Modeling and simulation of carbon nanotube-semiconductor heterojunction vertical field effect transistors

摘要

The scaling behavior of carbon nanotube (CNT)-organic semiconductor heterojunction enabled vertical field effect transistors are comprehensively examined by two-dimensional consistent device simulations. Tunneling current is modeled by introducing tunneling induced carrier generation into the current continuity equation. Modulation of both the CNT-semiconductor Shottky barrier height and thickness are examined. The tunneling current and thermionic current dominate at on-state and off-state, respectively. Barrier height modulation plays an important role and improves the on-off current ratio and sub-threshold swing considerably. Small diameter CNT is preferred for enhancing the gate control on the CNT-channel barrier height. Reducing the effective gate oxide thickness by either a thin oxide or a high-K gate insulator gives improvement of device performance, but the former one works more efficiently. The channel length and CNT spacing should be carefully engineered due to the trade-off between device characteristics in the sub-threshold and above-threshold region.