Optoelectronic device with axial 3D diode

Abstract

The present disclosure relates to an optoelectronic device (10) including an array (15) of axial light emitting diodes (LEDs), each having an active region (20) configured to emit electromagnetic radiation having an emission spectrum with a maximum at a first wavelength, and the array forming a photonic crystal configured to form three resonant peaks that amplify the intensity of the electromagnetic radiation at at least a second, third, and fourth wavelength.

Description

[Technical Field]

[0001] This disclosure relates to optoelectronic devices, particularly display screens or image projection devices comprising light-emitting diodes made of semiconductor materials, and methods for manufacturing the same. [Background technology]

[0002] Light-emitting diodes (LEDs) based on semiconductor materials generally have an active region, which is the area of ​​the LED from which the majority of the electromagnetic radiation provided by the LED is emitted. The structure and composition of the active region are configured to obtain electromagnetic radiation with desired properties. In particular, it is generally desired to obtain narrow-spectrum electromagnetic radiation that is ideally substantially monochromatic.

[0003] Here, optoelectronic devices comprising axial three-dimensional light-emitting diodes are considered. An axial three-dimensional light-emitting diode is a light-emitting diode comprising three-dimensional semiconductor elements, each extending along a preferred direction, and having an active region at the axial end of the three-dimensional semiconductor element.

[0004] Examples of three-dimensional semiconductor devices include microwires or nanowires comprising semiconductor materials based on compounds mainly comprising at least one group III element and one group V element, hereinafter referred to as III-V compounds (e.g., gallium nitride GaN), or compounds mainly comprising at least one group II element and one group VI element, hereinafter referred to as II-VI compounds (e.g., zinc oxide ZnO). Such devices are described, for example, in French Patent Application Publication No. 2995729 and French Patent Application Publication No. 2997558.

[0005] Confinement methods, particularly the formation of active regions comprising single quantum wells or multiple quantum wells, are known. A single quantum well is formed by sandwiching a layer of a second semiconductor material (e.g., an alloy of a III-V compound and a third element, particularly InGaN) having a different band gap from the first semiconductor material between two layers of a first semiconductor material (e.g., a III-V compound, particularly GaN) doped with P-type and N-type, respectively. A multiple quantum well structure comprises a laminate of semiconductor layers that alternately form quantum wells and barrier layers.

[0006] The wavelength of electromagnetic radiation emitted by the active region of a photoelectronic device depends particularly on the band gap of the second material forming the quantum well. When the second material is an alloy of III-V compounds and a third element (e.g., InGaN), the wavelength of the emitted radiation depends particularly on the atomic percentage of the third element (e.g., indium). In particular, the higher the atomic percentage of indium, the longer the wavelength.

[0007] The drawback is that when the atomic percentage of indium exceeds a threshold, differences in lattice parameters between GaN and InGaN in the quantum well are observed, potentially leading to the formation of non-radiative defects in the active region, such as dislocations, and a significant decrease in the quantum efficiency of the active region of the optoelectronic device. Therefore, there is a maximum wavelength of radiation emitted by optoelectronic devices having an active region with a single or multiple quantum well based on III-V or II-VI compounds. Forming light-emitting diodes made from III-V or II-VI compounds that emit red light can be particularly challenging.

[0008] However, the use of materials made from III-V or II-VI compounds is desirable because there are methods to grow such materials on large-sized substrates at low cost by epitaxy.

[0009] It is known to cover a light-emitting diode with a photoluminescence material that can convert electromagnetic radiation emitted by an active region into electromagnetic radiation of different wavelengths, particularly high wavelengths. However, such photoluminescence materials are costly, have low conversion efficiency, and may degrade in performance over time.

[0010] Also, it can be difficult to form an axial three-dimensional light-emitting diode based on a III-V or II-VI compound that has an active region with desired properties, particularly a narrow band including near the target emission frequency in the emission spectrum.

[0011] Furthermore, the industrial development of a method for manufacturing the active region of an axial three-dimensional light-emitting diode based on a III-V or II-VI compound requires delicate operations. Therefore, it is desirable to be able to form all the active regions of the light-emitting diodes of an optoelectronic device simultaneously with the same structure and the same composition, and then change the emission spectra of a group of light-emitting diodes without using a photoluminescence material.

Summary of the Invention

[0012] Therefore, an object of one embodiment is to overcome all or part of the drawbacks of the aforementioned optoelectronic device including a light-emitting diode.

[0013] Another object of one embodiment is that the active region of each light-emitting diode comprises a stack of semiconductor materials based on a III-V or II-VI compound.

[0014] Another object of one embodiment is that the optoelectronic device comprises a light-emitting diode configured to emit red light radiation without using a photoluminescence material.

[0015] Another object of one embodiment is that an axial three-dimensional light-emitting diode based on a III-V or II-VI compound has desired characteristics, particularly an active region having a light-emitting spectrum including a narrow band near a target emission frequency.

[0016] Another object of one embodiment is that the emission frequency of a light-emitting diode can be changed after forming the active region of the light-emitting diode without using a photoluminescence material.

[0017] One embodiment provides an optoelectronic device comprising an array of axial light-emitting diodes, each light-emitting diode comprising an active region configured to emit electromagnetic radiation having a light-emitting spectrum with a maximum value at a first wavelength, the array forming a photonic crystal configured to form three resonance peaks that amplify the intensity of the electromagnetic radiation at at least second, third, and fourth wavelengths.

[0018] According to one embodiment, each active region is configured to emit electromagnetic radiation having a light-emitting spectrum with a full width at half maximum in the range of 100 nm to 180 nm.

[0019] According to one embodiment, the photonic crystal is a two-dimensional photonic crystal.

[0020] According to one embodiment, the light-emitting diodes are arranged in the array at a pitch in the range of 400 nm to 475 nm, and each light-emitting diode is cylindrical with an average diameter in the range of 270 nm to 300 nm.

[0021] According to one embodiment, the light-emitting diodes are based on III-V or II-VI compounds.

[0022] According to one embodiment, the light-emitting diodes are separated by an electrically insulating material having a refractive index in the range of 1.3 to 1.6, preferably 1.45 to 1.56.

[0023] According to one embodiment, one of the second, third, and fourth wavelengths is in the range of 430 nm to 480 nm, another of the second, third, and fourth wavelengths is in the range of 510 nm to 570 nm, and yet another of the second, third, and fourth wavelengths is in the range of 600 nm to 720 nm.

