Electrical properties and carrier transport mechanism of Au/n-GaN Schottky contact modified using a copper pthalocyanine (CuPc) interlayer

We investigated the electrical characteristics of Au/n-GaN Schottky rectifier incorporating a copper pthalocyanine (CuPc) interlayer using current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G-V) measurements. The barrier height of the Au/CuPc/n-GaN Schottky contact was higher than that of the Au/n-GaN Schottky diode, indicating that the CuPc interlayer influenced the space charge region of the n-GaN layer. The series resistance of Au/CuPc/n-GaN Schottky contact extracted from the C-V and G-V methods was dependent on the frequency. In addition, the series resistance obtained from C-V and G-V characteristics was comparable to that from Cheung's method at sufficiently high frequencies and in strong accumulation regions. The forward log I-log V plot of Au/CuPc/n-GaN Schottky contact exhibited four distinct regions having different slopes, indicating different conduction mechanisms in each region. In particular, at higher forward bias, the trap-filled space-charge-limited current was the dominant conduction mechanism of Au/CuPc/n-GaN Schottky contact, implying that the most of traps were occupied by injected carriers at high injection level.