Optoelectronic device including a diode array

Abstract

The invention relates to an optoelectronic device comprising a matrix (200) of axial diodes (100), each diode forming a resonant cavity in which a stationary electromagnetic standing wave is formed, each light-emitting diode comprising an active region (104) substantially at the level of an extremum (110) of the electromagnetic wave, the matrix forming a photonic crystal configured to maximize the intensity of the electromagnetic radiation provided by the diode array.

Description

[0001] This patent application claims the priority benefit of French patent application FR 18 / 55450, which is incorporated herein by reference. Technical Field

[0002] The present disclosure relates to an optoelectronic device, in particular to a display screen or image projection device including a light emitting diode made of a semiconductor material, and a manufacturing method thereof. Background Art

[0003] It is known to project an image onto the input of a waveguide grating of a transparent screen, such as glasses, a car windshield or a glass sheet, which is then projected onto the user's eye. This is the case, for example, with smart glasses or augmented reality glasses. To this end, an optoelectronic device projects the image onto a screen, where it is then guided to a system that makes it visible to the user. The optoelectronic device may comprise, for example, a light-emitting diode made of semiconductor material. The display is usually configured to properly guide only the radiation emitted by the light-emitting diode, which radiation propagates substantially in a given direction. The directionality of the radiation provided by the light-emitting diode is therefore an important characteristic of such an optoelectronic device. Summary of the invention

[0004] Therefore, an embodiment provides an optoelectronic device comprising an array of axial diodes, each diode forming a resonant cavity, an electromagnetic standing wave being formed in the resonant cavity, each light emitting diode comprising an active region substantially located at an extreme level of the electromagnetic wave, the array forming a photonic crystal, and the photonic crystal being configured to maximize the intensity of the electromagnetic radiation provided by the diode array.

[0005] According to an embodiment, the array comprises a support on which the diodes rest, each diode comprising a first semiconductor region resting on the support, the active region in contact with the first semiconductor region, and a stack of second semiconductor regions in contact with the active region.

[0006] According to an embodiment, the device comprises a reflective layer between the support and the first region of the diode.

[0007] According to an embodiment, the reflective layer is made of metal.

[0008] According to an embodiment, the second region of the diode is covered by a conductive layer, which is at least partially transparent for the radiation emitted by the diode.

[0009] According to an embodiment, the height of at least one of the diodes is substantially proportional to kλ / 2n, where λ is the wavelength of the radiation emitted by the diode, k is a positive integer and n is substantially equal to the effective refractive index of the diode in the considered optical mode.

[0010] According to an embodiment, the diodes are separated by an electrically insulating material.

[0011] According to an embodiment, the array comprises at least a first and a second diode assembly, the diodes of the first assembly having a same first height and the diodes of the second assembly having a same second height, the first and second heights being different.

[0012] According to an embodiment, for at least one of the diodes, the first region of the diode includes at least two portions separated by an etch stop layer.

[0013] According to an embodiment, each etch stop layer has a thickness in the range of 1 to 200 nm.

[0014] According to an embodiment, a quotient of a pitch of the array and a wavelength of the provided electromagnetic radiation is in the range of about 0.4 to about 0.92.

[0015] According to an embodiment, the diode is a light emitting diode or a photodiode.

[0016] Another embodiment provides a method of manufacturing an optoelectronic device, the optoelectronic device comprising an array of axial diodes, each diode forming a resonant cavity, an electromagnetic standing wave formed in the resonant cavity, an active area of ​​each diode being substantially located at an extreme level of the electromagnetic wave, and a spacing of the array being configured to maximize the intensity provided by the diode array.

[0017] According to an embodiment, the forming of the diodes of the array comprises:

[0018] forming first regions on a substrate, the first regions being separated from each other by a pitch of the array;

[0019] forming an active region on each first region; and

[0020] A second region is formed on each active region.

[0021] According to an embodiment, the method comprises a first step of etching all of the second regions such that they have the same height.

[0022] According to an embodiment, the method comprises a second step of etching all of the first regions so that they have a height allowing the active region to be located at the extreme level of the electromagnetic wave.

[0023] According to an embodiment, the method comprises performing the second etching step before the forming of the active area.

[0024] According to an embodiment, the second etching step is preceded by a step of removing the substrate, the second etching step being performed from the end of the diode closest to the substrate.

[0025] According to an embodiment, the method includes forming at least one layer in the first region of at least one of the diodes that can serve as a stop layer for the second etching step.

