Optoelectronic device comprising a three-dimensional light emitting diode

Abstract

The present invention relates to an optoelectronic device (10), comprising: a three-dimensional semiconductor element (20) mainly made of a first chemical element and a second chemical element; an active region (24), at least partially covering the sidewall of the three-dimensional semiconductor element (20), and comprising at least one first layer mainly made of the first and second chemical elements, and a stack of at least one second layer mainly made of the first and second chemical elements and a third chemical element; a third layer (26), covering the active region, the third layer mainly made of the first, second, third and fourth chemical elements, and the mass ratio of the third and fourth chemical elements in the third layer increases or decreases as the distance from the substrate (12) increases; and a fourth layer (28), mainly made of the first and second chemical elements and covering the third layer (26).

Description

[0001] This patent application claims the priority of French patent application FR 17 / 63316, which is to be considered as an integral part of the present description. Background Art

[0002] The present application relates generally to optoelectronic devices including three-dimensional light emitting diodes made of semiconductor materials.

[0003] Discussions in related fields

[0004] The pixel of an image corresponds to a unit element of the image displayed by the optoelectronic device. For the display of a color image, the optoelectronic device generally includes at least three components for the display of each pixel of the image, also referred to as display sub-pixels, each component emitting light radiation substantially in a single color (such as red, green and blue). The superposition of the radiation emitted by the three display sub-pixels provides the observer with a color perception corresponding to the pixel of the displayed image. In this case, the component formed by the three display sub-pixels for displaying a pixel of the image is called a display pixel of the optoelectronic device.

[0005] There is an optoelectronic device that includes a three-dimensional semiconductor element that can form a three-dimensional light-emitting diode (or LED). Each light-emitting diode includes an active area covering the sidewalls of the three-dimensional semiconductor element. The active area is the area where the light-emitting diode emits most of the radiation emitted by the light-emitting diode. The active area is covered by an electron blocking layer (EBL). During the manufacturing process of the EBL, the content of some elements may be uneven on the EBL. Similarly, the active area can cover a hole blocking layer (HBL), and the content of some elements may be uneven on the HBL. This may result in uneven current distribution supplied to the active area. Therefore, the radiation intensity emitted by the active area may be uneven on the active area, and the efficiency of the light-emitting diode may be suboptimal. Summary of the invention

[0006] Therefore, an object of the present embodiment is to at least partially overcome the disadvantages of the above-mentioned optoelectronic devices.

[0007] Therefore, this embodiment provides an optoelectronic device, comprising:

[0008] substrate;

[0009] A three-dimensional semiconductor element, mainly made of a first chemical element and a second chemical element, is located on a substrate;

[0010] an active region at least partially covering the sidewalls of the three-dimensional semiconductor element and comprising a stack of at least one first layer made mainly of the first and second chemical elements and at least one second layer made mainly of the first and second chemical elements and a third chemical element;

[0011] a third layer covering the active region, the third layer being mainly made of the first, second and third chemical elements and a fourth chemical element, and the mass ratio of the third and fourth chemical elements of the third layer increasing or decreasing with increasing distance from the substrate; and

[0012] The fourth layer, mainly made of the first and second chemical elements, covers the third layer.

[0013] According to an embodiment, the active region is capable of emitting electromagnetic radiation and the third layer is a charge carrier blocking layer.

[0014] According to an embodiment, the content of the third chemical element in the third layer is in the range of 0.1% to 10%.

[0015] According to an embodiment, the content of the fourth chemical element in the third layer is in the range of 10% to 40%.

[0016] According to an embodiment, the first chemical element is a Group III element.

[0017] According to an embodiment, the first chemical element is gallium.

[0018] According to an embodiment, the second chemical element is a Group V element.

[0019] According to an embodiment, the second chemical element is nitrogen.

[0020] According to an embodiment, the third chemical element is a Group III element.

[0021] According to an embodiment, the third chemical element is indium.

[0022] According to an embodiment, the fourth chemical element is a Group III element.

[0023] According to an embodiment, the fourth chemical element is aluminum.

[0024] According to an embodiment, the semiconductor element is linear.

[0025] According to an embodiment, the semiconductor element is pyramidal.

