Method for manufacturing an optoelectronic device comprising a diode covered by an optical component

Abstract

The invention relates to a method for manufacturing an optoelectronic device comprising at least one photoemitting or photoreceiving diode having a front face intended to transmit or receive light radiation; at least one optical component for shaping the light radiation, located on the front face and covering the diode, and having a lateral variation of predefined optical index.The process comprises the following steps: supplying the diode; determining a lateral variation in porosity, based on a predefined target lateral variation in refractive index, of a semiconductor portion made of a crystalline material transparent to light radiation and located on the front face of and covering the diode; fabricating the semiconductor portion to be porosified; performing electrochemical porosification of the semiconductor portion, such that it exhibits the determined lateral variation in porosity, the porosified semiconductor portion then forming the optical component. Figure 1A for the abstract.

Description

Title of the invention: Method for manufacturing an optoelectronic device comprising a diode covered by an optical component. Technical field

[0001] The field of the invention is that of optoelectronic devices comprising a matrix of diodes, which are covered by optical components such as microlenses. PREVIOUS STATE OF THE ART

[0002] Optoelectronic devices can be formed from a matrix of diodes, for example light-emitting diodes made from a semiconductor material such as a III-V compound, for example GaN, where each diode is covered by a microlens intended to improve light extraction and shape the emitted light beam.

[0003] The fabrication of microlenses generally includes a step of structuring a photosensitive resin by photolithography, followed by a finishing step, and finally transfer by etching into a transparent organic or inorganic material, for example into GaN. These microlenses are usually hemispherical and centrosymmetric.

[0004] However, such a process has a number of limitations. For example, it is relatively complex, particularly due to the finishing and shape transfer steps in the transparent material. Furthermore, it offers few degrees of freedom in the dimensioning of the microlenses, which limits the choice of optical properties for shaping the light beam. In addition, the microlenses have a curved front face, so integrating additional elements, optical or otherwise, above the microlenses can be complicated. Description of the invention

[0005] The invention aims to remedy, at least in part, the drawbacks of the prior art. To this end, the invention relates to a method for manufacturing an optoelectronic device comprising at least one diode, photoemissive or photoreceptive, covered by an optical component having a lateral variation of optical index obtained by electrochemical porosification.

[0006] More specifically, the object of the invention is a method for manufacturing an optoelectronic device comprising: at least one photoemitting or photoreceiving diode having a front face for transmitting or receiving light radiation; at least one optical component for shaping the radiation luminous, located on the front face and covering the diode, and exhibiting a lateral variation of predefined optical index.

[0007] The manufacturing process comprises the following steps: supplying the diode; determining a lateral variation of a porosity ratio, from a predefined target lateral variation of optical index, of a semiconductor portion made of a crystalline material transparent to light radiation and located on the front face and covering the diode; producing the semiconductor portion to be porosified; carrying out an electrochemical porosification of the semiconductor portion, so that it exhibits the determined lateral variation of the porosity ratio, the semiconductor portion thus porosified then forming the optical component.

[0008] Some preferred but not limiting aspects of this manufacturing process are the following.

[0009] The semiconductor portion to be porosified may have a flat upper face opposite to the front face of the diode.

[0010] During the step of making the semiconductor portion to be porosified, it may include several adjacent doped areas, which may have a different level of doping from one doped area to another.

[0011] During the electrochemical porosification step, the doped areas can be porosified and may exhibit a different porosity rate from one doped area to another.

[0012] During the step of making the semiconductor portion to be porosified, each doped area can have a homogeneous level of doping laterally and vertically.

[0013] The optoelectronic device may comprise a diode array and several optical components formed from porosified semiconductor portions. During the fabrication step of the porosified semiconductor portions, these may be parts of the same continuous semiconductor layer that can extend over the diode array.

[0014] During the electrochemical porosification step, an electrical anodization signal can exhibit a constant value over time until the lateral variation of the porosity rate is obtained.

[0015] During the electrochemical porosification step, an intensity modulation of an electrical anodizing signal can be carried out, which can lead to obtaining the lateral variation of the porosity rate.

[0016] During the step of making the semiconductor portion to be porosified, the latter may have a laterally homogeneous level of doping.

[0017] During the step of making the semiconducting portion to be porosified, the latter may have a free lateral border.

[0018] During the step of making the semiconductor portion to be porosified, the latter may have an upper face covered by a thin protective portion made of a non-porous material during the electrochemical porosification step.

[0019] The semiconducting portion to be porosified can be made of a material based on (Al,In,Ga)N or InP.

[0020] The manufacturing process may include one or more of the following steps: fabricating the mesa-shaped semiconductor portion to be porosified from a growth substrate; fabricating the diode from the semiconductor portion to be porosified; transferring the diode and the semiconductor portion to be porosified onto a control substrate; performing the electrochemical porosification of the semiconductor portion.

