Electronic structures in amorphous In-Ga-Zn-O metal-oxide-semiconductor diodes with various gate insulators

Electronic structures in amorphous In-Ga-Zn-O (a-IGZO) were investigated using metal-oxide-semiconductor (MOS) diodes in terms of dependence on gate insulators (G/I). Thin film transistors (TFTs) with the same gate structure were fabricated to correlate the electronic properties with the TFT performances. From the capacitance-voltage characteristics and transient capacitance response, the space-charge density increased throughout the bulk region of the MOS diode with chemical vapor deposited (CVD) G/I after annealing, and formation of shallow trap states was observed. TFTs with the CVD G/I showed reduced mobility and the increased subthreshold-swing. These results indicated that the electronic structures in the a-IGZO films were strongly influenced by the nature of G/I as well as process conditions.