Method for adjusting the central wavelength of a three-dimensional LED optoelectronic device

Abstract

Method for adjusting the center wavelength of a three-dimensional LED optoelectronic device. This description relates to a method for adjusting the center wavelength of the radiation emitted by an optoelectronic device comprising three-dimensional LEDs. The method includes a step of measuring the center wavelength, a step of determining the current density per LED to obtain a target center wavelength, and a step of connecting / disconnecting LEDs to vary the current density per LED until the determined current density is reached. Figure for the abstract: Fig. 5

Description

Title of the invention: Method for adjusting the central wavelength of a three-dimensional LED optoelectronic device technical field

[0001] The present application relates to a method for adjusting the central wavelength of the radiation emitted by the light-emitting diodes of an optoelectronic device, in particular a display pixel for a display screen or for a backlight panel, comprising three-dimensional light-emitting diodes based on semiconductor materials, and an optoelectronic device adapted to implement such a method. Previous technique

[0002] A light-emitting diode (LED) based on semiconductor materials generally comprises an active region, which is the area of ​​the LED from which the majority of the electromagnetic radiation emitted by the LED is emitted. The structure and composition of the active region are adapted to obtain electromagnetic radiation with the desired properties. In particular, it is generally sought to obtain narrow-spectrum electromagnetic radiation, ideally substantially monochromatic.

[0003] We are particularly interested here in optoelectronic devices with three-dimensional light-emitting diodes, that is to say, light-emitting diodes each comprising a three-dimensional semiconductor element of micrometer or nanometer size extending along a preferred direction, for example a microwire or a nanowire, and whose active area covers the three-dimensional semiconductor element. In particular, a three-dimensional light-emitting diode is said to be of the radial type when its active area extends at least over the lateral walls of the three-dimensional semiconductor element.

[0004] The central wavelength of the radiation emitted by a three-dimensional radial-type light-emitting diode depends on many parameters, including the diameter of the three-dimensional semiconductor element on which the active area of ​​the light-emitting diode rests.

[0005] A method for manufacturing optoelectronic devices includes forming radial three-dimensional light-emitting diodes on a wafer and cutting the wafer to separate the optoelectronic devices. With known methods for manufacturing radial three-dimensional light-emitting diodes, including epitaxial growth steps, while the growth conditions While these conditions should theoretically lead to the production of identical light-emitting diodes (LEDs) on the same plate, in practice a significant overall dispersion of the central wavelengths of the radiation emitted by LEDs formed on the same plate is observed, reaching and exceeding 20 nm. This is due in particular to a significant overall dispersion of the diameters of the three-dimensional semiconductor elements across the entire plate, even if the local dispersion remains small. In practice, an overall dispersion of the central wavelengths of the radiation emitted by LEDs formed on different plates is also observed, even when the same growth conditions have been applied.

[0006] For the fabrication of an optoelectronic device such as a pixel for a display screen or for a backlight panel, a dispersion of the central wavelength of the radiation emitted by the optoelectronic device of less than 2 nm is generally required. It is then necessary to test each of the optoelectronic devices formed from the same wafer to select those that have the desired properties. These steps increase the manufacturing cost of the optoelectronic devices. Summary of the invention

[0007] An embodiment overcomes all or part of the drawbacks of known three-dimensional light-emitting diode optoelectronic devices and of methods for adjusting the central wavelength of the radiation emitted by the light-emitting diodes of the optoelectronic device.

[0008] An object of an embodiment is to precisely control the central wavelength of the radiation emitted by the optoelectronic device.

[0009] An object of an embodiment is to reduce, or even eliminate, the selection steps of optoelectronic devices formed from the same plate.

[0010] One embodiment provides a method for adjusting the central wavelength of the radiation emitted by an optoelectronic device comprising three-dimensional light-emitting diodes, particularly radial diodes, including a step of measuring the central wavelength, a step of determining a current density per light-emitting diode to obtain a target central wavelength, and a step of connecting / disconnecting light-emitting diodes among the light-emitting diodes to vary the current density per light-emitting diode until the determined current density is reached. Since the wavelength emitted by a three-dimensional light-emitting diode varies according to the current density passing through it, this advantageously allows the central wavelength of the optoelectronic device to be adjusted.

[0011] According to one embodiment, the optoelectronic device comprises a current source powering three-dimensional light-emitting diodes. This advantageously allows the current density to be varied simply by changing the number of light-emitting diodes powered by the current source.

[0012] According to one embodiment, the step of determining a current density by light-emitting diode to obtain a target center wavelength includes determining the current density by light-emitting diode, determining the current density difference to be achieved as a function of the difference between the measured center wavelength and the target center wavelength, and determining the current density from the current density and the determined current density difference.

[0013] According to one embodiment, the light-emitting diodes are distributed into groups of light-emitting diodes, the connection / disconnection step comprising the connection / disconnection of the light-emitting diodes of at least one of the groups of light-emitting diodes.

[0014] According to one embodiment, the optoelectronic device comprises programmable switches each connected to at least one of the light-emitting diodes, the connection / disconnection step comprising the opening / closing of the programmable switches.

[0015] In one embodiment, each programmable switch includes a fuse, the connection / disconnection step comprising the opening of fuses among the fuses. This advantageously allows for the realization of an optoelectronic device with a simple structure. In one embodiment, the opening of each fuse is achieved by laser processing of the optoelectronic device.

