DEVICE FOR DETECTING LIGHT RADIATION

Abstract

The invention relates to a photodetector for detecting incident light radiation of wavelength λ, comprising an array of pixels located in a detection plane. Each pixel comprises an absorption zone surrounding a central region of the pixel, a metallic pixel contact, located in the central region and a focusing element for transmitting the incident light radiation and generating focused transmitted light radiation in the absorption zone. The focusing element is further adapted to impart orbital angular momentum to the transmitted light radiation, the orbital angular momentum being centered on a propagation axis passing through the central region. Figure for abstract: Figure 1

Description

Title of the invention: DEVICE FOR DETECTING LIGHT RADIATION Technical field

[0001] The field of the invention is that of the detection and / or measurement of light radiation, and in particular that of imagers in the visible or infrared range. STATE OF THE PRIOR ART

[0002] Optoelectronic photodetection devices, also called photodetectors, may comprise a matrix of pixels each comprising a photodiode. Photodiodes are conventionally made in a semiconductor layer in which extend doped wells which define PN or PIN junctions. Thus, the photodiodes comprise photon absorption zones corresponding substantially to the space charge zones induced by the junctions. The semiconductor layer extends, for its part, along a main plane, called the detection plane, and has a front face and a rear face which are opposite and parallel to each other. When the photodetector is illuminated by incident light radiation, charges are photo-generated in the absorption zone and collected by a read-out circuit (ROIC) arranged at least partly on the front face.

[0003] The photodetectors may be of the front-facing illumination type, in which case the incident light radiation falls on the front face and passes through the reading circuit before reaching the absorption zone. When the incident light radiation falls on the rear face and does not pass through the reading circuit, the photodetector is said to be of the rear-facing illumination type.

[0004] Each photodiode may be of the planar type. In this case, it comprises for example a first n+ doped region flush with the front face, a second p+ doped region flush with the rear face, and an intrinsic or lightly p-doped intermediate region, located between the first and second doped regions so as to surround the first region to define a junction. An electrical contact connects the first region to the reading circuit. In this configuration, the absorption zone surrounds and delimits a central region of the pixel in which the aforementioned electrical contact is located, which is intended to collect the photo-generated charges in the absorption zone.

[0005] Each photodiode can also be of the loophole type. In this case, it comprises, for example, a first n+ doped region of cylindrical or truncated shape. extending entirely or almost entirely in a volume of the semiconductor layer in a direction orthogonal to the front and back faces. A second p-doped region surrounds the first region. The first and second regions then together define a PN junction, and therefore an absorption zone of truncated cone or cylindrical shape which surrounds and delimits a central region of the pixel. The semiconductor layer typically comprises a recess in the first region and coaxial with it accommodating an electrical contact connected to the reading circuit and intended to collect the photo-generated charges in the absorption zone.

[0006] For these two types of configuration at least, the arrangement of the electrical contact hinders the detection of the incident light radiation in the absorption zone. To overcome this problem, patent application EP3664141 proposes assigning to each pixel a focusing element to focus the incident light radiation in the absorption zone. The focusing element consists of a refractive structure formed by a first truncated pyramid and provided with a recess. The recess has the shape of a second full or truncated pyramid. The bases of the first and second pyramids are parallel to the detection plane. This type of structure makes it possible to collect substantially all the incident photons on a pixel and to transmit to the photodiode transmitted light radiation of substantially annular shape, adapted to the shape of the absorption zone, thus increasing the quantum efficiency of the photodetector.

[0007] To a large extent, the solution taught in patent application EP3664141 is based on the principles of geometric optics, which means that its efficiency drops when the size of the pixel relative to the wavelength of the incident light radiation decreases. The acceptable limit depends on several parameters, such as, for example, the refractive index of the materials present, in particular that of the focusing element. For example, simulation results have shown that for a pixel size of 7.5 pm, a refractive index of the focusing element of 3.5 and a wavelength of 4 pm, the annular shape of the transmitted light radiation is significantly degraded and disappears beyond a propagation distance greater than 2 pm. Statement of the invention

[0008] The invention aims to remedy at least in part the drawbacks of the prior art, and more particularly to propose a photodetector with increased quantum efficiency.

