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

Abstract

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.

Keywords:

• Off-current
• simulation
• thin-film transistors
• trap-assisted tunneling

Additional information

Funding

This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2018R1A2B6008815) and by Korea Electric Power Corporation (Grant number: R19XO01-05). M. Choi would also like to acknowledge the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (2017R1A4A1015565).