Influence of Grain Boundary Scattering on the Field-Effect Mobility of Solid-Phase Crystallized Hydrogenated...

Hydrogenated polycrystalline In₂O₃ (In₂O₃:H) thin-film transistors (TFTs) fabricated via the low-temperature solid-phase crystallization (SPC) process with a field-effect mobility (μ_FE) exceeding 100 cm² V^-1 s^-1 are promising candidates for future electronics applications. In this study, we investigated the effects of the SPC temperature of Ar + O₂ + H₂-sputtered In₂O₃:H films on the electron transport properties of In₂O₃:H TFTs. The In₂O₃:H TFT with an SPC temperature of 300 °C exhibited the best performance, having the largest µ_FE of 139.2 cm² V^-1 s^-1. In contrast, the µ_FE was slightly degraded with increasing SPC temperature (400 °C and higher). Extended X-ray absorption fine structure analysis revealed that the medium-range ordering in the In₂O₃:H network was further improved by annealing up to 600 °C, while a large amount of H₂O was desorbed from the In₂O₃:H films at SPC temperatures above 400 °C, resulting in the creation of defects at grain boundaries. The threshold temperature of H₂O desorption corresponded well with the carrier transport properties; the µ_FE of the TFTs started to deteriorate at SPC temperatures of 400 °C and higher. Thus, it was suggested that the hydrogen remaining in the film after SPC plays an important role in the passivation of electron traps, especially for grain boundaries, resulting in an enhancement of the µ_FE of In₂O₃:H TFTs.