[0016] In one embodiment, each programmable switch comprises a switch controllable by a binary signal, and the optoelectronic device includes a memory in which the binary signals are stored. This advantageously allows the connection / disconnection step to be performed without modifying the structure of the controllable switches. In one embodiment, the memory comprises memory cells, each comprising a fuse, and the connection / disconnection step includes opening fuses from among the fuses. In another embodiment, the opening of each fuse is performed by laser processing of the optoelectronic device. In yet another embodiment, the connection / disconnection step includes supplying the binary signals to the memory.

[0017] One embodiment also provides an optoelectronic device comprising three-dimensional light-emitting diodes, in particular of the radial type, and means for connecting / disconnecting light-emitting diodes among the light-emitting diodes to achieve a current density determined per diode. troluminescent.

[0018] According to one embodiment, the light-emitting diodes are arranged in groups of light-emitting diodes, each programmable switch being connected to one of the groups of light-emitting diodes. This advantageously reduces the number of programmable switches relative to the number of light-emitting diodes.

[0019] According to one embodiment, the light-emitting diodes each comprise a three-dimensional semiconductor element corresponding to a microwire, a nanowire, or a conical or truncated conical element of micrometric or nanometric size and an active area covering the three-dimensional semiconductor element and configured to emit electromagnetic radiation.

[0020] According to one embodiment, the device comprises at least fifty light-emitting diodes. Brief description of the drawings

[0021] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0022] [Fig.1] represents, for several plates, the median wavelength of the radiation emitted by the light-emitting diodes of the plate as a function of the median diameter of the light-emitting diodes of the plate;

[0023] [Fig.2] represents, for several plates, the maximum wavelength of the radiation emitted by the light-emitting diodes of the plate as a function of the median diameter of the light-emitting diodes of the plate;

[0024] [Fig.3] represents curves of evolution of the central wavelength of the radiation emitted by a light-emitting diode as a function of the current density through the light-emitting diode for light-emitting diodes of different diameters;

[0025] [Fig.4] represents curves of evolution of the external quantum efficiency of a light-emitting diode as a function of the current density through the light-emitting diode for light-emitting diodes of different diameters;

[0026] [Fig.5] is a block diagram of an embodiment of a method for adjusting the central wavelength of an optoelectronic device with light-emitting diodes;

[0027] [Fig.6] is a partial and schematic cross-sectional view of an embodiment of an optoelectronic device with light-emitting diodes;

[0028] [Fig.7] is an electrical diagram of an embodiment of an optoelectronic device with light-emitting diodes comprising programmable switches;

[0029] [Fig. 8] is an electrical diagram of another embodiment of an opto device LED electronics including programmable switches;

[0030] [Fig.9] is a top view of an embodiment of a programmable switch of the optoelectronic device shown in [Fig.7] or 8;

[0031] [Fig. 10] is an electrical diagram of another embodiment of the opto device electronics of [Fig.7] or 8;

[0032] [Fig.1 1] illustrates an embodiment of laser treatment of an optoelectronic device;

[0033] [Fig. 12] is a partial and schematic cross-sectional view of an embodiment more detailed view of part of the optoelectronic device in [Fig. 6]; and

[0034] [Fig. 13] is a partial and schematic cross-sectional view of an embodiment of a light-emitting diode. Description of the implementation methods

[0035] The same elements have been designated by the same reference numerals in the different figures. In particular, structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional, and material properties. For clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the electrical connections of the light-emitting diodes of an optoelectronic device are not described.

[0036] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0037] In the following description, when reference is made to absolute positional qualifiers, such as "front," "back," "top," "bottom," "left," "right," etc., or relative positional qualifiers, such as "above," "below," "superior," "inferior," etc., or to orientational qualifiers, such as "horizontal," "vertical," etc., unless otherwise specified, reference is made to the orientation of the figures or to an optoelectronic device in a normal operating position. Furthermore, unless otherwise indicated, the terms "insulator" and "conductor" are taken to mean "electrically insulating" and "electrically conductive," respectively.

[0038] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0039] In the following description, the internal transmittance of a layer corresponds to the ratio between the intensity of the radiation exiting the layer and the intensity of the radiation entering the layer. The absorption of the layer is equal to the difference between 1 and the internal transmittance. In the following description, a layer is said to be transparent to radiation when the absorption of radiation through the layer is less than 60%. In the following description, a layer is said to be absorbent to radiation when the absorption of radiation in the layer is greater than 60%.

[0040] In the following description, when radiation has a spectrum with a general "bell-shaped" form, for example, a Gaussian shape, having a maximum, the wavelength of the radiation, or central or principal wavelength of the radiation, is the wavelength at which the maximum of the spectrum is reached. The central wavelength of a light-emitting diode (LED) is the central wavelength of the radiation emitted by the LED, and more generally, the central wavelength of an optoelectronic device is the central wavelength of the radiation emitted by the optoelectronic device.

[0041] In the following description, the external quantum efficiency (EQE) of a light-emitting diode is defined as the ratio between the number of photons emitted by the light-emitting diode and the number of electrons passing through the active area of ​​the light-emitting diode.

[0042] The present invention relates to the manufacture of optoelectronic devices comprising light-emitting diodes formed from three-dimensional semiconductor elements of nanometric or micrometric size, in particular microwires, nanowires, or conical or truncated conical elements of micrometric or nanometric size, in particular pyramids.

