Convex photodiode imaging array

Abstract

To provide an array architecture in which photodiodes are spaced apart from one another and the geometry of the active area of each photodiode allows for better radiation concentration at the center of the pixel.SOLUTION: The present invention relates to an array (1) of at least two photodiodes (100a, 100b), each of the photodiode includes an absorber region (20) and a trapping region (70), the trapping region (70) includes a conductive pad (50), the absorber region (20) is in contact with the trapping region (70), the absorber region (20) is configured to absorb radiation incident on the photodiode and allow diffusion of charge carriers, each absorber region (20) is separated from the other absorber region (20), and the absorber region (20) of each photodiode (100a, 100b) is convex towards the incident radiation.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to the fabrication of photodiode arrays disposed on semiconductor substrates. For example, the present invention has particularly advantageous applications in the field of imaging, in particular in the field of imaging such as infrared imaging, where the pixel pitch is small and the operating temperatures are high. [Background technology]

[0002] Conventional photodiode arrays have a so-called planar architecture, in which the photodiodes of the array are arranged periodically over a flat surface. This planar architecture has the advantage that it is relatively simple to manufacture. However, in exchange, the planar architecture has limitations in terms of performance, since charge carriers photogenerated in the radiation absorbing regions within each photodiode diffuse to neighboring photodiodes. This contamination of charge carriers, known by the term "crosstalk", reduces the performance of high-density photodiode arrays by degrading the modulation transfer function (MTF).

[0003] To reduce crosstalk, it is possible to reduce the thickness of the absorbing layer, but this solution tends to reduce the quantum yield of the array.

[0004] Another solution consists in producing a pn junction photodiode array that is perpendicular to the substrate. The contact between the photodiodes and the readout integrated circuit (ROIC) is established by etching openings between the photodiodes through the multilayer and finally to the electrical pads. It would be difficult to produce such a high density photodiode array on a thick multilayer and the large volume occupied by the openings etched between the photodiodes would lead to quantum yield losses of the array.

[0005] Another existing solution is to fabricate mesa photodiodes by etching trenches between them deep enough to physically separate them. This solution allows confining the charge carriers within each pixel and overcomes the crosstalk problem. However, the presence of trenches can significantly reduce the quantum yield and increase leakage currents. Furthermore, the MTF can be degraded by the diffusion of radiation incident on the sides of these trenches into adjacent photodiodes.

[0006] The approach used in practice consists of depositing a microlens array on the photodiode array with the aim of concentrating the incident radiation on the center of each pixel of the array. Each microlens is capable of concentrating the incident radiation on the center of each pixel at a focal point that coincides with an area of ​​several photodetectors. This solution is difficult to implement since it requires a manufacturing step to form a 3D microstructure on the back surface of the array. Furthermore, its MTF may be limited by the diffraction of the incident radiation at the interface between the two microlenses and by the lateral diffusion of charge carriers in the case of planar photodiode arrays. Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to at least partially solve the above-mentioned problems by proposing an array architecture in which the photodiodes are spaced apart from each other and the geometric shape of the active area of ​​each photodiode allows a better radiation concentration in the center of the pixel. [Means for solving the problem]

[0008] To achieve the above object, according to one embodiment, an array of at least two photodiodes is provided, each photodiode comprising an absorber region and a trapping region, the trapping region comprising a conductive pad, the absorber region being in contact with the trapping region, the absorber region being configured to absorb radiation incident on the photodiode and allow diffusion of charge carriers, and each absorber region being separated from the other absorber region, the array being characterized in that the absorber region of each photodiode is convex towards the incident radiation.

[0009] According to a non-limiting embodiment, each photodiode of the array further comprises a coating region based on the first semiconductor, the coating region covering a top surface of the absorbing region facing the incident radiation.

[0010] One advantage of this architecture is the physical separation of the absorption regions, which has the effect of electrically isolating the photodiodes and reducing crosstalk in the array.

[0011] A second advantage is that the absorbing regions are convex in shape, which optimizes the radiation concentration at the center of each photodiode, thereby improving the quantum yield, lowering the amount of dark current, and increasing the operating temperature and MTF of the array.

