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InAs 양자점 형성 방법이 양자점 적외선 소자 특성에 미치는 효과
서동범,황제환,오보람,노삼규,김준오,이상준,김의태,Seo, Dong-Bum,Hwang, Je-hwan,Oh, Boram,Noh, Sam Kyu,Kim, Jun Oh,Lee, Sang Jun,Kim, Eui-Tae 한국재료학회 2018 한국재료학회지 Vol.28 No.11
We report the properties of infrared photodetectors based on two kinds of quantum dots(QDs): i) 2.0 ML InAs QDs by the Stranski-Krastanov growth mode(SK QDs) and ii) sub-monolayer QDs by $4{\times}[0.3ML/1nm\;In_{0.15}Ga_{0.85}As]$ deposition(SML QDs). The QD infrared photodetector(QDIP) structure of $n^+-n^-(QDs)-n^+$ is epitaxially grown on GaAs (100) wafers using molecular-beam epitaxy. Both the bottom and top contact GaAs layers are Si doped at $2{\times}10^{18}/cm^3$. The QD layers are grown with Si doping of $2{\times}10^{17}/cm^3$ and capped by an $In_{0.15}Ga_{0.85}As$ layer at $495^{\circ}C$. The photoluminescence peak(1.24 eV) of the SML QDIP is blue-shifted with respect to that (1.04 eV) of SK QDIPs, suggesting that the electron ground state of SML QDIP is higher than that of the SK QDIP. As a result, the photoresponse regime(${\sim}9-14{\mu}m$) of the SML QDIP is longer than that (${\sim}6-12{\mu}m$) of the SK QDIP. The dark current of the SML QDIP is two orders of magnitude smaller value than that of the SK QDIP because of the inserted $Al_{0.08}Ga_{0.92}As$ layer.
한임식,김종수,박동우,김진수,노삼규,Han, Im Sik,Kim, Jong Su,Park, Dong Woo,Kim, Jin Soo,Noh, Sam Kyu 한국진공학회 2013 Applied Science and Convergence Technology Vol.22 No.1
본 연구에서는 양자점(quantum dot, QD)에서의 전하트랩이 태양전지의 특성에 미치는 영향을 조사하기 위하여, GaAs 모체 태양전지(MSC)의 활성층에 InAs/GaAs QD을 삽입한 $p^+-QD-n/n^+$ 태양전지(QSC)를 제작하여 그 특성을 비교 조사하였다. Stranski-Krastanow (SK)와 준단층(quasi-monolayer, QML)의 2종류 QD를 도입하였으며, 표준 태양광(AM1.5)에서 얻은 전류-전압 곡선으로부터 태양전지의 특성인자(개방전압($V_{OC}$), 단락전류($I_{SC}$), 충만도(FF), 변환효율(CE))를 결정하였다. SK-QSC의 FF값은 80.0%로 MSC의 값(80.3%)과 비슷한 반면, $V_{OC}$와 $J_{SC}$는 각각 0.03 V와 $2.6mA/cm^2$만큼 감소하였다. $V_{OC}$ 및 $J_{SC}$ 감소 결과로 CE는 2.6% 저하되었는데, QD에 의한 전하트랩이 주요 원인으로 지적되었다. 전하트랩을 완화시키기 위한 구조로서 QML-QD 기반 태양전지를 본 연구에서 처음 시도하였으나, 예측과는 달리 부정적 결과를 보였다. In order to investigate an influence of carrier trap by quantum dots (QDs) on the solar parameters, in this study, the $p^+-QD-n/n^+$ solar cells with InAs/GaAs QD active layers are fabricated, and their characteristics are investigated and compared with those of a GaAs matrix solar cell (MSC). Two different types of QD structures, the Stranski-Krastanow (SK) QD and the quasi-monolayer (QML) QD, have been introduced for the QD solar cells, and the parameters (open-circuit voltage ($V_{OC}$), short-cirucuit current ($I_{SC}$), fill factor (FF), conversion efficiency (CE)) are determined from the current-voltage characteristic curves under a standard solar illumination (AM1.5). In SK-QSC, while FF of 80.0% is similar to that of MSC (80.3%), $V_{OC}$ and $J_{SC}$ are reduced by 0.03 V and $2.6mA/cm^2$, respectively. CE is lowered by 2.6% as results of reduced $V_{OC}$ and $J_{SC}$, which is due to a carrier trap into QDs. Though another alternative structure of QML-QD to be expected to relieve the carrier trap have been firstly tried for QSC in this study, it shows negative results contrary to our expectations.