[0026] According to an embodiment, the maximum variation of the band gap of the third layer is smaller than the maximum variation of the band gap of the same layer not comprising the third chemical element.

[0027] According to an embodiment, the third layer is an electron blocking layer or a hole blocking layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other features and advantages will be discussed in detail in the following non-limiting description of specific embodiments in conjunction with the accompanying drawings, in which:

[0029] Figure 1 is a simplified cross-sectional view of a portion of an optoelectronic device including a three-dimensional light emitting diode;

[0030] Figure 2 shows the variation curve of aluminum content, and Figure 1 A curve showing a variation of a band gap of one layer of a light emitting diode as a function of distance from a substrate having the light emitting diode formed thereon;

[0031] Figure 3 The variation curves of aluminum and indium content are shown, and Figure 1 A curve showing a variation of a band gap of one layer of a light emitting diode as a function of distance from a substrate having the light emitting diode formed thereon;

[0032] Figure 4 The results obtained through testing are shown in Figure 1 Shown is a graph of the band gap (in eV) of one of the layers of a light emitting diode as a function of the distance from a substrate having the light emitting diode formed thereon. DETAILED DESCRIPTION

[0033] In different figures, the same elements are designated by the same reference numerals, and, further, the different figures are not drawn to scale. For the sake of clarity, only those steps and elements that are helpful for understanding the described embodiments are shown and described in detail. In particular, the method for controlling the following optoelectronic device is within the capabilities of those skilled in the art and is not described.

[0034] In the following description, when referring to terms defining relative positions (such as the terms "upper", "lower", etc.), this refers to the orientation of the relevant elements in the drawings. The terms "approximately" and "substantially" are used herein to specify a tolerance of plus or minus 10% (preferably plus or minus 5%) of the value in question.

[0035] The present disclosure relates to an optoelectronic device including a light emitting diode having a radial three-dimensional shape, wherein an active region of the light emitting diode is formed on a semiconductor element having a three-dimensional shape (eg, the shape of a microwire, nanowire, or pyramid).

[0036] The term "microwire" or "nanowire" designates a three-dimensional structure having an elongated shape (such as a cylinder, cone, or pyramid) along a preferential direction, having at least two dimensions, called minor dimensions, ranging from 5 nm to 2.5 μm, preferably from 50 nm to 2.5 μm, and a third dimension, called major dimension, greater than or equal to 1 times the largest minor dimension, preferably greater than or equal to 5 times the largest minor dimension, and more preferably still greater than or equal to 10 times the largest minor dimension. 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, more preferably in the range of 100 nm to 800 nm. In some embodiments, the height of each microwire or nanowire may be greater than or equal to 50 nm, preferably in the range of 50 nm to 50 μm, more preferably in the range of 1 μm to 10 μm. For example, the base of the wire has an elliptical, circular or polygonal shape, in particular a triangle, rectangle, square or hexagon.

[0037] In the following description, the term "wire" is used to mean "microwire" or "nanowire".

[0038] In the following description, the term pyramid or truncated pyramid designates a three-dimensional structure having a pyramid shape. The pyramid structure may be truncated, i.e. the pyramid lacks a top and is replaced by a flat area. The base of the pyramid is inscribed in a polygon, the side length of which is from 100 nm to 10 μm, preferably from 1 to 3 μm. The polygon constituting the base of the pyramid may be a hexagon. The pyramid height between the base and the vertex or top platform of the pyramid varies from 100 nm to 25 μm, preferably from 1 μm to 10 μm.

[0039] Figure 1 is a simplified cross-sectional view of a portion of an optoelectronic device 10 capable of emitting electromagnetic radiation.

[0040] The device 10 comprises a substrate 12, such as a semiconductor, comprising parallel surfaces 14 and 16. Surface 14 is in contact with a first bias electrode 18.

[0041] Semiconductor element 20( Figure 1 A single semiconductor element is shown in FIG. 1 ) in contact with the surface 16 of the substrate 12. Figure 1 In the example shown in FIG. 1 , each semiconductor element 20 has a wire shape extending from the substrate 12. However, the semiconductor element 20 may have another three-dimensional shape.

[0042] The electrical insulating layer 22 covers the surface 16 of the substrate 12 and surrounds the lower portion of each conductive line 20 , ie, the portion of each conductive line 20 closest to the substrate 12 .

