USRE48642E1 - Application of reduced dark current photodetector - Google Patents

Abstract

A IDCA system with internal nBn photo-detector comprising: a photo-absorbing layer comprising an n-doped semiconductor exhibiting valence band energy level; a barrier layer, a first side of the barrier layer adjacent a first side of the photo-absorbing layer, the barrier layer exhibiting a valence band energy level substantially equal to the valence band energy level of the doped semiconductor of the photo absorbing layer; and a contact area comprising a doped semiconductor, the contact area being adjacent a second side of the barrier layer opposing the first side, the barrier layer exhibiting a thickness and conductance band gap sufficient to prevent tunneling of majority carriers from the photo-absorbing layer to the contact area, blocking the flow of thermalized majority carriers from the photo-absorbing layer to the contact area. Alternatively, a p-doped semiconductor is utilized, equalizing barrier conductance band energy levels and photo-absorbing layers.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patent application Ser. No. 13/167,992 which was filed on Jun. 24, 2011, which in turn is a continuation of, and claims priority of U.S. patent application Ser. No. 12/656,739 filed Feb. 16, 2010, and which in turn is a continuation of, and claims priority of U.S. patent application Ser. No. 11/276,962 filed Mar. 19, 2006.This application is a Reissue of U.S. Pat. No. 9,117,726, issued Aug. 25, 2015 on application Ser. No. 13/964,883, filed Aug. 12, 2013; which is in turn a continuation-in-part of patent application Ser. No. 13/167,992 filed on Jun. 24, 2011 now abandoned; which is in turn a continuation of patent application Ser. No. 12/656,739 filed Feb. 16, 2010, issued as U.S. Pat. No. 8,003,434 on Aug. 23, 2011; and which in turn is a divisional of patent application Ser. No. 11/276,962 filed Mar. 19, 2006, issued as U.S. Pat. No. 7,687,871 on Mar. 30, 2010. The entire contents of U.S. patent application Ser. No. 13/167,992 U.S. patent application Ser. No. 12/656,739, and U.S. patent application Ser. No. 11/276,962 are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates generally to the field of semiconductor based photo-detectors and in particular to a photo-detector exhibiting a barrier region between an active semiconductor region and a contact semiconductor region.

Photo-detectors are used in a wide variety of applications including imaging. A specific type of photo-detector sensitive to the infra-red wavelengths of light is also known as an infra-red detector. Infra-red covers a broad range of wavelengths, and many materials are only sensitive to a certain range of wavelengths. As a result, the infra-red band is further divided into sub-bands such as near infra-red defined conventionally as 0.75-1.4 μm; short wavelength infra-red defined conventionally as 1.3-3 μm; mid wavelength infra-red defined conventionally as 3-8 μm; and far infra-red defined conventionally as 15-1,000 μm. Infra-red in the range of 5 μm to 8 μm is not well transmitted in the atmosphere and thus for many infra-red detection applications mid-wavelength infra-red is referred to as 3-5 μm.

Infra-red detectors are used in a wide variety of applications, and in particular in the military field where they are used as thermal detectors in night vision equipment, air borne systems, naval systems and missile systems. Highly accurate thermal detectors have been produced using InSb and HgCdTe p-n junction diodes, however these thermal detectors require cooling to cryogenic temperatures of around 77 K which is costly. Examples of these existing technologies are presented inFIG. 5A toFIG. 5F. The cryogenic temperatures primarily are used to reduce the dark current generated in the p-n junction diode by among other effects Shockley Reed Hall (SRH) generation.

There are three main contributions to the dark current, denoted as I_dark, of photodiodes based on narrow band gap semiconductors. The fluctuations of the dark current components are a major factor in the noise that limits the device performance. These components are:

a) a generation current associated with the Shockley-Reed-Hall (SRH) process in the depletion region, I_srh;

b) a diffusion current associated with auger or radiative processes in the extrinsic area, I_diff; and

c) a surface current associated with the surface states in the junction, I_surf. The surface current depends primarily on the passivation process done for the device. Thus, I_darkcan be expressed as:
I_dark=I_srh+I_diff+I_surf  Equation 1

The SRH generation process is very efficient in the depletion region of photodiodes where the mid-gap traps are highly activated. It is the main source of the dark current in photodiodes operable for mid-wavelength infrared at temperatures below 200K. The current associated with this source is:

$\begin{array}{cc}{J}_{SRH}=q\frac{n_i}{{\tau }_{SRH}}{W}_{dep}& \mathrm{Equation}2\end{array}$
where n_iis the intrinsic concentration of the semiconductor, W_depis the depletion width (typically in the range of 1 μm), and τ_SRHis the SRH lifetime of minority carriers in the extrinsic area. The SRH lifetime of minority carriers in the extrinsic area depends on the quality of the material, i.e. the trap concentration, and is typically in the range of ˜1 μsec in low doped material (˜10¹⁶cm⁻³). The dependence of SRH current on n_iproduces an activation energy of

$\begin{array}{cc}{E}_g/2\left(n_i~\exp \left(-\frac{\frac{E_g}{2}}{\mathrm{kT}}\right)\right),& \end{array}$
because the source of this generation process is through mid-gap traps. A secondary source of dark current in photodiodes is thermal generation in the neutral regions and diffusion to the other side of the junction. This thermal generation current depends on the auger or radiative process in this area, and is expressed as:

$\begin{array}{cc}{J}_{\mathrm{diff}}\approx {\mathrm{qp}}_n\times \frac{1}{{\tau }_{\mathrm{diff}}}\times L=q\times \frac{n_i^2}{N_d}\times \frac{1}{{\tau }_{\mathrm{diff}}}\times L& \mathrm{Equation}3\end{array}$
where τ_diffis the lifetime, and in an n-type material exhibiting a doping concentration, denoted N_d, of ˜1-2·10¹⁶cm⁻³is in the range of ˜0.5 μsec, depending only slightly on temperature. L is the width of the neutral region of the device or the diffusion length of minority carriers (the smaller of the two) and p_nis the hole concentration in the active n type semiconductor in equilibrium and it equal to n_i²/N_d. The activation energy of the diffusion current is

$E_g,\left(n_i^2~\exp \left(-\frac{E_g}{\mathrm{kT}}\right)\right)$
as the process involves band to band excitation.

