▎ 摘　　要

Since transistor sizes are reducing with the help of sophisticated technologies and alternative materials, impact ionization is becoming a very important phenomenon for having noticeable effect on device properties such as sub-threshold current. In this paper, firstly, an analytical model relying on general lucky drift theory for ionization coefficient (alpha(G)) in Graphene nanoribbon (GNR) transistors is presented. Moreover, the effects of some parameters, such as threshold energy of ionization, average electron energy, and momentum mean free paths on alpha(G) are examined. Finally, ionization coefficient is calculated for GNR and compared with that of Silicon.