Low-current dark detector device for the detection of ionizing radiation

Abstract

The invention relates to a radiation detection structure (PDS) formed by a stack of layers comprising: an absorption layer (CA) made of a perovskite-structured material, an upper electrode (EL1), and a lower electrode (EL2). The absorption layer (CA) is positioned between the lower and upper electrodes. The stack further comprises a blocking layer (CB) made of a dielectric material, confined between: on the one hand, the absorption layer (CA), and on the other hand, an electrode selected from the upper electrode (EL1) or the lower electrode (EL2). The blocking layer (CB) includes at least one discontinuity (V1, V1) filled by the perovskite-structured material or by a third conductive material so as to form a direct electrical contact zone (DEZ) between the absorption layer (CA) and the electrode (EL1, EL2). See Fig. 1a for the abstract.

Description

Title of the invention: Low-current dark detector device for the detection of ionizing radiation

[0001] The present invention relates to the field of electronic and optoelectronic devices for the detection of ionizing radiation such as X-rays, gamma rays, alpha and beta charged particles, and neutrons. More particularly, the invention relates to multilayer planar radiation absorption structures based on perovskite-type materials.

[0002] The relevant technical field is the realization of hybrid systems, comprising: a conversion section based on at least one sensitive element for generating electric charge carriers from incident photons or particles; and an electronic section consisting of a readout circuit mounted wholly or partially on a substrate and for individually reading the signal from each pixel of the conversion section. Generally, the conversion section comprises an absorption layer confined between two electrodes. The semiconductor absorption layer converts the incident radiation into negative charge carriers ("electrons") in the conduction band and positive charge carriers ("holes") in the valence band. The materials used to create the absorption layer and the thickness of the absorption layer determine the proportion of radiation absorbed according to its energy.In the context of the invention, a radiation detection structure is understood to be a structure capable of converting ionizing radiation into an electronic signal readable by a reading circuit. The term ionizing radiation covers, by way of example, X-rays, gamma rays, alpha and beta charged particles, and neutrons.

[0003] Devices for the direct detection of ionizing radiation (X-rays) require absorption layers with larger lateral dimensions (width, length) compared to most other optical detection devices. Conventional materials used to produce absorption layers in this field are either incompatible with these large dimensions and reasonable manufacturing costs (e.g., single-crystal CdxZni xTe or CdTe), or have limited absorption at the high energies required for general radiography (e.g., amorphous selenium).

[0004] In this context, semiconductor materials with a perovskite-type crystal structure offer emerging solutions for the fabrication of absorption and conversion structures in optoelectronic devices. This type of material makes it possible to fabricate absorption layers with lateral dimensions greater than 10 cm while maintaining conversion performance comparable to that of conventional materials. For the purposes of this invention, a "perovskite layer" is defined as a layer made of a semiconductor material having a perovskite-type or perovskite-like crystal structure. In the context of this invention, the perovskites used may be 0D perovskites, 1D perovskites, 2D perovskites, 3D perovskites, or a mixture of these different perovskites.

[0005] A 0D perovskite is a perovskite-based crystalline material with a zero-dimensional nanometric structure. This means that the atoms in the crystal structure are arranged uniformly in a nanometric-scale configuration.

[0006] A 1D perovskite is a perovskite-based crystalline material with a linear, one-dimensional structure. This means that the atoms in the crystal structure are arranged uniformly along a single direction. 1D perovskites can take the form of nanowires, nanotubes, or nanofibers.

[0007] A 2D perovskite is a perovskite-based crystalline material with a two-dimensional planar structure. This means that the atoms in the crystal structure are arranged uniformly on a planar surface. 2D perovskites can take the form of ultrathin sheets or sheets. Examples include Ruddlesden-Popper or Dion-Jacobson perovskite structures.

[0008] A 3D perovskite is a perovskite-based crystalline material with a three-dimensional structure. This means that the atoms in the crystal structure are arranged uniformly in three-dimensional space. 3D perovskites can take the form of bulk crystals or crystalline powders.

[0009] The perovskite advantageously has an ABX3 type composition with: - Selected from an initial set of elements: • inorganic cations such as cesium Cs, rubidium Rb, potassium K, sodium Na, or lithium Li; • organic cations such as MA (methylammonium)=CH3-NH 3+, FA (formamidinium)=CH5N2+, GA (guanidinium)=CH6N3+; EA (ethylammonium)=CH3CH2NH3+; DMA (dimethylammonium)=C 2H6NH2+; AC (acetamidinium) = C2H3N2H4+; AZ (azetidinium)=C 3H6NH2+; TBA (tetrabutylammonium) = C4H9NH3+; PYRI (pyridium)=C5H5NH+; PYRO (pyrrolidium) = C4H8NH2+; isoP (iso-propylammonium)=C3H7NH3+; PIP (piperidium)= C5Hi0NH2+ • or an alloy of said elements from the first set of elements; - B selected from a second group of elements among: • inorganic cations such as lead Pb, tin Sn, germanium Ge, silicon Si, Sr, Ba, Eu, Tm, Yb, Hg; • organic cations such as MDABCO=N-methyl-1,4-diazabicyclo[2.2.2]octane, ODABC=N-hydroxy-N'-diazabicyclo[2.2.2]octonium; • or an alloy of said elements from the second set of elements; - X selected from a third set of elements among halogens such as bromine Br, iodine I, chlorine Cl, fluorine F or an alloy of said elements from the third set of elements.

[0010] Alternatively, perovskite has the formula A2C1+D3+X6> with: - A, X selected respectively from the first set of elements and the third set of elements; - C selected from a fourth group of elements among: • inorganic cations such as gold Au, silver Ag, copper Cu, thallium Tl, lithium Li; cesium Cs, sodium Na, rubidium Rb, potassium K; • or an alloy of said elements from the fourth set of elements; - D selected from a fifth group of elements among: • inorganic cations such as gold Au, aluminium Al, gallium Ga, indium In, tin Sn, bismuth Bi, antimony Sb; • or an alloy of said elements from the fourth set of elements;

[0011] Alternatively, the perovskite has the formula A2B4+X6 or A3B23+X9 with A, B, X selected respectively from the first set of elements, the second set of elements and the third set of elements.

