METHOD FOR MANUFACTURED A SUBSTRATE COMPRISING A RELAXED INGAN LAYER AND THE RESULTING SUBSTRATE FOR THE RESUMPTION OF GROWTH OF AN LED STRUCTURE

Abstract

A method for fabricating a relaxed epitaxially grown InGaN layer from a GaN / InGaN substrate comprising the following steps: a) providing a first stack (10) comprising a GaN or InGaN porosification layer (13) and a barrier layer (14), b) transferring the GaN or InGaN porosification layer (13) and the barrier layer (14) onto a porosification support (21) to form a second stack (20), c) forming a mask (50) on the GaN or InGaN porosification layer (13), d) porosifying the GaN or InGaN layer (13) through the mask (50), e) transferring the porosified GaN or InGaN layer (13) and the barrier layer (14) onto a support of interest (31), f) forming an InGaN layer (41) by epitaxy on the barrier layer (14), whereby a relaxed epitaxial InGaN layer is obtained. Figure for the abstract: 1F

Description

Title of the invention: METHOD FOR MANUFACTURED A SUBSTRATE COMPRISING A RELAXED INGAN LAYER AND THE RESULTING SUBSTRATE FOR THE RESUMPTION OF GROWTH OF AN LED STRUCTURE technical field

[0001] The present invention relates to the general field of color micro-displays.

[0002] The invention relates to a method for manufacturing a substrate or pseudo-substrate comprising a relaxed InGaN layer.

[0003] The invention also relates to a substrate or pseudo-substrate comprising a relaxed InGaN layer.

[0004] The invention has applications in many industrial fields, and in particular in the field of micro-color screens based on micro-LEDs with a pitch of less than 10 pm. PREVIOUS STATE OF THE ART

[0005] The color microscreens include red, green and blue pixels (RGB pixels).

[0006] Blue and green pixels can be made from nitride materials and red pixels from phosphor materials. To combine these three types of pixels on the same substrate, the so-called "pick and place" technique is generally used. However, in the case of microdisplays with pixels smaller than 10 pm, this technique can no longer be used because of not only alignment problems, but also the time required to implement such a technique on the scale of a microdisplay.

[0007] Another solution involves performing color conversion using quantum dots (QDs) or nanophosphors. However, controlling the deposition of these materials on small pixels is difficult, and their resistance to flux is not sufficiently robust.

[0008] It is therefore crucial to be able to obtain the three RGB pixels natively with the same family of materials and on the same substrate. For this, InGaN is the most promising material. This material can, in fact, theoretically cover the entire visible spectrum depending on its indium concentration. Blue InGaN-based micro-LEDs already exhibit high luminance, much higher than their organic counterparts. To emit at wavelengths in the green, the LED's quantum wells (PQs) must contain at least 25% indium, and for emission in the For red, it is necessary to have at least 35% indium. Unfortunately, the quality of InGaN material beyond 20% In is degraded due to the low miscibility of In in GaN, but also due to the high compressive stress inherent in the growth of the active InGaN region on GaN.

[0009] It is therefore essential to be able to reduce the overall stress in GaN / InGaN based structures.

[0010] To address this problem, several solutions have been considered.

[0011] A first solution consists of forming nanostructures, such as nanowires or pyramids, to relax the stresses at the free edges. The growth of axial nanowires can be achieved by molecular beam epitaxy (or MBE for Molecular Beam Epitaxy). In practice, the low growth temperature used in MBE growth leads to low internal quantum yields (IQE). Pyramids allow the dislocations to be bent. In particular, full pyramids have semipolar planes favorable to the incorporation of In and the reduction of the internal electric field of the active region. For truncated pyramids, the truncated faces allow the growth of quantum wells on the c-plane, which leads to more homogeneous emission compared to emission along the semipolar planes of a full pyramid.Alternatively, growth can also occur in a planar manner on planes other than the c-face of the wurtzite structure, such as growth on semi-polar planes which are more favorable to the incorporation of In.

[0012] Another solution is to reduce the stresses in the active region of the LED structure by using a substrate (or pseudo-substrate) with a lattice parameter closer to that of the InGaN alloy of the quantum wells. Thus, even with a planar configuration, the incorporation rate of In in the InGaN can be increased. It has been shown that as the lattice parameter of the substrate increases, the internal electric field is reduced and the emissions from the quantum wells are redshifted. The resulting relaxed InGaN layer allows the growth of an IILN heterostructure by metal-organic vapor phase epitaxy (MOVPE). However, to date, to our knowledge, the only substrate that has enabled this demonstration is the InGaNOS pseudo-substrate from Soitec. It is manufactured using the Smart Cut™ technique.The relaxation of the InGaN layer is achieved through various heat treatments [1]. However, with such a process, cracks may appear in the InGaN layer and / or the surface of this layer may lose its flatness.

[0013] Recently, it has been shown that porous GaN can be compliant [2]. A layer of InxGai_xN with 0.05 <x<0,125 de 200 nm est formée sur une couche de GaN dopée n de 800 nm, puis des mésas de 10 pm de côté sont structurées. La porosification par anodisation électrochimique de la couche de GaN type n conduit à une relaxation partial of the upper InGaN layer. Red micro-LEDs with an EQE of 0.2% have been produced using a similar process [3].

[0014] However, with such a process, the layer to be porosified must be doped. Furthermore, porosification occurs only through the lateral faces of the mesas. It is therefore difficult to obtain uniform porosity throughout the entire volume of the GaN layer.

[0015] The fabrication of a relaxed epitaxial InGaN layer from a GaN / InGaN substrate and the fabrication of a relaxed epitaxial InGaN layer on InGaN mesas were carried out using processes involving electrochemical porosification. The porosification step is implemented full-plate by means of various transfers [4,5].

[0016] Another technique for porosifying a GaN layer involves depositing a nanomask onto the GaN layer to be porosified and sublimating this layer through the mask's openings by means of high-temperature annealing. The pore size and density therefore depend primarily on the mask's dimensions. Devices comprising a porous GaN layer and (Ga,In)N / GaN quantum wells have been fabricated from a stack consisting successively of a silicon substrate, an AIN layer, a GaN layer, an InGaN layer, and a GaN layer. After forming a full-plate mask on this stack, the latter is subjected to the sublimation step. The GaN layer, as well as the layers covering it, are sublimated through the mask. The AIN layer acts as a stop layer. It has been shown that the use of a porous GaN substrate leads to better photoluminescence compared to a non-porous GaN substrate [6].Sublimation can be carried out, for example, in a molecular beam epitaxy (MBE) frame [6] or in a metal-organic vapor epitaxy (MOVE) frame [7]. This process can be implemented on doped or undoped GaN layers. However, not all substrates can be used due to the temperatures involved in sublimation. Description of the invention

[0017] An object of the present invention is to propose a method of obtaining an epitaxial InGaN layer, at least partially or even totally relaxed, from a GaN / InGaN substrate in order to manufacture, for example, red green blue pixels.

