【Device Papers】Impact of oxygen stoichiometry in NiOx/β-Ga₂O₃ heterojunction diodes

      Researchers from the North Carolina State University have published a dissertation titled "Impact of oxygen stoichiometry in NiO_x/β-Ga₂O₃ heterojunction diodes" in Journal of Applied Physics.

Abstract

      The properties of NiO_x/β-Ga₂O₃ heterojunctions and their impact on the device performance are theoretically investigated for different oxygen compositions x in NiO_x. Along with the stoichiometric NiO with a 1:1 ratio in nickel and oxygen, two non-stoichiometric cases (Ni₂O₃ and NiO₂) are examined as well in combination with β-Ga₂O₃ of two typical crystallographic orientations [i.e., (001) and (010)]. First-principles calculations show good agreement with the available experimental data. The results indicate that the bandgap of NiO_x shrinks from ~3.9 eV (NiO) to ~1.5 eV (NiO₂⁠) as the oxygen content increases. More interestingly, the obtained band offsets reveal that the band alignment makes a transition from type-II (NiO and Ni₂O₃⁠) to type-I (NiO₂⁠) due to the asymmetric nature of the band-edge shifts. These characteristics lead to surprisingly large differences in the p–n  junction breakdown voltage with the structures of high oxygen composition exhibiting drastically smaller values. The heterojunctions under consideration are also found to be generally free from the localized interface states even in non-stoichiometric compositions (Ni₂O₃ and NiO₂) with only minor charge polarizations. The results highlight the need for an accurate description of the heterointerfaces, including the crystallographic orientation in the design and optimization of NiO_x/ -Ga₂O₃ based devices for high-performance electronic applications.

DOI：

https://doi.org/10.1063/5.0319426