from the dispersion obtained on the diameters of the wires of the elementary light-emitting diodes LED on the wafer scale, in particular due to the epitaxial growth steps.

There schematically represents a curve C2 of the evolution of the luminous intensity I of the radiation R emitted by the optoelectronic device 5 of the for which the radiation RL emitted by the light-emitting diode GLED has the intensity curve C1. The curve C2 has a peak at the wavelength λ ₀ . According to one embodiment, the bandwidth of the curve C2 at mid-height for the peak at the wavelength λ ₀ is less than 50 nm, preferably less than 30 nm. The same curve C2 is obtained for the optoelectronic device for which the radiation emitted by the light-emitting diode has the intensity curve C1'. This therefore means that the radiation R emitted by the optoelectronic device 5 has the same spectrum regardless of the dimensional dispersion due to its manufacturing process. Since the spectrum of the radiation R emitted by the optoelectronic device 5 is obtained in a controlled manner, there is no need to carry out testing and sorting steps to select the optoelectronic device according to its emission spectrum.

The substrate 10 may correspond to a single-piece structure or correspond to a layer covering a support made of another material. The substrate 10 is preferably a semiconductor substrate, for example a substrate made of silicon, germanium, silicon carbide, a III-V compound, such as GaN or GaAs, or a ZnO substrate. Preferably, the substrate 10 is a monocrystalline silicon substrate. Preferably, it is a semiconductor substrate compatible with the manufacturing methods implemented in microelectronics. The substrate 10 may correspond to a multilayer structure of the silicon on insulator type, also called SOI (English acronym for Silicon On Insulator).

The cross section of the openings 20 may correspond to the desired cross section of the wires 21 or may be different from the cross section of the wires that will be obtained. The equivalent diameter of the wires 21 may be equal to or greater than the equivalent diameter of the openings 20.

The seed layer 16 is made of a material that promotes the growth of the wires. For example, the material composing the seed layer 16 may be a nitride, a carbide or a boride of a transition metal from column IV, V or VI of the periodic table of elements or a combination of these compounds. For example, the seed layer 16 may be aluminum nitride (AlN), boron (B), boron nitride (BN), titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), hafnium (Hf), hafnium nitride (HfN), niobium (Nb), niobium nitride (NbN), zirconium (Zr), zirconium borate (ZrB ₂ ), zirconium nitride (ZrN), silicon carbide (SiC), tantalum nitride and carbide (TaCN), magnesium nitride in the form Mg _x N _y , where x is approximately equal to 3 and y is approximately equal to 2, for example magnesium nitride in the form Mg ₃ N ₂ or magnesium gallium nitride (MgGaN), tungsten (W), magnesium nitride in the form Mg 3 N 2 or magnesium gallium nitride (MgGaN), tungsten (WN) or a combination thereof. The seed layer 16 may have a single-layer structure or correspond to a stack of at least two layers, each layer being for example in one of the materials described above.

According to another embodiment, the seed layer 16 may not be present. According to another embodiment, the seed layer 16 may be replaced by seed pads, for example formed at the bottom of the openings 20.

Each insulating layer 18, 24 may be made of a dielectric material, for example silicon oxide (SiO ₂ ), silicon nitride (Si _x N _y , where x is approximately equal to 3 and y is approximately equal to 4, for example Si ₃ N ₄ ), silicon oxynitride (in particular of general formula SiO _x N _y , for example Si ₂ ON ₂ ), aluminum oxide (Al ₂ O ₃ ), hafnium oxide (HfO ₂ ), titanium dioxide (TiO ₂ ) or diamond. The insulating layer 18, 24 may have a single-layer structure or correspond to a stack of two layers or more than two layers. When the insulating layer 18 corresponds to a stack of at least two layers, the upper layer of the stack is of the insulating type, for example made of a dielectric material.

The wires 21 comprise in majority, preferably more than 60% by mass, more preferably more than 80% by mass, at least one semiconductor material. The semiconductor material can be silicon, germanium, silicon carbide, a III-V compound, a II-VI compound or a combination of at least two of these compounds.

