Tunable Electrical and Optical Properties of Nickel Oxide (NiO x) Thin Films for Fully Transparent NiO x-Ga2O3 p-n Junction Diodes.

One of the major limitations of oxide semiconductors technology is the lack of proper p-type materials to enable devices such as pn junctions, light-emitting diodes, and photodetectors. This limitation has resulted in an increased research focus on these materials. In this work, p-type NiO x thin films with tunable optical and electrical properties as well as its dependence with oxygen pressure during pulsed laser deposition are demonstrated. The control of NiO x films resistivity ranged from ∼109 to ∼102 Ω cm, showing a p-type behavior with Eg tuning from 3.4 to 3.9 eV. Chemical composition and the resulting band diagrams are also discussed. The all-oxide NiO x-Ga2O3 pn junction showed very low leakage current, an ideality factor of ∼2, 105 on/off ratio, and 0.6 V built-in potential. Its J- V temperature dependence is also analyzed. C- V measurements demonstrate diodes with a carrier concentration of 1015 cm-3 for the Ga2O3 layer, which is fully depleted. These results show a stable, promising diode, attractive for future photoelectronic devices.