Effect of trap-assisted tunneling on off-current property of a-InGaZnO thin-film transistors.

We describe how the off-state current (I_off) property of amorphous InGaZnO (a-IGZO) thin-film transistors is caused by trap-assisted tunneling (TAT) by using a two-dimensional device simulation software application (Atlas 2 D, Silvaco). We found that I_off can be increased by controlling the bandgap energy (E_G) and the effective mass of electron (m_e) of a-IGZO transistors. When m_e was increased from 0.32 to 0.38 m_o (mass of a free electron), the point at which I_off started to increase in the region of negative gate voltage (V_GS) shifted from −4.7 to −7.4 V. In addition, when E_G was changed from 3.05 to 3.2 eV, the average value of I_off changed from 3.13 × 10⁻¹³ to 2.4 × 10⁻¹⁴ A. This implies that E_G and m_e influence the increase in I_off in a-IGZO TFTs because of the difficulty associated with TAT. [ABSTRACT FROM AUTHOR]