Additionally, p-n junction diodes, and particularly those produced for thermal imaging require a passivation layer in the metallurgic junction between the p and n layers. Unfortunately this is often difficult to achieve and significantly adds to the cost of production.

There is thus a long felt need for a thermal imaging device that uses a photo-detector with reduced dark noise. Preferably the photo-detector would be sensitive to the mid wavelength infra-red band and not require expensive passivation in production. Further preferably the photo-detector would be operable at significantly higher temperatures than 77K. Further preferably the thermal imaging device would be able to operate for longer periods, be lighter and require less power, when compared to the existing technology in the art.

SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the present disclosure to overcome the disadvantages of the existing technological deficiencies of photo-detectors and their application within thermal imaging devices, with particular reference to mid wavelength infra-red detectors. This is provided in the present invention by a photo-detector sensitive to a target waveband comprising a photo absorbing layer, preferably exhibiting a thickness on the order of the optical absorption length. In an exemplary embodiment the photo absorbing layer is deposited to a thickness of between one and two times the optical absorption length. A contact layer is further provided, and a barrier layer is interposed between the photo absorbing layer and the contact layer. The barrier layer exhibits a thickness sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact layer, and a band gap barrier sufficient to block the flow of thermalized majority carriers from the photo absorbing layer to the contact layer. The barrier layer does not significantly block minority carriers.

An infra-red detector in accordance with the principle of the invention can be produced using either an n-doped photo absorbing layer or a p-doped photo absorbing layer, in which the barrier layer is designed to have no offset for minority carriers and a band gap barrier for majority carriers. Current in the detector is thus almost exclusively by minority carriers. In particular, for an n-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero valence band offset, i.e. the band gap difference appears almost exclusively in the conduction band offset. For a p-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero conduction band offset, i.e. the band gap difference appears almost exclusively in the valence band offset.

Advantageously the photo-detector of the subject invention does not exhibit a depletion layer, and thus the dark current is significantly reduced. Furthermore, in an exemplary embodiment passivation is not required as the barrier layer further functions to achieve passivation.

An exemplary photo-detector of the present disclosure comprises: a photo absorbing layer comprising an n-doped semiconductor exhibiting a valence band energy level and a conducting band energy level; a barrier layer, a first side of the barrier layer adjacent a first side of the photo absorbing layer, the barrier layer exhibiting a valence band energy level substantially equal to the valence band energy level of the photo absorbing layer and a conduction band energy level exhibiting a significant band gap in relation to the conduction band of the photo absorbing layer; and a contact area comprising a doped semiconductor, the contact area being adjacent a second side of the barrier layer opposing the first side, the barrier layer exhibiting a thickness, the thickness and the band gap being sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact area and block the flow of thermalized majority carriers from the photo absorbing layer to the contact area.

In one embodiment of the photo detector the barrier layer comprises an undoped semiconductor. In another embodiment the contact area is n-doped. In a further embodiment, the contact area exhibits a valence band energy level substantially equal to the valence band energy level of the n-doped semiconductor of the photo absorbing layer.

In one embodiment of the photo detector the contact area is p-doped. In one further embodiment the contact area exhibits a valence band energy level greater than the valence band energy level of the n-doped semiconductor of the photo absorbing layer. In another further embodiment the barrier layer comprises an undoped semiconductor.

In one embodiment of the photo detector the photo absorbing layer is operable to generate minority carriers in the presence of light energy exhibiting a wavelength of 3-5 microns. In another embodiment the photo-detector further comprises a substrate exhibiting a first side adjacent a second side of the photo absorbing layer, the second side of the photo absorbing layer opposing the first side of the photo absorbing layer, the substrate exhibiting a second side in contact with a metal layer. Preferably, the photo-detector further comprises an additional metal layer in contact with the contact area.

In one embodiment of the photo detector the barrier layer comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb and HgZnTe. In a further embodiment the photo absorbing layer is constituted of one of n-doped InAs, n-doped InAsSb, n-doped InGaAs, n-doped Type II super lattice InAs/InGaSb and n-doped HgCdTe. In a yet further embodiment of the photo detector the contact area is constituted of one of InAs, InGaAs, InAsSb, Type II super lattice InAs/InGaSb, HgCdTe and GaSb. In a yet further embodiment the contact area and the photo absorbing layer exhibit substantially identical compositions.

In one embodiment of the photo detector the photo absorbing layer and the contact area arc constituted of n-doped HgCdTe and the barrier layer is constituted of HgZnTe, and in another embodiment the photo absorbing layer and the contact layer are constituted of n-doped type II super lattice InAs/InGaSb and the barrier layer is constituted of AlGaAsSb.

In another embodiment of the photo detector the photo absorbing layer is constituted of n-doped InAsSb, the barrier layer is constituted of AlGaAsSb and the contact layer is constituted of p-doped GaSb. In one embodiment the photo absorbing layer exhibits a thickness on the order of the optical absorption length.

Another embodiment of a photo-detector comprises: a photo absorbing layer comprising a p-doped semiconductor exhibiting a conduction band energy level and a valence band energy level; a barrier layer, a first side of the barrier layer adjacent a first side of the photo absorbing layer, the barrier layer exhibiting a conduction band energy level substantially equal to the conduction band energy level of the photo absorbing layer and a valence band energy level exhibiting a significant band gap in relation to the valence band of the photo absorbing layer; and a contact area comprising a doped semiconductor, the contact area adjacent a second side of the barrier layer opposing the first side, the barrier layer exhibiting a thickness, the thickness and the band gap being sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact area and to block the flow of thermalized majority carriers from the photo absorbing layer to the contact area.

