An improved parameter extraction method of SiGe HBTs' substrate network

In this letter, an improved method for substrate network parameter extraction of SiGe heterojunction bipolar transistors (HBTs) is proposed. It is found that, without taking the intrinsic circuit elements into consideration, the conductance of substrate network will be underestimated while the susceptance of substrate network will be overestimated. Therefore, an iteration procedure is developed to determine the intrinsic circuit elements of SiGe HBTs first. The intrinsic circuit elements are then applied to remove their influence on the substrate network parameter extraction. Compared with the conventional method, the proposed one can avoid some unphysical modeling results and provide reliable substrate network parameters.     

Gated-four-probe a-Si:H TFT structure: a new technique to measurethe intrinsic performance of a-Si:H TFT

In this letter, a new technique based on gated-four-probe hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) structure is proposed. This new technique allows the determination of the intrinsic performance of a-Si:H TFT without any influence from source/drain series resistances. In this method, two probes within a conventional a-Si:H TFT are used to measure the voltage difference within a channel. By correlating this voltage difference with the drain-source current induced by applied gate bias, the a-Si:H TFT intrinsic performance, such as mobility, threshold voltage, and field-effect conductance activation energy, can be accurately determined without any influence from source/drain series resistances     

Monte Carlo determination of the intrinsic small-signal equivalentcircuit of MESFET's

A Monte Carlo technique for the determination of the intrinsic elements of a broad-band small-signal equivalent circuit (SSEC) of MESFET's (and FET's in general) is described. The values of the different elements are calculated from the Y parameters of the intrinsic MESFET, which are obtained from the Fourier analysis of the device transient response to voltage-step perturbations at the drain and gate electrodes. An accurate estimator of the instantaneous currents at the terminals is used, which guarantees the precision of the method. Three different MESFET geometries have been analyzed. For low drain currents under saturation the intrinsic elements are found to be independent of frequency in the whole range of device operation. This fact validates the technique and the proposed equivalent circuit under these conditions. However, for high drain currents the gate-drain capacitance and the drain conductance depend on frequency due to the appearance of charge-accumulation effects     

A New Millimeter-Wave Small-Signal Modeling Approach for pHEMTs Accounting for the Output Conductance Time Delay

A new technique is developed for determining analytically a millimeter-wave small-signal equivalent-circuit model of GaAs pseudomorphic HEMTs from scattering parameter measurements. In order to obtain a good agreement between model simulations and measurements up to 90 GHz, the conventional intrinsic output conductance is substituted by a voltage-controlled current source with a time delay. Consequently, a simple and accurate extraction procedure is proposed for taking into account the introduction of the output conductance time delay.     

Parameter extraction from I-V characteristics ofsingle MOSFETs

A method is presented to extract the bias-dependent series resistances and intrinsic conductance factor of individual MOS transistors from measured I-V characteristics. If applied to groups of scaled channel length devices, it also allows determination of the effective channel length together with the transversal field dependence of the carrier mobility. The method is exactly derived from conventional MOS theory based on the gradual channel approximation, and the deviations from such an ideal case are studied by means of two-dimensional device simulations. Experimental results obtained with n- and p-channel transistors of conventional as well as LDD type are presented to show the correctness of the proposed extraction procedure     

Microwave properties of a proposed read-like device with variable current multiplication in the avalanche zone and an additional transverse field in the drift zone

A study of the high-frequency properties of a Read-like IMPATT device, which is arranged to have a variable current multiplication in the avalanche zone by means of controlled injection of minority carriers into the reverse biased junction, and also an additional transverse field in the intrinsic drift region, is presented. The additional field shifts the direction of space-charge waves emerging from the avalanche layer without altering the drift velocity which is already saturated. It is shown that the frequency of the maximum negative conductance, avalanche frequency, magnitude of the negative conductance, and susceptance of the device can be controlled over a wide range by varying the current multiplication in the avalanche zone. It is also shown that a fine variation of the negative conductance without altering the avalanche frequency or susceptance can be obtained by means of the additional transverse field.     

Analysis of current flow in polycrystalline TFTs

A model for predicting the change of currents at the surface of polycrystalline materials for both ohmic and blocking contacts is developed. The model includes electron/hole traps within grain boundaries that are comparable in thickness to that of the dielectric on the surface of the polycrystalline semiconductor. The grains and their interfaces with the dielectric are assumed to be trap free. Account is also taken of the reducing carrier Debye Length as the surface carrier concentration is increased, from its intrinsic value, by the field effect. The net surface conductance is obtained by integrating the carrier density across the surface region through to the back of the material. Four regimes are identified: quasi-drift and quasi-diffusion for the high and low current regimes when there is a good supply of carriers and generation and quasi-diffusion when there is a limited supply of carriers. The analytical relationships are found to give satisfactory agreement with results for the temperature and field dependence of surface conductance in polycrystalline silicon in these regimes. The dependence of surface conductance on field effect voltage is found, at lower currents, to be a means of determining the energy distribution of electron/hole traps.     

