▎ 摘　　要

This letter provides clear insight into the interplay between electron and hole characteristics of carriers within the forbidden gap during the band-to-band tunneling process, taking graphene-nanoribbons as an example. Accurate numerical models are presented and analytical formulas for tunneling probabilities are derived for both source/drain to channel and direct source-drain tunneling based on the Wentzel-Kramers-Brillouin (WKB) method. It is shown that not considering the electron-hole duality can lead to significant errors in numerical calculations, and more importantly, lack of proper understanding of the phenomenon gives rise to seriously misleading conclusions. Furthermore, the regime of validity of the WKB approximation for graphene-nanoribbon tunnel-field-effect-transistors is discussed in light of the electron-hole duality concept. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3528338]