WO2015004235A1

WO2015004235A1 - Semi-transparent photo-detector having a structured p-n junction

Info

Publication number: WO2015004235A1
Application number: PCT/EP2014/064809
Authority: WO
Inventors: Pierre Gidon; Salim Boutami
Original assignee: Commissariat à l'énergie atomique et aux énergies alternatives
Priority date: 2013-07-12
Filing date: 2014-07-10
Publication date: 2015-01-15
Also published as: FR3008546B1; FR3008546A1

Abstract

The invention relates to a photo-detection device (200) for detecting a set of wavelengths, comprising a plurality of stacked photo-detectors (100), the first one of which is capable of absorbing a first portion of the set and the second one of which is capable of absorbing a second portion of the set which is at least partially different from the first portion, wherein each photo-detector comprises first and second layers (102, 104) of doped semiconductor defining together a p-n junction, a dielectric material (109) transparent to the wavelengths flowing through the photo-detector, and in which a plurality of semiconducting or dielectric disjointed portions are such that the mean distance d between the centers of two adjacent portions is such that d is shorter than the shortest wavelength of the set.

Description

SEMI-TRANSPARENT PHOTODETECTOR WITH STRUCTURED P-N JUNCTION

DESCRIPTION

TECHNICAL FIELD AND PRIOR ART The invention relates to the field of photodetectors, in particular that of semi-transparent photodetectors. The invention also relates to the field of image sensors as well as that of photovoltaic devices using such photodetectors.

A photodetector is called semi-transparent when it passes through a portion of the light received by the photodetector and converts another portion of the received light into an electrical signal. The conversion of the received light into an electrical signal produced by the photodetector is proportional to the absorption of light by the photodetector. A semi-transparent photodetector is generally formed of a stack of at least two layers of semiconductor material, forming a photodiode through a metallurgical junction (pn junction) made between the semiconductor materials. These layers of semiconductor material are arranged between electrodes, generally transparent. Since the semiconductor materials have a certain light absorption coefficient, there is a range of thicknesses of the semiconductor material layers for which part of the light passes through the photodetector, another part of the light. being absorbed by the photodetector and the rest of the light being reflected. In general, this type semi-trapsparent photodetector is made such that it is the least reflective possible. The portion of the light that is absorbed will generate charges in the semiconductor materials. The metallurgical junction will then generate an electric field in an area of these semiconductor materials. This electric field will be able to separate the charges created by the absorption of light, and an electric potential or an electric current will then be obtained at the output of the semi-transparent photodetector. FIG. 1 schematically represents a part of a pixel of an image sensor 10 comprising three semi-transparent photodetectors 14, 16 and 18 superimposed one above the other and arranged above an integrated circuit 20 of pixel reading ("above IC" arrangement) made for example of crystalline silicon.

Each of the semi-transparent photodetectors 14, 16 and 18 is intended to detect one of the blue, green or red colors of the light received by the pixel.

The first semi-transparent photodetector 14 is disposed at the top of the pixel and comprises two layers 22 and 24 of hydrogenated amorphous silicon (a-Si: H) respectively doped p and n. The doping level of the layer 22 is greater than that of the layer 24. These two layers 22 and 24 are arranged between a first electrode 26 and a second electrode 28, both transparent and composed of ITO (indium oxide and tin). The upper electrode 26 here forms the layer through which the light received by the pixel of the image sensor 10 enters. The second semi-transparent photodetector 16 disposed under the first semi-transparent photodetector 14 also comprises two layers 30 and 32 of silicon hydrogenated amorphous respectively doped p and n. These two layers 30 and 32 are arranged between the second electrode 28, which is common to the two semi-transparent photodetectors 14 and 16, and a third transparent electrode 34. The third semi-transparent photodetector 18, arranged between the second semi-transparent photodetector 16 and the integrated circuit 20, comprises two layers 36 and 38 of hydrogenated amorphous silicon respectively doped p and n. These two layers 36 and 38 are disposed between the third electrode 34 which is common to the two semi-transparent photodetectors 16 and 18, and a fourth transparent electrode 40 disposed above the integrated circuit 20.

The thicknesses of the different semiconductor layers are adapted as a function of the wavelengths intended to be absorbed by the photodetector and those intended to pass through the photodetector without being absorbed.

Since within each semi-transparent photodetector, the most doped semiconductor layer (layers 22, 30 and 36) is formed as thin as possible, preferably less than about 10 nm, the total thickness of the semiconductor within each photodetector, determining the absorbed and transmitted wavelength ranges, is adapted via the choice of the thickness of the least doped semiconductor layer (layers 24, 32 and 38). Thus, the thickness of the semiconductor layer 24 is adapted so that the first semi-transparent photodetector 14 absorbs most of the wavelengths corresponding to the blue color and is as transparent as possible at the wavelengths corresponding to the colors. red and green. The thickness of the semiconductor layer 32 is adapted so that the second semi-transparent photodetector 16, which receives the light having passed through the first semi-transparent photodetector 14, absorbs most of the wavelengths corresponding to the green and either as transparent as possible at wavelengths corresponding to red (the wavelengths corresponding to blue that arrive in the second semi-transparent photodetector 16 are virtually non-existent because of the absorption carried out upstream by the first semi-transparent photodetector; transparent 14).

Finally, the thickness of the semiconductor layer 38 is adapted so that the third semi-transparent photodetector 18, which receives substantially only wavelengths corresponding to the red color, absorbs these wavelengths. The remaining red light having passed through the three semitransparent photodetectors 14, 16 and 18 may optionally make a second passage through these photodetectors through light reflection performed on the integrated circuit 20 and its electrical interconnections.

The thickness of the n-doped hydrogenated amorphous silicon layer 24 of the first semitransparent photodetector 14 is smaller than that of the n-doped hydrogenated amorphous silicon layer 32 of the second semitransparent photodetector 16, itself lower than that of the layer 38 of n-doped hydrogenated amorphous silicon of the third semi-transparent photodetector 18. The layer 24 has for example a thickness equal to about 15 nm, the layer 32 has for example a thickness equal to about 100 nm, and the layer 38 has a thickness of about 300 nm, these values being able to be calculated from the values of the absorption coefficient of the materials of these layers as a function of the wavelength to be absorbed. Two pixels, referenced 42a and 42b, of the image sensor 10 are shown diagrammatically in perspective in FIG. 2. Each of these pixels comprises three semi-transparent photodetectors similar to semitransparent photodetectors 14, 16 and 18 previously described in connection with FIG. FIG. 1. In this FIG. 2, in each photodetector, the two semiconductor layers forming the pn junction of the photodetector are represented in the form of a single layer of material, referenced 45. It can be seen in this FIG. of ITO 43 forming the electrodes are discontinuous, or interrupted, from one pixel to another, thus electrically isolating the pixels from each other, while the semiconductor layers 45 disposed between the electrodes 43 are continuous and common from one pixel to another. The electrodes 43 of the semi-transparent photodetectors are electrically connected to the integrated circuit 20 by conductive vias 44 passing through all the semiconductor layers. The semi-transparent photodetectors of the pixels are covered by a passivation layer 46 transparent and planarized.

A first difficulty in producing such semi-transparent photodetectors, and in particular that of a semi-transparent photodetector intended to absorb short wavelengths such as the first semi-transparent photodetector 14, comes from the fact that it is necessary to realize semiconductor layers sufficiently thin to absorb only the desired wavelengths (corresponding for example to the blue color which has a high absorption coefficient) and let the other wavelengths which have coefficients of lower absorption, while maintaining a semiconductor thickness sufficient to achieve the collection of electrical charges. Thus, for the first semi-transparent photodetector 14, it is generally desired to have a total semiconductor thickness of less than about 15 nm. However, such a small thickness of semiconductor can degrade the electrical behavior of the semiconductor material.

