A light-emitting diode including a light-emitting region based on ALN containing gallium atoms and / or indium atoms

Abstract

The present invention relates to a light-emitting diode (100) comprising: - a substrate (102); - an Al doped according to a first type of conductivity and disposed on the substrate; X1 Ga (1-X1-Y1) In Y1 an N portion (108), the portion (108) being said to be of the first type, where X1>0 and X1+Y1≦1; - a light-emitting portion (110) comprising a dilute AlN alloy containing gallium atoms and / or indium atoms at a concentration of less than 30%; and - an Al doped according to a second type of conductivity opposite to the first type of conductivity X2 Ga (1-X2-Y2) In Y2 an N portion (112), the portion (112) being said to be of the second type, where X2>0 and X2+Y2≦1, and the light-emitting portion being disposed between the first-type portion and the second-type portion.

Description

Technical Field

[0001] The present invention relates to the field of broadband semiconductor-based light-emitting diodes (LEDs). Advantageously, the present invention is particularly applicable to fabricating LEDs that emit light in the ultraviolet (UV) range, particularly in the wavelength range between about 230 nm and 310 nm, with respect to fields associated with disinfection, preservation, and / or agriculture.

Background Art

[0002] In particular, the bactericidal effect of UV radiation, more generally the disinfection effect, is derived from the absorption band of the DNA of microorganisms (bacteria, pathogens, viruses) in the wavelength range of about 230 nm to 310 nm. Damage to the DNA of microorganisms through the absorption of UV radiation results in preventing their reproduction and killing them. The maximum disinfection effect is achieved by radiation having a spectral distribution as close as possible to this absorption band of the DNA of the microorganisms to be destroyed.

[0003] Disinfection by exposure to UV radiation is currently carried out using different devices such as KrCl lamps or mercury vapor lamps. However, these devices have drawbacks.

[0004] KrCl lamps are excimer lamps, and their emission spectrum is narrow with respect to the absorption spectrum of the DNA of the microorganisms to be destroyed, and thus, it does not provide an optimal disinfection effect. In addition, these lamps generate ozone, which limits them to niche applications.

[0005] On the other hand, mercury vapor lamps are fragile and have a limited lifespan. Moreover, their fine emission lines do not cover the entire absorption spectrum of the DNA of the microorganisms to be destroyed. Finally, these lamps contain mercury, and the use of mercury has been prohibited in the long term due to its high toxicity.

[0006] In particular, semiconductor materials of the group III nitride family, including GaN, AlN, In, or alloys thereof (in particular, ternary and quaternary alloys), are adapted, inter alia, to fabricate LEDs that emit light in the UV range. Such LEDs are fabricated, for example, in the form of a stack of layers or nanowires, or even with a hybrid structure as described in document FR3109470A1. In these LEDs, varying the aluminum content in the composition of the semiconductor of the multi-quantum wells makes it possible to control the emission wavelength of the LED. Thus, with these LEDs, by varying the level of aluminum in the semiconductor composition of the multi-quantum wells, it is possible to cover the entire range of wavelengths that are desired to have an optimal disinfection effect. However, the fineness of the emission peaks generally obtained with such LEDs makes it difficult to cover the entire desired wavelength range with a single LED. Thus, in particular to cover the entire UV range, it is generally necessary to use several LEDs having emission peaks at different wavelengths.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] One object of the present invention is to provide a light-emitting diode having the widest possible emission spectrum in the UV range.

Means for Solving the Problems

[0009] To achieve this object, the present invention provides - a substrate, and - Al doped according to the conductivity of the first type, disposed on the substrateX1 Ga (1-X1-Y1) In Y1 The portion of N, which is said to be of the first type, where X1>0 and X1+Y1≦1, and the - A light-emitting portion including a dilute AlN alloy containing gallium atoms and / or indium atoms at a concentration of less than 30%, - Al doped according to the conductivity of the second type opposite to that of the first type X2 Ga (1-X2-Y2) In Y2 The portion of N, which is said to be of the second type, where X2>0 and X2+Y2≦1, and the light-emitting portion is arranged between the portion of the first type and the portion of the second type, and provide a light-emitting diode including at least.