[0012] These objects, features and advantages will become best apparent from the following detailed description of one latter embodiment, as illustrated in the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a top view of an imaging array comprising multiple photodiodes. [Diagram 2] FIG. 2 is a cross-sectional view of an array comprising at least two photodiodes. [Figure 3A] Figure 1 shows an embodiment of a photodiode array according to the invention, the figure showing a first embodiment in which the absorbing and covering regions on the one hand and the collecting regions on the other hand have different doping types; [Figure 3B] Figure 1 shows an embodiment of a photodiode array according to the invention, and Figure 2 shows a second embodiment of an array according to the invention, in which the absorbing and collecting regions on the one hand and the covering region on the other hand have different doping types. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] These figures are presented as examples and are not intended to limit the invention. These figures are basic schematic diagrams intended to facilitate understanding of the invention and are not necessarily drawn to scale in practical applications. In particular, their dimensions do not reflect reality.

[0015] Before commencing a detailed discussion of embodiments of the present invention, optional features are now described which may optionally be used in conjunction or as an alternative.

[0016] According to an advantageous embodiment, each photodiode 100a, 100b of the array 1 comprises an absorption region 20 and a capture region 70. The capture region 70 comprises a conductive pad 50, with which the absorption region 20 is in contact. The absorption region 20 is configured to absorb radiation incident on the photodiode and to allow diffusion of charge carriers. Each absorption region 20 is separated from the other absorption regions 20. The absorption region 20 of each photodiode 100a, 100b is convex towards the incident radiation. This allows to increase the travel distance of radiation inside the absorption region 20, which in turn allows to improve the radiation absorption and the quantum yield of the array.

[0017] According to an advantageous embodiment, each photodiode 100a, 100b further comprises a coating region 10 based on a first semiconductor. This coating region 10 covers the upper surface 20a of the absorption region 20 facing the incident radiation.

[0018] Advantageously, the coating region 10 has a first band gap energy E above 0.41 eV.10 This is advantageous for the transmission of the coating layer 10 at wavelengths above 3 μm.

[0019] According to one preferred example, the upper surface 10a of the coating area 10 facing the incident radiation has a convex surface with respect to the incident radiation.

[0020] Preferably, the absorption region 20 of each photodiode 100a, 100b has a curved convex shape, preferably a circular arc shape, preferably a hemispherical shape. According to another example, the absorption region 20 of each photodiode 100a, 100b has a cone shape or a truncated shape. According to another example, the absorption region 20 of each photodiode 100a, 100b has a truncated pyramid shape.

[0021] Advantageously, the absorption region 20 has a second band gap energy E 20 where E 10 >E 20 This band gap energy E 10 A high value of makes it possible to reduce the effect of defects present on the upper surface 20a of the photodiode.

[0022] Preferably, the capture region 70 further comprises a collection region 30 located between the absorbent region 20 and the conductive pad 50. The collection region 30 is based on a third semiconductor. The collection region 30 is in contact with the absorbent region 20 and the conductive pad 50.

[0023] Preferably, each photodiode 100a, 100b comprises a passivation layer 40 in contact with a lower surface 20b of the absorption region 20 opposite to an upper surface 20a of the absorption region 20 facing the incident radiation. The passivation layer 40 has openings 45a, 45b, each opening 45a, 45b facing an absorption region 20 of a different photodiode 100a, 100b. The capture region 70 of said photodiode 100a, 100b extends into said openings 45a, 45b.

[0024] According to one example, the absorber region 20 includes a gap opening zone 60 extending from a lower surface 20b of the absorber region 20 opposite to the upper surface 20a of the absorber region 20 facing the incident radiation. This gap opening zone 60 has a band gap energy that varies along a direction that is substantially perpendicular to the lower surface 20b of the absorber region 20, the so-called normal direction.

[0025] According to one example, the absorbing region 20 has a maximum height h along this normal direction. 20 and the gap opening zone 60 has a maximum height h along this normal direction. 60 where h 60 ≦0.5*h 20 and preferably h 60 ≦0.3*h 20 and preferably h 60 ≦0.1*h 20 It is.