High-frequency characteristics of inverted-mode heterojunction bipolar transistors

It is shown that in emitter-down heterojunction bipolar transistors (HBT's), parasitics can be reduced sufficiently that intrinsic transit-time delays become the dominant limitations to high-frequency performance. In this situation it is found that the dependence of the unilateral gain on frequency can be significantly different from the simple 6-dB/octave decrease usually assumed. It is found that the device exhibits negative output conductance over certain bands of frequencies, and that when this occurs a series of resonances are observed in the gain versus frequency characteristics. Explanations of this behavior are given in terms of the phase delay of the common-base current gain. The generality and relevance of these observations to other types of transistors, and the utilization of the negative output conductance to enhance high-frequency operation are also discussed.     

蓄电池容量与电导相关性的研究

通信电源系统中,蓄电池是直流供电系统的重要组成部分,是保证通信直流供电系统正常的最后一道防线,能否准确把握蓄电池容量现状,对保障通信具有重要指导意义。文中简要介绍蓄电池结构、模型及工作原理,阐述了蓄电池充放电机理,并通过对一组蓄电池电导、内阻进行长期跟踪测试,从大量实测数据中定量分析了蓄电池容量与电导之间的内在联系。最后利用福光蓄电池在线放电仪表FBI对目标蓄电池组进行容量测试,并得出蓄电池容量与电导具有相关性的结论。     

Electrical Analyses of Germanium MIS Structure and Spectroscopic Measurement of the Interface Trap Density in an Insulator/Germanium Interface at Room Temperature

In this paper, we present an equivalent circuit model of a germanium (Ge) MIS structure that is biased in the inversion region, which includes the effects of the high intrinsic carrier density and high diffusion-limited conductance of the Ge substrate at room temperature. The model can successfully express the gate bias and frequency dependences of the capacitance characteristics that are specific to the Ge MIS capacitor. Moreover, it will be shown that the interface trap density and its gate bias dependence in the inversion region can be spectroscopically determined from the gate bias and measurement frequency dependences of the equivalent parallel conductance of the Ge surface.     

模式耦合对量子线电子输运性质的影响

利用一般传输矩阵方法 (Transfer matrix method)和耦合模传输矩阵方法 (Coupledmode transfer matrix method) ,分别计算了几种处于弹道区的非均匀边界形状量子线的电导 ,研究量子线通道相邻分段区域电子传输模式之间的耦合对电导的影响。结果表明 ,这种耦合对空腔结构量子线电子输运性质有重要影响 ,是研究非均匀边界形状量子线电导必须考虑的关键因素。     

High-frequency network properties of MOS transistors including the substrate resistivity effects

The small-signal differential equations describing the intrinsic high-frequency characteristics of MOS transistors are derived under three basic modes of signal application: gate excitation, substrate excitation, and combined gate-substrate excitation. These equations are shown to be analogous to those of a double RC transmission line having a uniformly distributed common resistance but two separate capacitances distributed nonuniformly. High-frequency device admittances are calculated in terms of those of the analog RC transmission line using the method of "piecewise" uniformity for the capacitance distributions. Useful expressions are derived for the various Y-parameters which are explicitly related to the more readily measurable low-frequency input capacitance and transconductance parameters which, in turn, are related to the basic device physical parameters. The admittance expressions clearly indicate the influence of the substrate resistivity both on the forward transfer admittance magnitudes at low and high frequencies and on the input conductance at high frequencies. The intrinsic Y-parameters are combined with the associated extrinsic RC networks and presented in the form of equivalent circuits. Results of UHF admittance measurements on representative n-channel devices are given which support the overall validity of the proposed equivalent circuit models.     

Transient Performance Estimation of Charge Plasma Based Negative Capacitance Junctionless Tunnel FET

We investigate the transient behavior of an n-type double gate negative capacitance junctionless tunnel field effect transistor (NC-JLTFET). The structure is realized by using the work-function engineering of metal electrodes over a heavily doped n⁺ silicon channel and a ferroelectric gate stack to get negative capacitance behavior. The positive feedback in the electric dipoles of ferroelectric materials results in applied gate bias boosting. Various device transient parameters viz. transconductance, output resistance, output conductance, intrinsic gain, intrinsic gate delay, transconductance generation factor and unity gain frequency are analyzed using ac analysis of the device. To study the impact of the work-function variation of control and source gate on device performance, sensitivity analysis of the device has been carried out by varying these parameters. Simulation study reveals that it preserves inherent advantages of charge-plasma junctionless structure and exhibits improved transient behavior as well.     