Examples of group III elements include gallium (Ga), indium (In), or aluminum (Al). Examples of III-N compounds are GaN, AlN, InN, InGaN, AlGaN, or AlInGaN. Other group V elements may also be used, for example, phosphorus or arsenic. Generally, the elements in the III-V compound may be combined with different mole fractions. Examples of group II elements include group IIA elements, including beryllium (Be) and magnesium (Mg), and group IIB elements, including zinc (Zn), cadmium (Cd), and mercury (Hg). Examples of group VI elements include group VIA elements, including oxygen (O) and tellurium (Te). Examples of II-VI compounds are ZnO, ZnMgO, CdZnO, CdZnMgO, CdHgTe, CdTe or HgTe. In general, the elements in the II-VI compound can be combined with different mole fractions. The semiconductor material of the wires can have a dopant, for example silicon providing N-type doping of a III-N compound, or magnesium providing P-type doping of a III-N compound.

The conductive layer 28 preferably corresponds to a metal layer, for example made of aluminum, silver, copper, gold or zinc. The thickness of the conductive layer 28 may be between 0.01 µm and 1000 µm.

The electrode layer 26 may be a layer of a transparent and conductive material such as indium-tin oxide (or ITO), zinc oxide doped with aluminum or gallium, or graphene. The electrode layer 26 may be a metal layer, in particular made of silver, aluminum, or titanium, thin enough to be transparent to the radiation emitted by the elementary light-emitting diodes LED. The thickness of the electrode layer 26 may be between 0.01 μm and 10 μm.

The encapsulation layer 34 may be made of an inorganic material at least partially transparent to the radiation emitted by the photoluminescent particles and/or the elementary light-emitting diodes LED. For example, the inorganic material is chosen from the group comprising silicon oxides, of the SiO _x type where x is a real number that varies from 1 to 2, silicon nitrides (Si _x N _y , where x is approximately equal to 3 and y is approximately equal to 4, for example Si ₃ N ₄ ), silicon oxynitrides (in particular of general formula SiO _x N _y , for example Si ₂ ON ₂ ), titanium oxide, aluminum oxides, for example Al ₂ O ₃ , and mixtures of these compounds. The encapsulation layer 34 may be made of an organic material at least partially transparent. For example, the encapsulation layer 34 is a silicone polymer, an epoxy polymer, an acrylic polymer or a polycarbonate. The encapsulation layer 34 may have a single-layer or multi-layer structure, and may comprise, for example, a stack of organic and/or inorganic layers.

The filtering of the radiation emitted by the elementary light-emitting diodes LED of the light-emitting diode GLED can be carried out by any means. According to one embodiment, the filtering is obtained by covering the elementary light-emitting diodes LED of the light-emitting diode GLED with a layer of a colored material. According to another embodiment, the filtering is obtained by covering the elementary light-emitting diodes LED of the light-emitting diode GLED with an interference filter. Preferably, the optical filter F_LED comprises a layer of colored resin. The optical filter F_LED can have a thickness of between 10 nm and 200 µm.

There is a partial and schematic sectional view of an embodiment of an optoelectronic device 50 with nanowires or microwires. The optoelectronic device 50 comprises all of the elements of the optoelectronic device 5 shown in , three GLED light-emitting diodes being shown as an example in , and further includes from bottom to top in :
- a dielectric protection layer 30 extending over layers 26 and 28;
- photoluminescent blocks 32, 33 covering the elementary light-emitting diodes LED of some of the light-emitting diodes GLED (for example the two light-emitting diodes GLED on the left in ), the encapsulation layer 34 corresponding to encapsulation blocks 34 covering the elementary light-emitting diodes of other GLED light-emitting diodes (for example the GLED light-emitting diode on the right in ) ;
- an insulating layer 36 covering the upper face of each block 32, 33, 34, or only of some of the blocks 32, 33, 34, the insulating layer 36 possibly not being present;
- a protective layer 37 covering the insulating layers 36, the side faces of the blocks 32, 33, 34 and the electrode layer 26 between the blocks 32, 34;
- walls 38 between the blocks 32, 34, each wall 38 comprising a core 40 surrounded by a reflective coating 42;
- the optical filter F_LED covering the blocks 34, and possibly other optical filters 43, 44 covering the photoluminescent blocks 32 and 33, for example two filters 43, 44, the first being a green filter and the second being a red filter; and
- a protective layer 46 covering the entire structure, the protective layer 46 may not be present.