[0024] According to one embodiment, the emission spectrum of the active region has energy at a second wavelength.

[0025] According to one embodiment, the device further comprises a first optical filter covering at least a first portion of the array of light-emitting diodes, the first optical filter configured to block the amplified radiation over a first wavelength range including first, third, and fourth wavelengths and to allow the amplified radiation to pass over a second wavelength range including a second wavelength.

[0026] According to one embodiment, the emission spectrum of the active region has energy at a third wavelength.

[0027] According to one embodiment, the device further comprises a second optical filter covering at least a second portion of the array of light-emitting diodes. The second optical filter is configured to block the amplified radiation over a third wavelength range including first, second, and fourth wavelengths, and to allow the amplified radiation to pass over a fourth wavelength range including the third wavelength.

[0028] According to one embodiment, the emission spectrum of the active region has energy at a fourth wavelength.

[0029] According to one embodiment, the device further comprises a third optical filter covering at least a third portion of the array of light-emitting diodes, the third optical filter configured to block the amplified radiation over a fifth wavelength range including first, second, and third wavelengths, and to allow the amplified radiation to pass over a sixth wavelength range including a fourth wavelength.

[0030] According to one embodiment, the optoelectronic device comprises a support on which light-emitting diodes are mounted, and each light-emitting diode comprises a laminate of a first semiconductor portion mounted on the support, an active region in contact with the first semiconductor portion, and a second semiconductor portion in contact with the active region.

[0031] According to one embodiment, the second semiconductor portion of the light-emitting diode is covered with a conductive layer that is at least partially transparent to the radiation emitted by the light-emitting diode.

[0032] According to one embodiment, at least one of the resonance peaks is attenuated relative to the other resonance peaks.

[0033] According to one embodiment, the sidewalls of at least a portion of the first and second semiconductor portions of the light-emitting diode are covered with a sheath.

[0034] According to one embodiment, a first portion of the conductive layer covering a first group of light-emitting diodes has a first thickness, and a second portion of the conductive layer covering a second group of light-emitting diodes has a second thickness that is smaller than the first thickness.

[0035] According to one embodiment, the first group of light-emitting diodes is separated by a first electrical insulating material having a first refractive index, and the second group of light-emitting diodes is separated by a second electrical insulating material having a second refractive index different from the first refractive index.

[0036] Furthermore, one embodiment provides a method for manufacturing a photoelectronic device comprising an array of axial light-emitting diodes, each light-emitting diode having an active region configured to emit electromagnetic radiation having an emission spectrum with a maximum value at a first wavelength, and the array forms a photonic crystal configured to form three resonant peaks that amplify the intensity of the electromagnetic radiation at at least second, third, and fourth wavelengths.

[0037] According to one embodiment, the formation of an array of light-emitting diodes includes the steps of forming second semiconductor portions on a substrate that are separated from each other by the pitch of the array, forming active regions on each of the second semiconductor portions, and forming first semiconductor portions on each of the active regions.

[0038] According to one embodiment, the light-emitting diodes are divided into at least first and second groups. The method includes forming a first optical filter in the first group and forming a second optical filter in the second group that is different from the first optical filter.

[0039] According to one embodiment, the method includes attenuating at least one of the resonant peaks relative to other resonant peaks after forming a light-emitting diode. [Brief explanation of the drawing]

[0040] The above and other features and advantages are described in detail in the following specific embodiments, which are given as examples and do not limit the invention with reference to the accompanying drawings.

[0041] [Figure 1] This is a partially schematic cross-sectional view of one embodiment of an optoelectronic device comprising a light-emitting diode. [Figure 2] Figure 1 is a partial schematic perspective view of the optoelectronic device shown. [Figure 3] Figure 1 is a schematic diagram illustrating an example of the layout of a light-emitting diode in an optoelectronic device. [Figure 4] This figure schematically shows another example of the layout of the light-emitting diode in the optoelectronic device shown in Figure 1. [Figure 5] Figure 1 schematically shows the curve of change in the light intensity of radiation emitted by the photoelectron device, and illustrates a configuration with three resonances. [Figure 6] This diagram shows how to select one resonance of radiation in a configuration with three resonances. [Figure 7]This diagram shows how to select other resonances for radiation in a configuration with three resonances. [Figure 8] This diagram shows how to select two resonances for radiation in a configuration with three resonances. [Figure 9] This diagram shows how to select one resonance of radiation in a configuration with three resonances. [Figure 10] This figure schematically shows the curve of change in the light intensity of radiation emitted by a photoelectronic device, and illustrates a configuration with one resonance obtained from an initial configuration with three resonances. [Figure 11] Figure 10 is a partially schematic cross-sectional view of one embodiment of a photoelectronic device having an emission spectrum. [Figure 12] Figure 10 is a partially schematic cross-sectional view of one embodiment of a photoelectronic device having an emission spectrum. [Figure 13] Figure 10 is a partially schematic cross-sectional view of one embodiment of a photoelectronic device having an emission spectrum. [Figure 14A] Figure 1 shows the steps of one embodiment of a method for manufacturing the optoelectronic device shown in Figure 1. [Figure 14B] This diagram shows the other steps in the manufacturing process. [Figure 14C] This diagram shows the other steps in the manufacturing process. [Figure 14D] This diagram shows the other steps in the manufacturing process. [Figure 14E] This diagram shows the other steps in the manufacturing process. [Figure 14F] This diagram shows the other steps in the manufacturing process. [Figure 14G] This diagram shows the other steps in the manufacturing process. [Figure 15] This figure shows the steps of another embodiment of the method for manufacturing the optoelectronic device shown in Figure 1. [Figure 16] This is a grayscale map of the light intensity emitted at a first wavelength by a light-emitting diode in a photonic crystal of an optoelectronic device, corresponding to the pitch of the photonic crystal and the diameter of the light-emitting diode. [Figure 17]This is a grayscale map of the light intensity emitted at a second wavelength by a light-emitting diode in a photonic crystal of an optoelectronic device, corresponding to the pitch of the photonic crystal and the diameter of the light-emitting diode. [Figure 18] This is a grayscale map of the light intensity emitted at a third wavelength by a light-emitting diode in a photonic crystal of an optoelectronic device, corresponding to the pitch of the photonic crystal and the diameter of the light-emitting diode. [Figure 19] This figure shows the curve of the change in light intensity of a light-emitting diode as it changes with wavelength, as measured in the test. [Modes for carrying out the invention]

[0042] Similar features are designated by similar reference numerals in various drawings. In particular, structural and / or functional features common among various embodiments may have the same reference numerals and may have identical structural, dimensional, and material properties. For clarity, only steps and elements useful for understanding the embodiments described herein are illustrated and described in detail. In particular, the optoelectronic devices considered may optionally comprise other components, which are not described here.