In one embodiment of a photo-detector the barrier layer comprises an undoped semiconductor. In another embodiment the contact area is p-doped. In one further embodiment of a photo-detector the contact area exhibits a conduction band energy level substantially equal to the conduction band energy level of the p-doped semiconductor of the photo absorbing layer.

In one embodiment of a photo-detector the contact area is n-doped. In one further embodiment the contact area exhibits a conduction band energy level less than the conduction band energy level of the p-doped semiconductor of the photo absorbing layer. In another further embodiment the barrier layer comprises an undoped semiconductor.

In one embodiment of a photo-detector the photo absorbing layer is operable to generate minority carriers in the presence of light energy exhibiting a wavelength of 3-5 microns. In another embodiment the photo-detector further comprises a substrate exhibiting a first side adjacent a second side of the photo absorbing layer, the second side of the photo absorbing layer opposing the first side of the photo absorbing layer, the substrate exhibiting a second side in contact with a metal layer. In a further embodiment the photo-detector further comprises a metal layer in contact with the contact area.

In one embodiment of a photo-detector the barrier layer comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb, InAlAs, InAlAsSb, and HgZnTe. In one further embodiment the photo absorbing layer is constituted of one of p-doped InAs, p-doped InAsSb, p-doped InGaAs, p-doped Type II super lattice InAs/InGaSb and p-doped HgCdTe. In one yet further embodiment the contact area is constituted of one of InAs, InGaAs, InAsSb, Type II super lattice InAs/InGaSb, HgCdTe and GaSb. In one yet further embodiment the contact area and the photo absorbing layer exhibit substantially identical compositions.

An exemplary method of producing a photo-detector, comprises: providing a substrate; depositing on the substrate a photo absorbing layer comprising a doped semiconductor exhibiting an energy level associated with non-conducting majority carriers; depositing on the deposited photo absorbing layer a barrier layer exhibiting a thickness, an energy level associated with minority carriers of the photo absorbing layer substantially equal to the energy level of the photo absorbing layer and a band gap associated with majority carriers of the photo absorbing layer; and depositing on the deposited barrier layer a contact layer comprising a doped semiconductor, the thickness and the band gap of the barrier layer being sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact layer and to block the flow of thermalized majority carriers from the photo absorbing layer to the contact layer.

In one embodiment the method further comprises selectively etching the deposited contact layer to define a plurality of contact areas. In another embodiment at least one of depositing the photo absorbing layer, depositing the barrier layer and depositing the contact layer is done via one of molecular beam epitaxy, metal organic chemical vapor deposition, metal organic phase epitaxy and liquid phase epitaxy. Additional features and advantages of the invention will become apparent from the following drawings and description.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout.

With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the accompanying drawings:

FIG. 1A illustrates a high level schematic view of the layers of a single photo-detector according to an embodiment of the principle of the invention;

FIG. 1B illustrates a side view of a multi-pixel photo-detector according to an embodiment of the principle of the invention;

FIG. 1C illustrates a top level view of the multi-pixel photo-detector ofFIG. 1B according to a principle of the invention;

FIG. 2A illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is n-doped and the contact layer is n-doped;

FIG. 2B illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is p-doped and the contact layer is p-doped;

FIG. 3A illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is n-doped and the contact layer is p-doped;

FIG. 3B illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is p-doped and the contact layer is n-doped; and

FIG. 4 illustrates a high level flow chart of the process of manufacture of the multi pixel photo-detector ofFIGS. 1B-1C.

FIGS. 5a, 5B, 5C, 5D, 5E and 5F illustrate examples of existing applications of the prior-art photo-detector technology.

FIG. 6 illustrates the existing external components of an exemplary thermal imaging device with an integrated dewar cooler assembly, hereafter IDCA.

FIG. 7 illustrates the internal components of an exemplary application of the disclosed subject matter.

FIG. 8 illustrates the resultant output as a result of the application of the disclosed subject matter.

FIG. 9A illustrates an exemplary linear micro cooler (Ricor's K527 split) that is utilized in conjunction with the disclosed subject matter.

FIG. 9B illustrates an exemplary application of the disclosed subject matter's resultant improvement in cooling power requirements.

FIG. 10A illustrates a mother board joined to FPA.

FIG. 10B illustrates a FPA and motherboard located within IDCA arrangement.

FIG. 11 illustrates a schematic application of the disclosed subject matter.

FIG. 12 illustrates an operational flow chart of an exemplary optical imaging device with an IDCA comprising the disclosed FDA.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present embodiments enable a photo-detector sensitive to a target waveband comprising a photo absorbing layer, preferably exhibiting a thickness on the order of an optical absorption length of the target waveband. In an exemplary embodiment the photo absorbing layer is deposited to a thickness of between one and two times the optical absorption length. A contact layer is further provided, and a barrier layer is interposed between the photo absorbing layer and the contact layer. The barrier layer exhibits a thickness sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact layer, and a band gap barrier sufficient to block the flow of thermalized majority carriers from the photo absorbing layer to the contact layer. The barrier layer does not significantly block minority carriers.

An infra-red detector in accordance with the principle of the invention can be produced using either an n-doped photo absorbing layer or a p-doped photo absorbing layer, in which the barrier layer is designed to have substantially no offset for minority carriers and a band gap barrier for majority carriers. Current in the detector is thus almost exclusively by minority carriers. In particular, for an n-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero valence band offset, i.e. the band gap difference appears almost exclusively in the conduction band offset. For a p-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero conduction band offset, i.e. the band gap difference appears almost exclusively in the valence band offset.

Advantageously the photo-detector of the subject invention does not exhibit a depletion layer, and thus the dark current is significantly reduced. Furthermore, in an exemplary embodiment passivation is not required as the barrier layer further functions to achieve passivation.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting.