[0009] For this, the object of the invention is a photodetector for detecting incident light radiation of wavelength X, comprising a matrix of pixels located in a detection plane, each comprising: an absorption zone surrounding a central region of the pixel; a metallic pixel contact, located in the central region; a focusing element for transmitting the incident light radiation and generating focused transmitted light radiation in the absorption region. The photodetector is such that, for each pixel, the focusing element is adapted to impart orbital angular momentum to the transmitted light radiation, the orbital angular momentum being centered on a propagation axis passing through the central region.

[0010] Some preferred but non-limiting aspects of this photodetector are as follows.

[0011] For each pixel, the focusing element may have a refractive index N, and a thickness h which is a function of cylindrical coordinates of a cylindrical coordinate system with a z-axis perpendicular to the detection plane, measured parallel to the z-axis, monotonic as a function of 0 over an interval [+ 2tt]. h may satisfy the relationship > , i / . a \ , , to within 10% for all r and for a set « ( r, y ) — n ç r, uq ) + 4^ of at least four regularly spaced 0 values ​​in the interval [% ^o + ^7T], where 1 is a relative integer other than 0, preferably equal to 1 or -1.

[0012] The thickness h of each focusing element can be a decreasing function of r.

[0013] The focusing elements may be made of colored resins and at least one colored resin may be different from the others.

[0014] The absorption zones can extend into the volume of a crystalline semiconductor layer.

[0015] The photodetector may be of the backside illumination type and the focusing element may be in contact with the semiconductor layer.

[0016] The focusing elements may be based on a crystalline material with a lattice parameter adapted to the growth of the semiconductor layer.

[0017] The thickness h of each focusing element may be less than + ] q

[0018] The absorption zones can extend in the volume of a semiconductor layer based on CdHgTe or GaSb or CdZnTe or Si or Ge.

[0019] The invention also relates to a method of manufacturing a photodetector according to any one of the preceding characteristics, comprising a step of producing a focusing element by machining with a focused ion beam.

[0020] The manufacturing method may comprise a step of epitaxy of a semiconductor layer on a growth substrate made of a crystalline material with a lattice parameter adapted to the growth of the semiconductor layer.

[0021] The manufacturing method may comprise a step of thinning the growth substrate to obtain a blade with flat and parallel faces. Focused ion beam machining may be carried out on the blade during the step of producing the focusing element. Brief description of the drawings

[0022] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0023] [Fig. 1] is a schematic sectional view of a first embodiment of a front-illuminated photodetector implementing a planar-type photodiode.

[0024] [Fig.2] is a schematic top view of the first embodiment.

[0025] [Fig.3] is a simulation result of the first embodiment showing the mapping of the electric field modulus of the transmitted radiation in a section plane orthogonal to the detection plane, passing through the center of the focusing element.

[0026] [Fig.4] is a simulation result of the first embodiment showing the mapping of the electric field modulus of the transmitted radiation in a section plane parallel to the detection plane, at a distance of 23.4 pm from the focusing element.

[0027] [Fig.5] is a schematic sectional view of a second embodiment of a rear-illuminated photodetector implementing a loophole type photodiode.

[0028] [Fig.6] is a schematic sectional view of a variant of the second embodiment for which the focusing element is a metasurface.

[0029] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0030] In the figures and in the remainder of the description, the same references represent identical or similar elements. Furthermore, the different elements are not shown to scale so as to enhance the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and may be combined with each other. Unless otherwise indicated, the terms "substantially", "approximately", "of the order of" mean to within 10%, and preferably to within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are included, unless otherwise indicated.

[0031] The invention relates to a photodetector, as well as to a method of manufacturing such a photodetector. The photodetector comprises a matrix of pixels. Each pixel comprises: an absorption zone surrounding and delimiting a central region of the pixel; and a focusing element. The focusing element has the function of collecting substantially all the photons of a light radiation incident on the pixel to focus it in the absorption zone, that is to say that the light flux reaching the absorption zone is increased due to the presence of the focusing element. The focusing element may, for example, be made of a material with a homogeneous refractive index, or may be a metasurface. In the context of the invention, the focusing element transmits the incident light radiation to generate transmitted light radiation having an orbital angular momentum (OAM).

