Showing papers on "Mercury cadmium telluride published in 2018"

Atomically thin noble metal dichalcogenide: a broadband mid-infrared semiconductor.

Abstract: The interest in mid-infrared technologies surrounds plenty of important optoelectronic applications ranging from optical communications, biomedical imaging to night vision cameras, and so on. Although narrow bandgap semiconductors, such as Mercury Cadmium Telluride and Indium Antimonide, and quantum superlattices based on inter-subband transitions in wide bandgap semiconductors, have been employed for mid-infrared applications, it remains a daunting challenge to search for other materials that possess suitable bandgaps in this wavelength range. Here, we demonstrate experimentally for the first time that two-dimensional (2D) atomically thin PtSe2 has a variable bandgap in the mid-infrared via layer and defect engineering. Here, we show that bilayer PtSe2 combined with defects modulation possesses strong light absorption in the mid-infrared region, and we realize a mid-infrared photoconductive detector operating in a broadband mid-infrared range. Our results pave the way for atomically thin 2D noble metal dichalcogenides to be employed in high-performance mid-infrared optoelectronic devices.

Bilayer graphene/HgCdTe based very long infrared photodetector with superior external quantum efficiency, responsivity, and detectivity

Abstract: We present a high-performance bilayer graphene (BLG) and mercury cadmium telluride (Hg1−xCdx=0.1867Te) heterojunction based very long wavelength infrared (VLWIR) conductive photodetector. The unique absorption properties of graphene enable a long carrier lifetime of charge carriers contributing to the carrier-multiplication due to impact ionization and, hence, large photocurrent and high quantum efficiency. The proposed p+-BLG/n-Hg0.8133Cd0.1867Te photodetector is characterized and analyzed in terms of different electrical and optical characteristic parameters using computer simulations. The obtained results are further validated by developing an analytical model based on drift-diffusion, tunneling and Chu's methods. The photodetector has demonstrated a superior performance including improved dark current density (∼1.75 × 10−14 µA cm−2), photocurrent density (∼8.33 µA cm−2), internal quantum efficiency (QEint ∼ 99.49%), external quantum efficiency (QEext ∼ 89%), internal photocurrent responsivity (∼13.26 A W−1), external photocurrent responsivity (∼9.1 A W−1), noise equivalent power (∼8.3 × 10−18 W), total noise current (∼1.06 fA), signal to noise ratio (∼156.18 dB), 3 dB cut-off frequency (∼36.16 GHz), and response time of 9.4 ps at 77 K. Furthermore, the effects of different external biasing, light power intensity, and temperature are evaluated, suggesting a high QEext of 3337.70% with a bias of −0.5 V near room temperature.

Delta Doping in HgCdTe-Based Unipolar Barrier Photodetectors

Abstract: A method is described whereby the valence band (VB) discontinuity that is present in mercury cadmium telluride (HgCdTe)-based alloy-barrier nBn detectors can be minimized. It is numerically demonstrated that compositionally graded layers can provide the required transition between the wide bandgap CdTe barrier layer and the lattice-matched HgCdTe absorber and contact layers, although a large VB discontinuity is present. In addition, the incorporation of delta-doped ( $\delta $ -doped) layers in the vicinity of the barrier region can minimize the VB discontinuity, thus blocking the flow of majority carriers and allowing unimpeded flow of photogenerated minority carriers. This strategy results in diffusion-limited dark current at low reverse bias combined with efficient collection of photogenerated carriers. The nBn structure proposed in this paper can be applied to other semiconductor materials operating in various infrared wavelength bands. The method is not limited to the nBn structure and can be applied to any xBx barrier detector structure (with ${x} = \textit {n, p}$ ) configuration in order to minimize the energy band discontinuity in the corresponding minority carrier band.