[0012] We commonly speak of an organic-inorganic hybrid perovskite if the composition of the perovskite contains carbonaceous elements, and of an inorganic perovskite if the composition of the perovskite does not contain carbonaceous elements.

[0013] A problem to be solved in radiation detection devices, and more particularly image detectors, concerns the minimization of dark currents. Dark current represents the residual electrical flux through the detection device in the absence of radiation and in darkness. Strong dark currents generate signal background noise that hinders the detection of radiation fluxes below a certain threshold, while also limiting the sensor's dynamic range. Perovskite-based detectors typically exhibit dark currents on the order of pA / cm². For certain applications, such as flat panels used in medical radiography, technical specifications require dark currents on the order of nA / cm², which is three decades lower than the values ​​obtained with state-of-the-art solutions. Thus, it is necessary to find solutions for minimize dark current in perovskite detectors to meet increasing performance and accuracy requirements in various application areas.

[0014] The value of the dark current in optoelectronic devices depends on several factors, including the volumetric and surface effects of the semiconductor layer used for conversion. Volumetric effects include the band gap of the semiconductor material as well as point defects and chemical impurities in the semiconductor layer. These defects can, among other things, generate trapping levels in the band gap that can generate charge carriers under the effect of thermal agitation. These parameters influence the free charge density in the volume without irradiation, which increases the detector's dark current. Surface effects include surface conduction effects and the parasitic injection of electronic charges via the contact electrodes.For the detector to function correctly, polarization is necessary to create an electric field between the two electrodes and transport the charges generated during radiation exposure. However, in the absence of radiation, this polarization can cause charges to be injected from the electrodes into the conversion layer, which can generate dark current.

[0015] A technical problem to be solved is therefore to reduce the dark current of perovskite optoelectronic devices to achieve dark current values ​​on the order of nA / cm2.

[0016] A first known method for limiting dark currents in a detector structure is to use electrodes with different work outputs, one with a high work output (anode) and one with a low work output (cathode). This creates rectifying contacts, called Schottky contacts, for injecting charges from the electrodes into the semiconductor in the dark, while allowing the collection of charges generated from the semiconductor to the electrodes during illumination. However, obtaining good rectifying contacts requires surface states of the conversion layer that are difficult to achieve experimentally, especially in the case of a perovskite absorbing layer. Surface defects generate electron traps that modify the energy barrier between the semiconductor and the electrodes, thus preventing the formation of the rectifying contact and limiting the dark current blocking efficiency.

[0017] US patent US200201955662A1 describes an X-ray detector structure in which a dielectric layer is inserted between the upper electrode and the amorphous selenium absorption layer. The drawback of the solution described in this document is that the current generated following illumination is reduced due to the dielectric layer, thus reducing the sensitivity of the detector. Furthermore, the The described solution presents another drawback resulting from the fact that the dielectric interface can become electrically charged, causing parasitic temporal effects during successive image acquisitions.

[0018] To overcome the limitations of existing solutions regarding the reduction of dark current in a perovskite detector structure, the invention proposes several embodiments of a detector structure formed by a stack of layers in which a discontinuous dielectric blocking layer is arranged between the perovskite absorption layer and at least one charge-collecting electrode. Discontinuities in the blocking layer allow for the establishment of localized areas of direct electrical contact between the absorption layer and the charge-collecting electrode. The invention thus makes it possible to minimize the dark current without compromising the overall performance of the detector.

[0019] More specifically, the invention proposes solutions for obtaining dark currents below 5 nA / cm² without degrading detector sensitivity, thanks to the structure of the blocking layer according to the invention. In the context of the invention, sensitivity is characterized by the number of electrical charges generated for a given radiation dose and detector area.

[0020] The detector structure according to the invention makes it possible to design optoelectronic devices that meet the constraints of dark current and performance in various applications such as medical imaging (radiology, mammography, tomography...), non-destructive industrial inspection, security, scientific instruments.

[0021] The invention further proposes a method for manufacturing the detector structure according to the invention based on the "close-space sublimation" (CSS) technique. The use of the "close-space sublimation" technique is well established for producing perovskite layers.

[0022] In the context of the invention, in a layer stack, the term "confined layer" is interpreted as follows: when a layer is said to be "confined" between a first layer and a second layer, this means that said layer is arranged between the first layer on the one hand and the second layer on the other hand and that said confined layer is in physical contact with the first layer and with the second layer.

[0023] In the context of the invention, in a stack of layers, when a layer is said to be "arranged" between a first layer and a second layer, this means that said layer is placed between, on the one hand, the first layer and, on the other hand, the second layer, either directly with contact with the first and second layers or indirectly with the presence of one or more layers intermediates which separate said layer from the first layer and / or the second layer.

[0024] The invention relates to a radiation detection structure formed by a stack of layers comprising: - an absorption layer, made of a perovskite structure material, designed to convert an incident ray into electrical charges; - an upper electrode comprising at least one layer of a first conductive material, intended to collect electrical charges; - and a lower electrode comprising at least one layer of a second conductive material, intended to collect electrical charges; The absorption layer is arranged between the lower and upper electrodes. This stack further comprises a blocking layer, made of a dielectric material, confined between: on the one hand, the absorption layer, and on the other hand, an electrode selected from either the upper or lower electrode. The blocking layer includes at least one discontinuity filled by said perovskite-structured material or by a third conductive material so as to form a zone of direct electrical contact between the absorption layer and said electrode.

[0025] According to a particular aspect of the invention, the blocking layer is confined between the absorption layer and the upper electrode. The absorption layer has surface protrusions. Each discontinuity in the absorption layer is filled by a protrusion and opens towards the upper electrode so as to form at least one area of ​​direct electrical contact.

[0026] According to a particular aspect of the invention, the protuberances are in pyramidal or granular or columnar form or mesas.

[0027] According to a particular aspect of the invention, the height of a protuberance is between Ipmet lOOpm.

[0028] According to a particular aspect of the invention, the protrusions are separated by slots; the slots being filled with a semiconductor or conductive material so as to create a charge-carrying bridge between two adjacent protrusions.

