• Current Optics and Photonics
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• v.1 no.5
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• pp.544-550
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• 2017

This simulation based study reports a novel tunable, compact, room temperature terahertz (THz) transistor source, operated on the concept of charge plasma oscillation with the capability of radiating within a terahertz gap. A vertical cavity with a quasi-periodic distributed-Bragg-reflector has been attached to a THz plasma wave transistor to achieve a monochromatic coherent surface emission for single as well as multi-color operation. The resonance frequency has been tuned from 0.5 to 1.5 THz with the variable quality factor of the optical cavity from 5 to 290 and slope efficiency maximized to 11. The proposed surface emitting terahertz transistor is able to satisfy the demand for compact solid state terahertz sources in the field of teratronics. The proposed device can be integrated with Si CMOS technology and has opened the way towards the development of silicon photonics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.916-923
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• 2004

In this paper, the strained Si$_{0.9}$Ge$_{0.1}$ epitaxial layers grown by a reduced pressure chemical vapor deposition (RPCVD) on Si (100) were characterized by Rutherford backscattering spectrometery (RBS) for the fabrication of an SiGe heterojunction bipolar transistor(HBT). RBS spectra of the ${Si}_0.9{Ge}_0.1$epitaxial layers grown on the Si substrates which were implanted with the phosphorus (P) ion and annealed at a temperature between $850^{\circ}C$ - $1000^{\circ}C$ for 30min were analyzed to investigate the post thermal annealing effect on the grown${Si}_0.9{Ge}_0.1$epitaxial layer quality. Although a damage of the substrates by P ion-implantation might be cause of the increase of RBS yield ratios, but any defects such as dislocation or stacking fault in the grown ${Si}_0.9{Ge}_0.1$ epitaxial layer were not found in transmission electron microscope (TEM) photographs. The post high temperature rapid thermal annealing (RTA) effects on the crystalline quality of the ${Si}_0.9{Ge}_0.1$ epitaxial layers were also analyzed by RBS. The changes in the RBS yield ratios were negligible for RTA a temperature between $900^{\circ}C$ - $1000^{\circ}C$for 20 sec, or $950^{\circ}C$for 20 sec - 60 sec. A SiGe HBT array shows a good Gummel characteristics with post RTA at $950^{\circ}C$ for 20 sec.sec.sec.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.22-29
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• 2011

An infrared thermographic imaging module of [$320{\times}256$] focal-plane array (FPA) based on [InAs/GaSb] strained-layer superlattice (SLS) was fabricated, and its images were demonstrated. The p-i-n device consisted of an active layer (i) of 300-period [13/7]-ML [InAs/GaSb]-SLS and a pair of p/n-electrodes of (60/115)-period [InAs:(Be/Si)/GaSb]-SLS. FTIR photoresponse spectra taken from a test device revealed that the peak wavelength (${\lambda}_p$) and the cutoff wavelength (${\lambda}_{co}$) were approximately $3.1/2.7{\mu}m$ and $3.8{\mu}m$, respectively, and it was confirmed that the device was operated up to a temperature of 180 K. The $30/24-{\mu}m$ design rule was applied to single pixel pitch/mesa, and a standard photolithography was introduced for [$320{\times}256$]-FPA fabrication. An FPA-ROIC thermographic module was accomplished by using a $18/10-{\mu}m$ In-bump/UBM process and a flip-chip bonding technique, and the thermographic image was demonstrated by utilizing a mid-infrared camera and an image processor.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.202-202
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• 2010

최근 반도체 소자의 미세화에 따라, 단채널 효과에 의한 누설전류 및 소비전력증가 등이 문제가 되고 있다. DRAM의 경우, 캐패시터 영역의 축소문제가 소자집적화를 방해하는 요소로 작용하고 있다. 1T-DRAM은 기존의 DRAM과 달리 캐패시터 영역을 없애고 상부실리콘의 중성영역에 전하를 저장함으로써 소자집적화에 구조적인 이점을 갖는다. 또한 silicon-on-insulator (SOI) 기판을 이용할 경우, 뛰어난 전기적 절연 특성과 기생 정전용량의 감소, 소자의 저전력화를 실현할 수 있다. 본 연구에서는 silicon-germanium-on-insulator (SGOI) 기판을 이용한 1T-DRAM의 열처리온도에 따른 특성 변화를 평가하였다. 기존의 SOI 기판을 이용한 1T-DRAM과 달리, SGOI 기판을 사용할 경우, strained-Si 층과 relaxed-SiGe 층간의 격자상수 차에 의한 캐리어 이동도의 증가효과를 기대할 수 있다. 하지만 열처리 시, SiGe층의 Ge 확산으로 인해 상부실리콘 및 SiGe 층의 두께를 변화시켜, 소자의 특성에 영향을 줄 수 있다. 열처리는 급속 열처리 공정을 통해 $850^{\circ}C$와 $1000^{\circ}C$로 나누어 30초 동안 N2/O2 분위기에서 진행하였다. 그리고 Programming/Erasing (P/E)에 따라 달라지는 전류의 차를 감지하여 제작된 1T-DRAM의 메모리 특성을 평가하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.3 s.345
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• pp.1-8
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• 2006

In this paper, reliability (HCI, NBTI) and device performance of nano-scale CMOSFETs with different channel stress were investigated. It was shown that NMOS and PMOS performances were improved by tensile and compressive stress, respectively, as well known. It is shown that improved device performance is attributed to the increased mobility of electrons or holes in the channel region. However, reliability characteristics showed different dependence on the channel stress. Both of NMOS and PMOS showed improved hot carrier lifetime for compressive channel stress. NBTI of PMOS also showed improvement for compressive stress. It is shown that $N_{it}$ generation at the interface of $Si/SiO_2$ has a great effect on the reliability. It is also shown that generation of positive fixed charge has an effect in the NBTI. Therefore, reliability as well as device performance should be considered in developing strained-silicon MOSFET.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.156-157
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• 1998