[0018] To this end, the present invention proposes a method for fabricating a relaxed epitaxial InGaN layer from a GaN / InGaN substrate comprising the following steps:

[0019] a) provide a first stack comprising successively a layer to be porosified in GaN or InGaN and a barrier layer, preferably in AlInN, AIN, GaN or AlGaN,

[0020] b) transfer the layer to be porosified in GaN or InGaN and the barrier layer onto a porosification support, the barrier layer being arranged between the porosification support and the layer to be porosified in GaN or InGaN, so as to form a second stack,

[0021] c) form a mask on the layer to be porosified in GaN or InGaN,

[0022] d) porosify the GaN or InGaN layer through the mask, thereby forming a porous GaN or InGaN layer,

[0023] e) transferring the porous GaN or InGaN layer and the barrier layer onto a support of interest, thereby forming an intermediate substrate,

[0024] f) form an InGaN layer by epitaxy on the barrier layer, thereby obtaining a relaxed epitaxial InGaN layer on the intermediate substrate.

[0025] The invention differs fundamentally from the prior art by implementing a porosification step of the GaN or InGaN layer through a mask and by implementing various transfer steps. The porosification structures the surface of the GaN or InGaN layer and improves extraction efficiency, allowing for the incorporation of more In by stress relaxation.

[0026] The first transfer allows the porosification step to be carried out on the nitrogen (N) polarity face of the GaN or InGaN layer, thus achieving a higher degree of porosity compared to the Ga polarity face. The second transfer allows the non-porified barrier layer to be on the front face of the substrate, for subsequent epitaxial resumption. The barrier layer is not porosified during step e). It can therefore serve as the epitaxial resumption layer. Furthermore, the substrate used for porosification is not the final substrate, which allows for a wider choice of substrates of interest.

[0027] At the end of the process, an InGaNOX-type structure ("InGaN on Substrate X") is obtained with an undoped InGaN layer. The process can be carried out on a full-plate basis, which simplifies its implementation.

[0028] During the re-epitaxial process, the growth temperature used (typically from 800°C to 1000°C, and in particular from 800°C to 900°C for InGaN) allows modification of the porosified layer, notably by enlarging the pores of this layer, which provides an additional degree of freedom while maintaining the lattice parameter adapted to the re-epitaxial layer. This results in an InGaN layer that is at least partially relaxed, and preferably fully relaxed.

[0029] According to a first embodiment, step d) is carried out by sublimation through the mask. Sublimation porification consists of sublimating the GaN or InGaN layer through the openings in the mask. The pore size and density therefore depend primarily on the dimensions of the mask. Sublimation consists of high-temperature annealing. It can be carried out, for example, in a molecular beam epitaxy setup or in a metal-organic vapor deposition setup. (EPVOM).

[0030] According to this first embodiment, the mask is advantageously a SiN mask. The SiN mask can advantageously be formed in situ. The position of the mask openings can be random. Alternatively, the SiN mask can be formed ex situ with a process implementing an etching step through an organized mask, for example, a block copolymer mask. The barrier layer is selective with respect to (Ga,In)N during sublimation.

[0031] According to another embodiment, the layer to be porosified of GaN or InGaN is doped and step d) is carried out electrochemically through the mask.

[0032] According to this embodiment, the mask is advantageously made of a polymer material. Preferably, it is a block copolymer. Such a polymer has homogeneous and regularly spaced openings.

[0033] According to these different embodiments, the mask formed in step c) can have apertures from 1 nm to 50 nm in diameter. For example, apertures from 1 nm to 20 nm or even apertures from 20 nm to 40 nm in diameter may be chosen.

[0034] It is easy to adjust the dimensions of the pores of the porous layer according to the openings of the mask, the possible doping of the GaN or InGaN layer, the applied voltage and / or the chosen electrolyte (nature and / or concentration) or even the temperature and the duration of sublimation to obtain the percentage of relaxation necessary to reach the desired wavelength.

[0035] Advantageously, the mask comprises at least a first zone, a second zone, and a third zone, the openings of the first zone having a first dimension, the openings of the second zone having a second dimension, and the openings of the third zone having a third dimension, whereby, in step d), the porous GaN or InGaN layer exhibits a first degree of porosity, a second degree of porosity, and a third degree of porosity with respect to the first, second, and third zones, respectively. Thus, the In concentration of the InGaN layer re-epitaxed in each of the zones will be different, and it is possible to epitaxially grow an all-InGaN LED structure. A single growth step can lead to obtaining the three RGB colors.

[0036] Advantageously, the porosification support and / or the support of interest comprises a support layer, for example of sapphire, silicon carbide (SiC) or silicon, and a buried oxide layer.

[0037] According to a particular embodiment, step b) is advantageously carried out using a SmartCut™ type process comprising the following steps:

[0038] - implantation of atomic species to form a zone of embrittlement in the layer to be porosified in GaN or InGaN, at a depth close to the final thickness of the layer to be retained in the final substrate.

[0039] - bonding of the first stack onto the porification support, the barrier layer being positioned between the porification support and the layer to be porified,

[0040] - supply of thermal energy to decouple the layer to be porosified from the layer of GaN or InGaN at the level of the area of ​​fragility.

[0041] Advantageously, the first stack provided in step a) further comprises an additional InGaN layer.

[0042] According to this embodiment, step b) can be carried out according to two advantageous variants.

[0043] According to the first advantageous embodiment, step b) comprises the following steps:

[0044] - electrochemical anodizing on the additional InGaN layer to weaken it,

[0045] - separation of the barrier layer and the GaN or InGaN layer and the layer of additional InGaN, by thermal activation and / or mechanical action.

[0046] According to the second advantageous embodiment, step b) includes a step in which electrochemical anodizing is carried out on the additional InGaN layer until its dissolution, thereby separating the barrier layer and the GaN or InGaN layer from the additional InGaN layer. The dissolution of the additional InGaN layer may be carried out before or after the transfer of the layers onto the anodizing substrate.

