News Column

Patent Issued for Multicolor Detectors and Applications

July 16, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Trezza, John (Manalapan, NJ); Ettenberg, Martin (Princeton, NJ), filed on March 5, 2013, was published online on July 1, 2014.

The assignee for this patent, patent number 8766159, is Sensors Unlimited, Inc. (Princeton, NJ).

Reporters obtained the following quote from the background information supplied by the inventors: "Photonic sensing apparatus can derive significant benefits from the ability to provide a response over more than a single range of wavelengths. In recognition of this, several constructions have been proposed to provide photonic sensing apparatus multi-spectral functionality.

"In one construction, photosensitive layers having divergent radiation absorption profiles are presented in a stacked configuration to provide multi-spectral functionality, wherein photosensitive layers absorbing shorter wavelengths of radiation are positioned over photosensitive layers absorbing longer wavelengths of radiation to avoid potential attenuation and interference of short wavelength radiation by long wavelength photosensitive materials. Long wavelength photosensitive materials, for example, can absorb and/or scatter radiation of shorter wavelengths, thereby providing significant attenuation or even precluding such radiation from reaching a short wavelength photosensitive layer.

"Restriction to short wavelength photosensitive layers disposed over long wavelength photosensitive layers in a stacked photodetector configuration presents several disadvantages. One disadvantage is degradation of long wavelength photosensitive materials and structures resulting from the processing required for the subsequent deposition of one or more short wavelength photosensitive materials.

"Another disadvantage is the inability to thermally isolate long wavelength photosensitive layers in prior stacked configurations. Materials absorbing long wavelength electromagnetic radiation are often sensitive to thermal fluctuations and can suffer significant signal to noise (S/N) degradation resulting from dark currents in response to such thermal fluctuations. As a result, long wavelength photosensitive layers often require thermal isolation in order to provide the desired response.

"As an alternative to photosensitive layers presented in a stacked configuration, Photo detector constructions based on a plurality focal plane arrays have been proposed. In such constructions, each focal plane array is sensitive to radiation of a different spectral region. Optical assemblies are used to direct and distribute light received by the detector to the plurality of focal plane arrays. The various complexities of the optical assemblies used in directing the received light, nevertheless, are a significant disadvantage of multiple focal plane constructions.

"A similar disadvantage is encountered in the use of segmented focal plane arrays wherein each segment of the array is sensitive to electromagnetic radiation of a different spectral region. As with multiple focal plane array constructions, use of segmented focal plane arrays usually requires complex optical assemblies to ensure the correct distribution of received light over the segmented array."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "In one aspect, the present invention provides photodetectors and components thereof having multi-spectral sensing capabilities. In some embodiments, photodetectors of the present invention can overcome disadvantages associated with prior detectors discussed herein.

"The present invention, in some embodiments, provides a photodetector comprising a first photosensitive element coupled to a read-out integrated circuit, the first photosensitive element having an architecture operable for receiving a second photosensitive element and electrically connecting the second photosensitive element to the read-out integrated circuit. In some embodiments, for example, the first photosensitive element coupled to the read-out integrated circuit comprises an architecture facilitating the construction or processing of a second photosensitive element over the first photosensitive element resulting in a stacked configuration. In some embodiments, for example, the architecture of the first photosensitive element coupled to the read-out integrated circuit permits the construction or deposition of delicate long wavelength photosensitive structures over the first photosensitive element in the production of a photodetector having multi-spectral sensing capabilities.

"In one embodiment, the present invention provides a photodetector comprising a first photosensitive element comprising one or more electrical contacts for coupling to a read-out integrated circuit and at least one access way extending through the element and an electrical connection at least partially disposed in the access way, the electrical connection accessible for receiving a second photosensitive element. As provided herein, the accessible electrical connection, in some embodiments, permits electrical communication of a second photosensitive element with the read-out integrated circuit, the second photosensitive element being deposited, constructed or hybridized over the first photosensitive element in a stacked configuration. In some embodiments, the first photosensitive element comprises a plurality of access ways, each access way having an electrical connection at least partially disposed therein and accessible for receiving a second photosensitive element.

"Moreover, in some embodiments, the second photosensitive element of a photodetector of the present invention comprises an access way extending through the element and an electrical connection at least partially disposed in the access way, the electrical connection accessible for receiving a third photosensitive element. The electrical connection of the second photosensitive element, in some embodiments, facilitates electrical communication of a third photosensitive element with the read-out integrated circuit, the third photosensitive element being deposited, constructed or hybridized over the second photosensitive element in a stacked configuration. In some embodiments, the second photosensitive element comprises a plurality of access ways, each access way having an electrical connection at least partially disposed therein and accessible for receiving a third photosensitive element.