[0043] A three-dimensional semiconductor element of nanometer or micrometer size is defined as a three-dimensional structure of elongated shape, for example cylindrical, along a preferred direction, of which at least two dimensions, called minor dimensions, are between 5 nm and 2.5 pm, preferably between 50 nm and 2.5 pm. The third dimension, called the major dimension, is greater than or equal to 1 time, preferably greater than or equal to 5 times, and even more preferably greater than or equal to 10 times, the largest of the minor dimensions. In some embodiments, the minor dimensions may be less than or equal to about 1 pm, preferably between 100 nm and 1 pm, more preferably between 100 nm and 800 nm. In some embodiments, the height of the three-dimensional semiconductor element may be greater than or equal to 500 nm, preferably between 1 pm and 50 pm.The term "microwire" or "nanofil" refers to a three-dimensional semiconductor element with a cylindrical or substantially cylindrical shape. In the rest of the description, the term "wire" is used to mean "microwire or nanowire".

[0044] The cross-section of wires can have various shapes, for example, oval, circular, or polygonal, including triangular, rectangular, square, or hexagonal. It will be understood that the term "equivalent diameter" used in relation to a cross-section of a wire designates a quantity associated with the wire in that cross-section, corresponding, for example, to the diameter of the disk having the same area as the cross-section of the wire.

[0045] In the following description, embodiments will be described for an optoelectronic device with light-emitting diodes comprising three-dimensional semiconductor elements corresponding to wires. However, it is clear that these embodiments can also relate to an optoelectronic device with light-emitting diodes whose three-dimensional semiconductor elements are conical or frustoconical elements of micrometer or nanometer size, in particular pyramids.

[0046] Tests were carried out to characterize the dispersion of the central wavelength of the radiation emitted by light-emitting diodes (LEDs) formed on 200 mm diameter semiconductor wafers under identical formation conditions. For the tests, the LEDs were radial in type and formed by metal-organic chemical vapor deposition (MOCVD). Furthermore, the three-dimensional semiconductor elements of the LEDs were wires. The LEDs, and in particular the wires, were formed under identical growth conditions for all wafers, so that the LEDs should theoretically have the same structure and dimensions.

[0047] Figures 1 and 2 represent, for several plates as a function of the median diameter Dmed of the LED wires on the plate, respectively the median wavelength Xmed and the maximum wavelength Xmax of the radiation emitted by all the LEDs on the plate. In Figures 1 and 2, each point corresponds to a plate. The median diameter Dmed is determined from one hundred wires located at the center of the plate. In Figures 1 and 2, the lines D1 and D2 were obtained by linear regression. Figures 1 and 2 illustrate the wavelength dispersion resulting from the LED formation processes by epitaxial growth. This dispersion is particularly significant for three-dimensional radial LEDs since the active area of ​​such an LED covers the lateral walls of the wire.The structure and composition of the layers of the active zone are then particular. closely sensitive to the dimensions of the wire, in particular its diameter.

[0048] According to one embodiment, the dispersion of the central wavelength of the radiation emitted by an optoelectronic device with light-emitting diodes is reduced by modifying the current density through the light-emitting diodes. Indeed, the inventors have shown that, for three-dimensional radial light-emitting diodes, the central wavelength of the radiation emitted by the light-emitting diode varies significantly as a function of the current density through the light-emitting diode, such that an adjustment of the central wavelength emitted by the light-emitting diode can be achieved by varying the current density through the light-emitting diode.

[0049] Tests were carried out to characterize the variation in the central wavelength of the radiation emitted by light-emitting diodes (LEDs) formed on 200 mm diameter semiconductor plates under identical formation conditions. For the tests, the LEDs were radial in type and formed by metal-organic chemical vapor deposition (MOCVD). Furthermore, the three-dimensional semiconductor elements of the LEDs were wires. The LEDs, and in particular the wires, were formed under identical growth conditions for all plates, so that the LEDs should theoretically have the same structure and dimensions.

[0050] Figure 3 shows curves of the evolution of the central wavelength Xc of the radiation emitted by groups of wire LEDs (a group consisting of 256 wire LEDs) as a function of the current density J flowing through each wire LED in the LED group, the LED groups being formed on different plates or at different locations on the same plate. As shown in Figure 3, for the same current density J, the central wavelength Xc varies from one LED to another, and a variation in current density between 0.1 A / cm² and 10 A / cm² results in a variation of the central wavelength Xc of at least 10 nm.

[0051] Figure 4 shows the evolution curves of the external quantum efficiency EQE emitted by the groups of light-emitting diodes in Figure 3 as a function of the current density J flowing through each light-emitting diode in the group. As shown in Figure 4, a variation in current density between 0.1 A / cm² and 10 A / cm² results in a small variation in the external quantum efficiency EQE compared to the maximum external quantum efficiency. This means that the light-emitting diodes continue to operate essentially with maximum external quantum efficiency over a wide range of current densities. fluent.

[0052] Figure 5 is a block diagram of an embodiment of a method for adjusting the central wavelength Xc of the radiation emitted by an optoelectronic device comprising a plurality of light-emitting diodes, in particular three-dimensional radial light-emitting diodes. The adjustment method aims to modify the optoelectronic device so that the radiation emitted by the optoelectronic device has a central wavelength Xc equal to a target central wavelength.

[0053] The process comprises successive steps 1, 2, 3 and 4.

[0054] Step 1 comprises measuring a parameter representative of the central wavelength Xc of the radiation emitted by the optoelectronic device when it is powered by a current of determined constant intensity. Step 1 includes, for example, measuring the spectrum of the radiation emitted by the optoelectronic device and determining the central wavelength Xc of the radiation emitted by the optoelectronic device from the measured spectrum. In one embodiment, in step 1, all the light-emitting diodes of the optoelectronic device are active.

