Carrier transport mechanism of Ni/Ag Schottky contacts to n-type GaN grown on Si(111) substrate

We fabricated Ni/Ag Schottky contacts to n-GaN grown on Si substrate and investigated its electrical properties using current-voltage characteristics measured in the temperature range of 200-400 K. The barrier height and ideality factor of Ag/Ni/n-GaN Schottky diode showed strong temperature dependence. The barrier height decreased and ideality factor increased, with decrease in temperature indicating a deviation from ideal thermionic emission. A barrier height of 1.00 eV was obtained for unity ideality factor from the linear relation between the obtained barrier heights and ideality factor. The lateral inhomogeneity of the Schottky barrier at the interface between Ni/Ag and n-GaN could be the main cause of temperature dependence of barrier and ideality factor and has been explained on the basis of thermionic emission with a Gaussian distribution of barrier heights. The electric field dependence of reverse current revealed that the Poole-Frenkel emission mechanism dominates the current transport in the reverse bias.