[0021] The invention also relates to an optoelectronic device, comprising: at least one photoemitting or photoreceiving diode having a front face intended to transmit or receive light radiation; at least one optical component for shaping the light radiation, located on the front face and covering the diode, and having a lateral variation of predefined optical index, made of a transparent crystalline material, and having a lateral variation of a porosity rate of the transparent crystalline material. Brief description of the drawings

[0022] Other aspects, objects, advantages and features of the invention will become more apparent upon reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0023] Figures IA and IB are schematic and partial views, in cross-section ([Fig.1A]) and in top view ([Fig.1B]), of an optoelectronic device according to a first embodiment, where the optical components are obtained by electrochemical porosification of semiconductor portions exhibiting a lateral variation of the doping level;

[0024] [Fig.2] is a schematic and partial cross-sectional view of an optoelectronic device according to a second embodiment, where the optical components are obtained by electrochemical porosification with modulation of the anodization voltage Ea;

[0025] Figures 3A to 3F illustrate different stages of a manufacturing process for an optoelectronic device similar to that of [Fig. 1A];

[0026] Figures 4A to 4C illustrate different stages of a variant of a manufacturing process for an optoelectronic device similar to that of [Fig. 1A];

[0027] Figures 5A to 5C illustrate different stages of a manufacturing process for a optoelectronic device similar to that of [Fig.2];

[0028] Figures 6A to 6D illustrate different stages of a variant of a manufacturing process for an optoelectronic device similar to that of [Fig.2];

[0029] Figures 7A and 7B are schematic and partial views, in cross-section ([Fig.7A]) and in top view ([Fig.7B]), of an optoelectronic device according to a variant of the first embodiment;

[0030] [Fig.8] is a schematic and partial cross-sectional view of an optoelectronic device according to another variant of the first embodiment.

[0031] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0032] In the figures and throughout the description, the same reference numerals represent identical or similar elements. Furthermore, the various elements are not drawn to scale in order to enhance the clarity of the figures. Moreover, the different embodiments and variants are not mutually exclusive and may be combined. Unless otherwise indicated, the terms "approximately," "about," and "in the order of" mean within 10%, and preferably within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are inclusive, unless otherwise stated.

[0033] The invention relates to an optoelectronic device, and its manufacturing process, comprising at least one diode, and preferably a diode matrix, at least one planar optical component, covering at least the diode, adapted to shape light radiation emitted or received by the diode, this optical component having a lateral variation Axyn of optical index n obtained by electrochemical porosification.

[0034] According to the invention, the optical component is produced by electrochemical porosification of a transparent semiconductor portion, where the lateral variation Axyp of the porosity ratio p(x,y) results in a desired lateral variation Axyn of the optical index n. The semiconductor portion thus porosified therefore forms the optical component.

[0035] The porosity ratio p(x,y) (or porosity ratio) is defined here as the ratio between the volume of the pores (void volume) and the total volume of the optical component. It has a local value measured within the optical component, which can vary between a minimum value (0 when it contains no pores: absence of porosity) and a maximum value (1 when it is fully porous).

[0036] The porosity ratio p(x,y) varies laterally discretely (in steps) or continuously. Axyp denotes the lateral variation in the XY plane, that is, in a plane parallel to the front face of the diode(s). It may have an extremum located on the central axis of the optical component (which may be coaxial with the optical axis of the underlying diode) and an extremum located at the lateral edge. It may also displaying different values ​​in adjacent areas, like a QR code. These different examples are described later with reference to the figures.

[0037] Preferably, the porosity ratio p(x,y) is constant with respect to the thickness of the optical component. In other words, the porosity ratio p(x,y) preferably exhibits only a lateral variation and not also a vertical one, so that it can be denoted p(x,y). However, alternatively, a vertical variation Azp of the porosity ratio p(x,y,z) can also be obtained.

[0038] The optical index n(x,y) of the optical component is then an 'effective' or 'average' optical index whose local value depends on that of the porosity rate p(x,y). It is defined as the ratio of the optical index n0 of the integral or dense material of the optical component and the porosity rate p(x,y): n(x,y) = n0 xp(x,y).

[0039] Figures IA and IB are schematic and partial views, in cross-section ([Fig.1A]) and in top view ([Fig.1B]), of an optoelectronic device 1 according to a first embodiment.

[0040] Generally, the diodes 10 can be emitting diodes, so that the optoelectronic device 1 can be, for example, a display screen or a lighting system. They can thus be organic (OLED) or inorganic (LED) light-emitting diodes. Alternatively, the diodes can be detecting diodes, so that the optoelectronic device can be a matrix photodetector. These can be organic or inorganic photodetectors. In this example, the diodes 10 are light-emitting diodes.

[0041] Here and for the remainder of the description, a three-dimensional orthogonal XYZ direct frame is defined, where the X and Y axes form a principal plane in which the diode matrix 10 extends, and where the Z axis is oriented along the thickness of the diode matrix 10 in the direction of the optical components 50. The terms 'lower' and 'upper' are defined with respect to an increasing positioning along the +Z direction.

