LIGHT-EMITTING DIODE COMPRISING SEMICONDUCTOR BASED ON AlN P-DOPED WITH MAGNESIUM ATOMS AND LAYER OF DOPED DIAMOND

Abstract

To provide a light-emitting diode that does not require the presence of a strongly p-doped GaN layer on the p-doped side of the LED, and for which the design possibilities are not limited by the requirement to produce light emission from the back face of the LED.SOLUTION: A light-emitting diode (100) comprising: a first n-doped semiconductor portion (104); a second p-doped semiconductor portion (108); an active zone (106) disposed between the first and second portions and including at least one emitting semiconductor portion; and a layer (120) that is electrically conductive and optically transparent to at least one wavelength in the UV range configured to be emitted from the emitting portion, wherein the semiconductors of the first portion and the emitting portion include compounds comprising nitrogen atoms and atoms of aluminum and / or gallium, the semiconductor of the second portion includes p-doped AlGaInN in which the atomic concentration of magnesium is greater than 1017 atoms / cm3, and the electrically conductive layer includes doped diamond.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to the field of LEDs (i.e. light emitting diodes). Advantageously, the invention is applied to the manufacture of LEDs emitting light in the ultraviolet (UV) range. [Background technology]

[0002] Semiconductor heterostructure-based LEDs emitting in the UV range are composed of a stack of layers containing AlGaN of various compositions. Figure 1 shows a schematic diagram of the structure of such an LED 10. The LED 10 includes a p-n junction formed by a first layer 12 containing n-doped AlGaN and a second layer 14 containing p-doped AlGaN. The LED 10 also includes an active region 16 between layers 12 and 14, which forms the light-emitting region of the LED 10, i.e., the region where electron-hole combinations occur that generate photon emission. The active region 16 contains intentionally undoped AlGaN. The LED 10 also includes a heavily p-doped layer 18 of GaN in the second layer 14, as well as a conductive layer 20 disposed on the layer 18, comprising, for example, a Ni-Au bilayer stack.

[0003] The semiconductor composition of the active region 16 is selected as a function of the wavelength to be emitted. For emission in the UV range, the active region 16 is Al, with X such that 0≦X≦1. X Ga (1-X) The first layer 12 contains n-doped Al Y1 Ga (1-Y1) N, and the second layer 14 is p-doped Al Y2 Ga (1-Y2) N is included, and Y1>X and Y2>X.

[0004] Ideally, layers 12 and 14 would be formed of AlN (i.e., so that Y1=1 and Y2=1), simplifying the fabrication of LED 10. However, forming p-doped second layer 14 of AlN presents a problem because no technical solution exists that allows AlN to have a high enough level of p-type doping to ensure sufficient and necessary electrical conductivity for proper operation of LED 10. Therefore, layers 12 and 14 are currently fabricated so that Y1<1 and Y2<1.

[0005] Current injection, which must be performed from the layer 14 side of the LED 10, is another important limitation. This problem is currently solved by the presence of heavily p-doped GaN layer 18. However, absorption of UV radiation emitted from the active region 16 by that layer 18 limits the efficiency of the LED 10. Furthermore, the deposition of layer 20, which is necessary to ensure proper lateral spreading of the current flow lines and optimize current injection, contributes to further reducing the luminous efficiency of the LED due to the fact that this layer 20 absorbs a portion of the UV light emitted from the active region 16.

[0006] In the paper "GaN / AlGaN Nanocolumn Ultraviolet Light-Emitting Diode Using Double-Layer Graphene as Substrate and Transparent Electrode" by Ida Marie Hoiaas et al., Nano Lett. 2019, 19, 3, pp. 1649-1658, graphene is used as a substrate underneath the n-doped portion of the LED. The top of the structure uses heavily p-doped GaN, which suffers from the same drawbacks as mentioned above.

[0007] The use of graphene for contacting LEDs fabricated with a single wire has been proposed in a paper by M. Tchernycheva et al. (Nano Lett. 2014, 14, 5, pp. 2456-2465). While this solution is well-suited to the LED structure described in that paper, its implementation in LEDs with various structures is challenging, particularly due to the fragility of graphene and the variability of wire height. Furthermore, graphene is not deposited by epitaxy, and its transfer can be complicated. Furthermore, the sheet resistance remains high (~500 Ω / square, according to a paper by Y. Xu and J. Liun Small (2016, 12, No. 11, 1400-1419)).

[0008] Another solution consists in producing the LED so that light emission occurs from the back side (from the n-doped semiconductor layer side), through the sapphire substrate on which the various layers of the LED are formed. The sapphire substrate is transparent to the emitted UV light. However, this limits the design possibilities of the LED. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] GaN / AlGaN Nanocolumn Ultraviolet Light-Emitting Diode Using Double-Layer Graphene as Substrate and Transparent Electrode” by Ida Marie Hoiaas et al., Nano Lett. 2019, 19, 3, pp. 1649-1658 [Non-patent document 2] InGaN / GaN Core-Shell Single Nanowire Light Emitting Diodes with Graphene-Based P-Contact” by M. Tchernycheva et al., Nano Lett. 2014, 14, 5, pp. 2456-2465 [Non-patent document 3] Graphene as Transparent Electrodes: Fabrication and New Emerging Applications”, by Y.Xu and J. Liun Small 2016, 12, No. 11, 1400-1419 Summary of the Invention [Problem to be solved by the invention]

[0010] It is an object of the present invention to provide a light emitting diode that does not have the above drawbacks, i.e., that does not require the presence of a heavily p-doped GaN layer on the p-doped side of the LED and whose design possibilities are not limited by the requirement to produce light emission from the back surface of the LED. [Means for solving the problem]

[0011] For this purpose, a first n-doped semiconductor portion; a second p-doped semiconductor portion; and an active region disposed between the first and second portions and including at least one light emitting semiconductor portion; A light emitting diode comprising at least the semiconductor of the first portion and the light-emitting portion comprises a compound containing nitrogen atoms and aluminum and / or gallium atoms; The semiconductor of the second portion is Al doped with magnesium atoms. X2 Ga (1-X2-Y2) In Y2 N is contained, X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium is 10 17 atoms / cm 3 A light emitting diode is provided.