In the present embodiment, the electrode layer 26 is common to the GLED light-emitting diodes. The GLED light-emitting diodes can be controlled separately by specific connections, not shown, provided in the substrate 10. Generally, the anodes of the light-emitting diodes and/or the cathodes of the light-emitting diodes are not common in order to be able to control the GLED light-emitting diodes separately.

According to one embodiment, the radiation emitted by one of the photoluminescent blocks 33, 34, after passing through the optical filter 43, 44 covering the photoluminescent block when this optical filter is present, corresponds to green light, i.e. radiation whose wavelength is in the range from 510 nm to 570 nm. According to one embodiment, the radiation emitted by another of the photoluminescent blocks 33, 34, after passing through the optical filter 43, 44 covering the photoluminescent block when this optical filter is present, corresponds to red light, i.e. radiation whose wavelength is in the range from 600 nm to 720 nm.

According to one embodiment, the diameters of the wires 21 of all the elementary light-emitting diodes LED of the light-emitting diodes GLED of the optoelectronic device 50 are different as described for the optoelectronic device 5. As shown in , for the elementary light-emitting diodes LED covered with the photoluminescent blocks 32, 33, the optical filter F_LED may not be present between the elementary light-emitting diodes LED and the photoluminescent blocks 32, 33. The dispersion of the central wavelengths of the radiation emitted by the elementary light-emitting diodes LED which are covered with the photoluminescent blocks 32, 33 has substantially no impact on the spectrum of the radiation emitted by the photoluminescent blocks 32, 33. Indeed, the photoluminescent blocks 32, 33 are adapted to absorb the radiation emitted by the elementary light-emitting diodes LED over a wavelength range that is sufficiently wide to contain the central wavelengths of the radiation emitted by the elementary light-emitting diodes LED despite the dispersion of the central wavelengths of the radiation emitted by the elementary light-emitting diodes LED.

According to one embodiment, the optoelectronic device 50 corresponds to a display pixel in which each light-emitting diode GLED emits blue-colored radiation RL. The filter F_LED which covers one of the light-emitting diodes GLED is a band-pass filter centered on a wavelength in the blue and the photoluminescent blocks 32, 33 which cover the other light-emitting diodes GLED allow, for example, the obtaining of green and red colors. Advantageously, for each light emitting diode GLED covered by a photoluminescent block 32, 33, there is no loss of emission efficiency because the entire broad spectrum radiation of the light emitting diodes GLED is converted by the photoluminescent blocks 32, 33. As for obtaining white light, the proportion of blue light is approximately only 5%, the loss of emission efficiency due to the F_LED filter is reduced compared to the entire display pixel.

Each insulating layer 30, 36, 37, 46 may have the same composition as that previously described for the insulating layers 18, 24. The coating 42 may have the same composition as that previously described for the conductive layer 28.

According to one embodiment, each photoluminescent block 32, 33 is located opposite a set of elementary light-emitting diodes LED. Each photoluminescent block 32, 33 comprises phosphors adapted, when excited by the light emitted by the associated elementary light-emitting diodes LED, to emit light at a wavelength different from the wavelength of the light emitted by the associated elementary light-emitting diodes LED. According to one embodiment, the optoelectronic device 5 comprises at least two types of photoluminescent blocks 32, 33. Each photoluminescent block 32 of the first type is adapted to convert the radiation provided by the elementary light-emitting diodes that it covers into a first radiation at a first wavelength and each photoluminescent block 33 of the second type is adapted to convert the radiation provided by the elementary light-emitting diodes that it covers into a second radiation at a second wavelength. The aspect ratio of the blocks 32, 33, i.e. the ratio between the height and the maximum width of the block, may be between 0.01 and 10, preferably between 0.05 and 2.

According to one embodiment, each photoluminescent block 32, 33 comprises particles of at least one photoluminescent material, for example in a transparent matrix. An example of a photoluminescent material is yttrium aluminum garnet (YAG) activated by trivalent cerium ion, also called YAG:Ce or YAG:Ce ³⁺ . The average particle size of conventional photoluminescent materials is generally greater than 5 µm.

