Highly transparent solution processed In-Ga-Zn oxide thin films and thin film transistors

Highly transparent In-Ga-Zn oxide (IGZO) thin films were fabricated by spin coating using acetate- and chlorate-based precursors, and thin film transistors (TFTs) were further fabricated employing these IGZO films as the active channel layer. The impact of the post-annealing temperature on the physical properties of IGZO films and performance of IGZO TFTs were investigated. Compared to the nitrate-based IGZO precursor, the chlorate-based precursor increases the phase change temperature of IGZO thin films. The IGZO films changed from amorphous to nanocrystalline phase in an annealing temperature range of 600–700 °C. The transparency is more than 90% in the visible region for IGZO films annealed with temperatures higher than 600 °C. With the increase of post-annealing temperature, the carrier concentration of IGZO film decreases, while the sheet resistance increases firstly and then saturates. The bottom-gate TFT with IGZO channel annealed at 600 °C in oxygen showed the best performance, which was operated in n-type enhancement mode with a field effect mobility of 1.30 cm²/V s, a threshold voltage of 10 V, and a drain current on/off ratio of 2.5 × 10⁴.