Effect of channel thickness on radiation hardness of solution-processed oxide thin film transistors

Abstract

The effect of channel thickness on the radiation hardness of solution-processed amorphous zinc–indium–tin–oxide (a-ZITO) thin film transistors (TFTs) with a Zn : In : Sn ratio of 4 : 1 : 1 has been investigated. Proton ex situ device measurements and XPS analysis showed that oxide TFTs with smaller channel thickness exhibited greater radiation tolerance. Furthermore, from the energy bandgap and conduction band offset calculations, it was confirmed that a-ZITO TFTs with a thinner channel reduced the doping of electrons from shallow donor states to the conduction band minimum against proton irradiation. For in situ measurements of device characteristics during proton irradiation with electrical stress, a significant degradation was observed due to the generation of oxygen vacancies within the semiconductor lattice and localized traps by proton-induced electron–hole pairs in the gate dielectric. As a result, the thinnest a-ZITO TFT (4 nm channel thickness) exhibited the most stable electrical performance with ΔV_th of −10.7 V and −0.5 V, and Δμ of 4.0 cm² V⁻¹ s⁻¹ and 0.1 cm² V⁻¹ s⁻¹ during in situ and ex situ measurements, respectively. This study provided a relatively detailed analysis in real-time, compared to the present state of the art, and suggested the effect of channel thickness on radiation hardness.