Typically,infrared detectors require cryogenic cooling to limit dark current w hich is directly d... more Typically,infrared detectors require cryogenic cooling to limit dark current w hich is directly dependent on Auger generation-recombination mechanism and highly influential in Hg Cd Te-narrow band gap material.The Auger suppressed architectures have an advantage over conventional detectors allow ing operation at elevated temperatures>200 K.Architecture w ith combination of exclusion and extraction heterojunctions has been proposed to low er Auger contribution.The paper presents a new long-w ave(≈10μm)infrared Hg Cd Te architecture w ith graded gap/doping interfaces and extra barrier located in exclusion heterojunction to suppress dark current for high operating temperature conditions.Proper barrier implementation reduces dark current by more than 20 A/cm2for room temperature operation.
We report on the quadrant photon HgCdTe detectors optimized for 2-11 μm wavelength spectral range... more We report on the quadrant photon HgCdTe detectors optimized for 2-11 μm wavelength spectral range and Peltier or no cooling, and photosensitive area of a quad-cell of 1×1 to 4×4 mm. The devices are fabricated as photoconductors or multiple photovoltaic cells connected in series (PVM). The former are characterized by a relatively uniform photosensitive area. The PVM photovoltaic cells are distributed along the wafer surface, comprising a periodical stripe structure with a period of 20 μm. Within each period, there is an insensitive gap/trench < 9 μm wide between stripe mesas. The resulting spatial quantization error prevents positioning of the beam spot of size close to the period, but becomes negligible for the optimal spot size comparable to a quadrant-cell area. The photoconductors produce 1/f noise with about 10 kHz knee frequency, due to bias necessary for their operation. The PVM photodiodes are typically operated at 0 V bias, so they generate no 1/f noise and operation from...
In this paper, the results of the initial work on determining the photoelectric properties of gra... more In this paper, the results of the initial work on determining the photoelectric properties of graphene detector operating in a photoconductive mode are presented. Graphene is considered as a material for uncooled fast detectors. The investigation has been done by electrical and optical characterization. Two values of substrate resistivity have been used in the project – below 1 Ωcm and higher than 1.6 kΩcm. Measurements of detectors response to short, strong light pulses were conducted. Presented studies show that the use of high resistivity substrates is necessary to prevent capacitive shorting of the signal to the substrate, causing signal losses and increasing response time.
The paper reports on the design and fabrication of LPE-grown GaSb/n-InxGa1-xAsySb1-yp- AlxGa1-xAs... more The paper reports on the design and fabrication of LPE-grown GaSb/n-InxGa1-xAsySb1-yp- AlxGa1-xAsySb1-y heterojunction photodetectors operating in the 2-2.4 micrometers wavelength region. Experiments on LPE growth of high-x- content quaternaries as well as optimization of device processing has been carried out. LPE growth at Tapproximately equals 530DEGC enabled obtaining lattice matched heterostructures with 19% indium in the active layer In0.19Ga0.81As0.16Sb0.84/ Al0.24Ga0.76As0.04Sb0.96
Electro-Optical Remote Sensing, Photonic Technologies, and Applications III, 2009
Sensitive and broadband detection of MWIR and LWIR radiation with any wavelength within the 2 to ... more Sensitive and broadband detection of MWIR and LWIR radiation with any wavelength within the 2 to 16 mum spectral range and bandwidth from DC to GHz range is reported. Recent efforts have been concentrated on the extension of useful spectrum range above 13 micrometers. This was achieved with improved architecture of the active element, use of monolithic optical immersion technology,
We report an advanced Hg1-xCdxTe photovoltaic detector based on monolithic Hg1-xCdxTe heterostruc... more We report an advanced Hg1-xCdxTe photovoltaic detector based on monolithic Hg1-xCdxTe heterostructure with 3-dimensional architecture. It consists of a narrow gap, p-type Hg1-xCdxTe small size (approximately equals 10x10x7 micrometers ) absorber of infrared radiation buried in a graded gap Hg1-xCdxTe layer surrounding absorber and heterojunction contacts obtained by selective doping of the graded gap Hg1-xCdxTe layer surrounding the absorber region.
Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed o... more Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed optical communications due to their high quantum efficiency and large bandwidth. This is a consequence of placing the thin absorber of the photodetector inside a Fabry-Perot microcavity so the absorption could be enhanced by recycling the photons with resonance wavelength. The performance of uncooled resonant cavity enhanced InGaAs/InAlAs photovoltaic
Fast refractive microlenses are increasingly important as optical concentrators for uncooled infr... more Fast refractive microlenses are increasingly important as optical concentrators for uncooled infrared photodetectors. They are used in purpose to improve performance and speed of response. Refractive microlenses formed directly onto semiconductor materials draw much attention because they facilitate monolithic integration with active element of infrared photodetector. Gallium arsenide due to its superior optical and mechanical properties is a material of choice for fabrication of microlenses. We have developed process for fabrication of GaAs refractive microlenses monolithically integrated with InGaAs and HgCdTe photodetectors, both as single element devices and two-dimensional arrays. Specially designed machine tool has been used for preparation of relatively large single spherical GaAs microlenses with 0.5 mm-10 mm diameter. The microlens-detector arrays were prepared using a combination of ion milling and wet chemical etching. The typical process involves one photolithography, one ion milling and one or two chemical etching steps. More advanced procedures have also been proposed to improve quality of the lenses. The lenses can be optimized as optical concentrators for IR photodetectors with circular, square, rectangular and other geometries. This process is especially convenient for fabrication of lenses with size less than 50 mum, but larger lenses with size exceeding 300 mum can be prepared as well with some modifications of the fabrication procedures.
We report fast and sensitive long (10 mum) wavelength photodetectors operating at near room tempe... more We report fast and sensitive long (10 mum) wavelength photodetectors operating at near room temperature. The devices are based on HgCdTe multilayer heterostructures grown by MOCVD on (211) and (111) GaAs substrates. Device-quality heterostructures are obtained without any post growth anneal. The recent improvements of MOCVD growth were: optimized design of the device architecture to increase speed of response, better
Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed o... more Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed optical communications due to their high quantum efficiency and large bandwidth. This is a consequence of placing the thin absorber of the photodetector inside a Fabry-Perot microcavity so the absorption could be enhanced by recycling the photons with resonance wavelength. The performance of uncooled resonant cavity enhanced InGaAs/InAlAs photovoltaic
Typically,infrared detectors require cryogenic cooling to limit dark current w hich is directly d... more Typically,infrared detectors require cryogenic cooling to limit dark current w hich is directly dependent on Auger generation-recombination mechanism and highly influential in Hg Cd Te-narrow band gap material.The Auger suppressed architectures have an advantage over conventional detectors allow ing operation at elevated temperatures>200 K.Architecture w ith combination of exclusion and extraction heterojunctions has been proposed to low er Auger contribution.The paper presents a new long-w ave(≈10μm)infrared Hg Cd Te architecture w ith graded gap/doping interfaces and extra barrier located in exclusion heterojunction to suppress dark current for high operating temperature conditions.Proper barrier implementation reduces dark current by more than 20 A/cm2for room temperature operation.
We report on the quadrant photon HgCdTe detectors optimized for 2-11 μm wavelength spectral range... more We report on the quadrant photon HgCdTe detectors optimized for 2-11 μm wavelength spectral range and Peltier or no cooling, and photosensitive area of a quad-cell of 1×1 to 4×4 mm. The devices are fabricated as photoconductors or multiple photovoltaic cells connected in series (PVM). The former are characterized by a relatively uniform photosensitive area. The PVM photovoltaic cells are distributed along the wafer surface, comprising a periodical stripe structure with a period of 20 μm. Within each period, there is an insensitive gap/trench < 9 μm wide between stripe mesas. The resulting spatial quantization error prevents positioning of the beam spot of size close to the period, but becomes negligible for the optimal spot size comparable to a quadrant-cell area. The photoconductors produce 1/f noise with about 10 kHz knee frequency, due to bias necessary for their operation. The PVM photodiodes are typically operated at 0 V bias, so they generate no 1/f noise and operation from...
In this paper, the results of the initial work on determining the photoelectric properties of gra... more In this paper, the results of the initial work on determining the photoelectric properties of graphene detector operating in a photoconductive mode are presented. Graphene is considered as a material for uncooled fast detectors. The investigation has been done by electrical and optical characterization. Two values of substrate resistivity have been used in the project – below 1 Ωcm and higher than 1.6 kΩcm. Measurements of detectors response to short, strong light pulses were conducted. Presented studies show that the use of high resistivity substrates is necessary to prevent capacitive shorting of the signal to the substrate, causing signal losses and increasing response time.
