Influence of Growth Temperature on the Characteristics of Single-Junction p—i—n InGaP Solar Cells

Jung, Sang Hyun,Kim, Youngjo,Kim, Chang Zoo,Jun, Dong-Hwan,Kim, Kangho,Shin, Hyun-Beom,Choi, JeHyuk,Park, Won-Kyu,Lee, Jaejin,Kang, Ho Kwan American Scientific Publishers 2017 Journal of nanoscience and nanotechnology Vol.17 No.4

<P>Single-junction p-i-n InGaP solar cells are grown at various temperatures from 620 to 700 degrees C by low pressure metalorganic chemical vapor deposition on GaAs (001) substrates. The short circuit current density of the p-i-n InGaP solar cells increases by up to 38.8% when the growth temperature is reduced from 700 to 620 degrees C, while the open circuit voltage and fill factor show relatively small changes. The external quantum efficiency, especially, in the wavelength regime below 500 nm, is improved for the p-i-n InGaP solar cells grown at lower temperatures. The improvement might be attributed to the reduced absorption loss of the photons in the n-InGaP emitter region. The highest conversion efficiency of 11.01% is attributed from the p-i-n InGaP solar cell grown at 640 degrees C. Electron mobility and concentration of undoped InGaP layers are investigated as a function of the growth temperature and correlated with the p-i-n InGaP solar cell performance.</P>

Impact of Ground Plane Doping and Bottom-Gate Biasing on Electrical Properties in In_0.53Ga_0.47As-OI MOSFETs and Donor Wafer Reusability Toward Monolithic 3-D Integration With In_0.53Ga_0.47As Channel

Kim, Seong Kwang,Shim, Jae-Phil,Geum, Dae-Myeong,Kim, Jaewon,Kim, Chang Zoo,Kim, Han-Sung,Song, Jin Dong,Choi, Sung-Jin,Kim, Dae Hwan,Choi, Won Jun,Kim, Hyung-Jun,Kim, Dong Myong,Kim, Sanghyeon Institute of Electrical and Electronics Engineers 2018 IEEE transactions on electron devices Vol.65 No.5

<P>In this paper, we fabricated In<SUB>0.53</SUB>Ga<SUB>0.47</SUB>As-on insulator (OI) MOSFETs on Si substrates with different doping types to mimic ground plane doping using direct wafer bonding and epitaxial lift-off (ELO) techniques. We investigated the impact of doping types on the ground plane and the backgate biasing, which are important and preferable components in monolithic 3-D (M3D) integration, on the electrical properties of MOSFETs, such as the threshold voltage ( <TEX>${V} _{T}$</TEX>) and the effective mobility ( <TEX>$\mu _{\textsf {eff}}$</TEX>). It was found that <TEX>${V} _{T}$</TEX> and <TEX>$\mu _{\textsf {eff}}$</TEX> were significantly modulated by the backsubstrate doping and the backbiasing. These observations were explained by the change of carrier distributions, which were confirmed by technology computer-aided design simulation. Furthermore, we investigated the reusability of InP donor substrates for sequential epitaxial growth after ELO process toward a cost-effective M3D integration with the In<SUB>0.53</SUB>Ga<SUB>0.47</SUB>As channel.</P>

Fabrication and characterization of Pt/Al₂O₃/Y₂O₃/In_0.53Ga_0.47As MOSFETs with low interface trap density

Kim, Seong Kwang,Geum, Dae-Myeong,Shim, Jae-Phil,Kim, Chang Zoo,Kim, Hyung-jun,Song, Jin Dong,Choi, Won Jun,Choi, Sung-Jin,Kim, Dae Hwan,Kim, Sanghyeon,Kim, Dong Myong American Institute of Physics 2017 Applied Physics Letters Vol.110 No.4

Effect of antireflection facet coatings on the characteristics of a high-power red laser diode

Kim, Chang Zoo,Choi, Je Hyuk,Shin, Chan Soo,Kim, Hogyoung Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.10

We investigated the effect of antireflection (AR) coatings on the performance of high-power red laser diodes (LDs). The AR coating at the front facet and the high reflection (HR) coating at the rear facet were deposited on cleaved facets. As an AR coating, SiO2 or Si3N4 single layers with different thicknesses were employed. When the reflectivity of the AR coating was 25%, the best LD performance was obtained. The fitting to the threshold current density vs. effective optical length plot produced a transparent current density of 310 A/cm(2). Under continuous wave (cw) operation at 15 A degrees C, the operating current was 1.41 A, and the operating voltage was 2.33 V with an optical output of 280 mW. At an operating temperature of 0 A degrees C, we observed the maximum output power of about 390 mW.

