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 including an active region (20) configured to emit electromagnetic radiation having an emission spectrum including a maximum at a first wavelength, the array forming a photonic crystal configured to form a resonant peak that amplifies the intensity of said electromagnetic radiation at at least one second wavelength different from the first 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 adapted 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 in 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] The formation of active regions comprising single quantum wells or multiple quantum wells is 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 layer, such as dislocations and / or alloy separation effects, and causing 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. Consequently, the formation of light-emitting diodes made from III-V or II-VI compounds that emit red light can be 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-dimensional substrates at low cost by epitaxy.

[0009] It is known that light-emitting diodes (LEDs) can be covered with photoluminescent materials that can convert electromagnetic radiation emitted by the active region into electromagnetic radiation of different wavelengths. However, such photoluminescent materials are expensive, have low conversion efficiency, and their performance may degrade over time.

[0010] Furthermore, forming axial three-dimensional light-emitting diodes based on III-V or II-VI compounds that possess desired characteristics, particularly an active region with an emission spectrum that includes a narrow bandwidth near the target emission frequency, can be challenging. [Overview of the project]

[0011] One objective of this embodiment is to overcome all or part of the drawbacks of the aforementioned optoelectronic devices, including light-emitting diodes.

[0012] Another object of one embodiment is that the active region of each light-emitting diode comprises a laminate of semiconductor materials based on III-V or II-VI compounds.

[0013] Another object of one embodiment is that the optoelectronic device comprises a light-emitting diode configured to emit red light without using photoluminescent material.

[0014] Another object of one embodiment is an axial three-dimensional light-emitting diode based on a III-V or II-VI compound, having desired properties and an active region having an emission spectrum that includes a narrow bandwidth near the target emission frequency.

[0015] One embodiment provides a photoelectronic device comprising an array of axial light-emitting diodes, each light-emitting diode comprising an active region configured to emit electromagnetic radiation having an emission spectrum with a maximum value at a first wavelength, and the array forming a photonic crystal configured to form a resonant peak that amplifies the intensity of the aforementioned electromagnetic radiation at at least one second wavelength different from the first wavelength.

[0016] According to one embodiment, the device further comprises a first optical filter covering at least one first portion of the array of light-emitting diodes described above, the first optical filter being configured to block the amplified radiation described above over a first wavelength range including a first wavelength and to pass the amplified radiation described above over a second wavelength range including a second wavelength.

[0017] According to one embodiment, the emission spectrum of the active region has energy at the second wavelength.

[0018] According to one embodiment, the photonic crystal is configured to form a resonance peak that amplifies the intensity of the electromagnetic radiation described above at at least one third wavelength different from the first and second wavelengths.

[0019] According to one embodiment, the emission spectrum of the active region has energy at the third wavelength.

[0020] 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 described above. The second optical filter is configured to block the amplified radiation described above over a third wavelength range including the first and second wavelengths and to pass the amplified radiation described above over a fourth wavelength range including a third wavelength.

[0021] According to one embodiment, the photonic crystal is configured to form a resonance peak that amplifies the intensity of the electromagnetic radiation described above at at least one fourth wavelength different from the first, second, and third wavelengths.

[0022] According to one embodiment, the emission spectrum of the active region has energy at the fourth wavelength.

[0023] According to one embodiment, the device further comprises a third optical filter covering at least a third portion of the aforementioned array of light-emitting diodes, the third optical filter configured to block the aforementioned amplified radiation over a fifth wavelength range including first, second, and third wavelengths, and to allow the aforementioned amplified radiation to pass over a sixth wavelength range including a fourth wavelength.

[0024] According to one embodiment, the 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.

[0025] According to one embodiment, the device includes a reflective layer between the support and the first semiconductor portion of the light-emitting diode.

[0026] According to one embodiment, the reflective layer is made of metal.

[0027] 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.

[0028] According to one embodiment, the light-emitting diodes are isolated by an electrical insulating material.

[0029] Furthermore, one embodiment provides a method for manufacturing a photoelectronic device comprising an array of axial light-emitting diodes. Each light-emitting diode comprises an active layer configured to emit electromagnetic radiation having an emission spectrum that includes a maximum value at a first wavelength. The array forms a photonic crystal configured to form a resonant peak that amplifies the intensity of the electromagnetic radiation from the light-emitting diodes at at least one second wavelength different from the first wavelength.

[0030] According to one embodiment, forming 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 first semiconductor portion, and forming first semiconductor portions on each active region.

[0031] According to one embodiment, the method includes the step of removing the substrate. [Brief explanation of the drawing]

[0032] 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.

