Effect of Atmosphere Dependent Annealing on the Electrical Characteristics of a-In2O3 Thin-film Transistors

In2O3 has been recognized as a wide-gap transparent semiconductor oxide with high mobility, in which the oxygen plays an important role in its electronic properties. Here, we investigate the effects of air, O3 and N2 annealing on the electrical characteristics of a-In2O3 thin film transistors (TFTs) by analyzing the behavior of weakly bonded oxygen (
$\text{O}_{\text {wb}}$
), excess oxygen (
$\text{O}_{\text {ex}}$
), and oxygen vacancy (
$\text{V}_{\text {O}}$
) in the channel layer. X-ray diffraction (XRD) result indicates an amorphous phase of In2O3 layer after annealing. The oxygen behavior and bonding information before and after annealing of the In2O3 films are investigated via X-ray photoelectron spectroscopy (XPS) measurements. The a-In2O3 TFTs with field-effect mobility of 50–60 cm2/Vs and enhanced reliability are achieved by optimizing channel thickness and annealing conditions in air. The large threshold voltage shifting, reduced mobility, and low ON/OFF ratio of O3 -annealed In2 O3 TFT are attributed to the existence of
$\text{O}_{\text {ex}}$
. The hump-effect observed in N2 -annealed In2O3TFT is attributed to the creation of a parasitic channel with high
$\text{V}_{\text {O}}$
level above the main channel. The results reveal that
$\text{O}_{\text {wb}}$
can be removed by thermal treatment, and
$\text{V}_{\text {O}}$
can be partially filled and stabilized without introducing
$\text{O}_{\text {ex}}$
by annealing the as-deposited In2 O3 TFTs in air at appropriate condition.