Origin of Device Performance Degradation in InGaZnO Thin-Film Transistors after Crystallization

Abstract

This paper reports the crystallization of amorphous InGaZnO (a-IGZO) films using solid-phase crystallization and discusses the mechanisms responsible for degradation of device performance after crystallization. The field-effect mobility (µFE) and subthreshold gate swing (S) value of the nanocrystallite embedded-IGZO thin-film transistors (TFTs) were significantly degraded to 3.12 cm2 V-1 s-1 and 1.26 V/decade, respectively, compared to those (13.72 cm2 V-1 s-1 and 0.38 V/decade) for the a-IGZO TFTs. The decreased µFE is explained based on indium deficiency by diffusion of its atoms in the channel layer and grain-boundary trapping of mobile carriers. The predominant mechanism of increasing S value has been attributed to increased interface and grain-boundary trapping.