[0043] In the following description, when referring to terms that modify absolute positions, such as "front," "back," "top," "bottom," "left," and "right," terms that modify relative positions, such as "top," "bottom," "upper side," and "lower side," or terms that modify directions, such as "horizontal" and "vertical," it refers to the optoelectronic device in the orientation shown in the figure or in its normal operating position.

[0044] The expressions “approximately,” “about,” “substantially,” and “to the extent,” unless otherwise specified, represent a range of 10%, preferably 5%, of the value in question. Furthermore, the terms “insulating” and “conductive” are understood to mean “electrical insulating” and “electrical conductive,” respectively.

[0045] In the following explanation, the internal transmittance of a layer corresponds to the ratio of the radiation intensity emanating from the layer to the radiation intensity entering the layer. The absorptance of a layer is equal to the difference between 1 and the internal transmittance. In the following explanation, a layer is said to be transparent to radiation if the absorptance of radiation passing through it is less than 60%. In the following explanation, a layer is said to absorb radiation if the absorptance of radiation passing through it is greater than 60%. When radiation exhibits a generally "Bell" type spectrum, such as a Gaussian spectrum with a maximum value, the expressive wavelength of the radiation, or the central or dominant wavelength of the radiation, refers to the wavelength at which the spectrum reaches its maximum value. In the following explanation, the refractive index of a material corresponds to the refractive index of the material with respect to the wavelength range of radiation emitted by the optoelectronic device. Unless otherwise specified, the refractive index is considered to be substantially constant over the useful wavelength range of radiation, for example, equal to the average refractive index over the wavelength range of radiation emitted by the optoelectronic device.

[0046] Furthermore, "compounds mainly formed of materials" or "compounds based on materials" means that the proportion of the material in the compound is 95% or more, preferably 99% or more. The term axial light-emitting diode refers to a three-dimensional structure having, for example, a cylindrical elongated shape, which has at least two dimensions called minor dimensions along the principal direction, in the range of 5 nm to 2.5 μm, preferably in the range of 50 nm to 2.5 μm. A third dimension called the major dimension is at least 1 times, preferably 5 times or more, and more preferably 10 times or more, the largest minor dimension. In certain embodiments, the minor dimensions may be approximately 1 μm or less, preferably in the range of 100 nm to 1 μm, more preferably in the range of 100 nm to 800 nm. In certain embodiments, the height of each light-emitting diode may be 500 nm or more, preferably in the range of 1 μm to 50 μm. The diameter of a wire with a circular base having the same area as the area of ​​the base of the wire considered is called the average diameter of the wire.

[0047] Figures 1 and 2 are a partial schematic side cross-sectional view and a perspective view, respectively, of an embodiment of a photoelectronic device 10 comprising a light-emitting diode.

[0048] The optoelectronic device 10 comprises the following elements, from bottom to top in Figure 1: Support 12; A first electrode layer 14 is placed on a support 12 and has an upper surface 16; An array of axial light-emitting diodes (LEDs) 15 is placed on the upper surface 16: Each axial light-emitting diode comprises, from bottom to top in Figure 1, a lower semiconductor portion 18 (not shown in Figure 2) in contact with the electrode layer 14, an active region 20 (not shown in Figure 2) in contact with the semiconductor portion 18, and an upper semiconductor portion 22 (not shown in Figure 2) in contact with the active region 20; An insulating layer 24 extends between the light-emitting diodes (LEDs) along the entire height of the LED; A second electrode layer 26 (not shown in Figure 2) that contacts the upper semiconductor portion 22 of the light-emitting diode LED and covers the light-emitting diode LED; and A coating 28 (not shown in Figure 2) covers the second electrode layer 26 and defines the light-emitting surface 30 of the optoelectronic device 10.

[0049] Each light-emitting diode (LED) is called axial because its active region 20 is aligned with the lower portion 18 and its upper portion 22 is aligned with the active region 20. The assembly comprising the lower portion 18, the active region 20, and the upper portion 22 extends along an axis Δ, which is called the axis of the axial light-emitting diode. Preferably, the axis Δ of the light-emitting diode LED is parallel and perpendicular to the plane 16.

[0050] The support 12 may correspond to an electronic circuit. The electrode layer 14 may be made of a metal (e.g., silver, copper, or zinc). The thickness of the electrode layer 14 is sufficient for it to form a mirror. For example, the electrode layer 14 has a thickness greater than 100 nm. The electrode layer 14 may completely cover the support 12. As a variation, the electrode layer 14 may be divided into separate parts to allow separate control of groups of light-emitting diodes in an array of light-emitting diodes. According to one embodiment, the surface 16 may be reflective. In that case, the electrode layer 14 may have specular reflection. According to another embodiment, the electrode layer 14 may have Lambertian reflection. To obtain a surface with Lambertian reflection, irregularities can be created on the conductive surface. As an example, if the surface 16 corresponds to the surface of a conductive layer placed on a base, the surface of the base may be texturized before the deposition of the metal layer so that the surface 16 of the deposited metal layer shows raised portions.

[0051] The second electrode layer 26 is conductive and transparent. According to one embodiment, the electrode layer 26 is a transparent conductive oxide (TCO) layer such as indium tin oxide (ITO), aluminum or gallium-doped or undoped zinc oxide, or graphene. As an example, the electrode layer 26 has a thickness in the range of 5 nm to 200 nm, preferably in the range of 20 nm to 50 nm. The insulating layer 24 may be made of an inorganic material (e.g., silicon oxide or silicon nitride). The insulating layer 24 may be made of an organic material (e.g., a benzocyclobutene (BCB)-based insulating polymer). The coating 28 may comprise one optical filter or a plurality of optical filters arranged adjacent to each other, as will be further detailed later. According to one embodiment, the refractive index of the insulating layer 24 material is in the range of 1.3 to 1.6, preferably in the range of 1.45 to 1.56.

[0052] In the embodiments shown in Figures 1 and 2, all light-emitting diode LEDs have the same height. The thickness of the insulating layer 24 is selected, for example, to be equal to the height of the light-emitting diode LED so that the upper surface of the insulating layer 24 is flush with the upper surface of the light-emitting diode.

