Analytical model of shot noise in double-barrier resonant-tunnelingdiodes

The shot noise in double-barrier diodes is analyzed using the stationary-state approach to resonant tunneling through the first quasi-bound level. Significant deviations from full shot noise are predicted. Significant shot noise suppression occurs in the entire positive differential resistance region below the current peak, and shot noise enhancement occurs in the negative differential resistance region above the peak. The physical basis for these effects is assumed to be the modulation of the double-barrier transmission probability by charge stored in the first quasi-bound level in the quantum well. The analysis confirms microwave noise measurements of high-speed double-barrier diodes     

Noise in high-gain transistors and its application to the measurement of certain transistor parameters

Noise performance of a high-gain transistor is presented. It is shown that both burst noise and flicker noise in high-gain transistors are not as important as those in low-gain units. At very small biases, less than 10 µA for the given transistor, the limiting noise of the transistor is dominated by the shot noise. In the higher bias region the thermal noise of the base resistance is the dominant noise of the transistor. It is also demonstrated that from noise measurement the base resistance rb'b, the transconductance gm, and the small signal common emitter-current gain β can be accurately determined.     

Low frequency gate noise in a diode-connected MESFET: measurementsand modeling

The low frequency Schottky diode noise has been investigated in GaAs power MESFETs. For those devices, gate noise spectra are generally composed of 1/f and shot noise contributions. We have observed an increase by two orders of magnitude of the noise level when MESFETs are submitted to rf life-test. The increase of the 1/f noise can be explained by a modification of the gate space charge region extension. This interpretation is sustained by a reduction of the drain current transient magnitude and the inherent active trap density. A correlation is assumed between the increase of the shot noise level after rf life-test and a micro-plasma formation. Both 1/f noise and shot noise evolution might originate in a local increase of the electric field in the vicinity of the gate in drain access region. We have demonstrated that LF gate current noise is an early indicator of damage mechanisms occurring at the gate-semiconductor and passivation-semiconductor interfaces of the devices     

CMOS数字像素传感器噪声研究

在研究CMOS数字像素传感器(DPS)噪声特性的基础上,利用脉冲宽度调制(PWM)原理建立了关于PWM DPS完善的系统噪声数学模型。相比于传统CMOS图像传感器噪声研究,该模型考虑了系统中各像素单元积分时间不同和像素级模数转换的特点,推导出总噪声表达式。研究表明,低照度时噪声由暗电流散粒噪声主导,光强大时主要来源为光电二极管散粒噪声。模型中光电二极管散粒噪声与光照无关、暗电流散粒噪声与光照有关。研究结果表明针对PWM DPS系统,适当增大节点电容和比较器参考电压、改善比较器失配可有效降低噪声。     

Avalanche InP/InGaAs heterojunction phototransistor

We report on the characteristics of an avalanche InP/InGaAs heterojunction phototransistor. Below the turnover voltage, the gain is bias dependent and avalanching can be used to achieve significant (sim5times) improvement in the gain-bandwidth product. The noise current in this bias region has been measured and is shown to be predominantly shot noise of the photocurrent and the leakage current. Above the turnover voltage, negative resistance is observed and extremely high gains (>10⁴) are achieved. In this mode, the pulse response is a narrow spike (rise time ≃ 20 ns) whose width is independent of the width of the incident optical pulse.     

A noise model for the distributed transistor

A transistor model having a distributed base region and distributed sources of noise is analyzed. An equivalent lumped-noise model is derived. The model includes all the conventional sources of shot noise and thermal noise in the base region. It is found that the transistor shot noise is uneffected by the distributed nature of the base. Mean-square thermal noise is found to be proportional to the real part of a complex base impedance. An excess noise source due to the distributed base is found but is shown to be negligible compared to thermal noise generated in the base. The distributed-noise model reduces to the conventional lumped-noise model at low frequencies.     