[0032] Light radiation having orbital angular momentum is an electromagnetic wave propagating along a propagation axis that has a helical wavefront, i.e. the phase in a plane orthogonal to the propagation axis has an azimuthal component at e10, where 1 is a relative integer different from 0 and 0 is the angle around a propagation axis of the light radiation, and consequently, a zero electric field along the propagation axis. In the context of the invention, the propagation axis passes through the central region of the pixel to distribute the light intensity around the central region and therefore in the absorption zone.

[0033] By metasurface is meant a plate with flat and parallel faces capable of transmitting, respectively reflecting, incident light radiation of wavelength X comprising a set of structures having a dimension less than X, designed to control the phase and / or the amplitude and / or the polarization of the transmitted light radiation, respectively reflected. Examples of metasurface working in transmission capable of conferring an orbital angular momentum to light radiation transmitted by the metasurface are set out by the authors Zhang, K.; Wang, Y.; Yuan, Y.; Burokur, SN in the document entitled “A Review of Orbital Angular Momentum Vortex Beams Generation: From Traditional Methods to Metasurfaces” - Appl. Sci. 2020, 10, 1015. https: / / doi.org / 10.3390 / appl0031015.

[0034] By "based on", we mean that the material is a compound formed from at least the same elements of the semiconductor compound of interest.

[0035] By layer is meant an area of ​​a crystalline material whose thickness along the Z axis is less, for example ten times or even twenty times, than its longitudinal dimensions of width and length in the XY plane.

[0036] Particular embodiments will be described relating to a photodetector comprising an absorption zone surrounding a central region of a pixel. However, these embodiments can be adapted to other optoelectronic photodetection devices, for example bolometers, provided that the absorption zone surrounds a central region where a pixel contact is located.

[0037] [Fig.l] schematically illustrates a photodetector according to a first embodiment. The photodetector 1 comprises a plurality of pixels 5 arranged in a matrix. For the sake of clarity, a single pixel has been shown in [Fig.l]. [Fig.2] schematically shows, in top view, pixel 5 of [Fig.l] surrounded by its nearest neighbors.

[0038] The photodetector 1 comprises a semiconductor layer 30, an optical spacer 20, a focusing element 10, an interconnection stack and a support substrate 40. It is intended to detect incident light radiation 2 of wavelength X. The optical spacer 20 and the support substrate 40 are optional.

[0039] The semiconductor layer 30 is made of a semiconductor material. It extends along a main plane, called the detection plane, and has a front face 36 and a rear face 35 opposite and parallel to each other. The semiconductor material may be intrinsic or lightly p-doped. The front and / or rear face may optionally be passivated.

[0040] The semiconductor layer 30 comprises a first n+ doped region 31 flush with the front face 36, a second p+ doped region 33 flush with the rear face 35, and an intermediate region 32, respectively intrinsic or lightly p-doped, located between the first and second doped regions so as to surround the first region 31. These three regions together define a junction, respectively PIN or PN and therefore an absorption zone surrounding and delimiting a central region 34 of the pixel. A pixel contact 51 electrically connects the first region 31 to a reading circuit. The pixel contact 51 and the first region 31 occupy the central region 34 of the pixel. A substrate contact 52 electrically connects the second region 33 to the reading circuit. Several pixels may have a substrate contact 52 in common. The substrate contact 52 may also be offset to the edge of the pixel matrix.

[0041] The pixel contact 51 and the substrate contact 52 are part of the interconnect stack. The interconnect stack may contain metal interconnect lines of the read circuit. It is in contact with the front face of the semiconductor layer 30

[0042] The focusing element 10 is made of a first material transparent to the wavelength X and of refractive index N at the wavelength X. It has a flat base 11, oriented in the direction of the semiconductor layer 30, substantially parallel to the detection plane. The focusing element 10 also has a curved surface 12 opposite the base, intended to receive incident light radiation 2, in doing so, transmitted light radiation 3 emerges through the base. Its thickness measured along an axis perpendicular to its base at a point M of the curved surface 12 is designated by h.