[0053] According to one embodiment, the semiconductor portions 18, 22 and the active region 20 are made of a semiconductor material at least partially. The semiconductor material is selected from the group consisting of III-V compounds, II-VI compounds, and group IV semiconductors or compounds. Examples of group III elements include gallium (Ga), indium (In), or aluminum (Al). Examples of group V elements include nitrogen (N), phosphorus (P), or arsenic (As). Examples of III-N compounds are GaN, AlN, InN, InGaN, AlGaN, or AlInGaN. Examples of group II elements include group IIA elements (particularly beryllium (Be) and magnesium (Mg)) and group IIB elements (particularly zinc (Zn), cadmium (Cd), and mercury (Hg)). Examples of group VI elements include group VIA elements, partly oxygen (O) and tellurium (Te). Examples of II-VI compounds are ZnO, ZnMgO, CdZnO, CdZnMgO, CdHgTe, CdTe, or HgTe. In general, the elements of III-V or II-VI compounds may be combined in different mole fractions. Examples of Group IV semiconductor materials are silicon (Si), carbon (C), germanium (Ge), silicon carbide alloy (SiC), silicon germanium alloy (SiGe), or germanium carbide alloy (GeC). Semiconductor portions 18 and 22 may contain dopants. For example, in the case of III-V compounds, the dopant may be selected from the group consisting of P-type Group II dopants (e.g., magnesium (Mg), zinc (Zn), cadmium (Cd), or mercury (Hg)), P-type Group IV dopants (e.g., carbon (C)), or N-type Group IV dopants (e.g., silicon (Si), germanium (Ge), selenium (Se), sulfur (S), terbium (Tb), or tin (Sn)). Preferably, the semiconductor portion 18 is made of P-doped GaN and the semiconductor portion 22 is made of N-doped GaN.

[0054] For each light-emitting diode (LED), the active region 20 may be provided with a confinement means. For example, the active region 20 may be provided with a single quantum well. In that case, the active region 20 includes a semiconductor material different from the semiconductor material forming the semiconductor portions 18 and 22, and has a band gap smaller than the band gap of the material forming the semiconductor portions 18 and 22. The active region 20 may be provided with multiple quantum wells. In that case, it includes a laminate of semiconductor layers in which quantum wells and barrier layers are alternately formed.

[0055] In Figures 1 and 2, each light-emitting diode (LED) has a cylindrical shape with a circular base and an axis Δ. However, each light-emitting diode (LED) may have a cylindrical shape with an axis Δ and a polygonal (e.g., square, rectangular, or hexagonal) base. Preferably, each light-emitting diode (LED) has a cylindrical shape with a hexagonal base.

[0056] The sum of the height h1 of the lower portion 18, the height h2 of the active region 20, the height h3 of the upper portion 22, the thickness of the electrode layer 26, and the thickness of the coating 28 is called the height H of the light-emitting diode LED.

[0057] According to one embodiment, the light-emitting diodes (LEDs) are arranged to form a photonic crystal. Figure 2 shows an example of 12 light-emitting diodes. In practice, the array 15 may comprise 7 to 100,000 light-emitting diodes.

[0058] The light-emitting diode LEDs in array 15 are arranged in rows and columns (Figure 2 shows an example with 3 rows and 4 columns). The pitch "a" of array 15 is the distance between the axis of one light-emitting diode LED and the axis of a nearby light-emitting diode LED in the same row or an adjacent row. The pitch a is substantially constant. More specifically, the pitch a of the array is chosen so that array 15 forms a photonic crystal. The formed photonic crystal is, for example, a two-dimensional photonic crystal.

[0059] The properties of the photonic crystal formed by the array 15 are advantageously selected to achieve coupling and enhance the selective effect, particularly so that the array 15 of light-emitting diodes forms resonant cavities in a plane perpendicular to axis Δ and resonant cavities along axis Δ. This makes it possible to amplify the intensity of radiation emitted through the light-emitting surface 30 by the array of light-emitting diode LEDs of the array 15 at a specific wavelength, compared to an assembly of light-emitting diode LEDs that does not form a photonic crystal.

[0060] Figures 3 and 4 schematically show examples of the layout of the light-emitting diode (LED) array 15. In particular, Figure 3 shows a so-called square grid layout, and Figure 4 shows a so-called hexagonal grid layout. Figures 3 and 4 each show three rows, each having four LEDs. In the layout shown in Figure 3, the LEDs are located at each intersection of rows and columns, and the rows are perpendicular to the columns. In the layout shown in Figure 4, the diodes in one row are shifted by half a pitch a relative to the LEDs in the previous and next rows.

[0061] In the embodiments shown in Figures 3 and 4, each light-emitting diode LED has a circular cross-section with a diameter D in a plane parallel to the plane 16. In the case of a hexagonal or square grid layout, the diameter D may be in the range of 0.05 μm to 2 μm. The pitch a may be in the range of 0.1 μm to 4 μm.

[0062] Furthermore, according to one embodiment, the height H of the light-emitting diode LED is selected such that each light-emitting diode LED forms a resonant cavity along axis Δ at a desired central wavelength λ of radiation emitted by the optoelectronic device 10. According to one embodiment, the height H is selected to be substantially proportional to k × (λ / 2) × neff, where neff is the effective refractive index of the light-emitting diode in the optical mode under consideration, and k is a positive integer. The effective refractive index is defined, for example, in "Semiconductor Optoelectronic Devices: Introduction to Physics and Simulation" by Joachim Piprek.

[0063] However, even if the light-emitting diodes are divided into multiple groups of diodes that emit light at different central wavelengths, the height H of all the diodes may be the same. This height may be determined from the theoretical heights at which a resonant cavity can be obtained for the diodes in each group, for example, equal to the average of these theoretical heights.

[0064] According to one embodiment, the properties of the photonic crystal formed by the array of light-emitting diodes (LEDs) 15 are selected to increase the light intensity emitted by the array of light-emitting diodes 15 at at least three target wavelengths. According to one embodiment, the active region 20 of each light-emitting diode has a relatively broad emission spectrum, and in particular has a maximum value at a first wavelength, with a full width at half maximum greater than 100 nm, preferably greater than 180 nm, so as to cover three target wavelengths. That is, the energy of the emission spectrum of the active region 20 at the target wavelengths is not null. According to one embodiment, the maximum value of the spectrum of radiation emitted by the active region 20 is at wavelengths different from at least two target wavelengths.

