GB2239555A - Infrared image-sensing devices and their manufacture - Google Patents

Abstract

An infrared image-sensing device for the 3 to 5 or 8 to 10 micrometre wavebands comprises an array of infrared photodiodes (10) for example of cadmium mercury telluride, on a circuit substrate (31). Each photodiode (10) comprises a respective one of an array of vertical regions (3) which extends through the thickness of the array body (preferably at apertures 20) to form a diode junction (2) with an adjacent pan (14) of the body (1) and which is connected to a conductor pattern (33) providing individual connections to the photodiodes (10) at the surface of the circuit substrate (31). In order to permit operation at a higher temperature while retaining a closely-packed array geometry, the array body (1) in accordance with the invention comprises a multiplicity of alternating first and second layers (13 and 14) having therebetween junctions (12) such as p-n junctions and heterojunctions. The first layers (14) are connected in parallel to the vertical regions (3) to provide an output signal from each photodiode and are each depleted throughout their thickness at least in operation of the device thereby to isolate electrically from each other the vertical regions (3) of the individual photodiodes (10) of the array. The adjacent part of the body (1) comprises preferably thicker. second layers (14) which provide parallel conductive paths from the photodiodes (10) to a common connection (4, 24, 34) of the array. The junctions (13) serve to extract minority charge carriers from the layers (13 and 14) during operation of the photodiodes (10) to reduce the minority carrier concentration at the higher operating temperature and thereby to produce low noise and high responsivity characteristics. <IMAGE>

Description

DESCRIPTION INFRARED IMAGE~SENSING DEVICES AND THEIR MANUFACTURE This invention relates to infrared image-sensing devices comprising an array of infrared photodiodes (for example of cadmium mercury telluride) on a circuit substrate, for example a staring array device responsive to radiation in the 3 to 5 micrometre or 8 to 12 micrometry wavebands. The invention also relates to a method of manufacturing a particular form of such a device.

Published United Kingdom patent application GB-A-2 095 905 (PHB32767) describes an infrared imagesensing device comprising an array of infrared photodiodes present in an infrared-sensitive semiconductor body on a major surface of a circuit substrate. Each photodiode comprises a respective one of an array of vertical regions which extends through the thickness of the body to form a diode junction with an adjacent part of the body and which is connected to an electrical conductor pattern providing individual first electrical connections to the photodiodes at said major surface of the circuit substrate. A cation second electrical connection is made to said adjacent part of the body.By forming the vertical regions at an array of apertures through the body and by interfacing the body with the substrate as described in GB-A-2 095 905, a closely-packed array of high performance photodiodes can be obtained connected in an advantageous reliable and compact manner to the conductor pattern of the substrate. The whole contents of GB-A-2 095 905 are hereby incorporated as reference material into the present specification.

In the specific etibients described and shown in GE-A-2 095 905, the major part of the body is of p type cadmium mercury telluride in which the vertical regions are formed as n type side-wall regions of the apertures, and an n type surface region may also extend laterally from each vertical region at the top surface of the body to form a horizontal extension of the diode junction. The n type regions of the individual photodiodes are isolated from each other by the adjacent p type part of the body.

Furthermore these specific devices are cooled to a cryogenic operating temperature for detecting infrared radiation in the 3 to 5 micranetre or 8 to 14 micranetre wavebands.

As described in published European patent application EPA-Q 167 305, it has been conventional to cool cadmium mercury telluride photodiodes to about 80K for 8 to 14 micranetre waveband detection material and to about 200K for 3 to S micranetre waveband material.However, by designing the photodiodes so as to incorporate a minoritycarrier extraction region and to inhibit nanoritycarrier injection, the minoritycarrier concentration in the photosensitive region can be depressed to produce low noise and high responsivity characteristics such as are obtained by cooling, but without the need for complex, bulky and expensive cooling equipment. Thus, the resulting photodiodes for 3 to 5 micrametre waveband detection may be operated at ambient temperature (about 295K) and those for the 8 to 14 micranetre waveband at about 190K.

The whole contents of EP-A-O 167 305 are hereby incorporated as reference material into the present specification.