1×8배열, 7.8 ㎛ 최대반응 GaAs / AlGaAs 양자우물 적외선 검출기
박은영(Eunyoung Park),최정우(Jeong-woo Choe),노삼규(Sam-Kyu Noh),최우석(Woo-seok Choi),박승한(Seung-Han Park),조태희(Taehee Cho),홍성철(Songcheol Hong),오병성(Byungsung O),이승주(Seung-Joo Lee) 한국광학회 1998 한국광학회지 Vol.9 No.6
장파장영역의 적외선 검출을 위해 구속-비구속 상태간 전이를 이용한 GaAs/AlGaAs 이종접합 다중양자우물구조형태 검출기를 제작하여 전기적, 광학적 특성을 살펴보았다. 시료는 MBE를 이용하여 SI-GaAs(100) 기판 위에 장벽 500 Å, 폭 40 Å의 양자우물구조를 25층 성장시켰으며, Al의 몰분율은 0.28로 하였고 우물의 중심부 20 Å은 2×10^(18)㎝-³의 농도로 Si n-도핑을 하였다. 200×200 ㎛² 면적의 사각형 화소가 되도록 시료를 식각한 후 Au/Ge로 전극을 붙여 1×8 검출기 배열을 제작하였다. 10K의 온도에서 적외선 광원에 대한 광특성을 조사한 결과 1차원으로 배열한 8개의 단일소자 모두 7.8 ㎛파장에서 최대반응을 보였으며 검출률(D*)은 최대 4.9×10^9 ㎝ √㎐/W이었다. We fabricated 1×8 array of GaAs/AlGaAs quantum well infrared photodetectors for the long wavelength infrared detection which is based on the bound-to-continuum intersubband transition, and characterized its electrical and optical properties. The device was grown on SI-GaAs(100) by the molecular beam epitaxy and consisted of 25 period of 40 Å GaAs well and 500 Å Al_(0.28)Ga_(0.72)As barrier. To reduce the possibility of interface states only the center 20 Å of the well was doped with Si (N_D=2×10^(18)㎝-³). We etched the sample to make square mesas of 200×200 ㎛² and made an ohmic contact on each pixel with Au/Ge. Current-voltage characteristics and photo response spectrum of each detector reveal that the array was highly uniform and stable. The spectral responsivity and the detectivity D* were measured to be 180,260 V/W and 4.9×10^9 ㎝ √㎐/W respectively at the peak wavelength of λ = 7.8 ㎛ and at T = 10 K.
임채영(Jae-Young Leem),이철로(Cheul-Ro Lee),정광화(Kwang-Hwa Chung),노삼규(Sam-Kyu Noh),이연환(Yeon-Han Lee) 한국진공학회(ASCT) 1994 Applied Science and Convergence Technology Vol.3 No.2
박막성장을 위한 초고진공 응용시스템을 제작하고 이것의 특성을 사중극질량분석계로 측정하였다. 초고진공 시스템을 박막성장에 활용하기 위해서는 챔버 뿐만 아니라 펌프, 이온게이지, 전자총 등도 베이킹이 요구되었다. 또한 이온게이지와 전자총은 적어도 박막성장 20분 전에 탈가스를 하여야함을 알았다. 이 시스템으로 달성된 진공도는 7×10^(-11) torr이었다. An ultra high vacuum application system for growing thin film has been fabricated, and characteristics of the system have been measured by quadrupole mass spectrometer. Pumps, ion gage, electron gun as well as main chamber in order to use the system for thin film growth have to be baked. And also, Ion gage and electron gun must be degassed during at least 20 min before growing thin film. An ultra high vacuum of 7×10^(-11) torr was achieved using the system.