[0042] The optoelectronic device 1 comprises a control substrate 2, a matrix of light-emitting diodes 10, and optical components 50 which cover the diodes 10, each optical component 50 being here planar and with lateral variation Axyn of optical index n obtained by electrochemical porosification.

[0043] The control substrate 2 comprises a CMOS-type control circuit (not shown), and has electrical connection pads (not shown) that are flush with the upper face and come into contact with the lower conductive portions of the diodes 10. These lower conductive portions are distinct from one another, in the sense that each diode 10 is electrically distinct from the adjacent diode, and can be biased independently of its neighbors. This The configuration is described in detail in document WO 2017 / 194845 Al. Other configurations are possible.

[0044] The diodes 10 are inorganic light-emitting diodes. They can be fabricated conventionally, for example by epitaxy of semiconductor layers from a growth substrate, then transferred to the control substrate. Each diode 10 can be formed from a stack of: a lower semiconductor portion 11 (located on the control substrate side 2) doped with a first type of conductivity, for example, type P; an active region 12 where the light emitted by the light-emitting diode is produced; and an upper semiconductor portion 13 doped with a second type of conductivity, for example, type N. The diodes 10 can be fabricated from the same semiconductor compound, for example, based on a III-V compound, such as InP, and preferably based on an III-LN compound such as GaN, InGaN, or AlGaN.

[0045] In this example, the diodes 10 are structurally identical, so that the emitted light radiation is identical from one diode to another in terms of wavelength. Here, the diodes 10 can be adapted to emit light radiation in the blue, i.e., whose emission spectrum has a peak intensity at a wavelength between approximately 440 nm and 490 nm. Alternatively (as described with reference to [Fig. 0A] and following), the diodes can emit at different wavelengths. The diodes are separated here in pairs in the XY plane, and the interdiode space can be filled by an electrically insulating filler material 21 in contact with the lateral edge of portions 11, 12, and 13.

[0046] The diodes 10 are electrically biased by the control substrate 2. Thus, the P-type doped portions 11 are in electrical contact with underlying conductive pads (not shown). Furthermore, the N-type doped portions 13 can be biased in different ways. [Fig. 1A] illustrates an example where they are biased via a transparent conductive thin film 30, which extends above the diodes 10 and below the optical components 50, here made from an N-type doped IILV semiconductor compound. This biasing conductive thin film 30 can be connected to the control substrate 2 by one or more conductive vias (not shown) located between the diodes 10, or located on the lateral edge of the diode array 10. [Fig.[2] illustrates another example where the N-type doped portions 13 are laterally biased by a conductive material 22, located in the interdiode space, which comes into contact with the lateral edge of the N-type doped portions 13. A thin insulating layer 23 is located between this conductive material 22 and the lateral edge of the active areas 12 and the P-type doped portions 11. Other examples of biasing are possible.

[0047] The optoelectronic device comprises laterally varying planar optical components with refractive index n(x,y), each of which covers at least one underlying diode. In this example, each diode is covered by an optical component.

[0048] The optical component 50 here has length and width dimensions in the XY plane substantially equal to those of the underlying diode 10. Alternatively, the dimensions of the optical component 50 may be larger or smaller than those of the diode 10.

[0049] The optical component 50 is planar here insofar as it has a planar upper face, opposite the front face of the diodes 10. It is preferably parallel to the front face, and preferably, the upper faces of the optical components 50 are coplanar. They therefore all have the same thickness, thus facilitating the integration of additional elements.

[0050] The optical component 50 is formed of at least one semiconductor material transparent in the emission or detection spectral band of the diodes 10. It is a crystalline material that has been porosified by electrochemical anodizing. It may be a nitride compound of the type (Al,In,Ga)N, i.e., an AlxInyGazN component, where x+y+z=l with 0 <x<l, 0<y<l et 0<z<l. De préférence, x est inférieur ou égal à 0,75, voire inférieur ou égal à 0,5. Il peut également s’agir d’InP. Notons que la couche mince conductrice 30 de polarisation peut être formée en un matériau similaire, par exemple en un composé de type AlxInyGazN, dopé de type N. Il présente un niveau de dopage ND suffisant pour permettre la polarisation électrique des portions 13 dopées de type N, mais insuffisant pour subir une porosification électrochimique. A cet effet, un dopage par des atomes de germanium est préféré.The concentration of germanium atoms may be less than or equal to 1E22 at / cm3, preferably less than or equal to 1E21 at / cm3. For doping with silicon atoms, the concentration of silicon atoms may be less than or equal to 1.5E19 at / cm3. The conductive thin film 30 is more conductive the higher the level of ND doping.

[0051] Each optical component 50 exhibits a lateral variation Axyn of optical index n. As defined previously, the optical index n is an 'effective' optical index defined by the relation n = n0 xp(x,y). The optical index n0 has a constant value in the spectral emission or detection range of the diodes. In the case of GaN, the optical index n0 is approximately 2.4.

