带有AB环的T型结构中的电子输运性质

采用一维量子波导理论研究了带有AB环的类T型结构中的电子输运。在满足波函数的连续性以及电流的闭合性的情况下,得出了透射系数的解析表达式,并根据此表达式分析了电子的输运特性。结果显示：左右端的透射系数随磁通的变化产生典型的AB振荡。当改变中间的入射点的位置X时,左出射端的透射系数的大小随之改变,右输出端除 附近外,均产生与磁通无关的全反射现象。入射点位置X的变化对透射系数的影响出现一种周期性的调制现象。体系结构轻微的偏离对系统的输运特性影响不大。     

硅单电子晶体管的制造及特性

报道了采用电子束光刻、反应离子刻蚀及热氧化等工艺,在p型SIMOX(separation by implanted oxygen)硅片上成功制造的一种单电子晶体管.特别是,提供了一种制造量子线和量子点的工艺方法,在器件的电流-电压特性上观测到明显的库仑阻塞效应和单电子隧穿效应.器件的总电容约为9.16aF.在77K工作温度下,也观测到明显的电流-电压振荡特性.     

Analytical computation of electrical parameters in GAAQWT and CNTFET with identical configuration using NEGF method

A two-dimensional quantum mechanical model is presented for calculating carrier transport in ultra-thin gate-all-around quantum wire transistor (GAAQWT) and carbon nanotube field effect transistor (CNTFET) using coupled mode space approach. Schrödinger and Poisson’s equations are self-consistently solved involving Non-Equilibrium Green’s Function (NEGF) formalism under the ballistic limit along with dissipative effects in terms of self-energy at both the source and drain ends. Effect of structural parameters on drain current, channel length modulation parameter, quantum capacitance, transconductance, subthreshold swing (SS) and drain induced barrier lowering (DIBL) are studied assuming occupancy of only a few lower sub-bands, where comparison is performed taking all other factors, biases and dimensions identical. High-k dielectric (HfO₂) independently surrounding the quantum wire (GaAs) and carbon nanotube shows higher drain current and transconductance for GAAQWT but lower quantum capacitance than that obtained for CNTFET. A smaller variation of CLM for CNFET speaks in favour of it for digital quantum circuit applications, whereas GAAQWT is suitable candidate for low-power applications. Effect of structural parameters is investigated within fabrication limit to analyse the effect on electrical characteristics under lower biasing ranges.     

Self-Aligned SiGe MOS-Gate FET with Modulation-Doped Quantum Wire Channel for Millimeter Wave Application

This paper describes a self-aligned SiGe MOS-gate field-effect transistor (FET) having a modulation-doped (MOD) quantum wire channel. An analytical model based on modified charge control equations accounting for the quantum wire channel, is presented predicting the transport characteristics of the MOS-gate MODFET structure. In particular, transport characteristics of devices having strained SiGe layers, realized on Si or Ge substrates, are computed. The transconductance g_m and unity-current gain cutoff frequency (f_T) are also computed as a function of the gate voltage V_G. The calculated values of f_T suggest the operation of one-dimensional SiGe MODFETs to be around 200 GHz range at 77°K, and 120 GHz at 300°K.     

（英）中红外量子级联激光器输运特性的仿真

基于一种非局域化的输运模型,对不同结构不同温度下的中红外量子级联激光器的输运特性进行了仿真。在这个模型中,利用量子隧穿、微带隧穿以及热载流子输运等长程载流子输运模型,对传统的扩散-漂移方程进行了矫正.并将基于上述集成模型的计算结果和实验结果进行了比较,通过拟合参数的合理设置,计算结果和实验结果得到了很好的吻合.     

Analysis of waveguide antenna arrays with protruding dielectricelements

The two-dimensional problem of radiation of TE and TM waves from a waveguide array with protruding smooth dielectric elements of arbitrary shape is considered, and solution algorithms are suggested. The algorithms are based on applying the method of auxiliary sources for the representation of electromagnetic fields outside and inside the protrusions in combination with the method of integral equations for the electric field at the waveguide aperture. The point matching of the field tangential components on the protrusion-to-free-space boundary and at the waveguide aperture is used to reduce the problem to a system of linear algebraic equations for the amplitudes of the auxiliary filamentary currents and of the waveguide aperture electric field, which is assumed to be piecewise constant. The amplitudes obtained from the solution of the system are used for computing the array reflection coefficient and element pattern, which are shown in some cases to be significantly dependent on the protrusion shape. Examples of arrays with flat-topped element patterns resulting from array geometry numerical optimization are also presented     