Transient performance estimation of charge plasma based negative capacitance ewline junctionless tunnel FET

We investigate the transient behavior of an n-type double gate negative capacitance junctionless tunnel field effect transistor (NC-JLTFET). The structure is realized by using the work-function engineering of metal electrodes over a heavily doped n⁺ silicon channel and a ferroelectric gate stack to get negative capacitance behavior. The positive feedback in the electric dipoles of ferroelectric materials results in applied gate bias boosting. Various device transient parameters viz. transconductance, output resistance, output conductance, intrinsic gain, intrinsic gate delay, transconductance generation factor and unity gain frequency are analyzed using ac analysis of the device. To study the impact of the work-function variation of control and source gate on device performance, sensitivity analysis of the device has been carried out by varying these parameters. Simulation study reveals that it preserves inherent advantages of charge-plasma junctionless structure and exhibits improved transient behavior as well.     

Modeling of noise parameters of MESFETs and MODFETs and theirfrequency and temperature dependence

A simple noise model of a microwave MESFET (MODFET, HEMT, etc.) is described and verified at room and cryogenic temperatures. Closed-form expressions for the minimum noise temperature, the optimum generator impedance, the noise conductance, and the generator-impedance-minimizing noise measure are given in terms of the frequency, the elements of a FET equivalent circuit, and the equivalent temperatures of intrinsic gate resistance and drain conductance to be determined from noise measurements. These equivalent temperatures are demonstrated in the case of a Fujitsu FHR01FH MODFET to be independent of frequency in the frequency range in which 1/f noise is negligible. Thus, the model allows prediction of noise parameters for a broad frequency range from a single frequency noise parameter measurement. The relationships between this approach and other relevant studies are established     

Quantum interference and space charge effects in double barrier structures incorporating wide quantum wells

The current-voltage characteristics of resonant tunneling devices with well widths between 12 and 180 nm are studied. The voltage interval between the resonant peaks in the current is measured as a function of well width. For the wide wells the amplitude of the peaks in the differential conductance is modulated by an “over the barrier” interference effect involving the collector barrier. Space charge buildup and intrinsic bistability effects for a particular resonant state are found to depend critically on its energy difference from the top of the collector barrier and from lower lying standing wave states of the quantum well.     

Small-signal model parameter extraction of E-mode N-polar GaN MOS-HEMT using optimization algorithms and its comparison

An improved small-signal parameter extraction technique for short channel enhancement-mode N-polar GaN MOS-HEMT is proposed,which is a combination of a conventional analytical method and optimization techniques.The extrinsic parameters such as parasitic capacitance,inductance and resistance are extracted under the pinch-off condition.The intrinsic parameters of the small-signal equivalent circuit (SSEC) have been extracted including gate forward and backward conductance.Different optimization algorithms such as PSO,Quasi Newton and Firefly optimization algorithm is applied to the extracted parameters to minimize the error between modeled and measured S-parameters.The different optimized SSEC models have been validated by comparing the S-parameters and unity current-gain with TCAD simulations and available experimental data from the literature.It is observed that the Firefly algorithm based optimization approach accurately extracts the small-signal model parameters as compared to other optimization algorithm techniques with a minimum error percentage of 1.3％.     

Enumeration of Microorganisms by Their Dynamic ac Conductance Patterns

Bacterial growth affects the ac conductance of a two-terminal measuring cell containing growth media. The dynamic characteristics of the recorded conductance provide quick information about the microorganisms' initial concentration and their relative growth parameters. A simplified electrobacteriological model is described which explains the changes in the medium conductivity. The mathematical model was verified experimentally. This model establishes the use of conductance measurement as a rapid method to assess bacterial concentrations. High correlation existed between the conductance method and the conventional plate count method.     

A highly linear wideband 0.3-to-2.7 GHz variable-gain amplifier

A design of a differential variable-gain amplifier (VGA) with high IP3 (third-order intercept point) is discussed. To improve IP3, the third-order intermodulation products, which are generated by both an intrinsic third-order nonlinearity and a second-order interaction of a transistor, are minimized by using a nonlinear conductance. Unlike prior methods, the proposed method enables the achievement of both constant and broadband IP3 for various VGA gain settings. A design example with virtual but realistic BSIM4 transistor models is discussed to verify the analysis. The resultant amplifier example was designed and simulated in a 28-nm FDSOI CMOS technology. The amplifier achieved more than 15 dBm input-referred IP3 across a 2.4-GHz bandwidth from 0.3-to-2.7 GHz with a variable gain of 0-to-8.5 dB while consuming 3.3 mA from a 1.5-V supply.     

Mapping And Analysis of Aerial Conductivity Measurements from INPUT System over Geothermal Areas

Remotely sensed electromagnetic data taken with an INPUT system for the U.S. Geological Survey in aerial surveys over a known geothermal resource area have been reduced and plotted in a gray scale format for two-and three-dimensional projections of the apparent subsurface conductance. The apparent conductance is calculated using both the channel ratio method and the theoretical two-layer model of the earth. Matching the survey data to the two-layer model gave good results consistent with the ratio method of apparent conductance calculation and permitted the construction of maps of horizontal slices of apparent conductance at different depths into the earth, from one to fifty meters. The channel ratio and horizontal slice maps of apparent conductance give a picture of the apparent conductance which is consistent with known topographical features of the regions.