[0052] In the example of [Fig. 1A], the lateral variation Axyp of the porosity ratio p(x,y) was obtained by localized electrochemical porosification of transparent semiconductor portions 40 (see [Fig. 3F]), here parts of the same semiconductor layer continued 31. Each semiconductor portion 40 exhibited a lateral variation AxyND of the ND doping level, which results in a lateral variation Axyp of the porosity ratio p, and therefore not the desired lateral variation Axyn of the optical index n. The manufacturing process steps are detailed later with reference to [Fig.3A] and following.

[0053] The porosity ratio p(x,y) varies discretely in the XY plane and exhibits concentric zones 51.1, 51.2, 51.3, 51.4, centered on a central optical axis of the diode 10 and the optical component 50, within which it has a substantially constant value. These zones extend over substantially the entire thickness of the optical component 50. In this example, four concentric zones are shown, but the optical component 50 may have a greater or lesser number of zones, which may be arranged in different ways and have different dimensions in the XY plane. Here, these concentric zones are formed from a central zone 51.1, which here has a minimum porosity rate p and therefore a maximum optical index n, then from a succession of annular zones 51.2, 51.3, 51.4 which extend from the central zone 51.1 up to the lateral edge of the optical component 50, where the porosity ratio p increases from one area to another and therefore where the optical index n decreases accordingly.

[0054] The optical components 50 are here parts of the same semiconductor layer 31, which extends continuously over the diode array 10, being in contact with the thin conductive biasing layer 30. The parts of the continuous semiconductor layer 31, located between the optical components 50, are here non-porous, but could be.

[0055] Thus, by using optical components 50 whose lateral variation Axyp of the porosity ratio p, and therefore the lateral variation Axyn of the refractive index n, is obtained by electrochemical porosification, the constraints of the microlens manufacturing processes described above with reference to the prior art are avoided, particularly the limitations related to the finishing and shape transfer steps in the transparent material. Furthermore, such optical components 50 offer numerous manufacturing degrees of freedom, allowing their optical beam-shaping properties to be adjusted according to the intended applications. These degrees of freedom include, in particular, the choice of the lateral variation AxyND of the doping level ND in the semiconductor portions 40 to be porosified and / or the choice of operating conditions during the electrochemical porosification step, notably the value or modulation of the anodizing voltage Ea.Furthermore, the optical components 50 are preferably planar, thus facilitating integration. additional elements, optical or otherwise, after the optical components have been made.

[0056] The optical components 50 can form converging or diverging microlenses, with an optical axis that may or may not be coaxial with the optical axis of the diode. As described later with reference to Figures 7A, 7B and 8, the optical components 50 can form metasurfaces (of the “QR-code” type).

[0057] The optical components 50 can be intended to transmit the light beam in free space. They can also be coupled to an optical guide, for example an optical fiber, particularly in the context of a tele- or data-communication application.

[0058] It should also be noted that the porosity of the optical components 50 allows the incorporation of a material (colored resin) or color conversion semiconductor elements, such as quantum dots.

[0059] Figure 2 is a schematic and partial cross-sectional view of an optoelectronic device 1 according to a second embodiment. The optoelectronic device 1 differs from that of Figure 1A essentially in that the optical components 50 exhibit a continuous, rather than discrete, lateral variation Axyp of the porosity ratio p and therefore of the optical index n.

[0060] The optical components 50 are here distinct from one another in the XY plane and are not part of a single continuous semiconductor layer made of the same material. Each optical component 50 therefore has, in the XY plane, a free (uncovered) lateral edge through which the electrochemical porosification was carried out.

[0061] The porosity ratio p varies continuously in the XY plane, and therefore so does the optical index n. In this example, the porosity ratio p has a maximum value at the lateral edge of the optical components 50 and a minimum value at the center. The lateral gradient differs from one optical component to another. Note that other lateral variations are entirely possible.

[0062] In order to obtain a predominantly lateral rather than vertical variation of the porosity ratio p and therefore of the optical index n, each optical component 50 has a thin protective layer 33, which extends over the upper surface. It can be made of silicon oxide. Preferably, it is made of a material similar to that of the optical components 50, i.e., here in AlxInyGazN or InP, but is undoped or only slightly doped so that it has not been porosified during the electrochemical porosification step.

[0063] Here, the N-type doped portions 13 are laterally polarized by a conductive material 22, for example a metallic material such as copper, located in the interdiode space. As previously stated, a lateral thin layer 23, made of an electrically insulating material, extends over the lateral edge of the active area 12 and the P-doped portion 11, to isolate them from the conductive material 22. In order to prevent damage to this conductive material 22 during the electrochemical porosification step, a thin protective layer 32 extends between the optical components 50 and covers the conductive material 22 in the interdiode space. This thin protective layer 32 prevents the liquid electrolyte from coming into contact with the conductive material 22.

[0064] Figures 3A to 3F illustrate different steps in a manufacturing process for an optoelectronic device similar to that of [Fig. 1A]. Here, the lateral variation Axyp of the porosity ratio p is obtained by first performing a lateral variation AxyND of the ND doping level in the semiconductor portions 40. Furthermore, the pixelation step of the diodes 10 is carried out before the transfer step onto the control substrate 2.

