Unintentional doping effect in Si-doped MOCVD β-Ga2O3 films: Shallow donor states

High-quality beta-Ga2O3 films were epitaxially grown by using metalorganic chemical vapor deposition (MOCVD) with different donor concentrations, and their shallow donor states were investigated by the temperature-dependent Hall measurement and secondary ion mass spectroscopy (SIMS) analysis. Two donor levels with ionization energies of similar to 36 and similar to 140 meV were extracted. It is found that the unintentional doping (UID) effects in MOCVD contribute substantially to both these two levels: the first donor level may come not only from silicon doping but also from unintentional substitution of carbon for Ga sites, and the second donor level probably comes from doubly charged defects related to unintentional H doping. By analyzing the relationship between the growth conditions and donor states, combined with density functional theory calculations, it is found that reducing the oxygen partial pressure during the growth might be a feasible way to reduce the UID effect. This work paves the way to the precise control of carrier density in Si-doped MOCVD beta-Ga2O3 films.

Automated summary

In this study, high-quality β-Ga2O3 films were epitaxially grown using MOCVD with different donor concentrations, and their shallow donor states were investigated. The unintentional doping effects were found to have a significant impact on the donor states, and a method to reduce the unintentional doping effect was proposed.