[0012] Therefore, Al p-doped with magnesium atoms is preferred, given that this semiconductor in the second part allows for sufficient current injection and broadening of the current flow lines. X2 Ga (1-X2-Y2) In Y2 The N-containing second semiconductor portion provides an LED in which a heavily p-doped GaN layer is not required on the p-doped side of the LED.

[0013] Furthermore, the semiconductor of the second portion does not absorb UV radiation, and therefore the provided LED is well suited to emit UV radiation, and this can be achieved through the second p-doped semiconductor portion of the LED.

[0014] The absence of a highly p-doped GaN layer also represents a simplification in the fabrication of the LED.

[0015] The presence of indium in the semiconductor of the second portion (comprising AlGaInN) allows for the incorporation of more doping atoms of magnesium compared to the same semiconductor without indium (i.e., AlGaN) due to the fact that the resulting atomic concentration of magnesium is proportional to the amount of indium present in the semiconductor. Therefore, the level of p-type doping that can be achieved in the semiconductor of the second portion is greater, allowing for sufficient current injection and broadening of the current streamlines. The presence of indium in AlN or AlGaN can increase the limited solubility of magnesium in AlN or AlGaN, for example, by a factor of 10, thereby increasing the doping level that can be achieved in this semiconductor.

[0016] The possibility of incorporating more magnesium atoms when the semiconductor contains indium is unexpected because these two types of atoms, when added separately to AlN, would result in compressive stress. Therefore, there is no reason to expect that their simultaneous addition would be advantageous in terms of stored plastic energy, as the addition of indium would not contribute to the relaxation of the elastic stress induced by the addition of magnesium.

[0017] Furthermore, according to the present invention, the LED includes a layer on top that is electrically conductive and optically transparent to the UV radiation emitted by the LED, and that includes doped diamond. The second portion is disposed between the active region and the conductive layer. The use of p-doped diamond to form the transparent electrode facilitates "diffusion," i.e., uniform distribution of current flow across the entire surface of the LED's injection layer formed by the second portion, which is advantageous for optimizing the LED's light-emitting performance. The choice of doped diamond to form the conductive layer on top of the LED is particularly wise, given that diamond's transparency, especially in the UV-C range, allows for significantly better performance than that achieved with other transparent conductive materials, such as conductive transparent oxides.

[0018] The diamond used to form this conductive layer may be, for example, nanocrystalline diamond, such as polycrystalline diamond.

[0019] The doped diamond of this conductive layer is not "diamond-like carbon" (DLC), a name derived from various amorphous carbon-based materials that may resemble diamond in certain properties (see, for example, the literature "Diamond-like carbon: state of the art" by A. Grill, Diamond and Related Materials Volume 8, Issues 2-5, March 1999, pages 428-434). Depending on the various preparation methods (and hydrogenation rates), the band gap energy of this material can be between 1.0 and 4.0 eV, which limits its use as a coating for use in the infrared and visible range (see the literature above), but is not suitable for producing optically transparent layers at least in the UV range of wavelengths. Furthermore, its resistivity can be modulated (10 2 -10 16 Ω / cm -1 ), but still high. For this reason, DLC is used as an insulating material rather than as a conductive material (see the references mentioned above).

[0020] The use of diamond to produce layers that are both electrically conductive and transparent at wavelengths in the UV range is not clear to those skilled in the art. Firstly, the possibility of heavily doping diamond to form conductive layers is not well known. Furthermore, those skilled in the art do not consider diamond to be a low-cost material, nor one whose growth conditions (temperature, pressure, sample size) are compatible with the production of layers that are both transparent and electrically conductive for LEDs.

[0021] The doped diamond layer also allows heat to dissipate due to the excellent heat conduction properties of diamond. Such a layer of doped diamond also has the advantage of being biocompatible for biomedical applications (e.g., optogenetics, fluorescence, etc.).

[0022] The atomic concentration of magnesium in the semiconductor of the second part can be greater than 10 20 atoms / cm 3 For example, the ratio of the atomic concentration of magnesium to the atomic concentration of indium can be from 1 to 20, or from 1 to 50, or in some cases from 1 to 100, preferably on the order of 10.

[0023] The semiconductor of the first part and the light-emitting part can include GaN, or AlN, or AlGaN, or InGaN, or AlGaInN.

[0024] The LED can be as follows: Y2 satisfies 0 < Y2 ≤ 0.01, and / or the atomic concentration of magnesium in the semiconductor of the second part is from 10 20 atoms / cm 3 to 10 21 atoms / cm 3 is included.

[0025] With the above configuration, a good level of p-type doping of the semiconductor of the second part can be obtained due to a significant reduction in the effective ionization energy of magnesium at such doping levels, and thus good current injection into the LED can be obtained due to the electrical conduction of the second part being close to or similar to that of the metal electrode.

