Role of hydrogen in the post-annealing treatments for amorphous In-Ga-Zn oxide thin films

In-Ga-Zn-O thin films were prepared by magnetron sputtering at different deposition temperatures and annealed in pure hydrogen (H2) and nitrogen (N2), respectively. The carrier concentration increased to 9.6 × 1019 cm−3 and the Hall mobility reached to 9.3 cm2V-1s−1 upon 300 ℃ annealing in N2. However, the Hall mobility decreased to 4.3 cm2V-1s−1 upon thermal annealing in H2 despite of the carrier concentration increased to 1.1 × 1020 cm−3. Spectroscopic ellipsometry results show that the increased carrier concentration is related to the incremental shallow band edge state (D1), and the increasing of deep band edge state (D2) will lead to a rise in trap density and a reduction in Hall mobility.