[0029] According to a particular aspect of the invention, a direct electrical contact zone is formed by at least one through-through through the blocking layer and filled by the third conductive material or by the perovskite structural material.

[0030] According to a particular aspect of the invention, the sum of the contact areas between the direct electrical contact zones and the chosen electrode is less than 10% of the overall surface area of ​​said radiation detection structure.

[0031] According to a particular aspect of the invention, the radiation detection structure further comprises a protective layer disposed between the lower electrode and the absorption layer. The protective layer is made of an inert dielectric material. chemically relative to the absorption layer. The blocking layer is confined between the absorption layer and the upper electrode.

[0032] According to a particular aspect of the invention, the resistivity of the blocking layer is greater than 108 ohm.cm.

[0033] According to a particular aspect of the invention, the blocking layer is made of zirconia oxide stabilized with yttrium oxide (ZrO2:Y2O3).

[0034] According to a particular aspect of the invention, the dielectric material of the blocking layer comprises nitrogen and / or oxygen and / or carbon.

[0035] According to a particular aspect of the invention, the perovskite structure material is a compound material ABX3; A being selected from a first group of inorganic cations comprising cesium, rubidium, potassium or an alloy of said elements of the first group of inorganic cations; B being selected from a second group of inorganic cations comprising lead, tin, germanium, silicon or an alloy of said elements of the second group of inorganic cations; X being selected from a group of halogens comprising bromine, iodine, chlorine or an alloy of said elements of the group of cations.

[0036] The invention also relates to a radiation detection device comprising a pixel matrix including at least one pixel formed by means of the radiation detection structure according to the invention.

[0037] The invention also relates to a method for manufacturing a radiation detection structure comprising the following steps: - Depositing an absorption layer of a perovskite-structured material onto a substrate using near-space sublimation to obtain a rough upper surface with a plurality of protrusions - deposit a blocking layer, made of a dielectric material, on said upper surface with a thickness chosen so as to obtain at least one protrusion which opens from the upper surface of the blocking layer; - deposit a layer of conductive material on the blocking layer acting as the upper electrode covering all the protrusions that emerge from the blocking layer.

[0038] The invention also relates to a method for manufacturing a radiation detection structure comprising the following steps: - deposit an absorption layer of a perovskite structure material onto a support; - to form protrusions on the upper surface of the absorption layer; - deposit a blocking layer, made of a dielectric material, on the upper surface with a thickness chosen so as to obtain at least one protrusion which opens from the upper surface of the blocking layer; - place the upper electrode, made of a conductive material, on the blocking layer so as to cover all the protrusions protruding from the blocking layer.

[0039] The invention also relates to a method for manufacturing a radiation detection structure comprising the following steps: - deposit an absorption layer of a perovskite structure material onto a support; - deposit a blocking layer, made of a dielectric material, on the upper surface; - form at least one through-through the blocking layer - deposit a layer of conductive material on top of the blocking layer acting as the upper electrode so as to fill the vias with the conductive material and obtain a blocking layer comprising at least one discontinuity corresponding to said via.

[0040] The invention also relates to a method for manufacturing a radiation detection structure comprising the following steps: - deposit a blocking layer, made of a dielectric material, on the upper surface of a support comprising at least one lower electrode; - form at least one via opening through the blocking layer; - deposit an absorption layer of a perovskite-structured material on the blocking layer; - deposit a layer of conductive material on the absorption layer acting as the upper electrode.

[0041] Other features and advantages of the present invention will become more apparent from the following description in relation to the following accompanying drawings.

[0042] [Fig. la] illustrates a cross-sectional view of a radiation detection structure according to a first embodiment of the invention.

[0043] [Fig.lb] illustrates a cross-sectional view of a variant of the radiation detection structure according to the first embodiment of the invention.

[0044] [Fig.2a] illustrates a microscopic cross-sectional view of the upper surface of the absorption layer of the radiation detection structure according to the first embodiment of the invention.

[0045] [Fig.2b] illustrates a top microscopic view of the upper surface of the absorption layer of the radiation detection structure according to the first embodiment of the invention.

[0046] [Fig.2c] illustrates a zoomed microscopic cross-sectional view of the upper surface of the absorption layer of the radiation detection structure according to the first embodiment of the invention.

[0047] [Fig.3a] illustrates a cross-sectional view of a radiation detection structure according to a second embodiment of the invention.

[0048] [Fig.3b] illustrates a zoomed cross-sectional view of a radiation detection structure according to the second embodiment of the invention.

[0049] [Fig.3c] illustrates a top microscopic view of the upper surface of the absorption layer of the radiation detection structure according to the second embodiment of the invention.

[0050] [Fig.4] illustrates a cross-sectional view of a radiation detection structure according to a third embodiment of the invention.

[0051] [Fig.5] illustrates a cross-sectional view of a radiation detection structure according to a fourth embodiment of the invention.

[0052] [Fig.6] illustrates a cross-sectional view of a radiation detection structure according to a fifth embodiment of the invention.

[0053] [Fig.7] illustrates a cross-sectional view of an optoelectronic DI device comprising a radiation detection structure according to the invention.

[0054] [Fig.8a] illustrates a method for manufacturing a radiation detection structure according to a first embodiment of the invention.

[0055] [Fig.8b] illustrates a method of manufacturing a radiation detection structure according to a second embodiment of the invention.

[0056] [Fig.8c] illustrates a method of manufacturing a radiation detection structure according to a third embodiment of the invention.

[0057] [Fig.8d] illustrates a method of manufacturing a radiation detection structure according to a fourth embodiment of the invention.

[0058] Fig. 1a illustrates a cross-sectional view of an SPD radiation detection structure according to a first embodiment of the invention.