[0065] With reference to [Fig. 3A], a diode array 10 is fabricated from a growth substrate 60. The growth substrate 60 can be a thick substrate (wafer), for example made of silicon, sapphire, or other material, covered, for example, with a nucleation layer (not shown). The continuous semiconductor layer 31 is then fabricated by epitaxy from the nucleation layer. In this example, it can be made of undoped or lightly doped N-type GaN, for example, unintentionally undoped. This continuous semiconductor layer 31 is intended to form the semiconductor portions 40 and thus subsequently the optical components 50.

[0066] The continuous semiconductor layer 31 is covered by a thin conductive layer 30, made here of an N-type doped crystalline semiconductor material, for example GaN, by epitaxy from the continuous semiconductor layer 31. The thin conductive layer 30 is intended to provide electrical biasing to the N-type doped portions 13 of the diodes 10. However, its doping level is chosen so as not to undergo significant porosification during the subsequent electrochemical anodizing step.

[0067] The diodes 10 are made by epitaxy of an N-type doped semiconductor layer, then of an active layer which may include quantum wells, and of a P-type doped semiconductor layer. This stack is then pixelated to form the matrix of diodes 10. A filling material 21, here electrically insulating, fills the interdiode spacing.

[0068] With reference to [Fig. 3B], the stack is transferred to a control substrate 2, and then the growth substrate is removed, so as to free the upper face of the continuous semiconductor layer 31. The control substrate 2 has conductive pads (not shown) located below and in electrical contact with the P-type doped portions 11, and one or more conductive pads (not shown) in contact electrical with the conductive thin film 30 for the polarization of the N-type doped portions 13.

[0069] With reference to [Fig. 3C], [Fig. 3D] and [Fig. 3E], a lateral variation AxyND of the doping level ND(x,y) is achieved in parts of the continuous semiconductor layer 31, thereby forming doped semiconductor portions 40 intended to form, once porosified, the optical components 50. Here, this spatial distribution of the doping level ND(x,y) is achieved by ion implantation. However, in the case where the continuous semiconductor layer 31 had been N-type doped during growth, this spatial distribution of the doping level ND(x,y) can be achieved by localized dedoping, as indicated in particular in document WO 2024 / 134081 A1.

[0070] First, a desired phase law is determined. <p(x,y) du composant optique 50. Cette loi de phase dépend du type de composant optique souhaité et de ses propriétés de mise en forme du faisceau lumineux émis par la diode 10 sous-jacente. On en déduit une variation latérale Axync d’indice optique cible nc(x,y) à partir de la relation : nc(x,y) = X / (2irxh) x <p(x,y), où X est une longueur d’onde centrale du spectre d’émission de la diode et où h est l’épaisseur de la portion semiconductrice 40 à porosifier. Sur la [Fig.3C], cette variation cible nc(x,y) est représentée en trait linéaire continu (sans paliers).

[0071] A discrete lateral variation Axyn of the final optical index n(x,y), and therefore of the porosity rate p(x,y), is then determined, which adjusts (curve fitting) to the lateral variation of the target optical index nc(x,y). This variation Axyn is discrete here and is represented in [Fig. 3C] as a stepped dashed line. The corresponding lateral variation Axyp of the porosity rate p(x,y) is then deduced: p(x,y) = n(x,y) / n0. Note, as illustrated by the graph on the right of [Fig.3C], that, if the high values ​​of the target optical index nc are greater than the index of the integral material, here GaN (n0=2.4), it is possible to adapt the lateral variation Axync of the target optical index nc(x,y) by a modulation by 2ir of the phase law q>.

[0072] Figure 3D illustrates an example of the relationship between the doping level ND of a doped crystalline layer and the applied anodizing voltage Ea, highlighting the domain of electrochemical porosification. Such an example is described in particular in EP 3 840 016 A1. Below a minimum doping level ND > min and at low anodizing voltage Ea, the regime is that of channel formation and not that of porosification. This is referred to as pre-breakdown. Conversely, above a maximum doping level ND > max and at high anodizing voltage Ea, the regime is that of electropolishing etching of the material. Between these two regimes lies the regime of electrochemical porosification. Thus, this type of nomogram shows the relationship between the required ND doping level, for a given anodizing voltage Ea, and the porosity level p. Indeed, at a constant doping level, increasing the anodizing voltage Ea leads to an increase in the porosity level p. Similarly, at a constant anodizing voltage Ea, increasing the doping level leads to an increase in the porosity level p. Knowing the spatial variation Axyp that has been determined, we can deduce the corresponding spatial variation AxyND of the doping level for a given anodizing voltage Ea.

[0073] Finally, as illustrated in [Fig. 3E], the spatial distribution AxyND determined in each semiconductor portion 40 is achieved, here by ion implantation. In this example, there are several concentric zones 41.1, 41.2..., centered on the optical axis of each semiconductor portion 40 (coaxial here with that of the underlying diode 10), where the ND doping level is substantially homogeneous in the XY plane and along the Z direction. The semiconductor portions 40 are distinct in pairs, and are separated here by an unintentionally doped region.

