This work characterizes thin film p-NiOx layers deposited through low power magnetron sputtering. NiOx is of interest as a p-type oxide, which can form heterojunctions with ultrawide bandgap materials such as β-Ga2O3, where p-type doping is not available. In this work, deposition takes place at low powers to mitigate damage to the interface during sputtering. The impact of gas flow, pressure, deposition power, and annealing on the electrical properties of the NiOx thin films was explored. It was found that a low deposition power of 50 W achieved a modest growth rate of roughly 4 nm/h and that carrier concentration decreases as deposition power decreases. Annealing also resulted in an increase in stability over time of the resistivity of the NiOx thin films, compared to samples which had not been annealed. A higher oxygen content during deposition correlated with a rougher topology and higher carrier concentration. These results are encouraging for the application of low powered deposition of NiOx toward p-NiOx heterojunction structures, especially concerning n-β-Ga2O3.
Gilbert et al. (Wed,) studied this question.