[0026] The LED is the second part is disposed between the third part and the active region, the semiconductor of the third part includes Al X3 Ga (1-X3-Y3) In Y3 N, a portion of the third n-doped semiconductor such that X3 > 0, Y3 > 0, and X3 + Y3 ≤ 1, and / or a layer that is electrically conductive and optically transparent to at least one wavelength configured to be emitted from the light emitting portion, said layer being such that said second portion is disposed between said layer and an active region; It may further include:

[0027] The LED may further include a third n-doped semiconductor portion disposed between the conductive layer and the second portion, the semiconductor of the third portion being Al X3 Ga (1-X3-Y3) In Y3 N is included, X3>0, Y3>0, and X3+Y3≦1.

[0028] Such a third part and / or layer forms a transparent electrode on the LED structure, facilitating contact establishment while maintaining transparency to the emitted wavelength, especially when this wavelength is in the UV range. The semiconductor nature of the second part, which is the same as that of the third part, allows the third part to be manufactured. The third part allows for tunneling current injection in the LED. Furthermore, the third part and / or layer can promote "diffusion," i.e., obtain a uniform distribution of current flow lines across the entire surface of the injection layer of the LED, which is advantageous for optimizing the LED. Furthermore, when an LED simultaneously includes a third part and a conductive, optically transparent layer, the third part can be disposed between the second part and the conductive, optically transparent layer.

[0029] The layer that is electrically conductive and optically transparent to at least one wavelength configured to be emitted by the light emitting portion comprises, for example, a diamond layer having a thickness of less than 150 nm, preferably on the order of 60 nm, with a dopant concentration of, for example, 2.7×10 19 atoms / cm 3 or more commonly 1 × 10 15 From 2 x 10 21 atoms / cm 3 For example, the doped polycrystalline diamond may comprise a-8 Ω -1 m -1 and 75.1 Ω -1 m -1 It is possible to obtain an electronic conductivity comprised between . For example, the dopant used comprises boron atoms. The light absorption obtained for one or more wavelengths emitted from the light-emitting moiety is in this case, for example, taking into account a layer of doped diamond with a thickness equal to about 60 nm, less than about 25%, and the absorption coefficient is 1 × 10 for a wavelength of 310 nm. 4 cm -1 From 5 x 10 4 cm -1 It changes with.

[0030] Typically, the electrically conductive, optically transparent layer has an optical absorption of less than about 25% for one or more wavelengths emitted by the light emitting moiety.

[0031] The conductive layer may include diamond.

[0032] The semiconductor of the first portion is Al, with 0≦X1≦1, preferably 0.7≦X1≦0.9. X1 Ga (1-X1) The band gap value in this case is larger than that of the active region.

[0033] The semiconductors of the first and second portions may be such that X2=X1.

[0034] The semiconductor of the light-emitting part is Al, where X4≦0.9×X1. X4 Ga (1-X4)The semiconductor of the light-emitting portion may contain N. The semiconductor of the light-emitting portion is therefore such that the light emitted by the LED falls within the UV range, in particular between 210 nm and 340 nm, or between 210 nm and 400 nm, more particularly within the UV-C range, i.e., between 210 nm and 280 nm. For example, the LED may emit light with a wavelength comprised between 260 nm and 270 nm, so that the light emitted by the LED has bactericidal properties, and the LED can be used, for example, for air and / or water purification applications. According to another example, the semiconductor of the light-emitting portion may ensure that the wavelength of the light emitted from the active region of the LED is equal to 315 nm, making the LED suitable for medical applications, for example, for the treatment of psoriasis. Furthermore, the structure of this LED allows for very short wavelengths, for example, equal to 210 nm.

[0035] LEDs are a portion of AlGaN that is not intentionally doped, disposed between the first portion and the active region; and / or a portion of the AlGaInN that is not intentionally doped and is disposed between the active region and the second portion; It may further include:

[0036] This configuration allows for better spatial definition of the charge carrier recombination region. Furthermore, the intentionally undoped AlGaInN portion located between the active region and the second portion acts as an electron blocking layer (EBL) to prevent excess electrons in the p-doped region.

[0037] Semiconductors that are not intentionally doped, or nid, include semiconductors that have not undergone a doping step in which doping atoms are introduced into the semiconductor.

[0038] The LED further includes a substrate such that the first portion is disposed between the substrate and the active region.

[0039] The LED may further include at least one n-doped GaN layer disposed between the substrate and the first portion, allowing nanowire growth to begin before the AlGaN layer is deposited. Any type of substrate may be used, including semiconductor, amorphous, and metallic.

[0040] The diode may comprise a stack of layers forming different parts of the diode, or several nanowires arranged side by side that together form different parts of the diode.

[0041] When a diode includes several nanowires arranged side by side and forming various portions of the diode, the lateral dimensions of the portions of the nanowires forming the second portion are such that they form a semiconductor layer on top of the nanowires. In this case, the top portions of the nanowires have a larger lateral dimension and are in contact with each other to form the semiconductor layer. This semiconductor layer can advantageously form a base for generating the third n-doped semiconductor portion and the electrically conductive and optically transparent layer. The lateral dimensions of the nanowires are the dimensions of the nanowires substantially perpendicular to their length, which is their maximum dimension. Alternatively, this base for generating the electrically conductive and optically transparent layer, and optionally the third n-doped semiconductor portion, can be formed in another way, for example by filling the spaces between the nanowires with a non-light-absorbing insulating material.

