Amorphous Sn–Ga–Zn–O channel thin‐film transistors

Transparent amorphous oxide semiconductors (TAOS) such as a‐InGaZnO4 are expected to be applied for channels of low‐temperature high‐mobility thin‐film transistors (TFTs). This paper presents the fabrication and characteristics of amorphous Sn–Ga–Zn–O (a‐SGZO) channel TFTs. Bottom‐gate TFTs were fabricated using as‐deposited and annealed a‐SGZO channels on a‐SiO2/n+‐Si wafers. Contrary to a‐InGaZnO4 channel TFTs, the device performances of the as‐deposited channel TFTs were very poor, e.g., on‐currents (Ion) were <10–7 A and on/off current ratios (Ron/off) were <101. The TFTs using channels annealed at 500 °C showed good performances such as Ion > 10–5 A, Ron/off > 106 and μsat ∼ 1.8 cm2 V–1 s–1. Optical measurements indicate that the improvement is accompanied by a reduction of the density of subgap states. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)