量子线电子波导特性的讨论

电子波导器件是今后量子线十分重要的应用领域之一。本文从薛定谔方程出发，得出了有关量子线中传输电子特性的一组约束方程，也即描述量子线电子波导特性的方程组，用数值法求解该隐含方程组，可以得到电子能量Ｅ、传播常数β的关系曲线和量子线结构参数ｄｘ、ｄｙ之间的关系。     

Transport and optics in quantum wires fabricated by MBE overgrowth on the (110) cleaved edge

The MBE double-growth technique that we call cleaved-edge overgrowth has, over the past several years, proved itself to be especially suitable for making quantum wires of the very highest quality. We will review our recent progress in measuring the transport and quantum optics characteristics of these wires, and the MBE growth issues that arise with cleaved-edge overgrowth fabrication. Our transport experiments have resulted in 250 Å wide quantum wires with ballistic mean free paths exceeding 10 μm. We verify the prediction that in the ballistic regime the electron conductivity in a quantum wire is independent of the wire length and shows quantized steps proportional to e²/h. The deviation of our observed step heights from exactly e²/h is taken as evidence for correlated electron behaviour. The electrons are tightly confined on three sides by atomically smooth GaAs/AlGaAs heterojunctions and in the fourth direction by an electric field. This results in a quantum wire of nominal square cross-section 250 × 250 Å. Magneto-transport measurements reveal quantum wire sub-band separations in excess of 20 meV as well as the symmetries of the wave functions of the one-dimensional modes. For optics studies our quantum wires are made using cleaved-edge overgrowth to form a line junction as two quantum wells are made to intersect with the cross-section forming a letter ‘T’. This line intersection separately forms a quantum wire bound-state for holes, for electrons, and even for excitons. We have characterized our optical wires by PL, by PLE, and by scanning near-field optics. An important application of this work is our demonstration of the first quantum laser using this T-geometry.     

超导系统下利用量子非破坏性测量制备量子态

基于超导量子电路系统,我们提出了通过量子非 破坏性测量的方法来实现光子的量子态制备。由约 瑟夫森结构成的两能级超导量子比特,在与腔耦合的情况下,其能级会产生斯塔克位移,位 移的大小与腔 内光子数成正比。利用超导量子比特能级位移受到腔内光子影响这一性质,在波导与超导量 子比特耦合的 情况下,通过波导中光子透过率的测量,从而判断出腔内的光子数。这种测量方式对腔内的 光子不产生影 响,因而是量子非破坏性测量,进而实现腔内光子的量子态制备。此外,我们还讨论了相关 参数对制备效 果的影响,在此基础之上,提出了通过反馈重复测量的方法来提高制备效率,从而实现目标 量子态的快速制备。     

金属量子线材料的制备及其应用

金属量子线材料因具有独特的机械、电、磁等特性而具有重要的应用价值,是当今介观物理学研究的前沿领域,已成为基础研究与应用研究的热点。综述了国内外金属量子线材料的制备方法,主要包括机械可控断裂结技术、电化学法、扫描隧道显微镜法等。同时对金属量子线材料的应用做了较为详细的介绍,主要应用包括量子电导原子开关、传感应用等,突出了金属量子线在量子器件研究中的重要作用。最后讨论了金属量子线材料所面临的一些问题,并对该领域的发展方向作出了展望。期望能够提高国内研究者对该领域的研究兴趣,促进该领域的新进展。     

量子密钥分发系统中的相位调制器特性分析

在量子密钥分发系统(QKD)中,LiNbO3波导相位调制器是构成单光子干涉仪的关键器件。文章阐述了LiNbO3相位调制器的相位调制特性、偏振特性及其对量子密钥分发系统的影响,介绍了退火质子交换工艺制备的线性单偏振LiNbO3相位调制器与采用钛内扩散工艺制备的低偏振相关损耗(PDL)LiNbO3相位调制器的性能指标。     