[0042] The active region includes one or more layers of quantum dots, each formed by a light-emitting layer disposed between two barrier layers.

[0043] providing a first n-doped semiconductor portion; creating an active region in the first portion, the active region including at least one semiconductor light emitting portion; forming a second p-doped semiconductor portion in the active region; At least the semiconductor of the first portion and the light-emitting layer includes a compound containing a nitrogen atom and an aluminum and / or gallium atom; The semiconductor of the second portion is Al doped with magnesium atoms. X2 Ga (1-X2-Y2) In Y2 N is contained, X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium atoms is 10 17 atoms / cm 3 Also provided is a method for fabricating a light emitting diode.

[0044] providing a first n-doped semiconductor portion; creating an active region in the first portion, the active region including at least one semiconductor light emitting portion; forming a second p-doped semiconductor portion in the active region; providing a layer in the second portion that is electrically conductive and optically transparent to at least wavelengths in the UV range configured to be emitted from the light emitting portion; At least the semiconductor of the first portion and the light-emitting layer includes a compound containing a nitrogen atom and an aluminum and / or gallium atom; The semiconductor of the second portion is Al doped with magnesium atoms. X2 Ga (1-X2-Y2) In Y2 N is contained, X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium atoms is 10 17 atoms / cm 3 Beyond A method of manufacturing a light emitting diode is also provided, in which the conductive layer comprises doped diamond.

[0045] The growth of this layer can be carried out, for example, by chemical vapor deposition (ie, CVD). A continuous layer of polycrystalline diamond is then obtained by coalescence of the diamond nanocrystals grown on the surface.

[0046] Producing the second portion may involve performing metalorganic chemical vapor deposition (MOCVD) and / or molecular beam epitaxy (MBE).

[0047] After generating the second portion, the method forming a third n-doped semiconductor portion in the second portion, the semiconductor of the third portion being Al X3 Ga (1-X3-Y3) In Y3 N, where X3>0, Y3>0, and X3+Y3≦1; and / or The method may further include providing a layer in the second portion that is electrically conductive and optically transparent at least at the wavelength configured to be emitted from the light emitting portion.

[0048] When the third portion and the conductive layer are produced, the third portion can be produced before the conductive layer, which is produced next to the third portion.

[0049] The method may further comprise, after producing the second portion, activating the dopants in the semiconductor of the second portion, including thermal annealing and / or electron beam irradiation of the second portion.

[0050] The invention will be better understood from reading the description of exemplary embodiments, given purely by way of indication and in no way limiting, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0051] [Figure 1] 1 shows a prior art LED. [Figure 2] 1 shows an LED of the present invention according to a first embodiment; [Figure 3] 2 shows an LED of the present invention according to a second embodiment. [Figure 4] 3 shows an LED of the present invention according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0052] Identical, similar or equivalent parts in the various figures described below are labeled with the same reference numerals to identify transitions from one figure to another.

[0053] The various parts shown in the drawings are not necessarily to uniform scale in order to make the drawings easier to read.

[0054] It must be understood that the various possibilities (variants and embodiments) are not mutually exclusive and can be combined with one another.

[0055] An LED 100 according to a first embodiment will be described below in relation to Figure 2. In this first embodiment, the various portions of material forming the LED 100 are produced in the form of layers stacked on top of one another and produced by successive performance of epitaxy steps.

[0056] The LED 100 comprises a substrate 102. In this first embodiment, the substrate 102 comprises, for example, sapphire. Other types of substrates can be used, for example, comprising semiconductor materials.

[0057] Advantageously, the LED 100 includes a portion of n-doped GaN formed on a substrate 103 .

[0058] The LED 100 also includes a first portion 104 of an n-doped semiconductor disposed on the portion 103 (or directly on the substrate 102 if the LED 100 does not include the portion 103). The semiconductor of the first portion 104 includes a compound containing nitrogen atoms and aluminum and / or gallium atoms. The semiconductor of the first portion 104 is an Al 2 O 3 , where 0≦X1≦1, and preferably 0.7≦X1≦0.8. X1 Ga (1-X1) The semiconductor of the first portion 104 may also include indium atoms, in which case the compound of the first portion 104 may include AlGaInN or InGaN.

[0059] According to an exemplary embodiment, the n-type doping of the semiconductor of the first portion 104 is obtained by incorporating silicon atoms into the semiconductor of the first portion 104 during the growth of the semiconductor. The concentration of dopants in the semiconductor of the first portion 104 is, for example, 10 17 atoms / cm3 from 10 19 atoms / cm 3 is included in

[0060] The thickness of the first part 104 is, for example, equal to 1 μm, and more generally, is included in the range of 0.5 to 5 μm.

[0061] The LED 100 also includes an active region 106 disposed in the first part 104. This active region 106 includes at least one semiconductor light-emitting part configured to emit light. The semiconductor of the light-emitting part includes a compound containing atoms of aluminum and / or gallium and nitrogen atoms. For example, the semiconductor of the light-emitting part is Al X4 Ga (1-X4) N. This semiconductor is not intentionally doped, that is, during the manufacture of the LED 100, it is not subjected to the step of introducing doping atoms into the semiconductor.

[0062] The thickness of the active region 106 is, for example, equal to 100 nm, and more generally, is included in the range of about 100 nm to 300 nm.