[0074] With reference to [Fig. 3F], the optical components 50 are fabricated by electrochemical porosification of the doped areas 41 of the semiconductor portions 40. To do this, the free face of the continuous semiconductor layer 31 (and therefore of the semiconductor portions 40) is brought into contact with a liquid electrolyte. The liquid electrolyte can be acidic or basic, and can be oxalic acid. It can also be HCl, KOH, HF, HNO3, NaNO3, H2SO4, or a mixture thereof. A mixture of oxalic acid and NaNO3 can also be used. The structure is electrically connected to a power source, here for example via the conductive thin film 30, which polarizes the semiconductor portions 41 to be porosified. The conductive thin film 30 then forms a working electrode, here connected to the anode of the power source.A counter electrode (here a platinum grid) is immersed in the electrolyte and connected to the cathode of the electrical generator. The electrical generator applies an anodizing voltage Ea. Thus, the doped areas 41 of the different semiconductor portions 40 are porosified, each according to the level of doping, resulting in a porosity ratio p specific to each doped area. The porosified semiconductor portions 40 therefore exhibit the desired lateral variation Axyp of the porosity ratio p(x,y), and thus the lateral variation of the optical index n(x,y), thereby forming the optical components 50.

[0075] Figures 4A to 4C illustrate different stages of a variant of the manufacturing process of Figures 3A-3F, which differs essentially in that the pixelation stage of the diodes 10 is carried out after the localized doping stage of the semiconductor portions 40 to be porosified.

[0076] [Fig. 4A] is similar to that of [Fig. 3E], except that the diodes 10 have not yet been pixelated. Thus, a stack of semiconductor layers has been transferred onto the control substrate 2. This stack comprises, starting from the control substrate 2, a P-type doped semiconductor layer 61, an active layer 62, an N-type doped semiconductor layer 63, and finally the continuous semiconductor layer 31. This last layer includes the locally doped semiconductor portions 40, intended to be porosified to form the optical components 50.

[0077] With reference to [Fig. 4B], the locally doped semiconductor portions 40 and the diodes 10 are pixelated. This is achieved by localized etching of the continuous semiconductor layer 31 and the semiconductor layers 63, 62, 61, leading to the growth substrate. The locally doped semiconductor portions 40 and the diodes 10 are thus rendered distinct from one another.

[0078] The "N contacts" are then made by depositing a lateral thin layer 22, covering the lateral edges of the P-type doped portions 11 and the active portions 12, and then by depositing a metallic material 22 in contact with the lateral edge of the N-type doped portions 13. A protective thin layer 32, inert during the electrochemical porosification step, can be deposited on the metallic material 22, between the locally doped semiconductor portions 40, so as to protect it from any degradation during the electrochemical porosification.

[0079] With reference to [Fig. 4C], the optical components 50 are then fabricated by electrochemical porosification of the locally doped semiconductor portions 40. Their electrical polarization is achieved here via the N-type doped portions 13, polarized through the "N contact" and the control substrate 2. It could also be achieved via the semiconductor junction, as in patent application FR2213826 filed on 19 / 12 / 2022. The porosified semiconductor portions 40 thus exhibit the desired lateral variation Axyp of the porosity ratio p(x,y), and therefore the lateral variation Axyn of the refractive index n(x,y). They thus form the optical components 50.

[0080] Figures 5A to 5C illustrate different steps of a manufacturing process for an optoelectronic device 1 similar to that of [Fig. 2]. This process differs from that of Figs. 3A-3F and 4A-4C essentially in that the lateral variation Axyp of the porosity ratio p(x,y) is obtained by modulating the anodizing voltage Ea during the electrochemical porosification step.

[0081] With reference to [Fig. 5A], a structure similar to that of [Fig. 3A] is produced. It comprises a growth substrate 60, a protective semiconductor thin layer 64, the continuous semiconductor layer 31, and a conductive thin layer. 30, and the diode array 10. In this example, the biasing of the N-type doped portions 13 is provided by the conductive thin film 30. The diodes 10 are separated in pairs by an insulating separating material 21. Alternatively, however, "n-type contacts" similar to those in [Fig. 2] can be implemented. The continuous semiconductor layer 31 is N-type doped, with a doping level that allows for its subsequent porosification. The doping level is substantially homogeneous.

[0082] With reference to [Fig. 5B], the diode matrix 10 is transferred onto the control substrate 2, and the growth substrate 60 is removed, so as to expose the upper surface of the protective thin layer 64. The semiconductor portions 40 are then pixelated by localized etching of layers 64 and 31. The semiconductor portions 40 thus have a lateral border with a free surface. Finally, their upper surface is covered by a protective thin layer 33. A thin layer 32 can be deposited on the conductive thin layer 30, between the semiconductor portions 40, so as to protect it during the electrochemical porosification step.