A second drawback of these semi-transparent photodetectors comes from the common characteristics of the materials used. Indeed, the absorption coefficient of the semiconductors is not constant with the wavelength. These semi-transparent photodetectors behave like colored filters with respect to transmitted light. It is therefore not possible to use such photodetectors for applications requiring a very low absorption spectrum, for example in the visible range. In addition, the color of the filter obtained is never ideal. However, for a given thickness of semiconductor, the structure of the semitransparent photodetectors previously described does not make it possible to adjust the color filtered by the photodetector and therefore the absorption spectrum of the photodetector, nor to have a realized absorption of steadily according to the wavelengths.

STATEMENT OF THE INVENTION

An object of the present invention is to provide a semi-transparent photodetector for which the production constraints related to the thickness of its semiconductor layers are reduced, and to easily adjust, at the time of the design of the photodetector, the spectrum of wavelengths absorbed and converted by the photodetector and the wavelength spectrum transmitted without being absorbed by the photodetector.

For this, it is proposed a photodetector comprising at least:

a first p-doped semiconductor layer and a second n-doped semiconductor layer, together forming a pn junction able to be traversed by a first portion of the wavelengths of a light received by the photodetector and to absorb and converting a second portion of the wavelengths of said light into an electrical signal;

a transparent dielectric material with respect to at least the second portion of the wavelengths, passing through at least the first semiconductor layer and the second semiconductor layer;

wherein the dielectric material surrounds several semiconductor portions disjoined from each other, each formed by a portion of the first semiconductor layer and a portion of the second semiconductor layer and such that, in a plane parallel to a first face of the first semiconductor layer disposed opposite the second semiconductor layer, an average distance between the centers of two adjacent semiconductor portions is less than at the smallest wavelength among those of the first part and the second part of the wavelengths, or

wherein the dielectric material forms a plurality of dielectric portions disjoined from each other, surrounded by the semiconductors of the first semiconductor layer and the second semiconductor layer and such that, in said plane, a mean distance between the centers of two adjacent dielectric portions are smaller than the smallest wavelength among those of the first portion and the second portion of the wavelengths.

The present invention proposes a photodetection device of a range of wavelengths intended to be received by the photodetection device, comprising a plurality of superimposed photodetectors, in which a first of the photodetectors is capable of absorbing and photoelectrically converting a first part. of the range of wavelengths and to be traversed by wavelengths of the range other than those of the first part, and in which a second of the photodetectors is able to absorb and photoelectrically convert a second part, to less partially different from the first part of the range of wavelengths and to be traversed by wavelengths of the range other than those of the second part,

each of the photodetectors comprising at least:

first and second doped semiconductor layers together forming a p-n junction;

a transparent dielectric material with respect to at least the wavelengths intended to pass through said photodetector, and passing through at least the first and second semiconductor layers;

each of the photodetectors being such that:

the dielectric material surrounds several semiconductor portions disjoined from each other, each formed by a portion of the first and second semiconductor layers, or the dielectric material forms several dielectric portions disjoined from each other, surrounded by semiconductors; conductors of the first and second semiconductor layers, in a plane parallel to a first face of the first semiconductor layer arranged opposite the second semiconductor layer, an average distance d between the centers of two adjacent semiconductor portions or between the centers of two portions; adjacent dielectric is such that d _<m in A, with at least corresponding to the smallest wavelength of the range of wavelengths.

Thus, by structuring the semiconductor layers of the photodetector by forming such semiconductor portions or such transparent dielectric portions, the electronic and optical properties of the photodetector structure are modified, which makes it possible to parameterize the length ranges of waves absorbed and transmitted by the photodetector via the choice of characteristics (shape, dimensions, pitch, etc.) of these semiconductor or dielectric portions.

With such a photodetector structure, it is therefore possible to produce, for example, a semi-transparent photodetector capable of absorbing wavelengths corresponding to blue from semiconductor layers whose total thickness is greater than about 15 nm, and for example between about 20 nm and 60 nm.

In addition, with such a photodetector structure, it is also possible to produce semi-transparent photodetectors having an absorption spectrum which is much more regular, that is to say having an absorption coefficient whose value varies less for example in the wavelength range of the visible range (for example in the range 400 nm - 650 nm) as for a semitransparent photodetector of the prior art comprising unstructured semiconductor layers.

Such a photodetector may be used to produce trichromatic image sensors, three-dimensional image sensors, spectrometric image sensors, or glazed solar cells or shading sensors arranged on display screens or screens. feedback sensors (regulation) arranged on light sources or even a combination of these different functions.

A photodetector may be able to absorb and photoelectrically convert part of the wavelength range, for example when the absorption made by the photodetector for this part of the wavelength range is greater than the transmission and reflection of this part of the wavelength range. A photodetector may be adapted to be traversed by wavelengths of the range other than those of the absorbed portion when the absorption achieved by the photodetector for these wavelengths is less important than the transmission and / or reflection of these wavelengths.

The photodetection device thus has a multispectral operation thanks to the semi-transparent photodetector which absorbs portions at least partially different from the range of wavelengths received.

By checking the property d <X _mm , none of the photodetectors diffract the wavelengths of the range.

Each of the semiconductor portions or each of the dielectric portions of one or each of the photodetectors may comprise a section, in said plane, in the form of a rectangle or disk or triangle. It is also possible that the semiconductor portions or the dielectric portions of one or each of the photodetectors have sections of different shapes and / or sizes.

The first semiconductor layer and / or the second semiconductor layer of one or each of the photodetectors may comprise amorphous silicon, for example hydrogenated silicon. It is also possible that the first semiconductor layer and / or the second semiconductor layer of one or each of the photodetectors comprise an amorphous semiconductor other than silicon, for example germanium, SiGe, selenium, InSe on amorphous Sn0 ₂ , a polymer, or a crystalline semiconductor, or a material combining several of these elements.

The photodetector or each of the photodetectors may further comprise at least one first electrode electrically connected to the first semiconductor layer, and at least one second electrode electrically connected to the second semiconductor layer.

In one or each of the photodetectors, the first electrode may comprise a first layer of electrically conductive and transparent material to at least the first portion and the second portion of the wavelengths, or at least the range of wavelengths, disposed against a second face of the first semiconductor layer opposite to said first face and / or the second electrode may comprise a second layer of electrically conductive material and transparent with respect to at least the first portion and the second portion of the wavelengths, or at least the range wavelength, arranged against the second semiconductor layer such that the second semiconductor layer is disposed between the second layer of electrically conductive material and the first layer of semiconductor material.

In one or each of the photodetectors, the dielectric material may pass through a portion of the first electrode and / or a portion of the second electrode.

In one or each of the photodetectors, the semiconductor portions or the dielectric portions may be arranged next to each other in a pattern repeated periodically in said plane.

In one or each of the photodetectors, the semiconductor portions or the dielectric portions may be regularly arranged next to one another, for example with a pitch smaller than said smaller wavelength.

In one or each of the photodetectors, all semiconductor or dielectric material portions may have substantially similar dimensions and / or substantially similar shapes.

In one or each of the photodetectors, the distances between the centers of two adjacent semiconductor portions or of two adjacent dielectric portions may be substantially similar between all the semiconductor portions or all the dielectric portions. In variants, these distances may vary within the or each of the photodetectors.

