Biswajit Jena

Performance analysis of undoped cylindrical gate all around (GAA) MOSFET at subthreshold regime

In this work the sensitivity of process parameters like channel length (L), channel thickness (tSi), and gate work function (M) on various performance metrics of an undoped cylindrical gate all around (GAA) metal-oxide-semiconductor field effect transistor (MOSFET) are systematically analyzed. Undoped GAA MOSFET is a radical invention as it introduces a new direction for transistor scaling. In conventional MOSFET, generally the channel doping concentration is very high to provide high on-state current, but in contrary it causes random dopant fluctuation and threshold voltage variation. So, the undoped nature of GAA MOSFET solves the above complications. Hence, we have analyzed the electrical characteristics as well as the analog/RF performances of undoped GAA MOSFET through Sentaurus device simulator.

Conical surrounding gate MOSFET: a possibility in gate-all-around family

In this paper a new conical surrounding gate metal-oxide-semiconductor field effect transistor (MOSFET) with triple-material gate has been proposed and verified using TCAD device simulator from Synopsis. The electrostatic performance of conical model with different tapering ratios is extensively investigated and compared with that of cylindrical model (tapering ratio TR = 1). The present model exhibits improved electrostatic behavior for an optimized tapering ratio of 0.98 as compared to the conventional cylindrical model. The results reveal that the triple-material conical model provides better ON current performance, transconductance and reduced threshold voltage. On the contrary the single-material conical model exhibits maximum / ratio, minimum OFF current and reduced subthreshold swing (SS) in comparison to other models. Thus, the conical model with optimized tapering ratio can be a possible replacement of cylindrical model for low-power and high speed application.

RF analysis of work function modulated cylindrical surrounding gate MOSFET

The unique design along with greater accuracy in device performance has made cylindrical surrounding gate MOSFET (CSGM) a cutting edge device in the present VLSI technology. Due to its cylindrical geometry, this device provides higher packing density and higher scaling possibilities. The fabrication process of a surface channel device with proper threshold voltage (Vth) directly depends upon the work function of the gate electrode. By keeping it in mind, a work function engineering based metal gate with continuous mole fraction variation along the z-axis in a cylindrical surrounding gate MOSFET (WMCSGM) is introduced. The present WMCSGM model exhibits improved RF performance as compared to CSGM model. The RF performance of the model is extensively investigated in terms of different figure of merits such as cut-off frequency, transconductance and gate capacitance.

An analytical Nanowire Tunnel FET (NW-TFET) model with high-k dielectric to improve the electrostatic performance

This work presents both the analytical and simulation study of electrostatic performance for high-k dielectric (Si3N4) based Nanowire Tunnel FET. The analytical drain current for the model has been developed using minimum tunneling length and lateral electric field. The analysis is extended to measure the electrostatic parameters such as surface potential, electric field, and minimum tunneling distance and the results are compared with conventional low-k dielectric (SiO2) based model. It has been revealed that the high-k dielectric improves the drain current and reduces the threshold potential in the ON-condition. But the device produces large leakage current at OFF-state. The compared results have been authenticated using TCAD Sentaurus device simulator.