光电耦合器电离辐射损伤电流传输比1/f噪声表征

在研究光电耦合器电离辐射损伤机理基础上,分别建立光电耦合器电离辐射损伤电流传输比(CTR)表征模型和1/f噪声表征模型.结果表明CTR退化和噪声增加都归因于辐射后光敏三极管集电结和发射结处SiO₂/Si界面缺陷增多.根据CTR退化和噪声变化分别与辐射剂量的关系,建立起噪声变化与CTR退化之间的关系,辐照实验对表征模型正确性进行了验证.运用噪声变化与辐射剂量的关系,通过低剂量辐照实验可以预测高剂量辐射后光电耦合器退化程度,故可用于评价光电耦合器抗辐射能力. 关键词： f噪声')" href="#">1/f噪声 光电耦合器 缺陷 模型     

60Co γ-射线辐照对肖特基二极管1/f噪声的影响

在肖特基二极管(Schottky barrier diode,SBD)辐照损伤机理和总剂量效应分析的基础上,利用1/f噪声的迁移率涨落和载流子数涨落模型,深入研究辐照损伤对器件1/f噪声的影响. 研究结果表明,辐照诱生新的界面态,改变界面态密度分布,进而调制了肖特基势垒高度,增大表面复合速度是引起器件性能退化主要原因,也是1/f噪声剧烈增加的主要原因. 正因为如此,噪声与器件退化存在相关性,即噪声拟合参数B越大,偏离标准值越多,器件可靠性越差,抗辐照 关键词： 肖特基二极管 f噪声')" href="#">1/f噪声 60Co γ射线')" href="#">⁶⁰Co γ射线 界面态     

Si1-xGex合金半导体中CiCs和CiOi缺陷随Ge含量的变化

采用从头计算(ab initio)的方法对Si和Si_1-xGe_x合金半导体材料中C_iC_s缺陷的性质进行探讨,同时也对比调查了C_iO_i缺陷在Si和Si_1-xGe_x合金中的性质. 在不同Ge含量的Si_1-xGe_{x关键词： 1-x}Ge_x合金')" href="#">Si_1-xGe_x合金 从头计算法 iC_s缺陷')" href="#">C_iC_s缺陷 iO_i缺陷')" href="#">C_iO_i缺陷     

基于小波变换和维纳滤波的半导体器件1/f噪声滤波

针对半导体器件中普遍存在的1/f噪声提出了一种结合了提升小波变换和维纳滤波器的处理方法.首先利用重新加权迭代最小二乘法拟合1/f噪声的功率谱曲线得到噪声参数的估计,从而选择恰当的小波.其次,对包含了1/f噪声的信号进行提升小波变换.考虑到小波变换对1/f噪声的白化作用,利用维纳滤波器对每一层小波系数进行处理.设计了最优全通滤波器以校正维纳滤波器的相频特性,使得小波系数经滤波后相位不变.最后利用提升小波逆变换获得被1/f噪声淹没的信号.利用实验检验了提出方法的有效性,实验数据采自用于微创外科手术机器人的力传感器.结果表明提出的方法能够有效抑制1/f噪声,并使传感器的分辨力提高了25%. 关键词： 半导体器件 f噪声')" href="#">1/f噪声 提升小波变换 维纳滤波     

光电耦合器件1/f噪声和g-r噪声的机理研究

对光电耦合器件1/f噪声和g-r噪声(产生－复合噪声) 的偏置特性及其产生机理进行了实验和理论研究.结果表明：在低频段,光电耦合器件的g-r噪声通常表现为叠加1/f噪声,且两者均随输入电流的增加呈现先增大后减小的规律.通过测量前级噪声和后级噪声,发现光电耦合器件的g-r噪声源为后级光敏三极管.理论分析表明：光电耦合器件的1/f噪声主要为表面1/f噪声,g-r噪声则源于光敏三极管发射结空间电荷区的深能级对载流子的俘获和发射.     

