Barrier inhomogeneity and electrical properties of Pt/GaN Schottky contacts

The temperature dependence of the electrical properties of Pt/GaN Schottky barrier was studied. In particular, a Schottky barrier height of 0.96 eV and an ideality factor of 1.16 were found after a postdeposition annealing at 400 °C. Nanoscale electrical characterization was carried out by the conductive biased tip of an atomic force microscope both on the bare GaN surface and on the Pt/GaN contacts. The presence of a lateral inhomogeneity of the Schottky barrier, with a Gaussian distribution of the barrier height values, was demonstrated. Moreover, GaN surface defects were demonstrated to act as local preferential paths for the current conduction. The temperature dependent electrical characteristics of the diodes were discussed in terms of the existing models on inhomogeneous barriers and correlated to the nanoscale electrical characterization of the barrier. In this way, the anomalous electrical behavior of the ideality factor and of the Schottky barrier and the low experimental value of the Richardson's constant were explained