Effect of Si on the Modulation of Energy Band gap and thePerformance of Silicon Indium Zinc Oxide Thin Film Transistors
Journal
Scientific Reports
Date
2017.11.13
Abstract
A comprehensive study has been performed regarding band gap properties under different concentration of Si atoms in SiInZnO (SIZO) thin film transistor (TFT). Band gap engineering of SIZO by controlling Si contents has been investigated by the evolution of electronic structure, such as the change of band edge states and the modulation of band gap. Carrier generation originated from the oxygen vacancy can modify the band gap states of oxide thin films. This is also related with the origin of defect state which is involved with the creation of oxygen vacancies. It is important to investigate the relationship between controlled Fermi energy level and suppressing the oxygen vacancy resulting in the Fermi energy level away from conduction band to intrinsic level by doping Si atoms. However, it is difficult to derive directly the change of the band gap states of amorphous oxide semiconductor by electrical measurement. Thus, we derive band gap and Fermi energy level directly by using the combination of the ultraviolet photoelectron spectroscopy (UPS) characteristics, Kelvin probe (KP) and electron energy loss spectroscopy (EELS). The relation between the variation of energy band gap controlled by Si addition and the electrical performance of SIZO TFT has been systematically investigated via three measuremnet results.In order to verify the versatility of those electrical modulation properties of a-SIZO by controlling Si contents, high performance inverter circuits consisting of 1wt.％ and 3wt.％ Si-doped a-SIZO TFTs with depletion mode (D-mode) have been fabricated by using all n-type metal-oxide TFTs. These inverter models are operated by the difference of threshold voltage (Vth) simply controlled by changing Si-doping ratio. High voltage gains of two inverters have been obtained ~20.62 at VDD=15V and showed strongly depending on subthreshold swing (SS).