[0065] FIG. 5 schematically shows a change curve C1 (solid line) of the light intensity I emitted by the active region 20 of the light-emitting diode LED considered individually according to the wavelength λ, a change curve C2 (broken line in FIG. 5, solid line in FIGS. 6 to 10) of the amplification factor due to the coupling with the photonic crystal, and a change curve C3 (dotted line) of the light intensity emitted by the array 15 of the light-emitting diodes. The curve C1 has a general "bell" shape and has a peak at the center wavelength λ C . The curve C2 includes three narrow resonance peaks: a first resonance peak P1 centered on the target wavelength λ T1 , a second resonance peak P2 centered on the target wavelength λ T2 , and a third resonance peak P3 centered on the target wavelength λ T3 . The curve C3 includes intensity peaks P'1, P'2, and P'3 at the target wavelengths λ T1 , λ T2 , and λ T3 , and substantially follows the curve C1 at other wavelengths. In particular, the full width at half maximum at the peak S of the curve C1 is, for example, 2 times, particularly 10 times larger than the full width at half maximum at each of the peaks P'1, P'2, and P'3 of the curve C3.

[0066] According to one embodiment, the target wavelength λ T1 corresponds to radiation having a wavelength in the range of blue light, that is, 430 nm to 480 nm. According to one embodiment, the target wavelength λ T2 corresponds to radiation having a wavelength in the range of green light, that is, 510 nm to 570 nm. According to one embodiment, the target wavelength λ T3 corresponds to radiation having a wavelength in the range of red light, that is, 600 nm to 720 nm.

[0067] According to one embodiment, the target wavelengths λ T1 , λ T2 or λ T3One of these, a photoelectronic device 10 that emits narrow-spectrum light emission, can be obtained by filtering the radiation emitted by an array of light-emitting diodes (LEDs) 15 so as to retain only the intensity peak at a desired target wavelength. This may also be achieved by providing an optical filter in the coating 28.

[0068] Figures 6 and 7 illustrate the principle of filtering the radiation emitted by the array of light-emitting diodes 15. A photoelectronic device that emits narrow-spectrum light radiation centered on a target wavelength can be obtained by blocking unwanted portions of the emission spectrum of the array of light-emitting diodes 15. For example, in Figures 6 and 7, the blocked portions of the spectrum of radiation emitted by the array of light-emitting diodes 15 are hatched, leaving only one resonance peak. In Figure 6, the target wavelength λ is shown. T1 The resonance peak P1 is shown in Figure 7, and the target wavelength λ is shown in Figure 7. T3 The resonance peak P3 is retained.

[0069] Furthermore, the height h1 of the lower portion 18 and the height h2 of the upper portion 22 may be advantageously determined such that the peak light intensity at the target wavelength is maximized.

[0070] Filtering of radiation emitted by an array of light-emitting diodes may be performed by any means. According to one embodiment, filtering may be achieved by covering the light-emitting diodes with a layer of colored material. According to another embodiment, filtering may be achieved by covering the light-emitting diodes with an interference filter.

[0071] According to one embodiment, the light-emitting diodes in an array of light-emitting diodes may be divided into first and second groups of light-emitting diodes. First filtering is performed on the first group of light-emitting diodes to retain only a first resonance peak, and second filtering is performed on the second group of light-emitting diodes to retain only a second resonance peak. Thus, a photoelectronic device can be obtained that is configured to emit a first radiation at a first target wavelength and a second radiation at a second target wavelength, and the active regions of the first and second groups of light-emitting diodes and the array of light-emitting diodes have the same structure.

[0072] According to one embodiment, the light-emitting diodes (LEDs) may be divided into first, second, and third groups. First filtering is performed on the first group of LEDs to retain only the first resonance peak. Second filtering is performed on the second group of LEDs to retain only the second resonance peak. Third filtering is performed on the third group of LEDs to retain only the third resonance peak. Thus, a photoelectronic device can be obtained that is configured to emit a first radiation at a first target wavelength, a second radiation at a second target wavelength, and a third radiation at a third target wavelength, and the active regions of the first, second, and third groups of LEDs and the array of LEDs have the same structure. This makes it possible to form display subpixels of display pixels, in particular, on a color image display screen.

[0073] According to one embodiment, the filtered radiation from the first group of light-emitting diodes corresponds to blue light, i.e., radiation having a wavelength in the range of 430 nm to 480 nm. According to one embodiment, the filtered radiation from the second group of light-emitting diodes corresponds to green light, i.e., radiation having a wavelength in the range of 510 nm to 570 nm. According to one embodiment, the filtered radiation from the third group of light-emitting diodes corresponds to red light, i.e., radiation having a wavelength in the range of 600 nm to 720 nm.

[0074] Advantageously, active regions 20 having the same structure and composition may be used in the manufacture of optoelectronic devices capable of emitting narrow-spectrum radiation at different target wavelengths. This eliminates the need to design a new structure for the active region when designing new optoelectronic devices, thereby solving all the associated industrial development problems and thus simplifying the design method for new optoelectronic devices. In fact, since all light-emitting diodes can be formed with the same structure, at least the initial steps of the manufacturing method until the light-emitting diode is manufactured may be common to the manufacture of different optoelectronic devices.

[0075] The active region 20 is the target wavelength λ T1 , λ T2 , or λ T3 A different, or at least two different, central wavelength λ C Emitting maximum intensity radiation can be even more advantageous. In fact, for example, if the active region 20 comprises an InGaN layer, the central wavelength of the emitted radiation increases as the proportion of indium increases. However, to obtain an emission wavelength corresponding to red, a proportion of indium greater than 16% is required, which is interpreted as a decrease in the quantum efficiency of the active region. Target wavelength λ T1 Smaller than the center wavelength λ CThe fact that the active region 20 that emits radiation with maximum intensity is used makes it possible to use an active region 20 with improved quantum efficiency. Furthermore, it is easier to manufacture without using photoluminescent materials, and the central wavelength λ C By using the active region 20 that emits radiation with maximum intensity at the target wavelength λ, T1 It becomes possible to obtain radiation in that location.

[0076] An active region 20 that emits radiation having a spectrum broader than the desired spectrum of radiation emitted by the optoelectronic device may also be used. This simplifies the design and manufacture of the active region 20.

[0077] According to other embodiments, the selection of target wavelengths for radiation emitted by the optoelectronic device is broad, but there are three target wavelengths λ T1 , λ T2 , λ T3 This can be obtained by using an active region having an emission spectrum that does not cover the target wavelength λ. In that case, the target wavelength λ is in the band of the radiation emitted by the active region 20 in the radiation emitted by the array of light-emitting diodes 15. T1 , λ T2 , or λ T3 Only one or more intensity peaks may be obtained in this case.