"In another embodiment, the present invention provides one or more arrays of Photo detectors coupled to a read-out integrated circuit wafer, wherein at least one of the Photo detectors comprises a first photosensitive element electrically connected to the read-out integrated circuit wafer, the first photosensitive element having an access way extending through the element and an electrical connection at least partially disposed in the access way for receiving a second photosensitive element.

"The photosensitive elements of photodetectors of the present invention can have any desired absorption spectra. In some embodiments, the electromagnetic radiation absorption spectra of the photosensitive elements do not overlap. In one embodiment, for example, the absorption spectra of the first and second photosensitive elements do not overlap. In other embodiments, the electromagnetic radiation absorption spectra of photosensitive elements partially overlap.

"In some embodiments, the second photosensitive element absorbs radiation of a longer wavelength than the first photosensitive element. The second photosensitive element, in some embodiments, for example, absorbs electromagnetic radiation having a wavelength ranging from about 3 .mu.m to about 5 .mu.m, corresponding to mid-wavelength infrared (MWIR) radiation while the first photosensitive element absorbs electromagnetic radiation having a wavelength ranging from about 0.8 .mu.m to about 2.8 .mu.m corresponding to visible and short-wavelength infrared radiation (SWIR). In another embodiment, the second photosensitive element absorbs electromagnetic radiation having a wavelength ranging from about 8 .mu.m to about 15 .mu.m, corresponding to long-wavelength infrared (LWIR) radiation while the first photosensitive element absorbs SWIR or MWIR. In some embodiments, the second photosensitive element absorbs infrared radiation while the first photosensitive element absorbs visible radiation. In another embodiment, the second photosensitive element absorbs visible radiation while the first photosensitive element absorbs ultraviolet radiation. Alternatively, in some embodiments, the first photosensitive element absorbs radiation of a longer wavelength than the second photosensitive element.

"A photosensitive element of a photodetector of the present invention can comprise any material and/or construction consistent with providing the photosensitive element a response to the desired wavelength range of electromagnetic radiation. In some embodiments, photosensitive elements comprise photodiodes utilizing various semiconductor materials in the formation of pin junctions or p-i-n junctions. In some embodiments, semiconductor materials used in the formation of photodiode heterojunctions comprise Group III/V semiconductors, Group II/VI semiconductors or combinations thereof. In one embodiment wherein the absorption of SWIR is desired, a photodiode comprising InGaAs can be provided. In some embodiments, InGaAs comprises In.sub.0.53Ga.sub.0.47As.

"Moreover, a photosensitive element of a photodetector, in some embodiments of the present invention, comprises a single pixel constructed of a material having the desired absorption spectrum. In other embodiments, a photosensitive element of a photodetector comprises a plurality of pixels. A plurality of pixels, in some embodiments, comprises a one dimensional array or a two dimensional array of pixels.

"In some embodiments, photosensitive elements of a photodetector of the present invention have the same pixel pitch. In other embodiments, photosensitive elements of a photodetector have different pixel pitches.

"In another embodiment, the present invention provides a photodetector comprising a read-out integrated circuit, a first photosensitive element electrically connected to the read-out integrated circuit and a second photosensitive element at least partially covering the first photosensitive element and electrically connected to the read-out integrated circuit by one or more electrical connections passing through the first photosensitive element, the second photosensitive element absorbing electromagnetic radiation of a longer wavelength than the first photosensitive element.

"In another embodiment, the present invention provides one or more arrays of Photo detectors coupled to a read-out integrated circuit wafer, wherein at least one of the Photo detectors comprises a first photosensitive element electrically connected to the read-out integrated circuit wafer and a second photosensitive element at least partially covering the first photosensitive element and electrically connected to the read-out integrated circuit wafer by one or more electrical connections passing through the first photosensitive element, the second photosensitive element absorbing electromagnetic radiation of a longer wavelength than the first photosensitive element.

"As described herein, the first photosensitive element and the second photosensitive element are arranged in a stacked configuration wherein the second photosensitive element at least partially covers the first photosensitive element. As a result, in some embodiments, electromagnetic radiation received by a photodetector of the present invention reaches the second photosensitive element prior to reaching the first photosensitive element. In embodiments of the present invention, the second photosensitive element comprises a composition and/or structure operable to pass radiation to the first photosensitive element for detection while absorbing radiation outside the absorption spectrum of the first photosensitive element.

