部分耗尽结构绝缘体上硅器件的低频噪声特性

针对部分耗尽结构绝缘体上硅(silicon-on-insulator, SOI)器件低频噪声特性展开实验与理论研究. 实验结果表明, 器件低频噪声主要来源于SiO₂-Si界面附近缺陷态对载流子的俘获与释放过程; 基于此理论可提取前栅和背栅氧化层界面附近缺陷态密度分别为8×10¹⁷ eV^-1·cm^-3和2.76×10¹⁷ eV^-1·cm^-3. 基于电荷隧穿机理, 在考虑隧穿削弱因子、隧穿距离与时间常数之间关系的基础上, 提取了前、背栅氧化层内缺陷态密度随空间的分布情况. 此外, SOI器件沟道电流归一化噪声功率谱密度随沟道长度的增加而线性减小, 这表明器件低频噪声主要来源于沟道的闪烁噪声. 最后, 基于电荷耦合效应, 分析了背栅电压对前栅阈值电压、沟道电流以及沟道电流噪声功率谱密度的影响.     

Barkhausen noise studies in amorphous materials at vanishing anisotropies

In this work, Barkhausen noise measurements are shown for the amorphous ribbons Metglas 2605TCA and Fe_73.5Cu₁Nb₃Si_18.5B₄ FINEMET material which is the amorphous precursor of the well-known nanocrystalline material, under different stress, annealing and magnetizing frequency conditions. These parameters were varied in search for different dynamical regimes of the complex system composed by the set of domain walls interacting with a reservoir of defects.     

铟锌氧化物薄膜晶体管局域态分布的提取方法

本文针对铟锌氧化物薄膜晶体管(IZO TFT)的低频噪声特性与变频电容-电压特性展开试验研究,基于上述特性对有源层内局域态密度及其在禁带中的分布进行参数提取.首先,基于IZO TFT的亚阈区I-V特性提取器件表面势随栅源电压的变化关系.基于载流子数随机涨落模型,在考虑有源层内缺陷态俘获/释放载流子效应基础上,通过γ因子提取深能态陷阱的特征温度;基于沟道电流噪声功率谱密度及平带电压噪声功率谱密度的测量,提取IZO TFT有源层内局域态密度及其分布.试验结果表明,带尾态缺陷在禁带内随能量呈e指数变化趋势,其导带底密度N1TA约为3.42×10~(20)cm~(-3)·eV-,特征温度TTA约为135 K.随后,将C-V特性与线性区I-V特性相结合,对栅端寄生电阻、漏端寄生电阻、源端寄生电阻进行提取与分离.在考虑有源层内局域态所俘获电荷与自由载流子的情况下,基于变频C-V特性对IZO TFT有源层内局域态分布进行参数提取.试验结果表明,深能态与带尾态在禁带内随能量均呈e指数变化趋势,深能态在导带底密度NDA约为5.4×10~(15)cm~(-3)·eV~(-1),特征温度TDA约为711 K,而带尾态在导带底密度NTA约为1.99×10~(20)cm~(-3)·eV~(-1),特征温度TTA约为183 K.最后,对以上两种局域态提取方法进行对比与分析.     

氢化非晶硅薄膜晶体管的低频噪声特性

针对氢化非晶硅薄膜晶体管(hydrogenated amorphous silicon thin film transistor,a-Si:H TFT)的低频噪声特性展开实验研究.由测量结果可知,a-Si:H TFT的低频噪声特性遵循1/f~γ(f为频率,γ≈0.92)的变化规律,主要受迁移率随机涨落效应的影响.基于与迁移率涨落相关的载流子数随机涨落模型(?N-?μ模型),在考虑源漏接触电阻、局域态俘获及释放载流子效应等情况时,对器件低频噪声特性随沟道电流的变化进行分析与拟合.基于a-Si:H TFT的亚阈区电流-电压特性提取器件表面能带弯曲量与栅源电压之间的关系,通过沟道电流噪声功率谱密度提取a-Si:H TFT有源层内局域态密度及其分布.实验结果表明:局域态在禁带内随能量呈e指数变化,两种缺陷态在导带底密度分别约为6.31×10~(18)和1.26×10~(18)cm~(-3)·eV~(-1),特征温度分别约为192和290 K,这符合非晶硅层内带尾态密度及其分布特征.最后提取器件的平均Hooge因子,为评价非晶硅材料及其稳定性提供参考.     