In one or each of the photodetectors, the semiconductor portions or the dielectric portions may be arranged next to each other in a pattern having several circles of different diameters. One or each of the photodetectors may further comprise at least one third intrinsic semiconductor layer disposed between the first semiconductor layer and the second semiconductor layer, the dielectric material passing through the third semiconductor layer intrinsic.

In one or each of the photodetectors, additional transparent or weakly absorbing layers may be disposed between the electrodes and the semiconductor layers in order to reduce potential barrier phenomena at the interfaces between the different materials, and thus facilitate the passage semiconductor charges to the electrodes.

Advantageously, in one or each of the photodetectors, said dielectric material may be transparent with respect to said first portion of the wavelengths or wavelength range, thereby reducing the optical losses of the or photodetectors.

In one or each of the photodetectors, the distance d can be such

By checking the property d> _m in / 4, the photodetectors do not form, with respect to the wavelengths received, a medium of homogeneous index.

The semiconductors of the first and second layers of each of the photodetectors may be of the same nature. Thus, the optical absorption and transmission properties of the photodetectors are parameterized by changing the absorbent material but by adapting the geometric properties (shape, dimensions, thickness, period) of the semiconductor or dielectric material portions.

There is also provided an image sensor comprising a matrix of pixels disposed above an integrated pixel reading circuit, in which each pixel comprises at least two semi-transparent photodetectors arranged one above the other. other and such that at least one of the two semi-transparent photodetectors corresponds to a photodetector as described above. The invention also relates to an image sensor comprising a matrix of pixels disposed above an integrated pixel reading circuit, in which each pixel comprises at least one photodetection device according to the invention.

The first semiconductor layer, the second semiconductor layer, the dielectric material and at least one of a first and a second electrode of two semi-transparent photodetectors arranged next to the other and forming part of two different pixels can be electrically insulated from each other by at least a portion of dielectric material disposed between the two pixels.

It is also proposed a photovoltaic device comprising a transparent substrate on which are arranged photodetectors as described above and electrically connected to each other.

The invention further relates to a photovoltaic device comprising a transparent substrate on which are arranged photodetection devices according to the invention and electrically connected to each other.

It is also proposed a method of producing a photodetector, comprising at least the implementation of the following steps:

- Realization of at least a first p-doped semiconductor layer and a second n-doped semiconductor layer, together forming a pn junction able to be traversed by a first portion of the wavelengths of a light received by the photodetector and absorbing and converting a second portion of the wavelengths of said light into an electrical signal;

etching the first semiconductor layer and the second semiconductor layer and depositing a transparent dielectric material with respect to at least said second portion of the wavelengths in etched portions of the first semiconductor layer and the second semiconductor layer, wherein the etching and deposition steps are implemented such that the dielectric material surrounds a plurality of semiconductor portions disjoined from each other, each formed by a portion of the first semiconductor layer and a portion of the second semiconductor layer and such that in a plane parallel to a first face of the first semiconductor layer disposed opposite the second semiconductor layer, an average distance between the centers of two adjacent semiconductor portions is less than the smallest wavelength among those of the first portion and the second portion of the lengths of waves, or

wherein the etching and deposition steps are performed such that the dielectric material forms a plurality of dielectric portions disjoined from each other, surrounded by the semiconductors of the first semiconductor layer and the second semiconductor layer, and such that, in said plane, an average distance between the centers of two adjacent dielectric portions is less than the smallest wavelength among those of the first portion and the second portion of the wavelengths.

The present invention also relates to a method for producing a photodetection device of a range of wavelengths intended to be received by the photodetection device, comprising the production of a plurality of superimposed photodetectors, in which a first photodetector is suitable to absorb and photoelectrically convert a first part of the wavelength range and to be traversed by wavelengths of the range other than those of the first part, and in which a second of the photodetectors is able to absorb and photo-electrically converting a second portion, at least partially different from the first portion, of the range of wavelengths and being traversed by wavelengths of the range other than those of the second portion, wherein the realization of each of the photodetectors comprises at least the implementation of the following steps:

- Making at least first and second doped semiconductor layers together forming a p-n junction;

etching of the first and second semiconductor layers, and deposition of a dielectric material, transparent with respect to at least the wavelengths intended to pass through said photodetector, in etched portions of the first and second layers semiconductor, wherein the etching and deposition steps are carried out such that the dielectric material surrounds a plurality of semiconductor portions disjoined from each other, each formed by a portion of the first and second semiconductor layers, or the etching steps and deposition are implemented such that the dielectric material forms several dielectric portions disjoined from each other, surrounded by the semiconductors of the first and second semiconductor layers,

wherein, in a plane parallel to a first face of the first semiconductor layer disposed opposite the second semiconductor layer, an average distance d between the centers of two adjacent semiconductor portions or between the centers of two adjacent dielectric portions are such that d <X _mm , with X _mm corresponding to the smallest wavelength in the wavelength range.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be better understood on reading the description of exemplary embodiments given purely by way of indication and in no way limiting, with reference to the appended drawings in which:

FIG. 1 schematically represents a pixel of an image sensor comprising semitransparent photodetectors according to the prior art;

FIG. 2 diagrammatically represents a portion of an image sensor comprising a plurality of photodetectors according to the prior art;

- Figure 3 schematically shows a photodetector object of the present invention, according to a first embodiment;

FIGS. 4A to 4C show schematically examples of semiconductor portions made in a photodetector, object of the present invention;

FIG. 5 represents absorption, transmission and reflection spectra of a semi-transparent photodetector according to the prior art; FIG. 6 represents absorption, transparency and reflection spectra obtained with a semi-transparent photodetector, object of the present invention;

FIGS. 7A and 7B schematically represent examples of semiconductor portions made in a photodetector, object of the present invention;

- Figure 8 schematically shows a photodetector object of the present invention, according to a second embodiment;

FIG. 9 schematically represents an image sensor, object of the present invention, comprising photodetectors also according to the invention;

FIG. 10 schematically represents a photovoltaic device, object of the present invention, comprising photodetectors also according to the invention;

FIG. 11 represents absorption, transparency and reflection spectra obtained with a semi-transparent photodetector, object of the present invention;

FIG. 12 schematically represents two semi-transparent photodetectors, object of the present invention, isolated from each other;

- Figure 13 schematically shows a device comprising semi-transparent photodetectors, objects of the present invention, realizing a light intensity measurement;

FIGS. 14A and 14B show schematically a semi-transparent photodetector, object of the present invention, according to a third embodiment;

FIG. 14C schematically represents an array of photodetectors comprising a plurality of semi-transparent photodetectors, object of the present invention, according to the third embodiment;

FIGS. 15A to 15D schematically represent steps of an exemplary method for producing a semi-transparent photodetector, object of the present invention. Identical, similar or equivalent parts of the different figures described below bear the same numerical references so as to facilitate the passage from one figure to another.

The different parts shown in the figures are not necessarily in a uniform scale, to make the figures more readable.

The different possibilities (variants and embodiments) must be understood as not being exclusive of each other and can be combined with one another.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS Referring firstly to FIG. 3 which schematically represents a semi-transparent photodetector 100 according to a first embodiment.

The photodetector 100 comprises two layers 102 and 104 of semiconductor, here hydrogenated amorphous silicon (a-Si: H), respectively doped p and n, together forming a pn junction of the photodetector 100. The doping level of the p-doped layer 102 is greater than that of the n-doped layer 104, these doping levels being such that the pn junction formed by these two layers can convert part of the received light into electrical energy. These two layers 102 and 104 are disposed between a first electrode 106 and a second transparent electrode 108, both comprising ΙΊΤΟ. The first electrode 106 here forms the electrode by which enters the light received by the photodetector 100.

