Device performance and bias instability of Ta doped InZnO thin film transistor as a function of process pressure

The device performance and bias instability of radio frequency (RF) sputtered Ta doped InZnO thin film transistors (TFTs) were investigated as a function of deposition process pressure. Under low process pressure, the electrical characteristics of TaInZnO TFTs were enhanced with amorphous physical structure and the decrease of oxygen deficient bonding states. These changes were correlated with the evolution of electronic structure, such as band alignment and band edge states below the conduction band. As the process pressure decreased, the energy difference between conduction band minimum and Fermi level and the band edge states was decreased. In particular, the relative energy level of band edge states was moved into the deep level within bandgap, with the increase of process pressure.