[0063] Advantageously, the value of X4 is selected such that the wavelength of the light emitted from the light-emitting part of the active region 106 belongs to the UV range, particularly in the range of about 210 nm to 340 nm, more specifically the UV-C range (i.e., 210 nm to 280 nm), which corresponds to X4 where 0.7 < X4 < 1.

[0064] According to a variant embodiment, the LED 100 may include an undoped AlGaN part disposed between the first part 104 and the active region 106, and its thickness is, for example, equal to 20 nm. This part of AlGaN is not shown in FIG. 2.

[0065] The LED 100 also includes a second part 108 of a p-doped semiconductor disposed on the active region 106. The semiconductor of the second part 108 is Al X2 Ga (1-X2-Y2) InY2 It contains N, where X2 > 0, Y2 > 0, and X2 + Y2 ≤ 1. Advantageously, the semiconductor of the second portion 108 is such that X2 = X1. Further, it is advantageous that 0 < Y2 ≤ 0.01, preferably Y2 = 0.001.

[0066] The concentration of the dopant in the semiconductor of the second portion 108 is, for example, about 10 18 atoms / cm 3 to 10 21 atoms / cm 3 and is included therein.

[0067] The thickness of the second portion 10 eighty is, for example, equal to 1 μm, and more generally, it is about 0.2 μm to 1 μm.

[0068] The second portion 108 can be produced by MOCVD or MBE.

[0069] In the growth by MBE, the fluxes of various chemical elements of the semiconductor are sent to the growth surface. For the growth of the semiconductor of the second portion 108, the fluxes of aluminum, active nitrogen, indium, and optionally gallium are sent to the growth surface including the upper surface of the active region 106. To p-dope the produced semiconductor with magnesium atoms, a flux of magnesium is also sent. The values of these fluxes, that is, the amounts of atoms transmitted from each of these chemical elements, are selected according to the desired composition of the semiconductor of the second portion 108, particularly such that the atomic concentration of indium is equal to 0 to 1%, preferably 0.1%. When this is indium, the atomic concentration of magnesium in the semiconductor of the second portion 108 is proportional to the amount of indium incorporated in the semiconductor and is, for example, 10 17 atoms / cm 3 to 10 21 atoms / cm 3 and is included therein, advantageously 10 20 atoms / cm 3 to 10 21 atoms / cm 3 and is included therein, that is, the atomic concentration of magnesium is included between 0.1% and 1%.

[0070] During growth by MOCVD, the components used to grow the semiconductor are organometallic precursors, such as trimethylaluminum or triethylaluminum, which serve as the aluminum source, ammonia, which serves as the nitrogen source, trimethylindium or triethylindium, which serves as the indium source, and optionally trimethylgallium or triethylgallium, which serves as the gallium source. Magnesium atoms are obtained by suitable precursors, such as magnesocene or a solution of Mg(Cp)2. The indium and magnesium concentrations obtained by MOCVD may be similar to those obtained by MBE.

[0071] According to an alternative embodiment, the LED 100 may include a portion of intentionally undoped AlGaInN disposed between the active region 106 and the second portion 108, the thickness of which is, for example, equal to 20 nm. This portion of AlGaInN is not shown in FIG. 2. The portion of intentionally undoped AlGaInN is an electron blocking layer, which can prevent excess electrons in the p-doped region and promote the recombination of charge carriers in the active region.

[0072] In this first embodiment, the different parts of the LED 100 can be produced by performing several successive steps of epitaxy.

[0073] After creating the second portion 108, a step is carried out to activate the p-type dopants (i.e., magnesium atoms) present in the semiconductor of the second portion 108. This activation step can include carrying out thermal annealing and / or irradiation of the second portion 108 with an electron beam. The thermal annealing is carried out, for example, at a temperature equal to 100°C to 1000°C, preferably equal to 700°C. The electron beam irradiation consists of sending one or more electron beams to the LED 100 through the upper surface of the LED 100 formed by the second portion 108, the energy of the electrons being selected to limit their penetration into the semiconductor of the second portion 108 so as not to reach the material located below the second portion 108. This energy of the electrons is, for example, equal to 3 keV, or more generally between about 2 keV and 30 keV, and is selected in particular depending on the thickness of the second portion 108. The dose is set by the value of the electron beam current and is equal to 1 mA / cm. 2 to 20mA / cm 2 may vary by 7mA / cm 2 This electron irradiation is preferably carried out for a period equal to, for example, 10 minutes.

[0074] 2, the LED 100 may include a layer that is electrically conductive and optically transparent at least in the UV range of wavelengths configured to be emitted from the light emitting portion of the LED 100. In this case, the second portion 108 is disposed between the conductive layer and the active region 106. The conductive layer may include doped diamond.

[0075] An LED 100 according to a second embodiment is described below in relation to FIG. 3. In this second embodiment, the various portions of material of the LED 100 are formed by nanowires 109 arranged side by side on the substrate 102. Each nanowire 109 is successively grown, for example by epitaxy, and includes several portions comprising materials of various compositions that form the various portions of material of the LED 100. In the following description, the term "length" of each portion of the nanowire 109 refers to the dimension of that portion of the nanowire 109 perpendicular to the surface on which the nanowire 109 is formed and parallel to the z-axis shown in FIG. 3. The lengths of the various portions of the nanowire correspond to the thicknesses of the various portions of the LED 100.

[0076] As in the first embodiment, the LED 100 comprises a substrate 102. In this second embodiment, the substrate 102 is a conductive material, such as, for example, n-doped silicon.