[0043] Here and for the remainder of the description, a direct orthogonal Cartesian reference frame (0,X,Y,Z) attached to the focusing element 10 is defined, such that (0, X, Y) is a reference frame of the base 11 of the focusing element 10. The X and Y axes therefore form a plane parallel to the detection plane. The X axis is chosen to be parallel to an axis of

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[0051] the pixel matrix, and the Z axis is oriented from the base 11 towards the curved surface 12 of the focusing element 10. In the remainder of the description, the terms "vertical" and "vertically" are understood as relating to an orientation substantially parallel to the Z axis, and the terms "horizontal" and "horizontally" as relating to an orientation substantially parallel to the (X,Y) plane. Furthermore, the terms "lower" and "upper" are understood as relating to an increasing positioning when moving away from the focusing element 10 in the +Z direction. This Cartesian coordinate system makes it possible to define a cylindrical coordinate system such that any point with cylindrical coordinates (r, 0, z) has Cartesian coordinates (rcos(0), rsin(0), z) in the coordinate system (O, X, Y, Z). Thus, it is possible to associate with any point M of the curved surface 12 a set of coordinates (r, 0, h) in the cylindrical coordinate system, where h is the thickness of the focusing element 10 at the aforementioned point M. The thickness h is therefore a function of r, and 0. Here, h(r, 0) is a monotonic function of 0 over an interval of length 2ir, for all r. More precisely, the axis (OZ) and the curved surface 12 are such that there exists a Qq e [0, 2jt ] for which the thickness h verifies to within 10%, preferably 5%, the following relation: h(r, 6) = h(r, 0Q) equation 1 where 1 is a relative integer different from 0, preferably equal to 1 or -1, this for all r and all 0 included in the interval [ 9^ 90 + 2tt], Alternatively, h can verify the relationship of equation 1, to within 10%, preferably 5%, for a set of p values ​​of 0 regularly spaced in the interval [0, 2ir], for example 4, or 8. For example, the thickness h can approximate equation 1 by stairs in the interval [% 0O + 2tf]. h can then, at any point M with coordinates (r, 0) of the curved surface, verify the following relationship: equation 2, , h(r, 6) =h(r, + where p is a natural number greater than or equal to 4 and E denotes the integer part. Thus, the transmitted light radiation 3 has an orbital angular momentum, and therefore a substantially zero electric field in a dark region 4 centered on the axis (OZ). In each plane orthogonal to the axis (0, Z), the dark region 4 has a disc-shaped section centered on (0, Z), and contains 5% of the energy flux of the transmitted light radiation 3. The section of the dark region 4 increases as it moves away from the focusing element 10.

[0052] The optical spacer 20 is made of a second material transparent to the wavelength X. It has a first face and a second face that are planar and substantially parallel. The base 11 of the focusing element 10 is in contact with the first face of the optical spacer 20, possibly via one or more intercalary layers such as, for example, an antireflection layer at the wavelength X and / or a layer of glue. The second face of the optical spacer 20 is in contact with the interconnection stack, opposite the semiconductor layer 30. Here, the second face is planar and substantially parallel to the front face of the semiconductor layer 30. Alternatively, the second face may be spherical or aspherical, so as to produce a convergent diopter with the interconnection stack.

[0053] In the absence of the optical spacer 20, the base 11 of the focusing element 10 is directly in contact with the interconnection stack, possibly via one or more intercalary layers such as, for example, an anti-reflection layer at wavelength X and / or a layer of glue.

[0054] The semiconductor layer 30 rests on an optional support substrate 40. The support substrate 40 may, for example, be a substrate used for the epitaxial growth of the semiconductor layer 30, or contain electronic components of the reading or power supply circuit of the photodetector 1.

