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Analysis on temperature dependent current mechanism of tunnel field-effect transistors
Lee, Junil,Kwon, Dae Woong,Kim, Hyun Woo,Kim, Jang Hyun,Park, Euyhwan,Park, Taehyung,Kim, Sihyun,Lee, Ryoongbin,Lee, Jong-Ho,Park, Byung-Gook IOP Publishing 2016 Japanese journal of applied physics Vol.55 No.6
<P>In this paper, the total drain current (I-D) of a tunnel FET (TFET) is decomposed into each current component with different origins to analyze the ID formation mechanisms of the TFET as a function of gate voltage (V-GS). Transfer characteristics are firstly extracted with fabricated Silicon channel TFETs (Si TFETs) and silicon germanium channel TFETs (SiGe TFETs) at various temperatures. The subthreshold swings (SS) of both Si TFETs and SiGe TFETs get degraded and the SSs of SiGe TFETs get degraded more as temperature becomes higher. Then, all the I(D)s measured at various temperatures are decomposed into each current component through technology computer aided design (TCAD) simulations with a good agreement with experimental data. As a result, it is revealed that Shockley-Read-Hall (SRH) recombination mainly contribute to the I-D of a TFET before band to band tunneling (BTBT) occurs. Furthermore, the SS degradation by high temperature is explained successfully by the SRH recombination with electric field dependence. (C) 2016 The Japan Society of Applied Physics</P>
Fabrication Methods for Nanowire Tunnel FET with Locally Concentrated Silicon-germanium Channel
Junil Lee,Ryoongbin Lee,Sihyun Kim,Euyhwan Park,Hyun-Min Kim,Kitae Lee,Sangwan Kim,Byung-Gook Park 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.1
This paper proposes a method to fabricate tunnel field-effect transistors (TFETs) which have Silicon Germanium (SiGe) nanowire channel with graded Ge concentration on Silicon-on-insulator (SOI). To obtain the concentration-graded SiGe channel, Ge condensation method which is a kind of oxidation is adopted. The rectangular shape of the channel becomes a rounded nanowire through the Ge condensation process. The TFET with the concentration-graded SiGe channel can improve drive current due to a smaller band gap at the Gecondensed surface of the channel compared to Si or non-condensed SiGe channel TFETs. The electrical characteristics of the proposed TFET are verified by technology computer-aided design (TCAD) simulation.
Lee, Hongseok,Mo, Young Kyu,Lee, Onyou,Kim, Junil,Bang, Seungmin,Kang, Jong O,Nam, Seokho,Kang, Hyoungku The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.1
High voltage superconducting apparatuses have been developed presently around the world under AC and DC sources. In order to improve electrical reliability of superconducting apparatuses with AC and DC networks, a study on the DC as well as the AC electrical breakdown characteristics of cryogenic insulations should be conducted for developing a high voltage superconducting apparatus. Recently, a sub-cooled liquid nitrogen cooling system is known to be promising method for developing a high voltage superconducting apparatus. A sub-cooled liquid nitrogen cooling system uses gaseous nitrogen to control the pressure and enhance the dielectric characteristics. However, the dielectric characteristics of gaseous nitrogen are not enough to satisfy the grade of insulation for a high voltage superconducting apparatus. In this case, the application of solid insulating barriers is regarded as an effective method to reinforce the dielectric characteristics of a high voltage superconducting apparatus. In this paper, it is dealt with a barrier effect on the DC and AC dielectric characteristics of gaseous nitrogen with respect to the position and number of solid insulating barriers. As results, the DC and AC electrical breakdown characteristics by various barrier effects is verified.
Lee, Hong Seok,Kang, Jong O.,Lee, On You,Bang, Seung Min,Kim, Junil,Mo, Young Kyu,Hong, Jong Gi,Lee, Jae Hun,Jang, Cheo Lyeong,Kang, Hyoung Ku Trans Tech Publications 2015 Advanced materials research Vol.1125 No.-
<P>Recently, extensive studies have been carried out on developing a high voltage superconducting apparatus as a substitute for the conventional one. superconducting wires used for a high voltage superconducting apparatus can be damaged under high voltage condition due to electrical breakdown and the damaged superconducting wires may result in the degradation of the critical current (Ic) and index number. Therefore, a study on the degradation characteristics of superconducting wires in accordance with the electrical breakdown should be performed. In this paper, the degradation characteristics of second generation high temperature superconducting (2G HTS) wires with respect to electrical breakdown tests are studied. The applied electrical breakdown voltages to 2G HTS wire are AC and lightning impulse (Imp) ; 50, 60 and 70 kV. The electrical breakdown test is successively repeated five times. The Ic and index number of 2G HTS wires were measured. The relationship between electrical characteristics such as the Ic and index number and the electrical breakdown was analyzed.</P>
Kim, Junil,Lee, Onyou,Mo, Young Kyu,Bang, Seungmin,Kang, Jong O,Lee, Hongseok,Nam, Seokho,Kang, Hyoungku The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.3
A liquid nitrogen ($LN_2$) is usually used to be a coolant and insulant for a HTS coil system. HTS wires for a superconducting apparatus may be surrounded by gaseous nitrogen ($GN_2$) due to film boiling generated by a quench or voids occurred by electrical breakdown. The increased maximum electric field intensity at $GN_2$ may result in the degradation of dielectric strength of a HTS coil system. In this paper, a study on the dielectric characteristics of a composite insulation system composed of $LN_2$ and $GN_2$ is performed. A sphere-to-plane electrode system made with stainless steel is used to perform the experiments under AC and lightning impulse voltage condition. A sphere electrode is surrounded by $GN_2$ and a plane electrode is immersed into $LN_2$ to conduct dielectric experiments with a composite insulation system. The dielectric experiments are performed according to the level of $LN_2$ from the plane electrode to a sphere electrode. It is found that the dielectric characteristics of a composite insulation system are dependent on the level of $LN_2$ and the field utilization factor of an electrode system.