Highly efficient epitaxial Ge solar cells grown on GaAs (001) substrates by MOCVD using isobutylgermane

Kim, Youngjo,Kim, Kangho,Kim, Chang Zoo,Jung, Sang Hyun,Kang, Ho Kwan,Park, Won-Kyu,Lee, Jaejin North-Holland 2017 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>Single-junction Ge solar cells have been epitaxially grown on GaAs (001) substrates by a low pressure metalorganic chemical vapor deposition using isobutylgermane. Various growth conditions have been studied to reduce the high doping level of over 1×10<SUP>19</SUP> cm<SUP>−3</SUP> of the p-type Ge epitaxial layer, which is detrimental to the minority carrier collection efficiency. By increasing the growth rate and employing a discontinuous doping technique, the p-type doping level of the epitaxial Ge layer has been lowered to 2×10<SUP>18</SUP> cm<SUP>−3</SUP>, and the hole mobility increased from 44 to 162cm<SUP>2</SUP>/Vs. A high power conversion efficiency of 6.72% can be achieved under AM1.5G illumination by the epitaxial Ge solar cell with the lowered doping level in the p-type Ge base region. The spectral response of the epitaxial Ge solar cell with a 5µm thick base layer is good enough to use for InGaP/GaAs/Ge triple-junction solar cells.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Single-junction Ge solar cells are epitaxially grown on GaAs (001) substrates. </LI> <LI> Epitaxial Ge p-n junction is realized by MOCVD growth using isobutylgermane. </LI> <LI> Discontinuous doping technique is introduced to minimize the p-type Ge doping level. </LI> <LI> High efficiencies over 6.5% can be achieved by the epitaxial Ge solar cells. </LI> <LI> Ge epitaxy using MOCVD can be employed for III-V multi-junction solar cells. </LI> </UL> </P>

객관적인 마취심도 조절하에서 전신마취 및 수술 전·후 사시각의 변화

김창주(Chang Zoo Kim),남기엽(Ki Yup Nam),이승욱(Seung Uk Lee),이상준(Sang Joon Lee) 대한안과학회 2018 대한안과학회지 Vol.59 No.9