FIG. 1A illustrates a high level schematic view of the layers of a photo-detector10 according to an embodiment of the principle of the invention comprising asubstrate20, aphoto absorbing layer30, abarrier layer40, acontact layer50, ametal layer60 and ametal layer65.Substrate20 is provided as a base for deposition and has deposited on oneface metal layer60 for connection to electronic circuitry. In an exemplaryembodiment metal layer60 is constituted of gold.Photo absorbing layer30 is deposited on the second face ofsubstrate20 opposing the first face.Photo absorbing layer30 comprises a doped semiconductor responsive to photons of the object wavelength, and preferably is deposited to a thickness on the order of an optical absorption length. In one embodimentphoto absorbing layer30 is deposited to a thickness of between one and two times the optical absorption length. In an exemplary embodimentphoto absorbing layer30 comprises one of n-doped InAs; n-doped InAsSb; n-doped InGaAs; n-doped type II super lattice of the type InAs/InGaSb; and n-doped HgCdTe. In an alternativeembodiment absorbing layer30 comprises one of p-doped InAs; p-doped InAsSb; p-doped InGaAs; p-doped type II super lattice of the type InAs/InGaSb; and p-doped HgCdTe.

Barrier layer40 is deposited directly onphoto absorbing layer30 without requiring passivation. Barrier layer is deposited to a thickness sufficient to substantially prevent tunneling of majority carriers fromphoto absorbing layer30 to contactlayer50, and in an exemplary embodiment is deposited to a thickness of 50-100 nm.Barrier layer40 comprises a material selected to exhibit a high band gap barrier for majority carriers fromphoto absorbing layer30 and substantially no band gap barrier for minority carriers.Barrier layer40 is thus sufficient to block both the flow of thermalized majority carriers and the tunneling of majority carriers fromphoto absorbing layer30 to contactlayer50. Thus, for an n-typephoto absorbing layer30, the band gap difference appears in the conduction band, whereas substantially no band gap offset appears in the valence band. In oneembodiment barrier layer40 comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb and HgZnTe. In an exemplary embodimentphoto absorbing layer30 comprises n-doped InAs andbarrier layer40 is comprised of AlAs_xSb_1-xwith x˜0.15, and thus there is ˜0 valence band offset.

Contact layer50 is deposited onbarrier layer40.Contact layer50 functions to absorb the minority carriers diffused from the absorbinglayer30 and is essentially a contact layer. In an exemplaryembodiment contact layer50 is deposited to a thickness of 20-50 nm and is constituted of one of InAs; InAsSb; InGaAs; type II super lattice of the type InAs/InGaSb; HgCdTe and GaSb.Contact layer50 may be n-doped or p-doped without exceeding the scope of the invention. Advantageously,contact layer50 may be constituted of the same material asphoto absorbing layer30.Contact layer50 is etched, preferably by photolithography, to define the detector area. Advantageously etching ofbarrier layer40 or absorbinglayer30 is not required.Metal layer65 is deposited oncontact layer50, and in an exemplary embodiment is constituted of gold. Metal layers60,65 enable the connection of an appropriate bias, and a connection to detect a flow of current fromphoto absorbing layer30 to contactlayer50.

FIG. 1B illustrates a side view of a multi-pixel photo-detector100 according to an embodiment of the principle of theinvention comprising substrate20,photo absorbing layer30,barrier layer40, a first andsecond contact area110, a metal layer6 and ametal layer65.Substrate20 is provided as a base for deposition and has deposited on one face metal layer for connection to electronic circuitry. In an exemplaryembodiment metal layer60 is constituted of gold.Photo absorbing layer30 is deposited on the second face ofsubstrate20 opposing the first face.Photo absorbing layer30 comprises a doped semiconductor responsive to photons of the object wavelength, and preferably is deposited to a thickness on the order of an optical absorption length. In one embodimentphoto absorbing layer30 is deposited to between one and two times the optical absorption length. In an exemplary embodimentphoto absorbing layer30 comprises one of n-doped InAs; n-doped InAsSb; n-doped InGaAs; n-doped type II super lattice of the type InAs/InGaSb; and n-doped HgCdTe. In an alternativeembodiment absorbing layer30 comprises one of p-doped InAs; p-doped InAsSb; p-doped InGaAs; p-doped type II super lattice of the type InAs/InGaSb; and p-doped HgCdTe.

Barrier layer40 is deposited directly onphoto absorbing layer30 without requiring passivation. Barrier layer is deposited to a thickness sufficient to substantially prevent tunneling of majority carriers fromphoto absorbing layer30 to first andsecond contact area110, and in an exemplary embodiment is deposited to a thickness of 50-100 nm.Barrier layer40 comprises a material selected to exhibit a high band gap barrier for majority carriers fromphoto absorbing layer30 and substantially no band gap barrier for minority carriers.Barrier layer40 is thus sufficient to block both the flow of thermalized majority carriers and the tunneling of majority carriers fromphoto absorbing layer30 to first andsecond contact area110. Thus, for an n-typephoto absorbing layer30, the band gap difference appears in the conduction band, whereas substantially no band gap offset appears in the valence band. In oneembodiment barrier layer40 comprises one of AlSb, AlAsSb, GaAlAsSb, AlPSb, AlGaPSb and HgZnTe. In an exemplary embodimentphoto absorbing layer30 comprises n-doped InAs andbarrier layer40 is comprised of AlAs_xSb_1-xwith x˜0.15, and thus there is ˜0 valence band offset.

Contact layer50 as described above in relation toFIG. 1A is deposited onbarrier layer40.Contact layer50, which as will be described further is etched to define first andsecond contact area110, functions to absorb the minority carriers diffused from the absorbinglayer30 and is essentially a contact layer. In an exemplaryembodiment contact layer50 is deposited to a thickness of 20-50 nm and is constituted of one of InAs; InAsSb; InGaAs; type II super lattice of the type InAs/InGaSb; HgCdTe and GaSb.Contact layer50 may be n-doped or p-doped without exceeding the scope of the invention. Advantageously,contact layer50 may be constituted of the same material asphoto absorbing layer30.Contact layer50 is etched, preferably by photolithography, to define first andsecond contact area110. Advantageously etching ofbarrier layer40 or absorbinglayer30 is not required. In an exemplary embodiment a selective etchant is used which does not etchbarrier layer40.Metal layer65 is deposited on each of first andsecond contact area110, and in an exemplary embodiment is constituted of gold. Thus, a single photo absorbing layer and barrier layer is utilized, with each unetched portion ofcontact layer50 defining a pixel or individual detector.

