Guangxi Hu

An analytic model for channel potential and subthreshold swing of the symmetric and asymmetric double-gate MOSFETs

An analytical model for channel potential and subthreshold swing of the symmetric and asymmetric double-gate Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is presented. Two-dimensional Poisson equation is solved analytically using series method and channel potential is obtained. The analytical expression for subthreshold swing is achieved. Model results are compared with Medici simulation results, both of them turn out to agree very well. The results show the variation of channel potential and subthreshold swing with channel length, gate bias, and oxide thickness, which will provide some guidance for the integrated circuit designs.

Analytical Models for Electric Potential, Threshold Voltage, and Subthreshold Swing of Junctionless Surrounding-Gate Transistors

Analytical models for electric potential, threshold voltage, and subthreshold swing of the junctionless surrounding-gate field-effect transistors are presented. Poisson equation is solved and the electric potential is obtained. With the potential model, explicit expressions for threshold voltage and subthreshold swing are obtained. The analytical results are compared with those from simulations and excellent agreements are observed. The analytical models are useful not only for fast circuit simulations, but also for device design and optimization.

Theory of Short-Channel Surrounding-Gate Metal–Oxide–Semiconductor Field-Effect-Transistors

A model for a metal–oxide–semiconductor field-effect-transistor (MOSFET) with a surrounding gate (SG) is developed. Analytical solutions to the model are obtained by solving Poissons equation using series expansion. Taking short-channel effects into account, the analytical expressions for electric potential, electric field, and threshold voltage are obtained. It is found that the transistor is fully depleted for a small radius, and the threshold voltage increases as the radius increases or as the oxide capacitance per unit area decreases.

A Unified Carrier-Transport Model for the Nanoscale Surrounding-Gate MOSFET Comprising Quantum–Mechanical Effects

A unified carrier-transport model for a nanoscale surrounding-gate metal-oxide-semiconductor field-effect transistor (SG MOSFET) is developed. The model is based on McKelveys flux theory and includes quantum-mechanical effects. The model is applicable for both ballistic- and diffusive-transport regimes. The model results fit with the simulation results extremely well in both transport regimes for the small drain biases VDS <; 1 V. With the model, the characteristics of a drain-to-source current of an SG MOSFET working in the linear region can be very quickly and easily obtained. The model will provide some guidance for the practical use of SG nanowire transistors.

Quantum Mechanical Effects on the Threshold Voltage of Double-Gate Metal–Oxide–Semiconductor Field-Effect Transistors

A model for a metal–oxide–semiconductor field-effect transistor (MOSFET) with a double gate (DG) is developed. Quantum mechanical effects on the threshold voltage (VTH) are modeled and investigated analytically. The analytic model shows how VTH is increased with quantum mechanical effect. The model is applicable to both symmetric DG (SDG) and asymmetric DG (ADG) nMOSFETs, and is also applicable to both doped and undoped DG nMOSFETs. The analytic results are verified by comparing with the results obtained from simulations using Schred, and good agreement is observed. The VTH of an ADG nMOSFET will shift more than that of an SDG nMOSFET, and the VTH of a DG transistor with (110)-silicon (Si) orientation will shift more than that of a DG transistor with (100)-Si orientation. When the silicon thickness tsi 1018 cm-3, the higher the NA, the more the VTH shift.

Transition temperatures of Bose-Einstein condensation in traps

A careful study is made of the definitions of the transition temperature Tc of an ideal Bose system in traps. We review several physical quantities that are used to define the transition temperature, which corresponds to different kinds of Tc. The different definitions give different values for Tc and the differences are quite large for finite systems. This makes the comparisons of theoretical predictions of the transition temperature shift with experimental results quite difficult. We also find that the derivative of chemical potential with respect to temperature is nearly discontinuous. This implies that in the thermodynamic limit the system might undergo a first-order phase transition.

Analytical Model for Subthreshold Swing and Threshold Voltage of Surrounding Gate Metal–Oxide–Semiconductor Field-Effect Transistors

We investigate analytically the metal–oxide–semiconductor field-effect transistor (MOSFET) with a surrounding gate (SG). We develop and present an analytical model for subthreshold swing and threshold voltage. Poissons equation is solved analytically. The analytical expressions for electrical potential, drain current in the subthreshold region, subthreshold swing, and threshold voltage are obtained. The analytical results are compared with simulated results, and the two agree very well. The subthreshold swing of an SG MOSFET can be improved either by reducing the silicon body radius or by reducing the oxide thickness. The threshold voltage decreases with reductions in the channel length, the silicon body radius, or the oxide thickness. Based on the threshold voltage model, drain induced barrier lowering (DIBL) effect is explored, and we find that DIBL effect is more severe for a device with a larger silicon body radius, and/or with a shorter channel length.

An analytical model for the subthreshold swing of double-gate MOSFETs

A model for the Symmetric Double-Gate (SDG) n-MOSFET is presented. Poisson equation is solved analytically and channel potential is obtained. The analytical expression for subthreshold swing is achieved. Model results are compared with Medici simulations, good agreement is observed. The subthreshold swing of an SDG MOSFET will be improved by increasing the channel length, by reducing either the silicon body thickness or the gate oxide thickness, and by increasing the silicon body doping concentration.

Analytical models for channel potential, threshold voltage, and subthreshold swing of junctionless triple-gate FinFETs

Analytical models for channel potential, threshold voltage, and subthreshold swing of the short-channel fin-shaped field-effect transistor (FinFET) are obtained. The analytical model results are verified against simulations and good agreements are observed. Analytical expressions for subthreshold swing, drain induced barrier lowering effect, and threshold voltage roll-off characteristics are presented. The explicit expressions for threshold voltage and subthreshold swing make the model useful in the practical applications of the device.

Quasi-Ballistic Transport Model for Graphene Field-Effect Transistor

Based on McKelveys flux theory, a carrier transport model for a graphene field-effect transistor (GFET) is addressed. This model leads to an explicit expression for drain-to-source current with only a few fitting parameters. The model is verified with experiments and simulations, and good agreements are observed. With the model, the characteristics of drain-to-source current of the GFET with positive or negative gate biases can be obtained very quickly and easily. The model will provide some insights and guidance for the practical use of the GFETs and can be embedded in circuit simulation tools.