The effect of nitrogen incorporation in Ge-In-Ga-O semiconductor and the associated thin film transistors

Abstract

The effect of nitrogen doping in Ge-In-Ga-O (GIGO) semiconductors was investigated via thin film characterization and the evaluation of the associated thin film transistor (TFT) properties. As the nitrogen content [N-2/(Ar + O-2 + N-2)] increases from 0% to 40% during the sputter deposition, the threshold voltage (V-th) of the corresponding TFT devices shifts toward positive values (from -1.88 to 3.08 V) and the subthreshold swing decreases (from 0.40 to 0.18V/decade) accordingly, while the amount of V-th shift (Delta V-th) by hysteresis is suppressed (from 1.33 to 0.22V). In particular, the device stability under negative gate bias (-20V) stress for 3 h improves considerably with total threshold voltage shift (Delta V-th) values of -6.25 V and -0.69V. As the amount of nitrogen incorporated in the semiconductor increase, the device mu(FE) decreases significantly (from 193 to 5.76 cm(2)/Vs). Temperature dependent analyses suggest that Coulombic scattering of the carriers near the nitrogen species is the major mechanism of such mobility degradation.