Theoretical examination on a significantly low off-state current of a transistor using crystalline In-Ga-Zn-oxide

To investigate the origin of a significantly low off-state current of a field-effect transistor with a crystalline In-Ga-Zn-oxide (IGZO) semiconductor channel, this paper focuses on the drain-to-channel tunneling of holes and presents calculations of the tunneling current density. The calculations show that a hole has an effective mass about ten times as large as the mass of a bare electron, and that the tunneling barrier is large with a height of 2.8 eV and a width of 25 nm, which means hole tunneling current is practically negligible. These findings reveal that heavy holes in the crystalline IGZO are a key parameter to develop low power consumption displays.