[0083] With reference to [Fig.5C], the optical components 50 are then produced by electrochemical porosification of the semiconducting portions 40. As the Nd doping level is substantially homogeneous, the lateral variation Axyp of the porosity ratio p is obtained by modulating the anodizing voltage Ea, according to the approach described in patent application FR2406898, filed on 27 / 06 / 2024.

[0084] To achieve this, the free surface of the lateral edge of the semiconductor portions 40 is brought into contact with the liquid electrolyte, and the structure is connected to the electrical generator, here for example via the conductive thin film 30. As before, the conductive thin film 30 then forms a working electrode, here connected to the anode of the electrical generator. A counter electrode (here a platinum wire or grid) is immersed in the electrolyte and connected to the cathode of the electrical generator. The electrical generator applies an anodizing voltage Ea, the value of which is modulated over time. In other words, several values ​​of the voltage Ep are applied so as to induce porosification of the semiconductor portions 40 from the lateral edge, and to obtain the desired lateral variation Axyp of the porosity ratio p.

[0085] By way of example, a first anodizing voltage Ea is applied for a first duration, then a second anodizing voltage Ea for a second duration. Different values ​​of the anodizing voltage Ea can thus be applied for different durations. Indeed, implementing electrochemical porosification in several successive sequences, with different values ​​of anodizing voltage Ea, makes it possible to obtain the desired lateral variation Axyp of the porosity ratio. p of the semiconductor portions 40 in the XY plane. It is therefore not necessary to have previously established a spatial distribution of the doping level, as in the examples of Figures 3A-3F and 4A-4C. For this, a nomogram similar to that of [Fig. 3D] is used where, for an initial doping level, the modification of the value of the anodizing voltage Ea results in a different porosity rate.

[0086] It is possible to achieve any kind of spatial variation Axyp of the porosity ratio p. It is thus possible to obtain a core of the optical components 50 that is more porous than the lateral edge, or vice versa, with a monotonic variation (constant direction of variation) or not. Note that the presence of the thin protective sections 33 prevents the porosification of the semiconductor sections 40 from also occurring from the upper surface. This results in an essentially lateral variation of the porosity ratio, with a virtually zero vertical variation. However, it is possible to have a vertical variation of the porosity ratio: for this, the thin protective layer 64 is omitted (and therefore no thin protective sections 33), so as to also leave the upper surface of the semiconductor sections s free.

[0087] Note that, here, the semiconductor portions 40 are biased during the electrochemical porosification step by the same conductive thin film 30. The optical components 50 then exhibit the same lateral variation Axyp of the porosity ratio p. Alternatively, in the case where the diodes 10 are biased by "N-contacts" similar to those in [Fig. 2], it is possible to bias the semiconductor portions 40 independently during the electrochemical porosification step, either through the "N-contacts" or through the semiconductor junction. The optical components 50 can then exhibit different lateral variations Axyp of the porosity ratio p from one optical component to another.

[0088] Figures 6A to 6D illustrate different stages of another manufacturing process for an optoelectronic device similar to that of [Fig. 2]. In this example, the semiconductor portions 40, before the electrochemical porosification stage, exhibit a mesa-like growth shape of the diodes 10.

[0089] With reference to [Fig. 6A], a growth substrate 60 is formed and covered by semiconducting portions 40 intended to be porosified. Thin protective portions 33 are formed between the growth substrate 60 and the semiconducting portions 40. These portions are distinct from each other in the XY plane. They exhibit N-type doping, with a homogeneous doping level within each semiconducting portion.

[0090] With reference to [Fig. 6B], the diodes 10 are then fabricated from the free upper face of the semiconductor portions 40. A thin mask layer of Nucleation (not shown) may be present and may cover the lateral edge of the semiconductor portions 40 and the free upper face of the growth substrate 60.

[0091] Diodes can be made sequentially, one after the other (in groups of diodes), in cases where they have different optical emission or reception properties. For this purpose, they may, for example, have different indium concentrations in the quantum wells, thus emitting, for example, some in the green, others in the red, and still others in the blue.

[0092] Finally, the "N-type contacts" are made. For this purpose, the lateral edge of the N-type doped portions 13, and preferably also that of the semiconductor portions 40, is made free. A metallic material 22 then fills the interdiode space and comes into contact with the lateral edge of the N-type doped portions 13. A thin insulating layer 23 covers the lateral edge of the active portions 12 and the P-type doped portions 11 to prevent electrical contact with the metallic material 22.

[0093] With reference to [Fig. 6C], the diode array 10 is transferred onto the control substrate 2. The growth substrate 60 is then removed. This exposes the upper surface of the thin protective sections 33. The lateral edge of the semiconducting sections 40 is exposed by localized etching of the metallic material 22. This material is retained between the diodes to ensure the biasing of the N-type doped sections 13. Finally, preferably, a thin protective layer 32 is deposited on the metallic material 22, between the semiconducting sections 40, so as to protect the latter (if necessary) during the electrochemical porosification step.

[0094] With reference to [Fig. 6D], the optical components 50 are then produced by electrochemical porosification of the semiconductor portions 40. Since these portions have a homogeneous ND doping level and a free side edge, the porosification is carried out with modulation of the anodization voltage Ea. This step is similar or identical to that described in relation to [Fig. 5C].

