Sam Kyu Noh

Yonsei University, Sŏul, Seoul, South Korea

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Publications (162)255.81 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have investigated the feasibility of THz time-domain reflectometry for the discrimination of human early gastric cancer (EGC) from the normal gastric region. Eight fresh EGC tissues, which were resected by endoscopic submucosal dissection, were studied. Of them, six lesions were well discriminated on THz images and the regions well correlated with tumor regions on pathologically mapped images. Four THz parameters could be suggested for quantitative discrimination of EGCs.
    Biomedical Optics Express 04/2015; 6(4). DOI:10.1364/BOE.6.001398 · 3.65 Impact Factor
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    ABSTRACT: The temperature and the excitation-intensity dependences of the junction electric fields in the GaAs p-i-n solar cell structure have been investigated by using photoreflectance (PR) spectroscopy. In the p-i-n solar cell structure, two different electric fields are observed. The fast Fourier transform (FFT) analysis implies that the two electric fields can be assigned to the p-i and the i-n interfaces. The strengths of the electric fields at the p-i and the i-n interfaces are 38 and 44 kV/cm, respectively. The electric fields gradually increase due to the temperature-dependent photovoltage effect with increasing sample temperature. With increasing excitation intensity, the electric field at the p-i interface gradually decreases due to the photovoltage effect caused by carrier screening while that at the i-n interface is insensitive to the light’s intensity. This abnormal behavior can be explained by the anisotropy carrier dynamics at the p-i and the i-n interfaces., The relation between the open-circuit voltage (V OC ) and the ideality factor in concentration photovoltaic (CPV) devices is discussed.
    Journal- Korean Physical Society 02/2015; 66(4):667-671. DOI:10.3938/jkps.66.667 · 0.42 Impact Factor
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    ABSTRACT: We have investigated basic properties of normal gastrointestinal (GI) tract tissues, including glandular stomach (GS), fore stomach (FS), large intestine (LI), small intestine (SI), and esophagus (ESO), from a rat model using terahertz (THz) reflection imaging and spectroscopy. The THz images collected from stratified squamous epithelia (SSE) of FS and ESO show a lower peak-to-peak value compared to those from columnar epithelia (CE) of GS, LI, or SI because the SSE contains less water than CE. The refractive index and absorption coefficient of FS were less than those of GS or LI, both having values similar to those of water. Additionally, we report internal reflection THz signals from ESO, although we were unable to determine the exact interface for this internal reflection.
    Biomedical Optics Express 12/2014; 5(12). DOI:10.1364/BOE.5.004162 · 3.65 Impact Factor
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    ABSTRACT: We report the influences of a dot-in-a-well structure with a thin GaAs layer and the thickness of a waveguide (WG) on the lasing characteristics of InAs quantum dots (QDs) based on InP. The QD laser diodes (QDLDs) consist of seven-stacked InAs QDs separated by a 10 nm-thick InGaAsP (1.15 μm, 1.15Q-InGaAsP) layer, which is further sandwiched by a 800 nm-thick 1.15Q-InGaAsP WG (reference QDLD). For comparison, the InAs QDs were inserted into the InGaAsP (1.35 μm, 1.35Q-InGaAsP) quantum well embedded in the 1.15Q-InGaAsP matrix at the active layer. And a 2 monolayer (ML)-thick GaAs layer was additionally introduced right before the QD layer (GD-WELLLDs). Lasing emission from the reference QDLD with only the 1.15Q-InGaAsP structure was not observed at room temperature (RT). However, the lasing emission from the GDWELL-LDs was clearly observed at the wavelength of 1.46 μm at RT under continuous-wave (CW) mode. The threshold current density of the GDWELL-LD with the 800 nm-thick InGaAsP WG was measured to be 830 A/cm2, which was lower than that of the GDWELL-LD with the 200 nm-thick WG (900 A/cm2). Also, the slope efficiency of the GDWELL-LD was significantly improved with increasing thickness of the InGaAsP WG.
    Journal of Nanoscience and Nanotechnology 12/2014; 14(12):9623-7. DOI:10.1166/jnn.2014.10189 · 1.56 Impact Factor
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    ABSTRACT: We demonstrated that tumors in freshly excised whole brain tissue could be differentiated clearly from normal brain tissue using a reflection-type terahertz (THz) imaging system. THz binary images of brain tissues with tumors indicated that the tumor boundaries in the THz images corresponded well to those in visible images. Grey and white-matter regions were distinguishable owing to the different distribution of myelin in the brain tissue. THz images corresponded closely with magnetic resonance imaging (MRI) results. The MRI and hematoxylin and eosin-stained microscopic images were investigated to account for the intensity differences in the THz images for fresh and paraffin-embedded brain tissue. Our results indicated that the THz signals corresponded to the cell density when water was removed. Thus, THz imaging could be used as a tool for label-free and real-time imaging of brain tumors, which would be helpful for physicians to determine tumor margins during brain surgery.