목적: 사시 수술 전후와 전신마취하 수술 전후 사시각의 변화에 대해 알아보고자 한다. 대상과 방법: 2014년 1월부터 2017년 10월까지 동일 술자에 의해 시행된 간헐성 외사시 수술 환자 20명을 대상으로 하였다. 환자는 먼저 수술 전 외래(preoperative angle of deviation, PreAn)에서 사시각을 측정하였다. 술 중에는 수술 침대에 누운 상태에서 전신마취 후 Bispectral index를 참조하여 충분한 정도의 진정이 되었음을 확인 후(angle of deviation under general anesthesia, PostAn), 근육 수술이 끝난 직후(angle of deviation before waking from general anesthesia after strabismus surgery, OP end) 디지털 카메 라로 수직으로 40 cm 높이에서 촬영하였다. 마지막으로 술 후 6개월째 외래(angle of deviation at 6th month after strabismus operation, 6mon) 방문 시 사시각을 확인하였다. 술 중 사시각은 촬영된 사진을 분석하여 측정하였으며 눈벌어짐은 양의 값으로, 눈모 음은 음의 값으로 처리하였다. 결과: 대상자는 남자 10명, 여자 10명, 평균 나이는 7.31 ± 3.59세였다. 술 전 사시각(PreAn)은 원거리 기준 30.0 ± 13.87 PD였으며, 전신마취하 측정된 사시각(PostAn)은 26.46 ± 5.39 PD였다. 술 전 사시각과 전신마취 후 사시각(PostAn)의 변화량은 술 전 사시각과 유의한 양의 상관관계(PostAN-PreAn=-7.67×PreAn+19.57 [R 2 =0.872, p<0.00])를 보였다. 전신마취 전·후(PostAn-PreAn) 사시각의 변화량과 근육수술 직후와 6개월 후 사시각의 변화량(6mon - OP end) 사이에는 유의한 양의 상관관계(6mon-OP end=0.317× [PostAn-PreAn]+13.098 [R 2 =0.334, p=0.01])를 나타내었다. 결론: 전신마취 후 측정된 사시각은 마취 전 측정값과 유의한 양의 상관관계가 있었다. 마취 전후 사시각의 변화 정도에 따라 수술 직후 보인 사시각과 추후 안정된 각 사이의 변화의 정도를 추정해 볼 수 있을 것이다. <대한안과학회지 2018;59(9):848-853> Purpose: Changes in angular deviation before and after general anesthesia and strabismus surgery were examined. Methods: Twenty patients with intermittent exotropia who were operated on by the same surgeon from January 2014 to October 2017 were included. The basic angle of deviation (preoperative angle of deviation, PreAn) was measured at an outpatient clinic. While lying on a surgical bed under general anesthesia, the bispectral index was referenced, and it was confirmed that there was a sufficient degree of sedation. Photographs were then taken at a height of 40 cm (angle of deviation under general anesthesia, PostAn); while still under general anesthesia, the same procedure was followed immediately after the end of surgery. At 6 months after surgery, the angle of deviation was measured. Results: There were 10 males and 10 females, and the mean age was 7.31 ± 3.59 years. The preoperative angle of deviation was 30.0 ± 13.87 prism diopters (PD) at far fixation; under general anesthesia, 26.46 ± 5.39 PD. There was a significantly positive correlation between the PreAn and angle of deviation under general anesthesia (PostAn - PreAn = -7.67 × PreAn + 19.57; R 2 = 0.872; p < 0.00). The angle of deviation changes between pre- and post-anesthesia (PostAn-PreAn) and at the end point of surgery (OP end) and at 6 months after surgery (6mon) also showed a significantly positive correlation (6mon-OP end = 0.317 × [PostAn - PreAn] + 13.098; R 2 = 0.334; p = 0.01). Conclusions: There was a significant positive correlation between the measured angle of deviation pre- and post-anesthesia. We could estimate the degree of change between the angle of deviation immediately after surgery and the stable angle according to the degree of deviation before and after general anesthesia. J Korean Ophthalmol Soc 2018;59(9):848-853

Fabrication of InGaAs-on-Insulator Substrates Using Direct Wafer-Bonding and Epitaxial Lift-Off Techniques

Kim, Seong Kwang,Shim, Jae-Phil,Geum, Dae-Myeong,Kim, Chang Zoo,Kim, Han-Sung,Song, Jin Dong,Choi, Sung-Jin,Kim, Dae Hwan,Choi, Won Jun,Kim, Hyung-Jun,Kim, Dong Myong,Kim, Sanghyeon Institute of Electrical and Electronics Engineers 2017 IEEE transactions on electron devices Vol.64 No.9

<P>Defect less semiconductor-on-insulator (-OI) by a cost-effective and low-temperature process is strongly needed for monolithic 3-D integration. Toward this, in this paper, we present a cost-effective fabrication of the indium gallium arsenide-OI structure featuring the direct wafer bonding (DWB) and epitaxial lift-off (ELO) techniques as well as the reuse of the indium phosphide donor wafer. We systematically investigated the effects of the prepatterning of the III-V layer before DWB and surface reforming (hydrophilic) to speed up the ELO process for a fast and high-throughput process, which is essential for cost reduction. Thismethod provides an excellent crystal quality of In0.53Ga0.47As on Si. Crystal quality of the film was evaluated using Raman spectra, and transmission electron microscope. Finally, we achieved good electrical properties of In0.53Ga0.47As-OImetal-oxide-semiconductorfield-effect-transistors fabricated through the proposed DWB and ELO.</P>

Epitaxial Ge Solar Cells Directly Grown on Si (001) by MOCVD Using Isobutylgermane

Kim, Youngjo,Kim, Kangho,Lee, Jaejin,Kim, Chang Zoo,Kang, Ho Kwan,Park, Won-Kyu Korean Physical Society 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.5

