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

Abstract

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, Nss, values from the G/w versus w curves. The Nss value for the Ni/n-GaN interface ranges from 3.36 × 1011 cm−2 eV−1 at 0.0 V to 2.92 × 1011 cm−2 eV−1 at 0.40 V for 60 K, and 6.63 × 1011 cm−2 eV−1 at 0.0 V to 3.87 × 1011 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 Nss 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.