• Journal of Electrical Engineering and information Science
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• v.3 no.2
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• pp.239-244
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• 1998

Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin film have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers. Surface micromachining techniques have been applied in a GaAs MESFET process to form both microsensors and electronic circuits. The on-chip integration of microsensors such as pressure sensors and infrared detectors with GaAs integrated circuits is attractive because of the higher operating temperature up to 200 oC for GaAs devices compared to 125 oC for silicon devices and radiation hardness for infrared imaging applications. The microsensors incorporate a 1${\mu}$m-thick sputtered ZnO capacitor supported by a 2${\mu}$m-thick aluminum membrane formed on a semi-insulating GaAs substrate. The piezoelectric pressure sensor of an area 80${\times}$80 ${\mu}$m2 designed for use as a miniature microphone exhibits 2.99${\mu}$V/${\mu}$ bar sensitivity at 400Hz. The voltage responsivity and the detectivity of a single infrared detector of an area 80${\times}$80 $\mu\textrm{m}$2 is 700 V/W and 6${\times}$108cm$.$ Hz/W at 10Hz respectively, and the time constant of the sensor with the amplifying circuit is 53 ms. Circuits using 4${\mu}$m-gate GaAs MESFETs are fabricated in planar, direct ion-implanted process. The measured transconductance of a 4${\mu}$m-gate GaAs MESFET is 25.6 mS/mm and 12.4 mS/mm at 27 oC and 200oC, respectively. A differential amplifier whose voltage gain in 33.7 dB using 4${\mu}$m gate GaAs MESFETs is fabricated for high selectivity to the physical variable being sensed.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.4
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• pp.483-491
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• 2017

The interdigitated germanium (Ge) meta-lsemiconductor-metal (MSM) photodetectors (PDs) with and without an $SiO_2$ anti-reflection (AR) layer was fabricated, and the effect of $SiO_2$ AR layer on their optoelectronic response properties were investigated in detail. The lowest reflectance of 15.6% at the wavelength of 1550 nm was obtained with a $SiO_2$ AR layer with a thickness of 260 nm, which was in a good agreement with theoretically calculated film thickness for minimizing the reflection of Ge surface. The Ge MSM PD with 260 nm-thick $SiO_2$ AR layer exhibited enhanced device performance with the maximum values of responsivity of 0.65 A/W, the quantum efficiency of 52.2%, and the detectivity of $2.49{\times}10^9cm\;Hz^{0.5}W^{-1}$ under the light illumination with a wavelength of 1550 nm. Moreover, time-dependent switching analysis of Ge MSM PD with 260 nm- thick $SiO_2$ AR layer showed highest on/off ratio with excellent stability and reproducibility. All this investigation implies that 260 nm-thick $SiO_2$ AR layer, which is effective in the reduction in the reflection of Ge surface, has a great potential for Ge based optoelectronic devices.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.229-235
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• 2001

Uncooled pyroelectric thin-film (Ba,Sr)TiO$_3$ infrared detectors thermally isolated from Si-substrate by Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-membrane have been fabricated, and figures of merit for detectors were examined. The detector at $25^{\circ}C$ in air showed relatively high voltage responsivity of about 168.8 V/W and low specific detectivity of about 2.6$\times$10$^4$cm.Hz$^{1}$2//W at 1 Hz-chopping frequency because of very small signal-to-noise voltage ratio. It could be found that both thermal noise voltage and thermal time constant of the detector were very large by analyzing dependences of output waveforms on chopping frequency and temperature.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.88-93
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• 1994

We fabricated a large-scale photovoltaic device for detecting-3-5$\mu$m IR, by forming of n$^{+}$-p junction in the $Hg_{1-x}Cd_{x}$Te (MCT) layer which was grown by LPE on CdTe substrate. The composition x of the MCT epitaxial layer was 0.295 and the hole concentration was 1.3${\times}10^{13}/cm^{4}$. The n$^{+}$-p junction was formed by B+ implantation at 100 keV with a does 3${\times}10^{11}/cm^{2}. The n$^{+}$ region has a circular shape with 2.68mm diameter. The vacuum-evaporated ZnS with resistivity of 2${\times}10^{4}{\Omega}$cm is used as an insulating layer over the epitaxial layer. ZnS plays the role of the anti-reflection coating transmitting more than 90% of 3~5$\mu$m IR. For ohmic contacts, gole was used for p-MCT and indium was used for n$^{+}$-MCT. The fabrication took 5 photolithographic masks and all the processing temperatures of the MCT wafer were below 90$^{\circ}C$. The R,A of the fabricated devices was 7500${\Omega}cm^{2}$. The carrier lifetime of the devices was estimated 2.5ns. The junction was linearly-graded and the concentration slope was measured to be 1.7${\times}10^{17}/{\mu}m$. the normalized detectivity in 3~5$\mu$m IR was 1${\times}10^{11}cmHz^{12}$/W, which is sufficient for real application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.92-95
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• 2003