[0095] Specific embodiments have just been described. Various variants and modifications will be apparent to those skilled in the art.

[0096] Accordingly, Figures 7A and 7B are schematic and partial views, in cross-section ([Fig. 7A]) and top view ([Fig. 7B]), of an optoelectronic device 1 according to one embodiment. This example shows that any type of lateral variation can be considered, in particular metasurface-type optical components 50 where areas of different porosity (and therefore different refractive indices n) are adjacent in the XY plane.

[0097] Furthermore, [Fig. 8] is a schematic and partial cross-sectional view of an optoelectronic device 1 according to another embodiment. Here, the optoelectronic device comprises several optical components 50 stacked one on top of the other, which may have different thicknesses. The optical components 50 Stacked materials can exhibit different lateral variations in porosity rate and therefore in optical index.

[0098] Generally, optical components may be lined with a transparent or light-reflecting filling material. They may have dimensions substantially equal to, larger than, or smaller than, in the XY plane, those of diodes. Optical components may form converging, diverging, or specially shaped lenses for the transmitted light.

Claims

Demands

1. A method for manufacturing an optoelectronic device (1) comprising: at least one photoemitting or photoreceiving diode (10) having a front face for transmitting or receiving light radiation; at least one optical component (50) for shaping the light radiation, located on the front face and covering the diode, and having a lateral variation of predefined refractive index; • characterized in that it comprises the following steps: • providing the diode (10); • determining a lateral variation (Axyp) of a porosity ratio (p), from a lateral variation (Axync) of predefined target refractive index (nc), of a semiconductor portion (40) made of a crystalline material transparent to light radiation and located on the front face and covering the diode (10); • producing the semiconductor portion (40) to be porosified;• perform an electrochemical porosification of the semiconductor portion (40), so that it exhibits the determined lateral variation (Axyp) of the porosity ratio (p), the semiconductor portion thus porosified then forming the optical component (50). #;

2. A manufacturing method according to claim 1, wherein the semiconductor portion (40) to be porosified has a flat upper face opposite to the front face of the diode (10).

3. A manufacturing method according to claim 1 or 2, wherein: • during the fabrication step of the semiconductor portion (40) to be porosified, it comprises several adjacent doped zones (41.1, 41.2...), exhibiting a different level of doping from one doped zone to another; • during the electrochemical porosification step, the doped zones (41.1, 41.2) are porosified and exhibit a different porosity rate from one doped zone to another.

4. A manufacturing method according to claim 3, wherein, during the step of making the semiconducting portion (40) to be porosified, each doped zone (41.1, 41.2...) has a homogeneous level of doping laterally and vertically.

5. A manufacturing method according to claim 3 or 4, wherein: • the optoelectronic device comprises a diode matrix (10) and several optical components (40) formed from semiconductor portions (40) to be porosified, • during the step of producing the semiconductor portions (40) to be porosified, these are parts of the same continuous semiconductor layer (31) extending over the diode matrix (10).

6. A manufacturing method according to any one of claims 3 to 5, wherein, during the electrochemical porosification step, an electrical anodizing signal has a constant value over time until the lateral variation (Axyp) of the porosity ratio (p) is obtained.

7. A manufacturing method according to claim 1 or 2, wherein during the electrochemical porosification step, an intensity modulation of an electrical anodizing signal (Ea) is carried out, leading to the obtaining of the lateral variation (Axyp) of the porosity ratio (p).

8. A manufacturing method according to claim 7, wherein, during the step of producing the semiconducting portion (40) to be porosified, the latter has a laterally homogeneous level of doping.

9. A manufacturing method according to claim 7 or 8, wherein, during the step of making the semiconducting portion (40) to be porosified, the latter has a free lateral border.

10. A manufacturing method according to any one of claims 7 to 9, wherein, during the step of making the portion semiconductor (40) to be porosified, this has an upper face covered by a thin portion of protection (33) made of a non-porous material during the electrochemical porosification step.

11. A manufacturing method according to any one of claims 1 to 10, wherein the semiconducting portion (40) to be porosified is made of a material based on InP or (Al,In,Ga)N.

12. A manufacturing method according to any one of claims 1 to 11, comprising the following steps: • producing the mesa-shaped semiconductor portion (40) to be porosified from a growth substrate (60); • producing the diode (10) from the semiconductor portion (40) to be porosified; • transferring the diode (10) and the semiconductor portion (40) to be porosified onto a control substrate (2); • performing the electrochemical porosification of the semiconductor portion (40).

13. Optoelectronic device (1), comprising: • at least one photoemitting or photoreceiving diode (10) having a front face for transmitting or receiving light radiation; • at least one optical component (50) for shaping the light radiation, located on the front face and covering the diode, and having a lateral variation of predefined optical index; • characterized in that the optical component (50) is made of a transparent crystalline material, and has a lateral variation (Axyp) of a porosity ratio (p) of the transparent crystalline material.