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

Abstract

Here, we investigate the effect of increasing temperature on threshold voltage (V TH ) stability in self-aligned coplanar amorphous indium-zinc-tin oxide (a-IZTO) thin-film transistors (TFTs). An analytical model of the temperature dependency of V TH stability reveals the importance of device geometry and subgap density-of-state (DOS) reductions in highly stable a-IZTO TFTs. The validity of the analytical model is confirmed using experiments and technology computer-aided design simulations to predict quantitative relationships under various shifts in temperatures, subgap DOS, and V TH . The role of hydrogen impurity in performance and V TH stability is also examined. The incorporation of hydrogen in a-IZTO channels improves TFT performance and thermal stability (ΔV TH /ΔT = 3.18 mV/K) due to hydrogen's role as a passivation center. However, excessive incorporation of hydrogen increases subgap DOS distribution, causing a slight deterioration in thermal stability (ΔV TH /ΔT = 3.31 mV/K). This suggests that hydrogen can be converted from a shallow donor to an acceptor-like deep trap state. Our findings inform future designs of stable oxide semiconductor TFTs in terms of thermal stability in emerging organic light-emitting diode, augmented and virtual reality, memory, logic, and monolithic three-dimensional applications.