Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L25/00—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof
  • H01L25/16—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof the devices being of types provided for in two or more different main groups of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. forming hybrid circuits
  • H01L25/167—Assemblies consisting of a plurality of individual semiconductor or other solid state devices ; Multistep manufacturing processes thereof the devices being of types provided for in two or more different main groups of groups H01L27/00 - H01L33/00, or in a single subclass of H10K, H10N, e.g. forming hybrid circuits comprising optoelectronic devices, e.g. LED, photodiodes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/12—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto
  • H01L31/14—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto the light source or sources being controlled by the semiconductor device sensitive to radiation, e.g. image converters, image amplifiers or image storage devices
  • H01L31/147—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto the light source or sources being controlled by the semiconductor device sensitive to radiation, e.g. image converters, image amplifiers or image storage devices the light sources and the devices sensitive to radiation all being semiconductor devices characterised by potential barriers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/0004—Devices characterised by their operation
  • H01L33/002—Devices characterised by their operation having heterojunctions or graded gap
  • H01L33/0025—Devices characterised by their operation having heterojunctions or graded gap comprising only AIIIBV compounds
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
  • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• • H—ELECTRICITY
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  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/08—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/26—Materials of the light emitting region
  • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
  • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
  • H01L33/50—Wavelength conversion elements
  • H01L33/501—Wavelength conversion elements characterised by the materials, e.g. binder
  • H01L33/502—Wavelength conversion materials
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/10—Controlling the intensity of the light
  • H05B45/14—Controlling the intensity of the light using electrical feedback from LEDs or from LED modules
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
  • H05B45/20—Controlling the colour of the light
  • H05B45/24—Controlling the colour of the light using electrical feedback from LEDs or from LED modules
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/10—Bump connectors; Manufacturing methods related thereto
  • H01L2224/15—Structure, shape, material or disposition of the bump connectors after the connecting process
  • H01L2224/16—Structure, shape, material or disposition of the bump connectors after the connecting process of an individual bump connector
  • H01L2224/161—Disposition
  • H01L2224/16151—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
  • H01L2224/16221—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
  • H01L2224/16225—Disposition the bump connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/16—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
  • H01L33/18—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous within the light emitting region
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate
  • H01L33/24—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate of the light emitting region, e.g. non-planar junction

Definitions

• the invention relates to the field of light-emitting diodes (called LEDs or LEDs), and in particular that of light emitting devices comprising one or more LEDs (bulbs, screens, projectors, image walls, etc.).
• the invention also relates to a device and a method for adjusting the light emission characteristics of an LED, which can serve in particular to determine power supply parameters of the LED to obtain a light emission according to a length of light. wave and a desired light intensity.
• LEDs When producing certain LEDs, such as LEDs intended to be coupled with phosphor converting part of the blue light emitted by the LEDs into a yellow light and finally having a white light emission, these LEDs are sorted at the output to keep only those whose emission wavelength corresponds precisely to the desired wavelength, for example the optimal wavelength to excite phosphorus in the case of LEDs used to emit white light.
• the wavelength value emitted by the LEDs depends on several parameters of the LEDs, in particular the composition of the quantum well materials of the LEDS and the thickness of these quantum wells.
• a large substrate (100 mm, 150 mm, or 200 mm diameter) is used to grow various semiconductor materials (for example by epitaxy), these stacks of materials forming the corresponding quantum wells. to the emitting layers of the LEDs.
• the substrate is then cut into very small rectangles ("dies" in English), forming individual chips having one or more LEDs. Electrical contacts are then made and phosphorus is added in the form of a coating on the emitting part of the LEDs.
• Small variations in quantum well thickness and / or quantum well material composition due to the fabrication steps implemented, have a significant influence on the emission wavelength obtained at the output of the LEDs.
• an LED comprising several InGaN-based quantum wells and normally emitting at a wavelength of about 420 nm
• a modification of about 1% of the indium composition in the semiconductor of the quantum wells modifies by about 5 nm the wavelength emitted by the LED.
• a change of about 0.5 nm in the thickness of one of the InGaN quantum wells with a nominal thickness of about 2.5 nm of such an LED results in a wavelength shift. emission of about 10 nm.
• the values of these two parameters can vary greatly from one LED to another at the output of production, in particular because of the growth processes used for their manufacture, which can create important variations of the color finally emitted by the LEDs.
• An object of the present invention is to propose a light emitting device comprising at least one light-emitting diode and which makes it possible to overcome and compensate for any variations in the wavelength emitted by the light-emitting diode, for example due to variations the electroluminescent diode and in particular the thickness and / or the composition of the materials of the emitting layer (s) of the light-emitting diode.