[0077] The nanowires 109 of the LED 100 are here produced by growth from the front side of the substrate 102, i.e. by spontaneous nucleation, or preferably on a portion of the substrate 102 that has been predefined by masking. The nanowires 109 of the LED 100 are produced, for example, by MBE.

[0078] Each nanowire 109 is formed in substrate 102 and includes a first portion 110 comprising n-doped GaN. These first portions 110 together form n-doped GaN portion 103. For example, each first portion 110 has a length of 100 nm to 500 nm.

[0079] Each nanowire 109 also includes a second portion 112 formed on the first portion 110. These second portions 112 together form the n-doped semiconductor first portion 104. The semiconductor of the second portion 112 of one of the nanowires 109 includes a compound containing nitrogen atoms and aluminum and / or gallium atoms. The semiconductor of the second portion 112 is Al, where 0≦X1≦1, and preferably 0.7≦X1≦0.8. X1 Ga (1-X1)It contains N.

[0080] According to an exemplary embodiment, the n-type doping of the semiconductor of the second portion 112 of the nanowire 109 is obtained by incorporating silicon atoms into the semiconductor of these second portions 112 during their growth. The concentration of dopants in the semiconductor of the second portion 112 of the nanowire 109 is, for example, 10 17 atoms / cm 3 to 10 18 atoms / cm 3 and, more generally, 10 16 atoms / cm 3 to 10 20 atoms / cm 3 and is included therein.

[0081] For example, each second portion 112 has a length from 100 nm to 500 nm.

[0082] According to an alternative embodiment, the nanowire 109 does not include the first portion 110. In this case, the material of the nanowire 109 formed on the substrate 102 coincides with the material of the second portion 112.

[0083] Each nanowire 109 also includes a third portion 114 formed on the second portion 112. The third portions 114 of the nanowire 109 together form the active region 106 of the LED 100, and in particular, form the semiconductor light-emitting portion of the active region 106 configured to emit light. The semiconductor of the light-emitting portion includes a compound containing nitrogen atoms and atoms of aluminum and / or gallium. For example, the semiconductor of the light-emitting portion is Al X4 Ga (1-X4) N with X4 < X1, preferably X4 ≤ 0.1 × X1. This semiconductor is not intentionally doped, that is, during the manufacture of the LED 100, it is not subjected to the step of introducing doping atoms into the semiconductor.

[0084] For example, each third portion 114 has a length equal to 100 nm.

[0085] According to the modified embodiment, each nanowire 109 may include a portion of undoped AlGaN disposed between the second portion 112 and the third portion 114, the thickness of which is equal to, for example, 20 nm. This portion of AlGaN is not shown in FIG. 3.

[0086] Each nanowire 109 also includes a fourth portion 116 formed in the third portion 114. The fourth portions 116 of the nanowires 109 together form a second portion 108 of the p-doped semiconductor disposed in the active region 106. The semiconductor of the fourth portion 116 is Al doped p by magnesium atoms X2 Ga (1-X2-Y2) In Y2 N, where X2>0, Y2>0, and X2 + Y2 ≤ 1. Advantageously, the semiconductor of the fourth portion 116 is such that X2 = X1. Further, it is advantageous that 0 < Y2 ≤ 0.01, preferably Y2 = 0.001.

[0087] The concentration of the dopant in the semiconductor of the second portion 108 is, for example, about 10 18 atoms / cm 3 to 10 21 atoms / cm 3 and is included therein.

[0088] For example, each fourth portion 116 has a length included from 100 nm to 500 nm.

[0089] According to the modified embodiment, each nanowire 109 may include a portion of undoped AlGaInN disposed between the third portion 114 and the fourth portion 116, the thickness of which is equal to, for example, 20 nm. This portion of AlGaInN is not shown in FIG. 3.

[0090] Advantageously, the fourth portions 116 of the nanowires 109 are fabricated so that, at their tops, these fourth portions 116 have increasing lateral dimensions (dimensions in the plane (X, Y)) and are in physical contact with each other. This configuration allows for the formation of a layer 118 containing the material of the fourth portions 116 of the nanowires 109 at the top of the nanowires 109. This configuration can be obtained, for example, by changing the ratio between the metal flow (constituting the flow of aluminum and indium, and possibly gallium) and the flow of nitrogen when growing the nanowires 109 by MBE. For example, it is possible to obtain the layer 118 by increasing the metal flow by 50%. This allows for the deposition of p-type doped material on the sides of the nanowires 109 while minimizing the risk of electrical shorts with the bottom of the LED 100. This layer 118 can be obtained, for example, when the spacing between two nanowires 109 is less than approximately twice the diameter of one of the nanowires 109.

[0091] With respect to the first embodiment, after producing the fourth portion 116 of the nanowire 109 (and optionally the layer 118, if such a layer is produced), a step is carried out to activate the p-type dopants (i.e., magnesium atoms) present in the semiconductor of the fourth portion 116 of the nanowire 109. This activation step may include carrying out thermal annealing and / or irradiation with an electron beam in a manner similar to that described above for the first embodiment.

[0092] 3, LED 100 according to this second embodiment may include a layer that is electrically conductive and at least optically transparent in the UV range of wavelengths configured to be emitted from the light emitting portion of LED 100. In this case, this conductive layer is disposed on layer 118. This conductive layer may include doped diamond.

[0093] An LED 100 according to a third embodiment is described below in connection with FIG.