The above has been described in an embodiment in which two pixels, or detectors are defined, however this is not meant to be limiting in any way. A large array of photo-detectors produced as above is specifically included in the invention.

FIG. 1C illustrates a top level view of multi-pixel photo-detector100 ofFIG. 1B according to a principle of the invention showingbarrier layer40, first andsecond contact area110 andmetal layer65 defined on each of first andsecond contact area110.

FIG. 2A illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is n-doped and the contact layer is n-doped, in which the x-axis indicates position along the structure ofFIG. 1 and the y-axis indicates energy levels in an arbitrary illustrative manner. Three energy band levels are depicted: E_v, the valence band energy band level; E_f, the Fermi energy band level; and E_cthe conducting band energy level.Area100 represents the energy band levels withinphoto absorbing layer30,area110 represents the energy band levels withinbarrier layer40 andarea120 represent the energy band levels withincontact layer50.

The valence band energy level is substantially constant throughoutareas100,110 and120, and thus minority carriers are not obstructed from flowing fromphoto absorbing area100 to contactarea120. It is to be noted that due to the energy levels the minority carriers are captured incontact area120.Barrier layer40, represented byarea110, is thick enough so that there is negligible tunneling of majority carriers through it. In an exemplaryembodiment barrier layer40 is deposited to a thickness of 50-100 nm, and the band gap barrier ofarea110 is high enough so that there is negligible thermal excitation of majority carriers over it.Area120 shows energy band levels on a par with that ofarea100 however this is not meant to be limiting in any way. In one embodiment E_fincontact layer area120 is slightly higher than their values inphoto absorbing area100 with the increase being attributed to an increased doping concentration. It is to be noted that no depletion layer is present and therefore there is no SRH current. Photocurrent is a result of optically generated minority carriers which diffuse fromphoto absorbing area100 to contactarea120.

FIG. 2B illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is p-doped and the contact layer is p-doped; in which the x-axis indicates position along the structure ofFIG. 1 and the y-axis indicates energy levels in an arbitrary illustrative manner. Three energy band levels are depicted: E_v, the valence band energy level; E_f, the Fermi energy band level; and E_cthe conducting band energy level.Area150 represents the energy band levels withinphoto absorbing layer30,area160 represents the energy band levels withinbarrier layer40 andarea170 represent the energy band levels withincontact layer50.

The conduction band energy level is substantially constant throughoutareas150,160 and170, and thus minority carriers are not obstructed from flowing fromphoto absorbing area150 to contactarea170. It is to be noted that due to the energy levels the minority carriers are captured incontact area170.Barrier layer40, represented byarea160, is thick enough so that there is negligible tunneling of majority carriers through it. In an exemplaryembodiment barrier layer40 is deposited to a thickness of 50-100 nm, and the band gap barrier ofarea160 is high enough so that there is negligible thermal excitation of majority carriers over it.Area170 shows energy band levels on a par with that ofarea150 however this is not meant to be limiting in any way. In one embodiment E_fincontact layer area170 is slightly higher than their values inphoto absorbing area150 with the increase being attributed to an increased doping concentration. It is to be noted that no depletion layer is present and therefore there is no SRH current. Photocurrent is a result of optically generated minority carriers which diffuse fromphoto absorbing area150 to contactarea170.

FIG. 3A illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is n-doped and the contact layer is p-doped; in which the x-axis indicates position along the structure ofFIG. 1 and the y-axis indicates energy levels in an arbitrary illustrative manner. Three energy band levels are depicted: E_v, the valence band energy level; E_f, the Fermi energy band level; and E_cthe conducting band energy level.Area200 represents the energy band levels withinphoto absorbing layer30,area210 represents the energy band levels withinbarrier layer40 andarea220 represent the energy band levels withincontact layer50.

The valence band energy level is substantially constant throughoutareas200 and210 and is higher inarea220, and thus minority carriers are not obstructed from flowing fromphoto absorbing area200 to contactarea220. It is to be noted that due to the energy levels the minority carriers are captured incontact area220.Barrier layer40, represented byarea210, is thick enough so that there is negligible tunneling of majority carriers through it. In an exemplaryembodiment barrier layer40 is deposited to a thickness of 50-100 nm, and the band gap barrier ofarea210 is high enough so that there is negligible thermal excitation of majority carriers over it. It is to be noted that no depletion layer is present and therefore there is no SRH current. Photocurrent is a result of optically generated minority carriers which diffuse fromphoto absorbing area200 to contactarea220.

FIG. 3B illustrates the energy band levels of an embodiment of the structure ofFIG. 1 according to the principle of the invention in which the photo absorbing layer is p-doped and the contact layer is n-doped; in which the x-axis indicates position along the structure ofFIG. 1 and the y-axis indicates energy levels in an arbitrary illustrative manner. Three energy band levels are depicted: E_v, the valence band energy level; E_f, the Fermi energy band level; and E_cthe conducting band energy level.Area250 represents the energy band levels withinphoto absorbing layer30,area260 represents the energy band levels withinbarrier layer40 andarea270 represent the energy band levels withincontact layer50.