[0078] Figure 8 is similar to Figure 5, but the change curve C1 of the spectrum emitted by the active region 20 corresponds to the target wavelength λ of curve C2. T2 and λ T3 It differs from Figure 5 in that it covers only two narrow resonance peaks centered around λ. The corresponding curve C3 (not shown) has a center wavelength λ C The peak S is at the target wavelength λ. T2 The intensity peak at the target wavelength λ T3 Includes the intensity peak at [location].

[0079] Figure 9 is similar to Figure 5, but the change curve C1 of the spectrum emitted by the active region 20 corresponds to the target wavelength λ of curve C2. T3 It differs from Figure 5 in that it covers only a single, narrow resonance peak centered at λ. The corresponding curve C3 (not shown) has a center wavelength λ. C The vertex S and target wavelength λ at the vertex. T3 Includes the intensity peak at [location].

[0080] More generally, the epitaxial conditions for the growth of the active region 20 are such that the spectrum emitted by the active region 20 is of wavelength λ without altering the photonic crystal. T1 , λ T2 , or λ T3 It is possible to selectively choose to cover only one of these wavelengths. This can be achieved, for example, by changing only the indium concentration in the active region 20, if the active region 20 comprises an InGaN quantum well. This is advantageous because it allows for the industrial production of devices that emit light at three different target wavelengths with almost identical basic manufacturing parameters, except for the growth of the active region 20.

[0081] According to other embodiments, the selection of the target wavelength of radiation emitted by the optoelectronic device can be achieved by modifying the properties of the photonic crystal relative to a reference structure that causes the presence of three resonance peaks, as previously described in relation to Figures 1 and 2, to reduce the amplitude of one of the resonance peaks, preferably eliminating one of the resonance peaks, or by reducing the amplitude of two of the resonance peaks, preferably eliminating two of the resonance peaks. As a result, the spectrum of radiation emitted by the array of light-emitting diodes 15 contains fewer intensity peaks than those obtained with the reference structure. According to one embodiment, modifying the properties of the photonic crystal relative to the reference structure is performed after the array of light-emitting diodes 15 has been formed. One possibility is to introduce elements, particularly nanomaterials, around the wires to promote resonance. Another possibility is to change the material forming the insulating layer 24 and / or coating 28. Yet another possibility is to change the overall height H of the structure by, for example, changing the thickness of the electrode layer 26. As a result, all light-emitting diodes can be formed with the same structure, so that at least the initial steps of the manufacturing method until the light-emitting diodes are manufactured may be common to the manufacturing of different optoelectronic components.

[0082] Figure 10 is a diagram similar to Figure 8, and the target wavelength λ T2 The point where the resonance peak P2 of the amplification coefficient change curve C2 due to the photonic crystal has virtually disappeared, and the target wavelength λ of the change curve C2 T3 This differs from Figure 8 in that the amplitude of the resonance peak P3 is reduced. As a result, the radiation emitted by the array of light-emitting diodes 15 contains a single intensity peak, and there is no need to use an optical filter.

[0083] Figures 11, 12, and 13 are partial schematic cross-sectional views of embodiments of optoelectronic devices that can obtain curves C1 and C2 shown in Figure 10. Coating 28 is present in some cases but is not shown in Figures 11, 12, and 13. For each of the optoelectronic devices, in the first region Z1, the reference structure of the optoelectronic device 10 shown in Figure 1 is maintained so as to obtain radiation with three intensity peaks in the first region Z1, and in the second region Z2, the reference structure of the optoelectronic device 10 shown in Figure 1 is modified so as to obtain radiation with fewer intensity peaks in the second region Z2. In Figure 11, the height H of the light-emitting diode LED is changed in the second region Z2. In Figure 12, the diameter of the light-emitting diode LED is changed in the second region Z2. In Figure 13, the refractive index of the material forming the photonic sensor is changed in the second region Z2.

[0084] Figure 11 shows a photoelectronic device 32 comprising an assembly of elements of the photoelectronic device 10 shown in Figure 1, but differs from Figure 1 in that the electrode layer 26 does not have a constant thickness. For example, the thickness of the electrode layer 26 in the first region Z1 of the photoelectronic device 32 is greater than the thickness of the electrode layer 26 in the second region Z2 of the photoelectronic device 32. According to one embodiment, the thickness of the electrode layer 26 in the first region Z1 is the thickness determined for the reference structure, resulting in three intensity peaks in the radiation supplied by the array of light-emitting diodes (LEDs) 15 in the first region Z1. As the thickness of the electrode layer 26 in the second region Z2 decreases, the properties of the photonic crystal are changed, so that the array of light-emitting diodes (LEDs) 15 in the second region Z2 yields curves C1 and C2 shown in Figure 10.

[0085] Figure 12 shows a photoelectronic device 34 comprising all the elements of the photoelectronic device 10 shown in Figure 1, but differs from Figure 1 in that the sheath 35 surrounds the sidewall of each light-emitting diode LED in the second region Z2. According to one embodiment, each sheath 35 is made of a material having a refractive index close to that of the material forming the semiconductor portions 18 and 22. In this case, the diameter of the light-emitting diodes in the second region Z2 appears to increase with respect to the diameter of the light-emitting diodes in the first region Z1. The increase in diameter in the second region Z2 causes a change in the properties of the photonic crystal, so that the array of light-emitting diode LEDs 15 in the second region Z2 yields the curves C1 and C2 shown in Figure 10.

[0086] Figure 13 shows a photoelectronic device 36 comprising all the elements of the photoelectronic device 10 shown in Figure 1, but differs from Figure 1 in that the insulating layer 24 in the second region Z2 is made of a material having a different refractive index than the first region Z1, which is indicated by the boundary 38 between the two regions Z1 and Z2. The change in the refractive index of the insulating layer 24 in the second region Z2 causes a change in the properties of the photonic crystal, so that the array of light-emitting diodes 15 in the second region Z2 yields the curves C1 and C2 shown in Figure 10.

[0087] Figures 14A to 14G are partial schematic cross-sectional views of structures obtained in successive steps of another embodiment of the manufacturing method for the optoelectronic device 10 shown in Figure 1.

[0088] Figure 14A shows the structure obtained after the following formation steps.