In the case of an array of photodiodes, it is suggested in EP-A-O 167 305 (for example with reference to Figures 6 and 7) to sum the signals from several individual diode regions so that a group of the regions form each pixel area. However this is difficult to incorporate into the photodiode array structure of GB-A-2 095 905 without increasing the pixel area and so having a less compact, less closely-packed array of photodiodes.

According to one aspect of the present invention there is provided an infrared imagesensing device comprising an array of infrared photodiodes present in an infrared-sensitive semiconductor body on a major surface of a circuit substrate, each photodiode caiprising a respective one of an array of vertical regions which extends through the thickness of the body to form a diode junction with an adjacent part of the body and which is connected to an electrical conductor-pattern providing individual first electrical connections to the pactodiodes at said major surface of the circuit substrate, and a canyon second electrical connection being made to said adjacent part of the body, characterised in that the body comprises a plurality of alternating first and second layers having junctions therebetween, in that the first layers are connected in parallel to the vertical regions to provide an output signal from each photodiode and are each depleted throughout their thickness at least in operation of the device thereby to isolate electrically from each other the vertical regions of the individual photodiodes of the array, in that said adjacent part of the body comprises the second layers which provide parallel conductive paths from all the photodiodes to the common second electrical connection, and in that the junctions serve to extract minority charge carriers from the layers during operation of the photodiodes to reduce the minority carrier concentration at the operating temperature.

By providing the infrared-sensitive body comprising such alternating first and second layers, a compact, closely-packed array can be formed with the advantageous features of GB-A-2 095 905 while obtaining self-isolation of the individual photodiodes by depletion of the first layers, obtaining a common connection to the photodiodes via the second layers, and depressing the minoritycarrier concentration in the layers to reduce the cooling requirement for the operating temperature of the device.

Thus, with the operational biasing of the photodiodes, the junctions (for example E~ junctions and/or heterojunctions) between the first and second layers serve to extract minority charge carriers from the layers, and the sandwiching of the individual second layers between the alternate first layers inhibits minoritycarrier injection in the second layers. As a result of the junctions extracting the minority charge carriers, the electrons and holes of photogenerated electron-hole pairs are separated by the junctions and have a longer diffusion length as majority charge carriers in their respective layers. Because the alternating layers provide charge transport paths which are for the most part away from the surface of the body, surface reccitibination effects are reduced so enhancing the resposivity of the photodiodes. Furthenrore the first layers can be made sufficiently thin as to approach the dimension for a quantum well in which the charge carriers can have very high mobility and lifetime.

In the case of an infrared-sensitive body of cadmium mercury telluride, it is advantageous to form the body by deposition of alternate layers of cadmium telluride and mercury telluride which are interdiffused to form cadmium mercury telluride.

According to another aspect of the present invention, this deposition for cadmium mercury telluride may be performed with a source of acceptor dopant which is incorporated in the deposited material preferentially with the deposition of either the cadmium telluride or the mercury telluride so as to form said second layers with a higher acceptor doping level than said first layers. After the deposition, an array of apertures may be formed through the thickness of the first and second layers by ion-milling to determine an n type doping in said first layers and to form said vertical regions as n type regions which adjoin the sidewalls of the apertures and which form said diode junctions as Ern junctions with the second layers.

These and other features in accordance with the present invention are illustrated by way of example in a specific embodiment of the invention now to be described with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a partial cross-sectional, partial perspective view of part of an infrared imag#sensing device in accordance with the invention, Figure 2 is a simplified view of the device cross-section of Figure 1, Figure 3 is a plan view of the device of Figure 1, and Figure 4 is a cross-sectional view of a body of infraredrsensitive material at a stage in the manufacture of the device of Figure 1.

It should be noted that the drawings are diagrammatic and not drawn to scale. The relative dimensions and proportions of parts of these Figures have been shown exaggerated or reduced in size for the sake of clarity and convenience in the drawings. Cnly a small.

number of the multiplicity of alternating layers 13 and 14 is illustrated in Figures 1,2 and 4. In particular, Figure 2 is a greatly simplified schematic representation.

The infrared imagesensing device of Figures 1 to 3 comprises an array of infrared photodiodes 10 present in an infrared-sensitive semiconductor body 1 on a major surface of a circuit substrate 31. Each photodiode 10 comprises a respective one of an array of vertical regions 3 which extends through the thickness of the body 1 to form a diode junction 2 with an adjacent part 14 of the body and which is connected to an electrical conductor pattern 33 providing individual, first electrical connections to the photodiodes 10 at this major surface of the circuit substrate. A common, second electrical connection 34, 24, 4 is made to said adjacent part 14 of the body.