[0026] According to one example, the gap opening zone 60 has a minimum height h along this normal direction. 60 where preferably h 60 ≧100 nm.

[0027] According to one embodiment, the cladding region 10 and the absorbing region 20 are doped, with the cladding region 10 having the same doping type as the absorbing region 20 and the collecting region 30 having an opposite doping type to the absorbing region 20 .

[0028] According to one embodiment, the cladding region 10 and the absorber region 20 are doped, with the cladding region 10 having an opposite doping type to the absorber region 20, and the collection region 30 and the absorber region 20 having the same doping type.

[0029] According to one example, the covering regions 10 of at least two of the photodiodes 100a, 100b form a continuous layer.

[0030] According to a preferred embodiment, the absorbent region 20 is 10 16 cm -3Less than, preferably 2*10 15 cm -3 Less than, preferably 2*10 14 cm -3 This allows the photodiode to operate as a high temperature depletion PIN photodiode.

[0031] According to another preferred embodiment, the covering area 10 is 16 cm -3 More than 10 17 cm -3 This provides effective gap opening due to the Moss-Burstein effect for the N-type doping of the cladding region 10.

[0032] Preferably, the collection area 30 is 10 16 cm -3 The doping level is greater than 1.

[0033] According to a preferred embodiment, the absorption region 20 has a second band gap energy E between 0.23 and 0.3 eV. 20 has.

[0034] According to one example, the absorber region 20 is based on a second semiconductor, and the first, second and third semiconductors are identical, such as CdHgTe based, and its band gap energy is therefore controlled by varying the percentage of cadmium (Cd) in the CdHgTe composition.

[0035] According to a preferred embodiment, the absorber region 20 has an N-type doping.

[0036] According to one example, the absorber region 20 is CdHgTe-based. According to one example, the coating region 10 is CdHgTe-based. According to one example, the collecting region 30 is CdHgTe-based. The absorber region 20, the coating region 10, and the collecting region 30 can all be based on a material that may not be present in the same composition in the three regions. The percentage of each element that makes up the material can be different in each region. For example, if the absorber region 20, the coating region 10, and the collecting region 30 are all CdHgTe-based, the percentage of cadmium can be different in each region.

[0037] It is noted that within the scope of the present invention, "on", "located on", "covering", "under", "opposite" and their equivalents do not necessarily mean "in contact with". Thus, for example, depositing, transferring, bonding, assembling or applying a first layer onto a second layer does not necessarily mean that these two layers are in direct contact with each other, but rather means that the first layer at least partially covers the second layer, either by being in direct contact with the second layer or by being separated from the second layer by at least one other layer or element.

[0038] Furthermore, a layer can be composed of multiple sub-layers of one and the same material or of different materials.

[0039] A substrate, layer, or device "based on" a material M means a substrate, layer, or device that includes only this material M, or that includes this material M together with any other materials, such as alloying elements, impurities, or doping elements. Thus, a material based on a III-V material can include a III-V material to which a dopant has been added.

[0040] In figure 2 a preferably orthonormal system is shown with axes X, Y and Z. This system is extensible to other figures.

[0041] In this patent application, thickness is preferably for a layer and height is for a structure or device. Height is measured perpendicular to a horizontal plane XY. Thickness is measured along a normal direction to the main extension plane of the layer. Thus, typically, a layer has a thickness along Z if it extends mainly along the horizontal plane XY, and a protruding element, such as an isolation trench, has a height along Z. The relative terms "above", "below", and "under" preferably refer to a position along the Z direction.

[0042] The terms "substantially", "about" and "approximately" mean "plus or minus 10%, preferably plus or minus 5%".

[0043] The invention relates to an array 1 of photodiodes 100a, 100b arranged, for example, on a semiconductor substrate, such as that shown in a top view in Fig. 1. This array 1 comprises at least two photodiodes 100a and 100b. The array 1 can also be called a pixel array. Advantageously, each of the photodiodes 100a, 100b forms part of one pixel. A pixel can consist of a single photodiode 100a, 100b or of several photodiodes 100a, 100b.