Standoff detection of VOCs using external cavity quantum cascade laser spectroscopy

Abstract: Broadband tunable external cavity quantum cascade lasers (ECQCLs) have emerged as attractive laser sources for mid-infrared spectroscopic applications to detect various chemical agents. Here we report on the development of a pulsed, broadband ECQCL-based sensor for open-path sensing multiple volatile organic compounds (VOCs). Instead of using a standard infrared mercury cadmium telluride detector, a quartz crystal tuning fork with a high resonant frequency (~75 kHz) was used as a light detector for laser signal collection. For signal processing, a self-established spectral analysis model integrated with 1D cubic spline interpolation algorithm, multiple linear regression algorithm and fast Fourier transform was developed for quantitative and qualitative analysis of VOC components. The ECQCL sensor was successfully demonstrated for the stand-off detection of three VOCs mixing plume (i.e. ethanol, acetone and diethyl ether) at a distance of 40 m, proving its applicability for leak plumes in security fields.

Photoluminescence of Molecular Beam Epitaxy-Grown Mercury Cadmium Telluride: Comparison of HgCdTe/GaAs and HgCdTe/Si Technologies

Abstract: Properties of HgCdTe films grown by molecular beam epitaxy on GaAs and Si substrates have been studied by performing variable-temperature photoluminescence (PL) measurements. A substantial difference in defect structure between films grown on GaAs (013) and Si (013) substrates was revealed. HgCdTe/GaAs films were mostly free of defect-related energy levels within the bandgap, which was confirmed by PL and carrier lifetime measurements. By contrast, the properties of HgCdTe/Si films are affected by uncontrolled point defects. These could not be always associated with typical “intrinsic” HgCdTe defects, such as mercury vacancies, so consideration of other defects, possibly inherent in HgCdTe/Si structures, was required. The post-growth annealing was found to have a positive effect on the defect structure by reducing the full-widths at half-maximum of excitonic PL lines for both types of films and lowering the concentration of defects specific to HgCdTe/Si.

Type-II InAs/GaSb (InAsSb) superlattices for interband cascade midwavelength detectors

Abstract: Type-II superlattice (T2SL) interband cascade infrared detectors (IB CIDs) proved to be a promising candidate for short response time devices operating in room and higher temperatures. The current status of the higher operating temperature (HOT) T2SLs InAs/GaSb and InAs/InAsSb IB CID is presented. We compare both materials with HgCdTe alloy, which is widely described in literature. The detectivity of midwave infrared (MWIR) T2SLs InAs/GaSb and InAs/InAsSb based IB CID has been demonstrated up to 380 K.

Standoff detection from diffusely scattering surfaces using dual quantum cascade laser comb spectroscopy

Abstract: Using dual optical frequency comb (OFC) spectroscopy in the longwave infrared (LWIR), we demonstrate standoff detection of trace amounts of target compounds on diffusely scattering surfaces. The OFC is based on quantum cascade lasers (QCL) that emit ~1 Watt of optical power under cw operation at room temperature over coherent comb bandwidths approaching 100 cm-1. We overlap two nearly identical 1250 cm-1 QCL OFC sources so that the two interfering optical combs create via heterodyne a single comb in the radio frequency (rf) that represents the entire optical spectrum in a single acquisition. In a laboratory scale demonstration we show detection of two spectrally distinct fluorinated silicone oils, poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, that act as LWIR simulants for security relevant compounds whose room temperature vapor pressure is too low to be detected in the gas phase. These target compounds are applied at mass loadings of 0.3 to 90 μg/cm2 to sanded aluminum surfaces. Only the diffusely scattered light is collected by a primary collection optic and focused onto a high speed (0.5 GHz bandwidth) thermoelectrically cooled mercury cadmium telluride (MCT) detector. At standoff distances of both 0.3 and 1 meter, we demonstrate 3 μg/cm2 and 1 μg/cm2 detection limits against poly(methyl-3,3,3-trifluoropropylsiloxane) and Krytox™, respectively.