[0059] The SPD radiation detection structure is formed by a stack of layers along a Z-shaped stacking direction. The layer stack comprises an absorption layer CA, an upper electrode ELI, a lower electrode EL2, and a blocking layer CB. The absorption layer CA is made of a perovskite-structured material and is designed to convert an incident ray into positive and negative electrical charges. The upper electrode ELI, made of a conductive material, is designed to collect electrical charges of a predetermined sign, in this case, of the holes. The lower electrode EL2, made of a conductive material, is designed to collect oppositely charged electrons. The blocking layer CB, made of a dielectric material, is designed to limit the dark current in the SPD radiation detection structure. The absorption layer CA is located between the upper electrode ELI and the lower electrode EL2. The blocking layer is confined between the upper electrode ELI and the absorption layer CA. In the case of a pixel array created by arranging several detector structures according to the invention, the absorption layer CA, the blocking layer CB, and the upper electrode ELI can be shared between pixels. Pixelation is achieved by the separate lower electrodes EL2, which form the array.

[0060] The absorption layer is made of a perovskite-structured material, for example, CsPbBr3. For a DI detection device for X-rays or gamma rays, the thickness of the CsPbBr3 absorption layer CA is between 100 nm and 5000 pm. Those skilled in the art can adapt the thickness of the absorption layer CA according to the intended application. More specifically, when the DI detection device is intended for mammography, the average value of the absorbed energy spectrum is 20 keV. Thus, the absorption layer CA has a thickness between 50 pm and 300 pm, preferably 200 pm. Alternatively, when the DI detection device is intended for medical radiology with an average value of the absorbed energy spectrum of 50 keV, the absorption layer CA has a thickness between 300 pm and 1500 pm, preferably 1000 pm.Alternatively, when the DI detection device is intended for medical radiology with a central value of the absorbed energy spectrum of 90keV, the CA absorption layer has a thickness between 800pm and 2500pm, preferably equal to 2000pm.

[0061] The lower electrode EL2 is made of an electrically conductive material. For example, the lower electrode EL2 is made of indium tin oxide (ITO). For example, the lower electrode EL2 has a thickness between 50 nm and 1000 nm, preferably 200 nm.

[0062] Alternatively, the lower electrode EL2 is formed by a stack of layers comprising an electrically conductive layer and an intermediate semiconductive layer forming part of the lower electrode EL2. The intermediate semiconductive layer may be intercalated between the electrically conductive layer and the blocking layer CB.

[0063] The upper ELI electrode is made of a metal (chromium for example) or a conductive oxide (ITO for example) with a thickness between 50 nm and 1000 nm (preferably 200 nm). Alternatively, the upper ELI electrode is composed of a stack of metallic layers and conductive oxide. Alternatively, the upper ELI electrode is formed by a stack of layers comprising an electrically conductive layer and a semiconducting intermediate layer that is part of the upper ELI electrode. The semiconducting intermediate layer can be sandwiched between the electrically conductive layer and the CB blocking layer. Other types of conductive layers can also be used. These alternatives include metals, conductive polymers, carbon-based inks, carbon nanotubes, and metallic nanowires. As a reminder, an electrical voltage VDD is applied between the upper ELI electrode and the lower EL2 electrode to collect the generated charges towards both electrodes.

[0064] The CB blocking layer, made of a dielectric material, is confined between the upper surface of the CA absorption layer and the upper ELI electrode. The CB blocking layer, with a thickness between 1 m and 100 pm, is composed of an insulating dielectric material. It has a high resistivity greater than 10⁸ ohm·cm, preferably greater than 10¹² ohm·cm. The resulting resistivity reduces the measured dark currents to values ​​below 5 nA / cm². Possible dielectric materials include, but are not limited to, a range of organic and / or silicone polymers, thermosetting resins, oxides, or photolithography resins. In the example shown in [Fig. 1a], the CB blocking layer has a uniform thickness λ over the entire surface of the detection structure.The thickness el of the CB blocking layer is defined by the distance separating, on the one hand, the upper surface of the CB blocking layer and, on the other hand, the level of the base of the protuberances.

[0065] More particularly, the CB blocking layer can be made of a variety of materials, including organic polymers such as cellulose derivatives, polyolefins, styrenic polymers, chlorinated vinyl polymers, acrylic polymers, fluorinated polymers, polyethers, polyamides, polyesters, sulfur-containing polymers, polyurethanes, and poly(p-xylylene) (parylene C, parylene N, parylene D, parylene F-VT4, parylene F-AF4).

[0066] Alternatively, the blocking layer may be composed of thermosetting polymers such as phenoplasts, aminoplasts, unsaturated polyesters, epoxies, polyurethanes, polyimides, and silicones. It may also be a cured photolithography resin, such as an epoxy resin. Furthermore, it may be an oxide such as Al₂O₃, SiO₂, Si₃N₄, ZnO, ZTO, ZrO₂, SnO₂, ZrO₂:Y₂O₃, TiO₂, SrTiO₃, CaTiO₃, BaTiO₃, or CaSiO₃.

[0067] It is also possible to combine these materials in the form of a mixture and / or stacking of the aforementioned materials in any of the directions of space.

[0068] Advantageously, the composition and deposition method of the CB blocking layer as described make it possible to limit charge trapping at the perovskite / dielectric interface and reduce charge accumulation in the absence of illumination. The presence of chemical groups based on nitrogen, oxygen, sulfur, and phosphorus exhibiting Lewis base-like character is, for example, well suited.

[0069] The upper surface of the perovskite CB absorption layer exhibits a plurality of protrusions 11, 11'. The protrusions can be obtained spontaneously following the growth of the perovskite CA absorption layer by the "close-space sublimation" (CSS) technique. In this case, the protrusions 11, 11' have non-uniform heights hl; the number and spatial distribution of the protrusions are random. In the illustrated example, the protrusions 11 have a greater height than the protrusions 11'. Alternatively, the protrusions are microstructured on the upper surface of the CA absorption layer using microstructure fabrication techniques such as mechanical etching, molding, laser etching, lithography, photolithography followed by chemical and / or dry, chemical and / or physical etching.In this case, the dimensions and number of protrusions are better controlled and the height hl can be uniform.

[0070] The protrusions 11,11' may be pyramidal, granular, columnar, or mesa-shaped. A "mesa" is defined as any structure projecting from the upper surface of the absorption layer CA. In cases where the protrusions 11 result spontaneously from a sublimation deposition process in near-space CSS, the predominant shape is pyramidal. By way of non-limiting example, the height of the protrusions is between 1 pm and 100 pm. Alternatively, the protrusions may exhibit random and uncontrolled protruding shapes.