Relativistic Dynamics,Electromagnetic Field,and Spin,as All Quantum Effects

We consider a quantum particle as a wave packet in the coordinate space. When the conjugate wave packet in the momentum space is considered, we find that the group velocities of these two wave packets, which describe the particle dynamics, are in agreement with the Hamilton equations only if in the time dependent phases one considers the Lagrangian instead of the Hamiltonian which leads to the conventional Schrdinger equation. We define a relativistic quantum principle asserting that a quantum particle has a finite frequency spectrum, with a cutoff propagation velocity c as a universal constant not depending on the coordinate system, and that any time dependent phase variation is the same in any system of coordinates. From the time dependent phase invariance, the relativistic kinematics is obtained. We consider two types of possible interactions: 1) An interaction with an external field, by a modification of the time dependent phase differential with the terms proportional to the differentials of the space-time coordinates multiplied with the components of this field four-potential, and 2) an interaction by a deformation of the space-time coordinates, due to a gravitational field. From the invariance of the time dependent phase with field components, we obtain a mechanical force of the form of Lorentzs force, and three Maxwell equations: The Gauss-Maxwell equations for the electric and magnetic fluxes, and the Faraday-Maxwell equation for the electromagnetic induction. When the fourth equation, Ampre-Maxwell, is considered, the interaction field takes the form of the electromagnetic field. For a low propagation velocity of the particle waves, we get a packet of waves with the time dependent phases proportional to the relativistic Hamiltonian, as in Diracs famous theory of spin, and a slowly-varying amplitude with a phase proportional to the momentum and this velocity. In the framework of our theory, the spin is obtained as an all quantum effect, without any additional assumption to the quantum theory. When a space-time deformation is considered in the time dependent phase of a quantum particle, from the group velocity we get the particle dynamics according to the general theory of relativity. In this way, the relativistic dynamics, the electromagnetic field, and the spin of a quantum particle are obtained only from the invariance of the time dependent phases of the particle wave functions.     

基于NCP门库的一维量子行走可逆逻辑电路

本文提出了基于NCP门库的一维量子行走可逆逻辑电路设计方案.根据一维量子行走的特点,电路被划分为投掷硬币和S操作两个部分;文章详细分析一维量子行走,对其行为数学建模,巧妙利用可控加减电路实现了S操作.目前对于量子行走算法的研究多数局限于数学理论和数理解析层面,在量子电路理论层面对量子行走算法的研究为数不多.本文利用原始递归给出了一维量子行走中每一步在量子电路理论层面上的数学表达式;提出的可逆逻辑电路描述了一维量子行走的最基本操作,并且将其使用模块化表示,使一维量子行走算法的研究从理论到实现上前进了一步.     

Simulation of Saturation Effects in Electroabsorption Modulators

Saturation phenomena have a deep impact on the performance of electroabsorption (EA) modulators. It is important to develop algorithms which as well describe the phenomenon of electroabsorption as they include nonlinear carrier dependent effects, band filling and reduction of the band gap. Thus, a dynamical transport model has to be coupled to the density matrix equation for excitons.The density matrix equation for interband processes determines quantum optical effects, while a drift-diffusion model (DDM) adequately describes transport phenomena in the device. Within this approach quantum transport is considered by a correction of the classical potential, the Bohm potential.To demonstrate the presented algorithm, waveguide EA-modulators including strained lattice and full Fermi statistics are investigated.     

Numerical Analysis of Effective Thermal Conductivity of Microwire Array Element

We have used the finite-element method to calculate numerically the equations of electrical and thermal transport. The thermal conductivity of a wire array is analyzed. The influence of the wire array on the effective thermal conductivity of the element is discussed. The effective thermal conductivity decreases as the wire diameter is reduced. Decreasing the packing density significantly reduces the effective thermal conductivity. In the classical regime, the ratio of the effective electrical conductivity to the effective thermal conductivity of the wire array can be expressed as a function of packing density; this ratio decreases as the packing density decreases. The ratio for a wire array with realistic parameters is similar to that of bulk bismuth. Therefore, to improve the thermoelectric figure of merit, it is critical to enhance the intrinsic power factor in a wire by exploiting thermomagnetic or quantum effects.     

