Surface treatments on the characteristics of metal–oxide semiconductor capacitors

The properties of metal-oxide semiconductor (MOS) capacitors with different chemical treatments have been examined in this study. A MOS capacitor consists of an Al₂O₃/n-GaN/AlN buffer/Si substrate. Four chemical treatments, containing organic solvents, oxygen plasma and BCl₃ plasma, dilute acidic and alkali solvents, and hydrofluoric acid, were used to reduce the metal ions, native oxides, and organic contaminants. The n-GaN surface was treated with these chemical treatments before Al₂O₃ was grown on the treated n-GaN surface to reduce the interface state trap density (D_it). The value of D_it was calculated using the capacitance–voltage curve at 1 MHz. The D_it of a u-GaN surface was modified using various solutions, which further influenced the contact properties of GaN.