[0055] Step 2 includes determining the variation of the measured central wavelength Xc with respect to the target central wavelength, and determining the variation AJ of the current density of the device to be made to vary the central wavelength Xc until the target central wavelength is reached.

[0056] In one embodiment, determining the change in current density AJ comprises determining the initial current density J flowing through each LED of the optoelectronic device, selecting the curve shown in [Fig. 3] passing through the point corresponding to the pair (Xc, J), and determining a target current density to be applied to achieve the target central wavelength, the target current density being equal to the sum of the initial current density J and the change in current density AJ (positive or negative). In one embodiment, the current supplying the optoelectronic device is known, as is the initial number of LEDs supplied by the current and the way in which the LEDs are connected to each other.The initial current density J through each light-emitting diode can then be determined directly by calculation. According to another embodiment, the determination of the initial current density J includes a measurement step.

[0057] Step 3 comprises determining the connection / disconnection configuration of the light-emitting diodes to be implemented to obtain the variation AJ of the current density of the optoelectronic device. According to one embodiment, step 3 This includes determining the number of LEDs in the optoelectronic device to be switched off to obtain the change in current density AJ. Since the LEDs are powered by the same current source, which provides a constant current intensity, varying the number of LEDs connected, and therefore powered by the current source, results in a change in the current density per LED. In one embodiment, the LEDs are connected in parallel. In another embodiment, the LEDs can be connected / disconnected individually. In yet another embodiment, they can be connected / disconnected in groups.

[0058] Step 4 includes disconnecting the number of light-emitting diodes determined in step 3 from the optoelectronic device.

[0059] The method may further include a step of modifying the lighting duration of the set of light-emitting diodes to readjust the average flux emitted by the set of diodes after changing the current density.

[0060] According to one embodiment, the method comprises at least two iterations, each iteration comprising the cycle of steps 1, 2, 3, and 4 described above. However, in the second iteration of step 1, and possibly in subsequent iterations of step 1, the remaining number of LEDs that are activated is reduced by the number of LEDs that were turned off in step 4 of the previous iteration.

[0061] In the embodiment described above, all the LEDs of the optoelectronic device are activated in step 1, and some LEDs of the optoelectronic device are turned off in step 4. According to another embodiment, the number of LEDs of the optoelectronic device that are activated in step 1 is strictly less than the total number of LEDs of the optoelectronic device. In step 3, the variation AJ of the current density to be applied can cause a specified number of LEDs of the optoelectronic device that were activated to be disconnected, or a specified number of LEDs of the optoelectronic device that were deactivated to be connected / activated. The LEDs disconnected from the optoelectronic device are then activated in step 4.

[0062] In step 3, the selection of the light-emitting diodes to be disconnected or activated from among the light-emitting diodes of the optoelectronic device may depend on the position of the light-emitting diodes so as not to degrade the spatial homogeneity of the radiation emitted by the optoelectronic device.

[0063] Figure 6 is a partial, schematic cross-sectional view of one embodiment of a Pix optoelectronic device, for example, a display pixel. A screen The display can consist of 10 to 109 display pixels (Pix). Each display pixel (Pix) can occupy an area of ​​between 1 µm² and 100 mm² when viewed from above. The thickness of each display pixel (Pix) can be between 1 µm and 6 mm.

[0064] The Pix optoelectronic device comprises, from top to bottom in [Fig. 6]: - an optoelectronic circuit 5; and - an electronic circuit 30, referred to hereafter as the control circuit.

[0065] The optoelectronic circuit 5 comprises a support 10, also called a substrate, on which light-emitting diodes (LEDs) are formed, preferably at least ten LEDs, more preferably at least fifty LEDs, and even more preferably at least one hundred LEDs, three LEDs being shown by way of example in [Fig. 6]. According to another embodiment, the LEDs may be formed on an initial substrate other than the support 10 and then transferred to the support 10, the initial substrate being optionally removed at that point. The support 10 comprises an upper surface 12 on which the LEDs rest, the upper surface 12 preferably being flat at least at the level of the LEDs.The optoelectronic circuit 5 may include an encapsulation layer 6 covering the light-emitting diodes (LEDs) on the side opposite the control circuit 30. The encapsulation layer 6 may include one or more photoluminescent blocks or one or more blocks transparent to the radiation emitted by the LEDs. Each photoluminescent or transparent block is opposite at least one of the LEDs. When photoluminescent blocks are present, each photoluminescent block includes phosphors adapted, when excited by the light emitted by the associated LED, to emit light at a wavelength different from the wavelength of the light emitted by the associated LED.

[0066] The optoelectronic circuit 5 comprises conductive elements 7, located in the support 10, and connected to the electrodes of the light-emitting diodes (LEDs). The optoelectronic circuit 5 is electrically connected to the control circuit 30 by means of conductive pads, which can correspond to the conductive elements 7, and which are in contact with conductive pads of the control circuit 30.

[0067] Preferably, the optoelectronic circuit 5 comprises only the LEDs and the conductive elements 7 of these LEDs, and the control circuit 30 comprises all the electronic components necessary for controlling the LEDs of the optoelectronic circuit 5. Alternatively, the optoelectronic circuit 5 may also comprise other electronic components in addition to the LEDs. including conductive tracks connecting several light-emitting diodes (LEDs) together.