[0026] According to an embodiment, the diode is a light emitting diode or a photodiode. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The foregoing and other features and advantages are discussed in detail in the following non-limiting description of specific embodiments in conjunction with the accompanying drawings, in which:

[0028] Figure 1 is a simplified perspective view of a portion of an embodiment of an axial light emitting diode;

[0029] Figure 2 is a simplified perspective view of a portion of an embodiment of a light emitting diode array;

[0030] Figure 3A and Figure 3B Schematically shows Figure 2 Examples of layouts of arrays of light emitting diodes;

[0031] 4A to 4F It is shown in the manufacturing Figure 2 A local simplified cross-sectional view of a structure obtained in the steps of another embodiment of the method of array;

[0032] FIG. 5A to FIG. 5D It is shown in the manufacturing Figure 2 A local simplified cross-sectional view of the structure obtained in other steps of an embodiment of the array method;

[0033] Figure 6 It is shown in the manufacturing Figure 2 A local simplified cross-sectional view of a structure obtained in one step of an embodiment of the method of array;

[0034] Fig. 7A and Figure 7B It is shown in the manufacturing Figure 2 A local simplified cross-sectional view of a structure obtained in the steps of another embodiment of the method of array;

[0035] Figure 8 is shown by the array according to certain characteristics such as Figure 2A plot of the intensity of the array emission in;

[0036] 9A to 9E is a graph showing simulation results of an embodiment of a light emitting diode array; and

[0037] FIG. 10A to FIG. 10E is a graph showing simulation results of other embodiments of the light emitting diode array. DETAILED DESCRIPTION

[0038] In the various drawings, the same elements have been denoted by the same reference numerals, and in addition, the various drawings are not drawn to scale. For the sake of clarity, only those steps and elements useful for understanding the described embodiments are shown and described in detail. In particular, the optoelectronic device considered may optionally include other components that will not be described in detail.

[0039] In the following description, when referring to terms defining absolute positions such as the terms "front", "back", "top", "bottom", "left", "right", etc., or terms defining relative positions such as the terms "above", "below", "upper", "lower", etc., or when referring to terms defining directions such as the terms "horizontal", "vertical", etc., it refers to the orientation of the relevant elements in the figures. The terms "approximately", "approximately", "substantially" and "about" are used herein to indicate a tolerance of plus or minus 10%, preferably plus or minus 5%, of the value under consideration.

[0040] When referring to a "transparent" or "reflective" element, elements are considered that are transparent or reflective to the wavelength at which the device operates (eg, the wavelength of electromagnetic radiation emitted by the light emitting diode in question).

[0041] Furthermore, the term "active region" of a light emitting diode denotes the region of the light emitting diode from which the majority of the electromagnetic radiation provided by the light emitting diode is emitted.

[0042] The term "axial light-emitting diode" refers to a three-dimensional structure having an elongated shape (e.g., cylindrical) along the main direction, which has at least two dimensions, called minor dimensions, ranging from 5 nm to 2.5 μm, preferably from 50 nm3 to 2.5 μm. The third dimension, called the major dimension, is greater than or equal to 1 times the largest minor dimension, preferably greater than or equal to 5 times, and more preferably greater than or equal to 10 times. In some embodiments, the minor dimension may be less than or equal to about 1 μm, preferably in the range of 100 nm to 1 μm, and more preferably in the range of 100 nm to 800 nm. In some embodiments, the height of each light-emitting diode may be greater than or equal to 500 nm, preferably in the range of 1 μm to 50 μm.

[0043] Figure 1is a perspective view of an embodiment of an axial light emitting diode 100 .

[0044] The light emitting diode 100 includes a stack of a region 102, an active region 104, and a region 106. The upper surface of the region 102 is in contact with the lower surface of the active region 104. The upper surface of the active region 104 is in contact with the lower surface of the region 106.

[0045] LED 100 is referred to as an axial LED because active region 104 is aligned with region 102 and region 106 is aligned with active region 104. Axis Δ corresponds to the axis of the axial LED.

[0046] The region 102 is made of a doped semiconductor material of a first conductivity type (e.g., P-doped). The region 102 is located on a support 105, which is, for example, an electronic circuit, such as an interposer, comprising interconnections that are in contact with the region 102 and capable of controlling the light-emitting diode 100. Then, the axis Δ is orthogonal to the upper surface of the support 105. The lower surface 109 of the region 102 (i.e., the surface located on the side of the support 105) is in contact with the reflective layer. For example, the lower surface 109 can be separated from the support 105 by a layer 107 made of a metal (e.g., aluminum). For example, the metal layer 107 can cover the support 105 in whole or in part.

[0047] The region 106 is made of a semiconductor material of a second conductivity type (e.g., N-type) different from the first conductivity type. The upper surface 111 of the region 106 is, for example, covered by a layer (or layer stack) composed of one or more transparent or semi-reflective materials, which is not shown, for example, a layer of transparent conductive oxide (TCO).

[0048] Regions 102 and 106 may be at least partially comprised of a semiconductor material that primarily includes a III-V compound, such as a III-N compound. Examples of III-group elements include gallium (Ga), indium (In), or aluminum (Al). Examples of III-N compounds are GaN, AlN, InN, InGaN, AlGaN, or AlInGaN. Other V-group elements, such as phosphorus (P) or arsenic (As), may also be used. The elements in the III-V compound may be combined with different mole fractions.

[0049] Regions 102 and 106 may be at least partially composed of a semiconductor material that primarily contains a II-VI compound. Examples of Group II elements include Group IIA elements, particularly beryllium (Be) and magnesium (Mg), and Group IIB elements, particularly zinc (Zn), cadmium (Cd), and mercury (Hg). Examples of Group VI elements include Group VIA elements, particularly oxygen (O) and tellurium (Te). Examples of Group II-VI compounds are ZnO, ZnMgO, CdZnO, CdZnMgO, CdHgTe, CdTe, or HgTe. Typically, the elements in the Group II-VI compounds may be combined with different mole fractions.

