Experimental analysis of potential origin of p-type conductivity in LiGa5O8

Recently, LiGa5O8, with a bandgap of ∼5.4 eV, has been demonstrated as a p-type semiconductor, which can be used to form a pn junction with β-Ga2O3. However, the occurrence of the p-type conductivity remains undetermined. In this work, the influence of as-grown film compositions and post-growth annealing on the p-type conductivity were investigated. The results indicate that oxygen vacancies play an important role in achieving p-type conductivity, as films with lower oxygen content exhibit higher hole concentrations under Li-poor conditions. The impact of different annealing atmospheres was also studied, finding that argon annealing enhances hole conductivity without altering film composition, while oxygen annealing reduces p-conductivity. In addition, the uniformity of Li distribution in the films was confirmed via secondary ion mass spectrometry (SIMS) depth profiling. The effect of unintentional Cr impurity incorporation was probed via cathodoluminescence (CL), concluding that Cr impurity led to strong luminescence at 716 nm but did not show impact on p-type behavior. Results from this work provide a deeper understanding of the fundamental properties of LiGa5O8, paving the way for its integration into advanced power electronic devices.