[0068] The control circuit 30 comprises a lower face 32 and an upper face 34 opposite the lower face 32, the faces 32 and 34 preferably being parallel. The control circuit 30 further comprises conductive pads 36 on the lower face 32. The control circuit 30 may comprise a semiconductor substrate 38, a stack 40 of insulating layers covering the substrate 38, and conductive tracks 42 of several metallization levels formed between the insulating layers of the stack 40 and connected by conductive vias (not shown). The control circuit 30 may further comprise electronic components (not shown in [Fig. 6]), in particular transistors, formed in and / or on the substrate 38. An insulating layer (not shown) may cover the semiconductor substrate 38 on the side opposite the stack 40 and delimit the lower face 32 of the control circuit 30.The control circuit 30 may further include through-conductive vias, not shown, extending through the substrate 38, across its entire thickness, and electrically isolated from the substrate, allowing the pads 36 to be electrically connected to the front face of the substrate 38. The semiconductor substrate 38 is, for example, a silicon substrate, particularly monocrystalline silicon. The electronic components may then include insulated-gate field-effect transistors, also known as MOS (Metal-Oxide Semiconductor) transistors. In another embodiment, the substrate 38 may be a non-semiconductor substrate. In one embodiment, the electronic components may include thin-film transistors, also known as TFTs (Thin-Film Transistors), in which case the substrate 38 may not be present.

[0069] The optoelectronic circuit 5 is fixed to the upper face 34 of the control circuit 30. As an alternative, particularly when the electronic components include thin-film transistors, also known as TFT transistors, the control circuit 30 can be formed directly on the optoelectronic circuit 5.

[0070] Fig.7 and Fig.8 represent embodiments of an equivalent electrical diagram of the Pix optoelectronic device of Fig.6.

[0071] In Figures 7 and 8, the LEDs have a common anode electrode A and separate cathode electrodes K. The control circuit 30 includes an electronic circuit 44 comprising a MOS transistor circuit C for controlling the LEDs, having a terminal B connected to the cathode K of each operating LED. In one embodiment, the MOS transistor circuit C includes a controllable current source. The control circuit 30 may, furthermore, The system includes a terminal, not shown, intended to receive a low reference potential, such as ground, during operation, and a terminal, also not shown, intended to receive a high reference potential during operation. The high and low potentials can be applied between the conductive pads 36 of the control circuit 30 during operation. The control circuit 30 may further include terminals, not shown, for receiving binary or analog signals, and the electronic circuit 44 can be configured to process the received signals and drive the control circuit C to vary the current supplying the LEDs.

[0072] The Pix optoelectronic device further includes programmable switches 50 for disconnecting at least some of the LEDs. In [Fig. 7], the Pix optoelectronic device includes a programmable switch 50 between the cathode K of each LED and the circuit C. In [Fig. 8], the LEDs of the Pix optoelectronic device are arranged in LED sets, with two sets El, E2 of LEDs shown as examples in [Fig. 8], and the Pix optoelectronic device includes, for each set El, E2, a programmable switch 50 between the circuit C and the cathodes K of the LEDs in set El, E2. In another embodiment, at least some of the LEDs are not connected to the circuit C by a programmable switch 50.

[0073] The programmable switch 50 can be provided in the control circuit 30 as illustrated in Figures 7 and 8 or be provided in the optoelectronic circuit 5. According to one embodiment, the optoelectronic device Pix comprises at least five programmable switches 50, more preferably at least ten programmable switches 50, more preferably at least fifty programmable switches 50, even more preferably at least fifty programmable switches 50.

[0074] According to one embodiment, the switches 50 are used in step 4 described above for disconnecting or activating light-emitting diodes among the LEDs of the Pix optoelectronic device.

[0075] In one embodiment, each switch 50 corresponds to a programmable fuse-type element. In one embodiment, the programmable switch 50 includes a conductive track that can be interrupted, for example, by laser processing. When the programmable switch 50 is provided in the control circuit 30 as illustrated in Figures 7 and 8, the programmable switch 50 may be formed, at least in part, by some of the conductive tracks 42, in particular by conductive tracks of the first metallization level of the The control circuit 30 may be made of polycrystalline silicon or conductive tracks of a different metallization level, which may be metallic. When the programmable switch 50 is provided in the optoelectronic circuit 5, the programmable switch 50 may be formed at least in part by the conductive elements 7.

[0076] Figure 9 is a partial, schematic top view of an embodiment of a programmable switch 50 corresponding to a programmable element of the fuse type. The programmable element 50 comprises two access pads 52 and 54 and a conductive track 56 extending between the two access pads. The access pads 52 and 54 and the conductive track 56 may correspond to conductive tracks 42 of the control circuit 30 and / or to conductive elements 7 of the optoelectronic circuit 5. Generally, the conductive track 56 may be metallic or made of a non-metallic electrically conductive material, in particular doped monocrystalline or polycrystalline silicon. Each programmable element 50, once programmed, is in one of a first or second configuration. In the first configuration, the track 56 is uninterrupted and connects the two pads 52 and 54.In the second configuration, track 56 is interrupted and does not connect the two pads 52, 54.

[0077] According to one embodiment, the programmable element 50 can be programmed by laser processing. According to another embodiment, the programmable element 50 can be programmed by applying an electrical energy source (for example, a current source) to its terminals, injecting sufficient energy (for example, a current) to destroy it.

[0078] According to one embodiment, the programmable switch 50 corresponds to a transistor, for example a MOS transistor.

