Switching characteristics of polysilicon MISS devices

Experimental results on MISS devices are reported. The insulating layer was obtained by means of electron gun evaporation of undoped polycrystalline silicon. A model taking into account the specific conduction mechanisms in the semi-insulating polysilicon layer has been developed. This model explains the experimental I-V characteristics and gives rise to a switching condition relation similar to that of p-n-p-n devices.     

Resonant tunnel switching in MISS devices

The excess current experimentally observed in the Metal-Thin SiO₂ layer (n or p) Si(p⁺ or n⁺) (MISS) structures cannot be explained by any of the existing models based on a direct tunneling conduction through the insulator. In this paper we consider the existence of traps in the SiO₂ gap which support resonant tunneling conduction through the insulator. This allows to fit the experimental I-V characteristic of our structures with a reasonable agreement. The switching point dependences on the structure parameters are shown.     

Characterization of the switching in tunnel MISS devices

The observed bistable characteristics of metal-insulator-silicon switch (MISS) devices with moderate epi-layer doping levels are proven to be controlled by trap assisted tunneling. The switching current and the switching voltage are shown to depend on the reverse saturation current of the MIS substructure and on fabrication parameters (insulator thickness and epi-layer doping level). A method to obtain the metal-semiconductor barrier height, the injection factor at the interface and the trap density in the insulator is presented. The results have been applied to characterize AlSiO₂Si(n)Si(p⁺) structu in which the switching point and the reverse saturation current have been measured. The observed dispersion in the values of the current can be explained by assuming a unique value of the barrier height and the trap density for all devices, allowing the values of the tunneling damping factors to be different from those obtained in the two-band model, which validity is also discussed.     

A proposed model of MISS composed of two active devices

A model is proposed for MISS operation which explains the discrepancies in threshold voltage, switching current and the physical mechanism reported previously. A complete physical picture of the current-voltage characteristics of the device is given considering the coupled action of two devices; a bipolar transistor with open base and an amplifying MIS structure in non-equilibrium. An approximate value for holding voltage is given. Some experimental results supporting the suggested physical picture are reported showing the charge-storage effect anticipated by this model and a capacitive-current behaviour evidencing the existence of an internal positive feedback in the device.     

Switching behaviour of MISS diodes

A physical picture of the switching behaviour of MISS diodes is presented considering three phases of the turn-on process: a capacitive current rise time, an inversion charge delay time and a feedback regeneration time. Approximate calculations are derived based on the outlined physical picture and compared to the experimental results obtained in pulse experiments with polysilicon MISS diodes. A dynamic current-voltage characteristic is also presented which differs from the known static one.     

Modified diakoptic theory of antennas

The diakoptic theory of antennas, suggested by Goubau, is an independent approach to the numerical analysis of multi-element antennas of complex configuration. Based on physical reasoning, the theory is designed to be amenable to efficient computer evaluation. However, as an intermediate step, the theory involves hypothetical current sources with one terminal only, which violate the current continuity condition, so that Maxwell's equations cannot be applied without precautions. Here, a modified version of the diakoptic theory is presented which avoids this complication by a simple change in the basic approach while otherwise it preserves most features of Goubau's original theory. In addition, the modified version starts with a well-established, rigorous impedance matrix formulation of the problem and allows one to readily establish the relationships with the method of moments. Thus, it may facilitate understanding the diakoptic method.     

Microscopic theory of hydrogen in silicon devices

Incorporation of hydrogen has a strong effect on the characteristics of silicon devices. A fundamental understanding of the microscopic mechanisms is required in order to monitor and control the behavior of hydrogen. First-principles calculations have been instrumental in providing such understanding. We first outline the basic principles that govern the interaction between hydrogen and silicon, followed by an overview of recent first-principles results for hydrogen interactions with silicon. We show that H₂ molecules are far less inert than previously assumed. We then discuss results for motion of hydrogen through the material, as relating to diffusion and defect formation. We also discuss the enhanced stability of Si-D compared to Si-H bonds, which may provide a means of suppressing defect generation. We present a microscopic mechanism for hydrogen-hydrogen exchange, and examine the metastable ≡SiH₂ complex formed during the exchange process. Throughout, we highlight issues relevant for hydrogen in amorphous silicon (used in solar cells, sensors and displays) and in Si-SiO₂ structures (used in integrated circuits). The broader impact of first-principles calculations on computational electronics will also be discussed     

