The role of tunnel barriers in phase-state low electron-number drive transistors (PLEDTRs)

This paper presents a numerical analysis of the role of tunnel barriers in explaining the experimental I-V characteristics of a new vertical tunnel transistor called phase-state low electron-number drive transistor (PLEDTR), used for constructing a high-speed and high-capacity gain cell. Introducing the characteristic features of tunneling current through ultrathin barriers into a standard two-dimensional (2-D) drift-diffusion (DD) device simulator by way of calibrating it with a self-consistent one-dimensional (1-D) Poisson/Schrodinger equation solver, it is shown that the transistor characteristics at the ON-state are substantially affected by the thickness of the source barrier. Current saturation observed at low source-drain voltages is found to result from tunnelling injection via the source barrier. Asymmetric source and drain barrier (SDBs) structures are found to be responsible for the large asymmetry of the I-V characteristics at large source-drain voltages found experimentally. It is also shown that the central shutter barriers (CSBs) reduce the overall drain current in the subthreshold regime, leading to superior OFF current characteristics.