[0050] Regions 102 and 106 may be at least partially composed of a semiconductor material that primarily contains at least one Group IV compound. Examples of Group IV semiconductor materials are silicon (Si), carbon (C), germanium (Ge), silicon carbide alloy (SiC), silicon germanium alloy (SiGe), or germanium carbide alloy (GeC).

[0051] Regions 102 and 106 may include a dopant. For example, for a III-V compound, the dopant may be selected from a P-type II-group dopant, such as magnesium (Mg), zinc (Zn), cadmium (Cd), or mercury (Hg), a P-type IV-group dopant, such as carbon (C), or an N-type IV-group dopant, such as silicon (Si), germanium (Ge), selenium (Se), sulfur (S), terbium (Tb), or tin (Sn).

[0052] Preferably, the region 102 is a P-doped GaN region, and the region 106 is an N-doped GaN region.

[0053] For each light emitting diode, active region 104 may include a confinement device, for example, region 104 may contain a single quantum well and then include a semiconductor material that is different from the semiconductor material forming regions 102 and 160 and has a smaller band gap than the semiconductor material forming regions 102 and 160. Active region 104 may include multiple quantum wells and then include a stack of alternating semiconductor layers forming quantum wells and barrier layers.

[0054] exist Figure 1 In the embodiment, the light emitting diode 100 is shown in a cylindrical shape, including a circular bottom surface centered on the axis Δ. However, the light emitting diode 100 may also be in a cylindrical shape with a polygonal bottom surface (e.g., a square, a rectangle, or a hexagon) centered on the axis Δ. Preferably, the light emitting diode 100 is in a cylindrical shape with a hexagonal bottom surface.

[0055] The height h of the light emitting diode 100 (i.e. the distance between the lower surface 109 of the region 102 and the upper surface 111 of the region 106) is substantially proportional to k*λ / 2*neff, λ being the wavelength of the radiation emitted by the light emitting diode, neff being the effective refractive index of the light emitting diode in the optical mode under consideration, and k being a positive integer. The effective refractive index is defined, for example, in "Semiconductor Optoelectronics: An Introduction to Physics and Simulation" by Joachim Piprek.

[0056] The height h is equal to the sum of the height P1 of the region 102 , the height P2 of the active region 104 , the height P3 of the region 106 , and the height of an optional layer that may cover the surface 111 .

[0057] The light emitting diode 100 forms a resonant cavity along the axis Δ. Therefore, an electromagnetic standing wave along the axis Δ is formed in the light emitting diode during operation. Figure 1 This electromagnetic standing wave is very schematically shown in FIG by curve 108. Thus, if the light-emitting diode has a circular cross section, the wave has, for example, rotational symmetry. An electromagnetic standing wave along the axis Δ represents an electromagnetic wave whose nodes (e.g., points of zero intensity) are fixed in space, while its intensity at other points varies with time.

[0058] According to an embodiment, the active region 104 is advantageously located at the level of the extremum 110 of the electromagnetic wave. Then, the power intensity of the radiation emitted by the light-emitting diode is more significant, and the radiation escaping from the light-emitting diode is more intensive than in the case of a light-emitting diode with the same structure, but in which the active region is not at the extremum of the electromagnetic wave.

[0059] Figure 2 is a perspective view of an embodiment of an array 200 of light emitting diodes 100 .

[0060] The array 200 includes light emitting diodes 100 in a layer of filler material 202, such as an electrically insulating material, such as silicon oxide. Figure 2 In the embodiment of , all LEDs 100 have the same height. The thickness of layer 202 is, for example, selected to be equal to the height of the LEDs, so that the upper surface of layer 202 is coplanar with the upper surface of each LED (ie, with the upper surface 111 of each region 106).

[0061] An electrode layer not shown contacts the upper surface of the light emitting diode. The electrode layer may be a conductive layer of the cover layer 202. The electrode layer may be a transparent or semi-reflective layer.

[0062] The upper surface of the array corresponds to the surface of the electrode layer opposite to the light emitting diodes.

[0063] Figure 2Twelve light emitting diodes 100 are shown. In practice, array 200 may include, for example, 7 to 100,000 light emitting diodes.

[0064] The light emitting diodes 100 of the array 200 are arranged in rows and columns ( Figure 2 The spacing of the array is the distance between the axis of one light emitting diode 100 and the axis of the next light emitting diode 100 in the same row or in an adjacent row. The spacing a is substantially constant. More specifically, the spacing of the array is selected so that the array 200 forms a photonic crystal. The photonic crystal formed is, for example, a 2D photonic crystal.

[0065] Advantageously, the properties of the photonic crystal formed by the array 200 are chosen so that the intensity of the radiation emitted by all the light-emitting diodes 100 of the array is greater and the radiation is more directional than in the case of an assembly of light-emitting diodes 100 not forming a photonic crystal.

