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Magnetotransport Measurements on an AlGaN/GaN Two-Dimensional Electron System
Jyun-Ying Lin,C.-T. Liang,전창민,D.~H. Youn,김길호,H. Park,백정민,Jing-Han Chen,이종람,Y. F. Chen 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.3
We report on the transport properties of an AlGaN/GaN two-dimensional electron system in the presence of a perpendicular magnetic field B. At low magnetic fields, the measured longitudinal resistivity xx shows a B2 dependence at various temperatures. This eect can be ascribed to electron-electron interaction eects in a weakly disordered electron system. At high magnetic fields, there is a temperature-independent point in xx at the critical magnetic field Bc. We find that at this crossing point, the Hall-resistivity xy is approximately equal to xx. By analyzing the amplitude of the observed Shubnikov-de Hass oscillations at high fields, we find that at the crossing point, µqB = 0.17 < 1, where µq is the quantum mobility. Within the Drude-Boltzman theory, µq should be approximately equal to µ. The fact that µq < µ could be due to a high-field localization eect which gives rise to the formation of a quantum Hall liquid-like state because xx increases with increasing temperature for B > Bc.
E.S Kannan,Gil Ho Kim,D. H. Youn,Chi-Te Liang,Jing-Han Chen,Jyun-Ying Lin,Kuang Yao Chen,Kwang-Yong Kang,Li-Hung Lin,N.C. Chen,Zhi-Yao Zhang 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.6
We report comparative magnetoresistance measurements of the two-dimensional electron gas formed in two different GaN/AlGaN quantum well structures with different starting disorder. The longitudinal magnetoresistance measurements for both the samples exhibited temperature-independent crossing points, evidence for a weak insulator - quantum Hall transition. Our data suggest that the onset of Landau quantization does not correspond to the crossing point. Moreover, the effect of the electron-electron interaction must be taken into account because the Hall resistivity shows a strong temperature dependence in the more disordered sample. Our experimental results, therefore, urge further studies on the low-field weak insulator - quantum Hall transition
Jing-Han Chen,Chi-Te Liang,Chun-Feng Huang,Da-Ren Hang,David A. Ritchie,J. C. Hsiao,Jyun-Ying Lin,Michelle Y. Simmons,Ming-Gu Lin,S. H. Lo,Tsai-Yu Huang 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.3
By applying a magnetic field perpendicular to GaAs/AlGaAs two-dimensional electron systems (2DESs), we study the low-field Landau quantization when the thermal damping is reduced with decreasing temperature. Magneto-oscillations following the Shubnikov-de Haas (SdH) formula are observed even when their amplitudes are so large that the deviation to such a formula is expected. Our experimental results show the importance of the positive magneto-resistance to the extension of the SdH formula under the damping induced by the disorder.
Jing-Han Chen,C.-T. Liang,D.H. Youn,Eun-Jin Lee,Gil-Ho Kim,Hun Park,Hyun-Ick Cho,Jung-Hee Lee,Jung-Kai Tsai,Jyun-Ying Lin,Y. F. Chen 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
AlGaN/GaN heterostructures have been attracting a great deal of interest because of their great potential applications as light-emitting-diodes, high-electron-mobility transistors (HEMTs), and detectors operating in the visible-to-ultraviolet range. The performances of these devices are governed by the electronic properties of the two-dimensional electron gas (2DEG) formed at the interface of AlGaN/GaN heterostructure. In this work, we report transport measurements for an AlGaN/GaN 2DEG as functions of the magnetic field B over a wide range of temperature (4.682 K T 80 K). At the highest measurement temperature of 80 K, the longitudinal resistance is nominally Bindependent, compelling experimental evidence for Drude-Boltzmann-like transport in a 2D system.