[0010] Thus, the LED according to the present invention includes a light-emitting portion formed from a dilute AlN alloy containing gallium atoms and / or indium atoms, that is, not homogeneous at the nanometer scale from the viewpoint of the distribution of Al atoms and / or Ga atoms and / or In atoms. The potential experienced by the charge carriers circulating and recombining in the light-emitting portion is locally reduced by the presence of these Ga atoms and / or In atoms randomly incorporated into the dilute alloy, and thus induces a broader-band emission than the prior-art LEDs.

[0011] Unlike prior art LEDs that emit in the UV range due to potential wells formed between an n-type doped layer and a p-type doped layer, it has been proposed to fabricate an LED in which the light-emitting part is formed by a portion of AlN containing a small amount of gallium atoms and / or indium atoms so as to form a dilute alloy. Unlike quantum wells that form potential wells with defined emission energies, the light-emitting part of the LED according to the present invention is characterized by a light-emitting zone in which charge carriers are subjected to a potential having local variations generated by the presence of these Ga atoms and / or In atoms, which forms a light-emitting zone extending over a range that can be, in particular, from 230 nm to 310 nm.

[0012] Moreover, in the LED according to the present invention, the light-emitting part, unlike the light-emitting part of a quantum well disposed with respect to a barrier layer, can be disposed directly with respect to the n-type and p-type doped semiconductor parts of the LED (corresponding to the first type and second type parts).

[0013] In the dilute alloy of the light-emitting part, the AlN of the light-emitting part can contain gallium atoms and / or indium atoms randomly substituted for aluminum atoms, or can contain gallium atoms and / or indium atoms substituted for aluminum atoms that are sufficiently close to each other to locally form regions having the properties of an AlGaN or AlInN or AlGaInN alloy, or can contain gallium atoms and / or indium atoms that are bonded to nitrogen atoms and can locally form nanocrystals (or nanocrystallites or aggregates) of AlGaN or AlInN or AlGaInN.

[0014] The fact that the use of a dilute AlN alloy containing gallium atoms and / or indium atoms with a concentration of less than 30% leads to light emission in a wide spectrum in the UV range for forming the light-emitting part of an LED is surprising and not self-evident. In fact, in a homogeneous alloy of AlN containing 1% GaN molar fraction, the obtained gap is 203 nm or 6.1 eV, and for a 10% GaN molar fraction, the gap is 2225 nm or 5.5 eV. A person skilled in the art desiring to fabricate an AlGaN-based LED emitting at a wavelength of 280 nm or 4.43 eV would, of course, be led to devise a homogeneous ternary alloy containing a GaN molar fraction between 60% and 62% and would not be led to use a dilute alloy as proposed here.

[0015] Due to such a light-emitting part, the LED according to the present invention can emit light in a wavelength range much wider than the emission spectrum of a quantum well LED, for example, in a wavelength range from about 200 nm to about 350 nm, and preferably in a wavelength range from about 230 nm to about 310 nm. Therefore, such an LED is particularly effective when used for disinfection purposes.

[0016] Moreover, with respect to a device using several LEDs to cover the entire desired spectral range, the fact that the entire range can be covered by a single LED allows for the same or higher efficiency while consuming less power.

[0017] Another advantage is that fabricating such an LED does not require forming multiple quantum wells, and thus is easier to fabricate and does not have the inherent difficulties in controlling the composition of the semiconductors used to form such wells.

[0018] The provided LEDs are particularly suitable for disinfection applications (bacterial applications, pathogenic applications, viral applications), and in particular, are suitable for water and / or air. Such LEDs can also be used, for example, for skin disinfection applications when their radiation corresponds to light having a wavelength on the order of 230 nm, and the penetration depth is limited to the epidermal stratum corneum.

[0019] The provided LEDs are applicable to general-purpose household applications, such as, among other things, disinfecting refrigerators, disinfecting the interior of a vehicle, purifying water away from water distribution points such as fountains or faucets.

