Ni and Ni silicide Schottky contacts on n-GaN

The electrical characteristics of Ni and NiSi Schottky diodes on $n$ -GaN have been investigated as a function of annealing. Ni diodes were found to be stable up to 500 °C for 1 h in sequential annealing, with a barrier height φ $\mathrm{(I–V)}$ of 0.8–0.9 eV and an $n$ factor of ∼1.1. The barrier height deduced from $\mathrm{C–V}$ measurements, $\mathrm{\phi \hspace{0.17em}(C–V),}$ was typically 0.15 eV higher than $\mathrm{\phi \hspace{0.17em}(I–V).}$ At 600 °C the diodes failed, and Ga was found to migrate into the Ni layer. NiSi diodes were stable up to 600 °C for 1 h, $\mathrm{\phi \hspace{0.17em}(I–V)}$ was found to be about 0.8–1 eV with an $n$ -factor of about 1.15. The value of $\mathrm{\phi \hspace{0.17em}(C–V)}$ was between 0.3 to 0.6 eV higher than $\mathrm{\phi \hspace{0.17em}(I–V),}$ consistent with the notion of the presence of a thin insulating layer at the NiSi/GaN interface. The electrical characteristics obtained in this study are also compared with those obtained for Pt and PtSi Schottky diodes on $n$ -GaN.