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A computational method for energy level spin splitting simulation in InAs/GaAs semiconductor quantum dots
(2002-05-01)
Li, YM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
;
Tretyak, O
An impact of the spin-orbit interaction on the electron quantum confinement is considered theoretically for narrow gap semiconductor cylindrical quantum dots. To study the phenomena for InAs quantum dot embedded into GaAs semiconductor matrix, the effective one electronic band Hamiltonian, the energy position dependent electron effective mass approximation, and the spin-dependent Ben Daniel-Duke boundary conditions axe considered, formulated and solved numerically. To solve the nonlinear Schrodinger equation, we propose a nonlinear iterative algorithm. This calculation algorithm not only converges for all simulation cases but also has a good convergent rate. With the developed quantum dot simulator, we study the effect of the spin-orbit interaction for narrow gap InAs/GaAs semiconductor cylindrical quantum dots. From the numerical calculations, it has been observed that the spin-orbit interaction leads to a sizeable spin-splitting of the electron energy states with nonzero angular momentum. Numerical evidence is presented to show the splitting result is strongly dependent on the quantum dot size.
An investigation of magnetic field effects on energy states for nanoscale InAs/GaAs quantum rings and dots
(2003-03-01)
Li, YM
;
Lu, HM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper, we investigate the electron-hole energy states and energy gap in three-dimensional (313) InAs/GaAs quantum rings and dots with different shapes under external magnetic fields. Our realistic model formulation includes: (i) the effective mass Hamiltonian in non-parabolic approximation for electrons, (ii) the effective mass Hamiltonian in parabolic approximation for holes, (iii) the position- and energy-dependent quasi-particle effective mass approximation for electrons, (iv) the finite hard wall confinement potential, and (v) the Ben Daniel-Duke boundary conditions. To solve the 3D non-linear problem without any fitting parameters, we have applied the nonlinear iterative method to obtain self-consistent solutions. Due to the penetration of applied magnetic fields into torus ring region, for ellipsoidal- and rectangular-shaped quantum rings we find nonperiodical oscillations of the energy gap between the lowest electron and hole states as a function of external magnetic fields. The nonperiodical oscillation is different from 1D periodical argument and strongly dependent on structure shape and size. The result is useful to study magneto-optical properties of the nanoscale quantum rings and dots.
Numerical calculation of electron energy states for nanoscopic InAs/GaAs quantum rings
(2003-10-01)
Li, YM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper we study the electron energy states for nanoscopic semiconductor quantum rings. The effective one-band Hamiltonian approximation and the Ben Daniel-Duke boundary conditions axe simultaneously considered in our three-dimensional (3D) model. The rectangular and ellipsoidal torus-shaped rings have been investigated with the 3D model. The proposed model is numerically solved with nonlinear iterative method. This computational method calculates the solution without any fitting parameters and is robust for all simulation cases. For InAs/GaAs quantum rings, it is found that (1) there is a significant energy difference between the 2D and 3D models; (2) the electron energy state depends strongly on the ring shape and size; and (3) the dependency of the energy state on an external magnetic field is different from conventional 1D/2D periodical result. We find the electron energy state nonperiodically oscillates versus the applied magnetic field which is in agreement with the experimental observation.
A two-dimensional quantum transport simulation of nanoscale double-gate MOSFETs using parallel adaptive technique
(2004-07-01)
Li, YM
;
Yu, SM
;
奈米中心
;
友訊交大聯合研發中心
;
Nano Facility Center
In this paper we apply a parallel adaptive solution algorithm to simulate nanoscale double-gate metal-oxide-semiconductor field effect transistors (MOSFETs) on a personal computer (PC)-based Linux cluster with the message passing interface (MPI) libraries. Based on a posteriori error estimation, the triangular mesh generation, the adaptive finite volume method, the monotone iterative method, and the parallel domain decomposition algorithm, a set of two-dimensional quantum correction hydrodynamic (HD) equations is solved numerically on our constructed cluster system. This parallel adaptive simulation methodology with 1-irregular mesh was successfully developed and applied to deep-submicron semiconductor device simulation in our recent work. A 10 nm n-type double-gate MOSFET is simulated with the developed parallel adaptive simulator. In terms of physical quantities and refined adaptive mesh, simulation results demonstrate very good accuracy and computational efficiency. Benchmark results, such as load-balancing, speedup, and parallel efficiency are achieved and exhibit excellent, parallel performance. On a 16 nodes PC-based Linux cluster, the maximum difference among CPUs is less than 6%. A 12.8 times speedup and 80% parallel efficiency are simultaneously attained with respect to different simulation cases.
