• Title, Summary, Keyword: Junction-based

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A Transistor Based on 2D Material and Silicon Junction

  • Kim, Sanghoek;Lee, Seunghyun
    • Journal of the Korean Physical Society
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    • v.71 no.2
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    • pp.92-100
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    • 2017
  • A new type of graphene-silicon junction transistor based on bipolar charge-carrier injection was designed and investigated. In contrast to many recent studies on graphene field-effect transistor (FET), this device is a new type of bipolar junction transistor (BJT). The transistor fully utilizes the Fermi level tunability of graphene under bias to increase the minority-carrier injection efficiency of the base-emitter junction in the BJT. Single-layer graphene was used to form the emitter and the collector, and a p-type silicon was used as the base. The output of this transistor was compared with a metal-silicon junction transistor (i.e. surface-barrier transistor) to understand the difference between a graphene-silicon junction and metal-silicon Schottky junction. A significantly higher current gain was observed in the graphene-silicon junction transistor as the base current was increased. The graphene-semiconductor heterojunction transistor offers several unique advantages, such as an extremely thin device profile, a low-temperature (< $110^{\circ}C$) fabrication process, low cost (no furnace process), and high-temperature tolerance due to graphene's stability. A transistor current gain (${\beta}$) of 33.7 and a common-emitter amplifier voltage gain of 24.9 were achieved.

Employing Al Etch Stop Layer for Nb-based SNS Josephson Junction Fabrication Process (Al 식각정지층을 이용한 Nb-based SNS 조셉슨 접합의 제조공정)

  • Choi, J.S.;Park, J.H.;Song, W.;Chong, Y.
    • Progress in Superconductivity
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    • v.12 no.2
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    • pp.114-117
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    • 2011
  • We report our efforts on the development of Nb-based non-hysteretic Josephson junction fabrication process for quantu device applications. By adopting and modifying the existing Nb-aluminum oxide tunnel junction process, we develop a process for non-hysteretic Josephson junction circuits using metal-silicide as metallic barrier material. We use sputter deposition of Nb and $MoSi_2$, PECVD deposition of silicon oxide as insulator material, and ICP-RIE for metal and oxide etch. The advantage of the metal-silicide barrier in the Nb junction process is that it can be etched in $SF_6$ RIE together with Nb electrode. In order to define a junction area precisely and uniformly, end-point detection for the RIE process is critical. In this paper, we employed thin Al layer for the etch stop, and optimized the etch condition. We have successfully demonstrated that the etch stop properties of the inserted Al layer give a uniform etch profile and a precise thickness control of the base electrode in Nb trilayer junctions.

Bi-directional Two Terminal Switching Device based on SiGe for Spin Transfer Torque (STT) MRAM

  • Yang, Hyung-Jun;Kil, Gyu-Hyun;Lee, Sung-Hyun;Song, Yun-Heub
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.385-385
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    • 2012
  • A two terminal N+/P/N+ junction device to replace the conventional selective transistor was studied as a bilateral switching device for spin transfer torque (STT) MRAM based on 3D device simulation. An N+/P/N+ junction structure with $30{\times}30nm$ area requires bi-directional current flow enough to write a data by a drain induced barrier lowering (DIBL) under a reverse bias at N+/P (or P/N+ junction), and high current on/off ratio of 106. The SiGe materials are widely used in hetero-junction bipolar transistors, bipolar compensation metal-oxide semiconductors (BiCMOS) since the band gap of SiGe materials can be controlled by changing the fraction and the strain epilayers, and the drift mobility is increased with the increasing Ge content. In this work, N+/P/N+ SiGe material based junction provides that drive current is increased from 40 to $130{\mu}A$ by increased Ge content from 10~80%. When Ge content is about 20%, the drive current density of SiGe device substantially increased to 2~3 times better than Si-based junction device in case of 28 nm P length, which is sufficient current to operation of STT-MRAM.

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CONSERVATIVE FINITE VOLUME METHOD ON BOUNDARY TREATMENTS FOR FLOW NETWORK SYSTEM ANALYSES (유동망 시스템 해석을 위한 경계처리에 대한 보존형 유한체적법)

  • Hong, S.W.;Kim, C.
    • Journal of computational fluids engineering
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    • v.14 no.1
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    • pp.35-44
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    • 2009
  • To adequately analyze flows in pipe or duct network system, traditional node-based junction coupling methods require the junction loss which is specified by empirical or analytic correlations. In this paper, a new finite volume junction coupling method using a ghost junction cell is developed by considering the interchange of linear momentum as well as the important wall-effect at junction without requiring any correlation on the junction loss. Also, boundary treatment is modified to preserve the stagnation enthalpy across boundaries, such as pipe-end and the interface between junction and branch. Also, the computational accuracy and efficiency of the Godunov-type finite volume schemes are investigated by tracing the total mechanical energy of rapid transients due to sudden closure of valve at downstream end.