[0047] Advantageously, the process includes a step in which the GaN or InGaN layer is structured to form GaN or InGaN mesas. The formation of these mesas introduces an additional degree of relaxation to the InGaN layer, which will be epitaxially grown onto the barrier layer, taking advantage of the free edges of the mesas. The mesa structuring amplifies the relaxation phenomenon.

[0048] Structuring can be carried out before or after the porification step.

[0049] For example, the process includes, between step b) and step d), a step in which the barrier layer and the layer to be porosified in GaN or InGaN are structured, for example by photolithography, to form mesas. The mesas are thus formed before the porosification step, which allows the mesas to be porosified both by the lateral faces of the mesas and by the upper face in contact with the electrolytic solution.

[0050] Mesas could be formed during the porosification step. For this purpose, the mask formed in step c) can be deposited locally on the GaN or InGaN layer to be porosified, whereby, in step d), GaN or InGaN mesas are formed by sublimation of the portions of the GaN or InGaN layer not covered by the mask, while simultaneously porosifying the portions covered by the mask. Advantageously, the mask is deposited ex-situ.

[0051] Advantageously, the mesas have a thickness ranging from about ten na The thickness of mesas varies from nanometers to a few micrometers, depending on the nature of the layer 13. For example, a mesa containing a porous GaN layer 13 has a thickness of 500 nm to 2 pm. A mesa containing a porous InGaN layer 13 has a thickness of 10 to 200 nm. Advantageously, for thin mesas (typically less than 100 nm), the defect density is limited despite the high In concentration.

[0052] Advantageously, the process includes a step in which a doping step is performed by implantation or vapor-phase epitaxy with organometallics, optionally with different dopings, on the GaN or InGaN layer. Advantageously, this step is carried out before step d) of electrochemical porosification. It can be carried out directly on the InGaN or GaN mesas.

[0053] For example, it is possible to selectively implant an n-type dopant (such as silicon) or a p-type dopant (such as magnesium) to obtain a layer of GaN or InGaN or mesas with varying degrees of doping. This allows for a more or less relaxed structure.

[0054] Preferably, an implantation is carried out with an n-type dopant (e.g., Si) with different doping levels from one meso to the next. This yields pixels, for example, three pixels, with different doping levels and therefore different relaxation percentages, and thus different emission wavelengths. This embodiment is advantageous for forming a multispectral device, for example, simplified LEDs of different colors or a multi-color micro-display.

[0055] Advantageously, the barrier layer has a thickness of less than 3nm.

[0056] Advantageously, the indium content in the InGaN layer is greater than or equal to 8%. This ensures high-quality, In-rich re-epitaxy.

[0057] Advantageously, the process includes a subsequent step in which an LED structure, and in particular an all-InGaN red LED structure, is formed on the mesas. Since these mesas have a lattice parameter in the plane greater than that of GaN due to relaxation, they will serve as an InGaN pseudo-substrate to increase the incorporation rate of In in the all-InGaN LED structure.

[0058] This process has many advantages:

[0059] - it is simple to implement,

[0060] - it can be used for mesas of thin or thick thicknesses, - The mesa-structured approach brings about a compliance effect, - it leads to a partial or total relaxation of stresses, which results in a decrease in piezoelectric polarization compared to a stressed layer of the same In concentration, and above all to the incorporation of more In under the same growth conditions,

[0061] - it allows a so-called "bottom up" approach for the manufacture of pLEDs and pdisplays: The growth of optical structures (N, QW, P) is achieved after mesa pixelation, regardless of pixel size, and eliminates alignment problems as with the "pick and place" process. - there is no impact of the pixel etching process on the efficiency of micro-LEDs, which makes it possible to produce micrometric or even submicrometric pixels.

[0062] With this process, it is possible to achieve 40% of In in the wells and a quantum efficiency (EQE) greater than 2.9% in the red.

[0063] The invention also relates to a substrate comprising successively:

[0064] - a support of interest, preferably comprising a support layer, for example in sapphire, SiC or silicon, and a buried oxide layer, - a porous GaN or InGaN layer, possibly doped, the GaN or InGaN layer advantageously having a porosity greater than 1%, and preferably from 5% to 70%, and

[0065] - a barrier layer, preferably made of AlInN, AIN, GaN or AlGaN,

[0066] - possibly an additional InGaN layer.

[0067] The barrier layer is not porous.

[0068] Such a substrate allows the formation of a relaxed epitaxial InGaN layer and subsequent regrowth of a red-emitting LED structure. The relaxed InGaN layer promotes In incorporation and maintains good crystalline quality of the InGaN alloy even at high In concentrations.

[0069] The invention also relates to a light-emitting diode structure comprising successively a substrate as defined above and a re-epitaxial stack,

[0070] the substrate comprising:

[0071] - a support of interest,

[0072] - a porous layer of GaN or InGaN, optionally doped, and having, advantage ideally, a porosity greater than 1%, and preferably from 5% to 70%,

[0073] - a barrier layer,

[0074] - possibly, an additional InGaN layer.

[0075] the re-epitaxial stack comprising successively from the barrier layer of the substrate or, where applicable, from the additional InGaN layer:

[0076] - a relaxed epitaxial InGaN layer doped with a first type of conductivity,

[0077] - an active region with one or more InGaN / (Ga,In)N emitting quantum wells in the red, in the green, or in the blue to obtain all 3 colors via the mesas with different levels of doping,

[0078] - an InGaN layer doped with a second type of conductivity, different from the first type of conductivity.

[0079] Other features and advantages of the invention will become apparent from the following supplementary description.

[0080] It goes without saying that this additional description is given only as an illustration of the object of the invention and should in no way be interpreted as a limitation of this object. Brief description of the drawings

[0081] The present invention will be better understood upon reading the description of exemplary embodiments given by way of illustration only and in no way limiting, with reference to the accompanying drawings in which:

[0082] [Fig.1A]

[0083] [Fig.1B]

[0084] [Fig.lC]

[0085] [Fig.1D]

[0086] [Fig.1E]

[0087] [Fig.1F]

[0088] [Fig.1G] represent, schematically and in cross-section, a method for manufacturing an LED structure comprising a relaxed epitaxial InGaN layer, according to a particular embodiment of the invention.

