The interface state density characterization by temperature-dependent capacitance-conductance-frequency measurements in Au/Ni/n-GaN structures

Wehave fabricated the Au/Ni/n-GaN structures and measured their capacitance-frequency (C-f) and conductance (G/w)-angular frequency (w) characteristics in the temperature range of 60-320 K. The C-f curves for different reverse bias voltages have shown a behavior almost independent of the bias voltage at frequencies above 300 kHz at each measurement temperature. Wehave calculated the temperature-dependent interface state density, N-ss, values from the G/w versus w curves. The N-ss value for the Ni/n-GaN interface ranges from 3.36 x 10(11) cm(-2) eV(-1) at 0.0 V to 2.92 x 10(11) cm(-2) eV(-1) at 0.40 V for 60 K, and 6.63 x 10(11) cm(-2) eV(-1) at 0.0 V to 3.87 x 10(11) cm(-2) eV(-1) at 0.40 V for 320 K. That is, the interface state density value increases with increasing temperature. It has been seen that the values of N-ss obtained from the G/w versus w curves of the device are lower than the given values for metal/n-type GaN interface in the literature.