半导体量子电子和光电子器件

本阐述了半导体异质结构电子的量子特性,如电子波输运,库仑阻塞效应等,介绍了几种新颖,典型的量子电子器件和量子光电子器件的物理模型和基本原理,这些器件包括了单电子晶体管,共振隧穿二极管,高电子迁移率晶体管,δ掺杂场效应晶体管,量子点元胞自动机,量子阱红外探测器,埋沟异质结半导体激光器,量子级联激光器等,给出了作在半导体量子器件物理方面的最新研究结果。     

半导体量子电子和光电子器件

本文阐述了半导体异质结构电子的量子特性 ,如电子波输运、库仑阻塞效应等。介绍了几种新颖、典型的量子电子器件和量子光电子器件的物理模型和基本原理。这些器件包括了单电子晶体管、共振隧穿二极管、高电子迁移率晶体管、δ掺杂场效应晶体管、量子点元胞自动机、量子阱红外探测器、埋沟异质结半导体激光器、量子级联激光器等。给出了作者在半导体量子器件物理方面的最新研究结果。     

量子点器件的三端电测量研究

利用三端电测量方法，研究了调制掺杂二维电子气结构的量子点器件输运特性.报道了可分别测量二维电子气电阻和量子点隧穿电阻的实验方法.实验结果表明：量子点的横向耦合控制了量子点器件在小偏压下的电输运特性. 关键词： 自组装量子点 二维电子气 量子隧穿 肖特基接触     

固态量子比特的量子测量

文章介绍了作者用介观输运器件[如量子点接触（QPC）或单电子晶体管（SET）]测量固态量子比特的原理和特性，特别着重地介绍了作者最近在处理被测量子比特和介观测量仪器之间的关联方面的新进展。     

新型量子器件—共振隧穿二极管和三极管的原理及应用前景

量子器件是近年来电子器件研制的一个前沿领域．本文从电子共振隧穿双势垒的基本概念出发，介绍在此基础上发展起来的一类重要的量子器件，即量子共振隧穿二极管和三极管的基本原理．现在巳有可在室温下工作的这类器件原型，本文以两个具体的实例说明这类新型量子器件作为功能性器件的巨大潜力．     

磁量子结构中二维自旋电子的隧穿输运

研究了零偏压和偏置电压作用下磁量子结构中自旋电子的隧穿输运性质. 结果表明电子自旋 输运的性质不仅取决于磁量子结构的构型、入射电子的能量和波矢, 而且取决于偏置电压. 在零偏压下, 由等同的磁垒磁阱构成的磁量子结构不具有自旋过滤的特点, 而由不等同的磁 垒磁阱构成的磁量子结构却具有较好的自旋过滤特点. 偏置电压极大地改变了磁量子结构中 电子的极化程度, 使得电子隧穿等同的磁垒磁阱构成的磁量子结构的输运性质也显著地依赖 于电子的自旋指向. 关键词： 磁量子结构 自旋电子 隧穿输运 自旋极化     

电子双势垒量子隧穿的散射矩阵方法及其数值模拟

采用散射矩阵的方法研究了电子在由两个方势垒组成的双势垒结构中的隧穿特性.将电子在双势垒中的隧穿过程分为相干输运和非相干输运两部分来研究,相干输运导致了隧穿透射系数随中间层厚度变化产生量子振荡,而非相干输运导致了振荡振幅的衰减.双势垒总的透射系数与势垒高度、入射和出射波矢的匹配性有关,数值计算的结果证实了相关结论.     

导线非共线的分子器件输运性质的第一性原理研究

分子器件是电子器件向小体积化发展的极限,分子器件中的电子在输运过程中体现出明显的量子效应,分子导线与分子接触的位置和导线间的角度等器件结构因素都会对分子器件的输运性质产生较大的影响.迄今为止,尚未见利用第一性原理量子输运计算方法研究导线非共线的分子器件输运性质的报道.本文以金-苯(硫醇)-金结构的分子器件为例,利用基于非平衡格林函数理论和密度泛函理论的第一性原理量子输运计算方法对其输运性质进行了系统研究,特别注重于研究随着非共线导线间导线夹角角度的变化及导线和苯(硫醇)分子接触位置的不同对器件输运性质的影响.计算表明,金导线与苯(硫醇)的接触位置及导线的夹角等器件结构细节不仅能够定量地影响金-苯(硫醇)-金分子器件的电流大小,还能够定性地改变器件的输运性质,使得部分器件结构出现负微分电阻效应.研究结果对全面理解分子器件的输运性质具有一定的指导意义.     

