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     

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     

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     

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     

1/f frequency noise effects on self-heterodyne linewidthmeasurements

The effects of a 1/f frequency noise on self-heterodyne detection are described, and the results are applied to the problem of laser diode linewidth measurement. The self-heterodyne autocorrelation function and power spectrum are evaluated for both the white and the 1/ f components of the frequency noise. From numerical analysis, the power spectrum resulting from the 1/f frequency noise is shown to be approximately Gaussian, and an empirical expression is given for its linewidth. These results are applied to the problem of self-heterodyne linewidth measurements for coherent optical communications, and the amount of broadening due to 1/f frequency noise is predicted     

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     

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     

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     

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     

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     

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     

InGaAs/InAlAs/InP collector-up microwave heterojunction bipolartransistors

Collector-up InGaAs/InAlAs/InP heterojunction bipolar transistors (HBTs) were successfully fabricated, and their DC and microwave characteristics measured. High collector current density operation (J_c>30 kA/cm²) and high base-emitter junction saturation current density (J₀>10^-7 A/cm²) were achieved. A cutoff frequency of f _t=24 GHz and a maximum frequency of oscillation f _max=20 GHz at a collector current density of J₀ =23 kA/cm² were achieved on a nominal 5-μm×10-μm device     

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     

Digital system for 1/f fluctuation-speed control of asmall-fan motor

To produce a comfortable breeze similar to a natural one, a digital open-loop control system was utilized to control the speed of a small fan motor with 1/f fluctuation. The system was modeled as a first-order lag element with a time constant of 1.1 s. The output was controlled by commands and produced 1/f fluctuations, even though it was an open-loop system when the holding time of the data for 1/f fluctuation was set at more than 2 s     

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     

In0.52Al0.48As/InxGa1-xAs (0.53⩽x⩽0.70) lattice-matched and strainedheterostructure insulated-gate FETs

The DC and microwave properties of In_0.52Al_0.48 Al/In_xGa_1-xAs (0.53⩽x⩽0.70) heterostructure insulated gate field-effect transistors (HIGFETs) with a quantum well channel design are presented. DC and microwave transconductances (g_m) are enhanced as the In content is increased in the InGaAs channel. An intrinsic microwave g _m value of 428 mS/mm and a K-factor of 1140 mS/mm-V have been obtained for 1.0-μm gate length with the 65% In channel devices. The sheet charge density, drift mobility, transconductance, current-gain cutoff frequency (f_T), and maximum oscillation frequency (f _max) all show a continuous improvement up to 65% In content ( f_T=22.5 GHz with 53% and f_T=27 GHz with 65% In; the corresponding f_max change is from 6.5 to 8 GHz). The device performance degrades as the In content is increased to 70%. DC and microwave characteristics show the presence of negative differential resistance (NDR) up to 2.7 GHz     

Design and experimental characteristics of strained In0.52Al0.48As/InxGa1-xAs (x>0.53)HEMTs

Strained In_0.52Al_0.48 As/In_xGa _1-xAs (x>0.53) HEMTs (high electron mobility transistors) are studied theoretically and experimentally. A device design procedure is reported that is based on band structure and charge control self-consistent calculations. It predicts the sheet carrier density and electron confinement as a function of doping and thickness of layers. The DC performance at 300 K is presented. Wafer statistics demonstrate improvement of device characteristics with excess indium in the channel (g¯_{m, intr}=500 and 700 mS/mm for x=0.60 and 0.65). Microwave characterization shows the f_T improvement (f_T=40 and 45 GHz for x=0.60 and 0.65, respectively) and the R_ds limitations of the 1-μm-long-gate HEMTs     

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     

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     

Si/a-Si:H heterojunction microwave bipolar transistors with cut-offfrequencies ft above 5 GHz

The fabrication of a silicon heterojunction microwave bipolar transistor with an n⁺ a-Si:H emitter is discussed, and experimental results are given. The device provides a base sheet resistance of 2 kΩ/□ a base width 0.1 μm, a maximum current gain of 21 (V_CE=6 V, I_c=15 mA), and an emitter Gummel number G _E of about 1.4×10¹⁴ Scm^-4. From the measured S parameters, a cutoff frequency f_t of 5.5 GHz and maximum oscillating frequency f_max of 7.5 GHz at V_CE=10 V, I_c=10 mA are obtained