Analytical modeling and simulation of some high performance vertical tunnel fets for biosensing and low power circuit applications

Abstract

The semiconductor industry is actively looking for alternatives to MOSFETs due to the newlinelimitations they face in maintaining performance while scaling. In advanced nanometer technology newlinenodes, particularly below 10 nm, MOSFET experiences undesirable performance degradation. newlineIn addition to delivering high subthreshold leakage current, MOSFETs suffer from a newlinefundamental physical limitation of subthreshold swing of 60 mV/decade at room temperature. newlineThe current focus is on developing devices with operating principles different from thermionic newlineemission in MOSFETs. In line with the current requirements of the semiconductor industry, newlinevarious researchers have worked on innovative devices showing promising performance gains newlineover MOSFETs. This thesis focuses on advances in one such emerging device, the tunnel newlinefield effect transistor (TFET), which has been found to offer great potential in low power newlineapplications due to its fast subthreshold swing and low subthreshold leakage current. The newlinestructural configuration of a TFET closely resembles that of a MOSFET, with the exception newlinethat its source and drain regions are doped differently, with an intrinsic channel. Carrier transport newlinemechanism in TFETs is based on the inter-band tunneling of charge carriers, induced by newlineelectric field modulation at the source/channel junction through the gate electrode. newlineTowards improving device performance, this thesis presents two structures of TFET. Firstly, newlinea line tunneling based TFET with inverted T-shaped channel (ITGOSO-VTFET) is investigated newlineusing Synopsis TCAD 2-D simulator in which the gate is only on the source region. It is newlineobserved that the inverted T-shaped channel minimizes the off-state and ambipolar current by newlineconfiguring an orthogonal alignment between the source/channel and channel/drain junctions, newlinewhich prevents charge carriers traveling between the source and drain terminals. Furthermore, newlinecounter-doped pockets provide a sharp band bending at the input tunneling interface, thereby newlineimproving the on-state current, while the configuratio