一种用于铷原子频标的小型化低噪声10 MHz晶体振荡器设计

本文设计了一种应用于铷原子频标的小型化低噪声石英晶体振荡器,其振荡电路采用柯尔匹兹并联形式和SC切晶体谐振器.基于Leeson模型对石英晶体振荡器相位噪声进行分析,并利用ADS射频仿真软件对振荡电路进行仿真模拟,为振荡器设计与调试提供指导.最终实现体积为22 mm×28.5 mm×13 mm低噪声晶体振荡器,它具有良好的相位噪声特性,其近端相噪为−102.7 dBc/Hz@1 Hz、远端相噪为−164.2 dBc/Hz@10 kHz,且实测短期频率稳定度为1.73×10⁻¹²/s.     

Development of series SQUID array with on-chip filter for TES detector

A cold preamplifier based on superconducting quantum interference devices(SQUIDs)is currently the preferred readout technology for the low-noise transition edge sensor(TES).In this work,we have designed and fabricated a series SQUID array(SSA)amplifier for the TES detector readout circuit.In this SSA amplifier,each SQUID cell is composed of a first-order gradiometer formed using two equally large square washers,and an on-chip low pass filter(LPF)as a radiofrequency(RF)choke has been developed to reduce the Josephson oscillation interference between individual SQUID cells.In addition,a highly symmetric layout has been designed carefully to provide a fully consistent embedded electromagnetic environment and achieve coherent flux operation.The measured results show smooth V-Φcharacteristics and a swing voltage that increases linearly with increasing SQUID cell number N.A white flux noise level as low as 0.28μφ;/Hz;is achieved at 0.1 K,corresponding to a low current noise level of 7 pA/Hz;.We analyze the measured noise contribution at mK-scale temperatures and find that the dominant noise derives from a combination of the SSA intrinsic noise and the equivalent current noise of the room temperature electronics.     

TMR与GMR传感器1/f噪声的研究进展

隧道结磁阻(TMR) 传感器及巨磁阻(GMR) 传感器的1/f噪声在低频段噪声功率密度较大, 是影响其低频下分辨率和灵敏度的主要噪声形式. 本文详细介绍了近年来TMR传感器及GMR传感器1/f噪声的特点、来源、理论模型、检测方法及降噪措施等方面的研究进展, 并就隧道结磁阻传感器1/f噪声的物理模型进行了详细解释. 通过纳米模拟软件Virtual NanoLab对不同MgO厚度的Fe/MgO/Fe型磁性隧道结(MTJ) 进行了隧穿概率和TMR变化率的模拟计算, 得到保守估计与乐观估计的TMR变化率, 分别为98.1%与10324.55%, 同时通过MTJ的噪声模型分析了MgO厚度对TMR传感器噪声的影响. 制备了磁屏蔽系数大于10000的磁屏蔽筒并搭建了磁阻传感器1/f噪声的测试平台, 通过测试验证了磁屏蔽系统对环境磁场具有较好的屏蔽效果, 为噪声检测提供了稳定的磁场空间. 最后分析了TMR与GMR中各种因素对传感器噪声的影响, 提出了影响MTJ传感器1/f噪声的因素及一些降噪措施.     