量子阱无序的窗口结构InGaAs/GaAs/AlGaAs量子阱激光器

对ＳｉＯ２薄膜在快速热退火条件下引起的空位诱导ＩｎＧａＡｓ／ＧａＡｓ应变量子阱无序和ＳｒＦ２薄膜抑制其量子阱无序的方法进行了实验研究。并将这两种技术的结合（称为选择区域量子阱无序技术）应用于脊形波导ＩｎＧａＡｓ／ＧａＡｓ／ＡｌＧａＡｓ应变量子阱激光器，研制出具有无吸收镜面的窗口结构脊形波导量子阱激光器。该结构３μｍ条宽激光器的最大输出功率为３４０ｍＷ，和没有窗口的同样结构的量子阱激光器相比，最大输出功率提高了３６％。在１００ｍＷ输出功率下，发射光谱中心波长为９７８ｎｍ，光谱半宽为１．２ｎｍ。平行和垂直方向远场发散角分别为７．２°和３０°     

具有Stubs结构量子波导中电子的自旋传输特性

利用递归格林函数法研究了含Rashba自旋轨道耦合效应的具有Stubs结构的量子波导中电子的自旋极化传输特性.结果表明在含一个stub的量子波导系统中, 由于stub和Rashba自旋轨道耦合引起的势阱导致系统电导出现Fano共振形式的“山谷”和“针尖”结构, 通过改变自旋轨道耦合的强度可以调节它们的大小. 同时,在同样的位置自旋极化率也出现Fano共振或反共振结构. 当系统中出现多个周期性的stubs时, 在Fano共振点附近电导中出现一些小的带隙结构.但是,当系统加上磁场后, stubs和自旋轨道耦合带来的效应都被抑制, 系统的电导重新出现量子化台阶结构. 同时由于子带间干涉效应变小, 自旋电导也出现台阶结构.     

Far-infrared-study of shallow etched quantum wires on high mobility GaAs/AlGaAs heterostructures and quantum-wells

We report measurements of electronic excitations in the confinement regime between one and two dimensions. FIR transmission spectroscopy has been successfully used to detect two-dimensional plasmons dispersion, localized plasmons and depolarization shifted one-dimensional intersubband transitions. The far infrared response of arrays of periodic quantum wires has been investigated by cyclotron resonance transmission and photoconductivity (PC) measurements. Due to narrow geometrical dimensions (300 nm), quantum confinement arises and leads to the formation of one-dimensional electronic subbands with a typical energy separation of 1–3 meV in the case of the heterostructures, and up to 9 meV in the case of the quantum wells. The far infrared transmission spectra of the quantum wire structures show one strong resonance, which can be described by a harmonic oscillator model, assuming that the confining potential is of parabolic shape. Depending on the intensity of the bandgap illumination, a well pronounced transition from a one-dimensional electronic system behaviour to a modulated one-dimensional system and finally to a pure two-dimensional system can be achieved for the heterostructure samples. The position of the PC-peak can be assigned to the plasmon-shifted cyclotron resonance. In addition in the samples, which contain a low density (4 × 10¹⁰cm⁻²) and high mobility inversion channel, an extremely sharp line with a linewidth of 0.2 cm⁻¹ can be observed, depending on the temperature and on the illumination of the samples.     

A silicon quantum wire transistor with one-dimensional subband effects

A silicon quantum wire transistor, in which electrons are transported through a very narrow wire, has been fabricated using silicon-on-insulator technology, electron beam lithography, anisotropic dry etching, and thermal oxidation. We have obtained the quantum wire with a width of 65 nm, which is fully embedded in silicon dioxide. This narrow dimension of the wire and large potential barrier between silicon and silicon dioxide make the electrons moving through the wire experience one-dimensional confinement. The step-like structure in the conductance versus gate voltage curve, which is a typical evidence of one-dimensional conductance, has been observed at temperatures below 4.2 K. A period of step appearance and a step size have been analyzed to compare experimental characteristics with theoretical calculation.     

A broad theoretical approach to the investigation of mesoscopic electron devices

Nanofabrication technology has matured to a point where it is possible to realize mesoscopic semi-conductor structures with dimensions comparable to the phase coherence length of conducting electrons. Devices based on electron wave phenomena, like quantum interference, must be studied using quantum mechanical methods which are very computationally intensive. We have initially applied a tight-binding Green's function formalism to structures modelled as ideal electron wave-guides, looking at issues related to the realization of three-terminal quantum interference devices and to the more general problem of device interconnection. We also report on a highly efficient two-dimensional algorithm implementation for the self-consistent solution of the coupled Poisson and Schrödinger equations, necessary to investigate subband wavefunctions and energy levels in the cross-section of realistic electron waveguide structures, which we plan to incorporate in the approach.