MCT Avalanche Photodiode Detector FOR Two-MICRON Active Remote Sensing Applications

Abstract: Mercury Cadmium Telluride electron initiated avalanche photodiodes demonstrated a breakthrough in lidar active remote sensing technology. A lidar detection system, based on an array of these devices, was integrated and characterized for $2-\mu \mathrm{m}$ applications. Characterization experiments were focused on evaluating the dark current, gain and responsivity variations with bias voltage. Quantum efficiency and input dynamic range including noise-equivalent-power and maximum detectable power, were calculated from these results. Operating the detection system using four pixels at 77.6 K, 12 V bias resulted in a current responsivity of 615.8 A/W and a voltage responsivity of 1.45 GV/W. Minimum detectable power of 14 pW was obtained, which is equivalent to 5.7 fW/H z 1l2 noise-equivalent-power, indicating an average noise-equivalent-power of 1.4 fW/H z 1l2 per pixel. Work is in progress to integrate and validate this detection system using a newly developed triple-pulse integrated path differential absorption lidar for simultaneous and independent atmospheric measurements of water vapor and carbon dioxide.

The status of MCT detector development at ASELSAN

Abstract: ASELSAN A.S., the largest defense company in Turkey, initiated research activities on developing Mercury Cadmium Telluride (MCT) detectors in 2014. These research activities include bulk crystal growth and surface preparation of Cadmium Zinc Telluride (CZT) substrates, Molecular Beam Epitaxial (MBE) growth of MCT layers, MCT detector fabrication, Read-Out-Integrated-Circuit (ROIC) design and detector-dewar-cooler (DDCA) assembly development. Focal plane arrays with resolutions/pixel pitches of 320x256/30 μm and 640x512/15 μm are fabricated. Noise Equivalent Temperature Difference (NETD) of 320x256 FPA is 11 mK (f#/1.5, 77K) while the operability is 98.2%. 640x512 FPA provides NETD of 32 mK (f#/1.5, 77K) and the operability is 93.2%.

Achievement of high image quality MCT sensors with Sofradir vertical industrial model

Abstract: SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. This is the result of strong and continuous development efforts to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, dark current, quantum efficiency, low excess noise and high operability. On one hand the advanced performances of Sofradir product rely on a strong partnership with CEA-LETI materialized in a common laboratory named DEFIR. On the other hand, these cutting edge performances are made possible thanks to Sofradir vertical industrial model. From the CdZnTe (CZT) and HgCdTe (MCT) crystal growth to the last electro-optical characterization recipe before shipping, and all the intermediate steps in between like IDDCA (Integrated Detector Dewar Cooler Assembly) final pumping cycle, all the manufacturing steps are developed, performed and controlled inhouse. This allows direct feedback between IDDCA, system performances and process or material. State of the art relevant performances for IR detection and imaging will be presented, that is to say low excess noise defects, RFPN (Residual Fixed Pattern Noise), NUC (Non Uniformity Correction) table stability for Daphnis product, 10μm pitch XGA extended MW matrix at 110K and HOT (High Operating Temperature) p-on-n technology, VGA format with 15μm pitch MW at 160K.

Demonstration of time-of-flight technique with all-optical modulation and MCT detection in SWIR/MWIR range

Abstract: We report a feasibility study of Time-of-Flight technique in Short- and Mid-Wavelength Infrared spectral region using a Mercury Cadmium Telluride detector. For the demonstration we employed an all-optical modulator operated by optical pumping with 800 nm, 100 femtosecond pulses and measured the broadening of the signal pulses traversing through a few centimetres of silica rod. The measured signal was analysed to reconstruct the pulse broadening and to retrieve the group velocity dispersion of silica. We show that in Time-of-Flight measurements based on all-optical modulation in combination with Mercury Cadmium Telluride detector, the limiting resolution factor is the speed of the modulator rise time governed by the optical pump.