Simulation and evaluation of phase noise for optical amplification using semiconductor optical amplifiers in DPSK applications

A thorough simulation and evaluation of phase noise for optical amplification using semiconductor optical amplifier (SOA) is very important for predicting its performance in differential phase-shift keyed (DPSK) applications. In this paper, standard deviation and probability distribution of differential phase noise at the SOA output are obtained from the statistics of simulated differential phase noise. By using a full-wave model of SOA, the noise performance in the entire operation range can be investigated. It is shown that nonlinear phase noise substantially contributes to the total phase noise in case of a noisy signal amplified by a saturated SOA and the nonlinear contribution is larger with shorter SOA carrier lifetime. It is also shown that Gaussian distribution can be useful as a good approximation of the total differential phase noise statistics in the whole operation range. Power penalty due to differential phase noise is evaluated using a semi-analytical probability density function (PDF) of receiver noise. Obvious increase of power penalty at high signal input powers can be found for low input OSNR, which is due to both the large nonlinear differential phase noise and the dependence of BER vs. receiving power curvature on differential phase noise standard deviation.     

全频域下窄线宽激光器光谱线宽的分析

窄线宽激光器的线宽表征方式通常采用延时自外差法测量技术。该技术是通过延时光纤差拍产生一个与待测激光线宽相关的洛伦兹频谱,因此该频谱只具有单一的线宽表现形式。为了能够观察到激光器的线宽和频率噪声在其傅里叶频率分布下的完整特性,报道了一种基于β算法计算窄线宽激光器线宽的方法。该方法是结合频率噪声中的白噪声和1/f噪声分别诱导不同激光线型的理论,从而确定激光线宽。首先,对β算法的基本原理进行了详细的分析说明。通过基于维纳-辛钦定理,分析了窄线宽激光器不同频率范围内的频率噪声和激光线宽的依赖关系。阐明了在截止频率趋于0和无穷大的两个范围条件时,激光频谱特性从高斯线型向洛伦兹线型演变。同时推导出使两种线型转换的截止频率表达式,并将其转换为频率噪声函数,该函数定义为β分子线。此时频率噪声分量中高斯线型的总和即为激光线宽计算公式;其次,对窄线宽激光器的频率噪声和激光线型进行数值仿真。将通过OEwaves公司的OE4000互相关零差相位/频率噪声自动测试系统测得的频率噪声谱密度,带入β算法理论公式中。结果显示：1/f噪声导致激光呈现高斯线型,线宽随截止频率的增加而增大。而白噪声将导致洛伦兹线型,线宽不再随截止频率而改变。此外,在低频区域,频率噪声电平远大于其傅里叶频率,噪声调制系数较高,该部分噪声可以决定线宽大小。因此,高斯线型区域对应的频率噪声的积分,即为待测激光器的线宽;在高频区域,频率噪声电平与其傅里叶频率相差较小,频率波动较快,噪声对线宽影响可以忽略。并且频率带宽在截止频率范围内,计算的线宽误差较小。最后,实验上运用β算法对RIO公司的1 550 nm低噪声窄线宽激光器的频率噪声功率谱密度进行积分计算,成功获得了其不同傅里叶频率分布下对应的激光线宽值。其中β分子线将频率噪声中的白噪声和1/f噪声分隔两部分：当频率噪声谱密度大于β分子线时,激光即为高斯线型,线宽随频率积分带宽的增加而减少;而频率噪声谱密度小于β分子线时,激光呈现洛伦兹线型,线宽为定值不再改变。同时为了对β算法进行实验验证,搭建了延迟光纤为50 km、移频频率为60 MHz的延时自外差法测量系统。对注入电流为110 mA的RIO 1 550 nm低噪声窄线宽激光器的线宽进行实验测量,测量结果表明激光线宽为1.8 kHz,与上述β算法中2.8 kHz的频率带宽积分结果一致。充分证明了此算法的准确性。β算法可以对任意类型的窄线宽激光器进行线宽表征,对窄线宽激光器的研究具有重要意义。     

静电放电对功率肖特基二极管I-V及低频噪声特性的影响

本文基于人体放电模型分别对肖特基势垒二极管的阴极和阳极进行同一电压脉冲下的多次放电, 利用热电子发射理论、1/f噪声的迁移率涨落模型和白噪声理论, 分别深入研究静电放电损伤对器件I-V和低频噪声的影响. 结果表明, 静电放电作用于肖特基二极管阴极时损伤更严重, 噪声参量变化率更大. 随着放电次数的增加, 正向特性无变化, 反向电流总体增大, 偶有减小; 而正向和反向 1/f噪声均增大. 鉴于噪声与应力条件下器件内部产生的缺陷与损伤有关, 且更敏感, 故可将低频噪声特性用作肖特基二极管的静电放电损伤灵敏表征工具.     