• the present invention proposes a light emitting device comprising at least:
• an electroluminescent diode comprising:
• At least one emitting layer capable of forming a quantum well and comprising a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements A 1, Ga 2 and ⁇ whose atomic composition, or atomic percentage, varies along the thickness of the emissive layer, and / or
• At least two emissive layers capable of forming two quantum wells and each comprising a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements of A 1, Ga and In, atomic compositions, or the atomic percentages, of said chemical element in the emitting layers being different from each other,
• a switching power supply capable of supplying the electroluminescent diode electrically with a periodic signal comprising a cyclic ratio a such that ae] ⁇ ; ⁇ ],
• control device for the switching power supply capable of modifying a peak value and the cyclic ratio a of the periodic signal respectively as a function of the values of the wavelength and of the intensity of the light to be detected, and function of target values of wavelength and intensity.
• Such a light emitting device therefore makes it possible to compensate for any variations in the wavelength emitted by the light-emitting diode, for example due to variations in the structure of the emitting layers of the light-emitting diode, by acting on the power supply parameters.
• electroluminescent diode Indeed, if the light-emitting diode emits, when fed with a standard periodic signal, a light whose value of the wavelength does not correspond to the target value sought (for example the optimal wavelength of phosphorus excitation), this difference between the value of the emitted wavelength and the target value is detected by the light emitting device detection device.
• the control device of the light emitting device then adapts the peak value of the periodic signal supplying the light-emitting diode, thus modifying the current density passing through the light-emitting diode, which makes it possible to to shift the value of the wavelength emitted by the light-emitting diode towards the target value sought.
• control device also adapts the duty cycle of the periodic electric supply signal of the light-emitting diode so that the light emission produced by the light-emitting diode at the right wavelength is also achieved with a light-emitting diode. light intensity corresponding to the desired target intensity value.
• the light emitting device also uses a light-emitting diode comprising one or more emitting layers forming one or more quantum wells which exhibit variations in the atomic composition of a chemical element of the column 13, or NIA column, of the periodic table of the elements of the ternary or quaternary semiconductor (s) of this or these emitting layers, these corresponding variations either to variations of the atomic composition of said chemical element within the emissive layer or of each of the emissive layers, or to atomic compositions of said chemical element that are different from one layer to another.
• a light-emitting diode comprising one or more emitting layers forming one or more quantum wells which exhibit variations in the atomic composition of a chemical element of the column 13, or NIA column, of the periodic table of the elements of the ternary or quaternary semiconductor (s) of this or these emitting layers, these corresponding variations either to variations of the atomic composition of said chemical element within the emissive layer or of each of the emissive layers, or to atomic
• emission wave of the light-emitting diode with respect to a light-emitting diode which would comprise one or more emitting layers whose atomic composition of said semiconductor chemical element of this or these layers would be of constant value throughout the active zone which comprises this or these emissive layers.
• the ternary or quaternary semiconductor may comprise at least one chemical element of the column 13, or NIA column, of the periodic table of the elements of A 1, Ga and In, and may further comprise at least one chemical element. Column 15, or column VA, of the periodic table of elements.
• the chemical element of column 15 of the periodic table of the elements can be chosen by N, P, As and Sb. In the case of a ternary semiconductor, this may comprise a chemical element of column 15 of the periodic table of the elements and two chemical elements of column 13 of the periodic table of elements, corresponding, for example, to InGaN . In the case of a quaternary semiconductor, this may comprise a chemical element of column 15 of the periodic table of the elements and three chemical elements of column 13 of the periodic table of elements, corresponding for example to GaAlInN or GaAIlnP or GaAIInAs.
• the chemical elements of the semiconductors of the emissive layers may be of a similar nature in all the emissive layers, only the atomic compositions of said chemical element varying within the emissive layers or being different from one emissive layer to another.
• Said chemical element may be indium or aluminum.
• the expression "atomic composition of said chemical element" corresponds to the atomic percentage X of indium in this semiconductor.
• the gap of the quantum well varies according to the atomic percentage X of said chemical element in this semiconductor.
• the emission energy in the quantum well varies according to the thickness of the quantum well and this atomic percentage X.
• atomic composition of said chemical element corresponds to the atomic percentage of one of the elements of column 13, for example the atomic percentage of indium or aluminum, relative to atomic percentage of the other of the elements of column 13, for example the atomic percentage of gallium.
• the light-emitting diode, the device for detecting the value of the wavelength and the intensity of the light to be emitted, the control device and the switching power supply can thus together form a feedback loop enabling to control and regulate the wavelength and the intensity of the light emitted by the light-emitting diode of such a light emitting device.