[0020] The LED can further include an intermediate portion of GaN doped according to the conductivity of the first type, which is disposed between the substrate and the first type of portion. The presence of such an intermediate portion promotes the growth of the first type of portion, especially when the LED is fabricated in the form of nanowires.

[0021] The proportion of gallium atoms and / or indium atoms in the material of the light-emitting portion can advantageously be 10% or less, or between about 1% and 10%, or 5% or less, or even between 1% and 5%. Such a proportion of gallium atoms and / or indium atoms in the material of the light-emitting portion enables the LED to emit light in a wavelength range that is particularly well-suited for disinfection applications.

[0022] The light-emitting diode can further include a buffer layer, which is disposed between the substrate and the first type of portion, or, when the diode includes such an intermediate portion, between the substrate and the intermediate portion.

[0023] The material of the buffer layer can be based on GaN or AlN or AlGaN.

[0024] The first type of conductivity can correspond to the n-type, and the second type of conductivity can correspond to the p-type. However, the reverse is also possible.

[0025] Advantageously, - The n-type dopant present in one of the materials of either the first type or the second type of portion can correspond to silicon atoms and / or sulfur atoms and / or germanium atoms, - The p-type dopant present in the other of the materials of either the first type or the second type of portion can correspond to magnesium atoms and / or beryllium atoms.

[0026] The other material of the first type and second type of portions can contain indium atoms, which makes it possible to increase the amount of p-type dopant (in particular, magnesium atoms) incorporated into the material of this other portion, and thus to promote its doping.

[0027] The material of the first type of portion and / or the material of the second type of portion can contain AlN. This configuration prevents the first type of portion and the second type of portion from having a barrier effect with respect to the light-emitting portion that is AlN-based.

[0028] In a first embodiment, the LED can include a plurality of nanowires extending from a substrate, each of the nanowires including at least a first type of portion and a second type of portion as well as a light-emitting portion.

[0029] In a second embodiment, at least the first type of portion and the second type of portion as well as the light-emitting portion can form a stack of layers disposed on a substrate.

[0030] Also, the present invention is a method for manufacturing a light-emitting diode, the method comprising - On a substrate, Al doped according to the conductivity of a first type X1 Ga (1-X1-Y1) In Y1 A step of fabricating an N portion, where the portion is said to be of the first type, where X1 > 0 and X1 + Y1 ≤ 1 - On the first type portion, a step of fabricating a light emitting portion including a dilute AlN alloy containing gallium atoms and / or indium atoms at a concentration of less than 30%, and preferably less than 10%, or even less than 5% - On the light emitting portion, Al doped according to the conductivity of a second type opposite to that of the first type X2 Ga (1-X2-Y2) In Y2 A step of fabricating an N portion, where the portion is said to be of the second type, where X2 > 0 and X2 + Y2 ≤ 1 Providing a method that includes at least

[0031] Throughout the document, the term "on" is used without distinction with respect to the orientation in space of the element to which the term relates. For example, in the feature "an element formed on a substrate", the surface of the substrate on which the element is formed is not necessarily oriented upward, and can correspond to a surface oriented along any direction. Moreover, the arrangement of a first element on a second element must, in some cases, be understood as corresponding to the arrangement of the first element with respect to the second element in a state where there is no intermediate element between the first element and the second element, or, in some cases, as corresponding to the arrangement of the first element on the second element with one or more intermediate elements arranged between the first element and the second element.

[0032] The present invention will be better understood by reading the description of exemplary embodiments, which is given for illustrative purposes with reference to the accompanying drawings and not for limiting purposes at all. BRIEF DESCRIPTION OF THE DRAWINGS

[0033]

Figure 1

Figure 2

Figure 3

[0034] The same parts, similar parts, or equivalent parts in different figures described hereinafter are assigned the same reference numerals to facilitate switching from one figure to another.

[0035] The different parts shown in the figures are not necessarily drawn to a uniform scale in order to make the figures easier to read.

[0036] Different possibilities (alternatives and embodiments) should be understood as not being mutually exclusive and being combinable with each other.