长波长PIN／HBT集成光接收机前端噪声分析

文章研究磷化铟(InP)基异质结双极晶体管(HBT)和PIN光电二极管(PIN-PD)单片集成技术,利用器件的小信号等效电路详细计算了长波长PIN/HBT光电子集成电路(OEIC)光接收机前端等效输入噪声电流均方根(RMS)功率谱密度.分析表明:对于高速光电器件,当频率在100 MHz～2 GHz范围内时,基极电流引起的散粒噪声和基极电阻引起的热噪声起主要作用;频率大于5 GHz时,集电极电流引起的散粒噪声和基极电阻引起的热噪声起主要作用.在上述结论的基础上,文章最后讨论了在集成前端设计的过程中减小噪声影响的基本方法.     

Noise due to generation and recombination of carriers in p-n junction transition regions

The theory for the current noise associated with carrier generation and recombination in ap-njunction transition region is presented. The noise model is derived directly from the SRH defect center model. In a reverse biased junction the noise from this mechanism varies from two-thirds to full shot noise, depending upon frequency, and in a forward biased junction the noise ranges from three-fourths to full shot noise, depending upon injection level. These results approximately agree with published experimental results, but the agreement is not conclusive, especially in forward biased junctions. The theory shows that the noise associated with transition region generation-recombination current is not particularly significant in bipolar transistors.     

Analysis of gate shot noise in MOSFETs with ultrathin gate oxides

The impact of gate shot noise associated with gate leakage current in MOSFETs is studied by means of analytical models and numerical device simulation. The effects of shot noise on the main two-port noise parameters (minimum noise figure, equivalent noise resistance, and optimum source admittance) and their dependence on oxide thickness and on the level of tunneling leakage current are analyzed.     

Monte Carlo simulation of Schottky diodes operating under terahertz cyclostationary conditions

We report Monte Carlo simulations of the current response and noise spectrum in heavily doped nanometric GaAs Schottky-barrier diodes (SBDs) operating under periodic large-signal conditions in the forward bias region. Due to the rather thin depletion region and heavy doping of these diodes, we find that the returning carrier resonance is shifted well above the terahertz region, so that the low-frequency noise plateau extends over the terahertz region. Here, frequency multiplication and mixing can take place at noise levels equal or below than that of full shot noise. We show that the signal-to-noise ratio of these SBDs is definitely superior to that of bulk semiconductors exploiting velocity-field nonlinearity.     

Noise in a CMOS digital pixel sensor

Based on the study of noise performance in CMOS digital pixel sensor(DPS),a mathematical model of noise is established with the pulse-width-modulation(PWM) principle.Compared with traditional CMOS image sensors,the integration time is different and A/D conversion is implemented in each PWM DPS pixel.Then,the quantitative calculating formula of system noise is derived.It is found that dark current shot noise is the dominant noise source in low light region while photodiode shot noise becomes significantly important in the bright region. In this model,photodiode shot noise does not vary with luminance,but dark current shot noise does.According to increasing photodiode capacitance and the comparator’s reference voltage or optimizing the mismatch in the comparator,the total noise can be reduced.These results serve as a guideline for the design of PWM DPS.     

散粒噪声用于纳米电子器件与结构的量子效应表征

论述了纳米电子器件与结构中散粒噪声的产生机理和影响因素,表明散粒噪声与输运过程密切相关,按照噪声功率谱的幅值大小将散粒噪声分为泊松散粒噪声、亚泊松散粒噪声和超泊松散粒噪声四类。将散粒噪声的这些规律应用于纳米电子器件和结构,可表征不同器件与结构中的量子效应。利用散粒噪声已经成功检测到无序导线中的开放通道与量子点混沌腔中的波动性,测量出超导体与分数量子霍尔效应中的准粒子电荷。将散粒噪声用于检测纠缠态对量子计算具有重要的意义,自旋相干输运的检测是自旋电子学的重要研究课题。     