• Such a light emissive device also makes it possible to compensate for the effects of aging of the light emitting diode. Indeed, since the wavelength emitted by a light-emitting diode varies over time and its brightness decreases with time, such a light emitting device makes it possible to compensate for these effects due to the aging of the light-emitting diode and therefore to prolong its duration of use and its lifetime.
• the wavelength emitted by the light-emitting diode corresponds to the wavelength for which the light intensity is maximum in the emission spectrum of the light-emitting diode.
• Such a light emitting device may correspond, for example, to a light-emitting diode bulb (s) in which the device for detecting the value of the wavelength and the intensity of the light to be emitted, the control device and switching power supply are realized in the form of electronics integrated in the bulb.
• This luminous emitting device may also correspond to a screen, a projector or an image wall comprising a plurality of light-emitting diodes.
• the gap, or band gap energy, of an emissive layer capable of forming a quantum well may be less than the gap of barrier layers between which the emissive layer is disposed.
• the light emitting diode may comprise several emissive layers each capable of forming a quantum well, each of said emissive layers possibly comprising at least one ternary or quaternary semiconductor comprising at least one chemical element of column 13 of the periodic table of the elements Ga and In whose atomic composition varies along the thickness of said emissive layer, and / or whose atomic compositions in the emissive layers are different from each other.
• a difference between atomic compositions of said chemical element in two emissive layers may be greater than or equal to about 0.2%.
• the emitting layer or each of the emissive layers may be arranged against and between two barrier layers each comprising a semiconductor.
• the semiconductors of the barrier layers may advantageously be of the same family as that of the emissive layer or those of the emissive layers.
• the barrier layers may each comprise a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements of A 1, Ga and In whose atomic composition is of lesser value than that of the atomic composition of said chemical element in the emissive layer disposed against and between said barrier layers such that a gap in said emitting layer is less than a gap in said barrier layers, the semiconductor chemical elements of the barrier layers being of a similar nature to the chemical elements of the semiconductor of the emissive layer or layers.
• Such barrier layers allow to widen the range of values on which the wavelength to be emitted by the light emitting diode can be adjusted.
• the light-emitting diode may further comprise at least one n-doped semiconductor layer and at least one p-doped semiconductor layer between which at least the emitting layer or layers are located. These doped semiconductor layers form the pn junction of the light-emitting diode, the zone active electroluminescent diode comprising in particular the emitting layer or layers being disposed between these doped semiconductor layers.
• the semiconductors used to make the light emitting diode may all be of the family of nitrides, that is to say comprising nitrogen as a common element of the column 15, or column VA, of the periodic table of the elements.
• the value of this atomic composition may be, at a first face of said emissive layer or each of said emissive layers disposed on the side of the n-doped semiconductor layer, greater than the value of that at a second face, opposite to the first face and disposed on the side of the p-doped semiconductor layer, of said emitting layer or of each of said emissive layers, and / or, when the atomic compositions of said chemical element in the emissive layers are different from each other, the values of said atomic compositions can increase from one emitting layer to another in the direction of from the p-doped semiconductor layer to the n-doped semiconductor layer.
• the light emitting device may be such that:
• a variation of the atomic composition of said chemical element along the thickness of the or each of the emitting layers and / or a maximum difference between the atomic compositions of said chemical element in the emitting layers may be between about 0.2% and 2% (value of the variation of the atomic percentage of said chemical element), and / or
• the atomic composition of said chemical element along the thickness of the or each of the emissive layers and / or the atomic compositions of said chemical element in the emitting layers may be between about 15% and 17% (values of the atomic percentages of said chemical element).
• the semiconductor of the emissive layer or the semiconductors of the emissive layers may be InGaN.
• the device for detecting the value of the wavelength and the intensity of the light to be emitted by the light-emitting diode may have a plurality of photodiodes optically coupled to the light emitting diode and electrically connected to the control device of the switching power supply.
• Such photodiodes may in particular be made with the light-emitting diode in the same semiconductor substrate.
• the light-emitting diode may furthermore comprise, at the level of an exit face of the light, phosphor able to modify the wavelength of a part of the light intended to be emitted by the light-emitting diode.
• the periodic signal may be a square signal.
• This square signal may also be called a rectangular signal, the value of its duty ratio may vary and is not necessarily equal to 0.5.
• the frequency of the periodic signal may be between about 20 Hz and 1 MHz. In this way, the light emitted by the light emitting device and observed by a person is perceived as constant by this person because of the retinal persistence.