Systems Driven by Colored Poisson Noise: Unified Colored Noise Approximation

In this paper, unified colored noise approximation is extended to treat the systems driven by Poisson colored noise χ = ν(χ) + gε_cp(t). We arrive the evolution equation of the probability distribution pi(x, r) and the stationary probability distribution pt (χ, Υ). These equations are valid only if γ(χ,Υ) ≡ γ^-1/2[1 - ΥG(χ)/g(χ)] (G(χ) ≡ v'(χ)g(χ) - v(g)g'(χ)) is large enough (positive) and t >> Υ/γ(χ, Υ), but Υ is not restricted. As an application, we derive the nonlinear relaxation time (NLRT) for the processes driven by Poisson colored noise and evduate the NLRT for the approximative Ginzburg-Landon model under small Υ.     

小型化10 MHz恒温晶体振荡器设计

设计了用于高精度铷原子频标的一种小型化恒温压控晶体振荡器.振荡电路采用了稳定性好的并联型皮尔斯电路方案,采用2级?型LC级联滤波器抑制谐杂波,利用互补对称式金属-氧化物-半导体(CMOS)反相器实施隔离.振荡和放大电路选用了低噪声晶体管.晶体的温度控制在频率-温度曲线拐点处.实现了体积为4 mL晶振样件.晶振的短期频率稳定度为1.8?10-12/s,相噪对铷频标频率稳定度的贡献仅为3.2?10-13-1/2.     

PbS红外探测器低频噪声物理模型及缺陷表征研究

为了表征PbS薄膜光导红外探测器的材料缺陷,详细推导了1/f和产生-复合(g-r)噪声物理模型,并由实验数据验证了模型的准确性. 利用1/f噪声与表面缺陷关系,计算了不同偏压下表面陷阱密度. 得到该值随偏压升高而增加,由此得出1/f噪声与所加偏压成正比变化,与实验测试结果相一致. 在此模型基础上,研究了g-r噪声与深能级缺陷特征参量的关系,提出由低频噪声表征缺陷激活能、简并因子、俘获截面等缺陷参数的方法. 关键词： 红外探测器 1/f噪声')" href="#">1/f噪声 噪声')" href="#">g-r噪声 缺陷     

Au/SrTiO3/Au界面电阻翻转效应的低频噪声分析

本文研究了Au/SrTiO₃/Au三明治结构中的双极电阻翻转效应, 观察到高、低阻态的电阻弛豫现象. 低频噪声测量表明高、低阻态的电阻涨落表现出1/f行为. 对比试验表明, 高阻态的低频噪声来源于反向偏置肖特基势垒和氧空位的迁移, 强度较大, 低阻态的噪声则源于类欧姆接触底电极区域的氧空位迁移导致的载流子涨落, 强度较低. 同时, 界面上氧空位浓度的弛豫导致了高、低阻态的弛豫过程. 关键词： 电阻翻转效应 低频噪声 氧空位     

Spatial coherence resonance induced by coloured noise and parameter diversity in a neuronal network

Spatial coherence resonance in a two-dimensional neuronal network induced by additive Gaussian coloured noise and parameter diversity is studied. We focus on the ability of additive Gaussian coloured noise and parameter diversity to extract a particular spatial frequency (wave number) of excitatory waves in the excitable medium of this network. We show that there exists an intermediate noise level of the coloured noise and a particular value of diversity, where a characteristic spatial frequency of the system comes forth. Hereby, it is verified that spatial coherence resonance occurs in the studied model. Furthermore, we show that the optimal noise intensity for spatial coherence resonance decays exponentially with respect to the noise correlation time. Some explanations of the observed nonlinear phenomena are also presented.     

