Quantum capacitance

About: Quantum capacitance is a research topic. Over the lifetime, 954 publications have been published within this topic receiving 24165 citations.

Influence of Interface Traps and Electron-Hole Puddles on Quantum Capacitance and Conductivity in Graphene Field-Effect Transistors

Abstract: We study theoretically an influence of the near-interfacial insulator traps and electron-hole puddles on the small-signal capacitance and conductance characteristics of the gated graphene structures. Based on the self-consistent electrostatic consideration and taking into account the interface trap capacitance the explicit analytic expressions for charge carrier density and the quantum capacitance as functions of the gate voltage were obtained. This allows to extract the interface trap capacitance and density of interface states from the gate capacitance measurements. It has shown that self-consistent account of the interface trap capacitance enables to reconcile discrepancies in universal quantum capacitance vs the Fermi energy extracted for different samples. The electron-hole puddles and the interface traps impact on transfer I-V characteristics and conductivity has been investigated. It has been shown that variety of widths of resistivity peaks in various samples could be explained by different interface trap capacitance values.

Capacitance variation of electrolyte-gated bilayer graphene based transistors

Abstract: Quantum capacitance of electrolyte-gated bilayer graphene field-effect transistors is investigated in this paper. Bilayer graphene has received huge attention due to the fact that an energy gap could be opened by chemical doping or by applying external perpendicular electric field. So, this extraordinary property can be exploited to use bilayer graphene as a channel in electrolyte-gated field-effect transistors. The quantum capacitance of bi-layer graphene with an equivalent circuit is presented, and also based on the analytical model a numerical solution is reported. We begin by modeling the DOS, followed by carrier concentration as a function V in degenerate and nondegenerate regimes. To further confirm this viewpoint, the presented analytical model is compared with experimental data, and acceptable agreement is reported.

RF compressibility of topological surface and interface states in metal-hBN-Bi2Se3 capacitors

Abstract: The topological state that emerges at the surface of a topological insulator (TI) and at the TI-substrate interface are studied in metal-hBN-Bi2Se3 capacitors. By measuring the RF admittance of the capacitors versus gate voltage, we extract the compressibility of the Dirac state located at a gated TI surface. We show that even in the presence of an ungated surface that hosts a trivial electron accumulation layer, the other gated surface always exhibits an ambipolar effect in the quantum capacitance. We succeed in determining the velocity of surface Dirac fermions in two devices, one with a passivated surface and the other with a free surface that hosts trivial states. Our results demonstrate the potential of RF quantum capacitance techniques to probe surface states of systems in the presence of a parasitic density-of-states.

Quantum mechanical effects on the performance of strained silicon metal-oxide-semiconductor field-effect transistor

Abstract: In recent development of nanoelectronic devices, strained silicon Metal- Oxide-Semiconductor Field-Effect Transistor (MOSFET) has been identified as a promising structure for the future nanoscale device. Strained silicon is an attractive option due to the enhanced carrier mobility, high field velocity and carrier velocity overshoot. However, the aggressive geometry scaling has approached a limit where the classical mechanism is insufficient to clarify the characteristics of nanoscale MOSFET accurately. Beyond the classical limit, quantum-mechanical model becomes necessary to provide thorough assessment of the device performance. This research describes the modeling of nanoscale strained silicon MOSFET taking into account the critical quantum mechanical effects in terms of energy quantization and carrier charge distribution. Technology-Computer-Aided-Design (TCAD) simulations that apply the classical mechanisms are conducted to allow comparison with the developed models. It is shown that quantum mechanical effects become more dominant at channel length below 60nm. Significant discrepancy of threshold voltage as high as 90mV is found particularly in short channel regimes. The analytical model was also extended to the advanced structure of dual channel that provides higher electron and hole mobility compared to strained silicon MOSFET. The models were subsequently compared to the TCAD simulation results using a similar set of parameters as well as to the existing data from other literatures. Excellent agreements validate the models based on the physics of the quantum mechanical effects. In addition, the current-voltage model incorporating the quantum mechanical correction was also developed. The role of quantum capacitance over current drive in the channel was discussed. The developed models successfully replicate experimental data with proper physical explanation.

Theoretical Investigation of Dynamic Switching Functionality in Graphene-Based Waveguides

Abstract: Graphene offers new field-effect transistors with great capabilities, including fast switching speed, reconfigurability, and so on, which are suitable for other electronic devices. In order to analyze and design such devices, it is necessary to study a metal–graphene-dielectric-semiconductor–metal (MGDSM) stack. To accomplish this purpose, a physisorbed graphene strip is investigated to characterize the interaction of graphene with particular metals. Then, the MGDSM stack is examined for different regimes, and in addition, the quantum capacitance of graphene is employed to highlight its presence for computing the C-V curve regarding the stack. In this regard, the work function of the constituting materials is selected according to the reported experimental data in the literature to achieve a realistic C-V curve. This stack can be served as the building block for switching operation; consequently, it will have a fundamental role in designing high-speed transistors. Finally, the calculated C-V curve is compared with an experimental one that the calculated results are pretty close to the expected values.