In accordance with the present invention, the array body 1 comprises a plurality of alternating first and second layers 13 and 14 having junctions 12 therebetween. The junctions 12 serve to extract minority charge carriers from the layers 13 and 14 during operation of the photodiodes 10 to reduce the minority carrier concentration at the operating temperature. The first layers 13 are connected in parallel to the vertical regions 3 to provide an output signal from each photodiode. The layers 13 each have a sufficiently low doping level per square area of the layer 13 as to be depleted throughout their thickness at least in operation of the device and thereby to isolate electrically from each other the vertical regions 3 of the individual photodiodes 10 of the array.

The adjacent part of the body comprises the second layers 14 which have a sufficiently high conductivity-determining doping level per square area of each layer 14 as to be undepleted over a part of their thickness in operation of the device; these undepleted parts provide parallel conductive paths along the layers 14 from all the photodiodes 10 to the cairron, second electrical connection 34,24,4.

Apart from the multiple layer structure 13 and 14, the device of Figures 1 to 3 may be similar to that disclosed in GS 2 095 905. Thus, as illustrated in Figures 1 and 2, an array of apertures 20 correspanding to the array of vertical regions 3 extends through the thickness of the body 1 (and hence through the thickness of the first and second layers 13 and 14), and the vertical regions 3 adjoin the whole side-wall(s) of the apertures 20 and are connected to the substrate conductor pattern 33 by a metallization layer 23 on these sidewalls. The vertical regions 3 are of one conductivity type (for example n type) and form pn junctions with the second layers 14 which are of the opposite, second conductivity type (p type).The body 1 may comprise cadmium mercury telluride having a passivating layer 7 on its upper and lower major surfaces. The body 1 is separated from the circuit substrate 31 by an electrically-insulating adhesive layer which may be a separate adhesive layer 25 (for example of epoxy) or the body 1 may be adhered to the substrate 31 by its lower passivating layer 7, having been grown by deposition in situ.

The circuit substrate may comprise circuit elements (for example chargecoupled device elements, or M:)S transistors) for processing signals derived from the photodiodes 10 via their individual first connections 23,33.Thus, the substrate 31 may be a silicon or other semiconductor body comprising doped regions such as 32 therein and having an insulating layer structure 35 (for example of silicon dioxide and silicon nitride) on its top major surface. Crie or more levels of metallization forming electrodes and conductor tracks are present on and in the insulating layer structure 35, for example CCD or gate electrodes 36, an array of individual connections 33 for each photodiode 10, one or more common connections 34 for the photodiode array, and other connection tracks 37 (Figure 3) of the substrate circuit. Via the connections 23,33 the Ern junctions 2 of the individual photodiodes are reverse-biased by the substrate circuit in operation of the device, typically by about a few tens of millivolts, for example.

As illustrated in Figures 1 and 3, the photodiodes 10 (and hence the substrate conductors 33) may be organised in a 2-dimensional staring array, and the common connection may comprise a peripheral region 4 of the second conductivity type which extends around preferably all the sides of the array, one or more areas of netallizatian 24 contacting the peripheral region 4, and one or more substrate conductors 34.

In one particular embodiment, the whole body 1 (comprising the regions 3,4,13 and 14) is of cadmium mercury telluride of a substantially uniform composition which determines its bandgap sensitivity to the infrared radiation 40 to be detected, for example in the 3 to 5 micrometre or 8 to 14 micrometre wavebands at the desired operating temperature. The first layers 13 are n type and are connected in parallel by the n type vertical regions 3.

These layers 13 form Ern junctions with the p type layers 14 and with the p type peripheral region 4 which connects the layers 14 in parallel. Preferably, each of the second layers 14 has a thickness at least three times that of the first layers 13 so as to provide low resistance in the parallel p type conductive paths between the cation connection 4,24,34 and the individual photodiodes 10 of the array. Typically, the first layers 13 have a thickness dl of less than 50inn (nancmetres) and the second layers 14 have a thickness d2 of more than 50cm. In a particular example, dl may be 20rim and d2 may be 0.1 micrometres.Thus, for example, the itniltiplicity of alternating layers 13 and 14 may be more than 150 in a body 1 of, for example, about 10 micrometre thickness and may be more than 80 in a 5 micrametre thick body 1.

