Sungkyunkwan University · 工学
Hyung Koun Cho 교수의 연구실은 III-V 반도체, 특히 InGaN/GaN 다중 퀘이버 웰(MQW) 구조를 중심으로 한 고성능 전자 및 광전자 소자의 기초 연구를 수행하고 있습니다. 주요 연구 방향은 비정질 산화물 반도체(예: a-IGZO)를 활용한 저농도 기체 센서 개발과, 고임플란트된 GaN 기반 웨이퍼에서의 결함 구조(스택킹 결함, 스트레인 리laxation, 탈락 결함 등)가 광학적·전기적 성질에 미치는 영향을 전자현미경 및 광발광 분석을 통해 규명하는 데 집중되어 있습니다. 또한 비파괴 품질 검사 기술을 활용한 생물학적 표면 결함 진단 기술 개발도 함께 진행하고 있습니다.
Figures are computed from collected data and may differ slightly.
V-defect formation of the InxGa1−xN/GaN multiple quantum wells (MQWs) grown on GaN layers with different threading dislocation (TD) densities was investigated. From cross-sectional transmission electron microscopy, we found that all V defects are not always connected with TDs at their bottom. By increasing the indium composition in the InxGa1−xN well layer or decreasing the TD density of the thick GaN layer, many V defects are generated from the stacking mismatch boundaries induced by stacking f
InGaN/GaN multiple quantum wells (MQWs) grown with various growth interruptions between the InxGa1−xN well and GaN barrier by metalorganic chemical vapor deposition were investigated using photoluminescence (PL), high-resolution transmission electron microscopy, and energy filtered transmission electron microscopy (EFTEM). The integrated PL intensity of the MQWs with growth interruptions is abruptly reduced compared to that of the MQW without growth interruption. Also, as the interruption time i
We suggest the use of a thin-film transistor (TFT) composed of amorphous InGaZnO (a-IGZO) as a channel and a sensing layer for low-concentration NO<sub>2</sub> gas detection. Although amorphous oxide layers have a restricted surface area when reacting with NO<sub>2</sub> gas, such TFT sensors have incomparable advantages in the aspects of electrical stability, large-scale uniformity, and the possibility of miniaturization. The a-IGZO thin films do not possess typical reactive sites and grain bou
A nondestructive quality inspection technique using acoustic impulse response method was developed for thedetection of surface cracks in an eggshell. An experimental system was built to generate the impact force, measure theresponse signal, analyze the frequency spectrum, and classify the eggs as cracked or normal. This system includes animpulse generating unit, an egg holding seat, a microphone with a preamplifier, and a DSP board installed in a personalcomputer. A multivariate discriminant ana
We have studied the effect of the trimethylgallium (TMGa) flow rate in the GaN buffer layer on the optical and structural quality. From low temperature photoluminescence measurements, a GaN overlayer grown on a buffer layer with the TMGa flow rate of 80 μmol/min shows the intense donor-acceptor pair transition peak at 3.27 eV and the weak yellow band emission at 2.2 eV, which are related with stacking faults and threading dislocations from transmission electron microscopy images, respectively. A
Influence of strain relaxation on structural and optical properties of the InGaN/GaN multiple quantum wells (MQWs) with high indium composition grown by metalorganic chemical vapor deposition was investigated. From photoluminescence and transmission electron microscopy (TEM), we found that within the MQWs, the formation of misfit dislocation affects the degradation of optical properties more than the formation of stacking faults. For the MQWs with indium composition above the critical indium com
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