Bulk characterization and surface analysis of epitaxy ready cadmium zinc telluride substrates for use in IRFPA manufacturing for IR imaging

Abstract: Cadmium Zinc Telluride (Cd1-xZnxTe or CZT) is a ternary II-VI compound semiconductor material that has been widely used in infrared detector applications for many years. Due to its lattice spacing, CZT is the substrate of choice for stabilizing Mercury Cadmium Telluride (Hg1-xCdxTe or MCT) crystal layer growth where the lattice matching reduces stress during detector growth processes for high performance infrared detectors and focal plane (FPA) arrays used in guidance systems and a wide array of IR applications. The manufacturing of high performance MCT IR detectors requires CZT substrates of high quality for both bulk and surface conditions thus enabling high quality MCT epitaxial layer crystallinity and low defectivity. In this work, we report on results on bulk CZT material grown using the Travelling Heater Method (THM) that are suitable for infrared focal plane array (IRFPA) detector applications. This proven crystal growth process has been used to manufacture CZT substrates meeting industry requirements of IR transmission, tellurium precipitate size, dislocations and of larger single crystal area. We will present results on chemomechanical (CMP) polishing of CZT substrates of square, rectangular and state-of-the-art round geometries utilizing standard production tool sets that are identical to those used to produce epitaxy-ready surface finishes on related IR compound semiconductor materials such as GaSb and InSb. Surface quality will be assessed by various analytical and microscopy techniques to validate the suitability of this material for epitaxial growth.

Magnetoconductivity of a Mercury Cadmium Telluride Resonant THz Detector

Abstract: Magnetoconductivity of a Mercury Cadmium Telluride Resonant THz Detector M. Bąk, D. Yavorskiy, K. Karpierz, J. Łusakowskia,∗, D. But, J. Przybytek, I. Yahniuk, G. Cywiński, W. Knap, F. Teppe, S. Krishtopenko, N.N. Mikhailov, S.A. Dvoretsky and V.I. Gavrilenko Faculty of Physics, University of Warsaw, L. Pasteura 5, 02-093 Warsaw, Poland Institute of High Pressure Physics, PAS, Sokołowska 29/37, 01-142 Warsaw, Poland Laboratoire Charles Coulomb, UMR CNRS 5221, 34095 Montpellier, France A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branchm RAS, Novosibirsk 630090, Russia e Institute for Physics of Microstructures, RAS, GSP-105, 603950, N. Novgorod, Russia

Numerical analysis of the thermal effect of the spaceborne detector irradiated by the pulsed laser carried by the accompanying satelite

Abstract: Based on the heat conduction theory, the theoretical model of the spaceborne mercury cadmium telluride(HgCdTe) detector irradiated by the pulsed laser carried by the accompanying satelite is proposed. The method of applying the moving heat source on the focal plane of the detector is used to analyze the thermal effect of HgCdTe detector when the pulsed laser beam and the HgCdTe detector are under the condition of relative movement. The thermal effect of the detector under different moving velocities of the laser beam is studied, and the melting damage thresholds of the monopulse laser beam at different moving speeds are obtained. The results show that, when the spaceborne HgCdTe detector is irradiated by the satelite-borne pulsed laser, the faster the relative moving speed is, the lower the peak temperature is at the end of the pulse, the smaller of the slope of the temperature rise curve and the slower of the temperature rise. The damage threshold of the monopulse laser at different moving speeds increases with the increase of velocity, and is approximately linear with the moving velocity.

Focal plane array alignment and cryogenic surface topography measurements for the Prime Focus Spectrograph

Abstract: We describe the infrastructure developed to align and measure the focal plane arrays (FPA) for the Subaru Measurement of Images and Redshifts (SuMIRe) Prime Focus Spectrograph (PFS), and detail the results of these efforts at ambient and operating temperatures. PFS will employ four three-channel spectrographs with an operating wavelength range of 380 nm to 1260 nm. Each spectrograph will be comprised of two visible channels and one near infrared (NIR) channel, and each channel will use individual Schmidt cameras to image the captured spectra onto their respective detectors. In the visible channels, Hamamatsu 2k x 4k charge coupled devices (CCDs) will be mounted in pairs to create a 4k x 4k mosaic, while the NIR channel will use a single Teledyne H4RG 4k x 4k Mercury Cadmium Telluride (HgCdTe) complementary metal oxide semiconductor (CMOS) device.

