Effect of copper phthalocyanine (CuPc) interlayer on the electrical characteristics of Au/n-GaN Schottky rectifier

Electrical properties of Au/n-GaN Schottky rectifier with copper pthalocyanine (CuPc) interlayer were investigated using current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) characteristics. The barrier height obtained for the Au/CuPc/n-GaN Schottky diode was higher than that of the Au/n-GaN Schottky diode. This could be associated with the presence of the CuPc interlayer influencing the space-charge region of the Au/n-GaN structure. The Au/CuPc/n-GaN Schottky structure exhibits higher ideality factor, indicating the higher interface inhomogeneity in Au/CuPc/n-GaN as compared to Au/n-GaN Schottky structure. The density of interface states was extracted using I-V, C-V, and G-V characteristics. The results showed that the introduction of CuPc interlayer facilitated the reduction of interface state density (N_SS) of Au Schottky contact to n-GaN. Particularly, the N_SS obtained from frequency-dependent C-V characteristics was lower than that determined from forward I-V characteristics, which could be attributed to the inhomogeneous distribution of N_SS at Schottky interface.