[0066] exist Figure 2 In the example of , the refractive index neff is substantially equal to the average of the refractive indices of GaN of the light-emitting diode 100 and the material of the layer 202, weighted by the surface area ratio FF between the two materials. Thus, the refractive index neff is, for example, substantially equal to: FF*nGaN+(1-FF)*nSiO2, where nGaN is the refractive index of GaN of the light-emitting diode 100, nSiO2 is the refractive index of the material of the layer 202, and FF is equal to the quotient of the horizontal cross-sectional area of ​​the light-emitting diode 100 and the horizontal cross-sectional area of ​​the periodic elements of the array 200. For example, the periodic elements of the array 200 have a horizontal cross-sectional area of ​​a square centered on the light-emitting diode 100, and a side length equal to the distance between the axes Δ of two adjacent light-emitting diodes.

[0067] FIG. 3A to FIG. 3B An example of a layout of light emitting diodes 100 of an array 200 is schematically shown. In particular, Figure 3A shows a so-called square grid layout, while Figure 3B A so-called hexagonal grid layout is shown.

[0068] Figure 3A and 3B Further shown is the pitch a of the array, ie the distance between the axis of one light emitting diode and the axis of the immediately adjacent light emitting diode in the same row or in an adjacent row. Figure 3A and 3B Also shown is the radius R of a light emitting diode 100 having a circular bottom surface. In the case of a light emitting diode that does not have a circular bottom surface, the radius R corresponds to the radius of a circle in which the bottom surface is inscribed.

[0069] Figure 3AThree rows of four light emitting diodes 100 are shown. In this arrangement, a light emitting diode 100 is located at the intersection of each row and column, with the rows being perpendicular to the columns.

[0070] and Figure 3A similar, Figure 3B Three rows of four light emitting diodes 100 are shown. In this arrangement, the diodes in one row are shifted by half a pitch a relative to the light emitting diodes in the previous and next rows.

[0071] 4A to 4F It is shown in Figure 2 A cross-sectional view of a structure obtained in a step of an embodiment of a method for manufacturing an array 200 .

[0072] Figure 4A The structure obtained after the formation steps described below is shown.

[0073] A seed layer 302 is formed on a substrate 304. Then, light emitting diodes 100 are formed from the seed layer 302. More specifically, light emitting diodes 100 are formed in a manner that regions 106 contact the seed layer 302. Active regions 104 of each light emitting diode 100 are located on regions 106, and regions 102 are located on active regions 104.

[0074] Furthermore, the array 200 is formed by positioning the light emitting diodes 100 , ie, to form rows and columns having a desired pitch of the array 200 . 4A to 4F Only one row is shown.

[0075] Before forming the LED on the seed layer 302, a mask not shown may be formed to expose only a portion of the seed layer 302 where the LED is located. Alternatively, the seed layer may be etched to form pads where the LED is to be located.

[0076] The growth method of the light emitting diode 100 may be a method such as chemical vapor deposition (CVD) or metal organic chemical vapor deposition (MOCVD) (also referred to as metal organic vapor phase epitaxy (MOVPE)). However, methods such as molecular beam epitaxy (MBE), gas source MBE (GSMBE), metal organic MBE (MOMBE), plasma assisted MBE (PAMBE), atomic layer epitaxy (ALE) or hydride vapor phase epitaxy (HVPE) may also be used. However, electrochemical processes such as chemical bath deposition (CBD), hydrothermal processes, liquid aerosol pyrolysis or electrodeposition may also be used.

[0077] The growth conditions of LED 100 are such that all LEDs of array 200 are formed at substantially the same rate. Thus, the heights of regions 102 and 106 and the height of active region 104 are substantially the same for all LEDs of array 200.

[0078] It is further considered that the heights of region 102 and active region 104 substantially correspond to the previously described values ​​P1 and P2, which are determined so that in operation, active region 104 is located at the extremes of the electromagnetic wave. The height of region 106 is greater than the desired value P3. The height of region 106 is difficult to control accurately, especially because region 106 grows from seed layer 302. In addition, forming a semiconductor directly on the seed layer may result in crystal defects in the semiconductor material directly above the seed layer, so it is necessary to remove a portion of region 106.

[0079] Figure 4B The structure is shown after forming a layer 306 of a filling material (e.g., an electrically insulating material, such as silicon oxide) corresponding to the material of layer 202. Layer 306 is formed, for example, by depositing a layer of filling material on the structure, the thickness of which is greater than the height of light-emitting diode 100. The filling material layer is then partially removed to planarize it, thereby exposing the upper surfaces of regions 102, each of which corresponds to the upper surfaces of regions 102. Figure 1 Surface 109 is described. Thus, the upper surface of layer 306 is substantially coplanar with the upper surface of each region 102. As a variant, the method may comprise an etching step during which regions 102 are partially etched.

[0080] By selecting the filling material, the photonic crystal formed by the array 200 has the desired properties, namely, it improves the directionality and intensity of the radiation emitted by the light emitting diodes 100 .

[0081] Figure 4C The structure obtained after depositing a layer 308 on the structure obtained in the previous step is shown. The layer 308 is a reflective layer, for example a metal layer, for example an aluminum layer. The layer 308 is also a conductive layer, which connects all the regions 102 of the array 200 to each other. The light-emitting diodes 100 of the array 200 are thus controlled via the layer 308.