[0089] [Fig.2A]

[0090] [Fig.2B]

[0091] [Fig.2C]

[0092] [Fig.2D]

[0093] [Fig.2E]

[0094] [Fig.2F]

[0095] [Fig.2G] schematically and in cross-section represent a method for manufacturing an LED structure comprising a relaxed epitaxial InGaN layer according to another particular embodiment of the invention,

[0096] [Fig.3A]

[0097] [Fig.3B]

[0098] [Fig.3C]

[0099] [Fig.3D]

[0100] [Fig.3E]

[0101] [Fig.3F]

[0102] [Fig.3G] represent, schematically and in cross-section, a method for manufacturing an LED structure comprising a relaxed epitaxial InGaN layer according to another particular embodiment of the invention.

[0103] [Fig.4A] and

[0104] [Fig.4B] schematically and in three dimensions represent different stages of a sublimation process of a GaN layer through a SixNy mask, the GaN layer resting on a barrier layer of AIN transferred onto a silicon porosification substrate (111) according to a particular embodiment of the invention.

[0105] [Fig.5] is a SEM image of a porosified GaN layer through a Si mask xNy, the GaN layer resting on a barrier layer transferred onto a silicon porosification substrate (111) according to a particular embodiment of the invention,

[0106] [Fig.6A]

[0107] [Fig.6B]

[0108] [Fig.6C]

[0109] [Fig. 6D] are SEM images showing nanomasks formed by exposing the GaN surface to a Si flux for 5 min, 10 min, 20 min, and 75 min under the same sublimation conditions. The longer the nanomask deposition time, the higher the SixNy coverage. For the longest time, the coverage is greater than 1, and the GaN surface is completely covered with SixNy.

[0110] The different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible.

[0111] The different possibilities (variants and embodiments) should be understood as not being mutually exclusive and can be combined with each other.

[0112] In addition, in the description below, orientation-dependent terms such as "above", "below", etc. of a structure apply assuming that the structure is oriented in the manner illustrated in the figures.

[0113] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0114] Although this is by no means limiting, the invention finds particular applications in the field of color microdisplays, and more specifically for the fabrication of red, green, and blue pixels. However, it could also be used in the field of photovoltaics or water electrolysis ("water splitting") since, on the one hand, InGaN absorbs across the entire visible spectrum and, on the other hand, its valence and conduction bands are around the stability range of water, thermodynamic conditions necessary for water decomposition. The invention may also be of interest for the fabrication of LEDs or lasers emitting at long wavelengths.

[0115] The process, allowing to obtain a substrate or a pseudo-substrate, comprising at least one barrier layer 14 on a porosified layer of GaN or InGaN 13, implements a step in which the layer of GaN or InGaN 13 is porosified by electrochemical anodization or by sublimation.

[0116] It is then possible to perform a re-epitaxial regrowth of an InGaN layer on the barrier layer. The epitaxially treated InGaN layer is at least partially relaxed, or even totally relaxed, which allows the growth of an LED structure.

[0117] The percentage of relaxation corresponds to: [Math 1] ûa / a — (ac2 - aci) / açi with acb being the mesh parameter of the starting layer, and

[0118] ac2 the mesh parameter of the relaxed layer

[0119] The layer is 100% relaxed if ac2 corresponds to the lattice parameter of the bulk material.

[0120] When aci=ac2 the layer is said to be constrained.

[0121] By partially relaxed, we mean a percentage of relaxation greater than 50%.

[0122] We will now describe in more detail several manufacturing processes for a substrate covered by a relaxed epitaxial InGaN layer with reference to the different embodiment variants represented in figures IA to IG, in figures 2A to 2G as well as in figures 3A to 3G.

[0123] These different embodiments include at least the following steps:

[0124] a) provide a first stack 10 comprising a layer to be porosified 13 in GaN or InGaN and a barrier layer 14, preferably in AlInN, AIN, GaN or AlGaN (figures IA, 2A, 3A),

[0125] b) transferring the layer to be porosified 13 in GaN or InGaN and the barrier layer 14 onto a porosification support 21, the barrier layer 14 being disposed between the porosification support 21 and the layer to be porosified in GaN or InGaN 13, so as to form a second stack 20 (figures IB, 2B, 3B),

[0126] c) form a mask 50 on the layer to be porosified in GaN or InGaN 13 (figures IC, 2C, 3C),

[0127] d) porosify the GaN or InGaN layer through the mask 50, thereby forming a porous GaN or InGaN layer 13, then remove the mask 50 (figures 1D, 2D, 3D),

[0128] e) transfer the porous layer in GaN or InGaN 13 and the barrier layer 14 onto a support of interest 31 (figures 1E, 2E, 3E),

[0129] f) form an InGaN layer by epitaxy on the barrier layer 14, thereby obtaining a relaxed epitaxial InGaN layer (figures 1F, 2F, 3F),

[0130] g) preferably, form an LED structure on the epitaxially grown InGaN layer (Figures IG, 2G, 3G),

[0131] h) optionally, form micrometer-sized mesas (for example from 1 pm to several tens of micrometers, and preferably 5 to 10 pm on a side) to increase the percentage of relaxation, by relaxation through the free edges of the mesas.

[0132] Step h) can be carried out, for example, between step d) and step e) and preferably between step e) and step f).

[0133] The first stack 10 provided in step a) and shown in Figures IA, 2A, 3A preferably comprises an initial substrate 11, a growth layer 12, a layer to be porosified in GaN or InGaN 13 and a barrier layer 14.

[0134] The initial substrate 11 is, for example, made of sapphire, SiC, silicon, or glass. The substrate has, for example, a thickness ranging from 350 pm to 1.5 mm.

[0135] The GaN 12 growth layer 12 has, for example, a thickness ranging from 30 nm to 4 pm. The GaN layer is preferably unintentionally doped. Unintentionally doped GaN means a doping concentration of less than 5 x 10¹⁷ / cm³, for example, 1 x 10¹⁷ / cm³. Alternatively, the growth layer 12 may be made of AIN or AlGaN.

[0136] The porosified InGaN or GaN layer 13 to be porosified can be doped, in particular with n-type doping. For example, it has a thickness ranging from 10 to 200 nm for InGaN or from 800 nm to a few micrometers (e.g., 2 pm) for GaN. A thinner layer can contain a high In concentration while maintaining good material quality (few defects). Doped InGaN is defined as having an electron concentration between 2 x 10¹⁸ and 2 x 10¹⁹ / cm³. The doped InGaN layer 13 is electrically conductive. It is porosified in step d).

[0137] The InGaN or GaN 13 layer has two principal faces: a first principal face 13a and a second principal face 13b. The first principal face 13a is nitrogen (N) polarized. It is oriented opposite the GaN 12 growth layer. The second principal face 13b is gallium (Ga) polarized. It is oriented in contact with the barrier layer 14.

