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

We have 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. We have 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 × 10 11 cm −2 eV −1 at 0.0 V to 2.92 × 10 11 cm −2 eV −1 at 0.40 V for 60 K, and 6.63 × 10 11 cm −2 eV −1 at 0.0 V to 3.87 × 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.