Effects of Localized Back-Surface Defects on Bulk and Front-Channel Conduction of Amorphous InGaZnO TFTs

Abstract

This paper investigated physical mechanisms underlying the effects of localized back-surface defects ( $D_{\mathrm { {loc}}})$ on the performances of amorphous InGaZnO thin-film transistors (a-IGZO TFTs). Four bands of density of states were utilized to represent $D_{\mathrm { {loc}}}$ . The a-IGZO thickness ( $t_{\mathrm { {IGZO}}})$ was varied from 20 to 300 nm. When $D_{\mathrm {{loc}}}$ was absent, the TFT with $t_{\mathrm { {IGZO}}}$ of 20 nm can exhibit the best TFT performance. However, it got the severest performance degradation when $D_{\mathrm {{loc}}}$ was taken into consideration. We further changed acceptor-like tail and deep-level defect states at the back-channel surface from 0 to $10^{\mathrm { {20}}}$ cm $^{\mathrm { {-2}}}$ eV $^{\mathrm { {-1}}}$ and quantitatively studied their effects on energy band bendings, electric field distributions, carrier concentration distributions, and electrical characteristics of a-IGZO TFTs.