[0138] The barrier layer 14 is preferably made of AlInN, AIN, GaN or AlGaN. For example, a barrier layer made of AlInN will be chosen.

[0139] The barrier layer 14 preferably has a thickness of less than 3 nm, for example, a thickness of 1 nm. Its In concentration should be adjusted to match the lattice of the GaN or InGaN layer 13. The barrier layer 14 will serve both as a selective layer with respect to the sublimation technique and as an epitaxial reactivation layer. The sublimation technique will have no effect on the barrier layer 14. This layer is not porous during step d). After step d), the barrier layer 14 is non-porous (i.e., it has a porosity of less than 0.01%, and preferably less than 0.001%). The barrier layer 14 is a non-porous layer that can be used for epitaxial reactivation.

[0140] According to a first embodiment, shown in [Fig. 1 A], the first stack 10 consists of the layers mentioned above. In other words, it does not include any other layers.

[0141] According to another embodiment shown in [Fig. 2A] or [Fig. 3A], the first stack further comprises an additional InGaN layer 15. This additional layer has an In concentration greater than or equal to that of the InGaN layer 13, positioned between the GaN growth layer 12 and the barrier layer 14. The growth of this additional layer is carried out on the barrier layer 14. After the first transfer, the additional layer is in contact with the porification substrate 21 (Figures 2B, 3B). It is not porosified during step d) (Figures 2D, 3D). After the second transfer, the additional layer 15 is the top layer of the stack (Figures 2E, 3E), and thus the resumption of epitaxy is carried out directly from this layer 15 (Figures 2F, 3F).Advantageously, the presence of this layer 15 avoids or limits potential surface contamination problems between the different stages due to the presence of Al. Furthermore, when the additional InGaN layer 15 on the surface of the stack has an In concentration higher than that of the layer to be porosified, a first relaxation can occur after the second transfer and / or after the formation of the mesas.

[0142] The layers of the first stack 10 are advantageously deposited full plate on the initial substrate 11.

[0143] During step b), the barrier layer 14, the InGaN or GaN layer 13, and optionally the additional InGaN layer 15 are transferred onto a porosification support 21 (figures IB, 2B, 3B).

[0144] The porification support 21 advantageously comprises a support layer 22 and a buried oxide layer 23 called BOX (“Buried Oxide layer” also sometimes called continuous oxide layer).

[0145] The support layer (or support) 22 is, for example, made of sapphire, silicon, silicon carbide, or glass. The support layer 22 has, for example, a thickness ranging from 350 pm to 1.5 mm.

[0146] The oxide layer 23 BOX has, for example, a thickness ranging from 100 nm to 4 pm.

[0147] The free face of the barrier layer 14 or of the additional layer 15 in InGaN is transferred, on the porosification support 21, preferably, on the oxide layer 23 BOX of the porosification support 21, via for example a direct or molecular bonding.

[0148] According to an advantageous embodiment, this transfer is carried out using the Smart Cut™ technique. The process comprises the following steps:

[0149] - implantation of atomic species to form a zone of embrittlement in the layer to be porosified of GaN or InGaN 13, at a depth close to the final thickness of the layer to be retained in the final substrate;

[0150] - bonding of the first stack 10 onto the porification support 21,

[0151] - supply of thermal energy to decouple the InGaN or GaN 13 layer from level of the area of ​​fragility.

[0152] The initial substrate 11 and the GaN layer 12 of the first stack 10 are detached from the InGaN / GaN layer 13 by fracturing along the plane of the embrittlement zone. The fracture is achieved, for example, by heat treatment in a temperature range of 400°C to 600°C and for a duration ranging from a few minutes to a few hours. This fracturing results in the transfer of the layer to be porosified 13, the barrier layer 14, and possibly the additional layer 15 onto the porosification support 21.

[0153] According to a particular embodiment, the initial substrate 11 and the GaN layer 12 can be detached from the GaN layer 13 by a process of etching a sacrificial intermediate layer for example with a laser (also called the detachment or "lift off" technique).

[0154] At the end of step b), a second stack 20 is thus obtained, comprising successively the support layer 22, the buried oxide layer 23, the barrier layer 14, and the InGaN or GaN layer to be porosified 13 (Figures IB, 2B, 3B). The first face 13a of N polarity is thus accessible. The second stack 20 may further comprise the additional InGaN layer 15. The additional layer 15 is positioned between the buried oxide layer 23 and the barrier layer 14.

[0155] After implantation of the Smart Cut™, and before the porosification step, it is possible to carry out a Si implantation step to make the InGaN 13 layer electrically conductive or even more electrically conductive if this layer is already doped.

[0156] In step c), a mask 50 is formed on the layer to be porosified 13. The mask has a plurality of openings (or pores). The openings may be of identical or different dimensions. Advantageously, their dimensions are identical. The openings may be arranged regularly or randomly. The openings have, for example, a diameter of 1 nm to 20 nm. The openings are advantageously circular.

[0157] The mask can be formed from a fraction of a monolayer of material. It has, for example, a thickness of between 0.4 and 1 monolayer.

[0158] It is possible to form a full plate mask 50, i.e. of identical dimensions to the underlying layer to be porosified (figures IC, 2C).

[0159] According to a particular embodiment, shown in [Fig. 3C], the mask 50 is made to form three different zones, labeled 02, 03, with different coverage rates. The dimensions of the nanomasking of each of the three zones will control the degree of porosity of each zone during the sublimation step.

[0160] The nature of the mask 50 is chosen according to the technique used for porosification.

[0161] For porosification by sublimation, a 50 mask is advantageously chosen in SiN. Such a mask can be formed in situ or ex situ, via intermediate masking with an additional mask, for example, made of a polymer material. In the case of ex situ masking, the SiN mask advantageously has a thickness greater than one monolayer. Preferably, the additional mask is a block copolymer film. A block copolymer film has a large number of small openings (or pores). Advantageously, the openings have the same dimensions and / or are regularly spaced, which advantageously leads to obtaining a GaN / InGaN layer with organized porosity. Advantageously, such a mask is formed rapidly. For example, the block copolymer is poly(styrene-blockmethyl methacrylate), also denoted PS-b-PMMA.

[0162] Mask 50 is engraved opposite the openings of the additional mask to form the openings of mask 50.

[0163] Advantageously at the end of step c), the additional copolymer film is removed before porosification by sublimation.

[0164] For electrochemical porosification, a mask 50, preferably made of polymer, is chosen. For example, the mask 50 is a block copolymer film. Preferably, the block copolymer is PS-b-PMMA.