The photodetector 100 is semi-transparent because it is able to pass a first portion of the wavelengths of the light received and to convert a second portion of the wavelengths of this light. The electrodes 106 and 108 are transparent with respect to at least this first portion and this second portion of the wavelengths.

The semiconductor layers 102 and 104 are periodically structured with dielectric material 109, for example silica. This dielectric material is chosen such that it is at least transparent with respect to the wavelengths intended to be absorbed and converted electrically by the photodetector 100, and of Also preferably vis-à-vis the wavelengths for passing through the photodetector 100 so that the dielectric material does not generate light losses. This dielectric material 109 traverses the entire thickness (dimension along the Z axis shown in FIG. 3) of the semiconductor layers 102 and 104. The layers 102 and 104 are therefore discontinuous. In the example of FIG. 3, the thickness of the dielectric material 109 is equal to the sum of the thicknesses of the semiconductor layers 102 and 104.

The structuring of the layers 102 and 104 is such that the remaining portions of the layers 102 and 104 form semiconductor portions 110 disjoined from each other and surrounded by the dielectric material 109. Each of these semiconductor portions 110 is formed by a part of the layer 102 and a portion of the layer 104. The portions 110 thus form a regular tiling of semiconductor materials.

FIGS. 4A to 4C show sectional views, parallel to a plane (X, Y) parallel to the faces of the layers 102 and 104 in contact with one another, of examples of semiconductor portions 110. The section of each semiconductor portion 110, in the plane (X, Y), is in FIG. 4A, of rectangular or square shape, in the disk-shaped FIG 4B, and in FIG. 4C of triangular shape. The sections of the portions 110 may also be of different shapes of these examples, for example of oval or polygonal shape or any other shape. The dimension referenced "p" in each of these figures corresponds to the repetition step of the portions 110, that is to say the distance separating the centers of two adjacent portions 110. This pitch "p" is such that it is smaller than the smallest wavelength among those of the first part and the second part of the wavelengths, that is to say less than the shortest length among those intended to pass through the photodetector and those intended to be absorbed and converted by the photodetector. Thus, this pitch "p" is advantageously between about 100 nm and 350 nm for lights of wavelength greater than about 400 nm.

In general, the semiconductor portions 110 may be regularly arranged next to one another (as is the case in the examples represented in FIGS. 4A to 4C), the pitch "p" being in this case substantially constant between all the semiconductor portions 110 of the photodetector 100. In a variant, it is possible that the pitch "p" is not constant for the all of the photodetector 100, and therefore that the distances between the centers of two adjacent semiconductor portions 110 are not constant between the different portions 110 of the photodetector 100. In all cases (not "p" constant or not), the Semiconductor portions are made such that an average distance between the centers of two adjacent semiconductor portions is less than the smallest wavelength among those of the first portion and the second portion of the wavelengths.

As regards the dimensions of the semiconductor portions 110, these can be substantially constant for all the semiconductor portions 110 of the photodetector 100 (as in the examples of FIGS. 4A-4C) or not. The dimensions of the semiconductor portions 110 in the (X, Y) plane can vary from about 20% to about 80% of the pitch p depending on the locations of the semiconductor portions 110 and the intended application. Similarly, the shapes of the semiconductor portions 110 may be substantially similar for all the semiconductor portions 110 of the photodetector 100 (as in the examples of Figures 4A-4C) or not.

The curves 112, 114 and 116 shown in FIG. 5 respectively represent the absorption, transmission and reflection spectra (that is to say the values of the absorption, transmission and reflection coefficients, as a function of the wavelength) of a semitransparent photodetector of the prior art similar to the photodetectors of the previously described image sensor 10 and comprising solid layers, that is to say layers unstructured by dielectric material, amorphous silicon and of total thickness (sum of the thicknesses of the semiconductor layers of the photodetector) equal to about 40 nm. The curves 118, 120 and 122 represented in FIG. 6 respectively represent the absorption, transmission and reflection spectra of the photodetector 100, comprising layers of hydrogenated amorphous silicon whose total thickness (sum of the thicknesses of the layers 102 and 104 ) is equal to about 50 nm, and structured by Si0 ₂ surrounding semi- conductors 110 of square sections (sections considered in the plane (X, Y)) regularly spaced by a pitch p (along the X axis and the Y axis) equal to about 300 nm and of dimension equal to about 200 nm, this dimension corresponding to the length of one of the sides of the square sections. It can be seen in these figures that the photodetector 100 exhibits a higher value absorption coefficient at long wavelengths (for example at around 600 nm) than that of the photodetector of the prior art and of lower value at short lengths. of waves (for example at about 400 nm) than that of the photodetector of the prior art.

The nano-structuring of the semiconductor layers of the photodetector 100 by the transparent dielectric material forming the semiconductor portions 110 thus offers a greater freedom of realization and a better compromise with regard to absorption, transmission and reflection. photodetector, and makes it possible to use, for given optical properties (absorption, reflection, transmission), thicker semiconductor layers thanks to the structuring of these layers by the dielectric material, while retaining its electrical characteristics and optics.

It can be seen in FIG. 6 that the resulting spectra define transmission (and reflection) peaks by resonance of the waves. If the tiling made by the semiconductor portions 110 is chosen less periodic, then the resonance peaks obtained are wider and the absorption, reflection and transmission spectra are smooth, that is to say, varies less in function of the wavelength. Thus, it is possible to produce within a semitransparent photodetector a structuring of the semiconductor layers by dielectric portions spaced differently from one another and / or having different and / or non-aligned dimensions and / or of different shapes. In this case, the semiconductor portions 110 are made such that the average distance between the centers of two adjacent semiconductor portions is less than the smallest wavelength among those of the first part and the second part of the lengths. wave.

FIG. 7A represents an exemplary embodiment of semiconductor portions 110 having different dimensions in the (X, Y) plane. In this for example, some portions 110a have dimensions (diameter) greater than those of other portions 110b, the portions 110a and 110b being formed by portions of the semiconductor layers of a same photodetector. In the example of FIG. 7A, the distances between the centers of the different adjacent semiconductor portions 110 are substantially constant for the entire photodetector. In another variant shown in FIG. 7B, it is possible for the portions 110 to form blocks (referenced 124a, 124b, 124c, and 124d in this figure) periodically repeated in the semiconductor layers, but in which the portions 110 have irregularities in size and / or arrangement and / or shape (variations in the dimensions of the sections of the portions 110a and 110b in the example of Figure 7B). The semiconductor portions 110a and 110b of one of the blocks are substantially similar to those in each of the other blocks of the photodetector.

By this set of parameters to be chosen (dimensions and / or shape and / or arrangement of the transparent dielectric portions within the semiconductor layers of the semi-transparent photodetector), it is possible to vary the spectral response of the photodetector both in absorption in transmission, and therefore also in reflection. In general, the smaller the semiconductor surface within the semitransparent photodetector (i.e., the more the ratio between the surface in the (X, Y) plane within the semiconductor layers, semiconductor and the surface of the transparent dielectric portions is small), plus the absorption achieved by the semi-transparent photodetector is low. In addition, only the parts of the spectrum in which the absorption coefficient is non-zero or at least equal to about 3% are generally modified, at the level of the absorption achieved, by the transparent dielectric portions. The repeating pitch of the transparent dielectric portions, or more generally the average distance separating the centers from two adjacent transparent dielectric portions, is also chosen as a function of the semiconductor material used in the photodetector. Thus, in the case of amorphous silicon layer, the repetition pitch of the transparent dielectric portions, or this average distance, is advantageously between about 100 nm and 300 nm. In addition, the resonance phenomena occurring in the semiconductor as well structured can increase the absorption achieved at levels higher than that of the unstructured material, or on the contrary cancel it.

