• Transactions on Electrical and Electronic Materials
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• v.5 no.5
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• pp.173-179
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• 2004

The influence of heavily Si impurity doping in the GaN barrier of InGaN/GaN multi-quantum well structures of blue light emitting diodes were investigated by growing samples in metal-organic chemical vapor deposition. The delta-doped sample was compared to the sample with the undoped barrier. The delta-doped sample shows the tunneling behavior and forms the energy level of 0.32 eV for tunneling and the photoemission of the 450-nm band. The photo-luminescence shows the blue-shifted broad band of the radiative transition due to the inclusion of Si delta-doped layer indicating that the delta doping effect acts to form the higher energy level than that of quantum well. The dislocation may provide the carrier tunneling channel and plays as a source of acceptor. During the tunneling of hot carrier, there was no light emission.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.121-125
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• 2003

Time-resolved photoluminescence from InGaN/GaN multi-quantum well structures was investigated for two different shapes of square- and trapezoidal wells grown by metal-organic chemical vapor deposition. To compare to the conventional square well structure with a radiative recombination lifetime of 0.170 nsec, the large value of lifetime of 0.540 nsec from trapezoidal well were found at room temperature. This value is similar to the value for GaN host material indicating no confinement effect of quantum well. Furthermore, the high resolution transmission electron microscopy image provides the In clustering effect in the trapezoidal well structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.71-75
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• 2014

To observe the optical characteristic of oxide semiconductor depending on the degree of bonding structures, SiOC, ZnO and IGZO were prepared by the RF magnetron sputter system and chemical vapor deposition. Generally, crystal ZnO, amorphous SiOC and IGZO changed the optical characteristics in according to the electro-chemical behavior due to the oxygen vacancy at an interface between different groups. Transmittance of SiOC and IGZO with amorphous structures was higher than that of ZnO with crystal structure, because of lowering the carrier concentration due to the recombination of electron and holes carriers as oxygen vacancies. Besides, the energy gap of amorphous SiOC and IGZO was higher than the energy gap of crystal ZnO. The diffusion mobility of holes is higher than the drift mobility of electrons.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.723-730
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• 2003

The CN(carbon nitrogen) nanofibers were formed by HIP(high isostatic pressure) process. From the field emission measurement, CN nanofibers shows an excellent characteristics of emitter, better than CNTs and carbon nanofibers. The structures obtained can be divided into three groups : bamboo-like fibers, corrugated structures and bead necklace-like fib res. Emission properties of CN nanofibers were investigated for spacing, between anode and cathode, variation. Turn-on fields was 1.4 v/$\mu\textrm{m}$. The time reliability and light emission test were carried out for about 100 hours. We suggest that CN nanofibers can be possibly applied to the high brightness flat lamp because of low turn-on field and time reliability

• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.103-107
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• 2006

In this paper, a CMOS complementary bridge rectifier for driving RFID transponder chips is presented. The proposed RFID CMOS complementary bridge rectifier is designed with two NMOSs at the input, which are configured by cross-connected gate structures, and two PMOSs and two NMOSs at the output, which are configured by diode-connected MOS structures. Output characteristics of the proposed rectifier are analyzed with the high frequency small-signal equivalent circuit and verified with SPICE for RFID operating frequencies of 13.56 MHz HF for ISO 18000-3, 915MHz UHF for ISO 18000-6, and 2.45 GHz microwave for ISO 18000-4. Simulation results show well-rectified and high enough DC output voltages for driving the low power microchip in the RFID transponder for the frequency range from HF to microwave. DC output voltages are dropped by only around 0.7 V from the input peak-to-peak voltages.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.135-136
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• 2006

In this paper, isolation strategies for improving broadband circuit performance and preventing noise arising from circuit component coupling are presented. Equivalent circuit parameters, including parasitic elements, are determined for capacitor and inductor structures. The effects of the relative position of the components with regard to a ground plane are considered in the equivalent circuits. Novel meshed ground structures are investigated to determine a configuration that improves the overall circuit performance.

• ETRI Journal
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• v.13 no.4
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• pp.25-34
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• 1991

The stability and the electronic structure of $In_0.5$.$Ga_0.5$P-based superlattices are examined through self-consistent ab initio pseudopotential calculations. A chalcopyrite-like structure is found to be the lowest energy state over (001) and (111) monolayer superlattices (MLS). Our calculations indicate that all the ordered structures in bulk form are unstable against phase segregation into binary constituents at T = 0 while for epitaxial growth, the chalcopyrite phase is stabilized. The fundamental band gaps of the ordered structures are found to be direct and smaller than that of disordered alloys. The lowering of the band gap is explainable by band folding and pushing effects. We find the reduction of the band gap to be largest for the (111) MLS.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.350-353
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• 1999

This Paper Presents the optimized design of micro-heaters using 501(Si-on-insulator) substrate and oxide-filled trench structure In order to justify a lumped model approximation and thermal boundary assumptions, two-dimensional FDM(finite difference among which conduction is the dominant heat dissipation path. Compared with no-trenchs on the SOI structure, the micro-heaters with trench structures has properties of low heater loss and good thermal isolation. The simulation results show that the heater loss decreases as the number. width and distance of trenchs increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.557-560
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• 2000

Combination of SDB(Si-wafer Direct Bonding) and electrochemical etch-stop in TMAH anisotropic etchant can be used to create a variety of MEMS(Micro Electro Mechanical System). Especially, fabrication of SDB SOI structures using electrochemical etch-stop is accurate method to fabrication of 3D(three-dimensional) microstructures. This paper describes on the fabrication of SDB SOI structures with sealed cavity for MEMS applications and thickness control of active layer on the SDB SOI structure by electrochemical etch-stop. The flatness of fabricated SDB SOI structure is very uniform and can be improved by addition of TMAH to IPA and pyrazine.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.67-70
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• 2000

In this paper, all SCR recombination currents including setback and graded layer's recombination currents are analytically introduced for the first time. Different emitter-base structures are tested to prove the validity of the model. In 1995, the analytical equations of electric field, electrostatic potential, and junction capacitance for abrupt and linearly graded heterojunctions with or without a setback layer was derived. But setback layer and linearly graded layer's recombination current was considered numerically. In this paper, recombination current model included setback layer and graded layer is proposed. New recombination current model also includes abrupt heterojunction's recombination current model. In this paper, new recombination current model analytically explains effects of setback layer and graded layer.