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Quantum transport and dielectric response of nanometer scale transistors using empirical pseudopotentials.

机译：使用经验transport势的纳米级晶体管的量子传输和介电响应。

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摘要

As transistors, the most basic component of central processing units (CPU) in all electronic products, are scaling down to the nanometer scale, quantum mechanical effects must be studied to investigate their performance. A formalism to treat quantum electronic transport at the nanometer scale based on empirical pseudopotentials is presented in this dissertation. We develop the transport equations and show the expressions to calculate the device characteristics, such as device current and charge density. We apply this formalism to study ballistic transport in a gate-all-around (GAA) silicon nanowire field-effect transistor (FET) with a body-size of 0.39 nm, a gate length of 6.52 nm, and an effective oxide thickness of 0.43 nm. Simulation results show that this device exhibits a subthreshold slope (SS) of ∼66 mV/decade and a drain-induced barrier-lowering of ~2.5 mV/V. This formalism is also applied to assess the ballistic performance of FETs with armchair-edge graphene nanoribbon (aGNRs) and silicon nanowire (SiNWs) channels and with gate lengths ranging from 5 nm to 15 nm. The device characteristics of the transistors with a 5 nm gate length are compared. Source-to-drain tunneling effects are investigated for SiNWFETs and GNRFETs by comparing the I-V characteristics of each respective transistor with different channel lengths.;While a uniform dielectric constant is assumed in solving Poisson equation for the devices simulated above, the knowledge of the atomistic (i.e., local) dielectric permittivity that considers the atomistic electron distribution and quantum-confinement effect is necessary to treat the electrostatic properties accurately. The local permittivity can also provide information about the dielectric property at the interfaces. We use the random-phase approximation, first-order perturbation theory, and empirical pseudopotentials to calculate the static polarizability, susceptibility, and dielectric response function in graphene and GNRs. While the artifacts of the supercell method prevent us from calculating the longitudinal atomistic dielectric permittivity directly through the dielectric response function, we propose a microscopic Poisson equation which relates the external charge density to the total potential through the polarizability (also called density-density response function). Solving this equation permits the calculation of an atomistic dielectric tensor for anisotropic crystals. We show the atomistic distribution of the local dielectric tensor for an anisotropic GNR. This quantity can be used to solve Poisson equation properly for a self-consistent atomistic device simulation accounting for quantum effects on the nanodielectric.
机译：由于晶体管是所有电子产品中中央处理单元（CPU）的最基本组件，其尺寸已缩小至纳米级，因此必须研究量子力学效应以研究其性能。本文提出了一种基于经验pseudo势的纳米尺度量子电子传输形式化方法。我们开发了传输方程，并给出了用于计算器件特性的表达式，例如器件电流和电荷密度。我们采用这种形式主义来研究全尺寸（GAA）硅纳米线场效应晶体管（FET）的弹道传输，该体尺寸为0.39 nm，栅极长度为6.52 nm，有效氧化物厚度为0.43纳米仿真结果表明，该器件的亚阈值斜率（SS）为〜66 mV /十倍，漏极引起的势垒降低为〜2.5 mV / V。这种形式主义也可用于评估具有扶手椅状边缘石墨烯纳米带（aGNR）和硅纳米线（SiNWs）通道且栅极长度范围为5 nm至15 nm的FET的弹道性能。比较了栅极长度为5 nm的晶体管的器件特性。通过比较每个具有不同沟道长度的晶体管的IV特性，研究了SiNWFET和GNRFET的源极到漏极隧穿效应。;尽管在求解上面模拟的器件的泊松方程时假设了一致的介电常数，但原子能考虑到原子电子分布和量子约束效应的（即局部）介电常数对于精确处理静电性能是必要的。局部电容率还可提供有关界面介电特性的信息。我们使用随机相位近似，一阶微扰理论和经验伪势来计算石墨烯和GNR中的静态极化率，磁化率和介电响应函数。虽然超级电池方法的伪影使我们无法直接通过介电响应函数来计算纵向原子介电常数，但我们提出了一个微观泊松方程，该方程通过极化率将外部电荷密度与总电势相关（也称为密度-密度响应函数） ）。求解该方程式可以计算出各向异性晶体的原子介电张量。我们显示了各向异性GNR的局部介电张量的原子分布。该量可用于适当地求解泊松方程，从而进行自洽的原子器件模拟，从而考虑了纳米介电体的量子效应。

著录项

  • 作者

    Fang, Jingtian.;

  • 作者单位

    The University of Texas at Dallas.;

  • 授予单位 The University of Texas at Dallas.;
  • 学科 Materials science.;Electrical engineering.;Theoretical physics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 144 p.
  • 总页数 144
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 康复医学;
  • 关键词

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