FIG. 8 represents the photodetector 100 according to a second embodiment. With respect to the photodetector 100 previously described in connection with FIG. 3, the dielectric material 109 of the photodetector 100 shown in FIG. 8 also passes through a portion of the thickness of the transparent electrodes 106 and 108. These discontinuities made in the electrodes 106 and 108 do not interrupt the electrical continuity of the electrodes 106 and 108. In another variant embodiment, it is possible that only one of the electrodes 106 and 108 is partially traversed by the dielectric material 109.

In the previously described embodiments and embodiments, the semitransparent photodetector 100 comprises a p-n junction formed by two semiconductor layers 102 and 104 arranged one against the other. Alternatively, it is possible for an intrinsic semiconductor layer, for example intrinsic amorphous silicon, to be disposed between the semiconductor layers 102 and 104, thereby forming a PIN photodiode. In this case, each of the semiconductor portions 110 also comprise a part of this intrinsic semiconductor layer. In addition, it is also possible for the photodetector 100 to comprise another n-doped semiconductor layer, for example comprising a doping level similar to or close to that of the p-doped layer 102, such as the lightly doped layer 104. is disposed between the layer 102 and this other layer of highly doped semiconductor. In this case, each of the semiconductor portions 110 also comprises a part of this n-doped semiconductor layer. Finally, it is also possible for layer 102, having a doping level greater than that of layer 104, to be n-doped and layer 104 to be p-doped. In this case, it is possible to add another p-doped semiconductor layer against the layer 104, each of the semiconductor portions 110 then comprising a portion of this highly p-doped semiconductor layer.

As a variant of all the examples and embodiments previously described, it is possible for the portions 110 whose average distance between the centers of two adjacent portions 110 is smaller than the smallest wavelength among the wavelengths that pass through the photodetector and the wavelengths absorbed and converted by the photodetector are not semiconductor portions, but portions of the dielectric material formed through the semiconductor layers. The photodetector 100 comprises in this case the dielectric material which forms several dielectric portions disjoined from each other, surrounded at least by the semiconductors of the first layer 102 and the second layer 104 (and possibly other layers when the photodetector 100 comprises such additional layers) and such that, in said plane, an average distance between the centers of two adjacent dielectric portions is less than the smallest wavelength among those of the first portion and the second portion of the lengths of waves. The dielectric material forms a regular tiling of transparent dielectric material made through the semiconductor layers 102 and 104. Thus, in this configuration, the reference 110 used in the previous Figures 3, 4, 7 and 8, as well as in the Following figures described below, then designates the dielectric portions, and the reference 109 designates the semiconductor materials surrounding the dielectric portions. Each dielectric portion then forms a column of transparent dielectric material made through the layers 102 and 104. The various properties (shape, dimensions, spacing, regular and non, etc.) previously described for the semiconductor portions also apply to such dielectric portions made through the semiconductor layers of the photodetector 100.

FIG. 9 represents a pixel of an image sensor 1000 corresponding to a trichromatic sensor. The pixel of the image sensor 1000 comprises a photodetection device 200 formed of several superimposed photodetectors 100, here three semi-transparent photodetectors 100.1, 100.2 and 100.3 superposed one above the other, and arranged above a circuit integrated pixel readout 1002 ("above IC" layout), made for example from a crystalline silicon substrate.

The other pixels of the image sensor 1000 are similar to the pixel described here, and are for example arranged next to one another in a manner similar to the sensor of images 10 previously described in connection with Figure 2. Each of the semi-transparent photodetectors 100.1, 100.2 and 100.3 is intended to achieve the detection of the majority of one of the colors blue, green, or red respectively. In the image sensor 1000, the semi-transparent photodetectors 100, and thus also the photodetection devices 200, are therefore arranged in large numbers in the form of a matrix of pixels above the integrated circuit 1002. At least one electrode of each semi-transparent photodetector is electrically connected to the integrated circuit 1002 which is for example of the CMOS type, for example by conductive vias as previously described for the image sensor 10 shown in FIG. 2. The integrated circuit 1002 notably contains a addressing, amplification and digital conversion system for extracting (or reading) the electrical information delivered by each of the pixels of the matrix.

The first semi-transparent photodetector 100.1 disposed at the top of the pixel comprises two layers 102.1 and 104.1 of hydrogenated amorphous silicon respectively doped n and p, and together forming a pn junction of the first semi-transparent photodetector 100.1. These two layers 102.1 and 104.1 are arranged between a first electrode 106.1 and a second electrode 108.1, both transparent and comprising ΙΊΤΟ. The upper electrode 106.1 here forms the layer through which the light received by the pixel of the image sensor 1000 enters. The second semi-transparent photodetector 100.2 disposed under the first semi-transparent photodetector 100.1 comprises two amorphous silicon layers 102.2 and 104.2. hydrogenated respectively doped n and p, and together forming a pn junction of the second semi-transparent photodetector 100.2. These two layers 102.2 and 104.2 are arranged between the second electrode 108.1 (which is therefore common to the two semi-transparent photodetectors 100.1 and 100.2) and a third electrode 108.2 also comprising ΙΊΤΟ. The third semi-transparent photodetector 100.3, disposed between the second photodetector 100.2 and the integrated circuit 1002, comprises two layers 102.3 and 104.3 of hydrogenated amorphous silicon respectively doped n and p, and together forming a pn junction of the third semi-transparent photodetector 100.3. These two layers 102.3 and 104.3 are arranged between the third electrode 108.2 (which is therefore common to both semi-transparent photodetectors 100.2 and 100.3) and a fourth electrode 108.3 also comprising ΓΙΤΟ and disposed above the integrated circuit 1002.

Each of the three semi-transparent photodetectors 100.1, 100.2 and 100.3 also comprise a transparent dielectric material respectively referenced 109.1, 109.2 and 109.3, produced through the semiconductor layers of the semi-transparent photodetectors, and for example similar to the transparent dielectric material 109 previously described. In each of the three semi-transparent photodetectors 100.1, 100.2 and 100.3, the dielectric materials 109.1, 109.2 and 109.3 surround semiconductor portions 110.1, 110.2 and 110.3 similar to the semiconductor portions 110 previously described. Alternatively, the dielectric material may form, within one or more of the three semi-transparent photodetectors 100.1, 100.2 and 100.3, dielectric portions disjoined from each other, surrounded by the semiconductors of the first layer and the second semiconductor layer of the photodetector and such that, in said plane, an average distance between the centers of two adjacent dielectric portions is less than the smallest wavelength among those of the first part and the second part of the lengths wave.

The most heavily doped layers of each photodetector 100.1, 100.2 and 100.3, here corresponding to the p-doped layers 102.1, 102.2 and 102.3, may have substantially similar thicknesses, and preferably less than about 10 nm, or more generally between about 4 nm and 10 nm.

Alternatively, and for electrical reasons, one or more of the layers 102.1, 102.2 and 102.3 may be respectively disposed under one or more of the associated layers 104.1, 104.2 or 104.3.