[0033] [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 one resonance. [Figure 6] This diagram schematically shows the curve of change in light intensity and a configuration with two resonances. [Figure 7] This diagram schematically shows the curve of change in light intensity and a configuration with three resonances. [Figure 8] This figure shows a method for selecting radiation in a configuration with two resonances. [Figure 9] This diagram shows a method for selecting radiation in a configuration with three resonances. [Figure 10A]Figure 1 shows the steps of one embodiment of a method for manufacturing the optoelectronic device shown in Figure 1. [Figure 10B] This diagram shows the other steps in the manufacturing process. [Figure 10C] This diagram shows the other steps in the manufacturing process. [Figure 10D] This diagram shows the other steps in the manufacturing process. [Figure 10E] This diagram shows the other steps in the manufacturing process. [Figure 10F] This diagram shows the other steps in the manufacturing process. [Figure 10G] This diagram shows the other steps in the manufacturing process. [Figure 11] This figure shows the steps of another embodiment of the method for manufacturing the optoelectronic device shown in Figure 1. [Figure 12] 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 13] 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 14] 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 15] This figure shows the curve of change in the light intensity of the light-emitting diode according to the wavelength measured in the first test. [Figure 16] This figure shows the curve of change in the light intensity of the light-emitting diode according to the wavelength measured in the second test. [Modes for carrying out the invention]

[0034] 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.

[0035] 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.

[0036] The expressions "approximately," "about," "substantially," and "to the extent" represent a range of 10%, preferably 5%, of the relevant value, unless otherwise specified. Furthermore, the terms "insulating" and "conductive" are understood to mean "electrical insulation" and "electrical conductivity," respectively.

[0037] 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 absorption 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 absorption of radiation passing through it is less than 60%. In the following explanation, a layer is said to absorb radiation if the absorption of radiation passing through it is greater than 60%. When radiation has a generally "Bell" type spectrum, such as a Gaussian type 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.

[0038] 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, and more preferably 10 times, 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.

[0039] Figures 1 and 2 are a partially schematic side cross-sectional view and a perspective view, respectively, showing one embodiment of a photoelectronic device 10 equipped with a light-emitting diode.

[0040] 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 15 of axial light-emitting diodes (LEDs) 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 lower 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.

[0041] Each light-emitting diode (LED) is called axial because its active region 20 is aligned with the lower semiconductor portion 18 and its upper semiconductor portion 22 is aligned with the active region 20. The assembly comprising the lower semiconductor portion 18, the active region 20, and the upper semiconductor 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.

[0042] 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 metal layer, once deposited, has relief.

[0043] 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 multiple optical filters arranged adjacent to one another, as will be further detailed later.

[0044] 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.

[0045] According to one embodiment, the lower semiconductor portion 18, the upper semiconductor portion 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). The lower semiconductor portion 18 and the upper semiconductor portion 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 lower semiconductor portion 18 is made of P-doped GaN, and the upper semiconductor portion 22 is made of N-doped GaN.

[0046] 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. The active region 20 contains a semiconductor material different from the semiconductor material forming the lower semiconductor portion 18 and the upper semiconductor portion 22, and has a band gap smaller than the band gap of the material forming the lower semiconductor portion 18 and the upper semiconductor portion 22. The active region 20 may be provided with multiple quantum wells. In that case, it comprises a laminate of semiconductor layers in which quantum wells and barrier layers are alternately formed.

[0047] 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.

[0048] The sum of the height h1 of the lower semiconductor portion 18, the height h2 of the active region 20, the height h3 of the upper semiconductor portion 22, the thickness of the electrode layer 26, and the thickness 28 of the coating is called the height H of the light-emitting diode LED.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Figures 3 and 4 schematically show examples of the layout of the light-emitting diode LEDs in array 15. In particular, Figure 3 shows a so-called square grid layout, and Figure 4 shows a so-called hexagonal grid layout.

[0053] Figures 3 and 4 each show three rows, each containing four light-emitting diode (LED) units. In the layout shown in Figure 3, the LED units are located at each intersection of rows and columns, with the rows 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.

[0054] 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.

[0055] 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 Joachim Piprek's "Semiconductor Optoelectronic Devices: Introduction to Physics and Simulation".

[0056] 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.

[0057] 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 least at the target wavelength. According to one embodiment, the active region 20 of each light-emitting diode has an emission spectrum that has a maximum value at a wavelength different from the target wavelength. However, the emission spectrum of the active region 20 overlaps with the target wavelength, i.e., the energy of the emission spectrum of the active region 20 at the target wavelength is not zero.