[0037] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS FIG. 1 described below shows an LED 100 according to the first embodiment of the present invention.

[0038] In the following description, the term "thickness" is used to specify a dimension parallel to the axis Z shown in FIGS. 1 and 3 (i.e., in the first embodiment, the dimension parallel to the direction along which the nanowires of the LED 100 extend, or in the second embodiment, the dimension parallel to the stacking direction of the different layers of the LED 100).

[0039] The LED 100 includes a substrate 102, with other elements of the LED 100 being disposed on the substrate 102, and the substrate 102 serves as a mechanical support for these other elements. In this first embodiment, the substrate 102 includes, for example, sapphire. Other types of substrates can be used, which include, for example, semiconductor materials such as silicon. The thickness of the substrate 102 is, for example, several hundred microns.

[0040] In these figures, the LED 100 also includes a buffer layer 104 disposed on the substrate 102. Advantageously, the buffer layer 104 includes AlN or AlGaN or GaN. The thickness of the buffer layer 104 is, for example, between about 0.5 μm and 3 μm. It can optionally be electrically doped and can contain other chemical elements, particularly indium or boron. This buffer layer promotes the growth of the portion 106.

[0041] LED100 includes a plurality of nanowires on the buffer layer 104, and the plurality of nanowires substantially extend along the thickness direction of the LED100, that is, in a direction substantially perpendicular to the surface of the substrate 102 on which the buffer layer 104 is formed. In FIG. 1, all the nanowires are shown to be perpendicular to the surface of the buffer layer 104 on which the nanowires are fabricated. In practice, these nanowires may not all be exactly perpendicular to this surface of the buffer layer 104, and the angle formed between the growth surface of these nanowires and the growth direction of these nanowires can vary by several degrees, or even by more than 10 degrees. As an example, the diameter of each nanowire and the distance between the growth axes of two adjacent nanowires (i.e., their periodicity) can be between about 100 nm and 300 nm. Moreover, LED100 can include a plurality of nanowires between about 1 million (with respect to the surface area of 100x100μm 2 and 10 million (with respect to the surface area of 300x300μm 2 , and the average density can be, for example, equal to about 100 wires / μm on the substrate 102 2 .

[0042] In the exemplary embodiment of FIG. 1, each nanowire includes an intermediate portion 106 of GaN doped according to the conductivity of the first type (n-type in the exemplary embodiment of FIG. 1). As an example, the thickness of the intermediate portion 106 is between about 100 nm and 1 micron.

[0043] Alternatively, it is also possible that the nanowires of LED100 do not include these intermediate portions 106.

[0044] In each nanowire, the intermediate portion 106 has, above it, Al doped according to the conductivity of the first type X1 Ga (1-X1-Y1) In Y1It has a portion 108 of N (said to be of the first type), where X1>0 and X1 + Y1≤1. According to one advantageous embodiment, the material of this portion 108 contains sulfur atoms and / or silicon atoms and / or germanium atoms, and / or corresponds to AlN. By way of example, the thickness of the portion 108 is between about 100 nm and 1 μm.

[0045] According to one exemplary embodiment, the n-type doping of the semiconductors of portions 106, 108 is achieved by incorporating silicon atoms into the semiconductors of portions 106, 108, for example, implemented when depositing the semiconductors useful for fabricating these portions. The concentration of dopants in the semiconductors of portions 106, 108 is, for example, about 10 16 at / cm 3 to 10 21 at / cm 3 in between.

[0046] Each nanowire's portion 108 has, thereon, a light-emitting portion 110 (or active portion) of AlN containing gallium atoms and / or indium atoms. The proportion (or concentration) of Ga atoms and / or In atoms in the AlN of the light-emitting portion 110 is less than 30%, for example, between about 1% and 10%, or even between 1% and 5%. By way of example, the thickness of the light-emitting portion 110 is between about 25 nm and 100 nm.