[0165] Alternatively, a porous alumina mask 50 can be used. The nanoporous alumina mask 50 can be obtained by structuring an aluminum foil through various oxidation and etching steps. The nanopores of the alumina mask 50 advantageously have a diameter between 15 and 400 nm, for example 80 nm, and a pitch between 50 nm and 400 nm, for example on the order of 100 nm. The thickness of the alumina mask 50 is, for example, 250 nm.

[0166] In step d), the layer 13 of GaN or InGaN is porosified by sublimation or by electrochemical means.

[0167] To perform sublimation porosification, a molecular beam epitaxy (MBE) or metal-organic vapor epitaxy (MOVEP) frame can be used, for example. MBE epitaxy allows in situ control of growth, down to the monolayer level. Sublimation porosification advantageously leads to the production of well-defined pores, particularly cylindrical ones. The lateral wall of the pores is perpendicular to the principal faces 13a, 13b of layer 13.

[0168] Temperatures of 800°C to 900°C will be chosen, for example, for vacuum sublimation MBE. The higher the temperature, the greater the sublimation rate.

[0169] The barrier layer 14 acts as a sublimation arrest layer. This layer is not sublimated. It protects the underlying layers during porosification. It acts as a barrier layer or arrest layer. In particular, in the case of a first stacking comprising an additional layer of InGaN 15, the latter is protected by the barrier layer 14 during sublimation.

[0170] With this porosification technique, the GaN or InGaN 13 layer can be doped or undoped.

[0171] To perform electrochemical porosification, the layer to be porosified must be electrically conductive. Therefore, a doped GaN or InGaN layer is chosen. The porosification is applied to the N-face of the GaN or InGaN layer at the surface. Advantageously, porosification via the N-face results in greater porosification (porosity ratio, pore shape).

[0172] Step c) includes, for example, the following substeps:

[0173] - connect the doped GaN or InGaN layer 13 and a counter electrode to a ge voltage or current generator,

[0174] - immerse the second stack 20 and the counter electrode in an electrical solution trolytic,

[0175] - apply a voltage or current between the layer of doped GaN or InGaN 13 and the counter electrode so as to porosify the layer of doped GaN or InGaN 13.

[0176] The second stack 20 acts as a working electrode (WE).

[0177] The counter electrode is made of an electrically conductive material. The material of the counter electrode will be chosen so as not to form oxidizable by-products during the cathodic reaction, in order to avoid inducing a change in the electrolyte during porosification. A metal such as platinum will be chosen, for example.

[0178] In step d), the electrodes are immersed in an electrolyte, also called an electrolytic bath or electrolytic solution. The electrolyte can be acidic or basic. The electrolyte is, for example, oxalic acid. It can also be KOH, HF, HNO3, or H2SO4.

[0179] A voltage is applied between the device and the counter electrode. The voltage can range from 1V to 100V, preferably from 3V to 100V. It is applied, for example, for a duration ranging from a few seconds to a few hours. The anodizing reaction is complete when, at an imposed potential, the current becomes zero: in this case, there is no longer any charge transfer and the electrochemical reaction stops.

[0180] The electrochemical anodizing step can be carried out under ultraviolet (UV) light. The process can also include a first electrochemical anodizing without adding ultraviolet radiation and a second electrochemical anodizing with the addition of ultraviolet radiation.

[0181] Advantageously, the porification takes place throughout the entire volume of the 13-doped GaN or InGaN layer.

[0182] At the end of the porosification step d), the porosity rate of the GaN layer or The concentration of doped InGaN 13 is at least 1%. It preferably ranges from 5% to 70%.

[0183] The largest dimension (the height) of the pores can vary from a few nanometers to a few micrometers. The smallest dimension (the diameter) can vary from a few nanometers to a hundred nanometers, in particular from 1 nm to 70 nm, for example from 10 to 20 nm or from 30 to 70 nm, and preferably from 15 nm to 40 nm.

[0184] The resulting porosity (porosity rate and pore size) depends on the geometry of mask 50, possibly on the doping of layer 13 with GaN or InGaN, and on the process parameters (applied voltage, duration, nature and concentration of the electrolyte for electrochemical porosity, or duration and temperature for sublimation). Varying the porosity allows control of the In incorporation / segregation rate. The porosity, and in particular the pore size, can vary subsequently during the resumption of epitaxy as a function of the applied temperature.

[0185] In step e), the second stack 20, comprising the porosified layer 13 of GaN or InGaN, the barrier layer 14, and optionally the additional layer 15, is then transferred onto the support of interest 31 (Figures 1E, 2E, 3E) so that the second metal-polarized face 13b (Gallium) is on the front face. The support of interest 31 comprises, for example, a support layer 32 preferably made of Si, SiC, glass, or sapphire, and a BOX oxide layer 33. An oxide that can withstand high-temperature epitaxy (at least 950°C) is chosen.

[0186] The process thus yields a substrate 30 of the InGaNOX type (“InGaN on substrate X”) comprising, from the rear face to the front face (Figures 1E, 2E, 3E):

[0187] - a support of interest 31, preferably formed of a support layer 32, for example in sapphire, and with a layer of BOX 33 oxide,

[0188] - a porosified layer of GaN or InGaN 13, with a Ga polarity on the front face, - a non-porous barrier layer 14,

[0189] - and possibly an additional InGaN layer 15.

[0190] At the end of step e), the barrier layer 14 or the additional InGaN layer 15 is located on the front face. These layers are dense (i.e., they are not porous).

[0191] In step f), an InGaN layer is formed by re-epitaxial growth. The barrier layer 14 and / or the additional InGaN layer 15 is a continuous, non-porous 2D layer since it is not porosified during the electrochemical anodizing or sublimation step. The barrier layer 14 or the additional layer 15 allows re-epitaxial growth with an InGaN layer having a higher In concentration than the underlying GaN or InGaN layer. The growth of the re-epitaxial stack 40 is thus facilitated, and the epitaxial layer exhibits improved crystalline quality.

[0192] The surface InGaN layer will guide the deformation of the porous layer by its In concentration and its thickness. The porous layer can be made to deform in such a way that the surface InGaN layer can relax. Relaxation rates of around 70%, or even more, can advantageously be achieved.

[0193] According to an advantageous embodiment, the process may include a step in which the InGaN or GaN layer and the barrier layer 14 are structured to form mesas (step h).