Analysis of Carrier Transport in n -Type Hg 1−x Cd x Te with Ultra-Low Doping Concentration

Abstract: Mercury cadmium telluride (HgCdTe, or MCT) with low n-type indium doping concentration offers a means for obtaining high performance infrared detectors. Characterizing carrier transport in materials with ultra low doping (ND = 1014 cm−3 and lower), and multi-layer material structures designed for infrared detector devices, is particularly challenging using traditional methods. In this work, Hall effect measurements with a swept B-field were used in conjunction with a multi-carrier fitting procedure and Fourier-domain mobility spectrum analysis to analyze multi-layered MCT samples. Low temperature measurements (77 K) were able to identify multiple carrier species, including an epitaxial layer (x = 0.2195) with n-type carrier concentration of n = 1 × 1014 cm−3 and electron mobility of μ = 280000 cm2/Vs. The extracted electron mobility matches or exceeds prior empirical models for MCT, illustrating the outstanding material quality achievable using current epitaxial growth methods, and motivating further study to revisit previously published material parameters for MCT carrier transport. The high material quality is further demonstrated via observation of the quantum Hall effect at low temperature (5 K and below).

Mercury cadmium telluride avalanche diode detector capable of modulating surface energy band

Abstract: The invention discloses a mercury cadmium telluride avalanche diode detector capable of modulating a surface energy band. By adding an electrode above a passivation layer of a pn junction depletion region, the pn junction energy band at the interface between the passivation layer and the mercury cadmium telluride can be modulated, and the pn junction at the interface between the passivation layerand the mercury cadmium telluride tends to be flat, thereby suppressing surface generation-recombination, surface tunneling, and surface leakage currents. The detector has the advantages that the surface energy band of the pn junction region can be modulated to be flat, and the surface leakage current is suppressed to enable the diode to work in the Geiger mode under the reverse large bias voltage, which is advantageous for solving the problem that the mercury cadmium telluride avalanche diode device of the conventional structure may have large leakage current at the surface when the reverse bias voltage is greater than the avalanche breakdown voltage, causes the photodiode to undergo thermal-electric breakdown, and limits signal detection in a linear mode.

Optimization of chemical polishing by bromine-alcohol for detector-grade CdZnTe crystals and its effect on contacts (Conference Presentation)

Abstract: Cadmium Zinc Telluride (CdZnTe) is a good candidate for detection of x-ray and gamma-rays due to its high atomic number and large bandgap. CdZnTe is a II-VI group semiconductor and by changing ZnTe concentration, its properties can be altered. CdZnTe crystals having 4% ZnTe is commonly used as a substrate for Mercury Cadmium Telluride (HgCdTe) which is an important absorbing material for infrared imaging applications. For x-ray and gamma-ray detection, on the other hand, ZnTe concentration is kept around 10%. Due to high resistivity of CdZnTe crystals, preparation of surfaces prior to deposition of electrodes is important. After cutting and mechanical polishing, subsurface damages are observed on the crystals, which have a negative effect on the resistivity of the crystal near to the surface alongside with the dangling bonds on the surface. Decrease in the resistivity results in high leakage current that hinders the collection of electrons produced by absorption of photons. In addition, to have a strong bonding with electrode metal, surface should be clean from contaminants like oxygen and carbon. Achieving clean surface with low leakage current can be achieved by employment of chemical polishing step prior to electrode deposition. Bromine-alcohol solutions are used for chemical polishing without much control over the etching conditions. In this study, we report on the results of optimization study of chemical polishing by bromine-alcohol. Different alcohols (methanol, ethanol, propanol) were employed with different concentrations and etching durations. In addition, etching is conducted for different orientations to examine orientation dependency of the solution.