Numerical simulation of self-heating InGaP/GaAs heterojunction bipolar transistors
(2005)
Li, YM
;
Huang, KY
;
電子工程學系及電子研究所
;
友訊交大聯合研發中心
;
Department of Electronics Engineering and Institute of Electronics
We numerically simulate effects of the self-heating on the current-voltage characteristics of InGaP/GaAs heterojunction bipolar transistors (HBTs). A set of coupled nonlinear ordinary differential equations (ODEs) of the equivalent circuit of HBT is formed and solved numerically in the large-signal time domain. We decouple the corresponding ODEs using the waveform relaxation method and solve them with the monotone iterative method. The temperature-dependent energy band gap, the current gain, the saturation current, and the thermal conductivity are considered in the model formulation. The power-added efficiency and the 1-dB compression point of a three-finger HBT are calculated. This approach successfully explores the self-heating and the thermal coupling phenomena of the three-finger transistors under high power and high frequency conditions. The numerical algorithm reported here can be incorporated into electronic computer-aided design software to simulate ultra-large scale integrated and radio frequency circuits.
Parallelization of multiple genome alignment
(2005)
Li, YM
;
Chen, CK
;
電信工程研究所
;
友訊交大聯合研發中心
;
Institute of Communications Engineering
In this work, we implement a genome alignment system which applies parallelization schemes to the ClustalW algorithm and the interface of database querying. Parallel construction of the distance matrices and parallelization of progressive alignment in the ClustalW algorithm are performed on PC-based Linux cluster with message-passing interface libraries. Achieved experiments show good speedup and significant parallel performance.
Application of parallel adaptive computing technique to polysilicon thin-film transistor simulation
(2005)
Li, YM
;
電信工程研究所
;
Institute of Communications Engineering
In this paper, parallel adaptive finite volume simulation of polysilicon thin-film transistor (TFT) is developed using dynamic domain partition algorithm on a PC-based Linux cluster with message passing interface libraries. A set of coupled semiconductor device equations together with a two-dimensional model of grain boundary for polysilicon TFT is formulated. For the numerical simulation of polysilicon TFT, our computational technique consists of the Gummel's decoupling method, an adaptive 1-irregular meshing technique, a finite volume approximation, a monotone iterative method, and an a posteriori error estimation method. Parallel dynamic domain decomposition of adaptive computing technique provides scalable flexibility to simulate polysilicon TFT devices with highly complicated geometry. This parallel approach fully exploits the inherent parallelism of the monotone iterative method. Implementation shows that a well-designed load balancing simulation significantly reduces the execution time up to an order of magnitude. Numerical results are presented to show good efficiency of the parallelization technique in terms of different computational benchmarks.
Adaptive finite volume simulation of electrical characteristics of organic light emitting diodes
(2005)
Li, YM
;
Chen, P
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper a two-dimensional simulation of organic light emitting devices (OLEDs) using an adaptive computing technique is presented. A set of drift-diffusion equations including models of interface traps is solved numerically to explore the transport property of OLED structures. The adaptive simulation technique is mainly based on the Gummel's decoupling algorithm, a finite volume approximation, a monotone iterative method, a posteriori error estimation, and an unstructured meshing scheme. With this computational approach, we investigate the intrinsic and terminal voltage-current characteristics of OLEDs with respect to different material parameters, thickness of materials, and length of structure.
A computational efficient method for HBT intermodulation distortions and two-tone characteristics simulation
(2001)
Huang, KY
;
Li, YM
;
Lee, CP
;
Sze, SM
;
電子工程學系及電子研究所
In this paper, a new simulation method for two-tone characteristics calculations and the third-order intercept point (OIP3) of heterojunction bipolar transistor (HBT) in large-scale time domain is proposed. Base on waveform relaxation (WR) and monotone iterative (MI) methods, we solve a set of nonlinear ordinary differential equation (ODE) of equivalent circuit. With this approach, the two-tone characteristics in frequency domain for HBTs were directly computed from time domain result with fast Fourier transform (FFT). Simulation results on a realistic HBT are presented to show the accuracy and efficiency of the method.
A computational efficient algorithm for protein sequence classification
(2003)
Li, YM
;
Lu, HM
;
友訊交大聯合研發中心
;
D Link NCTU Joint Res Ctr
In this paper we present statistical algorithms to classify the stability of proteins by their sequence. A protein sequence consists of successive amino acid codes and can be considered as multivariate categorical data. Based on the statistical variance analysis for data set in each group (stable or unstable protein), the weights are calculated and become an important clue for the effects of the combination of amino acids codes on protein stability. Once the weights for every combination of amino acid codes have been decided, we can assign each protein a score presenting its stability. The distribution of the score for a stable protein is different from the score of an unstable protein. Our algorithm is well suit in the protein stability analysis by its sequence. We propose weighting algorithms and compare them as the results of protein stability classification. It provides an alternative for the protein stability classification and a predictable result as the reference before the protein mutation.

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