Abstract
Electronic structure and film composition at back channel surfaces of amorphous In-Ga-Zn-O (a-IGZO) thin films were characterized using photoelectron yield spectroscopy (PYS), ultraviolet photoelectron spectroscopy (UPS), and photoelectron spectroscopy for chemical analysis (ESCA). Surface gap states near the valence band maximum were observed. Downward band bending was also detected near the surface (up to 5~7 nm) region. In accordance with the band bending, the film composition was changed; the content of In increased as approaching to the surface, while that of Ga decreased. Photoluminescence spectra suggested that the composition change caused the increase in the gap states at the back channel surfaces of a-IGZO thin films.
Published Version
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