• Proceedings of the Optical Society of Korea Conference
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• 2008.02a
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• pp.223-224
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• 2008

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2020-2021
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• 2004

Distributed optical feedback by gain coupling in V-groove quantum-wire lasers is investigated using InGaAs/AlGaAs active materials grown by metalorganic chemical vapor deposition (MOCVD). In order to avoid grating overgrowth during the fabrication of DFB structures, a newly developed constant MOCVD growth method is employed. Gain anisotropy in emission spectra near Bragg wavelength, resulting from optical feedback along the DFB direction, is clearly observed at room temperature.

• Proceedings of the IEEK Conference
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• 2000.11b
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• pp.13-16
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• 2000

A quantum-wire field effect transistor(QW-FET) using asymmetric double InGaAs channel and Si-delta doped barrier has been fabricated. It exhibited good modulation and saturation characteristic in the range of ${\mu}\textrm{A}$ current level. For estimated channel width of 150nm QW-FET, maximum transconductance was about 400 mS/mm which is higher than a conventional heterostructure FET(HFET) with the same epi-structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.47-47
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• 2011

There have been numerous efforts to enhance the efficiency of light-emitting diodes (LEDs) by using low dimensional structures such as quantum dots (QDs), wire (QWRs), and wells (QWs). We demonstrate QD/QWR/QW hybrid structured LEDs by using nano-scaled pyramid structures of GaN with ~260 nm height. Photoluminescence (PL) showed three multi-peak spectra centered at around 535 nm, 600 nm, 665 nm for QWs, QWRs, and QDs, respectively. The QD emission survived at room temperature due to carrier localization, whereas the QW emission diminished from 10 K to 300 K. We confirmed that hybrid LEDs had zero-, one-, and two-dimensional behavior from a temperature-dependent time-resolved PL study. The radiative lifetime of the QDs was nearly constant over the temperature, while that of the QWs increased with increasing temperature, due to low dimensional behavior. Cathodoluminescence revealed spatial distributions of InGaN QDs, QWRs, and QWs on the vertices, edges, and sidewalls, respectively. We investigated the blue-shifted electroluminescence with increasing current due to the band-filling effect. The hybrid LEDs provided broad-band spectra with high internal quantum efficiency, and color-tunability for visible light-emitting sources.

• Nuclear Engineering and Technology
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• v.38 no.8
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• pp.753-762
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• 2006

In this paper, works related to enhancement of the CHF are reviewed in terms of fundamental mechanisms and practical applications. Studies on CHF enhancement in forced convection are divided into two categories, CHF enhancement of internal flow in tubes and enhancement of CHF in the nuclear fuel bundle. Methods of enhancing the CHF of internal flows in tubes include enhancement of the swirl flow using twisted tapes, a helical coil, and a grooved surface; promotion of flow mixing using a hypervapotron; altering the characteristics of the heated surface using porous coatings and nano-fluids; and changing the surface tension of the fluid using additives such as surfactants. In the fuel bundle, mixing vanes or wire wrapped rods can be employed to enhance the CHF by changing the flow distributions. These methods can be applied to practical heat exchange systems such as nuclear reactors, fossil boilers, fusion reactors, etc.

• Journal of Korea Society of Industrial Information Systems
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• v.19 no.6
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• pp.33-41
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• 2014

In this paper, we propose a D flip-flop based on quantum-dot cellular automata(QCA) clocking and design a programmable quantum-dot cell(QPCA) structure using the proposed D flip-flop. Previous D flip-flops on QCA are that input should be set to an arbitrary value, and wasted output values exist because it was utilized to duplicate by clock pulse and QCA clocking. In order to eliminate these defects, we propose a D flip-flop structure using binary wire and clocking technique on QCA. QPCA structure consists of wire control logic, rule control logic, D flip-flop and XOR logic gate. In experiment, we perform the simulation of QPCA structure using QCADesigner. As the result, we confirm the efficiency of the proposed structure.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.02a
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• pp.21-21
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• 1999

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.560-565
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• 2015

We report efficient direct coupling of THz dipole antenna pulses onto air spaced two-wire transmission lines and Teflon covered two-wire lines. The air spaced two-wire lines show TEM mode propagation with very small group velocity dispersion (GVD) and relatively low attenuation. The Teflon covered two-wire lines showed comparatively much higher attenuation and GVD. However, the Teflon covered two-wire lines show a very good guiding property when the lines are curved. Although the lines are circled only 5.0 cm in diameter, there is no additional attenuation compared to straight the lines.

• Journal of Radiation Industry
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• v.6 no.1
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• pp.31-40
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• 2012

There are two methods to fabricate the readout electronic to a large-area CMOS image sensor (LACIS). One is to design and manufacture the sensor part and signal processing electronics in a single chip and the other is to integrate both parts with bump bonding or wire bonding after manufacturing both parts separately. The latter method has an advantage of the high yield because the optimized and specialized fabrication process can be chosen in designing and manufacturing each part. In this paper, LACIS chip, that is optimized design for the latter method of fabrication, is presented. The LACIS chip consists of a 3-TR pixel photodiode array, row driver (or called as a gate driver) circuit, and bonding pads to the external readout ICs. Among 4 types of the photodiode structure available in a standard CMOS process, $N_{photo}/P_{epi}$ type photodiode showed the highest quantum efficiency in the simulation study, though it requires one additional mask to control the doping concentration of $N_{photo}$ layer. The optimized channel widths and lengths of 3 pixel transistors are also determined by simulation. The select transistor is not significantly affected by channel length and width. But source follower transistor is strongly influenced by length and width. In row driver, to reduce signal time delay by high capacitance at output node, three stage inverter drivers are used. And channel width of the inverter driver increases gradually in each step. The sensor has very long metal wire that is about 170 mm. The repeater consisted of inverters is applied proper amount of pixel rows. It can help to reduce the long metal-line delay.

• Journal of the Korean institute of surface engineering
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• v.29 no.6
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• pp.753-759
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• 1996

The artificial construction of well-defined low-dimensional (low-D) quantum structures, such as quantum wire (QWR) still attracts attention of many researchers due to their applications in room-temperature optoelectronic devices. In this work, the migration enhanced epitaxial growth (MEE) and the analysis of InAs/ AlAs QWR are reported. On the vicinal semi-insulating InP substrate of $3^o$ tilted cut from (100) surface towards (010) direction, InAs/ AlAs QWR superlattices have been successfully grown by MEE with the introduction of growth interruption at each shutter operation of MBE cell. The in-situ RHEED analyses show that MEE gives superior step-flow growth (SFG) and sharper interface formation over a conventional MBE growth. We have grown 4 samples in series varying the growth temperature. The QWR samples are analyzed by photoluminescence (PL) and atomic force microscopy (AFM). From the AFM images, we can get the definitely resolved 1-D structures. This structure is believed to be due to the MEE method and its separation is better than any other data from others. We are now studying the dependence of the structure on the growth temperature.