[0082] Figure 4D The structural support 310 obtained after being joined to the surface of the layer 308 not in contact with the layer 306, for example by metal-to-metal bonding, by hot pressing or by brazing using a eutectic alloy on the side of the support 310 is shown. The support 310 is for example an electronic circuit, such as an interposer, comprising interconnections not shown in contact with the layer 308.

[0083] Figure 4EThe structure obtained after removing the substrate 304 and the seed layer 302 is shown. Furthermore, the layer 306 and the regions 106 are etched in such a way that the height of each region 106 has a value P3, so that the active regions can be placed as before. This step advantageously enables precise control of the height h of the light-emitting diodes and removes a portion of the regions 106 that may have crystal defects.

[0084] Figure 4F The structure obtained after depositing a layer 312 on the structure obtained by the previous steps is shown. The layer 312 is transparent or semi-reflective to allow the emission of radiation, and is electrically conductive to control the light-emitting diode 100. The layer 312 is, for example, made of a transparent conductive oxide, for example of zinc oxide or indium tin oxide, or can be a stack of oxide layers so that the reflectivity of the stack can be adjusted depending on the thickness and the refractive index of the stacked materials.

[0085] FIG. 5A to FIG. 5D It is shown in the manufacturing Figure 2 200 is a cross-sectional view of a structure obtained in other steps of an embodiment of the method of array 200. More specifically, FIG. 5A to FIG. 5D The formation of region 106 is at least partially shown.

[0086] Figure 5A The resulting structure is shown after forming region 106 on seed layer 302 overlying substrate 304 .

[0087] This embodiment is suitable, for example, for a case where the growth conditions of the light emitting diode 100 enable regions 106 with different heights to be obtained.

[0088] Figure 5B The structure is shown after forming a layer 402 of filling material (eg silicon oxide) on the region 106. The formation of the layer 402 comprises, for example, depositing a layer of filling material having a thickness greater than the height of the region 106 located on the layer 302.

[0089] Figure 5C The structure obtained after etching the regions 106 and the layer 402 such that the upper surface of all regions 106 is coplanar with the upper surface of the layer 402 is shown. The regions 106 then all have the same height.

[0090] Figure 5D The structure obtained after removal of layer 402 is shown.

[0091] The growth of the light emitting diode 100 can then be resumed, for example to achieve about Figure 4A Then, the light emitting diodes 100 have a growth rate that is substantially the same. Figure 5DThe step of is followed, for example, by a step of growing the rest of region 106 and a step of growing active region 104 and region 102. As a variant, Figure 5D The step of may be followed by the step of growing active region 104 and region 102. In this case, Figure 5D The height of region 106 in the Figure 4A The height of region 106 in the array is thus substantially the same regardless of the number of LEDs in the array. 4A to 4F Description.

[0092] Figure 6 It is shown in the manufacturing Figure 2 A cross-sectional view of a structure obtained in a step of another embodiment of a method of an array. This step is for example Figure 5D Following the steps shown.

[0093] During this step, a portion 106a of the previously formed and planarized region 106 (e.g., FIG. 5A to FIG. 5D During the method described, an etch stop layer 502 is formed on the substrate. As an example, the material forming the etch stop layer 502 may be a nitride, carbide, metal or boride of a transition metal in column IV, V or VI of the periodic table, or a combination of these compounds. For example, the etch stop layer 502 may be made of aluminum nitride (AlN), aluminum oxide (Al2O3), boron (B), boron nitride (BN), titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN), hafnium (Hf), hafnium nitride (HfN), niobium (Nb), niobium nitride (NbN), zirconium (Zr), zirconium borate (ZrB2), zirconium nitride (ZrN), silicon carbide (SiC), tantalum carbonitride (TaCN), Mg X N Y The layer 502 may be a magnesium nitride in the form of Mg3NY2, wherein x is approximately equal to 3 and y is approximately equal to 2, for example, magnesium nitride in the form of Mg3NY2. The thickness of the layer 502 is, for example, in the range of approximately 1 to 100 nm.

[0094] Portion 106b of region 106 is then formed on layer 502. Active region 104 and region 102 are then formed on region 106.

[0095] The height of portion 106b substantially corresponds to the desired height P3. The height of portion 106a is large enough to include most of the crystal defects.

[0096] Then, in Figure 6 The steps can be followed by FIG. 4B to FIG. 4F The steps described previously about Figure 4EThe etching of the described steps stops at the etch stop layer 502 , and includes, for example, removing the etch stop layer 502 .

[0097] Fig. 7A and Figure 7B It is shown in the manufacturing Figure 2 A cross-sectional view of a structure obtained in the steps of another embodiment of the array method. More specifically, Fig. 7A and 7B The fabrication of an array comprising light emitting diodes having different heights is shown.

[0098] Fig. 7A The growth of the light emitting diode 100 is shown. Figure 4A The step is equivalent to the step of , except that during this step, a plurality of etching stop layers are formed in each region 106. Fig. 7A In the embodiment of the present invention, three etch stop layers 602a, 602b and 602c are formed in each region 106, layer 602a is closest to seed layer 302, and layer 602c is closest to active region 104. The etch stop layers are made of the same material and are separated from each other by a portion of region 106, for example.

