单岛单电子晶体管的电导分析

基于单电子经典理论,本文通过分析得出了单岛单电子晶体管的源漏电导模型,并对其进行了详细的分析讨论.单岛单电子晶体管的源漏电导随着源漏电压的变化发生周期性的振荡衰减,并随着源漏电压的增大逐渐收敛于本征电导值.源漏电导的这种特性受温度、结电阻、结电容等参数的影响.分析结果表明,源漏电导分析模型对单电子晶体管的大规模应用具有非常重要的意义. 关键词： 单电子晶体管 电导 库仑振荡 库仑阻塞     

库仑阻塞现象及其在纳米电子器件中的应用

对单隧穿结和双隧穿结中的库仑阻塞现象进行了介绍,分析了其中电子隧穿的物理过程;然后探讨在单电子盒中如何利用库仑阻塞控制单电子隧穿的物理原理;最后介绍库仑阻塞效应在单电子晶体管中的具体应用及其发展前景.     

单电子三势垒隧穿结I-V特性研究

在正统理论的基础上，提出了单电子三势垒隧穿结模型的主方程，并用线性方程组解法求出了其稳态解.通过数值模拟，得到了该系统的I-V特性曲线.发现其有别于双势垒隧穿结的情况，在传统库仑台阶的平台处曲线存在波纹状结构，分析得出这是由于第二个库仑岛上的电子数变化对I-V曲线的影响.此外，研究了各物理参数对I-V曲线的影响，发现三结系统可以降低对温度的要求，并应用Fermi能级处的能级间隔估算出出现库仑台阶现象的最高温度Tmax，为相关单电子器件的参数选择提供了理论依据. 关键词： 正统理论 库仑台阶 主方程 隧穿概率     

单电子效应与单电子晶体管

由于半导体超微细加工技术的发展，在半径为几百ｎｍ的量子点结构上观察到由单个电子的阻塞和隧穿引起的电流振荡，分别称为库仑阻塞，单电子隧穿和库仑振荡，与此效应有关的现象还有库仑台阶，旋转门效应，旋转门器件可利用作为电流标准测量，单电子晶体管将是下世纪大容量存贮器的最好选择，单电子效应的研究将开辟一门新的“人造原子物理学”。     

单电子晶体管通断图及其分析

通过研究单电子晶体管在电路中的静电能量的变化,得到了它的阻塞、导通情况与其两端偏压和控制栅压之间的关系,从而给出了它的通断图.并且发现单电子晶体管的对外特性主要由其对外的总电容决定;而单电子岛两个隧道结电容的不同主要反映在通断图上由隧道结电容所决定的晶体管阻塞、导通边界线上,这两条边界线同时也与外电路有关 关键词： 单电子晶体管 库仑阻塞 隧穿     

多岛单电子晶体管的实现及其源漏特性分析

在淀积有纳米间隙栅电极、源电极和漏电极的衬底上生长量子点，制作出多岛结构的单电子晶体管.在77K温度下对源漏特性进行了测试，得到了库仑阻塞特性.并且成功抑制了单岛单电子晶体管中易出现的共隧穿效应，观察到较大的库仑阈值电压.对试验数据进行了分析，阐明了岛的不同结构组态产生的不同输运效果. 关键词： 单电子晶体管 量子点 库仑阻塞     

介观LC电路中的量子隧道效应

考虑到电子在纳米电容器中的运动是一个单电子隧穿过程,因而将电容器作为一个隧道结,应用隧道模型的稳态法,研究了介观LC电路中的电流电压特性.结果表明:由于库仑力的作用,介观LC电路中存在着阈值电压.当外加电压小于阈值电压时,隧穿电流为零,显示出库仑阻塞现象;当外加电压远大于阈值电压时,隧穿电流与电压成正比. 关键词： 介观LC电路 库仑阻塞 单电子隧道过程     

基于库仑阻塞原理的多值存储器

设计了一种基于库仑阻塞原理的新型单电子多值存储器.器件包括两个多隧穿结结构和一个单电子晶体管，其中单电子晶体管起到一个静电计的作用来实现数据的读取.两个隧穿结库仑阻塞区域的大小不同使得器件具有三个稳定的存储状态.利用这个原理可以制备出多值的动态随机存储器和非挥发性的随机存储器.这种低功耗的单电子多值存储器可以实现信息的超高密度存储. 关键词： 库仑阻塞 单电子晶体管     

