• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.334-334
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• 2013

In the past decade, the infrared detectors based on intersubband transition in quantum dots (QDs) have attracted much attention due to lower dark currents and increased lifetimes, which are in turn due a three-dimensional confinement and a reduction of scattering, respectively. In parallel, focal plane array development for infrared imaging has proceeded from the first to third generations (linear arrays, 2D arrays for staring systems, and large format with enhanced capabilities, respectively). For a step further towards the next generation of FPAs, it is envisioned that a two-dimensional metal hole array (2D-MHA) structures will improve the FPA structure by enhancing the coupling to photodetectors via local field engineering, and will enable wavelength filtering. In regard to the improved performance at certain wavelengths, it is worth pointing out the structural difference between previous 2D-MHA integrated front-illuminated single pixel devices and back-illuminated devices. Apart from the pixel linear dimension, it is a distinct difference that there is a metal cladding (composed of a number of metals for ohmic contact and the read-out integrated circuit hybridization) in the FPA between the heavily doped gallium arsenide used as the contact layer and the ROIC; on the contrary, the front-illuminated single pixel device consists of two heavily doped contact layers separated by the QD-absorber on a semi-infinite GaAs substrate. This paper is focused on analyzing the impact of a two dimensional metal hole array structure integrated to the back-illuminated quantum dots-in-a-well (DWELL) infrared photodetectors. The metal hole array consisting of subwavelength-circular holes penetrating gold layer (2DAu-CHA) provides the enhanced responsivity of DWELL infrared photodetector at certain wavelengths. The performance of 2D-Au-CHA is investigated by calculating the absorption of active layer in the DWELL structure using a finite integration technique. Simulation results show the enhanced electric fields (thereby increasing the absorption in the active layer) resulting from a surface plasmon, a guided mode, and Fabry-Perot resonances. Simulation method accomplished in this paper provides a generalized approach to optimize the design of any type of couplers integrated to infrared photodetectors.

• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.261-264
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• 2017

$Ni_{0.79}Co_{0.15-x}Cu_xMn_{2.06}O_4$ ($0{\leq}x{\leq}0.09$) thick films were fabricated using the conventional solid-state reaction method and screen-printing method. Structural and electrical properties of specimens based on the amount of Cu were observed in order to investigate their applicability in the infrared detector. All specimens showed a single spinel phase with a homogeneous cubic structure. As the amount of Cu increased, the average grain size increased and was found to be approximately $5.01{\mu}m$ for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen. The thickness of all specimens was approximately $55{\sim}56{\mu}m$. As Cu content increased, the resistivity and TCR properties at room temperature decreased, and these values for the $Ni_{0.79}Co_{0.06}Cu_{0.09}Mn_{2.06}O_4$ specimen were $502{\Omega}-cm$ and $-3.32%/^{\circ}C$, respectively. The responsivity and noise properties decreased with an increase in Cu content, with the specimen with a Cu content of x=0.09 showing 0.0183 V/W and $5.21{\times}10^{-5}V$, respectively.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.1-8
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• 1996

High-sensitive pyroelectric infrared sensors have been fabricated with La-modified $PbTiO_{3}$(PLT) thin plates. The PLT thin plates have the composition of $(Pb_{0.9}La_{0.1}Ti_{0.75}O_{3})_{0.75}(PbO)_{0.25}$. Thickness of the thin plates is $100\;{\mu}m$. Top side electrodes exposed to IR are vacuum evaporated Ni-Cr, and bottom side electrodes are Ag. Each one takes the area of $1{\times}2\;mm^{2}$. The thin plates have a large resistivity of $6.41{\times}10^{10}{\Omega}{\cdot}cm$ and a relative dielectric constant of 341. They have a high figure of merit of $4.0{\times}10^{-11}\;Ccm/J$ due to its high pyroelectric coefficient of $4.45{\times}10^{-8}\;C/cm^{2}K$. The sensors show such a large voltage responsivity as 2501 V/W. That they can find practical applications like the pyroelectric infrared detectors.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.207-207
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• 2003

Uncooled infrared(IR) detectors that use a microbolometer with a large focal-plane array(FPA) have been developed with surface micromachining technology. There are many materials for microbolometers, such as metals, vanadium oxide, semiconductors and superconductors. Among theses, vanadium oxide is a promising material for uncooled microbolometers due to it high temperature coefficient of resistance(TCR) at room temperature. It is, however, is very difficult to deposit vanadium oxide thin films having a high TCR and low resistance because of the process limits in microbolometer fabrication. In general, vanadium oxides have been applied to microbolometer in mixed phases formed by ion beam deposition methods at low temperature with TCR in the range from -1.5 to -2.0%K.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.42-48
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• 1992

