Widely bandgap tunable amorphous Cd-Ga-O oxide semiconductors exhibiting electron mobilities ≥10-cm^2-V^-1-s^-1

Amorphous oxide semiconductors exhibit large electron mobilities; however, their bandgaps are either too large for solar cells or too small for deep ultraviolet applications depending on the materials system. Herein, we demonstrate that amorphous Cd-Ga-O semiconductors display bandgaps covering the entire 2.5-4.3-eV region while maintaining large electron mobilities ≥10-cm^2-V^-1-s^-1. The band alignment diagram obtained by ultraviolet photoemission spectroscopy and the bandgap values reveal that these semiconductors form type-II heterojunctions with p-type Cu₂O, which is suitable for solar cells and solar-blind ultraviolet sensors.