Microwave phototube design considerations

The general behavior of the traveling-wave microwave phototube (TWP) as a broadband light demodulator has been described in previous publications. This paper presents specific theoretical and experimental analyses. It is shown that at low average currents the microwave power output of a TWP is given byP = frac{1}{2}i^{2} R_{eq}whereiis the peak value of the microwave current modulation at the cathode (i.e., the ac current) and Reqis an "equivalent interaction resistance" given byR_{eq} = pi^{2}N^{2}Z_{c}whereNis the helix length in electronic wavelengths and Zcis the longitudinal beam-circuit interaction impedance. Typical values of Reqare from 10⁵to 10⁷ohms. The bandwidth is determined by the productf^{2}Z_{c}, which can vary less than 3 db over an octave. The major noise contributions are found to be shot noise and thermal noise. The power output and signal-to-noise calculations are verified by experiments on an S-band TWP at low average current levels. Preliminary analysis of the TWP at high average currents shows that even higher values of Reqshould be obtainable. However, in that case the frequency-dependent microwave interactions in the gun region may provide a serious bandwidth limitation.     

Effect of dimensionality on shot-noise suppression in nondegenerate diffusive conductors

We present a theoretical investigation of shot-noise suppression due to long-range Coulomb interaction in nondegenerate diffusive conductors. Calculations make use of an ensemble Monte-Carlo simulator, self-consistently coupled with a one-dimensional Poisson solver. We analyze the noise in a lightly doped active region surrounded by two contacts acting as thermal reservoirs. The effect of momentum space dimensionality on shot-noise suppression is analyzed. Provided significant space-charge effects take place inside the active region, long-range Coulomb interaction is found to play an essential role in suppressing the shot noise at qUk_BT. In the elastic diffusive regime, dimensionality is found to modify the suppression factor γ, which within numerical uncertainty takes values of about 1/3, 1/2 and 0.7 in the cases of 3, 2 and 1 dimensions, respectively.     

Investigation of compact models for RF noise in SiGe HBTs by hydrodynamic device simulation

A comprehensive investigation of the SPICE and unified compact noise models is performed by comparison with the more fundamental hierarchical hydrodynamic device model. It is shown that the rather simple SPICE and unified compact noise models yield good results for frequencies up to 10 GHz for state-of-the-art SiGe HBTs with a low base resistance. The base noise resistance, a key parameter of the compact noise models turns out to be independent of frequency and bias. It can be well estimated based on the sheet resistance of the intrinsic and extrinsic base or with the modified circle-fit method. The unified model, which in comparison to the SPICE model considers in addition the finite transit time of shot noise, is found to be somewhat more accurate than the SPICE model, especially at higher frequencies and collector currents. But this is achieved at the expense of a transit time parameter which cannot be determined without accurate and detailed noise measurements or physics-based numerical simulations.     

Scaling and technological limitations of 1/f noise and oscillator phase noise in SiGe HBTs

This paper examines the impact of SiGe HBT scaling on 1/f noise and phase noise of oscillators and frequency synthesizers. The increase of transistor speed with scaling is shown to significantly increase the sensitivity of oscillation frequency to 1/f noise and, thus, degrade close-in phase noise, but decrease the sensitivity of oscillation frequency to base current shot noise and base resistance thermal noises. The results show that corner offset frequency defined by the intersect of the 1/f³ and 1/f² phase noise has little to do with the traditional 1/f corner frequency. The relative importance of individual noise sources in determining phase noise is examined as a function of technology scaling, device sizing, and oscillation frequency. The collector current shot noise and base resistance noise are shown to set the fundamental limits of phase noise reduction. A methodology to identify the maximum tolerable 1/f K factor is established and demonstrated for the HBTs used     