[0044] During use of the array 1, the array 1 is exposed to incident radiation 15, which preferably has a non-zero component along the Z direction.

[0045] According to one embodiment, each photodiode 100a, 100b comprises the elements shown in Figure 2, which will be described in more detail below.

[0046] Each photodiode 100a, 100b comprises an absorption region 20 based on a semiconductor material. This absorption region 20 allows the absorption of radiation 15 incident on the photodiode 100a, 100b and the generation of electron-hole pairs. The charge carriers then diffuse through the absorption region 20 to the capture zone 70.

[0047] The absorber regions 20 of the different photodiodes 100a, 100b are physically separated or spaced apart from each other, in other words there is no contact between the absorber regions 20 of the array 1. This ensures confinement of the photogenerated charge carriers in each absorber region 20 and therefore good MTF levels.

[0048] In order to improve the sensitivity of the photodiodes 100a, 100b to the incident radiation, the geometry of the absorbing region 20 is optimized to concentrate the incident radiation at the center of the photodiodes 100a, 100b.

[0049] According to the invention, the absorbing region 20 of each photodiode 100a, 100b has a convex shape towards the incident radiation 15. The convex geometric shape of the absorbing region 20 can adopt one of the following configurations, namely that its upper surface facing the incident radiation 15 is curved convex, preferably circular arc shaped, preferably hemispherical, truncated conical, truncated pyramidal or any three-dimensional geometric shape E (such as all segments terminating at E being completely contained within E) and that allows the upper surface facing the incident radiation to concentrate the radiation in the center of the lower surface of E located opposite the upper surface of E. Advantageously, this convex shape is configured to make the propagation direction of the radiation propagating in the photodiode deviate from the direction of the incident radiation. This convex shape of the absorbing region 20 is given by the shape of its upper surface 20a. The absorbing region 20 also has a lower surface 20b facing the upper surface 20a.

[0050] The convex shape of region 20 allows the incident radiation to be refracted towards the center of photodiodes 100a, 100b, thereby increasing the distance the radiation travels within absorbing region 20, thereby improving the radiation absorption and quantum yield of array 1. It is important to note that this refraction of radiation is greater when the radiation is incident on the side of top surface 20a of absorbing region 20, which occupies the majority of the surface area of ​​the photodiode.

[0051] The absorption region 20 is made on the basis of a semiconductor material, preferably one of the following materials: II-VI semiconductors, for example CdHgTe (or HgCdTe), III-V semiconductors, for example solid materials such as InAsSb, or even materials with an effective energy band structure that can be obtained, for example in the case of type II super arrays.

[0052] Advantageously, the absorber region 20 is doped, preferably with N-type doping. Furthermore, the absorber region 20 has a band gap energy E 20 The energy is adapted to be suitable for detecting radiation in a given spectral band, preferably in the mid-infrared. 20 The value of is between 0.23 eV and 0.3 eV at a given operating temperature.

[0053] Advantageously, the doping level of the absorption region 20 is 10 16 cm -3 Less than 2*10 15 cm -3 Less than 2*10 14 cm -3The low doping of the absorber regions 20 allows the photodiodes to operate like depleted PIN photodiodes at high operating temperatures. The reduction or even elimination of the free carriers in the absorber regions 20 reduces or even eliminates the Auger generation of dark current, leading to very high operating temperatures. In this case, the electrical isolation of the absorber regions 20 of the different photodiodes eliminates the modulation of the electric field according to the current that would be detected if the photodiodes were mixed with a CMOS circuit operating under direct injection. The operation of the photodiode array 1 in which the absorber regions 20 are depleted according to this embodiment is therefore more stable than would be expected for a matrix made according to the prior art.

[0054] For extraction of the charge carriers into a silicon multiplexing circuit, often made in CMOS (Complementary Metal Oxide Semiconductor) technology, each photodiode 100a, 100b further comprises a capture region 70 in contact with the absorption region 20 as shown in Figure 2. The capture region 70 typically comprises a conductive pad 50 connected to an input node of the CMOS circuit.