• the invention also relates to a device for adjusting a wavelength and an intensity of a light intended to be emitted by a light emitting diode comprising at least one emitting layer capable of forming a quantum well and comprising at least a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements among A 1, Ga and In whose atomic composition varies along the thickness of the emitting layer, and / or at least two emissive layers capable of forming two quantum wells and each comprising at least one ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements A 1, Ga and In, the atomic compositions of said chemical element in the emitting layers being different from each other, the adjusting device comprising at least:
• a switching power supply capable of supplying the electroluminescent diode electrically with a periodic signal comprising a duty ratio a such that a e] ⁇ ; ⁇ ],
• control device for the switching power supply capable of modifying a peak value and the cyclic ratio a of the periodic signal respectively as a function of the values of the wavelength and of the intensity of the light intended to be detected, and according to target values of the wavelength and the intensity.
• Such an adjustment device may for example be used to test light-emitting diodes in order to determine, for each of these light-emitting diodes, the values of the duty cycle and the peak value of the power supply signal making it possible to obtain light emission. whose wavelength and intensity correspond to the target values sought.
• the invention also relates to a method for adjusting a wavelength and an intensity of a light intended to be emitted by a light-emitting diode comprising at least one emitting layer capable of forming a quantum well and comprising at least a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements of A 1, Ga and I n whose atomic composition varies along the thickness of the emitting layer, and / or at least two emissive layers capable of forming two quantum wells and each comprising at least one ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements A 1, Ga and l
• the atomic compositions of said chemical element in the emitting layers being different from each other, the method comprising at least the following steps: detection of the value of the wavelength and of the intensity of the light emitted by the light-emitting diode,
• FIG. 1 shows schematically a light emitting device, object of the present invention, according to a particular embodiment
• FIG. 2 diagrammatically represents an electrical signal supplying electrically an LED of the light emitting device object of the present invention
• FIG. 3 shows schematically a first embodiment of an LED light emitting device object of the present invention
• FIG. 4 represents the forbidden band energy within the active zone of the LED according to the first exemplary embodiment, as a function of the position along the thickness of the active zone of the LED;
• FIG. 5 represents the rate of radiative recombinations within the emitting layer of the LED according to the first exemplary embodiment, as a function of the position along the thickness of the emitting layer of the LED and for a current density. about 100 A / cm 2 crossing the LED;
• FIG. 6 represents the luminous intensity of the LED according to the first exemplary embodiment as a function of the emission energy when the LED is traversed by a current density of approximately 100 A / cm 2 ;
• FIG. 7 represents the rate of radiative recombinations within the emitting layer of the LED according to the first embodiment, as a function of the position along the thickness of the emitting layer of the LED and for a current density. about 450 A / cm 2 crossing the LED;
• FIG. 8 represents the luminous intensity of the LED according to the first exemplary embodiment as a function of the emission energy when the LED is traversed by a current density of approximately 450 A / cm 2 ;
• FIG. 9 schematically represents a second exemplary embodiment of an LED of the light emitting device which is the subject of the present invention.
• FIGS. 10 to 12 show band structures of the active zone of the LED, according to various exemplary embodiments, of the light emitting device of the present invention
• FIGS. 13A and 13B schematically represent exemplary embodiments of an LED, in the form of a nanowire, of the light emitting device that is the subject of the present invention.
• the light emitting device 100 comprises an LED 102 which is here intended to produce a light emission of white color.
• This white light emission is obtained thanks to an emitting structure of the LED 102 capable of emitting a blue light and phosphorus covering this emissive structure, this phosphor making it possible to convert part of the emitted blue light into a yellow light.
• the LED 102 is mechanically and electrically coupled to a substrate 104, for example made of silicon, via fusible material balls 106. As a variant, the LED 102 could be made directly by growth on the substrate 104.
• the LED 102 is able to emit both from a rear face facing the substrate 104 and from a front face opposite the rear face.
• the light emitting device 100 comprises a device for detecting the value of a wavelength and an intensity of the light emitted by the LED 102 comprising here two photodiodes 108 made in the substrate 104, and which are arranged opposite the back of the LED 102.
• a first of the two photodiodes 108 detects the wavelengths lower than a first cut-off wavelength called ⁇ and for example equal to about 450 nm.
• a second of the two photodiodes 108 detects the wavelengths greater than a second cut-off wavelength called ⁇ 2 which is such that ⁇ 2 > ⁇ and for example equal to approximately 470 nm.
• the first cut-off wavelength ⁇ is for example defined by a low-pass filter formed in front of the first of the two photodiodes 108 (between this first photodiode and the LED 102) and the second cut-off wavelength ⁇ 2 is by example defined by a high-pass filter formed in front of the second of the two photodiodes 108 (between this second photodiode and the LED 102).
• the device for detecting the value of a wavelength and intensity of the light emitted by the LED 102 also comprises calculation means (not shown in FIG. 1) coupled to the photodiodes 108 and making it possible to calculate, from the sum of the electrical signals, or photo-currents, delivered by the photodiodes 108 the intensity of the light, or total luminous power, emitted by the LED 102.
