Solution processed boron doped indium oxide thin-film as channel layer in thin-film transistors

In this work, boron–indium-oxide (BIO) thin-film transistors (TFT) have been fabricated by a solution based processing method. We have studied the structural, morphological, optical and electrical properties of solution processed BIO thin-film for TFT applications. The dopant boron was chosen as an effective carrier suppressor in indium oxide thin-film, owing to high Lewis acid strength, electro-negativity, small ionic size and high boron-oxygen bonding strength. The boron concentration in the indium oxide precursor solution was varied from 0 to 50 at.%. X-ray diffraction analysis confirms the transition of polycrystalline indium oxide thin film to amorphous nature from boron concentration of 20 at.% and above. The thin-films had a uniform smooth surface with an average surface roughness between 0.10 and 0.17 nm. Moreover, the thin-films were shown to be highly transparent (> 86%) in the visible region. The synthesized BIO thin-film was patterned and used as the active channel layer for TFT devices that were fabricated. The BIO (25 at.% boron) TFT post-annealed at 350 °C exhibited amorphous nature with a field effect mobility of 0.8 cm²/V s with threshold voltage at 6.8 V and I_ON/I_OFF of about 4.5 × 10⁸.