The paper reports on the design and fabrication of LPE-grown GaSb/n-InxGa1-xAsySb1-yp- AlxGa1-xAs... more The paper reports on the design and fabrication of LPE-grown GaSb/n-InxGa1-xAsySb1-yp- AlxGa1-xAsySb1-y heterojunction photodetectors operating in the 2-2.4 micrometers wavelength region. Experiments on LPE growth of high-x- content quaternaries as well as optimization of device processing has been carried out. LPE growth at Tapproximately equals 530DEGC enabled obtaining lattice matched heterostructures with 19% indium in the active layer In0.19Ga0.81As0.16Sb0.84/ Al0.24Ga0.76As0.04Sb0.96
Electro-Optical Remote Sensing, Photonic Technologies, and Applications III, 2009
Sensitive and broadband detection of MWIR and LWIR radiation with any wavelength within the 2 to ... more Sensitive and broadband detection of MWIR and LWIR radiation with any wavelength within the 2 to 16 mum spectral range and bandwidth from DC to GHz range is reported. Recent efforts have been concentrated on the extension of useful spectrum range above 13 micrometers. This was achieved with improved architecture of the active element, use of monolithic optical immersion technology,
We report an advanced Hg1-xCdxTe photovoltaic detector based on monolithic Hg1-xCdxTe heterostruc... more We report an advanced Hg1-xCdxTe photovoltaic detector based on monolithic Hg1-xCdxTe heterostructure with 3-dimensional architecture. It consists of a narrow gap, p-type Hg1-xCdxTe small size (approximately equals 10x10x7 micrometers ) absorber of infrared radiation buried in a graded gap Hg1-xCdxTe layer surrounding absorber and heterojunction contacts obtained by selective doping of the graded gap Hg1-xCdxTe layer surrounding the absorber region.
Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed o... more Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed optical communications due to their high quantum efficiency and large bandwidth. This is a consequence of placing the thin absorber of the photodetector inside a Fabry-Perot microcavity so the absorption could be enhanced by recycling the photons with resonance wavelength. The performance of uncooled resonant cavity enhanced InGaAs/InAlAs photovoltaic
Fast refractive microlenses are increasingly important as optical concentrators for uncooled infr... more Fast refractive microlenses are increasingly important as optical concentrators for uncooled infrared photodetectors. They are used in purpose to improve performance and speed of response. Refractive microlenses formed directly onto semiconductor materials draw much attention because they facilitate monolithic integration with active element of infrared photodetector. Gallium arsenide due to its superior optical and mechanical properties is a material of choice for fabrication of microlenses. We have developed process for fabrication of GaAs refractive microlenses monolithically integrated with InGaAs and HgCdTe photodetectors, both as single element devices and two-dimensional arrays. Specially designed machine tool has been used for preparation of relatively large single spherical GaAs microlenses with 0.5 mm-10 mm diameter. The microlens-detector arrays were prepared using a combination of ion milling and wet chemical etching. The typical process involves one photolithography, one ion milling and one or two chemical etching steps. More advanced procedures have also been proposed to improve quality of the lenses. The lenses can be optimized as optical concentrators for IR photodetectors with circular, square, rectangular and other geometries. This process is especially convenient for fabrication of lenses with size less than 50 mum, but larger lenses with size exceeding 300 mum can be prepared as well with some modifications of the fabrication procedures.
We report fast and sensitive long (10 mum) wavelength photodetectors operating at near room tempe... more We report fast and sensitive long (10 mum) wavelength photodetectors operating at near room temperature. The devices are based on HgCdTe multilayer heterostructures grown by MOCVD on (211) and (111) GaAs substrates. Device-quality heterostructures are obtained without any post growth anneal. The recent improvements of MOCVD growth were: optimized design of the device architecture to increase speed of response, better
Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed o... more Resonant cavity enhanced photodetectors are promising candidates for applications in high-speed optical communications due to their high quantum efficiency and large bandwidth. This is a consequence of placing the thin absorber of the photodetector inside a Fabry-Perot microcavity so the absorption could be enhanced by recycling the photons with resonance wavelength. The performance of uncooled resonant cavity enhanced InGaAs/InAlAs photovoltaic
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