[0089] A seed layer 40 is formed on the substrate 42. Then, a light-emitting diode LED is formed from the seed layer 40. More specifically, the light-emitting diode LED is formed so that the upper portion 22 is in contact with the seed layer 40. The seed layer 40 is made of a material that is favorable for the growth of the upper portion 22. For each light-emitting diode LED, an active region 20 is formed on the upper portion 22, and a lower portion 18 is formed on the active region 20.

[0090] Furthermore, the light-emitting diodes (LEDs) are arranged to form an array 15, that is, to form rows and columns at a desired pitch in the array 15. Figures 14A to 14G show only one row in part.

[0091] To expose only a portion of the seed layer 40 at the location where the light-emitting diode (LED) will be installed, a mask (not shown) may be formed on the seed layer 40 before the LED is formed. As a variation, the seed layer 40 may be etched before the LED is formed to form a pad that will be installed at the location where the LED is formed.

[0092] The growth method for light-emitting diode (LED) may be chemical vapor deposition (CVD) or metal-organic chemical vapor deposition (MOCVD) (also known as metal-organic vapor epitaxy (MOVPE)), or a combination of these methods. However, methods 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 deposition (HVPE) may be used. However, electrochemical processes, such as chemical bath deposition (CBD), hydrothermal processes, liquid aerosol pyrolysis, or electrodeposition, may also be used.

[0093] The growth conditions for the light-emitting diode LEDs are such that all light-emitting diodes in the array 15 are formed at substantially the same rate. Therefore, the heights of the semiconductor portions 22 and 18, as well as the height of the active region 20, are substantially the same for all light-emitting diodes in the array 15.

[0094] According to one embodiment, the height of the semiconductor portion 22 is greater than the desired value h3. In practice, it can be difficult to precisely control the height of the upper portion 22, especially due to the start of growth of the upper portion 22 from the seed layer 40. Furthermore, if the semiconductor material is formed directly on the seed layer 40, crystal defects may occur in the semiconductor material directly above the seed layer 40. Therefore, it may be desirable to remove a portion of the upper portion 22 to obtain a certain height before forming the active region 20.

[0095] Figure 14B shows a structure obtained after forming a layer 24 of a filler material, such as an electrical insulating material (e.g., silicon oxide). The layer 24 is formed, for example, by depositing a layer of filler material on the structure shown in Figure 14A, and the layer has a thickness greater than the height of the light-emitting diode LED. The layer of filler material is then partially removed and flattened to expose the upper surface of the semiconductor portion 18. The upper surface of the layer 24 is then made substantially flush with the upper surface of each semiconductor portion 18. In a modified example, the method may include an etching step of partially etching the semiconductor portion 18.

[0096] The packing material is selected so that the photonic crystal formed by the array 15 has desired properties, that is, so that the intensity of the radiation emitted by the array of light-emitting diodes (LEDs) is selectively improved with respect to wavelength.

[0097] Figure 14C shows the structure obtained after depositing the electrode layer 14 on the structure obtained in the previous step.

[0098] Figure 14D shows a structure obtained after bonding layer 14 to the support 12 by, for example, intermetallic bonding, thermocompression bonding, or soldering using eutectic on the support 12 side.

[0099] Figure 14E shows the structure obtained after removing the substrate 42 and seed layer 40. Furthermore, layer 24 and upper portions 22 are etched so that the height of each upper portion 22 has a desired value h3. This step advantageously allows for precise control of the height h of the light-emitting diode and removal of portions of the upper portion 22 that may have crystal defects.

[0100] Figure 14F shows the structure obtained after the deposition of the electrode layer 26.

[0101] Figure 14G shows a structure obtained after forming at least an optical filter that covers all or part of the structure shown in Figure 14E. As an example, first, second, and third optical filters F are located in the first, second, and third groups of light-emitting diodes (LEDs), respectively. R F G and F B This is shown.

[0102] Figure 15 shows a modified version of the method for manufacturing the optoelectronic device shown in Figure 1. In this method, before the electrode layer 26 is formed, a step is performed to partially etch the free ends of each upper portion 22 of the light-emitting diode LED. The partial etching step may include forming a sloping side portion 44 on the free end of the upper portion 22. This makes it possible to slightly modify the properties of the photonic crystal. Therefore, it is possible to more precisely change the position of the resonance peak of amplification by the photonic crystal.

[0103] Simulations and tests were performed. In these simulations and tests, for each light-emitting diode LED, the lower semiconductor portion 18 is made of P-type doped GaN. The upper semiconductor portion 22 is made of N-type doped GaN. The refractive index of the lower portion 18 and upper portion 22 is approximately 2.4. The active region 20 corresponds to the InGaN layer. The height h2 of the active region 20 is equal to 40 nm. The electrode layer 14 is made of aluminum. The insulating layer 24 is made of BCB polymer. The refractive index of the insulating layer 24 is in the range of 1.45 to 1.56. Specular reflection at surface 16 was considered in the simulations. The heights of portions 18 and 22 are not definitive parameters as they do not substantially change the position of the resonance peak, although they do affect the intensity of the resonance peak.

[0104] Figures 16, 17, and 18 are grayscale maps of the light intensity of radiation emitted from the array of light-emitting diodes (LEDs) 15 at the first, second, and third wavelengths, respectively, in a first direction tilted 5 degrees with respect to the direction perpendicular to the light-emitting surface 30, corresponding to the pitch "a" of the photonic crystal and the diameter "D" of each light-emitting diode. In the simulation, the first wavelength is 450 nm (blue), the second wavelength is 530 nm (green), and the third wavelength is 630 nm (red).

[0105] Each grayscale map contains bright areas corresponding to resonance peaks. These areas with resonance peaks are schematically shown by solid contour line B in Figure 16, dashed contour line G in Figure 17, and dashed contour line R in Figure 18.

[0106] This means that, for example, by selecting the pitch "a" of the photonic crystal and the diameter "D" of the light-emitting diode, the emission spectrum of the array 15 of light-emitting diodes (LEDs) located in one of the regions enclosed by contour B in Figure 16, obtained without filtering, has at least one resonant peak at a wavelength of 450 nm.

[0107] In Figure 17, contour B in Figure 16 is superimposed on contour G. This means that, for example, by selecting the pitch "a" of the photonic crystal and the diameter "D" of the light-emitting diode, the emission spectrum of the array 15 of light-emitting diodes (LEDs) located in one of the regions enclosed by contours B and G in Figure 17, obtained without filtering, has at least one resonant peak at a wavelength of 450 nm and one resonant peak at a wavelength of 530 nm.