[0058] Figure 5 schematically shows the curves of change in light intensity I emitted by the active region 20 of the light-emitting diodes (LEDs), C1 (solid line), the curve of change in the amplification coefficient due to coupling with the photonic crystal, C2 (dashed line), and the curve of change in light intensity emitted by the array of light-emitting diodes 15, all considered individually according to wavelength λ. Curve C1 has a general "bell" shape, with a center wavelength λ Chas vertices. Curve C2 corresponds to a narrow resonance peak centered at the target wavelength λ T1 Curve C3 includes the vertex S at the central wavelength λ C and the peak P1 at the target wavelength λ T1 In particular, the full width at half maximum of curve C3 at vertex S may be, for example, 2 times, especially 8 to 15 times, for example 10 times larger than the full width at half maximum of curve C3 at peak P1.

[0059] According to one embodiment, obtaining the optoelectronic device 10 that emits narrow-spectrum light radiation at the target wavelength λ T1 may be achieved by filtering the radiation emitted by the array 15 of light-emitting diodes LED so as to block wavelengths smaller than the target wavelength λ T1 This may be achieved by providing an optical filter in the coating 28. In FIG. 5, the blocked portion of the spectrum of the radiation emitted by the array 15 of light-emitting diodes is hatched. In that case, the spectrum of the radiation emitted by the light-emitting surface 30 of the optoelectronic device 10 mainly includes the peak P1.

[0060] Thereby, advantageously, it becomes possible to form the active region 20 that emits radiation having a maximum intensity at a central wavelength λ T1 different from the target wavelength λ C Also, advantageously, it becomes possible to use the active region 20 that emits radiation whose radiation band at half value is larger than the radiation band of the target radiation. Furthermore, advantageously, it becomes possible to facilitate the manufacture of the active region 20. In practice, as an example, when the active region 20 includes an InGaN layer, the central wavelength of the emitted radiation increases as the indium ratio increases. However, in order to obtain the emission wavelength corresponding to red, it is necessary to obtain an indium ratio greater than 16%, which is interpreted as a decrease in the quantum efficiency of the active region. The central wavelength λ T1 smaller than the target wavelength λ CThe fact that an 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 easy 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 This makes it possible to obtain radiation. Furthermore, the height h1 of the lower semiconductor portion 18 and the height h2 of the upper semiconductor portion 22 are such that the peak light intensity is at the target wavelength λ. T1 It is determined in a favorable way to maximize the result.

[0061] Figure 6 is similar to Figure 5, and the curve C2 of the change in the amplification coefficient due to the photonic crystal is shown for each target wavelength λ. T1 and λ T2 It differs in that it contains two narrow resonance peaks centered at λ. In that case, curve C3 is, C The peak S is at the point of the target wavelength λ. T1 Peak P1 and target wavelength λ T2 This includes peak P2.

[0062] Figure 7 is similar to Figure 5, and the curve C2 of the change in the amplification coefficient due to the photonic crystal is the target wavelength λ. T1 , λ T2 and λ T3 It differs in that it contains three narrow resonance peaks centered at λ. Curve C3 is centered at wavelength λ. C The peak S is at the point of the target wavelength λ. T1 Peak P1, target wavelength λ T2 The peak P2 in the region, and the center wavelength λ shown in Figure 7. C The target wavelength λ is substantially equal to T3 This includes peak P3.

[0063] Figures 8 and 9 illustrate the principle of filtering radiation emitted by an array of light-emitting diodes 15 having configurations with two and three resonant peaks, respectively. As previously mentioned in relation to Figure 5, the target wavelength λ T1Obtaining a photoelectronic device that emits narrow-spectrum light radiation centered on a specific point may be achieved by blocking unwanted portions of the emission spectrum of the light-emitting diodes. For example, in Figures 8 and 9, the blocked portions of the spectrum of radiation emitted by the array of light-emitting diodes 15 are hatched, leaving only one of the resonance peaks.

[0064] 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.

[0065] According to one embodiment, in a light-emitting configuration including at least two resonant peaks, the light-emitting diodes in the 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 the first resonant peak, and second filtering is performed on the second group of light-emitting diodes to retain only the second resonant peak. Thus, a photoelectronic device can be obtained that is configured to emit first radiation at a first target wavelength and 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.

[0066] According to one embodiment, in a light-emitting configuration including at least three resonant peaks, the light-emitting diodes may be divided into first, second, and third groups. First filtering is performed on the first group of light-emitting diodes to retain only the first resonant peak. Second filtering is performed on the second group of light-emitting diodes to retain only the second resonant peak. Third filtering is performed on the third group of light-emitting diodes to retain only the third resonant peak. The optoelectronic device is configured to emit first radiation at a first target wavelength, second radiation at a second target wavelength, and third radiation at a third target wavelength, and thus it can be achieved that the active regions of the first, second, and third groups of light-emitting diodes and the array of light-emitting diodes have the same structure. This makes it possible, in particular, to form display subpixels of display pixels on a color image display screen.