The conduction band energy level is substantially constant throughoutareas250 and260 and it is lower inarea270, and thus minority carriers are not obstructed from flowing from thephoto absorbing area250 to contactarea270. It is to be noted that due to the energy levels the minority carriers are captured incontact area270.Barrier layer40, represented byarea260, is thick enough so that there is negligible tunneling of majority carriers through it. In an exemplaryembodiment barrier layer40 is deposited to a thickness of 50-100 nm, and the band gap barrier ofarea260 is high enough so that there is negligible thermal excitation of majority carriers over it. It is to be noted that no depletion layer is present and therefore there is no SRH current. Photocurrent is a result of optically generated minority carriers which diffuse fromphoto absorbing area250 to contactarea270.

FIG. 4 illustrates a high level flow chart of the process of manufacture of the photo-detector ofFIG. 1. In stage1000 a substrate material is provided as a support for deposition. Instage1010, a photo absorbing layer is deposited on the substrate. Preferably the photo absorbing layer is deposited to a thickness on the order of the optical absorption length and in an exemplary embodiment is deposited to a thickness of between one and two times the optical absorption length.

Instage1020, a barrier material is selected such that the flow of thermalized majority carriers from the photo absorbing layer deposited instage1010 would be negligible, and the flow of minority carriers is not impeded. Instage1030, the barrier material selected instage1020 is deposited to a thickness sufficient to prevent tunneling of majority carriers through the barrier material. In an exemplary embodiment the thickness is between 50 and 100 nm. Preferably the barrier material is deposited directly on the photo absorbing layer deposited instage1010.

Instage1040, a contact layer is deposited, preferably directly on the barrier material deposited instage1030. Instage1050, the desired contact areas are defined. Preferably, the contact areas are defined by photolithography and a selective etchant which stops on the top of the barrier layer. Alternatively, the etchant may be controlled to stop once the uncovered portions ofcontact layer50 are removed. Thus, the depth of the etch is equivalent to the thickness of thecontact layer50. Advantageously, in an exemplary embodiment no other layer is etched.

In stage1060 a metal layer is deposited on the contact areas defined instage1050 so as to enable electrical connection. Preferably the metal layer is deposited directly on the contact areas defined instage1050. Instage1070, a metal layer is deposited onsubstrate20 provided instage1000 so as to enable electrical connection.

Deposition of the photo absorbing layer ofstage1010, the barrier layer ofstage1030 and the contact layer ofstage1040 may be accomplished by any means known to those skilled in the art including, without limitation molecular beam epitaxy, metal organic chemical vapor deposition, metal organic phase epitaxy or liquid phase epitaxy.

Thus the present embodiment enable a photo-detector sensitive to a target waveband comprising a photo absorbing layer, preferably exhibiting a thickness on the order of the optical absorption length. In an exemplary embodiment the photo absorbing layer is deposited to a thickness of between one and two times the optical absorption length. A contact layer is further provided, and a barrier layer is interposed between the photo absorbing layer and the contact layer. The barrier layer exhibits a thickness sufficient to prevent tunneling of majority carriers from the photo absorbing layer to the contact layer, and a band gap barrier sufficient to block the flow of thermalized majority carriers from the photo absorbing layer to the contact layer. The barrier layer does not block minority carriers.

An infra-red detector in accordance with the principle of the invention can be produced using either an n-doped photo absorbing layer or a p-doped photo absorbing layer, in which the barrier layer is designed to have no offset for minority carriers and a band gap barrier for majority carriers. Current in the detector is thus almost exclusively by minority carriers. In particular, for an n-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero valence band offset, i.e. the band gap difference appears almost exclusively in the conduction band offset. For a p-doped photo absorbing layer the junction between the barrier layer and the absorbing layer is such that there is substantially zero conduction band offset, i.e. the band gap difference appears almost exclusively in the valence band offset.

Advantageously the photo-detector of the subject invention does not exhibit a depletion layer, and thus the dark current is significantly reduced. Furthermore, in an exemplary embodiment passivation is not required as the barrier layer further functions to achieve passivation.

An exemplary application of the disclosed subject matter is the inclusion of an array of photo detectors within a focal plan array, hereafter FPA, which form an integral component of optical imaging devices, including thermal imaging devices. Use of the disclosed subject matter within the FPA enables improved thermal imaging device performance, including but not limited to, weight, duration of operation, power requirements, cost, pixel operability and durability.

FIGS. 5A, 5B, 5C and 5D present hand-held imaging systems, which utilize the existing photo detector technology.

FIGS. 5E and 5F present aviation technology, which utilize the existing photo detector technology, including the Lockheed Sniper Pod and the Northrop Grumman EOTS pod.

FIG. 6 presents a further example of the existing technology, wherein light enters the apparatus through thefront lens optic602, interacts with the apparatusinternal electroptic componentary604, where it is converted from infra-red light to a electric signal, which is transmitted and presented on the apparatus'display606.

FIG. 7 presents in greater detail the essential components of an exemplary integrated dewar cooler system, hereafter IDCS. In one embodiment, light enters the system700 through thefront optic704, the light than is received by the FPA, which is located on the cold finger of thedewar702, and is maintained at a cryogenic temperature. In one embodiment of the disclosure, the FPA operates at a temperature of 150K. In other embodiments, the FPA can operate across a temperature spectrum of between 77K and 150K. The IDCS further comprises a micro-cooler706, which is responsible for the refiguration of the FPA.

FIG. 8 presents an output image utilizing the disclosed subject matter, with a dewar operating temperature of 150K, a lens focal length of f/3.0, a noise equivalent differential temperature (NEDT) of 23 mK, and a 99.93% pixel operability.

FIG. 9A presents an exemplary split linear micro cooler system, comprising a cooler902 connected via tubing904 to a cold finger906, and a external controller908 connected via wiring910 to cooler. The exemplary cooler system presented is the Ricor k527 split linear micro cooler. In other embodiment a variety of micro cooler systems can be used.

FIG. 9B illustrates the micro-cooler power consumption per heat load across a spectrum of cold finger temperatures.

FIG. 10A presents theFPA1002 coupled to amotherboard1004, which forms a FPA arrangement that can connect to the cold finger.