[0055] The relative positions of the focusing element 10, the semiconductor layer 30 and the pixel contact 51 are such that the axis (O, Z) passes through the central region 34. Thus the dark region 4 intercepts the central region 34 of the pixel and the pixel contact 51, placed in the central region 34, does not block the photons of the transmitted light radiation 3 on their path towards the absorption zone. When the optical spacer 20 is present, its thickness may be such that the section of the dark region 4 is substantially the same size as the central region 34 at the front face of the semiconductor layer 30.

[0056] The optical spacer 20 and / or the focusing element 10 may be made of colored resin capable of filtering the incident light radiation 2. The photodetector 1 may then comprise a first group of at least one pixel 5 comprising optical spacers 20 (respectively focusing elements 10) made of colored resin of a first type and a second group of at least one pixel 5 distinct from the first comprising optical spacers 20 (respectively focusing elements) made of colored resin of a second type different from the first. It is then possible to carry out multispectral detection.

[0057] As shown in [Fig.l], the thickness h(r, 0) of the focusing element 10 may additionally be a monotonically decreasing function of r for all 0 in the interval [0, 2ir]. Thus the transmitted light radiation 3 is concentrated in a central part of the pixel, which further increases the quantity of photons absorbed, therefore the quantum efficiency and limits crosstalk. Crosstalk is the absorption by a neighboring pixel of a carrier generated by a photon incident on the pixel.

[0058] The semiconductor material of the semiconductor layer 30 may be based on CdHgTe, or GaSb, or CdZnTe, or Si, or Ge

[0059] The first material may be silicon oxide, silicon, germanium or CdZnTe.

[0060] The second material may be identical to the first material. The second material may be selected from silicon oxide, silicon, germanium or CdZnTe.

[0061] The semiconductor layer 30 typically has a thickness of the order of the wavelength X, for example around 1.5 pm for a germanium semiconductor layer 30, or between 6 pm and 10 pm for a CdHgTe semiconductor layer 30. The first region 31 has a dimension parallel to the front face 36 typically between 1 pm and 5 pm. The interconnection stack has, for example, a thickness between 100 nm and 15 pm. The pixel contact 51 has, for example, a section between 1 pm and 5 pm.

[0062] The focusing element 10 occupies substantially the entire surface of the pixel. Its thickness h is for example between 1 μm and 10 μm.

[0063] [Fig. 3] and 4 show a simulation result giving the modulus of the electric field in the optical spacer 20 for the first embodiment (the denser the filling of the level lines, the higher the modulus of the electric field). Here, the pixel is square with a side of 20 pm. The wavelength X is equal to 4 pm. The first and second materials are here based on CdZnTe.

[0064] [Fig. 3] shows the simulation result in a plane orthogonal to the detection plane, passing through the center of the pixel (plane AA in [Fig. 2]). [Fig. 4] gives the simulation result in a plane parallel to the detection plane, located at a distance of 23.4 pm from the base 11 of the focusing element 10. These two figures highlight a dark region around the propagation axis within which the electric field is substantially zero. In [Fig. 3], the diameter of the dark region 4 along the x axis increases as it moves away from the focusing element 10.

[0065] [Fig. 5] schematically illustrates a photodetector 100 according to a second embodiment implementing a loophole type photodiode. The photodetector 1 is of the rear face illumination type. Only the differences compared to the first embodiment will be described here.

[0066] The first region 31 has a recess in a central part. The recess accommodates the pixel contact 51. The photodetector 1 comprises a functional substrate 60 which contains at least a part of the reading circuit. The face front of the semiconductor layer 30 is passivated by a passivation layer 37. The passivation layer 37 is bonded to the functional substrate by a layer of glue 61, for example an epoxy glue. Alternatively, any other type of transfer technique can be used, such as oxide-oxide and / or copper-copper molecular bonding, thermocompression, beading, etc. In all cases, the pixel contact 51 electrically connects the first region 31 to the part of the reading circuit contained in the functional substrate 60.

