ZnO thin-film transistors (TFTs) using high-k hafnium oxide (HfO) x as the gate dielectrics achieve a low operating voltage of below 1 V. A negative threshold voltage shift of devices was observed after the negative bias illumination stress (NBIS) from a 635 nm laser. Plasma treatment of the HfOx dielectric surface using different gases (i.e., N2O and O2) was used to improve the TFTs' electrical stability. By calculating the subthreshold swing and analyzing the oxygen chemical bonding states nearby the ZnO/HfOx interface by x-ray photoelectron spectroscopy, we found that the interface trapped state and oxygen vacancies existed in ZnO active layer caused this unstable performance. The stability of ZnO TFTs is improved with using N2O plasma-treated HfOx dielectric, as this eliminate the defect in the ZnO layer.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)