[0071] The blocking layer CB deposited on the irregular surface of the absorption layer CA thus presents discontinuities filled by perovskite protrusions. The thickness e1 of the blocking layer CB is less than a set of protrusions 11, such that said protrusions open onto the upper electrode ELI through the entire thickness of the blocking layer CB. A through protrusion 11 that opens onto the electrode thus forms a direct electrical contact zone ZCD located between the absorption layer CA and the upper electrode ELI. The direct electrical contact zones ZCD prevent the degradation of the detector's sensitivity and reduce the residual signal. corresponds to the persistence of the signal from a first image acquisition on the next image relative to known solutions.

[0072] Advantageously, for each direct electrical contact zone ZCD, the height hl of a protrusion 11 is greater than twice the thickness el of the blocking layer CB. This maximizes the contact area between the protrusion 11 and the upper electrode ELI. Advantageously, the area of ​​a direct contact zone ZCD is between 1pm² and 100pm² and preferably between 1pm² and 10pm².

[0073] Advantageously, the sum of the contact areas between the direct electrical contact zones ZCD and the upper electrode ELI is less than 10% of the overall surface area of ​​the SPD radiation detection structure, forming a pixel, along the X,Y plane orthogonal to the stacking axis Z. This makes it possible to obtain a good compromise between, on the one hand, the limitation of dark currents and, on the other hand, the sensitivity of the SPD radiation detection structure.

[0074] In [Fig. 1a], illustrating the first embodiment, the blocking layer CB has a uniform thickness εl over the entire surface of the detection structure. However, the uniformity of the thickness εl depends on the deposition technique used to manufacture the blocking layer CB. [Fig. 1b] shows a cross-sectional view of a variant of the SPD detection structure according to the first embodiment of the invention, in which the thickness εl of the blocking layer CB exhibits variations due to the constraints of the deposition processes used. In this case, a direct electrical contact zone ZCD is obtained when the thickness of the blocking layer CB is less than the height of the protrusion locally at the level of said protrusion 11, 11”. This is referred to as a localized εl<εl inequality at the level of the protrusion.On the one hand, the height hliocai is defined as the distance along the Z-axis separating the apex of the prominence from its base. On the other hand, the thickness eliocai is defined as the distance along the Z-axis separating, on the one hand, the highest point of the blocking layer CB in the vicinity of the associated prominence and, on the other hand, the base of said prominence. Thus, in this case, the inequality criterion eliocai < hliocai is not evaluated absolutely but locally, relative to each prominence 11,11”.

[0075] Figure 2a illustrates a cross-sectional microscopic view of the upper surface of the absorption layer of the SPD radiation detection structure according to the first embodiment of the invention. It shows protrusions 11 extending along the Z-stack direction on the upper surface of a perovskite CA absorption layer deposited by CSS. Figure 2b illustrates a top microscopic view of the upper surface of the perovskite CA absorption layer deposited by CSS. Figure 2c illustrates a zoomed microscopic view in section of the protuberances 11 which extend along the Z stacking direction on the upper surface of a perovskite CA absorption layer deposited by CSS.

[0076] Figure 3a illustrates a cross-sectional view of an SPD radiation detection structure according to a second embodiment of the invention. The SPD radiation detection structure according to the second embodiment retains the characteristics and advantages of the first embodiment. When the protrusions 11, 11' are spontaneously obtained following CSS deposition of the absorption layer CA, slits 12 (or crevices) appear between the protrusions 11, 11'. The slits 12 propagate through the volume of the absorption layer CA and limit the sensitivity of the detector by reducing the number of charges collected by the upper electrode ELI. The protrusion 11 has a height greater than the thickness of the blocking layer CB, thus creating a direct electrical contact zone ZCD. The charges generated within the volume of the protrusion 11 can migrate to the upper electrode ELI through the direct electrical contact zone ZCD.The prominence 11' has a height less than the thickness of the blocking layer CB and is completely covered by the blocking layer CA. The charges generated within the volume of the prominence 11' are trapped and cannot be collected because the upper electrode ELI is isolated laterally by the slots 12 and above by the blocking layer CB. This leads to a reduction in the number of charges collected by the detector in response to an incident ray. To resolve this problem, the SPD radiation detection structure according to the second embodiment further includes a conductive or semiconducting layer 13 confined between the blocking layer CB and the absorption layer CA. The conductive or semiconducting material of layer 13 fills the slots 2 and the space separating the adjacent prominences 11 and 11', thus creating a bridge that carries the charges generated in the covered prominence 11'.This improves the sensitivity of the SPD radiation detection structure. The material of layer 13 can be a polymer semiconductor (such as PT AA, PBDTTT-C, MEH-PPV, PVD4650, TFB, F8BT) or semiconductor oligomer molecules (such as pentacene, TIPS-pentacene, anthradithiophene derivatives, acene diimide or perylene diimide) or any other inorganic or organic-inorganic hybrid semiconductor.

[0077] Figure 3b illustrates a zoomed cross-sectional view of the area comprising the prominences 11 and 11' in the SPD radiation detection structure according to the second embodiment. The zoomed area has been circled in Figure 3a. The charges generated in the covered prominence 11' can migrate to the uncovered prominence 11 through the charge-carrying bridge 13 to be collected by the upper electrode ELI via the direct electrical contact zone ZCD.

[0078] Figure 3c illustrates a top-view microscopic image of the upper surface of the CA absorption layer, highlighting the 12 slots before they are filled with the semiconductor material. The slots have a depth between 1 pm and 100 pm and a width of less than 50 pm and typically less than 20 pm.

[0079] Figure 4 illustrates a cross-sectional view of the SPD radiation detection structure according to a third embodiment of the invention. The SPD radiation detection structure according to the third embodiment retains the characteristics and advantages of the first embodiment but differs from it in the structure of the discontinuities in the blocking layer CB. In the third embodiment, the blocking layer comprises discontinuities consisting of vias VI filled by the conductive material of the upper electrode ELI. The vias V1 thus form direct electrical contact zones ZCD, making it possible to find a compromise between reducing dark currents and maintaining good detector sensitivity. Adjusting the diameter and number of vias VI per radiation detection structure allows for better control of the overall contact area between the absorption layer CA and the upper electrode ELI.This allows the sum of the contact areas to be less than 10% of the surface area of ​​the radiation detection structure along the (X,Y) plane.