Laser diodes in photon number squeezed state

A laser diode with an intrinsic layer as the space charge limited current region is expected to emit a low noise (less than the shot noise level) light. However, when one applies the intrinsic layer to the laser diode, severe difficulty is faced. Because the intrinsic layer has a very high resistivity, the applied voltage to operate the laser diode is too large and causes catastrophic damage to the laser diode. Here we propose novel laser diodes which emit a low noise light. The first is an AlGaAs laser diode having an undoped layer between the active layer and the cladding layer which acts as the space charge limited current region. Fano factor, F_m, of this laser diode is 28% smaller than the shot noise level (standard quantum limit, F_m=1) at 21 mA (output power, P₀=20 mW). The second one is an InGaAsP laser diode having two tunnel barrier layers whose bandgap energy is larger than that of the cladding layer. The region between the barriers acts as the space charge limited current region, Fano factor, F_m of this laser diode is 47% smaller than the shot noise level at 21 mA (P₀=10 mW). On the other hand, an AlGaAs laser diode with the two tunnel barrier layers has Fano factor, F_m which is 43% smaller than the shot noise level at 21 mA (P₀=20 mW). The calculated amplitude noise spectral densities of the latter two laser diodes are in good agreement with the calculated values from Langevin method. However, the calculated amplitude noise spectral density of the former laser diode does not agree with the calculated value from Langevin method. This disagreement is also discussed     

Noise model of gate-leakage current in ultrathin oxide MOSFETs

A physics-based analytical model of the gate-leakage current noise in ultrathin gate oxide MOSFETs is presented. The noise model is based on an inelastic trap-assisted tunneling transport. We employ the barrier height fluctuation model and the Lorentzian-modulated shot noise of the gate-leakage current stemming from the two-dimensional electron gas channel to explain the excess noise behavior. The excess noise can be interpreted as the sum of 1/f/sup /spl gamma// noise and the Lorentzian-modulated shot noise. Trap-related processes are the most likely cause of excess current noise because slow traps in the oxide can result in low-frequency dissipation in the conductance of oxides and fast traps can produce the Lorentzian-modulated shot noise associated with generation-recombination process at higher frequencies. In order to verify the proposed noise model, the simulation results are compared with experimental data, and excellent agreement is observed.     

Noise in solid-state devices and lasers

A survey is given of the most important noise problems in solid-state devices. Section II discusses shot noise in metal-semiconductor diodes, p-n junctions, and transistors at low injection; noise due to recombination and generation in the junction space-charge region; high-level injection effects; noise in photodiodes, avalanche diodes, and diode particle detectors, and shot noise in the leakage currents in field-effect transistors (FETs). Section III discusses thermal noise and induced gate noise in FETs; generation-recombination noise in FETs and transistors at low temperatures; noise due to recombination centers in the space-charge region(s) of FETs, and noise in space-charge-limited solid-state diodes. Section IV attempts to give a unified account of 1/f noise in solid-state devices in terms of the fluctuating occupancy of traps in the surface oxide; discusses the kinetics of these traps; applies this to flicker noise in junction diodes, transistors, and FETs, and briefly discusses flicker noise in Gunn diodes and burst noise in junction diodes and transistors. Section V discusses shot noise in the light emission of luminescent diodes and lasers, and noise in optical heterodyning. Section VI discusses circuit applications. It deals with the noise figure of negative conductance amplifiers (tunnel diodes and parametric amplifiers), and of FET, transistor, and mixer circuits. In the latter discussion capacitive up-converters, and diode, FET, and transistor mixers are dealt with.     

An accurate analysis of noise in rectangular bipolar transistors including current crowding

An accurate analysis of noise in rectangular bipolar transistors is developed from a distributed model using a collective approach and the transport noise theory. In this model, emitter current crowding effect are taken into account and noise behaviour at intermediate and low values of source impedance is precisely described. The structure of teh equivalent lumped circuit is established, and the analytical relationships characterizing its elements in an extended range of current and frequency are given. It is shown that; (a) the active base region must be represented by a nonlinear impedance with a generalized thermal noise source; (b) for low source impedances the equivalent input voltage shot noise generator is higher than predicted by low injection theories. Furthermore it is found that emitter crowding induces a uniform and important decrease in (a) base impedance (b) thermal noise and (c) the correlation between shot noise generators of the equivalent lumped circuit. Finally it appears that classical low injection theories are valid when crowding occurs in transistors biased with high source impedances.