[0067] The first region 31 preferably extends from the front face to the rear face of the semiconductor layer 30. The pixel contact 51 extends into the semiconductor layer 30 from its front face over a depth at least greater than half the thickness of the semiconductor layer 30, preferably greater than 80% of the thickness of the semiconductor layer 30. It may also be completely through. In all cases, it extends over a depth less than or equal to that of the first region 31.

[0068] The second region 33 is flush with the front surface of the semiconductor layer 30 and extends into the semiconductor layer 30 to a depth at least equal to that of the first region 31, preferably from the front face to the rear face of the semiconductor layer 30. The first and second regions thus together define a PN junction which may have a cylindrical or frustoconical shape and therefore an absorption zone surrounding and defining a central region 34 of the pixel. The pixel contact 51 and the first region 31 occupy the central region 34.

[0069] The thickness h of the focusing element 10 satisfies the same criteria as those set out in connection with the first embodiment. The base 11 of the focusing element 10 is here in contact with the rear face of the semiconductor layer 30. In this case, the focusing element may be made of a crystalline material with a lattice parameter adapted to the growth of the semiconductor layer 30 and the semiconductor layer 30 is a crystalline layer epitaxially grown on the base of the focusing element 10.

[0070] Alternatively, the base 11 of the focusing element 10 may be bonded to the rear face of the semiconductor layer 30 by molecular bonding, or using a layer of glue, for example an epoxy glue. One or more anti-reflection or bonding or passivation layers may be interposed between the focusing element 10 and the semiconductor layer 30.

[0071] An optional optical spacer 20, of the same nature and same function as those exposed in connection with the first embodiment, can be interposed between the base 11 of the focusing element 10 and the rear face of the semiconductor layer 30. It can for example be bonded to the base 11 of the focusing element 10 and to the rear face of the semiconductor layer 30 by any known technique, for example molecular bonding, glue film, it being understood that one or more anti-reflective or adhesion layers can be interposed between these different elements.

[0072] As for the first embodiment, the relative positions of the focusing element 10, the semiconductor layer 30 and the pixel contact 51 are such that the axis (O, Z) passes through the central region 34. Thus the dark region 4 intercepts the central region 34 of the pixel and the luminous flux transmitted to the absorption zone is maximized. When the optical spacer is present, its thickness is such that the section of the dark region 4 is substantially the same size as the central region 34 at the rear face of the semiconductor layer 30.

[0073] [Fig.6] schematically illustrates a photodetector 150 according to a variant of the second embodiment for which the focusing element 70 is a metasurface. Only the differences with respect to the second embodiment will be described here.

[0074] The rear face 35 of the semiconductor layer 30 is passivated by a passivation layer 38. The focusing element 70 is a metasurface designed to impart orbital angular momentum to the transmitted light radiation 3. Here, it is of substantially constant thickness. Its base 11 is bonded to the passivation layer 38 by a film of adhesive 15, for example an epoxy adhesive.

[0075] An example of a method for producing a photodetector 1 according to the first embodiment is now described.

[0076] In a first step, the constituent elements of the first embodiment are produced, with the exception of the optical spacer 20 and the focusing element, using process sub-steps known in the semiconductor industry.

[0077] During a second step, a layer of the second material is deposited on the interconnection stack to produce the optical spacer 20. Alternatively, a substrate made of the second material can be bonded to the interconnection stack by molecular bonding, for example oxide-oxide, followed by a thinning step by grinding and polishing.

[0078] During a third step, a substrate made of first material is bonded to the optical spacer 20 by molecular bonding, for example oxide-oxide, followed by a thinning step by grinding and polishing, to obtain a blade with flat and parallel faces.

[0079] In a fourth step, the blade is machined by focused ion beam (FIB) machining to obtain the curved surface 12. At the end of the fourth step, we therefore obtain the focusing element 10.

[0080] We will now describe an example of a method for producing the photodetector 1 according to the second embodiment.

[0081] In a first step, a semiconductor layer 30 made of first material is grown by epitaxy on a growth substrate made of first material with refractive index N.

[0082] In a second step, a loophole type photodiode matrix is ​​produced with its reading circuit intended to be exposed from the rear face, using process sub-steps known from the semiconductor industry. At the end of this step, the growth substrate is preserved.