[0194] Mesas, also called elevations, are raised features. They are obtained, for example, by etching a continuous layer or several superimposed continuous layers, so as to leave only a certain number of "reliefs" of this layer or these layers. The etching is generally plasma or dry etching (e.g., RIE plasma). The reliefs define pixels.

[0195] Preferably, the sides of the mesas are perpendicular to the stacking of the different layers of the substrate 30.

[0196] The dimensions (width and length) of the mesas range from 500 nm to 500 pm. Width and length refer to the dimensions parallel to the surface of the underlying stack. In particular, dimensions less than or equal to 1 µm x 1 µm will be chosen.

[0197] The spacing (“pitch”) between two consecutive 100 mesas can be between 50nm and 20pm.

[0198] The mesas include the InGaN or GaN layer 13, the barrier layer 14 and optionally the additional layer 15.

[0199] The thickness of the mesas depends in particular on the thickness of the InGaN or GaN 13 layer. For example, for a porous GaN 13 layer, the mesa height can be 700 nm (500 nm porous GaN + 200 nm non-porous InGaN). Thickness refers to the dimension of the mesa perpendicular to the underlying stack.

[0200] The mesas are formed, advantageously, before the growth of the LED structure, and even more advantageously before the resumption of epitaxy.

[0201] According to another advantageous embodiment, the mesas are advantageously formed after the porosification step.

[0202] According to another advantageous embodiment, the mesas can be formed before the porosification step. For example, after the masking step (step c), lithography can then be performed to obtain mesas. It is particularly advantageous to form one mesa per nanomask zone 01, 02, 03. Preferably, a single sublimation step is performed for all three zones.

[0203] According to another embodiment, the mesas are formed before or after the resumption of epitaxy of the InGaN layer.

[0204] The mesas can be structured and then doped. According to this embodiment, the process may include, before the porosification step, the following steps:

[0205] - structuring the InGaN or GaN layer 13 and the barrier layer 14, deposited full plate, to form mesas,

[0206] - advantageously, fill the space between the mesas with a suitable material and to flatten the resulting assembly to obtain a flat surface. - implant a dopant locally in the mesas at the same concentration or at different concentrations; it is for example possible to carry out several implantations with different sets of masks.

[0207] Alternatively, the doping can be carried out prior to the structuring of the mesas. According to this embodiment, the process may include, before the porosification step, the following steps:

[0208] - locally implanting a dopant in layer 13 of deposited InGaN or GaN In the entire plate, the doping concentration can vary along the layer to form areas with varying levels of doping.

[0209] - structure the InGaN or GaN layer 13 and the barrier layer 14, deposited full plate, to form mesas.

[0210] By way of illustration, it is possible, for example, to use a hard mask, such as a SiN or SiO2 type mask, for implantation and alignment marks (for example, in Al, Ti, TiN) to match the mesas and the implanted areas. With two different masks, two areas with different implantation energies can be created, and therefore two different dopings in addition to the initial doping of the doped plate, for example, by MOCVD. The alignment marks allow the two masks for implantation and the mask for etching the mesas to be aligned.

[0211] The same mask set will be used for implantation and mesas.

[0212] The structuring of the mesas can be achieved by photolithography.

[0213] Alternatively, implantation doping can be replaced by metal-organic vapor-phase epitaxial doping (MOCVD), using Si or Ge as the dopant, for example. It is possible, for instance, to perform three successive epitaxial steps to obtain three different doping levels in order to form blue, green, and red (RGB) mesas at the end of the process.

[0214] Preferably, the process includes a subsequent step in which an LED structure is formed on the epitaxially grown InGaN layer (step g).

[0215] This step is advantageously carried out to form re-epitaxial LEDs, in particular all InGaN red (or green) LEDs.

[0216] The LED structure is advantageously fabricated on mesas. Since these mesas have a lattice parameter in the plane greater than that of GaN due to relaxation, they will serve as an InGaN pseudo-substrate to increase the In incorporation rate in the all-InGaN LED structure. This will also allow for the maintenance of good crystalline quality despite the high In content.

[0217] Even more advantageously, the resumption of epitaxy is carried out on mesas having different degrees of porosity. During this step, the In concentration of the The InGaN layer re-epitaxed in each zone will vary because the relaxation rate of each mesa was already different before re-epitaxy (for example, if the additional InGaN layer 15 placed on the barrier layer 14 has a higher In concentration than the porosified layer). Therefore, it is possible to epitaxially grow the entire InGaN LED structure. The In concentration of the different layers of the structure will be guided by the relaxation rate. Thus, if each mesa has the appropriate lattice parameter, a single growth step allows for the production of the three RGB colors, with each mesa exhibiting a specific color. The required lattice parameters are: 3.184 Å for blue, 3.200 Å for green, and 3.238 Å for red.

[0218] The re-epitaxial stacking 40 of an all-InGaN LED comprises, for example, successively from the barrier layer 14 or, where appropriate, from the additional InGaN layer 15:

[0219] - an n-doped InxGaN layer (simple layer or InGaN supernetworks / GaN), preferably with the same In concentration as the InGaN layer of the relaxed substrate,

[0220] - an active zone 42 with one or more InyGai yN / InxGai_xN quantum wells (usually 5), emitting in the red (or blue or green to ultimately obtain the 3 RGB colors),

[0221] - an electron barrier 43 based on GaN or p-doped AlGaN (xAl ~ 10%),

[0222] - a layer of InxGai_xN doped p 44, preferably of the same In concentration as the n-InGaN layer or lower,

[0223] - a p++ 45-doped InGaN layer, preferably of the same In concentration as the p-InGaN layer.

[0224] More specifically, an all-InGaN LED structure may successively comprise:

[0225] - an InGaN substrate,

[0226] - a 350nm n-doped InGaN layer, formed of 15 x Ino^Gao^N / GaN (thicknesses 20nm / l,8nm)

[0227] - multiple quantum wells (MQWs), formed of 5 x InOj4oGaOj6oN / Ino^Gao^vN (thicknesses 2.3nm / 5, 7, 11 nm), - a layer of Ino^Gao^N nid (10nm), - a layer of AlojGao^N :Mg (20nm),

[0228] - a layer of Ino^Gao^N doped with Mg (125nm),

[0229] - a layer of Ino^Gao^N doped p+++ (25nm).

[0230] Different growth processes can be used to form epitaxial layers.

[0231] According to a first embodiment, the resumption of growth is lateral and a subsequent pixelation step by etching is advantageously carried out.

[0232] According to another embodiment, the resumption of growth occurs vertically above the mesas. In this variant, the pixels correspond to the underlying mesas.