FIG. 10B presents an IDCS in greater detail, wherein light enters thedewar1114 via theoptical window1110, with a micro-cooler1102 providing refrigeration for the FPA.

FIG. 11 illustrates an exemplary schematic IDCA arrangement. The system operates by allowing light through thefront element1110 which is an optical window located behind a fronting lens, not shown. Light enters through the optical window before interacting with theFPA1114. The FPA arrangement comprises an array of photo-detectors, coupled to a motherboard. The FPA arrangement is contained within the cold finger of a cryogenic vacuum sealed dewar1116-1112, which is refrigerated by themicro cooler1102. The dewar additional comprising: agetter unit1104; acold shield1108 contained within thewindow envelope1112, which are positioned on thecold finger1116. Light interacts with the FPA arrangement, which produces a photo-electronic signal in response. The photo-electronic signal is in turn transmitted from the FPA arrangement via wiring to the feed-through pins1106.

FIG. 12 presents an flow chart diagram of an exemplary operational process of the disclosed subject matter, comprising: light being generated atsource1202; light entering the apparatus through thefront lens element1204; light interacting with theFPA1206; the FPA generating aelectro message1208; the electro message being transmitted from the FPA to the IDCA'sfeeder tubes1210; the electro message being received by thedevices electronics1214; wherein the device either display theimage1216 or transmits the image to anexternal display device1218.

In one embodiment, the optical imaging device containing the IDCA has an interchangeable front lens element. In other embodiment, the front lens element may be fixed, may be fixed and variable, and other arrangements as standard in the art.

In one embodiment of the disclosed subject matter, the IDCA with an array of improved photo detector is accommodated within amateur, professional, or commercial optical devices. In other embodiments, the IDCA is located within military equipment. Aviation examples include precision targeting devices, or Electro Optic Targeting Systems (EOTS).

In yet another embodiment, the IDCA can comprise a plurality of FPA.

Examples of the above disclosure included but is not limited to, incorporation of the claimed IDCA within: Lockheed Sniper Pod Technology; Lockheed EOTS pods; AN/AAQ-37 F-35 Distributed Aperture System (DAS made by Northrop Grumman) and other similar technology; hand-held personal cameras; professional cameras; and security optical devices; another example is missile seeker. The disclosed IDCA apparatus could also be incorporated into the existing technologies outlined in the background of the invention.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

Unless otherwise defined, all technical and scientific terms used herein have the same meanings as are commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods are described herein.

All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the patent specification, including definitions, will prevail. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof, which would occur to persons skilled in the art upon reading the foregoing description.

Claims (20)

What is claimed is:

1. An integrated dewar cooler system comprising:

a light permitting optical window;

a cryogenic and vacuum sealed Dewar;

a motherboard;

a micro Cooler; and

a focal plan array,

wherein a portion of said focal plan array is connected to a portion of said motherboard and wherein said motherboard and FPA assembly are located within the dewar,

wherein said focal plan array is an array of photo detectors with a reduced dark current, comprising:

a photo absorbing layer comprising a doped semiconductor exhibiting a valence band energy and a conducting band energy during operation of the photo-detector;

a barrier layer comprising an undoped semiconductor, the barrier layer having a band energy gap and associated conduction and valence band energies, a first side of said barrier layer adjacent a first side of said photo absorbing layer; and

a contact layer comprising a doped semiconductor exhibiting a valence band energy and a conducting band energy during operation of the photo-detector, said contact layer being adjacent a second side of said barrier layer opposing said first side;

wherein the relationship between the photo absorbing layer and contact layer valence and conduction band energies and the barrier layer conduction and valance band energies facilitates minority carrier current flow while inhibiting majority carrier current flow between the contact and photo absorbing layers.

2. The system ofclaim 1, wherein said photo absorbing layer is constituted of one of InAs, InAsSb, InGaAs, Type II super lattice InAs/InGaSb and HgCdTe.

3. The system ofclaim 2, wherein said contact layer is constituted of one of InAs, InGaAs, InAsSb, Type II super lattice InAs/InGaSb, HgCdTe and GaSb.

4. The system ofclaim 3, wherein said contact layer and said photo absorbing layer exhibit substantially identical compositions.

5. The system ofclaim 1, wherein the photo absorbing layer and the contact layer are either both n-type or both p-type.

6. The system ofclaim 1, wherein said contact layer comprises individual sections which are separate from each other in a direction across the photo-detector, each section corresponding to an individual detector element, wherein said barrier layer extends past the individual sections of the contact layer in the direction across the photo-detector, and is monolithically provided for each of the individual detector elements, thereby passivating the photo-detector during operation by blocking the flow of majority carriers to exposed surfaces of said barrier layer.

7. The system ofclaim 1, wherein the contact layer forms a mesa on the barrier layer such that the second side of said barrier layer laterally extends beyond the contact layer thereby passivating the photo-detector during operation by preventing majority carriers from flowing to exposed surfaces of said barrier layer.

8. The system ofclaim 1, wherein the contact and photo-absorbing layers have the same majority carrier type such that the photo-detector has no substantial depletion layer.

9. The system ofclaim 1, wherein IDCA system is utilized in optical imaging devices, said optical imaging devices being at least one of: cameras; night vision equipment; military equipment; sniper pod; electronics optic targeting system; aviation optical equipment; missile seeker or thermal imaging devices.