According to one embodiment, each photoluminescent block 32, 33 comprises a matrix in which are dispersed nanometric-sized monocrystalline particles of a semiconductor material, also called semiconductor nanocrystals or nanoluminophore particles hereinafter. The internal quantum efficiency QY _int of a photoluminescent material is equal to the ratio between the number of photons emitted and the number of photons absorbed by the photoluminescent substance. The internal quantum efficiency QY _int of the semiconductor nanocrystals is greater than 5%, preferably greater than 10%, more preferably greater than 20%.

According to one embodiment, the average size of the nanocrystals is in the range of 0.5 nm and 1000 nm, preferably from 0.5 nm to 500 nm, even more preferably from 1 nm to 100 nm, in particular from 2 nm to 30 nm. For dimensions less than 50 nm, the photoconversion properties of the semiconductor nanocrystals depend essentially on quantum confinement phenomena. The semiconductor nanocrystals then correspond to quantum dots.

According to one embodiment, the semiconductor material of the semiconductor nanocrystals is selected from the group comprising cadmium selenide (CdSe), indium phosphide (InP), cadmium sulfide (CdS), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium telluride (CdTe), zinc telluride (ZnTe), cadmium oxide (CdO), zinc cadmium oxide (ZnCdO), zinc cadmium sulfide (CdZnS), zinc cadmium selenide (CdZnSe), silver indium sulfide (AgInS ₂ ), perovskites of the PbScX ₃ type, where X is a halogen atom, in particular iodine (I), bromine (Br) or chlorine (Cl), and a mixture of at least two of these compounds. According to one embodiment, the semiconductor material of the semiconductor nanocrystals is selected from the materials cited in the publication in the name of Le Blevenec et al. of Physica Status Solidi (RRL) - Rapid Research Letters Volume 8, No. 4, pages 349–352, April 2014.

According to one embodiment, the dimensions of the semiconductor nanocrystals are chosen according to the desired wavelength of the radiation emitted by the semiconductor nanocrystals. For example, CdSe nanocrystals whose average size is of the order of 3.6 nm are suitable for converting blue light into red light and CdSe nanocrystals whose average size is of the order of 1.3 nm are suitable for converting blue light into green light. According to another embodiment, the composition of the semiconductor nanocrystals is chosen according to the desired wavelength of the radiation emitted by the semiconductor nanocrystals.

The matrix is at least partly transparent to the radiation emitted by the photoluminescent particles and/or the elementary light-emitting diodes LED, preferably more than 80%. The matrix is, for example, made of silica. The matrix is, for example, made of any polymer that is at least partly transparent, in particular silicone, epoxy, acrylic resin of the poly(methyl methacrylate) (PMMA) type, or polyacetic acid (PLA). The matrix may in particular be made of an at least partly transparent polymer used with three-dimensional printers. The matrix may correspond to a glass deposited by centrifugation (SOG, acronym for Spin On Glass), photosensitive or non-photosensitive. According to one embodiment, the matrix contains from 2% to 90%, preferably from 10% to 60%, by weight of nanocrystals, for example approximately 30% by weight of nanocrystals.

The thickness of the photoluminescent blocks 32, 33 depends on the concentration of nanocrystals and the type of nanocrystals used. The height of the photoluminescent blocks 32, 33 is preferably greater than the height of the wires 21 and less than or equal to the height of the walls 38. In top view, each photoluminescent block 32, 33 may correspond to a square, a rectangle, an "L" shaped polygon, etc., the area of which may be equal to the area of a square having a side measuring from 1 µm to 100 µm, preferably from 3 µm to 15 µm.

The walls 38 are at least partially made of a reflective material. The reflective material may be a metallic material, including iron, copper, aluminum, tungsten, silver, titanium, hafnium, zirconium, or a combination of at least two of these compounds. Preferably, the walls 38 are formed of a material compatible with manufacturing processes used in microelectronics. Preferably, the walls 38 are formed of aluminum or silver.