硅纳米结构晶体管中与杂质量子点相关的量子输运

在小于10 nm的沟道空间中,杂质数目和杂质波动范围变得十分有限,这对器件性能有很大的影响.局域纳米空间中的电离杂质还能够展现出量子点特性,为电荷输运提供两个分立的杂质能级.利用杂质原子作为量子输运构件的硅纳米结构晶体管有望成为未来量子计算电路的基本组成器件.本文结合安德森定域化理论和Hubbard带模型对单个、分立和耦合杂质原子系统中的量子输运特性进行了综述,系统介绍了提升杂质原子晶体管工作温度的方法.     

一种新型的高频半导体量子点单电子泵

除了直流负电压外,还在浅法刻蚀出的GaAs/AlGaAs量子线上的两个金属指形门上分别叠加两个相位相差π的正弦信号,从而对形成量子点的两个势垒作不等幅调制.在无源漏偏压的情况下,通过周期形成的量子点实现了单电子的搬运.由于新的半导体量子点单电子泵不是依赖库仑阻塞效应通过隧穿进行单电子输运,因此,该器件就不会受到固定隧穿时间引起的低工作频率限制.在1.7K温度下,频率达到3GHz仍然可以观测到量子化电流平台,对应的电流值达到0.5nA量级.这种新器件提供了实现高速度、高精度搬运单电子的另一种可能途径. 关键词： 单电子输运 单电子旋转门 单电子泵 量子化电流平台     

Coulomb blockade and hopping transport behaviors of donor-induced quantum dots in junctionless transistors

The ionized dopants, working as quantum dots in silicon nanowires, exhibit potential advantages for the development of atomic-scale transistors. We investigate single electron tunneling through a phosphorus dopant induced quantum dots array in heavily n-doped junctionless nanowire transistors. Several subpeaks splittings in current oscillations are clearly observed due to the coupling of the quantum dots at the temperature of 6 K. The transport behaviors change from resonance tunneling to hoping conduction with increased temperature. The charging energy of the phosphorus donors is approximately 12.8 meV. This work helps clear the basic mechanism of electron transport through donor-induced quantum dots and electron transport properties in the heavily doped nanowire through dopant engineering.     

磁电子学器件应用原理

本文介绍几种重要的磁电子器件的基本结构和工作原理,包括巨磁电阻与隧穿磁电阻传感器、巨磁电阻隔离器、巨磁电阻与隧穿磁电阻硬盘读出磁头、磁电阻随机存取存储器、自旋转移磁化反转与微波振荡器。自旋晶体管作为未来磁电子学或自旋电子学时代的基本元素,目前大都还处在概念型阶段,本文也将对几种自旋晶体管的大致原理作简要介绍。     

自旋场效应晶体管中隧道磁阻的势垒相关反转效应

考虑自旋场效应晶体管中Rashba自旋轨道相互作用和自旋输运量子相干性,研究了势垒强度对自旋场效应晶体管的自旋相关量子输运的影响. 研究发现,势垒强度较低时,隧道结电导随Rashba自旋轨道相互作用强度的变化呈现明显的振荡现象,势垒强度较高时,电导表现出明显的势垒相关“电导开关”现象. 当势垒强度逐渐增强时,平行结构电导呈现出单调下降趋势,而反平行结构电导产生波动,这种波动导致该隧道磁阻也随势垒强度的变化表现出振荡现象,且在合适的准一维电子气厚度情况下隧道磁阻值可以产生正负反转,这个效应将会在基于自旋的电子器件信息的存储上获得应用. 关键词： 自旋场效应管 开关效应 量子相干 隧道磁阻     

Non-equilibrium effects and self-heating in single-electron Coulomb blockade devices

