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Spin-dependent delay time in electronic resonant tunneling at zero magnetic field
(2000)
Voskoboynikov, O
;
Liu, SS
;
Lee, CP
;
交大名義發表
;
National Chiao Tung University
The dependence of the phase tunneling time on electronic spin polarization in symmetric and asymmetric double-barrier semiconductor heterostructures is studied theoretically. The effective one-band Hamiltonian approximation and spin-dependent boundary conditions are used for theoretical investigation of the electron spin influence on the delay time in tunneling processes. It is shown that the spin-orbit splitting in the dispersion relation for the electrons can provide a dependence of the delay time on the electron spin polarization without additional magnetic field. This dependence can be controlled by an external electric field and can be very pronounced for realistic double-barrier semiconductor heterostrctures. (C) 2000 Elsevier Science Ltd. All rights reserved.
Electron spin filtering in all-semiconductor tunneling structures
(2003-09-01)
Yu, L
;
Huang, HC
;
Voskoboynikov, O
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this work we briefly review the present day perspectives for exploiting conventional nonmagnetic semiconductor nano-technology to design high speed spin-filter devices. In recent theoretical investigations a high spin polarization has been predicted for the ballistic tunneling current in semiconductor single- and double-barrier asymmetric tunnel structures of III-V semiconductors with strong Rashba spin-orbit coupling. We show in this paper that the polarization in the tunneling can probability be sufficiently increased for producing realistic single-barrier structures by including of the Dresselhaus term into consideration. (C) 2004 Published by Elsevier Ltd.
Vertical coupling effects and transition energies in multilayer InAs/GaAs quantum dots
(2004-09-20)
Li, YM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
We investigate the transition energy of vertically stacked semiconductor quantum dots with a complete three-dimensional (3D) model in an external magnetic field. In this study, the model formulation includes: (1) the position-dependent effective mass Hamiltonian in non-parabolic approximation for electrons, (2) the position-dependent effective mass Hamiltonian in parabolic approximation for holes, (3) the finite hard-wall confinement potential, and (4) the Ben Daniel-Duke boundary conditions. To solve the nonlinear problem, a nonlinear iterative method is implemented in our 3D nanostructure simulator. For multilayer small InAs/GaAs quantum dots, we find that the electron-hole transition energy is dominated by the number of stacked layers. The inter-distance d plays a crucial role in the tunable states of the quantum dots. Under zero magnetic field for a 10-layer QDs structure with d = 1.0 nm, there is about 30% variation in the electron ground state energy. Dependence of the magnetic field on the electron-hole transition energy is weakened when the number of stacked layers is increased. Our investigation is constructive in studying the magneto-optical phenomena and quantum optical structures. (C) 2004 Elsevier B.V. All rights reserved.
Gate Direct Tunneling Current in Uniaxially Compressive Strained nMOSFETs: A Sensitive Measure of Electron Piezo Effective Mass
(2011-01-01)
Lee, Wei-Han
;
Chen, Ming-Jer
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Currently, both the band-structure calculation and the mobility measurement are used to assess the electron piezo-effective-mass coefficients in strained nMOSFETs. In this paper, we present a new experimental method through a fitting of the strain-altered electron gate direct tunneling current. The core of this method lies in the sensitivity of the direct tunneling to the position of the subband level in the presence of the electron piezo-effective-mass coefficients. First, a correction-coefficient generating expression is systematically constructed to compensate for the error in the subband levels due to the use of a triangular potential approximation. Then, with the known deformation potential constants and uniaxially compressive stress in the channel as inputs, a strain quantum simulator is carried out. The resulting gate direct tunneling current is used to fit experimental data, thus leading to the values of the piezo-effective-mass coefficients associated with the twofold and fourfold valleys. The comparison of the extracted piezo-effective-mass coefficients to those published in the literature is made.
Low frequency noise degradation in ultra-thin oxide (I5A) analog n-MOSFETs resulting from valence-band tunneling
(2005)
Wu, JW
;
You, JW
;
Ma, HC
;
Cheng, CC
;
Hsu, C
Abnormal increase of low frequency flicker noise in analog n-MOSFETs with gate oxide in valence band tunneling domain is investigated. In 15 angstrom oxide devices, valence-band electron tunneling from Si substrate to poly-gate occurs at a positive gate voltage and results in the splitting of electron and hole quasi Fermi-levels in the channel. The excess low frequency noise is attributed to electron and hole recombination at interface traps between the two quasi Fermilevels. The trap capture and emission times in valence band tunneling domain are extracted from random telegraph signal. The dependence of measured trap times on gate voltage is consistent with our proposed model.