[0055] The capture region 70 may further comprise a collection region 30 located between the absorber region 20 and the conductive pad 50. The collection region 30 is based on a semiconductor material, preferably the same material as that constituting the absorber region 20, for example CdHgTe. If the collection region 30 and the absorber region 20 are based on the same semiconductor material, the composition of this semiconductor material may differ from one region 30 to the other region 20. For example, the cadmium present in the CdHgTe constituting the collection region 30 may be present in a different percentage than the cadmium present in the absorber region 20. The collection region 30 is in contact with the absorber region 20 and the conductive pad 50, and preferably ensures the transfer of charge carriers from the absorber region 20 to the pad 50.

[0056] Advantageously, the collection area 30 is 10 16 cm -33, which provides a good ohmic contact with pad 50 and limits the expansion of the space charge zone in region 30. Collection region 30 can have a doping type opposite to that of absorber region 20 according to a first embodiment, or the same doping type as absorber region 20 according to a second embodiment. These two specific embodiments will now be described in detail.

[0057] Preferably, each photodiode 100a, 100b comprises a passivation layer 40 that ensures its electrical, mechanical and chemical protection. Preferably, the passivation layer 40 is based on a material of the same group of semiconductors as the materials forming the covering region 10, the absorbing region 20 and the collecting region 30. If the covering region 10, the absorbing region 20 and the collecting region 30 are based on a II-VI material, for example CdHgTe, the passivation layer 40 is made based on another II-VI semiconductor material, for example ZnS. The passivation layer 40 is in contact with a part of the lower surface 20b of each photodiode 100a, 100b. The passivation layer 40 has openings 45a, 45b, each opening 45a, 45b facing the absorbing region 20 of a different photodiode 100a, 100b. The capture region 70 extends into the openings 45 a , 45 b in the passivation layer 40 to ensure electrical contact with the absorption region 20 .

[0058] Preferably, each photodiode 100a, 100b further comprises a covering region 10 based on a semiconductor material, preferably based on the same material as that constituting the absorber region 20, for example CdHgTe. If the covering region 10 and the absorber region 20 are based on the same semiconductor material, the composition of this semiconductor material can differ from one region 10 to the other region 20. For example, the cadmium contained in the CdHgTe constituting the covering region 10 can be present in a different percentage than the cadmium contained in the absorber region 20. The covering region 10 covers, preferably over its entirety, the upper surface 20a of the absorber region 20 facing the incident radiation. The covering region 10 can cover the entire surface of the array 1 continuously, so as to be continuous between the photodiodes 100a and 100b, or it can cover each different photodiode 100a, 100b discontinuously. The covering region 10 preferably has a constant or consistent thickness. This thickness is typically 0.1*h 20 ~0.25*h 20 Advantageously, the covering region 10 separates the photodiodes 100a, 100b from each other in the plane XY. The covering region 10 can therefore prevent minority carriers generated in the absorbing region 20 from diffusing between the photodiodes 100a, 100b of the array 1. This helps to increase the MTF of each photodiode 100a, 100b.

[0059] Preferably, the top surface 10a of the covering area 10 facing the incident radiation 15 has a convex shape towards the incident radiation. Said top surface 10a of the covering area 10 can adopt a curved convex shape, preferably a circular arc shape, preferably a hemispherical surface shape, a truncated cone surface shape or even a truncated pyramidal surface shape. Whatever the geometric shape of the top surface 10a of the covering area 10, it can cover the photodiodes 100a, 100b of the array 1 continuously between the photodiodes 100a and 100b or discontinuously between these different photodiodes. Moreover, advantageously, the top surface 10a of the covering area 10 and the top surface 20a of the absorbing area 20 can have the same type of geometric shape. For example, according to an advantageous embodiment, the top surface 10a of the covering area 10 and the top surface 20a of the absorbing area 20 both have a circular arc shape and are preferably concentric.