[0067] 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.

[0068] 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.

[0069] Figures 10A to 10G 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.

[0070] Figure 10A shows the structure obtained after the following formation steps.

[0071] A seed layer 42 is formed on the substrate 40. Then, a light-emitting diode LED is formed from the seed layer 42. More specifically, the light-emitting diode LED is formed so that the upper semiconductor portion 22 is in contact with the seed layer 42. The seed layer 42 is made of a material that is favorable for the growth of the upper semiconductor portion 22. For each light-emitting diode LED, an active region 20 is formed on the upper semiconductor portion 22, and a lower semiconductor portion 18 is formed on the active region 20.

[0072] 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 10A to 10G show only one row in part.

[0073] To expose only a portion of the seed layer 42 at the location where the light-emitting diode (LED) will be installed, a mask (not shown) may be formed on the seed layer 42 before the LED is formed. As a variation, the seed layer 42 may be etched before the LED is formed to form a pad that will be installed at the location where the LED is formed.

[0074] 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.

[0075] 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 lower semiconductor portion 18 and the upper semiconductor portion 22, as well as the height of the active region 20, are substantially the same for all light-emitting diodes in the array 15.

[0076] According to one embodiment, the height of the upper semiconductor portion 22 is greater than the desired height h3. In practice, it may be difficult to precisely control the height of the upper semiconductor portion 22, especially due to the start of growth of the upper semiconductor portion 22 from the seed layer 42. Furthermore, if the semiconductor is formed directly on the seed layer 42, crystal defects may occur in the semiconductor material directly above the seed layer 42. Therefore, it may be desirable to remove a portion of the upper semiconductor portion 22 to obtain a certain height before forming the active region 20.

[0077] Figure 10B 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 10A, 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 lower semiconductor portion 18. The upper surface of layer 24 is then made substantially flush with the upper surface of each lower semiconductor portion 18. In a modified example, the method may include an etching step of partially etching the lower semiconductor portion 18.

[0078] The packing material is selected so that the photonic crystal formed by the array 15 has the desired properties, that is, so that it selectively improves the intensity of the radiation emitted by the light-emitting diode LED with respect to wavelength.

[0079] Figure 10C shows the structure obtained after depositing the electrode layer 14 on the structure obtained in the previous step.

[0080] Figure 10D 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.

[0081] Figure 10E shows the structure obtained after removing the substrate 40 and seed layer 42. Furthermore, layer 24 and upper semiconductor portions 22 are etched so that the height of each upper semiconductor portion 22 has a desired value h3. This step advantageously allows for precise control of the height of the light-emitting diode and removal of portions of the upper semiconductor portion 22 that may have crystal defects.

[0082] Figure 10F shows the structure obtained after the deposition of the electrode layer 26.

[0083] Figure 10G shows the structure obtained after forming at least one optical filter on all or part of the structure shown in Figure 10E. For example, in the configuration having three resonance peaks as described above, the first, second, and third optical filters F are arranged in the first, second, and third groups of light-emitting diodes (LEDs), respectively. R F G F B This is shown.

[0084] Figure 11 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 semiconductor 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 semiconductor portion 22. This makes it possible to slightly modify the characteristics of the photonic crystal. Therefore, it becomes possible to more precisely change the position of the resonance peak of amplification by the photonic crystal.

[0085] 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 indices of the lower semiconductor portion 18 and the upper semiconductor portion 22 are in the range of 2.4 to 2.5. 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 the lower semiconductor portion 18 and the upper semiconductor portion 22 are not definitive parameters because they affect the intensity of the resonance peak but do not substantially change the position of the resonance peak.

[0086] Figures 12, 13, and 14 are grayscale maps of the light intensity of radiation emitted from the array of light-emitting diodes (LEDs) 15 at 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).

[0087] Each grayscale map contains bright areas corresponding to resonance peaks. These areas with resonance peaks are schematically shown by solid contour B in Figure 12, dashed contour G in Figure 13, and dashed contour R in Figure 14.

[0088] 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 12, obtained without filtering, has at least one resonant peak at a wavelength of 450 nm.

[0089] In Figure 13, contour B in Figure 12 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 of light-emitting diodes 15, obtained without filtering, is located in one of the regions enclosed by contours B and G in Figure 13 and has at least one resonant peak at a wavelength of 450 nm and one resonant peak at a wavelength of 530 nm.