Evidence for the Fourfold-Valley Confinement Electron Piezo-Effective-Mass Coefficient in Inversion Layers of < 110 > Uniaxial-Tensile-Strained (001) nMOSFETs
(2012-06-01)
Chen, Ming-Jer
;
Lee, Wei-Han
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have recently experimentally extracted the piezo-effective-mass coefficients of 2-D electrons via the gate tunneling current of (001) n-channel metal-oxide-semiconductor field-effect transistors under < 110 > uniaxial compressive stress. The results pointed to the existence of a piezo-effective-mass coefficient around the fourfold conduction-band valley in the out-of-plane (quantum confinement) direction. To strengthen this further, here, we provide extra evidence. First, explicit guidelines are drawn to distinguish all the piezo-effective-mass coefficients. Then, a self-consistent strain quantum simulation is executed to fit literature data of both the mobility enhancement and gate current suppression in the uniaxial tensile stress situation. It is found that neglecting the fourfold-valley out-of-plane piezo-effective-mass coefficient, as in existing band structure calculations, only leads to a poor fitting.
Evidence for a Very Small Tunneling Effective Mass (0.03m(0)) in MOSFET High-k (HfSiON) Gate Dielectrics
(2012-04-01)
Chen, Ming-Jer
;
Hsu, Chih-Yu
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have recently conducted experimental and modeling tasks on TaC/HfSiON/SiON n-type MOSFETs, leading to an effective mass of 0.03m(0) for 2-D electrons tunneling in high-k HfSiON dielectrics. In this letter, we present extra evidence obtained from complementary MOSFETs undergoing the same TaC/HfSiON/SiON processing, which shows that such a very small tunneling effective mass is existent not only for 3-D electrons but also for 2-D holes. This new finding is very important because it can substantially enhance the current understanding of gate tunneling leakage suppression in metal-gate high-k MOSFETs.
Transition energies of vertically coupled multilayer nanoscale InAs/GaAs semiconductor quantum dots of different shapes
(2005-04-01)
Li, YM
;
奈米中心
;
Nano Facility Center
The energy spectra of vertically coupled multilayer nanoscale semiconductor quantum dots (QDs) are theoretically studied using a unified three-dimensional (3D) model. The model formulation includes (1) the position-dependent effective mass Hamiltonian in a nonparabolic approximation for electrons, (2) the position-dependent effective mass Hamiltonian in a parabolic approximation for holes, (3) the finite hard wall confinement potential, and (4) Ben Daniel-Duke boundary conditions. To solve a nonlinear problem, a nonlinear iterative method is further improved in our developed 3D QD simulator. At an applied magnetic field (B), we explore the transition energy and the energy band gap of disk (DI), ellipsoid (EL)- and cone (CO)-shaped vertically coupled multilayer nanoscale semiconductor quantum dots. We find that the electron transition energy of vertically coupled rnultilayer InAs/GaAs QDs depends on their shape and is strongly dominated by the number of stacked layers (N). The interdistance (d) among InAs QDs plays a crucial role in the tunable states of these QDs. In DI-shaped vertically coupled 10-layer QDs at B = 0T and d = 1.0nm, we find approximately 40% variation in electron ground state energy, which is larger than that (similar to 20% variation) in CO-shaped QDs. In QDs at a nonzero magnetic field, the electron transition energy decreases with increasing N. In QDs with d = 1nm, the rate of decrease is low when N > 6. This results in QDs,with energy band gaps having similar dependences on N. This study implies different applications in magnetooptical phenomena and quantum optical structures.
Enhancing teredo IPv6 tunneling to traverse the symmetric NAT
(2006-05-01)
Huang, SM
;
Wu, Q
;
Lin, YB
;
資訊工程學系
;
Department of Computer Science
By tunneling IPv6 packets over IPv4 UDP, Teredo supports IPv4/IPv6 dual-stack nodes in private IPv4 networks behind Network Address Translation (NAT) to access IPv6 networks. However, the current Teredo protocol does not work with symmetric NAT. This letter proposes SymTeredo, an extension of Teredo with capability to traverse the symmetric NAT. Our extension preserves the Teredo architecture, and offers backward compatibility with the original Teredo protocol.
SIP mobility and IPv4/IPv6 dual-stack supports in 3G IP multimedia subsystem
(2006-08-01)
Huang, Shiang-Ming
;
Wu, Quincy
;
Lin, Yi-Bing
;
Yeh, Che-Hua
;
資訊工程學系
In the Universal Mobile Telecommunications System (UNITS), session initiation protocol (SIP) and IPv6 are the default protocols for IP multimedia core network subsystem (IMS). However, a user equipment (UE) may not be allowed to roam or hand off from UNITS to a private-lPv4 GPRS network. In this paper, we utilize SIP mobility and an automatic IPv6 tunneling mechanism, called Teredo, to support roaming/handoff of a UE between different networks. We have developed the first non-commercial Linux-based Teredo mechanism, and compared our solution with other Teredo implementations in the public domain. Our study indicates that our solution can reduce the tunneling overhead and transmission delay over two other implementations by 44-74%. Copyright (C) 2006 John Wiley & Sons, Ltd.

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