    Biomedical Optics Express 08/2014; 5(8). DOI:10.1364/BOE.5.002837 · 3.65 Impact Factor
  • H. W. Shin · J.-W. Choe · S.J. Lee · S. K. Noh · J. O. Kim · K.-S. Lee
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    ABSTRACT: A triple-band mid-/far-infrared (MIR/FIR) photodetector tunable by polarity is demonstrated by asymmetric quantum dot-in-double-well (DdWELL) structure that exhibits unique photoresponse (PR) transitions. In contrast to the MIR2 band with no dependence, the two MIR1/FIR PR bands are blue/red-shifted by the bias voltage, and the MIR2-FIR dual-band spectrum changes to a single-band feature due to the polarity. A four-level energy band model is proposed for the transition scheme, and the electric field dependence of the FIR band numerically calculated by a simplified DdWELL structure is in good agreement with the experimental PR spectra.
    Current Applied Physics 05/2014; 14(5). DOI:10.1016/j.cap.2014.02.019 · 2.21 Impact Factor
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    ABSTRACT: We report on morphological, optical, and lasing characteristics of InAs quantum dots (QDs) embedded in an In0.69Ga0.31As0.67P0.33 quantum well (having a bandgap energy corresponding to a wavelength of 1.35 μm (1.35Q-InGaAsP)), which formed a dot-in-a-well (DWELL) structure. This DWELL was further sandwiched in In0.85Ga0.15As0.32P0.68 layers (1.15 μm, 1.15Q-InGaAsP). A 2 monolayer-thick GaAs layer was simultaneously introduced right below the InAs QD layer in the DWELL structure (GDWELL). The emission wavelength of the InAs GDWELL was 1490 nm, which was slightly shorter than that of the InAs QDs embedded only in 1.15Q-InGaAsP layers. To evaluate the effects of the GDWELL structure on lasing characteristics, gain-guided broad-area (BA) and index-guided ridge-waveguide (RW) laser diodes (LDs) were fabricated. The BA-LDs with the InAs QDs embedded only in 1.15Q-InGaAsP layers did not show the lasing at room temperature (RT) even in pulsed mode. For the GDWELL structure, however, the lasing emissions from both the BA-LDs and RW-LDs were successfully achieved at RT in continuous-wave mode.
    Journal of Crystal Growth 04/2014; 393. DOI:10.1016/j.jcrysgro.2013.11.038 · 1.70 Impact Factor
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    ABSTRACT: We investigated the optical and the electrical properties of GaAs solar cells (SCs) by using photoreflectance (PR) spectroscopy and current-voltage (J-V) measurements. The electric fields (F-j) in p-n junctions were evaluated through an analysis of the Franz-Keldysh oscillations (FKOs) of the PR spectra. From the excitation light intensity (I-ex) dependence of the PR, we found that the photovoltaic effect resulted in a reduction of the F-j. The F-j was gradually reduced by up to 37% from the dark built-in electric field when the I-ex was increased (I-ex = 2.3 similar to 181 mW/cm(2)). We evaluated the ideality factor (n) of the SC via PR spectroscopy, and the results matched the results of the J-V measurements well. From these results, we demonstrate that the F-j and the n of the SCs can be evaluated by using PR spectroscopy.
    Journal- Korean Physical Society 03/2014; 64(7). DOI:10.3938/jkps.64.1031 · 0.42 Impact Factor
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    ABSTRACT: We investigated the optical and the electrical properties of InAs quantum-dot solar cells (QDSCs) with various InAs deposition thicknesses ( θ) via photoluminescence (PL), spectral response (SR), and current density-voltage (J-V) measurements. We fabricated three QDSCs with thicknesses of 2.0, 2.5, and 3.0 monolayers (MLs). Our measurements revealed the effects of the QD size on the spectral response, the conversion efficiency ( η) and the device parameters. The QDSCs had a maximum η of 17% for θ = 2.0 ML under AM1.5G conditions. The change of device parameters in various QDSCs could be explained by the effects of the balance between enhanced carrier production from the QD layers and carrier trapping/re-capturing by strain-induced defect/QD states.