The thickness of the n-doped hydrogenated amorphous silicon layer 104.1 of the first semitransparent photodetector 100.1 is smaller than that of the n-doped hydrogenated amorphous silicon layer 104.2 of the second semitransparent photodetector 100.2, itself lower than that of the layer 104.3 of n-doped hydrogenated amorphous silicon of the third semi-transparent photodetector 100.3. Indeed, the thickness of the layer 104.1 is adapted so that the first photodetector 100.1 absorbs most of the wavelengths of the light received by the pixel which correspond to the blue color (for example between about 400 nm and 500 nm and is predominantly transparent (achieving for example a transmission of about 80%) to wavelengths corresponding to the colors red (for example between about 600 nm and 700 nm) and green (for example between about 500 nm and 600 nm), that is to say absorbs (for example about 15% d absorption) and reflects (for example about 5% reflectance) a minority portion of these wavelengths due to the semiconductor portions 110.1 formed by the portions of semiconductor layers 102.1 and 104.1 of the first semitransparent photodetector 100.1 (which are here of square sections with side equal to about 80 nm and spaced from each other with a pitch equal to about 200 nm), the semiconductor thickness (sum of the thicknesses of the layers 102.1 and 104.1) of the first 100.1 photodetector is for example equal to about 60 nm, and is more generally between about 20 nm and 80 nm.

The thickness of the layer 104.2 is adapted so that the second semi-transparent photodetector 100.2 absorbs most of the wavelengths corresponding to the green of the light having passed through the first semitransparent photodetector 100.1 and is predominantly transparent to the lengths of light. waves corresponding to the red color (the wavelengths corresponding to the blue arriving in the second photodetector 100.2 being virtually zero). Due to the semiconductor portions 110.2 formed by the portions of semiconductor layers 102.2 and 104.2 of the second semitransparent photodetector 100.2 (which are here of shape and size, in the plane (X, Y), substantially similar to those of the portions 110.1 of the first photodetector 110.1), the semiconductor thickness (sum of the thicknesses of the layers 102.2 and 104.2) of the second photodetector 100.2 is for example between about 100 nm and 300 nm.

Finally, the third semi-transparent photodetector 100.3 receives practically only wavelengths corresponding to the red color that it will absorb. Because of the semiconductor portions 110.3 made in the semiconductor layers 102.3 and 104.3 of the third semi-transparent photodetector 100.3 (which are here of shape and dimensions, in the plane (X, Y), substantially similar to those portions 110.1 of the first photodetector 110.1), the semiconductor thickness (sum of the thicknesses of the layers 102.3 and 104.3) of the third photodetector 100.3 is adapted to absorb most of the wavelengths corresponding to the red color.

The light may optionally make a second pass through the semi-transparent photodetectors 100.1, 100.2 and 100.3 by reflection on the integrated circuit 1002 and its electrical interconnections.

In the image sensor 1000, the absorption, transmission and reflection spectra of the three semi-transparent photodetectors 100.1, 100.2 and 100.3 are finely adjusted thanks to the presence of the semiconductor portions 110.1, 110.2 and 110.3 formed by the semiconductor layers of these photodetectors. As a variant, it is possible for only one of the photodetectors (advantageously the photodetector intended to achieve absorption of the shortest wavelengths, for example the one intended to perform an absorption of the blue color, because this photodetector is intended for have the thinnest semiconductor layers among the three semi-transparent photodetectors of the pixel) or that two of the photodetectors (for example the photodetectors 100.1 and 100.2) are made with such semiconductor portions.

In addition, it is also possible for the semiconductor portions 110 of the different photodetectors of the image sensor 1000, and thus of the photodetection device 200, to be of different shape and / or size, and / or differently arranged in photodetectors. It is also possible that the dielectric material produced in one or more of the photodetectors of the image sensor 1000, and thus of the photodetection device 200, form dielectric portions which are disjoint from each other, surrounded by the semiconductors of the layers of the photodetectors, as previously described for the photodetector 100.

In general, the various embodiments and embodiments previously described for the photodetector 100 may be applied for one or more of the photodetectors 100.1, 100.2 and 100.3. The semi-transparent photodetector 100, or the photodetection device 200 formed of the superimposition of at least two semi-transparent photodetectors 100 having at least partially different absorption ranges, previously described, can also be used to produce a photovoltaic device comprising solar cells on glazing. Indeed, for the realization of such a photovoltaic device for example intended to be used for windows of houses or buildings, it is generally sought to produce photovoltaic cells having a spectrum of absorption the least variable possible in the field of visible wavelengths, so that the color obtained through the cells and the glazing substantially corresponds to a neutral color, for example gray. Such a photovoltaic device 2000 is partially shown in FIG. 10. In this device, several semi-transparent photodetectors (three semitransparent photodetectors 100.1, 100.2 and 100.3 are shown in FIG. 10) are arranged next to one another on a glazed surface 2002, for example a glass substrate, and electrically connected in them, in series and / or in parallel, in order to be able to collect on output terminals of the device 2000 the electrical energy generated by the semi-transparent photodetectors 100. The semiconductor portions (for example similar to the previously described portions 110) made in these semitransparent photodetectors each comprise, for example, a disk-shaped section with a diameter of about 150 nm, and arranged next to one another with a not equal to about 300 nm, the semiconductor layers having for example a total thickness, in each photodetector, equal to about 50 nm. The upper electrodes of the photodetectors are here covered by passivation layers 136 for protecting the photodetectors 100.1, 100.2 and 100.3.

The curves 130, 132 and 134 shown in FIG. 11 respectively correspond to the absorption, transmission and reflection spectra obtained for one of the semitransparent photodetectors of the device 2000. The curve 132 shows that the transmission obtained with such a device semitransparent photodetector has fewer variations than that obtained with a semitransparent photodetector comprising unstructured semiconductor layers (see FIG. 5, the transmission spectrum being uniformly growing from blue to red). In addition, we see in Figure 11 that this transmission spectrum has three peaks, whose central peak is approximately centered on the maximum sensitivity of the eye which corresponds to the wavelengths of the green color (at about 550 nm ) and the two lateral peaks correspond substantially to the wavelengths of red and blue (at about 450 nm and 650 nm). Such a transmission makes it possible to obtain, at the output of the device 2000, a light of a warm gray tone transmitted through these semi-transparent photodetectors, and therefore a light adapted for use of such a device in the field of construction. . In addition, the absorption spectrum (curve 130) of such a semi-transparent photodetector is not uniform but oscillates in a range of values between +/- 20% of an average value over the spectral range of visible domain, which is a very acceptable value. It is possible to optimize the structures of the semitransparent photodetectors to obtain smaller variations in the absorption spectrum of the photodetectors. Although not shown, the photovoltaic device 2000 may comprise other elements such as protection elements (freewheel diode, anti-lightning, etc.) coupled to the photodetectors.

As a variant, the device 2000 can comprise several photodetection devices 200 arranged next to each other on the glazed surface 2002 and electrically connected to each other, in series and / or in parallel, in order to be able to collect on output terminals of the device. 2000 the electrical energy generated by the photodetection devices 200.

Semitransparent photodetectors comprising structured semiconductor layers may also be used to produce spectroscopic image sensors or three-dimensional image sensors or adapted to perform de-focusing measurements (making it possible to carry out measurements). depth in a captured image). For such image sensors, the semi-transparent photodetectors are for example similar to those used for the photovoltaic device 2000 previously described, for example having a broad absorption spectrum and the most constant possible over the entire range of lengths of captured waves, while keeping a good transparency. Each pixel of this type of sensor may comprise at least two semi-transparent photodetectors superposed one above the other, that is to say a photodetection device 200, in order to capture different depths of field of the image. With regard to the absorption spectrum shown in FIG. 11 (curve 130), the semi-transparent photodetectors are made such that the peaks of this absorption spectrum are widened and / or attenuated, and this via a variation of the pitch and the size of the dielectric zones, and therefore also photodetector zones. The desired transmission values being greater (70 to 80%) in this type of application, the total thickness of the semiconductor layers in each photodetector is for example chosen thinner (for example between about 25 nm and 35 nm). . The dielectric portions are for example made with a pitch of between about 250 nm and 300 nm, essentially eliminating the natural absorption characteristic of the semiconductor material.