氮化镓基蓝光发光二极管伽马辐照的1/f噪声表征

通过电离辐照对氮化镓基蓝光发光二极管器件有源区光/暗电流产生机制的研究, 建立了电离辐照减小发光二极管有效输出功率电学模型.通过电离辐照对氮化镓基蓝光发光 二极管器件有源区1/f噪声影响机制的研究, 建立了电离辐照增大发光二极管1/f噪声的相关性模型.在I < 1 μA 的小注入区,空间电荷区的复合电流随辐照剂量的增加而增加. 同时, 随着电离辐照产生缺陷的增加, 1/f噪声幅度增大. 在 I> 1 mA 的大注入条件下, 由于串联电阻的影响占主导地位,表面复合速率和电流随辐照剂量的增加而增加.同时, 随着电离辐照产生缺陷的增加, 1/f噪声幅度增大.根据辐照前后电流电压试验结果噪声测试结论, 证实了实验结论与理论推导结果的一致性. 在1 μA < I < 5×10^-5 A 的中值电流情况下, 由于高能载流子散射相关的迁移率涨落与辐照新增缺陷引起的载流子数涨落竞争机制, 随着辐照剂量增大, 1/f噪声在频域变化没有明显规律. 但是, 通过1/f噪声时域多尺度熵复杂度分析方法, 得出随着辐照剂量增大, 1/f噪声时域多尺度熵复杂度的结果. 最终证实1/f噪声幅度可以敏感地反映小注入和大注入情况下氮化镓基蓝光发光二极管电离辐照的可靠性. 噪声幅值越大, 则说明辐照感应N_it越高, 暗电流相关的复合电流越大, 光电流相关的扩散电流比例减少, 使得器件发光效率、光输出功率等性能参数下降, 继而影响器件可靠性, 造成失效率显著增大. 1/f噪声时域多尺度熵复杂度可以敏感地反映中值电流情况下氮 化镓基蓝光发光二极管的电离辐照可靠性.多尺度熵复杂度越大, 则说明辐照感应越多, 复合电流越大,器件可靠性越差.本文结论提供了一种基于 1/f噪声的氮化镓基蓝光发光二极管电离辐照可靠性表征方法. 关键词： f噪声')" href="#">1/f噪声 电离辐照 氮化镓基蓝光发光二极管     

单壁BC3纳米管晶格动力学研究

基于力常数模型计算了一系列扶手椅型、锯齿型和手性单壁BC₃纳米管的声子色散关系.描述了单壁BC₃纳米管结构的表征方式,比较详细地给出了其结构、对称性和晶格动力学分析.基于数值计算结果,讨论了拉曼活性模和红外活性振动模的频率与管径的关系.由分析结果做出推断,BC₃纳米管的拉曼光谱和红外光谱比单壁碳纳米管更为复杂. 关键词： 3纳米管')" href="#">BC₃纳米管 声子色散关系 晶格动力学     

LaNi5储氢过程的热力学分析

分析了LaNi₅储氢过程的热力学平衡关系，根据平衡状态下的热力学函数，导出了能够完整描述整个实验范围P-C-T关系的平衡公式. 利用P-C-T平衡公式对不同温度下平衡压力与储氢量的变化曲线进行了拟合分析, 计算并讨论了储氢过程中平衡反应的热力学函数. 关键词： 5')" href="#">LaNi₅ 热力学 P-C-T 关系')" href="#">P-C-T 关系     

金属氧化物半导体场效应管热载流子退化的1/fγ噪声相关性研究

研究了金属氧化物半导体(MOS)器件在高、中、低三种栅压应力下的热载流子退化效应及其1/f^γ噪声特性.基于Si/SiO₂界面缺陷氧化层陷阱和界面陷阱的形成理论,结合MOS器件1/f噪声产生机制,并用双声子发射模型模拟了栅氧化层缺陷波函数与器件沟道自由载流子波函数及其相互作用产生能级跃迁、交换载流子的具体过程.建立了热载流子效应、材料缺陷与电参量、噪声之间的统一物理模型.还提出了用噪声参数Sf ^{关键词： 金属氧化物半导体场效应管 热载流子 fγ噪声')" href="#">1/fγ噪声}     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管辐照退化模型

基于金属-氧化物-半导体场效应晶体管(MOSFET)噪声的载流子数涨落和迁移率涨落理论,建立了MOSFET辐照前1/f噪声参量与辐照后分别由氧化层陷阱和界面陷阱诱使阈值电压漂移之间的定量数学模型,并通过实验予以验证.研究结果表明,辐照诱生的氧化层陷阱通过俘获和发射过程与沟道交换载流子,在引起载流子数涨落的同时也通过库仑散射导致沟道迁移率的涨落,因此辐照前的1/f噪声幅值正比于辐照诱生的氧化层陷阱数.利用该模型对MOSFET辐照前1/f噪声与辐照退化的相关性从理论上 关键词： f噪声')" href="#">1/f噪声 辐照 金属-氧化物-半导体场效应晶体管 陷阱     