    Journal- Korean Physical Society 02/2014; 64(6). DOI:10.3938/jkps.64.895 · 0.42 Impact Factor
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    ABSTRACT: We report on the effect of confinement barriers on the performance of InAs/InGaAs sub-monolayer quantum dot infrared photodetectors. Two samples with different AlxGa1-xAs barrier compositions (x = 0.07 for sample A and x = 0.20 for sample B) were grown with four-stacks of sub-monolayer quantum dot. Sample A had a peak response at ~7.8 μm, whereas sample B demonstrated three peaks at ~3.5, ~5, and ~7.0 μm with the intensity of the peaks strongly dependent on the applied bias. At 77 K, sample A and B had a detectivity of 1.2 × 1011 cm.Hz1/2/W (Vb = −0.4 V bias) and 5.4 × 1011 cm.Hz1/2/W (Vb = −1.5 V bias), respectively.
    Optical Materials Express 02/2014; 4(2). DOI:10.1364/OME.4.000198 · 2.84 Impact Factor
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    Sam Kyu Noh · Jong Soo Kim · Jin Soo Kim · Jae Su Yu
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    ABSTRACT: We have studied photovoltaic characteristics of single-junction GaAs solar cells with/without an anti-reflective coating (ARC) illuminated by low-density concentration (
    01/2014; 23(1). DOI:10.5757/ASCT.2014.23.1.27
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    ABSTRACT: A novel buried photomixer for integrated photonic terahertz devices is proposed. The active region of the mesa-structure InGaAs photomixer is buried in an InP layer grown by metalorganic chemical vapor deposition (MOCVD) to improve heat dissipation, which is an important problem for terahertz photomixers. The proposed photomixer shows good thermal properties compared to a conventional planar-type photomixer. The MOCVD regrowth process indicates the possibility for THz photomixers to be integrated monolithically with conventional photonic devices.
    Optics Letters 12/2013; 38(24):5466-9. DOI:10.1364/OL.38.005466 · 3.29 Impact Factor
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    ABSTRACT: We report on the evolution of the surface plasmon (SP) and waveguide mode (WM) as the core thickness is varied in InGaAs slab waveguides covered by metallic sub-wavelength slit arrays. By comparing transmission spectrum in the near-infrared region with numerical simulations, transmission dips were assigned to resonant excitations of either SPs or WMs. As the core thickness was smaller than the SP penetration depth, the resonance energy exhibits a blue shift, which scales with the field intrusion into the substrate region. For the core thickness of 400 nm supporting both the WM and SP, effective refractive index of the SP is almost constant due to the field decay within the InGaAs region, which is different to the case of the WM.
    Applied Physics B 07/2013; 115(1). DOI:10.1007/s00340-013-5575-2 · 1.86 Impact Factor
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    ABSTRACT: The structural and optical properties of InAs quantum dots (QDs) embedded in an In0.85Ga0.15As0.32P0.68 matrix with the emission wavelength of 1.10 µm (1.1Q-InGaAsP) on InP were modified by adopting an In0.69Ga0.31As0.67P0.33 (1.35 µm, 1.35Q-InGaAsP) quantum-well (QW) structure (dot-in-a-well, DWELL) and by inserting an additional GaAs layer right below the QDs. The spatial QD density with the DWELL structure and the GaAs insertion layer was reduced by 53% from that for the simple InAs QDs with only a 1.1Q-InGaAsP barrier (reference sample). However, the photoluminescence intensity was improved by more than 2.5 times compared to that of the reference sample. These results are discussed in terms of the increase in the capture probability of carriers due to the 1.35Q-InGaAsP QW and the relatively strong localization of carriers according to variations in the wetting layer and the distances among QDs.
    Journal- Korean Physical Society 05/2013; 62(9). DOI:10.3938/jkps.62.1274 · 0.42 Impact Factor
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    ABSTRACT: In order to investigate an influence of carrier trap by quantum dots (QDs) on the solar parameters, in this study, the 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 (), short-cirucuit current (), 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%), and are reduced by 0.03 V and , respectively. CE is lowered by 2.6% as results of reduced and , 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.
    01/2013; 22(1). DOI:10.5757/JKVS.2013.22.1.37
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    ABSTRACT: We report on the design and performance of multi-stack InAs/InGaAs sub-monolayer (SML) quantum dots (QD) based infrared photodetectors (SML-QDIP). SML-QDIPs are grown with the number of stacks varied from 2 to 6. From detailed radiometric characterization, it is determined that the sample with 4 SML stacks has the best performance. The s-to-p (s/p) polarized spectral response ratio of this device is measured to be 21.7%, which is significantly higher than conventional Stranski-Krastanov quantum dots (∼13%) and quantum wells (∼2.8%). This result makes the SML-QDIP an attractive candidate in applications that require normal incidence.