When semi-transparent photodetectors are used to form the pixels of an image sensor (tri-chromium, 3D, spectroscopic, etc.), it is generally sought that the light intended for a pixel does not overflow on the pixel neighbour.

For this, it is possible that the semiconductor layers of photodetectors belonging to two neighboring pixels are isolated from each other by dielectric portions. Such a configuration is shown diagrammatically in FIG. 12, in which the semiconductor layers 102.1, 102.2, 104.1 and 104.2 of two semi-transparent photodetectors 100.1 and 100.2 are surrounded by portions of dielectric material 140 thus delimiting the semiconductor portions. drivers of each pixel. These dielectric portions 140 also electrically isolate from each other the upper electrodes 106.1 and 106.2 of the two semi-transparent photodetectors 100.1 and 100.2. On the other hand, the electrodes 108.1 and 108.2 of the two photodetectors 100.1 and 100.2 are formed by a transparent conductive layer common to the two photodetectors 100.1 and 1002.2 and not interrupted by the dielectric portions 140.

In a variant, it is possible for the portions of dielectric material 140 to delimit only the electrodes of the pixels (upper or lower electrodes), and not the semiconductor layers. Semitransparent photodetectors with structured semiconductor layers can also be used to measure an emitted light intensity, for feedback purposes, on a point source. FIG. 13 schematically represents such a device 3000 comprising a substrate 3002 comprising light sources 3004.1, 3004.2, 3004.3. Semi-transparent photodetector devices 100.1, 100.2 and 100.3 are arranged above the light sources 3004 and thus allow a large part of the emitted light spectrum to be passed while measuring the light intensity emitted by the sources 3004. The portions of material transparent dielectric formed in such photodetectors are for example similar to those previously described for the photovoltaic device 2000. Given the high luminous intensity emitted and the little electrical signal required, the semiconductor layers produced are thin and the widths of the semi-conductor zones are -conductor narrow. In the example of FIG. 13, the semi-transparent photodetectors 100 are arranged directly against the light sources 3004. It is possible, however, that the semi-transparent photodetectors 100 are arranged at a certain distance (for example a focusing distance) from the light sources. 3004 light sources, depending on what is intended to be measured by the photodetectors 100.

These semi-transparent structured semiconductor layer photodetectors can also be used to act as detectors on a display screen for human / machine interaction with the person viewing the image.

The semi-transparent photodetectors are in this case made on the display screen, and can detect the presence of an element, for example a finger, on a specific area of the screen.

In a semitransparent photodetector, for example used to measure an emitted light intensity or to act as a detector on a screen, the semiconductor portions may advantageously be arranged in a zoned cylindrical network, that is to say such that the the area occupied by the semiconductor portions with respect to the surface occupied by the dielectric material (the dielectric material having an optical index greater than that of the semiconductor portions), in the plane of the surface through which the light is received, varies increasingly from the center of the photodetector to the edges of the photodetector, in order to additionally obtain a gradient-index type lens effect. An exemplary embodiment of such a semi-transparent photodetector 100 is shown schematically in FIGS. 14A and 14B, respectively representing a sectional view and a top view of this photodetector. In this photodetector 100, the semiconductor portions 110 are formed such that the centers of these portions 110 are on concentric circles 150 (represented symbolically by dashed lines) regularly spaced from each other (with however here a portion 110 arranged in the center of the photodetector 100). Thus, the average distance between the centers of two adjacent semiconductor portions 110 is smaller than the smallest wavelength among those intended to pass through the photodetector 100 and those intended to be absorbed and converted by the photodetector 100. the regular spacing between the semiconductor portions 110, the increasing variation of the area occupied by the semiconductor portions 110 relative to the surface occupied by the dielectric material 109 is obtained thanks to the dimensions of the semiconductor portions 110 which vary increasingly from the center of the photodetector 100 to the edges of the photodetector 100.

Thus, because the pitch with which the semiconductor portions 110 are made varies continuously and the dimensions of the semiconductor portions 110 increase as the distance from the center of the photodetector 100 increases, this leads to a convergence of the beams The average optical index obtained in the photodetector 100 varies from zone to zone, resulting in a behavior similar to a gradient of index. This lens effect, obtained by virtue of the ratio of the surfaces between the dielectric material and the semiconductor which varies and the fact that the repetition pitch of the dielectric portions is smaller than the smallest transmitted or absorbed wavelength, could also be obtained with semiconductor portions 110 of different shapes, for example of square section, and / or arranged in a pattern of different shape, for example along the sides of squares of different dimensions and arranged concentrically. It is also possible that the optical index of the dielectric material 109 is lower than that of the semiconductor portions 110. In this case, the center of the photodetector would form a center of divergence, which would induce a divergence of the light beams received from the center. of the photodetector 100.

A lens array can be made by arranging several lenses similar to that shown in Figs. 14A and 14B side by side. Part of such a matrix 4000 is schematically shown in FIG. 14C. This matrix portion 4000 here comprises 9 photodetectors 100.1 to 100.9 arranged in the form of a square matrix 3 * 3. According to the optical indices of the semiconductor materials and the dielectric material of the photodetectors 100.1 to 100.9 depending on whether the portions 110 are based on semiconductors or dielectrics, the portions 110 located in the center of each photodetector form centers of convergence or divergence of the light rays received by the photodetectors. Conversely, the portions 110 in the corners of the photodetectors form centers of divergence or convergence of these light rays.

In the examples described above, each of the photodetectors may be replaced by a photodetection device comprising at least two different superimposed photodetectors.

Semitransparent photodetectors with structured semiconductor layers can also be used to make an interferometer. Such an interferometer comprises a plurality of semi-transparent photodetectors superposed one above the other and made on a mirror. Such a device makes it possible to recover the spectrum received by the interferometer via a Fourier transform calculation, or via a so-called "inverse problem" calculation, from the data delivered by the photodetectors.

In the previously described embodiments, the semi-transparent photodetectors serve to provide light detection in the wavelength range of the visible range. However, it is possible that these semi-transparent photodetectors may be used to carry out detection in the infrared and / or ultraviolet range. In this case, the semiconductor or dielectric portions 110 are made such that the pitch "p" of these portions 110 is less than the shortest wavelengths traversing or absorbed by the photodetector. The wavelength domains will remain limited in width. Typically, the spectral width of such photodetectors is close to the value of the shortest wavelength of the detection domain. For example, amorphous germanium may be used for the production of semi-transparent photodetectors intended for light detection in the near-infrared range (up to about 1.4 μιη).

In all the embodiments and embodiments of the semi-transparent photodetectors previously described, the electrodes are made in the form of electrically conductive and transparent layers covering the front and rear faces of the photodetectors. Alternatively, it is possible that the doped semiconductor layers of the photodetectors are sufficiently conductive (i.e., when the product of the electrical resistance of the semiconductor layers by the photo-generated layer in the photodetector gives a fall voltage of less than about 10 mV) to not cause a voltage drop (or limit the current) to a few microns, which allows to achieve in this case electrodes in the form of narrow conductive elements, for example arranged on the periphery of the photodetectors, these conductive elements being opaque, which opacifies only very partially the semi-transparent photodetector.