It is a diffcult and challenging pproblem to control the growth of eppitaxial films. Heteroeppitaxy is esppecially idfficult because of the lattice mismatch between sub-strate and depposited layers. This mismatch leads usually to a three dimensional(3D) island growth. But the use of surfactants such as As, Sb, and Bi can be beneficial in obtaining high quality heteroeppitaxial films. In this study medium energy ion scattering sppectroscoppy(MEIS) was used in order to reveal the growth mode of Ge on Si(001) and the strain of depposited film without and with dynamically supplied atomic hydrogen at the growth thempperature of 35$0^{\circ}C$. It was ppossible to control the growth mode from layer-by-layer followed by 3D island to layer-by-layer by controlling the hydrogen flux. In the absent of hydro-gen the film grows in the layer-by-layer mode within the critical thickness(about 3ML) and the 3D island formation is followed(Fig1). The 3D island formation is suppressed by introducing hydrogen resulting in layer-by-layer growth beyond the critical thickness(Fig2) We measured angular shift of blocking dipp in order to obtain the structural information on the thin films. In the ppressence of atomic hydrogen the blocking 야 is shifted toward higher scattering angle about 1。. That means the film is distorted tetragonally and strained therefore(Fig4) In other case the shift of blocking dipp at 3ML is almost same as pprevious case. But above the critical thickness the pposition of blocking dipp is similar to that of Si bulk(Fig3). It means the films is relaxed from the first layer. There is 4.2% lattice mismatch between Ge and Si. That mismatch results in about 2。 shift of blocking dipp. We measured about 1。 shift. This fact could be due to the intermixing of Ge and Si. This expperimental results are consistent with Vegard's law which says that the lattice constant of alloys is linear combination of the lattic constants of the ppure materials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.176-177
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• 2014

The new algorithm was proposed to quantify symmetry recorded in convergent beam electron diffraction (CBED) patterns and symmetry mapping. The proposed algorithm is based on the normalized cross-correlation coefficient (${\gamma}$) for quantifying the amount of symmetry in a CBED pattern. The quantification and mapping procedures are automatically controlled by the script implemented in Gatan Digital Micrograph$^{(c)}$. We apply the quantitative CBED measurement to a strained Si sample to test the sensitivity to defects.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.656-662
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• 2006

We fabricated thermal evaporated 10 nm-$Ni_xCo_{1-x}$ (x=0.2, 0.5 and 0.8) /(poly)Si films to form nanothick cobalt nickel composite silicides by a rapid thermal annealing at $700{\sim}1100^{\circ}C$ for 40 seconds. A field emission scanning electron microscope and a micro-Raman spectrometer were employed for microstructure and silicon residual stress characterization, respectively. We observed self-aligned micro-pinholes on single crystal silicon substrates silicidized at $1100^{\circ}C$. Raman silicon peak shift indicates that the residual tensile strain of $10^{-3}$ in single crystal silicon substrates existed after the silicide process. We propose thermal stress from silicide exothermic reaction and high temperature silicidation annealing may cause the pinholes. Those pinholes are expected to be avoided by lowering the silicidation temperature. Our results imply that we may use our newly proposed composite silicides to induce the appropriate strained layer in silicion substrates.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.199-203
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• 2008

The effects of surface treatment by $O_2$ plasma on the Bio-FETs were investigated by using the pseudo-MOSFETs on the SOI substrates. After a surface treatment by $O_2$ plasma with different RF powers, the current-voltage and field effect mobility of pseudo-MOSFETs were measured by applying back gate bias. The subthreshold characteristics of pseudo-MOSFETs were significantly degraded with increase of RF power. Additionally, a forming gas anneal process in 2 % diluted $H_2/N_2$ ambient was developed to recover the plasma process induced surface damages. A considerable improvement of the subthreshold characteristics was achieved by the forming gas anneal. Therefore, it is concluded that the pseudo-MOSFETs are a powerful tool for monitoring the surface treatment of Bio-FETs and the forming gas anneal process is effective for improving the electrical characteristics of Bio-FETs.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.127-132
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• 2009

We have investigated the intrinsic defects remaining in epitaxial GaSb layers grown on SI-GaAs substrates compared to those in bulk GaSb crystal substrate, which is a basic material of Sb-based strained-layer superlattice infrared photodetectors. From the functional dependence of the band-to-band transition energy of the photomuminescence (PL) spectra observing up to near room-temperature (250 K), the temperature parameters of [$E_o$, $\alpha$, $\beta$] of undoped GaSb crystal are determined by using the Varshni empirical equation describing the temperature variation of the bandgap energy. Additionally to the antisite-Ga ([$Ga_{Sb}$]) with an ionization energy of 29 meV that is well known to a major intrinsic defect in GaSb, epitaxial GaSb layers show a pair of deep states at the emission energy of 732/711 meV that may be related with a complex of two antisite-Ga and antisite-Sb ([$Ga_{Sb}-Sb_{Ga}$]). Based on the analysis of the temperature and the excitation-power dependences of PL, it suggests that excess-Sb substitutes Ga-site by self-diffusion and two anti sites of [$Ga_{Sb}$] and [$Sb_{Ga}$] could form as a complex of [$Ga_{Sb}-Sb_{Ga}$] in GaSb epilayers grown under Sb-rich condition.