    Applied Physics Letters 01/2013; 102(1):011131. DOI:10.1063/1.4774383 · 3.30 Impact Factor
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    ABSTRACT: Ga droplets were totally removed from the top region of self-catalyzed GaAs nanowires (NWs) formed on Si(111), which was done by controlling the arsenic conditions during the growth period and the cooling process of the substrate temperature. From the spatial luminescence profiles of the GaAs NWs measured by using laser confocal scanning microscopy, the emission position from the NWs without Ga droplets was 896.4 nm. This was shorter than that with the Ga feature (912.7 nm). The difference in the emission wavelengths can be explained by the scattering probability of the photons from GaAs NWs in Ga droplets and by a modification in the energy level caused by the interface condition.
    Journal- Korean Physical Society 12/2012; 61(12-12):2017-2021. DOI:10.3938/jkps.61.2017 · 0.42 Impact Factor
  • Jun Oh Kim · Sam Kyu Noh
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    ABSTRACT: Electrical characteristics of p-GaSb are examined by applying the junction Hall effect measurement (JHEM) to homoepitaxially grown p-GaSb/n-GaSb layers, and analysis is made on the disagreement with those of an equivalent heteroepitial p-GaSb/semi-insulating (SI) GaAs. The photoluminescence spectra reveal that a large number of intrinsic defects are induced due to the lattice mismatch in p-GaSb/SI–GaAs, and the shallow donors of [SbGa] involved in the electrical conduction was significantly reduced in p-GaSb/n-GaSb. This proves that the homoepitaxial p-GaSb is quite different from the heteroepitaxial one in the electrical and the optical characteristics, and that the JHEM approach is correct in determining the Hall parameters of the epitaxial layers whose high-resistive substrates are not available.
    Current Applied Physics 11/2012; 12(6):1624–1627. DOI:10.1016/j.cap.2012.06.001 · 2.21 Impact Factor
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    ABSTRACT: By using droplet epitaxy, we fabricated asymmetrically-coupled GaAs quantum dot molecules (AQDMs) and symmetrically-coupled GaAs concentric quantum-double rings (SCQRs). The geometrical coupling distances, dot-to-dot for the AQDMs and ring-to-ring for the SCQRs, were 30 nm and 28 nm, respectively. The photoluminescence (PL) measurement was performed with a femtosecond laser as an excitation source to investigate the structure-dependent optical properties of the AQDMs and the SCQRs as functions of the excitation intensity (corresponding to the injection carrier density). The excitation-power-dependent PL showed that the emission peak of the AQDMs was systemically red-shifted with increasing excitation intensity while the emission peak of the SCQRs was blue-shifted. The anomalous behavior in the shift of the emission peak for the AQDMs can be explained by using the inhomogeneous carrier distribution due to the geometrical asymmetry of the coupled QDs.
    Journal- Korean Physical Society 08/2012; 61(3-3):455-459. DOI:10.3938/jkps.61.455 · 0.42 Impact Factor
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    ABSTRACT: We have investigated optical properties and device performance of sub-monolayer quantum dots infrared photodetector with confinement enhancing (CE) barrier and compared with conventional Stranski-Krastanov quantum dots with a similar design. This quantum dots-in-a-well structure with CE barrier enables higher quantum confinement and increased absorption efficiency due to stronger overlap of wavefunctions between the ground state and the excited state. Normal incidence photoresponse peak is obtained at 7.5 μm with a detectivity of 1.2 × 1011 cm Hz1/2 W−1 and responsivity of 0.5 A/W (77 K, 0.4 V, f/2 optics). Using photoluminescence and spectral response measurements, the bandstructure of the samples were deduced semi-empirically.
    Applied Physics Letters 05/2012; 100(19). DOI:10.1063/1.4711214 · 3.30 Impact Factor

Publication Stats

1k Citations
255.81 Total Impact Points


  • 2014
    • Yonsei University
      Sŏul, Seoul, South Korea
  • 1991–2014
    • Korea Research Institute of Standards and Science
      • Division of Industrial Metrology
      Daiden, Daejeon, South Korea
  • 2009–2010
    • University of New Mexico
      • • Center for High Technology Materials
      • • Department of Electrical and Computer Engineering
      Albuquerque, New Mexico, United States
  • 1994–2010
    • Chungnam National University
      • Department of Physics
      Daiden, Daejeon, South Korea
  • 2006
    • Chungbuk National University
      • Department of Physics
      Chinch'ŏn, North Chungcheong, South Korea
  • 2001
    • University of Michigan
      • Department of Electrical Engineering and Computer Science (EECS)
      Ann Arbor, Michigan, United States
  • 1998
    • Kwangwoon University
      • Department of Electronic Material Engineering
      Sŏul, Seoul, South Korea
  • 1997
    • Pohang University of Science and Technology
      • Department of Materials Science and Engineering
      Antō, North Gyeongsang, South Korea
  • 1996
    • Electronics and Telecommunications Research Institute
      Sŏul, Seoul, South Korea
  • 1992–1993
    • Korea Military Academy
      Sŏul, Seoul, South Korea