Effect of 1/f-type FM noise on semiconductor-laserlinewidth residual in high-power limit

The FM-noise spectrum and the linewidth of 1.3 μm DFB (distributed feedback) semiconductor lasers measured in the high-power state up to 20 mW are discussed. A 5-MHz residual linewidth is observed in the high-power limit. The FM-noise spectrum consists of white noise and 1/f noise. The spectral density of the white noise is reduced by the increase in the output power, whereas that of the 1/f noise is unchanged, which means that the linewidth residual in the high-power limit is caused by the 1/f noise rather than the white noise. The impact of the 1/f-type FM noise on coherent optical communication systems is also discussed     

Origin of residual semiconductor-laser linewidth in high-powerlimit

The FM noise spectrum and the spectral width of semiconductor lasers are measured in the high-power state up to 20 mW. The FM noise spectrum consists of the white noise and the 1/f noise. The spectral density of the white noise is suppressed by the increase in the output power, whereas that of the 1/f noise is kept constant. This fact means that the residual linewidth in the high-power limit is caused by the 1/f noise rather than the white noise     

Wavelength dependence of 1/f noise in the light output oflaser diodes: an experimental study

The optical power emitted by a monomode GaAlAs laser is filtered with a monochromator. The 1/f noise in the filtered emission is found to be directly dependent on the noncoherent emission, such as S_pαP_nc^m. Here s_p is the spectral density of the 1/f fluctuations, P_nc is the average noncoherent power, m=3/2 under spontaneous emission, and m=4 in the superradiation and laser regions. Study of the 1/f noise in the optical power in a band centered at the laser wavelength and with variable bandwidth shows three operating regions. (1) LED region (at low currents): the fluctuations with a 1/f spectrum are uncorrelated in wavelength. (2) Superradiation region (at currents close to the threshold): the fluctuations are correlated. (3) Laser region: the 1/f noise apparently is dominated by noncoherent emission within a small optical band around the laser wavelength     

On 1/f trapping noise in MOSTs

New calculations are given for the 1/f noise in metal-oxide-semiconductor transistors (MOSTs) based on the McWhorter model (number fluctuations). Particular attention is paid to two regions of the drain current-voltage characteristic: weak inversion and near saturation. The results are at variance with previous theories, where some errors have been made. The gravest error was the violation of the physical law whereby the variance of the number of carriers N in the channel is ⩽N. The calculations do not give a divergent noise power at current saturation, as found by other authors. In the ohmic region, the relation between the spectral density of the drain current fluctuations and the number of carriers is determined. The Langevin method and the Klaassen-Prins method for calculating the 1/f noise in MOSTs are discussed and shown to have been used incorrectly when the mobility and the Hooge 1/f noise parameter depend on position in the channel     

1/f noise in n-p-n GaAs/AlGaAs heterojunction bipolartransistors:iImpact of intrinsic transistor and parasitic seriesresistances

1/f noise experiments were performed for n-p-n GaAs/AlGaAs HBTs as a function of forward bias at room temperature. The experimental data are discussed with the help of new expressions for the 1/f noise in bipolar transistors where the influence of internal parasitic series resistances has been taken into account. At low forward currents the 1/f noise is determined by spontaneous fluctuations in the base and collector currents. At fixed bias, the collector current noise exceeds the base current noise. At higher forward currents the parasitic series resistances and their 1/f noise become important. Experimental results from the literature are compared with the results     

Correlation between 1/f noise and hFElong-term instability in silicon bipolar devices

Accelerated life tests with high-temperature storage and electric aging for n⁺-p-n silicon planar transistors were carried out. Current gain h_FE increases monotonously with time during the tests, and the h_FE drift is correlated with initial measured 1/f noise in the transistors, i.e. the drift amount significantly increases with the increase of noise level. The correlation coefficient of relative drift Δh_FE /h_FE and 1/f noise spectral density S_iB(f) is far larger than that of Δ h_FE/h_FE and initial DC parameters of the transistors. A quantitative theory model for the h _FE drift has been developed and explains the h _FE drift behavior in the tests, which suggests that the h _FE drift and 1/f noise can be attributed to the same physical origin, and both are caused by the modulation of the oxide traps near the Si-SiO₂ interface to Si surface recombination. 1/f noise measurement, therefore, may be used as a fast and nondestructive means to predict the long-term instability in bipolar transistors     

1/f noise in hot-carrier damaged MOSFET's: effects ofoxide charge and interface traps