[0060] The coating region 10 has a band gap energy E 10 where E 10 >E 20 Preferably, the band gap energy E 10 is greater than 0.41 eV, which is favorable for the transparency of the coating layer 10 at wavelengths above 3 μm. 10 The high value of further reduces the effect of defects present on the top surface 10a of the photodiode that may induce excessive dark and noise currents. 10 A high value of also allows for a low absorption of the incident radiation 15 in the coating area 10 .

[0061] The covering region 10 can have the same doping type as the absorbing region 20 according to a first embodiment, or the opposite doping type to the absorbing region 20 according to a second embodiment. 16 cm -3 More than 10 17 cm -3The doping level is greater than 1.

[0062] The high doping level of the cladding region 10, when the cladding region 10 and the absorbing region 20 have N-type doping, results in an effective gap opening due to the Moss-Burstein effect. This gap opening induces a curvature of the valence band of the cladding region 10. This has the effect of limiting the interaction of minority charge carriers with defects present at the top surface 10a of the photodiode, thereby facilitating a lower dark current and an increased quantum yield of each photodiode.

[0063] Preferably, in the photodiodes 100a, 100b, both the coating region 10 and the collecting region 30 can have a rotational symmetry about one and the same axis (parallel to the drawing axis Z). The symmetrical configuration of the coating region 10 around the collecting region 30 in conjunction with the reduction of the number of free carriers in the absorbing region 20 allows a very high or even complete depletion of the absorbing region 20 with only a few or even no undepleted pockets, which makes it possible to limit the dark current.

[0064] According to a variant of an embodiment of the invention, the absorber region 20 comprises a gap opening zone 60 extending from the lower surface 20b of the absorber region 20 as shown in Fig. 2. The gap opening zone 60 has a band gap energy that varies along a so-called normal direction that is substantially perpendicular to the lower surface 20b of the absorber region 20. This normal direction corresponds to the Z direction in the drawing. Preferably, the gap opening zone 60 extends over the entire periphery of the collection region 30 projecting into the plane XY.

[0065] The absorptive region 20 has a maximum height h, typically measured along the normal direction. 20 If the absorbent region 20 has the shape of a spherical cap, this maximum height h 20 typically corresponds to the height of the spherical cap. If the absorbent region 20 has a truncated or pyramidal shape, the maximum height h 20corresponds to the height typically measured between its small and large bases. The gap opening zone 60 has a maximum height h along the normal direction 60 Advantageously, h 60 ≦0.5*h 20 and preferably h 60 ≦0.3*h 20 and preferably h 60 ≦0.1*h 20 The height h of the gap opening zone 60 60 is preferably 100 nm or more.

[0066] According to a variant of an embodiment of the invention, the upper surface 10a of the covering area 10 is covered with a transparent layer for the incident radiation at the photodiodes 100a, 100b of the array 1. This layer aims to improve the transmission of the incident radiation to the absorbing area 20 by means of a carefully selected refractive index according to the present application.

[0067] According to one variant of this embodiment of the invention, a conductive region arranged on the exterior of the photodiode array 1 makes it possible to establish an ohmic contact with the covering region 10 .

[0068] By varying the doping types of the absorbing region 20, the cladding region 10 and the collecting region 30, two main embodiments of the present invention can optionally be considered.

[0069] As shown in FIG. 3A, according to the first of these two embodiments, the covering region 10 has the same doping type as the absorbing region 20, preferably N-type. Furthermore, the collecting region 30 has the opposite doping type as the absorbing region 20, preferably P-type, and thus forms a pn-junction with the absorbing region 20 in each photodiode 100a, 100b of the array 1. The pn-junction thus formed induces the separation of the photogenerated charges in the absorbing region 20 and the extraction of the charges to the pad 50. When the covering region 10 and the absorbing region 20 are N-type doped, an effective gap opening is possible. This effective gap opening and the separation of the absorbing regions of each photodiode 100a, 100b imply that the charge carriers separated by each pn-junction of the individual photodiodes are the charge carriers generated in the absorbing region 20 of the same photodiode. As a result, the MTF of the array 1 made according to this first embodiment is improved.