"In some embodiments of a stacked configuration, the second photosensitive element is adjacent to the first photosensitive element. In other embodiments, the second photosensitive element is spaced apart from the first photosensitive element. In some embodiments wherein the second photosensitive element is spaced apart from the first photosensitive element, a space or void can exist between the first and second photosensitive elements. In other embodiments, a radiation transmissive material can be disposed between the first and second photosensitive elements. A radiation transmissive material, as used herein, refers to a material that does not absorb or otherwise interfere with the transmission of electromagnetic radiation to be absorbed by the first and/or second photosensitive elements of the present invention.

"Spacing the second photosensitive element apart from the first photosensitive element by a void or an intervening radiation transmissive material, in some embodiments, can isolate the second photosensitive element from the first photosensitive element. As discussed further herein, spacing the second photosensitive element apart from the first photosensitive element is desirable in some embodiments wherein the second photosensitive element requires thermal isolation to minimize dark currents and other environmental factors that degrade the response of the second photosensitive element.

"In some embodiments, spacing the second photosensitive element from the first photosensitive element can be achieved by extending one more electrical connections disposed in access ways of the first photosensitive element above a surface of the first photosensitive element. In such embodiments, the one or more electrical connections can serve as a spacer in addition to placing the second photosensitive element in electrical communication with the read-out integrated circuit.

"In another aspect, the present invention provides methods of producing photodetectors. In one embodiment, a method of producing a photodetector comprises providing a first photosensitive element comprising one or more electrical contacts for connecting to a read-out integrated circuit, providing at least one access way through the first photosensitive element and at least partially disposing an electrical connection in the at least one access way for receiving a second photosensitive element. In some embodiments, a method of producing a photodetector further comprises providing a second photosensitive element and coupling the second photosensitive element to the electrical connection.

"In another embodiment, a method of producing a photodetector comprises providing a read-out integrated circuit, electrically connecting a first photosensitive element to the read-out integrated circuit and electrically connecting a second photosensitive element to the read-out integrated circuit by one more connections passing through the first photosensitive element, wherein the second photosensitive element absorbs electromagnetic radiation of a wavelength longer than the first photosensitive element. In some embodiments, the second photosensitive element at least partially covers the first photosensitive element when electrically connected to the read-out integrated circuit by one or more connections passing through the first photosensitive element.

"Moreover, in some embodiments, methods of producing photodetectors of the present invention further comprise spacing the second photosensitive element from the first photosensitive element. In some embodiments, a method of the present invention further comprises providing at least one access way in the second photosensitive element and at least partially disposing an electrical connection in the at least one access way for receiving a third photosensitive element. In some embodiments, a method of the present invention further comprises providing a third photosensitive element and coupling the third photosensitive element to the electrical connection.

"In another aspect, the present invention provides methods of detecting a plurality of wavelength ranges of electromagnetic radiation. In one embodiment, a method of detecting a plurality of wavelength ranges comprises providing a photodetector comprising a read-out integrated circuit, a first photosensitive element electrically connected to the read-out integrated circuit and a second photosensitive element electrically connected to the read-out integrated circuit and spaced apart from the first photosensitive element by one or more connections passing through the first photosensitive element and detecting electromagnetic radiation of a first wavelength range with the first photosensitive element and detecting electromagnetic radiation of a second wavelength range with the second photosensitive element.

"In another embodiment, a method of detecting a plurality of wavelength ranges comprises providing a photodetector comprising a read-out integrated circuit, a first photosensitive element electrically connected to the read-out integrated circuit and a second photosensitive element electrically connected to the read-out integrated circuit by one or more connections passing through the first photosensitive element and detecting electromagnetic radiation of a first wavelength range with the first photosensitive element and detecting electromagnetic radiation of a second wavelength range with the second photosensitive element, wherein the electromagnetic radiation of the second range has one or more wavelengths longer than the electromagnetic radiation of the first range.

"These and other embodiments are described in greater detail in the detailed description which follows."

For more information, see this patent: Trezza, John; Ettenberg, Martin. Multicolor Detectors and Applications. U.S. Patent Number 8766159, filed March 5, 2013, and published online on July 1, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8766159.PN.&OS=PN/8766159RS=PN/8766159

Keywords for this news article include: Electronics, Electromagnet, Semiconductor, Sensors Unlimited Inc, Electrical Communication.

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Source: Electronics Newsweekly


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