Effect of Al concentration on the electrical characteristics of solution-processed Al doped ZnSnO thin film transistors

Amorphous AlZnSnO (AZTO) channel layer thin film transistors (TFTs) with various Al doping ratios were fabricated using a solution process. Electrical, structural, and optical properties were systematically investigated as a function of Al doping. At an appropriate level of Al doping (3.45 at%), optimal electrical properties of AZTO TFTs were obtained, including mobility of 2.41 cm2/V s and a subthreshold swing of 0.68 V/decade. From analyses of the chemical bonding states and optical band structure, this is attributed to suppression of oxygen related defect formation and a decrease of the band gap.