• calculation means also make it possible to calculate the wavelength of the light emitted by the LED 102 from the ratio between the electrical signals delivered by the two photodiodes 108.
• the detection of the value of the wavelength emitted by the LED 102 and the detection of the intensity of the light emitted by the LED 102 could be carried out by two distinct devices.
• the light emitting device 100 also comprises a switching power supply 110 for electrically supplying the LED 102.
• This switching power supply 110 delivers a voltage or a current in the form of a periodic signal, for example a square signal, of period T and whose peak value Imax or Umax and a cycle ratio a are adjustable, the duty ratio a being such that a G] ⁇ ; ⁇ ].
• FIG. 2 represents an example of the periodic supply signal of the LED 102, here a current of the form of a square signal.
• control device 111 receiving as input the detected values of the wavelength and the intensity of the light emitted by the LED 102 and delivering as output a control signal sent to the switching power supply 110 (alternatively, it is possible that the control device 111 and the switching power supply 110 form a single element). These elements form a feedback loop such that the peak value Imax or Umax and the duty cycle a of the signal delivered by the switching power supply 110 are a function of the desired wavelength and intensity for the light intended to be emitted by the LED 102.
• the peak value and the cycle ratio of the feed signal are adjusted so that the sum and the ratio photocurrents delivered by the photodiodes 108 are of values equal to those obtained for a desired intensity and wavelength (these target values of the sum and the ratio of the photocurrents are known or determined beforehand with an LED serving reference).
• these two devices can be optically coupled to the LED 102 and electrically connected to the controller 111 by forming two feedback loops.
• the detection device of the light emitting device 100 can be made integrated to the substrate as described for example in the document US 2009/0040755 A1.
• a first embodiment of the LED 102 is shown schematically in FIG.
• the LED 102 has a p-n junction formed by an n-doped semiconductor layer 112 and a p-doped semiconductor layer 114.
• the semiconductor of the layers 112 and 114 is for example GaN.
• Layer 112 is n-doped with a donor concentration of between about 10 17 and 5.10 19 donors / cm 3 .
• the layer 114 is p-doped with an acceptor concentration of between 10 17 and 5.10 19 donors / cm 3 .
• These two layers 112 and 114 have for example each a thickness (dimension along the Z axis shown in Figure 3) between about 20 nm and 10 ⁇ .
• a first transparent electrode 116 is disposed against the n-doped layer 112 and forms a cathode of the LED 102
• a second transparent electrode 118 is disposed against the p-doped layer 114 and forms an anode of the LED 102.
• the LED 102 comprises, between the n-doped layer 112 and the p-doped layer 114, an active zone 120 comprising an emitting layer 122 comprising a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements 'Ai, Ga and In, here of the InGaN, forming a quantum well of the LED 102.
• This semiconductor may furthermore comprise at least one chemical element of the column 15 of the periodic table of the elements, which may be chosen by the N, the P, the Ace and the Sb.
• the thickness of the emitting layer 122 is for example equal to about 3 nm and more generally between about 0.5 nm and 10 nm.
• the active zone 120 also comprises two barrier layers 124.1 and 124.2 preferably comprising the same semiconductor as the basic semiconductor to which said chemical element, for example indium, is added to form the ternary or quaternary semiconductor. of the emitting layer 122, that is to say here GaN, between which the emitting layer 122 is disposed.
• the first barrier layer 124.1 is disposed between the n-doped layer 112 and the emitting layer 122
• the second barrier layer 124.2 is disposed between the p-doped layer 114 and the emitting layer 122.
• the thickness of each of the barrier layers 124.1 and 124.2 is for example between about 1 nm and 25 nm.
• All the layers of the active zone 120 of the LED 102 that is to say the emitting layer 122 and the barrier layers 124.1 and 124.2, comprise unintentionally doped materials (residual donor concentration n n id equal to about 10 17 donors / cm 3 , or between about 10 15 and 10 18 donors / cm 3 ).
• the atomic composition of said semiconductor chemical element of the emitting layer 122 corresponding here to the atomic composition of the indium in the InGaN of the emitting layer 122, or to the atomic percentage of indium in the InGaN, varies along the thickness (dimension along the Z axis shown in Figure 3) of the emitting layer 122.
• this indium composition varies in a decreasing manner in the direction from the n 112 doped layer to the p-doped layer 114.
• the indium composition of the emitting layer 122 at a first face 121 lying against the first barrier layer 124.1, that is to say on the side of the n 112 doped layer is equal to about 16% (atomic percentage value of indium), this indium composition varying substantially continuously and decreasing along the thickness of the emitting layer 122 to reach, at a second level f ace 123 of the emitting layer 122 lying against the second barrier layer 124.2, that is to say on the side of the p-doped layer 114, a value equal to about 15%.