[0090] In Figure 14, contour B in Figure 12 and contour G in Figure 13 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 14, 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.

[0091] Please note that optimization can be achieved by changing the heights h1 and h3.

[0092] 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 lower semiconductor portion 18, the upper semiconductor portion 22, and the active layer 20 are formed simultaneously by MOCVD in all photodiodes.

[0093] The first test was performed with parameters of a height H equal to approximately 1 μm, a photonic crystal pitch "a" equal to 400 nm, and a diameter of the circumscribed circle of the hexagonal base of the light-emitting diode of approximately 270 nm ± 25 nm. Considering the diameter of approximately 297 nm corrected in the simulation in Figure 14, resonance at a wavelength of 630 nm is expected.

[0094] Figure 15 shows the curve CR of the change in light intensity I (in arbitrary units) of the light-emitting diode array 15 with respect to wavelength λ in the first test. An intensity peak is effectively obtained at a wavelength equivalent to approximately 644 nm.

[0095] The second test was performed under epitaxial growth conditions for forming an active region (20), with the same base dimensions as the first test, but modified to slightly reduce the overall average diameter of each light-emitting diode so that it falls within contours R, G, and B in the simulation in Figure 14. Compared to the first test, the modified parameters were an increased quantum barrier thickness in the active region, an increased In / III input flow rate, and an increased temperature.

[0096] Figure 16 shows the wavelength-dependent change curve CRGB of the light intensity I (arbitrary unit) of the light-emitting diode array 15 in the second test. Three resonance peaks at wavelengths of 450 nm, 590 nm, and 700 nm are effectively obtained.

[0097] 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 include one or more additional layers other than optical filters. Specifically, the coating 28 may include an anti-reflective layer, a protective layer, and the like. 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.

[0098] This patent application claims priority to French Patent Application No. 20 / 13514, which is deemed to constitute 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 array forms a photonic crystal configured to form a resonant peak that amplifies the intensity of the electromagnetic radiation at at least one second wavelength different from the first wavelength, and further comprises a first optical filter covering at least one 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 the first wavelength and to pass the amplified radiation over a second wavelength range including the second wavelength. Optoelectronic devices.

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

3. The device according to claim 1, wherein the photonic crystal is configured to form a resonant peak that amplifies the intensity of the electromagnetic radiation at at least one third wavelength different from the first and second wavelengths.

4. The device according to claim 3, wherein the emission spectrum of the active region has energy at the third wavelength.

5. The device according to claim 3, further comprising a second optical filter covering at least a second portion of the array of light-emitting diodes, wherein the second optical filter is configured to block the amplified radiation over a third wavelength range including the first and second wavelengths and to allow the amplified radiation to pass over a fourth wavelength range including the third wavelength.

6. The device according to claim 3, wherein the photonic crystal is configured to form a resonant peak that amplifies the intensity of the electromagnetic radiation at at least one fourth wavelength different from the first, second, and third wavelengths.

7. The device according to claim 6, wherein the emission spectrum of the active region has energy at the fourth wavelength.

8. The device according to claim 6, further comprising a third optical filter covering at least a third portion of the array of 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.

9. The device according to claim 1, comprising a support on which the light-emitting diodes are mounted, wherein each of the 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.

10. The device according to claim 9, further comprising a reflective layer made of metal between the support and the first semiconductor portion of the light-emitting diode.

11. The device according to claim 9, wherein the second semiconductor portion of the light-emitting diode is covered with a conductive layer that is at least partially transparent to the electromagnetic radiation emitted by the light-emitting diode.

12. The device according to claim 1, wherein the light-emitting diode is separated by an electrical insulating material.

13. A method for manufacturing a photoelectronic device comprising an array of axial light-emitting diodes, each of the light-emitting diodes comprising an active layer configured to emit electromagnetic radiation having an emission spectrum having a maximum value at a first wavelength, the array comprising a photonic crystal configured to form a resonant peak that amplifies the intensity of the electromagnetic radiation from the light-emitting diodes at at least one second wavelength different from the first wavelength, and further comprising a first optical filter covering at least one 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 the first wavelength and to pass the amplified radiation over a second wavelength range including the second wavelength.

14. Forming the light-emitting diodes of the array is The steps include forming a second semiconductor portion on a substrate that is separated from each other by the pitch of the array, The steps include forming active regions on each second semiconductor portion, The first step is to form the semiconductor portion on each active region. The method according to claim 13, including the method described in claim 13.

15. The method according to claim 14, comprising the step of removing the substrate.

Images