[0043] The upper sidewall of each conductive line 20 , ie, the portion not surrounded by the insulating layer 22 , is at least partially covered by the active area 24 , and is completely covered in this case.

[0044] The active region 24 is covered by an electron blocking layer 26 or EBL.

[0045] The EBL 26 is covered by a semiconductor layer 28 and a conductive layer 30 forming a second electrode.

[0046] The assembly consisting of the wire 20, the active region 24, the EBL 26 and the semiconductor layer 28 constitutes a light emitting diode. When a voltage is applied between the electrodes 18 and 30, the active region 24 emits light radiation. When multiple light emitting diodes are formed on the substrate 12, they can be connected in series and / or in parallel and constitute a light emitting diode assembly. In particular, the layer 30 can cover the semiconductor layer 28 of multiple light emitting diodes. Similarly, the layers 26 and 28 can cover the active region 24 of multiple wires 20. The number of light emitting diodes in the optoelectronic device can vary from one to hundreds of millions.

[0047] Electrode 18 may correspond to a conductive layer extending on surface 14 of substrate 12. For example, the material forming electrode 18 is nickel silicide (NiSi), aluminum (Al), aluminum silicide (AlSi), titanium (Ti), or titanium silicide (TiSi).

[0048] The substrate 12 may correspond to a monolithic structure or a layer covering a support made of another material. The substrate 12 is preferably a semiconductor substrate, such as a substrate made of silicon, germanium, silicon carbide, a III-V compound or a II-VI compound (e.g., ZnO). The substrate 12 may also be made of sapphire or graphene. Preferably, the substrate 12 is a single crystal silicon substrate. Preferably, it is a semiconductor substrate compatible with the manufacturing methods implemented in microelectronics. The substrate 12 may correspond to a multilayer structure of insulating silicon (also referred to as SOI). The substrate 12 may be heavily doped, lightly doped or undoped.

[0049] Examples of Group II chemical elements include Group IIA chemical elements, particularly beryllium (Be) and magnesium (Mg); Group IIB chemical elements, particularly zinc (Zn), cadmium (Cd) and mercury (Hg). Examples of Group VI chemical elements include Group VIA chemical elements, particularly oxygen (O) and tellurium (Te). Examples of II-VI compounds are ZnO, ZnMgO, CdZnO, CdZnMgO, CdHgTe, CdTe or HgTe. In general, the chemical elements in the II-VI compounds can be combined with different mole fractions.

[0050] The insulating layer 22 may be made of a dielectric material or include a stack of dielectric layers, such as silicon dioxide (SiO2), silicon nitride (Si x Ny , wherein x is approximately equal to 3 and y is approximately equal to 4, for example, Si3N4), silicon oxynitride (particularly of the general formula SiO x N y , for example, Si2ON2), hafnium dioxide (HfO2), or diamond. For example, the thickness of the insulating layer 22 ranges from 1 nm to 20 μm, preferably from 5 nm to 150 nm.

[0051] Each semiconductor element 20 is in contact with the surface 16 of the substrate 12. As a variant, a seed layer made of a material that is conducive to the growth of the semiconductor element 20 can be inserted between the substrate 12 and the semiconductor element 20. For example, the material forming the seed layer may be a nitride, carbide or boride of a transition metal from column IV, column V or column VI of the periodic table of chemical elements, or a combination of these compounds. As an example, the seed layer 16 can be made of one of the following: 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), magnesium nitride in the form of MgxNy, where x is approximately equal to 3 and y is approximately equal to 2, such as magnesium nitride in the form of Mg3N2. The seed layer may be doped with the same conductivity type as the substrate 12. For example, the thickness of the seed layer is in the range of 1 to 100 nanometers, preferably in the range of 10 to 30 nanometers. As a variant, the seed layer may be replaced by a seed pad placed on the surface 16 of the substrate 12, each wire 20 being placed on one of the seed pads.

[0052] The semiconductor element 20 is mainly formed of a compound containing a first chemical element and a second chemical element, in particular, a binary compound. The first chemical element may be a group III element. The second chemical element may be a group V element. Therefore, the semiconductor element 20 may be made of a III-V compound.

