Investigations of SiO₂/n-GaN and Si₃N₄/n-GaN insulator-semiconductor interfaces with low interface state density

The electrical properties of electron beam (EB) evaporated silicon dioxide (SiO₂)/n-GaN, plasma enhanced chemical vapor deposited (PECVD) SiO₂/n-GaN, and PECVD silicon nitride (Si₃N₄)/n-GaN interfaces were investigated using high frequency capacitance-voltage measurements. Compositions of the deposited insulating layers (SiO₂ and Si₃N₄) were analyzed using x-ray photoelectron spectroscopy. Metal-insulator-semiconductor structures were fabricated on the metalorganic chemical vapor deposition grown n-type GaN layers using EB, PECVD grown SiO₂ and PECVD grown Si₃N₄ layers. Minimum interface state density (2.5×10¹¹eV^-1cm^-2) has been observed in the PECVD grown SiO₂/n-GaN interface when it was compared with EB evaporated SiO₂/n-GaN interface (5.3×10¹¹eV^-1cm^-2) and PECVD Si₃N₄/n-GaN interface (6.5×10¹¹eV^-1cm^-2). The interface state density (N_f) depends on the composition of deposited insulating layers.