[0070] As shown in FIG. 3B, according to the second of these two embodiments, the covering region 10 has the opposite doping type, preferably P-type, of the absorbing region 20, thus forming a pn-junction with the absorbing region 20 in each diode of the array 1. This pn-junction therefore allows the holes generated in the absorbing region 20 to be collected separately. The non-continuous nature of the absorbing region of each photodiode 100a, 100b results in the charge carriers separated by each pn-junction of the individual photodiodes being the charge carriers generated in the absorbing region 20 of the same photodiode. This improves the MTF of the array 1 made according to this second embodiment. Furthermore, the collecting region 30 has the same doping type, preferably N-type, as the absorbing region 20. This promotes a good ohmic contact with the pad 50.

[0071] Example of a manufacturing method enabling the realization of an array according to the invention An array 1 according to the invention comprising all the elements detailed above can be produced by a method comprising the following successive steps. 1. First, an epitaxially grown layer, preferably based on a CdHgTe material, is produced on a substrate, preferably based on a CdZnTe material, by liquid phase growth or molecular jetting. 2. Doping species are locally implanted in the epitaxially grown layer in zones that will form the collection regions 30 of the array 1 and of each photodiode 100a, 100b of the arrays 1. The doping species are preferably acceptor-type dopants and are preferably chosen from among the elements As and Sb. 3. A passivation layer 40 is then deposited over the epitaxially grown layers. 4. The assembly is then annealed, preferably under Hg pressure, to activate the local dopants, thus forming the collection region 30. This annealing then makes it possible to form the absorber region 20 by filling the potential gap with Hg ions and by carrying out an N-type doping in the epitaxially grown layer. This annealing then makes it possible to form the gap opening zone 60 by interdiffusion with a passivation layer 40, preferably made on the basis of the same semiconductor material as the absorber region 20. 5. Openings 45a, 45b are then locally etched in the passivation layer 40. Each opening 45a, 45b faces an individual collection area 30. 6. A pad 50 based on a conductive material is then locally deposited at each photodiode 100a, 100b of each array 1, in the openings 45a, 45b of the passivation layer 40, 45a, 45b and preferably in contact with the lower surface 40b of the passivation layer 40. 7. Etching of the substrate is performed around the periphery of each detector array 1 to form openings associated with each detector array 1. A continuous metal layer is then formed locally on the pads 50 of each photodiode array and in the openings associated with that array to form common contacts for all photodiodes 100a, 100b of each array 1. 8. The arrays 1 made from the same wafer are then cut to achieve the assembly of preferably identical arrays 1. Therefore, the following steps are carried out for each array individually with reference to the array 1 of the present invention. 9. The array 1 is then hybridized with a read-out circuit implemented in Si-CMOS technology. 10. The substrate on which the epitaxially grown layers are formed is then removed by polishing, chemical etching, or a combination of both. 11. The absorbent areas 20 of the array 1 are then structured in a convex shape. Preferably, this structuring is carried out by transfer of greyscale lithography, which results in a complex structure in the resin layer. This convex structure is then transferred into the absorbent areas 20 by dry etching, preferably ion etching. 12. The electrical properties of the surface portion of the absorber region 20 are then modified by a high doping level to form the covering region 10. This doping is preferably N-type, which results in effective gap opening due to the Moss-Burstein effect. The doping and modification of the band gap of the covering region 10 can be achieved by ion implantation of an element that acts as a donor in semiconductors, such as element B.

[0072] This method can be performed to fabricate a single array or multiple different arrays on a substrate, and in fact the steps can be performed simultaneously to form multiple arrays as well as multiple photodiodes.