[0053] Examples of Group III chemical elements include gallium (Ga), indium (In), or aluminum (Al). Examples of Group V chemical elements include nitrogen, phosphorus, or arsenic. Examples of III-V compounds are GaN, AlN, InN, InGaN, AlGaN, or AlInGaN. In general, the chemical elements in the III-V compounds can be combined with different mole fractions.

[0054] The semiconductor element 20 may also be mainly made of an AlGaInP type alloy.

[0055] Semiconductor element 20 may include a dopant. For example, for III-V compounds, the dopant may be selected from a group including: a P-type Group II dopant, such as magnesium (Mg), zinc (Zn), cadmium (Cd), or mercury (Hg); a P-type Group IV dopant, such as carbon (C); or an N-type Group IV dopant, such as silicon (Si), germanium (Ge), selenium (Se), sulfur (S), terbium (Tb), or tin (Sn).

[0056] When the three-dimensional semiconductor element 20 of the optoelectronic device corresponds to a wire, the height of each wire may be in the range of 50 nm to 50 μm. Each wire 20 may have a semiconductor structure elongated along an axis D substantially perpendicular to the surface 16 .

[0057] When the three-dimensional semiconductor elements 20 of the optoelectronic device 10 correspond to pyramids, the height of each pyramid may be in the range of 100 nm to 25 μm. Each pyramid 20 may have a semiconductor structure that is elongated along an axis that is substantially perpendicular to the surface 16 .

[0058] The cross section of each wire or each pyramid 20 may generally be elliptical, circular or polygonal, in particular triangular, rectangular, square or hexagonal. The centers of two adjacent wires 20 or pyramids may be 0.25 μm to 10 μm apart, preferably 1.5 μm to 5 μm apart. For example, the wires 20 or pyramids may be regularly distributed, in particular in a hexagonal mesh.

[0059] The active region 24 may include a single quantum well. Thus, the active region 24 may include a layer made primarily of a ternary III-V compound. Preferably, the active region 24 includes a layer primarily containing the first and second chemical elements described above with respect to the semiconductor element 20 and a third chemical element other than the first chemical element of the same group as the first chemical element.

[0060] The active layer 24 may include a plurality of quantum wells. It then includes a stack of semiconductor layers forming alternating quantum wells and barrier layers. It may be formed by alternating layers made mainly of binary III-V compounds and layers made mainly of ternary III-V compounds. Preferably, the active region includes alternations of layers mainly comprising the first and second chemical elements and layers mainly comprising the first, second and third chemical elements.

[0061] The semiconductor layer 28 may be made of the same element as the semiconductor element 20 . The semiconductor layer 28 mainly includes the first element and the second element. For example, the semiconductor layer 28 is doped with a doping type opposite to that of the semiconductor element 20 .

[0062] The electrode 30 is capable of biasing the active region 24 covering each semiconductor element 20 and giving way to the electromagnetic radiation emitted by the light-emitting diode. The material forming the electrode 30 may be a transparent conductive material such as indium tin oxide (ITO), zinc oxide, doped or undoped aluminum, gallium or graphene. For example, the thickness of the electrode layer 30 is in the range of 5nm to 200nm, preferably in the range of 20nm to 50nm.

[0063] In a known manner, the EBL 26 is made mainly of a ternary alloy comprising a first chemical element, a second chemical element and a fourth chemical element from the same group as the first chemical element but in addition to the first or third chemical element. If the wire 20 is made of GaN and the quantum well comprises an InyGa(1-y)N layer, where y is the proportion of In and is generally designated as InGaN, then it is known that the EBL is made mainly of aluminum gallium nitride AlxGa(1-x)N, where x is the proportion of aluminum and is generally designated as AlGaN, and is in contact with the active region 24, providing a well-distributed carrier in the active region 24. For example, the thickness of the layer 26 can range from 5 nm to 60 nm, and the proportion x of aluminum can vary from 5% to 60%, preferably from 15% to 25%. The proportion refers to the proportion of atoms that do not contain nitrogen. For example, in the case of an Al0,2Ga0,8N composition, 20% of the non-nitrogen atoms are aluminum and 80% of the non-nitrogen atoms are gallium.