<P>Epitaxial Ge layers have been grown on Si (001) substrates by metalorganic chemical vapor deposition (MOCVD) using an isobutylgermane (IBuGe) metalorganic source. Low and high temperature two-step growth and post annealing techniques are employed to overcome the lattice mismatch problem between Ge and Si. It is demonstrated that high quality Ge epitaxial layers can be grown on Si (001) by using IBuGe with surface RMS roughness of 2 nm and an estimated threading dislocation density of 4.9 x 10(7) cm (-2). Furthermore, single-junction Ge solar cells have been directly grown on Si substrates with an in situ MOCVD growth. The epitaxial Ge p-n junction structures are investigated with transmission electron microscopy and electrochemical C-V measurements. As a result, a power conversion efficiency of 1.69% was achieved for the Ge solar cell directly grown on Si substrate under AM1.5G condition.</P>

중심망막동맥 폐쇄로 인한 갑작스런 시력저하가 첫 증상으로 나타난 결절다발동맥염

김창주(Chang Zoo Kim),남기엽(Ki Yup Nam),이상준(Sang Joon Lee),이승욱(Seung Uk Lee) 대한안과학회 2015 대한안과학회지 Vol.56 No.12

목적: 결절다발동맥염은 눈 조직을 포함하여 몸 전체의 중간, 작은 크기의 동맥에 이환되는 괴사성 혈관염이다. 저자들은 결절다발동맥염을 진단 받기 전 선행한 환자의 일측성 중심망막동맥 폐쇄를 경험하였고 이는 눈 증상이 선행된 비전형적인 결절다발동맥염의 증례로 이를 보고하고자 한다. 증례요약: 58세 남자 환자가 갑작스런 우안의 시력저하를 주소로 안과에 내원하였다. 현성굴절 검사를 통한 최대교정시력 우안 0.05, 좌안 1.0으로 확인되었으며, 고혈압, 당뇨 등의 전신기저 질환은 없는 상태로 10일 전 갑자기 발생한 우안의 시력저하와 간헐적으로 나타난 우측 편두통을 호소하였다. 대광반사에서 우안에 상대적 구심성 동공운동장애가 관찰되었으며 안저검사 및 빛간섭단층촬영검사상 우안의 시신경유두 및 황반주변으로 안저의 전반적인 부종이 관찰되었다. 환자는 형광안저촬영 후 우안의 중심망막동맥 폐쇄로 진단 받았고 이후 임상소견과 검사실 결과, 영상검사를 근거로 결절다발동맥염 진단하에 면역억제치료를 시작하였다. 1개월 후 우안의 최대교정시력은 0.05로 확인되었다. 결론: 결절다발동맥염 환자에서 중심망막동맥폐쇄로 인한 시력저하가 첫 증상으로 나타날 수 있으며 안과에 내원하는 경우 관련 문진과 실험실 검사를 추가하여 빨리 진단 후 전신적인 치료를 시행하는 것이 추가적인 다른 합병증을 예방할 수 있을 것이다. Purpose: Polyarteritis nodosa (PAN) is the necrotic vasculitis affecting middle and small-sized arteries throughout the body including ocular tissue. We report an atypical PAN case of unilateral central retinal artery occlusion in which the ocular involvement occurred before systemic symptoms. Case summary: A 58-year-old male visited the ophthalmology department due to abruptly decreased visual acuity. Best corrected visual acuity (BCVA) was 0.05 (in the right eye) and 1.0 (in the left eye) basedon the Snellen chart. He complained of acute decreased vision occurring ten days prior and intermittent migraine on the right side with no underlying diseases, such as hypertension or diabetes mellitus. Relative afferent pupillary defect was observed in the right eye. Generalized edema was found around the optic disc and fovea on fundus examination and optical coherence tomography. The patient was diagnosed with central retinal artery occlusion (CRAO) based on a fluorescein angiography. Subsequently, PAN was diagnosed based on clinical features, laboratory test results and imaging studies. The treatment was started with an immunosuppressive agent. One month later, the BCVA was 0.05 based on the Snellen chart. Conclusions: In PAN patients, decreased vision can occur as a first symptom due to CRAO. If the patient visits the ophthalmology clinic, history taking and laboratory tests for PAN can aid in early diagnosis and treatment, as well as preventing additional complications of PAN.

배전계통 고장시 비대칭 고장전류를 고려한 초전도 한류기 동작 방안

김창환(Chang-Hwan Kim),배성우(Sungwoo Bae),김기채(Ki-Chai Kim),박원주(Won-Zoo Park),이광식(Kwang-Sik Lee),이상봉(Sang-Bong Rhee) 한국조명·전기설비학회 2013 한국조명·전기설비학회 학술대회논문집 Vol.2013 No.5