[0047] In each nanowire, the light-emitting portion 110 has, thereon, Al doped according to the conductivity of a second type (p-type in the exemplary embodiment of FIG. 1) opposite to that of the first type of conductivity X2 Ga (1-X2-Y2) In Y2It has a portion 112 of N (said to be of the second type), where X2 > 0 and X2 + Y2 ≤ 1. According to one advantageous embodiment, the material of this portion 112 contains beryllium atoms and / or magnesium atoms, and / or corresponds to AlN. By way of example, the thickness of the portion 112 is between about 10 nm and 100 nm, and advantageously between about 10 nm and 50 nm. The material of the portion 112 can contain indium atoms, which makes it possible to increase the amount of p-type dopant (in particular, magnesium atoms) incorporated into the material of this portion 112, and thus promotes its doping.

[0048] According to one exemplary embodiment, the p-type doping of the semiconductor of the portion 112 is realized, for example, by incorporating magnesium atoms into the semiconductor of the portion 112 when depositing this semiconductor. The concentration of the dopant in the semiconductor of the portion 112 is, for example, about 10 16 at / cm 3 to 10 21 at / cm 3 in between.

[0049] Finally, each portion 112 of the nanowire has, thereon, an ohmic contact layer 114, and the ohmic contact layer 114 is disposed on top of the nanowire and forms an electrical contact for one of the electrodes of the LED 100. This ohmic contact layer 114 contains at least one conductive material that is transparent to the wavelength that will be emitted by the LED 100, such as ITO or advantageously diamond, etc., or a highly electrically doped semiconductor.

[0050] Figure 2 shows the emission spectrum of a set of nanowires of the LED 100 described above when the light-emitting portion 110 contains AlN containing gallium atoms. In this spectrum, the amplitude is expressed in arbitrary units. This spectrum clearly illustrates the emission obtained in the wavelength range from about 230 nm to 340 nm, which, in particular, covers the absorption range of the DNA of the microorganisms to be killed (when this LED 100 is used to destroy these microorganisms).

[0051] An exemplary embodiment of a method for fabricating the LED 100 is described below.

[0052] The buffer layer 104 is first fabricated on the substrate 102, for example, by implementing deposition of the MOCVD (metalorganic chemical vapor deposition) type.

[0053] Next, a growth mask is fabricated on the buffer layer 104 to fabricate the nanowires. This mask includes, for example, circular openings, which are fabricated by lithography in a layer of a material adapted to fabricate this mask. The diameter and periodicity of these openings can be, for example, between about 100 nm and 300 nm.

[0054] Next, the intermediate portion 106 is fabricated on the buffer layer 104 by growth or deposition through the openings in the mask.

[0055] Next, the doping of the portion 106 is performed, for example, by incorporating silicon atoms into the semiconductor formed by growth.

[0056] Next, the first type of portion 108 is fabricated on the portion 106 by growth or deposition through the openings in the mask.

[0057] Next, the doping of portion 108 is performed, for example, by incorporating silicon atoms and / or sulfur atoms and / or germanium atoms.

[0058] Next, the light-emitting portion 110 is fabricated, for example, by growth or deposition, on top of portion 108. Gallium atoms and / or indium atoms are incorporated therein to form dilute alloys of these portions 110.

[0059] Next, a second type of portion 112 is fabricated, for example, by growth or deposition, on top of the light-emitting portion 110.

[0060] Next, the doping of portion 112 is performed, for example, by incorporating magnesium atoms and / or beryllium atoms.

[0061] Next, the ohmic contact layer 114 is fabricated, for example, by deposition, on top of the top of the nanowire.

[0062] The growth or deposition steps described above correspond, for example, to molecular beam epitaxy (MBE) or MOCVD type depositions. The doping operations can be implemented in situ in this growth or deposition equipment.

[0063] Figure 3 described below depicts the LED 100 according to the second embodiment.

[0064] Compared with the LED 100 according to the first embodiment described previously, the LED 100 according to this second embodiment is not formed by a set of nanowires fabricated on the buffer layer 104, but is formed by a stack of layers of materials fabricated on the buffer layer 104, and the respective lengths and widths of these layers (dimensions along the axes X and Y in FIG. 3) correspond to the length and width of the LED 100. Therefore, the materials of these layers 106, 108, 110, and 112 in FIG. 3, as well as the thicknesses of these layers, are the same as those of the respective material portions 106, 108, 110, and 112 of the nanowires of the LED 100 according to the first embodiment.

