Electrical and frequency-dependent properties of Au/Sm2O3/n-GaN MIS junction with a high-k rare-earth Sm2O3 as interlayer

High-k rare-earth samarium oxide (Sm 2 O 3 ) films are formed on n-GaN surface and analyzed its compositional properties by XPS measurements. XPS results specify that the Sm 2 O 3 films are formed at the interface. Then, the Au/Sm 2 O 3 /n-GaN MIS junction is prepared with a Sm 2 O 3 as insulating layer and correlated its electrical properties with the Au/n-GaN MS junction. The MIS junction shows highest barrier height ((0.81 eV (I-V)/1.0 eV (C-V)) for MIS junction than the MS junction (0.68 eV (I-V)/0.90 eV (C-V)). Excellent rectifying property is observed with lowest reverse leakage current and higher barrier height for the MIS junction than the MS junction, implying that the Sm 2 O 3 insulating layer effectively modified the barrier height. The barrier heights determined from I-V, Cheung's, Norde and Ψ S –V plot closely matched with each other, suggesting that these techniques are reliable and valid. The estimated interface state density of the MIS junction (1.990 × 10 11 cm −2 eV −1 (E C -0.82 eV)) is lower than the MS junction (9.204 × 10 12 cm −2 eV −1 (E C -0.70 eV)), which demonstrates that the Sm 2 O 3 insulating layer performs an important role in lowering the interface state density. The frequency-dependent characteristics of the MS and MIS junctions are discussed in the frequency range of 10 kHz to 1 MHz and found that the determined capacitance values decrease with increasing frequency. The forward I-V characteristic of the MS and MIS junctions reveals the ohmic behavior at low voltage regions and space-charge-limited conduction at higher voltage regions. Results reveal that the reverse leakage current in the studied MS and MIS junctions is controlled by a Poole-Frenkel emission.