[0094] As in the second embodiment, the various portions of material forming the LED 100 are formed by nanowires 109 arranged side by side on the substrate 102. Each nanowire 109 comprises several successively produced portions that comprise materials of different compositions and form the various portions of material of the LED 100.

[0095] The nanowires 109 of the LED 100 according to the third embodiment are similar to those described above for the LED 100 according to the second embodiment, and include portions 110, 112, 114 and 116, with a layer 118 formed thereon.

[0096] The LED 100 according to this third embodiment also includes n-doped AlN in layer 118, with X3>0, Y3>0, and X3+Y3≦1. X3 Ga (1-X3-Y3) In Y3 The semiconductor of the first portion 104 includes a layer of n-doped silicon. This layer is referred to herein as the third n-doped semiconductor portion of the LED 100 and is not shown in FIG. 4 . Advantageously, the atomic concentration X3 of aluminum in the semiconductor of the third portion is equal to the atomic concentration X1 of aluminum in the semiconductor of the first portion 104. For example, the n-type dopant present in the semiconductor of the third portion includes silicon or germanium atoms. The concentration of the dopant in the semiconductor of the third portion is, for example, about 10 17 atoms / cm 3 From 10 20 atoms / cm 3 The thickness of the third portion is, for example, equal to 100 nm, more generally between about 50 nm and 200 nm. This third portion makes it possible to achieve current injection by tunneling in the LED 100.

[0097] It is also possible for the atomic concentration X3 of aluminum in the semiconductor of the third portion to be less than the atomic concentration X1 of aluminum in the semiconductor of the first portion 104. This allows for a higher level of doping to be achieved in the semiconductor of the third portion while still ensuring transparency of this third portion with respect to the emission wavelength of the LED 100 when the LED 100 emits in the UV range.

[0098] Alternatively, the LED 100 may not include this third portion and may instead include a layer 120 comprising another material other than AlGaInN that is electrically conductive and transparent to the wavelengths emitted by the LED 100 (here, wavelengths in the UV range). For example, the layer 120 may comprise a layer of electrically conductive diamond, for example doped polycrystalline diamond, the thickness of which is for example equal to 100 nm. More generally, the thickness of the layer 120 is comprised between 30 nm and 500 nm.

[0099] Whatever the material of layer 120, this layer 120 may be present in LED 100 according to the first embodiment. Furthermore, if LED 100 includes nanowires 109 that do not form layer 118 on top of them, each of nanowires 109 may have on top of it an n-doped Al X3 Ga (1-X3-Y3) In Y3 N and may include a portion forming the third portion already described, where X3>0, Y3>0, and X3+Y3≦1.

[0100] This layer 120 allows for the formation of a transparent electrode on the structure of the LED 100, which allows for easy contact formation while maintaining transparency at the emitted wavelength. It also facilitates obtaining an even spreading of the current flow lines over the entire surface of the injection layer of the LED 100, which facilitates optimization of the LED 100.

[0101] In the three aforementioned embodiments, the active region 106 includes a light-emitting portion including a compound formed from nitrogen atoms and aluminum and / or gallium atoms. Alternatively, the active region 106 of the LED 100 can include one or more quantum wells, each formed from a light-emitting layer disposed between two barrier layers. In this case, the semiconductor of the or each light-emitting layer and each barrier layer can include AlGaN, but the semiconductor of the light-emitting layer can include AlGaN with a lower atomic concentration of aluminum than the atomic concentration in the semiconductor of the barrier layers, preferably less than 10% of the atomic concentration in the semiconductor of the barrier layers.

[0102] Alternatively, the active region 106 of the LED 100 can include one or more quantum dots, each formed from a light-emitting layer disposed between two barrier layers. In this case, the semiconductor of the or each light-emitting layer and the semiconductor of each barrier layer can include AlGaN, but the semiconductor of the light-emitting layer can include AlGaN with a lower atomic concentration of aluminum than the atomic concentration in the semiconductor of the barrier layers, preferably 10% lower than the atomic concentration in the semiconductor of the barrier layers. In this case, the or each light-emitting layer can include monolayers of GaN and AlN superimposed such that the aluminum percentage or composition in the average alloy of these layers is less than the aluminum percentage or composition in the semiconductor of the barrier layers, preferably less than 10% of the aluminum percentage or composition in the semiconductor of the barrier layers. The atomic element percentages of the "average alloy" of these layers are calculated by taking into account the percentage of that element in each of these layers and weighting these concentrations by the layer thickness. For example, consider a layer stack including a layer of GaN with a thickness equal to 2 mm and a layer of AlN with a thickness equal to 1 nm, this layer stack is repeated several times, and the percentage of aluminum in the average alloy is 33%, i.e., the average alloy is Al 0.33 Ga 0.67 N. In this case, if it is preferable that this aluminum percentage be less than 10% of the aluminum percentage in the semiconductor of the barrier layer, the aluminum percentage in the semiconductor of the barrier layer is 33% + 3.3% = 36.3%.

