Impact of Ag doping on subthreshold conduction in amorphous Ga2Te3 with threshold switching

Abstract

Threshold switching devices with Ag-doped amorphous chalcogenides show enhanced threshold switching characteristics of a high selectivity and a low current in the subthreshold region. However, the mechanism underlying the decrease in this subthreshold current caused by Ag doping is not well understood. In this study, the effects of Ag doping in amorphous Ga 2 Te 3 are investigated in terms of the change in bonding structure and localized states in conjunction with threshold switching characteristics. X-ray photoelectron and Raman spectroscopies reveal the formation of Ag–Te bonds with a reduction in the amount of Te–Te bonds in Ga 2 Te 3 . In addition, the UV absorption shows an increase in the optical bandgap and a decrease of Urbach energy with Ag doping. The subthreshold current of the Ag-doped Ga 2 Te 3 device decreases by a factor of seven, and accordingly, the selectivity increases with respect to that of the undoped device. In addition, analyzing on the subthreshold conduction with a thermally assisted hopping model demonstrates a decrease in the density of localized states. Thus, the enhanced threshold switching characteristics of Ag-doped Ga 2 Te 3 are associated with the reduction of Te-induced localized states and the formation of Ag–Te bonds. • Excellent threshold switching characteristics of Ag-doped Ga 2 Te 3 thin films with various Ag doping concentrations. • The bonding structure was affected as Ag-Te bonding was formed with increasing Ag doping concentration. • The optical bandgap and localized states were significantly affected by Ag doping. • Extremely low off current of Ag-doped chalcogenide is correlated to the bonding structure, bandgap and localized states.