Core-Shell Dual-Gate Nanowire Charge-Trap Memory for Synaptic Operations for Neuromorphic Applications

This work showcases the physical insights of a core-shell dual-gate (CSDG) nanowire transistor as an artificial synaptic device with short/long-term potentiation and long-term depression (LTD) operation. Short-term potentiation (STP) is a temporary potentiation of a neural network, and it can be transformed into long-term potentiation (LTP) through repetitive stimulus. In this work, floating body effects and charge trapping are utilized to show the transition from STP to LTP while de-trapping the holes from the nitride layer shows the LTD operation. Furthermore, linearity and symmetry in conductance are achieved through optimal device design and biases. In a system-level simulation, with CSDG nanowire transistor a recognition accuracy of up to 92.28% is obtained in the Modified National Institute of Standards and Technology (MNIST) pattern recognition task. Complementary metal-oxide-semiconductor (CMOS) compatibility and high recognition accuracy makes the CSDG nanowire transistor a promising candidate for the implementation of neuromorphic hardware.

An Approach For Drain Current Modeling Including Quantum Mechanical Effects For A DMDG Junctionless Field Effect Nanowire Transistor

This paper presents the effects of quantum confinements on the surface potential, threshold voltage, drain current, transconductance, and drain conductance of a Dual Material Double Gate Junctionless Field Effect Nanowire Transistor (DMDG-JLFENT). The carrier energy quantization on the threshold voltage of a DMDG-JLFENT is modeled, and subsequently, other parameters like drain current were analytically presented. The QME considered here is obtained under the quantum confinement condition for an ultra-thin channel, i.e., below 10 nm of Si thickness. The threshold voltage shift due to QME can be used as a quantum correction term for compact modeling of junctionless transistors. The analytical model proposed for surface potential, threshold voltage, drain current, transconductance, and drain conductance were verified by TCAD 3-D quantum simulation results which makes it suitable for SPICE compact modeling.

Nanodevices Tend to Be Round

Under several circumstances, a nanowire transistor with a square cross-section behaves as a circular. Taking the Gate-All-Around junctionless transistor as a primary example, we investigate the transition of the conductive region from square to circle-like. In this case, the metamorphosis is accentuated by smaller size, lower doping, and higher gate voltage. After defining the geometrical criterion for square-to-circle shift, simulation results are used to document the main consequences. This transition occurs naturally in nanowires thinner than 50 nm. The results are rather universal, and supportive evidence is gathered from inversion-mode Gate-All-Around (GAA) MOSFETs as well as from thermal diffusion process.

A Quasi 2-D Electrostatic Potential and Threshold Voltage Model for Junctionless Triple Material Cylindrical Surrounding Gate Si Nanowire Transistor

A mathematical model used for determining the threshold voltage characteristics and electrostatic potential of a Junctionless Triple Material Cylindrical Surrounding Gate Silicon Nanowire Transistor (JLTMCSGSiNWT) is proposed in this research work and is obtained by resolving the poison equation. Three materials with dissimilar metal functions are used in the construction of the device gate structure. Device parameters used to determine the electrical characteristics are also included in the model. Behavior of the device is investigated through its vertical electrical field distribution along the device channel. Higher drain bias conditions leading to DIBL are reduced in the proposed structure by minimal variation of voltages owing to three different gate materials that maintain a steady field distribution along the channel. This model explicitly shows the impact of various criteria like drain bias voltage, gate bias voltage, thickness of the silicon layer, thickness of the oxide layer, and length of the channel on electrostatic potential and the deterioration of threshold voltage. The proposed analytical model is validated with TCAD simulations and it could be further extended to study the advanced electrical characteristics of the JL Triple Material CSG Silicon Nanowire Transistor.