Effects of Ga2O3 deposition power on electrical properties of cosputtered In-Ga-Zn-O semiconductor films and thin-film transistors

Abstract

In this study, we have successfully fabricated In-Ga-Zn-O (IGZO) thin-film transistors (TFTs) with various Ga2O3 deposition powers prepared using a two radio-frequency (RF) (ceramics targets: In2O3 and Ga2O3) and one direct-current (DC) (metallic target: Zn) magnetron cosputtering system at room temperature. The carrier concentration for the IGZO films decreases to less than 3 x 10(16) cm(-3) when the Ga2O3 deposition power is 175W and Hall mobility decreases from 12.8cm(2)V(-1) s(-1) and saturates at 4.6 cm(2)V(-1) s(-1) with increasing Ga2O3 deposition power. The increase in the resistivity of the cosputtered films correlates with the decrease in the crystallinity of the InGaZn7O10 phase and the phase transformation from InGaZn7O10 to InGaZn2O5 with increasing Ga2O3 deposition power. With an optimum Ga2O3 deposition power of 150W, cosputtered IGZO TFTs with a higher, saturated drain current of 4.5 mu A, good saturation mobility, mu(sat) of 4.92cm(2)V(-1) s(-1), I-on/I-off of 10(9), a low subthreshold swing (SS) of 0.27V/decade, and R-SD of 30 k Omega have been successfully fabricated. (C) 2014 The Japan Society of Applied Physics