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

This paper investigated physical mechanisms underlying the effects of localized back-surface defects (D
_loc
) on the performances of amorphous InGaZnO thin-film transistors (a-IGZO TFTs). Four bands of density of states were utilized to represent D
_loc
. The a-IGZO thickness (t
_IGZO
) was varied from 20 to 300 nm. When D
_loc
was absent, the TFT with tIGZO of 20 nm can exhibit the best TFT performance. However, it got the severest performance degradation when D
_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
²⁰
cm
^-2
eV
^-1
and quantitatively studied their effects on energy band bendings, electric field distributions, carrier concentration distributions, and electrical characteristics of a-IGZO TFTs.