10. An integrated dewar cooler system comprising:

a light permitting Optical window;

a cryogenic and vacuum sealed dewar;

a motherboard;

a micro Cooler; and

a focal plan array,

wherein a portion of said focal plan array is connected to a portion of said motherboard and wherein said motherboard and FPA assembly are located within Dewar,

wherein said focal plan array is array of photo detectors, comprising:

a photo absorbing layer comprising a n-doped semiconductor exhibiting a conduction band energy and valence band energy;

a barrier layer exhibiting a thickness, a first side of said barrier layer adjacent a first side of said photo absorbing layer; and

a contact layer comprising a doped semiconductor, said contact layer being adjacent a second side of said barrier layer opposing said first side, wherein said barrier layer exhibits a valence band energy substantially equal to said valence band energy of said photo absorbing layer and a conduction band energy greater than the conduction band energy of said photo absorbing layer such that said barrier layer forms a conduction energy band offset between the photo absorbing layer and the contact layer, wherein said barrier layer thickness and said conduction energy band offsets are sufficient to prevent tunneling of majority carriers between said photo absorbing layer to and said contact area and substantially block the flow of thermalized majority carriers between said photo absorbing layer and said contact area, wherein said contact layer comprises individual sections which are separate from each other in a direction across the photo-detector, each section corresponding to an individual detector element, wherein said barrier layer extends past the plural individual sections of the contact layer in the direction across the photo-detector, and is monolithically provided for each of the individual detector elements, thereby passivating the photo-detector during operation by blocking the flow of majority carriers to exposed surfaces of said barrier layer.

11. The system ofclaim 10, wherein IDCA system is utilized in optical imaging devices, said optical imaging devices being at least one of: cameras; night vision equipment; military equipment; sniper pod; electronics optic targeting system; aviation optical equipment; missile seeker or thermal imaging devices.

12. An integrated dewar cooler system comprising:

a light permitting optical window;

a cryogenic and vacuum sealed dewar;

a motherboard;

a micro Cooler; and

a focal plan array,

wherein a portion of said focal plan array is connected to a portion of said motherboard and wherein said motherboard and FPA assembly are located within Dewar,

wherein said focal plan array is an array of photo detectors, comprising:

a first layer comprising a doped semiconductor exhibiting a valence band energy and a conduction band energy, a barrier layer comprising a semiconductor exhibiting a valence band energy and a conduction band energy, a first side of said barrier layer adjacent a first side of said first layer; and

a second layer comprising a doped semiconductor exhibiting a valence band energy and a conduction band energy, said second layer being adjacent a second side of said barrier layer opposing said first side, the second layer having the same majority carrier type as the first layer, wherein during operation of the photo-detector the respective valence band energy and conduction band energy of the first layer, the barrier layer, and the second layer allow the flow of photo-generated minority carriers and substantially block the flow of majority carriers between the first layer and the second layer, wherein said second layer comprises individual sections which are isolated from each other in a direction across the photo-detector, each section corresponding to an individual detector element, wherein said barrier layer extends past the plural individual sections of the second layer in the direction across the photo-detector, and is monolithically provided for each of the individual detector elements, thereby passivating the photo-detector during operation by blocking the flow of majority carriers to exposed surfaces of said barrier layer.

13. The system ofclaim 12, wherein IDCA system is utilized in optical imaging devices, said optical imaging devices being at least one of: cameras; night vision equipment; military equipment; sniper pod; electronics optic targeting system; aviation optical equipment; missile seeker or thermal imaging devices.

14. An integrated dewar cooler system comprising:

a light permitting optical window;

a cryogenic and vacuum sealed Dewar;

a motherboard;

a micro Cooler; and

a focal plan array,

wherein a portion of said focal plan array is connected to a portion of said motherboard and wherein said motherboard and FPA assembly are located within Dewar,

wherein said focal plan array is an array of photo detectors, comprising:

a first layer comprising an electrically conductive semiconductor having majority and minority carrier types with associated energy bands;

a barrier layer with a barrier energy gap and associated conduction and valence bands, a first side of said barrier layer being adjacent said first layer;

a second layer comprising an electrically conductive semiconductor having majority and minority carrier types and an associated second layer energy gap, said second layer being adjacent a second side of said barrier layer opposing said first side;

wherein the relationship between the first and second layer energy bands and the barrier layer conduction and valance band edges enables minority carrier current flow while blocking majority carrier current flow between the first and second layers wherein the barrier layer comprises an undoped semiconductor which does not provide electrical conduction laterally within the barrier layer.

15. The system ofclaim 14, wherein IDCA system is utilized in optical imaging devices, said optical imaging devices being at least one of: cameras; night vision equipment; military equipment; sniper pod; electronics optic targeting system; aviation optical equipment; missile seeker or thermal imaging devices.

16. The system ofclaim 14, wherein the first and second layers have the same majority carrier type such that the photo-detector has no substantial depletion layer.

17. An integrated dewar cooler system comprising:

a light permitting optical window;

a cryogenic and vacuum sealed dewar;

a motherboard;

a micro Cooler; and

a focal plan array,

wherein a portion of said focal plan array is connected to a portion of said motherboard and wherein said motherboard and FPA assembly are located within Dewar,

wherein said focal plan array is an array of photo detectors, comprising:

a first layer comprising an electrically conductive semiconductor having majority and minority carrier types with associated energy bands;

a barrier layer comprising a semiconductor with a barrier energy gap and associated conduction and valence bands, a first side of said barrier layer being adjacent said first layer;

a second layer comprising an electrically conductive semiconductor having majority and minority carrier types and an associated second layer energy gap, said second layer being adjacent a second side of said barrier layer opposing said first side;

wherein the relationship between the first and second layer energy bands and the barrier layer conduction and valance band edges enables minority carrier current flow while blocking majority carrier current flow between the first and second layers, and further wherein the second layer forms a mesa on the continuous barrier layer such that the first side of said barrier layer laterally extends beyond the mesa, thereby passivating the photo-detector by preventing majority carriers from reaching exposed portions of the barrier layer.

18. The system ofclaim 17, wherein the barrier layer is an undoped semiconductor which prevents majority carrier lateral conduction within said barrier layer.

19. The system ofclaim 17, wherein the first and second layers have the same majority carrier type such that the photo-detector has no substantial depletion layer.

20. The system ofclaim 17, wherein IDCA system is utilized in optical imaging devices, said optical imaging devices being at least one of: cameras; night vision equipment; military equipment; sniper pod; electronics optic targeting system; aviation optical equipment; missile seeker or thermal imaging devices.

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