The height of the walls 38, measured in a direction perpendicular to the face 12, is in the range of 300 nm to 200 µm, preferably 3 µm to 15 µm. The thickness of the walls 38, measured in a direction parallel to the face 12, is in the range of 100 nm to 50 µm, preferably 0.5 µm to 10 µm.

According to one embodiment, the walls 38 may be formed from a reflective material or covered with a coating reflecting the wavelength of the radiation emitted by the photoluminescent blocks 32, 33 and/or the elementary light-emitting diodes.

Preferably, the walls 38 surround the photoluminescent blocks 32, 33. The walls 38 then reduce crosstalk between adjacent photoluminescent blocks 32, 33.

The protective layer 46 is at least partially transparent to the radiation emitted by the photoluminescent particles and/or the elementary light-emitting diodes LED. The encapsulation layer may be made of an inorganic material at least partially transparent to the radiation emitted by the photoluminescent particles and/or the elementary light-emitting diodes LED. For example, the inorganic material is chosen from the group comprising silicon oxides, of the SiO _x type where x is a real number between 1 and 2 or SiO _y N _z where y and z are real numbers between 0 and 1, titanium oxide, aluminum oxides, for example Al ₂ O ₃ , and mixtures of these compounds. The encapsulation layer may be made of an organic material at least partially transparent. For example, the encapsulation layer is a silicone polymer, an epoxy polymer, an acrylic polymer or a polycarbonate. The encapsulation layer 46 may have a single-layer or multi-layer structure, and comprise, for example, a stack of organic and/or inorganic layers.

There , there , there , there , and the are cross-sectional views of structures obtained at successive stages of an embodiment of a method of manufacturing the optoelectronic device 5 of the .

There represents the structure obtained after the formation of the seed layer 16 on a substrate 10, which corresponds, at this stage of the process, to a plate having a diameter for example greater than 100 mm.

There represents the structure obtained after the deposition of the insulating layer 18 on the seed layer 16 and formation of the openings 20 in the insulating layer, for example by anisotropic etching, to expose the portions of the seed layer. According to one embodiment, the equivalent diameters of the openings 20 are different to obtain wires 21 of different equivalent diameters in the next step of the method.

There represents the structure obtained after the growth of the wires 21. The growth process of the wires 21 and the other layers of the elementary light-emitting diodes LED may be a process of the type or a combination of processes of the type chemical vapor deposition (CVD) or metal-organic chemical vapor deposition (MOCVD), also known as metal-organic vapor phase epitaxy (or MOVPE). However, processes such as molecular beam epitaxy (MBE), gas source MBE (GSMBE), metal-organic MBE (MOMBE), plasma-assisted MBE (PAMBE), atomic layer epitaxy (ALE) or hydride vapor phase epitaxy (HVPE) can be used. However, electrochemical processes can be used, for example, chemical bath deposition (CBD), hydrothermal processes, liquid aerosol pyrolysis or electrodeposition.

There represents, on a reduced scale compared to FIGS. 10A to 10C, the structure obtained after the formation of the rest of the elementary light-emitting diodes LED, the formation of the encapsulation layer 34 and the formation of the optical filter F_LED.

There represents the structure obtained after cutting the structure represented in to obtain several copies of the optoelectronic device 5. As an example, two cutting paths 52 are shown schematically in . The cutting step may include a step of sawing the structure shown in .

Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, although in the embodiments described above, the elementary light-emitting diodes are of the radial type, it is clear that the present embodiments can be implemented with elementary light-emitting diodes that are of the axial type for which the active zone of the elementary light-emitting diode is present only at the top of the wire.

Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims (19)