[0080] Figure 5 illustrates a cross-sectional view of an SPD radiation detection structure according to a fourth embodiment of the invention. The SPD radiation detection structure according to the fourth embodiment retains the features and advantages of the third embodiment and further comprises a second blocking layer CB2 disposed between the absorption layer CA and the lower electrode EL2. This makes it possible to promote the reduction of dark currents if the intended application requires it. In the illustrated example, the first blocking layer CB1 comprises contact areas formed by vias VI, and similarly, the second blocking layer CB2 comprises contact areas formed by vias VI filled by the conductive material of the lower electrode EL2 or by the semiconducting material of the absorption layer CA.

[0081] According to a particular aspect of this embodiment, the first blocking layer CB1 comprises contact zones formed by protrusions of the absorption layer CA (as described in the first or second embodiment), and the second blocking layer CB2 comprises contact zones formed by vias VI filled by the conductive material of the lower electrode EL2 or by the semiconducting material of the absorption layer CA. According to a particular aspect of this embodiment, the radiation detection structure SPD comprises a second blocking layer CB2 disposed between the absorption layer CA and the lower electrode EL2 as illustrated in [Fig.5] without the first blocking layer CB1.

[0082] Figure 6 illustrates a cross-sectional view of an SPD radiation detection structure according to a fifth embodiment of the invention. The SPD radiation detection structure according to the fifth embodiment retains the characteristics and advantages of the first embodiment, and further comprises a CP protective layer disposed between the lower electrode EL2 and the CA absorption layer.

[0083] The CP protective layer is made of a material that is chemically inert with respect to the perovskite of the CA absorption layer. The insertion of the CP protective layer prevents chemical reactions that would lead to degradation of the lower electrode EL2 by atoms from the CA absorption layer, and vice versa. In the case of an optoelectronic device comprising a pixel array formed by an arrangement of detection structures according to the invention, it is possible to use a CP protective layer common to all the pixels of said array. Sharing the CP protective layer simplifies the manufacturing process. In this case, the CP protective layer is made of a material that is not only chemically inert but also electrically insulating to prevent short circuits between the pixels.For example, the CP protective layer is made of yttrium oxide-stabilized zirconia (ZrO2:Y2O3), which is chemically inert compared to CsPbBr3 and electrically insulating (or poorly conductive) along the (X,Y) plane parallel to the substrate surface. It should be noted that the CP protective layer does not prevent the transfer of charge carriers (electrons and / or holes) from the absorption layer CA to the lower electrode EL2 along the Z stacking axis. As an example, the CP protective layer has a thickness between 10 nm and 1000 nm, preferably 200 nm.

[0084] Figure 7 illustrates a cross-sectional view of an optoelectronic DI device comprising a radiation detection structure according to the invention.

[0085] The optoelectronic device DI is a hybrid optoelectronic system, comprising: on the one hand, a conversion section formed by a plurality of SPD detection structures arranged in rows and columns to form a matrix of pixels Pxl, and on the other hand, an electronic section consisting of an integrated ROIC readout circuit. The ROIC readout circuit may constitute the substrate of the DI device or be itself implemented on a substrate. Each pixel Pxl is delimited by a dedicated lower electrode EL2 connected to the ROIC readout circuit to allow individual reading of each pixel Pxl. The conversion section is configured to convert an incident ray into a quantity of charge carriers. The section The electronics are configured to store the generated charges and then transmit them to a circuit that will convert these charges into a numerical value.

[0086] The ROIC readout integrated circuit is implemented using a plurality of transistors, such as those based on TFT (Thin Film Transistor) technology using amorphous silicon, and layers of conductive, semiconductor, or dielectric material deposited on the substrate. ROIC readout integrated circuits also exist using other technologies (CMOS, IGZO, LTPS, OTFT, etc.). The ROIC readout integrated circuit may also include a capacitor that integrates the current delivered by the detector device at pixel Pxl, stores it, and then delivers it to the external circuit during the image readout sequence. The assembly between the conversion section and the electronic section can be achieved by direct or indirect coupling. Direct coupling consists of directly depositing the layers constituting the SPD radiation detection structure onto the ROIC readout circuit.Indirect coupling consists of assembling the already manufactured conversion part to the already manufactured electronic part using hybridization techniques such as hybrid bonding, flip-chip, wire-bonding, or any other specific technique to electrically and optically couple two parts with different functions.

[0087] By way of example, the substrate undergoes is made of glass, or plastic, or polyamide, or a semiconductor, or metal, or a stack of several layers of the aforementioned materials.

[0088] Advantageously, the DI device includes at least one direct electrical contact zone ZCD per pixel Pxl to ensure optimization between sensitivity and dark current over the entire matrix.

[0089] Figure [8a] illustrates an IP method for manufacturing a radiation detection structure according to a first embodiment of the invention.

[0090] The first step i) consists of depositing a CA absorption layer in perovskite on the upper face of a support formed by the ROIC readout circuit disposed on the substrate undergone or formed by a separate substrate sub2. When the support is formed by the ROIC readout circuit and the substrate undergone, the deposition surface comprises an array of several separate lower electrodes EL2 previously fabricated.

[0091] In the PI process, the perovskite layer is deposited by the close-space sublimation (CSS) technique from a perovskite material source onto the support. The support is positioned at a distance of between 1 mm and 20 mm from the source, preferably 5 mm. The source is preheated to a first temperature T1 between 350°C and 500°C via a thermostat T1. The support is preheated to a second temperature T2. The assembly is placed in a closed chamber at a pressure below 100 Pa, and preferably below IPa. Generally speaking, in order to deposit a layer of a predetermined material using the sublimation technique in close space (CSS), a source of said predetermined material is used. The source can be obtained by mechanosynthesis. The two temperatures T1 and T2 are maintained at close values, with a difference between 50°C and 300°C. Since the distance between the source and the substrate is small, the vapor-transported material does not have time to cool and therefore cools slowly on the substrate surface. The use of this technique makes it possible to obtain a rough and irregular upper surface exhibiting the protrusions 11, predominantly pyramidal in shape as illustrated in Figures 2a, 2b, and 2c.