[0233] Advantageously, a passivation layer will be deposited on the sides of the mesas and / or re-epitaxial LEDs, for example by atomic layer deposition (ALD). The passivation layer may be made of alumina. The passivation layer may be a few nanometers thick, for example, from 2 to 5 nm.

[0234] A technological process will finally be applied for the fabrication of micro-LEDs. The micro-LEDs can be the initial size of the mesas.

[0235] Illustrative and non-limiting example:

[0236] Figure 4A schematically shows a GaN layer to be porosified by sublimation. The GaN layer is on a substrate comprising a silicon support and a AIN barrier layer. Nanomasking is performed in-situ by depositing SiN. Porification occurs through the holes in the mask via a vacuum sublimation step. Figure 4B schematically represents the sample after porosification by sublimation through the SiN mask.

[0237] Scanning electron microscopy (SEM) characterization confirms that porification has indeed occurred ([Fig. 5]). The AIN layer is intact: it has not been porified.

[0238] Figures 6A to 6D show the influence of the coverage rate of the in-situ SiN nanomasking (from 0 to 1 monolayer) on the porosity rate of a GaN layer after the sublimation step. REFERENCES

[0239] [1] A. Even et al., “Enhanced In incorporation in full InGaN heterostructure grown on relaxed InGaN pseudo-substrate », Appl. Phys. Lett. 110, 262103 (2017).

[0240] [2] S. Pasayat et al., « Compliant Micron-Sized Pattemed InGaN Pseudo-Substrates Utilizing Porous GaN”, Materials 13, 213 (2020).

[0241] [3] S. Pasayat et al., “Démonstration of ultra-small (<10 qm) 632 nm red InGaN micro-LEDs with useful on-wafer external quantum efficiency (>0.2%) for mini-displays”, “Appl. Phys. Exp. 14, 011004 (2021).

[0242] [4] demande de brevet européen EP 20215515.6 non encore publiée.

[0243] [5] demande de brevet européen EP 20214254.3 non encore publiée.

[0244] [6] B. Damilano, et al., "Photoluminescence properties of porous GaN and (Ga,In)N / GaN single quantum well made by sélective area sublimation," Optics Express 25, 33243 (2017).

[0245] [7] P.-M. Coulon, P. Feng, B. Damilano, S. Vézian, T. Wang, and P. A. Shields, "Influence of the reactor environment on the sélective area thermal etching of GaN nanohole arrays," Scientific Reports 10, (2020). https: / / doi.org / 10.1038 / s41598-020-62539-l.

Claims

Demands

1. A method for fabricating a relaxed epitaxial InGaN layer from a GaN / InGaN substrate comprising the following steps: a) providing a first stack (10) successively comprising a porosification layer of GaN or InGaN (13) and a barrier layer (14) preferably of AlInN, AIN, GaN or AlGaN, b) transferring the porosification layer of GaN or InGaN (13) and the barrier layer (14) onto a porosification support (21), the barrier layer (14) being disposed between the porosification support (21) and the porosification layer of GaN or InGaN (13), so as to form a second stack (20), c) forming a mask (50) on the porosification layer of GaN or InGaN (13), d) porosifying the GaN or InGaN layer (13) through the mask, whereby a porous layer of GaN or InGaN is formed (13), e) transfer the porous layer of GaN or InGaN (13) and the barrier layer (14) onto a support of interest (31),the porous GaN or InGaN layer (13) being disposed between the support of interest 31 and the barrier layer (14), thereby forming an intermediate substrate, f) forming an InGaN layer (41) by epitaxy on the intermediate substrate, thereby obtaining a relaxed epitaxial InGaN layer on the intermediate substrate.

2. A method according to claim 1, characterized in that step d) is carried out by sublimation through the mask (50), the mask (50) preferably being made of SiN.

3. Method according to claim 1, characterized in that the layer to be porosified (13) is doped and in that step d) is carried out electrochemically through the mask (50).

4. Method according to claim 3, characterized in that the mask (50) is made of a polymer material, preferably a block copolymer.

5. A method according to any one of the preceding claims, characterized in that the mask (50) formed in step c) has openings of 20 nm to 40 nm in diameter.

6. A method according to any one of the preceding claims, characterized in that the porosification support (21) and / or the support of interest (31) comprises a support layer (22, 32), for example of sapphire, SiC or silicon, and a buried oxide layer (23, 33).

7. A method according to any one of the preceding claims, characterized in that the first stack (10) provided in step a) further comprises an additional InGaN layer (15) covering the barrier layer (14) and in that in step b), the additional InGaN layer (15) is disposed between the porosification support (21) and the barrier layer (14).

8. A method according to any one of the preceding claims, characterized in that the method comprises an additional step in which a doping step is carried out by implantation or by vapor phase epitaxy with organometallics, optionally with different dopings, on the GaN or InGaN layer (13).

9. A method according to any one of the preceding claims, characterized in that the mask (50) formed in step c) is deposited locally on the layer to be porosified in GaN or InGaN (13), whereby, in step d), GaN or InGaN mesas are formed.

10. A method according to any one of the preceding claims, characterized in that the mask (50) has at least a first zone (0i), a second zone (02) and a third zone (03), the openings of the first zone (0i) having a first dimension, the openings of the second zone (02) having a second dimension and the openings of the third zone (03) having a third dimension, wherein in step d) the porous GaN or InGaN layer (13) has a first degree of porosity, a second degree of porosity and a third degree of porosity with respect respectively to the first zone (0i), the second zone (02) and the third zone (03).

11. Substrate (30) comprising successively: - a support of interest (31), comprising for example a support layer (32), for example of sapphire, SiC or silicon, and a buried oxide layer (33), - a porous layer of GaN or InGaN (13), advantageously having a porosity greater than 1%, and - a barrier layer (14) of AlInN, AIN or AlGaN, - an additional layer of InGaN (15).

12. Light-emitting diode comprising successively: a substrate (30) and a re-epitaxial stack (40), the substrate (30) comprising: - a support of interest (31), - a porous layer of GaN or InGaN (13), - a barrier layer (14) made of AlInN, AIN or AlGaN, - an additional InGaN layer (15). the re-epitaxial stacking (40) comprising successively from the barrier layer (14) or, where applicable, from the additional layer in InGaN (15): - a relaxed epitaxial InGaN layer doped with a first type of conductivity (41), - an active zone (42) with one or more InGaN / (Ga,In)N quantum wells emitting in the red or green, - an InGaN layer doped with a second type of conductivity, different from the first type of conductivity (44).

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