[0065] As an alternative to the first and second embodiments described above, it is also possible for the LED 100 not to include the buffer layer 104. In this case, the nanowires or layers are fabricated directly on the substrate 102.

Description of Reference Numerals

[0066] 100 LED 102 Substrate 104 Buffer Layer 106 Intermediate Portion 108 Portion 110 Light-Emitting Portion 112 Portion 114 Ohmic Contact Layer

Claims

1. - A substrate (102), - Al doped according to the conductivity of the first type, disposed on the substrate (102) Ｘ１ Ga （１－Ｘ１－Ｙ１） In Ｙ１ A portion (108) of N, where the portion (108) is said to be of the first type, where X1 > 0 and X1 + Y1 ≦ 1, and - A light-emitting part (110) including a dilute AlN alloy containing gallium atoms and / or indium atoms at a concentration of less than 30%, - Al doped according to the second type of conductivity opposite to the first type of conductivity Ｘ２ Ga （１－Ｘ２－Ｙ２） In Ｙ２ a portion (112) of N, wherein the portion (112) is said to be of the second type, where X2>0 and X2+Y2≤1, and the light-emitting portion (110) is disposed between the portion (108) of the first type and the portion (112) of the second type, portion (112) A light-emitting diode (100) comprising at least.

2. The light-emitting diode (100) according to claim 1, further comprising an intermediate part (106) of GaN doped according to the conductivity of the first type, disposed between the substrate (102) and the part (108) of the first type.

3. The proportion of gallium atoms and / or indium atoms in the material of the light-emitting part (110) is 10% or less, and in particular, 5% or less. The light-emitting diode (100) according to claim 1 or 2.

4. Further comprising a buffer layer (104), the buffer layer (104) being disposed between the substrate (102) and the part (108) of the first type, or, when the light-emitting diode (100) includes such an intermediate part (106), disposed between the substrate (102) and the intermediate part (106). The light-emitting diode (100) according to any one of claims 1 to 3.

5. The material of the buffer layer (104) is based on GaN or AlN or AlGaN. The light-emitting diode (100) according to claim 4.

6. - The n-type dopant present in the material of one of the parts (108, 112) of either the first type or the second type corresponds to silicon atoms and / or sulfur atoms and / or germanium atoms, - The p-type dopant present in the material of the other of the parts (108, 112) of either the first type or the second type corresponds to magnesium atoms and / or beryllium atoms. The light-emitting diode (100) according to any one of claims 1 to 5.

7. The material of the part (108) of the first type and / or the material of the part (112) of the second type includes AlN. The light-emitting diode (100) according to any one of claims 1 to 6.

8. The light-emitting diode (100) according to any one of claims 1 to 7, comprising a plurality of nanowires extending from the substrate (102), each of the nanowires including at least the first type and the second type of the portions (108, 112) and the light-emitting portion (110).

9. The light-emitting diode (100) according to any one of claims 1 to 7, wherein at least the first type and the second type of the portions (108, 112) and the light-emitting portion (110) form a stack of layers disposed on the substrate (102).

10. A method for fabricating a light-emitting diode (100), comprising: - On a substrate (102), Al doped according to the conductivity of the first type Ｘ１ Ga （１－Ｘ１－Ｙ１） In Ｙ１ A step of fabricating a portion (108) of N, said portion (108) being of the first type, where X1 > 0 and X1 + Y1 ≦ 1 - fabricating a light-emitting portion (110) including a dilute AlN alloy containing gallium atoms and / or indium atoms at a concentration of less than 30% on the portion (108) of the first type; - On the light emitting portion (110), Al doped according to the conductivity of the second type opposite to the first type of conductivity Ｘ２ Ga （１－Ｘ２－Ｙ２） In Ｙ２ A step of fabricating an N portion (112), said portion (112) being of the second type, where X2 > 0 and X2 + Y2 ≦ 1, the step The method comprising at least the above step.

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