• the band gap energy obtained within such an emitting layer 122, as well as in a part of the barrier layers 124.1 and 124.2 in contact with the emitting layer 122, as a function of the thickness of these layers, is represented on the figure 4.
• FIG. 5 represents the rate of radiative recombinations within the emitting layer 122, as a function of the position along the thickness of the emitting layer 122, for a current density of about 100 A / cm 2 crossing the LED. 102 (this current density value of about 100 A / cm 2 corresponding to a standard power supply of an LED).
• FIG. 5 shows that a maximum value, referenced 10, of the rate of radiative recombinations within the emitting layer 122 is obtained on the richest indium side, that is to say at the level of the first face. 121 of the emitting layer 122 lying against the first barrier layer 124.1 and having an indium composition equal to about 16%, where the band gap energy is lowest in the emitting layer 122, the side of the layer doped n 112.
• FIG. 6 represents the luminous intensity (in arbitrary units in this figure) of the LED 102 as a function of the emission energy (in eV) when the LED 102 is traversed by a current density of approximately 100 A / cm 2 . It can be seen in this FIG. 6 that the emission intensity is maximum for an emission energy of approximately 2.74 eV, which corresponds to a wavelength equal to approximately 452 nm. This value of 452 nm is therefore equivalent to the wavelength emitted by the LED 102 when it is powered with a current density equal to about 100 A / cm 2 .
• FIG. 7 represents the rate of radiative recombinations within the emitting layer 122, as a function of the position along the thickness of the emitting layer 122, for a current density of approximately 450 A / cm 2 crossing the LED. 102. It can be seen from this FIG. 7 that a maximum value, referenced 12, of the rate of radiative recombinations within the emitting layer 122 is obtained on the side that is less rich in indium, that is to say at the level of the second face 123 of the emitting layer 122 lying against the second barrier layer 124.2 and having an indium composition equal to about 15%, where the forbidden band energy is the strongest in the emitting layer 122, on the side of the p-doped layer 114.
• FIG. 8 represents the luminous intensity (in arbitrary units) of the LED 102 as a function of the emission energy (in eV) when the LED 102 is traversed by a current density of about 450 A / cm 2 . It can be seen in this FIG. 8 that the emission intensity is maximum for an emission energy of approximately 2.81 eV, which corresponds to a wavelength equal to approximately 441 nm. This value of 441 nm is therefore comparable to the wavelength emitted by the LED 102 when the latter is powered with a current density equal to about 450 A / cm 2 .
• the variation of the indium composition within the emitting layer 122 makes it possible to have a strong adaptability of the wavelength emitted by the emitting layer 122 by varying the density
• the "position" within the quantum well is varied, at the level of which the maximum of radiative recombinations occurs.
• the indium composition varies according to the position within this quantum well, the emission energy obtained, and therefore the wavelength emitted by the LED 102, then also varies as a function of this current density. .
• the emission wavelength of LED 102 varies by about 9 nm by varying the current density by a factor equal to about 4.5. More generally, with a variation of about 1% of the indium composition within the emitting layer of the LED, it is possible to adjust the emission wavelength over a range of about 10 nm. varying the current density by a factor of about 5.
• the wavelength emitted by the LED 102 is thus adjusted (within the adjustment range obtained by the variation of the indium composition of the emitting layer 122 ) by adjusting the peak value of the power supply signal of the LED 102, for example here the adjustment of the value Imax of the current delivered by the switching power supply 110 (the current density passing through the LED 102 being function of this value Imax), which is effected according to the desired emission wavelength.
• the control device 111 receiving the input signals delivered by the photodiodes 108 then commands the switching power supply 110 to output a current of greater amplitude. Conversely, if the photodiodes 108 detect that the LED 102 emits light of wavelength too low, the control device 111 then commands the switching power supply 110 to output a current of smaller amplitude.
• this emission light intensity of the LED 102 is adjusted to the desired level via the adjustment of the duty cycle a of the signal periodic power supply of LED 102.
• the intensity of the light emitted by the LED 102 will be dependent on the peak value but also on the value of a.
• the value of a is for example chosen equal at about 0.22 when the LED 102 is traversed by a current density equal to about 450 A / cm 2 to obtain a light of the same light intensity as when the LED 102 is traversed by a current density equal to about 100 A / cm 2 .
• the period T of the periodic power supply signal of the LED 102 is chosen sufficiently small not to observe any flickering or blinking of LED 102, and corresponding for example to a frequency between about 20 Hz and 1 MHz.
• the control device 111 receiving as input the signal delivered by this detection device then commands the switching power supply 110 to output the output current with a smaller duty cycle a. Conversely, if the light intensity detection device emitted by the LED 102 detects that the LED 102 emits light with too little intensity, the control device 111 then commands the switching power supply 110 to deliver the output current with a larger duty cycle a.