[0108] In Figure 18, contour B in Figure 16 and contour G in Figure 17 are superimposed on contour R. This means that, for example, by selecting the pitch "a" of the photonic crystal and the diameter "D" of the light-emitting diode so that they are located in one of the regions enclosed by contours B, G, and R in Figure 18, the emission spectrum of the array of light-emitting diodes 15 obtained without filtering has at least one resonant peak at 450 nm wavelength, a resonant peak at 530 nm wavelength, and a resonant peak at 630 nm wavelength. These three peaks are obtained when the height H is approximately equal to 1 μm, the pitch "a" of the photonic crystal is equal to 400 nm, and the diameter of the circle circumscribing the hexagonal base of the light-emitting diode varies between 260 nm and 270 nm ± 25 nm (corresponding to a correction diameter that varies between 280 nm and 290 nm).

[0109] Please note that optimization can be achieved by changing the heights h1 and h3.

[0110] In the test, the light-emitting diodes have a hexagonal base. It is believed that simulations performed on light-emitting diodes with a circular base of a predetermined radius are equivalent to simulations performed on light-emitting diodes with a hexagonal base where the radius of the circumscribed circle of the cross-section is equal to 1.1 times the predetermined radius. The semiconductor portions 18, 22 and the active region 20 are formed simultaneously by MOCVD in all photodiodes.

[0111] The tests were conducted using the dimensions mentioned above.

[0112] Figure 19 shows the wavelength-dependent change curve CRGB of the light intensity I (arbitrary unit) of the light-emitting diode array 15 in the test. Three resonance peaks at wavelengths of 450 nm, 590 nm, and 700 nm are effectively obtained.

[0113] Various embodiments and modifications have been described. Those skilled in the art will understand that specific features of these embodiments and modifications may be combined, and that other modifications are readily conceivable by those skilled in the art. In particular, the aforementioned coating 28 may comprise additional layers other than one or more optical filters. Specifically, the coating 28 may comprise an anti-reflective layer, a protective layer, and so on. Finally, the practical application of the embodiments and modifications described herein is within the capabilities of those skilled in the art, based on the functional descriptions provided herein.

[0114] This patent application claims priority to French Patent Application No. 20 / 13516, which is deemed to be part of this specification.

Claims

1. The array comprises an array of axial light-emitting diodes, each of which has an active region configured to emit electromagnetic radiation having an emission spectrum with a maximum value at a first wavelength, the axial light-emitting diodes are arranged in the array at substantially constant pitch, and the array forms a photonic crystal configured to form three resonant peaks that amplify the intensity of the electromagnetic radiation emitted by the array at at least second, third, and fourth wavelengths, one of which is 430 nm to 4 The array of axial light-emitting diodes further comprises a first optical filter covering at least a first portion of the array, the first optical filter being configured to block the amplified radiation over a first wavelength range including the first, third, and fourth wavelengths, and to allow the amplified radiation over a second wavelength range including the second wavelength. Optoelectronic devices.

2. Each active region is configured to emit electromagnetic radiation having an emission spectrum with a full width at half maximum greater than 100 nm. The device according to claim 1.

3. A photonic crystal is a two-dimensional photonic crystal. The device according to claim 1.

4. The pitch of the array is in the range of 400 nm to 475 nm, and each of the axial light-emitting diodes is cylindrical with an average diameter in the range of 270 nm to 300 nm. The device according to claim 1.

5. The axial light-emitting diode is separated by an electrical insulating material having a refractive index in the range of 1.3 to 1.

6. The device according to claim 1.

6. The emission spectrum of the active region has energy at the second wavelength, The device according to claim 1.

7. The emission spectrum of the active region has energy at a third wavelength. The device according to claim 6.

8. The array of axial light-emitting diodes further comprises a second optical filter covering at least a second portion of the array, the second optical filter being configured to block the amplified radiation over a third wavelength range including the first, second, and fourth wavelengths, and to allow the amplified radiation to pass over a fourth wavelength range including the third wavelength. The device according to claim 7.

9. The emission spectrum of the active region has energy at a fourth wavelength. The device according to claim 7.

10. The system further comprises a third optical filter covering at least a third portion of the array of axial light-emitting diodes, wherein the third optical filter is configured to block the amplified radiation over a fifth wavelength range including the first, second, and third wavelengths, and to allow the amplified radiation to pass over a sixth wavelength range including the fourth wavelength. The device according to claim 9.

11. The device comprises a support on which the axial light-emitting diodes are mounted, and each of the axial light-emitting diodes comprises a laminate of a first semiconductor portion mounted on the support, an active region in contact with the first semiconductor portion, and a second semiconductor portion in contact with the active region. The device according to claim 1.

12. The second semiconductor portion of the axial light-emitting diode is covered with a conductive layer that is at least partially transparent to radiation emitted by the axial light-emitting diode, at least one of the resonance peaks is attenuated relative to the other resonance peaks, the first portion of the conductive layer covering the first group of axial light-emitting diodes has a first thickness, and the second portion of the conductive layer covering the second group of axial light-emitting diodes has a second thickness that is smaller than the first thickness. The device according to claim 11.

13. A method for manufacturing optoelectronic devices, The optoelectronic device comprises an array of axial light-emitting diodes, each of which has an active region configured to emit electromagnetic radiation having an emission spectrum with a maximum value at a first wavelength, the axial light-emitting diodes are arranged in the array at substantially constant pitch, and the array forms a photonic crystal configured to form three resonant peaks that amplify the intensity of the electromagnetic radiation emitted by the array at at least second, third, and fourth wavelengths, one of which is 4 The array of axial light-emitting diodes further comprises a first optical filter covering at least a first portion of the array, the first optical filter being configured to block the amplified radiation over a first wavelength range including the first, third, and fourth wavelengths, and to allow the amplified radiation over a second wavelength range including the second wavelength. method.

14. Each active region is configured to emit electromagnetic radiation having an emission spectrum with a full width at half maximum greater than 100 nm. The method according to claim 13.

15. The axial light-emitting diodes are divided into at least a first and a second group of axial light-emitting diodes, and the method includes forming a first optical filter in the first group and forming a second optical filter in the second group that is different from the first optical filter. The method according to claim 13.

16. The process includes, after forming the axial light-emitting diode, attenuating at least one of the resonance peaks relative to the other resonance peaks. The method according to claim 13.

Images