The 1/f noise in the drain current of hot-carrier damaged MOSFETs biased in weak inversion has been studied. By the use of a biased annealing treatment to simultaneously decrease the density of oxide trapped charge (N_ot) and increase the density of interface traps (D_it), the authors have separated the contributions of these two kinds of defects. The results clearly indicate that, while the low-frequency 1/f noise is correlated with N_ot, the high-frequency 1/f noise is correlated with D_it     

1/f noise in MODFETs at low drain bias

The 1/f noise in normally-on MODFETs biased at low drain voltages is investigated. The experimentally observed relative noise in the drain current S_I/I² versus the effective gate voltage V_G=V_GS-V_off shows three regions which are explained. The observed dependencies are S_I/I²∝V_G ^m with the exponents m=-1, -3, 0 with increasing values of V_G. The model explains m =-1 as the region where the resistance and the 1/f noise stem from the 2-D electron gas under the gate electrode; the region with m=0 at large V_G or V_GS≅0 is due to the dominant contribution of the series resistance. In the region at intermediate V_G , m=-3, the 1/f noise stems from the channel under the gate electrode, and the drain-source resistance is already dominated by the series resistance     

延时自外差法线宽测量误差分析仿真及修正

讨论了移频延时自外差探测的基本原理,并对外差得到的功率谱进行了公式推导。在此基础上,对外差测量中出现的测量误差进行分析,同时设计了自外差测量实验装置进行实验对比,确定了由于延时线长度不够导致的线宽测量误差来源是因为延时时间短导致幂指数函数项波动加剧造成的;同时针对外差信号频谱为洛仑兹型和类高斯型的混合谱型,在高斯功率谱密度函数的基础上,对延时时间和1/f谱宽的影响进行了仿真计算,采用Voigt分析,提取出1/f导致的测量误差,提高了线宽测量的精度。以高斯谱宽4.5 kHz的谱型为例,对应的洛仑兹线宽约为0.68 kHz,提高了一个数量级的测量精度。     

1/f noise in GaAs filaments

A typical 1/f noise is excited in GaAs filament with the Hooge noise parameter of about α_H=2×10^-3 . The noise level increases in proportion to the square of the terminal voltage, and decreases approximately in inverse proportion to the total number of carriers within the device. A transition from the typical 1/f noise characteristics to the diffusion noise characteristics of MESFETs was observed when the electric field was increased above 1 kV/cm. The noise parameters were also investigated as a function of the device width between 2 and 200 μm. Deep levels within the n-GaAs active layer and the high electric field are the main factors of the nonideal 1/f characteristics     

Bulk and surface 1/f noise

The 1/f noise of an n-type silicon MOSFET has been studied under conditions ranging from accumulation to depletion at 300 K. The experimental results are interpreted in terms of a bulk phenomenon and are characterized by Hooge's empirical 1/f noise parameter α with values between 10^-7 and 10^-5. The α value for surface conduction at strong accumulation can be at least one order of magnitude larger than the value for bulk conduction     

Factors limiting the spectral linewidth of CPM-MQW-DFB lasers

A spectral linewidth of 56 kHz is achieved by a CPM-MQW-DFB (corrugation-pitch-modulated multiquantum-well distributed feedback) laser at an output power of 25 mW. To separate effects of the white noise and 1/f noise in limiting the linewidth, the authors measured the delayed-heterodyne lineshape by using a short delay-fiber. The minimum spectral linewidth is shown to be limited by white noise     

Absence of quantum 1/f noise in the photoelectric currentof junction of MIS photodetectors

Quantum 1/f noise is given by a simple engineering formula. It affects photodetectors through mobility and recombination speed fluctuations. The former are also in the diffusion constant, and all affect the dark current. However, there is no quantum 1/f noise in the photogeneration of carriers, as is shown     

Noise sources across a normal-to-superconducting boundary in bulkYBa2Cu3O7-x

Experiments in which a normal-to-superconducting (NS) boundary is created in an originally superconducting bar of bulk YBa₂Cu ₃O_7-x is described. The first noise measurements associated with such a boundary are presented. A high-density (5.20 g-cm ^-3) sample (sample A) and a low density (4.23 g-cm^-3 ) sample (sample B) have been investigated. Common to both samples is 1/f² noise observed in the frequency region between about 15 and 50 Hz that can be associated with the NS boundary itself. Sample A also exhibits conventional 1/f noise as expected for the normal part of the boundary, below about 15 Hz. In contrast, sample B shows 1/f^1.5 noise in this region; since the sample contains considerably fewer small grains than sample A, any 1/f noise is presumably masked in B. It is suggested that the 1/f² noise might be associated with flux-flow noise     

