Capacitance-conductance-frequency characteristics of Au/Ni/n-GaN/undoped GaN Structures

Frequency-dependent capacitance (C) and conductance (G) characteristics of the Au/Ni/n-GaN/undoped GaN device have been investigated in the reverse bias voltage range of 0.00–0.40 V. The GaN films have been epitaxially grown by metal organic chemical vapor deposition on c-plane Al2O3 substrate. The measurement frequency (f) ranges from 1.0 kHz to 10 MHz. The slow and fast interface states with two time constants differing by about two orders of magnitude have been calculated from analysis of the reverse bias C-f and G-f characteristics. The interface state density has values of 1010–1011 eV−1 cm−2 and time constant has taken the values which change in range of 10−5–10−7 s. The phase angle versus bias voltage curves have shown at four different frequencies at the room temperature that the device behaves more capacitive at the reverse bias region rather than the forward bias region at 100 and 200 kHz.