Semianalytical modeling of the depletion layers and their effects on the threshold voltage of a junctionless double‐gate MOSFET including trapped charges

Abstract

This paper considers the depletion regions at the source and drain sides in a symmetric junctionless double‐gate metal‐oxide‐semiconductor field‐effect transistor with trapped charges working in subthreshold condition. The effects of depletion layers on the potential, threshold voltage, drain‐induced barrier lowering (DIBL), and the current of the device have been investigated. The channel of the transistor is divided into 4 regions: 2 regions without and with trapped charges and 2 depletion regions on either side of the channel. Solving the 2‐dimensional Poisson's equation, a semianalytical model for the potential is achieved in these regions and the threshold voltage, the DIBL, and the current are calculated. Also, the depletion widths are calculated during the modeling and their variation against the positive and negative trapped charges is investigated. To show the importance of the depletion layers, another junctionless double‐gate metal‐oxide‐semiconductor field‐effect transistor without depletion layers is considered and the mentioned electrical properties of the 2 devices are compared with each other. Smaller central potential, threshold voltage, and current and higher DIBL are achieved when the depletion layers are considered. Good agreement between the results of the proposed model and the simulated results by TCAD software shows the physical validity of the proposed model.