Room-Temperature-Synthesized High-Mobility Transparent Amorphous CdO–Ga2O3Alloys with Widely Tunable Electronic Bands

In this work, we have synthesized Cd1–xGaxO1+δalloy thin films at room temperature over the entire composition range by radio frequency magnetron sputtering. We found that alloy films with high Ga contents of x> 0.3 are amorphous. Amorphous Cd1–xGaxO1+δalloys in the composition range of 0.3 < x< 0.5 exhibit a high electron mobility of 10–20 cm2V–1s–1with a resistivity in the range of 10–2to high 10–4Ω cm range. The resistivity of the amorphous alloys can also be controlled over 5 orders of magnitude from 7 × 10–4to 77 Ω cm by controlling the oxygen stoichiometry. Over the entire composition range, these crystalline and amorphous alloys have a large tunable intrinsic band gap range of 2.2–4.8 eV as well as a conduction band minimum range of 5.8–4.5 eV below the vacuum level. Our results suggest that amorphous Cd1–xGaxO1+δalloy films with 0.3 < x< 0.4 have favorable optoelectronic properties as transparent conductors on flexible and/or organic substrates, whereas the band edges and electrical conductivity of films with 0.3 < x< 0.7 can be manipulated for transparent thin-film transistors as well as electron transport layers.