[0099] Figure 7B shows that in a similar manner to the previous Figure 4B , 4C After the steps described in 4D, Fig. 7A An array of light emitting diodes is obtained by using the structure.

[0100] The method then includes etching steps. During these steps, for the assembly 604 of light-emitting diodes 100, the region 106 of each light-emitting diode 100 is etched from the free end to the etch stop layer 602c, which is also etched. For the assembly 606 of light-emitting diodes 100, the region 106 of each light-emitting diode 100 is etched from the free end to the etch stop layer 602b, and then the etch stop layer 602b is etched to expose the portion of the region 106 located between the etch stop layers 602b and 602c. For the assembly 608 of light-emitting diodes 100, the region 106 of each light-emitting diode 100 is etched from the free end to the etch stop layer 602a, and then the etch stop layer 602a is etched to expose the portion of the region 106 located between the etch stop layers 602b and 602a.

[0101] The light-emitting diodes of the different assemblies 604, 606 and 608 provide radiation with the same wavelength λ, for example, and have, for example, a total height h equal to different multiples of λ / 2n. As a variant, the light-emitting diodes of the different assemblies 604, 606 and 608 may be suitable for emitting radiation with different wavelengths and therefore have different heights.

[0102] The materials and dimensions of etch stop layers 602a, 602b, and 602c are selected so that they have negligible effect on the operation of the light emitting diodes.

[0103] A layer 312 is then deposited on the structure. The layer 312 may, for example, surround the upper portion of the region 106 of certain light emitting diode assemblies. The thickness of the layer 312 is selected to cover the upper surface of each light emitting diode 100.

[0104] The reflective layer 308 is, for example, divided into a plurality of non-connected portions, each portion being in contact with a component of a light emitting diode. Thus, different light emitting diode components can be controlled independently of each other.

[0105] Typically, the number of etch stop layers corresponds to the number of different light emitting diode heights desired in the array.

[0106] An advantage of the above-described manufacturing method embodiments is that they enable precise positioning of the active region 104 within the light-emitting diode 100 , ie the values ​​of the heights P1 , P2 and P3 can be controlled.

[0107] The following is attached Figure 8 , 9A 9E and 10A to 10E show simulation results related to an example of an array according to the above-described embodiment. Such simulations illustrate methods for determining the size of the light-emitting diodes and the spacing of the array. For the simulation, the light-emitting diodes of the array under consideration include GaN regions 102 and 106. The thickness of region 102 is greater than or equal to 30nm. The active region 104 includes a single InGaN layer, the thickness of which is equal to 40nm. Layer 306 is made of silicon oxide and the reflective material layer 308 is made of aluminum. Layer 312 has a thickness of 50nm. Layer 312 is made of a transparent conductive oxide having a refractive index substantially equal to 2 at the wavelength under consideration, such as ITO. The light-emitting diode 100 under consideration is in the shape of a column with a round bottom. The light-emitting diodes of the array are arranged in a square grid. Each row and each column includes seven light-emitting diodes. Therefore, the array here includes forty-nine light-emitting diodes. In the following simulations, all light-emitting diodes are considered to have the same height.

[0108] The following constraint is chosen to be imposed on the filling ratio of the square grid: 5% ≤ πR 2 / a 2 ≤65%, where R is the radius of each LED cross section and a is the array pitch.

[0109] Figure 8is a graph comprising curves of the variation of the intensity (power) of the radiation emitted by the array according to a first quotient a / λ, where λ is the wavelength of the radiation emitted by the array, one for each array example, and each curve corresponding to a different value of the second quotient 2πR / λ.

[0110] For the sake of clarity, Figure 8 Only 6 curves are shown. In practice, simulations have been performed by varying the second quotient 2πR / λ from 0.7 to 1.7.

[0111] The diagram can determine one or more value ranges of the first quotient a / λ in which an intensity peak occurs. Two regions 702 and 704 can be observed, each corresponding to such a value range. At least one of the two regions 702 and 704 includes a peak.

[0112] Region 702 corresponds to a range of values ​​of the first quotient a / λ substantially in the range of about 0.4 to about 0.82. Region 704 corresponds to a range of values ​​of the first quotient a / λ substantially in the range of about 0.8 to about 0.92.

[0113] 9A to 9E is a graph showing simulation results of an embodiment of a light emitting diode array. More specifically, Fig. 9A and Fig. 9B shows a simulation in which the first quotient a / λ of the array is within the range associated with the region 702, thereby allowing the optimal characteristics of the array to be determined, and FIG. 9C to FIG. 9E Simulation results with selected characteristics are shown.

[0114] The wavelength λ of the radiation emitted by the light-emitting diodes is selected, for example 450 nm for blue light, 530 nm for green light and 630 nm for red light. The selection of a curve having a maximum in the range corresponding to the area 702 and the value of the first quotient a / λ at the maximum of the selected curve allow the radius R of the light-emitting diodes and the pitch a of the array to be determined.