Optoelectronic device (5; 50) comprising:
- a first light-emitting diode (GLED) comprising three-dimensional semiconductor elements (21), each corresponding to a microwire, a nanowire, or a conical or truncated element of micrometric or nanometric size, and an active zone (23) covering each three-dimensional semiconductor element, the first light-emitting diode being configured to emit radiation (RL) with an emission spectrum for which the light intensity is greater than 80% of the maximum light intensity of the spectrum over a first wavelength range greater than 30 nm and for which the light intensity is greater than 50% of the maximum light intensity over a second wavelength range less than the first range increased by 30 nm; and
- a band-pass optical filter (F_LED) covering the first light-emitting diode. Optoelectronic device according to claim 1, wherein the overall dispersion of the equivalent diameters of the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED) is between 2% and 100% of the average equivalent diameter of the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED). Optoelectronic device according to claim 2, wherein the overall dispersion of the equivalent diameters of the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED) is between 3% and 25% of the average equivalent diameter of the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED). Optoelectronic device according to any one of claims 1 to 3, in which the central wavelengths of the radiation emitted by the active zones (23) of the first light-emitting diode (GLED) are between 400 nm and 480 nm. An optoelectronic device according to any one of claims 1 to 4, wherein each three-dimensional semiconductor element (21) has an equivalent diameter of between 0.05 µm and 2 µm. Optoelectronic device according to any one of claims 1 to 5, wherein the optical bandpass filter (F_LED) has a half-maximum bandwidth of less than 50 nm. Optoelectronic device according to any one of claims 1 to 6, in which the optical bandpass filter (F_LED) has a transmission maximum at a wavelength between 430 nm and 480 nm. Optoelectronic device according to any one of claims 1 to 7, comprising a second light-emitting diode (GLED) having the same structure as the first light-emitting diode, and a block (32) of a first photoluminescent material covering the second light-emitting diode. Optoelectronic device according to claim 8, wherein the optical band-pass filter (F_LED) does not cover the second light-emitting diode (GLED). Optoelectronic device according to claim 8 or 9, wherein the anode of the first light emitting diode is not common with the anode of the second light emitting diode and/or the cathode of the first light emitting diode is not common with the cathode of the second light emitting diode. Optoelectronic device according to any one of claims 8 to 10, wherein the optical bandpass filter (F_LED) has a transmission maximum at a wavelength between 430 nm and 480 nm, and wherein the block (32) of the first photoluminescent material is configured to absorb the radiation emitted by the second light-emitting diode and convert it into radiation at a wavelength between 510 nm and 570 nm. Optoelectronic device according to any one of claims 8 to 11, comprising a third light-emitting diode (GLED) having the same structure as the first light-emitting diode, and a block (33) of a second photoluminescent material, different from the first photoluminescent material, covering the third light-emitting diode. Optoelectronic device according to claim 12, wherein the optical band-pass filter (F_LED) does not cover the third light-emitting diode (GLED). Optoelectronic device according to claim 12 or 13, wherein the anode of the first light emitting diode is not common with the anode of the third light emitting diode and/or the cathode of the first light emitting diode is not common with the cathode of the third light emitting diode. Optoelectronic device according to any one of claims 12 to 14, wherein the optical bandpass filter (F_LED) has a transmission maximum at a wavelength between 430 nm and 480 nm, and wherein the block (33) of the second photoluminescent material is configured to absorb the radiation emitted by the third light-emitting diode and convert it into radiation at a wavelength between 600 nm and 720 nm. Optoelectronic device according to any one of claims 1 to 15, in which the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED) are based on a III-V or II-VI compound. Method for manufacturing optoelectronic devices (5; 50) comprising the following steps:
- forming on a plate first light-emitting diodes (GLEDs) each comprising three-dimensional semiconductor elements (21), each corresponding to a microwire, a nanowire, or a conical or truncated element of micrometric or nanometric size, and an active zone (23) covering each three-dimensional semiconductor element, each first light-emitting diode being configured to emit radiation (RL) with an emission spectrum for which the light intensity is greater than 80% of the maximum light intensity of the spectrum over a first wavelength range greater than 30 nm and for which the light intensity is greater than 50% of the maximum light intensity over a second wavelength range less than the first range increased by 30 nm;
- forming a band-pass optical filter (F_LED) covering the first light-emitting diode for each optoelectronic device; and
- cut the plate to separate the first light-emitting diodes. The method of claim 17, wherein the first light emitting diodes (GLEDs) are formed by epitaxial growth. A method according to claim 17 or 18, comprising a step of forming on the plate a mask (18) comprising openings (20), and a step of growing the three-dimensional semiconductor elements (21) in the openings, in which the overall dispersion of the equivalent diameters of the openings is between 2% and 100% of the average equivalent diameter of the three-dimensional semiconductor elements (21) of the first light-emitting diode (GLED).