[0064] The method of growing each semiconductor element 20, active region 24, EBL 26, and semiconductor layer 28 may be, for example, chemical vapor deposition (CVD) or metal organic chemical vapor deposition (MOCVD), which is 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.

[0065] For example, the method may include injecting a precursor of a first chemical element and a precursor of a second chemical element and optionally a precursor of a third chemical element and / or a precursor of a fourth chemical element into a reactor.

[0066] In the following description, it may be considered that the first chemical element is gallium (Ga), the second chemical element is nitride (N), the third chemical element is indium (In), and the fourth chemical element is aluminum (Al). However, the different phenomena described may be extended to other chemical elements, such as those described previously.

[0067] Figure 2 Shown in Figure 1Shown are a curve 40 of the aluminum content x (percentage) in an EBL 26 of a light-emitting diode, which is made predominantly of AlGaN, and a curve 42 of the band gap (electron volts) of the EBL 26 as a function of the distance from the substrate 12 .

[0068] During the formation of EBL 26, the inventors have shown that the content of the fourth chemical element (here, aluminum of the AlGaN compound) may be non-constant across layer 26. In fact, the aluminum content in layer 26 may increase or decrease as the distance between substrate 12 and a reference point of layer 26 increases. In the example shown by curve 40, the aluminum content increases between the lower portion ("bottom") of wire 20 and the upper portion ("top") of wire 20.

[0069] This content variation is similar to the variation shown by curve 42 of the band gap of the EBL 26 (predominantly made of AlGaN). The band gap variation can be determined as known in the prior art, in particular as described in the publication by Sakalauskas et al. entitled "Dielectric function and optical properties of quaternary AlInGaN alloys" (Journal of Applied Physics 110, 013102 (2011)). The band gap at the top level of the wire 20 is higher than the band gap at the lower level of the wire 20. Therefore, the distribution of the current flowing through the active region 24, as well as the intensity of the radiation emitted by the active region 24, are not uniform. Therefore, the efficiency of the light emitting diode is suboptimal.

[0070] According to an embodiment, a third element is added to the composition of the EBL 26. Therefore, the EBL 26 is mainly made of a quaternary compound including the first, second, third and fourth chemical elements. Figure 3 and Figure 4 In the depicted embodiment, EBL 26 is not made of AlGaN, but rather is made of AlxInzGa(1-xz)N, where x is the aluminum content and z is the indium content, which is generally designated as AlInGaN.

[0071] Figure 3 Shows Figure 1 The curves 43 and 44 showing the content (percentage) of aluminum and indium in the EBL 26 (here mainly made of AlInGaN) of the light-emitting diode are shown. Figure 3Also shown is a curve 46 of the variation of the band gap (in electron volts) of layers made of AlGaN and AlInGaN as a function of the distance from the substrate 12 , with the curve 42 plotted for comparison.

[0072] The change in aluminum content in EBL 26 shown in curve 43 is similar to the change in aluminum content of EBL 26 mainly made of AlGaN. In addition, the change in indium (In) content in EBL 26 mainly made of AlInGaN shown in curve 44 is also non-constant, increasing between the lower and upper parts of wire 20.

[0073] The inventors have shown that, compared to the EBL 26 made primarily of AlGaN as shown by curve 42, Figure 3 The bandgap variation of the EBL 26 made mainly of AlInGaN is reduced as schematically illustrated by the substantially constant curve 46 in FIG. Therefore, the current flowing through the active region 24 is distributed more evenly on the light emitting diode, and thus the radiation intensity emitted by the active region 24 is also more even, thereby improving the efficiency of the light emitting diode.

[0074] The content of the fourth chemical element of the EBL 26 mainly made of the compound of the first, second, third and fourth chemical elements is, for example, in the range of 10 to 40%, for example, in the range of 15 to 35%. The content of the third chemical element of the EBL 26 mainly made of the compound of the first, second, third and fourth chemical elements is, for example, in the range of 0.5 to 10%, for example, in the range of 1 to 5%.

[0075] Figure 4 The results obtained through testing are shown in Figure 1 The band gap of the EBL 26 of the light emitting diode is shown as a function of the distance from the substrate having the light emitting diode formed thereon. Figure 3 42, corresponding to the EBL 26 made mainly of AlGaN; and curve 50 and Figure 3 4, which corresponds to an EBL 26 made primarily of AlInGaN.