[0115] For example, a wavelength of 630 nm is chosen here, and the curve 706 having the extreme value corresponding to the strongest emission intensity of all the curves in the region 702. Then, the first quotient a / λ is substantially equal to 0.7111, and the second quotient 2πR / λ is therefore substantially equal to 1.1. Therefore, the spacing a is substantially equal to 448 nm, and the radius R is substantially equal to 110 nm.

[0116] Fig. 9A The intensity (maximum power) emitted by the upper surface of the light-emitting diodes of the array is shown according to the total height h of the light-emitting diodes under the conditions selected above.

[0117] Three intensity peaks corresponding to heights h equal to 190 nm, 375 nm and 550 nm can be observed.

[0118] A value of h is selected among these values. Although the intensity emitted from the upper surface is greater for a height h equal to 190 nm, for ease of manufacturing, the height h is selected here to be equal to 375 nm.

[0119] Fig. 9B The intensity emitted by an array of light-emitting diodes having the characteristics determined above is shown as a function of the thickness P1 of the region 102. Within the given range of values, a maximum can be observed which allows the value of the thickness P1 of the region 102 to be determined, here 40 nm.

[0120] Fig. 9C The intensity of the radiation emitted by the upper surface of the array is shown as a function of the wavelength λ of the radiation emitted by the light emitting diodes. Curve 802 corresponds to an array of light emitting diodes that do not form a photonic crystal, and curve 804 corresponds to an array that forms a photonic crystal and has the characteristics determined above. These values ​​have been normalized so that the maximum value of curve 802 corresponds to the value 1.

[0121] It can be observed that the array of light-emitting diodes according to the embodiment and having the characteristics determined above emits, at the level of its upper surface, radiation with an intensity 1.5 times greater than the radiation emitted by an array not forming a photonic crystal.

[0122] Fig.9D The intensity of the radiation emitted by the above array is shown as a function of the angle between the emission intensity and a direction normal to the upper surface of the array.The radiation emitted by the array is advantageously directional.

[0123] Fig.9E The intensity of the radiation emitted by the array is shown, cumulatively, as a function of the solid angle measured relative to the upper surface of the array. Fig.9E Included is curve 806 corresponding to an array of axial light emitting diodes that do not form a resonant cavity, and curve 808 corresponding to a photonic crystal formed by axial light emitting diodes that form a resonant cavity and have the characteristics identified above.

[0124] It can be observed that the array according to the embodiment (curve 808) provides a more directional intensity. In fact, the array corresponding to curve 808 provides 50% of its intensity at a solid angle of 30°, while the array corresponding to curve 806 provides 50% of its intensity at a solid angle of 45°.

[0125] Thus, compared to the radiation provided by the LED array corresponding to curve 806, the Figure 2An array of embodiments and having the characteristics identified above provides radiation that is more intense and more directional.

[0126] FIG. 10A to FIG. 10E is a graph showing simulation results of another embodiment of a light emitting diode array. More specifically, Fig. 10A and Fig. 10B shows simulation results for a case where the first quotient a / λ of the array is within the range associated with the region 704, thereby allowing the optimal characteristics of the array to be determined, and FIG. 10C to FIG. 10E Simulation results for selected characteristics are shown.

[0127] As mentioned above, a wavelength of 630 nm is selected here, and Figure 8 The curve 708 of which the extremum corresponds to the maximum emission intensity in the provided curve. The quotient a / λ corresponding to the extremum is substantially equal to 0.85 and the quotient 2πR / λ of the curve is substantially equal to 1.49. Therefore, the determined spacing a is equal to 536.7 nm and the determined radius R is equal to 150 nm.

[0128] Fig. 10A The intensity (maximum power) emitted from the upper surface of the light emitting diode according to the total height h of the light emitting diode under the conditions selected above is shown.

[0129] Two intensity peaks corresponding to heights h substantially equal to 180 nm and 325 nm can be observed.

[0130] A value of h is chosen among these values. Here h is chosen to be equal to 325 nm, corresponding to the strongest intensity.

[0131] Fig. 10B The intensity emitted by a light emitting diode array having the characteristics determined above is shown as a function of the thickness P1 of the region 102 .

[0132] Within the given range of values, a maximum is observed which allows the value of the thickness P1 of the region 102 to be determined, here 40 nm.

[0133] Fig. 10C The intensity of the radiation emitted by the upper surface of the array is shown as a function of the wavelength λ of the radiation emitted by the light emitting diodes. Curve 902 corresponds to an array of light emitting diodes that do not form a photonic crystal, and curve 904 corresponds to an array that forms a photonic crystal and has the characteristics determined above. These values ​​have been normalized so that the maximum value of curve 902 corresponds to the value 1.

[0134] It can be observed that the array of light-emitting diodes according to the embodiment and having the characteristics determined above emits, at the level of its upper surface, radiation with an intensity 1.6 times greater than the radiation emitted by the array without forming a photonic crystal.

[0135] Fig. 10D The intensity of the radiation emitted by the above array is shown as a function of the angle between the emission intensity and the direction normal to the upper surface of the array. It can be observed that 9A to 9E The radiation is more directional than described above.