Wavelet-based representations for the 1/f family offractal processes

It is demonstrated that 1/f fractal processes are, in a broad sense, optimally represented in terms of orthonormal wavelet bases. Specifically, via a useful frequency-domain characterization for 1/f processes, the wavelet expansion's role as a Karhunen-Loeve-type expansion for 1/f processes is developed. As an illustration of potential, it is shown that wavelet-based representations naturally lead to highly efficient solutions to some fundamental detection and estimation problems involving 1/f processes     

Low-frequency noise in p-channel heterostructure insulated-gatefield-effect transistors (HIGFETs) at 77 K and drain current 1μA

Measurements of the low-frequency spectral intensity of the current fluctuations in p-channel GaAs/AlGaAs heterostructure insulated-gate field-effect transistors are discussed. The measurements were performed at 77 K and a drain current of 1 μA. The spectra of two types of devices are compared, one grown directly on the substrate and the other embedded in an n-well. The latter type produced markedly less noise, its spectrum being almost perfect 1/f noise. The former type exhibited, in addition to the 1/f noise, a significant generation-recombination noise component in the spectrum     

A dispersion formula satisfying recent requirements in microstripCAD

A dispersion formula ϵ^*_eff(f)=ϵ^* -{ϵ^*-ϵ^*_eff(0)}/{1+( f/f₅₀)^m}, for the effective relative permittivity ϵ^*_eff(f) of an open microstrip line is derived for computer-aided design (CAD) use. The 50% dispersion point (the frequency f₅₀ at which ϵ^*_eff(f₅₀)={ϵ ^*+ϵ^*_eff(0)}/2}) is used a normalizing frequency in the proposed formula, and an expression for f₅₀ is derived. To obtain the best fit of ϵ ^*_eff(f) to the theoretical numerical model, the power m of the normalized frequency in the proposed formula is expressed as a function of width-to-height ratio w/ h for w/h⩾0.7 and as a function of w /h, f₅₀, and f for w/h⩽0.7. The present formula has a high degree of accuracy, better than 0.6% in the range 0.1<w/h⩽10, 1<ϵ^*⩽128, and any height-to-wavelength ratio h/λ₀     

Reconciliation of methods for estimating fmaxfor microwave heterojunction transistors

An attempt is made to reconcile the various approaches that have recently been used to estimate the maximum frequency of oscillation f_max in high-performance AlGaAs/GaAs HBTs. f_max is computed numerically from the full expression for Mason's invariant gain using y-parameters derived from the different approaches, i.e., the hybrid-π equivalent circuit, the T-equivalent circuit, and the drift-diffusion equations. It is shown that the results for f_max are essentially the same, irrespective of the source of the y-parameters, provided that the phase delays due to transit of carriers across the base and the collector-base depletion region are properly accounted for. It is also shown, for the particular device studied, that the widely used analytical expression for f_max, involving f _T and effective base resistance and collector capacitance, is remarkably accurate for frequencies below those at which transit-time effects become important     

Theory and experiments of 1/f noise in Schottky-barrierdiodes operating in the thermionic-emission mode

A 1/f noise model for diodes operating in the thermionic-emission mode under forward-bias conditions has been developed. The model is based on mobility and diffusivity fluctuations occurring in the space-charge region and accounts for the current-limiting role of the metal-semiconductor interface The bias dependence of the 1/f noise spectral density calculated from this model is in excellent agreement with the results of the authors' experiments but is at variance with the predictions of a model developed by T.G.M. Kleinpenning (1979). From the experimental data, a value of 4.2×10^-9 for the Hooge parameter is derived. This value is in good agreement with theoretical calculation for electrons in silicon     

Importance of source and drain resistance to the maximum fT of millimeter-wave MODFETs

The usual approximate expression for measured f_T =[g_m/2π (C_gs+C _gd)] is inadequate. At low drain voltages just beyond the knee of the DC I-V curves, where intrinsic f _t is a maximum for millimeter-wave MODFETs, the high values of C_gd and G_ds combine with the high g_m to make terms involving the source and drain resistance significant. It is shown that these resistances can degrade the measured f_T of a 0.30-μm GaAs-AlGaAs MODFET from an intrinsic maximum f_T value of 73 GHz to a measured maximum value of 59 GHz. The correct extraction of maximum f_T is essential for determining electron velocity and optimizing low-noise performance