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

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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 (2.5×1011 eV−1 cm−2) has been observed in the PECVD grown SiO2/n-GaN interface when it was compared with EB evaporated SiO2/n-GaN interface (5.3×1011 eV−1 cm−2) and PECVD Si3N4/n-GaN interface (6.5×1011 eV−1 cm−2). The interface state density (Nf) depends on the composition of deposited insulating layers.