A critique of the theory of p-n-p-n devices

A review of various papers dealing with p-n-p-n device characteristics shows essentially different interpretations of 1) the condition for switching and 2) the operating state defined byalpha_{p}+ alpha_{N} = 1. The present paper attempts to show the relationship between these various papers and to clarify the conditions which exist at the switching point and holding point.     

Charge-transfer noise theory for surface-channel charge-coupled devices

The detailed expression of charge-transfer noise for surface-channel CCD's is derived from the surface generation-recombination rate equation. Not only the charge fluctuation due to occupied interface states but also that due to unoccupied interface states are taken into account. The derived expression can explicitly predict the spectrum intensity dependences on the signal charge concentration and the clock frequency for various amounts of the fat-zero charge. The comparison between theory and experimental results shows good agreement over a wide range of signal charge concentration and clock frequency. It is shown that charge-transfer noise depends heavily on the ratio of the signal charge concentration to the clock frequency and the capture cross section in the absence of fat-zero charge. For the small ratio, the charge fluctuation is ruled by the transfer-process noise which is determined from the amount of unoccupied interface states. For the very large ratio, the storage-process noise which is determined from the interface state distribution over the band gap rules the charge fluctuation. Fat-zero charge hardly reduces the transfer-process noise for the small ratio. For the large ratio, the fat-zero charge enhances the total transfer noise.     

Spectral inverse scattering theory for inhomogeneous dielectricwaveguides and devices

The authors review electromagnetic inverse scattering theory for inhomogeneous dielectric waveguides and devices. Typically the parameters of these system components are expressed as functions of frequency or wavenumber, so that spectral, i.e. time-harmonic, methods are appropriate. Spectral, i.e. time-harmonic, inverse scattering theory is reviewed using the propagation of electromagnetic waves in inhomogeneous dielectric waveguides as a physical model. Permittivity profiles are reconstructed from scattering matrix data. Applications to the design of couplers, logical gates, and nonuniform transmission lines are discussed     

A theory of the Hooge parameters of solid-state devices

Handel's theory of quantum 1/f noise is applied to the Hooge parameters of bipolar transistors and various types of FET's. Very low values for the Hooge parameters αHnand αHpfor electrons and holes are obtained. For several cases the experimental data seem to agree with the predicted theoretical limit whereas in other cases the mobility 1/f noise is masked by other noise sources. In good GaAs devices the predicted quantum limit for αHnis reached within a factor 5-10. The theory is also applied to the Hg1-xCdxTe materials and devices. Because of the very low effective masses involved, the theory predicts values as high as 2 × 10^-4-2 × 10^-5, depending onx. What remains presently unexplained are the high values of αHfor semiconductor resistors and long p-n diodes.     

A general sampling theory for nonideal acquisition devices

The authors first describe the general class of approximation spaces generated by translation of a function ψ(x), and provide a full characterization of their basis functions. They then present a general sampling theorem for computing the approximation of signals in these subspaces based on a simple consistency principle. The theory puts no restrictions on the system input which can be an arbitrary finite energy signal; bandlimitedness is not required. In contrast to previous approaches, this formulation allows for an independent specification of the sampling (analysis) and approximation (synthesis) spaces. In particular, when both spaces are identical, the theorem provides a simple procedure for obtaining the least squares approximation of a signal. They discuss the properties of this new sampling procedure and present some examples of applications involving bandlimited, and polynomial spline signal representations. They also define a spectral coherence function that measures the “similarity” between the sampling and approximation spaces, and derive a relative performance bound for the comparison with the least squares solution     