[0079] Fig. 10 represents another, more detailed embodiment of the electrical circuit of Fig. 7 or 8. By way of example, four LEDs are shown in Fig. 10.

[0080] In [Fig. 10], the Pix optoelectronic device comprises a MOS transistor 50, for example of type N, for each LED. The drain of each transistor 50 is connected to the cathode of the associated LED. The anode of each LED receives a high reference potential Vcc. The gate of each transistor 50 is controlled by a control signal supplied by a MEM memory.

[0081] According to one embodiment, the MEM memory is a one-time programmable memory, also called an OTP memory (One-Time Programmable Memory). According to one embodiment, each memory cell of the MEM memory can correspond to a programmable element as described previously in relation to [Fig. 9]. According to one embodiment, the MEM memory can be programmed by laser processing. In this embodiment, after the fabrication of the optoelectronic device, track 56 of the programmable element of each memory cell is not interrupted, so the programmable element is in its first configuration. This corresponds to storing binary data in the memory cell in a first state. In step 4 described previously, for some of the memory cells, track 56 of the programmable element of the memory cell is interrupted to bring the programmable element into the second configuration. This corresponds to storing binary data in the memory cell in a second state. Each transistor 50 is controlled to the conducting or blocking state depending on the binary data stored in the associated memory cell of the MEM.

[0082] According to another embodiment, the MEM memory is a non-volatile memory, for example a random access memory, which is programmed during step 4. According to one embodiment, during step 4, control signals are transmitted to the optoelectronic device Pix to store the desired binary signal in each memory cell of the MEM memory.

[0083] Fig. 11 is a partial, schematic cross-sectional view of an embodiment of a laser processing system 70 of the Pix optoelectronic device of Fig. 7 or 8.

[0084] The processing system 70 comprises a laser source 71 and a focusing optical device 72 having an optical axis D. The source 71 is adapted to supply an incident laser beam 73 to the focusing device 72, which supplies a converging laser beam 74. The focusing optical device 72 may comprise one, two, or more optical components, an optical component corresponding, for example, to a lens. Preferably, the incident laser beam 73 is substantially collimated along the optical axis D of the focusing optical device 72.

[0085] Figure 11 shows a region 75 of the optoelectronic device Pix comprising the programmable elements to be programmed. Generally, to reach the region to be treated 75, the laser must pass through a portion 76, hereafter referred to as the substrate, of the optoelectronic device Pix and optionally through a support to which the optoelectronic device Pix is ​​attached. The substrate 76 includes a face 77 that receives the laser beam. Preferably, the face 77 is flat and polished. In one embodiment, the processing is carried out while the optoelectronic device Pix is ​​not attached to a support on the side of the control circuit 30. In this case, the face 77 can correspond to the face 32 of the electronic circuit 30, and the processing of the optoelectronic device Pix is ​​preferably carried out on the side of the face 32 of the electronic circuit 30. In another embodiment, the processing is carried out while the device The optoelectronic Pix is ​​fixed to a support on the side of the control circuit 30. In this case, the processing of the optoelectronic device Pix can be carried out on the side of the face 32 of the control circuit 30, through the support on which the electronic circuit 30 rests, or can be carried out through the optoelectronic circuit 5.

[0086] According to one embodiment, the treatment consists of exposing parts of the region to be treated 75 in such a way as to allow, for each exposed part, the destruction of the programmable element located in that part. The laser power can be adjusted so as to be high enough to destroy the programmable element, and low enough not to damage neighboring elements.

[0087] Fig. 12 is a partial, schematic cross-sectional view of a more detailed embodiment of the optoelectronic circuit 5 of Fig. 6. The optoelectronic circuit 5 comprises, from bottom to top in Fig. 12: - substrate 10; - a germination layer 16 made of a material promoting the growth of threads and disposed on the face 12, the germination layer 16 may not be present; - an insulating layer 18 covering the germination layer 16 and comprising openings 20 exposing portions of the germination layer 16; - the LEDs (six LEDs being shown as an example) each emitting an R_LED radiation, the set of R_LED radiations forming the R radiation of the optoelectronic device Pix, each LED being in contact with the germination layer 16 through one of the openings 20; - an insulating layer 24 extending over the lateral sides of a lower portion of each LED and extending over the insulating layer 18 between the LEDs; - a conductive layer 26 transparent to the electromagnetic radiation R_LED emitted by the LED light-emitting diodes, forming an electrode covering each LED light-emitting diode and extending further over the insulating layer 24 between the LED light-emitting diodes; - a reflective and conductive layer 28, extending over the conductive layer 26 between the LEDs, the reflective and conductive layer 28 being able, alternatively, to be interposed between the electrode layer 26 and the insulating layer 24 between the LEDs; and - the encapsulation layer 6 extending over layers 26 and 28, in physical contact with layers 26 and 28, completely covering the light-emitting diodes LEDs, and comprising a top face 35, preferably flat.

[0088] In [Fig. 12], lateral insulation trenches 11 extending into the substrate 10 are further shown. The lateral insulation trenches 11 electrically isolate from portions of the substrate, which allows each LED or groups of LEDs to be controlled separately.

[0089] In [Fig. 12], the conductive elements 7 are not shown. The optoelectronic circuit 5 may include additional layers not shown, in particular moisture- and / or air-tight protective layers, an anti-reflective layer, etc. Alternatively, the encapsulation layer 6 may not be present.