[0092] When the absorption layer CA is deposited on a separate substrate sub2, the process includes an assembly (hybridization) step of the absorption layer with the assembly formed by the readout circuit ROIC and its substrate.

[0093] Optionally, the PI process includes a step of depositing the semiconductor layer on the rough surface to fill the slots 12 and create conductive bridges between the adjacent protrusions 11,11'.

[0094] The second step ii) consists of depositing the blocking layer CB, made of a dielectric material, onto said upper surface of the absorption layer CA. The thickness of the blocking layer CB must be less than the height of at least one protrusion 11. It is sufficient that this inequality be valid locally at the level of at least one protrusion 11. It is not necessary that the inequality ei <hi soit générale sur toute la surface de la couche d’absorption. Cela permet d’obtenir un sommet de ladite protubérance qui reste apparent au niveau de la surface supérieure de la couche de blocage CB. Le dépôt de la couche de blocage CB est réalisable par des techniques de dépôt usuelles dans le domaine des micro / nanotechnologies, par exemple les techniques de dépôt par voie liquide ou sous vide.

[0095] The third step iii) consists of depositing the upper electrode ELI onto the blocking layer CB so as to cover all the protrusions 11 extending from the blocking layer CB. The upper electrode ELI is generally a metallic layer with a thickness ranging from 1 µm to 1 µm. This material can be chromium, copper, gold, platinum, tungsten, or titanium. Vacuum deposition techniques, such as evaporation or sputtering, are preferred for its deposition. However, it is also possible to use other types of conductive layers and other thicknesses. These alternatives include metals, conductive polymers, carbon-based inks, carbon nanotubes, and metallic nanowires. These layers can be deposited either by similar vacuum techniques or by printing techniques such as spraying, coating, spin-coating, or slot-die deposition.

[0096] The advantage of the PI process is that it allows the fabrication of surface protrusions at the same time as the absorption layer deposition step, which simplifies the manufacturing process and saves considerable time.

[0097] Figure [8b] illustrates a method P2 for manufacturing a radiation detection structure according to a second embodiment of the invention.

[0098] The first step i)' consists of depositing a CA absorption layer in perovskite on the upper face of a support formed by the ROIC readout circuit arranged on the substrate or formed by a separate substrate sub2. The deposition technique in the second process can be any layer deposition technique and not necessarily CSS deposition.

[0099] The second step ii)' consists of structuring the upper surface of the CA absorption layer to form protrusions 11 extending from said surface. The shape and dimensions of the protrusions are better controlled compared to the first PI process, resulting in more precise control of the overall surface area of ​​the direct contact zones. The machined protrusions can be pyramidal, granular, columnar, or mesa-shaped. The protrusions are microstructured on the upper surface of the CA absorption layer using microstructure fabrication techniques such as mechanical or chemical etching, molding, laser etching, lithography, photolithography followed by chemical and / or dry, chemical and / or physical etching.

[0100] The next step üi)' consists of depositing the CB blocking layer in a manner similar to the step described for the PL process. The next step iv)' consists of depositing the upper electrode ELI in the same manner as the step described for the PL process.

[0101] Figure 8c illustrates a P3 process for manufacturing a radiation detection structure according to a third embodiment of the invention.

[0102] The first step i)” consists of depositing a CA absorption layer in perovskite on the upper face of a support formed in the same way as the second process P2.

[0103] The second step ii)” consists of depositing the CB blocking layer in the same way as the step described for process PI or P2.

[0104] The third step iii) involves manufacturing vias through V1 that open through the blocking layer CB. The shape and dimensions of the vias are better controlled compared to the first process PI, resulting in more precise control of the overall surface area of ​​the direct contact zones. The vias V1 are drilled through the blocking layer CB by mechanical etching, laser etching, lithography, photolithography followed by chemical and / or dry, chemical and / or physical etching.

[0105] The next step iv)' consists of depositing the upper electrode ELI in a manner similar to the step described for the PI process but also of filling the vias VI at the same time with the material which constitutes the upper electrode ELI.

[0106] Alternatively, it is possible to fill the vias with a conductive material different from that used for the upper ELI electrode in a separate step. This allows the conductivity of the fabricated V1 vias to be modulated and thus the conductivity of the direct contact areas to be controlled.

[0107] Figure [8d] illustrates a method P4 for manufacturing an SPD radiation detection structure according to a fourth embodiment of the invention.

[0108] The first step i)'” consists of depositing a blocking layer CB, in a dielectric material, on the upper face of a formed support, in the same way as the second process P2.

[0109] The second step ii) consists of fabricating through-vias VI opening through the blocking layer CB in the same manner as the step described for process P3 and filling them with a conductive material to obtain a blocking layer CB comprising at least one discontinuity corresponding to the vias VL

[0110] The third step iii)' '' consists of depositing an absorption layer CA in a perovskite structure material on the blocking layer CB in a manner similar to the process P2. Alternatively to filling the vias with a conductive material in step ii)'”, the through vias VI can be filled directly with the perovskite material of the absorption layer CA simultaneously with the execution of the third step iii)”'.

[0111] The next step iv)'” consists of depositing the upper ELI electrode in a manner similar to the step described for the PI or P2 process.

[0112] Figure 8e illustrates a method P5 for manufacturing an SPD radiation detection structure according to the third embodiment of the invention. The method P5 is compatible with the assembly of the conversion part and the electronic part by indirect coupling. The first step a) consists of depositing the upper electrode ELI onto a transparent substrate. The second step b) consists of depositing a blocking layer CB, made of a dielectric material, onto the upper face of the upper electrode ELI. The following step c) consists of fabricating through-vias VI opening through the blocking layer CB in the same manner as the step described for the method P3 and filling them with a conductive material. The following step d) consists of depositing an absorption layer CA made of a perovskite-structured material onto the structured blocking layer CB.The filling of the vias in step c) with a conductive material can be replaced by filling the vias with the perovskite structural material simultaneously in step d). The next step e) consists of . reverse the resulting stack and assemble it by indirect coupling to a pixelated ROIC readout circuit comprising the lower electrodes EL2.