双栅调控的硅量子线中的库仑振荡效应

基于单电子隧穿和库仑阻塞效应,研究了硅量子线中的单电子输运特性.利用绝缘体上硅薄膜材料作为衬底构建侧栅结构的硅量子线单电子晶体管,通过背栅和侧栅对量子线的电子输运特性进行调制.实验发现,在硅量子线中分别观察到背栅和侧栅调制的单电子效应和库仑振荡现象.从微分电导的二维灰度轮廓图,清楚地观察到了库仑阻塞区,说明由于栅压导致在硅量子线中形成了库仑岛. 关键词： 库仑振荡 单电子效应 硅量子线     

高电子迁移率晶体管放大器高功率微波损伤机理

在TCAD半导体仿真环境中,建立了0.25 m栅长的AlGaAs/InGaAs高电子迁移率晶体管(HEMT)低噪声放大器与微波脉冲作用的仿真模型,基于器件内部的电场强度、电流密度和温度分布的变化,研究了1 GHz的微波从栅极和漏极注入的损伤机理。研究结果表明,从栅极注入约40.1 dBm的微波时,HEMT内部峰值温度随着时间的变化振荡上升,最终使得器件失效,栅下靠源侧电流通道和强电场的同时存在使得该位置最容易损伤;从漏极注入微波时,注入功率的高低会使器件内部出现不同的响应过程,注入功率存在一个临界值,高于该值,器件有可能在第一个周期内损伤,损伤位置均在漏极附近。在1 GHz的微波作用下,漏极注入比栅极注入更难损伤。     

Resonant tunneling single electron transistors

We use a modulation-doped double barrier heterostructure to fabricate a resonant tunneling single electron transistor. Irregular Coulomb blockade oscillations are observed when the gate voltage is swept to vary one-by-one the number of electrons in the dot close to 'pinch-off'. The oscillation period is not regular, and generally becomes longer as the electron number is decreased down to zero, reflecting the growing importance of electron-electron interactions and size quantization. Negative differential resistance associated with resonant tunneling through zero-dimensional states is pronounced for a dot holding just a few electrons. The temperature dependence of the Coulomb blockade oscillations and that for the negative differential resistance are not the same. This highlights the different effects of charging and resonant tunneling on the transport characteristics.     

Carrier conduction in a Si-nanocrystal-based single-electron transistor-I. Effect of gate bias

We have successfully fabricated a single-electron transistor based on undoped Si nanocrystals having radii of approximately 3 nm. Gate voltage oscillation was observed from low temperature to room temperature and Coulomb diamonds found to decrease in size with increasing gate voltage. The 3D calculation of the energy band structure of the Si nanocrystals and the interactions among the nanocrystals shows the increase of the quantum confinement effect when the dimensionality of the system decreases. At the same time the reduction in the dimensionality causes a decrease in the interaction among nanocrystals in an exponential manner. The carrier transport properties observed experimentally have been well understood in terms of carrier tunneling and Coulomb blockade effects. It is concluded that for the present single-electron transistor, the energy separation of the first excited sublevel and the ground state is rather large so that the Coulomb diamonds observed in the carrier transport characteristics are determined mainly by the Coulomb charging effect.     

Single-electron tunneling and Coulomb blockade in carbon-based quantum dots

Single-electron tunneling (SET) and Coulomb blockade (CB) phenomena have been widely observed in nanoscaled electronics and have received intense attention around the world. In the past few years, we have studied SET in carbon nanotube fragments and fullerenes by applying the so-called “Orthodox” theory [28]. As outlined in this review article, we investigated the single-electron charging and discharging process via current-voltage characteristics, gate effect, and electronic structure-related factors. Because the investigated geometric structures are three-dimensionally confined, resulting in a discrete spectrum of energy levels resembling the property of quantum dots, we evidenced the CB and Coulomb staircases in these structures. These nanostructures are sufficiently small that introducing even a single electron is sufficient to dramatically change the transport properties as a result of the charging energy associated with this extra electron. We found that the Coulomb staircases occur in the I–V characteristics only when the width of the left barrier junction is smaller than that of the right barrier junction. In this case, the transmission coefficient of the emitter junction is larger than that of the collector junction; also, occupied levels enter the bias window, thereby enhancing the tunneling extensively.      

