• Advances in nano research
• /
• v.1 no.3
• /
• pp.125-131
• /
• 2013

This study is aimed to calculate the radiative lifetime of Wannier-Mott excitons in nanoclusters of a narrow-bandgap semiconductor embedded in a wide-bandgap one. The nanocluster linear dimensions are assumed to be much larger than the radius of the exciton so that the latter is not destructed by the confinement potential as it takes place in small quantum dots. The calculations were carried out for an example of InAs nanoclusters put into the GaAs matrix. It is shown that the radiative lifetime of Wannier-Mott excitons in such clusters increases with the decrease of the cluster dimensions, this tendency being more pronounced at low temperatures. So, the creation of excitons in nanoclusters of a narrow-bandgap material embedded in a wide-bandgap one can be used to significantly prolong their radiative lifetime in comparison with that of excitons in a bulk semiconductor.

• Proceedings of the IEEK Conference
• /
• 2000.07b
• /
• pp.612-614
• /
• 2000

We propose a new curvature-compensated CMOS bandgap reference circuit that is achieved by varying a current ratio. The proposed circuit is shown to have small temperature coefficient that the output voltage variation is 0.4mV.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3340-3344
• /
• 2013

The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.41 no.2
• /
• pp.53-58
• /
• 2004

In this paper, the low-phase dual-band VCO, by adding switching circuit with PIN diode at feedback loop of the oscillation part having negative-resistance, is realized. In order to reduce the phase noise of the VCO, PBG structure applied to the ground plane of the resonator. When applying for PBG structure, output power is -9.17㏈m and phase noise is -102㏈c/Hz at 5.25㎓, output power is -5.17㏈m and phase noise is -101㏈c/Hz at 1.8㎓, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.1
• /
• pp.88-96
• /
• 2016

In this paper, the GaN FET based phase-shift full-bridge dc-dc converter design is implemented. Switch characteristics of GaN FET were analyzed in detail by comparing state-of-the-art Si MOSFET. Owing to the low conduction resistance and parasitic capacitance, it is expected to GaN FET based power conversion system has improved performance. However, GaN FET is vulnerable to electric interference due to the relatively low threshold voltage and fast switching transient. Therefore, it is necessary to consider PCB layout to design GaN FET based power system because PCB layout is the main reason of stray inductance. To reduce the electric noise, gate voltage of GaN FET is analyzed according to operation mode of phase-shift full-bridge dc-dc converter. Two 600W phase-shifted full-bridge dc-dc converter are designed based on the result to evaluate effects of stray inductance.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.111-111
• /
• 2003

The peroxo titanic acid solution was successfully prepared using titanium trichloride as a precursor. The basic properties of the TiO2 film prepared by the solution were investigated in view of phase change, bandgap energy, crystalline size etc. The film displayed amorphous TiO$_2$ at room temperature, anatase above 281$^{\circ}C$ and a mixture of anatase and rutile at 99$0^{\circ}C$, The crystalline size increases with annealing temperatures, while the bandgap energies decrease due to the quantum size effect and the formation of rutile phase which has low bandgap energy. As a result of TG-DTA, it was found that annealing treatment at 99$0^{\circ}C$ for 2h formed a mixtures of anatase and rutile through three steps: (1) the removal of physically adsorbed water (2) the decomposition of peroxo group (3) amorphous-anatase or anatase-rutile phase transformation.

• Journal of the Semiconductor & Display Technology
• /
• v.17 no.2
• /
• pp.53-56
• /
• 2018

In this paper, a CMOS bandgap voltage reference that is not sensitive to changes in the external environment is presented. Large OLED display panels need high supply voltage. MOSFET devices with high voltage are sensitive to the output voltage due to the channel length modulation effect. The self-cascode circuit was applied to the bandgap reference circuit. Simulation results show that the maximum output voltage change of the basic circuit is 77mV when the supply voltage is changed from 10.5V to 13.5V, but the proposed circuit change is improved to 0.0422mV. The improved circuit has a low temperature coefficient of $9.1ppm/^{\circ}C$ when changing the temperature from $-40^{\circ}C$ to $140^{\circ}C$. Therefore, the proposed circuit can be used as a reference voltage source for circuits that require a high supply voltage.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.1
• /
• pp.137-142
• /
• 2008

The band-gap reference voltage generator which can be operated by low voltage is proposed in this paper. The proposed BGR circuit can be realized in logic process by using parasitic NPN BJTs because a $Low-V_T$ transistors are not necessary. The proposed BGR circuit is designed and fabricated using $0.18{\mu}m$ triple-well process. The mean voltage of measured VREF is 0.72V and the three sigma$(3{\sigma})$ is 45.69mv.

• 한국신재생에너지학회:학술대회논문집
• /
• 2007.06a
• /
• pp.240-240
• /
• 2007

• Proceedings of the Optical Society of Korea Conference
• /
• 2006.02a
• /
• pp.87-88
• /
• 2006

Bragg fibers, consisting of a low index core (including air) surrounded by a series of periodic layers of alternate high and low refractive index materials, each being higher than that of the core, form a 1D photonic bandgap (PBG). In view of the multitude of individual physical parameters that characterize a Bragg fiber, they offer a wide choice of parametric avenues to tailor their propagation characteristics. Owing to their unique PBG guidance mechanism, Bragg fibers indeed exhibit unusual dispersion characteristics that are otherwise nearly impossible to achieve in conventional silica fibers. Solid core Bragg fibers, amenable to fabrication by the highly mature MCVD technology, could be designed to realize broadband supercontinuum light. This talk would review our recent works on modeling of propagation characteristics, dispersion tailoring in them for applications as metro as well as dispersion compensating fibers and also as supercontinuum light generators.