The donor doping concentration N1 of the n type layers 13 may be, for example, of the order of 1015 cm-3, whereas the acceptor doping concentration N2 for the p type layers 14 may be, for example, of the order of 1016 cm~3. The doping level per square area of the n type layers 13 (i.e. the product Nl.dl) is sufficiently low that the depletion layers formed at the #n# junctions 12 merge across the thickness of the n type layers 13 to deplete these layers 13 of electrons with normal operating bias applied to the photodiodes 10 or even at zero bias.If an n type layer 13 is present adjacent either the top or bottom surface of the body 1, its thickness may be only a half of that of layers 13 in the bulk so that it too is depleted. the doping level per square area of the p type layers 14 (i.e. the product N2.d2) is much higher so that a significant part of their thickness is depleted in operation of the device so as to form the camn parallel p type conductive paths from the individual photodiodes 10 to the cation connection 4,24,34.

Thermallygenerated electron-hole pairs in the body 10 are separated by the Ern junctions 12 by extraction of electrons fran the p layers 14 into the depleted layers 13 where they drift to the n regions 3 and by extraction of holes from the depleted layers 13 into the p conductive paths of the layers 14 where they drift to the canton connection 4,24,34 of the array. The p-I1 junctions 12 are very close to each other, for example less than lOOnm apart (which is much closer than extraction junctions in the particular arrangements described in EP-A-O 167 305).Because of this very close spacing of the junctions 12, the efficiency of minoritycarrier extraction from the layers 13 and 14 is very high in the layered structure 13 and 14 of devices in accordance with the invention. By the same mechanisms as described in EP-A-O 167 305, suspression of Auger generation-recatibination processes results with minority#arrier concentrations in the layers 13 and 14 reduced below the thermal equilibrium level.

Thus, the cooling requirement for operation of the device is reduced so that, for example, an infrared-image sensing device of Figures 1 to 3 detecting 3 to 5 micranetre waveband radiation 40 may be operated at ambient temperature, whereas for detecting 8 to 14 micranetre waveband radiation 40 a device constructed in accordance with Figures 1 to 3 may be operated at a temperature obtained using an inexpensive Peltier cooler. This reduced cooling requirement also simplifies the housing requirements for the device. Furthermore, it should be noted that these advantages are obtained while maintaining a compact, closely-packed array structure as in #A-2 095 905. Thus, for example, the vertical regions 3 at the apertures 20 may be about 40 micranetres or less apart.

Infrared radiation 40 to be detected from a distant scene is imaged in knawn manner onto the array via the front surface of the body 1. the infrared photons are absorbed in the layer structure 13 and 14 and generate electron-hole pairs therein. The electrons and holes are separated by the Ern junctions 12, the electrons being collected by the array of n type vertical regions 3 via the layers 13, while the holes pass along the common Ertype layers 14 to the catiron region 4. The photodiode signals from the vertical regions 3 are input to the signal-processing circuit substrate 31 by the individual connections 23,33.Because of the very close spacing of the junctions 12, very rapid charge separation occurs so giving a high quantum efficiency and effectively a wide and vertically uniform sensitive area of the photodiodes around the vertical regions 3. Because the transport of the photogenerated electrons is constrained by the layers 13, surface recatibination effects are significantly reduced and longer diffusion lengths are obtained with less surface sensitivity. Furthenrore, since a 20nm layer 13 is approximating towards a quantum well in cadmium mercury telluride, the electrons in the layers 13 may have very high mobility and lifetime.

The alternating layer structure 13 and 14 may be grown in various ways. Thus, for example, molecular beam epitaxy may be used. When the body 1 is of cadmium mercury telluride, alternate layers of cadmium telluride 114 and mercury telluride 113 (see Figure 4) may be deposited for example using vapour phase deposition techniques such as those described in published United Kingdom patent applications GB-A-2 146 663 and GB-A-2 203 757 (FHB33351), the whole contents of which are hereby incorporated herein as reference material. These cadmium telluride and mercury telluride layers 114 and 113 may be interdiffused (either during growth or subsequently) so as to form the cadmium mercury telluride of the desired coposition. The deposition can be performed with a source of acceptor dopant (for example, either arsenic or sodium) which is incorporated preferentially in the deposited material with the deposition of either the cadmium telluride 114 or the mercury telluride 113. In this way, the second layers 14 can be formed with a higher p type doping level than the first layers 13.