[0103] [1] a first n-doped semiconductor portion (104); a second p-doped semiconductor portion (108); an active region (106) disposed between the first and second portions (104, 108) and including at least one light emitting semiconductor portion; a layer (120) that is electrically conductive and optically transparent to at least one wavelength in the UV range configured to be emitted from the light emitting portion, the second portion (108) being disposed between the layer (120) and the active region (106); A light-emitting diode (100) comprising at least The semiconductor of the first part (104) and the light-emitting part contains a compound containing nitrogen atoms and atoms of aluminum and / or gallium, The semiconductor of the second part (108) contains AlX2Ga(1-X2-Y2)InY2N in which magnesium atoms are p-doped, X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium exceeds 1017 atoms / cm3, The light-emitting diode (100) in which the conductive layer (120) contains doped diamond. [2] Y2 satisfies 0<Y2≦0.01, and / or The light-emitting diode (100) according to [1], in which the atomic concentration of magnesium in the semiconductor of the second part (108) is included in the range from 1020 atoms / cm3 to 1021 atoms / cm3. [3] Further comprising a third part of an n-doped semiconductor disposed between the conductive layer (120) and the second part (108), the semiconductor of the third part containing AlX3Ga(1-X3-Y3)InY3N, X3>0, Y3>0, X3+Y3≦1, the light-emitting diode (100) according to [1] or [2]. [4] The semiconductor of the first part (104) contains AlX1Ga(1-X1)N with 0.7≦X1≦0.8, the light-emitting diode (100) according to any one of [1] to [3]. [5] The semiconductor of the light-emitting part contains AlX4Ga(1-X4)N with X4≦0.9×X1, the light-emitting diode (100) according to any one of [1] to [4]. [6] A part of unintentionally doped AlGaN disposed between the first part (104) and the active region (106), and / or The light-emitting diode (100) according to any one of [1] to [5], further comprising a part of unintentionally doped AlGaInN disposed between the active region (106) and the second part (108). [7] The light-emitting diode (100) according to any one of [1] to [6], further comprising a substrate (102), wherein the first portion (104) is disposed between the substrate (102) and the active region (106). [8] The light-emitting diode (100) according to [7], further comprising at least a portion of n-doped GaN disposed between the substrate (102) and the first portion. [9] A light-emitting diode (100) according to any one of [1] to [8], wherein the diode (100) comprises a stack of layers forming various parts of the diode (100) or several nanowires (109) arranged side by side and together forming various parts of the diode (100).

[10] 10. The light-emitting diode (100) according to claim 9, wherein when the diode (100) comprises several nanowires (109) arranged side by side and forming various portions of the diode (100), the lateral dimensions of the portions (116) of the nanowires (109) forming the second portion (108) are such that they form a semiconductor layer on top of the nanowires (109).

[11] 10. A light-emitting diode (100) according to any one of claims 1 to 10, wherein the active region comprises one or more layers of quantum dots, each formed by a light-emitting layer disposed between two barrier layers.

[12] forming a first n-doped semiconductor portion (104); creating an active region (106) in the first portion (104) that includes at least one semiconductor light emitting portion; forming a second p-doped semiconductor portion (108) in the active region (106); creating a layer (120) in the second portion (108) that is electrically conductive and optically transparent to at least the wavelengths in the UV range that are configured to be emitted by the light emitting portion; At least the semiconductor of the first portion (104) and the light-emitting layer includes a compound containing a nitrogen atom and an aluminum and / or gallium atom; the semiconductor of the second portion (108) comprises AlX2Ga(1-X2-Y2)InY2N p-doped with magnesium atoms, where X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium atoms exceeds 1017 atoms / cm3; A method of manufacturing a light emitting diode (100) wherein the conductive layer (120) comprises doped diamond.

[13] The method according to

[12] , wherein the step of producing the second portion (108) comprises performing metal organic chemical vapor deposition and / or molecular beam epitaxy.

[14]

[12] or

[13] . The method according to

[12] or

[13] , further comprising, after forming the second portion (108), forming a third portion of an n-doped semiconductor in the second portion (108), wherein the semiconductor of the third portion is AlX3Ga(1-X3-Y3)InY3N, where X3>0, Y3>0, and X3+Y3≦1, and the conductive layer (120) is formed in the third portion.

[15] The method according to any one of

[12] to

[14] , further comprising, after generating the second portion (108), activating the dopants of the semiconductor in the second portion (108), including thermal annealing and / or electron beam irradiation of the second portion (108). [Explanation of symbols]

[0104] 10. Light-emitting diode 12 First Layer 14 Second Layer 16 Active area 18 p-doped layer 20 Conductive layer 100 Light Emitting Diodes 102 Circuit Board 103 Substrate 104 first n-doped semiconductor portion 106 Active region 108 second p-doped semiconductor portion 109 Nanowires 110 First Part 112 Second Part 114 Third Part 116 Fourth Part 118 layers 120 conductive layer, optically transparent layer

Claims

[Claim 1] a first n-doped semiconductor portion (104); a second p-doped semiconductor portion (108); an active region (106) disposed between the first and second portions (104, 108), the active region including at least one light emitting semiconductor portion; a layer (120) that is electrically conductive and optically transparent to at least one wavelength in the UV range configured to be emitted from the light emitting portion, the second portion (108) being disposed between the layer (120) and the active region (106); A light emitting diode (100) comprising at least the semiconductor of the first portion (104) and the light-emitting portion comprises a compound containing nitrogen atoms and aluminum and / or gallium atoms; The semiconductor of the second portion (108) is Al p-doped with magnesium atoms. Ｘ２ Ga （１－Ｘ２－Ｙ２） In Ｙ２ N is contained, X2>0, Y2>0, X2+Y2≦1, and the atomic concentration of magnesium is 10 １７ atoms / cm ３ Beyond A light emitting diode (100) wherein the conductive layer (120) comprises doped diamond.

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