We present a comprehensive investigation of non-equilibrium effects and self-heating in single electron transfer devices based primarily on the Coulomb blockade effect. During an electron trapping process, a hot electron maybe deposited in a quantum dot or metal island, with an extra energy usually of the order of the Coulomb charging energy, which is much higher than the temperature in typical experiments. The hot electron may relax through three channels: tunneling back and forth to the feeding lead (or island), emitting phonons, and exciting background electrons. Depending on the magnitudes of the rates in the latter two channels relative to the device operation frequency and to each other, the system may be in one of three different regimes: equilibrium, non-equilibrium, and self-heating (partial equilibrium). In the equilibrium regime, a hot electron fully gives up its energy to phonons within a pump cycle. In the non-equilibrium regime, the relaxation is via tunneling with a distribution of characteristic rates; the approach to equilibrium goes like a power law of time (frequency) instead of an exponential. This channel is plagued completely in the continuum limit of the single-electron levels. In the self-heating regime, the hot electron thermalizes quickly with background electrons, whose temperature T_e is elevated above the lattice temperature T_ol. We have calculated the coefficient in the well-known T⁵ law of energy dissipation rate, and compared the results to experimental values for aluminum and copper islands and for a two-dimensional semiconductor quantum dot. Moreover, we have obtained different scaling relations between the electron temperature, the operation frequency and device size for various types of devices.     

The variably spaced superlattice energy filter

A new superlattice device concept which provides for high energy injection of electrons into a semiconductor layer is presented. The device is based on resonant tunneling of electrons between adjacent aligned quantum well levels in a variably spaced superlattice structure. By a judicial choice of well and barrier widths the energy levels under reverse bias become aligned such that resonant tunneling of electrons through the structure can occur. Thus, electrons are injected into a semiconductor layer at an energy corresponding to the energy of the first subband in the last quantum well. This structure has significant advantages over the conventional method of producing hot electrons in that a nearly monoenergetic high-energy electron distribution is created at low reverse bias and with high efficiency, since energy loss to phonons is inhibited as a consequence of the channeling of electrons through a narrow band of quantum states. Applications of the VSSEF structure to avalanche photodiodes, IMPATT diodes and electroluminescent devices are discussed.     

Fabrication of quantum dot transistors incorporating a single self-assembled quantum dot

We report on the fabrication and the characterization of quantum dot transistors incorporating a single self-assembled quantum dot. The current–voltage characteristics exhibit clear staircase structures at room temperature. They are attributed to electron tunneling through the quantized energy levels of a single quantum dot.     

A quantum electromechanical device: the electromechanical single-electron pillar

A new nanoelectromechanical device is introduced, useful for quantum electromechanics. The focus will be on single-electron transistors with a mechanical degree of freedom. The technical approach as well as the experimental realization of a new vertical mechanical single-electron tunneling device are discussed. This transistor is fabricated in a semiconductor material, forming a nanopillar between source and drain contacts. This concept can readily be transferred to large scale fabrication, being of importance for building integrated sensors and amplifier stages for quantum electromechanical circuits. Operation of the device at room temperature in the frequency range of 350–400 MHz is presented. A straightforward theoretical model of device operation is given.     

Frequency-selective single-photon detection using a double quantum dot

We use a double quantum dot as a frequency-tunable on-chip microwave detector to investigate the radiation from electron shot-noise in a near-by quantum point contact. The device is realized by monitoring the inelastic tunneling of electrons between the quantum dots due to photon absorption. The frequency of the absorbed radiation is set by the energy separation between the dots, which is easily tuned with gate voltages. Using time-resolved charge-detection techniques, we can directly relate the detection of a tunneling electron to the absorption of a single photon.     

Reprint of : Heat pump driven by the shot noise of a tunnel contact

We investigate a mechanism for cooling a lead based on a process that replaces hot electrons by cold ones. The central idea is that a double quantum dot with an inhomogeneous Zeeman splitting acts as energy filter for the transported electrons. The setup is such that hot electrons with spin up are removed, while cold electrons with spin down are added. The required non-equilibrium condition is provided by the capacitive coupling of one quantum dot to the shot noise of a strongly biased quantum point contact in the tunneling limit. Special attention is paid to the identification of an operating regime in which the net electrical current vanishes.