Simulation of nanowire tunneling transistors: From the Wentzel–Kramers–Brillouin approximation to full-band phonon-assisted tunneling

Abstract

Nanowire band-to-band tunneling field-effect transistors ͑TFETs͒ are simulated using the Wentzel-Kramers-Brillouin ͑WKB͒ approximation and an atomistic, full-band quantum transport solver including direct and phonon-assisted tunneling ͑PAT͒. It is found that the WKB approximation properly works if one single imaginary path connecting the valence band ͑VB͒ and the conduction band ͑CB͒ dominates the tunneling process as in direct band gap semiconductors. However, PAT is essential in Si and Ge nanowire TFETs where multiple, tightly-coupled, imaginary paths exist between the VB and the CB.

Engineering the Electron–Hole Bilayer Tunneling Field-Effect Transistor

“…( ) [17]. However, in silicon and germanium the band gap is indirect and there are many interacting bands and so the WKB model breaks down [17].…”

“…However, in silicon and germanium the band gap is indirect and there are many interacting bands and so the WKB model breaks down [17]. Consequently, we use an experimentally fitted tunneling effective mass derived in [5].…”

Designing a low-voltage, high-current tunneling transistor

“…Consequently: The WKB model and reduced mass work well in InAs where there are carriers in the conduction band tunneling to a single valence band. However, in silicon and germanium the band gap is indirect and there are many interacting bands and so the WKB model breaks down [9]. Consequently, we use an experimentally fitted tunneling effective mass derived in [1].…”

“…The tunneling probability, T, is [7]: For simplicity, we will assume that the electric field across the tunneling junction, F, is constant and equal to the peak electric field. The effective mass for tunneling [1,8,9] is * tunnel m 1 , and EG is the band gap. All of the parameters can be collected into a single constant, α.…”

Enhanced Characteristics of Square-Shaped Extended Source TFET Via Silicon Carbide Polytype (3C-SiC) and a Dopant Pocket Layer

“…On the other hand, an increase in on-current causes the RF performances of the TFETs to be enhanced. To enhance the TFET on-currents, many efforts have been made including hetero-structures 11,16,17 , bandgap engineering 18,20 , high mobility and low band-gap materials 20,23 , high-k dielectric materials 24,25 , heterogate-dielectric (HG) 26,27 , dual material gate 28,30 and vertical direction tunneling 31,32 .…”