Arsenic is found to be incorporated preferentially during the deposition of the cadmium telluride so that in this case the layers 114 can provide the second layers 14 of the alternating structure 13 and 14. Sodium however appears to be incorporated preferentially either with the deposition of the mercury telluride or at the interfaces between the mercury telluride and cadmium telluride so that in this case the layers 113 or the regions around the interface form the second layers 14. However, if desired, the acceptor dopant source may be switched on and off with the cadmium telluride/mercury-telluride deposition cycle. The n type doping of the layers 13, may be obtained by filling mercury vacancies in the deposited layers 13, for example by annealing the alternating structure 13 and 14 in mercury vapour or/and by ion-milling apertures 20 as described below.

The passivating layers 7 on the body 1 may be formed by, for example, undoped cadmium telluride layers 107 deposited in the same equipment before and after the deposition of the alternating layer structure 113 and 114. In some cases, the circuit substrate 31 may provide the substrate 101 on which the layer structure 107,113 and 114 is deposited. However, it is often easier to deposit the layer structure 107,113 and 114 on a separate substrate 101 which is subsequently etched away to leave the deposited layer structure as the body 1.

The array of photodiodes 10 can be formed in the layer structure 107,113 and 114 using known fabrication technologies, for example as described in GB-A-2 095 905. Thus, the apertures 20 may be formed by iorrrnilling the layer structure 107,113 and 114, the ion-milling simultaneously forming the vertical n type regions 3 around the apertures 20. The n type doping of the layers 13 may be determined (either for the most part or to a minor extent) by the same mercury diffusion resulting from the ion milling of the apertures 20.The p type peripheral region 4 may be formed by dopant diffusion or ion implantation. The metallizations 23 and 24 are deposited in knows manner.

It will be evident that many rodifications are possible within the scope of the present invention. Thus, for example, the body 1 need not be of uniform composition. The mifloritycarrier exclusion from the p type second layers 14 may be enhanced further by making the first layers 13 of a material having a larger bandgap than that of the second layers 14. Thus, for example, the layers 13 may still be of cadmium mercury telluride but with a higher proportion of cadmium telluride than the layers 14. The layers 13 may even be largely of cadmium telluride while the layers 14 are of cadmium mercury telluride so that a coppositional superlattice structure is formed.

Instead of cadmium mercury telluride, the infrared imagesensing device of Figures 1 to 3 may be designed using other ~ infrared-sensitive materials, for example indium antlitonide (InSb) doped to form n type regions 3 and 13 and p type regions 4 and 14.

Such a device may be used for detection in the 3 to 5 micrometre waveband. Other III-V compound semiconductor materials may be used to form superlattices from which an array of photodiodes on a circuit substrate, in accordance with the present invention may be fabricated. Many different forms of spperlattices have been proposed and/or used for single photodiode body structures as described in, for example, the articles:: "GaAs,#1GaAs Quantum -well long-wavelength infrared (LWIR) Detector with a Detectivity Comçarable to HgCdle" by B.F. Levine et al. in Electronics Letters 9th June 1988 Vol. 24, No. 12 pages 747 to 748; "III-V Compound Semiconductor Super lattices for Infrared Photodetector Applications" by R.C. Hughes in Optical Engineering march 1987 Vol. 26 No. 3 pages 249 to 255; and "A New Doping Superlattice Photodetectorll by Y. Horikoshi et al in Applied Physics A (Solids and Surfaces: Springer-Verlag) Vol. 37 pages 47 to 56 (1985).The whole contents of these three articles are hereby incorporated as reference material into the present specification. However it should be noted that the photodetector of the Electronics Letters article is of vertical configuration, whereas that of the Applied Physics A article has a high sensitivity in the 0.8 to 1.4 micranetre waveband but not at wavelengths in excess of 3 micrometres generally required for infrared imagesensing array devices.