HgCdTe APD Arrays for Astronomy: Natural Guide Star Wavefront Sensing and Space Astronomy.

Abstract: This dissertation describes work I have conducted over five academic years 2013/14 through 2017/18 as a NASA Space Technology Research Fellow at the University of Hawai'i Institute for Astronomy. The focus has been the characterization and improvement of the Selex Avalanche Photodiode HgCdTe InfraRed Array (SAPHIRA), a 320 x 256@24um pitch metal organic vapor phase epitaxy mercury cadmium telluride array that provides new capabilities and performance for near infrared (NIR) astronomy. This has involved more than a dozen arrays, working closely with the manufacturer so as to provide feedback for improvement of the next generation.

High operating temperature MCT discrete detector data and analysis

Abstract: High Density Vertically Integrated Photodiodes (HDVIP) MWIR detectors were fabricated in LPE-grown Mercury Cadmium Telluride material. Devices were fabricated with two different acceptor level concentrations. The low doped n-region was held at a single concentration but the dimensions are tailored to simultaneously maintain high quantum efficiency while minimizing dark current and 1/f noise. Since this study target was for operating at high temperatures, detector I-V data was collected between 120 K and 280 K for I-Vs and 180 to 280 K for noise to understand current mechanisms that limit device performance at these elevated temperatures. Noise as a function of frequency has also been collected over the same temperature range. 1/f noise has also been modeled for MWIR detectors as a function of temperature and will be covered.

Passivation method of mercury cadmium telluride material

Abstract: The invention provides a passivation method of a mercury cadmium telluride material, comprising the following steps: after the mercury cadmium telluride material is obtained in a molecular beam epitaxy device, a source required for the growth of the mercury cadmium telluride material other than the mercury source is turned off, and the temperature of the mercury cadmium telluride material is increased; when the temperature of the mercury cadmium telluride material rises to the single crystal growth temperature of cadmium telluride, the cadmium telluride source is turned on and the mercury source is turned off, and the cadmium telluride passivation film is grown on the mercury cadmium telluride material Passivation is directly performed in the molecular beam epitaxy device for growing themercury cadmium telluride after the mercury cadmium telluride is grown, and the surface leakage due to contamination of the material surface is avoided, furthermore the performance of the detector isimproved; at the same time, the cadmium telluride passivation film layer obtained by the method is a better quality single crystal material, and can form a better interdiffusion layer with the mercurycadmium telluride absorption layer, thereby reducing the surface leakage current and improving the performance of the infrared detector

Sofradir vertical industrial model for high-image-quality MCT detectors

Abstract: SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. This is the result of strong and continuous development efforts to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, dark current, quantum efficiency, low excess noise and high operability. On one hand the advanced performances of Sofradir product rely on a strong partnership with CEA-LETI materialized in a common laboratory named DEFIR. On the other hand, these cutting edge performances are made possible thanks to Sofradir vertical industrial model. From the CdZnTe (CZT) and HgCdTe (MCT) crystal growth to the last electro-optical characterization recipe before shipping, and all the intermediate steps in between like IDDCA (Integrated Detector Dewar Cooler Assembly) final pumping cycle, all the manufacturing steps are developed, performed and controlled inhouse. This allows direct feedback between IDDCA, system performances and process or material. State of the art relevant performances for IR detection and imaging will be presented, that is to say low excess noise defects, RFPN (Residual Fixed Pattern Noise), NUC (Non Uniformity Correction) table stability for Daphnis product, 10μm pitch XGA extended MW matrix at 110K and HOT (High Operating Temperature) p-on-n technology, VGA format with 15μm pitch MW at 160K.