[0083] In a third step, the growth substrate is thinned by face milling (or flycut, in English) to obtain a blade with flat and parallel faces of thickness comprised, for example, between -A. and 1^1, preferably greater than, typically equal to, the size of a pixel. For example, for a wavelength X greater than or equal to 4 pm, the thickness of the blade may be greater than or equal to 10 pm, for example comprised between 10 pm and + |q

[0084] In a fourth step, the blade is machined by focused ion beam (FIB) machining to obtain the curved surface 12. At the end of the fourth step, we therefore obtain the focusing element 10.

[0085] Only the third and fourth steps change to achieve the variant of the second embodiment illustrated in [Fig.6]

[0086] During the third step, the growth substrate is completely removed and the rear face of the semiconductor layer 30 is passivated.

[0087] In a fourth step, the focusing element 10 is bonded to the passivated rear face of the semiconductor layer 30.

[0088] Particular embodiments have just been described. Different variants and modifications will appear to those skilled in the art. It is in particular possible to reverse all the dopings mentioned.

Claims

Claims

1. Photodetector (1, 100, 150) for detecting incident light radiation (2) of wavelength X, comprising a matrix of pixels (5) located in a detection plane, each comprising: • an absorption zone surrounding a central region (34) of the pixel (5); • a metallic pixel contact (51), located in the central region (34); • a focusing element (10, 70) for transmitting the incident light radiation (2) and generating transmitted light radiation (3) focused in the absorption zone; the photodetector (1, 100, 150) being characterized in that, for each pixel (5), the focusing element (10, 70) is adapted to impart an orbital angular momentum to the transmitted light radiation (3), the orbital angular momentum being centered on a propagation axis passing through the central region (34).

2. Photodetector (1, 100) according to claim 1, in which, for each pixel (5), the focusing element (10) has a refractive index N, and a thickness h as a function of cylindrical coordinates (r, 0) of a cylindrical coordinate system (r, 0, z) with axis z perpendicular to the detection plane, measured parallel to the axis z, monotonic as a function of 0 over an interval [ 0® + 2æ ], and such that l / y fl) satisfies the following relation: h(r, 6) = h(r, +^âr to within 10% for all r and for a set of at least four values ​​of 0 regularly spaced in the interval [ + 2^], where 1 is a relative integer different from 0, preferably equal to 1 or -1.

3. A photodetector (1, 100) according to claim 2, wherein the thickness h of each focusing element (10) is a decreasing function of r.

4. A photodetector (1, 100) according to claims 2 or 3, wherein the focusing elements (10) are made of colored resins and at least one colored resin is different from the others.

5. Photodetector (1, 100, 150) according to any one of claims 2 to 4, in which the absorption zones extend in the volume of a crystalline semiconductor layer (30).

6. The photodetector (100, 150) of claim 5, wherein the photodetector (100, 150) is a back-illuminated type photodetector and wherein the focusing element (10, 70) is in contact with the semiconductor layer (30).

7. Photodetector (100) according to claim 6, wherein the focusing elements (10) are based on a crystalline material with a lattice parameter adapted to the growth of the semiconductor layer (30).

8. A photodetector (1, 100) according to any one of claims 2 to 7, wherein the thickness h of each focusing element (10) is less than + 10

9. Photodetector (1, 100, 150) according to any one of claims 1 to 8, wherein the absorption zones extend in the volume of a semiconductor layer (30) based on CdHgTe or GaSb or CdZnTe or Si or Ge.

10. A method of manufacturing a photodetector (1, 100, 150) according to any one of claims 1 to 10 comprising a step of producing a focusing element (10) by machining with a focused ion beam.

11. Manufacturing method according to claim 10 of a photodetector according to claim 7 comprising: - a step of epitaxy of a semiconductor layer (30) on a growth substrate made of a crystalline material with a lattice parameter adapted to the growth of the semiconductor layer (30), - a step of thinning the growth substrate to obtain a blade with flat and parallel faces, for which the machining by focused ion beam is carried out on the blade during the step of producing the focusing element (10).

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