On the theory of linear surface acoustic wave devices

Stationary distribution of the efficient wave sources excited by interdigital transducers (IDT) of arbitrary configuration has been derived on the basis of reciprocity of the generation and reception of surface acoustic waves (SAW) in piezoelectrics. It was shown that these sources represent a linear combination of two stationary distributions on the surface S between the piezoelectric and IDT: the distribution of the normal component of SAW flux density formed in the mode of SAW reception by the short-circuit IDT and the field distribution of the SAW electric potential at the same surface S but in the absence of piezoelectric. The Y-parameter matrix of the device was obtained as an electric M×2-terminal network containing M IDT. It was shown that the SAW transfer admittances and SAW radiation admittances contained additional frequency-dependent multipliers. The characteristics take into account the smoothed diffraction, spatial dispersion in IDT, reflections from IDT, and electric loads of the device.     

Modified `practical Bayes-estimators' [reliability theory]

This paper presents a new formulation of `practical Bayes-estimators' (PBE) for the 2-parameter Weibull model when both parameters are unknown. Overcoming some limitations of the first formulation gave rise to this work, but the results are beyond this intent. These estimators are a tool to improve technical knowledge by using a few experimental data. In this case, the controversy about whether to use Bayes or classical methods is surmounted since estimators, like maximum likelihood, give estimates that often appear unlikely on the basis of technical knowledge of the engineers. A Monte Carlo study supports the following conclusions: if the shape parameter is greater than one, modified PBE maintain the good properties of practical Bayes estimators; otherwise the modified PBE are much better and do not suffer from the past limitation regarding the formulation of the prior interval on the shape parameter itself; and when there are very few data the modified PBE work as a filter that always improves (on average) the prior information if it is poor, or substantially confirms it if it is good. From this viewpoint, Bayes theorem allows statistics to help engineering and not vice versa     

Decision theory solutions for nonlinear devices (Corresp.)

Relationships are derived showing that the optimum processor for a process that has been transformed by a memoryless nonlinear device is of the same form as that for the original untransformed process if we replace the measured values of the process by their inversely transformed values.     

Charge control approach to the small signal theory of field-effect devices

The operation of a field-effect device is described in terms of the total charge in the channel region. The analysis is primarily developed for the small-signal operation for which the charge control equations are linear and have constant coefficients. The complete expressions for the small signal admittance parameters are obtained in both the linear and the pinch-off regions leading directly to equivalent circuits. It is believed that the charge control approach not only simplifies the mathematics involved, but provides new insights into device operation as well.     

Dielectric materials, devices, and circuits

Dielectric materials are continuing to play a very important role in the microwave communication systems. These materials are key in realization of low-loss temperature-stable resonators and filters for satellite and broadcasting equipment, and in many other microwave devices. High dielectric-constant materials are critical to the miniaturization of wireless systems, both for the terminals and base-stations, as well as for handsets. In this paper, a sequential evolution of the dielectric materials applications in microwave devices will be reviewed. This includes dielectric waveguides, low-loss temperature-stable ceramic materials, dielectric resonators, and filters. The recent advances in the multilayer circuit modules, dielectric antennas, and ferroelectrics are also described     

General results in the mathematical theory of random signals and noise in nonlinear devices

An analysis is made of the output resulting from passing signals and noise through general zero memory nonlinear devices. New expressions are derived for the output time function and autocorrelation function in terms of weighted averages of the nonlinear characteristic and its derivatives. These expressions are not restricted to Gaussian noise and apply to any nonlinearity having no more than a finite number of discontinuities. The method of analysis used is heuristic.     

Modified theory of physical optics solution of impedance half plane problem

The scattering of electric polarized plane waves from an impedance half plane problem is examined by the method of modified theory of physical optics (MTPO). Two integrals, consisting of incident and reflected scattered fields, are obtained. These integrals are evaluated asymptotically by the methods of stationary phase and edge point. The obtained scattered fields are compared with the exact solution numerically.