• FIG. 9 schematically represents a second exemplary embodiment of the LED 102.
• the active zone 120 of the LED 102 according to this second exemplary embodiment comprises several quantum wells formed by an alternation of emitting layers 122.1 to 122.5 and barrier layers 124.1 to 124.6, each of the emitting layers 122.1 to 122.5 being disposed between and against two of the barrier layers 124.1 to 124.6.
• Each of the emitting layers 122.1 to 122.5 comprises InGaN whose indium composition varies along the thickness of these layers such that this composition varies increasingly in the direction from the p-doped layer 114 to the n-doped layer. 112, as for the emitting layer 122 previously described for the LED 102 according to the first embodiment.
• the emitting layers 122.1 to 122.5 are similar to each other, and each has an indium composition varying from 15% to 16% from one face to the other of each of them. of these layers in the direction from the p-doped layer 114 to the n-doped layer 112.
• Each of the emitting layers 122.1 to 122.5 for example, has a thickness (dimension along the axis
• each of the barrier layers 124.1 to 124.6 has, for example, a thickness equal to approximately 5 nm.
• the 0 V band structure of the active zone 120 of the LED 102 according to the second exemplary embodiment is shown schematically in FIG. 10 (in which the abscissa represents the direction of growth of the layers of the LED 102, and the ordinate represents the energy of bands within the layers of the LED 102).
• the references of the different layers of the active zone 120 are recalled in this figure. It can be seen in FIG. 10 that the variation of the indium composition in each of the emitting layers 122.1 to 122.5 generates variations of the valence and conduction bands within the quantum wells of the active zone 120 formed by these emissive layers 122.1 to 122.5 .
• the LED 102 As for the LED 102 according to the first exemplary embodiment, it is therefore possible to adjust the wavelength emitted by each quantum well by adjusting the current density passing through the LED 102. Because the indium composition in each of the Since the emitting layers 122.1 to 122.5 vary identically from one layer to another, the wavelength emitted from each of the quantum wells formed by these layers is substantially identical from one quantum well to another.
• each emitting layer 122.1 to 122.5 it is possible for each emitting layer 122.1 to 122.5 to comprise InGaN whose indium composition is constant within each of the emitting layers 122.1 to 122.5. , but which are different from one emissive layer to another.
• the filling of the quantum wells of the LED 102 by the charge carriers is modified.
• the quantum well, among those of the active zone 120, which produces the light emission of such an LED 102 therefore changes as a function of the value of the current density passing through the LED 102. Because the quantum wells have different compositions in indium, this therefore implies a variation of the wavelength emitted by LED 102.
• the difference in indium composition between the last emitting layer 122.5, which corresponds to that of which InGaN has the lowest indium composition, and the first emitting layer 122.1, which corresponds to the one whose InGaN has the highest indium composition, that is to say the maximum difference between the atomic compositions of indium in the emitting layers 122.1 to 122.5, may be the same order of magnitude as the difference in indium composition within a single emitting layer of LED 102 according to the second embodiment previously described in connection with FIG. if the indium composition varies within each of the emissive layers.
• the indium composition of the InGaN of the first emitting layer 122.1 is for example equal to about 16%, and that of the last emitting layer 122.5 is for example equal to about 15%.
• FIG. 11 represents the 0 V band structure of such an LED 102 according to this variant of the second exemplary embodiment (on which the abscissa represents the direction of growth of the layers of the LED 102, and the ordinate represents the band energy within the layers of
• the LED 102 may comprise two emissive layers, forming two quantum wells, each comprising a ternary or quaternary semiconductor comprising at least one chemical element of the column 13 of the periodic table of the elements by Al, Ga and In, the atomic compositions of said chemical element in these two emissive layers being different by at least 0.2%.
• This semiconductor may further comprise at least one chemical element of column 15 of the periodic table of the elements that may be chosen by N, P, As and Sb.
• These two emissive layers comprise, for example, InGaN respectively comprising atomic compositions of indium equal to approximately 16% and 16.2%.
• These two emissive layers are for example separated from each other by a GaN barrier layer of thickness equal to about 3 nm.
• the variation of the atomic composition of said chemical element of the column 13 of the periodic table of the elements for example the atomic composition of indium, along the thickness of the or each emissive layers, or a maximum difference between the atomic compositions of said chemical element in the emitting layers, may especially be between about 0.1% and 2%, or between about 0.2% and 2%, or between about 0%, 2% and 1%.
• this atomic composition of said chemical element along the thickness of the or each of the emissive layers or the atomic compositions of said chemical element in the emissive layers may be between about 15% and 17%, or between about 15% and 16%, or between about 16% and 17%.