투과전자현미경으로 살펴 본 자발형성 InAs/GaAs 양자점의 구조 및 응력 특성
김형석 ( Hyung Seok Kim ),서주형 ( Ju Hyung Suh ),박찬경 ( Chan Gyung Park ),이상준 ( Sang Jun Lee ),노삼규 ( Sam Kyu Noh ),송진동 ( Jin Dong Song ),박용주 ( Yong Ju Park ),최원준 ( Won Jun Choi ),이정일 ( Jung Il Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.7
Self-assembled InAs/GaAs quantum dots (QDs) were grown by molecular-beam epitaxy and their structure and strain characteristics were studied by using transmission electron microscopy (TEM). TEM investigations were performed by conventional bright field TEM, high-resolution electron microscopy (HREM), annular dark field (ADF) and high angle annular dark filed (HAADF)-STEM techniques. In addition, strain analysis was performed on an atomic-length scale by measuring the space of lattices in HREM. The QDs were found to form a lens-shaped structure with side facet. Compressive strain was induced to uncapped QDs from GaAs substrate and the strain increased more than 3.5% after GaAs cap layer growth. On the other hand, tensile strain by capped QDs was induced to GaAs up tolO nm over the QDs, i.e. 15 nm over the wetting layer. It was also confirmed that the tensile strain extension resulted in aligned QD growth with 15 nm thick spacers. Vertically aligned QDs could be grown by the tensile strain from predeposited QDs when the thickness of GaAs spacer was less than 15 nm.
AI 조성비 변화에 따른 GaAs/AIGaAs 다중양자우물구조 특성변화 연구
유연희,최정우,임재영,노삼규 慶熙大學校 材料科學技術硏究所 1998 材料科學技術硏究論集 Vol.11 No.-
We manufactured and characterized different sets of GaAs/AlGaAs multiple quantum well structures for the long wavelength infrared photodetection. The samples were grown by MBE. We changed the aluminum composition of barrier region from 0.24 to 0.30 in 0.02 steps, and performed double crystals X-ray diffraction(DCXRD) and the photoluminescence measurements. DCXRD measurements correctly gave the expected aluminum compositions. Photoluminescence measurements revealed that the ground state energy of the well increases with composition as desired, but the change was not very significant.
鄭重鉉,金哲久,金根默,盧三珪,李鐘男 연세대학교 자연과학연구소 1983 學術論文集 Vol.11 No.-
SSD법으로 반절연성 InP : Fe 단결정(Fe 함량;0.1, 0.5, 1.0 wt-%)을 생장하였으며 비저항과 hall 이동도는 실온에서 각각 10^6∼10^8Ω·㎝와 10^2∼10^4㎠/V·sec 이었다. 결정의 생장조건은 온도구배 15∼20℃/㎝, 생장온도 850∼870℃, 생장속도 2∼3㎜/day이었다. 비저항의 온도의존성과 광전도도를 측정하여 InP내의 Fe는 deep acceptor로서 에너지 준위는 E_c-0.66eV임을 알았다. Single crystals of InP : Fe (Fe contents ; 0.1, 0.5, 1.0 wt-%) have been grown by the SSD method. The Hall effect was investigated at room temperature; the resistivity was 10^6∼10^8Ω·㎝ and Hall mobility 10^2∼10^4㎠/V·sec. The crystals were grown by the following conditions; the temperature gradient was 15∼20℃/㎝, the growth temperature 850∼870℃, and the growth rate 2∼3㎜/day. From the temperature dependence of the resistivity and the photoconductivity measurements we determined the deep acceptor level of Fe InP, E_c 0.66eV.
정중현,김명욱,박승철,김근묵,엄영호,노삼규 연세대학교 자연과학연구소 1982 學術論文集 Vol.9 No.-
처음으로 반절연성 InP:Fe를 SSD법으로 생장시키었다. Fe를 각각 0.5와 1.0 wt-% 첨가한 결정의 비저항은 실온에서 각각 3.1×10^7와 1.5×10^7Ω·cm이었으며, 저항의 온도 위존성에서 얻은 Fe의 에너지 준위는 전도대의 바닥 아래로 0.66 eV이었다. For the first time we obtained the semi-insulating InP:Fe crystals grown by SSD method. Their resistivities were 3.1×10^7 and 1.5×10^7Ω·cm in the Fe-doped crystals with contents of 0.5 and 1.0 wt-%, respectively. Temperature dependence of the crystal revealed the energy level of Fe as 0.66 eV from the bottom of the conduction band.