Potential Wide-gap Materials as a Top Cell for Multi-junction c-Si Based Solar Cells: A Short Review

  • Pham, Duy Phong;Lee, Sunhwa;Kim, Sehyeon;Oh, Donghyun;Khokhar, Muhammad Quddamah;Kim, Sangho;Park, Jinjoo;Kim, Youngkuk;Cho, Eun-Chel;Cho, Young-Hyun;Yi, Junsin
    • Current Photovoltaic Research
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    • v.7 no.3
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    • pp.76-84
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    • 2019
  • Silicon heterojunction solar cells (SHJ) have dominated the photovoltaic market up till now but their conversion performance is practically limited to around 26% compared with the theoretical efficiency limit of 29.4%. A silicon based multi-junction devices are expected to overcome this limitation. In this report, we briefly review the state-of-art characteristic of wide-gap materials which has played a role as top sub-cells in silicon based multi-junction solar cells. In addition, we indicate significantly practical challenges and key issues of these multi-junction combination. Finally, we focus to some characteristics of III-V/c-Si tandem configuration which are reaching highly record performance in multi-junction silicon solar cells.

Conductance of a Single Molecule Junction Formed with Ni, Au, and Ag Electrodes

  • Kim, Taekyeong
    • Journal of the Korean Chemical Society
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    • v.58 no.6
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    • pp.513-516
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    • 2014
  • We measure the conductance of a 4,4'-diaminobiphenyl formed with Ni electrodes using a scanning tunneling microscope-based break-junction technique. For comparison, we use Au or Ag electrodes to form a metal-molecular junction. For molecules that conduct through the highest occupied molecular orbital, junctions formed with Ni show similar conductance as Au and are more conductive than those formed with Ag, consistent with the higher work function for Ni or Au. Furthermore, we observe that the measured molecular junction length that is formed with the Ni or Au electrodes was shorter than that formed with the Ag electrodes. These observations are attributed to a larger gap distance of the Ni or Au electrodes compared to that of the Ag electrodes after the metal contact ruptures. Since our work allows us to measure the conductance of a molecule formed with various electrodes, it should be relevant to molecular electronics with versatile materials.

Analysis of the Junction Temperature in the LED Chips using the Finite Element Method (유한요소법을 이용한 LED 칩의 접합부 온도 해석)

  • Han, Ji-Won;Park, Joo-Hun
    • Journal of the Korean Society of Safety
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    • v.27 no.6
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    • pp.26-30
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    • 2012
  • It is difficult to determine the junction temperature because LED lightings are manufactured using several chips with low power. This paper reports on the finite element method of the determination of junction temperature in the GaN-based LEDs. The calculated junction temperature of the LED chip using FEM was compared with the experimentally measured data. As the results of this study, the junction temperature of LED chips with via holes is lower than that of LED chips without via hole. Therefore, the research of via hole is necessary to decrease junction temperature of LED chips.

The Improvement of Junction Box Within Photovoltaic Power System

  • Sun, Ki-Ju;Cheon, Min-Woo
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.6
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    • pp.359-362
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    • 2016
  • In the PV (Photovoltaic) power system, a junction box collects the DC voltage generated from the PV module and transfers it to the PCS (power conditioning system). The junction box prevents damage caused by the voltage difference between the serially connected PV modules and provides convenience while repairing or inspecting the PV array. In addition, the junction box uses the diode to protect modules from the inverse current when the PV power system and electric power system are connected for use. However, by using the reverse blocking diode, heat is generated within the junction box while generating electric power, which decreases the generating efficiency, and causes short circuit and electric leakage. In this research, based on the purpose of improving the performance of the PV module by decreasing the heat generation within the junction box, a junction box with a built-in bypass circuit was designed/manufactured so that a certain capacity of current generated from the PV module does not run through the reverse blocking diode. The manufactured junction box was used to compare the electric power and heating power generated when the circuit was in the bypass/non-bypass modes. It was confirmed that the electric power loss and heat generation indicated a decrease when the circuit was in the bypass mode.

Electric properties Analysis and fabrication of ZnO:As/ZnO:Al homo-junction LED (ZnO:As/ZnO:Al homo-junction LED의 제조와 전기적 특성 분석)

  • Kim, Kyeong-Min;So, Soon-Jin;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.55-56
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    • 2007
  • The p-type ZnO thin film, fabricated by means of the ampoule-tube method, was used to make the ZnO p-n junction, and its characteristics was analyzed. The ampoule-tube method was used to make the p-type ZnO based on the As diffusion, and the hall measurement was used to confirm that the p-type is formed. the current-voltage characteristics of the ZnO p-n junction were measured to confirm the rectification characteristics of a typical p-n junction and the low leakage voltage characteristics. Using the ampoule-tube to fabricate the p-type ZnO will provide a very useful technology for producing the UV ZnO LED and ZnO-based devices.

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Analysis on the V-I Curve of ZnO:As/ZnO:Al homo-junction LED (ZnO:As/ZnO:Al homo-junction LED의 V-I 특성 분석)

  • Oh, Sang-Hyun;Jeong, Yun-Hwan;Liu, Yan-Yan;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.410-411
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    • 2007
  • To investigate the ZnO LED which are interested in the next generation of short wavelength LEDs and Lasers, the ZnO thin films were deposited by RF magnetron sputtering system. The p-type ZnO thin film, fabricated by means of the ampoule-tube method, was used to make the ZnO p-n junction, and its characteristics was analyzed. The ampoule-tube method was used to make the p-type ZnO based on the As diffusion, and the hall measurement was used to confirm that the p-type is formed. the current-voltage characteristics of the ZnO p-n junction were measured to confirm the rectification characteristics of a typical p-n junction and the low leakage voltage characteristics. Analysis of ZnO LED V-I curve will provide a very useful technology for producing the UV ZnO LED and ZnO-based devices.

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