I/f noise in systems showing stochastic resonance

Stochastic resonator systems with input and/or output 1/f noise have been studied. Disordered magnets/dielectrics serve as examples for the case of output 1/f noise with white noise (thermal excitation) at the input of the resonators. Due to the fluctuation-dissipation theorem, the output noise is related to the out-of-phase component of the periodic peak of the output spectrum. Spin glasses and ferromagnets serve as interesting examples of coupled stochastic resonators. A proper coupling can lead to an extremely large signal-to-noise ratio. As a model system, a l/f-noise-driven Schmitt trigger has been investigated experimentally to study stochastic resonance with input 1/f noise. Under proper conditions, we have found several new nonlinearity effects, such as peaks at even harmonics, holes at even harmonics, and 1/f noise also in the output spectrum.     

Current noise and long time tails in biased disordered random walks

We calculate the mean velocity and the velocity correlation function for a random walk with a uniform bias on a disordered chain. We find a new long time tail in the velocity correlation function due to the combined effects of the bias and of the disorder in the site variables. This long time tail persists to a low-frequency cutoff inversely proportional to the square of the bias. By associating the velocity correlation function with the spectrum of current fluctuations, we calculate the excess low-frequency current noise associated with this long time tail. The spectrum of current fluctuations goes as(I ²/N)f ^–1/2, whereI is the DC current,N is the number of charge carriers, andf is the frequency. The possible connection to 1/f noise is discussed. The calculation is done by a perturbation expansion in the strength of the disorder, but is shown to be exact to all orders for weak enough bias.Supported by a fellowship of the German Academic Exchange Service (DAAD).Supported by the National Science Foundation through Grant No. DMR-8108328 and through the Cornell Materials Science Center.     

Flicker noise in degenerately doped Si single crystals near the metal-insulator transition

In this paper we report some of the important results of experimental investigations of the flicker noise near the metal-insulator (MI) transition in doped silicon single crystals. This is the first comprehensive work to study low-frequency noise in heavily doped Si over an extensive temperature range (2 K<T<500 K). The measurements of conductance fluctuations (flicker noise) were carried out in the frequency range 10⁻²<f<4 × 10¹ Hz in single crystalline Si across the MI transition by doping with phosphorous and boron. The magnitude of noise in heavily doped Si is much larger than that seen in lightly doped Si over the whole temperature range. The extensive temperature range covered allowed us to detect two distinct noise mechanisms. At low temperatures (T<100 K) universal conductance fluctuations (UCF) dominate and the spectral dependence of the noise is determined by dephasing the electron from defects with two-levels (TLS). At higher temperatures (T>200 K) the noise arises from activated defect dynamics. As the MI transition is approached, the 1/f spectral power, typical of the metallic regime, gets modified by the presence of discrete Lorentzians which arise from generation-recombination process which is the characteristic of a semiconductor.     

Quality assessments of electrochromic devices: the possible use of 1/<Emphasis Type="Italic">f</Emphasis> current noise

Electrochromic (EC) devices, capable of modulating their optical transmittance by charge insertion/extraction, were produced by laminating films comprised of nanoporous W oxide and Ni–V oxide by a polymer electrolyte and having this three-layer stack between transparent conducting In₂O₃:Sn films backed by polyester foils. 1/f noise in the current (I) was observed when the charged (colored) EC device was discharged via a resistor. The power spectral density S _i at fixed frequency scaled as S _i  ∼ I ². Extended color/bleach cycling degraded the optical quality and homogeneity of the device and concomitantly increased the 1/f noise intensity. These initial data indicate that 1/f noise has a potential to serve as a quality measure for EC devices.     

基于辐照前1/f噪声的金属-氧化物-半导体场效应晶体管潜在缺陷退化模型

基于金属-氧化物-半导体-场效应管(MOSFET)辐射损伤的微观机理,推导出了MOSFET经历辐照之后氧化层空穴俘获与阈值电压漂移之间关系的表达式.又根据MOSFET中1/f噪声产生的微观机理,建立了辐照之前MOSFET的1/f噪声功率谱幅值与阈值电压漂移量之间的定量关系,并通过实验予以验证.结果表明,辐照之前的1/f噪声功率谱幅值与辐照之后的阈值电压漂移量存在正比例关系,阈值电压漂移量可以反映出MOSFET内部的潜在缺陷的退化程度,因此,该模型有助于利用1/f噪声参量来表征MOSFET内部潜在缺陷的数量和严重程度.