[0136] Fig.10E The intensity of the radiation emitted by the array is shown, cumulatively, as a function of the solid angle measured relative to the upper surface of the array. Fig.10E Included is curve 906 corresponding to an array including axial light emitting diodes that do not form a resonant cavity, and curve 908 corresponding to a photonic crystal including axial light emitting diodes that form a resonant cavity and have the characteristics determined above.

[0137] It can be observed that the array according to the embodiment (curve 908) provides a more directional intensity. In fact, the array corresponding to curve 908 provides 50% of its intensity at a solid angle of 33°, while the array corresponding to curve 906 provides 50% of its intensity at a solid angle of 45°.

[0138] Thus, compared to the radiation provided by the LED array corresponding to curve 906, the Figure 2 An array of embodiments and having the characteristics identified above provides radiation that is more intense and more directional.

[0139] The inventors have already addressed the following issues: Figure 1 and Figure 2 Similar simulations were performed for the described LED arrays with different characteristics, in particular for LEDs with cross-sections of different shapes, for LEDs whose active region comprises a plurality of quantum wells instead of a single quantum well, for LEDs with a hexagonal mesh layout instead of a square one, or for different materials. The simulation results then made it possible to determine the characteristic values ​​of the LEDs and arrays described above and to show an increase in the intensity and directivity of the radiation emitted by the LED array.

[0140] Specific embodiments have been described. Various changes and modifications will occur to those skilled in the art. In particular, although only the case of a light emitting diode is described here, the embodiments can also be applied to a photodiode.

[0141] Various embodiments with different variations have been described above. It should be noted that those skilled in the art can combine various elements of these various embodiments and variations without showing any creativity.

Claims

1. An optoelectronic device, comprising an array (200) of axial diodes (100), each diode forming a resonant cavity in which an electromagnetic standing wave is formed, each light emitting diode comprising an active region (104) substantially located at the level of an extremum (110) of the electromagnetic standing wave, the array forming a photonic crystal, the photonic crystal being configured to maximize the intensity of electromagnetic radiation provided by the diode array, wherein the array (200) comprises a support (105, 310) on which the diodes (100) rest, each diode comprising a stack of a first semiconductor region (102) resting on the support, the active region (104) in contact with the first semiconductor region, and a second semiconductor region (106) in contact with the active region, the device comprising a reflective layer (107, 308) bonded to the support and located between the support (105, 310) and the first semiconductor region (102) of the diode.

2. The device according to claim 1, wherein the reflective layer (107, 308) is made of metal.

3. A device according to claim 1 or 2, wherein the second semiconductor region (106) of the diode is covered by a conductive layer (312), which is at least partially transparent to the radiation emitted by the diode.

4. A device according to claim 1, wherein the height (h) of at least one of the diodes (100) is substantially proportional to kλ / 2n, where λ is the wavelength of the radiation emitted by the diode, k is a positive integer, and n is substantially equal to the effective refractive index of the diode in the optical mode considered.

5. The device of claim 1, wherein the diodes (100) are separated by an electrically insulating material (202, 306).

6. The device of claim 1, the array comprising at least first and second diode assemblies (604, 606, 608), the diodes of the first diode assembly having a same first height, the diodes of the second diode assembly having a same second height, the first height and the second height being different.

7. The device of claim 1, wherein for at least one of the diodes, the second semiconductor region of the diode comprises at least two portions (106a, 106b) separated by an etch stop layer (502, 602a, 602b, 602c).

8. The device of claim 7, wherein each etch stop layer (502, 602a, 602b, 602c) has a thickness in the range of 1 to 200 nm.

9. The device of claim 1, wherein a quotient of a pitch of the array and a wavelength of the provided electromagnetic radiation is in the range of 0.4 to 0.

92.

10. The device of claim 1, wherein the diode is a light emitting diode or a photodiode.

11. A method for manufacturing an optoelectronic device, the optoelectronic device comprising an array (200) of axial diodes (100), each diode forming a resonant cavity, an electromagnetic standing wave being formed in the resonant cavity, the active region (104) of each diode being substantially located at the level of an extremum (110) of the electromagnetic standing wave, the array forming a photonic crystal, the photonic crystal being configured to maximize the intensity of electromagnetic radiation provided by the diode array, wherein forming of said diodes of said array comprises: forming second semiconductor regions (106) on the substrate (304), the second semiconductor regions (106) being separated from each other by the spacing of the array; forming at least one layer capable of serving as a stop layer for a second etching step in the second semiconductor region of at least one of the diodes; forming an active region (104) on each second semiconductor region (106); and A first semiconductor region (102) is formed on each active region.

12. The method according to claim 11, comprising a first step of etching all of the first semiconductor regions (102) so that they have the same height.

13. Method according to claim 11 or 12, comprising a second step of etching all said second semiconductor regions (106) so that they have a height allowing said active region to be located at said extreme level of said standing electromagnetic wave. The method of claim 13 , wherein the second etching step is performed prior to formation of the active area.

15. The method of claim 13, wherein the second etching step is preceded by a step of removing the substrate, the second etching step being performed from an end of the diode closest to the substrate.

16. The method of claim 11, wherein the diode is a light emitting diode or a photodiode.

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