Manifestation of reversal conductivity on high pressurizing of solution-processed ZnSnO thin-film transistors at low temperature

We have investigated the reversal of conductivity of solution-processed ZnSnO (ZTO) films and thin-film transistors (TFTs) under high-pressure annealing (HPA) in terms of the field-effect mobility. When the ZTO TFTs had Zn : Sn ratios of 1 : 1 and 2 : 1 under HPA, the value of the field-effect mobility showed a reversal phenomenon compared to TFTs without HPA. This result was attributed to the increase in conductivity due to the Fermi level being shifted up near the conduction band minimum by Sn activation under HPA. Furthermore, strong hybridization of the Sn 5s and the oxygen 2p orbitals was induced by HPA. As a result, HPA could contribute to the orbital splitting related to electron transport in the conduction band. In addition, the reliability of the HPA-ZTO TFT was more stable than without HPA because of the reduction in interface charge traps.