[0076] In the test, the EBL 26 was formed at a pressure in the range of 75 to 500 Torr and a temperature in the range of 800 to 1000° C. The precursors used were, for example, trimethylgallium with a gallium flow rate of 82.75 sccm (standard cubic centimeters per minute), ammonia with a nitrogen flow rate of 50 l / min, trimethylindium with an indium flow rate of 900 sccm, and trimethylaluminum with an aluminum flow rate of 570 sccm.

[0077] As about Figure 3 As described, it can be observed that the curve 50 corresponding to AlInGaN has a significantly smaller variation than the curve 48 associated with AlGaN, especially in the upper part of the wire. Moreover, the bandgap value of the curve 50 is smaller than the bandgap value of the curve 48.

[0078] More specifically, according to the test conducted under the above conditions, in the lower portion (B) of the wire where the EBL is mainly made of AlGaN, the aluminum content is substantially equal to 15%, and the band gap is substantially equal to 3.75 eV. In the middle portion (M) of the wire, the aluminum content is substantially equal to 25%, and the band gap is substantially equal to 3.96 eV. In the upper portion (T) of the wire, the aluminum content is substantially equal to 30%, and the band gap is substantially equal to 4.1 eV.

[0079] According to the above test, in the lower part (B) of the wire where the EBL is mainly made of AlInGaN, the aluminum content is substantially equal to 15%, the indium content is substantially equal to 1%, and the band gap is substantially equal to 3.7 eV. In the middle part (M) of the wire, the aluminum content is substantially equal to 25%, the indium content is substantially equal to 2%, and the band gap is substantially equal to 3.88 eV. In the upper part (T) of the wire, the aluminum content is substantially equal to 30%, the indium content is substantially equal to 5%, and the band gap is substantially equal to 3.9 eV.

[0080] An advantage is that the third element added to the composition of the EBL is already present in the composition of other layers of the light-emitting diode, in particular in the active region. Thus, the implantation of the third element precursor is already provided. This reduces modifications to existing methods.

[0081] Specific embodiments have been described. Various changes and modifications will occur to those skilled in the art. In particular, the shape of the three-dimensional element is not limited to the examples described in this disclosure.

[0082] In the present disclosure, the optoelectronic device is considered to include a light emitting diode. However, the embodiments described herein can also be implemented in the context of a photodiode. In this case, the active region is capable of capturing electromagnetic radiation and converting the captured photons into charge carriers.

[0083] Furthermore, the above-described embodiments can also be applied to HBL. Furthermore, EBL or HBL can be inserted between the active region and the three-dimensional semiconductor element.

[0084] 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 embodiments and variations without showing any inventiveness.

Claims

1. A photovoltaic device (10), include: substrate(12); A linear or pyramidal three-dimensional semiconductor element (20), mainly made of gallium and nitrogen, and located on the substrate (12); an active region (24) at least partially covering the sidewalls of the three-dimensional semiconductor element (20) and capable of emitting electromagnetic radiation and comprising a stack of at least one first layer made essentially of gallium and nitrogen and at least one second layer made essentially of gallium, nitrogen and indium; an electron blocking layer (26), the electron blocking layer covering the active region, the electron blocking layer mainly made of gallium, nitrogen, indium and aluminum, the mass ratio of indium and aluminum in the electron blocking layer increasing from the bottom of the three-dimensional semiconductor element (20) to the top of the three-dimensional semiconductor element (20) as the distance from the substrate (12) increases, or the mass ratio decreases from the bottom of the three-dimensional semiconductor element (20) to the top of the three-dimensional semiconductor element (20); as well as The semiconductor layer (28) is mainly made of gallium and nitrogen and covers the electron blocking layer (26).

2. The optoelectronic device according to claim 1, in, The indium content in the electron blocking layer (26) is in the range of 0.1% to 10%.

3. The optoelectronic device according to claim 1 or 2, in, The aluminum content in the electron blocking layer (26) is in the range of 10% to 40%.

4. The optoelectronic device according to claim 1 or 2, in, The maximum variation of the band gap in the electron blocking layer (26) is less than the maximum variation of the band gap of the same layer not containing indium.

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