Out-of-equilibrium admittance of single electron box under strong Coulomb blockade

We study admittance and energy dissipation in an out-of-equilibrium single electron box. The system consists of a small metallic island coupled to a massive reservoir via single tunneling junction. The potential of electrons in the island is controlled by an additional gate electrode. The energy dissipation is caused by an AC gate voltage. The case of a strong Coulomb blockade is considered. We focus on the regime when electron coherence can be neglected but quantum fluctuations of charge are strong due to Coulomb interaction. We obtain the admittance under the specified conditions. It turns out that the energy dissipation rate can be expressed via charge relaxation resistance and renormalized gate capacitance even out of equilibrium. We suggest the admittance as a tool for a measurement of the bosonic distribution corresponding collective excitations in the system.     

Proximity effect of electron beam lithography on single-electron transistors

A simple method, based on the proximity effect of electron beam lithography, alleviated by exposing various shapes in the pattern of incident electron exposures with various intensities, was applied to fabricate silicon point-contact devices. The drain current (I _d) of the device oscillates against gate voltage. The electrical characteristics of the single-electron transistor were observed to be consistent with the expected behavior of electron transport through gated quantum dots, up to 150 K. The dependence of the electrical characteristics on the dot size reveals that the I _d oscillation follows from the Coulomb blockade by poly-Si grains in the poly-Si dot. The method of fabrication of this device is completely compatible with complementary metal-oxide-semiconductor technology, raising the possibility of manufacturing large-scale integrated nanoelectronic systems.     

Suppression of the tunneling effect by shallow junctions in field-effect transistor

We study the quantum wave transport in nanoscale field-effect transistors. It has been shown that the tunneling effect between the source and the drain in an ultra-short channel transistor significantly degrades the control of the drain current by the gate. However, the tunneling effect is suppressed by reducing the depth of the source and drain junctions which is designated to suppress the short-channel effects concerning the cut-off characteristics of the field-effect transistor. The reduced junction depth confines the carriers in the direction (y -direction) perpendicular to the transport direction (x -direction). The matching of y -direction wavefunctions at regional boundaries suppresses the tunneling effect and normal FET current–voltage characteristics has been obtained, which explains theoretically the successful fabrication of nanoscale field-effect transistors.     

Channel temperature determination of multifinger AlGaN/GaN high electron mobility transistor using micro-Raman technique

Self-heating in multifinger AlGaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy. The device temperature is probed on the die as a function of applied bias. The operating temperature of AlGaN/GaN HEMT is estimated from the calibration curve of passively heated AlGaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1 ℃ is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge.     

Size-dependent single electron tunneling effect in Au nanoparticles

We investigated single electron tunneling (SET) behavior of dodecanethiol-coated Au nanoparticles of two different sizes (average sizes are 5 nm and 2 nm) using nanogap electrodes, which have a well-defined gap size, at various temperatures. The Coulomb staircases and the Coulomb gap near-zero bias voltage caused by the suppression of the tunneling electrons due to the Coulomb blockade effect were observed in the current-voltage (I-V) curves of both sizes of nanoparticles at a low temperature (10 K). At room temperature, the Coulomb gap was observed only in the I-V curve of the smaller nanoparticles. This result indicates that the charging energy of the smaller nanoparticles is enough to overcome the thermal energy at room temperature. This suggests that it is possible to operate the SET devices at room temperature using the smaller nanoparticles as a Coulomb island.     

Tunneling spectroscopy of isolated gold clusters grown on thiol/dithiol mixed self-assembled monolayers

We report a scanning tunneling spectroscopy study on the size-tunable isolated gold nanoclusters grown on thiol/dithiol mixed self-assembled monolayers (SAMs) where the effect of neighboring clusters are practically excluded. The structure forms double tunnel junction system in which the spectra exhibit Coulomb staircases. With increasing cluster size the standard deviation of the offset charge distribution for clusters increases, accompanied with the increase of total capacitance. The results are qualitatively same with the previous ones where clusters are densely grown on the substrate, indicating that this behavior is an intrinsic property for the double tunnel junction structures of tip/vacuum/single cluster/SAMs/Au(1 1 1) systems.     

Channel temperature determination of a multifinger AlGaN/GaN high electron mobility transistor using a micro-Raman technique

Self-heating in a multifinger AlGaN/GaN high electron mobility transistor (HEMT) is investigated by micro-Raman spectroscopy. The device temperature is probed on the die as a function of applied bias. The operating temperature of the AlGaN/GaN HEMT is estimated from the calibration curve of a passively heated AlGaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1°C is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge.