• Transactions on Electrical and Electronic Materials
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• v.14 no.5
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• pp.250-253
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• 2013

In this paper, we fabricated 3D pillar type silicon-oxide-nitride-oxide-silicon (SONOS) devices for high density flash applications. To solve the limitation between erase speed and data retention of the conventional SONOS devices, bandgap-engineered (BE) tunneling oxide of oxide-nitride-oxide configuration is integrated with the 3D structure. In addition, the tunneling oxide is modulated by another method of $N_2$ ion implantation ($N_2$ I/I). The measured data shows that the BE-SONOS device has better electrical characteristics, such as a lower threshold voltage ($V_{\tau}$) of 0.13 V, and a higher $g_{m.max}$ of 18.6 ${\mu}A/V$ and mobility of 27.02 $cm^2/Vs$ than the conventional and $N_2$ I/I SONOS devices. Memory characteristics show that the modulated tunneling oxide devices have fast erase speed. Among the devices, the BE-SONOS device has faster program/erase (P/E) speed, and more stable endurance characteristics, than conventional and $N_2$ I/I devices. From the flicker noise analysis, however, the BE-SONOS device seems to have more interface traps between the tunneling oxide and silicon substrate, which should be considered in designing the process conditions. Finally, 3D structures, such as the pillar type BE-SONOS device, are more suitable for next generation memory devices than other modulated tunneling oxide devices.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.5
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• pp.294-300
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• 2017

$TeO_x$ thin films were deposited at various $O_2$/Ar gas-flow ratios by a reactive RFmagneton sputtering technique from $TeO_2$ and Te targets. X-ray diffraction (XRD) results revealed that the $TeO_x$ thin films were amorphous. The structure and chemical composition of the $TeO_x$ thin films were investigated by fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The optical characteristics of the $TeO_x$ thin films were investigated by an Ellipsometer and a UV-VIS-NIR spectrophotometer. According to the $O_2$/Ar gas-flow ratios, the atomic composition ratio of $TeO_x$ thin films was divided into two regions(x=1-2, 2-3). Different optical characteristics were shown in each region. With an increasing $O_2$/Ar gas-flow ratio, the refractive index of the $TeO_x$ thin films decreased and the optical bandgap of the films increased.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.268-269
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• 2000

We demonstrate a polarization insensitive waveguide filter using quantum well intermixing(QWI). The bandgap of epitaxial layer is modified from 1.55${\mu}{\textrm}{m}$ to 1.40${\mu}{\textrm}{m}$ using QWI and a Bragg grating filter is demonstrated using electron beam lithography technology. The fabricated waveguide filter has a 70% reflection efficiency and a 1.46nm filter bandwidth. Furthermore polarization insensitive transmission characteristics are observed. The device can be applied to photonic integrated circuits(PIC).

• Korean Chemical Engineering Research
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• v.56 no.4
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• pp.585-591
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• 2018

Characteristics of nano-structured $SiO_2:Zn$ hollow powders prepared in the micro drop fluidized reactor process were investigated with respect to bandgap energy and surface activity. The $SiO_2:Zn$ hollow powders were successfully prepared continuously in the one step process with reasonable production efficiency, with varying the amount of THAM (tris(hydroxymethyl)-aminomethane) additive and concentration of $Zn^{2+}$ ions. The doping of $Zn^{2+}$ ions into $SiO_2$ lattice led to the reduction of bandgap energy by forming the acceptor level of $Zn^{2+}$ below the conduction band of $Si^{4+}$ ions. The hollow shape also contributed to reduce the bandgap energy of $SiO_2:Zn$ powders. The doping of $Zn^{2+}$ ions into $SiO_2$ hollow powders could enhance the surface activity by forming SiO-H stretching and oxygen vacancies at the surface of $SiO_2:Zn$ powders.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.11
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• pp.760-765
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• 2014

MgZnO has attracted a lot of attention for flexible device. In the flexible substrate, the crystal structure of the thin films as well as the surface morphology is not good. Therefore, in this study, we studied on the effects of the oxygen pressure on the structure and crystallinity of $Mg_{0.3}Zn_{0.7}O$ thin films deposited on PES substrate by using pulsed laser deposition. We used X-ray diffraction and atomic force microscopy in order to observe the structural characteristics of $Mg_{0.3}Zn_{0.7}O$ thin films. The crystallinity of $Mg_{0.3}Zn_{0.7}O$ thin films with increasing temperature was improved, Grain size and RMS of the films were increased. UV-visible spectrophotometer was used to get the band gap energy and transmittance. $Mg_{0.3}Zn_{0.7}O$ thin films showed high transmittance over 90% in the visible region. As increased working pressure from 30 mTorr to 200 mTorr, the bandgap energy of $Mg_{0.3}Zn_{0.7}O$ thin film were decreased from 3.59 eV to 3.50 eV.

• Journal of the Korea Society of Computer and Information
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• v.27 no.8
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• pp.211-218
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• 2022

In this paper, a computer simulation program was developed to interpret the results measured by photoreflectance spectroscopy. The developed program is implemented so that the user can easily change the factors required for optical modulation characteristic interpretation, and the result of the value can be checked simultaneously with the actual measurement result. The results obtained by photoreflectance spectroscopy are obtained by mixing a third derivative function form (TDFF) modulated around a bandgap with a Franz-Keldysh oscillation (FKO) signal due to an electric field at a surface and an interface higher than the bandgap. Through the computer simulation program, the optical characteristics that appear in the GaSb Epi layer formed as a single layer were analyzed, and very useful results were obtained by specializing in optical modulation analysis. In addition, a Fast Fourier Transform (FFT) analysis tool was added to facilitate frequency characteristics analysis of FKO.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.2
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• pp.43-51
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• 2023

In this paper, we introduce the development trends of power devices which is the key component for power conversion system in electric vehicles, and discuss the characteristics of the next-generation wide-bandgap (WBG) power devices. We provide an overview of the characteristics of the present mainstream Si insulated gate bipolar transistor (IGBT) devices and technology roadmap of Si IGBT by different manufacturers. Next, recent progress and advantages of SiC metal-oxide-semiconductor field-effect transistor (MOSFET) which are the most important unipolar devices, is described compared with conventional Si IGBT. Furthermore, due to the limitations of the current GaN power device technology, the issues encountered in applying the power conversion module for electric vehicles were described.

• Journal of Power Electronics
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• v.12 no.1
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• pp.19-23
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• 2012

This paper presents a practical methodology for realistic simulation on reverse characteristics of Wide Bandgap (WBG) SiC and GaN p-n junctions. The adjustment on certain physic-based model parameters, such as the trap density and photo-generation for SiC junction, and impact ionization coefficients and critical field for GaN junction are described. The adjusted parameters were used in Synopsys Medici simulation to obtain a realistic p-n junction avalanche breakdown voltage. The simulation results were verified through benchmarking against independent data reported by others.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.101-106
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• 2005

This paper presents a new microwave oscillator incorporating a corrugated coplanar waveguide (CCPW) electromagnetic bandgap (EBG) structure as its terminating resonance component. The use of a compact CCPW EBG structure was effective in reducing the phase noise and improving the harmonic characteristics of the microwave oscillator circuit without additional backside processing and drastic size increment. The fully planar CCPW oscillator oscillating at the frequency of 5.41 GHz showed a phase noise characteristic of -90.7 dBc/Hz at 100kHz offset and a second harmonic suppression of 42.67 dB.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.12
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• pp.59-64
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• 1996

InSb MIS devices prepared by remote PECVD SiO$_{2}$ were fabricated. The SiO$_{2}$ films on InSb were deposited at atemperature range of 67~190$^{\circ}$C. The effects of deposition temperature on the structural characteristics of the SiO$_{2}$ films evaluated Auger electron spectroscopy showed that atomic raito of silicon to oxygen was 0.5 and composition toms were distributed uniformaly throuout the oxide film. The transition region is about 100$\AA$ for SiO$_{2}$/InSb interface. The leakage current density at 1MV/cm and the breakdownelectric field of the MiS device using SiO$_{2}$ film deposited at 105$^{\circ}$C were about 22 nA/cm$^{2}$ and 3.5MV/cm, respectively. The interface-state density at mid-bandgap extracted from 1 MHz high frequency C-V measurement was about 2X10$^{11}$ cm$^{-2}$eV$^{-1}$.