Electrical properties of thermally oxidized p-GaN metal–oxide–semiconductor diodes

We report on the electrical properties of thermally oxidized $\mathrm{p-}\mathrm{GaN}$ metal–oxide–semiconductor (MOS) diodes with $n^{+}$ source regions fabricated on sapphire substrates. The $n^{+}$ regions were selectively produced in Mg-doped GaN by $\mathrm{Si}+\mathrm{N}$ coimplantation and subsequent annealing at $\text{1300\hspace{0.05em}°}\mathrm{C},$ and then 100-nm-thick $\mathrm{\beta -}{\mathrm{Ga}}_2{\mathrm{O}}_3$ was grown by dry oxidation at $\text{880\hspace{0.05em}°}\mathrm{C}$ for 5 h. Capacitance–voltage measurements at room temperature display a surface inversion feature with an onset voltage of $\text{∼2.5\hspace{0.17em}}\mathrm{V}$ and show an extremely low interface trap density less than ${\text{1×10}}^{10}\hspace{0.17em}{\mathrm{eV}}^{\text{−1}} {\mathrm{cm}}^{\text{−2}}.$ These results suggest that the thermally grown $\mathrm{\beta -}{\mathrm{Ga}}_2{\mathrm{O}}_3\mathrm{/p-}\mathrm{GaN}$ MOS structure is a promising candidate for inversion-mode MOS field-effect transistors.