Energy Quantization Effects Research Articles

Multicomponent Conduction and Selectivity of Biological Channels

We consider multispecies conduction and selectivity of narrow biological filters such as KcsA [1] and NaChBac [2]. We use equilibrium statistical theory to find filter occupation and conductivities when coupled to the bath solutions with mixed types of conducting ions. The analysis of the filter conduction and selectivity conduction and selectivity is thus reduced to the analysis of the effective grand canonical distribution of ions within the filter [3], energy spectra, and density of the states within the filter [4]. The effects of energy quantization due to discrete number of ions and due to dehydration are taken into account. To account for the interaction between fluxes of different species within the channel we introduce Maxwell-Stefan theory [5] of the ion channel conduction. The fluxes of various species through the filter are obtained analytically in the limit of weak coupling. The theory is applied to derive Eisenman relations of the filter selectivity from the condition of nearly diffusion limited conduction in KscA channel. The model predictions are compared with experimental results using self-consistent kinetic equations. The transition rates in kinetic model are derived using effective grand canonical ensemble. A good agreement with the experiment is demonstrated. An application of the theory to analysis of the channel mutation experiments are discussed.

Analysis of Energy Quantization Effects on Single-Electron Transistor Circuits

In this paper, the effects of energy quantization on different single-electron transistor (SET) circuits (logic inverter, current-biased circuits, and hybrid MOS-SET circuits) are analyzed through analytical modeling and Monte Carlo simulations. It is shown that energy quantization mainly increases the Coulomb blockade area and Coulomb blockade oscillation periodicity, and thus, affects the SET circuit performance. A new model for the noise margin of the SET inverter is proposed, which includes the energy quantization effects. Using the noise margin as a metric, the robustness of the SET inverter is studied against the effects of energy quantization. An analytical expression is developed, which explicitly defines the maximum energy quantization (termed as ? quantization threshold?) that an SET inverter can withstand before its noise margin falls below a specified tolerance level. The effects of energy quantization are further studied for the current-biased negative differential resistance (NDR) circuit and hybrid SETMOS circuit. A new model for the conductance of NDR characteristics is also formulated that explains the energy quantization effects.

Impact of Energy Quantization on the Performance of Current-Biased SET Circuits

The current-biased single electron transistor (SET) (CBS) is an integral part of almost all hybrid CMOS SET circuits. In this paper, for the first time, the effects of energy quantization on the performance of CBS-based circuits are studied through analytical modeling and Monte Carlo simulations. It is demonstrated that energy quantization has no impact on the gain of the CBS characteristics, although it changes the output voltage levels and oscillation periodicity. The effects of energy quantization are further studied for two circuits: negative differential resistance (NDR) and neuron cell, which use the CBS. A new model for the conductance of NDR characteristics is also formulated that includes the energy quantization term.

Modeling and analysis of energy quantization effects on single electron inverter performance

In this paper, for the first time, the effects of energy quantization on single electron transistor (SET) inverter performance are analyzed through analytical modeling and Monte Carlo simulations. It is shown that energy quantization mainly changes the Coulomb blockade region and drain current of SET devices and thus affects the noise margin, power dissipation, and the propagation delay of SET inverter. A new analytical model for the noise margin of SET inverter is proposed which includes the energy quantization effects. Using the noise margin as a metric, the robustness of SET inverter is studied against the effects of energy quantization. A compact expression is developed for a novel parameter quantization threshold which is introduced for the first time in this paper. Quantization threshold explicitly defines the maximum energy quantization that an SET inverter logic circuit can withstand before its noise margin falls below a specified tolerance level. It is found that SET inverter designed with C T : C G = 1 / 3 (where C T and C G are tunnel junction and gate capacitances, respectively) offers maximum robustness against energy quantization.

Off-State Current and Performance Analysis for Double-Gate CMOS With Non-Self-Aligned Back Gate

Numerical simulation-based study of double-gate (DG) field-effect transistors (FETs) leads to the possibly viable concept of extremely scaled but nonself-aligned DG CMOS. Predictions of off-state current, on-state current, and circuit performance, accounting for short-channel effects and energy-quantization effects, in 25-nm DG FETs suggest that moderate back-gate underlap does not severely undermine the superior performance and leakage current of nanoscale DG CMOS relative to those of bulk-Si CMOS. The reverse back-gate biasing scheme for leakage reduction in DG CMOS is shown to be much more efficient than the reverse body biasing scheme in bulk Si even with moderate back-gate underlap.

Investigations of Silicon Nano-crystal Floating Gate Memories

AbstractAs memory continues to be scaled to ever smaller dimensions, the floating-gate memory transistor, which offers a single-element storage cell, becomes more attractive. Typically, this structure has been reserved for nonvolatile applications, where the comparatively high voltages, slow write speeds, and limited cyclability could be tolerated. However, if the floating-gate, which is usually a continuous film of polysilicon, is replaced with a discontinuous film of small floating islands (nano-crystals), a new set of tradeoffs in these performance factors becomes possible, opening the door to broader applications. If these islands are further reduced to the point where Coulomb charging or energy quantization effects become relevant, it is possible to control the charge on the islands at a single (or few) electron level, which offers very low power operation and may enable new functionality. This paper will discuss design and fabrication of these memories, experimental results on fabricated devices, and modeling of what could ultimately be achieved, as well as what limitations will ultimately be reached.

Electron energy quantization effects in the very thin film GAA SOI transistor

Analysis of the energy quantization effects on the semiconductor region of the Gate-All-Around SOI transistor, based on the self-consistent solution to the Schrödinger and Poisson equations is presented in dependence on the gate voltage and semiconductor film thickness. For thicker semiconductor films the energy quantization manifests mainly at high surface potentials due to the confinement of electron wave functions in the potential wells at the surfaces. When the semiconductor film is very thin the quantization due to the confinement of electrons in the semiconductor film dominates and the maximum of electron concentration is located in the middle of it, supporting the concept of volume inversion. Upon increasing the gate voltage the concentration peak splits into two ones.

Monte Carlo particle simulation of a quantum well heterojunction field-effect transistor: Comparison with experimental data

A heterojunction field-effect transistor with a quantum well channel has been studied using the Monte Carlo particle model. The transport in the channel has been calculated both considering and neglecting the effect of energy quantization of the conduction band. The results of the two approaches were found to agree well with each other and with experimental data. The significant differences between classical and quantum mechanical calculations are the better confinement of the carrier in the channel and the better agreement of the transfer characteristics with experiment for the latter.

Theory of single-electron charging of quantum wells and dots.

Single-electron charging effects similar to those in small-area metallic tunnel junctions should take place in semiconductor heterostructures, in particular, small-area quantum wells. Our analysis shows that dc current-voltage characteristics of such a well should exhibit an interplay between single-electron charging and energy-quantization effects. Relative magnitude of the single-electron charging effects is determined by the same parameter which scales multielectron charging in the conventional (large-area) quantum wells.