[0090] According to one embodiment, the optoelectronic circuit 5 comprises a light-emitting diode (LED) density greater than 10,000 / mm², preferably greater than 20,000 / mm², and even more preferably greater than 40,000 / mm², in particular greater than 10⁶ / mm². The LEDs may be arranged in a square grid, with one LED located at each intersection of a row and a column. The spacing along the rows and / or columns may be between 0.1 pm and 100 pm, preferably between 0.1 pm and 6 pm. Alternatively, the LEDs may be arranged in another configuration, for example, in a hexagonal arrangement.

[0091] According to one embodiment, each LED is adapted to emit radiation R_LED whose central wavelength is in the range of 400 nm to 480 nm, or 480 nm to 560 nm, or 570 nm to 650 nm.

[0092] According to another embodiment, the substrate 10 is present only at intermediate stages of the process of making the optoelectronic circuit 5 but is then removed and is not present on the final product.

[0093] Figure 13 represents an embodiment of LEDs. Each LED comprises a wire 21 in contact with the seed layer 16 through one of the openings 20 and a shell 22 comprising a stack of semiconductor layers covering the side walls and the top of the wire 21. The assembly formed by each wire 21 and the associated shell 22 constitutes an LED.

[0094] The shell 22 may comprise a stack of several layers, including an active layer 23 and a bonding layer 25. The active layer 23 is the layer from which the majority of the radiation supplied by the light-emitting diode (LED) is emitted. By way of example, the active layer 23 may include confinement means, such as a single quantum well or multiple quantum wells. The bonding layer 25 may comprise a stack of semiconductor layers of the same material as the wire 21 but with the opposite conductivity to that of the wire 21. The thickness of the active layer 23 may be between 1 nm and 100 nm.

[0095] A method for manufacturing the optoelectronic circuit 5 includes forming three-dimensional light-emitting diodes (LEDs) on a plate, and cutting the plate to separate the optoelectronic device from the rest of the plate. The formation The three-dimensional light-emitting diode (LED) growth process on the wafer includes, in particular, epitaxial growth steps. Several copies of the optoelectronic circuit 5 can be produced simultaneously on the same wafer and then separated. The growth process for the wires 21 and other layers of the LEDs can be a process of the type or a combination of processes of the type of chemical vapor deposition (CVD) or metal-organic chemical vapor deposition (MOCVD), also known as metal-organic vapor phase epitaxy (MOVPE).However, processes such as molecular beam epitaxy (MBE), gas-source MBE (GSMBE), metal-organic MBE (MOMBE), plasma-assisted MBE (PAMBE), atomic layer epitaxy (ALE), or hydride vapor phase epitaxy (HVPE) can be used. Electrochemical processes can also be employed, for example, chemical bath deposition (CBD), hydrothermal processes, liquid aerosol pyrolysis, or electrodeposition.

[0096] The substrate 10 may be a single-piece structure or a layer covering a support made of another material. The substrate 10 is preferably a semiconductor substrate, for example, a silicon, germanium, silicon carbide, III-V compound such as GaN or GaAs, or a ZnO substrate. Preferably, the substrate 10 is a single-crystal silicon substrate. Preferably, it is a semiconductor substrate compatible with the manufacturing processes used in microelectronics. The substrate 10 may be a multilayer silicon-on-insulator (SOI) structure.

[0097] The cross-section of the openings 20 may correspond to the desired cross-section of the wires 21 or may be different from the cross-section of the wires that will be obtained. The equivalent diameter of the wires 21 may be equal to or greater than the equivalent diameter of the openings 20.

[0098] The germination layer 16 is made of a material that promotes wire growth. By way of example, the material composing the germination layer 16 may be a nitride, a carbide, or a boride of a transition metal from group IV, V, or VI of the periodic table of elements, or a combination of these compounds. By way of example, the germination layer 16 may be made of aluminum nitride (AIN), boron (B), boron nitride (BN), titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), hafnium (Hf), hafnium nitride (HfN), or niobium (Nb), niobium nitride (NbN), zirconium (Zr), zirconium borate (ZrB2), zirconium nitride (ZrN), silicon carbide (SiC), tantalum nitride and carbide (TaCN), magnesium nitride in the form MgxNy, where x is approximately 3 and y is approximately 2, for example magnesium nitride in the form Mg3N2 or gallium magnesium nitride (MgGaN), tungsten (W), tungsten nitride (WN), or a combination thereof. The nucleation layer 16 may have a single-layer structure or correspond to a stack of at least two layers, each layer being, for example, one of the materials described above.

[0099] According to another embodiment, the germination layer 16 may not be present. According to another embodiment, the germination layer 16 may be replaced by germination pads, for example formed at the bottom of the openings 20.

[0100] Each insulating layer 18, 24 may be made of a dielectric material, for example, silicon dioxide (SiO2), silicon nitride (SiNy, where x is approximately equal to 3 and y is approximately equal to 4, for example, Si3N4), silicon oxynitride (in particular, of general formula SiOxNy, for example, Si2ON2), aluminum oxide (Al2O3), hafnium oxide (HfO2), titanium dioxide (TiO2), or diamond. The insulating layer 18, 24 may have a single-layer structure or correspond to a stack of two or more layers. When the insulating layer 18 corresponds to a stack of at least two layers, the top layer of the stack is insulating, for example, made of a dielectric material.

[0101] The wires 21 comprise predominantly, preferably more than 60% by mass, more preferably more than 80% by mass, at least one semiconductor material. The semiconductor material may be silicon, germanium, silicon carbide, an IILV compound, an ILVI compound, or a combination of at least two of these compounds.

