Reduction of the kink effect in a SELBOX tunnel FET and its RF/analog performance

Abstract

The kink effect in a fully depleted silicon-on-insulator (SOI) tunnel field-effect transistor (TFET) is studied and compared with the results for a SOI metal–oxide–semiconductor field-effect transistor (MOSFET) using a model that is calibrated against experimental results available in literature. A technique for eliminating the kink effect is proposed. The structure with a small gap in the buried oxide, known as the selective buried oxide (SELBOX) structure, is capable of reducing the kink effect. The impact of the kink effect on the device performance for different gap positions, thicknesses, and buried oxide thicknesses is examined. A better current–voltage characteristic is obtained for a position of the gap near the source. The effect of varying the temperature and the presence of a uniform trap charge on the kink effect for the SOI TFET, SOI MOSFET, and SELBOX structures is also studied. Various electrical parameters such as the subthreshold swing and ION/IOFF ratio are investigated for the TFET in the presence and absence of uniform trap charge. Although the SELBOX structure can minimize the kink effect, it is still present for such devices with narrow and wider gaps. Therefore, the gap thickness is optimized based on technology computer-aided design (TCAD) simulations. Furthermore, radio frequency (RF)/analog performance parameters such as the transconductance (gm), cutoff frequency (ft), transconductance generation factor (TGF = gm/ID), transconductance frequency product, gain transconductance frequency product, and 1-dB compression point are investigated using TCAD simulations and compared between the SELBOX MOSFET and SELBOX TFET devices.