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

Abstract

The electrical properties of electron beam (EB) evaporated silicon dioxide $({\mathrm{SiO}}_{\mathrm{2}}\mathrm{)/n-}\mathrm{GaN},$ plasma enhanced chemical vapor deposited (PECVD) ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/n-}\mathrm{GaN},$ and PECVD silicon nitride $({\mathrm{Si}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}}\mathrm{)/n-}\mathrm{GaN}$ interfaces were investigated using high frequency capacitance–voltage measurements. Compositions of the deposited insulating layers $({\mathrm{SiO}}_{\mathrm{2}}$ and ${\mathrm{Si}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}})$ 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 ${\mathrm{SiO}}_{\mathrm{2}}$ and PECVD grown ${\mathrm{Si}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}}$ layers. Minimum interface state density ${\text{(2.5×10}}^{11}\hspace{0.17em}{\mathrm{eV}}^{\mathrm{-1}}{\mathrm{\hspace{0.17em}cm}}^{\mathrm{-2}})$ has been observed in the PECVD grown ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/n-}\mathrm{GaN}$ interface when it was compared with EB evaporated ${\mathrm{SiO}}_{\mathrm{2}}\mathrm{/n-}\mathrm{GaN}$ interface ${\text{(5.3×10}}^{11}\hspace{0.17em}{\mathrm{eV}}^{\mathrm{-1}}{\mathrm{\hspace{0.17em}cm}}^{\mathrm{-2}})$ and PECVD ${\mathrm{Si}}_{\mathrm{3}}{\mathrm{N}}_{\mathrm{4}}\mathrm{/n-}\mathrm{GaN}$ interface ${\text{(6.5×10}}^{11}\hspace{0.17em}{\mathrm{eV}}^{\mathrm{-1}}{\mathrm{\hspace{0.17em}cm}}^{\mathrm{-2}}\mathrm{).}$ The interface state density ${\mathrm{(N}}_f)$ depends on the composition of deposited insulating layers.