Optical and electrical properties of amorphous Cd-In-Ga-O thin films: Effect of Cd/In ratios

摘要

In order to design semiconductor devices, energy positions of the conduction band minimum (CBM) and the valence band maximum (VBM) of semiconductors are important parameters. In the case of amorphous oxide semiconductors (AOSs), the energy positions can be tuned widely by varying their composition compared with crystalline oxide semiconductors because of the difference of solubility limits. Ternary CdO (E_g = 2.1eV) - In2O3 (3.3eV) - Ga2O3 (4.7eV) system was a possible AOS system whose CBM and VBM are controllable because these simple oxides have (n – 1)d~(10) ns~0 electron configurations, which is mandatorily required for high mobility, and different energy positions of CBMs and VBMs with each other. In this study, effects of varying Cd/In ratio were investigated.