• the LED 102 may comprise a different number of emitting layers each forming a quantum well of light emission, advantageously greater than 5 and for example equal to 10.
• the first emitting layer that located on the side of the n-doped layer 112 may comprise InGaN with an indium concentration equal to about 17% and the last emitting layer (that lying on the side of the p-doped layer 114) may comprise InGaN with an indium concentration equal to about 15%.
• LED 102 With such an LED 102, it is possible to vary the emitted wavelength over a range of about 15 nm, for example between about 455 nm and 440 nm for current densities ranging from 10 A / cm 2 to 100 nm. A / cm 2 .
• the barrier layers can be based on at least one ternary or quaternary semiconductor, for example InGaN, comprising at least one chemical element.
• ternary or quaternary semiconductor for example InGaN, comprising at least one chemical element.
• the n-doped layer 112 may also comprise a semiconductor similar to that of the emissive layers such as InGaN.
• FIG. 12 shows the 0 V band structure of an LED 102 having 10 InGaN emitting layers 122.1 to 122.10 with different indium atomic compositions ranging from about 17% on the n 112 doped layer side to about 15% on the side of the p-doped layer 114.
• the n 112 doped layer may comprise of the InGaN with an indium atomic composition equal to about 12%, and the p-doped layer 114 may comprise GaN.
• the InGaN barrier layers 124.1 to 124.11 also comprise indium whose atomic composition varies increasingly in the direction from the p-doped layer 114 to the n-doped layer 112.
• the semiconductor used for the different elements of the LED 102 comprises GaN (with addition of indium for producing the emitting layers, and possibly for producing the barrier layers and / or the doped layer n 112).
• GaN with addition of indium for producing the emitting layers, and possibly for producing the barrier layers and / or the doped layer n 112).
• the LED 102 from any semiconductor for performing pn junctions suitable for light-emitting diodes to one or more quantum wells comprising a ternary or quaternary semiconductor having at least one element chemical of column 13 of the periodic table of the elements chosen by Ai, Ga and ⁇ .
• large-gap semiconductors such as, for example, GalnN, ZnO, or ZnMgO potentially capable of producing light emission in the wavelength range.
• the chemical element of the column 13 of the periodic table of the elements added for the production of the emitting layers and possibly for the production of the barrier layers and / or the doped layer n being be indium or aluminum or gallium. It is also possible to use smaller gap semiconductors such as, for example, ⁇ , GaP, InGaP, InAs, GaAs, InGaAs, AIGalnP, of AIGaAs.
• the LED 102 previously described according to the various embodiments can be made in the form of a planar diode, that is to say in the form of a stack of layers formed for example by epitaxial growth on a substrate, the main faces of the different layers being arranged parallel to the plane of the substrate (parallel to the (X, Y) plane).
• LED 102 may also be in the form of a nanowire.
• FIG. 13A shows such an LED 102 made in the form of an axial nanowire, this nanowire comprising a stack formed of the first electrode 116, a semiconductor substrate 126 (for example silicon) of the n-type, a nucleation layer 128 for growing the nanowire, the first n-doped semiconductor layer 112, the active area 120, the second p-doped semiconductor layer 114, and the second electrode 118.
• An insulating material 130 may surround at least a portion of this nanowire which extends parallel to the Z axis.
• FIG. 13B represents an LED 102 made in the form of a radial nanowire, this nanowire comprising a stack formed of the first electrode 116, the semiconductor substrate 126, the nucleation layer 128 and the first layer 112 of doped semiconductor n. Insulating portions 130 partially surround the first layer 112 and the nucleation layer 128.
• the active zone 120 formed of the barrier layers 124 and the emitting layers 122, is made such that it surrounds a portion of the n-doped layer 112.
• the second p-doped semiconductor layer 114 is made as it surrounds the active area 120.
• the second electrode 118 is made by covering the second layer 114.
• the structure of these nanowires can be reversed, with in this case a p-type semiconductor substrate 128 on which the second layer 114 is made and then the other elements of the LED 102 in the reverse order of that described in Figures 13A and 13B.
• planar-type LED 102 may be similar for the LED 102 made in the form of a nanowire.
• the device 100 previously described may not be intended to achieve a light emission, and correspond to a device for adjusting a wavelength and intensity of a light intended to be emitted by an LED.
• a device for adjusting a wavelength and intensity of a light intended to be emitted by an LED may for example be used to test light-emitting diodes in order to determine, for each of these diodes electroluminescent values, the values of the duty cycle and the peak value of the power supply signal making it possible to obtain a light emission whose wavelength and intensity correspond to the desired target values.
• the device 100 may include a location (not shown) for temporarily connecting the LEDs tested.

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