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 (4.) were < 10(-7) A and on/off current ratios (R-on/off) were < 10(1). The TFTs using channels annealed at 500 degrees C showed good performances such as mu sat 1.8 cm(2) V-1 s(-1). Optical measurements indicate that the improvement is accompanied by a reduction ofthe density of subgap states. (c) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.