[0073] The invention is not limited to the above-described embodiments, but extends to all embodiments falling within the scope of the invention. [Explanation of symbols]

[0074] 1 Photodiode array 10 Covering area, covering layer 10a top surface 15 Incident radiation 20 Absorption Area 20a top side 20b Bottom side 30 Collection Area 40 Passivation Layer 40b Bottom side 45a opening 45b opening 50 Conductive Pad 60 Gap Opening Zone 70 Capture area, capture zone 100a photodiode 100b Photodiode E 10 First band gap energy E 20 Second band gap energy

Claims

1. 1. An array (1) of at least two photodiodes (100a, 100b), each photodiode comprising an absorption region (20) and a capture region (70), the capture region (70) comprising a conductive pad (50), the absorption region (20) being in contact with the capture region (70), the absorption region (20) being configured to absorb radiation incident on the photodiode and to allow diffusion of charge carriers, each absorption region (20) being separated from the other absorption regions (20), characterized in that the absorption region (20) of each photodiode (100a, 100b) is convex towards the incident radiation.

2. Each photodiode (100a, 100b) further comprises a coating region (10) based on a first semiconductor, said coating region (10) covering a top surface (20a) of said absorbing region (20) facing said incident radiation, said coating region (10) having a first band gap energy E １０ Array (1) according to claim 1, having:

3. The first band gap energy E １０ The array (1) of claim 2, wherein the .lambda.

4. The absorption region (20) has a second band gap energy E ２０ where E １０ >E ２０ The array (1) according to claim 2 or 3,

5. 5. The array (1) according to any one of claims 2 to 4, wherein the upper surface (10a) of the covering area (10) facing the incident radiation has a convex surface towards the incident radiation.

6. Array (1) according to any one of claims 1 to 5, wherein the absorption area (20) of each photodiode (100a, 100b) has a curved convex shape.

7. 7. The array (1) according to claim 6, wherein the absorption area (20) of each photodiode (100a, 100b) has an arcuate shape, preferably a hemispherical shape.

8. 8. The array (1) of claim 1, wherein the capture region (70) further comprises a collection region (30) located between the absorption region (20) and the conductive pad (50), the collection region (30) being based on a third semiconductor, the collection region (30) being in contact with the absorption region (20) and the conductive pad (50).

9. 9. The array (1) of claim 1, further comprising a passivation layer (40) in contact with a lower surface (20b) of the absorption region (20) opposite an upper surface (20a) of the absorption region (20) facing the incident radiation, the passivation layer (40) having openings (45a, 45b), each opening (45a, 45b) facing the absorption region (20) of a different photodiode (100a, 100b), the capture region (70) of the photodiode (100a, 100b) extending into the openings (45a, 45b).

10. 10. The array (1) according to any one of claims 1 to 9, wherein the absorber region (20) comprises a gap opening zone (60) extending from a lower surface (20b) of the absorber region (20) opposite to a top surface (20a) of the absorber region (20) facing the incident radiation, the gap opening zone (60) having a band gap energy that varies along a direction substantially perpendicular to the lower surface (20b) of the absorber region (20), the so-called normal direction.

11. Array (1) according to any one of claims 1 to 10 in combination with claim 2, wherein the covering region (10) and the absorbing region (20) are doped, the covering region (10) having the same doping type as the absorbing region (20).

12. Array (1) according to claim 11 in combination with claim 8, wherein the collecting region (30) has an opposite doping type to the absorbing region (20).

13. Array (1) according to any one of claims 1 to 10 in combination with claim 2, wherein the covering region (10) and the absorbing region (20) are doped, the covering region (10) having an opposite doping type to the absorbing region (20).

14. Array (1) according to claim 13 in combination with claim 8, wherein the collecting region (30) and the absorbing region (20) have the same doping type.

15. Array (1) according to any one of claims 1 to 14 in combination with claim 2, wherein the covering regions (10) of at least two of the photodiodes (100a, 100b) form a continuous layer.

16. The absorbent region (20) is 10 １６ cm －３ Less than 2*10 １５ cm －３ Less than 2*10 １４ cm －３ Array (1) according to any one of claims 1 to 15, having a doping level of less than 1000 nm.

17. The covering region (10) is 10 １６ cm －３ More than 10 １７ cm －３ Array (1) according to any one of claims 1 to 16 in combination with claim 2, having a doping level of more than

18. The collection area (30) is 10 １６ cm －３ Array (1) according to any one of claims 1 to 17 in combination with claim 8, having a doping level of more than

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