Double-gate MOS Transistors Research Articles

Physics based compact modeling of symmetric double gate MOS transistors with high mobility III-V channel material

In this work, we report a physics-based core model of surface potential, inversion charge, and drain current of a symmetric double-gate MOSFET with high mobility III-V channel material. The model efficiently captures all essential device physics of III-V MOSFETs. The carrier quantization effect inside the quantum well formed between oxide and channel region, is modeled by solving time-independent Schrödinger wave equation. The surface potential and inversion charge are obtained from the explicit solution of the Poisson and Schrödinger equation. A first-order correction has been applied to incorporate the modifications in sub-band energy due to applied gate bias voltages. The conduction band non-parabolicity effect is also included in our proposed model. The drain current has been derived using drift-diffusion transport including the velocity overshoot effect. The core model is free from any empirical parameters. The model predicted results have been validated with self-consistent Schrödinger-Poisson solver and commercial device simulator (TCAD) for different channel thicknesses, effective masses, a wide range of gate and drain bias voltages, and different non-parabolicity factor. The model predicted results are found to be in reasonable agreement with numerical simulation data.

RADIOMEASURING GAS CONCENTRATION TRANSDUCER BASED ON TRANSISTOR STRUCTURE WITH NDR FOR THE DIAGNOSIS OF STRAINS OF THE BACTERIUM HELICOBACTER PYLORI

The article discusses a radiomeasuring gas concentration transducer for the diagnosis of strains of the bacterium Helicobacter pylori. One of the promising directions in the construction of gas concentration transducers for respiratory diagnostics is the use of gas concentration frequency transducers based on the reactive properties of transistor structures with negative differential resistance (NDR). This type of transducers allows you to solve the problem of using analog-to-digital converters, because it implements the method of converting "informative signal - frequency", which is one of the best for further processing on a computer. Theoretical and practical studies have shown that using the reactive properties of semiconductor devices and transistor structures in which there is a negative differential resistance, it is possible to significantly increase the sensitivity and accuracy of measuring gas concentration, in particular NH3. The authors proposed and studied a gas concentration measuring transducer, which is built on the basis of a transistor structure with negative differential resistance and a gas-sensitive element to NH3. With a change in gas concentration, the conductivity of the sensitive element changes, which adsorbs NH3 molecules, which in turn changes the active and reactive components of the impedance of the transistors structure. The reactive component of the impedance of the transistors structure is capacitive in nature. This capacitance is part of the total capacitance that occurs at the electrodes of the drain of a double-gate MOS transistor and collector of a bipolar transistor, which together with the inductance L form a resonant oscillatory circuit. A dynamic mathematical model of the frequency transducer of gas concentration by the method of variable states is developed. The dynamic model of the self-generating secondary transducer of gas concentration allows you to determine the value of the frequency of the output signal depending on the change in gas concentration at any time. Analytical expressions of the transformation function and sensitivity equations are obtained. The sensitivity of the developed device for the diagnosis of strains of the bacterium Helicobacter pylori ranges from 2.1 kHz/ppm to 3.4 kHz/ppm.

Analysis of gate underlap channel double gate MOS transistor for electrical detection of bio-molecules

In this paper, an analytical model for gate drain underlap channel Double-Gate Metal-Oxide-Semiconductor Field-Effect Transistor (DG-MOSFET) for label free electrical detection of biomolecules has been proposed. The conformal mapping technique has been used to derive the expressions for surface potential, lateral electric field, energy bands (i.e. conduction and valence band) and threshold voltage (Vth). Subsequently a full drain current model to analyze the sensitivity of the biosensor has been developed. The shift in the threshold voltage and drain current (after the biomolecules interaction with the gate underlap channel region of the MOS transistor) has been used as a sensing metric. All the characteristic trends have been verified through ATLAS (SILVACO) device simulation results.

Numerical Study on Schottky-Barrier Double-Gate MOS Transistor with Recessed Channel and Asymmetric Contact

Numerical Study on Schottky-Barrier Double-Gate MOS Transistor with Recessed Channel and Asymmetric Contact

Analytical Subthreshold Potential Distribution Model for Gate Underlap Double-Gate MOS Transistors

We propose an analytical model to compute the potential distribution in gate underlap double-gate symmetric MOS transistors in the subthreshold condition Ggs < Vth . Gate underlap increases the effective channel length, which results in reducing the short-channel effect and, hence, relaxing the constraint on silicon body thickness. We use the proposed model to obtain suitable gate underlap length and silicon thickness for iso subthreshold slope and drain-induced-barrier lowering. Gate fringing field, modulating the potential in gate underlapped regions, is modeled using a conformal mapping technique. Extensive simulations were carried out to confirm the validity of our model to gate lengths ~20 nm.

Simulation of the gate tunnel current in the double gate (DG) MOS transistor

A model of the double gate MOS transistor, based on a quantum-mechanical description of the carrier concentration and including tunneling between the channel and the gates, is developed and used to consider the gate tunnel current in dependence on the bias voltages, semiconductor layer thickness and the gate oxide layer thickness.

An analytical subthreshold current model for ballistic quantum-wire double-gate MOS transistors

The subthreshold characteristic of ultra-thin (i.e. quantum-wire), ultra-short double-gate transistors (symmetric structures) working in the ballistic regime has been analytically modeled. This model takes into account short-channel effects, quantization effects and source-to-drain tunneling (WKB approximation) in the expression of the subthreshold drain current. Important device parameters, such as Ioff-current or subthreshold swing, can be easily evaluated through this full analytical approach, which also provides a complete set of equations for developing equivalent-circuit model used in ICs simulation.

A self-aligned, electrically separable double-gate MOS transistor technology for dynamic threshold voltage application

In this brief, a self-aligned electrically separable double-gate (SA ESDG) MOS transistor technology is proposed and demonstrated. The SA ESDG structure is implemented by defining a dummy top gate that is self-aligned to the bottom gate and then later replacing the dummy using a real top gate. The proposed process is applied to the single-grain Si film formed by recrystallizing a low-pressure chemical vapor deposition a-Si with a metal induced unilateral crystallization technique and enhancing the grain sizes in a subsequent high temperature annealing step. The ideal device structure resulting from the process is verified by scanning electron microscope imaging. The good current-voltage characteristics and the noticeable dynamic threshold voltage effects are also observed in the implemented SA ESDG device.