Electrical properties and the determination of interface state density from $I$–$V$, $C$–$f$ and $G$–$f$ measurements in Ir/Ru/$n$-InGaN Schottky barrier diode

The electrical properties of the Ir/Ru Schottky contacts on $n$-InGaN have been investigated by current-voltage ($I$–$V$), capacitance-voltage ($C$–$V$), capacitance-frequency ($C$–$f$) and conductance-frequency ($C$–$f$) measurements. The obtained mean barrier height and ideality factor from $I$–$V$ are 0.61 eV and 1.89. The built-in potential, doping concentration and barrier height values are also estimated from the $C$–$V$ measurements and the corresponding values are 0.62 V, 1.20 $\times$ 10$^{17}$ cm$^{-3}$ and 0.79 eV, respectively. The interface state density $(N_{SS})$ obtained from forward bias $I$–$V$ characteristics by considering the series resistance $(R_{S})$ values are lower without considering the series resistance $(R_{S})$. Furthermore, the interface state density $(N_{SS})$ and relaxation time $(\tau)$ are also calculated from the experimental $C$–$f$ and $G$–$f$ measurements. The $N_{SS}$ values obtained from the $I$–$V$ characteristics are almost three orders higher than the $N_{SS}$ values obtained from the $C$–$f$ and $G$–$f$ measurements. The experimental results depict that $N_{SS}$ and $\tau$ are decreased with bias voltage. The frequency dependence of the series resistance $(R_{S})$ is attributed to the particular distribution density of interface states.