Capacitance-voltage characteristics of (Al/Ti)/Al$_2$O$_3$/$n$-GaN MIS structures

The capacitance-voltage characteristics of (Al/Ti)/Al$_2$O$_3$/$n$-GaN metal–insulator-semiconductor (MIS) structures are measured and analyzed. $n$-Type GaN films are grown on sapphire (0001) substrates by the metal-organic chemical vapor deposition method. An aluminum-oxide layer with a thickness of 60 nm is deposited onto the surface of GaN by the method of atomic-layer deposition from the gas phase. Metallic contacts are deposited by the electron-beam evaporation of titanium and aluminum in vacuum. According to the measurement results, the breakdown-field strength of the oxide, its dielectric constant, and the integrated electron density of states at the oxide-semiconductor interface are 5 $\times$ 10$^6$ V/cm, 7.5, and 3 $\times$ 10$^{12}$ cm$^{-2}$ , respectively.