An analytical model for the electro-thermal feedback effect in a microbolometer infrared focal plane array is presented. The presented model is the integrated optical-electro-thermal model, in which the electro-thermal feedback effect incorporated with the response of incident IR can be described. In addition, since the model is based on physics, the model parameters also have their own physical meaning. This analytical model can be easily utilized to describe the temperature increase caused by the applied heat sources and has a unique feature describing capability of optical-electro-thermal analysis in a quasi-steady-state, which can hardly be performed with thermal analysis tools based on the finite element method. The model shows that the temperature of the microbolometer in this study can be increased 7.1% to 18.6% more by the electro-thermal feedback effect.
We present a thermal property estimation method required for a bolometer design and demonstrate the utilization of a
presented method to the scaled μ-bolometers. The estimated thermal properties of 25μm pitch VOx bolometers with our
presented method shows K=1.33x10-8 W/K, H=1.36x10-10 J/K, τth=10.2 ms for an active bolometer and K=1.64x10-6
W/K, H=1.82x10-10 J/K, τth=111 μs for a reference bolometer. These estimated thermal properties have a good agreement
with the previous reports and with results from the FEM analyses carried on the same bolometer designs. The presented
method is useful to estimate thermal properties of a scaled bolometer and to estimate thermal properties of a specific
design.
In this paper, the performance enhancing method by increasing optical fill factor of a μ-bolometer is proposed. The main
idea of increasing optical fill factor of a μ-bolometer is the reducing the leg area without deteriorating the thermal and
electrical properties of its legs. We propose 'the self align leg' structure in order to reduce the leg area without
deteriorating electrical and thermal properties. From the analysis, this method can give some benefits, the improvement
of responsivity up to 9% and noise equivalent temperature difference 13% through fill factor increasing by 5 to 7%. A
new plausible method of increasing fill factor can easily be incorporated with a conventional process without
considerable change of process.
It is very important to investigate hemodynamic and hemorheologic features of blood flow from fluid mechanical point of view because they play major roles in understanding the pathogenesis on cardiovascular disorders. Generally, hemorheologic characteristics of blood flow near the vessel wall are well-known as the most important factor in thrombosis generation according to several hypotheses. To investigate the hemodynamic and hemorheological features related to circulatory diseases, in-vitro experiments were carried out using Micro-PIV technique. Numerical simulation methods using conventional CFD codes were also used to compare with experimental results. The vessel models with stenotic lesion and clinical stent implantation were made of PDMS channel based on Right Coronary Artery (RCA) from clinical angiogram
for the patient with stenotic lesion. The hemodynamic and hemorheologic behaviors for control volume near stenotic lesion
were evaluated by velocity profiles.
This paper reviews the development history and current status of HgCdTe based IR detector of which the study had
started from 1980's in South Korea. It covers the fields from single element diode to 2-dimensional IR detector as well as
dewar technology. The past studies of large area single element diode, linear array detector, 2-D IRFPAs are reported
which include HgCdTe diode array, ROIC and hybridization technologies. Thanks to the sound cooperation between
academia, research institute, industry, and government, current progress of 2-D IR detector shows high performance and
reliability to be able to be utilized in fields. Finally, prospective future of IR detector in Korea is addressed.
This paper reports the development of mid-wave 320x256 HgCdTe IRFPA with 30μm pixel pitch since 2002 in Korea.
All key technologies such as HgCdTe photodiode array fabrication process, the design of silicon readout integrated
circuit and hybridization process between HgCdTe photodiode array and ROIC including underfill encapsulation process
are studied and realized. The fabricated IRFPA shows good electro-optical performances such as operability over 99%,
NETD of ~ 17mK and there is no degradation in the operability during 500 thermal cycles.
A new device concept and implementation procedure of a monolithic two-color IR detector using MOVPE grown p-HgCdTe/N- HgCdTe/CdTe/GaAs is discussed. Newly introduced two-color IR detector consists of simple n-p-N structure, which can be realized using simple p-N double layer HgCdTe material. Formation of potential barrier in the conduction band of p-N heterojunction is a key to the successful operation of monolithic two-color IR detector. It prevents photogenerated minority carriers in small band gap region (p-HgCdTe) from diffusing to N-HgCdTe. The monolithic two-color IR detector was firstly fabricated using MOVPE grown p-Hg0.69Cd0.31Te/N-Hg0.64Cd0.36Te/CdTe/GaAs for SW/MWIR. SWIR diode shows RoA value of 752 (Omega) cm2, while MWIR diode shows RoA value of 140 (Omega) cm2.
In this paper, we report electrical and optical properties of the rapid thermal diffused (RTD) p-n junction photodiodes fabricated on LPE-grown p-type Hg0.70Cd0.30Te/CdZnTe substrate. In comparison with the ion implanted p-n junction on the same substrate, the reverse bias tunneling current is drastically suppressed in the RTD junction. The spectral photo-response of indium diffused HgCdTe photodiode shows the high quantum efficiency and the detectivity of 1.3 by 1011 cm/Hz1/2W. The suppression of the reverse bias leakage current, high quantum efficiency and low noise of the RTD photodiode could be explained by the suppression of the electrical active defects generation in the depletion region during the junction formation. The extracted carrier lifetime in the junction depletion region of the RTD HgCdTe photodiodes is larger than that of the ion-implanted one.
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