Claims

Demands

1. Radiation detection structure (DTS) formed by a stack of layers comprising: - an absorption layer (AL), made of a perovskite-structured material, intended to convert an incident ray into electrical charges; - an upper electrode (UEL) comprising at least one layer made of a first conductive material, intended to collect the electrical charges; - and a lower electrode (LEL2) comprising at least one layer made of a second conductive material, intended to collect the electrical charges; the absorption layer (AL) being disposed between the lower electrode and the upper electrode; said stack further comprising a blocking layer (BL), made of a dielectric material, confined between: on the one hand the absorption layer (AL), and on the other hand an electrode selected from the upper electrode (UEL) or the lower electrode (LEL2);the blocking layer (CB) comprising at least one discontinuity (11, VI) filled by said perovskite structure material or by a third conductive material so as to form a direct electrical contact zone (CDZ) between the absorption layer (CA) and said electrode (ELI, EL2).;

2. Radiation detection structure (SPD) according to claim 1 wherein the blocking layer (CB) is confined between the absorption layer (CA) and the upper electrode (ELI); the absorption layer (CA) having surface protrusions (11); at least one discontinuity in the absorption layer (CA) being filled by a protrusion (11) and opening towards the upper electrode so as to form at least one direct electrical contact zone (CDZ).

3. Radiation detection structure (SPD) according to claim 2 wherein the protrusions are in pyramidal or granular or columnar or mesa form.

4. Radiation detection structure (SPD) according to any one of claims 2 to 3 wherein the height (hl) of a protrusion (11) is between Ipm and lOOpm.

5. Radiation detection structure (SPD) according to any one of claims 2 to 4 wherein the protrusions (11) are separated by slots (12); the slots being filled with a semiconductor (13) or conductive material so as to create a charge-carrying bridge (SC) between two adjacent protrusions (11, 11').

6. Radiation detection structure (SPD) according to claim 1 wherein a direct electrical contact zone (CDZ) is formed by at least one through-through via (VI) through the blocking layer (CB) and filled by the third conductive material or by the perovskite structural material.

7. Radiation detection structure (SPD) according to any one of claims 1 to 6 wherein the sum of the contact areas between the direct electrical contact zones (CDZ) and the selected electrode (ELI, EL2) is less than 10% of the overall area of ​​said radiation detection structure (SPD).

8. Radiation detection structure (SPD) according to any one of claims 1 to 7 further comprising a protective layer (CP) disposed between the lower electrode (EL2) and the absorption layer (CA), the protective layer (CP) being made of a dielectric material chemically inert to the absorption layer (CA); the blocking layer (CB) being confined between the absorption layer (CA) and the upper electrode (ELI).

9. Radiation detection structure (SPD) according to any one of claims 1 to 8 wherein the resistivity of the blocking layer (CB) is greater than 10⁸ ohm.cm

10. Radiation detection structure (SPD) according to any one of claims 1 to 9 wherein the dielectric material of the blocking layer (CB) comprises nitrogen and / or oxygen and / or carbon.

11. Radiation detection structure (SPD) according to any one of claims 1 to 10 wherein the perovskite structure material is an ABX3 compound material; A being chosen from a first group of inorganic cations consisting of the following elements: cesium (Cs), rubidium (Rb), potassium (K) or an alloy of said elements from the first group of inorganic cations; B being chosen from a second group of inorganic cations consisting of the following elements: lead (Pb), tin (Sn), germanium (Ge), silicon (Si) or an alloy of said elements from the second group of inorganic cations; X being chosen from a group of halogens consisting of the following elements: bromine (Br), iodine (I), chlorine (Cl) or an alloy of said elements from the group of cations.

12. Optoelectronic device (Dl) comprising a pixel array comprising at least one pixel (Pxl) formed by means of the radiation detection structure (SPD) according to any one of claims 1 to 11.

13. A manufacturing method (PI) for a radiation detection structure (PDS) comprising the following steps: - depositing an absorption layer (CA) of a perovskite structure material by near-space sublimation (CSS) on a support (sub2, ROIC, subi) to obtain a rough top surface having a plurality of protrusions (11); - depositing a blocking layer (CB), of a dielectric material, on said top surface with a thickness chosen so as to obtain at least one protrusion that emerges from the top surface of the blocking layer (CB); - depositing a layer of a conductive material, on the blocking layer (CB) acting as a top electrode (ELI) covering all the protrusions (11) that emerge from the blocking layer (CB).

14. Method of manufacturing (P2) a radiation detection structure (SPD) comprising the following steps: - depositing an absorption layer (CA) of a perovskite structure material on a support (sub2, ROIC, subi); - forming protrusions (11) on the upper surface of the absorption layer (CA); - deposit a blocking layer (CB), made of a dielectric material, on the upper surface with a thickness (el) chosen so as to obtain at least one protrusion which opens from the upper surface of the blocking layer (CB); - deposit the upper electrode (ELI), made of a conductive material, on the blocking layer (CB) so as to cover all the protrusions (11) emerging from the blocking layer (CB).

15. Method for manufacturing (P3) a radiation detection structure (SPD) comprising the following steps: - deposit an absorption layer (CA) in a perovskite structure material on a support (sub2, RO IC, subi); - deposit a blocking layer (CB), made of a dielectric material, on the upper surface of the absorption layer (CA); - form at least one via opening through the blocking layer (CB) - deposit a layer of conductive material on the blocking layer (CB) acting as the upper electrode (ELI) so as to fill the vias with the conductive material and obtain a blocking layer (CB) comprising at least one discontinuity (VI) corresponding to said via (VI).

16. Method for manufacturing (P4) a radiation detection structure (SPD) comprising the following steps: - deposit a blocking layer (CB), in a dielectric material, on the upper surface of a support (ROIC, undergone) comprising at least one lower electrode (EL2); - form at least one via opening through the blocking layer (CB); - deposit an absorption layer (CA) in a perovskite structure material on the blocking layer (CB); - deposit a layer of conductive material on the absorption layer (CA) acting as the upper electrode (ELI).

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