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Hwang, Sungmin,Kim, Hyungjin,Kwon, Dae Woong,Lee, Jong-Ho,Park, Byung-Gook The Institute of Electronics and Information Engin 2017 Journal of semiconductor technology and science Vol.17 No.2
The most prominent challenge for MOSFET scaling is to reduce power consumption; however, the supply voltage ($V_{DD}$) cannot be scaled down because of the carrier injection mechanism. To overcome this limit, a new type of field-effect transistor using positive feedback as a carrier injection mechanism (FBFET) has been proposed. In this study we have investigated the electrical characteristics of a $Si_{1-x}Ge_x$ FBFET with one gate and one-sided $Si_3N_4$ spacer using TCAD simulations. To reduce the drain bias dependency, $Si_{1-x}Ge_x$ was introduced as a low-bandgap material, and the minimum subthreshold swing was obtained as 2.87 mV/dec. This result suggests that a $Si_{1-x}Ge_x$ FBFET is a promising candidate for future low-power devices.
Sungmin Hwang,심종인,Kyungyul Yoo 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.1
We present a planar InGaAs/InP separated absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode (APD) with a thin multiplication layer of 0.2 μm in thickness operating up to 10 Gb/s. It has two floating guard rings (FGRs) and a deep floating ring (DFGR). The multiplication layer thickness and the doping concentration of the charge layer are carefully designed in terms of both the gain and the bandwidth by utilizing the nonlocal model. The simple fabrication processes of recess etching and one-step diffusion are applied. The experimental results show good agreement with the design. Superior characteristics, such as a large gain-bandwidth (GB) product of above 110 GHz, a low dark current of less than 1 nA at 90 % of the breakdown voltage, and a uniform 2-dimensional gain profile within the active region, are obtained.
Hwang Sungmin,심종인,유경렬 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
This paper investigates the impact of the waveguide structure on ripples in the far-field pattern of a laser diode, 405-nm In$_{0.08}$Ga$_{0.92}$N/In$_{0.015}$Ga$_{0.085}$N grown on a sapphire substrate. The leakage of the transverse mode to an n-GaN buffer layer is found to induce ripples in the far field patterns perpendicular to the junction plane. We numerically computed the far-field patterns and the optical confinement factor of n-GaN waveguide layers of various thicknesses. An optimal thickness of the layer was derived from the numerical simulation, with a minor modification through measurements. Experiments showed remarkably smooth far-field patterns with a minimum ripple ratio of 4.2 \% are attainable using the proposed thicknesses of the n-Al$_{0.08}$Ga$_{0.92}$N/GaN cladding and the n-GaN waveguide layers
Hwang Sungmin,Yang Jun Hyeok,Sim Ho Seok,Choi Sung Ho,Lee Byounghee,Bang Woo Young,문기환 한국미생물·생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.11
The need to discover new types of antimicrobial agents has grown since the emergence of antibioticresistant pathogens that threaten human health. The world’s oceans, comprising complex niches of biodiversity, are a promising environment from which to extract new antibiotics-like compounds. In this study, we newly isolated Pseudomonas sp. NIBR-H-19 from the gut of the sea roach Ligia exotica and present both phenotypes and genomic information consisting of 6,184,379 bp in a single chromosome possessing a total of 5,644 protein-coding genes. Genomic analysis of the isolated species revealed that numerous genes involved in antimicrobial secondary metabolites are predicted throughout the whole genome. Moreover, our analysis showed that among twenty-five pathogenic bacteria, the growth of three pathogens, including Staphylococcus aureus, Streptococcus hominis and Rhodococcus equi, was significantly inhibited by the culture of Pseudomonas sp. NIBR-H19. The characterization of marine microorganisms with biochemical assays and genomics tools will help uncover the biosynthesis and action mechanism of antimicrobial metabolites for development as antagonistic probiotics against fish pathogens in an aquatic culture system.
Effect of electrode pattern on light emission distribution in InGaN/GaN light emitting diode
Hwang, Sungmin,Yoon, Joosun,Shim, Jongin,Yoo, Kyungyul WILEY-VCH Verlag 2008 Physica status solidi. PSS. C, Current topics in s Vol.5 No.6
<P>The effect of geometrical electrode pattern on the blue InGaN/GaN multi-quantum well (MQW) light emitting diode (LED) devices is investigated both theoretically and experimentally. A 3-dimensional circuit model of an LED is constructed and then the corresponding circuit parameters are extracted. Circuit parameters of an LED consist of the resistances of the metallic film and epitaxial layer, and intrinsic diodes representing the light-emitting active region. Both the transmission line model (TLM) and current-voltage (I-V) characteristics of LED are employed to extract circuit parameters experimentally. These circuit parameters are then applied to the circuit model to generate light emission patterns in a top-surface emitting-type LED. Experiment results verify that the emitting light distribution from fabricated LED coincides reasonably well with the theoretical results. This makes it possible to design an LED theoretically and predict its actual properties. The LED structure proposed using the model is shown to exhibit not only good light uniformity, but also higher light output power and lower voltage drop. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Ohmic contacts of Pd/Zn/M(=Pd or Pt)/Au to p-type InP
Sungmin Hwang,심종인,어영선 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.4
We have investigated the ohmic properties of Au/M(= Pd or Pt)/Zn/Pd/p-InP, focusing on the role of the third metal M in Au-free metallization. Both the lowest specific contact resistivity of 7 × 10−6 ·cm2 and a flat diffusion front were obtained for a sample with a Au/Pt/Zn/Pd/p-InP contact material after annealing at 400 C for 4 min, indicating that the Pt layer was more effective than the Pd layer in preventing Zn out-diffusion during the annealing process. In addition to Aufree metallizations, we fabricated the Au-based metallization of Au/Cr/AuZn/Au/p-InP in order to justify our ohmic contact process, and we compared its ohmic characteristics.
Hwang, Sungmin,Kim, Hyungjin,Park, Jungjin,Kwon, Min-Woo,Baek, Myung-Hyun,Lee, Jeong-Jun,Park, Byung-Gook IEEE 2018 IEEE electron device letters Vol.39 No.9
<P>We perform a system-level simulation of hardware spiking neural network (SNN) consisting of silicon-based synaptic transistors and integrate-and-fire (I&F) neuron circuits. Using electrical models of the synaptic device and I&F neuron circuit, a three-layer fully connected SNN in hardware is presented for MNIST pattern recognition by means of <I>ex situ</I> training. Right-justified rate coding is employed as an information encoding method, and negative weight values are implemented by a pair of the synaptic transistors (specifically, excitatory and inhibitory synapses). Furthermore, the variability effect occurring in the devices and circuits is demonstrated. This result indicates that the system has tolerance to the variations and how precisely the variations need to be controlled for hardware SNN applications.</P>