RoA is an important figure of merits for estimating the performance of p-n junction infrared detectors. This paper presents the tunneling current contribution to RoA of $Hg_{1-x}Cd_{x}$Te n$^{+}$-p juction photodiodes. Then, a diffusion model, a thermal generation-recombination model, an indirect tunneling model via trap, and a band-to-band direct tunneling model are considered to calculate RoA. Using these models, RoA depending on temperature, doping concentration, and mole fraction is calculated. Also from these results, under various operating conditions the dominant dark current mechanisms cna be understood.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2160-2164
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• 2008

Miniature Joule-Thomson cryocoolers have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The cool-down time, the temperature at the cold end, the running time and the gas consumption are the important indicators of the performance of the J-T cryocooler. In this study, the initial cool-down stages of the J-T cryocooler were investigated by numerical simulations. The results show the effects of the initial charging pressures of gas on the cool-down time and the temperature at the cold end and the gas consumptions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11A
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• pp.904-908
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• 2009

The PZT(lead, zirconium, titanium) based ceramics which, are reported to be ferroelectric materials have their important applications in the areas of surface acoustic waves (SAW), filters, infrared detectors, actuators, ferroelectric random acess memory, speakers, electronic switches etc. Moreover, these PZT materials possess the large electromechanical coupling factor, large spontaneous polarization, low dielectric loss and low internal stress etc. Hence, keeping in view the unique properties of PZT piezoelectric ceramics we also tried to synthesize indigenously the small sized PZT ceramic powder in the laboratory by using the modified sol-gel approach. In this paper, Propyl alcohol based sol-gel method was used for preparation of PZT piezoelectric ceramic. The powder obtained by this sol-gel process was calcined and sintering to reach a pyrochlore-free crystal phase. The characterization of synthesized material was carried out by the XRD analysis and the surface morphology was determined by high resolution scanning electron microscopy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.448-451
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• 2004

Vanadium oxides have been widely used in a variety of technological applications such electrochromic devices as infrared detectors and are expected as a material suitable for gas sensing applications. Thin films of Vanadium oxide (VOx) have been deposited by r.f magnetron sputtering under different oxygen partial pressure ratios and substrate temperatures. Humidity-sensitive properties of resistive sensors having interdigitated electrode structure are characterized. Our sensors show good response to humidity over 20%RH to 80%RH. Vanadium oxide films deposited with 0% $O_2$ partial pressure at foot exhibit greater sensitivity to humidity change than others.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.659-662
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• 2018

We report the properties of infrared photodetectors based on two kinds of quantum dots(QDs): i) 2.0 ML InAs QDs by the Stranski-Krastanov growth mode(SK QDs) and ii) sub-monolayer QDs by $4{\times}[0.3ML/1nm\;In_{0.15}Ga_{0.85}As]$ deposition(SML QDs). The QD infrared photodetector(QDIP) structure of $n^+-n^-(QDs)-n^+$ is epitaxially grown on GaAs (100) wafers using molecular-beam epitaxy. Both the bottom and top contact GaAs layers are Si doped at $2{\times}10^{18}/cm^3$. The QD layers are grown with Si doping of $2{\times}10^{17}/cm^3$ and capped by an $In_{0.15}Ga_{0.85}As$ layer at $495^{\circ}C$. The photoluminescence peak(1.24 eV) of the SML QDIP is blue-shifted with respect to that (1.04 eV) of SK QDIPs, suggesting that the electron ground state of SML QDIP is higher than that of the SK QDIP. As a result, the photoresponse regime(${\sim}9-14{\mu}m$) of the SML QDIP is longer than that (${\sim}6-12{\mu}m$) of the SK QDIP. The dark current of the SML QDIP is two orders of magnitude smaller value than that of the SK QDIP because of the inserted $Al_{0.08}Ga_{0.92}As$ layer.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.23-31
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• 2012

In this paper, we developed a frequency-domain diffuse optical imaging (DOI) system for imaging non-invasively using near-infrared (NIR) light sources and detectors. 70-MHz modulation and a homodyne scheme were adopted. By calibration of the coupling coefficients, concurrent detection measurements by 4 detector sets were optimized. We presented experimental reconstruction images of absorption and scattering coefficients in a liquid phantom, located an anomaly in the phantom and determined its optical properties. The images by the multi-channel concurrent detection were improved over the results by single-channel sequential detection. Tomographic slices of absorption and scattering coefficients in the phantom with an anomaly were also presented.