光纤激光经过模清洁器后的强度噪声分析

对1560 nm单频光纤激光光源通过一个光学模清洁器后的强度噪声进行了分析研究.实验观察到模清洁器虽然对于激光的高频强度噪声有明显的抑制作用,但强度噪声特性随频率呈一定周期变化,且在低频处模清洁器对强度噪声有放大作用.本文认为这是由于模清洁器具有类似于光纤延迟线的时延效应,将激光源的部分相位噪声转化为强度噪声.通过理论分析,由相位噪声转化的相对强度噪声幅度与激光相干时间、模清洁器的平均延时参数以及分析频率相关.分析结果与实验测量结果符合良好.此外,通过在光路中加入声光调制器进行反馈调制,激光的线宽从26 kHz压窄至16 kHz,模清洁器的锁定质量明显提高,经过模清洁器后的激光强度噪声有所减小,与理论相符.该结果进一步证实了由相位噪声转化而来的强度噪声与模清洁器的锁定质量无直接关系.通过该研究,完善了光学模清洁器对激光的噪声抑制模型.     

平衡接收直接检测DPSK接收机噪声统计特性分析

以带光前置放大器且采用MZI相干和直接检测方式的DPSK接收机为分析模型,从考虑线性附加噪声和非线性相位噪声入手,对噪声统计特性进行了数学分析,并推导出了概率密度函数和BER公式。结果表明:数值计算结果与已发表论文的试验结果较为吻合;非线性相位噪声会对系统性能造成严重影响;高斯近似法不能很好的分析此模型。     

Influence of Nonlinear Gain and Nonradiative Recombination on the Quantum Noise in InGaAsP Semiconductor Lasers

Effects of nonlinear gain and nonradiative recombination on characteristics of intensity and phase noises of InGaAsP lasers emitting in a wavelength of 1.55 Μm are investigated. The investigations are performed based on a self consistent numerical approach that takes into account the cross correlation of fluctuations among the injected electron number, photon number and the optical phase. Time variations of the fluctuations of the intensity and the shift of the lasing frequency are statistically analyzed. The corresponding frequency dependencies of intensity and frequency noises are characterized. The results show that both intensity and frequency noises around the relaxation frequency are suppressed when counting the nonlinear gain in the rate equations. The intensity noise is enhanced in the low frequency regime by increasing the nonradiative recombination. The results fit well with those predicted by the small-signal analysis.     

散弹噪声极限稳定度优于1×10-13τ-1/2的铷频标物理系统

近年来,铷原子频标研究取得长足进展,频率稳定度达到10^-13τ^-1/2量级.为进一步改善铷频标稳定度性能,本文设计了一种高信噪比物理系统.物理系统中的腔泡组件采用微波场磁力线与量子化轴方向高度平行的开槽管式微波腔,滤光泡和吸收泡独立控温.抽运光源采用了光学滤光和同位素滤光双重滤光方案.本文实测了背景光电流I₀和鉴频斜率K_d,结果分别为95 μA和7.7 nA/Hz,在此基础上计算物理系统的散弹噪声极限稳定度为7.5×10^-14τ^-1/2.研究结果表明,只要锁频环路的电子学噪声得到有效控制,铷频标的频率稳定度突破1×10^-13τ^-1/2,进入10^-14τ^-1/2量级是完全可能的.     

A modified pitchfork bifurcation as a model of the TI–TII transition in liquid helium counterflow with external noise

An amended pitchfork bifurcation is introduced to model recent experiments by Griswold and Tough on superfluid turbulence in liquid helium counterflow subject to strong external noise. We adopt the generalized white noise limit of Blankenship and Papanicolaou to take a short-correlation-time limit of the nonlinear noise which enters into the model, and we implement this limit by means of the wideband perturbation expansion. Novel boundary conditions are applied to the resultant diffusion process in order to obtain behavior in qualitative agreement with the observations at low vortex line density. We are able to account for the sharp peak in probability observed experimentally at a small positive line density. The drift and diffusion of our diffusion process may be estimated experimentally; we describe how to do this.