In addition, in all the embodiments and embodiments of the semi-transparent photodetectors previously described, the electrodes are arranged directly in contact with the semiconductor layers. Alternatively, it is possible to interpose electrically conductive layers, for example comprising a metal-semiconductor alloy such as silicide, between the electrodes and the semiconductor layers. These additional conductive layers reduce potential barrier phenomena at the interfaces between the different materials and facilitate the passage of charges from the semiconductor to the electrodes.

FIGS. 15A to 15D now describe an exemplary method for producing a semi-transparent photodetector 100.

It is first deposited on a substrate 160, corresponding for example to an integrated circuit comprising a semiconductor such as silicon, a ITO layer forming the lower electrode 108, the n-doped semiconductor layer 104, the p-doped semiconductor layer 102, and another ITO layer 162 forming a portion of the upper electrode (Fig. 15A ).

An etching of the layers 162, 102 and 104 is then implemented to form holes 164 corresponding to the future locations of the dielectric material in these layers, and thus defining the semiconductor portions 110 (Figure 15B). It is also possible that the lower electrode 108 is partially etched if the dielectric material is intended to pass through a portion of this electrode.

The transparent dielectric material is then deposited in these holes 164. The transparent dielectric material protruding from these holes on the layer 162 is then planarized, with a stop on the ITO layer 162 (FIG. 15C).

The semi-transparent photodetector 100 is then completed via the deposition of another layer of ITO forming, with the layer 162, the electrode 106 (FIG. 15D).

When the portions 110 do not pass through any of the electrodes, the electrode 106 can be made only at the end of the process.

For the production of a photodetection device 200, the above steps are repeated to obtain at least two superimposed photodetectors 100.

Claims

A photodetection device (200) having a range of wavelengths to be received by the photodetection device (200), having a plurality of superimposed photodetectors (100), wherein a first photodetector (100) is adapted to absorbing and photoelectrically converting a first portion of the wavelength range and being traversed by wavelengths of the range other than those of the first part, and in which a second of the photodetectors (100) is suitable absorbing and photoelectrically converting a second part, at least partially different from the first part, of the range of wavelengths and to be traversed by wavelengths of the range other than those of the second part,

each of the photodetectors (100) comprising at least:

first and second doped semiconductor layers (102, 104) together forming a p-n junction;

a dielectric material (109) transparent with respect to at least the wavelengths intended to pass through said photodetector (100), and passing through at least the first and second semiconductor layers (102, 104);

each of the photodetectors (100) being such that:

the dielectric material (109) surrounds a plurality of semiconductor portions (110) disjoined from one another, each formed by a portion of the first and second semiconductor layers (102, 104), or the dielectric material (109) forms a plurality of dielectric portions disjoined from each other, surrounded by the semiconductors of the first and second semiconductor layers (102, 104),

in a plane parallel to a first face of the first semiconductor layer (102) arranged opposite the second semiconductor layer (104), an average distance d between the centers of two semi-conductor portions (110); adjacent conductors or between the centers of two adjacent dielectric portions is such that d <Amin, with X _mm corresponding to the smallest wavelength in the wavelength range.

The photodetection device (200) according to claim 1, wherein each of the semiconductor portions (110) or each of the dielectric portions of each of the photodetectors (100) has a section, in said plane, in the shape of a rectangle or disc or triangle.

The photodetection device (200) according to one of the preceding claims, wherein the first semiconductor layer (102) and / or the second semiconductor layer (104) of each of the photodetectors (100) comprise amorphous silicon.

The photodetection device (200) according to one of the preceding claims, wherein each of the photodetectors (100) further comprises at least a first electrode (106) electrically connected to the first semiconductor layer (102), and at least one a second electrode (108) electrically connected to the second semiconductor layer (104).

The photodetection device (200) according to claim 4, wherein in each of the photodetectors (100), the first electrode (106) has a first layer of electrically conductive material and is transparent to at least the wavelength range, disposed against a second face of the first semiconductor layer (102) opposite to said first face, and / or the second electrode (108) having a second layer of transparent electrically conductive material at least the wavelength range disposed against the second semiconductor layer (104) such that the second semiconductor layer (104) is disposed between the second layer of electrically conductive material and the first layer (102) of semiconductor material.

6. A photodetection device (200) according to one of claims 4 or 5, wherein in each of the photodetectors (100), the dielectric material further crosses a portion of the first electrode (106) and / or a portion of the second electrode (108).

Photodetection device (200) according to one of the preceding claims, in which, in each of the photodetectors (100), the semiconductor portions (110) or the dielectric portions are arranged next to one another in a pattern repeated periodically in said plane.

8. photodetection device (200) according to one of the preceding claims, wherein in each of the photodetectors (100), the portions (110) semiconductor or dielectric portions are regularly arranged next to each other.

9. Photodetection device (200) according to one of the preceding claims, wherein, in each of the photodetectors (100), all the portions

(110) semiconductors or dielectric portions have substantially similar dimensions and / or are substantially similar shapes.

10. photodetection device (200) according to one of claims 1 to 6, wherein in each of the photodetectors (100), the portions (110) semiconductor or dielectric portions are arranged next to each other according to a pattern with several circles of different diameters.

The photodetection device (200) according to one of the preceding claims, wherein each of the photodetectors (100) further comprises at least one third intrinsic semiconductor layer disposed between the first semiconductor layer (102) and the second semiconductor layer (104), the dielectric material (109) passing through the third intrinsic semiconductor layer.

The photodetection device (200) according to one of the preceding claims, wherein in each of the photodetectors (100) the dielectric material (109) is transparent to the wavelength range.

13. Photodetection device (200) according to one of the preceding claims, wherein in each of the photodetectors (100), the distance d is such

AT,

that d e λ.

The photodetection device (200) according to one of the preceding claims, wherein the semiconductors of the first and second layers (102, 104) of each of the photodetectors (100) are of the same nature.

An image sensor (1000) comprising a matrix of pixels disposed above a pixel readout integrated circuit (1002), wherein each pixel has at least one photodetection device (200) according to one of the preceding claims.

16. Photovoltaic device (2000) comprising a transparent substrate (2002) on which are arranged photodetection devices (200) according to one of claims 1 to 14 and electrically connected to each other.

17. A method of producing a photodetection device (200) of a range of wavelengths intended to be received by the photodetection device (200), comprising the production of a plurality of superimposed photodetectors (100), in which a first photodetector (100) is capable of absorbing and photoelectrically converting a first portion of the wavelength range and to be traversed by wavelengths of the range other than those of the first part, and in which a second of the photodetectors (100) is capable of absorbing and photoelectrically converting a second part, at least partially different from the first part of the range of wavelengths and to be traversed by wavelengths of the range other than those of the second part, in which the production of each of the photodetectors (100) comprises at least the implementation of the following steps:

producing at least first and second doped semiconductor layers (102, 104) together forming a p-n junction;

etching the first and second semiconductor layers (102, 104) and depositing a dielectric material (109) transparent to at least the wavelengths for passing through said photodetector (100), in etched portions of the first and second semiconductor layers (102, 104),

wherein the etching and deposition steps are performed such that the dielectric material (109) surrounds a plurality of semiconductor portions (110) disjoined from each other, each formed by a portion of the first and second layers (102, 104 semiconductor, or the etching and deposition steps are implemented such that the dielectric material (109) forms a plurality of dielectric portions disjoined from each other, surrounded by the semiconductors of the first and second layers (102, 104) of semiconductor,

wherein, in a plane parallel to a first face of the first semiconductor layer (102) disposed opposite the second semiconductor layer (104), an average distance d between the centers of two portions (110) semiconductors adjacent or between the centers of two adjacent dielectric portions, such that d <X _mm , with X _mm corresponding to the smallest wavelength in the wavelength range.