Instead of the vertical regions 3 around apertures 20, it is possible to form vertical regions through the thickness of thin bodies 1 by dopant diffusion or alloying from the top and/or bottom surfaces of the body 1, and the resulting photodiode array may be connected to the circuit substrate 31 by means of solder studs between body 1 and substrate 31. However, this diffusion or alloying treatment requires higher temperatures than the ionrmilling technology disclosed in GB-A-2 095 905 and so it is not so easy (especially with cadmium mercury telluride) to preserve the alternating layer structure 13 and 14 while forming these particular regions 3 and 4.Furthermore, the solder stud connection is not as reliable as the metal-lined aperture connection of GE-A-2 095 905. With same materials, it would be possible to form the vertical regions 3 (connected to the first layers 13 and isolated from the second layers 14) by appropriate metallization 23 at the side walls of the apertures 20, and/or the peripheral cation region 4 (connected to the second layers 14 and isolated from the first layers 13) may be formed by different appropriate metallization 24 around the periphery of the layer structure 13 and 14.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already knawn in the design, manufacture and use of infrared nnagesensing systems and devices, and coppont parts thereof, and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims (11)

aAIM(S)

1. An infrared imagesensing device comprising an array of infrared photodiodes present in an infrared-sensitive semiconductOr body on a major surface of a circuit substrate, each photodiode comprising a respective one of an array of vertical regions which extends through the thickness of the body to form a diode junction with an adjacent part of the body and which is connected to an electrical conductor pattern providing individual first electrical connections to the photodiodes at said major surface of the circuit substrate, and a cairo second electrical connection being made to said adjacent part of the body, characterised in that the body comprises a plurality of alternating first and second layers having junctions therebetween, in that the first layers are connected in parallel to the vertical regions to provide an output signal from each photodiode and are each depleted throughout their thickness at least in operation of the device thereby to isolate electrically from each other the vertical regions of the individual photodiodes of the array, in that said adjacent part of the body comprises the second layers which provide parallel conductive paths from the photodiodes to the common second electrical connection, and in that the junctions serve to extract minority charge carriers from the layers during operation of the photodiodes to reduce the minority carrier concentration at the operating temperature.

2. A device as claimed in Claim 1, further characterised in that each of the second layers has a thickness at least three times that of the first layers to provide low resistance in the conAuctive paths between the common second connection and the individual ptstodiodes of the array.

3. A device as claimed in Claim 1 or Claim 2, further characterised in that the first layers and the vertical regions are of a first ccndLctivity type, and the second layers are of the opposite, second conductivity type so as to form #n junctions with the first layers and with the vertical regions.

4. A device as claimed in anyone of the preceding claims, further characterised in that the first layers are of a material having a larger bandgap than that of the second layers.

5. A device as claimed in anyone of the preceding claims, further characterised in that the first layers have a thickness of less than 50nm and the second layers have a thickness of more than 50nm.

6. A device as claimed in anyone of the preceding claims, further characterised in that an array of apertures corresponding to the vertical regions extends through the thickness of the first and second layers, and in that the vertical regions adjoin the sidewall(s) of the apertures and are connected to the conductor pattern by a metallization layer on said sidewall(s).

7. A device as claimed in anyone of the preceding claims, further characterised in that the semiconductor body comprises cadmium mercury telluride.

8. A method of manufacturing the device of claim 7, wherein the semiconductor body is formed by deposition of alternate layers of cadmium telluride and mercury telluride which are interdiffused to form cadmium mercury telluride, and wherein said second layers are formed with a higher acceptor doping level than said first layers by performing the deposition with a source of acceptor dopant which is incorporated in the deposited material preferentially with the deposition of either the cadmium telluride or the mercury telluride.

9. A method as claimed in Claim 8, wherein the acceptor dopant is either arsenic or sodium.

10. A method as claimed in Claim 8 or Claim 9, wherein after the deposition an array of apertures are formed through the thickness of the first and second layers by iamnilling to determine an n type doping in said first layers and to form said vertical regions as n type regions which adjoin the sidewall(s) of the apertures and which form said diode junctions as Ern junctions with the second layers.

11. An infrared imagesensing device or a method for its manufacture, substantially as described with reference to and/or illustrated in any of the accxnçxulying drawings.