Theoretical Modeling of a Temperature-Dependent Threshold-Voltage Shift in Self-Aligned Coplanar IZTO Thin-Film Transistors

Here,we investigate the effect of increasing temperature on thresholdvoltage (V (TH)) stability in self-alignedcoplanar amorphous indium-zinc-tin oxide (a-IZTO)thin-film transistors (TFTs). An analytical model of the temperaturedependency of V (TH) stability reveals theimportance of device geometry and subgap density-of-state (DOS) reductionsin highly stable a-IZTO TFTs. The validity of theanalytical model is confirmed using experiments and technology computer-aideddesign simulations to predict quantitative relationships under variousshifts in temperatures, subgap DOS, and V (TH). The role of hydrogen impurity in performance and V (TH) stability is also examined. The incorporation of hydrogenin a-IZTO channels improves TFT performance and thermalstability (Delta V (TH)/Delta T = 3.18 mV/K) due to hydrogen's role as a passivation center.However, excessive incorporation of hydrogen increases subgap DOSdistribution, causing a slight deterioration in thermal stability(Delta V (TH)/Delta T =3.31 mV/K). This suggests that hydrogen can be converted from a shallowdonor to an acceptor-like deep trap state. Our findings inform futuredesigns of stable oxide semiconductor TFTs in terms of thermal stabilityin emerging organic light-emitting diode, augmented and virtual reality,memory, logic, and monolithic three-dimensional applications.