[0102] Examples of Group III elements include gallium (Ga), indium (In), or aluminum (Al). Examples of Group IIIN compounds are GaN, AIN, InN, InGaN, AlGaN, or AlInGaN. Other Group V elements may also be used, for example, phosphorus or arsenic. Generally, the elements in the IILV compound may be combined in different mole fractions. Examples of Group II elements include Group IIA elements, notably beryllium (Be) and magnesium (Mg), and Group IIB elements, notably zinc (Zn), cadmium (Cd), and mercury (Hg). Examples of Group VI elements include Group VIA elements, notably oxygen (O) and tellurium (Te). Examples of ILVI compounds are ZnO, ZnMgO, CdZnO, CdZnMgO, CdHgTe, CdTe, and HgTe. Generally, the elements in an ILVI compound can be combined in different mole fractions. The semi-solid material conductor of wires may include a dopant, for example silicon providing N-type doping of a III-N compound, or magnesium providing P-type doping of a III-N compound.

[0103] The conductive layer 28 preferably corresponds to a metallic layer, for example of aluminium, silver, copper, gold or zinc. The thickness of the conductive layer 28 can be between 0.01 pm and 1000 pm.

[0104] The electrode layer 26 may be a layer of a transparent and conductive material such as indium tin oxide (ITO), aluminum- or gallium-doped zinc oxide, or graphene. The thickness of the electrode layer 26 may be between 0.01 pm and 10 pm.

[0105] The encapsulation layer 34 may be made of an inorganic material that is at least partially transparent to the radiation emitted by photoluminescent particles and / or light-emitting diodes (LEDs). By way of example, the inorganic material may be chosen from the group comprising silicon oxides, of the type SiOx where x is a real number ranging from 1 to 2, silicon nitrides (SixNy, where x is approximately equal to 3 and y is approximately equal to 4, for example Si3N4), silicon oxynitrides (in particular of the general formula SiOxNy, for example Si2ON2), titanium dioxide, aluminum oxides, for example Al2O3, and mixtures of these compounds. The encapsulation layer 34 may be made of an organic material that is at least partially transparent. By way of example, the encapsulation layer 34 may be a silicone polymer, an epoxy polymer, an acrylic polymer, or a polycarbonate.The encapsulation layer 34 can have a single-layer or multi-layer structure, and include, for example, a stack of organic and / or inorganic layers.

[0106] According to one embodiment, the radiation emitted by one of the photoluminescent blocks corresponds to green light, that is to say, radiation with a wavelength in the range of 490 nm to 580 nm. According to another embodiment, the radiation emitted by another of the photoluminescent blocks corresponds to red light, that is to say, radiation with a wavelength in the range of 590 nm to 720 nm.

[0107] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to those skilled in the art. In particular, although in the embodiments described above the light-emitting diodes are radial, it is clear that the present embodiments can be implemented with axial light-emitting diodes in which the active area of ​​the LED is present only at the top of the wire.

[0108] Finally, the practical implementation of the embodiments and variants described is to be completed. scope of the person's profession based on the functional indications given above.

Claims

Demands

1. Method of adjusting the center wavelength (Xc) of the radiation emitted by an optoelectronic device (Pix) comprising three-dimensional light-emitting diodes (LEDs) comprising a step of measuring the center wavelength, a step of determining a current density (J) per LED to obtain a target center wavelength, and a step of connecting / disconnecting LEDs among the LEDs to vary the current density per LED until the determined current density.

2. A method according to claim 1, wherein each three-dimensional light-emitting diode (LED) is of the radial type.

3. A method according to claim 1 or 2, wherein the optoelectronic device (Pix) comprises a current source powering the three-dimensional light-emitting diodes (LEDs).

4. A method according to any one of claims 1 to 3, wherein the step of determining a current density (J) by light-emitting diode to obtain a target center wavelength comprises determining the current density of the light-emitting diode (LED), determining the current density difference to be achieved as a function of the difference between the measured center wavelength and the target center wavelength, and determining the current density from the current density and the determined current density difference.

5. A method according to any one of claims 1 to 4, wherein the light-emitting diodes (LEDs) are distributed into groups of light-emitting diodes, the connection / disconnection step comprising connecting / disconnecting the light-emitting diodes from at least one of the groups of light-emitting diodes.

6. A method according to any one of claims 1 to 5, wherein the optoelectronic device (Pix) comprises programmable switches (50) each connected to at least one of the light-emitting diodes (LEDs), the connection / disconnection step comprising the opening / closing of the programmable switches (50).

7. Method according to claim 6, wherein each programmable switch (50) includes a fuse, the connection / disconnection step including the opening of fuses among the fuses.

8. Method according to claim 7, wherein the opening of each fuse is achieved by a laser treatment of the optoelectronic device (Pix).

9. A method according to claim 6, wherein each programmable switch (50) comprises a switch controllable by a binary signal and wherein the optoelectronic device (Pix) comprises a memory (MEM) in which the binary signals are stored.

10. Method according to claim 9, wherein the memory (MEM) comprises memory cells each comprising a fuse, the connection / disconnection step comprising opening fuses among the fuses.

11. Method according to claim 10, wherein the opening of each fuse is achieved by a laser treatment of the optoelectronic device (Pix).

12. Method according to claim 9, wherein the connection / disconnection step includes supplying binary signals to memory (MEM).

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