초전형 센서의 특성 평가 방법에는 여러 가지 방법들이 존재하며, 이에 대한 표준화된 특성 평가방법의 개발이 필요로 한다. 측정 평가의 방법이나 조건 등에 따라서 평가 결과가 크게 변할 수 있는 사항들이며, 따라서 국내 뿐 아니라 대외적으로 다른 나라의 제품들과 신뢰성을 가지고 경쟁을 하기 위해서는 평가항목이나 평가방법의 표준화가 절실하게 요구된다. 초전형 적외선 센서를 평가하는 항목에는 기본적으로 입력에 대한 출력신호의 크기를 평가하는 감도(responsivity), 잡음과 관련되어 센서가 검출할 수 있는 최소의 신호를 나타내는 NEP(Noise Equivalent Power)와 이것을 센서의 감지 면적으로 정규화 시킨 검출능(detectivity), 응답 속도를 나타내는 시정수(time constant)가 있으며 이러한 항목들이 표준화의 대상이 된다. 본 실험에서는 기존의 상용화된 센서들을 가지고 초전형 적외선 센서의 특성을 측정 하였다. 특성을 측정할 때 다른 요인들 보다 노이즈로 인한 영향이 상당히 크므로 측정시 노이즈 발생 문제를 해결하는 방법으로 본 논문에서는 센서 측정에 사용되는 증폭 회로에서 노이즈를 해결하려고 하였다. 우리는 증폭 회로구성에서 노이즈를 제거하기 위해서 신호입력단과 전압 압력에 잡음제거 필터로 R, C를 사용하였다. 회로설계로 제작된 증폭회로와 측정 장치를 가지고 측정을 한 결과 센서의 감도는 $3.0mV_{p-p}$, 응답시간은 20ms정도의 값으로 가장 일반적인(typical) 값을 보인다.

• Journal of Sensor Science and Technology
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• v.11 no.4
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• pp.247-253
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• 2002

For fabrication of the pyroelectric IR sensor $(Pb,La)TiO_3(PLT)$/$LiTaO_3$/(LTO)/PLT ferroelectric thin films was deposited by rf magnetron sputtering followed by rapid thermal annealing and the crystallinity as a function of annealing temperature and time was investigated. Permittivity and dielectric loss factor of ferroelectric thin films as a function of c-axis preffered orientation was measured. Also pyroelectric coefficient of ferroelectric thin films with largest c-axis preffered orientation was measured and obtain figure of merit of voltage response($F_V$) and detectivity($F_D$). In this case $F_V$, $F_D$ was $5.63{\times}10^{-10}\;C{\cdot}cm/J$, $1.98{\times}10^{-8}\;C{\cdot}cm/J$, respectively.

• Journal of Sensor Science and Technology
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• v.7 no.2
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• pp.103-110
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• 1998

Pyroelectric infrared detectors based on La-modified $PbTiO_{3}$ (PLT) thin films have been fabricated by RF magnetron sputtering and rnicrornachining technology. The detectors form $Pb_{l-x}La_{x}Ti_{1-x/4}O_{3}$ (x=0.05) thin film ferroelectric capacitors epitaxially grown by RF magnetron sputtering on Pt/MgO (100) substrate. The sputtered PLT thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency. Polymide is coated on top of the sensing elements to support the fragile structure and the backside of the MgO substrate is selectively etched to reduce the heat loss. The sensing element exhibited a very high detectivity D* of $8.5{\times}10^{8}cm{\cdot}\sqrt{Hz}/W$ at room temperature and it is about 100 times higher than the case of micromachining technology is not used. A sensing system that detects the position as well as the existence of a human body is realized using the array sensor.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.419-423
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• 2011

Unlike other non-destructive inspection method, AE Structural defects that are likely to grow in the operation status can be detected, and the advantage of being due to the continuous monitoring of large structures has been widely used to evaluate the stability. AE sensor used to detect sound wave that occurs between 20kHz to 20MHz. and Sound wave result may vary depending on sensor's sensitivity. In this paper, Tensile test conducted on STS 304 and SS400, and tries to detect the crack signal. In tensile test, specimens were conducted using different sensor sensitivity to the same tensile test condition. The crack signal parameters divided into 4 types of communities by conducting cluster analysis. It was demonstrated that crack signal of two sensor is not different by statistical analysis of null hypotheses. Based on the results, waveform of this tension test is crack signal.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.42-47
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• 2000

Long-wavelength infrared (LWIR) detectors made of self-assembled quantum dots embedded in the channel region of high electron mobility transistor (HEMT) is demonstrated. Above 180 K, the detector shows low dark currents due to strong confinement effect of electrons in InAs quantum dots and exhibits the broad spectral response ranging from 7 mm to 11 mm. The peak detectivity ($D^*$) of $1.93{\times}10^{10}cmHz^{1/2}/W$ is obtained at 9.4 mm. The photocurrent characteristics as a function of applied bias are similar to that of normal FETs, while the photocurrent decreases as the applied electric field exceeds $2{\times}10^3V/cm$ because of the increased dark current.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.11
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• pp.7-13
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• 2002

BSCT 320${\times}$240 IRFPA detector module is implemented, which is a key component in uncooled thermal imaging systems. The detector module consists of two parts, infrared sensitive pixel array and read-out integrated circuit(ROIC). The BSCT 320${\times}$240 pixels are made by laser scribe process and 10-${\mu}m$ micro-bump to satisfy 50-${\mu}m$ pitch and 95-% fill-factor. The ROIC has been designed to electrically address the pixels sequentailly and to improve signal-to-noise ratio with single transistor amplifier, HPF, tunable LPF and clamp circuit. The fabricated hybrid chip of detector and ROIC has been mounted on the TEC built-in ceramic package for more stable operation and tested for lots of electrical and optical properties. The IRFA sample has shown successful properties and met with good results of fill-factor, detectivity and responsivity.